1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
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, 2006@*
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, 2006
89 Free Software Foundation, Inc.
91 Published by the Free Software Foundation @*
92 51 Franklin Street, Fifth Floor,
93 Boston, MA 02110-1301, 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) 1988-2006 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 6.3, 6.2, 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.
487 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
488 unwinder framework, this consisting of a fresh new design featuring
489 frame IDs, independent frame sniffers, and the sentinel frame. Mark
490 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
491 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
492 trad unwinders. The architecture specific changes, each involving a
493 complete rewrite of the architecture's frame code, were carried out by
494 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
495 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
496 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
497 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
501 @chapter A Sample @value{GDBN} Session
503 You can use this manual at your leisure to read all about @value{GDBN}.
504 However, a handful of commands are enough to get started using the
505 debugger. This chapter illustrates those commands.
508 In this sample session, we emphasize user input like this: @b{input},
509 to make it easier to pick out from the surrounding output.
512 @c FIXME: this example may not be appropriate for some configs, where
513 @c FIXME...primary interest is in remote use.
515 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
516 processor) exhibits the following bug: sometimes, when we change its
517 quote strings from the default, the commands used to capture one macro
518 definition within another stop working. In the following short @code{m4}
519 session, we define a macro @code{foo} which expands to @code{0000}; we
520 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
521 same thing. However, when we change the open quote string to
522 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
523 procedure fails to define a new synonym @code{baz}:
532 @b{define(bar,defn(`foo'))}
536 @b{changequote(<QUOTE>,<UNQUOTE>)}
538 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
541 m4: End of input: 0: fatal error: EOF in string
545 Let us use @value{GDBN} to try to see what is going on.
548 $ @b{@value{GDBP} m4}
549 @c FIXME: this falsifies the exact text played out, to permit smallbook
550 @c FIXME... format to come out better.
551 @value{GDBN} is free software and you are welcome to distribute copies
552 of it under certain conditions; type "show copying" to see
554 There is absolutely no warranty for @value{GDBN}; type "show warranty"
557 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
562 @value{GDBN} reads only enough symbol data to know where to find the
563 rest when needed; as a result, the first prompt comes up very quickly.
564 We now tell @value{GDBN} to use a narrower display width than usual, so
565 that examples fit in this manual.
568 (@value{GDBP}) @b{set width 70}
572 We need to see how the @code{m4} built-in @code{changequote} works.
573 Having looked at the source, we know the relevant subroutine is
574 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
575 @code{break} command.
578 (@value{GDBP}) @b{break m4_changequote}
579 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
583 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
584 control; as long as control does not reach the @code{m4_changequote}
585 subroutine, the program runs as usual:
588 (@value{GDBP}) @b{run}
589 Starting program: /work/Editorial/gdb/gnu/m4/m4
597 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
598 suspends execution of @code{m4}, displaying information about the
599 context where it stops.
602 @b{changequote(<QUOTE>,<UNQUOTE>)}
604 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
606 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
610 Now we use the command @code{n} (@code{next}) to advance execution to
611 the next line of the current function.
615 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
620 @code{set_quotes} looks like a promising subroutine. We can go into it
621 by using the command @code{s} (@code{step}) instead of @code{next}.
622 @code{step} goes to the next line to be executed in @emph{any}
623 subroutine, so it steps into @code{set_quotes}.
627 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
629 530 if (lquote != def_lquote)
633 The display that shows the subroutine where @code{m4} is now
634 suspended (and its arguments) is called a stack frame display. It
635 shows a summary of the stack. We can use the @code{backtrace}
636 command (which can also be spelled @code{bt}), to see where we are
637 in the stack as a whole: the @code{backtrace} command displays a
638 stack frame for each active subroutine.
641 (@value{GDBP}) @b{bt}
642 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
644 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
646 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
647 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
649 #4 0x79dc in expand_input () at macro.c:40
650 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
654 We step through a few more lines to see what happens. The first two
655 times, we can use @samp{s}; the next two times we use @code{n} to avoid
656 falling into the @code{xstrdup} subroutine.
660 0x3b5c 532 if (rquote != def_rquote)
662 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
663 def_lquote : xstrdup(lq);
665 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
668 538 len_lquote = strlen(rquote);
672 The last line displayed looks a little odd; we can examine the variables
673 @code{lquote} and @code{rquote} to see if they are in fact the new left
674 and right quotes we specified. We use the command @code{p}
675 (@code{print}) to see their values.
678 (@value{GDBP}) @b{p lquote}
679 $1 = 0x35d40 "<QUOTE>"
680 (@value{GDBP}) @b{p rquote}
681 $2 = 0x35d50 "<UNQUOTE>"
685 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
686 To look at some context, we can display ten lines of source
687 surrounding the current line with the @code{l} (@code{list}) command.
693 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
695 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
698 538 len_lquote = strlen(rquote);
699 539 len_rquote = strlen(lquote);
706 Let us step past the two lines that set @code{len_lquote} and
707 @code{len_rquote}, and then examine the values of those variables.
711 539 len_rquote = strlen(lquote);
714 (@value{GDBP}) @b{p len_lquote}
716 (@value{GDBP}) @b{p len_rquote}
721 That certainly looks wrong, assuming @code{len_lquote} and
722 @code{len_rquote} are meant to be the lengths of @code{lquote} and
723 @code{rquote} respectively. We can set them to better values using
724 the @code{p} command, since it can print the value of
725 any expression---and that expression can include subroutine calls and
729 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
731 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
736 Is that enough to fix the problem of using the new quotes with the
737 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
738 executing with the @code{c} (@code{continue}) command, and then try the
739 example that caused trouble initially:
745 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
752 Success! The new quotes now work just as well as the default ones. The
753 problem seems to have been just the two typos defining the wrong
754 lengths. We allow @code{m4} exit by giving it an EOF as input:
758 Program exited normally.
762 The message @samp{Program exited normally.} is from @value{GDBN}; it
763 indicates @code{m4} has finished executing. We can end our @value{GDBN}
764 session with the @value{GDBN} @code{quit} command.
767 (@value{GDBP}) @b{quit}
771 @chapter Getting In and Out of @value{GDBN}
773 This chapter discusses how to start @value{GDBN}, and how to get out of it.
777 type @samp{@value{GDBP}} to start @value{GDBN}.
779 type @kbd{quit} or @kbd{C-d} to exit.
783 * Invoking GDB:: How to start @value{GDBN}
784 * Quitting GDB:: How to quit @value{GDBN}
785 * Shell Commands:: How to use shell commands inside @value{GDBN}
786 * Logging output:: How to log @value{GDBN}'s output to a file
790 @section Invoking @value{GDBN}
792 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
793 @value{GDBN} reads commands from the terminal until you tell it to exit.
795 You can also run @code{@value{GDBP}} with a variety of arguments and options,
796 to specify more of your debugging environment at the outset.
798 The command-line options described here are designed
799 to cover a variety of situations; in some environments, some of these
800 options may effectively be unavailable.
802 The most usual way to start @value{GDBN} is with one argument,
803 specifying an executable program:
806 @value{GDBP} @var{program}
810 You can also start with both an executable program and a core file
814 @value{GDBP} @var{program} @var{core}
817 You can, instead, specify a process ID as a second argument, if you want
818 to debug a running process:
821 @value{GDBP} @var{program} 1234
825 would attach @value{GDBN} to process @code{1234} (unless you also have a file
826 named @file{1234}; @value{GDBN} does check for a core file first).
828 Taking advantage of the second command-line argument requires a fairly
829 complete operating system; when you use @value{GDBN} as a remote
830 debugger attached to a bare board, there may not be any notion of
831 ``process'', and there is often no way to get a core dump. @value{GDBN}
832 will warn you if it is unable to attach or to read core dumps.
834 You can optionally have @code{@value{GDBP}} pass any arguments after the
835 executable file to the inferior using @code{--args}. This option stops
838 gdb --args gcc -O2 -c foo.c
840 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
841 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
843 You can run @code{@value{GDBP}} without printing the front material, which describes
844 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
851 You can further control how @value{GDBN} starts up by using command-line
852 options. @value{GDBN} itself can remind you of the options available.
862 to display all available options and briefly describe their use
863 (@samp{@value{GDBP} -h} is a shorter equivalent).
865 All options and command line arguments you give are processed
866 in sequential order. The order makes a difference when the
867 @samp{-x} option is used.
871 * File Options:: Choosing files
872 * Mode Options:: Choosing modes
873 * Startup:: What @value{GDBN} does during startup
877 @subsection Choosing files
879 When @value{GDBN} starts, it reads any arguments other than options as
880 specifying an executable file and core file (or process ID). This is
881 the same as if the arguments were specified by the @samp{-se} and
882 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
883 first argument that does not have an associated option flag as
884 equivalent to the @samp{-se} option followed by that argument; and the
885 second argument that does not have an associated option flag, if any, as
886 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
887 If the second argument begins with a decimal digit, @value{GDBN} will
888 first attempt to attach to it as a process, and if that fails, attempt
889 to open it as a corefile. If you have a corefile whose name begins with
890 a digit, you can prevent @value{GDBN} from treating it as a pid by
891 prefixing it with @file{./}, e.g.@: @file{./12345}.
893 If @value{GDBN} has not been configured to included core file support,
894 such as for most embedded targets, then it will complain about a second
895 argument and ignore it.
897 Many options have both long and short forms; both are shown in the
898 following list. @value{GDBN} also recognizes the long forms if you truncate
899 them, so long as enough of the option is present to be unambiguous.
900 (If you prefer, you can flag option arguments with @samp{--} rather
901 than @samp{-}, though we illustrate the more usual convention.)
903 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
904 @c way, both those who look for -foo and --foo in the index, will find
908 @item -symbols @var{file}
910 @cindex @code{--symbols}
912 Read symbol table from file @var{file}.
914 @item -exec @var{file}
916 @cindex @code{--exec}
918 Use file @var{file} as the executable file to execute when appropriate,
919 and for examining pure data in conjunction with a core dump.
923 Read symbol table from file @var{file} and use it as the executable
926 @item -core @var{file}
928 @cindex @code{--core}
930 Use file @var{file} as a core dump to examine.
932 @item -c @var{number}
933 @item -pid @var{number}
934 @itemx -p @var{number}
937 Connect to process ID @var{number}, as with the @code{attach} command.
938 If there is no such process, @value{GDBN} will attempt to open a core
939 file named @var{number}.
941 @item -command @var{file}
943 @cindex @code{--command}
945 Execute @value{GDBN} commands from file @var{file}. @xref{Command
946 Files,, Command files}.
948 @item -eval-command @var{command}
949 @itemx -ex @var{command}
950 @cindex @code{--eval-command}
952 Execute a single @value{GDBN} command.
954 This option may be used multiple times to call multiple commands. It may
955 also be interleaved with @samp{-command} as required.
958 @value{GDBP} -ex 'target sim' -ex 'load' \
959 -x setbreakpoints -ex 'run' a.out
962 @item -directory @var{directory}
963 @itemx -d @var{directory}
964 @cindex @code{--directory}
966 Add @var{directory} to the path to search for source and script files.
970 @cindex @code{--readnow}
972 Read each symbol file's entire symbol table immediately, rather than
973 the default, which is to read it incrementally as it is needed.
974 This makes startup slower, but makes future operations faster.
979 @subsection Choosing modes
981 You can run @value{GDBN} in various alternative modes---for example, in
982 batch mode or quiet mode.
989 Do not execute commands found in any initialization files. Normally,
990 @value{GDBN} executes the commands in these files after all the command
991 options and arguments have been processed. @xref{Command Files,,Command
997 @cindex @code{--quiet}
998 @cindex @code{--silent}
1000 ``Quiet''. Do not print the introductory and copyright messages. These
1001 messages are also suppressed in batch mode.
1004 @cindex @code{--batch}
1005 Run in batch mode. Exit with status @code{0} after processing all the
1006 command files specified with @samp{-x} (and all commands from
1007 initialization files, if not inhibited with @samp{-n}). Exit with
1008 nonzero status if an error occurs in executing the @value{GDBN} commands
1009 in the command files.
1011 Batch mode may be useful for running @value{GDBN} as a filter, for
1012 example to download and run a program on another computer; in order to
1013 make this more useful, the message
1016 Program exited normally.
1020 (which is ordinarily issued whenever a program running under
1021 @value{GDBN} control terminates) is not issued when running in batch
1025 @cindex @code{--batch-silent}
1026 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1027 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1028 unaffected). This is much quieter than @samp{-silent} and would be useless
1029 for an interactive session.
1031 This is particularly useful when using targets that give @samp{Loading section}
1032 messages, for example.
1034 Note that targets that give their output via @value{GDBN}, as opposed to
1035 writing directly to @code{stdout}, will also be made silent.
1037 @item -return-child-result
1038 @cindex @code{--return-child-result}
1039 The return code from @value{GDBN} will be the return code from the child
1040 process (the process being debugged), with the following exceptions:
1044 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1045 internal error. In this case the exit code is the same as it would have been
1046 without @samp{-return-child-result}.
1048 The user quits with an explicit value. E.g., @samp{quit 1}.
1050 The child process never runs, or is not allowed to terminate, in which case
1051 the exit code will be -1.
1054 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1055 when @value{GDBN} is being used as a remote program loader or simulator
1060 @cindex @code{--nowindows}
1062 ``No windows''. If @value{GDBN} comes with a graphical user interface
1063 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1064 interface. If no GUI is available, this option has no effect.
1068 @cindex @code{--windows}
1070 If @value{GDBN} includes a GUI, then this option requires it to be
1073 @item -cd @var{directory}
1075 Run @value{GDBN} using @var{directory} as its working directory,
1076 instead of the current directory.
1080 @cindex @code{--fullname}
1082 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1083 subprocess. It tells @value{GDBN} to output the full file name and line
1084 number in a standard, recognizable fashion each time a stack frame is
1085 displayed (which includes each time your program stops). This
1086 recognizable format looks like two @samp{\032} characters, followed by
1087 the file name, line number and character position separated by colons,
1088 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1089 @samp{\032} characters as a signal to display the source code for the
1093 @cindex @code{--epoch}
1094 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1095 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1096 routines so as to allow Epoch to display values of expressions in a
1099 @item -annotate @var{level}
1100 @cindex @code{--annotate}
1101 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1102 effect is identical to using @samp{set annotate @var{level}}
1103 (@pxref{Annotations}). The annotation @var{level} controls how much
1104 information @value{GDBN} prints together with its prompt, values of
1105 expressions, source lines, and other types of output. Level 0 is the
1106 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1107 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1108 that control @value{GDBN}, and level 2 has been deprecated.
1110 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1114 @cindex @code{--args}
1115 Change interpretation of command line so that arguments following the
1116 executable file are passed as command line arguments to the inferior.
1117 This option stops option processing.
1119 @item -baud @var{bps}
1121 @cindex @code{--baud}
1123 Set the line speed (baud rate or bits per second) of any serial
1124 interface used by @value{GDBN} for remote debugging.
1126 @item -l @var{timeout}
1128 Set the timeout (in seconds) of any communication used by @value{GDBN}
1129 for remote debugging.
1131 @item -tty @var{device}
1132 @itemx -t @var{device}
1133 @cindex @code{--tty}
1135 Run using @var{device} for your program's standard input and output.
1136 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1138 @c resolve the situation of these eventually
1140 @cindex @code{--tui}
1141 Activate the @dfn{Text User Interface} when starting. The Text User
1142 Interface manages several text windows on the terminal, showing
1143 source, assembly, registers and @value{GDBN} command outputs
1144 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1145 Text User Interface can be enabled by invoking the program
1146 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1147 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1150 @c @cindex @code{--xdb}
1151 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1152 @c For information, see the file @file{xdb_trans.html}, which is usually
1153 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1156 @item -interpreter @var{interp}
1157 @cindex @code{--interpreter}
1158 Use the interpreter @var{interp} for interface with the controlling
1159 program or device. This option is meant to be set by programs which
1160 communicate with @value{GDBN} using it as a back end.
1161 @xref{Interpreters, , Command Interpreters}.
1163 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1164 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1165 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1166 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1167 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1168 @sc{gdb/mi} interfaces are no longer supported.
1171 @cindex @code{--write}
1172 Open the executable and core files for both reading and writing. This
1173 is equivalent to the @samp{set write on} command inside @value{GDBN}
1177 @cindex @code{--statistics}
1178 This option causes @value{GDBN} to print statistics about time and
1179 memory usage after it completes each command and returns to the prompt.
1182 @cindex @code{--version}
1183 This option causes @value{GDBN} to print its version number and
1184 no-warranty blurb, and exit.
1189 @subsection What @value{GDBN} does during startup
1190 @cindex @value{GDBN} startup
1192 Here's the description of what @value{GDBN} does during session startup:
1196 Sets up the command interpreter as specified by the command line
1197 (@pxref{Mode Options, interpreter}).
1201 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1202 DOS/Windows systems, the home directory is the one pointed to by the
1203 @code{HOME} environment variable.} and executes all the commands in
1207 Processes command line options and operands.
1210 Reads and executes the commands from init file (if any) in the current
1211 working directory. This is only done if the current directory is
1212 different from your home directory. Thus, you can have more than one
1213 init file, one generic in your home directory, and another, specific
1214 to the program you are debugging, in the directory where you invoke
1218 Reads command files specified by the @samp{-x} option. @xref{Command
1219 Files}, for more details about @value{GDBN} command files.
1222 Reads the command history recorded in the @dfn{history file}.
1223 @xref{Command History}, for more details about the command history and the
1224 files where @value{GDBN} records it.
1227 Init files use the same syntax as @dfn{command files} (@pxref{Command
1228 Files}) and are processed by @value{GDBN} in the same way. The init
1229 file in your home directory can set options (such as @samp{set
1230 complaints}) that affect subsequent processing of command line options
1231 and operands. Init files are not executed if you use the @samp{-nx}
1232 option (@pxref{Mode Options, ,Choosing modes}).
1234 @cindex init file name
1235 @cindex @file{.gdbinit}
1236 The @value{GDBN} init files are normally called @file{.gdbinit}.
1237 On some configurations of @value{GDBN}, the init file is known by a
1238 different name (these are typically environments where a specialized
1239 form of @value{GDBN} may need to coexist with other forms, hence a
1240 different name for the specialized version's init file). These are the
1241 environments with special init file names:
1244 @cindex @file{gdb.ini}
1246 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1247 the limitations of file names imposed by DOS filesystems. The Windows
1248 ports of @value{GDBN} use the standard name, but if they find a
1249 @file{gdb.ini} file, they warn you about that and suggest to rename
1250 the file to the standard name.
1252 @cindex @file{.vxgdbinit}
1254 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1256 @cindex @file{.os68gdbinit}
1258 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1260 @cindex @file{.esgdbinit}
1262 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1265 CISCO 68k: @file{.cisco-gdbinit}
1270 @section Quitting @value{GDBN}
1271 @cindex exiting @value{GDBN}
1272 @cindex leaving @value{GDBN}
1275 @kindex quit @r{[}@var{expression}@r{]}
1276 @kindex q @r{(@code{quit})}
1277 @item quit @r{[}@var{expression}@r{]}
1279 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1280 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1281 do not supply @var{expression}, @value{GDBN} will terminate normally;
1282 otherwise it will terminate using the result of @var{expression} as the
1287 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1288 terminates the action of any @value{GDBN} command that is in progress and
1289 returns to @value{GDBN} command level. It is safe to type the interrupt
1290 character at any time because @value{GDBN} does not allow it to take effect
1291 until a time when it is safe.
1293 If you have been using @value{GDBN} to control an attached process or
1294 device, you can release it with the @code{detach} command
1295 (@pxref{Attach, ,Debugging an already-running process}).
1297 @node Shell Commands
1298 @section Shell commands
1300 If you need to execute occasional shell commands during your
1301 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1302 just use the @code{shell} command.
1306 @cindex shell escape
1307 @item shell @var{command string}
1308 Invoke a standard shell to execute @var{command string}.
1309 If it exists, the environment variable @code{SHELL} determines which
1310 shell to run. Otherwise @value{GDBN} uses the default shell
1311 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1314 The utility @code{make} is often needed in development environments.
1315 You do not have to use the @code{shell} command for this purpose in
1320 @cindex calling make
1321 @item make @var{make-args}
1322 Execute the @code{make} program with the specified
1323 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1326 @node Logging output
1327 @section Logging output
1328 @cindex logging @value{GDBN} output
1329 @cindex save @value{GDBN} output to a file
1331 You may want to save the output of @value{GDBN} commands to a file.
1332 There are several commands to control @value{GDBN}'s logging.
1336 @item set logging on
1338 @item set logging off
1340 @cindex logging file name
1341 @item set logging file @var{file}
1342 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1343 @item set logging overwrite [on|off]
1344 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1345 you want @code{set logging on} to overwrite the logfile instead.
1346 @item set logging redirect [on|off]
1347 By default, @value{GDBN} output will go to both the terminal and the logfile.
1348 Set @code{redirect} if you want output to go only to the log file.
1349 @kindex show logging
1351 Show the current values of the logging settings.
1355 @chapter @value{GDBN} Commands
1357 You can abbreviate a @value{GDBN} command to the first few letters of the command
1358 name, if that abbreviation is unambiguous; and you can repeat certain
1359 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1360 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1361 show you the alternatives available, if there is more than one possibility).
1364 * Command Syntax:: How to give commands to @value{GDBN}
1365 * Completion:: Command completion
1366 * Help:: How to ask @value{GDBN} for help
1369 @node Command Syntax
1370 @section Command syntax
1372 A @value{GDBN} command is a single line of input. There is no limit on
1373 how long it can be. It starts with a command name, which is followed by
1374 arguments whose meaning depends on the command name. For example, the
1375 command @code{step} accepts an argument which is the number of times to
1376 step, as in @samp{step 5}. You can also use the @code{step} command
1377 with no arguments. Some commands do not allow any arguments.
1379 @cindex abbreviation
1380 @value{GDBN} command names may always be truncated if that abbreviation is
1381 unambiguous. Other possible command abbreviations are listed in the
1382 documentation for individual commands. In some cases, even ambiguous
1383 abbreviations are allowed; for example, @code{s} is specially defined as
1384 equivalent to @code{step} even though there are other commands whose
1385 names start with @code{s}. You can test abbreviations by using them as
1386 arguments to the @code{help} command.
1388 @cindex repeating commands
1389 @kindex RET @r{(repeat last command)}
1390 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1391 repeat the previous command. Certain commands (for example, @code{run})
1392 will not repeat this way; these are commands whose unintentional
1393 repetition might cause trouble and which you are unlikely to want to
1394 repeat. User-defined commands can disable this feature; see
1395 @ref{Define, dont-repeat}.
1397 The @code{list} and @code{x} commands, when you repeat them with
1398 @key{RET}, construct new arguments rather than repeating
1399 exactly as typed. This permits easy scanning of source or memory.
1401 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1402 output, in a way similar to the common utility @code{more}
1403 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1404 @key{RET} too many in this situation, @value{GDBN} disables command
1405 repetition after any command that generates this sort of display.
1407 @kindex # @r{(a comment)}
1409 Any text from a @kbd{#} to the end of the line is a comment; it does
1410 nothing. This is useful mainly in command files (@pxref{Command
1411 Files,,Command files}).
1413 @cindex repeating command sequences
1414 @kindex C-o @r{(operate-and-get-next)}
1415 The @kbd{C-o} binding is useful for repeating a complex sequence of
1416 commands. This command accepts the current line, like @key{RET}, and
1417 then fetches the next line relative to the current line from the history
1421 @section Command completion
1424 @cindex word completion
1425 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1426 only one possibility; it can also show you what the valid possibilities
1427 are for the next word in a command, at any time. This works for @value{GDBN}
1428 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1430 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1431 of a word. If there is only one possibility, @value{GDBN} fills in the
1432 word, and waits for you to finish the command (or press @key{RET} to
1433 enter it). For example, if you type
1435 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1436 @c complete accuracy in these examples; space introduced for clarity.
1437 @c If texinfo enhancements make it unnecessary, it would be nice to
1438 @c replace " @key" by "@key" in the following...
1440 (@value{GDBP}) info bre @key{TAB}
1444 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1445 the only @code{info} subcommand beginning with @samp{bre}:
1448 (@value{GDBP}) info breakpoints
1452 You can either press @key{RET} at this point, to run the @code{info
1453 breakpoints} command, or backspace and enter something else, if
1454 @samp{breakpoints} does not look like the command you expected. (If you
1455 were sure you wanted @code{info breakpoints} in the first place, you
1456 might as well just type @key{RET} immediately after @samp{info bre},
1457 to exploit command abbreviations rather than command completion).
1459 If there is more than one possibility for the next word when you press
1460 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1461 characters and try again, or just press @key{TAB} a second time;
1462 @value{GDBN} displays all the possible completions for that word. For
1463 example, you might want to set a breakpoint on a subroutine whose name
1464 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1465 just sounds the bell. Typing @key{TAB} again displays all the
1466 function names in your program that begin with those characters, for
1470 (@value{GDBP}) b make_ @key{TAB}
1471 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1472 make_a_section_from_file make_environ
1473 make_abs_section make_function_type
1474 make_blockvector make_pointer_type
1475 make_cleanup make_reference_type
1476 make_command make_symbol_completion_list
1477 (@value{GDBP}) b make_
1481 After displaying the available possibilities, @value{GDBN} copies your
1482 partial input (@samp{b make_} in the example) so you can finish the
1485 If you just want to see the list of alternatives in the first place, you
1486 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1487 means @kbd{@key{META} ?}. You can type this either by holding down a
1488 key designated as the @key{META} shift on your keyboard (if there is
1489 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1491 @cindex quotes in commands
1492 @cindex completion of quoted strings
1493 Sometimes the string you need, while logically a ``word'', may contain
1494 parentheses or other characters that @value{GDBN} normally excludes from
1495 its notion of a word. To permit word completion to work in this
1496 situation, you may enclose words in @code{'} (single quote marks) in
1497 @value{GDBN} commands.
1499 The most likely situation where you might need this is in typing the
1500 name of a C@t{++} function. This is because C@t{++} allows function
1501 overloading (multiple definitions of the same function, distinguished
1502 by argument type). For example, when you want to set a breakpoint you
1503 may need to distinguish whether you mean the version of @code{name}
1504 that takes an @code{int} parameter, @code{name(int)}, or the version
1505 that takes a @code{float} parameter, @code{name(float)}. To use the
1506 word-completion facilities in this situation, type a single quote
1507 @code{'} at the beginning of the function name. This alerts
1508 @value{GDBN} that it may need to consider more information than usual
1509 when you press @key{TAB} or @kbd{M-?} to request word completion:
1512 (@value{GDBP}) b 'bubble( @kbd{M-?}
1513 bubble(double,double) bubble(int,int)
1514 (@value{GDBP}) b 'bubble(
1517 In some cases, @value{GDBN} can tell that completing a name requires using
1518 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1519 completing as much as it can) if you do not type the quote in the first
1523 (@value{GDBP}) b bub @key{TAB}
1524 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1525 (@value{GDBP}) b 'bubble(
1529 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1530 you have not yet started typing the argument list when you ask for
1531 completion on an overloaded symbol.
1533 For more information about overloaded functions, see @ref{C plus plus
1534 expressions, ,C@t{++} expressions}. You can use the command @code{set
1535 overload-resolution off} to disable overload resolution;
1536 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1540 @section Getting help
1541 @cindex online documentation
1544 You can always ask @value{GDBN} itself for information on its commands,
1545 using the command @code{help}.
1548 @kindex h @r{(@code{help})}
1551 You can use @code{help} (abbreviated @code{h}) with no arguments to
1552 display a short list of named classes of commands:
1556 List of classes of commands:
1558 aliases -- Aliases of other commands
1559 breakpoints -- Making program stop at certain points
1560 data -- Examining data
1561 files -- Specifying and examining files
1562 internals -- Maintenance commands
1563 obscure -- Obscure features
1564 running -- Running the program
1565 stack -- Examining the stack
1566 status -- Status inquiries
1567 support -- Support facilities
1568 tracepoints -- Tracing of program execution without@*
1569 stopping the program
1570 user-defined -- User-defined commands
1572 Type "help" followed by a class name for a list of
1573 commands in that class.
1574 Type "help" followed by command name for full
1576 Command name abbreviations are allowed if unambiguous.
1579 @c the above line break eliminates huge line overfull...
1581 @item help @var{class}
1582 Using one of the general help classes as an argument, you can get a
1583 list of the individual commands in that class. For example, here is the
1584 help display for the class @code{status}:
1587 (@value{GDBP}) help status
1592 @c Line break in "show" line falsifies real output, but needed
1593 @c to fit in smallbook page size.
1594 info -- Generic command for showing things
1595 about the program being debugged
1596 show -- Generic command for showing things
1599 Type "help" followed by command name for full
1601 Command name abbreviations are allowed if unambiguous.
1605 @item help @var{command}
1606 With a command name as @code{help} argument, @value{GDBN} displays a
1607 short paragraph on how to use that command.
1610 @item apropos @var{args}
1611 The @code{apropos} command searches through all of the @value{GDBN}
1612 commands, and their documentation, for the regular expression specified in
1613 @var{args}. It prints out all matches found. For example:
1624 set symbol-reloading -- Set dynamic symbol table reloading
1625 multiple times in one run
1626 show symbol-reloading -- Show dynamic symbol table reloading
1627 multiple times in one run
1632 @item complete @var{args}
1633 The @code{complete @var{args}} command lists all the possible completions
1634 for the beginning of a command. Use @var{args} to specify the beginning of the
1635 command you want completed. For example:
1641 @noindent results in:
1652 @noindent This is intended for use by @sc{gnu} Emacs.
1655 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1656 and @code{show} to inquire about the state of your program, or the state
1657 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1658 manual introduces each of them in the appropriate context. The listings
1659 under @code{info} and under @code{show} in the Index point to
1660 all the sub-commands. @xref{Index}.
1665 @kindex i @r{(@code{info})}
1667 This command (abbreviated @code{i}) is for describing the state of your
1668 program. For example, you can list the arguments given to your program
1669 with @code{info args}, list the registers currently in use with @code{info
1670 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1671 You can get a complete list of the @code{info} sub-commands with
1672 @w{@code{help info}}.
1676 You can assign the result of an expression to an environment variable with
1677 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1678 @code{set prompt $}.
1682 In contrast to @code{info}, @code{show} is for describing the state of
1683 @value{GDBN} itself.
1684 You can change most of the things you can @code{show}, by using the
1685 related command @code{set}; for example, you can control what number
1686 system is used for displays with @code{set radix}, or simply inquire
1687 which is currently in use with @code{show radix}.
1690 To display all the settable parameters and their current
1691 values, you can use @code{show} with no arguments; you may also use
1692 @code{info set}. Both commands produce the same display.
1693 @c FIXME: "info set" violates the rule that "info" is for state of
1694 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1695 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1699 Here are three miscellaneous @code{show} subcommands, all of which are
1700 exceptional in lacking corresponding @code{set} commands:
1703 @kindex show version
1704 @cindex @value{GDBN} version number
1706 Show what version of @value{GDBN} is running. You should include this
1707 information in @value{GDBN} bug-reports. If multiple versions of
1708 @value{GDBN} are in use at your site, you may need to determine which
1709 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1710 commands are introduced, and old ones may wither away. Also, many
1711 system vendors ship variant versions of @value{GDBN}, and there are
1712 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1713 The version number is the same as the one announced when you start
1716 @kindex show copying
1717 @kindex info copying
1718 @cindex display @value{GDBN} copyright
1721 Display information about permission for copying @value{GDBN}.
1723 @kindex show warranty
1724 @kindex info warranty
1726 @itemx info warranty
1727 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1728 if your version of @value{GDBN} comes with one.
1733 @chapter Running Programs Under @value{GDBN}
1735 When you run a program under @value{GDBN}, you must first generate
1736 debugging information when you compile it.
1738 You may start @value{GDBN} with its arguments, if any, in an environment
1739 of your choice. If you are doing native debugging, you may redirect
1740 your program's input and output, debug an already running process, or
1741 kill a child process.
1744 * Compilation:: Compiling for debugging
1745 * Starting:: Starting your program
1746 * Arguments:: Your program's arguments
1747 * Environment:: Your program's environment
1749 * Working Directory:: Your program's working directory
1750 * Input/Output:: Your program's input and output
1751 * Attach:: Debugging an already-running process
1752 * Kill Process:: Killing the child process
1754 * Threads:: Debugging programs with multiple threads
1755 * Processes:: Debugging programs with multiple processes
1756 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1760 @section Compiling for debugging
1762 In order to debug a program effectively, you need to generate
1763 debugging information when you compile it. This debugging information
1764 is stored in the object file; it describes the data type of each
1765 variable or function and the correspondence between source line numbers
1766 and addresses in the executable code.
1768 To request debugging information, specify the @samp{-g} option when you run
1771 Programs that are to be shipped to your customers are compiled with
1772 optimizations, using the @samp{-O} compiler option. However, many
1773 compilers are unable to handle the @samp{-g} and @samp{-O} options
1774 together. Using those compilers, you cannot generate optimized
1775 executables containing debugging information.
1777 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1778 without @samp{-O}, making it possible to debug optimized code. We
1779 recommend that you @emph{always} use @samp{-g} whenever you compile a
1780 program. You may think your program is correct, but there is no sense
1781 in pushing your luck.
1783 @cindex optimized code, debugging
1784 @cindex debugging optimized code
1785 When you debug a program compiled with @samp{-g -O}, remember that the
1786 optimizer is rearranging your code; the debugger shows you what is
1787 really there. Do not be too surprised when the execution path does not
1788 exactly match your source file! An extreme example: if you define a
1789 variable, but never use it, @value{GDBN} never sees that
1790 variable---because the compiler optimizes it out of existence.
1792 Some things do not work as well with @samp{-g -O} as with just
1793 @samp{-g}, particularly on machines with instruction scheduling. If in
1794 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1795 please report it to us as a bug (including a test case!).
1796 @xref{Variables}, for more information about debugging optimized code.
1798 Older versions of the @sc{gnu} C compiler permitted a variant option
1799 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1800 format; if your @sc{gnu} C compiler has this option, do not use it.
1802 @value{GDBN} knows about preprocessor macros and can show you their
1803 expansion (@pxref{Macros}). Most compilers do not include information
1804 about preprocessor macros in the debugging information if you specify
1805 the @option{-g} flag alone, because this information is rather large.
1806 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1807 provides macro information if you specify the options
1808 @option{-gdwarf-2} and @option{-g3}; the former option requests
1809 debugging information in the Dwarf 2 format, and the latter requests
1810 ``extra information''. In the future, we hope to find more compact
1811 ways to represent macro information, so that it can be included with
1816 @section Starting your program
1822 @kindex r @r{(@code{run})}
1825 Use the @code{run} command to start your program under @value{GDBN}.
1826 You must first specify the program name (except on VxWorks) with an
1827 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1828 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1829 (@pxref{Files, ,Commands to specify files}).
1833 If you are running your program in an execution environment that
1834 supports processes, @code{run} creates an inferior process and makes
1835 that process run your program. (In environments without processes,
1836 @code{run} jumps to the start of your program.)
1838 The execution of a program is affected by certain information it
1839 receives from its superior. @value{GDBN} provides ways to specify this
1840 information, which you must do @emph{before} starting your program. (You
1841 can change it after starting your program, but such changes only affect
1842 your program the next time you start it.) This information may be
1843 divided into four categories:
1846 @item The @emph{arguments.}
1847 Specify the arguments to give your program as the arguments of the
1848 @code{run} command. If a shell is available on your target, the shell
1849 is used to pass the arguments, so that you may use normal conventions
1850 (such as wildcard expansion or variable substitution) in describing
1852 In Unix systems, you can control which shell is used with the
1853 @code{SHELL} environment variable.
1854 @xref{Arguments, ,Your program's arguments}.
1856 @item The @emph{environment.}
1857 Your program normally inherits its environment from @value{GDBN}, but you can
1858 use the @value{GDBN} commands @code{set environment} and @code{unset
1859 environment} to change parts of the environment that affect
1860 your program. @xref{Environment, ,Your program's environment}.
1862 @item The @emph{working directory.}
1863 Your program inherits its working directory from @value{GDBN}. You can set
1864 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1865 @xref{Working Directory, ,Your program's working directory}.
1867 @item The @emph{standard input and output.}
1868 Your program normally uses the same device for standard input and
1869 standard output as @value{GDBN} is using. You can redirect input and output
1870 in the @code{run} command line, or you can use the @code{tty} command to
1871 set a different device for your program.
1872 @xref{Input/Output, ,Your program's input and output}.
1875 @emph{Warning:} While input and output redirection work, you cannot use
1876 pipes to pass the output of the program you are debugging to another
1877 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1881 When you issue the @code{run} command, your program begins to execute
1882 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1883 of how to arrange for your program to stop. Once your program has
1884 stopped, you may call functions in your program, using the @code{print}
1885 or @code{call} commands. @xref{Data, ,Examining Data}.
1887 If the modification time of your symbol file has changed since the last
1888 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1889 table, and reads it again. When it does this, @value{GDBN} tries to retain
1890 your current breakpoints.
1895 @cindex run to main procedure
1896 The name of the main procedure can vary from language to language.
1897 With C or C@t{++}, the main procedure name is always @code{main}, but
1898 other languages such as Ada do not require a specific name for their
1899 main procedure. The debugger provides a convenient way to start the
1900 execution of the program and to stop at the beginning of the main
1901 procedure, depending on the language used.
1903 The @samp{start} command does the equivalent of setting a temporary
1904 breakpoint at the beginning of the main procedure and then invoking
1905 the @samp{run} command.
1907 @cindex elaboration phase
1908 Some programs contain an @dfn{elaboration} phase where some startup code is
1909 executed before the main procedure is called. This depends on the
1910 languages used to write your program. In C@t{++}, for instance,
1911 constructors for static and global objects are executed before
1912 @code{main} is called. It is therefore possible that the debugger stops
1913 before reaching the main procedure. However, the temporary breakpoint
1914 will remain to halt execution.
1916 Specify the arguments to give to your program as arguments to the
1917 @samp{start} command. These arguments will be given verbatim to the
1918 underlying @samp{run} command. Note that the same arguments will be
1919 reused if no argument is provided during subsequent calls to
1920 @samp{start} or @samp{run}.
1922 It is sometimes necessary to debug the program during elaboration. In
1923 these cases, using the @code{start} command would stop the execution of
1924 your program too late, as the program would have already completed the
1925 elaboration phase. Under these circumstances, insert breakpoints in your
1926 elaboration code before running your program.
1930 @section Your program's arguments
1932 @cindex arguments (to your program)
1933 The arguments to your program can be specified by the arguments of the
1935 They are passed to a shell, which expands wildcard characters and
1936 performs redirection of I/O, and thence to your program. Your
1937 @code{SHELL} environment variable (if it exists) specifies what shell
1938 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1939 the default shell (@file{/bin/sh} on Unix).
1941 On non-Unix systems, the program is usually invoked directly by
1942 @value{GDBN}, which emulates I/O redirection via the appropriate system
1943 calls, and the wildcard characters are expanded by the startup code of
1944 the program, not by the shell.
1946 @code{run} with no arguments uses the same arguments used by the previous
1947 @code{run}, or those set by the @code{set args} command.
1952 Specify the arguments to be used the next time your program is run. If
1953 @code{set args} has no arguments, @code{run} executes your program
1954 with no arguments. Once you have run your program with arguments,
1955 using @code{set args} before the next @code{run} is the only way to run
1956 it again without arguments.
1960 Show the arguments to give your program when it is started.
1964 @section Your program's environment
1966 @cindex environment (of your program)
1967 The @dfn{environment} consists of a set of environment variables and
1968 their values. Environment variables conventionally record such things as
1969 your user name, your home directory, your terminal type, and your search
1970 path for programs to run. Usually you set up environment variables with
1971 the shell and they are inherited by all the other programs you run. When
1972 debugging, it can be useful to try running your program with a modified
1973 environment without having to start @value{GDBN} over again.
1977 @item path @var{directory}
1978 Add @var{directory} to the front of the @code{PATH} environment variable
1979 (the search path for executables) that will be passed to your program.
1980 The value of @code{PATH} used by @value{GDBN} does not change.
1981 You may specify several directory names, separated by whitespace or by a
1982 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1983 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1984 is moved to the front, so it is searched sooner.
1986 You can use the string @samp{$cwd} to refer to whatever is the current
1987 working directory at the time @value{GDBN} searches the path. If you
1988 use @samp{.} instead, it refers to the directory where you executed the
1989 @code{path} command. @value{GDBN} replaces @samp{.} in the
1990 @var{directory} argument (with the current path) before adding
1991 @var{directory} to the search path.
1992 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1993 @c document that, since repeating it would be a no-op.
1997 Display the list of search paths for executables (the @code{PATH}
1998 environment variable).
2000 @kindex show environment
2001 @item show environment @r{[}@var{varname}@r{]}
2002 Print the value of environment variable @var{varname} to be given to
2003 your program when it starts. If you do not supply @var{varname},
2004 print the names and values of all environment variables to be given to
2005 your program. You can abbreviate @code{environment} as @code{env}.
2007 @kindex set environment
2008 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2009 Set environment variable @var{varname} to @var{value}. The value
2010 changes for your program only, not for @value{GDBN} itself. @var{value} may
2011 be any string; the values of environment variables are just strings, and
2012 any interpretation is supplied by your program itself. The @var{value}
2013 parameter is optional; if it is eliminated, the variable is set to a
2015 @c "any string" here does not include leading, trailing
2016 @c blanks. Gnu asks: does anyone care?
2018 For example, this command:
2025 tells the debugged program, when subsequently run, that its user is named
2026 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2027 are not actually required.)
2029 @kindex unset environment
2030 @item unset environment @var{varname}
2031 Remove variable @var{varname} from the environment to be passed to your
2032 program. This is different from @samp{set env @var{varname} =};
2033 @code{unset environment} removes the variable from the environment,
2034 rather than assigning it an empty value.
2037 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2039 by your @code{SHELL} environment variable if it exists (or
2040 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2041 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2042 @file{.bashrc} for BASH---any variables you set in that file affect
2043 your program. You may wish to move setting of environment variables to
2044 files that are only run when you sign on, such as @file{.login} or
2047 @node Working Directory
2048 @section Your program's working directory
2050 @cindex working directory (of your program)
2051 Each time you start your program with @code{run}, it inherits its
2052 working directory from the current working directory of @value{GDBN}.
2053 The @value{GDBN} working directory is initially whatever it inherited
2054 from its parent process (typically the shell), but you can specify a new
2055 working directory in @value{GDBN} with the @code{cd} command.
2057 The @value{GDBN} working directory also serves as a default for the commands
2058 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2063 @cindex change working directory
2064 @item cd @var{directory}
2065 Set the @value{GDBN} working directory to @var{directory}.
2069 Print the @value{GDBN} working directory.
2072 It is generally impossible to find the current working directory of
2073 the process being debugged (since a program can change its directory
2074 during its run). If you work on a system where @value{GDBN} is
2075 configured with the @file{/proc} support, you can use the @code{info
2076 proc} command (@pxref{SVR4 Process Information}) to find out the
2077 current working directory of the debuggee.
2080 @section Your program's input and output
2085 By default, the program you run under @value{GDBN} does input and output to
2086 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2087 to its own terminal modes to interact with you, but it records the terminal
2088 modes your program was using and switches back to them when you continue
2089 running your program.
2092 @kindex info terminal
2094 Displays information recorded by @value{GDBN} about the terminal modes your
2098 You can redirect your program's input and/or output using shell
2099 redirection with the @code{run} command. For example,
2106 starts your program, diverting its output to the file @file{outfile}.
2109 @cindex controlling terminal
2110 Another way to specify where your program should do input and output is
2111 with the @code{tty} command. This command accepts a file name as
2112 argument, and causes this file to be the default for future @code{run}
2113 commands. It also resets the controlling terminal for the child
2114 process, for future @code{run} commands. For example,
2121 directs that processes started with subsequent @code{run} commands
2122 default to do input and output on the terminal @file{/dev/ttyb} and have
2123 that as their controlling terminal.
2125 An explicit redirection in @code{run} overrides the @code{tty} command's
2126 effect on the input/output device, but not its effect on the controlling
2129 When you use the @code{tty} command or redirect input in the @code{run}
2130 command, only the input @emph{for your program} is affected. The input
2131 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2132 for @code{set inferior-tty}.
2134 @cindex inferior tty
2135 @cindex set inferior controlling terminal
2136 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2137 display the name of the terminal that will be used for future runs of your
2141 @item set inferior-tty /dev/ttyb
2142 @kindex set inferior-tty
2143 Set the tty for the program being debugged to /dev/ttyb.
2145 @item show inferior-tty
2146 @kindex show inferior-tty
2147 Show the current tty for the program being debugged.
2151 @section Debugging an already-running process
2156 @item attach @var{process-id}
2157 This command attaches to a running process---one that was started
2158 outside @value{GDBN}. (@code{info files} shows your active
2159 targets.) The command takes as argument a process ID. The usual way to
2160 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2161 or with the @samp{jobs -l} shell command.
2163 @code{attach} does not repeat if you press @key{RET} a second time after
2164 executing the command.
2167 To use @code{attach}, your program must be running in an environment
2168 which supports processes; for example, @code{attach} does not work for
2169 programs on bare-board targets that lack an operating system. You must
2170 also have permission to send the process a signal.
2172 When you use @code{attach}, the debugger finds the program running in
2173 the process first by looking in the current working directory, then (if
2174 the program is not found) by using the source file search path
2175 (@pxref{Source Path, ,Specifying source directories}). You can also use
2176 the @code{file} command to load the program. @xref{Files, ,Commands to
2179 The first thing @value{GDBN} does after arranging to debug the specified
2180 process is to stop it. You can examine and modify an attached process
2181 with all the @value{GDBN} commands that are ordinarily available when
2182 you start processes with @code{run}. You can insert breakpoints; you
2183 can step and continue; you can modify storage. If you would rather the
2184 process continue running, you may use the @code{continue} command after
2185 attaching @value{GDBN} to the process.
2190 When you have finished debugging the attached process, you can use the
2191 @code{detach} command to release it from @value{GDBN} control. Detaching
2192 the process continues its execution. After the @code{detach} command,
2193 that process and @value{GDBN} become completely independent once more, and you
2194 are ready to @code{attach} another process or start one with @code{run}.
2195 @code{detach} does not repeat if you press @key{RET} again after
2196 executing the command.
2199 If you exit @value{GDBN} or use the @code{run} command while you have an
2200 attached process, you kill that process. By default, @value{GDBN} asks
2201 for confirmation if you try to do either of these things; you can
2202 control whether or not you need to confirm by using the @code{set
2203 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2207 @section Killing the child process
2212 Kill the child process in which your program is running under @value{GDBN}.
2215 This command is useful if you wish to debug a core dump instead of a
2216 running process. @value{GDBN} ignores any core dump file while your program
2219 On some operating systems, a program cannot be executed outside @value{GDBN}
2220 while you have breakpoints set on it inside @value{GDBN}. You can use the
2221 @code{kill} command in this situation to permit running your program
2222 outside the debugger.
2224 The @code{kill} command is also useful if you wish to recompile and
2225 relink your program, since on many systems it is impossible to modify an
2226 executable file while it is running in a process. In this case, when you
2227 next type @code{run}, @value{GDBN} notices that the file has changed, and
2228 reads the symbol table again (while trying to preserve your current
2229 breakpoint settings).
2232 @section Debugging programs with multiple threads
2234 @cindex threads of execution
2235 @cindex multiple threads
2236 @cindex switching threads
2237 In some operating systems, such as HP-UX and Solaris, a single program
2238 may have more than one @dfn{thread} of execution. The precise semantics
2239 of threads differ from one operating system to another, but in general
2240 the threads of a single program are akin to multiple processes---except
2241 that they share one address space (that is, they can all examine and
2242 modify the same variables). On the other hand, each thread has its own
2243 registers and execution stack, and perhaps private memory.
2245 @value{GDBN} provides these facilities for debugging multi-thread
2249 @item automatic notification of new threads
2250 @item @samp{thread @var{threadno}}, a command to switch among threads
2251 @item @samp{info threads}, a command to inquire about existing threads
2252 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2253 a command to apply a command to a list of threads
2254 @item thread-specific breakpoints
2258 @emph{Warning:} These facilities are not yet available on every
2259 @value{GDBN} configuration where the operating system supports threads.
2260 If your @value{GDBN} does not support threads, these commands have no
2261 effect. For example, a system without thread support shows no output
2262 from @samp{info threads}, and always rejects the @code{thread} command,
2266 (@value{GDBP}) info threads
2267 (@value{GDBP}) thread 1
2268 Thread ID 1 not known. Use the "info threads" command to
2269 see the IDs of currently known threads.
2271 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2272 @c doesn't support threads"?
2275 @cindex focus of debugging
2276 @cindex current thread
2277 The @value{GDBN} thread debugging facility allows you to observe all
2278 threads while your program runs---but whenever @value{GDBN} takes
2279 control, one thread in particular is always the focus of debugging.
2280 This thread is called the @dfn{current thread}. Debugging commands show
2281 program information from the perspective of the current thread.
2283 @cindex @code{New} @var{systag} message
2284 @cindex thread identifier (system)
2285 @c FIXME-implementors!! It would be more helpful if the [New...] message
2286 @c included GDB's numeric thread handle, so you could just go to that
2287 @c thread without first checking `info threads'.
2288 Whenever @value{GDBN} detects a new thread in your program, it displays
2289 the target system's identification for the thread with a message in the
2290 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2291 whose form varies depending on the particular system. For example, on
2292 LynxOS, you might see
2295 [New process 35 thread 27]
2299 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2300 the @var{systag} is simply something like @samp{process 368}, with no
2303 @c FIXME!! (1) Does the [New...] message appear even for the very first
2304 @c thread of a program, or does it only appear for the
2305 @c second---i.e.@: when it becomes obvious we have a multithread
2307 @c (2) *Is* there necessarily a first thread always? Or do some
2308 @c multithread systems permit starting a program with multiple
2309 @c threads ab initio?
2311 @cindex thread number
2312 @cindex thread identifier (GDB)
2313 For debugging purposes, @value{GDBN} associates its own thread
2314 number---always a single integer---with each thread in your program.
2317 @kindex info threads
2319 Display a summary of all threads currently in your
2320 program. @value{GDBN} displays for each thread (in this order):
2324 the thread number assigned by @value{GDBN}
2327 the target system's thread identifier (@var{systag})
2330 the current stack frame summary for that thread
2334 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2335 indicates the current thread.
2339 @c end table here to get a little more width for example
2342 (@value{GDBP}) info threads
2343 3 process 35 thread 27 0x34e5 in sigpause ()
2344 2 process 35 thread 23 0x34e5 in sigpause ()
2345 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2351 @cindex debugging multithreaded programs (on HP-UX)
2352 @cindex thread identifier (GDB), on HP-UX
2353 For debugging purposes, @value{GDBN} associates its own thread
2354 number---a small integer assigned in thread-creation order---with each
2355 thread in your program.
2357 @cindex @code{New} @var{systag} message, on HP-UX
2358 @cindex thread identifier (system), on HP-UX
2359 @c FIXME-implementors!! It would be more helpful if the [New...] message
2360 @c included GDB's numeric thread handle, so you could just go to that
2361 @c thread without first checking `info threads'.
2362 Whenever @value{GDBN} detects a new thread in your program, it displays
2363 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2364 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2365 whose form varies depending on the particular system. For example, on
2369 [New thread 2 (system thread 26594)]
2373 when @value{GDBN} notices a new thread.
2376 @kindex info threads (HP-UX)
2378 Display a summary of all threads currently in your
2379 program. @value{GDBN} displays for each thread (in this order):
2382 @item the thread number assigned by @value{GDBN}
2384 @item the target system's thread identifier (@var{systag})
2386 @item the current stack frame summary for that thread
2390 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2391 indicates the current thread.
2395 @c end table here to get a little more width for example
2398 (@value{GDBP}) info threads
2399 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2401 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2402 from /usr/lib/libc.2
2403 1 system thread 27905 0x7b003498 in _brk () \@*
2404 from /usr/lib/libc.2
2407 On Solaris, you can display more information about user threads with a
2408 Solaris-specific command:
2411 @item maint info sol-threads
2412 @kindex maint info sol-threads
2413 @cindex thread info (Solaris)
2414 Display info on Solaris user threads.
2418 @kindex thread @var{threadno}
2419 @item thread @var{threadno}
2420 Make thread number @var{threadno} the current thread. The command
2421 argument @var{threadno} is the internal @value{GDBN} thread number, as
2422 shown in the first field of the @samp{info threads} display.
2423 @value{GDBN} responds by displaying the system identifier of the thread
2424 you selected, and its current stack frame summary:
2427 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2428 (@value{GDBP}) thread 2
2429 [Switching to process 35 thread 23]
2430 0x34e5 in sigpause ()
2434 As with the @samp{[New @dots{}]} message, the form of the text after
2435 @samp{Switching to} depends on your system's conventions for identifying
2438 @kindex thread apply
2439 @cindex apply command to several threads
2440 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2441 The @code{thread apply} command allows you to apply the named
2442 @var{command} to one or more threads. Specify the numbers of the
2443 threads that you want affected with the command argument
2444 @var{threadno}. It can be a single thread number, one of the numbers
2445 shown in the first field of the @samp{info threads} display; or it
2446 could be a range of thread numbers, as in @code{2-4}. To apply a
2447 command to all threads, type @kbd{thread apply all @var{command}}.
2450 @cindex automatic thread selection
2451 @cindex switching threads automatically
2452 @cindex threads, automatic switching
2453 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2454 signal, it automatically selects the thread where that breakpoint or
2455 signal happened. @value{GDBN} alerts you to the context switch with a
2456 message of the form @samp{[Switching to @var{systag}]} to identify the
2459 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2460 more information about how @value{GDBN} behaves when you stop and start
2461 programs with multiple threads.
2463 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2464 watchpoints in programs with multiple threads.
2467 @section Debugging programs with multiple processes
2469 @cindex fork, debugging programs which call
2470 @cindex multiple processes
2471 @cindex processes, multiple
2472 On most systems, @value{GDBN} has no special support for debugging
2473 programs which create additional processes using the @code{fork}
2474 function. When a program forks, @value{GDBN} will continue to debug the
2475 parent process and the child process will run unimpeded. If you have
2476 set a breakpoint in any code which the child then executes, the child
2477 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2478 will cause it to terminate.
2480 However, if you want to debug the child process there is a workaround
2481 which isn't too painful. Put a call to @code{sleep} in the code which
2482 the child process executes after the fork. It may be useful to sleep
2483 only if a certain environment variable is set, or a certain file exists,
2484 so that the delay need not occur when you don't want to run @value{GDBN}
2485 on the child. While the child is sleeping, use the @code{ps} program to
2486 get its process ID. Then tell @value{GDBN} (a new invocation of
2487 @value{GDBN} if you are also debugging the parent process) to attach to
2488 the child process (@pxref{Attach}). From that point on you can debug
2489 the child process just like any other process which you attached to.
2491 On some systems, @value{GDBN} provides support for debugging programs that
2492 create additional processes using the @code{fork} or @code{vfork} functions.
2493 Currently, the only platforms with this feature are HP-UX (11.x and later
2494 only?) and GNU/Linux (kernel version 2.5.60 and later).
2496 By default, when a program forks, @value{GDBN} will continue to debug
2497 the parent process and the child process will run unimpeded.
2499 If you want to follow the child process instead of the parent process,
2500 use the command @w{@code{set follow-fork-mode}}.
2503 @kindex set follow-fork-mode
2504 @item set follow-fork-mode @var{mode}
2505 Set the debugger response to a program call of @code{fork} or
2506 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2507 process. The @var{mode} argument can be:
2511 The original process is debugged after a fork. The child process runs
2512 unimpeded. This is the default.
2515 The new process is debugged after a fork. The parent process runs
2520 @kindex show follow-fork-mode
2521 @item show follow-fork-mode
2522 Display the current debugger response to a @code{fork} or @code{vfork} call.
2525 @cindex debugging multiple processes
2526 On Linux, if you want to debug both the parent and child processes, use the
2527 command @w{@code{set detach-on-fork}}.
2530 @kindex set detach-on-fork
2531 @item set detach-on-fork @var{mode}
2532 Tells gdb whether to detach one of the processes after a fork, or
2533 retain debugger control over them both.
2537 The child process (or parent process, depending on the value of
2538 @code{follow-fork-mode}) will be detached and allowed to run
2539 independently. This is the default.
2542 Both processes will be held under the control of @value{GDBN}.
2543 One process (child or parent, depending on the value of
2544 @code{follow-fork-mode}) is debugged as usual, while the other
2549 @kindex show detach-on-follow
2550 @item show detach-on-follow
2551 Show whether detach-on-follow mode is on/off.
2554 If you choose to set @var{detach-on-follow} mode off, then
2555 @value{GDBN} will retain control of all forked processes (including
2556 nested forks). You can list the forked processes under the control of
2557 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2558 from one fork to another by using the @w{@code{fork}} command.
2563 Print a list of all forked processes under the control of @value{GDBN}.
2564 The listing will include a fork id, a process id, and the current
2565 position (program counter) of the process.
2568 @kindex fork @var{fork-id}
2569 @item fork @var{fork-id}
2570 Make fork number @var{fork-id} the current process. The argument
2571 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2572 as shown in the first field of the @samp{info forks} display.
2576 To quit debugging one of the forked processes, you can either detach
2577 from it by using the @w{@code{detach-fork}} command (allowing it to
2578 run independently), or delete (and kill) it using the
2579 @w{@code{delete fork}} command.
2582 @kindex detach-fork @var{fork-id}
2583 @item detach-fork @var{fork-id}
2584 Detach from the process identified by @value{GDBN} fork number
2585 @var{fork-id}, and remove it from the fork list. The process will be
2586 allowed to run independently.
2588 @kindex delete fork @var{fork-id}
2589 @item delete fork @var{fork-id}
2590 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2591 and remove it from the fork list.
2595 If you ask to debug a child process and a @code{vfork} is followed by an
2596 @code{exec}, @value{GDBN} executes the new target up to the first
2597 breakpoint in the new target. If you have a breakpoint set on
2598 @code{main} in your original program, the breakpoint will also be set on
2599 the child process's @code{main}.
2601 When a child process is spawned by @code{vfork}, you cannot debug the
2602 child or parent until an @code{exec} call completes.
2604 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2605 call executes, the new target restarts. To restart the parent process,
2606 use the @code{file} command with the parent executable name as its
2609 You can use the @code{catch} command to make @value{GDBN} stop whenever
2610 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2611 Catchpoints, ,Setting catchpoints}.
2613 @node Checkpoint/Restart
2614 @section Setting a @emph{bookmark} to return to later
2619 @cindex snapshot of a process
2620 @cindex rewind program state
2622 On certain operating systems@footnote{Currently, only
2623 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2624 program's state, called a @dfn{checkpoint}, and come back to it
2627 Returning to a checkpoint effectively undoes everything that has
2628 happened in the program since the @code{checkpoint} was saved. This
2629 includes changes in memory, registers, and even (within some limits)
2630 system state. Effectively, it is like going back in time to the
2631 moment when the checkpoint was saved.
2633 Thus, if you're stepping thru a program and you think you're
2634 getting close to the point where things go wrong, you can save
2635 a checkpoint. Then, if you accidentally go too far and miss
2636 the critical statement, instead of having to restart your program
2637 from the beginning, you can just go back to the checkpoint and
2638 start again from there.
2640 This can be especially useful if it takes a lot of time or
2641 steps to reach the point where you think the bug occurs.
2643 To use the @code{checkpoint}/@code{restart} method of debugging:
2648 Save a snapshot of the debugged program's current execution state.
2649 The @code{checkpoint} command takes no arguments, but each checkpoint
2650 is assigned a small integer id, similar to a breakpoint id.
2652 @kindex info checkpoints
2653 @item info checkpoints
2654 List the checkpoints that have been saved in the current debugging
2655 session. For each checkpoint, the following information will be
2662 @item Source line, or label
2665 @kindex restart @var{checkpoint-id}
2666 @item restart @var{checkpoint-id}
2667 Restore the program state that was saved as checkpoint number
2668 @var{checkpoint-id}. All program variables, registers, stack frames
2669 etc.@: will be returned to the values that they had when the checkpoint
2670 was saved. In essence, gdb will ``wind back the clock'' to the point
2671 in time when the checkpoint was saved.
2673 Note that breakpoints, @value{GDBN} variables, command history etc.
2674 are not affected by restoring a checkpoint. In general, a checkpoint
2675 only restores things that reside in the program being debugged, not in
2678 @kindex delete checkpoint @var{checkpoint-id}
2679 @item delete checkpoint @var{checkpoint-id}
2680 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2684 Returning to a previously saved checkpoint will restore the user state
2685 of the program being debugged, plus a significant subset of the system
2686 (OS) state, including file pointers. It won't ``un-write'' data from
2687 a file, but it will rewind the file pointer to the previous location,
2688 so that the previously written data can be overwritten. For files
2689 opened in read mode, the pointer will also be restored so that the
2690 previously read data can be read again.
2692 Of course, characters that have been sent to a printer (or other
2693 external device) cannot be ``snatched back'', and characters received
2694 from eg.@: a serial device can be removed from internal program buffers,
2695 but they cannot be ``pushed back'' into the serial pipeline, ready to
2696 be received again. Similarly, the actual contents of files that have
2697 been changed cannot be restored (at this time).
2699 However, within those constraints, you actually can ``rewind'' your
2700 program to a previously saved point in time, and begin debugging it
2701 again --- and you can change the course of events so as to debug a
2702 different execution path this time.
2704 @cindex checkpoints and process id
2705 Finally, there is one bit of internal program state that will be
2706 different when you return to a checkpoint --- the program's process
2707 id. Each checkpoint will have a unique process id (or @var{pid}),
2708 and each will be different from the program's original @var{pid}.
2709 If your program has saved a local copy of its process id, this could
2710 potentially pose a problem.
2712 @subsection A non-obvious benefit of using checkpoints
2714 On some systems such as @sc{gnu}/Linux, address space randomization
2715 is performed on new processes for security reasons. This makes it
2716 difficult or impossible to set a breakpoint, or watchpoint, on an
2717 absolute address if you have to restart the program, since the
2718 absolute location of a symbol will change from one execution to the
2721 A checkpoint, however, is an @emph{identical} copy of a process.
2722 Therefore if you create a checkpoint at (eg.@:) the start of main,
2723 and simply return to that checkpoint instead of restarting the
2724 process, you can avoid the effects of address randomization and
2725 your symbols will all stay in the same place.
2728 @chapter Stopping and Continuing
2730 The principal purposes of using a debugger are so that you can stop your
2731 program before it terminates; or so that, if your program runs into
2732 trouble, you can investigate and find out why.
2734 Inside @value{GDBN}, your program may stop for any of several reasons,
2735 such as a signal, a breakpoint, or reaching a new line after a
2736 @value{GDBN} command such as @code{step}. You may then examine and
2737 change variables, set new breakpoints or remove old ones, and then
2738 continue execution. Usually, the messages shown by @value{GDBN} provide
2739 ample explanation of the status of your program---but you can also
2740 explicitly request this information at any time.
2743 @kindex info program
2745 Display information about the status of your program: whether it is
2746 running or not, what process it is, and why it stopped.
2750 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2751 * Continuing and Stepping:: Resuming execution
2753 * Thread Stops:: Stopping and starting multi-thread programs
2757 @section Breakpoints, watchpoints, and catchpoints
2760 A @dfn{breakpoint} makes your program stop whenever a certain point in
2761 the program is reached. For each breakpoint, you can add conditions to
2762 control in finer detail whether your program stops. You can set
2763 breakpoints with the @code{break} command and its variants (@pxref{Set
2764 Breaks, ,Setting breakpoints}), to specify the place where your program
2765 should stop by line number, function name or exact address in the
2768 On some systems, you can set breakpoints in shared libraries before
2769 the executable is run. There is a minor limitation on HP-UX systems:
2770 you must wait until the executable is run in order to set breakpoints
2771 in shared library routines that are not called directly by the program
2772 (for example, routines that are arguments in a @code{pthread_create}
2776 @cindex memory tracing
2777 @cindex breakpoint on memory address
2778 @cindex breakpoint on variable modification
2779 A @dfn{watchpoint} is a special breakpoint that stops your program
2780 when the value of an expression changes. You must use a different
2781 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2782 watchpoints}), but aside from that, you can manage a watchpoint like
2783 any other breakpoint: you enable, disable, and delete both breakpoints
2784 and watchpoints using the same commands.
2786 You can arrange to have values from your program displayed automatically
2787 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2791 @cindex breakpoint on events
2792 A @dfn{catchpoint} is another special breakpoint that stops your program
2793 when a certain kind of event occurs, such as the throwing of a C@t{++}
2794 exception or the loading of a library. As with watchpoints, you use a
2795 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2796 catchpoints}), but aside from that, you can manage a catchpoint like any
2797 other breakpoint. (To stop when your program receives a signal, use the
2798 @code{handle} command; see @ref{Signals, ,Signals}.)
2800 @cindex breakpoint numbers
2801 @cindex numbers for breakpoints
2802 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2803 catchpoint when you create it; these numbers are successive integers
2804 starting with one. In many of the commands for controlling various
2805 features of breakpoints you use the breakpoint number to say which
2806 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2807 @dfn{disabled}; if disabled, it has no effect on your program until you
2810 @cindex breakpoint ranges
2811 @cindex ranges of breakpoints
2812 Some @value{GDBN} commands accept a range of breakpoints on which to
2813 operate. A breakpoint range is either a single breakpoint number, like
2814 @samp{5}, or two such numbers, in increasing order, separated by a
2815 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2816 all breakpoint in that range are operated on.
2819 * Set Breaks:: Setting breakpoints
2820 * Set Watchpoints:: Setting watchpoints
2821 * Set Catchpoints:: Setting catchpoints
2822 * Delete Breaks:: Deleting breakpoints
2823 * Disabling:: Disabling breakpoints
2824 * Conditions:: Break conditions
2825 * Break Commands:: Breakpoint command lists
2826 * Breakpoint Menus:: Breakpoint menus
2827 * Error in Breakpoints:: ``Cannot insert breakpoints''
2828 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2832 @subsection Setting breakpoints
2834 @c FIXME LMB what does GDB do if no code on line of breakpt?
2835 @c consider in particular declaration with/without initialization.
2837 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2840 @kindex b @r{(@code{break})}
2841 @vindex $bpnum@r{, convenience variable}
2842 @cindex latest breakpoint
2843 Breakpoints are set with the @code{break} command (abbreviated
2844 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2845 number of the breakpoint you've set most recently; see @ref{Convenience
2846 Vars,, Convenience variables}, for a discussion of what you can do with
2847 convenience variables.
2849 You have several ways to say where the breakpoint should go.
2852 @item break @var{function}
2853 Set a breakpoint at entry to function @var{function}.
2854 When using source languages that permit overloading of symbols, such as
2855 C@t{++}, @var{function} may refer to more than one possible place to break.
2856 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2858 @item break +@var{offset}
2859 @itemx break -@var{offset}
2860 Set a breakpoint some number of lines forward or back from the position
2861 at which execution stopped in the currently selected @dfn{stack frame}.
2862 (@xref{Frames, ,Frames}, for a description of stack frames.)
2864 @item break @var{linenum}
2865 Set a breakpoint at line @var{linenum} in the current source file.
2866 The current source file is the last file whose source text was printed.
2867 The breakpoint will stop your program just before it executes any of the
2870 @item break @var{filename}:@var{linenum}
2871 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2873 @item break @var{filename}:@var{function}
2874 Set a breakpoint at entry to function @var{function} found in file
2875 @var{filename}. Specifying a file name as well as a function name is
2876 superfluous except when multiple files contain similarly named
2879 @item break *@var{address}
2880 Set a breakpoint at address @var{address}. You can use this to set
2881 breakpoints in parts of your program which do not have debugging
2882 information or source files.
2885 When called without any arguments, @code{break} sets a breakpoint at
2886 the next instruction to be executed in the selected stack frame
2887 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2888 innermost, this makes your program stop as soon as control
2889 returns to that frame. This is similar to the effect of a
2890 @code{finish} command in the frame inside the selected frame---except
2891 that @code{finish} does not leave an active breakpoint. If you use
2892 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2893 the next time it reaches the current location; this may be useful
2896 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2897 least one instruction has been executed. If it did not do this, you
2898 would be unable to proceed past a breakpoint without first disabling the
2899 breakpoint. This rule applies whether or not the breakpoint already
2900 existed when your program stopped.
2902 @item break @dots{} if @var{cond}
2903 Set a breakpoint with condition @var{cond}; evaluate the expression
2904 @var{cond} each time the breakpoint is reached, and stop only if the
2905 value is nonzero---that is, if @var{cond} evaluates as true.
2906 @samp{@dots{}} stands for one of the possible arguments described
2907 above (or no argument) specifying where to break. @xref{Conditions,
2908 ,Break conditions}, for more information on breakpoint conditions.
2911 @item tbreak @var{args}
2912 Set a breakpoint enabled only for one stop. @var{args} are the
2913 same as for the @code{break} command, and the breakpoint is set in the same
2914 way, but the breakpoint is automatically deleted after the first time your
2915 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2918 @cindex hardware breakpoints
2919 @item hbreak @var{args}
2920 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2921 @code{break} command and the breakpoint is set in the same way, but the
2922 breakpoint requires hardware support and some target hardware may not
2923 have this support. The main purpose of this is EPROM/ROM code
2924 debugging, so you can set a breakpoint at an instruction without
2925 changing the instruction. This can be used with the new trap-generation
2926 provided by SPARClite DSU and most x86-based targets. These targets
2927 will generate traps when a program accesses some data or instruction
2928 address that is assigned to the debug registers. However the hardware
2929 breakpoint registers can take a limited number of breakpoints. For
2930 example, on the DSU, only two data breakpoints can be set at a time, and
2931 @value{GDBN} will reject this command if more than two are used. Delete
2932 or disable unused hardware breakpoints before setting new ones
2933 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2934 For remote targets, you can restrict the number of hardware
2935 breakpoints @value{GDBN} will use, see @ref{set remote
2936 hardware-breakpoint-limit}.
2940 @item thbreak @var{args}
2941 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2942 are the same as for the @code{hbreak} command and the breakpoint is set in
2943 the same way. However, like the @code{tbreak} command,
2944 the breakpoint is automatically deleted after the
2945 first time your program stops there. Also, like the @code{hbreak}
2946 command, the breakpoint requires hardware support and some target hardware
2947 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2948 See also @ref{Conditions, ,Break conditions}.
2951 @cindex regular expression
2952 @cindex breakpoints in functions matching a regexp
2953 @cindex set breakpoints in many functions
2954 @item rbreak @var{regex}
2955 Set breakpoints on all functions matching the regular expression
2956 @var{regex}. This command sets an unconditional breakpoint on all
2957 matches, printing a list of all breakpoints it set. Once these
2958 breakpoints are set, they are treated just like the breakpoints set with
2959 the @code{break} command. You can delete them, disable them, or make
2960 them conditional the same way as any other breakpoint.
2962 The syntax of the regular expression is the standard one used with tools
2963 like @file{grep}. Note that this is different from the syntax used by
2964 shells, so for instance @code{foo*} matches all functions that include
2965 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2966 @code{.*} leading and trailing the regular expression you supply, so to
2967 match only functions that begin with @code{foo}, use @code{^foo}.
2969 @cindex non-member C@t{++} functions, set breakpoint in
2970 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2971 breakpoints on overloaded functions that are not members of any special
2974 @cindex set breakpoints on all functions
2975 The @code{rbreak} command can be used to set breakpoints in
2976 @strong{all} the functions in a program, like this:
2979 (@value{GDBP}) rbreak .
2982 @kindex info breakpoints
2983 @cindex @code{$_} and @code{info breakpoints}
2984 @item info breakpoints @r{[}@var{n}@r{]}
2985 @itemx info break @r{[}@var{n}@r{]}
2986 @itemx info watchpoints @r{[}@var{n}@r{]}
2987 Print a table of all breakpoints, watchpoints, and catchpoints set and
2988 not deleted, with the following columns for each breakpoint:
2991 @item Breakpoint Numbers
2993 Breakpoint, watchpoint, or catchpoint.
2995 Whether the breakpoint is marked to be disabled or deleted when hit.
2996 @item Enabled or Disabled
2997 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2998 that are not enabled.
3000 Where the breakpoint is in your program, as a memory address. If the
3001 breakpoint is pending (see below for details) on a future load of a shared library, the address
3002 will be listed as @samp{<PENDING>}.
3004 Where the breakpoint is in the source for your program, as a file and
3005 line number. For a pending breakpoint, the original string passed to
3006 the breakpoint command will be listed as it cannot be resolved until
3007 the appropriate shared library is loaded in the future.
3011 If a breakpoint is conditional, @code{info break} shows the condition on
3012 the line following the affected breakpoint; breakpoint commands, if any,
3013 are listed after that. A pending breakpoint is allowed to have a condition
3014 specified for it. The condition is not parsed for validity until a shared
3015 library is loaded that allows the pending breakpoint to resolve to a
3019 @code{info break} with a breakpoint
3020 number @var{n} as argument lists only that breakpoint. The
3021 convenience variable @code{$_} and the default examining-address for
3022 the @code{x} command are set to the address of the last breakpoint
3023 listed (@pxref{Memory, ,Examining memory}).
3026 @code{info break} displays a count of the number of times the breakpoint
3027 has been hit. This is especially useful in conjunction with the
3028 @code{ignore} command. You can ignore a large number of breakpoint
3029 hits, look at the breakpoint info to see how many times the breakpoint
3030 was hit, and then run again, ignoring one less than that number. This
3031 will get you quickly to the last hit of that breakpoint.
3034 @value{GDBN} allows you to set any number of breakpoints at the same place in
3035 your program. There is nothing silly or meaningless about this. When
3036 the breakpoints are conditional, this is even useful
3037 (@pxref{Conditions, ,Break conditions}).
3039 @cindex pending breakpoints
3040 If a specified breakpoint location cannot be found, it may be due to the fact
3041 that the location is in a shared library that is yet to be loaded. In such
3042 a case, you may want @value{GDBN} to create a special breakpoint (known as
3043 a @dfn{pending breakpoint}) that
3044 attempts to resolve itself in the future when an appropriate shared library
3047 Pending breakpoints are useful to set at the start of your
3048 @value{GDBN} session for locations that you know will be dynamically loaded
3049 later by the program being debugged. When shared libraries are loaded,
3050 a check is made to see if the load resolves any pending breakpoint locations.
3051 If a pending breakpoint location gets resolved,
3052 a regular breakpoint is created and the original pending breakpoint is removed.
3054 @value{GDBN} provides some additional commands for controlling pending
3057 @kindex set breakpoint pending
3058 @kindex show breakpoint pending
3060 @item set breakpoint pending auto
3061 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3062 location, it queries you whether a pending breakpoint should be created.
3064 @item set breakpoint pending on
3065 This indicates that an unrecognized breakpoint location should automatically
3066 result in a pending breakpoint being created.
3068 @item set breakpoint pending off
3069 This indicates that pending breakpoints are not to be created. Any
3070 unrecognized breakpoint location results in an error. This setting does
3071 not affect any pending breakpoints previously created.
3073 @item show breakpoint pending
3074 Show the current behavior setting for creating pending breakpoints.
3077 @cindex operations allowed on pending breakpoints
3078 Normal breakpoint operations apply to pending breakpoints as well. You may
3079 specify a condition for a pending breakpoint and/or commands to run when the
3080 breakpoint is reached. You can also enable or disable
3081 the pending breakpoint. When you specify a condition for a pending breakpoint,
3082 the parsing of the condition will be deferred until the point where the
3083 pending breakpoint location is resolved. Disabling a pending breakpoint
3084 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
3085 shared library load. When a pending breakpoint is re-enabled,
3086 @value{GDBN} checks to see if the location is already resolved.
3087 This is done because any number of shared library loads could have
3088 occurred since the time the breakpoint was disabled and one or more
3089 of these loads could resolve the location.
3091 @cindex negative breakpoint numbers
3092 @cindex internal @value{GDBN} breakpoints
3093 @value{GDBN} itself sometimes sets breakpoints in your program for
3094 special purposes, such as proper handling of @code{longjmp} (in C
3095 programs). These internal breakpoints are assigned negative numbers,
3096 starting with @code{-1}; @samp{info breakpoints} does not display them.
3097 You can see these breakpoints with the @value{GDBN} maintenance command
3098 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3101 @node Set Watchpoints
3102 @subsection Setting watchpoints
3104 @cindex setting watchpoints
3105 You can use a watchpoint to stop execution whenever the value of an
3106 expression changes, without having to predict a particular place where
3109 @cindex software watchpoints
3110 @cindex hardware watchpoints
3111 Depending on your system, watchpoints may be implemented in software or
3112 hardware. @value{GDBN} does software watchpointing by single-stepping your
3113 program and testing the variable's value each time, which is hundreds of
3114 times slower than normal execution. (But this may still be worth it, to
3115 catch errors where you have no clue what part of your program is the
3118 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
3119 x86-based targets, @value{GDBN} includes support for hardware
3120 watchpoints, which do not slow down the running of your program.
3124 @item watch @var{expr}
3125 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
3126 is written into by the program and its value changes.
3129 @item rwatch @var{expr}
3130 Set a watchpoint that will break when the value of @var{expr} is read
3134 @item awatch @var{expr}
3135 Set a watchpoint that will break when @var{expr} is either read from
3136 or written into by the program.
3138 @kindex info watchpoints
3139 @item info watchpoints
3140 This command prints a list of watchpoints, breakpoints, and catchpoints;
3141 it is the same as @code{info break} (@pxref{Set Breaks}).
3144 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3145 watchpoints execute very quickly, and the debugger reports a change in
3146 value at the exact instruction where the change occurs. If @value{GDBN}
3147 cannot set a hardware watchpoint, it sets a software watchpoint, which
3148 executes more slowly and reports the change in value at the next
3149 @emph{statement}, not the instruction, after the change occurs.
3151 @cindex use only software watchpoints
3152 You can force @value{GDBN} to use only software watchpoints with the
3153 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3154 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3155 the underlying system supports them. (Note that hardware-assisted
3156 watchpoints that were set @emph{before} setting
3157 @code{can-use-hw-watchpoints} to zero will still use the hardware
3158 mechanism of watching expressiion values.)
3161 @item set can-use-hw-watchpoints
3162 @kindex set can-use-hw-watchpoints
3163 Set whether or not to use hardware watchpoints.
3165 @item show can-use-hw-watchpoints
3166 @kindex show can-use-hw-watchpoints
3167 Show the current mode of using hardware watchpoints.
3170 For remote targets, you can restrict the number of hardware
3171 watchpoints @value{GDBN} will use, see @ref{set remote
3172 hardware-breakpoint-limit}.
3174 When you issue the @code{watch} command, @value{GDBN} reports
3177 Hardware watchpoint @var{num}: @var{expr}
3181 if it was able to set a hardware watchpoint.
3183 Currently, the @code{awatch} and @code{rwatch} commands can only set
3184 hardware watchpoints, because accesses to data that don't change the
3185 value of the watched expression cannot be detected without examining
3186 every instruction as it is being executed, and @value{GDBN} does not do
3187 that currently. If @value{GDBN} finds that it is unable to set a
3188 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3189 will print a message like this:
3192 Expression cannot be implemented with read/access watchpoint.
3195 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3196 data type of the watched expression is wider than what a hardware
3197 watchpoint on the target machine can handle. For example, some systems
3198 can only watch regions that are up to 4 bytes wide; on such systems you
3199 cannot set hardware watchpoints for an expression that yields a
3200 double-precision floating-point number (which is typically 8 bytes
3201 wide). As a work-around, it might be possible to break the large region
3202 into a series of smaller ones and watch them with separate watchpoints.
3204 If you set too many hardware watchpoints, @value{GDBN} might be unable
3205 to insert all of them when you resume the execution of your program.
3206 Since the precise number of active watchpoints is unknown until such
3207 time as the program is about to be resumed, @value{GDBN} might not be
3208 able to warn you about this when you set the watchpoints, and the
3209 warning will be printed only when the program is resumed:
3212 Hardware watchpoint @var{num}: Could not insert watchpoint
3216 If this happens, delete or disable some of the watchpoints.
3218 The SPARClite DSU will generate traps when a program accesses some data
3219 or instruction address that is assigned to the debug registers. For the
3220 data addresses, DSU facilitates the @code{watch} command. However the
3221 hardware breakpoint registers can only take two data watchpoints, and
3222 both watchpoints must be the same kind. For example, you can set two
3223 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3224 @strong{or} two with @code{awatch} commands, but you cannot set one
3225 watchpoint with one command and the other with a different command.
3226 @value{GDBN} will reject the command if you try to mix watchpoints.
3227 Delete or disable unused watchpoint commands before setting new ones.
3229 If you call a function interactively using @code{print} or @code{call},
3230 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3231 kind of breakpoint or the call completes.
3233 @value{GDBN} automatically deletes watchpoints that watch local
3234 (automatic) variables, or expressions that involve such variables, when
3235 they go out of scope, that is, when the execution leaves the block in
3236 which these variables were defined. In particular, when the program
3237 being debugged terminates, @emph{all} local variables go out of scope,
3238 and so only watchpoints that watch global variables remain set. If you
3239 rerun the program, you will need to set all such watchpoints again. One
3240 way of doing that would be to set a code breakpoint at the entry to the
3241 @code{main} function and when it breaks, set all the watchpoints.
3244 @cindex watchpoints and threads
3245 @cindex threads and watchpoints
3246 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3247 usefulness. With the current watchpoint implementation, @value{GDBN}
3248 can only watch the value of an expression @emph{in a single thread}. If
3249 you are confident that the expression can only change due to the current
3250 thread's activity (and if you are also confident that no other thread
3251 can become current), then you can use watchpoints as usual. However,
3252 @value{GDBN} may not notice when a non-current thread's activity changes
3255 @c FIXME: this is almost identical to the previous paragraph.
3256 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3257 have only limited usefulness. If @value{GDBN} creates a software
3258 watchpoint, it can only watch the value of an expression @emph{in a
3259 single thread}. If you are confident that the expression can only
3260 change due to the current thread's activity (and if you are also
3261 confident that no other thread can become current), then you can use
3262 software watchpoints as usual. However, @value{GDBN} may not notice
3263 when a non-current thread's activity changes the expression. (Hardware
3264 watchpoints, in contrast, watch an expression in all threads.)
3267 @xref{set remote hardware-watchpoint-limit}.
3269 @node Set Catchpoints
3270 @subsection Setting catchpoints
3271 @cindex catchpoints, setting
3272 @cindex exception handlers
3273 @cindex event handling
3275 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3276 kinds of program events, such as C@t{++} exceptions or the loading of a
3277 shared library. Use the @code{catch} command to set a catchpoint.
3281 @item catch @var{event}
3282 Stop when @var{event} occurs. @var{event} can be any of the following:
3285 @cindex stop on C@t{++} exceptions
3286 The throwing of a C@t{++} exception.
3289 The catching of a C@t{++} exception.
3292 @cindex break on fork/exec
3293 A call to @code{exec}. This is currently only available for HP-UX.
3296 A call to @code{fork}. This is currently only available for HP-UX.
3299 A call to @code{vfork}. This is currently only available for HP-UX.
3302 @itemx load @var{libname}
3303 @cindex break on load/unload of shared library
3304 The dynamic loading of any shared library, or the loading of the library
3305 @var{libname}. This is currently only available for HP-UX.
3308 @itemx unload @var{libname}
3309 The unloading of any dynamically loaded shared library, or the unloading
3310 of the library @var{libname}. This is currently only available for HP-UX.
