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 FSF's Back-Cover Text is: ``You are free to copy and modify
66 this GNU Manual. Buying copies from GNU Press supports the FSF in
67 developing GNU and promoting software freedom.''
71 @title Debugging with @value{GDBN}
72 @subtitle The @sc{gnu} Source-Level Debugger
74 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
75 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
79 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
80 \hfill {\it Debugging with @value{GDBN}}\par
81 \hfill \TeX{}info \texinfoversion\par
85 @vskip 0pt plus 1filll
86 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
87 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
88 Free Software Foundation, Inc.
90 Published by the Free Software Foundation @*
91 51 Franklin Street, Fifth Floor,
92 Boston, MA 02110-1301, USA@*
95 Permission is granted to copy, distribute and/or modify this document
96 under the terms of the GNU Free Documentation License, Version 1.1 or
97 any later version published by the Free Software Foundation; with the
98 Invariant Sections being ``Free Software'' and ``Free Software Needs
99 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
100 and with the Back-Cover Texts as in (a) below.
102 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
103 this GNU Manual. Buying copies from GNU Press supports the FSF in
104 developing GNU and promoting software freedom.''
106 This edition of the GDB manual is dedicated to the memory of Fred
107 Fish. Fred was a long-standing contributor to GDB and to Free
108 software in general. We will miss him.
113 @node Top, Summary, (dir), (dir)
115 @top Debugging with @value{GDBN}
117 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
119 This is the @value{EDITION} Edition, for @value{GDBN} Version
122 Copyright (C) 1988-2006 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Stack:: Examining the stack
137 * Source:: Examining source files
138 * Data:: Examining data
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Sequences:: Canned sequences of commands
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
159 * GDB Bugs:: Reporting bugs in @value{GDBN}
161 * Command Line Editing:: Command Line Editing
162 * Using History Interactively:: Using History Interactively
163 * Formatting Documentation:: How to format and print @value{GDBN} documentation
164 * Installing GDB:: Installing GDB
165 * Maintenance Commands:: Maintenance Commands
166 * Remote Protocol:: GDB Remote Serial Protocol
167 * Agent Expressions:: The GDB Agent Expression Mechanism
168 * Target Descriptions:: How targets can describe themselves to
170 * Copying:: GNU General Public License says
171 how you can copy and share GDB
172 * GNU Free Documentation License:: The license for this documentation
181 @unnumbered Summary of @value{GDBN}
183 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
184 going on ``inside'' another program while it executes---or what another
185 program was doing at the moment it crashed.
187 @value{GDBN} can do four main kinds of things (plus other things in support of
188 these) to help you catch bugs in the act:
192 Start your program, specifying anything that might affect its behavior.
195 Make your program stop on specified conditions.
198 Examine what has happened, when your program has stopped.
201 Change things in your program, so you can experiment with correcting the
202 effects of one bug and go on to learn about another.
205 You can use @value{GDBN} to debug programs written in C and C@t{++}.
206 For more information, see @ref{Supported Languages,,Supported Languages}.
207 For more information, see @ref{C,,C and C++}.
210 Support for Modula-2 is partial. For information on Modula-2, see
211 @ref{Modula-2,,Modula-2}.
214 Debugging Pascal programs which use sets, subranges, file variables, or
215 nested functions does not currently work. @value{GDBN} does not support
216 entering expressions, printing values, or similar features using Pascal
220 @value{GDBN} can be used to debug programs written in Fortran, although
221 it may be necessary to refer to some variables with a trailing
224 @value{GDBN} can be used to debug programs written in Objective-C,
225 using either the Apple/NeXT or the GNU Objective-C runtime.
228 * Free Software:: Freely redistributable software
229 * Contributors:: Contributors to GDB
233 @unnumberedsec Free Software
235 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
236 General Public License
237 (GPL). The GPL gives you the freedom to copy or adapt a licensed
238 program---but every person getting a copy also gets with it the
239 freedom to modify that copy (which means that they must get access to
240 the source code), and the freedom to distribute further copies.
241 Typical software companies use copyrights to limit your freedoms; the
242 Free Software Foundation uses the GPL to preserve these freedoms.
244 Fundamentally, the General Public License is a license which says that
245 you have these freedoms and that you cannot take these freedoms away
248 @unnumberedsec Free Software Needs Free Documentation
250 The biggest deficiency in the free software community today is not in
251 the software---it is the lack of good free documentation that we can
252 include with the free software. Many of our most important
253 programs do not come with free reference manuals and free introductory
254 texts. Documentation is an essential part of any software package;
255 when an important free software package does not come with a free
256 manual and a free tutorial, that is a major gap. We have many such
259 Consider Perl, for instance. The tutorial manuals that people
260 normally use are non-free. How did this come about? Because the
261 authors of those manuals published them with restrictive terms---no
262 copying, no modification, source files not available---which exclude
263 them from the free software world.
265 That wasn't the first time this sort of thing happened, and it was far
266 from the last. Many times we have heard a GNU user eagerly describe a
267 manual that he is writing, his intended contribution to the community,
268 only to learn that he had ruined everything by signing a publication
269 contract to make it non-free.
271 Free documentation, like free software, is a matter of freedom, not
272 price. The problem with the non-free manual is not that publishers
273 charge a price for printed copies---that in itself is fine. (The Free
274 Software Foundation sells printed copies of manuals, too.) The
275 problem is the restrictions on the use of the manual. Free manuals
276 are available in source code form, and give you permission to copy and
277 modify. Non-free manuals do not allow this.
279 The criteria of freedom for a free manual are roughly the same as for
280 free software. Redistribution (including the normal kinds of
281 commercial redistribution) must be permitted, so that the manual can
282 accompany every copy of the program, both on-line and on paper.
284 Permission for modification of the technical content is crucial too.
285 When people modify the software, adding or changing features, if they
286 are conscientious they will change the manual too---so they can
287 provide accurate and clear documentation for the modified program. A
288 manual that leaves you no choice but to write a new manual to document
289 a changed version of the program is not really available to our
292 Some kinds of limits on the way modification is handled are
293 acceptable. For example, requirements to preserve the original
294 author's copyright notice, the distribution terms, or the list of
295 authors, are ok. It is also no problem to require modified versions
296 to include notice that they were modified. Even entire sections that
297 may not be deleted or changed are acceptable, as long as they deal
298 with nontechnical topics (like this one). These kinds of restrictions
299 are acceptable because they don't obstruct the community's normal use
302 However, it must be possible to modify all the @emph{technical}
303 content of the manual, and then distribute the result in all the usual
304 media, through all the usual channels. Otherwise, the restrictions
305 obstruct the use of the manual, it is not free, and we need another
306 manual to replace it.
308 Please spread the word about this issue. Our community continues to
309 lose manuals to proprietary publishing. If we spread the word that
310 free software needs free reference manuals and free tutorials, perhaps
311 the next person who wants to contribute by writing documentation will
312 realize, before it is too late, that only free manuals contribute to
313 the free software community.
315 If you are writing documentation, please insist on publishing it under
316 the GNU Free Documentation License or another free documentation
317 license. Remember that this decision requires your approval---you
318 don't have to let the publisher decide. Some commercial publishers
319 will use a free license if you insist, but they will not propose the
320 option; it is up to you to raise the issue and say firmly that this is
321 what you want. If the publisher you are dealing with refuses, please
322 try other publishers. If you're not sure whether a proposed license
323 is free, write to @email{licensing@@gnu.org}.
325 You can encourage commercial publishers to sell more free, copylefted
326 manuals and tutorials by buying them, and particularly by buying
327 copies from the publishers that paid for their writing or for major
328 improvements. Meanwhile, try to avoid buying non-free documentation
329 at all. Check the distribution terms of a manual before you buy it,
330 and insist that whoever seeks your business must respect your freedom.
331 Check the history of the book, and try to reward the publishers that
332 have paid or pay the authors to work on it.
334 The Free Software Foundation maintains a list of free documentation
335 published by other publishers, at
336 @url{http://www.fsf.org/doc/other-free-books.html}.
339 @unnumberedsec Contributors to @value{GDBN}
341 Richard Stallman was the original author of @value{GDBN}, and of many
342 other @sc{gnu} programs. Many others have contributed to its
343 development. This section attempts to credit major contributors. One
344 of the virtues of free software is that everyone is free to contribute
345 to it; with regret, we cannot actually acknowledge everyone here. The
346 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
347 blow-by-blow account.
349 Changes much prior to version 2.0 are lost in the mists of time.
352 @emph{Plea:} Additions to this section are particularly welcome. If you
353 or your friends (or enemies, to be evenhanded) have been unfairly
354 omitted from this list, we would like to add your names!
357 So that they may not regard their many labors as thankless, we
358 particularly thank those who shepherded @value{GDBN} through major
360 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
361 Jim Blandy (release 4.18);
362 Jason Molenda (release 4.17);
363 Stan Shebs (release 4.14);
364 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
365 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
366 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
367 Jim Kingdon (releases 3.5, 3.4, and 3.3);
368 and Randy Smith (releases 3.2, 3.1, and 3.0).
370 Richard Stallman, assisted at various times by Peter TerMaat, Chris
371 Hanson, and Richard Mlynarik, handled releases through 2.8.
373 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
374 in @value{GDBN}, with significant additional contributions from Per
375 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
376 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
377 much general update work leading to release 3.0).
379 @value{GDBN} uses the BFD subroutine library to examine multiple
380 object-file formats; BFD was a joint project of David V.
381 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
383 David Johnson wrote the original COFF support; Pace Willison did
384 the original support for encapsulated COFF.
386 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
388 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
389 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
391 Jean-Daniel Fekete contributed Sun 386i support.
392 Chris Hanson improved the HP9000 support.
393 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
394 David Johnson contributed Encore Umax support.
395 Jyrki Kuoppala contributed Altos 3068 support.
396 Jeff Law contributed HP PA and SOM support.
397 Keith Packard contributed NS32K support.
398 Doug Rabson contributed Acorn Risc Machine support.
399 Bob Rusk contributed Harris Nighthawk CX-UX support.
400 Chris Smith contributed Convex support (and Fortran debugging).
401 Jonathan Stone contributed Pyramid support.
402 Michael Tiemann contributed SPARC support.
403 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
404 Pace Willison contributed Intel 386 support.
405 Jay Vosburgh contributed Symmetry support.
406 Marko Mlinar contributed OpenRISC 1000 support.
408 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
410 Rich Schaefer and Peter Schauer helped with support of SunOS shared
413 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
414 about several machine instruction sets.
416 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
417 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
418 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
419 and RDI targets, respectively.
421 Brian Fox is the author of the readline libraries providing
422 command-line editing and command history.
424 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
425 Modula-2 support, and contributed the Languages chapter of this manual.
427 Fred Fish wrote most of the support for Unix System Vr4.
428 He also enhanced the command-completion support to cover C@t{++} overloaded
431 Hitachi America (now Renesas America), Ltd. sponsored the support for
432 H8/300, H8/500, and Super-H processors.
434 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
436 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
439 Toshiba sponsored the support for the TX39 Mips processor.
441 Matsushita sponsored the support for the MN10200 and MN10300 processors.
443 Fujitsu sponsored the support for SPARClite and FR30 processors.
445 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
448 Michael Snyder added support for tracepoints.
450 Stu Grossman wrote gdbserver.
452 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
453 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
455 The following people at the Hewlett-Packard Company contributed
456 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
457 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
458 compiler, and the Text User Interface (nee Terminal User Interface):
459 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
460 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
461 provided HP-specific information in this manual.
463 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
464 Robert Hoehne made significant contributions to the DJGPP port.
466 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
467 development since 1991. Cygnus engineers who have worked on @value{GDBN}
468 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
469 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
470 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
471 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
472 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
473 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
474 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
475 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
476 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
477 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
478 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
479 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
480 Zuhn have made contributions both large and small.
482 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
483 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
485 Jim Blandy added support for preprocessor macros, while working for Red
488 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
489 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
490 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
491 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
492 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
493 with the migration of old architectures to this new framework.
495 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
496 unwinder framework, this consisting of a fresh new design featuring
497 frame IDs, independent frame sniffers, and the sentinel frame. Mark
498 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
499 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
500 trad unwinders. The architecture-specific changes, each involving a
501 complete rewrite of the architecture's frame code, were carried out by
502 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
503 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
504 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
505 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
508 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
509 Tensilica, Inc.@: contributed support for Xtensa processors. Others
510 who have worked on the Xtensa port of @value{GDBN} in the past include
511 Steve Tjiang, John Newlin, and Scott Foehner.
514 @chapter A Sample @value{GDBN} Session
516 You can use this manual at your leisure to read all about @value{GDBN}.
517 However, a handful of commands are enough to get started using the
518 debugger. This chapter illustrates those commands.
521 In this sample session, we emphasize user input like this: @b{input},
522 to make it easier to pick out from the surrounding output.
525 @c FIXME: this example may not be appropriate for some configs, where
526 @c FIXME...primary interest is in remote use.
528 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
529 processor) exhibits the following bug: sometimes, when we change its
530 quote strings from the default, the commands used to capture one macro
531 definition within another stop working. In the following short @code{m4}
532 session, we define a macro @code{foo} which expands to @code{0000}; we
533 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
534 same thing. However, when we change the open quote string to
535 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
536 procedure fails to define a new synonym @code{baz}:
545 @b{define(bar,defn(`foo'))}
549 @b{changequote(<QUOTE>,<UNQUOTE>)}
551 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
554 m4: End of input: 0: fatal error: EOF in string
558 Let us use @value{GDBN} to try to see what is going on.
561 $ @b{@value{GDBP} m4}
562 @c FIXME: this falsifies the exact text played out, to permit smallbook
563 @c FIXME... format to come out better.
564 @value{GDBN} is free software and you are welcome to distribute copies
565 of it under certain conditions; type "show copying" to see
567 There is absolutely no warranty for @value{GDBN}; type "show warranty"
570 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
575 @value{GDBN} reads only enough symbol data to know where to find the
576 rest when needed; as a result, the first prompt comes up very quickly.
577 We now tell @value{GDBN} to use a narrower display width than usual, so
578 that examples fit in this manual.
581 (@value{GDBP}) @b{set width 70}
585 We need to see how the @code{m4} built-in @code{changequote} works.
586 Having looked at the source, we know the relevant subroutine is
587 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
588 @code{break} command.
591 (@value{GDBP}) @b{break m4_changequote}
592 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
596 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
597 control; as long as control does not reach the @code{m4_changequote}
598 subroutine, the program runs as usual:
601 (@value{GDBP}) @b{run}
602 Starting program: /work/Editorial/gdb/gnu/m4/m4
610 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
611 suspends execution of @code{m4}, displaying information about the
612 context where it stops.
615 @b{changequote(<QUOTE>,<UNQUOTE>)}
617 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
619 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
623 Now we use the command @code{n} (@code{next}) to advance execution to
624 the next line of the current function.
628 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
633 @code{set_quotes} looks like a promising subroutine. We can go into it
634 by using the command @code{s} (@code{step}) instead of @code{next}.
635 @code{step} goes to the next line to be executed in @emph{any}
636 subroutine, so it steps into @code{set_quotes}.
640 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
642 530 if (lquote != def_lquote)
646 The display that shows the subroutine where @code{m4} is now
647 suspended (and its arguments) is called a stack frame display. It
648 shows a summary of the stack. We can use the @code{backtrace}
649 command (which can also be spelled @code{bt}), to see where we are
650 in the stack as a whole: the @code{backtrace} command displays a
651 stack frame for each active subroutine.
654 (@value{GDBP}) @b{bt}
655 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
657 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
659 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
660 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
662 #4 0x79dc in expand_input () at macro.c:40
663 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
667 We step through a few more lines to see what happens. The first two
668 times, we can use @samp{s}; the next two times we use @code{n} to avoid
669 falling into the @code{xstrdup} subroutine.
673 0x3b5c 532 if (rquote != def_rquote)
675 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
676 def_lquote : xstrdup(lq);
678 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
681 538 len_lquote = strlen(rquote);
685 The last line displayed looks a little odd; we can examine the variables
686 @code{lquote} and @code{rquote} to see if they are in fact the new left
687 and right quotes we specified. We use the command @code{p}
688 (@code{print}) to see their values.
691 (@value{GDBP}) @b{p lquote}
692 $1 = 0x35d40 "<QUOTE>"
693 (@value{GDBP}) @b{p rquote}
694 $2 = 0x35d50 "<UNQUOTE>"
698 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
699 To look at some context, we can display ten lines of source
700 surrounding the current line with the @code{l} (@code{list}) command.
706 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
708 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
711 538 len_lquote = strlen(rquote);
712 539 len_rquote = strlen(lquote);
719 Let us step past the two lines that set @code{len_lquote} and
720 @code{len_rquote}, and then examine the values of those variables.
724 539 len_rquote = strlen(lquote);
727 (@value{GDBP}) @b{p len_lquote}
729 (@value{GDBP}) @b{p len_rquote}
734 That certainly looks wrong, assuming @code{len_lquote} and
735 @code{len_rquote} are meant to be the lengths of @code{lquote} and
736 @code{rquote} respectively. We can set them to better values using
737 the @code{p} command, since it can print the value of
738 any expression---and that expression can include subroutine calls and
742 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
744 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
749 Is that enough to fix the problem of using the new quotes with the
750 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
751 executing with the @code{c} (@code{continue}) command, and then try the
752 example that caused trouble initially:
758 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
765 Success! The new quotes now work just as well as the default ones. The
766 problem seems to have been just the two typos defining the wrong
767 lengths. We allow @code{m4} exit by giving it an EOF as input:
771 Program exited normally.
775 The message @samp{Program exited normally.} is from @value{GDBN}; it
776 indicates @code{m4} has finished executing. We can end our @value{GDBN}
777 session with the @value{GDBN} @code{quit} command.
780 (@value{GDBP}) @b{quit}
784 @chapter Getting In and Out of @value{GDBN}
786 This chapter discusses how to start @value{GDBN}, and how to get out of it.
790 type @samp{@value{GDBP}} to start @value{GDBN}.
792 type @kbd{quit} or @kbd{Ctrl-d} to exit.
796 * Invoking GDB:: How to start @value{GDBN}
797 * Quitting GDB:: How to quit @value{GDBN}
798 * Shell Commands:: How to use shell commands inside @value{GDBN}
799 * Logging Output:: How to log @value{GDBN}'s output to a file
803 @section Invoking @value{GDBN}
805 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
806 @value{GDBN} reads commands from the terminal until you tell it to exit.
808 You can also run @code{@value{GDBP}} with a variety of arguments and options,
809 to specify more of your debugging environment at the outset.
811 The command-line options described here are designed
812 to cover a variety of situations; in some environments, some of these
813 options may effectively be unavailable.
815 The most usual way to start @value{GDBN} is with one argument,
816 specifying an executable program:
819 @value{GDBP} @var{program}
823 You can also start with both an executable program and a core file
827 @value{GDBP} @var{program} @var{core}
830 You can, instead, specify a process ID as a second argument, if you want
831 to debug a running process:
834 @value{GDBP} @var{program} 1234
838 would attach @value{GDBN} to process @code{1234} (unless you also have a file
839 named @file{1234}; @value{GDBN} does check for a core file first).
841 Taking advantage of the second command-line argument requires a fairly
842 complete operating system; when you use @value{GDBN} as a remote
843 debugger attached to a bare board, there may not be any notion of
844 ``process'', and there is often no way to get a core dump. @value{GDBN}
845 will warn you if it is unable to attach or to read core dumps.
847 You can optionally have @code{@value{GDBP}} pass any arguments after the
848 executable file to the inferior using @code{--args}. This option stops
851 @value{GDBP} --args gcc -O2 -c foo.c
853 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
854 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
856 You can run @code{@value{GDBP}} without printing the front material, which describes
857 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
864 You can further control how @value{GDBN} starts up by using command-line
865 options. @value{GDBN} itself can remind you of the options available.
875 to display all available options and briefly describe their use
876 (@samp{@value{GDBP} -h} is a shorter equivalent).
878 All options and command line arguments you give are processed
879 in sequential order. The order makes a difference when the
880 @samp{-x} option is used.
884 * File Options:: Choosing files
885 * Mode Options:: Choosing modes
886 * Startup:: What @value{GDBN} does during startup
890 @subsection Choosing Files
892 When @value{GDBN} starts, it reads any arguments other than options as
893 specifying an executable file and core file (or process ID). This is
894 the same as if the arguments were specified by the @samp{-se} and
895 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
896 first argument that does not have an associated option flag as
897 equivalent to the @samp{-se} option followed by that argument; and the
898 second argument that does not have an associated option flag, if any, as
899 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
900 If the second argument begins with a decimal digit, @value{GDBN} will
901 first attempt to attach to it as a process, and if that fails, attempt
902 to open it as a corefile. If you have a corefile whose name begins with
903 a digit, you can prevent @value{GDBN} from treating it as a pid by
904 prefixing it with @file{./}, e.g.@: @file{./12345}.
906 If @value{GDBN} has not been configured to included core file support,
907 such as for most embedded targets, then it will complain about a second
908 argument and ignore it.
910 Many options have both long and short forms; both are shown in the
911 following list. @value{GDBN} also recognizes the long forms if you truncate
912 them, so long as enough of the option is present to be unambiguous.
913 (If you prefer, you can flag option arguments with @samp{--} rather
914 than @samp{-}, though we illustrate the more usual convention.)
916 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
917 @c way, both those who look for -foo and --foo in the index, will find
921 @item -symbols @var{file}
923 @cindex @code{--symbols}
925 Read symbol table from file @var{file}.
927 @item -exec @var{file}
929 @cindex @code{--exec}
931 Use file @var{file} as the executable file to execute when appropriate,
932 and for examining pure data in conjunction with a core dump.
936 Read symbol table from file @var{file} and use it as the executable
939 @item -core @var{file}
941 @cindex @code{--core}
943 Use file @var{file} as a core dump to examine.
945 @item -c @var{number}
946 @item -pid @var{number}
947 @itemx -p @var{number}
950 Connect to process ID @var{number}, as with the @code{attach} command.
951 If there is no such process, @value{GDBN} will attempt to open a core
952 file named @var{number}.
954 @item -command @var{file}
956 @cindex @code{--command}
958 Execute @value{GDBN} commands from file @var{file}. @xref{Command
959 Files,, Command files}.
961 @item -eval-command @var{command}
962 @itemx -ex @var{command}
963 @cindex @code{--eval-command}
965 Execute a single @value{GDBN} command.
967 This option may be used multiple times to call multiple commands. It may
968 also be interleaved with @samp{-command} as required.
971 @value{GDBP} -ex 'target sim' -ex 'load' \
972 -x setbreakpoints -ex 'run' a.out
975 @item -directory @var{directory}
976 @itemx -d @var{directory}
977 @cindex @code{--directory}
979 Add @var{directory} to the path to search for source and script files.
983 @cindex @code{--readnow}
985 Read each symbol file's entire symbol table immediately, rather than
986 the default, which is to read it incrementally as it is needed.
987 This makes startup slower, but makes future operations faster.
992 @subsection Choosing Modes
994 You can run @value{GDBN} in various alternative modes---for example, in
995 batch mode or quiet mode.
1002 Do not execute commands found in any initialization files. Normally,
1003 @value{GDBN} executes the commands in these files after all the command
1004 options and arguments have been processed. @xref{Command Files,,Command
1010 @cindex @code{--quiet}
1011 @cindex @code{--silent}
1013 ``Quiet''. Do not print the introductory and copyright messages. These
1014 messages are also suppressed in batch mode.
1017 @cindex @code{--batch}
1018 Run in batch mode. Exit with status @code{0} after processing all the
1019 command files specified with @samp{-x} (and all commands from
1020 initialization files, if not inhibited with @samp{-n}). Exit with
1021 nonzero status if an error occurs in executing the @value{GDBN} commands
1022 in the command files.
1024 Batch mode may be useful for running @value{GDBN} as a filter, for
1025 example to download and run a program on another computer; in order to
1026 make this more useful, the message
1029 Program exited normally.
1033 (which is ordinarily issued whenever a program running under
1034 @value{GDBN} control terminates) is not issued when running in batch
1038 @cindex @code{--batch-silent}
1039 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1040 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1041 unaffected). This is much quieter than @samp{-silent} and would be useless
1042 for an interactive session.
1044 This is particularly useful when using targets that give @samp{Loading section}
1045 messages, for example.
1047 Note that targets that give their output via @value{GDBN}, as opposed to
1048 writing directly to @code{stdout}, will also be made silent.
1050 @item -return-child-result
1051 @cindex @code{--return-child-result}
1052 The return code from @value{GDBN} will be the return code from the child
1053 process (the process being debugged), with the following exceptions:
1057 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1058 internal error. In this case the exit code is the same as it would have been
1059 without @samp{-return-child-result}.
1061 The user quits with an explicit value. E.g., @samp{quit 1}.
1063 The child process never runs, or is not allowed to terminate, in which case
1064 the exit code will be -1.
1067 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1068 when @value{GDBN} is being used as a remote program loader or simulator
1073 @cindex @code{--nowindows}
1075 ``No windows''. If @value{GDBN} comes with a graphical user interface
1076 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1077 interface. If no GUI is available, this option has no effect.
1081 @cindex @code{--windows}
1083 If @value{GDBN} includes a GUI, then this option requires it to be
1086 @item -cd @var{directory}
1088 Run @value{GDBN} using @var{directory} as its working directory,
1089 instead of the current directory.
1093 @cindex @code{--fullname}
1095 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1096 subprocess. It tells @value{GDBN} to output the full file name and line
1097 number in a standard, recognizable fashion each time a stack frame is
1098 displayed (which includes each time your program stops). This
1099 recognizable format looks like two @samp{\032} characters, followed by
1100 the file name, line number and character position separated by colons,
1101 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1102 @samp{\032} characters as a signal to display the source code for the
1106 @cindex @code{--epoch}
1107 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1108 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1109 routines so as to allow Epoch to display values of expressions in a
1112 @item -annotate @var{level}
1113 @cindex @code{--annotate}
1114 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1115 effect is identical to using @samp{set annotate @var{level}}
1116 (@pxref{Annotations}). The annotation @var{level} controls how much
1117 information @value{GDBN} prints together with its prompt, values of
1118 expressions, source lines, and other types of output. Level 0 is the
1119 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1120 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1121 that control @value{GDBN}, and level 2 has been deprecated.
1123 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1127 @cindex @code{--args}
1128 Change interpretation of command line so that arguments following the
1129 executable file are passed as command line arguments to the inferior.
1130 This option stops option processing.
1132 @item -baud @var{bps}
1134 @cindex @code{--baud}
1136 Set the line speed (baud rate or bits per second) of any serial
1137 interface used by @value{GDBN} for remote debugging.
1139 @item -l @var{timeout}
1141 Set the timeout (in seconds) of any communication used by @value{GDBN}
1142 for remote debugging.
1144 @item -tty @var{device}
1145 @itemx -t @var{device}
1146 @cindex @code{--tty}
1148 Run using @var{device} for your program's standard input and output.
1149 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1151 @c resolve the situation of these eventually
1153 @cindex @code{--tui}
1154 Activate the @dfn{Text User Interface} when starting. The Text User
1155 Interface manages several text windows on the terminal, showing
1156 source, assembly, registers and @value{GDBN} command outputs
1157 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1158 Text User Interface can be enabled by invoking the program
1159 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1160 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1163 @c @cindex @code{--xdb}
1164 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1165 @c For information, see the file @file{xdb_trans.html}, which is usually
1166 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1169 @item -interpreter @var{interp}
1170 @cindex @code{--interpreter}
1171 Use the interpreter @var{interp} for interface with the controlling
1172 program or device. This option is meant to be set by programs which
1173 communicate with @value{GDBN} using it as a back end.
1174 @xref{Interpreters, , Command Interpreters}.
1176 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1177 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1178 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1179 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1180 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1181 @sc{gdb/mi} interfaces are no longer supported.
1184 @cindex @code{--write}
1185 Open the executable and core files for both reading and writing. This
1186 is equivalent to the @samp{set write on} command inside @value{GDBN}
1190 @cindex @code{--statistics}
1191 This option causes @value{GDBN} to print statistics about time and
1192 memory usage after it completes each command and returns to the prompt.
1195 @cindex @code{--version}
1196 This option causes @value{GDBN} to print its version number and
1197 no-warranty blurb, and exit.
1202 @subsection What @value{GDBN} Does During Startup
1203 @cindex @value{GDBN} startup
1205 Here's the description of what @value{GDBN} does during session startup:
1209 Sets up the command interpreter as specified by the command line
1210 (@pxref{Mode Options, interpreter}).
1214 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1215 DOS/Windows systems, the home directory is the one pointed to by the
1216 @code{HOME} environment variable.} and executes all the commands in
1220 Processes command line options and operands.
1223 Reads and executes the commands from init file (if any) in the current
1224 working directory. This is only done if the current directory is
1225 different from your home directory. Thus, you can have more than one
1226 init file, one generic in your home directory, and another, specific
1227 to the program you are debugging, in the directory where you invoke
1231 Reads command files specified by the @samp{-x} option. @xref{Command
1232 Files}, for more details about @value{GDBN} command files.
1235 Reads the command history recorded in the @dfn{history file}.
1236 @xref{Command History}, for more details about the command history and the
1237 files where @value{GDBN} records it.
1240 Init files use the same syntax as @dfn{command files} (@pxref{Command
1241 Files}) and are processed by @value{GDBN} in the same way. The init
1242 file in your home directory can set options (such as @samp{set
1243 complaints}) that affect subsequent processing of command line options
1244 and operands. Init files are not executed if you use the @samp{-nx}
1245 option (@pxref{Mode Options, ,Choosing Modes}).
1247 @cindex init file name
1248 @cindex @file{.gdbinit}
1249 @cindex @file{gdb.ini}
1250 The @value{GDBN} init files are normally called @file{.gdbinit}.
1251 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1252 the limitations of file names imposed by DOS filesystems. The Windows
1253 ports of @value{GDBN} use the standard name, but if they find a
1254 @file{gdb.ini} file, they warn you about that and suggest to rename
1255 the file to the standard name.
1259 @section Quitting @value{GDBN}
1260 @cindex exiting @value{GDBN}
1261 @cindex leaving @value{GDBN}
1264 @kindex quit @r{[}@var{expression}@r{]}
1265 @kindex q @r{(@code{quit})}
1266 @item quit @r{[}@var{expression}@r{]}
1268 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1269 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1270 do not supply @var{expression}, @value{GDBN} will terminate normally;
1271 otherwise it will terminate using the result of @var{expression} as the
1276 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1277 terminates the action of any @value{GDBN} command that is in progress and
1278 returns to @value{GDBN} command level. It is safe to type the interrupt
1279 character at any time because @value{GDBN} does not allow it to take effect
1280 until a time when it is safe.
1282 If you have been using @value{GDBN} to control an attached process or
1283 device, you can release it with the @code{detach} command
1284 (@pxref{Attach, ,Debugging an Already-running Process}).
1286 @node Shell Commands
1287 @section Shell Commands
1289 If you need to execute occasional shell commands during your
1290 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1291 just use the @code{shell} command.
1295 @cindex shell escape
1296 @item shell @var{command string}
1297 Invoke a standard shell to execute @var{command string}.
1298 If it exists, the environment variable @code{SHELL} determines which
1299 shell to run. Otherwise @value{GDBN} uses the default shell
1300 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1303 The utility @code{make} is often needed in development environments.
1304 You do not have to use the @code{shell} command for this purpose in
1309 @cindex calling make
1310 @item make @var{make-args}
1311 Execute the @code{make} program with the specified
1312 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1315 @node Logging Output
1316 @section Logging Output
1317 @cindex logging @value{GDBN} output
1318 @cindex save @value{GDBN} output to a file
1320 You may want to save the output of @value{GDBN} commands to a file.
1321 There are several commands to control @value{GDBN}'s logging.
1325 @item set logging on
1327 @item set logging off
1329 @cindex logging file name
1330 @item set logging file @var{file}
1331 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1332 @item set logging overwrite [on|off]
1333 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1334 you want @code{set logging on} to overwrite the logfile instead.
1335 @item set logging redirect [on|off]
1336 By default, @value{GDBN} output will go to both the terminal and the logfile.
1337 Set @code{redirect} if you want output to go only to the log file.
1338 @kindex show logging
1340 Show the current values of the logging settings.
1344 @chapter @value{GDBN} Commands
1346 You can abbreviate a @value{GDBN} command to the first few letters of the command
1347 name, if that abbreviation is unambiguous; and you can repeat certain
1348 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1349 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1350 show you the alternatives available, if there is more than one possibility).
1353 * Command Syntax:: How to give commands to @value{GDBN}
1354 * Completion:: Command completion
1355 * Help:: How to ask @value{GDBN} for help
1358 @node Command Syntax
1359 @section Command Syntax
1361 A @value{GDBN} command is a single line of input. There is no limit on
1362 how long it can be. It starts with a command name, which is followed by
1363 arguments whose meaning depends on the command name. For example, the
1364 command @code{step} accepts an argument which is the number of times to
1365 step, as in @samp{step 5}. You can also use the @code{step} command
1366 with no arguments. Some commands do not allow any arguments.
1368 @cindex abbreviation
1369 @value{GDBN} command names may always be truncated if that abbreviation is
1370 unambiguous. Other possible command abbreviations are listed in the
1371 documentation for individual commands. In some cases, even ambiguous
1372 abbreviations are allowed; for example, @code{s} is specially defined as
1373 equivalent to @code{step} even though there are other commands whose
1374 names start with @code{s}. You can test abbreviations by using them as
1375 arguments to the @code{help} command.
1377 @cindex repeating commands
1378 @kindex RET @r{(repeat last command)}
1379 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1380 repeat the previous command. Certain commands (for example, @code{run})
1381 will not repeat this way; these are commands whose unintentional
1382 repetition might cause trouble and which you are unlikely to want to
1383 repeat. User-defined commands can disable this feature; see
1384 @ref{Define, dont-repeat}.
1386 The @code{list} and @code{x} commands, when you repeat them with
1387 @key{RET}, construct new arguments rather than repeating
1388 exactly as typed. This permits easy scanning of source or memory.
1390 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1391 output, in a way similar to the common utility @code{more}
1392 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1393 @key{RET} too many in this situation, @value{GDBN} disables command
1394 repetition after any command that generates this sort of display.
1396 @kindex # @r{(a comment)}
1398 Any text from a @kbd{#} to the end of the line is a comment; it does
1399 nothing. This is useful mainly in command files (@pxref{Command
1400 Files,,Command Files}).
1402 @cindex repeating command sequences
1403 @kindex Ctrl-o @r{(operate-and-get-next)}
1404 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1405 commands. This command accepts the current line, like @key{RET}, and
1406 then fetches the next line relative to the current line from the history
1410 @section Command Completion
1413 @cindex word completion
1414 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1415 only one possibility; it can also show you what the valid possibilities
1416 are for the next word in a command, at any time. This works for @value{GDBN}
1417 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1419 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1420 of a word. If there is only one possibility, @value{GDBN} fills in the
1421 word, and waits for you to finish the command (or press @key{RET} to
1422 enter it). For example, if you type
1424 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1425 @c complete accuracy in these examples; space introduced for clarity.
1426 @c If texinfo enhancements make it unnecessary, it would be nice to
1427 @c replace " @key" by "@key" in the following...
1429 (@value{GDBP}) info bre @key{TAB}
1433 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1434 the only @code{info} subcommand beginning with @samp{bre}:
1437 (@value{GDBP}) info breakpoints
1441 You can either press @key{RET} at this point, to run the @code{info
1442 breakpoints} command, or backspace and enter something else, if
1443 @samp{breakpoints} does not look like the command you expected. (If you
1444 were sure you wanted @code{info breakpoints} in the first place, you
1445 might as well just type @key{RET} immediately after @samp{info bre},
1446 to exploit command abbreviations rather than command completion).
1448 If there is more than one possibility for the next word when you press
1449 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1450 characters and try again, or just press @key{TAB} a second time;
1451 @value{GDBN} displays all the possible completions for that word. For
1452 example, you might want to set a breakpoint on a subroutine whose name
1453 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1454 just sounds the bell. Typing @key{TAB} again displays all the
1455 function names in your program that begin with those characters, for
1459 (@value{GDBP}) b make_ @key{TAB}
1460 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1461 make_a_section_from_file make_environ
1462 make_abs_section make_function_type
1463 make_blockvector make_pointer_type
1464 make_cleanup make_reference_type
1465 make_command make_symbol_completion_list
1466 (@value{GDBP}) b make_
1470 After displaying the available possibilities, @value{GDBN} copies your
1471 partial input (@samp{b make_} in the example) so you can finish the
1474 If you just want to see the list of alternatives in the first place, you
1475 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1476 means @kbd{@key{META} ?}. You can type this either by holding down a
1477 key designated as the @key{META} shift on your keyboard (if there is
1478 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1480 @cindex quotes in commands
1481 @cindex completion of quoted strings
1482 Sometimes the string you need, while logically a ``word'', may contain
1483 parentheses or other characters that @value{GDBN} normally excludes from
1484 its notion of a word. To permit word completion to work in this
1485 situation, you may enclose words in @code{'} (single quote marks) in
1486 @value{GDBN} commands.
1488 The most likely situation where you might need this is in typing the
1489 name of a C@t{++} function. This is because C@t{++} allows function
1490 overloading (multiple definitions of the same function, distinguished
1491 by argument type). For example, when you want to set a breakpoint you
1492 may need to distinguish whether you mean the version of @code{name}
1493 that takes an @code{int} parameter, @code{name(int)}, or the version
1494 that takes a @code{float} parameter, @code{name(float)}. To use the
1495 word-completion facilities in this situation, type a single quote
1496 @code{'} at the beginning of the function name. This alerts
1497 @value{GDBN} that it may need to consider more information than usual
1498 when you press @key{TAB} or @kbd{M-?} to request word completion:
1501 (@value{GDBP}) b 'bubble( @kbd{M-?}
1502 bubble(double,double) bubble(int,int)
1503 (@value{GDBP}) b 'bubble(
1506 In some cases, @value{GDBN} can tell that completing a name requires using
1507 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1508 completing as much as it can) if you do not type the quote in the first
1512 (@value{GDBP}) b bub @key{TAB}
1513 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1514 (@value{GDBP}) b 'bubble(
1518 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1519 you have not yet started typing the argument list when you ask for
1520 completion on an overloaded symbol.
1522 For more information about overloaded functions, see @ref{C Plus Plus
1523 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1524 overload-resolution off} to disable overload resolution;
1525 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1529 @section Getting Help
1530 @cindex online documentation
1533 You can always ask @value{GDBN} itself for information on its commands,
1534 using the command @code{help}.
1537 @kindex h @r{(@code{help})}
1540 You can use @code{help} (abbreviated @code{h}) with no arguments to
1541 display a short list of named classes of commands:
1545 List of classes of commands:
1547 aliases -- Aliases of other commands
1548 breakpoints -- Making program stop at certain points
1549 data -- Examining data
1550 files -- Specifying and examining files
1551 internals -- Maintenance commands
1552 obscure -- Obscure features
1553 running -- Running the program
1554 stack -- Examining the stack
1555 status -- Status inquiries
1556 support -- Support facilities
1557 tracepoints -- Tracing of program execution without
1558 stopping the program
1559 user-defined -- User-defined commands
1561 Type "help" followed by a class name for a list of
1562 commands in that class.
1563 Type "help" followed by command name for full
1565 Command name abbreviations are allowed if unambiguous.
1568 @c the above line break eliminates huge line overfull...
1570 @item help @var{class}
1571 Using one of the general help classes as an argument, you can get a
1572 list of the individual commands in that class. For example, here is the
1573 help display for the class @code{status}:
1576 (@value{GDBP}) help status
1581 @c Line break in "show" line falsifies real output, but needed
1582 @c to fit in smallbook page size.
1583 info -- Generic command for showing things
1584 about the program being debugged
1585 show -- Generic command for showing things
1588 Type "help" followed by command name for full
1590 Command name abbreviations are allowed if unambiguous.
1594 @item help @var{command}
1595 With a command name as @code{help} argument, @value{GDBN} displays a
1596 short paragraph on how to use that command.
1599 @item apropos @var{args}
1600 The @code{apropos} command searches through all of the @value{GDBN}
1601 commands, and their documentation, for the regular expression specified in
1602 @var{args}. It prints out all matches found. For example:
1613 set symbol-reloading -- Set dynamic symbol table reloading
1614 multiple times in one run
1615 show symbol-reloading -- Show dynamic symbol table reloading
1616 multiple times in one run
1621 @item complete @var{args}
1622 The @code{complete @var{args}} command lists all the possible completions
1623 for the beginning of a command. Use @var{args} to specify the beginning of the
1624 command you want completed. For example:
1630 @noindent results in:
1641 @noindent This is intended for use by @sc{gnu} Emacs.
1644 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1645 and @code{show} to inquire about the state of your program, or the state
1646 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1647 manual introduces each of them in the appropriate context. The listings
1648 under @code{info} and under @code{show} in the Index point to
1649 all the sub-commands. @xref{Index}.
1654 @kindex i @r{(@code{info})}
1656 This command (abbreviated @code{i}) is for describing the state of your
1657 program. For example, you can list the arguments given to your program
1658 with @code{info args}, list the registers currently in use with @code{info
1659 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1660 You can get a complete list of the @code{info} sub-commands with
1661 @w{@code{help info}}.
1665 You can assign the result of an expression to an environment variable with
1666 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1667 @code{set prompt $}.
1671 In contrast to @code{info}, @code{show} is for describing the state of
1672 @value{GDBN} itself.
1673 You can change most of the things you can @code{show}, by using the
1674 related command @code{set}; for example, you can control what number
1675 system is used for displays with @code{set radix}, or simply inquire
1676 which is currently in use with @code{show radix}.
1679 To display all the settable parameters and their current
1680 values, you can use @code{show} with no arguments; you may also use
1681 @code{info set}. Both commands produce the same display.
1682 @c FIXME: "info set" violates the rule that "info" is for state of
1683 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1684 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1688 Here are three miscellaneous @code{show} subcommands, all of which are
1689 exceptional in lacking corresponding @code{set} commands:
1692 @kindex show version
1693 @cindex @value{GDBN} version number
1695 Show what version of @value{GDBN} is running. You should include this
1696 information in @value{GDBN} bug-reports. If multiple versions of
1697 @value{GDBN} are in use at your site, you may need to determine which
1698 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1699 commands are introduced, and old ones may wither away. Also, many
1700 system vendors ship variant versions of @value{GDBN}, and there are
1701 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1702 The version number is the same as the one announced when you start
1705 @kindex show copying
1706 @kindex info copying
1707 @cindex display @value{GDBN} copyright
1710 Display information about permission for copying @value{GDBN}.
1712 @kindex show warranty
1713 @kindex info warranty
1715 @itemx info warranty
1716 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1717 if your version of @value{GDBN} comes with one.
1722 @chapter Running Programs Under @value{GDBN}
1724 When you run a program under @value{GDBN}, you must first generate
1725 debugging information when you compile it.
1727 You may start @value{GDBN} with its arguments, if any, in an environment
1728 of your choice. If you are doing native debugging, you may redirect
1729 your program's input and output, debug an already running process, or
1730 kill a child process.
1733 * Compilation:: Compiling for debugging
1734 * Starting:: Starting your program
1735 * Arguments:: Your program's arguments
1736 * Environment:: Your program's environment
1738 * Working Directory:: Your program's working directory
1739 * Input/Output:: Your program's input and output
1740 * Attach:: Debugging an already-running process
1741 * Kill Process:: Killing the child process
1743 * Threads:: Debugging programs with multiple threads
1744 * Processes:: Debugging programs with multiple processes
1745 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1749 @section Compiling for Debugging
1751 In order to debug a program effectively, you need to generate
1752 debugging information when you compile it. This debugging information
1753 is stored in the object file; it describes the data type of each
1754 variable or function and the correspondence between source line numbers
1755 and addresses in the executable code.
1757 To request debugging information, specify the @samp{-g} option when you run
1760 Programs that are to be shipped to your customers are compiled with
1761 optimizations, using the @samp{-O} compiler option. However, many
1762 compilers are unable to handle the @samp{-g} and @samp{-O} options
1763 together. Using those compilers, you cannot generate optimized
1764 executables containing debugging information.
1766 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1767 without @samp{-O}, making it possible to debug optimized code. We
1768 recommend that you @emph{always} use @samp{-g} whenever you compile a
1769 program. You may think your program is correct, but there is no sense
1770 in pushing your luck.
1772 @cindex optimized code, debugging
1773 @cindex debugging optimized code
1774 When you debug a program compiled with @samp{-g -O}, remember that the
1775 optimizer is rearranging your code; the debugger shows you what is
1776 really there. Do not be too surprised when the execution path does not
1777 exactly match your source file! An extreme example: if you define a
1778 variable, but never use it, @value{GDBN} never sees that
1779 variable---because the compiler optimizes it out of existence.
1781 Some things do not work as well with @samp{-g -O} as with just
1782 @samp{-g}, particularly on machines with instruction scheduling. If in
1783 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1784 please report it to us as a bug (including a test case!).
1785 @xref{Variables}, for more information about debugging optimized code.
1787 Older versions of the @sc{gnu} C compiler permitted a variant option
1788 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1789 format; if your @sc{gnu} C compiler has this option, do not use it.
1791 @value{GDBN} knows about preprocessor macros and can show you their
1792 expansion (@pxref{Macros}). Most compilers do not include information
1793 about preprocessor macros in the debugging information if you specify
1794 the @option{-g} flag alone, because this information is rather large.
1795 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1796 provides macro information if you specify the options
1797 @option{-gdwarf-2} and @option{-g3}; the former option requests
1798 debugging information in the Dwarf 2 format, and the latter requests
1799 ``extra information''. In the future, we hope to find more compact
1800 ways to represent macro information, so that it can be included with
1805 @section Starting your Program
1811 @kindex r @r{(@code{run})}
1814 Use the @code{run} command to start your program under @value{GDBN}.
1815 You must first specify the program name (except on VxWorks) with an
1816 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1817 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1818 (@pxref{Files, ,Commands to Specify Files}).
1822 If you are running your program in an execution environment that
1823 supports processes, @code{run} creates an inferior process and makes
1824 that process run your program. (In environments without processes,
1825 @code{run} jumps to the start of your program.)
1827 The execution of a program is affected by certain information it
1828 receives from its superior. @value{GDBN} provides ways to specify this
1829 information, which you must do @emph{before} starting your program. (You
1830 can change it after starting your program, but such changes only affect
1831 your program the next time you start it.) This information may be
1832 divided into four categories:
1835 @item The @emph{arguments.}
1836 Specify the arguments to give your program as the arguments of the
1837 @code{run} command. If a shell is available on your target, the shell
1838 is used to pass the arguments, so that you may use normal conventions
1839 (such as wildcard expansion or variable substitution) in describing
1841 In Unix systems, you can control which shell is used with the
1842 @code{SHELL} environment variable.
1843 @xref{Arguments, ,Your Program's Arguments}.
1845 @item The @emph{environment.}
1846 Your program normally inherits its environment from @value{GDBN}, but you can
1847 use the @value{GDBN} commands @code{set environment} and @code{unset
1848 environment} to change parts of the environment that affect
1849 your program. @xref{Environment, ,Your Program's Environment}.
1851 @item The @emph{working directory.}
1852 Your program inherits its working directory from @value{GDBN}. You can set
1853 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1854 @xref{Working Directory, ,Your Program's Working Directory}.
1856 @item The @emph{standard input and output.}
1857 Your program normally uses the same device for standard input and
1858 standard output as @value{GDBN} is using. You can redirect input and output
1859 in the @code{run} command line, or you can use the @code{tty} command to
1860 set a different device for your program.
1861 @xref{Input/Output, ,Your Program's Input and Output}.
1864 @emph{Warning:} While input and output redirection work, you cannot use
1865 pipes to pass the output of the program you are debugging to another
1866 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1870 When you issue the @code{run} command, your program begins to execute
1871 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1872 of how to arrange for your program to stop. Once your program has
1873 stopped, you may call functions in your program, using the @code{print}
1874 or @code{call} commands. @xref{Data, ,Examining Data}.
1876 If the modification time of your symbol file has changed since the last
1877 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1878 table, and reads it again. When it does this, @value{GDBN} tries to retain
1879 your current breakpoints.
1884 @cindex run to main procedure
1885 The name of the main procedure can vary from language to language.
1886 With C or C@t{++}, the main procedure name is always @code{main}, but
1887 other languages such as Ada do not require a specific name for their
1888 main procedure. The debugger provides a convenient way to start the
1889 execution of the program and to stop at the beginning of the main
1890 procedure, depending on the language used.
1892 The @samp{start} command does the equivalent of setting a temporary
1893 breakpoint at the beginning of the main procedure and then invoking
1894 the @samp{run} command.
1896 @cindex elaboration phase
1897 Some programs contain an @dfn{elaboration} phase where some startup code is
1898 executed before the main procedure is called. This depends on the
1899 languages used to write your program. In C@t{++}, for instance,
1900 constructors for static and global objects are executed before
1901 @code{main} is called. It is therefore possible that the debugger stops
1902 before reaching the main procedure. However, the temporary breakpoint
1903 will remain to halt execution.
1905 Specify the arguments to give to your program as arguments to the
1906 @samp{start} command. These arguments will be given verbatim to the
1907 underlying @samp{run} command. Note that the same arguments will be
1908 reused if no argument is provided during subsequent calls to
1909 @samp{start} or @samp{run}.
1911 It is sometimes necessary to debug the program during elaboration. In
1912 these cases, using the @code{start} command would stop the execution of
1913 your program too late, as the program would have already completed the
1914 elaboration phase. Under these circumstances, insert breakpoints in your
1915 elaboration code before running your program.
1919 @section Your Program's Arguments
1921 @cindex arguments (to your program)
1922 The arguments to your program can be specified by the arguments of the
1924 They are passed to a shell, which expands wildcard characters and
1925 performs redirection of I/O, and thence to your program. Your
1926 @code{SHELL} environment variable (if it exists) specifies what shell
1927 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1928 the default shell (@file{/bin/sh} on Unix).
1930 On non-Unix systems, the program is usually invoked directly by
1931 @value{GDBN}, which emulates I/O redirection via the appropriate system
1932 calls, and the wildcard characters are expanded by the startup code of
1933 the program, not by the shell.
1935 @code{run} with no arguments uses the same arguments used by the previous
1936 @code{run}, or those set by the @code{set args} command.
1941 Specify the arguments to be used the next time your program is run. If
1942 @code{set args} has no arguments, @code{run} executes your program
1943 with no arguments. Once you have run your program with arguments,
1944 using @code{set args} before the next @code{run} is the only way to run
1945 it again without arguments.
1949 Show the arguments to give your program when it is started.
1953 @section Your Program's Environment
1955 @cindex environment (of your program)
1956 The @dfn{environment} consists of a set of environment variables and
1957 their values. Environment variables conventionally record such things as
1958 your user name, your home directory, your terminal type, and your search
1959 path for programs to run. Usually you set up environment variables with
1960 the shell and they are inherited by all the other programs you run. When
1961 debugging, it can be useful to try running your program with a modified
1962 environment without having to start @value{GDBN} over again.
1966 @item path @var{directory}
1967 Add @var{directory} to the front of the @code{PATH} environment variable
1968 (the search path for executables) that will be passed to your program.
1969 The value of @code{PATH} used by @value{GDBN} does not change.
1970 You may specify several directory names, separated by whitespace or by a
1971 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1972 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1973 is moved to the front, so it is searched sooner.
1975 You can use the string @samp{$cwd} to refer to whatever is the current
1976 working directory at the time @value{GDBN} searches the path. If you
1977 use @samp{.} instead, it refers to the directory where you executed the
1978 @code{path} command. @value{GDBN} replaces @samp{.} in the
1979 @var{directory} argument (with the current path) before adding
1980 @var{directory} to the search path.
1981 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1982 @c document that, since repeating it would be a no-op.
1986 Display the list of search paths for executables (the @code{PATH}
1987 environment variable).
1989 @kindex show environment
1990 @item show environment @r{[}@var{varname}@r{]}
1991 Print the value of environment variable @var{varname} to be given to
1992 your program when it starts. If you do not supply @var{varname},
1993 print the names and values of all environment variables to be given to
1994 your program. You can abbreviate @code{environment} as @code{env}.
1996 @kindex set environment
1997 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1998 Set environment variable @var{varname} to @var{value}. The value
1999 changes for your program only, not for @value{GDBN} itself. @var{value} may
2000 be any string; the values of environment variables are just strings, and
2001 any interpretation is supplied by your program itself. The @var{value}
2002 parameter is optional; if it is eliminated, the variable is set to a
2004 @c "any string" here does not include leading, trailing
2005 @c blanks. Gnu asks: does anyone care?
2007 For example, this command:
2014 tells the debugged program, when subsequently run, that its user is named
2015 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2016 are not actually required.)
2018 @kindex unset environment
2019 @item unset environment @var{varname}
2020 Remove variable @var{varname} from the environment to be passed to your
2021 program. This is different from @samp{set env @var{varname} =};
2022 @code{unset environment} removes the variable from the environment,
2023 rather than assigning it an empty value.
2026 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2028 by your @code{SHELL} environment variable if it exists (or
2029 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2030 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2031 @file{.bashrc} for BASH---any variables you set in that file affect
2032 your program. You may wish to move setting of environment variables to
2033 files that are only run when you sign on, such as @file{.login} or
2036 @node Working Directory
2037 @section Your Program's Working Directory
2039 @cindex working directory (of your program)
2040 Each time you start your program with @code{run}, it inherits its
2041 working directory from the current working directory of @value{GDBN}.
2042 The @value{GDBN} working directory is initially whatever it inherited
2043 from its parent process (typically the shell), but you can specify a new
2044 working directory in @value{GDBN} with the @code{cd} command.
2046 The @value{GDBN} working directory also serves as a default for the commands
2047 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2052 @cindex change working directory
2053 @item cd @var{directory}
2054 Set the @value{GDBN} working directory to @var{directory}.
2058 Print the @value{GDBN} working directory.
2061 It is generally impossible to find the current working directory of
2062 the process being debugged (since a program can change its directory
2063 during its run). If you work on a system where @value{GDBN} is
2064 configured with the @file{/proc} support, you can use the @code{info
2065 proc} command (@pxref{SVR4 Process Information}) to find out the
2066 current working directory of the debuggee.
2069 @section Your Program's Input and Output
2074 By default, the program you run under @value{GDBN} does input and output to
2075 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2076 to its own terminal modes to interact with you, but it records the terminal
2077 modes your program was using and switches back to them when you continue
2078 running your program.
2081 @kindex info terminal
2083 Displays information recorded by @value{GDBN} about the terminal modes your
2087 You can redirect your program's input and/or output using shell
2088 redirection with the @code{run} command. For example,
2095 starts your program, diverting its output to the file @file{outfile}.
2098 @cindex controlling terminal
2099 Another way to specify where your program should do input and output is
2100 with the @code{tty} command. This command accepts a file name as
2101 argument, and causes this file to be the default for future @code{run}
2102 commands. It also resets the controlling terminal for the child
2103 process, for future @code{run} commands. For example,
2110 directs that processes started with subsequent @code{run} commands
2111 default to do input and output on the terminal @file{/dev/ttyb} and have
2112 that as their controlling terminal.
2114 An explicit redirection in @code{run} overrides the @code{tty} command's
2115 effect on the input/output device, but not its effect on the controlling
2118 When you use the @code{tty} command or redirect input in the @code{run}
2119 command, only the input @emph{for your program} is affected. The input
2120 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2121 for @code{set inferior-tty}.
2123 @cindex inferior tty
2124 @cindex set inferior controlling terminal
2125 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2126 display the name of the terminal that will be used for future runs of your
2130 @item set inferior-tty /dev/ttyb
2131 @kindex set inferior-tty
2132 Set the tty for the program being debugged to /dev/ttyb.
2134 @item show inferior-tty
2135 @kindex show inferior-tty
2136 Show the current tty for the program being debugged.
2140 @section Debugging an Already-running Process
2145 @item attach @var{process-id}
2146 This command attaches to a running process---one that was started
2147 outside @value{GDBN}. (@code{info files} shows your active
2148 targets.) The command takes as argument a process ID. The usual way to
2149 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2150 or with the @samp{jobs -l} shell command.
2152 @code{attach} does not repeat if you press @key{RET} a second time after
2153 executing the command.
2156 To use @code{attach}, your program must be running in an environment
2157 which supports processes; for example, @code{attach} does not work for
2158 programs on bare-board targets that lack an operating system. You must
2159 also have permission to send the process a signal.
2161 When you use @code{attach}, the debugger finds the program running in
2162 the process first by looking in the current working directory, then (if
2163 the program is not found) by using the source file search path
2164 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2165 the @code{file} command to load the program. @xref{Files, ,Commands to
2168 The first thing @value{GDBN} does after arranging to debug the specified
2169 process is to stop it. You can examine and modify an attached process
2170 with all the @value{GDBN} commands that are ordinarily available when
2171 you start processes with @code{run}. You can insert breakpoints; you
2172 can step and continue; you can modify storage. If you would rather the
2173 process continue running, you may use the @code{continue} command after
2174 attaching @value{GDBN} to the process.
2179 When you have finished debugging the attached process, you can use the
2180 @code{detach} command to release it from @value{GDBN} control. Detaching
2181 the process continues its execution. After the @code{detach} command,
2182 that process and @value{GDBN} become completely independent once more, and you
2183 are ready to @code{attach} another process or start one with @code{run}.
2184 @code{detach} does not repeat if you press @key{RET} again after
2185 executing the command.
2188 If you exit @value{GDBN} while you have an attached process, you detach
2189 that process. If you use the @code{run} command, you kill that process.
2190 By default, @value{GDBN} asks for confirmation if you try to do either of these
2191 things; you can control whether or not you need to confirm by using the
2192 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2196 @section Killing the Child Process
2201 Kill the child process in which your program is running under @value{GDBN}.
2204 This command is useful if you wish to debug a core dump instead of a
2205 running process. @value{GDBN} ignores any core dump file while your program
2208 On some operating systems, a program cannot be executed outside @value{GDBN}
2209 while you have breakpoints set on it inside @value{GDBN}. You can use the
2210 @code{kill} command in this situation to permit running your program
2211 outside the debugger.
2213 The @code{kill} command is also useful if you wish to recompile and
2214 relink your program, since on many systems it is impossible to modify an
2215 executable file while it is running in a process. In this case, when you
2216 next type @code{run}, @value{GDBN} notices that the file has changed, and
2217 reads the symbol table again (while trying to preserve your current
2218 breakpoint settings).
2221 @section Debugging Programs with Multiple Threads
2223 @cindex threads of execution
2224 @cindex multiple threads
2225 @cindex switching threads
2226 In some operating systems, such as HP-UX and Solaris, a single program
2227 may have more than one @dfn{thread} of execution. The precise semantics
2228 of threads differ from one operating system to another, but in general
2229 the threads of a single program are akin to multiple processes---except
2230 that they share one address space (that is, they can all examine and
2231 modify the same variables). On the other hand, each thread has its own
2232 registers and execution stack, and perhaps private memory.
2234 @value{GDBN} provides these facilities for debugging multi-thread
2238 @item automatic notification of new threads
2239 @item @samp{thread @var{threadno}}, a command to switch among threads
2240 @item @samp{info threads}, a command to inquire about existing threads
2241 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2242 a command to apply a command to a list of threads
2243 @item thread-specific breakpoints
2247 @emph{Warning:} These facilities are not yet available on every
2248 @value{GDBN} configuration where the operating system supports threads.
2249 If your @value{GDBN} does not support threads, these commands have no
2250 effect. For example, a system without thread support shows no output
2251 from @samp{info threads}, and always rejects the @code{thread} command,
2255 (@value{GDBP}) info threads
2256 (@value{GDBP}) thread 1
2257 Thread ID 1 not known. Use the "info threads" command to
2258 see the IDs of currently known threads.
2260 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2261 @c doesn't support threads"?
2264 @cindex focus of debugging
2265 @cindex current thread
2266 The @value{GDBN} thread debugging facility allows you to observe all
2267 threads while your program runs---but whenever @value{GDBN} takes
2268 control, one thread in particular is always the focus of debugging.
2269 This thread is called the @dfn{current thread}. Debugging commands show
2270 program information from the perspective of the current thread.
2272 @cindex @code{New} @var{systag} message
2273 @cindex thread identifier (system)
2274 @c FIXME-implementors!! It would be more helpful if the [New...] message
2275 @c included GDB's numeric thread handle, so you could just go to that
2276 @c thread without first checking `info threads'.
2277 Whenever @value{GDBN} detects a new thread in your program, it displays
2278 the target system's identification for the thread with a message in the
2279 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2280 whose form varies depending on the particular system. For example, on
2281 @sc{gnu}/Linux, you might see
2284 [New Thread 46912507313328 (LWP 25582)]
2288 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2289 the @var{systag} is simply something like @samp{process 368}, with no
2292 @c FIXME!! (1) Does the [New...] message appear even for the very first
2293 @c thread of a program, or does it only appear for the
2294 @c second---i.e.@: when it becomes obvious we have a multithread
2296 @c (2) *Is* there necessarily a first thread always? Or do some
2297 @c multithread systems permit starting a program with multiple
2298 @c threads ab initio?
2300 @cindex thread number
2301 @cindex thread identifier (GDB)
2302 For debugging purposes, @value{GDBN} associates its own thread
2303 number---always a single integer---with each thread in your program.
2306 @kindex info threads
2308 Display a summary of all threads currently in your
2309 program. @value{GDBN} displays for each thread (in this order):
2313 the thread number assigned by @value{GDBN}
2316 the target system's thread identifier (@var{systag})
2319 the current stack frame summary for that thread
2323 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2324 indicates the current thread.
2328 @c end table here to get a little more width for example
2331 (@value{GDBP}) info threads
2332 3 process 35 thread 27 0x34e5 in sigpause ()
2333 2 process 35 thread 23 0x34e5 in sigpause ()
2334 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2340 @cindex debugging multithreaded programs (on HP-UX)
2341 @cindex thread identifier (GDB), on HP-UX
2342 For debugging purposes, @value{GDBN} associates its own thread
2343 number---a small integer assigned in thread-creation order---with each
2344 thread in your program.
2346 @cindex @code{New} @var{systag} message, on HP-UX
2347 @cindex thread identifier (system), on HP-UX
2348 @c FIXME-implementors!! It would be more helpful if the [New...] message
2349 @c included GDB's numeric thread handle, so you could just go to that
2350 @c thread without first checking `info threads'.
2351 Whenever @value{GDBN} detects a new thread in your program, it displays
2352 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2353 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2354 whose form varies depending on the particular system. For example, on
2358 [New thread 2 (system thread 26594)]
2362 when @value{GDBN} notices a new thread.
2365 @kindex info threads (HP-UX)
2367 Display a summary of all threads currently in your
2368 program. @value{GDBN} displays for each thread (in this order):
2371 @item the thread number assigned by @value{GDBN}
2373 @item the target system's thread identifier (@var{systag})
2375 @item the current stack frame summary for that thread
2379 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2380 indicates the current thread.
2384 @c end table here to get a little more width for example
2387 (@value{GDBP}) info threads
2388 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2390 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2391 from /usr/lib/libc.2
2392 1 system thread 27905 0x7b003498 in _brk () \@*
2393 from /usr/lib/libc.2
2396 On Solaris, you can display more information about user threads with a
2397 Solaris-specific command:
2400 @item maint info sol-threads
2401 @kindex maint info sol-threads
2402 @cindex thread info (Solaris)
2403 Display info on Solaris user threads.
2407 @kindex thread @var{threadno}
2408 @item thread @var{threadno}
2409 Make thread number @var{threadno} the current thread. The command
2410 argument @var{threadno} is the internal @value{GDBN} thread number, as
2411 shown in the first field of the @samp{info threads} display.
2412 @value{GDBN} responds by displaying the system identifier of the thread
2413 you selected, and its current stack frame summary:
2416 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2417 (@value{GDBP}) thread 2
2418 [Switching to process 35 thread 23]
2419 0x34e5 in sigpause ()
2423 As with the @samp{[New @dots{}]} message, the form of the text after
2424 @samp{Switching to} depends on your system's conventions for identifying
2427 @kindex thread apply
2428 @cindex apply command to several threads
2429 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2430 The @code{thread apply} command allows you to apply the named
2431 @var{command} to one or more threads. Specify the numbers of the
2432 threads that you want affected with the command argument
2433 @var{threadno}. It can be a single thread number, one of the numbers
2434 shown in the first field of the @samp{info threads} display; or it
2435 could be a range of thread numbers, as in @code{2-4}. To apply a
2436 command to all threads, type @kbd{thread apply all @var{command}}.
2439 @cindex automatic thread selection
2440 @cindex switching threads automatically
2441 @cindex threads, automatic switching
2442 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2443 signal, it automatically selects the thread where that breakpoint or
2444 signal happened. @value{GDBN} alerts you to the context switch with a
2445 message of the form @samp{[Switching to @var{systag}]} to identify the
2448 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2449 more information about how @value{GDBN} behaves when you stop and start
2450 programs with multiple threads.
2452 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2453 watchpoints in programs with multiple threads.
2456 @section Debugging Programs with Multiple Processes
2458 @cindex fork, debugging programs which call
2459 @cindex multiple processes
2460 @cindex processes, multiple
2461 On most systems, @value{GDBN} has no special support for debugging
2462 programs which create additional processes using the @code{fork}
2463 function. When a program forks, @value{GDBN} will continue to debug the
2464 parent process and the child process will run unimpeded. If you have
2465 set a breakpoint in any code which the child then executes, the child
2466 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2467 will cause it to terminate.
2469 However, if you want to debug the child process there is a workaround
2470 which isn't too painful. Put a call to @code{sleep} in the code which
2471 the child process executes after the fork. It may be useful to sleep
2472 only if a certain environment variable is set, or a certain file exists,
2473 so that the delay need not occur when you don't want to run @value{GDBN}
2474 on the child. While the child is sleeping, use the @code{ps} program to
2475 get its process ID. Then tell @value{GDBN} (a new invocation of
2476 @value{GDBN} if you are also debugging the parent process) to attach to
2477 the child process (@pxref{Attach}). From that point on you can debug
2478 the child process just like any other process which you attached to.
2480 On some systems, @value{GDBN} provides support for debugging programs that
2481 create additional processes using the @code{fork} or @code{vfork} functions.
2482 Currently, the only platforms with this feature are HP-UX (11.x and later
2483 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2485 By default, when a program forks, @value{GDBN} will continue to debug
2486 the parent process and the child process will run unimpeded.
2488 If you want to follow the child process instead of the parent process,
2489 use the command @w{@code{set follow-fork-mode}}.
2492 @kindex set follow-fork-mode
2493 @item set follow-fork-mode @var{mode}
2494 Set the debugger response to a program call of @code{fork} or
2495 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2496 process. The @var{mode} argument can be:
2500 The original process is debugged after a fork. The child process runs
2501 unimpeded. This is the default.
2504 The new process is debugged after a fork. The parent process runs
2509 @kindex show follow-fork-mode
2510 @item show follow-fork-mode
2511 Display the current debugger response to a @code{fork} or @code{vfork} call.
2514 @cindex debugging multiple processes
2515 On Linux, if you want to debug both the parent and child processes, use the
2516 command @w{@code{set detach-on-fork}}.
2519 @kindex set detach-on-fork
2520 @item set detach-on-fork @var{mode}
2521 Tells gdb whether to detach one of the processes after a fork, or
2522 retain debugger control over them both.
2526 The child process (or parent process, depending on the value of
2527 @code{follow-fork-mode}) will be detached and allowed to run
2528 independently. This is the default.
2531 Both processes will be held under the control of @value{GDBN}.
2532 One process (child or parent, depending on the value of
2533 @code{follow-fork-mode}) is debugged as usual, while the other
2538 @kindex show detach-on-follow
2539 @item show detach-on-follow
2540 Show whether detach-on-follow mode is on/off.
2543 If you choose to set @var{detach-on-follow} mode off, then
2544 @value{GDBN} will retain control of all forked processes (including
2545 nested forks). You can list the forked processes under the control of
2546 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2547 from one fork to another by using the @w{@code{fork}} command.
2552 Print a list of all forked processes under the control of @value{GDBN}.
2553 The listing will include a fork id, a process id, and the current
2554 position (program counter) of the process.
2557 @kindex fork @var{fork-id}
2558 @item fork @var{fork-id}
2559 Make fork number @var{fork-id} the current process. The argument
2560 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2561 as shown in the first field of the @samp{info forks} display.
2565 To quit debugging one of the forked processes, you can either detach
2566 from it by using the @w{@code{detach fork}} command (allowing it to
2567 run independently), or delete (and kill) it using the
2568 @w{@code{delete fork}} command.
2571 @kindex detach fork @var{fork-id}
2572 @item detach fork @var{fork-id}
2573 Detach from the process identified by @value{GDBN} fork number
2574 @var{fork-id}, and remove it from the fork list. The process will be
2575 allowed to run independently.
2577 @kindex delete fork @var{fork-id}
2578 @item delete fork @var{fork-id}
2579 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2580 and remove it from the fork list.
2584 If you ask to debug a child process and a @code{vfork} is followed by an
2585 @code{exec}, @value{GDBN} executes the new target up to the first
2586 breakpoint in the new target. If you have a breakpoint set on
2587 @code{main} in your original program, the breakpoint will also be set on
2588 the child process's @code{main}.
2590 When a child process is spawned by @code{vfork}, you cannot debug the
2591 child or parent until an @code{exec} call completes.
2593 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2594 call executes, the new target restarts. To restart the parent process,
2595 use the @code{file} command with the parent executable name as its
2598 You can use the @code{catch} command to make @value{GDBN} stop whenever
2599 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2600 Catchpoints, ,Setting Catchpoints}.
2602 @node Checkpoint/Restart
2603 @section Setting a @emph{Bookmark} to Return to Later
2608 @cindex snapshot of a process
2609 @cindex rewind program state
2611 On certain operating systems@footnote{Currently, only
2612 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2613 program's state, called a @dfn{checkpoint}, and come back to it
2616 Returning to a checkpoint effectively undoes everything that has
2617 happened in the program since the @code{checkpoint} was saved. This
2618 includes changes in memory, registers, and even (within some limits)
2619 system state. Effectively, it is like going back in time to the
2620 moment when the checkpoint was saved.
2622 Thus, if you're stepping thru a program and you think you're
2623 getting close to the point where things go wrong, you can save
2624 a checkpoint. Then, if you accidentally go too far and miss
2625 the critical statement, instead of having to restart your program
2626 from the beginning, you can just go back to the checkpoint and
2627 start again from there.
2629 This can be especially useful if it takes a lot of time or
2630 steps to reach the point where you think the bug occurs.
2632 To use the @code{checkpoint}/@code{restart} method of debugging:
2637 Save a snapshot of the debugged program's current execution state.
2638 The @code{checkpoint} command takes no arguments, but each checkpoint
2639 is assigned a small integer id, similar to a breakpoint id.
2641 @kindex info checkpoints
2642 @item info checkpoints
2643 List the checkpoints that have been saved in the current debugging
2644 session. For each checkpoint, the following information will be
2651 @item Source line, or label
2654 @kindex restart @var{checkpoint-id}
2655 @item restart @var{checkpoint-id}
2656 Restore the program state that was saved as checkpoint number
2657 @var{checkpoint-id}. All program variables, registers, stack frames
2658 etc.@: will be returned to the values that they had when the checkpoint
2659 was saved. In essence, gdb will ``wind back the clock'' to the point
2660 in time when the checkpoint was saved.
2662 Note that breakpoints, @value{GDBN} variables, command history etc.
2663 are not affected by restoring a checkpoint. In general, a checkpoint
2664 only restores things that reside in the program being debugged, not in
2667 @kindex delete checkpoint @var{checkpoint-id}
2668 @item delete checkpoint @var{checkpoint-id}
2669 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2673 Returning to a previously saved checkpoint will restore the user state
2674 of the program being debugged, plus a significant subset of the system
2675 (OS) state, including file pointers. It won't ``un-write'' data from
2676 a file, but it will rewind the file pointer to the previous location,
2677 so that the previously written data can be overwritten. For files
2678 opened in read mode, the pointer will also be restored so that the
2679 previously read data can be read again.
2681 Of course, characters that have been sent to a printer (or other
2682 external device) cannot be ``snatched back'', and characters received
2683 from eg.@: a serial device can be removed from internal program buffers,
2684 but they cannot be ``pushed back'' into the serial pipeline, ready to
2685 be received again. Similarly, the actual contents of files that have
2686 been changed cannot be restored (at this time).
2688 However, within those constraints, you actually can ``rewind'' your
2689 program to a previously saved point in time, and begin debugging it
2690 again --- and you can change the course of events so as to debug a
2691 different execution path this time.
2693 @cindex checkpoints and process id
2694 Finally, there is one bit of internal program state that will be
2695 different when you return to a checkpoint --- the program's process
2696 id. Each checkpoint will have a unique process id (or @var{pid}),
2697 and each will be different from the program's original @var{pid}.
2698 If your program has saved a local copy of its process id, this could
2699 potentially pose a problem.
2701 @subsection A Non-obvious Benefit of Using Checkpoints
2703 On some systems such as @sc{gnu}/Linux, address space randomization
2704 is performed on new processes for security reasons. This makes it
2705 difficult or impossible to set a breakpoint, or watchpoint, on an
2706 absolute address if you have to restart the program, since the
2707 absolute location of a symbol will change from one execution to the
2710 A checkpoint, however, is an @emph{identical} copy of a process.
2711 Therefore if you create a checkpoint at (eg.@:) the start of main,
2712 and simply return to that checkpoint instead of restarting the
2713 process, you can avoid the effects of address randomization and
2714 your symbols will all stay in the same place.
2717 @chapter Stopping and Continuing
2719 The principal purposes of using a debugger are so that you can stop your
2720 program before it terminates; or so that, if your program runs into
2721 trouble, you can investigate and find out why.
2723 Inside @value{GDBN}, your program may stop for any of several reasons,
2724 such as a signal, a breakpoint, or reaching a new line after a
2725 @value{GDBN} command such as @code{step}. You may then examine and
2726 change variables, set new breakpoints or remove old ones, and then
2727 continue execution. Usually, the messages shown by @value{GDBN} provide
2728 ample explanation of the status of your program---but you can also
2729 explicitly request this information at any time.
2732 @kindex info program
2734 Display information about the status of your program: whether it is
2735 running or not, what process it is, and why it stopped.
2739 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2740 * Continuing and Stepping:: Resuming execution
2742 * Thread Stops:: Stopping and starting multi-thread programs
2746 @section Breakpoints, Watchpoints, and Catchpoints
2749 A @dfn{breakpoint} makes your program stop whenever a certain point in
2750 the program is reached. For each breakpoint, you can add conditions to
2751 control in finer detail whether your program stops. You can set
2752 breakpoints with the @code{break} command and its variants (@pxref{Set
2753 Breaks, ,Setting Breakpoints}), to specify the place where your program
2754 should stop by line number, function name or exact address in the
2757 On some systems, you can set breakpoints in shared libraries before
2758 the executable is run. There is a minor limitation on HP-UX systems:
2759 you must wait until the executable is run in order to set breakpoints
2760 in shared library routines that are not called directly by the program
2761 (for example, routines that are arguments in a @code{pthread_create}
2765 @cindex data breakpoints
2766 @cindex memory tracing
2767 @cindex breakpoint on memory address
2768 @cindex breakpoint on variable modification
2769 A @dfn{watchpoint} is a special breakpoint that stops your program
2770 when the value of an expression changes. The expression may be a value
2771 of a variable, or it could involve values of one or more variables
2772 combined by operators, such as @samp{a + b}. This is sometimes called
2773 @dfn{data breakpoints}. You must use a different command to set
2774 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2775 from that, you can manage a watchpoint like any other breakpoint: you
2776 enable, disable, and delete both breakpoints and watchpoints using the
2779 You can arrange to have values from your program displayed automatically
2780 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2784 @cindex breakpoint on events
2785 A @dfn{catchpoint} is another special breakpoint that stops your program
2786 when a certain kind of event occurs, such as the throwing of a C@t{++}
2787 exception or the loading of a library. As with watchpoints, you use a
2788 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2789 Catchpoints}), but aside from that, you can manage a catchpoint like any
2790 other breakpoint. (To stop when your program receives a signal, use the
2791 @code{handle} command; see @ref{Signals, ,Signals}.)
2793 @cindex breakpoint numbers
2794 @cindex numbers for breakpoints
2795 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2796 catchpoint when you create it; these numbers are successive integers
2797 starting with one. In many of the commands for controlling various
2798 features of breakpoints you use the breakpoint number to say which
2799 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2800 @dfn{disabled}; if disabled, it has no effect on your program until you
2803 @cindex breakpoint ranges
2804 @cindex ranges of breakpoints
2805 Some @value{GDBN} commands accept a range of breakpoints on which to
2806 operate. A breakpoint range is either a single breakpoint number, like
2807 @samp{5}, or two such numbers, in increasing order, separated by a
2808 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2809 all breakpoints in that range are operated on.
2812 * Set Breaks:: Setting breakpoints
2813 * Set Watchpoints:: Setting watchpoints
2814 * Set Catchpoints:: Setting catchpoints
2815 * Delete Breaks:: Deleting breakpoints
2816 * Disabling:: Disabling breakpoints
2817 * Conditions:: Break conditions
2818 * Break Commands:: Breakpoint command lists
2819 * Breakpoint Menus:: Breakpoint menus
2820 * Error in Breakpoints:: ``Cannot insert breakpoints''
2821 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2825 @subsection Setting Breakpoints
2827 @c FIXME LMB what does GDB do if no code on line of breakpt?
2828 @c consider in particular declaration with/without initialization.
2830 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2833 @kindex b @r{(@code{break})}
2834 @vindex $bpnum@r{, convenience variable}
2835 @cindex latest breakpoint
2836 Breakpoints are set with the @code{break} command (abbreviated
2837 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2838 number of the breakpoint you've set most recently; see @ref{Convenience
2839 Vars,, Convenience Variables}, for a discussion of what you can do with
2840 convenience variables.
2842 You have several ways to say where the breakpoint should go.
2845 @item break @var{function}
2846 Set a breakpoint at entry to function @var{function}.
2847 When using source languages that permit overloading of symbols, such as
2848 C@t{++}, @var{function} may refer to more than one possible place to break.
2849 @xref{Breakpoint Menus,,Breakpoint Menus}, for a discussion of that situation.
2851 @item break +@var{offset}
2852 @itemx break -@var{offset}
2853 Set a breakpoint some number of lines forward or back from the position
2854 at which execution stopped in the currently selected @dfn{stack frame}.
2855 (@xref{Frames, ,Frames}, for a description of stack frames.)
2857 @item break @var{linenum}
2858 Set a breakpoint at line @var{linenum} in the current source file.
2859 The current source file is the last file whose source text was printed.
2860 The breakpoint will stop your program just before it executes any of the
2863 @item break @var{filename}:@var{linenum}
2864 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2866 @item break @var{filename}:@var{function}
2867 Set a breakpoint at entry to function @var{function} found in file
2868 @var{filename}. Specifying a file name as well as a function name is
2869 superfluous except when multiple files contain similarly named
2872 @item break *@var{address}
2873 Set a breakpoint at address @var{address}. You can use this to set
2874 breakpoints in parts of your program which do not have debugging
2875 information or source files.
2878 When called without any arguments, @code{break} sets a breakpoint at
2879 the next instruction to be executed in the selected stack frame
2880 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2881 innermost, this makes your program stop as soon as control
2882 returns to that frame. This is similar to the effect of a
2883 @code{finish} command in the frame inside the selected frame---except
2884 that @code{finish} does not leave an active breakpoint. If you use
2885 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2886 the next time it reaches the current location; this may be useful
2889 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2890 least one instruction has been executed. If it did not do this, you
2891 would be unable to proceed past a breakpoint without first disabling the
2892 breakpoint. This rule applies whether or not the breakpoint already
2893 existed when your program stopped.
2895 @item break @dots{} if @var{cond}
2896 Set a breakpoint with condition @var{cond}; evaluate the expression
2897 @var{cond} each time the breakpoint is reached, and stop only if the
2898 value is nonzero---that is, if @var{cond} evaluates as true.
2899 @samp{@dots{}} stands for one of the possible arguments described
2900 above (or no argument) specifying where to break. @xref{Conditions,
2901 ,Break Conditions}, for more information on breakpoint conditions.
2904 @item tbreak @var{args}
2905 Set a breakpoint enabled only for one stop. @var{args} are the
2906 same as for the @code{break} command, and the breakpoint is set in the same
2907 way, but the breakpoint is automatically deleted after the first time your
2908 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2911 @cindex hardware breakpoints
2912 @item hbreak @var{args}
2913 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2914 @code{break} command and the breakpoint is set in the same way, but the
2915 breakpoint requires hardware support and some target hardware may not
2916 have this support. The main purpose of this is EPROM/ROM code
2917 debugging, so you can set a breakpoint at an instruction without
2918 changing the instruction. This can be used with the new trap-generation
2919 provided by SPARClite DSU and most x86-based targets. These targets
2920 will generate traps when a program accesses some data or instruction
2921 address that is assigned to the debug registers. However the hardware
2922 breakpoint registers can take a limited number of breakpoints. For
2923 example, on the DSU, only two data breakpoints can be set at a time, and
2924 @value{GDBN} will reject this command if more than two are used. Delete
2925 or disable unused hardware breakpoints before setting new ones
2926 (@pxref{Disabling, ,Disabling Breakpoints}).
2927 @xref{Conditions, ,Break Conditions}.
2928 For remote targets, you can restrict the number of hardware
2929 breakpoints @value{GDBN} will use, see @ref{set remote
2930 hardware-breakpoint-limit}.
2934 @item thbreak @var{args}
2935 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2936 are the same as for the @code{hbreak} command and the breakpoint is set in
2937 the same way. However, like the @code{tbreak} command,
2938 the breakpoint is automatically deleted after the
2939 first time your program stops there. Also, like the @code{hbreak}
2940 command, the breakpoint requires hardware support and some target hardware
2941 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2942 See also @ref{Conditions, ,Break Conditions}.
2945 @cindex regular expression
2946 @cindex breakpoints in functions matching a regexp
2947 @cindex set breakpoints in many functions
2948 @item rbreak @var{regex}
2949 Set breakpoints on all functions matching the regular expression
2950 @var{regex}. This command sets an unconditional breakpoint on all
2951 matches, printing a list of all breakpoints it set. Once these
2952 breakpoints are set, they are treated just like the breakpoints set with
2953 the @code{break} command. You can delete them, disable them, or make
2954 them conditional the same way as any other breakpoint.
2956 The syntax of the regular expression is the standard one used with tools
2957 like @file{grep}. Note that this is different from the syntax used by
2958 shells, so for instance @code{foo*} matches all functions that include
2959 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2960 @code{.*} leading and trailing the regular expression you supply, so to
2961 match only functions that begin with @code{foo}, use @code{^foo}.
2963 @cindex non-member C@t{++} functions, set breakpoint in
2964 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2965 breakpoints on overloaded functions that are not members of any special
2968 @cindex set breakpoints on all functions
2969 The @code{rbreak} command can be used to set breakpoints in
2970 @strong{all} the functions in a program, like this:
2973 (@value{GDBP}) rbreak .
2976 @kindex info breakpoints
2977 @cindex @code{$_} and @code{info breakpoints}
2978 @item info breakpoints @r{[}@var{n}@r{]}
2979 @itemx info break @r{[}@var{n}@r{]}
2980 @itemx info watchpoints @r{[}@var{n}@r{]}
2981 Print a table of all breakpoints, watchpoints, and catchpoints set and
2982 not deleted. Optional argument @var{n} means print information only
2983 about the specified breakpoint (or watchpoint or catchpoint). For
2984 each breakpoint, following columns are printed:
2987 @item Breakpoint Numbers
2989 Breakpoint, watchpoint, or catchpoint.
2991 Whether the breakpoint is marked to be disabled or deleted when hit.
2992 @item Enabled or Disabled
2993 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2994 that are not enabled. An optional @samp{(p)} suffix marks pending
2995 breakpoints---breakpoints for which address is either not yet
2996 resolved, pending load of a shared library, or for which address was
2997 in a shared library that was since unloaded. Such breakpoint won't
2998 fire until a shared library that has the symbol or line referred by
2999 breakpoint is loaded. See below for details.
3001 Where the breakpoint is in your program, as a memory address. For a
3002 pending breakpoint whose address is not yet known, this field will
3003 contain @samp{<PENDING>}. A breakpoint with several locations will
3004 have @samp{<MULTIPLE>} in this field---see below for details.
3006 Where the breakpoint is in the source for your program, as a file and
3007 line number. For a pending breakpoint, the original string passed to
3008 the breakpoint command will be listed as it cannot be resolved until
3009 the appropriate shared library is loaded in the future.
3013 If a breakpoint is conditional, @code{info break} shows the condition on
3014 the line following the affected breakpoint; breakpoint commands, if any,
3015 are listed after that. A pending breakpoint is allowed to have a condition
3016 specified for it. The condition is not parsed for validity until a shared
3017 library is loaded that allows the pending breakpoint to resolve to a
3021 @code{info break} with a breakpoint
3022 number @var{n} as argument lists only that breakpoint. The
3023 convenience variable @code{$_} and the default examining-address for
3024 the @code{x} command are set to the address of the last breakpoint
3025 listed (@pxref{Memory, ,Examining Memory}).
3028 @code{info break} displays a count of the number of times the breakpoint
3029 has been hit. This is especially useful in conjunction with the
3030 @code{ignore} command. You can ignore a large number of breakpoint
3031 hits, look at the breakpoint info to see how many times the breakpoint
3032 was hit, and then run again, ignoring one less than that number. This
3033 will get you quickly to the last hit of that breakpoint.
3036 @value{GDBN} allows you to set any number of breakpoints at the same place in
3037 your program. There is nothing silly or meaningless about this. When
3038 the breakpoints are conditional, this is even useful
3039 (@pxref{Conditions, ,Break Conditions}).
3041 It is possible that a breakpoint corresponds to several locations
3042 in your program. Examples of this situation are:
3047 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3048 instances of the function body, used in different cases.
3051 For a C@t{++} template function, a given line in the function can
3052 correspond to any number of instantiations.
3055 For an inlined function, a given source line can correspond to
3056 several places where that function is inlined.
3060 In all those cases, @value{GDBN} will insert a breakpoint at all
3061 the relevant locations.
3063 A breakpoint with multiple locations is displayed in the breakpoint
3064 table using several rows---one header row, followed by one row for
3065 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3066 address column. The rows for individual locations contain the actual
3067 addresses for locations, and show the functions to which those
3068 locations belong. The number column for a location is of the form
3069 @var{breakpoint-number}.@var{location-number}.
3074 Num Type Disp Enb Address What
3075 1 breakpoint keep y <MULTIPLE>
3077 breakpoint already hit 1 time
3078 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3079 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3082 Each location can be individually enabled or disabled by passing
3083 @var{breakpoint-number}.@var{location-number} as argument to the
3084 @code{enable} and @code{disable} commands. Note that you cannot
3085 delete the individual locations from the list, you can only delete the
3086 entire list of locations that belong to their parent breakpoint (with
3087 the @kbd{delete @var{num}} command, where @var{num} is the number of
3088 the parent breakpoint, 1 in the above example). Disabling or enabling
3089 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3090 that belong to that breakpoint.
3092 @cindex pending breakpoints
3093 It's quite common to have a breakpoint inside a shared library.
3094 Shared libraries can be loaded and unloaded explicitly,
3095 and possibly repeatedly, as the program is executed. To support
3096 this use case, @value{GDBN} updates breakpoint locations whenever
3097 any shared library is loaded or unloaded. Typically, you would
3098 set a breakpoint in a shared library at the beginning of your
3099 debugging session, when the library is not loaded, and when the
3100 symbols from the library are not available. When you try to set
3101 breakpoint, @value{GDBN} will ask you if you want to set
3102 a so called @dfn{pending breakpoint}---breakpoint whose address
3103 is not yet resolved.
3105 After the program is run, whenever a new shared library is loaded,
3106 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3107 shared library contains the symbol or line referred to by some
3108 pending breakpoint, that breakpoint is resolved and becomes an
3109 ordinary breakpoint. When a library is unloaded, all breakpoints
3110 that refer to its symbols or source lines become pending again.
3112 This logic works for breakpoints with multiple locations, too. For
3113 example, if you have a breakpoint in a C@t{++} template function, and
3114 a newly loaded shared library has an instantiation of that template,
3115 a new location is added to the list of locations for the breakpoint.
3117 Except for having unresolved address, pending breakpoints do not
3118 differ from regular breakpoints. You can set conditions or commands,
3119 enable and disable them and perform other breakpoint operations.
3121 @value{GDBN} provides some additional commands for controlling what
3122 happens when the @samp{break} command cannot resolve breakpoint
3123 address specification to an address:
3125 @kindex set breakpoint pending
3126 @kindex show breakpoint pending
3128 @item set breakpoint pending auto
3129 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3130 location, it queries you whether a pending breakpoint should be created.
3132 @item set breakpoint pending on
3133 This indicates that an unrecognized breakpoint location should automatically
3134 result in a pending breakpoint being created.
