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 -pid @var{number}
946 @itemx -p @var{number}
949 Connect to process ID @var{number}, as with the @code{attach} command.
951 @item -command @var{file}
953 @cindex @code{--command}
955 Execute @value{GDBN} commands from file @var{file}. @xref{Command
956 Files,, Command files}.
958 @item -eval-command @var{command}
959 @itemx -ex @var{command}
960 @cindex @code{--eval-command}
962 Execute a single @value{GDBN} command.
964 This option may be used multiple times to call multiple commands. It may
965 also be interleaved with @samp{-command} as required.
968 @value{GDBP} -ex 'target sim' -ex 'load' \
969 -x setbreakpoints -ex 'run' a.out
972 @item -directory @var{directory}
973 @itemx -d @var{directory}
974 @cindex @code{--directory}
976 Add @var{directory} to the path to search for source and script files.
980 @cindex @code{--readnow}
982 Read each symbol file's entire symbol table immediately, rather than
983 the default, which is to read it incrementally as it is needed.
984 This makes startup slower, but makes future operations faster.
989 @subsection Choosing Modes
991 You can run @value{GDBN} in various alternative modes---for example, in
992 batch mode or quiet mode.
999 Do not execute commands found in any initialization files. Normally,
1000 @value{GDBN} executes the commands in these files after all the command
1001 options and arguments have been processed. @xref{Command Files,,Command
1007 @cindex @code{--quiet}
1008 @cindex @code{--silent}
1010 ``Quiet''. Do not print the introductory and copyright messages. These
1011 messages are also suppressed in batch mode.
1014 @cindex @code{--batch}
1015 Run in batch mode. Exit with status @code{0} after processing all the
1016 command files specified with @samp{-x} (and all commands from
1017 initialization files, if not inhibited with @samp{-n}). Exit with
1018 nonzero status if an error occurs in executing the @value{GDBN} commands
1019 in the command files.
1021 Batch mode may be useful for running @value{GDBN} as a filter, for
1022 example to download and run a program on another computer; in order to
1023 make this more useful, the message
1026 Program exited normally.
1030 (which is ordinarily issued whenever a program running under
1031 @value{GDBN} control terminates) is not issued when running in batch
1035 @cindex @code{--batch-silent}
1036 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1037 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1038 unaffected). This is much quieter than @samp{-silent} and would be useless
1039 for an interactive session.
1041 This is particularly useful when using targets that give @samp{Loading section}
1042 messages, for example.
1044 Note that targets that give their output via @value{GDBN}, as opposed to
1045 writing directly to @code{stdout}, will also be made silent.
1047 @item -return-child-result
1048 @cindex @code{--return-child-result}
1049 The return code from @value{GDBN} will be the return code from the child
1050 process (the process being debugged), with the following exceptions:
1054 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1055 internal error. In this case the exit code is the same as it would have been
1056 without @samp{-return-child-result}.
1058 The user quits with an explicit value. E.g., @samp{quit 1}.
1060 The child process never runs, or is not allowed to terminate, in which case
1061 the exit code will be -1.
1064 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1065 when @value{GDBN} is being used as a remote program loader or simulator
1070 @cindex @code{--nowindows}
1072 ``No windows''. If @value{GDBN} comes with a graphical user interface
1073 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1074 interface. If no GUI is available, this option has no effect.
1078 @cindex @code{--windows}
1080 If @value{GDBN} includes a GUI, then this option requires it to be
1083 @item -cd @var{directory}
1085 Run @value{GDBN} using @var{directory} as its working directory,
1086 instead of the current directory.
1090 @cindex @code{--fullname}
1092 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1093 subprocess. It tells @value{GDBN} to output the full file name and line
1094 number in a standard, recognizable fashion each time a stack frame is
1095 displayed (which includes each time your program stops). This
1096 recognizable format looks like two @samp{\032} characters, followed by
1097 the file name, line number and character position separated by colons,
1098 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1099 @samp{\032} characters as a signal to display the source code for the
1103 @cindex @code{--epoch}
1104 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1105 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1106 routines so as to allow Epoch to display values of expressions in a
1109 @item -annotate @var{level}
1110 @cindex @code{--annotate}
1111 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1112 effect is identical to using @samp{set annotate @var{level}}
1113 (@pxref{Annotations}). The annotation @var{level} controls how much
1114 information @value{GDBN} prints together with its prompt, values of
1115 expressions, source lines, and other types of output. Level 0 is the
1116 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1117 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1118 that control @value{GDBN}, and level 2 has been deprecated.
1120 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1124 @cindex @code{--args}
1125 Change interpretation of command line so that arguments following the
1126 executable file are passed as command line arguments to the inferior.
1127 This option stops option processing.
1129 @item -baud @var{bps}
1131 @cindex @code{--baud}
1133 Set the line speed (baud rate or bits per second) of any serial
1134 interface used by @value{GDBN} for remote debugging.
1136 @item -l @var{timeout}
1138 Set the timeout (in seconds) of any communication used by @value{GDBN}
1139 for remote debugging.
1141 @item -tty @var{device}
1142 @itemx -t @var{device}
1143 @cindex @code{--tty}
1145 Run using @var{device} for your program's standard input and output.
1146 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1148 @c resolve the situation of these eventually
1150 @cindex @code{--tui}
1151 Activate the @dfn{Text User Interface} when starting. The Text User
1152 Interface manages several text windows on the terminal, showing
1153 source, assembly, registers and @value{GDBN} command outputs
1154 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1155 Text User Interface can be enabled by invoking the program
1156 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1157 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1160 @c @cindex @code{--xdb}
1161 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1162 @c For information, see the file @file{xdb_trans.html}, which is usually
1163 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1166 @item -interpreter @var{interp}
1167 @cindex @code{--interpreter}
1168 Use the interpreter @var{interp} for interface with the controlling
1169 program or device. This option is meant to be set by programs which
1170 communicate with @value{GDBN} using it as a back end.
1171 @xref{Interpreters, , Command Interpreters}.
1173 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1174 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1175 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1176 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1177 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1178 @sc{gdb/mi} interfaces are no longer supported.
1181 @cindex @code{--write}
1182 Open the executable and core files for both reading and writing. This
1183 is equivalent to the @samp{set write on} command inside @value{GDBN}
1187 @cindex @code{--statistics}
1188 This option causes @value{GDBN} to print statistics about time and
1189 memory usage after it completes each command and returns to the prompt.
1192 @cindex @code{--version}
1193 This option causes @value{GDBN} to print its version number and
1194 no-warranty blurb, and exit.
1199 @subsection What @value{GDBN} Does During Startup
1200 @cindex @value{GDBN} startup
1202 Here's the description of what @value{GDBN} does during session startup:
1206 Sets up the command interpreter as specified by the command line
1207 (@pxref{Mode Options, interpreter}).
1211 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1212 DOS/Windows systems, the home directory is the one pointed to by the
1213 @code{HOME} environment variable.} and executes all the commands in
1217 Processes command line options and operands.
1220 Reads and executes the commands from init file (if any) in the current
1221 working directory. This is only done if the current directory is
1222 different from your home directory. Thus, you can have more than one
1223 init file, one generic in your home directory, and another, specific
1224 to the program you are debugging, in the directory where you invoke
1228 Reads command files specified by the @samp{-x} option. @xref{Command
1229 Files}, for more details about @value{GDBN} command files.
1232 Reads the command history recorded in the @dfn{history file}.
1233 @xref{Command History}, for more details about the command history and the
1234 files where @value{GDBN} records it.
1237 Init files use the same syntax as @dfn{command files} (@pxref{Command
1238 Files}) and are processed by @value{GDBN} in the same way. The init
1239 file in your home directory can set options (such as @samp{set
1240 complaints}) that affect subsequent processing of command line options
1241 and operands. Init files are not executed if you use the @samp{-nx}
1242 option (@pxref{Mode Options, ,Choosing Modes}).
1244 @cindex init file name
1245 @cindex @file{.gdbinit}
1246 @cindex @file{gdb.ini}
1247 The @value{GDBN} init files are normally called @file{.gdbinit}.
1248 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1249 the limitations of file names imposed by DOS filesystems. The Windows
1250 ports of @value{GDBN} use the standard name, but if they find a
1251 @file{gdb.ini} file, they warn you about that and suggest to rename
1252 the file to the standard name.
1256 @section Quitting @value{GDBN}
1257 @cindex exiting @value{GDBN}
1258 @cindex leaving @value{GDBN}
1261 @kindex quit @r{[}@var{expression}@r{]}
1262 @kindex q @r{(@code{quit})}
1263 @item quit @r{[}@var{expression}@r{]}
1265 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1266 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1267 do not supply @var{expression}, @value{GDBN} will terminate normally;
1268 otherwise it will terminate using the result of @var{expression} as the
1273 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1274 terminates the action of any @value{GDBN} command that is in progress and
1275 returns to @value{GDBN} command level. It is safe to type the interrupt
1276 character at any time because @value{GDBN} does not allow it to take effect
1277 until a time when it is safe.
1279 If you have been using @value{GDBN} to control an attached process or
1280 device, you can release it with the @code{detach} command
1281 (@pxref{Attach, ,Debugging an Already-running Process}).
1283 @node Shell Commands
1284 @section Shell Commands
1286 If you need to execute occasional shell commands during your
1287 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1288 just use the @code{shell} command.
1292 @cindex shell escape
1293 @item shell @var{command string}
1294 Invoke a standard shell to execute @var{command string}.
1295 If it exists, the environment variable @code{SHELL} determines which
1296 shell to run. Otherwise @value{GDBN} uses the default shell
1297 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1300 The utility @code{make} is often needed in development environments.
1301 You do not have to use the @code{shell} command for this purpose in
1306 @cindex calling make
1307 @item make @var{make-args}
1308 Execute the @code{make} program with the specified
1309 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1312 @node Logging Output
1313 @section Logging Output
1314 @cindex logging @value{GDBN} output
1315 @cindex save @value{GDBN} output to a file
1317 You may want to save the output of @value{GDBN} commands to a file.
1318 There are several commands to control @value{GDBN}'s logging.
1322 @item set logging on
1324 @item set logging off
1326 @cindex logging file name
1327 @item set logging file @var{file}
1328 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1329 @item set logging overwrite [on|off]
1330 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1331 you want @code{set logging on} to overwrite the logfile instead.
1332 @item set logging redirect [on|off]
1333 By default, @value{GDBN} output will go to both the terminal and the logfile.
1334 Set @code{redirect} if you want output to go only to the log file.
1335 @kindex show logging
1337 Show the current values of the logging settings.
1341 @chapter @value{GDBN} Commands
1343 You can abbreviate a @value{GDBN} command to the first few letters of the command
1344 name, if that abbreviation is unambiguous; and you can repeat certain
1345 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1346 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1347 show you the alternatives available, if there is more than one possibility).
1350 * Command Syntax:: How to give commands to @value{GDBN}
1351 * Completion:: Command completion
1352 * Help:: How to ask @value{GDBN} for help
1355 @node Command Syntax
1356 @section Command Syntax
1358 A @value{GDBN} command is a single line of input. There is no limit on
1359 how long it can be. It starts with a command name, which is followed by
1360 arguments whose meaning depends on the command name. For example, the
1361 command @code{step} accepts an argument which is the number of times to
1362 step, as in @samp{step 5}. You can also use the @code{step} command
1363 with no arguments. Some commands do not allow any arguments.
1365 @cindex abbreviation
1366 @value{GDBN} command names may always be truncated if that abbreviation is
1367 unambiguous. Other possible command abbreviations are listed in the
1368 documentation for individual commands. In some cases, even ambiguous
1369 abbreviations are allowed; for example, @code{s} is specially defined as
1370 equivalent to @code{step} even though there are other commands whose
1371 names start with @code{s}. You can test abbreviations by using them as
1372 arguments to the @code{help} command.
1374 @cindex repeating commands
1375 @kindex RET @r{(repeat last command)}
1376 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1377 repeat the previous command. Certain commands (for example, @code{run})
1378 will not repeat this way; these are commands whose unintentional
1379 repetition might cause trouble and which you are unlikely to want to
1380 repeat. User-defined commands can disable this feature; see
1381 @ref{Define, dont-repeat}.
1383 The @code{list} and @code{x} commands, when you repeat them with
1384 @key{RET}, construct new arguments rather than repeating
1385 exactly as typed. This permits easy scanning of source or memory.
1387 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1388 output, in a way similar to the common utility @code{more}
1389 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1390 @key{RET} too many in this situation, @value{GDBN} disables command
1391 repetition after any command that generates this sort of display.
1393 @kindex # @r{(a comment)}
1395 Any text from a @kbd{#} to the end of the line is a comment; it does
1396 nothing. This is useful mainly in command files (@pxref{Command
1397 Files,,Command Files}).
1399 @cindex repeating command sequences
1400 @kindex Ctrl-o @r{(operate-and-get-next)}
1401 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1402 commands. This command accepts the current line, like @key{RET}, and
1403 then fetches the next line relative to the current line from the history
1407 @section Command Completion
1410 @cindex word completion
1411 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1412 only one possibility; it can also show you what the valid possibilities
1413 are for the next word in a command, at any time. This works for @value{GDBN}
1414 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1416 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1417 of a word. If there is only one possibility, @value{GDBN} fills in the
1418 word, and waits for you to finish the command (or press @key{RET} to
1419 enter it). For example, if you type
1421 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1422 @c complete accuracy in these examples; space introduced for clarity.
1423 @c If texinfo enhancements make it unnecessary, it would be nice to
1424 @c replace " @key" by "@key" in the following...
1426 (@value{GDBP}) info bre @key{TAB}
1430 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1431 the only @code{info} subcommand beginning with @samp{bre}:
1434 (@value{GDBP}) info breakpoints
1438 You can either press @key{RET} at this point, to run the @code{info
1439 breakpoints} command, or backspace and enter something else, if
1440 @samp{breakpoints} does not look like the command you expected. (If you
1441 were sure you wanted @code{info breakpoints} in the first place, you
1442 might as well just type @key{RET} immediately after @samp{info bre},
1443 to exploit command abbreviations rather than command completion).
1445 If there is more than one possibility for the next word when you press
1446 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1447 characters and try again, or just press @key{TAB} a second time;
1448 @value{GDBN} displays all the possible completions for that word. For
1449 example, you might want to set a breakpoint on a subroutine whose name
1450 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1451 just sounds the bell. Typing @key{TAB} again displays all the
1452 function names in your program that begin with those characters, for
1456 (@value{GDBP}) b make_ @key{TAB}
1457 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1458 make_a_section_from_file make_environ
1459 make_abs_section make_function_type
1460 make_blockvector make_pointer_type
1461 make_cleanup make_reference_type
1462 make_command make_symbol_completion_list
1463 (@value{GDBP}) b make_
1467 After displaying the available possibilities, @value{GDBN} copies your
1468 partial input (@samp{b make_} in the example) so you can finish the
1471 If you just want to see the list of alternatives in the first place, you
1472 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1473 means @kbd{@key{META} ?}. You can type this either by holding down a
1474 key designated as the @key{META} shift on your keyboard (if there is
1475 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1477 @cindex quotes in commands
1478 @cindex completion of quoted strings
1479 Sometimes the string you need, while logically a ``word'', may contain
1480 parentheses or other characters that @value{GDBN} normally excludes from
1481 its notion of a word. To permit word completion to work in this
1482 situation, you may enclose words in @code{'} (single quote marks) in
1483 @value{GDBN} commands.
1485 The most likely situation where you might need this is in typing the
1486 name of a C@t{++} function. This is because C@t{++} allows function
1487 overloading (multiple definitions of the same function, distinguished
1488 by argument type). For example, when you want to set a breakpoint you
1489 may need to distinguish whether you mean the version of @code{name}
1490 that takes an @code{int} parameter, @code{name(int)}, or the version
1491 that takes a @code{float} parameter, @code{name(float)}. To use the
1492 word-completion facilities in this situation, type a single quote
1493 @code{'} at the beginning of the function name. This alerts
1494 @value{GDBN} that it may need to consider more information than usual
1495 when you press @key{TAB} or @kbd{M-?} to request word completion:
1498 (@value{GDBP}) b 'bubble( @kbd{M-?}
1499 bubble(double,double) bubble(int,int)
1500 (@value{GDBP}) b 'bubble(
1503 In some cases, @value{GDBN} can tell that completing a name requires using
1504 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1505 completing as much as it can) if you do not type the quote in the first
1509 (@value{GDBP}) b bub @key{TAB}
1510 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1511 (@value{GDBP}) b 'bubble(
1515 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1516 you have not yet started typing the argument list when you ask for
1517 completion on an overloaded symbol.
1519 For more information about overloaded functions, see @ref{C Plus Plus
1520 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1521 overload-resolution off} to disable overload resolution;
1522 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1526 @section Getting Help
1527 @cindex online documentation
1530 You can always ask @value{GDBN} itself for information on its commands,
1531 using the command @code{help}.
1534 @kindex h @r{(@code{help})}
1537 You can use @code{help} (abbreviated @code{h}) with no arguments to
1538 display a short list of named classes of commands:
1542 List of classes of commands:
1544 aliases -- Aliases of other commands
1545 breakpoints -- Making program stop at certain points
1546 data -- Examining data
1547 files -- Specifying and examining files
1548 internals -- Maintenance commands
1549 obscure -- Obscure features
1550 running -- Running the program
1551 stack -- Examining the stack
1552 status -- Status inquiries
1553 support -- Support facilities
1554 tracepoints -- Tracing of program execution without
1555 stopping the program
1556 user-defined -- User-defined commands
1558 Type "help" followed by a class name for a list of
1559 commands in that class.
1560 Type "help" followed by command name for full
1562 Command name abbreviations are allowed if unambiguous.
1565 @c the above line break eliminates huge line overfull...
1567 @item help @var{class}
1568 Using one of the general help classes as an argument, you can get a
1569 list of the individual commands in that class. For example, here is the
1570 help display for the class @code{status}:
1573 (@value{GDBP}) help status
1578 @c Line break in "show" line falsifies real output, but needed
1579 @c to fit in smallbook page size.
1580 info -- Generic command for showing things
1581 about the program being debugged
1582 show -- Generic command for showing things
1585 Type "help" followed by command name for full
1587 Command name abbreviations are allowed if unambiguous.
1591 @item help @var{command}
1592 With a command name as @code{help} argument, @value{GDBN} displays a
1593 short paragraph on how to use that command.
1596 @item apropos @var{args}
1597 The @code{apropos} command searches through all of the @value{GDBN}
1598 commands, and their documentation, for the regular expression specified in
1599 @var{args}. It prints out all matches found. For example:
1610 set symbol-reloading -- Set dynamic symbol table reloading
1611 multiple times in one run
1612 show symbol-reloading -- Show dynamic symbol table reloading
1613 multiple times in one run
1618 @item complete @var{args}
1619 The @code{complete @var{args}} command lists all the possible completions
1620 for the beginning of a command. Use @var{args} to specify the beginning of the
1621 command you want completed. For example:
1627 @noindent results in:
1638 @noindent This is intended for use by @sc{gnu} Emacs.
1641 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1642 and @code{show} to inquire about the state of your program, or the state
1643 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1644 manual introduces each of them in the appropriate context. The listings
1645 under @code{info} and under @code{show} in the Index point to
1646 all the sub-commands. @xref{Index}.
1651 @kindex i @r{(@code{info})}
1653 This command (abbreviated @code{i}) is for describing the state of your
1654 program. For example, you can list the arguments given to your program
1655 with @code{info args}, list the registers currently in use with @code{info
1656 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1657 You can get a complete list of the @code{info} sub-commands with
1658 @w{@code{help info}}.
1662 You can assign the result of an expression to an environment variable with
1663 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1664 @code{set prompt $}.
1668 In contrast to @code{info}, @code{show} is for describing the state of
1669 @value{GDBN} itself.
1670 You can change most of the things you can @code{show}, by using the
1671 related command @code{set}; for example, you can control what number
1672 system is used for displays with @code{set radix}, or simply inquire
1673 which is currently in use with @code{show radix}.
1676 To display all the settable parameters and their current
1677 values, you can use @code{show} with no arguments; you may also use
1678 @code{info set}. Both commands produce the same display.
1679 @c FIXME: "info set" violates the rule that "info" is for state of
1680 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1681 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1685 Here are three miscellaneous @code{show} subcommands, all of which are
1686 exceptional in lacking corresponding @code{set} commands:
1689 @kindex show version
1690 @cindex @value{GDBN} version number
1692 Show what version of @value{GDBN} is running. You should include this
1693 information in @value{GDBN} bug-reports. If multiple versions of
1694 @value{GDBN} are in use at your site, you may need to determine which
1695 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1696 commands are introduced, and old ones may wither away. Also, many
1697 system vendors ship variant versions of @value{GDBN}, and there are
1698 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1699 The version number is the same as the one announced when you start
1702 @kindex show copying
1703 @kindex info copying
1704 @cindex display @value{GDBN} copyright
1707 Display information about permission for copying @value{GDBN}.
1709 @kindex show warranty
1710 @kindex info warranty
1712 @itemx info warranty
1713 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1714 if your version of @value{GDBN} comes with one.
1719 @chapter Running Programs Under @value{GDBN}
1721 When you run a program under @value{GDBN}, you must first generate
1722 debugging information when you compile it.
1724 You may start @value{GDBN} with its arguments, if any, in an environment
1725 of your choice. If you are doing native debugging, you may redirect
1726 your program's input and output, debug an already running process, or
1727 kill a child process.
1730 * Compilation:: Compiling for debugging
1731 * Starting:: Starting your program
1732 * Arguments:: Your program's arguments
1733 * Environment:: Your program's environment
1735 * Working Directory:: Your program's working directory
1736 * Input/Output:: Your program's input and output
1737 * Attach:: Debugging an already-running process
1738 * Kill Process:: Killing the child process
1740 * Threads:: Debugging programs with multiple threads
1741 * Processes:: Debugging programs with multiple processes
1742 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1746 @section Compiling for Debugging
1748 In order to debug a program effectively, you need to generate
1749 debugging information when you compile it. This debugging information
1750 is stored in the object file; it describes the data type of each
1751 variable or function and the correspondence between source line numbers
1752 and addresses in the executable code.
1754 To request debugging information, specify the @samp{-g} option when you run
1757 Programs that are to be shipped to your customers are compiled with
1758 optimizations, using the @samp{-O} compiler option. However, many
1759 compilers are unable to handle the @samp{-g} and @samp{-O} options
1760 together. Using those compilers, you cannot generate optimized
1761 executables containing debugging information.
1763 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1764 without @samp{-O}, making it possible to debug optimized code. We
1765 recommend that you @emph{always} use @samp{-g} whenever you compile a
1766 program. You may think your program is correct, but there is no sense
1767 in pushing your luck.
1769 @cindex optimized code, debugging
1770 @cindex debugging optimized code
1771 When you debug a program compiled with @samp{-g -O}, remember that the
1772 optimizer is rearranging your code; the debugger shows you what is
1773 really there. Do not be too surprised when the execution path does not
1774 exactly match your source file! An extreme example: if you define a
1775 variable, but never use it, @value{GDBN} never sees that
1776 variable---because the compiler optimizes it out of existence.
1778 Some things do not work as well with @samp{-g -O} as with just
1779 @samp{-g}, particularly on machines with instruction scheduling. If in
1780 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1781 please report it to us as a bug (including a test case!).
1782 @xref{Variables}, for more information about debugging optimized code.
1784 Older versions of the @sc{gnu} C compiler permitted a variant option
1785 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1786 format; if your @sc{gnu} C compiler has this option, do not use it.
1788 @value{GDBN} knows about preprocessor macros and can show you their
1789 expansion (@pxref{Macros}). Most compilers do not include information
1790 about preprocessor macros in the debugging information if you specify
1791 the @option{-g} flag alone, because this information is rather large.
1792 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1793 provides macro information if you specify the options
1794 @option{-gdwarf-2} and @option{-g3}; the former option requests
1795 debugging information in the Dwarf 2 format, and the latter requests
1796 ``extra information''. In the future, we hope to find more compact
1797 ways to represent macro information, so that it can be included with
1802 @section Starting your Program
1808 @kindex r @r{(@code{run})}
1811 Use the @code{run} command to start your program under @value{GDBN}.
1812 You must first specify the program name (except on VxWorks) with an
1813 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1814 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1815 (@pxref{Files, ,Commands to Specify Files}).
1819 If you are running your program in an execution environment that
1820 supports processes, @code{run} creates an inferior process and makes
1821 that process run your program. (In environments without processes,
1822 @code{run} jumps to the start of your program.)
1824 The execution of a program is affected by certain information it
1825 receives from its superior. @value{GDBN} provides ways to specify this
1826 information, which you must do @emph{before} starting your program. (You
1827 can change it after starting your program, but such changes only affect
1828 your program the next time you start it.) This information may be
1829 divided into four categories:
1832 @item The @emph{arguments.}
1833 Specify the arguments to give your program as the arguments of the
1834 @code{run} command. If a shell is available on your target, the shell
1835 is used to pass the arguments, so that you may use normal conventions
1836 (such as wildcard expansion or variable substitution) in describing
1838 In Unix systems, you can control which shell is used with the
1839 @code{SHELL} environment variable.
1840 @xref{Arguments, ,Your Program's Arguments}.
1842 @item The @emph{environment.}
1843 Your program normally inherits its environment from @value{GDBN}, but you can
1844 use the @value{GDBN} commands @code{set environment} and @code{unset
1845 environment} to change parts of the environment that affect
1846 your program. @xref{Environment, ,Your Program's Environment}.
1848 @item The @emph{working directory.}
1849 Your program inherits its working directory from @value{GDBN}. You can set
1850 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1851 @xref{Working Directory, ,Your Program's Working Directory}.
1853 @item The @emph{standard input and output.}
1854 Your program normally uses the same device for standard input and
1855 standard output as @value{GDBN} is using. You can redirect input and output
1856 in the @code{run} command line, or you can use the @code{tty} command to
1857 set a different device for your program.
1858 @xref{Input/Output, ,Your Program's Input and Output}.
1861 @emph{Warning:} While input and output redirection work, you cannot use
1862 pipes to pass the output of the program you are debugging to another
1863 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1867 When you issue the @code{run} command, your program begins to execute
1868 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1869 of how to arrange for your program to stop. Once your program has
1870 stopped, you may call functions in your program, using the @code{print}
1871 or @code{call} commands. @xref{Data, ,Examining Data}.
1873 If the modification time of your symbol file has changed since the last
1874 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1875 table, and reads it again. When it does this, @value{GDBN} tries to retain
1876 your current breakpoints.
1881 @cindex run to main procedure
1882 The name of the main procedure can vary from language to language.
1883 With C or C@t{++}, the main procedure name is always @code{main}, but
1884 other languages such as Ada do not require a specific name for their
1885 main procedure. The debugger provides a convenient way to start the
1886 execution of the program and to stop at the beginning of the main
1887 procedure, depending on the language used.
1889 The @samp{start} command does the equivalent of setting a temporary
1890 breakpoint at the beginning of the main procedure and then invoking
1891 the @samp{run} command.
1893 @cindex elaboration phase
1894 Some programs contain an @dfn{elaboration} phase where some startup code is
1895 executed before the main procedure is called. This depends on the
1896 languages used to write your program. In C@t{++}, for instance,
1897 constructors for static and global objects are executed before
1898 @code{main} is called. It is therefore possible that the debugger stops
1899 before reaching the main procedure. However, the temporary breakpoint
1900 will remain to halt execution.
1902 Specify the arguments to give to your program as arguments to the
1903 @samp{start} command. These arguments will be given verbatim to the
1904 underlying @samp{run} command. Note that the same arguments will be
1905 reused if no argument is provided during subsequent calls to
1906 @samp{start} or @samp{run}.
1908 It is sometimes necessary to debug the program during elaboration. In
1909 these cases, using the @code{start} command would stop the execution of
1910 your program too late, as the program would have already completed the
1911 elaboration phase. Under these circumstances, insert breakpoints in your
1912 elaboration code before running your program.
1916 @section Your Program's Arguments
1918 @cindex arguments (to your program)
1919 The arguments to your program can be specified by the arguments of the
1921 They are passed to a shell, which expands wildcard characters and
1922 performs redirection of I/O, and thence to your program. Your
1923 @code{SHELL} environment variable (if it exists) specifies what shell
1924 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1925 the default shell (@file{/bin/sh} on Unix).
1927 On non-Unix systems, the program is usually invoked directly by
1928 @value{GDBN}, which emulates I/O redirection via the appropriate system
1929 calls, and the wildcard characters are expanded by the startup code of
1930 the program, not by the shell.
1932 @code{run} with no arguments uses the same arguments used by the previous
1933 @code{run}, or those set by the @code{set args} command.
1938 Specify the arguments to be used the next time your program is run. If
1939 @code{set args} has no arguments, @code{run} executes your program
1940 with no arguments. Once you have run your program with arguments,
1941 using @code{set args} before the next @code{run} is the only way to run
1942 it again without arguments.
1946 Show the arguments to give your program when it is started.
1950 @section Your Program's Environment
1952 @cindex environment (of your program)
1953 The @dfn{environment} consists of a set of environment variables and
1954 their values. Environment variables conventionally record such things as
1955 your user name, your home directory, your terminal type, and your search
1956 path for programs to run. Usually you set up environment variables with
1957 the shell and they are inherited by all the other programs you run. When
1958 debugging, it can be useful to try running your program with a modified
1959 environment without having to start @value{GDBN} over again.
1963 @item path @var{directory}
1964 Add @var{directory} to the front of the @code{PATH} environment variable
1965 (the search path for executables) that will be passed to your program.
1966 The value of @code{PATH} used by @value{GDBN} does not change.
1967 You may specify several directory names, separated by whitespace or by a
1968 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1969 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1970 is moved to the front, so it is searched sooner.
1972 You can use the string @samp{$cwd} to refer to whatever is the current
1973 working directory at the time @value{GDBN} searches the path. If you
1974 use @samp{.} instead, it refers to the directory where you executed the
1975 @code{path} command. @value{GDBN} replaces @samp{.} in the
1976 @var{directory} argument (with the current path) before adding
1977 @var{directory} to the search path.
1978 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1979 @c document that, since repeating it would be a no-op.
1983 Display the list of search paths for executables (the @code{PATH}
1984 environment variable).
1986 @kindex show environment
1987 @item show environment @r{[}@var{varname}@r{]}
1988 Print the value of environment variable @var{varname} to be given to
1989 your program when it starts. If you do not supply @var{varname},
1990 print the names and values of all environment variables to be given to
1991 your program. You can abbreviate @code{environment} as @code{env}.
1993 @kindex set environment
1994 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1995 Set environment variable @var{varname} to @var{value}. The value
1996 changes for your program only, not for @value{GDBN} itself. @var{value} may
1997 be any string; the values of environment variables are just strings, and
1998 any interpretation is supplied by your program itself. The @var{value}
1999 parameter is optional; if it is eliminated, the variable is set to a
2001 @c "any string" here does not include leading, trailing
2002 @c blanks. Gnu asks: does anyone care?
2004 For example, this command:
2011 tells the debugged program, when subsequently run, that its user is named
2012 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2013 are not actually required.)
2015 @kindex unset environment
2016 @item unset environment @var{varname}
2017 Remove variable @var{varname} from the environment to be passed to your
2018 program. This is different from @samp{set env @var{varname} =};
2019 @code{unset environment} removes the variable from the environment,
2020 rather than assigning it an empty value.
2023 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2025 by your @code{SHELL} environment variable if it exists (or
2026 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2027 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2028 @file{.bashrc} for BASH---any variables you set in that file affect
2029 your program. You may wish to move setting of environment variables to
2030 files that are only run when you sign on, such as @file{.login} or
2033 @node Working Directory
2034 @section Your Program's Working Directory
2036 @cindex working directory (of your program)
2037 Each time you start your program with @code{run}, it inherits its
2038 working directory from the current working directory of @value{GDBN}.
2039 The @value{GDBN} working directory is initially whatever it inherited
2040 from its parent process (typically the shell), but you can specify a new
2041 working directory in @value{GDBN} with the @code{cd} command.
2043 The @value{GDBN} working directory also serves as a default for the commands
2044 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2049 @cindex change working directory
2050 @item cd @var{directory}
2051 Set the @value{GDBN} working directory to @var{directory}.
2055 Print the @value{GDBN} working directory.
2058 It is generally impossible to find the current working directory of
2059 the process being debugged (since a program can change its directory
2060 during its run). If you work on a system where @value{GDBN} is
2061 configured with the @file{/proc} support, you can use the @code{info
2062 proc} command (@pxref{SVR4 Process Information}) to find out the
2063 current working directory of the debuggee.
2066 @section Your Program's Input and Output
2071 By default, the program you run under @value{GDBN} does input and output to
2072 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2073 to its own terminal modes to interact with you, but it records the terminal
2074 modes your program was using and switches back to them when you continue
2075 running your program.
2078 @kindex info terminal
2080 Displays information recorded by @value{GDBN} about the terminal modes your
2084 You can redirect your program's input and/or output using shell
2085 redirection with the @code{run} command. For example,
2092 starts your program, diverting its output to the file @file{outfile}.
2095 @cindex controlling terminal
2096 Another way to specify where your program should do input and output is
2097 with the @code{tty} command. This command accepts a file name as
2098 argument, and causes this file to be the default for future @code{run}
2099 commands. It also resets the controlling terminal for the child
2100 process, for future @code{run} commands. For example,
2107 directs that processes started with subsequent @code{run} commands
2108 default to do input and output on the terminal @file{/dev/ttyb} and have
2109 that as their controlling terminal.
2111 An explicit redirection in @code{run} overrides the @code{tty} command's
2112 effect on the input/output device, but not its effect on the controlling
2115 When you use the @code{tty} command or redirect input in the @code{run}
2116 command, only the input @emph{for your program} is affected. The input
2117 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2118 for @code{set inferior-tty}.
2120 @cindex inferior tty
2121 @cindex set inferior controlling terminal
2122 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2123 display the name of the terminal that will be used for future runs of your
2127 @item set inferior-tty /dev/ttyb
2128 @kindex set inferior-tty
2129 Set the tty for the program being debugged to /dev/ttyb.
2131 @item show inferior-tty
2132 @kindex show inferior-tty
2133 Show the current tty for the program being debugged.
2137 @section Debugging an Already-running Process
2142 @item attach @var{process-id}
2143 This command attaches to a running process---one that was started
2144 outside @value{GDBN}. (@code{info files} shows your active
2145 targets.) The command takes as argument a process ID. The usual way to
2146 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2147 or with the @samp{jobs -l} shell command.
2149 @code{attach} does not repeat if you press @key{RET} a second time after
2150 executing the command.
2153 To use @code{attach}, your program must be running in an environment
2154 which supports processes; for example, @code{attach} does not work for
2155 programs on bare-board targets that lack an operating system. You must
2156 also have permission to send the process a signal.
2158 When you use @code{attach}, the debugger finds the program running in
2159 the process first by looking in the current working directory, then (if
2160 the program is not found) by using the source file search path
2161 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2162 the @code{file} command to load the program. @xref{Files, ,Commands to
2165 The first thing @value{GDBN} does after arranging to debug the specified
2166 process is to stop it. You can examine and modify an attached process
2167 with all the @value{GDBN} commands that are ordinarily available when
2168 you start processes with @code{run}. You can insert breakpoints; you
2169 can step and continue; you can modify storage. If you would rather the
2170 process continue running, you may use the @code{continue} command after
2171 attaching @value{GDBN} to the process.
2176 When you have finished debugging the attached process, you can use the
2177 @code{detach} command to release it from @value{GDBN} control. Detaching
2178 the process continues its execution. After the @code{detach} command,
2179 that process and @value{GDBN} become completely independent once more, and you
2180 are ready to @code{attach} another process or start one with @code{run}.
2181 @code{detach} does not repeat if you press @key{RET} again after
2182 executing the command.
2185 If you exit @value{GDBN} while you have an attached process, you detach
2186 that process. If you use the @code{run} command, you kill that process.
2187 By default, @value{GDBN} asks for confirmation if you try to do either of these
2188 things; you can control whether or not you need to confirm by using the
2189 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2193 @section Killing the Child Process
2198 Kill the child process in which your program is running under @value{GDBN}.
2201 This command is useful if you wish to debug a core dump instead of a
2202 running process. @value{GDBN} ignores any core dump file while your program
2205 On some operating systems, a program cannot be executed outside @value{GDBN}
2206 while you have breakpoints set on it inside @value{GDBN}. You can use the
2207 @code{kill} command in this situation to permit running your program
2208 outside the debugger.
2210 The @code{kill} command is also useful if you wish to recompile and
2211 relink your program, since on many systems it is impossible to modify an
2212 executable file while it is running in a process. In this case, when you
2213 next type @code{run}, @value{GDBN} notices that the file has changed, and
2214 reads the symbol table again (while trying to preserve your current
2215 breakpoint settings).
2218 @section Debugging Programs with Multiple Threads
2220 @cindex threads of execution
2221 @cindex multiple threads
2222 @cindex switching threads
2223 In some operating systems, such as HP-UX and Solaris, a single program
2224 may have more than one @dfn{thread} of execution. The precise semantics
2225 of threads differ from one operating system to another, but in general
2226 the threads of a single program are akin to multiple processes---except
2227 that they share one address space (that is, they can all examine and
2228 modify the same variables). On the other hand, each thread has its own
2229 registers and execution stack, and perhaps private memory.
2231 @value{GDBN} provides these facilities for debugging multi-thread
2235 @item automatic notification of new threads
2236 @item @samp{thread @var{threadno}}, a command to switch among threads
2237 @item @samp{info threads}, a command to inquire about existing threads
2238 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2239 a command to apply a command to a list of threads
2240 @item thread-specific breakpoints
2244 @emph{Warning:} These facilities are not yet available on every
2245 @value{GDBN} configuration where the operating system supports threads.
2246 If your @value{GDBN} does not support threads, these commands have no
2247 effect. For example, a system without thread support shows no output
2248 from @samp{info threads}, and always rejects the @code{thread} command,
2252 (@value{GDBP}) info threads
2253 (@value{GDBP}) thread 1
2254 Thread ID 1 not known. Use the "info threads" command to
2255 see the IDs of currently known threads.
2257 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2258 @c doesn't support threads"?
2261 @cindex focus of debugging
2262 @cindex current thread
2263 The @value{GDBN} thread debugging facility allows you to observe all
2264 threads while your program runs---but whenever @value{GDBN} takes
2265 control, one thread in particular is always the focus of debugging.
2266 This thread is called the @dfn{current thread}. Debugging commands show
2267 program information from the perspective of the current thread.
2269 @cindex @code{New} @var{systag} message
2270 @cindex thread identifier (system)
2271 @c FIXME-implementors!! It would be more helpful if the [New...] message
2272 @c included GDB's numeric thread handle, so you could just go to that
2273 @c thread without first checking `info threads'.
2274 Whenever @value{GDBN} detects a new thread in your program, it displays
2275 the target system's identification for the thread with a message in the
2276 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2277 whose form varies depending on the particular system. For example, on
2278 @sc{gnu}/Linux, you might see
2281 [New Thread 46912507313328 (LWP 25582)]
2285 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2286 the @var{systag} is simply something like @samp{process 368}, with no
2289 @c FIXME!! (1) Does the [New...] message appear even for the very first
2290 @c thread of a program, or does it only appear for the
2291 @c second---i.e.@: when it becomes obvious we have a multithread
2293 @c (2) *Is* there necessarily a first thread always? Or do some
2294 @c multithread systems permit starting a program with multiple
2295 @c threads ab initio?
2297 @cindex thread number
2298 @cindex thread identifier (GDB)
2299 For debugging purposes, @value{GDBN} associates its own thread
2300 number---always a single integer---with each thread in your program.
2303 @kindex info threads
2305 Display a summary of all threads currently in your
2306 program. @value{GDBN} displays for each thread (in this order):
2310 the thread number assigned by @value{GDBN}
2313 the target system's thread identifier (@var{systag})
2316 the current stack frame summary for that thread
2320 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2321 indicates the current thread.
2325 @c end table here to get a little more width for example
2328 (@value{GDBP}) info threads
2329 3 process 35 thread 27 0x34e5 in sigpause ()
2330 2 process 35 thread 23 0x34e5 in sigpause ()
2331 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2337 @cindex debugging multithreaded programs (on HP-UX)
2338 @cindex thread identifier (GDB), on HP-UX
2339 For debugging purposes, @value{GDBN} associates its own thread
2340 number---a small integer assigned in thread-creation order---with each
2341 thread in your program.
2343 @cindex @code{New} @var{systag} message, on HP-UX
2344 @cindex thread identifier (system), on HP-UX
2345 @c FIXME-implementors!! It would be more helpful if the [New...] message
2346 @c included GDB's numeric thread handle, so you could just go to that
2347 @c thread without first checking `info threads'.
2348 Whenever @value{GDBN} detects a new thread in your program, it displays
2349 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2350 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2351 whose form varies depending on the particular system. For example, on
2355 [New thread 2 (system thread 26594)]
2359 when @value{GDBN} notices a new thread.
2362 @kindex info threads (HP-UX)
2364 Display a summary of all threads currently in your
2365 program. @value{GDBN} displays for each thread (in this order):
2368 @item the thread number assigned by @value{GDBN}
2370 @item the target system's thread identifier (@var{systag})
2372 @item the current stack frame summary for that thread
2376 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2377 indicates the current thread.
2381 @c end table here to get a little more width for example
2384 (@value{GDBP}) info threads
2385 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2387 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2388 from /usr/lib/libc.2
2389 1 system thread 27905 0x7b003498 in _brk () \@*
2390 from /usr/lib/libc.2
2393 On Solaris, you can display more information about user threads with a
2394 Solaris-specific command:
2397 @item maint info sol-threads
2398 @kindex maint info sol-threads
2399 @cindex thread info (Solaris)
2400 Display info on Solaris user threads.
2404 @kindex thread @var{threadno}
2405 @item thread @var{threadno}
2406 Make thread number @var{threadno} the current thread. The command
2407 argument @var{threadno} is the internal @value{GDBN} thread number, as
2408 shown in the first field of the @samp{info threads} display.
2409 @value{GDBN} responds by displaying the system identifier of the thread
2410 you selected, and its current stack frame summary:
2413 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2414 (@value{GDBP}) thread 2
2415 [Switching to process 35 thread 23]
2416 0x34e5 in sigpause ()
2420 As with the @samp{[New @dots{}]} message, the form of the text after
2421 @samp{Switching to} depends on your system's conventions for identifying
2424 @kindex thread apply
2425 @cindex apply command to several threads
2426 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2427 The @code{thread apply} command allows you to apply the named
2428 @var{command} to one or more threads. Specify the numbers of the
2429 threads that you want affected with the command argument
2430 @var{threadno}. It can be a single thread number, one of the numbers
2431 shown in the first field of the @samp{info threads} display; or it
2432 could be a range of thread numbers, as in @code{2-4}. To apply a
2433 command to all threads, type @kbd{thread apply all @var{command}}.
2436 @cindex automatic thread selection
2437 @cindex switching threads automatically
2438 @cindex threads, automatic switching
2439 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2440 signal, it automatically selects the thread where that breakpoint or
2441 signal happened. @value{GDBN} alerts you to the context switch with a
2442 message of the form @samp{[Switching to @var{systag}]} to identify the
2445 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2446 more information about how @value{GDBN} behaves when you stop and start
2447 programs with multiple threads.
2449 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2450 watchpoints in programs with multiple threads.
2453 @section Debugging Programs with Multiple Processes
2455 @cindex fork, debugging programs which call
2456 @cindex multiple processes
2457 @cindex processes, multiple
2458 On most systems, @value{GDBN} has no special support for debugging
2459 programs which create additional processes using the @code{fork}
2460 function. When a program forks, @value{GDBN} will continue to debug the
2461 parent process and the child process will run unimpeded. If you have
2462 set a breakpoint in any code which the child then executes, the child
2463 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2464 will cause it to terminate.
2466 However, if you want to debug the child process there is a workaround
2467 which isn't too painful. Put a call to @code{sleep} in the code which
2468 the child process executes after the fork. It may be useful to sleep
2469 only if a certain environment variable is set, or a certain file exists,
2470 so that the delay need not occur when you don't want to run @value{GDBN}
2471 on the child. While the child is sleeping, use the @code{ps} program to
2472 get its process ID. Then tell @value{GDBN} (a new invocation of
2473 @value{GDBN} if you are also debugging the parent process) to attach to
2474 the child process (@pxref{Attach}). From that point on you can debug
2475 the child process just like any other process which you attached to.
2477 On some systems, @value{GDBN} provides support for debugging programs that
2478 create additional processes using the @code{fork} or @code{vfork} functions.
2479 Currently, the only platforms with this feature are HP-UX (11.x and later
2480 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2482 By default, when a program forks, @value{GDBN} will continue to debug
2483 the parent process and the child process will run unimpeded.
2485 If you want to follow the child process instead of the parent process,
2486 use the command @w{@code{set follow-fork-mode}}.
2489 @kindex set follow-fork-mode
2490 @item set follow-fork-mode @var{mode}
2491 Set the debugger response to a program call of @code{fork} or
2492 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2493 process. The @var{mode} argument can be:
2497 The original process is debugged after a fork. The child process runs
2498 unimpeded. This is the default.
2501 The new process is debugged after a fork. The parent process runs
2506 @kindex show follow-fork-mode
2507 @item show follow-fork-mode
2508 Display the current debugger response to a @code{fork} or @code{vfork} call.
2511 @cindex debugging multiple processes
2512 On Linux, if you want to debug both the parent and child processes, use the
2513 command @w{@code{set detach-on-fork}}.
2516 @kindex set detach-on-fork
2517 @item set detach-on-fork @var{mode}
2518 Tells gdb whether to detach one of the processes after a fork, or
2519 retain debugger control over them both.
2523 The child process (or parent process, depending on the value of
2524 @code{follow-fork-mode}) will be detached and allowed to run
2525 independently. This is the default.
2528 Both processes will be held under the control of @value{GDBN}.
2529 One process (child or parent, depending on the value of
2530 @code{follow-fork-mode}) is debugged as usual, while the other
2535 @kindex show detach-on-follow
2536 @item show detach-on-follow
2537 Show whether detach-on-follow mode is on/off.
2540 If you choose to set @var{detach-on-follow} mode off, then
2541 @value{GDBN} will retain control of all forked processes (including
2542 nested forks). You can list the forked processes under the control of
2543 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2544 from one fork to another by using the @w{@code{fork}} command.
2549 Print a list of all forked processes under the control of @value{GDBN}.
2550 The listing will include a fork id, a process id, and the current
2551 position (program counter) of the process.
2554 @kindex fork @var{fork-id}
2555 @item fork @var{fork-id}
2556 Make fork number @var{fork-id} the current process. The argument
2557 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2558 as shown in the first field of the @samp{info forks} display.
2562 To quit debugging one of the forked processes, you can either detach
2563 from it by using the @w{@code{detach fork}} command (allowing it to
2564 run independently), or delete (and kill) it using the
2565 @w{@code{delete fork}} command.
2568 @kindex detach fork @var{fork-id}
2569 @item detach fork @var{fork-id}
2570 Detach from the process identified by @value{GDBN} fork number
2571 @var{fork-id}, and remove it from the fork list. The process will be
2572 allowed to run independently.
2574 @kindex delete fork @var{fork-id}
2575 @item delete fork @var{fork-id}
2576 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2577 and remove it from the fork list.
2581 If you ask to debug a child process and a @code{vfork} is followed by an
2582 @code{exec}, @value{GDBN} executes the new target up to the first
2583 breakpoint in the new target. If you have a breakpoint set on
2584 @code{main} in your original program, the breakpoint will also be set on
2585 the child process's @code{main}.
2587 When a child process is spawned by @code{vfork}, you cannot debug the
2588 child or parent until an @code{exec} call completes.
2590 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2591 call executes, the new target restarts. To restart the parent process,
2592 use the @code{file} command with the parent executable name as its
2595 You can use the @code{catch} command to make @value{GDBN} stop whenever
2596 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2597 Catchpoints, ,Setting Catchpoints}.
2599 @node Checkpoint/Restart
2600 @section Setting a @emph{Bookmark} to Return to Later
2605 @cindex snapshot of a process
2606 @cindex rewind program state
2608 On certain operating systems@footnote{Currently, only
2609 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2610 program's state, called a @dfn{checkpoint}, and come back to it
2613 Returning to a checkpoint effectively undoes everything that has
2614 happened in the program since the @code{checkpoint} was saved. This
2615 includes changes in memory, registers, and even (within some limits)
2616 system state. Effectively, it is like going back in time to the
2617 moment when the checkpoint was saved.
2619 Thus, if you're stepping thru a program and you think you're
2620 getting close to the point where things go wrong, you can save
2621 a checkpoint. Then, if you accidentally go too far and miss
2622 the critical statement, instead of having to restart your program
2623 from the beginning, you can just go back to the checkpoint and
2624 start again from there.
2626 This can be especially useful if it takes a lot of time or
2627 steps to reach the point where you think the bug occurs.
2629 To use the @code{checkpoint}/@code{restart} method of debugging:
2634 Save a snapshot of the debugged program's current execution state.
2635 The @code{checkpoint} command takes no arguments, but each checkpoint
2636 is assigned a small integer id, similar to a breakpoint id.
2638 @kindex info checkpoints
2639 @item info checkpoints
2640 List the checkpoints that have been saved in the current debugging
2641 session. For each checkpoint, the following information will be
2648 @item Source line, or label
2651 @kindex restart @var{checkpoint-id}
2652 @item restart @var{checkpoint-id}
2653 Restore the program state that was saved as checkpoint number
2654 @var{checkpoint-id}. All program variables, registers, stack frames
2655 etc.@: will be returned to the values that they had when the checkpoint
2656 was saved. In essence, gdb will ``wind back the clock'' to the point
2657 in time when the checkpoint was saved.
2659 Note that breakpoints, @value{GDBN} variables, command history etc.
2660 are not affected by restoring a checkpoint. In general, a checkpoint
2661 only restores things that reside in the program being debugged, not in
2664 @kindex delete checkpoint @var{checkpoint-id}
2665 @item delete checkpoint @var{checkpoint-id}
2666 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2670 Returning to a previously saved checkpoint will restore the user state
2671 of the program being debugged, plus a significant subset of the system
2672 (OS) state, including file pointers. It won't ``un-write'' data from
2673 a file, but it will rewind the file pointer to the previous location,
2674 so that the previously written data can be overwritten. For files
2675 opened in read mode, the pointer will also be restored so that the
2676 previously read data can be read again.
2678 Of course, characters that have been sent to a printer (or other
2679 external device) cannot be ``snatched back'', and characters received
2680 from eg.@: a serial device can be removed from internal program buffers,
2681 but they cannot be ``pushed back'' into the serial pipeline, ready to
2682 be received again. Similarly, the actual contents of files that have
2683 been changed cannot be restored (at this time).
2685 However, within those constraints, you actually can ``rewind'' your
2686 program to a previously saved point in time, and begin debugging it
2687 again --- and you can change the course of events so as to debug a
2688 different execution path this time.
2690 @cindex checkpoints and process id
2691 Finally, there is one bit of internal program state that will be
2692 different when you return to a checkpoint --- the program's process
2693 id. Each checkpoint will have a unique process id (or @var{pid}),
2694 and each will be different from the program's original @var{pid}.
2695 If your program has saved a local copy of its process id, this could
2696 potentially pose a problem.
2698 @subsection A Non-obvious Benefit of Using Checkpoints
2700 On some systems such as @sc{gnu}/Linux, address space randomization
2701 is performed on new processes for security reasons. This makes it
2702 difficult or impossible to set a breakpoint, or watchpoint, on an
2703 absolute address if you have to restart the program, since the
2704 absolute location of a symbol will change from one execution to the
2707 A checkpoint, however, is an @emph{identical} copy of a process.
2708 Therefore if you create a checkpoint at (eg.@:) the start of main,
2709 and simply return to that checkpoint instead of restarting the
2710 process, you can avoid the effects of address randomization and
2711 your symbols will all stay in the same place.
2714 @chapter Stopping and Continuing
2716 The principal purposes of using a debugger are so that you can stop your
2717 program before it terminates; or so that, if your program runs into
2718 trouble, you can investigate and find out why.
2720 Inside @value{GDBN}, your program may stop for any of several reasons,
2721 such as a signal, a breakpoint, or reaching a new line after a
2722 @value{GDBN} command such as @code{step}. You may then examine and
2723 change variables, set new breakpoints or remove old ones, and then
2724 continue execution. Usually, the messages shown by @value{GDBN} provide
2725 ample explanation of the status of your program---but you can also
2726 explicitly request this information at any time.
2729 @kindex info program
2731 Display information about the status of your program: whether it is
2732 running or not, what process it is, and why it stopped.
2736 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2737 * Continuing and Stepping:: Resuming execution
2739 * Thread Stops:: Stopping and starting multi-thread programs
2743 @section Breakpoints, Watchpoints, and Catchpoints
2746 A @dfn{breakpoint} makes your program stop whenever a certain point in
2747 the program is reached. For each breakpoint, you can add conditions to
2748 control in finer detail whether your program stops. You can set
2749 breakpoints with the @code{break} command and its variants (@pxref{Set
2750 Breaks, ,Setting Breakpoints}), to specify the place where your program
2751 should stop by line number, function name or exact address in the
2754 On some systems, you can set breakpoints in shared libraries before
2755 the executable is run. There is a minor limitation on HP-UX systems:
2756 you must wait until the executable is run in order to set breakpoints
2757 in shared library routines that are not called directly by the program
2758 (for example, routines that are arguments in a @code{pthread_create}
2762 @cindex data breakpoints
2763 @cindex memory tracing
2764 @cindex breakpoint on memory address
2765 @cindex breakpoint on variable modification
2766 A @dfn{watchpoint} is a special breakpoint that stops your program
2767 when the value of an expression changes. The expression may be a value
2768 of a variable, or it could involve values of one or more variables
2769 combined by operators, such as @samp{a + b}. This is sometimes called
2770 @dfn{data breakpoints}. You must use a different command to set
2771 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2772 from that, you can manage a watchpoint like any other breakpoint: you
2773 enable, disable, and delete both breakpoints and watchpoints using the
2776 You can arrange to have values from your program displayed automatically
2777 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2781 @cindex breakpoint on events
2782 A @dfn{catchpoint} is another special breakpoint that stops your program
2783 when a certain kind of event occurs, such as the throwing of a C@t{++}
2784 exception or the loading of a library. As with watchpoints, you use a
2785 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2786 Catchpoints}), but aside from that, you can manage a catchpoint like any
2787 other breakpoint. (To stop when your program receives a signal, use the
2788 @code{handle} command; see @ref{Signals, ,Signals}.)
2790 @cindex breakpoint numbers
2791 @cindex numbers for breakpoints
2792 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2793 catchpoint when you create it; these numbers are successive integers
2794 starting with one. In many of the commands for controlling various
2795 features of breakpoints you use the breakpoint number to say which
2796 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2797 @dfn{disabled}; if disabled, it has no effect on your program until you
2800 @cindex breakpoint ranges
2801 @cindex ranges of breakpoints
2802 Some @value{GDBN} commands accept a range of breakpoints on which to
2803 operate. A breakpoint range is either a single breakpoint number, like
2804 @samp{5}, or two such numbers, in increasing order, separated by a
2805 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2806 all breakpoints in that range are operated on.
2809 * Set Breaks:: Setting breakpoints
2810 * Set Watchpoints:: Setting watchpoints
2811 * Set Catchpoints:: Setting catchpoints
2812 * Delete Breaks:: Deleting breakpoints
2813 * Disabling:: Disabling breakpoints
2814 * Conditions:: Break conditions
2815 * Break Commands:: Breakpoint command lists
2816 * Breakpoint Menus:: Breakpoint menus
2817 * Error in Breakpoints:: ``Cannot insert breakpoints''
2818 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2822 @subsection Setting Breakpoints
2824 @c FIXME LMB what does GDB do if no code on line of breakpt?
2825 @c consider in particular declaration with/without initialization.
2827 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2830 @kindex b @r{(@code{break})}
2831 @vindex $bpnum@r{, convenience variable}
2832 @cindex latest breakpoint
2833 Breakpoints are set with the @code{break} command (abbreviated
2834 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2835 number of the breakpoint you've set most recently; see @ref{Convenience
2836 Vars,, Convenience Variables}, for a discussion of what you can do with
2837 convenience variables.
2839 You have several ways to say where the breakpoint should go.
2842 @item break @var{function}
2843 Set a breakpoint at entry to function @var{function}.
2844 When using source languages that permit overloading of symbols, such as
2845 C@t{++}, @var{function} may refer to more than one possible place to break.
2846 @xref{Breakpoint Menus,,Breakpoint Menus}, for a discussion of that situation.
2848 @item break +@var{offset}
2849 @itemx break -@var{offset}
2850 Set a breakpoint some number of lines forward or back from the position
2851 at which execution stopped in the currently selected @dfn{stack frame}.
2852 (@xref{Frames, ,Frames}, for a description of stack frames.)
2854 @item break @var{linenum}
2855 Set a breakpoint at line @var{linenum} in the current source file.
2856 The current source file is the last file whose source text was printed.
2857 The breakpoint will stop your program just before it executes any of the
2860 @item break @var{filename}:@var{linenum}
2861 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2863 @item break @var{filename}:@var{function}
2864 Set a breakpoint at entry to function @var{function} found in file
2865 @var{filename}. Specifying a file name as well as a function name is
2866 superfluous except when multiple files contain similarly named
2869 @item break *@var{address}
2870 Set a breakpoint at address @var{address}. You can use this to set
2871 breakpoints in parts of your program which do not have debugging
2872 information or source files.
2875 When called without any arguments, @code{break} sets a breakpoint at
2876 the next instruction to be executed in the selected stack frame
2877 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2878 innermost, this makes your program stop as soon as control
2879 returns to that frame. This is similar to the effect of a
2880 @code{finish} command in the frame inside the selected frame---except
2881 that @code{finish} does not leave an active breakpoint. If you use
2882 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2883 the next time it reaches the current location; this may be useful
2886 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2887 least one instruction has been executed. If it did not do this, you
2888 would be unable to proceed past a breakpoint without first disabling the
2889 breakpoint. This rule applies whether or not the breakpoint already
2890 existed when your program stopped.
2892 @item break @dots{} if @var{cond}
2893 Set a breakpoint with condition @var{cond}; evaluate the expression
2894 @var{cond} each time the breakpoint is reached, and stop only if the
2895 value is nonzero---that is, if @var{cond} evaluates as true.
2896 @samp{@dots{}} stands for one of the possible arguments described
2897 above (or no argument) specifying where to break. @xref{Conditions,
2898 ,Break Conditions}, for more information on breakpoint conditions.
2901 @item tbreak @var{args}
2902 Set a breakpoint enabled only for one stop. @var{args} are the
2903 same as for the @code{break} command, and the breakpoint is set in the same
2904 way, but the breakpoint is automatically deleted after the first time your
2905 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2908 @cindex hardware breakpoints
2909 @item hbreak @var{args}
2910 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2911 @code{break} command and the breakpoint is set in the same way, but the
2912 breakpoint requires hardware support and some target hardware may not
2913 have this support. The main purpose of this is EPROM/ROM code
2914 debugging, so you can set a breakpoint at an instruction without
2915 changing the instruction. This can be used with the new trap-generation
2916 provided by SPARClite DSU and most x86-based targets. These targets
2917 will generate traps when a program accesses some data or instruction
2918 address that is assigned to the debug registers. However the hardware
2919 breakpoint registers can take a limited number of breakpoints. For
2920 example, on the DSU, only two data breakpoints can be set at a time, and
2921 @value{GDBN} will reject this command if more than two are used. Delete
2922 or disable unused hardware breakpoints before setting new ones
2923 (@pxref{Disabling, ,Disabling Breakpoints}).
2924 @xref{Conditions, ,Break Conditions}.
2925 For remote targets, you can restrict the number of hardware
2926 breakpoints @value{GDBN} will use, see @ref{set remote
2927 hardware-breakpoint-limit}.
2931 @item thbreak @var{args}
2932 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2933 are the same as for the @code{hbreak} command and the breakpoint is set in
2934 the same way. However, like the @code{tbreak} command,
2935 the breakpoint is automatically deleted after the
2936 first time your program stops there. Also, like the @code{hbreak}
2937 command, the breakpoint requires hardware support and some target hardware
2938 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2939 See also @ref{Conditions, ,Break Conditions}.
2942 @cindex regular expression
2943 @cindex breakpoints in functions matching a regexp
2944 @cindex set breakpoints in many functions
2945 @item rbreak @var{regex}
2946 Set breakpoints on all functions matching the regular expression
2947 @var{regex}. This command sets an unconditional breakpoint on all
2948 matches, printing a list of all breakpoints it set. Once these
2949 breakpoints are set, they are treated just like the breakpoints set with
2950 the @code{break} command. You can delete them, disable them, or make
2951 them conditional the same way as any other breakpoint.
2953 The syntax of the regular expression is the standard one used with tools
2954 like @file{grep}. Note that this is different from the syntax used by
2955 shells, so for instance @code{foo*} matches all functions that include
2956 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2957 @code{.*} leading and trailing the regular expression you supply, so to
2958 match only functions that begin with @code{foo}, use @code{^foo}.
2960 @cindex non-member C@t{++} functions, set breakpoint in
2961 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2962 breakpoints on overloaded functions that are not members of any special
2965 @cindex set breakpoints on all functions
2966 The @code{rbreak} command can be used to set breakpoints in
2967 @strong{all} the functions in a program, like this:
2970 (@value{GDBP}) rbreak .
2973 @kindex info breakpoints
2974 @cindex @code{$_} and @code{info breakpoints}
2975 @item info breakpoints @r{[}@var{n}@r{]}
2976 @itemx info break @r{[}@var{n}@r{]}
2977 @itemx info watchpoints @r{[}@var{n}@r{]}
2978 Print a table of all breakpoints, watchpoints, and catchpoints set and
2979 not deleted. Optional argument @var{n} means print information only
2980 about the specified breakpoint (or watchpoint or catchpoint). For
2981 each breakpoint, following columns are printed:
2984 @item Breakpoint Numbers
2986 Breakpoint, watchpoint, or catchpoint.
2988 Whether the breakpoint is marked to be disabled or deleted when hit.
2989 @item Enabled or Disabled
2990 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2991 that are not enabled. An optional @samp{(p)} suffix marks pending
2992 breakpoints---breakpoints for which address is either not yet
2993 resolved, pending load of a shared library, or for which address was
2994 in a shared library that was since unloaded. Such breakpoint won't
2995 fire until a shared library that has the symbol or line referred by
2996 breakpoint is loaded. See below for details.
2998 Where the breakpoint is in your program, as a memory address. For a
2999 pending breakpoint whose address is not yet known, this field will
3000 contain @samp{<PENDING>}. A breakpoint with several locations will
3001 have @samp{<MULTIPLE>} in this field---see below for details.
3003 Where the breakpoint is in the source for your program, as a file and
3004 line number. For a pending breakpoint, the original string passed to
3005 the breakpoint command will be listed as it cannot be resolved until
3006 the appropriate shared library is loaded in the future.
3010 If a breakpoint is conditional, @code{info break} shows the condition on
3011 the line following the affected breakpoint; breakpoint commands, if any,
3012 are listed after that. A pending breakpoint is allowed to have a condition
3013 specified for it. The condition is not parsed for validity until a shared
3014 library is loaded that allows the pending breakpoint to resolve to a
3018 @code{info break} with a breakpoint
3019 number @var{n} as argument lists only that breakpoint. The
3020 convenience variable @code{$_} and the default examining-address for
3021 the @code{x} command are set to the address of the last breakpoint
3022 listed (@pxref{Memory, ,Examining Memory}).
3025 @code{info break} displays a count of the number of times the breakpoint
3026 has been hit. This is especially useful in conjunction with the
3027 @code{ignore} command. You can ignore a large number of breakpoint
3028 hits, look at the breakpoint info to see how many times the breakpoint
3029 was hit, and then run again, ignoring one less than that number. This
3030 will get you quickly to the last hit of that breakpoint.
3033 @value{GDBN} allows you to set any number of breakpoints at the same place in
3034 your program. There is nothing silly or meaningless about this. When
3035 the breakpoints are conditional, this is even useful
3036 (@pxref{Conditions, ,Break Conditions}).
3038 It is possible that a breakpoint corresponds to several locations
3039 in your program. Examples of this situation are:
3044 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3045 instances of the function body, used in different cases.
3048 For a C@t{++} template function, a given line in the function can
3049 correspond to any number of instantiations.
3052 For an inlined function, a given source line can correspond to
3053 several places where that function is inlined.
3057 In all those cases, @value{GDBN} will insert a breakpoint at all
3058 the relevant locations.
3060 A breakpoint with multiple locations is displayed in the breakpoint
3061 table using several rows---one header row, followed by one row for
3062 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3063 address column. The rows for individual locations contain the actual
3064 addresses for locations, and show the functions to which those
3065 locations belong. The number column for a location is of the form
3066 @var{breakpoint-number}.@var{location-number}.
3071 Num Type Disp Enb Address What
3072 1 breakpoint keep y <MULTIPLE>
3074 breakpoint already hit 1 time
3075 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3076 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3079 Each location can be individually enabled or disabled by passing
3080 @var{breakpoint-number}.@var{location-number} as argument to the
3081 @code{enable} and @code{disable} commands. Note that you cannot
3082 delete the individual locations from the list, you can only delete the
3083 entire list of locations that belong to their parent breakpoint (with
3084 the @kbd{delete @var{num}} command, where @var{num} is the number of
3085 the parent breakpoint, 1 in the above example). Disabling or enabling
3086 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3087 that belong to that breakpoint.
3089 @cindex pending breakpoints
3090 It's quite common to have a breakpoint inside a shared library.
3091 Shared libraries can be loaded and unloaded explicitly,
3092 and possibly repeatedly, as the program is executed. To support
3093 this use case, @value{GDBN} updates breakpoint locations whenever
3094 any shared library is loaded or unloaded. Typically, you would
3095 set a breakpoint in a shared library at the beginning of your
3096 debugging session, when the library is not loaded, and when the
3097 symbols from the library are not available. When you try to set
3098 breakpoint, @value{GDBN} will ask you if you want to set
3099 a so called @dfn{pending breakpoint}---breakpoint whose address
3100 is not yet resolved.
3102 After the program is run, whenever a new shared library is loaded,
3103 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3104 shared library contains the symbol or line referred to by some
3105 pending breakpoint, that breakpoint is resolved and becomes an
3106 ordinary breakpoint. When a library is unloaded, all breakpoints
3107 that refer to its symbols or source lines become pending again.
3109 This logic works for breakpoints with multiple locations, too. For
3110 example, if you have a breakpoint in a C@t{++} template function, and
3111 a newly loaded shared library has an instantiation of that template,
3112 a new location is added to the list of locations for the breakpoint.
3114 Except for having unresolved address, pending breakpoints do not
3115 differ from regular breakpoints. You can set conditions or commands,
3116 enable and disable them and perform other breakpoint operations.
3118 @value{GDBN} provides some additional commands for controlling what
3119 happens when the @samp{break} command cannot resolve breakpoint
3120 address specification to an address:
3122 @kindex set breakpoint pending
3123 @kindex show breakpoint pending
3125 @item set breakpoint pending auto
3126 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3127 location, it queries you whether a pending breakpoint should be created.
3129 @item set breakpoint pending on
3130 This indicates that an unrecognized breakpoint location should automatically
3131 result in a pending breakpoint being created.
3133 @item set breakpoint pending off
3134 This indicates that pending breakpoints are not to be created. Any
3135 unrecognized breakpoint location results in an error. This setting does
3136 not affect any pending breakpoints previously created.
3138 @item show breakpoint pending
3139 Show the current behavior setting for creating pending breakpoints.
3142 The settings above only affect the @code{break} command and its
3143 variants. Once breakpoint is set, it will be automatically updated
3144 as shared libraries are loaded and unloaded.
3146 @cindex automatic hardware breakpoints
3147 For some targets, @value{GDBN} can automatically decide if hardware or
3148 software breakpoints should be used, depending on whether the
3149 breakpoint address is read-only or read-write. This applies to
3150 breakpoints set with the @code{break} command as well as to internal
3151 breakpoints set by commands like @code{next} and @code{finish}. For
3152 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3155 You can control this automatic behaviour with the following commands::
3157 @kindex set breakpoint auto-hw
3158 @kindex show breakpoint auto-hw
3160 @item set breakpoint auto-hw on
3161 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3162 will try to use the target memory map to decide if software or hardware
3163 breakpoint must be used.
3165 @item set breakpoint auto-hw off
3166 This indicates @value{GDBN} should not automatically select breakpoint
3167 type. If the target provides a memory map, @value{GDBN} will warn when
3168 trying to set software breakpoint at a read-only address.
3172 @cindex negative breakpoint numbers
3173 @cindex internal @value{GDBN} breakpoints
3174 @value{GDBN} itself sometimes sets breakpoints in your program for
3175 special purposes, such as proper handling of @code{longjmp} (in C
3176 programs). These internal breakpoints are assigned negative numbers,
3177 starting with @code{-1}; @samp{info breakpoints} does not display them.
3178 You can see these breakpoints with the @value{GDBN} maintenance command
3179 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3182 @node Set Watchpoints
3183 @subsection Setting Watchpoints
3185 @cindex setting watchpoints
3186 You can use a watchpoint to stop execution whenever the value of an
3187 expression changes, without having to predict a particular place where
3188 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3189 The expression may be as simple as the value of a single variable, or
3190 as complex as many variables combined by operators. Examples include:
3194 A reference to the value of a single variable.
3197 An address cast to an appropriate data type. For example,
3198 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3199 address (assuming an @code{int} occupies 4 bytes).
3202 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3203 expression can use any operators valid in the program's native
3204 language (@pxref{Languages}).
3207 @cindex software watchpoints
3208 @cindex hardware watchpoints
3209 Depending on your system, watchpoints may be implemented in software or
3210 hardware. @value{GDBN} does software watchpointing by single-stepping your
3211 program and testing the variable's value each time, which is hundreds of
3212 times slower than normal execution. (But this may still be worth it, to
3213 catch errors where you have no clue what part of your program is the
3216 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3217 x86-based targets, @value{GDBN} includes support for hardware
3218 watchpoints, which do not slow down the running of your program.
3222 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3223 Set a watchpoint for an expression. @value{GDBN} will break when the
3224 expression @var{expr} is written into by the program and its value
3225 changes. The simplest (and the most popular) use of this command is
3226 to watch the value of a single variable:
3229 (@value{GDBP}) watch foo
3232 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3233 clause, @value{GDBN} breaks only when the thread identified by
3234 @var{threadnum} changes the value of @var{expr}. If any other threads
3235 change the value of @var{expr}, @value{GDBN} will not break. Note
3236 that watchpoints restricted to a single thread in this way only work
3237 with Hardware Watchpoints.
3240 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3241 Set a watchpoint that will break when the value of @var{expr} is read
3245 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3246 Set a watchpoint that will break when @var{expr} is either read from
3247 or written into by the program.
3249 @kindex info watchpoints @r{[}@var{n}@r{]}
3250 @item info watchpoints
3251 This command prints a list of watchpoints, breakpoints, and catchpoints;
3252 it is the same as @code{info break} (@pxref{Set Breaks}).
3255 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3256 watchpoints execute very quickly, and the debugger reports a change in
3257 value at the exact instruction where the change occurs. If @value{GDBN}
3258 cannot set a hardware watchpoint, it sets a software watchpoint, which
3259 executes more slowly and reports the change in value at the next
3260 @emph{statement}, not the instruction, after the change occurs.
3262 @cindex use only software watchpoints
3263 You can force @value{GDBN} to use only software watchpoints with the
3264 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3265 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3266 the underlying system supports them. (Note that hardware-assisted
3267 watchpoints that were set @emph{before} setting
3268 @code{can-use-hw-watchpoints} to zero will still use the hardware
3269 mechanism of watching expression values.)
3272 @item set can-use-hw-watchpoints
3273 @kindex set can-use-hw-watchpoints
3274 Set whether or not to use hardware watchpoints.
3276 @item show can-use-hw-watchpoints
3277 @kindex show can-use-hw-watchpoints
3278 Show the current mode of using hardware watchpoints.
3281 For remote targets, you can restrict the number of hardware
3282 watchpoints @value{GDBN} will use, see @ref{set remote
3283 hardware-breakpoint-limit}.