3313 @item tcatch @var{event}
3314 Set a catchpoint that is enabled only for one stop. The catchpoint is
3315 automatically deleted after the first time the event is caught.
3319 Use the @code{info break} command to list the current catchpoints.
3321 There are currently some limitations to C@t{++} exception handling
3322 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3326 If you call a function interactively, @value{GDBN} normally returns
3327 control to you when the function has finished executing. If the call
3328 raises an exception, however, the call may bypass the mechanism that
3329 returns control to you and cause your program either to abort or to
3330 simply continue running until it hits a breakpoint, catches a signal
3331 that @value{GDBN} is listening for, or exits. This is the case even if
3332 you set a catchpoint for the exception; catchpoints on exceptions are
3333 disabled within interactive calls.
3336 You cannot raise an exception interactively.
3339 You cannot install an exception handler interactively.
3342 @cindex raise exceptions
3343 Sometimes @code{catch} is not the best way to debug exception handling:
3344 if you need to know exactly where an exception is raised, it is better to
3345 stop @emph{before} the exception handler is called, since that way you
3346 can see the stack before any unwinding takes place. If you set a
3347 breakpoint in an exception handler instead, it may not be easy to find
3348 out where the exception was raised.
3350 To stop just before an exception handler is called, you need some
3351 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3352 raised by calling a library function named @code{__raise_exception}
3353 which has the following ANSI C interface:
3356 /* @var{addr} is where the exception identifier is stored.
3357 @var{id} is the exception identifier. */
3358 void __raise_exception (void **addr, void *id);
3362 To make the debugger catch all exceptions before any stack
3363 unwinding takes place, set a breakpoint on @code{__raise_exception}
3364 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3366 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3367 that depends on the value of @var{id}, you can stop your program when
3368 a specific exception is raised. You can use multiple conditional
3369 breakpoints to stop your program when any of a number of exceptions are
3374 @subsection Deleting breakpoints
3376 @cindex clearing breakpoints, watchpoints, catchpoints
3377 @cindex deleting breakpoints, watchpoints, catchpoints
3378 It is often necessary to eliminate a breakpoint, watchpoint, or
3379 catchpoint once it has done its job and you no longer want your program
3380 to stop there. This is called @dfn{deleting} the breakpoint. A
3381 breakpoint that has been deleted no longer exists; it is forgotten.
3383 With the @code{clear} command you can delete breakpoints according to
3384 where they are in your program. With the @code{delete} command you can
3385 delete individual breakpoints, watchpoints, or catchpoints by specifying
3386 their breakpoint numbers.
3388 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3389 automatically ignores breakpoints on the first instruction to be executed
3390 when you continue execution without changing the execution address.
3395 Delete any breakpoints at the next instruction to be executed in the
3396 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3397 the innermost frame is selected, this is a good way to delete a
3398 breakpoint where your program just stopped.
3400 @item clear @var{function}
3401 @itemx clear @var{filename}:@var{function}
3402 Delete any breakpoints set at entry to the named @var{function}.
3404 @item clear @var{linenum}
3405 @itemx clear @var{filename}:@var{linenum}
3406 Delete any breakpoints set at or within the code of the specified
3407 @var{linenum} of the specified @var{filename}.
3409 @cindex delete breakpoints
3411 @kindex d @r{(@code{delete})}
3412 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3413 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3414 ranges specified as arguments. If no argument is specified, delete all
3415 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3416 confirm off}). You can abbreviate this command as @code{d}.
3420 @subsection Disabling breakpoints
3422 @cindex enable/disable a breakpoint
3423 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3424 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3425 it had been deleted, but remembers the information on the breakpoint so
3426 that you can @dfn{enable} it again later.
3428 You disable and enable breakpoints, watchpoints, and catchpoints with
3429 the @code{enable} and @code{disable} commands, optionally specifying one
3430 or more breakpoint numbers as arguments. Use @code{info break} or
3431 @code{info watch} to print a list of breakpoints, watchpoints, and
3432 catchpoints if you do not know which numbers to use.
3434 A breakpoint, watchpoint, or catchpoint can have any of four different
3435 states of enablement:
3439 Enabled. The breakpoint stops your program. A breakpoint set
3440 with the @code{break} command starts out in this state.
3442 Disabled. The breakpoint has no effect on your program.
3444 Enabled once. The breakpoint stops your program, but then becomes
3447 Enabled for deletion. The breakpoint stops your program, but
3448 immediately after it does so it is deleted permanently. A breakpoint
3449 set with the @code{tbreak} command starts out in this state.
3452 You can use the following commands to enable or disable breakpoints,
3453 watchpoints, and catchpoints:
3457 @kindex dis @r{(@code{disable})}
3458 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3459 Disable the specified breakpoints---or all breakpoints, if none are
3460 listed. A disabled breakpoint has no effect but is not forgotten. All
3461 options such as ignore-counts, conditions and commands are remembered in
3462 case the breakpoint is enabled again later. You may abbreviate
3463 @code{disable} as @code{dis}.
3466 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3467 Enable the specified breakpoints (or all defined breakpoints). They
3468 become effective once again in stopping your program.
3470 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3471 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3472 of these breakpoints immediately after stopping your program.
3474 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3475 Enable the specified breakpoints to work once, then die. @value{GDBN}
3476 deletes any of these breakpoints as soon as your program stops there.
3477 Breakpoints set by the @code{tbreak} command start out in this state.
3480 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3481 @c confusing: tbreak is also initially enabled.
3482 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3483 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3484 subsequently, they become disabled or enabled only when you use one of
3485 the commands above. (The command @code{until} can set and delete a
3486 breakpoint of its own, but it does not change the state of your other
3487 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3491 @subsection Break conditions
3492 @cindex conditional breakpoints
3493 @cindex breakpoint conditions
3495 @c FIXME what is scope of break condition expr? Context where wanted?
3496 @c in particular for a watchpoint?
3497 The simplest sort of breakpoint breaks every time your program reaches a
3498 specified place. You can also specify a @dfn{condition} for a
3499 breakpoint. A condition is just a Boolean expression in your
3500 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3501 a condition evaluates the expression each time your program reaches it,
3502 and your program stops only if the condition is @emph{true}.
3504 This is the converse of using assertions for program validation; in that
3505 situation, you want to stop when the assertion is violated---that is,
3506 when the condition is false. In C, if you want to test an assertion expressed
3507 by the condition @var{assert}, you should set the condition
3508 @samp{! @var{assert}} on the appropriate breakpoint.
3510 Conditions are also accepted for watchpoints; you may not need them,
3511 since a watchpoint is inspecting the value of an expression anyhow---but
3512 it might be simpler, say, to just set a watchpoint on a variable name,
3513 and specify a condition that tests whether the new value is an interesting
3516 Break conditions can have side effects, and may even call functions in
3517 your program. This can be useful, for example, to activate functions
3518 that log program progress, or to use your own print functions to
3519 format special data structures. The effects are completely predictable
3520 unless there is another enabled breakpoint at the same address. (In
3521 that case, @value{GDBN} might see the other breakpoint first and stop your
3522 program without checking the condition of this one.) Note that
3523 breakpoint commands are usually more convenient and flexible than break
3525 purpose of performing side effects when a breakpoint is reached
3526 (@pxref{Break Commands, ,Breakpoint command lists}).
3528 Break conditions can be specified when a breakpoint is set, by using
3529 @samp{if} in the arguments to the @code{break} command. @xref{Set
3530 Breaks, ,Setting breakpoints}. They can also be changed at any time
3531 with the @code{condition} command.
3533 You can also use the @code{if} keyword with the @code{watch} command.
3534 The @code{catch} command does not recognize the @code{if} keyword;
3535 @code{condition} is the only way to impose a further condition on a
3540 @item condition @var{bnum} @var{expression}
3541 Specify @var{expression} as the break condition for breakpoint,
3542 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3543 breakpoint @var{bnum} stops your program only if the value of
3544 @var{expression} is true (nonzero, in C). When you use
3545 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3546 syntactic correctness, and to determine whether symbols in it have
3547 referents in the context of your breakpoint. If @var{expression} uses
3548 symbols not referenced in the context of the breakpoint, @value{GDBN}
3549 prints an error message:
3552 No symbol "foo" in current context.
3557 not actually evaluate @var{expression} at the time the @code{condition}
3558 command (or a command that sets a breakpoint with a condition, like
3559 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3561 @item condition @var{bnum}
3562 Remove the condition from breakpoint number @var{bnum}. It becomes
3563 an ordinary unconditional breakpoint.
3566 @cindex ignore count (of breakpoint)
3567 A special case of a breakpoint condition is to stop only when the
3568 breakpoint has been reached a certain number of times. This is so
3569 useful that there is a special way to do it, using the @dfn{ignore
3570 count} of the breakpoint. Every breakpoint has an ignore count, which
3571 is an integer. Most of the time, the ignore count is zero, and
3572 therefore has no effect. But if your program reaches a breakpoint whose
3573 ignore count is positive, then instead of stopping, it just decrements
3574 the ignore count by one and continues. As a result, if the ignore count
3575 value is @var{n}, the breakpoint does not stop the next @var{n} times
3576 your program reaches it.
3580 @item ignore @var{bnum} @var{count}
3581 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3582 The next @var{count} times the breakpoint is reached, your program's
3583 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3586 To make the breakpoint stop the next time it is reached, specify
3589 When you use @code{continue} to resume execution of your program from a
3590 breakpoint, you can specify an ignore count directly as an argument to
3591 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3592 Stepping,,Continuing and stepping}.
3594 If a breakpoint has a positive ignore count and a condition, the
3595 condition is not checked. Once the ignore count reaches zero,
3596 @value{GDBN} resumes checking the condition.
3598 You could achieve the effect of the ignore count with a condition such
3599 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3600 is decremented each time. @xref{Convenience Vars, ,Convenience
3604 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3607 @node Break Commands
3608 @subsection Breakpoint command lists
3610 @cindex breakpoint commands
3611 You can give any breakpoint (or watchpoint or catchpoint) a series of
3612 commands to execute when your program stops due to that breakpoint. For
3613 example, you might want to print the values of certain expressions, or
3614 enable other breakpoints.
3618 @kindex end@r{ (breakpoint commands)}
3619 @item commands @r{[}@var{bnum}@r{]}
3620 @itemx @dots{} @var{command-list} @dots{}
3622 Specify a list of commands for breakpoint number @var{bnum}. The commands
3623 themselves appear on the following lines. Type a line containing just
3624 @code{end} to terminate the commands.
3626 To remove all commands from a breakpoint, type @code{commands} and
3627 follow it immediately with @code{end}; that is, give no commands.
3629 With no @var{bnum} argument, @code{commands} refers to the last
3630 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3631 recently encountered).
3634 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3635 disabled within a @var{command-list}.
3637 You can use breakpoint commands to start your program up again. Simply
3638 use the @code{continue} command, or @code{step}, or any other command
3639 that resumes execution.
3641 Any other commands in the command list, after a command that resumes
3642 execution, are ignored. This is because any time you resume execution
3643 (even with a simple @code{next} or @code{step}), you may encounter
3644 another breakpoint---which could have its own command list, leading to
3645 ambiguities about which list to execute.
3648 If the first command you specify in a command list is @code{silent}, the
3649 usual message about stopping at a breakpoint is not printed. This may
3650 be desirable for breakpoints that are to print a specific message and
3651 then continue. If none of the remaining commands print anything, you
3652 see no sign that the breakpoint was reached. @code{silent} is
3653 meaningful only at the beginning of a breakpoint command list.
3655 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3656 print precisely controlled output, and are often useful in silent
3657 breakpoints. @xref{Output, ,Commands for controlled output}.
3659 For example, here is how you could use breakpoint commands to print the
3660 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3666 printf "x is %d\n",x
3671 One application for breakpoint commands is to compensate for one bug so
3672 you can test for another. Put a breakpoint just after the erroneous line
3673 of code, give it a condition to detect the case in which something
3674 erroneous has been done, and give it commands to assign correct values
3675 to any variables that need them. End with the @code{continue} command
3676 so that your program does not stop, and start with the @code{silent}
3677 command so that no output is produced. Here is an example:
3688 @node Breakpoint Menus
3689 @subsection Breakpoint menus
3691 @cindex symbol overloading
3693 Some programming languages (notably C@t{++} and Objective-C) permit a
3694 single function name
3695 to be defined several times, for application in different contexts.
3696 This is called @dfn{overloading}. When a function name is overloaded,
3697 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3698 a breakpoint. If you realize this is a problem, you can use
3699 something like @samp{break @var{function}(@var{types})} to specify which
3700 particular version of the function you want. Otherwise, @value{GDBN} offers
3701 you a menu of numbered choices for different possible breakpoints, and
3702 waits for your selection with the prompt @samp{>}. The first two
3703 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3704 sets a breakpoint at each definition of @var{function}, and typing
3705 @kbd{0} aborts the @code{break} command without setting any new
3708 For example, the following session excerpt shows an attempt to set a
3709 breakpoint at the overloaded symbol @code{String::after}.
3710 We choose three particular definitions of that function name:
3712 @c FIXME! This is likely to change to show arg type lists, at least
3715 (@value{GDBP}) b String::after
3718 [2] file:String.cc; line number:867
3719 [3] file:String.cc; line number:860
3720 [4] file:String.cc; line number:875
3721 [5] file:String.cc; line number:853
3722 [6] file:String.cc; line number:846
3723 [7] file:String.cc; line number:735
3725 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3726 Breakpoint 2 at 0xb344: file String.cc, line 875.
3727 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3728 Multiple breakpoints were set.
3729 Use the "delete" command to delete unwanted
3735 @c @ifclear BARETARGET
3736 @node Error in Breakpoints
3737 @subsection ``Cannot insert breakpoints''
3739 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3741 Under some operating systems, breakpoints cannot be used in a program if
3742 any other process is running that program. In this situation,
3743 attempting to run or continue a program with a breakpoint causes
3744 @value{GDBN} to print an error message:
3747 Cannot insert breakpoints.
3748 The same program may be running in another process.
3751 When this happens, you have three ways to proceed:
3755 Remove or disable the breakpoints, then continue.
3758 Suspend @value{GDBN}, and copy the file containing your program to a new
3759 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3760 that @value{GDBN} should run your program under that name.
3761 Then start your program again.
3764 Relink your program so that the text segment is nonsharable, using the
3765 linker option @samp{-N}. The operating system limitation may not apply
3766 to nonsharable executables.
3770 A similar message can be printed if you request too many active
3771 hardware-assisted breakpoints and watchpoints:
3773 @c FIXME: the precise wording of this message may change; the relevant
3774 @c source change is not committed yet (Sep 3, 1999).
3776 Stopped; cannot insert breakpoints.
3777 You may have requested too many hardware breakpoints and watchpoints.
3781 This message is printed when you attempt to resume the program, since
3782 only then @value{GDBN} knows exactly how many hardware breakpoints and
3783 watchpoints it needs to insert.
3785 When this message is printed, you need to disable or remove some of the
3786 hardware-assisted breakpoints and watchpoints, and then continue.
3788 @node Breakpoint related warnings
3789 @subsection ``Breakpoint address adjusted...''
3790 @cindex breakpoint address adjusted
3792 Some processor architectures place constraints on the addresses at
3793 which breakpoints may be placed. For architectures thus constrained,
3794 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3795 with the constraints dictated by the architecture.
3797 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3798 a VLIW architecture in which a number of RISC-like instructions may be
3799 bundled together for parallel execution. The FR-V architecture
3800 constrains the location of a breakpoint instruction within such a
3801 bundle to the instruction with the lowest address. @value{GDBN}
3802 honors this constraint by adjusting a breakpoint's address to the
3803 first in the bundle.
3805 It is not uncommon for optimized code to have bundles which contain
3806 instructions from different source statements, thus it may happen that
3807 a breakpoint's address will be adjusted from one source statement to
3808 another. Since this adjustment may significantly alter @value{GDBN}'s
3809 breakpoint related behavior from what the user expects, a warning is
3810 printed when the breakpoint is first set and also when the breakpoint
3813 A warning like the one below is printed when setting a breakpoint
3814 that's been subject to address adjustment:
3817 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3820 Such warnings are printed both for user settable and @value{GDBN}'s
3821 internal breakpoints. If you see one of these warnings, you should
3822 verify that a breakpoint set at the adjusted address will have the
3823 desired affect. If not, the breakpoint in question may be removed and
3824 other breakpoints may be set which will have the desired behavior.
3825 E.g., it may be sufficient to place the breakpoint at a later
3826 instruction. A conditional breakpoint may also be useful in some
3827 cases to prevent the breakpoint from triggering too often.
3829 @value{GDBN} will also issue a warning when stopping at one of these
3830 adjusted breakpoints:
3833 warning: Breakpoint 1 address previously adjusted from 0x00010414
3837 When this warning is encountered, it may be too late to take remedial
3838 action except in cases where the breakpoint is hit earlier or more
3839 frequently than expected.
3841 @node Continuing and Stepping
3842 @section Continuing and stepping
3846 @cindex resuming execution
3847 @dfn{Continuing} means resuming program execution until your program
3848 completes normally. In contrast, @dfn{stepping} means executing just
3849 one more ``step'' of your program, where ``step'' may mean either one
3850 line of source code, or one machine instruction (depending on what
3851 particular command you use). Either when continuing or when stepping,
3852 your program may stop even sooner, due to a breakpoint or a signal. (If
3853 it stops due to a signal, you may want to use @code{handle}, or use
3854 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3858 @kindex c @r{(@code{continue})}
3859 @kindex fg @r{(resume foreground execution)}
3860 @item continue @r{[}@var{ignore-count}@r{]}
3861 @itemx c @r{[}@var{ignore-count}@r{]}
3862 @itemx fg @r{[}@var{ignore-count}@r{]}
3863 Resume program execution, at the address where your program last stopped;
3864 any breakpoints set at that address are bypassed. The optional argument
3865 @var{ignore-count} allows you to specify a further number of times to
3866 ignore a breakpoint at this location; its effect is like that of
3867 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3869 The argument @var{ignore-count} is meaningful only when your program
3870 stopped due to a breakpoint. At other times, the argument to
3871 @code{continue} is ignored.
3873 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3874 debugged program is deemed to be the foreground program) are provided
3875 purely for convenience, and have exactly the same behavior as
3879 To resume execution at a different place, you can use @code{return}
3880 (@pxref{Returning, ,Returning from a function}) to go back to the
3881 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3882 different address}) to go to an arbitrary location in your program.
3884 A typical technique for using stepping is to set a breakpoint
3885 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3886 beginning of the function or the section of your program where a problem
3887 is believed to lie, run your program until it stops at that breakpoint,
3888 and then step through the suspect area, examining the variables that are
3889 interesting, until you see the problem happen.
3893 @kindex s @r{(@code{step})}
3895 Continue running your program until control reaches a different source
3896 line, then stop it and return control to @value{GDBN}. This command is
3897 abbreviated @code{s}.
3900 @c "without debugging information" is imprecise; actually "without line
3901 @c numbers in the debugging information". (gcc -g1 has debugging info but
3902 @c not line numbers). But it seems complex to try to make that
3903 @c distinction here.
3904 @emph{Warning:} If you use the @code{step} command while control is
3905 within a function that was compiled without debugging information,
3906 execution proceeds until control reaches a function that does have
3907 debugging information. Likewise, it will not step into a function which
3908 is compiled without debugging information. To step through functions
3909 without debugging information, use the @code{stepi} command, described
3913 The @code{step} command only stops at the first instruction of a source
3914 line. This prevents the multiple stops that could otherwise occur in
3915 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3916 to stop if a function that has debugging information is called within
3917 the line. In other words, @code{step} @emph{steps inside} any functions
3918 called within the line.
3920 Also, the @code{step} command only enters a function if there is line
3921 number information for the function. Otherwise it acts like the
3922 @code{next} command. This avoids problems when using @code{cc -gl}
3923 on MIPS machines. Previously, @code{step} entered subroutines if there
3924 was any debugging information about the routine.
3926 @item step @var{count}
3927 Continue running as in @code{step}, but do so @var{count} times. If a
3928 breakpoint is reached, or a signal not related to stepping occurs before
3929 @var{count} steps, stepping stops right away.
3932 @kindex n @r{(@code{next})}
3933 @item next @r{[}@var{count}@r{]}
3934 Continue to the next source line in the current (innermost) stack frame.
3935 This is similar to @code{step}, but function calls that appear within
3936 the line of code are executed without stopping. Execution stops when
3937 control reaches a different line of code at the original stack level
3938 that was executing when you gave the @code{next} command. This command
3939 is abbreviated @code{n}.
3941 An argument @var{count} is a repeat count, as for @code{step}.
3944 @c FIX ME!! Do we delete this, or is there a way it fits in with
3945 @c the following paragraph? --- Vctoria
3947 @c @code{next} within a function that lacks debugging information acts like
3948 @c @code{step}, but any function calls appearing within the code of the
3949 @c function are executed without stopping.
3951 The @code{next} command only stops at the first instruction of a
3952 source line. This prevents multiple stops that could otherwise occur in
3953 @code{switch} statements, @code{for} loops, etc.
3955 @kindex set step-mode
3957 @cindex functions without line info, and stepping
3958 @cindex stepping into functions with no line info
3959 @itemx set step-mode on
3960 The @code{set step-mode on} command causes the @code{step} command to
3961 stop at the first instruction of a function which contains no debug line
3962 information rather than stepping over it.
3964 This is useful in cases where you may be interested in inspecting the
3965 machine instructions of a function which has no symbolic info and do not
3966 want @value{GDBN} to automatically skip over this function.
3968 @item set step-mode off
3969 Causes the @code{step} command to step over any functions which contains no
3970 debug information. This is the default.
3972 @item show step-mode
3973 Show whether @value{GDBN} will stop in or step over functions without
3974 source line debug information.
3978 Continue running until just after function in the selected stack frame
3979 returns. Print the returned value (if any).
3981 Contrast this with the @code{return} command (@pxref{Returning,
3982 ,Returning from a function}).
3985 @kindex u @r{(@code{until})}
3986 @cindex run until specified location
3989 Continue running until a source line past the current line, in the
3990 current stack frame, is reached. This command is used to avoid single
3991 stepping through a loop more than once. It is like the @code{next}
3992 command, except that when @code{until} encounters a jump, it
3993 automatically continues execution until the program counter is greater
3994 than the address of the jump.
3996 This means that when you reach the end of a loop after single stepping
3997 though it, @code{until} makes your program continue execution until it
3998 exits the loop. In contrast, a @code{next} command at the end of a loop
3999 simply steps back to the beginning of the loop, which forces you to step
4000 through the next iteration.
4002 @code{until} always stops your program if it attempts to exit the current
4005 @code{until} may produce somewhat counterintuitive results if the order
4006 of machine code does not match the order of the source lines. For
4007 example, in the following excerpt from a debugging session, the @code{f}
4008 (@code{frame}) command shows that execution is stopped at line
4009 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4013 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4015 (@value{GDBP}) until
4016 195 for ( ; argc > 0; NEXTARG) @{
4019 This happened because, for execution efficiency, the compiler had
4020 generated code for the loop closure test at the end, rather than the
4021 start, of the loop---even though the test in a C @code{for}-loop is
4022 written before the body of the loop. The @code{until} command appeared
4023 to step back to the beginning of the loop when it advanced to this
4024 expression; however, it has not really gone to an earlier
4025 statement---not in terms of the actual machine code.
4027 @code{until} with no argument works by means of single
4028 instruction stepping, and hence is slower than @code{until} with an
4031 @item until @var{location}
4032 @itemx u @var{location}
4033 Continue running your program until either the specified location is
4034 reached, or the current stack frame returns. @var{location} is any of
4035 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4036 ,Setting breakpoints}). This form of the command uses breakpoints, and
4037 hence is quicker than @code{until} without an argument. The specified
4038 location is actually reached only if it is in the current frame. This
4039 implies that @code{until} can be used to skip over recursive function
4040 invocations. For instance in the code below, if the current location is
4041 line @code{96}, issuing @code{until 99} will execute the program up to
4042 line @code{99} in the same invocation of factorial, i.e. after the inner
4043 invocations have returned.
4046 94 int factorial (int value)
4048 96 if (value > 1) @{
4049 97 value *= factorial (value - 1);
4056 @kindex advance @var{location}
4057 @itemx advance @var{location}
4058 Continue running the program up to the given @var{location}. An argument is
4059 required, which should be of the same form as arguments for the @code{break}
4060 command. Execution will also stop upon exit from the current stack
4061 frame. This command is similar to @code{until}, but @code{advance} will
4062 not skip over recursive function calls, and the target location doesn't
4063 have to be in the same frame as the current one.
4067 @kindex si @r{(@code{stepi})}
4069 @itemx stepi @var{arg}
4071 Execute one machine instruction, then stop and return to the debugger.
4073 It is often useful to do @samp{display/i $pc} when stepping by machine
4074 instructions. This makes @value{GDBN} automatically display the next
4075 instruction to be executed, each time your program stops. @xref{Auto
4076 Display,, Automatic display}.
4078 An argument is a repeat count, as in @code{step}.
4082 @kindex ni @r{(@code{nexti})}
4084 @itemx nexti @var{arg}
4086 Execute one machine instruction, but if it is a function call,
4087 proceed until the function returns.
4089 An argument is a repeat count, as in @code{next}.
4096 A signal is an asynchronous event that can happen in a program. The
4097 operating system defines the possible kinds of signals, and gives each
4098 kind a name and a number. For example, in Unix @code{SIGINT} is the
4099 signal a program gets when you type an interrupt character (often @kbd{C-c});
4100 @code{SIGSEGV} is the signal a program gets from referencing a place in
4101 memory far away from all the areas in use; @code{SIGALRM} occurs when
4102 the alarm clock timer goes off (which happens only if your program has
4103 requested an alarm).
4105 @cindex fatal signals
4106 Some signals, including @code{SIGALRM}, are a normal part of the
4107 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4108 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4109 program has not specified in advance some other way to handle the signal.
4110 @code{SIGINT} does not indicate an error in your program, but it is normally
4111 fatal so it can carry out the purpose of the interrupt: to kill the program.
4113 @value{GDBN} has the ability to detect any occurrence of a signal in your
4114 program. You can tell @value{GDBN} in advance what to do for each kind of
4117 @cindex handling signals
4118 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4119 @code{SIGALRM} be silently passed to your program
4120 (so as not to interfere with their role in the program's functioning)
4121 but to stop your program immediately whenever an error signal happens.
4122 You can change these settings with the @code{handle} command.
4125 @kindex info signals
4129 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4130 handle each one. You can use this to see the signal numbers of all
4131 the defined types of signals.
4133 @code{info handle} is an alias for @code{info signals}.
4136 @item handle @var{signal} @var{keywords}@dots{}
4137 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4138 can be the number of a signal or its name (with or without the
4139 @samp{SIG} at the beginning); a list of signal numbers of the form
4140 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4141 known signals. The @var{keywords} say what change to make.
4145 The keywords allowed by the @code{handle} command can be abbreviated.
4146 Their full names are:
4150 @value{GDBN} should not stop your program when this signal happens. It may
4151 still print a message telling you that the signal has come in.
4154 @value{GDBN} should stop your program when this signal happens. This implies
4155 the @code{print} keyword as well.
4158 @value{GDBN} should print a message when this signal happens.
4161 @value{GDBN} should not mention the occurrence of the signal at all. This
4162 implies the @code{nostop} keyword as well.
4166 @value{GDBN} should allow your program to see this signal; your program
4167 can handle the signal, or else it may terminate if the signal is fatal
4168 and not handled. @code{pass} and @code{noignore} are synonyms.
4172 @value{GDBN} should not allow your program to see this signal.
4173 @code{nopass} and @code{ignore} are synonyms.
4177 When a signal stops your program, the signal is not visible to the
4179 continue. Your program sees the signal then, if @code{pass} is in
4180 effect for the signal in question @emph{at that time}. In other words,
4181 after @value{GDBN} reports a signal, you can use the @code{handle}
4182 command with @code{pass} or @code{nopass} to control whether your
4183 program sees that signal when you continue.
4185 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4186 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4187 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4190 You can also use the @code{signal} command to prevent your program from
4191 seeing a signal, or cause it to see a signal it normally would not see,
4192 or to give it any signal at any time. For example, if your program stopped
4193 due to some sort of memory reference error, you might store correct
4194 values into the erroneous variables and continue, hoping to see more
4195 execution; but your program would probably terminate immediately as
4196 a result of the fatal signal once it saw the signal. To prevent this,
4197 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4201 @section Stopping and starting multi-thread programs
4203 When your program has multiple threads (@pxref{Threads,, Debugging
4204 programs with multiple threads}), you can choose whether to set
4205 breakpoints on all threads, or on a particular thread.
4208 @cindex breakpoints and threads
4209 @cindex thread breakpoints
4210 @kindex break @dots{} thread @var{threadno}
4211 @item break @var{linespec} thread @var{threadno}
4212 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4213 @var{linespec} specifies source lines; there are several ways of
4214 writing them, but the effect is always to specify some source line.
4216 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4217 to specify that you only want @value{GDBN} to stop the program when a
4218 particular thread reaches this breakpoint. @var{threadno} is one of the
4219 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4220 column of the @samp{info threads} display.
4222 If you do not specify @samp{thread @var{threadno}} when you set a
4223 breakpoint, the breakpoint applies to @emph{all} threads of your
4226 You can use the @code{thread} qualifier on conditional breakpoints as
4227 well; in this case, place @samp{thread @var{threadno}} before the
4228 breakpoint condition, like this:
4231 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4236 @cindex stopped threads
4237 @cindex threads, stopped
4238 Whenever your program stops under @value{GDBN} for any reason,
4239 @emph{all} threads of execution stop, not just the current thread. This
4240 allows you to examine the overall state of the program, including
4241 switching between threads, without worrying that things may change
4244 @cindex thread breakpoints and system calls
4245 @cindex system calls and thread breakpoints
4246 @cindex premature return from system calls
4247 There is an unfortunate side effect. If one thread stops for a
4248 breakpoint, or for some other reason, and another thread is blocked in a
4249 system call, then the system call may return prematurely. This is a
4250 consequence of the interaction between multiple threads and the signals
4251 that @value{GDBN} uses to implement breakpoints and other events that
4254 To handle this problem, your program should check the return value of
4255 each system call and react appropriately. This is good programming
4258 For example, do not write code like this:
4264 The call to @code{sleep} will return early if a different thread stops
4265 at a breakpoint or for some other reason.
4267 Instead, write this:
4272 unslept = sleep (unslept);
4275 A system call is allowed to return early, so the system is still
4276 conforming to its specification. But @value{GDBN} does cause your
4277 multi-threaded program to behave differently than it would without
4280 Also, @value{GDBN} uses internal breakpoints in the thread library to
4281 monitor certain events such as thread creation and thread destruction.
4282 When such an event happens, a system call in another thread may return
4283 prematurely, even though your program does not appear to stop.
4285 @cindex continuing threads
4286 @cindex threads, continuing
4287 Conversely, whenever you restart the program, @emph{all} threads start
4288 executing. @emph{This is true even when single-stepping} with commands
4289 like @code{step} or @code{next}.
4291 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4292 Since thread scheduling is up to your debugging target's operating
4293 system (not controlled by @value{GDBN}), other threads may
4294 execute more than one statement while the current thread completes a
4295 single step. Moreover, in general other threads stop in the middle of a
4296 statement, rather than at a clean statement boundary, when the program
4299 You might even find your program stopped in another thread after
4300 continuing or even single-stepping. This happens whenever some other
4301 thread runs into a breakpoint, a signal, or an exception before the
4302 first thread completes whatever you requested.
4304 On some OSes, you can lock the OS scheduler and thus allow only a single
4308 @item set scheduler-locking @var{mode}
4309 @cindex scheduler locking mode
4310 @cindex lock scheduler
4311 Set the scheduler locking mode. If it is @code{off}, then there is no
4312 locking and any thread may run at any time. If @code{on}, then only the
4313 current thread may run when the inferior is resumed. The @code{step}
4314 mode optimizes for single-stepping. It stops other threads from
4315 ``seizing the prompt'' by preempting the current thread while you are
4316 stepping. Other threads will only rarely (or never) get a chance to run
4317 when you step. They are more likely to run when you @samp{next} over a
4318 function call, and they are completely free to run when you use commands
4319 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4320 thread hits a breakpoint during its timeslice, they will never steal the
4321 @value{GDBN} prompt away from the thread that you are debugging.
4323 @item show scheduler-locking
4324 Display the current scheduler locking mode.
4329 @chapter Examining the Stack
4331 When your program has stopped, the first thing you need to know is where it
4332 stopped and how it got there.
4335 Each time your program performs a function call, information about the call
4337 That information includes the location of the call in your program,
4338 the arguments of the call,
4339 and the local variables of the function being called.
4340 The information is saved in a block of data called a @dfn{stack frame}.
4341 The stack frames are allocated in a region of memory called the @dfn{call
4344 When your program stops, the @value{GDBN} commands for examining the
4345 stack allow you to see all of this information.
4347 @cindex selected frame
4348 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4349 @value{GDBN} commands refer implicitly to the selected frame. In
4350 particular, whenever you ask @value{GDBN} for the value of a variable in
4351 your program, the value is found in the selected frame. There are
4352 special @value{GDBN} commands to select whichever frame you are
4353 interested in. @xref{Selection, ,Selecting a frame}.
4355 When your program stops, @value{GDBN} automatically selects the
4356 currently executing frame and describes it briefly, similar to the
4357 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4360 * Frames:: Stack frames
4361 * Backtrace:: Backtraces
4362 * Selection:: Selecting a frame
4363 * Frame Info:: Information on a frame
4368 @section Stack frames
4370 @cindex frame, definition
4372 The call stack is divided up into contiguous pieces called @dfn{stack
4373 frames}, or @dfn{frames} for short; each frame is the data associated
4374 with one call to one function. The frame contains the arguments given
4375 to the function, the function's local variables, and the address at
4376 which the function is executing.
4378 @cindex initial frame
4379 @cindex outermost frame
4380 @cindex innermost frame
4381 When your program is started, the stack has only one frame, that of the
4382 function @code{main}. This is called the @dfn{initial} frame or the
4383 @dfn{outermost} frame. Each time a function is called, a new frame is
4384 made. Each time a function returns, the frame for that function invocation
4385 is eliminated. If a function is recursive, there can be many frames for
4386 the same function. The frame for the function in which execution is
4387 actually occurring is called the @dfn{innermost} frame. This is the most
4388 recently created of all the stack frames that still exist.
4390 @cindex frame pointer
4391 Inside your program, stack frames are identified by their addresses. A
4392 stack frame consists of many bytes, each of which has its own address; each
4393 kind of computer has a convention for choosing one byte whose
4394 address serves as the address of the frame. Usually this address is kept
4395 in a register called the @dfn{frame pointer register}
4396 (@pxref{Registers, $fp}) while execution is going on in that frame.
4398 @cindex frame number
4399 @value{GDBN} assigns numbers to all existing stack frames, starting with
4400 zero for the innermost frame, one for the frame that called it,
4401 and so on upward. These numbers do not really exist in your program;
4402 they are assigned by @value{GDBN} to give you a way of designating stack
4403 frames in @value{GDBN} commands.
4405 @c The -fomit-frame-pointer below perennially causes hbox overflow
4406 @c underflow problems.
4407 @cindex frameless execution
4408 Some compilers provide a way to compile functions so that they operate
4409 without stack frames. (For example, the @value{GCC} option
4411 @samp{-fomit-frame-pointer}
4413 generates functions without a frame.)
4414 This is occasionally done with heavily used library functions to save
4415 the frame setup time. @value{GDBN} has limited facilities for dealing
4416 with these function invocations. If the innermost function invocation
4417 has no stack frame, @value{GDBN} nevertheless regards it as though
4418 it had a separate frame, which is numbered zero as usual, allowing
4419 correct tracing of the function call chain. However, @value{GDBN} has
4420 no provision for frameless functions elsewhere in the stack.
4423 @kindex frame@r{, command}
4424 @cindex current stack frame
4425 @item frame @var{args}
4426 The @code{frame} command allows you to move from one stack frame to another,
4427 and to print the stack frame you select. @var{args} may be either the
4428 address of the frame or the stack frame number. Without an argument,
4429 @code{frame} prints the current stack frame.
4431 @kindex select-frame
4432 @cindex selecting frame silently
4434 The @code{select-frame} command allows you to move from one stack frame
4435 to another without printing the frame. This is the silent version of
4443 @cindex call stack traces
4444 A backtrace is a summary of how your program got where it is. It shows one
4445 line per frame, for many frames, starting with the currently executing
4446 frame (frame zero), followed by its caller (frame one), and on up the
4451 @kindex bt @r{(@code{backtrace})}
4454 Print a backtrace of the entire stack: one line per frame for all
4455 frames in the stack.
4457 You can stop the backtrace at any time by typing the system interrupt
4458 character, normally @kbd{C-c}.
4460 @item backtrace @var{n}
4462 Similar, but print only the innermost @var{n} frames.
4464 @item backtrace -@var{n}
4466 Similar, but print only the outermost @var{n} frames.
4468 @item backtrace full
4470 @itemx bt full @var{n}
4471 @itemx bt full -@var{n}
4472 Print the values of the local variables also.
4477 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4478 are additional aliases for @code{backtrace}.
4480 @cindex multiple threads, backtrace
4481 In a multi-threaded program, @value{GDBN} by default shows the
4482 backtrace only for the current thread. To display the backtrace for
4483 several or all of the threads, use the command @code{thread apply}
4484 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4485 apply all backtrace}, @value{GDBN} will display the backtrace for all
4486 the threads; this is handy when you debug a core dump of a
4487 multi-threaded program.
4489 Each line in the backtrace shows the frame number and the function name.
4490 The program counter value is also shown---unless you use @code{set
4491 print address off}. The backtrace also shows the source file name and
4492 line number, as well as the arguments to the function. The program
4493 counter value is omitted if it is at the beginning of the code for that
4496 Here is an example of a backtrace. It was made with the command
4497 @samp{bt 3}, so it shows the innermost three frames.
4501 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4503 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4504 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4506 (More stack frames follow...)
4511 The display for frame zero does not begin with a program counter
4512 value, indicating that your program has stopped at the beginning of the
4513 code for line @code{993} of @code{builtin.c}.
4515 @cindex value optimized out, in backtrace
4516 @cindex function call arguments, optimized out
4517 If your program was compiled with optimizations, some compilers will
4518 optimize away arguments passed to functions if those arguments are
4519 never used after the call. Such optimizations generate code that
4520 passes arguments through registers, but doesn't store those arguments
4521 in the stack frame. @value{GDBN} has no way of displaying such
4522 arguments in stack frames other than the innermost one. Here's what
4523 such a backtrace might look like:
4527 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4529 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4530 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4532 (More stack frames follow...)
4537 The values of arguments that were not saved in their stack frames are
4538 shown as @samp{<value optimized out>}.
4540 If you need to display the values of such optimized-out arguments,
4541 either deduce that from other variables whose values depend on the one
4542 you are interested in, or recompile without optimizations.
4544 @cindex backtrace beyond @code{main} function
4545 @cindex program entry point
4546 @cindex startup code, and backtrace
4547 Most programs have a standard user entry point---a place where system
4548 libraries and startup code transition into user code. For C this is
4549 @code{main}@footnote{
4550 Note that embedded programs (the so-called ``free-standing''
4551 environment) are not required to have a @code{main} function as the
4552 entry point. They could even have multiple entry points.}.
4553 When @value{GDBN} finds the entry function in a backtrace
4554 it will terminate the backtrace, to avoid tracing into highly
4555 system-specific (and generally uninteresting) code.
4557 If you need to examine the startup code, or limit the number of levels
4558 in a backtrace, you can change this behavior:
4561 @item set backtrace past-main
4562 @itemx set backtrace past-main on
4563 @kindex set backtrace
4564 Backtraces will continue past the user entry point.
4566 @item set backtrace past-main off
4567 Backtraces will stop when they encounter the user entry point. This is the
4570 @item show backtrace past-main
4571 @kindex show backtrace
4572 Display the current user entry point backtrace policy.
4574 @item set backtrace past-entry
4575 @itemx set backtrace past-entry on
4576 Backtraces will continue past the internal entry point of an application.
4577 This entry point is encoded by the linker when the application is built,
4578 and is likely before the user entry point @code{main} (or equivalent) is called.
4580 @item set backtrace past-entry off
4581 Backtraces will stop when they encouter the internal entry point of an
4582 application. This is the default.
4584 @item show backtrace past-entry
4585 Display the current internal entry point backtrace policy.
4587 @item set backtrace limit @var{n}
4588 @itemx set backtrace limit 0
4589 @cindex backtrace limit
4590 Limit the backtrace to @var{n} levels. A value of zero means
4593 @item show backtrace limit
4594 Display the current limit on backtrace levels.
4598 @section Selecting a frame
4600 Most commands for examining the stack and other data in your program work on
4601 whichever stack frame is selected at the moment. Here are the commands for
4602 selecting a stack frame; all of them finish by printing a brief description
4603 of the stack frame just selected.
4606 @kindex frame@r{, selecting}
4607 @kindex f @r{(@code{frame})}
4610 Select frame number @var{n}. Recall that frame zero is the innermost
4611 (currently executing) frame, frame one is the frame that called the
4612 innermost one, and so on. The highest-numbered frame is the one for
4615 @item frame @var{addr}
4617 Select the frame at address @var{addr}. This is useful mainly if the
4618 chaining of stack frames has been damaged by a bug, making it
4619 impossible for @value{GDBN} to assign numbers properly to all frames. In
4620 addition, this can be useful when your program has multiple stacks and
4621 switches between them.
4623 On the SPARC architecture, @code{frame} needs two addresses to
4624 select an arbitrary frame: a frame pointer and a stack pointer.
4626 On the MIPS and Alpha architecture, it needs two addresses: a stack
4627 pointer and a program counter.
4629 On the 29k architecture, it needs three addresses: a register stack
4630 pointer, a program counter, and a memory stack pointer.
4634 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4635 advances toward the outermost frame, to higher frame numbers, to frames
4636 that have existed longer. @var{n} defaults to one.
4639 @kindex do @r{(@code{down})}
4641 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4642 advances toward the innermost frame, to lower frame numbers, to frames
4643 that were created more recently. @var{n} defaults to one. You may
4644 abbreviate @code{down} as @code{do}.
4647 All of these commands end by printing two lines of output describing the
4648 frame. The first line shows the frame number, the function name, the
4649 arguments, and the source file and line number of execution in that
4650 frame. The second line shows the text of that source line.
4658 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4660 10 read_input_file (argv[i]);
4664 After such a printout, the @code{list} command with no arguments
4665 prints ten lines centered on the point of execution in the frame.
4666 You can also edit the program at the point of execution with your favorite
4667 editing program by typing @code{edit}.
4668 @xref{List, ,Printing source lines},
4672 @kindex down-silently
4674 @item up-silently @var{n}
4675 @itemx down-silently @var{n}
4676 These two commands are variants of @code{up} and @code{down},
4677 respectively; they differ in that they do their work silently, without
4678 causing display of the new frame. They are intended primarily for use
4679 in @value{GDBN} command scripts, where the output might be unnecessary and
4684 @section Information about a frame
4686 There are several other commands to print information about the selected
4692 When used without any argument, this command does not change which
4693 frame is selected, but prints a brief description of the currently
4694 selected stack frame. It can be abbreviated @code{f}. With an
4695 argument, this command is used to select a stack frame.
4696 @xref{Selection, ,Selecting a frame}.
4699 @kindex info f @r{(@code{info frame})}
4702 This command prints a verbose description of the selected stack frame,
4707 the address of the frame
4709 the address of the next frame down (called by this frame)
4711 the address of the next frame up (caller of this frame)
4713 the language in which the source code corresponding to this frame is written
4715 the address of the frame's arguments
4717 the address of the frame's local variables
4719 the program counter saved in it (the address of execution in the caller frame)
4721 which registers were saved in the frame
4724 @noindent The verbose description is useful when
4725 something has gone wrong that has made the stack format fail to fit
4726 the usual conventions.
4728 @item info frame @var{addr}
4729 @itemx info f @var{addr}
4730 Print a verbose description of the frame at address @var{addr}, without
4731 selecting that frame. The selected frame remains unchanged by this
4732 command. This requires the same kind of address (more than one for some
4733 architectures) that you specify in the @code{frame} command.
4734 @xref{Selection, ,Selecting a frame}.
4738 Print the arguments of the selected frame, each on a separate line.
4742 Print the local variables of the selected frame, each on a separate
4743 line. These are all variables (declared either static or automatic)
4744 accessible at the point of execution of the selected frame.
4747 @cindex catch exceptions, list active handlers
4748 @cindex exception handlers, how to list
4750 Print a list of all the exception handlers that are active in the
4751 current stack frame at the current point of execution. To see other
4752 exception handlers, visit the associated frame (using the @code{up},
4753 @code{down}, or @code{frame} commands); then type @code{info catch}.
4754 @xref{Set Catchpoints, , Setting catchpoints}.
4760 @chapter Examining Source Files
4762 @value{GDBN} can print parts of your program's source, since the debugging
4763 information recorded in the program tells @value{GDBN} what source files were
4764 used to build it. When your program stops, @value{GDBN} spontaneously prints
4765 the line where it stopped. Likewise, when you select a stack frame
4766 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4767 execution in that frame has stopped. You can print other portions of
4768 source files by explicit command.
4770 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4771 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4772 @value{GDBN} under @sc{gnu} Emacs}.
4775 * List:: Printing source lines
4776 * Edit:: Editing source files
4777 * Search:: Searching source files
4778 * Source Path:: Specifying source directories
4779 * Machine Code:: Source and machine code
4783 @section Printing source lines
4786 @kindex l @r{(@code{list})}
4787 To print lines from a source file, use the @code{list} command
4788 (abbreviated @code{l}). By default, ten lines are printed.
4789 There are several ways to specify what part of the file you want to print.
4791 Here are the forms of the @code{list} command most commonly used:
4794 @item list @var{linenum}
4795 Print lines centered around line number @var{linenum} in the
4796 current source file.
4798 @item list @var{function}
4799 Print lines centered around the beginning of function
4803 Print more lines. If the last lines printed were printed with a
4804 @code{list} command, this prints lines following the last lines
4805 printed; however, if the last line printed was a solitary line printed
4806 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4807 Stack}), this prints lines centered around that line.
4810 Print lines just before the lines last printed.
4813 @cindex @code{list}, how many lines to display
4814 By default, @value{GDBN} prints ten source lines with any of these forms of
4815 the @code{list} command. You can change this using @code{set listsize}:
4818 @kindex set listsize
4819 @item set listsize @var{count}
4820 Make the @code{list} command display @var{count} source lines (unless
4821 the @code{list} argument explicitly specifies some other number).
4823 @kindex show listsize
4825 Display the number of lines that @code{list} prints.
4828 Repeating a @code{list} command with @key{RET} discards the argument,
4829 so it is equivalent to typing just @code{list}. This is more useful
4830 than listing the same lines again. An exception is made for an
4831 argument of @samp{-}; that argument is preserved in repetition so that
4832 each repetition moves up in the source file.
4835 In general, the @code{list} command expects you to supply zero, one or two
4836 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4837 of writing them, but the effect is always to specify some source line.
4838 Here is a complete description of the possible arguments for @code{list}:
4841 @item list @var{linespec}
4842 Print lines centered around the line specified by @var{linespec}.
4844 @item list @var{first},@var{last}
4845 Print lines from @var{first} to @var{last}. Both arguments are
4848 @item list ,@var{last}
4849 Print lines ending with @var{last}.
4851 @item list @var{first},
4852 Print lines starting with @var{first}.
4855 Print lines just after the lines last printed.
4858 Print lines just before the lines last printed.
4861 As described in the preceding table.
4864 Here are the ways of specifying a single source line---all the
4869 Specifies line @var{number} of the current source file.
4870 When a @code{list} command has two linespecs, this refers to
4871 the same source file as the first linespec.
4874 Specifies the line @var{offset} lines after the last line printed.
4875 When used as the second linespec in a @code{list} command that has
4876 two, this specifies the line @var{offset} lines down from the
4880 Specifies the line @var{offset} lines before the last line printed.
4882 @item @var{filename}:@var{number}
4883 Specifies line @var{number} in the source file @var{filename}.
4885 @item @var{function}
4886 Specifies the line that begins the body of the function @var{function}.
4887 For example: in C, this is the line with the open brace.
4889 @item @var{filename}:@var{function}
4890 Specifies the line of the open-brace that begins the body of the
4891 function @var{function} in the file @var{filename}. You only need the
4892 file name with a function name to avoid ambiguity when there are
4893 identically named functions in different source files.
4895 @item *@var{address}
4896 Specifies the line containing the program address @var{address}.
4897 @var{address} may be any expression.
4901 @section Editing source files
4902 @cindex editing source files
4905 @kindex e @r{(@code{edit})}
4906 To edit the lines in a source file, use the @code{edit} command.
4907 The editing program of your choice
4908 is invoked with the current line set to
4909 the active line in the program.
4910 Alternatively, there are several ways to specify what part of the file you
4911 want to print if you want to see other parts of the program.
4913 Here are the forms of the @code{edit} command most commonly used:
4917 Edit the current source file at the active line number in the program.
4919 @item edit @var{number}
4920 Edit the current source file with @var{number} as the active line number.
4922 @item edit @var{function}
4923 Edit the file containing @var{function} at the beginning of its definition.
4925 @item edit @var{filename}:@var{number}
4926 Specifies line @var{number} in the source file @var{filename}.
4928 @item edit @var{filename}:@var{function}
4929 Specifies the line that begins the body of the
4930 function @var{function} in the file @var{filename}. You only need the
4931 file name with a function name to avoid ambiguity when there are
4932 identically named functions in different source files.
4934 @item edit *@var{address}
4935 Specifies the line containing the program address @var{address}.
4936 @var{address} may be any expression.
4939 @subsection Choosing your editor
4940 You can customize @value{GDBN} to use any editor you want
4942 The only restriction is that your editor (say @code{ex}), recognizes the
4943 following command-line syntax:
4945 ex +@var{number} file
4947 The optional numeric value +@var{number} specifies the number of the line in
4948 the file where to start editing.}.
4949 By default, it is @file{@value{EDITOR}}, but you can change this
4950 by setting the environment variable @code{EDITOR} before using
4951 @value{GDBN}. For example, to configure @value{GDBN} to use the
4952 @code{vi} editor, you could use these commands with the @code{sh} shell:
4958 or in the @code{csh} shell,
4960 setenv EDITOR /usr/bin/vi
4965 @section Searching source files
4966 @cindex searching source files
4968 There are two commands for searching through the current source file for a
4973 @kindex forward-search
4974 @item forward-search @var{regexp}
4975 @itemx search @var{regexp}
4976 The command @samp{forward-search @var{regexp}} checks each line,
4977 starting with the one following the last line listed, for a match for
4978 @var{regexp}. It lists the line that is found. You can use the
4979 synonym @samp{search @var{regexp}} or abbreviate the command name as
4982 @kindex reverse-search
4983 @item reverse-search @var{regexp}
4984 The command @samp{reverse-search @var{regexp}} checks each line, starting
4985 with the one before the last line listed and going backward, for a match
4986 for @var{regexp}. It lists the line that is found. You can abbreviate
4987 this command as @code{rev}.
4991 @section Specifying source directories
4994 @cindex directories for source files
4995 Executable programs sometimes do not record the directories of the source
4996 files from which they were compiled, just the names. Even when they do,
4997 the directories could be moved between the compilation and your debugging
4998 session. @value{GDBN} has a list of directories to search for source files;
4999 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5000 it tries all the directories in the list, in the order they are present
5001 in the list, until it finds a file with the desired name.
5003 For example, suppose an executable references the file
5004 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5005 @file{/mnt/cross}. The file is first looked up literally; if this
5006 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5007 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5008 message is printed. @value{GDBN} does not look up the parts of the
5009 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5010 Likewise, the subdirectories of the source path are not searched: if
5011 the source path is @file{/mnt/cross}, and the binary refers to
5012 @file{foo.c}, @value{GDBN} would not find it under
5013 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5015 Plain file names, relative file names with leading directories, file
5016 names containing dots, etc.@: are all treated as described above; for
5017 instance, if the source path is @file{/mnt/cross}, and the source file
5018 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5019 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5020 that---@file{/mnt/cross/foo.c}.
5022 Note that the executable search path is @emph{not} used to locate the
5025 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5026 any information it has cached about where source files are found and where
5027 each line is in the file.
5031 When you start @value{GDBN}, its source path includes only @samp{cdir}
5032 and @samp{cwd}, in that order.
5033 To add other directories, use the @code{directory} command.
5035 The search path is used to find both program source files and @value{GDBN}
5036 script files (read using the @samp{-command} option and @samp{source} command).
5038 In addition to the source path, @value{GDBN} provides a set of commands
5039 that manage a list of source path substitution rules. A @dfn{substitution
5040 rule} specifies how to rewrite source directories stored in the program's
5041 debug information in case the sources were moved to a different
5042 directory between compilation and debugging. A rule is made of
5043 two strings, the first specifying what needs to be rewritten in
5044 the path, and the second specifying how it should be rewritten.
5045 In @ref{set substitute-path}, we name these two parts @var{from} and
5046 @var{to} respectively. @value{GDBN} does a simple string replacement
5047 of @var{from} with @var{to} at the start of the directory part of the
5048 source file name, and uses that result instead of the original file
5049 name to look up the sources.
5051 Using the previous example, suppose the @file{foo-1.0} tree has been
5052 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5053 GDB to replace @file{/usr/src} in all source path names with
5054 @file{/mnt/cross}. The first lookup will then be
5055 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5056 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5057 substitution rule, use the @code{set substitute-path} command
5058 (@pxref{set substitute-path}).
5060 To avoid unexpected substitution results, a rule is applied only if the
5061 @var{from} part of the directory name ends at a directory separator.
5062 For instance, a rule substituting @file{/usr/source} into
5063 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5064 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5065 is applied only at the begining of the directory name, this rule will
5066 not be applied to @file{/root/usr/source/baz.c} either.
5068 In many cases, you can achieve the same result using the @code{directory}
5069 command. However, @code{set substitute-path} can be more efficient in
5070 the case where the sources are organized in a complex tree with multiple
5071 subdirectories. With the @code{directory} command, you need to add each
5072 subdirectory of your project. If you moved the entire tree while
5073 preserving its internal organization, then @code{set substitute-path}
5074 allows you to direct the debugger to all the sources with one single
5077 @code{set substitute-path} is also more than just a shortcut command.
5078 The source path is only used if the file at the original location no
5079 longer exists. On the other hand, @code{set substitute-path} modifies
5080 the debugger behavior to look at the rewritten location instead. So, if
5081 for any reason a source file that is not relevant to your executable is
5082 located at the original location, a substitution rule is the only
5083 method available to point GDB at the new location.
5086 @item directory @var{dirname} @dots{}
5087 @item dir @var{dirname} @dots{}
5088 Add directory @var{dirname} to the front of the source path. Several
5089 directory names may be given to this command, separated by @samp{:}
5090 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5091 part of absolute file names) or
5092 whitespace. You may specify a directory that is already in the source
5093 path; this moves it forward, so @value{GDBN} searches it sooner.
5097 @vindex $cdir@r{, convenience variable}
5098 @vindex $cwdr@r{, convenience variable}
5099 @cindex compilation directory
5100 @cindex current directory
5101 @cindex working directory
5102 @cindex directory, current
5103 @cindex directory, compilation
5104 You can use the string @samp{$cdir} to refer to the compilation
5105 directory (if one is recorded), and @samp{$cwd} to refer to the current
5106 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5107 tracks the current working directory as it changes during your @value{GDBN}
5108 session, while the latter is immediately expanded to the current
5109 directory at the time you add an entry to the source path.
5112 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5114 @c RET-repeat for @code{directory} is explicitly disabled, but since
5115 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5117 @item show directories
5118 @kindex show directories
5119 Print the source path: show which directories it contains.
5121 @anchor{set substitute-path}
5122 @item set substitute-path @var{from} @var{to}
5123 @kindex set substitute-path
5124 Define a source path substitution rule, and add it at the end of the
5125 current list of existing substitution rules. If a rule with the same
5126 @var{from} was already defined, then the old rule is also deleted.
5128 For example, if the file @file{/foo/bar/baz.c} was moved to
5129 @file{/mnt/cross/baz.c}, then the command
5132 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5136 will tell @value{GDBN} to replace @samp{/usr/src} with
5137 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5138 @file{baz.c} even though it was moved.
5140 In the case when more than one substitution rule have been defined,
5141 the rules are evaluated one by one in the order where they have been
5142 defined. The first one matching, if any, is selected to perform
5145 For instance, if we had entered the following commands:
5148 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5149 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5153 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5154 @file{/mnt/include/defs.h} by using the first rule. However, it would
5155 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5156 @file{/mnt/src/lib/foo.c}.
5159 @item unset substitute-path [path]
5160 @kindex unset substitute-path
5161 If a path is specified, search the current list of substitution rules
5162 for a rule that would rewrite that path. Delete that rule if found.
5163 A warning is emitted by the debugger if no rule could be found.
5165 If no path is specified, then all substitution rules are deleted.
5167 @item show substitute-path [path]
5168 @kindex show substitute-path
5169 If a path is specified, then print the source path substitution rule
5170 which would rewrite that path, if any.
5172 If no path is specified, then print all existing source path substitution
5177 If your source path is cluttered with directories that are no longer of
5178 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5179 versions of source. You can correct the situation as follows:
5183 Use @code{directory} with no argument to reset the source path to its default value.
5186 Use @code{directory} with suitable arguments to reinstall the
5187 directories you want in the source path. You can add all the
5188 directories in one command.
5192 @section Source and machine code
5193 @cindex source line and its code address
5195 You can use the command @code{info line} to map source lines to program
5196 addresses (and vice versa), and the command @code{disassemble} to display
5197 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5198 mode, the @code{info line} command causes the arrow to point to the
5199 line specified. Also, @code{info line} prints addresses in symbolic form as
5204 @item info line @var{linespec}
5205 Print the starting and ending addresses of the compiled code for
5206 source line @var{linespec}. You can specify source lines in any of
5207 the ways understood by the @code{list} command (@pxref{List, ,Printing
5211 For example, we can use @code{info line} to discover the location of
5212 the object code for the first line of function
5213 @code{m4_changequote}:
5215 @c FIXME: I think this example should also show the addresses in
5216 @c symbolic form, as they usually would be displayed.
5218 (@value{GDBP}) info line m4_changequote
5219 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5223 @cindex code address and its source line
5224 We can also inquire (using @code{*@var{addr}} as the form for
5225 @var{linespec}) what source line covers a particular address:
5227 (@value{GDBP}) info line *0x63ff
5228 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5231 @cindex @code{$_} and @code{info line}
5232 @cindex @code{x} command, default address
5233 @kindex x@r{(examine), and} info line
5234 After @code{info line}, the default address for the @code{x} command
5235 is changed to the starting address of the line, so that @samp{x/i} is
5236 sufficient to begin examining the machine code (@pxref{Memory,
5237 ,Examining memory}). Also, this address is saved as the value of the
5238 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5243 @cindex assembly instructions
5244 @cindex instructions, assembly
5245 @cindex machine instructions
5246 @cindex listing machine instructions
5248 This specialized command dumps a range of memory as machine
5249 instructions. The default memory range is the function surrounding the
5250 program counter of the selected frame. A single argument to this
5251 command is a program counter value; @value{GDBN} dumps the function
5252 surrounding this value. Two arguments specify a range of addresses
5253 (first inclusive, second exclusive) to dump.
5256 The following example shows the disassembly of a range of addresses of
5257 HP PA-RISC 2.0 code:
5260 (@value{GDBP}) disas 0x32c4 0x32e4
5261 Dump of assembler code from 0x32c4 to 0x32e4:
5262 0x32c4 <main+204>: addil 0,dp
5263 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5264 0x32cc <main+212>: ldil 0x3000,r31
5265 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5266 0x32d4 <main+220>: ldo 0(r31),rp
5267 0x32d8 <main+224>: addil -0x800,dp
5268 0x32dc <main+228>: ldo 0x588(r1),r26
5269 0x32e0 <main+232>: ldil 0x3000,r31
5270 End of assembler dump.
5273 Some architectures have more than one commonly-used set of instruction
5274 mnemonics or other syntax.
5276 For programs that were dynamically linked and use shared libraries,
5277 instructions that call functions or branch to locations in the shared
5278 libraries might show a seemingly bogus location---it's actually a
5279 location of the relocation table. On some architectures, @value{GDBN}
5280 might be able to resolve these to actual function names.
5283 @kindex set disassembly-flavor
5284 @cindex Intel disassembly flavor
5285 @cindex AT&T disassembly flavor
5286 @item set disassembly-flavor @var{instruction-set}
5287 Select the instruction set to use when disassembling the
5288 program via the @code{disassemble} or @code{x/i} commands.
5290 Currently this command is only defined for the Intel x86 family. You
5291 can set @var{instruction-set} to either @code{intel} or @code{att}.
5292 The default is @code{att}, the AT&T flavor used by default by Unix
5293 assemblers for x86-based targets.
5295 @kindex show disassembly-flavor
5296 @item show disassembly-flavor
5297 Show the current setting of the disassembly flavor.
5302 @chapter Examining Data
5304 @cindex printing data
5305 @cindex examining data
5308 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5309 @c document because it is nonstandard... Under Epoch it displays in a
5310 @c different window or something like that.
5311 The usual way to examine data in your program is with the @code{print}
5312 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5313 evaluates and prints the value of an expression of the language your
5314 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5315 Different Languages}).
5318 @item print @var{expr}
5319 @itemx print /@var{f} @var{expr}
5320 @var{expr} is an expression (in the source language). By default the
5321 value of @var{expr} is printed in a format appropriate to its data type;
5322 you can choose a different format by specifying @samp{/@var{f}}, where
5323 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5327 @itemx print /@var{f}
5328 @cindex reprint the last value
5329 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5330 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
5331 conveniently inspect the same value in an alternative format.
5334 A more low-level way of examining data is with the @code{x} command.
5335 It examines data in memory at a specified address and prints it in a
5336 specified format. @xref{Memory, ,Examining memory}.
5338 If you are interested in information about types, or about how the
5339 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5340 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5344 * Expressions:: Expressions
5345 * Variables:: Program variables
5346 * Arrays:: Artificial arrays
5347 * Output Formats:: Output formats
5348 * Memory:: Examining memory
5349 * Auto Display:: Automatic display
5350 * Print Settings:: Print settings
5351 * Value History:: Value history
5352 * Convenience Vars:: Convenience variables
5353 * Registers:: Registers
5354 * Floating Point Hardware:: Floating point hardware
5355 * Vector Unit:: Vector Unit
5356 * OS Information:: Auxiliary data provided by operating system
5357 * Memory Region Attributes:: Memory region attributes
5358 * Dump/Restore Files:: Copy between memory and a file
5359 * Core File Generation:: Cause a program dump its core
5360 * Character Sets:: Debugging programs that use a different
5361 character set than GDB does
5362 * Caching Remote Data:: Data caching for remote targets
5366 @section Expressions
5369 @code{print} and many other @value{GDBN} commands accept an expression and
5370 compute its value. Any kind of constant, variable or operator defined
5371 by the programming language you are using is valid in an expression in
5372 @value{GDBN}. This includes conditional expressions, function calls,
5373 casts, and string constants. It also includes preprocessor macros, if
5374 you compiled your program to include this information; see
5377 @cindex arrays in expressions
5378 @value{GDBN} supports array constants in expressions input by
5379 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5380 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5381 memory that is @code{malloc}ed in the target program.
5383 Because C is so widespread, most of the expressions shown in examples in
5384 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5385 Languages}, for information on how to use expressions in other
5388 In this section, we discuss operators that you can use in @value{GDBN}
5389 expressions regardless of your programming language.
5391 @cindex casts, in expressions
5392 Casts are supported in all languages, not just in C, because it is so
5393 useful to cast a number into a pointer in order to examine a structure
5394 at that address in memory.
5395 @c FIXME: casts supported---Mod2 true?
5397 @value{GDBN} supports these operators, in addition to those common
5398 to programming languages:
5402 @samp{@@} is a binary operator for treating parts of memory as arrays.
5403 @xref{Arrays, ,Artificial arrays}, for more information.
5406 @samp{::} allows you to specify a variable in terms of the file or
5407 function where it is defined. @xref{Variables, ,Program variables}.
5409 @cindex @{@var{type}@}
5410 @cindex type casting memory
5411 @cindex memory, viewing as typed object
5412 @cindex casts, to view memory
5413 @item @{@var{type}@} @var{addr}
5414 Refers to an object of type @var{type} stored at address @var{addr} in
5415 memory. @var{addr} may be any expression whose value is an integer or
5416 pointer (but parentheses are required around binary operators, just as in
5417 a cast). This construct is allowed regardless of what kind of data is
5418 normally supposed to reside at @var{addr}.
5422 @section Program variables
5424 The most common kind of expression to use is the name of a variable
5427 Variables in expressions are understood in the selected stack frame
5428 (@pxref{Selection, ,Selecting a frame}); they must be either:
5432 global (or file-static)
5439 visible according to the scope rules of the
5440 programming language from the point of execution in that frame
5443 @noindent This means that in the function
5458 you can examine and use the variable @code{a} whenever your program is
5459 executing within the function @code{foo}, but you can only use or
5460 examine the variable @code{b} while your program is executing inside
5461 the block where @code{b} is declared.
5463 @cindex variable name conflict
5464 There is an exception: you can refer to a variable or function whose
5465 scope is a single source file even if the current execution point is not
5466 in this file. But it is possible to have more than one such variable or
5467 function with the same name (in different source files). If that
5468 happens, referring to that name has unpredictable effects. If you wish,
5469 you can specify a static variable in a particular function or file,
5470 using the colon-colon (@code{::}) notation:
5472 @cindex colon-colon, context for variables/functions
5474 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5475 @cindex @code{::}, context for variables/functions
5478 @var{file}::@var{variable}
5479 @var{function}::@var{variable}
5483 Here @var{file} or @var{function} is the name of the context for the
5484 static @var{variable}. In the case of file names, you can use quotes to
5485 make sure @value{GDBN} parses the file name as a single word---for example,
5486 to print a global value of @code{x} defined in @file{f2.c}:
5489 (@value{GDBP}) p 'f2.c'::x
5492 @cindex C@t{++} scope resolution
5493 This use of @samp{::} is very rarely in conflict with the very similar
5494 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5495 scope resolution operator in @value{GDBN} expressions.
5496 @c FIXME: Um, so what happens in one of those rare cases where it's in
5499 @cindex wrong values
5500 @cindex variable values, wrong
5501 @cindex function entry/exit, wrong values of variables
5502 @cindex optimized code, wrong values of variables
5504 @emph{Warning:} Occasionally, a local variable may appear to have the
5505 wrong value at certain points in a function---just after entry to a new
5506 scope, and just before exit.
5508 You may see this problem when you are stepping by machine instructions.
5509 This is because, on most machines, it takes more than one instruction to
5510 set up a stack frame (including local variable definitions); if you are
5511 stepping by machine instructions, variables may appear to have the wrong
5512 values until the stack frame is completely built. On exit, it usually
5513 also takes more than one machine instruction to destroy a stack frame;
5514 after you begin stepping through that group of instructions, local
5515 variable definitions may be gone.
5517 This may also happen when the compiler does significant optimizations.
5518 To be sure of always seeing accurate values, turn off all optimization
5521 @cindex ``No symbol "foo" in current context''
5522 Another possible effect of compiler optimizations is to optimize
5523 unused variables out of existence, or assign variables to registers (as
5524 opposed to memory addresses). Depending on the support for such cases
5525 offered by the debug info format used by the compiler, @value{GDBN}
5526 might not be able to display values for such local variables. If that
5527 happens, @value{GDBN} will print a message like this:
5530 No symbol "foo" in current context.
5533 To solve such problems, either recompile without optimizations, or use a
5534 different debug info format, if the compiler supports several such
5535 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5536 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5537 produces debug info in a format that is superior to formats such as
5538 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5539 an effective form for debug info. @xref{Debugging Options,,Options
5540 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5541 @xref{C, , Debugging C++}, for more info about debug info formats
5542 that are best suited to C@t{++} programs.
5544 If you ask to print an object whose contents are unknown to
5545 @value{GDBN}, e.g., because its data type is not completely specified
5546 by the debug information, @value{GDBN} will say @samp{<incomplete
5547 type>}. @xref{Symbols, incomplete type}, for more about this.
5550 @section Artificial arrays
5552 @cindex artificial array
5554 @kindex @@@r{, referencing memory as an array}
5555 It is often useful to print out several successive objects of the
5556 same type in memory; a section of an array, or an array of
5557 dynamically determined size for which only a pointer exists in the
5560 You can do this by referring to a contiguous span of memory as an
5561 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5562 operand of @samp{@@} should be the first element of the desired array
5563 and be an individual object. The right operand should be the desired length
5564 of the array. The result is an array value whose elements are all of
5565 the type of the left argument. The first element is actually the left
5566 argument; the second element comes from bytes of memory immediately
5567 following those that hold the first element, and so on. Here is an
5568 example. If a program says
5571 int *array = (int *) malloc (len * sizeof (int));
5575 you can print the contents of @code{array} with
5581 The left operand of @samp{@@} must reside in memory. Array values made
5582 with @samp{@@} in this way behave just like other arrays in terms of
5583 subscripting, and are coerced to pointers when used in expressions.
5584 Artificial arrays most often appear in expressions via the value history
5585 (@pxref{Value History, ,Value history}), after printing one out.
5587 Another way to create an artificial array is to use a cast.
5588 This re-interprets a value as if it were an array.
5589 The value need not be in memory:
5591 (@value{GDBP}) p/x (short[2])0x12345678
5592 $1 = @{0x1234, 0x5678@}
5595 As a convenience, if you leave the array length out (as in
5596 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5597 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5599 (@value{GDBP}) p/x (short[])0x12345678
5600 $2 = @{0x1234, 0x5678@}
5603 Sometimes the artificial array mechanism is not quite enough; in
5604 moderately complex data structures, the elements of interest may not
5605 actually be adjacent---for example, if you are interested in the values
5606 of pointers in an array. One useful work-around in this situation is
5607 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5608 variables}) as a counter in an expression that prints the first
5609 interesting value, and then repeat that expression via @key{RET}. For
5610 instance, suppose you have an array @code{dtab} of pointers to
5611 structures, and you are interested in the values of a field @code{fv}
5612 in each structure. Here is an example of what you might type:
5622 @node Output Formats
5623 @section Output formats
5625 @cindex formatted output
5626 @cindex output formats
5627 By default, @value{GDBN} prints a value according to its data type. Sometimes
5628 this is not what you want. For example, you might want to print a number
5629 in hex, or a pointer in decimal. Or you might want to view data in memory
5630 at a certain address as a character string or as an instruction. To do
5631 these things, specify an @dfn{output format} when you print a value.
5633 The simplest use of output formats is to say how to print a value
5634 already computed. This is done by starting the arguments of the
5635 @code{print} command with a slash and a format letter. The format
5636 letters supported are:
5640 Regard the bits of the value as an integer, and print the integer in
5644 Print as integer in signed decimal.
5647 Print as integer in unsigned decimal.
5650 Print as integer in octal.
5653 Print as integer in binary. The letter @samp{t} stands for ``two''.
5654 @footnote{@samp{b} cannot be used because these format letters are also
5655 used with the @code{x} command, where @samp{b} stands for ``byte'';
5656 see @ref{Memory,,Examining memory}.}
5659 @cindex unknown address, locating
5660 @cindex locate address
5661 Print as an address, both absolute in hexadecimal and as an offset from
5662 the nearest preceding symbol. You can use this format used to discover
5663 where (in what function) an unknown address is located:
5666 (@value{GDBP}) p/a 0x54320
5667 $3 = 0x54320 <_initialize_vx+396>
5671 The command @code{info symbol 0x54320} yields similar results.
5672 @xref{Symbols, info symbol}.
5675 Regard as an integer and print it as a character constant. This
5676 prints both the numerical value and its character representation. The
5677 character representation is replaced with the octal escape @samp{\nnn}
5678 for characters outside the 7-bit @sc{ascii} range.
5681 Regard the bits of the value as a floating point number and print
5682 using typical floating point syntax.
5685 For example, to print the program counter in hex (@pxref{Registers}), type
5692 Note that no space is required before the slash; this is because command
5693 names in @value{GDBN} cannot contain a slash.
5695 To reprint the last value in the value history with a different format,
5696 you can use the @code{print} command with just a format and no
5697 expression. For example, @samp{p/x} reprints the last value in hex.
5700 @section Examining memory
5702 You can use the command @code{x} (for ``examine'') to examine memory in
5703 any of several formats, independently of your program's data types.
5705 @cindex examining memory
5707 @kindex x @r{(examine memory)}
5708 @item x/@var{nfu} @var{addr}
5711 Use the @code{x} command to examine memory.
5714 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5715 much memory to display and how to format it; @var{addr} is an
5716 expression giving the address where you want to start displaying memory.
5717 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5718 Several commands set convenient defaults for @var{addr}.
5721 @item @var{n}, the repeat count
5722 The repeat count is a decimal integer; the default is 1. It specifies
5723 how much memory (counting by units @var{u}) to display.
5724 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5727 @item @var{f}, the display format
5728 The display format is one of the formats used by @code{print}
5729 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5730 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5731 @samp{i} (for machine instructions). The default is @samp{x}
5732 (hexadecimal) initially. The default changes each time you use either
5733 @code{x} or @code{print}.
5735 @item @var{u}, the unit size
5736 The unit size is any of
5742 Halfwords (two bytes).
5744 Words (four bytes). This is the initial default.
5746 Giant words (eight bytes).
5749 Each time you specify a unit size with @code{x}, that size becomes the
5750 default unit the next time you use @code{x}. (For the @samp{s} and
5751 @samp{i} formats, the unit size is ignored and is normally not written.)
5753 @item @var{addr}, starting display address
5754 @var{addr} is the address where you want @value{GDBN} to begin displaying
5755 memory. The expression need not have a pointer value (though it may);
5756 it is always interpreted as an integer address of a byte of memory.
5757 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5758 @var{addr} is usually just after the last address examined---but several
5759 other commands also set the default address: @code{info breakpoints} (to
5760 the address of the last breakpoint listed), @code{info line} (to the
5761 starting address of a line), and @code{print} (if you use it to display
5762 a value from memory).
5765 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5766 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5767 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5768 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5769 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5771 Since the letters indicating unit sizes are all distinct from the
5772 letters specifying output formats, you do not have to remember whether
5773 unit size or format comes first; either order works. The output
5774 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5775 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5777 Even though the unit size @var{u} is ignored for the formats @samp{s}
5778 and @samp{i}, you might still want to use a count @var{n}; for example,
5779 @samp{3i} specifies that you want to see three machine instructions,
5780 including any operands. The command @code{disassemble} gives an
5781 alternative way of inspecting machine instructions; see @ref{Machine
5782 Code,,Source and machine code}.
5784 All the defaults for the arguments to @code{x} are designed to make it
5785 easy to continue scanning memory with minimal specifications each time
5786 you use @code{x}. For example, after you have inspected three machine
5787 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5788 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5789 the repeat count @var{n} is used again; the other arguments default as
5790 for successive uses of @code{x}.
5792 @cindex @code{$_}, @code{$__}, and value history
5793 The addresses and contents printed by the @code{x} command are not saved
5794 in the value history because there is often too much of them and they
5795 would get in the way. Instead, @value{GDBN} makes these values available for
5796 subsequent use in expressions as values of the convenience variables
5797 @code{$_} and @code{$__}. After an @code{x} command, the last address
5798 examined is available for use in expressions in the convenience variable
5799 @code{$_}. The contents of that address, as examined, are available in
5800 the convenience variable @code{$__}.
5802 If the @code{x} command has a repeat count, the address and contents saved
5803 are from the last memory unit printed; this is not the same as the last
5804 address printed if several units were printed on the last line of output.
5806 @cindex remote memory comparison
5807 @cindex verify remote memory image
5808 When you are debugging a program running on a remote target machine
5809 (@pxref{Remote}), you may wish to verify the program's image in the
5810 remote machine's memory against the executable file you downloaded to
5811 the target. The @code{compare-sections} command is provided for such
5815 @kindex compare-sections
5816 @item compare-sections @r{[}@var{section-name}@r{]}
5817 Compare the data of a loadable section @var{section-name} in the
5818 executable file of the program being debugged with the same section in
5819 the remote machine's memory, and report any mismatches. With no
5820 arguments, compares all loadable sections. This command's
5821 availability depends on the target's support for the @code{"qCRC"}
5826 @section Automatic display
5827 @cindex automatic display
5828 @cindex display of expressions
5830 If you find that you want to print the value of an expression frequently
5831 (to see how it changes), you might want to add it to the @dfn{automatic
5832 display list} so that @value{GDBN} prints its value each time your program stops.
5833 Each expression added to the list is given a number to identify it;
5834 to remove an expression from the list, you specify that number.
5835 The automatic display looks like this:
5839 3: bar[5] = (struct hack *) 0x3804
5843 This display shows item numbers, expressions and their current values. As with
5844 displays you request manually using @code{x} or @code{print}, you can
5845 specify the output format you prefer; in fact, @code{display} decides
5846 whether to use @code{print} or @code{x} depending on how elaborate your
5847 format specification is---it uses @code{x} if you specify a unit size,
5848 or one of the two formats (@samp{i} and @samp{s}) that are only
5849 supported by @code{x}; otherwise it uses @code{print}.
5853 @item display @var{expr}
5854 Add the expression @var{expr} to the list of expressions to display
5855 each time your program stops. @xref{Expressions, ,Expressions}.
5857 @code{display} does not repeat if you press @key{RET} again after using it.
5859 @item display/@var{fmt} @var{expr}
5860 For @var{fmt} specifying only a display format and not a size or
5861 count, add the expression @var{expr} to the auto-display list but
5862 arrange to display it each time in the specified format @var{fmt}.
5863 @xref{Output Formats,,Output formats}.
5865 @item display/@var{fmt} @var{addr}
5866 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5867 number of units, add the expression @var{addr} as a memory address to
5868 be examined each time your program stops. Examining means in effect
5869 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5872 For example, @samp{display/i $pc} can be helpful, to see the machine
5873 instruction about to be executed each time execution stops (@samp{$pc}
5874 is a common name for the program counter; @pxref{Registers, ,Registers}).
5877 @kindex delete display
5879 @item undisplay @var{dnums}@dots{}
5880 @itemx delete display @var{dnums}@dots{}
5881 Remove item numbers @var{dnums} from the list of expressions to display.
5883 @code{undisplay} does not repeat if you press @key{RET} after using it.
5884 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5886 @kindex disable display
5887 @item disable display @var{dnums}@dots{}
5888 Disable the display of item numbers @var{dnums}. A disabled display
5889 item is not printed automatically, but is not forgotten. It may be
5890 enabled again later.
5892 @kindex enable display
5893 @item enable display @var{dnums}@dots{}
5894 Enable display of item numbers @var{dnums}. It becomes effective once
5895 again in auto display of its expression, until you specify otherwise.
5898 Display the current values of the expressions on the list, just as is
5899 done when your program stops.
5901 @kindex info display
5903 Print the list of expressions previously set up to display
5904 automatically, each one with its item number, but without showing the
5905 values. This includes disabled expressions, which are marked as such.
5906 It also includes expressions which would not be displayed right now
5907 because they refer to automatic variables not currently available.
5910 @cindex display disabled out of scope
5911 If a display expression refers to local variables, then it does not make
5912 sense outside the lexical context for which it was set up. Such an
5913 expression is disabled when execution enters a context where one of its
5914 variables is not defined. For example, if you give the command
5915 @code{display last_char} while inside a function with an argument
5916 @code{last_char}, @value{GDBN} displays this argument while your program
5917 continues to stop inside that function. When it stops elsewhere---where
5918 there is no variable @code{last_char}---the display is disabled
5919 automatically. The next time your program stops where @code{last_char}
5920 is meaningful, you can enable the display expression once again.
5922 @node Print Settings
5923 @section Print settings
5925 @cindex format options
5926 @cindex print settings
5927 @value{GDBN} provides the following ways to control how arrays, structures,
5928 and symbols are printed.
5931 These settings are useful for debugging programs in any language:
5935 @item set print address
5936 @itemx set print address on
5937 @cindex print/don't print memory addresses
5938 @value{GDBN} prints memory addresses showing the location of stack
5939 traces, structure values, pointer values, breakpoints, and so forth,
5940 even when it also displays the contents of those addresses. The default
5941 is @code{on}. For example, this is what a stack frame display looks like with
5942 @code{set print address on}:
5947 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5949 530 if (lquote != def_lquote)
5953 @item set print address off
5954 Do not print addresses when displaying their contents. For example,
5955 this is the same stack frame displayed with @code{set print address off}:
5959 (@value{GDBP}) set print addr off
5961 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5962 530 if (lquote != def_lquote)
5966 You can use @samp{set print address off} to eliminate all machine
5967 dependent displays from the @value{GDBN} interface. For example, with
5968 @code{print address off}, you should get the same text for backtraces on
5969 all machines---whether or not they involve pointer arguments.
5972 @item show print address
5973 Show whether or not addresses are to be printed.
5976 When @value{GDBN} prints a symbolic address, it normally prints the
5977 closest earlier symbol plus an offset. If that symbol does not uniquely
5978 identify the address (for example, it is a name whose scope is a single
5979 source file), you may need to clarify. One way to do this is with
5980 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5981 you can set @value{GDBN} to print the source file and line number when
5982 it prints a symbolic address:
5985 @item set print symbol-filename on
5986 @cindex source file and line of a symbol
5987 @cindex symbol, source file and line
5988 Tell @value{GDBN} to print the source file name and line number of a
5989 symbol in the symbolic form of an address.
5991 @item set print symbol-filename off
5992 Do not print source file name and line number of a symbol. This is the
5995 @item show print symbol-filename
5996 Show whether or not @value{GDBN} will print the source file name and
5997 line number of a symbol in the symbolic form of an address.
6000 Another situation where it is helpful to show symbol filenames and line
6001 numbers is when disassembling code; @value{GDBN} shows you the line
6002 number and source file that corresponds to each instruction.
6004 Also, you may wish to see the symbolic form only if the address being
6005 printed is reasonably close to the closest earlier symbol:
6008 @item set print max-symbolic-offset @var{max-offset}
6009 @cindex maximum value for offset of closest symbol
6010 Tell @value{GDBN} to only display the symbolic form of an address if the
6011 offset between the closest earlier symbol and the address is less than
6012 @var{max-offset}. The default is 0, which tells @value{GDBN}
6013 to always print the symbolic form of an address if any symbol precedes it.
6015 @item show print max-symbolic-offset
6016 Ask how large the maximum offset is that @value{GDBN} prints in a
6020 @cindex wild pointer, interpreting
6021 @cindex pointer, finding referent
6022 If you have a pointer and you are not sure where it points, try
6023 @samp{set print symbol-filename on}. Then you can determine the name
6024 and source file location of the variable where it points, using
6025 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6026 For example, here @value{GDBN} shows that a variable @code{ptt} points
6027 at another variable @code{t}, defined in @file{hi2.c}:
6030 (@value{GDBP}) set print symbol-filename on
6031 (@value{GDBP}) p/a ptt
6032 $4 = 0xe008 <t in hi2.c>
6036 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6037 does not show the symbol name and filename of the referent, even with
6038 the appropriate @code{set print} options turned on.
6041 Other settings control how different kinds of objects are printed:
6044 @item set print array
6045 @itemx set print array on
6046 @cindex pretty print arrays
6047 Pretty print arrays. This format is more convenient to read,
6048 but uses more space. The default is off.