3136 @item set breakpoint pending off
3137 This indicates that pending breakpoints are not to be created. Any
3138 unrecognized breakpoint location results in an error. This setting does
3139 not affect any pending breakpoints previously created.
3141 @item show breakpoint pending
3142 Show the current behavior setting for creating pending breakpoints.
3145 The settings above only affect the @code{break} command and its
3146 variants. Once breakpoint is set, it will be automatically updated
3147 as shared libraries are loaded and unloaded.
3149 @cindex automatic hardware breakpoints
3150 For some targets, @value{GDBN} can automatically decide if hardware or
3151 software breakpoints should be used, depending on whether the
3152 breakpoint address is read-only or read-write. This applies to
3153 breakpoints set with the @code{break} command as well as to internal
3154 breakpoints set by commands like @code{next} and @code{finish}. For
3155 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3158 You can control this automatic behaviour with the following commands::
3160 @kindex set breakpoint auto-hw
3161 @kindex show breakpoint auto-hw
3163 @item set breakpoint auto-hw on
3164 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3165 will try to use the target memory map to decide if software or hardware
3166 breakpoint must be used.
3168 @item set breakpoint auto-hw off
3169 This indicates @value{GDBN} should not automatically select breakpoint
3170 type. If the target provides a memory map, @value{GDBN} will warn when
3171 trying to set software breakpoint at a read-only address.
3175 @cindex negative breakpoint numbers
3176 @cindex internal @value{GDBN} breakpoints
3177 @value{GDBN} itself sometimes sets breakpoints in your program for
3178 special purposes, such as proper handling of @code{longjmp} (in C
3179 programs). These internal breakpoints are assigned negative numbers,
3180 starting with @code{-1}; @samp{info breakpoints} does not display them.
3181 You can see these breakpoints with the @value{GDBN} maintenance command
3182 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3185 @node Set Watchpoints
3186 @subsection Setting Watchpoints
3188 @cindex setting watchpoints
3189 You can use a watchpoint to stop execution whenever the value of an
3190 expression changes, without having to predict a particular place where
3191 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3192 The expression may be as simple as the value of a single variable, or
3193 as complex as many variables combined by operators. Examples include:
3197 A reference to the value of a single variable.
3200 An address cast to an appropriate data type. For example,
3201 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3202 address (assuming an @code{int} occupies 4 bytes).
3205 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3206 expression can use any operators valid in the program's native
3207 language (@pxref{Languages}).
3210 @cindex software watchpoints
3211 @cindex hardware watchpoints
3212 Depending on your system, watchpoints may be implemented in software or
3213 hardware. @value{GDBN} does software watchpointing by single-stepping your
3214 program and testing the variable's value each time, which is hundreds of
3215 times slower than normal execution. (But this may still be worth it, to
3216 catch errors where you have no clue what part of your program is the
3219 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3220 x86-based targets, @value{GDBN} includes support for hardware
3221 watchpoints, which do not slow down the running of your program.
3225 @item watch @var{expr}
3226 Set a watchpoint for an expression. @value{GDBN} will break when the
3227 expression @var{expr} is written into by the program and its value
3228 changes. The simplest (and the most popular) use of this command is
3229 to watch the value of a single variable:
3232 (@value{GDBP}) watch foo
3236 @item rwatch @var{expr}
3237 Set a watchpoint that will break when the value of @var{expr} is read
3241 @item awatch @var{expr}
3242 Set a watchpoint that will break when @var{expr} is either read from
3243 or written into by the program.
3245 @kindex info watchpoints @r{[}@var{n}@r{]}
3246 @item info watchpoints
3247 This command prints a list of watchpoints, breakpoints, and catchpoints;
3248 it is the same as @code{info break} (@pxref{Set Breaks}).
3251 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3252 watchpoints execute very quickly, and the debugger reports a change in
3253 value at the exact instruction where the change occurs. If @value{GDBN}
3254 cannot set a hardware watchpoint, it sets a software watchpoint, which
3255 executes more slowly and reports the change in value at the next
3256 @emph{statement}, not the instruction, after the change occurs.
3258 @cindex use only software watchpoints
3259 You can force @value{GDBN} to use only software watchpoints with the
3260 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3261 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3262 the underlying system supports them. (Note that hardware-assisted
3263 watchpoints that were set @emph{before} setting
3264 @code{can-use-hw-watchpoints} to zero will still use the hardware
3265 mechanism of watching expression values.)
3268 @item set can-use-hw-watchpoints
3269 @kindex set can-use-hw-watchpoints
3270 Set whether or not to use hardware watchpoints.
3272 @item show can-use-hw-watchpoints
3273 @kindex show can-use-hw-watchpoints
3274 Show the current mode of using hardware watchpoints.
3277 For remote targets, you can restrict the number of hardware
3278 watchpoints @value{GDBN} will use, see @ref{set remote
3279 hardware-breakpoint-limit}.
3281 When you issue the @code{watch} command, @value{GDBN} reports
3284 Hardware watchpoint @var{num}: @var{expr}
3288 if it was able to set a hardware watchpoint.
3290 Currently, the @code{awatch} and @code{rwatch} commands can only set
3291 hardware watchpoints, because accesses to data that don't change the
3292 value of the watched expression cannot be detected without examining
3293 every instruction as it is being executed, and @value{GDBN} does not do
3294 that currently. If @value{GDBN} finds that it is unable to set a
3295 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3296 will print a message like this:
3299 Expression cannot be implemented with read/access watchpoint.
3302 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3303 data type of the watched expression is wider than what a hardware
3304 watchpoint on the target machine can handle. For example, some systems
3305 can only watch regions that are up to 4 bytes wide; on such systems you
3306 cannot set hardware watchpoints for an expression that yields a
3307 double-precision floating-point number (which is typically 8 bytes
3308 wide). As a work-around, it might be possible to break the large region
3309 into a series of smaller ones and watch them with separate watchpoints.
3311 If you set too many hardware watchpoints, @value{GDBN} might be unable
3312 to insert all of them when you resume the execution of your program.
3313 Since the precise number of active watchpoints is unknown until such
3314 time as the program is about to be resumed, @value{GDBN} might not be
3315 able to warn you about this when you set the watchpoints, and the
3316 warning will be printed only when the program is resumed:
3319 Hardware watchpoint @var{num}: Could not insert watchpoint
3323 If this happens, delete or disable some of the watchpoints.
3325 Watching complex expressions that reference many variables can also
3326 exhaust the resources available for hardware-assisted watchpoints.
3327 That's because @value{GDBN} needs to watch every variable in the
3328 expression with separately allocated resources.
3330 The SPARClite DSU will generate traps when a program accesses some data
3331 or instruction address that is assigned to the debug registers. For the
3332 data addresses, DSU facilitates the @code{watch} command. However the
3333 hardware breakpoint registers can only take two data watchpoints, and
3334 both watchpoints must be the same kind. For example, you can set two
3335 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3336 @strong{or} two with @code{awatch} commands, but you cannot set one
3337 watchpoint with one command and the other with a different command.
3338 @value{GDBN} will reject the command if you try to mix watchpoints.
3339 Delete or disable unused watchpoint commands before setting new ones.
3341 If you call a function interactively using @code{print} or @code{call},
3342 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3343 kind of breakpoint or the call completes.
3345 @value{GDBN} automatically deletes watchpoints that watch local
3346 (automatic) variables, or expressions that involve such variables, when
3347 they go out of scope, that is, when the execution leaves the block in
3348 which these variables were defined. In particular, when the program
3349 being debugged terminates, @emph{all} local variables go out of scope,
3350 and so only watchpoints that watch global variables remain set. If you
3351 rerun the program, you will need to set all such watchpoints again. One
3352 way of doing that would be to set a code breakpoint at the entry to the
3353 @code{main} function and when it breaks, set all the watchpoints.
3355 @cindex watchpoints and threads
3356 @cindex threads and watchpoints
3357 In multi-threaded programs, watchpoints will detect changes to the
3358 watched expression from every thread.
3360 @kindex watch thread thread_num
3361 @item watch @var{expr} thread @var{threadnum}
3362 Set a watchpoint that will break when @var{expr} is either read from
3363 or written into by the thread identified by @var{threadnum}. If @var{expr}
3364 is modified by any other threads not matching @var{threadnum}, @value{GDBN}
3365 will not break. Note that this will only work with Hardware Watchpoints.
3368 @emph{Warning:} In multi-threaded programs, software watchpoints
3369 have only limited usefulness. If @value{GDBN} creates a software
3370 watchpoint, it can only watch the value of an expression @emph{in a
3371 single thread}. If you are confident that the expression can only
3372 change due to the current thread's activity (and if you are also
3373 confident that no other thread can become current), then you can use
3374 software watchpoints as usual. However, @value{GDBN} may not notice
3375 when a non-current thread's activity changes the expression. (Hardware
3376 watchpoints, in contrast, watch an expression in all threads.)
3379 @xref{set remote hardware-watchpoint-limit}.
3381 @node Set Catchpoints
3382 @subsection Setting Catchpoints
3383 @cindex catchpoints, setting
3384 @cindex exception handlers
3385 @cindex event handling
3387 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3388 kinds of program events, such as C@t{++} exceptions or the loading of a
3389 shared library. Use the @code{catch} command to set a catchpoint.
3393 @item catch @var{event}
3394 Stop when @var{event} occurs. @var{event} can be any of the following:
3397 @cindex stop on C@t{++} exceptions
3398 The throwing of a C@t{++} exception.
3401 The catching of a C@t{++} exception.
3404 @cindex Ada exception catching
3405 @cindex catch Ada exceptions
3406 An Ada exception being raised. If an exception name is specified
3407 at the end of the command (eg @code{catch exception Program_Error}),
3408 the debugger will stop only when this specific exception is raised.
3409 Otherwise, the debugger stops execution when any Ada exception is raised.
3411 @item exception unhandled
3412 An exception that was raised but is not handled by the program.
3415 A failed Ada assertion.
3418 @cindex break on fork/exec
3419 A call to @code{exec}. This is currently only available for HP-UX.
3422 A call to @code{fork}. This is currently only available for HP-UX.
3425 A call to @code{vfork}. This is currently only available for HP-UX.
3428 @itemx load @var{libname}
3429 @cindex break on load/unload of shared library
3430 The dynamic loading of any shared library, or the loading of the library
3431 @var{libname}. This is currently only available for HP-UX.
3434 @itemx unload @var{libname}
3435 The unloading of any dynamically loaded shared library, or the unloading
3436 of the library @var{libname}. This is currently only available for HP-UX.
3439 @item tcatch @var{event}
3440 Set a catchpoint that is enabled only for one stop. The catchpoint is
3441 automatically deleted after the first time the event is caught.
3445 Use the @code{info break} command to list the current catchpoints.
3447 There are currently some limitations to C@t{++} exception handling
3448 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3452 If you call a function interactively, @value{GDBN} normally returns
3453 control to you when the function has finished executing. If the call
3454 raises an exception, however, the call may bypass the mechanism that
3455 returns control to you and cause your program either to abort or to
3456 simply continue running until it hits a breakpoint, catches a signal
3457 that @value{GDBN} is listening for, or exits. This is the case even if
3458 you set a catchpoint for the exception; catchpoints on exceptions are
3459 disabled within interactive calls.
3462 You cannot raise an exception interactively.
3465 You cannot install an exception handler interactively.
3468 @cindex raise exceptions
3469 Sometimes @code{catch} is not the best way to debug exception handling:
3470 if you need to know exactly where an exception is raised, it is better to
3471 stop @emph{before} the exception handler is called, since that way you
3472 can see the stack before any unwinding takes place. If you set a
3473 breakpoint in an exception handler instead, it may not be easy to find
3474 out where the exception was raised.
3476 To stop just before an exception handler is called, you need some
3477 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3478 raised by calling a library function named @code{__raise_exception}
3479 which has the following ANSI C interface:
3482 /* @var{addr} is where the exception identifier is stored.
3483 @var{id} is the exception identifier. */
3484 void __raise_exception (void **addr, void *id);
3488 To make the debugger catch all exceptions before any stack
3489 unwinding takes place, set a breakpoint on @code{__raise_exception}
3490 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3492 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3493 that depends on the value of @var{id}, you can stop your program when
3494 a specific exception is raised. You can use multiple conditional
3495 breakpoints to stop your program when any of a number of exceptions are
3500 @subsection Deleting Breakpoints
3502 @cindex clearing breakpoints, watchpoints, catchpoints
3503 @cindex deleting breakpoints, watchpoints, catchpoints
3504 It is often necessary to eliminate a breakpoint, watchpoint, or
3505 catchpoint once it has done its job and you no longer want your program
3506 to stop there. This is called @dfn{deleting} the breakpoint. A
3507 breakpoint that has been deleted no longer exists; it is forgotten.
3509 With the @code{clear} command you can delete breakpoints according to
3510 where they are in your program. With the @code{delete} command you can
3511 delete individual breakpoints, watchpoints, or catchpoints by specifying
3512 their breakpoint numbers.
3514 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3515 automatically ignores breakpoints on the first instruction to be executed
3516 when you continue execution without changing the execution address.
3521 Delete any breakpoints at the next instruction to be executed in the
3522 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3523 the innermost frame is selected, this is a good way to delete a
3524 breakpoint where your program just stopped.
3526 @item clear @var{function}
3527 @itemx clear @var{filename}:@var{function}
3528 Delete any breakpoints set at entry to the named @var{function}.
3530 @item clear @var{linenum}
3531 @itemx clear @var{filename}:@var{linenum}
3532 Delete any breakpoints set at or within the code of the specified
3533 @var{linenum} of the specified @var{filename}.
3535 @cindex delete breakpoints
3537 @kindex d @r{(@code{delete})}
3538 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3539 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3540 ranges specified as arguments. If no argument is specified, delete all
3541 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3542 confirm off}). You can abbreviate this command as @code{d}.
3546 @subsection Disabling Breakpoints
3548 @cindex enable/disable a breakpoint
3549 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3550 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3551 it had been deleted, but remembers the information on the breakpoint so
3552 that you can @dfn{enable} it again later.
3554 You disable and enable breakpoints, watchpoints, and catchpoints with
3555 the @code{enable} and @code{disable} commands, optionally specifying one
3556 or more breakpoint numbers as arguments. Use @code{info break} or
3557 @code{info watch} to print a list of breakpoints, watchpoints, and
3558 catchpoints if you do not know which numbers to use.
3560 Disabling and enabling a breakpoint that has multiple locations
3561 affects all of its locations.
3563 A breakpoint, watchpoint, or catchpoint can have any of four different
3564 states of enablement:
3568 Enabled. The breakpoint stops your program. A breakpoint set
3569 with the @code{break} command starts out in this state.
3571 Disabled. The breakpoint has no effect on your program.
3573 Enabled once. The breakpoint stops your program, but then becomes
3576 Enabled for deletion. The breakpoint stops your program, but
3577 immediately after it does so it is deleted permanently. A breakpoint
3578 set with the @code{tbreak} command starts out in this state.
3581 You can use the following commands to enable or disable breakpoints,
3582 watchpoints, and catchpoints:
3586 @kindex dis @r{(@code{disable})}
3587 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3588 Disable the specified breakpoints---or all breakpoints, if none are
3589 listed. A disabled breakpoint has no effect but is not forgotten. All
3590 options such as ignore-counts, conditions and commands are remembered in
3591 case the breakpoint is enabled again later. You may abbreviate
3592 @code{disable} as @code{dis}.
3595 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3596 Enable the specified breakpoints (or all defined breakpoints). They
3597 become effective once again in stopping your program.
3599 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3600 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3601 of these breakpoints immediately after stopping your program.
3603 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3604 Enable the specified breakpoints to work once, then die. @value{GDBN}
3605 deletes any of these breakpoints as soon as your program stops there.
3606 Breakpoints set by the @code{tbreak} command start out in this state.
3609 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3610 @c confusing: tbreak is also initially enabled.
3611 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3612 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3613 subsequently, they become disabled or enabled only when you use one of
3614 the commands above. (The command @code{until} can set and delete a
3615 breakpoint of its own, but it does not change the state of your other
3616 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3620 @subsection Break Conditions
3621 @cindex conditional breakpoints
3622 @cindex breakpoint conditions
3624 @c FIXME what is scope of break condition expr? Context where wanted?
3625 @c in particular for a watchpoint?
3626 The simplest sort of breakpoint breaks every time your program reaches a
3627 specified place. You can also specify a @dfn{condition} for a
3628 breakpoint. A condition is just a Boolean expression in your
3629 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3630 a condition evaluates the expression each time your program reaches it,
3631 and your program stops only if the condition is @emph{true}.
3633 This is the converse of using assertions for program validation; in that
3634 situation, you want to stop when the assertion is violated---that is,
3635 when the condition is false. In C, if you want to test an assertion expressed
3636 by the condition @var{assert}, you should set the condition
3637 @samp{! @var{assert}} on the appropriate breakpoint.
3639 Conditions are also accepted for watchpoints; you may not need them,
3640 since a watchpoint is inspecting the value of an expression anyhow---but
3641 it might be simpler, say, to just set a watchpoint on a variable name,
3642 and specify a condition that tests whether the new value is an interesting
3645 Break conditions can have side effects, and may even call functions in
3646 your program. This can be useful, for example, to activate functions
3647 that log program progress, or to use your own print functions to
3648 format special data structures. The effects are completely predictable
3649 unless there is another enabled breakpoint at the same address. (In
3650 that case, @value{GDBN} might see the other breakpoint first and stop your
3651 program without checking the condition of this one.) Note that
3652 breakpoint commands are usually more convenient and flexible than break
3654 purpose of performing side effects when a breakpoint is reached
3655 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3657 Break conditions can be specified when a breakpoint is set, by using
3658 @samp{if} in the arguments to the @code{break} command. @xref{Set
3659 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3660 with the @code{condition} command.
3662 You can also use the @code{if} keyword with the @code{watch} command.
3663 The @code{catch} command does not recognize the @code{if} keyword;
3664 @code{condition} is the only way to impose a further condition on a
3669 @item condition @var{bnum} @var{expression}
3670 Specify @var{expression} as the break condition for breakpoint,
3671 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3672 breakpoint @var{bnum} stops your program only if the value of
3673 @var{expression} is true (nonzero, in C). When you use
3674 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3675 syntactic correctness, and to determine whether symbols in it have
3676 referents in the context of your breakpoint. If @var{expression} uses
3677 symbols not referenced in the context of the breakpoint, @value{GDBN}
3678 prints an error message:
3681 No symbol "foo" in current context.
3686 not actually evaluate @var{expression} at the time the @code{condition}
3687 command (or a command that sets a breakpoint with a condition, like
3688 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3690 @item condition @var{bnum}
3691 Remove the condition from breakpoint number @var{bnum}. It becomes
3692 an ordinary unconditional breakpoint.
3695 @cindex ignore count (of breakpoint)
3696 A special case of a breakpoint condition is to stop only when the
3697 breakpoint has been reached a certain number of times. This is so
3698 useful that there is a special way to do it, using the @dfn{ignore
3699 count} of the breakpoint. Every breakpoint has an ignore count, which
3700 is an integer. Most of the time, the ignore count is zero, and
3701 therefore has no effect. But if your program reaches a breakpoint whose
3702 ignore count is positive, then instead of stopping, it just decrements
3703 the ignore count by one and continues. As a result, if the ignore count
3704 value is @var{n}, the breakpoint does not stop the next @var{n} times
3705 your program reaches it.
3709 @item ignore @var{bnum} @var{count}
3710 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3711 The next @var{count} times the breakpoint is reached, your program's
3712 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3715 To make the breakpoint stop the next time it is reached, specify
3718 When you use @code{continue} to resume execution of your program from a
3719 breakpoint, you can specify an ignore count directly as an argument to
3720 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3721 Stepping,,Continuing and Stepping}.
3723 If a breakpoint has a positive ignore count and a condition, the
3724 condition is not checked. Once the ignore count reaches zero,
3725 @value{GDBN} resumes checking the condition.
3727 You could achieve the effect of the ignore count with a condition such
3728 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3729 is decremented each time. @xref{Convenience Vars, ,Convenience
3733 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3736 @node Break Commands
3737 @subsection Breakpoint Command Lists
3739 @cindex breakpoint commands
3740 You can give any breakpoint (or watchpoint or catchpoint) a series of
3741 commands to execute when your program stops due to that breakpoint. For
3742 example, you might want to print the values of certain expressions, or
3743 enable other breakpoints.
3747 @kindex end@r{ (breakpoint commands)}
3748 @item commands @r{[}@var{bnum}@r{]}
3749 @itemx @dots{} @var{command-list} @dots{}
3751 Specify a list of commands for breakpoint number @var{bnum}. The commands
3752 themselves appear on the following lines. Type a line containing just
3753 @code{end} to terminate the commands.
3755 To remove all commands from a breakpoint, type @code{commands} and
3756 follow it immediately with @code{end}; that is, give no commands.
3758 With no @var{bnum} argument, @code{commands} refers to the last
3759 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3760 recently encountered).
3763 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3764 disabled within a @var{command-list}.
3766 You can use breakpoint commands to start your program up again. Simply
3767 use the @code{continue} command, or @code{step}, or any other command
3768 that resumes execution.
3770 Any other commands in the command list, after a command that resumes
3771 execution, are ignored. This is because any time you resume execution
3772 (even with a simple @code{next} or @code{step}), you may encounter
3773 another breakpoint---which could have its own command list, leading to
3774 ambiguities about which list to execute.
3777 If the first command you specify in a command list is @code{silent}, the
3778 usual message about stopping at a breakpoint is not printed. This may
3779 be desirable for breakpoints that are to print a specific message and
3780 then continue. If none of the remaining commands print anything, you
3781 see no sign that the breakpoint was reached. @code{silent} is
3782 meaningful only at the beginning of a breakpoint command list.
3784 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3785 print precisely controlled output, and are often useful in silent
3786 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3788 For example, here is how you could use breakpoint commands to print the
3789 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3795 printf "x is %d\n",x
3800 One application for breakpoint commands is to compensate for one bug so
3801 you can test for another. Put a breakpoint just after the erroneous line
3802 of code, give it a condition to detect the case in which something
3803 erroneous has been done, and give it commands to assign correct values
3804 to any variables that need them. End with the @code{continue} command
3805 so that your program does not stop, and start with the @code{silent}
3806 command so that no output is produced. Here is an example:
3817 @node Breakpoint Menus
3818 @subsection Breakpoint Menus
3820 @cindex symbol overloading
3822 Some programming languages (notably C@t{++} and Objective-C) permit a
3823 single function name
3824 to be defined several times, for application in different contexts.
3825 This is called @dfn{overloading}. When a function name is overloaded,
3826 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3827 a breakpoint. You can use explicit signature of the function, as in
3828 @samp{break @var{function}(@var{types})}, to specify which
3829 particular version of the function you want. Otherwise, @value{GDBN} offers
3830 you a menu of numbered choices for different possible breakpoints, and
3831 waits for your selection with the prompt @samp{>}. The first two
3832 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3833 sets a breakpoint at each definition of @var{function}, and typing
3834 @kbd{0} aborts the @code{break} command without setting any new
3837 For example, the following session excerpt shows an attempt to set a
3838 breakpoint at the overloaded symbol @code{String::after}.
3839 We choose three particular definitions of that function name:
3841 @c FIXME! This is likely to change to show arg type lists, at least
3844 (@value{GDBP}) b String::after
3847 [2] file:String.cc; line number:867
3848 [3] file:String.cc; line number:860
3849 [4] file:String.cc; line number:875
3850 [5] file:String.cc; line number:853
3851 [6] file:String.cc; line number:846
3852 [7] file:String.cc; line number:735
3854 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3855 Breakpoint 2 at 0xb344: file String.cc, line 875.
3856 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3857 Multiple breakpoints were set.
3858 Use the "delete" command to delete unwanted
3864 @c @ifclear BARETARGET
3865 @node Error in Breakpoints
3866 @subsection ``Cannot insert breakpoints''
3868 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3870 Under some operating systems, breakpoints cannot be used in a program if
3871 any other process is running that program. In this situation,
3872 attempting to run or continue a program with a breakpoint causes
3873 @value{GDBN} to print an error message:
3876 Cannot insert breakpoints.
3877 The same program may be running in another process.
3880 When this happens, you have three ways to proceed:
3884 Remove or disable the breakpoints, then continue.
3887 Suspend @value{GDBN}, and copy the file containing your program to a new
3888 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3889 that @value{GDBN} should run your program under that name.
3890 Then start your program again.
3893 Relink your program so that the text segment is nonsharable, using the
3894 linker option @samp{-N}. The operating system limitation may not apply
3895 to nonsharable executables.
3899 A similar message can be printed if you request too many active
3900 hardware-assisted breakpoints and watchpoints:
3902 @c FIXME: the precise wording of this message may change; the relevant
3903 @c source change is not committed yet (Sep 3, 1999).
3905 Stopped; cannot insert breakpoints.
3906 You may have requested too many hardware breakpoints and watchpoints.
3910 This message is printed when you attempt to resume the program, since
3911 only then @value{GDBN} knows exactly how many hardware breakpoints and
3912 watchpoints it needs to insert.
3914 When this message is printed, you need to disable or remove some of the
3915 hardware-assisted breakpoints and watchpoints, and then continue.
3917 @node Breakpoint-related Warnings
3918 @subsection ``Breakpoint address adjusted...''
3919 @cindex breakpoint address adjusted
3921 Some processor architectures place constraints on the addresses at
3922 which breakpoints may be placed. For architectures thus constrained,
3923 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3924 with the constraints dictated by the architecture.
3926 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3927 a VLIW architecture in which a number of RISC-like instructions may be
3928 bundled together for parallel execution. The FR-V architecture
3929 constrains the location of a breakpoint instruction within such a
3930 bundle to the instruction with the lowest address. @value{GDBN}
3931 honors this constraint by adjusting a breakpoint's address to the
3932 first in the bundle.
3934 It is not uncommon for optimized code to have bundles which contain
3935 instructions from different source statements, thus it may happen that
3936 a breakpoint's address will be adjusted from one source statement to
3937 another. Since this adjustment may significantly alter @value{GDBN}'s
3938 breakpoint related behavior from what the user expects, a warning is
3939 printed when the breakpoint is first set and also when the breakpoint
3942 A warning like the one below is printed when setting a breakpoint
3943 that's been subject to address adjustment:
3946 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3949 Such warnings are printed both for user settable and @value{GDBN}'s
3950 internal breakpoints. If you see one of these warnings, you should
3951 verify that a breakpoint set at the adjusted address will have the
3952 desired affect. If not, the breakpoint in question may be removed and
3953 other breakpoints may be set which will have the desired behavior.
3954 E.g., it may be sufficient to place the breakpoint at a later
3955 instruction. A conditional breakpoint may also be useful in some
3956 cases to prevent the breakpoint from triggering too often.
3958 @value{GDBN} will also issue a warning when stopping at one of these
3959 adjusted breakpoints:
3962 warning: Breakpoint 1 address previously adjusted from 0x00010414
3966 When this warning is encountered, it may be too late to take remedial
3967 action except in cases where the breakpoint is hit earlier or more
3968 frequently than expected.
3970 @node Continuing and Stepping
3971 @section Continuing and Stepping
3975 @cindex resuming execution
3976 @dfn{Continuing} means resuming program execution until your program
3977 completes normally. In contrast, @dfn{stepping} means executing just
3978 one more ``step'' of your program, where ``step'' may mean either one
3979 line of source code, or one machine instruction (depending on what
3980 particular command you use). Either when continuing or when stepping,
3981 your program may stop even sooner, due to a breakpoint or a signal. (If
3982 it stops due to a signal, you may want to use @code{handle}, or use
3983 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3987 @kindex c @r{(@code{continue})}
3988 @kindex fg @r{(resume foreground execution)}
3989 @item continue @r{[}@var{ignore-count}@r{]}
3990 @itemx c @r{[}@var{ignore-count}@r{]}
3991 @itemx fg @r{[}@var{ignore-count}@r{]}
3992 Resume program execution, at the address where your program last stopped;
3993 any breakpoints set at that address are bypassed. The optional argument
3994 @var{ignore-count} allows you to specify a further number of times to
3995 ignore a breakpoint at this location; its effect is like that of
3996 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
3998 The argument @var{ignore-count} is meaningful only when your program
3999 stopped due to a breakpoint. At other times, the argument to
4000 @code{continue} is ignored.
4002 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4003 debugged program is deemed to be the foreground program) are provided
4004 purely for convenience, and have exactly the same behavior as
4008 To resume execution at a different place, you can use @code{return}
4009 (@pxref{Returning, ,Returning from a Function}) to go back to the
4010 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4011 Different Address}) to go to an arbitrary location in your program.
4013 A typical technique for using stepping is to set a breakpoint
4014 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4015 beginning of the function or the section of your program where a problem
4016 is believed to lie, run your program until it stops at that breakpoint,
4017 and then step through the suspect area, examining the variables that are
4018 interesting, until you see the problem happen.
4022 @kindex s @r{(@code{step})}
4024 Continue running your program until control reaches a different source
4025 line, then stop it and return control to @value{GDBN}. This command is
4026 abbreviated @code{s}.
4029 @c "without debugging information" is imprecise; actually "without line
4030 @c numbers in the debugging information". (gcc -g1 has debugging info but
4031 @c not line numbers). But it seems complex to try to make that
4032 @c distinction here.
4033 @emph{Warning:} If you use the @code{step} command while control is
4034 within a function that was compiled without debugging information,
4035 execution proceeds until control reaches a function that does have
4036 debugging information. Likewise, it will not step into a function which
4037 is compiled without debugging information. To step through functions
4038 without debugging information, use the @code{stepi} command, described
4042 The @code{step} command only stops at the first instruction of a source
4043 line. This prevents the multiple stops that could otherwise occur in
4044 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4045 to stop if a function that has debugging information is called within
4046 the line. In other words, @code{step} @emph{steps inside} any functions
4047 called within the line.
4049 Also, the @code{step} command only enters a function if there is line
4050 number information for the function. Otherwise it acts like the
4051 @code{next} command. This avoids problems when using @code{cc -gl}
4052 on MIPS machines. Previously, @code{step} entered subroutines if there
4053 was any debugging information about the routine.
4055 @item step @var{count}
4056 Continue running as in @code{step}, but do so @var{count} times. If a
4057 breakpoint is reached, or a signal not related to stepping occurs before
4058 @var{count} steps, stepping stops right away.
4061 @kindex n @r{(@code{next})}
4062 @item next @r{[}@var{count}@r{]}
4063 Continue to the next source line in the current (innermost) stack frame.
4064 This is similar to @code{step}, but function calls that appear within
4065 the line of code are executed without stopping. Execution stops when
4066 control reaches a different line of code at the original stack level
4067 that was executing when you gave the @code{next} command. This command
4068 is abbreviated @code{n}.
4070 An argument @var{count} is a repeat count, as for @code{step}.
4073 @c FIX ME!! Do we delete this, or is there a way it fits in with
4074 @c the following paragraph? --- Vctoria
4076 @c @code{next} within a function that lacks debugging information acts like
4077 @c @code{step}, but any function calls appearing within the code of the
4078 @c function are executed without stopping.
4080 The @code{next} command only stops at the first instruction of a
4081 source line. This prevents multiple stops that could otherwise occur in
4082 @code{switch} statements, @code{for} loops, etc.
4084 @kindex set step-mode
4086 @cindex functions without line info, and stepping
4087 @cindex stepping into functions with no line info
4088 @itemx set step-mode on
4089 The @code{set step-mode on} command causes the @code{step} command to
4090 stop at the first instruction of a function which contains no debug line
4091 information rather than stepping over it.
4093 This is useful in cases where you may be interested in inspecting the
4094 machine instructions of a function which has no symbolic info and do not
4095 want @value{GDBN} to automatically skip over this function.
4097 @item set step-mode off
4098 Causes the @code{step} command to step over any functions which contains no
4099 debug information. This is the default.
4101 @item show step-mode
4102 Show whether @value{GDBN} will stop in or step over functions without
4103 source line debug information.
4107 Continue running until just after function in the selected stack frame
4108 returns. Print the returned value (if any).
4110 Contrast this with the @code{return} command (@pxref{Returning,
4111 ,Returning from a Function}).
4114 @kindex u @r{(@code{until})}
4115 @cindex run until specified location
4118 Continue running until a source line past the current line, in the
4119 current stack frame, is reached. This command is used to avoid single
4120 stepping through a loop more than once. It is like the @code{next}
4121 command, except that when @code{until} encounters a jump, it
4122 automatically continues execution until the program counter is greater
4123 than the address of the jump.
4125 This means that when you reach the end of a loop after single stepping
4126 though it, @code{until} makes your program continue execution until it
4127 exits the loop. In contrast, a @code{next} command at the end of a loop
4128 simply steps back to the beginning of the loop, which forces you to step
4129 through the next iteration.
4131 @code{until} always stops your program if it attempts to exit the current
4134 @code{until} may produce somewhat counterintuitive results if the order
4135 of machine code does not match the order of the source lines. For
4136 example, in the following excerpt from a debugging session, the @code{f}
4137 (@code{frame}) command shows that execution is stopped at line
4138 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4142 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4144 (@value{GDBP}) until
4145 195 for ( ; argc > 0; NEXTARG) @{
4148 This happened because, for execution efficiency, the compiler had
4149 generated code for the loop closure test at the end, rather than the
4150 start, of the loop---even though the test in a C @code{for}-loop is
4151 written before the body of the loop. The @code{until} command appeared
4152 to step back to the beginning of the loop when it advanced to this
4153 expression; however, it has not really gone to an earlier
4154 statement---not in terms of the actual machine code.
4156 @code{until} with no argument works by means of single
4157 instruction stepping, and hence is slower than @code{until} with an
4160 @item until @var{location}
4161 @itemx u @var{location}
4162 Continue running your program until either the specified location is
4163 reached, or the current stack frame returns. @var{location} is any of
4164 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4165 ,Setting Breakpoints}). This form of the command uses breakpoints, and
4166 hence is quicker than @code{until} without an argument. The specified
4167 location is actually reached only if it is in the current frame. This
4168 implies that @code{until} can be used to skip over recursive function
4169 invocations. For instance in the code below, if the current location is
4170 line @code{96}, issuing @code{until 99} will execute the program up to
4171 line @code{99} in the same invocation of factorial, i.e., after the inner
4172 invocations have returned.
4175 94 int factorial (int value)
4177 96 if (value > 1) @{
4178 97 value *= factorial (value - 1);
4185 @kindex advance @var{location}
4186 @itemx advance @var{location}
4187 Continue running the program up to the given @var{location}. An argument is
4188 required, which should be of the same form as arguments for the @code{break}
4189 command. Execution will also stop upon exit from the current stack
4190 frame. This command is similar to @code{until}, but @code{advance} will
4191 not skip over recursive function calls, and the target location doesn't
4192 have to be in the same frame as the current one.
4196 @kindex si @r{(@code{stepi})}
4198 @itemx stepi @var{arg}
4200 Execute one machine instruction, then stop and return to the debugger.
4202 It is often useful to do @samp{display/i $pc} when stepping by machine
4203 instructions. This makes @value{GDBN} automatically display the next
4204 instruction to be executed, each time your program stops. @xref{Auto
4205 Display,, Automatic Display}.
4207 An argument is a repeat count, as in @code{step}.
4211 @kindex ni @r{(@code{nexti})}
4213 @itemx nexti @var{arg}
4215 Execute one machine instruction, but if it is a function call,
4216 proceed until the function returns.
4218 An argument is a repeat count, as in @code{next}.
4225 A signal is an asynchronous event that can happen in a program. The
4226 operating system defines the possible kinds of signals, and gives each
4227 kind a name and a number. For example, in Unix @code{SIGINT} is the
4228 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4229 @code{SIGSEGV} is the signal a program gets from referencing a place in
4230 memory far away from all the areas in use; @code{SIGALRM} occurs when
4231 the alarm clock timer goes off (which happens only if your program has
4232 requested an alarm).
4234 @cindex fatal signals
4235 Some signals, including @code{SIGALRM}, are a normal part of the
4236 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4237 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4238 program has not specified in advance some other way to handle the signal.
4239 @code{SIGINT} does not indicate an error in your program, but it is normally
4240 fatal so it can carry out the purpose of the interrupt: to kill the program.
4242 @value{GDBN} has the ability to detect any occurrence of a signal in your
4243 program. You can tell @value{GDBN} in advance what to do for each kind of
4246 @cindex handling signals
4247 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4248 @code{SIGALRM} be silently passed to your program
4249 (so as not to interfere with their role in the program's functioning)
4250 but to stop your program immediately whenever an error signal happens.
4251 You can change these settings with the @code{handle} command.
4254 @kindex info signals
4258 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4259 handle each one. You can use this to see the signal numbers of all
4260 the defined types of signals.
4262 @item info signals @var{sig}
4263 Similar, but print information only about the specified signal number.
4265 @code{info handle} is an alias for @code{info signals}.
4268 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4269 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4270 can be the number of a signal or its name (with or without the
4271 @samp{SIG} at the beginning); a list of signal numbers of the form
4272 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4273 known signals. Optional arguments @var{keywords}, described below,
4274 say what change to make.
4278 The keywords allowed by the @code{handle} command can be abbreviated.
4279 Their full names are:
4283 @value{GDBN} should not stop your program when this signal happens. It may
4284 still print a message telling you that the signal has come in.
4287 @value{GDBN} should stop your program when this signal happens. This implies
4288 the @code{print} keyword as well.
4291 @value{GDBN} should print a message when this signal happens.
4294 @value{GDBN} should not mention the occurrence of the signal at all. This
4295 implies the @code{nostop} keyword as well.
4299 @value{GDBN} should allow your program to see this signal; your program
4300 can handle the signal, or else it may terminate if the signal is fatal
4301 and not handled. @code{pass} and @code{noignore} are synonyms.
4305 @value{GDBN} should not allow your program to see this signal.
4306 @code{nopass} and @code{ignore} are synonyms.
4310 When a signal stops your program, the signal is not visible to the
4312 continue. Your program sees the signal then, if @code{pass} is in
4313 effect for the signal in question @emph{at that time}. In other words,
4314 after @value{GDBN} reports a signal, you can use the @code{handle}
4315 command with @code{pass} or @code{nopass} to control whether your
4316 program sees that signal when you continue.
4318 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4319 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4320 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4323 You can also use the @code{signal} command to prevent your program from
4324 seeing a signal, or cause it to see a signal it normally would not see,
4325 or to give it any signal at any time. For example, if your program stopped
4326 due to some sort of memory reference error, you might store correct
4327 values into the erroneous variables and continue, hoping to see more
4328 execution; but your program would probably terminate immediately as
4329 a result of the fatal signal once it saw the signal. To prevent this,
4330 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4334 @section Stopping and Starting Multi-thread Programs
4336 When your program has multiple threads (@pxref{Threads,, Debugging
4337 Programs with Multiple Threads}), you can choose whether to set
4338 breakpoints on all threads, or on a particular thread.
4341 @cindex breakpoints and threads
4342 @cindex thread breakpoints
4343 @kindex break @dots{} thread @var{threadno}
4344 @item break @var{linespec} thread @var{threadno}
4345 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4346 @var{linespec} specifies source lines; there are several ways of
4347 writing them, but the effect is always to specify some source line.
4349 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4350 to specify that you only want @value{GDBN} to stop the program when a
4351 particular thread reaches this breakpoint. @var{threadno} is one of the
4352 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4353 column of the @samp{info threads} display.
4355 If you do not specify @samp{thread @var{threadno}} when you set a
4356 breakpoint, the breakpoint applies to @emph{all} threads of your
4359 You can use the @code{thread} qualifier on conditional breakpoints as
4360 well; in this case, place @samp{thread @var{threadno}} before the
4361 breakpoint condition, like this:
4364 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4369 @cindex stopped threads
4370 @cindex threads, stopped
4371 Whenever your program stops under @value{GDBN} for any reason,
4372 @emph{all} threads of execution stop, not just the current thread. This
4373 allows you to examine the overall state of the program, including
4374 switching between threads, without worrying that things may change
4377 @cindex thread breakpoints and system calls
4378 @cindex system calls and thread breakpoints
4379 @cindex premature return from system calls
4380 There is an unfortunate side effect. If one thread stops for a
4381 breakpoint, or for some other reason, and another thread is blocked in a
4382 system call, then the system call may return prematurely. This is a
4383 consequence of the interaction between multiple threads and the signals
4384 that @value{GDBN} uses to implement breakpoints and other events that
4387 To handle this problem, your program should check the return value of
4388 each system call and react appropriately. This is good programming
4391 For example, do not write code like this:
4397 The call to @code{sleep} will return early if a different thread stops
4398 at a breakpoint or for some other reason.
4400 Instead, write this:
4405 unslept = sleep (unslept);
4408 A system call is allowed to return early, so the system is still
4409 conforming to its specification. But @value{GDBN} does cause your
4410 multi-threaded program to behave differently than it would without
4413 Also, @value{GDBN} uses internal breakpoints in the thread library to
4414 monitor certain events such as thread creation and thread destruction.
4415 When such an event happens, a system call in another thread may return
4416 prematurely, even though your program does not appear to stop.
4418 @cindex continuing threads
4419 @cindex threads, continuing
4420 Conversely, whenever you restart the program, @emph{all} threads start
4421 executing. @emph{This is true even when single-stepping} with commands
4422 like @code{step} or @code{next}.
4424 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4425 Since thread scheduling is up to your debugging target's operating
4426 system (not controlled by @value{GDBN}), other threads may
4427 execute more than one statement while the current thread completes a
4428 single step. Moreover, in general other threads stop in the middle of a
4429 statement, rather than at a clean statement boundary, when the program
4432 You might even find your program stopped in another thread after
4433 continuing or even single-stepping. This happens whenever some other
4434 thread runs into a breakpoint, a signal, or an exception before the
4435 first thread completes whatever you requested.
4437 On some OSes, you can lock the OS scheduler and thus allow only a single
4441 @item set scheduler-locking @var{mode}
4442 @cindex scheduler locking mode
4443 @cindex lock scheduler
4444 Set the scheduler locking mode. If it is @code{off}, then there is no
4445 locking and any thread may run at any time. If @code{on}, then only the
4446 current thread may run when the inferior is resumed. The @code{step}
4447 mode optimizes for single-stepping. It stops other threads from
4448 ``seizing the prompt'' by preempting the current thread while you are
4449 stepping. Other threads will only rarely (or never) get a chance to run
4450 when you step. They are more likely to run when you @samp{next} over a
4451 function call, and they are completely free to run when you use commands
4452 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4453 thread hits a breakpoint during its timeslice, they will never steal the
4454 @value{GDBN} prompt away from the thread that you are debugging.
4456 @item show scheduler-locking
4457 Display the current scheduler locking mode.
4462 @chapter Examining the Stack
4464 When your program has stopped, the first thing you need to know is where it
4465 stopped and how it got there.
4468 Each time your program performs a function call, information about the call
4470 That information includes the location of the call in your program,
4471 the arguments of the call,
4472 and the local variables of the function being called.
4473 The information is saved in a block of data called a @dfn{stack frame}.
4474 The stack frames are allocated in a region of memory called the @dfn{call
4477 When your program stops, the @value{GDBN} commands for examining the
4478 stack allow you to see all of this information.
4480 @cindex selected frame
4481 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4482 @value{GDBN} commands refer implicitly to the selected frame. In
4483 particular, whenever you ask @value{GDBN} for the value of a variable in
4484 your program, the value is found in the selected frame. There are
4485 special @value{GDBN} commands to select whichever frame you are
4486 interested in. @xref{Selection, ,Selecting a Frame}.
4488 When your program stops, @value{GDBN} automatically selects the
4489 currently executing frame and describes it briefly, similar to the
4490 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4493 * Frames:: Stack frames
4494 * Backtrace:: Backtraces
4495 * Selection:: Selecting a frame
4496 * Frame Info:: Information on a frame
4501 @section Stack Frames
4503 @cindex frame, definition
4505 The call stack is divided up into contiguous pieces called @dfn{stack
4506 frames}, or @dfn{frames} for short; each frame is the data associated
4507 with one call to one function. The frame contains the arguments given
4508 to the function, the function's local variables, and the address at
4509 which the function is executing.
4511 @cindex initial frame
4512 @cindex outermost frame
4513 @cindex innermost frame
4514 When your program is started, the stack has only one frame, that of the
4515 function @code{main}. This is called the @dfn{initial} frame or the
4516 @dfn{outermost} frame. Each time a function is called, a new frame is
4517 made. Each time a function returns, the frame for that function invocation
4518 is eliminated. If a function is recursive, there can be many frames for
4519 the same function. The frame for the function in which execution is
4520 actually occurring is called the @dfn{innermost} frame. This is the most
4521 recently created of all the stack frames that still exist.
4523 @cindex frame pointer
4524 Inside your program, stack frames are identified by their addresses. A
4525 stack frame consists of many bytes, each of which has its own address; each
4526 kind of computer has a convention for choosing one byte whose
4527 address serves as the address of the frame. Usually this address is kept
4528 in a register called the @dfn{frame pointer register}
4529 (@pxref{Registers, $fp}) while execution is going on in that frame.
4531 @cindex frame number
4532 @value{GDBN} assigns numbers to all existing stack frames, starting with
4533 zero for the innermost frame, one for the frame that called it,
4534 and so on upward. These numbers do not really exist in your program;
4535 they are assigned by @value{GDBN} to give you a way of designating stack
4536 frames in @value{GDBN} commands.
4538 @c The -fomit-frame-pointer below perennially causes hbox overflow
4539 @c underflow problems.
4540 @cindex frameless execution
4541 Some compilers provide a way to compile functions so that they operate
4542 without stack frames. (For example, the @value{NGCC} option
4544 @samp{-fomit-frame-pointer}
4546 generates functions without a frame.)
4547 This is occasionally done with heavily used library functions to save
4548 the frame setup time. @value{GDBN} has limited facilities for dealing
4549 with these function invocations. If the innermost function invocation
4550 has no stack frame, @value{GDBN} nevertheless regards it as though
4551 it had a separate frame, which is numbered zero as usual, allowing
4552 correct tracing of the function call chain. However, @value{GDBN} has
4553 no provision for frameless functions elsewhere in the stack.
4556 @kindex frame@r{, command}
4557 @cindex current stack frame
4558 @item frame @var{args}
4559 The @code{frame} command allows you to move from one stack frame to another,
4560 and to print the stack frame you select. @var{args} may be either the
4561 address of the frame or the stack frame number. Without an argument,
4562 @code{frame} prints the current stack frame.
4564 @kindex select-frame
4565 @cindex selecting frame silently
4567 The @code{select-frame} command allows you to move from one stack frame
4568 to another without printing the frame. This is the silent version of
4576 @cindex call stack traces
4577 A backtrace is a summary of how your program got where it is. It shows one
4578 line per frame, for many frames, starting with the currently executing
4579 frame (frame zero), followed by its caller (frame one), and on up the
4584 @kindex bt @r{(@code{backtrace})}
4587 Print a backtrace of the entire stack: one line per frame for all
4588 frames in the stack.
4590 You can stop the backtrace at any time by typing the system interrupt
4591 character, normally @kbd{Ctrl-c}.
4593 @item backtrace @var{n}
4595 Similar, but print only the innermost @var{n} frames.
4597 @item backtrace -@var{n}
4599 Similar, but print only the outermost @var{n} frames.
4601 @item backtrace full
4603 @itemx bt full @var{n}
4604 @itemx bt full -@var{n}
4605 Print the values of the local variables also. @var{n} specifies the
4606 number of frames to print, as described above.
4611 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4612 are additional aliases for @code{backtrace}.
4614 @cindex multiple threads, backtrace
4615 In a multi-threaded program, @value{GDBN} by default shows the
4616 backtrace only for the current thread. To display the backtrace for
4617 several or all of the threads, use the command @code{thread apply}
4618 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4619 apply all backtrace}, @value{GDBN} will display the backtrace for all
4620 the threads; this is handy when you debug a core dump of a
4621 multi-threaded program.
4623 Each line in the backtrace shows the frame number and the function name.
4624 The program counter value is also shown---unless you use @code{set
4625 print address off}. The backtrace also shows the source file name and
4626 line number, as well as the arguments to the function. The program
4627 counter value is omitted if it is at the beginning of the code for that
4630 Here is an example of a backtrace. It was made with the command
4631 @samp{bt 3}, so it shows the innermost three frames.
4635 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4637 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4638 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4640 (More stack frames follow...)
4645 The display for frame zero does not begin with a program counter
4646 value, indicating that your program has stopped at the beginning of the
4647 code for line @code{993} of @code{builtin.c}.
4649 @cindex value optimized out, in backtrace
4650 @cindex function call arguments, optimized out
4651 If your program was compiled with optimizations, some compilers will
4652 optimize away arguments passed to functions if those arguments are
4653 never used after the call. Such optimizations generate code that
4654 passes arguments through registers, but doesn't store those arguments
4655 in the stack frame. @value{GDBN} has no way of displaying such
4656 arguments in stack frames other than the innermost one. Here's what
4657 such a backtrace might look like:
4661 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4663 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4664 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4666 (More stack frames follow...)
4671 The values of arguments that were not saved in their stack frames are
4672 shown as @samp{<value optimized out>}.
4674 If you need to display the values of such optimized-out arguments,
4675 either deduce that from other variables whose values depend on the one
4676 you are interested in, or recompile without optimizations.
4678 @cindex backtrace beyond @code{main} function
4679 @cindex program entry point
4680 @cindex startup code, and backtrace
4681 Most programs have a standard user entry point---a place where system
4682 libraries and startup code transition into user code. For C this is
4683 @code{main}@footnote{
4684 Note that embedded programs (the so-called ``free-standing''
4685 environment) are not required to have a @code{main} function as the
4686 entry point. They could even have multiple entry points.}.
4687 When @value{GDBN} finds the entry function in a backtrace
4688 it will terminate the backtrace, to avoid tracing into highly
4689 system-specific (and generally uninteresting) code.
4691 If you need to examine the startup code, or limit the number of levels
4692 in a backtrace, you can change this behavior:
4695 @item set backtrace past-main
4696 @itemx set backtrace past-main on
4697 @kindex set backtrace
4698 Backtraces will continue past the user entry point.
4700 @item set backtrace past-main off
4701 Backtraces will stop when they encounter the user entry point. This is the
4704 @item show backtrace past-main
4705 @kindex show backtrace
4706 Display the current user entry point backtrace policy.
4708 @item set backtrace past-entry
4709 @itemx set backtrace past-entry on
4710 Backtraces will continue past the internal entry point of an application.
4711 This entry point is encoded by the linker when the application is built,
4712 and is likely before the user entry point @code{main} (or equivalent) is called.
4714 @item set backtrace past-entry off
4715 Backtraces will stop when they encounter the internal entry point of an
4716 application. This is the default.
4718 @item show backtrace past-entry
4719 Display the current internal entry point backtrace policy.
4721 @item set backtrace limit @var{n}
4722 @itemx set backtrace limit 0
4723 @cindex backtrace limit
4724 Limit the backtrace to @var{n} levels. A value of zero means
4727 @item show backtrace limit
4728 Display the current limit on backtrace levels.
4732 @section Selecting a Frame
4734 Most commands for examining the stack and other data in your program work on
4735 whichever stack frame is selected at the moment. Here are the commands for
4736 selecting a stack frame; all of them finish by printing a brief description
4737 of the stack frame just selected.
4740 @kindex frame@r{, selecting}
4741 @kindex f @r{(@code{frame})}
4744 Select frame number @var{n}. Recall that frame zero is the innermost
4745 (currently executing) frame, frame one is the frame that called the
4746 innermost one, and so on. The highest-numbered frame is the one for
4749 @item frame @var{addr}
4751 Select the frame at address @var{addr}. This is useful mainly if the
4752 chaining of stack frames has been damaged by a bug, making it
4753 impossible for @value{GDBN} to assign numbers properly to all frames. In
4754 addition, this can be useful when your program has multiple stacks and
4755 switches between them.
4757 On the SPARC architecture, @code{frame} needs two addresses to
4758 select an arbitrary frame: a frame pointer and a stack pointer.
4760 On the MIPS and Alpha architecture, it needs two addresses: a stack
4761 pointer and a program counter.
4763 On the 29k architecture, it needs three addresses: a register stack
4764 pointer, a program counter, and a memory stack pointer.
4768 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4769 advances toward the outermost frame, to higher frame numbers, to frames
4770 that have existed longer. @var{n} defaults to one.
4773 @kindex do @r{(@code{down})}
4775 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4776 advances toward the innermost frame, to lower frame numbers, to frames
4777 that were created more recently. @var{n} defaults to one. You may
4778 abbreviate @code{down} as @code{do}.
4781 All of these commands end by printing two lines of output describing the
4782 frame. The first line shows the frame number, the function name, the
4783 arguments, and the source file and line number of execution in that
4784 frame. The second line shows the text of that source line.
4792 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4794 10 read_input_file (argv[i]);
4798 After such a printout, the @code{list} command with no arguments
4799 prints ten lines centered on the point of execution in the frame.
4800 You can also edit the program at the point of execution with your favorite
4801 editing program by typing @code{edit}.
4802 @xref{List, ,Printing Source Lines},
4806 @kindex down-silently
4808 @item up-silently @var{n}
4809 @itemx down-silently @var{n}
4810 These two commands are variants of @code{up} and @code{down},
4811 respectively; they differ in that they do their work silently, without
4812 causing display of the new frame. They are intended primarily for use
4813 in @value{GDBN} command scripts, where the output might be unnecessary and
4818 @section Information About a Frame
4820 There are several other commands to print information about the selected
4826 When used without any argument, this command does not change which
4827 frame is selected, but prints a brief description of the currently
4828 selected stack frame. It can be abbreviated @code{f}. With an
4829 argument, this command is used to select a stack frame.
4830 @xref{Selection, ,Selecting a Frame}.
4833 @kindex info f @r{(@code{info frame})}
4836 This command prints a verbose description of the selected stack frame,
4841 the address of the frame
4843 the address of the next frame down (called by this frame)
4845 the address of the next frame up (caller of this frame)
4847 the language in which the source code corresponding to this frame is written
4849 the address of the frame's arguments
4851 the address of the frame's local variables
4853 the program counter saved in it (the address of execution in the caller frame)
4855 which registers were saved in the frame
4858 @noindent The verbose description is useful when
4859 something has gone wrong that has made the stack format fail to fit
4860 the usual conventions.
4862 @item info frame @var{addr}
4863 @itemx info f @var{addr}
4864 Print a verbose description of the frame at address @var{addr}, without
4865 selecting that frame. The selected frame remains unchanged by this
4866 command. This requires the same kind of address (more than one for some
4867 architectures) that you specify in the @code{frame} command.
4868 @xref{Selection, ,Selecting a Frame}.
4872 Print the arguments of the selected frame, each on a separate line.
4876 Print the local variables of the selected frame, each on a separate
4877 line. These are all variables (declared either static or automatic)
4878 accessible at the point of execution of the selected frame.
4881 @cindex catch exceptions, list active handlers
4882 @cindex exception handlers, how to list
4884 Print a list of all the exception handlers that are active in the
4885 current stack frame at the current point of execution. To see other
4886 exception handlers, visit the associated frame (using the @code{up},
4887 @code{down}, or @code{frame} commands); then type @code{info catch}.
4888 @xref{Set Catchpoints, , Setting Catchpoints}.
4894 @chapter Examining Source Files
4896 @value{GDBN} can print parts of your program's source, since the debugging
4897 information recorded in the program tells @value{GDBN} what source files were
4898 used to build it. When your program stops, @value{GDBN} spontaneously prints
4899 the line where it stopped. Likewise, when you select a stack frame
4900 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4901 execution in that frame has stopped. You can print other portions of
4902 source files by explicit command.
4904 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4905 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4906 @value{GDBN} under @sc{gnu} Emacs}.
4909 * List:: Printing source lines
4910 * Edit:: Editing source files
4911 * Search:: Searching source files
4912 * Source Path:: Specifying source directories
4913 * Machine Code:: Source and machine code
4917 @section Printing Source Lines
4920 @kindex l @r{(@code{list})}
4921 To print lines from a source file, use the @code{list} command
4922 (abbreviated @code{l}). By default, ten lines are printed.
4923 There are several ways to specify what part of the file you want to print.
4925 Here are the forms of the @code{list} command most commonly used:
4928 @item list @var{linenum}
4929 Print lines centered around line number @var{linenum} in the
4930 current source file.
4932 @item list @var{function}
4933 Print lines centered around the beginning of function
4937 Print more lines. If the last lines printed were printed with a
4938 @code{list} command, this prints lines following the last lines
4939 printed; however, if the last line printed was a solitary line printed
4940 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4941 Stack}), this prints lines centered around that line.
4944 Print lines just before the lines last printed.
4947 @cindex @code{list}, how many lines to display
4948 By default, @value{GDBN} prints ten source lines with any of these forms of
4949 the @code{list} command. You can change this using @code{set listsize}:
4952 @kindex set listsize
4953 @item set listsize @var{count}
4954 Make the @code{list} command display @var{count} source lines (unless
4955 the @code{list} argument explicitly specifies some other number).
4957 @kindex show listsize
4959 Display the number of lines that @code{list} prints.
4962 Repeating a @code{list} command with @key{RET} discards the argument,
4963 so it is equivalent to typing just @code{list}. This is more useful
4964 than listing the same lines again. An exception is made for an
4965 argument of @samp{-}; that argument is preserved in repetition so that
4966 each repetition moves up in the source file.
4969 In general, the @code{list} command expects you to supply zero, one or two
4970 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4971 of writing them, but the effect is always to specify some source line.
4972 Here is a complete description of the possible arguments for @code{list}:
4975 @item list @var{linespec}
4976 Print lines centered around the line specified by @var{linespec}.
4978 @item list @var{first},@var{last}
4979 Print lines from @var{first} to @var{last}. Both arguments are
4982 @item list ,@var{last}
4983 Print lines ending with @var{last}.
4985 @item list @var{first},
4986 Print lines starting with @var{first}.
4989 Print lines just after the lines last printed.
4992 Print lines just before the lines last printed.
4995 As described in the preceding table.
4998 Here are the ways of specifying a single source line---all the
5003 Specifies line @var{number} of the current source file.
5004 When a @code{list} command has two linespecs, this refers to
5005 the same source file as the first linespec.
5008 Specifies the line @var{offset} lines after the last line printed.
5009 When used as the second linespec in a @code{list} command that has
5010 two, this specifies the line @var{offset} lines down from the
5014 Specifies the line @var{offset} lines before the last line printed.
5016 @item @var{filename}:@var{number}
5017 Specifies line @var{number} in the source file @var{filename}.
5019 @item @var{function}
5020 Specifies the line that begins the body of the function @var{function}.
5021 For example: in C, this is the line with the open brace.
5023 @item @var{filename}:@var{function}
5024 Specifies the line of the open-brace that begins the body of the
5025 function @var{function} in the file @var{filename}. You only need the
5026 file name with a function name to avoid ambiguity when there are
5027 identically named functions in different source files.
5029 @item *@var{address}
5030 Specifies the line containing the program address @var{address}.
5031 @var{address} may be any expression.
5035 @section Editing Source Files
5036 @cindex editing source files
5039 @kindex e @r{(@code{edit})}
5040 To edit the lines in a source file, use the @code{edit} command.
5041 The editing program of your choice
5042 is invoked with the current line set to
5043 the active line in the program.
5044 Alternatively, there are several ways to specify what part of the file you
5045 want to print if you want to see other parts of the program.
5047 Here are the forms of the @code{edit} command most commonly used:
5051 Edit the current source file at the active line number in the program.
5053 @item edit @var{number}
5054 Edit the current source file with @var{number} as the active line number.
5056 @item edit @var{function}
5057 Edit the file containing @var{function} at the beginning of its definition.
5059 @item edit @var{filename}:@var{number}
5060 Specifies line @var{number} in the source file @var{filename}.
5062 @item edit @var{filename}:@var{function}
5063 Specifies the line that begins the body of the
5064 function @var{function} in the file @var{filename}. You only need the
5065 file name with a function name to avoid ambiguity when there are
5066 identically named functions in different source files.
5068 @item edit *@var{address}
5069 Specifies the line containing the program address @var{address}.
5070 @var{address} may be any expression.
5073 @subsection Choosing your Editor
5074 You can customize @value{GDBN} to use any editor you want
5076 The only restriction is that your editor (say @code{ex}), recognizes the
5077 following command-line syntax:
5079 ex +@var{number} file
5081 The optional numeric value +@var{number} specifies the number of the line in
5082 the file where to start editing.}.
5083 By default, it is @file{@value{EDITOR}}, but you can change this
5084 by setting the environment variable @code{EDITOR} before using
5085 @value{GDBN}. For example, to configure @value{GDBN} to use the
5086 @code{vi} editor, you could use these commands with the @code{sh} shell:
5092 or in the @code{csh} shell,
5094 setenv EDITOR /usr/bin/vi
5099 @section Searching Source Files
5100 @cindex searching source files
5102 There are two commands for searching through the current source file for a
5107 @kindex forward-search
5108 @item forward-search @var{regexp}
5109 @itemx search @var{regexp}
5110 The command @samp{forward-search @var{regexp}} checks each line,
5111 starting with the one following the last line listed, for a match for
5112 @var{regexp}. It lists the line that is found. You can use the
5113 synonym @samp{search @var{regexp}} or abbreviate the command name as
5116 @kindex reverse-search
5117 @item reverse-search @var{regexp}
5118 The command @samp{reverse-search @var{regexp}} checks each line, starting
5119 with the one before the last line listed and going backward, for a match
5120 for @var{regexp}. It lists the line that is found. You can abbreviate
5121 this command as @code{rev}.
5125 @section Specifying Source Directories
5128 @cindex directories for source files
5129 Executable programs sometimes do not record the directories of the source
5130 files from which they were compiled, just the names. Even when they do,
5131 the directories could be moved between the compilation and your debugging
5132 session. @value{GDBN} has a list of directories to search for source files;
5133 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5134 it tries all the directories in the list, in the order they are present
5135 in the list, until it finds a file with the desired name.
5137 For example, suppose an executable references the file
5138 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5139 @file{/mnt/cross}. The file is first looked up literally; if this
5140 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5141 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5142 message is printed. @value{GDBN} does not look up the parts of the
5143 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5144 Likewise, the subdirectories of the source path are not searched: if
5145 the source path is @file{/mnt/cross}, and the binary refers to
5146 @file{foo.c}, @value{GDBN} would not find it under
5147 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5149 Plain file names, relative file names with leading directories, file
5150 names containing dots, etc.@: are all treated as described above; for
5151 instance, if the source path is @file{/mnt/cross}, and the source file
5152 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5153 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5154 that---@file{/mnt/cross/foo.c}.
5156 Note that the executable search path is @emph{not} used to locate the
5159 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5160 any information it has cached about where source files are found and where
5161 each line is in the file.
5165 When you start @value{GDBN}, its source path includes only @samp{cdir}
5166 and @samp{cwd}, in that order.
5167 To add other directories, use the @code{directory} command.
5169 The search path is used to find both program source files and @value{GDBN}
5170 script files (read using the @samp{-command} option and @samp{source} command).
5172 In addition to the source path, @value{GDBN} provides a set of commands
5173 that manage a list of source path substitution rules. A @dfn{substitution
5174 rule} specifies how to rewrite source directories stored in the program's
5175 debug information in case the sources were moved to a different
5176 directory between compilation and debugging. A rule is made of
5177 two strings, the first specifying what needs to be rewritten in
5178 the path, and the second specifying how it should be rewritten.
5179 In @ref{set substitute-path}, we name these two parts @var{from} and
5180 @var{to} respectively. @value{GDBN} does a simple string replacement
5181 of @var{from} with @var{to} at the start of the directory part of the
5182 source file name, and uses that result instead of the original file
5183 name to look up the sources.
5185 Using the previous example, suppose the @file{foo-1.0} tree has been
5186 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5187 @value{GDBN} to replace @file{/usr/src} in all source path names with
5188 @file{/mnt/cross}. The first lookup will then be
5189 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5190 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5191 substitution rule, use the @code{set substitute-path} command
5192 (@pxref{set substitute-path}).
5194 To avoid unexpected substitution results, a rule is applied only if the
5195 @var{from} part of the directory name ends at a directory separator.
5196 For instance, a rule substituting @file{/usr/source} into
5197 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5198 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5199 is applied only at the beginning of the directory name, this rule will
5200 not be applied to @file{/root/usr/source/baz.c} either.
5202 In many cases, you can achieve the same result using the @code{directory}
5203 command. However, @code{set substitute-path} can be more efficient in
5204 the case where the sources are organized in a complex tree with multiple
5205 subdirectories. With the @code{directory} command, you need to add each
5206 subdirectory of your project. If you moved the entire tree while
5207 preserving its internal organization, then @code{set substitute-path}
5208 allows you to direct the debugger to all the sources with one single
5211 @code{set substitute-path} is also more than just a shortcut command.
5212 The source path is only used if the file at the original location no
5213 longer exists. On the other hand, @code{set substitute-path} modifies
5214 the debugger behavior to look at the rewritten location instead. So, if
5215 for any reason a source file that is not relevant to your executable is
5216 located at the original location, a substitution rule is the only
5217 method available to point @value{GDBN} at the new location.
5220 @item directory @var{dirname} @dots{}
5221 @item dir @var{dirname} @dots{}
5222 Add directory @var{dirname} to the front of the source path. Several
5223 directory names may be given to this command, separated by @samp{:}
5224 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5225 part of absolute file names) or
5226 whitespace. You may specify a directory that is already in the source
5227 path; this moves it forward, so @value{GDBN} searches it sooner.
5231 @vindex $cdir@r{, convenience variable}
5232 @vindex $cwd@r{, convenience variable}
5233 @cindex compilation directory
5234 @cindex current directory
5235 @cindex working directory
5236 @cindex directory, current
5237 @cindex directory, compilation
5238 You can use the string @samp{$cdir} to refer to the compilation
5239 directory (if one is recorded), and @samp{$cwd} to refer to the current
5240 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5241 tracks the current working directory as it changes during your @value{GDBN}
5242 session, while the latter is immediately expanded to the current
5243 directory at the time you add an entry to the source path.
5246 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5248 @c RET-repeat for @code{directory} is explicitly disabled, but since
5249 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5251 @item show directories
5252 @kindex show directories
5253 Print the source path: show which directories it contains.
5255 @anchor{set substitute-path}
5256 @item set substitute-path @var{from} @var{to}
5257 @kindex set substitute-path
5258 Define a source path substitution rule, and add it at the end of the
5259 current list of existing substitution rules. If a rule with the same
5260 @var{from} was already defined, then the old rule is also deleted.
5262 For example, if the file @file{/foo/bar/baz.c} was moved to
5263 @file{/mnt/cross/baz.c}, then the command
5266 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5270 will tell @value{GDBN} to replace @samp{/usr/src} with
5271 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5272 @file{baz.c} even though it was moved.
5274 In the case when more than one substitution rule have been defined,
5275 the rules are evaluated one by one in the order where they have been
5276 defined. The first one matching, if any, is selected to perform
5279 For instance, if we had entered the following commands:
5282 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5283 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5287 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5288 @file{/mnt/include/defs.h} by using the first rule. However, it would
5289 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5290 @file{/mnt/src/lib/foo.c}.
5293 @item unset substitute-path [path]
5294 @kindex unset substitute-path
5295 If a path is specified, search the current list of substitution rules
5296 for a rule that would rewrite that path. Delete that rule if found.
5297 A warning is emitted by the debugger if no rule could be found.
5299 If no path is specified, then all substitution rules are deleted.
5301 @item show substitute-path [path]
5302 @kindex show substitute-path
5303 If a path is specified, then print the source path substitution rule
5304 which would rewrite that path, if any.
5306 If no path is specified, then print all existing source path substitution
5311 If your source path is cluttered with directories that are no longer of
5312 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5313 versions of source. You can correct the situation as follows:
5317 Use @code{directory} with no argument to reset the source path to its default value.
5320 Use @code{directory} with suitable arguments to reinstall the
5321 directories you want in the source path. You can add all the
5322 directories in one command.
5326 @section Source and Machine Code
5327 @cindex source line and its code address
5329 You can use the command @code{info line} to map source lines to program
5330 addresses (and vice versa), and the command @code{disassemble} to display
5331 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5332 mode, the @code{info line} command causes the arrow to point to the
5333 line specified. Also, @code{info line} prints addresses in symbolic form as
5338 @item info line @var{linespec}
5339 Print the starting and ending addresses of the compiled code for
5340 source line @var{linespec}. You can specify source lines in any of
5341 the ways understood by the @code{list} command (@pxref{List, ,Printing
5345 For example, we can use @code{info line} to discover the location of
5346 the object code for the first line of function
5347 @code{m4_changequote}:
5349 @c FIXME: I think this example should also show the addresses in
5350 @c symbolic form, as they usually would be displayed.
5352 (@value{GDBP}) info line m4_changequote
5353 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5357 @cindex code address and its source line
5358 We can also inquire (using @code{*@var{addr}} as the form for
5359 @var{linespec}) what source line covers a particular address:
5361 (@value{GDBP}) info line *0x63ff
5362 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5365 @cindex @code{$_} and @code{info line}
5366 @cindex @code{x} command, default address
5367 @kindex x@r{(examine), and} info line
5368 After @code{info line}, the default address for the @code{x} command
5369 is changed to the starting address of the line, so that @samp{x/i} is
5370 sufficient to begin examining the machine code (@pxref{Memory,
5371 ,Examining Memory}). Also, this address is saved as the value of the
5372 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5377 @cindex assembly instructions
5378 @cindex instructions, assembly
5379 @cindex machine instructions
5380 @cindex listing machine instructions
5382 This specialized command dumps a range of memory as machine
5383 instructions. The default memory range is the function surrounding the
5384 program counter of the selected frame. A single argument to this
5385 command is a program counter value; @value{GDBN} dumps the function
5386 surrounding this value. Two arguments specify a range of addresses
5387 (first inclusive, second exclusive) to dump.
5390 The following example shows the disassembly of a range of addresses of
5391 HP PA-RISC 2.0 code:
5394 (@value{GDBP}) disas 0x32c4 0x32e4
5395 Dump of assembler code from 0x32c4 to 0x32e4:
5396 0x32c4 <main+204>: addil 0,dp
5397 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5398 0x32cc <main+212>: ldil 0x3000,r31
5399 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5400 0x32d4 <main+220>: ldo 0(r31),rp
5401 0x32d8 <main+224>: addil -0x800,dp
5402 0x32dc <main+228>: ldo 0x588(r1),r26
5403 0x32e0 <main+232>: ldil 0x3000,r31
5404 End of assembler dump.
5407 Some architectures have more than one commonly-used set of instruction
5408 mnemonics or other syntax.
5410 For programs that were dynamically linked and use shared libraries,
5411 instructions that call functions or branch to locations in the shared
5412 libraries might show a seemingly bogus location---it's actually a
5413 location of the relocation table. On some architectures, @value{GDBN}
5414 might be able to resolve these to actual function names.
5417 @kindex set disassembly-flavor
5418 @cindex Intel disassembly flavor
5419 @cindex AT&T disassembly flavor
5420 @item set disassembly-flavor @var{instruction-set}
5421 Select the instruction set to use when disassembling the
5422 program via the @code{disassemble} or @code{x/i} commands.
5424 Currently this command is only defined for the Intel x86 family. You
5425 can set @var{instruction-set} to either @code{intel} or @code{att}.
5426 The default is @code{att}, the AT&T flavor used by default by Unix
5427 assemblers for x86-based targets.
5429 @kindex show disassembly-flavor
5430 @item show disassembly-flavor
5431 Show the current setting of the disassembly flavor.
5436 @chapter Examining Data
5438 @cindex printing data
5439 @cindex examining data
5442 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5443 @c document because it is nonstandard... Under Epoch it displays in a
5444 @c different window or something like that.
5445 The usual way to examine data in your program is with the @code{print}
5446 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5447 evaluates and prints the value of an expression of the language your
5448 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5449 Different Languages}).
5452 @item print @var{expr}
5453 @itemx print /@var{f} @var{expr}
5454 @var{expr} is an expression (in the source language). By default the
5455 value of @var{expr} is printed in a format appropriate to its data type;
5456 you can choose a different format by specifying @samp{/@var{f}}, where
5457 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5461 @itemx print /@var{f}
5462 @cindex reprint the last value
5463 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5464 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5465 conveniently inspect the same value in an alternative format.
5468 A more low-level way of examining data is with the @code{x} command.
5469 It examines data in memory at a specified address and prints it in a
5470 specified format. @xref{Memory, ,Examining Memory}.
5472 If you are interested in information about types, or about how the
5473 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5474 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5478 * Expressions:: Expressions
5479 * Variables:: Program variables
5480 * Arrays:: Artificial arrays
5481 * Output Formats:: Output formats
5482 * Memory:: Examining memory
5483 * Auto Display:: Automatic display
5484 * Print Settings:: Print settings
5485 * Value History:: Value history
5486 * Convenience Vars:: Convenience variables
5487 * Registers:: Registers
5488 * Floating Point Hardware:: Floating point hardware
5489 * Vector Unit:: Vector Unit
5490 * OS Information:: Auxiliary data provided by operating system
5491 * Memory Region Attributes:: Memory region attributes
5492 * Dump/Restore Files:: Copy between memory and a file
5493 * Core File Generation:: Cause a program dump its core
5494 * Character Sets:: Debugging programs that use a different
5495 character set than GDB does
5496 * Caching Remote Data:: Data caching for remote targets
5500 @section Expressions
5503 @code{print} and many other @value{GDBN} commands accept an expression and
5504 compute its value. Any kind of constant, variable or operator defined
5505 by the programming language you are using is valid in an expression in
5506 @value{GDBN}. This includes conditional expressions, function calls,
5507 casts, and string constants. It also includes preprocessor macros, if
5508 you compiled your program to include this information; see
5511 @cindex arrays in expressions
5512 @value{GDBN} supports array constants in expressions input by
5513 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5514 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5515 memory that is @code{malloc}ed in the target program.
5517 Because C is so widespread, most of the expressions shown in examples in
5518 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5519 Languages}, for information on how to use expressions in other
5522 In this section, we discuss operators that you can use in @value{GDBN}
5523 expressions regardless of your programming language.
5525 @cindex casts, in expressions
5526 Casts are supported in all languages, not just in C, because it is so
5527 useful to cast a number into a pointer in order to examine a structure
5528 at that address in memory.
5529 @c FIXME: casts supported---Mod2 true?
5531 @value{GDBN} supports these operators, in addition to those common
5532 to programming languages:
5536 @samp{@@} is a binary operator for treating parts of memory as arrays.
5537 @xref{Arrays, ,Artificial Arrays}, for more information.
5540 @samp{::} allows you to specify a variable in terms of the file or
5541 function where it is defined. @xref{Variables, ,Program Variables}.
5543 @cindex @{@var{type}@}
5544 @cindex type casting memory
5545 @cindex memory, viewing as typed object
5546 @cindex casts, to view memory
5547 @item @{@var{type}@} @var{addr}
5548 Refers to an object of type @var{type} stored at address @var{addr} in
5549 memory. @var{addr} may be any expression whose value is an integer or
5550 pointer (but parentheses are required around binary operators, just as in
5551 a cast). This construct is allowed regardless of what kind of data is
5552 normally supposed to reside at @var{addr}.
5556 @section Program Variables
5558 The most common kind of expression to use is the name of a variable
5561 Variables in expressions are understood in the selected stack frame
5562 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5566 global (or file-static)
5573 visible according to the scope rules of the
5574 programming language from the point of execution in that frame
5577 @noindent This means that in the function
5592 you can examine and use the variable @code{a} whenever your program is
5593 executing within the function @code{foo}, but you can only use or
5594 examine the variable @code{b} while your program is executing inside
5595 the block where @code{b} is declared.
5597 @cindex variable name conflict
5598 There is an exception: you can refer to a variable or function whose
5599 scope is a single source file even if the current execution point is not
5600 in this file. But it is possible to have more than one such variable or
5601 function with the same name (in different source files). If that
5602 happens, referring to that name has unpredictable effects. If you wish,
5603 you can specify a static variable in a particular function or file,
5604 using the colon-colon (@code{::}) notation:
5606 @cindex colon-colon, context for variables/functions
5608 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5609 @cindex @code{::}, context for variables/functions
5612 @var{file}::@var{variable}
5613 @var{function}::@var{variable}
5617 Here @var{file} or @var{function} is the name of the context for the
5618 static @var{variable}. In the case of file names, you can use quotes to
5619 make sure @value{GDBN} parses the file name as a single word---for example,
5620 to print a global value of @code{x} defined in @file{f2.c}:
5623 (@value{GDBP}) p 'f2.c'::x
5626 @cindex C@t{++} scope resolution
5627 This use of @samp{::} is very rarely in conflict with the very similar
5628 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5629 scope resolution operator in @value{GDBN} expressions.
5630 @c FIXME: Um, so what happens in one of those rare cases where it's in
5633 @cindex wrong values
5634 @cindex variable values, wrong
5635 @cindex function entry/exit, wrong values of variables
5636 @cindex optimized code, wrong values of variables
5638 @emph{Warning:} Occasionally, a local variable may appear to have the
5639 wrong value at certain points in a function---just after entry to a new
5640 scope, and just before exit.
5642 You may see this problem when you are stepping by machine instructions.
5643 This is because, on most machines, it takes more than one instruction to
5644 set up a stack frame (including local variable definitions); if you are
5645 stepping by machine instructions, variables may appear to have the wrong
5646 values until the stack frame is completely built. On exit, it usually
5647 also takes more than one machine instruction to destroy a stack frame;
5648 after you begin stepping through that group of instructions, local
5649 variable definitions may be gone.
5651 This may also happen when the compiler does significant optimizations.
5652 To be sure of always seeing accurate values, turn off all optimization
5655 @cindex ``No symbol "foo" in current context''
5656 Another possible effect of compiler optimizations is to optimize
5657 unused variables out of existence, or assign variables to registers (as
5658 opposed to memory addresses). Depending on the support for such cases
5659 offered by the debug info format used by the compiler, @value{GDBN}
5660 might not be able to display values for such local variables. If that
5661 happens, @value{GDBN} will print a message like this:
5664 No symbol "foo" in current context.
5667 To solve such problems, either recompile without optimizations, or use a
5668 different debug info format, if the compiler supports several such
5669 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5670 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5671 produces debug info in a format that is superior to formats such as
5672 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5673 an effective form for debug info. @xref{Debugging Options,,Options
5674 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5675 Compiler Collection (GCC)}.
5676 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5677 that are best suited to C@t{++} programs.
5679 If you ask to print an object whose contents are unknown to
5680 @value{GDBN}, e.g., because its data type is not completely specified
5681 by the debug information, @value{GDBN} will say @samp{<incomplete
5682 type>}. @xref{Symbols, incomplete type}, for more about this.
5684 Strings are identified as arrays of @code{char} values without specified
5685 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5686 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5687 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5688 defines literal string type @code{"char"} as @code{char} without a sign.
5693 signed char var1[] = "A";
5696 You get during debugging
5701 $2 = @{65 'A', 0 '\0'@}
5705 @section Artificial Arrays
5707 @cindex artificial array
5709 @kindex @@@r{, referencing memory as an array}
5710 It is often useful to print out several successive objects of the
5711 same type in memory; a section of an array, or an array of
5712 dynamically determined size for which only a pointer exists in the
5715 You can do this by referring to a contiguous span of memory as an
5716 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5717 operand of @samp{@@} should be the first element of the desired array
5718 and be an individual object. The right operand should be the desired length
5719 of the array. The result is an array value whose elements are all of
5720 the type of the left argument. The first element is actually the left
5721 argument; the second element comes from bytes of memory immediately
5722 following those that hold the first element, and so on. Here is an
5723 example. If a program says
5726 int *array = (int *) malloc (len * sizeof (int));
5730 you can print the contents of @code{array} with
5736 The left operand of @samp{@@} must reside in memory. Array values made
5737 with @samp{@@} in this way behave just like other arrays in terms of
5738 subscripting, and are coerced to pointers when used in expressions.
5739 Artificial arrays most often appear in expressions via the value history
5740 (@pxref{Value History, ,Value History}), after printing one out.
5742 Another way to create an artificial array is to use a cast.
5743 This re-interprets a value as if it were an array.
5744 The value need not be in memory:
5746 (@value{GDBP}) p/x (short[2])0x12345678
5747 $1 = @{0x1234, 0x5678@}
5750 As a convenience, if you leave the array length out (as in
5751 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5752 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5754 (@value{GDBP}) p/x (short[])0x12345678
5755 $2 = @{0x1234, 0x5678@}
5758 Sometimes the artificial array mechanism is not quite enough; in
5759 moderately complex data structures, the elements of interest may not
5760 actually be adjacent---for example, if you are interested in the values
5761 of pointers in an array. One useful work-around in this situation is
5762 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5763 Variables}) as a counter in an expression that prints the first
5764 interesting value, and then repeat that expression via @key{RET}. For
5765 instance, suppose you have an array @code{dtab} of pointers to
5766 structures, and you are interested in the values of a field @code{fv}
5767 in each structure. Here is an example of what you might type:
5777 @node Output Formats
5778 @section Output Formats
5780 @cindex formatted output
5781 @cindex output formats
5782 By default, @value{GDBN} prints a value according to its data type. Sometimes
5783 this is not what you want. For example, you might want to print a number
5784 in hex, or a pointer in decimal. Or you might want to view data in memory
5785 at a certain address as a character string or as an instruction. To do
5786 these things, specify an @dfn{output format} when you print a value.
5788 The simplest use of output formats is to say how to print a value
5789 already computed. This is done by starting the arguments of the
5790 @code{print} command with a slash and a format letter. The format
5791 letters supported are:
5795 Regard the bits of the value as an integer, and print the integer in
5799 Print as integer in signed decimal.
5802 Print as integer in unsigned decimal.
5805 Print as integer in octal.
5808 Print as integer in binary. The letter @samp{t} stands for ``two''.
5809 @footnote{@samp{b} cannot be used because these format letters are also
5810 used with the @code{x} command, where @samp{b} stands for ``byte'';
5811 see @ref{Memory,,Examining Memory}.}
5814 @cindex unknown address, locating
5815 @cindex locate address
5816 Print as an address, both absolute in hexadecimal and as an offset from
5817 the nearest preceding symbol. You can use this format used to discover
5818 where (in what function) an unknown address is located:
5821 (@value{GDBP}) p/a 0x54320
5822 $3 = 0x54320 <_initialize_vx+396>
5826 The command @code{info symbol 0x54320} yields similar results.
5827 @xref{Symbols, info symbol}.
5830 Regard as an integer and print it as a character constant. This
5831 prints both the numerical value and its character representation. The
5832 character representation is replaced with the octal escape @samp{\nnn}
5833 for characters outside the 7-bit @sc{ascii} range.
5835 Without this format, @value{GDBN} displays @code{char},
5836 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
5837 constants. Single-byte members of vectors are displayed as integer
5841 Regard the bits of the value as a floating point number and print
5842 using typical floating point syntax.
5845 @cindex printing strings
5846 @cindex printing byte arrays
5847 Regard as a string, if possible. With this format, pointers to single-byte
5848 data are displayed as null-terminated strings and arrays of single-byte data
5849 are displayed as fixed-length strings. Other values are displayed in their
5852 Without this format, @value{GDBN} displays pointers to and arrays of
5853 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
5854 strings. Single-byte members of a vector are displayed as an integer
5858 For example, to print the program counter in hex (@pxref{Registers}), type
5865 Note that no space is required before the slash; this is because command
5866 names in @value{GDBN} cannot contain a slash.
5868 To reprint the last value in the value history with a different format,
5869 you can use the @code{print} command with just a format and no
5870 expression. For example, @samp{p/x} reprints the last value in hex.
5873 @section Examining Memory
5875 You can use the command @code{x} (for ``examine'') to examine memory in
5876 any of several formats, independently of your program's data types.
5878 @cindex examining memory
5880 @kindex x @r{(examine memory)}
5881 @item x/@var{nfu} @var{addr}
5884 Use the @code{x} command to examine memory.
5887 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5888 much memory to display and how to format it; @var{addr} is an
5889 expression giving the address where you want to start displaying memory.
5890 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5891 Several commands set convenient defaults for @var{addr}.
5894 @item @var{n}, the repeat count
5895 The repeat count is a decimal integer; the default is 1. It specifies
5896 how much memory (counting by units @var{u}) to display.
5897 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5900 @item @var{f}, the display format
5901 The display format is one of the formats used by @code{print}
5902 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5903 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
5904 The default is @samp{x} (hexadecimal) initially. The default changes
5905 each time you use either @code{x} or @code{print}.
5907 @item @var{u}, the unit size
5908 The unit size is any of
5914 Halfwords (two bytes).
5916 Words (four bytes). This is the initial default.
5918 Giant words (eight bytes).
5921 Each time you specify a unit size with @code{x}, that size becomes the
5922 default unit the next time you use @code{x}. (For the @samp{s} and
5923 @samp{i} formats, the unit size is ignored and is normally not written.)
5925 @item @var{addr}, starting display address
5926 @var{addr} is the address where you want @value{GDBN} to begin displaying
5927 memory. The expression need not have a pointer value (though it may);
5928 it is always interpreted as an integer address of a byte of memory.
5929 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5930 @var{addr} is usually just after the last address examined---but several
5931 other commands also set the default address: @code{info breakpoints} (to
5932 the address of the last breakpoint listed), @code{info line} (to the
5933 starting address of a line), and @code{print} (if you use it to display
5934 a value from memory).
5937 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5938 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5939 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5940 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5941 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5943 Since the letters indicating unit sizes are all distinct from the
5944 letters specifying output formats, you do not have to remember whether
5945 unit size or format comes first; either order works. The output
5946 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5947 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5949 Even though the unit size @var{u} is ignored for the formats @samp{s}
5950 and @samp{i}, you might still want to use a count @var{n}; for example,
5951 @samp{3i} specifies that you want to see three machine instructions,
5952 including any operands. For convenience, especially when used with
5953 the @code{display} command, the @samp{i} format also prints branch delay
5954 slot instructions, if any, beyond the count specified, which immediately
5955 follow the last instruction that is within the count. The command
5956 @code{disassemble} gives an alternative way of inspecting machine
5957 instructions; see @ref{Machine Code,,Source and Machine Code}.
5959 All the defaults for the arguments to @code{x} are designed to make it
5960 easy to continue scanning memory with minimal specifications each time
5961 you use @code{x}. For example, after you have inspected three machine
5962 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5963 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5964 the repeat count @var{n} is used again; the other arguments default as
5965 for successive uses of @code{x}.
5967 @cindex @code{$_}, @code{$__}, and value history
5968 The addresses and contents printed by the @code{x} command are not saved
5969 in the value history because there is often too much of them and they
5970 would get in the way. Instead, @value{GDBN} makes these values available for
5971 subsequent use in expressions as values of the convenience variables
5972 @code{$_} and @code{$__}. After an @code{x} command, the last address
5973 examined is available for use in expressions in the convenience variable
5974 @code{$_}. The contents of that address, as examined, are available in
5975 the convenience variable @code{$__}.
5977 If the @code{x} command has a repeat count, the address and contents saved
5978 are from the last memory unit printed; this is not the same as the last
5979 address printed if several units were printed on the last line of output.
5981 @cindex remote memory comparison
5982 @cindex verify remote memory image
5983 When you are debugging a program running on a remote target machine
5984 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
5985 remote machine's memory against the executable file you downloaded to
5986 the target. The @code{compare-sections} command is provided for such
5990 @kindex compare-sections
5991 @item compare-sections @r{[}@var{section-name}@r{]}
5992 Compare the data of a loadable section @var{section-name} in the
5993 executable file of the program being debugged with the same section in
5994 the remote machine's memory, and report any mismatches. With no
5995 arguments, compares all loadable sections. This command's
5996 availability depends on the target's support for the @code{"qCRC"}
6001 @section Automatic Display
6002 @cindex automatic display
6003 @cindex display of expressions
6005 If you find that you want to print the value of an expression frequently
6006 (to see how it changes), you might want to add it to the @dfn{automatic
6007 display list} so that @value{GDBN} prints its value each time your program stops.
6008 Each expression added to the list is given a number to identify it;
6009 to remove an expression from the list, you specify that number.
6010 The automatic display looks like this:
6014 3: bar[5] = (struct hack *) 0x3804
6018 This display shows item numbers, expressions and their current values. As with
6019 displays you request manually using @code{x} or @code{print}, you can
6020 specify the output format you prefer; in fact, @code{display} decides
6021 whether to use @code{print} or @code{x} depending your format
6022 specification---it uses @code{x} if you specify either the @samp{i}
6023 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6027 @item display @var{expr}
6028 Add the expression @var{expr} to the list of expressions to display
6029 each time your program stops. @xref{Expressions, ,Expressions}.
6031 @code{display} does not repeat if you press @key{RET} again after using it.
6033 @item display/@var{fmt} @var{expr}
6034 For @var{fmt} specifying only a display format and not a size or
6035 count, add the expression @var{expr} to the auto-display list but
6036 arrange to display it each time in the specified format @var{fmt}.
6037 @xref{Output Formats,,Output Formats}.