3285 When you issue the @code{watch} command, @value{GDBN} reports
3288 Hardware watchpoint @var{num}: @var{expr}
3292 if it was able to set a hardware watchpoint.
3294 Currently, the @code{awatch} and @code{rwatch} commands can only set
3295 hardware watchpoints, because accesses to data that don't change the
3296 value of the watched expression cannot be detected without examining
3297 every instruction as it is being executed, and @value{GDBN} does not do
3298 that currently. If @value{GDBN} finds that it is unable to set a
3299 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3300 will print a message like this:
3303 Expression cannot be implemented with read/access watchpoint.
3306 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3307 data type of the watched expression is wider than what a hardware
3308 watchpoint on the target machine can handle. For example, some systems
3309 can only watch regions that are up to 4 bytes wide; on such systems you
3310 cannot set hardware watchpoints for an expression that yields a
3311 double-precision floating-point number (which is typically 8 bytes
3312 wide). As a work-around, it might be possible to break the large region
3313 into a series of smaller ones and watch them with separate watchpoints.
3315 If you set too many hardware watchpoints, @value{GDBN} might be unable
3316 to insert all of them when you resume the execution of your program.
3317 Since the precise number of active watchpoints is unknown until such
3318 time as the program is about to be resumed, @value{GDBN} might not be
3319 able to warn you about this when you set the watchpoints, and the
3320 warning will be printed only when the program is resumed:
3323 Hardware watchpoint @var{num}: Could not insert watchpoint
3327 If this happens, delete or disable some of the watchpoints.
3329 Watching complex expressions that reference many variables can also
3330 exhaust the resources available for hardware-assisted watchpoints.
3331 That's because @value{GDBN} needs to watch every variable in the
3332 expression with separately allocated resources.
3334 The SPARClite DSU will generate traps when a program accesses some data
3335 or instruction address that is assigned to the debug registers. For the
3336 data addresses, DSU facilitates the @code{watch} command. However the
3337 hardware breakpoint registers can only take two data watchpoints, and
3338 both watchpoints must be the same kind. For example, you can set two
3339 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3340 @strong{or} two with @code{awatch} commands, but you cannot set one
3341 watchpoint with one command and the other with a different command.
3342 @value{GDBN} will reject the command if you try to mix watchpoints.
3343 Delete or disable unused watchpoint commands before setting new ones.
3345 If you call a function interactively using @code{print} or @code{call},
3346 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3347 kind of breakpoint or the call completes.
3349 @value{GDBN} automatically deletes watchpoints that watch local
3350 (automatic) variables, or expressions that involve such variables, when
3351 they go out of scope, that is, when the execution leaves the block in
3352 which these variables were defined. In particular, when the program
3353 being debugged terminates, @emph{all} local variables go out of scope,
3354 and so only watchpoints that watch global variables remain set. If you
3355 rerun the program, you will need to set all such watchpoints again. One
3356 way of doing that would be to set a code breakpoint at the entry to the
3357 @code{main} function and when it breaks, set all the watchpoints.
3359 @cindex watchpoints and threads
3360 @cindex threads and watchpoints
3361 In multi-threaded programs, watchpoints will detect changes to the
3362 watched expression from every thread.
3365 @emph{Warning:} In multi-threaded programs, software watchpoints
3366 have only limited usefulness. If @value{GDBN} creates a software
3367 watchpoint, it can only watch the value of an expression @emph{in a
3368 single thread}. If you are confident that the expression can only
3369 change due to the current thread's activity (and if you are also
3370 confident that no other thread can become current), then you can use
3371 software watchpoints as usual. However, @value{GDBN} may not notice
3372 when a non-current thread's activity changes the expression. (Hardware
3373 watchpoints, in contrast, watch an expression in all threads.)
3376 @xref{set remote hardware-watchpoint-limit}.
3378 @node Set Catchpoints
3379 @subsection Setting Catchpoints
3380 @cindex catchpoints, setting
3381 @cindex exception handlers
3382 @cindex event handling
3384 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3385 kinds of program events, such as C@t{++} exceptions or the loading of a
3386 shared library. Use the @code{catch} command to set a catchpoint.
3390 @item catch @var{event}
3391 Stop when @var{event} occurs. @var{event} can be any of the following:
3394 @cindex stop on C@t{++} exceptions
3395 The throwing of a C@t{++} exception.
3398 The catching of a C@t{++} exception.
3401 @cindex Ada exception catching
3402 @cindex catch Ada exceptions
3403 An Ada exception being raised. If an exception name is specified
3404 at the end of the command (eg @code{catch exception Program_Error}),
3405 the debugger will stop only when this specific exception is raised.
3406 Otherwise, the debugger stops execution when any Ada exception is raised.
3408 @item exception unhandled
3409 An exception that was raised but is not handled by the program.
3412 A failed Ada assertion.
3415 @cindex break on fork/exec
3416 A call to @code{exec}. This is currently only available for HP-UX.
3419 A call to @code{fork}. This is currently only available for HP-UX.
3422 A call to @code{vfork}. This is currently only available for HP-UX.
3425 @itemx load @var{libname}
3426 @cindex break on load/unload of shared library
3427 The dynamic loading of any shared library, or the loading of the library
3428 @var{libname}. This is currently only available for HP-UX.
3431 @itemx unload @var{libname}
3432 The unloading of any dynamically loaded shared library, or the unloading
3433 of the library @var{libname}. This is currently only available for HP-UX.
3436 @item tcatch @var{event}
3437 Set a catchpoint that is enabled only for one stop. The catchpoint is
3438 automatically deleted after the first time the event is caught.
3442 Use the @code{info break} command to list the current catchpoints.
3444 There are currently some limitations to C@t{++} exception handling
3445 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3449 If you call a function interactively, @value{GDBN} normally returns
3450 control to you when the function has finished executing. If the call
3451 raises an exception, however, the call may bypass the mechanism that
3452 returns control to you and cause your program either to abort or to
3453 simply continue running until it hits a breakpoint, catches a signal
3454 that @value{GDBN} is listening for, or exits. This is the case even if
3455 you set a catchpoint for the exception; catchpoints on exceptions are
3456 disabled within interactive calls.
3459 You cannot raise an exception interactively.
3462 You cannot install an exception handler interactively.
3465 @cindex raise exceptions
3466 Sometimes @code{catch} is not the best way to debug exception handling:
3467 if you need to know exactly where an exception is raised, it is better to
3468 stop @emph{before} the exception handler is called, since that way you
3469 can see the stack before any unwinding takes place. If you set a
3470 breakpoint in an exception handler instead, it may not be easy to find
3471 out where the exception was raised.
3473 To stop just before an exception handler is called, you need some
3474 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3475 raised by calling a library function named @code{__raise_exception}
3476 which has the following ANSI C interface:
3479 /* @var{addr} is where the exception identifier is stored.
3480 @var{id} is the exception identifier. */
3481 void __raise_exception (void **addr, void *id);
3485 To make the debugger catch all exceptions before any stack
3486 unwinding takes place, set a breakpoint on @code{__raise_exception}
3487 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3489 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3490 that depends on the value of @var{id}, you can stop your program when
3491 a specific exception is raised. You can use multiple conditional
3492 breakpoints to stop your program when any of a number of exceptions are
3497 @subsection Deleting Breakpoints
3499 @cindex clearing breakpoints, watchpoints, catchpoints
3500 @cindex deleting breakpoints, watchpoints, catchpoints
3501 It is often necessary to eliminate a breakpoint, watchpoint, or
3502 catchpoint once it has done its job and you no longer want your program
3503 to stop there. This is called @dfn{deleting} the breakpoint. A
3504 breakpoint that has been deleted no longer exists; it is forgotten.
3506 With the @code{clear} command you can delete breakpoints according to
3507 where they are in your program. With the @code{delete} command you can
3508 delete individual breakpoints, watchpoints, or catchpoints by specifying
3509 their breakpoint numbers.
3511 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3512 automatically ignores breakpoints on the first instruction to be executed
3513 when you continue execution without changing the execution address.
3518 Delete any breakpoints at the next instruction to be executed in the
3519 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3520 the innermost frame is selected, this is a good way to delete a
3521 breakpoint where your program just stopped.
3523 @item clear @var{function}
3524 @itemx clear @var{filename}:@var{function}
3525 Delete any breakpoints set at entry to the named @var{function}.
3527 @item clear @var{linenum}
3528 @itemx clear @var{filename}:@var{linenum}
3529 Delete any breakpoints set at or within the code of the specified
3530 @var{linenum} of the specified @var{filename}.
3532 @cindex delete breakpoints
3534 @kindex d @r{(@code{delete})}
3535 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3536 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3537 ranges specified as arguments. If no argument is specified, delete all
3538 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3539 confirm off}). You can abbreviate this command as @code{d}.
3543 @subsection Disabling Breakpoints
3545 @cindex enable/disable a breakpoint
3546 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3547 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3548 it had been deleted, but remembers the information on the breakpoint so
3549 that you can @dfn{enable} it again later.
3551 You disable and enable breakpoints, watchpoints, and catchpoints with
3552 the @code{enable} and @code{disable} commands, optionally specifying one
3553 or more breakpoint numbers as arguments. Use @code{info break} or
3554 @code{info watch} to print a list of breakpoints, watchpoints, and
3555 catchpoints if you do not know which numbers to use.
3557 Disabling and enabling a breakpoint that has multiple locations
3558 affects all of its locations.
3560 A breakpoint, watchpoint, or catchpoint can have any of four different
3561 states of enablement:
3565 Enabled. The breakpoint stops your program. A breakpoint set
3566 with the @code{break} command starts out in this state.
3568 Disabled. The breakpoint has no effect on your program.
3570 Enabled once. The breakpoint stops your program, but then becomes
3573 Enabled for deletion. The breakpoint stops your program, but
3574 immediately after it does so it is deleted permanently. A breakpoint
3575 set with the @code{tbreak} command starts out in this state.
3578 You can use the following commands to enable or disable breakpoints,
3579 watchpoints, and catchpoints:
3583 @kindex dis @r{(@code{disable})}
3584 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3585 Disable the specified breakpoints---or all breakpoints, if none are
3586 listed. A disabled breakpoint has no effect but is not forgotten. All
3587 options such as ignore-counts, conditions and commands are remembered in
3588 case the breakpoint is enabled again later. You may abbreviate
3589 @code{disable} as @code{dis}.
3592 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3593 Enable the specified breakpoints (or all defined breakpoints). They
3594 become effective once again in stopping your program.
3596 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3597 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3598 of these breakpoints immediately after stopping your program.
3600 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3601 Enable the specified breakpoints to work once, then die. @value{GDBN}
3602 deletes any of these breakpoints as soon as your program stops there.
3603 Breakpoints set by the @code{tbreak} command start out in this state.
3606 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3607 @c confusing: tbreak is also initially enabled.
3608 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3609 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3610 subsequently, they become disabled or enabled only when you use one of
3611 the commands above. (The command @code{until} can set and delete a
3612 breakpoint of its own, but it does not change the state of your other
3613 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3617 @subsection Break Conditions
3618 @cindex conditional breakpoints
3619 @cindex breakpoint conditions
3621 @c FIXME what is scope of break condition expr? Context where wanted?
3622 @c in particular for a watchpoint?
3623 The simplest sort of breakpoint breaks every time your program reaches a
3624 specified place. You can also specify a @dfn{condition} for a
3625 breakpoint. A condition is just a Boolean expression in your
3626 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3627 a condition evaluates the expression each time your program reaches it,
3628 and your program stops only if the condition is @emph{true}.
3630 This is the converse of using assertions for program validation; in that
3631 situation, you want to stop when the assertion is violated---that is,
3632 when the condition is false. In C, if you want to test an assertion expressed
3633 by the condition @var{assert}, you should set the condition
3634 @samp{! @var{assert}} on the appropriate breakpoint.
3636 Conditions are also accepted for watchpoints; you may not need them,
3637 since a watchpoint is inspecting the value of an expression anyhow---but
3638 it might be simpler, say, to just set a watchpoint on a variable name,
3639 and specify a condition that tests whether the new value is an interesting
3642 Break conditions can have side effects, and may even call functions in
3643 your program. This can be useful, for example, to activate functions
3644 that log program progress, or to use your own print functions to
3645 format special data structures. The effects are completely predictable
3646 unless there is another enabled breakpoint at the same address. (In
3647 that case, @value{GDBN} might see the other breakpoint first and stop your
3648 program without checking the condition of this one.) Note that
3649 breakpoint commands are usually more convenient and flexible than break
3651 purpose of performing side effects when a breakpoint is reached
3652 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3654 Break conditions can be specified when a breakpoint is set, by using
3655 @samp{if} in the arguments to the @code{break} command. @xref{Set
3656 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3657 with the @code{condition} command.
3659 You can also use the @code{if} keyword with the @code{watch} command.
3660 The @code{catch} command does not recognize the @code{if} keyword;
3661 @code{condition} is the only way to impose a further condition on a
3666 @item condition @var{bnum} @var{expression}
3667 Specify @var{expression} as the break condition for breakpoint,
3668 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3669 breakpoint @var{bnum} stops your program only if the value of
3670 @var{expression} is true (nonzero, in C). When you use
3671 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3672 syntactic correctness, and to determine whether symbols in it have
3673 referents in the context of your breakpoint. If @var{expression} uses
3674 symbols not referenced in the context of the breakpoint, @value{GDBN}
3675 prints an error message:
3678 No symbol "foo" in current context.
3683 not actually evaluate @var{expression} at the time the @code{condition}
3684 command (or a command that sets a breakpoint with a condition, like
3685 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3687 @item condition @var{bnum}
3688 Remove the condition from breakpoint number @var{bnum}. It becomes
3689 an ordinary unconditional breakpoint.
3692 @cindex ignore count (of breakpoint)
3693 A special case of a breakpoint condition is to stop only when the
3694 breakpoint has been reached a certain number of times. This is so
3695 useful that there is a special way to do it, using the @dfn{ignore
3696 count} of the breakpoint. Every breakpoint has an ignore count, which
3697 is an integer. Most of the time, the ignore count is zero, and
3698 therefore has no effect. But if your program reaches a breakpoint whose
3699 ignore count is positive, then instead of stopping, it just decrements
3700 the ignore count by one and continues. As a result, if the ignore count
3701 value is @var{n}, the breakpoint does not stop the next @var{n} times
3702 your program reaches it.
3706 @item ignore @var{bnum} @var{count}
3707 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3708 The next @var{count} times the breakpoint is reached, your program's
3709 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3712 To make the breakpoint stop the next time it is reached, specify
3715 When you use @code{continue} to resume execution of your program from a
3716 breakpoint, you can specify an ignore count directly as an argument to
3717 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3718 Stepping,,Continuing and Stepping}.
3720 If a breakpoint has a positive ignore count and a condition, the
3721 condition is not checked. Once the ignore count reaches zero,
3722 @value{GDBN} resumes checking the condition.
3724 You could achieve the effect of the ignore count with a condition such
3725 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3726 is decremented each time. @xref{Convenience Vars, ,Convenience
3730 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3733 @node Break Commands
3734 @subsection Breakpoint Command Lists
3736 @cindex breakpoint commands
3737 You can give any breakpoint (or watchpoint or catchpoint) a series of
3738 commands to execute when your program stops due to that breakpoint. For
3739 example, you might want to print the values of certain expressions, or
3740 enable other breakpoints.
3744 @kindex end@r{ (breakpoint commands)}
3745 @item commands @r{[}@var{bnum}@r{]}
3746 @itemx @dots{} @var{command-list} @dots{}
3748 Specify a list of commands for breakpoint number @var{bnum}. The commands
3749 themselves appear on the following lines. Type a line containing just
3750 @code{end} to terminate the commands.
3752 To remove all commands from a breakpoint, type @code{commands} and
3753 follow it immediately with @code{end}; that is, give no commands.
3755 With no @var{bnum} argument, @code{commands} refers to the last
3756 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3757 recently encountered).
3760 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3761 disabled within a @var{command-list}.
3763 You can use breakpoint commands to start your program up again. Simply
3764 use the @code{continue} command, or @code{step}, or any other command
3765 that resumes execution.
3767 Any other commands in the command list, after a command that resumes
3768 execution, are ignored. This is because any time you resume execution
3769 (even with a simple @code{next} or @code{step}), you may encounter
3770 another breakpoint---which could have its own command list, leading to
3771 ambiguities about which list to execute.
3774 If the first command you specify in a command list is @code{silent}, the
3775 usual message about stopping at a breakpoint is not printed. This may
3776 be desirable for breakpoints that are to print a specific message and
3777 then continue. If none of the remaining commands print anything, you
3778 see no sign that the breakpoint was reached. @code{silent} is
3779 meaningful only at the beginning of a breakpoint command list.
3781 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3782 print precisely controlled output, and are often useful in silent
3783 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3785 For example, here is how you could use breakpoint commands to print the
3786 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3792 printf "x is %d\n",x
3797 One application for breakpoint commands is to compensate for one bug so
3798 you can test for another. Put a breakpoint just after the erroneous line
3799 of code, give it a condition to detect the case in which something
3800 erroneous has been done, and give it commands to assign correct values
3801 to any variables that need them. End with the @code{continue} command
3802 so that your program does not stop, and start with the @code{silent}
3803 command so that no output is produced. Here is an example:
3814 @node Breakpoint Menus
3815 @subsection Breakpoint Menus
3817 @cindex symbol overloading
3819 Some programming languages (notably C@t{++} and Objective-C) permit a
3820 single function name
3821 to be defined several times, for application in different contexts.
3822 This is called @dfn{overloading}. When a function name is overloaded,
3823 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3824 a breakpoint. You can use explicit signature of the function, as in
3825 @samp{break @var{function}(@var{types})}, to specify which
3826 particular version of the function you want. Otherwise, @value{GDBN} offers
3827 you a menu of numbered choices for different possible breakpoints, and
3828 waits for your selection with the prompt @samp{>}. The first two
3829 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3830 sets a breakpoint at each definition of @var{function}, and typing
3831 @kbd{0} aborts the @code{break} command without setting any new
3834 For example, the following session excerpt shows an attempt to set a
3835 breakpoint at the overloaded symbol @code{String::after}.
3836 We choose three particular definitions of that function name:
3838 @c FIXME! This is likely to change to show arg type lists, at least
3841 (@value{GDBP}) b String::after
3844 [2] file:String.cc; line number:867
3845 [3] file:String.cc; line number:860
3846 [4] file:String.cc; line number:875
3847 [5] file:String.cc; line number:853
3848 [6] file:String.cc; line number:846
3849 [7] file:String.cc; line number:735
3851 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3852 Breakpoint 2 at 0xb344: file String.cc, line 875.
3853 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3854 Multiple breakpoints were set.
3855 Use the "delete" command to delete unwanted
3861 @c @ifclear BARETARGET
3862 @node Error in Breakpoints
3863 @subsection ``Cannot insert breakpoints''
3865 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3867 Under some operating systems, breakpoints cannot be used in a program if
3868 any other process is running that program. In this situation,
3869 attempting to run or continue a program with a breakpoint causes
3870 @value{GDBN} to print an error message:
3873 Cannot insert breakpoints.
3874 The same program may be running in another process.
3877 When this happens, you have three ways to proceed:
3881 Remove or disable the breakpoints, then continue.
3884 Suspend @value{GDBN}, and copy the file containing your program to a new
3885 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3886 that @value{GDBN} should run your program under that name.
3887 Then start your program again.
3890 Relink your program so that the text segment is nonsharable, using the
3891 linker option @samp{-N}. The operating system limitation may not apply
3892 to nonsharable executables.
3896 A similar message can be printed if you request too many active
3897 hardware-assisted breakpoints and watchpoints:
3899 @c FIXME: the precise wording of this message may change; the relevant
3900 @c source change is not committed yet (Sep 3, 1999).
3902 Stopped; cannot insert breakpoints.
3903 You may have requested too many hardware breakpoints and watchpoints.
3907 This message is printed when you attempt to resume the program, since
3908 only then @value{GDBN} knows exactly how many hardware breakpoints and
3909 watchpoints it needs to insert.
3911 When this message is printed, you need to disable or remove some of the
3912 hardware-assisted breakpoints and watchpoints, and then continue.
3914 @node Breakpoint-related Warnings
3915 @subsection ``Breakpoint address adjusted...''
3916 @cindex breakpoint address adjusted
3918 Some processor architectures place constraints on the addresses at
3919 which breakpoints may be placed. For architectures thus constrained,
3920 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3921 with the constraints dictated by the architecture.
3923 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3924 a VLIW architecture in which a number of RISC-like instructions may be
3925 bundled together for parallel execution. The FR-V architecture
3926 constrains the location of a breakpoint instruction within such a
3927 bundle to the instruction with the lowest address. @value{GDBN}
3928 honors this constraint by adjusting a breakpoint's address to the
3929 first in the bundle.
3931 It is not uncommon for optimized code to have bundles which contain
3932 instructions from different source statements, thus it may happen that
3933 a breakpoint's address will be adjusted from one source statement to
3934 another. Since this adjustment may significantly alter @value{GDBN}'s
3935 breakpoint related behavior from what the user expects, a warning is
3936 printed when the breakpoint is first set and also when the breakpoint
3939 A warning like the one below is printed when setting a breakpoint
3940 that's been subject to address adjustment:
3943 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3946 Such warnings are printed both for user settable and @value{GDBN}'s
3947 internal breakpoints. If you see one of these warnings, you should
3948 verify that a breakpoint set at the adjusted address will have the
3949 desired affect. If not, the breakpoint in question may be removed and
3950 other breakpoints may be set which will have the desired behavior.
3951 E.g., it may be sufficient to place the breakpoint at a later
3952 instruction. A conditional breakpoint may also be useful in some
3953 cases to prevent the breakpoint from triggering too often.
3955 @value{GDBN} will also issue a warning when stopping at one of these
3956 adjusted breakpoints:
3959 warning: Breakpoint 1 address previously adjusted from 0x00010414
3963 When this warning is encountered, it may be too late to take remedial
3964 action except in cases where the breakpoint is hit earlier or more
3965 frequently than expected.
3967 @node Continuing and Stepping
3968 @section Continuing and Stepping
3972 @cindex resuming execution
3973 @dfn{Continuing} means resuming program execution until your program
3974 completes normally. In contrast, @dfn{stepping} means executing just
3975 one more ``step'' of your program, where ``step'' may mean either one
3976 line of source code, or one machine instruction (depending on what
3977 particular command you use). Either when continuing or when stepping,
3978 your program may stop even sooner, due to a breakpoint or a signal. (If
3979 it stops due to a signal, you may want to use @code{handle}, or use
3980 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3984 @kindex c @r{(@code{continue})}
3985 @kindex fg @r{(resume foreground execution)}
3986 @item continue @r{[}@var{ignore-count}@r{]}
3987 @itemx c @r{[}@var{ignore-count}@r{]}
3988 @itemx fg @r{[}@var{ignore-count}@r{]}
3989 Resume program execution, at the address where your program last stopped;
3990 any breakpoints set at that address are bypassed. The optional argument
3991 @var{ignore-count} allows you to specify a further number of times to
3992 ignore a breakpoint at this location; its effect is like that of
3993 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
3995 The argument @var{ignore-count} is meaningful only when your program
3996 stopped due to a breakpoint. At other times, the argument to
3997 @code{continue} is ignored.
3999 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4000 debugged program is deemed to be the foreground program) are provided
4001 purely for convenience, and have exactly the same behavior as
4005 To resume execution at a different place, you can use @code{return}
4006 (@pxref{Returning, ,Returning from a Function}) to go back to the
4007 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4008 Different Address}) to go to an arbitrary location in your program.
4010 A typical technique for using stepping is to set a breakpoint
4011 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4012 beginning of the function or the section of your program where a problem
4013 is believed to lie, run your program until it stops at that breakpoint,
4014 and then step through the suspect area, examining the variables that are
4015 interesting, until you see the problem happen.
4019 @kindex s @r{(@code{step})}
4021 Continue running your program until control reaches a different source
4022 line, then stop it and return control to @value{GDBN}. This command is
4023 abbreviated @code{s}.
4026 @c "without debugging information" is imprecise; actually "without line
4027 @c numbers in the debugging information". (gcc -g1 has debugging info but
4028 @c not line numbers). But it seems complex to try to make that
4029 @c distinction here.
4030 @emph{Warning:} If you use the @code{step} command while control is
4031 within a function that was compiled without debugging information,
4032 execution proceeds until control reaches a function that does have
4033 debugging information. Likewise, it will not step into a function which
4034 is compiled without debugging information. To step through functions
4035 without debugging information, use the @code{stepi} command, described
4039 The @code{step} command only stops at the first instruction of a source
4040 line. This prevents the multiple stops that could otherwise occur in
4041 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4042 to stop if a function that has debugging information is called within
4043 the line. In other words, @code{step} @emph{steps inside} any functions
4044 called within the line.
4046 Also, the @code{step} command only enters a function if there is line
4047 number information for the function. Otherwise it acts like the
4048 @code{next} command. This avoids problems when using @code{cc -gl}
4049 on MIPS machines. Previously, @code{step} entered subroutines if there
4050 was any debugging information about the routine.
4052 @item step @var{count}
4053 Continue running as in @code{step}, but do so @var{count} times. If a
4054 breakpoint is reached, or a signal not related to stepping occurs before
4055 @var{count} steps, stepping stops right away.
4058 @kindex n @r{(@code{next})}
4059 @item next @r{[}@var{count}@r{]}
4060 Continue to the next source line in the current (innermost) stack frame.
4061 This is similar to @code{step}, but function calls that appear within
4062 the line of code are executed without stopping. Execution stops when
4063 control reaches a different line of code at the original stack level
4064 that was executing when you gave the @code{next} command. This command
4065 is abbreviated @code{n}.
4067 An argument @var{count} is a repeat count, as for @code{step}.
4070 @c FIX ME!! Do we delete this, or is there a way it fits in with
4071 @c the following paragraph? --- Vctoria
4073 @c @code{next} within a function that lacks debugging information acts like
4074 @c @code{step}, but any function calls appearing within the code of the
4075 @c function are executed without stopping.
4077 The @code{next} command only stops at the first instruction of a
4078 source line. This prevents multiple stops that could otherwise occur in
4079 @code{switch} statements, @code{for} loops, etc.
4081 @kindex set step-mode
4083 @cindex functions without line info, and stepping
4084 @cindex stepping into functions with no line info
4085 @itemx set step-mode on
4086 The @code{set step-mode on} command causes the @code{step} command to
4087 stop at the first instruction of a function which contains no debug line
4088 information rather than stepping over it.
4090 This is useful in cases where you may be interested in inspecting the
4091 machine instructions of a function which has no symbolic info and do not
4092 want @value{GDBN} to automatically skip over this function.
4094 @item set step-mode off
4095 Causes the @code{step} command to step over any functions which contains no
4096 debug information. This is the default.
4098 @item show step-mode
4099 Show whether @value{GDBN} will stop in or step over functions without
4100 source line debug information.
4104 Continue running until just after function in the selected stack frame
4105 returns. Print the returned value (if any).
4107 Contrast this with the @code{return} command (@pxref{Returning,
4108 ,Returning from a Function}).
4111 @kindex u @r{(@code{until})}
4112 @cindex run until specified location
4115 Continue running until a source line past the current line, in the
4116 current stack frame, is reached. This command is used to avoid single
4117 stepping through a loop more than once. It is like the @code{next}
4118 command, except that when @code{until} encounters a jump, it
4119 automatically continues execution until the program counter is greater
4120 than the address of the jump.
4122 This means that when you reach the end of a loop after single stepping
4123 though it, @code{until} makes your program continue execution until it
4124 exits the loop. In contrast, a @code{next} command at the end of a loop
4125 simply steps back to the beginning of the loop, which forces you to step
4126 through the next iteration.
4128 @code{until} always stops your program if it attempts to exit the current
4131 @code{until} may produce somewhat counterintuitive results if the order
4132 of machine code does not match the order of the source lines. For
4133 example, in the following excerpt from a debugging session, the @code{f}
4134 (@code{frame}) command shows that execution is stopped at line
4135 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4139 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4141 (@value{GDBP}) until
4142 195 for ( ; argc > 0; NEXTARG) @{
4145 This happened because, for execution efficiency, the compiler had
4146 generated code for the loop closure test at the end, rather than the
4147 start, of the loop---even though the test in a C @code{for}-loop is
4148 written before the body of the loop. The @code{until} command appeared
4149 to step back to the beginning of the loop when it advanced to this
4150 expression; however, it has not really gone to an earlier
4151 statement---not in terms of the actual machine code.
4153 @code{until} with no argument works by means of single
4154 instruction stepping, and hence is slower than @code{until} with an
4157 @item until @var{location}
4158 @itemx u @var{location}
4159 Continue running your program until either the specified location is
4160 reached, or the current stack frame returns. @var{location} is any of
4161 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4162 ,Setting Breakpoints}). This form of the command uses breakpoints, and
4163 hence is quicker than @code{until} without an argument. The specified
4164 location is actually reached only if it is in the current frame. This
4165 implies that @code{until} can be used to skip over recursive function
4166 invocations. For instance in the code below, if the current location is
4167 line @code{96}, issuing @code{until 99} will execute the program up to
4168 line @code{99} in the same invocation of factorial, i.e., after the inner
4169 invocations have returned.
4172 94 int factorial (int value)
4174 96 if (value > 1) @{
4175 97 value *= factorial (value - 1);
4182 @kindex advance @var{location}
4183 @itemx advance @var{location}
4184 Continue running the program up to the given @var{location}. An argument is
4185 required, which should be of the same form as arguments for the @code{break}
4186 command. Execution will also stop upon exit from the current stack
4187 frame. This command is similar to @code{until}, but @code{advance} will
4188 not skip over recursive function calls, and the target location doesn't
4189 have to be in the same frame as the current one.
4193 @kindex si @r{(@code{stepi})}
4195 @itemx stepi @var{arg}
4197 Execute one machine instruction, then stop and return to the debugger.
4199 It is often useful to do @samp{display/i $pc} when stepping by machine
4200 instructions. This makes @value{GDBN} automatically display the next
4201 instruction to be executed, each time your program stops. @xref{Auto
4202 Display,, Automatic Display}.
4204 An argument is a repeat count, as in @code{step}.
4208 @kindex ni @r{(@code{nexti})}
4210 @itemx nexti @var{arg}
4212 Execute one machine instruction, but if it is a function call,
4213 proceed until the function returns.
4215 An argument is a repeat count, as in @code{next}.
4222 A signal is an asynchronous event that can happen in a program. The
4223 operating system defines the possible kinds of signals, and gives each
4224 kind a name and a number. For example, in Unix @code{SIGINT} is the
4225 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4226 @code{SIGSEGV} is the signal a program gets from referencing a place in
4227 memory far away from all the areas in use; @code{SIGALRM} occurs when
4228 the alarm clock timer goes off (which happens only if your program has
4229 requested an alarm).
4231 @cindex fatal signals
4232 Some signals, including @code{SIGALRM}, are a normal part of the
4233 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4234 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4235 program has not specified in advance some other way to handle the signal.
4236 @code{SIGINT} does not indicate an error in your program, but it is normally
4237 fatal so it can carry out the purpose of the interrupt: to kill the program.
4239 @value{GDBN} has the ability to detect any occurrence of a signal in your
4240 program. You can tell @value{GDBN} in advance what to do for each kind of
4243 @cindex handling signals
4244 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4245 @code{SIGALRM} be silently passed to your program
4246 (so as not to interfere with their role in the program's functioning)
4247 but to stop your program immediately whenever an error signal happens.
4248 You can change these settings with the @code{handle} command.
4251 @kindex info signals
4255 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4256 handle each one. You can use this to see the signal numbers of all
4257 the defined types of signals.
4259 @item info signals @var{sig}
4260 Similar, but print information only about the specified signal number.
4262 @code{info handle} is an alias for @code{info signals}.
4265 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4266 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4267 can be the number of a signal or its name (with or without the
4268 @samp{SIG} at the beginning); a list of signal numbers of the form
4269 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4270 known signals. Optional arguments @var{keywords}, described below,
4271 say what change to make.
4275 The keywords allowed by the @code{handle} command can be abbreviated.
4276 Their full names are:
4280 @value{GDBN} should not stop your program when this signal happens. It may
4281 still print a message telling you that the signal has come in.
4284 @value{GDBN} should stop your program when this signal happens. This implies
4285 the @code{print} keyword as well.
4288 @value{GDBN} should print a message when this signal happens.
4291 @value{GDBN} should not mention the occurrence of the signal at all. This
4292 implies the @code{nostop} keyword as well.
4296 @value{GDBN} should allow your program to see this signal; your program
4297 can handle the signal, or else it may terminate if the signal is fatal
4298 and not handled. @code{pass} and @code{noignore} are synonyms.
4302 @value{GDBN} should not allow your program to see this signal.
4303 @code{nopass} and @code{ignore} are synonyms.
4307 When a signal stops your program, the signal is not visible to the
4309 continue. Your program sees the signal then, if @code{pass} is in
4310 effect for the signal in question @emph{at that time}. In other words,
4311 after @value{GDBN} reports a signal, you can use the @code{handle}
4312 command with @code{pass} or @code{nopass} to control whether your
4313 program sees that signal when you continue.
4315 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4316 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4317 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4320 You can also use the @code{signal} command to prevent your program from
4321 seeing a signal, or cause it to see a signal it normally would not see,
4322 or to give it any signal at any time. For example, if your program stopped
4323 due to some sort of memory reference error, you might store correct
4324 values into the erroneous variables and continue, hoping to see more
4325 execution; but your program would probably terminate immediately as
4326 a result of the fatal signal once it saw the signal. To prevent this,
4327 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4331 @section Stopping and Starting Multi-thread Programs
4333 When your program has multiple threads (@pxref{Threads,, Debugging
4334 Programs with Multiple Threads}), you can choose whether to set
4335 breakpoints on all threads, or on a particular thread.
4338 @cindex breakpoints and threads
4339 @cindex thread breakpoints
4340 @kindex break @dots{} thread @var{threadno}
4341 @item break @var{linespec} thread @var{threadno}
4342 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4343 @var{linespec} specifies source lines; there are several ways of
4344 writing them, but the effect is always to specify some source line.
4346 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4347 to specify that you only want @value{GDBN} to stop the program when a
4348 particular thread reaches this breakpoint. @var{threadno} is one of the
4349 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4350 column of the @samp{info threads} display.
4352 If you do not specify @samp{thread @var{threadno}} when you set a
4353 breakpoint, the breakpoint applies to @emph{all} threads of your
4356 You can use the @code{thread} qualifier on conditional breakpoints as
4357 well; in this case, place @samp{thread @var{threadno}} before the
4358 breakpoint condition, like this:
4361 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4366 @cindex stopped threads
4367 @cindex threads, stopped
4368 Whenever your program stops under @value{GDBN} for any reason,
4369 @emph{all} threads of execution stop, not just the current thread. This
4370 allows you to examine the overall state of the program, including
4371 switching between threads, without worrying that things may change
4374 @cindex thread breakpoints and system calls
4375 @cindex system calls and thread breakpoints
4376 @cindex premature return from system calls
4377 There is an unfortunate side effect. If one thread stops for a
4378 breakpoint, or for some other reason, and another thread is blocked in a
4379 system call, then the system call may return prematurely. This is a
4380 consequence of the interaction between multiple threads and the signals
4381 that @value{GDBN} uses to implement breakpoints and other events that
4384 To handle this problem, your program should check the return value of
4385 each system call and react appropriately. This is good programming
4388 For example, do not write code like this:
4394 The call to @code{sleep} will return early if a different thread stops
4395 at a breakpoint or for some other reason.
4397 Instead, write this:
4402 unslept = sleep (unslept);
4405 A system call is allowed to return early, so the system is still
4406 conforming to its specification. But @value{GDBN} does cause your
4407 multi-threaded program to behave differently than it would without
4410 Also, @value{GDBN} uses internal breakpoints in the thread library to
4411 monitor certain events such as thread creation and thread destruction.
4412 When such an event happens, a system call in another thread may return
4413 prematurely, even though your program does not appear to stop.
4415 @cindex continuing threads
4416 @cindex threads, continuing
4417 Conversely, whenever you restart the program, @emph{all} threads start
4418 executing. @emph{This is true even when single-stepping} with commands
4419 like @code{step} or @code{next}.
4421 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4422 Since thread scheduling is up to your debugging target's operating
4423 system (not controlled by @value{GDBN}), other threads may
4424 execute more than one statement while the current thread completes a
4425 single step. Moreover, in general other threads stop in the middle of a
4426 statement, rather than at a clean statement boundary, when the program
4429 You might even find your program stopped in another thread after
4430 continuing or even single-stepping. This happens whenever some other
4431 thread runs into a breakpoint, a signal, or an exception before the
4432 first thread completes whatever you requested.
4434 On some OSes, you can lock the OS scheduler and thus allow only a single
4438 @item set scheduler-locking @var{mode}
4439 @cindex scheduler locking mode
4440 @cindex lock scheduler
4441 Set the scheduler locking mode. If it is @code{off}, then there is no
4442 locking and any thread may run at any time. If @code{on}, then only the
4443 current thread may run when the inferior is resumed. The @code{step}
4444 mode optimizes for single-stepping. It stops other threads from
4445 ``seizing the prompt'' by preempting the current thread while you are
4446 stepping. Other threads will only rarely (or never) get a chance to run
4447 when you step. They are more likely to run when you @samp{next} over a
4448 function call, and they are completely free to run when you use commands
4449 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4450 thread hits a breakpoint during its timeslice, they will never steal the
4451 @value{GDBN} prompt away from the thread that you are debugging.
4453 @item show scheduler-locking
4454 Display the current scheduler locking mode.
4459 @chapter Examining the Stack
4461 When your program has stopped, the first thing you need to know is where it
4462 stopped and how it got there.
4465 Each time your program performs a function call, information about the call
4467 That information includes the location of the call in your program,
4468 the arguments of the call,
4469 and the local variables of the function being called.
4470 The information is saved in a block of data called a @dfn{stack frame}.
4471 The stack frames are allocated in a region of memory called the @dfn{call
4474 When your program stops, the @value{GDBN} commands for examining the
4475 stack allow you to see all of this information.
4477 @cindex selected frame
4478 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4479 @value{GDBN} commands refer implicitly to the selected frame. In
4480 particular, whenever you ask @value{GDBN} for the value of a variable in
4481 your program, the value is found in the selected frame. There are
4482 special @value{GDBN} commands to select whichever frame you are
4483 interested in. @xref{Selection, ,Selecting a Frame}.
4485 When your program stops, @value{GDBN} automatically selects the
4486 currently executing frame and describes it briefly, similar to the
4487 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4490 * Frames:: Stack frames
4491 * Backtrace:: Backtraces
4492 * Selection:: Selecting a frame
4493 * Frame Info:: Information on a frame
4498 @section Stack Frames
4500 @cindex frame, definition
4502 The call stack is divided up into contiguous pieces called @dfn{stack
4503 frames}, or @dfn{frames} for short; each frame is the data associated
4504 with one call to one function. The frame contains the arguments given
4505 to the function, the function's local variables, and the address at
4506 which the function is executing.
4508 @cindex initial frame
4509 @cindex outermost frame
4510 @cindex innermost frame
4511 When your program is started, the stack has only one frame, that of the
4512 function @code{main}. This is called the @dfn{initial} frame or the
4513 @dfn{outermost} frame. Each time a function is called, a new frame is
4514 made. Each time a function returns, the frame for that function invocation
4515 is eliminated. If a function is recursive, there can be many frames for
4516 the same function. The frame for the function in which execution is
4517 actually occurring is called the @dfn{innermost} frame. This is the most
4518 recently created of all the stack frames that still exist.
4520 @cindex frame pointer
4521 Inside your program, stack frames are identified by their addresses. A
4522 stack frame consists of many bytes, each of which has its own address; each
4523 kind of computer has a convention for choosing one byte whose
4524 address serves as the address of the frame. Usually this address is kept
4525 in a register called the @dfn{frame pointer register}
4526 (@pxref{Registers, $fp}) while execution is going on in that frame.
4528 @cindex frame number
4529 @value{GDBN} assigns numbers to all existing stack frames, starting with
4530 zero for the innermost frame, one for the frame that called it,
4531 and so on upward. These numbers do not really exist in your program;
4532 they are assigned by @value{GDBN} to give you a way of designating stack
4533 frames in @value{GDBN} commands.
4535 @c The -fomit-frame-pointer below perennially causes hbox overflow
4536 @c underflow problems.
4537 @cindex frameless execution
4538 Some compilers provide a way to compile functions so that they operate
4539 without stack frames. (For example, the @value{NGCC} option
4541 @samp{-fomit-frame-pointer}
4543 generates functions without a frame.)
4544 This is occasionally done with heavily used library functions to save
4545 the frame setup time. @value{GDBN} has limited facilities for dealing
4546 with these function invocations. If the innermost function invocation
4547 has no stack frame, @value{GDBN} nevertheless regards it as though
4548 it had a separate frame, which is numbered zero as usual, allowing
4549 correct tracing of the function call chain. However, @value{GDBN} has
4550 no provision for frameless functions elsewhere in the stack.
4553 @kindex frame@r{, command}
4554 @cindex current stack frame
4555 @item frame @var{args}
4556 The @code{frame} command allows you to move from one stack frame to another,
4557 and to print the stack frame you select. @var{args} may be either the
4558 address of the frame or the stack frame number. Without an argument,
4559 @code{frame} prints the current stack frame.
4561 @kindex select-frame
4562 @cindex selecting frame silently
4564 The @code{select-frame} command allows you to move from one stack frame
4565 to another without printing the frame. This is the silent version of
4573 @cindex call stack traces
4574 A backtrace is a summary of how your program got where it is. It shows one
4575 line per frame, for many frames, starting with the currently executing
4576 frame (frame zero), followed by its caller (frame one), and on up the
4581 @kindex bt @r{(@code{backtrace})}
4584 Print a backtrace of the entire stack: one line per frame for all
4585 frames in the stack.
4587 You can stop the backtrace at any time by typing the system interrupt
4588 character, normally @kbd{Ctrl-c}.
4590 @item backtrace @var{n}
4592 Similar, but print only the innermost @var{n} frames.
4594 @item backtrace -@var{n}
4596 Similar, but print only the outermost @var{n} frames.
4598 @item backtrace full
4600 @itemx bt full @var{n}
4601 @itemx bt full -@var{n}
4602 Print the values of the local variables also. @var{n} specifies the
4603 number of frames to print, as described above.
4608 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4609 are additional aliases for @code{backtrace}.
4611 @cindex multiple threads, backtrace
4612 In a multi-threaded program, @value{GDBN} by default shows the
4613 backtrace only for the current thread. To display the backtrace for
4614 several or all of the threads, use the command @code{thread apply}
4615 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4616 apply all backtrace}, @value{GDBN} will display the backtrace for all
4617 the threads; this is handy when you debug a core dump of a
4618 multi-threaded program.
4620 Each line in the backtrace shows the frame number and the function name.
4621 The program counter value is also shown---unless you use @code{set
4622 print address off}. The backtrace also shows the source file name and
4623 line number, as well as the arguments to the function. The program
4624 counter value is omitted if it is at the beginning of the code for that
4627 Here is an example of a backtrace. It was made with the command
4628 @samp{bt 3}, so it shows the innermost three frames.
4632 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4634 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4635 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4637 (More stack frames follow...)
4642 The display for frame zero does not begin with a program counter
4643 value, indicating that your program has stopped at the beginning of the
4644 code for line @code{993} of @code{builtin.c}.
4646 @cindex value optimized out, in backtrace
4647 @cindex function call arguments, optimized out
4648 If your program was compiled with optimizations, some compilers will
4649 optimize away arguments passed to functions if those arguments are
4650 never used after the call. Such optimizations generate code that
4651 passes arguments through registers, but doesn't store those arguments
4652 in the stack frame. @value{GDBN} has no way of displaying such
4653 arguments in stack frames other than the innermost one. Here's what
4654 such a backtrace might look like:
4658 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4660 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4661 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4663 (More stack frames follow...)
4668 The values of arguments that were not saved in their stack frames are
4669 shown as @samp{<value optimized out>}.
4671 If you need to display the values of such optimized-out arguments,
4672 either deduce that from other variables whose values depend on the one
4673 you are interested in, or recompile without optimizations.
4675 @cindex backtrace beyond @code{main} function
4676 @cindex program entry point
4677 @cindex startup code, and backtrace
4678 Most programs have a standard user entry point---a place where system
4679 libraries and startup code transition into user code. For C this is
4680 @code{main}@footnote{
4681 Note that embedded programs (the so-called ``free-standing''
4682 environment) are not required to have a @code{main} function as the
4683 entry point. They could even have multiple entry points.}.
4684 When @value{GDBN} finds the entry function in a backtrace
4685 it will terminate the backtrace, to avoid tracing into highly
4686 system-specific (and generally uninteresting) code.
4688 If you need to examine the startup code, or limit the number of levels
4689 in a backtrace, you can change this behavior:
4692 @item set backtrace past-main
4693 @itemx set backtrace past-main on
4694 @kindex set backtrace
4695 Backtraces will continue past the user entry point.
4697 @item set backtrace past-main off
4698 Backtraces will stop when they encounter the user entry point. This is the
4701 @item show backtrace past-main
4702 @kindex show backtrace
4703 Display the current user entry point backtrace policy.
4705 @item set backtrace past-entry
4706 @itemx set backtrace past-entry on
4707 Backtraces will continue past the internal entry point of an application.
4708 This entry point is encoded by the linker when the application is built,
4709 and is likely before the user entry point @code{main} (or equivalent) is called.
4711 @item set backtrace past-entry off
4712 Backtraces will stop when they encounter the internal entry point of an
4713 application. This is the default.
4715 @item show backtrace past-entry
4716 Display the current internal entry point backtrace policy.
4718 @item set backtrace limit @var{n}
4719 @itemx set backtrace limit 0
4720 @cindex backtrace limit
4721 Limit the backtrace to @var{n} levels. A value of zero means
4724 @item show backtrace limit
4725 Display the current limit on backtrace levels.
4729 @section Selecting a Frame
4731 Most commands for examining the stack and other data in your program work on
4732 whichever stack frame is selected at the moment. Here are the commands for
4733 selecting a stack frame; all of them finish by printing a brief description
4734 of the stack frame just selected.
4737 @kindex frame@r{, selecting}
4738 @kindex f @r{(@code{frame})}
4741 Select frame number @var{n}. Recall that frame zero is the innermost
4742 (currently executing) frame, frame one is the frame that called the
4743 innermost one, and so on. The highest-numbered frame is the one for
4746 @item frame @var{addr}
4748 Select the frame at address @var{addr}. This is useful mainly if the
4749 chaining of stack frames has been damaged by a bug, making it
4750 impossible for @value{GDBN} to assign numbers properly to all frames. In
4751 addition, this can be useful when your program has multiple stacks and
4752 switches between them.
4754 On the SPARC architecture, @code{frame} needs two addresses to
4755 select an arbitrary frame: a frame pointer and a stack pointer.
4757 On the MIPS and Alpha architecture, it needs two addresses: a stack
4758 pointer and a program counter.
4760 On the 29k architecture, it needs three addresses: a register stack
4761 pointer, a program counter, and a memory stack pointer.
4765 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4766 advances toward the outermost frame, to higher frame numbers, to frames
4767 that have existed longer. @var{n} defaults to one.
4770 @kindex do @r{(@code{down})}
4772 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4773 advances toward the innermost frame, to lower frame numbers, to frames
4774 that were created more recently. @var{n} defaults to one. You may
4775 abbreviate @code{down} as @code{do}.
4778 All of these commands end by printing two lines of output describing the
4779 frame. The first line shows the frame number, the function name, the
4780 arguments, and the source file and line number of execution in that
4781 frame. The second line shows the text of that source line.
4789 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4791 10 read_input_file (argv[i]);
4795 After such a printout, the @code{list} command with no arguments
4796 prints ten lines centered on the point of execution in the frame.
4797 You can also edit the program at the point of execution with your favorite
4798 editing program by typing @code{edit}.
4799 @xref{List, ,Printing Source Lines},
4803 @kindex down-silently
4805 @item up-silently @var{n}
4806 @itemx down-silently @var{n}
4807 These two commands are variants of @code{up} and @code{down},
4808 respectively; they differ in that they do their work silently, without
4809 causing display of the new frame. They are intended primarily for use
4810 in @value{GDBN} command scripts, where the output might be unnecessary and
4815 @section Information About a Frame
4817 There are several other commands to print information about the selected
4823 When used without any argument, this command does not change which
4824 frame is selected, but prints a brief description of the currently
4825 selected stack frame. It can be abbreviated @code{f}. With an
4826 argument, this command is used to select a stack frame.
4827 @xref{Selection, ,Selecting a Frame}.
4830 @kindex info f @r{(@code{info frame})}
4833 This command prints a verbose description of the selected stack frame,
4838 the address of the frame
4840 the address of the next frame down (called by this frame)
4842 the address of the next frame up (caller of this frame)
4844 the language in which the source code corresponding to this frame is written
4846 the address of the frame's arguments
4848 the address of the frame's local variables
4850 the program counter saved in it (the address of execution in the caller frame)
4852 which registers were saved in the frame
4855 @noindent The verbose description is useful when
4856 something has gone wrong that has made the stack format fail to fit
4857 the usual conventions.
4859 @item info frame @var{addr}
4860 @itemx info f @var{addr}
4861 Print a verbose description of the frame at address @var{addr}, without
4862 selecting that frame. The selected frame remains unchanged by this
4863 command. This requires the same kind of address (more than one for some
4864 architectures) that you specify in the @code{frame} command.
4865 @xref{Selection, ,Selecting a Frame}.
4869 Print the arguments of the selected frame, each on a separate line.
4873 Print the local variables of the selected frame, each on a separate
4874 line. These are all variables (declared either static or automatic)
4875 accessible at the point of execution of the selected frame.
4878 @cindex catch exceptions, list active handlers
4879 @cindex exception handlers, how to list
4881 Print a list of all the exception handlers that are active in the
4882 current stack frame at the current point of execution. To see other
4883 exception handlers, visit the associated frame (using the @code{up},
4884 @code{down}, or @code{frame} commands); then type @code{info catch}.
4885 @xref{Set Catchpoints, , Setting Catchpoints}.
4891 @chapter Examining Source Files
4893 @value{GDBN} can print parts of your program's source, since the debugging
4894 information recorded in the program tells @value{GDBN} what source files were
4895 used to build it. When your program stops, @value{GDBN} spontaneously prints
4896 the line where it stopped. Likewise, when you select a stack frame
4897 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4898 execution in that frame has stopped. You can print other portions of
4899 source files by explicit command.
4901 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4902 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4903 @value{GDBN} under @sc{gnu} Emacs}.
4906 * List:: Printing source lines
4907 * Edit:: Editing source files
4908 * Search:: Searching source files
4909 * Source Path:: Specifying source directories
4910 * Machine Code:: Source and machine code
4914 @section Printing Source Lines
4917 @kindex l @r{(@code{list})}
4918 To print lines from a source file, use the @code{list} command
4919 (abbreviated @code{l}). By default, ten lines are printed.
4920 There are several ways to specify what part of the file you want to print.
4922 Here are the forms of the @code{list} command most commonly used:
4925 @item list @var{linenum}
4926 Print lines centered around line number @var{linenum} in the
4927 current source file.
4929 @item list @var{function}
4930 Print lines centered around the beginning of function
4934 Print more lines. If the last lines printed were printed with a
4935 @code{list} command, this prints lines following the last lines
4936 printed; however, if the last line printed was a solitary line printed
4937 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4938 Stack}), this prints lines centered around that line.
4941 Print lines just before the lines last printed.
4944 @cindex @code{list}, how many lines to display
4945 By default, @value{GDBN} prints ten source lines with any of these forms of
4946 the @code{list} command. You can change this using @code{set listsize}:
4949 @kindex set listsize
4950 @item set listsize @var{count}
4951 Make the @code{list} command display @var{count} source lines (unless
4952 the @code{list} argument explicitly specifies some other number).
4954 @kindex show listsize
4956 Display the number of lines that @code{list} prints.
4959 Repeating a @code{list} command with @key{RET} discards the argument,
4960 so it is equivalent to typing just @code{list}. This is more useful
4961 than listing the same lines again. An exception is made for an
4962 argument of @samp{-}; that argument is preserved in repetition so that
4963 each repetition moves up in the source file.
4966 In general, the @code{list} command expects you to supply zero, one or two
4967 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4968 of writing them, but the effect is always to specify some source line.
4969 Here is a complete description of the possible arguments for @code{list}:
4972 @item list @var{linespec}
4973 Print lines centered around the line specified by @var{linespec}.
4975 @item list @var{first},@var{last}
4976 Print lines from @var{first} to @var{last}. Both arguments are
4979 @item list ,@var{last}
4980 Print lines ending with @var{last}.
4982 @item list @var{first},
4983 Print lines starting with @var{first}.
4986 Print lines just after the lines last printed.
4989 Print lines just before the lines last printed.
4992 As described in the preceding table.
4995 Here are the ways of specifying a single source line---all the
5000 Specifies line @var{number} of the current source file.
5001 When a @code{list} command has two linespecs, this refers to
5002 the same source file as the first linespec.
5005 Specifies the line @var{offset} lines after the last line printed.
5006 When used as the second linespec in a @code{list} command that has
5007 two, this specifies the line @var{offset} lines down from the
5011 Specifies the line @var{offset} lines before the last line printed.
5013 @item @var{filename}:@var{number}
5014 Specifies line @var{number} in the source file @var{filename}.
5016 @item @var{function}
5017 Specifies the line that begins the body of the function @var{function}.
5018 For example: in C, this is the line with the open brace.
5020 @item @var{filename}:@var{function}
5021 Specifies the line of the open-brace that begins the body of the
5022 function @var{function} in the file @var{filename}. You only need the
5023 file name with a function name to avoid ambiguity when there are
5024 identically named functions in different source files.
5026 @item *@var{address}
5027 Specifies the line containing the program address @var{address}.
5028 @var{address} may be any expression.
5032 @section Editing Source Files
5033 @cindex editing source files
5036 @kindex e @r{(@code{edit})}
5037 To edit the lines in a source file, use the @code{edit} command.
5038 The editing program of your choice
5039 is invoked with the current line set to
5040 the active line in the program.
5041 Alternatively, there are several ways to specify what part of the file you
5042 want to print if you want to see other parts of the program.
5044 Here are the forms of the @code{edit} command most commonly used:
5048 Edit the current source file at the active line number in the program.
5050 @item edit @var{number}
5051 Edit the current source file with @var{number} as the active line number.
5053 @item edit @var{function}
5054 Edit the file containing @var{function} at the beginning of its definition.
5056 @item edit @var{filename}:@var{number}
5057 Specifies line @var{number} in the source file @var{filename}.
5059 @item edit @var{filename}:@var{function}
5060 Specifies the line that begins the body of the
5061 function @var{function} in the file @var{filename}. You only need the
5062 file name with a function name to avoid ambiguity when there are
5063 identically named functions in different source files.
5065 @item edit *@var{address}
5066 Specifies the line containing the program address @var{address}.
5067 @var{address} may be any expression.
5070 @subsection Choosing your Editor
5071 You can customize @value{GDBN} to use any editor you want
5073 The only restriction is that your editor (say @code{ex}), recognizes the
5074 following command-line syntax:
5076 ex +@var{number} file
5078 The optional numeric value +@var{number} specifies the number of the line in
5079 the file where to start editing.}.
5080 By default, it is @file{@value{EDITOR}}, but you can change this
5081 by setting the environment variable @code{EDITOR} before using
5082 @value{GDBN}. For example, to configure @value{GDBN} to use the
5083 @code{vi} editor, you could use these commands with the @code{sh} shell:
5089 or in the @code{csh} shell,
5091 setenv EDITOR /usr/bin/vi
5096 @section Searching Source Files
5097 @cindex searching source files
5099 There are two commands for searching through the current source file for a
5104 @kindex forward-search
5105 @item forward-search @var{regexp}
5106 @itemx search @var{regexp}
5107 The command @samp{forward-search @var{regexp}} checks each line,
5108 starting with the one following the last line listed, for a match for
5109 @var{regexp}. It lists the line that is found. You can use the
5110 synonym @samp{search @var{regexp}} or abbreviate the command name as
5113 @kindex reverse-search
5114 @item reverse-search @var{regexp}
5115 The command @samp{reverse-search @var{regexp}} checks each line, starting
5116 with the one before the last line listed and going backward, for a match
5117 for @var{regexp}. It lists the line that is found. You can abbreviate
5118 this command as @code{rev}.
5122 @section Specifying Source Directories
5125 @cindex directories for source files
5126 Executable programs sometimes do not record the directories of the source
5127 files from which they were compiled, just the names. Even when they do,
5128 the directories could be moved between the compilation and your debugging
5129 session. @value{GDBN} has a list of directories to search for source files;
5130 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5131 it tries all the directories in the list, in the order they are present
5132 in the list, until it finds a file with the desired name.
5134 For example, suppose an executable references the file
5135 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5136 @file{/mnt/cross}. The file is first looked up literally; if this
5137 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5138 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5139 message is printed. @value{GDBN} does not look up the parts of the
5140 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5141 Likewise, the subdirectories of the source path are not searched: if
5142 the source path is @file{/mnt/cross}, and the binary refers to
5143 @file{foo.c}, @value{GDBN} would not find it under
5144 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5146 Plain file names, relative file names with leading directories, file
5147 names containing dots, etc.@: are all treated as described above; for
5148 instance, if the source path is @file{/mnt/cross}, and the source file
5149 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5150 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5151 that---@file{/mnt/cross/foo.c}.
5153 Note that the executable search path is @emph{not} used to locate the
5156 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5157 any information it has cached about where source files are found and where
5158 each line is in the file.
5162 When you start @value{GDBN}, its source path includes only @samp{cdir}
5163 and @samp{cwd}, in that order.
5164 To add other directories, use the @code{directory} command.
5166 The search path is used to find both program source files and @value{GDBN}
5167 script files (read using the @samp{-command} option and @samp{source} command).
5169 In addition to the source path, @value{GDBN} provides a set of commands
5170 that manage a list of source path substitution rules. A @dfn{substitution
5171 rule} specifies how to rewrite source directories stored in the program's
5172 debug information in case the sources were moved to a different
5173 directory between compilation and debugging. A rule is made of
5174 two strings, the first specifying what needs to be rewritten in
5175 the path, and the second specifying how it should be rewritten.
5176 In @ref{set substitute-path}, we name these two parts @var{from} and
5177 @var{to} respectively. @value{GDBN} does a simple string replacement
5178 of @var{from} with @var{to} at the start of the directory part of the
5179 source file name, and uses that result instead of the original file
5180 name to look up the sources.
5182 Using the previous example, suppose the @file{foo-1.0} tree has been
5183 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5184 @value{GDBN} to replace @file{/usr/src} in all source path names with
5185 @file{/mnt/cross}. The first lookup will then be
5186 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5187 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5188 substitution rule, use the @code{set substitute-path} command
5189 (@pxref{set substitute-path}).
5191 To avoid unexpected substitution results, a rule is applied only if the
5192 @var{from} part of the directory name ends at a directory separator.
5193 For instance, a rule substituting @file{/usr/source} into
5194 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5195 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5196 is applied only at the beginning of the directory name, this rule will
5197 not be applied to @file{/root/usr/source/baz.c} either.
5199 In many cases, you can achieve the same result using the @code{directory}
5200 command. However, @code{set substitute-path} can be more efficient in
5201 the case where the sources are organized in a complex tree with multiple
5202 subdirectories. With the @code{directory} command, you need to add each
5203 subdirectory of your project. If you moved the entire tree while
5204 preserving its internal organization, then @code{set substitute-path}
5205 allows you to direct the debugger to all the sources with one single
5208 @code{set substitute-path} is also more than just a shortcut command.
5209 The source path is only used if the file at the original location no
5210 longer exists. On the other hand, @code{set substitute-path} modifies
5211 the debugger behavior to look at the rewritten location instead. So, if
5212 for any reason a source file that is not relevant to your executable is
5213 located at the original location, a substitution rule is the only
5214 method available to point @value{GDBN} at the new location.
5217 @item directory @var{dirname} @dots{}
5218 @item dir @var{dirname} @dots{}
5219 Add directory @var{dirname} to the front of the source path. Several
5220 directory names may be given to this command, separated by @samp{:}
5221 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5222 part of absolute file names) or
5223 whitespace. You may specify a directory that is already in the source
5224 path; this moves it forward, so @value{GDBN} searches it sooner.
5228 @vindex $cdir@r{, convenience variable}
5229 @vindex $cwd@r{, convenience variable}
5230 @cindex compilation directory
5231 @cindex current directory
5232 @cindex working directory
5233 @cindex directory, current
5234 @cindex directory, compilation
5235 You can use the string @samp{$cdir} to refer to the compilation
5236 directory (if one is recorded), and @samp{$cwd} to refer to the current
5237 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5238 tracks the current working directory as it changes during your @value{GDBN}
5239 session, while the latter is immediately expanded to the current
5240 directory at the time you add an entry to the source path.
5243 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5245 @c RET-repeat for @code{directory} is explicitly disabled, but since
5246 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5248 @item show directories
5249 @kindex show directories
5250 Print the source path: show which directories it contains.
5252 @anchor{set substitute-path}
5253 @item set substitute-path @var{from} @var{to}
5254 @kindex set substitute-path
5255 Define a source path substitution rule, and add it at the end of the
5256 current list of existing substitution rules. If a rule with the same
5257 @var{from} was already defined, then the old rule is also deleted.
5259 For example, if the file @file{/foo/bar/baz.c} was moved to
5260 @file{/mnt/cross/baz.c}, then the command
5263 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5267 will tell @value{GDBN} to replace @samp{/usr/src} with
5268 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5269 @file{baz.c} even though it was moved.
5271 In the case when more than one substitution rule have been defined,
5272 the rules are evaluated one by one in the order where they have been
5273 defined. The first one matching, if any, is selected to perform
5276 For instance, if we had entered the following commands:
5279 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5280 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5284 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5285 @file{/mnt/include/defs.h} by using the first rule. However, it would
5286 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5287 @file{/mnt/src/lib/foo.c}.
5290 @item unset substitute-path [path]
5291 @kindex unset substitute-path
5292 If a path is specified, search the current list of substitution rules
5293 for a rule that would rewrite that path. Delete that rule if found.
5294 A warning is emitted by the debugger if no rule could be found.
5296 If no path is specified, then all substitution rules are deleted.
5298 @item show substitute-path [path]
5299 @kindex show substitute-path
5300 If a path is specified, then print the source path substitution rule
5301 which would rewrite that path, if any.
5303 If no path is specified, then print all existing source path substitution
5308 If your source path is cluttered with directories that are no longer of
5309 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5310 versions of source. You can correct the situation as follows:
5314 Use @code{directory} with no argument to reset the source path to its default value.
5317 Use @code{directory} with suitable arguments to reinstall the
5318 directories you want in the source path. You can add all the
5319 directories in one command.
5323 @section Source and Machine Code
5324 @cindex source line and its code address
5326 You can use the command @code{info line} to map source lines to program
5327 addresses (and vice versa), and the command @code{disassemble} to display
5328 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5329 mode, the @code{info line} command causes the arrow to point to the
5330 line specified. Also, @code{info line} prints addresses in symbolic form as
5335 @item info line @var{linespec}
5336 Print the starting and ending addresses of the compiled code for
5337 source line @var{linespec}. You can specify source lines in any of
5338 the ways understood by the @code{list} command (@pxref{List, ,Printing
5342 For example, we can use @code{info line} to discover the location of
5343 the object code for the first line of function
5344 @code{m4_changequote}:
5346 @c FIXME: I think this example should also show the addresses in
5347 @c symbolic form, as they usually would be displayed.
5349 (@value{GDBP}) info line m4_changequote
5350 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5354 @cindex code address and its source line
5355 We can also inquire (using @code{*@var{addr}} as the form for
5356 @var{linespec}) what source line covers a particular address:
5358 (@value{GDBP}) info line *0x63ff
5359 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5362 @cindex @code{$_} and @code{info line}
5363 @cindex @code{x} command, default address
5364 @kindex x@r{(examine), and} info line
5365 After @code{info line}, the default address for the @code{x} command
5366 is changed to the starting address of the line, so that @samp{x/i} is
5367 sufficient to begin examining the machine code (@pxref{Memory,
5368 ,Examining Memory}). Also, this address is saved as the value of the
5369 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5374 @cindex assembly instructions
5375 @cindex instructions, assembly
5376 @cindex machine instructions
5377 @cindex listing machine instructions
5379 This specialized command dumps a range of memory as machine
5380 instructions. The default memory range is the function surrounding the
5381 program counter of the selected frame. A single argument to this
5382 command is a program counter value; @value{GDBN} dumps the function
5383 surrounding this value. Two arguments specify a range of addresses
5384 (first inclusive, second exclusive) to dump.
5387 The following example shows the disassembly of a range of addresses of
5388 HP PA-RISC 2.0 code:
5391 (@value{GDBP}) disas 0x32c4 0x32e4
5392 Dump of assembler code from 0x32c4 to 0x32e4:
5393 0x32c4 <main+204>: addil 0,dp
5394 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5395 0x32cc <main+212>: ldil 0x3000,r31
5396 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5397 0x32d4 <main+220>: ldo 0(r31),rp
5398 0x32d8 <main+224>: addil -0x800,dp
5399 0x32dc <main+228>: ldo 0x588(r1),r26
5400 0x32e0 <main+232>: ldil 0x3000,r31
5401 End of assembler dump.
5404 Some architectures have more than one commonly-used set of instruction
5405 mnemonics or other syntax.
5407 For programs that were dynamically linked and use shared libraries,
5408 instructions that call functions or branch to locations in the shared
5409 libraries might show a seemingly bogus location---it's actually a
5410 location of the relocation table. On some architectures, @value{GDBN}
5411 might be able to resolve these to actual function names.
5414 @kindex set disassembly-flavor
5415 @cindex Intel disassembly flavor
5416 @cindex AT&T disassembly flavor
5417 @item set disassembly-flavor @var{instruction-set}
5418 Select the instruction set to use when disassembling the
5419 program via the @code{disassemble} or @code{x/i} commands.
5421 Currently this command is only defined for the Intel x86 family. You
5422 can set @var{instruction-set} to either @code{intel} or @code{att}.
5423 The default is @code{att}, the AT&T flavor used by default by Unix
5424 assemblers for x86-based targets.
5426 @kindex show disassembly-flavor
5427 @item show disassembly-flavor
5428 Show the current setting of the disassembly flavor.
5433 @chapter Examining Data
5435 @cindex printing data
5436 @cindex examining data
5439 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5440 @c document because it is nonstandard... Under Epoch it displays in a
5441 @c different window or something like that.
5442 The usual way to examine data in your program is with the @code{print}
5443 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5444 evaluates and prints the value of an expression of the language your
5445 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5446 Different Languages}).
5449 @item print @var{expr}
5450 @itemx print /@var{f} @var{expr}
5451 @var{expr} is an expression (in the source language). By default the
5452 value of @var{expr} is printed in a format appropriate to its data type;
5453 you can choose a different format by specifying @samp{/@var{f}}, where
5454 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5458 @itemx print /@var{f}
5459 @cindex reprint the last value
5460 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5461 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5462 conveniently inspect the same value in an alternative format.
5465 A more low-level way of examining data is with the @code{x} command.
5466 It examines data in memory at a specified address and prints it in a
5467 specified format. @xref{Memory, ,Examining Memory}.
5469 If you are interested in information about types, or about how the
5470 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5471 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5475 * Expressions:: Expressions
5476 * Variables:: Program variables
5477 * Arrays:: Artificial arrays
5478 * Output Formats:: Output formats
5479 * Memory:: Examining memory
5480 * Auto Display:: Automatic display
5481 * Print Settings:: Print settings
5482 * Value History:: Value history
5483 * Convenience Vars:: Convenience variables
5484 * Registers:: Registers
5485 * Floating Point Hardware:: Floating point hardware
5486 * Vector Unit:: Vector Unit
5487 * OS Information:: Auxiliary data provided by operating system
5488 * Memory Region Attributes:: Memory region attributes
5489 * Dump/Restore Files:: Copy between memory and a file
5490 * Core File Generation:: Cause a program dump its core
5491 * Character Sets:: Debugging programs that use a different
5492 character set than GDB does
5493 * Caching Remote Data:: Data caching for remote targets
5497 @section Expressions
5500 @code{print} and many other @value{GDBN} commands accept an expression and
5501 compute its value. Any kind of constant, variable or operator defined
5502 by the programming language you are using is valid in an expression in
5503 @value{GDBN}. This includes conditional expressions, function calls,
5504 casts, and string constants. It also includes preprocessor macros, if
5505 you compiled your program to include this information; see
5508 @cindex arrays in expressions
5509 @value{GDBN} supports array constants in expressions input by
5510 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5511 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5512 memory that is @code{malloc}ed in the target program.
5514 Because C is so widespread, most of the expressions shown in examples in
5515 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5516 Languages}, for information on how to use expressions in other
5519 In this section, we discuss operators that you can use in @value{GDBN}
5520 expressions regardless of your programming language.
5522 @cindex casts, in expressions
5523 Casts are supported in all languages, not just in C, because it is so
5524 useful to cast a number into a pointer in order to examine a structure
5525 at that address in memory.
5526 @c FIXME: casts supported---Mod2 true?
5528 @value{GDBN} supports these operators, in addition to those common
5529 to programming languages:
5533 @samp{@@} is a binary operator for treating parts of memory as arrays.
5534 @xref{Arrays, ,Artificial Arrays}, for more information.
5537 @samp{::} allows you to specify a variable in terms of the file or
5538 function where it is defined. @xref{Variables, ,Program Variables}.
5540 @cindex @{@var{type}@}
5541 @cindex type casting memory
5542 @cindex memory, viewing as typed object
5543 @cindex casts, to view memory
5544 @item @{@var{type}@} @var{addr}
5545 Refers to an object of type @var{type} stored at address @var{addr} in
5546 memory. @var{addr} may be any expression whose value is an integer or
5547 pointer (but parentheses are required around binary operators, just as in
5548 a cast). This construct is allowed regardless of what kind of data is
5549 normally supposed to reside at @var{addr}.
5553 @section Program Variables
5555 The most common kind of expression to use is the name of a variable
5558 Variables in expressions are understood in the selected stack frame
5559 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5563 global (or file-static)
5570 visible according to the scope rules of the
5571 programming language from the point of execution in that frame
5574 @noindent This means that in the function
5589 you can examine and use the variable @code{a} whenever your program is
5590 executing within the function @code{foo}, but you can only use or
5591 examine the variable @code{b} while your program is executing inside
5592 the block where @code{b} is declared.
5594 @cindex variable name conflict
5595 There is an exception: you can refer to a variable or function whose
5596 scope is a single source file even if the current execution point is not
5597 in this file. But it is possible to have more than one such variable or
5598 function with the same name (in different source files). If that
5599 happens, referring to that name has unpredictable effects. If you wish,
5600 you can specify a static variable in a particular function or file,
5601 using the colon-colon (@code{::}) notation:
5603 @cindex colon-colon, context for variables/functions
5605 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5606 @cindex @code{::}, context for variables/functions
5609 @var{file}::@var{variable}
5610 @var{function}::@var{variable}
5614 Here @var{file} or @var{function} is the name of the context for the
5615 static @var{variable}. In the case of file names, you can use quotes to
5616 make sure @value{GDBN} parses the file name as a single word---for example,
5617 to print a global value of @code{x} defined in @file{f2.c}:
5620 (@value{GDBP}) p 'f2.c'::x
5623 @cindex C@t{++} scope resolution
5624 This use of @samp{::} is very rarely in conflict with the very similar
5625 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5626 scope resolution operator in @value{GDBN} expressions.
5627 @c FIXME: Um, so what happens in one of those rare cases where it's in
5630 @cindex wrong values
5631 @cindex variable values, wrong
5632 @cindex function entry/exit, wrong values of variables
5633 @cindex optimized code, wrong values of variables
5635 @emph{Warning:} Occasionally, a local variable may appear to have the
5636 wrong value at certain points in a function---just after entry to a new
5637 scope, and just before exit.