6050 @item set print array off
6051 Return to compressed format for arrays.
6053 @item show print array
6054 Show whether compressed or pretty format is selected for displaying
6057 @cindex print array indexes
6058 @item set print array-indexes
6059 @itemx set print array-indexes on
6060 Print the index of each element when displaying arrays. May be more
6061 convenient to locate a given element in the array or quickly find the
6062 index of a given element in that printed array. The default is off.
6064 @item set print array-indexes off
6065 Stop printing element indexes when displaying arrays.
6067 @item show print array-indexes
6068 Show whether the index of each element is printed when displaying
6071 @item set print elements @var{number-of-elements}
6072 @cindex number of array elements to print
6073 @cindex limit on number of printed array elements
6074 Set a limit on how many elements of an array @value{GDBN} will print.
6075 If @value{GDBN} is printing a large array, it stops printing after it has
6076 printed the number of elements set by the @code{set print elements} command.
6077 This limit also applies to the display of strings.
6078 When @value{GDBN} starts, this limit is set to 200.
6079 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6081 @item show print elements
6082 Display the number of elements of a large array that @value{GDBN} will print.
6083 If the number is 0, then the printing is unlimited.
6085 @item set print repeats
6086 @cindex repeated array elements
6087 Set the threshold for suppressing display of repeated array
6088 elelments. When the number of consecutive identical elements of an
6089 array exceeds the threshold, @value{GDBN} prints the string
6090 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6091 identical repetitions, instead of displaying the identical elements
6092 themselves. Setting the threshold to zero will cause all elements to
6093 be individually printed. The default threshold is 10.
6095 @item show print repeats
6096 Display the current threshold for printing repeated identical
6099 @item set print null-stop
6100 @cindex @sc{null} elements in arrays
6101 Cause @value{GDBN} to stop printing the characters of an array when the first
6102 @sc{null} is encountered. This is useful when large arrays actually
6103 contain only short strings.
6106 @item show print null-stop
6107 Show whether @value{GDBN} stops printing an array on the first
6108 @sc{null} character.
6110 @item set print pretty on
6111 @cindex print structures in indented form
6112 @cindex indentation in structure display
6113 Cause @value{GDBN} to print structures in an indented format with one member
6114 per line, like this:
6129 @item set print pretty off
6130 Cause @value{GDBN} to print structures in a compact format, like this:
6134 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6135 meat = 0x54 "Pork"@}
6140 This is the default format.
6142 @item show print pretty
6143 Show which format @value{GDBN} is using to print structures.
6145 @item set print sevenbit-strings on
6146 @cindex eight-bit characters in strings
6147 @cindex octal escapes in strings
6148 Print using only seven-bit characters; if this option is set,
6149 @value{GDBN} displays any eight-bit characters (in strings or
6150 character values) using the notation @code{\}@var{nnn}. This setting is
6151 best if you are working in English (@sc{ascii}) and you use the
6152 high-order bit of characters as a marker or ``meta'' bit.
6154 @item set print sevenbit-strings off
6155 Print full eight-bit characters. This allows the use of more
6156 international character sets, and is the default.
6158 @item show print sevenbit-strings
6159 Show whether or not @value{GDBN} is printing only seven-bit characters.
6161 @item set print union on
6162 @cindex unions in structures, printing
6163 Tell @value{GDBN} to print unions which are contained in structures
6164 and other unions. This is the default setting.
6166 @item set print union off
6167 Tell @value{GDBN} not to print unions which are contained in
6168 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6171 @item show print union
6172 Ask @value{GDBN} whether or not it will print unions which are contained in
6173 structures and other unions.
6175 For example, given the declarations
6178 typedef enum @{Tree, Bug@} Species;
6179 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6180 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6191 struct thing foo = @{Tree, @{Acorn@}@};
6195 with @code{set print union on} in effect @samp{p foo} would print
6198 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6202 and with @code{set print union off} in effect it would print
6205 $1 = @{it = Tree, form = @{...@}@}
6209 @code{set print union} affects programs written in C-like languages
6215 These settings are of interest when debugging C@t{++} programs:
6218 @cindex demangling C@t{++} names
6219 @item set print demangle
6220 @itemx set print demangle on
6221 Print C@t{++} names in their source form rather than in the encoded
6222 (``mangled'') form passed to the assembler and linker for type-safe
6223 linkage. The default is on.
6225 @item show print demangle
6226 Show whether C@t{++} names are printed in mangled or demangled form.
6228 @item set print asm-demangle
6229 @itemx set print asm-demangle on
6230 Print C@t{++} names in their source form rather than their mangled form, even
6231 in assembler code printouts such as instruction disassemblies.
6234 @item show print asm-demangle
6235 Show whether C@t{++} names in assembly listings are printed in mangled
6238 @cindex C@t{++} symbol decoding style
6239 @cindex symbol decoding style, C@t{++}
6240 @kindex set demangle-style
6241 @item set demangle-style @var{style}
6242 Choose among several encoding schemes used by different compilers to
6243 represent C@t{++} names. The choices for @var{style} are currently:
6247 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6250 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6251 This is the default.
6254 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6257 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6260 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6261 @strong{Warning:} this setting alone is not sufficient to allow
6262 debugging @code{cfront}-generated executables. @value{GDBN} would
6263 require further enhancement to permit that.
6266 If you omit @var{style}, you will see a list of possible formats.
6268 @item show demangle-style
6269 Display the encoding style currently in use for decoding C@t{++} symbols.
6271 @item set print object
6272 @itemx set print object on
6273 @cindex derived type of an object, printing
6274 @cindex display derived types
6275 When displaying a pointer to an object, identify the @emph{actual}
6276 (derived) type of the object rather than the @emph{declared} type, using
6277 the virtual function table.
6279 @item set print object off
6280 Display only the declared type of objects, without reference to the
6281 virtual function table. This is the default setting.
6283 @item show print object
6284 Show whether actual, or declared, object types are displayed.
6286 @item set print static-members
6287 @itemx set print static-members on
6288 @cindex static members of C@t{++} objects
6289 Print static members when displaying a C@t{++} object. The default is on.
6291 @item set print static-members off
6292 Do not print static members when displaying a C@t{++} object.
6294 @item show print static-members
6295 Show whether C@t{++} static members are printed or not.
6297 @item set print pascal_static-members
6298 @itemx set print pascal_static-members on
6299 @cindex static members of Pacal objects
6300 @cindex Pacal objects, static members display
6301 Print static members when displaying a Pascal object. The default is on.
6303 @item set print pascal_static-members off
6304 Do not print static members when displaying a Pascal object.
6306 @item show print pascal_static-members
6307 Show whether Pascal static members are printed or not.
6309 @c These don't work with HP ANSI C++ yet.
6310 @item set print vtbl
6311 @itemx set print vtbl on
6312 @cindex pretty print C@t{++} virtual function tables
6313 @cindex virtual functions (C@t{++}) display
6314 @cindex VTBL display
6315 Pretty print C@t{++} virtual function tables. The default is off.
6316 (The @code{vtbl} commands do not work on programs compiled with the HP
6317 ANSI C@t{++} compiler (@code{aCC}).)
6319 @item set print vtbl off
6320 Do not pretty print C@t{++} virtual function tables.
6322 @item show print vtbl
6323 Show whether C@t{++} virtual function tables are pretty printed, or not.
6327 @section Value history
6329 @cindex value history
6330 @cindex history of values printed by @value{GDBN}
6331 Values printed by the @code{print} command are saved in the @value{GDBN}
6332 @dfn{value history}. This allows you to refer to them in other expressions.
6333 Values are kept until the symbol table is re-read or discarded
6334 (for example with the @code{file} or @code{symbol-file} commands).
6335 When the symbol table changes, the value history is discarded,
6336 since the values may contain pointers back to the types defined in the
6341 @cindex history number
6342 The values printed are given @dfn{history numbers} by which you can
6343 refer to them. These are successive integers starting with one.
6344 @code{print} shows you the history number assigned to a value by
6345 printing @samp{$@var{num} = } before the value; here @var{num} is the
6348 To refer to any previous value, use @samp{$} followed by the value's
6349 history number. The way @code{print} labels its output is designed to
6350 remind you of this. Just @code{$} refers to the most recent value in
6351 the history, and @code{$$} refers to the value before that.
6352 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6353 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6354 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6356 For example, suppose you have just printed a pointer to a structure and
6357 want to see the contents of the structure. It suffices to type
6363 If you have a chain of structures where the component @code{next} points
6364 to the next one, you can print the contents of the next one with this:
6371 You can print successive links in the chain by repeating this
6372 command---which you can do by just typing @key{RET}.
6374 Note that the history records values, not expressions. If the value of
6375 @code{x} is 4 and you type these commands:
6383 then the value recorded in the value history by the @code{print} command
6384 remains 4 even though the value of @code{x} has changed.
6389 Print the last ten values in the value history, with their item numbers.
6390 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6391 values} does not change the history.
6393 @item show values @var{n}
6394 Print ten history values centered on history item number @var{n}.
6397 Print ten history values just after the values last printed. If no more
6398 values are available, @code{show values +} produces no display.
6401 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6402 same effect as @samp{show values +}.
6404 @node Convenience Vars
6405 @section Convenience variables
6407 @cindex convenience variables
6408 @cindex user-defined variables
6409 @value{GDBN} provides @dfn{convenience variables} that you can use within
6410 @value{GDBN} to hold on to a value and refer to it later. These variables
6411 exist entirely within @value{GDBN}; they are not part of your program, and
6412 setting a convenience variable has no direct effect on further execution
6413 of your program. That is why you can use them freely.
6415 Convenience variables are prefixed with @samp{$}. Any name preceded by
6416 @samp{$} can be used for a convenience variable, unless it is one of
6417 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6418 (Value history references, in contrast, are @emph{numbers} preceded
6419 by @samp{$}. @xref{Value History, ,Value history}.)
6421 You can save a value in a convenience variable with an assignment
6422 expression, just as you would set a variable in your program.
6426 set $foo = *object_ptr
6430 would save in @code{$foo} the value contained in the object pointed to by
6433 Using a convenience variable for the first time creates it, but its
6434 value is @code{void} until you assign a new value. You can alter the
6435 value with another assignment at any time.
6437 Convenience variables have no fixed types. You can assign a convenience
6438 variable any type of value, including structures and arrays, even if
6439 that variable already has a value of a different type. The convenience
6440 variable, when used as an expression, has the type of its current value.
6443 @kindex show convenience
6444 @cindex show all user variables
6445 @item show convenience
6446 Print a list of convenience variables used so far, and their values.
6447 Abbreviated @code{show conv}.
6449 @kindex init-if-undefined
6450 @cindex convenience variables, initializing
6451 @item init-if-undefined $@var{variable} = @var{expression}
6452 Set a convenience variable if it has not already been set. This is useful
6453 for user-defined commands that keep some state. It is similar, in concept,
6454 to using local static variables with initializers in C (except that
6455 convenience variables are global). It can also be used to allow users to
6456 override default values used in a command script.
6458 If the variable is already defined then the expression is not evaluated so
6459 any side-effects do not occur.
6462 One of the ways to use a convenience variable is as a counter to be
6463 incremented or a pointer to be advanced. For example, to print
6464 a field from successive elements of an array of structures:
6468 print bar[$i++]->contents
6472 Repeat that command by typing @key{RET}.
6474 Some convenience variables are created automatically by @value{GDBN} and given
6475 values likely to be useful.
6478 @vindex $_@r{, convenience variable}
6480 The variable @code{$_} is automatically set by the @code{x} command to
6481 the last address examined (@pxref{Memory, ,Examining memory}). Other
6482 commands which provide a default address for @code{x} to examine also
6483 set @code{$_} to that address; these commands include @code{info line}
6484 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6485 except when set by the @code{x} command, in which case it is a pointer
6486 to the type of @code{$__}.
6488 @vindex $__@r{, convenience variable}
6490 The variable @code{$__} is automatically set by the @code{x} command
6491 to the value found in the last address examined. Its type is chosen
6492 to match the format in which the data was printed.
6495 @vindex $_exitcode@r{, convenience variable}
6496 The variable @code{$_exitcode} is automatically set to the exit code when
6497 the program being debugged terminates.
6500 On HP-UX systems, if you refer to a function or variable name that
6501 begins with a dollar sign, @value{GDBN} searches for a user or system
6502 name first, before it searches for a convenience variable.
6508 You can refer to machine register contents, in expressions, as variables
6509 with names starting with @samp{$}. The names of registers are different
6510 for each machine; use @code{info registers} to see the names used on
6514 @kindex info registers
6515 @item info registers
6516 Print the names and values of all registers except floating-point
6517 and vector registers (in the selected stack frame).
6519 @kindex info all-registers
6520 @cindex floating point registers
6521 @item info all-registers
6522 Print the names and values of all registers, including floating-point
6523 and vector registers (in the selected stack frame).
6525 @item info registers @var{regname} @dots{}
6526 Print the @dfn{relativized} value of each specified register @var{regname}.
6527 As discussed in detail below, register values are normally relative to
6528 the selected stack frame. @var{regname} may be any register name valid on
6529 the machine you are using, with or without the initial @samp{$}.
6532 @cindex stack pointer register
6533 @cindex program counter register
6534 @cindex process status register
6535 @cindex frame pointer register
6536 @cindex standard registers
6537 @value{GDBN} has four ``standard'' register names that are available (in
6538 expressions) on most machines---whenever they do not conflict with an
6539 architecture's canonical mnemonics for registers. The register names
6540 @code{$pc} and @code{$sp} are used for the program counter register and
6541 the stack pointer. @code{$fp} is used for a register that contains a
6542 pointer to the current stack frame, and @code{$ps} is used for a
6543 register that contains the processor status. For example,
6544 you could print the program counter in hex with
6551 or print the instruction to be executed next with
6558 or add four to the stack pointer@footnote{This is a way of removing
6559 one word from the stack, on machines where stacks grow downward in
6560 memory (most machines, nowadays). This assumes that the innermost
6561 stack frame is selected; setting @code{$sp} is not allowed when other
6562 stack frames are selected. To pop entire frames off the stack,
6563 regardless of machine architecture, use @code{return};
6564 see @ref{Returning, ,Returning from a function}.} with
6570 Whenever possible, these four standard register names are available on
6571 your machine even though the machine has different canonical mnemonics,
6572 so long as there is no conflict. The @code{info registers} command
6573 shows the canonical names. For example, on the SPARC, @code{info
6574 registers} displays the processor status register as @code{$psr} but you
6575 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6576 is an alias for the @sc{eflags} register.
6578 @value{GDBN} always considers the contents of an ordinary register as an
6579 integer when the register is examined in this way. Some machines have
6580 special registers which can hold nothing but floating point; these
6581 registers are considered to have floating point values. There is no way
6582 to refer to the contents of an ordinary register as floating point value
6583 (although you can @emph{print} it as a floating point value with
6584 @samp{print/f $@var{regname}}).
6586 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6587 means that the data format in which the register contents are saved by
6588 the operating system is not the same one that your program normally
6589 sees. For example, the registers of the 68881 floating point
6590 coprocessor are always saved in ``extended'' (raw) format, but all C
6591 programs expect to work with ``double'' (virtual) format. In such
6592 cases, @value{GDBN} normally works with the virtual format only (the format
6593 that makes sense for your program), but the @code{info registers} command
6594 prints the data in both formats.
6596 @cindex SSE registers (x86)
6597 @cindex MMX registers (x86)
6598 Some machines have special registers whose contents can be interpreted
6599 in several different ways. For example, modern x86-based machines
6600 have SSE and MMX registers that can hold several values packed
6601 together in several different formats. @value{GDBN} refers to such
6602 registers in @code{struct} notation:
6605 (@value{GDBP}) print $xmm1
6607 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6608 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6609 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6610 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6611 v4_int32 = @{0, 20657912, 11, 13@},
6612 v2_int64 = @{88725056443645952, 55834574859@},
6613 uint128 = 0x0000000d0000000b013b36f800000000
6618 To set values of such registers, you need to tell @value{GDBN} which
6619 view of the register you wish to change, as if you were assigning
6620 value to a @code{struct} member:
6623 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6626 Normally, register values are relative to the selected stack frame
6627 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6628 value that the register would contain if all stack frames farther in
6629 were exited and their saved registers restored. In order to see the
6630 true contents of hardware registers, you must select the innermost
6631 frame (with @samp{frame 0}).
6633 However, @value{GDBN} must deduce where registers are saved, from the machine
6634 code generated by your compiler. If some registers are not saved, or if
6635 @value{GDBN} is unable to locate the saved registers, the selected stack
6636 frame makes no difference.
6638 @node Floating Point Hardware
6639 @section Floating point hardware
6640 @cindex floating point
6642 Depending on the configuration, @value{GDBN} may be able to give
6643 you more information about the status of the floating point hardware.
6648 Display hardware-dependent information about the floating
6649 point unit. The exact contents and layout vary depending on the
6650 floating point chip. Currently, @samp{info float} is supported on
6651 the ARM and x86 machines.
6655 @section Vector Unit
6658 Depending on the configuration, @value{GDBN} may be able to give you
6659 more information about the status of the vector unit.
6664 Display information about the vector unit. The exact contents and
6665 layout vary depending on the hardware.
6668 @node OS Information
6669 @section Operating system auxiliary information
6670 @cindex OS information
6672 @value{GDBN} provides interfaces to useful OS facilities that can help
6673 you debug your program.
6675 @cindex @code{ptrace} system call
6676 @cindex @code{struct user} contents
6677 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6678 machines), it interfaces with the inferior via the @code{ptrace}
6679 system call. The operating system creates a special sata structure,
6680 called @code{struct user}, for this interface. You can use the
6681 command @code{info udot} to display the contents of this data
6687 Display the contents of the @code{struct user} maintained by the OS
6688 kernel for the program being debugged. @value{GDBN} displays the
6689 contents of @code{struct user} as a list of hex numbers, similar to
6690 the @code{examine} command.
6693 @cindex auxiliary vector
6694 @cindex vector, auxiliary
6695 Some operating systems supply an @dfn{auxiliary vector} to programs at
6696 startup. This is akin to the arguments and environment that you
6697 specify for a program, but contains a system-dependent variety of
6698 binary values that tell system libraries important details about the
6699 hardware, operating system, and process. Each value's purpose is
6700 identified by an integer tag; the meanings are well-known but system-specific.
6701 Depending on the configuration and operating system facilities,
6702 @value{GDBN} may be able to show you this information. For remote
6703 targets, this functionality may further depend on the remote stub's
6704 support of the @samp{qXfer:auxv:read} packet, see @ref{Remote
6705 configuration, auxiliary vector}.
6710 Display the auxiliary vector of the inferior, which can be either a
6711 live process or a core dump file. @value{GDBN} prints each tag value
6712 numerically, and also shows names and text descriptions for recognized
6713 tags. Some values in the vector are numbers, some bit masks, and some
6714 pointers to strings or other data. @value{GDBN} displays each value in the
6715 most appropriate form for a recognized tag, and in hexadecimal for
6716 an unrecognized tag.
6720 @node Memory Region Attributes
6721 @section Memory region attributes
6722 @cindex memory region attributes
6724 @dfn{Memory region attributes} allow you to describe special handling
6725 required by regions of your target's memory. @value{GDBN} uses
6726 attributes to determine whether to allow certain types of memory
6727 accesses; whether to use specific width accesses; and whether to cache
6728 target memory. By default the description of memory regions is
6729 fetched from the target (if the current target supports this), but the
6730 user can override the fetched regions.
6732 Defined memory regions can be individually enabled and disabled. When a
6733 memory region is disabled, @value{GDBN} uses the default attributes when
6734 accessing memory in that region. Similarly, if no memory regions have
6735 been defined, @value{GDBN} uses the default attributes when accessing
6738 When a memory region is defined, it is given a number to identify it;
6739 to enable, disable, or remove a memory region, you specify that number.
6743 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6744 Define a memory region bounded by @var{lower} and @var{upper} with
6745 attributes @var{attributes}@dots{}, and add it to the list of regions
6746 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6747 case: it is treated as the the target's maximum memory address.
6748 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6751 Discard any user changes to the memory regions and use target-supplied
6752 regions, if available, or no regions if the target does not support.
6755 @item delete mem @var{nums}@dots{}
6756 Remove memory regions @var{nums}@dots{} from the list of regions
6757 monitored by @value{GDBN}.
6760 @item disable mem @var{nums}@dots{}
6761 Disable monitoring of memory regions @var{nums}@dots{}.
6762 A disabled memory region is not forgotten.
6763 It may be enabled again later.
6766 @item enable mem @var{nums}@dots{}
6767 Enable monitoring of memory regions @var{nums}@dots{}.
6771 Print a table of all defined memory regions, with the following columns
6775 @item Memory Region Number
6776 @item Enabled or Disabled.
6777 Enabled memory regions are marked with @samp{y}.
6778 Disabled memory regions are marked with @samp{n}.
6781 The address defining the inclusive lower bound of the memory region.
6784 The address defining the exclusive upper bound of the memory region.
6787 The list of attributes set for this memory region.
6792 @subsection Attributes
6794 @subsubsection Memory Access Mode
6795 The access mode attributes set whether @value{GDBN} may make read or
6796 write accesses to a memory region.
6798 While these attributes prevent @value{GDBN} from performing invalid
6799 memory accesses, they do nothing to prevent the target system, I/O DMA,
6800 etc.@: from accessing memory.
6804 Memory is read only.
6806 Memory is write only.
6808 Memory is read/write. This is the default.
6811 @subsubsection Memory Access Size
6812 The acccess size attributes tells @value{GDBN} to use specific sized
6813 accesses in the memory region. Often memory mapped device registers
6814 require specific sized accesses. If no access size attribute is
6815 specified, @value{GDBN} may use accesses of any size.
6819 Use 8 bit memory accesses.
6821 Use 16 bit memory accesses.
6823 Use 32 bit memory accesses.
6825 Use 64 bit memory accesses.
6828 @c @subsubsection Hardware/Software Breakpoints
6829 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6830 @c will use hardware or software breakpoints for the internal breakpoints
6831 @c used by the step, next, finish, until, etc. commands.
6835 @c Always use hardware breakpoints
6836 @c @item swbreak (default)
6839 @subsubsection Data Cache
6840 The data cache attributes set whether @value{GDBN} will cache target
6841 memory. While this generally improves performance by reducing debug
6842 protocol overhead, it can lead to incorrect results because @value{GDBN}
6843 does not know about volatile variables or memory mapped device
6848 Enable @value{GDBN} to cache target memory.
6850 Disable @value{GDBN} from caching target memory. This is the default.
6853 @c @subsubsection Memory Write Verification
6854 @c The memory write verification attributes set whether @value{GDBN}
6855 @c will re-reads data after each write to verify the write was successful.
6859 @c @item noverify (default)
6862 @node Dump/Restore Files
6863 @section Copy between memory and a file
6864 @cindex dump/restore files
6865 @cindex append data to a file
6866 @cindex dump data to a file
6867 @cindex restore data from a file
6869 You can use the commands @code{dump}, @code{append}, and
6870 @code{restore} to copy data between target memory and a file. The
6871 @code{dump} and @code{append} commands write data to a file, and the
6872 @code{restore} command reads data from a file back into the inferior's
6873 memory. Files may be in binary, Motorola S-record, Intel hex, or
6874 Tektronix Hex format; however, @value{GDBN} can only append to binary
6880 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6881 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6882 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6883 or the value of @var{expr}, to @var{filename} in the given format.
6885 The @var{format} parameter may be any one of:
6892 Motorola S-record format.
6894 Tektronix Hex format.
6897 @value{GDBN} uses the same definitions of these formats as the
6898 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6899 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6903 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6904 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6905 Append the contents of memory from @var{start_addr} to @var{end_addr},
6906 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6907 (@value{GDBN} can only append data to files in raw binary form.)
6910 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6911 Restore the contents of file @var{filename} into memory. The
6912 @code{restore} command can automatically recognize any known @sc{bfd}
6913 file format, except for raw binary. To restore a raw binary file you
6914 must specify the optional keyword @code{binary} after the filename.
6916 If @var{bias} is non-zero, its value will be added to the addresses
6917 contained in the file. Binary files always start at address zero, so
6918 they will be restored at address @var{bias}. Other bfd files have
6919 a built-in location; they will be restored at offset @var{bias}
6922 If @var{start} and/or @var{end} are non-zero, then only data between
6923 file offset @var{start} and file offset @var{end} will be restored.
6924 These offsets are relative to the addresses in the file, before
6925 the @var{bias} argument is applied.
6929 @node Core File Generation
6930 @section How to Produce a Core File from Your Program
6931 @cindex dump core from inferior
6933 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6934 image of a running process and its process status (register values
6935 etc.). Its primary use is post-mortem debugging of a program that
6936 crashed while it ran outside a debugger. A program that crashes
6937 automatically produces a core file, unless this feature is disabled by
6938 the user. @xref{Files}, for information on invoking @value{GDBN} in
6939 the post-mortem debugging mode.
6941 Occasionally, you may wish to produce a core file of the program you
6942 are debugging in order to preserve a snapshot of its state.
6943 @value{GDBN} has a special command for that.
6947 @kindex generate-core-file
6948 @item generate-core-file [@var{file}]
6949 @itemx gcore [@var{file}]
6950 Produce a core dump of the inferior process. The optional argument
6951 @var{file} specifies the file name where to put the core dump. If not
6952 specified, the file name defaults to @file{core.@var{pid}}, where
6953 @var{pid} is the inferior process ID.
6955 Note that this command is implemented only for some systems (as of
6956 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6959 @node Character Sets
6960 @section Character Sets
6961 @cindex character sets
6963 @cindex translating between character sets
6964 @cindex host character set
6965 @cindex target character set
6967 If the program you are debugging uses a different character set to
6968 represent characters and strings than the one @value{GDBN} uses itself,
6969 @value{GDBN} can automatically translate between the character sets for
6970 you. The character set @value{GDBN} uses we call the @dfn{host
6971 character set}; the one the inferior program uses we call the
6972 @dfn{target character set}.
6974 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6975 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6976 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6977 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6978 then the host character set is Latin-1, and the target character set is
6979 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6980 target-charset EBCDIC-US}, then @value{GDBN} translates between
6981 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6982 character and string literals in expressions.
6984 @value{GDBN} has no way to automatically recognize which character set
6985 the inferior program uses; you must tell it, using the @code{set
6986 target-charset} command, described below.
6988 Here are the commands for controlling @value{GDBN}'s character set
6992 @item set target-charset @var{charset}
6993 @kindex set target-charset
6994 Set the current target character set to @var{charset}. We list the
6995 character set names @value{GDBN} recognizes below, but if you type
6996 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6997 list the target character sets it supports.
7001 @item set host-charset @var{charset}
7002 @kindex set host-charset
7003 Set the current host character set to @var{charset}.
7005 By default, @value{GDBN} uses a host character set appropriate to the
7006 system it is running on; you can override that default using the
7007 @code{set host-charset} command.
7009 @value{GDBN} can only use certain character sets as its host character
7010 set. We list the character set names @value{GDBN} recognizes below, and
7011 indicate which can be host character sets, but if you type
7012 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7013 list the host character sets it supports.
7015 @item set charset @var{charset}
7017 Set the current host and target character sets to @var{charset}. As
7018 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7019 @value{GDBN} will list the name of the character sets that can be used
7020 for both host and target.
7024 @kindex show charset
7025 Show the names of the current host and target charsets.
7027 @itemx show host-charset
7028 @kindex show host-charset
7029 Show the name of the current host charset.
7031 @itemx show target-charset
7032 @kindex show target-charset
7033 Show the name of the current target charset.
7037 @value{GDBN} currently includes support for the following character
7043 @cindex ASCII character set
7044 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7048 @cindex ISO 8859-1 character set
7049 @cindex ISO Latin 1 character set
7050 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7051 characters needed for French, German, and Spanish. @value{GDBN} can use
7052 this as its host character set.
7056 @cindex EBCDIC character set
7057 @cindex IBM1047 character set
7058 Variants of the @sc{ebcdic} character set, used on some of IBM's
7059 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7060 @value{GDBN} cannot use these as its host character set.
7064 Note that these are all single-byte character sets. More work inside
7065 GDB is needed to support multi-byte or variable-width character
7066 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7068 Here is an example of @value{GDBN}'s character set support in action.
7069 Assume that the following source code has been placed in the file
7070 @file{charset-test.c}:
7076 = @{72, 101, 108, 108, 111, 44, 32, 119,
7077 111, 114, 108, 100, 33, 10, 0@};
7078 char ibm1047_hello[]
7079 = @{200, 133, 147, 147, 150, 107, 64, 166,
7080 150, 153, 147, 132, 90, 37, 0@};
7084 printf ("Hello, world!\n");
7088 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7089 containing the string @samp{Hello, world!} followed by a newline,
7090 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7092 We compile the program, and invoke the debugger on it:
7095 $ gcc -g charset-test.c -o charset-test
7096 $ gdb -nw charset-test
7097 GNU gdb 2001-12-19-cvs
7098 Copyright 2001 Free Software Foundation, Inc.
7103 We can use the @code{show charset} command to see what character sets
7104 @value{GDBN} is currently using to interpret and display characters and
7108 (@value{GDBP}) show charset
7109 The current host and target character set is `ISO-8859-1'.
7113 For the sake of printing this manual, let's use @sc{ascii} as our
7114 initial character set:
7116 (@value{GDBP}) set charset ASCII
7117 (@value{GDBP}) show charset
7118 The current host and target character set is `ASCII'.
7122 Let's assume that @sc{ascii} is indeed the correct character set for our
7123 host system --- in other words, let's assume that if @value{GDBN} prints
7124 characters using the @sc{ascii} character set, our terminal will display
7125 them properly. Since our current target character set is also
7126 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7129 (@value{GDBP}) print ascii_hello
7130 $1 = 0x401698 "Hello, world!\n"
7131 (@value{GDBP}) print ascii_hello[0]
7136 @value{GDBN} uses the target character set for character and string
7137 literals you use in expressions:
7140 (@value{GDBP}) print '+'
7145 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7148 @value{GDBN} relies on the user to tell it which character set the
7149 target program uses. If we print @code{ibm1047_hello} while our target
7150 character set is still @sc{ascii}, we get jibberish:
7153 (@value{GDBP}) print ibm1047_hello
7154 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7155 (@value{GDBP}) print ibm1047_hello[0]
7160 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7161 @value{GDBN} tells us the character sets it supports:
7164 (@value{GDBP}) set target-charset
7165 ASCII EBCDIC-US IBM1047 ISO-8859-1
7166 (@value{GDBP}) set target-charset
7169 We can select @sc{ibm1047} as our target character set, and examine the
7170 program's strings again. Now the @sc{ascii} string is wrong, but
7171 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7172 target character set, @sc{ibm1047}, to the host character set,
7173 @sc{ascii}, and they display correctly:
7176 (@value{GDBP}) set target-charset IBM1047
7177 (@value{GDBP}) show charset
7178 The current host character set is `ASCII'.
7179 The current target character set is `IBM1047'.
7180 (@value{GDBP}) print ascii_hello
7181 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7182 (@value{GDBP}) print ascii_hello[0]
7184 (@value{GDBP}) print ibm1047_hello
7185 $8 = 0x4016a8 "Hello, world!\n"
7186 (@value{GDBP}) print ibm1047_hello[0]
7191 As above, @value{GDBN} uses the target character set for character and
7192 string literals you use in expressions:
7195 (@value{GDBP}) print '+'
7200 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7203 @node Caching Remote Data
7204 @section Caching Data of Remote Targets
7205 @cindex caching data of remote targets
7207 @value{GDBN} can cache data exchanged between the debugger and a
7208 remote target (@pxref{Remote}). Such caching generally improves
7209 performance, because it reduces the overhead of the remote protocol by
7210 bundling memory reads and writes into large chunks. Unfortunately,
7211 @value{GDBN} does not currently know anything about volatile
7212 registers, and thus data caching will produce incorrect results when
7213 volatile registers are in use.
7216 @kindex set remotecache
7217 @item set remotecache on
7218 @itemx set remotecache off
7219 Set caching state for remote targets. When @code{ON}, use data
7220 caching. By default, this option is @code{OFF}.
7222 @kindex show remotecache
7223 @item show remotecache
7224 Show the current state of data caching for remote targets.
7228 Print the information about the data cache performance. The
7229 information displayed includes: the dcache width and depth; and for
7230 each cache line, how many times it was referenced, and its data and
7231 state (dirty, bad, ok, etc.). This command is useful for debugging
7232 the data cache operation.
7237 @chapter C Preprocessor Macros
7239 Some languages, such as C and C@t{++}, provide a way to define and invoke
7240 ``preprocessor macros'' which expand into strings of tokens.
7241 @value{GDBN} can evaluate expressions containing macro invocations, show
7242 the result of macro expansion, and show a macro's definition, including
7243 where it was defined.
7245 You may need to compile your program specially to provide @value{GDBN}
7246 with information about preprocessor macros. Most compilers do not
7247 include macros in their debugging information, even when you compile
7248 with the @option{-g} flag. @xref{Compilation}.
7250 A program may define a macro at one point, remove that definition later,
7251 and then provide a different definition after that. Thus, at different
7252 points in the program, a macro may have different definitions, or have
7253 no definition at all. If there is a current stack frame, @value{GDBN}
7254 uses the macros in scope at that frame's source code line. Otherwise,
7255 @value{GDBN} uses the macros in scope at the current listing location;
7258 At the moment, @value{GDBN} does not support the @code{##}
7259 token-splicing operator, the @code{#} stringification operator, or
7260 variable-arity macros.
7262 Whenever @value{GDBN} evaluates an expression, it always expands any
7263 macro invocations present in the expression. @value{GDBN} also provides
7264 the following commands for working with macros explicitly.
7268 @kindex macro expand
7269 @cindex macro expansion, showing the results of preprocessor
7270 @cindex preprocessor macro expansion, showing the results of
7271 @cindex expanding preprocessor macros
7272 @item macro expand @var{expression}
7273 @itemx macro exp @var{expression}
7274 Show the results of expanding all preprocessor macro invocations in
7275 @var{expression}. Since @value{GDBN} simply expands macros, but does
7276 not parse the result, @var{expression} need not be a valid expression;
7277 it can be any string of tokens.
7280 @item macro expand-once @var{expression}
7281 @itemx macro exp1 @var{expression}
7282 @cindex expand macro once
7283 @i{(This command is not yet implemented.)} Show the results of
7284 expanding those preprocessor macro invocations that appear explicitly in
7285 @var{expression}. Macro invocations appearing in that expansion are
7286 left unchanged. This command allows you to see the effect of a
7287 particular macro more clearly, without being confused by further
7288 expansions. Since @value{GDBN} simply expands macros, but does not
7289 parse the result, @var{expression} need not be a valid expression; it
7290 can be any string of tokens.
7293 @cindex macro definition, showing
7294 @cindex definition, showing a macro's
7295 @item info macro @var{macro}
7296 Show the definition of the macro named @var{macro}, and describe the
7297 source location where that definition was established.
7299 @kindex macro define
7300 @cindex user-defined macros
7301 @cindex defining macros interactively
7302 @cindex macros, user-defined
7303 @item macro define @var{macro} @var{replacement-list}
7304 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7305 @i{(This command is not yet implemented.)} Introduce a definition for a
7306 preprocessor macro named @var{macro}, invocations of which are replaced
7307 by the tokens given in @var{replacement-list}. The first form of this
7308 command defines an ``object-like'' macro, which takes no arguments; the
7309 second form defines a ``function-like'' macro, which takes the arguments
7310 given in @var{arglist}.
7312 A definition introduced by this command is in scope in every expression
7313 evaluated in @value{GDBN}, until it is removed with the @command{macro
7314 undef} command, described below. The definition overrides all
7315 definitions for @var{macro} present in the program being debugged, as
7316 well as any previous user-supplied definition.
7319 @item macro undef @var{macro}
7320 @i{(This command is not yet implemented.)} Remove any user-supplied
7321 definition for the macro named @var{macro}. This command only affects
7322 definitions provided with the @command{macro define} command, described
7323 above; it cannot remove definitions present in the program being
7328 @i{(This command is not yet implemented.)} List all the macros
7329 defined using the @code{macro define} command.
7332 @cindex macros, example of debugging with
7333 Here is a transcript showing the above commands in action. First, we
7334 show our source files:
7342 #define ADD(x) (M + x)
7347 printf ("Hello, world!\n");
7349 printf ("We're so creative.\n");
7351 printf ("Goodbye, world!\n");
7358 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7359 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7360 compiler includes information about preprocessor macros in the debugging
7364 $ gcc -gdwarf-2 -g3 sample.c -o sample
7368 Now, we start @value{GDBN} on our sample program:
7372 GNU gdb 2002-05-06-cvs
7373 Copyright 2002 Free Software Foundation, Inc.
7374 GDB is free software, @dots{}
7378 We can expand macros and examine their definitions, even when the
7379 program is not running. @value{GDBN} uses the current listing position
7380 to decide which macro definitions are in scope:
7383 (@value{GDBP}) list main
7386 5 #define ADD(x) (M + x)
7391 10 printf ("Hello, world!\n");
7393 12 printf ("We're so creative.\n");
7394 (@value{GDBP}) info macro ADD
7395 Defined at /home/jimb/gdb/macros/play/sample.c:5
7396 #define ADD(x) (M + x)
7397 (@value{GDBP}) info macro Q
7398 Defined at /home/jimb/gdb/macros/play/sample.h:1
7399 included at /home/jimb/gdb/macros/play/sample.c:2
7401 (@value{GDBP}) macro expand ADD(1)
7402 expands to: (42 + 1)
7403 (@value{GDBP}) macro expand-once ADD(1)
7404 expands to: once (M + 1)
7408 In the example above, note that @command{macro expand-once} expands only
7409 the macro invocation explicit in the original text --- the invocation of
7410 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7411 which was introduced by @code{ADD}.
7413 Once the program is running, GDB uses the macro definitions in force at
7414 the source line of the current stack frame:
7417 (@value{GDBP}) break main
7418 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7420 Starting program: /home/jimb/gdb/macros/play/sample
7422 Breakpoint 1, main () at sample.c:10
7423 10 printf ("Hello, world!\n");
7427 At line 10, the definition of the macro @code{N} at line 9 is in force:
7430 (@value{GDBP}) info macro N
7431 Defined at /home/jimb/gdb/macros/play/sample.c:9
7433 (@value{GDBP}) macro expand N Q M
7435 (@value{GDBP}) print N Q M
7440 As we step over directives that remove @code{N}'s definition, and then
7441 give it a new definition, @value{GDBN} finds the definition (or lack
7442 thereof) in force at each point:
7447 12 printf ("We're so creative.\n");
7448 (@value{GDBP}) info macro N
7449 The symbol `N' has no definition as a C/C++ preprocessor macro
7450 at /home/jimb/gdb/macros/play/sample.c:12
7453 14 printf ("Goodbye, world!\n");
7454 (@value{GDBP}) info macro N
7455 Defined at /home/jimb/gdb/macros/play/sample.c:13
7457 (@value{GDBP}) macro expand N Q M
7458 expands to: 1729 < 42
7459 (@value{GDBP}) print N Q M
7466 @chapter Tracepoints
7467 @c This chapter is based on the documentation written by Michael
7468 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7471 In some applications, it is not feasible for the debugger to interrupt
7472 the program's execution long enough for the developer to learn
7473 anything helpful about its behavior. If the program's correctness
7474 depends on its real-time behavior, delays introduced by a debugger
7475 might cause the program to change its behavior drastically, or perhaps
7476 fail, even when the code itself is correct. It is useful to be able
7477 to observe the program's behavior without interrupting it.
7479 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7480 specify locations in the program, called @dfn{tracepoints}, and
7481 arbitrary expressions to evaluate when those tracepoints are reached.
7482 Later, using the @code{tfind} command, you can examine the values
7483 those expressions had when the program hit the tracepoints. The
7484 expressions may also denote objects in memory---structures or arrays,
7485 for example---whose values @value{GDBN} should record; while visiting
7486 a particular tracepoint, you may inspect those objects as if they were
7487 in memory at that moment. However, because @value{GDBN} records these
7488 values without interacting with you, it can do so quickly and
7489 unobtrusively, hopefully not disturbing the program's behavior.
7491 The tracepoint facility is currently available only for remote
7492 targets. @xref{Targets}. In addition, your remote target must know
7493 how to collect trace data. This functionality is implemented in the
7494 remote stub; however, none of the stubs distributed with @value{GDBN}
7495 support tracepoints as of this writing. The format of the remote
7496 packets used to implement tracepoints are described in @ref{Tracepoint
7499 This chapter describes the tracepoint commands and features.
7503 * Analyze Collected Data::
7504 * Tracepoint Variables::
7507 @node Set Tracepoints
7508 @section Commands to Set Tracepoints
7510 Before running such a @dfn{trace experiment}, an arbitrary number of
7511 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7512 tracepoint has a number assigned to it by @value{GDBN}. Like with
7513 breakpoints, tracepoint numbers are successive integers starting from
7514 one. Many of the commands associated with tracepoints take the
7515 tracepoint number as their argument, to identify which tracepoint to
7518 For each tracepoint, you can specify, in advance, some arbitrary set
7519 of data that you want the target to collect in the trace buffer when
7520 it hits that tracepoint. The collected data can include registers,
7521 local variables, or global data. Later, you can use @value{GDBN}
7522 commands to examine the values these data had at the time the
7525 This section describes commands to set tracepoints and associated
7526 conditions and actions.
7529 * Create and Delete Tracepoints::
7530 * Enable and Disable Tracepoints::
7531 * Tracepoint Passcounts::
7532 * Tracepoint Actions::
7533 * Listing Tracepoints::
7534 * Starting and Stopping Trace Experiment::
7537 @node Create and Delete Tracepoints
7538 @subsection Create and Delete Tracepoints
7541 @cindex set tracepoint
7544 The @code{trace} command is very similar to the @code{break} command.
7545 Its argument can be a source line, a function name, or an address in
7546 the target program. @xref{Set Breaks}. The @code{trace} command
7547 defines a tracepoint, which is a point in the target program where the
7548 debugger will briefly stop, collect some data, and then allow the
7549 program to continue. Setting a tracepoint or changing its commands
7550 doesn't take effect until the next @code{tstart} command; thus, you
7551 cannot change the tracepoint attributes once a trace experiment is
7554 Here are some examples of using the @code{trace} command:
7557 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7559 (@value{GDBP}) @b{trace +2} // 2 lines forward
7561 (@value{GDBP}) @b{trace my_function} // first source line of function
7563 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7565 (@value{GDBP}) @b{trace *0x2117c4} // an address
7569 You can abbreviate @code{trace} as @code{tr}.
7572 @cindex last tracepoint number
7573 @cindex recent tracepoint number
7574 @cindex tracepoint number
7575 The convenience variable @code{$tpnum} records the tracepoint number
7576 of the most recently set tracepoint.
7578 @kindex delete tracepoint
7579 @cindex tracepoint deletion
7580 @item delete tracepoint @r{[}@var{num}@r{]}
7581 Permanently delete one or more tracepoints. With no argument, the
7582 default is to delete all tracepoints.
7587 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7589 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7593 You can abbreviate this command as @code{del tr}.
7596 @node Enable and Disable Tracepoints
7597 @subsection Enable and Disable Tracepoints
7600 @kindex disable tracepoint
7601 @item disable tracepoint @r{[}@var{num}@r{]}
7602 Disable tracepoint @var{num}, or all tracepoints if no argument
7603 @var{num} is given. A disabled tracepoint will have no effect during
7604 the next trace experiment, but it is not forgotten. You can re-enable
7605 a disabled tracepoint using the @code{enable tracepoint} command.
7607 @kindex enable tracepoint
7608 @item enable tracepoint @r{[}@var{num}@r{]}
7609 Enable tracepoint @var{num}, or all tracepoints. The enabled
7610 tracepoints will become effective the next time a trace experiment is
7614 @node Tracepoint Passcounts
7615 @subsection Tracepoint Passcounts
7619 @cindex tracepoint pass count
7620 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7621 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7622 automatically stop a trace experiment. If a tracepoint's passcount is
7623 @var{n}, then the trace experiment will be automatically stopped on
7624 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7625 @var{num} is not specified, the @code{passcount} command sets the
7626 passcount of the most recently defined tracepoint. If no passcount is
7627 given, the trace experiment will run until stopped explicitly by the
7633 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7634 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7636 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7637 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7638 (@value{GDBP}) @b{trace foo}
7639 (@value{GDBP}) @b{pass 3}
7640 (@value{GDBP}) @b{trace bar}
7641 (@value{GDBP}) @b{pass 2}
7642 (@value{GDBP}) @b{trace baz}
7643 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7644 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7645 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7646 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7650 @node Tracepoint Actions
7651 @subsection Tracepoint Action Lists
7655 @cindex tracepoint actions
7656 @item actions @r{[}@var{num}@r{]}
7657 This command will prompt for a list of actions to be taken when the
7658 tracepoint is hit. If the tracepoint number @var{num} is not
7659 specified, this command sets the actions for the one that was most
7660 recently defined (so that you can define a tracepoint and then say
7661 @code{actions} without bothering about its number). You specify the
7662 actions themselves on the following lines, one action at a time, and
7663 terminate the actions list with a line containing just @code{end}. So
7664 far, the only defined actions are @code{collect} and
7665 @code{while-stepping}.
7667 @cindex remove actions from a tracepoint
7668 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7669 and follow it immediately with @samp{end}.
7672 (@value{GDBP}) @b{collect @var{data}} // collect some data
7674 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7676 (@value{GDBP}) @b{end} // signals the end of actions.
7679 In the following example, the action list begins with @code{collect}
7680 commands indicating the things to be collected when the tracepoint is
7681 hit. Then, in order to single-step and collect additional data
7682 following the tracepoint, a @code{while-stepping} command is used,
7683 followed by the list of things to be collected while stepping. The
7684 @code{while-stepping} command is terminated by its own separate
7685 @code{end} command. Lastly, the action list is terminated by an
7689 (@value{GDBP}) @b{trace foo}
7690 (@value{GDBP}) @b{actions}
7691 Enter actions for tracepoint 1, one per line:
7700 @kindex collect @r{(tracepoints)}
7701 @item collect @var{expr1}, @var{expr2}, @dots{}
7702 Collect values of the given expressions when the tracepoint is hit.
7703 This command accepts a comma-separated list of any valid expressions.
7704 In addition to global, static, or local variables, the following
7705 special arguments are supported:
7709 collect all registers
7712 collect all function arguments
7715 collect all local variables.
7718 You can give several consecutive @code{collect} commands, each one
7719 with a single argument, or one @code{collect} command with several
7720 arguments separated by commas: the effect is the same.
7722 The command @code{info scope} (@pxref{Symbols, info scope}) is
7723 particularly useful for figuring out what data to collect.
7725 @kindex while-stepping @r{(tracepoints)}
7726 @item while-stepping @var{n}
7727 Perform @var{n} single-step traces after the tracepoint, collecting
7728 new data at each step. The @code{while-stepping} command is
7729 followed by the list of what to collect while stepping (followed by
7730 its own @code{end} command):
7734 > collect $regs, myglobal
7740 You may abbreviate @code{while-stepping} as @code{ws} or
7744 @node Listing Tracepoints
7745 @subsection Listing Tracepoints
7748 @kindex info tracepoints
7750 @cindex information about tracepoints
7751 @item info tracepoints @r{[}@var{num}@r{]}
7752 Display information about the tracepoint @var{num}. If you don't specify
7753 a tracepoint number, displays information about all the tracepoints
7754 defined so far. For each tracepoint, the following information is
7761 whether it is enabled or disabled
7765 its passcount as given by the @code{passcount @var{n}} command
7767 its step count as given by the @code{while-stepping @var{n}} command
7769 where in the source files is the tracepoint set
7771 its action list as given by the @code{actions} command
7775 (@value{GDBP}) @b{info trace}
7776 Num Enb Address PassC StepC What
7777 1 y 0x002117c4 0 0 <gdb_asm>
7778 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7779 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7784 This command can be abbreviated @code{info tp}.
7787 @node Starting and Stopping Trace Experiment
7788 @subsection Starting and Stopping Trace Experiment
7792 @cindex start a new trace experiment
7793 @cindex collected data discarded
7795 This command takes no arguments. It starts the trace experiment, and
7796 begins collecting data. This has the side effect of discarding all
7797 the data collected in the trace buffer during the previous trace
7801 @cindex stop a running trace experiment
7803 This command takes no arguments. It ends the trace experiment, and
7804 stops collecting data.
7806 @strong{Note}: a trace experiment and data collection may stop
7807 automatically if any tracepoint's passcount is reached
7808 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7811 @cindex status of trace data collection
7812 @cindex trace experiment, status of
7814 This command displays the status of the current trace data
7818 Here is an example of the commands we described so far:
7821 (@value{GDBP}) @b{trace gdb_c_test}
7822 (@value{GDBP}) @b{actions}
7823 Enter actions for tracepoint #1, one per line.
7824 > collect $regs,$locals,$args
7829 (@value{GDBP}) @b{tstart}
7830 [time passes @dots{}]
7831 (@value{GDBP}) @b{tstop}
7835 @node Analyze Collected Data
7836 @section Using the collected data
7838 After the tracepoint experiment ends, you use @value{GDBN} commands
7839 for examining the trace data. The basic idea is that each tracepoint
7840 collects a trace @dfn{snapshot} every time it is hit and another
7841 snapshot every time it single-steps. All these snapshots are
7842 consecutively numbered from zero and go into a buffer, and you can
7843 examine them later. The way you examine them is to @dfn{focus} on a
7844 specific trace snapshot. When the remote stub is focused on a trace
7845 snapshot, it will respond to all @value{GDBN} requests for memory and
7846 registers by reading from the buffer which belongs to that snapshot,
7847 rather than from @emph{real} memory or registers of the program being
7848 debugged. This means that @strong{all} @value{GDBN} commands
7849 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7850 behave as if we were currently debugging the program state as it was
7851 when the tracepoint occurred. Any requests for data that are not in
7852 the buffer will fail.
7855 * tfind:: How to select a trace snapshot
7856 * tdump:: How to display all data for a snapshot
7857 * save-tracepoints:: How to save tracepoints for a future run
7861 @subsection @code{tfind @var{n}}
7864 @cindex select trace snapshot
7865 @cindex find trace snapshot
7866 The basic command for selecting a trace snapshot from the buffer is
7867 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7868 counting from zero. If no argument @var{n} is given, the next
7869 snapshot is selected.
7871 Here are the various forms of using the @code{tfind} command.
7875 Find the first snapshot in the buffer. This is a synonym for
7876 @code{tfind 0} (since 0 is the number of the first snapshot).
7879 Stop debugging trace snapshots, resume @emph{live} debugging.
7882 Same as @samp{tfind none}.
7885 No argument means find the next trace snapshot.
7888 Find the previous trace snapshot before the current one. This permits
7889 retracing earlier steps.
7891 @item tfind tracepoint @var{num}
7892 Find the next snapshot associated with tracepoint @var{num}. Search
7893 proceeds forward from the last examined trace snapshot. If no
7894 argument @var{num} is given, it means find the next snapshot collected
7895 for the same tracepoint as the current snapshot.
7897 @item tfind pc @var{addr}
7898 Find the next snapshot associated with the value @var{addr} of the
7899 program counter. Search proceeds forward from the last examined trace
7900 snapshot. If no argument @var{addr} is given, it means find the next
7901 snapshot with the same value of PC as the current snapshot.
7903 @item tfind outside @var{addr1}, @var{addr2}
7904 Find the next snapshot whose PC is outside the given range of
7907 @item tfind range @var{addr1}, @var{addr2}
7908 Find the next snapshot whose PC is between @var{addr1} and
7909 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7911 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7912 Find the next snapshot associated with the source line @var{n}. If
7913 the optional argument @var{file} is given, refer to line @var{n} in
7914 that source file. Search proceeds forward from the last examined
7915 trace snapshot. If no argument @var{n} is given, it means find the
7916 next line other than the one currently being examined; thus saying
7917 @code{tfind line} repeatedly can appear to have the same effect as
7918 stepping from line to line in a @emph{live} debugging session.
7921 The default arguments for the @code{tfind} commands are specifically
7922 designed to make it easy to scan through the trace buffer. For
7923 instance, @code{tfind} with no argument selects the next trace
7924 snapshot, and @code{tfind -} with no argument selects the previous
7925 trace snapshot. So, by giving one @code{tfind} command, and then
7926 simply hitting @key{RET} repeatedly you can examine all the trace
7927 snapshots in order. Or, by saying @code{tfind -} and then hitting
7928 @key{RET} repeatedly you can examine the snapshots in reverse order.
7929 The @code{tfind line} command with no argument selects the snapshot
7930 for the next source line executed. The @code{tfind pc} command with
7931 no argument selects the next snapshot with the same program counter
7932 (PC) as the current frame. The @code{tfind tracepoint} command with
7933 no argument selects the next trace snapshot collected by the same
7934 tracepoint as the current one.
7936 In addition to letting you scan through the trace buffer manually,
7937 these commands make it easy to construct @value{GDBN} scripts that
7938 scan through the trace buffer and print out whatever collected data
7939 you are interested in. Thus, if we want to examine the PC, FP, and SP
7940 registers from each trace frame in the buffer, we can say this:
7943 (@value{GDBP}) @b{tfind start}
7944 (@value{GDBP}) @b{while ($trace_frame != -1)}
7945 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7946 $trace_frame, $pc, $sp, $fp
7950 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7951 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7952 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7953 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7954 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7955 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7956 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7957 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7958 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7959 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7960 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7963 Or, if we want to examine the variable @code{X} at each source line in
7967 (@value{GDBP}) @b{tfind start}
7968 (@value{GDBP}) @b{while ($trace_frame != -1)}
7969 > printf "Frame %d, X == %d\n", $trace_frame, X
7979 @subsection @code{tdump}
7981 @cindex dump all data collected at tracepoint
7982 @cindex tracepoint data, display
7984 This command takes no arguments. It prints all the data collected at
7985 the current trace snapshot.
7988 (@value{GDBP}) @b{trace 444}
7989 (@value{GDBP}) @b{actions}
7990 Enter actions for tracepoint #2, one per line:
7991 > collect $regs, $locals, $args, gdb_long_test
7994 (@value{GDBP}) @b{tstart}
7996 (@value{GDBP}) @b{tfind line 444}
7997 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7999 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8001 (@value{GDBP}) @b{tdump}
8002 Data collected at tracepoint 2, trace frame 1:
8003 d0 0xc4aa0085 -995491707
8007 d4 0x71aea3d 119204413
8012 a1 0x3000668 50333288
8015 a4 0x3000698 50333336
8017 fp 0x30bf3c 0x30bf3c
8018 sp 0x30bf34 0x30bf34
8020 pc 0x20b2c8 0x20b2c8
8024 p = 0x20e5b4 "gdb-test"
8031 gdb_long_test = 17 '\021'
8036 @node save-tracepoints
8037 @subsection @code{save-tracepoints @var{filename}}
8038 @kindex save-tracepoints
8039 @cindex save tracepoints for future sessions
8041 This command saves all current tracepoint definitions together with
8042 their actions and passcounts, into a file @file{@var{filename}}
8043 suitable for use in a later debugging session. To read the saved
8044 tracepoint definitions, use the @code{source} command (@pxref{Command
8047 @node Tracepoint Variables
8048 @section Convenience Variables for Tracepoints
8049 @cindex tracepoint variables
8050 @cindex convenience variables for tracepoints
8053 @vindex $trace_frame
8054 @item (int) $trace_frame
8055 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8056 snapshot is selected.
8059 @item (int) $tracepoint
8060 The tracepoint for the current trace snapshot.
8063 @item (int) $trace_line
8064 The line number for the current trace snapshot.
8067 @item (char []) $trace_file
8068 The source file for the current trace snapshot.
8071 @item (char []) $trace_func
8072 The name of the function containing @code{$tracepoint}.
8075 Note: @code{$trace_file} is not suitable for use in @code{printf},
8076 use @code{output} instead.
8078 Here's a simple example of using these convenience variables for
8079 stepping through all the trace snapshots and printing some of their
8083 (@value{GDBP}) @b{tfind start}
8085 (@value{GDBP}) @b{while $trace_frame != -1}
8086 > output $trace_file
8087 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8093 @chapter Debugging Programs That Use Overlays
8096 If your program is too large to fit completely in your target system's
8097 memory, you can sometimes use @dfn{overlays} to work around this
8098 problem. @value{GDBN} provides some support for debugging programs that
8102 * How Overlays Work:: A general explanation of overlays.
8103 * Overlay Commands:: Managing overlays in @value{GDBN}.
8104 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8105 mapped by asking the inferior.
8106 * Overlay Sample Program:: A sample program using overlays.
8109 @node How Overlays Work
8110 @section How Overlays Work
8111 @cindex mapped overlays
8112 @cindex unmapped overlays
8113 @cindex load address, overlay's
8114 @cindex mapped address
8115 @cindex overlay area
8117 Suppose you have a computer whose instruction address space is only 64
8118 kilobytes long, but which has much more memory which can be accessed by
8119 other means: special instructions, segment registers, or memory
8120 management hardware, for example. Suppose further that you want to
8121 adapt a program which is larger than 64 kilobytes to run on this system.
8123 One solution is to identify modules of your program which are relatively
8124 independent, and need not call each other directly; call these modules
8125 @dfn{overlays}. Separate the overlays from the main program, and place
8126 their machine code in the larger memory. Place your main program in
8127 instruction memory, but leave at least enough space there to hold the
8128 largest overlay as well.
8130 Now, to call a function located in an overlay, you must first copy that
8131 overlay's machine code from the large memory into the space set aside
8132 for it in the instruction memory, and then jump to its entry point
8135 @c NB: In the below the mapped area's size is greater or equal to the
8136 @c size of all overlays. This is intentional to remind the developer
8137 @c that overlays don't necessarily need to be the same size.
8141 Data Instruction Larger
8142 Address Space Address Space Address Space
8143 +-----------+ +-----------+ +-----------+
8145 +-----------+ +-----------+ +-----------+<-- overlay 1
8146 | program | | main | .----| overlay 1 | load address
8147 | variables | | program | | +-----------+
8148 | and heap | | | | | |
8149 +-----------+ | | | +-----------+<-- overlay 2
8150 | | +-----------+ | | | load address
8151 +-----------+ | | | .-| overlay 2 |
8153 mapped --->+-----------+ | | +-----------+
8155 | overlay | <-' | | |
8156 | area | <---' +-----------+<-- overlay 3
8157 | | <---. | | load address
8158 +-----------+ `--| overlay 3 |
8165 @anchor{A code overlay}A code overlay
8169 The diagram (@pxref{A code overlay}) shows a system with separate data
8170 and instruction address spaces. To map an overlay, the program copies
8171 its code from the larger address space to the instruction address space.
8172 Since the overlays shown here all use the same mapped address, only one
8173 may be mapped at a time. For a system with a single address space for
8174 data and instructions, the diagram would be similar, except that the
8175 program variables and heap would share an address space with the main
8176 program and the overlay area.
8178 An overlay loaded into instruction memory and ready for use is called a
8179 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8180 instruction memory. An overlay not present (or only partially present)
8181 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8182 is its address in the larger memory. The mapped address is also called
8183 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8184 called the @dfn{load memory address}, or @dfn{LMA}.
8186 Unfortunately, overlays are not a completely transparent way to adapt a
8187 program to limited instruction memory. They introduce a new set of
8188 global constraints you must keep in mind as you design your program:
8193 Before calling or returning to a function in an overlay, your program
8194 must make sure that overlay is actually mapped. Otherwise, the call or
8195 return will transfer control to the right address, but in the wrong
8196 overlay, and your program will probably crash.
8199 If the process of mapping an overlay is expensive on your system, you
8200 will need to choose your overlays carefully to minimize their effect on
8201 your program's performance.
8204 The executable file you load onto your system must contain each
8205 overlay's instructions, appearing at the overlay's load address, not its
8206 mapped address. However, each overlay's instructions must be relocated
8207 and its symbols defined as if the overlay were at its mapped address.
8208 You can use GNU linker scripts to specify different load and relocation
8209 addresses for pieces of your program; see @ref{Overlay Description,,,
8210 ld.info, Using ld: the GNU linker}.
8213 The procedure for loading executable files onto your system must be able
8214 to load their contents into the larger address space as well as the
8215 instruction and data spaces.
8219 The overlay system described above is rather simple, and could be
8220 improved in many ways:
8225 If your system has suitable bank switch registers or memory management
8226 hardware, you could use those facilities to make an overlay's load area
8227 contents simply appear at their mapped address in instruction space.
8228 This would probably be faster than copying the overlay to its mapped
8229 area in the usual way.
8232 If your overlays are small enough, you could set aside more than one
8233 overlay area, and have more than one overlay mapped at a time.
8236 You can use overlays to manage data, as well as instructions. In
8237 general, data overlays are even less transparent to your design than
8238 code overlays: whereas code overlays only require care when you call or
8239 return to functions, data overlays require care every time you access
8240 the data. Also, if you change the contents of a data overlay, you
8241 must copy its contents back out to its load address before you can copy a
8242 different data overlay into the same mapped area.
8247 @node Overlay Commands
8248 @section Overlay Commands
8250 To use @value{GDBN}'s overlay support, each overlay in your program must
8251 correspond to a separate section of the executable file. The section's
8252 virtual memory address and load memory address must be the overlay's
8253 mapped and load addresses. Identifying overlays with sections allows
8254 @value{GDBN} to determine the appropriate address of a function or
8255 variable, depending on whether the overlay is mapped or not.
8257 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8258 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8263 Disable @value{GDBN}'s overlay support. When overlay support is
8264 disabled, @value{GDBN} assumes that all functions and variables are
8265 always present at their mapped addresses. By default, @value{GDBN}'s
8266 overlay support is disabled.
8268 @item overlay manual
8269 @cindex manual overlay debugging
8270 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8271 relies on you to tell it which overlays are mapped, and which are not,
8272 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8273 commands described below.
8275 @item overlay map-overlay @var{overlay}
8276 @itemx overlay map @var{overlay}
8277 @cindex map an overlay
8278 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8279 be the name of the object file section containing the overlay. When an
8280 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8281 functions and variables at their mapped addresses. @value{GDBN} assumes
8282 that any other overlays whose mapped ranges overlap that of
8283 @var{overlay} are now unmapped.
8285 @item overlay unmap-overlay @var{overlay}
8286 @itemx overlay unmap @var{overlay}
8287 @cindex unmap an overlay
8288 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8289 must be the name of the object file section containing the overlay.
8290 When an overlay is unmapped, @value{GDBN} assumes it can find the
8291 overlay's functions and variables at their load addresses.
8294 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8295 consults a data structure the overlay manager maintains in the inferior
8296 to see which overlays are mapped. For details, see @ref{Automatic
8299 @item overlay load-target
8301 @cindex reloading the overlay table
8302 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8303 re-reads the table @value{GDBN} automatically each time the inferior
8304 stops, so this command should only be necessary if you have changed the
8305 overlay mapping yourself using @value{GDBN}. This command is only
8306 useful when using automatic overlay debugging.
8308 @item overlay list-overlays
8310 @cindex listing mapped overlays
8311 Display a list of the overlays currently mapped, along with their mapped
8312 addresses, load addresses, and sizes.
8316 Normally, when @value{GDBN} prints a code address, it includes the name
8317 of the function the address falls in:
8320 (@value{GDBP}) print main
8321 $3 = @{int ()@} 0x11a0 <main>
8324 When overlay debugging is enabled, @value{GDBN} recognizes code in
8325 unmapped overlays, and prints the names of unmapped functions with
8326 asterisks around them. For example, if @code{foo} is a function in an
8327 unmapped overlay, @value{GDBN} prints it this way:
8330 (@value{GDBP}) overlay list
8331 No sections are mapped.
8332 (@value{GDBP}) print foo
8333 $5 = @{int (int)@} 0x100000 <*foo*>
8336 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8340 (@value{GDBP}) overlay list
8341 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8342 mapped at 0x1016 - 0x104a
8343 (@value{GDBP}) print foo
8344 $6 = @{int (int)@} 0x1016 <foo>
8347 When overlay debugging is enabled, @value{GDBN} can find the correct
8348 address for functions and variables in an overlay, whether or not the
8349 overlay is mapped. This allows most @value{GDBN} commands, like
8350 @code{break} and @code{disassemble}, to work normally, even on unmapped
8351 code. However, @value{GDBN}'s breakpoint support has some limitations:
8355 @cindex breakpoints in overlays
8356 @cindex overlays, setting breakpoints in
8357 You can set breakpoints in functions in unmapped overlays, as long as
8358 @value{GDBN} can write to the overlay at its load address.
8360 @value{GDBN} can not set hardware or simulator-based breakpoints in
8361 unmapped overlays. However, if you set a breakpoint at the end of your
8362 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8363 you are using manual overlay management), @value{GDBN} will re-set its
8364 breakpoints properly.
8368 @node Automatic Overlay Debugging
8369 @section Automatic Overlay Debugging
8370 @cindex automatic overlay debugging
8372 @value{GDBN} can automatically track which overlays are mapped and which
8373 are not, given some simple co-operation from the overlay manager in the
8374 inferior. If you enable automatic overlay debugging with the
8375 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8376 looks in the inferior's memory for certain variables describing the
8377 current state of the overlays.
8379 Here are the variables your overlay manager must define to support
8380 @value{GDBN}'s automatic overlay debugging:
8384 @item @code{_ovly_table}:
8385 This variable must be an array of the following structures:
8390 /* The overlay's mapped address. */
8393 /* The size of the overlay, in bytes. */
8396 /* The overlay's load address. */
8399 /* Non-zero if the overlay is currently mapped;
8401 unsigned long mapped;
8405 @item @code{_novlys}:
8406 This variable must be a four-byte signed integer, holding the total
8407 number of elements in @code{_ovly_table}.
8411 To decide whether a particular overlay is mapped or not, @value{GDBN}
8412 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8413 @code{lma} members equal the VMA and LMA of the overlay's section in the
8414 executable file. When @value{GDBN} finds a matching entry, it consults
8415 the entry's @code{mapped} member to determine whether the overlay is
8418 In addition, your overlay manager may define a function called
8419 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8420 will silently set a breakpoint there. If the overlay manager then
8421 calls this function whenever it has changed the overlay table, this
8422 will enable @value{GDBN} to accurately keep track of which overlays
8423 are in program memory, and update any breakpoints that may be set
8424 in overlays. This will allow breakpoints to work even if the
8425 overlays are kept in ROM or other non-writable memory while they
8426 are not being executed.
8428 @node Overlay Sample Program
8429 @section Overlay Sample Program
8430 @cindex overlay example program
8432 When linking a program which uses overlays, you must place the overlays
8433 at their load addresses, while relocating them to run at their mapped
8434 addresses. To do this, you must write a linker script (@pxref{Overlay
8435 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8436 since linker scripts are specific to a particular host system, target
8437 architecture, and target memory layout, this manual cannot provide
8438 portable sample code demonstrating @value{GDBN}'s overlay support.
8440 However, the @value{GDBN} source distribution does contain an overlaid
8441 program, with linker scripts for a few systems, as part of its test
8442 suite. The program consists of the following files from
8443 @file{gdb/testsuite/gdb.base}:
8447 The main program file.
8449 A simple overlay manager, used by @file{overlays.c}.
8454 Overlay modules, loaded and used by @file{overlays.c}.
8457 Linker scripts for linking the test program on the @code{d10v-elf}
8458 and @code{m32r-elf} targets.
8461 You can build the test program using the @code{d10v-elf} GCC
8462 cross-compiler like this:
8465 $ d10v-elf-gcc -g -c overlays.c
8466 $ d10v-elf-gcc -g -c ovlymgr.c
8467 $ d10v-elf-gcc -g -c foo.c
8468 $ d10v-elf-gcc -g -c bar.c
8469 $ d10v-elf-gcc -g -c baz.c
8470 $ d10v-elf-gcc -g -c grbx.c
8471 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8472 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8475 The build process is identical for any other architecture, except that
8476 you must substitute the appropriate compiler and linker script for the
8477 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8481 @chapter Using @value{GDBN} with Different Languages
8484 Although programming languages generally have common aspects, they are
8485 rarely expressed in the same manner. For instance, in ANSI C,
8486 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8487 Modula-2, it is accomplished by @code{p^}. Values can also be
8488 represented (and displayed) differently. Hex numbers in C appear as
8489 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8491 @cindex working language
8492 Language-specific information is built into @value{GDBN} for some languages,
8493 allowing you to express operations like the above in your program's
8494 native language, and allowing @value{GDBN} to output values in a manner
8495 consistent with the syntax of your program's native language. The
8496 language you use to build expressions is called the @dfn{working
8500 * Setting:: Switching between source languages
8501 * Show:: Displaying the language
8502 * Checks:: Type and range checks
8503 * Supported languages:: Supported languages
8504 * Unsupported languages:: Unsupported languages
8508 @section Switching between source languages
8510 There are two ways to control the working language---either have @value{GDBN}
8511 set it automatically, or select it manually yourself. You can use the
8512 @code{set language} command for either purpose. On startup, @value{GDBN}
8513 defaults to setting the language automatically. The working language is
8514 used to determine how expressions you type are interpreted, how values
8517 In addition to the working language, every source file that
8518 @value{GDBN} knows about has its own working language. For some object
8519 file formats, the compiler might indicate which language a particular
8520 source file is in. However, most of the time @value{GDBN} infers the
8521 language from the name of the file. The language of a source file
8522 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8523 show each frame appropriately for its own language. There is no way to
8524 set the language of a source file from within @value{GDBN}, but you can
8525 set the language associated with a filename extension. @xref{Show, ,
8526 Displaying the language}.
8528 This is most commonly a problem when you use a program, such
8529 as @code{cfront} or @code{f2c}, that generates C but is written in
8530 another language. In that case, make the
8531 program use @code{#line} directives in its C output; that way
8532 @value{GDBN} will know the correct language of the source code of the original
8533 program, and will display that source code, not the generated C code.
8536 * Filenames:: Filename extensions and languages.
8537 * Manually:: Setting the working language manually
8538 * Automatically:: Having @value{GDBN} infer the source language
8542 @subsection List of filename extensions and languages
8544 If a source file name ends in one of the following extensions, then
8545 @value{GDBN} infers that its language is the one indicated.
8566 Objective-C source file
8573 Modula-2 source file
8577 Assembler source file. This actually behaves almost like C, but
8578 @value{GDBN} does not skip over function prologues when stepping.
8581 In addition, you may set the language associated with a filename
8582 extension. @xref{Show, , Displaying the language}.
8585 @subsection Setting the working language
8587 If you allow @value{GDBN} to set the language automatically,
8588 expressions are interpreted the same way in your debugging session and
8591 @kindex set language
8592 If you wish, you may set the language manually. To do this, issue the
8593 command @samp{set language @var{lang}}, where @var{lang} is the name of
8595 @code{c} or @code{modula-2}.
8596 For a list of the supported languages, type @samp{set language}.
8598 Setting the language manually prevents @value{GDBN} from updating the working
8599 language automatically. This can lead to confusion if you try
8600 to debug a program when the working language is not the same as the
8601 source language, when an expression is acceptable to both
8602 languages---but means different things. For instance, if the current
8603 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8611 might not have the effect you intended. In C, this means to add
8612 @code{b} and @code{c} and place the result in @code{a}. The result
8613 printed would be the value of @code{a}. In Modula-2, this means to compare
8614 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8617 @subsection Having @value{GDBN} infer the source language
8619 To have @value{GDBN} set the working language automatically, use
8620 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8621 then infers the working language. That is, when your program stops in a
8622 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8623 working language to the language recorded for the function in that
8624 frame. If the language for a frame is unknown (that is, if the function
8625 or block corresponding to the frame was defined in a source file that
8626 does not have a recognized extension), the current working language is
8627 not changed, and @value{GDBN} issues a warning.
8629 This may not seem necessary for most programs, which are written
8630 entirely in one source language. However, program modules and libraries
8631 written in one source language can be used by a main program written in
8632 a different source language. Using @samp{set language auto} in this
8633 case frees you from having to set the working language manually.
8636 @section Displaying the language
8638 The following commands help you find out which language is the
8639 working language, and also what language source files were written in.
8643 @kindex show language
8644 Display the current working language. This is the
8645 language you can use with commands such as @code{print} to
8646 build and compute expressions that may involve variables in your program.
8649 @kindex info frame@r{, show the source language}
8650 Display the source language for this frame. This language becomes the
8651 working language if you use an identifier from this frame.
8652 @xref{Frame Info, ,Information about a frame}, to identify the other
8653 information listed here.
8656 @kindex info source@r{, show the source language}
8657 Display the source language of this source file.
8658 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8659 information listed here.
8662 In unusual circumstances, you may have source files with extensions
8663 not in the standard list. You can then set the extension associated
8664 with a language explicitly:
8667 @item set extension-language @var{ext} @var{language}
8668 @kindex set extension-language
8669 Tell @value{GDBN} that source files with extension @var{ext} are to be
8670 assumed as written in the source language @var{language}.
8672 @item info extensions
8673 @kindex info extensions
8674 List all the filename extensions and the associated languages.
8678 @section Type and range checking
8681 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8682 checking are included, but they do not yet have any effect. This
8683 section documents the intended facilities.
8685 @c FIXME remove warning when type/range code added
8687 Some languages are designed to guard you against making seemingly common
8688 errors through a series of compile- and run-time checks. These include
8689 checking the type of arguments to functions and operators, and making
8690 sure mathematical overflows are caught at run time. Checks such as
8691 these help to ensure a program's correctness once it has been compiled
8692 by eliminating type mismatches, and providing active checks for range
8693 errors when your program is running.
8695 @value{GDBN} can check for conditions like the above if you wish.
8696 Although @value{GDBN} does not check the statements in your program,
8697 it can check expressions entered directly into @value{GDBN} for
8698 evaluation via the @code{print} command, for example. As with the
8699 working language, @value{GDBN} can also decide whether or not to check
8700 automatically based on your program's source language.
8701 @xref{Supported languages, ,Supported languages}, for the default
8702 settings of supported languages.
8705 * Type Checking:: An overview of type checking
8706 * Range Checking:: An overview of range checking
8709 @cindex type checking
8710 @cindex checks, type
8712 @subsection An overview of type checking
8714 Some languages, such as Modula-2, are strongly typed, meaning that the
8715 arguments to operators and functions have to be of the correct type,
8716 otherwise an error occurs. These checks prevent type mismatch
8717 errors from ever causing any run-time problems. For example,
8725 The second example fails because the @code{CARDINAL} 1 is not
8726 type-compatible with the @code{REAL} 2.3.
8728 For the expressions you use in @value{GDBN} commands, you can tell the
8729 @value{GDBN} type checker to skip checking;
8730 to treat any mismatches as errors and abandon the expression;
8731 or to only issue warnings when type mismatches occur,
8732 but evaluate the expression anyway. When you choose the last of
8733 these, @value{GDBN} evaluates expressions like the second example above, but
8734 also issues a warning.
8736 Even if you turn type checking off, there may be other reasons
8737 related to type that prevent @value{GDBN} from evaluating an expression.
8738 For instance, @value{GDBN} does not know how to add an @code{int} and
8739 a @code{struct foo}. These particular type errors have nothing to do
8740 with the language in use, and usually arise from expressions, such as
8741 the one described above, which make little sense to evaluate anyway.
8743 Each language defines to what degree it is strict about type. For
8744 instance, both Modula-2 and C require the arguments to arithmetical
8745 operators to be numbers. In C, enumerated types and pointers can be
8746 represented as numbers, so that they are valid arguments to mathematical
8747 operators. @xref{Supported languages, ,Supported languages}, for further
8748 details on specific languages.
8750 @value{GDBN} provides some additional commands for controlling the type checker:
8752 @kindex set check type
8753 @kindex show check type
8755 @item set check type auto
8756 Set type checking on or off based on the current working language.
8757 @xref{Supported languages, ,Supported languages}, for the default settings for
8760 @item set check type on
8761 @itemx set check type off
8762 Set type checking on or off, overriding the default setting for the
8763 current working language. Issue a warning if the setting does not
8764 match the language default. If any type mismatches occur in
8765 evaluating an expression while type checking is on, @value{GDBN} prints a
8766 message and aborts evaluation of the expression.
8768 @item set check type warn
8769 Cause the type checker to issue warnings, but to always attempt to
8770 evaluate the expression. Evaluating the expression may still
8771 be impossible for other reasons. For example, @value{GDBN} cannot add
8772 numbers and structures.
8775 Show the current setting of the type checker, and whether or not @value{GDBN}
8776 is setting it automatically.
8779 @cindex range checking
8780 @cindex checks, range
8781 @node Range Checking
8782 @subsection An overview of range checking
8784 In some languages (such as Modula-2), it is an error to exceed the
8785 bounds of a type; this is enforced with run-time checks. Such range
8786 checking is meant to ensure program correctness by making sure
8787 computations do not overflow, or indices on an array element access do
8788 not exceed the bounds of the array.
8790 For expressions you use in @value{GDBN} commands, you can tell
8791 @value{GDBN} to treat range errors in one of three ways: ignore them,
8792 always treat them as errors and abandon the expression, or issue
8793 warnings but evaluate the expression anyway.
8795 A range error can result from numerical overflow, from exceeding an
8796 array index bound, or when you type a constant that is not a member
8797 of any type. Some languages, however, do not treat overflows as an
8798 error. In many implementations of C, mathematical overflow causes the
8799 result to ``wrap around'' to lower values---for example, if @var{m} is
8800 the largest integer value, and @var{s} is the smallest, then
8803 @var{m} + 1 @result{} @var{s}
8806 This, too, is specific to individual languages, and in some cases
8807 specific to individual compilers or machines. @xref{Supported languages, ,
8808 Supported languages}, for further details on specific languages.
8810 @value{GDBN} provides some additional commands for controlling the range checker:
8812 @kindex set check range
8813 @kindex show check range
8815 @item set check range auto
8816 Set range checking on or off based on the current working language.
8817 @xref{Supported languages, ,Supported languages}, for the default settings for
8820 @item set check range on
8821 @itemx set check range off
8822 Set range checking on or off, overriding the default setting for the
8823 current working language. A warning is issued if the setting does not
8824 match the language default. If a range error occurs and range checking is on,
8825 then a message is printed and evaluation of the expression is aborted.
8827 @item set check range warn
8828 Output messages when the @value{GDBN} range checker detects a range error,
8829 but attempt to evaluate the expression anyway. Evaluating the
8830 expression may still be impossible for other reasons, such as accessing
8831 memory that the process does not own (a typical example from many Unix
8835 Show the current setting of the range checker, and whether or not it is
8836 being set automatically by @value{GDBN}.
8839 @node Supported languages
8840 @section Supported languages
8842 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8843 assembly, Modula-2, and Ada.
8844 @c This is false ...
8845 Some @value{GDBN} features may be used in expressions regardless of the
8846 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8847 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8848 ,Expressions}) can be used with the constructs of any supported
8851 The following sections detail to what degree each source language is
8852 supported by @value{GDBN}. These sections are not meant to be language
8853 tutorials or references, but serve only as a reference guide to what the
8854 @value{GDBN} expression parser accepts, and what input and output
8855 formats should look like for different languages. There are many good
8856 books written on each of these languages; please look to these for a
8857 language reference or tutorial.
8861 * Objective-C:: Objective-C
8864 * Modula-2:: Modula-2
8869 @subsection C and C@t{++}
8871 @cindex C and C@t{++}
8872 @cindex expressions in C or C@t{++}
8874 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8875 to both languages. Whenever this is the case, we discuss those languages
8879 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8880 @cindex @sc{gnu} C@t{++}
8881 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8882 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8883 effectively, you must compile your C@t{++} programs with a supported
8884 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8885 compiler (@code{aCC}).
8887 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8888 format; if it doesn't work on your system, try the stabs+ debugging
8889 format. You can select those formats explicitly with the @code{g++}
8890 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8891 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8892 CC, gcc.info, Using @sc{gnu} CC}.
8895 * C Operators:: C and C@t{++} operators
8896 * C Constants:: C and C@t{++} constants
8897 * C plus plus expressions:: C@t{++} expressions
8898 * C Defaults:: Default settings for C and C@t{++}
8899 * C Checks:: C and C@t{++} type and range checks
8900 * Debugging C:: @value{GDBN} and C
8901 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8905 @subsubsection C and C@t{++} operators
8907 @cindex C and C@t{++} operators
8909 Operators must be defined on values of specific types. For instance,
8910 @code{+} is defined on numbers, but not on structures. Operators are
8911 often defined on groups of types.
8913 For the purposes of C and C@t{++}, the following definitions hold:
8918 @emph{Integral types} include @code{int} with any of its storage-class
8919 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8922 @emph{Floating-point types} include @code{float}, @code{double}, and
8923 @code{long double} (if supported by the target platform).
8926 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8929 @emph{Scalar types} include all of the above.
8934 The following operators are supported. They are listed here
8935 in order of increasing precedence:
8939 The comma or sequencing operator. Expressions in a comma-separated list
8940 are evaluated from left to right, with the result of the entire
8941 expression being the last expression evaluated.
8944 Assignment. The value of an assignment expression is the value
8945 assigned. Defined on scalar types.
8948 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8949 and translated to @w{@code{@var{a} = @var{a op b}}}.
8950 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8951 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8952 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8955 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8956 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8960 Logical @sc{or}. Defined on integral types.
8963 Logical @sc{and}. Defined on integral types.
8966 Bitwise @sc{or}. Defined on integral types.
8969 Bitwise exclusive-@sc{or}. Defined on integral types.
8972 Bitwise @sc{and}. Defined on integral types.
8975 Equality and inequality. Defined on scalar types. The value of these
8976 expressions is 0 for false and non-zero for true.
8978 @item <@r{, }>@r{, }<=@r{, }>=
8979 Less than, greater than, less than or equal, greater than or equal.
8980 Defined on scalar types. The value of these expressions is 0 for false
8981 and non-zero for true.
8984 left shift, and right shift. Defined on integral types.
8987 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8990 Addition and subtraction. Defined on integral types, floating-point types and
8993 @item *@r{, }/@r{, }%
8994 Multiplication, division, and modulus. Multiplication and division are
8995 defined on integral and floating-point types. Modulus is defined on
8999 Increment and decrement. When appearing before a variable, the
9000 operation is performed before the variable is used in an expression;
9001 when appearing after it, the variable's value is used before the
9002 operation takes place.
9005 Pointer dereferencing. Defined on pointer types. Same precedence as
9009 Address operator. Defined on variables. Same precedence as @code{++}.
9011 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9012 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9013 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
9014 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9018 Negative. Defined on integral and floating-point types. Same
9019 precedence as @code{++}.
9022 Logical negation. Defined on integral types. Same precedence as
9026 Bitwise complement operator. Defined on integral types. Same precedence as
9031 Structure member, and pointer-to-structure member. For convenience,
9032 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9033 pointer based on the stored type information.
9034 Defined on @code{struct} and @code{union} data.
9037 Dereferences of pointers to members.
9040 Array indexing. @code{@var{a}[@var{i}]} is defined as
9041 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9044 Function parameter list. Same precedence as @code{->}.
9047 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9048 and @code{class} types.
9051 Doubled colons also represent the @value{GDBN} scope operator
9052 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9056 If an operator is redefined in the user code, @value{GDBN} usually
9057 attempts to invoke the redefined version instead of using the operator's
9065 @subsubsection C and C@t{++} constants
9067 @cindex C and C@t{++} constants
9069 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9074 Integer constants are a sequence of digits. Octal constants are
9075 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9076 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9077 @samp{l}, specifying that the constant should be treated as a
9081 Floating point constants are a sequence of digits, followed by a decimal
9082 point, followed by a sequence of digits, and optionally followed by an
9083 exponent. An exponent is of the form:
9084 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9085 sequence of digits. The @samp{+} is optional for positive exponents.