6039 @item display/@var{fmt} @var{addr}
6040 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6041 number of units, add the expression @var{addr} as a memory address to
6042 be examined each time your program stops. Examining means in effect
6043 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6046 For example, @samp{display/i $pc} can be helpful, to see the machine
6047 instruction about to be executed each time execution stops (@samp{$pc}
6048 is a common name for the program counter; @pxref{Registers, ,Registers}).
6051 @kindex delete display
6053 @item undisplay @var{dnums}@dots{}
6054 @itemx delete display @var{dnums}@dots{}
6055 Remove item numbers @var{dnums} from the list of expressions to display.
6057 @code{undisplay} does not repeat if you press @key{RET} after using it.
6058 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6060 @kindex disable display
6061 @item disable display @var{dnums}@dots{}
6062 Disable the display of item numbers @var{dnums}. A disabled display
6063 item is not printed automatically, but is not forgotten. It may be
6064 enabled again later.
6066 @kindex enable display
6067 @item enable display @var{dnums}@dots{}
6068 Enable display of item numbers @var{dnums}. It becomes effective once
6069 again in auto display of its expression, until you specify otherwise.
6072 Display the current values of the expressions on the list, just as is
6073 done when your program stops.
6075 @kindex info display
6077 Print the list of expressions previously set up to display
6078 automatically, each one with its item number, but without showing the
6079 values. This includes disabled expressions, which are marked as such.
6080 It also includes expressions which would not be displayed right now
6081 because they refer to automatic variables not currently available.
6084 @cindex display disabled out of scope
6085 If a display expression refers to local variables, then it does not make
6086 sense outside the lexical context for which it was set up. Such an
6087 expression is disabled when execution enters a context where one of its
6088 variables is not defined. For example, if you give the command
6089 @code{display last_char} while inside a function with an argument
6090 @code{last_char}, @value{GDBN} displays this argument while your program
6091 continues to stop inside that function. When it stops elsewhere---where
6092 there is no variable @code{last_char}---the display is disabled
6093 automatically. The next time your program stops where @code{last_char}
6094 is meaningful, you can enable the display expression once again.
6096 @node Print Settings
6097 @section Print Settings
6099 @cindex format options
6100 @cindex print settings
6101 @value{GDBN} provides the following ways to control how arrays, structures,
6102 and symbols are printed.
6105 These settings are useful for debugging programs in any language:
6109 @item set print address
6110 @itemx set print address on
6111 @cindex print/don't print memory addresses
6112 @value{GDBN} prints memory addresses showing the location of stack
6113 traces, structure values, pointer values, breakpoints, and so forth,
6114 even when it also displays the contents of those addresses. The default
6115 is @code{on}. For example, this is what a stack frame display looks like with
6116 @code{set print address on}:
6121 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6123 530 if (lquote != def_lquote)
6127 @item set print address off
6128 Do not print addresses when displaying their contents. For example,
6129 this is the same stack frame displayed with @code{set print address off}:
6133 (@value{GDBP}) set print addr off
6135 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6136 530 if (lquote != def_lquote)
6140 You can use @samp{set print address off} to eliminate all machine
6141 dependent displays from the @value{GDBN} interface. For example, with
6142 @code{print address off}, you should get the same text for backtraces on
6143 all machines---whether or not they involve pointer arguments.
6146 @item show print address
6147 Show whether or not addresses are to be printed.
6150 When @value{GDBN} prints a symbolic address, it normally prints the
6151 closest earlier symbol plus an offset. If that symbol does not uniquely
6152 identify the address (for example, it is a name whose scope is a single
6153 source file), you may need to clarify. One way to do this is with
6154 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6155 you can set @value{GDBN} to print the source file and line number when
6156 it prints a symbolic address:
6159 @item set print symbol-filename on
6160 @cindex source file and line of a symbol
6161 @cindex symbol, source file and line
6162 Tell @value{GDBN} to print the source file name and line number of a
6163 symbol in the symbolic form of an address.
6165 @item set print symbol-filename off
6166 Do not print source file name and line number of a symbol. This is the
6169 @item show print symbol-filename
6170 Show whether or not @value{GDBN} will print the source file name and
6171 line number of a symbol in the symbolic form of an address.
6174 Another situation where it is helpful to show symbol filenames and line
6175 numbers is when disassembling code; @value{GDBN} shows you the line
6176 number and source file that corresponds to each instruction.
6178 Also, you may wish to see the symbolic form only if the address being
6179 printed is reasonably close to the closest earlier symbol:
6182 @item set print max-symbolic-offset @var{max-offset}
6183 @cindex maximum value for offset of closest symbol
6184 Tell @value{GDBN} to only display the symbolic form of an address if the
6185 offset between the closest earlier symbol and the address is less than
6186 @var{max-offset}. The default is 0, which tells @value{GDBN}
6187 to always print the symbolic form of an address if any symbol precedes it.
6189 @item show print max-symbolic-offset
6190 Ask how large the maximum offset is that @value{GDBN} prints in a
6194 @cindex wild pointer, interpreting
6195 @cindex pointer, finding referent
6196 If you have a pointer and you are not sure where it points, try
6197 @samp{set print symbol-filename on}. Then you can determine the name
6198 and source file location of the variable where it points, using
6199 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6200 For example, here @value{GDBN} shows that a variable @code{ptt} points
6201 at another variable @code{t}, defined in @file{hi2.c}:
6204 (@value{GDBP}) set print symbol-filename on
6205 (@value{GDBP}) p/a ptt
6206 $4 = 0xe008 <t in hi2.c>
6210 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6211 does not show the symbol name and filename of the referent, even with
6212 the appropriate @code{set print} options turned on.
6215 Other settings control how different kinds of objects are printed:
6218 @item set print array
6219 @itemx set print array on
6220 @cindex pretty print arrays
6221 Pretty print arrays. This format is more convenient to read,
6222 but uses more space. The default is off.
6224 @item set print array off
6225 Return to compressed format for arrays.
6227 @item show print array
6228 Show whether compressed or pretty format is selected for displaying
6231 @cindex print array indexes
6232 @item set print array-indexes
6233 @itemx set print array-indexes on
6234 Print the index of each element when displaying arrays. May be more
6235 convenient to locate a given element in the array or quickly find the
6236 index of a given element in that printed array. The default is off.
6238 @item set print array-indexes off
6239 Stop printing element indexes when displaying arrays.
6241 @item show print array-indexes
6242 Show whether the index of each element is printed when displaying
6245 @item set print elements @var{number-of-elements}
6246 @cindex number of array elements to print
6247 @cindex limit on number of printed array elements
6248 Set a limit on how many elements of an array @value{GDBN} will print.
6249 If @value{GDBN} is printing a large array, it stops printing after it has
6250 printed the number of elements set by the @code{set print elements} command.
6251 This limit also applies to the display of strings.
6252 When @value{GDBN} starts, this limit is set to 200.
6253 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6255 @item show print elements
6256 Display the number of elements of a large array that @value{GDBN} will print.
6257 If the number is 0, then the printing is unlimited.
6259 @item set print frame-arguments @var{value}
6260 @cindex printing frame argument values
6261 @cindex print all frame argument values
6262 @cindex print frame argument values for scalars only
6263 @cindex do not print frame argument values
6264 This command allows to control how the values of arguments are printed
6265 when the debugger prints a frame (@pxref{Frames}). The possible
6270 The values of all arguments are printed. This is the default.
6273 Print the value of an argument only if it is a scalar. The value of more
6274 complex arguments such as arrays, structures, unions, etc, is replaced
6275 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6278 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6283 None of the argument values are printed. Instead, the value of each argument
6284 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6287 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6292 By default, all argument values are always printed. But this command
6293 can be useful in several cases. For instance, it can be used to reduce
6294 the amount of information printed in each frame, making the backtrace
6295 more readable. Also, this command can be used to improve performance
6296 when displaying Ada frames, because the computation of large arguments
6297 can sometimes be CPU-intensive, especiallly in large applications.
6298 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6299 avoids this computation, thus speeding up the display of each Ada frame.
6301 @item show print frame-arguments
6302 Show how the value of arguments should be displayed when printing a frame.
6304 @item set print repeats
6305 @cindex repeated array elements
6306 Set the threshold for suppressing display of repeated array
6307 elements. When the number of consecutive identical elements of an
6308 array exceeds the threshold, @value{GDBN} prints the string
6309 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6310 identical repetitions, instead of displaying the identical elements
6311 themselves. Setting the threshold to zero will cause all elements to
6312 be individually printed. The default threshold is 10.
6314 @item show print repeats
6315 Display the current threshold for printing repeated identical
6318 @item set print null-stop
6319 @cindex @sc{null} elements in arrays
6320 Cause @value{GDBN} to stop printing the characters of an array when the first
6321 @sc{null} is encountered. This is useful when large arrays actually
6322 contain only short strings.
6325 @item show print null-stop
6326 Show whether @value{GDBN} stops printing an array on the first
6327 @sc{null} character.
6329 @item set print pretty on
6330 @cindex print structures in indented form
6331 @cindex indentation in structure display
6332 Cause @value{GDBN} to print structures in an indented format with one member
6333 per line, like this:
6348 @item set print pretty off
6349 Cause @value{GDBN} to print structures in a compact format, like this:
6353 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6354 meat = 0x54 "Pork"@}
6359 This is the default format.
6361 @item show print pretty
6362 Show which format @value{GDBN} is using to print structures.
6364 @item set print sevenbit-strings on
6365 @cindex eight-bit characters in strings
6366 @cindex octal escapes in strings
6367 Print using only seven-bit characters; if this option is set,
6368 @value{GDBN} displays any eight-bit characters (in strings or
6369 character values) using the notation @code{\}@var{nnn}. This setting is
6370 best if you are working in English (@sc{ascii}) and you use the
6371 high-order bit of characters as a marker or ``meta'' bit.
6373 @item set print sevenbit-strings off
6374 Print full eight-bit characters. This allows the use of more
6375 international character sets, and is the default.
6377 @item show print sevenbit-strings
6378 Show whether or not @value{GDBN} is printing only seven-bit characters.
6380 @item set print union on
6381 @cindex unions in structures, printing
6382 Tell @value{GDBN} to print unions which are contained in structures
6383 and other unions. This is the default setting.
6385 @item set print union off
6386 Tell @value{GDBN} not to print unions which are contained in
6387 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6390 @item show print union
6391 Ask @value{GDBN} whether or not it will print unions which are contained in
6392 structures and other unions.
6394 For example, given the declarations
6397 typedef enum @{Tree, Bug@} Species;
6398 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6399 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6410 struct thing foo = @{Tree, @{Acorn@}@};
6414 with @code{set print union on} in effect @samp{p foo} would print
6417 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6421 and with @code{set print union off} in effect it would print
6424 $1 = @{it = Tree, form = @{...@}@}
6428 @code{set print union} affects programs written in C-like languages
6434 These settings are of interest when debugging C@t{++} programs:
6437 @cindex demangling C@t{++} names
6438 @item set print demangle
6439 @itemx set print demangle on
6440 Print C@t{++} names in their source form rather than in the encoded
6441 (``mangled'') form passed to the assembler and linker for type-safe
6442 linkage. The default is on.
6444 @item show print demangle
6445 Show whether C@t{++} names are printed in mangled or demangled form.
6447 @item set print asm-demangle
6448 @itemx set print asm-demangle on
6449 Print C@t{++} names in their source form rather than their mangled form, even
6450 in assembler code printouts such as instruction disassemblies.
6453 @item show print asm-demangle
6454 Show whether C@t{++} names in assembly listings are printed in mangled
6457 @cindex C@t{++} symbol decoding style
6458 @cindex symbol decoding style, C@t{++}
6459 @kindex set demangle-style
6460 @item set demangle-style @var{style}
6461 Choose among several encoding schemes used by different compilers to
6462 represent C@t{++} names. The choices for @var{style} are currently:
6466 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6469 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6470 This is the default.
6473 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6476 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6479 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6480 @strong{Warning:} this setting alone is not sufficient to allow
6481 debugging @code{cfront}-generated executables. @value{GDBN} would
6482 require further enhancement to permit that.
6485 If you omit @var{style}, you will see a list of possible formats.
6487 @item show demangle-style
6488 Display the encoding style currently in use for decoding C@t{++} symbols.
6490 @item set print object
6491 @itemx set print object on
6492 @cindex derived type of an object, printing
6493 @cindex display derived types
6494 When displaying a pointer to an object, identify the @emph{actual}
6495 (derived) type of the object rather than the @emph{declared} type, using
6496 the virtual function table.
6498 @item set print object off
6499 Display only the declared type of objects, without reference to the
6500 virtual function table. This is the default setting.
6502 @item show print object
6503 Show whether actual, or declared, object types are displayed.
6505 @item set print static-members
6506 @itemx set print static-members on
6507 @cindex static members of C@t{++} objects
6508 Print static members when displaying a C@t{++} object. The default is on.
6510 @item set print static-members off
6511 Do not print static members when displaying a C@t{++} object.
6513 @item show print static-members
6514 Show whether C@t{++} static members are printed or not.
6516 @item set print pascal_static-members
6517 @itemx set print pascal_static-members on
6518 @cindex static members of Pascal objects
6519 @cindex Pascal objects, static members display
6520 Print static members when displaying a Pascal object. The default is on.
6522 @item set print pascal_static-members off
6523 Do not print static members when displaying a Pascal object.
6525 @item show print pascal_static-members
6526 Show whether Pascal static members are printed or not.
6528 @c These don't work with HP ANSI C++ yet.
6529 @item set print vtbl
6530 @itemx set print vtbl on
6531 @cindex pretty print C@t{++} virtual function tables
6532 @cindex virtual functions (C@t{++}) display
6533 @cindex VTBL display
6534 Pretty print C@t{++} virtual function tables. The default is off.
6535 (The @code{vtbl} commands do not work on programs compiled with the HP
6536 ANSI C@t{++} compiler (@code{aCC}).)
6538 @item set print vtbl off
6539 Do not pretty print C@t{++} virtual function tables.
6541 @item show print vtbl
6542 Show whether C@t{++} virtual function tables are pretty printed, or not.
6546 @section Value History
6548 @cindex value history
6549 @cindex history of values printed by @value{GDBN}
6550 Values printed by the @code{print} command are saved in the @value{GDBN}
6551 @dfn{value history}. This allows you to refer to them in other expressions.
6552 Values are kept until the symbol table is re-read or discarded
6553 (for example with the @code{file} or @code{symbol-file} commands).
6554 When the symbol table changes, the value history is discarded,
6555 since the values may contain pointers back to the types defined in the
6560 @cindex history number
6561 The values printed are given @dfn{history numbers} by which you can
6562 refer to them. These are successive integers starting with one.
6563 @code{print} shows you the history number assigned to a value by
6564 printing @samp{$@var{num} = } before the value; here @var{num} is the
6567 To refer to any previous value, use @samp{$} followed by the value's
6568 history number. The way @code{print} labels its output is designed to
6569 remind you of this. Just @code{$} refers to the most recent value in
6570 the history, and @code{$$} refers to the value before that.
6571 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6572 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6573 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6575 For example, suppose you have just printed a pointer to a structure and
6576 want to see the contents of the structure. It suffices to type
6582 If you have a chain of structures where the component @code{next} points
6583 to the next one, you can print the contents of the next one with this:
6590 You can print successive links in the chain by repeating this
6591 command---which you can do by just typing @key{RET}.
6593 Note that the history records values, not expressions. If the value of
6594 @code{x} is 4 and you type these commands:
6602 then the value recorded in the value history by the @code{print} command
6603 remains 4 even though the value of @code{x} has changed.
6608 Print the last ten values in the value history, with their item numbers.
6609 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6610 values} does not change the history.
6612 @item show values @var{n}
6613 Print ten history values centered on history item number @var{n}.
6616 Print ten history values just after the values last printed. If no more
6617 values are available, @code{show values +} produces no display.
6620 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6621 same effect as @samp{show values +}.
6623 @node Convenience Vars
6624 @section Convenience Variables
6626 @cindex convenience variables
6627 @cindex user-defined variables
6628 @value{GDBN} provides @dfn{convenience variables} that you can use within
6629 @value{GDBN} to hold on to a value and refer to it later. These variables
6630 exist entirely within @value{GDBN}; they are not part of your program, and
6631 setting a convenience variable has no direct effect on further execution
6632 of your program. That is why you can use them freely.
6634 Convenience variables are prefixed with @samp{$}. Any name preceded by
6635 @samp{$} can be used for a convenience variable, unless it is one of
6636 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6637 (Value history references, in contrast, are @emph{numbers} preceded
6638 by @samp{$}. @xref{Value History, ,Value History}.)
6640 You can save a value in a convenience variable with an assignment
6641 expression, just as you would set a variable in your program.
6645 set $foo = *object_ptr
6649 would save in @code{$foo} the value contained in the object pointed to by
6652 Using a convenience variable for the first time creates it, but its
6653 value is @code{void} until you assign a new value. You can alter the
6654 value with another assignment at any time.
6656 Convenience variables have no fixed types. You can assign a convenience
6657 variable any type of value, including structures and arrays, even if
6658 that variable already has a value of a different type. The convenience
6659 variable, when used as an expression, has the type of its current value.
6662 @kindex show convenience
6663 @cindex show all user variables
6664 @item show convenience
6665 Print a list of convenience variables used so far, and their values.
6666 Abbreviated @code{show conv}.
6668 @kindex init-if-undefined
6669 @cindex convenience variables, initializing
6670 @item init-if-undefined $@var{variable} = @var{expression}
6671 Set a convenience variable if it has not already been set. This is useful
6672 for user-defined commands that keep some state. It is similar, in concept,
6673 to using local static variables with initializers in C (except that
6674 convenience variables are global). It can also be used to allow users to
6675 override default values used in a command script.
6677 If the variable is already defined then the expression is not evaluated so
6678 any side-effects do not occur.
6681 One of the ways to use a convenience variable is as a counter to be
6682 incremented or a pointer to be advanced. For example, to print
6683 a field from successive elements of an array of structures:
6687 print bar[$i++]->contents
6691 Repeat that command by typing @key{RET}.
6693 Some convenience variables are created automatically by @value{GDBN} and given
6694 values likely to be useful.
6697 @vindex $_@r{, convenience variable}
6699 The variable @code{$_} is automatically set by the @code{x} command to
6700 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6701 commands which provide a default address for @code{x} to examine also
6702 set @code{$_} to that address; these commands include @code{info line}
6703 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6704 except when set by the @code{x} command, in which case it is a pointer
6705 to the type of @code{$__}.
6707 @vindex $__@r{, convenience variable}
6709 The variable @code{$__} is automatically set by the @code{x} command
6710 to the value found in the last address examined. Its type is chosen
6711 to match the format in which the data was printed.
6714 @vindex $_exitcode@r{, convenience variable}
6715 The variable @code{$_exitcode} is automatically set to the exit code when
6716 the program being debugged terminates.
6719 On HP-UX systems, if you refer to a function or variable name that
6720 begins with a dollar sign, @value{GDBN} searches for a user or system
6721 name first, before it searches for a convenience variable.
6727 You can refer to machine register contents, in expressions, as variables
6728 with names starting with @samp{$}. The names of registers are different
6729 for each machine; use @code{info registers} to see the names used on
6733 @kindex info registers
6734 @item info registers
6735 Print the names and values of all registers except floating-point
6736 and vector registers (in the selected stack frame).
6738 @kindex info all-registers
6739 @cindex floating point registers
6740 @item info all-registers
6741 Print the names and values of all registers, including floating-point
6742 and vector registers (in the selected stack frame).
6744 @item info registers @var{regname} @dots{}
6745 Print the @dfn{relativized} value of each specified register @var{regname}.
6746 As discussed in detail below, register values are normally relative to
6747 the selected stack frame. @var{regname} may be any register name valid on
6748 the machine you are using, with or without the initial @samp{$}.
6751 @cindex stack pointer register
6752 @cindex program counter register
6753 @cindex process status register
6754 @cindex frame pointer register
6755 @cindex standard registers
6756 @value{GDBN} has four ``standard'' register names that are available (in
6757 expressions) on most machines---whenever they do not conflict with an
6758 architecture's canonical mnemonics for registers. The register names
6759 @code{$pc} and @code{$sp} are used for the program counter register and
6760 the stack pointer. @code{$fp} is used for a register that contains a
6761 pointer to the current stack frame, and @code{$ps} is used for a
6762 register that contains the processor status. For example,
6763 you could print the program counter in hex with
6770 or print the instruction to be executed next with
6777 or add four to the stack pointer@footnote{This is a way of removing
6778 one word from the stack, on machines where stacks grow downward in
6779 memory (most machines, nowadays). This assumes that the innermost
6780 stack frame is selected; setting @code{$sp} is not allowed when other
6781 stack frames are selected. To pop entire frames off the stack,
6782 regardless of machine architecture, use @code{return};
6783 see @ref{Returning, ,Returning from a Function}.} with
6789 Whenever possible, these four standard register names are available on
6790 your machine even though the machine has different canonical mnemonics,
6791 so long as there is no conflict. The @code{info registers} command
6792 shows the canonical names. For example, on the SPARC, @code{info
6793 registers} displays the processor status register as @code{$psr} but you
6794 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6795 is an alias for the @sc{eflags} register.
6797 @value{GDBN} always considers the contents of an ordinary register as an
6798 integer when the register is examined in this way. Some machines have
6799 special registers which can hold nothing but floating point; these
6800 registers are considered to have floating point values. There is no way
6801 to refer to the contents of an ordinary register as floating point value
6802 (although you can @emph{print} it as a floating point value with
6803 @samp{print/f $@var{regname}}).
6805 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6806 means that the data format in which the register contents are saved by
6807 the operating system is not the same one that your program normally
6808 sees. For example, the registers of the 68881 floating point
6809 coprocessor are always saved in ``extended'' (raw) format, but all C
6810 programs expect to work with ``double'' (virtual) format. In such
6811 cases, @value{GDBN} normally works with the virtual format only (the format
6812 that makes sense for your program), but the @code{info registers} command
6813 prints the data in both formats.
6815 @cindex SSE registers (x86)
6816 @cindex MMX registers (x86)
6817 Some machines have special registers whose contents can be interpreted
6818 in several different ways. For example, modern x86-based machines
6819 have SSE and MMX registers that can hold several values packed
6820 together in several different formats. @value{GDBN} refers to such
6821 registers in @code{struct} notation:
6824 (@value{GDBP}) print $xmm1
6826 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6827 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6828 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6829 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6830 v4_int32 = @{0, 20657912, 11, 13@},
6831 v2_int64 = @{88725056443645952, 55834574859@},
6832 uint128 = 0x0000000d0000000b013b36f800000000
6837 To set values of such registers, you need to tell @value{GDBN} which
6838 view of the register you wish to change, as if you were assigning
6839 value to a @code{struct} member:
6842 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6845 Normally, register values are relative to the selected stack frame
6846 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
6847 value that the register would contain if all stack frames farther in
6848 were exited and their saved registers restored. In order to see the
6849 true contents of hardware registers, you must select the innermost
6850 frame (with @samp{frame 0}).
6852 However, @value{GDBN} must deduce where registers are saved, from the machine
6853 code generated by your compiler. If some registers are not saved, or if
6854 @value{GDBN} is unable to locate the saved registers, the selected stack
6855 frame makes no difference.
6857 @node Floating Point Hardware
6858 @section Floating Point Hardware
6859 @cindex floating point
6861 Depending on the configuration, @value{GDBN} may be able to give
6862 you more information about the status of the floating point hardware.
6867 Display hardware-dependent information about the floating
6868 point unit. The exact contents and layout vary depending on the
6869 floating point chip. Currently, @samp{info float} is supported on
6870 the ARM and x86 machines.
6874 @section Vector Unit
6877 Depending on the configuration, @value{GDBN} may be able to give you
6878 more information about the status of the vector unit.
6883 Display information about the vector unit. The exact contents and
6884 layout vary depending on the hardware.
6887 @node OS Information
6888 @section Operating System Auxiliary Information
6889 @cindex OS information
6891 @value{GDBN} provides interfaces to useful OS facilities that can help
6892 you debug your program.
6894 @cindex @code{ptrace} system call
6895 @cindex @code{struct user} contents
6896 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6897 machines), it interfaces with the inferior via the @code{ptrace}
6898 system call. The operating system creates a special sata structure,
6899 called @code{struct user}, for this interface. You can use the
6900 command @code{info udot} to display the contents of this data
6906 Display the contents of the @code{struct user} maintained by the OS
6907 kernel for the program being debugged. @value{GDBN} displays the
6908 contents of @code{struct user} as a list of hex numbers, similar to
6909 the @code{examine} command.
6912 @cindex auxiliary vector
6913 @cindex vector, auxiliary
6914 Some operating systems supply an @dfn{auxiliary vector} to programs at
6915 startup. This is akin to the arguments and environment that you
6916 specify for a program, but contains a system-dependent variety of
6917 binary values that tell system libraries important details about the
6918 hardware, operating system, and process. Each value's purpose is
6919 identified by an integer tag; the meanings are well-known but system-specific.
6920 Depending on the configuration and operating system facilities,
6921 @value{GDBN} may be able to show you this information. For remote
6922 targets, this functionality may further depend on the remote stub's
6923 support of the @samp{qXfer:auxv:read} packet, see
6924 @ref{qXfer auxiliary vector read}.
6929 Display the auxiliary vector of the inferior, which can be either a
6930 live process or a core dump file. @value{GDBN} prints each tag value
6931 numerically, and also shows names and text descriptions for recognized
6932 tags. Some values in the vector are numbers, some bit masks, and some
6933 pointers to strings or other data. @value{GDBN} displays each value in the
6934 most appropriate form for a recognized tag, and in hexadecimal for
6935 an unrecognized tag.
6939 @node Memory Region Attributes
6940 @section Memory Region Attributes
6941 @cindex memory region attributes
6943 @dfn{Memory region attributes} allow you to describe special handling
6944 required by regions of your target's memory. @value{GDBN} uses
6945 attributes to determine whether to allow certain types of memory
6946 accesses; whether to use specific width accesses; and whether to cache
6947 target memory. By default the description of memory regions is
6948 fetched from the target (if the current target supports this), but the
6949 user can override the fetched regions.
6951 Defined memory regions can be individually enabled and disabled. When a
6952 memory region is disabled, @value{GDBN} uses the default attributes when
6953 accessing memory in that region. Similarly, if no memory regions have
6954 been defined, @value{GDBN} uses the default attributes when accessing
6957 When a memory region is defined, it is given a number to identify it;
6958 to enable, disable, or remove a memory region, you specify that number.
6962 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6963 Define a memory region bounded by @var{lower} and @var{upper} with
6964 attributes @var{attributes}@dots{}, and add it to the list of regions
6965 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6966 case: it is treated as the target's maximum memory address.
6967 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6970 Discard any user changes to the memory regions and use target-supplied
6971 regions, if available, or no regions if the target does not support.
6974 @item delete mem @var{nums}@dots{}
6975 Remove memory regions @var{nums}@dots{} from the list of regions
6976 monitored by @value{GDBN}.
6979 @item disable mem @var{nums}@dots{}
6980 Disable monitoring of memory regions @var{nums}@dots{}.
6981 A disabled memory region is not forgotten.
6982 It may be enabled again later.
6985 @item enable mem @var{nums}@dots{}
6986 Enable monitoring of memory regions @var{nums}@dots{}.
6990 Print a table of all defined memory regions, with the following columns
6994 @item Memory Region Number
6995 @item Enabled or Disabled.
6996 Enabled memory regions are marked with @samp{y}.
6997 Disabled memory regions are marked with @samp{n}.
7000 The address defining the inclusive lower bound of the memory region.
7003 The address defining the exclusive upper bound of the memory region.
7006 The list of attributes set for this memory region.
7011 @subsection Attributes
7013 @subsubsection Memory Access Mode
7014 The access mode attributes set whether @value{GDBN} may make read or
7015 write accesses to a memory region.
7017 While these attributes prevent @value{GDBN} from performing invalid
7018 memory accesses, they do nothing to prevent the target system, I/O DMA,
7019 etc.@: from accessing memory.
7023 Memory is read only.
7025 Memory is write only.
7027 Memory is read/write. This is the default.
7030 @subsubsection Memory Access Size
7031 The access size attribute tells @value{GDBN} to use specific sized
7032 accesses in the memory region. Often memory mapped device registers
7033 require specific sized accesses. If no access size attribute is
7034 specified, @value{GDBN} may use accesses of any size.
7038 Use 8 bit memory accesses.
7040 Use 16 bit memory accesses.
7042 Use 32 bit memory accesses.
7044 Use 64 bit memory accesses.
7047 @c @subsubsection Hardware/Software Breakpoints
7048 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7049 @c will use hardware or software breakpoints for the internal breakpoints
7050 @c used by the step, next, finish, until, etc. commands.
7054 @c Always use hardware breakpoints
7055 @c @item swbreak (default)
7058 @subsubsection Data Cache
7059 The data cache attributes set whether @value{GDBN} will cache target
7060 memory. While this generally improves performance by reducing debug
7061 protocol overhead, it can lead to incorrect results because @value{GDBN}
7062 does not know about volatile variables or memory mapped device
7067 Enable @value{GDBN} to cache target memory.
7069 Disable @value{GDBN} from caching target memory. This is the default.
7072 @subsection Memory Access Checking
7073 @value{GDBN} can be instructed to refuse accesses to memory that is
7074 not explicitly described. This can be useful if accessing such
7075 regions has undesired effects for a specific target, or to provide
7076 better error checking. The following commands control this behaviour.
7079 @kindex set mem inaccessible-by-default
7080 @item set mem inaccessible-by-default [on|off]
7081 If @code{on} is specified, make @value{GDBN} treat memory not
7082 explicitly described by the memory ranges as non-existent and refuse accesses
7083 to such memory. The checks are only performed if there's at least one
7084 memory range defined. If @code{off} is specified, make @value{GDBN}
7085 treat the memory not explicitly described by the memory ranges as RAM.
7086 The default value is @code{on}.
7087 @kindex show mem inaccessible-by-default
7088 @item show mem inaccessible-by-default
7089 Show the current handling of accesses to unknown memory.
7093 @c @subsubsection Memory Write Verification
7094 @c The memory write verification attributes set whether @value{GDBN}
7095 @c will re-reads data after each write to verify the write was successful.
7099 @c @item noverify (default)
7102 @node Dump/Restore Files
7103 @section Copy Between Memory and a File
7104 @cindex dump/restore files
7105 @cindex append data to a file
7106 @cindex dump data to a file
7107 @cindex restore data from a file
7109 You can use the commands @code{dump}, @code{append}, and
7110 @code{restore} to copy data between target memory and a file. The
7111 @code{dump} and @code{append} commands write data to a file, and the
7112 @code{restore} command reads data from a file back into the inferior's
7113 memory. Files may be in binary, Motorola S-record, Intel hex, or
7114 Tektronix Hex format; however, @value{GDBN} can only append to binary
7120 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7121 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7122 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7123 or the value of @var{expr}, to @var{filename} in the given format.
7125 The @var{format} parameter may be any one of:
7132 Motorola S-record format.
7134 Tektronix Hex format.
7137 @value{GDBN} uses the same definitions of these formats as the
7138 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7139 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7143 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7144 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7145 Append the contents of memory from @var{start_addr} to @var{end_addr},
7146 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7147 (@value{GDBN} can only append data to files in raw binary form.)
7150 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7151 Restore the contents of file @var{filename} into memory. The
7152 @code{restore} command can automatically recognize any known @sc{bfd}
7153 file format, except for raw binary. To restore a raw binary file you
7154 must specify the optional keyword @code{binary} after the filename.
7156 If @var{bias} is non-zero, its value will be added to the addresses
7157 contained in the file. Binary files always start at address zero, so
7158 they will be restored at address @var{bias}. Other bfd files have
7159 a built-in location; they will be restored at offset @var{bias}
7162 If @var{start} and/or @var{end} are non-zero, then only data between
7163 file offset @var{start} and file offset @var{end} will be restored.
7164 These offsets are relative to the addresses in the file, before
7165 the @var{bias} argument is applied.
7169 @node Core File Generation
7170 @section How to Produce a Core File from Your Program
7171 @cindex dump core from inferior
7173 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7174 image of a running process and its process status (register values
7175 etc.). Its primary use is post-mortem debugging of a program that
7176 crashed while it ran outside a debugger. A program that crashes
7177 automatically produces a core file, unless this feature is disabled by
7178 the user. @xref{Files}, for information on invoking @value{GDBN} in
7179 the post-mortem debugging mode.
7181 Occasionally, you may wish to produce a core file of the program you
7182 are debugging in order to preserve a snapshot of its state.
7183 @value{GDBN} has a special command for that.
7187 @kindex generate-core-file
7188 @item generate-core-file [@var{file}]
7189 @itemx gcore [@var{file}]
7190 Produce a core dump of the inferior process. The optional argument
7191 @var{file} specifies the file name where to put the core dump. If not
7192 specified, the file name defaults to @file{core.@var{pid}}, where
7193 @var{pid} is the inferior process ID.
7195 Note that this command is implemented only for some systems (as of
7196 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7199 @node Character Sets
7200 @section Character Sets
7201 @cindex character sets
7203 @cindex translating between character sets
7204 @cindex host character set
7205 @cindex target character set
7207 If the program you are debugging uses a different character set to
7208 represent characters and strings than the one @value{GDBN} uses itself,
7209 @value{GDBN} can automatically translate between the character sets for
7210 you. The character set @value{GDBN} uses we call the @dfn{host
7211 character set}; the one the inferior program uses we call the
7212 @dfn{target character set}.
7214 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7215 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7216 remote protocol (@pxref{Remote Debugging}) to debug a program
7217 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7218 then the host character set is Latin-1, and the target character set is
7219 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7220 target-charset EBCDIC-US}, then @value{GDBN} translates between
7221 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7222 character and string literals in expressions.
7224 @value{GDBN} has no way to automatically recognize which character set
7225 the inferior program uses; you must tell it, using the @code{set
7226 target-charset} command, described below.
7228 Here are the commands for controlling @value{GDBN}'s character set
7232 @item set target-charset @var{charset}
7233 @kindex set target-charset
7234 Set the current target character set to @var{charset}. We list the
7235 character set names @value{GDBN} recognizes below, but if you type
7236 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7237 list the target character sets it supports.
7241 @item set host-charset @var{charset}
7242 @kindex set host-charset
7243 Set the current host character set to @var{charset}.
7245 By default, @value{GDBN} uses a host character set appropriate to the
7246 system it is running on; you can override that default using the
7247 @code{set host-charset} command.
7249 @value{GDBN} can only use certain character sets as its host character
7250 set. We list the character set names @value{GDBN} recognizes below, and
7251 indicate which can be host character sets, but if you type
7252 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7253 list the host character sets it supports.
7255 @item set charset @var{charset}
7257 Set the current host and target character sets to @var{charset}. As
7258 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7259 @value{GDBN} will list the name of the character sets that can be used
7260 for both host and target.
7264 @kindex show charset
7265 Show the names of the current host and target charsets.
7267 @itemx show host-charset
7268 @kindex show host-charset
7269 Show the name of the current host charset.
7271 @itemx show target-charset
7272 @kindex show target-charset
7273 Show the name of the current target charset.
7277 @value{GDBN} currently includes support for the following character
7283 @cindex ASCII character set
7284 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7288 @cindex ISO 8859-1 character set
7289 @cindex ISO Latin 1 character set
7290 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7291 characters needed for French, German, and Spanish. @value{GDBN} can use
7292 this as its host character set.
7296 @cindex EBCDIC character set
7297 @cindex IBM1047 character set
7298 Variants of the @sc{ebcdic} character set, used on some of IBM's
7299 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7300 @value{GDBN} cannot use these as its host character set.
7304 Note that these are all single-byte character sets. More work inside
7305 @value{GDBN} is needed to support multi-byte or variable-width character
7306 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7308 Here is an example of @value{GDBN}'s character set support in action.
7309 Assume that the following source code has been placed in the file
7310 @file{charset-test.c}:
7316 = @{72, 101, 108, 108, 111, 44, 32, 119,
7317 111, 114, 108, 100, 33, 10, 0@};
7318 char ibm1047_hello[]
7319 = @{200, 133, 147, 147, 150, 107, 64, 166,
7320 150, 153, 147, 132, 90, 37, 0@};
7324 printf ("Hello, world!\n");
7328 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7329 containing the string @samp{Hello, world!} followed by a newline,
7330 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7332 We compile the program, and invoke the debugger on it:
7335 $ gcc -g charset-test.c -o charset-test
7336 $ gdb -nw charset-test
7337 GNU gdb 2001-12-19-cvs
7338 Copyright 2001 Free Software Foundation, Inc.
7343 We can use the @code{show charset} command to see what character sets
7344 @value{GDBN} is currently using to interpret and display characters and
7348 (@value{GDBP}) show charset
7349 The current host and target character set is `ISO-8859-1'.
7353 For the sake of printing this manual, let's use @sc{ascii} as our
7354 initial character set:
7356 (@value{GDBP}) set charset ASCII
7357 (@value{GDBP}) show charset
7358 The current host and target character set is `ASCII'.
7362 Let's assume that @sc{ascii} is indeed the correct character set for our
7363 host system --- in other words, let's assume that if @value{GDBN} prints
7364 characters using the @sc{ascii} character set, our terminal will display
7365 them properly. Since our current target character set is also
7366 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7369 (@value{GDBP}) print ascii_hello
7370 $1 = 0x401698 "Hello, world!\n"
7371 (@value{GDBP}) print ascii_hello[0]
7376 @value{GDBN} uses the target character set for character and string
7377 literals you use in expressions:
7380 (@value{GDBP}) print '+'
7385 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7388 @value{GDBN} relies on the user to tell it which character set the
7389 target program uses. If we print @code{ibm1047_hello} while our target
7390 character set is still @sc{ascii}, we get jibberish:
7393 (@value{GDBP}) print ibm1047_hello
7394 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7395 (@value{GDBP}) print ibm1047_hello[0]
7400 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7401 @value{GDBN} tells us the character sets it supports:
7404 (@value{GDBP}) set target-charset
7405 ASCII EBCDIC-US IBM1047 ISO-8859-1
7406 (@value{GDBP}) set target-charset
7409 We can select @sc{ibm1047} as our target character set, and examine the
7410 program's strings again. Now the @sc{ascii} string is wrong, but
7411 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7412 target character set, @sc{ibm1047}, to the host character set,
7413 @sc{ascii}, and they display correctly:
7416 (@value{GDBP}) set target-charset IBM1047
7417 (@value{GDBP}) show charset
7418 The current host character set is `ASCII'.
7419 The current target character set is `IBM1047'.
7420 (@value{GDBP}) print ascii_hello
7421 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7422 (@value{GDBP}) print ascii_hello[0]
7424 (@value{GDBP}) print ibm1047_hello
7425 $8 = 0x4016a8 "Hello, world!\n"
7426 (@value{GDBP}) print ibm1047_hello[0]
7431 As above, @value{GDBN} uses the target character set for character and
7432 string literals you use in expressions:
7435 (@value{GDBP}) print '+'
7440 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7443 @node Caching Remote Data
7444 @section Caching Data of Remote Targets
7445 @cindex caching data of remote targets
7447 @value{GDBN} can cache data exchanged between the debugger and a
7448 remote target (@pxref{Remote Debugging}). Such caching generally improves
7449 performance, because it reduces the overhead of the remote protocol by
7450 bundling memory reads and writes into large chunks. Unfortunately,
7451 @value{GDBN} does not currently know anything about volatile
7452 registers, and thus data caching will produce incorrect results when
7453 volatile registers are in use.
7456 @kindex set remotecache
7457 @item set remotecache on
7458 @itemx set remotecache off
7459 Set caching state for remote targets. When @code{ON}, use data
7460 caching. By default, this option is @code{OFF}.
7462 @kindex show remotecache
7463 @item show remotecache
7464 Show the current state of data caching for remote targets.
7468 Print the information about the data cache performance. The
7469 information displayed includes: the dcache width and depth; and for
7470 each cache line, how many times it was referenced, and its data and
7471 state (dirty, bad, ok, etc.). This command is useful for debugging
7472 the data cache operation.
7477 @chapter C Preprocessor Macros
7479 Some languages, such as C and C@t{++}, provide a way to define and invoke
7480 ``preprocessor macros'' which expand into strings of tokens.
7481 @value{GDBN} can evaluate expressions containing macro invocations, show
7482 the result of macro expansion, and show a macro's definition, including
7483 where it was defined.
7485 You may need to compile your program specially to provide @value{GDBN}
7486 with information about preprocessor macros. Most compilers do not
7487 include macros in their debugging information, even when you compile
7488 with the @option{-g} flag. @xref{Compilation}.
7490 A program may define a macro at one point, remove that definition later,
7491 and then provide a different definition after that. Thus, at different
7492 points in the program, a macro may have different definitions, or have
7493 no definition at all. If there is a current stack frame, @value{GDBN}
7494 uses the macros in scope at that frame's source code line. Otherwise,
7495 @value{GDBN} uses the macros in scope at the current listing location;
7498 At the moment, @value{GDBN} does not support the @code{##}
7499 token-splicing operator, the @code{#} stringification operator, or
7500 variable-arity macros.
7502 Whenever @value{GDBN} evaluates an expression, it always expands any
7503 macro invocations present in the expression. @value{GDBN} also provides
7504 the following commands for working with macros explicitly.
7508 @kindex macro expand
7509 @cindex macro expansion, showing the results of preprocessor
7510 @cindex preprocessor macro expansion, showing the results of
7511 @cindex expanding preprocessor macros
7512 @item macro expand @var{expression}
7513 @itemx macro exp @var{expression}
7514 Show the results of expanding all preprocessor macro invocations in
7515 @var{expression}. Since @value{GDBN} simply expands macros, but does
7516 not parse the result, @var{expression} need not be a valid expression;
7517 it can be any string of tokens.
7520 @item macro expand-once @var{expression}
7521 @itemx macro exp1 @var{expression}
7522 @cindex expand macro once
7523 @i{(This command is not yet implemented.)} Show the results of
7524 expanding those preprocessor macro invocations that appear explicitly in
7525 @var{expression}. Macro invocations appearing in that expansion are
7526 left unchanged. This command allows you to see the effect of a
7527 particular macro more clearly, without being confused by further
7528 expansions. Since @value{GDBN} simply expands macros, but does not
7529 parse the result, @var{expression} need not be a valid expression; it
7530 can be any string of tokens.
7533 @cindex macro definition, showing
7534 @cindex definition, showing a macro's
7535 @item info macro @var{macro}
7536 Show the definition of the macro named @var{macro}, and describe the
7537 source location where that definition was established.
7539 @kindex macro define
7540 @cindex user-defined macros
7541 @cindex defining macros interactively
7542 @cindex macros, user-defined
7543 @item macro define @var{macro} @var{replacement-list}
7544 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7545 @i{(This command is not yet implemented.)} Introduce a definition for a
7546 preprocessor macro named @var{macro}, invocations of which are replaced
7547 by the tokens given in @var{replacement-list}. The first form of this
7548 command defines an ``object-like'' macro, which takes no arguments; the
7549 second form defines a ``function-like'' macro, which takes the arguments
7550 given in @var{arglist}.
7552 A definition introduced by this command is in scope in every expression
7553 evaluated in @value{GDBN}, until it is removed with the @command{macro
7554 undef} command, described below. The definition overrides all
7555 definitions for @var{macro} present in the program being debugged, as
7556 well as any previous user-supplied definition.
7559 @item macro undef @var{macro}
7560 @i{(This command is not yet implemented.)} Remove any user-supplied
7561 definition for the macro named @var{macro}. This command only affects
7562 definitions provided with the @command{macro define} command, described
7563 above; it cannot remove definitions present in the program being
7568 @i{(This command is not yet implemented.)} List all the macros
7569 defined using the @code{macro define} command.
7572 @cindex macros, example of debugging with
7573 Here is a transcript showing the above commands in action. First, we
7574 show our source files:
7582 #define ADD(x) (M + x)
7587 printf ("Hello, world!\n");
7589 printf ("We're so creative.\n");
7591 printf ("Goodbye, world!\n");
7598 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7599 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7600 compiler includes information about preprocessor macros in the debugging
7604 $ gcc -gdwarf-2 -g3 sample.c -o sample
7608 Now, we start @value{GDBN} on our sample program:
7612 GNU gdb 2002-05-06-cvs
7613 Copyright 2002 Free Software Foundation, Inc.
7614 GDB is free software, @dots{}
7618 We can expand macros and examine their definitions, even when the
7619 program is not running. @value{GDBN} uses the current listing position
7620 to decide which macro definitions are in scope:
7623 (@value{GDBP}) list main
7626 5 #define ADD(x) (M + x)
7631 10 printf ("Hello, world!\n");
7633 12 printf ("We're so creative.\n");
7634 (@value{GDBP}) info macro ADD
7635 Defined at /home/jimb/gdb/macros/play/sample.c:5
7636 #define ADD(x) (M + x)
7637 (@value{GDBP}) info macro Q
7638 Defined at /home/jimb/gdb/macros/play/sample.h:1
7639 included at /home/jimb/gdb/macros/play/sample.c:2
7641 (@value{GDBP}) macro expand ADD(1)
7642 expands to: (42 + 1)
7643 (@value{GDBP}) macro expand-once ADD(1)
7644 expands to: once (M + 1)
7648 In the example above, note that @command{macro expand-once} expands only
7649 the macro invocation explicit in the original text --- the invocation of
7650 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7651 which was introduced by @code{ADD}.
7653 Once the program is running, @value{GDBN} uses the macro definitions in
7654 force at the source line of the current stack frame:
7657 (@value{GDBP}) break main
7658 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7660 Starting program: /home/jimb/gdb/macros/play/sample
7662 Breakpoint 1, main () at sample.c:10
7663 10 printf ("Hello, world!\n");
7667 At line 10, the definition of the macro @code{N} at line 9 is in force:
7670 (@value{GDBP}) info macro N
7671 Defined at /home/jimb/gdb/macros/play/sample.c:9
7673 (@value{GDBP}) macro expand N Q M
7675 (@value{GDBP}) print N Q M
7680 As we step over directives that remove @code{N}'s definition, and then
7681 give it a new definition, @value{GDBN} finds the definition (or lack
7682 thereof) in force at each point:
7687 12 printf ("We're so creative.\n");
7688 (@value{GDBP}) info macro N
7689 The symbol `N' has no definition as a C/C++ preprocessor macro
7690 at /home/jimb/gdb/macros/play/sample.c:12
7693 14 printf ("Goodbye, world!\n");
7694 (@value{GDBP}) info macro N
7695 Defined at /home/jimb/gdb/macros/play/sample.c:13
7697 (@value{GDBP}) macro expand N Q M
7698 expands to: 1729 < 42
7699 (@value{GDBP}) print N Q M
7706 @chapter Tracepoints
7707 @c This chapter is based on the documentation written by Michael
7708 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7711 In some applications, it is not feasible for the debugger to interrupt
7712 the program's execution long enough for the developer to learn
7713 anything helpful about its behavior. If the program's correctness
7714 depends on its real-time behavior, delays introduced by a debugger
7715 might cause the program to change its behavior drastically, or perhaps
7716 fail, even when the code itself is correct. It is useful to be able
7717 to observe the program's behavior without interrupting it.
7719 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7720 specify locations in the program, called @dfn{tracepoints}, and
7721 arbitrary expressions to evaluate when those tracepoints are reached.
7722 Later, using the @code{tfind} command, you can examine the values
7723 those expressions had when the program hit the tracepoints. The
7724 expressions may also denote objects in memory---structures or arrays,
7725 for example---whose values @value{GDBN} should record; while visiting
7726 a particular tracepoint, you may inspect those objects as if they were
7727 in memory at that moment. However, because @value{GDBN} records these
7728 values without interacting with you, it can do so quickly and
7729 unobtrusively, hopefully not disturbing the program's behavior.
7731 The tracepoint facility is currently available only for remote
7732 targets. @xref{Targets}. In addition, your remote target must know
7733 how to collect trace data. This functionality is implemented in the
7734 remote stub; however, none of the stubs distributed with @value{GDBN}
7735 support tracepoints as of this writing. The format of the remote
7736 packets used to implement tracepoints are described in @ref{Tracepoint
7739 This chapter describes the tracepoint commands and features.
7743 * Analyze Collected Data::
7744 * Tracepoint Variables::
7747 @node Set Tracepoints
7748 @section Commands to Set Tracepoints
7750 Before running such a @dfn{trace experiment}, an arbitrary number of
7751 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7752 tracepoint has a number assigned to it by @value{GDBN}. Like with
7753 breakpoints, tracepoint numbers are successive integers starting from
7754 one. Many of the commands associated with tracepoints take the
7755 tracepoint number as their argument, to identify which tracepoint to
7758 For each tracepoint, you can specify, in advance, some arbitrary set
7759 of data that you want the target to collect in the trace buffer when
7760 it hits that tracepoint. The collected data can include registers,
7761 local variables, or global data. Later, you can use @value{GDBN}
7762 commands to examine the values these data had at the time the
7765 This section describes commands to set tracepoints and associated
7766 conditions and actions.
7769 * Create and Delete Tracepoints::
7770 * Enable and Disable Tracepoints::
7771 * Tracepoint Passcounts::
7772 * Tracepoint Actions::
7773 * Listing Tracepoints::
7774 * Starting and Stopping Trace Experiments::
7777 @node Create and Delete Tracepoints
7778 @subsection Create and Delete Tracepoints
7781 @cindex set tracepoint
7784 The @code{trace} command is very similar to the @code{break} command.
7785 Its argument can be a source line, a function name, or an address in
7786 the target program. @xref{Set Breaks}. The @code{trace} command
7787 defines a tracepoint, which is a point in the target program where the
7788 debugger will briefly stop, collect some data, and then allow the
7789 program to continue. Setting a tracepoint or changing its commands
7790 doesn't take effect until the next @code{tstart} command; thus, you
7791 cannot change the tracepoint attributes once a trace experiment is
7794 Here are some examples of using the @code{trace} command:
7797 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7799 (@value{GDBP}) @b{trace +2} // 2 lines forward
7801 (@value{GDBP}) @b{trace my_function} // first source line of function
7803 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7805 (@value{GDBP}) @b{trace *0x2117c4} // an address
7809 You can abbreviate @code{trace} as @code{tr}.
7812 @cindex last tracepoint number
7813 @cindex recent tracepoint number
7814 @cindex tracepoint number
7815 The convenience variable @code{$tpnum} records the tracepoint number
7816 of the most recently set tracepoint.
7818 @kindex delete tracepoint
7819 @cindex tracepoint deletion
7820 @item delete tracepoint @r{[}@var{num}@r{]}
7821 Permanently delete one or more tracepoints. With no argument, the
7822 default is to delete all tracepoints.
7827 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7829 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7833 You can abbreviate this command as @code{del tr}.
7836 @node Enable and Disable Tracepoints
7837 @subsection Enable and Disable Tracepoints
7840 @kindex disable tracepoint
7841 @item disable tracepoint @r{[}@var{num}@r{]}
7842 Disable tracepoint @var{num}, or all tracepoints if no argument
7843 @var{num} is given. A disabled tracepoint will have no effect during
7844 the next trace experiment, but it is not forgotten. You can re-enable
7845 a disabled tracepoint using the @code{enable tracepoint} command.
7847 @kindex enable tracepoint
7848 @item enable tracepoint @r{[}@var{num}@r{]}
7849 Enable tracepoint @var{num}, or all tracepoints. The enabled
7850 tracepoints will become effective the next time a trace experiment is
7854 @node Tracepoint Passcounts
7855 @subsection Tracepoint Passcounts
7859 @cindex tracepoint pass count
7860 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7861 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7862 automatically stop a trace experiment. If a tracepoint's passcount is
7863 @var{n}, then the trace experiment will be automatically stopped on
7864 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7865 @var{num} is not specified, the @code{passcount} command sets the
7866 passcount of the most recently defined tracepoint. If no passcount is
7867 given, the trace experiment will run until stopped explicitly by the
7873 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7874 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7876 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7877 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7878 (@value{GDBP}) @b{trace foo}
7879 (@value{GDBP}) @b{pass 3}
7880 (@value{GDBP}) @b{trace bar}
7881 (@value{GDBP}) @b{pass 2}
7882 (@value{GDBP}) @b{trace baz}
7883 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7884 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7885 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7886 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7890 @node Tracepoint Actions
7891 @subsection Tracepoint Action Lists
7895 @cindex tracepoint actions
7896 @item actions @r{[}@var{num}@r{]}
7897 This command will prompt for a list of actions to be taken when the
7898 tracepoint is hit. If the tracepoint number @var{num} is not
7899 specified, this command sets the actions for the one that was most
7900 recently defined (so that you can define a tracepoint and then say
7901 @code{actions} without bothering about its number). You specify the
7902 actions themselves on the following lines, one action at a time, and
7903 terminate the actions list with a line containing just @code{end}. So
7904 far, the only defined actions are @code{collect} and
7905 @code{while-stepping}.
7907 @cindex remove actions from a tracepoint
7908 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7909 and follow it immediately with @samp{end}.
7912 (@value{GDBP}) @b{collect @var{data}} // collect some data
7914 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7916 (@value{GDBP}) @b{end} // signals the end of actions.
7919 In the following example, the action list begins with @code{collect}
7920 commands indicating the things to be collected when the tracepoint is
7921 hit. Then, in order to single-step and collect additional data
7922 following the tracepoint, a @code{while-stepping} command is used,
7923 followed by the list of things to be collected while stepping. The
7924 @code{while-stepping} command is terminated by its own separate
7925 @code{end} command. Lastly, the action list is terminated by an
7929 (@value{GDBP}) @b{trace foo}
7930 (@value{GDBP}) @b{actions}
7931 Enter actions for tracepoint 1, one per line:
7940 @kindex collect @r{(tracepoints)}
7941 @item collect @var{expr1}, @var{expr2}, @dots{}
7942 Collect values of the given expressions when the tracepoint is hit.
7943 This command accepts a comma-separated list of any valid expressions.
7944 In addition to global, static, or local variables, the following
7945 special arguments are supported:
7949 collect all registers
7952 collect all function arguments
7955 collect all local variables.
7958 You can give several consecutive @code{collect} commands, each one
7959 with a single argument, or one @code{collect} command with several
7960 arguments separated by commas: the effect is the same.
7962 The command @code{info scope} (@pxref{Symbols, info scope}) is
7963 particularly useful for figuring out what data to collect.
7965 @kindex while-stepping @r{(tracepoints)}
7966 @item while-stepping @var{n}
7967 Perform @var{n} single-step traces after the tracepoint, collecting
7968 new data at each step. The @code{while-stepping} command is
7969 followed by the list of what to collect while stepping (followed by
7970 its own @code{end} command):
7974 > collect $regs, myglobal
7980 You may abbreviate @code{while-stepping} as @code{ws} or
7984 @node Listing Tracepoints
7985 @subsection Listing Tracepoints
7988 @kindex info tracepoints
7990 @cindex information about tracepoints
7991 @item info tracepoints @r{[}@var{num}@r{]}
7992 Display information about the tracepoint @var{num}. If you don't specify
7993 a tracepoint number, displays information about all the tracepoints
7994 defined so far. For each tracepoint, the following information is
8001 whether it is enabled or disabled
8005 its passcount as given by the @code{passcount @var{n}} command
8007 its step count as given by the @code{while-stepping @var{n}} command
8009 where in the source files is the tracepoint set
8011 its action list as given by the @code{actions} command
8015 (@value{GDBP}) @b{info trace}
8016 Num Enb Address PassC StepC What
8017 1 y 0x002117c4 0 0 <gdb_asm>
8018 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8019 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8024 This command can be abbreviated @code{info tp}.
8027 @node Starting and Stopping Trace Experiments
8028 @subsection Starting and Stopping Trace Experiments
8032 @cindex start a new trace experiment
8033 @cindex collected data discarded
8035 This command takes no arguments. It starts the trace experiment, and
8036 begins collecting data. This has the side effect of discarding all
8037 the data collected in the trace buffer during the previous trace
8041 @cindex stop a running trace experiment
8043 This command takes no arguments. It ends the trace experiment, and
8044 stops collecting data.
8046 @strong{Note}: a trace experiment and data collection may stop
8047 automatically if any tracepoint's passcount is reached
8048 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8051 @cindex status of trace data collection
8052 @cindex trace experiment, status of
8054 This command displays the status of the current trace data
8058 Here is an example of the commands we described so far:
8061 (@value{GDBP}) @b{trace gdb_c_test}
8062 (@value{GDBP}) @b{actions}
8063 Enter actions for tracepoint #1, one per line.
8064 > collect $regs,$locals,$args
8069 (@value{GDBP}) @b{tstart}
8070 [time passes @dots{}]
8071 (@value{GDBP}) @b{tstop}
8075 @node Analyze Collected Data
8076 @section Using the Collected Data
8078 After the tracepoint experiment ends, you use @value{GDBN} commands
8079 for examining the trace data. The basic idea is that each tracepoint
8080 collects a trace @dfn{snapshot} every time it is hit and another
8081 snapshot every time it single-steps. All these snapshots are
8082 consecutively numbered from zero and go into a buffer, and you can
8083 examine them later. The way you examine them is to @dfn{focus} on a
8084 specific trace snapshot. When the remote stub is focused on a trace
8085 snapshot, it will respond to all @value{GDBN} requests for memory and
8086 registers by reading from the buffer which belongs to that snapshot,
8087 rather than from @emph{real} memory or registers of the program being
8088 debugged. This means that @strong{all} @value{GDBN} commands
8089 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8090 behave as if we were currently debugging the program state as it was
8091 when the tracepoint occurred. Any requests for data that are not in
8092 the buffer will fail.
8095 * tfind:: How to select a trace snapshot
8096 * tdump:: How to display all data for a snapshot
8097 * save-tracepoints:: How to save tracepoints for a future run
8101 @subsection @code{tfind @var{n}}
8104 @cindex select trace snapshot
8105 @cindex find trace snapshot
8106 The basic command for selecting a trace snapshot from the buffer is
8107 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8108 counting from zero. If no argument @var{n} is given, the next
8109 snapshot is selected.
8111 Here are the various forms of using the @code{tfind} command.
8115 Find the first snapshot in the buffer. This is a synonym for
8116 @code{tfind 0} (since 0 is the number of the first snapshot).
8119 Stop debugging trace snapshots, resume @emph{live} debugging.
8122 Same as @samp{tfind none}.
8125 No argument means find the next trace snapshot.
8128 Find the previous trace snapshot before the current one. This permits
8129 retracing earlier steps.
8131 @item tfind tracepoint @var{num}
8132 Find the next snapshot associated with tracepoint @var{num}. Search
8133 proceeds forward from the last examined trace snapshot. If no
8134 argument @var{num} is given, it means find the next snapshot collected
8135 for the same tracepoint as the current snapshot.
8137 @item tfind pc @var{addr}
8138 Find the next snapshot associated with the value @var{addr} of the
8139 program counter. Search proceeds forward from the last examined trace
8140 snapshot. If no argument @var{addr} is given, it means find the next
8141 snapshot with the same value of PC as the current snapshot.
8143 @item tfind outside @var{addr1}, @var{addr2}
8144 Find the next snapshot whose PC is outside the given range of
8147 @item tfind range @var{addr1}, @var{addr2}
8148 Find the next snapshot whose PC is between @var{addr1} and
8149 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8151 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8152 Find the next snapshot associated with the source line @var{n}. If
8153 the optional argument @var{file} is given, refer to line @var{n} in
8154 that source file. Search proceeds forward from the last examined
8155 trace snapshot. If no argument @var{n} is given, it means find the
8156 next line other than the one currently being examined; thus saying
8157 @code{tfind line} repeatedly can appear to have the same effect as
8158 stepping from line to line in a @emph{live} debugging session.
8161 The default arguments for the @code{tfind} commands are specifically
8162 designed to make it easy to scan through the trace buffer. For
8163 instance, @code{tfind} with no argument selects the next trace
8164 snapshot, and @code{tfind -} with no argument selects the previous
8165 trace snapshot. So, by giving one @code{tfind} command, and then
8166 simply hitting @key{RET} repeatedly you can examine all the trace
8167 snapshots in order. Or, by saying @code{tfind -} and then hitting
8168 @key{RET} repeatedly you can examine the snapshots in reverse order.
8169 The @code{tfind line} command with no argument selects the snapshot
8170 for the next source line executed. The @code{tfind pc} command with
8171 no argument selects the next snapshot with the same program counter
8172 (PC) as the current frame. The @code{tfind tracepoint} command with
8173 no argument selects the next trace snapshot collected by the same
8174 tracepoint as the current one.
8176 In addition to letting you scan through the trace buffer manually,
8177 these commands make it easy to construct @value{GDBN} scripts that
8178 scan through the trace buffer and print out whatever collected data
8179 you are interested in. Thus, if we want to examine the PC, FP, and SP
8180 registers from each trace frame in the buffer, we can say this:
8183 (@value{GDBP}) @b{tfind start}
8184 (@value{GDBP}) @b{while ($trace_frame != -1)}
8185 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8186 $trace_frame, $pc, $sp, $fp
8190 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8191 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8192 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8193 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8194 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8195 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8196 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8197 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8198 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8199 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8200 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8203 Or, if we want to examine the variable @code{X} at each source line in
8207 (@value{GDBP}) @b{tfind start}
8208 (@value{GDBP}) @b{while ($trace_frame != -1)}
8209 > printf "Frame %d, X == %d\n", $trace_frame, X
8219 @subsection @code{tdump}
8221 @cindex dump all data collected at tracepoint
8222 @cindex tracepoint data, display
8224 This command takes no arguments. It prints all the data collected at
8225 the current trace snapshot.
8228 (@value{GDBP}) @b{trace 444}
8229 (@value{GDBP}) @b{actions}
8230 Enter actions for tracepoint #2, one per line:
8231 > collect $regs, $locals, $args, gdb_long_test
8234 (@value{GDBP}) @b{tstart}
8236 (@value{GDBP}) @b{tfind line 444}
8237 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8239 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8241 (@value{GDBP}) @b{tdump}
8242 Data collected at tracepoint 2, trace frame 1:
8243 d0 0xc4aa0085 -995491707
8247 d4 0x71aea3d 119204413
8252 a1 0x3000668 50333288
8255 a4 0x3000698 50333336
8257 fp 0x30bf3c 0x30bf3c
8258 sp 0x30bf34 0x30bf34
8260 pc 0x20b2c8 0x20b2c8
8264 p = 0x20e5b4 "gdb-test"
8271 gdb_long_test = 17 '\021'
8276 @node save-tracepoints
8277 @subsection @code{save-tracepoints @var{filename}}
8278 @kindex save-tracepoints
8279 @cindex save tracepoints for future sessions
8281 This command saves all current tracepoint definitions together with
8282 their actions and passcounts, into a file @file{@var{filename}}
8283 suitable for use in a later debugging session. To read the saved
8284 tracepoint definitions, use the @code{source} command (@pxref{Command
8287 @node Tracepoint Variables
8288 @section Convenience Variables for Tracepoints
8289 @cindex tracepoint variables
8290 @cindex convenience variables for tracepoints
8293 @vindex $trace_frame
8294 @item (int) $trace_frame
8295 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8296 snapshot is selected.
8299 @item (int) $tracepoint
8300 The tracepoint for the current trace snapshot.
8303 @item (int) $trace_line
8304 The line number for the current trace snapshot.
8307 @item (char []) $trace_file
8308 The source file for the current trace snapshot.
8311 @item (char []) $trace_func
8312 The name of the function containing @code{$tracepoint}.
8315 Note: @code{$trace_file} is not suitable for use in @code{printf},
8316 use @code{output} instead.
8318 Here's a simple example of using these convenience variables for
8319 stepping through all the trace snapshots and printing some of their
8323 (@value{GDBP}) @b{tfind start}
8325 (@value{GDBP}) @b{while $trace_frame != -1}
8326 > output $trace_file
8327 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8333 @chapter Debugging Programs That Use Overlays
8336 If your program is too large to fit completely in your target system's
8337 memory, you can sometimes use @dfn{overlays} to work around this
8338 problem. @value{GDBN} provides some support for debugging programs that
8342 * How Overlays Work:: A general explanation of overlays.
8343 * Overlay Commands:: Managing overlays in @value{GDBN}.
8344 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8345 mapped by asking the inferior.
8346 * Overlay Sample Program:: A sample program using overlays.
8349 @node How Overlays Work
8350 @section How Overlays Work
8351 @cindex mapped overlays
8352 @cindex unmapped overlays
8353 @cindex load address, overlay's
8354 @cindex mapped address
8355 @cindex overlay area
8357 Suppose you have a computer whose instruction address space is only 64
8358 kilobytes long, but which has much more memory which can be accessed by
8359 other means: special instructions, segment registers, or memory
8360 management hardware, for example. Suppose further that you want to
8361 adapt a program which is larger than 64 kilobytes to run on this system.
8363 One solution is to identify modules of your program which are relatively
8364 independent, and need not call each other directly; call these modules
8365 @dfn{overlays}. Separate the overlays from the main program, and place
8366 their machine code in the larger memory. Place your main program in
8367 instruction memory, but leave at least enough space there to hold the
8368 largest overlay as well.
8370 Now, to call a function located in an overlay, you must first copy that
8371 overlay's machine code from the large memory into the space set aside
8372 for it in the instruction memory, and then jump to its entry point
8375 @c NB: In the below the mapped area's size is greater or equal to the
8376 @c size of all overlays. This is intentional to remind the developer
8377 @c that overlays don't necessarily need to be the same size.
8381 Data Instruction Larger
8382 Address Space Address Space Address Space
8383 +-----------+ +-----------+ +-----------+
8385 +-----------+ +-----------+ +-----------+<-- overlay 1
8386 | program | | main | .----| overlay 1 | load address
8387 | variables | | program | | +-----------+
8388 | and heap | | | | | |
8389 +-----------+ | | | +-----------+<-- overlay 2
8390 | | +-----------+ | | | load address
8391 +-----------+ | | | .-| overlay 2 |
8393 mapped --->+-----------+ | | +-----------+
8395 | overlay | <-' | | |
8396 | area | <---' +-----------+<-- overlay 3
8397 | | <---. | | load address
8398 +-----------+ `--| overlay 3 |
8405 @anchor{A code overlay}A code overlay
8409 The diagram (@pxref{A code overlay}) shows a system with separate data
8410 and instruction address spaces. To map an overlay, the program copies
8411 its code from the larger address space to the instruction address space.
8412 Since the overlays shown here all use the same mapped address, only one
8413 may be mapped at a time. For a system with a single address space for
8414 data and instructions, the diagram would be similar, except that the
8415 program variables and heap would share an address space with the main
8416 program and the overlay area.
8418 An overlay loaded into instruction memory and ready for use is called a
8419 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8420 instruction memory. An overlay not present (or only partially present)
8421 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8422 is its address in the larger memory. The mapped address is also called
8423 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8424 called the @dfn{load memory address}, or @dfn{LMA}.
8426 Unfortunately, overlays are not a completely transparent way to adapt a
8427 program to limited instruction memory. They introduce a new set of
8428 global constraints you must keep in mind as you design your program:
8433 Before calling or returning to a function in an overlay, your program
8434 must make sure that overlay is actually mapped. Otherwise, the call or
8435 return will transfer control to the right address, but in the wrong
8436 overlay, and your program will probably crash.
8439 If the process of mapping an overlay is expensive on your system, you
8440 will need to choose your overlays carefully to minimize their effect on
8441 your program's performance.
8444 The executable file you load onto your system must contain each
8445 overlay's instructions, appearing at the overlay's load address, not its
8446 mapped address. However, each overlay's instructions must be relocated
8447 and its symbols defined as if the overlay were at its mapped address.
8448 You can use GNU linker scripts to specify different load and relocation
8449 addresses for pieces of your program; see @ref{Overlay Description,,,
8450 ld.info, Using ld: the GNU linker}.
8453 The procedure for loading executable files onto your system must be able
8454 to load their contents into the larger address space as well as the
8455 instruction and data spaces.
8459 The overlay system described above is rather simple, and could be
8460 improved in many ways:
8465 If your system has suitable bank switch registers or memory management
8466 hardware, you could use those facilities to make an overlay's load area
8467 contents simply appear at their mapped address in instruction space.
8468 This would probably be faster than copying the overlay to its mapped
8469 area in the usual way.
8472 If your overlays are small enough, you could set aside more than one
8473 overlay area, and have more than one overlay mapped at a time.
8476 You can use overlays to manage data, as well as instructions. In
8477 general, data overlays are even less transparent to your design than
8478 code overlays: whereas code overlays only require care when you call or
8479 return to functions, data overlays require care every time you access
8480 the data. Also, if you change the contents of a data overlay, you
8481 must copy its contents back out to its load address before you can copy a
8482 different data overlay into the same mapped area.
8487 @node Overlay Commands
8488 @section Overlay Commands
8490 To use @value{GDBN}'s overlay support, each overlay in your program must
8491 correspond to a separate section of the executable file. The section's
8492 virtual memory address and load memory address must be the overlay's
8493 mapped and load addresses. Identifying overlays with sections allows
8494 @value{GDBN} to determine the appropriate address of a function or
8495 variable, depending on whether the overlay is mapped or not.
8497 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8498 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8503 Disable @value{GDBN}'s overlay support. When overlay support is
8504 disabled, @value{GDBN} assumes that all functions and variables are
8505 always present at their mapped addresses. By default, @value{GDBN}'s
8506 overlay support is disabled.
8508 @item overlay manual
8509 @cindex manual overlay debugging
8510 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8511 relies on you to tell it which overlays are mapped, and which are not,
8512 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8513 commands described below.
8515 @item overlay map-overlay @var{overlay}
8516 @itemx overlay map @var{overlay}
8517 @cindex map an overlay
8518 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8519 be the name of the object file section containing the overlay. When an
8520 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8521 functions and variables at their mapped addresses. @value{GDBN} assumes
8522 that any other overlays whose mapped ranges overlap that of
8523 @var{overlay} are now unmapped.
8525 @item overlay unmap-overlay @var{overlay}
8526 @itemx overlay unmap @var{overlay}
8527 @cindex unmap an overlay
8528 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8529 must be the name of the object file section containing the overlay.
8530 When an overlay is unmapped, @value{GDBN} assumes it can find the
8531 overlay's functions and variables at their load addresses.
8534 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8535 consults a data structure the overlay manager maintains in the inferior
8536 to see which overlays are mapped. For details, see @ref{Automatic
8539 @item overlay load-target
8541 @cindex reloading the overlay table
8542 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8543 re-reads the table @value{GDBN} automatically each time the inferior
8544 stops, so this command should only be necessary if you have changed the
8545 overlay mapping yourself using @value{GDBN}. This command is only
8546 useful when using automatic overlay debugging.
8548 @item overlay list-overlays
8550 @cindex listing mapped overlays
8551 Display a list of the overlays currently mapped, along with their mapped
8552 addresses, load addresses, and sizes.
8556 Normally, when @value{GDBN} prints a code address, it includes the name
8557 of the function the address falls in:
8560 (@value{GDBP}) print main
8561 $3 = @{int ()@} 0x11a0 <main>
8564 When overlay debugging is enabled, @value{GDBN} recognizes code in
8565 unmapped overlays, and prints the names of unmapped functions with
8566 asterisks around them. For example, if @code{foo} is a function in an
8567 unmapped overlay, @value{GDBN} prints it this way:
8570 (@value{GDBP}) overlay list
8571 No sections are mapped.
8572 (@value{GDBP}) print foo
8573 $5 = @{int (int)@} 0x100000 <*foo*>
8576 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8580 (@value{GDBP}) overlay list
8581 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8582 mapped at 0x1016 - 0x104a
8583 (@value{GDBP}) print foo
8584 $6 = @{int (int)@} 0x1016 <foo>
8587 When overlay debugging is enabled, @value{GDBN} can find the correct
8588 address for functions and variables in an overlay, whether or not the
8589 overlay is mapped. This allows most @value{GDBN} commands, like
8590 @code{break} and @code{disassemble}, to work normally, even on unmapped
8591 code. However, @value{GDBN}'s breakpoint support has some limitations:
8595 @cindex breakpoints in overlays
8596 @cindex overlays, setting breakpoints in
8597 You can set breakpoints in functions in unmapped overlays, as long as
8598 @value{GDBN} can write to the overlay at its load address.
8600 @value{GDBN} can not set hardware or simulator-based breakpoints in
8601 unmapped overlays. However, if you set a breakpoint at the end of your
8602 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8603 you are using manual overlay management), @value{GDBN} will re-set its
8604 breakpoints properly.
8608 @node Automatic Overlay Debugging
8609 @section Automatic Overlay Debugging
8610 @cindex automatic overlay debugging
8612 @value{GDBN} can automatically track which overlays are mapped and which
8613 are not, given some simple co-operation from the overlay manager in the
8614 inferior. If you enable automatic overlay debugging with the
8615 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8616 looks in the inferior's memory for certain variables describing the
8617 current state of the overlays.
8619 Here are the variables your overlay manager must define to support
8620 @value{GDBN}'s automatic overlay debugging:
8624 @item @code{_ovly_table}:
8625 This variable must be an array of the following structures:
8630 /* The overlay's mapped address. */
8633 /* The size of the overlay, in bytes. */
8636 /* The overlay's load address. */
8639 /* Non-zero if the overlay is currently mapped;
8641 unsigned long mapped;
8645 @item @code{_novlys}:
8646 This variable must be a four-byte signed integer, holding the total
8647 number of elements in @code{_ovly_table}.
8651 To decide whether a particular overlay is mapped or not, @value{GDBN}
8652 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8653 @code{lma} members equal the VMA and LMA of the overlay's section in the
8654 executable file. When @value{GDBN} finds a matching entry, it consults
8655 the entry's @code{mapped} member to determine whether the overlay is
8658 In addition, your overlay manager may define a function called
8659 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8660 will silently set a breakpoint there. If the overlay manager then
8661 calls this function whenever it has changed the overlay table, this
8662 will enable @value{GDBN} to accurately keep track of which overlays
8663 are in program memory, and update any breakpoints that may be set
8664 in overlays. This will allow breakpoints to work even if the
8665 overlays are kept in ROM or other non-writable memory while they
8666 are not being executed.
8668 @node Overlay Sample Program
8669 @section Overlay Sample Program
8670 @cindex overlay example program
8672 When linking a program which uses overlays, you must place the overlays
8673 at their load addresses, while relocating them to run at their mapped
8674 addresses. To do this, you must write a linker script (@pxref{Overlay
8675 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8676 since linker scripts are specific to a particular host system, target
8677 architecture, and target memory layout, this manual cannot provide
8678 portable sample code demonstrating @value{GDBN}'s overlay support.
8680 However, the @value{GDBN} source distribution does contain an overlaid
8681 program, with linker scripts for a few systems, as part of its test
8682 suite. The program consists of the following files from
8683 @file{gdb/testsuite/gdb.base}:
8687 The main program file.
8689 A simple overlay manager, used by @file{overlays.c}.
8694 Overlay modules, loaded and used by @file{overlays.c}.
8697 Linker scripts for linking the test program on the @code{d10v-elf}
8698 and @code{m32r-elf} targets.
8701 You can build the test program using the @code{d10v-elf} GCC
8702 cross-compiler like this:
8705 $ d10v-elf-gcc -g -c overlays.c
8706 $ d10v-elf-gcc -g -c ovlymgr.c
8707 $ d10v-elf-gcc -g -c foo.c
8708 $ d10v-elf-gcc -g -c bar.c
8709 $ d10v-elf-gcc -g -c baz.c
8710 $ d10v-elf-gcc -g -c grbx.c
8711 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8712 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8715 The build process is identical for any other architecture, except that
8716 you must substitute the appropriate compiler and linker script for the
8717 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8721 @chapter Using @value{GDBN} with Different Languages
8724 Although programming languages generally have common aspects, they are
8725 rarely expressed in the same manner. For instance, in ANSI C,
8726 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8727 Modula-2, it is accomplished by @code{p^}. Values can also be
8728 represented (and displayed) differently. Hex numbers in C appear as
8729 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8731 @cindex working language
8732 Language-specific information is built into @value{GDBN} for some languages,
8733 allowing you to express operations like the above in your program's
8734 native language, and allowing @value{GDBN} to output values in a manner
8735 consistent with the syntax of your program's native language. The
8736 language you use to build expressions is called the @dfn{working
8740 * Setting:: Switching between source languages
8741 * Show:: Displaying the language
8742 * Checks:: Type and range checks
8743 * Supported Languages:: Supported languages
8744 * Unsupported Languages:: Unsupported languages
8748 @section Switching Between Source Languages
8750 There are two ways to control the working language---either have @value{GDBN}
8751 set it automatically, or select it manually yourself. You can use the
8752 @code{set language} command for either purpose. On startup, @value{GDBN}
8753 defaults to setting the language automatically. The working language is
8754 used to determine how expressions you type are interpreted, how values
8757 In addition to the working language, every source file that
8758 @value{GDBN} knows about has its own working language. For some object
8759 file formats, the compiler might indicate which language a particular
8760 source file is in. However, most of the time @value{GDBN} infers the
8761 language from the name of the file. The language of a source file
8762 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8763 show each frame appropriately for its own language. There is no way to
8764 set the language of a source file from within @value{GDBN}, but you can
8765 set the language associated with a filename extension. @xref{Show, ,
8766 Displaying the Language}.
8768 This is most commonly a problem when you use a program, such
8769 as @code{cfront} or @code{f2c}, that generates C but is written in
8770 another language. In that case, make the
8771 program use @code{#line} directives in its C output; that way
8772 @value{GDBN} will know the correct language of the source code of the original
8773 program, and will display that source code, not the generated C code.
8776 * Filenames:: Filename extensions and languages.
8777 * Manually:: Setting the working language manually
8778 * Automatically:: Having @value{GDBN} infer the source language
8782 @subsection List of Filename Extensions and Languages
8784 If a source file name ends in one of the following extensions, then
8785 @value{GDBN} infers that its language is the one indicated.
8806 Objective-C source file
8813 Modula-2 source file
8817 Assembler source file. This actually behaves almost like C, but
8818 @value{GDBN} does not skip over function prologues when stepping.
8821 In addition, you may set the language associated with a filename
8822 extension. @xref{Show, , Displaying the Language}.
8825 @subsection Setting the Working Language
8827 If you allow @value{GDBN} to set the language automatically,
8828 expressions are interpreted the same way in your debugging session and
8831 @kindex set language
8832 If you wish, you may set the language manually. To do this, issue the
8833 command @samp{set language @var{lang}}, where @var{lang} is the name of
8835 @code{c} or @code{modula-2}.
8836 For a list of the supported languages, type @samp{set language}.
8838 Setting the language manually prevents @value{GDBN} from updating the working
8839 language automatically. This can lead to confusion if you try
8840 to debug a program when the working language is not the same as the
8841 source language, when an expression is acceptable to both
8842 languages---but means different things. For instance, if the current
8843 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8851 might not have the effect you intended. In C, this means to add
8852 @code{b} and @code{c} and place the result in @code{a}. The result
8853 printed would be the value of @code{a}. In Modula-2, this means to compare
8854 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8857 @subsection Having @value{GDBN} Infer the Source Language
8859 To have @value{GDBN} set the working language automatically, use
8860 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8861 then infers the working language. That is, when your program stops in a
8862 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8863 working language to the language recorded for the function in that
8864 frame. If the language for a frame is unknown (that is, if the function
8865 or block corresponding to the frame was defined in a source file that
8866 does not have a recognized extension), the current working language is
8867 not changed, and @value{GDBN} issues a warning.
8869 This may not seem necessary for most programs, which are written
8870 entirely in one source language. However, program modules and libraries
8871 written in one source language can be used by a main program written in
8872 a different source language. Using @samp{set language auto} in this
8873 case frees you from having to set the working language manually.
8876 @section Displaying the Language
8878 The following commands help you find out which language is the
8879 working language, and also what language source files were written in.
8883 @kindex show language
8884 Display the current working language. This is the
8885 language you can use with commands such as @code{print} to
8886 build and compute expressions that may involve variables in your program.
8889 @kindex info frame@r{, show the source language}
8890 Display the source language for this frame. This language becomes the
8891 working language if you use an identifier from this frame.
8892 @xref{Frame Info, ,Information about a Frame}, to identify the other
8893 information listed here.
8896 @kindex info source@r{, show the source language}
8897 Display the source language of this source file.
8898 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8899 information listed here.
8902 In unusual circumstances, you may have source files with extensions
8903 not in the standard list. You can then set the extension associated
8904 with a language explicitly:
8907 @item set extension-language @var{ext} @var{language}
8908 @kindex set extension-language
8909 Tell @value{GDBN} that source files with extension @var{ext} are to be
8910 assumed as written in the source language @var{language}.
8912 @item info extensions
8913 @kindex info extensions
8914 List all the filename extensions and the associated languages.
8918 @section Type and Range Checking
8921 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8922 checking are included, but they do not yet have any effect. This
8923 section documents the intended facilities.
8925 @c FIXME remove warning when type/range code added
8927 Some languages are designed to guard you against making seemingly common
8928 errors through a series of compile- and run-time checks. These include
8929 checking the type of arguments to functions and operators, and making
8930 sure mathematical overflows are caught at run time. Checks such as
8931 these help to ensure a program's correctness once it has been compiled
8932 by eliminating type mismatches, and providing active checks for range
8933 errors when your program is running.
8935 @value{GDBN} can check for conditions like the above if you wish.
8936 Although @value{GDBN} does not check the statements in your program,
8937 it can check expressions entered directly into @value{GDBN} for
8938 evaluation via the @code{print} command, for example. As with the
8939 working language, @value{GDBN} can also decide whether or not to check
8940 automatically based on your program's source language.
8941 @xref{Supported Languages, ,Supported Languages}, for the default
8942 settings of supported languages.
8945 * Type Checking:: An overview of type checking
8946 * Range Checking:: An overview of range checking
8949 @cindex type checking
8950 @cindex checks, type
8952 @subsection An Overview of Type Checking
8954 Some languages, such as Modula-2, are strongly typed, meaning that the
8955 arguments to operators and functions have to be of the correct type,
8956 otherwise an error occurs. These checks prevent type mismatch
8957 errors from ever causing any run-time problems. For example,
8965 The second example fails because the @code{CARDINAL} 1 is not
8966 type-compatible with the @code{REAL} 2.3.
8968 For the expressions you use in @value{GDBN} commands, you can tell the
8969 @value{GDBN} type checker to skip checking;
8970 to treat any mismatches as errors and abandon the expression;
8971 or to only issue warnings when type mismatches occur,
8972 but evaluate the expression anyway. When you choose the last of
8973 these, @value{GDBN} evaluates expressions like the second example above, but
8974 also issues a warning.
8976 Even if you turn type checking off, there may be other reasons
8977 related to type that prevent @value{GDBN} from evaluating an expression.
8978 For instance, @value{GDBN} does not know how to add an @code{int} and
8979 a @code{struct foo}. These particular type errors have nothing to do
8980 with the language in use, and usually arise from expressions, such as
8981 the one described above, which make little sense to evaluate anyway.
8983 Each language defines to what degree it is strict about type. For
8984 instance, both Modula-2 and C require the arguments to arithmetical
8985 operators to be numbers. In C, enumerated types and pointers can be
8986 represented as numbers, so that they are valid arguments to mathematical
8987 operators. @xref{Supported Languages, ,Supported Languages}, for further
8988 details on specific languages.
8990 @value{GDBN} provides some additional commands for controlling the type checker:
8992 @kindex set check type
8993 @kindex show check type
8995 @item set check type auto
8996 Set type checking on or off based on the current working language.
8997 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9000 @item set check type on
9001 @itemx set check type off
9002 Set type checking on or off, overriding the default setting for the
9003 current working language. Issue a warning if the setting does not
9004 match the language default. If any type mismatches occur in
9005 evaluating an expression while type checking is on, @value{GDBN} prints a
9006 message and aborts evaluation of the expression.
9008 @item set check type warn
9009 Cause the type checker to issue warnings, but to always attempt to
9010 evaluate the expression. Evaluating the expression may still
9011 be impossible for other reasons. For example, @value{GDBN} cannot add
9012 numbers and structures.
9015 Show the current setting of the type checker, and whether or not @value{GDBN}
9016 is setting it automatically.
9019 @cindex range checking
9020 @cindex checks, range
9021 @node Range Checking
9022 @subsection An Overview of Range Checking
9024 In some languages (such as Modula-2), it is an error to exceed the
9025 bounds of a type; this is enforced with run-time checks. Such range
9026 checking is meant to ensure program correctness by making sure
9027 computations do not overflow, or indices on an array element access do
9028 not exceed the bounds of the array.
9030 For expressions you use in @value{GDBN} commands, you can tell
9031 @value{GDBN} to treat range errors in one of three ways: ignore them,
9032 always treat them as errors and abandon the expression, or issue
9033 warnings but evaluate the expression anyway.
9035 A range error can result from numerical overflow, from exceeding an
9036 array index bound, or when you type a constant that is not a member
9037 of any type. Some languages, however, do not treat overflows as an
9038 error. In many implementations of C, mathematical overflow causes the
9039 result to ``wrap around'' to lower values---for example, if @var{m} is
9040 the largest integer value, and @var{s} is the smallest, then
9043 @var{m} + 1 @result{} @var{s}
9046 This, too, is specific to individual languages, and in some cases
9047 specific to individual compilers or machines. @xref{Supported Languages, ,
9048 Supported Languages}, for further details on specific languages.
9050 @value{GDBN} provides some additional commands for controlling the range checker:
9052 @kindex set check range
9053 @kindex show check range
9055 @item set check range auto
9056 Set range checking on or off based on the current working language.
9057 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9060 @item set check range on
9061 @itemx set check range off
9062 Set range checking on or off, overriding the default setting for the
9063 current working language. A warning is issued if the setting does not
9064 match the language default. If a range error occurs and range checking is on,
9065 then a message is printed and evaluation of the expression is aborted.
9067 @item set check range warn
9068 Output messages when the @value{GDBN} range checker detects a range error,
9069 but attempt to evaluate the expression anyway. Evaluating the
9070 expression may still be impossible for other reasons, such as accessing
9071 memory that the process does not own (a typical example from many Unix
9075 Show the current setting of the range checker, and whether or not it is
9076 being set automatically by @value{GDBN}.
9079 @node Supported Languages
9080 @section Supported Languages
9082 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9083 assembly, Modula-2, and Ada.
9084 @c This is false ...
9085 Some @value{GDBN} features may be used in expressions regardless of the
9086 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9087 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9088 ,Expressions}) can be used with the constructs of any supported
9091 The following sections detail to what degree each source language is
9092 supported by @value{GDBN}. These sections are not meant to be language
9093 tutorials or references, but serve only as a reference guide to what the
9094 @value{GDBN} expression parser accepts, and what input and output
9095 formats should look like for different languages. There are many good
9096 books written on each of these languages; please look to these for a
9097 language reference or tutorial.
9101 * Objective-C:: Objective-C
9104 * Modula-2:: Modula-2
9109 @subsection C and C@t{++}
9111 @cindex C and C@t{++}
9112 @cindex expressions in C or C@t{++}
9114 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9115 to both languages. Whenever this is the case, we discuss those languages
9119 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9120 @cindex @sc{gnu} C@t{++}
9121 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9122 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9123 effectively, you must compile your C@t{++} programs with a supported
9124 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9125 compiler (@code{aCC}).
9127 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9128 format; if it doesn't work on your system, try the stabs+ debugging
9129 format. You can select those formats explicitly with the @code{g++}
9130 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9131 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9132 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9135 * C Operators:: C and C@t{++} operators
9136 * C Constants:: C and C@t{++} constants
9137 * C Plus Plus Expressions:: C@t{++} expressions
9138 * C Defaults:: Default settings for C and C@t{++}
9139 * C Checks:: C and C@t{++} type and range checks
9140 * Debugging C:: @value{GDBN} and C
9141 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9145 @subsubsection C and C@t{++} Operators
9147 @cindex C and C@t{++} operators
9149 Operators must be defined on values of specific types. For instance,
9150 @code{+} is defined on numbers, but not on structures. Operators are
9151 often defined on groups of types.
9153 For the purposes of C and C@t{++}, the following definitions hold:
9158 @emph{Integral types} include @code{int} with any of its storage-class
9159 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9162 @emph{Floating-point types} include @code{float}, @code{double}, and
9163 @code{long double} (if supported by the target platform).
9166 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9169 @emph{Scalar types} include all of the above.
9174 The following operators are supported. They are listed here
9175 in order of increasing precedence:
9179 The comma or sequencing operator. Expressions in a comma-separated list
9180 are evaluated from left to right, with the result of the entire
9181 expression being the last expression evaluated.
9184 Assignment. The value of an assignment expression is the value
9185 assigned. Defined on scalar types.
9188 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9189 and translated to @w{@code{@var{a} = @var{a op b}}}.
9190 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9191 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9192 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9195 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9196 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9200 Logical @sc{or}. Defined on integral types.
9203 Logical @sc{and}. Defined on integral types.
9206 Bitwise @sc{or}. Defined on integral types.
9209 Bitwise exclusive-@sc{or}. Defined on integral types.
9212 Bitwise @sc{and}. Defined on integral types.
9215 Equality and inequality. Defined on scalar types. The value of these
9216 expressions is 0 for false and non-zero for true.