5639 You may see this problem when you are stepping by machine instructions.
5640 This is because, on most machines, it takes more than one instruction to
5641 set up a stack frame (including local variable definitions); if you are
5642 stepping by machine instructions, variables may appear to have the wrong
5643 values until the stack frame is completely built. On exit, it usually
5644 also takes more than one machine instruction to destroy a stack frame;
5645 after you begin stepping through that group of instructions, local
5646 variable definitions may be gone.
5648 This may also happen when the compiler does significant optimizations.
5649 To be sure of always seeing accurate values, turn off all optimization
5652 @cindex ``No symbol "foo" in current context''
5653 Another possible effect of compiler optimizations is to optimize
5654 unused variables out of existence, or assign variables to registers (as
5655 opposed to memory addresses). Depending on the support for such cases
5656 offered by the debug info format used by the compiler, @value{GDBN}
5657 might not be able to display values for such local variables. If that
5658 happens, @value{GDBN} will print a message like this:
5661 No symbol "foo" in current context.
5664 To solve such problems, either recompile without optimizations, or use a
5665 different debug info format, if the compiler supports several such
5666 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5667 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5668 produces debug info in a format that is superior to formats such as
5669 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5670 an effective form for debug info. @xref{Debugging Options,,Options
5671 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5672 Compiler Collection (GCC)}.
5673 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5674 that are best suited to C@t{++} programs.
5676 If you ask to print an object whose contents are unknown to
5677 @value{GDBN}, e.g., because its data type is not completely specified
5678 by the debug information, @value{GDBN} will say @samp{<incomplete
5679 type>}. @xref{Symbols, incomplete type}, for more about this.
5681 Strings are identified as arrays of @code{char} values without specified
5682 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5683 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5684 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5685 defines literal string type @code{"char"} as @code{char} without a sign.
5690 signed char var1[] = "A";
5693 You get during debugging
5698 $2 = @{65 'A', 0 '\0'@}
5702 @section Artificial Arrays
5704 @cindex artificial array
5706 @kindex @@@r{, referencing memory as an array}
5707 It is often useful to print out several successive objects of the
5708 same type in memory; a section of an array, or an array of
5709 dynamically determined size for which only a pointer exists in the
5712 You can do this by referring to a contiguous span of memory as an
5713 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5714 operand of @samp{@@} should be the first element of the desired array
5715 and be an individual object. The right operand should be the desired length
5716 of the array. The result is an array value whose elements are all of
5717 the type of the left argument. The first element is actually the left
5718 argument; the second element comes from bytes of memory immediately
5719 following those that hold the first element, and so on. Here is an
5720 example. If a program says
5723 int *array = (int *) malloc (len * sizeof (int));
5727 you can print the contents of @code{array} with
5733 The left operand of @samp{@@} must reside in memory. Array values made
5734 with @samp{@@} in this way behave just like other arrays in terms of
5735 subscripting, and are coerced to pointers when used in expressions.
5736 Artificial arrays most often appear in expressions via the value history
5737 (@pxref{Value History, ,Value History}), after printing one out.
5739 Another way to create an artificial array is to use a cast.
5740 This re-interprets a value as if it were an array.
5741 The value need not be in memory:
5743 (@value{GDBP}) p/x (short[2])0x12345678
5744 $1 = @{0x1234, 0x5678@}
5747 As a convenience, if you leave the array length out (as in
5748 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5749 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5751 (@value{GDBP}) p/x (short[])0x12345678
5752 $2 = @{0x1234, 0x5678@}
5755 Sometimes the artificial array mechanism is not quite enough; in
5756 moderately complex data structures, the elements of interest may not
5757 actually be adjacent---for example, if you are interested in the values
5758 of pointers in an array. One useful work-around in this situation is
5759 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5760 Variables}) as a counter in an expression that prints the first
5761 interesting value, and then repeat that expression via @key{RET}. For
5762 instance, suppose you have an array @code{dtab} of pointers to
5763 structures, and you are interested in the values of a field @code{fv}
5764 in each structure. Here is an example of what you might type:
5774 @node Output Formats
5775 @section Output Formats
5777 @cindex formatted output
5778 @cindex output formats
5779 By default, @value{GDBN} prints a value according to its data type. Sometimes
5780 this is not what you want. For example, you might want to print a number
5781 in hex, or a pointer in decimal. Or you might want to view data in memory
5782 at a certain address as a character string or as an instruction. To do
5783 these things, specify an @dfn{output format} when you print a value.
5785 The simplest use of output formats is to say how to print a value
5786 already computed. This is done by starting the arguments of the
5787 @code{print} command with a slash and a format letter. The format
5788 letters supported are:
5792 Regard the bits of the value as an integer, and print the integer in
5796 Print as integer in signed decimal.
5799 Print as integer in unsigned decimal.
5802 Print as integer in octal.
5805 Print as integer in binary. The letter @samp{t} stands for ``two''.
5806 @footnote{@samp{b} cannot be used because these format letters are also
5807 used with the @code{x} command, where @samp{b} stands for ``byte'';
5808 see @ref{Memory,,Examining Memory}.}
5811 @cindex unknown address, locating
5812 @cindex locate address
5813 Print as an address, both absolute in hexadecimal and as an offset from
5814 the nearest preceding symbol. You can use this format used to discover
5815 where (in what function) an unknown address is located:
5818 (@value{GDBP}) p/a 0x54320
5819 $3 = 0x54320 <_initialize_vx+396>
5823 The command @code{info symbol 0x54320} yields similar results.
5824 @xref{Symbols, info symbol}.
5827 Regard as an integer and print it as a character constant. This
5828 prints both the numerical value and its character representation. The
5829 character representation is replaced with the octal escape @samp{\nnn}
5830 for characters outside the 7-bit @sc{ascii} range.
5832 Without this format, @value{GDBN} displays @code{char},
5833 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
5834 constants. Single-byte members of vectors are displayed as integer
5838 Regard the bits of the value as a floating point number and print
5839 using typical floating point syntax.
5842 @cindex printing strings
5843 @cindex printing byte arrays
5844 Regard as a string, if possible. With this format, pointers to single-byte
5845 data are displayed as null-terminated strings and arrays of single-byte data
5846 are displayed as fixed-length strings. Other values are displayed in their
5849 Without this format, @value{GDBN} displays pointers to and arrays of
5850 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
5851 strings. Single-byte members of a vector are displayed as an integer
5855 For example, to print the program counter in hex (@pxref{Registers}), type
5862 Note that no space is required before the slash; this is because command
5863 names in @value{GDBN} cannot contain a slash.
5865 To reprint the last value in the value history with a different format,
5866 you can use the @code{print} command with just a format and no
5867 expression. For example, @samp{p/x} reprints the last value in hex.
5870 @section Examining Memory
5872 You can use the command @code{x} (for ``examine'') to examine memory in
5873 any of several formats, independently of your program's data types.
5875 @cindex examining memory
5877 @kindex x @r{(examine memory)}
5878 @item x/@var{nfu} @var{addr}
5881 Use the @code{x} command to examine memory.
5884 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5885 much memory to display and how to format it; @var{addr} is an
5886 expression giving the address where you want to start displaying memory.
5887 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5888 Several commands set convenient defaults for @var{addr}.
5891 @item @var{n}, the repeat count
5892 The repeat count is a decimal integer; the default is 1. It specifies
5893 how much memory (counting by units @var{u}) to display.
5894 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5897 @item @var{f}, the display format
5898 The display format is one of the formats used by @code{print}
5899 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5900 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
5901 The default is @samp{x} (hexadecimal) initially. The default changes
5902 each time you use either @code{x} or @code{print}.
5904 @item @var{u}, the unit size
5905 The unit size is any of
5911 Halfwords (two bytes).
5913 Words (four bytes). This is the initial default.
5915 Giant words (eight bytes).
5918 Each time you specify a unit size with @code{x}, that size becomes the
5919 default unit the next time you use @code{x}. (For the @samp{s} and
5920 @samp{i} formats, the unit size is ignored and is normally not written.)
5922 @item @var{addr}, starting display address
5923 @var{addr} is the address where you want @value{GDBN} to begin displaying
5924 memory. The expression need not have a pointer value (though it may);
5925 it is always interpreted as an integer address of a byte of memory.
5926 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5927 @var{addr} is usually just after the last address examined---but several
5928 other commands also set the default address: @code{info breakpoints} (to
5929 the address of the last breakpoint listed), @code{info line} (to the
5930 starting address of a line), and @code{print} (if you use it to display
5931 a value from memory).
5934 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5935 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5936 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5937 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5938 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5940 Since the letters indicating unit sizes are all distinct from the
5941 letters specifying output formats, you do not have to remember whether
5942 unit size or format comes first; either order works. The output
5943 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5944 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5946 Even though the unit size @var{u} is ignored for the formats @samp{s}
5947 and @samp{i}, you might still want to use a count @var{n}; for example,
5948 @samp{3i} specifies that you want to see three machine instructions,
5949 including any operands. For convenience, especially when used with
5950 the @code{display} command, the @samp{i} format also prints branch delay
5951 slot instructions, if any, beyond the count specified, which immediately
5952 follow the last instruction that is within the count. The command
5953 @code{disassemble} gives an alternative way of inspecting machine
5954 instructions; see @ref{Machine Code,,Source and Machine Code}.
5956 All the defaults for the arguments to @code{x} are designed to make it
5957 easy to continue scanning memory with minimal specifications each time
5958 you use @code{x}. For example, after you have inspected three machine
5959 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5960 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5961 the repeat count @var{n} is used again; the other arguments default as
5962 for successive uses of @code{x}.
5964 @cindex @code{$_}, @code{$__}, and value history
5965 The addresses and contents printed by the @code{x} command are not saved
5966 in the value history because there is often too much of them and they
5967 would get in the way. Instead, @value{GDBN} makes these values available for
5968 subsequent use in expressions as values of the convenience variables
5969 @code{$_} and @code{$__}. After an @code{x} command, the last address
5970 examined is available for use in expressions in the convenience variable
5971 @code{$_}. The contents of that address, as examined, are available in
5972 the convenience variable @code{$__}.
5974 If the @code{x} command has a repeat count, the address and contents saved
5975 are from the last memory unit printed; this is not the same as the last
5976 address printed if several units were printed on the last line of output.
5978 @cindex remote memory comparison
5979 @cindex verify remote memory image
5980 When you are debugging a program running on a remote target machine
5981 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
5982 remote machine's memory against the executable file you downloaded to
5983 the target. The @code{compare-sections} command is provided for such
5987 @kindex compare-sections
5988 @item compare-sections @r{[}@var{section-name}@r{]}
5989 Compare the data of a loadable section @var{section-name} in the
5990 executable file of the program being debugged with the same section in
5991 the remote machine's memory, and report any mismatches. With no
5992 arguments, compares all loadable sections. This command's
5993 availability depends on the target's support for the @code{"qCRC"}
5998 @section Automatic Display
5999 @cindex automatic display
6000 @cindex display of expressions
6002 If you find that you want to print the value of an expression frequently
6003 (to see how it changes), you might want to add it to the @dfn{automatic
6004 display list} so that @value{GDBN} prints its value each time your program stops.
6005 Each expression added to the list is given a number to identify it;
6006 to remove an expression from the list, you specify that number.
6007 The automatic display looks like this:
6011 3: bar[5] = (struct hack *) 0x3804
6015 This display shows item numbers, expressions and their current values. As with
6016 displays you request manually using @code{x} or @code{print}, you can
6017 specify the output format you prefer; in fact, @code{display} decides
6018 whether to use @code{print} or @code{x} depending your format
6019 specification---it uses @code{x} if you specify either the @samp{i}
6020 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6024 @item display @var{expr}
6025 Add the expression @var{expr} to the list of expressions to display
6026 each time your program stops. @xref{Expressions, ,Expressions}.
6028 @code{display} does not repeat if you press @key{RET} again after using it.
6030 @item display/@var{fmt} @var{expr}
6031 For @var{fmt} specifying only a display format and not a size or
6032 count, add the expression @var{expr} to the auto-display list but
6033 arrange to display it each time in the specified format @var{fmt}.
6034 @xref{Output Formats,,Output Formats}.
6036 @item display/@var{fmt} @var{addr}
6037 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6038 number of units, add the expression @var{addr} as a memory address to
6039 be examined each time your program stops. Examining means in effect
6040 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6043 For example, @samp{display/i $pc} can be helpful, to see the machine
6044 instruction about to be executed each time execution stops (@samp{$pc}
6045 is a common name for the program counter; @pxref{Registers, ,Registers}).
6048 @kindex delete display
6050 @item undisplay @var{dnums}@dots{}
6051 @itemx delete display @var{dnums}@dots{}
6052 Remove item numbers @var{dnums} from the list of expressions to display.
6054 @code{undisplay} does not repeat if you press @key{RET} after using it.
6055 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6057 @kindex disable display
6058 @item disable display @var{dnums}@dots{}
6059 Disable the display of item numbers @var{dnums}. A disabled display
6060 item is not printed automatically, but is not forgotten. It may be
6061 enabled again later.
6063 @kindex enable display
6064 @item enable display @var{dnums}@dots{}
6065 Enable display of item numbers @var{dnums}. It becomes effective once
6066 again in auto display of its expression, until you specify otherwise.
6069 Display the current values of the expressions on the list, just as is
6070 done when your program stops.
6072 @kindex info display
6074 Print the list of expressions previously set up to display
6075 automatically, each one with its item number, but without showing the
6076 values. This includes disabled expressions, which are marked as such.
6077 It also includes expressions which would not be displayed right now
6078 because they refer to automatic variables not currently available.
6081 @cindex display disabled out of scope
6082 If a display expression refers to local variables, then it does not make
6083 sense outside the lexical context for which it was set up. Such an
6084 expression is disabled when execution enters a context where one of its
6085 variables is not defined. For example, if you give the command
6086 @code{display last_char} while inside a function with an argument
6087 @code{last_char}, @value{GDBN} displays this argument while your program
6088 continues to stop inside that function. When it stops elsewhere---where
6089 there is no variable @code{last_char}---the display is disabled
6090 automatically. The next time your program stops where @code{last_char}
6091 is meaningful, you can enable the display expression once again.
6093 @node Print Settings
6094 @section Print Settings
6096 @cindex format options
6097 @cindex print settings
6098 @value{GDBN} provides the following ways to control how arrays, structures,
6099 and symbols are printed.
6102 These settings are useful for debugging programs in any language:
6106 @item set print address
6107 @itemx set print address on
6108 @cindex print/don't print memory addresses
6109 @value{GDBN} prints memory addresses showing the location of stack
6110 traces, structure values, pointer values, breakpoints, and so forth,
6111 even when it also displays the contents of those addresses. The default
6112 is @code{on}. For example, this is what a stack frame display looks like with
6113 @code{set print address on}:
6118 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6120 530 if (lquote != def_lquote)
6124 @item set print address off
6125 Do not print addresses when displaying their contents. For example,
6126 this is the same stack frame displayed with @code{set print address off}:
6130 (@value{GDBP}) set print addr off
6132 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6133 530 if (lquote != def_lquote)
6137 You can use @samp{set print address off} to eliminate all machine
6138 dependent displays from the @value{GDBN} interface. For example, with
6139 @code{print address off}, you should get the same text for backtraces on
6140 all machines---whether or not they involve pointer arguments.
6143 @item show print address
6144 Show whether or not addresses are to be printed.
6147 When @value{GDBN} prints a symbolic address, it normally prints the
6148 closest earlier symbol plus an offset. If that symbol does not uniquely
6149 identify the address (for example, it is a name whose scope is a single
6150 source file), you may need to clarify. One way to do this is with
6151 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6152 you can set @value{GDBN} to print the source file and line number when
6153 it prints a symbolic address:
6156 @item set print symbol-filename on
6157 @cindex source file and line of a symbol
6158 @cindex symbol, source file and line
6159 Tell @value{GDBN} to print the source file name and line number of a
6160 symbol in the symbolic form of an address.
6162 @item set print symbol-filename off
6163 Do not print source file name and line number of a symbol. This is the
6166 @item show print symbol-filename
6167 Show whether or not @value{GDBN} will print the source file name and
6168 line number of a symbol in the symbolic form of an address.
6171 Another situation where it is helpful to show symbol filenames and line
6172 numbers is when disassembling code; @value{GDBN} shows you the line
6173 number and source file that corresponds to each instruction.
6175 Also, you may wish to see the symbolic form only if the address being
6176 printed is reasonably close to the closest earlier symbol:
6179 @item set print max-symbolic-offset @var{max-offset}
6180 @cindex maximum value for offset of closest symbol
6181 Tell @value{GDBN} to only display the symbolic form of an address if the
6182 offset between the closest earlier symbol and the address is less than
6183 @var{max-offset}. The default is 0, which tells @value{GDBN}
6184 to always print the symbolic form of an address if any symbol precedes it.
6186 @item show print max-symbolic-offset
6187 Ask how large the maximum offset is that @value{GDBN} prints in a
6191 @cindex wild pointer, interpreting
6192 @cindex pointer, finding referent
6193 If you have a pointer and you are not sure where it points, try
6194 @samp{set print symbol-filename on}. Then you can determine the name
6195 and source file location of the variable where it points, using
6196 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6197 For example, here @value{GDBN} shows that a variable @code{ptt} points
6198 at another variable @code{t}, defined in @file{hi2.c}:
6201 (@value{GDBP}) set print symbol-filename on
6202 (@value{GDBP}) p/a ptt
6203 $4 = 0xe008 <t in hi2.c>
6207 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6208 does not show the symbol name and filename of the referent, even with
6209 the appropriate @code{set print} options turned on.
6212 Other settings control how different kinds of objects are printed:
6215 @item set print array
6216 @itemx set print array on
6217 @cindex pretty print arrays
6218 Pretty print arrays. This format is more convenient to read,
6219 but uses more space. The default is off.
6221 @item set print array off
6222 Return to compressed format for arrays.
6224 @item show print array
6225 Show whether compressed or pretty format is selected for displaying
6228 @cindex print array indexes
6229 @item set print array-indexes
6230 @itemx set print array-indexes on
6231 Print the index of each element when displaying arrays. May be more
6232 convenient to locate a given element in the array or quickly find the
6233 index of a given element in that printed array. The default is off.
6235 @item set print array-indexes off
6236 Stop printing element indexes when displaying arrays.
6238 @item show print array-indexes
6239 Show whether the index of each element is printed when displaying
6242 @item set print elements @var{number-of-elements}
6243 @cindex number of array elements to print
6244 @cindex limit on number of printed array elements
6245 Set a limit on how many elements of an array @value{GDBN} will print.
6246 If @value{GDBN} is printing a large array, it stops printing after it has
6247 printed the number of elements set by the @code{set print elements} command.
6248 This limit also applies to the display of strings.
6249 When @value{GDBN} starts, this limit is set to 200.
6250 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6252 @item show print elements
6253 Display the number of elements of a large array that @value{GDBN} will print.
6254 If the number is 0, then the printing is unlimited.
6256 @item set print frame-arguments @var{value}
6257 @cindex printing frame argument values
6258 @cindex print all frame argument values
6259 @cindex print frame argument values for scalars only
6260 @cindex do not print frame argument values
6261 This command allows to control how the values of arguments are printed
6262 when the debugger prints a frame (@pxref{Frames}). The possible
6267 The values of all arguments are printed. This is the default.
6270 Print the value of an argument only if it is a scalar. The value of more
6271 complex arguments such as arrays, structures, unions, etc, is replaced
6272 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6275 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6280 None of the argument values are printed. Instead, the value of each argument
6281 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6284 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6289 By default, all argument values are always printed. But this command
6290 can be useful in several cases. For instance, it can be used to reduce
6291 the amount of information printed in each frame, making the backtrace
6292 more readable. Also, this command can be used to improve performance
6293 when displaying Ada frames, because the computation of large arguments
6294 can sometimes be CPU-intensive, especiallly in large applications.
6295 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6296 avoids this computation, thus speeding up the display of each Ada frame.
6298 @item show print frame-arguments
6299 Show how the value of arguments should be displayed when printing a frame.
6301 @item set print repeats
6302 @cindex repeated array elements
6303 Set the threshold for suppressing display of repeated array
6304 elements. When the number of consecutive identical elements of an
6305 array exceeds the threshold, @value{GDBN} prints the string
6306 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6307 identical repetitions, instead of displaying the identical elements
6308 themselves. Setting the threshold to zero will cause all elements to
6309 be individually printed. The default threshold is 10.
6311 @item show print repeats
6312 Display the current threshold for printing repeated identical
6315 @item set print null-stop
6316 @cindex @sc{null} elements in arrays
6317 Cause @value{GDBN} to stop printing the characters of an array when the first
6318 @sc{null} is encountered. This is useful when large arrays actually
6319 contain only short strings.
6322 @item show print null-stop
6323 Show whether @value{GDBN} stops printing an array on the first
6324 @sc{null} character.
6326 @item set print pretty on
6327 @cindex print structures in indented form
6328 @cindex indentation in structure display
6329 Cause @value{GDBN} to print structures in an indented format with one member
6330 per line, like this:
6345 @item set print pretty off
6346 Cause @value{GDBN} to print structures in a compact format, like this:
6350 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6351 meat = 0x54 "Pork"@}
6356 This is the default format.
6358 @item show print pretty
6359 Show which format @value{GDBN} is using to print structures.
6361 @item set print sevenbit-strings on
6362 @cindex eight-bit characters in strings
6363 @cindex octal escapes in strings
6364 Print using only seven-bit characters; if this option is set,
6365 @value{GDBN} displays any eight-bit characters (in strings or
6366 character values) using the notation @code{\}@var{nnn}. This setting is
6367 best if you are working in English (@sc{ascii}) and you use the
6368 high-order bit of characters as a marker or ``meta'' bit.
6370 @item set print sevenbit-strings off
6371 Print full eight-bit characters. This allows the use of more
6372 international character sets, and is the default.
6374 @item show print sevenbit-strings
6375 Show whether or not @value{GDBN} is printing only seven-bit characters.
6377 @item set print union on
6378 @cindex unions in structures, printing
6379 Tell @value{GDBN} to print unions which are contained in structures
6380 and other unions. This is the default setting.
6382 @item set print union off
6383 Tell @value{GDBN} not to print unions which are contained in
6384 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6387 @item show print union
6388 Ask @value{GDBN} whether or not it will print unions which are contained in
6389 structures and other unions.
6391 For example, given the declarations
6394 typedef enum @{Tree, Bug@} Species;
6395 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6396 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6407 struct thing foo = @{Tree, @{Acorn@}@};
6411 with @code{set print union on} in effect @samp{p foo} would print
6414 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6418 and with @code{set print union off} in effect it would print
6421 $1 = @{it = Tree, form = @{...@}@}
6425 @code{set print union} affects programs written in C-like languages
6431 These settings are of interest when debugging C@t{++} programs:
6434 @cindex demangling C@t{++} names
6435 @item set print demangle
6436 @itemx set print demangle on
6437 Print C@t{++} names in their source form rather than in the encoded
6438 (``mangled'') form passed to the assembler and linker for type-safe
6439 linkage. The default is on.
6441 @item show print demangle
6442 Show whether C@t{++} names are printed in mangled or demangled form.
6444 @item set print asm-demangle
6445 @itemx set print asm-demangle on
6446 Print C@t{++} names in their source form rather than their mangled form, even
6447 in assembler code printouts such as instruction disassemblies.
6450 @item show print asm-demangle
6451 Show whether C@t{++} names in assembly listings are printed in mangled
6454 @cindex C@t{++} symbol decoding style
6455 @cindex symbol decoding style, C@t{++}
6456 @kindex set demangle-style
6457 @item set demangle-style @var{style}
6458 Choose among several encoding schemes used by different compilers to
6459 represent C@t{++} names. The choices for @var{style} are currently:
6463 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6466 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6467 This is the default.
6470 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6473 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6476 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6477 @strong{Warning:} this setting alone is not sufficient to allow
6478 debugging @code{cfront}-generated executables. @value{GDBN} would
6479 require further enhancement to permit that.
6482 If you omit @var{style}, you will see a list of possible formats.
6484 @item show demangle-style
6485 Display the encoding style currently in use for decoding C@t{++} symbols.
6487 @item set print object
6488 @itemx set print object on
6489 @cindex derived type of an object, printing
6490 @cindex display derived types
6491 When displaying a pointer to an object, identify the @emph{actual}
6492 (derived) type of the object rather than the @emph{declared} type, using
6493 the virtual function table.
6495 @item set print object off
6496 Display only the declared type of objects, without reference to the
6497 virtual function table. This is the default setting.
6499 @item show print object
6500 Show whether actual, or declared, object types are displayed.
6502 @item set print static-members
6503 @itemx set print static-members on
6504 @cindex static members of C@t{++} objects
6505 Print static members when displaying a C@t{++} object. The default is on.
6507 @item set print static-members off
6508 Do not print static members when displaying a C@t{++} object.
6510 @item show print static-members
6511 Show whether C@t{++} static members are printed or not.
6513 @item set print pascal_static-members
6514 @itemx set print pascal_static-members on
6515 @cindex static members of Pascal objects
6516 @cindex Pascal objects, static members display
6517 Print static members when displaying a Pascal object. The default is on.
6519 @item set print pascal_static-members off
6520 Do not print static members when displaying a Pascal object.
6522 @item show print pascal_static-members
6523 Show whether Pascal static members are printed or not.
6525 @c These don't work with HP ANSI C++ yet.
6526 @item set print vtbl
6527 @itemx set print vtbl on
6528 @cindex pretty print C@t{++} virtual function tables
6529 @cindex virtual functions (C@t{++}) display
6530 @cindex VTBL display
6531 Pretty print C@t{++} virtual function tables. The default is off.
6532 (The @code{vtbl} commands do not work on programs compiled with the HP
6533 ANSI C@t{++} compiler (@code{aCC}).)
6535 @item set print vtbl off
6536 Do not pretty print C@t{++} virtual function tables.
6538 @item show print vtbl
6539 Show whether C@t{++} virtual function tables are pretty printed, or not.
6543 @section Value History
6545 @cindex value history
6546 @cindex history of values printed by @value{GDBN}
6547 Values printed by the @code{print} command are saved in the @value{GDBN}
6548 @dfn{value history}. This allows you to refer to them in other expressions.
6549 Values are kept until the symbol table is re-read or discarded
6550 (for example with the @code{file} or @code{symbol-file} commands).
6551 When the symbol table changes, the value history is discarded,
6552 since the values may contain pointers back to the types defined in the
6557 @cindex history number
6558 The values printed are given @dfn{history numbers} by which you can
6559 refer to them. These are successive integers starting with one.
6560 @code{print} shows you the history number assigned to a value by
6561 printing @samp{$@var{num} = } before the value; here @var{num} is the
6564 To refer to any previous value, use @samp{$} followed by the value's
6565 history number. The way @code{print} labels its output is designed to
6566 remind you of this. Just @code{$} refers to the most recent value in
6567 the history, and @code{$$} refers to the value before that.
6568 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6569 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6570 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6572 For example, suppose you have just printed a pointer to a structure and
6573 want to see the contents of the structure. It suffices to type
6579 If you have a chain of structures where the component @code{next} points
6580 to the next one, you can print the contents of the next one with this:
6587 You can print successive links in the chain by repeating this
6588 command---which you can do by just typing @key{RET}.
6590 Note that the history records values, not expressions. If the value of
6591 @code{x} is 4 and you type these commands:
6599 then the value recorded in the value history by the @code{print} command
6600 remains 4 even though the value of @code{x} has changed.
6605 Print the last ten values in the value history, with their item numbers.
6606 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6607 values} does not change the history.
6609 @item show values @var{n}
6610 Print ten history values centered on history item number @var{n}.
6613 Print ten history values just after the values last printed. If no more
6614 values are available, @code{show values +} produces no display.
6617 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6618 same effect as @samp{show values +}.
6620 @node Convenience Vars
6621 @section Convenience Variables
6623 @cindex convenience variables
6624 @cindex user-defined variables
6625 @value{GDBN} provides @dfn{convenience variables} that you can use within
6626 @value{GDBN} to hold on to a value and refer to it later. These variables
6627 exist entirely within @value{GDBN}; they are not part of your program, and
6628 setting a convenience variable has no direct effect on further execution
6629 of your program. That is why you can use them freely.
6631 Convenience variables are prefixed with @samp{$}. Any name preceded by
6632 @samp{$} can be used for a convenience variable, unless it is one of
6633 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6634 (Value history references, in contrast, are @emph{numbers} preceded
6635 by @samp{$}. @xref{Value History, ,Value History}.)
6637 You can save a value in a convenience variable with an assignment
6638 expression, just as you would set a variable in your program.
6642 set $foo = *object_ptr
6646 would save in @code{$foo} the value contained in the object pointed to by
6649 Using a convenience variable for the first time creates it, but its
6650 value is @code{void} until you assign a new value. You can alter the
6651 value with another assignment at any time.
6653 Convenience variables have no fixed types. You can assign a convenience
6654 variable any type of value, including structures and arrays, even if
6655 that variable already has a value of a different type. The convenience
6656 variable, when used as an expression, has the type of its current value.
6659 @kindex show convenience
6660 @cindex show all user variables
6661 @item show convenience
6662 Print a list of convenience variables used so far, and their values.
6663 Abbreviated @code{show conv}.
6665 @kindex init-if-undefined
6666 @cindex convenience variables, initializing
6667 @item init-if-undefined $@var{variable} = @var{expression}
6668 Set a convenience variable if it has not already been set. This is useful
6669 for user-defined commands that keep some state. It is similar, in concept,
6670 to using local static variables with initializers in C (except that
6671 convenience variables are global). It can also be used to allow users to
6672 override default values used in a command script.
6674 If the variable is already defined then the expression is not evaluated so
6675 any side-effects do not occur.
6678 One of the ways to use a convenience variable is as a counter to be
6679 incremented or a pointer to be advanced. For example, to print
6680 a field from successive elements of an array of structures:
6684 print bar[$i++]->contents
6688 Repeat that command by typing @key{RET}.
6690 Some convenience variables are created automatically by @value{GDBN} and given
6691 values likely to be useful.
6694 @vindex $_@r{, convenience variable}
6696 The variable @code{$_} is automatically set by the @code{x} command to
6697 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6698 commands which provide a default address for @code{x} to examine also
6699 set @code{$_} to that address; these commands include @code{info line}
6700 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6701 except when set by the @code{x} command, in which case it is a pointer
6702 to the type of @code{$__}.
6704 @vindex $__@r{, convenience variable}
6706 The variable @code{$__} is automatically set by the @code{x} command
6707 to the value found in the last address examined. Its type is chosen
6708 to match the format in which the data was printed.
6711 @vindex $_exitcode@r{, convenience variable}
6712 The variable @code{$_exitcode} is automatically set to the exit code when
6713 the program being debugged terminates.
6716 On HP-UX systems, if you refer to a function or variable name that
6717 begins with a dollar sign, @value{GDBN} searches for a user or system
6718 name first, before it searches for a convenience variable.
6724 You can refer to machine register contents, in expressions, as variables
6725 with names starting with @samp{$}. The names of registers are different
6726 for each machine; use @code{info registers} to see the names used on
6730 @kindex info registers
6731 @item info registers
6732 Print the names and values of all registers except floating-point
6733 and vector registers (in the selected stack frame).
6735 @kindex info all-registers
6736 @cindex floating point registers
6737 @item info all-registers
6738 Print the names and values of all registers, including floating-point
6739 and vector registers (in the selected stack frame).
6741 @item info registers @var{regname} @dots{}
6742 Print the @dfn{relativized} value of each specified register @var{regname}.
6743 As discussed in detail below, register values are normally relative to
6744 the selected stack frame. @var{regname} may be any register name valid on
6745 the machine you are using, with or without the initial @samp{$}.
6748 @cindex stack pointer register
6749 @cindex program counter register
6750 @cindex process status register
6751 @cindex frame pointer register
6752 @cindex standard registers
6753 @value{GDBN} has four ``standard'' register names that are available (in
6754 expressions) on most machines---whenever they do not conflict with an
6755 architecture's canonical mnemonics for registers. The register names
6756 @code{$pc} and @code{$sp} are used for the program counter register and
6757 the stack pointer. @code{$fp} is used for a register that contains a
6758 pointer to the current stack frame, and @code{$ps} is used for a
6759 register that contains the processor status. For example,
6760 you could print the program counter in hex with
6767 or print the instruction to be executed next with
6774 or add four to the stack pointer@footnote{This is a way of removing
6775 one word from the stack, on machines where stacks grow downward in
6776 memory (most machines, nowadays). This assumes that the innermost
6777 stack frame is selected; setting @code{$sp} is not allowed when other
6778 stack frames are selected. To pop entire frames off the stack,
6779 regardless of machine architecture, use @code{return};
6780 see @ref{Returning, ,Returning from a Function}.} with
6786 Whenever possible, these four standard register names are available on
6787 your machine even though the machine has different canonical mnemonics,
6788 so long as there is no conflict. The @code{info registers} command
6789 shows the canonical names. For example, on the SPARC, @code{info
6790 registers} displays the processor status register as @code{$psr} but you
6791 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6792 is an alias for the @sc{eflags} register.
6794 @value{GDBN} always considers the contents of an ordinary register as an
6795 integer when the register is examined in this way. Some machines have
6796 special registers which can hold nothing but floating point; these
6797 registers are considered to have floating point values. There is no way
6798 to refer to the contents of an ordinary register as floating point value
6799 (although you can @emph{print} it as a floating point value with
6800 @samp{print/f $@var{regname}}).
6802 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6803 means that the data format in which the register contents are saved by
6804 the operating system is not the same one that your program normally
6805 sees. For example, the registers of the 68881 floating point
6806 coprocessor are always saved in ``extended'' (raw) format, but all C
6807 programs expect to work with ``double'' (virtual) format. In such
6808 cases, @value{GDBN} normally works with the virtual format only (the format
6809 that makes sense for your program), but the @code{info registers} command
6810 prints the data in both formats.
6812 @cindex SSE registers (x86)
6813 @cindex MMX registers (x86)
6814 Some machines have special registers whose contents can be interpreted
6815 in several different ways. For example, modern x86-based machines
6816 have SSE and MMX registers that can hold several values packed
6817 together in several different formats. @value{GDBN} refers to such
6818 registers in @code{struct} notation:
6821 (@value{GDBP}) print $xmm1
6823 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6824 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6825 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6826 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6827 v4_int32 = @{0, 20657912, 11, 13@},
6828 v2_int64 = @{88725056443645952, 55834574859@},
6829 uint128 = 0x0000000d0000000b013b36f800000000
6834 To set values of such registers, you need to tell @value{GDBN} which
6835 view of the register you wish to change, as if you were assigning
6836 value to a @code{struct} member:
6839 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6842 Normally, register values are relative to the selected stack frame
6843 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
6844 value that the register would contain if all stack frames farther in
6845 were exited and their saved registers restored. In order to see the
6846 true contents of hardware registers, you must select the innermost
6847 frame (with @samp{frame 0}).
6849 However, @value{GDBN} must deduce where registers are saved, from the machine
6850 code generated by your compiler. If some registers are not saved, or if
6851 @value{GDBN} is unable to locate the saved registers, the selected stack
6852 frame makes no difference.
6854 @node Floating Point Hardware
6855 @section Floating Point Hardware
6856 @cindex floating point
6858 Depending on the configuration, @value{GDBN} may be able to give
6859 you more information about the status of the floating point hardware.
6864 Display hardware-dependent information about the floating
6865 point unit. The exact contents and layout vary depending on the
6866 floating point chip. Currently, @samp{info float} is supported on
6867 the ARM and x86 machines.
6871 @section Vector Unit
6874 Depending on the configuration, @value{GDBN} may be able to give you
6875 more information about the status of the vector unit.
6880 Display information about the vector unit. The exact contents and
6881 layout vary depending on the hardware.
6884 @node OS Information
6885 @section Operating System Auxiliary Information
6886 @cindex OS information
6888 @value{GDBN} provides interfaces to useful OS facilities that can help
6889 you debug your program.
6891 @cindex @code{ptrace} system call
6892 @cindex @code{struct user} contents
6893 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6894 machines), it interfaces with the inferior via the @code{ptrace}
6895 system call. The operating system creates a special sata structure,
6896 called @code{struct user}, for this interface. You can use the
6897 command @code{info udot} to display the contents of this data
6903 Display the contents of the @code{struct user} maintained by the OS
6904 kernel for the program being debugged. @value{GDBN} displays the
6905 contents of @code{struct user} as a list of hex numbers, similar to
6906 the @code{examine} command.
6909 @cindex auxiliary vector
6910 @cindex vector, auxiliary
6911 Some operating systems supply an @dfn{auxiliary vector} to programs at
6912 startup. This is akin to the arguments and environment that you
6913 specify for a program, but contains a system-dependent variety of
6914 binary values that tell system libraries important details about the
6915 hardware, operating system, and process. Each value's purpose is
6916 identified by an integer tag; the meanings are well-known but system-specific.
6917 Depending on the configuration and operating system facilities,
6918 @value{GDBN} may be able to show you this information. For remote
6919 targets, this functionality may further depend on the remote stub's
6920 support of the @samp{qXfer:auxv:read} packet, see
6921 @ref{qXfer auxiliary vector read}.
6926 Display the auxiliary vector of the inferior, which can be either a
6927 live process or a core dump file. @value{GDBN} prints each tag value
6928 numerically, and also shows names and text descriptions for recognized
6929 tags. Some values in the vector are numbers, some bit masks, and some
6930 pointers to strings or other data. @value{GDBN} displays each value in the
6931 most appropriate form for a recognized tag, and in hexadecimal for
6932 an unrecognized tag.
6936 @node Memory Region Attributes
6937 @section Memory Region Attributes
6938 @cindex memory region attributes
6940 @dfn{Memory region attributes} allow you to describe special handling
6941 required by regions of your target's memory. @value{GDBN} uses
6942 attributes to determine whether to allow certain types of memory
6943 accesses; whether to use specific width accesses; and whether to cache
6944 target memory. By default the description of memory regions is
6945 fetched from the target (if the current target supports this), but the
6946 user can override the fetched regions.
6948 Defined memory regions can be individually enabled and disabled. When a
6949 memory region is disabled, @value{GDBN} uses the default attributes when
6950 accessing memory in that region. Similarly, if no memory regions have
6951 been defined, @value{GDBN} uses the default attributes when accessing
6954 When a memory region is defined, it is given a number to identify it;
6955 to enable, disable, or remove a memory region, you specify that number.
6959 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6960 Define a memory region bounded by @var{lower} and @var{upper} with
6961 attributes @var{attributes}@dots{}, and add it to the list of regions
6962 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6963 case: it is treated as the target's maximum memory address.
6964 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6967 Discard any user changes to the memory regions and use target-supplied
6968 regions, if available, or no regions if the target does not support.
6971 @item delete mem @var{nums}@dots{}
6972 Remove memory regions @var{nums}@dots{} from the list of regions
6973 monitored by @value{GDBN}.
6976 @item disable mem @var{nums}@dots{}
6977 Disable monitoring of memory regions @var{nums}@dots{}.
6978 A disabled memory region is not forgotten.
6979 It may be enabled again later.
6982 @item enable mem @var{nums}@dots{}
6983 Enable monitoring of memory regions @var{nums}@dots{}.
6987 Print a table of all defined memory regions, with the following columns
6991 @item Memory Region Number
6992 @item Enabled or Disabled.
6993 Enabled memory regions are marked with @samp{y}.
6994 Disabled memory regions are marked with @samp{n}.
6997 The address defining the inclusive lower bound of the memory region.
7000 The address defining the exclusive upper bound of the memory region.
7003 The list of attributes set for this memory region.
7008 @subsection Attributes
7010 @subsubsection Memory Access Mode
7011 The access mode attributes set whether @value{GDBN} may make read or
7012 write accesses to a memory region.
7014 While these attributes prevent @value{GDBN} from performing invalid
7015 memory accesses, they do nothing to prevent the target system, I/O DMA,
7016 etc.@: from accessing memory.
7020 Memory is read only.
7022 Memory is write only.
7024 Memory is read/write. This is the default.
7027 @subsubsection Memory Access Size
7028 The access size attribute tells @value{GDBN} to use specific sized
7029 accesses in the memory region. Often memory mapped device registers
7030 require specific sized accesses. If no access size attribute is
7031 specified, @value{GDBN} may use accesses of any size.
7035 Use 8 bit memory accesses.
7037 Use 16 bit memory accesses.
7039 Use 32 bit memory accesses.
7041 Use 64 bit memory accesses.
7044 @c @subsubsection Hardware/Software Breakpoints
7045 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7046 @c will use hardware or software breakpoints for the internal breakpoints
7047 @c used by the step, next, finish, until, etc. commands.
7051 @c Always use hardware breakpoints
7052 @c @item swbreak (default)
7055 @subsubsection Data Cache
7056 The data cache attributes set whether @value{GDBN} will cache target
7057 memory. While this generally improves performance by reducing debug
7058 protocol overhead, it can lead to incorrect results because @value{GDBN}
7059 does not know about volatile variables or memory mapped device
7064 Enable @value{GDBN} to cache target memory.
7066 Disable @value{GDBN} from caching target memory. This is the default.
7069 @subsection Memory Access Checking
7070 @value{GDBN} can be instructed to refuse accesses to memory that is
7071 not explicitly described. This can be useful if accessing such
7072 regions has undesired effects for a specific target, or to provide
7073 better error checking. The following commands control this behaviour.
7076 @kindex set mem inaccessible-by-default
7077 @item set mem inaccessible-by-default [on|off]
7078 If @code{on} is specified, make @value{GDBN} treat memory not
7079 explicitly described by the memory ranges as non-existent and refuse accesses
7080 to such memory. The checks are only performed if there's at least one
7081 memory range defined. If @code{off} is specified, make @value{GDBN}
7082 treat the memory not explicitly described by the memory ranges as RAM.
7083 The default value is @code{on}.
7084 @kindex show mem inaccessible-by-default
7085 @item show mem inaccessible-by-default
7086 Show the current handling of accesses to unknown memory.
7090 @c @subsubsection Memory Write Verification
7091 @c The memory write verification attributes set whether @value{GDBN}
7092 @c will re-reads data after each write to verify the write was successful.
7096 @c @item noverify (default)
7099 @node Dump/Restore Files
7100 @section Copy Between Memory and a File
7101 @cindex dump/restore files
7102 @cindex append data to a file
7103 @cindex dump data to a file
7104 @cindex restore data from a file
7106 You can use the commands @code{dump}, @code{append}, and
7107 @code{restore} to copy data between target memory and a file. The
7108 @code{dump} and @code{append} commands write data to a file, and the
7109 @code{restore} command reads data from a file back into the inferior's
7110 memory. Files may be in binary, Motorola S-record, Intel hex, or
7111 Tektronix Hex format; however, @value{GDBN} can only append to binary
7117 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7118 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7119 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7120 or the value of @var{expr}, to @var{filename} in the given format.
7122 The @var{format} parameter may be any one of:
7129 Motorola S-record format.
7131 Tektronix Hex format.
7134 @value{GDBN} uses the same definitions of these formats as the
7135 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7136 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7140 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7141 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7142 Append the contents of memory from @var{start_addr} to @var{end_addr},
7143 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7144 (@value{GDBN} can only append data to files in raw binary form.)
7147 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7148 Restore the contents of file @var{filename} into memory. The
7149 @code{restore} command can automatically recognize any known @sc{bfd}
7150 file format, except for raw binary. To restore a raw binary file you
7151 must specify the optional keyword @code{binary} after the filename.
7153 If @var{bias} is non-zero, its value will be added to the addresses
7154 contained in the file. Binary files always start at address zero, so
7155 they will be restored at address @var{bias}. Other bfd files have
7156 a built-in location; they will be restored at offset @var{bias}
7159 If @var{start} and/or @var{end} are non-zero, then only data between
7160 file offset @var{start} and file offset @var{end} will be restored.
7161 These offsets are relative to the addresses in the file, before
7162 the @var{bias} argument is applied.
7166 @node Core File Generation
7167 @section How to Produce a Core File from Your Program
7168 @cindex dump core from inferior
7170 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7171 image of a running process and its process status (register values
7172 etc.). Its primary use is post-mortem debugging of a program that
7173 crashed while it ran outside a debugger. A program that crashes
7174 automatically produces a core file, unless this feature is disabled by
7175 the user. @xref{Files}, for information on invoking @value{GDBN} in
7176 the post-mortem debugging mode.
7178 Occasionally, you may wish to produce a core file of the program you
7179 are debugging in order to preserve a snapshot of its state.
7180 @value{GDBN} has a special command for that.
7184 @kindex generate-core-file
7185 @item generate-core-file [@var{file}]
7186 @itemx gcore [@var{file}]
7187 Produce a core dump of the inferior process. The optional argument
7188 @var{file} specifies the file name where to put the core dump. If not
7189 specified, the file name defaults to @file{core.@var{pid}}, where
7190 @var{pid} is the inferior process ID.
7192 Note that this command is implemented only for some systems (as of
7193 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7196 @node Character Sets
7197 @section Character Sets
7198 @cindex character sets
7200 @cindex translating between character sets
7201 @cindex host character set
7202 @cindex target character set
7204 If the program you are debugging uses a different character set to
7205 represent characters and strings than the one @value{GDBN} uses itself,
7206 @value{GDBN} can automatically translate between the character sets for
7207 you. The character set @value{GDBN} uses we call the @dfn{host
7208 character set}; the one the inferior program uses we call the
7209 @dfn{target character set}.
7211 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7212 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7213 remote protocol (@pxref{Remote Debugging}) to debug a program
7214 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7215 then the host character set is Latin-1, and the target character set is
7216 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7217 target-charset EBCDIC-US}, then @value{GDBN} translates between
7218 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7219 character and string literals in expressions.
7221 @value{GDBN} has no way to automatically recognize which character set
7222 the inferior program uses; you must tell it, using the @code{set
7223 target-charset} command, described below.
7225 Here are the commands for controlling @value{GDBN}'s character set
7229 @item set target-charset @var{charset}
7230 @kindex set target-charset
7231 Set the current target character set to @var{charset}. We list the
7232 character set names @value{GDBN} recognizes below, but if you type
7233 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7234 list the target character sets it supports.
7238 @item set host-charset @var{charset}
7239 @kindex set host-charset
7240 Set the current host character set to @var{charset}.
7242 By default, @value{GDBN} uses a host character set appropriate to the
7243 system it is running on; you can override that default using the
7244 @code{set host-charset} command.
7246 @value{GDBN} can only use certain character sets as its host character
7247 set. We list the character set names @value{GDBN} recognizes below, and
7248 indicate which can be host character sets, but if you type
7249 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7250 list the host character sets it supports.
7252 @item set charset @var{charset}
7254 Set the current host and target character sets to @var{charset}. As
7255 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7256 @value{GDBN} will list the name of the character sets that can be used
7257 for both host and target.
7261 @kindex show charset
7262 Show the names of the current host and target charsets.
7264 @itemx show host-charset
7265 @kindex show host-charset
7266 Show the name of the current host charset.
7268 @itemx show target-charset
7269 @kindex show target-charset
7270 Show the name of the current target charset.
7274 @value{GDBN} currently includes support for the following character
7280 @cindex ASCII character set
7281 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7285 @cindex ISO 8859-1 character set
7286 @cindex ISO Latin 1 character set
7287 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7288 characters needed for French, German, and Spanish. @value{GDBN} can use
7289 this as its host character set.
7293 @cindex EBCDIC character set
7294 @cindex IBM1047 character set
7295 Variants of the @sc{ebcdic} character set, used on some of IBM's
7296 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7297 @value{GDBN} cannot use these as its host character set.
7301 Note that these are all single-byte character sets. More work inside
7302 @value{GDBN} is needed to support multi-byte or variable-width character
7303 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7305 Here is an example of @value{GDBN}'s character set support in action.
7306 Assume that the following source code has been placed in the file
7307 @file{charset-test.c}:
7313 = @{72, 101, 108, 108, 111, 44, 32, 119,
7314 111, 114, 108, 100, 33, 10, 0@};
7315 char ibm1047_hello[]
7316 = @{200, 133, 147, 147, 150, 107, 64, 166,
7317 150, 153, 147, 132, 90, 37, 0@};
7321 printf ("Hello, world!\n");
7325 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7326 containing the string @samp{Hello, world!} followed by a newline,
7327 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7329 We compile the program, and invoke the debugger on it:
7332 $ gcc -g charset-test.c -o charset-test
7333 $ gdb -nw charset-test
7334 GNU gdb 2001-12-19-cvs
7335 Copyright 2001 Free Software Foundation, Inc.
7340 We can use the @code{show charset} command to see what character sets
7341 @value{GDBN} is currently using to interpret and display characters and
7345 (@value{GDBP}) show charset
7346 The current host and target character set is `ISO-8859-1'.
7350 For the sake of printing this manual, let's use @sc{ascii} as our
7351 initial character set:
7353 (@value{GDBP}) set charset ASCII
7354 (@value{GDBP}) show charset
7355 The current host and target character set is `ASCII'.
7359 Let's assume that @sc{ascii} is indeed the correct character set for our
7360 host system --- in other words, let's assume that if @value{GDBN} prints
7361 characters using the @sc{ascii} character set, our terminal will display
7362 them properly. Since our current target character set is also
7363 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7366 (@value{GDBP}) print ascii_hello
7367 $1 = 0x401698 "Hello, world!\n"
7368 (@value{GDBP}) print ascii_hello[0]
7373 @value{GDBN} uses the target character set for character and string
7374 literals you use in expressions:
7377 (@value{GDBP}) print '+'
7382 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7385 @value{GDBN} relies on the user to tell it which character set the
7386 target program uses. If we print @code{ibm1047_hello} while our target
7387 character set is still @sc{ascii}, we get jibberish:
7390 (@value{GDBP}) print ibm1047_hello
7391 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7392 (@value{GDBP}) print ibm1047_hello[0]
7397 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7398 @value{GDBN} tells us the character sets it supports:
7401 (@value{GDBP}) set target-charset
7402 ASCII EBCDIC-US IBM1047 ISO-8859-1
7403 (@value{GDBP}) set target-charset
7406 We can select @sc{ibm1047} as our target character set, and examine the
7407 program's strings again. Now the @sc{ascii} string is wrong, but
7408 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7409 target character set, @sc{ibm1047}, to the host character set,
7410 @sc{ascii}, and they display correctly:
7413 (@value{GDBP}) set target-charset IBM1047
7414 (@value{GDBP}) show charset
7415 The current host character set is `ASCII'.
7416 The current target character set is `IBM1047'.
7417 (@value{GDBP}) print ascii_hello
7418 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7419 (@value{GDBP}) print ascii_hello[0]
7421 (@value{GDBP}) print ibm1047_hello
7422 $8 = 0x4016a8 "Hello, world!\n"
7423 (@value{GDBP}) print ibm1047_hello[0]
7428 As above, @value{GDBN} uses the target character set for character and
7429 string literals you use in expressions:
7432 (@value{GDBP}) print '+'
7437 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7440 @node Caching Remote Data
7441 @section Caching Data of Remote Targets
7442 @cindex caching data of remote targets
7444 @value{GDBN} can cache data exchanged between the debugger and a
7445 remote target (@pxref{Remote Debugging}). Such caching generally improves
7446 performance, because it reduces the overhead of the remote protocol by
7447 bundling memory reads and writes into large chunks. Unfortunately,
7448 @value{GDBN} does not currently know anything about volatile
7449 registers, and thus data caching will produce incorrect results when
7450 volatile registers are in use.
7453 @kindex set remotecache
7454 @item set remotecache on
7455 @itemx set remotecache off
7456 Set caching state for remote targets. When @code{ON}, use data
7457 caching. By default, this option is @code{OFF}.
7459 @kindex show remotecache
7460 @item show remotecache
7461 Show the current state of data caching for remote targets.
7465 Print the information about the data cache performance. The
7466 information displayed includes: the dcache width and depth; and for
7467 each cache line, how many times it was referenced, and its data and
7468 state (dirty, bad, ok, etc.). This command is useful for debugging
7469 the data cache operation.
7474 @chapter C Preprocessor Macros
7476 Some languages, such as C and C@t{++}, provide a way to define and invoke
7477 ``preprocessor macros'' which expand into strings of tokens.
7478 @value{GDBN} can evaluate expressions containing macro invocations, show
7479 the result of macro expansion, and show a macro's definition, including
7480 where it was defined.
7482 You may need to compile your program specially to provide @value{GDBN}
7483 with information about preprocessor macros. Most compilers do not
7484 include macros in their debugging information, even when you compile
7485 with the @option{-g} flag. @xref{Compilation}.
7487 A program may define a macro at one point, remove that definition later,
7488 and then provide a different definition after that. Thus, at different
7489 points in the program, a macro may have different definitions, or have
7490 no definition at all. If there is a current stack frame, @value{GDBN}
7491 uses the macros in scope at that frame's source code line. Otherwise,
7492 @value{GDBN} uses the macros in scope at the current listing location;
7495 At the moment, @value{GDBN} does not support the @code{##}
7496 token-splicing operator, the @code{#} stringification operator, or
7497 variable-arity macros.
7499 Whenever @value{GDBN} evaluates an expression, it always expands any
7500 macro invocations present in the expression. @value{GDBN} also provides
7501 the following commands for working with macros explicitly.
7505 @kindex macro expand
7506 @cindex macro expansion, showing the results of preprocessor
7507 @cindex preprocessor macro expansion, showing the results of
7508 @cindex expanding preprocessor macros
7509 @item macro expand @var{expression}
7510 @itemx macro exp @var{expression}
7511 Show the results of expanding all preprocessor macro invocations in
7512 @var{expression}. Since @value{GDBN} simply expands macros, but does
7513 not parse the result, @var{expression} need not be a valid expression;
7514 it can be any string of tokens.
7517 @item macro expand-once @var{expression}
7518 @itemx macro exp1 @var{expression}
7519 @cindex expand macro once
7520 @i{(This command is not yet implemented.)} Show the results of
7521 expanding those preprocessor macro invocations that appear explicitly in
7522 @var{expression}. Macro invocations appearing in that expansion are
7523 left unchanged. This command allows you to see the effect of a
7524 particular macro more clearly, without being confused by further
7525 expansions. Since @value{GDBN} simply expands macros, but does not
7526 parse the result, @var{expression} need not be a valid expression; it
7527 can be any string of tokens.
7530 @cindex macro definition, showing
7531 @cindex definition, showing a macro's
7532 @item info macro @var{macro}
7533 Show the definition of the macro named @var{macro}, and describe the
7534 source location where that definition was established.
7536 @kindex macro define
7537 @cindex user-defined macros
7538 @cindex defining macros interactively
7539 @cindex macros, user-defined
7540 @item macro define @var{macro} @var{replacement-list}
7541 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7542 @i{(This command is not yet implemented.)} Introduce a definition for a
7543 preprocessor macro named @var{macro}, invocations of which are replaced
7544 by the tokens given in @var{replacement-list}. The first form of this
7545 command defines an ``object-like'' macro, which takes no arguments; the
7546 second form defines a ``function-like'' macro, which takes the arguments
7547 given in @var{arglist}.
7549 A definition introduced by this command is in scope in every expression
7550 evaluated in @value{GDBN}, until it is removed with the @command{macro
7551 undef} command, described below. The definition overrides all
7552 definitions for @var{macro} present in the program being debugged, as
7553 well as any previous user-supplied definition.
7556 @item macro undef @var{macro}
7557 @i{(This command is not yet implemented.)} Remove any user-supplied
7558 definition for the macro named @var{macro}. This command only affects
7559 definitions provided with the @command{macro define} command, described
7560 above; it cannot remove definitions present in the program being
7565 @i{(This command is not yet implemented.)} List all the macros
7566 defined using the @code{macro define} command.
7569 @cindex macros, example of debugging with
7570 Here is a transcript showing the above commands in action. First, we
7571 show our source files:
7579 #define ADD(x) (M + x)
7584 printf ("Hello, world!\n");
7586 printf ("We're so creative.\n");
7588 printf ("Goodbye, world!\n");
7595 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7596 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7597 compiler includes information about preprocessor macros in the debugging
7601 $ gcc -gdwarf-2 -g3 sample.c -o sample
7605 Now, we start @value{GDBN} on our sample program:
7609 GNU gdb 2002-05-06-cvs
7610 Copyright 2002 Free Software Foundation, Inc.
7611 GDB is free software, @dots{}
7615 We can expand macros and examine their definitions, even when the
7616 program is not running. @value{GDBN} uses the current listing position
7617 to decide which macro definitions are in scope:
7620 (@value{GDBP}) list main
7623 5 #define ADD(x) (M + x)
7628 10 printf ("Hello, world!\n");
7630 12 printf ("We're so creative.\n");
7631 (@value{GDBP}) info macro ADD
7632 Defined at /home/jimb/gdb/macros/play/sample.c:5
7633 #define ADD(x) (M + x)
7634 (@value{GDBP}) info macro Q
7635 Defined at /home/jimb/gdb/macros/play/sample.h:1
7636 included at /home/jimb/gdb/macros/play/sample.c:2
7638 (@value{GDBP}) macro expand ADD(1)
7639 expands to: (42 + 1)
7640 (@value{GDBP}) macro expand-once ADD(1)
7641 expands to: once (M + 1)
7645 In the example above, note that @command{macro expand-once} expands only
7646 the macro invocation explicit in the original text --- the invocation of
7647 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7648 which was introduced by @code{ADD}.
7650 Once the program is running, @value{GDBN} uses the macro definitions in
7651 force at the source line of the current stack frame:
7654 (@value{GDBP}) break main
7655 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7657 Starting program: /home/jimb/gdb/macros/play/sample
7659 Breakpoint 1, main () at sample.c:10
7660 10 printf ("Hello, world!\n");
7664 At line 10, the definition of the macro @code{N} at line 9 is in force:
7667 (@value{GDBP}) info macro N
7668 Defined at /home/jimb/gdb/macros/play/sample.c:9
7670 (@value{GDBP}) macro expand N Q M
7672 (@value{GDBP}) print N Q M
7677 As we step over directives that remove @code{N}'s definition, and then
7678 give it a new definition, @value{GDBN} finds the definition (or lack
7679 thereof) in force at each point:
7684 12 printf ("We're so creative.\n");
7685 (@value{GDBP}) info macro N
7686 The symbol `N' has no definition as a C/C++ preprocessor macro
7687 at /home/jimb/gdb/macros/play/sample.c:12
7690 14 printf ("Goodbye, world!\n");
7691 (@value{GDBP}) info macro N
7692 Defined at /home/jimb/gdb/macros/play/sample.c:13
7694 (@value{GDBP}) macro expand N Q M
7695 expands to: 1729 < 42
7696 (@value{GDBP}) print N Q M
7703 @chapter Tracepoints
7704 @c This chapter is based on the documentation written by Michael
7705 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7708 In some applications, it is not feasible for the debugger to interrupt
7709 the program's execution long enough for the developer to learn
7710 anything helpful about its behavior. If the program's correctness
7711 depends on its real-time behavior, delays introduced by a debugger
7712 might cause the program to change its behavior drastically, or perhaps
7713 fail, even when the code itself is correct. It is useful to be able
7714 to observe the program's behavior without interrupting it.
7716 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7717 specify locations in the program, called @dfn{tracepoints}, and
7718 arbitrary expressions to evaluate when those tracepoints are reached.
7719 Later, using the @code{tfind} command, you can examine the values
7720 those expressions had when the program hit the tracepoints. The
7721 expressions may also denote objects in memory---structures or arrays,
7722 for example---whose values @value{GDBN} should record; while visiting
7723 a particular tracepoint, you may inspect those objects as if they were
7724 in memory at that moment. However, because @value{GDBN} records these
7725 values without interacting with you, it can do so quickly and
7726 unobtrusively, hopefully not disturbing the program's behavior.
7728 The tracepoint facility is currently available only for remote
7729 targets. @xref{Targets}. In addition, your remote target must know
7730 how to collect trace data. This functionality is implemented in the
7731 remote stub; however, none of the stubs distributed with @value{GDBN}
7732 support tracepoints as of this writing. The format of the remote
7733 packets used to implement tracepoints are described in @ref{Tracepoint
7736 This chapter describes the tracepoint commands and features.
7740 * Analyze Collected Data::
7741 * Tracepoint Variables::
7744 @node Set Tracepoints
7745 @section Commands to Set Tracepoints
7747 Before running such a @dfn{trace experiment}, an arbitrary number of
7748 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7749 tracepoint has a number assigned to it by @value{GDBN}. Like with
7750 breakpoints, tracepoint numbers are successive integers starting from
7751 one. Many of the commands associated with tracepoints take the
7752 tracepoint number as their argument, to identify which tracepoint to
7755 For each tracepoint, you can specify, in advance, some arbitrary set
7756 of data that you want the target to collect in the trace buffer when
7757 it hits that tracepoint. The collected data can include registers,
7758 local variables, or global data. Later, you can use @value{GDBN}
7759 commands to examine the values these data had at the time the
7762 This section describes commands to set tracepoints and associated
7763 conditions and actions.
7766 * Create and Delete Tracepoints::
7767 * Enable and Disable Tracepoints::
7768 * Tracepoint Passcounts::
7769 * Tracepoint Actions::
7770 * Listing Tracepoints::
7771 * Starting and Stopping Trace Experiments::
7774 @node Create and Delete Tracepoints
7775 @subsection Create and Delete Tracepoints
7778 @cindex set tracepoint
7781 The @code{trace} command is very similar to the @code{break} command.
7782 Its argument can be a source line, a function name, or an address in
7783 the target program. @xref{Set Breaks}. The @code{trace} command
7784 defines a tracepoint, which is a point in the target program where the
7785 debugger will briefly stop, collect some data, and then allow the
7786 program to continue. Setting a tracepoint or changing its commands
7787 doesn't take effect until the next @code{tstart} command; thus, you
7788 cannot change the tracepoint attributes once a trace experiment is
7791 Here are some examples of using the @code{trace} command:
7794 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7796 (@value{GDBP}) @b{trace +2} // 2 lines forward
7798 (@value{GDBP}) @b{trace my_function} // first source line of function
7800 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7802 (@value{GDBP}) @b{trace *0x2117c4} // an address
7806 You can abbreviate @code{trace} as @code{tr}.
7809 @cindex last tracepoint number
7810 @cindex recent tracepoint number
7811 @cindex tracepoint number
7812 The convenience variable @code{$tpnum} records the tracepoint number
7813 of the most recently set tracepoint.
7815 @kindex delete tracepoint
7816 @cindex tracepoint deletion
7817 @item delete tracepoint @r{[}@var{num}@r{]}
7818 Permanently delete one or more tracepoints. With no argument, the
7819 default is to delete all tracepoints.
7824 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7826 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7830 You can abbreviate this command as @code{del tr}.
7833 @node Enable and Disable Tracepoints
7834 @subsection Enable and Disable Tracepoints
7837 @kindex disable tracepoint
7838 @item disable tracepoint @r{[}@var{num}@r{]}
7839 Disable tracepoint @var{num}, or all tracepoints if no argument
7840 @var{num} is given. A disabled tracepoint will have no effect during
7841 the next trace experiment, but it is not forgotten. You can re-enable
7842 a disabled tracepoint using the @code{enable tracepoint} command.
7844 @kindex enable tracepoint
7845 @item enable tracepoint @r{[}@var{num}@r{]}
7846 Enable tracepoint @var{num}, or all tracepoints. The enabled
7847 tracepoints will become effective the next time a trace experiment is
7851 @node Tracepoint Passcounts
7852 @subsection Tracepoint Passcounts
7856 @cindex tracepoint pass count
7857 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7858 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7859 automatically stop a trace experiment. If a tracepoint's passcount is
7860 @var{n}, then the trace experiment will be automatically stopped on
7861 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7862 @var{num} is not specified, the @code{passcount} command sets the
7863 passcount of the most recently defined tracepoint. If no passcount is
7864 given, the trace experiment will run until stopped explicitly by the
7870 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7871 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7873 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7874 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7875 (@value{GDBP}) @b{trace foo}
7876 (@value{GDBP}) @b{pass 3}
7877 (@value{GDBP}) @b{trace bar}
7878 (@value{GDBP}) @b{pass 2}
7879 (@value{GDBP}) @b{trace baz}
7880 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7881 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7882 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7883 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7887 @node Tracepoint Actions
7888 @subsection Tracepoint Action Lists
7892 @cindex tracepoint actions
7893 @item actions @r{[}@var{num}@r{]}
7894 This command will prompt for a list of actions to be taken when the
7895 tracepoint is hit. If the tracepoint number @var{num} is not
7896 specified, this command sets the actions for the one that was most
7897 recently defined (so that you can define a tracepoint and then say
7898 @code{actions} without bothering about its number). You specify the
7899 actions themselves on the following lines, one action at a time, and
7900 terminate the actions list with a line containing just @code{end}. So
7901 far, the only defined actions are @code{collect} and
7902 @code{while-stepping}.
7904 @cindex remove actions from a tracepoint
7905 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7906 and follow it immediately with @samp{end}.
7909 (@value{GDBP}) @b{collect @var{data}} // collect some data
7911 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7913 (@value{GDBP}) @b{end} // signals the end of actions.
7916 In the following example, the action list begins with @code{collect}
7917 commands indicating the things to be collected when the tracepoint is
7918 hit. Then, in order to single-step and collect additional data
7919 following the tracepoint, a @code{while-stepping} command is used,
7920 followed by the list of things to be collected while stepping. The
7921 @code{while-stepping} command is terminated by its own separate
7922 @code{end} command. Lastly, the action list is terminated by an
7926 (@value{GDBP}) @b{trace foo}
7927 (@value{GDBP}) @b{actions}
7928 Enter actions for tracepoint 1, one per line:
7937 @kindex collect @r{(tracepoints)}
7938 @item collect @var{expr1}, @var{expr2}, @dots{}
7939 Collect values of the given expressions when the tracepoint is hit.
7940 This command accepts a comma-separated list of any valid expressions.
7941 In addition to global, static, or local variables, the following
7942 special arguments are supported:
7946 collect all registers
7949 collect all function arguments
7952 collect all local variables.
7955 You can give several consecutive @code{collect} commands, each one
7956 with a single argument, or one @code{collect} command with several
7957 arguments separated by commas: the effect is the same.
7959 The command @code{info scope} (@pxref{Symbols, info scope}) is
7960 particularly useful for figuring out what data to collect.
7962 @kindex while-stepping @r{(tracepoints)}
7963 @item while-stepping @var{n}
7964 Perform @var{n} single-step traces after the tracepoint, collecting
7965 new data at each step. The @code{while-stepping} command is
7966 followed by the list of what to collect while stepping (followed by
7967 its own @code{end} command):
7971 > collect $regs, myglobal
7977 You may abbreviate @code{while-stepping} as @code{ws} or
7981 @node Listing Tracepoints
7982 @subsection Listing Tracepoints
7985 @kindex info tracepoints
7987 @cindex information about tracepoints
7988 @item info tracepoints @r{[}@var{num}@r{]}
7989 Display information about the tracepoint @var{num}. If you don't specify
7990 a tracepoint number, displays information about all the tracepoints
7991 defined so far. For each tracepoint, the following information is
7998 whether it is enabled or disabled
8002 its passcount as given by the @code{passcount @var{n}} command
8004 its step count as given by the @code{while-stepping @var{n}} command
8006 where in the source files is the tracepoint set
8008 its action list as given by the @code{actions} command
8012 (@value{GDBP}) @b{info trace}
8013 Num Enb Address PassC StepC What
8014 1 y 0x002117c4 0 0 <gdb_asm>
8015 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8016 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8021 This command can be abbreviated @code{info tp}.
8024 @node Starting and Stopping Trace Experiments
8025 @subsection Starting and Stopping Trace Experiments
8029 @cindex start a new trace experiment
8030 @cindex collected data discarded
8032 This command takes no arguments. It starts the trace experiment, and
8033 begins collecting data. This has the side effect of discarding all
8034 the data collected in the trace buffer during the previous trace
8038 @cindex stop a running trace experiment
8040 This command takes no arguments. It ends the trace experiment, and
8041 stops collecting data.
8043 @strong{Note}: a trace experiment and data collection may stop
8044 automatically if any tracepoint's passcount is reached
8045 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8048 @cindex status of trace data collection
8049 @cindex trace experiment, status of
8051 This command displays the status of the current trace data
8055 Here is an example of the commands we described so far:
8058 (@value{GDBP}) @b{trace gdb_c_test}
8059 (@value{GDBP}) @b{actions}
8060 Enter actions for tracepoint #1, one per line.
8061 > collect $regs,$locals,$args
8066 (@value{GDBP}) @b{tstart}
8067 [time passes @dots{}]
8068 (@value{GDBP}) @b{tstop}
8072 @node Analyze Collected Data
8073 @section Using the Collected Data
8075 After the tracepoint experiment ends, you use @value{GDBN} commands
8076 for examining the trace data. The basic idea is that each tracepoint
8077 collects a trace @dfn{snapshot} every time it is hit and another
8078 snapshot every time it single-steps. All these snapshots are
8079 consecutively numbered from zero and go into a buffer, and you can
8080 examine them later. The way you examine them is to @dfn{focus} on a
8081 specific trace snapshot. When the remote stub is focused on a trace
8082 snapshot, it will respond to all @value{GDBN} requests for memory and
8083 registers by reading from the buffer which belongs to that snapshot,
8084 rather than from @emph{real} memory or registers of the program being
8085 debugged. This means that @strong{all} @value{GDBN} commands
8086 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8087 behave as if we were currently debugging the program state as it was
8088 when the tracepoint occurred. Any requests for data that are not in
8089 the buffer will fail.
8092 * tfind:: How to select a trace snapshot
8093 * tdump:: How to display all data for a snapshot
8094 * save-tracepoints:: How to save tracepoints for a future run
8098 @subsection @code{tfind @var{n}}
8101 @cindex select trace snapshot
8102 @cindex find trace snapshot
8103 The basic command for selecting a trace snapshot from the buffer is
8104 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8105 counting from zero. If no argument @var{n} is given, the next
8106 snapshot is selected.
8108 Here are the various forms of using the @code{tfind} command.
8112 Find the first snapshot in the buffer. This is a synonym for
8113 @code{tfind 0} (since 0 is the number of the first snapshot).
8116 Stop debugging trace snapshots, resume @emph{live} debugging.
8119 Same as @samp{tfind none}.
8122 No argument means find the next trace snapshot.
8125 Find the previous trace snapshot before the current one. This permits
8126 retracing earlier steps.
8128 @item tfind tracepoint @var{num}
8129 Find the next snapshot associated with tracepoint @var{num}. Search
8130 proceeds forward from the last examined trace snapshot. If no
8131 argument @var{num} is given, it means find the next snapshot collected
8132 for the same tracepoint as the current snapshot.
8134 @item tfind pc @var{addr}
8135 Find the next snapshot associated with the value @var{addr} of the
8136 program counter. Search proceeds forward from the last examined trace
8137 snapshot. If no argument @var{addr} is given, it means find the next
8138 snapshot with the same value of PC as the current snapshot.
8140 @item tfind outside @var{addr1}, @var{addr2}
8141 Find the next snapshot whose PC is outside the given range of
8144 @item tfind range @var{addr1}, @var{addr2}
8145 Find the next snapshot whose PC is between @var{addr1} and
8146 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8148 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8149 Find the next snapshot associated with the source line @var{n}. If
8150 the optional argument @var{file} is given, refer to line @var{n} in
8151 that source file. Search proceeds forward from the last examined
8152 trace snapshot. If no argument @var{n} is given, it means find the
8153 next line other than the one currently being examined; thus saying
8154 @code{tfind line} repeatedly can appear to have the same effect as
8155 stepping from line to line in a @emph{live} debugging session.
8158 The default arguments for the @code{tfind} commands are specifically
8159 designed to make it easy to scan through the trace buffer. For
8160 instance, @code{tfind} with no argument selects the next trace
8161 snapshot, and @code{tfind -} with no argument selects the previous
8162 trace snapshot. So, by giving one @code{tfind} command, and then
8163 simply hitting @key{RET} repeatedly you can examine all the trace
8164 snapshots in order. Or, by saying @code{tfind -} and then hitting
8165 @key{RET} repeatedly you can examine the snapshots in reverse order.