9086 A floating-point constant may also end with a letter @samp{f} or
9087 @samp{F}, specifying that the constant should be treated as being of
9088 the @code{float} (as opposed to the default @code{double}) type; or with
9089 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9093 Enumerated constants consist of enumerated identifiers, or their
9094 integral equivalents.
9097 Character constants are a single character surrounded by single quotes
9098 (@code{'}), or a number---the ordinal value of the corresponding character
9099 (usually its @sc{ascii} value). Within quotes, the single character may
9100 be represented by a letter or by @dfn{escape sequences}, which are of
9101 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9102 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9103 @samp{@var{x}} is a predefined special character---for example,
9104 @samp{\n} for newline.
9107 String constants are a sequence of character constants surrounded by
9108 double quotes (@code{"}). Any valid character constant (as described
9109 above) may appear. Double quotes within the string must be preceded by
9110 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9114 Pointer constants are an integral value. You can also write pointers
9115 to constants using the C operator @samp{&}.
9118 Array constants are comma-separated lists surrounded by braces @samp{@{}
9119 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9120 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9121 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9125 * C plus plus expressions::
9132 @node C plus plus expressions
9133 @subsubsection C@t{++} expressions
9135 @cindex expressions in C@t{++}
9136 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9138 @cindex debugging C@t{++} programs
9139 @cindex C@t{++} compilers
9140 @cindex debug formats and C@t{++}
9141 @cindex @value{NGCC} and C@t{++}
9143 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9144 proper compiler and the proper debug format. Currently, @value{GDBN}
9145 works best when debugging C@t{++} code that is compiled with
9146 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9147 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9148 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9149 stabs+ as their default debug format, so you usually don't need to
9150 specify a debug format explicitly. Other compilers and/or debug formats
9151 are likely to work badly or not at all when using @value{GDBN} to debug
9157 @cindex member functions
9159 Member function calls are allowed; you can use expressions like
9162 count = aml->GetOriginal(x, y)
9165 @vindex this@r{, inside C@t{++} member functions}
9166 @cindex namespace in C@t{++}
9168 While a member function is active (in the selected stack frame), your
9169 expressions have the same namespace available as the member function;
9170 that is, @value{GDBN} allows implicit references to the class instance
9171 pointer @code{this} following the same rules as C@t{++}.
9173 @cindex call overloaded functions
9174 @cindex overloaded functions, calling
9175 @cindex type conversions in C@t{++}
9177 You can call overloaded functions; @value{GDBN} resolves the function
9178 call to the right definition, with some restrictions. @value{GDBN} does not
9179 perform overload resolution involving user-defined type conversions,
9180 calls to constructors, or instantiations of templates that do not exist
9181 in the program. It also cannot handle ellipsis argument lists or
9184 It does perform integral conversions and promotions, floating-point
9185 promotions, arithmetic conversions, pointer conversions, conversions of
9186 class objects to base classes, and standard conversions such as those of
9187 functions or arrays to pointers; it requires an exact match on the
9188 number of function arguments.
9190 Overload resolution is always performed, unless you have specified
9191 @code{set overload-resolution off}. @xref{Debugging C plus plus,
9192 ,@value{GDBN} features for C@t{++}}.
9194 You must specify @code{set overload-resolution off} in order to use an
9195 explicit function signature to call an overloaded function, as in
9197 p 'foo(char,int)'('x', 13)
9200 The @value{GDBN} command-completion facility can simplify this;
9201 see @ref{Completion, ,Command completion}.
9203 @cindex reference declarations
9205 @value{GDBN} understands variables declared as C@t{++} references; you can use
9206 them in expressions just as you do in C@t{++} source---they are automatically
9209 In the parameter list shown when @value{GDBN} displays a frame, the values of
9210 reference variables are not displayed (unlike other variables); this
9211 avoids clutter, since references are often used for large structures.
9212 The @emph{address} of a reference variable is always shown, unless
9213 you have specified @samp{set print address off}.
9216 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9217 expressions can use it just as expressions in your program do. Since
9218 one scope may be defined in another, you can use @code{::} repeatedly if
9219 necessary, for example in an expression like
9220 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9221 resolving name scope by reference to source files, in both C and C@t{++}
9222 debugging (@pxref{Variables, ,Program variables}).
9225 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9226 calling virtual functions correctly, printing out virtual bases of
9227 objects, calling functions in a base subobject, casting objects, and
9228 invoking user-defined operators.
9231 @subsubsection C and C@t{++} defaults
9233 @cindex C and C@t{++} defaults
9235 If you allow @value{GDBN} to set type and range checking automatically, they
9236 both default to @code{off} whenever the working language changes to
9237 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9238 selects the working language.
9240 If you allow @value{GDBN} to set the language automatically, it
9241 recognizes source files whose names end with @file{.c}, @file{.C}, or
9242 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9243 these files, it sets the working language to C or C@t{++}.
9244 @xref{Automatically, ,Having @value{GDBN} infer the source language},
9245 for further details.
9247 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9248 @c unimplemented. If (b) changes, it might make sense to let this node
9249 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9252 @subsubsection C and C@t{++} type and range checks
9254 @cindex C and C@t{++} checks
9256 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9257 is not used. However, if you turn type checking on, @value{GDBN}
9258 considers two variables type equivalent if:
9262 The two variables are structured and have the same structure, union, or
9266 The two variables have the same type name, or types that have been
9267 declared equivalent through @code{typedef}.
9270 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9273 The two @code{struct}, @code{union}, or @code{enum} variables are
9274 declared in the same declaration. (Note: this may not be true for all C
9279 Range checking, if turned on, is done on mathematical operations. Array
9280 indices are not checked, since they are often used to index a pointer
9281 that is not itself an array.
9284 @subsubsection @value{GDBN} and C
9286 The @code{set print union} and @code{show print union} commands apply to
9287 the @code{union} type. When set to @samp{on}, any @code{union} that is
9288 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9289 appears as @samp{@{...@}}.
9291 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9292 with pointers and a memory allocation function. @xref{Expressions,
9296 * Debugging C plus plus::
9299 @node Debugging C plus plus
9300 @subsubsection @value{GDBN} features for C@t{++}
9302 @cindex commands for C@t{++}
9304 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9305 designed specifically for use with C@t{++}. Here is a summary:
9308 @cindex break in overloaded functions
9309 @item @r{breakpoint menus}
9310 When you want a breakpoint in a function whose name is overloaded,
9311 @value{GDBN} breakpoint menus help you specify which function definition
9312 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
9314 @cindex overloading in C@t{++}
9315 @item rbreak @var{regex}
9316 Setting breakpoints using regular expressions is helpful for setting
9317 breakpoints on overloaded functions that are not members of any special
9319 @xref{Set Breaks, ,Setting breakpoints}.
9321 @cindex C@t{++} exception handling
9324 Debug C@t{++} exception handling using these commands. @xref{Set
9325 Catchpoints, , Setting catchpoints}.
9328 @item ptype @var{typename}
9329 Print inheritance relationships as well as other information for type
9331 @xref{Symbols, ,Examining the Symbol Table}.
9333 @cindex C@t{++} symbol display
9334 @item set print demangle
9335 @itemx show print demangle
9336 @itemx set print asm-demangle
9337 @itemx show print asm-demangle
9338 Control whether C@t{++} symbols display in their source form, both when
9339 displaying code as C@t{++} source and when displaying disassemblies.
9340 @xref{Print Settings, ,Print settings}.
9342 @item set print object
9343 @itemx show print object
9344 Choose whether to print derived (actual) or declared types of objects.
9345 @xref{Print Settings, ,Print settings}.
9347 @item set print vtbl
9348 @itemx show print vtbl
9349 Control the format for printing virtual function tables.
9350 @xref{Print Settings, ,Print settings}.
9351 (The @code{vtbl} commands do not work on programs compiled with the HP
9352 ANSI C@t{++} compiler (@code{aCC}).)
9354 @kindex set overload-resolution
9355 @cindex overloaded functions, overload resolution
9356 @item set overload-resolution on
9357 Enable overload resolution for C@t{++} expression evaluation. The default
9358 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9359 and searches for a function whose signature matches the argument types,
9360 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
9361 expressions}, for details). If it cannot find a match, it emits a
9364 @item set overload-resolution off
9365 Disable overload resolution for C@t{++} expression evaluation. For
9366 overloaded functions that are not class member functions, @value{GDBN}
9367 chooses the first function of the specified name that it finds in the
9368 symbol table, whether or not its arguments are of the correct type. For
9369 overloaded functions that are class member functions, @value{GDBN}
9370 searches for a function whose signature @emph{exactly} matches the
9373 @kindex show overload-resolution
9374 @item show overload-resolution
9375 Show the current setting of overload resolution.
9377 @item @r{Overloaded symbol names}
9378 You can specify a particular definition of an overloaded symbol, using
9379 the same notation that is used to declare such symbols in C@t{++}: type
9380 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9381 also use the @value{GDBN} command-line word completion facilities to list the
9382 available choices, or to finish the type list for you.
9383 @xref{Completion,, Command completion}, for details on how to do this.
9387 @subsection Objective-C
9390 This section provides information about some commands and command
9391 options that are useful for debugging Objective-C code. See also
9392 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9393 few more commands specific to Objective-C support.
9396 * Method Names in Commands::
9397 * The Print Command with Objective-C::
9400 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
9401 @subsubsection Method Names in Commands
9403 The following commands have been extended to accept Objective-C method
9404 names as line specifications:
9406 @kindex clear@r{, and Objective-C}
9407 @kindex break@r{, and Objective-C}
9408 @kindex info line@r{, and Objective-C}
9409 @kindex jump@r{, and Objective-C}
9410 @kindex list@r{, and Objective-C}
9414 @item @code{info line}
9419 A fully qualified Objective-C method name is specified as
9422 -[@var{Class} @var{methodName}]
9425 where the minus sign is used to indicate an instance method and a
9426 plus sign (not shown) is used to indicate a class method. The class
9427 name @var{Class} and method name @var{methodName} are enclosed in
9428 brackets, similar to the way messages are specified in Objective-C
9429 source code. For example, to set a breakpoint at the @code{create}
9430 instance method of class @code{Fruit} in the program currently being
9434 break -[Fruit create]
9437 To list ten program lines around the @code{initialize} class method,
9441 list +[NSText initialize]
9444 In the current version of @value{GDBN}, the plus or minus sign is
9445 required. In future versions of @value{GDBN}, the plus or minus
9446 sign will be optional, but you can use it to narrow the search. It
9447 is also possible to specify just a method name:
9453 You must specify the complete method name, including any colons. If
9454 your program's source files contain more than one @code{create} method,
9455 you'll be presented with a numbered list of classes that implement that
9456 method. Indicate your choice by number, or type @samp{0} to exit if
9459 As another example, to clear a breakpoint established at the
9460 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9463 clear -[NSWindow makeKeyAndOrderFront:]
9466 @node The Print Command with Objective-C
9467 @subsubsection The Print Command With Objective-C
9468 @cindex Objective-C, print objects
9469 @kindex print-object
9470 @kindex po @r{(@code{print-object})}
9472 The print command has also been extended to accept methods. For example:
9475 print -[@var{object} hash]
9478 @cindex print an Objective-C object description
9479 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9481 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9482 and print the result. Also, an additional command has been added,
9483 @code{print-object} or @code{po} for short, which is meant to print
9484 the description of an object. However, this command may only work
9485 with certain Objective-C libraries that have a particular hook
9486 function, @code{_NSPrintForDebugger}, defined.
9490 @cindex Fortran-specific support in @value{GDBN}
9492 @value{GDBN} can be used to debug programs written in Fortran, but it
9493 currently supports only the features of Fortran 77 language.
9495 @cindex trailing underscore, in Fortran symbols
9496 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9497 among them) append an underscore to the names of variables and
9498 functions. When you debug programs compiled by those compilers, you
9499 will need to refer to variables and functions with a trailing
9503 * Fortran Operators:: Fortran operators and expressions
9504 * Fortran Defaults:: Default settings for Fortran
9505 * Special Fortran commands:: Special @value{GDBN} commands for Fortran
9508 @node Fortran Operators
9509 @subsubsection Fortran operators and expressions
9511 @cindex Fortran operators and expressions
9513 Operators must be defined on values of specific types. For instance,
9514 @code{+} is defined on numbers, but not on characters or other non-
9515 arithmetic types. Operators are often defined on groups of types.
9519 The exponentiation operator. It raises the first operand to the power
9523 The range operator. Normally used in the form of array(low:high) to
9524 represent a section of array.
9527 @node Fortran Defaults
9528 @subsubsection Fortran Defaults
9530 @cindex Fortran Defaults
9532 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9533 default uses case-insensitive matches for Fortran symbols. You can
9534 change that with the @samp{set case-insensitive} command, see
9535 @ref{Symbols}, for the details.
9537 @node Special Fortran commands
9538 @subsubsection Special Fortran commands
9540 @cindex Special Fortran commands
9542 @value{GDBN} had some commands to support Fortran specific feature,
9543 such as common block displaying.
9546 @cindex @code{COMMON} blocks, Fortran
9548 @item info common @r{[}@var{common-name}@r{]}
9549 This command prints the values contained in the Fortran @code{COMMON}
9550 block whose name is @var{common-name}. With no argument, the names of
9551 all @code{COMMON} blocks visible at current program location are
9558 @cindex Pascal support in @value{GDBN}, limitations
9559 Debugging Pascal programs which use sets, subranges, file variables, or
9560 nested functions does not currently work. @value{GDBN} does not support
9561 entering expressions, printing values, or similar features using Pascal
9564 The Pascal-specific command @code{set print pascal_static-members}
9565 controls whether static members of Pascal objects are displayed.
9566 @xref{Print Settings, pascal_static-members}.
9569 @subsection Modula-2
9571 @cindex Modula-2, @value{GDBN} support
9573 The extensions made to @value{GDBN} to support Modula-2 only support
9574 output from the @sc{gnu} Modula-2 compiler (which is currently being
9575 developed). Other Modula-2 compilers are not currently supported, and
9576 attempting to debug executables produced by them is most likely
9577 to give an error as @value{GDBN} reads in the executable's symbol
9580 @cindex expressions in Modula-2
9582 * M2 Operators:: Built-in operators
9583 * Built-In Func/Proc:: Built-in functions and procedures
9584 * M2 Constants:: Modula-2 constants
9585 * M2 Types:: Modula-2 types
9586 * M2 Defaults:: Default settings for Modula-2
9587 * Deviations:: Deviations from standard Modula-2
9588 * M2 Checks:: Modula-2 type and range checks
9589 * M2 Scope:: The scope operators @code{::} and @code{.}
9590 * GDB/M2:: @value{GDBN} and Modula-2
9594 @subsubsection Operators
9595 @cindex Modula-2 operators
9597 Operators must be defined on values of specific types. For instance,
9598 @code{+} is defined on numbers, but not on structures. Operators are
9599 often defined on groups of types. For the purposes of Modula-2, the
9600 following definitions hold:
9605 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9609 @emph{Character types} consist of @code{CHAR} and its subranges.
9612 @emph{Floating-point types} consist of @code{REAL}.
9615 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9619 @emph{Scalar types} consist of all of the above.
9622 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9625 @emph{Boolean types} consist of @code{BOOLEAN}.
9629 The following operators are supported, and appear in order of
9630 increasing precedence:
9634 Function argument or array index separator.
9637 Assignment. The value of @var{var} @code{:=} @var{value} is
9641 Less than, greater than on integral, floating-point, or enumerated
9645 Less than or equal to, greater than or equal to
9646 on integral, floating-point and enumerated types, or set inclusion on
9647 set types. Same precedence as @code{<}.
9649 @item =@r{, }<>@r{, }#
9650 Equality and two ways of expressing inequality, valid on scalar types.
9651 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9652 available for inequality, since @code{#} conflicts with the script
9656 Set membership. Defined on set types and the types of their members.
9657 Same precedence as @code{<}.
9660 Boolean disjunction. Defined on boolean types.
9663 Boolean conjunction. Defined on boolean types.
9666 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9669 Addition and subtraction on integral and floating-point types, or union
9670 and difference on set types.
9673 Multiplication on integral and floating-point types, or set intersection
9677 Division on floating-point types, or symmetric set difference on set
9678 types. Same precedence as @code{*}.
9681 Integer division and remainder. Defined on integral types. Same
9682 precedence as @code{*}.
9685 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9688 Pointer dereferencing. Defined on pointer types.
9691 Boolean negation. Defined on boolean types. Same precedence as
9695 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9696 precedence as @code{^}.
9699 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9702 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9706 @value{GDBN} and Modula-2 scope operators.
9710 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9711 treats the use of the operator @code{IN}, or the use of operators
9712 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9713 @code{<=}, and @code{>=} on sets as an error.
9717 @node Built-In Func/Proc
9718 @subsubsection Built-in functions and procedures
9719 @cindex Modula-2 built-ins
9721 Modula-2 also makes available several built-in procedures and functions.
9722 In describing these, the following metavariables are used:
9727 represents an @code{ARRAY} variable.
9730 represents a @code{CHAR} constant or variable.
9733 represents a variable or constant of integral type.
9736 represents an identifier that belongs to a set. Generally used in the
9737 same function with the metavariable @var{s}. The type of @var{s} should
9738 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9741 represents a variable or constant of integral or floating-point type.
9744 represents a variable or constant of floating-point type.
9750 represents a variable.
9753 represents a variable or constant of one of many types. See the
9754 explanation of the function for details.
9757 All Modula-2 built-in procedures also return a result, described below.
9761 Returns the absolute value of @var{n}.
9764 If @var{c} is a lower case letter, it returns its upper case
9765 equivalent, otherwise it returns its argument.
9768 Returns the character whose ordinal value is @var{i}.
9771 Decrements the value in the variable @var{v} by one. Returns the new value.
9773 @item DEC(@var{v},@var{i})
9774 Decrements the value in the variable @var{v} by @var{i}. Returns the
9777 @item EXCL(@var{m},@var{s})
9778 Removes the element @var{m} from the set @var{s}. Returns the new
9781 @item FLOAT(@var{i})
9782 Returns the floating point equivalent of the integer @var{i}.
9785 Returns the index of the last member of @var{a}.
9788 Increments the value in the variable @var{v} by one. Returns the new value.
9790 @item INC(@var{v},@var{i})
9791 Increments the value in the variable @var{v} by @var{i}. Returns the
9794 @item INCL(@var{m},@var{s})
9795 Adds the element @var{m} to the set @var{s} if it is not already
9796 there. Returns the new set.
9799 Returns the maximum value of the type @var{t}.
9802 Returns the minimum value of the type @var{t}.
9805 Returns boolean TRUE if @var{i} is an odd number.
9808 Returns the ordinal value of its argument. For example, the ordinal
9809 value of a character is its @sc{ascii} value (on machines supporting the
9810 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9811 integral, character and enumerated types.
9814 Returns the size of its argument. @var{x} can be a variable or a type.
9816 @item TRUNC(@var{r})
9817 Returns the integral part of @var{r}.
9819 @item VAL(@var{t},@var{i})
9820 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9824 @emph{Warning:} Sets and their operations are not yet supported, so
9825 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9829 @cindex Modula-2 constants
9831 @subsubsection Constants
9833 @value{GDBN} allows you to express the constants of Modula-2 in the following
9839 Integer constants are simply a sequence of digits. When used in an
9840 expression, a constant is interpreted to be type-compatible with the
9841 rest of the expression. Hexadecimal integers are specified by a
9842 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9845 Floating point constants appear as a sequence of digits, followed by a
9846 decimal point and another sequence of digits. An optional exponent can
9847 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9848 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9849 digits of the floating point constant must be valid decimal (base 10)
9853 Character constants consist of a single character enclosed by a pair of
9854 like quotes, either single (@code{'}) or double (@code{"}). They may
9855 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9856 followed by a @samp{C}.
9859 String constants consist of a sequence of characters enclosed by a
9860 pair of like quotes, either single (@code{'}) or double (@code{"}).
9861 Escape sequences in the style of C are also allowed. @xref{C
9862 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9866 Enumerated constants consist of an enumerated identifier.
9869 Boolean constants consist of the identifiers @code{TRUE} and
9873 Pointer constants consist of integral values only.
9876 Set constants are not yet supported.
9880 @subsubsection Modula-2 Types
9881 @cindex Modula-2 types
9883 Currently @value{GDBN} can print the following data types in Modula-2
9884 syntax: array types, record types, set types, pointer types, procedure
9885 types, enumerated types, subrange types and base types. You can also
9886 print the contents of variables declared using these type.
9887 This section gives a number of simple source code examples together with
9888 sample @value{GDBN} sessions.
9890 The first example contains the following section of code:
9899 and you can request @value{GDBN} to interrogate the type and value of
9900 @code{r} and @code{s}.
9903 (@value{GDBP}) print s
9905 (@value{GDBP}) ptype s
9907 (@value{GDBP}) print r
9909 (@value{GDBP}) ptype r
9914 Likewise if your source code declares @code{s} as:
9922 then you may query the type of @code{s} by:
9925 (@value{GDBP}) ptype s
9926 type = SET ['A'..'Z']
9930 Note that at present you cannot interactively manipulate set
9931 expressions using the debugger.
9933 The following example shows how you might declare an array in Modula-2
9934 and how you can interact with @value{GDBN} to print its type and contents:
9938 s: ARRAY [-10..10] OF CHAR ;
9942 (@value{GDBP}) ptype s
9943 ARRAY [-10..10] OF CHAR
9946 Note that the array handling is not yet complete and although the type
9947 is printed correctly, expression handling still assumes that all
9948 arrays have a lower bound of zero and not @code{-10} as in the example
9949 above. Unbounded arrays are also not yet recognized in @value{GDBN}.
9951 Here are some more type related Modula-2 examples:
9955 colour = (blue, red, yellow, green) ;
9956 t = [blue..yellow] ;
9964 The @value{GDBN} interaction shows how you can query the data type
9965 and value of a variable.
9968 (@value{GDBP}) print s
9970 (@value{GDBP}) ptype t
9971 type = [blue..yellow]
9975 In this example a Modula-2 array is declared and its contents
9976 displayed. Observe that the contents are written in the same way as
9977 their @code{C} counterparts.
9981 s: ARRAY [1..5] OF CARDINAL ;
9987 (@value{GDBP}) print s
9988 $1 = @{1, 0, 0, 0, 0@}
9989 (@value{GDBP}) ptype s
9990 type = ARRAY [1..5] OF CARDINAL
9993 The Modula-2 language interface to @value{GDBN} also understands
9994 pointer types as shown in this example:
9998 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10005 and you can request that @value{GDBN} describes the type of @code{s}.
10008 (@value{GDBP}) ptype s
10009 type = POINTER TO ARRAY [1..5] OF CARDINAL
10012 @value{GDBN} handles compound types as we can see in this example.
10013 Here we combine array types, record types, pointer types and subrange
10024 myarray = ARRAY myrange OF CARDINAL ;
10025 myrange = [-2..2] ;
10027 s: POINTER TO ARRAY myrange OF foo ;
10031 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10035 (@value{GDBP}) ptype s
10036 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10039 f3 : ARRAY [-2..2] OF CARDINAL;
10044 @subsubsection Modula-2 defaults
10045 @cindex Modula-2 defaults
10047 If type and range checking are set automatically by @value{GDBN}, they
10048 both default to @code{on} whenever the working language changes to
10049 Modula-2. This happens regardless of whether you or @value{GDBN}
10050 selected the working language.
10052 If you allow @value{GDBN} to set the language automatically, then entering
10053 code compiled from a file whose name ends with @file{.mod} sets the
10054 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
10055 the language automatically}, for further details.
10058 @subsubsection Deviations from standard Modula-2
10059 @cindex Modula-2, deviations from
10061 A few changes have been made to make Modula-2 programs easier to debug.
10062 This is done primarily via loosening its type strictness:
10066 Unlike in standard Modula-2, pointer constants can be formed by
10067 integers. This allows you to modify pointer variables during
10068 debugging. (In standard Modula-2, the actual address contained in a
10069 pointer variable is hidden from you; it can only be modified
10070 through direct assignment to another pointer variable or expression that
10071 returned a pointer.)
10074 C escape sequences can be used in strings and characters to represent
10075 non-printable characters. @value{GDBN} prints out strings with these
10076 escape sequences embedded. Single non-printable characters are
10077 printed using the @samp{CHR(@var{nnn})} format.
10080 The assignment operator (@code{:=}) returns the value of its right-hand
10084 All built-in procedures both modify @emph{and} return their argument.
10088 @subsubsection Modula-2 type and range checks
10089 @cindex Modula-2 checks
10092 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10095 @c FIXME remove warning when type/range checks added
10097 @value{GDBN} considers two Modula-2 variables type equivalent if:
10101 They are of types that have been declared equivalent via a @code{TYPE
10102 @var{t1} = @var{t2}} statement
10105 They have been declared on the same line. (Note: This is true of the
10106 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10109 As long as type checking is enabled, any attempt to combine variables
10110 whose types are not equivalent is an error.
10112 Range checking is done on all mathematical operations, assignment, array
10113 index bounds, and all built-in functions and procedures.
10116 @subsubsection The scope operators @code{::} and @code{.}
10118 @cindex @code{.}, Modula-2 scope operator
10119 @cindex colon, doubled as scope operator
10121 @vindex colon-colon@r{, in Modula-2}
10122 @c Info cannot handle :: but TeX can.
10125 @vindex ::@r{, in Modula-2}
10128 There are a few subtle differences between the Modula-2 scope operator
10129 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10134 @var{module} . @var{id}
10135 @var{scope} :: @var{id}
10139 where @var{scope} is the name of a module or a procedure,
10140 @var{module} the name of a module, and @var{id} is any declared
10141 identifier within your program, except another module.
10143 Using the @code{::} operator makes @value{GDBN} search the scope
10144 specified by @var{scope} for the identifier @var{id}. If it is not
10145 found in the specified scope, then @value{GDBN} searches all scopes
10146 enclosing the one specified by @var{scope}.
10148 Using the @code{.} operator makes @value{GDBN} search the current scope for
10149 the identifier specified by @var{id} that was imported from the
10150 definition module specified by @var{module}. With this operator, it is
10151 an error if the identifier @var{id} was not imported from definition
10152 module @var{module}, or if @var{id} is not an identifier in
10156 @subsubsection @value{GDBN} and Modula-2
10158 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10159 Five subcommands of @code{set print} and @code{show print} apply
10160 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10161 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10162 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10163 analogue in Modula-2.
10165 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10166 with any language, is not useful with Modula-2. Its
10167 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10168 created in Modula-2 as they can in C or C@t{++}. However, because an
10169 address can be specified by an integral constant, the construct
10170 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10172 @cindex @code{#} in Modula-2
10173 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10174 interpreted as the beginning of a comment. Use @code{<>} instead.
10180 The extensions made to @value{GDBN} for Ada only support
10181 output from the @sc{gnu} Ada (GNAT) compiler.
10182 Other Ada compilers are not currently supported, and
10183 attempting to debug executables produced by them is most likely
10187 @cindex expressions in Ada
10189 * Ada Mode Intro:: General remarks on the Ada syntax
10190 and semantics supported by Ada mode
10192 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10193 * Additions to Ada:: Extensions of the Ada expression syntax.
10194 * Stopping Before Main Program:: Debugging the program during elaboration.
10195 * Ada Glitches:: Known peculiarities of Ada mode.
10198 @node Ada Mode Intro
10199 @subsubsection Introduction
10200 @cindex Ada mode, general
10202 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10203 syntax, with some extensions.
10204 The philosophy behind the design of this subset is
10208 That @value{GDBN} should provide basic literals and access to operations for
10209 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10210 leaving more sophisticated computations to subprograms written into the
10211 program (which therefore may be called from @value{GDBN}).
10214 That type safety and strict adherence to Ada language restrictions
10215 are not particularly important to the @value{GDBN} user.
10218 That brevity is important to the @value{GDBN} user.
10221 Thus, for brevity, the debugger acts as if there were
10222 implicit @code{with} and @code{use} clauses in effect for all user-written
10223 packages, making it unnecessary to fully qualify most names with
10224 their packages, regardless of context. Where this causes ambiguity,
10225 @value{GDBN} asks the user's intent.
10227 The debugger will start in Ada mode if it detects an Ada main program.
10228 As for other languages, it will enter Ada mode when stopped in a program that
10229 was translated from an Ada source file.
10231 While in Ada mode, you may use `@t{--}' for comments. This is useful
10232 mostly for documenting command files. The standard @value{GDBN} comment
10233 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10234 middle (to allow based literals).
10236 The debugger supports limited overloading. Given a subprogram call in which
10237 the function symbol has multiple definitions, it will use the number of
10238 actual parameters and some information about their types to attempt to narrow
10239 the set of definitions. It also makes very limited use of context, preferring
10240 procedures to functions in the context of the @code{call} command, and
10241 functions to procedures elsewhere.
10243 @node Omissions from Ada
10244 @subsubsection Omissions from Ada
10245 @cindex Ada, omissions from
10247 Here are the notable omissions from the subset:
10251 Only a subset of the attributes are supported:
10255 @t{'First}, @t{'Last}, and @t{'Length}
10256 on array objects (not on types and subtypes).
10259 @t{'Min} and @t{'Max}.
10262 @t{'Pos} and @t{'Val}.
10268 @t{'Range} on array objects (not subtypes), but only as the right
10269 operand of the membership (@code{in}) operator.
10272 @t{'Access}, @t{'Unchecked_Access}, and
10273 @t{'Unrestricted_Access} (a GNAT extension).
10281 @code{Characters.Latin_1} are not available and
10282 concatenation is not implemented. Thus, escape characters in strings are
10283 not currently available.
10286 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10287 equality of representations. They will generally work correctly
10288 for strings and arrays whose elements have integer or enumeration types.
10289 They may not work correctly for arrays whose element
10290 types have user-defined equality, for arrays of real values
10291 (in particular, IEEE-conformant floating point, because of negative
10292 zeroes and NaNs), and for arrays whose elements contain unused bits with
10293 indeterminate values.
10296 The other component-by-component array operations (@code{and}, @code{or},
10297 @code{xor}, @code{not}, and relational tests other than equality)
10298 are not implemented.
10301 @cindex array aggregates (Ada)
10302 @cindex record aggregates (Ada)
10303 @cindex aggregates (Ada)
10304 There is limited support for array and record aggregates. They are
10305 permitted only on the right sides of assignments, as in these examples:
10308 set An_Array := (1, 2, 3, 4, 5, 6)
10309 set An_Array := (1, others => 0)
10310 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10311 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10312 set A_Record := (1, "Peter", True);
10313 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10317 discriminant's value by assigning an aggregate has an
10318 undefined effect if that discriminant is used within the record.
10319 However, you can first modify discriminants by directly assigning to
10320 them (which normally would not be allowed in Ada), and then performing an
10321 aggregate assignment. For example, given a variable @code{A_Rec}
10322 declared to have a type such as:
10325 type Rec (Len : Small_Integer := 0) is record
10327 Vals : IntArray (1 .. Len);
10331 you can assign a value with a different size of @code{Vals} with two
10336 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10339 As this example also illustrates, @value{GDBN} is very loose about the usual
10340 rules concerning aggregates. You may leave out some of the
10341 components of an array or record aggregate (such as the @code{Len}
10342 component in the assignment to @code{A_Rec} above); they will retain their
10343 original values upon assignment. You may freely use dynamic values as
10344 indices in component associations. You may even use overlapping or
10345 redundant component associations, although which component values are
10346 assigned in such cases is not defined.
10349 Calls to dispatching subprograms are not implemented.
10352 The overloading algorithm is much more limited (i.e., less selective)
10353 than that of real Ada. It makes only limited use of the context in which a subexpression
10354 appears to resolve its meaning, and it is much looser in its rules for allowing
10355 type matches. As a result, some function calls will be ambiguous, and the user
10356 will be asked to choose the proper resolution.
10359 The @code{new} operator is not implemented.
10362 Entry calls are not implemented.
10365 Aside from printing, arithmetic operations on the native VAX floating-point
10366 formats are not supported.
10369 It is not possible to slice a packed array.
10372 @node Additions to Ada
10373 @subsubsection Additions to Ada
10374 @cindex Ada, deviations from
10376 As it does for other languages, @value{GDBN} makes certain generic
10377 extensions to Ada (@pxref{Expressions}):
10381 If the expression @var{E} is a variable residing in memory
10382 (typically a local variable or array element) and @var{N} is
10383 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
10384 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
10385 In Ada, this operator is generally not necessary, since its prime use
10386 is in displaying parts of an array, and slicing will usually do this in Ada.
10387 However, there are occasional uses when debugging programs
10388 in which certain debugging information has been optimized away.
10391 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
10392 in function or file @var{B}.'' When @var{B} is a file name, you must typically
10393 surround it in single quotes.
10396 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10397 @var{type} that appears at address @var{addr}.''
10400 A name starting with @samp{$} is a convenience variable
10401 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10404 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
10409 The assignment statement is allowed as an expression, returning
10410 its right-hand operand as its value. Thus, you may enter
10414 print A(tmp := y + 1)
10418 The semicolon is allowed as an ``operator,'' returning as its value
10419 the value of its right-hand operand.
10420 This allows, for example,
10421 complex conditional breaks:
10425 condition 1 (report(i); k += 1; A(k) > 100)
10429 Rather than use catenation and symbolic character names to introduce special
10430 characters into strings, one may instead use a special bracket notation,
10431 which is also used to print strings. A sequence of characters of the form
10432 @samp{["@var{XX}"]} within a string or character literal denotes the
10433 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10434 sequence of characters @samp{["""]} also denotes a single quotation mark
10435 in strings. For example,
10437 "One line.["0a"]Next line.["0a"]"
10440 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
10444 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10445 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10453 When printing arrays, @value{GDBN} uses positional notation when the
10454 array has a lower bound of 1, and uses a modified named notation otherwise.
10455 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
10462 That is, in contrast to valid Ada, only the first component has a @code{=>}
10466 You may abbreviate attributes in expressions with any unique,
10467 multi-character subsequence of
10468 their names (an exact match gets preference).
10469 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10470 in place of @t{a'length}.
10473 @cindex quoting Ada internal identifiers
10474 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10475 to lower case. The GNAT compiler uses upper-case characters for
10476 some of its internal identifiers, which are normally of no interest to users.
10477 For the rare occasions when you actually have to look at them,
10478 enclose them in angle brackets to avoid the lower-case mapping.
10481 @value{GDBP} print <JMPBUF_SAVE>[0]
10485 Printing an object of class-wide type or dereferencing an
10486 access-to-class-wide value will display all the components of the object's
10487 specific type (as indicated by its run-time tag). Likewise, component
10488 selection on such a value will operate on the specific type of the
10493 @node Stopping Before Main Program
10494 @subsubsection Stopping at the Very Beginning
10496 @cindex breakpointing Ada elaboration code
10497 It is sometimes necessary to debug the program during elaboration, and
10498 before reaching the main procedure.
10499 As defined in the Ada Reference
10500 Manual, the elaboration code is invoked from a procedure called
10501 @code{adainit}. To run your program up to the beginning of
10502 elaboration, simply use the following two commands:
10503 @code{tbreak adainit} and @code{run}.
10506 @subsubsection Known Peculiarities of Ada Mode
10507 @cindex Ada, problems
10509 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10510 we know of several problems with and limitations of Ada mode in
10512 some of which will be fixed with planned future releases of the debugger
10513 and the GNU Ada compiler.
10517 Currently, the debugger
10518 has insufficient information to determine whether certain pointers represent
10519 pointers to objects or the objects themselves.
10520 Thus, the user may have to tack an extra @code{.all} after an expression
10521 to get it printed properly.
10524 Static constants that the compiler chooses not to materialize as objects in
10525 storage are invisible to the debugger.
10528 Named parameter associations in function argument lists are ignored (the
10529 argument lists are treated as positional).
10532 Many useful library packages are currently invisible to the debugger.
10535 Fixed-point arithmetic, conversions, input, and output is carried out using
10536 floating-point arithmetic, and may give results that only approximate those on
10540 The type of the @t{'Address} attribute may not be @code{System.Address}.
10543 The GNAT compiler never generates the prefix @code{Standard} for any of
10544 the standard symbols defined by the Ada language. @value{GDBN} knows about
10545 this: it will strip the prefix from names when you use it, and will never
10546 look for a name you have so qualified among local symbols, nor match against
10547 symbols in other packages or subprograms. If you have
10548 defined entities anywhere in your program other than parameters and
10549 local variables whose simple names match names in @code{Standard},
10550 GNAT's lack of qualification here can cause confusion. When this happens,
10551 you can usually resolve the confusion
10552 by qualifying the problematic names with package
10553 @code{Standard} explicitly.
10556 @node Unsupported languages
10557 @section Unsupported languages
10559 @cindex unsupported languages
10560 @cindex minimal language
10561 In addition to the other fully-supported programming languages,
10562 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10563 It does not represent a real programming language, but provides a set
10564 of capabilities close to what the C or assembly languages provide.
10565 This should allow most simple operations to be performed while debugging
10566 an application that uses a language currently not supported by @value{GDBN}.
10568 If the language is set to @code{auto}, @value{GDBN} will automatically
10569 select this language if the current frame corresponds to an unsupported
10573 @chapter Examining the Symbol Table
10575 The commands described in this chapter allow you to inquire about the
10576 symbols (names of variables, functions and types) defined in your
10577 program. This information is inherent in the text of your program and
10578 does not change as your program executes. @value{GDBN} finds it in your
10579 program's symbol table, in the file indicated when you started @value{GDBN}
10580 (@pxref{File Options, ,Choosing files}), or by one of the
10581 file-management commands (@pxref{Files, ,Commands to specify files}).
10583 @cindex symbol names
10584 @cindex names of symbols
10585 @cindex quoting names
10586 Occasionally, you may need to refer to symbols that contain unusual
10587 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10588 most frequent case is in referring to static variables in other
10589 source files (@pxref{Variables,,Program variables}). File names
10590 are recorded in object files as debugging symbols, but @value{GDBN} would
10591 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10592 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10593 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10600 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10603 @cindex case-insensitive symbol names
10604 @cindex case sensitivity in symbol names
10605 @kindex set case-sensitive
10606 @item set case-sensitive on
10607 @itemx set case-sensitive off
10608 @itemx set case-sensitive auto
10609 Normally, when @value{GDBN} looks up symbols, it matches their names
10610 with case sensitivity determined by the current source language.
10611 Occasionally, you may wish to control that. The command @code{set
10612 case-sensitive} lets you do that by specifying @code{on} for
10613 case-sensitive matches or @code{off} for case-insensitive ones. If
10614 you specify @code{auto}, case sensitivity is reset to the default
10615 suitable for the source language. The default is case-sensitive
10616 matches for all languages except for Fortran, for which the default is
10617 case-insensitive matches.
10619 @kindex show case-sensitive
10620 @item show case-sensitive
10621 This command shows the current setting of case sensitivity for symbols
10624 @kindex info address
10625 @cindex address of a symbol
10626 @item info address @var{symbol}
10627 Describe where the data for @var{symbol} is stored. For a register
10628 variable, this says which register it is kept in. For a non-register
10629 local variable, this prints the stack-frame offset at which the variable
10632 Note the contrast with @samp{print &@var{symbol}}, which does not work
10633 at all for a register variable, and for a stack local variable prints
10634 the exact address of the current instantiation of the variable.
10636 @kindex info symbol
10637 @cindex symbol from address
10638 @cindex closest symbol and offset for an address
10639 @item info symbol @var{addr}
10640 Print the name of a symbol which is stored at the address @var{addr}.
10641 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10642 nearest symbol and an offset from it:
10645 (@value{GDBP}) info symbol 0x54320
10646 _initialize_vx + 396 in section .text
10650 This is the opposite of the @code{info address} command. You can use
10651 it to find out the name of a variable or a function given its address.
10654 @item whatis [@var{arg}]
10655 Print the data type of @var{arg}, which can be either an expression or
10656 a data type. With no argument, print the data type of @code{$}, the
10657 last value in the value history. If @var{arg} is an expression, it is
10658 not actually evaluated, and any side-effecting operations (such as
10659 assignments or function calls) inside it do not take place. If
10660 @var{arg} is a type name, it may be the name of a type or typedef, or
10661 for C code it may have the form @samp{class @var{class-name}},
10662 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10663 @samp{enum @var{enum-tag}}.
10664 @xref{Expressions, ,Expressions}.
10667 @item ptype [@var{arg}]
10668 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10669 detailed description of the type, instead of just the name of the type.
10670 @xref{Expressions, ,Expressions}.
10672 For example, for this variable declaration:
10675 struct complex @{double real; double imag;@} v;
10679 the two commands give this output:
10683 (@value{GDBP}) whatis v
10684 type = struct complex
10685 (@value{GDBP}) ptype v
10686 type = struct complex @{
10694 As with @code{whatis}, using @code{ptype} without an argument refers to
10695 the type of @code{$}, the last value in the value history.
10697 @cindex incomplete type
10698 Sometimes, programs use opaque data types or incomplete specifications
10699 of complex data structure. If the debug information included in the
10700 program does not allow @value{GDBN} to display a full declaration of
10701 the data type, it will say @samp{<incomplete type>}. For example,
10702 given these declarations:
10706 struct foo *fooptr;
10710 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10713 (@value{GDBP}) ptype foo
10714 $1 = <incomplete type>
10718 ``Incomplete type'' is C terminology for data types that are not
10719 completely specified.
10722 @item info types @var{regexp}
10724 Print a brief description of all types whose names match the regular
10725 expression @var{regexp} (or all types in your program, if you supply
10726 no argument). Each complete typename is matched as though it were a
10727 complete line; thus, @samp{i type value} gives information on all
10728 types in your program whose names include the string @code{value}, but
10729 @samp{i type ^value$} gives information only on types whose complete
10730 name is @code{value}.
10732 This command differs from @code{ptype} in two ways: first, like
10733 @code{whatis}, it does not print a detailed description; second, it
10734 lists all source files where a type is defined.
10737 @cindex local variables
10738 @item info scope @var{location}
10739 List all the variables local to a particular scope. This command
10740 accepts a @var{location} argument---a function name, a source line, or
10741 an address preceded by a @samp{*}, and prints all the variables local
10742 to the scope defined by that location. For example:
10745 (@value{GDBP}) @b{info scope command_line_handler}
10746 Scope for command_line_handler:
10747 Symbol rl is an argument at stack/frame offset 8, length 4.
10748 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10749 Symbol linelength is in static storage at address 0x150a1c, length 4.
10750 Symbol p is a local variable in register $esi, length 4.
10751 Symbol p1 is a local variable in register $ebx, length 4.
10752 Symbol nline is a local variable in register $edx, length 4.
10753 Symbol repeat is a local variable at frame offset -8, length 4.
10757 This command is especially useful for determining what data to collect
10758 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10761 @kindex info source
10763 Show information about the current source file---that is, the source file for
10764 the function containing the current point of execution:
10767 the name of the source file, and the directory containing it,
10769 the directory it was compiled in,
10771 its length, in lines,
10773 which programming language it is written in,
10775 whether the executable includes debugging information for that file, and
10776 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10778 whether the debugging information includes information about
10779 preprocessor macros.
10783 @kindex info sources
10785 Print the names of all source files in your program for which there is
10786 debugging information, organized into two lists: files whose symbols
10787 have already been read, and files whose symbols will be read when needed.
10789 @kindex info functions
10790 @item info functions
10791 Print the names and data types of all defined functions.
10793 @item info functions @var{regexp}
10794 Print the names and data types of all defined functions
10795 whose names contain a match for regular expression @var{regexp}.
10796 Thus, @samp{info fun step} finds all functions whose names
10797 include @code{step}; @samp{info fun ^step} finds those whose names
10798 start with @code{step}. If a function name contains characters
10799 that conflict with the regular expression language (e.g.@:
10800 @samp{operator*()}), they may be quoted with a backslash.
10802 @kindex info variables
10803 @item info variables
10804 Print the names and data types of all variables that are declared
10805 outside of functions (i.e.@: excluding local variables).
10807 @item info variables @var{regexp}
10808 Print the names and data types of all variables (except for local
10809 variables) whose names contain a match for regular expression
10812 @kindex info classes
10813 @cindex Objective-C, classes and selectors
10815 @itemx info classes @var{regexp}
10816 Display all Objective-C classes in your program, or
10817 (with the @var{regexp} argument) all those matching a particular regular
10820 @kindex info selectors
10821 @item info selectors
10822 @itemx info selectors @var{regexp}
10823 Display all Objective-C selectors in your program, or
10824 (with the @var{regexp} argument) all those matching a particular regular
10828 This was never implemented.
10829 @kindex info methods
10831 @itemx info methods @var{regexp}
10832 The @code{info methods} command permits the user to examine all defined
10833 methods within C@t{++} program, or (with the @var{regexp} argument) a
10834 specific set of methods found in the various C@t{++} classes. Many
10835 C@t{++} classes provide a large number of methods. Thus, the output
10836 from the @code{ptype} command can be overwhelming and hard to use. The
10837 @code{info-methods} command filters the methods, printing only those
10838 which match the regular-expression @var{regexp}.
10841 @cindex reloading symbols
10842 Some systems allow individual object files that make up your program to
10843 be replaced without stopping and restarting your program. For example,
10844 in VxWorks you can simply recompile a defective object file and keep on
10845 running. If you are running on one of these systems, you can allow
10846 @value{GDBN} to reload the symbols for automatically relinked modules:
10849 @kindex set symbol-reloading
10850 @item set symbol-reloading on
10851 Replace symbol definitions for the corresponding source file when an
10852 object file with a particular name is seen again.
10854 @item set symbol-reloading off
10855 Do not replace symbol definitions when encountering object files of the
10856 same name more than once. This is the default state; if you are not
10857 running on a system that permits automatic relinking of modules, you
10858 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10859 may discard symbols when linking large programs, that may contain
10860 several modules (from different directories or libraries) with the same
10863 @kindex show symbol-reloading
10864 @item show symbol-reloading
10865 Show the current @code{on} or @code{off} setting.
10868 @cindex opaque data types
10869 @kindex set opaque-type-resolution
10870 @item set opaque-type-resolution on
10871 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10872 declared as a pointer to a @code{struct}, @code{class}, or
10873 @code{union}---for example, @code{struct MyType *}---that is used in one
10874 source file although the full declaration of @code{struct MyType} is in
10875 another source file. The default is on.
10877 A change in the setting of this subcommand will not take effect until
10878 the next time symbols for a file are loaded.
10880 @item set opaque-type-resolution off
10881 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10882 is printed as follows:
10884 @{<no data fields>@}
10887 @kindex show opaque-type-resolution
10888 @item show opaque-type-resolution
10889 Show whether opaque types are resolved or not.
10891 @kindex maint print symbols
10892 @cindex symbol dump
10893 @kindex maint print psymbols
10894 @cindex partial symbol dump
10895 @item maint print symbols @var{filename}
10896 @itemx maint print psymbols @var{filename}
10897 @itemx maint print msymbols @var{filename}
10898 Write a dump of debugging symbol data into the file @var{filename}.
10899 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10900 symbols with debugging data are included. If you use @samp{maint print
10901 symbols}, @value{GDBN} includes all the symbols for which it has already
10902 collected full details: that is, @var{filename} reflects symbols for
10903 only those files whose symbols @value{GDBN} has read. You can use the
10904 command @code{info sources} to find out which files these are. If you
10905 use @samp{maint print psymbols} instead, the dump shows information about
10906 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10907 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10908 @samp{maint print msymbols} dumps just the minimal symbol information
10909 required for each object file from which @value{GDBN} has read some symbols.
10910 @xref{Files, ,Commands to specify files}, for a discussion of how
10911 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10913 @kindex maint info symtabs
10914 @kindex maint info psymtabs
10915 @cindex listing @value{GDBN}'s internal symbol tables
10916 @cindex symbol tables, listing @value{GDBN}'s internal
10917 @cindex full symbol tables, listing @value{GDBN}'s internal
10918 @cindex partial symbol tables, listing @value{GDBN}'s internal
10919 @item maint info symtabs @r{[} @var{regexp} @r{]}
10920 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10922 List the @code{struct symtab} or @code{struct partial_symtab}
10923 structures whose names match @var{regexp}. If @var{regexp} is not
10924 given, list them all. The output includes expressions which you can
10925 copy into a @value{GDBN} debugging this one to examine a particular
10926 structure in more detail. For example:
10929 (@value{GDBP}) maint info psymtabs dwarf2read
10930 @{ objfile /home/gnu/build/gdb/gdb
10931 ((struct objfile *) 0x82e69d0)
10932 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10933 ((struct partial_symtab *) 0x8474b10)
10936 text addresses 0x814d3c8 -- 0x8158074
10937 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10938 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10939 dependencies (none)
10942 (@value{GDBP}) maint info symtabs
10946 We see that there is one partial symbol table whose filename contains
10947 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10948 and we see that @value{GDBN} has not read in any symtabs yet at all.
10949 If we set a breakpoint on a function, that will cause @value{GDBN} to
10950 read the symtab for the compilation unit containing that function:
10953 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10954 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10956 (@value{GDBP}) maint info symtabs
10957 @{ objfile /home/gnu/build/gdb/gdb
10958 ((struct objfile *) 0x82e69d0)
10959 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10960 ((struct symtab *) 0x86c1f38)
10963 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10964 debugformat DWARF 2
10973 @chapter Altering Execution
10975 Once you think you have found an error in your program, you might want to
10976 find out for certain whether correcting the apparent error would lead to
10977 correct results in the rest of the run. You can find the answer by
10978 experiment, using the @value{GDBN} features for altering execution of the
10981 For example, you can store new values into variables or memory
10982 locations, give your program a signal, restart it at a different
10983 address, or even return prematurely from a function.
10986 * Assignment:: Assignment to variables
10987 * Jumping:: Continuing at a different address
10988 * Signaling:: Giving your program a signal
10989 * Returning:: Returning from a function
10990 * Calling:: Calling your program's functions
10991 * Patching:: Patching your program
10995 @section Assignment to variables
10998 @cindex setting variables
10999 To alter the value of a variable, evaluate an assignment expression.
11000 @xref{Expressions, ,Expressions}. For example,
11007 stores the value 4 into the variable @code{x}, and then prints the
11008 value of the assignment expression (which is 4).
11009 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11010 information on operators in supported languages.
11012 @kindex set variable
11013 @cindex variables, setting
11014 If you are not interested in seeing the value of the assignment, use the
11015 @code{set} command instead of the @code{print} command. @code{set} is
11016 really the same as @code{print} except that the expression's value is
11017 not printed and is not put in the value history (@pxref{Value History,
11018 ,Value history}). The expression is evaluated only for its effects.
11020 If the beginning of the argument string of the @code{set} command
11021 appears identical to a @code{set} subcommand, use the @code{set
11022 variable} command instead of just @code{set}. This command is identical
11023 to @code{set} except for its lack of subcommands. For example, if your
11024 program has a variable @code{width}, you get an error if you try to set
11025 a new value with just @samp{set width=13}, because @value{GDBN} has the
11026 command @code{set width}:
11029 (@value{GDBP}) whatis width
11031 (@value{GDBP}) p width
11033 (@value{GDBP}) set width=47
11034 Invalid syntax in expression.
11038 The invalid expression, of course, is @samp{=47}. In
11039 order to actually set the program's variable @code{width}, use
11042 (@value{GDBP}) set var width=47
11045 Because the @code{set} command has many subcommands that can conflict
11046 with the names of program variables, it is a good idea to use the
11047 @code{set variable} command instead of just @code{set}. For example, if
11048 your program has a variable @code{g}, you run into problems if you try
11049 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11050 the command @code{set gnutarget}, abbreviated @code{set g}:
11054 (@value{GDBP}) whatis g
11058 (@value{GDBP}) set g=4
11062 The program being debugged has been started already.
11063 Start it from the beginning? (y or n) y
11064 Starting program: /home/smith/cc_progs/a.out
11065 "/home/smith/cc_progs/a.out": can't open to read symbols:
11066 Invalid bfd target.
11067 (@value{GDBP}) show g
11068 The current BFD target is "=4".
11073 The program variable @code{g} did not change, and you silently set the
11074 @code{gnutarget} to an invalid value. In order to set the variable
11078 (@value{GDBP}) set var g=4
11081 @value{GDBN} allows more implicit conversions in assignments than C; you can
11082 freely store an integer value into a pointer variable or vice versa,
11083 and you can convert any structure to any other structure that is the
11084 same length or shorter.
11085 @comment FIXME: how do structs align/pad in these conversions?
11086 @comment /doc@cygnus.com 18dec1990
11088 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11089 construct to generate a value of specified type at a specified address
11090 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11091 to memory location @code{0x83040} as an integer (which implies a certain size
11092 and representation in memory), and
11095 set @{int@}0x83040 = 4
11099 stores the value 4 into that memory location.
11102 @section Continuing at a different address
11104 Ordinarily, when you continue your program, you do so at the place where
11105 it stopped, with the @code{continue} command. You can instead continue at
11106 an address of your own choosing, with the following commands:
11110 @item jump @var{linespec}
11111 Resume execution at line @var{linespec}. Execution stops again
11112 immediately if there is a breakpoint there. @xref{List, ,Printing
11113 source lines}, for a description of the different forms of
11114 @var{linespec}. It is common practice to use the @code{tbreak} command
11115 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11118 The @code{jump} command does not change the current stack frame, or
11119 the stack pointer, or the contents of any memory location or any
11120 register other than the program counter. If line @var{linespec} is in
11121 a different function from the one currently executing, the results may
11122 be bizarre if the two functions expect different patterns of arguments or
11123 of local variables. For this reason, the @code{jump} command requests
11124 confirmation if the specified line is not in the function currently
11125 executing. However, even bizarre results are predictable if you are
11126 well acquainted with the machine-language code of your program.
11128 @item jump *@var{address}
11129 Resume execution at the instruction at address @var{address}.
11132 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11133 On many systems, you can get much the same effect as the @code{jump}
11134 command by storing a new value into the register @code{$pc}. The
11135 difference is that this does not start your program running; it only
11136 changes the address of where it @emph{will} run when you continue. For
11144 makes the next @code{continue} command or stepping command execute at
11145 address @code{0x485}, rather than at the address where your program stopped.
11146 @xref{Continuing and Stepping, ,Continuing and stepping}.
11148 The most common occasion to use the @code{jump} command is to back
11149 up---perhaps with more breakpoints set---over a portion of a program
11150 that has already executed, in order to examine its execution in more
11155 @section Giving your program a signal
11156 @cindex deliver a signal to a program
11160 @item signal @var{signal}
11161 Resume execution where your program stopped, but immediately give it the
11162 signal @var{signal}. @var{signal} can be the name or the number of a
11163 signal. For example, on many systems @code{signal 2} and @code{signal
11164 SIGINT} are both ways of sending an interrupt signal.
11166 Alternatively, if @var{signal} is zero, continue execution without
11167 giving a signal. This is useful when your program stopped on account of
11168 a signal and would ordinary see the signal when resumed with the
11169 @code{continue} command; @samp{signal 0} causes it to resume without a
11172 @code{signal} does not repeat when you press @key{RET} a second time
11173 after executing the command.
11177 Invoking the @code{signal} command is not the same as invoking the
11178 @code{kill} utility from the shell. Sending a signal with @code{kill}
11179 causes @value{GDBN} to decide what to do with the signal depending on
11180 the signal handling tables (@pxref{Signals}). The @code{signal} command
11181 passes the signal directly to your program.
11185 @section Returning from a function
11188 @cindex returning from a function
11191 @itemx return @var{expression}
11192 You can cancel execution of a function call with the @code{return}
11193 command. If you give an
11194 @var{expression} argument, its value is used as the function's return
11198 When you use @code{return}, @value{GDBN} discards the selected stack frame
11199 (and all frames within it). You can think of this as making the
11200 discarded frame return prematurely. If you wish to specify a value to
11201 be returned, give that value as the argument to @code{return}.
11203 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11204 frame}), and any other frames inside of it, leaving its caller as the
11205 innermost remaining frame. That frame becomes selected. The
11206 specified value is stored in the registers used for returning values
11209 The @code{return} command does not resume execution; it leaves the
11210 program stopped in the state that would exist if the function had just
11211 returned. In contrast, the @code{finish} command (@pxref{Continuing
11212 and Stepping, ,Continuing and stepping}) resumes execution until the
11213 selected stack frame returns naturally.
11216 @section Calling program functions
11219 @cindex calling functions
11220 @cindex inferior functions, calling
11221 @item print @var{expr}
11222 Evaluate the expression @var{expr} and display the resuling value.
11223 @var{expr} may include calls to functions in the program being
11227 @item call @var{expr}
11228 Evaluate the expression @var{expr} without displaying @code{void}
11231 You can use this variant of the @code{print} command if you want to
11232 execute a function from your program that does not return anything
11233 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11234 with @code{void} returned values that @value{GDBN} will otherwise
11235 print. If the result is not void, it is printed and saved in the
11239 It is possible for the function you call via the @code{print} or
11240 @code{call} command to generate a signal (e.g., if there's a bug in
11241 the function, or if you passed it incorrect arguments). What happens
11242 in that case is controlled by the @code{set unwindonsignal} command.
11245 @item set unwindonsignal
11246 @kindex set unwindonsignal
11247 @cindex unwind stack in called functions
11248 @cindex call dummy stack unwinding
11249 Set unwinding of the stack if a signal is received while in a function
11250 that @value{GDBN} called in the program being debugged. If set to on,
11251 @value{GDBN} unwinds the stack it created for the call and restores
11252 the context to what it was before the call. If set to off (the
11253 default), @value{GDBN} stops in the frame where the signal was
11256 @item show unwindonsignal
11257 @kindex show unwindonsignal
11258 Show the current setting of stack unwinding in the functions called by
11262 @cindex weak alias functions
11263 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11264 for another function. In such case, @value{GDBN} might not pick up
11265 the type information, including the types of the function arguments,
11266 which causes @value{GDBN} to call the inferior function incorrectly.
11267 As a result, the called function will function erroneously and may
11268 even crash. A solution to that is to use the name of the aliased
11272 @section Patching programs
11274 @cindex patching binaries
11275 @cindex writing into executables
11276 @cindex writing into corefiles
11278 By default, @value{GDBN} opens the file containing your program's
11279 executable code (or the corefile) read-only. This prevents accidental
11280 alterations to machine code; but it also prevents you from intentionally
11281 patching your program's binary.
11283 If you'd like to be able to patch the binary, you can specify that
11284 explicitly with the @code{set write} command. For example, you might
11285 want to turn on internal debugging flags, or even to make emergency
11291 @itemx set write off
11292 If you specify @samp{set write on}, @value{GDBN} opens executable and
11293 core files for both reading and writing; if you specify @samp{set write
11294 off} (the default), @value{GDBN} opens them read-only.
11296 If you have already loaded a file, you must load it again (using the
11297 @code{exec-file} or @code{core-file} command) after changing @code{set
11298 write}, for your new setting to take effect.
11302 Display whether executable files and core files are opened for writing
11303 as well as reading.
11307 @chapter @value{GDBN} Files
11309 @value{GDBN} needs to know the file name of the program to be debugged,
11310 both in order to read its symbol table and in order to start your
11311 program. To debug a core dump of a previous run, you must also tell
11312 @value{GDBN} the name of the core dump file.
11315 * Files:: Commands to specify files
11316 * Separate Debug Files:: Debugging information in separate files
11317 * Symbol Errors:: Errors reading symbol files
11321 @section Commands to specify files
11323 @cindex symbol table
11324 @cindex core dump file
11326 You may want to specify executable and core dump file names. The usual
11327 way to do this is at start-up time, using the arguments to
11328 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11329 Out of @value{GDBN}}).
11331 Occasionally it is necessary to change to a different file during a
11332 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11333 specify a file you want to use. Or you are debugging a remote target
11334 via @code{gdbserver} (@pxref{Server, file}). In these situations the
11335 @value{GDBN} commands to specify new files are useful.
11338 @cindex executable file
11340 @item file @var{filename}
11341 Use @var{filename} as the program to be debugged. It is read for its
11342 symbols and for the contents of pure memory. It is also the program
11343 executed when you use the @code{run} command. If you do not specify a
11344 directory and the file is not found in the @value{GDBN} working directory,
11345 @value{GDBN} uses the environment variable @code{PATH} as a list of
11346 directories to search, just as the shell does when looking for a program
11347 to run. You can change the value of this variable, for both @value{GDBN}
11348 and your program, using the @code{path} command.
11350 @cindex unlinked object files
11351 @cindex patching object files
11352 You can load unlinked object @file{.o} files into @value{GDBN} using
11353 the @code{file} command. You will not be able to ``run'' an object
11354 file, but you can disassemble functions and inspect variables. Also,
11355 if the underlying BFD functionality supports it, you could use
11356 @kbd{gdb -write} to patch object files using this technique. Note
11357 that @value{GDBN} can neither interpret nor modify relocations in this
11358 case, so branches and some initialized variables will appear to go to
11359 the wrong place. But this feature is still handy from time to time.
11362 @code{file} with no argument makes @value{GDBN} discard any information it
11363 has on both executable file and the symbol table.
11366 @item exec-file @r{[} @var{filename} @r{]}
11367 Specify that the program to be run (but not the symbol table) is found
11368 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11369 if necessary to locate your program. Omitting @var{filename} means to
11370 discard information on the executable file.
11372 @kindex symbol-file
11373 @item symbol-file @r{[} @var{filename} @r{]}
11374 Read symbol table information from file @var{filename}. @code{PATH} is
11375 searched when necessary. Use the @code{file} command to get both symbol
11376 table and program to run from the same file.
11378 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11379 program's symbol table.
11381 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11382 some breakpoints and auto-display expressions. This is because they may
11383 contain pointers to the internal data recording symbols and data types,
11384 which are part of the old symbol table data being discarded inside
11387 @code{symbol-file} does not repeat if you press @key{RET} again after
11390 When @value{GDBN} is configured for a particular environment, it
11391 understands debugging information in whatever format is the standard
11392 generated for that environment; you may use either a @sc{gnu} compiler, or
11393 other compilers that adhere to the local conventions.
11394 Best results are usually obtained from @sc{gnu} compilers; for example,
11395 using @code{@value{GCC}} you can generate debugging information for
11398 For most kinds of object files, with the exception of old SVR3 systems
11399 using COFF, the @code{symbol-file} command does not normally read the
11400 symbol table in full right away. Instead, it scans the symbol table
11401 quickly to find which source files and which symbols are present. The
11402 details are read later, one source file at a time, as they are needed.
11404 The purpose of this two-stage reading strategy is to make @value{GDBN}
11405 start up faster. For the most part, it is invisible except for
11406 occasional pauses while the symbol table details for a particular source
11407 file are being read. (The @code{set verbose} command can turn these
11408 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11409 warnings and messages}.)
11411 We have not implemented the two-stage strategy for COFF yet. When the
11412 symbol table is stored in COFF format, @code{symbol-file} reads the
11413 symbol table data in full right away. Note that ``stabs-in-COFF''
11414 still does the two-stage strategy, since the debug info is actually
11418 @cindex reading symbols immediately
11419 @cindex symbols, reading immediately
11420 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11421 @itemx file @var{filename} @r{[} -readnow @r{]}
11422 You can override the @value{GDBN} two-stage strategy for reading symbol
11423 tables by using the @samp{-readnow} option with any of the commands that
11424 load symbol table information, if you want to be sure @value{GDBN} has the
11425 entire symbol table available.
11427 @c FIXME: for now no mention of directories, since this seems to be in
11428 @c flux. 13mar1992 status is that in theory GDB would look either in
11429 @c current dir or in same dir as myprog; but issues like competing
11430 @c GDB's, or clutter in system dirs, mean that in practice right now
11431 @c only current dir is used. FFish says maybe a special GDB hierarchy
11432 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11436 @item core-file @r{[}@var{filename}@r{]}
11438 Specify the whereabouts of a core dump file to be used as the ``contents
11439 of memory''. Traditionally, core files contain only some parts of the
11440 address space of the process that generated them; @value{GDBN} can access the
11441 executable file itself for other parts.
11443 @code{core-file} with no argument specifies that no core file is
11446 Note that the core file is ignored when your program is actually running
11447 under @value{GDBN}. So, if you have been running your program and you
11448 wish to debug a core file instead, you must kill the subprocess in which
11449 the program is running. To do this, use the @code{kill} command
11450 (@pxref{Kill Process, ,Killing the child process}).
11452 @kindex add-symbol-file
11453 @cindex dynamic linking
11454 @item add-symbol-file @var{filename} @var{address}
11455 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11456 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11457 The @code{add-symbol-file} command reads additional symbol table
11458 information from the file @var{filename}. You would use this command
11459 when @var{filename} has been dynamically loaded (by some other means)
11460 into the program that is running. @var{address} should be the memory
11461 address at which the file has been loaded; @value{GDBN} cannot figure
11462 this out for itself. You can additionally specify an arbitrary number
11463 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11464 section name and base address for that section. You can specify any
11465 @var{address} as an expression.
11467 The symbol table of the file @var{filename} is added to the symbol table
11468 originally read with the @code{symbol-file} command. You can use the
11469 @code{add-symbol-file} command any number of times; the new symbol data
11470 thus read keeps adding to the old. To discard all old symbol data
11471 instead, use the @code{symbol-file} command without any arguments.
11473 @cindex relocatable object files, reading symbols from
11474 @cindex object files, relocatable, reading symbols from
11475 @cindex reading symbols from relocatable object files
11476 @cindex symbols, reading from relocatable object files
11477 @cindex @file{.o} files, reading symbols from
11478 Although @var{filename} is typically a shared library file, an
11479 executable file, or some other object file which has been fully
11480 relocated for loading into a process, you can also load symbolic
11481 information from relocatable @file{.o} files, as long as:
11485 the file's symbolic information refers only to linker symbols defined in
11486 that file, not to symbols defined by other object files,
11488 every section the file's symbolic information refers to has actually
11489 been loaded into the inferior, as it appears in the file, and
11491 you can determine the address at which every section was loaded, and
11492 provide these to the @code{add-symbol-file} command.
11496 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11497 relocatable files into an already running program; such systems
11498 typically make the requirements above easy to meet. However, it's
11499 important to recognize that many native systems use complex link
11500 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11501 assembly, for example) that make the requirements difficult to meet. In
11502 general, one cannot assume that using @code{add-symbol-file} to read a
11503 relocatable object file's symbolic information will have the same effect
11504 as linking the relocatable object file into the program in the normal
11507 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11509 @kindex add-symbol-file-from-memory
11510 @cindex @code{syscall DSO}
11511 @cindex load symbols from memory
11512 @item add-symbol-file-from-memory @var{address}
11513 Load symbols from the given @var{address} in a dynamically loaded
11514 object file whose image is mapped directly into the inferior's memory.
11515 For example, the Linux kernel maps a @code{syscall DSO} into each
11516 process's address space; this DSO provides kernel-specific code for
11517 some system calls. The argument can be any expression whose
11518 evaluation yields the address of the file's shared object file header.
11519 For this command to work, you must have used @code{symbol-file} or
11520 @code{exec-file} commands in advance.
11522 @kindex add-shared-symbol-files
11524 @item add-shared-symbol-files @var{library-file}
11525 @itemx assf @var{library-file}
11526 The @code{add-shared-symbol-files} command can currently be used only
11527 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11528 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11529 @value{GDBN} automatically looks for shared libraries, however if
11530 @value{GDBN} does not find yours, you can invoke
11531 @code{add-shared-symbol-files}. It takes one argument: the shared
11532 library's file name. @code{assf} is a shorthand alias for
11533 @code{add-shared-symbol-files}.
11536 @item section @var{section} @var{addr}
11537 The @code{section} command changes the base address of the named
11538 @var{section} of the exec file to @var{addr}. This can be used if the
11539 exec file does not contain section addresses, (such as in the
11540 @code{a.out} format), or when the addresses specified in the file
11541 itself are wrong. Each section must be changed separately. The
11542 @code{info files} command, described below, lists all the sections and
11546 @kindex info target
11549 @code{info files} and @code{info target} are synonymous; both print the
11550 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11551 including the names of the executable and core dump files currently in
11552 use by @value{GDBN}, and the files from which symbols were loaded. The
11553 command @code{help target} lists all possible targets rather than
11556 @kindex maint info sections
11557 @item maint info sections
11558 Another command that can give you extra information about program sections
11559 is @code{maint info sections}. In addition to the section information
11560 displayed by @code{info files}, this command displays the flags and file
11561 offset of each section in the executable and core dump files. In addition,
11562 @code{maint info sections} provides the following command options (which
11563 may be arbitrarily combined):
11567 Display sections for all loaded object files, including shared libraries.
11568 @item @var{sections}
11569 Display info only for named @var{sections}.
11570 @item @var{section-flags}
11571 Display info only for sections for which @var{section-flags} are true.
11572 The section flags that @value{GDBN} currently knows about are:
11575 Section will have space allocated in the process when loaded.
11576 Set for all sections except those containing debug information.
11578 Section will be loaded from the file into the child process memory.
11579 Set for pre-initialized code and data, clear for @code{.bss} sections.
11581 Section needs to be relocated before loading.
11583 Section cannot be modified by the child process.
11585 Section contains executable code only.
11587 Section contains data only (no executable code).
11589 Section will reside in ROM.
11591 Section contains data for constructor/destructor lists.
11593 Section is not empty.
11595 An instruction to the linker to not output the section.
11596 @item COFF_SHARED_LIBRARY
11597 A notification to the linker that the section contains
11598 COFF shared library information.
11600 Section contains common symbols.
11603 @kindex set trust-readonly-sections
11604 @cindex read-only sections
11605 @item set trust-readonly-sections on
11606 Tell @value{GDBN} that readonly sections in your object file
11607 really are read-only (i.e.@: that their contents will not change).
11608 In that case, @value{GDBN} can fetch values from these sections
11609 out of the object file, rather than from the target program.
11610 For some targets (notably embedded ones), this can be a significant
11611 enhancement to debugging performance.
11613 The default is off.
11615 @item set trust-readonly-sections off
11616 Tell @value{GDBN} not to trust readonly sections. This means that
11617 the contents of the section might change while the program is running,
11618 and must therefore be fetched from the target when needed.
11620 @item show trust-readonly-sections
11621 Show the current setting of trusting readonly sections.
11624 All file-specifying commands allow both absolute and relative file names
11625 as arguments. @value{GDBN} always converts the file name to an absolute file
11626 name and remembers it that way.
11628 @cindex shared libraries
11629 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11630 and IBM RS/6000 AIX shared libraries.
11632 @value{GDBN} automatically loads symbol definitions from shared libraries
11633 when you use the @code{run} command, or when you examine a core file.
11634 (Before you issue the @code{run} command, @value{GDBN} does not understand
11635 references to a function in a shared library, however---unless you are
11636 debugging a core file).
11638 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11639 automatically loads the symbols at the time of the @code{shl_load} call.
11641 @c FIXME: some @value{GDBN} release may permit some refs to undef
11642 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11643 @c FIXME...lib; check this from time to time when updating manual
11645 There are times, however, when you may wish to not automatically load
11646 symbol definitions from shared libraries, such as when they are
11647 particularly large or there are many of them.
11649 To control the automatic loading of shared library symbols, use the
11653 @kindex set auto-solib-add
11654 @item set auto-solib-add @var{mode}
11655 If @var{mode} is @code{on}, symbols from all shared object libraries
11656 will be loaded automatically when the inferior begins execution, you
11657 attach to an independently started inferior, or when the dynamic linker
11658 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11659 is @code{off}, symbols must be loaded manually, using the
11660 @code{sharedlibrary} command. The default value is @code{on}.
11662 @cindex memory used for symbol tables
11663 If your program uses lots of shared libraries with debug info that
11664 takes large amounts of memory, you can decrease the @value{GDBN}
11665 memory footprint by preventing it from automatically loading the
11666 symbols from shared libraries. To that end, type @kbd{set
11667 auto-solib-add off} before running the inferior, then load each
11668 library whose debug symbols you do need with @kbd{sharedlibrary
11669 @var{regexp}}, where @var{regexp} is a regular expresion that matches
11670 the libraries whose symbols you want to be loaded.
11672 @kindex show auto-solib-add
11673 @item show auto-solib-add
11674 Display the current autoloading mode.
11677 @cindex load shared library
11678 To explicitly load shared library symbols, use the @code{sharedlibrary}
11682 @kindex info sharedlibrary
11685 @itemx info sharedlibrary
11686 Print the names of the shared libraries which are currently loaded.
11688 @kindex sharedlibrary
11690 @item sharedlibrary @var{regex}
11691 @itemx share @var{regex}
11692 Load shared object library symbols for files matching a
11693 Unix regular expression.
11694 As with files loaded automatically, it only loads shared libraries
11695 required by your program for a core file or after typing @code{run}. If
11696 @var{regex} is omitted all shared libraries required by your program are
11699 @item nosharedlibrary
11700 @kindex nosharedlibrary
11701 @cindex unload symbols from shared libraries
11702 Unload all shared object library symbols. This discards all symbols
11703 that have been loaded from all shared libraries. Symbols from shared
11704 libraries that were loaded by explicit user requests are not
11708 Sometimes you may wish that @value{GDBN} stops and gives you control
11709 when any of shared library events happen. Use the @code{set
11710 stop-on-solib-events} command for this:
11713 @item set stop-on-solib-events
11714 @kindex set stop-on-solib-events
11715 This command controls whether @value{GDBN} should give you control
11716 when the dynamic linker notifies it about some shared library event.
11717 The most common event of interest is loading or unloading of a new
11720 @item show stop-on-solib-events
11721 @kindex show stop-on-solib-events
11722 Show whether @value{GDBN} stops and gives you control when shared
11723 library events happen.
11726 Shared libraries are also supported in many cross or remote debugging
11727 configurations. A copy of the target's libraries need to be present on the
11728 host system; they need to be the same as the target libraries, although the
11729 copies on the target can be stripped as long as the copies on the host are
11732 @cindex where to look for shared libraries
11733 For remote debugging, you need to tell @value{GDBN} where the target
11734 libraries are, so that it can load the correct copies---otherwise, it
11735 may try to load the host's libraries. @value{GDBN} has two variables
11736 to specify the search directories for target libraries.
11739 @cindex prefix for shared library file names
11740 @kindex set solib-absolute-prefix
11741 @item set solib-absolute-prefix @var{path}
11742 If this variable is set, @var{path} will be used as a prefix for any
11743 absolute shared library paths; many runtime loaders store the absolute
11744 paths to the shared library in the target program's memory. If you use
11745 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11746 out in the same way that they are on the target, with e.g.@: a
11747 @file{/usr/lib} hierarchy under @var{path}.
11749 @cindex default value of @samp{solib-absolute-prefix}
11750 @cindex @samp{--with-sysroot}
11751 You can set the default value of @samp{solib-absolute-prefix} by using the
11752 configure-time @samp{--with-sysroot} option.
11754 @kindex show solib-absolute-prefix
11755 @item show solib-absolute-prefix
11756 Display the current shared library prefix.
11758 @kindex set solib-search-path
11759 @item set solib-search-path @var{path}
11760 If this variable is set, @var{path} is a colon-separated list of directories
11761 to search for shared libraries. @samp{solib-search-path} is used after
11762 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11763 the library is relative instead of absolute. If you want to use
11764 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11765 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11766 @value{GDBN} from finding your host's libraries.
11768 @kindex show solib-search-path
11769 @item show solib-search-path
11770 Display the current shared library search path.
11774 @node Separate Debug Files
11775 @section Debugging Information in Separate Files
11776 @cindex separate debugging information files
11777 @cindex debugging information in separate files
11778 @cindex @file{.debug} subdirectories
11779 @cindex debugging information directory, global
11780 @cindex global debugging information directory
11782 @value{GDBN} allows you to put a program's debugging information in a
11783 file separate from the executable itself, in a way that allows
11784 @value{GDBN} to find and load the debugging information automatically.
11785 Since debugging information can be very large --- sometimes larger
11786 than the executable code itself --- some systems distribute debugging
11787 information for their executables in separate files, which users can
11788 install only when they need to debug a problem.
11790 If an executable's debugging information has been extracted to a
11791 separate file, the executable should contain a @dfn{debug link} giving
11792 the name of the debugging information file (with no directory
11793 components), and a checksum of its contents. (The exact form of a
11794 debug link is described below.) If the full name of the directory
11795 containing the executable is @var{execdir}, and the executable has a
11796 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11797 will automatically search for the debugging information file in three
11802 the directory containing the executable file (that is, it will look
11803 for a file named @file{@var{execdir}/@var{debugfile}},
11805 a subdirectory of that directory named @file{.debug} (that is, the
11806 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11808 a subdirectory of the global debug file directory that includes the
11809 executable's full path, and the name from the link (that is, the file
11810 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11811 @var{globaldebugdir} is the global debug file directory, and
11812 @var{execdir} has been turned into a relative path).
11815 @value{GDBN} checks under each of these names for a debugging
11816 information file whose checksum matches that given in the link, and
11817 reads the debugging information from the first one it finds.
11819 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11820 which has a link containing the name @file{ls.debug}, and the global
11821 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11822 for debug information in @file{/usr/bin/ls.debug},
11823 @file{/usr/bin/.debug/ls.debug}, and
11824 @file{/usr/lib/debug/usr/bin/ls.debug}.
11826 You can set the global debugging info directory's name, and view the
11827 name @value{GDBN} is currently using.
11831 @kindex set debug-file-directory
11832 @item set debug-file-directory @var{directory}
11833 Set the directory which @value{GDBN} searches for separate debugging
11834 information files to @var{directory}.
11836 @kindex show debug-file-directory
11837 @item show debug-file-directory
11838 Show the directory @value{GDBN} searches for separate debugging
11843 @cindex @code{.gnu_debuglink} sections
11844 @cindex debug links
11845 A debug link is a special section of the executable file named
11846 @code{.gnu_debuglink}. The section must contain:
11850 A filename, with any leading directory components removed, followed by
11853 zero to three bytes of padding, as needed to reach the next four-byte
11854 boundary within the section, and
11856 a four-byte CRC checksum, stored in the same endianness used for the
11857 executable file itself. The checksum is computed on the debugging
11858 information file's full contents by the function given below, passing
11859 zero as the @var{crc} argument.
11862 Any executable file format can carry a debug link, as long as it can
11863 contain a section named @code{.gnu_debuglink} with the contents
11866 The debugging information file itself should be an ordinary
11867 executable, containing a full set of linker symbols, sections, and
11868 debugging information. The sections of the debugging information file
11869 should have the same names, addresses and sizes as the original file,
11870 but they need not contain any data --- much like a @code{.bss} section
11871 in an ordinary executable.
11873 As of December 2002, there is no standard GNU utility to produce
11874 separated executable / debugging information file pairs. Ulrich
11875 Drepper's @file{elfutils} package, starting with version 0.53,
11876 contains a version of the @code{strip} command such that the command
11877 @kbd{strip foo -f foo.debug} removes the debugging information from
11878 the executable file @file{foo}, places it in the file
11879 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11881 Since there are many different ways to compute CRC's (different
11882 polynomials, reversals, byte ordering, etc.), the simplest way to
11883 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11884 complete code for a function that computes it:
11886 @kindex gnu_debuglink_crc32
11889 gnu_debuglink_crc32 (unsigned long crc,
11890 unsigned char *buf, size_t len)
11892 static const unsigned long crc32_table[256] =
11894 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11895 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11896 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11897 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11898 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11899 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11900 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11901 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11902 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11903 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11904 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11905 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11906 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11907 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11908 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11909 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11910 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11911 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11912 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11913 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11914 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11915 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11916 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11917 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11918 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11919 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11920 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11921 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11922 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11923 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11924 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11925 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11926 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11927 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11928 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11929 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11930 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11931 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11932 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11933 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11934 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11935 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11936 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11937 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11938 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11939 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11940 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11941 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11942 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11943 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11944 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11947 unsigned char *end;
11949 crc = ~crc & 0xffffffff;
11950 for (end = buf + len; buf < end; ++buf)
11951 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11952 return ~crc & 0xffffffff;
11957 @node Symbol Errors
11958 @section Errors reading symbol files
11960 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11961 such as symbol types it does not recognize, or known bugs in compiler
11962 output. By default, @value{GDBN} does not notify you of such problems, since
11963 they are relatively common and primarily of interest to people
11964 debugging compilers. If you are interested in seeing information
11965 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11966 only one message about each such type of problem, no matter how many
11967 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11968 to see how many times the problems occur, with the @code{set
11969 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11972 The messages currently printed, and their meanings, include:
11975 @item inner block not inside outer block in @var{symbol}
11977 The symbol information shows where symbol scopes begin and end
11978 (such as at the start of a function or a block of statements). This
11979 error indicates that an inner scope block is not fully contained
11980 in its outer scope blocks.
11982 @value{GDBN} circumvents the problem by treating the inner block as if it had
11983 the same scope as the outer block. In the error message, @var{symbol}
11984 may be shown as ``@code{(don't know)}'' if the outer block is not a
11987 @item block at @var{address} out of order
11989 The symbol information for symbol scope blocks should occur in
11990 order of increasing addresses. This error indicates that it does not
11993 @value{GDBN} does not circumvent this problem, and has trouble
11994 locating symbols in the source file whose symbols it is reading. (You
11995 can often determine what source file is affected by specifying
11996 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11999 @item bad block start address patched
12001 The symbol information for a symbol scope block has a start address
12002 smaller than the address of the preceding source line. This is known
12003 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12005 @value{GDBN} circumvents the problem by treating the symbol scope block as
12006 starting on the previous source line.
12008 @item bad string table offset in symbol @var{n}
12011 Symbol number @var{n} contains a pointer into the string table which is
12012 larger than the size of the string table.
12014 @value{GDBN} circumvents the problem by considering the symbol to have the
12015 name @code{foo}, which may cause other problems if many symbols end up
12018 @item unknown symbol type @code{0x@var{nn}}
12020 The symbol information contains new data types that @value{GDBN} does
12021 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12022 uncomprehended information, in hexadecimal.
12024 @value{GDBN} circumvents the error by ignoring this symbol information.
12025 This usually allows you to debug your program, though certain symbols
12026 are not accessible. If you encounter such a problem and feel like
12027 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12028 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12029 and examine @code{*bufp} to see the symbol.
12031 @item stub type has NULL name
12033 @value{GDBN} could not find the full definition for a struct or class.
12035 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12036 The symbol information for a C@t{++} member function is missing some
12037 information that recent versions of the compiler should have output for
12040 @item info mismatch between compiler and debugger
12042 @value{GDBN} could not parse a type specification output by the compiler.
12047 @chapter Specifying a Debugging Target
12049 @cindex debugging target
12050 A @dfn{target} is the execution environment occupied by your program.
12052 Often, @value{GDBN} runs in the same host environment as your program;
12053 in that case, the debugging target is specified as a side effect when
12054 you use the @code{file} or @code{core} commands. When you need more
12055 flexibility---for example, running @value{GDBN} on a physically separate
12056 host, or controlling a standalone system over a serial port or a
12057 realtime system over a TCP/IP connection---you can use the @code{target}
12058 command to specify one of the target types configured for @value{GDBN}
12059 (@pxref{Target Commands, ,Commands for managing targets}).
12061 @cindex target architecture
12062 It is possible to build @value{GDBN} for several different @dfn{target
12063 architectures}. When @value{GDBN} is built like that, you can choose
12064 one of the available architectures with the @kbd{set architecture}
12068 @kindex set architecture
12069 @kindex show architecture
12070 @item set architecture @var{arch}
12071 This command sets the current target architecture to @var{arch}. The
12072 value of @var{arch} can be @code{"auto"}, in addition to one of the
12073 supported architectures.