9218 @item <@r{, }>@r{, }<=@r{, }>=
9219 Less than, greater than, less than or equal, greater than or equal.
9220 Defined on scalar types. The value of these expressions is 0 for false
9221 and non-zero for true.
9224 left shift, and right shift. Defined on integral types.
9227 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9230 Addition and subtraction. Defined on integral types, floating-point types and
9233 @item *@r{, }/@r{, }%
9234 Multiplication, division, and modulus. Multiplication and division are
9235 defined on integral and floating-point types. Modulus is defined on
9239 Increment and decrement. When appearing before a variable, the
9240 operation is performed before the variable is used in an expression;
9241 when appearing after it, the variable's value is used before the
9242 operation takes place.
9245 Pointer dereferencing. Defined on pointer types. Same precedence as
9249 Address operator. Defined on variables. Same precedence as @code{++}.
9251 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9252 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9253 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
9254 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9258 Negative. Defined on integral and floating-point types. Same
9259 precedence as @code{++}.
9262 Logical negation. Defined on integral types. Same precedence as
9266 Bitwise complement operator. Defined on integral types. Same precedence as
9271 Structure member, and pointer-to-structure member. For convenience,
9272 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9273 pointer based on the stored type information.
9274 Defined on @code{struct} and @code{union} data.
9277 Dereferences of pointers to members.
9280 Array indexing. @code{@var{a}[@var{i}]} is defined as
9281 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9284 Function parameter list. Same precedence as @code{->}.
9287 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9288 and @code{class} types.
9291 Doubled colons also represent the @value{GDBN} scope operator
9292 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9296 If an operator is redefined in the user code, @value{GDBN} usually
9297 attempts to invoke the redefined version instead of using the operator's
9301 @subsubsection C and C@t{++} Constants
9303 @cindex C and C@t{++} constants
9305 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9310 Integer constants are a sequence of digits. Octal constants are
9311 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9312 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9313 @samp{l}, specifying that the constant should be treated as a
9317 Floating point constants are a sequence of digits, followed by a decimal
9318 point, followed by a sequence of digits, and optionally followed by an
9319 exponent. An exponent is of the form:
9320 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9321 sequence of digits. The @samp{+} is optional for positive exponents.
9322 A floating-point constant may also end with a letter @samp{f} or
9323 @samp{F}, specifying that the constant should be treated as being of
9324 the @code{float} (as opposed to the default @code{double}) type; or with
9325 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9329 Enumerated constants consist of enumerated identifiers, or their
9330 integral equivalents.
9333 Character constants are a single character surrounded by single quotes
9334 (@code{'}), or a number---the ordinal value of the corresponding character
9335 (usually its @sc{ascii} value). Within quotes, the single character may
9336 be represented by a letter or by @dfn{escape sequences}, which are of
9337 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9338 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9339 @samp{@var{x}} is a predefined special character---for example,
9340 @samp{\n} for newline.
9343 String constants are a sequence of character constants surrounded by
9344 double quotes (@code{"}). Any valid character constant (as described
9345 above) may appear. Double quotes within the string must be preceded by
9346 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9350 Pointer constants are an integral value. You can also write pointers
9351 to constants using the C operator @samp{&}.
9354 Array constants are comma-separated lists surrounded by braces @samp{@{}
9355 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9356 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9357 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9360 @node C Plus Plus Expressions
9361 @subsubsection C@t{++} Expressions
9363 @cindex expressions in C@t{++}
9364 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9366 @cindex debugging C@t{++} programs
9367 @cindex C@t{++} compilers
9368 @cindex debug formats and C@t{++}
9369 @cindex @value{NGCC} and C@t{++}
9371 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9372 proper compiler and the proper debug format. Currently, @value{GDBN}
9373 works best when debugging C@t{++} code that is compiled with
9374 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9375 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9376 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9377 stabs+ as their default debug format, so you usually don't need to
9378 specify a debug format explicitly. Other compilers and/or debug formats
9379 are likely to work badly or not at all when using @value{GDBN} to debug
9385 @cindex member functions
9387 Member function calls are allowed; you can use expressions like
9390 count = aml->GetOriginal(x, y)
9393 @vindex this@r{, inside C@t{++} member functions}
9394 @cindex namespace in C@t{++}
9396 While a member function is active (in the selected stack frame), your
9397 expressions have the same namespace available as the member function;
9398 that is, @value{GDBN} allows implicit references to the class instance
9399 pointer @code{this} following the same rules as C@t{++}.
9401 @cindex call overloaded functions
9402 @cindex overloaded functions, calling
9403 @cindex type conversions in C@t{++}
9405 You can call overloaded functions; @value{GDBN} resolves the function
9406 call to the right definition, with some restrictions. @value{GDBN} does not
9407 perform overload resolution involving user-defined type conversions,
9408 calls to constructors, or instantiations of templates that do not exist
9409 in the program. It also cannot handle ellipsis argument lists or
9412 It does perform integral conversions and promotions, floating-point
9413 promotions, arithmetic conversions, pointer conversions, conversions of
9414 class objects to base classes, and standard conversions such as those of
9415 functions or arrays to pointers; it requires an exact match on the
9416 number of function arguments.
9418 Overload resolution is always performed, unless you have specified
9419 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9420 ,@value{GDBN} Features for C@t{++}}.
9422 You must specify @code{set overload-resolution off} in order to use an
9423 explicit function signature to call an overloaded function, as in
9425 p 'foo(char,int)'('x', 13)
9428 The @value{GDBN} command-completion facility can simplify this;
9429 see @ref{Completion, ,Command Completion}.
9431 @cindex reference declarations
9433 @value{GDBN} understands variables declared as C@t{++} references; you can use
9434 them in expressions just as you do in C@t{++} source---they are automatically
9437 In the parameter list shown when @value{GDBN} displays a frame, the values of
9438 reference variables are not displayed (unlike other variables); this
9439 avoids clutter, since references are often used for large structures.
9440 The @emph{address} of a reference variable is always shown, unless
9441 you have specified @samp{set print address off}.
9444 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9445 expressions can use it just as expressions in your program do. Since
9446 one scope may be defined in another, you can use @code{::} repeatedly if
9447 necessary, for example in an expression like
9448 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9449 resolving name scope by reference to source files, in both C and C@t{++}
9450 debugging (@pxref{Variables, ,Program Variables}).
9453 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9454 calling virtual functions correctly, printing out virtual bases of
9455 objects, calling functions in a base subobject, casting objects, and
9456 invoking user-defined operators.
9459 @subsubsection C and C@t{++} Defaults
9461 @cindex C and C@t{++} defaults
9463 If you allow @value{GDBN} to set type and range checking automatically, they
9464 both default to @code{off} whenever the working language changes to
9465 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9466 selects the working language.
9468 If you allow @value{GDBN} to set the language automatically, it
9469 recognizes source files whose names end with @file{.c}, @file{.C}, or
9470 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9471 these files, it sets the working language to C or C@t{++}.
9472 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9473 for further details.
9475 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9476 @c unimplemented. If (b) changes, it might make sense to let this node
9477 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9480 @subsubsection C and C@t{++} Type and Range Checks
9482 @cindex C and C@t{++} checks
9484 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9485 is not used. However, if you turn type checking on, @value{GDBN}
9486 considers two variables type equivalent if:
9490 The two variables are structured and have the same structure, union, or
9494 The two variables have the same type name, or types that have been
9495 declared equivalent through @code{typedef}.
9498 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9501 The two @code{struct}, @code{union}, or @code{enum} variables are
9502 declared in the same declaration. (Note: this may not be true for all C
9507 Range checking, if turned on, is done on mathematical operations. Array
9508 indices are not checked, since they are often used to index a pointer
9509 that is not itself an array.
9512 @subsubsection @value{GDBN} and C
9514 The @code{set print union} and @code{show print union} commands apply to
9515 the @code{union} type. When set to @samp{on}, any @code{union} that is
9516 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9517 appears as @samp{@{...@}}.
9519 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9520 with pointers and a memory allocation function. @xref{Expressions,
9523 @node Debugging C Plus Plus
9524 @subsubsection @value{GDBN} Features for C@t{++}
9526 @cindex commands for C@t{++}
9528 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9529 designed specifically for use with C@t{++}. Here is a summary:
9532 @cindex break in overloaded functions
9533 @item @r{breakpoint menus}
9534 When you want a breakpoint in a function whose name is overloaded,
9535 @value{GDBN} breakpoint menus help you specify which function definition
9536 you want. @xref{Breakpoint Menus,,Breakpoint Menus}.
9538 @cindex overloading in C@t{++}
9539 @item rbreak @var{regex}
9540 Setting breakpoints using regular expressions is helpful for setting
9541 breakpoints on overloaded functions that are not members of any special
9543 @xref{Set Breaks, ,Setting Breakpoints}.
9545 @cindex C@t{++} exception handling
9548 Debug C@t{++} exception handling using these commands. @xref{Set
9549 Catchpoints, , Setting Catchpoints}.
9552 @item ptype @var{typename}
9553 Print inheritance relationships as well as other information for type
9555 @xref{Symbols, ,Examining the Symbol Table}.
9557 @cindex C@t{++} symbol display
9558 @item set print demangle
9559 @itemx show print demangle
9560 @itemx set print asm-demangle
9561 @itemx show print asm-demangle
9562 Control whether C@t{++} symbols display in their source form, both when
9563 displaying code as C@t{++} source and when displaying disassemblies.
9564 @xref{Print Settings, ,Print Settings}.
9566 @item set print object
9567 @itemx show print object
9568 Choose whether to print derived (actual) or declared types of objects.
9569 @xref{Print Settings, ,Print Settings}.
9571 @item set print vtbl
9572 @itemx show print vtbl
9573 Control the format for printing virtual function tables.
9574 @xref{Print Settings, ,Print Settings}.
9575 (The @code{vtbl} commands do not work on programs compiled with the HP
9576 ANSI C@t{++} compiler (@code{aCC}).)
9578 @kindex set overload-resolution
9579 @cindex overloaded functions, overload resolution
9580 @item set overload-resolution on
9581 Enable overload resolution for C@t{++} expression evaluation. The default
9582 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9583 and searches for a function whose signature matches the argument types,
9584 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9585 Expressions, ,C@t{++} Expressions}, for details).
9586 If it cannot find a match, it emits a message.
9588 @item set overload-resolution off
9589 Disable overload resolution for C@t{++} expression evaluation. For
9590 overloaded functions that are not class member functions, @value{GDBN}
9591 chooses the first function of the specified name that it finds in the
9592 symbol table, whether or not its arguments are of the correct type. For
9593 overloaded functions that are class member functions, @value{GDBN}
9594 searches for a function whose signature @emph{exactly} matches the
9597 @kindex show overload-resolution
9598 @item show overload-resolution
9599 Show the current setting of overload resolution.
9601 @item @r{Overloaded symbol names}
9602 You can specify a particular definition of an overloaded symbol, using
9603 the same notation that is used to declare such symbols in C@t{++}: type
9604 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9605 also use the @value{GDBN} command-line word completion facilities to list the
9606 available choices, or to finish the type list for you.
9607 @xref{Completion,, Command Completion}, for details on how to do this.
9611 @subsection Objective-C
9614 This section provides information about some commands and command
9615 options that are useful for debugging Objective-C code. See also
9616 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9617 few more commands specific to Objective-C support.
9620 * Method Names in Commands::
9621 * The Print Command with Objective-C::
9624 @node Method Names in Commands
9625 @subsubsection Method Names in Commands
9627 The following commands have been extended to accept Objective-C method
9628 names as line specifications:
9630 @kindex clear@r{, and Objective-C}
9631 @kindex break@r{, and Objective-C}
9632 @kindex info line@r{, and Objective-C}
9633 @kindex jump@r{, and Objective-C}
9634 @kindex list@r{, and Objective-C}
9638 @item @code{info line}
9643 A fully qualified Objective-C method name is specified as
9646 -[@var{Class} @var{methodName}]
9649 where the minus sign is used to indicate an instance method and a
9650 plus sign (not shown) is used to indicate a class method. The class
9651 name @var{Class} and method name @var{methodName} are enclosed in
9652 brackets, similar to the way messages are specified in Objective-C
9653 source code. For example, to set a breakpoint at the @code{create}
9654 instance method of class @code{Fruit} in the program currently being
9658 break -[Fruit create]
9661 To list ten program lines around the @code{initialize} class method,
9665 list +[NSText initialize]
9668 In the current version of @value{GDBN}, the plus or minus sign is
9669 required. In future versions of @value{GDBN}, the plus or minus
9670 sign will be optional, but you can use it to narrow the search. It
9671 is also possible to specify just a method name:
9677 You must specify the complete method name, including any colons. If
9678 your program's source files contain more than one @code{create} method,
9679 you'll be presented with a numbered list of classes that implement that
9680 method. Indicate your choice by number, or type @samp{0} to exit if
9683 As another example, to clear a breakpoint established at the
9684 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9687 clear -[NSWindow makeKeyAndOrderFront:]
9690 @node The Print Command with Objective-C
9691 @subsubsection The Print Command With Objective-C
9692 @cindex Objective-C, print objects
9693 @kindex print-object
9694 @kindex po @r{(@code{print-object})}
9696 The print command has also been extended to accept methods. For example:
9699 print -[@var{object} hash]
9702 @cindex print an Objective-C object description
9703 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9705 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9706 and print the result. Also, an additional command has been added,
9707 @code{print-object} or @code{po} for short, which is meant to print
9708 the description of an object. However, this command may only work
9709 with certain Objective-C libraries that have a particular hook
9710 function, @code{_NSPrintForDebugger}, defined.
9714 @cindex Fortran-specific support in @value{GDBN}
9716 @value{GDBN} can be used to debug programs written in Fortran, but it
9717 currently supports only the features of Fortran 77 language.
9719 @cindex trailing underscore, in Fortran symbols
9720 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9721 among them) append an underscore to the names of variables and
9722 functions. When you debug programs compiled by those compilers, you
9723 will need to refer to variables and functions with a trailing
9727 * Fortran Operators:: Fortran operators and expressions
9728 * Fortran Defaults:: Default settings for Fortran
9729 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
9732 @node Fortran Operators
9733 @subsubsection Fortran Operators and Expressions
9735 @cindex Fortran operators and expressions
9737 Operators must be defined on values of specific types. For instance,
9738 @code{+} is defined on numbers, but not on characters or other non-
9739 arithmetic types. Operators are often defined on groups of types.
9743 The exponentiation operator. It raises the first operand to the power
9747 The range operator. Normally used in the form of array(low:high) to
9748 represent a section of array.
9751 @node Fortran Defaults
9752 @subsubsection Fortran Defaults
9754 @cindex Fortran Defaults
9756 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9757 default uses case-insensitive matches for Fortran symbols. You can
9758 change that with the @samp{set case-insensitive} command, see
9759 @ref{Symbols}, for the details.
9761 @node Special Fortran Commands
9762 @subsubsection Special Fortran Commands
9764 @cindex Special Fortran commands
9766 @value{GDBN} has some commands to support Fortran-specific features,
9767 such as displaying common blocks.
9770 @cindex @code{COMMON} blocks, Fortran
9772 @item info common @r{[}@var{common-name}@r{]}
9773 This command prints the values contained in the Fortran @code{COMMON}
9774 block whose name is @var{common-name}. With no argument, the names of
9775 all @code{COMMON} blocks visible at the current program location are
9782 @cindex Pascal support in @value{GDBN}, limitations
9783 Debugging Pascal programs which use sets, subranges, file variables, or
9784 nested functions does not currently work. @value{GDBN} does not support
9785 entering expressions, printing values, or similar features using Pascal
9788 The Pascal-specific command @code{set print pascal_static-members}
9789 controls whether static members of Pascal objects are displayed.
9790 @xref{Print Settings, pascal_static-members}.
9793 @subsection Modula-2
9795 @cindex Modula-2, @value{GDBN} support
9797 The extensions made to @value{GDBN} to support Modula-2 only support
9798 output from the @sc{gnu} Modula-2 compiler (which is currently being
9799 developed). Other Modula-2 compilers are not currently supported, and
9800 attempting to debug executables produced by them is most likely
9801 to give an error as @value{GDBN} reads in the executable's symbol
9804 @cindex expressions in Modula-2
9806 * M2 Operators:: Built-in operators
9807 * Built-In Func/Proc:: Built-in functions and procedures
9808 * M2 Constants:: Modula-2 constants
9809 * M2 Types:: Modula-2 types
9810 * M2 Defaults:: Default settings for Modula-2
9811 * Deviations:: Deviations from standard Modula-2
9812 * M2 Checks:: Modula-2 type and range checks
9813 * M2 Scope:: The scope operators @code{::} and @code{.}
9814 * GDB/M2:: @value{GDBN} and Modula-2
9818 @subsubsection Operators
9819 @cindex Modula-2 operators
9821 Operators must be defined on values of specific types. For instance,
9822 @code{+} is defined on numbers, but not on structures. Operators are
9823 often defined on groups of types. For the purposes of Modula-2, the
9824 following definitions hold:
9829 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9833 @emph{Character types} consist of @code{CHAR} and its subranges.
9836 @emph{Floating-point types} consist of @code{REAL}.
9839 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9843 @emph{Scalar types} consist of all of the above.
9846 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9849 @emph{Boolean types} consist of @code{BOOLEAN}.
9853 The following operators are supported, and appear in order of
9854 increasing precedence:
9858 Function argument or array index separator.
9861 Assignment. The value of @var{var} @code{:=} @var{value} is
9865 Less than, greater than on integral, floating-point, or enumerated
9869 Less than or equal to, greater than or equal to
9870 on integral, floating-point and enumerated types, or set inclusion on
9871 set types. Same precedence as @code{<}.
9873 @item =@r{, }<>@r{, }#
9874 Equality and two ways of expressing inequality, valid on scalar types.
9875 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9876 available for inequality, since @code{#} conflicts with the script
9880 Set membership. Defined on set types and the types of their members.
9881 Same precedence as @code{<}.
9884 Boolean disjunction. Defined on boolean types.
9887 Boolean conjunction. Defined on boolean types.
9890 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9893 Addition and subtraction on integral and floating-point types, or union
9894 and difference on set types.
9897 Multiplication on integral and floating-point types, or set intersection
9901 Division on floating-point types, or symmetric set difference on set
9902 types. Same precedence as @code{*}.
9905 Integer division and remainder. Defined on integral types. Same
9906 precedence as @code{*}.
9909 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9912 Pointer dereferencing. Defined on pointer types.
9915 Boolean negation. Defined on boolean types. Same precedence as
9919 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9920 precedence as @code{^}.
9923 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9926 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9930 @value{GDBN} and Modula-2 scope operators.
9934 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9935 treats the use of the operator @code{IN}, or the use of operators
9936 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9937 @code{<=}, and @code{>=} on sets as an error.
9941 @node Built-In Func/Proc
9942 @subsubsection Built-in Functions and Procedures
9943 @cindex Modula-2 built-ins
9945 Modula-2 also makes available several built-in procedures and functions.
9946 In describing these, the following metavariables are used:
9951 represents an @code{ARRAY} variable.
9954 represents a @code{CHAR} constant or variable.
9957 represents a variable or constant of integral type.
9960 represents an identifier that belongs to a set. Generally used in the
9961 same function with the metavariable @var{s}. The type of @var{s} should
9962 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9965 represents a variable or constant of integral or floating-point type.
9968 represents a variable or constant of floating-point type.
9974 represents a variable.
9977 represents a variable or constant of one of many types. See the
9978 explanation of the function for details.
9981 All Modula-2 built-in procedures also return a result, described below.
9985 Returns the absolute value of @var{n}.
9988 If @var{c} is a lower case letter, it returns its upper case
9989 equivalent, otherwise it returns its argument.
9992 Returns the character whose ordinal value is @var{i}.
9995 Decrements the value in the variable @var{v} by one. Returns the new value.
9997 @item DEC(@var{v},@var{i})
9998 Decrements the value in the variable @var{v} by @var{i}. Returns the
10001 @item EXCL(@var{m},@var{s})
10002 Removes the element @var{m} from the set @var{s}. Returns the new
10005 @item FLOAT(@var{i})
10006 Returns the floating point equivalent of the integer @var{i}.
10008 @item HIGH(@var{a})
10009 Returns the index of the last member of @var{a}.
10012 Increments the value in the variable @var{v} by one. Returns the new value.
10014 @item INC(@var{v},@var{i})
10015 Increments the value in the variable @var{v} by @var{i}. Returns the
10018 @item INCL(@var{m},@var{s})
10019 Adds the element @var{m} to the set @var{s} if it is not already
10020 there. Returns the new set.
10023 Returns the maximum value of the type @var{t}.
10026 Returns the minimum value of the type @var{t}.
10029 Returns boolean TRUE if @var{i} is an odd number.
10032 Returns the ordinal value of its argument. For example, the ordinal
10033 value of a character is its @sc{ascii} value (on machines supporting the
10034 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10035 integral, character and enumerated types.
10037 @item SIZE(@var{x})
10038 Returns the size of its argument. @var{x} can be a variable or a type.
10040 @item TRUNC(@var{r})
10041 Returns the integral part of @var{r}.
10043 @item TSIZE(@var{x})
10044 Returns the size of its argument. @var{x} can be a variable or a type.
10046 @item VAL(@var{t},@var{i})
10047 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10051 @emph{Warning:} Sets and their operations are not yet supported, so
10052 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10056 @cindex Modula-2 constants
10058 @subsubsection Constants
10060 @value{GDBN} allows you to express the constants of Modula-2 in the following
10066 Integer constants are simply a sequence of digits. When used in an
10067 expression, a constant is interpreted to be type-compatible with the
10068 rest of the expression. Hexadecimal integers are specified by a
10069 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10072 Floating point constants appear as a sequence of digits, followed by a
10073 decimal point and another sequence of digits. An optional exponent can
10074 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10075 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10076 digits of the floating point constant must be valid decimal (base 10)
10080 Character constants consist of a single character enclosed by a pair of
10081 like quotes, either single (@code{'}) or double (@code{"}). They may
10082 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10083 followed by a @samp{C}.
10086 String constants consist of a sequence of characters enclosed by a
10087 pair of like quotes, either single (@code{'}) or double (@code{"}).
10088 Escape sequences in the style of C are also allowed. @xref{C
10089 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10093 Enumerated constants consist of an enumerated identifier.
10096 Boolean constants consist of the identifiers @code{TRUE} and
10100 Pointer constants consist of integral values only.
10103 Set constants are not yet supported.
10107 @subsubsection Modula-2 Types
10108 @cindex Modula-2 types
10110 Currently @value{GDBN} can print the following data types in Modula-2
10111 syntax: array types, record types, set types, pointer types, procedure
10112 types, enumerated types, subrange types and base types. You can also
10113 print the contents of variables declared using these type.
10114 This section gives a number of simple source code examples together with
10115 sample @value{GDBN} sessions.
10117 The first example contains the following section of code:
10126 and you can request @value{GDBN} to interrogate the type and value of
10127 @code{r} and @code{s}.
10130 (@value{GDBP}) print s
10132 (@value{GDBP}) ptype s
10134 (@value{GDBP}) print r
10136 (@value{GDBP}) ptype r
10141 Likewise if your source code declares @code{s} as:
10145 s: SET ['A'..'Z'] ;
10149 then you may query the type of @code{s} by:
10152 (@value{GDBP}) ptype s
10153 type = SET ['A'..'Z']
10157 Note that at present you cannot interactively manipulate set
10158 expressions using the debugger.
10160 The following example shows how you might declare an array in Modula-2
10161 and how you can interact with @value{GDBN} to print its type and contents:
10165 s: ARRAY [-10..10] OF CHAR ;
10169 (@value{GDBP}) ptype s
10170 ARRAY [-10..10] OF CHAR
10173 Note that the array handling is not yet complete and although the type
10174 is printed correctly, expression handling still assumes that all
10175 arrays have a lower bound of zero and not @code{-10} as in the example
10178 Here are some more type related Modula-2 examples:
10182 colour = (blue, red, yellow, green) ;
10183 t = [blue..yellow] ;
10191 The @value{GDBN} interaction shows how you can query the data type
10192 and value of a variable.
10195 (@value{GDBP}) print s
10197 (@value{GDBP}) ptype t
10198 type = [blue..yellow]
10202 In this example a Modula-2 array is declared and its contents
10203 displayed. Observe that the contents are written in the same way as
10204 their @code{C} counterparts.
10208 s: ARRAY [1..5] OF CARDINAL ;
10214 (@value{GDBP}) print s
10215 $1 = @{1, 0, 0, 0, 0@}
10216 (@value{GDBP}) ptype s
10217 type = ARRAY [1..5] OF CARDINAL
10220 The Modula-2 language interface to @value{GDBN} also understands
10221 pointer types as shown in this example:
10225 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10232 and you can request that @value{GDBN} describes the type of @code{s}.
10235 (@value{GDBP}) ptype s
10236 type = POINTER TO ARRAY [1..5] OF CARDINAL
10239 @value{GDBN} handles compound types as we can see in this example.
10240 Here we combine array types, record types, pointer types and subrange
10251 myarray = ARRAY myrange OF CARDINAL ;
10252 myrange = [-2..2] ;
10254 s: POINTER TO ARRAY myrange OF foo ;
10258 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10262 (@value{GDBP}) ptype s
10263 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10266 f3 : ARRAY [-2..2] OF CARDINAL;
10271 @subsubsection Modula-2 Defaults
10272 @cindex Modula-2 defaults
10274 If type and range checking are set automatically by @value{GDBN}, they
10275 both default to @code{on} whenever the working language changes to
10276 Modula-2. This happens regardless of whether you or @value{GDBN}
10277 selected the working language.
10279 If you allow @value{GDBN} to set the language automatically, then entering
10280 code compiled from a file whose name ends with @file{.mod} sets the
10281 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10282 Infer the Source Language}, for further details.
10285 @subsubsection Deviations from Standard Modula-2
10286 @cindex Modula-2, deviations from
10288 A few changes have been made to make Modula-2 programs easier to debug.
10289 This is done primarily via loosening its type strictness:
10293 Unlike in standard Modula-2, pointer constants can be formed by
10294 integers. This allows you to modify pointer variables during
10295 debugging. (In standard Modula-2, the actual address contained in a
10296 pointer variable is hidden from you; it can only be modified
10297 through direct assignment to another pointer variable or expression that
10298 returned a pointer.)
10301 C escape sequences can be used in strings and characters to represent
10302 non-printable characters. @value{GDBN} prints out strings with these
10303 escape sequences embedded. Single non-printable characters are
10304 printed using the @samp{CHR(@var{nnn})} format.
10307 The assignment operator (@code{:=}) returns the value of its right-hand
10311 All built-in procedures both modify @emph{and} return their argument.
10315 @subsubsection Modula-2 Type and Range Checks
10316 @cindex Modula-2 checks
10319 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10322 @c FIXME remove warning when type/range checks added
10324 @value{GDBN} considers two Modula-2 variables type equivalent if:
10328 They are of types that have been declared equivalent via a @code{TYPE
10329 @var{t1} = @var{t2}} statement
10332 They have been declared on the same line. (Note: This is true of the
10333 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10336 As long as type checking is enabled, any attempt to combine variables
10337 whose types are not equivalent is an error.
10339 Range checking is done on all mathematical operations, assignment, array
10340 index bounds, and all built-in functions and procedures.
10343 @subsubsection The Scope Operators @code{::} and @code{.}
10345 @cindex @code{.}, Modula-2 scope operator
10346 @cindex colon, doubled as scope operator
10348 @vindex colon-colon@r{, in Modula-2}
10349 @c Info cannot handle :: but TeX can.
10352 @vindex ::@r{, in Modula-2}
10355 There are a few subtle differences between the Modula-2 scope operator
10356 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10361 @var{module} . @var{id}
10362 @var{scope} :: @var{id}
10366 where @var{scope} is the name of a module or a procedure,
10367 @var{module} the name of a module, and @var{id} is any declared
10368 identifier within your program, except another module.
10370 Using the @code{::} operator makes @value{GDBN} search the scope
10371 specified by @var{scope} for the identifier @var{id}. If it is not
10372 found in the specified scope, then @value{GDBN} searches all scopes
10373 enclosing the one specified by @var{scope}.
10375 Using the @code{.} operator makes @value{GDBN} search the current scope for
10376 the identifier specified by @var{id} that was imported from the
10377 definition module specified by @var{module}. With this operator, it is
10378 an error if the identifier @var{id} was not imported from definition
10379 module @var{module}, or if @var{id} is not an identifier in
10383 @subsubsection @value{GDBN} and Modula-2
10385 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10386 Five subcommands of @code{set print} and @code{show print} apply
10387 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10388 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10389 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10390 analogue in Modula-2.
10392 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10393 with any language, is not useful with Modula-2. Its
10394 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10395 created in Modula-2 as they can in C or C@t{++}. However, because an
10396 address can be specified by an integral constant, the construct
10397 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10399 @cindex @code{#} in Modula-2
10400 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10401 interpreted as the beginning of a comment. Use @code{<>} instead.
10407 The extensions made to @value{GDBN} for Ada only support
10408 output from the @sc{gnu} Ada (GNAT) compiler.
10409 Other Ada compilers are not currently supported, and
10410 attempting to debug executables produced by them is most likely
10414 @cindex expressions in Ada
10416 * Ada Mode Intro:: General remarks on the Ada syntax
10417 and semantics supported by Ada mode
10419 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10420 * Additions to Ada:: Extensions of the Ada expression syntax.
10421 * Stopping Before Main Program:: Debugging the program during elaboration.
10422 * Ada Glitches:: Known peculiarities of Ada mode.
10425 @node Ada Mode Intro
10426 @subsubsection Introduction
10427 @cindex Ada mode, general
10429 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10430 syntax, with some extensions.
10431 The philosophy behind the design of this subset is
10435 That @value{GDBN} should provide basic literals and access to operations for
10436 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10437 leaving more sophisticated computations to subprograms written into the
10438 program (which therefore may be called from @value{GDBN}).
10441 That type safety and strict adherence to Ada language restrictions
10442 are not particularly important to the @value{GDBN} user.
10445 That brevity is important to the @value{GDBN} user.
10448 Thus, for brevity, the debugger acts as if there were
10449 implicit @code{with} and @code{use} clauses in effect for all user-written
10450 packages, making it unnecessary to fully qualify most names with
10451 their packages, regardless of context. Where this causes ambiguity,
10452 @value{GDBN} asks the user's intent.
10454 The debugger will start in Ada mode if it detects an Ada main program.
10455 As for other languages, it will enter Ada mode when stopped in a program that
10456 was translated from an Ada source file.
10458 While in Ada mode, you may use `@t{--}' for comments. This is useful
10459 mostly for documenting command files. The standard @value{GDBN} comment
10460 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10461 middle (to allow based literals).
10463 The debugger supports limited overloading. Given a subprogram call in which
10464 the function symbol has multiple definitions, it will use the number of
10465 actual parameters and some information about their types to attempt to narrow
10466 the set of definitions. It also makes very limited use of context, preferring
10467 procedures to functions in the context of the @code{call} command, and
10468 functions to procedures elsewhere.
10470 @node Omissions from Ada
10471 @subsubsection Omissions from Ada
10472 @cindex Ada, omissions from
10474 Here are the notable omissions from the subset:
10478 Only a subset of the attributes are supported:
10482 @t{'First}, @t{'Last}, and @t{'Length}
10483 on array objects (not on types and subtypes).
10486 @t{'Min} and @t{'Max}.
10489 @t{'Pos} and @t{'Val}.
10495 @t{'Range} on array objects (not subtypes), but only as the right
10496 operand of the membership (@code{in}) operator.
10499 @t{'Access}, @t{'Unchecked_Access}, and
10500 @t{'Unrestricted_Access} (a GNAT extension).
10508 @code{Characters.Latin_1} are not available and
10509 concatenation is not implemented. Thus, escape characters in strings are
10510 not currently available.
10513 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10514 equality of representations. They will generally work correctly
10515 for strings and arrays whose elements have integer or enumeration types.
10516 They may not work correctly for arrays whose element
10517 types have user-defined equality, for arrays of real values
10518 (in particular, IEEE-conformant floating point, because of negative
10519 zeroes and NaNs), and for arrays whose elements contain unused bits with
10520 indeterminate values.
10523 The other component-by-component array operations (@code{and}, @code{or},
10524 @code{xor}, @code{not}, and relational tests other than equality)
10525 are not implemented.
10528 @cindex array aggregates (Ada)
10529 @cindex record aggregates (Ada)
10530 @cindex aggregates (Ada)
10531 There is limited support for array and record aggregates. They are
10532 permitted only on the right sides of assignments, as in these examples:
10535 set An_Array := (1, 2, 3, 4, 5, 6)
10536 set An_Array := (1, others => 0)
10537 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10538 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10539 set A_Record := (1, "Peter", True);
10540 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10544 discriminant's value by assigning an aggregate has an
10545 undefined effect if that discriminant is used within the record.
10546 However, you can first modify discriminants by directly assigning to
10547 them (which normally would not be allowed in Ada), and then performing an
10548 aggregate assignment. For example, given a variable @code{A_Rec}
10549 declared to have a type such as:
10552 type Rec (Len : Small_Integer := 0) is record
10554 Vals : IntArray (1 .. Len);
10558 you can assign a value with a different size of @code{Vals} with two
10563 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10566 As this example also illustrates, @value{GDBN} is very loose about the usual
10567 rules concerning aggregates. You may leave out some of the
10568 components of an array or record aggregate (such as the @code{Len}
10569 component in the assignment to @code{A_Rec} above); they will retain their
10570 original values upon assignment. You may freely use dynamic values as
10571 indices in component associations. You may even use overlapping or
10572 redundant component associations, although which component values are
10573 assigned in such cases is not defined.
10576 Calls to dispatching subprograms are not implemented.
10579 The overloading algorithm is much more limited (i.e., less selective)
10580 than that of real Ada. It makes only limited use of the context in
10581 which a subexpression appears to resolve its meaning, and it is much
10582 looser in its rules for allowing type matches. As a result, some
10583 function calls will be ambiguous, and the user will be asked to choose
10584 the proper resolution.
10587 The @code{new} operator is not implemented.
10590 Entry calls are not implemented.
10593 Aside from printing, arithmetic operations on the native VAX floating-point
10594 formats are not supported.
10597 It is not possible to slice a packed array.
10600 @node Additions to Ada
10601 @subsubsection Additions to Ada
10602 @cindex Ada, deviations from
10604 As it does for other languages, @value{GDBN} makes certain generic
10605 extensions to Ada (@pxref{Expressions}):
10609 If the expression @var{E} is a variable residing in memory (typically
10610 a local variable or array element) and @var{N} is a positive integer,
10611 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10612 @var{N}-1 adjacent variables following it in memory as an array. In
10613 Ada, this operator is generally not necessary, since its prime use is
10614 in displaying parts of an array, and slicing will usually do this in
10615 Ada. However, there are occasional uses when debugging programs in
10616 which certain debugging information has been optimized away.
10619 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10620 appears in function or file @var{B}.'' When @var{B} is a file name,
10621 you must typically surround it in single quotes.
10624 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10625 @var{type} that appears at address @var{addr}.''
10628 A name starting with @samp{$} is a convenience variable
10629 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10632 In addition, @value{GDBN} provides a few other shortcuts and outright
10633 additions specific to Ada:
10637 The assignment statement is allowed as an expression, returning
10638 its right-hand operand as its value. Thus, you may enter
10642 print A(tmp := y + 1)
10646 The semicolon is allowed as an ``operator,'' returning as its value
10647 the value of its right-hand operand.
10648 This allows, for example,
10649 complex conditional breaks:
10653 condition 1 (report(i); k += 1; A(k) > 100)
10657 Rather than use catenation and symbolic character names to introduce special
10658 characters into strings, one may instead use a special bracket notation,
10659 which is also used to print strings. A sequence of characters of the form
10660 @samp{["@var{XX}"]} within a string or character literal denotes the
10661 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10662 sequence of characters @samp{["""]} also denotes a single quotation mark
10663 in strings. For example,
10665 "One line.["0a"]Next line.["0a"]"
10668 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10672 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10673 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10681 When printing arrays, @value{GDBN} uses positional notation when the
10682 array has a lower bound of 1, and uses a modified named notation otherwise.
10683 For example, a one-dimensional array of three integers with a lower bound
10684 of 3 might print as
10691 That is, in contrast to valid Ada, only the first component has a @code{=>}
10695 You may abbreviate attributes in expressions with any unique,
10696 multi-character subsequence of
10697 their names (an exact match gets preference).
10698 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10699 in place of @t{a'length}.
10702 @cindex quoting Ada internal identifiers
10703 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10704 to lower case. The GNAT compiler uses upper-case characters for
10705 some of its internal identifiers, which are normally of no interest to users.
10706 For the rare occasions when you actually have to look at them,
10707 enclose them in angle brackets to avoid the lower-case mapping.
10710 @value{GDBP} print <JMPBUF_SAVE>[0]
10714 Printing an object of class-wide type or dereferencing an
10715 access-to-class-wide value will display all the components of the object's
10716 specific type (as indicated by its run-time tag). Likewise, component
10717 selection on such a value will operate on the specific type of the
10722 @node Stopping Before Main Program
10723 @subsubsection Stopping at the Very Beginning
10725 @cindex breakpointing Ada elaboration code
10726 It is sometimes necessary to debug the program during elaboration, and
10727 before reaching the main procedure.
10728 As defined in the Ada Reference
10729 Manual, the elaboration code is invoked from a procedure called
10730 @code{adainit}. To run your program up to the beginning of
10731 elaboration, simply use the following two commands:
10732 @code{tbreak adainit} and @code{run}.
10735 @subsubsection Known Peculiarities of Ada Mode
10736 @cindex Ada, problems
10738 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10739 we know of several problems with and limitations of Ada mode in
10741 some of which will be fixed with planned future releases of the debugger
10742 and the GNU Ada compiler.
10746 Currently, the debugger
10747 has insufficient information to determine whether certain pointers represent
10748 pointers to objects or the objects themselves.
10749 Thus, the user may have to tack an extra @code{.all} after an expression
10750 to get it printed properly.
10753 Static constants that the compiler chooses not to materialize as objects in
10754 storage are invisible to the debugger.
10757 Named parameter associations in function argument lists are ignored (the
10758 argument lists are treated as positional).
10761 Many useful library packages are currently invisible to the debugger.
10764 Fixed-point arithmetic, conversions, input, and output is carried out using
10765 floating-point arithmetic, and may give results that only approximate those on
10769 The type of the @t{'Address} attribute may not be @code{System.Address}.
10772 The GNAT compiler never generates the prefix @code{Standard} for any of
10773 the standard symbols defined by the Ada language. @value{GDBN} knows about
10774 this: it will strip the prefix from names when you use it, and will never
10775 look for a name you have so qualified among local symbols, nor match against
10776 symbols in other packages or subprograms. If you have
10777 defined entities anywhere in your program other than parameters and
10778 local variables whose simple names match names in @code{Standard},
10779 GNAT's lack of qualification here can cause confusion. When this happens,
10780 you can usually resolve the confusion
10781 by qualifying the problematic names with package
10782 @code{Standard} explicitly.
10785 @node Unsupported Languages
10786 @section Unsupported Languages
10788 @cindex unsupported languages
10789 @cindex minimal language
10790 In addition to the other fully-supported programming languages,
10791 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10792 It does not represent a real programming language, but provides a set
10793 of capabilities close to what the C or assembly languages provide.
10794 This should allow most simple operations to be performed while debugging
10795 an application that uses a language currently not supported by @value{GDBN}.
10797 If the language is set to @code{auto}, @value{GDBN} will automatically
10798 select this language if the current frame corresponds to an unsupported
10802 @chapter Examining the Symbol Table
10804 The commands described in this chapter allow you to inquire about the
10805 symbols (names of variables, functions and types) defined in your
10806 program. This information is inherent in the text of your program and
10807 does not change as your program executes. @value{GDBN} finds it in your
10808 program's symbol table, in the file indicated when you started @value{GDBN}
10809 (@pxref{File Options, ,Choosing Files}), or by one of the
10810 file-management commands (@pxref{Files, ,Commands to Specify Files}).
10812 @cindex symbol names
10813 @cindex names of symbols
10814 @cindex quoting names
10815 Occasionally, you may need to refer to symbols that contain unusual
10816 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10817 most frequent case is in referring to static variables in other
10818 source files (@pxref{Variables,,Program Variables}). File names
10819 are recorded in object files as debugging symbols, but @value{GDBN} would
10820 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10821 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10822 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10829 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10832 @cindex case-insensitive symbol names
10833 @cindex case sensitivity in symbol names
10834 @kindex set case-sensitive
10835 @item set case-sensitive on
10836 @itemx set case-sensitive off
10837 @itemx set case-sensitive auto
10838 Normally, when @value{GDBN} looks up symbols, it matches their names
10839 with case sensitivity determined by the current source language.
10840 Occasionally, you may wish to control that. The command @code{set
10841 case-sensitive} lets you do that by specifying @code{on} for
10842 case-sensitive matches or @code{off} for case-insensitive ones. If
10843 you specify @code{auto}, case sensitivity is reset to the default
10844 suitable for the source language. The default is case-sensitive
10845 matches for all languages except for Fortran, for which the default is
10846 case-insensitive matches.
10848 @kindex show case-sensitive
10849 @item show case-sensitive
10850 This command shows the current setting of case sensitivity for symbols
10853 @kindex info address
10854 @cindex address of a symbol
10855 @item info address @var{symbol}
10856 Describe where the data for @var{symbol} is stored. For a register
10857 variable, this says which register it is kept in. For a non-register
10858 local variable, this prints the stack-frame offset at which the variable
10861 Note the contrast with @samp{print &@var{symbol}}, which does not work
10862 at all for a register variable, and for a stack local variable prints
10863 the exact address of the current instantiation of the variable.
10865 @kindex info symbol
10866 @cindex symbol from address
10867 @cindex closest symbol and offset for an address
10868 @item info symbol @var{addr}
10869 Print the name of a symbol which is stored at the address @var{addr}.
10870 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10871 nearest symbol and an offset from it:
10874 (@value{GDBP}) info symbol 0x54320
10875 _initialize_vx + 396 in section .text
10879 This is the opposite of the @code{info address} command. You can use
10880 it to find out the name of a variable or a function given its address.
10883 @item whatis [@var{arg}]
10884 Print the data type of @var{arg}, which can be either an expression or
10885 a data type. With no argument, print the data type of @code{$}, the
10886 last value in the value history. If @var{arg} is an expression, it is
10887 not actually evaluated, and any side-effecting operations (such as
10888 assignments or function calls) inside it do not take place. If
10889 @var{arg} is a type name, it may be the name of a type or typedef, or
10890 for C code it may have the form @samp{class @var{class-name}},
10891 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10892 @samp{enum @var{enum-tag}}.
10893 @xref{Expressions, ,Expressions}.
10896 @item ptype [@var{arg}]
10897 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10898 detailed description of the type, instead of just the name of the type.
10899 @xref{Expressions, ,Expressions}.
10901 For example, for this variable declaration:
10904 struct complex @{double real; double imag;@} v;
10908 the two commands give this output:
10912 (@value{GDBP}) whatis v
10913 type = struct complex
10914 (@value{GDBP}) ptype v
10915 type = struct complex @{
10923 As with @code{whatis}, using @code{ptype} without an argument refers to
10924 the type of @code{$}, the last value in the value history.
10926 @cindex incomplete type
10927 Sometimes, programs use opaque data types or incomplete specifications
10928 of complex data structure. If the debug information included in the
10929 program does not allow @value{GDBN} to display a full declaration of
10930 the data type, it will say @samp{<incomplete type>}. For example,
10931 given these declarations:
10935 struct foo *fooptr;
10939 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10942 (@value{GDBP}) ptype foo
10943 $1 = <incomplete type>
10947 ``Incomplete type'' is C terminology for data types that are not
10948 completely specified.
10951 @item info types @var{regexp}
10953 Print a brief description of all types whose names match the regular
10954 expression @var{regexp} (or all types in your program, if you supply
10955 no argument). Each complete typename is matched as though it were a
10956 complete line; thus, @samp{i type value} gives information on all
10957 types in your program whose names include the string @code{value}, but
10958 @samp{i type ^value$} gives information only on types whose complete
10959 name is @code{value}.
10961 This command differs from @code{ptype} in two ways: first, like
10962 @code{whatis}, it does not print a detailed description; second, it
10963 lists all source files where a type is defined.
10966 @cindex local variables
10967 @item info scope @var{location}
10968 List all the variables local to a particular scope. This command
10969 accepts a @var{location} argument---a function name, a source line, or
10970 an address preceded by a @samp{*}, and prints all the variables local
10971 to the scope defined by that location. For example:
10974 (@value{GDBP}) @b{info scope command_line_handler}
10975 Scope for command_line_handler:
10976 Symbol rl is an argument at stack/frame offset 8, length 4.
10977 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10978 Symbol linelength is in static storage at address 0x150a1c, length 4.
10979 Symbol p is a local variable in register $esi, length 4.
10980 Symbol p1 is a local variable in register $ebx, length 4.
10981 Symbol nline is a local variable in register $edx, length 4.
10982 Symbol repeat is a local variable at frame offset -8, length 4.
10986 This command is especially useful for determining what data to collect
10987 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10990 @kindex info source
10992 Show information about the current source file---that is, the source file for
10993 the function containing the current point of execution:
10996 the name of the source file, and the directory containing it,
10998 the directory it was compiled in,
11000 its length, in lines,
11002 which programming language it is written in,
11004 whether the executable includes debugging information for that file, and
11005 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11007 whether the debugging information includes information about
11008 preprocessor macros.
11012 @kindex info sources
11014 Print the names of all source files in your program for which there is
11015 debugging information, organized into two lists: files whose symbols
11016 have already been read, and files whose symbols will be read when needed.
11018 @kindex info functions
11019 @item info functions
11020 Print the names and data types of all defined functions.
11022 @item info functions @var{regexp}
11023 Print the names and data types of all defined functions
11024 whose names contain a match for regular expression @var{regexp}.
11025 Thus, @samp{info fun step} finds all functions whose names
11026 include @code{step}; @samp{info fun ^step} finds those whose names
11027 start with @code{step}. If a function name contains characters
11028 that conflict with the regular expression language (e.g.@:
11029 @samp{operator*()}), they may be quoted with a backslash.
11031 @kindex info variables
11032 @item info variables
11033 Print the names and data types of all variables that are declared
11034 outside of functions (i.e.@: excluding local variables).
11036 @item info variables @var{regexp}
11037 Print the names and data types of all variables (except for local
11038 variables) whose names contain a match for regular expression
11041 @kindex info classes
11042 @cindex Objective-C, classes and selectors
11044 @itemx info classes @var{regexp}
11045 Display all Objective-C classes in your program, or
11046 (with the @var{regexp} argument) all those matching a particular regular
11049 @kindex info selectors
11050 @item info selectors
11051 @itemx info selectors @var{regexp}
11052 Display all Objective-C selectors in your program, or
11053 (with the @var{regexp} argument) all those matching a particular regular
11057 This was never implemented.
11058 @kindex info methods
11060 @itemx info methods @var{regexp}
11061 The @code{info methods} command permits the user to examine all defined
11062 methods within C@t{++} program, or (with the @var{regexp} argument) a
11063 specific set of methods found in the various C@t{++} classes. Many
11064 C@t{++} classes provide a large number of methods. Thus, the output
11065 from the @code{ptype} command can be overwhelming and hard to use. The
11066 @code{info-methods} command filters the methods, printing only those
11067 which match the regular-expression @var{regexp}.
11070 @cindex reloading symbols
11071 Some systems allow individual object files that make up your program to
11072 be replaced without stopping and restarting your program. For example,
11073 in VxWorks you can simply recompile a defective object file and keep on
11074 running. If you are running on one of these systems, you can allow
11075 @value{GDBN} to reload the symbols for automatically relinked modules:
11078 @kindex set symbol-reloading
11079 @item set symbol-reloading on
11080 Replace symbol definitions for the corresponding source file when an
11081 object file with a particular name is seen again.
11083 @item set symbol-reloading off
11084 Do not replace symbol definitions when encountering object files of the
11085 same name more than once. This is the default state; if you are not
11086 running on a system that permits automatic relinking of modules, you
11087 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11088 may discard symbols when linking large programs, that may contain
11089 several modules (from different directories or libraries) with the same
11092 @kindex show symbol-reloading
11093 @item show symbol-reloading
11094 Show the current @code{on} or @code{off} setting.
11097 @cindex opaque data types
11098 @kindex set opaque-type-resolution
11099 @item set opaque-type-resolution on
11100 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11101 declared as a pointer to a @code{struct}, @code{class}, or
11102 @code{union}---for example, @code{struct MyType *}---that is used in one
11103 source file although the full declaration of @code{struct MyType} is in
11104 another source file. The default is on.
11106 A change in the setting of this subcommand will not take effect until
11107 the next time symbols for a file are loaded.
11109 @item set opaque-type-resolution off
11110 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11111 is printed as follows:
11113 @{<no data fields>@}
11116 @kindex show opaque-type-resolution
11117 @item show opaque-type-resolution
11118 Show whether opaque types are resolved or not.
11120 @kindex maint print symbols
11121 @cindex symbol dump
11122 @kindex maint print psymbols
11123 @cindex partial symbol dump
11124 @item maint print symbols @var{filename}
11125 @itemx maint print psymbols @var{filename}
11126 @itemx maint print msymbols @var{filename}
11127 Write a dump of debugging symbol data into the file @var{filename}.
11128 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11129 symbols with debugging data are included. If you use @samp{maint print
11130 symbols}, @value{GDBN} includes all the symbols for which it has already
11131 collected full details: that is, @var{filename} reflects symbols for
11132 only those files whose symbols @value{GDBN} has read. You can use the
11133 command @code{info sources} to find out which files these are. If you
11134 use @samp{maint print psymbols} instead, the dump shows information about
11135 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11136 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11137 @samp{maint print msymbols} dumps just the minimal symbol information
11138 required for each object file from which @value{GDBN} has read some symbols.
11139 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11140 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11142 @kindex maint info symtabs
11143 @kindex maint info psymtabs
11144 @cindex listing @value{GDBN}'s internal symbol tables
11145 @cindex symbol tables, listing @value{GDBN}'s internal
11146 @cindex full symbol tables, listing @value{GDBN}'s internal
11147 @cindex partial symbol tables, listing @value{GDBN}'s internal
11148 @item maint info symtabs @r{[} @var{regexp} @r{]}
11149 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11151 List the @code{struct symtab} or @code{struct partial_symtab}
11152 structures whose names match @var{regexp}. If @var{regexp} is not
11153 given, list them all. The output includes expressions which you can
11154 copy into a @value{GDBN} debugging this one to examine a particular
11155 structure in more detail. For example:
11158 (@value{GDBP}) maint info psymtabs dwarf2read
11159 @{ objfile /home/gnu/build/gdb/gdb
11160 ((struct objfile *) 0x82e69d0)
11161 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11162 ((struct partial_symtab *) 0x8474b10)
11165 text addresses 0x814d3c8 -- 0x8158074
11166 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11167 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11168 dependencies (none)
11171 (@value{GDBP}) maint info symtabs
11175 We see that there is one partial symbol table whose filename contains
11176 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11177 and we see that @value{GDBN} has not read in any symtabs yet at all.
11178 If we set a breakpoint on a function, that will cause @value{GDBN} to
11179 read the symtab for the compilation unit containing that function:
11182 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11183 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11185 (@value{GDBP}) maint info symtabs
11186 @{ objfile /home/gnu/build/gdb/gdb
11187 ((struct objfile *) 0x82e69d0)
11188 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11189 ((struct symtab *) 0x86c1f38)
11192 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11193 linetable ((struct linetable *) 0x8370fa0)
11194 debugformat DWARF 2
11203 @chapter Altering Execution
11205 Once you think you have found an error in your program, you might want to
11206 find out for certain whether correcting the apparent error would lead to
11207 correct results in the rest of the run. You can find the answer by
11208 experiment, using the @value{GDBN} features for altering execution of the
11211 For example, you can store new values into variables or memory
11212 locations, give your program a signal, restart it at a different
11213 address, or even return prematurely from a function.
11216 * Assignment:: Assignment to variables
11217 * Jumping:: Continuing at a different address
11218 * Signaling:: Giving your program a signal
11219 * Returning:: Returning from a function
11220 * Calling:: Calling your program's functions
11221 * Patching:: Patching your program
11225 @section Assignment to Variables
11228 @cindex setting variables
11229 To alter the value of a variable, evaluate an assignment expression.
11230 @xref{Expressions, ,Expressions}. For example,
11237 stores the value 4 into the variable @code{x}, and then prints the
11238 value of the assignment expression (which is 4).
11239 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11240 information on operators in supported languages.
11242 @kindex set variable
11243 @cindex variables, setting
11244 If you are not interested in seeing the value of the assignment, use the
11245 @code{set} command instead of the @code{print} command. @code{set} is
11246 really the same as @code{print} except that the expression's value is
11247 not printed and is not put in the value history (@pxref{Value History,
11248 ,Value History}). The expression is evaluated only for its effects.
11250 If the beginning of the argument string of the @code{set} command
11251 appears identical to a @code{set} subcommand, use the @code{set
11252 variable} command instead of just @code{set}. This command is identical
11253 to @code{set} except for its lack of subcommands. For example, if your
11254 program has a variable @code{width}, you get an error if you try to set
11255 a new value with just @samp{set width=13}, because @value{GDBN} has the
11256 command @code{set width}:
11259 (@value{GDBP}) whatis width
11261 (@value{GDBP}) p width
11263 (@value{GDBP}) set width=47
11264 Invalid syntax in expression.
11268 The invalid expression, of course, is @samp{=47}. In
11269 order to actually set the program's variable @code{width}, use
11272 (@value{GDBP}) set var width=47
11275 Because the @code{set} command has many subcommands that can conflict
11276 with the names of program variables, it is a good idea to use the
11277 @code{set variable} command instead of just @code{set}. For example, if
11278 your program has a variable @code{g}, you run into problems if you try
11279 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11280 the command @code{set gnutarget}, abbreviated @code{set g}:
11284 (@value{GDBP}) whatis g
11288 (@value{GDBP}) set g=4
11292 The program being debugged has been started already.
11293 Start it from the beginning? (y or n) y
11294 Starting program: /home/smith/cc_progs/a.out
11295 "/home/smith/cc_progs/a.out": can't open to read symbols:
11296 Invalid bfd target.
11297 (@value{GDBP}) show g
11298 The current BFD target is "=4".
11303 The program variable @code{g} did not change, and you silently set the
11304 @code{gnutarget} to an invalid value. In order to set the variable
11308 (@value{GDBP}) set var g=4
11311 @value{GDBN} allows more implicit conversions in assignments than C; you can
11312 freely store an integer value into a pointer variable or vice versa,
11313 and you can convert any structure to any other structure that is the
11314 same length or shorter.
11315 @comment FIXME: how do structs align/pad in these conversions?
11316 @comment /doc@cygnus.com 18dec1990
11318 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11319 construct to generate a value of specified type at a specified address
11320 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11321 to memory location @code{0x83040} as an integer (which implies a certain size
11322 and representation in memory), and
11325 set @{int@}0x83040 = 4
11329 stores the value 4 into that memory location.
11332 @section Continuing at a Different Address
11334 Ordinarily, when you continue your program, you do so at the place where
11335 it stopped, with the @code{continue} command. You can instead continue at
11336 an address of your own choosing, with the following commands:
11340 @item jump @var{linespec}
11341 Resume execution at line @var{linespec}. Execution stops again
11342 immediately if there is a breakpoint there. @xref{List, ,Printing
11343 Source Lines}, for a description of the different forms of
11344 @var{linespec}. It is common practice to use the @code{tbreak} command
11345 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11348 The @code{jump} command does not change the current stack frame, or
11349 the stack pointer, or the contents of any memory location or any
11350 register other than the program counter. If line @var{linespec} is in
11351 a different function from the one currently executing, the results may
11352 be bizarre if the two functions expect different patterns of arguments or
11353 of local variables. For this reason, the @code{jump} command requests
11354 confirmation if the specified line is not in the function currently
11355 executing. However, even bizarre results are predictable if you are
11356 well acquainted with the machine-language code of your program.
11358 @item jump *@var{address}
11359 Resume execution at the instruction at address @var{address}.
11362 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11363 On many systems, you can get much the same effect as the @code{jump}
11364 command by storing a new value into the register @code{$pc}. The
11365 difference is that this does not start your program running; it only
11366 changes the address of where it @emph{will} run when you continue. For
11374 makes the next @code{continue} command or stepping command execute at
11375 address @code{0x485}, rather than at the address where your program stopped.
11376 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11378 The most common occasion to use the @code{jump} command is to back
11379 up---perhaps with more breakpoints set---over a portion of a program
11380 that has already executed, in order to examine its execution in more
11385 @section Giving your Program a Signal
11386 @cindex deliver a signal to a program
11390 @item signal @var{signal}
11391 Resume execution where your program stopped, but immediately give it the
11392 signal @var{signal}. @var{signal} can be the name or the number of a
11393 signal. For example, on many systems @code{signal 2} and @code{signal
11394 SIGINT} are both ways of sending an interrupt signal.
11396 Alternatively, if @var{signal} is zero, continue execution without
11397 giving a signal. This is useful when your program stopped on account of
11398 a signal and would ordinary see the signal when resumed with the
11399 @code{continue} command; @samp{signal 0} causes it to resume without a
11402 @code{signal} does not repeat when you press @key{RET} a second time
11403 after executing the command.
11407 Invoking the @code{signal} command is not the same as invoking the
11408 @code{kill} utility from the shell. Sending a signal with @code{kill}
11409 causes @value{GDBN} to decide what to do with the signal depending on
11410 the signal handling tables (@pxref{Signals}). The @code{signal} command
11411 passes the signal directly to your program.
11415 @section Returning from a Function
11418 @cindex returning from a function
11421 @itemx return @var{expression}
11422 You can cancel execution of a function call with the @code{return}
11423 command. If you give an
11424 @var{expression} argument, its value is used as the function's return
11428 When you use @code{return}, @value{GDBN} discards the selected stack frame
11429 (and all frames within it). You can think of this as making the
11430 discarded frame return prematurely. If you wish to specify a value to
11431 be returned, give that value as the argument to @code{return}.
11433 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11434 Frame}), and any other frames inside of it, leaving its caller as the
11435 innermost remaining frame. That frame becomes selected. The
11436 specified value is stored in the registers used for returning values
11439 The @code{return} command does not resume execution; it leaves the
11440 program stopped in the state that would exist if the function had just
11441 returned. In contrast, the @code{finish} command (@pxref{Continuing
11442 and Stepping, ,Continuing and Stepping}) resumes execution until the
11443 selected stack frame returns naturally.
11446 @section Calling Program Functions
11449 @cindex calling functions
11450 @cindex inferior functions, calling
11451 @item print @var{expr}
11452 Evaluate the expression @var{expr} and display the resulting value.
11453 @var{expr} may include calls to functions in the program being
11457 @item call @var{expr}
11458 Evaluate the expression @var{expr} without displaying @code{void}
11461 You can use this variant of the @code{print} command if you want to
11462 execute a function from your program that does not return anything
11463 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11464 with @code{void} returned values that @value{GDBN} will otherwise
11465 print. If the result is not void, it is printed and saved in the
11469 It is possible for the function you call via the @code{print} or
11470 @code{call} command to generate a signal (e.g., if there's a bug in
11471 the function, or if you passed it incorrect arguments). What happens
11472 in that case is controlled by the @code{set unwindonsignal} command.
11475 @item set unwindonsignal
11476 @kindex set unwindonsignal
11477 @cindex unwind stack in called functions
11478 @cindex call dummy stack unwinding
11479 Set unwinding of the stack if a signal is received while in a function
11480 that @value{GDBN} called in the program being debugged. If set to on,
11481 @value{GDBN} unwinds the stack it created for the call and restores
11482 the context to what it was before the call. If set to off (the
11483 default), @value{GDBN} stops in the frame where the signal was
11486 @item show unwindonsignal
11487 @kindex show unwindonsignal
11488 Show the current setting of stack unwinding in the functions called by
11492 @cindex weak alias functions
11493 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11494 for another function. In such case, @value{GDBN} might not pick up
11495 the type information, including the types of the function arguments,
11496 which causes @value{GDBN} to call the inferior function incorrectly.
11497 As a result, the called function will function erroneously and may
11498 even crash. A solution to that is to use the name of the aliased
11502 @section Patching Programs
11504 @cindex patching binaries
11505 @cindex writing into executables
11506 @cindex writing into corefiles
11508 By default, @value{GDBN} opens the file containing your program's
11509 executable code (or the corefile) read-only. This prevents accidental
11510 alterations to machine code; but it also prevents you from intentionally
11511 patching your program's binary.
11513 If you'd like to be able to patch the binary, you can specify that
11514 explicitly with the @code{set write} command. For example, you might
11515 want to turn on internal debugging flags, or even to make emergency
11521 @itemx set write off
11522 If you specify @samp{set write on}, @value{GDBN} opens executable and
11523 core files for both reading and writing; if you specify @samp{set write
11524 off} (the default), @value{GDBN} opens them read-only.
11526 If you have already loaded a file, you must load it again (using the
11527 @code{exec-file} or @code{core-file} command) after changing @code{set
11528 write}, for your new setting to take effect.
11532 Display whether executable files and core files are opened for writing
11533 as well as reading.
11537 @chapter @value{GDBN} Files
11539 @value{GDBN} needs to know the file name of the program to be debugged,
11540 both in order to read its symbol table and in order to start your
11541 program. To debug a core dump of a previous run, you must also tell
11542 @value{GDBN} the name of the core dump file.
11545 * Files:: Commands to specify files
11546 * Separate Debug Files:: Debugging information in separate files
11547 * Symbol Errors:: Errors reading symbol files
11551 @section Commands to Specify Files
11553 @cindex symbol table
11554 @cindex core dump file
11556 You may want to specify executable and core dump file names. The usual
11557 way to do this is at start-up time, using the arguments to
11558 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11559 Out of @value{GDBN}}).
11561 Occasionally it is necessary to change to a different file during a
11562 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11563 specify a file you want to use. Or you are debugging a remote target
11564 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11565 Program}). In these situations the @value{GDBN} commands to specify
11566 new files are useful.
11569 @cindex executable file
11571 @item file @var{filename}
11572 Use @var{filename} as the program to be debugged. It is read for its
11573 symbols and for the contents of pure memory. It is also the program
11574 executed when you use the @code{run} command. If you do not specify a
11575 directory and the file is not found in the @value{GDBN} working directory,
11576 @value{GDBN} uses the environment variable @code{PATH} as a list of
11577 directories to search, just as the shell does when looking for a program
11578 to run. You can change the value of this variable, for both @value{GDBN}
11579 and your program, using the @code{path} command.
11581 @cindex unlinked object files
11582 @cindex patching object files
11583 You can load unlinked object @file{.o} files into @value{GDBN} using
11584 the @code{file} command. You will not be able to ``run'' an object
11585 file, but you can disassemble functions and inspect variables. Also,
11586 if the underlying BFD functionality supports it, you could use
11587 @kbd{gdb -write} to patch object files using this technique. Note
11588 that @value{GDBN} can neither interpret nor modify relocations in this
11589 case, so branches and some initialized variables will appear to go to
11590 the wrong place. But this feature is still handy from time to time.
11593 @code{file} with no argument makes @value{GDBN} discard any information it
11594 has on both executable file and the symbol table.
11597 @item exec-file @r{[} @var{filename} @r{]}
11598 Specify that the program to be run (but not the symbol table) is found
11599 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11600 if necessary to locate your program. Omitting @var{filename} means to
11601 discard information on the executable file.
11603 @kindex symbol-file
11604 @item symbol-file @r{[} @var{filename} @r{]}
11605 Read symbol table information from file @var{filename}. @code{PATH} is
11606 searched when necessary. Use the @code{file} command to get both symbol
11607 table and program to run from the same file.
11609 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11610 program's symbol table.
11612 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11613 some breakpoints and auto-display expressions. This is because they may
11614 contain pointers to the internal data recording symbols and data types,
11615 which are part of the old symbol table data being discarded inside
11618 @code{symbol-file} does not repeat if you press @key{RET} again after
11621 When @value{GDBN} is configured for a particular environment, it
11622 understands debugging information in whatever format is the standard
11623 generated for that environment; you may use either a @sc{gnu} compiler, or
11624 other compilers that adhere to the local conventions.
11625 Best results are usually obtained from @sc{gnu} compilers; for example,
11626 using @code{@value{NGCC}} you can generate debugging information for
11629 For most kinds of object files, with the exception of old SVR3 systems
11630 using COFF, the @code{symbol-file} command does not normally read the
11631 symbol table in full right away. Instead, it scans the symbol table
11632 quickly to find which source files and which symbols are present. The
11633 details are read later, one source file at a time, as they are needed.
11635 The purpose of this two-stage reading strategy is to make @value{GDBN}
11636 start up faster. For the most part, it is invisible except for
11637 occasional pauses while the symbol table details for a particular source
11638 file are being read. (The @code{set verbose} command can turn these
11639 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11640 Warnings and Messages}.)
11642 We have not implemented the two-stage strategy for COFF yet. When the
11643 symbol table is stored in COFF format, @code{symbol-file} reads the
11644 symbol table data in full right away. Note that ``stabs-in-COFF''
11645 still does the two-stage strategy, since the debug info is actually
11649 @cindex reading symbols immediately
11650 @cindex symbols, reading immediately
11651 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11652 @itemx file @var{filename} @r{[} -readnow @r{]}
11653 You can override the @value{GDBN} two-stage strategy for reading symbol
11654 tables by using the @samp{-readnow} option with any of the commands that
11655 load symbol table information, if you want to be sure @value{GDBN} has the
11656 entire symbol table available.
11658 @c FIXME: for now no mention of directories, since this seems to be in
11659 @c flux. 13mar1992 status is that in theory GDB would look either in
11660 @c current dir or in same dir as myprog; but issues like competing
11661 @c GDB's, or clutter in system dirs, mean that in practice right now
11662 @c only current dir is used. FFish says maybe a special GDB hierarchy
11663 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11667 @item core-file @r{[}@var{filename}@r{]}
11669 Specify the whereabouts of a core dump file to be used as the ``contents
11670 of memory''. Traditionally, core files contain only some parts of the
11671 address space of the process that generated them; @value{GDBN} can access the
11672 executable file itself for other parts.
11674 @code{core-file} with no argument specifies that no core file is
11677 Note that the core file is ignored when your program is actually running
11678 under @value{GDBN}. So, if you have been running your program and you
11679 wish to debug a core file instead, you must kill the subprocess in which
11680 the program is running. To do this, use the @code{kill} command
11681 (@pxref{Kill Process, ,Killing the Child Process}).
11683 @kindex add-symbol-file
11684 @cindex dynamic linking
11685 @item add-symbol-file @var{filename} @var{address}
11686 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11687 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11688 The @code{add-symbol-file} command reads additional symbol table
11689 information from the file @var{filename}. You would use this command
11690 when @var{filename} has been dynamically loaded (by some other means)
11691 into the program that is running. @var{address} should be the memory
11692 address at which the file has been loaded; @value{GDBN} cannot figure
11693 this out for itself. You can additionally specify an arbitrary number
11694 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11695 section name and base address for that section. You can specify any
11696 @var{address} as an expression.
11698 The symbol table of the file @var{filename} is added to the symbol table
11699 originally read with the @code{symbol-file} command. You can use the
11700 @code{add-symbol-file} command any number of times; the new symbol data
11701 thus read keeps adding to the old. To discard all old symbol data
11702 instead, use the @code{symbol-file} command without any arguments.
11704 @cindex relocatable object files, reading symbols from
11705 @cindex object files, relocatable, reading symbols from
11706 @cindex reading symbols from relocatable object files
11707 @cindex symbols, reading from relocatable object files
11708 @cindex @file{.o} files, reading symbols from
11709 Although @var{filename} is typically a shared library file, an
11710 executable file, or some other object file which has been fully
11711 relocated for loading into a process, you can also load symbolic
11712 information from relocatable @file{.o} files, as long as:
11716 the file's symbolic information refers only to linker symbols defined in
11717 that file, not to symbols defined by other object files,
11719 every section the file's symbolic information refers to has actually
11720 been loaded into the inferior, as it appears in the file, and
11722 you can determine the address at which every section was loaded, and
11723 provide these to the @code{add-symbol-file} command.
11727 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11728 relocatable files into an already running program; such systems
11729 typically make the requirements above easy to meet. However, it's
11730 important to recognize that many native systems use complex link
11731 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11732 assembly, for example) that make the requirements difficult to meet. In
11733 general, one cannot assume that using @code{add-symbol-file} to read a
11734 relocatable object file's symbolic information will have the same effect
11735 as linking the relocatable object file into the program in the normal
11738 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11740 @kindex add-symbol-file-from-memory
11741 @cindex @code{syscall DSO}
11742 @cindex load symbols from memory
11743 @item add-symbol-file-from-memory @var{address}
11744 Load symbols from the given @var{address} in a dynamically loaded
11745 object file whose image is mapped directly into the inferior's memory.
11746 For example, the Linux kernel maps a @code{syscall DSO} into each
11747 process's address space; this DSO provides kernel-specific code for
11748 some system calls. The argument can be any expression whose
11749 evaluation yields the address of the file's shared object file header.
11750 For this command to work, you must have used @code{symbol-file} or
11751 @code{exec-file} commands in advance.
11753 @kindex add-shared-symbol-files
11755 @item add-shared-symbol-files @var{library-file}
11756 @itemx assf @var{library-file}
11757 The @code{add-shared-symbol-files} command can currently be used only
11758 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11759 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11760 @value{GDBN} automatically looks for shared libraries, however if
11761 @value{GDBN} does not find yours, you can invoke
11762 @code{add-shared-symbol-files}. It takes one argument: the shared
11763 library's file name. @code{assf} is a shorthand alias for
11764 @code{add-shared-symbol-files}.
11767 @item section @var{section} @var{addr}
11768 The @code{section} command changes the base address of the named
11769 @var{section} of the exec file to @var{addr}. This can be used if the
11770 exec file does not contain section addresses, (such as in the
11771 @code{a.out} format), or when the addresses specified in the file
11772 itself are wrong. Each section must be changed separately. The
11773 @code{info files} command, described below, lists all the sections and
11777 @kindex info target
11780 @code{info files} and @code{info target} are synonymous; both print the
11781 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11782 including the names of the executable and core dump files currently in
11783 use by @value{GDBN}, and the files from which symbols were loaded. The
11784 command @code{help target} lists all possible targets rather than
11787 @kindex maint info sections
11788 @item maint info sections
11789 Another command that can give you extra information about program sections
11790 is @code{maint info sections}. In addition to the section information
11791 displayed by @code{info files}, this command displays the flags and file
11792 offset of each section in the executable and core dump files. In addition,
11793 @code{maint info sections} provides the following command options (which
11794 may be arbitrarily combined):
11798 Display sections for all loaded object files, including shared libraries.
11799 @item @var{sections}
11800 Display info only for named @var{sections}.
11801 @item @var{section-flags}
11802 Display info only for sections for which @var{section-flags} are true.
11803 The section flags that @value{GDBN} currently knows about are:
11806 Section will have space allocated in the process when loaded.
11807 Set for all sections except those containing debug information.
11809 Section will be loaded from the file into the child process memory.
11810 Set for pre-initialized code and data, clear for @code{.bss} sections.
11812 Section needs to be relocated before loading.
11814 Section cannot be modified by the child process.
11816 Section contains executable code only.
11818 Section contains data only (no executable code).
11820 Section will reside in ROM.
11822 Section contains data for constructor/destructor lists.
11824 Section is not empty.
11826 An instruction to the linker to not output the section.
11827 @item COFF_SHARED_LIBRARY
11828 A notification to the linker that the section contains
11829 COFF shared library information.
11831 Section contains common symbols.
11834 @kindex set trust-readonly-sections
11835 @cindex read-only sections
11836 @item set trust-readonly-sections on
11837 Tell @value{GDBN} that readonly sections in your object file
11838 really are read-only (i.e.@: that their contents will not change).
11839 In that case, @value{GDBN} can fetch values from these sections
11840 out of the object file, rather than from the target program.
11841 For some targets (notably embedded ones), this can be a significant
11842 enhancement to debugging performance.
11844 The default is off.
11846 @item set trust-readonly-sections off
11847 Tell @value{GDBN} not to trust readonly sections. This means that
11848 the contents of the section might change while the program is running,
11849 and must therefore be fetched from the target when needed.
11851 @item show trust-readonly-sections
11852 Show the current setting of trusting readonly sections.
11855 All file-specifying commands allow both absolute and relative file names
11856 as arguments. @value{GDBN} always converts the file name to an absolute file
11857 name and remembers it that way.
11859 @cindex shared libraries
11860 @anchor{Shared Libraries}
11861 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11862 and IBM RS/6000 AIX shared libraries.
11864 On MS-Windows @value{GDBN} must be linked with the Expat library to support
11865 shared libraries. @xref{Expat}.
11867 @value{GDBN} automatically loads symbol definitions from shared libraries
11868 when you use the @code{run} command, or when you examine a core file.
11869 (Before you issue the @code{run} command, @value{GDBN} does not understand
11870 references to a function in a shared library, however---unless you are
11871 debugging a core file).
11873 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11874 automatically loads the symbols at the time of the @code{shl_load} call.
11876 @c FIXME: some @value{GDBN} release may permit some refs to undef
11877 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11878 @c FIXME...lib; check this from time to time when updating manual
11880 There are times, however, when you may wish to not automatically load
11881 symbol definitions from shared libraries, such as when they are
11882 particularly large or there are many of them.
11884 To control the automatic loading of shared library symbols, use the
11888 @kindex set auto-solib-add
11889 @item set auto-solib-add @var{mode}
11890 If @var{mode} is @code{on}, symbols from all shared object libraries
11891 will be loaded automatically when the inferior begins execution, you
11892 attach to an independently started inferior, or when the dynamic linker
11893 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11894 is @code{off}, symbols must be loaded manually, using the
11895 @code{sharedlibrary} command. The default value is @code{on}.
11897 @cindex memory used for symbol tables
11898 If your program uses lots of shared libraries with debug info that
11899 takes large amounts of memory, you can decrease the @value{GDBN}
11900 memory footprint by preventing it from automatically loading the
11901 symbols from shared libraries. To that end, type @kbd{set
11902 auto-solib-add off} before running the inferior, then load each
11903 library whose debug symbols you do need with @kbd{sharedlibrary
11904 @var{regexp}}, where @var{regexp} is a regular expression that matches
11905 the libraries whose symbols you want to be loaded.
11907 @kindex show auto-solib-add
11908 @item show auto-solib-add
11909 Display the current autoloading mode.
11912 @cindex load shared library
11913 To explicitly load shared library symbols, use the @code{sharedlibrary}
11917 @kindex info sharedlibrary
11920 @itemx info sharedlibrary
11921 Print the names of the shared libraries which are currently loaded.
11923 @kindex sharedlibrary
11925 @item sharedlibrary @var{regex}
11926 @itemx share @var{regex}
11927 Load shared object library symbols for files matching a
11928 Unix regular expression.
11929 As with files loaded automatically, it only loads shared libraries
11930 required by your program for a core file or after typing @code{run}. If
11931 @var{regex} is omitted all shared libraries required by your program are
11934 @item nosharedlibrary
11935 @kindex nosharedlibrary
11936 @cindex unload symbols from shared libraries
11937 Unload all shared object library symbols. This discards all symbols
11938 that have been loaded from all shared libraries. Symbols from shared
11939 libraries that were loaded by explicit user requests are not
11943 Sometimes you may wish that @value{GDBN} stops and gives you control
11944 when any of shared library events happen. Use the @code{set
11945 stop-on-solib-events} command for this:
11948 @item set stop-on-solib-events
11949 @kindex set stop-on-solib-events
11950 This command controls whether @value{GDBN} should give you control
11951 when the dynamic linker notifies it about some shared library event.
11952 The most common event of interest is loading or unloading of a new
11955 @item show stop-on-solib-events
11956 @kindex show stop-on-solib-events
11957 Show whether @value{GDBN} stops and gives you control when shared
11958 library events happen.
11961 Shared libraries are also supported in many cross or remote debugging
11962 configurations. A copy of the target's libraries need to be present on the
11963 host system; they need to be the same as the target libraries, although the
11964 copies on the target can be stripped as long as the copies on the host are
11967 @cindex where to look for shared libraries
11968 For remote debugging, you need to tell @value{GDBN} where the target
11969 libraries are, so that it can load the correct copies---otherwise, it
11970 may try to load the host's libraries. @value{GDBN} has two variables
11971 to specify the search directories for target libraries.
11974 @cindex prefix for shared library file names
11975 @cindex system root, alternate
11976 @kindex set solib-absolute-prefix
11977 @kindex set sysroot
11978 @item set sysroot @var{path}
11979 Use @var{path} as the system root for the program being debugged. Any
11980 absolute shared library paths will be prefixed with @var{path}; many
11981 runtime loaders store the absolute paths to the shared library in the
11982 target program's memory. If you use @code{set sysroot} to find shared
11983 libraries, they need to be laid out in the same way that they are on
11984 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
11987 The @code{set solib-absolute-prefix} command is an alias for @code{set
11990 @cindex default system root
11991 @cindex @samp{--with-sysroot}
11992 You can set the default system root by using the configure-time
11993 @samp{--with-sysroot} option. If the system root is inside
11994 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
11995 @samp{--exec-prefix}), then the default system root will be updated
11996 automatically if the installed @value{GDBN} is moved to a new
11999 @kindex show sysroot
12001 Display the current shared library prefix.
12003 @kindex set solib-search-path
12004 @item set solib-search-path @var{path}
12005 If this variable is set, @var{path} is a colon-separated list of
12006 directories to search for shared libraries. @samp{solib-search-path}
12007 is used after @samp{sysroot} fails to locate the library, or if the
12008 path to the library is relative instead of absolute. If you want to
12009 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12010 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12011 finding your host's libraries. @samp{sysroot} is preferred; setting
12012 it to a nonexistent directory may interfere with automatic loading
12013 of shared library symbols.
12015 @kindex show solib-search-path
12016 @item show solib-search-path
12017 Display the current shared library search path.
12021 @node Separate Debug Files
12022 @section Debugging Information in Separate Files
12023 @cindex separate debugging information files
12024 @cindex debugging information in separate files
12025 @cindex @file{.debug} subdirectories
12026 @cindex debugging information directory, global
12027 @cindex global debugging information directory
12028 @cindex build ID, and separate debugging files
12029 @cindex @file{.build-id} directory
12031 @value{GDBN} allows you to put a program's debugging information in a
12032 file separate from the executable itself, in a way that allows
12033 @value{GDBN} to find and load the debugging information automatically.
12034 Since debugging information can be very large---sometimes larger
12035 than the executable code itself---some systems distribute debugging
12036 information for their executables in separate files, which users can
12037 install only when they need to debug a problem.
12039 @value{GDBN} supports two ways of specifying the separate debug info
12044 The executable contains a @dfn{debug link} that specifies the name of
12045 the separate debug info file. The separate debug file's name is
12046 usually @file{@var{executable}.debug}, where @var{executable} is the
12047 name of the corresponding executable file without leading directories
12048 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12049 debug link specifies a CRC32 checksum for the debug file, which
12050 @value{GDBN} uses to validate that the executable and the debug file
12051 came from the same build.
12054 The executable contains a @dfn{build ID}, a unique bit string that is
12055 also present in the corresponding debug info file. (This is supported
12056 only on some operating systems, notably those which use the ELF format
12057 for binary files and the @sc{gnu} Binutils.) For more details about
12058 this feature, see the description of the @option{--build-id}
12059 command-line option in @ref{Options, , Command Line Options, ld.info,
12060 The GNU Linker}. The debug info file's name is not specified
12061 explicitly by the build ID, but can be computed from the build ID, see
12065 Depending on the way the debug info file is specified, @value{GDBN}
12066 uses two different methods of looking for the debug file:
12070 For the ``debug link'' method, @value{GDBN} looks up the named file in
12071 the directory of the executable file, then in a subdirectory of that
12072 directory named @file{.debug}, and finally under the global debug
12073 directory, in a subdirectory whose name is identical to the leading
12074 directories of the executable's absolute file name.
12077 For the ``build ID'' method, @value{GDBN} looks in the
12078 @file{.build-id} subdirectory of the global debug directory for a file
12079 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12080 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12081 are the rest of the bit string. (Real build ID strings are 32 or more
12082 hex characters, not 10.)
12085 So, for example, suppose you ask @value{GDBN} to debug
12086 @file{/usr/bin/ls}, which has a debug link that specifies the
12087 file @file{ls.debug}, and a build ID whose value in hex is
12088 @code{abcdef1234}. If the global debug directory is
12089 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12090 debug information files, in the indicated order:
12094 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12096 @file{/usr/bin/ls.debug}
12098 @file{/usr/bin/.debug/ls.debug}
12100 @file{/usr/lib/debug/usr/bin/ls.debug}.
12103 You can set the global debugging info directory's name, and view the
12104 name @value{GDBN} is currently using.
12108 @kindex set debug-file-directory
12109 @item set debug-file-directory @var{directory}
12110 Set the directory which @value{GDBN} searches for separate debugging
12111 information files to @var{directory}.
12113 @kindex show debug-file-directory
12114 @item show debug-file-directory
12115 Show the directory @value{GDBN} searches for separate debugging
12120 @cindex @code{.gnu_debuglink} sections
12121 @cindex debug link sections
12122 A debug link is a special section of the executable file named
12123 @code{.gnu_debuglink}. The section must contain:
12127 A filename, with any leading directory components removed, followed by
12130 zero to three bytes of padding, as needed to reach the next four-byte
12131 boundary within the section, and
12133 a four-byte CRC checksum, stored in the same endianness used for the
12134 executable file itself. The checksum is computed on the debugging
12135 information file's full contents by the function given below, passing
12136 zero as the @var{crc} argument.
12139 Any executable file format can carry a debug link, as long as it can
12140 contain a section named @code{.gnu_debuglink} with the contents
12143 @cindex @code{.note.gnu.build-id} sections
12144 @cindex build ID sections
12145 The build ID is a special section in the executable file (and in other
12146 ELF binary files that @value{GDBN} may consider). This section is
12147 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12148 It contains unique identification for the built files---the ID remains
12149 the same across multiple builds of the same build tree. The default
12150 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12151 content for the build ID string. The same section with an identical
12152 value is present in the original built binary with symbols, in its
12153 stripped variant, and in the separate debugging information file.
12155 The debugging information file itself should be an ordinary
12156 executable, containing a full set of linker symbols, sections, and
12157 debugging information. The sections of the debugging information file
12158 should have the same names, addresses, and sizes as the original file,
12159 but they need not contain any data---much like a @code{.bss} section
12160 in an ordinary executable.
12162 The @sc{gnu} binary utilities (Binutils) package includes the
12163 @samp{objcopy} utility that can produce
12164 the separated executable / debugging information file pairs using the
12165 following commands:
12168 @kbd{objcopy --only-keep-debug foo foo.debug}
12173 These commands remove the debugging
12174 information from the executable file @file{foo} and place it in the file
12175 @file{foo.debug}. You can use the first, second or both methods to link the
12180 The debug link method needs the following additional command to also leave
12181 behind a debug link in @file{foo}:
12184 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12187 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12188 a version of the @code{strip} command such that the command @kbd{strip foo -f
12189 foo.debug} has the same functionality as the two @code{objcopy} commands and
12190 the @code{ln -s} command above, together.
12193 Build ID gets embedded into the main executable using @code{ld --build-id} or
12194 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12195 compatibility fixes for debug files separation are present in @sc{gnu} binary
12196 utilities (Binutils) package since version 2.18.
12201 Since there are many different ways to compute CRC's for the debug
12202 link (different polynomials, reversals, byte ordering, etc.), the
12203 simplest way to describe the CRC used in @code{.gnu_debuglink}
12204 sections is to give the complete code for a function that computes it:
12206 @kindex gnu_debuglink_crc32
12209 gnu_debuglink_crc32 (unsigned long crc,
12210 unsigned char *buf, size_t len)
12212 static const unsigned long crc32_table[256] =
12214 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12215 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12216 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12217 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12218 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12219 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12220 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12221 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12222 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12223 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12224 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12225 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12226 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12227 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12228 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12229 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12230 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12231 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12232 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12233 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12234 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12235 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12236 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12237 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12238 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12239 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12240 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12241 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12242 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12243 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12244 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12245 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12246 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12247 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12248 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12249 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12250 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12251 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12252 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12253 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12254 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12255 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12256 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12257 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12258 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12259 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12260 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12261 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12262 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12263 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12264 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12267 unsigned char *end;
12269 crc = ~crc & 0xffffffff;
12270 for (end = buf + len; buf < end; ++buf)
12271 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12272 return ~crc & 0xffffffff;
12277 This computation does not apply to the ``build ID'' method.
12280 @node Symbol Errors
12281 @section Errors Reading Symbol Files
12283 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12284 such as symbol types it does not recognize, or known bugs in compiler
12285 output. By default, @value{GDBN} does not notify you of such problems, since
12286 they are relatively common and primarily of interest to people
12287 debugging compilers. If you are interested in seeing information
12288 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12289 only one message about each such type of problem, no matter how many
12290 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12291 to see how many times the problems occur, with the @code{set
12292 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12295 The messages currently printed, and their meanings, include:
12298 @item inner block not inside outer block in @var{symbol}
12300 The symbol information shows where symbol scopes begin and end
12301 (such as at the start of a function or a block of statements). This
12302 error indicates that an inner scope block is not fully contained
12303 in its outer scope blocks.
12305 @value{GDBN} circumvents the problem by treating the inner block as if it had
12306 the same scope as the outer block. In the error message, @var{symbol}
12307 may be shown as ``@code{(don't know)}'' if the outer block is not a
12310 @item block at @var{address} out of order
12312 The symbol information for symbol scope blocks should occur in
12313 order of increasing addresses. This error indicates that it does not
12316 @value{GDBN} does not circumvent this problem, and has trouble
12317 locating symbols in the source file whose symbols it is reading. (You
12318 can often determine what source file is affected by specifying
12319 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12322 @item bad block start address patched
12324 The symbol information for a symbol scope block has a start address
12325 smaller than the address of the preceding source line. This is known
12326 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12328 @value{GDBN} circumvents the problem by treating the symbol scope block as
12329 starting on the previous source line.
12331 @item bad string table offset in symbol @var{n}
12334 Symbol number @var{n} contains a pointer into the string table which is
12335 larger than the size of the string table.
12337 @value{GDBN} circumvents the problem by considering the symbol to have the
12338 name @code{foo}, which may cause other problems if many symbols end up
12341 @item unknown symbol type @code{0x@var{nn}}
12343 The symbol information contains new data types that @value{GDBN} does
12344 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12345 uncomprehended information, in hexadecimal.
12347 @value{GDBN} circumvents the error by ignoring this symbol information.
12348 This usually allows you to debug your program, though certain symbols
12349 are not accessible. If you encounter such a problem and feel like
12350 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12351 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12352 and examine @code{*bufp} to see the symbol.
12354 @item stub type has NULL name
12356 @value{GDBN} could not find the full definition for a struct or class.
12358 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12359 The symbol information for a C@t{++} member function is missing some
12360 information that recent versions of the compiler should have output for
12363 @item info mismatch between compiler and debugger
12365 @value{GDBN} could not parse a type specification output by the compiler.
12370 @chapter Specifying a Debugging Target
12372 @cindex debugging target
12373 A @dfn{target} is the execution environment occupied by your program.
12375 Often, @value{GDBN} runs in the same host environment as your program;
12376 in that case, the debugging target is specified as a side effect when
12377 you use the @code{file} or @code{core} commands. When you need more
12378 flexibility---for example, running @value{GDBN} on a physically separate
12379 host, or controlling a standalone system over a serial port or a
12380 realtime system over a TCP/IP connection---you can use the @code{target}
12381 command to specify one of the target types configured for @value{GDBN}
12382 (@pxref{Target Commands, ,Commands for Managing Targets}).
12384 @cindex target architecture
12385 It is possible to build @value{GDBN} for several different @dfn{target
12386 architectures}. When @value{GDBN} is built like that, you can choose
12387 one of the available architectures with the @kbd{set architecture}
12391 @kindex set architecture
12392 @kindex show architecture
12393 @item set architecture @var{arch}
12394 This command sets the current target architecture to @var{arch}. The
12395 value of @var{arch} can be @code{"auto"}, in addition to one of the
12396 supported architectures.
12398 @item show architecture
12399 Show the current target architecture.
12401 @item set processor
12403 @kindex set processor
12404 @kindex show processor
12405 These are alias commands for, respectively, @code{set architecture}
12406 and @code{show architecture}.
12410 * Active Targets:: Active targets
12411 * Target Commands:: Commands for managing targets
12412 * Byte Order:: Choosing target byte order
12415 @node Active Targets
12416 @section Active Targets
12418 @cindex stacking targets
12419 @cindex active targets
12420 @cindex multiple targets
12422 There are three classes of targets: processes, core files, and
12423 executable files. @value{GDBN} can work concurrently on up to three
12424 active targets, one in each class. This allows you to (for example)
12425 start a process and inspect its activity without abandoning your work on
12428 For example, if you execute @samp{gdb a.out}, then the executable file
12429 @code{a.out} is the only active target. If you designate a core file as
12430 well---presumably from a prior run that crashed and coredumped---then
12431 @value{GDBN} has two active targets and uses them in tandem, looking
12432 first in the corefile target, then in the executable file, to satisfy
12433 requests for memory addresses. (Typically, these two classes of target
12434 are complementary, since core files contain only a program's
12435 read-write memory---variables and so on---plus machine status, while
12436 executable files contain only the program text and initialized data.)