8166 The @code{tfind line} command with no argument selects the snapshot
8167 for the next source line executed. The @code{tfind pc} command with
8168 no argument selects the next snapshot with the same program counter
8169 (PC) as the current frame. The @code{tfind tracepoint} command with
8170 no argument selects the next trace snapshot collected by the same
8171 tracepoint as the current one.
8173 In addition to letting you scan through the trace buffer manually,
8174 these commands make it easy to construct @value{GDBN} scripts that
8175 scan through the trace buffer and print out whatever collected data
8176 you are interested in. Thus, if we want to examine the PC, FP, and SP
8177 registers from each trace frame in the buffer, we can say this:
8180 (@value{GDBP}) @b{tfind start}
8181 (@value{GDBP}) @b{while ($trace_frame != -1)}
8182 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8183 $trace_frame, $pc, $sp, $fp
8187 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8188 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8189 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8190 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8191 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8192 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8193 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8194 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8195 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8196 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8197 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8200 Or, if we want to examine the variable @code{X} at each source line in
8204 (@value{GDBP}) @b{tfind start}
8205 (@value{GDBP}) @b{while ($trace_frame != -1)}
8206 > printf "Frame %d, X == %d\n", $trace_frame, X
8216 @subsection @code{tdump}
8218 @cindex dump all data collected at tracepoint
8219 @cindex tracepoint data, display
8221 This command takes no arguments. It prints all the data collected at
8222 the current trace snapshot.
8225 (@value{GDBP}) @b{trace 444}
8226 (@value{GDBP}) @b{actions}
8227 Enter actions for tracepoint #2, one per line:
8228 > collect $regs, $locals, $args, gdb_long_test
8231 (@value{GDBP}) @b{tstart}
8233 (@value{GDBP}) @b{tfind line 444}
8234 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8236 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8238 (@value{GDBP}) @b{tdump}
8239 Data collected at tracepoint 2, trace frame 1:
8240 d0 0xc4aa0085 -995491707
8244 d4 0x71aea3d 119204413
8249 a1 0x3000668 50333288
8252 a4 0x3000698 50333336
8254 fp 0x30bf3c 0x30bf3c
8255 sp 0x30bf34 0x30bf34
8257 pc 0x20b2c8 0x20b2c8
8261 p = 0x20e5b4 "gdb-test"
8268 gdb_long_test = 17 '\021'
8273 @node save-tracepoints
8274 @subsection @code{save-tracepoints @var{filename}}
8275 @kindex save-tracepoints
8276 @cindex save tracepoints for future sessions
8278 This command saves all current tracepoint definitions together with
8279 their actions and passcounts, into a file @file{@var{filename}}
8280 suitable for use in a later debugging session. To read the saved
8281 tracepoint definitions, use the @code{source} command (@pxref{Command
8284 @node Tracepoint Variables
8285 @section Convenience Variables for Tracepoints
8286 @cindex tracepoint variables
8287 @cindex convenience variables for tracepoints
8290 @vindex $trace_frame
8291 @item (int) $trace_frame
8292 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8293 snapshot is selected.
8296 @item (int) $tracepoint
8297 The tracepoint for the current trace snapshot.
8300 @item (int) $trace_line
8301 The line number for the current trace snapshot.
8304 @item (char []) $trace_file
8305 The source file for the current trace snapshot.
8308 @item (char []) $trace_func
8309 The name of the function containing @code{$tracepoint}.
8312 Note: @code{$trace_file} is not suitable for use in @code{printf},
8313 use @code{output} instead.
8315 Here's a simple example of using these convenience variables for
8316 stepping through all the trace snapshots and printing some of their
8320 (@value{GDBP}) @b{tfind start}
8322 (@value{GDBP}) @b{while $trace_frame != -1}
8323 > output $trace_file
8324 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8330 @chapter Debugging Programs That Use Overlays
8333 If your program is too large to fit completely in your target system's
8334 memory, you can sometimes use @dfn{overlays} to work around this
8335 problem. @value{GDBN} provides some support for debugging programs that
8339 * How Overlays Work:: A general explanation of overlays.
8340 * Overlay Commands:: Managing overlays in @value{GDBN}.
8341 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8342 mapped by asking the inferior.
8343 * Overlay Sample Program:: A sample program using overlays.
8346 @node How Overlays Work
8347 @section How Overlays Work
8348 @cindex mapped overlays
8349 @cindex unmapped overlays
8350 @cindex load address, overlay's
8351 @cindex mapped address
8352 @cindex overlay area
8354 Suppose you have a computer whose instruction address space is only 64
8355 kilobytes long, but which has much more memory which can be accessed by
8356 other means: special instructions, segment registers, or memory
8357 management hardware, for example. Suppose further that you want to
8358 adapt a program which is larger than 64 kilobytes to run on this system.
8360 One solution is to identify modules of your program which are relatively
8361 independent, and need not call each other directly; call these modules
8362 @dfn{overlays}. Separate the overlays from the main program, and place
8363 their machine code in the larger memory. Place your main program in
8364 instruction memory, but leave at least enough space there to hold the
8365 largest overlay as well.
8367 Now, to call a function located in an overlay, you must first copy that
8368 overlay's machine code from the large memory into the space set aside
8369 for it in the instruction memory, and then jump to its entry point
8372 @c NB: In the below the mapped area's size is greater or equal to the
8373 @c size of all overlays. This is intentional to remind the developer
8374 @c that overlays don't necessarily need to be the same size.
8378 Data Instruction Larger
8379 Address Space Address Space Address Space
8380 +-----------+ +-----------+ +-----------+
8382 +-----------+ +-----------+ +-----------+<-- overlay 1
8383 | program | | main | .----| overlay 1 | load address
8384 | variables | | program | | +-----------+
8385 | and heap | | | | | |
8386 +-----------+ | | | +-----------+<-- overlay 2
8387 | | +-----------+ | | | load address
8388 +-----------+ | | | .-| overlay 2 |
8390 mapped --->+-----------+ | | +-----------+
8392 | overlay | <-' | | |
8393 | area | <---' +-----------+<-- overlay 3
8394 | | <---. | | load address
8395 +-----------+ `--| overlay 3 |
8402 @anchor{A code overlay}A code overlay
8406 The diagram (@pxref{A code overlay}) shows a system with separate data
8407 and instruction address spaces. To map an overlay, the program copies
8408 its code from the larger address space to the instruction address space.
8409 Since the overlays shown here all use the same mapped address, only one
8410 may be mapped at a time. For a system with a single address space for
8411 data and instructions, the diagram would be similar, except that the
8412 program variables and heap would share an address space with the main
8413 program and the overlay area.
8415 An overlay loaded into instruction memory and ready for use is called a
8416 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8417 instruction memory. An overlay not present (or only partially present)
8418 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8419 is its address in the larger memory. The mapped address is also called
8420 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8421 called the @dfn{load memory address}, or @dfn{LMA}.
8423 Unfortunately, overlays are not a completely transparent way to adapt a
8424 program to limited instruction memory. They introduce a new set of
8425 global constraints you must keep in mind as you design your program:
8430 Before calling or returning to a function in an overlay, your program
8431 must make sure that overlay is actually mapped. Otherwise, the call or
8432 return will transfer control to the right address, but in the wrong
8433 overlay, and your program will probably crash.
8436 If the process of mapping an overlay is expensive on your system, you
8437 will need to choose your overlays carefully to minimize their effect on
8438 your program's performance.
8441 The executable file you load onto your system must contain each
8442 overlay's instructions, appearing at the overlay's load address, not its
8443 mapped address. However, each overlay's instructions must be relocated
8444 and its symbols defined as if the overlay were at its mapped address.
8445 You can use GNU linker scripts to specify different load and relocation
8446 addresses for pieces of your program; see @ref{Overlay Description,,,
8447 ld.info, Using ld: the GNU linker}.
8450 The procedure for loading executable files onto your system must be able
8451 to load their contents into the larger address space as well as the
8452 instruction and data spaces.
8456 The overlay system described above is rather simple, and could be
8457 improved in many ways:
8462 If your system has suitable bank switch registers or memory management
8463 hardware, you could use those facilities to make an overlay's load area
8464 contents simply appear at their mapped address in instruction space.
8465 This would probably be faster than copying the overlay to its mapped
8466 area in the usual way.
8469 If your overlays are small enough, you could set aside more than one
8470 overlay area, and have more than one overlay mapped at a time.
8473 You can use overlays to manage data, as well as instructions. In
8474 general, data overlays are even less transparent to your design than
8475 code overlays: whereas code overlays only require care when you call or
8476 return to functions, data overlays require care every time you access
8477 the data. Also, if you change the contents of a data overlay, you
8478 must copy its contents back out to its load address before you can copy a
8479 different data overlay into the same mapped area.
8484 @node Overlay Commands
8485 @section Overlay Commands
8487 To use @value{GDBN}'s overlay support, each overlay in your program must
8488 correspond to a separate section of the executable file. The section's
8489 virtual memory address and load memory address must be the overlay's
8490 mapped and load addresses. Identifying overlays with sections allows
8491 @value{GDBN} to determine the appropriate address of a function or
8492 variable, depending on whether the overlay is mapped or not.
8494 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8495 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8500 Disable @value{GDBN}'s overlay support. When overlay support is
8501 disabled, @value{GDBN} assumes that all functions and variables are
8502 always present at their mapped addresses. By default, @value{GDBN}'s
8503 overlay support is disabled.
8505 @item overlay manual
8506 @cindex manual overlay debugging
8507 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8508 relies on you to tell it which overlays are mapped, and which are not,
8509 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8510 commands described below.
8512 @item overlay map-overlay @var{overlay}
8513 @itemx overlay map @var{overlay}
8514 @cindex map an overlay
8515 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8516 be the name of the object file section containing the overlay. When an
8517 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8518 functions and variables at their mapped addresses. @value{GDBN} assumes
8519 that any other overlays whose mapped ranges overlap that of
8520 @var{overlay} are now unmapped.
8522 @item overlay unmap-overlay @var{overlay}
8523 @itemx overlay unmap @var{overlay}
8524 @cindex unmap an overlay
8525 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8526 must be the name of the object file section containing the overlay.
8527 When an overlay is unmapped, @value{GDBN} assumes it can find the
8528 overlay's functions and variables at their load addresses.
8531 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8532 consults a data structure the overlay manager maintains in the inferior
8533 to see which overlays are mapped. For details, see @ref{Automatic
8536 @item overlay load-target
8538 @cindex reloading the overlay table
8539 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8540 re-reads the table @value{GDBN} automatically each time the inferior
8541 stops, so this command should only be necessary if you have changed the
8542 overlay mapping yourself using @value{GDBN}. This command is only
8543 useful when using automatic overlay debugging.
8545 @item overlay list-overlays
8547 @cindex listing mapped overlays
8548 Display a list of the overlays currently mapped, along with their mapped
8549 addresses, load addresses, and sizes.
8553 Normally, when @value{GDBN} prints a code address, it includes the name
8554 of the function the address falls in:
8557 (@value{GDBP}) print main
8558 $3 = @{int ()@} 0x11a0 <main>
8561 When overlay debugging is enabled, @value{GDBN} recognizes code in
8562 unmapped overlays, and prints the names of unmapped functions with
8563 asterisks around them. For example, if @code{foo} is a function in an
8564 unmapped overlay, @value{GDBN} prints it this way:
8567 (@value{GDBP}) overlay list
8568 No sections are mapped.
8569 (@value{GDBP}) print foo
8570 $5 = @{int (int)@} 0x100000 <*foo*>
8573 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8577 (@value{GDBP}) overlay list
8578 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8579 mapped at 0x1016 - 0x104a
8580 (@value{GDBP}) print foo
8581 $6 = @{int (int)@} 0x1016 <foo>
8584 When overlay debugging is enabled, @value{GDBN} can find the correct
8585 address for functions and variables in an overlay, whether or not the
8586 overlay is mapped. This allows most @value{GDBN} commands, like
8587 @code{break} and @code{disassemble}, to work normally, even on unmapped
8588 code. However, @value{GDBN}'s breakpoint support has some limitations:
8592 @cindex breakpoints in overlays
8593 @cindex overlays, setting breakpoints in
8594 You can set breakpoints in functions in unmapped overlays, as long as
8595 @value{GDBN} can write to the overlay at its load address.
8597 @value{GDBN} can not set hardware or simulator-based breakpoints in
8598 unmapped overlays. However, if you set a breakpoint at the end of your
8599 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8600 you are using manual overlay management), @value{GDBN} will re-set its
8601 breakpoints properly.
8605 @node Automatic Overlay Debugging
8606 @section Automatic Overlay Debugging
8607 @cindex automatic overlay debugging
8609 @value{GDBN} can automatically track which overlays are mapped and which
8610 are not, given some simple co-operation from the overlay manager in the
8611 inferior. If you enable automatic overlay debugging with the
8612 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8613 looks in the inferior's memory for certain variables describing the
8614 current state of the overlays.
8616 Here are the variables your overlay manager must define to support
8617 @value{GDBN}'s automatic overlay debugging:
8621 @item @code{_ovly_table}:
8622 This variable must be an array of the following structures:
8627 /* The overlay's mapped address. */
8630 /* The size of the overlay, in bytes. */
8633 /* The overlay's load address. */
8636 /* Non-zero if the overlay is currently mapped;
8638 unsigned long mapped;
8642 @item @code{_novlys}:
8643 This variable must be a four-byte signed integer, holding the total
8644 number of elements in @code{_ovly_table}.
8648 To decide whether a particular overlay is mapped or not, @value{GDBN}
8649 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8650 @code{lma} members equal the VMA and LMA of the overlay's section in the
8651 executable file. When @value{GDBN} finds a matching entry, it consults
8652 the entry's @code{mapped} member to determine whether the overlay is
8655 In addition, your overlay manager may define a function called
8656 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8657 will silently set a breakpoint there. If the overlay manager then
8658 calls this function whenever it has changed the overlay table, this
8659 will enable @value{GDBN} to accurately keep track of which overlays
8660 are in program memory, and update any breakpoints that may be set
8661 in overlays. This will allow breakpoints to work even if the
8662 overlays are kept in ROM or other non-writable memory while they
8663 are not being executed.
8665 @node Overlay Sample Program
8666 @section Overlay Sample Program
8667 @cindex overlay example program
8669 When linking a program which uses overlays, you must place the overlays
8670 at their load addresses, while relocating them to run at their mapped
8671 addresses. To do this, you must write a linker script (@pxref{Overlay
8672 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8673 since linker scripts are specific to a particular host system, target
8674 architecture, and target memory layout, this manual cannot provide
8675 portable sample code demonstrating @value{GDBN}'s overlay support.
8677 However, the @value{GDBN} source distribution does contain an overlaid
8678 program, with linker scripts for a few systems, as part of its test
8679 suite. The program consists of the following files from
8680 @file{gdb/testsuite/gdb.base}:
8684 The main program file.
8686 A simple overlay manager, used by @file{overlays.c}.
8691 Overlay modules, loaded and used by @file{overlays.c}.
8694 Linker scripts for linking the test program on the @code{d10v-elf}
8695 and @code{m32r-elf} targets.
8698 You can build the test program using the @code{d10v-elf} GCC
8699 cross-compiler like this:
8702 $ d10v-elf-gcc -g -c overlays.c
8703 $ d10v-elf-gcc -g -c ovlymgr.c
8704 $ d10v-elf-gcc -g -c foo.c
8705 $ d10v-elf-gcc -g -c bar.c
8706 $ d10v-elf-gcc -g -c baz.c
8707 $ d10v-elf-gcc -g -c grbx.c
8708 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8709 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8712 The build process is identical for any other architecture, except that
8713 you must substitute the appropriate compiler and linker script for the
8714 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8718 @chapter Using @value{GDBN} with Different Languages
8721 Although programming languages generally have common aspects, they are
8722 rarely expressed in the same manner. For instance, in ANSI C,
8723 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8724 Modula-2, it is accomplished by @code{p^}. Values can also be
8725 represented (and displayed) differently. Hex numbers in C appear as
8726 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8728 @cindex working language
8729 Language-specific information is built into @value{GDBN} for some languages,
8730 allowing you to express operations like the above in your program's
8731 native language, and allowing @value{GDBN} to output values in a manner
8732 consistent with the syntax of your program's native language. The
8733 language you use to build expressions is called the @dfn{working
8737 * Setting:: Switching between source languages
8738 * Show:: Displaying the language
8739 * Checks:: Type and range checks
8740 * Supported Languages:: Supported languages
8741 * Unsupported Languages:: Unsupported languages
8745 @section Switching Between Source Languages
8747 There are two ways to control the working language---either have @value{GDBN}
8748 set it automatically, or select it manually yourself. You can use the
8749 @code{set language} command for either purpose. On startup, @value{GDBN}
8750 defaults to setting the language automatically. The working language is
8751 used to determine how expressions you type are interpreted, how values
8754 In addition to the working language, every source file that
8755 @value{GDBN} knows about has its own working language. For some object
8756 file formats, the compiler might indicate which language a particular
8757 source file is in. However, most of the time @value{GDBN} infers the
8758 language from the name of the file. The language of a source file
8759 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8760 show each frame appropriately for its own language. There is no way to
8761 set the language of a source file from within @value{GDBN}, but you can
8762 set the language associated with a filename extension. @xref{Show, ,
8763 Displaying the Language}.
8765 This is most commonly a problem when you use a program, such
8766 as @code{cfront} or @code{f2c}, that generates C but is written in
8767 another language. In that case, make the
8768 program use @code{#line} directives in its C output; that way
8769 @value{GDBN} will know the correct language of the source code of the original
8770 program, and will display that source code, not the generated C code.
8773 * Filenames:: Filename extensions and languages.
8774 * Manually:: Setting the working language manually
8775 * Automatically:: Having @value{GDBN} infer the source language
8779 @subsection List of Filename Extensions and Languages
8781 If a source file name ends in one of the following extensions, then
8782 @value{GDBN} infers that its language is the one indicated.
8803 Objective-C source file
8810 Modula-2 source file
8814 Assembler source file. This actually behaves almost like C, but
8815 @value{GDBN} does not skip over function prologues when stepping.
8818 In addition, you may set the language associated with a filename
8819 extension. @xref{Show, , Displaying the Language}.
8822 @subsection Setting the Working Language
8824 If you allow @value{GDBN} to set the language automatically,
8825 expressions are interpreted the same way in your debugging session and
8828 @kindex set language
8829 If you wish, you may set the language manually. To do this, issue the
8830 command @samp{set language @var{lang}}, where @var{lang} is the name of
8832 @code{c} or @code{modula-2}.
8833 For a list of the supported languages, type @samp{set language}.
8835 Setting the language manually prevents @value{GDBN} from updating the working
8836 language automatically. This can lead to confusion if you try
8837 to debug a program when the working language is not the same as the
8838 source language, when an expression is acceptable to both
8839 languages---but means different things. For instance, if the current
8840 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8848 might not have the effect you intended. In C, this means to add
8849 @code{b} and @code{c} and place the result in @code{a}. The result
8850 printed would be the value of @code{a}. In Modula-2, this means to compare
8851 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8854 @subsection Having @value{GDBN} Infer the Source Language
8856 To have @value{GDBN} set the working language automatically, use
8857 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8858 then infers the working language. That is, when your program stops in a
8859 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8860 working language to the language recorded for the function in that
8861 frame. If the language for a frame is unknown (that is, if the function
8862 or block corresponding to the frame was defined in a source file that
8863 does not have a recognized extension), the current working language is
8864 not changed, and @value{GDBN} issues a warning.
8866 This may not seem necessary for most programs, which are written
8867 entirely in one source language. However, program modules and libraries
8868 written in one source language can be used by a main program written in
8869 a different source language. Using @samp{set language auto} in this
8870 case frees you from having to set the working language manually.
8873 @section Displaying the Language
8875 The following commands help you find out which language is the
8876 working language, and also what language source files were written in.
8880 @kindex show language
8881 Display the current working language. This is the
8882 language you can use with commands such as @code{print} to
8883 build and compute expressions that may involve variables in your program.
8886 @kindex info frame@r{, show the source language}
8887 Display the source language for this frame. This language becomes the
8888 working language if you use an identifier from this frame.
8889 @xref{Frame Info, ,Information about a Frame}, to identify the other
8890 information listed here.
8893 @kindex info source@r{, show the source language}
8894 Display the source language of this source file.
8895 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8896 information listed here.
8899 In unusual circumstances, you may have source files with extensions
8900 not in the standard list. You can then set the extension associated
8901 with a language explicitly:
8904 @item set extension-language @var{ext} @var{language}
8905 @kindex set extension-language
8906 Tell @value{GDBN} that source files with extension @var{ext} are to be
8907 assumed as written in the source language @var{language}.
8909 @item info extensions
8910 @kindex info extensions
8911 List all the filename extensions and the associated languages.
8915 @section Type and Range Checking
8918 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8919 checking are included, but they do not yet have any effect. This
8920 section documents the intended facilities.
8922 @c FIXME remove warning when type/range code added
8924 Some languages are designed to guard you against making seemingly common
8925 errors through a series of compile- and run-time checks. These include
8926 checking the type of arguments to functions and operators, and making
8927 sure mathematical overflows are caught at run time. Checks such as
8928 these help to ensure a program's correctness once it has been compiled
8929 by eliminating type mismatches, and providing active checks for range
8930 errors when your program is running.
8932 @value{GDBN} can check for conditions like the above if you wish.
8933 Although @value{GDBN} does not check the statements in your program,
8934 it can check expressions entered directly into @value{GDBN} for
8935 evaluation via the @code{print} command, for example. As with the
8936 working language, @value{GDBN} can also decide whether or not to check
8937 automatically based on your program's source language.
8938 @xref{Supported Languages, ,Supported Languages}, for the default
8939 settings of supported languages.
8942 * Type Checking:: An overview of type checking
8943 * Range Checking:: An overview of range checking
8946 @cindex type checking
8947 @cindex checks, type
8949 @subsection An Overview of Type Checking
8951 Some languages, such as Modula-2, are strongly typed, meaning that the
8952 arguments to operators and functions have to be of the correct type,
8953 otherwise an error occurs. These checks prevent type mismatch
8954 errors from ever causing any run-time problems. For example,
8962 The second example fails because the @code{CARDINAL} 1 is not
8963 type-compatible with the @code{REAL} 2.3.
8965 For the expressions you use in @value{GDBN} commands, you can tell the
8966 @value{GDBN} type checker to skip checking;
8967 to treat any mismatches as errors and abandon the expression;
8968 or to only issue warnings when type mismatches occur,
8969 but evaluate the expression anyway. When you choose the last of
8970 these, @value{GDBN} evaluates expressions like the second example above, but
8971 also issues a warning.
8973 Even if you turn type checking off, there may be other reasons
8974 related to type that prevent @value{GDBN} from evaluating an expression.
8975 For instance, @value{GDBN} does not know how to add an @code{int} and
8976 a @code{struct foo}. These particular type errors have nothing to do
8977 with the language in use, and usually arise from expressions, such as
8978 the one described above, which make little sense to evaluate anyway.
8980 Each language defines to what degree it is strict about type. For
8981 instance, both Modula-2 and C require the arguments to arithmetical
8982 operators to be numbers. In C, enumerated types and pointers can be
8983 represented as numbers, so that they are valid arguments to mathematical
8984 operators. @xref{Supported Languages, ,Supported Languages}, for further
8985 details on specific languages.
8987 @value{GDBN} provides some additional commands for controlling the type checker:
8989 @kindex set check type
8990 @kindex show check type
8992 @item set check type auto
8993 Set type checking on or off based on the current working language.
8994 @xref{Supported Languages, ,Supported Languages}, for the default settings for
8997 @item set check type on
8998 @itemx set check type off
8999 Set type checking on or off, overriding the default setting for the
9000 current working language. Issue a warning if the setting does not
9001 match the language default. If any type mismatches occur in
9002 evaluating an expression while type checking is on, @value{GDBN} prints a
9003 message and aborts evaluation of the expression.
9005 @item set check type warn
9006 Cause the type checker to issue warnings, but to always attempt to
9007 evaluate the expression. Evaluating the expression may still
9008 be impossible for other reasons. For example, @value{GDBN} cannot add
9009 numbers and structures.
9012 Show the current setting of the type checker, and whether or not @value{GDBN}
9013 is setting it automatically.
9016 @cindex range checking
9017 @cindex checks, range
9018 @node Range Checking
9019 @subsection An Overview of Range Checking
9021 In some languages (such as Modula-2), it is an error to exceed the
9022 bounds of a type; this is enforced with run-time checks. Such range
9023 checking is meant to ensure program correctness by making sure
9024 computations do not overflow, or indices on an array element access do
9025 not exceed the bounds of the array.
9027 For expressions you use in @value{GDBN} commands, you can tell
9028 @value{GDBN} to treat range errors in one of three ways: ignore them,
9029 always treat them as errors and abandon the expression, or issue
9030 warnings but evaluate the expression anyway.
9032 A range error can result from numerical overflow, from exceeding an
9033 array index bound, or when you type a constant that is not a member
9034 of any type. Some languages, however, do not treat overflows as an
9035 error. In many implementations of C, mathematical overflow causes the
9036 result to ``wrap around'' to lower values---for example, if @var{m} is
9037 the largest integer value, and @var{s} is the smallest, then
9040 @var{m} + 1 @result{} @var{s}
9043 This, too, is specific to individual languages, and in some cases
9044 specific to individual compilers or machines. @xref{Supported Languages, ,
9045 Supported Languages}, for further details on specific languages.
9047 @value{GDBN} provides some additional commands for controlling the range checker:
9049 @kindex set check range
9050 @kindex show check range
9052 @item set check range auto
9053 Set range checking on or off based on the current working language.
9054 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9057 @item set check range on
9058 @itemx set check range off
9059 Set range checking on or off, overriding the default setting for the
9060 current working language. A warning is issued if the setting does not
9061 match the language default. If a range error occurs and range checking is on,
9062 then a message is printed and evaluation of the expression is aborted.
9064 @item set check range warn
9065 Output messages when the @value{GDBN} range checker detects a range error,
9066 but attempt to evaluate the expression anyway. Evaluating the
9067 expression may still be impossible for other reasons, such as accessing
9068 memory that the process does not own (a typical example from many Unix
9072 Show the current setting of the range checker, and whether or not it is
9073 being set automatically by @value{GDBN}.
9076 @node Supported Languages
9077 @section Supported Languages
9079 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9080 assembly, Modula-2, and Ada.
9081 @c This is false ...
9082 Some @value{GDBN} features may be used in expressions regardless of the
9083 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9084 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9085 ,Expressions}) can be used with the constructs of any supported
9088 The following sections detail to what degree each source language is
9089 supported by @value{GDBN}. These sections are not meant to be language
9090 tutorials or references, but serve only as a reference guide to what the
9091 @value{GDBN} expression parser accepts, and what input and output
9092 formats should look like for different languages. There are many good
9093 books written on each of these languages; please look to these for a
9094 language reference or tutorial.
9098 * Objective-C:: Objective-C
9101 * Modula-2:: Modula-2
9106 @subsection C and C@t{++}
9108 @cindex C and C@t{++}
9109 @cindex expressions in C or C@t{++}
9111 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9112 to both languages. Whenever this is the case, we discuss those languages
9116 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9117 @cindex @sc{gnu} C@t{++}
9118 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9119 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9120 effectively, you must compile your C@t{++} programs with a supported
9121 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9122 compiler (@code{aCC}).
9124 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9125 format; if it doesn't work on your system, try the stabs+ debugging
9126 format. You can select those formats explicitly with the @code{g++}
9127 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9128 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9129 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9132 * C Operators:: C and C@t{++} operators
9133 * C Constants:: C and C@t{++} constants
9134 * C Plus Plus Expressions:: C@t{++} expressions
9135 * C Defaults:: Default settings for C and C@t{++}
9136 * C Checks:: C and C@t{++} type and range checks
9137 * Debugging C:: @value{GDBN} and C
9138 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9142 @subsubsection C and C@t{++} Operators
9144 @cindex C and C@t{++} operators
9146 Operators must be defined on values of specific types. For instance,
9147 @code{+} is defined on numbers, but not on structures. Operators are
9148 often defined on groups of types.
9150 For the purposes of C and C@t{++}, the following definitions hold:
9155 @emph{Integral types} include @code{int} with any of its storage-class
9156 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9159 @emph{Floating-point types} include @code{float}, @code{double}, and
9160 @code{long double} (if supported by the target platform).
9163 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9166 @emph{Scalar types} include all of the above.
9171 The following operators are supported. They are listed here
9172 in order of increasing precedence:
9176 The comma or sequencing operator. Expressions in a comma-separated list
9177 are evaluated from left to right, with the result of the entire
9178 expression being the last expression evaluated.
9181 Assignment. The value of an assignment expression is the value
9182 assigned. Defined on scalar types.
9185 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9186 and translated to @w{@code{@var{a} = @var{a op b}}}.
9187 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9188 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9189 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9192 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9193 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9197 Logical @sc{or}. Defined on integral types.
9200 Logical @sc{and}. Defined on integral types.
9203 Bitwise @sc{or}. Defined on integral types.
9206 Bitwise exclusive-@sc{or}. Defined on integral types.
9209 Bitwise @sc{and}. Defined on integral types.
9212 Equality and inequality. Defined on scalar types. The value of these
9213 expressions is 0 for false and non-zero for true.
9215 @item <@r{, }>@r{, }<=@r{, }>=
9216 Less than, greater than, less than or equal, greater than or equal.
9217 Defined on scalar types. The value of these expressions is 0 for false
9218 and non-zero for true.
9221 left shift, and right shift. Defined on integral types.
9224 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9227 Addition and subtraction. Defined on integral types, floating-point types and
9230 @item *@r{, }/@r{, }%
9231 Multiplication, division, and modulus. Multiplication and division are
9232 defined on integral and floating-point types. Modulus is defined on
9236 Increment and decrement. When appearing before a variable, the
9237 operation is performed before the variable is used in an expression;
9238 when appearing after it, the variable's value is used before the
9239 operation takes place.
9242 Pointer dereferencing. Defined on pointer types. Same precedence as
9246 Address operator. Defined on variables. Same precedence as @code{++}.
9248 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9249 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9250 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
9251 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9255 Negative. Defined on integral and floating-point types. Same
9256 precedence as @code{++}.
9259 Logical negation. Defined on integral types. Same precedence as
9263 Bitwise complement operator. Defined on integral types. Same precedence as
9268 Structure member, and pointer-to-structure member. For convenience,
9269 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9270 pointer based on the stored type information.
9271 Defined on @code{struct} and @code{union} data.
9274 Dereferences of pointers to members.
9277 Array indexing. @code{@var{a}[@var{i}]} is defined as
9278 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9281 Function parameter list. Same precedence as @code{->}.
9284 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9285 and @code{class} types.
9288 Doubled colons also represent the @value{GDBN} scope operator
9289 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9293 If an operator is redefined in the user code, @value{GDBN} usually
9294 attempts to invoke the redefined version instead of using the operator's
9298 @subsubsection C and C@t{++} Constants
9300 @cindex C and C@t{++} constants
9302 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9307 Integer constants are a sequence of digits. Octal constants are
9308 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9309 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9310 @samp{l}, specifying that the constant should be treated as a
9314 Floating point constants are a sequence of digits, followed by a decimal
9315 point, followed by a sequence of digits, and optionally followed by an
9316 exponent. An exponent is of the form:
9317 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9318 sequence of digits. The @samp{+} is optional for positive exponents.
9319 A floating-point constant may also end with a letter @samp{f} or
9320 @samp{F}, specifying that the constant should be treated as being of
9321 the @code{float} (as opposed to the default @code{double}) type; or with
9322 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9326 Enumerated constants consist of enumerated identifiers, or their
9327 integral equivalents.
9330 Character constants are a single character surrounded by single quotes
9331 (@code{'}), or a number---the ordinal value of the corresponding character
9332 (usually its @sc{ascii} value). Within quotes, the single character may
9333 be represented by a letter or by @dfn{escape sequences}, which are of
9334 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9335 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9336 @samp{@var{x}} is a predefined special character---for example,
9337 @samp{\n} for newline.
9340 String constants are a sequence of character constants surrounded by
9341 double quotes (@code{"}). Any valid character constant (as described
9342 above) may appear. Double quotes within the string must be preceded by
9343 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9347 Pointer constants are an integral value. You can also write pointers
9348 to constants using the C operator @samp{&}.
9351 Array constants are comma-separated lists surrounded by braces @samp{@{}
9352 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9353 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9354 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9357 @node C Plus Plus Expressions
9358 @subsubsection C@t{++} Expressions
9360 @cindex expressions in C@t{++}
9361 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9363 @cindex debugging C@t{++} programs
9364 @cindex C@t{++} compilers
9365 @cindex debug formats and C@t{++}
9366 @cindex @value{NGCC} and C@t{++}
9368 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9369 proper compiler and the proper debug format. Currently, @value{GDBN}
9370 works best when debugging C@t{++} code that is compiled with
9371 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9372 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9373 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9374 stabs+ as their default debug format, so you usually don't need to
9375 specify a debug format explicitly. Other compilers and/or debug formats
9376 are likely to work badly or not at all when using @value{GDBN} to debug
9382 @cindex member functions
9384 Member function calls are allowed; you can use expressions like
9387 count = aml->GetOriginal(x, y)
9390 @vindex this@r{, inside C@t{++} member functions}
9391 @cindex namespace in C@t{++}
9393 While a member function is active (in the selected stack frame), your
9394 expressions have the same namespace available as the member function;
9395 that is, @value{GDBN} allows implicit references to the class instance
9396 pointer @code{this} following the same rules as C@t{++}.
9398 @cindex call overloaded functions
9399 @cindex overloaded functions, calling
9400 @cindex type conversions in C@t{++}
9402 You can call overloaded functions; @value{GDBN} resolves the function
9403 call to the right definition, with some restrictions. @value{GDBN} does not
9404 perform overload resolution involving user-defined type conversions,
9405 calls to constructors, or instantiations of templates that do not exist
9406 in the program. It also cannot handle ellipsis argument lists or
9409 It does perform integral conversions and promotions, floating-point
9410 promotions, arithmetic conversions, pointer conversions, conversions of
9411 class objects to base classes, and standard conversions such as those of
9412 functions or arrays to pointers; it requires an exact match on the
9413 number of function arguments.
9415 Overload resolution is always performed, unless you have specified
9416 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9417 ,@value{GDBN} Features for C@t{++}}.
9419 You must specify @code{set overload-resolution off} in order to use an
9420 explicit function signature to call an overloaded function, as in
9422 p 'foo(char,int)'('x', 13)
9425 The @value{GDBN} command-completion facility can simplify this;
9426 see @ref{Completion, ,Command Completion}.
9428 @cindex reference declarations
9430 @value{GDBN} understands variables declared as C@t{++} references; you can use
9431 them in expressions just as you do in C@t{++} source---they are automatically
9434 In the parameter list shown when @value{GDBN} displays a frame, the values of
9435 reference variables are not displayed (unlike other variables); this
9436 avoids clutter, since references are often used for large structures.
9437 The @emph{address} of a reference variable is always shown, unless
9438 you have specified @samp{set print address off}.
9441 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9442 expressions can use it just as expressions in your program do. Since
9443 one scope may be defined in another, you can use @code{::} repeatedly if
9444 necessary, for example in an expression like
9445 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9446 resolving name scope by reference to source files, in both C and C@t{++}
9447 debugging (@pxref{Variables, ,Program Variables}).
9450 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9451 calling virtual functions correctly, printing out virtual bases of
9452 objects, calling functions in a base subobject, casting objects, and
9453 invoking user-defined operators.
9456 @subsubsection C and C@t{++} Defaults
9458 @cindex C and C@t{++} defaults
9460 If you allow @value{GDBN} to set type and range checking automatically, they
9461 both default to @code{off} whenever the working language changes to
9462 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9463 selects the working language.
9465 If you allow @value{GDBN} to set the language automatically, it
9466 recognizes source files whose names end with @file{.c}, @file{.C}, or
9467 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9468 these files, it sets the working language to C or C@t{++}.
9469 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9470 for further details.
9472 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9473 @c unimplemented. If (b) changes, it might make sense to let this node
9474 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9477 @subsubsection C and C@t{++} Type and Range Checks
9479 @cindex C and C@t{++} checks
9481 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9482 is not used. However, if you turn type checking on, @value{GDBN}
9483 considers two variables type equivalent if:
9487 The two variables are structured and have the same structure, union, or
9491 The two variables have the same type name, or types that have been
9492 declared equivalent through @code{typedef}.
9495 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9498 The two @code{struct}, @code{union}, or @code{enum} variables are
9499 declared in the same declaration. (Note: this may not be true for all C
9504 Range checking, if turned on, is done on mathematical operations. Array
9505 indices are not checked, since they are often used to index a pointer
9506 that is not itself an array.
9509 @subsubsection @value{GDBN} and C
9511 The @code{set print union} and @code{show print union} commands apply to
9512 the @code{union} type. When set to @samp{on}, any @code{union} that is
9513 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9514 appears as @samp{@{...@}}.
9516 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9517 with pointers and a memory allocation function. @xref{Expressions,
9520 @node Debugging C Plus Plus
9521 @subsubsection @value{GDBN} Features for C@t{++}
9523 @cindex commands for C@t{++}
9525 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9526 designed specifically for use with C@t{++}. Here is a summary:
9529 @cindex break in overloaded functions
9530 @item @r{breakpoint menus}
9531 When you want a breakpoint in a function whose name is overloaded,
9532 @value{GDBN} breakpoint menus help you specify which function definition
9533 you want. @xref{Breakpoint Menus,,Breakpoint Menus}.
9535 @cindex overloading in C@t{++}
9536 @item rbreak @var{regex}
9537 Setting breakpoints using regular expressions is helpful for setting
9538 breakpoints on overloaded functions that are not members of any special
9540 @xref{Set Breaks, ,Setting Breakpoints}.
9542 @cindex C@t{++} exception handling
9545 Debug C@t{++} exception handling using these commands. @xref{Set
9546 Catchpoints, , Setting Catchpoints}.
9549 @item ptype @var{typename}
9550 Print inheritance relationships as well as other information for type
9552 @xref{Symbols, ,Examining the Symbol Table}.
9554 @cindex C@t{++} symbol display
9555 @item set print demangle
9556 @itemx show print demangle
9557 @itemx set print asm-demangle
9558 @itemx show print asm-demangle
9559 Control whether C@t{++} symbols display in their source form, both when
9560 displaying code as C@t{++} source and when displaying disassemblies.
9561 @xref{Print Settings, ,Print Settings}.
9563 @item set print object
9564 @itemx show print object
9565 Choose whether to print derived (actual) or declared types of objects.
9566 @xref{Print Settings, ,Print Settings}.
9568 @item set print vtbl
9569 @itemx show print vtbl
9570 Control the format for printing virtual function tables.
9571 @xref{Print Settings, ,Print Settings}.
9572 (The @code{vtbl} commands do not work on programs compiled with the HP
9573 ANSI C@t{++} compiler (@code{aCC}).)
9575 @kindex set overload-resolution
9576 @cindex overloaded functions, overload resolution
9577 @item set overload-resolution on
9578 Enable overload resolution for C@t{++} expression evaluation. The default
9579 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9580 and searches for a function whose signature matches the argument types,
9581 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9582 Expressions, ,C@t{++} Expressions}, for details).
9583 If it cannot find a match, it emits a message.
9585 @item set overload-resolution off
9586 Disable overload resolution for C@t{++} expression evaluation. For
9587 overloaded functions that are not class member functions, @value{GDBN}
9588 chooses the first function of the specified name that it finds in the
9589 symbol table, whether or not its arguments are of the correct type. For
9590 overloaded functions that are class member functions, @value{GDBN}
9591 searches for a function whose signature @emph{exactly} matches the
9594 @kindex show overload-resolution
9595 @item show overload-resolution
9596 Show the current setting of overload resolution.
9598 @item @r{Overloaded symbol names}
9599 You can specify a particular definition of an overloaded symbol, using
9600 the same notation that is used to declare such symbols in C@t{++}: type
9601 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9602 also use the @value{GDBN} command-line word completion facilities to list the
9603 available choices, or to finish the type list for you.
9604 @xref{Completion,, Command Completion}, for details on how to do this.
9608 @subsection Objective-C
9611 This section provides information about some commands and command
9612 options that are useful for debugging Objective-C code. See also
9613 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9614 few more commands specific to Objective-C support.
9617 * Method Names in Commands::
9618 * The Print Command with Objective-C::
9621 @node Method Names in Commands
9622 @subsubsection Method Names in Commands
9624 The following commands have been extended to accept Objective-C method
9625 names as line specifications:
9627 @kindex clear@r{, and Objective-C}
9628 @kindex break@r{, and Objective-C}
9629 @kindex info line@r{, and Objective-C}
9630 @kindex jump@r{, and Objective-C}
9631 @kindex list@r{, and Objective-C}
9635 @item @code{info line}
9640 A fully qualified Objective-C method name is specified as
9643 -[@var{Class} @var{methodName}]
9646 where the minus sign is used to indicate an instance method and a
9647 plus sign (not shown) is used to indicate a class method. The class
9648 name @var{Class} and method name @var{methodName} are enclosed in
9649 brackets, similar to the way messages are specified in Objective-C
9650 source code. For example, to set a breakpoint at the @code{create}
9651 instance method of class @code{Fruit} in the program currently being
9655 break -[Fruit create]
9658 To list ten program lines around the @code{initialize} class method,
9662 list +[NSText initialize]
9665 In the current version of @value{GDBN}, the plus or minus sign is
9666 required. In future versions of @value{GDBN}, the plus or minus
9667 sign will be optional, but you can use it to narrow the search. It
9668 is also possible to specify just a method name:
9674 You must specify the complete method name, including any colons. If
9675 your program's source files contain more than one @code{create} method,
9676 you'll be presented with a numbered list of classes that implement that
9677 method. Indicate your choice by number, or type @samp{0} to exit if
9680 As another example, to clear a breakpoint established at the
9681 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9684 clear -[NSWindow makeKeyAndOrderFront:]
9687 @node The Print Command with Objective-C
9688 @subsubsection The Print Command With Objective-C
9689 @cindex Objective-C, print objects
9690 @kindex print-object
9691 @kindex po @r{(@code{print-object})}
9693 The print command has also been extended to accept methods. For example:
9696 print -[@var{object} hash]
9699 @cindex print an Objective-C object description
9700 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9702 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9703 and print the result. Also, an additional command has been added,
9704 @code{print-object} or @code{po} for short, which is meant to print
9705 the description of an object. However, this command may only work
9706 with certain Objective-C libraries that have a particular hook
9707 function, @code{_NSPrintForDebugger}, defined.
9711 @cindex Fortran-specific support in @value{GDBN}
9713 @value{GDBN} can be used to debug programs written in Fortran, but it
9714 currently supports only the features of Fortran 77 language.
9716 @cindex trailing underscore, in Fortran symbols
9717 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9718 among them) append an underscore to the names of variables and
9719 functions. When you debug programs compiled by those compilers, you
9720 will need to refer to variables and functions with a trailing
9724 * Fortran Operators:: Fortran operators and expressions
9725 * Fortran Defaults:: Default settings for Fortran
9726 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
9729 @node Fortran Operators
9730 @subsubsection Fortran Operators and Expressions
9732 @cindex Fortran operators and expressions
9734 Operators must be defined on values of specific types. For instance,
9735 @code{+} is defined on numbers, but not on characters or other non-
9736 arithmetic types. Operators are often defined on groups of types.
9740 The exponentiation operator. It raises the first operand to the power
9744 The range operator. Normally used in the form of array(low:high) to
9745 represent a section of array.
9748 @node Fortran Defaults
9749 @subsubsection Fortran Defaults
9751 @cindex Fortran Defaults
9753 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9754 default uses case-insensitive matches for Fortran symbols. You can
9755 change that with the @samp{set case-insensitive} command, see
9756 @ref{Symbols}, for the details.
9758 @node Special Fortran Commands
9759 @subsubsection Special Fortran Commands
9761 @cindex Special Fortran commands
9763 @value{GDBN} has some commands to support Fortran-specific features,
9764 such as displaying common blocks.
9767 @cindex @code{COMMON} blocks, Fortran
9769 @item info common @r{[}@var{common-name}@r{]}
9770 This command prints the values contained in the Fortran @code{COMMON}
9771 block whose name is @var{common-name}. With no argument, the names of
9772 all @code{COMMON} blocks visible at the current program location are
9779 @cindex Pascal support in @value{GDBN}, limitations
9780 Debugging Pascal programs which use sets, subranges, file variables, or
9781 nested functions does not currently work. @value{GDBN} does not support
9782 entering expressions, printing values, or similar features using Pascal
9785 The Pascal-specific command @code{set print pascal_static-members}
9786 controls whether static members of Pascal objects are displayed.
9787 @xref{Print Settings, pascal_static-members}.
9790 @subsection Modula-2
9792 @cindex Modula-2, @value{GDBN} support
9794 The extensions made to @value{GDBN} to support Modula-2 only support
9795 output from the @sc{gnu} Modula-2 compiler (which is currently being
9796 developed). Other Modula-2 compilers are not currently supported, and
9797 attempting to debug executables produced by them is most likely
9798 to give an error as @value{GDBN} reads in the executable's symbol
9801 @cindex expressions in Modula-2
9803 * M2 Operators:: Built-in operators
9804 * Built-In Func/Proc:: Built-in functions and procedures
9805 * M2 Constants:: Modula-2 constants
9806 * M2 Types:: Modula-2 types
9807 * M2 Defaults:: Default settings for Modula-2
9808 * Deviations:: Deviations from standard Modula-2
9809 * M2 Checks:: Modula-2 type and range checks
9810 * M2 Scope:: The scope operators @code{::} and @code{.}
9811 * GDB/M2:: @value{GDBN} and Modula-2
9815 @subsubsection Operators
9816 @cindex Modula-2 operators
9818 Operators must be defined on values of specific types. For instance,
9819 @code{+} is defined on numbers, but not on structures. Operators are
9820 often defined on groups of types. For the purposes of Modula-2, the
9821 following definitions hold:
9826 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9830 @emph{Character types} consist of @code{CHAR} and its subranges.
9833 @emph{Floating-point types} consist of @code{REAL}.
9836 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9840 @emph{Scalar types} consist of all of the above.
9843 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9846 @emph{Boolean types} consist of @code{BOOLEAN}.
9850 The following operators are supported, and appear in order of
9851 increasing precedence:
9855 Function argument or array index separator.
9858 Assignment. The value of @var{var} @code{:=} @var{value} is
9862 Less than, greater than on integral, floating-point, or enumerated
9866 Less than or equal to, greater than or equal to
9867 on integral, floating-point and enumerated types, or set inclusion on
9868 set types. Same precedence as @code{<}.
9870 @item =@r{, }<>@r{, }#
9871 Equality and two ways of expressing inequality, valid on scalar types.
9872 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9873 available for inequality, since @code{#} conflicts with the script
9877 Set membership. Defined on set types and the types of their members.
9878 Same precedence as @code{<}.
9881 Boolean disjunction. Defined on boolean types.
9884 Boolean conjunction. Defined on boolean types.
9887 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9890 Addition and subtraction on integral and floating-point types, or union
9891 and difference on set types.
9894 Multiplication on integral and floating-point types, or set intersection
9898 Division on floating-point types, or symmetric set difference on set
9899 types. Same precedence as @code{*}.
9902 Integer division and remainder. Defined on integral types. Same
9903 precedence as @code{*}.
9906 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9909 Pointer dereferencing. Defined on pointer types.
9912 Boolean negation. Defined on boolean types. Same precedence as
9916 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9917 precedence as @code{^}.
9920 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9923 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9927 @value{GDBN} and Modula-2 scope operators.
9931 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9932 treats the use of the operator @code{IN}, or the use of operators
9933 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9934 @code{<=}, and @code{>=} on sets as an error.
9938 @node Built-In Func/Proc
9939 @subsubsection Built-in Functions and Procedures
9940 @cindex Modula-2 built-ins
9942 Modula-2 also makes available several built-in procedures and functions.
9943 In describing these, the following metavariables are used:
9948 represents an @code{ARRAY} variable.
9951 represents a @code{CHAR} constant or variable.
9954 represents a variable or constant of integral type.
9957 represents an identifier that belongs to a set. Generally used in the
9958 same function with the metavariable @var{s}. The type of @var{s} should
9959 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9962 represents a variable or constant of integral or floating-point type.
9965 represents a variable or constant of floating-point type.
9971 represents a variable.
9974 represents a variable or constant of one of many types. See the
9975 explanation of the function for details.
9978 All Modula-2 built-in procedures also return a result, described below.
9982 Returns the absolute value of @var{n}.
9985 If @var{c} is a lower case letter, it returns its upper case
9986 equivalent, otherwise it returns its argument.
9989 Returns the character whose ordinal value is @var{i}.
9992 Decrements the value in the variable @var{v} by one. Returns the new value.
9994 @item DEC(@var{v},@var{i})
9995 Decrements the value in the variable @var{v} by @var{i}. Returns the
9998 @item EXCL(@var{m},@var{s})
9999 Removes the element @var{m} from the set @var{s}. Returns the new
10002 @item FLOAT(@var{i})
10003 Returns the floating point equivalent of the integer @var{i}.
10005 @item HIGH(@var{a})
10006 Returns the index of the last member of @var{a}.
10009 Increments the value in the variable @var{v} by one. Returns the new value.
10011 @item INC(@var{v},@var{i})
10012 Increments the value in the variable @var{v} by @var{i}. Returns the
10015 @item INCL(@var{m},@var{s})
10016 Adds the element @var{m} to the set @var{s} if it is not already
10017 there. Returns the new set.
10020 Returns the maximum value of the type @var{t}.
10023 Returns the minimum value of the type @var{t}.
10026 Returns boolean TRUE if @var{i} is an odd number.
10029 Returns the ordinal value of its argument. For example, the ordinal
10030 value of a character is its @sc{ascii} value (on machines supporting the
10031 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10032 integral, character and enumerated types.
10034 @item SIZE(@var{x})
10035 Returns the size of its argument. @var{x} can be a variable or a type.
10037 @item TRUNC(@var{r})
10038 Returns the integral part of @var{r}.
10040 @item TSIZE(@var{x})
10041 Returns the size of its argument. @var{x} can be a variable or a type.
10043 @item VAL(@var{t},@var{i})
10044 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10048 @emph{Warning:} Sets and their operations are not yet supported, so
10049 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10053 @cindex Modula-2 constants
10055 @subsubsection Constants
10057 @value{GDBN} allows you to express the constants of Modula-2 in the following
10063 Integer constants are simply a sequence of digits. When used in an
10064 expression, a constant is interpreted to be type-compatible with the
10065 rest of the expression. Hexadecimal integers are specified by a
10066 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10069 Floating point constants appear as a sequence of digits, followed by a
10070 decimal point and another sequence of digits. An optional exponent can
10071 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10072 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10073 digits of the floating point constant must be valid decimal (base 10)
10077 Character constants consist of a single character enclosed by a pair of
10078 like quotes, either single (@code{'}) or double (@code{"}). They may
10079 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10080 followed by a @samp{C}.
10083 String constants consist of a sequence of characters enclosed by a
10084 pair of like quotes, either single (@code{'}) or double (@code{"}).
10085 Escape sequences in the style of C are also allowed. @xref{C
10086 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10090 Enumerated constants consist of an enumerated identifier.
10093 Boolean constants consist of the identifiers @code{TRUE} and
10097 Pointer constants consist of integral values only.
10100 Set constants are not yet supported.
10104 @subsubsection Modula-2 Types
10105 @cindex Modula-2 types
10107 Currently @value{GDBN} can print the following data types in Modula-2
10108 syntax: array types, record types, set types, pointer types, procedure
10109 types, enumerated types, subrange types and base types. You can also
10110 print the contents of variables declared using these type.
10111 This section gives a number of simple source code examples together with
10112 sample @value{GDBN} sessions.
10114 The first example contains the following section of code:
10123 and you can request @value{GDBN} to interrogate the type and value of
10124 @code{r} and @code{s}.
10127 (@value{GDBP}) print s
10129 (@value{GDBP}) ptype s
10131 (@value{GDBP}) print r
10133 (@value{GDBP}) ptype r
10138 Likewise if your source code declares @code{s} as:
10142 s: SET ['A'..'Z'] ;
10146 then you may query the type of @code{s} by:
10149 (@value{GDBP}) ptype s
10150 type = SET ['A'..'Z']
10154 Note that at present you cannot interactively manipulate set
10155 expressions using the debugger.
10157 The following example shows how you might declare an array in Modula-2
10158 and how you can interact with @value{GDBN} to print its type and contents:
10162 s: ARRAY [-10..10] OF CHAR ;
10166 (@value{GDBP}) ptype s
10167 ARRAY [-10..10] OF CHAR
10170 Note that the array handling is not yet complete and although the type
10171 is printed correctly, expression handling still assumes that all
10172 arrays have a lower bound of zero and not @code{-10} as in the example
10175 Here are some more type related Modula-2 examples:
10179 colour = (blue, red, yellow, green) ;
10180 t = [blue..yellow] ;
10188 The @value{GDBN} interaction shows how you can query the data type
10189 and value of a variable.
10192 (@value{GDBP}) print s
10194 (@value{GDBP}) ptype t
10195 type = [blue..yellow]
10199 In this example a Modula-2 array is declared and its contents
10200 displayed. Observe that the contents are written in the same way as
10201 their @code{C} counterparts.
10205 s: ARRAY [1..5] OF CARDINAL ;
10211 (@value{GDBP}) print s
10212 $1 = @{1, 0, 0, 0, 0@}
10213 (@value{GDBP}) ptype s
10214 type = ARRAY [1..5] OF CARDINAL
10217 The Modula-2 language interface to @value{GDBN} also understands
10218 pointer types as shown in this example:
10222 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10229 and you can request that @value{GDBN} describes the type of @code{s}.
10232 (@value{GDBP}) ptype s
10233 type = POINTER TO ARRAY [1..5] OF CARDINAL
10236 @value{GDBN} handles compound types as we can see in this example.
10237 Here we combine array types, record types, pointer types and subrange
10248 myarray = ARRAY myrange OF CARDINAL ;
10249 myrange = [-2..2] ;
10251 s: POINTER TO ARRAY myrange OF foo ;
10255 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10259 (@value{GDBP}) ptype s
10260 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10263 f3 : ARRAY [-2..2] OF CARDINAL;
10268 @subsubsection Modula-2 Defaults
10269 @cindex Modula-2 defaults
10271 If type and range checking are set automatically by @value{GDBN}, they
10272 both default to @code{on} whenever the working language changes to
10273 Modula-2. This happens regardless of whether you or @value{GDBN}
10274 selected the working language.
10276 If you allow @value{GDBN} to set the language automatically, then entering
10277 code compiled from a file whose name ends with @file{.mod} sets the
10278 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10279 Infer the Source Language}, for further details.
10282 @subsubsection Deviations from Standard Modula-2
10283 @cindex Modula-2, deviations from
10285 A few changes have been made to make Modula-2 programs easier to debug.
10286 This is done primarily via loosening its type strictness:
10290 Unlike in standard Modula-2, pointer constants can be formed by
10291 integers. This allows you to modify pointer variables during
10292 debugging. (In standard Modula-2, the actual address contained in a
10293 pointer variable is hidden from you; it can only be modified
10294 through direct assignment to another pointer variable or expression that
10295 returned a pointer.)
10298 C escape sequences can be used in strings and characters to represent
10299 non-printable characters. @value{GDBN} prints out strings with these
10300 escape sequences embedded. Single non-printable characters are
10301 printed using the @samp{CHR(@var{nnn})} format.
10304 The assignment operator (@code{:=}) returns the value of its right-hand
10308 All built-in procedures both modify @emph{and} return their argument.
10312 @subsubsection Modula-2 Type and Range Checks
10313 @cindex Modula-2 checks
10316 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10319 @c FIXME remove warning when type/range checks added
10321 @value{GDBN} considers two Modula-2 variables type equivalent if:
10325 They are of types that have been declared equivalent via a @code{TYPE
10326 @var{t1} = @var{t2}} statement
10329 They have been declared on the same line. (Note: This is true of the
10330 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10333 As long as type checking is enabled, any attempt to combine variables
10334 whose types are not equivalent is an error.
10336 Range checking is done on all mathematical operations, assignment, array
10337 index bounds, and all built-in functions and procedures.
10340 @subsubsection The Scope Operators @code{::} and @code{.}
10342 @cindex @code{.}, Modula-2 scope operator
10343 @cindex colon, doubled as scope operator
10345 @vindex colon-colon@r{, in Modula-2}
10346 @c Info cannot handle :: but TeX can.
10349 @vindex ::@r{, in Modula-2}
10352 There are a few subtle differences between the Modula-2 scope operator
10353 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10358 @var{module} . @var{id}
10359 @var{scope} :: @var{id}
10363 where @var{scope} is the name of a module or a procedure,
10364 @var{module} the name of a module, and @var{id} is any declared
10365 identifier within your program, except another module.
10367 Using the @code{::} operator makes @value{GDBN} search the scope
10368 specified by @var{scope} for the identifier @var{id}. If it is not
10369 found in the specified scope, then @value{GDBN} searches all scopes
10370 enclosing the one specified by @var{scope}.
10372 Using the @code{.} operator makes @value{GDBN} search the current scope for
10373 the identifier specified by @var{id} that was imported from the
10374 definition module specified by @var{module}. With this operator, it is
10375 an error if the identifier @var{id} was not imported from definition
10376 module @var{module}, or if @var{id} is not an identifier in
10380 @subsubsection @value{GDBN} and Modula-2
10382 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10383 Five subcommands of @code{set print} and @code{show print} apply
10384 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10385 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10386 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10387 analogue in Modula-2.
10389 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10390 with any language, is not useful with Modula-2. Its
10391 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10392 created in Modula-2 as they can in C or C@t{++}. However, because an
10393 address can be specified by an integral constant, the construct
10394 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10396 @cindex @code{#} in Modula-2
10397 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10398 interpreted as the beginning of a comment. Use @code{<>} instead.
10404 The extensions made to @value{GDBN} for Ada only support
10405 output from the @sc{gnu} Ada (GNAT) compiler.
10406 Other Ada compilers are not currently supported, and
10407 attempting to debug executables produced by them is most likely
10411 @cindex expressions in Ada
10413 * Ada Mode Intro:: General remarks on the Ada syntax
10414 and semantics supported by Ada mode
10416 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10417 * Additions to Ada:: Extensions of the Ada expression syntax.
10418 * Stopping Before Main Program:: Debugging the program during elaboration.
10419 * Ada Glitches:: Known peculiarities of Ada mode.
10422 @node Ada Mode Intro
10423 @subsubsection Introduction
10424 @cindex Ada mode, general
10426 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10427 syntax, with some extensions.
10428 The philosophy behind the design of this subset is
10432 That @value{GDBN} should provide basic literals and access to operations for
10433 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10434 leaving more sophisticated computations to subprograms written into the
10435 program (which therefore may be called from @value{GDBN}).
10438 That type safety and strict adherence to Ada language restrictions
10439 are not particularly important to the @value{GDBN} user.
10442 That brevity is important to the @value{GDBN} user.
10445 Thus, for brevity, the debugger acts as if there were
10446 implicit @code{with} and @code{use} clauses in effect for all user-written
10447 packages, making it unnecessary to fully qualify most names with
10448 their packages, regardless of context. Where this causes ambiguity,
10449 @value{GDBN} asks the user's intent.
10451 The debugger will start in Ada mode if it detects an Ada main program.
10452 As for other languages, it will enter Ada mode when stopped in a program that
10453 was translated from an Ada source file.
10455 While in Ada mode, you may use `@t{--}' for comments. This is useful
10456 mostly for documenting command files. The standard @value{GDBN} comment
10457 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10458 middle (to allow based literals).
10460 The debugger supports limited overloading. Given a subprogram call in which
10461 the function symbol has multiple definitions, it will use the number of
10462 actual parameters and some information about their types to attempt to narrow
10463 the set of definitions. It also makes very limited use of context, preferring
10464 procedures to functions in the context of the @code{call} command, and
10465 functions to procedures elsewhere.
10467 @node Omissions from Ada
10468 @subsubsection Omissions from Ada
10469 @cindex Ada, omissions from
10471 Here are the notable omissions from the subset:
10475 Only a subset of the attributes are supported:
10479 @t{'First}, @t{'Last}, and @t{'Length}
10480 on array objects (not on types and subtypes).
10483 @t{'Min} and @t{'Max}.
10486 @t{'Pos} and @t{'Val}.
10492 @t{'Range} on array objects (not subtypes), but only as the right
10493 operand of the membership (@code{in}) operator.
10496 @t{'Access}, @t{'Unchecked_Access}, and
10497 @t{'Unrestricted_Access} (a GNAT extension).
10505 @code{Characters.Latin_1} are not available and
10506 concatenation is not implemented. Thus, escape characters in strings are
10507 not currently available.
10510 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10511 equality of representations. They will generally work correctly
10512 for strings and arrays whose elements have integer or enumeration types.
10513 They may not work correctly for arrays whose element
10514 types have user-defined equality, for arrays of real values
10515 (in particular, IEEE-conformant floating point, because of negative
10516 zeroes and NaNs), and for arrays whose elements contain unused bits with
10517 indeterminate values.
10520 The other component-by-component array operations (@code{and}, @code{or},
10521 @code{xor}, @code{not}, and relational tests other than equality)
10522 are not implemented.
10525 @cindex array aggregates (Ada)
10526 @cindex record aggregates (Ada)
10527 @cindex aggregates (Ada)
10528 There is limited support for array and record aggregates. They are
10529 permitted only on the right sides of assignments, as in these examples:
10532 set An_Array := (1, 2, 3, 4, 5, 6)
10533 set An_Array := (1, others => 0)
10534 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10535 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10536 set A_Record := (1, "Peter", True);
10537 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10541 discriminant's value by assigning an aggregate has an
10542 undefined effect if that discriminant is used within the record.
10543 However, you can first modify discriminants by directly assigning to
10544 them (which normally would not be allowed in Ada), and then performing an
10545 aggregate assignment. For example, given a variable @code{A_Rec}
10546 declared to have a type such as:
10549 type Rec (Len : Small_Integer := 0) is record
10551 Vals : IntArray (1 .. Len);
10555 you can assign a value with a different size of @code{Vals} with two
10560 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10563 As this example also illustrates, @value{GDBN} is very loose about the usual
10564 rules concerning aggregates. You may leave out some of the
10565 components of an array or record aggregate (such as the @code{Len}
10566 component in the assignment to @code{A_Rec} above); they will retain their
10567 original values upon assignment. You may freely use dynamic values as
10568 indices in component associations. You may even use overlapping or
10569 redundant component associations, although which component values are
10570 assigned in such cases is not defined.
10573 Calls to dispatching subprograms are not implemented.
10576 The overloading algorithm is much more limited (i.e., less selective)
10577 than that of real Ada. It makes only limited use of the context in
10578 which a subexpression appears to resolve its meaning, and it is much
10579 looser in its rules for allowing type matches. As a result, some
10580 function calls will be ambiguous, and the user will be asked to choose
10581 the proper resolution.
10584 The @code{new} operator is not implemented.
10587 Entry calls are not implemented.
10590 Aside from printing, arithmetic operations on the native VAX floating-point
10591 formats are not supported.
10594 It is not possible to slice a packed array.
10597 @node Additions to Ada
10598 @subsubsection Additions to Ada
10599 @cindex Ada, deviations from
10601 As it does for other languages, @value{GDBN} makes certain generic
10602 extensions to Ada (@pxref{Expressions}):
10606 If the expression @var{E} is a variable residing in memory (typically
10607 a local variable or array element) and @var{N} is a positive integer,
10608 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10609 @var{N}-1 adjacent variables following it in memory as an array. In
10610 Ada, this operator is generally not necessary, since its prime use is
10611 in displaying parts of an array, and slicing will usually do this in
10612 Ada. However, there are occasional uses when debugging programs in
10613 which certain debugging information has been optimized away.
10616 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10617 appears in function or file @var{B}.'' When @var{B} is a file name,
10618 you must typically surround it in single quotes.
10621 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10622 @var{type} that appears at address @var{addr}.''
10625 A name starting with @samp{$} is a convenience variable
10626 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10629 In addition, @value{GDBN} provides a few other shortcuts and outright
10630 additions specific to Ada:
10634 The assignment statement is allowed as an expression, returning
10635 its right-hand operand as its value. Thus, you may enter
10639 print A(tmp := y + 1)
10643 The semicolon is allowed as an ``operator,'' returning as its value
10644 the value of its right-hand operand.
10645 This allows, for example,
10646 complex conditional breaks:
10650 condition 1 (report(i); k += 1; A(k) > 100)
10654 Rather than use catenation and symbolic character names to introduce special
10655 characters into strings, one may instead use a special bracket notation,
10656 which is also used to print strings. A sequence of characters of the form
10657 @samp{["@var{XX}"]} within a string or character literal denotes the
10658 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10659 sequence of characters @samp{["""]} also denotes a single quotation mark
10660 in strings. For example,
10662 "One line.["0a"]Next line.["0a"]"
10665 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10669 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10670 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10678 When printing arrays, @value{GDBN} uses positional notation when the
10679 array has a lower bound of 1, and uses a modified named notation otherwise.
10680 For example, a one-dimensional array of three integers with a lower bound
10681 of 3 might print as
10688 That is, in contrast to valid Ada, only the first component has a @code{=>}
10692 You may abbreviate attributes in expressions with any unique,
10693 multi-character subsequence of
10694 their names (an exact match gets preference).
10695 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10696 in place of @t{a'length}.
10699 @cindex quoting Ada internal identifiers
10700 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10701 to lower case. The GNAT compiler uses upper-case characters for
10702 some of its internal identifiers, which are normally of no interest to users.
10703 For the rare occasions when you actually have to look at them,
10704 enclose them in angle brackets to avoid the lower-case mapping.
10707 @value{GDBP} print <JMPBUF_SAVE>[0]
10711 Printing an object of class-wide type or dereferencing an
10712 access-to-class-wide value will display all the components of the object's
10713 specific type (as indicated by its run-time tag). Likewise, component
10714 selection on such a value will operate on the specific type of the
10719 @node Stopping Before Main Program
10720 @subsubsection Stopping at the Very Beginning
10722 @cindex breakpointing Ada elaboration code
10723 It is sometimes necessary to debug the program during elaboration, and
10724 before reaching the main procedure.
10725 As defined in the Ada Reference
10726 Manual, the elaboration code is invoked from a procedure called
10727 @code{adainit}. To run your program up to the beginning of
10728 elaboration, simply use the following two commands:
10729 @code{tbreak adainit} and @code{run}.
10732 @subsubsection Known Peculiarities of Ada Mode
10733 @cindex Ada, problems
10735 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10736 we know of several problems with and limitations of Ada mode in
10738 some of which will be fixed with planned future releases of the debugger
10739 and the GNU Ada compiler.
10743 Currently, the debugger
10744 has insufficient information to determine whether certain pointers represent
10745 pointers to objects or the objects themselves.
10746 Thus, the user may have to tack an extra @code{.all} after an expression
10747 to get it printed properly.
10750 Static constants that the compiler chooses not to materialize as objects in
10751 storage are invisible to the debugger.
10754 Named parameter associations in function argument lists are ignored (the
10755 argument lists are treated as positional).
10758 Many useful library packages are currently invisible to the debugger.
10761 Fixed-point arithmetic, conversions, input, and output is carried out using
10762 floating-point arithmetic, and may give results that only approximate those on
10766 The type of the @t{'Address} attribute may not be @code{System.Address}.
10769 The GNAT compiler never generates the prefix @code{Standard} for any of
10770 the standard symbols defined by the Ada language. @value{GDBN} knows about
10771 this: it will strip the prefix from names when you use it, and will never
10772 look for a name you have so qualified among local symbols, nor match against
10773 symbols in other packages or subprograms. If you have
10774 defined entities anywhere in your program other than parameters and
10775 local variables whose simple names match names in @code{Standard},
10776 GNAT's lack of qualification here can cause confusion. When this happens,
10777 you can usually resolve the confusion
10778 by qualifying the problematic names with package
10779 @code{Standard} explicitly.
10782 @node Unsupported Languages
10783 @section Unsupported Languages
10785 @cindex unsupported languages
10786 @cindex minimal language
10787 In addition to the other fully-supported programming languages,
10788 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10789 It does not represent a real programming language, but provides a set
10790 of capabilities close to what the C or assembly languages provide.
10791 This should allow most simple operations to be performed while debugging
10792 an application that uses a language currently not supported by @value{GDBN}.
10794 If the language is set to @code{auto}, @value{GDBN} will automatically
10795 select this language if the current frame corresponds to an unsupported
10799 @chapter Examining the Symbol Table
10801 The commands described in this chapter allow you to inquire about the
10802 symbols (names of variables, functions and types) defined in your
10803 program. This information is inherent in the text of your program and
10804 does not change as your program executes. @value{GDBN} finds it in your
10805 program's symbol table, in the file indicated when you started @value{GDBN}
10806 (@pxref{File Options, ,Choosing Files}), or by one of the
10807 file-management commands (@pxref{Files, ,Commands to Specify Files}).
10809 @cindex symbol names
10810 @cindex names of symbols
10811 @cindex quoting names
10812 Occasionally, you may need to refer to symbols that contain unusual
10813 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10814 most frequent case is in referring to static variables in other
10815 source files (@pxref{Variables,,Program Variables}). File names
10816 are recorded in object files as debugging symbols, but @value{GDBN} would
10817 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10818 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10819 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10826 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10829 @cindex case-insensitive symbol names
10830 @cindex case sensitivity in symbol names
10831 @kindex set case-sensitive
10832 @item set case-sensitive on
10833 @itemx set case-sensitive off
10834 @itemx set case-sensitive auto
10835 Normally, when @value{GDBN} looks up symbols, it matches their names
10836 with case sensitivity determined by the current source language.
10837 Occasionally, you may wish to control that. The command @code{set
10838 case-sensitive} lets you do that by specifying @code{on} for
10839 case-sensitive matches or @code{off} for case-insensitive ones. If
10840 you specify @code{auto}, case sensitivity is reset to the default
10841 suitable for the source language. The default is case-sensitive
10842 matches for all languages except for Fortran, for which the default is
10843 case-insensitive matches.
10845 @kindex show case-sensitive
10846 @item show case-sensitive
10847 This command shows the current setting of case sensitivity for symbols
10850 @kindex info address
10851 @cindex address of a symbol
10852 @item info address @var{symbol}
10853 Describe where the data for @var{symbol} is stored. For a register
10854 variable, this says which register it is kept in. For a non-register
10855 local variable, this prints the stack-frame offset at which the variable
10858 Note the contrast with @samp{print &@var{symbol}}, which does not work
10859 at all for a register variable, and for a stack local variable prints
10860 the exact address of the current instantiation of the variable.
10862 @kindex info symbol
10863 @cindex symbol from address
10864 @cindex closest symbol and offset for an address
10865 @item info symbol @var{addr}
10866 Print the name of a symbol which is stored at the address @var{addr}.
10867 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10868 nearest symbol and an offset from it:
10871 (@value{GDBP}) info symbol 0x54320
10872 _initialize_vx + 396 in section .text
10876 This is the opposite of the @code{info address} command. You can use
10877 it to find out the name of a variable or a function given its address.
10880 @item whatis [@var{arg}]
10881 Print the data type of @var{arg}, which can be either an expression or
10882 a data type. With no argument, print the data type of @code{$}, the
10883 last value in the value history. If @var{arg} is an expression, it is
10884 not actually evaluated, and any side-effecting operations (such as
10885 assignments or function calls) inside it do not take place. If
10886 @var{arg} is a type name, it may be the name of a type or typedef, or
10887 for C code it may have the form @samp{class @var{class-name}},
10888 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10889 @samp{enum @var{enum-tag}}.
10890 @xref{Expressions, ,Expressions}.
10893 @item ptype [@var{arg}]
10894 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10895 detailed description of the type, instead of just the name of the type.
10896 @xref{Expressions, ,Expressions}.