12075 @item show architecture
12076 Show the current target architecture.
12078 @item set processor
12080 @kindex set processor
12081 @kindex show processor
12082 These are alias commands for, respectively, @code{set architecture}
12083 and @code{show architecture}.
12087 * Active Targets:: Active targets
12088 * Target Commands:: Commands for managing targets
12089 * Byte Order:: Choosing target byte order
12090 * Remote:: Remote debugging
12094 @node Active Targets
12095 @section Active targets
12097 @cindex stacking targets
12098 @cindex active targets
12099 @cindex multiple targets
12101 There are three classes of targets: processes, core files, and
12102 executable files. @value{GDBN} can work concurrently on up to three
12103 active targets, one in each class. This allows you to (for example)
12104 start a process and inspect its activity without abandoning your work on
12107 For example, if you execute @samp{gdb a.out}, then the executable file
12108 @code{a.out} is the only active target. If you designate a core file as
12109 well---presumably from a prior run that crashed and coredumped---then
12110 @value{GDBN} has two active targets and uses them in tandem, looking
12111 first in the corefile target, then in the executable file, to satisfy
12112 requests for memory addresses. (Typically, these two classes of target
12113 are complementary, since core files contain only a program's
12114 read-write memory---variables and so on---plus machine status, while
12115 executable files contain only the program text and initialized data.)
12117 When you type @code{run}, your executable file becomes an active process
12118 target as well. When a process target is active, all @value{GDBN}
12119 commands requesting memory addresses refer to that target; addresses in
12120 an active core file or executable file target are obscured while the
12121 process target is active.
12123 Use the @code{core-file} and @code{exec-file} commands to select a new
12124 core file or executable target (@pxref{Files, ,Commands to specify
12125 files}). To specify as a target a process that is already running, use
12126 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
12129 @node Target Commands
12130 @section Commands for managing targets
12133 @item target @var{type} @var{parameters}
12134 Connects the @value{GDBN} host environment to a target machine or
12135 process. A target is typically a protocol for talking to debugging
12136 facilities. You use the argument @var{type} to specify the type or
12137 protocol of the target machine.
12139 Further @var{parameters} are interpreted by the target protocol, but
12140 typically include things like device names or host names to connect
12141 with, process numbers, and baud rates.
12143 The @code{target} command does not repeat if you press @key{RET} again
12144 after executing the command.
12146 @kindex help target
12148 Displays the names of all targets available. To display targets
12149 currently selected, use either @code{info target} or @code{info files}
12150 (@pxref{Files, ,Commands to specify files}).
12152 @item help target @var{name}
12153 Describe a particular target, including any parameters necessary to
12156 @kindex set gnutarget
12157 @item set gnutarget @var{args}
12158 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12159 knows whether it is reading an @dfn{executable},
12160 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12161 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12162 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12165 @emph{Warning:} To specify a file format with @code{set gnutarget},
12166 you must know the actual BFD name.
12170 @xref{Files, , Commands to specify files}.
12172 @kindex show gnutarget
12173 @item show gnutarget
12174 Use the @code{show gnutarget} command to display what file format
12175 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12176 @value{GDBN} will determine the file format for each file automatically,
12177 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12180 @cindex common targets
12181 Here are some common targets (available, or not, depending on the GDB
12186 @item target exec @var{program}
12187 @cindex executable file target
12188 An executable file. @samp{target exec @var{program}} is the same as
12189 @samp{exec-file @var{program}}.
12191 @item target core @var{filename}
12192 @cindex core dump file target
12193 A core dump file. @samp{target core @var{filename}} is the same as
12194 @samp{core-file @var{filename}}.
12196 @item target remote @var{medium}
12197 @cindex remote target
12198 A remote system connected to @value{GDBN} via a serial line or network
12199 connection. This command tells @value{GDBN} to use its own remote
12200 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12202 For example, if you have a board connected to @file{/dev/ttya} on the
12203 machine running @value{GDBN}, you could say:
12206 target remote /dev/ttya
12209 @code{target remote} supports the @code{load} command. This is only
12210 useful if you have some other way of getting the stub to the target
12211 system, and you can put it somewhere in memory where it won't get
12212 clobbered by the download.
12215 @cindex built-in simulator target
12216 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12224 works; however, you cannot assume that a specific memory map, device
12225 drivers, or even basic I/O is available, although some simulators do
12226 provide these. For info about any processor-specific simulator details,
12227 see the appropriate section in @ref{Embedded Processors, ,Embedded
12232 Some configurations may include these targets as well:
12236 @item target nrom @var{dev}
12237 @cindex NetROM ROM emulator target
12238 NetROM ROM emulator. This target only supports downloading.
12242 Different targets are available on different configurations of @value{GDBN};
12243 your configuration may have more or fewer targets.
12245 Many remote targets require you to download the executable's code once
12246 you've successfully established a connection. You may wish to control
12247 various aspects of this process.
12252 @kindex set hash@r{, for remote monitors}
12253 @cindex hash mark while downloading
12254 This command controls whether a hash mark @samp{#} is displayed while
12255 downloading a file to the remote monitor. If on, a hash mark is
12256 displayed after each S-record is successfully downloaded to the
12260 @kindex show hash@r{, for remote monitors}
12261 Show the current status of displaying the hash mark.
12263 @item set debug monitor
12264 @kindex set debug monitor
12265 @cindex display remote monitor communications
12266 Enable or disable display of communications messages between
12267 @value{GDBN} and the remote monitor.
12269 @item show debug monitor
12270 @kindex show debug monitor
12271 Show the current status of displaying communications between
12272 @value{GDBN} and the remote monitor.
12277 @kindex load @var{filename}
12278 @item load @var{filename}
12279 Depending on what remote debugging facilities are configured into
12280 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12281 is meant to make @var{filename} (an executable) available for debugging
12282 on the remote system---by downloading, or dynamic linking, for example.
12283 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12284 the @code{add-symbol-file} command.
12286 If your @value{GDBN} does not have a @code{load} command, attempting to
12287 execute it gets the error message ``@code{You can't do that when your
12288 target is @dots{}}''
12290 The file is loaded at whatever address is specified in the executable.
12291 For some object file formats, you can specify the load address when you
12292 link the program; for other formats, like a.out, the object file format
12293 specifies a fixed address.
12294 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12296 Depending on the remote side capabilities, @value{GDBN} may be able to
12297 load programs into flash memory.
12299 @code{load} does not repeat if you press @key{RET} again after using it.
12303 @section Choosing target byte order
12305 @cindex choosing target byte order
12306 @cindex target byte order
12308 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12309 offer the ability to run either big-endian or little-endian byte
12310 orders. Usually the executable or symbol will include a bit to
12311 designate the endian-ness, and you will not need to worry about
12312 which to use. However, you may still find it useful to adjust
12313 @value{GDBN}'s idea of processor endian-ness manually.
12317 @item set endian big
12318 Instruct @value{GDBN} to assume the target is big-endian.
12320 @item set endian little
12321 Instruct @value{GDBN} to assume the target is little-endian.
12323 @item set endian auto
12324 Instruct @value{GDBN} to use the byte order associated with the
12328 Display @value{GDBN}'s current idea of the target byte order.
12332 Note that these commands merely adjust interpretation of symbolic
12333 data on the host, and that they have absolutely no effect on the
12337 @section Remote debugging
12338 @cindex remote debugging
12340 If you are trying to debug a program running on a machine that cannot run
12341 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12342 For example, you might use remote debugging on an operating system kernel,
12343 or on a small system which does not have a general purpose operating system
12344 powerful enough to run a full-featured debugger.
12346 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12347 to make this work with particular debugging targets. In addition,
12348 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12349 but not specific to any particular target system) which you can use if you
12350 write the remote stubs---the code that runs on the remote system to
12351 communicate with @value{GDBN}.
12353 Other remote targets may be available in your
12354 configuration of @value{GDBN}; use @code{help target} to list them.
12356 Once you've connected to the remote target, @value{GDBN} allows you to
12357 send arbitrary commands to the remote monitor:
12360 @item remote @var{command}
12361 @kindex remote@r{, a command}
12362 @cindex send command to remote monitor
12363 Send an arbitrary @var{command} string to the remote monitor.
12367 @node Remote Debugging
12368 @chapter Debugging remote programs
12371 * Connecting:: Connecting to a remote target
12372 * Server:: Using the gdbserver program
12373 * Remote configuration:: Remote configuration
12374 * remote stub:: Implementing a remote stub
12378 @section Connecting to a remote target
12380 On the @value{GDBN} host machine, you will need an unstripped copy of
12381 your program, since @value{GDBN} needs symobl and debugging information.
12382 Start up @value{GDBN} as usual, using the name of the local copy of your
12383 program as the first argument.
12385 @cindex @code{target remote}
12386 @value{GDBN} can communicate with the target over a serial line, or
12387 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12388 each case, @value{GDBN} uses the same protocol for debugging your
12389 program; only the medium carrying the debugging packets varies. The
12390 @code{target remote} command establishes a connection to the target.
12391 Its arguments indicate which medium to use:
12395 @item target remote @var{serial-device}
12396 @cindex serial line, @code{target remote}
12397 Use @var{serial-device} to communicate with the target. For example,
12398 to use a serial line connected to the device named @file{/dev/ttyb}:
12401 target remote /dev/ttyb
12404 If you're using a serial line, you may want to give @value{GDBN} the
12405 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12406 (@pxref{Remote configuration, set remotebaud}) before the
12407 @code{target} command.
12409 @item target remote @code{@var{host}:@var{port}}
12410 @itemx target remote @code{tcp:@var{host}:@var{port}}
12411 @cindex @acronym{TCP} port, @code{target remote}
12412 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12413 The @var{host} may be either a host name or a numeric @acronym{IP}
12414 address; @var{port} must be a decimal number. The @var{host} could be
12415 the target machine itself, if it is directly connected to the net, or
12416 it might be a terminal server which in turn has a serial line to the
12419 For example, to connect to port 2828 on a terminal server named
12423 target remote manyfarms:2828
12426 If your remote target is actually running on the same machine as your
12427 debugger session (e.g.@: a simulator for your target running on the
12428 same host), you can omit the hostname. For example, to connect to
12429 port 1234 on your local machine:
12432 target remote :1234
12436 Note that the colon is still required here.
12438 @item target remote @code{udp:@var{host}:@var{port}}
12439 @cindex @acronym{UDP} port, @code{target remote}
12440 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12441 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12444 target remote udp:manyfarms:2828
12447 When using a @acronym{UDP} connection for remote debugging, you should
12448 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12449 can silently drop packets on busy or unreliable networks, which will
12450 cause havoc with your debugging session.
12452 @item target remote | @var{command}
12453 @cindex pipe, @code{target remote} to
12454 Run @var{command} in the background and communicate with it using a
12455 pipe. The @var{command} is a shell command, to be parsed and expanded
12456 by the system's command shell, @code{/bin/sh}; it should expect remote
12457 protocol packets on its standard input, and send replies on its
12458 standard output. You could use this to run a stand-alone simulator
12459 that speaks the remote debugging protocol, to make net connections
12460 using programs like @code{ssh}, or for other similar tricks.
12462 If @var{command} closes its standard output (perhaps by exiting),
12463 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12464 program has already exited, this will have no effect.)
12468 Once the connection has been established, you can use all the usual
12469 commands to examine and change data and to step and continue the
12472 @cindex interrupting remote programs
12473 @cindex remote programs, interrupting
12474 Whenever @value{GDBN} is waiting for the remote program, if you type the
12475 interrupt character (often @kbd{C-c}), @value{GDBN} attempts to stop the
12476 program. This may or may not succeed, depending in part on the hardware
12477 and the serial drivers the remote system uses. If you type the
12478 interrupt character once again, @value{GDBN} displays this prompt:
12481 Interrupted while waiting for the program.
12482 Give up (and stop debugging it)? (y or n)
12485 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12486 (If you decide you want to try again later, you can use @samp{target
12487 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12488 goes back to waiting.
12491 @kindex detach (remote)
12493 When you have finished debugging the remote program, you can use the
12494 @code{detach} command to release it from @value{GDBN} control.
12495 Detaching from the target normally resumes its execution, but the results
12496 will depend on your particular remote stub. After the @code{detach}
12497 command, @value{GDBN} is free to connect to another target.
12501 The @code{disconnect} command behaves like @code{detach}, except that
12502 the target is generally not resumed. It will wait for @value{GDBN}
12503 (this instance or another one) to connect and continue debugging. After
12504 the @code{disconnect} command, @value{GDBN} is again free to connect to
12507 @cindex send command to remote monitor
12508 @cindex extend @value{GDBN} for remote targets
12509 @cindex add new commands for external monitor
12511 @item monitor @var{cmd}
12512 This command allows you to send arbitrary commands directly to the
12513 remote monitor. Since @value{GDBN} doesn't care about the commands it
12514 sends like this, this command is the way to extend @value{GDBN}---you
12515 can add new commands that only the external monitor will understand
12520 @section Using the @code{gdbserver} program
12523 @cindex remote connection without stubs
12524 @code{gdbserver} is a control program for Unix-like systems, which
12525 allows you to connect your program with a remote @value{GDBN} via
12526 @code{target remote}---but without linking in the usual debugging stub.
12528 @code{gdbserver} is not a complete replacement for the debugging stubs,
12529 because it requires essentially the same operating-system facilities
12530 that @value{GDBN} itself does. In fact, a system that can run
12531 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12532 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12533 because it is a much smaller program than @value{GDBN} itself. It is
12534 also easier to port than all of @value{GDBN}, so you may be able to get
12535 started more quickly on a new system by using @code{gdbserver}.
12536 Finally, if you develop code for real-time systems, you may find that
12537 the tradeoffs involved in real-time operation make it more convenient to
12538 do as much development work as possible on another system, for example
12539 by cross-compiling. You can use @code{gdbserver} to make a similar
12540 choice for debugging.
12542 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12543 or a TCP connection, using the standard @value{GDBN} remote serial
12547 @item On the target machine,
12548 you need to have a copy of the program you want to debug.
12549 @code{gdbserver} does not need your program's symbol table, so you can
12550 strip the program if necessary to save space. @value{GDBN} on the host
12551 system does all the symbol handling.
12553 To use the server, you must tell it how to communicate with @value{GDBN};
12554 the name of your program; and the arguments for your program. The usual
12558 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12561 @var{comm} is either a device name (to use a serial line) or a TCP
12562 hostname and portnumber. For example, to debug Emacs with the argument
12563 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12567 target> gdbserver /dev/com1 emacs foo.txt
12570 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12573 To use a TCP connection instead of a serial line:
12576 target> gdbserver host:2345 emacs foo.txt
12579 The only difference from the previous example is the first argument,
12580 specifying that you are communicating with the host @value{GDBN} via
12581 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12582 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12583 (Currently, the @samp{host} part is ignored.) You can choose any number
12584 you want for the port number as long as it does not conflict with any
12585 TCP ports already in use on the target system (for example, @code{23} is
12586 reserved for @code{telnet}).@footnote{If you choose a port number that
12587 conflicts with another service, @code{gdbserver} prints an error message
12588 and exits.} You must use the same port number with the host @value{GDBN}
12589 @code{target remote} command.
12591 On some targets, @code{gdbserver} can also attach to running programs.
12592 This is accomplished via the @code{--attach} argument. The syntax is:
12595 target> gdbserver @var{comm} --attach @var{pid}
12598 @var{pid} is the process ID of a currently running process. It isn't necessary
12599 to point @code{gdbserver} at a binary for the running process.
12602 @cindex attach to a program by name
12603 You can debug processes by name instead of process ID if your target has the
12604 @code{pidof} utility:
12607 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
12610 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
12611 has multiple threads, most versions of @code{pidof} support the
12612 @code{-s} option to only return the first process ID.
12614 @item On the host machine,
12615 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
12616 For TCP connections, you must start up @code{gdbserver} prior to using
12617 the @code{target remote} command. Otherwise you may get an error whose
12618 text depends on the host system, but which usually looks something like
12619 @samp{Connection refused}. You don't need to use the @code{load}
12620 command in @value{GDBN} when using @code{gdbserver}, since the program is
12621 already on the target. However, if you want to load the symbols (as
12622 you normally would), do that with the @code{file} command, and issue
12623 it @emph{before} connecting to the server; otherwise, you will get an
12624 error message saying @code{"Program is already running"}, since the
12625 program is considered running after the connection.
12629 @node Remote configuration
12630 @section Remote configuration
12633 @kindex show remote
12634 This section documents the configuration options available when
12635 debugging remote programs. For the options related to the File I/O
12636 extensions of the remote protocol, see @ref{system,
12637 system-call-allowed}.
12640 @item set remoteaddresssize @var{bits}
12641 @cindex adress size for remote targets
12642 @cindex bits in remote address
12643 Set the maximum size of address in a memory packet to the specified
12644 number of bits. @value{GDBN} will mask off the address bits above
12645 that number, when it passes addresses to the remote target. The
12646 default value is the number of bits in the target's address.
12648 @item show remoteaddresssize
12649 Show the current value of remote address size in bits.
12651 @item set remotebaud @var{n}
12652 @cindex baud rate for remote targets
12653 Set the baud rate for the remote serial I/O to @var{n} baud. The
12654 value is used to set the speed of the serial port used for debugging
12657 @item show remotebaud
12658 Show the current speed of the remote connection.
12660 @item set remotebreak
12661 @cindex interrupt remote programs
12662 @cindex BREAK signal instead of Ctrl-C
12663 @anchor{set remotebreak}
12664 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12665 when you type @kbd{C-c} to interrupt the program running
12666 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12667 character instead. The default is off, since most remote systems
12668 expect to see @samp{Ctrl-C} as the interrupt signal.
12670 @item show remotebreak
12671 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12672 interrupt the remote program.
12674 @item set remotedevice @var{device}
12675 @cindex serial port name
12676 Set the name of the serial port through which to communicate to the
12677 remote target to @var{device}. This is the device used by
12678 @value{GDBN} to open the serial communications line to the remote
12679 target. There's no default, so you must set a valid port name for the
12680 remote serial communications to work. (Some varieties of the
12681 @code{target} command accept the port name as part of their
12684 @item show remotedevice
12685 Show the current name of the serial port.
12687 @item set remotelogbase @var{base}
12688 Set the base (a.k.a.@: radix) of logging serial protocol
12689 communications to @var{base}. Supported values of @var{base} are:
12690 @code{ascii}, @code{octal}, and @code{hex}. The default is
12693 @item show remotelogbase
12694 Show the current setting of the radix for logging remote serial
12697 @item set remotelogfile @var{file}
12698 @cindex record serial communications on file
12699 Record remote serial communications on the named @var{file}. The
12700 default is not to record at all.
12702 @item show remotelogfile.
12703 Show the current setting of the file name on which to record the
12704 serial communications.
12706 @item set remotetimeout @var{num}
12707 @cindex timeout for serial communications
12708 @cindex remote timeout
12709 Set the timeout limit to wait for the remote target to respond to
12710 @var{num} seconds. The default is 2 seconds.
12712 @item show remotetimeout
12713 Show the current number of seconds to wait for the remote target
12716 @cindex limit hardware breakpoints and watchpoints
12717 @cindex remote target, limit break- and watchpoints
12718 @anchor{set remote hardware-watchpoint-limit}
12719 @anchor{set remote hardware-breakpoint-limit}
12720 @item set remote hardware-watchpoint-limit @var{limit}
12721 @itemx set remote hardware-breakpoint-limit @var{limit}
12722 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12723 watchpoints. A limit of -1, the default, is treated as unlimited.
12725 @item set remote fetch-register-packet
12726 @itemx set remote set-register-packet
12727 @itemx set remote P-packet
12728 @itemx set remote p-packet
12730 @cindex fetch registers from remote targets
12731 @cindex set registers in remote targets
12732 Determine whether @value{GDBN} can set and fetch registers from the
12733 remote target using the @samp{P} packets. The default depends on the
12734 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12735 the stub when this packet is first required).
12737 @item show remote fetch-register-packet
12738 @itemx show remote set-register-packet
12739 @itemx show remote P-packet
12740 @itemx show remote p-packet
12741 Show the current setting of using the @samp{P} packets for setting and
12742 fetching registers from the remote target.
12744 @cindex binary downloads
12746 @item set remote binary-download-packet
12747 @itemx set remote X-packet
12748 Determine whether @value{GDBN} sends downloads in binary mode using
12749 the @samp{X} packets. The default is on.
12751 @item show remote binary-download-packet
12752 @itemx show remote X-packet
12753 Show the current setting of using the @samp{X} packets for binary
12756 @item set remote read-aux-vector-packet
12757 @cindex auxiliary vector of remote target
12758 @cindex @code{auxv}, and remote targets
12759 Set the use of the remote protocol's @samp{qXfer:auxv:read} (target
12760 auxiliary vector) request. This request is used to fetch the
12761 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12762 Auxiliary Vector}. The default setting depends on the remote stub's
12763 support of this request (@value{GDBN} queries the stub when this
12764 request is first required). @xref{General Query Packets, qXfer}, for
12765 more information about this request.
12767 @item show remote read-aux-vector-packet
12768 Show the current setting of use of the @samp{qXfer:auxv:read} request.
12770 @item set remote symbol-lookup-packet
12771 @cindex remote symbol lookup request
12772 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12773 lookup) request. This request is used to communicate symbol
12774 information to the remote target, e.g., whenever a new shared library
12775 is loaded by the remote (@pxref{Files, shared libraries}). The
12776 default setting depends on the remote stub's support of this request
12777 (@value{GDBN} queries the stub when this request is first required).
12778 @xref{General Query Packets, qSymbol}, for more information about this
12781 @item show remote symbol-lookup-packet
12782 Show the current setting of use of the @samp{qSymbol} request.
12784 @item set remote verbose-resume-packet
12785 @cindex resume remote target
12786 @cindex signal thread, and remote targets
12787 @cindex single-step thread, and remote targets
12788 @cindex thread-specific operations on remote targets
12789 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12790 request. This request is used to resume specific threads in the
12791 remote target, and to single-step or signal them. The default setting
12792 depends on the remote stub's support of this request (@value{GDBN}
12793 queries the stub when this request is first required). This setting
12794 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12795 used, @value{GDBN} might be unable to single-step a specific thread,
12796 especially under @code{set scheduler-locking off}; it is also
12797 impossible to pause a specific thread. @xref{Packets, vCont}, for
12800 @item show remote verbose-resume-packet
12801 Show the current setting of use of the @samp{vCont} request
12803 @item set remote software-breakpoint-packet
12804 @itemx set remote hardware-breakpoint-packet
12805 @itemx set remote write-watchpoint-packet
12806 @itemx set remote read-watchpoint-packet
12807 @itemx set remote access-watchpoint-packet
12808 @itemx set remote Z-packet
12810 @cindex remote hardware breakpoints and watchpoints
12811 These commands enable or disable the use of @samp{Z} packets for
12812 setting breakpoints and watchpoints in the remote target. The default
12813 depends on the remote stub's support of the @samp{Z} packets
12814 (@value{GDBN} queries the stub when each packet is first required).
12815 The command @code{set remote Z-packet}, kept for back-compatibility,
12816 turns on or off all the features that require the use of @samp{Z}
12819 @item show remote software-breakpoint-packet
12820 @itemx show remote hardware-breakpoint-packet
12821 @itemx show remote write-watchpoint-packet
12822 @itemx show remote read-watchpoint-packet
12823 @itemx show remote access-watchpoint-packet
12824 @itemx show remote Z-packet
12825 Show the current setting of @samp{Z} packets usage.
12827 @item set remote get-thread-local-storage-address
12828 @kindex set remote get-thread-local-storage-address
12829 @cindex thread local storage of remote targets
12830 This command enables or disables the use of the @samp{qGetTLSAddr}
12831 (Get Thread Local Storage Address) request packet. The default
12832 depends on whether the remote stub supports this request.
12833 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12836 @item show remote get-thread-local-storage-address
12837 @kindex show remote get-thread-local-storage-address
12838 Show the current setting of @samp{qGetTLSAddr} packet usage.
12840 @item set remote supported-packets
12841 @kindex set remote supported-packets
12842 @cindex query supported packets of remote targets
12843 This command enables or disables the use of the @samp{qSupported}
12844 request packet. @xref{General Query Packets, qSupported}, for more
12845 details about this packet. The default is to use @samp{qSupported}.
12847 @item show remote supported-packets
12848 @kindex show remote supported-packets
12849 Show the current setting of @samp{qSupported} packet usage.
12853 @section Implementing a remote stub
12855 @cindex debugging stub, example
12856 @cindex remote stub, example
12857 @cindex stub example, remote debugging
12858 The stub files provided with @value{GDBN} implement the target side of the
12859 communication protocol, and the @value{GDBN} side is implemented in the
12860 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12861 these subroutines to communicate, and ignore the details. (If you're
12862 implementing your own stub file, you can still ignore the details: start
12863 with one of the existing stub files. @file{sparc-stub.c} is the best
12864 organized, and therefore the easiest to read.)
12866 @cindex remote serial debugging, overview
12867 To debug a program running on another machine (the debugging
12868 @dfn{target} machine), you must first arrange for all the usual
12869 prerequisites for the program to run by itself. For example, for a C
12874 A startup routine to set up the C runtime environment; these usually
12875 have a name like @file{crt0}. The startup routine may be supplied by
12876 your hardware supplier, or you may have to write your own.
12879 A C subroutine library to support your program's
12880 subroutine calls, notably managing input and output.
12883 A way of getting your program to the other machine---for example, a
12884 download program. These are often supplied by the hardware
12885 manufacturer, but you may have to write your own from hardware
12889 The next step is to arrange for your program to use a serial port to
12890 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12891 machine). In general terms, the scheme looks like this:
12895 @value{GDBN} already understands how to use this protocol; when everything
12896 else is set up, you can simply use the @samp{target remote} command
12897 (@pxref{Targets,,Specifying a Debugging Target}).
12899 @item On the target,
12900 you must link with your program a few special-purpose subroutines that
12901 implement the @value{GDBN} remote serial protocol. The file containing these
12902 subroutines is called a @dfn{debugging stub}.
12904 On certain remote targets, you can use an auxiliary program
12905 @code{gdbserver} instead of linking a stub into your program.
12906 @xref{Server,,Using the @code{gdbserver} program}, for details.
12909 The debugging stub is specific to the architecture of the remote
12910 machine; for example, use @file{sparc-stub.c} to debug programs on
12913 @cindex remote serial stub list
12914 These working remote stubs are distributed with @value{GDBN}:
12919 @cindex @file{i386-stub.c}
12922 For Intel 386 and compatible architectures.
12925 @cindex @file{m68k-stub.c}
12926 @cindex Motorola 680x0
12928 For Motorola 680x0 architectures.
12931 @cindex @file{sh-stub.c}
12934 For Renesas SH architectures.
12937 @cindex @file{sparc-stub.c}
12939 For @sc{sparc} architectures.
12941 @item sparcl-stub.c
12942 @cindex @file{sparcl-stub.c}
12945 For Fujitsu @sc{sparclite} architectures.
12949 The @file{README} file in the @value{GDBN} distribution may list other
12950 recently added stubs.
12953 * Stub Contents:: What the stub can do for you
12954 * Bootstrapping:: What you must do for the stub
12955 * Debug Session:: Putting it all together
12958 @node Stub Contents
12959 @subsection What the stub can do for you
12961 @cindex remote serial stub
12962 The debugging stub for your architecture supplies these three
12966 @item set_debug_traps
12967 @findex set_debug_traps
12968 @cindex remote serial stub, initialization
12969 This routine arranges for @code{handle_exception} to run when your
12970 program stops. You must call this subroutine explicitly near the
12971 beginning of your program.
12973 @item handle_exception
12974 @findex handle_exception
12975 @cindex remote serial stub, main routine
12976 This is the central workhorse, but your program never calls it
12977 explicitly---the setup code arranges for @code{handle_exception} to
12978 run when a trap is triggered.
12980 @code{handle_exception} takes control when your program stops during
12981 execution (for example, on a breakpoint), and mediates communications
12982 with @value{GDBN} on the host machine. This is where the communications
12983 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12984 representative on the target machine. It begins by sending summary
12985 information on the state of your program, then continues to execute,
12986 retrieving and transmitting any information @value{GDBN} needs, until you
12987 execute a @value{GDBN} command that makes your program resume; at that point,
12988 @code{handle_exception} returns control to your own code on the target
12992 @cindex @code{breakpoint} subroutine, remote
12993 Use this auxiliary subroutine to make your program contain a
12994 breakpoint. Depending on the particular situation, this may be the only
12995 way for @value{GDBN} to get control. For instance, if your target
12996 machine has some sort of interrupt button, you won't need to call this;
12997 pressing the interrupt button transfers control to
12998 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12999 simply receiving characters on the serial port may also trigger a trap;
13000 again, in that situation, you don't need to call @code{breakpoint} from
13001 your own program---simply running @samp{target remote} from the host
13002 @value{GDBN} session gets control.
13004 Call @code{breakpoint} if none of these is true, or if you simply want
13005 to make certain your program stops at a predetermined point for the
13006 start of your debugging session.
13009 @node Bootstrapping
13010 @subsection What you must do for the stub
13012 @cindex remote stub, support routines
13013 The debugging stubs that come with @value{GDBN} are set up for a particular
13014 chip architecture, but they have no information about the rest of your
13015 debugging target machine.
13017 First of all you need to tell the stub how to communicate with the
13021 @item int getDebugChar()
13022 @findex getDebugChar
13023 Write this subroutine to read a single character from the serial port.
13024 It may be identical to @code{getchar} for your target system; a
13025 different name is used to allow you to distinguish the two if you wish.
13027 @item void putDebugChar(int)
13028 @findex putDebugChar
13029 Write this subroutine to write a single character to the serial port.
13030 It may be identical to @code{putchar} for your target system; a
13031 different name is used to allow you to distinguish the two if you wish.
13034 @cindex control C, and remote debugging
13035 @cindex interrupting remote targets
13036 If you want @value{GDBN} to be able to stop your program while it is
13037 running, you need to use an interrupt-driven serial driver, and arrange
13038 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13039 character). That is the character which @value{GDBN} uses to tell the
13040 remote system to stop.
13042 Getting the debugging target to return the proper status to @value{GDBN}
13043 probably requires changes to the standard stub; one quick and dirty way
13044 is to just execute a breakpoint instruction (the ``dirty'' part is that
13045 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13047 Other routines you need to supply are:
13050 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13051 @findex exceptionHandler
13052 Write this function to install @var{exception_address} in the exception
13053 handling tables. You need to do this because the stub does not have any
13054 way of knowing what the exception handling tables on your target system
13055 are like (for example, the processor's table might be in @sc{rom},
13056 containing entries which point to a table in @sc{ram}).
13057 @var{exception_number} is the exception number which should be changed;
13058 its meaning is architecture-dependent (for example, different numbers
13059 might represent divide by zero, misaligned access, etc). When this
13060 exception occurs, control should be transferred directly to
13061 @var{exception_address}, and the processor state (stack, registers,
13062 and so on) should be just as it is when a processor exception occurs. So if
13063 you want to use a jump instruction to reach @var{exception_address}, it
13064 should be a simple jump, not a jump to subroutine.
13066 For the 386, @var{exception_address} should be installed as an interrupt
13067 gate so that interrupts are masked while the handler runs. The gate
13068 should be at privilege level 0 (the most privileged level). The
13069 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13070 help from @code{exceptionHandler}.
13072 @item void flush_i_cache()
13073 @findex flush_i_cache
13074 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13075 instruction cache, if any, on your target machine. If there is no
13076 instruction cache, this subroutine may be a no-op.
13078 On target machines that have instruction caches, @value{GDBN} requires this
13079 function to make certain that the state of your program is stable.
13083 You must also make sure this library routine is available:
13086 @item void *memset(void *, int, int)
13088 This is the standard library function @code{memset} that sets an area of
13089 memory to a known value. If you have one of the free versions of
13090 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13091 either obtain it from your hardware manufacturer, or write your own.
13094 If you do not use the GNU C compiler, you may need other standard
13095 library subroutines as well; this varies from one stub to another,
13096 but in general the stubs are likely to use any of the common library
13097 subroutines which @code{@value{GCC}} generates as inline code.
13100 @node Debug Session
13101 @subsection Putting it all together
13103 @cindex remote serial debugging summary
13104 In summary, when your program is ready to debug, you must follow these
13109 Make sure you have defined the supporting low-level routines
13110 (@pxref{Bootstrapping,,What you must do for the stub}):
13112 @code{getDebugChar}, @code{putDebugChar},
13113 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13117 Insert these lines near the top of your program:
13125 For the 680x0 stub only, you need to provide a variable called
13126 @code{exceptionHook}. Normally you just use:
13129 void (*exceptionHook)() = 0;
13133 but if before calling @code{set_debug_traps}, you set it to point to a
13134 function in your program, that function is called when
13135 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13136 error). The function indicated by @code{exceptionHook} is called with
13137 one parameter: an @code{int} which is the exception number.
13140 Compile and link together: your program, the @value{GDBN} debugging stub for
13141 your target architecture, and the supporting subroutines.
13144 Make sure you have a serial connection between your target machine and
13145 the @value{GDBN} host, and identify the serial port on the host.
13148 @c The "remote" target now provides a `load' command, so we should
13149 @c document that. FIXME.
13150 Download your program to your target machine (or get it there by
13151 whatever means the manufacturer provides), and start it.
13154 Start @value{GDBN} on the host, and connect to the target
13155 (@pxref{Connecting,,Connecting to a remote target}).
13159 @node Configurations
13160 @chapter Configuration-Specific Information
13162 While nearly all @value{GDBN} commands are available for all native and
13163 cross versions of the debugger, there are some exceptions. This chapter
13164 describes things that are only available in certain configurations.
13166 There are three major categories of configurations: native
13167 configurations, where the host and target are the same, embedded
13168 operating system configurations, which are usually the same for several
13169 different processor architectures, and bare embedded processors, which
13170 are quite different from each other.
13175 * Embedded Processors::
13182 This section describes details specific to particular native
13187 * BSD libkvm Interface:: Debugging BSD kernel memory images
13188 * SVR4 Process Information:: SVR4 process information
13189 * DJGPP Native:: Features specific to the DJGPP port
13190 * Cygwin Native:: Features specific to the Cygwin port
13191 * Hurd Native:: Features specific to @sc{gnu} Hurd
13192 * Neutrino:: Features specific to QNX Neutrino
13198 On HP-UX systems, if you refer to a function or variable name that
13199 begins with a dollar sign, @value{GDBN} searches for a user or system
13200 name first, before it searches for a convenience variable.
13203 @node BSD libkvm Interface
13204 @subsection BSD libkvm Interface
13207 @cindex kernel memory image
13208 @cindex kernel crash dump
13210 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13211 interface that provides a uniform interface for accessing kernel virtual
13212 memory images, including live systems and crash dumps. @value{GDBN}
13213 uses this interface to allow you to debug live kernels and kernel crash
13214 dumps on many native BSD configurations. This is implemented as a
13215 special @code{kvm} debugging target. For debugging a live system, load
13216 the currently running kernel into @value{GDBN} and connect to the
13220 (@value{GDBP}) @b{target kvm}
13223 For debugging crash dumps, provide the file name of the crash dump as an
13227 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13230 Once connected to the @code{kvm} target, the following commands are
13236 Set current context from the @dfn{Process Control Block} (PCB) address.
13239 Set current context from proc address. This command isn't available on
13240 modern FreeBSD systems.
13243 @node SVR4 Process Information
13244 @subsection SVR4 process information
13246 @cindex examine process image
13247 @cindex process info via @file{/proc}
13249 Many versions of SVR4 and compatible systems provide a facility called
13250 @samp{/proc} that can be used to examine the image of a running
13251 process using file-system subroutines. If @value{GDBN} is configured
13252 for an operating system with this facility, the command @code{info
13253 proc} is available to report information about the process running
13254 your program, or about any process running on your system. @code{info
13255 proc} works only on SVR4 systems that include the @code{procfs} code.
13256 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13257 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13263 @itemx info proc @var{process-id}
13264 Summarize available information about any running process. If a
13265 process ID is specified by @var{process-id}, display information about
13266 that process; otherwise display information about the program being
13267 debugged. The summary includes the debugged process ID, the command
13268 line used to invoke it, its current working directory, and its
13269 executable file's absolute file name.
13271 On some systems, @var{process-id} can be of the form
13272 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13273 within a process. If the optional @var{pid} part is missing, it means
13274 a thread from the process being debugged (the leading @samp{/} still
13275 needs to be present, or else @value{GDBN} will interpret the number as
13276 a process ID rather than a thread ID).
13278 @item info proc mappings
13279 @cindex memory address space mappings
13280 Report the memory address space ranges accessible in the program, with
13281 information on whether the process has read, write, or execute access
13282 rights to each range. On @sc{gnu}/Linux systems, each memory range
13283 includes the object file which is mapped to that range, instead of the
13284 memory access rights to that range.
13286 @item info proc stat
13287 @itemx info proc status
13288 @cindex process detailed status information
13289 These subcommands are specific to @sc{gnu}/Linux systems. They show
13290 the process-related information, including the user ID and group ID;
13291 how many threads are there in the process; its virtual memory usage;
13292 the signals that are pending, blocked, and ignored; its TTY; its
13293 consumption of system and user time; its stack size; its @samp{nice}
13294 value; etc. For more information, see the @samp{proc} man page
13295 (type @kbd{man 5 proc} from your shell prompt).
13297 @item info proc all
13298 Show all the information about the process described under all of the
13299 above @code{info proc} subcommands.
13302 @comment These sub-options of 'info proc' were not included when
13303 @comment procfs.c was re-written. Keep their descriptions around
13304 @comment against the day when someone finds the time to put them back in.
13305 @kindex info proc times
13306 @item info proc times
13307 Starting time, user CPU time, and system CPU time for your program and
13310 @kindex info proc id
13312 Report on the process IDs related to your program: its own process ID,
13313 the ID of its parent, the process group ID, and the session ID.
13316 @item set procfs-trace
13317 @kindex set procfs-trace
13318 @cindex @code{procfs} API calls
13319 This command enables and disables tracing of @code{procfs} API calls.
13321 @item show procfs-trace
13322 @kindex show procfs-trace
13323 Show the current state of @code{procfs} API call tracing.
13325 @item set procfs-file @var{file}
13326 @kindex set procfs-file
13327 Tell @value{GDBN} to write @code{procfs} API trace to the named
13328 @var{file}. @value{GDBN} appends the trace info to the previous
13329 contents of the file. The default is to display the trace on the
13332 @item show procfs-file
13333 @kindex show procfs-file
13334 Show the file to which @code{procfs} API trace is written.
13336 @item proc-trace-entry
13337 @itemx proc-trace-exit
13338 @itemx proc-untrace-entry
13339 @itemx proc-untrace-exit
13340 @kindex proc-trace-entry
13341 @kindex proc-trace-exit
13342 @kindex proc-untrace-entry
13343 @kindex proc-untrace-exit
13344 These commands enable and disable tracing of entries into and exits
13345 from the @code{syscall} interface.
13348 @kindex info pidlist
13349 @cindex process list, QNX Neutrino
13350 For QNX Neutrino only, this command displays the list of all the
13351 processes and all the threads within each process.
13354 @kindex info meminfo
13355 @cindex mapinfo list, QNX Neutrino
13356 For QNX Neutrino only, this command displays the list of all mapinfos.
13360 @subsection Features for Debugging @sc{djgpp} Programs
13361 @cindex @sc{djgpp} debugging
13362 @cindex native @sc{djgpp} debugging
13363 @cindex MS-DOS-specific commands
13366 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13367 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13368 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13369 top of real-mode DOS systems and their emulations.
13371 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13372 defines a few commands specific to the @sc{djgpp} port. This
13373 subsection describes those commands.
13378 This is a prefix of @sc{djgpp}-specific commands which print
13379 information about the target system and important OS structures.
13382 @cindex MS-DOS system info
13383 @cindex free memory information (MS-DOS)
13384 @item info dos sysinfo
13385 This command displays assorted information about the underlying
13386 platform: the CPU type and features, the OS version and flavor, the
13387 DPMI version, and the available conventional and DPMI memory.
13392 @cindex segment descriptor tables
13393 @cindex descriptor tables display
13395 @itemx info dos ldt
13396 @itemx info dos idt
13397 These 3 commands display entries from, respectively, Global, Local,
13398 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13399 tables are data structures which store a descriptor for each segment
13400 that is currently in use. The segment's selector is an index into a
13401 descriptor table; the table entry for that index holds the
13402 descriptor's base address and limit, and its attributes and access
13405 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13406 segment (used for both data and the stack), and a DOS segment (which
13407 allows access to DOS/BIOS data structures and absolute addresses in
13408 conventional memory). However, the DPMI host will usually define
13409 additional segments in order to support the DPMI environment.
13411 @cindex garbled pointers
13412 These commands allow to display entries from the descriptor tables.
13413 Without an argument, all entries from the specified table are
13414 displayed. An argument, which should be an integer expression, means
13415 display a single entry whose index is given by the argument. For
13416 example, here's a convenient way to display information about the
13417 debugged program's data segment:
13420 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13421 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13425 This comes in handy when you want to see whether a pointer is outside
13426 the data segment's limit (i.e.@: @dfn{garbled}).
13428 @cindex page tables display (MS-DOS)
13430 @itemx info dos pte
13431 These two commands display entries from, respectively, the Page
13432 Directory and the Page Tables. Page Directories and Page Tables are
13433 data structures which control how virtual memory addresses are mapped
13434 into physical addresses. A Page Table includes an entry for every
13435 page of memory that is mapped into the program's address space; there
13436 may be several Page Tables, each one holding up to 4096 entries. A
13437 Page Directory has up to 4096 entries, one each for every Page Table
13438 that is currently in use.
13440 Without an argument, @kbd{info dos pde} displays the entire Page
13441 Directory, and @kbd{info dos pte} displays all the entries in all of
13442 the Page Tables. An argument, an integer expression, given to the
13443 @kbd{info dos pde} command means display only that entry from the Page
13444 Directory table. An argument given to the @kbd{info dos pte} command
13445 means display entries from a single Page Table, the one pointed to by
13446 the specified entry in the Page Directory.
13448 @cindex direct memory access (DMA) on MS-DOS
13449 These commands are useful when your program uses @dfn{DMA} (Direct
13450 Memory Access), which needs physical addresses to program the DMA
13453 These commands are supported only with some DPMI servers.
13455 @cindex physical address from linear address
13456 @item info dos address-pte @var{addr}
13457 This command displays the Page Table entry for a specified linear
13458 address. The argument @var{addr} is a linear address which should
13459 already have the appropriate segment's base address added to it,
13460 because this command accepts addresses which may belong to @emph{any}
13461 segment. For example, here's how to display the Page Table entry for
13462 the page where a variable @code{i} is stored:
13465 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13466 @exdent @code{Page Table entry for address 0x11a00d30:}
13467 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13471 This says that @code{i} is stored at offset @code{0xd30} from the page
13472 whose physical base address is @code{0x02698000}, and shows all the
13473 attributes of that page.
13475 Note that you must cast the addresses of variables to a @code{char *},
13476 since otherwise the value of @code{__djgpp_base_address}, the base
13477 address of all variables and functions in a @sc{djgpp} program, will
13478 be added using the rules of C pointer arithmetics: if @code{i} is
13479 declared an @code{int}, @value{GDBN} will add 4 times the value of
13480 @code{__djgpp_base_address} to the address of @code{i}.
13482 Here's another example, it displays the Page Table entry for the
13486 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13487 @exdent @code{Page Table entry for address 0x29110:}
13488 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13492 (The @code{+ 3} offset is because the transfer buffer's address is the
13493 3rd member of the @code{_go32_info_block} structure.) The output
13494 clearly shows that this DPMI server maps the addresses in conventional
13495 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13496 linear (@code{0x29110}) addresses are identical.
13498 This command is supported only with some DPMI servers.
13501 @cindex DOS serial data link, remote debugging
13502 In addition to native debugging, the DJGPP port supports remote
13503 debugging via a serial data link. The following commands are specific
13504 to remote serial debugging in the DJGPP port of @value{GDBN}.
13507 @kindex set com1base
13508 @kindex set com1irq
13509 @kindex set com2base
13510 @kindex set com2irq
13511 @kindex set com3base
13512 @kindex set com3irq
13513 @kindex set com4base
13514 @kindex set com4irq
13515 @item set com1base @var{addr}
13516 This command sets the base I/O port address of the @file{COM1} serial
13519 @item set com1irq @var{irq}
13520 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13521 for the @file{COM1} serial port.
13523 There are similar commands @samp{set com2base}, @samp{set com3irq},
13524 etc.@: for setting the port address and the @code{IRQ} lines for the
13527 @kindex show com1base
13528 @kindex show com1irq
13529 @kindex show com2base
13530 @kindex show com2irq
13531 @kindex show com3base
13532 @kindex show com3irq
13533 @kindex show com4base
13534 @kindex show com4irq
13535 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13536 display the current settings of the base address and the @code{IRQ}
13537 lines used by the COM ports.
13540 @kindex info serial
13541 @cindex DOS serial port status
13542 This command prints the status of the 4 DOS serial ports. For each
13543 port, it prints whether it's active or not, its I/O base address and
13544 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13545 counts of various errors encountered so far.
13549 @node Cygwin Native
13550 @subsection Features for Debugging MS Windows PE executables
13551 @cindex MS Windows debugging
13552 @cindex native Cygwin debugging
13553 @cindex Cygwin-specific commands
13555 @value{GDBN} supports native debugging of MS Windows programs, including
13556 DLLs with and without symbolic debugging information. There are various
13557 additional Cygwin-specific commands, described in this subsection. The
13558 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
13559 that have no debugging symbols.
13565 This is a prefix of MS Windows specific commands which print
13566 information about the target system and important OS structures.
13568 @item info w32 selector
13569 This command displays information returned by
13570 the Win32 API @code{GetThreadSelectorEntry} function.
13571 It takes an optional argument that is evaluated to
13572 a long value to give the information about this given selector.
13573 Without argument, this command displays information
13574 about the the six segment registers.
13578 This is a Cygwin specific alias of info shared.
13580 @kindex dll-symbols
13582 This command loads symbols from a dll similarly to
13583 add-sym command but without the need to specify a base address.
13585 @kindex set cygwin-exceptions
13586 @cindex debugging the Cygwin DLL
13587 @cindex Cygwin DLL, debugging
13588 @item set cygwin-exceptions @var{mode}
13589 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13590 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13591 @value{GDBN} will delay recognition of exceptions, and may ignore some
13592 exceptions which seem to be caused by internal Cygwin DLL
13593 ``bookkeeping''. This option is meant primarily for debugging the
13594 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13595 @value{GDBN} users with false @code{SIGSEGV} signals.
13597 @kindex show cygwin-exceptions
13598 @item show cygwin-exceptions
13599 Displays whether @value{GDBN} will break on exceptions that happen
13600 inside the Cygwin DLL itself.
13602 @kindex set new-console
13603 @item set new-console @var{mode}
13604 If @var{mode} is @code{on} the debuggee will
13605 be started in a new console on next start.
13606 If @var{mode} is @code{off}i, the debuggee will
13607 be started in the same console as the debugger.
13609 @kindex show new-console
13610 @item show new-console
13611 Displays whether a new console is used
13612 when the debuggee is started.
13614 @kindex set new-group
13615 @item set new-group @var{mode}
13616 This boolean value controls whether the debuggee should
13617 start a new group or stay in the same group as the debugger.
13618 This affects the way the Windows OS handles
13621 @kindex show new-group
13622 @item show new-group
13623 Displays current value of new-group boolean.
13625 @kindex set debugevents
13626 @item set debugevents
13627 This boolean value adds debug output concerning kernel events related
13628 to the debuggee seen by the debugger. This includes events that
13629 signal thread and process creation and exit, DLL loading and
13630 unloading, console interrupts, and debugging messages produced by the
13631 Windows @code{OutputDebugString} API call.
13633 @kindex set debugexec
13634 @item set debugexec
13635 This boolean value adds debug output concerning execute events
13636 (such as resume thread) seen by the debugger.
13638 @kindex set debugexceptions
13639 @item set debugexceptions
13640 This boolean value adds debug output concerning exceptions in the
13641 debuggee seen by the debugger.
13643 @kindex set debugmemory
13644 @item set debugmemory
13645 This boolean value adds debug output concerning debuggee memory reads
13646 and writes by the debugger.
13650 This boolean values specifies whether the debuggee is called
13651 via a shell or directly (default value is on).
13655 Displays if the debuggee will be started with a shell.
13660 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13663 @node Non-debug DLL symbols
13664 @subsubsection Support for DLLs without debugging symbols
13665 @cindex DLLs with no debugging symbols
13666 @cindex Minimal symbols and DLLs
13668 Very often on windows, some of the DLLs that your program relies on do
13669 not include symbolic debugging information (for example,
13670 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13671 symbols in a DLL, it relies on the minimal amount of symbolic
13672 information contained in the DLL's export table. This subsubsection
13673 describes working with such symbols, known internally to @value{GDBN} as
13674 ``minimal symbols''.
13676 Note that before the debugged program has started execution, no DLLs
13677 will have been loaded. The easiest way around this problem is simply to
13678 start the program --- either by setting a breakpoint or letting the
13679 program run once to completion. It is also possible to force
13680 @value{GDBN} to load a particular DLL before starting the executable ---
13681 see the shared library information in @pxref{Files} or the
13682 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13683 explicitly loading symbols from a DLL with no debugging information will
13684 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13685 which may adversely affect symbol lookup performance.
13687 @subsubsection DLL name prefixes
13689 In keeping with the naming conventions used by the Microsoft debugging
13690 tools, DLL export symbols are made available with a prefix based on the
13691 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13692 also entered into the symbol table, so @code{CreateFileA} is often
13693 sufficient. In some cases there will be name clashes within a program
13694 (particularly if the executable itself includes full debugging symbols)
13695 necessitating the use of the fully qualified name when referring to the
13696 contents of the DLL. Use single-quotes around the name to avoid the
13697 exclamation mark (``!'') being interpreted as a language operator.
13699 Note that the internal name of the DLL may be all upper-case, even
13700 though the file name of the DLL is lower-case, or vice-versa. Since
13701 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13702 some confusion. If in doubt, try the @code{info functions} and
13703 @code{info variables} commands or even @code{maint print msymbols} (see
13704 @pxref{Symbols}). Here's an example:
13707 (@value{GDBP}) info function CreateFileA
13708 All functions matching regular expression "CreateFileA":
13710 Non-debugging symbols:
13711 0x77e885f4 CreateFileA
13712 0x77e885f4 KERNEL32!CreateFileA
13716 (@value{GDBP}) info function !
13717 All functions matching regular expression "!":
13719 Non-debugging symbols:
13720 0x6100114c cygwin1!__assert
13721 0x61004034 cygwin1!_dll_crt0@@0
13722 0x61004240 cygwin1!dll_crt0(per_process *)
13726 @subsubsection Working with minimal symbols
13728 Symbols extracted from a DLL's export table do not contain very much
13729 type information. All that @value{GDBN} can do is guess whether a symbol
13730 refers to a function or variable depending on the linker section that
13731 contains the symbol. Also note that the actual contents of the memory
13732 contained in a DLL are not available unless the program is running. This
13733 means that you cannot examine the contents of a variable or disassemble
13734 a function within a DLL without a running program.
13736 Variables are generally treated as pointers and dereferenced
13737 automatically. For this reason, it is often necessary to prefix a
13738 variable name with the address-of operator (``&'') and provide explicit
13739 type information in the command. Here's an example of the type of
13743 (@value{GDBP}) print 'cygwin1!__argv'
13748 (@value{GDBP}) x 'cygwin1!__argv'
13749 0x10021610: "\230y\""
13752 And two possible solutions:
13755 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13756 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13760 (@value{GDBP}) x/2x &'cygwin1!__argv'
13761 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13762 (@value{GDBP}) x/x 0x10021608
13763 0x10021608: 0x0022fd98
13764 (@value{GDBP}) x/s 0x0022fd98
13765 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13768 Setting a break point within a DLL is possible even before the program
13769 starts execution. However, under these circumstances, @value{GDBN} can't
13770 examine the initial instructions of the function in order to skip the
13771 function's frame set-up code. You can work around this by using ``*&''
13772 to set the breakpoint at a raw memory address:
13775 (@value{GDBP}) break *&'python22!PyOS_Readline'
13776 Breakpoint 1 at 0x1e04eff0
13779 The author of these extensions is not entirely convinced that setting a
13780 break point within a shared DLL like @file{kernel32.dll} is completely
13784 @subsection Commands specific to @sc{gnu} Hurd systems
13785 @cindex @sc{gnu} Hurd debugging
13787 This subsection describes @value{GDBN} commands specific to the
13788 @sc{gnu} Hurd native debugging.
13793 @kindex set signals@r{, Hurd command}
13794 @kindex set sigs@r{, Hurd command}
13795 This command toggles the state of inferior signal interception by
13796 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13797 affected by this command. @code{sigs} is a shorthand alias for
13802 @kindex show signals@r{, Hurd command}
13803 @kindex show sigs@r{, Hurd command}
13804 Show the current state of intercepting inferior's signals.
13806 @item set signal-thread
13807 @itemx set sigthread
13808 @kindex set signal-thread
13809 @kindex set sigthread
13810 This command tells @value{GDBN} which thread is the @code{libc} signal
13811 thread. That thread is run when a signal is delivered to a running
13812 process. @code{set sigthread} is the shorthand alias of @code{set
13815 @item show signal-thread
13816 @itemx show sigthread
13817 @kindex show signal-thread
13818 @kindex show sigthread
13819 These two commands show which thread will run when the inferior is
13820 delivered a signal.
13823 @kindex set stopped@r{, Hurd command}
13824 This commands tells @value{GDBN} that the inferior process is stopped,
13825 as with the @code{SIGSTOP} signal. The stopped process can be
13826 continued by delivering a signal to it.
13829 @kindex show stopped@r{, Hurd command}
13830 This command shows whether @value{GDBN} thinks the debuggee is
13833 @item set exceptions
13834 @kindex set exceptions@r{, Hurd command}
13835 Use this command to turn off trapping of exceptions in the inferior.
13836 When exception trapping is off, neither breakpoints nor
13837 single-stepping will work. To restore the default, set exception
13840 @item show exceptions
13841 @kindex show exceptions@r{, Hurd command}
13842 Show the current state of trapping exceptions in the inferior.
13844 @item set task pause
13845 @kindex set task@r{, Hurd commands}
13846 @cindex task attributes (@sc{gnu} Hurd)
13847 @cindex pause current task (@sc{gnu} Hurd)
13848 This command toggles task suspension when @value{GDBN} has control.
13849 Setting it to on takes effect immediately, and the task is suspended
13850 whenever @value{GDBN} gets control. Setting it to off will take
13851 effect the next time the inferior is continued. If this option is set
13852 to off, you can use @code{set thread default pause on} or @code{set
13853 thread pause on} (see below) to pause individual threads.
13855 @item show task pause
13856 @kindex show task@r{, Hurd commands}
13857 Show the current state of task suspension.
13859 @item set task detach-suspend-count
13860 @cindex task suspend count
13861 @cindex detach from task, @sc{gnu} Hurd
13862 This command sets the suspend count the task will be left with when
13863 @value{GDBN} detaches from it.
13865 @item show task detach-suspend-count
13866 Show the suspend count the task will be left with when detaching.
13868 @item set task exception-port
13869 @itemx set task excp
13870 @cindex task exception port, @sc{gnu} Hurd
13871 This command sets the task exception port to which @value{GDBN} will
13872 forward exceptions. The argument should be the value of the @dfn{send
13873 rights} of the task. @code{set task excp} is a shorthand alias.
13875 @item set noninvasive
13876 @cindex noninvasive task options
13877 This command switches @value{GDBN} to a mode that is the least
13878 invasive as far as interfering with the inferior is concerned. This
13879 is the same as using @code{set task pause}, @code{set exceptions}, and
13880 @code{set signals} to values opposite to the defaults.
13882 @item info send-rights
13883 @itemx info receive-rights
13884 @itemx info port-rights
13885 @itemx info port-sets
13886 @itemx info dead-names
13889 @cindex send rights, @sc{gnu} Hurd
13890 @cindex receive rights, @sc{gnu} Hurd
13891 @cindex port rights, @sc{gnu} Hurd
13892 @cindex port sets, @sc{gnu} Hurd
13893 @cindex dead names, @sc{gnu} Hurd
13894 These commands display information about, respectively, send rights,
13895 receive rights, port rights, port sets, and dead names of a task.
13896 There are also shorthand aliases: @code{info ports} for @code{info
13897 port-rights} and @code{info psets} for @code{info port-sets}.
13899 @item set thread pause
13900 @kindex set thread@r{, Hurd command}
13901 @cindex thread properties, @sc{gnu} Hurd
13902 @cindex pause current thread (@sc{gnu} Hurd)
13903 This command toggles current thread suspension when @value{GDBN} has
13904 control. Setting it to on takes effect immediately, and the current
13905 thread is suspended whenever @value{GDBN} gets control. Setting it to
13906 off will take effect the next time the inferior is continued.
13907 Normally, this command has no effect, since when @value{GDBN} has
13908 control, the whole task is suspended. However, if you used @code{set
13909 task pause off} (see above), this command comes in handy to suspend
13910 only the current thread.
13912 @item show thread pause
13913 @kindex show thread@r{, Hurd command}
13914 This command shows the state of current thread suspension.
13916 @item set thread run
13917 This comamnd sets whether the current thread is allowed to run.
13919 @item show thread run
13920 Show whether the current thread is allowed to run.
13922 @item set thread detach-suspend-count
13923 @cindex thread suspend count, @sc{gnu} Hurd
13924 @cindex detach from thread, @sc{gnu} Hurd
13925 This command sets the suspend count @value{GDBN} will leave on a
13926 thread when detaching. This number is relative to the suspend count
13927 found by @value{GDBN} when it notices the thread; use @code{set thread
13928 takeover-suspend-count} to force it to an absolute value.
13930 @item show thread detach-suspend-count
13931 Show the suspend count @value{GDBN} will leave on the thread when
13934 @item set thread exception-port
13935 @itemx set thread excp
13936 Set the thread exception port to which to forward exceptions. This
13937 overrides the port set by @code{set task exception-port} (see above).
13938 @code{set thread excp} is the shorthand alias.
13940 @item set thread takeover-suspend-count
13941 Normally, @value{GDBN}'s thread suspend counts are relative to the
13942 value @value{GDBN} finds when it notices each thread. This command
13943 changes the suspend counts to be absolute instead.
13945 @item set thread default
13946 @itemx show thread default
13947 @cindex thread default settings, @sc{gnu} Hurd
13948 Each of the above @code{set thread} commands has a @code{set thread
13949 default} counterpart (e.g., @code{set thread default pause}, @code{set
13950 thread default exception-port}, etc.). The @code{thread default}
13951 variety of commands sets the default thread properties for all
13952 threads; you can then change the properties of individual threads with
13953 the non-default commands.
13958 @subsection QNX Neutrino
13959 @cindex QNX Neutrino
13961 @value{GDBN} provides the following commands specific to the QNX
13965 @item set debug nto-debug
13966 @kindex set debug nto-debug
13967 When set to on, enables debugging messages specific to the QNX
13970 @item show debug nto-debug
13971 @kindex show debug nto-debug
13972 Show the current state of QNX Neutrino messages.
13977 @section Embedded Operating Systems
13979 This section describes configurations involving the debugging of
13980 embedded operating systems that are available for several different
13984 * VxWorks:: Using @value{GDBN} with VxWorks
13987 @value{GDBN} includes the ability to debug programs running on
13988 various real-time operating systems.
13991 @subsection Using @value{GDBN} with VxWorks
13997 @kindex target vxworks
13998 @item target vxworks @var{machinename}
13999 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14000 is the target system's machine name or IP address.
14004 On VxWorks, @code{load} links @var{filename} dynamically on the
14005 current target system as well as adding its symbols in @value{GDBN}.
14007 @value{GDBN} enables developers to spawn and debug tasks running on networked
14008 VxWorks targets from a Unix host. Already-running tasks spawned from
14009 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14010 both the Unix host and on the VxWorks target. The program
14011 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14012 installed with the name @code{vxgdb}, to distinguish it from a
14013 @value{GDBN} for debugging programs on the host itself.)
14016 @item VxWorks-timeout @var{args}
14017 @kindex vxworks-timeout
14018 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14019 This option is set by the user, and @var{args} represents the number of
14020 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14021 your VxWorks target is a slow software simulator or is on the far side
14022 of a thin network line.
14025 The following information on connecting to VxWorks was current when
14026 this manual was produced; newer releases of VxWorks may use revised
14029 @findex INCLUDE_RDB
14030 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14031 to include the remote debugging interface routines in the VxWorks
14032 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14033 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14034 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14035 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14036 information on configuring and remaking VxWorks, see the manufacturer's
14038 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14040 Once you have included @file{rdb.a} in your VxWorks system image and set
14041 your Unix execution search path to find @value{GDBN}, you are ready to
14042 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14043 @code{vxgdb}, depending on your installation).
14045 @value{GDBN} comes up showing the prompt:
14052 * VxWorks Connection:: Connecting to VxWorks
14053 * VxWorks Download:: VxWorks download
14054 * VxWorks Attach:: Running tasks
14057 @node VxWorks Connection
14058 @subsubsection Connecting to VxWorks
14060 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14061 network. To connect to a target whose host name is ``@code{tt}'', type:
14064 (vxgdb) target vxworks tt
14068 @value{GDBN} displays messages like these:
14071 Attaching remote machine across net...
14076 @value{GDBN} then attempts to read the symbol tables of any object modules
14077 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14078 these files by searching the directories listed in the command search
14079 path (@pxref{Environment, ,Your program's environment}); if it fails
14080 to find an object file, it displays a message such as:
14083 prog.o: No such file or directory.
14086 When this happens, add the appropriate directory to the search path with
14087 the @value{GDBN} command @code{path}, and execute the @code{target}
14090 @node VxWorks Download
14091 @subsubsection VxWorks download
14093 @cindex download to VxWorks
14094 If you have connected to the VxWorks target and you want to debug an
14095 object that has not yet been loaded, you can use the @value{GDBN}
14096 @code{load} command to download a file from Unix to VxWorks
14097 incrementally. The object file given as an argument to the @code{load}
14098 command is actually opened twice: first by the VxWorks target in order
14099 to download the code, then by @value{GDBN} in order to read the symbol
14100 table. This can lead to problems if the current working directories on
14101 the two systems differ. If both systems have NFS mounted the same
14102 filesystems, you can avoid these problems by using absolute paths.
14103 Otherwise, it is simplest to set the working directory on both systems
14104 to the directory in which the object file resides, and then to reference
14105 the file by its name, without any path. For instance, a program
14106 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14107 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14108 program, type this on VxWorks:
14111 -> cd "@var{vxpath}/vw/demo/rdb"
14115 Then, in @value{GDBN}, type:
14118 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14119 (vxgdb) load prog.o
14122 @value{GDBN} displays a response similar to this:
14125 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14128 You can also use the @code{load} command to reload an object module
14129 after editing and recompiling the corresponding source file. Note that
14130 this makes @value{GDBN} delete all currently-defined breakpoints,
14131 auto-displays, and convenience variables, and to clear the value
14132 history. (This is necessary in order to preserve the integrity of
14133 debugger's data structures that reference the target system's symbol
14136 @node VxWorks Attach
14137 @subsubsection Running tasks
14139 @cindex running VxWorks tasks
14140 You can also attach to an existing task using the @code{attach} command as
14144 (vxgdb) attach @var{task}
14148 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14149 or suspended when you attach to it. Running tasks are suspended at
14150 the time of attachment.
14152 @node Embedded Processors
14153 @section Embedded Processors
14155 This section goes into details specific to particular embedded
14158 @cindex send command to simulator
14159 Whenever a specific embedded processor has a simulator, @value{GDBN}
14160 allows to send an arbitrary command to the simulator.
14163 @item sim @var{command}
14164 @kindex sim@r{, a command}
14165 Send an arbitrary @var{command} string to the simulator. Consult the
14166 documentation for the specific simulator in use for information about
14167 acceptable commands.
14173 * H8/300:: Renesas H8/300
14174 * H8/500:: Renesas H8/500
14175 * M32R/D:: Renesas M32R/D
14176 * M68K:: Motorola M68K
14177 * MIPS Embedded:: MIPS Embedded
14178 * OpenRISC 1000:: OpenRisc 1000
14179 * PA:: HP PA Embedded
14182 * Sparclet:: Tsqware Sparclet
14183 * Sparclite:: Fujitsu Sparclite
14184 * ST2000:: Tandem ST2000
14185 * Z8000:: Zilog Z8000
14188 * Super-H:: Renesas Super-H
14189 * WinCE:: Windows CE child processes
14198 @item target rdi @var{dev}
14199 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14200 use this target to communicate with both boards running the Angel
14201 monitor, or with the EmbeddedICE JTAG debug device.
14204 @item target rdp @var{dev}
14209 @value{GDBN} provides the following ARM-specific commands:
14212 @item set arm disassembler
14214 This commands selects from a list of disassembly styles. The
14215 @code{"std"} style is the standard style.
14217 @item show arm disassembler
14219 Show the current disassembly style.
14221 @item set arm apcs32
14222 @cindex ARM 32-bit mode
14223 This command toggles ARM operation mode between 32-bit and 26-bit.
14225 @item show arm apcs32
14226 Display the current usage of the ARM 32-bit mode.
14228 @item set arm fpu @var{fputype}
14229 This command sets the ARM floating-point unit (FPU) type. The
14230 argument @var{fputype} can be one of these:
14234 Determine the FPU type by querying the OS ABI.
14236 Software FPU, with mixed-endian doubles on little-endian ARM
14239 GCC-compiled FPA co-processor.
14241 Software FPU with pure-endian doubles.
14247 Show the current type of the FPU.
14250 This command forces @value{GDBN} to use the specified ABI.
14253 Show the currently used ABI.
14255 @item set debug arm
14256 Toggle whether to display ARM-specific debugging messages from the ARM
14257 target support subsystem.
14259 @item show debug arm
14260 Show whether ARM-specific debugging messages are enabled.
14263 The following commands are available when an ARM target is debugged
14264 using the RDI interface:
14267 @item rdilogfile @r{[}@var{file}@r{]}
14269 @cindex ADP (Angel Debugger Protocol) logging
14270 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14271 With an argument, sets the log file to the specified @var{file}. With
14272 no argument, show the current log file name. The default log file is
14275 @item rdilogenable @r{[}@var{arg}@r{]}
14276 @kindex rdilogenable
14277 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14278 enables logging, with an argument 0 or @code{"no"} disables it. With
14279 no arguments displays the current setting. When logging is enabled,
14280 ADP packets exchanged between @value{GDBN} and the RDI target device
14281 are logged to a file.
14283 @item set rdiromatzero
14284 @kindex set rdiromatzero
14285 @cindex ROM at zero address, RDI
14286 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14287 vector catching is disabled, so that zero address can be used. If off
14288 (the default), vector catching is enabled. For this command to take
14289 effect, it needs to be invoked prior to the @code{target rdi} command.
14291 @item show rdiromatzero
14292 @kindex show rdiromatzero
14293 Show the current setting of ROM at zero address.
14295 @item set rdiheartbeat
14296 @kindex set rdiheartbeat
14297 @cindex RDI heartbeat
14298 Enable or disable RDI heartbeat packets. It is not recommended to
14299 turn on this option, since it confuses ARM and EPI JTAG interface, as
14300 well as the Angel monitor.
14302 @item show rdiheartbeat
14303 @kindex show rdiheartbeat
14304 Show the setting of RDI heartbeat packets.
14309 @subsection Renesas H8/300
14313 @kindex target hms@r{, with H8/300}
14314 @item target hms @var{dev}
14315 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
14316 Use special commands @code{device} and @code{speed} to control the serial
14317 line and the communications speed used.
14319 @kindex target e7000@r{, with H8/300}
14320 @item target e7000 @var{dev}
14321 E7000 emulator for Renesas H8 and SH.
14323 @kindex target sh3@r{, with H8/300}
14324 @kindex target sh3e@r{, with H8/300}
14325 @item target sh3 @var{dev}
14326 @itemx target sh3e @var{dev}
14327 Renesas SH-3 and SH-3E target systems.
14331 @cindex download to H8/300 or H8/500
14332 @cindex H8/300 or H8/500 download
14333 @cindex download to Renesas SH
14334 @cindex Renesas SH download
14335 When you select remote debugging to a Renesas SH, H8/300, or H8/500
14336 board, the @code{load} command downloads your program to the Renesas
14337 board and also opens it as the current executable target for
14338 @value{GDBN} on your host (like the @code{file} command).
14340 @value{GDBN} needs to know these things to talk to your
14341 Renesas SH, H8/300, or H8/500:
14345 that you want to use @samp{target hms}, the remote debugging interface
14346 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
14347 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
14348 the default when @value{GDBN} is configured specifically for the Renesas SH,
14349 H8/300, or H8/500.)
14352 what serial device connects your host to your Renesas board (the first
14353 serial device available on your host is the default).
14356 what speed to use over the serial device.
14360 * Renesas Boards:: Connecting to Renesas boards.
14361 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
14362 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
14365 @node Renesas Boards
14366 @subsubsection Connecting to Renesas boards
14368 @c only for Unix hosts
14370 @cindex serial device, Renesas micros
14371 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
14372 need to explicitly set the serial device. The default @var{port} is the
14373 first available port on your host. This is only necessary on Unix
14374 hosts, where it is typically something like @file{/dev/ttya}.
14377 @cindex serial line speed, Renesas micros
14378 @code{@value{GDBN}} has another special command to set the communications
14379 speed: @samp{speed @var{bps}}. This command also is only used from Unix
14380 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
14381 the DOS @code{mode} command (for instance,
14382 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
14384 The @samp{device} and @samp{speed} commands are available only when you
14385 use a Unix host to debug your Renesas microprocessor programs. If you
14387 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
14388 called @code{asynctsr} to communicate with the development board
14389 through a PC serial port. You must also use the DOS @code{mode} command
14390 to set up the serial port on the DOS side.
14392 The following sample session illustrates the steps needed to start a
14393 program under @value{GDBN} control on an H8/300. The example uses a
14394 sample H8/300 program called @file{t.x}. The procedure is the same for
14395 the Renesas SH and the H8/500.
14397 First hook up your development board. In this example, we use a
14398 board attached to serial port @code{COM2}; if you use a different serial
14399 port, substitute its name in the argument of the @code{mode} command.
14400 When you call @code{asynctsr}, the auxiliary comms program used by the
14401 debugger, you give it just the numeric part of the serial port's name;
14402 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
14406 C:\H8300\TEST> asynctsr 2
14407 C:\H8300\TEST> mode com2:9600,n,8,1,p
14409 Resident portion of MODE loaded
14411 COM2: 9600, n, 8, 1, p
14416 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
14417 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
14418 disable it, or even boot without it, to use @code{asynctsr} to control
14419 your development board.
14422 @kindex target hms@r{, and serial protocol}
14423 Now that serial communications are set up, and the development board is
14424 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
14425 the name of your program as the argument. @code{@value{GDBN}} prompts
14426 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
14427 commands to begin your debugging session: @samp{target hms} to specify
14428 cross-debugging to the Renesas board, and the @code{load} command to
14429 download your program to the board. @code{load} displays the names of
14430 the program's sections, and a @samp{*} for each 2K of data downloaded.
14431 (If you want to refresh @value{GDBN} data on symbols or on the
14432 executable file without downloading, use the @value{GDBN} commands
14433 @code{file} or @code{symbol-file}. These commands, and @code{load}
14434 itself, are described in @ref{Files,,Commands to specify files}.)
14437 (eg-C:\H8300\TEST) @value{GDBP} t.x
14438 @value{GDBN} is free software and you are welcome to distribute copies
14439 of it under certain conditions; type "show copying" to see
14441 There is absolutely no warranty for @value{GDBN}; type "show warranty"
14443 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
14444 (@value{GDBP}) target hms
14445 Connected to remote H8/300 HMS system.
14446 (@value{GDBP}) load t.x
14447 .text : 0x8000 .. 0xabde ***********
14448 .data : 0xabde .. 0xad30 *
14449 .stack : 0xf000 .. 0xf014 *
14452 At this point, you're ready to run or debug your program. From here on,
14453 you can use all the usual @value{GDBN} commands. The @code{break} command
14454 sets breakpoints; the @code{run} command starts your program;
14455 @code{print} or @code{x} display data; the @code{continue} command
14456 resumes execution after stopping at a breakpoint. You can use the
14457 @code{help} command at any time to find out more about @value{GDBN} commands.
14459 Remember, however, that @emph{operating system} facilities aren't
14460 available on your development board; for example, if your program hangs,
14461 you can't send an interrupt---but you can press the @sc{reset} switch!
14463 Use the @sc{reset} button on the development board
14466 to interrupt your program (don't use @kbd{C-c} on the DOS host---it has
14467 no way to pass an interrupt signal to the development board); and
14470 to return to the @value{GDBN} command prompt after your program finishes
14471 normally. The communications protocol provides no other way for @value{GDBN}
14472 to detect program completion.
14475 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
14476 development board as a ``normal exit'' of your program.
14479 @subsubsection Using the E7000 in-circuit emulator
14481 @kindex target e7000@r{, with Renesas ICE}
14482 You can use the E7000 in-circuit emulator to develop code for either the
14483 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
14484 e7000} command to connect @value{GDBN} to your E7000:
14487 @item target e7000 @var{port} @var{speed}
14488 Use this form if your E7000 is connected to a serial port. The
14489 @var{port} argument identifies what serial port to use (for example,
14490 @samp{com2}). The third argument is the line speed in bits per second
14491 (for example, @samp{9600}).
14493 @item target e7000 @var{hostname}
14494 If your E7000 is installed as a host on a TCP/IP network, you can just
14495 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
14498 The following special commands are available when debugging with the
14502 @item e7000 @var{command}
14504 @cindex send command to E7000 monitor
14505 This sends the specified @var{command} to the E7000 monitor.
14507 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
14508 @kindex ftplogin@r{, E7000}
14509 This command records information for subsequent interface with the
14510 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
14511 named @var{machine} using specified @var{username} and @var{password},
14512 and then chdir to the named directory @var{dir}.
14514 @item ftpload @var{file}
14515 @kindex ftpload@r{, E7000}
14516 This command uses credentials recorded by @code{ftplogin} to fetch and
14517 load the named @var{file} from the E7000 monitor.
14520 @kindex drain@r{, E7000}
14521 This command drains any pending text buffers stored on the E7000.
14523 @item set usehardbreakpoints
14524 @itemx show usehardbreakpoints
14525 @kindex set usehardbreakpoints@r{, E7000}
14526 @kindex show usehardbreakpoints@r{, E7000}
14527 @cindex hardware breakpoints, and E7000
14528 These commands set and show the use of hardware breakpoints for all
14529 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
14530 more information about using hardware breakpoints selectively.
14533 @node Renesas Special
14534 @subsubsection Special @value{GDBN} commands for Renesas micros
14536 Some @value{GDBN} commands are available only for the H8/300:
14540 @kindex set machine
14541 @kindex show machine
14542 @item set machine h8300
14543 @itemx set machine h8300h
14544 Condition @value{GDBN} for one of the two variants of the H8/300
14545 architecture with @samp{set machine}. You can use @samp{show machine}
14546 to check which variant is currently in effect.
14555 @kindex set memory @var{mod}
14556 @cindex memory models, H8/500
14557 @item set memory @var{mod}
14559 Specify which H8/500 memory model (@var{mod}) you are using with
14560 @samp{set memory}; check which memory model is in effect with @samp{show
14561 memory}. The accepted values for @var{mod} are @code{small},
14562 @code{big}, @code{medium}, and @code{compact}.
14567 @subsection Renesas M32R/D and M32R/SDI
14570 @kindex target m32r
14571 @item target m32r @var{dev}
14572 Renesas M32R/D ROM monitor.
14574 @kindex target m32rsdi
14575 @item target m32rsdi @var{dev}
14576 Renesas M32R SDI server, connected via parallel port to the board.
14579 The following @value{GDBN} commands are specific to the M32R monitor:
14582 @item set download-path @var{path}
14583 @kindex set download-path
14584 @cindex find downloadable @sc{srec} files (M32R)
14585 Set the default path for finding donwloadable @sc{srec} files.
14587 @item show download-path
14588 @kindex show download-path
14589 Show the default path for downloadable @sc{srec} files.
14591 @item set board-address @var{addr}
14592 @kindex set board-address
14593 @cindex M32-EVA target board address
14594 Set the IP address for the M32R-EVA target board.
14596 @item show board-address
14597 @kindex show board-address
14598 Show the current IP address of the target board.
14600 @item set server-address @var{addr}
14601 @kindex set server-address
14602 @cindex download server address (M32R)
14603 Set the IP address for the download server, which is the @value{GDBN}'s
14606 @item show server-address
14607 @kindex show server-address
14608 Display the IP address of the download server.
14610 @item upload @r{[}@var{file}@r{]}
14611 @kindex upload@r{, M32R}
14612 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14613 upload capability. If no @var{file} argument is given, the current
14614 executable file is uploaded.
14616 @item tload @r{[}@var{file}@r{]}
14617 @kindex tload@r{, M32R}
14618 Test the @code{upload} command.
14621 The following commands are available for M32R/SDI:
14626 @cindex reset SDI connection, M32R
14627 This command resets the SDI connection.
14631 This command shows the SDI connection status.
14634 @kindex debug_chaos
14635 @cindex M32R/Chaos debugging
14636 Instructs the remote that M32R/Chaos debugging is to be used.
14638 @item use_debug_dma
14639 @kindex use_debug_dma
14640 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14643 @kindex use_mon_code
14644 Instructs the remote to use the MON_CODE method of accessing memory.
14647 @kindex use_ib_break
14648 Instructs the remote to set breakpoints by IB break.
14650 @item use_dbt_break
14651 @kindex use_dbt_break
14652 Instructs the remote to set breakpoints by DBT.
14658 The Motorola m68k configuration includes ColdFire support, and
14659 target command for the following ROM monitors.
14663 @kindex target abug
14664 @item target abug @var{dev}
14665 ABug ROM monitor for M68K.
14667 @kindex target cpu32bug
14668 @item target cpu32bug @var{dev}
14669 CPU32BUG monitor, running on a CPU32 (M68K) board.
14671 @kindex target dbug
14672 @item target dbug @var{dev}
14673 dBUG ROM monitor for Motorola ColdFire.
14676 @item target est @var{dev}
14677 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14679 @kindex target rom68k
14680 @item target rom68k @var{dev}
14681 ROM 68K monitor, running on an M68K IDP board.
14687 @kindex target rombug
14688 @item target rombug @var{dev}
14689 ROMBUG ROM monitor for OS/9000.
14693 @node MIPS Embedded
14694 @subsection MIPS Embedded
14696 @cindex MIPS boards
14697 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14698 MIPS board attached to a serial line. This is available when
14699 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14702 Use these @value{GDBN} commands to specify the connection to your target board:
14705 @item target mips @var{port}
14706 @kindex target mips @var{port}
14707 To run a program on the board, start up @code{@value{GDBP}} with the
14708 name of your program as the argument. To connect to the board, use the
14709 command @samp{target mips @var{port}}, where @var{port} is the name of
14710 the serial port connected to the board. If the program has not already
14711 been downloaded to the board, you may use the @code{load} command to
14712 download it. You can then use all the usual @value{GDBN} commands.
14714 For example, this sequence connects to the target board through a serial
14715 port, and loads and runs a program called @var{prog} through the
14719 host$ @value{GDBP} @var{prog}
14720 @value{GDBN} is free software and @dots{}
14721 (@value{GDBP}) target mips /dev/ttyb
14722 (@value{GDBP}) load @var{prog}
14726 @item target mips @var{hostname}:@var{portnumber}
14727 On some @value{GDBN} host configurations, you can specify a TCP
14728 connection (for instance, to a serial line managed by a terminal
14729 concentrator) instead of a serial port, using the syntax
14730 @samp{@var{hostname}:@var{portnumber}}.
14732 @item target pmon @var{port}
14733 @kindex target pmon @var{port}
14736 @item target ddb @var{port}
14737 @kindex target ddb @var{port}
14738 NEC's DDB variant of PMON for Vr4300.
14740 @item target lsi @var{port}
14741 @kindex target lsi @var{port}
14742 LSI variant of PMON.
14744 @kindex target r3900
14745 @item target r3900 @var{dev}
14746 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14748 @kindex target array
14749 @item target array @var{dev}
14750 Array Tech LSI33K RAID controller board.
14756 @value{GDBN} also supports these special commands for MIPS targets:
14759 @item set mipsfpu double
14760 @itemx set mipsfpu single
14761 @itemx set mipsfpu none
14762 @itemx set mipsfpu auto
14763 @itemx show mipsfpu
14764 @kindex set mipsfpu
14765 @kindex show mipsfpu
14766 @cindex MIPS remote floating point
14767 @cindex floating point, MIPS remote
14768 If your target board does not support the MIPS floating point
14769 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14770 need this, you may wish to put the command in your @value{GDBN} init
14771 file). This tells @value{GDBN} how to find the return value of
14772 functions which return floating point values. It also allows
14773 @value{GDBN} to avoid saving the floating point registers when calling
14774 functions on the board. If you are using a floating point coprocessor
14775 with only single precision floating point support, as on the @sc{r4650}
14776 processor, use the command @samp{set mipsfpu single}. The default
14777 double precision floating point coprocessor may be selected using
14778 @samp{set mipsfpu double}.
14780 In previous versions the only choices were double precision or no
14781 floating point, so @samp{set mipsfpu on} will select double precision
14782 and @samp{set mipsfpu off} will select no floating point.
14784 As usual, you can inquire about the @code{mipsfpu} variable with
14785 @samp{show mipsfpu}.
14787 @item set timeout @var{seconds}
14788 @itemx set retransmit-timeout @var{seconds}
14789 @itemx show timeout
14790 @itemx show retransmit-timeout
14791 @cindex @code{timeout}, MIPS protocol
14792 @cindex @code{retransmit-timeout}, MIPS protocol
14793 @kindex set timeout
14794 @kindex show timeout
14795 @kindex set retransmit-timeout
14796 @kindex show retransmit-timeout
14797 You can control the timeout used while waiting for a packet, in the MIPS
14798 remote protocol, with the @code{set timeout @var{seconds}} command. The
14799 default is 5 seconds. Similarly, you can control the timeout used while
14800 waiting for an acknowledgement of a packet with the @code{set
14801 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14802 You can inspect both values with @code{show timeout} and @code{show
14803 retransmit-timeout}. (These commands are @emph{only} available when
14804 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14806 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14807 is waiting for your program to stop. In that case, @value{GDBN} waits
14808 forever because it has no way of knowing how long the program is going
14809 to run before stopping.
14811 @item set syn-garbage-limit @var{num}
14812 @kindex set syn-garbage-limit@r{, MIPS remote}
14813 @cindex synchronize with remote MIPS target
14814 Limit the maximum number of characters @value{GDBN} should ignore when
14815 it tries to synchronize with the remote target. The default is 10
14816 characters. Setting the limit to -1 means there's no limit.
14818 @item show syn-garbage-limit
14819 @kindex show syn-garbage-limit@r{, MIPS remote}
14820 Show the current limit on the number of characters to ignore when
14821 trying to synchronize with the remote system.