12438 When you type @code{run}, your executable file becomes an active process
12439 target as well. When a process target is active, all @value{GDBN}
12440 commands requesting memory addresses refer to that target; addresses in
12441 an active core file or executable file target are obscured while the
12442 process target is active.
12444 Use the @code{core-file} and @code{exec-file} commands to select a new
12445 core file or executable target (@pxref{Files, ,Commands to Specify
12446 Files}). To specify as a target a process that is already running, use
12447 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12450 @node Target Commands
12451 @section Commands for Managing Targets
12454 @item target @var{type} @var{parameters}
12455 Connects the @value{GDBN} host environment to a target machine or
12456 process. A target is typically a protocol for talking to debugging
12457 facilities. You use the argument @var{type} to specify the type or
12458 protocol of the target machine.
12460 Further @var{parameters} are interpreted by the target protocol, but
12461 typically include things like device names or host names to connect
12462 with, process numbers, and baud rates.
12464 The @code{target} command does not repeat if you press @key{RET} again
12465 after executing the command.
12467 @kindex help target
12469 Displays the names of all targets available. To display targets
12470 currently selected, use either @code{info target} or @code{info files}
12471 (@pxref{Files, ,Commands to Specify Files}).
12473 @item help target @var{name}
12474 Describe a particular target, including any parameters necessary to
12477 @kindex set gnutarget
12478 @item set gnutarget @var{args}
12479 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12480 knows whether it is reading an @dfn{executable},
12481 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12482 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12483 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12486 @emph{Warning:} To specify a file format with @code{set gnutarget},
12487 you must know the actual BFD name.
12491 @xref{Files, , Commands to Specify Files}.
12493 @kindex show gnutarget
12494 @item show gnutarget
12495 Use the @code{show gnutarget} command to display what file format
12496 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12497 @value{GDBN} will determine the file format for each file automatically,
12498 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12501 @cindex common targets
12502 Here are some common targets (available, or not, depending on the GDB
12507 @item target exec @var{program}
12508 @cindex executable file target
12509 An executable file. @samp{target exec @var{program}} is the same as
12510 @samp{exec-file @var{program}}.
12512 @item target core @var{filename}
12513 @cindex core dump file target
12514 A core dump file. @samp{target core @var{filename}} is the same as
12515 @samp{core-file @var{filename}}.
12517 @item target remote @var{medium}
12518 @cindex remote target
12519 A remote system connected to @value{GDBN} via a serial line or network
12520 connection. This command tells @value{GDBN} to use its own remote
12521 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12523 For example, if you have a board connected to @file{/dev/ttya} on the
12524 machine running @value{GDBN}, you could say:
12527 target remote /dev/ttya
12530 @code{target remote} supports the @code{load} command. This is only
12531 useful if you have some other way of getting the stub to the target
12532 system, and you can put it somewhere in memory where it won't get
12533 clobbered by the download.
12536 @cindex built-in simulator target
12537 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12545 works; however, you cannot assume that a specific memory map, device
12546 drivers, or even basic I/O is available, although some simulators do
12547 provide these. For info about any processor-specific simulator details,
12548 see the appropriate section in @ref{Embedded Processors, ,Embedded
12553 Some configurations may include these targets as well:
12557 @item target nrom @var{dev}
12558 @cindex NetROM ROM emulator target
12559 NetROM ROM emulator. This target only supports downloading.
12563 Different targets are available on different configurations of @value{GDBN};
12564 your configuration may have more or fewer targets.
12566 Many remote targets require you to download the executable's code once
12567 you've successfully established a connection. You may wish to control
12568 various aspects of this process.
12573 @kindex set hash@r{, for remote monitors}
12574 @cindex hash mark while downloading
12575 This command controls whether a hash mark @samp{#} is displayed while
12576 downloading a file to the remote monitor. If on, a hash mark is
12577 displayed after each S-record is successfully downloaded to the
12581 @kindex show hash@r{, for remote monitors}
12582 Show the current status of displaying the hash mark.
12584 @item set debug monitor
12585 @kindex set debug monitor
12586 @cindex display remote monitor communications
12587 Enable or disable display of communications messages between
12588 @value{GDBN} and the remote monitor.
12590 @item show debug monitor
12591 @kindex show debug monitor
12592 Show the current status of displaying communications between
12593 @value{GDBN} and the remote monitor.
12598 @kindex load @var{filename}
12599 @item load @var{filename}
12600 Depending on what remote debugging facilities are configured into
12601 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12602 is meant to make @var{filename} (an executable) available for debugging
12603 on the remote system---by downloading, or dynamic linking, for example.
12604 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12605 the @code{add-symbol-file} command.
12607 If your @value{GDBN} does not have a @code{load} command, attempting to
12608 execute it gets the error message ``@code{You can't do that when your
12609 target is @dots{}}''
12611 The file is loaded at whatever address is specified in the executable.
12612 For some object file formats, you can specify the load address when you
12613 link the program; for other formats, like a.out, the object file format
12614 specifies a fixed address.
12615 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12617 Depending on the remote side capabilities, @value{GDBN} may be able to
12618 load programs into flash memory.
12620 @code{load} does not repeat if you press @key{RET} again after using it.
12624 @section Choosing Target Byte Order
12626 @cindex choosing target byte order
12627 @cindex target byte order
12629 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12630 offer the ability to run either big-endian or little-endian byte
12631 orders. Usually the executable or symbol will include a bit to
12632 designate the endian-ness, and you will not need to worry about
12633 which to use. However, you may still find it useful to adjust
12634 @value{GDBN}'s idea of processor endian-ness manually.
12638 @item set endian big
12639 Instruct @value{GDBN} to assume the target is big-endian.
12641 @item set endian little
12642 Instruct @value{GDBN} to assume the target is little-endian.
12644 @item set endian auto
12645 Instruct @value{GDBN} to use the byte order associated with the
12649 Display @value{GDBN}'s current idea of the target byte order.
12653 Note that these commands merely adjust interpretation of symbolic
12654 data on the host, and that they have absolutely no effect on the
12658 @node Remote Debugging
12659 @chapter Debugging Remote Programs
12660 @cindex remote debugging
12662 If you are trying to debug a program running on a machine that cannot run
12663 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12664 For example, you might use remote debugging on an operating system kernel,
12665 or on a small system which does not have a general purpose operating system
12666 powerful enough to run a full-featured debugger.
12668 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12669 to make this work with particular debugging targets. In addition,
12670 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12671 but not specific to any particular target system) which you can use if you
12672 write the remote stubs---the code that runs on the remote system to
12673 communicate with @value{GDBN}.
12675 Other remote targets may be available in your
12676 configuration of @value{GDBN}; use @code{help target} to list them.
12679 * Connecting:: Connecting to a remote target
12680 * File Transfer:: Sending files to a remote system
12681 * Server:: Using the gdbserver program
12682 * Remote Configuration:: Remote configuration
12683 * Remote Stub:: Implementing a remote stub
12687 @section Connecting to a Remote Target
12689 On the @value{GDBN} host machine, you will need an unstripped copy of
12690 your program, since @value{GDBN} needs symbol and debugging information.
12691 Start up @value{GDBN} as usual, using the name of the local copy of your
12692 program as the first argument.
12694 @cindex @code{target remote}
12695 @value{GDBN} can communicate with the target over a serial line, or
12696 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12697 each case, @value{GDBN} uses the same protocol for debugging your
12698 program; only the medium carrying the debugging packets varies. The
12699 @code{target remote} command establishes a connection to the target.
12700 Its arguments indicate which medium to use:
12704 @item target remote @var{serial-device}
12705 @cindex serial line, @code{target remote}
12706 Use @var{serial-device} to communicate with the target. For example,
12707 to use a serial line connected to the device named @file{/dev/ttyb}:
12710 target remote /dev/ttyb
12713 If you're using a serial line, you may want to give @value{GDBN} the
12714 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12715 (@pxref{Remote Configuration, set remotebaud}) before the
12716 @code{target} command.
12718 @item target remote @code{@var{host}:@var{port}}
12719 @itemx target remote @code{tcp:@var{host}:@var{port}}
12720 @cindex @acronym{TCP} port, @code{target remote}
12721 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12722 The @var{host} may be either a host name or a numeric @acronym{IP}
12723 address; @var{port} must be a decimal number. The @var{host} could be
12724 the target machine itself, if it is directly connected to the net, or
12725 it might be a terminal server which in turn has a serial line to the
12728 For example, to connect to port 2828 on a terminal server named
12732 target remote manyfarms:2828
12735 If your remote target is actually running on the same machine as your
12736 debugger session (e.g.@: a simulator for your target running on the
12737 same host), you can omit the hostname. For example, to connect to
12738 port 1234 on your local machine:
12741 target remote :1234
12745 Note that the colon is still required here.
12747 @item target remote @code{udp:@var{host}:@var{port}}
12748 @cindex @acronym{UDP} port, @code{target remote}
12749 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12750 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12753 target remote udp:manyfarms:2828
12756 When using a @acronym{UDP} connection for remote debugging, you should
12757 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12758 can silently drop packets on busy or unreliable networks, which will
12759 cause havoc with your debugging session.
12761 @item target remote | @var{command}
12762 @cindex pipe, @code{target remote} to
12763 Run @var{command} in the background and communicate with it using a
12764 pipe. The @var{command} is a shell command, to be parsed and expanded
12765 by the system's command shell, @code{/bin/sh}; it should expect remote
12766 protocol packets on its standard input, and send replies on its
12767 standard output. You could use this to run a stand-alone simulator
12768 that speaks the remote debugging protocol, to make net connections
12769 using programs like @code{ssh}, or for other similar tricks.
12771 If @var{command} closes its standard output (perhaps by exiting),
12772 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12773 program has already exited, this will have no effect.)
12777 Once the connection has been established, you can use all the usual
12778 commands to examine and change data and to step and continue the
12781 @cindex interrupting remote programs
12782 @cindex remote programs, interrupting
12783 Whenever @value{GDBN} is waiting for the remote program, if you type the
12784 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12785 program. This may or may not succeed, depending in part on the hardware
12786 and the serial drivers the remote system uses. If you type the
12787 interrupt character once again, @value{GDBN} displays this prompt:
12790 Interrupted while waiting for the program.
12791 Give up (and stop debugging it)? (y or n)
12794 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12795 (If you decide you want to try again later, you can use @samp{target
12796 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12797 goes back to waiting.
12800 @kindex detach (remote)
12802 When you have finished debugging the remote program, you can use the
12803 @code{detach} command to release it from @value{GDBN} control.
12804 Detaching from the target normally resumes its execution, but the results
12805 will depend on your particular remote stub. After the @code{detach}
12806 command, @value{GDBN} is free to connect to another target.
12810 The @code{disconnect} command behaves like @code{detach}, except that
12811 the target is generally not resumed. It will wait for @value{GDBN}
12812 (this instance or another one) to connect and continue debugging. After
12813 the @code{disconnect} command, @value{GDBN} is again free to connect to
12816 @cindex send command to remote monitor
12817 @cindex extend @value{GDBN} for remote targets
12818 @cindex add new commands for external monitor
12820 @item monitor @var{cmd}
12821 This command allows you to send arbitrary commands directly to the
12822 remote monitor. Since @value{GDBN} doesn't care about the commands it
12823 sends like this, this command is the way to extend @value{GDBN}---you
12824 can add new commands that only the external monitor will understand
12828 @node File Transfer
12829 @section Sending files to a remote system
12830 @cindex remote target, file transfer
12831 @cindex file transfer
12832 @cindex sending files to remote systems
12834 Some remote targets offer the ability to transfer files over the same
12835 connection used to communicate with @value{GDBN}. This is convenient
12836 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
12837 running @code{gdbserver} over a network interface. For other targets,
12838 e.g.@: embedded devices with only a single serial port, this may be
12839 the only way to upload or download files.
12841 Not all remote targets support these commands.
12845 @item remote put @var{hostfile} @var{targetfile}
12846 Copy file @var{hostfile} from the host system (the machine running
12847 @value{GDBN}) to @var{targetfile} on the target system.
12850 @item remote get @var{targetfile} @var{hostfile}
12851 Copy file @var{targetfile} from the target system to @var{hostfile}
12852 on the host system.
12854 @kindex remote delete
12855 @item remote delete @var{targetfile}
12856 Delete @var{targetfile} from the target system.
12861 @section Using the @code{gdbserver} Program
12864 @cindex remote connection without stubs
12865 @code{gdbserver} is a control program for Unix-like systems, which
12866 allows you to connect your program with a remote @value{GDBN} via
12867 @code{target remote}---but without linking in the usual debugging stub.
12869 @code{gdbserver} is not a complete replacement for the debugging stubs,
12870 because it requires essentially the same operating-system facilities
12871 that @value{GDBN} itself does. In fact, a system that can run
12872 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12873 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12874 because it is a much smaller program than @value{GDBN} itself. It is
12875 also easier to port than all of @value{GDBN}, so you may be able to get
12876 started more quickly on a new system by using @code{gdbserver}.
12877 Finally, if you develop code for real-time systems, you may find that
12878 the tradeoffs involved in real-time operation make it more convenient to
12879 do as much development work as possible on another system, for example
12880 by cross-compiling. You can use @code{gdbserver} to make a similar
12881 choice for debugging.
12883 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12884 or a TCP connection, using the standard @value{GDBN} remote serial
12888 @item On the target machine,
12889 you need to have a copy of the program you want to debug.
12890 @code{gdbserver} does not need your program's symbol table, so you can
12891 strip the program if necessary to save space. @value{GDBN} on the host
12892 system does all the symbol handling.
12894 To use the server, you must tell it how to communicate with @value{GDBN};
12895 the name of your program; and the arguments for your program. The usual
12899 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12902 @var{comm} is either a device name (to use a serial line) or a TCP
12903 hostname and portnumber. For example, to debug Emacs with the argument
12904 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12908 target> gdbserver /dev/com1 emacs foo.txt
12911 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12914 To use a TCP connection instead of a serial line:
12917 target> gdbserver host:2345 emacs foo.txt
12920 The only difference from the previous example is the first argument,
12921 specifying that you are communicating with the host @value{GDBN} via
12922 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12923 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12924 (Currently, the @samp{host} part is ignored.) You can choose any number
12925 you want for the port number as long as it does not conflict with any
12926 TCP ports already in use on the target system (for example, @code{23} is
12927 reserved for @code{telnet}).@footnote{If you choose a port number that
12928 conflicts with another service, @code{gdbserver} prints an error message
12929 and exits.} You must use the same port number with the host @value{GDBN}
12930 @code{target remote} command.
12932 On some targets, @code{gdbserver} can also attach to running programs.
12933 This is accomplished via the @code{--attach} argument. The syntax is:
12936 target> gdbserver @var{comm} --attach @var{pid}
12939 @var{pid} is the process ID of a currently running process. It isn't necessary
12940 to point @code{gdbserver} at a binary for the running process.
12943 @cindex attach to a program by name
12944 You can debug processes by name instead of process ID if your target has the
12945 @code{pidof} utility:
12948 target> gdbserver @var{comm} --attach `pidof @var{program}`
12951 In case more than one copy of @var{program} is running, or @var{program}
12952 has multiple threads, most versions of @code{pidof} support the
12953 @code{-s} option to only return the first process ID.
12955 @item On the host machine,
12956 first make sure you have the necessary symbol files. Load symbols for
12957 your application using the @code{file} command before you connect. Use
12958 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
12959 was compiled with the correct sysroot using @code{--with-system-root}).
12961 The symbol file and target libraries must exactly match the executable
12962 and libraries on the target, with one exception: the files on the host
12963 system should not be stripped, even if the files on the target system
12964 are. Mismatched or missing files will lead to confusing results
12965 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
12966 files may also prevent @code{gdbserver} from debugging multi-threaded
12969 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
12970 For TCP connections, you must start up @code{gdbserver} prior to using
12971 the @code{target remote} command. Otherwise you may get an error whose
12972 text depends on the host system, but which usually looks something like
12973 @samp{Connection refused}. You don't need to use the @code{load}
12974 command in @value{GDBN} when using @code{gdbserver}, since the program is
12975 already on the target.
12979 @subsection Monitor Commands for @code{gdbserver}
12980 @cindex monitor commands, for @code{gdbserver}
12982 During a @value{GDBN} session using @code{gdbserver}, you can use the
12983 @code{monitor} command to send special requests to @code{gdbserver}.
12984 Here are the available commands; they are only of interest when
12985 debugging @value{GDBN} or @code{gdbserver}.
12989 List the available monitor commands.
12991 @item monitor set debug 0
12992 @itemx monitor set debug 1
12993 Disable or enable general debugging messages.
12995 @item monitor set remote-debug 0
12996 @itemx monitor set remote-debug 1
12997 Disable or enable specific debugging messages associated with the remote
12998 protocol (@pxref{Remote Protocol}).
13002 @node Remote Configuration
13003 @section Remote Configuration
13006 @kindex show remote
13007 This section documents the configuration options available when
13008 debugging remote programs. For the options related to the File I/O
13009 extensions of the remote protocol, see @ref{system,
13010 system-call-allowed}.
13013 @item set remoteaddresssize @var{bits}
13014 @cindex address size for remote targets
13015 @cindex bits in remote address
13016 Set the maximum size of address in a memory packet to the specified
13017 number of bits. @value{GDBN} will mask off the address bits above
13018 that number, when it passes addresses to the remote target. The
13019 default value is the number of bits in the target's address.
13021 @item show remoteaddresssize
13022 Show the current value of remote address size in bits.
13024 @item set remotebaud @var{n}
13025 @cindex baud rate for remote targets
13026 Set the baud rate for the remote serial I/O to @var{n} baud. The
13027 value is used to set the speed of the serial port used for debugging
13030 @item show remotebaud
13031 Show the current speed of the remote connection.
13033 @item set remotebreak
13034 @cindex interrupt remote programs
13035 @cindex BREAK signal instead of Ctrl-C
13036 @anchor{set remotebreak}
13037 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13038 when you type @kbd{Ctrl-c} to interrupt the program running
13039 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13040 character instead. The default is off, since most remote systems
13041 expect to see @samp{Ctrl-C} as the interrupt signal.
13043 @item show remotebreak
13044 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13045 interrupt the remote program.
13047 @item set remoteflow on
13048 @itemx set remoteflow off
13049 @kindex set remoteflow
13050 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13051 on the serial port used to communicate to the remote target.
13053 @item show remoteflow
13054 @kindex show remoteflow
13055 Show the current setting of hardware flow control.
13057 @item set remotelogbase @var{base}
13058 Set the base (a.k.a.@: radix) of logging serial protocol
13059 communications to @var{base}. Supported values of @var{base} are:
13060 @code{ascii}, @code{octal}, and @code{hex}. The default is
13063 @item show remotelogbase
13064 Show the current setting of the radix for logging remote serial
13067 @item set remotelogfile @var{file}
13068 @cindex record serial communications on file
13069 Record remote serial communications on the named @var{file}. The
13070 default is not to record at all.
13072 @item show remotelogfile.
13073 Show the current setting of the file name on which to record the
13074 serial communications.
13076 @item set remotetimeout @var{num}
13077 @cindex timeout for serial communications
13078 @cindex remote timeout
13079 Set the timeout limit to wait for the remote target to respond to
13080 @var{num} seconds. The default is 2 seconds.
13082 @item show remotetimeout
13083 Show the current number of seconds to wait for the remote target
13086 @cindex limit hardware breakpoints and watchpoints
13087 @cindex remote target, limit break- and watchpoints
13088 @anchor{set remote hardware-watchpoint-limit}
13089 @anchor{set remote hardware-breakpoint-limit}
13090 @item set remote hardware-watchpoint-limit @var{limit}
13091 @itemx set remote hardware-breakpoint-limit @var{limit}
13092 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13093 watchpoints. A limit of -1, the default, is treated as unlimited.
13096 @cindex remote packets, enabling and disabling
13097 The @value{GDBN} remote protocol autodetects the packets supported by
13098 your debugging stub. If you need to override the autodetection, you
13099 can use these commands to enable or disable individual packets. Each
13100 packet can be set to @samp{on} (the remote target supports this
13101 packet), @samp{off} (the remote target does not support this packet),
13102 or @samp{auto} (detect remote target support for this packet). They
13103 all default to @samp{auto}. For more information about each packet,
13104 see @ref{Remote Protocol}.
13106 During normal use, you should not have to use any of these commands.
13107 If you do, that may be a bug in your remote debugging stub, or a bug
13108 in @value{GDBN}. You may want to report the problem to the
13109 @value{GDBN} developers.
13111 For each packet @var{name}, the command to enable or disable the
13112 packet is @code{set remote @var{name}-packet}. The available settings
13115 @multitable @columnfractions 0.28 0.32 0.25
13118 @tab Related Features
13120 @item @code{fetch-register}
13122 @tab @code{info registers}
13124 @item @code{set-register}
13128 @item @code{binary-download}
13130 @tab @code{load}, @code{set}
13132 @item @code{read-aux-vector}
13133 @tab @code{qXfer:auxv:read}
13134 @tab @code{info auxv}
13136 @item @code{symbol-lookup}
13137 @tab @code{qSymbol}
13138 @tab Detecting multiple threads
13140 @item @code{verbose-resume}
13142 @tab Stepping or resuming multiple threads
13144 @item @code{software-breakpoint}
13148 @item @code{hardware-breakpoint}
13152 @item @code{write-watchpoint}
13156 @item @code{read-watchpoint}
13160 @item @code{access-watchpoint}
13164 @item @code{target-features}
13165 @tab @code{qXfer:features:read}
13166 @tab @code{set architecture}
13168 @item @code{library-info}
13169 @tab @code{qXfer:libraries:read}
13170 @tab @code{info sharedlibrary}
13172 @item @code{memory-map}
13173 @tab @code{qXfer:memory-map:read}
13174 @tab @code{info mem}
13176 @item @code{read-spu-object}
13177 @tab @code{qXfer:spu:read}
13178 @tab @code{info spu}
13180 @item @code{write-spu-object}
13181 @tab @code{qXfer:spu:write}
13182 @tab @code{info spu}
13184 @item @code{get-thread-local-@*storage-address}
13185 @tab @code{qGetTLSAddr}
13186 @tab Displaying @code{__thread} variables
13188 @item @code{supported-packets}
13189 @tab @code{qSupported}
13190 @tab Remote communications parameters
13192 @item @code{pass-signals}
13193 @tab @code{QPassSignals}
13194 @tab @code{handle @var{signal}}
13196 @item @code{hostio-close-packet}
13197 @tab @code{vFile:close}
13198 @tab @code{remote get}, @code{remote put}
13200 @item @code{hostio-open-packet}
13201 @tab @code{vFile:open}
13202 @tab @code{remote get}, @code{remote put}
13204 @item @code{hostio-pread-packet}
13205 @tab @code{vFile:pread}
13206 @tab @code{remote get}, @code{remote put}
13208 @item @code{hostio-pwrite-packet}
13209 @tab @code{vFile:pwrite}
13210 @tab @code{remote get}, @code{remote put}
13212 @item @code{hostio-unlink-packet}
13213 @tab @code{vFile:unlink}
13214 @tab @code{remote delete}
13218 @section Implementing a Remote Stub
13220 @cindex debugging stub, example
13221 @cindex remote stub, example
13222 @cindex stub example, remote debugging
13223 The stub files provided with @value{GDBN} implement the target side of the
13224 communication protocol, and the @value{GDBN} side is implemented in the
13225 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13226 these subroutines to communicate, and ignore the details. (If you're
13227 implementing your own stub file, you can still ignore the details: start
13228 with one of the existing stub files. @file{sparc-stub.c} is the best
13229 organized, and therefore the easiest to read.)
13231 @cindex remote serial debugging, overview
13232 To debug a program running on another machine (the debugging
13233 @dfn{target} machine), you must first arrange for all the usual
13234 prerequisites for the program to run by itself. For example, for a C
13239 A startup routine to set up the C runtime environment; these usually
13240 have a name like @file{crt0}. The startup routine may be supplied by
13241 your hardware supplier, or you may have to write your own.
13244 A C subroutine library to support your program's
13245 subroutine calls, notably managing input and output.
13248 A way of getting your program to the other machine---for example, a
13249 download program. These are often supplied by the hardware
13250 manufacturer, but you may have to write your own from hardware
13254 The next step is to arrange for your program to use a serial port to
13255 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13256 machine). In general terms, the scheme looks like this:
13260 @value{GDBN} already understands how to use this protocol; when everything
13261 else is set up, you can simply use the @samp{target remote} command
13262 (@pxref{Targets,,Specifying a Debugging Target}).
13264 @item On the target,
13265 you must link with your program a few special-purpose subroutines that
13266 implement the @value{GDBN} remote serial protocol. The file containing these
13267 subroutines is called a @dfn{debugging stub}.
13269 On certain remote targets, you can use an auxiliary program
13270 @code{gdbserver} instead of linking a stub into your program.
13271 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13274 The debugging stub is specific to the architecture of the remote
13275 machine; for example, use @file{sparc-stub.c} to debug programs on
13278 @cindex remote serial stub list
13279 These working remote stubs are distributed with @value{GDBN}:
13284 @cindex @file{i386-stub.c}
13287 For Intel 386 and compatible architectures.
13290 @cindex @file{m68k-stub.c}
13291 @cindex Motorola 680x0
13293 For Motorola 680x0 architectures.
13296 @cindex @file{sh-stub.c}
13299 For Renesas SH architectures.
13302 @cindex @file{sparc-stub.c}
13304 For @sc{sparc} architectures.
13306 @item sparcl-stub.c
13307 @cindex @file{sparcl-stub.c}
13310 For Fujitsu @sc{sparclite} architectures.
13314 The @file{README} file in the @value{GDBN} distribution may list other
13315 recently added stubs.
13318 * Stub Contents:: What the stub can do for you
13319 * Bootstrapping:: What you must do for the stub
13320 * Debug Session:: Putting it all together
13323 @node Stub Contents
13324 @subsection What the Stub Can Do for You
13326 @cindex remote serial stub
13327 The debugging stub for your architecture supplies these three
13331 @item set_debug_traps
13332 @findex set_debug_traps
13333 @cindex remote serial stub, initialization
13334 This routine arranges for @code{handle_exception} to run when your
13335 program stops. You must call this subroutine explicitly near the
13336 beginning of your program.
13338 @item handle_exception
13339 @findex handle_exception
13340 @cindex remote serial stub, main routine
13341 This is the central workhorse, but your program never calls it
13342 explicitly---the setup code arranges for @code{handle_exception} to
13343 run when a trap is triggered.
13345 @code{handle_exception} takes control when your program stops during
13346 execution (for example, on a breakpoint), and mediates communications
13347 with @value{GDBN} on the host machine. This is where the communications
13348 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13349 representative on the target machine. It begins by sending summary
13350 information on the state of your program, then continues to execute,
13351 retrieving and transmitting any information @value{GDBN} needs, until you
13352 execute a @value{GDBN} command that makes your program resume; at that point,
13353 @code{handle_exception} returns control to your own code on the target
13357 @cindex @code{breakpoint} subroutine, remote
13358 Use this auxiliary subroutine to make your program contain a
13359 breakpoint. Depending on the particular situation, this may be the only
13360 way for @value{GDBN} to get control. For instance, if your target
13361 machine has some sort of interrupt button, you won't need to call this;
13362 pressing the interrupt button transfers control to
13363 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13364 simply receiving characters on the serial port may also trigger a trap;
13365 again, in that situation, you don't need to call @code{breakpoint} from
13366 your own program---simply running @samp{target remote} from the host
13367 @value{GDBN} session gets control.
13369 Call @code{breakpoint} if none of these is true, or if you simply want
13370 to make certain your program stops at a predetermined point for the
13371 start of your debugging session.
13374 @node Bootstrapping
13375 @subsection What You Must Do for the Stub
13377 @cindex remote stub, support routines
13378 The debugging stubs that come with @value{GDBN} are set up for a particular
13379 chip architecture, but they have no information about the rest of your
13380 debugging target machine.
13382 First of all you need to tell the stub how to communicate with the
13386 @item int getDebugChar()
13387 @findex getDebugChar
13388 Write this subroutine to read a single character from the serial port.
13389 It may be identical to @code{getchar} for your target system; a
13390 different name is used to allow you to distinguish the two if you wish.
13392 @item void putDebugChar(int)
13393 @findex putDebugChar
13394 Write this subroutine to write a single character to the serial port.
13395 It may be identical to @code{putchar} for your target system; a
13396 different name is used to allow you to distinguish the two if you wish.
13399 @cindex control C, and remote debugging
13400 @cindex interrupting remote targets
13401 If you want @value{GDBN} to be able to stop your program while it is
13402 running, you need to use an interrupt-driven serial driver, and arrange
13403 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13404 character). That is the character which @value{GDBN} uses to tell the
13405 remote system to stop.
13407 Getting the debugging target to return the proper status to @value{GDBN}
13408 probably requires changes to the standard stub; one quick and dirty way
13409 is to just execute a breakpoint instruction (the ``dirty'' part is that
13410 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13412 Other routines you need to supply are:
13415 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13416 @findex exceptionHandler
13417 Write this function to install @var{exception_address} in the exception
13418 handling tables. You need to do this because the stub does not have any
13419 way of knowing what the exception handling tables on your target system
13420 are like (for example, the processor's table might be in @sc{rom},
13421 containing entries which point to a table in @sc{ram}).
13422 @var{exception_number} is the exception number which should be changed;
13423 its meaning is architecture-dependent (for example, different numbers
13424 might represent divide by zero, misaligned access, etc). When this
13425 exception occurs, control should be transferred directly to
13426 @var{exception_address}, and the processor state (stack, registers,
13427 and so on) should be just as it is when a processor exception occurs. So if
13428 you want to use a jump instruction to reach @var{exception_address}, it
13429 should be a simple jump, not a jump to subroutine.
13431 For the 386, @var{exception_address} should be installed as an interrupt
13432 gate so that interrupts are masked while the handler runs. The gate
13433 should be at privilege level 0 (the most privileged level). The
13434 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13435 help from @code{exceptionHandler}.
13437 @item void flush_i_cache()
13438 @findex flush_i_cache
13439 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13440 instruction cache, if any, on your target machine. If there is no
13441 instruction cache, this subroutine may be a no-op.
13443 On target machines that have instruction caches, @value{GDBN} requires this
13444 function to make certain that the state of your program is stable.
13448 You must also make sure this library routine is available:
13451 @item void *memset(void *, int, int)
13453 This is the standard library function @code{memset} that sets an area of
13454 memory to a known value. If you have one of the free versions of
13455 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13456 either obtain it from your hardware manufacturer, or write your own.
13459 If you do not use the GNU C compiler, you may need other standard
13460 library subroutines as well; this varies from one stub to another,
13461 but in general the stubs are likely to use any of the common library
13462 subroutines which @code{@value{NGCC}} generates as inline code.
13465 @node Debug Session
13466 @subsection Putting it All Together
13468 @cindex remote serial debugging summary
13469 In summary, when your program is ready to debug, you must follow these
13474 Make sure you have defined the supporting low-level routines
13475 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13477 @code{getDebugChar}, @code{putDebugChar},
13478 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13482 Insert these lines near the top of your program:
13490 For the 680x0 stub only, you need to provide a variable called
13491 @code{exceptionHook}. Normally you just use:
13494 void (*exceptionHook)() = 0;
13498 but if before calling @code{set_debug_traps}, you set it to point to a
13499 function in your program, that function is called when
13500 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13501 error). The function indicated by @code{exceptionHook} is called with
13502 one parameter: an @code{int} which is the exception number.
13505 Compile and link together: your program, the @value{GDBN} debugging stub for
13506 your target architecture, and the supporting subroutines.
13509 Make sure you have a serial connection between your target machine and
13510 the @value{GDBN} host, and identify the serial port on the host.
13513 @c The "remote" target now provides a `load' command, so we should
13514 @c document that. FIXME.
13515 Download your program to your target machine (or get it there by
13516 whatever means the manufacturer provides), and start it.
13519 Start @value{GDBN} on the host, and connect to the target
13520 (@pxref{Connecting,,Connecting to a Remote Target}).
13524 @node Configurations
13525 @chapter Configuration-Specific Information
13527 While nearly all @value{GDBN} commands are available for all native and
13528 cross versions of the debugger, there are some exceptions. This chapter
13529 describes things that are only available in certain configurations.
13531 There are three major categories of configurations: native
13532 configurations, where the host and target are the same, embedded
13533 operating system configurations, which are usually the same for several
13534 different processor architectures, and bare embedded processors, which
13535 are quite different from each other.
13540 * Embedded Processors::
13547 This section describes details specific to particular native
13552 * BSD libkvm Interface:: Debugging BSD kernel memory images
13553 * SVR4 Process Information:: SVR4 process information
13554 * DJGPP Native:: Features specific to the DJGPP port
13555 * Cygwin Native:: Features specific to the Cygwin port
13556 * Hurd Native:: Features specific to @sc{gnu} Hurd
13557 * Neutrino:: Features specific to QNX Neutrino
13563 On HP-UX systems, if you refer to a function or variable name that
13564 begins with a dollar sign, @value{GDBN} searches for a user or system
13565 name first, before it searches for a convenience variable.
13568 @node BSD libkvm Interface
13569 @subsection BSD libkvm Interface
13572 @cindex kernel memory image
13573 @cindex kernel crash dump
13575 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13576 interface that provides a uniform interface for accessing kernel virtual
13577 memory images, including live systems and crash dumps. @value{GDBN}
13578 uses this interface to allow you to debug live kernels and kernel crash
13579 dumps on many native BSD configurations. This is implemented as a
13580 special @code{kvm} debugging target. For debugging a live system, load
13581 the currently running kernel into @value{GDBN} and connect to the
13585 (@value{GDBP}) @b{target kvm}
13588 For debugging crash dumps, provide the file name of the crash dump as an
13592 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13595 Once connected to the @code{kvm} target, the following commands are
13601 Set current context from the @dfn{Process Control Block} (PCB) address.
13604 Set current context from proc address. This command isn't available on
13605 modern FreeBSD systems.
13608 @node SVR4 Process Information
13609 @subsection SVR4 Process Information
13611 @cindex examine process image
13612 @cindex process info via @file{/proc}
13614 Many versions of SVR4 and compatible systems provide a facility called
13615 @samp{/proc} that can be used to examine the image of a running
13616 process using file-system subroutines. If @value{GDBN} is configured
13617 for an operating system with this facility, the command @code{info
13618 proc} is available to report information about the process running
13619 your program, or about any process running on your system. @code{info
13620 proc} works only on SVR4 systems that include the @code{procfs} code.
13621 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13622 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13628 @itemx info proc @var{process-id}
13629 Summarize available information about any running process. If a
13630 process ID is specified by @var{process-id}, display information about
13631 that process; otherwise display information about the program being
13632 debugged. The summary includes the debugged process ID, the command
13633 line used to invoke it, its current working directory, and its
13634 executable file's absolute file name.
13636 On some systems, @var{process-id} can be of the form
13637 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13638 within a process. If the optional @var{pid} part is missing, it means
13639 a thread from the process being debugged (the leading @samp{/} still
13640 needs to be present, or else @value{GDBN} will interpret the number as
13641 a process ID rather than a thread ID).
13643 @item info proc mappings
13644 @cindex memory address space mappings
13645 Report the memory address space ranges accessible in the program, with
13646 information on whether the process has read, write, or execute access
13647 rights to each range. On @sc{gnu}/Linux systems, each memory range
13648 includes the object file which is mapped to that range, instead of the
13649 memory access rights to that range.
13651 @item info proc stat
13652 @itemx info proc status
13653 @cindex process detailed status information
13654 These subcommands are specific to @sc{gnu}/Linux systems. They show
13655 the process-related information, including the user ID and group ID;
13656 how many threads are there in the process; its virtual memory usage;
13657 the signals that are pending, blocked, and ignored; its TTY; its
13658 consumption of system and user time; its stack size; its @samp{nice}
13659 value; etc. For more information, see the @samp{proc} man page
13660 (type @kbd{man 5 proc} from your shell prompt).
13662 @item info proc all
13663 Show all the information about the process described under all of the
13664 above @code{info proc} subcommands.
13667 @comment These sub-options of 'info proc' were not included when
13668 @comment procfs.c was re-written. Keep their descriptions around
13669 @comment against the day when someone finds the time to put them back in.
13670 @kindex info proc times
13671 @item info proc times
13672 Starting time, user CPU time, and system CPU time for your program and
13675 @kindex info proc id
13677 Report on the process IDs related to your program: its own process ID,
13678 the ID of its parent, the process group ID, and the session ID.
13681 @item set procfs-trace
13682 @kindex set procfs-trace
13683 @cindex @code{procfs} API calls
13684 This command enables and disables tracing of @code{procfs} API calls.
13686 @item show procfs-trace
13687 @kindex show procfs-trace
13688 Show the current state of @code{procfs} API call tracing.
13690 @item set procfs-file @var{file}
13691 @kindex set procfs-file
13692 Tell @value{GDBN} to write @code{procfs} API trace to the named
13693 @var{file}. @value{GDBN} appends the trace info to the previous
13694 contents of the file. The default is to display the trace on the
13697 @item show procfs-file
13698 @kindex show procfs-file
13699 Show the file to which @code{procfs} API trace is written.
13701 @item proc-trace-entry
13702 @itemx proc-trace-exit
13703 @itemx proc-untrace-entry
13704 @itemx proc-untrace-exit
13705 @kindex proc-trace-entry
13706 @kindex proc-trace-exit
13707 @kindex proc-untrace-entry
13708 @kindex proc-untrace-exit
13709 These commands enable and disable tracing of entries into and exits
13710 from the @code{syscall} interface.
13713 @kindex info pidlist
13714 @cindex process list, QNX Neutrino
13715 For QNX Neutrino only, this command displays the list of all the
13716 processes and all the threads within each process.
13719 @kindex info meminfo
13720 @cindex mapinfo list, QNX Neutrino
13721 For QNX Neutrino only, this command displays the list of all mapinfos.
13725 @subsection Features for Debugging @sc{djgpp} Programs
13726 @cindex @sc{djgpp} debugging
13727 @cindex native @sc{djgpp} debugging
13728 @cindex MS-DOS-specific commands
13731 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13732 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13733 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13734 top of real-mode DOS systems and their emulations.
13736 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13737 defines a few commands specific to the @sc{djgpp} port. This
13738 subsection describes those commands.
13743 This is a prefix of @sc{djgpp}-specific commands which print
13744 information about the target system and important OS structures.
13747 @cindex MS-DOS system info
13748 @cindex free memory information (MS-DOS)
13749 @item info dos sysinfo
13750 This command displays assorted information about the underlying
13751 platform: the CPU type and features, the OS version and flavor, the
13752 DPMI version, and the available conventional and DPMI memory.
13757 @cindex segment descriptor tables
13758 @cindex descriptor tables display
13760 @itemx info dos ldt
13761 @itemx info dos idt
13762 These 3 commands display entries from, respectively, Global, Local,
13763 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13764 tables are data structures which store a descriptor for each segment
13765 that is currently in use. The segment's selector is an index into a
13766 descriptor table; the table entry for that index holds the
13767 descriptor's base address and limit, and its attributes and access
13770 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13771 segment (used for both data and the stack), and a DOS segment (which
13772 allows access to DOS/BIOS data structures and absolute addresses in
13773 conventional memory). However, the DPMI host will usually define
13774 additional segments in order to support the DPMI environment.
13776 @cindex garbled pointers
13777 These commands allow to display entries from the descriptor tables.
13778 Without an argument, all entries from the specified table are
13779 displayed. An argument, which should be an integer expression, means
13780 display a single entry whose index is given by the argument. For
13781 example, here's a convenient way to display information about the
13782 debugged program's data segment:
13785 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13786 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13790 This comes in handy when you want to see whether a pointer is outside
13791 the data segment's limit (i.e.@: @dfn{garbled}).
13793 @cindex page tables display (MS-DOS)
13795 @itemx info dos pte
13796 These two commands display entries from, respectively, the Page
13797 Directory and the Page Tables. Page Directories and Page Tables are
13798 data structures which control how virtual memory addresses are mapped
13799 into physical addresses. A Page Table includes an entry for every
13800 page of memory that is mapped into the program's address space; there
13801 may be several Page Tables, each one holding up to 4096 entries. A
13802 Page Directory has up to 4096 entries, one each for every Page Table
13803 that is currently in use.
13805 Without an argument, @kbd{info dos pde} displays the entire Page
13806 Directory, and @kbd{info dos pte} displays all the entries in all of
13807 the Page Tables. An argument, an integer expression, given to the
13808 @kbd{info dos pde} command means display only that entry from the Page
13809 Directory table. An argument given to the @kbd{info dos pte} command
13810 means display entries from a single Page Table, the one pointed to by
13811 the specified entry in the Page Directory.
13813 @cindex direct memory access (DMA) on MS-DOS
13814 These commands are useful when your program uses @dfn{DMA} (Direct
13815 Memory Access), which needs physical addresses to program the DMA
13818 These commands are supported only with some DPMI servers.
13820 @cindex physical address from linear address
13821 @item info dos address-pte @var{addr}
13822 This command displays the Page Table entry for a specified linear
13823 address. The argument @var{addr} is a linear address which should
13824 already have the appropriate segment's base address added to it,
13825 because this command accepts addresses which may belong to @emph{any}
13826 segment. For example, here's how to display the Page Table entry for
13827 the page where a variable @code{i} is stored:
13830 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13831 @exdent @code{Page Table entry for address 0x11a00d30:}
13832 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13836 This says that @code{i} is stored at offset @code{0xd30} from the page
13837 whose physical base address is @code{0x02698000}, and shows all the
13838 attributes of that page.
13840 Note that you must cast the addresses of variables to a @code{char *},
13841 since otherwise the value of @code{__djgpp_base_address}, the base
13842 address of all variables and functions in a @sc{djgpp} program, will
13843 be added using the rules of C pointer arithmetics: if @code{i} is
13844 declared an @code{int}, @value{GDBN} will add 4 times the value of
13845 @code{__djgpp_base_address} to the address of @code{i}.
13847 Here's another example, it displays the Page Table entry for the
13851 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13852 @exdent @code{Page Table entry for address 0x29110:}
13853 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13857 (The @code{+ 3} offset is because the transfer buffer's address is the
13858 3rd member of the @code{_go32_info_block} structure.) The output
13859 clearly shows that this DPMI server maps the addresses in conventional
13860 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13861 linear (@code{0x29110}) addresses are identical.
13863 This command is supported only with some DPMI servers.
13866 @cindex DOS serial data link, remote debugging
13867 In addition to native debugging, the DJGPP port supports remote
13868 debugging via a serial data link. The following commands are specific
13869 to remote serial debugging in the DJGPP port of @value{GDBN}.
13872 @kindex set com1base
13873 @kindex set com1irq
13874 @kindex set com2base
13875 @kindex set com2irq
13876 @kindex set com3base
13877 @kindex set com3irq
13878 @kindex set com4base
13879 @kindex set com4irq
13880 @item set com1base @var{addr}
13881 This command sets the base I/O port address of the @file{COM1} serial
13884 @item set com1irq @var{irq}
13885 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13886 for the @file{COM1} serial port.
13888 There are similar commands @samp{set com2base}, @samp{set com3irq},
13889 etc.@: for setting the port address and the @code{IRQ} lines for the
13892 @kindex show com1base
13893 @kindex show com1irq
13894 @kindex show com2base
13895 @kindex show com2irq
13896 @kindex show com3base
13897 @kindex show com3irq
13898 @kindex show com4base
13899 @kindex show com4irq
13900 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13901 display the current settings of the base address and the @code{IRQ}
13902 lines used by the COM ports.
13905 @kindex info serial
13906 @cindex DOS serial port status
13907 This command prints the status of the 4 DOS serial ports. For each
13908 port, it prints whether it's active or not, its I/O base address and
13909 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13910 counts of various errors encountered so far.
13914 @node Cygwin Native
13915 @subsection Features for Debugging MS Windows PE Executables
13916 @cindex MS Windows debugging
13917 @cindex native Cygwin debugging
13918 @cindex Cygwin-specific commands
13920 @value{GDBN} supports native debugging of MS Windows programs, including
13921 DLLs with and without symbolic debugging information. There are various
13922 additional Cygwin-specific commands, described in this section.
13923 Working with DLLs that have no debugging symbols is described in
13924 @ref{Non-debug DLL Symbols}.
13929 This is a prefix of MS Windows-specific commands which print
13930 information about the target system and important OS structures.
13932 @item info w32 selector
13933 This command displays information returned by
13934 the Win32 API @code{GetThreadSelectorEntry} function.
13935 It takes an optional argument that is evaluated to
13936 a long value to give the information about this given selector.
13937 Without argument, this command displays information
13938 about the six segment registers.
13942 This is a Cygwin-specific alias of @code{info shared}.
13944 @kindex dll-symbols
13946 This command loads symbols from a dll similarly to
13947 add-sym command but without the need to specify a base address.
13949 @kindex set cygwin-exceptions
13950 @cindex debugging the Cygwin DLL
13951 @cindex Cygwin DLL, debugging
13952 @item set cygwin-exceptions @var{mode}
13953 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13954 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13955 @value{GDBN} will delay recognition of exceptions, and may ignore some
13956 exceptions which seem to be caused by internal Cygwin DLL
13957 ``bookkeeping''. This option is meant primarily for debugging the
13958 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13959 @value{GDBN} users with false @code{SIGSEGV} signals.
13961 @kindex show cygwin-exceptions
13962 @item show cygwin-exceptions
13963 Displays whether @value{GDBN} will break on exceptions that happen
13964 inside the Cygwin DLL itself.
13966 @kindex set new-console
13967 @item set new-console @var{mode}
13968 If @var{mode} is @code{on} the debuggee will
13969 be started in a new console on next start.
13970 If @var{mode} is @code{off}i, the debuggee will
13971 be started in the same console as the debugger.
13973 @kindex show new-console
13974 @item show new-console
13975 Displays whether a new console is used
13976 when the debuggee is started.
13978 @kindex set new-group
13979 @item set new-group @var{mode}
13980 This boolean value controls whether the debuggee should
13981 start a new group or stay in the same group as the debugger.
13982 This affects the way the Windows OS handles
13985 @kindex show new-group
13986 @item show new-group
13987 Displays current value of new-group boolean.
13989 @kindex set debugevents
13990 @item set debugevents
13991 This boolean value adds debug output concerning kernel events related
13992 to the debuggee seen by the debugger. This includes events that
13993 signal thread and process creation and exit, DLL loading and
13994 unloading, console interrupts, and debugging messages produced by the
13995 Windows @code{OutputDebugString} API call.
13997 @kindex set debugexec
13998 @item set debugexec
13999 This boolean value adds debug output concerning execute events
14000 (such as resume thread) seen by the debugger.
14002 @kindex set debugexceptions
14003 @item set debugexceptions
14004 This boolean value adds debug output concerning exceptions in the
14005 debuggee seen by the debugger.
14007 @kindex set debugmemory
14008 @item set debugmemory
14009 This boolean value adds debug output concerning debuggee memory reads
14010 and writes by the debugger.
14014 This boolean values specifies whether the debuggee is called
14015 via a shell or directly (default value is on).
14019 Displays if the debuggee will be started with a shell.
14024 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14027 @node Non-debug DLL Symbols
14028 @subsubsection Support for DLLs without Debugging Symbols
14029 @cindex DLLs with no debugging symbols
14030 @cindex Minimal symbols and DLLs
14032 Very often on windows, some of the DLLs that your program relies on do
14033 not include symbolic debugging information (for example,
14034 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14035 symbols in a DLL, it relies on the minimal amount of symbolic
14036 information contained in the DLL's export table. This section
14037 describes working with such symbols, known internally to @value{GDBN} as
14038 ``minimal symbols''.
14040 Note that before the debugged program has started execution, no DLLs
14041 will have been loaded. The easiest way around this problem is simply to
14042 start the program --- either by setting a breakpoint or letting the
14043 program run once to completion. It is also possible to force
14044 @value{GDBN} to load a particular DLL before starting the executable ---
14045 see the shared library information in @ref{Files}, or the
14046 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14047 explicitly loading symbols from a DLL with no debugging information will
14048 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14049 which may adversely affect symbol lookup performance.
14051 @subsubsection DLL Name Prefixes
14053 In keeping with the naming conventions used by the Microsoft debugging
14054 tools, DLL export symbols are made available with a prefix based on the
14055 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14056 also entered into the symbol table, so @code{CreateFileA} is often
14057 sufficient. In some cases there will be name clashes within a program
14058 (particularly if the executable itself includes full debugging symbols)
14059 necessitating the use of the fully qualified name when referring to the
14060 contents of the DLL. Use single-quotes around the name to avoid the
14061 exclamation mark (``!'') being interpreted as a language operator.
14063 Note that the internal name of the DLL may be all upper-case, even
14064 though the file name of the DLL is lower-case, or vice-versa. Since
14065 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14066 some confusion. If in doubt, try the @code{info functions} and
14067 @code{info variables} commands or even @code{maint print msymbols}
14068 (@pxref{Symbols}). Here's an example:
14071 (@value{GDBP}) info function CreateFileA
14072 All functions matching regular expression "CreateFileA":
14074 Non-debugging symbols:
14075 0x77e885f4 CreateFileA
14076 0x77e885f4 KERNEL32!CreateFileA
14080 (@value{GDBP}) info function !
14081 All functions matching regular expression "!":
14083 Non-debugging symbols:
14084 0x6100114c cygwin1!__assert
14085 0x61004034 cygwin1!_dll_crt0@@0
14086 0x61004240 cygwin1!dll_crt0(per_process *)
14090 @subsubsection Working with Minimal Symbols
14092 Symbols extracted from a DLL's export table do not contain very much
14093 type information. All that @value{GDBN} can do is guess whether a symbol
14094 refers to a function or variable depending on the linker section that
14095 contains the symbol. Also note that the actual contents of the memory
14096 contained in a DLL are not available unless the program is running. This
14097 means that you cannot examine the contents of a variable or disassemble
14098 a function within a DLL without a running program.
14100 Variables are generally treated as pointers and dereferenced
14101 automatically. For this reason, it is often necessary to prefix a
14102 variable name with the address-of operator (``&'') and provide explicit
14103 type information in the command. Here's an example of the type of
14107 (@value{GDBP}) print 'cygwin1!__argv'
14112 (@value{GDBP}) x 'cygwin1!__argv'
14113 0x10021610: "\230y\""
14116 And two possible solutions:
14119 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14120 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14124 (@value{GDBP}) x/2x &'cygwin1!__argv'
14125 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14126 (@value{GDBP}) x/x 0x10021608
14127 0x10021608: 0x0022fd98
14128 (@value{GDBP}) x/s 0x0022fd98
14129 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14132 Setting a break point within a DLL is possible even before the program
14133 starts execution. However, under these circumstances, @value{GDBN} can't
14134 examine the initial instructions of the function in order to skip the
14135 function's frame set-up code. You can work around this by using ``*&''
14136 to set the breakpoint at a raw memory address:
14139 (@value{GDBP}) break *&'python22!PyOS_Readline'
14140 Breakpoint 1 at 0x1e04eff0
14143 The author of these extensions is not entirely convinced that setting a
14144 break point within a shared DLL like @file{kernel32.dll} is completely
14148 @subsection Commands Specific to @sc{gnu} Hurd Systems
14149 @cindex @sc{gnu} Hurd debugging
14151 This subsection describes @value{GDBN} commands specific to the
14152 @sc{gnu} Hurd native debugging.
14157 @kindex set signals@r{, Hurd command}
14158 @kindex set sigs@r{, Hurd command}
14159 This command toggles the state of inferior signal interception by
14160 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14161 affected by this command. @code{sigs} is a shorthand alias for
14166 @kindex show signals@r{, Hurd command}
14167 @kindex show sigs@r{, Hurd command}
14168 Show the current state of intercepting inferior's signals.
14170 @item set signal-thread
14171 @itemx set sigthread
14172 @kindex set signal-thread
14173 @kindex set sigthread
14174 This command tells @value{GDBN} which thread is the @code{libc} signal
14175 thread. That thread is run when a signal is delivered to a running
14176 process. @code{set sigthread} is the shorthand alias of @code{set
14179 @item show signal-thread
14180 @itemx show sigthread
14181 @kindex show signal-thread
14182 @kindex show sigthread
14183 These two commands show which thread will run when the inferior is
14184 delivered a signal.
14187 @kindex set stopped@r{, Hurd command}
14188 This commands tells @value{GDBN} that the inferior process is stopped,
14189 as with the @code{SIGSTOP} signal. The stopped process can be
14190 continued by delivering a signal to it.
14193 @kindex show stopped@r{, Hurd command}
14194 This command shows whether @value{GDBN} thinks the debuggee is
14197 @item set exceptions
14198 @kindex set exceptions@r{, Hurd command}
14199 Use this command to turn off trapping of exceptions in the inferior.
14200 When exception trapping is off, neither breakpoints nor
14201 single-stepping will work. To restore the default, set exception
14204 @item show exceptions
14205 @kindex show exceptions@r{, Hurd command}
14206 Show the current state of trapping exceptions in the inferior.
14208 @item set task pause
14209 @kindex set task@r{, Hurd commands}
14210 @cindex task attributes (@sc{gnu} Hurd)
14211 @cindex pause current task (@sc{gnu} Hurd)
14212 This command toggles task suspension when @value{GDBN} has control.
14213 Setting it to on takes effect immediately, and the task is suspended
14214 whenever @value{GDBN} gets control. Setting it to off will take
14215 effect the next time the inferior is continued. If this option is set
14216 to off, you can use @code{set thread default pause on} or @code{set
14217 thread pause on} (see below) to pause individual threads.
14219 @item show task pause
14220 @kindex show task@r{, Hurd commands}
14221 Show the current state of task suspension.
14223 @item set task detach-suspend-count
14224 @cindex task suspend count
14225 @cindex detach from task, @sc{gnu} Hurd
14226 This command sets the suspend count the task will be left with when
14227 @value{GDBN} detaches from it.
14229 @item show task detach-suspend-count
14230 Show the suspend count the task will be left with when detaching.
14232 @item set task exception-port
14233 @itemx set task excp
14234 @cindex task exception port, @sc{gnu} Hurd
14235 This command sets the task exception port to which @value{GDBN} will
14236 forward exceptions. The argument should be the value of the @dfn{send
14237 rights} of the task. @code{set task excp} is a shorthand alias.
14239 @item set noninvasive
14240 @cindex noninvasive task options
14241 This command switches @value{GDBN} to a mode that is the least
14242 invasive as far as interfering with the inferior is concerned. This
14243 is the same as using @code{set task pause}, @code{set exceptions}, and
14244 @code{set signals} to values opposite to the defaults.
14246 @item info send-rights
14247 @itemx info receive-rights
14248 @itemx info port-rights
14249 @itemx info port-sets
14250 @itemx info dead-names
14253 @cindex send rights, @sc{gnu} Hurd
14254 @cindex receive rights, @sc{gnu} Hurd
14255 @cindex port rights, @sc{gnu} Hurd
14256 @cindex port sets, @sc{gnu} Hurd
14257 @cindex dead names, @sc{gnu} Hurd
14258 These commands display information about, respectively, send rights,
14259 receive rights, port rights, port sets, and dead names of a task.
14260 There are also shorthand aliases: @code{info ports} for @code{info
14261 port-rights} and @code{info psets} for @code{info port-sets}.
14263 @item set thread pause
14264 @kindex set thread@r{, Hurd command}
14265 @cindex thread properties, @sc{gnu} Hurd
14266 @cindex pause current thread (@sc{gnu} Hurd)
14267 This command toggles current thread suspension when @value{GDBN} has
14268 control. Setting it to on takes effect immediately, and the current
14269 thread is suspended whenever @value{GDBN} gets control. Setting it to
14270 off will take effect the next time the inferior is continued.
14271 Normally, this command has no effect, since when @value{GDBN} has
14272 control, the whole task is suspended. However, if you used @code{set
14273 task pause off} (see above), this command comes in handy to suspend
14274 only the current thread.
14276 @item show thread pause
14277 @kindex show thread@r{, Hurd command}
14278 This command shows the state of current thread suspension.
14280 @item set thread run
14281 This command sets whether the current thread is allowed to run.
14283 @item show thread run
14284 Show whether the current thread is allowed to run.
14286 @item set thread detach-suspend-count
14287 @cindex thread suspend count, @sc{gnu} Hurd
14288 @cindex detach from thread, @sc{gnu} Hurd
14289 This command sets the suspend count @value{GDBN} will leave on a
14290 thread when detaching. This number is relative to the suspend count
14291 found by @value{GDBN} when it notices the thread; use @code{set thread
14292 takeover-suspend-count} to force it to an absolute value.
14294 @item show thread detach-suspend-count
14295 Show the suspend count @value{GDBN} will leave on the thread when
14298 @item set thread exception-port
14299 @itemx set thread excp
14300 Set the thread exception port to which to forward exceptions. This
14301 overrides the port set by @code{set task exception-port} (see above).
14302 @code{set thread excp} is the shorthand alias.
14304 @item set thread takeover-suspend-count
14305 Normally, @value{GDBN}'s thread suspend counts are relative to the
14306 value @value{GDBN} finds when it notices each thread. This command
14307 changes the suspend counts to be absolute instead.
14309 @item set thread default
14310 @itemx show thread default
14311 @cindex thread default settings, @sc{gnu} Hurd
14312 Each of the above @code{set thread} commands has a @code{set thread
14313 default} counterpart (e.g., @code{set thread default pause}, @code{set
14314 thread default exception-port}, etc.). The @code{thread default}
14315 variety of commands sets the default thread properties for all
14316 threads; you can then change the properties of individual threads with
14317 the non-default commands.
14322 @subsection QNX Neutrino
14323 @cindex QNX Neutrino
14325 @value{GDBN} provides the following commands specific to the QNX
14329 @item set debug nto-debug
14330 @kindex set debug nto-debug
14331 When set to on, enables debugging messages specific to the QNX
14334 @item show debug nto-debug
14335 @kindex show debug nto-debug
14336 Show the current state of QNX Neutrino messages.
14341 @section Embedded Operating Systems
14343 This section describes configurations involving the debugging of
14344 embedded operating systems that are available for several different
14348 * VxWorks:: Using @value{GDBN} with VxWorks
14351 @value{GDBN} includes the ability to debug programs running on
14352 various real-time operating systems.
14355 @subsection Using @value{GDBN} with VxWorks
14361 @kindex target vxworks
14362 @item target vxworks @var{machinename}
14363 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14364 is the target system's machine name or IP address.
14368 On VxWorks, @code{load} links @var{filename} dynamically on the
14369 current target system as well as adding its symbols in @value{GDBN}.
14371 @value{GDBN} enables developers to spawn and debug tasks running on networked
14372 VxWorks targets from a Unix host. Already-running tasks spawned from
14373 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14374 both the Unix host and on the VxWorks target. The program
14375 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14376 installed with the name @code{vxgdb}, to distinguish it from a
14377 @value{GDBN} for debugging programs on the host itself.)
14380 @item VxWorks-timeout @var{args}
14381 @kindex vxworks-timeout
14382 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14383 This option is set by the user, and @var{args} represents the number of
14384 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14385 your VxWorks target is a slow software simulator or is on the far side
14386 of a thin network line.
14389 The following information on connecting to VxWorks was current when
14390 this manual was produced; newer releases of VxWorks may use revised
14393 @findex INCLUDE_RDB
14394 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14395 to include the remote debugging interface routines in the VxWorks
14396 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14397 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14398 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14399 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14400 information on configuring and remaking VxWorks, see the manufacturer's
14402 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14404 Once you have included @file{rdb.a} in your VxWorks system image and set
14405 your Unix execution search path to find @value{GDBN}, you are ready to
14406 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14407 @code{vxgdb}, depending on your installation).
14409 @value{GDBN} comes up showing the prompt:
14416 * VxWorks Connection:: Connecting to VxWorks
14417 * VxWorks Download:: VxWorks download
14418 * VxWorks Attach:: Running tasks
14421 @node VxWorks Connection
14422 @subsubsection Connecting to VxWorks
14424 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14425 network. To connect to a target whose host name is ``@code{tt}'', type:
14428 (vxgdb) target vxworks tt
14432 @value{GDBN} displays messages like these:
14435 Attaching remote machine across net...
14440 @value{GDBN} then attempts to read the symbol tables of any object modules
14441 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14442 these files by searching the directories listed in the command search
14443 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14444 to find an object file, it displays a message such as:
14447 prog.o: No such file or directory.
14450 When this happens, add the appropriate directory to the search path with
14451 the @value{GDBN} command @code{path}, and execute the @code{target}
14454 @node VxWorks Download
14455 @subsubsection VxWorks Download
14457 @cindex download to VxWorks
14458 If you have connected to the VxWorks target and you want to debug an
14459 object that has not yet been loaded, you can use the @value{GDBN}
14460 @code{load} command to download a file from Unix to VxWorks
14461 incrementally. The object file given as an argument to the @code{load}
14462 command is actually opened twice: first by the VxWorks target in order
14463 to download the code, then by @value{GDBN} in order to read the symbol
14464 table. This can lead to problems if the current working directories on
14465 the two systems differ. If both systems have NFS mounted the same
14466 filesystems, you can avoid these problems by using absolute paths.
14467 Otherwise, it is simplest to set the working directory on both systems
14468 to the directory in which the object file resides, and then to reference
14469 the file by its name, without any path. For instance, a program
14470 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14471 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14472 program, type this on VxWorks:
14475 -> cd "@var{vxpath}/vw/demo/rdb"
14479 Then, in @value{GDBN}, type:
14482 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14483 (vxgdb) load prog.o
14486 @value{GDBN} displays a response similar to this:
14489 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14492 You can also use the @code{load} command to reload an object module
14493 after editing and recompiling the corresponding source file. Note that
14494 this makes @value{GDBN} delete all currently-defined breakpoints,
14495 auto-displays, and convenience variables, and to clear the value
14496 history. (This is necessary in order to preserve the integrity of
14497 debugger's data structures that reference the target system's symbol
14500 @node VxWorks Attach
14501 @subsubsection Running Tasks
14503 @cindex running VxWorks tasks
14504 You can also attach to an existing task using the @code{attach} command as
14508 (vxgdb) attach @var{task}
14512 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14513 or suspended when you attach to it. Running tasks are suspended at
14514 the time of attachment.
14516 @node Embedded Processors
14517 @section Embedded Processors
14519 This section goes into details specific to particular embedded
14522 @cindex send command to simulator
14523 Whenever a specific embedded processor has a simulator, @value{GDBN}
14524 allows to send an arbitrary command to the simulator.
14527 @item sim @var{command}
14528 @kindex sim@r{, a command}
14529 Send an arbitrary @var{command} string to the simulator. Consult the
14530 documentation for the specific simulator in use for information about
14531 acceptable commands.
14537 * M32R/D:: Renesas M32R/D
14538 * M68K:: Motorola M68K
14539 * MIPS Embedded:: MIPS Embedded
14540 * OpenRISC 1000:: OpenRisc 1000
14541 * PA:: HP PA Embedded
14542 * PowerPC:: PowerPC
14543 * Sparclet:: Tsqware Sparclet
14544 * Sparclite:: Fujitsu Sparclite
14545 * Z8000:: Zilog Z8000
14548 * Super-H:: Renesas Super-H
14557 @item target rdi @var{dev}
14558 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14559 use this target to communicate with both boards running the Angel
14560 monitor, or with the EmbeddedICE JTAG debug device.
14563 @item target rdp @var{dev}
14568 @value{GDBN} provides the following ARM-specific commands:
14571 @item set arm disassembler
14573 This commands selects from a list of disassembly styles. The
14574 @code{"std"} style is the standard style.
14576 @item show arm disassembler
14578 Show the current disassembly style.
14580 @item set arm apcs32
14581 @cindex ARM 32-bit mode
14582 This command toggles ARM operation mode between 32-bit and 26-bit.
14584 @item show arm apcs32
14585 Display the current usage of the ARM 32-bit mode.
14587 @item set arm fpu @var{fputype}
14588 This command sets the ARM floating-point unit (FPU) type. The
14589 argument @var{fputype} can be one of these:
14593 Determine the FPU type by querying the OS ABI.
14595 Software FPU, with mixed-endian doubles on little-endian ARM
14598 GCC-compiled FPA co-processor.
14600 Software FPU with pure-endian doubles.
14606 Show the current type of the FPU.
14609 This command forces @value{GDBN} to use the specified ABI.
14612 Show the currently used ABI.
14614 @item set debug arm
14615 Toggle whether to display ARM-specific debugging messages from the ARM
14616 target support subsystem.
14618 @item show debug arm
14619 Show whether ARM-specific debugging messages are enabled.
14622 The following commands are available when an ARM target is debugged
14623 using the RDI interface:
14626 @item rdilogfile @r{[}@var{file}@r{]}
14628 @cindex ADP (Angel Debugger Protocol) logging
14629 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14630 With an argument, sets the log file to the specified @var{file}. With
14631 no argument, show the current log file name. The default log file is
14634 @item rdilogenable @r{[}@var{arg}@r{]}
14635 @kindex rdilogenable
14636 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14637 enables logging, with an argument 0 or @code{"no"} disables it. With
14638 no arguments displays the current setting. When logging is enabled,
14639 ADP packets exchanged between @value{GDBN} and the RDI target device
14640 are logged to a file.
14642 @item set rdiromatzero
14643 @kindex set rdiromatzero
14644 @cindex ROM at zero address, RDI
14645 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14646 vector catching is disabled, so that zero address can be used. If off
14647 (the default), vector catching is enabled. For this command to take
14648 effect, it needs to be invoked prior to the @code{target rdi} command.
14650 @item show rdiromatzero
14651 @kindex show rdiromatzero
14652 Show the current setting of ROM at zero address.
14654 @item set rdiheartbeat
14655 @kindex set rdiheartbeat
14656 @cindex RDI heartbeat
14657 Enable or disable RDI heartbeat packets. It is not recommended to
14658 turn on this option, since it confuses ARM and EPI JTAG interface, as
14659 well as the Angel monitor.
14661 @item show rdiheartbeat
14662 @kindex show rdiheartbeat
14663 Show the setting of RDI heartbeat packets.
14668 @subsection Renesas M32R/D and M32R/SDI
14671 @kindex target m32r
14672 @item target m32r @var{dev}
14673 Renesas M32R/D ROM monitor.
14675 @kindex target m32rsdi
14676 @item target m32rsdi @var{dev}
14677 Renesas M32R SDI server, connected via parallel port to the board.
14680 The following @value{GDBN} commands are specific to the M32R monitor:
14683 @item set download-path @var{path}
14684 @kindex set download-path
14685 @cindex find downloadable @sc{srec} files (M32R)
14686 Set the default path for finding downloadable @sc{srec} files.
14688 @item show download-path
14689 @kindex show download-path
14690 Show the default path for downloadable @sc{srec} files.
14692 @item set board-address @var{addr}
14693 @kindex set board-address
14694 @cindex M32-EVA target board address
14695 Set the IP address for the M32R-EVA target board.
14697 @item show board-address
14698 @kindex show board-address
14699 Show the current IP address of the target board.
14701 @item set server-address @var{addr}
14702 @kindex set server-address
14703 @cindex download server address (M32R)
14704 Set the IP address for the download server, which is the @value{GDBN}'s
14707 @item show server-address
14708 @kindex show server-address
14709 Display the IP address of the download server.
14711 @item upload @r{[}@var{file}@r{]}
14712 @kindex upload@r{, M32R}
14713 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14714 upload capability. If no @var{file} argument is given, the current
14715 executable file is uploaded.
14717 @item tload @r{[}@var{file}@r{]}
14718 @kindex tload@r{, M32R}
14719 Test the @code{upload} command.
14722 The following commands are available for M32R/SDI:
14727 @cindex reset SDI connection, M32R
14728 This command resets the SDI connection.
14732 This command shows the SDI connection status.
14735 @kindex debug_chaos
14736 @cindex M32R/Chaos debugging
14737 Instructs the remote that M32R/Chaos debugging is to be used.
14739 @item use_debug_dma
14740 @kindex use_debug_dma
14741 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14744 @kindex use_mon_code
14745 Instructs the remote to use the MON_CODE method of accessing memory.
14748 @kindex use_ib_break
14749 Instructs the remote to set breakpoints by IB break.
14751 @item use_dbt_break
14752 @kindex use_dbt_break
14753 Instructs the remote to set breakpoints by DBT.
14759 The Motorola m68k configuration includes ColdFire support, and a
14760 target command for the following ROM monitor.
14764 @kindex target dbug
14765 @item target dbug @var{dev}
14766 dBUG ROM monitor for Motorola ColdFire.
14770 @node MIPS Embedded
14771 @subsection MIPS Embedded
14773 @cindex MIPS boards
14774 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14775 MIPS board attached to a serial line. This is available when
14776 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14779 Use these @value{GDBN} commands to specify the connection to your target board:
14782 @item target mips @var{port}
14783 @kindex target mips @var{port}
14784 To run a program on the board, start up @code{@value{GDBP}} with the
14785 name of your program as the argument. To connect to the board, use the
14786 command @samp{target mips @var{port}}, where @var{port} is the name of
14787 the serial port connected to the board. If the program has not already
14788 been downloaded to the board, you may use the @code{load} command to
14789 download it. You can then use all the usual @value{GDBN} commands.
14791 For example, this sequence connects to the target board through a serial
14792 port, and loads and runs a program called @var{prog} through the
14796 host$ @value{GDBP} @var{prog}
14797 @value{GDBN} is free software and @dots{}
14798 (@value{GDBP}) target mips /dev/ttyb
14799 (@value{GDBP}) load @var{prog}
14803 @item target mips @var{hostname}:@var{portnumber}
14804 On some @value{GDBN} host configurations, you can specify a TCP
14805 connection (for instance, to a serial line managed by a terminal
14806 concentrator) instead of a serial port, using the syntax
14807 @samp{@var{hostname}:@var{portnumber}}.
14809 @item target pmon @var{port}
14810 @kindex target pmon @var{port}
14813 @item target ddb @var{port}
14814 @kindex target ddb @var{port}
14815 NEC's DDB variant of PMON for Vr4300.
14817 @item target lsi @var{port}
14818 @kindex target lsi @var{port}
14819 LSI variant of PMON.
14821 @kindex target r3900
14822 @item target r3900 @var{dev}
14823 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14825 @kindex target array
14826 @item target array @var{dev}
14827 Array Tech LSI33K RAID controller board.
14833 @value{GDBN} also supports these special commands for MIPS targets:
14836 @item set mipsfpu double
14837 @itemx set mipsfpu single
14838 @itemx set mipsfpu none
14839 @itemx set mipsfpu auto
14840 @itemx show mipsfpu
14841 @kindex set mipsfpu
14842 @kindex show mipsfpu
14843 @cindex MIPS remote floating point
14844 @cindex floating point, MIPS remote
14845 If your target board does not support the MIPS floating point
14846 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14847 need this, you may wish to put the command in your @value{GDBN} init
14848 file). This tells @value{GDBN} how to find the return value of
14849 functions which return floating point values. It also allows
14850 @value{GDBN} to avoid saving the floating point registers when calling
14851 functions on the board. If you are using a floating point coprocessor
14852 with only single precision floating point support, as on the @sc{r4650}
14853 processor, use the command @samp{set mipsfpu single}. The default
14854 double precision floating point coprocessor may be selected using
14855 @samp{set mipsfpu double}.
14857 In previous versions the only choices were double precision or no
14858 floating point, so @samp{set mipsfpu on} will select double precision
14859 and @samp{set mipsfpu off} will select no floating point.
14861 As usual, you can inquire about the @code{mipsfpu} variable with
14862 @samp{show mipsfpu}.
14864 @item set timeout @var{seconds}
14865 @itemx set retransmit-timeout @var{seconds}
14866 @itemx show timeout
14867 @itemx show retransmit-timeout
14868 @cindex @code{timeout}, MIPS protocol
14869 @cindex @code{retransmit-timeout}, MIPS protocol
14870 @kindex set timeout
14871 @kindex show timeout
14872 @kindex set retransmit-timeout
14873 @kindex show retransmit-timeout
14874 You can control the timeout used while waiting for a packet, in the MIPS
14875 remote protocol, with the @code{set timeout @var{seconds}} command. The
14876 default is 5 seconds. Similarly, you can control the timeout used while
14877 waiting for an acknowledgement of a packet with the @code{set
14878 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14879 You can inspect both values with @code{show timeout} and @code{show
14880 retransmit-timeout}. (These commands are @emph{only} available when
14881 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14883 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14884 is waiting for your program to stop. In that case, @value{GDBN} waits
14885 forever because it has no way of knowing how long the program is going
14886 to run before stopping.
14888 @item set syn-garbage-limit @var{num}
14889 @kindex set syn-garbage-limit@r{, MIPS remote}
14890 @cindex synchronize with remote MIPS target
14891 Limit the maximum number of characters @value{GDBN} should ignore when
14892 it tries to synchronize with the remote target. The default is 10
14893 characters. Setting the limit to -1 means there's no limit.
14895 @item show syn-garbage-limit
14896 @kindex show syn-garbage-limit@r{, MIPS remote}
14897 Show the current limit on the number of characters to ignore when
14898 trying to synchronize with the remote system.
14900 @item set monitor-prompt @var{prompt}
14901 @kindex set monitor-prompt@r{, MIPS remote}
14902 @cindex remote monitor prompt
14903 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14904 remote monitor. The default depends on the target:
14914 @item show monitor-prompt
14915 @kindex show monitor-prompt@r{, MIPS remote}
14916 Show the current strings @value{GDBN} expects as the prompt from the
14919 @item set monitor-warnings
14920 @kindex set monitor-warnings@r{, MIPS remote}
14921 Enable or disable monitor warnings about hardware breakpoints. This
14922 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14923 display warning messages whose codes are returned by the @code{lsi}
14924 PMON monitor for breakpoint commands.
14926 @item show monitor-warnings
14927 @kindex show monitor-warnings@r{, MIPS remote}
14928 Show the current setting of printing monitor warnings.
14930 @item pmon @var{command}
14931 @kindex pmon@r{, MIPS remote}
14932 @cindex send PMON command
14933 This command allows sending an arbitrary @var{command} string to the
14934 monitor. The monitor must be in debug mode for this to work.
14937 @node OpenRISC 1000
14938 @subsection OpenRISC 1000
14939 @cindex OpenRISC 1000
14941 @cindex or1k boards
14942 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14943 about platform and commands.
14947 @kindex target jtag
14948 @item target jtag jtag://@var{host}:@var{port}
14950 Connects to remote JTAG server.
14951 JTAG remote server can be either an or1ksim or JTAG server,
14952 connected via parallel port to the board.
14954 Example: @code{target jtag jtag://localhost:9999}
14957 @item or1ksim @var{command}
14958 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14959 Simulator, proprietary commands can be executed.
14961 @kindex info or1k spr
14962 @item info or1k spr
14963 Displays spr groups.
14965 @item info or1k spr @var{group}
14966 @itemx info or1k spr @var{groupno}
14967 Displays register names in selected group.
14969 @item info or1k spr @var{group} @var{register}
14970 @itemx info or1k spr @var{register}
14971 @itemx info or1k spr @var{groupno} @var{registerno}
14972 @itemx info or1k spr @var{registerno}
14973 Shows information about specified spr register.
14976 @item spr @var{group} @var{register} @var{value}
14977 @itemx spr @var{register @var{value}}
14978 @itemx spr @var{groupno} @var{registerno @var{value}}
14979 @itemx spr @var{registerno @var{value}}
14980 Writes @var{value} to specified spr register.
14983 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14984 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14985 program execution and is thus much faster. Hardware breakpoints/watchpoint
14986 triggers can be set using:
14989 Load effective address/data
14991 Store effective address/data
14993 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14998 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14999 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15001 @code{htrace} commands:
15002 @cindex OpenRISC 1000 htrace
15005 @item hwatch @var{conditional}
15006 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15007 or Data. For example:
15009 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15011 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15015 Display information about current HW trace configuration.
15017 @item htrace trigger @var{conditional}
15018 Set starting criteria for HW trace.
15020 @item htrace qualifier @var{conditional}
15021 Set acquisition qualifier for HW trace.
15023 @item htrace stop @var{conditional}
15024 Set HW trace stopping criteria.
15026 @item htrace record [@var{data}]*
15027 Selects the data to be recorded, when qualifier is met and HW trace was
15030 @item htrace enable
15031 @itemx htrace disable
15032 Enables/disables the HW trace.
15034 @item htrace rewind [@var{filename}]
15035 Clears currently recorded trace data.
15037 If filename is specified, new trace file is made and any newly collected data
15038 will be written there.
15040 @item htrace print [@var{start} [@var{len}]]
15041 Prints trace buffer, using current record configuration.
15043 @item htrace mode continuous
15044 Set continuous trace mode.
15046 @item htrace mode suspend
15047 Set suspend trace mode.
15052 @subsection PowerPC
15054 @value{GDBN} provides the following PowerPC-specific commands:
15057 @kindex set powerpc
15058 @item set powerpc soft-float
15059 @itemx show powerpc soft-float
15060 Force @value{GDBN} to use (or not use) a software floating point calling
15061 convention. By default, @value{GDBN} selects the calling convention based
15062 on the selected architecture and the provided executable file.
15064 @item set powerpc vector-abi
15065 @itemx show powerpc vector-abi
15066 Force @value{GDBN} to use the specified calling convention for vector
15067 arguments and return values. The valid options are @samp{auto};
15068 @samp{generic}, to avoid vector registers even if they are present;
15069 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15070 registers. By default, @value{GDBN} selects the calling convention
15071 based on the selected architecture and the provided executable file.
15073 @kindex target dink32
15074 @item target dink32 @var{dev}
15075 DINK32 ROM monitor.
15077 @kindex target ppcbug
15078 @item target ppcbug @var{dev}
15079 @kindex target ppcbug1
15080 @item target ppcbug1 @var{dev}
15081 PPCBUG ROM monitor for PowerPC.
15084 @item target sds @var{dev}
15085 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15088 @cindex SDS protocol
15089 The following commands specific to the SDS protocol are supported
15093 @item set sdstimeout @var{nsec}
15094 @kindex set sdstimeout
15095 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15096 default is 2 seconds.
15098 @item show sdstimeout
15099 @kindex show sdstimeout
15100 Show the current value of the SDS timeout.
15102 @item sds @var{command}
15103 @kindex sds@r{, a command}
15104 Send the specified @var{command} string to the SDS monitor.
15109 @subsection HP PA Embedded
15113 @kindex target op50n
15114 @item target op50n @var{dev}
15115 OP50N monitor, running on an OKI HPPA board.
15117 @kindex target w89k
15118 @item target w89k @var{dev}
15119 W89K monitor, running on a Winbond HPPA board.
15124 @subsection Tsqware Sparclet
15128 @value{GDBN} enables developers to debug tasks running on
15129 Sparclet targets from a Unix host.
15130 @value{GDBN} uses code that runs on
15131 both the Unix host and on the Sparclet target. The program
15132 @code{@value{GDBP}} is installed and executed on the Unix host.
15135 @item remotetimeout @var{args}
15136 @kindex remotetimeout
15137 @value{GDBN} supports the option @code{remotetimeout}.
15138 This option is set by the user, and @var{args} represents the number of
15139 seconds @value{GDBN} waits for responses.
15142 @cindex compiling, on Sparclet
15143 When compiling for debugging, include the options @samp{-g} to get debug
15144 information and @samp{-Ttext} to relocate the program to where you wish to
15145 load it on the target. You may also want to add the options @samp{-n} or
15146 @samp{-N} in order to reduce the size of the sections. Example:
15149 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15152 You can use @code{objdump} to verify that the addresses are what you intended:
15155 sparclet-aout-objdump --headers --syms prog
15158 @cindex running, on Sparclet
15160 your Unix execution search path to find @value{GDBN}, you are ready to
15161 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15162 (or @code{sparclet-aout-gdb}, depending on your installation).
15164 @value{GDBN} comes up showing the prompt:
15171 * Sparclet File:: Setting the file to debug
15172 * Sparclet Connection:: Connecting to Sparclet
15173 * Sparclet Download:: Sparclet download
15174 * Sparclet Execution:: Running and debugging
15177 @node Sparclet File
15178 @subsubsection Setting File to Debug
15180 The @value{GDBN} command @code{file} lets you choose with program to debug.
15183 (gdbslet) file prog
15187 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15188 @value{GDBN} locates
15189 the file by searching the directories listed in the command search
15191 If the file was compiled with debug information (option @samp{-g}), source
15192 files will be searched as well.
15193 @value{GDBN} locates
15194 the source files by searching the directories listed in the directory search
15195 path (@pxref{Environment, ,Your Program's Environment}).
15197 to find a file, it displays a message such as:
15200 prog: No such file or directory.
15203 When this happens, add the appropriate directories to the search paths with
15204 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15205 @code{target} command again.
15207 @node Sparclet Connection
15208 @subsubsection Connecting to Sparclet
15210 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15211 To connect to a target on serial port ``@code{ttya}'', type:
15214 (gdbslet) target sparclet /dev/ttya
15215 Remote target sparclet connected to /dev/ttya
15216 main () at ../prog.c:3
15220 @value{GDBN} displays messages like these:
15226 @node Sparclet Download
15227 @subsubsection Sparclet Download
15229 @cindex download to Sparclet
15230 Once connected to the Sparclet target,
15231 you can use the @value{GDBN}
15232 @code{load} command to download the file from the host to the target.
15233 The file name and load offset should be given as arguments to the @code{load}
15235 Since the file format is aout, the program must be loaded to the starting
15236 address. You can use @code{objdump} to find out what this value is. The load
15237 offset is an offset which is added to the VMA (virtual memory address)
15238 of each of the file's sections.
15239 For instance, if the program
15240 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15241 and bss at 0x12010170, in @value{GDBN}, type:
15244 (gdbslet) load prog 0x12010000
15245 Loading section .text, size 0xdb0 vma 0x12010000
15248 If the code is loaded at a different address then what the program was linked
15249 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15250 to tell @value{GDBN} where to map the symbol table.
15252 @node Sparclet Execution
15253 @subsubsection Running and Debugging
15255 @cindex running and debugging Sparclet programs
15256 You can now begin debugging the task using @value{GDBN}'s execution control
15257 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15258 manual for the list of commands.
15262 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15264 Starting program: prog
15265 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15266 3 char *symarg = 0;
15268 4 char *execarg = "hello!";
15273 @subsection Fujitsu Sparclite
15277 @kindex target sparclite
15278 @item target sparclite @var{dev}
15279 Fujitsu sparclite boards, used only for the purpose of loading.
15280 You must use an additional command to debug the program.
15281 For example: target remote @var{dev} using @value{GDBN} standard
15287 @subsection Zilog Z8000
15290 @cindex simulator, Z8000
15291 @cindex Zilog Z8000 simulator
15293 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15296 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15297 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15298 segmented variant). The simulator recognizes which architecture is
15299 appropriate by inspecting the object code.
15302 @item target sim @var{args}
15304 @kindex target sim@r{, with Z8000}
15305 Debug programs on a simulated CPU. If the simulator supports setup
15306 options, specify them via @var{args}.
15310 After specifying this target, you can debug programs for the simulated
15311 CPU in the same style as programs for your host computer; use the
15312 @code{file} command to load a new program image, the @code{run} command
15313 to run your program, and so on.
15315 As well as making available all the usual machine registers
15316 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15317 additional items of information as specially named registers:
15322 Counts clock-ticks in the simulator.
15325 Counts instructions run in the simulator.
15328 Execution time in 60ths of a second.
15332 You can refer to these values in @value{GDBN} expressions with the usual
15333 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15334 conditional breakpoint that suspends only after at least 5000
15335 simulated clock ticks.
15338 @subsection Atmel AVR
15341 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15342 following AVR-specific commands:
15345 @item info io_registers
15346 @kindex info io_registers@r{, AVR}
15347 @cindex I/O registers (Atmel AVR)
15348 This command displays information about the AVR I/O registers. For
15349 each register, @value{GDBN} prints its number and value.
15356 When configured for debugging CRIS, @value{GDBN} provides the
15357 following CRIS-specific commands:
15360 @item set cris-version @var{ver}
15361 @cindex CRIS version
15362 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15363 The CRIS version affects register names and sizes. This command is useful in
15364 case autodetection of the CRIS version fails.
15366 @item show cris-version
15367 Show the current CRIS version.
15369 @item set cris-dwarf2-cfi
15370 @cindex DWARF-2 CFI and CRIS
15371 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15372 Change to @samp{off} when using @code{gcc-cris} whose version is below
15375 @item show cris-dwarf2-cfi
15376 Show the current state of using DWARF-2 CFI.
15378 @item set cris-mode @var{mode}
15380 Set the current CRIS mode to @var{mode}. It should only be changed when
15381 debugging in guru mode, in which case it should be set to
15382 @samp{guru} (the default is @samp{normal}).
15384 @item show cris-mode
15385 Show the current CRIS mode.
15389 @subsection Renesas Super-H
15392 For the Renesas Super-H processor, @value{GDBN} provides these
15397 @kindex regs@r{, Super-H}
15398 Show the values of all Super-H registers.
15402 @node Architectures
15403 @section Architectures
15405 This section describes characteristics of architectures that affect
15406 all uses of @value{GDBN} with the architecture, both native and cross.
15413 * HPPA:: HP PA architecture
15414 * SPU:: Cell Broadband Engine SPU architecture
15418 @subsection x86 Architecture-specific Issues
15421 @item set struct-convention @var{mode}
15422 @kindex set struct-convention
15423 @cindex struct return convention
15424 @cindex struct/union returned in registers
15425 Set the convention used by the inferior to return @code{struct}s and
15426 @code{union}s from functions to @var{mode}. Possible values of
15427 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15428 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15429 are returned on the stack, while @code{"reg"} means that a
15430 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15431 be returned in a register.
15433 @item show struct-convention
15434 @kindex show struct-convention
15435 Show the current setting of the convention to return @code{struct}s
15444 @kindex set rstack_high_address
15445 @cindex AMD 29K register stack
15446 @cindex register stack, AMD29K
15447 @item set rstack_high_address @var{address}
15448 On AMD 29000 family processors, registers are saved in a separate
15449 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15450 extent of this stack. Normally, @value{GDBN} just assumes that the
15451 stack is ``large enough''. This may result in @value{GDBN} referencing
15452 memory locations that do not exist. If necessary, you can get around
15453 this problem by specifying the ending address of the register stack with
15454 the @code{set rstack_high_address} command. The argument should be an
15455 address, which you probably want to precede with @samp{0x} to specify in
15458 @kindex show rstack_high_address
15459 @item show rstack_high_address
15460 Display the current limit of the register stack, on AMD 29000 family
15468 See the following section.
15473 @cindex stack on Alpha
15474 @cindex stack on MIPS
15475 @cindex Alpha stack
15477 Alpha- and MIPS-based computers use an unusual stack frame, which
15478 sometimes requires @value{GDBN} to search backward in the object code to
15479 find the beginning of a function.
15481 @cindex response time, MIPS debugging
15482 To improve response time (especially for embedded applications, where
15483 @value{GDBN} may be restricted to a slow serial line for this search)
15484 you may want to limit the size of this search, using one of these
15488 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15489 @item set heuristic-fence-post @var{limit}
15490 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15491 search for the beginning of a function. A value of @var{0} (the
15492 default) means there is no limit. However, except for @var{0}, the
15493 larger the limit the more bytes @code{heuristic-fence-post} must search
15494 and therefore the longer it takes to run. You should only need to use
15495 this command when debugging a stripped executable.
15497 @item show heuristic-fence-post
15498 Display the current limit.
15502 These commands are available @emph{only} when @value{GDBN} is configured
15503 for debugging programs on Alpha or MIPS processors.
15505 Several MIPS-specific commands are available when debugging MIPS
15509 @item set mips abi @var{arg}
15510 @kindex set mips abi
15511 @cindex set ABI for MIPS
15512 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15513 values of @var{arg} are:
15517 The default ABI associated with the current binary (this is the
15528 @item show mips abi
15529 @kindex show mips abi
15530 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15533 @itemx show mipsfpu
15534 @xref{MIPS Embedded, set mipsfpu}.
15536 @item set mips mask-address @var{arg}
15537 @kindex set mips mask-address
15538 @cindex MIPS addresses, masking
15539 This command determines whether the most-significant 32 bits of 64-bit
15540 MIPS addresses are masked off. The argument @var{arg} can be
15541 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15542 setting, which lets @value{GDBN} determine the correct value.
15544 @item show mips mask-address
15545 @kindex show mips mask-address
15546 Show whether the upper 32 bits of MIPS addresses are masked off or
15549 @item set remote-mips64-transfers-32bit-regs
15550 @kindex set remote-mips64-transfers-32bit-regs
15551 This command controls compatibility with 64-bit MIPS targets that
15552 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15553 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15554 and 64 bits for other registers, set this option to @samp{on}.