10898 For example, for this variable declaration:
10901 struct complex @{double real; double imag;@} v;
10905 the two commands give this output:
10909 (@value{GDBP}) whatis v
10910 type = struct complex
10911 (@value{GDBP}) ptype v
10912 type = struct complex @{
10920 As with @code{whatis}, using @code{ptype} without an argument refers to
10921 the type of @code{$}, the last value in the value history.
10923 @cindex incomplete type
10924 Sometimes, programs use opaque data types or incomplete specifications
10925 of complex data structure. If the debug information included in the
10926 program does not allow @value{GDBN} to display a full declaration of
10927 the data type, it will say @samp{<incomplete type>}. For example,
10928 given these declarations:
10932 struct foo *fooptr;
10936 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10939 (@value{GDBP}) ptype foo
10940 $1 = <incomplete type>
10944 ``Incomplete type'' is C terminology for data types that are not
10945 completely specified.
10948 @item info types @var{regexp}
10950 Print a brief description of all types whose names match the regular
10951 expression @var{regexp} (or all types in your program, if you supply
10952 no argument). Each complete typename is matched as though it were a
10953 complete line; thus, @samp{i type value} gives information on all
10954 types in your program whose names include the string @code{value}, but
10955 @samp{i type ^value$} gives information only on types whose complete
10956 name is @code{value}.
10958 This command differs from @code{ptype} in two ways: first, like
10959 @code{whatis}, it does not print a detailed description; second, it
10960 lists all source files where a type is defined.
10963 @cindex local variables
10964 @item info scope @var{location}
10965 List all the variables local to a particular scope. This command
10966 accepts a @var{location} argument---a function name, a source line, or
10967 an address preceded by a @samp{*}, and prints all the variables local
10968 to the scope defined by that location. For example:
10971 (@value{GDBP}) @b{info scope command_line_handler}
10972 Scope for command_line_handler:
10973 Symbol rl is an argument at stack/frame offset 8, length 4.
10974 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10975 Symbol linelength is in static storage at address 0x150a1c, length 4.
10976 Symbol p is a local variable in register $esi, length 4.
10977 Symbol p1 is a local variable in register $ebx, length 4.
10978 Symbol nline is a local variable in register $edx, length 4.
10979 Symbol repeat is a local variable at frame offset -8, length 4.
10983 This command is especially useful for determining what data to collect
10984 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10987 @kindex info source
10989 Show information about the current source file---that is, the source file for
10990 the function containing the current point of execution:
10993 the name of the source file, and the directory containing it,
10995 the directory it was compiled in,
10997 its length, in lines,
10999 which programming language it is written in,
11001 whether the executable includes debugging information for that file, and
11002 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11004 whether the debugging information includes information about
11005 preprocessor macros.
11009 @kindex info sources
11011 Print the names of all source files in your program for which there is
11012 debugging information, organized into two lists: files whose symbols
11013 have already been read, and files whose symbols will be read when needed.
11015 @kindex info functions
11016 @item info functions
11017 Print the names and data types of all defined functions.
11019 @item info functions @var{regexp}
11020 Print the names and data types of all defined functions
11021 whose names contain a match for regular expression @var{regexp}.
11022 Thus, @samp{info fun step} finds all functions whose names
11023 include @code{step}; @samp{info fun ^step} finds those whose names
11024 start with @code{step}. If a function name contains characters
11025 that conflict with the regular expression language (e.g.@:
11026 @samp{operator*()}), they may be quoted with a backslash.
11028 @kindex info variables
11029 @item info variables
11030 Print the names and data types of all variables that are declared
11031 outside of functions (i.e.@: excluding local variables).
11033 @item info variables @var{regexp}
11034 Print the names and data types of all variables (except for local
11035 variables) whose names contain a match for regular expression
11038 @kindex info classes
11039 @cindex Objective-C, classes and selectors
11041 @itemx info classes @var{regexp}
11042 Display all Objective-C classes in your program, or
11043 (with the @var{regexp} argument) all those matching a particular regular
11046 @kindex info selectors
11047 @item info selectors
11048 @itemx info selectors @var{regexp}
11049 Display all Objective-C selectors in your program, or
11050 (with the @var{regexp} argument) all those matching a particular regular
11054 This was never implemented.
11055 @kindex info methods
11057 @itemx info methods @var{regexp}
11058 The @code{info methods} command permits the user to examine all defined
11059 methods within C@t{++} program, or (with the @var{regexp} argument) a
11060 specific set of methods found in the various C@t{++} classes. Many
11061 C@t{++} classes provide a large number of methods. Thus, the output
11062 from the @code{ptype} command can be overwhelming and hard to use. The
11063 @code{info-methods} command filters the methods, printing only those
11064 which match the regular-expression @var{regexp}.
11067 @cindex reloading symbols
11068 Some systems allow individual object files that make up your program to
11069 be replaced without stopping and restarting your program. For example,
11070 in VxWorks you can simply recompile a defective object file and keep on
11071 running. If you are running on one of these systems, you can allow
11072 @value{GDBN} to reload the symbols for automatically relinked modules:
11075 @kindex set symbol-reloading
11076 @item set symbol-reloading on
11077 Replace symbol definitions for the corresponding source file when an
11078 object file with a particular name is seen again.
11080 @item set symbol-reloading off
11081 Do not replace symbol definitions when encountering object files of the
11082 same name more than once. This is the default state; if you are not
11083 running on a system that permits automatic relinking of modules, you
11084 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11085 may discard symbols when linking large programs, that may contain
11086 several modules (from different directories or libraries) with the same
11089 @kindex show symbol-reloading
11090 @item show symbol-reloading
11091 Show the current @code{on} or @code{off} setting.
11094 @cindex opaque data types
11095 @kindex set opaque-type-resolution
11096 @item set opaque-type-resolution on
11097 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11098 declared as a pointer to a @code{struct}, @code{class}, or
11099 @code{union}---for example, @code{struct MyType *}---that is used in one
11100 source file although the full declaration of @code{struct MyType} is in
11101 another source file. The default is on.
11103 A change in the setting of this subcommand will not take effect until
11104 the next time symbols for a file are loaded.
11106 @item set opaque-type-resolution off
11107 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11108 is printed as follows:
11110 @{<no data fields>@}
11113 @kindex show opaque-type-resolution
11114 @item show opaque-type-resolution
11115 Show whether opaque types are resolved or not.
11117 @kindex maint print symbols
11118 @cindex symbol dump
11119 @kindex maint print psymbols
11120 @cindex partial symbol dump
11121 @item maint print symbols @var{filename}
11122 @itemx maint print psymbols @var{filename}
11123 @itemx maint print msymbols @var{filename}
11124 Write a dump of debugging symbol data into the file @var{filename}.
11125 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11126 symbols with debugging data are included. If you use @samp{maint print
11127 symbols}, @value{GDBN} includes all the symbols for which it has already
11128 collected full details: that is, @var{filename} reflects symbols for
11129 only those files whose symbols @value{GDBN} has read. You can use the
11130 command @code{info sources} to find out which files these are. If you
11131 use @samp{maint print psymbols} instead, the dump shows information about
11132 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11133 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11134 @samp{maint print msymbols} dumps just the minimal symbol information
11135 required for each object file from which @value{GDBN} has read some symbols.
11136 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11137 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11139 @kindex maint info symtabs
11140 @kindex maint info psymtabs
11141 @cindex listing @value{GDBN}'s internal symbol tables
11142 @cindex symbol tables, listing @value{GDBN}'s internal
11143 @cindex full symbol tables, listing @value{GDBN}'s internal
11144 @cindex partial symbol tables, listing @value{GDBN}'s internal
11145 @item maint info symtabs @r{[} @var{regexp} @r{]}
11146 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11148 List the @code{struct symtab} or @code{struct partial_symtab}
11149 structures whose names match @var{regexp}. If @var{regexp} is not
11150 given, list them all. The output includes expressions which you can
11151 copy into a @value{GDBN} debugging this one to examine a particular
11152 structure in more detail. For example:
11155 (@value{GDBP}) maint info psymtabs dwarf2read
11156 @{ objfile /home/gnu/build/gdb/gdb
11157 ((struct objfile *) 0x82e69d0)
11158 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11159 ((struct partial_symtab *) 0x8474b10)
11162 text addresses 0x814d3c8 -- 0x8158074
11163 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11164 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11165 dependencies (none)
11168 (@value{GDBP}) maint info symtabs
11172 We see that there is one partial symbol table whose filename contains
11173 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11174 and we see that @value{GDBN} has not read in any symtabs yet at all.
11175 If we set a breakpoint on a function, that will cause @value{GDBN} to
11176 read the symtab for the compilation unit containing that function:
11179 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11180 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11182 (@value{GDBP}) maint info symtabs
11183 @{ objfile /home/gnu/build/gdb/gdb
11184 ((struct objfile *) 0x82e69d0)
11185 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11186 ((struct symtab *) 0x86c1f38)
11189 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11190 linetable ((struct linetable *) 0x8370fa0)
11191 debugformat DWARF 2
11200 @chapter Altering Execution
11202 Once you think you have found an error in your program, you might want to
11203 find out for certain whether correcting the apparent error would lead to
11204 correct results in the rest of the run. You can find the answer by
11205 experiment, using the @value{GDBN} features for altering execution of the
11208 For example, you can store new values into variables or memory
11209 locations, give your program a signal, restart it at a different
11210 address, or even return prematurely from a function.
11213 * Assignment:: Assignment to variables
11214 * Jumping:: Continuing at a different address
11215 * Signaling:: Giving your program a signal
11216 * Returning:: Returning from a function
11217 * Calling:: Calling your program's functions
11218 * Patching:: Patching your program
11222 @section Assignment to Variables
11225 @cindex setting variables
11226 To alter the value of a variable, evaluate an assignment expression.
11227 @xref{Expressions, ,Expressions}. For example,
11234 stores the value 4 into the variable @code{x}, and then prints the
11235 value of the assignment expression (which is 4).
11236 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11237 information on operators in supported languages.
11239 @kindex set variable
11240 @cindex variables, setting
11241 If you are not interested in seeing the value of the assignment, use the
11242 @code{set} command instead of the @code{print} command. @code{set} is
11243 really the same as @code{print} except that the expression's value is
11244 not printed and is not put in the value history (@pxref{Value History,
11245 ,Value History}). The expression is evaluated only for its effects.
11247 If the beginning of the argument string of the @code{set} command
11248 appears identical to a @code{set} subcommand, use the @code{set
11249 variable} command instead of just @code{set}. This command is identical
11250 to @code{set} except for its lack of subcommands. For example, if your
11251 program has a variable @code{width}, you get an error if you try to set
11252 a new value with just @samp{set width=13}, because @value{GDBN} has the
11253 command @code{set width}:
11256 (@value{GDBP}) whatis width
11258 (@value{GDBP}) p width
11260 (@value{GDBP}) set width=47
11261 Invalid syntax in expression.
11265 The invalid expression, of course, is @samp{=47}. In
11266 order to actually set the program's variable @code{width}, use
11269 (@value{GDBP}) set var width=47
11272 Because the @code{set} command has many subcommands that can conflict
11273 with the names of program variables, it is a good idea to use the
11274 @code{set variable} command instead of just @code{set}. For example, if
11275 your program has a variable @code{g}, you run into problems if you try
11276 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11277 the command @code{set gnutarget}, abbreviated @code{set g}:
11281 (@value{GDBP}) whatis g
11285 (@value{GDBP}) set g=4
11289 The program being debugged has been started already.
11290 Start it from the beginning? (y or n) y
11291 Starting program: /home/smith/cc_progs/a.out
11292 "/home/smith/cc_progs/a.out": can't open to read symbols:
11293 Invalid bfd target.
11294 (@value{GDBP}) show g
11295 The current BFD target is "=4".
11300 The program variable @code{g} did not change, and you silently set the
11301 @code{gnutarget} to an invalid value. In order to set the variable
11305 (@value{GDBP}) set var g=4
11308 @value{GDBN} allows more implicit conversions in assignments than C; you can
11309 freely store an integer value into a pointer variable or vice versa,
11310 and you can convert any structure to any other structure that is the
11311 same length or shorter.
11312 @comment FIXME: how do structs align/pad in these conversions?
11313 @comment /doc@cygnus.com 18dec1990
11315 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11316 construct to generate a value of specified type at a specified address
11317 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11318 to memory location @code{0x83040} as an integer (which implies a certain size
11319 and representation in memory), and
11322 set @{int@}0x83040 = 4
11326 stores the value 4 into that memory location.
11329 @section Continuing at a Different Address
11331 Ordinarily, when you continue your program, you do so at the place where
11332 it stopped, with the @code{continue} command. You can instead continue at
11333 an address of your own choosing, with the following commands:
11337 @item jump @var{linespec}
11338 Resume execution at line @var{linespec}. Execution stops again
11339 immediately if there is a breakpoint there. @xref{List, ,Printing
11340 Source Lines}, for a description of the different forms of
11341 @var{linespec}. It is common practice to use the @code{tbreak} command
11342 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11345 The @code{jump} command does not change the current stack frame, or
11346 the stack pointer, or the contents of any memory location or any
11347 register other than the program counter. If line @var{linespec} is in
11348 a different function from the one currently executing, the results may
11349 be bizarre if the two functions expect different patterns of arguments or
11350 of local variables. For this reason, the @code{jump} command requests
11351 confirmation if the specified line is not in the function currently
11352 executing. However, even bizarre results are predictable if you are
11353 well acquainted with the machine-language code of your program.
11355 @item jump *@var{address}
11356 Resume execution at the instruction at address @var{address}.
11359 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11360 On many systems, you can get much the same effect as the @code{jump}
11361 command by storing a new value into the register @code{$pc}. The
11362 difference is that this does not start your program running; it only
11363 changes the address of where it @emph{will} run when you continue. For
11371 makes the next @code{continue} command or stepping command execute at
11372 address @code{0x485}, rather than at the address where your program stopped.
11373 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11375 The most common occasion to use the @code{jump} command is to back
11376 up---perhaps with more breakpoints set---over a portion of a program
11377 that has already executed, in order to examine its execution in more
11382 @section Giving your Program a Signal
11383 @cindex deliver a signal to a program
11387 @item signal @var{signal}
11388 Resume execution where your program stopped, but immediately give it the
11389 signal @var{signal}. @var{signal} can be the name or the number of a
11390 signal. For example, on many systems @code{signal 2} and @code{signal
11391 SIGINT} are both ways of sending an interrupt signal.
11393 Alternatively, if @var{signal} is zero, continue execution without
11394 giving a signal. This is useful when your program stopped on account of
11395 a signal and would ordinary see the signal when resumed with the
11396 @code{continue} command; @samp{signal 0} causes it to resume without a
11399 @code{signal} does not repeat when you press @key{RET} a second time
11400 after executing the command.
11404 Invoking the @code{signal} command is not the same as invoking the
11405 @code{kill} utility from the shell. Sending a signal with @code{kill}
11406 causes @value{GDBN} to decide what to do with the signal depending on
11407 the signal handling tables (@pxref{Signals}). The @code{signal} command
11408 passes the signal directly to your program.
11412 @section Returning from a Function
11415 @cindex returning from a function
11418 @itemx return @var{expression}
11419 You can cancel execution of a function call with the @code{return}
11420 command. If you give an
11421 @var{expression} argument, its value is used as the function's return
11425 When you use @code{return}, @value{GDBN} discards the selected stack frame
11426 (and all frames within it). You can think of this as making the
11427 discarded frame return prematurely. If you wish to specify a value to
11428 be returned, give that value as the argument to @code{return}.
11430 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11431 Frame}), and any other frames inside of it, leaving its caller as the
11432 innermost remaining frame. That frame becomes selected. The
11433 specified value is stored in the registers used for returning values
11436 The @code{return} command does not resume execution; it leaves the
11437 program stopped in the state that would exist if the function had just
11438 returned. In contrast, the @code{finish} command (@pxref{Continuing
11439 and Stepping, ,Continuing and Stepping}) resumes execution until the
11440 selected stack frame returns naturally.
11443 @section Calling Program Functions
11446 @cindex calling functions
11447 @cindex inferior functions, calling
11448 @item print @var{expr}
11449 Evaluate the expression @var{expr} and display the resulting value.
11450 @var{expr} may include calls to functions in the program being
11454 @item call @var{expr}
11455 Evaluate the expression @var{expr} without displaying @code{void}
11458 You can use this variant of the @code{print} command if you want to
11459 execute a function from your program that does not return anything
11460 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11461 with @code{void} returned values that @value{GDBN} will otherwise
11462 print. If the result is not void, it is printed and saved in the
11466 It is possible for the function you call via the @code{print} or
11467 @code{call} command to generate a signal (e.g., if there's a bug in
11468 the function, or if you passed it incorrect arguments). What happens
11469 in that case is controlled by the @code{set unwindonsignal} command.
11472 @item set unwindonsignal
11473 @kindex set unwindonsignal
11474 @cindex unwind stack in called functions
11475 @cindex call dummy stack unwinding
11476 Set unwinding of the stack if a signal is received while in a function
11477 that @value{GDBN} called in the program being debugged. If set to on,
11478 @value{GDBN} unwinds the stack it created for the call and restores
11479 the context to what it was before the call. If set to off (the
11480 default), @value{GDBN} stops in the frame where the signal was
11483 @item show unwindonsignal
11484 @kindex show unwindonsignal
11485 Show the current setting of stack unwinding in the functions called by
11489 @cindex weak alias functions
11490 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11491 for another function. In such case, @value{GDBN} might not pick up
11492 the type information, including the types of the function arguments,
11493 which causes @value{GDBN} to call the inferior function incorrectly.
11494 As a result, the called function will function erroneously and may
11495 even crash. A solution to that is to use the name of the aliased
11499 @section Patching Programs
11501 @cindex patching binaries
11502 @cindex writing into executables
11503 @cindex writing into corefiles
11505 By default, @value{GDBN} opens the file containing your program's
11506 executable code (or the corefile) read-only. This prevents accidental
11507 alterations to machine code; but it also prevents you from intentionally
11508 patching your program's binary.
11510 If you'd like to be able to patch the binary, you can specify that
11511 explicitly with the @code{set write} command. For example, you might
11512 want to turn on internal debugging flags, or even to make emergency
11518 @itemx set write off
11519 If you specify @samp{set write on}, @value{GDBN} opens executable and
11520 core files for both reading and writing; if you specify @samp{set write
11521 off} (the default), @value{GDBN} opens them read-only.
11523 If you have already loaded a file, you must load it again (using the
11524 @code{exec-file} or @code{core-file} command) after changing @code{set
11525 write}, for your new setting to take effect.
11529 Display whether executable files and core files are opened for writing
11530 as well as reading.
11534 @chapter @value{GDBN} Files
11536 @value{GDBN} needs to know the file name of the program to be debugged,
11537 both in order to read its symbol table and in order to start your
11538 program. To debug a core dump of a previous run, you must also tell
11539 @value{GDBN} the name of the core dump file.
11542 * Files:: Commands to specify files
11543 * Separate Debug Files:: Debugging information in separate files
11544 * Symbol Errors:: Errors reading symbol files
11548 @section Commands to Specify Files
11550 @cindex symbol table
11551 @cindex core dump file
11553 You may want to specify executable and core dump file names. The usual
11554 way to do this is at start-up time, using the arguments to
11555 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11556 Out of @value{GDBN}}).
11558 Occasionally it is necessary to change to a different file during a
11559 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11560 specify a file you want to use. Or you are debugging a remote target
11561 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11562 Program}). In these situations the @value{GDBN} commands to specify
11563 new files are useful.
11566 @cindex executable file
11568 @item file @var{filename}
11569 Use @var{filename} as the program to be debugged. It is read for its
11570 symbols and for the contents of pure memory. It is also the program
11571 executed when you use the @code{run} command. If you do not specify a
11572 directory and the file is not found in the @value{GDBN} working directory,
11573 @value{GDBN} uses the environment variable @code{PATH} as a list of
11574 directories to search, just as the shell does when looking for a program
11575 to run. You can change the value of this variable, for both @value{GDBN}
11576 and your program, using the @code{path} command.
11578 @cindex unlinked object files
11579 @cindex patching object files
11580 You can load unlinked object @file{.o} files into @value{GDBN} using
11581 the @code{file} command. You will not be able to ``run'' an object
11582 file, but you can disassemble functions and inspect variables. Also,
11583 if the underlying BFD functionality supports it, you could use
11584 @kbd{gdb -write} to patch object files using this technique. Note
11585 that @value{GDBN} can neither interpret nor modify relocations in this
11586 case, so branches and some initialized variables will appear to go to
11587 the wrong place. But this feature is still handy from time to time.
11590 @code{file} with no argument makes @value{GDBN} discard any information it
11591 has on both executable file and the symbol table.
11594 @item exec-file @r{[} @var{filename} @r{]}
11595 Specify that the program to be run (but not the symbol table) is found
11596 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11597 if necessary to locate your program. Omitting @var{filename} means to
11598 discard information on the executable file.
11600 @kindex symbol-file
11601 @item symbol-file @r{[} @var{filename} @r{]}
11602 Read symbol table information from file @var{filename}. @code{PATH} is
11603 searched when necessary. Use the @code{file} command to get both symbol
11604 table and program to run from the same file.
11606 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11607 program's symbol table.
11609 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11610 some breakpoints and auto-display expressions. This is because they may
11611 contain pointers to the internal data recording symbols and data types,
11612 which are part of the old symbol table data being discarded inside
11615 @code{symbol-file} does not repeat if you press @key{RET} again after
11618 When @value{GDBN} is configured for a particular environment, it
11619 understands debugging information in whatever format is the standard
11620 generated for that environment; you may use either a @sc{gnu} compiler, or
11621 other compilers that adhere to the local conventions.
11622 Best results are usually obtained from @sc{gnu} compilers; for example,
11623 using @code{@value{NGCC}} you can generate debugging information for
11626 For most kinds of object files, with the exception of old SVR3 systems
11627 using COFF, the @code{symbol-file} command does not normally read the
11628 symbol table in full right away. Instead, it scans the symbol table
11629 quickly to find which source files and which symbols are present. The
11630 details are read later, one source file at a time, as they are needed.
11632 The purpose of this two-stage reading strategy is to make @value{GDBN}
11633 start up faster. For the most part, it is invisible except for
11634 occasional pauses while the symbol table details for a particular source
11635 file are being read. (The @code{set verbose} command can turn these
11636 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11637 Warnings and Messages}.)
11639 We have not implemented the two-stage strategy for COFF yet. When the
11640 symbol table is stored in COFF format, @code{symbol-file} reads the
11641 symbol table data in full right away. Note that ``stabs-in-COFF''
11642 still does the two-stage strategy, since the debug info is actually
11646 @cindex reading symbols immediately
11647 @cindex symbols, reading immediately
11648 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11649 @itemx file @var{filename} @r{[} -readnow @r{]}
11650 You can override the @value{GDBN} two-stage strategy for reading symbol
11651 tables by using the @samp{-readnow} option with any of the commands that
11652 load symbol table information, if you want to be sure @value{GDBN} has the
11653 entire symbol table available.
11655 @c FIXME: for now no mention of directories, since this seems to be in
11656 @c flux. 13mar1992 status is that in theory GDB would look either in
11657 @c current dir or in same dir as myprog; but issues like competing
11658 @c GDB's, or clutter in system dirs, mean that in practice right now
11659 @c only current dir is used. FFish says maybe a special GDB hierarchy
11660 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11664 @item core-file @r{[}@var{filename}@r{]}
11666 Specify the whereabouts of a core dump file to be used as the ``contents
11667 of memory''. Traditionally, core files contain only some parts of the
11668 address space of the process that generated them; @value{GDBN} can access the
11669 executable file itself for other parts.
11671 @code{core-file} with no argument specifies that no core file is
11674 Note that the core file is ignored when your program is actually running
11675 under @value{GDBN}. So, if you have been running your program and you
11676 wish to debug a core file instead, you must kill the subprocess in which
11677 the program is running. To do this, use the @code{kill} command
11678 (@pxref{Kill Process, ,Killing the Child Process}).
11680 @kindex add-symbol-file
11681 @cindex dynamic linking
11682 @item add-symbol-file @var{filename} @var{address}
11683 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11684 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11685 The @code{add-symbol-file} command reads additional symbol table
11686 information from the file @var{filename}. You would use this command
11687 when @var{filename} has been dynamically loaded (by some other means)
11688 into the program that is running. @var{address} should be the memory
11689 address at which the file has been loaded; @value{GDBN} cannot figure
11690 this out for itself. You can additionally specify an arbitrary number
11691 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11692 section name and base address for that section. You can specify any
11693 @var{address} as an expression.
11695 The symbol table of the file @var{filename} is added to the symbol table
11696 originally read with the @code{symbol-file} command. You can use the
11697 @code{add-symbol-file} command any number of times; the new symbol data
11698 thus read keeps adding to the old. To discard all old symbol data
11699 instead, use the @code{symbol-file} command without any arguments.
11701 @cindex relocatable object files, reading symbols from
11702 @cindex object files, relocatable, reading symbols from
11703 @cindex reading symbols from relocatable object files
11704 @cindex symbols, reading from relocatable object files
11705 @cindex @file{.o} files, reading symbols from
11706 Although @var{filename} is typically a shared library file, an
11707 executable file, or some other object file which has been fully
11708 relocated for loading into a process, you can also load symbolic
11709 information from relocatable @file{.o} files, as long as:
11713 the file's symbolic information refers only to linker symbols defined in
11714 that file, not to symbols defined by other object files,
11716 every section the file's symbolic information refers to has actually
11717 been loaded into the inferior, as it appears in the file, and
11719 you can determine the address at which every section was loaded, and
11720 provide these to the @code{add-symbol-file} command.
11724 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11725 relocatable files into an already running program; such systems
11726 typically make the requirements above easy to meet. However, it's
11727 important to recognize that many native systems use complex link
11728 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11729 assembly, for example) that make the requirements difficult to meet. In
11730 general, one cannot assume that using @code{add-symbol-file} to read a
11731 relocatable object file's symbolic information will have the same effect
11732 as linking the relocatable object file into the program in the normal
11735 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11737 @kindex add-symbol-file-from-memory
11738 @cindex @code{syscall DSO}
11739 @cindex load symbols from memory
11740 @item add-symbol-file-from-memory @var{address}
11741 Load symbols from the given @var{address} in a dynamically loaded
11742 object file whose image is mapped directly into the inferior's memory.
11743 For example, the Linux kernel maps a @code{syscall DSO} into each
11744 process's address space; this DSO provides kernel-specific code for
11745 some system calls. The argument can be any expression whose
11746 evaluation yields the address of the file's shared object file header.
11747 For this command to work, you must have used @code{symbol-file} or
11748 @code{exec-file} commands in advance.
11750 @kindex add-shared-symbol-files
11752 @item add-shared-symbol-files @var{library-file}
11753 @itemx assf @var{library-file}
11754 The @code{add-shared-symbol-files} command can currently be used only
11755 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11756 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11757 @value{GDBN} automatically looks for shared libraries, however if
11758 @value{GDBN} does not find yours, you can invoke
11759 @code{add-shared-symbol-files}. It takes one argument: the shared
11760 library's file name. @code{assf} is a shorthand alias for
11761 @code{add-shared-symbol-files}.
11764 @item section @var{section} @var{addr}
11765 The @code{section} command changes the base address of the named
11766 @var{section} of the exec file to @var{addr}. This can be used if the
11767 exec file does not contain section addresses, (such as in the
11768 @code{a.out} format), or when the addresses specified in the file
11769 itself are wrong. Each section must be changed separately. The
11770 @code{info files} command, described below, lists all the sections and
11774 @kindex info target
11777 @code{info files} and @code{info target} are synonymous; both print the
11778 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11779 including the names of the executable and core dump files currently in
11780 use by @value{GDBN}, and the files from which symbols were loaded. The
11781 command @code{help target} lists all possible targets rather than
11784 @kindex maint info sections
11785 @item maint info sections
11786 Another command that can give you extra information about program sections
11787 is @code{maint info sections}. In addition to the section information
11788 displayed by @code{info files}, this command displays the flags and file
11789 offset of each section in the executable and core dump files. In addition,
11790 @code{maint info sections} provides the following command options (which
11791 may be arbitrarily combined):
11795 Display sections for all loaded object files, including shared libraries.
11796 @item @var{sections}
11797 Display info only for named @var{sections}.
11798 @item @var{section-flags}
11799 Display info only for sections for which @var{section-flags} are true.
11800 The section flags that @value{GDBN} currently knows about are:
11803 Section will have space allocated in the process when loaded.
11804 Set for all sections except those containing debug information.
11806 Section will be loaded from the file into the child process memory.
11807 Set for pre-initialized code and data, clear for @code{.bss} sections.
11809 Section needs to be relocated before loading.
11811 Section cannot be modified by the child process.
11813 Section contains executable code only.
11815 Section contains data only (no executable code).
11817 Section will reside in ROM.
11819 Section contains data for constructor/destructor lists.
11821 Section is not empty.
11823 An instruction to the linker to not output the section.
11824 @item COFF_SHARED_LIBRARY
11825 A notification to the linker that the section contains
11826 COFF shared library information.
11828 Section contains common symbols.
11831 @kindex set trust-readonly-sections
11832 @cindex read-only sections
11833 @item set trust-readonly-sections on
11834 Tell @value{GDBN} that readonly sections in your object file
11835 really are read-only (i.e.@: that their contents will not change).
11836 In that case, @value{GDBN} can fetch values from these sections
11837 out of the object file, rather than from the target program.
11838 For some targets (notably embedded ones), this can be a significant
11839 enhancement to debugging performance.
11841 The default is off.
11843 @item set trust-readonly-sections off
11844 Tell @value{GDBN} not to trust readonly sections. This means that
11845 the contents of the section might change while the program is running,
11846 and must therefore be fetched from the target when needed.
11848 @item show trust-readonly-sections
11849 Show the current setting of trusting readonly sections.
11852 All file-specifying commands allow both absolute and relative file names
11853 as arguments. @value{GDBN} always converts the file name to an absolute file
11854 name and remembers it that way.
11856 @cindex shared libraries
11857 @anchor{Shared Libraries}
11858 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11859 and IBM RS/6000 AIX shared libraries.
11861 On MS-Windows @value{GDBN} must be linked with the Expat library to support
11862 shared libraries. @xref{Expat}.
11864 @value{GDBN} automatically loads symbol definitions from shared libraries
11865 when you use the @code{run} command, or when you examine a core file.
11866 (Before you issue the @code{run} command, @value{GDBN} does not understand
11867 references to a function in a shared library, however---unless you are
11868 debugging a core file).
11870 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11871 automatically loads the symbols at the time of the @code{shl_load} call.
11873 @c FIXME: some @value{GDBN} release may permit some refs to undef
11874 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11875 @c FIXME...lib; check this from time to time when updating manual
11877 There are times, however, when you may wish to not automatically load
11878 symbol definitions from shared libraries, such as when they are
11879 particularly large or there are many of them.
11881 To control the automatic loading of shared library symbols, use the
11885 @kindex set auto-solib-add
11886 @item set auto-solib-add @var{mode}
11887 If @var{mode} is @code{on}, symbols from all shared object libraries
11888 will be loaded automatically when the inferior begins execution, you
11889 attach to an independently started inferior, or when the dynamic linker
11890 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11891 is @code{off}, symbols must be loaded manually, using the
11892 @code{sharedlibrary} command. The default value is @code{on}.
11894 @cindex memory used for symbol tables
11895 If your program uses lots of shared libraries with debug info that
11896 takes large amounts of memory, you can decrease the @value{GDBN}
11897 memory footprint by preventing it from automatically loading the
11898 symbols from shared libraries. To that end, type @kbd{set
11899 auto-solib-add off} before running the inferior, then load each
11900 library whose debug symbols you do need with @kbd{sharedlibrary
11901 @var{regexp}}, where @var{regexp} is a regular expression that matches
11902 the libraries whose symbols you want to be loaded.
11904 @kindex show auto-solib-add
11905 @item show auto-solib-add
11906 Display the current autoloading mode.
11909 @cindex load shared library
11910 To explicitly load shared library symbols, use the @code{sharedlibrary}
11914 @kindex info sharedlibrary
11917 @itemx info sharedlibrary
11918 Print the names of the shared libraries which are currently loaded.
11920 @kindex sharedlibrary
11922 @item sharedlibrary @var{regex}
11923 @itemx share @var{regex}
11924 Load shared object library symbols for files matching a
11925 Unix regular expression.
11926 As with files loaded automatically, it only loads shared libraries
11927 required by your program for a core file or after typing @code{run}. If
11928 @var{regex} is omitted all shared libraries required by your program are
11931 @item nosharedlibrary
11932 @kindex nosharedlibrary
11933 @cindex unload symbols from shared libraries
11934 Unload all shared object library symbols. This discards all symbols
11935 that have been loaded from all shared libraries. Symbols from shared
11936 libraries that were loaded by explicit user requests are not
11940 Sometimes you may wish that @value{GDBN} stops and gives you control
11941 when any of shared library events happen. Use the @code{set
11942 stop-on-solib-events} command for this:
11945 @item set stop-on-solib-events
11946 @kindex set stop-on-solib-events
11947 This command controls whether @value{GDBN} should give you control
11948 when the dynamic linker notifies it about some shared library event.
11949 The most common event of interest is loading or unloading of a new
11952 @item show stop-on-solib-events
11953 @kindex show stop-on-solib-events
11954 Show whether @value{GDBN} stops and gives you control when shared
11955 library events happen.
11958 Shared libraries are also supported in many cross or remote debugging
11959 configurations. A copy of the target's libraries need to be present on the
11960 host system; they need to be the same as the target libraries, although the
11961 copies on the target can be stripped as long as the copies on the host are
11964 @cindex where to look for shared libraries
11965 For remote debugging, you need to tell @value{GDBN} where the target
11966 libraries are, so that it can load the correct copies---otherwise, it
11967 may try to load the host's libraries. @value{GDBN} has two variables
11968 to specify the search directories for target libraries.
11971 @cindex prefix for shared library file names
11972 @cindex system root, alternate
11973 @kindex set solib-absolute-prefix
11974 @kindex set sysroot
11975 @item set sysroot @var{path}
11976 Use @var{path} as the system root for the program being debugged. Any
11977 absolute shared library paths will be prefixed with @var{path}; many
11978 runtime loaders store the absolute paths to the shared library in the
11979 target program's memory. If you use @code{set sysroot} to find shared
11980 libraries, they need to be laid out in the same way that they are on
11981 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
11984 The @code{set solib-absolute-prefix} command is an alias for @code{set
11987 @cindex default system root
11988 @cindex @samp{--with-sysroot}
11989 You can set the default system root by using the configure-time
11990 @samp{--with-sysroot} option. If the system root is inside
11991 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
11992 @samp{--exec-prefix}), then the default system root will be updated
11993 automatically if the installed @value{GDBN} is moved to a new
11996 @kindex show sysroot
11998 Display the current shared library prefix.
12000 @kindex set solib-search-path
12001 @item set solib-search-path @var{path}
12002 If this variable is set, @var{path} is a colon-separated list of
12003 directories to search for shared libraries. @samp{solib-search-path}
12004 is used after @samp{sysroot} fails to locate the library, or if the
12005 path to the library is relative instead of absolute. If you want to
12006 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12007 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12008 finding your host's libraries. @samp{sysroot} is preferred; setting
12009 it to a nonexistent directory may interfere with automatic loading
12010 of shared library symbols.
12012 @kindex show solib-search-path
12013 @item show solib-search-path
12014 Display the current shared library search path.
12018 @node Separate Debug Files
12019 @section Debugging Information in Separate Files
12020 @cindex separate debugging information files
12021 @cindex debugging information in separate files
12022 @cindex @file{.debug} subdirectories
12023 @cindex debugging information directory, global
12024 @cindex global debugging information directory
12025 @cindex build ID, and separate debugging files
12026 @cindex @file{.build-id} directory
12028 @value{GDBN} allows you to put a program's debugging information in a
12029 file separate from the executable itself, in a way that allows
12030 @value{GDBN} to find and load the debugging information automatically.
12031 Since debugging information can be very large---sometimes larger
12032 than the executable code itself---some systems distribute debugging
12033 information for their executables in separate files, which users can
12034 install only when they need to debug a problem.
12036 @value{GDBN} supports two ways of specifying the separate debug info
12041 The executable contains a @dfn{debug link} that specifies the name of
12042 the separate debug info file. The separate debug file's name is
12043 usually @file{@var{executable}.debug}, where @var{executable} is the
12044 name of the corresponding executable file without leading directories
12045 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12046 debug link specifies a CRC32 checksum for the debug file, which
12047 @value{GDBN} uses to validate that the executable and the debug file
12048 came from the same build.
12051 The executable contains a @dfn{build ID}, a unique bit string that is
12052 also present in the corresponding debug info file. (This is supported
12053 only on some operating systems, notably those which use the ELF format
12054 for binary files and the @sc{gnu} Binutils.) For more details about
12055 this feature, see the description of the @option{--build-id}
12056 command-line option in @ref{Options, , Command Line Options, ld.info,
12057 The GNU Linker}. The debug info file's name is not specified
12058 explicitly by the build ID, but can be computed from the build ID, see
12062 Depending on the way the debug info file is specified, @value{GDBN}
12063 uses two different methods of looking for the debug file:
12067 For the ``debug link'' method, @value{GDBN} looks up the named file in
12068 the directory of the executable file, then in a subdirectory of that
12069 directory named @file{.debug}, and finally under the global debug
12070 directory, in a subdirectory whose name is identical to the leading
12071 directories of the executable's absolute file name.
12074 For the ``build ID'' method, @value{GDBN} looks in the
12075 @file{.build-id} subdirectory of the global debug directory for a file
12076 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12077 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12078 are the rest of the bit string. (Real build ID strings are 32 or more
12079 hex characters, not 10.)
12082 So, for example, suppose you ask @value{GDBN} to debug
12083 @file{/usr/bin/ls}, which has a debug link that specifies the
12084 file @file{ls.debug}, and a build ID whose value in hex is
12085 @code{abcdef1234}. If the global debug directory is
12086 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12087 debug information files, in the indicated order:
12091 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12093 @file{/usr/bin/ls.debug}
12095 @file{/usr/bin/.debug/ls.debug}
12097 @file{/usr/lib/debug/usr/bin/ls.debug}.
12100 You can set the global debugging info directory's name, and view the
12101 name @value{GDBN} is currently using.
12105 @kindex set debug-file-directory
12106 @item set debug-file-directory @var{directory}
12107 Set the directory which @value{GDBN} searches for separate debugging
12108 information files to @var{directory}.
12110 @kindex show debug-file-directory
12111 @item show debug-file-directory
12112 Show the directory @value{GDBN} searches for separate debugging
12117 @cindex @code{.gnu_debuglink} sections
12118 @cindex debug link sections
12119 A debug link is a special section of the executable file named
12120 @code{.gnu_debuglink}. The section must contain:
12124 A filename, with any leading directory components removed, followed by
12127 zero to three bytes of padding, as needed to reach the next four-byte
12128 boundary within the section, and
12130 a four-byte CRC checksum, stored in the same endianness used for the
12131 executable file itself. The checksum is computed on the debugging
12132 information file's full contents by the function given below, passing
12133 zero as the @var{crc} argument.
12136 Any executable file format can carry a debug link, as long as it can
12137 contain a section named @code{.gnu_debuglink} with the contents
12140 @cindex @code{.note.gnu.build-id} sections
12141 @cindex build ID sections
12142 The build ID is a special section in the executable file (and in other
12143 ELF binary files that @value{GDBN} may consider). This section is
12144 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12145 It contains unique identification for the built files---the ID remains
12146 the same across multiple builds of the same build tree. The default
12147 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12148 content for the build ID string. The same section with an identical
12149 value is present in the original built binary with symbols, in its
12150 stripped variant, and in the separate debugging information file.
12152 The debugging information file itself should be an ordinary
12153 executable, containing a full set of linker symbols, sections, and
12154 debugging information. The sections of the debugging information file
12155 should have the same names, addresses, and sizes as the original file,
12156 but they need not contain any data---much like a @code{.bss} section
12157 in an ordinary executable.
12159 The @sc{gnu} binary utilities (Binutils) package includes the
12160 @samp{objcopy} utility that can produce
12161 the separated executable / debugging information file pairs using the
12162 following commands:
12165 @kbd{objcopy --only-keep-debug foo foo.debug}
12170 These commands remove the debugging
12171 information from the executable file @file{foo} and place it in the file
12172 @file{foo.debug}. You can use the first, second or both methods to link the
12177 The debug link method needs the following additional command to also leave
12178 behind a debug link in @file{foo}:
12181 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12184 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12185 a version of the @code{strip} command such that the command @kbd{strip foo -f
12186 foo.debug} has the same functionality as the two @code{objcopy} commands and
12187 the @code{ln -s} command above, together.
12190 Build ID gets embedded into the main executable using @code{ld --build-id} or
12191 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12192 compatibility fixes for debug files separation are present in @sc{gnu} binary
12193 utilities (Binutils) package since version 2.18.
12198 Since there are many different ways to compute CRC's for the debug
12199 link (different polynomials, reversals, byte ordering, etc.), the
12200 simplest way to describe the CRC used in @code{.gnu_debuglink}
12201 sections is to give the complete code for a function that computes it:
12203 @kindex gnu_debuglink_crc32
12206 gnu_debuglink_crc32 (unsigned long crc,
12207 unsigned char *buf, size_t len)
12209 static const unsigned long crc32_table[256] =
12211 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12212 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12213 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12214 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12215 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12216 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12217 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12218 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12219 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12220 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12221 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12222 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12223 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12224 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12225 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12226 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12227 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12228 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12229 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12230 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12231 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12232 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12233 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12234 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12235 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12236 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12237 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12238 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12239 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12240 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12241 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12242 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12243 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12244 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12245 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12246 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12247 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12248 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12249 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12250 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12251 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12252 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12253 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12254 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12255 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12256 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12257 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12258 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12259 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12260 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12261 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12264 unsigned char *end;
12266 crc = ~crc & 0xffffffff;
12267 for (end = buf + len; buf < end; ++buf)
12268 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12269 return ~crc & 0xffffffff;
12274 This computation does not apply to the ``build ID'' method.
12277 @node Symbol Errors
12278 @section Errors Reading Symbol Files
12280 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12281 such as symbol types it does not recognize, or known bugs in compiler
12282 output. By default, @value{GDBN} does not notify you of such problems, since
12283 they are relatively common and primarily of interest to people
12284 debugging compilers. If you are interested in seeing information
12285 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12286 only one message about each such type of problem, no matter how many
12287 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12288 to see how many times the problems occur, with the @code{set
12289 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12292 The messages currently printed, and their meanings, include:
12295 @item inner block not inside outer block in @var{symbol}
12297 The symbol information shows where symbol scopes begin and end
12298 (such as at the start of a function or a block of statements). This
12299 error indicates that an inner scope block is not fully contained
12300 in its outer scope blocks.
12302 @value{GDBN} circumvents the problem by treating the inner block as if it had
12303 the same scope as the outer block. In the error message, @var{symbol}
12304 may be shown as ``@code{(don't know)}'' if the outer block is not a
12307 @item block at @var{address} out of order
12309 The symbol information for symbol scope blocks should occur in
12310 order of increasing addresses. This error indicates that it does not
12313 @value{GDBN} does not circumvent this problem, and has trouble
12314 locating symbols in the source file whose symbols it is reading. (You
12315 can often determine what source file is affected by specifying
12316 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12319 @item bad block start address patched
12321 The symbol information for a symbol scope block has a start address
12322 smaller than the address of the preceding source line. This is known
12323 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12325 @value{GDBN} circumvents the problem by treating the symbol scope block as
12326 starting on the previous source line.
12328 @item bad string table offset in symbol @var{n}
12331 Symbol number @var{n} contains a pointer into the string table which is
12332 larger than the size of the string table.
12334 @value{GDBN} circumvents the problem by considering the symbol to have the
12335 name @code{foo}, which may cause other problems if many symbols end up
12338 @item unknown symbol type @code{0x@var{nn}}
12340 The symbol information contains new data types that @value{GDBN} does
12341 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12342 uncomprehended information, in hexadecimal.
12344 @value{GDBN} circumvents the error by ignoring this symbol information.
12345 This usually allows you to debug your program, though certain symbols
12346 are not accessible. If you encounter such a problem and feel like
12347 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12348 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12349 and examine @code{*bufp} to see the symbol.
12351 @item stub type has NULL name
12353 @value{GDBN} could not find the full definition for a struct or class.
12355 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12356 The symbol information for a C@t{++} member function is missing some
12357 information that recent versions of the compiler should have output for
12360 @item info mismatch between compiler and debugger
12362 @value{GDBN} could not parse a type specification output by the compiler.
12367 @chapter Specifying a Debugging Target
12369 @cindex debugging target
12370 A @dfn{target} is the execution environment occupied by your program.
12372 Often, @value{GDBN} runs in the same host environment as your program;
12373 in that case, the debugging target is specified as a side effect when
12374 you use the @code{file} or @code{core} commands. When you need more
12375 flexibility---for example, running @value{GDBN} on a physically separate
12376 host, or controlling a standalone system over a serial port or a
12377 realtime system over a TCP/IP connection---you can use the @code{target}
12378 command to specify one of the target types configured for @value{GDBN}
12379 (@pxref{Target Commands, ,Commands for Managing Targets}).
12381 @cindex target architecture
12382 It is possible to build @value{GDBN} for several different @dfn{target
12383 architectures}. When @value{GDBN} is built like that, you can choose
12384 one of the available architectures with the @kbd{set architecture}
12388 @kindex set architecture
12389 @kindex show architecture
12390 @item set architecture @var{arch}
12391 This command sets the current target architecture to @var{arch}. The
12392 value of @var{arch} can be @code{"auto"}, in addition to one of the
12393 supported architectures.
12395 @item show architecture
12396 Show the current target architecture.
12398 @item set processor
12400 @kindex set processor
12401 @kindex show processor
12402 These are alias commands for, respectively, @code{set architecture}
12403 and @code{show architecture}.
12407 * Active Targets:: Active targets
12408 * Target Commands:: Commands for managing targets
12409 * Byte Order:: Choosing target byte order
12412 @node Active Targets
12413 @section Active Targets
12415 @cindex stacking targets
12416 @cindex active targets
12417 @cindex multiple targets
12419 There are three classes of targets: processes, core files, and
12420 executable files. @value{GDBN} can work concurrently on up to three
12421 active targets, one in each class. This allows you to (for example)
12422 start a process and inspect its activity without abandoning your work on
12425 For example, if you execute @samp{gdb a.out}, then the executable file
12426 @code{a.out} is the only active target. If you designate a core file as
12427 well---presumably from a prior run that crashed and coredumped---then
12428 @value{GDBN} has two active targets and uses them in tandem, looking
12429 first in the corefile target, then in the executable file, to satisfy
12430 requests for memory addresses. (Typically, these two classes of target
12431 are complementary, since core files contain only a program's
12432 read-write memory---variables and so on---plus machine status, while
12433 executable files contain only the program text and initialized data.)
12435 When you type @code{run}, your executable file becomes an active process
12436 target as well. When a process target is active, all @value{GDBN}
12437 commands requesting memory addresses refer to that target; addresses in
12438 an active core file or executable file target are obscured while the
12439 process target is active.
12441 Use the @code{core-file} and @code{exec-file} commands to select a new
12442 core file or executable target (@pxref{Files, ,Commands to Specify
12443 Files}). To specify as a target a process that is already running, use
12444 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12447 @node Target Commands
12448 @section Commands for Managing Targets
12451 @item target @var{type} @var{parameters}
12452 Connects the @value{GDBN} host environment to a target machine or
12453 process. A target is typically a protocol for talking to debugging
12454 facilities. You use the argument @var{type} to specify the type or
12455 protocol of the target machine.
12457 Further @var{parameters} are interpreted by the target protocol, but
12458 typically include things like device names or host names to connect
12459 with, process numbers, and baud rates.
12461 The @code{target} command does not repeat if you press @key{RET} again
12462 after executing the command.
12464 @kindex help target
12466 Displays the names of all targets available. To display targets
12467 currently selected, use either @code{info target} or @code{info files}
12468 (@pxref{Files, ,Commands to Specify Files}).
12470 @item help target @var{name}
12471 Describe a particular target, including any parameters necessary to
12474 @kindex set gnutarget
12475 @item set gnutarget @var{args}
12476 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12477 knows whether it is reading an @dfn{executable},
12478 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12479 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12480 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12483 @emph{Warning:} To specify a file format with @code{set gnutarget},
12484 you must know the actual BFD name.
12488 @xref{Files, , Commands to Specify Files}.
12490 @kindex show gnutarget
12491 @item show gnutarget
12492 Use the @code{show gnutarget} command to display what file format
12493 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12494 @value{GDBN} will determine the file format for each file automatically,
12495 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12498 @cindex common targets
12499 Here are some common targets (available, or not, depending on the GDB
12504 @item target exec @var{program}
12505 @cindex executable file target
12506 An executable file. @samp{target exec @var{program}} is the same as
12507 @samp{exec-file @var{program}}.
12509 @item target core @var{filename}
12510 @cindex core dump file target
12511 A core dump file. @samp{target core @var{filename}} is the same as
12512 @samp{core-file @var{filename}}.
12514 @item target remote @var{medium}
12515 @cindex remote target
12516 A remote system connected to @value{GDBN} via a serial line or network
12517 connection. This command tells @value{GDBN} to use its own remote
12518 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12520 For example, if you have a board connected to @file{/dev/ttya} on the
12521 machine running @value{GDBN}, you could say:
12524 target remote /dev/ttya
12527 @code{target remote} supports the @code{load} command. This is only
12528 useful if you have some other way of getting the stub to the target
12529 system, and you can put it somewhere in memory where it won't get
12530 clobbered by the download.
12533 @cindex built-in simulator target
12534 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12542 works; however, you cannot assume that a specific memory map, device
12543 drivers, or even basic I/O is available, although some simulators do
12544 provide these. For info about any processor-specific simulator details,
12545 see the appropriate section in @ref{Embedded Processors, ,Embedded
12550 Some configurations may include these targets as well:
12554 @item target nrom @var{dev}
12555 @cindex NetROM ROM emulator target
12556 NetROM ROM emulator. This target only supports downloading.
12560 Different targets are available on different configurations of @value{GDBN};
12561 your configuration may have more or fewer targets.
12563 Many remote targets require you to download the executable's code once
12564 you've successfully established a connection. You may wish to control
12565 various aspects of this process.
12570 @kindex set hash@r{, for remote monitors}
12571 @cindex hash mark while downloading
12572 This command controls whether a hash mark @samp{#} is displayed while
12573 downloading a file to the remote monitor. If on, a hash mark is
12574 displayed after each S-record is successfully downloaded to the
12578 @kindex show hash@r{, for remote monitors}
12579 Show the current status of displaying the hash mark.
12581 @item set debug monitor
12582 @kindex set debug monitor
12583 @cindex display remote monitor communications
12584 Enable or disable display of communications messages between
12585 @value{GDBN} and the remote monitor.
12587 @item show debug monitor
12588 @kindex show debug monitor
12589 Show the current status of displaying communications between
12590 @value{GDBN} and the remote monitor.
12595 @kindex load @var{filename}
12596 @item load @var{filename}
12597 Depending on what remote debugging facilities are configured into
12598 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12599 is meant to make @var{filename} (an executable) available for debugging
12600 on the remote system---by downloading, or dynamic linking, for example.
12601 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12602 the @code{add-symbol-file} command.
12604 If your @value{GDBN} does not have a @code{load} command, attempting to
12605 execute it gets the error message ``@code{You can't do that when your
12606 target is @dots{}}''
12608 The file is loaded at whatever address is specified in the executable.
12609 For some object file formats, you can specify the load address when you
12610 link the program; for other formats, like a.out, the object file format
12611 specifies a fixed address.
12612 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12614 Depending on the remote side capabilities, @value{GDBN} may be able to
12615 load programs into flash memory.
12617 @code{load} does not repeat if you press @key{RET} again after using it.
12621 @section Choosing Target Byte Order
12623 @cindex choosing target byte order
12624 @cindex target byte order
12626 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12627 offer the ability to run either big-endian or little-endian byte
12628 orders. Usually the executable or symbol will include a bit to
12629 designate the endian-ness, and you will not need to worry about
12630 which to use. However, you may still find it useful to adjust
12631 @value{GDBN}'s idea of processor endian-ness manually.
12635 @item set endian big
12636 Instruct @value{GDBN} to assume the target is big-endian.
12638 @item set endian little
12639 Instruct @value{GDBN} to assume the target is little-endian.
12641 @item set endian auto
12642 Instruct @value{GDBN} to use the byte order associated with the
12646 Display @value{GDBN}'s current idea of the target byte order.
12650 Note that these commands merely adjust interpretation of symbolic
12651 data on the host, and that they have absolutely no effect on the
12655 @node Remote Debugging
12656 @chapter Debugging Remote Programs
12657 @cindex remote debugging
12659 If you are trying to debug a program running on a machine that cannot run
12660 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12661 For example, you might use remote debugging on an operating system kernel,
12662 or on a small system which does not have a general purpose operating system
12663 powerful enough to run a full-featured debugger.
12665 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12666 to make this work with particular debugging targets. In addition,
12667 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12668 but not specific to any particular target system) which you can use if you
12669 write the remote stubs---the code that runs on the remote system to
12670 communicate with @value{GDBN}.
12672 Other remote targets may be available in your
12673 configuration of @value{GDBN}; use @code{help target} to list them.
12676 * Connecting:: Connecting to a remote target
12677 * File Transfer:: Sending files to a remote system
12678 * Server:: Using the gdbserver program
12679 * Remote Configuration:: Remote configuration
12680 * Remote Stub:: Implementing a remote stub
12684 @section Connecting to a Remote Target
12686 On the @value{GDBN} host machine, you will need an unstripped copy of
12687 your program, since @value{GDBN} needs symbol and debugging information.
12688 Start up @value{GDBN} as usual, using the name of the local copy of your
12689 program as the first argument.
12691 @cindex @code{target remote}
12692 @value{GDBN} can communicate with the target over a serial line, or
12693 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12694 each case, @value{GDBN} uses the same protocol for debugging your
12695 program; only the medium carrying the debugging packets varies. The
12696 @code{target remote} command establishes a connection to the target.
12697 Its arguments indicate which medium to use:
12701 @item target remote @var{serial-device}
12702 @cindex serial line, @code{target remote}
12703 Use @var{serial-device} to communicate with the target. For example,
12704 to use a serial line connected to the device named @file{/dev/ttyb}:
12707 target remote /dev/ttyb
12710 If you're using a serial line, you may want to give @value{GDBN} the
12711 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12712 (@pxref{Remote Configuration, set remotebaud}) before the
12713 @code{target} command.
12715 @item target remote @code{@var{host}:@var{port}}
12716 @itemx target remote @code{tcp:@var{host}:@var{port}}
12717 @cindex @acronym{TCP} port, @code{target remote}
12718 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12719 The @var{host} may be either a host name or a numeric @acronym{IP}
12720 address; @var{port} must be a decimal number. The @var{host} could be
12721 the target machine itself, if it is directly connected to the net, or
12722 it might be a terminal server which in turn has a serial line to the
12725 For example, to connect to port 2828 on a terminal server named
12729 target remote manyfarms:2828
12732 If your remote target is actually running on the same machine as your
12733 debugger session (e.g.@: a simulator for your target running on the
12734 same host), you can omit the hostname. For example, to connect to
12735 port 1234 on your local machine:
12738 target remote :1234
12742 Note that the colon is still required here.
12744 @item target remote @code{udp:@var{host}:@var{port}}
12745 @cindex @acronym{UDP} port, @code{target remote}
12746 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12747 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12750 target remote udp:manyfarms:2828
12753 When using a @acronym{UDP} connection for remote debugging, you should
12754 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12755 can silently drop packets on busy or unreliable networks, which will
12756 cause havoc with your debugging session.
12758 @item target remote | @var{command}
12759 @cindex pipe, @code{target remote} to
12760 Run @var{command} in the background and communicate with it using a
12761 pipe. The @var{command} is a shell command, to be parsed and expanded
12762 by the system's command shell, @code{/bin/sh}; it should expect remote
12763 protocol packets on its standard input, and send replies on its
12764 standard output. You could use this to run a stand-alone simulator
12765 that speaks the remote debugging protocol, to make net connections
12766 using programs like @code{ssh}, or for other similar tricks.
12768 If @var{command} closes its standard output (perhaps by exiting),
12769 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12770 program has already exited, this will have no effect.)
12774 Once the connection has been established, you can use all the usual
12775 commands to examine and change data and to step and continue the
12778 @cindex interrupting remote programs
12779 @cindex remote programs, interrupting
12780 Whenever @value{GDBN} is waiting for the remote program, if you type the
12781 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12782 program. This may or may not succeed, depending in part on the hardware
12783 and the serial drivers the remote system uses. If you type the
12784 interrupt character once again, @value{GDBN} displays this prompt:
12787 Interrupted while waiting for the program.
12788 Give up (and stop debugging it)? (y or n)
12791 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12792 (If you decide you want to try again later, you can use @samp{target
12793 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12794 goes back to waiting.
12797 @kindex detach (remote)
12799 When you have finished debugging the remote program, you can use the
12800 @code{detach} command to release it from @value{GDBN} control.
12801 Detaching from the target normally resumes its execution, but the results
12802 will depend on your particular remote stub. After the @code{detach}
12803 command, @value{GDBN} is free to connect to another target.
12807 The @code{disconnect} command behaves like @code{detach}, except that
12808 the target is generally not resumed. It will wait for @value{GDBN}
12809 (this instance or another one) to connect and continue debugging. After
12810 the @code{disconnect} command, @value{GDBN} is again free to connect to
12813 @cindex send command to remote monitor
12814 @cindex extend @value{GDBN} for remote targets
12815 @cindex add new commands for external monitor
12817 @item monitor @var{cmd}
12818 This command allows you to send arbitrary commands directly to the
12819 remote monitor. Since @value{GDBN} doesn't care about the commands it
12820 sends like this, this command is the way to extend @value{GDBN}---you
12821 can add new commands that only the external monitor will understand
12825 @node File Transfer
12826 @section Sending files to a remote system
12827 @cindex remote target, file transfer
12828 @cindex file transfer
12829 @cindex sending files to remote systems
12831 Some remote targets offer the ability to transfer files over the same
12832 connection used to communicate with @value{GDBN}. This is convenient
12833 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
12834 running @code{gdbserver} over a network interface. For other targets,
12835 e.g.@: embedded devices with only a single serial port, this may be
12836 the only way to upload or download files.
12838 Not all remote targets support these commands.
12842 @item remote put @var{hostfile} @var{targetfile}
12843 Copy file @var{hostfile} from the host system (the machine running
12844 @value{GDBN}) to @var{targetfile} on the target system.
12847 @item remote get @var{targetfile} @var{hostfile}
12848 Copy file @var{targetfile} from the target system to @var{hostfile}
12849 on the host system.
12851 @kindex remote delete
12852 @item remote delete @var{targetfile}
12853 Delete @var{targetfile} from the target system.
12858 @section Using the @code{gdbserver} Program
12861 @cindex remote connection without stubs
12862 @code{gdbserver} is a control program for Unix-like systems, which
12863 allows you to connect your program with a remote @value{GDBN} via
12864 @code{target remote}---but without linking in the usual debugging stub.
12866 @code{gdbserver} is not a complete replacement for the debugging stubs,
12867 because it requires essentially the same operating-system facilities
12868 that @value{GDBN} itself does. In fact, a system that can run
12869 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12870 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12871 because it is a much smaller program than @value{GDBN} itself. It is
12872 also easier to port than all of @value{GDBN}, so you may be able to get
12873 started more quickly on a new system by using @code{gdbserver}.
12874 Finally, if you develop code for real-time systems, you may find that
12875 the tradeoffs involved in real-time operation make it more convenient to
12876 do as much development work as possible on another system, for example
12877 by cross-compiling. You can use @code{gdbserver} to make a similar
12878 choice for debugging.
12880 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12881 or a TCP connection, using the standard @value{GDBN} remote serial
12885 @item On the target machine,
12886 you need to have a copy of the program you want to debug.
12887 @code{gdbserver} does not need your program's symbol table, so you can
12888 strip the program if necessary to save space. @value{GDBN} on the host
12889 system does all the symbol handling.
12891 To use the server, you must tell it how to communicate with @value{GDBN};
12892 the name of your program; and the arguments for your program. The usual
12896 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12899 @var{comm} is either a device name (to use a serial line) or a TCP
12900 hostname and portnumber. For example, to debug Emacs with the argument
12901 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12905 target> gdbserver /dev/com1 emacs foo.txt
12908 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12911 To use a TCP connection instead of a serial line:
12914 target> gdbserver host:2345 emacs foo.txt
12917 The only difference from the previous example is the first argument,
12918 specifying that you are communicating with the host @value{GDBN} via
12919 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12920 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12921 (Currently, the @samp{host} part is ignored.) You can choose any number
12922 you want for the port number as long as it does not conflict with any
12923 TCP ports already in use on the target system (for example, @code{23} is
12924 reserved for @code{telnet}).@footnote{If you choose a port number that
12925 conflicts with another service, @code{gdbserver} prints an error message
12926 and exits.} You must use the same port number with the host @value{GDBN}
12927 @code{target remote} command.
12929 On some targets, @code{gdbserver} can also attach to running programs.
12930 This is accomplished via the @code{--attach} argument. The syntax is:
12933 target> gdbserver @var{comm} --attach @var{pid}
12936 @var{pid} is the process ID of a currently running process. It isn't necessary
12937 to point @code{gdbserver} at a binary for the running process.
12940 @cindex attach to a program by name
12941 You can debug processes by name instead of process ID if your target has the
12942 @code{pidof} utility:
12945 target> gdbserver @var{comm} --attach `pidof @var{program}`
12948 In case more than one copy of @var{program} is running, or @var{program}
12949 has multiple threads, most versions of @code{pidof} support the
12950 @code{-s} option to only return the first process ID.
12952 @item On the host machine,
12953 first make sure you have the necessary symbol files. Load symbols for
12954 your application using the @code{file} command before you connect. Use
12955 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
12956 was compiled with the correct sysroot using @code{--with-system-root}).
12958 The symbol file and target libraries must exactly match the executable
12959 and libraries on the target, with one exception: the files on the host
12960 system should not be stripped, even if the files on the target system
12961 are. Mismatched or missing files will lead to confusing results
12962 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
12963 files may also prevent @code{gdbserver} from debugging multi-threaded
12966 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
12967 For TCP connections, you must start up @code{gdbserver} prior to using
12968 the @code{target remote} command. Otherwise you may get an error whose
12969 text depends on the host system, but which usually looks something like
12970 @samp{Connection refused}. You don't need to use the @code{load}
12971 command in @value{GDBN} when using @code{gdbserver}, since the program is
12972 already on the target.
12976 @subsection Monitor Commands for @code{gdbserver}
12977 @cindex monitor commands, for @code{gdbserver}
12979 During a @value{GDBN} session using @code{gdbserver}, you can use the
12980 @code{monitor} command to send special requests to @code{gdbserver}.
12981 Here are the available commands; they are only of interest when
12982 debugging @value{GDBN} or @code{gdbserver}.
12986 List the available monitor commands.
12988 @item monitor set debug 0
12989 @itemx monitor set debug 1
12990 Disable or enable general debugging messages.
12992 @item monitor set remote-debug 0
12993 @itemx monitor set remote-debug 1
12994 Disable or enable specific debugging messages associated with the remote
12995 protocol (@pxref{Remote Protocol}).
12999 @node Remote Configuration
13000 @section Remote Configuration
13003 @kindex show remote
13004 This section documents the configuration options available when
13005 debugging remote programs. For the options related to the File I/O
13006 extensions of the remote protocol, see @ref{system,
13007 system-call-allowed}.
13010 @item set remoteaddresssize @var{bits}
13011 @cindex address size for remote targets
13012 @cindex bits in remote address
13013 Set the maximum size of address in a memory packet to the specified
13014 number of bits. @value{GDBN} will mask off the address bits above
13015 that number, when it passes addresses to the remote target. The
13016 default value is the number of bits in the target's address.
13018 @item show remoteaddresssize
13019 Show the current value of remote address size in bits.
13021 @item set remotebaud @var{n}
13022 @cindex baud rate for remote targets
13023 Set the baud rate for the remote serial I/O to @var{n} baud. The
13024 value is used to set the speed of the serial port used for debugging
13027 @item show remotebaud
13028 Show the current speed of the remote connection.
13030 @item set remotebreak
13031 @cindex interrupt remote programs
13032 @cindex BREAK signal instead of Ctrl-C
13033 @anchor{set remotebreak}
13034 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13035 when you type @kbd{Ctrl-c} to interrupt the program running
13036 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13037 character instead. The default is off, since most remote systems
13038 expect to see @samp{Ctrl-C} as the interrupt signal.
13040 @item show remotebreak
13041 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13042 interrupt the remote program.
13044 @item set remoteflow on
13045 @itemx set remoteflow off
13046 @kindex set remoteflow
13047 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13048 on the serial port used to communicate to the remote target.
13050 @item show remoteflow
13051 @kindex show remoteflow
13052 Show the current setting of hardware flow control.
13054 @item set remotelogbase @var{base}
13055 Set the base (a.k.a.@: radix) of logging serial protocol
13056 communications to @var{base}. Supported values of @var{base} are:
13057 @code{ascii}, @code{octal}, and @code{hex}. The default is
13060 @item show remotelogbase
13061 Show the current setting of the radix for logging remote serial
13064 @item set remotelogfile @var{file}
13065 @cindex record serial communications on file
13066 Record remote serial communications on the named @var{file}. The
13067 default is not to record at all.
13069 @item show remotelogfile.
13070 Show the current setting of the file name on which to record the
13071 serial communications.
13073 @item set remotetimeout @var{num}
13074 @cindex timeout for serial communications
13075 @cindex remote timeout
13076 Set the timeout limit to wait for the remote target to respond to
13077 @var{num} seconds. The default is 2 seconds.
13079 @item show remotetimeout
13080 Show the current number of seconds to wait for the remote target
13083 @cindex limit hardware breakpoints and watchpoints
13084 @cindex remote target, limit break- and watchpoints
13085 @anchor{set remote hardware-watchpoint-limit}
13086 @anchor{set remote hardware-breakpoint-limit}
13087 @item set remote hardware-watchpoint-limit @var{limit}
13088 @itemx set remote hardware-breakpoint-limit @var{limit}
13089 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13090 watchpoints. A limit of -1, the default, is treated as unlimited.
13093 @cindex remote packets, enabling and disabling
13094 The @value{GDBN} remote protocol autodetects the packets supported by
13095 your debugging stub. If you need to override the autodetection, you
13096 can use these commands to enable or disable individual packets. Each
13097 packet can be set to @samp{on} (the remote target supports this
13098 packet), @samp{off} (the remote target does not support this packet),
13099 or @samp{auto} (detect remote target support for this packet). They
13100 all default to @samp{auto}. For more information about each packet,
13101 see @ref{Remote Protocol}.
13103 During normal use, you should not have to use any of these commands.
13104 If you do, that may be a bug in your remote debugging stub, or a bug
13105 in @value{GDBN}. You may want to report the problem to the
13106 @value{GDBN} developers.
13108 For each packet @var{name}, the command to enable or disable the
13109 packet is @code{set remote @var{name}-packet}. The available settings
13112 @multitable @columnfractions 0.28 0.32 0.25
13115 @tab Related Features
13117 @item @code{fetch-register}
13119 @tab @code{info registers}
13121 @item @code{set-register}
13125 @item @code{binary-download}
13127 @tab @code{load}, @code{set}
13129 @item @code{read-aux-vector}
13130 @tab @code{qXfer:auxv:read}
13131 @tab @code{info auxv}
13133 @item @code{symbol-lookup}
13134 @tab @code{qSymbol}
13135 @tab Detecting multiple threads
13137 @item @code{verbose-resume}
13139 @tab Stepping or resuming multiple threads
13141 @item @code{software-breakpoint}
13145 @item @code{hardware-breakpoint}
13149 @item @code{write-watchpoint}
13153 @item @code{read-watchpoint}
13157 @item @code{access-watchpoint}
13161 @item @code{target-features}
13162 @tab @code{qXfer:features:read}
13163 @tab @code{set architecture}
13165 @item @code{library-info}
13166 @tab @code{qXfer:libraries:read}
13167 @tab @code{info sharedlibrary}
13169 @item @code{memory-map}
13170 @tab @code{qXfer:memory-map:read}
13171 @tab @code{info mem}
13173 @item @code{read-spu-object}
13174 @tab @code{qXfer:spu:read}
13175 @tab @code{info spu}
13177 @item @code{write-spu-object}
13178 @tab @code{qXfer:spu:write}
13179 @tab @code{info spu}
13181 @item @code{get-thread-local-@*storage-address}
13182 @tab @code{qGetTLSAddr}
13183 @tab Displaying @code{__thread} variables
13185 @item @code{supported-packets}
13186 @tab @code{qSupported}
13187 @tab Remote communications parameters
13189 @item @code{pass-signals}
13190 @tab @code{QPassSignals}
13191 @tab @code{handle @var{signal}}
13193 @item @code{hostio-close-packet}
13194 @tab @code{vFile:close}
13195 @tab @code{remote get}, @code{remote put}
13197 @item @code{hostio-open-packet}
13198 @tab @code{vFile:open}
13199 @tab @code{remote get}, @code{remote put}
13201 @item @code{hostio-pread-packet}
13202 @tab @code{vFile:pread}
13203 @tab @code{remote get}, @code{remote put}
13205 @item @code{hostio-pwrite-packet}
13206 @tab @code{vFile:pwrite}
13207 @tab @code{remote get}, @code{remote put}
13209 @item @code{hostio-unlink-packet}
13210 @tab @code{vFile:unlink}
13211 @tab @code{remote delete}
13215 @section Implementing a Remote Stub
13217 @cindex debugging stub, example
13218 @cindex remote stub, example
13219 @cindex stub example, remote debugging
13220 The stub files provided with @value{GDBN} implement the target side of the
13221 communication protocol, and the @value{GDBN} side is implemented in the
13222 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13223 these subroutines to communicate, and ignore the details. (If you're
13224 implementing your own stub file, you can still ignore the details: start
13225 with one of the existing stub files. @file{sparc-stub.c} is the best
13226 organized, and therefore the easiest to read.)
13228 @cindex remote serial debugging, overview
13229 To debug a program running on another machine (the debugging
13230 @dfn{target} machine), you must first arrange for all the usual
13231 prerequisites for the program to run by itself. For example, for a C
13236 A startup routine to set up the C runtime environment; these usually
13237 have a name like @file{crt0}. The startup routine may be supplied by
13238 your hardware supplier, or you may have to write your own.
13241 A C subroutine library to support your program's
13242 subroutine calls, notably managing input and output.
13245 A way of getting your program to the other machine---for example, a
13246 download program. These are often supplied by the hardware
13247 manufacturer, but you may have to write your own from hardware
13251 The next step is to arrange for your program to use a serial port to
13252 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13253 machine). In general terms, the scheme looks like this:
13257 @value{GDBN} already understands how to use this protocol; when everything
13258 else is set up, you can simply use the @samp{target remote} command
13259 (@pxref{Targets,,Specifying a Debugging Target}).
13261 @item On the target,
13262 you must link with your program a few special-purpose subroutines that
13263 implement the @value{GDBN} remote serial protocol. The file containing these
13264 subroutines is called a @dfn{debugging stub}.
13266 On certain remote targets, you can use an auxiliary program
13267 @code{gdbserver} instead of linking a stub into your program.
13268 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13271 The debugging stub is specific to the architecture of the remote
13272 machine; for example, use @file{sparc-stub.c} to debug programs on
13275 @cindex remote serial stub list
13276 These working remote stubs are distributed with @value{GDBN}:
13281 @cindex @file{i386-stub.c}
13284 For Intel 386 and compatible architectures.
13287 @cindex @file{m68k-stub.c}
13288 @cindex Motorola 680x0
13290 For Motorola 680x0 architectures.
13293 @cindex @file{sh-stub.c}
13296 For Renesas SH architectures.
13299 @cindex @file{sparc-stub.c}
13301 For @sc{sparc} architectures.
13303 @item sparcl-stub.c
13304 @cindex @file{sparcl-stub.c}
13307 For Fujitsu @sc{sparclite} architectures.
13311 The @file{README} file in the @value{GDBN} distribution may list other
13312 recently added stubs.