14823 @item set monitor-prompt @var{prompt}
14824 @kindex set monitor-prompt@r{, MIPS remote}
14825 @cindex remote monitor prompt
14826 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14827 remote monitor. The default depends on the target:
14837 @item show monitor-prompt
14838 @kindex show monitor-prompt@r{, MIPS remote}
14839 Show the current strings @value{GDBN} expects as the prompt from the
14842 @item set monitor-warnings
14843 @kindex set monitor-warnings@r{, MIPS remote}
14844 Enable or disable monitor warnings about hardware breakpoints. This
14845 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14846 display warning messages whose codes are returned by the @code{lsi}
14847 PMON monitor for breakpoint commands.
14849 @item show monitor-warnings
14850 @kindex show monitor-warnings@r{, MIPS remote}
14851 Show the current setting of printing monitor warnings.
14853 @item pmon @var{command}
14854 @kindex pmon@r{, MIPS remote}
14855 @cindex send PMON command
14856 This command allows sending an arbitrary @var{command} string to the
14857 monitor. The monitor must be in debug mode for this to work.
14860 @node OpenRISC 1000
14861 @subsection OpenRISC 1000
14862 @cindex OpenRISC 1000
14864 @cindex or1k boards
14865 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14866 about platform and commands.
14870 @kindex target jtag
14871 @item target jtag jtag://@var{host}:@var{port}
14873 Connects to remote JTAG server.
14874 JTAG remote server can be either an or1ksim or JTAG server,
14875 connected via parallel port to the board.
14877 Example: @code{target jtag jtag://localhost:9999}
14880 @item or1ksim @var{command}
14881 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14882 Simulator, proprietary commands can be executed.
14884 @kindex info or1k spr
14885 @item info or1k spr
14886 Displays spr groups.
14888 @item info or1k spr @var{group}
14889 @itemx info or1k spr @var{groupno}
14890 Displays register names in selected group.
14892 @item info or1k spr @var{group} @var{register}
14893 @itemx info or1k spr @var{register}
14894 @itemx info or1k spr @var{groupno} @var{registerno}
14895 @itemx info or1k spr @var{registerno}
14896 Shows information about specified spr register.
14899 @item spr @var{group} @var{register} @var{value}
14900 @itemx spr @var{register @var{value}}
14901 @itemx spr @var{groupno} @var{registerno @var{value}}
14902 @itemx spr @var{registerno @var{value}}
14903 Writes @var{value} to specified spr register.
14906 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14907 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14908 program execution and is thus much faster. Hardware breakpoints/watchpoint
14909 triggers can be set using:
14912 Load effective address/data
14914 Store effective address/data
14916 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14921 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14922 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14924 @code{htrace} commands:
14925 @cindex OpenRISC 1000 htrace
14928 @item hwatch @var{conditional}
14929 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14930 or Data. For example:
14932 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14934 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14938 Display information about current HW trace configuration.
14940 @item htrace trigger @var{conditional}
14941 Set starting criteria for HW trace.
14943 @item htrace qualifier @var{conditional}
14944 Set acquisition qualifier for HW trace.
14946 @item htrace stop @var{conditional}
14947 Set HW trace stopping criteria.
14949 @item htrace record [@var{data}]*
14950 Selects the data to be recorded, when qualifier is met and HW trace was
14953 @item htrace enable
14954 @itemx htrace disable
14955 Enables/disables the HW trace.
14957 @item htrace rewind [@var{filename}]
14958 Clears currently recorded trace data.
14960 If filename is specified, new trace file is made and any newly collected data
14961 will be written there.
14963 @item htrace print [@var{start} [@var{len}]]
14964 Prints trace buffer, using current record configuration.
14966 @item htrace mode continuous
14967 Set continuous trace mode.
14969 @item htrace mode suspend
14970 Set suspend trace mode.
14975 @subsection PowerPC
14978 @kindex target dink32
14979 @item target dink32 @var{dev}
14980 DINK32 ROM monitor.
14982 @kindex target ppcbug
14983 @item target ppcbug @var{dev}
14984 @kindex target ppcbug1
14985 @item target ppcbug1 @var{dev}
14986 PPCBUG ROM monitor for PowerPC.
14989 @item target sds @var{dev}
14990 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14993 @cindex SDS protocol
14994 The following commands specifi to the SDS protocol are supported
14998 @item set sdstimeout @var{nsec}
14999 @kindex set sdstimeout
15000 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15001 default is 2 seconds.
15003 @item show sdstimeout
15004 @kindex show sdstimeout
15005 Show the current value of the SDS timeout.
15007 @item sds @var{command}
15008 @kindex sds@r{, a command}
15009 Send the specified @var{command} string to the SDS monitor.
15014 @subsection HP PA Embedded
15018 @kindex target op50n
15019 @item target op50n @var{dev}
15020 OP50N monitor, running on an OKI HPPA board.
15022 @kindex target w89k
15023 @item target w89k @var{dev}
15024 W89K monitor, running on a Winbond HPPA board.
15029 @subsection Renesas SH
15033 @kindex target hms@r{, with Renesas SH}
15034 @item target hms @var{dev}
15035 A Renesas SH board attached via serial line to your host. Use special
15036 commands @code{device} and @code{speed} to control the serial line and
15037 the communications speed used.
15039 @kindex target e7000@r{, with Renesas SH}
15040 @item target e7000 @var{dev}
15041 E7000 emulator for Renesas SH.
15043 @kindex target sh3@r{, with SH}
15044 @kindex target sh3e@r{, with SH}
15045 @item target sh3 @var{dev}
15046 @item target sh3e @var{dev}
15047 Renesas SH-3 and SH-3E target systems.
15052 @subsection Tsqware Sparclet
15056 @value{GDBN} enables developers to debug tasks running on
15057 Sparclet targets from a Unix host.
15058 @value{GDBN} uses code that runs on
15059 both the Unix host and on the Sparclet target. The program
15060 @code{@value{GDBP}} is installed and executed on the Unix host.
15063 @item remotetimeout @var{args}
15064 @kindex remotetimeout
15065 @value{GDBN} supports the option @code{remotetimeout}.
15066 This option is set by the user, and @var{args} represents the number of
15067 seconds @value{GDBN} waits for responses.
15070 @cindex compiling, on Sparclet
15071 When compiling for debugging, include the options @samp{-g} to get debug
15072 information and @samp{-Ttext} to relocate the program to where you wish to
15073 load it on the target. You may also want to add the options @samp{-n} or
15074 @samp{-N} in order to reduce the size of the sections. Example:
15077 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15080 You can use @code{objdump} to verify that the addresses are what you intended:
15083 sparclet-aout-objdump --headers --syms prog
15086 @cindex running, on Sparclet
15088 your Unix execution search path to find @value{GDBN}, you are ready to
15089 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15090 (or @code{sparclet-aout-gdb}, depending on your installation).
15092 @value{GDBN} comes up showing the prompt:
15099 * Sparclet File:: Setting the file to debug
15100 * Sparclet Connection:: Connecting to Sparclet
15101 * Sparclet Download:: Sparclet download
15102 * Sparclet Execution:: Running and debugging
15105 @node Sparclet File
15106 @subsubsection Setting file to debug
15108 The @value{GDBN} command @code{file} lets you choose with program to debug.
15111 (gdbslet) file prog
15115 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15116 @value{GDBN} locates
15117 the file by searching the directories listed in the command search
15119 If the file was compiled with debug information (option "-g"), source
15120 files will be searched as well.
15121 @value{GDBN} locates
15122 the source files by searching the directories listed in the directory search
15123 path (@pxref{Environment, ,Your program's environment}).
15125 to find a file, it displays a message such as:
15128 prog: No such file or directory.
15131 When this happens, add the appropriate directories to the search paths with
15132 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15133 @code{target} command again.
15135 @node Sparclet Connection
15136 @subsubsection Connecting to Sparclet
15138 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15139 To connect to a target on serial port ``@code{ttya}'', type:
15142 (gdbslet) target sparclet /dev/ttya
15143 Remote target sparclet connected to /dev/ttya
15144 main () at ../prog.c:3
15148 @value{GDBN} displays messages like these:
15154 @node Sparclet Download
15155 @subsubsection Sparclet download
15157 @cindex download to Sparclet
15158 Once connected to the Sparclet target,
15159 you can use the @value{GDBN}
15160 @code{load} command to download the file from the host to the target.
15161 The file name and load offset should be given as arguments to the @code{load}
15163 Since the file format is aout, the program must be loaded to the starting
15164 address. You can use @code{objdump} to find out what this value is. The load
15165 offset is an offset which is added to the VMA (virtual memory address)
15166 of each of the file's sections.
15167 For instance, if the program
15168 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15169 and bss at 0x12010170, in @value{GDBN}, type:
15172 (gdbslet) load prog 0x12010000
15173 Loading section .text, size 0xdb0 vma 0x12010000
15176 If the code is loaded at a different address then what the program was linked
15177 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15178 to tell @value{GDBN} where to map the symbol table.
15180 @node Sparclet Execution
15181 @subsubsection Running and debugging
15183 @cindex running and debugging Sparclet programs
15184 You can now begin debugging the task using @value{GDBN}'s execution control
15185 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15186 manual for the list of commands.
15190 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15192 Starting program: prog
15193 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15194 3 char *symarg = 0;
15196 4 char *execarg = "hello!";
15201 @subsection Fujitsu Sparclite
15205 @kindex target sparclite
15206 @item target sparclite @var{dev}
15207 Fujitsu sparclite boards, used only for the purpose of loading.
15208 You must use an additional command to debug the program.
15209 For example: target remote @var{dev} using @value{GDBN} standard
15215 @subsection Tandem ST2000
15217 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
15220 To connect your ST2000 to the host system, see the manufacturer's
15221 manual. Once the ST2000 is physically attached, you can run:
15224 target st2000 @var{dev} @var{speed}
15228 to establish it as your debugging environment. @var{dev} is normally
15229 the name of a serial device, such as @file{/dev/ttya}, connected to the
15230 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
15231 connection (for example, to a serial line attached via a terminal
15232 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
15234 The @code{load} and @code{attach} commands are @emph{not} defined for
15235 this target; you must load your program into the ST2000 as you normally
15236 would for standalone operation. @value{GDBN} reads debugging information
15237 (such as symbols) from a separate, debugging version of the program
15238 available on your host computer.
15239 @c FIXME!! This is terribly vague; what little content is here is
15240 @c basically hearsay.
15242 @cindex ST2000 auxiliary commands
15243 These auxiliary @value{GDBN} commands are available to help you with the ST2000
15247 @item st2000 @var{command}
15248 @kindex st2000 @var{cmd}
15249 @cindex STDBUG commands (ST2000)
15250 @cindex commands to STDBUG (ST2000)
15251 Send a @var{command} to the STDBUG monitor. See the manufacturer's
15252 manual for available commands.
15255 @cindex connect (to STDBUG)
15256 Connect the controlling terminal to the STDBUG command monitor. When
15257 you are done interacting with STDBUG, typing either of two character
15258 sequences gets you back to the @value{GDBN} command prompt:
15259 @kbd{@key{RET} ~ .} (Return, followed by tilde and period) or
15260 @kbd{@key{RET} ~ C-d} (Return, followed by tilde and control-D).
15264 @subsection Zilog Z8000
15267 @cindex simulator, Z8000
15268 @cindex Zilog Z8000 simulator
15270 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15273 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15274 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15275 segmented variant). The simulator recognizes which architecture is
15276 appropriate by inspecting the object code.
15279 @item target sim @var{args}
15281 @kindex target sim@r{, with Z8000}
15282 Debug programs on a simulated CPU. If the simulator supports setup
15283 options, specify them via @var{args}.
15287 After specifying this target, you can debug programs for the simulated
15288 CPU in the same style as programs for your host computer; use the
15289 @code{file} command to load a new program image, the @code{run} command
15290 to run your program, and so on.
15292 As well as making available all the usual machine registers
15293 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15294 additional items of information as specially named registers:
15299 Counts clock-ticks in the simulator.
15302 Counts instructions run in the simulator.
15305 Execution time in 60ths of a second.
15309 You can refer to these values in @value{GDBN} expressions with the usual
15310 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15311 conditional breakpoint that suspends only after at least 5000
15312 simulated clock ticks.
15315 @subsection Atmel AVR
15318 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15319 following AVR-specific commands:
15322 @item info io_registers
15323 @kindex info io_registers@r{, AVR}
15324 @cindex I/O registers (Atmel AVR)
15325 This command displays information about the AVR I/O registers. For
15326 each register, @value{GDBN} prints its number and value.
15333 When configured for debugging CRIS, @value{GDBN} provides the
15334 following CRIS-specific commands:
15337 @item set cris-version @var{ver}
15338 @cindex CRIS version
15339 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15340 The CRIS version affects register names and sizes. This command is useful in
15341 case autodetection of the CRIS version fails.
15343 @item show cris-version
15344 Show the current CRIS version.
15346 @item set cris-dwarf2-cfi
15347 @cindex DWARF-2 CFI and CRIS
15348 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15349 Change to @samp{off} when using @code{gcc-cris} whose version is below
15352 @item show cris-dwarf2-cfi
15353 Show the current state of using DWARF-2 CFI.
15355 @item set cris-mode @var{mode}
15357 Set the current CRIS mode to @var{mode}. It should only be changed when
15358 debugging in guru mode, in which case it should be set to
15359 @samp{guru} (the default is @samp{normal}).
15361 @item show cris-mode
15362 Show the current CRIS mode.
15366 @subsection Renesas Super-H
15369 For the Renesas Super-H processor, @value{GDBN} provides these
15374 @kindex regs@r{, Super-H}
15375 Show the values of all Super-H registers.
15379 @subsection Windows CE
15382 The following commands are available for Windows CE:
15385 @item set remotedirectory @var{dir}
15386 @kindex set remotedirectory
15387 Tell @value{GDBN} to upload files from the named directory @var{dir}.
15388 The default is @file{/gdb}, i.e.@: the root directory on the current
15391 @item show remotedirectory
15392 @kindex show remotedirectory
15393 Show the current value of the upload directory.
15395 @item set remoteupload @var{method}
15396 @kindex set remoteupload
15397 Set the method used to upload files to remote device. Valid values
15398 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
15399 The default is @samp{newer}.
15401 @item show remoteupload
15402 @kindex show remoteupload
15403 Show the current setting of the upload method.
15405 @item set remoteaddhost
15406 @kindex set remoteaddhost
15407 Tell @value{GDBN} whether to add this host to the remote stub's
15408 arguments when you debug over a network.
15410 @item show remoteaddhost
15411 @kindex show remoteaddhost
15412 Show whether to add this host to remote stub's arguments when
15413 debugging over a network.
15417 @node Architectures
15418 @section Architectures
15420 This section describes characteristics of architectures that affect
15421 all uses of @value{GDBN} with the architecture, both native and cross.
15428 * HPPA:: HP PA architecture
15432 @subsection x86 Architecture-specific issues.
15435 @item set struct-convention @var{mode}
15436 @kindex set struct-convention
15437 @cindex struct return convention
15438 @cindex struct/union returned in registers
15439 Set the convention used by the inferior to return @code{struct}s and
15440 @code{union}s from functions to @var{mode}. Possible values of
15441 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15442 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15443 are returned on the stack, while @code{"reg"} means that a
15444 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15445 be returned in a register.
15447 @item show struct-convention
15448 @kindex show struct-convention
15449 Show the current setting of the convention to return @code{struct}s
15458 @kindex set rstack_high_address
15459 @cindex AMD 29K register stack
15460 @cindex register stack, AMD29K
15461 @item set rstack_high_address @var{address}
15462 On AMD 29000 family processors, registers are saved in a separate
15463 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15464 extent of this stack. Normally, @value{GDBN} just assumes that the
15465 stack is ``large enough''. This may result in @value{GDBN} referencing
15466 memory locations that do not exist. If necessary, you can get around
15467 this problem by specifying the ending address of the register stack with
15468 the @code{set rstack_high_address} command. The argument should be an
15469 address, which you probably want to precede with @samp{0x} to specify in
15472 @kindex show rstack_high_address
15473 @item show rstack_high_address
15474 Display the current limit of the register stack, on AMD 29000 family
15482 See the following section.
15487 @cindex stack on Alpha
15488 @cindex stack on MIPS
15489 @cindex Alpha stack
15491 Alpha- and MIPS-based computers use an unusual stack frame, which
15492 sometimes requires @value{GDBN} to search backward in the object code to
15493 find the beginning of a function.
15495 @cindex response time, MIPS debugging
15496 To improve response time (especially for embedded applications, where
15497 @value{GDBN} may be restricted to a slow serial line for this search)
15498 you may want to limit the size of this search, using one of these
15502 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15503 @item set heuristic-fence-post @var{limit}
15504 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15505 search for the beginning of a function. A value of @var{0} (the
15506 default) means there is no limit. However, except for @var{0}, the
15507 larger the limit the more bytes @code{heuristic-fence-post} must search
15508 and therefore the longer it takes to run. You should only need to use
15509 this command when debugging a stripped executable.
15511 @item show heuristic-fence-post
15512 Display the current limit.
15516 These commands are available @emph{only} when @value{GDBN} is configured
15517 for debugging programs on Alpha or MIPS processors.
15519 Several MIPS-specific commands are available when debugging MIPS
15523 @item set mips saved-gpreg-size @var{size}
15524 @kindex set mips saved-gpreg-size
15525 @cindex MIPS GP register size on stack
15526 Set the size of MIPS general-purpose registers saved on the stack.
15527 The argument @var{size} can be one of the following:
15531 32-bit GP registers
15533 64-bit GP registers
15535 Use the target's default setting or autodetect the saved size from the
15536 information contained in the executable. This is the default
15539 @item show mips saved-gpreg-size
15540 @kindex show mips saved-gpreg-size
15541 Show the current size of MIPS GP registers on the stack.
15543 @item set mips stack-arg-size @var{size}
15544 @kindex set mips stack-arg-size
15545 @cindex MIPS stack space for arguments
15546 Set the amount of stack space reserved for arguments to functions.
15547 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
15550 @item set mips abi @var{arg}
15551 @kindex set mips abi
15552 @cindex set ABI for MIPS
15553 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15554 values of @var{arg} are:
15558 The default ABI associated with the current binary (this is the
15569 @item show mips abi
15570 @kindex show mips abi
15571 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15574 @itemx show mipsfpu
15575 @xref{MIPS Embedded, set mipsfpu}.
15577 @item set mips mask-address @var{arg}
15578 @kindex set mips mask-address
15579 @cindex MIPS addresses, masking
15580 This command determines whether the most-significant 32 bits of 64-bit
15581 MIPS addresses are masked off. The argument @var{arg} can be
15582 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15583 setting, which lets @value{GDBN} determine the correct value.
15585 @item show mips mask-address
15586 @kindex show mips mask-address
15587 Show whether the upper 32 bits of MIPS addresses are masked off or
15590 @item set remote-mips64-transfers-32bit-regs
15591 @kindex set remote-mips64-transfers-32bit-regs
15592 This command controls compatibility with 64-bit MIPS targets that
15593 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15594 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15595 and 64 bits for other registers, set this option to @samp{on}.
15597 @item show remote-mips64-transfers-32bit-regs
15598 @kindex show remote-mips64-transfers-32bit-regs
15599 Show the current setting of compatibility with older MIPS 64 targets.
15601 @item set debug mips
15602 @kindex set debug mips
15603 This command turns on and off debugging messages for the MIPS-specific
15604 target code in @value{GDBN}.
15606 @item show debug mips
15607 @kindex show debug mips
15608 Show the current setting of MIPS debugging messages.
15614 @cindex HPPA support
15616 When @value{GDBN} is debugging te HP PA architecture, it provides the
15617 following special commands:
15620 @item set debug hppa
15621 @kindex set debug hppa
15622 THis command determines whether HPPA architecture specific debugging
15623 messages are to be displayed.
15625 @item show debug hppa
15626 Show whether HPPA debugging messages are displayed.
15628 @item maint print unwind @var{address}
15629 @kindex maint print unwind@r{, HPPA}
15630 This command displays the contents of the unwind table entry at the
15631 given @var{address}.
15636 @node Controlling GDB
15637 @chapter Controlling @value{GDBN}
15639 You can alter the way @value{GDBN} interacts with you by using the
15640 @code{set} command. For commands controlling how @value{GDBN} displays
15641 data, see @ref{Print Settings, ,Print settings}. Other settings are
15646 * Editing:: Command editing
15647 * Command History:: Command history
15648 * Screen Size:: Screen size
15649 * Numbers:: Numbers
15650 * ABI:: Configuring the current ABI
15651 * Messages/Warnings:: Optional warnings and messages
15652 * Debugging Output:: Optional messages about internal happenings
15660 @value{GDBN} indicates its readiness to read a command by printing a string
15661 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15662 can change the prompt string with the @code{set prompt} command. For
15663 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15664 the prompt in one of the @value{GDBN} sessions so that you can always tell
15665 which one you are talking to.
15667 @emph{Note:} @code{set prompt} does not add a space for you after the
15668 prompt you set. This allows you to set a prompt which ends in a space
15669 or a prompt that does not.
15673 @item set prompt @var{newprompt}
15674 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15676 @kindex show prompt
15678 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15682 @section Command editing
15684 @cindex command line editing
15686 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15687 @sc{gnu} library provides consistent behavior for programs which provide a
15688 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15689 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15690 substitution, and a storage and recall of command history across
15691 debugging sessions.
15693 You may control the behavior of command line editing in @value{GDBN} with the
15694 command @code{set}.
15697 @kindex set editing
15700 @itemx set editing on
15701 Enable command line editing (enabled by default).
15703 @item set editing off
15704 Disable command line editing.
15706 @kindex show editing
15708 Show whether command line editing is enabled.
15711 @xref{Command Line Editing}, for more details about the Readline
15712 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15713 encouraged to read that chapter.
15715 @node Command History
15716 @section Command history
15717 @cindex command history
15719 @value{GDBN} can keep track of the commands you type during your
15720 debugging sessions, so that you can be certain of precisely what
15721 happened. Use these commands to manage the @value{GDBN} command
15724 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15725 package, to provide the history facility. @xref{Using History
15726 Interactively}, for the detailed description of the History library.
15728 To issue a command to @value{GDBN} without affecting certain aspects of
15729 the state which is seen by users, prefix it with @samp{server }. This
15730 means that this command will not affect the command history, nor will it
15731 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15732 pressed on a line by itself.
15734 @cindex @code{server}, command prefix
15735 The server prefix does not affect the recording of values into the value
15736 history; to print a value without recording it into the value history,
15737 use the @code{output} command instead of the @code{print} command.
15739 Here is the description of @value{GDBN} commands related to command
15743 @cindex history substitution
15744 @cindex history file
15745 @kindex set history filename
15746 @cindex @env{GDBHISTFILE}, environment variable
15747 @item set history filename @var{fname}
15748 Set the name of the @value{GDBN} command history file to @var{fname}.
15749 This is the file where @value{GDBN} reads an initial command history
15750 list, and where it writes the command history from this session when it
15751 exits. You can access this list through history expansion or through
15752 the history command editing characters listed below. This file defaults
15753 to the value of the environment variable @code{GDBHISTFILE}, or to
15754 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15757 @cindex save command history
15758 @kindex set history save
15759 @item set history save
15760 @itemx set history save on
15761 Record command history in a file, whose name may be specified with the
15762 @code{set history filename} command. By default, this option is disabled.
15764 @item set history save off
15765 Stop recording command history in a file.
15767 @cindex history size
15768 @kindex set history size
15769 @cindex @env{HISTSIZE}, environment variable
15770 @item set history size @var{size}
15771 Set the number of commands which @value{GDBN} keeps in its history list.
15772 This defaults to the value of the environment variable
15773 @code{HISTSIZE}, or to 256 if this variable is not set.
15776 History expansion assigns special meaning to the character @kbd{!}.
15777 @xref{Event Designators}, for more details.
15779 @cindex history expansion, turn on/off
15780 Since @kbd{!} is also the logical not operator in C, history expansion
15781 is off by default. If you decide to enable history expansion with the
15782 @code{set history expansion on} command, you may sometimes need to
15783 follow @kbd{!} (when it is used as logical not, in an expression) with
15784 a space or a tab to prevent it from being expanded. The readline
15785 history facilities do not attempt substitution on the strings
15786 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15788 The commands to control history expansion are:
15791 @item set history expansion on
15792 @itemx set history expansion
15793 @kindex set history expansion
15794 Enable history expansion. History expansion is off by default.
15796 @item set history expansion off
15797 Disable history expansion.
15800 @kindex show history
15802 @itemx show history filename
15803 @itemx show history save
15804 @itemx show history size
15805 @itemx show history expansion
15806 These commands display the state of the @value{GDBN} history parameters.
15807 @code{show history} by itself displays all four states.
15812 @kindex show commands
15813 @cindex show last commands
15814 @cindex display command history
15815 @item show commands
15816 Display the last ten commands in the command history.
15818 @item show commands @var{n}
15819 Print ten commands centered on command number @var{n}.
15821 @item show commands +
15822 Print ten commands just after the commands last printed.
15826 @section Screen size
15827 @cindex size of screen
15828 @cindex pauses in output
15830 Certain commands to @value{GDBN} may produce large amounts of
15831 information output to the screen. To help you read all of it,
15832 @value{GDBN} pauses and asks you for input at the end of each page of
15833 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15834 to discard the remaining output. Also, the screen width setting
15835 determines when to wrap lines of output. Depending on what is being
15836 printed, @value{GDBN} tries to break the line at a readable place,
15837 rather than simply letting it overflow onto the following line.
15839 Normally @value{GDBN} knows the size of the screen from the terminal
15840 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15841 together with the value of the @code{TERM} environment variable and the
15842 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15843 you can override it with the @code{set height} and @code{set
15850 @kindex show height
15851 @item set height @var{lpp}
15853 @itemx set width @var{cpl}
15855 These @code{set} commands specify a screen height of @var{lpp} lines and
15856 a screen width of @var{cpl} characters. The associated @code{show}
15857 commands display the current settings.
15859 If you specify a height of zero lines, @value{GDBN} does not pause during
15860 output no matter how long the output is. This is useful if output is to a
15861 file or to an editor buffer.
15863 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15864 from wrapping its output.
15866 @item set pagination on
15867 @itemx set pagination off
15868 @kindex set pagination
15869 Turn the output pagination on or off; the default is on. Turning
15870 pagination off is the alternative to @code{set height 0}.
15872 @item show pagination
15873 @kindex show pagination
15874 Show the current pagination mode.
15879 @cindex number representation
15880 @cindex entering numbers
15882 You can always enter numbers in octal, decimal, or hexadecimal in
15883 @value{GDBN} by the usual conventions: octal numbers begin with
15884 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15885 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15886 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15887 10; likewise, the default display for numbers---when no particular
15888 format is specified---is base 10. You can change the default base for
15889 both input and output with the commands described below.
15892 @kindex set input-radix
15893 @item set input-radix @var{base}
15894 Set the default base for numeric input. Supported choices
15895 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15896 specified either unambiguously or using the current input radix; for
15900 set input-radix 012
15901 set input-radix 10.
15902 set input-radix 0xa
15906 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15907 leaves the input radix unchanged, no matter what it was, since
15908 @samp{10}, being without any leading or trailing signs of its base, is
15909 interpreted in the current radix. Thus, if the current radix is 16,
15910 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15913 @kindex set output-radix
15914 @item set output-radix @var{base}
15915 Set the default base for numeric display. Supported choices
15916 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15917 specified either unambiguously or using the current input radix.
15919 @kindex show input-radix
15920 @item show input-radix
15921 Display the current default base for numeric input.
15923 @kindex show output-radix
15924 @item show output-radix
15925 Display the current default base for numeric display.
15927 @item set radix @r{[}@var{base}@r{]}
15931 These commands set and show the default base for both input and output
15932 of numbers. @code{set radix} sets the radix of input and output to
15933 the same base; without an argument, it resets the radix back to its
15934 default value of 10.
15939 @section Configuring the current ABI
15941 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15942 application automatically. However, sometimes you need to override its
15943 conclusions. Use these commands to manage @value{GDBN}'s view of the
15950 One @value{GDBN} configuration can debug binaries for multiple operating
15951 system targets, either via remote debugging or native emulation.
15952 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15953 but you can override its conclusion using the @code{set osabi} command.
15954 One example where this is useful is in debugging of binaries which use
15955 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15956 not have the same identifying marks that the standard C library for your
15961 Show the OS ABI currently in use.
15964 With no argument, show the list of registered available OS ABI's.
15966 @item set osabi @var{abi}
15967 Set the current OS ABI to @var{abi}.
15970 @cindex float promotion
15972 Generally, the way that an argument of type @code{float} is passed to a
15973 function depends on whether the function is prototyped. For a prototyped
15974 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15975 according to the architecture's convention for @code{float}. For unprototyped
15976 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15977 @code{double} and then passed.
15979 Unfortunately, some forms of debug information do not reliably indicate whether
15980 a function is prototyped. If @value{GDBN} calls a function that is not marked
15981 as prototyped, it consults @kbd{set coerce-float-to-double}.
15984 @kindex set coerce-float-to-double
15985 @item set coerce-float-to-double
15986 @itemx set coerce-float-to-double on
15987 Arguments of type @code{float} will be promoted to @code{double} when passed
15988 to an unprototyped function. This is the default setting.
15990 @item set coerce-float-to-double off
15991 Arguments of type @code{float} will be passed directly to unprototyped
15994 @kindex show coerce-float-to-double
15995 @item show coerce-float-to-double
15996 Show the current setting of promoting @code{float} to @code{double}.
16000 @kindex show cp-abi
16001 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16002 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16003 used to build your application. @value{GDBN} only fully supports
16004 programs with a single C@t{++} ABI; if your program contains code using
16005 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16006 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16007 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16008 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16009 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16010 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16015 Show the C@t{++} ABI currently in use.
16018 With no argument, show the list of supported C@t{++} ABI's.
16020 @item set cp-abi @var{abi}
16021 @itemx set cp-abi auto
16022 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16025 @node Messages/Warnings
16026 @section Optional warnings and messages
16028 @cindex verbose operation
16029 @cindex optional warnings
16030 By default, @value{GDBN} is silent about its inner workings. If you are
16031 running on a slow machine, you may want to use the @code{set verbose}
16032 command. This makes @value{GDBN} tell you when it does a lengthy
16033 internal operation, so you will not think it has crashed.
16035 Currently, the messages controlled by @code{set verbose} are those
16036 which announce that the symbol table for a source file is being read;
16037 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
16040 @kindex set verbose
16041 @item set verbose on
16042 Enables @value{GDBN} output of certain informational messages.
16044 @item set verbose off
16045 Disables @value{GDBN} output of certain informational messages.
16047 @kindex show verbose
16049 Displays whether @code{set verbose} is on or off.
16052 By default, if @value{GDBN} encounters bugs in the symbol table of an
16053 object file, it is silent; but if you are debugging a compiler, you may
16054 find this information useful (@pxref{Symbol Errors, ,Errors reading
16059 @kindex set complaints
16060 @item set complaints @var{limit}
16061 Permits @value{GDBN} to output @var{limit} complaints about each type of
16062 unusual symbols before becoming silent about the problem. Set
16063 @var{limit} to zero to suppress all complaints; set it to a large number
16064 to prevent complaints from being suppressed.
16066 @kindex show complaints
16067 @item show complaints
16068 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16072 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16073 lot of stupid questions to confirm certain commands. For example, if
16074 you try to run a program which is already running:
16078 The program being debugged has been started already.
16079 Start it from the beginning? (y or n)
16082 If you are willing to unflinchingly face the consequences of your own
16083 commands, you can disable this ``feature'':
16087 @kindex set confirm
16089 @cindex confirmation
16090 @cindex stupid questions
16091 @item set confirm off
16092 Disables confirmation requests.
16094 @item set confirm on
16095 Enables confirmation requests (the default).
16097 @kindex show confirm
16099 Displays state of confirmation requests.
16103 @cindex command tracing
16104 If you need to debug user-defined commands or sourced files you may find it
16105 useful to enable @dfn{command tracing}. In this mode each command will be
16106 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16107 quantity denoting the call depth of each command.
16110 @kindex set trace-commands
16111 @cindex command scripts, debugging
16112 @item set trace-commands on
16113 Enable command tracing.
16114 @item set trace-commands off
16115 Disable command tracing.
16116 @item show trace-commands
16117 Display the current state of command tracing.
16120 @node Debugging Output
16121 @section Optional messages about internal happenings
16122 @cindex optional debugging messages
16124 @value{GDBN} has commands that enable optional debugging messages from
16125 various @value{GDBN} subsystems; normally these commands are of
16126 interest to @value{GDBN} maintainers, or when reporting a bug. This
16127 section documents those commands.
16130 @kindex set exec-done-display
16131 @item set exec-done-display
16132 Turns on or off the notification of asynchronous commands'
16133 completion. When on, @value{GDBN} will print a message when an
16134 asynchronous command finishes its execution. The default is off.
16135 @kindex show exec-done-display
16136 @item show exec-done-display
16137 Displays the current setting of asynchronous command completion
16140 @cindex gdbarch debugging info
16141 @cindex architecture debugging info
16142 @item set debug arch
16143 Turns on or off display of gdbarch debugging info. The default is off
16145 @item show debug arch
16146 Displays the current state of displaying gdbarch debugging info.
16147 @item set debug aix-thread
16148 @cindex AIX threads
16149 Display debugging messages about inner workings of the AIX thread
16151 @item show debug aix-thread
16152 Show the current state of AIX thread debugging info display.
16153 @item set debug event
16154 @cindex event debugging info
16155 Turns on or off display of @value{GDBN} event debugging info. The
16157 @item show debug event
16158 Displays the current state of displaying @value{GDBN} event debugging
16160 @item set debug expression
16161 @cindex expression debugging info
16162 Turns on or off display of debugging info about @value{GDBN}
16163 expression parsing. The default is off.
16164 @item show debug expression
16165 Displays the current state of displaying debugging info about
16166 @value{GDBN} expression parsing.
16167 @item set debug frame
16168 @cindex frame debugging info
16169 Turns on or off display of @value{GDBN} frame debugging info. The
16171 @item show debug frame
16172 Displays the current state of displaying @value{GDBN} frame debugging
16174 @item set debug infrun
16175 @cindex inferior debugging info
16176 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16177 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16178 for implementing operations such as single-stepping the inferior.
16179 @item show debug infrun
16180 Displays the current state of @value{GDBN} inferior debugging.
16181 @item set debug lin-lwp
16182 @cindex @sc{gnu}/Linux LWP debug messages
16183 @cindex Linux lightweight processes
16184 Turns on or off debugging messages from the Linux LWP debug support.
16185 @item show debug lin-lwp
16186 Show the current state of Linux LWP debugging messages.
16187 @item set debug observer
16188 @cindex observer debugging info
16189 Turns on or off display of @value{GDBN} observer debugging. This
16190 includes info such as the notification of observable events.
16191 @item show debug observer
16192 Displays the current state of observer debugging.
16193 @item set debug overload
16194 @cindex C@t{++} overload debugging info
16195 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16196 info. This includes info such as ranking of functions, etc. The default
16198 @item show debug overload
16199 Displays the current state of displaying @value{GDBN} C@t{++} overload
16201 @cindex packets, reporting on stdout
16202 @cindex serial connections, debugging
16203 @cindex debug remote protocol
16204 @cindex remote protocol debugging
16205 @cindex display remote packets
16206 @item set debug remote
16207 Turns on or off display of reports on all packets sent back and forth across
16208 the serial line to the remote machine. The info is printed on the
16209 @value{GDBN} standard output stream. The default is off.
16210 @item show debug remote
16211 Displays the state of display of remote packets.
16212 @item set debug serial
16213 Turns on or off display of @value{GDBN} serial debugging info. The
16215 @item show debug serial
16216 Displays the current state of displaying @value{GDBN} serial debugging
16218 @item set debug solib-frv
16219 @cindex FR-V shared-library debugging
16220 Turns on or off debugging messages for FR-V shared-library code.
16221 @item show debug solib-frv
16222 Display the current state of FR-V shared-library code debugging
16224 @item set debug target
16225 @cindex target debugging info
16226 Turns on or off display of @value{GDBN} target debugging info. This info
16227 includes what is going on at the target level of GDB, as it happens. The
16228 default is 0. Set it to 1 to track events, and to 2 to also track the
16229 value of large memory transfers. Changes to this flag do not take effect
16230 until the next time you connect to a target or use the @code{run} command.
16231 @item show debug target
16232 Displays the current state of displaying @value{GDBN} target debugging
16234 @item set debugvarobj
16235 @cindex variable object debugging info
16236 Turns on or off display of @value{GDBN} variable object debugging
16237 info. The default is off.
16238 @item show debugvarobj
16239 Displays the current state of displaying @value{GDBN} variable object
16244 @chapter Canned Sequences of Commands
16246 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16247 command lists}), @value{GDBN} provides two ways to store sequences of
16248 commands for execution as a unit: user-defined commands and command
16252 * Define:: How to define your own commands
16253 * Hooks:: Hooks for user-defined commands
16254 * Command Files:: How to write scripts of commands to be stored in a file
16255 * Output:: Commands for controlled output
16259 @section User-defined commands
16261 @cindex user-defined command
16262 @cindex arguments, to user-defined commands
16263 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16264 which you assign a new name as a command. This is done with the
16265 @code{define} command. User commands may accept up to 10 arguments
16266 separated by whitespace. Arguments are accessed within the user command
16267 via @code{$arg0@dots{}$arg9}. A trivial example:
16271 print $arg0 + $arg1 + $arg2
16276 To execute the command use:
16283 This defines the command @code{adder}, which prints the sum of
16284 its three arguments. Note the arguments are text substitutions, so they may
16285 reference variables, use complex expressions, or even perform inferior
16288 @cindex argument count in user-defined commands
16289 @cindex how many arguments (user-defined commands)
16290 In addition, @code{$argc} may be used to find out how many arguments have
16291 been passed. This expands to a number in the range 0@dots{}10.
16296 print $arg0 + $arg1
16299 print $arg0 + $arg1 + $arg2
16307 @item define @var{commandname}
16308 Define a command named @var{commandname}. If there is already a command
16309 by that name, you are asked to confirm that you want to redefine it.
16311 The definition of the command is made up of other @value{GDBN} command lines,
16312 which are given following the @code{define} command. The end of these
16313 commands is marked by a line containing @code{end}.
16316 @kindex end@r{ (user-defined commands)}
16317 @item document @var{commandname}
16318 Document the user-defined command @var{commandname}, so that it can be
16319 accessed by @code{help}. The command @var{commandname} must already be
16320 defined. This command reads lines of documentation just as @code{define}
16321 reads the lines of the command definition, ending with @code{end}.
16322 After the @code{document} command is finished, @code{help} on command
16323 @var{commandname} displays the documentation you have written.
16325 You may use the @code{document} command again to change the
16326 documentation of a command. Redefining the command with @code{define}
16327 does not change the documentation.
16329 @kindex dont-repeat
16330 @cindex don't repeat command
16332 Used inside a user-defined command, this tells @value{GDBN} that this
16333 command should not be repeated when the user hits @key{RET}
16334 (@pxref{Command Syntax, repeat last command}).
16336 @kindex help user-defined
16337 @item help user-defined
16338 List all user-defined commands, with the first line of the documentation
16343 @itemx show user @var{commandname}
16344 Display the @value{GDBN} commands used to define @var{commandname} (but
16345 not its documentation). If no @var{commandname} is given, display the
16346 definitions for all user-defined commands.
16348 @cindex infinite recursion in user-defined commands
16349 @kindex show max-user-call-depth
16350 @kindex set max-user-call-depth
16351 @item show max-user-call-depth
16352 @itemx set max-user-call-depth
16353 The value of @code{max-user-call-depth} controls how many recursion
16354 levels are allowed in user-defined commands before GDB suspects an
16355 infinite recursion and aborts the command.
16358 In addition to the above commands, user-defined commands frequently
16359 use control flow commands, described in @ref{Command Files}.
16361 When user-defined commands are executed, the
16362 commands of the definition are not printed. An error in any command
16363 stops execution of the user-defined command.
16365 If used interactively, commands that would ask for confirmation proceed
16366 without asking when used inside a user-defined command. Many @value{GDBN}
16367 commands that normally print messages to say what they are doing omit the
16368 messages when used in a user-defined command.
16371 @section User-defined command hooks
16372 @cindex command hooks
16373 @cindex hooks, for commands
16374 @cindex hooks, pre-command
16377 You may define @dfn{hooks}, which are a special kind of user-defined
16378 command. Whenever you run the command @samp{foo}, if the user-defined
16379 command @samp{hook-foo} exists, it is executed (with no arguments)
16380 before that command.
16382 @cindex hooks, post-command
16384 A hook may also be defined which is run after the command you executed.
16385 Whenever you run the command @samp{foo}, if the user-defined command
16386 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16387 that command. Post-execution hooks may exist simultaneously with
16388 pre-execution hooks, for the same command.
16390 It is valid for a hook to call the command which it hooks. If this
16391 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16393 @c It would be nice if hookpost could be passed a parameter indicating
16394 @c if the command it hooks executed properly or not. FIXME!
16396 @kindex stop@r{, a pseudo-command}
16397 In addition, a pseudo-command, @samp{stop} exists. Defining
16398 (@samp{hook-stop}) makes the associated commands execute every time
16399 execution stops in your program: before breakpoint commands are run,
16400 displays are printed, or the stack frame is printed.
16402 For example, to ignore @code{SIGALRM} signals while
16403 single-stepping, but treat them normally during normal execution,
16408 handle SIGALRM nopass
16412 handle SIGALRM pass
16415 define hook-continue
16416 handle SIGLARM pass
16420 As a further example, to hook at the begining and end of the @code{echo}
16421 command, and to add extra text to the beginning and end of the message,
16429 define hookpost-echo
16433 (@value{GDBP}) echo Hello World
16434 <<<---Hello World--->>>
16439 You can define a hook for any single-word command in @value{GDBN}, but
16440 not for command aliases; you should define a hook for the basic command
16441 name, e.g.@: @code{backtrace} rather than @code{bt}.
16442 @c FIXME! So how does Joe User discover whether a command is an alias
16444 If an error occurs during the execution of your hook, execution of
16445 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16446 (before the command that you actually typed had a chance to run).
16448 If you try to define a hook which does not match any known command, you
16449 get a warning from the @code{define} command.
16451 @node Command Files
16452 @section Command files
16454 @cindex command files
16455 @cindex scripting commands
16456 A command file for @value{GDBN} is a text file made of lines that are
16457 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16458 also be included. An empty line in a command file does nothing; it
16459 does not mean to repeat the last command, as it would from the
16462 You can request the execution of a command file with the @code{source}
16467 @cindex execute commands from a file
16468 @item source [@code{-v}] @var{filename}
16469 Execute the command file @var{filename}.
16472 The lines in a command file are generally executed sequentially,
16473 unless the order of execution is changed by one of the
16474 @emph{flow-control commands} described below. The commands are not
16475 printed as they are executed. An error in any command terminates
16476 execution of the command file and control is returned to the console.
16478 @value{GDBN} searches for @var{filename} in the current directory and then
16479 on the search path (specified with the @samp{directory} command).
16481 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16482 each command as it is executed. The option must be given before
16483 @var{filename}, and is interpreted as part of the filename anywhere else.
16485 Commands that would ask for confirmation if used interactively proceed
16486 without asking when used in a command file. Many @value{GDBN} commands that
16487 normally print messages to say what they are doing omit the messages
16488 when called from command files.
16490 @value{GDBN} also accepts command input from standard input. In this
16491 mode, normal output goes to standard output and error output goes to
16492 standard error. Errors in a command file supplied on standard input do
16493 not terminate execution of the command file---execution continues with
16497 gdb < cmds > log 2>&1
16500 (The syntax above will vary depending on the shell used.) This example
16501 will execute commands from the file @file{cmds}. All output and errors
16502 would be directed to @file{log}.
16504 Since commands stored on command files tend to be more general than
16505 commands typed interactively, they frequently need to deal with
16506 complicated situations, such as different or unexpected values of
16507 variables and symbols, changes in how the program being debugged is
16508 built, etc. @value{GDBN} provides a set of flow-control commands to
16509 deal with these complexities. Using these commands, you can write
16510 complex scripts that loop over data structures, execute commands
16511 conditionally, etc.
16518 This command allows to include in your script conditionally executed
16519 commands. The @code{if} command takes a single argument, which is an
16520 expression to evaluate. It is followed by a series of commands that
16521 are executed only if the expression is true (its value is nonzero).
16522 There can then optionally be an @code{else} line, followed by a series
16523 of commands that are only executed if the expression was false. The
16524 end of the list is marked by a line containing @code{end}.
16528 This command allows to write loops. Its syntax is similar to
16529 @code{if}: the command takes a single argument, which is an expression
16530 to evaluate, and must be followed by the commands to execute, one per
16531 line, terminated by an @code{end}. These commands are called the
16532 @dfn{body} of the loop. The commands in the body of @code{while} are
16533 executed repeatedly as long as the expression evaluates to true.
16537 This command exits the @code{while} loop in whose body it is included.
16538 Execution of the script continues after that @code{while}s @code{end}
16541 @kindex loop_continue
16542 @item loop_continue
16543 This command skips the execution of the rest of the body of commands
16544 in the @code{while} loop in whose body it is included. Execution
16545 branches to the beginning of the @code{while} loop, where it evaluates
16546 the controlling expression.
16548 @kindex end@r{ (if/else/while commands)}
16550 Terminate the block of commands that are the body of @code{if},
16551 @code{else}, or @code{while} flow-control commands.
16556 @section Commands for controlled output
16558 During the execution of a command file or a user-defined command, normal
16559 @value{GDBN} output is suppressed; the only output that appears is what is
16560 explicitly printed by the commands in the definition. This section
16561 describes three commands useful for generating exactly the output you
16566 @item echo @var{text}
16567 @c I do not consider backslash-space a standard C escape sequence
16568 @c because it is not in ANSI.
16569 Print @var{text}. Nonprinting characters can be included in
16570 @var{text} using C escape sequences, such as @samp{\n} to print a
16571 newline. @strong{No newline is printed unless you specify one.}
16572 In addition to the standard C escape sequences, a backslash followed
16573 by a space stands for a space. This is useful for displaying a
16574 string with spaces at the beginning or the end, since leading and
16575 trailing spaces are otherwise trimmed from all arguments.
16576 To print @samp{@w{ }and foo =@w{ }}, use the command
16577 @samp{echo \@w{ }and foo = \@w{ }}.
16579 A backslash at the end of @var{text} can be used, as in C, to continue
16580 the command onto subsequent lines. For example,
16583 echo This is some text\n\
16584 which is continued\n\
16585 onto several lines.\n
16588 produces the same output as
16591 echo This is some text\n
16592 echo which is continued\n
16593 echo onto several lines.\n
16597 @item output @var{expression}
16598 Print the value of @var{expression} and nothing but that value: no
16599 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16600 value history either. @xref{Expressions, ,Expressions}, for more information
16603 @item output/@var{fmt} @var{expression}
16604 Print the value of @var{expression} in format @var{fmt}. You can use
16605 the same formats as for @code{print}. @xref{Output Formats,,Output
16606 formats}, for more information.
16609 @item printf @var{string}, @var{expressions}@dots{}
16610 Print the values of the @var{expressions} under the control of
16611 @var{string}. The @var{expressions} are separated by commas and may be
16612 either numbers or pointers. Their values are printed as specified by
16613 @var{string}, exactly as if your program were to execute the C
16615 @c FIXME: the above implies that at least all ANSI C formats are
16616 @c supported, but it isn't true: %E and %G don't work (or so it seems).
16617 @c Either this is a bug, or the manual should document what formats are
16621 printf (@var{string}, @var{expressions}@dots{});
16624 For example, you can print two values in hex like this:
16627 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16630 The only backslash-escape sequences that you can use in the format
16631 string are the simple ones that consist of backslash followed by a
16636 @chapter Command Interpreters
16637 @cindex command interpreters
16639 @value{GDBN} supports multiple command interpreters, and some command
16640 infrastructure to allow users or user interface writers to switch
16641 between interpreters or run commands in other interpreters.
16643 @value{GDBN} currently supports two command interpreters, the console
16644 interpreter (sometimes called the command-line interpreter or @sc{cli})
16645 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16646 describes both of these interfaces in great detail.
16648 By default, @value{GDBN} will start with the console interpreter.
16649 However, the user may choose to start @value{GDBN} with another
16650 interpreter by specifying the @option{-i} or @option{--interpreter}
16651 startup options. Defined interpreters include:
16655 @cindex console interpreter
16656 The traditional console or command-line interpreter. This is the most often
16657 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16658 @value{GDBN} will use this interpreter.
16661 @cindex mi interpreter
16662 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16663 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16664 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16668 @cindex mi2 interpreter
16669 The current @sc{gdb/mi} interface.
16672 @cindex mi1 interpreter
16673 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16677 @cindex invoke another interpreter
16678 The interpreter being used by @value{GDBN} may not be dynamically
16679 switched at runtime. Although possible, this could lead to a very
16680 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16681 enters the command "interpreter-set console" in a console view,
16682 @value{GDBN} would switch to using the console interpreter, rendering
16683 the IDE inoperable!
16685 @kindex interpreter-exec
16686 Although you may only choose a single interpreter at startup, you may execute
16687 commands in any interpreter from the current interpreter using the appropriate
16688 command. If you are running the console interpreter, simply use the
16689 @code{interpreter-exec} command:
16692 interpreter-exec mi "-data-list-register-names"
16695 @sc{gdb/mi} has a similar command, although it is only available in versions of
16696 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16699 @chapter @value{GDBN} Text User Interface
16701 @cindex Text User Interface
16704 * TUI Overview:: TUI overview
16705 * TUI Keys:: TUI key bindings
16706 * TUI Single Key Mode:: TUI single key mode
16707 * TUI Commands:: TUI specific commands
16708 * TUI Configuration:: TUI configuration variables
16711 The @value{GDBN} Text User Interface, TUI in short, is a terminal
16712 interface which uses the @code{curses} library to show the source
16713 file, the assembly output, the program registers and @value{GDBN}
16714 commands in separate text windows.
16716 The TUI is enabled by invoking @value{GDBN} using either
16718 @samp{gdbtui} or @samp{gdb -tui}.
16721 @section TUI overview
16723 The TUI has two display modes that can be switched while
16728 A curses (or TUI) mode in which it displays several text
16729 windows on the terminal.
16732 A standard mode which corresponds to the @value{GDBN} configured without
16736 In the TUI mode, @value{GDBN} can display several text window
16741 This window is the @value{GDBN} command window with the @value{GDBN}
16742 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
16743 managed using readline but through the TUI. The @emph{command}
16744 window is always visible.
16747 The source window shows the source file of the program. The current
16748 line as well as active breakpoints are displayed in this window.
16751 The assembly window shows the disassembly output of the program.
16754 This window shows the processor registers. It detects when
16755 a register is changed and when this is the case, registers that have
16756 changed are highlighted.
16760 The source and assembly windows show the current program position
16761 by highlighting the current line and marking them with the @samp{>} marker.
16762 Breakpoints are also indicated with two markers. A first one
16763 indicates the breakpoint type:
16767 Breakpoint which was hit at least once.
16770 Breakpoint which was never hit.
16773 Hardware breakpoint which was hit at least once.
16776 Hardware breakpoint which was never hit.
16780 The second marker indicates whether the breakpoint is enabled or not:
16784 Breakpoint is enabled.
16787 Breakpoint is disabled.
16791 The source, assembly and register windows are attached to the thread
16792 and the frame position. They are updated when the current thread
16793 changes, when the frame changes or when the program counter changes.
16794 These three windows are arranged by the TUI according to several
16795 layouts. The layout defines which of these three windows are visible.
16796 The following layouts are available:
16806 source and assembly
16809 source and registers
16812 assembly and registers
16816 On top of the command window a status line gives various information
16817 concerning the current process begin debugged. The status line is
16818 updated when the information it shows changes. The following fields
16823 Indicates the current gdb target
16824 (@pxref{Targets, ,Specifying a Debugging Target}).
16827 Gives information about the current process or thread number.
16828 When no process is being debugged, this field is set to @code{No process}.
16831 Gives the current function name for the selected frame.
16832 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16833 When there is no symbol corresponding to the current program counter
16834 the string @code{??} is displayed.
16837 Indicates the current line number for the selected frame.
16838 When the current line number is not known the string @code{??} is displayed.
16841 Indicates the current program counter address.
16846 @section TUI Key Bindings
16847 @cindex TUI key bindings
16849 The TUI installs several key bindings in the readline keymaps
16850 (@pxref{Command Line Editing}).
16851 They allow to leave or enter in the TUI mode or they operate
16852 directly on the TUI layout and windows. The TUI also provides
16853 a @emph{SingleKey} keymap which binds several keys directly to
16854 @value{GDBN} commands. The following key bindings
16855 are installed for both TUI mode and the @value{GDBN} standard mode.
16864 Enter or leave the TUI mode. When the TUI mode is left,
16865 the curses window management is left and @value{GDBN} operates using
16866 its standard mode writing on the terminal directly. When the TUI
16867 mode is entered, the control is given back to the curses windows.
16868 The screen is then refreshed.
16872 Use a TUI layout with only one window. The layout will
16873 either be @samp{source} or @samp{assembly}. When the TUI mode
16874 is not active, it will switch to the TUI mode.
16876 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16880 Use a TUI layout with at least two windows. When the current
16881 layout shows already two windows, a next layout with two windows is used.
16882 When a new layout is chosen, one window will always be common to the
16883 previous layout and the new one.
16885 Think of it as the Emacs @kbd{C-x 2} binding.
16889 Change the active window. The TUI associates several key bindings
16890 (like scrolling and arrow keys) to the active window. This command
16891 gives the focus to the next TUI window.
16893 Think of it as the Emacs @kbd{C-x o} binding.
16897 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16898 (@pxref{TUI Single Key Mode}).
16902 The following key bindings are handled only by the TUI mode:
16907 Scroll the active window one page up.
16911 Scroll the active window one page down.
16915 Scroll the active window one line up.
16919 Scroll the active window one line down.
16923 Scroll the active window one column left.
16927 Scroll the active window one column right.
16931 Refresh the screen.
16935 In the TUI mode, the arrow keys are used by the active window
16936 for scrolling. This means they are available for readline when the
16937 active window is the command window. When the command window
16938 does not have the focus, it is necessary to use other readline
16939 key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b} and @kbd{C-f}.
16941 @node TUI Single Key Mode
16942 @section TUI Single Key Mode
16943 @cindex TUI single key mode
16945 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16946 key binding in the readline keymaps to connect single keys to
16950 @kindex c @r{(SingleKey TUI key)}
16954 @kindex d @r{(SingleKey TUI key)}
16958 @kindex f @r{(SingleKey TUI key)}
16962 @kindex n @r{(SingleKey TUI key)}
16966 @kindex q @r{(SingleKey TUI key)}
16968 exit the @emph{SingleKey} mode.
16970 @kindex r @r{(SingleKey TUI key)}
16974 @kindex s @r{(SingleKey TUI key)}
16978 @kindex u @r{(SingleKey TUI key)}
16982 @kindex v @r{(SingleKey TUI key)}
16986 @kindex w @r{(SingleKey TUI key)}
16992 Other keys temporarily switch to the @value{GDBN} command prompt.
16993 The key that was pressed is inserted in the editing buffer so that
16994 it is possible to type most @value{GDBN} commands without interaction
16995 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16996 @emph{SingleKey} mode is restored. The only way to permanently leave
16997 this mode is by typing @kbd{q} or @kbd{C-x s}.
17001 @section TUI specific commands
17002 @cindex TUI commands
17004 The TUI has specific commands to control the text windows.
17005 These commands are always available, that is they do not depend on
17006 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
17007 is in the standard mode, using these commands will automatically switch
17013 List and give the size of all displayed windows.
17017 Display the next layout.
17020 Display the previous layout.
17023 Display the source window only.
17026 Display the assembly window only.
17029 Display the source and assembly window.
17032 Display the register window together with the source or assembly window.
17034 @item focus next | prev | src | asm | regs | split
17036 Set the focus to the named window.
17037 This command allows to change the active window so that scrolling keys
17038 can be affected to another window.
17042 Refresh the screen. This is similar to typing @kbd{C-L}.
17044 @item tui reg float
17046 Show the floating point registers in the register window.
17048 @item tui reg general
17049 Show the general registers in the register window.
17052 Show the next register group. The list of register groups as well as
17053 their order is target specific. The predefined register groups are the
17054 following: @code{general}, @code{float}, @code{system}, @code{vector},
17055 @code{all}, @code{save}, @code{restore}.
17057 @item tui reg system
17058 Show the system registers in the register window.
17062 Update the source window and the current execution point.
17064 @item winheight @var{name} +@var{count}
17065 @itemx winheight @var{name} -@var{count}
17067 Change the height of the window @var{name} by @var{count}
17068 lines. Positive counts increase the height, while negative counts
17072 @kindex tabset @var{nchars}
17073 Set the width of tab stops to be @var{nchars} characters.
17077 @node TUI Configuration
17078 @section TUI configuration variables
17079 @cindex TUI configuration variables
17081 The TUI has several configuration variables that control the
17082 appearance of windows on the terminal.
17085 @item set tui border-kind @var{kind}
17086 @kindex set tui border-kind
17087 Select the border appearance for the source, assembly and register windows.
17088 The possible values are the following:
17091 Use a space character to draw the border.
17094 Use ascii characters + - and | to draw the border.
17097 Use the Alternate Character Set to draw the border. The border is
17098 drawn using character line graphics if the terminal supports them.
17102 @item set tui active-border-mode @var{mode}
17103 @kindex set tui active-border-mode
17104 Select the attributes to display the border of the active window.
17105 The possible values are @code{normal}, @code{standout}, @code{reverse},
17106 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
17108 @item set tui border-mode @var{mode}
17109 @kindex set tui border-mode
17110 Select the attributes to display the border of other windows.
17111 The @var{mode} can be one of the following:
17114 Use normal attributes to display the border.
17120 Use reverse video mode.
17123 Use half bright mode.
17125 @item half-standout
17126 Use half bright and standout mode.
17129 Use extra bright or bold mode.
17131 @item bold-standout
17132 Use extra bright or bold and standout mode.
17139 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17142 @cindex @sc{gnu} Emacs
17143 A special interface allows you to use @sc{gnu} Emacs to view (and
17144 edit) the source files for the program you are debugging with
17147 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17148 executable file you want to debug as an argument. This command starts
17149 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17150 created Emacs buffer.
17151 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17153 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
17158 All ``terminal'' input and output goes through the Emacs buffer.
17161 This applies both to @value{GDBN} commands and their output, and to the input
17162 and output done by the program you are debugging.
17164 This is useful because it means that you can copy the text of previous
17165 commands and input them again; you can even use parts of the output
17168 All the facilities of Emacs' Shell mode are available for interacting
17169 with your program. In particular, you can send signals the usual
17170 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17175 @value{GDBN} displays source code through Emacs.
17178 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17179 source file for that frame and puts an arrow (@samp{=>}) at the
17180 left margin of the current line. Emacs uses a separate buffer for
17181 source display, and splits the screen to show both your @value{GDBN} session
17184 Explicit @value{GDBN} @code{list} or search commands still produce output as
17185 usual, but you probably have no reason to use them from Emacs.
17187 If you specify an absolute file name when prompted for the @kbd{M-x
17188 gdb} argument, then Emacs sets your current working directory to where
17189 your program resides. If you only specify the file name, then Emacs
17190 sets your current working directory to to the directory associated
17191 with the previous buffer. In this case, @value{GDBN} may find your
17192 program by searching your environment's @code{PATH} variable, but on
17193 some operating systems it might not find the source. So, although the
17194 @value{GDBN} input and output session proceeds normally, the auxiliary
17195 buffer does not display the current source and line of execution.
17197 The initial working directory of @value{GDBN} is printed on the top
17198 line of the @value{GDBN} I/O buffer and this serves as a default for
17199 the commands that specify files for @value{GDBN} to operate
17200 on. @xref{Files, ,Commands to specify files}.
17202 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17203 need to call @value{GDBN} by a different name (for example, if you
17204 keep several configurations around, with different names) you can
17205 customize the Emacs variable @code{gud-gdb-command-name} to run the
17208 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
17209 addition to the standard Shell mode commands:
17213 Describe the features of Emacs' @value{GDBN} Mode.
17216 Execute to another source line, like the @value{GDBN} @code{step} command; also
17217 update the display window to show the current file and location.
17220 Execute to next source line in this function, skipping all function
17221 calls, like the @value{GDBN} @code{next} command. Then update the display window
17222 to show the current file and location.
17225 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17226 display window accordingly.
17229 Execute until exit from the selected stack frame, like the @value{GDBN}
17230 @code{finish} command.
17233 Continue execution of your program, like the @value{GDBN} @code{continue}
17237 Go up the number of frames indicated by the numeric argument
17238 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17239 like the @value{GDBN} @code{up} command.
17242 Go down the number of frames indicated by the numeric argument, like the
17243 @value{GDBN} @code{down} command.
17246 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17247 tells @value{GDBN} to set a breakpoint on the source line point is on.
17249 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
17250 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
17251 point to any frame in the stack and type @key{RET} to make it become the
17252 current frame and display the associated source in the source buffer.
17253 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
17256 If you accidentally delete the source-display buffer, an easy way to get
17257 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17258 request a frame display; when you run under Emacs, this recreates
17259 the source buffer if necessary to show you the context of the current
17262 The source files displayed in Emacs are in ordinary Emacs buffers
17263 which are visiting the source files in the usual way. You can edit
17264 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17265 communicates with Emacs in terms of line numbers. If you add or
17266 delete lines from the text, the line numbers that @value{GDBN} knows cease
17267 to correspond properly with the code.
17269 The description given here is for GNU Emacs version 21.3 and a more
17270 detailed description of its interaction with @value{GDBN} is given in
17271 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
17273 @c The following dropped because Epoch is nonstandard. Reactivate
17274 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17276 @kindex Emacs Epoch environment
17280 Version 18 of @sc{gnu} Emacs has a built-in window system
17281 called the @code{epoch}
17282 environment. Users of this environment can use a new command,
17283 @code{inspect} which performs identically to @code{print} except that
17284 each value is printed in its own window.
17289 @chapter The @sc{gdb/mi} Interface
17291 @unnumberedsec Function and Purpose
17293 @cindex @sc{gdb/mi}, its purpose
17294 @sc{gdb/mi} is a line based machine oriented text interface to
17295 @value{GDBN} and is activated by specifying using the
17296 @option{--interpreter} command line option (@pxref{Mode Options}). It
17297 is specifically intended to support the development of systems which
17298 use the debugger as just one small component of a larger system.
17300 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17301 in the form of a reference manual.
17303 Note that @sc{gdb/mi} is still under construction, so some of the
17304 features described below are incomplete and subject to change
17305 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17307 @unnumberedsec Notation and Terminology
17309 @cindex notational conventions, for @sc{gdb/mi}
17310 This chapter uses the following notation:
17314 @code{|} separates two alternatives.
17317 @code{[ @var{something} ]} indicates that @var{something} is optional:
17318 it may or may not be given.
17321 @code{( @var{group} )*} means that @var{group} inside the parentheses
17322 may repeat zero or more times.
17325 @code{( @var{group} )+} means that @var{group} inside the parentheses
17326 may repeat one or more times.
17329 @code{"@var{string}"} means a literal @var{string}.
17333 @heading Dependencies
17337 * GDB/MI Command Syntax::
17338 * GDB/MI Compatibility with CLI::
17339 * GDB/MI Development and Front Ends::
17340 * GDB/MI Output Records::
17341 * GDB/MI Simple Examples::
17342 * GDB/MI Command Description Format::
17343 * GDB/MI Breakpoint Commands::
17344 * GDB/MI Program Context::
17345 * GDB/MI Thread Commands::
17346 * GDB/MI Program Execution::
17347 * GDB/MI Stack Manipulation::
17348 * GDB/MI Variable Objects::
17349 * GDB/MI Data Manipulation::
17350 * GDB/MI Tracepoint Commands::
17351 * GDB/MI Symbol Query::
17352 * GDB/MI File Commands::
17354 * GDB/MI Kod Commands::
17355 * GDB/MI Memory Overlay Commands::
17356 * GDB/MI Signal Handling Commands::
17358 * GDB/MI Target Manipulation::
17359 * GDB/MI Miscellaneous Commands::
17362 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17363 @node GDB/MI Command Syntax
17364 @section @sc{gdb/mi} Command Syntax
17367 * GDB/MI Input Syntax::
17368 * GDB/MI Output Syntax::
17371 @node GDB/MI Input Syntax
17372 @subsection @sc{gdb/mi} Input Syntax
17374 @cindex input syntax for @sc{gdb/mi}
17375 @cindex @sc{gdb/mi}, input syntax
17377 @item @var{command} @expansion{}
17378 @code{@var{cli-command} | @var{mi-command}}
17380 @item @var{cli-command} @expansion{}
17381 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17382 @var{cli-command} is any existing @value{GDBN} CLI command.
17384 @item @var{mi-command} @expansion{}
17385 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17386 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17388 @item @var{token} @expansion{}
17389 "any sequence of digits"
17391 @item @var{option} @expansion{}
17392 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17394 @item @var{parameter} @expansion{}
17395 @code{@var{non-blank-sequence} | @var{c-string}}
17397 @item @var{operation} @expansion{}
17398 @emph{any of the operations described in this chapter}
17400 @item @var{non-blank-sequence} @expansion{}
17401 @emph{anything, provided it doesn't contain special characters such as
17402 "-", @var{nl}, """ and of course " "}
17404 @item @var{c-string} @expansion{}
17405 @code{""" @var{seven-bit-iso-c-string-content} """}
17407 @item @var{nl} @expansion{}
17416 The CLI commands are still handled by the @sc{mi} interpreter; their
17417 output is described below.
17420 The @code{@var{token}}, when present, is passed back when the command
17424 Some @sc{mi} commands accept optional arguments as part of the parameter
17425 list. Each option is identified by a leading @samp{-} (dash) and may be
17426 followed by an optional argument parameter. Options occur first in the
17427 parameter list and can be delimited from normal parameters using
17428 @samp{--} (this is useful when some parameters begin with a dash).
17435 We want easy access to the existing CLI syntax (for debugging).
17438 We want it to be easy to spot a @sc{mi} operation.
17441 @node GDB/MI Output Syntax
17442 @subsection @sc{gdb/mi} Output Syntax
17444 @cindex output syntax of @sc{gdb/mi}
17445 @cindex @sc{gdb/mi}, output syntax
17446 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17447 followed, optionally, by a single result record. This result record
17448 is for the most recent command. The sequence of output records is
17449 terminated by @samp{(gdb)}.
17451 If an input command was prefixed with a @code{@var{token}} then the
17452 corresponding output for that command will also be prefixed by that same
17456 @item @var{output} @expansion{}
17457 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17459 @item @var{result-record} @expansion{}
17460 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17462 @item @var{out-of-band-record} @expansion{}
17463 @code{@var{async-record} | @var{stream-record}}
17465 @item @var{async-record} @expansion{}
17466 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17468 @item @var{exec-async-output} @expansion{}
17469 @code{[ @var{token} ] "*" @var{async-output}}
17471 @item @var{status-async-output} @expansion{}
17472 @code{[ @var{token} ] "+" @var{async-output}}
17474 @item @var{notify-async-output} @expansion{}
17475 @code{[ @var{token} ] "=" @var{async-output}}
17477 @item @var{async-output} @expansion{}
17478 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17480 @item @var{result-class} @expansion{}
17481 @code{"done" | "running" | "connected" | "error" | "exit"}
17483 @item @var{async-class} @expansion{}
17484 @code{"stopped" | @var{others}} (where @var{others} will be added
17485 depending on the needs---this is still in development).
17487 @item @var{result} @expansion{}
17488 @code{ @var{variable} "=" @var{value}}
17490 @item @var{variable} @expansion{}
17491 @code{ @var{string} }
17493 @item @var{value} @expansion{}
17494 @code{ @var{const} | @var{tuple} | @var{list} }
17496 @item @var{const} @expansion{}
17497 @code{@var{c-string}}
17499 @item @var{tuple} @expansion{}
17500 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17502 @item @var{list} @expansion{}
17503 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17504 @var{result} ( "," @var{result} )* "]" }
17506 @item @var{stream-record} @expansion{}
17507 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17509 @item @var{console-stream-output} @expansion{}
17510 @code{"~" @var{c-string}}
17512 @item @var{target-stream-output} @expansion{}
17513 @code{"@@" @var{c-string}}
17515 @item @var{log-stream-output} @expansion{}
17516 @code{"&" @var{c-string}}
17518 @item @var{nl} @expansion{}
17521 @item @var{token} @expansion{}
17522 @emph{any sequence of digits}.
17530 All output sequences end in a single line containing a period.
17533 The @code{@var{token}} is from the corresponding request. If an execution
17534 command is interrupted by the @samp{-exec-interrupt} command, the
17535 @var{token} associated with the @samp{*stopped} message is the one of the
17536 original execution command, not the one of the interrupt command.
17539 @cindex status output in @sc{gdb/mi}
17540 @var{status-async-output} contains on-going status information about the
17541 progress of a slow operation. It can be discarded. All status output is
17542 prefixed by @samp{+}.
17545 @cindex async output in @sc{gdb/mi}
17546 @var{exec-async-output} contains asynchronous state change on the target
17547 (stopped, started, disappeared). All async output is prefixed by
17551 @cindex notify output in @sc{gdb/mi}
17552 @var{notify-async-output} contains supplementary information that the
17553 client should handle (e.g., a new breakpoint information). All notify
17554 output is prefixed by @samp{=}.
17557 @cindex console output in @sc{gdb/mi}
17558 @var{console-stream-output} is output that should be displayed as is in the
17559 console. It is the textual response to a CLI command. All the console
17560 output is prefixed by @samp{~}.
17563 @cindex target output in @sc{gdb/mi}
17564 @var{target-stream-output} is the output produced by the target program.
17565 All the target output is prefixed by @samp{@@}.
17568 @cindex log output in @sc{gdb/mi}
17569 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17570 instance messages that should be displayed as part of an error log. All
17571 the log output is prefixed by @samp{&}.
17574 @cindex list output in @sc{gdb/mi}
17575 New @sc{gdb/mi} commands should only output @var{lists} containing
17581 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17582 details about the various output records.
17584 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17585 @node GDB/MI Compatibility with CLI
17586 @section @sc{gdb/mi} Compatibility with CLI
17588 @cindex compatibility, @sc{gdb/mi} and CLI
17589 @cindex @sc{gdb/mi}, compatibility with CLI
17591 For the developers convenience CLI commands can be entered directly,
17592 but there may be some unexpected behaviour. For example, commands
17593 that query the user will behave as if the user replied yes, breakpoint
17594 command lists are not executed and some CLI commands, such as
17595 @code{if}, @code{when} and @code{define}, prompt for further input with
17596 @samp{>}, which is not valid MI output.
17598 This feature may be removed at some stage in the future and it is
17599 recommended that front ends use the @code{-interpreter-exec} command
17600 (@pxref{-interpreter-exec}).
17602 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17603 @node GDB/MI Development and Front Ends
17604 @section @sc{gdb/mi} Development and Front Ends
17605 @cindex @sc{gdb/mi} development
17607 The application which takes the MI output and presents the state of the
17608 program being debugged to the user is called a @dfn{front end}.
17610 Although @sc{gdb/mi} is still incomplete, it is currently being used
17611 by a variety of front ends to @value{GDBN}. This makes it difficult
17612 to introduce new functionality without breaking existing usage. This
17613 section tries to minimize the problems by describing how the protocol
17616 Some changes in MI need not break a carefully designed front end, and
17617 for these the MI version will remain unchanged. The following is a
17618 list of changes that may occur within one level, so front ends should
17619 parse MI output in a way that can handle them:
17623 New MI commands may be added.
17626 New fields may be added to the output of any MI command.
17628 @c The format of field's content e.g type prefix, may change so parse it
17629 @c at your own risk. Yes, in general?
17631 @c The order of fields may change? Shouldn't really matter but it might
17632 @c resolve inconsistencies.
17635 If the changes are likely to break front ends, the MI version level
17636 will be increased by one. This will allow the front end to parse the
17637 output according to the MI version. Apart from mi0, new versions of
17638 @value{GDBN} will not support old versions of MI and it will be the
17639 responsibility of the front end to work with the new one.
17641 @c Starting with mi3, add a new command -mi-version that prints the MI
17644 The best way to avoid unexpected changes in MI that might break your front
17645 end is to make your project known to @value{GDBN} developers and
17646 follow development on @email{gdb@@sourceware.org} and
17647 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17648 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17649 Group, which has the aim of creating a a more general MI protocol
17650 called Debugger Machine Interface (DMI) that will become a standard
17651 for all debuggers, not just @value{GDBN}.
17652 @cindex mailing lists
17654 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17655 @node GDB/MI Output Records
17656 @section @sc{gdb/mi} Output Records
17659 * GDB/MI Result Records::
17660 * GDB/MI Stream Records::
17661 * GDB/MI Out-of-band Records::
17664 @node GDB/MI Result Records
17665 @subsection @sc{gdb/mi} Result Records
17667 @cindex result records in @sc{gdb/mi}
17668 @cindex @sc{gdb/mi}, result records
17669 In addition to a number of out-of-band notifications, the response to a
17670 @sc{gdb/mi} command includes one of the following result indications:
17674 @item "^done" [ "," @var{results} ]
17675 The synchronous operation was successful, @code{@var{results}} are the return
17680 @c Is this one correct? Should it be an out-of-band notification?
17681 The asynchronous operation was successfully started. The target is
17686 GDB has connected to a remote target.
17688 @item "^error" "," @var{c-string}
17690 The operation failed. The @code{@var{c-string}} contains the corresponding
17695 GDB has terminated.
17699 @node GDB/MI Stream Records
17700 @subsection @sc{gdb/mi} Stream Records
17702 @cindex @sc{gdb/mi}, stream records
17703 @cindex stream records in @sc{gdb/mi}
17704 @value{GDBN} internally maintains a number of output streams: the console, the
17705 target, and the log. The output intended for each of these streams is
17706 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17708 Each stream record begins with a unique @dfn{prefix character} which
17709 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17710 Syntax}). In addition to the prefix, each stream record contains a
17711 @code{@var{string-output}}. This is either raw text (with an implicit new
17712 line) or a quoted C string (which does not contain an implicit newline).
17715 @item "~" @var{string-output}
17716 The console output stream contains text that should be displayed in the
17717 CLI console window. It contains the textual responses to CLI commands.
17719 @item "@@" @var{string-output}
17720 The target output stream contains any textual output from the running
17721 target. This is only present when GDB's event loop is truly
17722 asynchronous, which is currently only the case for remote targets.
17724 @item "&" @var{string-output}
17725 The log stream contains debugging messages being produced by @value{GDBN}'s
17729 @node GDB/MI Out-of-band Records
17730 @subsection @sc{gdb/mi} Out-of-band Records
17732 @cindex out-of-band records in @sc{gdb/mi}
17733 @cindex @sc{gdb/mi}, out-of-band records
17734 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17735 additional changes that have occurred. Those changes can either be a
17736 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17737 target activity (e.g., target stopped).
17739 The following is a preliminary list of possible out-of-band records.
17740 In particular, the @var{exec-async-output} records.
17743 @item *stopped,reason="@var{reason}"
17746 @var{reason} can be one of the following:
17749 @item breakpoint-hit
17750 A breakpoint was reached.
17751 @item watchpoint-trigger
17752 A watchpoint was triggered.
17753 @item read-watchpoint-trigger
17754 A read watchpoint was triggered.
17755 @item access-watchpoint-trigger
17756 An access watchpoint was triggered.
17757 @item function-finished
17758 An -exec-finish or similar CLI command was accomplished.
17759 @item location-reached
17760 An -exec-until or similar CLI command was accomplished.
17761 @item watchpoint-scope
17762 A watchpoint has gone out of scope.
17763 @item end-stepping-range
17764 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17765 similar CLI command was accomplished.
17766 @item exited-signalled
17767 The inferior exited because of a signal.
17769 The inferior exited.
17770 @item exited-normally
17771 The inferior exited normally.
17772 @item signal-received
17773 A signal was received by the inferior.
17777 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17778 @node GDB/MI Simple Examples
17779 @section Simple Examples of @sc{gdb/mi} Interaction
17780 @cindex @sc{gdb/mi}, simple examples
17782 This subsection presents several simple examples of interaction using
17783 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17784 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17785 the output received from @sc{gdb/mi}.
17787 Note the the line breaks shown in the examples are here only for
17788 readability, they don't appear in the real output.
17790 @subheading Setting a breakpoint
17792 Setting a breakpoint generates synchronous output which contains detailed
17793 information of the breakpoint.
17796 -> -break-insert main
17797 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17798 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17799 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17803 @subheading Program Execution
17805 Program execution generates asynchronous records and MI gives the
17806 reason that execution stopped.
17812 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17813 frame=@{addr="0x08048564",func="main",
17814 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17815 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17820 <- *stopped,reason="exited-normally"
17824 @subheading Quitting GDB
17826 Quitting GDB just prints the result class @samp{^exit}.
17834 @subheading A Bad Command
17836 Here's what happens if you pass a non-existent command:
17840 <- ^error,msg="Undefined MI command: rubbish"
17845 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17846 @node GDB/MI Command Description Format
17847 @section @sc{gdb/mi} Command Description Format
17849 The remaining sections describe blocks of commands. Each block of
17850 commands is laid out in a fashion similar to this section.
17852 @subheading Motivation
17854 The motivation for this collection of commands.
17856 @subheading Introduction
17858 A brief introduction to this collection of commands as a whole.
17860 @subheading Commands
17862 For each command in the block, the following is described:
17864 @subsubheading Synopsis
17867 -command @var{args}@dots{}
17870 @subsubheading Result
17872 @subsubheading @value{GDBN} Command
17874 The corresponding @value{GDBN} CLI command(s), if any.
17876 @subsubheading Example
17878 Example(s) formatted for readability. Some of the described commands have
17879 not been implemented yet and these are labeled N.A.@: (not available).
17882 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17883 @node GDB/MI Breakpoint Commands
17884 @section @sc{gdb/mi} Breakpoint Commands
17886 @cindex breakpoint commands for @sc{gdb/mi}
17887 @cindex @sc{gdb/mi}, breakpoint commands
17888 This section documents @sc{gdb/mi} commands for manipulating
17891 @subheading The @code{-break-after} Command
17892 @findex -break-after
17894 @subsubheading Synopsis
17897 -break-after @var{number} @var{count}
17900 The breakpoint number @var{number} is not in effect until it has been
17901 hit @var{count} times. To see how this is reflected in the output of
17902 the @samp{-break-list} command, see the description of the
17903 @samp{-break-list} command below.
17905 @subsubheading @value{GDBN} Command
17907 The corresponding @value{GDBN} command is @samp{ignore}.
17909 @subsubheading Example
17914 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17915 fullname="/home/foo/hello.c",line="5",times="0"@}
17922 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17923 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17924 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17925 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17926 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17927 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17928 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17929 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17930 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17931 line="5",times="0",ignore="3"@}]@}
17936 @subheading The @code{-break-catch} Command
17937 @findex -break-catch
17939 @subheading The @code{-break-commands} Command
17940 @findex -break-commands
17944 @subheading The @code{-break-condition} Command
17945 @findex -break-condition
17947 @subsubheading Synopsis
17950 -break-condition @var{number} @var{expr}
17953 Breakpoint @var{number} will stop the program only if the condition in
17954 @var{expr} is true. The condition becomes part of the
17955 @samp{-break-list} output (see the description of the @samp{-break-list}
17958 @subsubheading @value{GDBN} Command
17960 The corresponding @value{GDBN} command is @samp{condition}.
17962 @subsubheading Example
17966 -break-condition 1 1
17970 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17971 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17972 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17973 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17974 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17975 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17976 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17977 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17978 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17979 line="5",cond="1",times="0",ignore="3"@}]@}
17983 @subheading The @code{-break-delete} Command
17984 @findex -break-delete
17986 @subsubheading Synopsis
17989 -break-delete ( @var{breakpoint} )+
17992 Delete the breakpoint(s) whose number(s) are specified in the argument
17993 list. This is obviously reflected in the breakpoint list.
17995 @subsubheading @value{GDBN} command
17997 The corresponding @value{GDBN} command is @samp{delete}.
17999 @subsubheading Example
18007 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18008 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18009 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18010 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18011 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18012 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18013 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18018 @subheading The @code{-break-disable} Command
18019 @findex -break-disable
18021 @subsubheading Synopsis
18024 -break-disable ( @var{breakpoint} )+
18027 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18028 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18030 @subsubheading @value{GDBN} Command
18032 The corresponding @value{GDBN} command is @samp{disable}.
18034 @subsubheading Example
18042 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18043 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18044 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18045 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18046 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18047 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18048 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18049 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18050 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18051 line="5",times="0"@}]@}
18055 @subheading The @code{-break-enable} Command
18056 @findex -break-enable
18058 @subsubheading Synopsis
18061 -break-enable ( @var{breakpoint} )+
18064 Enable (previously disabled) @var{breakpoint}(s).
18066 @subsubheading @value{GDBN} Command
18068 The corresponding @value{GDBN} command is @samp{enable}.
18070 @subsubheading Example
18078 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18079 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18080 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18081 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18082 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18083 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18084 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18085 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18086 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18087 line="5",times="0"@}]@}
18091 @subheading The @code{-break-info} Command
18092 @findex -break-info
18094 @subsubheading Synopsis
18097 -break-info @var{breakpoint}
18101 Get information about a single breakpoint.
18103 @subsubheading @value{GDBN} command
18105 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18107 @subsubheading Example
18110 @subheading The @code{-break-insert} Command
18111 @findex -break-insert
18113 @subsubheading Synopsis
18116 -break-insert [ -t ] [ -h ] [ -r ]
18117 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18118 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
18122 If specified, @var{line}, can be one of:
18129 @item filename:linenum
18130 @item filename:function
18134 The possible optional parameters of this command are:
18138 Insert a temporary breakpoint.
18140 Insert a hardware breakpoint.
18141 @item -c @var{condition}
18142 Make the breakpoint conditional on @var{condition}.
18143 @item -i @var{ignore-count}
18144 Initialize the @var{ignore-count}.
18146 Insert a regular breakpoint in all the functions whose names match the
18147 given regular expression. Other flags are not applicable to regular
18151 @subsubheading Result
18153 The result is in the form:
18156 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18157 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18158 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18159 times="@var{times}"@}
18163 where @var{number} is the @value{GDBN} number for this breakpoint,
18164 @var{funcname} is the name of the function where the breakpoint was
18165 inserted, @var{filename} is the name of the source file which contains
18166 this function, @var{lineno} is the source line number within that file
18167 and @var{times} the number of times that the breakpoint has been hit
18168 (always 0 for -break-insert but may be greater for -break-info or -break-list
18169 which use the same output).
18171 Note: this format is open to change.
18172 @c An out-of-band breakpoint instead of part of the result?
18174 @subsubheading @value{GDBN} Command
18176 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18177 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18179 @subsubheading Example
18184 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18185 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18187 -break-insert -t foo
18188 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18189 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18192 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18193 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18194 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18195 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18196 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18197 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18198 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18199 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18200 addr="0x0001072c", func="main",file="recursive2.c",
18201 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18202 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18203 addr="0x00010774",func="foo",file="recursive2.c",
18204 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18206 -break-insert -r foo.*
18207 ~int foo(int, int);
18208 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18209 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18213 @subheading The @code{-break-list} Command
18214 @findex -break-list
18216 @subsubheading Synopsis
18222 Displays the list of inserted breakpoints, showing the following fields:
18226 number of the breakpoint
18228 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18230 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18233 is the breakpoint enabled or no: @samp{y} or @samp{n}
18235 memory location at which the breakpoint is set
18237 logical location of the breakpoint, expressed by function name, file
18240 number of times the breakpoint has been hit
18243 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18244 @code{body} field is an empty list.