15556 @item show remote-mips64-transfers-32bit-regs
15557 @kindex show remote-mips64-transfers-32bit-regs
15558 Show the current setting of compatibility with older MIPS 64 targets.
15560 @item set debug mips
15561 @kindex set debug mips
15562 This command turns on and off debugging messages for the MIPS-specific
15563 target code in @value{GDBN}.
15565 @item show debug mips
15566 @kindex show debug mips
15567 Show the current setting of MIPS debugging messages.
15573 @cindex HPPA support
15575 When @value{GDBN} is debugging the HP PA architecture, it provides the
15576 following special commands:
15579 @item set debug hppa
15580 @kindex set debug hppa
15581 This command determines whether HPPA architecture-specific debugging
15582 messages are to be displayed.
15584 @item show debug hppa
15585 Show whether HPPA debugging messages are displayed.
15587 @item maint print unwind @var{address}
15588 @kindex maint print unwind@r{, HPPA}
15589 This command displays the contents of the unwind table entry at the
15590 given @var{address}.
15596 @subsection Cell Broadband Engine SPU architecture
15597 @cindex Cell Broadband Engine
15600 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
15601 it provides the following special commands:
15604 @item info spu event
15606 Display SPU event facility status. Shows current event mask
15607 and pending event status.
15609 @item info spu signal
15610 Display SPU signal notification facility status. Shows pending
15611 signal-control word and signal notification mode of both signal
15612 notification channels.
15614 @item info spu mailbox
15615 Display SPU mailbox facility status. Shows all pending entries,
15616 in order of processing, in each of the SPU Write Outbound,
15617 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
15620 Display MFC DMA status. Shows all pending commands in the MFC
15621 DMA queue. For each entry, opcode, tag, class IDs, effective
15622 and local store addresses and transfer size are shown.
15624 @item info spu proxydma
15625 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
15626 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
15627 and local store addresses and transfer size are shown.
15632 @node Controlling GDB
15633 @chapter Controlling @value{GDBN}
15635 You can alter the way @value{GDBN} interacts with you by using the
15636 @code{set} command. For commands controlling how @value{GDBN} displays
15637 data, see @ref{Print Settings, ,Print Settings}. Other settings are
15642 * Editing:: Command editing
15643 * Command History:: Command history
15644 * Screen Size:: Screen size
15645 * Numbers:: Numbers
15646 * ABI:: Configuring the current ABI
15647 * Messages/Warnings:: Optional warnings and messages
15648 * Debugging Output:: Optional messages about internal happenings
15656 @value{GDBN} indicates its readiness to read a command by printing a string
15657 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15658 can change the prompt string with the @code{set prompt} command. For
15659 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15660 the prompt in one of the @value{GDBN} sessions so that you can always tell
15661 which one you are talking to.
15663 @emph{Note:} @code{set prompt} does not add a space for you after the
15664 prompt you set. This allows you to set a prompt which ends in a space
15665 or a prompt that does not.
15669 @item set prompt @var{newprompt}
15670 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15672 @kindex show prompt
15674 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15678 @section Command Editing
15680 @cindex command line editing
15682 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15683 @sc{gnu} library provides consistent behavior for programs which provide a
15684 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15685 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15686 substitution, and a storage and recall of command history across
15687 debugging sessions.
15689 You may control the behavior of command line editing in @value{GDBN} with the
15690 command @code{set}.
15693 @kindex set editing
15696 @itemx set editing on
15697 Enable command line editing (enabled by default).
15699 @item set editing off
15700 Disable command line editing.
15702 @kindex show editing
15704 Show whether command line editing is enabled.
15707 @xref{Command Line Editing}, for more details about the Readline
15708 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15709 encouraged to read that chapter.
15711 @node Command History
15712 @section Command History
15713 @cindex command history
15715 @value{GDBN} can keep track of the commands you type during your
15716 debugging sessions, so that you can be certain of precisely what
15717 happened. Use these commands to manage the @value{GDBN} command
15720 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15721 package, to provide the history facility. @xref{Using History
15722 Interactively}, for the detailed description of the History library.
15724 To issue a command to @value{GDBN} without affecting certain aspects of
15725 the state which is seen by users, prefix it with @samp{server }
15726 (@pxref{Server Prefix}). This
15727 means that this command will not affect the command history, nor will it
15728 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15729 pressed on a line by itself.
15731 @cindex @code{server}, command prefix
15732 The server prefix does not affect the recording of values into the value
15733 history; to print a value without recording it into the value history,
15734 use the @code{output} command instead of the @code{print} command.
15736 Here is the description of @value{GDBN} commands related to command
15740 @cindex history substitution
15741 @cindex history file
15742 @kindex set history filename
15743 @cindex @env{GDBHISTFILE}, environment variable
15744 @item set history filename @var{fname}
15745 Set the name of the @value{GDBN} command history file to @var{fname}.
15746 This is the file where @value{GDBN} reads an initial command history
15747 list, and where it writes the command history from this session when it
15748 exits. You can access this list through history expansion or through
15749 the history command editing characters listed below. This file defaults
15750 to the value of the environment variable @code{GDBHISTFILE}, or to
15751 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15754 @cindex save command history
15755 @kindex set history save
15756 @item set history save
15757 @itemx set history save on
15758 Record command history in a file, whose name may be specified with the
15759 @code{set history filename} command. By default, this option is disabled.
15761 @item set history save off
15762 Stop recording command history in a file.
15764 @cindex history size
15765 @kindex set history size
15766 @cindex @env{HISTSIZE}, environment variable
15767 @item set history size @var{size}
15768 Set the number of commands which @value{GDBN} keeps in its history list.
15769 This defaults to the value of the environment variable
15770 @code{HISTSIZE}, or to 256 if this variable is not set.
15773 History expansion assigns special meaning to the character @kbd{!}.
15774 @xref{Event Designators}, for more details.
15776 @cindex history expansion, turn on/off
15777 Since @kbd{!} is also the logical not operator in C, history expansion
15778 is off by default. If you decide to enable history expansion with the
15779 @code{set history expansion on} command, you may sometimes need to
15780 follow @kbd{!} (when it is used as logical not, in an expression) with
15781 a space or a tab to prevent it from being expanded. The readline
15782 history facilities do not attempt substitution on the strings
15783 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15785 The commands to control history expansion are:
15788 @item set history expansion on
15789 @itemx set history expansion
15790 @kindex set history expansion
15791 Enable history expansion. History expansion is off by default.
15793 @item set history expansion off
15794 Disable history expansion.
15797 @kindex show history
15799 @itemx show history filename
15800 @itemx show history save
15801 @itemx show history size
15802 @itemx show history expansion
15803 These commands display the state of the @value{GDBN} history parameters.
15804 @code{show history} by itself displays all four states.
15809 @kindex show commands
15810 @cindex show last commands
15811 @cindex display command history
15812 @item show commands
15813 Display the last ten commands in the command history.
15815 @item show commands @var{n}
15816 Print ten commands centered on command number @var{n}.
15818 @item show commands +
15819 Print ten commands just after the commands last printed.
15823 @section Screen Size
15824 @cindex size of screen
15825 @cindex pauses in output
15827 Certain commands to @value{GDBN} may produce large amounts of
15828 information output to the screen. To help you read all of it,
15829 @value{GDBN} pauses and asks you for input at the end of each page of
15830 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15831 to discard the remaining output. Also, the screen width setting
15832 determines when to wrap lines of output. Depending on what is being
15833 printed, @value{GDBN} tries to break the line at a readable place,
15834 rather than simply letting it overflow onto the following line.
15836 Normally @value{GDBN} knows the size of the screen from the terminal
15837 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15838 together with the value of the @code{TERM} environment variable and the
15839 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15840 you can override it with the @code{set height} and @code{set
15847 @kindex show height
15848 @item set height @var{lpp}
15850 @itemx set width @var{cpl}
15852 These @code{set} commands specify a screen height of @var{lpp} lines and
15853 a screen width of @var{cpl} characters. The associated @code{show}
15854 commands display the current settings.
15856 If you specify a height of zero lines, @value{GDBN} does not pause during
15857 output no matter how long the output is. This is useful if output is to a
15858 file or to an editor buffer.
15860 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15861 from wrapping its output.
15863 @item set pagination on
15864 @itemx set pagination off
15865 @kindex set pagination
15866 Turn the output pagination on or off; the default is on. Turning
15867 pagination off is the alternative to @code{set height 0}.
15869 @item show pagination
15870 @kindex show pagination
15871 Show the current pagination mode.
15876 @cindex number representation
15877 @cindex entering numbers
15879 You can always enter numbers in octal, decimal, or hexadecimal in
15880 @value{GDBN} by the usual conventions: octal numbers begin with
15881 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15882 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15883 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15884 10; likewise, the default display for numbers---when no particular
15885 format is specified---is base 10. You can change the default base for
15886 both input and output with the commands described below.
15889 @kindex set input-radix
15890 @item set input-radix @var{base}
15891 Set the default base for numeric input. Supported choices
15892 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15893 specified either unambiguously or using the current input radix; for
15897 set input-radix 012
15898 set input-radix 10.
15899 set input-radix 0xa
15903 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15904 leaves the input radix unchanged, no matter what it was, since
15905 @samp{10}, being without any leading or trailing signs of its base, is
15906 interpreted in the current radix. Thus, if the current radix is 16,
15907 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15910 @kindex set output-radix
15911 @item set output-radix @var{base}
15912 Set the default base for numeric display. Supported choices
15913 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15914 specified either unambiguously or using the current input radix.
15916 @kindex show input-radix
15917 @item show input-radix
15918 Display the current default base for numeric input.
15920 @kindex show output-radix
15921 @item show output-radix
15922 Display the current default base for numeric display.
15924 @item set radix @r{[}@var{base}@r{]}
15928 These commands set and show the default base for both input and output
15929 of numbers. @code{set radix} sets the radix of input and output to
15930 the same base; without an argument, it resets the radix back to its
15931 default value of 10.
15936 @section Configuring the Current ABI
15938 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15939 application automatically. However, sometimes you need to override its
15940 conclusions. Use these commands to manage @value{GDBN}'s view of the
15947 One @value{GDBN} configuration can debug binaries for multiple operating
15948 system targets, either via remote debugging or native emulation.
15949 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15950 but you can override its conclusion using the @code{set osabi} command.
15951 One example where this is useful is in debugging of binaries which use
15952 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15953 not have the same identifying marks that the standard C library for your
15958 Show the OS ABI currently in use.
15961 With no argument, show the list of registered available OS ABI's.
15963 @item set osabi @var{abi}
15964 Set the current OS ABI to @var{abi}.
15967 @cindex float promotion
15969 Generally, the way that an argument of type @code{float} is passed to a
15970 function depends on whether the function is prototyped. For a prototyped
15971 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15972 according to the architecture's convention for @code{float}. For unprototyped
15973 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15974 @code{double} and then passed.
15976 Unfortunately, some forms of debug information do not reliably indicate whether
15977 a function is prototyped. If @value{GDBN} calls a function that is not marked
15978 as prototyped, it consults @kbd{set coerce-float-to-double}.
15981 @kindex set coerce-float-to-double
15982 @item set coerce-float-to-double
15983 @itemx set coerce-float-to-double on
15984 Arguments of type @code{float} will be promoted to @code{double} when passed
15985 to an unprototyped function. This is the default setting.
15987 @item set coerce-float-to-double off
15988 Arguments of type @code{float} will be passed directly to unprototyped
15991 @kindex show coerce-float-to-double
15992 @item show coerce-float-to-double
15993 Show the current setting of promoting @code{float} to @code{double}.
15997 @kindex show cp-abi
15998 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15999 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16000 used to build your application. @value{GDBN} only fully supports
16001 programs with a single C@t{++} ABI; if your program contains code using
16002 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16003 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16004 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16005 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16006 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16007 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16012 Show the C@t{++} ABI currently in use.
16015 With no argument, show the list of supported C@t{++} ABI's.
16017 @item set cp-abi @var{abi}
16018 @itemx set cp-abi auto
16019 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16022 @node Messages/Warnings
16023 @section Optional Warnings and Messages
16025 @cindex verbose operation
16026 @cindex optional warnings
16027 By default, @value{GDBN} is silent about its inner workings. If you are
16028 running on a slow machine, you may want to use the @code{set verbose}
16029 command. This makes @value{GDBN} tell you when it does a lengthy
16030 internal operation, so you will not think it has crashed.
16032 Currently, the messages controlled by @code{set verbose} are those
16033 which announce that the symbol table for a source file is being read;
16034 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16037 @kindex set verbose
16038 @item set verbose on
16039 Enables @value{GDBN} output of certain informational messages.
16041 @item set verbose off
16042 Disables @value{GDBN} output of certain informational messages.
16044 @kindex show verbose
16046 Displays whether @code{set verbose} is on or off.
16049 By default, if @value{GDBN} encounters bugs in the symbol table of an
16050 object file, it is silent; but if you are debugging a compiler, you may
16051 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16056 @kindex set complaints
16057 @item set complaints @var{limit}
16058 Permits @value{GDBN} to output @var{limit} complaints about each type of
16059 unusual symbols before becoming silent about the problem. Set
16060 @var{limit} to zero to suppress all complaints; set it to a large number
16061 to prevent complaints from being suppressed.
16063 @kindex show complaints
16064 @item show complaints
16065 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16069 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16070 lot of stupid questions to confirm certain commands. For example, if
16071 you try to run a program which is already running:
16075 The program being debugged has been started already.
16076 Start it from the beginning? (y or n)
16079 If you are willing to unflinchingly face the consequences of your own
16080 commands, you can disable this ``feature'':
16084 @kindex set confirm
16086 @cindex confirmation
16087 @cindex stupid questions
16088 @item set confirm off
16089 Disables confirmation requests.
16091 @item set confirm on
16092 Enables confirmation requests (the default).
16094 @kindex show confirm
16096 Displays state of confirmation requests.
16100 @cindex command tracing
16101 If you need to debug user-defined commands or sourced files you may find it
16102 useful to enable @dfn{command tracing}. In this mode each command will be
16103 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16104 quantity denoting the call depth of each command.
16107 @kindex set trace-commands
16108 @cindex command scripts, debugging
16109 @item set trace-commands on
16110 Enable command tracing.
16111 @item set trace-commands off
16112 Disable command tracing.
16113 @item show trace-commands
16114 Display the current state of command tracing.
16117 @node Debugging Output
16118 @section Optional Messages about Internal Happenings
16119 @cindex optional debugging messages
16121 @value{GDBN} has commands that enable optional debugging messages from
16122 various @value{GDBN} subsystems; normally these commands are of
16123 interest to @value{GDBN} maintainers, or when reporting a bug. This
16124 section documents those commands.
16127 @kindex set exec-done-display
16128 @item set exec-done-display
16129 Turns on or off the notification of asynchronous commands'
16130 completion. When on, @value{GDBN} will print a message when an
16131 asynchronous command finishes its execution. The default is off.
16132 @kindex show exec-done-display
16133 @item show exec-done-display
16134 Displays the current setting of asynchronous command completion
16137 @cindex gdbarch debugging info
16138 @cindex architecture debugging info
16139 @item set debug arch
16140 Turns on or off display of gdbarch debugging info. The default is off
16142 @item show debug arch
16143 Displays the current state of displaying gdbarch debugging info.
16144 @item set debug aix-thread
16145 @cindex AIX threads
16146 Display debugging messages about inner workings of the AIX thread
16148 @item show debug aix-thread
16149 Show the current state of AIX thread debugging info display.
16150 @item set debug event
16151 @cindex event debugging info
16152 Turns on or off display of @value{GDBN} event debugging info. The
16154 @item show debug event
16155 Displays the current state of displaying @value{GDBN} event debugging
16157 @item set debug expression
16158 @cindex expression debugging info
16159 Turns on or off display of debugging info about @value{GDBN}
16160 expression parsing. The default is off.
16161 @item show debug expression
16162 Displays the current state of displaying debugging info about
16163 @value{GDBN} expression parsing.
16164 @item set debug frame
16165 @cindex frame debugging info
16166 Turns on or off display of @value{GDBN} frame debugging info. The
16168 @item show debug frame
16169 Displays the current state of displaying @value{GDBN} frame debugging
16171 @item set debug infrun
16172 @cindex inferior debugging info
16173 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16174 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16175 for implementing operations such as single-stepping the inferior.
16176 @item show debug infrun
16177 Displays the current state of @value{GDBN} inferior debugging.
16178 @item set debug lin-lwp
16179 @cindex @sc{gnu}/Linux LWP debug messages
16180 @cindex Linux lightweight processes
16181 Turns on or off debugging messages from the Linux LWP debug support.
16182 @item show debug lin-lwp
16183 Show the current state of Linux LWP debugging messages.
16184 @item set debug observer
16185 @cindex observer debugging info
16186 Turns on or off display of @value{GDBN} observer debugging. This
16187 includes info such as the notification of observable events.
16188 @item show debug observer
16189 Displays the current state of observer debugging.
16190 @item set debug overload
16191 @cindex C@t{++} overload debugging info
16192 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16193 info. This includes info such as ranking of functions, etc. The default
16195 @item show debug overload
16196 Displays the current state of displaying @value{GDBN} C@t{++} overload
16198 @cindex packets, reporting on stdout
16199 @cindex serial connections, debugging
16200 @cindex debug remote protocol
16201 @cindex remote protocol debugging
16202 @cindex display remote packets
16203 @item set debug remote
16204 Turns on or off display of reports on all packets sent back and forth across
16205 the serial line to the remote machine. The info is printed on the
16206 @value{GDBN} standard output stream. The default is off.
16207 @item show debug remote
16208 Displays the state of display of remote packets.
16209 @item set debug serial
16210 Turns on or off display of @value{GDBN} serial debugging info. The
16212 @item show debug serial
16213 Displays the current state of displaying @value{GDBN} serial debugging
16215 @item set debug solib-frv
16216 @cindex FR-V shared-library debugging
16217 Turns on or off debugging messages for FR-V shared-library code.
16218 @item show debug solib-frv
16219 Display the current state of FR-V shared-library code debugging
16221 @item set debug target
16222 @cindex target debugging info
16223 Turns on or off display of @value{GDBN} target debugging info. This info
16224 includes what is going on at the target level of GDB, as it happens. The
16225 default is 0. Set it to 1 to track events, and to 2 to also track the
16226 value of large memory transfers. Changes to this flag do not take effect
16227 until the next time you connect to a target or use the @code{run} command.
16228 @item show debug target
16229 Displays the current state of displaying @value{GDBN} target debugging
16231 @item set debugvarobj
16232 @cindex variable object debugging info
16233 Turns on or off display of @value{GDBN} variable object debugging
16234 info. The default is off.
16235 @item show debugvarobj
16236 Displays the current state of displaying @value{GDBN} variable object
16238 @item set debug xml
16239 @cindex XML parser debugging
16240 Turns on or off debugging messages for built-in XML parsers.
16241 @item show debug xml
16242 Displays the current state of XML debugging messages.
16246 @chapter Canned Sequences of Commands
16248 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16249 Command Lists}), @value{GDBN} provides two ways to store sequences of
16250 commands for execution as a unit: user-defined commands and command
16254 * Define:: How to define your own commands
16255 * Hooks:: Hooks for user-defined commands
16256 * Command Files:: How to write scripts of commands to be stored in a file
16257 * Output:: Commands for controlled output
16261 @section User-defined Commands
16263 @cindex user-defined command
16264 @cindex arguments, to user-defined commands
16265 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16266 which you assign a new name as a command. This is done with the
16267 @code{define} command. User commands may accept up to 10 arguments
16268 separated by whitespace. Arguments are accessed within the user command
16269 via @code{$arg0@dots{}$arg9}. A trivial example:
16273 print $arg0 + $arg1 + $arg2
16278 To execute the command use:
16285 This defines the command @code{adder}, which prints the sum of
16286 its three arguments. Note the arguments are text substitutions, so they may
16287 reference variables, use complex expressions, or even perform inferior
16290 @cindex argument count in user-defined commands
16291 @cindex how many arguments (user-defined commands)
16292 In addition, @code{$argc} may be used to find out how many arguments have
16293 been passed. This expands to a number in the range 0@dots{}10.
16298 print $arg0 + $arg1
16301 print $arg0 + $arg1 + $arg2
16309 @item define @var{commandname}
16310 Define a command named @var{commandname}. If there is already a command
16311 by that name, you are asked to confirm that you want to redefine it.
16313 The definition of the command is made up of other @value{GDBN} command lines,
16314 which are given following the @code{define} command. The end of these
16315 commands is marked by a line containing @code{end}.
16318 @kindex end@r{ (user-defined commands)}
16319 @item document @var{commandname}
16320 Document the user-defined command @var{commandname}, so that it can be
16321 accessed by @code{help}. The command @var{commandname} must already be
16322 defined. This command reads lines of documentation just as @code{define}
16323 reads the lines of the command definition, ending with @code{end}.
16324 After the @code{document} command is finished, @code{help} on command
16325 @var{commandname} displays the documentation you have written.
16327 You may use the @code{document} command again to change the
16328 documentation of a command. Redefining the command with @code{define}
16329 does not change the documentation.
16331 @kindex dont-repeat
16332 @cindex don't repeat command
16334 Used inside a user-defined command, this tells @value{GDBN} that this
16335 command should not be repeated when the user hits @key{RET}
16336 (@pxref{Command Syntax, repeat last command}).
16338 @kindex help user-defined
16339 @item help user-defined
16340 List all user-defined commands, with the first line of the documentation
16345 @itemx show user @var{commandname}
16346 Display the @value{GDBN} commands used to define @var{commandname} (but
16347 not its documentation). If no @var{commandname} is given, display the
16348 definitions for all user-defined commands.
16350 @cindex infinite recursion in user-defined commands
16351 @kindex show max-user-call-depth
16352 @kindex set max-user-call-depth
16353 @item show max-user-call-depth
16354 @itemx set max-user-call-depth
16355 The value of @code{max-user-call-depth} controls how many recursion
16356 levels are allowed in user-defined commands before @value{GDBN} suspects an
16357 infinite recursion and aborts the command.
16360 In addition to the above commands, user-defined commands frequently
16361 use control flow commands, described in @ref{Command Files}.
16363 When user-defined commands are executed, the
16364 commands of the definition are not printed. An error in any command
16365 stops execution of the user-defined command.
16367 If used interactively, commands that would ask for confirmation proceed
16368 without asking when used inside a user-defined command. Many @value{GDBN}
16369 commands that normally print messages to say what they are doing omit the
16370 messages when used in a user-defined command.
16373 @section User-defined Command Hooks
16374 @cindex command hooks
16375 @cindex hooks, for commands
16376 @cindex hooks, pre-command
16379 You may define @dfn{hooks}, which are a special kind of user-defined
16380 command. Whenever you run the command @samp{foo}, if the user-defined
16381 command @samp{hook-foo} exists, it is executed (with no arguments)
16382 before that command.
16384 @cindex hooks, post-command
16386 A hook may also be defined which is run after the command you executed.
16387 Whenever you run the command @samp{foo}, if the user-defined command
16388 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16389 that command. Post-execution hooks may exist simultaneously with
16390 pre-execution hooks, for the same command.
16392 It is valid for a hook to call the command which it hooks. If this
16393 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16395 @c It would be nice if hookpost could be passed a parameter indicating
16396 @c if the command it hooks executed properly or not. FIXME!
16398 @kindex stop@r{, a pseudo-command}
16399 In addition, a pseudo-command, @samp{stop} exists. Defining
16400 (@samp{hook-stop}) makes the associated commands execute every time
16401 execution stops in your program: before breakpoint commands are run,
16402 displays are printed, or the stack frame is printed.
16404 For example, to ignore @code{SIGALRM} signals while
16405 single-stepping, but treat them normally during normal execution,
16410 handle SIGALRM nopass
16414 handle SIGALRM pass
16417 define hook-continue
16418 handle SIGALRM pass
16422 As a further example, to hook at the beginning and end of the @code{echo}
16423 command, and to add extra text to the beginning and end of the message,
16431 define hookpost-echo
16435 (@value{GDBP}) echo Hello World
16436 <<<---Hello World--->>>
16441 You can define a hook for any single-word command in @value{GDBN}, but
16442 not for command aliases; you should define a hook for the basic command
16443 name, e.g.@: @code{backtrace} rather than @code{bt}.
16444 @c FIXME! So how does Joe User discover whether a command is an alias
16446 If an error occurs during the execution of your hook, execution of
16447 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16448 (before the command that you actually typed had a chance to run).
16450 If you try to define a hook which does not match any known command, you
16451 get a warning from the @code{define} command.
16453 @node Command Files
16454 @section Command Files
16456 @cindex command files
16457 @cindex scripting commands
16458 A command file for @value{GDBN} is a text file made of lines that are
16459 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16460 also be included. An empty line in a command file does nothing; it
16461 does not mean to repeat the last command, as it would from the
16464 You can request the execution of a command file with the @code{source}
16469 @cindex execute commands from a file
16470 @item source [@code{-v}] @var{filename}
16471 Execute the command file @var{filename}.
16474 The lines in a command file are generally executed sequentially,
16475 unless the order of execution is changed by one of the
16476 @emph{flow-control commands} described below. The commands are not
16477 printed as they are executed. An error in any command terminates
16478 execution of the command file and control is returned to the console.
16480 @value{GDBN} searches for @var{filename} in the current directory and then
16481 on the search path (specified with the @samp{directory} command).
16483 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16484 each command as it is executed. The option must be given before
16485 @var{filename}, and is interpreted as part of the filename anywhere else.
16487 Commands that would ask for confirmation if used interactively proceed
16488 without asking when used in a command file. Many @value{GDBN} commands that
16489 normally print messages to say what they are doing omit the messages
16490 when called from command files.
16492 @value{GDBN} also accepts command input from standard input. In this
16493 mode, normal output goes to standard output and error output goes to
16494 standard error. Errors in a command file supplied on standard input do
16495 not terminate execution of the command file---execution continues with
16499 gdb < cmds > log 2>&1
16502 (The syntax above will vary depending on the shell used.) This example
16503 will execute commands from the file @file{cmds}. All output and errors
16504 would be directed to @file{log}.
16506 Since commands stored on command files tend to be more general than
16507 commands typed interactively, they frequently need to deal with
16508 complicated situations, such as different or unexpected values of
16509 variables and symbols, changes in how the program being debugged is
16510 built, etc. @value{GDBN} provides a set of flow-control commands to
16511 deal with these complexities. Using these commands, you can write
16512 complex scripts that loop over data structures, execute commands
16513 conditionally, etc.
16520 This command allows to include in your script conditionally executed
16521 commands. The @code{if} command takes a single argument, which is an
16522 expression to evaluate. It is followed by a series of commands that
16523 are executed only if the expression is true (its value is nonzero).
16524 There can then optionally be an @code{else} line, followed by a series
16525 of commands that are only executed if the expression was false. The
16526 end of the list is marked by a line containing @code{end}.
16530 This command allows to write loops. Its syntax is similar to
16531 @code{if}: the command takes a single argument, which is an expression
16532 to evaluate, and must be followed by the commands to execute, one per
16533 line, terminated by an @code{end}. These commands are called the
16534 @dfn{body} of the loop. The commands in the body of @code{while} are
16535 executed repeatedly as long as the expression evaluates to true.
16539 This command exits the @code{while} loop in whose body it is included.
16540 Execution of the script continues after that @code{while}s @code{end}
16543 @kindex loop_continue
16544 @item loop_continue
16545 This command skips the execution of the rest of the body of commands
16546 in the @code{while} loop in whose body it is included. Execution
16547 branches to the beginning of the @code{while} loop, where it evaluates
16548 the controlling expression.
16550 @kindex end@r{ (if/else/while commands)}
16552 Terminate the block of commands that are the body of @code{if},
16553 @code{else}, or @code{while} flow-control commands.
16558 @section Commands for Controlled Output
16560 During the execution of a command file or a user-defined command, normal
16561 @value{GDBN} output is suppressed; the only output that appears is what is
16562 explicitly printed by the commands in the definition. This section
16563 describes three commands useful for generating exactly the output you
16568 @item echo @var{text}
16569 @c I do not consider backslash-space a standard C escape sequence
16570 @c because it is not in ANSI.
16571 Print @var{text}. Nonprinting characters can be included in
16572 @var{text} using C escape sequences, such as @samp{\n} to print a
16573 newline. @strong{No newline is printed unless you specify one.}
16574 In addition to the standard C escape sequences, a backslash followed
16575 by a space stands for a space. This is useful for displaying a
16576 string with spaces at the beginning or the end, since leading and
16577 trailing spaces are otherwise trimmed from all arguments.
16578 To print @samp{@w{ }and foo =@w{ }}, use the command
16579 @samp{echo \@w{ }and foo = \@w{ }}.
16581 A backslash at the end of @var{text} can be used, as in C, to continue
16582 the command onto subsequent lines. For example,
16585 echo This is some text\n\
16586 which is continued\n\
16587 onto several lines.\n
16590 produces the same output as
16593 echo This is some text\n
16594 echo which is continued\n
16595 echo onto several lines.\n
16599 @item output @var{expression}
16600 Print the value of @var{expression} and nothing but that value: no
16601 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16602 value history either. @xref{Expressions, ,Expressions}, for more information
16605 @item output/@var{fmt} @var{expression}
16606 Print the value of @var{expression} in format @var{fmt}. You can use
16607 the same formats as for @code{print}. @xref{Output Formats,,Output
16608 Formats}, for more information.
16611 @item printf @var{template}, @var{expressions}@dots{}
16612 Print the values of one or more @var{expressions} under the control of
16613 the string @var{template}. To print several values, make
16614 @var{expressions} be a comma-separated list of individual expressions,
16615 which may be either numbers or pointers. Their values are printed as
16616 specified by @var{template}, exactly as a C program would do by
16617 executing the code below:
16620 printf (@var{template}, @var{expressions}@dots{});
16623 As in @code{C} @code{printf}, ordinary characters in @var{template}
16624 are printed verbatim, while @dfn{conversion specification} introduced
16625 by the @samp{%} character cause subsequent @var{expressions} to be
16626 evaluated, their values converted and formatted according to type and
16627 style information encoded in the conversion specifications, and then
16630 For example, you can print two values in hex like this:
16633 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16636 @code{printf} supports all the standard @code{C} conversion
16637 specifications, including the flags and modifiers between the @samp{%}
16638 character and the conversion letter, with the following exceptions:
16642 The argument-ordering modifiers, such as @samp{2$}, are not supported.
16645 The modifier @samp{*} is not supported for specifying precision or
16649 The @samp{'} flag (for separation of digits into groups according to
16650 @code{LC_NUMERIC'}) is not supported.
16653 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
16657 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
16660 The conversion letters @samp{a} and @samp{A} are not supported.
16664 Note that the @samp{ll} type modifier is supported only if the
16665 underlying @code{C} implementation used to build @value{GDBN} supports
16666 the @code{long long int} type, and the @samp{L} type modifier is
16667 supported only if @code{long double} type is available.
16669 As in @code{C}, @code{printf} supports simple backslash-escape
16670 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
16671 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
16672 single character. Octal and hexadecimal escape sequences are not
16675 Additionally, @code{printf} supports conversion specifications for DFP
16676 (@dfn{Decimal Floating Point}) types using the following conversion
16681 @samp{H} for printing @code{Decimal32} types.
16684 @samp{D} for printing @code{Decimal64} types.
16687 @samp{DD} for printing @code{Decimal128} types.
16690 If the underlying @code{C} implementation used to build @value{GDBN} has
16691 support for the three conversion letters for DFP types, other modifiers
16692 such as width and precision will also be available for @value{GDBN} to use.
16694 In case there is no such @code{C} support, no additional modifiers will be
16695 available and the value will be printed in the standard way.
16697 Here's an example of printing DFP types using the above conversion letters:
16699 printf "D32: %H - D64: %D - D128: %DD\n",1.2345df,1.2E10dd,1.2E1dl
16705 @chapter Command Interpreters
16706 @cindex command interpreters
16708 @value{GDBN} supports multiple command interpreters, and some command
16709 infrastructure to allow users or user interface writers to switch
16710 between interpreters or run commands in other interpreters.
16712 @value{GDBN} currently supports two command interpreters, the console
16713 interpreter (sometimes called the command-line interpreter or @sc{cli})
16714 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16715 describes both of these interfaces in great detail.
16717 By default, @value{GDBN} will start with the console interpreter.
16718 However, the user may choose to start @value{GDBN} with another
16719 interpreter by specifying the @option{-i} or @option{--interpreter}
16720 startup options. Defined interpreters include:
16724 @cindex console interpreter
16725 The traditional console or command-line interpreter. This is the most often
16726 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16727 @value{GDBN} will use this interpreter.
16730 @cindex mi interpreter
16731 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16732 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16733 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16737 @cindex mi2 interpreter
16738 The current @sc{gdb/mi} interface.
16741 @cindex mi1 interpreter
16742 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16746 @cindex invoke another interpreter
16747 The interpreter being used by @value{GDBN} may not be dynamically
16748 switched at runtime. Although possible, this could lead to a very
16749 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16750 enters the command "interpreter-set console" in a console view,
16751 @value{GDBN} would switch to using the console interpreter, rendering
16752 the IDE inoperable!
16754 @kindex interpreter-exec
16755 Although you may only choose a single interpreter at startup, you may execute
16756 commands in any interpreter from the current interpreter using the appropriate
16757 command. If you are running the console interpreter, simply use the
16758 @code{interpreter-exec} command:
16761 interpreter-exec mi "-data-list-register-names"
16764 @sc{gdb/mi} has a similar command, although it is only available in versions of
16765 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16768 @chapter @value{GDBN} Text User Interface
16770 @cindex Text User Interface
16773 * TUI Overview:: TUI overview
16774 * TUI Keys:: TUI key bindings
16775 * TUI Single Key Mode:: TUI single key mode
16776 * TUI Commands:: TUI-specific commands
16777 * TUI Configuration:: TUI configuration variables
16780 The @value{GDBN} Text User Interface (TUI) is a terminal
16781 interface which uses the @code{curses} library to show the source
16782 file, the assembly output, the program registers and @value{GDBN}
16783 commands in separate text windows. The TUI mode is supported only
16784 on platforms where a suitable version of the @code{curses} library
16787 @pindex @value{GDBTUI}
16788 The TUI mode is enabled by default when you invoke @value{GDBN} as
16789 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
16790 You can also switch in and out of TUI mode while @value{GDBN} runs by
16791 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
16792 @xref{TUI Keys, ,TUI Key Bindings}.
16795 @section TUI Overview
16797 In TUI mode, @value{GDBN} can display several text windows:
16801 This window is the @value{GDBN} command window with the @value{GDBN}
16802 prompt and the @value{GDBN} output. The @value{GDBN} input is still
16803 managed using readline.
16806 The source window shows the source file of the program. The current
16807 line and active breakpoints are displayed in this window.
16810 The assembly window shows the disassembly output of the program.
16813 This window shows the processor registers. Registers are highlighted
16814 when their values change.
16817 The source and assembly windows show the current program position
16818 by highlighting the current line and marking it with a @samp{>} marker.
16819 Breakpoints are indicated with two markers. The first marker
16820 indicates the breakpoint type:
16824 Breakpoint which was hit at least once.
16827 Breakpoint which was never hit.
16830 Hardware breakpoint which was hit at least once.
16833 Hardware breakpoint which was never hit.
16836 The second marker indicates whether the breakpoint is enabled or not:
16840 Breakpoint is enabled.
16843 Breakpoint is disabled.
16846 The source, assembly and register windows are updated when the current
16847 thread changes, when the frame changes, or when the program counter
16850 These windows are not all visible at the same time. The command
16851 window is always visible. The others can be arranged in several
16862 source and assembly,
16865 source and registers, or
16868 assembly and registers.
16871 A status line above the command window shows the following information:
16875 Indicates the current @value{GDBN} target.
16876 (@pxref{Targets, ,Specifying a Debugging Target}).
16879 Gives the current process or thread number.
16880 When no process is being debugged, this field is set to @code{No process}.
16883 Gives the current function name for the selected frame.
16884 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16885 When there is no symbol corresponding to the current program counter,
16886 the string @code{??} is displayed.
16889 Indicates the current line number for the selected frame.
16890 When the current line number is not known, the string @code{??} is displayed.
16893 Indicates the current program counter address.
16897 @section TUI Key Bindings
16898 @cindex TUI key bindings
16900 The TUI installs several key bindings in the readline keymaps
16901 (@pxref{Command Line Editing}). The following key bindings
16902 are installed for both TUI mode and the @value{GDBN} standard mode.
16911 Enter or leave the TUI mode. When leaving the TUI mode,
16912 the curses window management stops and @value{GDBN} operates using
16913 its standard mode, writing on the terminal directly. When reentering
16914 the TUI mode, control is given back to the curses windows.
16915 The screen is then refreshed.
16919 Use a TUI layout with only one window. The layout will
16920 either be @samp{source} or @samp{assembly}. When the TUI mode
16921 is not active, it will switch to the TUI mode.
16923 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16927 Use a TUI layout with at least two windows. When the current
16928 layout already has two windows, the next layout with two windows is used.
16929 When a new layout is chosen, one window will always be common to the
16930 previous layout and the new one.
16932 Think of it as the Emacs @kbd{C-x 2} binding.
16936 Change the active window. The TUI associates several key bindings
16937 (like scrolling and arrow keys) with the active window. This command
16938 gives the focus to the next TUI window.
16940 Think of it as the Emacs @kbd{C-x o} binding.
16944 Switch in and out of the TUI SingleKey mode that binds single
16945 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
16948 The following key bindings only work in the TUI mode:
16953 Scroll the active window one page up.
16957 Scroll the active window one page down.
16961 Scroll the active window one line up.
16965 Scroll the active window one line down.
16969 Scroll the active window one column left.
16973 Scroll the active window one column right.
16977 Refresh the screen.
16980 Because the arrow keys scroll the active window in the TUI mode, they
16981 are not available for their normal use by readline unless the command
16982 window has the focus. When another window is active, you must use
16983 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
16984 and @kbd{C-f} to control the command window.
16986 @node TUI Single Key Mode
16987 @section TUI Single Key Mode
16988 @cindex TUI single key mode
16990 The TUI also provides a @dfn{SingleKey} mode, which binds several
16991 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
16992 switch into this mode, where the following key bindings are used:
16995 @kindex c @r{(SingleKey TUI key)}
16999 @kindex d @r{(SingleKey TUI key)}
17003 @kindex f @r{(SingleKey TUI key)}
17007 @kindex n @r{(SingleKey TUI key)}
17011 @kindex q @r{(SingleKey TUI key)}
17013 exit the SingleKey mode.
17015 @kindex r @r{(SingleKey TUI key)}
17019 @kindex s @r{(SingleKey TUI key)}
17023 @kindex u @r{(SingleKey TUI key)}
17027 @kindex v @r{(SingleKey TUI key)}
17031 @kindex w @r{(SingleKey TUI key)}
17036 Other keys temporarily switch to the @value{GDBN} command prompt.
17037 The key that was pressed is inserted in the editing buffer so that
17038 it is possible to type most @value{GDBN} commands without interaction
17039 with the TUI SingleKey mode. Once the command is entered the TUI
17040 SingleKey mode is restored. The only way to permanently leave
17041 this mode is by typing @kbd{q} or @kbd{C-x s}.
17045 @section TUI-specific Commands
17046 @cindex TUI commands
17048 The TUI has specific commands to control the text windows.
17049 These commands are always available, even when @value{GDBN} is not in
17050 the TUI mode. When @value{GDBN} is in the standard mode, most
17051 of these commands will automatically switch to the TUI mode.
17056 List and give the size of all displayed windows.
17060 Display the next layout.
17063 Display the previous layout.
17066 Display the source window only.
17069 Display the assembly window only.
17072 Display the source and assembly window.
17075 Display the register window together with the source or assembly window.
17079 Make the next window active for scrolling.
17082 Make the previous window active for scrolling.
17085 Make the source window active for scrolling.
17088 Make the assembly window active for scrolling.
17091 Make the register window active for scrolling.
17094 Make the command window active for scrolling.
17098 Refresh the screen. This is similar to typing @kbd{C-L}.
17100 @item tui reg float
17102 Show the floating point registers in the register window.
17104 @item tui reg general
17105 Show the general registers in the register window.
17108 Show the next register group. The list of register groups as well as
17109 their order is target specific. The predefined register groups are the
17110 following: @code{general}, @code{float}, @code{system}, @code{vector},
17111 @code{all}, @code{save}, @code{restore}.
17113 @item tui reg system
17114 Show the system registers in the register window.
17118 Update the source window and the current execution point.
17120 @item winheight @var{name} +@var{count}
17121 @itemx winheight @var{name} -@var{count}
17123 Change the height of the window @var{name} by @var{count}
17124 lines. Positive counts increase the height, while negative counts
17127 @item tabset @var{nchars}
17129 Set the width of tab stops to be @var{nchars} characters.
17132 @node TUI Configuration
17133 @section TUI Configuration Variables
17134 @cindex TUI configuration variables
17136 Several configuration variables control the appearance of TUI windows.
17139 @item set tui border-kind @var{kind}
17140 @kindex set tui border-kind
17141 Select the border appearance for the source, assembly and register windows.
17142 The possible values are the following:
17145 Use a space character to draw the border.
17148 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
17151 Use the Alternate Character Set to draw the border. The border is
17152 drawn using character line graphics if the terminal supports them.
17155 @item set tui border-mode @var{mode}
17156 @kindex set tui border-mode
17157 @itemx set tui active-border-mode @var{mode}
17158 @kindex set tui active-border-mode
17159 Select the display attributes for the borders of the inactive windows
17160 or the active window. The @var{mode} can be one of the following:
17163 Use normal attributes to display the border.
17169 Use reverse video mode.
17172 Use half bright mode.
17174 @item half-standout
17175 Use half bright and standout mode.
17178 Use extra bright or bold mode.
17180 @item bold-standout
17181 Use extra bright or bold and standout mode.
17186 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17189 @cindex @sc{gnu} Emacs
17190 A special interface allows you to use @sc{gnu} Emacs to view (and
17191 edit) the source files for the program you are debugging with
17194 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17195 executable file you want to debug as an argument. This command starts
17196 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17197 created Emacs buffer.
17198 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17200 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17205 All ``terminal'' input and output goes through an Emacs buffer, called
17208 This applies both to @value{GDBN} commands and their output, and to the input
17209 and output done by the program you are debugging.
17211 This is useful because it means that you can copy the text of previous
17212 commands and input them again; you can even use parts of the output
17215 All the facilities of Emacs' Shell mode are available for interacting
17216 with your program. In particular, you can send signals the usual
17217 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17221 @value{GDBN} displays source code through Emacs.
17223 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17224 source file for that frame and puts an arrow (@samp{=>}) at the
17225 left margin of the current line. Emacs uses a separate buffer for
17226 source display, and splits the screen to show both your @value{GDBN} session
17229 Explicit @value{GDBN} @code{list} or search commands still produce output as
17230 usual, but you probably have no reason to use them from Emacs.
17233 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17234 a graphical mode, enabled by default, which provides further buffers
17235 that can control the execution and describe the state of your program.
17236 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17238 If you specify an absolute file name when prompted for the @kbd{M-x
17239 gdb} argument, then Emacs sets your current working directory to where
17240 your program resides. If you only specify the file name, then Emacs
17241 sets your current working directory to to the directory associated
17242 with the previous buffer. In this case, @value{GDBN} may find your
17243 program by searching your environment's @code{PATH} variable, but on
17244 some operating systems it might not find the source. So, although the
17245 @value{GDBN} input and output session proceeds normally, the auxiliary
17246 buffer does not display the current source and line of execution.
17248 The initial working directory of @value{GDBN} is printed on the top
17249 line of the GUD buffer and this serves as a default for the commands
17250 that specify files for @value{GDBN} to operate on. @xref{Files,
17251 ,Commands to Specify Files}.
17253 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17254 need to call @value{GDBN} by a different name (for example, if you
17255 keep several configurations around, with different names) you can
17256 customize the Emacs variable @code{gud-gdb-command-name} to run the
17259 In the GUD buffer, you can use these special Emacs commands in
17260 addition to the standard Shell mode commands:
17264 Describe the features of Emacs' GUD Mode.
17267 Execute to another source line, like the @value{GDBN} @code{step} command; also
17268 update the display window to show the current file and location.
17271 Execute to next source line in this function, skipping all function
17272 calls, like the @value{GDBN} @code{next} command. Then update the display window
17273 to show the current file and location.
17276 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17277 display window accordingly.
17280 Execute until exit from the selected stack frame, like the @value{GDBN}
17281 @code{finish} command.
17284 Continue execution of your program, like the @value{GDBN} @code{continue}
17288 Go up the number of frames indicated by the numeric argument
17289 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17290 like the @value{GDBN} @code{up} command.
17293 Go down the number of frames indicated by the numeric argument, like the
17294 @value{GDBN} @code{down} command.
17297 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17298 tells @value{GDBN} to set a breakpoint on the source line point is on.
17300 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17301 separate frame which shows a backtrace when the GUD buffer is current.
17302 Move point to any frame in the stack and type @key{RET} to make it
17303 become the current frame and display the associated source in the
17304 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17305 selected frame become the current one. In graphical mode, the
17306 speedbar displays watch expressions.
17308 If you accidentally delete the source-display buffer, an easy way to get
17309 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17310 request a frame display; when you run under Emacs, this recreates
17311 the source buffer if necessary to show you the context of the current
17314 The source files displayed in Emacs are in ordinary Emacs buffers
17315 which are visiting the source files in the usual way. You can edit
17316 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17317 communicates with Emacs in terms of line numbers. If you add or
17318 delete lines from the text, the line numbers that @value{GDBN} knows cease
17319 to correspond properly with the code.
17321 A more detailed description of Emacs' interaction with @value{GDBN} is
17322 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17325 @c The following dropped because Epoch is nonstandard. Reactivate
17326 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17328 @kindex Emacs Epoch environment
17332 Version 18 of @sc{gnu} Emacs has a built-in window system
17333 called the @code{epoch}
17334 environment. Users of this environment can use a new command,
17335 @code{inspect} which performs identically to @code{print} except that
17336 each value is printed in its own window.
17341 @chapter The @sc{gdb/mi} Interface
17343 @unnumberedsec Function and Purpose
17345 @cindex @sc{gdb/mi}, its purpose
17346 @sc{gdb/mi} is a line based machine oriented text interface to
17347 @value{GDBN} and is activated by specifying using the
17348 @option{--interpreter} command line option (@pxref{Mode Options}). It
17349 is specifically intended to support the development of systems which
17350 use the debugger as just one small component of a larger system.
17352 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17353 in the form of a reference manual.
17355 Note that @sc{gdb/mi} is still under construction, so some of the
17356 features described below are incomplete and subject to change
17357 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17359 @unnumberedsec Notation and Terminology
17361 @cindex notational conventions, for @sc{gdb/mi}
17362 This chapter uses the following notation:
17366 @code{|} separates two alternatives.
17369 @code{[ @var{something} ]} indicates that @var{something} is optional:
17370 it may or may not be given.
17373 @code{( @var{group} )*} means that @var{group} inside the parentheses
17374 may repeat zero or more times.
17377 @code{( @var{group} )+} means that @var{group} inside the parentheses
17378 may repeat one or more times.
17381 @code{"@var{string}"} means a literal @var{string}.
17385 @heading Dependencies
17389 * GDB/MI Command Syntax::
17390 * GDB/MI Compatibility with CLI::
17391 * GDB/MI Development and Front Ends::
17392 * GDB/MI Output Records::
17393 * GDB/MI Simple Examples::
17394 * GDB/MI Command Description Format::
17395 * GDB/MI Breakpoint Commands::
17396 * GDB/MI Program Context::
17397 * GDB/MI Thread Commands::
17398 * GDB/MI Program Execution::
17399 * GDB/MI Stack Manipulation::
17400 * GDB/MI Variable Objects::
17401 * GDB/MI Data Manipulation::
17402 * GDB/MI Tracepoint Commands::
17403 * GDB/MI Symbol Query::
17404 * GDB/MI File Commands::
17406 * GDB/MI Kod Commands::
17407 * GDB/MI Memory Overlay Commands::
17408 * GDB/MI Signal Handling Commands::
17410 * GDB/MI Target Manipulation::
17411 * GDB/MI File Transfer Commands::
17412 * GDB/MI Miscellaneous Commands::
17415 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17416 @node GDB/MI Command Syntax
17417 @section @sc{gdb/mi} Command Syntax
17420 * GDB/MI Input Syntax::
17421 * GDB/MI Output Syntax::
17424 @node GDB/MI Input Syntax
17425 @subsection @sc{gdb/mi} Input Syntax
17427 @cindex input syntax for @sc{gdb/mi}
17428 @cindex @sc{gdb/mi}, input syntax
17430 @item @var{command} @expansion{}
17431 @code{@var{cli-command} | @var{mi-command}}
17433 @item @var{cli-command} @expansion{}
17434 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17435 @var{cli-command} is any existing @value{GDBN} CLI command.
17437 @item @var{mi-command} @expansion{}
17438 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17439 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17441 @item @var{token} @expansion{}
17442 "any sequence of digits"
17444 @item @var{option} @expansion{}
17445 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17447 @item @var{parameter} @expansion{}
17448 @code{@var{non-blank-sequence} | @var{c-string}}
17450 @item @var{operation} @expansion{}
17451 @emph{any of the operations described in this chapter}
17453 @item @var{non-blank-sequence} @expansion{}
17454 @emph{anything, provided it doesn't contain special characters such as
17455 "-", @var{nl}, """ and of course " "}
17457 @item @var{c-string} @expansion{}
17458 @code{""" @var{seven-bit-iso-c-string-content} """}
17460 @item @var{nl} @expansion{}
17469 The CLI commands are still handled by the @sc{mi} interpreter; their
17470 output is described below.
17473 The @code{@var{token}}, when present, is passed back when the command
17477 Some @sc{mi} commands accept optional arguments as part of the parameter
17478 list. Each option is identified by a leading @samp{-} (dash) and may be
17479 followed by an optional argument parameter. Options occur first in the
17480 parameter list and can be delimited from normal parameters using
17481 @samp{--} (this is useful when some parameters begin with a dash).
17488 We want easy access to the existing CLI syntax (for debugging).
17491 We want it to be easy to spot a @sc{mi} operation.
17494 @node GDB/MI Output Syntax
17495 @subsection @sc{gdb/mi} Output Syntax
17497 @cindex output syntax of @sc{gdb/mi}
17498 @cindex @sc{gdb/mi}, output syntax
17499 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17500 followed, optionally, by a single result record. This result record
17501 is for the most recent command. The sequence of output records is
17502 terminated by @samp{(gdb)}.
17504 If an input command was prefixed with a @code{@var{token}} then the
17505 corresponding output for that command will also be prefixed by that same
17509 @item @var{output} @expansion{}
17510 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17512 @item @var{result-record} @expansion{}
17513 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17515 @item @var{out-of-band-record} @expansion{}
17516 @code{@var{async-record} | @var{stream-record}}
17518 @item @var{async-record} @expansion{}
17519 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17521 @item @var{exec-async-output} @expansion{}
17522 @code{[ @var{token} ] "*" @var{async-output}}
17524 @item @var{status-async-output} @expansion{}
17525 @code{[ @var{token} ] "+" @var{async-output}}
17527 @item @var{notify-async-output} @expansion{}
17528 @code{[ @var{token} ] "=" @var{async-output}}
17530 @item @var{async-output} @expansion{}
17531 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17533 @item @var{result-class} @expansion{}
17534 @code{"done" | "running" | "connected" | "error" | "exit"}
17536 @item @var{async-class} @expansion{}
17537 @code{"stopped" | @var{others}} (where @var{others} will be added
17538 depending on the needs---this is still in development).
17540 @item @var{result} @expansion{}
17541 @code{ @var{variable} "=" @var{value}}
17543 @item @var{variable} @expansion{}
17544 @code{ @var{string} }
17546 @item @var{value} @expansion{}
17547 @code{ @var{const} | @var{tuple} | @var{list} }
17549 @item @var{const} @expansion{}
17550 @code{@var{c-string}}
17552 @item @var{tuple} @expansion{}
17553 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17555 @item @var{list} @expansion{}
17556 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17557 @var{result} ( "," @var{result} )* "]" }
17559 @item @var{stream-record} @expansion{}
17560 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17562 @item @var{console-stream-output} @expansion{}
17563 @code{"~" @var{c-string}}
17565 @item @var{target-stream-output} @expansion{}
17566 @code{"@@" @var{c-string}}
17568 @item @var{log-stream-output} @expansion{}
17569 @code{"&" @var{c-string}}
17571 @item @var{nl} @expansion{}
17574 @item @var{token} @expansion{}
17575 @emph{any sequence of digits}.
17583 All output sequences end in a single line containing a period.
17586 The @code{@var{token}} is from the corresponding request. If an execution
17587 command is interrupted by the @samp{-exec-interrupt} command, the
17588 @var{token} associated with the @samp{*stopped} message is the one of the
17589 original execution command, not the one of the interrupt command.
17592 @cindex status output in @sc{gdb/mi}
17593 @var{status-async-output} contains on-going status information about the
17594 progress of a slow operation. It can be discarded. All status output is
17595 prefixed by @samp{+}.
17598 @cindex async output in @sc{gdb/mi}
17599 @var{exec-async-output} contains asynchronous state change on the target
17600 (stopped, started, disappeared). All async output is prefixed by
17604 @cindex notify output in @sc{gdb/mi}
17605 @var{notify-async-output} contains supplementary information that the
17606 client should handle (e.g., a new breakpoint information). All notify
17607 output is prefixed by @samp{=}.
17610 @cindex console output in @sc{gdb/mi}
17611 @var{console-stream-output} is output that should be displayed as is in the
17612 console. It is the textual response to a CLI command. All the console
17613 output is prefixed by @samp{~}.
17616 @cindex target output in @sc{gdb/mi}
17617 @var{target-stream-output} is the output produced by the target program.
17618 All the target output is prefixed by @samp{@@}.
17621 @cindex log output in @sc{gdb/mi}
17622 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17623 instance messages that should be displayed as part of an error log. All
17624 the log output is prefixed by @samp{&}.
17627 @cindex list output in @sc{gdb/mi}
17628 New @sc{gdb/mi} commands should only output @var{lists} containing
17634 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17635 details about the various output records.
17637 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17638 @node GDB/MI Compatibility with CLI
17639 @section @sc{gdb/mi} Compatibility with CLI
17641 @cindex compatibility, @sc{gdb/mi} and CLI
17642 @cindex @sc{gdb/mi}, compatibility with CLI
17644 For the developers convenience CLI commands can be entered directly,
17645 but there may be some unexpected behaviour. For example, commands
17646 that query the user will behave as if the user replied yes, breakpoint
17647 command lists are not executed and some CLI commands, such as
17648 @code{if}, @code{when} and @code{define}, prompt for further input with
17649 @samp{>}, which is not valid MI output.
17651 This feature may be removed at some stage in the future and it is
17652 recommended that front ends use the @code{-interpreter-exec} command
17653 (@pxref{-interpreter-exec}).
17655 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17656 @node GDB/MI Development and Front Ends
17657 @section @sc{gdb/mi} Development and Front Ends
17658 @cindex @sc{gdb/mi} development
17660 The application which takes the MI output and presents the state of the
17661 program being debugged to the user is called a @dfn{front end}.
17663 Although @sc{gdb/mi} is still incomplete, it is currently being used
17664 by a variety of front ends to @value{GDBN}. This makes it difficult
17665 to introduce new functionality without breaking existing usage. This
17666 section tries to minimize the problems by describing how the protocol
17669 Some changes in MI need not break a carefully designed front end, and
17670 for these the MI version will remain unchanged. The following is a
17671 list of changes that may occur within one level, so front ends should
17672 parse MI output in a way that can handle them:
17676 New MI commands may be added.
17679 New fields may be added to the output of any MI command.
17682 The range of values for fields with specified values, e.g.,
17683 @code{in_scope} (@pxref{-var-update}) may be extended.
17685 @c The format of field's content e.g type prefix, may change so parse it
17686 @c at your own risk. Yes, in general?
17688 @c The order of fields may change? Shouldn't really matter but it might
17689 @c resolve inconsistencies.
17692 If the changes are likely to break front ends, the MI version level
17693 will be increased by one. This will allow the front end to parse the
17694 output according to the MI version. Apart from mi0, new versions of
17695 @value{GDBN} will not support old versions of MI and it will be the
17696 responsibility of the front end to work with the new one.
17698 @c Starting with mi3, add a new command -mi-version that prints the MI
17701 The best way to avoid unexpected changes in MI that might break your front
17702 end is to make your project known to @value{GDBN} developers and
17703 follow development on @email{gdb@@sourceware.org} and
17704 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17705 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17706 Group, which has the aim of creating a more general MI protocol
17707 called Debugger Machine Interface (DMI) that will become a standard
17708 for all debuggers, not just @value{GDBN}.
17709 @cindex mailing lists
17711 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17712 @node GDB/MI Output Records
17713 @section @sc{gdb/mi} Output Records
17716 * GDB/MI Result Records::
17717 * GDB/MI Stream Records::
17718 * GDB/MI Out-of-band Records::
17721 @node GDB/MI Result Records
17722 @subsection @sc{gdb/mi} Result Records
17724 @cindex result records in @sc{gdb/mi}
17725 @cindex @sc{gdb/mi}, result records
17726 In addition to a number of out-of-band notifications, the response to a
17727 @sc{gdb/mi} command includes one of the following result indications:
17731 @item "^done" [ "," @var{results} ]
17732 The synchronous operation was successful, @code{@var{results}} are the return
17737 @c Is this one correct? Should it be an out-of-band notification?
17738 The asynchronous operation was successfully started. The target is
17743 @value{GDBN} has connected to a remote target.
17745 @item "^error" "," @var{c-string}
17747 The operation failed. The @code{@var{c-string}} contains the corresponding
17752 @value{GDBN} has terminated.
17756 @node GDB/MI Stream Records
17757 @subsection @sc{gdb/mi} Stream Records
17759 @cindex @sc{gdb/mi}, stream records
17760 @cindex stream records in @sc{gdb/mi}
17761 @value{GDBN} internally maintains a number of output streams: the console, the
17762 target, and the log. The output intended for each of these streams is
17763 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17765 Each stream record begins with a unique @dfn{prefix character} which
17766 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17767 Syntax}). In addition to the prefix, each stream record contains a
17768 @code{@var{string-output}}. This is either raw text (with an implicit new
17769 line) or a quoted C string (which does not contain an implicit newline).
17772 @item "~" @var{string-output}
17773 The console output stream contains text that should be displayed in the
17774 CLI console window. It contains the textual responses to CLI commands.
17776 @item "@@" @var{string-output}
17777 The target output stream contains any textual output from the running
17778 target. This is only present when GDB's event loop is truly
17779 asynchronous, which is currently only the case for remote targets.
17781 @item "&" @var{string-output}
17782 The log stream contains debugging messages being produced by @value{GDBN}'s
17786 @node GDB/MI Out-of-band Records
17787 @subsection @sc{gdb/mi} Out-of-band Records
17789 @cindex out-of-band records in @sc{gdb/mi}
17790 @cindex @sc{gdb/mi}, out-of-band records
17791 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17792 additional changes that have occurred. Those changes can either be a
17793 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17794 target activity (e.g., target stopped).
17796 The following is a preliminary list of possible out-of-band records.
17797 In particular, the @var{exec-async-output} records.
17800 @item *stopped,reason="@var{reason}"
17803 @var{reason} can be one of the following:
17806 @item breakpoint-hit
17807 A breakpoint was reached.
17808 @item watchpoint-trigger
17809 A watchpoint was triggered.
17810 @item read-watchpoint-trigger
17811 A read watchpoint was triggered.
17812 @item access-watchpoint-trigger
17813 An access watchpoint was triggered.
17814 @item function-finished
17815 An -exec-finish or similar CLI command was accomplished.
17816 @item location-reached
17817 An -exec-until or similar CLI command was accomplished.
17818 @item watchpoint-scope
17819 A watchpoint has gone out of scope.
17820 @item end-stepping-range
17821 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17822 similar CLI command was accomplished.
17823 @item exited-signalled
17824 The inferior exited because of a signal.
17826 The inferior exited.
17827 @item exited-normally
17828 The inferior exited normally.
17829 @item signal-received
17830 A signal was received by the inferior.
17834 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17835 @node GDB/MI Simple Examples
17836 @section Simple Examples of @sc{gdb/mi} Interaction
17837 @cindex @sc{gdb/mi}, simple examples
17839 This subsection presents several simple examples of interaction using
17840 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17841 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17842 the output received from @sc{gdb/mi}.
17844 Note the line breaks shown in the examples are here only for
17845 readability, they don't appear in the real output.
17847 @subheading Setting a Breakpoint
17849 Setting a breakpoint generates synchronous output which contains detailed
17850 information of the breakpoint.
17853 -> -break-insert main
17854 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17855 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17856 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17860 @subheading Program Execution
17862 Program execution generates asynchronous records and MI gives the
17863 reason that execution stopped.
17869 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17870 frame=@{addr="0x08048564",func="main",
17871 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17872 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17877 <- *stopped,reason="exited-normally"
17881 @subheading Quitting @value{GDBN}
17883 Quitting @value{GDBN} just prints the result class @samp{^exit}.
17891 @subheading A Bad Command
17893 Here's what happens if you pass a non-existent command:
17897 <- ^error,msg="Undefined MI command: rubbish"
17902 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17903 @node GDB/MI Command Description Format
17904 @section @sc{gdb/mi} Command Description Format
17906 The remaining sections describe blocks of commands. Each block of
17907 commands is laid out in a fashion similar to this section.
17909 @subheading Motivation
17911 The motivation for this collection of commands.
17913 @subheading Introduction
17915 A brief introduction to this collection of commands as a whole.
17917 @subheading Commands
17919 For each command in the block, the following is described:
17921 @subsubheading Synopsis
17924 -command @var{args}@dots{}
17927 @subsubheading Result
17929 @subsubheading @value{GDBN} Command
17931 The corresponding @value{GDBN} CLI command(s), if any.
17933 @subsubheading Example
17935 Example(s) formatted for readability. Some of the described commands have
17936 not been implemented yet and these are labeled N.A.@: (not available).
17939 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17940 @node GDB/MI Breakpoint Commands
17941 @section @sc{gdb/mi} Breakpoint Commands
17943 @cindex breakpoint commands for @sc{gdb/mi}
17944 @cindex @sc{gdb/mi}, breakpoint commands
17945 This section documents @sc{gdb/mi} commands for manipulating
17948 @subheading The @code{-break-after} Command
17949 @findex -break-after
17951 @subsubheading Synopsis
17954 -break-after @var{number} @var{count}
17957 The breakpoint number @var{number} is not in effect until it has been
17958 hit @var{count} times. To see how this is reflected in the output of
17959 the @samp{-break-list} command, see the description of the
17960 @samp{-break-list} command below.
17962 @subsubheading @value{GDBN} Command
17964 The corresponding @value{GDBN} command is @samp{ignore}.
17966 @subsubheading Example
17971 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17972 fullname="/home/foo/hello.c",line="5",times="0"@}
17979 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17980 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17981 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17982 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17983 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17984 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17985 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17986 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17987 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17988 line="5",times="0",ignore="3"@}]@}
17993 @subheading The @code{-break-catch} Command
17994 @findex -break-catch
17996 @subheading The @code{-break-commands} Command
17997 @findex -break-commands
18001 @subheading The @code{-break-condition} Command
18002 @findex -break-condition
18004 @subsubheading Synopsis
18007 -break-condition @var{number} @var{expr}
18010 Breakpoint @var{number} will stop the program only if the condition in
18011 @var{expr} is true. The condition becomes part of the
18012 @samp{-break-list} output (see the description of the @samp{-break-list}
18015 @subsubheading @value{GDBN} Command
18017 The corresponding @value{GDBN} command is @samp{condition}.
18019 @subsubheading Example
18023 -break-condition 1 1
18027 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18028 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18029 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18030 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18031 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18032 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18033 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18034 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18035 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18036 line="5",cond="1",times="0",ignore="3"@}]@}
18040 @subheading The @code{-break-delete} Command
18041 @findex -break-delete
18043 @subsubheading Synopsis
18046 -break-delete ( @var{breakpoint} )+
18049 Delete the breakpoint(s) whose number(s) are specified in the argument
18050 list. This is obviously reflected in the breakpoint list.
18052 @subsubheading @value{GDBN} Command
18054 The corresponding @value{GDBN} command is @samp{delete}.
18056 @subsubheading Example
18064 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18065 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18066 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18067 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18068 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18069 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18070 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18075 @subheading The @code{-break-disable} Command
18076 @findex -break-disable
18078 @subsubheading Synopsis
18081 -break-disable ( @var{breakpoint} )+
18084 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18085 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18087 @subsubheading @value{GDBN} Command
18089 The corresponding @value{GDBN} command is @samp{disable}.
18091 @subsubheading Example
18099 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18100 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18101 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18102 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18103 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18104 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18105 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18106 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18107 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18108 line="5",times="0"@}]@}
18112 @subheading The @code{-break-enable} Command
18113 @findex -break-enable
18115 @subsubheading Synopsis
18118 -break-enable ( @var{breakpoint} )+
18121 Enable (previously disabled) @var{breakpoint}(s).
18123 @subsubheading @value{GDBN} Command
18125 The corresponding @value{GDBN} command is @samp{enable}.
18127 @subsubheading Example
18135 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18136 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18137 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18138 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18139 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18140 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18141 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18142 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18143 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18144 line="5",times="0"@}]@}
18148 @subheading The @code{-break-info} Command
18149 @findex -break-info
18151 @subsubheading Synopsis
18154 -break-info @var{breakpoint}
18158 Get information about a single breakpoint.
18160 @subsubheading @value{GDBN} Command
18162 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18164 @subsubheading Example
18167 @subheading The @code{-break-insert} Command
18168 @findex -break-insert
18170 @subsubheading Synopsis
18173 -break-insert [ -t ] [ -h ] [ -f ]
18174 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18175 [ -p @var{thread} ] [ @var{location} ]
18179 If specified, @var{location}, can be one of:
18186 @item filename:linenum
18187 @item filename:function
18191 The possible optional parameters of this command are:
18195 Insert a temporary breakpoint.
18197 Insert a hardware breakpoint.
18198 @item -c @var{condition}
18199 Make the breakpoint conditional on @var{condition}.
18200 @item -i @var{ignore-count}
18201 Initialize the @var{ignore-count}.
18203 If @var{location} cannot be parsed (for example if it
18204 refers to unknown files or functions), create a pending
18205 breakpoint. Without this flag, @value{GDBN} will report
18206 an error, and won't create a breakpoint, if @var{location}
18210 @subsubheading Result
18212 The result is in the form:
18215 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18216 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18217 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18218 times="@var{times}"@}
18222 where @var{number} is the @value{GDBN} number for this breakpoint,
18223 @var{funcname} is the name of the function where the breakpoint was
18224 inserted, @var{filename} is the name of the source file which contains
18225 this function, @var{lineno} is the source line number within that file
18226 and @var{times} the number of times that the breakpoint has been hit
18227 (always 0 for -break-insert but may be greater for -break-info or -break-list
18228 which use the same output).
18230 Note: this format is open to change.
18231 @c An out-of-band breakpoint instead of part of the result?
18233 @subsubheading @value{GDBN} Command
18235 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18236 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18238 @subsubheading Example
18243 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18244 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18246 -break-insert -t foo
18247 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18248 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18251 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18252 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18253 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18254 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18255 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18256 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18257 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18258 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18259 addr="0x0001072c", func="main",file="recursive2.c",
18260 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18261 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18262 addr="0x00010774",func="foo",file="recursive2.c",
18263 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18265 -break-insert -r foo.*
18266 ~int foo(int, int);
18267 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18268 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18272 @subheading The @code{-break-list} Command
18273 @findex -break-list
18275 @subsubheading Synopsis
18281 Displays the list of inserted breakpoints, showing the following fields:
18285 number of the breakpoint
18287 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18289 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18292 is the breakpoint enabled or no: @samp{y} or @samp{n}
18294 memory location at which the breakpoint is set
18296 logical location of the breakpoint, expressed by function name, file
18299 number of times the breakpoint has been hit
18302 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18303 @code{body} field is an empty list.
18305 @subsubheading @value{GDBN} Command
18307 The corresponding @value{GDBN} command is @samp{info break}.
18309 @subsubheading Example
18314 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18315 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18316 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18317 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18318 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18319 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18320 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18321 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18322 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18323 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18324 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18325 line="13",times="0"@}]@}
18329 Here's an example of the result when there are no breakpoints:
18334 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18335 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18336 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18337 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18338 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18339 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18340 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18345 @subheading The @code{-break-watch} Command
18346 @findex -break-watch
18348 @subsubheading Synopsis
18351 -break-watch [ -a | -r ]
18354 Create a watchpoint. With the @samp{-a} option it will create an
18355 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18356 read from or on a write to the memory location. With the @samp{-r}
18357 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18358 trigger only when the memory location is accessed for reading. Without
18359 either of the options, the watchpoint created is a regular watchpoint,
18360 i.e., it will trigger when the memory location is accessed for writing.
18361 @xref{Set Watchpoints, , Setting Watchpoints}.
18363 Note that @samp{-break-list} will report a single list of watchpoints and
18364 breakpoints inserted.
18366 @subsubheading @value{GDBN} Command
18368 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18371 @subsubheading Example
18373 Setting a watchpoint on a variable in the @code{main} function:
18378 ^done,wpt=@{number="2",exp="x"@}
18383 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18384 value=@{old="-268439212",new="55"@},
18385 frame=@{func="main",args=[],file="recursive2.c",
18386 fullname="/home/foo/bar/recursive2.c",line="5"@}
18390 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18391 the program execution twice: first for the variable changing value, then
18392 for the watchpoint going out of scope.
18397 ^done,wpt=@{number="5",exp="C"@}
18402 *stopped,reason="watchpoint-trigger",
18403 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18404 frame=@{func="callee4",args=[],
18405 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18406 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18411 *stopped,reason="watchpoint-scope",wpnum="5",
18412 frame=@{func="callee3",args=[@{name="strarg",
18413 value="0x11940 \"A string argument.\""@}],
18414 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18415 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18419 Listing breakpoints and watchpoints, at different points in the program
18420 execution. Note that once the watchpoint goes out of scope, it is
18426 ^done,wpt=@{number="2",exp="C"@}
18429 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18430 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18431 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18432 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18433 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18434 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18435 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18436 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18437 addr="0x00010734",func="callee4",
18438 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18439 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18440 bkpt=@{number="2",type="watchpoint",disp="keep",
18441 enabled="y",addr="",what="C",times="0"@}]@}
18446 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18447 value=@{old="-276895068",new="3"@},
18448 frame=@{func="callee4",args=[],
18449 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18450 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18453 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18454 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18455 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18456 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18457 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18458 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18459 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18460 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18461 addr="0x00010734",func="callee4",
18462 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18463 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18464 bkpt=@{number="2",type="watchpoint",disp="keep",
18465 enabled="y",addr="",what="C",times="-5"@}]@}
18469 ^done,reason="watchpoint-scope",wpnum="2",
18470 frame=@{func="callee3",args=[@{name="strarg",
18471 value="0x11940 \"A string argument.\""@}],
18472 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18473 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18476 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18477 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18478 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18479 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18480 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18481 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18482 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18483 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18484 addr="0x00010734",func="callee4",
18485 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18486 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18491 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18492 @node GDB/MI Program Context
18493 @section @sc{gdb/mi} Program Context
18495 @subheading The @code{-exec-arguments} Command
18496 @findex -exec-arguments
18499 @subsubheading Synopsis
18502 -exec-arguments @var{args}
18505 Set the inferior program arguments, to be used in the next
18508 @subsubheading @value{GDBN} Command
18510 The corresponding @value{GDBN} command is @samp{set args}.
18512 @subsubheading Example
18515 Don't have one around.
18518 @subheading The @code{-exec-show-arguments} Command
18519 @findex -exec-show-arguments
18521 @subsubheading Synopsis
18524 -exec-show-arguments
18527 Print the arguments of the program.
18529 @subsubheading @value{GDBN} Command
18531 The corresponding @value{GDBN} command is @samp{show args}.
18533 @subsubheading Example
18537 @subheading The @code{-environment-cd} Command
18538 @findex -environment-cd
18540 @subsubheading Synopsis
18543 -environment-cd @var{pathdir}
18546 Set @value{GDBN}'s working directory.
18548 @subsubheading @value{GDBN} Command
18550 The corresponding @value{GDBN} command is @samp{cd}.
18552 @subsubheading Example
18556 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18562 @subheading The @code{-environment-directory} Command
18563 @findex -environment-directory
18565 @subsubheading Synopsis
18568 -environment-directory [ -r ] [ @var{pathdir} ]+
18571 Add directories @var{pathdir} to beginning of search path for source files.
18572 If the @samp{-r} option is used, the search path is reset to the default
18573 search path. If directories @var{pathdir} are supplied in addition to the
18574 @samp{-r} option, the search path is first reset and then addition
18576 Multiple directories may be specified, separated by blanks. Specifying
18577 multiple directories in a single command
18578 results in the directories added to the beginning of the
18579 search path in the same order they were presented in the command.
18580 If blanks are needed as
18581 part of a directory name, double-quotes should be used around
18582 the name. In the command output, the path will show up separated
18583 by the system directory-separator character. The directory-separator
18584 character must not be used
18585 in any directory name.
18586 If no directories are specified, the current search path is displayed.
18588 @subsubheading @value{GDBN} Command
18590 The corresponding @value{GDBN} command is @samp{dir}.
18592 @subsubheading Example
18596 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18597 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18599 -environment-directory ""
18600 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18602 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18603 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18605 -environment-directory -r
18606 ^done,source-path="$cdir:$cwd"
18611 @subheading The @code{-environment-path} Command
18612 @findex -environment-path
18614 @subsubheading Synopsis
18617 -environment-path [ -r ] [ @var{pathdir} ]+
18620 Add directories @var{pathdir} to beginning of search path for object files.
18621 If the @samp{-r} option is used, the search path is reset to the original
18622 search path that existed at gdb start-up. If directories @var{pathdir} are
18623 supplied in addition to the
18624 @samp{-r} option, the search path is first reset and then addition
18626 Multiple directories may be specified, separated by blanks. Specifying
18627 multiple directories in a single command
18628 results in the directories added to the beginning of the
18629 search path in the same order they were presented in the command.
18630 If blanks are needed as
18631 part of a directory name, double-quotes should be used around
18632 the name. In the command output, the path will show up separated
18633 by the system directory-separator character. The directory-separator
18634 character must not be used
18635 in any directory name.
18636 If no directories are specified, the current path is displayed.
18639 @subsubheading @value{GDBN} Command
18641 The corresponding @value{GDBN} command is @samp{path}.
18643 @subsubheading Example
18648 ^done,path="/usr/bin"
18650 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18651 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18653 -environment-path -r /usr/local/bin
18654 ^done,path="/usr/local/bin:/usr/bin"
18659 @subheading The @code{-environment-pwd} Command
18660 @findex -environment-pwd
18662 @subsubheading Synopsis
18668 Show the current working directory.
18670 @subsubheading @value{GDBN} Command
18672 The corresponding @value{GDBN} command is @samp{pwd}.
18674 @subsubheading Example
18679 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18683 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18684 @node GDB/MI Thread Commands
18685 @section @sc{gdb/mi} Thread Commands
18688 @subheading The @code{-thread-info} Command
18689 @findex -thread-info
18691 @subsubheading Synopsis
18697 @subsubheading @value{GDBN} Command
18701 @subsubheading Example
18705 @subheading The @code{-thread-list-all-threads} Command
18706 @findex -thread-list-all-threads
18708 @subsubheading Synopsis
18711 -thread-list-all-threads
18714 @subsubheading @value{GDBN} Command
18716 The equivalent @value{GDBN} command is @samp{info threads}.
18718 @subsubheading Example
18722 @subheading The @code{-thread-list-ids} Command
18723 @findex -thread-list-ids
18725 @subsubheading Synopsis
18731 Produces a list of the currently known @value{GDBN} thread ids. At the
18732 end of the list it also prints the total number of such threads.
18734 @subsubheading @value{GDBN} Command
18736 Part of @samp{info threads} supplies the same information.
18738 @subsubheading Example
18740 No threads present, besides the main process:
18745 ^done,thread-ids=@{@},number-of-threads="0"
18755 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18756 number-of-threads="3"
18761 @subheading The @code{-thread-select} Command
18762 @findex -thread-select
18764 @subsubheading Synopsis
18767 -thread-select @var{threadnum}
18770 Make @var{threadnum} the current thread. It prints the number of the new
18771 current thread, and the topmost frame for that thread.
18773 @subsubheading @value{GDBN} Command
18775 The corresponding @value{GDBN} command is @samp{thread}.
18777 @subsubheading Example
18784 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18785 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18789 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18790 number-of-threads="3"
18793 ^done,new-thread-id="3",
18794 frame=@{level="0",func="vprintf",
18795 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18796 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18801 @node GDB/MI Program Execution
18802 @section @sc{gdb/mi} Program Execution
18804 These are the asynchronous commands which generate the out-of-band
18805 record @samp{*stopped}. Currently @value{GDBN} only really executes
18806 asynchronously with remote targets and this interaction is mimicked in
18809 @subheading The @code{-exec-continue} Command
18810 @findex -exec-continue
18812 @subsubheading Synopsis
18818 Resumes the execution of the inferior program until a breakpoint is
18819 encountered, or until the inferior exits.
18821 @subsubheading @value{GDBN} Command
18823 The corresponding @value{GDBN} corresponding is @samp{continue}.
18825 @subsubheading Example
18832 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18833 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18838 @subheading The @code{-exec-finish} Command
18839 @findex -exec-finish
18841 @subsubheading Synopsis
18847 Resumes the execution of the inferior program until the current
18848 function is exited. Displays the results returned by the function.
18850 @subsubheading @value{GDBN} Command
18852 The corresponding @value{GDBN} command is @samp{finish}.
18854 @subsubheading Example
18856 Function returning @code{void}.
18863 *stopped,reason="function-finished",frame=@{func="main",args=[],
18864 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18868 Function returning other than @code{void}. The name of the internal
18869 @value{GDBN} variable storing the result is printed, together with the
18876 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18877 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18878 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18879 gdb-result-var="$1",return-value="0"
18884 @subheading The @code{-exec-interrupt} Command
18885 @findex -exec-interrupt
18887 @subsubheading Synopsis
18893 Interrupts the background execution of the target. Note how the token
18894 associated with the stop message is the one for the execution command
18895 that has been interrupted. The token for the interrupt itself only
18896 appears in the @samp{^done} output. If the user is trying to
18897 interrupt a non-running program, an error message will be printed.
18899 @subsubheading @value{GDBN} Command
18901 The corresponding @value{GDBN} command is @samp{interrupt}.
18903 @subsubheading Example
18914 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18915 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18916 fullname="/home/foo/bar/try.c",line="13"@}
18921 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18926 @subheading The @code{-exec-next} Command
18929 @subsubheading Synopsis
18935 Resumes execution of the inferior program, stopping when the beginning
18936 of the next source line is reached.
18938 @subsubheading @value{GDBN} Command
18940 The corresponding @value{GDBN} command is @samp{next}.
18942 @subsubheading Example
18948 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18953 @subheading The @code{-exec-next-instruction} Command
18954 @findex -exec-next-instruction
18956 @subsubheading Synopsis
18959 -exec-next-instruction
18962 Executes one machine instruction. If the instruction is a function
18963 call, continues until the function returns. If the program stops at an
18964 instruction in the middle of a source line, the address will be
18967 @subsubheading @value{GDBN} Command
18969 The corresponding @value{GDBN} command is @samp{nexti}.
18971 @subsubheading Example
18975 -exec-next-instruction
18979 *stopped,reason="end-stepping-range",
18980 addr="0x000100d4",line="5",file="hello.c"
18985 @subheading The @code{-exec-return} Command
18986 @findex -exec-return
18988 @subsubheading Synopsis
18994 Makes current function return immediately. Doesn't execute the inferior.
18995 Displays the new current frame.
18997 @subsubheading @value{GDBN} Command
18999 The corresponding @value{GDBN} command is @samp{return}.
19001 @subsubheading Example
19005 200-break-insert callee4
19006 200^done,bkpt=@{number="1",addr="0x00010734",
19007 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19012 000*stopped,reason="breakpoint-hit",bkptno="1",
19013 frame=@{func="callee4",args=[],
19014 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19015 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19021 111^done,frame=@{level="0",func="callee3",
19022 args=[@{name="strarg",
19023 value="0x11940 \"A string argument.\""@}],
19024 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19025 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19030 @subheading The @code{-exec-run} Command
19033 @subsubheading Synopsis
19039 Starts execution of the inferior from the beginning. The inferior
19040 executes until either a breakpoint is encountered or the program
19041 exits. In the latter case the output will include an exit code, if
19042 the program has exited exceptionally.
19044 @subsubheading @value{GDBN} Command
19046 The corresponding @value{GDBN} command is @samp{run}.
19048 @subsubheading Examples
19053 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19058 *stopped,reason="breakpoint-hit",bkptno="1",
19059 frame=@{func="main",args=[],file="recursive2.c",
19060 fullname="/home/foo/bar/recursive2.c",line="4"@}
19065 Program exited normally:
19073 *stopped,reason="exited-normally"
19078 Program exited exceptionally:
19086 *stopped,reason="exited",exit-code="01"
19090 Another way the program can terminate is if it receives a signal such as
19091 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19095 *stopped,reason="exited-signalled",signal-name="SIGINT",
19096 signal-meaning="Interrupt"
19100 @c @subheading -exec-signal
19103 @subheading The @code{-exec-step} Command
19106 @subsubheading Synopsis
19112 Resumes execution of the inferior program, stopping when the beginning
19113 of the next source line is reached, if the next source line is not a
19114 function call. If it is, stop at the first instruction of the called
19117 @subsubheading @value{GDBN} Command
19119 The corresponding @value{GDBN} command is @samp{step}.
19121 @subsubheading Example
19123 Stepping into a function:
19129 *stopped,reason="end-stepping-range",
19130 frame=@{func="foo",args=[@{name="a",value="10"@},
19131 @{name="b",value="0"@}],file="recursive2.c",
19132 fullname="/home/foo/bar/recursive2.c",line="11"@}
19142 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19147 @subheading The @code{-exec-step-instruction} Command
19148 @findex -exec-step-instruction
19150 @subsubheading Synopsis
19153 -exec-step-instruction
19156 Resumes the inferior which executes one machine instruction. The
19157 output, once @value{GDBN} has stopped, will vary depending on whether
19158 we have stopped in the middle of a source line or not. In the former
19159 case, the address at which the program stopped will be printed as
19162 @subsubheading @value{GDBN} Command
19164 The corresponding @value{GDBN} command is @samp{stepi}.
19166 @subsubheading Example
19170 -exec-step-instruction
19174 *stopped,reason="end-stepping-range",
19175 frame=@{func="foo",args=[],file="try.c",
19176 fullname="/home/foo/bar/try.c",line="10"@}
19178 -exec-step-instruction
19182 *stopped,reason="end-stepping-range",
19183 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19184 fullname="/home/foo/bar/try.c",line="10"@}
19189 @subheading The @code{-exec-until} Command
19190 @findex -exec-until
19192 @subsubheading Synopsis
19195 -exec-until [ @var{location} ]
19198 Executes the inferior until the @var{location} specified in the
19199 argument is reached. If there is no argument, the inferior executes
19200 until a source line greater than the current one is reached. The
19201 reason for stopping in this case will be @samp{location-reached}.
19203 @subsubheading @value{GDBN} Command
19205 The corresponding @value{GDBN} command is @samp{until}.
19207 @subsubheading Example
19211 -exec-until recursive2.c:6
19215 *stopped,reason="location-reached",frame=@{func="main",args=[],
19216 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19221 @subheading -file-clear
19222 Is this going away????
19225 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19226 @node GDB/MI Stack Manipulation
19227 @section @sc{gdb/mi} Stack Manipulation Commands
19230 @subheading The @code{-stack-info-frame} Command
19231 @findex -stack-info-frame
19233 @subsubheading Synopsis
19239 Get info on the selected frame.
19241 @subsubheading @value{GDBN} Command
19243 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19244 (without arguments).
19246 @subsubheading Example
19251 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19252 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19253 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19257 @subheading The @code{-stack-info-depth} Command
19258 @findex -stack-info-depth
19260 @subsubheading Synopsis
19263 -stack-info-depth [ @var{max-depth} ]
19266 Return the depth of the stack. If the integer argument @var{max-depth}
19267 is specified, do not count beyond @var{max-depth} frames.
19269 @subsubheading @value{GDBN} Command
19271 There's no equivalent @value{GDBN} command.
19273 @subsubheading Example
19275 For a stack with frame levels 0 through 11:
19282 -stack-info-depth 4
19285 -stack-info-depth 12
19288 -stack-info-depth 11
19291 -stack-info-depth 13
19296 @subheading The @code{-stack-list-arguments} Command
19297 @findex -stack-list-arguments
19299 @subsubheading Synopsis
19302 -stack-list-arguments @var{show-values}
19303 [ @var{low-frame} @var{high-frame} ]
19306 Display a list of the arguments for the frames between @var{low-frame}
19307 and @var{high-frame} (inclusive). If @var{low-frame} and
19308 @var{high-frame} are not provided, list the arguments for the whole
19309 call stack. If the two arguments are equal, show the single frame
19310 at the corresponding level. It is an error if @var{low-frame} is
19311 larger than the actual number of frames. On the other hand,
19312 @var{high-frame} may be larger than the actual number of frames, in
19313 which case only existing frames will be returned.
19315 The @var{show-values} argument must have a value of 0 or 1. A value of
19316 0 means that only the names of the arguments are listed, a value of 1
19317 means that both names and values of the arguments are printed.
19319 @subsubheading @value{GDBN} Command
19321 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19322 @samp{gdb_get_args} command which partially overlaps with the
19323 functionality of @samp{-stack-list-arguments}.
19325 @subsubheading Example
19332 frame=@{level="0",addr="0x00010734",func="callee4",
19333 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19334 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19335 frame=@{level="1",addr="0x0001076c",func="callee3",
19336 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19337 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19338 frame=@{level="2",addr="0x0001078c",func="callee2",
19339 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19340 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19341 frame=@{level="3",addr="0x000107b4",func="callee1",
19342 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19343 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19344 frame=@{level="4",addr="0x000107e0",func="main",
19345 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19346 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19348 -stack-list-arguments 0
19351 frame=@{level="0",args=[]@},
19352 frame=@{level="1",args=[name="strarg"]@},
19353 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19354 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19355 frame=@{level="4",args=[]@}]
19357 -stack-list-arguments 1
19360 frame=@{level="0",args=[]@},
19362 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19363 frame=@{level="2",args=[
19364 @{name="intarg",value="2"@},
19365 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19366 @{frame=@{level="3",args=[
19367 @{name="intarg",value="2"@},
19368 @{name="strarg",value="0x11940 \"A string argument.\""@},
19369 @{name="fltarg",value="3.5"@}]@},
19370 frame=@{level="4",args=[]@}]
19372 -stack-list-arguments 0 2 2
19373 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19375 -stack-list-arguments 1 2 2
19376 ^done,stack-args=[frame=@{level="2",
19377 args=[@{name="intarg",value="2"@},
19378 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19382 @c @subheading -stack-list-exception-handlers
19385 @subheading The @code{-stack-list-frames} Command
19386 @findex -stack-list-frames
19388 @subsubheading Synopsis
19391 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19394 List the frames currently on the stack. For each frame it displays the
19399 The frame number, 0 being the topmost frame, i.e., the innermost function.
19401 The @code{$pc} value for that frame.
19405 File name of the source file where the function lives.
19407 Line number corresponding to the @code{$pc}.
19410 If invoked without arguments, this command prints a backtrace for the
19411 whole stack. If given two integer arguments, it shows the frames whose
19412 levels are between the two arguments (inclusive). If the two arguments
19413 are equal, it shows the single frame at the corresponding level. It is
19414 an error if @var{low-frame} is larger than the actual number of
19415 frames. On the other hand, @var{high-frame} may be larger than the
19416 actual number of frames, in which case only existing frames will be returned.