13315 * Stub Contents:: What the stub can do for you
13316 * Bootstrapping:: What you must do for the stub
13317 * Debug Session:: Putting it all together
13320 @node Stub Contents
13321 @subsection What the Stub Can Do for You
13323 @cindex remote serial stub
13324 The debugging stub for your architecture supplies these three
13328 @item set_debug_traps
13329 @findex set_debug_traps
13330 @cindex remote serial stub, initialization
13331 This routine arranges for @code{handle_exception} to run when your
13332 program stops. You must call this subroutine explicitly near the
13333 beginning of your program.
13335 @item handle_exception
13336 @findex handle_exception
13337 @cindex remote serial stub, main routine
13338 This is the central workhorse, but your program never calls it
13339 explicitly---the setup code arranges for @code{handle_exception} to
13340 run when a trap is triggered.
13342 @code{handle_exception} takes control when your program stops during
13343 execution (for example, on a breakpoint), and mediates communications
13344 with @value{GDBN} on the host machine. This is where the communications
13345 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13346 representative on the target machine. It begins by sending summary
13347 information on the state of your program, then continues to execute,
13348 retrieving and transmitting any information @value{GDBN} needs, until you
13349 execute a @value{GDBN} command that makes your program resume; at that point,
13350 @code{handle_exception} returns control to your own code on the target
13354 @cindex @code{breakpoint} subroutine, remote
13355 Use this auxiliary subroutine to make your program contain a
13356 breakpoint. Depending on the particular situation, this may be the only
13357 way for @value{GDBN} to get control. For instance, if your target
13358 machine has some sort of interrupt button, you won't need to call this;
13359 pressing the interrupt button transfers control to
13360 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13361 simply receiving characters on the serial port may also trigger a trap;
13362 again, in that situation, you don't need to call @code{breakpoint} from
13363 your own program---simply running @samp{target remote} from the host
13364 @value{GDBN} session gets control.
13366 Call @code{breakpoint} if none of these is true, or if you simply want
13367 to make certain your program stops at a predetermined point for the
13368 start of your debugging session.
13371 @node Bootstrapping
13372 @subsection What You Must Do for the Stub
13374 @cindex remote stub, support routines
13375 The debugging stubs that come with @value{GDBN} are set up for a particular
13376 chip architecture, but they have no information about the rest of your
13377 debugging target machine.
13379 First of all you need to tell the stub how to communicate with the
13383 @item int getDebugChar()
13384 @findex getDebugChar
13385 Write this subroutine to read a single character from the serial port.
13386 It may be identical to @code{getchar} for your target system; a
13387 different name is used to allow you to distinguish the two if you wish.
13389 @item void putDebugChar(int)
13390 @findex putDebugChar
13391 Write this subroutine to write a single character to the serial port.
13392 It may be identical to @code{putchar} for your target system; a
13393 different name is used to allow you to distinguish the two if you wish.
13396 @cindex control C, and remote debugging
13397 @cindex interrupting remote targets
13398 If you want @value{GDBN} to be able to stop your program while it is
13399 running, you need to use an interrupt-driven serial driver, and arrange
13400 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13401 character). That is the character which @value{GDBN} uses to tell the
13402 remote system to stop.
13404 Getting the debugging target to return the proper status to @value{GDBN}
13405 probably requires changes to the standard stub; one quick and dirty way
13406 is to just execute a breakpoint instruction (the ``dirty'' part is that
13407 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13409 Other routines you need to supply are:
13412 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13413 @findex exceptionHandler
13414 Write this function to install @var{exception_address} in the exception
13415 handling tables. You need to do this because the stub does not have any
13416 way of knowing what the exception handling tables on your target system
13417 are like (for example, the processor's table might be in @sc{rom},
13418 containing entries which point to a table in @sc{ram}).
13419 @var{exception_number} is the exception number which should be changed;
13420 its meaning is architecture-dependent (for example, different numbers
13421 might represent divide by zero, misaligned access, etc). When this
13422 exception occurs, control should be transferred directly to
13423 @var{exception_address}, and the processor state (stack, registers,
13424 and so on) should be just as it is when a processor exception occurs. So if
13425 you want to use a jump instruction to reach @var{exception_address}, it
13426 should be a simple jump, not a jump to subroutine.
13428 For the 386, @var{exception_address} should be installed as an interrupt
13429 gate so that interrupts are masked while the handler runs. The gate
13430 should be at privilege level 0 (the most privileged level). The
13431 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13432 help from @code{exceptionHandler}.
13434 @item void flush_i_cache()
13435 @findex flush_i_cache
13436 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13437 instruction cache, if any, on your target machine. If there is no
13438 instruction cache, this subroutine may be a no-op.
13440 On target machines that have instruction caches, @value{GDBN} requires this
13441 function to make certain that the state of your program is stable.
13445 You must also make sure this library routine is available:
13448 @item void *memset(void *, int, int)
13450 This is the standard library function @code{memset} that sets an area of
13451 memory to a known value. If you have one of the free versions of
13452 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13453 either obtain it from your hardware manufacturer, or write your own.
13456 If you do not use the GNU C compiler, you may need other standard
13457 library subroutines as well; this varies from one stub to another,
13458 but in general the stubs are likely to use any of the common library
13459 subroutines which @code{@value{NGCC}} generates as inline code.
13462 @node Debug Session
13463 @subsection Putting it All Together
13465 @cindex remote serial debugging summary
13466 In summary, when your program is ready to debug, you must follow these
13471 Make sure you have defined the supporting low-level routines
13472 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13474 @code{getDebugChar}, @code{putDebugChar},
13475 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13479 Insert these lines near the top of your program:
13487 For the 680x0 stub only, you need to provide a variable called
13488 @code{exceptionHook}. Normally you just use:
13491 void (*exceptionHook)() = 0;
13495 but if before calling @code{set_debug_traps}, you set it to point to a
13496 function in your program, that function is called when
13497 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13498 error). The function indicated by @code{exceptionHook} is called with
13499 one parameter: an @code{int} which is the exception number.
13502 Compile and link together: your program, the @value{GDBN} debugging stub for
13503 your target architecture, and the supporting subroutines.
13506 Make sure you have a serial connection between your target machine and
13507 the @value{GDBN} host, and identify the serial port on the host.
13510 @c The "remote" target now provides a `load' command, so we should
13511 @c document that. FIXME.
13512 Download your program to your target machine (or get it there by
13513 whatever means the manufacturer provides), and start it.
13516 Start @value{GDBN} on the host, and connect to the target
13517 (@pxref{Connecting,,Connecting to a Remote Target}).
13521 @node Configurations
13522 @chapter Configuration-Specific Information
13524 While nearly all @value{GDBN} commands are available for all native and
13525 cross versions of the debugger, there are some exceptions. This chapter
13526 describes things that are only available in certain configurations.
13528 There are three major categories of configurations: native
13529 configurations, where the host and target are the same, embedded
13530 operating system configurations, which are usually the same for several
13531 different processor architectures, and bare embedded processors, which
13532 are quite different from each other.
13537 * Embedded Processors::
13544 This section describes details specific to particular native
13549 * BSD libkvm Interface:: Debugging BSD kernel memory images
13550 * SVR4 Process Information:: SVR4 process information
13551 * DJGPP Native:: Features specific to the DJGPP port
13552 * Cygwin Native:: Features specific to the Cygwin port
13553 * Hurd Native:: Features specific to @sc{gnu} Hurd
13554 * Neutrino:: Features specific to QNX Neutrino
13560 On HP-UX systems, if you refer to a function or variable name that
13561 begins with a dollar sign, @value{GDBN} searches for a user or system
13562 name first, before it searches for a convenience variable.
13565 @node BSD libkvm Interface
13566 @subsection BSD libkvm Interface
13569 @cindex kernel memory image
13570 @cindex kernel crash dump
13572 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13573 interface that provides a uniform interface for accessing kernel virtual
13574 memory images, including live systems and crash dumps. @value{GDBN}
13575 uses this interface to allow you to debug live kernels and kernel crash
13576 dumps on many native BSD configurations. This is implemented as a
13577 special @code{kvm} debugging target. For debugging a live system, load
13578 the currently running kernel into @value{GDBN} and connect to the
13582 (@value{GDBP}) @b{target kvm}
13585 For debugging crash dumps, provide the file name of the crash dump as an
13589 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13592 Once connected to the @code{kvm} target, the following commands are
13598 Set current context from the @dfn{Process Control Block} (PCB) address.
13601 Set current context from proc address. This command isn't available on
13602 modern FreeBSD systems.
13605 @node SVR4 Process Information
13606 @subsection SVR4 Process Information
13608 @cindex examine process image
13609 @cindex process info via @file{/proc}
13611 Many versions of SVR4 and compatible systems provide a facility called
13612 @samp{/proc} that can be used to examine the image of a running
13613 process using file-system subroutines. If @value{GDBN} is configured
13614 for an operating system with this facility, the command @code{info
13615 proc} is available to report information about the process running
13616 your program, or about any process running on your system. @code{info
13617 proc} works only on SVR4 systems that include the @code{procfs} code.
13618 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13619 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13625 @itemx info proc @var{process-id}
13626 Summarize available information about any running process. If a
13627 process ID is specified by @var{process-id}, display information about
13628 that process; otherwise display information about the program being
13629 debugged. The summary includes the debugged process ID, the command
13630 line used to invoke it, its current working directory, and its
13631 executable file's absolute file name.
13633 On some systems, @var{process-id} can be of the form
13634 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13635 within a process. If the optional @var{pid} part is missing, it means
13636 a thread from the process being debugged (the leading @samp{/} still
13637 needs to be present, or else @value{GDBN} will interpret the number as
13638 a process ID rather than a thread ID).
13640 @item info proc mappings
13641 @cindex memory address space mappings
13642 Report the memory address space ranges accessible in the program, with
13643 information on whether the process has read, write, or execute access
13644 rights to each range. On @sc{gnu}/Linux systems, each memory range
13645 includes the object file which is mapped to that range, instead of the
13646 memory access rights to that range.
13648 @item info proc stat
13649 @itemx info proc status
13650 @cindex process detailed status information
13651 These subcommands are specific to @sc{gnu}/Linux systems. They show
13652 the process-related information, including the user ID and group ID;
13653 how many threads are there in the process; its virtual memory usage;
13654 the signals that are pending, blocked, and ignored; its TTY; its
13655 consumption of system and user time; its stack size; its @samp{nice}
13656 value; etc. For more information, see the @samp{proc} man page
13657 (type @kbd{man 5 proc} from your shell prompt).
13659 @item info proc all
13660 Show all the information about the process described under all of the
13661 above @code{info proc} subcommands.
13664 @comment These sub-options of 'info proc' were not included when
13665 @comment procfs.c was re-written. Keep their descriptions around
13666 @comment against the day when someone finds the time to put them back in.
13667 @kindex info proc times
13668 @item info proc times
13669 Starting time, user CPU time, and system CPU time for your program and
13672 @kindex info proc id
13674 Report on the process IDs related to your program: its own process ID,
13675 the ID of its parent, the process group ID, and the session ID.
13678 @item set procfs-trace
13679 @kindex set procfs-trace
13680 @cindex @code{procfs} API calls
13681 This command enables and disables tracing of @code{procfs} API calls.
13683 @item show procfs-trace
13684 @kindex show procfs-trace
13685 Show the current state of @code{procfs} API call tracing.
13687 @item set procfs-file @var{file}
13688 @kindex set procfs-file
13689 Tell @value{GDBN} to write @code{procfs} API trace to the named
13690 @var{file}. @value{GDBN} appends the trace info to the previous
13691 contents of the file. The default is to display the trace on the
13694 @item show procfs-file
13695 @kindex show procfs-file
13696 Show the file to which @code{procfs} API trace is written.
13698 @item proc-trace-entry
13699 @itemx proc-trace-exit
13700 @itemx proc-untrace-entry
13701 @itemx proc-untrace-exit
13702 @kindex proc-trace-entry
13703 @kindex proc-trace-exit
13704 @kindex proc-untrace-entry
13705 @kindex proc-untrace-exit
13706 These commands enable and disable tracing of entries into and exits
13707 from the @code{syscall} interface.
13710 @kindex info pidlist
13711 @cindex process list, QNX Neutrino
13712 For QNX Neutrino only, this command displays the list of all the
13713 processes and all the threads within each process.
13716 @kindex info meminfo
13717 @cindex mapinfo list, QNX Neutrino
13718 For QNX Neutrino only, this command displays the list of all mapinfos.
13722 @subsection Features for Debugging @sc{djgpp} Programs
13723 @cindex @sc{djgpp} debugging
13724 @cindex native @sc{djgpp} debugging
13725 @cindex MS-DOS-specific commands
13728 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13729 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13730 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13731 top of real-mode DOS systems and their emulations.
13733 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13734 defines a few commands specific to the @sc{djgpp} port. This
13735 subsection describes those commands.
13740 This is a prefix of @sc{djgpp}-specific commands which print
13741 information about the target system and important OS structures.
13744 @cindex MS-DOS system info
13745 @cindex free memory information (MS-DOS)
13746 @item info dos sysinfo
13747 This command displays assorted information about the underlying
13748 platform: the CPU type and features, the OS version and flavor, the
13749 DPMI version, and the available conventional and DPMI memory.
13754 @cindex segment descriptor tables
13755 @cindex descriptor tables display
13757 @itemx info dos ldt
13758 @itemx info dos idt
13759 These 3 commands display entries from, respectively, Global, Local,
13760 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13761 tables are data structures which store a descriptor for each segment
13762 that is currently in use. The segment's selector is an index into a
13763 descriptor table; the table entry for that index holds the
13764 descriptor's base address and limit, and its attributes and access
13767 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13768 segment (used for both data and the stack), and a DOS segment (which
13769 allows access to DOS/BIOS data structures and absolute addresses in
13770 conventional memory). However, the DPMI host will usually define
13771 additional segments in order to support the DPMI environment.
13773 @cindex garbled pointers
13774 These commands allow to display entries from the descriptor tables.
13775 Without an argument, all entries from the specified table are
13776 displayed. An argument, which should be an integer expression, means
13777 display a single entry whose index is given by the argument. For
13778 example, here's a convenient way to display information about the
13779 debugged program's data segment:
13782 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13783 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13787 This comes in handy when you want to see whether a pointer is outside
13788 the data segment's limit (i.e.@: @dfn{garbled}).
13790 @cindex page tables display (MS-DOS)
13792 @itemx info dos pte
13793 These two commands display entries from, respectively, the Page
13794 Directory and the Page Tables. Page Directories and Page Tables are
13795 data structures which control how virtual memory addresses are mapped
13796 into physical addresses. A Page Table includes an entry for every
13797 page of memory that is mapped into the program's address space; there
13798 may be several Page Tables, each one holding up to 4096 entries. A
13799 Page Directory has up to 4096 entries, one each for every Page Table
13800 that is currently in use.
13802 Without an argument, @kbd{info dos pde} displays the entire Page
13803 Directory, and @kbd{info dos pte} displays all the entries in all of
13804 the Page Tables. An argument, an integer expression, given to the
13805 @kbd{info dos pde} command means display only that entry from the Page
13806 Directory table. An argument given to the @kbd{info dos pte} command
13807 means display entries from a single Page Table, the one pointed to by
13808 the specified entry in the Page Directory.
13810 @cindex direct memory access (DMA) on MS-DOS
13811 These commands are useful when your program uses @dfn{DMA} (Direct
13812 Memory Access), which needs physical addresses to program the DMA
13815 These commands are supported only with some DPMI servers.
13817 @cindex physical address from linear address
13818 @item info dos address-pte @var{addr}
13819 This command displays the Page Table entry for a specified linear
13820 address. The argument @var{addr} is a linear address which should
13821 already have the appropriate segment's base address added to it,
13822 because this command accepts addresses which may belong to @emph{any}
13823 segment. For example, here's how to display the Page Table entry for
13824 the page where a variable @code{i} is stored:
13827 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13828 @exdent @code{Page Table entry for address 0x11a00d30:}
13829 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13833 This says that @code{i} is stored at offset @code{0xd30} from the page
13834 whose physical base address is @code{0x02698000}, and shows all the
13835 attributes of that page.
13837 Note that you must cast the addresses of variables to a @code{char *},
13838 since otherwise the value of @code{__djgpp_base_address}, the base
13839 address of all variables and functions in a @sc{djgpp} program, will
13840 be added using the rules of C pointer arithmetics: if @code{i} is
13841 declared an @code{int}, @value{GDBN} will add 4 times the value of
13842 @code{__djgpp_base_address} to the address of @code{i}.
13844 Here's another example, it displays the Page Table entry for the
13848 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13849 @exdent @code{Page Table entry for address 0x29110:}
13850 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13854 (The @code{+ 3} offset is because the transfer buffer's address is the
13855 3rd member of the @code{_go32_info_block} structure.) The output
13856 clearly shows that this DPMI server maps the addresses in conventional
13857 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13858 linear (@code{0x29110}) addresses are identical.
13860 This command is supported only with some DPMI servers.
13863 @cindex DOS serial data link, remote debugging
13864 In addition to native debugging, the DJGPP port supports remote
13865 debugging via a serial data link. The following commands are specific
13866 to remote serial debugging in the DJGPP port of @value{GDBN}.
13869 @kindex set com1base
13870 @kindex set com1irq
13871 @kindex set com2base
13872 @kindex set com2irq
13873 @kindex set com3base
13874 @kindex set com3irq
13875 @kindex set com4base
13876 @kindex set com4irq
13877 @item set com1base @var{addr}
13878 This command sets the base I/O port address of the @file{COM1} serial
13881 @item set com1irq @var{irq}
13882 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13883 for the @file{COM1} serial port.
13885 There are similar commands @samp{set com2base}, @samp{set com3irq},
13886 etc.@: for setting the port address and the @code{IRQ} lines for the
13889 @kindex show com1base
13890 @kindex show com1irq
13891 @kindex show com2base
13892 @kindex show com2irq
13893 @kindex show com3base
13894 @kindex show com3irq
13895 @kindex show com4base
13896 @kindex show com4irq
13897 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13898 display the current settings of the base address and the @code{IRQ}
13899 lines used by the COM ports.
13902 @kindex info serial
13903 @cindex DOS serial port status
13904 This command prints the status of the 4 DOS serial ports. For each
13905 port, it prints whether it's active or not, its I/O base address and
13906 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13907 counts of various errors encountered so far.
13911 @node Cygwin Native
13912 @subsection Features for Debugging MS Windows PE Executables
13913 @cindex MS Windows debugging
13914 @cindex native Cygwin debugging
13915 @cindex Cygwin-specific commands
13917 @value{GDBN} supports native debugging of MS Windows programs, including
13918 DLLs with and without symbolic debugging information. There are various
13919 additional Cygwin-specific commands, described in this section.
13920 Working with DLLs that have no debugging symbols is described in
13921 @ref{Non-debug DLL Symbols}.
13926 This is a prefix of MS Windows-specific commands which print
13927 information about the target system and important OS structures.
13929 @item info w32 selector
13930 This command displays information returned by
13931 the Win32 API @code{GetThreadSelectorEntry} function.
13932 It takes an optional argument that is evaluated to
13933 a long value to give the information about this given selector.
13934 Without argument, this command displays information
13935 about the six segment registers.
13939 This is a Cygwin-specific alias of @code{info shared}.
13941 @kindex dll-symbols
13943 This command loads symbols from a dll similarly to
13944 add-sym command but without the need to specify a base address.
13946 @kindex set cygwin-exceptions
13947 @cindex debugging the Cygwin DLL
13948 @cindex Cygwin DLL, debugging
13949 @item set cygwin-exceptions @var{mode}
13950 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13951 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13952 @value{GDBN} will delay recognition of exceptions, and may ignore some
13953 exceptions which seem to be caused by internal Cygwin DLL
13954 ``bookkeeping''. This option is meant primarily for debugging the
13955 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13956 @value{GDBN} users with false @code{SIGSEGV} signals.
13958 @kindex show cygwin-exceptions
13959 @item show cygwin-exceptions
13960 Displays whether @value{GDBN} will break on exceptions that happen
13961 inside the Cygwin DLL itself.
13963 @kindex set new-console
13964 @item set new-console @var{mode}
13965 If @var{mode} is @code{on} the debuggee will
13966 be started in a new console on next start.
13967 If @var{mode} is @code{off}i, the debuggee will
13968 be started in the same console as the debugger.
13970 @kindex show new-console
13971 @item show new-console
13972 Displays whether a new console is used
13973 when the debuggee is started.
13975 @kindex set new-group
13976 @item set new-group @var{mode}
13977 This boolean value controls whether the debuggee should
13978 start a new group or stay in the same group as the debugger.
13979 This affects the way the Windows OS handles
13982 @kindex show new-group
13983 @item show new-group
13984 Displays current value of new-group boolean.
13986 @kindex set debugevents
13987 @item set debugevents
13988 This boolean value adds debug output concerning kernel events related
13989 to the debuggee seen by the debugger. This includes events that
13990 signal thread and process creation and exit, DLL loading and
13991 unloading, console interrupts, and debugging messages produced by the
13992 Windows @code{OutputDebugString} API call.
13994 @kindex set debugexec
13995 @item set debugexec
13996 This boolean value adds debug output concerning execute events
13997 (such as resume thread) seen by the debugger.
13999 @kindex set debugexceptions
14000 @item set debugexceptions
14001 This boolean value adds debug output concerning exceptions in the
14002 debuggee seen by the debugger.
14004 @kindex set debugmemory
14005 @item set debugmemory
14006 This boolean value adds debug output concerning debuggee memory reads
14007 and writes by the debugger.
14011 This boolean values specifies whether the debuggee is called
14012 via a shell or directly (default value is on).
14016 Displays if the debuggee will be started with a shell.
14021 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14024 @node Non-debug DLL Symbols
14025 @subsubsection Support for DLLs without Debugging Symbols
14026 @cindex DLLs with no debugging symbols
14027 @cindex Minimal symbols and DLLs
14029 Very often on windows, some of the DLLs that your program relies on do
14030 not include symbolic debugging information (for example,
14031 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14032 symbols in a DLL, it relies on the minimal amount of symbolic
14033 information contained in the DLL's export table. This section
14034 describes working with such symbols, known internally to @value{GDBN} as
14035 ``minimal symbols''.
14037 Note that before the debugged program has started execution, no DLLs
14038 will have been loaded. The easiest way around this problem is simply to
14039 start the program --- either by setting a breakpoint or letting the
14040 program run once to completion. It is also possible to force
14041 @value{GDBN} to load a particular DLL before starting the executable ---
14042 see the shared library information in @ref{Files}, or the
14043 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14044 explicitly loading symbols from a DLL with no debugging information will
14045 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14046 which may adversely affect symbol lookup performance.
14048 @subsubsection DLL Name Prefixes
14050 In keeping with the naming conventions used by the Microsoft debugging
14051 tools, DLL export symbols are made available with a prefix based on the
14052 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14053 also entered into the symbol table, so @code{CreateFileA} is often
14054 sufficient. In some cases there will be name clashes within a program
14055 (particularly if the executable itself includes full debugging symbols)
14056 necessitating the use of the fully qualified name when referring to the
14057 contents of the DLL. Use single-quotes around the name to avoid the
14058 exclamation mark (``!'') being interpreted as a language operator.
14060 Note that the internal name of the DLL may be all upper-case, even
14061 though the file name of the DLL is lower-case, or vice-versa. Since
14062 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14063 some confusion. If in doubt, try the @code{info functions} and
14064 @code{info variables} commands or even @code{maint print msymbols}
14065 (@pxref{Symbols}). Here's an example:
14068 (@value{GDBP}) info function CreateFileA
14069 All functions matching regular expression "CreateFileA":
14071 Non-debugging symbols:
14072 0x77e885f4 CreateFileA
14073 0x77e885f4 KERNEL32!CreateFileA
14077 (@value{GDBP}) info function !
14078 All functions matching regular expression "!":
14080 Non-debugging symbols:
14081 0x6100114c cygwin1!__assert
14082 0x61004034 cygwin1!_dll_crt0@@0
14083 0x61004240 cygwin1!dll_crt0(per_process *)
14087 @subsubsection Working with Minimal Symbols
14089 Symbols extracted from a DLL's export table do not contain very much
14090 type information. All that @value{GDBN} can do is guess whether a symbol
14091 refers to a function or variable depending on the linker section that
14092 contains the symbol. Also note that the actual contents of the memory
14093 contained in a DLL are not available unless the program is running. This
14094 means that you cannot examine the contents of a variable or disassemble
14095 a function within a DLL without a running program.
14097 Variables are generally treated as pointers and dereferenced
14098 automatically. For this reason, it is often necessary to prefix a
14099 variable name with the address-of operator (``&'') and provide explicit
14100 type information in the command. Here's an example of the type of
14104 (@value{GDBP}) print 'cygwin1!__argv'
14109 (@value{GDBP}) x 'cygwin1!__argv'
14110 0x10021610: "\230y\""
14113 And two possible solutions:
14116 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14117 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14121 (@value{GDBP}) x/2x &'cygwin1!__argv'
14122 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14123 (@value{GDBP}) x/x 0x10021608
14124 0x10021608: 0x0022fd98
14125 (@value{GDBP}) x/s 0x0022fd98
14126 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14129 Setting a break point within a DLL is possible even before the program
14130 starts execution. However, under these circumstances, @value{GDBN} can't
14131 examine the initial instructions of the function in order to skip the
14132 function's frame set-up code. You can work around this by using ``*&''
14133 to set the breakpoint at a raw memory address:
14136 (@value{GDBP}) break *&'python22!PyOS_Readline'
14137 Breakpoint 1 at 0x1e04eff0
14140 The author of these extensions is not entirely convinced that setting a
14141 break point within a shared DLL like @file{kernel32.dll} is completely
14145 @subsection Commands Specific to @sc{gnu} Hurd Systems
14146 @cindex @sc{gnu} Hurd debugging
14148 This subsection describes @value{GDBN} commands specific to the
14149 @sc{gnu} Hurd native debugging.
14154 @kindex set signals@r{, Hurd command}
14155 @kindex set sigs@r{, Hurd command}
14156 This command toggles the state of inferior signal interception by
14157 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14158 affected by this command. @code{sigs} is a shorthand alias for
14163 @kindex show signals@r{, Hurd command}
14164 @kindex show sigs@r{, Hurd command}
14165 Show the current state of intercepting inferior's signals.
14167 @item set signal-thread
14168 @itemx set sigthread
14169 @kindex set signal-thread
14170 @kindex set sigthread
14171 This command tells @value{GDBN} which thread is the @code{libc} signal
14172 thread. That thread is run when a signal is delivered to a running
14173 process. @code{set sigthread} is the shorthand alias of @code{set
14176 @item show signal-thread
14177 @itemx show sigthread
14178 @kindex show signal-thread
14179 @kindex show sigthread
14180 These two commands show which thread will run when the inferior is
14181 delivered a signal.
14184 @kindex set stopped@r{, Hurd command}
14185 This commands tells @value{GDBN} that the inferior process is stopped,
14186 as with the @code{SIGSTOP} signal. The stopped process can be
14187 continued by delivering a signal to it.
14190 @kindex show stopped@r{, Hurd command}
14191 This command shows whether @value{GDBN} thinks the debuggee is
14194 @item set exceptions
14195 @kindex set exceptions@r{, Hurd command}
14196 Use this command to turn off trapping of exceptions in the inferior.
14197 When exception trapping is off, neither breakpoints nor
14198 single-stepping will work. To restore the default, set exception
14201 @item show exceptions
14202 @kindex show exceptions@r{, Hurd command}
14203 Show the current state of trapping exceptions in the inferior.
14205 @item set task pause
14206 @kindex set task@r{, Hurd commands}
14207 @cindex task attributes (@sc{gnu} Hurd)
14208 @cindex pause current task (@sc{gnu} Hurd)
14209 This command toggles task suspension when @value{GDBN} has control.
14210 Setting it to on takes effect immediately, and the task is suspended
14211 whenever @value{GDBN} gets control. Setting it to off will take
14212 effect the next time the inferior is continued. If this option is set
14213 to off, you can use @code{set thread default pause on} or @code{set
14214 thread pause on} (see below) to pause individual threads.
14216 @item show task pause
14217 @kindex show task@r{, Hurd commands}
14218 Show the current state of task suspension.
14220 @item set task detach-suspend-count
14221 @cindex task suspend count
14222 @cindex detach from task, @sc{gnu} Hurd
14223 This command sets the suspend count the task will be left with when
14224 @value{GDBN} detaches from it.
14226 @item show task detach-suspend-count
14227 Show the suspend count the task will be left with when detaching.
14229 @item set task exception-port
14230 @itemx set task excp
14231 @cindex task exception port, @sc{gnu} Hurd
14232 This command sets the task exception port to which @value{GDBN} will
14233 forward exceptions. The argument should be the value of the @dfn{send
14234 rights} of the task. @code{set task excp} is a shorthand alias.
14236 @item set noninvasive
14237 @cindex noninvasive task options
14238 This command switches @value{GDBN} to a mode that is the least
14239 invasive as far as interfering with the inferior is concerned. This
14240 is the same as using @code{set task pause}, @code{set exceptions}, and
14241 @code{set signals} to values opposite to the defaults.
14243 @item info send-rights
14244 @itemx info receive-rights
14245 @itemx info port-rights
14246 @itemx info port-sets
14247 @itemx info dead-names
14250 @cindex send rights, @sc{gnu} Hurd
14251 @cindex receive rights, @sc{gnu} Hurd
14252 @cindex port rights, @sc{gnu} Hurd
14253 @cindex port sets, @sc{gnu} Hurd
14254 @cindex dead names, @sc{gnu} Hurd
14255 These commands display information about, respectively, send rights,
14256 receive rights, port rights, port sets, and dead names of a task.
14257 There are also shorthand aliases: @code{info ports} for @code{info
14258 port-rights} and @code{info psets} for @code{info port-sets}.
14260 @item set thread pause
14261 @kindex set thread@r{, Hurd command}
14262 @cindex thread properties, @sc{gnu} Hurd
14263 @cindex pause current thread (@sc{gnu} Hurd)
14264 This command toggles current thread suspension when @value{GDBN} has
14265 control. Setting it to on takes effect immediately, and the current
14266 thread is suspended whenever @value{GDBN} gets control. Setting it to
14267 off will take effect the next time the inferior is continued.
14268 Normally, this command has no effect, since when @value{GDBN} has
14269 control, the whole task is suspended. However, if you used @code{set
14270 task pause off} (see above), this command comes in handy to suspend
14271 only the current thread.
14273 @item show thread pause
14274 @kindex show thread@r{, Hurd command}
14275 This command shows the state of current thread suspension.
14277 @item set thread run
14278 This command sets whether the current thread is allowed to run.
14280 @item show thread run
14281 Show whether the current thread is allowed to run.
14283 @item set thread detach-suspend-count
14284 @cindex thread suspend count, @sc{gnu} Hurd
14285 @cindex detach from thread, @sc{gnu} Hurd
14286 This command sets the suspend count @value{GDBN} will leave on a
14287 thread when detaching. This number is relative to the suspend count
14288 found by @value{GDBN} when it notices the thread; use @code{set thread
14289 takeover-suspend-count} to force it to an absolute value.
14291 @item show thread detach-suspend-count
14292 Show the suspend count @value{GDBN} will leave on the thread when
14295 @item set thread exception-port
14296 @itemx set thread excp
14297 Set the thread exception port to which to forward exceptions. This
14298 overrides the port set by @code{set task exception-port} (see above).
14299 @code{set thread excp} is the shorthand alias.
14301 @item set thread takeover-suspend-count
14302 Normally, @value{GDBN}'s thread suspend counts are relative to the
14303 value @value{GDBN} finds when it notices each thread. This command
14304 changes the suspend counts to be absolute instead.
14306 @item set thread default
14307 @itemx show thread default
14308 @cindex thread default settings, @sc{gnu} Hurd
14309 Each of the above @code{set thread} commands has a @code{set thread
14310 default} counterpart (e.g., @code{set thread default pause}, @code{set
14311 thread default exception-port}, etc.). The @code{thread default}
14312 variety of commands sets the default thread properties for all
14313 threads; you can then change the properties of individual threads with
14314 the non-default commands.
14319 @subsection QNX Neutrino
14320 @cindex QNX Neutrino
14322 @value{GDBN} provides the following commands specific to the QNX
14326 @item set debug nto-debug
14327 @kindex set debug nto-debug
14328 When set to on, enables debugging messages specific to the QNX
14331 @item show debug nto-debug
14332 @kindex show debug nto-debug
14333 Show the current state of QNX Neutrino messages.
14338 @section Embedded Operating Systems
14340 This section describes configurations involving the debugging of
14341 embedded operating systems that are available for several different
14345 * VxWorks:: Using @value{GDBN} with VxWorks
14348 @value{GDBN} includes the ability to debug programs running on
14349 various real-time operating systems.
14352 @subsection Using @value{GDBN} with VxWorks
14358 @kindex target vxworks
14359 @item target vxworks @var{machinename}
14360 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14361 is the target system's machine name or IP address.
14365 On VxWorks, @code{load} links @var{filename} dynamically on the
14366 current target system as well as adding its symbols in @value{GDBN}.
14368 @value{GDBN} enables developers to spawn and debug tasks running on networked
14369 VxWorks targets from a Unix host. Already-running tasks spawned from
14370 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14371 both the Unix host and on the VxWorks target. The program
14372 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14373 installed with the name @code{vxgdb}, to distinguish it from a
14374 @value{GDBN} for debugging programs on the host itself.)
14377 @item VxWorks-timeout @var{args}
14378 @kindex vxworks-timeout
14379 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14380 This option is set by the user, and @var{args} represents the number of
14381 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14382 your VxWorks target is a slow software simulator or is on the far side
14383 of a thin network line.
14386 The following information on connecting to VxWorks was current when
14387 this manual was produced; newer releases of VxWorks may use revised
14390 @findex INCLUDE_RDB
14391 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14392 to include the remote debugging interface routines in the VxWorks
14393 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14394 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14395 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14396 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14397 information on configuring and remaking VxWorks, see the manufacturer's
14399 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14401 Once you have included @file{rdb.a} in your VxWorks system image and set
14402 your Unix execution search path to find @value{GDBN}, you are ready to
14403 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14404 @code{vxgdb}, depending on your installation).
14406 @value{GDBN} comes up showing the prompt:
14413 * VxWorks Connection:: Connecting to VxWorks
14414 * VxWorks Download:: VxWorks download
14415 * VxWorks Attach:: Running tasks
14418 @node VxWorks Connection
14419 @subsubsection Connecting to VxWorks
14421 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14422 network. To connect to a target whose host name is ``@code{tt}'', type:
14425 (vxgdb) target vxworks tt
14429 @value{GDBN} displays messages like these:
14432 Attaching remote machine across net...
14437 @value{GDBN} then attempts to read the symbol tables of any object modules
14438 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14439 these files by searching the directories listed in the command search
14440 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14441 to find an object file, it displays a message such as:
14444 prog.o: No such file or directory.
14447 When this happens, add the appropriate directory to the search path with
14448 the @value{GDBN} command @code{path}, and execute the @code{target}
14451 @node VxWorks Download
14452 @subsubsection VxWorks Download
14454 @cindex download to VxWorks
14455 If you have connected to the VxWorks target and you want to debug an
14456 object that has not yet been loaded, you can use the @value{GDBN}
14457 @code{load} command to download a file from Unix to VxWorks
14458 incrementally. The object file given as an argument to the @code{load}
14459 command is actually opened twice: first by the VxWorks target in order
14460 to download the code, then by @value{GDBN} in order to read the symbol
14461 table. This can lead to problems if the current working directories on
14462 the two systems differ. If both systems have NFS mounted the same
14463 filesystems, you can avoid these problems by using absolute paths.
14464 Otherwise, it is simplest to set the working directory on both systems
14465 to the directory in which the object file resides, and then to reference
14466 the file by its name, without any path. For instance, a program
14467 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14468 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14469 program, type this on VxWorks:
14472 -> cd "@var{vxpath}/vw/demo/rdb"
14476 Then, in @value{GDBN}, type:
14479 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14480 (vxgdb) load prog.o
14483 @value{GDBN} displays a response similar to this:
14486 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14489 You can also use the @code{load} command to reload an object module
14490 after editing and recompiling the corresponding source file. Note that
14491 this makes @value{GDBN} delete all currently-defined breakpoints,
14492 auto-displays, and convenience variables, and to clear the value
14493 history. (This is necessary in order to preserve the integrity of
14494 debugger's data structures that reference the target system's symbol
14497 @node VxWorks Attach
14498 @subsubsection Running Tasks
14500 @cindex running VxWorks tasks
14501 You can also attach to an existing task using the @code{attach} command as
14505 (vxgdb) attach @var{task}
14509 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14510 or suspended when you attach to it. Running tasks are suspended at
14511 the time of attachment.
14513 @node Embedded Processors
14514 @section Embedded Processors
14516 This section goes into details specific to particular embedded
14519 @cindex send command to simulator
14520 Whenever a specific embedded processor has a simulator, @value{GDBN}
14521 allows to send an arbitrary command to the simulator.
14524 @item sim @var{command}
14525 @kindex sim@r{, a command}
14526 Send an arbitrary @var{command} string to the simulator. Consult the
14527 documentation for the specific simulator in use for information about
14528 acceptable commands.
14534 * M32R/D:: Renesas M32R/D
14535 * M68K:: Motorola M68K
14536 * MIPS Embedded:: MIPS Embedded
14537 * OpenRISC 1000:: OpenRisc 1000
14538 * PA:: HP PA Embedded
14539 * PowerPC:: PowerPC
14540 * Sparclet:: Tsqware Sparclet
14541 * Sparclite:: Fujitsu Sparclite
14542 * Z8000:: Zilog Z8000
14545 * Super-H:: Renesas Super-H
14554 @item target rdi @var{dev}
14555 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14556 use this target to communicate with both boards running the Angel
14557 monitor, or with the EmbeddedICE JTAG debug device.
14560 @item target rdp @var{dev}
14565 @value{GDBN} provides the following ARM-specific commands:
14568 @item set arm disassembler
14570 This commands selects from a list of disassembly styles. The
14571 @code{"std"} style is the standard style.
14573 @item show arm disassembler
14575 Show the current disassembly style.
14577 @item set arm apcs32
14578 @cindex ARM 32-bit mode
14579 This command toggles ARM operation mode between 32-bit and 26-bit.
14581 @item show arm apcs32
14582 Display the current usage of the ARM 32-bit mode.
14584 @item set arm fpu @var{fputype}
14585 This command sets the ARM floating-point unit (FPU) type. The
14586 argument @var{fputype} can be one of these:
14590 Determine the FPU type by querying the OS ABI.
14592 Software FPU, with mixed-endian doubles on little-endian ARM
14595 GCC-compiled FPA co-processor.
14597 Software FPU with pure-endian doubles.
14603 Show the current type of the FPU.
14606 This command forces @value{GDBN} to use the specified ABI.
14609 Show the currently used ABI.
14611 @item set debug arm
14612 Toggle whether to display ARM-specific debugging messages from the ARM
14613 target support subsystem.
14615 @item show debug arm
14616 Show whether ARM-specific debugging messages are enabled.
14619 The following commands are available when an ARM target is debugged
14620 using the RDI interface:
14623 @item rdilogfile @r{[}@var{file}@r{]}
14625 @cindex ADP (Angel Debugger Protocol) logging
14626 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14627 With an argument, sets the log file to the specified @var{file}. With
14628 no argument, show the current log file name. The default log file is
14631 @item rdilogenable @r{[}@var{arg}@r{]}
14632 @kindex rdilogenable
14633 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14634 enables logging, with an argument 0 or @code{"no"} disables it. With
14635 no arguments displays the current setting. When logging is enabled,
14636 ADP packets exchanged between @value{GDBN} and the RDI target device
14637 are logged to a file.
14639 @item set rdiromatzero
14640 @kindex set rdiromatzero
14641 @cindex ROM at zero address, RDI
14642 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14643 vector catching is disabled, so that zero address can be used. If off
14644 (the default), vector catching is enabled. For this command to take
14645 effect, it needs to be invoked prior to the @code{target rdi} command.
14647 @item show rdiromatzero
14648 @kindex show rdiromatzero
14649 Show the current setting of ROM at zero address.
14651 @item set rdiheartbeat
14652 @kindex set rdiheartbeat
14653 @cindex RDI heartbeat
14654 Enable or disable RDI heartbeat packets. It is not recommended to
14655 turn on this option, since it confuses ARM and EPI JTAG interface, as
14656 well as the Angel monitor.
14658 @item show rdiheartbeat
14659 @kindex show rdiheartbeat
14660 Show the setting of RDI heartbeat packets.
14665 @subsection Renesas M32R/D and M32R/SDI
14668 @kindex target m32r
14669 @item target m32r @var{dev}
14670 Renesas M32R/D ROM monitor.
14672 @kindex target m32rsdi
14673 @item target m32rsdi @var{dev}
14674 Renesas M32R SDI server, connected via parallel port to the board.
14677 The following @value{GDBN} commands are specific to the M32R monitor:
14680 @item set download-path @var{path}
14681 @kindex set download-path
14682 @cindex find downloadable @sc{srec} files (M32R)
14683 Set the default path for finding downloadable @sc{srec} files.
14685 @item show download-path
14686 @kindex show download-path
14687 Show the default path for downloadable @sc{srec} files.
14689 @item set board-address @var{addr}
14690 @kindex set board-address
14691 @cindex M32-EVA target board address
14692 Set the IP address for the M32R-EVA target board.
14694 @item show board-address
14695 @kindex show board-address
14696 Show the current IP address of the target board.
14698 @item set server-address @var{addr}
14699 @kindex set server-address
14700 @cindex download server address (M32R)
14701 Set the IP address for the download server, which is the @value{GDBN}'s
14704 @item show server-address
14705 @kindex show server-address
14706 Display the IP address of the download server.
14708 @item upload @r{[}@var{file}@r{]}
14709 @kindex upload@r{, M32R}
14710 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14711 upload capability. If no @var{file} argument is given, the current
14712 executable file is uploaded.
14714 @item tload @r{[}@var{file}@r{]}
14715 @kindex tload@r{, M32R}
14716 Test the @code{upload} command.
14719 The following commands are available for M32R/SDI:
14724 @cindex reset SDI connection, M32R
14725 This command resets the SDI connection.
14729 This command shows the SDI connection status.
14732 @kindex debug_chaos
14733 @cindex M32R/Chaos debugging
14734 Instructs the remote that M32R/Chaos debugging is to be used.
14736 @item use_debug_dma
14737 @kindex use_debug_dma
14738 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14741 @kindex use_mon_code
14742 Instructs the remote to use the MON_CODE method of accessing memory.
14745 @kindex use_ib_break
14746 Instructs the remote to set breakpoints by IB break.
14748 @item use_dbt_break
14749 @kindex use_dbt_break
14750 Instructs the remote to set breakpoints by DBT.
14756 The Motorola m68k configuration includes ColdFire support, and a
14757 target command for the following ROM monitor.
14761 @kindex target dbug
14762 @item target dbug @var{dev}
14763 dBUG ROM monitor for Motorola ColdFire.
14767 @node MIPS Embedded
14768 @subsection MIPS Embedded
14770 @cindex MIPS boards
14771 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14772 MIPS board attached to a serial line. This is available when
14773 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14776 Use these @value{GDBN} commands to specify the connection to your target board:
14779 @item target mips @var{port}
14780 @kindex target mips @var{port}
14781 To run a program on the board, start up @code{@value{GDBP}} with the
14782 name of your program as the argument. To connect to the board, use the
14783 command @samp{target mips @var{port}}, where @var{port} is the name of
14784 the serial port connected to the board. If the program has not already
14785 been downloaded to the board, you may use the @code{load} command to
14786 download it. You can then use all the usual @value{GDBN} commands.
14788 For example, this sequence connects to the target board through a serial
14789 port, and loads and runs a program called @var{prog} through the
14793 host$ @value{GDBP} @var{prog}
14794 @value{GDBN} is free software and @dots{}
14795 (@value{GDBP}) target mips /dev/ttyb
14796 (@value{GDBP}) load @var{prog}
14800 @item target mips @var{hostname}:@var{portnumber}
14801 On some @value{GDBN} host configurations, you can specify a TCP
14802 connection (for instance, to a serial line managed by a terminal
14803 concentrator) instead of a serial port, using the syntax
14804 @samp{@var{hostname}:@var{portnumber}}.
14806 @item target pmon @var{port}
14807 @kindex target pmon @var{port}
14810 @item target ddb @var{port}
14811 @kindex target ddb @var{port}
14812 NEC's DDB variant of PMON for Vr4300.
14814 @item target lsi @var{port}
14815 @kindex target lsi @var{port}
14816 LSI variant of PMON.
14818 @kindex target r3900
14819 @item target r3900 @var{dev}
14820 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14822 @kindex target array
14823 @item target array @var{dev}
14824 Array Tech LSI33K RAID controller board.
14830 @value{GDBN} also supports these special commands for MIPS targets:
14833 @item set mipsfpu double
14834 @itemx set mipsfpu single
14835 @itemx set mipsfpu none
14836 @itemx set mipsfpu auto
14837 @itemx show mipsfpu
14838 @kindex set mipsfpu
14839 @kindex show mipsfpu
14840 @cindex MIPS remote floating point
14841 @cindex floating point, MIPS remote
14842 If your target board does not support the MIPS floating point
14843 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14844 need this, you may wish to put the command in your @value{GDBN} init
14845 file). This tells @value{GDBN} how to find the return value of
14846 functions which return floating point values. It also allows
14847 @value{GDBN} to avoid saving the floating point registers when calling
14848 functions on the board. If you are using a floating point coprocessor
14849 with only single precision floating point support, as on the @sc{r4650}
14850 processor, use the command @samp{set mipsfpu single}. The default
14851 double precision floating point coprocessor may be selected using
14852 @samp{set mipsfpu double}.
14854 In previous versions the only choices were double precision or no
14855 floating point, so @samp{set mipsfpu on} will select double precision
14856 and @samp{set mipsfpu off} will select no floating point.
14858 As usual, you can inquire about the @code{mipsfpu} variable with
14859 @samp{show mipsfpu}.
14861 @item set timeout @var{seconds}
14862 @itemx set retransmit-timeout @var{seconds}
14863 @itemx show timeout
14864 @itemx show retransmit-timeout
14865 @cindex @code{timeout}, MIPS protocol
14866 @cindex @code{retransmit-timeout}, MIPS protocol
14867 @kindex set timeout
14868 @kindex show timeout
14869 @kindex set retransmit-timeout
14870 @kindex show retransmit-timeout
14871 You can control the timeout used while waiting for a packet, in the MIPS
14872 remote protocol, with the @code{set timeout @var{seconds}} command. The
14873 default is 5 seconds. Similarly, you can control the timeout used while
14874 waiting for an acknowledgement of a packet with the @code{set
14875 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14876 You can inspect both values with @code{show timeout} and @code{show
14877 retransmit-timeout}. (These commands are @emph{only} available when
14878 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14880 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14881 is waiting for your program to stop. In that case, @value{GDBN} waits
14882 forever because it has no way of knowing how long the program is going
14883 to run before stopping.
14885 @item set syn-garbage-limit @var{num}
14886 @kindex set syn-garbage-limit@r{, MIPS remote}
14887 @cindex synchronize with remote MIPS target
14888 Limit the maximum number of characters @value{GDBN} should ignore when
14889 it tries to synchronize with the remote target. The default is 10
14890 characters. Setting the limit to -1 means there's no limit.
14892 @item show syn-garbage-limit
14893 @kindex show syn-garbage-limit@r{, MIPS remote}
14894 Show the current limit on the number of characters to ignore when
14895 trying to synchronize with the remote system.
14897 @item set monitor-prompt @var{prompt}
14898 @kindex set monitor-prompt@r{, MIPS remote}
14899 @cindex remote monitor prompt
14900 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14901 remote monitor. The default depends on the target:
14911 @item show monitor-prompt
14912 @kindex show monitor-prompt@r{, MIPS remote}
14913 Show the current strings @value{GDBN} expects as the prompt from the
14916 @item set monitor-warnings
14917 @kindex set monitor-warnings@r{, MIPS remote}
14918 Enable or disable monitor warnings about hardware breakpoints. This
14919 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14920 display warning messages whose codes are returned by the @code{lsi}
14921 PMON monitor for breakpoint commands.
14923 @item show monitor-warnings
14924 @kindex show monitor-warnings@r{, MIPS remote}
14925 Show the current setting of printing monitor warnings.
14927 @item pmon @var{command}
14928 @kindex pmon@r{, MIPS remote}
14929 @cindex send PMON command
14930 This command allows sending an arbitrary @var{command} string to the
14931 monitor. The monitor must be in debug mode for this to work.
14934 @node OpenRISC 1000
14935 @subsection OpenRISC 1000
14936 @cindex OpenRISC 1000
14938 @cindex or1k boards
14939 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14940 about platform and commands.
14944 @kindex target jtag
14945 @item target jtag jtag://@var{host}:@var{port}
14947 Connects to remote JTAG server.
14948 JTAG remote server can be either an or1ksim or JTAG server,
14949 connected via parallel port to the board.
14951 Example: @code{target jtag jtag://localhost:9999}
14954 @item or1ksim @var{command}
14955 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14956 Simulator, proprietary commands can be executed.
14958 @kindex info or1k spr
14959 @item info or1k spr
14960 Displays spr groups.
14962 @item info or1k spr @var{group}
14963 @itemx info or1k spr @var{groupno}
14964 Displays register names in selected group.
14966 @item info or1k spr @var{group} @var{register}
14967 @itemx info or1k spr @var{register}
14968 @itemx info or1k spr @var{groupno} @var{registerno}
14969 @itemx info or1k spr @var{registerno}
14970 Shows information about specified spr register.
14973 @item spr @var{group} @var{register} @var{value}
14974 @itemx spr @var{register @var{value}}
14975 @itemx spr @var{groupno} @var{registerno @var{value}}
14976 @itemx spr @var{registerno @var{value}}
14977 Writes @var{value} to specified spr register.
14980 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14981 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14982 program execution and is thus much faster. Hardware breakpoints/watchpoint
14983 triggers can be set using:
14986 Load effective address/data
14988 Store effective address/data
14990 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14995 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14996 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14998 @code{htrace} commands:
14999 @cindex OpenRISC 1000 htrace
15002 @item hwatch @var{conditional}
15003 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15004 or Data. For example:
15006 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15008 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15012 Display information about current HW trace configuration.
15014 @item htrace trigger @var{conditional}
15015 Set starting criteria for HW trace.
15017 @item htrace qualifier @var{conditional}
15018 Set acquisition qualifier for HW trace.
15020 @item htrace stop @var{conditional}
15021 Set HW trace stopping criteria.
15023 @item htrace record [@var{data}]*
15024 Selects the data to be recorded, when qualifier is met and HW trace was
15027 @item htrace enable
15028 @itemx htrace disable
15029 Enables/disables the HW trace.
15031 @item htrace rewind [@var{filename}]
15032 Clears currently recorded trace data.
15034 If filename is specified, new trace file is made and any newly collected data
15035 will be written there.
15037 @item htrace print [@var{start} [@var{len}]]
15038 Prints trace buffer, using current record configuration.
15040 @item htrace mode continuous
15041 Set continuous trace mode.
15043 @item htrace mode suspend
15044 Set suspend trace mode.
15049 @subsection PowerPC
15051 @value{GDBN} provides the following PowerPC-specific commands:
15054 @kindex set powerpc
15055 @item set powerpc soft-float
15056 @itemx show powerpc soft-float
15057 Force @value{GDBN} to use (or not use) a software floating point calling
15058 convention. By default, @value{GDBN} selects the calling convention based
15059 on the selected architecture and the provided executable file.
15061 @item set powerpc vector-abi
15062 @itemx show powerpc vector-abi
15063 Force @value{GDBN} to use the specified calling convention for vector
15064 arguments and return values. The valid options are @samp{auto};
15065 @samp{generic}, to avoid vector registers even if they are present;
15066 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15067 registers. By default, @value{GDBN} selects the calling convention
15068 based on the selected architecture and the provided executable file.
15070 @kindex target dink32
15071 @item target dink32 @var{dev}
15072 DINK32 ROM monitor.
15074 @kindex target ppcbug
15075 @item target ppcbug @var{dev}
15076 @kindex target ppcbug1
15077 @item target ppcbug1 @var{dev}
15078 PPCBUG ROM monitor for PowerPC.
15081 @item target sds @var{dev}
15082 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15085 @cindex SDS protocol
15086 The following commands specific to the SDS protocol are supported
15090 @item set sdstimeout @var{nsec}
15091 @kindex set sdstimeout
15092 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15093 default is 2 seconds.
15095 @item show sdstimeout
15096 @kindex show sdstimeout
15097 Show the current value of the SDS timeout.
15099 @item sds @var{command}
15100 @kindex sds@r{, a command}
15101 Send the specified @var{command} string to the SDS monitor.
15106 @subsection HP PA Embedded
15110 @kindex target op50n
15111 @item target op50n @var{dev}
15112 OP50N monitor, running on an OKI HPPA board.
15114 @kindex target w89k
15115 @item target w89k @var{dev}
15116 W89K monitor, running on a Winbond HPPA board.
15121 @subsection Tsqware Sparclet
15125 @value{GDBN} enables developers to debug tasks running on
15126 Sparclet targets from a Unix host.
15127 @value{GDBN} uses code that runs on
15128 both the Unix host and on the Sparclet target. The program
15129 @code{@value{GDBP}} is installed and executed on the Unix host.
15132 @item remotetimeout @var{args}
15133 @kindex remotetimeout
15134 @value{GDBN} supports the option @code{remotetimeout}.
15135 This option is set by the user, and @var{args} represents the number of
15136 seconds @value{GDBN} waits for responses.
15139 @cindex compiling, on Sparclet
15140 When compiling for debugging, include the options @samp{-g} to get debug
15141 information and @samp{-Ttext} to relocate the program to where you wish to
15142 load it on the target. You may also want to add the options @samp{-n} or
15143 @samp{-N} in order to reduce the size of the sections. Example:
15146 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15149 You can use @code{objdump} to verify that the addresses are what you intended:
15152 sparclet-aout-objdump --headers --syms prog
15155 @cindex running, on Sparclet
15157 your Unix execution search path to find @value{GDBN}, you are ready to
15158 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15159 (or @code{sparclet-aout-gdb}, depending on your installation).
15161 @value{GDBN} comes up showing the prompt:
15168 * Sparclet File:: Setting the file to debug
15169 * Sparclet Connection:: Connecting to Sparclet
15170 * Sparclet Download:: Sparclet download
15171 * Sparclet Execution:: Running and debugging
15174 @node Sparclet File
15175 @subsubsection Setting File to Debug
15177 The @value{GDBN} command @code{file} lets you choose with program to debug.
15180 (gdbslet) file prog
15184 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15185 @value{GDBN} locates
15186 the file by searching the directories listed in the command search
15188 If the file was compiled with debug information (option @samp{-g}), source
15189 files will be searched as well.
15190 @value{GDBN} locates
15191 the source files by searching the directories listed in the directory search
15192 path (@pxref{Environment, ,Your Program's Environment}).
15194 to find a file, it displays a message such as:
15197 prog: No such file or directory.
15200 When this happens, add the appropriate directories to the search paths with
15201 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15202 @code{target} command again.
15204 @node Sparclet Connection
15205 @subsubsection Connecting to Sparclet
15207 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15208 To connect to a target on serial port ``@code{ttya}'', type:
15211 (gdbslet) target sparclet /dev/ttya
15212 Remote target sparclet connected to /dev/ttya
15213 main () at ../prog.c:3
15217 @value{GDBN} displays messages like these:
15223 @node Sparclet Download
15224 @subsubsection Sparclet Download
15226 @cindex download to Sparclet
15227 Once connected to the Sparclet target,
15228 you can use the @value{GDBN}
15229 @code{load} command to download the file from the host to the target.
15230 The file name and load offset should be given as arguments to the @code{load}
15232 Since the file format is aout, the program must be loaded to the starting
15233 address. You can use @code{objdump} to find out what this value is. The load
15234 offset is an offset which is added to the VMA (virtual memory address)
15235 of each of the file's sections.
15236 For instance, if the program
15237 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15238 and bss at 0x12010170, in @value{GDBN}, type:
15241 (gdbslet) load prog 0x12010000
15242 Loading section .text, size 0xdb0 vma 0x12010000
15245 If the code is loaded at a different address then what the program was linked
15246 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15247 to tell @value{GDBN} where to map the symbol table.
15249 @node Sparclet Execution
15250 @subsubsection Running and Debugging
15252 @cindex running and debugging Sparclet programs
15253 You can now begin debugging the task using @value{GDBN}'s execution control
15254 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15255 manual for the list of commands.
15259 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15261 Starting program: prog
15262 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15263 3 char *symarg = 0;
15265 4 char *execarg = "hello!";
15270 @subsection Fujitsu Sparclite
15274 @kindex target sparclite
15275 @item target sparclite @var{dev}
15276 Fujitsu sparclite boards, used only for the purpose of loading.
15277 You must use an additional command to debug the program.
15278 For example: target remote @var{dev} using @value{GDBN} standard
15284 @subsection Zilog Z8000
15287 @cindex simulator, Z8000
15288 @cindex Zilog Z8000 simulator
15290 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15293 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15294 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15295 segmented variant). The simulator recognizes which architecture is
15296 appropriate by inspecting the object code.
15299 @item target sim @var{args}
15301 @kindex target sim@r{, with Z8000}
15302 Debug programs on a simulated CPU. If the simulator supports setup
15303 options, specify them via @var{args}.
15307 After specifying this target, you can debug programs for the simulated
15308 CPU in the same style as programs for your host computer; use the
15309 @code{file} command to load a new program image, the @code{run} command
15310 to run your program, and so on.
15312 As well as making available all the usual machine registers
15313 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15314 additional items of information as specially named registers:
15319 Counts clock-ticks in the simulator.
15322 Counts instructions run in the simulator.
15325 Execution time in 60ths of a second.
15329 You can refer to these values in @value{GDBN} expressions with the usual
15330 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15331 conditional breakpoint that suspends only after at least 5000
15332 simulated clock ticks.
15335 @subsection Atmel AVR
15338 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15339 following AVR-specific commands:
15342 @item info io_registers
15343 @kindex info io_registers@r{, AVR}
15344 @cindex I/O registers (Atmel AVR)
15345 This command displays information about the AVR I/O registers. For
15346 each register, @value{GDBN} prints its number and value.
15353 When configured for debugging CRIS, @value{GDBN} provides the
15354 following CRIS-specific commands:
15357 @item set cris-version @var{ver}
15358 @cindex CRIS version
15359 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15360 The CRIS version affects register names and sizes. This command is useful in
15361 case autodetection of the CRIS version fails.
15363 @item show cris-version
15364 Show the current CRIS version.
15366 @item set cris-dwarf2-cfi
15367 @cindex DWARF-2 CFI and CRIS
15368 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15369 Change to @samp{off} when using @code{gcc-cris} whose version is below
15372 @item show cris-dwarf2-cfi
15373 Show the current state of using DWARF-2 CFI.
15375 @item set cris-mode @var{mode}
15377 Set the current CRIS mode to @var{mode}. It should only be changed when
15378 debugging in guru mode, in which case it should be set to
15379 @samp{guru} (the default is @samp{normal}).
15381 @item show cris-mode
15382 Show the current CRIS mode.
15386 @subsection Renesas Super-H
15389 For the Renesas Super-H processor, @value{GDBN} provides these
15394 @kindex regs@r{, Super-H}
15395 Show the values of all Super-H registers.
15399 @node Architectures
15400 @section Architectures
15402 This section describes characteristics of architectures that affect
15403 all uses of @value{GDBN} with the architecture, both native and cross.
15410 * HPPA:: HP PA architecture
15411 * SPU:: Cell Broadband Engine SPU architecture
15415 @subsection x86 Architecture-specific Issues
15418 @item set struct-convention @var{mode}
15419 @kindex set struct-convention
15420 @cindex struct return convention
15421 @cindex struct/union returned in registers
15422 Set the convention used by the inferior to return @code{struct}s and
15423 @code{union}s from functions to @var{mode}. Possible values of
15424 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15425 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15426 are returned on the stack, while @code{"reg"} means that a
15427 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15428 be returned in a register.
15430 @item show struct-convention
15431 @kindex show struct-convention
15432 Show the current setting of the convention to return @code{struct}s
15441 @kindex set rstack_high_address
15442 @cindex AMD 29K register stack
15443 @cindex register stack, AMD29K
15444 @item set rstack_high_address @var{address}
15445 On AMD 29000 family processors, registers are saved in a separate
15446 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15447 extent of this stack. Normally, @value{GDBN} just assumes that the
15448 stack is ``large enough''. This may result in @value{GDBN} referencing
15449 memory locations that do not exist. If necessary, you can get around
15450 this problem by specifying the ending address of the register stack with
15451 the @code{set rstack_high_address} command. The argument should be an
15452 address, which you probably want to precede with @samp{0x} to specify in
15455 @kindex show rstack_high_address
15456 @item show rstack_high_address
15457 Display the current limit of the register stack, on AMD 29000 family
15465 See the following section.
15470 @cindex stack on Alpha
15471 @cindex stack on MIPS
15472 @cindex Alpha stack
15474 Alpha- and MIPS-based computers use an unusual stack frame, which
15475 sometimes requires @value{GDBN} to search backward in the object code to
15476 find the beginning of a function.
15478 @cindex response time, MIPS debugging
15479 To improve response time (especially for embedded applications, where
15480 @value{GDBN} may be restricted to a slow serial line for this search)
15481 you may want to limit the size of this search, using one of these
15485 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15486 @item set heuristic-fence-post @var{limit}
15487 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15488 search for the beginning of a function. A value of @var{0} (the
15489 default) means there is no limit. However, except for @var{0}, the
15490 larger the limit the more bytes @code{heuristic-fence-post} must search
15491 and therefore the longer it takes to run. You should only need to use
15492 this command when debugging a stripped executable.
15494 @item show heuristic-fence-post
15495 Display the current limit.
15499 These commands are available @emph{only} when @value{GDBN} is configured
15500 for debugging programs on Alpha or MIPS processors.
15502 Several MIPS-specific commands are available when debugging MIPS
15506 @item set mips abi @var{arg}
15507 @kindex set mips abi
15508 @cindex set ABI for MIPS
15509 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15510 values of @var{arg} are:
15514 The default ABI associated with the current binary (this is the
15525 @item show mips abi
15526 @kindex show mips abi
15527 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15530 @itemx show mipsfpu
15531 @xref{MIPS Embedded, set mipsfpu}.
15533 @item set mips mask-address @var{arg}
15534 @kindex set mips mask-address
15535 @cindex MIPS addresses, masking
15536 This command determines whether the most-significant 32 bits of 64-bit
15537 MIPS addresses are masked off. The argument @var{arg} can be
15538 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15539 setting, which lets @value{GDBN} determine the correct value.
15541 @item show mips mask-address
15542 @kindex show mips mask-address
15543 Show whether the upper 32 bits of MIPS addresses are masked off or
15546 @item set remote-mips64-transfers-32bit-regs
15547 @kindex set remote-mips64-transfers-32bit-regs
15548 This command controls compatibility with 64-bit MIPS targets that
15549 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15550 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15551 and 64 bits for other registers, set this option to @samp{on}.
15553 @item show remote-mips64-transfers-32bit-regs
15554 @kindex show remote-mips64-transfers-32bit-regs
15555 Show the current setting of compatibility with older MIPS 64 targets.
15557 @item set debug mips
15558 @kindex set debug mips
15559 This command turns on and off debugging messages for the MIPS-specific
15560 target code in @value{GDBN}.
15562 @item show debug mips
15563 @kindex show debug mips
15564 Show the current setting of MIPS debugging messages.
15570 @cindex HPPA support
15572 When @value{GDBN} is debugging the HP PA architecture, it provides the
15573 following special commands:
15576 @item set debug hppa
15577 @kindex set debug hppa
15578 This command determines whether HPPA architecture-specific debugging
15579 messages are to be displayed.
15581 @item show debug hppa
15582 Show whether HPPA debugging messages are displayed.
15584 @item maint print unwind @var{address}
15585 @kindex maint print unwind@r{, HPPA}
15586 This command displays the contents of the unwind table entry at the
15587 given @var{address}.
15593 @subsection Cell Broadband Engine SPU architecture
15594 @cindex Cell Broadband Engine
15597 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
15598 it provides the following special commands:
15601 @item info spu event
15603 Display SPU event facility status. Shows current event mask
15604 and pending event status.
15606 @item info spu signal
15607 Display SPU signal notification facility status. Shows pending
15608 signal-control word and signal notification mode of both signal
15609 notification channels.
15611 @item info spu mailbox
15612 Display SPU mailbox facility status. Shows all pending entries,
15613 in order of processing, in each of the SPU Write Outbound,
15614 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
15617 Display MFC DMA status. Shows all pending commands in the MFC
15618 DMA queue. For each entry, opcode, tag, class IDs, effective
15619 and local store addresses and transfer size are shown.
15621 @item info spu proxydma
15622 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
15623 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
15624 and local store addresses and transfer size are shown.
15629 @node Controlling GDB
15630 @chapter Controlling @value{GDBN}
15632 You can alter the way @value{GDBN} interacts with you by using the
15633 @code{set} command. For commands controlling how @value{GDBN} displays
15634 data, see @ref{Print Settings, ,Print Settings}. Other settings are
15639 * Editing:: Command editing
15640 * Command History:: Command history
15641 * Screen Size:: Screen size
15642 * Numbers:: Numbers
15643 * ABI:: Configuring the current ABI
15644 * Messages/Warnings:: Optional warnings and messages
15645 * Debugging Output:: Optional messages about internal happenings
15653 @value{GDBN} indicates its readiness to read a command by printing a string
15654 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15655 can change the prompt string with the @code{set prompt} command. For
15656 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15657 the prompt in one of the @value{GDBN} sessions so that you can always tell
15658 which one you are talking to.
15660 @emph{Note:} @code{set prompt} does not add a space for you after the
15661 prompt you set. This allows you to set a prompt which ends in a space
15662 or a prompt that does not.
15666 @item set prompt @var{newprompt}
15667 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15669 @kindex show prompt
15671 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15675 @section Command Editing
15677 @cindex command line editing
15679 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15680 @sc{gnu} library provides consistent behavior for programs which provide a
15681 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15682 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15683 substitution, and a storage and recall of command history across
15684 debugging sessions.
15686 You may control the behavior of command line editing in @value{GDBN} with the
15687 command @code{set}.
15690 @kindex set editing
15693 @itemx set editing on
15694 Enable command line editing (enabled by default).
15696 @item set editing off
15697 Disable command line editing.
15699 @kindex show editing
15701 Show whether command line editing is enabled.
15704 @xref{Command Line Editing}, for more details about the Readline
15705 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15706 encouraged to read that chapter.
15708 @node Command History
15709 @section Command History
15710 @cindex command history
15712 @value{GDBN} can keep track of the commands you type during your
15713 debugging sessions, so that you can be certain of precisely what
15714 happened. Use these commands to manage the @value{GDBN} command
15717 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15718 package, to provide the history facility. @xref{Using History
15719 Interactively}, for the detailed description of the History library.
15721 To issue a command to @value{GDBN} without affecting certain aspects of
15722 the state which is seen by users, prefix it with @samp{server }
15723 (@pxref{Server Prefix}). This
15724 means that this command will not affect the command history, nor will it
15725 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15726 pressed on a line by itself.
15728 @cindex @code{server}, command prefix
15729 The server prefix does not affect the recording of values into the value
15730 history; to print a value without recording it into the value history,
15731 use the @code{output} command instead of the @code{print} command.
15733 Here is the description of @value{GDBN} commands related to command
15737 @cindex history substitution
15738 @cindex history file
15739 @kindex set history filename
15740 @cindex @env{GDBHISTFILE}, environment variable
15741 @item set history filename @var{fname}
15742 Set the name of the @value{GDBN} command history file to @var{fname}.
15743 This is the file where @value{GDBN} reads an initial command history
15744 list, and where it writes the command history from this session when it
15745 exits. You can access this list through history expansion or through
15746 the history command editing characters listed below. This file defaults
15747 to the value of the environment variable @code{GDBHISTFILE}, or to
15748 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15751 @cindex save command history
15752 @kindex set history save
15753 @item set history save
15754 @itemx set history save on
15755 Record command history in a file, whose name may be specified with the
15756 @code{set history filename} command. By default, this option is disabled.
15758 @item set history save off
15759 Stop recording command history in a file.
15761 @cindex history size
15762 @kindex set history size
15763 @cindex @env{HISTSIZE}, environment variable
15764 @item set history size @var{size}
15765 Set the number of commands which @value{GDBN} keeps in its history list.
15766 This defaults to the value of the environment variable
15767 @code{HISTSIZE}, or to 256 if this variable is not set.
15770 History expansion assigns special meaning to the character @kbd{!}.
15771 @xref{Event Designators}, for more details.
15773 @cindex history expansion, turn on/off
15774 Since @kbd{!} is also the logical not operator in C, history expansion
15775 is off by default. If you decide to enable history expansion with the
15776 @code{set history expansion on} command, you may sometimes need to
15777 follow @kbd{!} (when it is used as logical not, in an expression) with
15778 a space or a tab to prevent it from being expanded. The readline
15779 history facilities do not attempt substitution on the strings
15780 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15782 The commands to control history expansion are:
15785 @item set history expansion on
15786 @itemx set history expansion
15787 @kindex set history expansion
15788 Enable history expansion. History expansion is off by default.
15790 @item set history expansion off
15791 Disable history expansion.
15794 @kindex show history
15796 @itemx show history filename
15797 @itemx show history save
15798 @itemx show history size
15799 @itemx show history expansion
15800 These commands display the state of the @value{GDBN} history parameters.
15801 @code{show history} by itself displays all four states.
15806 @kindex show commands
15807 @cindex show last commands
15808 @cindex display command history
15809 @item show commands
15810 Display the last ten commands in the command history.
15812 @item show commands @var{n}
15813 Print ten commands centered on command number @var{n}.
15815 @item show commands +
15816 Print ten commands just after the commands last printed.
15820 @section Screen Size
15821 @cindex size of screen
15822 @cindex pauses in output
15824 Certain commands to @value{GDBN} may produce large amounts of
15825 information output to the screen. To help you read all of it,
15826 @value{GDBN} pauses and asks you for input at the end of each page of
15827 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15828 to discard the remaining output. Also, the screen width setting
15829 determines when to wrap lines of output. Depending on what is being
15830 printed, @value{GDBN} tries to break the line at a readable place,
15831 rather than simply letting it overflow onto the following line.
15833 Normally @value{GDBN} knows the size of the screen from the terminal
15834 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15835 together with the value of the @code{TERM} environment variable and the
15836 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15837 you can override it with the @code{set height} and @code{set
15844 @kindex show height
15845 @item set height @var{lpp}
15847 @itemx set width @var{cpl}
15849 These @code{set} commands specify a screen height of @var{lpp} lines and
15850 a screen width of @var{cpl} characters. The associated @code{show}
15851 commands display the current settings.
15853 If you specify a height of zero lines, @value{GDBN} does not pause during
15854 output no matter how long the output is. This is useful if output is to a
15855 file or to an editor buffer.
15857 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15858 from wrapping its output.
15860 @item set pagination on
15861 @itemx set pagination off
15862 @kindex set pagination
15863 Turn the output pagination on or off; the default is on. Turning
15864 pagination off is the alternative to @code{set height 0}.
15866 @item show pagination
15867 @kindex show pagination
15868 Show the current pagination mode.
15873 @cindex number representation
15874 @cindex entering numbers
15876 You can always enter numbers in octal, decimal, or hexadecimal in
15877 @value{GDBN} by the usual conventions: octal numbers begin with
15878 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15879 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15880 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15881 10; likewise, the default display for numbers---when no particular
15882 format is specified---is base 10. You can change the default base for
15883 both input and output with the commands described below.