18246 @subsubheading @value{GDBN} Command
18248 The corresponding @value{GDBN} command is @samp{info break}.
18250 @subsubheading Example
18255 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18256 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18257 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18258 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18259 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18260 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18261 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18262 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18263 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18264 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18265 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18266 line="13",times="0"@}]@}
18270 Here's an example of the result when there are no breakpoints:
18275 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18276 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18277 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18278 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18279 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18280 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18281 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18286 @subheading The @code{-break-watch} Command
18287 @findex -break-watch
18289 @subsubheading Synopsis
18292 -break-watch [ -a | -r ]
18295 Create a watchpoint. With the @samp{-a} option it will create an
18296 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
18297 read from or on a write to the memory location. With the @samp{-r}
18298 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
18299 trigger only when the memory location is accessed for reading. Without
18300 either of the options, the watchpoint created is a regular watchpoint,
18301 i.e. it will trigger when the memory location is accessed for writing.
18302 @xref{Set Watchpoints, , Setting watchpoints}.
18304 Note that @samp{-break-list} will report a single list of watchpoints and
18305 breakpoints inserted.
18307 @subsubheading @value{GDBN} Command
18309 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18312 @subsubheading Example
18314 Setting a watchpoint on a variable in the @code{main} function:
18319 ^done,wpt=@{number="2",exp="x"@}
18323 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18324 value=@{old="-268439212",new="55"@},
18325 frame=@{func="main",args=[],file="recursive2.c",
18326 fullname="/home/foo/bar/recursive2.c",line="5"@}
18330 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18331 the program execution twice: first for the variable changing value, then
18332 for the watchpoint going out of scope.
18337 ^done,wpt=@{number="5",exp="C"@}
18341 ^done,reason="watchpoint-trigger",
18342 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18343 frame=@{func="callee4",args=[],
18344 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18345 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18349 ^done,reason="watchpoint-scope",wpnum="5",
18350 frame=@{func="callee3",args=[@{name="strarg",
18351 value="0x11940 \"A string argument.\""@}],
18352 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18353 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18357 Listing breakpoints and watchpoints, at different points in the program
18358 execution. Note that once the watchpoint goes out of scope, it is
18364 ^done,wpt=@{number="2",exp="C"@}
18367 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18368 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18369 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18370 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18371 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18372 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18373 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18374 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18375 addr="0x00010734",func="callee4",
18376 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18377 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18378 bkpt=@{number="2",type="watchpoint",disp="keep",
18379 enabled="y",addr="",what="C",times="0"@}]@}
18383 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18384 value=@{old="-276895068",new="3"@},
18385 frame=@{func="callee4",args=[],
18386 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18387 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18390 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18391 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18392 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18393 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18394 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18395 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18396 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18397 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18398 addr="0x00010734",func="callee4",
18399 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18400 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18401 bkpt=@{number="2",type="watchpoint",disp="keep",
18402 enabled="y",addr="",what="C",times="-5"@}]@}
18406 ^done,reason="watchpoint-scope",wpnum="2",
18407 frame=@{func="callee3",args=[@{name="strarg",
18408 value="0x11940 \"A string argument.\""@}],
18409 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18410 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18413 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18414 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18415 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18416 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18417 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18418 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18419 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18420 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18421 addr="0x00010734",func="callee4",
18422 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18423 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18428 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18429 @node GDB/MI Program Context
18430 @section @sc{gdb/mi} Program Context
18432 @subheading The @code{-exec-arguments} Command
18433 @findex -exec-arguments
18436 @subsubheading Synopsis
18439 -exec-arguments @var{args}
18442 Set the inferior program arguments, to be used in the next
18445 @subsubheading @value{GDBN} Command
18447 The corresponding @value{GDBN} command is @samp{set args}.
18449 @subsubheading Example
18452 Don't have one around.
18455 @subheading The @code{-exec-show-arguments} Command
18456 @findex -exec-show-arguments
18458 @subsubheading Synopsis
18461 -exec-show-arguments
18464 Print the arguments of the program.
18466 @subsubheading @value{GDBN} Command
18468 The corresponding @value{GDBN} command is @samp{show args}.
18470 @subsubheading Example
18474 @subheading The @code{-environment-cd} Command
18475 @findex -environment-cd
18477 @subsubheading Synopsis
18480 -environment-cd @var{pathdir}
18483 Set @value{GDBN}'s working directory.
18485 @subsubheading @value{GDBN} Command
18487 The corresponding @value{GDBN} command is @samp{cd}.
18489 @subsubheading Example
18493 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18499 @subheading The @code{-environment-directory} Command
18500 @findex -environment-directory
18502 @subsubheading Synopsis
18505 -environment-directory [ -r ] [ @var{pathdir} ]+
18508 Add directories @var{pathdir} to beginning of search path for source files.
18509 If the @samp{-r} option is used, the search path is reset to the default
18510 search path. If directories @var{pathdir} are supplied in addition to the
18511 @samp{-r} option, the search path is first reset and then addition
18513 Multiple directories may be specified, separated by blanks. Specifying
18514 multiple directories in a single command
18515 results in the directories added to the beginning of the
18516 search path in the same order they were presented in the command.
18517 If blanks are needed as
18518 part of a directory name, double-quotes should be used around
18519 the name. In the command output, the path will show up separated
18520 by the system directory-separator character. The directory-seperator
18521 character must not be used
18522 in any directory name.
18523 If no directories are specified, the current search path is displayed.
18525 @subsubheading @value{GDBN} Command
18527 The corresponding @value{GDBN} command is @samp{dir}.
18529 @subsubheading Example
18533 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18534 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18536 -environment-directory ""
18537 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18539 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18540 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18542 -environment-directory -r
18543 ^done,source-path="$cdir:$cwd"
18548 @subheading The @code{-environment-path} Command
18549 @findex -environment-path
18551 @subsubheading Synopsis
18554 -environment-path [ -r ] [ @var{pathdir} ]+
18557 Add directories @var{pathdir} to beginning of search path for object files.
18558 If the @samp{-r} option is used, the search path is reset to the original
18559 search path that existed at gdb start-up. If directories @var{pathdir} are
18560 supplied in addition to the
18561 @samp{-r} option, the search path is first reset and then addition
18563 Multiple directories may be specified, separated by blanks. Specifying
18564 multiple directories in a single command
18565 results in the directories added to the beginning of the
18566 search path in the same order they were presented in the command.
18567 If blanks are needed as
18568 part of a directory name, double-quotes should be used around
18569 the name. In the command output, the path will show up separated
18570 by the system directory-separator character. The directory-seperator
18571 character must not be used
18572 in any directory name.
18573 If no directories are specified, the current path is displayed.
18576 @subsubheading @value{GDBN} Command
18578 The corresponding @value{GDBN} command is @samp{path}.
18580 @subsubheading Example
18585 ^done,path="/usr/bin"
18587 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18588 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18590 -environment-path -r /usr/local/bin
18591 ^done,path="/usr/local/bin:/usr/bin"
18596 @subheading The @code{-environment-pwd} Command
18597 @findex -environment-pwd
18599 @subsubheading Synopsis
18605 Show the current working directory.
18607 @subsubheading @value{GDBN} command
18609 The corresponding @value{GDBN} command is @samp{pwd}.
18611 @subsubheading Example
18616 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18620 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18621 @node GDB/MI Thread Commands
18622 @section @sc{gdb/mi} Thread Commands
18625 @subheading The @code{-thread-info} Command
18626 @findex -thread-info
18628 @subsubheading Synopsis
18634 @subsubheading @value{GDBN} command
18638 @subsubheading Example
18642 @subheading The @code{-thread-list-all-threads} Command
18643 @findex -thread-list-all-threads
18645 @subsubheading Synopsis
18648 -thread-list-all-threads
18651 @subsubheading @value{GDBN} Command
18653 The equivalent @value{GDBN} command is @samp{info threads}.
18655 @subsubheading Example
18659 @subheading The @code{-thread-list-ids} Command
18660 @findex -thread-list-ids
18662 @subsubheading Synopsis
18668 Produces a list of the currently known @value{GDBN} thread ids. At the
18669 end of the list it also prints the total number of such threads.
18671 @subsubheading @value{GDBN} Command
18673 Part of @samp{info threads} supplies the same information.
18675 @subsubheading Example
18677 No threads present, besides the main process:
18682 ^done,thread-ids=@{@},number-of-threads="0"
18692 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18693 number-of-threads="3"
18698 @subheading The @code{-thread-select} Command
18699 @findex -thread-select
18701 @subsubheading Synopsis
18704 -thread-select @var{threadnum}
18707 Make @var{threadnum} the current thread. It prints the number of the new
18708 current thread, and the topmost frame for that thread.
18710 @subsubheading @value{GDBN} Command
18712 The corresponding @value{GDBN} command is @samp{thread}.
18714 @subsubheading Example
18721 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18722 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18726 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18727 number-of-threads="3"
18730 ^done,new-thread-id="3",
18731 frame=@{level="0",func="vprintf",
18732 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18733 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18737 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18738 @node GDB/MI Program Execution
18739 @section @sc{gdb/mi} Program Execution
18741 These are the asynchronous commands which generate the out-of-band
18742 record @samp{*stopped}. Currently GDB only really executes
18743 asynchronously with remote targets and this interaction is mimicked in
18746 @subheading The @code{-exec-continue} Command
18747 @findex -exec-continue
18749 @subsubheading Synopsis
18755 Resumes the execution of the inferior program until a breakpoint is
18756 encountered, or until the inferior exits.
18758 @subsubheading @value{GDBN} Command
18760 The corresponding @value{GDBN} corresponding is @samp{continue}.
18762 @subsubheading Example
18769 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18770 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18775 @subheading The @code{-exec-finish} Command
18776 @findex -exec-finish
18778 @subsubheading Synopsis
18784 Resumes the execution of the inferior program until the current
18785 function is exited. Displays the results returned by the function.
18787 @subsubheading @value{GDBN} Command
18789 The corresponding @value{GDBN} command is @samp{finish}.
18791 @subsubheading Example
18793 Function returning @code{void}.
18800 *stopped,reason="function-finished",frame=@{func="main",args=[],
18801 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18805 Function returning other than @code{void}. The name of the internal
18806 @value{GDBN} variable storing the result is printed, together with the
18813 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18814 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18815 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18816 gdb-result-var="$1",return-value="0"
18821 @subheading The @code{-exec-interrupt} Command
18822 @findex -exec-interrupt
18824 @subsubheading Synopsis
18830 Interrupts the background execution of the target. Note how the token
18831 associated with the stop message is the one for the execution command
18832 that has been interrupted. The token for the interrupt itself only
18833 appears in the @samp{^done} output. If the user is trying to
18834 interrupt a non-running program, an error message will be printed.
18836 @subsubheading @value{GDBN} Command
18838 The corresponding @value{GDBN} command is @samp{interrupt}.
18840 @subsubheading Example
18851 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18852 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18853 fullname="/home/foo/bar/try.c",line="13"@}
18858 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18863 @subheading The @code{-exec-next} Command
18866 @subsubheading Synopsis
18872 Resumes execution of the inferior program, stopping when the beginning
18873 of the next source line is reached.
18875 @subsubheading @value{GDBN} Command
18877 The corresponding @value{GDBN} command is @samp{next}.
18879 @subsubheading Example
18885 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18890 @subheading The @code{-exec-next-instruction} Command
18891 @findex -exec-next-instruction
18893 @subsubheading Synopsis
18896 -exec-next-instruction
18899 Executes one machine instruction. If the instruction is a function
18900 call, continues until the function returns. If the program stops at an
18901 instruction in the middle of a source line, the address will be
18904 @subsubheading @value{GDBN} Command
18906 The corresponding @value{GDBN} command is @samp{nexti}.
18908 @subsubheading Example
18912 -exec-next-instruction
18916 *stopped,reason="end-stepping-range",
18917 addr="0x000100d4",line="5",file="hello.c"
18922 @subheading The @code{-exec-return} Command
18923 @findex -exec-return
18925 @subsubheading Synopsis
18931 Makes current function return immediately. Doesn't execute the inferior.
18932 Displays the new current frame.
18934 @subsubheading @value{GDBN} Command
18936 The corresponding @value{GDBN} command is @samp{return}.
18938 @subsubheading Example
18942 200-break-insert callee4
18943 200^done,bkpt=@{number="1",addr="0x00010734",
18944 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18949 000*stopped,reason="breakpoint-hit",bkptno="1",
18950 frame=@{func="callee4",args=[],
18951 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18952 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18958 111^done,frame=@{level="0",func="callee3",
18959 args=[@{name="strarg",
18960 value="0x11940 \"A string argument.\""@}],
18961 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18962 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18967 @subheading The @code{-exec-run} Command
18970 @subsubheading Synopsis
18976 Starts execution of the inferior from the beginning. The inferior
18977 executes until either a breakpoint is encountered or the program
18978 exits. In the latter case the output will include an exit code, if
18979 the program has exited exceptionally.
18981 @subsubheading @value{GDBN} Command
18983 The corresponding @value{GDBN} command is @samp{run}.
18985 @subsubheading Examples
18990 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18995 *stopped,reason="breakpoint-hit",bkptno="1",
18996 frame=@{func="main",args=[],file="recursive2.c",
18997 fullname="/home/foo/bar/recursive2.c",line="4"@}
19002 Program exited normally:
19010 *stopped,reason="exited-normally"
19015 Program exited exceptionally:
19023 *stopped,reason="exited",exit-code="01"
19027 Another way the program can terminate is if it receives a signal such as
19028 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19032 *stopped,reason="exited-signalled",signal-name="SIGINT",
19033 signal-meaning="Interrupt"
19037 @c @subheading -exec-signal
19040 @subheading The @code{-exec-step} Command
19043 @subsubheading Synopsis
19049 Resumes execution of the inferior program, stopping when the beginning
19050 of the next source line is reached, if the next source line is not a
19051 function call. If it is, stop at the first instruction of the called
19054 @subsubheading @value{GDBN} Command
19056 The corresponding @value{GDBN} command is @samp{step}.
19058 @subsubheading Example
19060 Stepping into a function:
19066 *stopped,reason="end-stepping-range",
19067 frame=@{func="foo",args=[@{name="a",value="10"@},
19068 @{name="b",value="0"@}],file="recursive2.c",
19069 fullname="/home/foo/bar/recursive2.c",line="11"@}
19079 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19084 @subheading The @code{-exec-step-instruction} Command
19085 @findex -exec-step-instruction
19087 @subsubheading Synopsis
19090 -exec-step-instruction
19093 Resumes the inferior which executes one machine instruction. The
19094 output, once @value{GDBN} has stopped, will vary depending on whether
19095 we have stopped in the middle of a source line or not. In the former
19096 case, the address at which the program stopped will be printed as
19099 @subsubheading @value{GDBN} Command
19101 The corresponding @value{GDBN} command is @samp{stepi}.
19103 @subsubheading Example
19107 -exec-step-instruction
19111 *stopped,reason="end-stepping-range",
19112 frame=@{func="foo",args=[],file="try.c",
19113 fullname="/home/foo/bar/try.c",line="10"@}
19115 -exec-step-instruction
19119 *stopped,reason="end-stepping-range",
19120 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19121 fullname="/home/foo/bar/try.c",line="10"@}
19126 @subheading The @code{-exec-until} Command
19127 @findex -exec-until
19129 @subsubheading Synopsis
19132 -exec-until [ @var{location} ]
19135 Executes the inferior until the @var{location} specified in the
19136 argument is reached. If there is no argument, the inferior executes
19137 until a source line greater than the current one is reached. The
19138 reason for stopping in this case will be @samp{location-reached}.
19140 @subsubheading @value{GDBN} Command
19142 The corresponding @value{GDBN} command is @samp{until}.
19144 @subsubheading Example
19148 -exec-until recursive2.c:6
19152 *stopped,reason="location-reached",frame=@{func="main",args=[],
19153 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19158 @subheading -file-clear
19159 Is this going away????
19162 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19163 @node GDB/MI Stack Manipulation
19164 @section @sc{gdb/mi} Stack Manipulation Commands
19167 @subheading The @code{-stack-info-frame} Command
19168 @findex -stack-info-frame
19170 @subsubheading Synopsis
19176 Get info on the selected frame.
19178 @subsubheading @value{GDBN} Command
19180 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19181 (without arguments).
19183 @subsubheading Example
19188 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19189 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19190 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19194 @subheading The @code{-stack-info-depth} Command
19195 @findex -stack-info-depth
19197 @subsubheading Synopsis
19200 -stack-info-depth [ @var{max-depth} ]
19203 Return the depth of the stack. If the integer argument @var{max-depth}
19204 is specified, do not count beyond @var{max-depth} frames.
19206 @subsubheading @value{GDBN} Command
19208 There's no equivalent @value{GDBN} command.
19210 @subsubheading Example
19212 For a stack with frame levels 0 through 11:
19219 -stack-info-depth 4
19222 -stack-info-depth 12
19225 -stack-info-depth 11
19228 -stack-info-depth 13
19233 @subheading The @code{-stack-list-arguments} Command
19234 @findex -stack-list-arguments
19236 @subsubheading Synopsis
19239 -stack-list-arguments @var{show-values}
19240 [ @var{low-frame} @var{high-frame} ]
19243 Display a list of the arguments for the frames between @var{low-frame}
19244 and @var{high-frame} (inclusive). If @var{low-frame} and
19245 @var{high-frame} are not provided, list the arguments for the whole
19246 call stack. If the two arguments are equal, show the single frame
19247 at the corresponding level. It is an error if @var{low-frame} is
19248 larger than the actual number of frames. On the other hand,
19249 @var{high-frame} may be larger than the actual number of frames, in
19250 which case only existing frames will be returned.
19252 The @var{show-values} argument must have a value of 0 or 1. A value of
19253 0 means that only the names of the arguments are listed, a value of 1
19254 means that both names and values of the arguments are printed.
19256 @subsubheading @value{GDBN} Command
19258 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19259 @samp{gdb_get_args} command which partially overlaps with the
19260 functionality of @samp{-stack-list-arguments}.
19262 @subsubheading Example
19269 frame=@{level="0",addr="0x00010734",func="callee4",
19270 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19271 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19272 frame=@{level="1",addr="0x0001076c",func="callee3",
19273 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19274 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19275 frame=@{level="2",addr="0x0001078c",func="callee2",
19276 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19277 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19278 frame=@{level="3",addr="0x000107b4",func="callee1",
19279 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19280 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19281 frame=@{level="4",addr="0x000107e0",func="main",
19282 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19283 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19285 -stack-list-arguments 0
19288 frame=@{level="0",args=[]@},
19289 frame=@{level="1",args=[name="strarg"]@},
19290 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19291 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19292 frame=@{level="4",args=[]@}]
19294 -stack-list-arguments 1
19297 frame=@{level="0",args=[]@},
19299 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19300 frame=@{level="2",args=[
19301 @{name="intarg",value="2"@},
19302 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19303 @{frame=@{level="3",args=[
19304 @{name="intarg",value="2"@},
19305 @{name="strarg",value="0x11940 \"A string argument.\""@},
19306 @{name="fltarg",value="3.5"@}]@},
19307 frame=@{level="4",args=[]@}]
19309 -stack-list-arguments 0 2 2
19310 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19312 -stack-list-arguments 1 2 2
19313 ^done,stack-args=[frame=@{level="2",
19314 args=[@{name="intarg",value="2"@},
19315 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19319 @c @subheading -stack-list-exception-handlers
19322 @subheading The @code{-stack-list-frames} Command
19323 @findex -stack-list-frames
19325 @subsubheading Synopsis
19328 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19331 List the frames currently on the stack. For each frame it displays the
19336 The frame number, 0 being the topmost frame, i.e. the innermost function.
19338 The @code{$pc} value for that frame.
19342 File name of the source file where the function lives.
19344 Line number corresponding to the @code{$pc}.
19347 If invoked without arguments, this command prints a backtrace for the
19348 whole stack. If given two integer arguments, it shows the frames whose
19349 levels are between the two arguments (inclusive). If the two arguments
19350 are equal, it shows the single frame at the corresponding level. It is
19351 an error if @var{low-frame} is larger than the actual number of
19352 frames. On the other hand, @var{high-frame} may be larger than the
19353 actual number of frames, in which case only existing frames will be returned.
19355 @subsubheading @value{GDBN} Command
19357 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19359 @subsubheading Example
19361 Full stack backtrace:
19367 [frame=@{level="0",addr="0x0001076c",func="foo",
19368 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19369 frame=@{level="1",addr="0x000107a4",func="foo",
19370 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19371 frame=@{level="2",addr="0x000107a4",func="foo",
19372 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19373 frame=@{level="3",addr="0x000107a4",func="foo",
19374 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19375 frame=@{level="4",addr="0x000107a4",func="foo",
19376 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19377 frame=@{level="5",addr="0x000107a4",func="foo",
19378 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19379 frame=@{level="6",addr="0x000107a4",func="foo",
19380 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19381 frame=@{level="7",addr="0x000107a4",func="foo",
19382 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19383 frame=@{level="8",addr="0x000107a4",func="foo",
19384 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19385 frame=@{level="9",addr="0x000107a4",func="foo",
19386 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19387 frame=@{level="10",addr="0x000107a4",func="foo",
19388 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19389 frame=@{level="11",addr="0x00010738",func="main",
19390 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19394 Show frames between @var{low_frame} and @var{high_frame}:
19398 -stack-list-frames 3 5
19400 [frame=@{level="3",addr="0x000107a4",func="foo",
19401 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19402 frame=@{level="4",addr="0x000107a4",func="foo",
19403 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19404 frame=@{level="5",addr="0x000107a4",func="foo",
19405 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19409 Show a single frame:
19413 -stack-list-frames 3 3
19415 [frame=@{level="3",addr="0x000107a4",func="foo",
19416 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19421 @subheading The @code{-stack-list-locals} Command
19422 @findex -stack-list-locals
19424 @subsubheading Synopsis
19427 -stack-list-locals @var{print-values}
19430 Display the local variable names for the selected frame. If
19431 @var{print-values} is 0 or @code{--no-values}, print only the names of
19432 the variables; if it is 1 or @code{--all-values}, print also their
19433 values; and if it is 2 or @code{--simple-values}, print the name,
19434 type and value for simple data types and the name and type for arrays,
19435 structures and unions. In this last case, a frontend can immediately
19436 display the value of simple data types and create variable objects for
19437 other data types when the the user wishes to explore their values in
19440 @subsubheading @value{GDBN} Command
19442 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19444 @subsubheading Example
19448 -stack-list-locals 0
19449 ^done,locals=[name="A",name="B",name="C"]
19451 -stack-list-locals --all-values
19452 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19453 @{name="C",value="@{1, 2, 3@}"@}]
19454 -stack-list-locals --simple-values
19455 ^done,locals=[@{name="A",type="int",value="1"@},
19456 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19461 @subheading The @code{-stack-select-frame} Command
19462 @findex -stack-select-frame
19464 @subsubheading Synopsis
19467 -stack-select-frame @var{framenum}
19470 Change the selected frame. Select a different frame @var{framenum} on
19473 @subsubheading @value{GDBN} Command
19475 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19476 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19478 @subsubheading Example
19482 -stack-select-frame 2
19487 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19488 @node GDB/MI Variable Objects
19489 @section @sc{gdb/mi} Variable Objects
19492 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19494 For the implementation of a variable debugger window (locals, watched
19495 expressions, etc.), we are proposing the adaptation of the existing code
19496 used by @code{Insight}.
19498 The two main reasons for that are:
19502 It has been proven in practice (it is already on its second generation).
19505 It will shorten development time (needless to say how important it is
19509 The original interface was designed to be used by Tcl code, so it was
19510 slightly changed so it could be used through @sc{gdb/mi}. This section
19511 describes the @sc{gdb/mi} operations that will be available and gives some
19512 hints about their use.
19514 @emph{Note}: In addition to the set of operations described here, we
19515 expect the @sc{gui} implementation of a variable window to require, at
19516 least, the following operations:
19519 @item @code{-gdb-show} @code{output-radix}
19520 @item @code{-stack-list-arguments}
19521 @item @code{-stack-list-locals}
19522 @item @code{-stack-select-frame}
19525 @subheading Introduction to Variable Objects in @sc{gdb/mi}
19527 @cindex variable objects in @sc{gdb/mi}
19528 The basic idea behind variable objects is the creation of a named object
19529 to represent a variable, an expression, a memory location or even a CPU
19530 register. For each object created, a set of operations is available for
19531 examining or changing its properties.
19533 Furthermore, complex data types, such as C structures, are represented
19534 in a tree format. For instance, the @code{struct} type variable is the
19535 root and the children will represent the struct members. If a child
19536 is itself of a complex type, it will also have children of its own.
19537 Appropriate language differences are handled for C, C@t{++} and Java.
19539 When returning the actual values of the objects, this facility allows
19540 for the individual selection of the display format used in the result
19541 creation. It can be chosen among: binary, decimal, hexadecimal, octal
19542 and natural. Natural refers to a default format automatically
19543 chosen based on the variable type (like decimal for an @code{int}, hex
19544 for pointers, etc.).
19546 The following is the complete set of @sc{gdb/mi} operations defined to
19547 access this functionality:
19549 @multitable @columnfractions .4 .6
19550 @item @strong{Operation}
19551 @tab @strong{Description}
19553 @item @code{-var-create}
19554 @tab create a variable object
19555 @item @code{-var-delete}
19556 @tab delete the variable object and its children
19557 @item @code{-var-set-format}
19558 @tab set the display format of this variable
19559 @item @code{-var-show-format}
19560 @tab show the display format of this variable
19561 @item @code{-var-info-num-children}
19562 @tab tells how many children this object has
19563 @item @code{-var-list-children}
19564 @tab return a list of the object's children
19565 @item @code{-var-info-type}
19566 @tab show the type of this variable object
19567 @item @code{-var-info-expression}
19568 @tab print what this variable object represents
19569 @item @code{-var-show-attributes}
19570 @tab is this variable editable? does it exist here?
19571 @item @code{-var-evaluate-expression}
19572 @tab get the value of this variable
19573 @item @code{-var-assign}
19574 @tab set the value of this variable
19575 @item @code{-var-update}
19576 @tab update the variable and its children
19579 In the next subsection we describe each operation in detail and suggest
19580 how it can be used.
19582 @subheading Description And Use of Operations on Variable Objects
19584 @subheading The @code{-var-create} Command
19585 @findex -var-create
19587 @subsubheading Synopsis
19590 -var-create @{@var{name} | "-"@}
19591 @{@var{frame-addr} | "*"@} @var{expression}
19594 This operation creates a variable object, which allows the monitoring of
19595 a variable, the result of an expression, a memory cell or a CPU
19598 The @var{name} parameter is the string by which the object can be
19599 referenced. It must be unique. If @samp{-} is specified, the varobj
19600 system will generate a string ``varNNNNNN'' automatically. It will be
19601 unique provided that one does not specify @var{name} on that format.
19602 The command fails if a duplicate name is found.
19604 The frame under which the expression should be evaluated can be
19605 specified by @var{frame-addr}. A @samp{*} indicates that the current
19606 frame should be used.
19608 @var{expression} is any expression valid on the current language set (must not
19609 begin with a @samp{*}), or one of the following:
19613 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19616 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19619 @samp{$@var{regname}} --- a CPU register name
19622 @subsubheading Result
19624 This operation returns the name, number of children and the type of the
19625 object created. Type is returned as a string as the ones generated by
19626 the @value{GDBN} CLI:
19629 name="@var{name}",numchild="N",type="@var{type}"
19633 @subheading The @code{-var-delete} Command
19634 @findex -var-delete
19636 @subsubheading Synopsis
19639 -var-delete @var{name}
19642 Deletes a previously created variable object and all of its children.
19644 Returns an error if the object @var{name} is not found.
19647 @subheading The @code{-var-set-format} Command
19648 @findex -var-set-format
19650 @subsubheading Synopsis
19653 -var-set-format @var{name} @var{format-spec}
19656 Sets the output format for the value of the object @var{name} to be
19659 The syntax for the @var{format-spec} is as follows:
19662 @var{format-spec} @expansion{}
19663 @{binary | decimal | hexadecimal | octal | natural@}
19667 @subheading The @code{-var-show-format} Command
19668 @findex -var-show-format
19670 @subsubheading Synopsis
19673 -var-show-format @var{name}
19676 Returns the format used to display the value of the object @var{name}.
19679 @var{format} @expansion{}
19684 @subheading The @code{-var-info-num-children} Command
19685 @findex -var-info-num-children
19687 @subsubheading Synopsis
19690 -var-info-num-children @var{name}
19693 Returns the number of children of a variable object @var{name}:
19700 @subheading The @code{-var-list-children} Command
19701 @findex -var-list-children
19703 @subsubheading Synopsis
19706 -var-list-children [@var{print-values}] @var{name}
19708 @anchor{-var-list-children}
19710 Return a list of the children of the specified variable object and
19711 create variable objects for them, if they do not already exist. With
19712 a single argument or if @var{print-values} has a value for of 0 or
19713 @code{--no-values}, print only the names of the variables; if
19714 @var{print-values} is 1 or @code{--all-values}, also print their
19715 values; and if it is 2 or @code{--simple-values} print the name and
19716 value for simple data types and just the name for arrays, structures
19719 @subsubheading Example
19723 -var-list-children n
19724 ^done,numchild=@var{n},children=[@{name=@var{name},
19725 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19727 -var-list-children --all-values n
19728 ^done,numchild=@var{n},children=[@{name=@var{name},
19729 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19733 @subheading The @code{-var-info-type} Command
19734 @findex -var-info-type
19736 @subsubheading Synopsis
19739 -var-info-type @var{name}
19742 Returns the type of the specified variable @var{name}. The type is
19743 returned as a string in the same format as it is output by the
19747 type=@var{typename}
19751 @subheading The @code{-var-info-expression} Command
19752 @findex -var-info-expression
19754 @subsubheading Synopsis
19757 -var-info-expression @var{name}
19760 Returns what is represented by the variable object @var{name}:
19763 lang=@var{lang-spec},exp=@var{expression}
19767 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
19769 @subheading The @code{-var-show-attributes} Command
19770 @findex -var-show-attributes
19772 @subsubheading Synopsis
19775 -var-show-attributes @var{name}
19778 List attributes of the specified variable object @var{name}:
19781 status=@var{attr} [ ( ,@var{attr} )* ]
19785 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19787 @subheading The @code{-var-evaluate-expression} Command
19788 @findex -var-evaluate-expression
19790 @subsubheading Synopsis
19793 -var-evaluate-expression @var{name}
19796 Evaluates the expression that is represented by the specified variable
19797 object and returns its value as a string in the current format specified
19804 Note that one must invoke @code{-var-list-children} for a variable
19805 before the value of a child variable can be evaluated.
19807 @subheading The @code{-var-assign} Command
19808 @findex -var-assign
19810 @subsubheading Synopsis
19813 -var-assign @var{name} @var{expression}
19816 Assigns the value of @var{expression} to the variable object specified
19817 by @var{name}. The object must be @samp{editable}. If the variable's
19818 value is altered by the assign, the variable will show up in any
19819 subsequent @code{-var-update} list.
19821 @subsubheading Example
19829 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19833 @subheading The @code{-var-update} Command
19834 @findex -var-update
19836 @subsubheading Synopsis
19839 -var-update [@var{print-values}] @{@var{name} | "*"@}
19842 Update the value of the variable object @var{name} by evaluating its
19843 expression after fetching all the new values from memory or registers.
19844 A @samp{*} causes all existing variable objects to be updated. The
19845 option @var{print-values} determines whether names both and values, or
19846 just names are printed in the manner described for
19847 @code{-var-list-children} (@pxref{-var-list-children}).
19849 @subsubheading Example
19856 -var-update --all-values var1
19857 ^done,changelist=[@{name="var1",value="3",in_scope="true",
19858 type_changed="false"@}]
19862 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19863 @node GDB/MI Data Manipulation
19864 @section @sc{gdb/mi} Data Manipulation
19866 @cindex data manipulation, in @sc{gdb/mi}
19867 @cindex @sc{gdb/mi}, data manipulation
19868 This section describes the @sc{gdb/mi} commands that manipulate data:
19869 examine memory and registers, evaluate expressions, etc.
19871 @c REMOVED FROM THE INTERFACE.
19872 @c @subheading -data-assign
19873 @c Change the value of a program variable. Plenty of side effects.
19874 @c @subsubheading GDB command
19876 @c @subsubheading Example
19879 @subheading The @code{-data-disassemble} Command
19880 @findex -data-disassemble
19882 @subsubheading Synopsis
19886 [ -s @var{start-addr} -e @var{end-addr} ]
19887 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
19895 @item @var{start-addr}
19896 is the beginning address (or @code{$pc})
19897 @item @var{end-addr}
19899 @item @var{filename}
19900 is the name of the file to disassemble
19901 @item @var{linenum}
19902 is the line number to disassemble around
19904 is the the number of disassembly lines to be produced. If it is -1,
19905 the whole function will be disassembled, in case no @var{end-addr} is
19906 specified. If @var{end-addr} is specified as a non-zero value, and
19907 @var{lines} is lower than the number of disassembly lines between
19908 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
19909 displayed; if @var{lines} is higher than the number of lines between
19910 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
19913 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
19917 @subsubheading Result
19919 The output for each instruction is composed of four fields:
19928 Note that whatever included in the instruction field, is not manipulated
19929 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
19931 @subsubheading @value{GDBN} Command
19933 There's no direct mapping from this command to the CLI.
19935 @subsubheading Example
19937 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
19941 -data-disassemble -s $pc -e "$pc + 20" -- 0
19944 @{address="0x000107c0",func-name="main",offset="4",
19945 inst="mov 2, %o0"@},
19946 @{address="0x000107c4",func-name="main",offset="8",
19947 inst="sethi %hi(0x11800), %o2"@},
19948 @{address="0x000107c8",func-name="main",offset="12",
19949 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
19950 @{address="0x000107cc",func-name="main",offset="16",
19951 inst="sethi %hi(0x11800), %o2"@},
19952 @{address="0x000107d0",func-name="main",offset="20",
19953 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
19957 Disassemble the whole @code{main} function. Line 32 is part of
19961 -data-disassemble -f basics.c -l 32 -- 0
19963 @{address="0x000107bc",func-name="main",offset="0",
19964 inst="save %sp, -112, %sp"@},
19965 @{address="0x000107c0",func-name="main",offset="4",
19966 inst="mov 2, %o0"@},
19967 @{address="0x000107c4",func-name="main",offset="8",
19968 inst="sethi %hi(0x11800), %o2"@},
19970 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
19971 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
19975 Disassemble 3 instructions from the start of @code{main}:
19979 -data-disassemble -f basics.c -l 32 -n 3 -- 0
19981 @{address="0x000107bc",func-name="main",offset="0",
19982 inst="save %sp, -112, %sp"@},
19983 @{address="0x000107c0",func-name="main",offset="4",
19984 inst="mov 2, %o0"@},
19985 @{address="0x000107c4",func-name="main",offset="8",
19986 inst="sethi %hi(0x11800), %o2"@}]
19990 Disassemble 3 instructions from the start of @code{main} in mixed mode:
19994 -data-disassemble -f basics.c -l 32 -n 3 -- 1
19996 src_and_asm_line=@{line="31",
19997 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
19998 testsuite/gdb.mi/basics.c",line_asm_insn=[
19999 @{address="0x000107bc",func-name="main",offset="0",
20000 inst="save %sp, -112, %sp"@}]@},
20001 src_and_asm_line=@{line="32",
20002 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20003 testsuite/gdb.mi/basics.c",line_asm_insn=[
20004 @{address="0x000107c0",func-name="main",offset="4",
20005 inst="mov 2, %o0"@},
20006 @{address="0x000107c4",func-name="main",offset="8",
20007 inst="sethi %hi(0x11800), %o2"@}]@}]
20012 @subheading The @code{-data-evaluate-expression} Command
20013 @findex -data-evaluate-expression
20015 @subsubheading Synopsis
20018 -data-evaluate-expression @var{expr}
20021 Evaluate @var{expr} as an expression. The expression could contain an
20022 inferior function call. The function call will execute synchronously.
20023 If the expression contains spaces, it must be enclosed in double quotes.
20025 @subsubheading @value{GDBN} Command
20027 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20028 @samp{call}. In @code{gdbtk} only, there's a corresponding
20029 @samp{gdb_eval} command.
20031 @subsubheading Example
20033 In the following example, the numbers that precede the commands are the
20034 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20035 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20039 211-data-evaluate-expression A
20042 311-data-evaluate-expression &A
20043 311^done,value="0xefffeb7c"
20045 411-data-evaluate-expression A+3
20048 511-data-evaluate-expression "A + 3"
20054 @subheading The @code{-data-list-changed-registers} Command
20055 @findex -data-list-changed-registers
20057 @subsubheading Synopsis
20060 -data-list-changed-registers
20063 Display a list of the registers that have changed.
20065 @subsubheading @value{GDBN} Command
20067 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20068 has the corresponding command @samp{gdb_changed_register_list}.
20070 @subsubheading Example
20072 On a PPC MBX board:
20080 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20081 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20083 -data-list-changed-registers
20084 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20085 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20086 "24","25","26","27","28","30","31","64","65","66","67","69"]
20091 @subheading The @code{-data-list-register-names} Command
20092 @findex -data-list-register-names
20094 @subsubheading Synopsis
20097 -data-list-register-names [ ( @var{regno} )+ ]
20100 Show a list of register names for the current target. If no arguments
20101 are given, it shows a list of the names of all the registers. If
20102 integer numbers are given as arguments, it will print a list of the
20103 names of the registers corresponding to the arguments. To ensure
20104 consistency between a register name and its number, the output list may
20105 include empty register names.
20107 @subsubheading @value{GDBN} Command
20109 @value{GDBN} does not have a command which corresponds to
20110 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20111 corresponding command @samp{gdb_regnames}.
20113 @subsubheading Example
20115 For the PPC MBX board:
20118 -data-list-register-names
20119 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20120 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20121 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20122 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20123 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20124 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20125 "", "pc","ps","cr","lr","ctr","xer"]
20127 -data-list-register-names 1 2 3
20128 ^done,register-names=["r1","r2","r3"]
20132 @subheading The @code{-data-list-register-values} Command
20133 @findex -data-list-register-values
20135 @subsubheading Synopsis
20138 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20141 Display the registers' contents. @var{fmt} is the format according to
20142 which the registers' contents are to be returned, followed by an optional
20143 list of numbers specifying the registers to display. A missing list of
20144 numbers indicates that the contents of all the registers must be returned.
20146 Allowed formats for @var{fmt} are:
20163 @subsubheading @value{GDBN} Command
20165 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20166 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20168 @subsubheading Example
20170 For a PPC MBX board (note: line breaks are for readability only, they
20171 don't appear in the actual output):
20175 -data-list-register-values r 64 65
20176 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20177 @{number="65",value="0x00029002"@}]
20179 -data-list-register-values x
20180 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20181 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20182 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20183 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20184 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20185 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20186 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20187 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20188 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20189 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20190 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20191 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20192 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20193 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20194 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20195 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20196 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20197 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20198 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20199 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20200 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20201 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20202 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20203 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20204 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20205 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20206 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20207 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20208 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20209 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20210 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20211 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20212 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20213 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20214 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20215 @{number="69",value="0x20002b03"@}]
20220 @subheading The @code{-data-read-memory} Command
20221 @findex -data-read-memory
20223 @subsubheading Synopsis
20226 -data-read-memory [ -o @var{byte-offset} ]
20227 @var{address} @var{word-format} @var{word-size}
20228 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20235 @item @var{address}
20236 An expression specifying the address of the first memory word to be
20237 read. Complex expressions containing embedded white space should be
20238 quoted using the C convention.
20240 @item @var{word-format}
20241 The format to be used to print the memory words. The notation is the
20242 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20245 @item @var{word-size}
20246 The size of each memory word in bytes.
20248 @item @var{nr-rows}
20249 The number of rows in the output table.
20251 @item @var{nr-cols}
20252 The number of columns in the output table.
20255 If present, indicates that each row should include an @sc{ascii} dump. The
20256 value of @var{aschar} is used as a padding character when a byte is not a
20257 member of the printable @sc{ascii} character set (printable @sc{ascii}
20258 characters are those whose code is between 32 and 126, inclusively).
20260 @item @var{byte-offset}
20261 An offset to add to the @var{address} before fetching memory.
20264 This command displays memory contents as a table of @var{nr-rows} by
20265 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20266 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20267 (returned as @samp{total-bytes}). Should less than the requested number
20268 of bytes be returned by the target, the missing words are identified
20269 using @samp{N/A}. The number of bytes read from the target is returned
20270 in @samp{nr-bytes} and the starting address used to read memory in
20273 The address of the next/previous row or page is available in
20274 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20277 @subsubheading @value{GDBN} Command
20279 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20280 @samp{gdb_get_mem} memory read command.
20282 @subsubheading Example
20284 Read six bytes of memory starting at @code{bytes+6} but then offset by
20285 @code{-6} bytes. Format as three rows of two columns. One byte per
20286 word. Display each word in hex.
20290 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20291 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20292 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20293 prev-page="0x0000138a",memory=[
20294 @{addr="0x00001390",data=["0x00","0x01"]@},
20295 @{addr="0x00001392",data=["0x02","0x03"]@},
20296 @{addr="0x00001394",data=["0x04","0x05"]@}]
20300 Read two bytes of memory starting at address @code{shorts + 64} and
20301 display as a single word formatted in decimal.
20305 5-data-read-memory shorts+64 d 2 1 1
20306 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20307 next-row="0x00001512",prev-row="0x0000150e",
20308 next-page="0x00001512",prev-page="0x0000150e",memory=[
20309 @{addr="0x00001510",data=["128"]@}]
20313 Read thirty two bytes of memory starting at @code{bytes+16} and format
20314 as eight rows of four columns. Include a string encoding with @samp{x}
20315 used as the non-printable character.
20319 4-data-read-memory bytes+16 x 1 8 4 x
20320 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20321 next-row="0x000013c0",prev-row="0x0000139c",
20322 next-page="0x000013c0",prev-page="0x00001380",memory=[
20323 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20324 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20325 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20326 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20327 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20328 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20329 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20330 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20334 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20335 @node GDB/MI Tracepoint Commands
20336 @section @sc{gdb/mi} Tracepoint Commands
20338 The tracepoint commands are not yet implemented.
20340 @c @subheading -trace-actions
20342 @c @subheading -trace-delete
20344 @c @subheading -trace-disable
20346 @c @subheading -trace-dump
20348 @c @subheading -trace-enable
20350 @c @subheading -trace-exists
20352 @c @subheading -trace-find
20354 @c @subheading -trace-frame-number
20356 @c @subheading -trace-info
20358 @c @subheading -trace-insert
20360 @c @subheading -trace-list
20362 @c @subheading -trace-pass-count
20364 @c @subheading -trace-save
20366 @c @subheading -trace-start
20368 @c @subheading -trace-stop
20371 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20372 @node GDB/MI Symbol Query
20373 @section @sc{gdb/mi} Symbol Query Commands
20376 @subheading The @code{-symbol-info-address} Command
20377 @findex -symbol-info-address
20379 @subsubheading Synopsis
20382 -symbol-info-address @var{symbol}
20385 Describe where @var{symbol} is stored.
20387 @subsubheading @value{GDBN} Command
20389 The corresponding @value{GDBN} command is @samp{info address}.
20391 @subsubheading Example
20395 @subheading The @code{-symbol-info-file} Command
20396 @findex -symbol-info-file
20398 @subsubheading Synopsis
20404 Show the file for the symbol.
20406 @subsubheading @value{GDBN} Command
20408 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20409 @samp{gdb_find_file}.
20411 @subsubheading Example
20415 @subheading The @code{-symbol-info-function} Command
20416 @findex -symbol-info-function
20418 @subsubheading Synopsis
20421 -symbol-info-function
20424 Show which function the symbol lives in.
20426 @subsubheading @value{GDBN} Command
20428 @samp{gdb_get_function} in @code{gdbtk}.
20430 @subsubheading Example
20434 @subheading The @code{-symbol-info-line} Command
20435 @findex -symbol-info-line
20437 @subsubheading Synopsis
20443 Show the core addresses of the code for a source line.
20445 @subsubheading @value{GDBN} Command
20447 The corresponding @value{GDBN} command is @samp{info line}.
20448 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20450 @subsubheading Example
20454 @subheading The @code{-symbol-info-symbol} Command
20455 @findex -symbol-info-symbol
20457 @subsubheading Synopsis
20460 -symbol-info-symbol @var{addr}
20463 Describe what symbol is at location @var{addr}.
20465 @subsubheading @value{GDBN} Command
20467 The corresponding @value{GDBN} command is @samp{info symbol}.
20469 @subsubheading Example
20473 @subheading The @code{-symbol-list-functions} Command
20474 @findex -symbol-list-functions
20476 @subsubheading Synopsis
20479 -symbol-list-functions
20482 List the functions in the executable.
20484 @subsubheading @value{GDBN} Command
20486 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20487 @samp{gdb_search} in @code{gdbtk}.
20489 @subsubheading Example
20493 @subheading The @code{-symbol-list-lines} Command
20494 @findex -symbol-list-lines
20496 @subsubheading Synopsis
20499 -symbol-list-lines @var{filename}
20502 Print the list of lines that contain code and their associated program
20503 addresses for the given source filename. The entries are sorted in
20504 ascending PC order.
20506 @subsubheading @value{GDBN} Command
20508 There is no corresponding @value{GDBN} command.
20510 @subsubheading Example
20513 -symbol-list-lines basics.c
20514 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20519 @subheading The @code{-symbol-list-types} Command
20520 @findex -symbol-list-types
20522 @subsubheading Synopsis
20528 List all the type names.
20530 @subsubheading @value{GDBN} Command
20532 The corresponding commands are @samp{info types} in @value{GDBN},
20533 @samp{gdb_search} in @code{gdbtk}.
20535 @subsubheading Example
20539 @subheading The @code{-symbol-list-variables} Command
20540 @findex -symbol-list-variables
20542 @subsubheading Synopsis
20545 -symbol-list-variables
20548 List all the global and static variable names.
20550 @subsubheading @value{GDBN} Command
20552 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20554 @subsubheading Example
20558 @subheading The @code{-symbol-locate} Command
20559 @findex -symbol-locate
20561 @subsubheading Synopsis
20567 @subsubheading @value{GDBN} Command
20569 @samp{gdb_loc} in @code{gdbtk}.
20571 @subsubheading Example
20575 @subheading The @code{-symbol-type} Command
20576 @findex -symbol-type
20578 @subsubheading Synopsis
20581 -symbol-type @var{variable}
20584 Show type of @var{variable}.
20586 @subsubheading @value{GDBN} Command
20588 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20589 @samp{gdb_obj_variable}.
20591 @subsubheading Example
20595 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20596 @node GDB/MI File Commands
20597 @section @sc{gdb/mi} File Commands
20599 This section describes the GDB/MI commands to specify executable file names
20600 and to read in and obtain symbol table information.
20602 @subheading The @code{-file-exec-and-symbols} Command
20603 @findex -file-exec-and-symbols
20605 @subsubheading Synopsis
20608 -file-exec-and-symbols @var{file}
20611 Specify the executable file to be debugged. This file is the one from
20612 which the symbol table is also read. If no file is specified, the
20613 command clears the executable and symbol information. If breakpoints
20614 are set when using this command with no arguments, @value{GDBN} will produce
20615 error messages. Otherwise, no output is produced, except a completion
20618 @subsubheading @value{GDBN} Command
20620 The corresponding @value{GDBN} command is @samp{file}.
20622 @subsubheading Example
20626 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20632 @subheading The @code{-file-exec-file} Command
20633 @findex -file-exec-file
20635 @subsubheading Synopsis
20638 -file-exec-file @var{file}
20641 Specify the executable file to be debugged. Unlike
20642 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20643 from this file. If used without argument, @value{GDBN} clears the information
20644 about the executable file. No output is produced, except a completion
20647 @subsubheading @value{GDBN} Command
20649 The corresponding @value{GDBN} command is @samp{exec-file}.
20651 @subsubheading Example
20655 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20661 @subheading The @code{-file-list-exec-sections} Command
20662 @findex -file-list-exec-sections
20664 @subsubheading Synopsis
20667 -file-list-exec-sections
20670 List the sections of the current executable file.
20672 @subsubheading @value{GDBN} Command
20674 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20675 information as this command. @code{gdbtk} has a corresponding command
20676 @samp{gdb_load_info}.
20678 @subsubheading Example
20682 @subheading The @code{-file-list-exec-source-file} Command
20683 @findex -file-list-exec-source-file
20685 @subsubheading Synopsis
20688 -file-list-exec-source-file
20691 List the line number, the current source file, and the absolute path
20692 to the current source file for the current executable.
20694 @subsubheading @value{GDBN} Command
20696 The @value{GDBN} equivalent is @samp{info source}
20698 @subsubheading Example
20702 123-file-list-exec-source-file
20703 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20708 @subheading The @code{-file-list-exec-source-files} Command
20709 @findex -file-list-exec-source-files
20711 @subsubheading Synopsis
20714 -file-list-exec-source-files
20717 List the source files for the current executable.
20719 It will always output the filename, but only when GDB can find the absolute
20720 file name of a source file, will it output the fullname.
20722 @subsubheading @value{GDBN} Command
20724 The @value{GDBN} equivalent is @samp{info sources}.
20725 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20727 @subsubheading Example
20730 -file-list-exec-source-files
20732 @{file=foo.c,fullname=/home/foo.c@},
20733 @{file=/home/bar.c,fullname=/home/bar.c@},
20734 @{file=gdb_could_not_find_fullpath.c@}]
20738 @subheading The @code{-file-list-shared-libraries} Command
20739 @findex -file-list-shared-libraries
20741 @subsubheading Synopsis
20744 -file-list-shared-libraries
20747 List the shared libraries in the program.
20749 @subsubheading @value{GDBN} Command
20751 The corresponding @value{GDBN} command is @samp{info shared}.
20753 @subsubheading Example
20757 @subheading The @code{-file-list-symbol-files} Command
20758 @findex -file-list-symbol-files
20760 @subsubheading Synopsis
20763 -file-list-symbol-files
20768 @subsubheading @value{GDBN} Command
20770 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20772 @subsubheading Example
20776 @subheading The @code{-file-symbol-file} Command
20777 @findex -file-symbol-file
20779 @subsubheading Synopsis
20782 -file-symbol-file @var{file}
20785 Read symbol table info from the specified @var{file} argument. When
20786 used without arguments, clears @value{GDBN}'s symbol table info. No output is
20787 produced, except for a completion notification.
20789 @subsubheading @value{GDBN} Command
20791 The corresponding @value{GDBN} command is @samp{symbol-file}.
20793 @subsubheading Example
20797 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20803 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20804 @node GDB/MI Memory Overlay Commands
20805 @section @sc{gdb/mi} Memory Overlay Commands
20807 The memory overlay commands are not implemented.
20809 @c @subheading -overlay-auto
20811 @c @subheading -overlay-list-mapping-state
20813 @c @subheading -overlay-list-overlays
20815 @c @subheading -overlay-map
20817 @c @subheading -overlay-off
20819 @c @subheading -overlay-on
20821 @c @subheading -overlay-unmap
20823 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20824 @node GDB/MI Signal Handling Commands
20825 @section @sc{gdb/mi} Signal Handling Commands
20827 Signal handling commands are not implemented.
20829 @c @subheading -signal-handle
20831 @c @subheading -signal-list-handle-actions
20833 @c @subheading -signal-list-signal-types
20837 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20838 @node GDB/MI Target Manipulation
20839 @section @sc{gdb/mi} Target Manipulation Commands
20842 @subheading The @code{-target-attach} Command
20843 @findex -target-attach
20845 @subsubheading Synopsis
20848 -target-attach @var{pid} | @var{file}
20851 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
20853 @subsubheading @value{GDBN} command
20855 The corresponding @value{GDBN} command is @samp{attach}.
20857 @subsubheading Example
20861 @subheading The @code{-target-compare-sections} Command
20862 @findex -target-compare-sections
20864 @subsubheading Synopsis
20867 -target-compare-sections [ @var{section} ]
20870 Compare data of section @var{section} on target to the exec file.
20871 Without the argument, all sections are compared.
20873 @subsubheading @value{GDBN} Command
20875 The @value{GDBN} equivalent is @samp{compare-sections}.
20877 @subsubheading Example
20881 @subheading The @code{-target-detach} Command
20882 @findex -target-detach
20884 @subsubheading Synopsis
20890 Detach from the remote target which normally resumes its execution.
20893 @subsubheading @value{GDBN} command
20895 The corresponding @value{GDBN} command is @samp{detach}.
20897 @subsubheading Example
20907 @subheading The @code{-target-disconnect} Command
20908 @findex -target-disconnect
20910 @subsubheading Synopsis
20916 Disconnect from the remote target. There's no output and the target is
20917 generally not resumed.
20919 @subsubheading @value{GDBN} command
20921 The corresponding @value{GDBN} command is @samp{disconnect}.
20923 @subsubheading Example
20933 @subheading The @code{-target-download} Command
20934 @findex -target-download
20936 @subsubheading Synopsis
20942 Loads the executable onto the remote target.
20943 It prints out an update message every half second, which includes the fields:
20947 The name of the section.
20949 The size of what has been sent so far for that section.
20951 The size of the section.
20953 The total size of what was sent so far (the current and the previous sections).
20955 The size of the overall executable to download.
20959 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
20960 @sc{gdb/mi} Output Syntax}).
20962 In addition, it prints the name and size of the sections, as they are
20963 downloaded. These messages include the following fields:
20967 The name of the section.
20969 The size of the section.
20971 The size of the overall executable to download.
20975 At the end, a summary is printed.
20977 @subsubheading @value{GDBN} Command
20979 The corresponding @value{GDBN} command is @samp{load}.
20981 @subsubheading Example
20983 Note: each status message appears on a single line. Here the messages
20984 have been broken down so that they can fit onto a page.
20989 +download,@{section=".text",section-size="6668",total-size="9880"@}
20990 +download,@{section=".text",section-sent="512",section-size="6668",
20991 total-sent="512",total-size="9880"@}
20992 +download,@{section=".text",section-sent="1024",section-size="6668",
20993 total-sent="1024",total-size="9880"@}
20994 +download,@{section=".text",section-sent="1536",section-size="6668",
20995 total-sent="1536",total-size="9880"@}
20996 +download,@{section=".text",section-sent="2048",section-size="6668",
20997 total-sent="2048",total-size="9880"@}
20998 +download,@{section=".text",section-sent="2560",section-size="6668",
20999 total-sent="2560",total-size="9880"@}
21000 +download,@{section=".text",section-sent="3072",section-size="6668",
21001 total-sent="3072",total-size="9880"@}
21002 +download,@{section=".text",section-sent="3584",section-size="6668",
21003 total-sent="3584",total-size="9880"@}
21004 +download,@{section=".text",section-sent="4096",section-size="6668",
21005 total-sent="4096",total-size="9880"@}
21006 +download,@{section=".text",section-sent="4608",section-size="6668",
21007 total-sent="4608",total-size="9880"@}
21008 +download,@{section=".text",section-sent="5120",section-size="6668",
21009 total-sent="5120",total-size="9880"@}
21010 +download,@{section=".text",section-sent="5632",section-size="6668",
21011 total-sent="5632",total-size="9880"@}
21012 +download,@{section=".text",section-sent="6144",section-size="6668",
21013 total-sent="6144",total-size="9880"@}
21014 +download,@{section=".text",section-sent="6656",section-size="6668",
21015 total-sent="6656",total-size="9880"@}
21016 +download,@{section=".init",section-size="28",total-size="9880"@}
21017 +download,@{section=".fini",section-size="28",total-size="9880"@}
21018 +download,@{section=".data",section-size="3156",total-size="9880"@}
21019 +download,@{section=".data",section-sent="512",section-size="3156",
21020 total-sent="7236",total-size="9880"@}
21021 +download,@{section=".data",section-sent="1024",section-size="3156",
21022 total-sent="7748",total-size="9880"@}
21023 +download,@{section=".data",section-sent="1536",section-size="3156",
21024 total-sent="8260",total-size="9880"@}
21025 +download,@{section=".data",section-sent="2048",section-size="3156",
21026 total-sent="8772",total-size="9880"@}
21027 +download,@{section=".data",section-sent="2560",section-size="3156",
21028 total-sent="9284",total-size="9880"@}
21029 +download,@{section=".data",section-sent="3072",section-size="3156",
21030 total-sent="9796",total-size="9880"@}
21031 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21037 @subheading The @code{-target-exec-status} Command
21038 @findex -target-exec-status
21040 @subsubheading Synopsis
21043 -target-exec-status
21046 Provide information on the state of the target (whether it is running or
21047 not, for instance).
21049 @subsubheading @value{GDBN} Command
21051 There's no equivalent @value{GDBN} command.
21053 @subsubheading Example
21057 @subheading The @code{-target-list-available-targets} Command
21058 @findex -target-list-available-targets
21060 @subsubheading Synopsis
21063 -target-list-available-targets
21066 List the possible targets to connect to.
21068 @subsubheading @value{GDBN} Command
21070 The corresponding @value{GDBN} command is @samp{help target}.
21072 @subsubheading Example
21076 @subheading The @code{-target-list-current-targets} Command
21077 @findex -target-list-current-targets
21079 @subsubheading Synopsis
21082 -target-list-current-targets
21085 Describe the current target.
21087 @subsubheading @value{GDBN} Command
21089 The corresponding information is printed by @samp{info file} (among
21092 @subsubheading Example
21096 @subheading The @code{-target-list-parameters} Command
21097 @findex -target-list-parameters
21099 @subsubheading Synopsis
21102 -target-list-parameters
21107 @subsubheading @value{GDBN} Command
21111 @subsubheading Example
21115 @subheading The @code{-target-select} Command
21116 @findex -target-select
21118 @subsubheading Synopsis
21121 -target-select @var{type} @var{parameters @dots{}}
21124 Connect @value{GDBN} to the remote target. This command takes two args:
21128 The type of target, for instance @samp{async}, @samp{remote}, etc.
21129 @item @var{parameters}
21130 Device names, host names and the like. @xref{Target Commands, ,
21131 Commands for managing targets}, for more details.
21134 The output is a connection notification, followed by the address at
21135 which the target program is, in the following form:
21138 ^connected,addr="@var{address}",func="@var{function name}",
21139 args=[@var{arg list}]
21142 @subsubheading @value{GDBN} Command
21144 The corresponding @value{GDBN} command is @samp{target}.
21146 @subsubheading Example
21150 -target-select async /dev/ttya
21151 ^connected,addr="0xfe00a300",func="??",args=[]
21155 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21156 @node GDB/MI Miscellaneous Commands
21157 @section Miscellaneous @sc{gdb/mi} Commands
21159 @c @subheading -gdb-complete
21161 @subheading The @code{-gdb-exit} Command
21164 @subsubheading Synopsis
21170 Exit @value{GDBN} immediately.
21172 @subsubheading @value{GDBN} Command
21174 Approximately corresponds to @samp{quit}.
21176 @subsubheading Example
21185 @subheading The @code{-exec-abort} Command
21186 @findex -exec-abort
21188 @subsubheading Synopsis
21194 Kill the inferior running program.
21196 @subsubheading @value{GDBN} Command
21198 The corresponding @value{GDBN} command is @samp{kill}.
21200 @subsubheading Example
21204 @subheading The @code{-gdb-set} Command
21207 @subsubheading Synopsis
21213 Set an internal @value{GDBN} variable.
21214 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21216 @subsubheading @value{GDBN} Command
21218 The corresponding @value{GDBN} command is @samp{set}.
21220 @subsubheading Example
21230 @subheading The @code{-gdb-show} Command
21233 @subsubheading Synopsis
21239 Show the current value of a @value{GDBN} variable.
21241 @subsubheading @value{GDBN} command
21243 The corresponding @value{GDBN} command is @samp{show}.
21245 @subsubheading Example
21254 @c @subheading -gdb-source
21257 @subheading The @code{-gdb-version} Command
21258 @findex -gdb-version
21260 @subsubheading Synopsis
21266 Show version information for @value{GDBN}. Used mostly in testing.
21268 @subsubheading @value{GDBN} Command
21270 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21271 default shows this information when you start an interactive session.
21273 @subsubheading Example
21275 @c This example modifies the actual output from GDB to avoid overfull
21281 ~Copyright 2000 Free Software Foundation, Inc.
21282 ~GDB is free software, covered by the GNU General Public License, and
21283 ~you are welcome to change it and/or distribute copies of it under
21284 ~ certain conditions.
21285 ~Type "show copying" to see the conditions.
21286 ~There is absolutely no warranty for GDB. Type "show warranty" for
21288 ~This GDB was configured as
21289 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21294 @subheading The @code{-interpreter-exec} Command
21295 @findex -interpreter-exec
21297 @subheading Synopsis
21300 -interpreter-exec @var{interpreter} @var{command}
21302 @anchor{-interpreter-exec}
21304 Execute the specified @var{command} in the given @var{interpreter}.
21306 @subheading @value{GDBN} Command
21308 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21310 @subheading Example
21314 -interpreter-exec console "break main"
21315 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21316 &"During symbol reading, bad structure-type format.\n"
21317 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21322 @subheading The @code{-inferior-tty-set} Command
21323 @findex -inferior-tty-set
21325 @subheading Synopsis
21328 -inferior-tty-set /dev/pts/1
21331 Set terminal for future runs of the program being debugged.
21333 @subheading @value{GDBN} Command
21335 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21337 @subheading Example
21341 -inferior-tty-set /dev/pts/1
21346 @subheading The @code{-inferior-tty-show} Command
21347 @findex -inferior-tty-show
21349 @subheading Synopsis
21355 Show terminal for future runs of program being debugged.
21357 @subheading @value{GDBN} Command
21359 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21361 @subheading Example
21365 -inferior-tty-set /dev/pts/1
21369 ^done,inferior_tty_terminal="/dev/pts/1"
21374 @chapter @value{GDBN} Annotations
21376 This chapter describes annotations in @value{GDBN}. Annotations were
21377 designed to interface @value{GDBN} to graphical user interfaces or other
21378 similar programs which want to interact with @value{GDBN} at a
21379 relatively high level.
21381 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
21385 This is Edition @value{EDITION}, @value{DATE}.
21389 * Annotations Overview:: What annotations are; the general syntax.
21390 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21391 * Errors:: Annotations for error messages.
21392 * Invalidation:: Some annotations describe things now invalid.
21393 * Annotations for Running::
21394 Whether the program is running, how it stopped, etc.
21395 * Source Annotations:: Annotations describing source code.
21398 @node Annotations Overview
21399 @section What is an Annotation?
21400 @cindex annotations
21402 Annotations start with a newline character, two @samp{control-z}
21403 characters, and the name of the annotation. If there is no additional
21404 information associated with this annotation, the name of the annotation
21405 is followed immediately by a newline. If there is additional
21406 information, the name of the annotation is followed by a space, the
21407 additional information, and a newline. The additional information
21408 cannot contain newline characters.
21410 Any output not beginning with a newline and two @samp{control-z}
21411 characters denotes literal output from @value{GDBN}. Currently there is
21412 no need for @value{GDBN} to output a newline followed by two
21413 @samp{control-z} characters, but if there was such a need, the
21414 annotations could be extended with an @samp{escape} annotation which
21415 means those three characters as output.
21417 The annotation @var{level}, which is specified using the
21418 @option{--annotate} command line option (@pxref{Mode Options}), controls
21419 how much information @value{GDBN} prints together with its prompt,
21420 values of expressions, source lines, and other types of output. Level 0
21421 is for no anntations, level 1 is for use when @value{GDBN} is run as a
21422 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21423 for programs that control @value{GDBN}, and level 2 annotations have
21424 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21425 Interface, annotate, GDB's Obsolete Annotations}).
21428 @kindex set annotate
21429 @item set annotate @var{level}
21430 The @value{GDBN} command @code{set annotate} sets the level of
21431 annotations to the specified @var{level}.
21433 @item show annotate
21434 @kindex show annotate
21435 Show the current annotation level.
21438 This chapter describes level 3 annotations.
21440 A simple example of starting up @value{GDBN} with annotations is:
21443 $ @kbd{gdb --annotate=3}
21445 Copyright 2003 Free Software Foundation, Inc.
21446 GDB is free software, covered by the GNU General Public License,
21447 and you are welcome to change it and/or distribute copies of it
21448 under certain conditions.
21449 Type "show copying" to see the conditions.
21450 There is absolutely no warranty for GDB. Type "show warranty"
21452 This GDB was configured as "i386-pc-linux-gnu"
21463 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21464 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21465 denotes a @samp{control-z} character) are annotations; the rest is
21466 output from @value{GDBN}.
21469 @section Annotation for @value{GDBN} Input
21471 @cindex annotations for prompts
21472 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21473 to know when to send output, when the output from a given command is
21476 Different kinds of input each have a different @dfn{input type}. Each
21477 input type has three annotations: a @code{pre-} annotation, which
21478 denotes the beginning of any prompt which is being output, a plain
21479 annotation, which denotes the end of the prompt, and then a @code{post-}
21480 annotation which denotes the end of any echo which may (or may not) be
21481 associated with the input. For example, the @code{prompt} input type
21482 features the following annotations:
21490 The input types are
21495 @findex post-prompt
21497 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21499 @findex pre-commands
21501 @findex post-commands
21503 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21504 command. The annotations are repeated for each command which is input.
21506 @findex pre-overload-choice
21507 @findex overload-choice
21508 @findex post-overload-choice
21509 @item overload-choice
21510 When @value{GDBN} wants the user to select between various overloaded functions.
21516 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21518 @findex pre-prompt-for-continue
21519 @findex prompt-for-continue
21520 @findex post-prompt-for-continue
21521 @item prompt-for-continue
21522 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21523 expect this to work well; instead use @code{set height 0} to disable
21524 prompting. This is because the counting of lines is buggy in the
21525 presence of annotations.
21530 @cindex annotations for errors, warnings and interrupts
21537 This annotation occurs right before @value{GDBN} responds to an interrupt.
21544 This annotation occurs right before @value{GDBN} responds to an error.
21546 Quit and error annotations indicate that any annotations which @value{GDBN} was
21547 in the middle of may end abruptly. For example, if a
21548 @code{value-history-begin} annotation is followed by a @code{error}, one
21549 cannot expect to receive the matching @code{value-history-end}. One
21550 cannot expect not to receive it either, however; an error annotation
21551 does not necessarily mean that @value{GDBN} is immediately returning all the way
21554 @findex error-begin
21555 A quit or error annotation may be preceded by
21561 Any output between that and the quit or error annotation is the error
21564 Warning messages are not yet annotated.
21565 @c If we want to change that, need to fix warning(), type_error(),
21566 @c range_error(), and possibly other places.
21569 @section Invalidation Notices
21571 @cindex annotations for invalidation messages
21572 The following annotations say that certain pieces of state may have
21576 @findex frames-invalid
21577 @item ^Z^Zframes-invalid
21579 The frames (for example, output from the @code{backtrace} command) may
21582 @findex breakpoints-invalid
21583 @item ^Z^Zbreakpoints-invalid
21585 The breakpoints may have changed. For example, the user just added or
21586 deleted a breakpoint.
21589 @node Annotations for Running
21590 @section Running the Program
21591 @cindex annotations for running programs
21595 When the program starts executing due to a @value{GDBN} command such as
21596 @code{step} or @code{continue},
21602 is output. When the program stops,
21608 is output. Before the @code{stopped} annotation, a variety of
21609 annotations describe how the program stopped.
21613 @item ^Z^Zexited @var{exit-status}
21614 The program exited, and @var{exit-status} is the exit status (zero for
21615 successful exit, otherwise nonzero).
21618 @findex signal-name
21619 @findex signal-name-end
21620 @findex signal-string
21621 @findex signal-string-end
21622 @item ^Z^Zsignalled
21623 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21624 annotation continues:
21630 ^Z^Zsignal-name-end
21634 ^Z^Zsignal-string-end
21639 where @var{name} is the name of the signal, such as @code{SIGILL} or
21640 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21641 as @code{Illegal Instruction} or @code{Segmentation fault}.
21642 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21643 user's benefit and have no particular format.
21647 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21648 just saying that the program received the signal, not that it was
21649 terminated with it.
21652 @item ^Z^Zbreakpoint @var{number}
21653 The program hit breakpoint number @var{number}.
21656 @item ^Z^Zwatchpoint @var{number}
21657 The program hit watchpoint number @var{number}.
21660 @node Source Annotations
21661 @section Displaying Source
21662 @cindex annotations for source display
21665 The following annotation is used instead of displaying source code:
21668 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21671 where @var{filename} is an absolute file name indicating which source
21672 file, @var{line} is the line number within that file (where 1 is the
21673 first line in the file), @var{character} is the character position
21674 within the file (where 0 is the first character in the file) (for most
21675 debug formats this will necessarily point to the beginning of a line),
21676 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21677 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21678 @var{addr} is the address in the target program associated with the
21679 source which is being displayed. @var{addr} is in the form @samp{0x}
21680 followed by one or more lowercase hex digits (note that this does not
21681 depend on the language).
21684 @chapter Reporting Bugs in @value{GDBN}
21685 @cindex bugs in @value{GDBN}
21686 @cindex reporting bugs in @value{GDBN}
21688 Your bug reports play an essential role in making @value{GDBN} reliable.
21690 Reporting a bug may help you by bringing a solution to your problem, or it
21691 may not. But in any case the principal function of a bug report is to help
21692 the entire community by making the next version of @value{GDBN} work better. Bug
21693 reports are your contribution to the maintenance of @value{GDBN}.
21695 In order for a bug report to serve its purpose, you must include the
21696 information that enables us to fix the bug.
21699 * Bug Criteria:: Have you found a bug?
21700 * Bug Reporting:: How to report bugs
21704 @section Have you found a bug?
21705 @cindex bug criteria
21707 If you are not sure whether you have found a bug, here are some guidelines:
21710 @cindex fatal signal
21711 @cindex debugger crash
21712 @cindex crash of debugger
21714 If the debugger gets a fatal signal, for any input whatever, that is a
21715 @value{GDBN} bug. Reliable debuggers never crash.
21717 @cindex error on valid input
21719 If @value{GDBN} produces an error message for valid input, that is a
21720 bug. (Note that if you're cross debugging, the problem may also be
21721 somewhere in the connection to the target.)
21723 @cindex invalid input
21725 If @value{GDBN} does not produce an error message for invalid input,
21726 that is a bug. However, you should note that your idea of
21727 ``invalid input'' might be our idea of ``an extension'' or ``support
21728 for traditional practice''.
21731 If you are an experienced user of debugging tools, your suggestions
21732 for improvement of @value{GDBN} are welcome in any case.
21735 @node Bug Reporting
21736 @section How to report bugs
21737 @cindex bug reports
21738 @cindex @value{GDBN} bugs, reporting
21740 A number of companies and individuals offer support for @sc{gnu} products.
21741 If you obtained @value{GDBN} from a support organization, we recommend you
21742 contact that organization first.
21744 You can find contact information for many support companies and
21745 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21747 @c should add a web page ref...
21749 In any event, we also recommend that you submit bug reports for
21750 @value{GDBN}. The prefered method is to submit them directly using
21751 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21752 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21755 @strong{Do not send bug reports to @samp{info-gdb}, or to
21756 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21757 not want to receive bug reports. Those that do have arranged to receive
21760 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21761 serves as a repeater. The mailing list and the newsgroup carry exactly
21762 the same messages. Often people think of posting bug reports to the
21763 newsgroup instead of mailing them. This appears to work, but it has one
21764 problem which can be crucial: a newsgroup posting often lacks a mail
21765 path back to the sender. Thus, if we need to ask for more information,
21766 we may be unable to reach you. For this reason, it is better to send
21767 bug reports to the mailing list.
21769 The fundamental principle of reporting bugs usefully is this:
21770 @strong{report all the facts}. If you are not sure whether to state a
21771 fact or leave it out, state it!
21773 Often people omit facts because they think they know what causes the
21774 problem and assume that some details do not matter. Thus, you might
21775 assume that the name of the variable you use in an example does not matter.
21776 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21777 stray memory reference which happens to fetch from the location where that
21778 name is stored in memory; perhaps, if the name were different, the contents
21779 of that location would fool the debugger into doing the right thing despite
21780 the bug. Play it safe and give a specific, complete example. That is the
21781 easiest thing for you to do, and the most helpful.
21783 Keep in mind that the purpose of a bug report is to enable us to fix the
21784 bug. It may be that the bug has been reported previously, but neither
21785 you nor we can know that unless your bug report is complete and
21788 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21789 bell?'' Those bug reports are useless, and we urge everyone to
21790 @emph{refuse to respond to them} except to chide the sender to report
21793 To enable us to fix the bug, you should include all these things:
21797 The version of @value{GDBN}. @value{GDBN} announces it if you start
21798 with no arguments; you can also print it at any time using @code{show
21801 Without this, we will not know whether there is any point in looking for
21802 the bug in the current version of @value{GDBN}.
21805 The type of machine you are using, and the operating system name and
21809 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21810 ``@value{GCC}--2.8.1''.
21813 What compiler (and its version) was used to compile the program you are
21814 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21815 C Compiler''. For GCC, you can say @code{gcc --version} to get this
21816 information; for other compilers, see the documentation for those
21820 The command arguments you gave the compiler to compile your example and
21821 observe the bug. For example, did you use @samp{-O}? To guarantee
21822 you will not omit something important, list them all. A copy of the
21823 Makefile (or the output from make) is sufficient.
21825 If we were to try to guess the arguments, we would probably guess wrong
21826 and then we might not encounter the bug.
21829 A complete input script, and all necessary source files, that will
21833 A description of what behavior you observe that you believe is
21834 incorrect. For example, ``It gets a fatal signal.''
21836 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21837 will certainly notice it. But if the bug is incorrect output, we might
21838 not notice unless it is glaringly wrong. You might as well not give us
21839 a chance to make a mistake.
21841 Even if the problem you experience is a fatal signal, you should still
21842 say so explicitly. Suppose something strange is going on, such as, your
21843 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21844 the C library on your system. (This has happened!) Your copy might
21845 crash and ours would not. If you told us to expect a crash, then when
21846 ours fails to crash, we would know that the bug was not happening for
21847 us. If you had not told us to expect a crash, then we would not be able
21848 to draw any conclusion from our observations.
21851 @cindex recording a session script
21852 To collect all this information, you can use a session recording program
21853 such as @command{script}, which is available on many Unix systems.
21854 Just run your @value{GDBN} session inside @command{script} and then
21855 include the @file{typescript} file with your bug report.
21857 Another way to record a @value{GDBN} session is to run @value{GDBN}
21858 inside Emacs and then save the entire buffer to a file.
21861 If you wish to suggest changes to the @value{GDBN} source, send us context
21862 diffs. If you even discuss something in the @value{GDBN} source, refer to
21863 it by context, not by line number.
21865 The line numbers in our development sources will not match those in your
21866 sources. Your line numbers would convey no useful information to us.
21870 Here are some things that are not necessary:
21874 A description of the envelope of the bug.
21876 Often people who encounter a bug spend a lot of time investigating
21877 which changes to the input file will make the bug go away and which
21878 changes will not affect it.
21880 This is often time consuming and not very useful, because the way we
21881 will find the bug is by running a single example under the debugger
21882 with breakpoints, not by pure deduction from a series of examples.
21883 We recommend that you save your time for something else.
21885 Of course, if you can find a simpler example to report @emph{instead}
21886 of the original one, that is a convenience for us. Errors in the
21887 output will be easier to spot, running under the debugger will take
21888 less time, and so on.
21890 However, simplification is not vital; if you do not want to do this,
21891 report the bug anyway and send us the entire test case you used.
21894 A patch for the bug.
21896 A patch for the bug does help us if it is a good one. But do not omit
21897 the necessary information, such as the test case, on the assumption that
21898 a patch is all we need. We might see problems with your patch and decide
21899 to fix the problem another way, or we might not understand it at all.
21901 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21902 construct an example that will make the program follow a certain path
21903 through the code. If you do not send us the example, we will not be able
21904 to construct one, so we will not be able to verify that the bug is fixed.
21906 And if we cannot understand what bug you are trying to fix, or why your
21907 patch should be an improvement, we will not install it. A test case will
21908 help us to understand.
21911 A guess about what the bug is or what it depends on.
21913 Such guesses are usually wrong. Even we cannot guess right about such
21914 things without first using the debugger to find the facts.
21917 @c The readline documentation is distributed with the readline code
21918 @c and consists of the two following files:
21920 @c inc-hist.texinfo
21921 @c Use -I with makeinfo to point to the appropriate directory,
21922 @c environment var TEXINPUTS with TeX.
21923 @include rluser.texi
21924 @include inc-hist.texinfo
21927 @node Formatting Documentation
21928 @appendix Formatting Documentation
21930 @cindex @value{GDBN} reference card
21931 @cindex reference card
21932 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21933 for printing with PostScript or Ghostscript, in the @file{gdb}
21934 subdirectory of the main source directory@footnote{In
21935 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21936 release.}. If you can use PostScript or Ghostscript with your printer,
21937 you can print the reference card immediately with @file{refcard.ps}.
21939 The release also includes the source for the reference card. You
21940 can format it, using @TeX{}, by typing:
21946 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21947 mode on US ``letter'' size paper;
21948 that is, on a sheet 11 inches wide by 8.5 inches
21949 high. You will need to specify this form of printing as an option to
21950 your @sc{dvi} output program.
21952 @cindex documentation
21954 All the documentation for @value{GDBN} comes as part of the machine-readable
21955 distribution. The documentation is written in Texinfo format, which is
21956 a documentation system that uses a single source file to produce both
21957 on-line information and a printed manual. You can use one of the Info
21958 formatting commands to create the on-line version of the documentation
21959 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21961 @value{GDBN} includes an already formatted copy of the on-line Info
21962 version of this manual in the @file{gdb} subdirectory. The main Info
21963 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21964 subordinate files matching @samp{gdb.info*} in the same directory. If
21965 necessary, you can print out these files, or read them with any editor;
21966 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21967 Emacs or the standalone @code{info} program, available as part of the
21968 @sc{gnu} Texinfo distribution.
21970 If you want to format these Info files yourself, you need one of the
21971 Info formatting programs, such as @code{texinfo-format-buffer} or
21974 If you have @code{makeinfo} installed, and are in the top level
21975 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21976 version @value{GDBVN}), you can make the Info file by typing:
21983 If you want to typeset and print copies of this manual, you need @TeX{},
21984 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21985 Texinfo definitions file.
21987 @TeX{} is a typesetting program; it does not print files directly, but
21988 produces output files called @sc{dvi} files. To print a typeset
21989 document, you need a program to print @sc{dvi} files. If your system
21990 has @TeX{} installed, chances are it has such a program. The precise
21991 command to use depends on your system; @kbd{lpr -d} is common; another
21992 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21993 require a file name without any extension or a @samp{.dvi} extension.
21995 @TeX{} also requires a macro definitions file called
21996 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21997 written in Texinfo format. On its own, @TeX{} cannot either read or
21998 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21999 and is located in the @file{gdb-@var{version-number}/texinfo}
22002 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22003 typeset and print this manual. First switch to the the @file{gdb}
22004 subdirectory of the main source directory (for example, to
22005 @file{gdb-@value{GDBVN}/gdb}) and type:
22011 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22013 @node Installing GDB
22014 @appendix Installing @value{GDBN}
22015 @cindex installation
22018 * Requirements:: Requirements for building @value{GDBN}
22019 * Running Configure:: Invoking the @value{GDBN} @code{configure} script
22020 * Separate Objdir:: Compiling @value{GDBN} in another directory
22021 * Config Names:: Specifying names for hosts and targets
22022 * Configure Options:: Summary of options for configure
22026 @section Requirements for building @value{GDBN}
22027 @cindex building @value{GDBN}, requirements for
22029 Building @value{GDBN} requires various tools and packages to be available.
22030 Other packages will be used only if they are found.
22032 @heading Tools/packages necessary for building @value{GDBN}
22034 @item ISO C90 compiler
22035 @value{GDBN} is written in ISO C90. It should be buildable with any
22036 working C90 compiler, e.g.@: GCC.
22040 @heading Tools/packages optional for building @value{GDBN}
22043 @value{GDBN} can use the Expat XML parsing library. This library may be
22044 included with your operating system distribution; if it is not, you
22045 can get the latest version from @url{http://expat.sourceforge.net}.
22046 The @code{configure} script will search for this library in several
22047 standard locations; if it is installed in an unusual path, you can
22048 use the @option{--with-libexpat-prefix} option to specify its location.
22050 Expat is used currently only used to implement some remote-specific
22055 @node Running Configure
22056 @section Invoking the @value{GDBN} @code{configure} script
22057 @cindex configuring @value{GDBN}
22058 @value{GDBN} comes with a @code{configure} script that automates the process
22059 of preparing @value{GDBN} for installation; you can then use @code{make} to
22060 build the @code{gdb} program.
22062 @c irrelevant in info file; it's as current as the code it lives with.
22063 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22064 look at the @file{README} file in the sources; we may have improved the
22065 installation procedures since publishing this manual.}
22068 The @value{GDBN} distribution includes all the source code you need for
22069 @value{GDBN} in a single directory, whose name is usually composed by
22070 appending the version number to @samp{gdb}.
22072 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22073 @file{gdb-@value{GDBVN}} directory. That directory contains:
22076 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22077 script for configuring @value{GDBN} and all its supporting libraries
22079 @item gdb-@value{GDBVN}/gdb
22080 the source specific to @value{GDBN} itself
22082 @item gdb-@value{GDBVN}/bfd
22083 source for the Binary File Descriptor library
22085 @item gdb-@value{GDBVN}/include
22086 @sc{gnu} include files
22088 @item gdb-@value{GDBVN}/libiberty
22089 source for the @samp{-liberty} free software library
22091 @item gdb-@value{GDBVN}/opcodes
22092 source for the library of opcode tables and disassemblers
22094 @item gdb-@value{GDBVN}/readline
22095 source for the @sc{gnu} command-line interface
22097 @item gdb-@value{GDBVN}/glob
22098 source for the @sc{gnu} filename pattern-matching subroutine
22100 @item gdb-@value{GDBVN}/mmalloc
22101 source for the @sc{gnu} memory-mapped malloc package
22104 The simplest way to configure and build @value{GDBN} is to run @code{configure}
22105 from the @file{gdb-@var{version-number}} source directory, which in
22106 this example is the @file{gdb-@value{GDBVN}} directory.
22108 First switch to the @file{gdb-@var{version-number}} source directory
22109 if you are not already in it; then run @code{configure}. Pass the
22110 identifier for the platform on which @value{GDBN} will run as an
22116 cd gdb-@value{GDBVN}
22117 ./configure @var{host}
22122 where @var{host} is an identifier such as @samp{sun4} or
22123 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22124 (You can often leave off @var{host}; @code{configure} tries to guess the
22125 correct value by examining your system.)
22127 Running @samp{configure @var{host}} and then running @code{make} builds the
22128 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22129 libraries, then @code{gdb} itself. The configured source files, and the
22130 binaries, are left in the corresponding source directories.
22133 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22134 system does not recognize this automatically when you run a different
22135 shell, you may need to run @code{sh} on it explicitly:
22138 sh configure @var{host}
22141 If you run @code{configure} from a directory that contains source
22142 directories for multiple libraries or programs, such as the
22143 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
22144 creates configuration files for every directory level underneath (unless
22145 you tell it not to, with the @samp{--norecursion} option).