19418 @subsubheading @value{GDBN} Command
19420 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19422 @subsubheading Example
19424 Full stack backtrace:
19430 [frame=@{level="0",addr="0x0001076c",func="foo",
19431 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19432 frame=@{level="1",addr="0x000107a4",func="foo",
19433 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19434 frame=@{level="2",addr="0x000107a4",func="foo",
19435 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19436 frame=@{level="3",addr="0x000107a4",func="foo",
19437 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19438 frame=@{level="4",addr="0x000107a4",func="foo",
19439 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19440 frame=@{level="5",addr="0x000107a4",func="foo",
19441 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19442 frame=@{level="6",addr="0x000107a4",func="foo",
19443 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19444 frame=@{level="7",addr="0x000107a4",func="foo",
19445 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19446 frame=@{level="8",addr="0x000107a4",func="foo",
19447 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19448 frame=@{level="9",addr="0x000107a4",func="foo",
19449 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19450 frame=@{level="10",addr="0x000107a4",func="foo",
19451 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19452 frame=@{level="11",addr="0x00010738",func="main",
19453 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19457 Show frames between @var{low_frame} and @var{high_frame}:
19461 -stack-list-frames 3 5
19463 [frame=@{level="3",addr="0x000107a4",func="foo",
19464 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19465 frame=@{level="4",addr="0x000107a4",func="foo",
19466 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19467 frame=@{level="5",addr="0x000107a4",func="foo",
19468 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19472 Show a single frame:
19476 -stack-list-frames 3 3
19478 [frame=@{level="3",addr="0x000107a4",func="foo",
19479 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19484 @subheading The @code{-stack-list-locals} Command
19485 @findex -stack-list-locals
19487 @subsubheading Synopsis
19490 -stack-list-locals @var{print-values}
19493 Display the local variable names for the selected frame. If
19494 @var{print-values} is 0 or @code{--no-values}, print only the names of
19495 the variables; if it is 1 or @code{--all-values}, print also their
19496 values; and if it is 2 or @code{--simple-values}, print the name,
19497 type and value for simple data types and the name and type for arrays,
19498 structures and unions. In this last case, a frontend can immediately
19499 display the value of simple data types and create variable objects for
19500 other data types when the user wishes to explore their values in
19503 @subsubheading @value{GDBN} Command
19505 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19507 @subsubheading Example
19511 -stack-list-locals 0
19512 ^done,locals=[name="A",name="B",name="C"]
19514 -stack-list-locals --all-values
19515 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19516 @{name="C",value="@{1, 2, 3@}"@}]
19517 -stack-list-locals --simple-values
19518 ^done,locals=[@{name="A",type="int",value="1"@},
19519 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19524 @subheading The @code{-stack-select-frame} Command
19525 @findex -stack-select-frame
19527 @subsubheading Synopsis
19530 -stack-select-frame @var{framenum}
19533 Change the selected frame. Select a different frame @var{framenum} on
19536 @subsubheading @value{GDBN} Command
19538 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19539 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19541 @subsubheading Example
19545 -stack-select-frame 2
19550 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19551 @node GDB/MI Variable Objects
19552 @section @sc{gdb/mi} Variable Objects
19556 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19558 For the implementation of a variable debugger window (locals, watched
19559 expressions, etc.), we are proposing the adaptation of the existing code
19560 used by @code{Insight}.
19562 The two main reasons for that are:
19566 It has been proven in practice (it is already on its second generation).
19569 It will shorten development time (needless to say how important it is
19573 The original interface was designed to be used by Tcl code, so it was
19574 slightly changed so it could be used through @sc{gdb/mi}. This section
19575 describes the @sc{gdb/mi} operations that will be available and gives some
19576 hints about their use.
19578 @emph{Note}: In addition to the set of operations described here, we
19579 expect the @sc{gui} implementation of a variable window to require, at
19580 least, the following operations:
19583 @item @code{-gdb-show} @code{output-radix}
19584 @item @code{-stack-list-arguments}
19585 @item @code{-stack-list-locals}
19586 @item @code{-stack-select-frame}
19591 @subheading Introduction to Variable Objects
19593 @cindex variable objects in @sc{gdb/mi}
19595 Variable objects are "object-oriented" MI interface for examining and
19596 changing values of expressions. Unlike some other MI interfaces that
19597 work with expressions, variable objects are specifically designed for
19598 simple and efficient presentation in the frontend. A variable object
19599 is identified by string name. When a variable object is created, the
19600 frontend specifies the expression for that variable object. The
19601 expression can be a simple variable, or it can be an arbitrary complex
19602 expression, and can even involve CPU registers. After creating a
19603 variable object, the frontend can invoke other variable object
19604 operations---for example to obtain or change the value of a variable
19605 object, or to change display format.
19607 Variable objects have hierarchical tree structure. Any variable object
19608 that corresponds to a composite type, such as structure in C, has
19609 a number of child variable objects, for example corresponding to each
19610 element of a structure. A child variable object can itself have
19611 children, recursively. Recursion ends when we reach
19612 leaf variable objects, which always have built-in types. Child variable
19613 objects are created only by explicit request, so if a frontend
19614 is not interested in the children of a particular variable object, no
19615 child will be created.
19617 For a leaf variable object it is possible to obtain its value as a
19618 string, or set the value from a string. String value can be also
19619 obtained for a non-leaf variable object, but it's generally a string
19620 that only indicates the type of the object, and does not list its
19621 contents. Assignment to a non-leaf variable object is not allowed.
19623 A frontend does not need to read the values of all variable objects each time
19624 the program stops. Instead, MI provides an update command that lists all
19625 variable objects whose values has changed since the last update
19626 operation. This considerably reduces the amount of data that must
19627 be transferred to the frontend. As noted above, children variable
19628 objects are created on demand, and only leaf variable objects have a
19629 real value. As result, gdb will read target memory only for leaf
19630 variables that frontend has created.
19632 The automatic update is not always desirable. For example, a frontend
19633 might want to keep a value of some expression for future reference,
19634 and never update it. For another example, fetching memory is
19635 relatively slow for embedded targets, so a frontend might want
19636 to disable automatic update for the variables that are either not
19637 visible on the screen, or ``closed''. This is possible using so
19638 called ``frozen variable objects''. Such variable objects are never
19639 implicitly updated.
19641 The following is the complete set of @sc{gdb/mi} operations defined to
19642 access this functionality:
19644 @multitable @columnfractions .4 .6
19645 @item @strong{Operation}
19646 @tab @strong{Description}
19648 @item @code{-var-create}
19649 @tab create a variable object
19650 @item @code{-var-delete}
19651 @tab delete the variable object and/or its children
19652 @item @code{-var-set-format}
19653 @tab set the display format of this variable
19654 @item @code{-var-show-format}
19655 @tab show the display format of this variable
19656 @item @code{-var-info-num-children}
19657 @tab tells how many children this object has
19658 @item @code{-var-list-children}
19659 @tab return a list of the object's children
19660 @item @code{-var-info-type}
19661 @tab show the type of this variable object
19662 @item @code{-var-info-expression}
19663 @tab print parent-relative expression that this variable object represents
19664 @item @code{-var-info-path-expression}
19665 @tab print full expression that this variable object represents
19666 @item @code{-var-show-attributes}
19667 @tab is this variable editable? does it exist here?
19668 @item @code{-var-evaluate-expression}
19669 @tab get the value of this variable
19670 @item @code{-var-assign}
19671 @tab set the value of this variable
19672 @item @code{-var-update}
19673 @tab update the variable and its children
19674 @item @code{-var-set-frozen}
19675 @tab set frozeness attribute
19678 In the next subsection we describe each operation in detail and suggest
19679 how it can be used.
19681 @subheading Description And Use of Operations on Variable Objects
19683 @subheading The @code{-var-create} Command
19684 @findex -var-create
19686 @subsubheading Synopsis
19689 -var-create @{@var{name} | "-"@}
19690 @{@var{frame-addr} | "*"@} @var{expression}
19693 This operation creates a variable object, which allows the monitoring of
19694 a variable, the result of an expression, a memory cell or a CPU
19697 The @var{name} parameter is the string by which the object can be
19698 referenced. It must be unique. If @samp{-} is specified, the varobj
19699 system will generate a string ``varNNNNNN'' automatically. It will be
19700 unique provided that one does not specify @var{name} on that format.
19701 The command fails if a duplicate name is found.
19703 The frame under which the expression should be evaluated can be
19704 specified by @var{frame-addr}. A @samp{*} indicates that the current
19705 frame should be used.
19707 @var{expression} is any expression valid on the current language set (must not
19708 begin with a @samp{*}), or one of the following:
19712 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19715 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19718 @samp{$@var{regname}} --- a CPU register name
19721 @subsubheading Result
19723 This operation returns the name, number of children and the type of the
19724 object created. Type is returned as a string as the ones generated by
19725 the @value{GDBN} CLI:
19728 name="@var{name}",numchild="N",type="@var{type}"
19732 @subheading The @code{-var-delete} Command
19733 @findex -var-delete
19735 @subsubheading Synopsis
19738 -var-delete [ -c ] @var{name}
19741 Deletes a previously created variable object and all of its children.
19742 With the @samp{-c} option, just deletes the children.
19744 Returns an error if the object @var{name} is not found.
19747 @subheading The @code{-var-set-format} Command
19748 @findex -var-set-format
19750 @subsubheading Synopsis
19753 -var-set-format @var{name} @var{format-spec}
19756 Sets the output format for the value of the object @var{name} to be
19759 The syntax for the @var{format-spec} is as follows:
19762 @var{format-spec} @expansion{}
19763 @{binary | decimal | hexadecimal | octal | natural@}
19766 The natural format is the default format choosen automatically
19767 based on the variable type (like decimal for an @code{int}, hex
19768 for pointers, etc.).
19770 For a variable with children, the format is set only on the
19771 variable itself, and the children are not affected.
19773 @subheading The @code{-var-show-format} Command
19774 @findex -var-show-format
19776 @subsubheading Synopsis
19779 -var-show-format @var{name}
19782 Returns the format used to display the value of the object @var{name}.
19785 @var{format} @expansion{}
19790 @subheading The @code{-var-info-num-children} Command
19791 @findex -var-info-num-children
19793 @subsubheading Synopsis
19796 -var-info-num-children @var{name}
19799 Returns the number of children of a variable object @var{name}:
19806 @subheading The @code{-var-list-children} Command
19807 @findex -var-list-children
19809 @subsubheading Synopsis
19812 -var-list-children [@var{print-values}] @var{name}
19814 @anchor{-var-list-children}
19816 Return a list of the children of the specified variable object and
19817 create variable objects for them, if they do not already exist. With
19818 a single argument or if @var{print-values} has a value for of 0 or
19819 @code{--no-values}, print only the names of the variables; if
19820 @var{print-values} is 1 or @code{--all-values}, also print their
19821 values; and if it is 2 or @code{--simple-values} print the name and
19822 value for simple data types and just the name for arrays, structures
19825 @subsubheading Example
19829 -var-list-children n
19830 ^done,numchild=@var{n},children=[@{name=@var{name},
19831 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19833 -var-list-children --all-values n
19834 ^done,numchild=@var{n},children=[@{name=@var{name},
19835 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19839 @subheading The @code{-var-info-type} Command
19840 @findex -var-info-type
19842 @subsubheading Synopsis
19845 -var-info-type @var{name}
19848 Returns the type of the specified variable @var{name}. The type is
19849 returned as a string in the same format as it is output by the
19853 type=@var{typename}
19857 @subheading The @code{-var-info-expression} Command
19858 @findex -var-info-expression
19860 @subsubheading Synopsis
19863 -var-info-expression @var{name}
19866 Returns a string that is suitable for presenting this
19867 variable object in user interface. The string is generally
19868 not valid expression in the current language, and cannot be evaluated.
19870 For example, if @code{a} is an array, and variable object
19871 @code{A} was created for @code{a}, then we'll get this output:
19874 (gdb) -var-info-expression A.1
19875 ^done,lang="C",exp="1"
19879 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
19881 Note that the output of the @code{-var-list-children} command also
19882 includes those expressions, so the @code{-var-info-expression} command
19885 @subheading The @code{-var-info-path-expression} Command
19886 @findex -var-info-path-expression
19888 @subsubheading Synopsis
19891 -var-info-path-expression @var{name}
19894 Returns an expression that can be evaluated in the current
19895 context and will yield the same value that a variable object has.
19896 Compare this with the @code{-var-info-expression} command, which
19897 result can be used only for UI presentation. Typical use of
19898 the @code{-var-info-path-expression} command is creating a
19899 watchpoint from a variable object.
19901 For example, suppose @code{C} is a C@t{++} class, derived from class
19902 @code{Base}, and that the @code{Base} class has a member called
19903 @code{m_size}. Assume a variable @code{c} is has the type of
19904 @code{C} and a variable object @code{C} was created for variable
19905 @code{c}. Then, we'll get this output:
19907 (gdb) -var-info-path-expression C.Base.public.m_size
19908 ^done,path_expr=((Base)c).m_size)
19911 @subheading The @code{-var-show-attributes} Command
19912 @findex -var-show-attributes
19914 @subsubheading Synopsis
19917 -var-show-attributes @var{name}
19920 List attributes of the specified variable object @var{name}:
19923 status=@var{attr} [ ( ,@var{attr} )* ]
19927 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19929 @subheading The @code{-var-evaluate-expression} Command
19930 @findex -var-evaluate-expression
19932 @subsubheading Synopsis
19935 -var-evaluate-expression @var{name}
19938 Evaluates the expression that is represented by the specified variable
19939 object and returns its value as a string. The format of the
19940 string can be changed using the @code{-var-set-format} command.
19946 Note that one must invoke @code{-var-list-children} for a variable
19947 before the value of a child variable can be evaluated.
19949 @subheading The @code{-var-assign} Command
19950 @findex -var-assign
19952 @subsubheading Synopsis
19955 -var-assign @var{name} @var{expression}
19958 Assigns the value of @var{expression} to the variable object specified
19959 by @var{name}. The object must be @samp{editable}. If the variable's
19960 value is altered by the assign, the variable will show up in any
19961 subsequent @code{-var-update} list.
19963 @subsubheading Example
19971 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19975 @subheading The @code{-var-update} Command
19976 @findex -var-update
19978 @subsubheading Synopsis
19981 -var-update [@var{print-values}] @{@var{name} | "*"@}
19984 Reevaluate the expressions corresponding to the variable object
19985 @var{name} and all its direct and indirect children, and return the
19986 list of variable objects whose values have changed; @var{name} must
19987 be a root variable object. Here, ``changed'' means that the result of
19988 @code{-var-evaluate-expression} before and after the
19989 @code{-var-update} is different. If @samp{*} is used as the variable
19990 object names, all existing variable objects are updated, except
19991 for frozen ones (@pxref{-var-set-frozen}). The option
19992 @var{print-values} determines whether both names and values, or just
19993 names are printed. The possible values of this options are the same
19994 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
19995 recommended to use the @samp{--all-values} option, to reduce the
19996 number of MI commands needed on each program stop.
19999 @subsubheading Example
20006 -var-update --all-values var1
20007 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20008 type_changed="false"@}]
20012 @anchor{-var-update}
20013 The field in_scope may take three values:
20017 The variable object's current value is valid.
20020 The variable object does not currently hold a valid value but it may
20021 hold one in the future if its associated expression comes back into
20025 The variable object no longer holds a valid value.
20026 This can occur when the executable file being debugged has changed,
20027 either through recompilation or by using the @value{GDBN} @code{file}
20028 command. The front end should normally choose to delete these variable
20032 In the future new values may be added to this list so the front should
20033 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
20035 @subheading The @code{-var-set-frozen} Command
20036 @findex -var-set-frozen
20037 @anchor{-var-set-frozen}
20039 @subsubheading Synopsis
20042 -var-set-frozen @var{name} @var{flag}
20045 Set the frozenness flag on the variable object @var{name}. The
20046 @var{flag} parameter should be either @samp{1} to make the variable
20047 frozen or @samp{0} to make it unfrozen. If a variable object is
20048 frozen, then neither itself, nor any of its children, are
20049 implicitly updated by @code{-var-update} of
20050 a parent variable or by @code{-var-update *}. Only
20051 @code{-var-update} of the variable itself will update its value and
20052 values of its children. After a variable object is unfrozen, it is
20053 implicitly updated by all subsequent @code{-var-update} operations.
20054 Unfreezing a variable does not update it, only subsequent
20055 @code{-var-update} does.
20057 @subsubheading Example
20061 -var-set-frozen V 1
20067 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20068 @node GDB/MI Data Manipulation
20069 @section @sc{gdb/mi} Data Manipulation
20071 @cindex data manipulation, in @sc{gdb/mi}
20072 @cindex @sc{gdb/mi}, data manipulation
20073 This section describes the @sc{gdb/mi} commands that manipulate data:
20074 examine memory and registers, evaluate expressions, etc.
20076 @c REMOVED FROM THE INTERFACE.
20077 @c @subheading -data-assign
20078 @c Change the value of a program variable. Plenty of side effects.
20079 @c @subsubheading GDB Command
20081 @c @subsubheading Example
20084 @subheading The @code{-data-disassemble} Command
20085 @findex -data-disassemble
20087 @subsubheading Synopsis
20091 [ -s @var{start-addr} -e @var{end-addr} ]
20092 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20100 @item @var{start-addr}
20101 is the beginning address (or @code{$pc})
20102 @item @var{end-addr}
20104 @item @var{filename}
20105 is the name of the file to disassemble
20106 @item @var{linenum}
20107 is the line number to disassemble around
20109 is the number of disassembly lines to be produced. If it is -1,
20110 the whole function will be disassembled, in case no @var{end-addr} is
20111 specified. If @var{end-addr} is specified as a non-zero value, and
20112 @var{lines} is lower than the number of disassembly lines between
20113 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20114 displayed; if @var{lines} is higher than the number of lines between
20115 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20118 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20122 @subsubheading Result
20124 The output for each instruction is composed of four fields:
20133 Note that whatever included in the instruction field, is not manipulated
20134 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20136 @subsubheading @value{GDBN} Command
20138 There's no direct mapping from this command to the CLI.
20140 @subsubheading Example
20142 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20146 -data-disassemble -s $pc -e "$pc + 20" -- 0
20149 @{address="0x000107c0",func-name="main",offset="4",
20150 inst="mov 2, %o0"@},
20151 @{address="0x000107c4",func-name="main",offset="8",
20152 inst="sethi %hi(0x11800), %o2"@},
20153 @{address="0x000107c8",func-name="main",offset="12",
20154 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20155 @{address="0x000107cc",func-name="main",offset="16",
20156 inst="sethi %hi(0x11800), %o2"@},
20157 @{address="0x000107d0",func-name="main",offset="20",
20158 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20162 Disassemble the whole @code{main} function. Line 32 is part of
20166 -data-disassemble -f basics.c -l 32 -- 0
20168 @{address="0x000107bc",func-name="main",offset="0",
20169 inst="save %sp, -112, %sp"@},
20170 @{address="0x000107c0",func-name="main",offset="4",
20171 inst="mov 2, %o0"@},
20172 @{address="0x000107c4",func-name="main",offset="8",
20173 inst="sethi %hi(0x11800), %o2"@},
20175 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20176 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20180 Disassemble 3 instructions from the start of @code{main}:
20184 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20186 @{address="0x000107bc",func-name="main",offset="0",
20187 inst="save %sp, -112, %sp"@},
20188 @{address="0x000107c0",func-name="main",offset="4",
20189 inst="mov 2, %o0"@},
20190 @{address="0x000107c4",func-name="main",offset="8",
20191 inst="sethi %hi(0x11800), %o2"@}]
20195 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20199 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20201 src_and_asm_line=@{line="31",
20202 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20203 testsuite/gdb.mi/basics.c",line_asm_insn=[
20204 @{address="0x000107bc",func-name="main",offset="0",
20205 inst="save %sp, -112, %sp"@}]@},
20206 src_and_asm_line=@{line="32",
20207 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20208 testsuite/gdb.mi/basics.c",line_asm_insn=[
20209 @{address="0x000107c0",func-name="main",offset="4",
20210 inst="mov 2, %o0"@},
20211 @{address="0x000107c4",func-name="main",offset="8",
20212 inst="sethi %hi(0x11800), %o2"@}]@}]
20217 @subheading The @code{-data-evaluate-expression} Command
20218 @findex -data-evaluate-expression
20220 @subsubheading Synopsis
20223 -data-evaluate-expression @var{expr}
20226 Evaluate @var{expr} as an expression. The expression could contain an
20227 inferior function call. The function call will execute synchronously.
20228 If the expression contains spaces, it must be enclosed in double quotes.
20230 @subsubheading @value{GDBN} Command
20232 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20233 @samp{call}. In @code{gdbtk} only, there's a corresponding
20234 @samp{gdb_eval} command.
20236 @subsubheading Example
20238 In the following example, the numbers that precede the commands are the
20239 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20240 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20244 211-data-evaluate-expression A
20247 311-data-evaluate-expression &A
20248 311^done,value="0xefffeb7c"
20250 411-data-evaluate-expression A+3
20253 511-data-evaluate-expression "A + 3"
20259 @subheading The @code{-data-list-changed-registers} Command
20260 @findex -data-list-changed-registers
20262 @subsubheading Synopsis
20265 -data-list-changed-registers
20268 Display a list of the registers that have changed.
20270 @subsubheading @value{GDBN} Command
20272 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20273 has the corresponding command @samp{gdb_changed_register_list}.
20275 @subsubheading Example
20277 On a PPC MBX board:
20285 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20286 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20288 -data-list-changed-registers
20289 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20290 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20291 "24","25","26","27","28","30","31","64","65","66","67","69"]
20296 @subheading The @code{-data-list-register-names} Command
20297 @findex -data-list-register-names
20299 @subsubheading Synopsis
20302 -data-list-register-names [ ( @var{regno} )+ ]
20305 Show a list of register names for the current target. If no arguments
20306 are given, it shows a list of the names of all the registers. If
20307 integer numbers are given as arguments, it will print a list of the
20308 names of the registers corresponding to the arguments. To ensure
20309 consistency between a register name and its number, the output list may
20310 include empty register names.
20312 @subsubheading @value{GDBN} Command
20314 @value{GDBN} does not have a command which corresponds to
20315 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20316 corresponding command @samp{gdb_regnames}.
20318 @subsubheading Example
20320 For the PPC MBX board:
20323 -data-list-register-names
20324 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20325 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20326 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20327 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20328 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20329 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20330 "", "pc","ps","cr","lr","ctr","xer"]
20332 -data-list-register-names 1 2 3
20333 ^done,register-names=["r1","r2","r3"]
20337 @subheading The @code{-data-list-register-values} Command
20338 @findex -data-list-register-values
20340 @subsubheading Synopsis
20343 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20346 Display the registers' contents. @var{fmt} is the format according to
20347 which the registers' contents are to be returned, followed by an optional
20348 list of numbers specifying the registers to display. A missing list of
20349 numbers indicates that the contents of all the registers must be returned.
20351 Allowed formats for @var{fmt} are:
20368 @subsubheading @value{GDBN} Command
20370 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20371 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20373 @subsubheading Example
20375 For a PPC MBX board (note: line breaks are for readability only, they
20376 don't appear in the actual output):
20380 -data-list-register-values r 64 65
20381 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20382 @{number="65",value="0x00029002"@}]
20384 -data-list-register-values x
20385 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20386 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20387 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20388 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20389 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20390 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20391 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20392 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20393 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20394 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20395 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20396 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20397 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20398 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20399 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20400 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20401 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20402 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20403 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20404 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20405 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20406 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20407 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20408 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20409 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20410 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20411 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20412 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20413 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20414 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20415 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20416 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20417 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20418 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20419 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20420 @{number="69",value="0x20002b03"@}]
20425 @subheading The @code{-data-read-memory} Command
20426 @findex -data-read-memory
20428 @subsubheading Synopsis
20431 -data-read-memory [ -o @var{byte-offset} ]
20432 @var{address} @var{word-format} @var{word-size}
20433 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20440 @item @var{address}
20441 An expression specifying the address of the first memory word to be
20442 read. Complex expressions containing embedded white space should be
20443 quoted using the C convention.
20445 @item @var{word-format}
20446 The format to be used to print the memory words. The notation is the
20447 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20450 @item @var{word-size}
20451 The size of each memory word in bytes.
20453 @item @var{nr-rows}
20454 The number of rows in the output table.
20456 @item @var{nr-cols}
20457 The number of columns in the output table.
20460 If present, indicates that each row should include an @sc{ascii} dump. The
20461 value of @var{aschar} is used as a padding character when a byte is not a
20462 member of the printable @sc{ascii} character set (printable @sc{ascii}
20463 characters are those whose code is between 32 and 126, inclusively).
20465 @item @var{byte-offset}
20466 An offset to add to the @var{address} before fetching memory.
20469 This command displays memory contents as a table of @var{nr-rows} by
20470 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20471 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20472 (returned as @samp{total-bytes}). Should less than the requested number
20473 of bytes be returned by the target, the missing words are identified
20474 using @samp{N/A}. The number of bytes read from the target is returned
20475 in @samp{nr-bytes} and the starting address used to read memory in
20478 The address of the next/previous row or page is available in
20479 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20482 @subsubheading @value{GDBN} Command
20484 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20485 @samp{gdb_get_mem} memory read command.
20487 @subsubheading Example
20489 Read six bytes of memory starting at @code{bytes+6} but then offset by
20490 @code{-6} bytes. Format as three rows of two columns. One byte per
20491 word. Display each word in hex.
20495 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20496 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20497 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20498 prev-page="0x0000138a",memory=[
20499 @{addr="0x00001390",data=["0x00","0x01"]@},
20500 @{addr="0x00001392",data=["0x02","0x03"]@},
20501 @{addr="0x00001394",data=["0x04","0x05"]@}]
20505 Read two bytes of memory starting at address @code{shorts + 64} and
20506 display as a single word formatted in decimal.
20510 5-data-read-memory shorts+64 d 2 1 1
20511 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20512 next-row="0x00001512",prev-row="0x0000150e",
20513 next-page="0x00001512",prev-page="0x0000150e",memory=[
20514 @{addr="0x00001510",data=["128"]@}]
20518 Read thirty two bytes of memory starting at @code{bytes+16} and format
20519 as eight rows of four columns. Include a string encoding with @samp{x}
20520 used as the non-printable character.
20524 4-data-read-memory bytes+16 x 1 8 4 x
20525 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20526 next-row="0x000013c0",prev-row="0x0000139c",
20527 next-page="0x000013c0",prev-page="0x00001380",memory=[
20528 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20529 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20530 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20531 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20532 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20533 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20534 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20535 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20539 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20540 @node GDB/MI Tracepoint Commands
20541 @section @sc{gdb/mi} Tracepoint Commands
20543 The tracepoint commands are not yet implemented.
20545 @c @subheading -trace-actions
20547 @c @subheading -trace-delete
20549 @c @subheading -trace-disable
20551 @c @subheading -trace-dump
20553 @c @subheading -trace-enable
20555 @c @subheading -trace-exists
20557 @c @subheading -trace-find
20559 @c @subheading -trace-frame-number
20561 @c @subheading -trace-info
20563 @c @subheading -trace-insert
20565 @c @subheading -trace-list
20567 @c @subheading -trace-pass-count
20569 @c @subheading -trace-save
20571 @c @subheading -trace-start
20573 @c @subheading -trace-stop
20576 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20577 @node GDB/MI Symbol Query
20578 @section @sc{gdb/mi} Symbol Query Commands
20581 @subheading The @code{-symbol-info-address} Command
20582 @findex -symbol-info-address
20584 @subsubheading Synopsis
20587 -symbol-info-address @var{symbol}
20590 Describe where @var{symbol} is stored.
20592 @subsubheading @value{GDBN} Command
20594 The corresponding @value{GDBN} command is @samp{info address}.
20596 @subsubheading Example
20600 @subheading The @code{-symbol-info-file} Command
20601 @findex -symbol-info-file
20603 @subsubheading Synopsis
20609 Show the file for the symbol.
20611 @subsubheading @value{GDBN} Command
20613 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20614 @samp{gdb_find_file}.
20616 @subsubheading Example
20620 @subheading The @code{-symbol-info-function} Command
20621 @findex -symbol-info-function
20623 @subsubheading Synopsis
20626 -symbol-info-function
20629 Show which function the symbol lives in.
20631 @subsubheading @value{GDBN} Command
20633 @samp{gdb_get_function} in @code{gdbtk}.
20635 @subsubheading Example
20639 @subheading The @code{-symbol-info-line} Command
20640 @findex -symbol-info-line
20642 @subsubheading Synopsis
20648 Show the core addresses of the code for a source line.
20650 @subsubheading @value{GDBN} Command
20652 The corresponding @value{GDBN} command is @samp{info line}.
20653 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20655 @subsubheading Example
20659 @subheading The @code{-symbol-info-symbol} Command
20660 @findex -symbol-info-symbol
20662 @subsubheading Synopsis
20665 -symbol-info-symbol @var{addr}
20668 Describe what symbol is at location @var{addr}.
20670 @subsubheading @value{GDBN} Command
20672 The corresponding @value{GDBN} command is @samp{info symbol}.
20674 @subsubheading Example
20678 @subheading The @code{-symbol-list-functions} Command
20679 @findex -symbol-list-functions
20681 @subsubheading Synopsis
20684 -symbol-list-functions
20687 List the functions in the executable.
20689 @subsubheading @value{GDBN} Command
20691 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20692 @samp{gdb_search} in @code{gdbtk}.
20694 @subsubheading Example
20698 @subheading The @code{-symbol-list-lines} Command
20699 @findex -symbol-list-lines
20701 @subsubheading Synopsis
20704 -symbol-list-lines @var{filename}
20707 Print the list of lines that contain code and their associated program
20708 addresses for the given source filename. The entries are sorted in
20709 ascending PC order.
20711 @subsubheading @value{GDBN} Command
20713 There is no corresponding @value{GDBN} command.
20715 @subsubheading Example
20718 -symbol-list-lines basics.c
20719 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20724 @subheading The @code{-symbol-list-types} Command
20725 @findex -symbol-list-types
20727 @subsubheading Synopsis
20733 List all the type names.
20735 @subsubheading @value{GDBN} Command
20737 The corresponding commands are @samp{info types} in @value{GDBN},
20738 @samp{gdb_search} in @code{gdbtk}.
20740 @subsubheading Example
20744 @subheading The @code{-symbol-list-variables} Command
20745 @findex -symbol-list-variables
20747 @subsubheading Synopsis
20750 -symbol-list-variables
20753 List all the global and static variable names.
20755 @subsubheading @value{GDBN} Command
20757 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20759 @subsubheading Example
20763 @subheading The @code{-symbol-locate} Command
20764 @findex -symbol-locate
20766 @subsubheading Synopsis
20772 @subsubheading @value{GDBN} Command
20774 @samp{gdb_loc} in @code{gdbtk}.
20776 @subsubheading Example
20780 @subheading The @code{-symbol-type} Command
20781 @findex -symbol-type
20783 @subsubheading Synopsis
20786 -symbol-type @var{variable}
20789 Show type of @var{variable}.
20791 @subsubheading @value{GDBN} Command
20793 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20794 @samp{gdb_obj_variable}.
20796 @subsubheading Example
20800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20801 @node GDB/MI File Commands
20802 @section @sc{gdb/mi} File Commands
20804 This section describes the GDB/MI commands to specify executable file names
20805 and to read in and obtain symbol table information.
20807 @subheading The @code{-file-exec-and-symbols} Command
20808 @findex -file-exec-and-symbols
20810 @subsubheading Synopsis
20813 -file-exec-and-symbols @var{file}
20816 Specify the executable file to be debugged. This file is the one from
20817 which the symbol table is also read. If no file is specified, the
20818 command clears the executable and symbol information. If breakpoints
20819 are set when using this command with no arguments, @value{GDBN} will produce
20820 error messages. Otherwise, no output is produced, except a completion
20823 @subsubheading @value{GDBN} Command
20825 The corresponding @value{GDBN} command is @samp{file}.
20827 @subsubheading Example
20831 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20837 @subheading The @code{-file-exec-file} Command
20838 @findex -file-exec-file
20840 @subsubheading Synopsis
20843 -file-exec-file @var{file}
20846 Specify the executable file to be debugged. Unlike
20847 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20848 from this file. If used without argument, @value{GDBN} clears the information
20849 about the executable file. No output is produced, except a completion
20852 @subsubheading @value{GDBN} Command
20854 The corresponding @value{GDBN} command is @samp{exec-file}.
20856 @subsubheading Example
20860 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20866 @subheading The @code{-file-list-exec-sections} Command
20867 @findex -file-list-exec-sections
20869 @subsubheading Synopsis
20872 -file-list-exec-sections
20875 List the sections of the current executable file.
20877 @subsubheading @value{GDBN} Command
20879 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20880 information as this command. @code{gdbtk} has a corresponding command
20881 @samp{gdb_load_info}.
20883 @subsubheading Example
20887 @subheading The @code{-file-list-exec-source-file} Command
20888 @findex -file-list-exec-source-file
20890 @subsubheading Synopsis
20893 -file-list-exec-source-file
20896 List the line number, the current source file, and the absolute path
20897 to the current source file for the current executable.
20899 @subsubheading @value{GDBN} Command
20901 The @value{GDBN} equivalent is @samp{info source}
20903 @subsubheading Example
20907 123-file-list-exec-source-file
20908 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20913 @subheading The @code{-file-list-exec-source-files} Command
20914 @findex -file-list-exec-source-files
20916 @subsubheading Synopsis
20919 -file-list-exec-source-files
20922 List the source files for the current executable.
20924 It will always output the filename, but only when @value{GDBN} can find
20925 the absolute file name of a source file, will it output the fullname.
20927 @subsubheading @value{GDBN} Command
20929 The @value{GDBN} equivalent is @samp{info sources}.
20930 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20932 @subsubheading Example
20935 -file-list-exec-source-files
20937 @{file=foo.c,fullname=/home/foo.c@},
20938 @{file=/home/bar.c,fullname=/home/bar.c@},
20939 @{file=gdb_could_not_find_fullpath.c@}]
20943 @subheading The @code{-file-list-shared-libraries} Command
20944 @findex -file-list-shared-libraries
20946 @subsubheading Synopsis
20949 -file-list-shared-libraries
20952 List the shared libraries in the program.
20954 @subsubheading @value{GDBN} Command
20956 The corresponding @value{GDBN} command is @samp{info shared}.
20958 @subsubheading Example
20962 @subheading The @code{-file-list-symbol-files} Command
20963 @findex -file-list-symbol-files
20965 @subsubheading Synopsis
20968 -file-list-symbol-files
20973 @subsubheading @value{GDBN} Command
20975 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20977 @subsubheading Example
20981 @subheading The @code{-file-symbol-file} Command
20982 @findex -file-symbol-file
20984 @subsubheading Synopsis
20987 -file-symbol-file @var{file}
20990 Read symbol table info from the specified @var{file} argument. When
20991 used without arguments, clears @value{GDBN}'s symbol table info. No output is
20992 produced, except for a completion notification.
20994 @subsubheading @value{GDBN} Command
20996 The corresponding @value{GDBN} command is @samp{symbol-file}.
20998 @subsubheading Example
21002 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21008 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21009 @node GDB/MI Memory Overlay Commands
21010 @section @sc{gdb/mi} Memory Overlay Commands
21012 The memory overlay commands are not implemented.
21014 @c @subheading -overlay-auto
21016 @c @subheading -overlay-list-mapping-state
21018 @c @subheading -overlay-list-overlays
21020 @c @subheading -overlay-map
21022 @c @subheading -overlay-off
21024 @c @subheading -overlay-on
21026 @c @subheading -overlay-unmap
21028 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21029 @node GDB/MI Signal Handling Commands
21030 @section @sc{gdb/mi} Signal Handling Commands
21032 Signal handling commands are not implemented.
21034 @c @subheading -signal-handle
21036 @c @subheading -signal-list-handle-actions
21038 @c @subheading -signal-list-signal-types
21042 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21043 @node GDB/MI Target Manipulation
21044 @section @sc{gdb/mi} Target Manipulation Commands
21047 @subheading The @code{-target-attach} Command
21048 @findex -target-attach
21050 @subsubheading Synopsis
21053 -target-attach @var{pid} | @var{file}
21056 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
21058 @subsubheading @value{GDBN} Command
21060 The corresponding @value{GDBN} command is @samp{attach}.
21062 @subsubheading Example
21066 @subheading The @code{-target-compare-sections} Command
21067 @findex -target-compare-sections
21069 @subsubheading Synopsis
21072 -target-compare-sections [ @var{section} ]
21075 Compare data of section @var{section} on target to the exec file.
21076 Without the argument, all sections are compared.
21078 @subsubheading @value{GDBN} Command
21080 The @value{GDBN} equivalent is @samp{compare-sections}.
21082 @subsubheading Example
21086 @subheading The @code{-target-detach} Command
21087 @findex -target-detach
21089 @subsubheading Synopsis
21095 Detach from the remote target which normally resumes its execution.
21098 @subsubheading @value{GDBN} Command
21100 The corresponding @value{GDBN} command is @samp{detach}.
21102 @subsubheading Example
21112 @subheading The @code{-target-disconnect} Command
21113 @findex -target-disconnect
21115 @subsubheading Synopsis
21121 Disconnect from the remote target. There's no output and the target is
21122 generally not resumed.
21124 @subsubheading @value{GDBN} Command
21126 The corresponding @value{GDBN} command is @samp{disconnect}.
21128 @subsubheading Example
21138 @subheading The @code{-target-download} Command
21139 @findex -target-download
21141 @subsubheading Synopsis
21147 Loads the executable onto the remote target.
21148 It prints out an update message every half second, which includes the fields:
21152 The name of the section.
21154 The size of what has been sent so far for that section.
21156 The size of the section.
21158 The total size of what was sent so far (the current and the previous sections).
21160 The size of the overall executable to download.
21164 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21165 @sc{gdb/mi} Output Syntax}).
21167 In addition, it prints the name and size of the sections, as they are
21168 downloaded. These messages include the following fields:
21172 The name of the section.
21174 The size of the section.
21176 The size of the overall executable to download.
21180 At the end, a summary is printed.
21182 @subsubheading @value{GDBN} Command
21184 The corresponding @value{GDBN} command is @samp{load}.
21186 @subsubheading Example
21188 Note: each status message appears on a single line. Here the messages
21189 have been broken down so that they can fit onto a page.
21194 +download,@{section=".text",section-size="6668",total-size="9880"@}
21195 +download,@{section=".text",section-sent="512",section-size="6668",
21196 total-sent="512",total-size="9880"@}
21197 +download,@{section=".text",section-sent="1024",section-size="6668",
21198 total-sent="1024",total-size="9880"@}
21199 +download,@{section=".text",section-sent="1536",section-size="6668",
21200 total-sent="1536",total-size="9880"@}
21201 +download,@{section=".text",section-sent="2048",section-size="6668",
21202 total-sent="2048",total-size="9880"@}
21203 +download,@{section=".text",section-sent="2560",section-size="6668",
21204 total-sent="2560",total-size="9880"@}
21205 +download,@{section=".text",section-sent="3072",section-size="6668",
21206 total-sent="3072",total-size="9880"@}
21207 +download,@{section=".text",section-sent="3584",section-size="6668",
21208 total-sent="3584",total-size="9880"@}
21209 +download,@{section=".text",section-sent="4096",section-size="6668",
21210 total-sent="4096",total-size="9880"@}
21211 +download,@{section=".text",section-sent="4608",section-size="6668",
21212 total-sent="4608",total-size="9880"@}
21213 +download,@{section=".text",section-sent="5120",section-size="6668",
21214 total-sent="5120",total-size="9880"@}
21215 +download,@{section=".text",section-sent="5632",section-size="6668",
21216 total-sent="5632",total-size="9880"@}
21217 +download,@{section=".text",section-sent="6144",section-size="6668",
21218 total-sent="6144",total-size="9880"@}
21219 +download,@{section=".text",section-sent="6656",section-size="6668",
21220 total-sent="6656",total-size="9880"@}
21221 +download,@{section=".init",section-size="28",total-size="9880"@}
21222 +download,@{section=".fini",section-size="28",total-size="9880"@}
21223 +download,@{section=".data",section-size="3156",total-size="9880"@}
21224 +download,@{section=".data",section-sent="512",section-size="3156",
21225 total-sent="7236",total-size="9880"@}
21226 +download,@{section=".data",section-sent="1024",section-size="3156",
21227 total-sent="7748",total-size="9880"@}
21228 +download,@{section=".data",section-sent="1536",section-size="3156",
21229 total-sent="8260",total-size="9880"@}
21230 +download,@{section=".data",section-sent="2048",section-size="3156",
21231 total-sent="8772",total-size="9880"@}
21232 +download,@{section=".data",section-sent="2560",section-size="3156",
21233 total-sent="9284",total-size="9880"@}
21234 +download,@{section=".data",section-sent="3072",section-size="3156",
21235 total-sent="9796",total-size="9880"@}
21236 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21242 @subheading The @code{-target-exec-status} Command
21243 @findex -target-exec-status
21245 @subsubheading Synopsis
21248 -target-exec-status
21251 Provide information on the state of the target (whether it is running or
21252 not, for instance).
21254 @subsubheading @value{GDBN} Command
21256 There's no equivalent @value{GDBN} command.
21258 @subsubheading Example
21262 @subheading The @code{-target-list-available-targets} Command
21263 @findex -target-list-available-targets
21265 @subsubheading Synopsis
21268 -target-list-available-targets
21271 List the possible targets to connect to.
21273 @subsubheading @value{GDBN} Command
21275 The corresponding @value{GDBN} command is @samp{help target}.
21277 @subsubheading Example
21281 @subheading The @code{-target-list-current-targets} Command
21282 @findex -target-list-current-targets
21284 @subsubheading Synopsis
21287 -target-list-current-targets
21290 Describe the current target.
21292 @subsubheading @value{GDBN} Command
21294 The corresponding information is printed by @samp{info file} (among
21297 @subsubheading Example
21301 @subheading The @code{-target-list-parameters} Command
21302 @findex -target-list-parameters
21304 @subsubheading Synopsis
21307 -target-list-parameters
21312 @subsubheading @value{GDBN} Command
21316 @subsubheading Example
21320 @subheading The @code{-target-select} Command
21321 @findex -target-select
21323 @subsubheading Synopsis
21326 -target-select @var{type} @var{parameters @dots{}}
21329 Connect @value{GDBN} to the remote target. This command takes two args:
21333 The type of target, for instance @samp{async}, @samp{remote}, etc.
21334 @item @var{parameters}
21335 Device names, host names and the like. @xref{Target Commands, ,
21336 Commands for Managing Targets}, for more details.
21339 The output is a connection notification, followed by the address at
21340 which the target program is, in the following form:
21343 ^connected,addr="@var{address}",func="@var{function name}",
21344 args=[@var{arg list}]
21347 @subsubheading @value{GDBN} Command
21349 The corresponding @value{GDBN} command is @samp{target}.
21351 @subsubheading Example
21355 -target-select async /dev/ttya
21356 ^connected,addr="0xfe00a300",func="??",args=[]
21360 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21361 @node GDB/MI File Transfer Commands
21362 @section @sc{gdb/mi} File Transfer Commands
21365 @subheading The @code{-target-file-put} Command
21366 @findex -target-file-put
21368 @subsubheading Synopsis
21371 -target-file-put @var{hostfile} @var{targetfile}
21374 Copy file @var{hostfile} from the host system (the machine running
21375 @value{GDBN}) to @var{targetfile} on the target system.
21377 @subsubheading @value{GDBN} Command
21379 The corresponding @value{GDBN} command is @samp{remote put}.
21381 @subsubheading Example
21385 -target-file-put localfile remotefile
21391 @subheading The @code{-target-file-put} Command
21392 @findex -target-file-get
21394 @subsubheading Synopsis
21397 -target-file-get @var{targetfile} @var{hostfile}
21400 Copy file @var{targetfile} from the target system to @var{hostfile}
21401 on the host system.
21403 @subsubheading @value{GDBN} Command
21405 The corresponding @value{GDBN} command is @samp{remote get}.
21407 @subsubheading Example
21411 -target-file-get remotefile localfile
21417 @subheading The @code{-target-file-delete} Command
21418 @findex -target-file-delete
21420 @subsubheading Synopsis
21423 -target-file-delete @var{targetfile}
21426 Delete @var{targetfile} from the target system.
21428 @subsubheading @value{GDBN} Command
21430 The corresponding @value{GDBN} command is @samp{remote delete}.
21432 @subsubheading Example
21436 -target-file-delete remotefile
21442 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21443 @node GDB/MI Miscellaneous Commands
21444 @section Miscellaneous @sc{gdb/mi} Commands
21446 @c @subheading -gdb-complete
21448 @subheading The @code{-gdb-exit} Command
21451 @subsubheading Synopsis
21457 Exit @value{GDBN} immediately.
21459 @subsubheading @value{GDBN} Command
21461 Approximately corresponds to @samp{quit}.
21463 @subsubheading Example
21472 @subheading The @code{-exec-abort} Command
21473 @findex -exec-abort
21475 @subsubheading Synopsis
21481 Kill the inferior running program.
21483 @subsubheading @value{GDBN} Command
21485 The corresponding @value{GDBN} command is @samp{kill}.
21487 @subsubheading Example
21491 @subheading The @code{-gdb-set} Command
21494 @subsubheading Synopsis
21500 Set an internal @value{GDBN} variable.
21501 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21503 @subsubheading @value{GDBN} Command
21505 The corresponding @value{GDBN} command is @samp{set}.
21507 @subsubheading Example
21517 @subheading The @code{-gdb-show} Command
21520 @subsubheading Synopsis
21526 Show the current value of a @value{GDBN} variable.
21528 @subsubheading @value{GDBN} Command
21530 The corresponding @value{GDBN} command is @samp{show}.
21532 @subsubheading Example
21541 @c @subheading -gdb-source
21544 @subheading The @code{-gdb-version} Command
21545 @findex -gdb-version
21547 @subsubheading Synopsis
21553 Show version information for @value{GDBN}. Used mostly in testing.
21555 @subsubheading @value{GDBN} Command
21557 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21558 default shows this information when you start an interactive session.
21560 @subsubheading Example
21562 @c This example modifies the actual output from GDB to avoid overfull
21568 ~Copyright 2000 Free Software Foundation, Inc.
21569 ~GDB is free software, covered by the GNU General Public License, and
21570 ~you are welcome to change it and/or distribute copies of it under
21571 ~ certain conditions.
21572 ~Type "show copying" to see the conditions.
21573 ~There is absolutely no warranty for GDB. Type "show warranty" for
21575 ~This GDB was configured as
21576 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21581 @subheading The @code{-list-features} Command
21582 @findex -list-features
21584 Returns a list of particular features of the MI protocol that
21585 this version of gdb implements. A feature can be a command,
21586 or a new field in an output of some command, or even an
21587 important bugfix. While a frontend can sometimes detect presence
21588 of a feature at runtime, it is easier to perform detection at debugger
21591 The command returns a list of strings, with each string naming an
21592 available feature. Each returned string is just a name, it does not
21593 have any internal structure. The list of possible feature names
21599 (gdb) -list-features
21600 ^done,result=["feature1","feature2"]
21603 The current list of features is:
21607 @samp{frozen-varobjs}---indicates presence of the
21608 @code{-var-set-frozen} command, as well as possible presense of the
21609 @code{frozen} field in the output of @code{-varobj-create}.
21611 @samp{pending-breakpoints}---indicates presence of the @code{-f}
21612 option to the @code{-break-insert} command.
21616 @subheading The @code{-interpreter-exec} Command
21617 @findex -interpreter-exec
21619 @subheading Synopsis
21622 -interpreter-exec @var{interpreter} @var{command}
21624 @anchor{-interpreter-exec}
21626 Execute the specified @var{command} in the given @var{interpreter}.
21628 @subheading @value{GDBN} Command
21630 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21632 @subheading Example
21636 -interpreter-exec console "break main"
21637 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21638 &"During symbol reading, bad structure-type format.\n"
21639 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21644 @subheading The @code{-inferior-tty-set} Command
21645 @findex -inferior-tty-set
21647 @subheading Synopsis
21650 -inferior-tty-set /dev/pts/1
21653 Set terminal for future runs of the program being debugged.
21655 @subheading @value{GDBN} Command
21657 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21659 @subheading Example
21663 -inferior-tty-set /dev/pts/1
21668 @subheading The @code{-inferior-tty-show} Command
21669 @findex -inferior-tty-show
21671 @subheading Synopsis
21677 Show terminal for future runs of program being debugged.
21679 @subheading @value{GDBN} Command
21681 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21683 @subheading Example
21687 -inferior-tty-set /dev/pts/1
21691 ^done,inferior_tty_terminal="/dev/pts/1"
21695 @subheading The @code{-enable-timings} Command
21696 @findex -enable-timings
21698 @subheading Synopsis
21701 -enable-timings [yes | no]
21704 Toggle the printing of the wallclock, user and system times for an MI
21705 command as a field in its output. This command is to help frontend
21706 developers optimize the performance of their code. No argument is
21707 equivalent to @samp{yes}.
21709 @subheading @value{GDBN} Command
21713 @subheading Example
21721 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21722 addr="0x080484ed",func="main",file="myprog.c",
21723 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
21724 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
21732 *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
21733 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
21734 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
21735 fullname="/home/nickrob/myprog.c",line="73"@}
21740 @chapter @value{GDBN} Annotations
21742 This chapter describes annotations in @value{GDBN}. Annotations were
21743 designed to interface @value{GDBN} to graphical user interfaces or other
21744 similar programs which want to interact with @value{GDBN} at a
21745 relatively high level.
21747 The annotation mechanism has largely been superseded by @sc{gdb/mi}
21751 This is Edition @value{EDITION}, @value{DATE}.
21755 * Annotations Overview:: What annotations are; the general syntax.
21756 * Server Prefix:: Issuing a command without affecting user state.
21757 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21758 * Errors:: Annotations for error messages.
21759 * Invalidation:: Some annotations describe things now invalid.
21760 * Annotations for Running::
21761 Whether the program is running, how it stopped, etc.
21762 * Source Annotations:: Annotations describing source code.
21765 @node Annotations Overview
21766 @section What is an Annotation?
21767 @cindex annotations
21769 Annotations start with a newline character, two @samp{control-z}
21770 characters, and the name of the annotation. If there is no additional
21771 information associated with this annotation, the name of the annotation
21772 is followed immediately by a newline. If there is additional
21773 information, the name of the annotation is followed by a space, the
21774 additional information, and a newline. The additional information
21775 cannot contain newline characters.
21777 Any output not beginning with a newline and two @samp{control-z}
21778 characters denotes literal output from @value{GDBN}. Currently there is
21779 no need for @value{GDBN} to output a newline followed by two
21780 @samp{control-z} characters, but if there was such a need, the
21781 annotations could be extended with an @samp{escape} annotation which
21782 means those three characters as output.
21784 The annotation @var{level}, which is specified using the
21785 @option{--annotate} command line option (@pxref{Mode Options}), controls
21786 how much information @value{GDBN} prints together with its prompt,
21787 values of expressions, source lines, and other types of output. Level 0
21788 is for no annotations, level 1 is for use when @value{GDBN} is run as a
21789 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21790 for programs that control @value{GDBN}, and level 2 annotations have
21791 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21792 Interface, annotate, GDB's Obsolete Annotations}).
21795 @kindex set annotate
21796 @item set annotate @var{level}
21797 The @value{GDBN} command @code{set annotate} sets the level of
21798 annotations to the specified @var{level}.
21800 @item show annotate
21801 @kindex show annotate
21802 Show the current annotation level.
21805 This chapter describes level 3 annotations.
21807 A simple example of starting up @value{GDBN} with annotations is:
21810 $ @kbd{gdb --annotate=3}
21812 Copyright 2003 Free Software Foundation, Inc.
21813 GDB is free software, covered by the GNU General Public License,
21814 and you are welcome to change it and/or distribute copies of it
21815 under certain conditions.
21816 Type "show copying" to see the conditions.
21817 There is absolutely no warranty for GDB. Type "show warranty"
21819 This GDB was configured as "i386-pc-linux-gnu"
21830 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21831 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21832 denotes a @samp{control-z} character) are annotations; the rest is
21833 output from @value{GDBN}.
21835 @node Server Prefix
21836 @section The Server Prefix
21837 @cindex server prefix
21839 If you prefix a command with @samp{server } then it will not affect
21840 the command history, nor will it affect @value{GDBN}'s notion of which
21841 command to repeat if @key{RET} is pressed on a line by itself. This
21842 means that commands can be run behind a user's back by a front-end in
21843 a transparent manner.
21845 The server prefix does not affect the recording of values into the value
21846 history; to print a value without recording it into the value history,
21847 use the @code{output} command instead of the @code{print} command.
21850 @section Annotation for @value{GDBN} Input
21852 @cindex annotations for prompts
21853 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21854 to know when to send output, when the output from a given command is
21857 Different kinds of input each have a different @dfn{input type}. Each
21858 input type has three annotations: a @code{pre-} annotation, which
21859 denotes the beginning of any prompt which is being output, a plain
21860 annotation, which denotes the end of the prompt, and then a @code{post-}
21861 annotation which denotes the end of any echo which may (or may not) be
21862 associated with the input. For example, the @code{prompt} input type
21863 features the following annotations:
21871 The input types are
21874 @findex pre-prompt annotation
21875 @findex prompt annotation
21876 @findex post-prompt annotation
21878 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21880 @findex pre-commands annotation
21881 @findex commands annotation
21882 @findex post-commands annotation
21884 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21885 command. The annotations are repeated for each command which is input.
21887 @findex pre-overload-choice annotation
21888 @findex overload-choice annotation
21889 @findex post-overload-choice annotation
21890 @item overload-choice
21891 When @value{GDBN} wants the user to select between various overloaded functions.
21893 @findex pre-query annotation
21894 @findex query annotation
21895 @findex post-query annotation
21897 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21899 @findex pre-prompt-for-continue annotation
21900 @findex prompt-for-continue annotation
21901 @findex post-prompt-for-continue annotation
21902 @item prompt-for-continue
21903 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21904 expect this to work well; instead use @code{set height 0} to disable
21905 prompting. This is because the counting of lines is buggy in the
21906 presence of annotations.
21911 @cindex annotations for errors, warnings and interrupts
21913 @findex quit annotation
21918 This annotation occurs right before @value{GDBN} responds to an interrupt.
21920 @findex error annotation
21925 This annotation occurs right before @value{GDBN} responds to an error.
21927 Quit and error annotations indicate that any annotations which @value{GDBN} was
21928 in the middle of may end abruptly. For example, if a
21929 @code{value-history-begin} annotation is followed by a @code{error}, one
21930 cannot expect to receive the matching @code{value-history-end}. One
21931 cannot expect not to receive it either, however; an error annotation
21932 does not necessarily mean that @value{GDBN} is immediately returning all the way
21935 @findex error-begin annotation
21936 A quit or error annotation may be preceded by
21942 Any output between that and the quit or error annotation is the error
21945 Warning messages are not yet annotated.
21946 @c If we want to change that, need to fix warning(), type_error(),
21947 @c range_error(), and possibly other places.
21950 @section Invalidation Notices
21952 @cindex annotations for invalidation messages
21953 The following annotations say that certain pieces of state may have
21957 @findex frames-invalid annotation
21958 @item ^Z^Zframes-invalid
21960 The frames (for example, output from the @code{backtrace} command) may
21963 @findex breakpoints-invalid annotation
21964 @item ^Z^Zbreakpoints-invalid
21966 The breakpoints may have changed. For example, the user just added or
21967 deleted a breakpoint.
21970 @node Annotations for Running
21971 @section Running the Program
21972 @cindex annotations for running programs
21974 @findex starting annotation
21975 @findex stopping annotation
21976 When the program starts executing due to a @value{GDBN} command such as
21977 @code{step} or @code{continue},
21983 is output. When the program stops,
21989 is output. Before the @code{stopped} annotation, a variety of
21990 annotations describe how the program stopped.
21993 @findex exited annotation
21994 @item ^Z^Zexited @var{exit-status}
21995 The program exited, and @var{exit-status} is the exit status (zero for
21996 successful exit, otherwise nonzero).
21998 @findex signalled annotation
21999 @findex signal-name annotation
22000 @findex signal-name-end annotation
22001 @findex signal-string annotation
22002 @findex signal-string-end annotation
22003 @item ^Z^Zsignalled
22004 The program exited with a signal. After the @code{^Z^Zsignalled}, the
22005 annotation continues:
22011 ^Z^Zsignal-name-end
22015 ^Z^Zsignal-string-end
22020 where @var{name} is the name of the signal, such as @code{SIGILL} or
22021 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
22022 as @code{Illegal Instruction} or @code{Segmentation fault}.
22023 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
22024 user's benefit and have no particular format.
22026 @findex signal annotation
22028 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
22029 just saying that the program received the signal, not that it was
22030 terminated with it.
22032 @findex breakpoint annotation
22033 @item ^Z^Zbreakpoint @var{number}
22034 The program hit breakpoint number @var{number}.
22036 @findex watchpoint annotation
22037 @item ^Z^Zwatchpoint @var{number}
22038 The program hit watchpoint number @var{number}.
22041 @node Source Annotations
22042 @section Displaying Source
22043 @cindex annotations for source display
22045 @findex source annotation
22046 The following annotation is used instead of displaying source code:
22049 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
22052 where @var{filename} is an absolute file name indicating which source
22053 file, @var{line} is the line number within that file (where 1 is the
22054 first line in the file), @var{character} is the character position
22055 within the file (where 0 is the first character in the file) (for most
22056 debug formats this will necessarily point to the beginning of a line),
22057 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
22058 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
22059 @var{addr} is the address in the target program associated with the
22060 source which is being displayed. @var{addr} is in the form @samp{0x}
22061 followed by one or more lowercase hex digits (note that this does not
22062 depend on the language).
22065 @chapter Reporting Bugs in @value{GDBN}
22066 @cindex bugs in @value{GDBN}
22067 @cindex reporting bugs in @value{GDBN}
22069 Your bug reports play an essential role in making @value{GDBN} reliable.
22071 Reporting a bug may help you by bringing a solution to your problem, or it
22072 may not. But in any case the principal function of a bug report is to help
22073 the entire community by making the next version of @value{GDBN} work better. Bug
22074 reports are your contribution to the maintenance of @value{GDBN}.
22076 In order for a bug report to serve its purpose, you must include the
22077 information that enables us to fix the bug.
22080 * Bug Criteria:: Have you found a bug?
22081 * Bug Reporting:: How to report bugs
22085 @section Have You Found a Bug?
22086 @cindex bug criteria
22088 If you are not sure whether you have found a bug, here are some guidelines:
22091 @cindex fatal signal
22092 @cindex debugger crash
22093 @cindex crash of debugger
22095 If the debugger gets a fatal signal, for any input whatever, that is a
22096 @value{GDBN} bug. Reliable debuggers never crash.
22098 @cindex error on valid input
22100 If @value{GDBN} produces an error message for valid input, that is a
22101 bug. (Note that if you're cross debugging, the problem may also be
22102 somewhere in the connection to the target.)
22104 @cindex invalid input
22106 If @value{GDBN} does not produce an error message for invalid input,
22107 that is a bug. However, you should note that your idea of
22108 ``invalid input'' might be our idea of ``an extension'' or ``support
22109 for traditional practice''.
22112 If you are an experienced user of debugging tools, your suggestions
22113 for improvement of @value{GDBN} are welcome in any case.
22116 @node Bug Reporting
22117 @section How to Report Bugs
22118 @cindex bug reports
22119 @cindex @value{GDBN} bugs, reporting
22121 A number of companies and individuals offer support for @sc{gnu} products.
22122 If you obtained @value{GDBN} from a support organization, we recommend you
22123 contact that organization first.
22125 You can find contact information for many support companies and
22126 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
22128 @c should add a web page ref...
22130 In any event, we also recommend that you submit bug reports for
22131 @value{GDBN}. The preferred method is to submit them directly using
22132 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
22133 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
22136 @strong{Do not send bug reports to @samp{info-gdb}, or to
22137 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
22138 not want to receive bug reports. Those that do have arranged to receive
22141 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
22142 serves as a repeater. The mailing list and the newsgroup carry exactly
22143 the same messages. Often people think of posting bug reports to the
22144 newsgroup instead of mailing them. This appears to work, but it has one
22145 problem which can be crucial: a newsgroup posting often lacks a mail
22146 path back to the sender. Thus, if we need to ask for more information,
22147 we may be unable to reach you. For this reason, it is better to send
22148 bug reports to the mailing list.
22150 The fundamental principle of reporting bugs usefully is this:
22151 @strong{report all the facts}. If you are not sure whether to state a
22152 fact or leave it out, state it!
22154 Often people omit facts because they think they know what causes the
22155 problem and assume that some details do not matter. Thus, you might
22156 assume that the name of the variable you use in an example does not matter.
22157 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
22158 stray memory reference which happens to fetch from the location where that
22159 name is stored in memory; perhaps, if the name were different, the contents
22160 of that location would fool the debugger into doing the right thing despite
22161 the bug. Play it safe and give a specific, complete example. That is the
22162 easiest thing for you to do, and the most helpful.
22164 Keep in mind that the purpose of a bug report is to enable us to fix the
22165 bug. It may be that the bug has been reported previously, but neither
22166 you nor we can know that unless your bug report is complete and
22169 Sometimes people give a few sketchy facts and ask, ``Does this ring a
22170 bell?'' Those bug reports are useless, and we urge everyone to
22171 @emph{refuse to respond to them} except to chide the sender to report
22174 To enable us to fix the bug, you should include all these things:
22178 The version of @value{GDBN}. @value{GDBN} announces it if you start
22179 with no arguments; you can also print it at any time using @code{show
22182 Without this, we will not know whether there is any point in looking for
22183 the bug in the current version of @value{GDBN}.
22186 The type of machine you are using, and the operating system name and
22190 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
22191 ``@value{GCC}--2.8.1''.
22194 What compiler (and its version) was used to compile the program you are
22195 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
22196 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
22197 to get this information; for other compilers, see the documentation for
22201 The command arguments you gave the compiler to compile your example and
22202 observe the bug. For example, did you use @samp{-O}? To guarantee
22203 you will not omit something important, list them all. A copy of the
22204 Makefile (or the output from make) is sufficient.
22206 If we were to try to guess the arguments, we would probably guess wrong
22207 and then we might not encounter the bug.
22210 A complete input script, and all necessary source files, that will
22214 A description of what behavior you observe that you believe is
22215 incorrect. For example, ``It gets a fatal signal.''
22217 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
22218 will certainly notice it. But if the bug is incorrect output, we might
22219 not notice unless it is glaringly wrong. You might as well not give us
22220 a chance to make a mistake.
22222 Even if the problem you experience is a fatal signal, you should still
22223 say so explicitly. Suppose something strange is going on, such as, your
22224 copy of @value{GDBN} is out of synch, or you have encountered a bug in
22225 the C library on your system. (This has happened!) Your copy might
22226 crash and ours would not. If you told us to expect a crash, then when
22227 ours fails to crash, we would know that the bug was not happening for
22228 us. If you had not told us to expect a crash, then we would not be able
22229 to draw any conclusion from our observations.
22232 @cindex recording a session script
22233 To collect all this information, you can use a session recording program
22234 such as @command{script}, which is available on many Unix systems.
22235 Just run your @value{GDBN} session inside @command{script} and then
22236 include the @file{typescript} file with your bug report.
22238 Another way to record a @value{GDBN} session is to run @value{GDBN}
22239 inside Emacs and then save the entire buffer to a file.
22242 If you wish to suggest changes to the @value{GDBN} source, send us context
22243 diffs. If you even discuss something in the @value{GDBN} source, refer to
22244 it by context, not by line number.
22246 The line numbers in our development sources will not match those in your
22247 sources. Your line numbers would convey no useful information to us.
22251 Here are some things that are not necessary:
22255 A description of the envelope of the bug.
22257 Often people who encounter a bug spend a lot of time investigating
22258 which changes to the input file will make the bug go away and which
22259 changes will not affect it.
22261 This is often time consuming and not very useful, because the way we
22262 will find the bug is by running a single example under the debugger
22263 with breakpoints, not by pure deduction from a series of examples.
22264 We recommend that you save your time for something else.
22266 Of course, if you can find a simpler example to report @emph{instead}
22267 of the original one, that is a convenience for us. Errors in the
22268 output will be easier to spot, running under the debugger will take
22269 less time, and so on.
22271 However, simplification is not vital; if you do not want to do this,
22272 report the bug anyway and send us the entire test case you used.
22275 A patch for the bug.
22277 A patch for the bug does help us if it is a good one. But do not omit
22278 the necessary information, such as the test case, on the assumption that
22279 a patch is all we need. We might see problems with your patch and decide
22280 to fix the problem another way, or we might not understand it at all.
22282 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22283 construct an example that will make the program follow a certain path
22284 through the code. If you do not send us the example, we will not be able
22285 to construct one, so we will not be able to verify that the bug is fixed.
22287 And if we cannot understand what bug you are trying to fix, or why your
22288 patch should be an improvement, we will not install it. A test case will
22289 help us to understand.
22292 A guess about what the bug is or what it depends on.
22294 Such guesses are usually wrong. Even we cannot guess right about such
22295 things without first using the debugger to find the facts.
22298 @c The readline documentation is distributed with the readline code
22299 @c and consists of the two following files:
22301 @c inc-hist.texinfo
22302 @c Use -I with makeinfo to point to the appropriate directory,
22303 @c environment var TEXINPUTS with TeX.
22304 @include rluser.texi
22305 @include inc-hist.texinfo
22308 @node Formatting Documentation
22309 @appendix Formatting Documentation
22311 @cindex @value{GDBN} reference card
22312 @cindex reference card
22313 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22314 for printing with PostScript or Ghostscript, in the @file{gdb}
22315 subdirectory of the main source directory@footnote{In
22316 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22317 release.}. If you can use PostScript or Ghostscript with your printer,
22318 you can print the reference card immediately with @file{refcard.ps}.
22320 The release also includes the source for the reference card. You
22321 can format it, using @TeX{}, by typing:
22327 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22328 mode on US ``letter'' size paper;
22329 that is, on a sheet 11 inches wide by 8.5 inches
22330 high. You will need to specify this form of printing as an option to
22331 your @sc{dvi} output program.
22333 @cindex documentation
22335 All the documentation for @value{GDBN} comes as part of the machine-readable
22336 distribution. The documentation is written in Texinfo format, which is
22337 a documentation system that uses a single source file to produce both
22338 on-line information and a printed manual. You can use one of the Info
22339 formatting commands to create the on-line version of the documentation
22340 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22342 @value{GDBN} includes an already formatted copy of the on-line Info
22343 version of this manual in the @file{gdb} subdirectory. The main Info
22344 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22345 subordinate files matching @samp{gdb.info*} in the same directory. If
22346 necessary, you can print out these files, or read them with any editor;
22347 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22348 Emacs or the standalone @code{info} program, available as part of the
22349 @sc{gnu} Texinfo distribution.
22351 If you want to format these Info files yourself, you need one of the
22352 Info formatting programs, such as @code{texinfo-format-buffer} or
22355 If you have @code{makeinfo} installed, and are in the top level
22356 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22357 version @value{GDBVN}), you can make the Info file by typing:
22364 If you want to typeset and print copies of this manual, you need @TeX{},
22365 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22366 Texinfo definitions file.
22368 @TeX{} is a typesetting program; it does not print files directly, but
22369 produces output files called @sc{dvi} files. To print a typeset
22370 document, you need a program to print @sc{dvi} files. If your system
22371 has @TeX{} installed, chances are it has such a program. The precise
22372 command to use depends on your system; @kbd{lpr -d} is common; another
22373 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22374 require a file name without any extension or a @samp{.dvi} extension.
22376 @TeX{} also requires a macro definitions file called
22377 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22378 written in Texinfo format. On its own, @TeX{} cannot either read or
22379 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22380 and is located in the @file{gdb-@var{version-number}/texinfo}
22383 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22384 typeset and print this manual. First switch to the @file{gdb}
22385 subdirectory of the main source directory (for example, to
22386 @file{gdb-@value{GDBVN}/gdb}) and type:
22392 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22394 @node Installing GDB
22395 @appendix Installing @value{GDBN}
22396 @cindex installation
22399 * Requirements:: Requirements for building @value{GDBN}
22400 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22401 * Separate Objdir:: Compiling @value{GDBN} in another directory
22402 * Config Names:: Specifying names for hosts and targets
22403 * Configure Options:: Summary of options for configure
22407 @section Requirements for Building @value{GDBN}
22408 @cindex building @value{GDBN}, requirements for
22410 Building @value{GDBN} requires various tools and packages to be available.
22411 Other packages will be used only if they are found.
22413 @heading Tools/Packages Necessary for Building @value{GDBN}
22415 @item ISO C90 compiler
22416 @value{GDBN} is written in ISO C90. It should be buildable with any
22417 working C90 compiler, e.g.@: GCC.
22421 @heading Tools/Packages Optional for Building @value{GDBN}
22425 @value{GDBN} can use the Expat XML parsing library. This library may be
22426 included with your operating system distribution; if it is not, you
22427 can get the latest version from @url{http://expat.sourceforge.net}.
22428 The @file{configure} script will search for this library in several
22429 standard locations; if it is installed in an unusual path, you can
22430 use the @option{--with-libexpat-prefix} option to specify its location.
22436 Remote protocol memory maps (@pxref{Memory Map Format})
22438 Target descriptions (@pxref{Target Descriptions})
22440 Remote shared library lists (@pxref{Library List Format})
22442 MS-Windows shared libraries (@pxref{Shared Libraries})
22447 @node Running Configure
22448 @section Invoking the @value{GDBN} @file{configure} Script
22449 @cindex configuring @value{GDBN}
22450 @value{GDBN} comes with a @file{configure} script that automates the process
22451 of preparing @value{GDBN} for installation; you can then use @code{make} to
22452 build the @code{gdb} program.
22454 @c irrelevant in info file; it's as current as the code it lives with.
22455 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22456 look at the @file{README} file in the sources; we may have improved the
22457 installation procedures since publishing this manual.}
22460 The @value{GDBN} distribution includes all the source code you need for
22461 @value{GDBN} in a single directory, whose name is usually composed by
22462 appending the version number to @samp{gdb}.
22464 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22465 @file{gdb-@value{GDBVN}} directory. That directory contains:
22468 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22469 script for configuring @value{GDBN} and all its supporting libraries
22471 @item gdb-@value{GDBVN}/gdb
22472 the source specific to @value{GDBN} itself
22474 @item gdb-@value{GDBVN}/bfd
22475 source for the Binary File Descriptor library
22477 @item gdb-@value{GDBVN}/include
22478 @sc{gnu} include files
22480 @item gdb-@value{GDBVN}/libiberty
22481 source for the @samp{-liberty} free software library
22483 @item gdb-@value{GDBVN}/opcodes
22484 source for the library of opcode tables and disassemblers
22486 @item gdb-@value{GDBVN}/readline
22487 source for the @sc{gnu} command-line interface
22489 @item gdb-@value{GDBVN}/glob
22490 source for the @sc{gnu} filename pattern-matching subroutine
22492 @item gdb-@value{GDBVN}/mmalloc
22493 source for the @sc{gnu} memory-mapped malloc package
22496 The simplest way to configure and build @value{GDBN} is to run @file{configure}
22497 from the @file{gdb-@var{version-number}} source directory, which in
22498 this example is the @file{gdb-@value{GDBVN}} directory.
22500 First switch to the @file{gdb-@var{version-number}} source directory
22501 if you are not already in it; then run @file{configure}. Pass the
22502 identifier for the platform on which @value{GDBN} will run as an
22508 cd gdb-@value{GDBVN}
22509 ./configure @var{host}
22514 where @var{host} is an identifier such as @samp{sun4} or
22515 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22516 (You can often leave off @var{host}; @file{configure} tries to guess the
22517 correct value by examining your system.)
22519 Running @samp{configure @var{host}} and then running @code{make} builds the
22520 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22521 libraries, then @code{gdb} itself. The configured source files, and the
22522 binaries, are left in the corresponding source directories.
22525 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22526 system does not recognize this automatically when you run a different
22527 shell, you may need to run @code{sh} on it explicitly:
22530 sh configure @var{host}
22533 If you run @file{configure} from a directory that contains source
22534 directories for multiple libraries or programs, such as the
22535 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
22537 creates configuration files for every directory level underneath (unless
22538 you tell it not to, with the @samp{--norecursion} option).
22540 You should run the @file{configure} script from the top directory in the
22541 source tree, the @file{gdb-@var{version-number}} directory. If you run
22542 @file{configure} from one of the subdirectories, you will configure only
22543 that subdirectory. That is usually not what you want. In particular,
22544 if you run the first @file{configure} from the @file{gdb} subdirectory
22545 of the @file{gdb-@var{version-number}} directory, you will omit the
22546 configuration of @file{bfd}, @file{readline}, and other sibling
22547 directories of the @file{gdb} subdirectory. This leads to build errors
22548 about missing include files such as @file{bfd/bfd.h}.
22550 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22551 However, you should make sure that the shell on your path (named by
22552 the @samp{SHELL} environment variable) is publicly readable. Remember
22553 that @value{GDBN} uses the shell to start your program---some systems refuse to
22554 let @value{GDBN} debug child processes whose programs are not readable.
22556 @node Separate Objdir
22557 @section Compiling @value{GDBN} in Another Directory
22559 If you want to run @value{GDBN} versions for several host or target machines,
22560 you need a different @code{gdb} compiled for each combination of
22561 host and target. @file{configure} is designed to make this easy by
22562 allowing you to generate each configuration in a separate subdirectory,
22563 rather than in the source directory. If your @code{make} program
22564 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22565 @code{make} in each of these directories builds the @code{gdb}
22566 program specified there.
22568 To build @code{gdb} in a separate directory, run @file{configure}
22569 with the @samp{--srcdir} option to specify where to find the source.
22570 (You also need to specify a path to find @file{configure}
22571 itself from your working directory. If the path to @file{configure}
22572 would be the same as the argument to @samp{--srcdir}, you can leave out
22573 the @samp{--srcdir} option; it is assumed.)
22575 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22576 separate directory for a Sun 4 like this:
22580 cd gdb-@value{GDBVN}
22583 ../gdb-@value{GDBVN}/configure sun4
22588 When @file{configure} builds a configuration using a remote source
22589 directory, it creates a tree for the binaries with the same structure
22590 (and using the same names) as the tree under the source directory. In
22591 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22592 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22593 @file{gdb-sun4/gdb}.
22595 Make sure that your path to the @file{configure} script has just one
22596 instance of @file{gdb} in it. If your path to @file{configure} looks
22597 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22598 one subdirectory of @value{GDBN}, not the whole package. This leads to
22599 build errors about missing include files such as @file{bfd/bfd.h}.
22601 One popular reason to build several @value{GDBN} configurations in separate
22602 directories is to configure @value{GDBN} for cross-compiling (where
22603 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22604 programs that run on another machine---the @dfn{target}).
22605 You specify a cross-debugging target by
22606 giving the @samp{--target=@var{target}} option to @file{configure}.
22608 When you run @code{make} to build a program or library, you must run
22609 it in a configured directory---whatever directory you were in when you
22610 called @file{configure} (or one of its subdirectories).
22612 The @code{Makefile} that @file{configure} generates in each source
22613 directory also runs recursively. If you type @code{make} in a source
22614 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22615 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22616 will build all the required libraries, and then build GDB.
22618 When you have multiple hosts or targets configured in separate
22619 directories, you can run @code{make} on them in parallel (for example,
22620 if they are NFS-mounted on each of the hosts); they will not interfere
22624 @section Specifying Names for Hosts and Targets
22626 The specifications used for hosts and targets in the @file{configure}
22627 script are based on a three-part naming scheme, but some short predefined
22628 aliases are also supported. The full naming scheme encodes three pieces
22629 of information in the following pattern:
22632 @var{architecture}-@var{vendor}-@var{os}
22635 For example, you can use the alias @code{sun4} as a @var{host} argument,
22636 or as the value for @var{target} in a @code{--target=@var{target}}
22637 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22639 The @file{configure} script accompanying @value{GDBN} does not provide
22640 any query facility to list all supported host and target names or
22641 aliases. @file{configure} calls the Bourne shell script
22642 @code{config.sub} to map abbreviations to full names; you can read the
22643 script, if you wish, or you can use it to test your guesses on
22644 abbreviations---for example:
22647 % sh config.sub i386-linux
22649 % sh config.sub alpha-linux
22650 alpha-unknown-linux-gnu
22651 % sh config.sub hp9k700
22653 % sh config.sub sun4
22654 sparc-sun-sunos4.1.1
22655 % sh config.sub sun3
22656 m68k-sun-sunos4.1.1
22657 % sh config.sub i986v
22658 Invalid configuration `i986v': machine `i986v' not recognized
22662 @code{config.sub} is also distributed in the @value{GDBN} source
22663 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22665 @node Configure Options
22666 @section @file{configure} Options
22668 Here is a summary of the @file{configure} options and arguments that
22669 are most often useful for building @value{GDBN}. @file{configure} also has
22670 several other options not listed here. @inforef{What Configure
22671 Does,,configure.info}, for a full explanation of @file{configure}.
22674 configure @r{[}--help@r{]}
22675 @r{[}--prefix=@var{dir}@r{]}
22676 @r{[}--exec-prefix=@var{dir}@r{]}
22677 @r{[}--srcdir=@var{dirname}@r{]}
22678 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22679 @r{[}--target=@var{target}@r{]}
22684 You may introduce options with a single @samp{-} rather than
22685 @samp{--} if you prefer; but you may abbreviate option names if you use
22690 Display a quick summary of how to invoke @file{configure}.
22692 @item --prefix=@var{dir}
22693 Configure the source to install programs and files under directory
22696 @item --exec-prefix=@var{dir}
22697 Configure the source to install programs under directory
22700 @c avoid splitting the warning from the explanation:
22702 @item --srcdir=@var{dirname}
22703 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22704 @code{make} that implements the @code{VPATH} feature.}@*
22705 Use this option to make configurations in directories separate from the
22706 @value{GDBN} source directories. Among other things, you can use this to
22707 build (or maintain) several configurations simultaneously, in separate
22708 directories. @file{configure} writes configuration-specific files in
22709 the current directory, but arranges for them to use the source in the
22710 directory @var{dirname}. @file{configure} creates directories under
22711 the working directory in parallel to the source directories below
22714 @item --norecursion
22715 Configure only the directory level where @file{configure} is executed; do not
22716 propagate configuration to subdirectories.
22718 @item --target=@var{target}
22719 Configure @value{GDBN} for cross-debugging programs running on the specified
22720 @var{target}. Without this option, @value{GDBN} is configured to debug
22721 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22723 There is no convenient way to generate a list of all available targets.
22725 @item @var{host} @dots{}
22726 Configure @value{GDBN} to run on the specified @var{host}.
22728 There is no convenient way to generate a list of all available hosts.
22731 There are many other options available as well, but they are generally
22732 needed for special purposes only.
22734 @node Maintenance Commands
22735 @appendix Maintenance Commands
22736 @cindex maintenance commands
22737 @cindex internal commands
22739 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22740 includes a number of commands intended for @value{GDBN} developers,
22741 that are not documented elsewhere in this manual. These commands are
22742 provided here for reference. (For commands that turn on debugging
22743 messages, see @ref{Debugging Output}.)
22746 @kindex maint agent
22747 @item maint agent @var{expression}
22748 Translate the given @var{expression} into remote agent bytecodes.
22749 This command is useful for debugging the Agent Expression mechanism
22750 (@pxref{Agent Expressions}).
22752 @kindex maint info breakpoints
22753 @item @anchor{maint info breakpoints}maint info breakpoints
22754 Using the same format as @samp{info breakpoints}, display both the
22755 breakpoints you've set explicitly, and those @value{GDBN} is using for
22756 internal purposes. Internal breakpoints are shown with negative
22757 breakpoint numbers. The type column identifies what kind of breakpoint
22762 Normal, explicitly set breakpoint.
22765 Normal, explicitly set watchpoint.
22768 Internal breakpoint, used to handle correctly stepping through
22769 @code{longjmp} calls.
22771 @item longjmp resume
22772 Internal breakpoint at the target of a @code{longjmp}.
22775 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22778 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22781 Shared library events.
22785 @kindex maint check-symtabs
22786 @item maint check-symtabs
22787 Check the consistency of psymtabs and symtabs.
22789 @kindex maint cplus first_component
22790 @item maint cplus first_component @var{name}
22791 Print the first C@t{++} class/namespace component of @var{name}.
22793 @kindex maint cplus namespace
22794 @item maint cplus namespace
22795 Print the list of possible C@t{++} namespaces.
22797 @kindex maint demangle
22798 @item maint demangle @var{name}
22799 Demangle a C@t{++} or Objective-C mangled @var{name}.
22801 @kindex maint deprecate
22802 @kindex maint undeprecate
22803 @cindex deprecated commands
22804 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22805 @itemx maint undeprecate @var{command}
22806 Deprecate or undeprecate the named @var{command}. Deprecated commands
22807 cause @value{GDBN} to issue a warning when you use them. The optional
22808 argument @var{replacement} says which newer command should be used in
22809 favor of the deprecated one; if it is given, @value{GDBN} will mention
22810 the replacement as part of the warning.
22812 @kindex maint dump-me
22813 @item maint dump-me
22814 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22815 Cause a fatal signal in the debugger and force it to dump its core.
22816 This is supported only on systems which support aborting a program
22817 with the @code{SIGQUIT} signal.
22819 @kindex maint internal-error
22820 @kindex maint internal-warning
22821 @item maint internal-error @r{[}@var{message-text}@r{]}
22822 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22823 Cause @value{GDBN} to call the internal function @code{internal_error}
22824 or @code{internal_warning} and hence behave as though an internal error
22825 or internal warning has been detected. In addition to reporting the
22826 internal problem, these functions give the user the opportunity to
22827 either quit @value{GDBN} or create a core file of the current
22828 @value{GDBN} session.
22830 These commands take an optional parameter @var{message-text} that is
22831 used as the text of the error or warning message.
22833 Here's an example of using @code{internal-error}:
22836 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22837 @dots{}/maint.c:121: internal-error: testing, 1, 2
22838 A problem internal to GDB has been detected. Further
22839 debugging may prove unreliable.
22840 Quit this debugging session? (y or n) @kbd{n}
22841 Create a core file? (y or n) @kbd{n}
22845 @kindex maint packet
22846 @item maint packet @var{text}
22847 If @value{GDBN} is talking to an inferior via the serial protocol,
22848 then this command sends the string @var{text} to the inferior, and
22849 displays the response packet. @value{GDBN} supplies the initial
22850 @samp{$} character, the terminating @samp{#} character, and the
22853 @kindex maint print architecture
22854 @item maint print architecture @r{[}@var{file}@r{]}
22855 Print the entire architecture configuration. The optional argument
22856 @var{file} names the file where the output goes.
22858 @kindex maint print c-tdesc
22859 @item maint print c-tdesc
22860 Print the current target description (@pxref{Target Descriptions}) as
22861 a C source file. The created source file can be used in @value{GDBN}
22862 when an XML parser is not available to parse the description.
22864 @kindex maint print dummy-frames
22865 @item maint print dummy-frames
22866 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22869 (@value{GDBP}) @kbd{b add}
22871 (@value{GDBP}) @kbd{print add(2,3)}
22872 Breakpoint 2, add (a=2, b=3) at @dots{}
22874 The program being debugged stopped while in a function called from GDB.
22876 (@value{GDBP}) @kbd{maint print dummy-frames}
22877 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22878 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22879 call_lo=0x01014000 call_hi=0x01014001
22883 Takes an optional file parameter.
22885 @kindex maint print registers
22886 @kindex maint print raw-registers
22887 @kindex maint print cooked-registers
22888 @kindex maint print register-groups
22889 @item maint print registers @r{[}@var{file}@r{]}
22890 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22891 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22892 @itemx maint print register-groups @r{[}@var{file}@r{]}
22893 Print @value{GDBN}'s internal register data structures.
22895 The command @code{maint print raw-registers} includes the contents of
22896 the raw register cache; the command @code{maint print cooked-registers}
22897 includes the (cooked) value of all registers; and the command
22898 @code{maint print register-groups} includes the groups that each
22899 register is a member of. @xref{Registers,, Registers, gdbint,
22900 @value{GDBN} Internals}.
22902 These commands take an optional parameter, a file name to which to
22903 write the information.
22905 @kindex maint print reggroups
22906 @item maint print reggroups @r{[}@var{file}@r{]}
22907 Print @value{GDBN}'s internal register group data structures. The
22908 optional argument @var{file} tells to what file to write the
22911 The register groups info looks like this:
22914 (@value{GDBP}) @kbd{maint print reggroups}
22927 This command forces @value{GDBN} to flush its internal register cache.
22929 @kindex maint print objfiles
22930 @cindex info for known object files
22931 @item maint print objfiles
22932 Print a dump of all known object files. For each object file, this
22933 command prints its name, address in memory, and all of its psymtabs
22936 @kindex maint print statistics
22937 @cindex bcache statistics
22938 @item maint print statistics
22939 This command prints, for each object file in the program, various data
22940 about that object file followed by the byte cache (@dfn{bcache})
22941 statistics for the object file. The objfile data includes the number
22942 of minimal, partial, full, and stabs symbols, the number of types
22943 defined by the objfile, the number of as yet unexpanded psym tables,
22944 the number of line tables and string tables, and the amount of memory
22945 used by the various tables. The bcache statistics include the counts,
22946 sizes, and counts of duplicates of all and unique objects, max,
22947 average, and median entry size, total memory used and its overhead and
22948 savings, and various measures of the hash table size and chain
22951 @kindex maint print target-stack
22952 @cindex target stack description
22953 @item maint print target-stack
22954 A @dfn{target} is an interface between the debugger and a particular
22955 kind of file or process. Targets can be stacked in @dfn{strata},
22956 so that more than one target can potentially respond to a request.
22957 In particular, memory accesses will walk down the stack of targets
22958 until they find a target that is interested in handling that particular
22961 This command prints a short description of each layer that was pushed on
22962 the @dfn{target stack}, starting from the top layer down to the bottom one.
22964 @kindex maint print type
22965 @cindex type chain of a data type
22966 @item maint print type @var{expr}
22967 Print the type chain for a type specified by @var{expr}. The argument
22968 can be either a type name or a symbol. If it is a symbol, the type of
22969 that symbol is described. The type chain produced by this command is
22970 a recursive definition of the data type as stored in @value{GDBN}'s
22971 data structures, including its flags and contained types.
22973 @kindex maint set dwarf2 max-cache-age
22974 @kindex maint show dwarf2 max-cache-age
22975 @item maint set dwarf2 max-cache-age
22976 @itemx maint show dwarf2 max-cache-age
22977 Control the DWARF 2 compilation unit cache.
22979 @cindex DWARF 2 compilation units cache
22980 In object files with inter-compilation-unit references, such as those
22981 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22982 reader needs to frequently refer to previously read compilation units.
22983 This setting controls how long a compilation unit will remain in the
22984 cache if it is not referenced. A higher limit means that cached
22985 compilation units will be stored in memory longer, and more total
22986 memory will be used. Setting it to zero disables caching, which will
22987 slow down @value{GDBN} startup, but reduce memory consumption.
22989 @kindex maint set profile
22990 @kindex maint show profile
22991 @cindex profiling GDB
22992 @item maint set profile
22993 @itemx maint show profile
22994 Control profiling of @value{GDBN}.
22996 Profiling will be disabled until you use the @samp{maint set profile}
22997 command to enable it. When you enable profiling, the system will begin
22998 collecting timing and execution count data; when you disable profiling or
22999 exit @value{GDBN}, the results will be written to a log file. Remember that
23000 if you use profiling, @value{GDBN} will overwrite the profiling log file
23001 (often called @file{gmon.out}). If you have a record of important profiling
23002 data in a @file{gmon.out} file, be sure to move it to a safe location.
23004 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
23005 compiled with the @samp{-pg} compiler option.
23007 @kindex maint show-debug-regs
23008 @cindex x86 hardware debug registers
23009 @item maint show-debug-regs
23010 Control whether to show variables that mirror the x86 hardware debug
23011 registers. Use @code{ON} to enable, @code{OFF} to disable. If
23012 enabled, the debug registers values are shown when @value{GDBN} inserts or
23013 removes a hardware breakpoint or watchpoint, and when the inferior
23014 triggers a hardware-assisted breakpoint or watchpoint.
23016 @kindex maint space
23017 @cindex memory used by commands
23019 Control whether to display memory usage for each command. If set to a
23020 nonzero value, @value{GDBN} will display how much memory each command
23021 took, following the command's own output. This can also be requested
23022 by invoking @value{GDBN} with the @option{--statistics} command-line
23023 switch (@pxref{Mode Options}).
23026 @cindex time of command execution
23028 Control whether to display the execution time for each command. If
23029 set to a nonzero value, @value{GDBN} will display how much time it
23030 took to execute each command, following the command's own output.
23031 This can also be requested by invoking @value{GDBN} with the
23032 @option{--statistics} command-line switch (@pxref{Mode Options}).
23034 @kindex maint translate-address
23035 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
23036 Find the symbol stored at the location specified by the address
23037 @var{addr} and an optional section name @var{section}. If found,
23038 @value{GDBN} prints the name of the closest symbol and an offset from
23039 the symbol's location to the specified address. This is similar to
23040 the @code{info address} command (@pxref{Symbols}), except that this
23041 command also allows to find symbols in other sections.
23045 The following command is useful for non-interactive invocations of
23046 @value{GDBN}, such as in the test suite.
23049 @item set watchdog @var{nsec}
23050 @kindex set watchdog
23051 @cindex watchdog timer
23052 @cindex timeout for commands
23053 Set the maximum number of seconds @value{GDBN} will wait for the
23054 target operation to finish. If this time expires, @value{GDBN}
23055 reports and error and the command is aborted.