15886 @kindex set input-radix
15887 @item set input-radix @var{base}
15888 Set the default base for numeric input. Supported choices
15889 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15890 specified either unambiguously or using the current input radix; for
15894 set input-radix 012
15895 set input-radix 10.
15896 set input-radix 0xa
15900 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15901 leaves the input radix unchanged, no matter what it was, since
15902 @samp{10}, being without any leading or trailing signs of its base, is
15903 interpreted in the current radix. Thus, if the current radix is 16,
15904 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15907 @kindex set output-radix
15908 @item set output-radix @var{base}
15909 Set the default base for numeric display. Supported choices
15910 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15911 specified either unambiguously or using the current input radix.
15913 @kindex show input-radix
15914 @item show input-radix
15915 Display the current default base for numeric input.
15917 @kindex show output-radix
15918 @item show output-radix
15919 Display the current default base for numeric display.
15921 @item set radix @r{[}@var{base}@r{]}
15925 These commands set and show the default base for both input and output
15926 of numbers. @code{set radix} sets the radix of input and output to
15927 the same base; without an argument, it resets the radix back to its
15928 default value of 10.
15933 @section Configuring the Current ABI
15935 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15936 application automatically. However, sometimes you need to override its
15937 conclusions. Use these commands to manage @value{GDBN}'s view of the
15944 One @value{GDBN} configuration can debug binaries for multiple operating
15945 system targets, either via remote debugging or native emulation.
15946 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15947 but you can override its conclusion using the @code{set osabi} command.
15948 One example where this is useful is in debugging of binaries which use
15949 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15950 not have the same identifying marks that the standard C library for your
15955 Show the OS ABI currently in use.
15958 With no argument, show the list of registered available OS ABI's.
15960 @item set osabi @var{abi}
15961 Set the current OS ABI to @var{abi}.
15964 @cindex float promotion
15966 Generally, the way that an argument of type @code{float} is passed to a
15967 function depends on whether the function is prototyped. For a prototyped
15968 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15969 according to the architecture's convention for @code{float}. For unprototyped
15970 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15971 @code{double} and then passed.
15973 Unfortunately, some forms of debug information do not reliably indicate whether
15974 a function is prototyped. If @value{GDBN} calls a function that is not marked
15975 as prototyped, it consults @kbd{set coerce-float-to-double}.
15978 @kindex set coerce-float-to-double
15979 @item set coerce-float-to-double
15980 @itemx set coerce-float-to-double on
15981 Arguments of type @code{float} will be promoted to @code{double} when passed
15982 to an unprototyped function. This is the default setting.
15984 @item set coerce-float-to-double off
15985 Arguments of type @code{float} will be passed directly to unprototyped
15988 @kindex show coerce-float-to-double
15989 @item show coerce-float-to-double
15990 Show the current setting of promoting @code{float} to @code{double}.
15994 @kindex show cp-abi
15995 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15996 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15997 used to build your application. @value{GDBN} only fully supports
15998 programs with a single C@t{++} ABI; if your program contains code using
15999 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16000 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16001 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16002 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16003 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16004 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16009 Show the C@t{++} ABI currently in use.
16012 With no argument, show the list of supported C@t{++} ABI's.
16014 @item set cp-abi @var{abi}
16015 @itemx set cp-abi auto
16016 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16019 @node Messages/Warnings
16020 @section Optional Warnings and Messages
16022 @cindex verbose operation
16023 @cindex optional warnings
16024 By default, @value{GDBN} is silent about its inner workings. If you are
16025 running on a slow machine, you may want to use the @code{set verbose}
16026 command. This makes @value{GDBN} tell you when it does a lengthy
16027 internal operation, so you will not think it has crashed.
16029 Currently, the messages controlled by @code{set verbose} are those
16030 which announce that the symbol table for a source file is being read;
16031 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16034 @kindex set verbose
16035 @item set verbose on
16036 Enables @value{GDBN} output of certain informational messages.
16038 @item set verbose off
16039 Disables @value{GDBN} output of certain informational messages.
16041 @kindex show verbose
16043 Displays whether @code{set verbose} is on or off.
16046 By default, if @value{GDBN} encounters bugs in the symbol table of an
16047 object file, it is silent; but if you are debugging a compiler, you may
16048 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16053 @kindex set complaints
16054 @item set complaints @var{limit}
16055 Permits @value{GDBN} to output @var{limit} complaints about each type of
16056 unusual symbols before becoming silent about the problem. Set
16057 @var{limit} to zero to suppress all complaints; set it to a large number
16058 to prevent complaints from being suppressed.
16060 @kindex show complaints
16061 @item show complaints
16062 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16066 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16067 lot of stupid questions to confirm certain commands. For example, if
16068 you try to run a program which is already running:
16072 The program being debugged has been started already.
16073 Start it from the beginning? (y or n)
16076 If you are willing to unflinchingly face the consequences of your own
16077 commands, you can disable this ``feature'':
16081 @kindex set confirm
16083 @cindex confirmation
16084 @cindex stupid questions
16085 @item set confirm off
16086 Disables confirmation requests.
16088 @item set confirm on
16089 Enables confirmation requests (the default).
16091 @kindex show confirm
16093 Displays state of confirmation requests.
16097 @cindex command tracing
16098 If you need to debug user-defined commands or sourced files you may find it
16099 useful to enable @dfn{command tracing}. In this mode each command will be
16100 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16101 quantity denoting the call depth of each command.
16104 @kindex set trace-commands
16105 @cindex command scripts, debugging
16106 @item set trace-commands on
16107 Enable command tracing.
16108 @item set trace-commands off
16109 Disable command tracing.
16110 @item show trace-commands
16111 Display the current state of command tracing.
16114 @node Debugging Output
16115 @section Optional Messages about Internal Happenings
16116 @cindex optional debugging messages
16118 @value{GDBN} has commands that enable optional debugging messages from
16119 various @value{GDBN} subsystems; normally these commands are of
16120 interest to @value{GDBN} maintainers, or when reporting a bug. This
16121 section documents those commands.
16124 @kindex set exec-done-display
16125 @item set exec-done-display
16126 Turns on or off the notification of asynchronous commands'
16127 completion. When on, @value{GDBN} will print a message when an
16128 asynchronous command finishes its execution. The default is off.
16129 @kindex show exec-done-display
16130 @item show exec-done-display
16131 Displays the current setting of asynchronous command completion
16134 @cindex gdbarch debugging info
16135 @cindex architecture debugging info
16136 @item set debug arch
16137 Turns on or off display of gdbarch debugging info. The default is off
16139 @item show debug arch
16140 Displays the current state of displaying gdbarch debugging info.
16141 @item set debug aix-thread
16142 @cindex AIX threads
16143 Display debugging messages about inner workings of the AIX thread
16145 @item show debug aix-thread
16146 Show the current state of AIX thread debugging info display.
16147 @item set debug event
16148 @cindex event debugging info
16149 Turns on or off display of @value{GDBN} event debugging info. The
16151 @item show debug event
16152 Displays the current state of displaying @value{GDBN} event debugging
16154 @item set debug expression
16155 @cindex expression debugging info
16156 Turns on or off display of debugging info about @value{GDBN}
16157 expression parsing. The default is off.
16158 @item show debug expression
16159 Displays the current state of displaying debugging info about
16160 @value{GDBN} expression parsing.
16161 @item set debug frame
16162 @cindex frame debugging info
16163 Turns on or off display of @value{GDBN} frame debugging info. The
16165 @item show debug frame
16166 Displays the current state of displaying @value{GDBN} frame debugging
16168 @item set debug infrun
16169 @cindex inferior debugging info
16170 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16171 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16172 for implementing operations such as single-stepping the inferior.
16173 @item show debug infrun
16174 Displays the current state of @value{GDBN} inferior debugging.
16175 @item set debug lin-lwp
16176 @cindex @sc{gnu}/Linux LWP debug messages
16177 @cindex Linux lightweight processes
16178 Turns on or off debugging messages from the Linux LWP debug support.
16179 @item show debug lin-lwp
16180 Show the current state of Linux LWP debugging messages.
16181 @item set debug observer
16182 @cindex observer debugging info
16183 Turns on or off display of @value{GDBN} observer debugging. This
16184 includes info such as the notification of observable events.
16185 @item show debug observer
16186 Displays the current state of observer debugging.
16187 @item set debug overload
16188 @cindex C@t{++} overload debugging info
16189 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16190 info. This includes info such as ranking of functions, etc. The default
16192 @item show debug overload
16193 Displays the current state of displaying @value{GDBN} C@t{++} overload
16195 @cindex packets, reporting on stdout
16196 @cindex serial connections, debugging
16197 @cindex debug remote protocol
16198 @cindex remote protocol debugging
16199 @cindex display remote packets
16200 @item set debug remote
16201 Turns on or off display of reports on all packets sent back and forth across
16202 the serial line to the remote machine. The info is printed on the
16203 @value{GDBN} standard output stream. The default is off.
16204 @item show debug remote
16205 Displays the state of display of remote packets.
16206 @item set debug serial
16207 Turns on or off display of @value{GDBN} serial debugging info. The
16209 @item show debug serial
16210 Displays the current state of displaying @value{GDBN} serial debugging
16212 @item set debug solib-frv
16213 @cindex FR-V shared-library debugging
16214 Turns on or off debugging messages for FR-V shared-library code.
16215 @item show debug solib-frv
16216 Display the current state of FR-V shared-library code debugging
16218 @item set debug target
16219 @cindex target debugging info
16220 Turns on or off display of @value{GDBN} target debugging info. This info
16221 includes what is going on at the target level of GDB, as it happens. The
16222 default is 0. Set it to 1 to track events, and to 2 to also track the
16223 value of large memory transfers. Changes to this flag do not take effect
16224 until the next time you connect to a target or use the @code{run} command.
16225 @item show debug target
16226 Displays the current state of displaying @value{GDBN} target debugging
16228 @item set debugvarobj
16229 @cindex variable object debugging info
16230 Turns on or off display of @value{GDBN} variable object debugging
16231 info. The default is off.
16232 @item show debugvarobj
16233 Displays the current state of displaying @value{GDBN} variable object
16235 @item set debug xml
16236 @cindex XML parser debugging
16237 Turns on or off debugging messages for built-in XML parsers.
16238 @item show debug xml
16239 Displays the current state of XML debugging messages.
16243 @chapter Canned Sequences of Commands
16245 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16246 Command Lists}), @value{GDBN} provides two ways to store sequences of
16247 commands for execution as a unit: user-defined commands and command
16251 * Define:: How to define your own commands
16252 * Hooks:: Hooks for user-defined commands
16253 * Command Files:: How to write scripts of commands to be stored in a file
16254 * Output:: Commands for controlled output
16258 @section User-defined Commands
16260 @cindex user-defined command
16261 @cindex arguments, to user-defined commands
16262 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16263 which you assign a new name as a command. This is done with the
16264 @code{define} command. User commands may accept up to 10 arguments
16265 separated by whitespace. Arguments are accessed within the user command
16266 via @code{$arg0@dots{}$arg9}. A trivial example:
16270 print $arg0 + $arg1 + $arg2
16275 To execute the command use:
16282 This defines the command @code{adder}, which prints the sum of
16283 its three arguments. Note the arguments are text substitutions, so they may
16284 reference variables, use complex expressions, or even perform inferior
16287 @cindex argument count in user-defined commands
16288 @cindex how many arguments (user-defined commands)
16289 In addition, @code{$argc} may be used to find out how many arguments have
16290 been passed. This expands to a number in the range 0@dots{}10.
16295 print $arg0 + $arg1
16298 print $arg0 + $arg1 + $arg2
16306 @item define @var{commandname}
16307 Define a command named @var{commandname}. If there is already a command
16308 by that name, you are asked to confirm that you want to redefine it.
16310 The definition of the command is made up of other @value{GDBN} command lines,
16311 which are given following the @code{define} command. The end of these
16312 commands is marked by a line containing @code{end}.
16315 @kindex end@r{ (user-defined commands)}
16316 @item document @var{commandname}
16317 Document the user-defined command @var{commandname}, so that it can be
16318 accessed by @code{help}. The command @var{commandname} must already be
16319 defined. This command reads lines of documentation just as @code{define}
16320 reads the lines of the command definition, ending with @code{end}.
16321 After the @code{document} command is finished, @code{help} on command
16322 @var{commandname} displays the documentation you have written.
16324 You may use the @code{document} command again to change the
16325 documentation of a command. Redefining the command with @code{define}
16326 does not change the documentation.
16328 @kindex dont-repeat
16329 @cindex don't repeat command
16331 Used inside a user-defined command, this tells @value{GDBN} that this
16332 command should not be repeated when the user hits @key{RET}
16333 (@pxref{Command Syntax, repeat last command}).
16335 @kindex help user-defined
16336 @item help user-defined
16337 List all user-defined commands, with the first line of the documentation
16342 @itemx show user @var{commandname}
16343 Display the @value{GDBN} commands used to define @var{commandname} (but
16344 not its documentation). If no @var{commandname} is given, display the
16345 definitions for all user-defined commands.
16347 @cindex infinite recursion in user-defined commands
16348 @kindex show max-user-call-depth
16349 @kindex set max-user-call-depth
16350 @item show max-user-call-depth
16351 @itemx set max-user-call-depth
16352 The value of @code{max-user-call-depth} controls how many recursion
16353 levels are allowed in user-defined commands before @value{GDBN} suspects an
16354 infinite recursion and aborts the command.
16357 In addition to the above commands, user-defined commands frequently
16358 use control flow commands, described in @ref{Command Files}.
16360 When user-defined commands are executed, the
16361 commands of the definition are not printed. An error in any command
16362 stops execution of the user-defined command.
16364 If used interactively, commands that would ask for confirmation proceed
16365 without asking when used inside a user-defined command. Many @value{GDBN}
16366 commands that normally print messages to say what they are doing omit the
16367 messages when used in a user-defined command.
16370 @section User-defined Command Hooks
16371 @cindex command hooks
16372 @cindex hooks, for commands
16373 @cindex hooks, pre-command
16376 You may define @dfn{hooks}, which are a special kind of user-defined
16377 command. Whenever you run the command @samp{foo}, if the user-defined
16378 command @samp{hook-foo} exists, it is executed (with no arguments)
16379 before that command.
16381 @cindex hooks, post-command
16383 A hook may also be defined which is run after the command you executed.
16384 Whenever you run the command @samp{foo}, if the user-defined command
16385 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16386 that command. Post-execution hooks may exist simultaneously with
16387 pre-execution hooks, for the same command.
16389 It is valid for a hook to call the command which it hooks. If this
16390 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16392 @c It would be nice if hookpost could be passed a parameter indicating
16393 @c if the command it hooks executed properly or not. FIXME!
16395 @kindex stop@r{, a pseudo-command}
16396 In addition, a pseudo-command, @samp{stop} exists. Defining
16397 (@samp{hook-stop}) makes the associated commands execute every time
16398 execution stops in your program: before breakpoint commands are run,
16399 displays are printed, or the stack frame is printed.
16401 For example, to ignore @code{SIGALRM} signals while
16402 single-stepping, but treat them normally during normal execution,
16407 handle SIGALRM nopass
16411 handle SIGALRM pass
16414 define hook-continue
16415 handle SIGALRM pass
16419 As a further example, to hook at the beginning and end of the @code{echo}
16420 command, and to add extra text to the beginning and end of the message,
16428 define hookpost-echo
16432 (@value{GDBP}) echo Hello World
16433 <<<---Hello World--->>>
16438 You can define a hook for any single-word command in @value{GDBN}, but
16439 not for command aliases; you should define a hook for the basic command
16440 name, e.g.@: @code{backtrace} rather than @code{bt}.
16441 @c FIXME! So how does Joe User discover whether a command is an alias
16443 If an error occurs during the execution of your hook, execution of
16444 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16445 (before the command that you actually typed had a chance to run).
16447 If you try to define a hook which does not match any known command, you
16448 get a warning from the @code{define} command.
16450 @node Command Files
16451 @section Command Files
16453 @cindex command files
16454 @cindex scripting commands
16455 A command file for @value{GDBN} is a text file made of lines that are
16456 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16457 also be included. An empty line in a command file does nothing; it
16458 does not mean to repeat the last command, as it would from the
16461 You can request the execution of a command file with the @code{source}
16466 @cindex execute commands from a file
16467 @item source [@code{-v}] @var{filename}
16468 Execute the command file @var{filename}.
16471 The lines in a command file are generally executed sequentially,
16472 unless the order of execution is changed by one of the
16473 @emph{flow-control commands} described below. The commands are not
16474 printed as they are executed. An error in any command terminates
16475 execution of the command file and control is returned to the console.
16477 @value{GDBN} searches for @var{filename} in the current directory and then
16478 on the search path (specified with the @samp{directory} command).
16480 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16481 each command as it is executed. The option must be given before
16482 @var{filename}, and is interpreted as part of the filename anywhere else.
16484 Commands that would ask for confirmation if used interactively proceed
16485 without asking when used in a command file. Many @value{GDBN} commands that
16486 normally print messages to say what they are doing omit the messages
16487 when called from command files.
16489 @value{GDBN} also accepts command input from standard input. In this
16490 mode, normal output goes to standard output and error output goes to
16491 standard error. Errors in a command file supplied on standard input do
16492 not terminate execution of the command file---execution continues with
16496 gdb < cmds > log 2>&1
16499 (The syntax above will vary depending on the shell used.) This example
16500 will execute commands from the file @file{cmds}. All output and errors
16501 would be directed to @file{log}.
16503 Since commands stored on command files tend to be more general than
16504 commands typed interactively, they frequently need to deal with
16505 complicated situations, such as different or unexpected values of
16506 variables and symbols, changes in how the program being debugged is
16507 built, etc. @value{GDBN} provides a set of flow-control commands to
16508 deal with these complexities. Using these commands, you can write
16509 complex scripts that loop over data structures, execute commands
16510 conditionally, etc.
16517 This command allows to include in your script conditionally executed
16518 commands. The @code{if} command takes a single argument, which is an
16519 expression to evaluate. It is followed by a series of commands that
16520 are executed only if the expression is true (its value is nonzero).
16521 There can then optionally be an @code{else} line, followed by a series
16522 of commands that are only executed if the expression was false. The
16523 end of the list is marked by a line containing @code{end}.
16527 This command allows to write loops. Its syntax is similar to
16528 @code{if}: the command takes a single argument, which is an expression
16529 to evaluate, and must be followed by the commands to execute, one per
16530 line, terminated by an @code{end}. These commands are called the
16531 @dfn{body} of the loop. The commands in the body of @code{while} are
16532 executed repeatedly as long as the expression evaluates to true.
16536 This command exits the @code{while} loop in whose body it is included.
16537 Execution of the script continues after that @code{while}s @code{end}
16540 @kindex loop_continue
16541 @item loop_continue
16542 This command skips the execution of the rest of the body of commands
16543 in the @code{while} loop in whose body it is included. Execution
16544 branches to the beginning of the @code{while} loop, where it evaluates
16545 the controlling expression.
16547 @kindex end@r{ (if/else/while commands)}
16549 Terminate the block of commands that are the body of @code{if},
16550 @code{else}, or @code{while} flow-control commands.
16555 @section Commands for Controlled Output
16557 During the execution of a command file or a user-defined command, normal
16558 @value{GDBN} output is suppressed; the only output that appears is what is
16559 explicitly printed by the commands in the definition. This section
16560 describes three commands useful for generating exactly the output you
16565 @item echo @var{text}
16566 @c I do not consider backslash-space a standard C escape sequence
16567 @c because it is not in ANSI.
16568 Print @var{text}. Nonprinting characters can be included in
16569 @var{text} using C escape sequences, such as @samp{\n} to print a
16570 newline. @strong{No newline is printed unless you specify one.}
16571 In addition to the standard C escape sequences, a backslash followed
16572 by a space stands for a space. This is useful for displaying a
16573 string with spaces at the beginning or the end, since leading and
16574 trailing spaces are otherwise trimmed from all arguments.
16575 To print @samp{@w{ }and foo =@w{ }}, use the command
16576 @samp{echo \@w{ }and foo = \@w{ }}.
16578 A backslash at the end of @var{text} can be used, as in C, to continue
16579 the command onto subsequent lines. For example,
16582 echo This is some text\n\
16583 which is continued\n\
16584 onto several lines.\n
16587 produces the same output as
16590 echo This is some text\n
16591 echo which is continued\n
16592 echo onto several lines.\n
16596 @item output @var{expression}
16597 Print the value of @var{expression} and nothing but that value: no
16598 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16599 value history either. @xref{Expressions, ,Expressions}, for more information
16602 @item output/@var{fmt} @var{expression}
16603 Print the value of @var{expression} in format @var{fmt}. You can use
16604 the same formats as for @code{print}. @xref{Output Formats,,Output
16605 Formats}, for more information.
16608 @item printf @var{template}, @var{expressions}@dots{}
16609 Print the values of one or more @var{expressions} under the control of
16610 the string @var{template}. To print several values, make
16611 @var{expressions} be a comma-separated list of individual expressions,
16612 which may be either numbers or pointers. Their values are printed as
16613 specified by @var{template}, exactly as a C program would do by
16614 executing the code below:
16617 printf (@var{template}, @var{expressions}@dots{});
16620 As in @code{C} @code{printf}, ordinary characters in @var{template}
16621 are printed verbatim, while @dfn{conversion specification} introduced
16622 by the @samp{%} character cause subsequent @var{expressions} to be
16623 evaluated, their values converted and formatted according to type and
16624 style information encoded in the conversion specifications, and then
16627 For example, you can print two values in hex like this:
16630 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16633 @code{printf} supports all the standard @code{C} conversion
16634 specifications, including the flags and modifiers between the @samp{%}
16635 character and the conversion letter, with the following exceptions:
16639 The argument-ordering modifiers, such as @samp{2$}, are not supported.
16642 The modifier @samp{*} is not supported for specifying precision or
16646 The @samp{'} flag (for separation of digits into groups according to
16647 @code{LC_NUMERIC'}) is not supported.
16650 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
16654 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
16657 The conversion letters @samp{a} and @samp{A} are not supported.
16661 Note that the @samp{ll} type modifier is supported only if the
16662 underlying @code{C} implementation used to build @value{GDBN} supports
16663 the @code{long long int} type, and the @samp{L} type modifier is
16664 supported only if @code{long double} type is available.
16666 As in @code{C}, @code{printf} supports simple backslash-escape
16667 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
16668 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
16669 single character. Octal and hexadecimal escape sequences are not
16672 Additionally, @code{printf} supports conversion specifications for DFP
16673 (@dfn{Decimal Floating Point}) types using the following conversion
16678 @samp{H} for printing @code{Decimal32} types.
16681 @samp{D} for printing @code{Decimal64} types.
16684 @samp{DD} for printing @code{Decimal128} types.
16687 If the underlying @code{C} implementation used to build @value{GDBN} has
16688 support for the three conversion letters for DFP types, other modifiers
16689 such as width and precision will also be available for @value{GDBN} to use.
16691 In case there is no such @code{C} support, no additional modifiers will be
16692 available and the value will be printed in the standard way.
16694 Here's an example of printing DFP types using the above conversion letters:
16696 printf "D32: %H - D64: %D - D128: %DD\n",1.2345df,1.2E10dd,1.2E1dl
16702 @chapter Command Interpreters
16703 @cindex command interpreters
16705 @value{GDBN} supports multiple command interpreters, and some command
16706 infrastructure to allow users or user interface writers to switch
16707 between interpreters or run commands in other interpreters.
16709 @value{GDBN} currently supports two command interpreters, the console
16710 interpreter (sometimes called the command-line interpreter or @sc{cli})
16711 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16712 describes both of these interfaces in great detail.
16714 By default, @value{GDBN} will start with the console interpreter.
16715 However, the user may choose to start @value{GDBN} with another
16716 interpreter by specifying the @option{-i} or @option{--interpreter}
16717 startup options. Defined interpreters include:
16721 @cindex console interpreter
16722 The traditional console or command-line interpreter. This is the most often
16723 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16724 @value{GDBN} will use this interpreter.
16727 @cindex mi interpreter
16728 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16729 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16730 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16734 @cindex mi2 interpreter
16735 The current @sc{gdb/mi} interface.
16738 @cindex mi1 interpreter
16739 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16743 @cindex invoke another interpreter
16744 The interpreter being used by @value{GDBN} may not be dynamically
16745 switched at runtime. Although possible, this could lead to a very
16746 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16747 enters the command "interpreter-set console" in a console view,
16748 @value{GDBN} would switch to using the console interpreter, rendering
16749 the IDE inoperable!
16751 @kindex interpreter-exec
16752 Although you may only choose a single interpreter at startup, you may execute
16753 commands in any interpreter from the current interpreter using the appropriate
16754 command. If you are running the console interpreter, simply use the
16755 @code{interpreter-exec} command:
16758 interpreter-exec mi "-data-list-register-names"
16761 @sc{gdb/mi} has a similar command, although it is only available in versions of
16762 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16765 @chapter @value{GDBN} Text User Interface
16767 @cindex Text User Interface
16770 * TUI Overview:: TUI overview
16771 * TUI Keys:: TUI key bindings
16772 * TUI Single Key Mode:: TUI single key mode
16773 * TUI Commands:: TUI-specific commands
16774 * TUI Configuration:: TUI configuration variables
16777 The @value{GDBN} Text User Interface (TUI) is a terminal
16778 interface which uses the @code{curses} library to show the source
16779 file, the assembly output, the program registers and @value{GDBN}
16780 commands in separate text windows. The TUI mode is supported only
16781 on platforms where a suitable version of the @code{curses} library
16784 @pindex @value{GDBTUI}
16785 The TUI mode is enabled by default when you invoke @value{GDBN} as
16786 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
16787 You can also switch in and out of TUI mode while @value{GDBN} runs by
16788 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
16789 @xref{TUI Keys, ,TUI Key Bindings}.
16792 @section TUI Overview
16794 In TUI mode, @value{GDBN} can display several text windows:
16798 This window is the @value{GDBN} command window with the @value{GDBN}
16799 prompt and the @value{GDBN} output. The @value{GDBN} input is still
16800 managed using readline.
16803 The source window shows the source file of the program. The current
16804 line and active breakpoints are displayed in this window.
16807 The assembly window shows the disassembly output of the program.
16810 This window shows the processor registers. Registers are highlighted
16811 when their values change.
16814 The source and assembly windows show the current program position
16815 by highlighting the current line and marking it with a @samp{>} marker.
16816 Breakpoints are indicated with two markers. The first marker
16817 indicates the breakpoint type:
16821 Breakpoint which was hit at least once.
16824 Breakpoint which was never hit.
16827 Hardware breakpoint which was hit at least once.
16830 Hardware breakpoint which was never hit.
16833 The second marker indicates whether the breakpoint is enabled or not:
16837 Breakpoint is enabled.
16840 Breakpoint is disabled.
16843 The source, assembly and register windows are updated when the current
16844 thread changes, when the frame changes, or when the program counter
16847 These windows are not all visible at the same time. The command
16848 window is always visible. The others can be arranged in several
16859 source and assembly,
16862 source and registers, or
16865 assembly and registers.
16868 A status line above the command window shows the following information:
16872 Indicates the current @value{GDBN} target.
16873 (@pxref{Targets, ,Specifying a Debugging Target}).
16876 Gives the current process or thread number.
16877 When no process is being debugged, this field is set to @code{No process}.
16880 Gives the current function name for the selected frame.
16881 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16882 When there is no symbol corresponding to the current program counter,
16883 the string @code{??} is displayed.
16886 Indicates the current line number for the selected frame.
16887 When the current line number is not known, the string @code{??} is displayed.
16890 Indicates the current program counter address.
16894 @section TUI Key Bindings
16895 @cindex TUI key bindings
16897 The TUI installs several key bindings in the readline keymaps
16898 (@pxref{Command Line Editing}). The following key bindings
16899 are installed for both TUI mode and the @value{GDBN} standard mode.
16908 Enter or leave the TUI mode. When leaving the TUI mode,
16909 the curses window management stops and @value{GDBN} operates using
16910 its standard mode, writing on the terminal directly. When reentering
16911 the TUI mode, control is given back to the curses windows.
16912 The screen is then refreshed.
16916 Use a TUI layout with only one window. The layout will
16917 either be @samp{source} or @samp{assembly}. When the TUI mode
16918 is not active, it will switch to the TUI mode.
16920 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16924 Use a TUI layout with at least two windows. When the current
16925 layout already has two windows, the next layout with two windows is used.
16926 When a new layout is chosen, one window will always be common to the
16927 previous layout and the new one.
16929 Think of it as the Emacs @kbd{C-x 2} binding.
16933 Change the active window. The TUI associates several key bindings
16934 (like scrolling and arrow keys) with the active window. This command
16935 gives the focus to the next TUI window.
16937 Think of it as the Emacs @kbd{C-x o} binding.
16941 Switch in and out of the TUI SingleKey mode that binds single
16942 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
16945 The following key bindings only work in the TUI mode:
16950 Scroll the active window one page up.
16954 Scroll the active window one page down.
16958 Scroll the active window one line up.
16962 Scroll the active window one line down.
16966 Scroll the active window one column left.
16970 Scroll the active window one column right.
16974 Refresh the screen.
16977 Because the arrow keys scroll the active window in the TUI mode, they
16978 are not available for their normal use by readline unless the command
16979 window has the focus. When another window is active, you must use
16980 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
16981 and @kbd{C-f} to control the command window.
16983 @node TUI Single Key Mode
16984 @section TUI Single Key Mode
16985 @cindex TUI single key mode
16987 The TUI also provides a @dfn{SingleKey} mode, which binds several
16988 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
16989 switch into this mode, where the following key bindings are used:
16992 @kindex c @r{(SingleKey TUI key)}
16996 @kindex d @r{(SingleKey TUI key)}
17000 @kindex f @r{(SingleKey TUI key)}
17004 @kindex n @r{(SingleKey TUI key)}
17008 @kindex q @r{(SingleKey TUI key)}
17010 exit the SingleKey mode.
17012 @kindex r @r{(SingleKey TUI key)}
17016 @kindex s @r{(SingleKey TUI key)}
17020 @kindex u @r{(SingleKey TUI key)}
17024 @kindex v @r{(SingleKey TUI key)}
17028 @kindex w @r{(SingleKey TUI key)}
17033 Other keys temporarily switch to the @value{GDBN} command prompt.
17034 The key that was pressed is inserted in the editing buffer so that
17035 it is possible to type most @value{GDBN} commands without interaction
17036 with the TUI SingleKey mode. Once the command is entered the TUI
17037 SingleKey mode is restored. The only way to permanently leave
17038 this mode is by typing @kbd{q} or @kbd{C-x s}.
17042 @section TUI-specific Commands
17043 @cindex TUI commands
17045 The TUI has specific commands to control the text windows.
17046 These commands are always available, even when @value{GDBN} is not in
17047 the TUI mode. When @value{GDBN} is in the standard mode, most
17048 of these commands will automatically switch to the TUI mode.
17053 List and give the size of all displayed windows.
17057 Display the next layout.
17060 Display the previous layout.
17063 Display the source window only.
17066 Display the assembly window only.
17069 Display the source and assembly window.
17072 Display the register window together with the source or assembly window.
17076 Make the next window active for scrolling.
17079 Make the previous window active for scrolling.
17082 Make the source window active for scrolling.
17085 Make the assembly window active for scrolling.
17088 Make the register window active for scrolling.
17091 Make the command window active for scrolling.
17095 Refresh the screen. This is similar to typing @kbd{C-L}.
17097 @item tui reg float
17099 Show the floating point registers in the register window.
17101 @item tui reg general
17102 Show the general registers in the register window.
17105 Show the next register group. The list of register groups as well as
17106 their order is target specific. The predefined register groups are the
17107 following: @code{general}, @code{float}, @code{system}, @code{vector},
17108 @code{all}, @code{save}, @code{restore}.
17110 @item tui reg system
17111 Show the system registers in the register window.
17115 Update the source window and the current execution point.
17117 @item winheight @var{name} +@var{count}
17118 @itemx winheight @var{name} -@var{count}
17120 Change the height of the window @var{name} by @var{count}
17121 lines. Positive counts increase the height, while negative counts
17124 @item tabset @var{nchars}
17126 Set the width of tab stops to be @var{nchars} characters.
17129 @node TUI Configuration
17130 @section TUI Configuration Variables
17131 @cindex TUI configuration variables
17133 Several configuration variables control the appearance of TUI windows.
17136 @item set tui border-kind @var{kind}
17137 @kindex set tui border-kind
17138 Select the border appearance for the source, assembly and register windows.
17139 The possible values are the following:
17142 Use a space character to draw the border.
17145 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
17148 Use the Alternate Character Set to draw the border. The border is
17149 drawn using character line graphics if the terminal supports them.
17152 @item set tui border-mode @var{mode}
17153 @kindex set tui border-mode
17154 @itemx set tui active-border-mode @var{mode}
17155 @kindex set tui active-border-mode
17156 Select the display attributes for the borders of the inactive windows
17157 or the active window. The @var{mode} can be one of the following:
17160 Use normal attributes to display the border.
17166 Use reverse video mode.
17169 Use half bright mode.
17171 @item half-standout
17172 Use half bright and standout mode.
17175 Use extra bright or bold mode.
17177 @item bold-standout
17178 Use extra bright or bold and standout mode.
17183 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17186 @cindex @sc{gnu} Emacs
17187 A special interface allows you to use @sc{gnu} Emacs to view (and
17188 edit) the source files for the program you are debugging with
17191 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17192 executable file you want to debug as an argument. This command starts
17193 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17194 created Emacs buffer.
17195 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17197 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17202 All ``terminal'' input and output goes through an Emacs buffer, called
17205 This applies both to @value{GDBN} commands and their output, and to the input
17206 and output done by the program you are debugging.
17208 This is useful because it means that you can copy the text of previous
17209 commands and input them again; you can even use parts of the output
17212 All the facilities of Emacs' Shell mode are available for interacting
17213 with your program. In particular, you can send signals the usual
17214 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17218 @value{GDBN} displays source code through Emacs.
17220 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17221 source file for that frame and puts an arrow (@samp{=>}) at the
17222 left margin of the current line. Emacs uses a separate buffer for
17223 source display, and splits the screen to show both your @value{GDBN} session
17226 Explicit @value{GDBN} @code{list} or search commands still produce output as
17227 usual, but you probably have no reason to use them from Emacs.
17230 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17231 a graphical mode, enabled by default, which provides further buffers
17232 that can control the execution and describe the state of your program.
17233 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17235 If you specify an absolute file name when prompted for the @kbd{M-x
17236 gdb} argument, then Emacs sets your current working directory to where
17237 your program resides. If you only specify the file name, then Emacs
17238 sets your current working directory to to the directory associated
17239 with the previous buffer. In this case, @value{GDBN} may find your
17240 program by searching your environment's @code{PATH} variable, but on
17241 some operating systems it might not find the source. So, although the
17242 @value{GDBN} input and output session proceeds normally, the auxiliary
17243 buffer does not display the current source and line of execution.
17245 The initial working directory of @value{GDBN} is printed on the top
17246 line of the GUD buffer and this serves as a default for the commands
17247 that specify files for @value{GDBN} to operate on. @xref{Files,
17248 ,Commands to Specify Files}.
17250 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17251 need to call @value{GDBN} by a different name (for example, if you
17252 keep several configurations around, with different names) you can
17253 customize the Emacs variable @code{gud-gdb-command-name} to run the
17256 In the GUD buffer, you can use these special Emacs commands in
17257 addition to the standard Shell mode commands:
17261 Describe the features of Emacs' GUD Mode.
17264 Execute to another source line, like the @value{GDBN} @code{step} command; also
17265 update the display window to show the current file and location.
17268 Execute to next source line in this function, skipping all function
17269 calls, like the @value{GDBN} @code{next} command. Then update the display window
17270 to show the current file and location.
17273 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17274 display window accordingly.
17277 Execute until exit from the selected stack frame, like the @value{GDBN}
17278 @code{finish} command.
17281 Continue execution of your program, like the @value{GDBN} @code{continue}
17285 Go up the number of frames indicated by the numeric argument
17286 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17287 like the @value{GDBN} @code{up} command.
17290 Go down the number of frames indicated by the numeric argument, like the
17291 @value{GDBN} @code{down} command.
17294 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17295 tells @value{GDBN} to set a breakpoint on the source line point is on.
17297 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17298 separate frame which shows a backtrace when the GUD buffer is current.
17299 Move point to any frame in the stack and type @key{RET} to make it
17300 become the current frame and display the associated source in the
17301 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17302 selected frame become the current one. In graphical mode, the
17303 speedbar displays watch expressions.
17305 If you accidentally delete the source-display buffer, an easy way to get
17306 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17307 request a frame display; when you run under Emacs, this recreates
17308 the source buffer if necessary to show you the context of the current
17311 The source files displayed in Emacs are in ordinary Emacs buffers
17312 which are visiting the source files in the usual way. You can edit
17313 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17314 communicates with Emacs in terms of line numbers. If you add or
17315 delete lines from the text, the line numbers that @value{GDBN} knows cease
17316 to correspond properly with the code.
17318 A more detailed description of Emacs' interaction with @value{GDBN} is
17319 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17322 @c The following dropped because Epoch is nonstandard. Reactivate
17323 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17325 @kindex Emacs Epoch environment
17329 Version 18 of @sc{gnu} Emacs has a built-in window system
17330 called the @code{epoch}
17331 environment. Users of this environment can use a new command,
17332 @code{inspect} which performs identically to @code{print} except that
17333 each value is printed in its own window.
17338 @chapter The @sc{gdb/mi} Interface
17340 @unnumberedsec Function and Purpose
17342 @cindex @sc{gdb/mi}, its purpose
17343 @sc{gdb/mi} is a line based machine oriented text interface to
17344 @value{GDBN} and is activated by specifying using the
17345 @option{--interpreter} command line option (@pxref{Mode Options}). It
17346 is specifically intended to support the development of systems which
17347 use the debugger as just one small component of a larger system.
17349 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17350 in the form of a reference manual.
17352 Note that @sc{gdb/mi} is still under construction, so some of the
17353 features described below are incomplete and subject to change
17354 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17356 @unnumberedsec Notation and Terminology
17358 @cindex notational conventions, for @sc{gdb/mi}
17359 This chapter uses the following notation:
17363 @code{|} separates two alternatives.
17366 @code{[ @var{something} ]} indicates that @var{something} is optional:
17367 it may or may not be given.
17370 @code{( @var{group} )*} means that @var{group} inside the parentheses
17371 may repeat zero or more times.
17374 @code{( @var{group} )+} means that @var{group} inside the parentheses
17375 may repeat one or more times.
17378 @code{"@var{string}"} means a literal @var{string}.
17382 @heading Dependencies
17386 * GDB/MI Command Syntax::
17387 * GDB/MI Compatibility with CLI::
17388 * GDB/MI Development and Front Ends::
17389 * GDB/MI Output Records::
17390 * GDB/MI Simple Examples::
17391 * GDB/MI Command Description Format::
17392 * GDB/MI Breakpoint Commands::
17393 * GDB/MI Program Context::
17394 * GDB/MI Thread Commands::
17395 * GDB/MI Program Execution::
17396 * GDB/MI Stack Manipulation::
17397 * GDB/MI Variable Objects::
17398 * GDB/MI Data Manipulation::
17399 * GDB/MI Tracepoint Commands::
17400 * GDB/MI Symbol Query::
17401 * GDB/MI File Commands::
17403 * GDB/MI Kod Commands::
17404 * GDB/MI Memory Overlay Commands::
17405 * GDB/MI Signal Handling Commands::
17407 * GDB/MI Target Manipulation::
17408 * GDB/MI File Transfer Commands::
17409 * GDB/MI Miscellaneous Commands::
17412 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17413 @node GDB/MI Command Syntax
17414 @section @sc{gdb/mi} Command Syntax
17417 * GDB/MI Input Syntax::
17418 * GDB/MI Output Syntax::
17421 @node GDB/MI Input Syntax
17422 @subsection @sc{gdb/mi} Input Syntax
17424 @cindex input syntax for @sc{gdb/mi}
17425 @cindex @sc{gdb/mi}, input syntax
17427 @item @var{command} @expansion{}
17428 @code{@var{cli-command} | @var{mi-command}}
17430 @item @var{cli-command} @expansion{}
17431 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17432 @var{cli-command} is any existing @value{GDBN} CLI command.
17434 @item @var{mi-command} @expansion{}
17435 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17436 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17438 @item @var{token} @expansion{}
17439 "any sequence of digits"
17441 @item @var{option} @expansion{}
17442 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17444 @item @var{parameter} @expansion{}
17445 @code{@var{non-blank-sequence} | @var{c-string}}
17447 @item @var{operation} @expansion{}
17448 @emph{any of the operations described in this chapter}
17450 @item @var{non-blank-sequence} @expansion{}
17451 @emph{anything, provided it doesn't contain special characters such as
17452 "-", @var{nl}, """ and of course " "}
17454 @item @var{c-string} @expansion{}
17455 @code{""" @var{seven-bit-iso-c-string-content} """}
17457 @item @var{nl} @expansion{}
17466 The CLI commands are still handled by the @sc{mi} interpreter; their
17467 output is described below.
17470 The @code{@var{token}}, when present, is passed back when the command
17474 Some @sc{mi} commands accept optional arguments as part of the parameter
17475 list. Each option is identified by a leading @samp{-} (dash) and may be
17476 followed by an optional argument parameter. Options occur first in the
17477 parameter list and can be delimited from normal parameters using
17478 @samp{--} (this is useful when some parameters begin with a dash).
17485 We want easy access to the existing CLI syntax (for debugging).
17488 We want it to be easy to spot a @sc{mi} operation.
17491 @node GDB/MI Output Syntax
17492 @subsection @sc{gdb/mi} Output Syntax
17494 @cindex output syntax of @sc{gdb/mi}
17495 @cindex @sc{gdb/mi}, output syntax
17496 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17497 followed, optionally, by a single result record. This result record
17498 is for the most recent command. The sequence of output records is
17499 terminated by @samp{(gdb)}.
17501 If an input command was prefixed with a @code{@var{token}} then the
17502 corresponding output for that command will also be prefixed by that same
17506 @item @var{output} @expansion{}
17507 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17509 @item @var{result-record} @expansion{}
17510 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17512 @item @var{out-of-band-record} @expansion{}
17513 @code{@var{async-record} | @var{stream-record}}
17515 @item @var{async-record} @expansion{}
17516 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17518 @item @var{exec-async-output} @expansion{}
17519 @code{[ @var{token} ] "*" @var{async-output}}
17521 @item @var{status-async-output} @expansion{}
17522 @code{[ @var{token} ] "+" @var{async-output}}
17524 @item @var{notify-async-output} @expansion{}
17525 @code{[ @var{token} ] "=" @var{async-output}}
17527 @item @var{async-output} @expansion{}
17528 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17530 @item @var{result-class} @expansion{}
17531 @code{"done" | "running" | "connected" | "error" | "exit"}
17533 @item @var{async-class} @expansion{}
17534 @code{"stopped" | @var{others}} (where @var{others} will be added
17535 depending on the needs---this is still in development).
17537 @item @var{result} @expansion{}
17538 @code{ @var{variable} "=" @var{value}}
17540 @item @var{variable} @expansion{}
17541 @code{ @var{string} }
17543 @item @var{value} @expansion{}
17544 @code{ @var{const} | @var{tuple} | @var{list} }
17546 @item @var{const} @expansion{}
17547 @code{@var{c-string}}
17549 @item @var{tuple} @expansion{}
17550 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17552 @item @var{list} @expansion{}
17553 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17554 @var{result} ( "," @var{result} )* "]" }
17556 @item @var{stream-record} @expansion{}
17557 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17559 @item @var{console-stream-output} @expansion{}
17560 @code{"~" @var{c-string}}
17562 @item @var{target-stream-output} @expansion{}
17563 @code{"@@" @var{c-string}}
17565 @item @var{log-stream-output} @expansion{}
17566 @code{"&" @var{c-string}}
17568 @item @var{nl} @expansion{}
17571 @item @var{token} @expansion{}
17572 @emph{any sequence of digits}.
17580 All output sequences end in a single line containing a period.
17583 The @code{@var{token}} is from the corresponding request. If an execution
17584 command is interrupted by the @samp{-exec-interrupt} command, the
17585 @var{token} associated with the @samp{*stopped} message is the one of the
17586 original execution command, not the one of the interrupt command.
17589 @cindex status output in @sc{gdb/mi}
17590 @var{status-async-output} contains on-going status information about the
17591 progress of a slow operation. It can be discarded. All status output is
17592 prefixed by @samp{+}.
17595 @cindex async output in @sc{gdb/mi}
17596 @var{exec-async-output} contains asynchronous state change on the target
17597 (stopped, started, disappeared). All async output is prefixed by
17601 @cindex notify output in @sc{gdb/mi}
17602 @var{notify-async-output} contains supplementary information that the
17603 client should handle (e.g., a new breakpoint information). All notify
17604 output is prefixed by @samp{=}.
17607 @cindex console output in @sc{gdb/mi}
17608 @var{console-stream-output} is output that should be displayed as is in the
17609 console. It is the textual response to a CLI command. All the console
17610 output is prefixed by @samp{~}.
17613 @cindex target output in @sc{gdb/mi}
17614 @var{target-stream-output} is the output produced by the target program.
17615 All the target output is prefixed by @samp{@@}.
17618 @cindex log output in @sc{gdb/mi}
17619 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17620 instance messages that should be displayed as part of an error log. All
17621 the log output is prefixed by @samp{&}.
17624 @cindex list output in @sc{gdb/mi}
17625 New @sc{gdb/mi} commands should only output @var{lists} containing
17631 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17632 details about the various output records.
17634 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17635 @node GDB/MI Compatibility with CLI
17636 @section @sc{gdb/mi} Compatibility with CLI
17638 @cindex compatibility, @sc{gdb/mi} and CLI
17639 @cindex @sc{gdb/mi}, compatibility with CLI
17641 For the developers convenience CLI commands can be entered directly,
17642 but there may be some unexpected behaviour. For example, commands
17643 that query the user will behave as if the user replied yes, breakpoint
17644 command lists are not executed and some CLI commands, such as
17645 @code{if}, @code{when} and @code{define}, prompt for further input with
17646 @samp{>}, which is not valid MI output.
17648 This feature may be removed at some stage in the future and it is
17649 recommended that front ends use the @code{-interpreter-exec} command
17650 (@pxref{-interpreter-exec}).
17652 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17653 @node GDB/MI Development and Front Ends
17654 @section @sc{gdb/mi} Development and Front Ends
17655 @cindex @sc{gdb/mi} development
17657 The application which takes the MI output and presents the state of the
17658 program being debugged to the user is called a @dfn{front end}.
17660 Although @sc{gdb/mi} is still incomplete, it is currently being used
17661 by a variety of front ends to @value{GDBN}. This makes it difficult
17662 to introduce new functionality without breaking existing usage. This
17663 section tries to minimize the problems by describing how the protocol
17666 Some changes in MI need not break a carefully designed front end, and
17667 for these the MI version will remain unchanged. The following is a
17668 list of changes that may occur within one level, so front ends should
17669 parse MI output in a way that can handle them:
17673 New MI commands may be added.
17676 New fields may be added to the output of any MI command.
17679 The range of values for fields with specified values, e.g.,
17680 @code{in_scope} (@pxref{-var-update}) may be extended.
17682 @c The format of field's content e.g type prefix, may change so parse it
17683 @c at your own risk. Yes, in general?
17685 @c The order of fields may change? Shouldn't really matter but it might
17686 @c resolve inconsistencies.
17689 If the changes are likely to break front ends, the MI version level
17690 will be increased by one. This will allow the front end to parse the
17691 output according to the MI version. Apart from mi0, new versions of
17692 @value{GDBN} will not support old versions of MI and it will be the
17693 responsibility of the front end to work with the new one.
17695 @c Starting with mi3, add a new command -mi-version that prints the MI
17698 The best way to avoid unexpected changes in MI that might break your front
17699 end is to make your project known to @value{GDBN} developers and
17700 follow development on @email{gdb@@sourceware.org} and
17701 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17702 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17703 Group, which has the aim of creating a more general MI protocol
17704 called Debugger Machine Interface (DMI) that will become a standard
17705 for all debuggers, not just @value{GDBN}.
17706 @cindex mailing lists
17708 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17709 @node GDB/MI Output Records
17710 @section @sc{gdb/mi} Output Records
17713 * GDB/MI Result Records::
17714 * GDB/MI Stream Records::
17715 * GDB/MI Out-of-band Records::
17718 @node GDB/MI Result Records
17719 @subsection @sc{gdb/mi} Result Records
17721 @cindex result records in @sc{gdb/mi}
17722 @cindex @sc{gdb/mi}, result records
17723 In addition to a number of out-of-band notifications, the response to a
17724 @sc{gdb/mi} command includes one of the following result indications:
17728 @item "^done" [ "," @var{results} ]
17729 The synchronous operation was successful, @code{@var{results}} are the return
17734 @c Is this one correct? Should it be an out-of-band notification?
17735 The asynchronous operation was successfully started. The target is
17740 @value{GDBN} has connected to a remote target.
17742 @item "^error" "," @var{c-string}
17744 The operation failed. The @code{@var{c-string}} contains the corresponding
17749 @value{GDBN} has terminated.
17753 @node GDB/MI Stream Records
17754 @subsection @sc{gdb/mi} Stream Records
17756 @cindex @sc{gdb/mi}, stream records
17757 @cindex stream records in @sc{gdb/mi}
17758 @value{GDBN} internally maintains a number of output streams: the console, the
17759 target, and the log. The output intended for each of these streams is
17760 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17762 Each stream record begins with a unique @dfn{prefix character} which
17763 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17764 Syntax}). In addition to the prefix, each stream record contains a
17765 @code{@var{string-output}}. This is either raw text (with an implicit new
17766 line) or a quoted C string (which does not contain an implicit newline).
17769 @item "~" @var{string-output}
17770 The console output stream contains text that should be displayed in the
17771 CLI console window. It contains the textual responses to CLI commands.
17773 @item "@@" @var{string-output}
17774 The target output stream contains any textual output from the running
17775 target. This is only present when GDB's event loop is truly
17776 asynchronous, which is currently only the case for remote targets.
17778 @item "&" @var{string-output}
17779 The log stream contains debugging messages being produced by @value{GDBN}'s
17783 @node GDB/MI Out-of-band Records
17784 @subsection @sc{gdb/mi} Out-of-band Records
17786 @cindex out-of-band records in @sc{gdb/mi}
17787 @cindex @sc{gdb/mi}, out-of-band records
17788 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17789 additional changes that have occurred. Those changes can either be a
17790 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17791 target activity (e.g., target stopped).
17793 The following is a preliminary list of possible out-of-band records.
17794 In particular, the @var{exec-async-output} records.
17797 @item *stopped,reason="@var{reason}"
17800 @var{reason} can be one of the following:
17803 @item breakpoint-hit
17804 A breakpoint was reached.
17805 @item watchpoint-trigger
17806 A watchpoint was triggered.
17807 @item read-watchpoint-trigger
17808 A read watchpoint was triggered.
17809 @item access-watchpoint-trigger
17810 An access watchpoint was triggered.
17811 @item function-finished
17812 An -exec-finish or similar CLI command was accomplished.
17813 @item location-reached
17814 An -exec-until or similar CLI command was accomplished.
17815 @item watchpoint-scope
17816 A watchpoint has gone out of scope.
17817 @item end-stepping-range
17818 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17819 similar CLI command was accomplished.
17820 @item exited-signalled
17821 The inferior exited because of a signal.
17823 The inferior exited.
17824 @item exited-normally
17825 The inferior exited normally.
17826 @item signal-received
17827 A signal was received by the inferior.
17831 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17832 @node GDB/MI Simple Examples
17833 @section Simple Examples of @sc{gdb/mi} Interaction
17834 @cindex @sc{gdb/mi}, simple examples
17836 This subsection presents several simple examples of interaction using
17837 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17838 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17839 the output received from @sc{gdb/mi}.
17841 Note the line breaks shown in the examples are here only for
17842 readability, they don't appear in the real output.
17844 @subheading Setting a Breakpoint
17846 Setting a breakpoint generates synchronous output which contains detailed
17847 information of the breakpoint.
17850 -> -break-insert main
17851 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17852 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17853 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17857 @subheading Program Execution
17859 Program execution generates asynchronous records and MI gives the
17860 reason that execution stopped.
17866 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17867 frame=@{addr="0x08048564",func="main",
17868 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17869 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17874 <- *stopped,reason="exited-normally"
17878 @subheading Quitting @value{GDBN}
17880 Quitting @value{GDBN} just prints the result class @samp{^exit}.
17888 @subheading A Bad Command
17890 Here's what happens if you pass a non-existent command:
17894 <- ^error,msg="Undefined MI command: rubbish"
17899 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17900 @node GDB/MI Command Description Format
17901 @section @sc{gdb/mi} Command Description Format
17903 The remaining sections describe blocks of commands. Each block of
17904 commands is laid out in a fashion similar to this section.
17906 @subheading Motivation
17908 The motivation for this collection of commands.
17910 @subheading Introduction
17912 A brief introduction to this collection of commands as a whole.
17914 @subheading Commands
17916 For each command in the block, the following is described:
17918 @subsubheading Synopsis
17921 -command @var{args}@dots{}
17924 @subsubheading Result
17926 @subsubheading @value{GDBN} Command
17928 The corresponding @value{GDBN} CLI command(s), if any.
17930 @subsubheading Example
17932 Example(s) formatted for readability. Some of the described commands have
17933 not been implemented yet and these are labeled N.A.@: (not available).
17936 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17937 @node GDB/MI Breakpoint Commands
17938 @section @sc{gdb/mi} Breakpoint Commands
17940 @cindex breakpoint commands for @sc{gdb/mi}
17941 @cindex @sc{gdb/mi}, breakpoint commands
17942 This section documents @sc{gdb/mi} commands for manipulating
17945 @subheading The @code{-break-after} Command
17946 @findex -break-after
17948 @subsubheading Synopsis
17951 -break-after @var{number} @var{count}
17954 The breakpoint number @var{number} is not in effect until it has been
17955 hit @var{count} times. To see how this is reflected in the output of
17956 the @samp{-break-list} command, see the description of the
17957 @samp{-break-list} command below.
17959 @subsubheading @value{GDBN} Command
17961 The corresponding @value{GDBN} command is @samp{ignore}.
17963 @subsubheading Example
17968 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17969 fullname="/home/foo/hello.c",line="5",times="0"@}
17976 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17977 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17978 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17979 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17980 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17981 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17982 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17983 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17984 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17985 line="5",times="0",ignore="3"@}]@}
17990 @subheading The @code{-break-catch} Command
17991 @findex -break-catch
17993 @subheading The @code{-break-commands} Command
17994 @findex -break-commands
17998 @subheading The @code{-break-condition} Command
17999 @findex -break-condition
18001 @subsubheading Synopsis
18004 -break-condition @var{number} @var{expr}
18007 Breakpoint @var{number} will stop the program only if the condition in
18008 @var{expr} is true. The condition becomes part of the
18009 @samp{-break-list} output (see the description of the @samp{-break-list}
18012 @subsubheading @value{GDBN} Command
18014 The corresponding @value{GDBN} command is @samp{condition}.
18016 @subsubheading Example
18020 -break-condition 1 1
18024 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18025 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18026 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18027 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18028 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18029 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18030 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18031 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18032 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18033 line="5",cond="1",times="0",ignore="3"@}]@}
18037 @subheading The @code{-break-delete} Command
18038 @findex -break-delete
18040 @subsubheading Synopsis
18043 -break-delete ( @var{breakpoint} )+
18046 Delete the breakpoint(s) whose number(s) are specified in the argument
18047 list. This is obviously reflected in the breakpoint list.
18049 @subsubheading @value{GDBN} Command
18051 The corresponding @value{GDBN} command is @samp{delete}.
18053 @subsubheading Example
18061 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18062 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18063 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18064 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18065 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18066 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18067 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18072 @subheading The @code{-break-disable} Command
18073 @findex -break-disable
18075 @subsubheading Synopsis
18078 -break-disable ( @var{breakpoint} )+
18081 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18082 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18084 @subsubheading @value{GDBN} Command
18086 The corresponding @value{GDBN} command is @samp{disable}.
18088 @subsubheading Example
18096 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18097 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18098 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18099 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18100 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18101 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18102 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18103 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18104 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18105 line="5",times="0"@}]@}
18109 @subheading The @code{-break-enable} Command
18110 @findex -break-enable
18112 @subsubheading Synopsis
18115 -break-enable ( @var{breakpoint} )+
18118 Enable (previously disabled) @var{breakpoint}(s).
18120 @subsubheading @value{GDBN} Command
18122 The corresponding @value{GDBN} command is @samp{enable}.
18124 @subsubheading Example
18132 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18133 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18134 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18135 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18136 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18137 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18138 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18139 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18140 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18141 line="5",times="0"@}]@}
18145 @subheading The @code{-break-info} Command
18146 @findex -break-info
18148 @subsubheading Synopsis
18151 -break-info @var{breakpoint}
18155 Get information about a single breakpoint.
18157 @subsubheading @value{GDBN} Command
18159 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18161 @subsubheading Example
18164 @subheading The @code{-break-insert} Command
18165 @findex -break-insert
18167 @subsubheading Synopsis
18170 -break-insert [ -t ] [ -h ] [ -f ]
18171 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18172 [ -p @var{thread} ] [ @var{location} ]
18176 If specified, @var{location}, can be one of:
18183 @item filename:linenum
18184 @item filename:function
18188 The possible optional parameters of this command are:
18192 Insert a temporary breakpoint.
18194 Insert a hardware breakpoint.
18195 @item -c @var{condition}
18196 Make the breakpoint conditional on @var{condition}.
18197 @item -i @var{ignore-count}
18198 Initialize the @var{ignore-count}.
18200 If @var{location} cannot be parsed (for example if it
18201 refers to unknown files or functions), create a pending
18202 breakpoint. Without this flag, @value{GDBN} will report
18203 an error, and won't create a breakpoint, if @var{location}
18207 @subsubheading Result
18209 The result is in the form:
18212 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18213 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18214 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18215 times="@var{times}"@}
18219 where @var{number} is the @value{GDBN} number for this breakpoint,
18220 @var{funcname} is the name of the function where the breakpoint was
18221 inserted, @var{filename} is the name of the source file which contains
18222 this function, @var{lineno} is the source line number within that file
18223 and @var{times} the number of times that the breakpoint has been hit
18224 (always 0 for -break-insert but may be greater for -break-info or -break-list
18225 which use the same output).
18227 Note: this format is open to change.
18228 @c An out-of-band breakpoint instead of part of the result?
18230 @subsubheading @value{GDBN} Command
18232 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18233 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18235 @subsubheading Example
18240 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18241 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18243 -break-insert -t foo
18244 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18245 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18248 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18249 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18250 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18251 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18252 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18253 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18254 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18255 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18256 addr="0x0001072c", func="main",file="recursive2.c",
18257 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18258 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18259 addr="0x00010774",func="foo",file="recursive2.c",
18260 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18262 -break-insert -r foo.*
18263 ~int foo(int, int);
18264 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18265 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18269 @subheading The @code{-break-list} Command
18270 @findex -break-list
18272 @subsubheading Synopsis
18278 Displays the list of inserted breakpoints, showing the following fields:
18282 number of the breakpoint
18284 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18286 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18289 is the breakpoint enabled or no: @samp{y} or @samp{n}
18291 memory location at which the breakpoint is set
18293 logical location of the breakpoint, expressed by function name, file
18296 number of times the breakpoint has been hit
18299 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18300 @code{body} field is an empty list.
18302 @subsubheading @value{GDBN} Command
18304 The corresponding @value{GDBN} command is @samp{info break}.
18306 @subsubheading Example
18311 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18312 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18313 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18314 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18315 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18316 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18317 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18318 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18319 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18320 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18321 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18322 line="13",times="0"@}]@}
18326 Here's an example of the result when there are no breakpoints:
18331 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18332 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18333 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18334 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18335 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18336 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18337 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18342 @subheading The @code{-break-watch} Command
18343 @findex -break-watch
18345 @subsubheading Synopsis
18348 -break-watch [ -a | -r ]
18351 Create a watchpoint. With the @samp{-a} option it will create an
18352 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18353 read from or on a write to the memory location. With the @samp{-r}
18354 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18355 trigger only when the memory location is accessed for reading. Without
18356 either of the options, the watchpoint created is a regular watchpoint,
18357 i.e., it will trigger when the memory location is accessed for writing.
18358 @xref{Set Watchpoints, , Setting Watchpoints}.
18360 Note that @samp{-break-list} will report a single list of watchpoints and
18361 breakpoints inserted.
18363 @subsubheading @value{GDBN} Command
18365 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18368 @subsubheading Example
18370 Setting a watchpoint on a variable in the @code{main} function:
18375 ^done,wpt=@{number="2",exp="x"@}
18380 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18381 value=@{old="-268439212",new="55"@},
18382 frame=@{func="main",args=[],file="recursive2.c",
18383 fullname="/home/foo/bar/recursive2.c",line="5"@}
18387 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18388 the program execution twice: first for the variable changing value, then
18389 for the watchpoint going out of scope.
18394 ^done,wpt=@{number="5",exp="C"@}
18399 *stopped,reason="watchpoint-trigger",
18400 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18401 frame=@{func="callee4",args=[],
18402 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18403 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18408 *stopped,reason="watchpoint-scope",wpnum="5",
18409 frame=@{func="callee3",args=[@{name="strarg",
18410 value="0x11940 \"A string argument.\""@}],
18411 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18412 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18416 Listing breakpoints and watchpoints, at different points in the program
18417 execution. Note that once the watchpoint goes out of scope, it is
18423 ^done,wpt=@{number="2",exp="C"@}
18426 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18427 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18428 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18429 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18430 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18431 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18432 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18433 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18434 addr="0x00010734",func="callee4",
18435 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18436 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18437 bkpt=@{number="2",type="watchpoint",disp="keep",
18438 enabled="y",addr="",what="C",times="0"@}]@}
18443 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18444 value=@{old="-276895068",new="3"@},
18445 frame=@{func="callee4",args=[],
18446 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18447 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18450 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18451 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18452 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18453 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18454 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18455 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18456 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18457 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18458 addr="0x00010734",func="callee4",
18459 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18460 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18461 bkpt=@{number="2",type="watchpoint",disp="keep",
18462 enabled="y",addr="",what="C",times="-5"@}]@}
18466 ^done,reason="watchpoint-scope",wpnum="2",
18467 frame=@{func="callee3",args=[@{name="strarg",
18468 value="0x11940 \"A string argument.\""@}],
18469 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18470 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18473 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18474 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18475 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18476 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18477 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18478 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18479 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18480 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18481 addr="0x00010734",func="callee4",
18482 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18483 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18488 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18489 @node GDB/MI Program Context
18490 @section @sc{gdb/mi} Program Context
18492 @subheading The @code{-exec-arguments} Command
18493 @findex -exec-arguments
18496 @subsubheading Synopsis
18499 -exec-arguments @var{args}
18502 Set the inferior program arguments, to be used in the next
18505 @subsubheading @value{GDBN} Command
18507 The corresponding @value{GDBN} command is @samp{set args}.
18509 @subsubheading Example
18512 Don't have one around.
18515 @subheading The @code{-exec-show-arguments} Command
18516 @findex -exec-show-arguments
18518 @subsubheading Synopsis
18521 -exec-show-arguments
18524 Print the arguments of the program.
18526 @subsubheading @value{GDBN} Command
18528 The corresponding @value{GDBN} command is @samp{show args}.
18530 @subsubheading Example
18534 @subheading The @code{-environment-cd} Command
18535 @findex -environment-cd
18537 @subsubheading Synopsis
18540 -environment-cd @var{pathdir}
18543 Set @value{GDBN}'s working directory.
18545 @subsubheading @value{GDBN} Command
18547 The corresponding @value{GDBN} command is @samp{cd}.
18549 @subsubheading Example
18553 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18559 @subheading The @code{-environment-directory} Command
18560 @findex -environment-directory
18562 @subsubheading Synopsis
18565 -environment-directory [ -r ] [ @var{pathdir} ]+
18568 Add directories @var{pathdir} to beginning of search path for source files.
18569 If the @samp{-r} option is used, the search path is reset to the default
18570 search path. If directories @var{pathdir} are supplied in addition to the
18571 @samp{-r} option, the search path is first reset and then addition
18573 Multiple directories may be specified, separated by blanks. Specifying
18574 multiple directories in a single command
18575 results in the directories added to the beginning of the
18576 search path in the same order they were presented in the command.
18577 If blanks are needed as
18578 part of a directory name, double-quotes should be used around
18579 the name. In the command output, the path will show up separated
18580 by the system directory-separator character. The directory-separator
18581 character must not be used
18582 in any directory name.
18583 If no directories are specified, the current search path is displayed.
18585 @subsubheading @value{GDBN} Command
18587 The corresponding @value{GDBN} command is @samp{dir}.
18589 @subsubheading Example
18593 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18594 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18596 -environment-directory ""
18597 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18599 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18600 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18602 -environment-directory -r
18603 ^done,source-path="$cdir:$cwd"
18608 @subheading The @code{-environment-path} Command
18609 @findex -environment-path
18611 @subsubheading Synopsis
18614 -environment-path [ -r ] [ @var{pathdir} ]+
18617 Add directories @var{pathdir} to beginning of search path for object files.
18618 If the @samp{-r} option is used, the search path is reset to the original
18619 search path that existed at gdb start-up. If directories @var{pathdir} are
18620 supplied in addition to the
18621 @samp{-r} option, the search path is first reset and then addition
18623 Multiple directories may be specified, separated by blanks. Specifying
18624 multiple directories in a single command
18625 results in the directories added to the beginning of the
18626 search path in the same order they were presented in the command.
18627 If blanks are needed as
18628 part of a directory name, double-quotes should be used around
18629 the name. In the command output, the path will show up separated
18630 by the system directory-separator character. The directory-separator
18631 character must not be used
18632 in any directory name.
18633 If no directories are specified, the current path is displayed.
18636 @subsubheading @value{GDBN} Command
18638 The corresponding @value{GDBN} command is @samp{path}.
18640 @subsubheading Example
18645 ^done,path="/usr/bin"
18647 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18648 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18650 -environment-path -r /usr/local/bin
18651 ^done,path="/usr/local/bin:/usr/bin"
18656 @subheading The @code{-environment-pwd} Command
18657 @findex -environment-pwd
18659 @subsubheading Synopsis
18665 Show the current working directory.
18667 @subsubheading @value{GDBN} Command
18669 The corresponding @value{GDBN} command is @samp{pwd}.
18671 @subsubheading Example
18676 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18680 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18681 @node GDB/MI Thread Commands
18682 @section @sc{gdb/mi} Thread Commands
18685 @subheading The @code{-thread-info} Command
18686 @findex -thread-info
18688 @subsubheading Synopsis
18694 @subsubheading @value{GDBN} Command
18698 @subsubheading Example
18702 @subheading The @code{-thread-list-all-threads} Command
18703 @findex -thread-list-all-threads
18705 @subsubheading Synopsis
18708 -thread-list-all-threads
18711 @subsubheading @value{GDBN} Command
18713 The equivalent @value{GDBN} command is @samp{info threads}.
18715 @subsubheading Example
18719 @subheading The @code{-thread-list-ids} Command
18720 @findex -thread-list-ids
18722 @subsubheading Synopsis
18728 Produces a list of the currently known @value{GDBN} thread ids. At the
18729 end of the list it also prints the total number of such threads.
18731 @subsubheading @value{GDBN} Command
18733 Part of @samp{info threads} supplies the same information.
18735 @subsubheading Example
18737 No threads present, besides the main process:
18742 ^done,thread-ids=@{@},number-of-threads="0"
18752 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18753 number-of-threads="3"
18758 @subheading The @code{-thread-select} Command
18759 @findex -thread-select
18761 @subsubheading Synopsis
18764 -thread-select @var{threadnum}
18767 Make @var{threadnum} the current thread. It prints the number of the new
18768 current thread, and the topmost frame for that thread.
18770 @subsubheading @value{GDBN} Command
18772 The corresponding @value{GDBN} command is @samp{thread}.
18774 @subsubheading Example
18781 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18782 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18786 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18787 number-of-threads="3"
18790 ^done,new-thread-id="3",
18791 frame=@{level="0",func="vprintf",
18792 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18793 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18797 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18798 @node GDB/MI Program Execution
18799 @section @sc{gdb/mi} Program Execution
18801 These are the asynchronous commands which generate the out-of-band
18802 record @samp{*stopped}. Currently @value{GDBN} only really executes
18803 asynchronously with remote targets and this interaction is mimicked in
18806 @subheading The @code{-exec-continue} Command
18807 @findex -exec-continue
18809 @subsubheading Synopsis
18815 Resumes the execution of the inferior program until a breakpoint is
18816 encountered, or until the inferior exits.
18818 @subsubheading @value{GDBN} Command
18820 The corresponding @value{GDBN} corresponding is @samp{continue}.
18822 @subsubheading Example
18829 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18830 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18835 @subheading The @code{-exec-finish} Command
18836 @findex -exec-finish
18838 @subsubheading Synopsis
18844 Resumes the execution of the inferior program until the current
18845 function is exited. Displays the results returned by the function.
18847 @subsubheading @value{GDBN} Command
18849 The corresponding @value{GDBN} command is @samp{finish}.
18851 @subsubheading Example
18853 Function returning @code{void}.
18860 *stopped,reason="function-finished",frame=@{func="main",args=[],
18861 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18865 Function returning other than @code{void}. The name of the internal
18866 @value{GDBN} variable storing the result is printed, together with the
18873 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18874 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18875 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18876 gdb-result-var="$1",return-value="0"
18881 @subheading The @code{-exec-interrupt} Command
18882 @findex -exec-interrupt
18884 @subsubheading Synopsis
18890 Interrupts the background execution of the target. Note how the token
18891 associated with the stop message is the one for the execution command
18892 that has been interrupted. The token for the interrupt itself only
18893 appears in the @samp{^done} output. If the user is trying to
18894 interrupt a non-running program, an error message will be printed.
18896 @subsubheading @value{GDBN} Command
18898 The corresponding @value{GDBN} command is @samp{interrupt}.
18900 @subsubheading Example
18911 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18912 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18913 fullname="/home/foo/bar/try.c",line="13"@}
18918 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18923 @subheading The @code{-exec-next} Command
18926 @subsubheading Synopsis
18932 Resumes execution of the inferior program, stopping when the beginning
18933 of the next source line is reached.
18935 @subsubheading @value{GDBN} Command
18937 The corresponding @value{GDBN} command is @samp{next}.
18939 @subsubheading Example
18945 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18950 @subheading The @code{-exec-next-instruction} Command
18951 @findex -exec-next-instruction
18953 @subsubheading Synopsis
18956 -exec-next-instruction
18959 Executes one machine instruction. If the instruction is a function
18960 call, continues until the function returns. If the program stops at an
18961 instruction in the middle of a source line, the address will be
18964 @subsubheading @value{GDBN} Command
18966 The corresponding @value{GDBN} command is @samp{nexti}.
18968 @subsubheading Example
18972 -exec-next-instruction
18976 *stopped,reason="end-stepping-range",
18977 addr="0x000100d4",line="5",file="hello.c"
18982 @subheading The @code{-exec-return} Command
18983 @findex -exec-return
18985 @subsubheading Synopsis
18991 Makes current function return immediately. Doesn't execute the inferior.
18992 Displays the new current frame.
18994 @subsubheading @value{GDBN} Command
18996 The corresponding @value{GDBN} command is @samp{return}.
18998 @subsubheading Example
19002 200-break-insert callee4
19003 200^done,bkpt=@{number="1",addr="0x00010734",
19004 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19009 000*stopped,reason="breakpoint-hit",bkptno="1",
19010 frame=@{func="callee4",args=[],
19011 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19012 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19018 111^done,frame=@{level="0",func="callee3",
19019 args=[@{name="strarg",
19020 value="0x11940 \"A string argument.\""@}],
19021 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19022 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19027 @subheading The @code{-exec-run} Command
19030 @subsubheading Synopsis
19036 Starts execution of the inferior from the beginning. The inferior
19037 executes until either a breakpoint is encountered or the program
19038 exits. In the latter case the output will include an exit code, if
19039 the program has exited exceptionally.