22147 You should run the @code{configure} script from the top directory in the
22148 source tree, the @file{gdb-@var{version-number}} directory. If you run
22149 @code{configure} from one of the subdirectories, you will configure only
22150 that subdirectory. That is usually not what you want. In particular,
22151 if you run the first @code{configure} from the @file{gdb} subdirectory
22152 of the @file{gdb-@var{version-number}} directory, you will omit the
22153 configuration of @file{bfd}, @file{readline}, and other sibling
22154 directories of the @file{gdb} subdirectory. This leads to build errors
22155 about missing include files such as @file{bfd/bfd.h}.
22157 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22158 However, you should make sure that the shell on your path (named by
22159 the @samp{SHELL} environment variable) is publicly readable. Remember
22160 that @value{GDBN} uses the shell to start your program---some systems refuse to
22161 let @value{GDBN} debug child processes whose programs are not readable.
22163 @node Separate Objdir
22164 @section Compiling @value{GDBN} in another directory
22166 If you want to run @value{GDBN} versions for several host or target machines,
22167 you need a different @code{gdb} compiled for each combination of
22168 host and target. @code{configure} is designed to make this easy by
22169 allowing you to generate each configuration in a separate subdirectory,
22170 rather than in the source directory. If your @code{make} program
22171 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22172 @code{make} in each of these directories builds the @code{gdb}
22173 program specified there.
22175 To build @code{gdb} in a separate directory, run @code{configure}
22176 with the @samp{--srcdir} option to specify where to find the source.
22177 (You also need to specify a path to find @code{configure}
22178 itself from your working directory. If the path to @code{configure}
22179 would be the same as the argument to @samp{--srcdir}, you can leave out
22180 the @samp{--srcdir} option; it is assumed.)
22182 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22183 separate directory for a Sun 4 like this:
22187 cd gdb-@value{GDBVN}
22190 ../gdb-@value{GDBVN}/configure sun4
22195 When @code{configure} builds a configuration using a remote source
22196 directory, it creates a tree for the binaries with the same structure
22197 (and using the same names) as the tree under the source directory. In
22198 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22199 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22200 @file{gdb-sun4/gdb}.
22202 Make sure that your path to the @file{configure} script has just one
22203 instance of @file{gdb} in it. If your path to @file{configure} looks
22204 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22205 one subdirectory of @value{GDBN}, not the whole package. This leads to
22206 build errors about missing include files such as @file{bfd/bfd.h}.
22208 One popular reason to build several @value{GDBN} configurations in separate
22209 directories is to configure @value{GDBN} for cross-compiling (where
22210 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22211 programs that run on another machine---the @dfn{target}).
22212 You specify a cross-debugging target by
22213 giving the @samp{--target=@var{target}} option to @code{configure}.
22215 When you run @code{make} to build a program or library, you must run
22216 it in a configured directory---whatever directory you were in when you
22217 called @code{configure} (or one of its subdirectories).
22219 The @code{Makefile} that @code{configure} generates in each source
22220 directory also runs recursively. If you type @code{make} in a source
22221 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22222 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22223 will build all the required libraries, and then build GDB.
22225 When you have multiple hosts or targets configured in separate
22226 directories, you can run @code{make} on them in parallel (for example,
22227 if they are NFS-mounted on each of the hosts); they will not interfere
22231 @section Specifying names for hosts and targets
22233 The specifications used for hosts and targets in the @code{configure}
22234 script are based on a three-part naming scheme, but some short predefined
22235 aliases are also supported. The full naming scheme encodes three pieces
22236 of information in the following pattern:
22239 @var{architecture}-@var{vendor}-@var{os}
22242 For example, you can use the alias @code{sun4} as a @var{host} argument,
22243 or as the value for @var{target} in a @code{--target=@var{target}}
22244 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22246 The @code{configure} script accompanying @value{GDBN} does not provide
22247 any query facility to list all supported host and target names or
22248 aliases. @code{configure} calls the Bourne shell script
22249 @code{config.sub} to map abbreviations to full names; you can read the
22250 script, if you wish, or you can use it to test your guesses on
22251 abbreviations---for example:
22254 % sh config.sub i386-linux
22256 % sh config.sub alpha-linux
22257 alpha-unknown-linux-gnu
22258 % sh config.sub hp9k700
22260 % sh config.sub sun4
22261 sparc-sun-sunos4.1.1
22262 % sh config.sub sun3
22263 m68k-sun-sunos4.1.1
22264 % sh config.sub i986v
22265 Invalid configuration `i986v': machine `i986v' not recognized
22269 @code{config.sub} is also distributed in the @value{GDBN} source
22270 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22272 @node Configure Options
22273 @section @code{configure} options
22275 Here is a summary of the @code{configure} options and arguments that
22276 are most often useful for building @value{GDBN}. @code{configure} also has
22277 several other options not listed here. @inforef{What Configure
22278 Does,,configure.info}, for a full explanation of @code{configure}.
22281 configure @r{[}--help@r{]}
22282 @r{[}--prefix=@var{dir}@r{]}
22283 @r{[}--exec-prefix=@var{dir}@r{]}
22284 @r{[}--srcdir=@var{dirname}@r{]}
22285 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22286 @r{[}--target=@var{target}@r{]}
22291 You may introduce options with a single @samp{-} rather than
22292 @samp{--} if you prefer; but you may abbreviate option names if you use
22297 Display a quick summary of how to invoke @code{configure}.
22299 @item --prefix=@var{dir}
22300 Configure the source to install programs and files under directory
22303 @item --exec-prefix=@var{dir}
22304 Configure the source to install programs under directory
22307 @c avoid splitting the warning from the explanation:
22309 @item --srcdir=@var{dirname}
22310 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22311 @code{make} that implements the @code{VPATH} feature.}@*
22312 Use this option to make configurations in directories separate from the
22313 @value{GDBN} source directories. Among other things, you can use this to
22314 build (or maintain) several configurations simultaneously, in separate
22315 directories. @code{configure} writes configuration specific files in
22316 the current directory, but arranges for them to use the source in the
22317 directory @var{dirname}. @code{configure} creates directories under
22318 the working directory in parallel to the source directories below
22321 @item --norecursion
22322 Configure only the directory level where @code{configure} is executed; do not
22323 propagate configuration to subdirectories.
22325 @item --target=@var{target}
22326 Configure @value{GDBN} for cross-debugging programs running on the specified
22327 @var{target}. Without this option, @value{GDBN} is configured to debug
22328 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22330 There is no convenient way to generate a list of all available targets.
22332 @item @var{host} @dots{}
22333 Configure @value{GDBN} to run on the specified @var{host}.
22335 There is no convenient way to generate a list of all available hosts.
22338 There are many other options available as well, but they are generally
22339 needed for special purposes only.
22341 @node Maintenance Commands
22342 @appendix Maintenance Commands
22343 @cindex maintenance commands
22344 @cindex internal commands
22346 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22347 includes a number of commands intended for @value{GDBN} developers,
22348 that are not documented elsewhere in this manual. These commands are
22349 provided here for reference. (For commands that turn on debugging
22350 messages, see @ref{Debugging Output}.)
22353 @kindex maint agent
22354 @item maint agent @var{expression}
22355 Translate the given @var{expression} into remote agent bytecodes.
22356 This command is useful for debugging the Agent Expression mechanism
22357 (@pxref{Agent Expressions}).
22359 @kindex maint info breakpoints
22360 @item @anchor{maint info breakpoints}maint info breakpoints
22361 Using the same format as @samp{info breakpoints}, display both the
22362 breakpoints you've set explicitly, and those @value{GDBN} is using for
22363 internal purposes. Internal breakpoints are shown with negative
22364 breakpoint numbers. The type column identifies what kind of breakpoint
22369 Normal, explicitly set breakpoint.
22372 Normal, explicitly set watchpoint.
22375 Internal breakpoint, used to handle correctly stepping through
22376 @code{longjmp} calls.
22378 @item longjmp resume
22379 Internal breakpoint at the target of a @code{longjmp}.
22382 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22385 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22388 Shared library events.
22392 @kindex maint check-symtabs
22393 @item maint check-symtabs
22394 Check the consistency of psymtabs and symtabs.
22396 @kindex maint cplus first_component
22397 @item maint cplus first_component @var{name}
22398 Print the first C@t{++} class/namespace component of @var{name}.
22400 @kindex maint cplus namespace
22401 @item maint cplus namespace
22402 Print the list of possible C@t{++} namespaces.
22404 @kindex maint demangle
22405 @item maint demangle @var{name}
22406 Demangle a C@t{++} or Objective-C manled @var{name}.
22408 @kindex maint deprecate
22409 @kindex maint undeprecate
22410 @cindex deprecated commands
22411 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22412 @itemx maint undeprecate @var{command}
22413 Deprecate or undeprecate the named @var{command}. Deprecated commands
22414 cause @value{GDBN} to issue a warning when you use them. The optional
22415 argument @var{replacement} says which newer command should be used in
22416 favor of the deprecated one; if it is given, @value{GDBN} will mention
22417 the replacement as part of the warning.
22419 @kindex maint dump-me
22420 @item maint dump-me
22421 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22422 Cause a fatal signal in the debugger and force it to dump its core.
22423 This is supported only on systems which support aborting a program
22424 with the @code{SIGQUIT} signal.
22426 @kindex maint internal-error
22427 @kindex maint internal-warning
22428 @item maint internal-error @r{[}@var{message-text}@r{]}
22429 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22430 Cause @value{GDBN} to call the internal function @code{internal_error}
22431 or @code{internal_warning} and hence behave as though an internal error
22432 or internal warning has been detected. In addition to reporting the
22433 internal problem, these functions give the user the opportunity to
22434 either quit @value{GDBN} or create a core file of the current
22435 @value{GDBN} session.
22437 These commands take an optional parameter @var{message-text} that is
22438 used as the text of the error or warning message.
22440 Here's an example of using @code{indernal-error}:
22443 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22444 @dots{}/maint.c:121: internal-error: testing, 1, 2
22445 A problem internal to GDB has been detected. Further
22446 debugging may prove unreliable.
22447 Quit this debugging session? (y or n) @kbd{n}
22448 Create a core file? (y or n) @kbd{n}
22452 @kindex maint packet
22453 @item maint packet @var{text}
22454 If @value{GDBN} is talking to an inferior via the serial protocol,
22455 then this command sends the string @var{text} to the inferior, and
22456 displays the response packet. @value{GDBN} supplies the initial
22457 @samp{$} character, the terminating @samp{#} character, and the
22460 @kindex maint print architecture
22461 @item maint print architecture @r{[}@var{file}@r{]}
22462 Print the entire architecture configuration. The optional argument
22463 @var{file} names the file where the output goes.
22465 @kindex maint print dummy-frames
22466 @item maint print dummy-frames
22467 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22470 (@value{GDBP}) @kbd{b add}
22472 (@value{GDBP}) @kbd{print add(2,3)}
22473 Breakpoint 2, add (a=2, b=3) at @dots{}
22475 The program being debugged stopped while in a function called from GDB.
22477 (@value{GDBP}) @kbd{maint print dummy-frames}
22478 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22479 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22480 call_lo=0x01014000 call_hi=0x01014001
22484 Takes an optional file parameter.
22486 @kindex maint print registers
22487 @kindex maint print raw-registers
22488 @kindex maint print cooked-registers
22489 @kindex maint print register-groups
22490 @item maint print registers @r{[}@var{file}@r{]}
22491 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22492 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22493 @itemx maint print register-groups @r{[}@var{file}@r{]}
22494 Print @value{GDBN}'s internal register data structures.
22496 The command @code{maint print raw-registers} includes the contents of
22497 the raw register cache; the command @code{maint print cooked-registers}
22498 includes the (cooked) value of all registers; and the command
22499 @code{maint print register-groups} includes the groups that each
22500 register is a member of. @xref{Registers,, Registers, gdbint,
22501 @value{GDBN} Internals}.
22503 These commands take an optional parameter, a file name to which to
22504 write the information.
22506 @kindex maint print reggroups
22507 @item maint print reggroups @r{[}@var{file}@r{]}
22508 Print @value{GDBN}'s internal register group data structures. The
22509 optional argument @var{file} tells to what file to write the
22512 The register groups info looks like this:
22515 (@value{GDBP}) @kbd{maint print reggroups}
22528 This command forces @value{GDBN} to flush its internal register cache.
22530 @kindex maint print objfiles
22531 @cindex info for known object files
22532 @item maint print objfiles
22533 Print a dump of all known object files. For each object file, this
22534 command prints its name, address in memory, and all of its psymtabs
22537 @kindex maint print statistics
22538 @cindex bcache statistics
22539 @item maint print statistics
22540 This command prints, for each object file in the program, various data
22541 about that object file followed by the byte cache (@dfn{bcache})
22542 statistics for the object file. The objfile data includes the number
22543 of minimal, partical, full, and stabs symbols, the number of types
22544 defined by the objfile, the number of as yet unexpanded psym tables,
22545 the number of line tables and string tables, and the amount of memory
22546 used by the various tables. The bcache statistics include the counts,
22547 sizes, and counts of duplicates of all and unique objects, max,
22548 average, and median entry size, total memory used and its overhead and
22549 savings, and various measures of the hash table size and chain
22552 @kindex maint print type
22553 @cindex type chain of a data type
22554 @item maint print type @var{expr}
22555 Print the type chain for a type specified by @var{expr}. The argument
22556 can be either a type name or a symbol. If it is a symbol, the type of
22557 that symbol is described. The type chain produced by this command is
22558 a recursive definition of the data type as stored in @value{GDBN}'s
22559 data structures, including its flags and contained types.
22561 @kindex maint set dwarf2 max-cache-age
22562 @kindex maint show dwarf2 max-cache-age
22563 @item maint set dwarf2 max-cache-age
22564 @itemx maint show dwarf2 max-cache-age
22565 Control the DWARF 2 compilation unit cache.
22567 @cindex DWARF 2 compilation units cache
22568 In object files with inter-compilation-unit references, such as those
22569 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22570 reader needs to frequently refer to previously read compilation units.
22571 This setting controls how long a compilation unit will remain in the
22572 cache if it is not referenced. A higher limit means that cached
22573 compilation units will be stored in memory longer, and more total
22574 memory will be used. Setting it to zero disables caching, which will
22575 slow down @value{GDBN} startup, but reduce memory consumption.
22577 @kindex maint set profile
22578 @kindex maint show profile
22579 @cindex profiling GDB
22580 @item maint set profile
22581 @itemx maint show profile
22582 Control profiling of @value{GDBN}.
22584 Profiling will be disabled until you use the @samp{maint set profile}
22585 command to enable it. When you enable profiling, the system will begin
22586 collecting timing and execution count data; when you disable profiling or
22587 exit @value{GDBN}, the results will be written to a log file. Remember that
22588 if you use profiling, @value{GDBN} will overwrite the profiling log file
22589 (often called @file{gmon.out}). If you have a record of important profiling
22590 data in a @file{gmon.out} file, be sure to move it to a safe location.
22592 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
22593 compiled with the @samp{-pg} compiler option.
22595 @kindex maint show-debug-regs
22596 @cindex x86 hardware debug registers
22597 @item maint show-debug-regs
22598 Control whether to show variables that mirror the x86 hardware debug
22599 registers. Use @code{ON} to enable, @code{OFF} to disable. If
22600 enabled, the debug registers values are shown when GDB inserts or
22601 removes a hardware breakpoint or watchpoint, and when the inferior
22602 triggers a hardware-assisted breakpoint or watchpoint.
22604 @kindex maint space
22605 @cindex memory used by commands
22607 Control whether to display memory usage for each command. If set to a
22608 nonzero value, @value{GDBN} will display how much memory each command
22609 took, following the command's own output. This can also be requested
22610 by invoking @value{GDBN} with the @option{--statistics} command-line
22611 switch (@pxref{Mode Options}).
22614 @cindex time of command execution
22616 Control whether to display the execution time for each command. If
22617 set to a nonzero value, @value{GDBN} will display how much time it
22618 took to execute each command, following the command's own output.
22619 This can also be requested by invoking @value{GDBN} with the
22620 @option{--statistics} command-line switch (@pxref{Mode Options}).
22622 @kindex maint translate-address
22623 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22624 Find the symbol stored at the location specified by the address
22625 @var{addr} and an optional section name @var{section}. If found,
22626 @value{GDBN} prints the name of the closest symbol and an offset from
22627 the symbol's location to the specified address. This is similar to
22628 the @code{info address} command (@pxref{Symbols}), except that this
22629 command also allows to find symbols in other sections.
22633 The following command is useful for non-interactive invocations of
22634 @value{GDBN}, such as in the test suite.
22637 @item set watchdog @var{nsec}
22638 @kindex set watchdog
22639 @cindex watchdog timer
22640 @cindex timeout for commands
22641 Set the maximum number of seconds @value{GDBN} will wait for the
22642 target operation to finish. If this time expires, @value{GDBN}
22643 reports and error and the command is aborted.
22645 @item show watchdog
22646 Show the current setting of the target wait timeout.
22649 @node Remote Protocol
22650 @appendix @value{GDBN} Remote Serial Protocol
22655 * Stop Reply Packets::
22656 * General Query Packets::
22657 * Register Packet Format::
22658 * Tracepoint Packets::
22661 * File-I/O remote protocol extension::
22662 * Memory map format::
22668 There may be occasions when you need to know something about the
22669 protocol---for example, if there is only one serial port to your target
22670 machine, you might want your program to do something special if it
22671 recognizes a packet meant for @value{GDBN}.
22673 In the examples below, @samp{->} and @samp{<-} are used to indicate
22674 transmitted and received data respectfully.
22676 @cindex protocol, @value{GDBN} remote serial
22677 @cindex serial protocol, @value{GDBN} remote
22678 @cindex remote serial protocol
22679 All @value{GDBN} commands and responses (other than acknowledgments) are
22680 sent as a @var{packet}. A @var{packet} is introduced with the character
22681 @samp{$}, the actual @var{packet-data}, and the terminating character
22682 @samp{#} followed by a two-digit @var{checksum}:
22685 @code{$}@var{packet-data}@code{#}@var{checksum}
22689 @cindex checksum, for @value{GDBN} remote
22691 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22692 characters between the leading @samp{$} and the trailing @samp{#} (an
22693 eight bit unsigned checksum).
22695 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22696 specification also included an optional two-digit @var{sequence-id}:
22699 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22702 @cindex sequence-id, for @value{GDBN} remote
22704 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22705 has never output @var{sequence-id}s. Stubs that handle packets added
22706 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22708 @cindex acknowledgment, for @value{GDBN} remote
22709 When either the host or the target machine receives a packet, the first
22710 response expected is an acknowledgment: either @samp{+} (to indicate
22711 the package was received correctly) or @samp{-} (to request
22715 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22720 The host (@value{GDBN}) sends @var{command}s, and the target (the
22721 debugging stub incorporated in your program) sends a @var{response}. In
22722 the case of step and continue @var{command}s, the response is only sent
22723 when the operation has completed (the target has again stopped).
22725 @var{packet-data} consists of a sequence of characters with the
22726 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22729 @cindex remote protocol, field separator
22730 Fields within the packet should be separated using @samp{,} @samp{;} or
22731 @samp{:}. Except where otherwise noted all numbers are represented in
22732 @sc{hex} with leading zeros suppressed.
22734 Implementors should note that prior to @value{GDBN} 5.0, the character
22735 @samp{:} could not appear as the third character in a packet (as it
22736 would potentially conflict with the @var{sequence-id}).
22738 @cindex remote protocol, binary data
22739 @anchor{Binary Data}
22740 Binary data in most packets is encoded either as two hexadecimal
22741 digits per byte of binary data. This allowed the traditional remote
22742 protocol to work over connections which were only seven-bit clean.
22743 Some packets designed more recently assume an eight-bit clean
22744 connection, and use a more efficient encoding to send and receive
22747 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
22748 as an escape character. Any escaped byte is transmitted as the escape
22749 character followed by the original character XORed with @code{0x20}.
22750 For example, the byte @code{0x7d} would be transmitted as the two
22751 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
22752 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
22753 @samp{@}}) must always be escaped. Responses sent by the stub
22754 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
22755 is not interpreted as the start of a run-length encoded sequence
22758 Response @var{data} can be run-length encoded to save space. A @samp{*}
22759 means that the next character is an @sc{ascii} encoding giving a repeat count
22760 which stands for that many repetitions of the character preceding the
22761 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22762 where @code{n >=3} (which is where rle starts to win). The printable
22763 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22764 value greater than 126 should not be used.
22771 means the same as "0000".
22773 The error response returned for some packets includes a two character
22774 error number. That number is not well defined.
22776 @cindex empty response, for unsupported packets
22777 For any @var{command} not supported by the stub, an empty response
22778 (@samp{$#00}) should be returned. That way it is possible to extend the
22779 protocol. A newer @value{GDBN} can tell if a packet is supported based
22782 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22783 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22789 The following table provides a complete list of all currently defined
22790 @var{command}s and their corresponding response @var{data}.
22791 @xref{File-I/O remote protocol extension}, for details about the File
22792 I/O extension of the remote protocol.
22794 Each packet's description has a template showing the packet's overall
22795 syntax, followed by an explanation of the packet's meaning. We
22796 include spaces in some of the templates for clarity; these are not
22797 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22798 separate its components. For example, a template like @samp{foo
22799 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22800 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22801 @var{baz}. GDB does not transmit a space character between the
22802 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22805 Note that all packet forms beginning with an upper- or lower-case
22806 letter, other than those described here, are reserved for future use.
22808 Here are the packet descriptions.
22813 @cindex @samp{!} packet
22814 Enable extended mode. In extended mode, the remote server is made
22815 persistent. The @samp{R} packet is used to restart the program being
22821 The remote target both supports and has enabled extended mode.
22825 @cindex @samp{?} packet
22826 Indicate the reason the target halted. The reply is the same as for
22830 @xref{Stop Reply Packets}, for the reply specifications.
22832 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22833 @cindex @samp{A} packet
22834 Initialized @code{argv[]} array passed into program. @var{arglen}
22835 specifies the number of bytes in the hex encoded byte stream
22836 @var{arg}. See @code{gdbserver} for more details.
22841 The arguments were set.
22847 @cindex @samp{b} packet
22848 (Don't use this packet; its behavior is not well-defined.)
22849 Change the serial line speed to @var{baud}.
22851 JTC: @emph{When does the transport layer state change? When it's
22852 received, or after the ACK is transmitted. In either case, there are
22853 problems if the command or the acknowledgment packet is dropped.}
22855 Stan: @emph{If people really wanted to add something like this, and get
22856 it working for the first time, they ought to modify ser-unix.c to send
22857 some kind of out-of-band message to a specially-setup stub and have the
22858 switch happen "in between" packets, so that from remote protocol's point
22859 of view, nothing actually happened.}
22861 @item B @var{addr},@var{mode}
22862 @cindex @samp{B} packet
22863 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
22864 breakpoint at @var{addr}.
22866 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
22867 (@pxref{insert breakpoint or watchpoint packet}).
22869 @item c @r{[}@var{addr}@r{]}
22870 @cindex @samp{c} packet
22871 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
22872 resume at current address.
22875 @xref{Stop Reply Packets}, for the reply specifications.
22877 @item C @var{sig}@r{[};@var{addr}@r{]}
22878 @cindex @samp{C} packet
22879 Continue with signal @var{sig} (hex signal number). If
22880 @samp{;@var{addr}} is omitted, resume at same address.
22883 @xref{Stop Reply Packets}, for the reply specifications.
22886 @cindex @samp{d} packet
22889 Don't use this packet; instead, define a general set packet
22890 (@pxref{General Query Packets}).
22893 @cindex @samp{D} packet
22894 Detach @value{GDBN} from the remote system. Sent to the remote target
22895 before @value{GDBN} disconnects via the @code{detach} command.
22905 @item F @var{RC},@var{EE},@var{CF};@var{XX}
22906 @cindex @samp{F} packet
22907 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
22908 This is part of the File-I/O protocol extension. @xref{File-I/O
22909 remote protocol extension}, for the specification.
22912 @anchor{read registers packet}
22913 @cindex @samp{g} packet
22914 Read general registers.
22918 @item @var{XX@dots{}}
22919 Each byte of register data is described by two hex digits. The bytes
22920 with the register are transmitted in target byte order. The size of
22921 each register and their position within the @samp{g} packet are
22922 determined by the @value{GDBN} internal macros
22923 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{REGISTER_NAME} macros. The
22924 specification of several standard @samp{g} packets is specified below.
22929 @item G @var{XX@dots{}}
22930 @cindex @samp{G} packet
22931 Write general registers. @xref{read registers packet}, for a
22932 description of the @var{XX@dots{}} data.
22942 @item H @var{c} @var{t}
22943 @cindex @samp{H} packet
22944 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22945 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22946 should be @samp{c} for step and continue operations, @samp{g} for other
22947 operations. The thread designator @var{t} may be @samp{-1}, meaning all
22948 the threads, a thread number, or @samp{0} which means pick any thread.
22959 @c 'H': How restrictive (or permissive) is the thread model. If a
22960 @c thread is selected and stopped, are other threads allowed
22961 @c to continue to execute? As I mentioned above, I think the
22962 @c semantics of each command when a thread is selected must be
22963 @c described. For example:
22965 @c 'g': If the stub supports threads and a specific thread is
22966 @c selected, returns the register block from that thread;
22967 @c otherwise returns current registers.
22969 @c 'G' If the stub supports threads and a specific thread is
22970 @c selected, sets the registers of the register block of
22971 @c that thread; otherwise sets current registers.
22973 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
22974 @anchor{cycle step packet}
22975 @cindex @samp{i} packet
22976 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
22977 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22978 step starting at that address.
22981 @cindex @samp{I} packet
22982 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
22986 @cindex @samp{k} packet
22989 FIXME: @emph{There is no description of how to operate when a specific
22990 thread context has been selected (i.e.@: does 'k' kill only that
22993 @item m @var{addr},@var{length}
22994 @cindex @samp{m} packet
22995 Read @var{length} bytes of memory starting at address @var{addr}.
22996 Note that @var{addr} may not be aligned to any particular boundary.
22998 The stub need not use any particular size or alignment when gathering
22999 data from memory for the response; even if @var{addr} is word-aligned
23000 and @var{length} is a multiple of the word size, the stub is free to
23001 use byte accesses, or not. For this reason, this packet may not be
23002 suitable for accessing memory-mapped I/O devices.
23003 @cindex alignment of remote memory accesses
23004 @cindex size of remote memory accesses
23005 @cindex memory, alignment and size of remote accesses
23009 @item @var{XX@dots{}}
23010 Memory contents; each byte is transmitted as a two-digit hexadecimal
23011 number. The reply may contain fewer bytes than requested if the
23012 server was able to read only part of the region of memory.
23017 @item M @var{addr},@var{length}:@var{XX@dots{}}
23018 @cindex @samp{M} packet
23019 Write @var{length} bytes of memory starting at address @var{addr}.
23020 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23021 hexadecimal number.
23028 for an error (this includes the case where only part of the data was
23033 @cindex @samp{p} packet
23034 Read the value of register @var{n}; @var{n} is in hex.
23035 @xref{read registers packet}, for a description of how the returned
23036 register value is encoded.
23040 @item @var{XX@dots{}}
23041 the register's value
23045 Indicating an unrecognized @var{query}.
23048 @item P @var{n@dots{}}=@var{r@dots{}}
23049 @anchor{write register packet}
23050 @cindex @samp{P} packet
23051 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23052 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23053 digits for each byte in the register (target byte order).
23063 @item q @var{name} @var{params}@dots{}
23064 @itemx Q @var{name} @var{params}@dots{}
23065 @cindex @samp{q} packet
23066 @cindex @samp{Q} packet
23067 General query (@samp{q}) and set (@samp{Q}). These packets are
23068 described fully in @ref{General Query Packets}.
23071 @cindex @samp{r} packet
23072 Reset the entire system.
23074 Don't use this packet; use the @samp{R} packet instead.
23077 @cindex @samp{R} packet
23078 Restart the program being debugged. @var{XX}, while needed, is ignored.
23079 This packet is only available in extended mode.
23081 The @samp{R} packet has no reply.
23083 @item s @r{[}@var{addr}@r{]}
23084 @cindex @samp{s} packet
23085 Single step. @var{addr} is the address at which to resume. If
23086 @var{addr} is omitted, resume at same address.
23089 @xref{Stop Reply Packets}, for the reply specifications.
23091 @item S @var{sig}@r{[};@var{addr}@r{]}
23092 @anchor{step with signal packet}
23093 @cindex @samp{S} packet
23094 Step with signal. This is analogous to the @samp{C} packet, but
23095 requests a single-step, rather than a normal resumption of execution.
23098 @xref{Stop Reply Packets}, for the reply specifications.
23100 @item t @var{addr}:@var{PP},@var{MM}
23101 @cindex @samp{t} packet
23102 Search backwards starting at address @var{addr} for a match with pattern
23103 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23104 @var{addr} must be at least 3 digits.
23107 @cindex @samp{T} packet
23108 Find out if the thread XX is alive.
23113 thread is still alive
23119 Packets starting with @samp{v} are identified by a multi-letter name,
23120 up to the first @samp{;} or @samp{?} (or the end of the packet).
23122 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23123 @cindex @samp{vCont} packet
23124 Resume the inferior, specifying different actions for each thread.
23125 If an action is specified with no @var{tid}, then it is applied to any
23126 threads that don't have a specific action specified; if no default action is
23127 specified then other threads should remain stopped. Specifying multiple
23128 default actions is an error; specifying no actions is also an error.
23129 Thread IDs are specified in hexadecimal. Currently supported actions are:
23135 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23139 Step with signal @var{sig}. @var{sig} should be two hex digits.
23142 The optional @var{addr} argument normally associated with these packets is
23143 not supported in @samp{vCont}.
23146 @xref{Stop Reply Packets}, for the reply specifications.
23149 @cindex @samp{vCont?} packet
23150 Request a list of actions supporetd by the @samp{vCont} packet.
23154 @item vCont@r{[};@var{action}@dots{}@r{]}
23155 The @samp{vCont} packet is supported. Each @var{action} is a supported
23156 command in the @samp{vCont} packet.
23158 The @samp{vCont} packet is not supported.
23161 @item vFlashErase:@var{addr},@var{length}
23162 @cindex @samp{vFlashErase} packet
23163 Direct the stub to erase @var{length} bytes of flash starting at
23164 @var{addr}. The region may enclose any number of flash blocks, but
23165 its start and end must fall on block boundaries, as indicated by the
23166 flash block size appearing in the memory map (@pxref{Memory map
23167 format}). @value{GDBN} groups flash memory programming operations
23168 together, and sends a @samp{vFlashDone} request after each group; the
23169 stub is allowed to delay erase operation until the @samp{vFlashDone}
23170 packet is received.
23180 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23181 @cindex @samp{vFlashWrite} packet
23182 Direct the stub to write data to flash address @var{addr}. The data
23183 is passed in binary form using the same encoding as for the @samp{X}
23184 packet (@pxref{Binary Data}). The memory ranges specified by
23185 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23186 not overlap, and must appear in order of increasing addresses
23187 (although @samp{vFlashErase} packets for higher addresses may already
23188 have been received; the ordering is guaranteed only between
23189 @samp{vFlashWrite} packets). If a packet writes to an address that was
23190 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23191 target-specific method, the results are unpredictable.
23199 for vFlashWrite addressing non-flash memory
23205 @cindex @samp{vFlashDone} packet
23206 Indicate to the stub that flash programming operation is finished.
23207 The stub is permitted to delay or batch the effects of a group of
23208 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23209 @samp{vFlashDone} packet is received. The contents of the affected
23210 regions of flash memory are unpredictable until the @samp{vFlashDone}
23211 request is completed.
23213 @item X @var{addr},@var{length}:@var{XX@dots{}}
23215 @cindex @samp{X} packet
23216 Write data to memory, where the data is transmitted in binary.
23217 @var{addr} is address, @var{length} is number of bytes,
23218 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23228 @item z @var{type},@var{addr},@var{length}
23229 @itemx Z @var{type},@var{addr},@var{length}
23230 @anchor{insert breakpoint or watchpoint packet}
23231 @cindex @samp{z} packet
23232 @cindex @samp{Z} packets
23233 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23234 watchpoint starting at address @var{address} and covering the next
23235 @var{length} bytes.
23237 Each breakpoint and watchpoint packet @var{type} is documented
23240 @emph{Implementation notes: A remote target shall return an empty string
23241 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23242 remote target shall support either both or neither of a given
23243 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23244 avoid potential problems with duplicate packets, the operations should
23245 be implemented in an idempotent way.}
23247 @item z0,@var{addr},@var{length}
23248 @itemx Z0,@var{addr},@var{length}
23249 @cindex @samp{z0} packet
23250 @cindex @samp{Z0} packet
23251 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23252 @var{addr} of size @var{length}.
23254 A memory breakpoint is implemented by replacing the instruction at
23255 @var{addr} with a software breakpoint or trap instruction. The
23256 @var{length} is used by targets that indicates the size of the
23257 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23258 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23260 @emph{Implementation note: It is possible for a target to copy or move
23261 code that contains memory breakpoints (e.g., when implementing
23262 overlays). The behavior of this packet, in the presence of such a
23263 target, is not defined.}
23275 @item z1,@var{addr},@var{length}
23276 @itemx Z1,@var{addr},@var{length}
23277 @cindex @samp{z1} packet
23278 @cindex @samp{Z1} packet
23279 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23280 address @var{addr} of size @var{length}.
23282 A hardware breakpoint is implemented using a mechanism that is not
23283 dependant on being able to modify the target's memory.
23285 @emph{Implementation note: A hardware breakpoint is not affected by code
23298 @item z2,@var{addr},@var{length}
23299 @itemx Z2,@var{addr},@var{length}
23300 @cindex @samp{z2} packet
23301 @cindex @samp{Z2} packet
23302 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23314 @item z3,@var{addr},@var{length}
23315 @itemx Z3,@var{addr},@var{length}
23316 @cindex @samp{z3} packet
23317 @cindex @samp{Z3} packet
23318 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23330 @item z4,@var{addr},@var{length}
23331 @itemx Z4,@var{addr},@var{length}
23332 @cindex @samp{z4} packet
23333 @cindex @samp{Z4} packet
23334 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23348 @node Stop Reply Packets
23349 @section Stop Reply Packets
23350 @cindex stop reply packets
23352 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23353 receive any of the below as a reply. In the case of the @samp{C},
23354 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23355 when the target halts. In the below the exact meaning of @dfn{signal
23356 number} is poorly defined. In general one of the UNIX signal
23357 numbering conventions is used.
23359 As in the description of request packets, we include spaces in the
23360 reply templates for clarity; these are not part of the reply packet's
23361 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23367 The program received signal number @var{AA} (a two-digit hexadecimal
23368 number). This is equivalent to a @samp{T} response with no
23369 @var{n}:@var{r} pairs.
23371 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23372 @cindex @samp{T} packet reply
23373 The program received signal number @var{AA} (a two-digit hexadecimal
23374 number). This is equivalent to an @samp{S} response, except that the
23375 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23376 and other information directly in the stop reply packet, reducing
23377 round-trip latency. Single-step and breakpoint traps are reported
23378 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23381 If @var{n} is a hexadecimal number, it is a register number, and the
23382 corresponding @var{r} gives that register's value. @var{r} is a
23383 series of bytes in target byte order, with each byte given by a
23384 two-digit hex number.
23386 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23389 If @var{n} is @samp{watch}, @samp{rwatch}, or @samp{awatch}, then the
23390 packet indicates a watchpoint hit, and @var{r} is the data address, in
23393 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23394 and go on to the next; this allows us to extend the protocol in the
23399 The process exited, and @var{AA} is the exit status. This is only
23400 applicable to certain targets.
23403 The process terminated with signal @var{AA}.
23405 @item O @var{XX}@dots{}
23406 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23407 written as the program's console output. This can happen at any time
23408 while the program is running and the debugger should continue to wait
23409 for @samp{W}, @samp{T}, etc.
23411 @item F @var{call-id},@var{parameter}@dots{}
23412 @var{call-id} is the identifier which says which host system call should
23413 be called. This is just the name of the function. Translation into the
23414 correct system call is only applicable as it's defined in @value{GDBN}.
23415 @xref{File-I/O remote protocol extension}, for a list of implemented
23418 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23419 this very system call.
23421 The target replies with this packet when it expects @value{GDBN} to
23422 call a host system call on behalf of the target. @value{GDBN} replies
23423 with an appropriate @samp{F} packet and keeps up waiting for the next
23424 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23425 or @samp{s} action is expected to be continued. @xref{File-I/O remote
23426 protocol extension}, for more details.
23430 @node General Query Packets
23431 @section General Query Packets
23432 @cindex remote query requests
23434 Packets starting with @samp{q} are @dfn{general query packets};
23435 packets starting with @samp{Q} are @dfn{general set packets}. General
23436 query and set packets are a semi-unified form for retrieving and
23437 sending information to and from the stub.
23439 The initial letter of a query or set packet is followed by a name
23440 indicating what sort of thing the packet applies to. For example,
23441 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23442 definitions with the stub. These packet names follow some
23447 The name must not contain commas, colons or semicolons.
23449 Most @value{GDBN} query and set packets have a leading upper case
23452 The names of custom vendor packets should use a company prefix, in
23453 lower case, followed by a period. For example, packets designed at
23454 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23455 foos) or @samp{Qacme.bar} (for setting bars).
23458 The name of a query or set packet should be separated from any
23459 parameters by a @samp{:}; the parameters themselves should be
23460 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23461 full packet name, and check for a separator or the end of the packet,
23462 in case two packet names share a common prefix. New packets should not begin
23463 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23464 packets predate these conventions, and have arguments without any terminator
23465 for the packet name; we suspect they are in widespread use in places that
23466 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23467 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23470 Like the descriptions of the other packets, each description here
23471 has a template showing the packet's overall syntax, followed by an
23472 explanation of the packet's meaning. We include spaces in some of the
23473 templates for clarity; these are not part of the packet's syntax. No
23474 @value{GDBN} packet uses spaces to separate its components.
23476 Here are the currently defined query and set packets:
23481 @cindex current thread, remote request
23482 @cindex @samp{qC} packet
23483 Return the current thread id.
23488 Where @var{pid} is an unsigned hexadecimal process id.
23489 @item @r{(anything else)}
23490 Any other reply implies the old pid.
23493 @item qCRC:@var{addr},@var{length}
23494 @cindex CRC of memory block, remote request
23495 @cindex @samp{qCRC} packet
23496 Compute the CRC checksum of a block of memory.
23500 An error (such as memory fault)
23501 @item C @var{crc32}
23502 The specified memory region's checksum is @var{crc32}.
23506 @itemx qsThreadInfo
23507 @cindex list active threads, remote request
23508 @cindex @samp{qfThreadInfo} packet
23509 @cindex @samp{qsThreadInfo} packet
23510 Obtain a list of all active thread ids from the target (OS). Since there
23511 may be too many active threads to fit into one reply packet, this query
23512 works iteratively: it may require more than one query/reply sequence to
23513 obtain the entire list of threads. The first query of the sequence will
23514 be the @samp{qfThreadInfo} query; subsequent queries in the
23515 sequence will be the @samp{qsThreadInfo} query.
23517 NOTE: This packet replaces the @samp{qL} query (see below).
23523 @item m @var{id},@var{id}@dots{}
23524 a comma-separated list of thread ids
23526 (lower case letter @samp{L}) denotes end of list.
23529 In response to each query, the target will reply with a list of one or
23530 more thread ids, in big-endian unsigned hex, separated by commas.
23531 @value{GDBN} will respond to each reply with a request for more thread
23532 ids (using the @samp{qs} form of the query), until the target responds
23533 with @samp{l} (lower-case el, for @dfn{last}).
23535 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23536 @cindex get thread-local storage address, remote request
23537 @cindex @samp{qGetTLSAddr} packet
23538 Fetch the address associated with thread local storage specified
23539 by @var{thread-id}, @var{offset}, and @var{lm}.
23541 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23542 thread for which to fetch the TLS address.
23544 @var{offset} is the (big endian, hex encoded) offset associated with the
23545 thread local variable. (This offset is obtained from the debug
23546 information associated with the variable.)
23548 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
23549 the load module associated with the thread local storage. For example,
23550 a @sc{gnu}/Linux system will pass the link map address of the shared
23551 object associated with the thread local storage under consideration.
23552 Other operating environments may choose to represent the load module
23553 differently, so the precise meaning of this parameter will vary.
23557 @item @var{XX}@dots{}
23558 Hex encoded (big endian) bytes representing the address of the thread
23559 local storage requested.
23562 An error occurred. @var{nn} are hex digits.
23565 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
23568 Use of this request packet is controlled by the @code{set remote
23569 get-thread-local-storage-address} command (@pxref{Remote
23570 configuration, set remote get-thread-local-storage-address}).
23572 @item qL @var{startflag} @var{threadcount} @var{nextthread}
23573 Obtain thread information from RTOS. Where: @var{startflag} (one hex
23574 digit) is one to indicate the first query and zero to indicate a
23575 subsequent query; @var{threadcount} (two hex digits) is the maximum
23576 number of threads the response packet can contain; and @var{nextthread}
23577 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
23578 returned in the response as @var{argthread}.
23580 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
23584 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
23585 Where: @var{count} (two hex digits) is the number of threads being
23586 returned; @var{done} (one hex digit) is zero to indicate more threads
23587 and one indicates no further threads; @var{argthreadid} (eight hex
23588 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
23589 is a sequence of thread IDs from the target. @var{threadid} (eight hex
23590 digits). See @code{remote.c:parse_threadlist_response()}.
23594 @cindex section offsets, remote request
23595 @cindex @samp{qOffsets} packet
23596 Get section offsets that the target used when re-locating the downloaded
23597 image. @emph{Note: while a @code{Bss} offset is included in the
23598 response, @value{GDBN} ignores this and instead applies the @code{Data}
23599 offset to the @code{Bss} section.}
23603 @item Text=@var{xxx};Data=@var{yyy};Bss=@var{zzz}
23606 @item qP @var{mode} @var{threadid}
23607 @cindex thread information, remote request
23608 @cindex @samp{qP} packet
23609 Returns information on @var{threadid}. Where: @var{mode} is a hex
23610 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
23612 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
23615 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
23617 @item qRcmd,@var{command}
23618 @cindex execute remote command, remote request
23619 @cindex @samp{qRcmd} packet
23620 @var{command} (hex encoded) is passed to the local interpreter for
23621 execution. Invalid commands should be reported using the output
23622 string. Before the final result packet, the target may also respond
23623 with a number of intermediate @samp{O@var{output}} console output
23624 packets. @emph{Implementors should note that providing access to a
23625 stubs's interpreter may have security implications}.
23630 A command response with no output.
23632 A command response with the hex encoded output string @var{OUTPUT}.
23634 Indicate a badly formed request.
23636 An empty reply indicates that @samp{qRcmd} is not recognized.
23639 (Note that the @code{qRcmd} packet's name is separated from the
23640 command by a @samp{,}, not a @samp{:}, contrary to the naming
23641 conventions above. Please don't use this packet as a model for new
23644 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
23645 @cindex supported packets, remote query
23646 @cindex features of the remote protocol
23647 @cindex @samp{qSupported} packet
23648 @anchor{qSupported}
23649 Tell the remote stub about features supported by @value{GDBN}, and
23650 query the stub for features it supports. This packet allows
23651 @value{GDBN} and the remote stub to take advantage of each others'
23652 features. @samp{qSupported} also consolidates multiple feature probes
23653 at startup, to improve @value{GDBN} performance---a single larger
23654 packet performs better than multiple smaller probe packets on
23655 high-latency links. Some features may enable behavior which must not
23656 be on by default, e.g.@: because it would confuse older clients or
23657 stubs. Other features may describe packets which could be
23658 automatically probed for, but are not. These features must be
23659 reported before @value{GDBN} will use them. This ``default
23660 unsupported'' behavior is not appropriate for all packets, but it
23661 helps to keep the initial connection time under control with new
23662 versions of @value{GDBN} which support increasing numbers of packets.
23666 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
23667 The stub supports or does not support each returned @var{stubfeature},
23668 depending on the form of each @var{stubfeature} (see below for the
23671 An empty reply indicates that @samp{qSupported} is not recognized,
23672 or that no features needed to be reported to @value{GDBN}.
23675 The allowed forms for each feature (either a @var{gdbfeature} in the
23676 @samp{qSupported} packet, or a @var{stubfeature} in the response)
23680 @item @var{name}=@var{value}
23681 The remote protocol feature @var{name} is supported, and associated
23682 with the specified @var{value}. The format of @var{value} depends
23683 on the feature, but it must not include a semicolon.
23685 The remote protocol feature @var{name} is supported, and does not
23686 need an associated value.
23688 The remote protocol feature @var{name} is not supported.
23690 The remote protocol feature @var{name} may be supported, and
23691 @value{GDBN} should auto-detect support in some other way when it is
23692 needed. This form will not be used for @var{gdbfeature} notifications,
23693 but may be used for @var{stubfeature} responses.
23696 Whenever the stub receives a @samp{qSupported} request, the
23697 supplied set of @value{GDBN} features should override any previous
23698 request. This allows @value{GDBN} to put the stub in a known
23699 state, even if the stub had previously been communicating with
23700 a different version of @value{GDBN}.
23702 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
23703 are defined yet. Stubs should ignore any unknown values for
23704 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
23705 packet supports receiving packets of unlimited length (earlier
23706 versions of @value{GDBN} may reject overly long responses). Values
23707 for @var{gdbfeature} may be defined in the future to let the stub take
23708 advantage of new features in @value{GDBN}, e.g.@: incompatible
23709 improvements in the remote protocol---support for unlimited length
23710 responses would be a @var{gdbfeature} example, if it were not implied by
23711 the @samp{qSupported} query. The stub's reply should be independent
23712 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
23713 describes all the features it supports, and then the stub replies with
23714 all the features it supports.
23716 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
23717 responses, as long as each response uses one of the standard forms.
23719 Some features are flags. A stub which supports a flag feature
23720 should respond with a @samp{+} form response. Other features
23721 require values, and the stub should respond with an @samp{=}
23724 Each feature has a default value, which @value{GDBN} will use if
23725 @samp{qSupported} is not available or if the feature is not mentioned
23726 in the @samp{qSupported} response. The default values are fixed; a
23727 stub is free to omit any feature responses that match the defaults.
23729 Not all features can be probed, but for those which can, the probing
23730 mechanism is useful: in some cases, a stub's internal
23731 architecture may not allow the protocol layer to know some information
23732 about the underlying target in advance. This is especially common in
23733 stubs which may be configured for multiple targets.
23735 These are the currently defined stub features and their properties:
23737 @multitable @columnfractions 0.25 0.2 0.2 0.2
23738 @c NOTE: The first row should be @headitem, but we do not yet require
23739 @c a new enough version of Texinfo (4.7) to use @headitem.
23741 @tab Value Required
23745 @item @samp{PacketSize}
23750 @item @samp{qXfer:auxv:read}
23755 @item @samp{qXfer:memory-map:read}
23762 These are the currently defined stub features, in more detail:
23765 @cindex packet size, remote protocol
23766 @item PacketSize=@var{bytes}
23767 The remote stub can accept packets up to at least @var{bytes} in
23768 length. @value{GDBN} will send packets up to this size for bulk
23769 transfers, and will never send larger packets. This is a limit on the
23770 data characters in the packet, including the frame and checksum.
23771 There is no trailing NUL byte in a remote protocol packet; if the stub
23772 stores packets in a NUL-terminated format, it should allow an extra
23773 byte in its buffer for the NUL. If this stub feature is not supported,
23774 @value{GDBN} guesses based on the size of the @samp{g} packet response.
23776 @item qXfer:auxv:read
23777 The remote stub understands the @samp{qXfer:auxv:read} packet
23778 (@pxref{qXfer auxiliary vector read}).
23783 @cindex symbol lookup, remote request
23784 @cindex @samp{qSymbol} packet
23785 Notify the target that @value{GDBN} is prepared to serve symbol lookup
23786 requests. Accept requests from the target for the values of symbols.
23791 The target does not need to look up any (more) symbols.
23792 @item qSymbol:@var{sym_name}
23793 The target requests the value of symbol @var{sym_name} (hex encoded).
23794 @value{GDBN} may provide the value by using the
23795 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
23799 @item qSymbol:@var{sym_value}:@var{sym_name}
23800 Set the value of @var{sym_name} to @var{sym_value}.
23802 @var{sym_name} (hex encoded) is the name of a symbol whose value the
23803 target has previously requested.
23805 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
23806 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
23812 The target does not need to look up any (more) symbols.
23813 @item qSymbol:@var{sym_name}
23814 The target requests the value of a new symbol @var{sym_name} (hex
23815 encoded). @value{GDBN} will continue to supply the values of symbols
23816 (if available), until the target ceases to request them.
23821 @xref{Tracepoint Packets}.
23823 @item qThreadExtraInfo,@var{id}
23824 @cindex thread attributes info, remote request
23825 @cindex @samp{qThreadExtraInfo} packet
23826 Obtain a printable string description of a thread's attributes from
23827 the target OS. @var{id} is a thread-id in big-endian hex. This
23828 string may contain anything that the target OS thinks is interesting
23829 for @value{GDBN} to tell the user about the thread. The string is
23830 displayed in @value{GDBN}'s @code{info threads} display. Some
23831 examples of possible thread extra info strings are @samp{Runnable}, or
23832 @samp{Blocked on Mutex}.
23836 @item @var{XX}@dots{}
23837 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
23838 comprising the printable string containing the extra information about
23839 the thread's attributes.
23842 (Note that the @code{qThreadExtraInfo} packet's name is separated from
23843 the command by a @samp{,}, not a @samp{:}, contrary to the naming
23844 conventions above. Please don't use this packet as a model for new
23852 @xref{Tracepoint Packets}.
23854 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
23855 @cindex read special object, remote request
23856 @cindex @samp{qXfer} packet
23857 @anchor{qXfer read}
23858 Read uninterpreted bytes from the target's special data area
23859 identified by the keyword @var{object}. Request @var{length} bytes
23860 starting at @var{offset} bytes into the data. The content and
23861 encoding of @var{annex} is specific to the object; it can supply
23862 additional details about what data to access.
23864 Here are the specific requests of this form defined so far. All
23865 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
23866 formats, listed below.
23869 @item qXfer:auxv:read::@var{offset},@var{length}
23870 @anchor{qXfer auxiliary vector read}
23871 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
23872 auxiliary vector}, and @ref{Remote configuration,
23873 read-aux-vector-packet}. Note @var{annex} must be empty.
23875 This packet is not probed by default; the remote stub must request it,
23876 by suppling an appropriate @samp{qSupported} response (@pxref{qSupported}).
23880 @item qXfer:memory-map:read::@var{offset},@var{length}
23881 @anchor{qXfer memory map read}
23882 Access the target's @dfn{memory-map}. @xref{Memory map format}. The
23883 annex part of the generic @samp{qXfer} packet must be empty
23884 (@pxref{qXfer read}).
23886 This packet is not probed by default; the remote stub must request it,
23887 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23893 Data @var{data} (@pxref{Binary Data}) has been read from the
23894 target. There may be more data at a higher address (although
23895 it is permitted to return @samp{m} even for the last valid
23896 block of data, as long as at least one byte of data was read).
23897 @var{data} may have fewer bytes than the @var{length} in the
23901 Data @var{data} (@pxref{Binary Data}) has been read from the target.
23902 There is no more data to be read. @var{data} may have fewer bytes
23903 than the @var{length} in the request.
23906 The @var{offset} in the request is at the end of the data.
23907 There is no more data to be read.
23910 The request was malformed, or @var{annex} was invalid.
23913 The offset was invalid, or there was an error encountered reading the data.
23914 @var{nn} is a hex-encoded @code{errno} value.
23917 An empty reply indicates the @var{object} string was not recognized by
23918 the stub, or that the object does not support reading.
23921 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
23922 @cindex write data into object, remote request
23923 Write uninterpreted bytes into the target's special data area
23924 identified by the keyword @var{object}, starting at @var{offset} bytes
23925 into the data. @samp{@var{data}@dots{}} is the binary-encoded data
23926 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
23927 is specific to the object; it can supply additional details about what data
23930 No requests of this form are presently in use. This specification
23931 serves as a placeholder to document the common format that new
23932 specific request specifications ought to use.
23937 @var{nn} (hex encoded) is the number of bytes written.
23938 This may be fewer bytes than supplied in the request.
23941 The request was malformed, or @var{annex} was invalid.
23944 The offset was invalid, or there was an error encountered writing the data.
23945 @var{nn} is a hex-encoded @code{errno} value.
23948 An empty reply indicates the @var{object} string was not
23949 recognized by the stub, or that the object does not support writing.
23952 @item qXfer:@var{object}:@var{operation}:@dots{}
23953 Requests of this form may be added in the future. When a stub does
23954 not recognize the @var{object} keyword, or its support for
23955 @var{object} does not recognize the @var{operation} keyword, the stub
23956 must respond with an empty packet.
23960 @node Register Packet Format
23961 @section Register Packet Format
23963 The following @code{g}/@code{G} packets have previously been defined.
23964 In the below, some thirty-two bit registers are transferred as
23965 sixty-four bits. Those registers should be zero/sign extended (which?)
23966 to fill the space allocated. Register bytes are transferred in target
23967 byte order. The two nibbles within a register byte are transferred
23968 most-significant - least-significant.
23974 All registers are transferred as thirty-two bit quantities in the order:
23975 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
23976 registers; fsr; fir; fp.
23980 All registers are transferred as sixty-four bit quantities (including
23981 thirty-two bit registers such as @code{sr}). The ordering is the same
23986 @node Tracepoint Packets
23987 @section Tracepoint Packets
23988 @cindex tracepoint packets
23989 @cindex packets, tracepoint
23991 Here we describe the packets @value{GDBN} uses to implement
23992 tracepoints (@pxref{Tracepoints}).
23996 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
23997 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
23998 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
23999 the tracepoint is disabled. @var{step} is the tracepoint's step
24000 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24001 present, further @samp{QTDP} packets will follow to specify this
24002 tracepoint's actions.
24007 The packet was understood and carried out.
24009 The packet was not recognized.
24012 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24013 Define actions to be taken when a tracepoint is hit. @var{n} and
24014 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24015 this tracepoint. This packet may only be sent immediately after
24016 another @samp{QTDP} packet that ended with a @samp{-}. If the
24017 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24018 specifying more actions for this tracepoint.
24020 In the series of action packets for a given tracepoint, at most one
24021 can have an @samp{S} before its first @var{action}. If such a packet
24022 is sent, it and the following packets define ``while-stepping''
24023 actions. Any prior packets define ordinary actions --- that is, those
24024 taken when the tracepoint is first hit. If no action packet has an
24025 @samp{S}, then all the packets in the series specify ordinary
24026 tracepoint actions.
24028 The @samp{@var{action}@dots{}} portion of the packet is a series of
24029 actions, concatenated without separators. Each action has one of the
24035 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24036 a hexadecimal number whose @var{i}'th bit is set if register number
24037 @var{i} should be collected. (The least significant bit is numbered
24038 zero.) Note that @var{mask} may be any number of digits long; it may
24039 not fit in a 32-bit word.
24041 @item M @var{basereg},@var{offset},@var{len}
24042 Collect @var{len} bytes of memory starting at the address in register
24043 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24044 @samp{-1}, then the range has a fixed address: @var{offset} is the
24045 address of the lowest byte to collect. The @var{basereg},
24046 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24047 values (the @samp{-1} value for @var{basereg} is a special case).
24049 @item X @var{len},@var{expr}
24050 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24051 it directs. @var{expr} is an agent expression, as described in
24052 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24053 two-digit hex number in the packet; @var{len} is the number of bytes
24054 in the expression (and thus one-half the number of hex digits in the
24059 Any number of actions may be packed together in a single @samp{QTDP}
24060 packet, as long as the packet does not exceed the maximum packet
24061 length (400 bytes, for many stubs). There may be only one @samp{R}
24062 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24063 actions. Any registers referred to by @samp{M} and @samp{X} actions
24064 must be collected by a preceding @samp{R} action. (The
24065 ``while-stepping'' actions are treated as if they were attached to a
24066 separate tracepoint, as far as these restrictions are concerned.)
24071 The packet was understood and carried out.
24073 The packet was not recognized.
24076 @item QTFrame:@var{n}
24077 Select the @var{n}'th tracepoint frame from the buffer, and use the
24078 register and memory contents recorded there to answer subsequent
24079 request packets from @value{GDBN}.
24081 A successful reply from the stub indicates that the stub has found the
24082 requested frame. The response is a series of parts, concatenated
24083 without separators, describing the frame we selected. Each part has
24084 one of the following forms:
24088 The selected frame is number @var{n} in the trace frame buffer;
24089 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24090 was no frame matching the criteria in the request packet.
24093 The selected trace frame records a hit of tracepoint number @var{t};
24094 @var{t} is a hexadecimal number.
24098 @item QTFrame:pc:@var{addr}
24099 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24100 currently selected frame whose PC is @var{addr};
24101 @var{addr} is a hexadecimal number.
24103 @item QTFrame:tdp:@var{t}
24104 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24105 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24106 is a hexadecimal number.
24108 @item QTFrame:range:@var{start}:@var{end}
24109 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24110 currently selected frame whose PC is between @var{start} (inclusive)
24111 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24114 @item QTFrame:outside:@var{start}:@var{end}
24115 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24116 frame @emph{outside} the given range of addresses.
24119 Begin the tracepoint experiment. Begin collecting data from tracepoint
24120 hits in the trace frame buffer.
24123 End the tracepoint experiment. Stop collecting trace frames.
24126 Clear the table of tracepoints, and empty the trace frame buffer.
24128 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24129 Establish the given ranges of memory as ``transparent''. The stub
24130 will answer requests for these ranges from memory's current contents,
24131 if they were not collected as part of the tracepoint hit.
24133 @value{GDBN} uses this to mark read-only regions of memory, like those
24134 containing program code. Since these areas never change, they should
24135 still have the same contents they did when the tracepoint was hit, so
24136 there's no reason for the stub to refuse to provide their contents.
24139 Ask the stub if there is a trace experiment running right now.
24144 There is no trace experiment running.
24146 There is a trace experiment running.
24153 @section Interrupts
24154 @cindex interrupts (remote protocol)
24156 When a program on the remote target is running, @value{GDBN} may
24157 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24158 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24159 setting (@pxref{set remotebreak}).
24161 The precise meaning of @code{BREAK} is defined by the transport
24162 mechanism and may, in fact, be undefined. @value{GDBN} does
24163 not currently define a @code{BREAK} mechanism for any of the network
24166 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24167 transport mechanisms. It is represented by sending the single byte
24168 @code{0x03} without any of the usual packet overhead described in
24169 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24170 transmitted as part of a packet, it is considered to be packet data
24171 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24172 (@pxref{X packet}), used for binary downloads, may include an unescaped
24173 @code{0x03} as part of its packet.
24175 Stubs are not required to recognize these interrupt mechanisms and the
24176 precise meaning associated with receipt of the interrupt is
24177 implementation defined. If the stub is successful at interrupting the
24178 running program, it is expected that it will send one of the Stop
24179 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24180 of successfully stopping the program. Interrupts received while the
24181 program is stopped will be discarded.
24186 Example sequence of a target being re-started. Notice how the restart
24187 does not get any direct output:
24192 @emph{target restarts}
24195 <- @code{T001:1234123412341234}
24199 Example sequence of a target being stepped by a single instruction:
24202 -> @code{G1445@dots{}}
24207 <- @code{T001:1234123412341234}
24211 <- @code{1455@dots{}}
24215 @node File-I/O remote protocol extension
24216 @section File-I/O remote protocol extension
24217 @cindex File-I/O remote protocol extension
24220 * File-I/O Overview::
24221 * Protocol basics::
24222 * The F request packet::
24223 * The F reply packet::
24224 * The Ctrl-C message::
24226 * List of supported calls::
24227 * Protocol specific representation of datatypes::
24229 * File-I/O Examples::
24232 @node File-I/O Overview
24233 @subsection File-I/O Overview
24234 @cindex file-i/o overview
24236 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24237 target to use the host's file system and console I/O to perform various
24238 system calls. System calls on the target system are translated into a
24239 remote protocol packet to the host system, which then performs the needed
24240 actions and returns a response packet to the target system.
24241 This simulates file system operations even on targets that lack file systems.
24243 The protocol is defined to be independent of both the host and target systems.
24244 It uses its own internal representation of datatypes and values. Both
24245 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24246 translating the system-dependent value representations into the internal
24247 protocol representations when data is transmitted.
24249 The communication is synchronous. A system call is possible only when
24250 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24251 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24252 the target is stopped to allow deterministic access to the target's
24253 memory. Therefore File-I/O is not interruptible by target signals. On
24254 the other hand, it is possible to interrupt File-I/O by a user interrupt
24255 (Ctrl-C) within @value{GDBN}.
24257 The target's request to perform a host system call does not finish
24258 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24259 after finishing the system call, the target returns to continuing the
24260 previous activity (continue, step). No additional continue or step
24261 request from @value{GDBN} is required.
24264 (@value{GDBP}) continue
24265 <- target requests 'system call X'
24266 target is stopped, @value{GDBN} executes system call
24267 -> GDB returns result
24268 ... target continues, GDB returns to wait for the target
24269 <- target hits breakpoint and sends a Txx packet
24272 The protocol only supports I/O on the console and to regular files on
24273 the host file system. Character or block special devices, pipes,
24274 named pipes, sockets or any other communication method on the host
24275 system are not supported by this protocol.
24277 @node Protocol basics
24278 @subsection Protocol basics
24279 @cindex protocol basics, file-i/o
24281 The File-I/O protocol uses the @code{F} packet as the request as well
24282 as reply packet. Since a File-I/O system call can only occur when
24283 @value{GDBN} is waiting for a response from the continuing or stepping target,
24284 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24285 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24286 This @code{F} packet contains all information needed to allow @value{GDBN}
24287 to call the appropriate host system call:
24291 A unique identifier for the requested system call.
24294 All parameters to the system call. Pointers are given as addresses
24295 in the target memory address space. Pointers to strings are given as
24296 pointer/length pair. Numerical values are given as they are.
24297 Numerical control flags are given in a protocol specific representation.
24301 At this point, @value{GDBN} has to perform the following actions.
24305 If the parameters include pointer values to data needed as input to a
24306 system call, @value{GDBN} requests this data from the target with a
24307 standard @code{m} packet request. This additional communication has to be
24308 expected by the target implementation and is handled as any other @code{m}
24312 @value{GDBN} translates all value from protocol representation to host
24313 representation as needed. Datatypes are coerced into the host types.
24316 @value{GDBN} calls the system call.
24319 It then coerces datatypes back to protocol representation.
24322 If the system call is expected to return data in buffer space specified
24323 by pointer parameters to the call, the data is transmitted to the
24324 target using a @code{M} or @code{X} packet. This packet has to be expected
24325 by the target implementation and is handled as any other @code{M} or @code{X}
24330 Eventually @value{GDBN} replies with another @code{F} packet which contains all
24331 necessary information for the target to continue. This at least contains
24338 @code{errno}, if has been changed by the system call.
24345 After having done the needed type and value coercion, the target continues
24346 the latest continue or step action.
24348 @node The F request packet
24349 @subsection The @code{F} request packet
24350 @cindex file-i/o request packet
24351 @cindex @code{F} request packet
24353 The @code{F} request packet has the following format:
24356 @item F@var{call-id},@var{parameter@dots{}}
24358 @var{call-id} is the identifier to indicate the host system call to be called.
24359 This is just the name of the function.
24361 @var{parameter@dots{}} are the parameters to the system call.
24362 Parameters are hexadecimal integer values, either the actual values in case
24363 of scalar datatypes, pointers to target buffer space in case of compound
24364 datatypes and unspecified memory areas, or pointer/length pairs in case
24365 of string parameters. These are appended to the @var{call-id} as a
24366 comma-delimited list. All values are transmitted in ASCII
24367 string representation, pointer/length pairs separated by a slash.
24373 @node The F reply packet
24374 @subsection The @code{F} reply packet
24375 @cindex file-i/o reply packet
24376 @cindex @code{F} reply packet
24378 The @code{F} reply packet has the following format:
24382 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call specific attachment}
24384 @var{retcode} is the return code of the system call as hexadecimal value.
24386 @var{errno} is the @code{errno} set by the call, in protocol specific representation.
24387 This parameter can be omitted if the call was successful.
24389 @var{Ctrl-C flag} is only sent if the user requested a break. In this
24390 case, @var{errno} must be sent as well, even if the call was successful.
24391 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
24398 or, if the call was interrupted before the host call has been performed:
24405 assuming 4 is the protocol specific representation of @code{EINTR}.
24410 @node The Ctrl-C message
24411 @subsection The Ctrl-C message
24412 @cindex ctrl-c message, in file-i/o protocol
24414 If the Ctrl-C flag is set in the @value{GDBN}
24415 reply packet (@pxref{The F reply packet}),
24416 the target should behave as if it had
24417 gotten a break message. The meaning for the target is ``system call
24418 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
24419 (as with a break message) and return to @value{GDBN} with a @code{T02}
24422 It's important for the target to know in which
24423 state the system call was interrupted. There are two possible cases:
24427 The system call hasn't been performed on the host yet.
24430 The system call on the host has been finished.
24434 These two states can be distinguished by the target by the value of the
24435 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
24436 call hasn't been performed. This is equivalent to the @code{EINTR} handling
24437 on POSIX systems. In any other case, the target may presume that the
24438 system call has been finished --- successfully or not --- and should behave
24439 as if the break message arrived right after the system call.
24441 @value{GDBN} must behave reliably. If the system call has not been called
24442 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
24443 @code{errno} in the packet. If the system call on the host has been finished
24444 before the user requests a break, the full action must be finished by
24445 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
24446 The @code{F} packet may only be sent when either nothing has happened
24447 or the full action has been completed.
24450 @subsection Console I/O
24451 @cindex console i/o as part of file-i/o
24453 By default and if not explicitely closed by the target system, the file
24454 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
24455 on the @value{GDBN} console is handled as any other file output operation
24456 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
24457 by @value{GDBN} so that after the target read request from file descriptor
24458 0 all following typing is buffered until either one of the following
24463 The user types @kbd{C-c}. The behaviour is as explained above, and the
24465 system call is treated as finished.
24468 The user presses @key{RET}. This is treated as end of input with a trailing
24472 The user types @kbd{C-d}. This is treated as end of input. No trailing
24473 character (neither newline nor Ctrl-D) is appended to the input.
24477 If the user has typed more characters than fit in the buffer given to
24478 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
24479 either another @code{read(0, @dots{})} is requested by the target, or debugging
24480 is stopped at the user's request.
24483 @node List of supported calls
24484 @subsection List of supported calls
24485 @cindex list of supported file-i/o calls
24502 @unnumberedsubsubsec open
24503 @cindex open, file-i/o system call
24508 int open(const char *pathname, int flags);
24509 int open(const char *pathname, int flags, mode_t mode);
24513 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
24516 @var{flags} is the bitwise @code{OR} of the following values:
24520 If the file does not exist it will be created. The host
24521 rules apply as far as file ownership and time stamps
24525 When used with @code{O_CREAT}, if the file already exists it is
24526 an error and open() fails.
24529 If the file already exists and the open mode allows
24530 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
24531 truncated to zero length.
24534 The file is opened in append mode.
24537 The file is opened for reading only.
24540 The file is opened for writing only.
24543 The file is opened for reading and writing.
24547 Other bits are silently ignored.
24551 @var{mode} is the bitwise @code{OR} of the following values:
24555 User has read permission.
24558 User has write permission.
24561 Group has read permission.
24564 Group has write permission.
24567 Others have read permission.
24570 Others have write permission.
24574 Other bits are silently ignored.
24577 @item Return value:
24578 @code{open} returns the new file descriptor or -1 if an error
24585 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
24588 @var{pathname} refers to a directory.
24591 The requested access is not allowed.
24594 @var{pathname} was too long.
24597 A directory component in @var{pathname} does not exist.
24600 @var{pathname} refers to a device, pipe, named pipe or socket.
24603 @var{pathname} refers to a file on a read-only filesystem and
24604 write access was requested.
24607 @var{pathname} is an invalid pointer value.
24610 No space on device to create the file.
24613 The process already has the maximum number of files open.
24616 The limit on the total number of files open on the system
24620 The call was interrupted by the user.
24626 @unnumberedsubsubsec close
24627 @cindex close, file-i/o system call
24636 @samp{Fclose,@var{fd}}
24638 @item Return value:
24639 @code{close} returns zero on success, or -1 if an error occurred.
24645 @var{fd} isn't a valid open file descriptor.
24648 The call was interrupted by the user.
24654 @unnumberedsubsubsec read
24655 @cindex read, file-i/o system call
24660 int read(int fd, void *buf, unsigned int count);
24664 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
24666 @item Return value:
24667 On success, the number of bytes read is returned.
24668 Zero indicates end of file. If count is zero, read
24669 returns zero as well. On error, -1 is returned.
24675 @var{fd} is not a valid file descriptor or is not open for
24679 @var{bufptr} is an invalid pointer value.
24682 The call was interrupted by the user.
24688 @unnumberedsubsubsec write
24689 @cindex write, file-i/o system call
24694 int write(int fd, const void *buf, unsigned int count);
24698 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
24700 @item Return value:
24701 On success, the number of bytes written are returned.
24702 Zero indicates nothing was written. On error, -1
24709 @var{fd} is not a valid file descriptor or is not open for
24713 @var{bufptr} is an invalid pointer value.
24716 An attempt was made to write a file that exceeds the
24717 host specific maximum file size allowed.
24720 No space on device to write the data.
24723 The call was interrupted by the user.
24729 @unnumberedsubsubsec lseek
24730 @cindex lseek, file-i/o system call
24735 long lseek (int fd, long offset, int flag);
24739 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
24741 @var{flag} is one of:
24745 The offset is set to @var{offset} bytes.
24748 The offset is set to its current location plus @var{offset}
24752 The offset is set to the size of the file plus @var{offset}
24756 @item Return value:
24757 On success, the resulting unsigned offset in bytes from
24758 the beginning of the file is returned. Otherwise, a
24759 value of -1 is returned.
24765 @var{fd} is not a valid open file descriptor.
24768 @var{fd} is associated with the @value{GDBN} console.
24771 @var{flag} is not a proper value.
24774 The call was interrupted by the user.
24780 @unnumberedsubsubsec rename
24781 @cindex rename, file-i/o system call
24786 int rename(const char *oldpath, const char *newpath);
24790 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
24792 @item Return value:
24793 On success, zero is returned. On error, -1 is returned.
24799 @var{newpath} is an existing directory, but @var{oldpath} is not a
24803 @var{newpath} is a non-empty directory.
24806 @var{oldpath} or @var{newpath} is a directory that is in use by some
24810 An attempt was made to make a directory a subdirectory
24814 A component used as a directory in @var{oldpath} or new
24815 path is not a directory. Or @var{oldpath} is a directory
24816 and @var{newpath} exists but is not a directory.
24819 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
24822 No access to the file or the path of the file.
24826 @var{oldpath} or @var{newpath} was too long.
24829 A directory component in @var{oldpath} or @var{newpath} does not exist.
24832 The file is on a read-only filesystem.
24835 The device containing the file has no room for the new
24839 The call was interrupted by the user.
24845 @unnumberedsubsubsec unlink
24846 @cindex unlink, file-i/o system call
24851 int unlink(const char *pathname);
24855 @samp{Funlink,@var{pathnameptr}/@var{len}}
24857 @item Return value:
24858 On success, zero is returned. On error, -1 is returned.
24864 No access to the file or the path of the file.
24867 The system does not allow unlinking of directories.
24870 The file @var{pathname} cannot be unlinked because it's
24871 being used by another process.
24874 @var{pathnameptr} is an invalid pointer value.
24877 @var{pathname} was too long.
24880 A directory component in @var{pathname} does not exist.
24883 A component of the path is not a directory.
24886 The file is on a read-only filesystem.
24889 The call was interrupted by the user.
24895 @unnumberedsubsubsec stat/fstat
24896 @cindex fstat, file-i/o system call
24897 @cindex stat, file-i/o system call
24902 int stat(const char *pathname, struct stat *buf);
24903 int fstat(int fd, struct stat *buf);
24907 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
24908 @samp{Ffstat,@var{fd},@var{bufptr}}
24910 @item Return value:
24911 On success, zero is returned. On error, -1 is returned.
24917 @var{fd} is not a valid open file.
24920 A directory component in @var{pathname} does not exist or the
24921 path is an empty string.
24924 A component of the path is not a directory.
24927 @var{pathnameptr} is an invalid pointer value.
24930 No access to the file or the path of the file.
24933 @var{pathname} was too long.
24936 The call was interrupted by the user.
24942 @unnumberedsubsubsec gettimeofday
24943 @cindex gettimeofday, file-i/o system call
24948 int gettimeofday(struct timeval *tv, void *tz);
24952 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
24954 @item Return value:
24955 On success, 0 is returned, -1 otherwise.
24961 @var{tz} is a non-NULL pointer.
24964 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
24970 @unnumberedsubsubsec isatty
24971 @cindex isatty, file-i/o system call
24976 int isatty(int fd);
24980 @samp{Fisatty,@var{fd}}
24982 @item Return value:
24983 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
24989 The call was interrupted by the user.
24994 Note that the @code{isatty} call is treated as a special case: it returns
24995 1 to the target if the file descriptor is attached
24996 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
24997 would require implementing @code{ioctl} and would be more complex than
25002 @unnumberedsubsubsec system
25003 @cindex system, file-i/o system call
25008 int system(const char *command);
25012 @samp{Fsystem,@var{commandptr}/@var{len}}
25014 @item Return value:
25015 If @var{len} is zero, the return value indicates whether a shell is
25016 available. A zero return value indicates a shell is not available.
25017 For non-zero @var{len}, the value returned is -1 on error and the
25018 return status of the command otherwise. Only the exit status of the
25019 command is returned, which is extracted from the host's @code{system}
25020 return value by calling @code{WEXITSTATUS(retval)}. In case
25021 @file{/bin/sh} could not be executed, 127 is returned.
25027 The call was interrupted by the user.
25032 @value{GDBN} takes over the full task of calling the necessary host calls
25033 to perform the @code{system} call. The return value of @code{system} on
25034 the host is simplified before it's returned
25035 to the target. Any termination signal information from the child process
25036 is discarded, and the return value consists
25037 entirely of the exit status of the called command.
25039 Due to security concerns, the @code{system} call is by default refused
25040 by @value{GDBN}. The user has to allow this call explicitly with the
25041 @code{set remote system-call-allowed 1} command.
25044 @item set remote system-call-allowed
25045 @kindex set remote system-call-allowed
25046 Control whether to allow the @code{system} calls in the File I/O
25047 protocol for the remote target. The default is zero (disabled).
25049 @item show remote system-call-allowed
25050 @kindex show remote system-call-allowed
25051 Show whether the @code{system} calls are allowed in the File I/O
25055 @node Protocol specific representation of datatypes
25056 @subsection Protocol specific representation of datatypes
25057 @cindex protocol specific representation of datatypes, in file-i/o protocol
25060 * Integral datatypes::
25062 * Memory transfer::
25067 @node Integral datatypes
25068 @unnumberedsubsubsec Integral datatypes
25069 @cindex integral datatypes, in file-i/o protocol
25071 The integral datatypes used in the system calls are @code{int},
25072 @code{unsigned int}, @code{long}, @code{unsigned long},
25073 @code{mode_t}, and @code{time_t}.
25075 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25076 implemented as 32 bit values in this protocol.
25078 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25080 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25081 in @file{limits.h}) to allow range checking on host and target.
25083 @code{time_t} datatypes are defined as seconds since the Epoch.
25085 All integral datatypes transferred as part of a memory read or write of a
25086 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25089 @node Pointer values
25090 @unnumberedsubsubsec Pointer values
25091 @cindex pointer values, in file-i/o protocol
25093 Pointers to target data are transmitted as they are. An exception
25094 is made for pointers to buffers for which the length isn't
25095 transmitted as part of the function call, namely strings. Strings
25096 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25103 which is a pointer to data of length 18 bytes at position 0x1aaf.
25104 The length is defined as the full string length in bytes, including
25105 the trailing null byte. For example, the string @code{"hello world"}
25106 at address 0x123456 is transmitted as
25112 @node Memory transfer
25113 @unnumberedsubsubsec Memory transfer
25114 @cindex memory transfer, in file-i/o protocol
25116 Structured data which is transferred using a memory read or write (for
25117 example, a @code{struct stat}) is expected to be in a protocol specific format
25118 with all scalar multibyte datatypes being big endian. Translation to
25119 this representation needs to be done both by the target before the @code{F}
25120 packet is sent, and by @value{GDBN} before
25121 it transfers memory to the target. Transferred pointers to structured
25122 data should point to the already-coerced data at any time.
25126 @unnumberedsubsubsec struct stat
25127 @cindex struct stat, in file-i/o protocol
25129 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25130 is defined as follows:
25134 unsigned int st_dev; /* device */
25135 unsigned int st_ino; /* inode */
25136 mode_t st_mode; /* protection */
25137 unsigned int st_nlink; /* number of hard links */
25138 unsigned int st_uid; /* user ID of owner */
25139 unsigned int st_gid; /* group ID of owner */
25140 unsigned int st_rdev; /* device type (if inode device) */
25141 unsigned long st_size; /* total size, in bytes */
25142 unsigned long st_blksize; /* blocksize for filesystem I/O */
25143 unsigned long st_blocks; /* number of blocks allocated */
25144 time_t st_atime; /* time of last access */
25145 time_t st_mtime; /* time of last modification */
25146 time_t st_ctime; /* time of last change */
25150 The integral datatypes conform to the definitions given in the
25151 appropriate section (see @ref{Integral datatypes}, for details) so this
25152 structure is of size 64 bytes.
25154 The values of several fields have a restricted meaning and/or
25160 A value of 0 represents a file, 1 the console.
25163 No valid meaning for the target. Transmitted unchanged.
25166 Valid mode bits are described in @ref{Constants}. Any other
25167 bits have currently no meaning for the target.
25172 No valid meaning for the target. Transmitted unchanged.
25177 These values have a host and file system dependent
25178 accuracy. Especially on Windows hosts, the file system may not
25179 support exact timing values.
25182 The target gets a @code{struct stat} of the above representation and is
25183 responsible for coercing it to the target representation before
25186 Note that due to size differences between the host, target, and protocol
25187 representations of @code{struct stat} members, these members could eventually
25188 get truncated on the target.
25190 @node struct timeval
25191 @unnumberedsubsubsec struct timeval
25192 @cindex struct timeval, in file-i/o protocol
25194 The buffer of type @code{struct timeval} used by the File-I/O protocol
25195 is defined as follows:
25199 time_t tv_sec; /* second */
25200 long tv_usec; /* microsecond */
25204 The integral datatypes conform to the definitions given in the
25205 appropriate section (see @ref{Integral datatypes}, for details) so this
25206 structure is of size 8 bytes.
25209 @subsection Constants
25210 @cindex constants, in file-i/o protocol
25212 The following values are used for the constants inside of the
25213 protocol. @value{GDBN} and target are responsible for translating these
25214 values before and after the call as needed.
25225 @unnumberedsubsubsec Open flags
25226 @cindex open flags, in file-i/o protocol
25228 All values are given in hexadecimal representation.
25240 @node mode_t values
25241 @unnumberedsubsubsec mode_t values
25242 @cindex mode_t values, in file-i/o protocol
25244 All values are given in octal representation.
25261 @unnumberedsubsubsec Errno values
25262 @cindex errno values, in file-i/o protocol
25264 All values are given in decimal representation.
25289 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25290 any error value not in the list of supported error numbers.
25293 @unnumberedsubsubsec Lseek flags
25294 @cindex lseek flags, in file-i/o protocol
25303 @unnumberedsubsubsec Limits
25304 @cindex limits, in file-i/o protocol
25306 All values are given in decimal representation.
25309 INT_MIN -2147483648
25311 UINT_MAX 4294967295
25312 LONG_MIN -9223372036854775808
25313 LONG_MAX 9223372036854775807
25314 ULONG_MAX 18446744073709551615
25317 @node File-I/O Examples
25318 @subsection File-I/O Examples
25319 @cindex file-i/o examples
25321 Example sequence of a write call, file descriptor 3, buffer is at target
25322 address 0x1234, 6 bytes should be written:
25325 <- @code{Fwrite,3,1234,6}
25326 @emph{request memory read from target}
25329 @emph{return "6 bytes written"}
25333 Example sequence of a read call, file descriptor 3, buffer is at target
25334 address 0x1234, 6 bytes should be read:
25337 <- @code{Fread,3,1234,6}
25338 @emph{request memory write to target}
25339 -> @code{X1234,6:XXXXXX}
25340 @emph{return "6 bytes read"}
25344 Example sequence of a read call, call fails on the host due to invalid
25345 file descriptor (@code{EBADF}):
25348 <- @code{Fread,3,1234,6}
25352 Example sequence of a read call, user presses Ctrl-C before syscall on
25356 <- @code{Fread,3,1234,6}
25361 Example sequence of a read call, user presses Ctrl-C after syscall on
25365 <- @code{Fread,3,1234,6}
25366 -> @code{X1234,6:XXXXXX}
25370 @node Memory map format
25371 @section Memory map format
25372 @cindex memory map format
25374 To be able to write into flash memory, @value{GDBN} needs to obtain a
25375 memory map from the target. This section describes the format of the
25378 The memory map is obtained using the @samp{qXfer:memory-map:read}
25379 (@pxref{qXfer memory map read}) packet and is an XML document that
25380 lists memory regions. The top-level structure of the document is shown below:
25383 <?xml version="1.0"?>
25384 <!DOCTYPE memory-map
25385 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
25386 "http://sourceware.org/gdb/gdb-memory-map.dtd">
25392 Each region can be either:
25397 A region of RAM starting at @var{addr} and extending for @var{length}
25401 <memory type="ram" start="@var{addr}" length="@var{length}"/>
25406 A region of read-only memory:
25409 <memory type="rom" start="@var{addr}" length="@var{length}"/>
25414 A region of flash memory, with erasure blocks @var{blocksize}
25418 <memory type="flash" start="@var{addr}" length="@var{length}">
25419 <property name="blocksize">@var{blocksize}</property>
25425 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
25426 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
25427 packets to write to addresses in such ranges.
25429 The formal DTD for memory map format is given below:
25432 <!-- ................................................... -->
25433 <!-- Memory Map XML DTD ................................ -->
25434 <!-- File: memory-map.dtd .............................. -->
25435 <!-- .................................... .............. -->
25436 <!-- memory-map.dtd -->
25437 <!-- memory-map: Root element with versioning -->
25438 <!ELEMENT memory-map (memory | property)>
25439 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
25440 <!ELEMENT memory (property)>
25441 <!-- memory: Specifies a memory region,
25442 and its type, or device. -->
25443 <!ATTLIST memory type CDATA #REQUIRED
25444 start CDATA #REQUIRED
25445 length CDATA #REQUIRED
25446 device CDATA #IMPLIED>
25447 <!-- property: Generic attribute tag -->
25448 <!ELEMENT property (#PCDATA | property)*>
25449 <!ATTLIST property name CDATA #REQUIRED>
25452 @include agentexpr.texi
25466 % I think something like @colophon should be in texinfo. In the
25468 \long\def\colophon{\hbox to0pt{}\vfill
25469 \centerline{The body of this manual is set in}
25470 \centerline{\fontname\tenrm,}
25471 \centerline{with headings in {\bf\fontname\tenbf}}
25472 \centerline{and examples in {\tt\fontname\tentt}.}
25473 \centerline{{\it\fontname\tenit\/},}
25474 \centerline{{\bf\fontname\tenbf}, and}
25475 \centerline{{\sl\fontname\tensl\/}}
25476 \centerline{are used for emphasis.}\vfill}
25478 % Blame: doc@cygnus.com, 1991.