23057 @item show watchdog
23058 Show the current setting of the target wait timeout.
23061 @node Remote Protocol
23062 @appendix @value{GDBN} Remote Serial Protocol
23067 * Stop Reply Packets::
23068 * General Query Packets::
23069 * Register Packet Format::
23070 * Tracepoint Packets::
23071 * Host I/O Packets::
23074 * File-I/O Remote Protocol Extension::
23075 * Library List Format::
23076 * Memory Map Format::
23082 There may be occasions when you need to know something about the
23083 protocol---for example, if there is only one serial port to your target
23084 machine, you might want your program to do something special if it
23085 recognizes a packet meant for @value{GDBN}.
23087 In the examples below, @samp{->} and @samp{<-} are used to indicate
23088 transmitted and received data, respectively.
23090 @cindex protocol, @value{GDBN} remote serial
23091 @cindex serial protocol, @value{GDBN} remote
23092 @cindex remote serial protocol
23093 All @value{GDBN} commands and responses (other than acknowledgments) are
23094 sent as a @var{packet}. A @var{packet} is introduced with the character
23095 @samp{$}, the actual @var{packet-data}, and the terminating character
23096 @samp{#} followed by a two-digit @var{checksum}:
23099 @code{$}@var{packet-data}@code{#}@var{checksum}
23103 @cindex checksum, for @value{GDBN} remote
23105 The two-digit @var{checksum} is computed as the modulo 256 sum of all
23106 characters between the leading @samp{$} and the trailing @samp{#} (an
23107 eight bit unsigned checksum).
23109 Implementors should note that prior to @value{GDBN} 5.0 the protocol
23110 specification also included an optional two-digit @var{sequence-id}:
23113 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
23116 @cindex sequence-id, for @value{GDBN} remote
23118 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
23119 has never output @var{sequence-id}s. Stubs that handle packets added
23120 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
23122 @cindex acknowledgment, for @value{GDBN} remote
23123 When either the host or the target machine receives a packet, the first
23124 response expected is an acknowledgment: either @samp{+} (to indicate
23125 the package was received correctly) or @samp{-} (to request
23129 -> @code{$}@var{packet-data}@code{#}@var{checksum}
23134 The host (@value{GDBN}) sends @var{command}s, and the target (the
23135 debugging stub incorporated in your program) sends a @var{response}. In
23136 the case of step and continue @var{command}s, the response is only sent
23137 when the operation has completed (the target has again stopped).
23139 @var{packet-data} consists of a sequence of characters with the
23140 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
23143 @cindex remote protocol, field separator
23144 Fields within the packet should be separated using @samp{,} @samp{;} or
23145 @samp{:}. Except where otherwise noted all numbers are represented in
23146 @sc{hex} with leading zeros suppressed.
23148 Implementors should note that prior to @value{GDBN} 5.0, the character
23149 @samp{:} could not appear as the third character in a packet (as it
23150 would potentially conflict with the @var{sequence-id}).
23152 @cindex remote protocol, binary data
23153 @anchor{Binary Data}
23154 Binary data in most packets is encoded either as two hexadecimal
23155 digits per byte of binary data. This allowed the traditional remote
23156 protocol to work over connections which were only seven-bit clean.
23157 Some packets designed more recently assume an eight-bit clean
23158 connection, and use a more efficient encoding to send and receive
23161 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
23162 as an escape character. Any escaped byte is transmitted as the escape
23163 character followed by the original character XORed with @code{0x20}.
23164 For example, the byte @code{0x7d} would be transmitted as the two
23165 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
23166 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
23167 @samp{@}}) must always be escaped. Responses sent by the stub
23168 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
23169 is not interpreted as the start of a run-length encoded sequence
23172 Response @var{data} can be run-length encoded to save space.
23173 Run-length encoding replaces runs of identical characters with one
23174 instance of the repeated character, followed by a @samp{*} and a
23175 repeat count. The repeat count is itself sent encoded, to avoid
23176 binary characters in @var{data}: a value of @var{n} is sent as
23177 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
23178 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
23179 code 32) for a repeat count of 3. (This is because run-length
23180 encoding starts to win for counts 3 or more.) Thus, for example,
23181 @samp{0* } is a run-length encoding of ``0000'': the space character
23182 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
23185 The printable characters @samp{#} and @samp{$} or with a numeric value
23186 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
23187 seven repeats (@samp{$}) can be expanded using a repeat count of only
23188 five (@samp{"}). For example, @samp{00000000} can be encoded as
23191 The error response returned for some packets includes a two character
23192 error number. That number is not well defined.
23194 @cindex empty response, for unsupported packets
23195 For any @var{command} not supported by the stub, an empty response
23196 (@samp{$#00}) should be returned. That way it is possible to extend the
23197 protocol. A newer @value{GDBN} can tell if a packet is supported based
23200 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
23201 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
23207 The following table provides a complete list of all currently defined
23208 @var{command}s and their corresponding response @var{data}.
23209 @xref{File-I/O Remote Protocol Extension}, for details about the File
23210 I/O extension of the remote protocol.
23212 Each packet's description has a template showing the packet's overall
23213 syntax, followed by an explanation of the packet's meaning. We
23214 include spaces in some of the templates for clarity; these are not
23215 part of the packet's syntax. No @value{GDBN} packet uses spaces to
23216 separate its components. For example, a template like @samp{foo
23217 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
23218 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
23219 @var{baz}. @value{GDBN} does not transmit a space character between the
23220 @samp{foo} and the @var{bar}, or between the @var{bar} and the
23223 Note that all packet forms beginning with an upper- or lower-case
23224 letter, other than those described here, are reserved for future use.
23226 Here are the packet descriptions.
23231 @cindex @samp{!} packet
23232 Enable extended mode. In extended mode, the remote server is made
23233 persistent. The @samp{R} packet is used to restart the program being
23239 The remote target both supports and has enabled extended mode.
23243 @cindex @samp{?} packet
23244 Indicate the reason the target halted. The reply is the same as for
23248 @xref{Stop Reply Packets}, for the reply specifications.
23250 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
23251 @cindex @samp{A} packet
23252 Initialized @code{argv[]} array passed into program. @var{arglen}
23253 specifies the number of bytes in the hex encoded byte stream
23254 @var{arg}. See @code{gdbserver} for more details.
23259 The arguments were set.
23265 @cindex @samp{b} packet
23266 (Don't use this packet; its behavior is not well-defined.)
23267 Change the serial line speed to @var{baud}.
23269 JTC: @emph{When does the transport layer state change? When it's
23270 received, or after the ACK is transmitted. In either case, there are
23271 problems if the command or the acknowledgment packet is dropped.}
23273 Stan: @emph{If people really wanted to add something like this, and get
23274 it working for the first time, they ought to modify ser-unix.c to send
23275 some kind of out-of-band message to a specially-setup stub and have the
23276 switch happen "in between" packets, so that from remote protocol's point
23277 of view, nothing actually happened.}
23279 @item B @var{addr},@var{mode}
23280 @cindex @samp{B} packet
23281 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23282 breakpoint at @var{addr}.
23284 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23285 (@pxref{insert breakpoint or watchpoint packet}).
23287 @item c @r{[}@var{addr}@r{]}
23288 @cindex @samp{c} packet
23289 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23290 resume at current address.
23293 @xref{Stop Reply Packets}, for the reply specifications.
23295 @item C @var{sig}@r{[};@var{addr}@r{]}
23296 @cindex @samp{C} packet
23297 Continue with signal @var{sig} (hex signal number). If
23298 @samp{;@var{addr}} is omitted, resume at same address.
23301 @xref{Stop Reply Packets}, for the reply specifications.
23304 @cindex @samp{d} packet
23307 Don't use this packet; instead, define a general set packet
23308 (@pxref{General Query Packets}).
23311 @cindex @samp{D} packet
23312 Detach @value{GDBN} from the remote system. Sent to the remote target
23313 before @value{GDBN} disconnects via the @code{detach} command.
23323 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23324 @cindex @samp{F} packet
23325 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23326 This is part of the File-I/O protocol extension. @xref{File-I/O
23327 Remote Protocol Extension}, for the specification.
23330 @anchor{read registers packet}
23331 @cindex @samp{g} packet
23332 Read general registers.
23336 @item @var{XX@dots{}}
23337 Each byte of register data is described by two hex digits. The bytes
23338 with the register are transmitted in target byte order. The size of
23339 each register and their position within the @samp{g} packet are
23340 determined by the @value{GDBN} internal gdbarch functions
23341 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
23342 specification of several standard @samp{g} packets is specified below.
23347 @item G @var{XX@dots{}}
23348 @cindex @samp{G} packet
23349 Write general registers. @xref{read registers packet}, for a
23350 description of the @var{XX@dots{}} data.
23360 @item H @var{c} @var{t}
23361 @cindex @samp{H} packet
23362 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23363 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23364 should be @samp{c} for step and continue operations, @samp{g} for other
23365 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23366 the threads, a thread number, or @samp{0} which means pick any thread.
23377 @c 'H': How restrictive (or permissive) is the thread model. If a
23378 @c thread is selected and stopped, are other threads allowed
23379 @c to continue to execute? As I mentioned above, I think the
23380 @c semantics of each command when a thread is selected must be
23381 @c described. For example:
23383 @c 'g': If the stub supports threads and a specific thread is
23384 @c selected, returns the register block from that thread;
23385 @c otherwise returns current registers.
23387 @c 'G' If the stub supports threads and a specific thread is
23388 @c selected, sets the registers of the register block of
23389 @c that thread; otherwise sets current registers.
23391 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23392 @anchor{cycle step packet}
23393 @cindex @samp{i} packet
23394 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23395 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23396 step starting at that address.
23399 @cindex @samp{I} packet
23400 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23404 @cindex @samp{k} packet
23407 FIXME: @emph{There is no description of how to operate when a specific
23408 thread context has been selected (i.e.@: does 'k' kill only that
23411 @item m @var{addr},@var{length}
23412 @cindex @samp{m} packet
23413 Read @var{length} bytes of memory starting at address @var{addr}.
23414 Note that @var{addr} may not be aligned to any particular boundary.
23416 The stub need not use any particular size or alignment when gathering
23417 data from memory for the response; even if @var{addr} is word-aligned
23418 and @var{length} is a multiple of the word size, the stub is free to
23419 use byte accesses, or not. For this reason, this packet may not be
23420 suitable for accessing memory-mapped I/O devices.
23421 @cindex alignment of remote memory accesses
23422 @cindex size of remote memory accesses
23423 @cindex memory, alignment and size of remote accesses
23427 @item @var{XX@dots{}}
23428 Memory contents; each byte is transmitted as a two-digit hexadecimal
23429 number. The reply may contain fewer bytes than requested if the
23430 server was able to read only part of the region of memory.
23435 @item M @var{addr},@var{length}:@var{XX@dots{}}
23436 @cindex @samp{M} packet
23437 Write @var{length} bytes of memory starting at address @var{addr}.
23438 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23439 hexadecimal number.
23446 for an error (this includes the case where only part of the data was
23451 @cindex @samp{p} packet
23452 Read the value of register @var{n}; @var{n} is in hex.
23453 @xref{read registers packet}, for a description of how the returned
23454 register value is encoded.
23458 @item @var{XX@dots{}}
23459 the register's value
23463 Indicating an unrecognized @var{query}.
23466 @item P @var{n@dots{}}=@var{r@dots{}}
23467 @anchor{write register packet}
23468 @cindex @samp{P} packet
23469 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23470 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23471 digits for each byte in the register (target byte order).
23481 @item q @var{name} @var{params}@dots{}
23482 @itemx Q @var{name} @var{params}@dots{}
23483 @cindex @samp{q} packet
23484 @cindex @samp{Q} packet
23485 General query (@samp{q}) and set (@samp{Q}). These packets are
23486 described fully in @ref{General Query Packets}.
23489 @cindex @samp{r} packet
23490 Reset the entire system.
23492 Don't use this packet; use the @samp{R} packet instead.
23495 @cindex @samp{R} packet
23496 Restart the program being debugged. @var{XX}, while needed, is ignored.
23497 This packet is only available in extended mode.
23499 The @samp{R} packet has no reply.
23501 @item s @r{[}@var{addr}@r{]}
23502 @cindex @samp{s} packet
23503 Single step. @var{addr} is the address at which to resume. If
23504 @var{addr} is omitted, resume at same address.
23507 @xref{Stop Reply Packets}, for the reply specifications.
23509 @item S @var{sig}@r{[};@var{addr}@r{]}
23510 @anchor{step with signal packet}
23511 @cindex @samp{S} packet
23512 Step with signal. This is analogous to the @samp{C} packet, but
23513 requests a single-step, rather than a normal resumption of execution.
23516 @xref{Stop Reply Packets}, for the reply specifications.
23518 @item t @var{addr}:@var{PP},@var{MM}
23519 @cindex @samp{t} packet
23520 Search backwards starting at address @var{addr} for a match with pattern
23521 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23522 @var{addr} must be at least 3 digits.
23525 @cindex @samp{T} packet
23526 Find out if the thread XX is alive.
23531 thread is still alive
23537 Packets starting with @samp{v} are identified by a multi-letter name,
23538 up to the first @samp{;} or @samp{?} (or the end of the packet).
23540 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23541 @cindex @samp{vCont} packet
23542 Resume the inferior, specifying different actions for each thread.
23543 If an action is specified with no @var{tid}, then it is applied to any
23544 threads that don't have a specific action specified; if no default action is
23545 specified then other threads should remain stopped. Specifying multiple
23546 default actions is an error; specifying no actions is also an error.
23547 Thread IDs are specified in hexadecimal. Currently supported actions are:
23553 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23557 Step with signal @var{sig}. @var{sig} should be two hex digits.
23560 The optional @var{addr} argument normally associated with these packets is
23561 not supported in @samp{vCont}.
23564 @xref{Stop Reply Packets}, for the reply specifications.
23567 @cindex @samp{vCont?} packet
23568 Request a list of actions supported by the @samp{vCont} packet.
23572 @item vCont@r{[};@var{action}@dots{}@r{]}
23573 The @samp{vCont} packet is supported. Each @var{action} is a supported
23574 command in the @samp{vCont} packet.
23576 The @samp{vCont} packet is not supported.
23579 @item vFile:@var{operation}:@var{parameter}@dots{}
23580 @cindex @samp{vFile} packet
23581 Perform a file operation on the target system. For details,
23582 see @ref{Host I/O Packets}.
23584 @item vFlashErase:@var{addr},@var{length}
23585 @cindex @samp{vFlashErase} packet
23586 Direct the stub to erase @var{length} bytes of flash starting at
23587 @var{addr}. The region may enclose any number of flash blocks, but
23588 its start and end must fall on block boundaries, as indicated by the
23589 flash block size appearing in the memory map (@pxref{Memory Map
23590 Format}). @value{GDBN} groups flash memory programming operations
23591 together, and sends a @samp{vFlashDone} request after each group; the
23592 stub is allowed to delay erase operation until the @samp{vFlashDone}
23593 packet is received.
23603 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23604 @cindex @samp{vFlashWrite} packet
23605 Direct the stub to write data to flash address @var{addr}. The data
23606 is passed in binary form using the same encoding as for the @samp{X}
23607 packet (@pxref{Binary Data}). The memory ranges specified by
23608 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23609 not overlap, and must appear in order of increasing addresses
23610 (although @samp{vFlashErase} packets for higher addresses may already
23611 have been received; the ordering is guaranteed only between
23612 @samp{vFlashWrite} packets). If a packet writes to an address that was
23613 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23614 target-specific method, the results are unpredictable.
23622 for vFlashWrite addressing non-flash memory
23628 @cindex @samp{vFlashDone} packet
23629 Indicate to the stub that flash programming operation is finished.
23630 The stub is permitted to delay or batch the effects of a group of
23631 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23632 @samp{vFlashDone} packet is received. The contents of the affected
23633 regions of flash memory are unpredictable until the @samp{vFlashDone}
23634 request is completed.
23636 @item X @var{addr},@var{length}:@var{XX@dots{}}
23638 @cindex @samp{X} packet
23639 Write data to memory, where the data is transmitted in binary.
23640 @var{addr} is address, @var{length} is number of bytes,
23641 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23651 @item z @var{type},@var{addr},@var{length}
23652 @itemx Z @var{type},@var{addr},@var{length}
23653 @anchor{insert breakpoint or watchpoint packet}
23654 @cindex @samp{z} packet
23655 @cindex @samp{Z} packets
23656 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23657 watchpoint starting at address @var{address} and covering the next
23658 @var{length} bytes.
23660 Each breakpoint and watchpoint packet @var{type} is documented
23663 @emph{Implementation notes: A remote target shall return an empty string
23664 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23665 remote target shall support either both or neither of a given
23666 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23667 avoid potential problems with duplicate packets, the operations should
23668 be implemented in an idempotent way.}
23670 @item z0,@var{addr},@var{length}
23671 @itemx Z0,@var{addr},@var{length}
23672 @cindex @samp{z0} packet
23673 @cindex @samp{Z0} packet
23674 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23675 @var{addr} of size @var{length}.
23677 A memory breakpoint is implemented by replacing the instruction at
23678 @var{addr} with a software breakpoint or trap instruction. The
23679 @var{length} is used by targets that indicates the size of the
23680 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23681 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23683 @emph{Implementation note: It is possible for a target to copy or move
23684 code that contains memory breakpoints (e.g., when implementing
23685 overlays). The behavior of this packet, in the presence of such a
23686 target, is not defined.}
23698 @item z1,@var{addr},@var{length}
23699 @itemx Z1,@var{addr},@var{length}
23700 @cindex @samp{z1} packet
23701 @cindex @samp{Z1} packet
23702 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23703 address @var{addr} of size @var{length}.
23705 A hardware breakpoint is implemented using a mechanism that is not
23706 dependant on being able to modify the target's memory.
23708 @emph{Implementation note: A hardware breakpoint is not affected by code
23721 @item z2,@var{addr},@var{length}
23722 @itemx Z2,@var{addr},@var{length}
23723 @cindex @samp{z2} packet
23724 @cindex @samp{Z2} packet
23725 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23737 @item z3,@var{addr},@var{length}
23738 @itemx Z3,@var{addr},@var{length}
23739 @cindex @samp{z3} packet
23740 @cindex @samp{Z3} packet
23741 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23753 @item z4,@var{addr},@var{length}
23754 @itemx Z4,@var{addr},@var{length}
23755 @cindex @samp{z4} packet
23756 @cindex @samp{Z4} packet
23757 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23771 @node Stop Reply Packets
23772 @section Stop Reply Packets
23773 @cindex stop reply packets
23775 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23776 receive any of the below as a reply. In the case of the @samp{C},
23777 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23778 when the target halts. In the below the exact meaning of @dfn{signal
23779 number} is defined by the header @file{include/gdb/signals.h} in the
23780 @value{GDBN} source code.
23782 As in the description of request packets, we include spaces in the
23783 reply templates for clarity; these are not part of the reply packet's
23784 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23790 The program received signal number @var{AA} (a two-digit hexadecimal
23791 number). This is equivalent to a @samp{T} response with no
23792 @var{n}:@var{r} pairs.
23794 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23795 @cindex @samp{T} packet reply
23796 The program received signal number @var{AA} (a two-digit hexadecimal
23797 number). This is equivalent to an @samp{S} response, except that the
23798 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23799 and other information directly in the stop reply packet, reducing
23800 round-trip latency. Single-step and breakpoint traps are reported
23801 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23805 If @var{n} is a hexadecimal number, it is a register number, and the
23806 corresponding @var{r} gives that register's value. @var{r} is a
23807 series of bytes in target byte order, with each byte given by a
23808 two-digit hex number.
23811 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23815 If @var{n} is a recognized @dfn{stop reason}, it describes a more
23816 specific event that stopped the target. The currently defined stop
23817 reasons are listed below. @var{aa} should be @samp{05}, the trap
23818 signal. At most one stop reason should be present.
23821 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23822 and go on to the next; this allows us to extend the protocol in the
23826 The currently defined stop reasons are:
23832 The packet indicates a watchpoint hit, and @var{r} is the data address, in
23835 @cindex shared library events, remote reply
23837 The packet indicates that the loaded libraries have changed.
23838 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
23839 list of loaded libraries. @var{r} is ignored.
23843 The process exited, and @var{AA} is the exit status. This is only
23844 applicable to certain targets.
23847 The process terminated with signal @var{AA}.
23849 @item O @var{XX}@dots{}
23850 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23851 written as the program's console output. This can happen at any time
23852 while the program is running and the debugger should continue to wait
23853 for @samp{W}, @samp{T}, etc.
23855 @item F @var{call-id},@var{parameter}@dots{}
23856 @var{call-id} is the identifier which says which host system call should
23857 be called. This is just the name of the function. Translation into the
23858 correct system call is only applicable as it's defined in @value{GDBN}.
23859 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
23862 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23863 this very system call.
23865 The target replies with this packet when it expects @value{GDBN} to
23866 call a host system call on behalf of the target. @value{GDBN} replies
23867 with an appropriate @samp{F} packet and keeps up waiting for the next
23868 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23869 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
23870 Protocol Extension}, for more details.
23874 @node General Query Packets
23875 @section General Query Packets
23876 @cindex remote query requests
23878 Packets starting with @samp{q} are @dfn{general query packets};
23879 packets starting with @samp{Q} are @dfn{general set packets}. General
23880 query and set packets are a semi-unified form for retrieving and
23881 sending information to and from the stub.
23883 The initial letter of a query or set packet is followed by a name
23884 indicating what sort of thing the packet applies to. For example,
23885 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23886 definitions with the stub. These packet names follow some
23891 The name must not contain commas, colons or semicolons.
23893 Most @value{GDBN} query and set packets have a leading upper case
23896 The names of custom vendor packets should use a company prefix, in
23897 lower case, followed by a period. For example, packets designed at
23898 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23899 foos) or @samp{Qacme.bar} (for setting bars).
23902 The name of a query or set packet should be separated from any
23903 parameters by a @samp{:}; the parameters themselves should be
23904 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23905 full packet name, and check for a separator or the end of the packet,
23906 in case two packet names share a common prefix. New packets should not begin
23907 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23908 packets predate these conventions, and have arguments without any terminator
23909 for the packet name; we suspect they are in widespread use in places that
23910 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23911 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23914 Like the descriptions of the other packets, each description here
23915 has a template showing the packet's overall syntax, followed by an
23916 explanation of the packet's meaning. We include spaces in some of the
23917 templates for clarity; these are not part of the packet's syntax. No
23918 @value{GDBN} packet uses spaces to separate its components.
23920 Here are the currently defined query and set packets:
23925 @cindex current thread, remote request
23926 @cindex @samp{qC} packet
23927 Return the current thread id.
23932 Where @var{pid} is an unsigned hexadecimal process id.
23933 @item @r{(anything else)}
23934 Any other reply implies the old pid.
23937 @item qCRC:@var{addr},@var{length}
23938 @cindex CRC of memory block, remote request
23939 @cindex @samp{qCRC} packet
23940 Compute the CRC checksum of a block of memory.
23944 An error (such as memory fault)
23945 @item C @var{crc32}
23946 The specified memory region's checksum is @var{crc32}.
23950 @itemx qsThreadInfo
23951 @cindex list active threads, remote request
23952 @cindex @samp{qfThreadInfo} packet
23953 @cindex @samp{qsThreadInfo} packet
23954 Obtain a list of all active thread ids from the target (OS). Since there
23955 may be too many active threads to fit into one reply packet, this query
23956 works iteratively: it may require more than one query/reply sequence to
23957 obtain the entire list of threads. The first query of the sequence will
23958 be the @samp{qfThreadInfo} query; subsequent queries in the
23959 sequence will be the @samp{qsThreadInfo} query.
23961 NOTE: This packet replaces the @samp{qL} query (see below).
23967 @item m @var{id},@var{id}@dots{}
23968 a comma-separated list of thread ids
23970 (lower case letter @samp{L}) denotes end of list.
23973 In response to each query, the target will reply with a list of one or
23974 more thread ids, in big-endian unsigned hex, separated by commas.
23975 @value{GDBN} will respond to each reply with a request for more thread
23976 ids (using the @samp{qs} form of the query), until the target responds
23977 with @samp{l} (lower-case el, for @dfn{last}).
23979 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23980 @cindex get thread-local storage address, remote request
23981 @cindex @samp{qGetTLSAddr} packet
23982 Fetch the address associated with thread local storage specified
23983 by @var{thread-id}, @var{offset}, and @var{lm}.
23985 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23986 thread for which to fetch the TLS address.
23988 @var{offset} is the (big endian, hex encoded) offset associated with the
23989 thread local variable. (This offset is obtained from the debug
23990 information associated with the variable.)
23992 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
23993 the load module associated with the thread local storage. For example,
23994 a @sc{gnu}/Linux system will pass the link map address of the shared
23995 object associated with the thread local storage under consideration.
23996 Other operating environments may choose to represent the load module
23997 differently, so the precise meaning of this parameter will vary.
24001 @item @var{XX}@dots{}
24002 Hex encoded (big endian) bytes representing the address of the thread
24003 local storage requested.
24006 An error occurred. @var{nn} are hex digits.
24009 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
24012 @item qL @var{startflag} @var{threadcount} @var{nextthread}
24013 Obtain thread information from RTOS. Where: @var{startflag} (one hex
24014 digit) is one to indicate the first query and zero to indicate a
24015 subsequent query; @var{threadcount} (two hex digits) is the maximum
24016 number of threads the response packet can contain; and @var{nextthread}
24017 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
24018 returned in the response as @var{argthread}.
24020 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
24024 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
24025 Where: @var{count} (two hex digits) is the number of threads being
24026 returned; @var{done} (one hex digit) is zero to indicate more threads
24027 and one indicates no further threads; @var{argthreadid} (eight hex
24028 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
24029 is a sequence of thread IDs from the target. @var{threadid} (eight hex
24030 digits). See @code{remote.c:parse_threadlist_response()}.
24034 @cindex section offsets, remote request
24035 @cindex @samp{qOffsets} packet
24036 Get section offsets that the target used when relocating the downloaded
24041 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
24042 Relocate the @code{Text} section by @var{xxx} from its original address.
24043 Relocate the @code{Data} section by @var{yyy} from its original address.
24044 If the object file format provides segment information (e.g.@: @sc{elf}
24045 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
24046 segments by the supplied offsets.
24048 @emph{Note: while a @code{Bss} offset may be included in the response,
24049 @value{GDBN} ignores this and instead applies the @code{Data} offset
24050 to the @code{Bss} section.}
24052 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
24053 Relocate the first segment of the object file, which conventionally
24054 contains program code, to a starting address of @var{xxx}. If
24055 @samp{DataSeg} is specified, relocate the second segment, which
24056 conventionally contains modifiable data, to a starting address of
24057 @var{yyy}. @value{GDBN} will report an error if the object file
24058 does not contain segment information, or does not contain at least
24059 as many segments as mentioned in the reply. Extra segments are
24060 kept at fixed offsets relative to the last relocated segment.
24063 @item qP @var{mode} @var{threadid}
24064 @cindex thread information, remote request
24065 @cindex @samp{qP} packet
24066 Returns information on @var{threadid}. Where: @var{mode} is a hex
24067 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
24069 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
24072 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
24074 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
24075 @cindex pass signals to inferior, remote request
24076 @cindex @samp{QPassSignals} packet
24077 @anchor{QPassSignals}
24078 Each listed @var{signal} should be passed directly to the inferior process.
24079 Signals are numbered identically to continue packets and stop replies
24080 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
24081 strictly greater than the previous item. These signals do not need to stop
24082 the inferior, or be reported to @value{GDBN}. All other signals should be
24083 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
24084 combine; any earlier @samp{QPassSignals} list is completely replaced by the
24085 new list. This packet improves performance when using @samp{handle
24086 @var{signal} nostop noprint pass}.
24091 The request succeeded.
24094 An error occurred. @var{nn} are hex digits.
24097 An empty reply indicates that @samp{QPassSignals} is not supported by
24101 Use of this packet is controlled by the @code{set remote pass-signals}
24102 command (@pxref{Remote Configuration, set remote pass-signals}).
24103 This packet is not probed by default; the remote stub must request it,
24104 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24106 @item qRcmd,@var{command}
24107 @cindex execute remote command, remote request
24108 @cindex @samp{qRcmd} packet
24109 @var{command} (hex encoded) is passed to the local interpreter for
24110 execution. Invalid commands should be reported using the output
24111 string. Before the final result packet, the target may also respond
24112 with a number of intermediate @samp{O@var{output}} console output
24113 packets. @emph{Implementors should note that providing access to a
24114 stubs's interpreter may have security implications}.
24119 A command response with no output.
24121 A command response with the hex encoded output string @var{OUTPUT}.
24123 Indicate a badly formed request.
24125 An empty reply indicates that @samp{qRcmd} is not recognized.
24128 (Note that the @code{qRcmd} packet's name is separated from the
24129 command by a @samp{,}, not a @samp{:}, contrary to the naming
24130 conventions above. Please don't use this packet as a model for new
24133 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
24134 @cindex supported packets, remote query
24135 @cindex features of the remote protocol
24136 @cindex @samp{qSupported} packet
24137 @anchor{qSupported}
24138 Tell the remote stub about features supported by @value{GDBN}, and
24139 query the stub for features it supports. This packet allows
24140 @value{GDBN} and the remote stub to take advantage of each others'
24141 features. @samp{qSupported} also consolidates multiple feature probes
24142 at startup, to improve @value{GDBN} performance---a single larger
24143 packet performs better than multiple smaller probe packets on
24144 high-latency links. Some features may enable behavior which must not
24145 be on by default, e.g.@: because it would confuse older clients or
24146 stubs. Other features may describe packets which could be
24147 automatically probed for, but are not. These features must be
24148 reported before @value{GDBN} will use them. This ``default
24149 unsupported'' behavior is not appropriate for all packets, but it
24150 helps to keep the initial connection time under control with new
24151 versions of @value{GDBN} which support increasing numbers of packets.
24155 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
24156 The stub supports or does not support each returned @var{stubfeature},
24157 depending on the form of each @var{stubfeature} (see below for the
24160 An empty reply indicates that @samp{qSupported} is not recognized,
24161 or that no features needed to be reported to @value{GDBN}.
24164 The allowed forms for each feature (either a @var{gdbfeature} in the
24165 @samp{qSupported} packet, or a @var{stubfeature} in the response)
24169 @item @var{name}=@var{value}
24170 The remote protocol feature @var{name} is supported, and associated
24171 with the specified @var{value}. The format of @var{value} depends
24172 on the feature, but it must not include a semicolon.
24174 The remote protocol feature @var{name} is supported, and does not
24175 need an associated value.
24177 The remote protocol feature @var{name} is not supported.
24179 The remote protocol feature @var{name} may be supported, and
24180 @value{GDBN} should auto-detect support in some other way when it is
24181 needed. This form will not be used for @var{gdbfeature} notifications,
24182 but may be used for @var{stubfeature} responses.
24185 Whenever the stub receives a @samp{qSupported} request, the
24186 supplied set of @value{GDBN} features should override any previous
24187 request. This allows @value{GDBN} to put the stub in a known
24188 state, even if the stub had previously been communicating with
24189 a different version of @value{GDBN}.
24191 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
24192 are defined yet. Stubs should ignore any unknown values for
24193 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
24194 packet supports receiving packets of unlimited length (earlier
24195 versions of @value{GDBN} may reject overly long responses). Values
24196 for @var{gdbfeature} may be defined in the future to let the stub take
24197 advantage of new features in @value{GDBN}, e.g.@: incompatible
24198 improvements in the remote protocol---support for unlimited length
24199 responses would be a @var{gdbfeature} example, if it were not implied by
24200 the @samp{qSupported} query. The stub's reply should be independent
24201 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
24202 describes all the features it supports, and then the stub replies with
24203 all the features it supports.
24205 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
24206 responses, as long as each response uses one of the standard forms.
24208 Some features are flags. A stub which supports a flag feature
24209 should respond with a @samp{+} form response. Other features
24210 require values, and the stub should respond with an @samp{=}
24213 Each feature has a default value, which @value{GDBN} will use if
24214 @samp{qSupported} is not available or if the feature is not mentioned
24215 in the @samp{qSupported} response. The default values are fixed; a
24216 stub is free to omit any feature responses that match the defaults.
24218 Not all features can be probed, but for those which can, the probing
24219 mechanism is useful: in some cases, a stub's internal
24220 architecture may not allow the protocol layer to know some information
24221 about the underlying target in advance. This is especially common in
24222 stubs which may be configured for multiple targets.
24224 These are the currently defined stub features and their properties:
24226 @multitable @columnfractions 0.35 0.2 0.12 0.2
24227 @c NOTE: The first row should be @headitem, but we do not yet require
24228 @c a new enough version of Texinfo (4.7) to use @headitem.
24230 @tab Value Required
24234 @item @samp{PacketSize}
24239 @item @samp{qXfer:auxv:read}
24244 @item @samp{qXfer:features:read}
24249 @item @samp{qXfer:libraries:read}
24254 @item @samp{qXfer:memory-map:read}
24259 @item @samp{qXfer:spu:read}
24264 @item @samp{qXfer:spu:write}
24269 @item @samp{QPassSignals}
24276 These are the currently defined stub features, in more detail:
24279 @cindex packet size, remote protocol
24280 @item PacketSize=@var{bytes}
24281 The remote stub can accept packets up to at least @var{bytes} in
24282 length. @value{GDBN} will send packets up to this size for bulk
24283 transfers, and will never send larger packets. This is a limit on the
24284 data characters in the packet, including the frame and checksum.
24285 There is no trailing NUL byte in a remote protocol packet; if the stub
24286 stores packets in a NUL-terminated format, it should allow an extra
24287 byte in its buffer for the NUL. If this stub feature is not supported,
24288 @value{GDBN} guesses based on the size of the @samp{g} packet response.
24290 @item qXfer:auxv:read
24291 The remote stub understands the @samp{qXfer:auxv:read} packet
24292 (@pxref{qXfer auxiliary vector read}).
24294 @item qXfer:features:read
24295 The remote stub understands the @samp{qXfer:features:read} packet
24296 (@pxref{qXfer target description read}).
24298 @item qXfer:libraries:read
24299 The remote stub understands the @samp{qXfer:libraries:read} packet
24300 (@pxref{qXfer library list read}).
24302 @item qXfer:memory-map:read
24303 The remote stub understands the @samp{qXfer:memory-map:read} packet
24304 (@pxref{qXfer memory map read}).
24306 @item qXfer:spu:read
24307 The remote stub understands the @samp{qXfer:spu:read} packet
24308 (@pxref{qXfer spu read}).
24310 @item qXfer:spu:write
24311 The remote stub understands the @samp{qXfer:spu:write} packet
24312 (@pxref{qXfer spu write}).
24315 The remote stub understands the @samp{QPassSignals} packet
24316 (@pxref{QPassSignals}).
24321 @cindex symbol lookup, remote request
24322 @cindex @samp{qSymbol} packet
24323 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24324 requests. Accept requests from the target for the values of symbols.
24329 The target does not need to look up any (more) symbols.
24330 @item qSymbol:@var{sym_name}
24331 The target requests the value of symbol @var{sym_name} (hex encoded).
24332 @value{GDBN} may provide the value by using the
24333 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24337 @item qSymbol:@var{sym_value}:@var{sym_name}
24338 Set the value of @var{sym_name} to @var{sym_value}.
24340 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24341 target has previously requested.
24343 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24344 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24350 The target does not need to look up any (more) symbols.
24351 @item qSymbol:@var{sym_name}
24352 The target requests the value of a new symbol @var{sym_name} (hex
24353 encoded). @value{GDBN} will continue to supply the values of symbols
24354 (if available), until the target ceases to request them.
24359 @xref{Tracepoint Packets}.
24361 @item qThreadExtraInfo,@var{id}
24362 @cindex thread attributes info, remote request
24363 @cindex @samp{qThreadExtraInfo} packet
24364 Obtain a printable string description of a thread's attributes from
24365 the target OS. @var{id} is a thread-id in big-endian hex. This
24366 string may contain anything that the target OS thinks is interesting
24367 for @value{GDBN} to tell the user about the thread. The string is
24368 displayed in @value{GDBN}'s @code{info threads} display. Some
24369 examples of possible thread extra info strings are @samp{Runnable}, or
24370 @samp{Blocked on Mutex}.
24374 @item @var{XX}@dots{}
24375 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
24376 comprising the printable string containing the extra information about
24377 the thread's attributes.
24380 (Note that the @code{qThreadExtraInfo} packet's name is separated from
24381 the command by a @samp{,}, not a @samp{:}, contrary to the naming
24382 conventions above. Please don't use this packet as a model for new
24390 @xref{Tracepoint Packets}.
24392 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
24393 @cindex read special object, remote request
24394 @cindex @samp{qXfer} packet
24395 @anchor{qXfer read}
24396 Read uninterpreted bytes from the target's special data area
24397 identified by the keyword @var{object}. Request @var{length} bytes
24398 starting at @var{offset} bytes into the data. The content and
24399 encoding of @var{annex} is specific to @var{object}; it can supply
24400 additional details about what data to access.
24402 Here are the specific requests of this form defined so far. All
24403 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
24404 formats, listed below.
24407 @item qXfer:auxv:read::@var{offset},@var{length}
24408 @anchor{qXfer auxiliary vector read}
24409 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
24410 auxiliary vector}. Note @var{annex} must be empty.
24412 This packet is not probed by default; the remote stub must request it,
24413 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24415 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
24416 @anchor{qXfer target description read}
24417 Access the @dfn{target description}. @xref{Target Descriptions}. The
24418 annex specifies which XML document to access. The main description is
24419 always loaded from the @samp{target.xml} annex.
24421 This packet is not probed by default; the remote stub must request it,
24422 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24424 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
24425 @anchor{qXfer library list read}
24426 Access the target's list of loaded libraries. @xref{Library List Format}.
24427 The annex part of the generic @samp{qXfer} packet must be empty
24428 (@pxref{qXfer read}).
24430 Targets which maintain a list of libraries in the program's memory do
24431 not need to implement this packet; it is designed for platforms where
24432 the operating system manages the list of loaded libraries.
24434 This packet is not probed by default; the remote stub must request it,
24435 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24437 @item qXfer:memory-map:read::@var{offset},@var{length}
24438 @anchor{qXfer memory map read}
24439 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
24440 annex part of the generic @samp{qXfer} packet must be empty
24441 (@pxref{qXfer read}).
24443 This packet is not probed by default; the remote stub must request it,
24444 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24446 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
24447 @anchor{qXfer spu read}
24448 Read contents of an @code{spufs} file on the target system. The
24449 annex specifies which file to read; it must be of the form
24450 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24451 in the target process, and @var{name} identifes the @code{spufs} file
24452 in that context to be accessed.
24454 This packet is not probed by default; the remote stub must request it,
24455 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24461 Data @var{data} (@pxref{Binary Data}) has been read from the
24462 target. There may be more data at a higher address (although
24463 it is permitted to return @samp{m} even for the last valid
24464 block of data, as long as at least one byte of data was read).
24465 @var{data} may have fewer bytes than the @var{length} in the
24469 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24470 There is no more data to be read. @var{data} may have fewer bytes
24471 than the @var{length} in the request.
24474 The @var{offset} in the request is at the end of the data.
24475 There is no more data to be read.
24478 The request was malformed, or @var{annex} was invalid.
24481 The offset was invalid, or there was an error encountered reading the data.
24482 @var{nn} is a hex-encoded @code{errno} value.
24485 An empty reply indicates the @var{object} string was not recognized by
24486 the stub, or that the object does not support reading.
24489 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24490 @cindex write data into object, remote request
24491 Write uninterpreted bytes into the target's special data area
24492 identified by the keyword @var{object}, starting at @var{offset} bytes
24493 into the data. @var{data}@dots{} is the binary-encoded data
24494 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24495 is specific to @var{object}; it can supply additional details about what data
24498 Here are the specific requests of this form defined so far. All
24499 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
24500 formats, listed below.
24503 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24504 @anchor{qXfer spu write}
24505 Write @var{data} to an @code{spufs} file on the target system. The
24506 annex specifies which file to write; it must be of the form
24507 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24508 in the target process, and @var{name} identifes the @code{spufs} file
24509 in that context to be accessed.
24511 This packet is not probed by default; the remote stub must request it,
24512 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24518 @var{nn} (hex encoded) is the number of bytes written.
24519 This may be fewer bytes than supplied in the request.
24522 The request was malformed, or @var{annex} was invalid.
24525 The offset was invalid, or there was an error encountered writing the data.
24526 @var{nn} is a hex-encoded @code{errno} value.
24529 An empty reply indicates the @var{object} string was not
24530 recognized by the stub, or that the object does not support writing.
24533 @item qXfer:@var{object}:@var{operation}:@dots{}
24534 Requests of this form may be added in the future. When a stub does
24535 not recognize the @var{object} keyword, or its support for
24536 @var{object} does not recognize the @var{operation} keyword, the stub
24537 must respond with an empty packet.
24541 @node Register Packet Format
24542 @section Register Packet Format
24544 The following @code{g}/@code{G} packets have previously been defined.
24545 In the below, some thirty-two bit registers are transferred as
24546 sixty-four bits. Those registers should be zero/sign extended (which?)
24547 to fill the space allocated. Register bytes are transferred in target
24548 byte order. The two nibbles within a register byte are transferred
24549 most-significant - least-significant.
24555 All registers are transferred as thirty-two bit quantities in the order:
24556 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24557 registers; fsr; fir; fp.
24561 All registers are transferred as sixty-four bit quantities (including
24562 thirty-two bit registers such as @code{sr}). The ordering is the same
24567 @node Tracepoint Packets
24568 @section Tracepoint Packets
24569 @cindex tracepoint packets
24570 @cindex packets, tracepoint
24572 Here we describe the packets @value{GDBN} uses to implement
24573 tracepoints (@pxref{Tracepoints}).
24577 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24578 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24579 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24580 the tracepoint is disabled. @var{step} is the tracepoint's step
24581 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24582 present, further @samp{QTDP} packets will follow to specify this
24583 tracepoint's actions.
24588 The packet was understood and carried out.
24590 The packet was not recognized.
24593 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24594 Define actions to be taken when a tracepoint is hit. @var{n} and
24595 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24596 this tracepoint. This packet may only be sent immediately after
24597 another @samp{QTDP} packet that ended with a @samp{-}. If the
24598 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24599 specifying more actions for this tracepoint.
24601 In the series of action packets for a given tracepoint, at most one
24602 can have an @samp{S} before its first @var{action}. If such a packet
24603 is sent, it and the following packets define ``while-stepping''
24604 actions. Any prior packets define ordinary actions --- that is, those
24605 taken when the tracepoint is first hit. If no action packet has an
24606 @samp{S}, then all the packets in the series specify ordinary
24607 tracepoint actions.
24609 The @samp{@var{action}@dots{}} portion of the packet is a series of
24610 actions, concatenated without separators. Each action has one of the
24616 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24617 a hexadecimal number whose @var{i}'th bit is set if register number
24618 @var{i} should be collected. (The least significant bit is numbered
24619 zero.) Note that @var{mask} may be any number of digits long; it may
24620 not fit in a 32-bit word.
24622 @item M @var{basereg},@var{offset},@var{len}
24623 Collect @var{len} bytes of memory starting at the address in register
24624 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24625 @samp{-1}, then the range has a fixed address: @var{offset} is the
24626 address of the lowest byte to collect. The @var{basereg},
24627 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24628 values (the @samp{-1} value for @var{basereg} is a special case).
24630 @item X @var{len},@var{expr}
24631 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24632 it directs. @var{expr} is an agent expression, as described in
24633 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24634 two-digit hex number in the packet; @var{len} is the number of bytes
24635 in the expression (and thus one-half the number of hex digits in the
24640 Any number of actions may be packed together in a single @samp{QTDP}
24641 packet, as long as the packet does not exceed the maximum packet
24642 length (400 bytes, for many stubs). There may be only one @samp{R}
24643 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24644 actions. Any registers referred to by @samp{M} and @samp{X} actions
24645 must be collected by a preceding @samp{R} action. (The
24646 ``while-stepping'' actions are treated as if they were attached to a
24647 separate tracepoint, as far as these restrictions are concerned.)
24652 The packet was understood and carried out.
24654 The packet was not recognized.
24657 @item QTFrame:@var{n}
24658 Select the @var{n}'th tracepoint frame from the buffer, and use the
24659 register and memory contents recorded there to answer subsequent
24660 request packets from @value{GDBN}.
24662 A successful reply from the stub indicates that the stub has found the
24663 requested frame. The response is a series of parts, concatenated
24664 without separators, describing the frame we selected. Each part has
24665 one of the following forms:
24669 The selected frame is number @var{n} in the trace frame buffer;
24670 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24671 was no frame matching the criteria in the request packet.
24674 The selected trace frame records a hit of tracepoint number @var{t};
24675 @var{t} is a hexadecimal number.
24679 @item QTFrame:pc:@var{addr}
24680 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24681 currently selected frame whose PC is @var{addr};
24682 @var{addr} is a hexadecimal number.
24684 @item QTFrame:tdp:@var{t}
24685 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24686 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24687 is a hexadecimal number.
24689 @item QTFrame:range:@var{start}:@var{end}
24690 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24691 currently selected frame whose PC is between @var{start} (inclusive)
24692 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24695 @item QTFrame:outside:@var{start}:@var{end}
24696 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24697 frame @emph{outside} the given range of addresses.
24700 Begin the tracepoint experiment. Begin collecting data from tracepoint
24701 hits in the trace frame buffer.
24704 End the tracepoint experiment. Stop collecting trace frames.
24707 Clear the table of tracepoints, and empty the trace frame buffer.
24709 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24710 Establish the given ranges of memory as ``transparent''. The stub
24711 will answer requests for these ranges from memory's current contents,
24712 if they were not collected as part of the tracepoint hit.
24714 @value{GDBN} uses this to mark read-only regions of memory, like those
24715 containing program code. Since these areas never change, they should
24716 still have the same contents they did when the tracepoint was hit, so
24717 there's no reason for the stub to refuse to provide their contents.
24720 Ask the stub if there is a trace experiment running right now.
24725 There is no trace experiment running.
24727 There is a trace experiment running.
24733 @node Host I/O Packets
24734 @section Host I/O Packets
24735 @cindex Host I/O, remote protocol
24736 @cindex file transfer, remote protocol
24738 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
24739 operations on the far side of a remote link. For example, Host I/O is
24740 used to upload and download files to a remote target with its own
24741 filesystem. Host I/O uses the same constant values and data structure
24742 layout as the target-initiated File-I/O protocol. However, the
24743 Host I/O packets are structured differently. The target-initiated
24744 protocol relies on target memory to store parameters and buffers.
24745 Host I/O requests are initiated by @value{GDBN}, and the
24746 target's memory is not involved. @xref{File-I/O Remote Protocol
24747 Extension}, for more details on the target-initiated protocol.
24749 The Host I/O request packets all encode a single operation along with
24750 its arguments. They have this format:
24754 @item vFile:@var{operation}: @var{parameter}@dots{}
24755 @var{operation} is the name of the particular request; the target
24756 should compare the entire packet name up to the second colon when checking
24757 for a supported operation. The format of @var{parameter} depends on
24758 the operation. Numbers are always passed in hexadecimal. Negative
24759 numbers have an explicit minus sign (i.e.@: two's complement is not
24760 used). Strings (e.g.@: filenames) are encoded as a series of
24761 hexadecimal bytes. The last argument to a system call may be a
24762 buffer of escaped binary data (@pxref{Binary Data}).
24766 The valid responses to Host I/O packets are:
24770 @item F @var{result} [, @var{errno}] [; @var{attachment}]
24771 @var{result} is the integer value returned by this operation, usually
24772 non-negative for success and -1 for errors. If an error has occured,
24773 @var{errno} will be included in the result. @var{errno} will have a
24774 value defined by the File-I/O protocol (@pxref{Errno Values}). For
24775 operations which return data, @var{attachment} supplies the data as a
24776 binary buffer. Binary buffers in response packets are escaped in the
24777 normal way (@pxref{Binary Data}). See the individual packet
24778 documentation for the interpretation of @var{result} and
24782 An empty response indicates that this operation is not recognized.
24786 These are the supported Host I/O operations:
24789 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
24790 Open a file at @var{pathname} and return a file descriptor for it, or
24791 return -1 if an error occurs. @var{pathname} is a string,
24792 @var{flags} is an integer indicating a mask of open flags
24793 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
24794 of mode bits to use if the file is created (@pxref{mode_t Values}).
24795 @xref{open}, for details of the open flags and mode values.
24797 @item vFile:close: @var{fd}
24798 Close the open file corresponding to @var{fd} and return 0, or
24799 -1 if an error occurs.
24801 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
24802 Read data from the open file corresponding to @var{fd}. Up to
24803 @var{count} bytes will be read from the file, starting at @var{offset}
24804 relative to the start of the file. The target may read fewer bytes;
24805 common reasons include packet size limits and an end-of-file
24806 condition. The number of bytes read is returned. Zero should only be
24807 returned for a successful read at the end of the file, or if
24808 @var{count} was zero.
24810 The data read should be returned as a binary attachment on success.
24811 If zero bytes were read, the response should include an empty binary
24812 attachment (i.e.@: a trailing semicolon). The return value is the
24813 number of target bytes read; the binary attachment may be longer if
24814 some characters were escaped.
24816 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
24817 Write @var{data} (a binary buffer) to the open file corresponding
24818 to @var{fd}. Start the write at @var{offset} from the start of the
24819 file. Unlike many @code{write} system calls, there is no
24820 separate @var{count} argument; the length of @var{data} in the
24821 packet is used. @samp{vFile:write} returns the number of bytes written,
24822 which may be shorter than the length of @var{data}, or -1 if an
24825 @item vFile:unlink: @var{pathname}
24826 Delete the file at @var{pathname} on the target. Return 0,
24827 or -1 if an error occurs. @var{pathname} is a string.
24832 @section Interrupts
24833 @cindex interrupts (remote protocol)
24835 When a program on the remote target is running, @value{GDBN} may
24836 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24837 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24838 setting (@pxref{set remotebreak}).
24840 The precise meaning of @code{BREAK} is defined by the transport
24841 mechanism and may, in fact, be undefined. @value{GDBN} does
24842 not currently define a @code{BREAK} mechanism for any of the network
24845 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24846 transport mechanisms. It is represented by sending the single byte
24847 @code{0x03} without any of the usual packet overhead described in
24848 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24849 transmitted as part of a packet, it is considered to be packet data
24850 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24851 (@pxref{X packet}), used for binary downloads, may include an unescaped
24852 @code{0x03} as part of its packet.
24854 Stubs are not required to recognize these interrupt mechanisms and the
24855 precise meaning associated with receipt of the interrupt is
24856 implementation defined. If the stub is successful at interrupting the
24857 running program, it is expected that it will send one of the Stop
24858 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24859 of successfully stopping the program. Interrupts received while the
24860 program is stopped will be discarded.
24865 Example sequence of a target being re-started. Notice how the restart
24866 does not get any direct output:
24871 @emph{target restarts}
24874 <- @code{T001:1234123412341234}
24878 Example sequence of a target being stepped by a single instruction:
24881 -> @code{G1445@dots{}}
24886 <- @code{T001:1234123412341234}
24890 <- @code{1455@dots{}}
24894 @node File-I/O Remote Protocol Extension
24895 @section File-I/O Remote Protocol Extension
24896 @cindex File-I/O remote protocol extension
24899 * File-I/O Overview::
24900 * Protocol Basics::
24901 * The F Request Packet::
24902 * The F Reply Packet::
24903 * The Ctrl-C Message::
24905 * List of Supported Calls::
24906 * Protocol-specific Representation of Datatypes::
24908 * File-I/O Examples::
24911 @node File-I/O Overview
24912 @subsection File-I/O Overview
24913 @cindex file-i/o overview
24915 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24916 target to use the host's file system and console I/O to perform various
24917 system calls. System calls on the target system are translated into a
24918 remote protocol packet to the host system, which then performs the needed
24919 actions and returns a response packet to the target system.
24920 This simulates file system operations even on targets that lack file systems.
24922 The protocol is defined to be independent of both the host and target systems.
24923 It uses its own internal representation of datatypes and values. Both
24924 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24925 translating the system-dependent value representations into the internal
24926 protocol representations when data is transmitted.
24928 The communication is synchronous. A system call is possible only when
24929 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24930 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24931 the target is stopped to allow deterministic access to the target's
24932 memory. Therefore File-I/O is not interruptible by target signals. On
24933 the other hand, it is possible to interrupt File-I/O by a user interrupt
24934 (@samp{Ctrl-C}) within @value{GDBN}.
24936 The target's request to perform a host system call does not finish
24937 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24938 after finishing the system call, the target returns to continuing the
24939 previous activity (continue, step). No additional continue or step
24940 request from @value{GDBN} is required.
24943 (@value{GDBP}) continue
24944 <- target requests 'system call X'
24945 target is stopped, @value{GDBN} executes system call
24946 -> @value{GDBN} returns result
24947 ... target continues, @value{GDBN} returns to wait for the target
24948 <- target hits breakpoint and sends a Txx packet
24951 The protocol only supports I/O on the console and to regular files on
24952 the host file system. Character or block special devices, pipes,
24953 named pipes, sockets or any other communication method on the host
24954 system are not supported by this protocol.
24956 @node Protocol Basics
24957 @subsection Protocol Basics
24958 @cindex protocol basics, file-i/o
24960 The File-I/O protocol uses the @code{F} packet as the request as well
24961 as reply packet. Since a File-I/O system call can only occur when
24962 @value{GDBN} is waiting for a response from the continuing or stepping target,
24963 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24964 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24965 This @code{F} packet contains all information needed to allow @value{GDBN}
24966 to call the appropriate host system call:
24970 A unique identifier for the requested system call.
24973 All parameters to the system call. Pointers are given as addresses
24974 in the target memory address space. Pointers to strings are given as
24975 pointer/length pair. Numerical values are given as they are.
24976 Numerical control flags are given in a protocol-specific representation.
24980 At this point, @value{GDBN} has to perform the following actions.
24984 If the parameters include pointer values to data needed as input to a
24985 system call, @value{GDBN} requests this data from the target with a
24986 standard @code{m} packet request. This additional communication has to be
24987 expected by the target implementation and is handled as any other @code{m}
24991 @value{GDBN} translates all value from protocol representation to host
24992 representation as needed. Datatypes are coerced into the host types.
24995 @value{GDBN} calls the system call.
24998 It then coerces datatypes back to protocol representation.
25001 If the system call is expected to return data in buffer space specified
25002 by pointer parameters to the call, the data is transmitted to the
25003 target using a @code{M} or @code{X} packet. This packet has to be expected
25004 by the target implementation and is handled as any other @code{M} or @code{X}
25009 Eventually @value{GDBN} replies with another @code{F} packet which contains all
25010 necessary information for the target to continue. This at least contains
25017 @code{errno}, if has been changed by the system call.
25024 After having done the needed type and value coercion, the target continues
25025 the latest continue or step action.
25027 @node The F Request Packet
25028 @subsection The @code{F} Request Packet
25029 @cindex file-i/o request packet
25030 @cindex @code{F} request packet
25032 The @code{F} request packet has the following format:
25035 @item F@var{call-id},@var{parameter@dots{}}
25037 @var{call-id} is the identifier to indicate the host system call to be called.
25038 This is just the name of the function.
25040 @var{parameter@dots{}} are the parameters to the system call.
25041 Parameters are hexadecimal integer values, either the actual values in case
25042 of scalar datatypes, pointers to target buffer space in case of compound
25043 datatypes and unspecified memory areas, or pointer/length pairs in case
25044 of string parameters. These are appended to the @var{call-id} as a
25045 comma-delimited list. All values are transmitted in ASCII
25046 string representation, pointer/length pairs separated by a slash.
25052 @node The F Reply Packet
25053 @subsection The @code{F} Reply Packet
25054 @cindex file-i/o reply packet
25055 @cindex @code{F} reply packet
25057 The @code{F} reply packet has the following format:
25061 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
25063 @var{retcode} is the return code of the system call as hexadecimal value.
25065 @var{errno} is the @code{errno} set by the call, in protocol-specific
25067 This parameter can be omitted if the call was successful.
25069 @var{Ctrl-C flag} is only sent if the user requested a break. In this
25070 case, @var{errno} must be sent as well, even if the call was successful.
25071 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
25078 or, if the call was interrupted before the host call has been performed:
25085 assuming 4 is the protocol-specific representation of @code{EINTR}.
25090 @node The Ctrl-C Message
25091 @subsection The @samp{Ctrl-C} Message
25092 @cindex ctrl-c message, in file-i/o protocol
25094 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
25095 reply packet (@pxref{The F Reply Packet}),
25096 the target should behave as if it had
25097 gotten a break message. The meaning for the target is ``system call
25098 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
25099 (as with a break message) and return to @value{GDBN} with a @code{T02}
25102 It's important for the target to know in which
25103 state the system call was interrupted. There are two possible cases:
25107 The system call hasn't been performed on the host yet.
25110 The system call on the host has been finished.
25114 These two states can be distinguished by the target by the value of the
25115 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
25116 call hasn't been performed. This is equivalent to the @code{EINTR} handling
25117 on POSIX systems. In any other case, the target may presume that the
25118 system call has been finished --- successfully or not --- and should behave
25119 as if the break message arrived right after the system call.
25121 @value{GDBN} must behave reliably. If the system call has not been called
25122 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
25123 @code{errno} in the packet. If the system call on the host has been finished
25124 before the user requests a break, the full action must be finished by
25125 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
25126 The @code{F} packet may only be sent when either nothing has happened
25127 or the full action has been completed.
25130 @subsection Console I/O
25131 @cindex console i/o as part of file-i/o
25133 By default and if not explicitly closed by the target system, the file
25134 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
25135 on the @value{GDBN} console is handled as any other file output operation
25136 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
25137 by @value{GDBN} so that after the target read request from file descriptor
25138 0 all following typing is buffered until either one of the following
25143 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
25145 system call is treated as finished.
25148 The user presses @key{RET}. This is treated as end of input with a trailing
25152 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
25153 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
25157 If the user has typed more characters than fit in the buffer given to
25158 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
25159 either another @code{read(0, @dots{})} is requested by the target, or debugging
25160 is stopped at the user's request.
25163 @node List of Supported Calls
25164 @subsection List of Supported Calls
25165 @cindex list of supported file-i/o calls
25182 @unnumberedsubsubsec open
25183 @cindex open, file-i/o system call
25188 int open(const char *pathname, int flags);
25189 int open(const char *pathname, int flags, mode_t mode);
25193 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
25196 @var{flags} is the bitwise @code{OR} of the following values:
25200 If the file does not exist it will be created. The host
25201 rules apply as far as file ownership and time stamps
25205 When used with @code{O_CREAT}, if the file already exists it is
25206 an error and open() fails.
25209 If the file already exists and the open mode allows
25210 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
25211 truncated to zero length.
25214 The file is opened in append mode.
25217 The file is opened for reading only.
25220 The file is opened for writing only.
25223 The file is opened for reading and writing.
25227 Other bits are silently ignored.
25231 @var{mode} is the bitwise @code{OR} of the following values:
25235 User has read permission.
25238 User has write permission.
25241 Group has read permission.
25244 Group has write permission.
25247 Others have read permission.
25250 Others have write permission.
25254 Other bits are silently ignored.
25257 @item Return value:
25258 @code{open} returns the new file descriptor or -1 if an error
25265 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
25268 @var{pathname} refers to a directory.
25271 The requested access is not allowed.
25274 @var{pathname} was too long.
25277 A directory component in @var{pathname} does not exist.
25280 @var{pathname} refers to a device, pipe, named pipe or socket.
25283 @var{pathname} refers to a file on a read-only filesystem and
25284 write access was requested.
25287 @var{pathname} is an invalid pointer value.
25290 No space on device to create the file.
25293 The process already has the maximum number of files open.
25296 The limit on the total number of files open on the system
25300 The call was interrupted by the user.
25306 @unnumberedsubsubsec close
25307 @cindex close, file-i/o system call
25316 @samp{Fclose,@var{fd}}
25318 @item Return value:
25319 @code{close} returns zero on success, or -1 if an error occurred.
25325 @var{fd} isn't a valid open file descriptor.
25328 The call was interrupted by the user.
25334 @unnumberedsubsubsec read
25335 @cindex read, file-i/o system call
25340 int read(int fd, void *buf, unsigned int count);
25344 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
25346 @item Return value:
25347 On success, the number of bytes read is returned.
25348 Zero indicates end of file. If count is zero, read
25349 returns zero as well. On error, -1 is returned.
25355 @var{fd} is not a valid file descriptor or is not open for
25359 @var{bufptr} is an invalid pointer value.
25362 The call was interrupted by the user.
25368 @unnumberedsubsubsec write
25369 @cindex write, file-i/o system call
25374 int write(int fd, const void *buf, unsigned int count);
25378 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
25380 @item Return value:
25381 On success, the number of bytes written are returned.
25382 Zero indicates nothing was written. On error, -1
25389 @var{fd} is not a valid file descriptor or is not open for
25393 @var{bufptr} is an invalid pointer value.
25396 An attempt was made to write a file that exceeds the
25397 host-specific maximum file size allowed.
25400 No space on device to write the data.
25403 The call was interrupted by the user.
25409 @unnumberedsubsubsec lseek
25410 @cindex lseek, file-i/o system call
25415 long lseek (int fd, long offset, int flag);
25419 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
25421 @var{flag} is one of:
25425 The offset is set to @var{offset} bytes.
25428 The offset is set to its current location plus @var{offset}
25432 The offset is set to the size of the file plus @var{offset}
25436 @item Return value:
25437 On success, the resulting unsigned offset in bytes from
25438 the beginning of the file is returned. Otherwise, a
25439 value of -1 is returned.
25445 @var{fd} is not a valid open file descriptor.
25448 @var{fd} is associated with the @value{GDBN} console.
25451 @var{flag} is not a proper value.
25454 The call was interrupted by the user.
25460 @unnumberedsubsubsec rename
25461 @cindex rename, file-i/o system call
25466 int rename(const char *oldpath, const char *newpath);
25470 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
25472 @item Return value:
25473 On success, zero is returned. On error, -1 is returned.
25479 @var{newpath} is an existing directory, but @var{oldpath} is not a
25483 @var{newpath} is a non-empty directory.
25486 @var{oldpath} or @var{newpath} is a directory that is in use by some
25490 An attempt was made to make a directory a subdirectory
25494 A component used as a directory in @var{oldpath} or new
25495 path is not a directory. Or @var{oldpath} is a directory
25496 and @var{newpath} exists but is not a directory.
25499 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
25502 No access to the file or the path of the file.
25506 @var{oldpath} or @var{newpath} was too long.
25509 A directory component in @var{oldpath} or @var{newpath} does not exist.
25512 The file is on a read-only filesystem.
25515 The device containing the file has no room for the new
25519 The call was interrupted by the user.
25525 @unnumberedsubsubsec unlink
25526 @cindex unlink, file-i/o system call
25531 int unlink(const char *pathname);
25535 @samp{Funlink,@var{pathnameptr}/@var{len}}
25537 @item Return value:
25538 On success, zero is returned. On error, -1 is returned.
25544 No access to the file or the path of the file.
25547 The system does not allow unlinking of directories.
25550 The file @var{pathname} cannot be unlinked because it's
25551 being used by another process.
25554 @var{pathnameptr} is an invalid pointer value.
25557 @var{pathname} was too long.
25560 A directory component in @var{pathname} does not exist.
25563 A component of the path is not a directory.
25566 The file is on a read-only filesystem.
25569 The call was interrupted by the user.
25575 @unnumberedsubsubsec stat/fstat
25576 @cindex fstat, file-i/o system call
25577 @cindex stat, file-i/o system call
25582 int stat(const char *pathname, struct stat *buf);
25583 int fstat(int fd, struct stat *buf);
25587 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25588 @samp{Ffstat,@var{fd},@var{bufptr}}
25590 @item Return value:
25591 On success, zero is returned. On error, -1 is returned.
25597 @var{fd} is not a valid open file.
25600 A directory component in @var{pathname} does not exist or the
25601 path is an empty string.
25604 A component of the path is not a directory.
25607 @var{pathnameptr} is an invalid pointer value.
25610 No access to the file or the path of the file.
25613 @var{pathname} was too long.
25616 The call was interrupted by the user.
25622 @unnumberedsubsubsec gettimeofday
25623 @cindex gettimeofday, file-i/o system call
25628 int gettimeofday(struct timeval *tv, void *tz);
25632 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25634 @item Return value:
25635 On success, 0 is returned, -1 otherwise.
25641 @var{tz} is a non-NULL pointer.
25644 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25650 @unnumberedsubsubsec isatty
25651 @cindex isatty, file-i/o system call
25656 int isatty(int fd);
25660 @samp{Fisatty,@var{fd}}
25662 @item Return value:
25663 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
25669 The call was interrupted by the user.
25674 Note that the @code{isatty} call is treated as a special case: it returns
25675 1 to the target if the file descriptor is attached
25676 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
25677 would require implementing @code{ioctl} and would be more complex than
25682 @unnumberedsubsubsec system
25683 @cindex system, file-i/o system call
25688 int system(const char *command);
25692 @samp{Fsystem,@var{commandptr}/@var{len}}
25694 @item Return value:
25695 If @var{len} is zero, the return value indicates whether a shell is
25696 available. A zero return value indicates a shell is not available.
25697 For non-zero @var{len}, the value returned is -1 on error and the
25698 return status of the command otherwise. Only the exit status of the
25699 command is returned, which is extracted from the host's @code{system}
25700 return value by calling @code{WEXITSTATUS(retval)}. In case
25701 @file{/bin/sh} could not be executed, 127 is returned.
25707 The call was interrupted by the user.
25712 @value{GDBN} takes over the full task of calling the necessary host calls
25713 to perform the @code{system} call. The return value of @code{system} on
25714 the host is simplified before it's returned
25715 to the target. Any termination signal information from the child process
25716 is discarded, and the return value consists
25717 entirely of the exit status of the called command.
25719 Due to security concerns, the @code{system} call is by default refused
25720 by @value{GDBN}. The user has to allow this call explicitly with the
25721 @code{set remote system-call-allowed 1} command.
25724 @item set remote system-call-allowed
25725 @kindex set remote system-call-allowed
25726 Control whether to allow the @code{system} calls in the File I/O
25727 protocol for the remote target. The default is zero (disabled).
25729 @item show remote system-call-allowed
25730 @kindex show remote system-call-allowed
25731 Show whether the @code{system} calls are allowed in the File I/O
25735 @node Protocol-specific Representation of Datatypes
25736 @subsection Protocol-specific Representation of Datatypes
25737 @cindex protocol-specific representation of datatypes, in file-i/o protocol
25740 * Integral Datatypes::
25742 * Memory Transfer::
25747 @node Integral Datatypes
25748 @unnumberedsubsubsec Integral Datatypes
25749 @cindex integral datatypes, in file-i/o protocol
25751 The integral datatypes used in the system calls are @code{int},
25752 @code{unsigned int}, @code{long}, @code{unsigned long},
25753 @code{mode_t}, and @code{time_t}.
25755 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25756 implemented as 32 bit values in this protocol.
25758 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25760 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25761 in @file{limits.h}) to allow range checking on host and target.
25763 @code{time_t} datatypes are defined as seconds since the Epoch.
25765 All integral datatypes transferred as part of a memory read or write of a
25766 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25769 @node Pointer Values
25770 @unnumberedsubsubsec Pointer Values
25771 @cindex pointer values, in file-i/o protocol
25773 Pointers to target data are transmitted as they are. An exception
25774 is made for pointers to buffers for which the length isn't
25775 transmitted as part of the function call, namely strings. Strings
25776 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25783 which is a pointer to data of length 18 bytes at position 0x1aaf.
25784 The length is defined as the full string length in bytes, including
25785 the trailing null byte. For example, the string @code{"hello world"}
25786 at address 0x123456 is transmitted as
25792 @node Memory Transfer
25793 @unnumberedsubsubsec Memory Transfer
25794 @cindex memory transfer, in file-i/o protocol
25796 Structured data which is transferred using a memory read or write (for
25797 example, a @code{struct stat}) is expected to be in a protocol-specific format
25798 with all scalar multibyte datatypes being big endian. Translation to
25799 this representation needs to be done both by the target before the @code{F}
25800 packet is sent, and by @value{GDBN} before
25801 it transfers memory to the target. Transferred pointers to structured
25802 data should point to the already-coerced data at any time.
25806 @unnumberedsubsubsec struct stat
25807 @cindex struct stat, in file-i/o protocol
25809 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25810 is defined as follows:
25814 unsigned int st_dev; /* device */
25815 unsigned int st_ino; /* inode */
25816 mode_t st_mode; /* protection */
25817 unsigned int st_nlink; /* number of hard links */
25818 unsigned int st_uid; /* user ID of owner */
25819 unsigned int st_gid; /* group ID of owner */
25820 unsigned int st_rdev; /* device type (if inode device) */
25821 unsigned long st_size; /* total size, in bytes */
25822 unsigned long st_blksize; /* blocksize for filesystem I/O */
25823 unsigned long st_blocks; /* number of blocks allocated */
25824 time_t st_atime; /* time of last access */
25825 time_t st_mtime; /* time of last modification */
25826 time_t st_ctime; /* time of last change */
25830 The integral datatypes conform to the definitions given in the
25831 appropriate section (see @ref{Integral Datatypes}, for details) so this
25832 structure is of size 64 bytes.
25834 The values of several fields have a restricted meaning and/or
25840 A value of 0 represents a file, 1 the console.
25843 No valid meaning for the target. Transmitted unchanged.
25846 Valid mode bits are described in @ref{Constants}. Any other
25847 bits have currently no meaning for the target.
25852 No valid meaning for the target. Transmitted unchanged.
25857 These values have a host and file system dependent
25858 accuracy. Especially on Windows hosts, the file system may not
25859 support exact timing values.
25862 The target gets a @code{struct stat} of the above representation and is
25863 responsible for coercing it to the target representation before
25866 Note that due to size differences between the host, target, and protocol
25867 representations of @code{struct stat} members, these members could eventually
25868 get truncated on the target.
25870 @node struct timeval
25871 @unnumberedsubsubsec struct timeval
25872 @cindex struct timeval, in file-i/o protocol
25874 The buffer of type @code{struct timeval} used by the File-I/O protocol
25875 is defined as follows:
25879 time_t tv_sec; /* second */
25880 long tv_usec; /* microsecond */
25884 The integral datatypes conform to the definitions given in the
25885 appropriate section (see @ref{Integral Datatypes}, for details) so this
25886 structure is of size 8 bytes.
25889 @subsection Constants
25890 @cindex constants, in file-i/o protocol
25892 The following values are used for the constants inside of the
25893 protocol. @value{GDBN} and target are responsible for translating these
25894 values before and after the call as needed.
25905 @unnumberedsubsubsec Open Flags
25906 @cindex open flags, in file-i/o protocol
25908 All values are given in hexadecimal representation.
25920 @node mode_t Values
25921 @unnumberedsubsubsec mode_t Values
25922 @cindex mode_t values, in file-i/o protocol
25924 All values are given in octal representation.
25941 @unnumberedsubsubsec Errno Values
25942 @cindex errno values, in file-i/o protocol
25944 All values are given in decimal representation.
25969 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25970 any error value not in the list of supported error numbers.
25973 @unnumberedsubsubsec Lseek Flags
25974 @cindex lseek flags, in file-i/o protocol
25983 @unnumberedsubsubsec Limits
25984 @cindex limits, in file-i/o protocol
25986 All values are given in decimal representation.
25989 INT_MIN -2147483648
25991 UINT_MAX 4294967295
25992 LONG_MIN -9223372036854775808
25993 LONG_MAX 9223372036854775807
25994 ULONG_MAX 18446744073709551615
25997 @node File-I/O Examples
25998 @subsection File-I/O Examples
25999 @cindex file-i/o examples
26001 Example sequence of a write call, file descriptor 3, buffer is at target
26002 address 0x1234, 6 bytes should be written:
26005 <- @code{Fwrite,3,1234,6}
26006 @emph{request memory read from target}
26009 @emph{return "6 bytes written"}
26013 Example sequence of a read call, file descriptor 3, buffer is at target
26014 address 0x1234, 6 bytes should be read:
26017 <- @code{Fread,3,1234,6}
26018 @emph{request memory write to target}
26019 -> @code{X1234,6:XXXXXX}
26020 @emph{return "6 bytes read"}
26024 Example sequence of a read call, call fails on the host due to invalid
26025 file descriptor (@code{EBADF}):
26028 <- @code{Fread,3,1234,6}
26032 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
26036 <- @code{Fread,3,1234,6}
26041 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
26045 <- @code{Fread,3,1234,6}
26046 -> @code{X1234,6:XXXXXX}
26050 @node Library List Format
26051 @section Library List Format
26052 @cindex library list format, remote protocol
26054 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
26055 same process as your application to manage libraries. In this case,
26056 @value{GDBN} can use the loader's symbol table and normal memory
26057 operations to maintain a list of shared libraries. On other
26058 platforms, the operating system manages loaded libraries.
26059 @value{GDBN} can not retrieve the list of currently loaded libraries
26060 through memory operations, so it uses the @samp{qXfer:libraries:read}
26061 packet (@pxref{qXfer library list read}) instead. The remote stub
26062 queries the target's operating system and reports which libraries
26065 The @samp{qXfer:libraries:read} packet returns an XML document which
26066 lists loaded libraries and their offsets. Each library has an
26067 associated name and one or more segment base addresses, which report
26068 where the library was loaded in memory. The segment bases are start
26069 addresses, not relocation offsets; they do not depend on the library's
26070 link-time base addresses.
26072 @value{GDBN} must be linked with the Expat library to support XML
26073 library lists. @xref{Expat}.
26075 A simple memory map, with one loaded library relocated by a single
26076 offset, looks like this:
26080 <library name="/lib/libc.so.6">
26081 <segment address="0x10000000"/>
26086 The format of a library list is described by this DTD:
26089 <!-- library-list: Root element with versioning -->
26090 <!ELEMENT library-list (library)*>
26091 <!ATTLIST library-list version CDATA #FIXED "1.0">
26092 <!ELEMENT library (segment)*>
26093 <!ATTLIST library name CDATA #REQUIRED>
26094 <!ELEMENT segment EMPTY>
26095 <!ATTLIST segment address CDATA #REQUIRED>
26098 @node Memory Map Format
26099 @section Memory Map Format
26100 @cindex memory map format
26102 To be able to write into flash memory, @value{GDBN} needs to obtain a
26103 memory map from the target. This section describes the format of the
26106 The memory map is obtained using the @samp{qXfer:memory-map:read}
26107 (@pxref{qXfer memory map read}) packet and is an XML document that
26108 lists memory regions.
26110 @value{GDBN} must be linked with the Expat library to support XML
26111 memory maps. @xref{Expat}.
26113 The top-level structure of the document is shown below:
26116 <?xml version="1.0"?>
26117 <!DOCTYPE memory-map
26118 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
26119 "http://sourceware.org/gdb/gdb-memory-map.dtd">
26125 Each region can be either:
26130 A region of RAM starting at @var{addr} and extending for @var{length}
26134 <memory type="ram" start="@var{addr}" length="@var{length}"/>
26139 A region of read-only memory:
26142 <memory type="rom" start="@var{addr}" length="@var{length}"/>
26147 A region of flash memory, with erasure blocks @var{blocksize}
26151 <memory type="flash" start="@var{addr}" length="@var{length}">
26152 <property name="blocksize">@var{blocksize}</property>
26158 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
26159 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
26160 packets to write to addresses in such ranges.
26162 The formal DTD for memory map format is given below:
26165 <!-- ................................................... -->
26166 <!-- Memory Map XML DTD ................................ -->
26167 <!-- File: memory-map.dtd .............................. -->
26168 <!-- .................................... .............. -->
26169 <!-- memory-map.dtd -->
26170 <!-- memory-map: Root element with versioning -->
26171 <!ELEMENT memory-map (memory | property)>
26172 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
26173 <!ELEMENT memory (property)>
26174 <!-- memory: Specifies a memory region,
26175 and its type, or device. -->
26176 <!ATTLIST memory type CDATA #REQUIRED
26177 start CDATA #REQUIRED
26178 length CDATA #REQUIRED
26179 device CDATA #IMPLIED>
26180 <!-- property: Generic attribute tag -->
26181 <!ELEMENT property (#PCDATA | property)*>
26182 <!ATTLIST property name CDATA #REQUIRED>
26185 @include agentexpr.texi
26187 @node Target Descriptions
26188 @appendix Target Descriptions
26189 @cindex target descriptions
26191 @strong{Warning:} target descriptions are still under active development,
26192 and the contents and format may change between @value{GDBN} releases.
26193 The format is expected to stabilize in the future.
26195 One of the challenges of using @value{GDBN} to debug embedded systems
26196 is that there are so many minor variants of each processor
26197 architecture in use. It is common practice for vendors to start with
26198 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
26199 and then make changes to adapt it to a particular market niche. Some
26200 architectures have hundreds of variants, available from dozens of
26201 vendors. This leads to a number of problems:
26205 With so many different customized processors, it is difficult for
26206 the @value{GDBN} maintainers to keep up with the changes.
26208 Since individual variants may have short lifetimes or limited
26209 audiences, it may not be worthwhile to carry information about every
26210 variant in the @value{GDBN} source tree.
26212 When @value{GDBN} does support the architecture of the embedded system
26213 at hand, the task of finding the correct architecture name to give the
26214 @command{set architecture} command can be error-prone.
26217 To address these problems, the @value{GDBN} remote protocol allows a
26218 target system to not only identify itself to @value{GDBN}, but to
26219 actually describe its own features. This lets @value{GDBN} support
26220 processor variants it has never seen before --- to the extent that the
26221 descriptions are accurate, and that @value{GDBN} understands them.
26223 @value{GDBN} must be linked with the Expat library to support XML
26224 target descriptions. @xref{Expat}.
26227 * Retrieving Descriptions:: How descriptions are fetched from a target.
26228 * Target Description Format:: The contents of a target description.
26229 * Predefined Target Types:: Standard types available for target
26231 * Standard Target Features:: Features @value{GDBN} knows about.
26234 @node Retrieving Descriptions
26235 @section Retrieving Descriptions
26237 Target descriptions can be read from the target automatically, or
26238 specified by the user manually. The default behavior is to read the
26239 description from the target. @value{GDBN} retrieves it via the remote
26240 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
26241 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
26242 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
26243 XML document, of the form described in @ref{Target Description
26246 Alternatively, you can specify a file to read for the target description.
26247 If a file is set, the target will not be queried. The commands to
26248 specify a file are:
26251 @cindex set tdesc filename
26252 @item set tdesc filename @var{path}
26253 Read the target description from @var{path}.
26255 @cindex unset tdesc filename
26256 @item unset tdesc filename
26257 Do not read the XML target description from a file. @value{GDBN}
26258 will use the description supplied by the current target.
26260 @cindex show tdesc filename
26261 @item show tdesc filename
26262 Show the filename to read for a target description, if any.
26266 @node Target Description Format
26267 @section Target Description Format
26268 @cindex target descriptions, XML format
26270 A target description annex is an @uref{http://www.w3.org/XML/, XML}
26271 document which complies with the Document Type Definition provided in
26272 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
26273 means you can use generally available tools like @command{xmllint} to
26274 check that your feature descriptions are well-formed and valid.
26275 However, to help people unfamiliar with XML write descriptions for
26276 their targets, we also describe the grammar here.
26278 Target descriptions can identify the architecture of the remote target
26279 and (for some architectures) provide information about custom register
26280 sets. @value{GDBN} can use this information to autoconfigure for your
26281 target, or to warn you if you connect to an unsupported target.
26283 Here is a simple target description:
26286 <target version="1.0">
26287 <architecture>i386:x86-64</architecture>
26292 This minimal description only says that the target uses
26293 the x86-64 architecture.
26295 A target description has the following overall form, with [ ] marking
26296 optional elements and @dots{} marking repeatable elements. The elements
26297 are explained further below.
26300 <?xml version="1.0"?>
26301 <!DOCTYPE target SYSTEM "gdb-target.dtd">
26302 <target version="1.0">
26303 @r{[}@var{architecture}@r{]}
26304 @r{[}@var{feature}@dots{}@r{]}
26309 The description is generally insensitive to whitespace and line
26310 breaks, under the usual common-sense rules. The XML version
26311 declaration and document type declaration can generally be omitted
26312 (@value{GDBN} does not require them), but specifying them may be
26313 useful for XML validation tools. The @samp{version} attribute for
26314 @samp{<target>} may also be omitted, but we recommend
26315 including it; if future versions of @value{GDBN} use an incompatible
26316 revision of @file{gdb-target.dtd}, they will detect and report
26317 the version mismatch.
26319 @subsection Inclusion
26320 @cindex target descriptions, inclusion
26323 @cindex <xi:include>
26326 It can sometimes be valuable to split a target description up into
26327 several different annexes, either for organizational purposes, or to
26328 share files between different possible target descriptions. You can
26329 divide a description into multiple files by replacing any element of
26330 the target description with an inclusion directive of the form:
26333 <xi:include href="@var{document}"/>
26337 When @value{GDBN} encounters an element of this form, it will retrieve
26338 the named XML @var{document}, and replace the inclusion directive with
26339 the contents of that document. If the current description was read
26340 using @samp{qXfer}, then so will be the included document;
26341 @var{document} will be interpreted as the name of an annex. If the
26342 current description was read from a file, @value{GDBN} will look for
26343 @var{document} as a file in the same directory where it found the
26344 original description.
26346 @subsection Architecture
26347 @cindex <architecture>
26349 An @samp{<architecture>} element has this form:
26352 <architecture>@var{arch}</architecture>
26355 @var{arch} is an architecture name from the same selection
26356 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
26357 Debugging Target}).
26359 @subsection Features
26362 Each @samp{<feature>} describes some logical portion of the target
26363 system. Features are currently used to describe available CPU
26364 registers and the types of their contents. A @samp{<feature>} element
26368 <feature name="@var{name}">
26369 @r{[}@var{type}@dots{}@r{]}
26375 Each feature's name should be unique within the description. The name
26376 of a feature does not matter unless @value{GDBN} has some special
26377 knowledge of the contents of that feature; if it does, the feature
26378 should have its standard name. @xref{Standard Target Features}.
26382 Any register's value is a collection of bits which @value{GDBN} must
26383 interpret. The default interpretation is a two's complement integer,
26384 but other types can be requested by name in the register description.
26385 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
26386 Target Types}), and the description can define additional composite types.
26388 Each type element must have an @samp{id} attribute, which gives
26389 a unique (within the containing @samp{<feature>}) name to the type.
26390 Types must be defined before they are used.
26393 Some targets offer vector registers, which can be treated as arrays
26394 of scalar elements. These types are written as @samp{<vector>} elements,
26395 specifying the array element type, @var{type}, and the number of elements,
26399 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
26403 If a register's value is usefully viewed in multiple ways, define it
26404 with a union type containing the useful representations. The
26405 @samp{<union>} element contains one or more @samp{<field>} elements,
26406 each of which has a @var{name} and a @var{type}:
26409 <union id="@var{id}">
26410 <field name="@var{name}" type="@var{type}"/>
26415 @subsection Registers
26418 Each register is represented as an element with this form:
26421 <reg name="@var{name}"
26422 bitsize="@var{size}"
26423 @r{[}regnum="@var{num}"@r{]}
26424 @r{[}save-restore="@var{save-restore}"@r{]}
26425 @r{[}type="@var{type}"@r{]}
26426 @r{[}group="@var{group}"@r{]}/>
26430 The components are as follows:
26435 The register's name; it must be unique within the target description.
26438 The register's size, in bits.
26441 The register's number. If omitted, a register's number is one greater
26442 than that of the previous register (either in the current feature or in
26443 a preceeding feature); the first register in the target description
26444 defaults to zero. This register number is used to read or write
26445 the register; e.g.@: it is used in the remote @code{p} and @code{P}
26446 packets, and registers appear in the @code{g} and @code{G} packets
26447 in order of increasing register number.
26450 Whether the register should be preserved across inferior function
26451 calls; this must be either @code{yes} or @code{no}. The default is
26452 @code{yes}, which is appropriate for most registers except for
26453 some system control registers; this is not related to the target's
26457 The type of the register. @var{type} may be a predefined type, a type
26458 defined in the current feature, or one of the special types @code{int}
26459 and @code{float}. @code{int} is an integer type of the correct size
26460 for @var{bitsize}, and @code{float} is a floating point type (in the
26461 architecture's normal floating point format) of the correct size for
26462 @var{bitsize}. The default is @code{int}.
26465 The register group to which this register belongs. @var{group} must
26466 be either @code{general}, @code{float}, or @code{vector}. If no
26467 @var{group} is specified, @value{GDBN} will not display the register
26468 in @code{info registers}.
26472 @node Predefined Target Types
26473 @section Predefined Target Types
26474 @cindex target descriptions, predefined types
26476 Type definitions in the self-description can build up composite types
26477 from basic building blocks, but can not define fundamental types. Instead,
26478 standard identifiers are provided by @value{GDBN} for the fundamental
26479 types. The currently supported types are:
26488 Signed integer types holding the specified number of bits.
26495 Unsigned integer types holding the specified number of bits.
26499 Pointers to unspecified code and data. The program counter and
26500 any dedicated return address register may be marked as code
26501 pointers; printing a code pointer converts it into a symbolic
26502 address. The stack pointer and any dedicated address registers
26503 may be marked as data pointers.
26506 Single precision IEEE floating point.
26509 Double precision IEEE floating point.
26512 The 12-byte extended precision format used by ARM FPA registers.
26516 @node Standard Target Features
26517 @section Standard Target Features
26518 @cindex target descriptions, standard features
26520 A target description must contain either no registers or all the
26521 target's registers. If the description contains no registers, then
26522 @value{GDBN} will assume a default register layout, selected based on
26523 the architecture. If the description contains any registers, the
26524 default layout will not be used; the standard registers must be
26525 described in the target description, in such a way that @value{GDBN}
26526 can recognize them.
26528 This is accomplished by giving specific names to feature elements
26529 which contain standard registers. @value{GDBN} will look for features
26530 with those names and verify that they contain the expected registers;
26531 if any known feature is missing required registers, or if any required
26532 feature is missing, @value{GDBN} will reject the target
26533 description. You can add additional registers to any of the
26534 standard features --- @value{GDBN} will display them just as if
26535 they were added to an unrecognized feature.
26537 This section lists the known features and their expected contents.
26538 Sample XML documents for these features are included in the
26539 @value{GDBN} source tree, in the directory @file{gdb/features}.
26541 Names recognized by @value{GDBN} should include the name of the
26542 company or organization which selected the name, and the overall
26543 architecture to which the feature applies; so e.g.@: the feature
26544 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
26546 The names of registers are not case sensitive for the purpose
26547 of recognizing standard features, but @value{GDBN} will only display
26548 registers using the capitalization used in the description.
26557 @subsection ARM Features
26558 @cindex target descriptions, ARM features
26560 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
26561 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
26562 @samp{lr}, @samp{pc}, and @samp{cpsr}.
26564 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
26565 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
26567 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
26568 it should contain at least registers @samp{wR0} through @samp{wR15} and
26569 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
26570 @samp{wCSSF}, and @samp{wCASF} registers are optional.
26572 @subsection MIPS Features
26573 @cindex target descriptions, MIPS features
26575 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
26576 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
26577 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
26580 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
26581 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
26582 registers. They may be 32-bit or 64-bit depending on the target.
26584 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
26585 it may be optional in a future version of @value{GDBN}. It should
26586 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
26587 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
26589 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
26590 contain a single register, @samp{restart}, which is used by the
26591 Linux kernel to control restartable syscalls.
26593 @node M68K Features
26594 @subsection M68K Features
26595 @cindex target descriptions, M68K features
26598 @item @samp{org.gnu.gdb.m68k.core}
26599 @itemx @samp{org.gnu.gdb.coldfire.core}
26600 @itemx @samp{org.gnu.gdb.fido.core}
26601 One of those features must be always present.
26602 The feature that is present determines which flavor of m86k is
26603 used. The feature that is present should contain registers
26604 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
26605 @samp{sp}, @samp{ps} and @samp{pc}.
26607 @item @samp{org.gnu.gdb.coldfire.fp}
26608 This feature is optional. If present, it should contain registers
26609 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
26613 @subsection PowerPC Features
26614 @cindex target descriptions, PowerPC features
26616 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
26617 targets. It should contain registers @samp{r0} through @samp{r31},
26618 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
26619 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
26621 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
26622 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
26624 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
26625 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
26628 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
26629 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
26630 @samp{spefscr}. SPE targets should provide 32-bit registers in
26631 @samp{org.gnu.gdb.power.core} and provide the upper halves in
26632 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
26633 these to present registers @samp{ev0} through @samp{ev31} to the
26648 % I think something like @colophon should be in texinfo. In the
26650 \long\def\colophon{\hbox to0pt{}\vfill
26651 \centerline{The body of this manual is set in}
26652 \centerline{\fontname\tenrm,}
26653 \centerline{with headings in {\bf\fontname\tenbf}}
26654 \centerline{and examples in {\tt\fontname\tentt}.}
26655 \centerline{{\it\fontname\tenit\/},}
26656 \centerline{{\bf\fontname\tenbf}, and}
26657 \centerline{{\sl\fontname\tensl\/}}
26658 \centerline{are used for emphasis.}\vfill}
26660 % Blame: doc@cygnus.com, 1991.