19041 @subsubheading @value{GDBN} Command
19043 The corresponding @value{GDBN} command is @samp{run}.
19045 @subsubheading Examples
19050 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19055 *stopped,reason="breakpoint-hit",bkptno="1",
19056 frame=@{func="main",args=[],file="recursive2.c",
19057 fullname="/home/foo/bar/recursive2.c",line="4"@}
19062 Program exited normally:
19070 *stopped,reason="exited-normally"
19075 Program exited exceptionally:
19083 *stopped,reason="exited",exit-code="01"
19087 Another way the program can terminate is if it receives a signal such as
19088 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19092 *stopped,reason="exited-signalled",signal-name="SIGINT",
19093 signal-meaning="Interrupt"
19097 @c @subheading -exec-signal
19100 @subheading The @code{-exec-step} Command
19103 @subsubheading Synopsis
19109 Resumes execution of the inferior program, stopping when the beginning
19110 of the next source line is reached, if the next source line is not a
19111 function call. If it is, stop at the first instruction of the called
19114 @subsubheading @value{GDBN} Command
19116 The corresponding @value{GDBN} command is @samp{step}.
19118 @subsubheading Example
19120 Stepping into a function:
19126 *stopped,reason="end-stepping-range",
19127 frame=@{func="foo",args=[@{name="a",value="10"@},
19128 @{name="b",value="0"@}],file="recursive2.c",
19129 fullname="/home/foo/bar/recursive2.c",line="11"@}
19139 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19144 @subheading The @code{-exec-step-instruction} Command
19145 @findex -exec-step-instruction
19147 @subsubheading Synopsis
19150 -exec-step-instruction
19153 Resumes the inferior which executes one machine instruction. The
19154 output, once @value{GDBN} has stopped, will vary depending on whether
19155 we have stopped in the middle of a source line or not. In the former
19156 case, the address at which the program stopped will be printed as
19159 @subsubheading @value{GDBN} Command
19161 The corresponding @value{GDBN} command is @samp{stepi}.
19163 @subsubheading Example
19167 -exec-step-instruction
19171 *stopped,reason="end-stepping-range",
19172 frame=@{func="foo",args=[],file="try.c",
19173 fullname="/home/foo/bar/try.c",line="10"@}
19175 -exec-step-instruction
19179 *stopped,reason="end-stepping-range",
19180 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19181 fullname="/home/foo/bar/try.c",line="10"@}
19186 @subheading The @code{-exec-until} Command
19187 @findex -exec-until
19189 @subsubheading Synopsis
19192 -exec-until [ @var{location} ]
19195 Executes the inferior until the @var{location} specified in the
19196 argument is reached. If there is no argument, the inferior executes
19197 until a source line greater than the current one is reached. The
19198 reason for stopping in this case will be @samp{location-reached}.
19200 @subsubheading @value{GDBN} Command
19202 The corresponding @value{GDBN} command is @samp{until}.
19204 @subsubheading Example
19208 -exec-until recursive2.c:6
19212 *stopped,reason="location-reached",frame=@{func="main",args=[],
19213 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19218 @subheading -file-clear
19219 Is this going away????
19222 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19223 @node GDB/MI Stack Manipulation
19224 @section @sc{gdb/mi} Stack Manipulation Commands
19227 @subheading The @code{-stack-info-frame} Command
19228 @findex -stack-info-frame
19230 @subsubheading Synopsis
19236 Get info on the selected frame.
19238 @subsubheading @value{GDBN} Command
19240 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19241 (without arguments).
19243 @subsubheading Example
19248 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19249 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19250 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19254 @subheading The @code{-stack-info-depth} Command
19255 @findex -stack-info-depth
19257 @subsubheading Synopsis
19260 -stack-info-depth [ @var{max-depth} ]
19263 Return the depth of the stack. If the integer argument @var{max-depth}
19264 is specified, do not count beyond @var{max-depth} frames.
19266 @subsubheading @value{GDBN} Command
19268 There's no equivalent @value{GDBN} command.
19270 @subsubheading Example
19272 For a stack with frame levels 0 through 11:
19279 -stack-info-depth 4
19282 -stack-info-depth 12
19285 -stack-info-depth 11
19288 -stack-info-depth 13
19293 @subheading The @code{-stack-list-arguments} Command
19294 @findex -stack-list-arguments
19296 @subsubheading Synopsis
19299 -stack-list-arguments @var{show-values}
19300 [ @var{low-frame} @var{high-frame} ]
19303 Display a list of the arguments for the frames between @var{low-frame}
19304 and @var{high-frame} (inclusive). If @var{low-frame} and
19305 @var{high-frame} are not provided, list the arguments for the whole
19306 call stack. If the two arguments are equal, show the single frame
19307 at the corresponding level. It is an error if @var{low-frame} is
19308 larger than the actual number of frames. On the other hand,
19309 @var{high-frame} may be larger than the actual number of frames, in
19310 which case only existing frames will be returned.
19312 The @var{show-values} argument must have a value of 0 or 1. A value of
19313 0 means that only the names of the arguments are listed, a value of 1
19314 means that both names and values of the arguments are printed.
19316 @subsubheading @value{GDBN} Command
19318 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19319 @samp{gdb_get_args} command which partially overlaps with the
19320 functionality of @samp{-stack-list-arguments}.
19322 @subsubheading Example
19329 frame=@{level="0",addr="0x00010734",func="callee4",
19330 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19331 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19332 frame=@{level="1",addr="0x0001076c",func="callee3",
19333 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19334 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19335 frame=@{level="2",addr="0x0001078c",func="callee2",
19336 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19337 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19338 frame=@{level="3",addr="0x000107b4",func="callee1",
19339 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19340 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19341 frame=@{level="4",addr="0x000107e0",func="main",
19342 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19343 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19345 -stack-list-arguments 0
19348 frame=@{level="0",args=[]@},
19349 frame=@{level="1",args=[name="strarg"]@},
19350 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19351 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19352 frame=@{level="4",args=[]@}]
19354 -stack-list-arguments 1
19357 frame=@{level="0",args=[]@},
19359 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19360 frame=@{level="2",args=[
19361 @{name="intarg",value="2"@},
19362 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19363 @{frame=@{level="3",args=[
19364 @{name="intarg",value="2"@},
19365 @{name="strarg",value="0x11940 \"A string argument.\""@},
19366 @{name="fltarg",value="3.5"@}]@},
19367 frame=@{level="4",args=[]@}]
19369 -stack-list-arguments 0 2 2
19370 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19372 -stack-list-arguments 1 2 2
19373 ^done,stack-args=[frame=@{level="2",
19374 args=[@{name="intarg",value="2"@},
19375 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19379 @c @subheading -stack-list-exception-handlers
19382 @subheading The @code{-stack-list-frames} Command
19383 @findex -stack-list-frames
19385 @subsubheading Synopsis
19388 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19391 List the frames currently on the stack. For each frame it displays the
19396 The frame number, 0 being the topmost frame, i.e., the innermost function.
19398 The @code{$pc} value for that frame.
19402 File name of the source file where the function lives.
19404 Line number corresponding to the @code{$pc}.
19407 If invoked without arguments, this command prints a backtrace for the
19408 whole stack. If given two integer arguments, it shows the frames whose
19409 levels are between the two arguments (inclusive). If the two arguments
19410 are equal, it shows the single frame at the corresponding level. It is
19411 an error if @var{low-frame} is larger than the actual number of
19412 frames. On the other hand, @var{high-frame} may be larger than the
19413 actual number of frames, in which case only existing frames will be returned.
19415 @subsubheading @value{GDBN} Command
19417 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19419 @subsubheading Example
19421 Full stack backtrace:
19427 [frame=@{level="0",addr="0x0001076c",func="foo",
19428 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19429 frame=@{level="1",addr="0x000107a4",func="foo",
19430 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19431 frame=@{level="2",addr="0x000107a4",func="foo",
19432 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19433 frame=@{level="3",addr="0x000107a4",func="foo",
19434 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19435 frame=@{level="4",addr="0x000107a4",func="foo",
19436 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19437 frame=@{level="5",addr="0x000107a4",func="foo",
19438 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19439 frame=@{level="6",addr="0x000107a4",func="foo",
19440 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19441 frame=@{level="7",addr="0x000107a4",func="foo",
19442 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19443 frame=@{level="8",addr="0x000107a4",func="foo",
19444 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19445 frame=@{level="9",addr="0x000107a4",func="foo",
19446 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19447 frame=@{level="10",addr="0x000107a4",func="foo",
19448 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19449 frame=@{level="11",addr="0x00010738",func="main",
19450 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19454 Show frames between @var{low_frame} and @var{high_frame}:
19458 -stack-list-frames 3 5
19460 [frame=@{level="3",addr="0x000107a4",func="foo",
19461 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19462 frame=@{level="4",addr="0x000107a4",func="foo",
19463 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19464 frame=@{level="5",addr="0x000107a4",func="foo",
19465 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19469 Show a single frame:
19473 -stack-list-frames 3 3
19475 [frame=@{level="3",addr="0x000107a4",func="foo",
19476 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19481 @subheading The @code{-stack-list-locals} Command
19482 @findex -stack-list-locals
19484 @subsubheading Synopsis
19487 -stack-list-locals @var{print-values}
19490 Display the local variable names for the selected frame. If
19491 @var{print-values} is 0 or @code{--no-values}, print only the names of
19492 the variables; if it is 1 or @code{--all-values}, print also their
19493 values; and if it is 2 or @code{--simple-values}, print the name,
19494 type and value for simple data types and the name and type for arrays,
19495 structures and unions. In this last case, a frontend can immediately
19496 display the value of simple data types and create variable objects for
19497 other data types when the user wishes to explore their values in
19500 @subsubheading @value{GDBN} Command
19502 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19504 @subsubheading Example
19508 -stack-list-locals 0
19509 ^done,locals=[name="A",name="B",name="C"]
19511 -stack-list-locals --all-values
19512 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19513 @{name="C",value="@{1, 2, 3@}"@}]
19514 -stack-list-locals --simple-values
19515 ^done,locals=[@{name="A",type="int",value="1"@},
19516 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19521 @subheading The @code{-stack-select-frame} Command
19522 @findex -stack-select-frame
19524 @subsubheading Synopsis
19527 -stack-select-frame @var{framenum}
19530 Change the selected frame. Select a different frame @var{framenum} on
19533 @subsubheading @value{GDBN} Command
19535 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19536 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19538 @subsubheading Example
19542 -stack-select-frame 2
19547 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19548 @node GDB/MI Variable Objects
19549 @section @sc{gdb/mi} Variable Objects
19553 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19555 For the implementation of a variable debugger window (locals, watched
19556 expressions, etc.), we are proposing the adaptation of the existing code
19557 used by @code{Insight}.
19559 The two main reasons for that are:
19563 It has been proven in practice (it is already on its second generation).
19566 It will shorten development time (needless to say how important it is
19570 The original interface was designed to be used by Tcl code, so it was
19571 slightly changed so it could be used through @sc{gdb/mi}. This section
19572 describes the @sc{gdb/mi} operations that will be available and gives some
19573 hints about their use.
19575 @emph{Note}: In addition to the set of operations described here, we
19576 expect the @sc{gui} implementation of a variable window to require, at
19577 least, the following operations:
19580 @item @code{-gdb-show} @code{output-radix}
19581 @item @code{-stack-list-arguments}
19582 @item @code{-stack-list-locals}
19583 @item @code{-stack-select-frame}
19588 @subheading Introduction to Variable Objects
19590 @cindex variable objects in @sc{gdb/mi}
19592 Variable objects are "object-oriented" MI interface for examining and
19593 changing values of expressions. Unlike some other MI interfaces that
19594 work with expressions, variable objects are specifically designed for
19595 simple and efficient presentation in the frontend. A variable object
19596 is identified by string name. When a variable object is created, the
19597 frontend specifies the expression for that variable object. The
19598 expression can be a simple variable, or it can be an arbitrary complex
19599 expression, and can even involve CPU registers. After creating a
19600 variable object, the frontend can invoke other variable object
19601 operations---for example to obtain or change the value of a variable
19602 object, or to change display format.
19604 Variable objects have hierarchical tree structure. Any variable object
19605 that corresponds to a composite type, such as structure in C, has
19606 a number of child variable objects, for example corresponding to each
19607 element of a structure. A child variable object can itself have
19608 children, recursively. Recursion ends when we reach
19609 leaf variable objects, which always have built-in types. Child variable
19610 objects are created only by explicit request, so if a frontend
19611 is not interested in the children of a particular variable object, no
19612 child will be created.
19614 For a leaf variable object it is possible to obtain its value as a
19615 string, or set the value from a string. String value can be also
19616 obtained for a non-leaf variable object, but it's generally a string
19617 that only indicates the type of the object, and does not list its
19618 contents. Assignment to a non-leaf variable object is not allowed.
19620 A frontend does not need to read the values of all variable objects each time
19621 the program stops. Instead, MI provides an update command that lists all
19622 variable objects whose values has changed since the last update
19623 operation. This considerably reduces the amount of data that must
19624 be transferred to the frontend. As noted above, children variable
19625 objects are created on demand, and only leaf variable objects have a
19626 real value. As result, gdb will read target memory only for leaf
19627 variables that frontend has created.
19629 The automatic update is not always desirable. For example, a frontend
19630 might want to keep a value of some expression for future reference,
19631 and never update it. For another example, fetching memory is
19632 relatively slow for embedded targets, so a frontend might want
19633 to disable automatic update for the variables that are either not
19634 visible on the screen, or ``closed''. This is possible using so
19635 called ``frozen variable objects''. Such variable objects are never
19636 implicitly updated.
19638 The following is the complete set of @sc{gdb/mi} operations defined to
19639 access this functionality:
19641 @multitable @columnfractions .4 .6
19642 @item @strong{Operation}
19643 @tab @strong{Description}
19645 @item @code{-var-create}
19646 @tab create a variable object
19647 @item @code{-var-delete}
19648 @tab delete the variable object and/or its children
19649 @item @code{-var-set-format}
19650 @tab set the display format of this variable
19651 @item @code{-var-show-format}
19652 @tab show the display format of this variable
19653 @item @code{-var-info-num-children}
19654 @tab tells how many children this object has
19655 @item @code{-var-list-children}
19656 @tab return a list of the object's children
19657 @item @code{-var-info-type}
19658 @tab show the type of this variable object
19659 @item @code{-var-info-expression}
19660 @tab print parent-relative expression that this variable object represents
19661 @item @code{-var-info-path-expression}
19662 @tab print full expression that this variable object represents
19663 @item @code{-var-show-attributes}
19664 @tab is this variable editable? does it exist here?
19665 @item @code{-var-evaluate-expression}
19666 @tab get the value of this variable
19667 @item @code{-var-assign}
19668 @tab set the value of this variable
19669 @item @code{-var-update}
19670 @tab update the variable and its children
19671 @item @code{-var-set-frozen}
19672 @tab set frozeness attribute
19675 In the next subsection we describe each operation in detail and suggest
19676 how it can be used.
19678 @subheading Description And Use of Operations on Variable Objects
19680 @subheading The @code{-var-create} Command
19681 @findex -var-create
19683 @subsubheading Synopsis
19686 -var-create @{@var{name} | "-"@}
19687 @{@var{frame-addr} | "*"@} @var{expression}
19690 This operation creates a variable object, which allows the monitoring of
19691 a variable, the result of an expression, a memory cell or a CPU
19694 The @var{name} parameter is the string by which the object can be
19695 referenced. It must be unique. If @samp{-} is specified, the varobj
19696 system will generate a string ``varNNNNNN'' automatically. It will be
19697 unique provided that one does not specify @var{name} on that format.
19698 The command fails if a duplicate name is found.
19700 The frame under which the expression should be evaluated can be
19701 specified by @var{frame-addr}. A @samp{*} indicates that the current
19702 frame should be used.
19704 @var{expression} is any expression valid on the current language set (must not
19705 begin with a @samp{*}), or one of the following:
19709 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19712 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19715 @samp{$@var{regname}} --- a CPU register name
19718 @subsubheading Result
19720 This operation returns the name, number of children and the type of the
19721 object created. Type is returned as a string as the ones generated by
19722 the @value{GDBN} CLI:
19725 name="@var{name}",numchild="N",type="@var{type}"
19729 @subheading The @code{-var-delete} Command
19730 @findex -var-delete
19732 @subsubheading Synopsis
19735 -var-delete [ -c ] @var{name}
19738 Deletes a previously created variable object and all of its children.
19739 With the @samp{-c} option, just deletes the children.
19741 Returns an error if the object @var{name} is not found.
19744 @subheading The @code{-var-set-format} Command
19745 @findex -var-set-format
19747 @subsubheading Synopsis
19750 -var-set-format @var{name} @var{format-spec}
19753 Sets the output format for the value of the object @var{name} to be
19756 The syntax for the @var{format-spec} is as follows:
19759 @var{format-spec} @expansion{}
19760 @{binary | decimal | hexadecimal | octal | natural@}
19763 The natural format is the default format choosen automatically
19764 based on the variable type (like decimal for an @code{int}, hex
19765 for pointers, etc.).
19767 For a variable with children, the format is set only on the
19768 variable itself, and the children are not affected.
19770 @subheading The @code{-var-show-format} Command
19771 @findex -var-show-format
19773 @subsubheading Synopsis
19776 -var-show-format @var{name}
19779 Returns the format used to display the value of the object @var{name}.
19782 @var{format} @expansion{}
19787 @subheading The @code{-var-info-num-children} Command
19788 @findex -var-info-num-children
19790 @subsubheading Synopsis
19793 -var-info-num-children @var{name}
19796 Returns the number of children of a variable object @var{name}:
19803 @subheading The @code{-var-list-children} Command
19804 @findex -var-list-children
19806 @subsubheading Synopsis
19809 -var-list-children [@var{print-values}] @var{name}
19811 @anchor{-var-list-children}
19813 Return a list of the children of the specified variable object and
19814 create variable objects for them, if they do not already exist. With
19815 a single argument or if @var{print-values} has a value for of 0 or
19816 @code{--no-values}, print only the names of the variables; if
19817 @var{print-values} is 1 or @code{--all-values}, also print their
19818 values; and if it is 2 or @code{--simple-values} print the name and
19819 value for simple data types and just the name for arrays, structures
19822 @subsubheading Example
19826 -var-list-children n
19827 ^done,numchild=@var{n},children=[@{name=@var{name},
19828 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19830 -var-list-children --all-values n
19831 ^done,numchild=@var{n},children=[@{name=@var{name},
19832 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19836 @subheading The @code{-var-info-type} Command
19837 @findex -var-info-type
19839 @subsubheading Synopsis
19842 -var-info-type @var{name}
19845 Returns the type of the specified variable @var{name}. The type is
19846 returned as a string in the same format as it is output by the
19850 type=@var{typename}
19854 @subheading The @code{-var-info-expression} Command
19855 @findex -var-info-expression
19857 @subsubheading Synopsis
19860 -var-info-expression @var{name}
19863 Returns a string that is suitable for presenting this
19864 variable object in user interface. The string is generally
19865 not valid expression in the current language, and cannot be evaluated.
19867 For example, if @code{a} is an array, and variable object
19868 @code{A} was created for @code{a}, then we'll get this output:
19871 (gdb) -var-info-expression A.1
19872 ^done,lang="C",exp="1"
19876 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
19878 Note that the output of the @code{-var-list-children} command also
19879 includes those expressions, so the @code{-var-info-expression} command
19882 @subheading The @code{-var-info-path-expression} Command
19883 @findex -var-info-path-expression
19885 @subsubheading Synopsis
19888 -var-info-path-expression @var{name}
19891 Returns an expression that can be evaluated in the current
19892 context and will yield the same value that a variable object has.
19893 Compare this with the @code{-var-info-expression} command, which
19894 result can be used only for UI presentation. Typical use of
19895 the @code{-var-info-path-expression} command is creating a
19896 watchpoint from a variable object.
19898 For example, suppose @code{C} is a C@t{++} class, derived from class
19899 @code{Base}, and that the @code{Base} class has a member called
19900 @code{m_size}. Assume a variable @code{c} is has the type of
19901 @code{C} and a variable object @code{C} was created for variable
19902 @code{c}. Then, we'll get this output:
19904 (gdb) -var-info-path-expression C.Base.public.m_size
19905 ^done,path_expr=((Base)c).m_size)
19908 @subheading The @code{-var-show-attributes} Command
19909 @findex -var-show-attributes
19911 @subsubheading Synopsis
19914 -var-show-attributes @var{name}
19917 List attributes of the specified variable object @var{name}:
19920 status=@var{attr} [ ( ,@var{attr} )* ]
19924 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19926 @subheading The @code{-var-evaluate-expression} Command
19927 @findex -var-evaluate-expression
19929 @subsubheading Synopsis
19932 -var-evaluate-expression @var{name}
19935 Evaluates the expression that is represented by the specified variable
19936 object and returns its value as a string. The format of the
19937 string can be changed using the @code{-var-set-format} command.
19943 Note that one must invoke @code{-var-list-children} for a variable
19944 before the value of a child variable can be evaluated.
19946 @subheading The @code{-var-assign} Command
19947 @findex -var-assign
19949 @subsubheading Synopsis
19952 -var-assign @var{name} @var{expression}
19955 Assigns the value of @var{expression} to the variable object specified
19956 by @var{name}. The object must be @samp{editable}. If the variable's
19957 value is altered by the assign, the variable will show up in any
19958 subsequent @code{-var-update} list.
19960 @subsubheading Example
19968 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19972 @subheading The @code{-var-update} Command
19973 @findex -var-update
19975 @subsubheading Synopsis
19978 -var-update [@var{print-values}] @{@var{name} | "*"@}
19981 Reevaluate the expressions corresponding to the variable object
19982 @var{name} and all its direct and indirect children, and return the
19983 list of variable objects whose values have changed; @var{name} must
19984 be a root variable object. Here, ``changed'' means that the result of
19985 @code{-var-evaluate-expression} before and after the
19986 @code{-var-update} is different. If @samp{*} is used as the variable
19987 object names, all existing variable objects are updated, except
19988 for frozen ones (@pxref{-var-set-frozen}). The option
19989 @var{print-values} determines whether both names and values, or just
19990 names are printed. The possible values of this options are the same
19991 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
19992 recommended to use the @samp{--all-values} option, to reduce the
19993 number of MI commands needed on each program stop.
19996 @subsubheading Example
20003 -var-update --all-values var1
20004 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20005 type_changed="false"@}]
20009 @anchor{-var-update}
20010 The field in_scope may take three values:
20014 The variable object's current value is valid.
20017 The variable object does not currently hold a valid value but it may
20018 hold one in the future if its associated expression comes back into
20022 The variable object no longer holds a valid value.
20023 This can occur when the executable file being debugged has changed,
20024 either through recompilation or by using the @value{GDBN} @code{file}
20025 command. The front end should normally choose to delete these variable
20029 In the future new values may be added to this list so the front should
20030 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
20032 @subheading The @code{-var-set-frozen} Command
20033 @findex -var-set-frozen
20034 @anchor{-var-set-frozen}
20036 @subsubheading Synopsis
20039 -var-set-frozen @var{name} @var{flag}
20042 Set the frozenness flag on the variable object @var{name}. The
20043 @var{flag} parameter should be either @samp{1} to make the variable
20044 frozen or @samp{0} to make it unfrozen. If a variable object is
20045 frozen, then neither itself, nor any of its children, are
20046 implicitly updated by @code{-var-update} of
20047 a parent variable or by @code{-var-update *}. Only
20048 @code{-var-update} of the variable itself will update its value and
20049 values of its children. After a variable object is unfrozen, it is
20050 implicitly updated by all subsequent @code{-var-update} operations.
20051 Unfreezing a variable does not update it, only subsequent
20052 @code{-var-update} does.
20054 @subsubheading Example
20058 -var-set-frozen V 1
20064 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20065 @node GDB/MI Data Manipulation
20066 @section @sc{gdb/mi} Data Manipulation
20068 @cindex data manipulation, in @sc{gdb/mi}
20069 @cindex @sc{gdb/mi}, data manipulation
20070 This section describes the @sc{gdb/mi} commands that manipulate data:
20071 examine memory and registers, evaluate expressions, etc.
20073 @c REMOVED FROM THE INTERFACE.
20074 @c @subheading -data-assign
20075 @c Change the value of a program variable. Plenty of side effects.
20076 @c @subsubheading GDB Command
20078 @c @subsubheading Example
20081 @subheading The @code{-data-disassemble} Command
20082 @findex -data-disassemble
20084 @subsubheading Synopsis
20088 [ -s @var{start-addr} -e @var{end-addr} ]
20089 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20097 @item @var{start-addr}
20098 is the beginning address (or @code{$pc})
20099 @item @var{end-addr}
20101 @item @var{filename}
20102 is the name of the file to disassemble
20103 @item @var{linenum}
20104 is the line number to disassemble around
20106 is the number of disassembly lines to be produced. If it is -1,
20107 the whole function will be disassembled, in case no @var{end-addr} is
20108 specified. If @var{end-addr} is specified as a non-zero value, and
20109 @var{lines} is lower than the number of disassembly lines between
20110 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20111 displayed; if @var{lines} is higher than the number of lines between
20112 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20115 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20119 @subsubheading Result
20121 The output for each instruction is composed of four fields:
20130 Note that whatever included in the instruction field, is not manipulated
20131 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20133 @subsubheading @value{GDBN} Command
20135 There's no direct mapping from this command to the CLI.
20137 @subsubheading Example
20139 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20143 -data-disassemble -s $pc -e "$pc + 20" -- 0
20146 @{address="0x000107c0",func-name="main",offset="4",
20147 inst="mov 2, %o0"@},
20148 @{address="0x000107c4",func-name="main",offset="8",
20149 inst="sethi %hi(0x11800), %o2"@},
20150 @{address="0x000107c8",func-name="main",offset="12",
20151 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20152 @{address="0x000107cc",func-name="main",offset="16",
20153 inst="sethi %hi(0x11800), %o2"@},
20154 @{address="0x000107d0",func-name="main",offset="20",
20155 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20159 Disassemble the whole @code{main} function. Line 32 is part of
20163 -data-disassemble -f basics.c -l 32 -- 0
20165 @{address="0x000107bc",func-name="main",offset="0",
20166 inst="save %sp, -112, %sp"@},
20167 @{address="0x000107c0",func-name="main",offset="4",
20168 inst="mov 2, %o0"@},
20169 @{address="0x000107c4",func-name="main",offset="8",
20170 inst="sethi %hi(0x11800), %o2"@},
20172 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20173 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20177 Disassemble 3 instructions from the start of @code{main}:
20181 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20183 @{address="0x000107bc",func-name="main",offset="0",
20184 inst="save %sp, -112, %sp"@},
20185 @{address="0x000107c0",func-name="main",offset="4",
20186 inst="mov 2, %o0"@},
20187 @{address="0x000107c4",func-name="main",offset="8",
20188 inst="sethi %hi(0x11800), %o2"@}]
20192 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20196 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20198 src_and_asm_line=@{line="31",
20199 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20200 testsuite/gdb.mi/basics.c",line_asm_insn=[
20201 @{address="0x000107bc",func-name="main",offset="0",
20202 inst="save %sp, -112, %sp"@}]@},
20203 src_and_asm_line=@{line="32",
20204 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20205 testsuite/gdb.mi/basics.c",line_asm_insn=[
20206 @{address="0x000107c0",func-name="main",offset="4",
20207 inst="mov 2, %o0"@},
20208 @{address="0x000107c4",func-name="main",offset="8",
20209 inst="sethi %hi(0x11800), %o2"@}]@}]
20214 @subheading The @code{-data-evaluate-expression} Command
20215 @findex -data-evaluate-expression
20217 @subsubheading Synopsis
20220 -data-evaluate-expression @var{expr}
20223 Evaluate @var{expr} as an expression. The expression could contain an
20224 inferior function call. The function call will execute synchronously.
20225 If the expression contains spaces, it must be enclosed in double quotes.
20227 @subsubheading @value{GDBN} Command
20229 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20230 @samp{call}. In @code{gdbtk} only, there's a corresponding
20231 @samp{gdb_eval} command.
20233 @subsubheading Example
20235 In the following example, the numbers that precede the commands are the
20236 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20237 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20241 211-data-evaluate-expression A
20244 311-data-evaluate-expression &A
20245 311^done,value="0xefffeb7c"
20247 411-data-evaluate-expression A+3
20250 511-data-evaluate-expression "A + 3"
20256 @subheading The @code{-data-list-changed-registers} Command
20257 @findex -data-list-changed-registers
20259 @subsubheading Synopsis
20262 -data-list-changed-registers
20265 Display a list of the registers that have changed.
20267 @subsubheading @value{GDBN} Command
20269 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20270 has the corresponding command @samp{gdb_changed_register_list}.
20272 @subsubheading Example
20274 On a PPC MBX board:
20282 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20283 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20285 -data-list-changed-registers
20286 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20287 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20288 "24","25","26","27","28","30","31","64","65","66","67","69"]
20293 @subheading The @code{-data-list-register-names} Command
20294 @findex -data-list-register-names
20296 @subsubheading Synopsis
20299 -data-list-register-names [ ( @var{regno} )+ ]
20302 Show a list of register names for the current target. If no arguments
20303 are given, it shows a list of the names of all the registers. If
20304 integer numbers are given as arguments, it will print a list of the
20305 names of the registers corresponding to the arguments. To ensure
20306 consistency between a register name and its number, the output list may
20307 include empty register names.
20309 @subsubheading @value{GDBN} Command
20311 @value{GDBN} does not have a command which corresponds to
20312 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20313 corresponding command @samp{gdb_regnames}.
20315 @subsubheading Example
20317 For the PPC MBX board:
20320 -data-list-register-names
20321 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20322 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20323 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20324 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20325 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20326 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20327 "", "pc","ps","cr","lr","ctr","xer"]
20329 -data-list-register-names 1 2 3
20330 ^done,register-names=["r1","r2","r3"]
20334 @subheading The @code{-data-list-register-values} Command
20335 @findex -data-list-register-values
20337 @subsubheading Synopsis
20340 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20343 Display the registers' contents. @var{fmt} is the format according to
20344 which the registers' contents are to be returned, followed by an optional
20345 list of numbers specifying the registers to display. A missing list of
20346 numbers indicates that the contents of all the registers must be returned.
20348 Allowed formats for @var{fmt} are:
20365 @subsubheading @value{GDBN} Command
20367 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20368 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20370 @subsubheading Example
20372 For a PPC MBX board (note: line breaks are for readability only, they
20373 don't appear in the actual output):
20377 -data-list-register-values r 64 65
20378 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20379 @{number="65",value="0x00029002"@}]
20381 -data-list-register-values x
20382 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20383 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20384 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20385 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20386 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20387 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20388 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20389 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20390 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20391 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20392 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20393 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20394 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20395 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20396 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20397 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20398 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20399 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20400 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20401 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20402 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20403 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20404 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20405 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20406 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20407 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20408 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20409 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20410 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20411 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20412 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20413 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20414 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20415 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20416 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20417 @{number="69",value="0x20002b03"@}]
20422 @subheading The @code{-data-read-memory} Command
20423 @findex -data-read-memory
20425 @subsubheading Synopsis
20428 -data-read-memory [ -o @var{byte-offset} ]
20429 @var{address} @var{word-format} @var{word-size}
20430 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20437 @item @var{address}
20438 An expression specifying the address of the first memory word to be
20439 read. Complex expressions containing embedded white space should be
20440 quoted using the C convention.
20442 @item @var{word-format}
20443 The format to be used to print the memory words. The notation is the
20444 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20447 @item @var{word-size}
20448 The size of each memory word in bytes.
20450 @item @var{nr-rows}
20451 The number of rows in the output table.
20453 @item @var{nr-cols}
20454 The number of columns in the output table.
20457 If present, indicates that each row should include an @sc{ascii} dump. The
20458 value of @var{aschar} is used as a padding character when a byte is not a
20459 member of the printable @sc{ascii} character set (printable @sc{ascii}
20460 characters are those whose code is between 32 and 126, inclusively).
20462 @item @var{byte-offset}
20463 An offset to add to the @var{address} before fetching memory.
20466 This command displays memory contents as a table of @var{nr-rows} by
20467 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20468 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20469 (returned as @samp{total-bytes}). Should less than the requested number
20470 of bytes be returned by the target, the missing words are identified
20471 using @samp{N/A}. The number of bytes read from the target is returned
20472 in @samp{nr-bytes} and the starting address used to read memory in
20475 The address of the next/previous row or page is available in
20476 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20479 @subsubheading @value{GDBN} Command
20481 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20482 @samp{gdb_get_mem} memory read command.
20484 @subsubheading Example
20486 Read six bytes of memory starting at @code{bytes+6} but then offset by
20487 @code{-6} bytes. Format as three rows of two columns. One byte per
20488 word. Display each word in hex.
20492 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20493 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20494 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20495 prev-page="0x0000138a",memory=[
20496 @{addr="0x00001390",data=["0x00","0x01"]@},
20497 @{addr="0x00001392",data=["0x02","0x03"]@},
20498 @{addr="0x00001394",data=["0x04","0x05"]@}]
20502 Read two bytes of memory starting at address @code{shorts + 64} and
20503 display as a single word formatted in decimal.
20507 5-data-read-memory shorts+64 d 2 1 1
20508 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20509 next-row="0x00001512",prev-row="0x0000150e",
20510 next-page="0x00001512",prev-page="0x0000150e",memory=[
20511 @{addr="0x00001510",data=["128"]@}]
20515 Read thirty two bytes of memory starting at @code{bytes+16} and format
20516 as eight rows of four columns. Include a string encoding with @samp{x}
20517 used as the non-printable character.
20521 4-data-read-memory bytes+16 x 1 8 4 x
20522 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20523 next-row="0x000013c0",prev-row="0x0000139c",
20524 next-page="0x000013c0",prev-page="0x00001380",memory=[
20525 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20526 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20527 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20528 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20529 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20530 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20531 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20532 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20536 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20537 @node GDB/MI Tracepoint Commands
20538 @section @sc{gdb/mi} Tracepoint Commands
20540 The tracepoint commands are not yet implemented.
20542 @c @subheading -trace-actions
20544 @c @subheading -trace-delete
20546 @c @subheading -trace-disable
20548 @c @subheading -trace-dump
20550 @c @subheading -trace-enable
20552 @c @subheading -trace-exists
20554 @c @subheading -trace-find
20556 @c @subheading -trace-frame-number
20558 @c @subheading -trace-info
20560 @c @subheading -trace-insert
20562 @c @subheading -trace-list
20564 @c @subheading -trace-pass-count
20566 @c @subheading -trace-save
20568 @c @subheading -trace-start
20570 @c @subheading -trace-stop
20573 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20574 @node GDB/MI Symbol Query
20575 @section @sc{gdb/mi} Symbol Query Commands
20578 @subheading The @code{-symbol-info-address} Command
20579 @findex -symbol-info-address
20581 @subsubheading Synopsis
20584 -symbol-info-address @var{symbol}
20587 Describe where @var{symbol} is stored.
20589 @subsubheading @value{GDBN} Command
20591 The corresponding @value{GDBN} command is @samp{info address}.
20593 @subsubheading Example
20597 @subheading The @code{-symbol-info-file} Command
20598 @findex -symbol-info-file
20600 @subsubheading Synopsis
20606 Show the file for the symbol.
20608 @subsubheading @value{GDBN} Command
20610 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20611 @samp{gdb_find_file}.
20613 @subsubheading Example
20617 @subheading The @code{-symbol-info-function} Command
20618 @findex -symbol-info-function
20620 @subsubheading Synopsis
20623 -symbol-info-function
20626 Show which function the symbol lives in.
20628 @subsubheading @value{GDBN} Command
20630 @samp{gdb_get_function} in @code{gdbtk}.
20632 @subsubheading Example
20636 @subheading The @code{-symbol-info-line} Command
20637 @findex -symbol-info-line
20639 @subsubheading Synopsis
20645 Show the core addresses of the code for a source line.
20647 @subsubheading @value{GDBN} Command
20649 The corresponding @value{GDBN} command is @samp{info line}.
20650 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20652 @subsubheading Example
20656 @subheading The @code{-symbol-info-symbol} Command
20657 @findex -symbol-info-symbol
20659 @subsubheading Synopsis
20662 -symbol-info-symbol @var{addr}
20665 Describe what symbol is at location @var{addr}.
20667 @subsubheading @value{GDBN} Command
20669 The corresponding @value{GDBN} command is @samp{info symbol}.
20671 @subsubheading Example
20675 @subheading The @code{-symbol-list-functions} Command
20676 @findex -symbol-list-functions
20678 @subsubheading Synopsis
20681 -symbol-list-functions
20684 List the functions in the executable.
20686 @subsubheading @value{GDBN} Command
20688 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20689 @samp{gdb_search} in @code{gdbtk}.
20691 @subsubheading Example
20695 @subheading The @code{-symbol-list-lines} Command
20696 @findex -symbol-list-lines
20698 @subsubheading Synopsis
20701 -symbol-list-lines @var{filename}
20704 Print the list of lines that contain code and their associated program
20705 addresses for the given source filename. The entries are sorted in
20706 ascending PC order.
20708 @subsubheading @value{GDBN} Command
20710 There is no corresponding @value{GDBN} command.
20712 @subsubheading Example
20715 -symbol-list-lines basics.c
20716 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20721 @subheading The @code{-symbol-list-types} Command
20722 @findex -symbol-list-types
20724 @subsubheading Synopsis
20730 List all the type names.
20732 @subsubheading @value{GDBN} Command
20734 The corresponding commands are @samp{info types} in @value{GDBN},
20735 @samp{gdb_search} in @code{gdbtk}.
20737 @subsubheading Example
20741 @subheading The @code{-symbol-list-variables} Command
20742 @findex -symbol-list-variables
20744 @subsubheading Synopsis
20747 -symbol-list-variables
20750 List all the global and static variable names.
20752 @subsubheading @value{GDBN} Command
20754 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20756 @subsubheading Example
20760 @subheading The @code{-symbol-locate} Command
20761 @findex -symbol-locate
20763 @subsubheading Synopsis
20769 @subsubheading @value{GDBN} Command
20771 @samp{gdb_loc} in @code{gdbtk}.
20773 @subsubheading Example
20777 @subheading The @code{-symbol-type} Command
20778 @findex -symbol-type
20780 @subsubheading Synopsis
20783 -symbol-type @var{variable}
20786 Show type of @var{variable}.
20788 @subsubheading @value{GDBN} Command
20790 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20791 @samp{gdb_obj_variable}.
20793 @subsubheading Example
20797 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20798 @node GDB/MI File Commands
20799 @section @sc{gdb/mi} File Commands
20801 This section describes the GDB/MI commands to specify executable file names
20802 and to read in and obtain symbol table information.
20804 @subheading The @code{-file-exec-and-symbols} Command
20805 @findex -file-exec-and-symbols
20807 @subsubheading Synopsis
20810 -file-exec-and-symbols @var{file}
20813 Specify the executable file to be debugged. This file is the one from
20814 which the symbol table is also read. If no file is specified, the
20815 command clears the executable and symbol information. If breakpoints
20816 are set when using this command with no arguments, @value{GDBN} will produce
20817 error messages. Otherwise, no output is produced, except a completion
20820 @subsubheading @value{GDBN} Command
20822 The corresponding @value{GDBN} command is @samp{file}.
20824 @subsubheading Example
20828 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20834 @subheading The @code{-file-exec-file} Command
20835 @findex -file-exec-file
20837 @subsubheading Synopsis
20840 -file-exec-file @var{file}
20843 Specify the executable file to be debugged. Unlike
20844 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20845 from this file. If used without argument, @value{GDBN} clears the information
20846 about the executable file. No output is produced, except a completion
20849 @subsubheading @value{GDBN} Command
20851 The corresponding @value{GDBN} command is @samp{exec-file}.
20853 @subsubheading Example
20857 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20863 @subheading The @code{-file-list-exec-sections} Command
20864 @findex -file-list-exec-sections
20866 @subsubheading Synopsis
20869 -file-list-exec-sections
20872 List the sections of the current executable file.
20874 @subsubheading @value{GDBN} Command
20876 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20877 information as this command. @code{gdbtk} has a corresponding command
20878 @samp{gdb_load_info}.
20880 @subsubheading Example
20884 @subheading The @code{-file-list-exec-source-file} Command
20885 @findex -file-list-exec-source-file
20887 @subsubheading Synopsis
20890 -file-list-exec-source-file
20893 List the line number, the current source file, and the absolute path
20894 to the current source file for the current executable.
20896 @subsubheading @value{GDBN} Command
20898 The @value{GDBN} equivalent is @samp{info source}
20900 @subsubheading Example
20904 123-file-list-exec-source-file
20905 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20910 @subheading The @code{-file-list-exec-source-files} Command
20911 @findex -file-list-exec-source-files
20913 @subsubheading Synopsis
20916 -file-list-exec-source-files
20919 List the source files for the current executable.
20921 It will always output the filename, but only when @value{GDBN} can find
20922 the absolute file name of a source file, will it output the fullname.
20924 @subsubheading @value{GDBN} Command
20926 The @value{GDBN} equivalent is @samp{info sources}.
20927 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20929 @subsubheading Example
20932 -file-list-exec-source-files
20934 @{file=foo.c,fullname=/home/foo.c@},
20935 @{file=/home/bar.c,fullname=/home/bar.c@},
20936 @{file=gdb_could_not_find_fullpath.c@}]
20940 @subheading The @code{-file-list-shared-libraries} Command
20941 @findex -file-list-shared-libraries
20943 @subsubheading Synopsis
20946 -file-list-shared-libraries
20949 List the shared libraries in the program.
20951 @subsubheading @value{GDBN} Command
20953 The corresponding @value{GDBN} command is @samp{info shared}.
20955 @subsubheading Example
20959 @subheading The @code{-file-list-symbol-files} Command
20960 @findex -file-list-symbol-files
20962 @subsubheading Synopsis
20965 -file-list-symbol-files
20970 @subsubheading @value{GDBN} Command
20972 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20974 @subsubheading Example
20978 @subheading The @code{-file-symbol-file} Command
20979 @findex -file-symbol-file
20981 @subsubheading Synopsis
20984 -file-symbol-file @var{file}
20987 Read symbol table info from the specified @var{file} argument. When
20988 used without arguments, clears @value{GDBN}'s symbol table info. No output is
20989 produced, except for a completion notification.
20991 @subsubheading @value{GDBN} Command
20993 The corresponding @value{GDBN} command is @samp{symbol-file}.
20995 @subsubheading Example
20999 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21005 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21006 @node GDB/MI Memory Overlay Commands
21007 @section @sc{gdb/mi} Memory Overlay Commands
21009 The memory overlay commands are not implemented.
21011 @c @subheading -overlay-auto
21013 @c @subheading -overlay-list-mapping-state
21015 @c @subheading -overlay-list-overlays
21017 @c @subheading -overlay-map
21019 @c @subheading -overlay-off
21021 @c @subheading -overlay-on
21023 @c @subheading -overlay-unmap
21025 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21026 @node GDB/MI Signal Handling Commands
21027 @section @sc{gdb/mi} Signal Handling Commands
21029 Signal handling commands are not implemented.
21031 @c @subheading -signal-handle
21033 @c @subheading -signal-list-handle-actions
21035 @c @subheading -signal-list-signal-types
21039 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21040 @node GDB/MI Target Manipulation
21041 @section @sc{gdb/mi} Target Manipulation Commands
21044 @subheading The @code{-target-attach} Command
21045 @findex -target-attach
21047 @subsubheading Synopsis
21050 -target-attach @var{pid} | @var{file}
21053 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
21055 @subsubheading @value{GDBN} Command
21057 The corresponding @value{GDBN} command is @samp{attach}.
21059 @subsubheading Example
21063 @subheading The @code{-target-compare-sections} Command
21064 @findex -target-compare-sections
21066 @subsubheading Synopsis
21069 -target-compare-sections [ @var{section} ]
21072 Compare data of section @var{section} on target to the exec file.
21073 Without the argument, all sections are compared.
21075 @subsubheading @value{GDBN} Command
21077 The @value{GDBN} equivalent is @samp{compare-sections}.
21079 @subsubheading Example
21083 @subheading The @code{-target-detach} Command
21084 @findex -target-detach
21086 @subsubheading Synopsis
21092 Detach from the remote target which normally resumes its execution.
21095 @subsubheading @value{GDBN} Command
21097 The corresponding @value{GDBN} command is @samp{detach}.
21099 @subsubheading Example
21109 @subheading The @code{-target-disconnect} Command
21110 @findex -target-disconnect
21112 @subsubheading Synopsis
21118 Disconnect from the remote target. There's no output and the target is
21119 generally not resumed.
21121 @subsubheading @value{GDBN} Command
21123 The corresponding @value{GDBN} command is @samp{disconnect}.
21125 @subsubheading Example
21135 @subheading The @code{-target-download} Command
21136 @findex -target-download
21138 @subsubheading Synopsis
21144 Loads the executable onto the remote target.
21145 It prints out an update message every half second, which includes the fields:
21149 The name of the section.
21151 The size of what has been sent so far for that section.
21153 The size of the section.
21155 The total size of what was sent so far (the current and the previous sections).
21157 The size of the overall executable to download.
21161 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21162 @sc{gdb/mi} Output Syntax}).
21164 In addition, it prints the name and size of the sections, as they are
21165 downloaded. These messages include the following fields:
21169 The name of the section.
21171 The size of the section.
21173 The size of the overall executable to download.
21177 At the end, a summary is printed.
21179 @subsubheading @value{GDBN} Command
21181 The corresponding @value{GDBN} command is @samp{load}.
21183 @subsubheading Example
21185 Note: each status message appears on a single line. Here the messages
21186 have been broken down so that they can fit onto a page.
21191 +download,@{section=".text",section-size="6668",total-size="9880"@}
21192 +download,@{section=".text",section-sent="512",section-size="6668",
21193 total-sent="512",total-size="9880"@}
21194 +download,@{section=".text",section-sent="1024",section-size="6668",
21195 total-sent="1024",total-size="9880"@}
21196 +download,@{section=".text",section-sent="1536",section-size="6668",
21197 total-sent="1536",total-size="9880"@}
21198 +download,@{section=".text",section-sent="2048",section-size="6668",
21199 total-sent="2048",total-size="9880"@}
21200 +download,@{section=".text",section-sent="2560",section-size="6668",
21201 total-sent="2560",total-size="9880"@}
21202 +download,@{section=".text",section-sent="3072",section-size="6668",
21203 total-sent="3072",total-size="9880"@}
21204 +download,@{section=".text",section-sent="3584",section-size="6668",
21205 total-sent="3584",total-size="9880"@}
21206 +download,@{section=".text",section-sent="4096",section-size="6668",
21207 total-sent="4096",total-size="9880"@}
21208 +download,@{section=".text",section-sent="4608",section-size="6668",
21209 total-sent="4608",total-size="9880"@}
21210 +download,@{section=".text",section-sent="5120",section-size="6668",
21211 total-sent="5120",total-size="9880"@}
21212 +download,@{section=".text",section-sent="5632",section-size="6668",
21213 total-sent="5632",total-size="9880"@}
21214 +download,@{section=".text",section-sent="6144",section-size="6668",
21215 total-sent="6144",total-size="9880"@}
21216 +download,@{section=".text",section-sent="6656",section-size="6668",
21217 total-sent="6656",total-size="9880"@}
21218 +download,@{section=".init",section-size="28",total-size="9880"@}
21219 +download,@{section=".fini",section-size="28",total-size="9880"@}
21220 +download,@{section=".data",section-size="3156",total-size="9880"@}
21221 +download,@{section=".data",section-sent="512",section-size="3156",
21222 total-sent="7236",total-size="9880"@}
21223 +download,@{section=".data",section-sent="1024",section-size="3156",
21224 total-sent="7748",total-size="9880"@}
21225 +download,@{section=".data",section-sent="1536",section-size="3156",
21226 total-sent="8260",total-size="9880"@}
21227 +download,@{section=".data",section-sent="2048",section-size="3156",
21228 total-sent="8772",total-size="9880"@}
21229 +download,@{section=".data",section-sent="2560",section-size="3156",
21230 total-sent="9284",total-size="9880"@}
21231 +download,@{section=".data",section-sent="3072",section-size="3156",
21232 total-sent="9796",total-size="9880"@}
21233 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21239 @subheading The @code{-target-exec-status} Command
21240 @findex -target-exec-status
21242 @subsubheading Synopsis
21245 -target-exec-status
21248 Provide information on the state of the target (whether it is running or
21249 not, for instance).
21251 @subsubheading @value{GDBN} Command
21253 There's no equivalent @value{GDBN} command.
21255 @subsubheading Example
21259 @subheading The @code{-target-list-available-targets} Command
21260 @findex -target-list-available-targets
21262 @subsubheading Synopsis
21265 -target-list-available-targets
21268 List the possible targets to connect to.
21270 @subsubheading @value{GDBN} Command
21272 The corresponding @value{GDBN} command is @samp{help target}.
21274 @subsubheading Example
21278 @subheading The @code{-target-list-current-targets} Command
21279 @findex -target-list-current-targets
21281 @subsubheading Synopsis
21284 -target-list-current-targets
21287 Describe the current target.
21289 @subsubheading @value{GDBN} Command
21291 The corresponding information is printed by @samp{info file} (among
21294 @subsubheading Example
21298 @subheading The @code{-target-list-parameters} Command
21299 @findex -target-list-parameters
21301 @subsubheading Synopsis
21304 -target-list-parameters
21309 @subsubheading @value{GDBN} Command
21313 @subsubheading Example
21317 @subheading The @code{-target-select} Command
21318 @findex -target-select
21320 @subsubheading Synopsis
21323 -target-select @var{type} @var{parameters @dots{}}
21326 Connect @value{GDBN} to the remote target. This command takes two args:
21330 The type of target, for instance @samp{async}, @samp{remote}, etc.
21331 @item @var{parameters}
21332 Device names, host names and the like. @xref{Target Commands, ,
21333 Commands for Managing Targets}, for more details.
21336 The output is a connection notification, followed by the address at
21337 which the target program is, in the following form:
21340 ^connected,addr="@var{address}",func="@var{function name}",
21341 args=[@var{arg list}]
21344 @subsubheading @value{GDBN} Command
21346 The corresponding @value{GDBN} command is @samp{target}.
21348 @subsubheading Example
21352 -target-select async /dev/ttya
21353 ^connected,addr="0xfe00a300",func="??",args=[]
21357 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21358 @node GDB/MI File Transfer Commands
21359 @section @sc{gdb/mi} File Transfer Commands
21362 @subheading The @code{-target-file-put} Command
21363 @findex -target-file-put
21365 @subsubheading Synopsis
21368 -target-file-put @var{hostfile} @var{targetfile}
21371 Copy file @var{hostfile} from the host system (the machine running
21372 @value{GDBN}) to @var{targetfile} on the target system.
21374 @subsubheading @value{GDBN} Command
21376 The corresponding @value{GDBN} command is @samp{remote put}.
21378 @subsubheading Example
21382 -target-file-put localfile remotefile
21388 @subheading The @code{-target-file-put} Command
21389 @findex -target-file-get
21391 @subsubheading Synopsis
21394 -target-file-get @var{targetfile} @var{hostfile}
21397 Copy file @var{targetfile} from the target system to @var{hostfile}
21398 on the host system.
21400 @subsubheading @value{GDBN} Command
21402 The corresponding @value{GDBN} command is @samp{remote get}.
21404 @subsubheading Example
21408 -target-file-get remotefile localfile
21414 @subheading The @code{-target-file-delete} Command
21415 @findex -target-file-delete
21417 @subsubheading Synopsis
21420 -target-file-delete @var{targetfile}
21423 Delete @var{targetfile} from the target system.
21425 @subsubheading @value{GDBN} Command
21427 The corresponding @value{GDBN} command is @samp{remote delete}.
21429 @subsubheading Example
21433 -target-file-delete remotefile
21439 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21440 @node GDB/MI Miscellaneous Commands
21441 @section Miscellaneous @sc{gdb/mi} Commands
21443 @c @subheading -gdb-complete
21445 @subheading The @code{-gdb-exit} Command
21448 @subsubheading Synopsis
21454 Exit @value{GDBN} immediately.
21456 @subsubheading @value{GDBN} Command
21458 Approximately corresponds to @samp{quit}.
21460 @subsubheading Example
21469 @subheading The @code{-exec-abort} Command
21470 @findex -exec-abort
21472 @subsubheading Synopsis
21478 Kill the inferior running program.
21480 @subsubheading @value{GDBN} Command
21482 The corresponding @value{GDBN} command is @samp{kill}.
21484 @subsubheading Example
21488 @subheading The @code{-gdb-set} Command
21491 @subsubheading Synopsis
21497 Set an internal @value{GDBN} variable.
21498 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21500 @subsubheading @value{GDBN} Command
21502 The corresponding @value{GDBN} command is @samp{set}.
21504 @subsubheading Example
21514 @subheading The @code{-gdb-show} Command
21517 @subsubheading Synopsis
21523 Show the current value of a @value{GDBN} variable.
21525 @subsubheading @value{GDBN} Command
21527 The corresponding @value{GDBN} command is @samp{show}.
21529 @subsubheading Example
21538 @c @subheading -gdb-source
21541 @subheading The @code{-gdb-version} Command
21542 @findex -gdb-version
21544 @subsubheading Synopsis
21550 Show version information for @value{GDBN}. Used mostly in testing.
21552 @subsubheading @value{GDBN} Command
21554 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21555 default shows this information when you start an interactive session.
21557 @subsubheading Example
21559 @c This example modifies the actual output from GDB to avoid overfull
21565 ~Copyright 2000 Free Software Foundation, Inc.
21566 ~GDB is free software, covered by the GNU General Public License, and
21567 ~you are welcome to change it and/or distribute copies of it under
21568 ~ certain conditions.
21569 ~Type "show copying" to see the conditions.
21570 ~There is absolutely no warranty for GDB. Type "show warranty" for
21572 ~This GDB was configured as
21573 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21578 @subheading The @code{-list-features} Command
21579 @findex -list-features
21581 Returns a list of particular features of the MI protocol that
21582 this version of gdb implements. A feature can be a command,
21583 or a new field in an output of some command, or even an
21584 important bugfix. While a frontend can sometimes detect presence
21585 of a feature at runtime, it is easier to perform detection at debugger
21588 The command returns a list of strings, with each string naming an
21589 available feature. Each returned string is just a name, it does not
21590 have any internal structure. The list of possible feature names
21596 (gdb) -list-features
21597 ^done,result=["feature1","feature2"]
21600 The current list of features is:
21604 @samp{frozen-varobjs}---indicates presence of the
21605 @code{-var-set-frozen} command, as well as possible presense of the
21606 @code{frozen} field in the output of @code{-varobj-create}.
21608 @samp{pending-breakpoints}---indicates presence of the @code{-f}
21609 option to the @code{-break-insert} command.
21613 @subheading The @code{-interpreter-exec} Command
21614 @findex -interpreter-exec
21616 @subheading Synopsis
21619 -interpreter-exec @var{interpreter} @var{command}
21621 @anchor{-interpreter-exec}
21623 Execute the specified @var{command} in the given @var{interpreter}.
21625 @subheading @value{GDBN} Command
21627 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21629 @subheading Example
21633 -interpreter-exec console "break main"
21634 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21635 &"During symbol reading, bad structure-type format.\n"
21636 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21641 @subheading The @code{-inferior-tty-set} Command
21642 @findex -inferior-tty-set
21644 @subheading Synopsis
21647 -inferior-tty-set /dev/pts/1
21650 Set terminal for future runs of the program being debugged.
21652 @subheading @value{GDBN} Command
21654 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21656 @subheading Example
21660 -inferior-tty-set /dev/pts/1
21665 @subheading The @code{-inferior-tty-show} Command
21666 @findex -inferior-tty-show
21668 @subheading Synopsis
21674 Show terminal for future runs of program being debugged.
21676 @subheading @value{GDBN} Command
21678 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21680 @subheading Example
21684 -inferior-tty-set /dev/pts/1
21688 ^done,inferior_tty_terminal="/dev/pts/1"
21692 @subheading The @code{-enable-timings} Command
21693 @findex -enable-timings
21695 @subheading Synopsis
21698 -enable-timings [yes | no]
21701 Toggle the printing of the wallclock, user and system times for an MI
21702 command as a field in its output. This command is to help frontend
21703 developers optimize the performance of their code. No argument is
21704 equivalent to @samp{yes}.
21706 @subheading @value{GDBN} Command
21710 @subheading Example
21718 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21719 addr="0x080484ed",func="main",file="myprog.c",
21720 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
21721 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
21729 *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
21730 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
21731 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
21732 fullname="/home/nickrob/myprog.c",line="73"@}
21737 @chapter @value{GDBN} Annotations
21739 This chapter describes annotations in @value{GDBN}. Annotations were
21740 designed to interface @value{GDBN} to graphical user interfaces or other
21741 similar programs which want to interact with @value{GDBN} at a
21742 relatively high level.
21744 The annotation mechanism has largely been superseded by @sc{gdb/mi}
21748 This is Edition @value{EDITION}, @value{DATE}.
21752 * Annotations Overview:: What annotations are; the general syntax.
21753 * Server Prefix:: Issuing a command without affecting user state.
21754 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21755 * Errors:: Annotations for error messages.
21756 * Invalidation:: Some annotations describe things now invalid.
21757 * Annotations for Running::
21758 Whether the program is running, how it stopped, etc.
21759 * Source Annotations:: Annotations describing source code.
21762 @node Annotations Overview
21763 @section What is an Annotation?
21764 @cindex annotations
21766 Annotations start with a newline character, two @samp{control-z}
21767 characters, and the name of the annotation. If there is no additional
21768 information associated with this annotation, the name of the annotation
21769 is followed immediately by a newline. If there is additional
21770 information, the name of the annotation is followed by a space, the
21771 additional information, and a newline. The additional information
21772 cannot contain newline characters.
21774 Any output not beginning with a newline and two @samp{control-z}
21775 characters denotes literal output from @value{GDBN}. Currently there is
21776 no need for @value{GDBN} to output a newline followed by two
21777 @samp{control-z} characters, but if there was such a need, the
21778 annotations could be extended with an @samp{escape} annotation which
21779 means those three characters as output.
21781 The annotation @var{level}, which is specified using the
21782 @option{--annotate} command line option (@pxref{Mode Options}), controls
21783 how much information @value{GDBN} prints together with its prompt,
21784 values of expressions, source lines, and other types of output. Level 0
21785 is for no annotations, level 1 is for use when @value{GDBN} is run as a
21786 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21787 for programs that control @value{GDBN}, and level 2 annotations have
21788 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21789 Interface, annotate, GDB's Obsolete Annotations}).
21792 @kindex set annotate
21793 @item set annotate @var{level}
21794 The @value{GDBN} command @code{set annotate} sets the level of
21795 annotations to the specified @var{level}.
21797 @item show annotate
21798 @kindex show annotate
21799 Show the current annotation level.
21802 This chapter describes level 3 annotations.
21804 A simple example of starting up @value{GDBN} with annotations is:
21807 $ @kbd{gdb --annotate=3}
21809 Copyright 2003 Free Software Foundation, Inc.
21810 GDB is free software, covered by the GNU General Public License,
21811 and you are welcome to change it and/or distribute copies of it
21812 under certain conditions.
21813 Type "show copying" to see the conditions.
21814 There is absolutely no warranty for GDB. Type "show warranty"
21816 This GDB was configured as "i386-pc-linux-gnu"
21827 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21828 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21829 denotes a @samp{control-z} character) are annotations; the rest is
21830 output from @value{GDBN}.
21832 @node Server Prefix
21833 @section The Server Prefix
21834 @cindex server prefix
21836 If you prefix a command with @samp{server } then it will not affect
21837 the command history, nor will it affect @value{GDBN}'s notion of which
21838 command to repeat if @key{RET} is pressed on a line by itself. This
21839 means that commands can be run behind a user's back by a front-end in
21840 a transparent manner.
21842 The server prefix does not affect the recording of values into the value
21843 history; to print a value without recording it into the value history,
21844 use the @code{output} command instead of the @code{print} command.
21847 @section Annotation for @value{GDBN} Input
21849 @cindex annotations for prompts
21850 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21851 to know when to send output, when the output from a given command is
21854 Different kinds of input each have a different @dfn{input type}. Each
21855 input type has three annotations: a @code{pre-} annotation, which
21856 denotes the beginning of any prompt which is being output, a plain
21857 annotation, which denotes the end of the prompt, and then a @code{post-}
21858 annotation which denotes the end of any echo which may (or may not) be
21859 associated with the input. For example, the @code{prompt} input type
21860 features the following annotations:
21868 The input types are
21871 @findex pre-prompt annotation
21872 @findex prompt annotation
21873 @findex post-prompt annotation
21875 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21877 @findex pre-commands annotation
21878 @findex commands annotation
21879 @findex post-commands annotation
21881 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21882 command. The annotations are repeated for each command which is input.
21884 @findex pre-overload-choice annotation
21885 @findex overload-choice annotation
21886 @findex post-overload-choice annotation
21887 @item overload-choice
21888 When @value{GDBN} wants the user to select between various overloaded functions.
21890 @findex pre-query annotation
21891 @findex query annotation
21892 @findex post-query annotation
21894 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21896 @findex pre-prompt-for-continue annotation
21897 @findex prompt-for-continue annotation
21898 @findex post-prompt-for-continue annotation
21899 @item prompt-for-continue
21900 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21901 expect this to work well; instead use @code{set height 0} to disable
21902 prompting. This is because the counting of lines is buggy in the
21903 presence of annotations.
21908 @cindex annotations for errors, warnings and interrupts
21910 @findex quit annotation
21915 This annotation occurs right before @value{GDBN} responds to an interrupt.
21917 @findex error annotation
21922 This annotation occurs right before @value{GDBN} responds to an error.
21924 Quit and error annotations indicate that any annotations which @value{GDBN} was
21925 in the middle of may end abruptly. For example, if a
21926 @code{value-history-begin} annotation is followed by a @code{error}, one
21927 cannot expect to receive the matching @code{value-history-end}. One
21928 cannot expect not to receive it either, however; an error annotation
21929 does not necessarily mean that @value{GDBN} is immediately returning all the way
21932 @findex error-begin annotation
21933 A quit or error annotation may be preceded by
21939 Any output between that and the quit or error annotation is the error
21942 Warning messages are not yet annotated.
21943 @c If we want to change that, need to fix warning(), type_error(),
21944 @c range_error(), and possibly other places.
21947 @section Invalidation Notices
21949 @cindex annotations for invalidation messages
21950 The following annotations say that certain pieces of state may have
21954 @findex frames-invalid annotation
21955 @item ^Z^Zframes-invalid
21957 The frames (for example, output from the @code{backtrace} command) may
21960 @findex breakpoints-invalid annotation
21961 @item ^Z^Zbreakpoints-invalid
21963 The breakpoints may have changed. For example, the user just added or
21964 deleted a breakpoint.
21967 @node Annotations for Running
21968 @section Running the Program
21969 @cindex annotations for running programs
21971 @findex starting annotation
21972 @findex stopping annotation
21973 When the program starts executing due to a @value{GDBN} command such as
21974 @code{step} or @code{continue},
21980 is output. When the program stops,
21986 is output. Before the @code{stopped} annotation, a variety of
21987 annotations describe how the program stopped.
21990 @findex exited annotation
21991 @item ^Z^Zexited @var{exit-status}
21992 The program exited, and @var{exit-status} is the exit status (zero for
21993 successful exit, otherwise nonzero).
21995 @findex signalled annotation
21996 @findex signal-name annotation
21997 @findex signal-name-end annotation
21998 @findex signal-string annotation
21999 @findex signal-string-end annotation
22000 @item ^Z^Zsignalled
22001 The program exited with a signal. After the @code{^Z^Zsignalled}, the
22002 annotation continues:
22008 ^Z^Zsignal-name-end
22012 ^Z^Zsignal-string-end
22017 where @var{name} is the name of the signal, such as @code{SIGILL} or
22018 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
22019 as @code{Illegal Instruction} or @code{Segmentation fault}.
22020 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
22021 user's benefit and have no particular format.
22023 @findex signal annotation
22025 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
22026 just saying that the program received the signal, not that it was
22027 terminated with it.
22029 @findex breakpoint annotation
22030 @item ^Z^Zbreakpoint @var{number}
22031 The program hit breakpoint number @var{number}.
22033 @findex watchpoint annotation
22034 @item ^Z^Zwatchpoint @var{number}
22035 The program hit watchpoint number @var{number}.
22038 @node Source Annotations
22039 @section Displaying Source
22040 @cindex annotations for source display
22042 @findex source annotation
22043 The following annotation is used instead of displaying source code:
22046 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
22049 where @var{filename} is an absolute file name indicating which source
22050 file, @var{line} is the line number within that file (where 1 is the
22051 first line in the file), @var{character} is the character position
22052 within the file (where 0 is the first character in the file) (for most
22053 debug formats this will necessarily point to the beginning of a line),
22054 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
22055 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
22056 @var{addr} is the address in the target program associated with the
22057 source which is being displayed. @var{addr} is in the form @samp{0x}
22058 followed by one or more lowercase hex digits (note that this does not
22059 depend on the language).
22062 @chapter Reporting Bugs in @value{GDBN}
22063 @cindex bugs in @value{GDBN}
22064 @cindex reporting bugs in @value{GDBN}
22066 Your bug reports play an essential role in making @value{GDBN} reliable.
22068 Reporting a bug may help you by bringing a solution to your problem, or it
22069 may not. But in any case the principal function of a bug report is to help
22070 the entire community by making the next version of @value{GDBN} work better. Bug
22071 reports are your contribution to the maintenance of @value{GDBN}.
22073 In order for a bug report to serve its purpose, you must include the
22074 information that enables us to fix the bug.
22077 * Bug Criteria:: Have you found a bug?
22078 * Bug Reporting:: How to report bugs
22082 @section Have You Found a Bug?
22083 @cindex bug criteria
22085 If you are not sure whether you have found a bug, here are some guidelines:
22088 @cindex fatal signal
22089 @cindex debugger crash
22090 @cindex crash of debugger
22092 If the debugger gets a fatal signal, for any input whatever, that is a
22093 @value{GDBN} bug. Reliable debuggers never crash.
22095 @cindex error on valid input
22097 If @value{GDBN} produces an error message for valid input, that is a
22098 bug. (Note that if you're cross debugging, the problem may also be
22099 somewhere in the connection to the target.)
22101 @cindex invalid input
22103 If @value{GDBN} does not produce an error message for invalid input,
22104 that is a bug. However, you should note that your idea of
22105 ``invalid input'' might be our idea of ``an extension'' or ``support
22106 for traditional practice''.
22109 If you are an experienced user of debugging tools, your suggestions
22110 for improvement of @value{GDBN} are welcome in any case.
22113 @node Bug Reporting
22114 @section How to Report Bugs
22115 @cindex bug reports
22116 @cindex @value{GDBN} bugs, reporting
22118 A number of companies and individuals offer support for @sc{gnu} products.
22119 If you obtained @value{GDBN} from a support organization, we recommend you
22120 contact that organization first.
22122 You can find contact information for many support companies and
22123 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
22125 @c should add a web page ref...
22127 In any event, we also recommend that you submit bug reports for
22128 @value{GDBN}. The preferred method is to submit them directly using
22129 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
22130 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
22133 @strong{Do not send bug reports to @samp{info-gdb}, or to
22134 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
22135 not want to receive bug reports. Those that do have arranged to receive
22138 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
22139 serves as a repeater. The mailing list and the newsgroup carry exactly
22140 the same messages. Often people think of posting bug reports to the
22141 newsgroup instead of mailing them. This appears to work, but it has one
22142 problem which can be crucial: a newsgroup posting often lacks a mail
22143 path back to the sender. Thus, if we need to ask for more information,
22144 we may be unable to reach you. For this reason, it is better to send
22145 bug reports to the mailing list.
22147 The fundamental principle of reporting bugs usefully is this:
22148 @strong{report all the facts}. If you are not sure whether to state a
22149 fact or leave it out, state it!
22151 Often people omit facts because they think they know what causes the
22152 problem and assume that some details do not matter. Thus, you might
22153 assume that the name of the variable you use in an example does not matter.
22154 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
22155 stray memory reference which happens to fetch from the location where that
22156 name is stored in memory; perhaps, if the name were different, the contents
22157 of that location would fool the debugger into doing the right thing despite
22158 the bug. Play it safe and give a specific, complete example. That is the
22159 easiest thing for you to do, and the most helpful.
22161 Keep in mind that the purpose of a bug report is to enable us to fix the
22162 bug. It may be that the bug has been reported previously, but neither
22163 you nor we can know that unless your bug report is complete and
22166 Sometimes people give a few sketchy facts and ask, ``Does this ring a
22167 bell?'' Those bug reports are useless, and we urge everyone to
22168 @emph{refuse to respond to them} except to chide the sender to report
22171 To enable us to fix the bug, you should include all these things:
22175 The version of @value{GDBN}. @value{GDBN} announces it if you start
22176 with no arguments; you can also print it at any time using @code{show
22179 Without this, we will not know whether there is any point in looking for
22180 the bug in the current version of @value{GDBN}.
22183 The type of machine you are using, and the operating system name and
22187 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
22188 ``@value{GCC}--2.8.1''.
22191 What compiler (and its version) was used to compile the program you are
22192 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
22193 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
22194 to get this information; for other compilers, see the documentation for
22198 The command arguments you gave the compiler to compile your example and
22199 observe the bug. For example, did you use @samp{-O}? To guarantee
22200 you will not omit something important, list them all. A copy of the
22201 Makefile (or the output from make) is sufficient.
22203 If we were to try to guess the arguments, we would probably guess wrong
22204 and then we might not encounter the bug.
22207 A complete input script, and all necessary source files, that will
22211 A description of what behavior you observe that you believe is
22212 incorrect. For example, ``It gets a fatal signal.''
22214 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
22215 will certainly notice it. But if the bug is incorrect output, we might
22216 not notice unless it is glaringly wrong. You might as well not give us
22217 a chance to make a mistake.
22219 Even if the problem you experience is a fatal signal, you should still
22220 say so explicitly. Suppose something strange is going on, such as, your
22221 copy of @value{GDBN} is out of synch, or you have encountered a bug in
22222 the C library on your system. (This has happened!) Your copy might
22223 crash and ours would not. If you told us to expect a crash, then when
22224 ours fails to crash, we would know that the bug was not happening for
22225 us. If you had not told us to expect a crash, then we would not be able
22226 to draw any conclusion from our observations.
22229 @cindex recording a session script
22230 To collect all this information, you can use a session recording program
22231 such as @command{script}, which is available on many Unix systems.
22232 Just run your @value{GDBN} session inside @command{script} and then
22233 include the @file{typescript} file with your bug report.
22235 Another way to record a @value{GDBN} session is to run @value{GDBN}
22236 inside Emacs and then save the entire buffer to a file.
22239 If you wish to suggest changes to the @value{GDBN} source, send us context
22240 diffs. If you even discuss something in the @value{GDBN} source, refer to
22241 it by context, not by line number.
22243 The line numbers in our development sources will not match those in your
22244 sources. Your line numbers would convey no useful information to us.
22248 Here are some things that are not necessary:
22252 A description of the envelope of the bug.
22254 Often people who encounter a bug spend a lot of time investigating
22255 which changes to the input file will make the bug go away and which
22256 changes will not affect it.
22258 This is often time consuming and not very useful, because the way we
22259 will find the bug is by running a single example under the debugger
22260 with breakpoints, not by pure deduction from a series of examples.
22261 We recommend that you save your time for something else.
22263 Of course, if you can find a simpler example to report @emph{instead}
22264 of the original one, that is a convenience for us. Errors in the
22265 output will be easier to spot, running under the debugger will take
22266 less time, and so on.
22268 However, simplification is not vital; if you do not want to do this,
22269 report the bug anyway and send us the entire test case you used.
22272 A patch for the bug.
22274 A patch for the bug does help us if it is a good one. But do not omit
22275 the necessary information, such as the test case, on the assumption that
22276 a patch is all we need. We might see problems with your patch and decide
22277 to fix the problem another way, or we might not understand it at all.
22279 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22280 construct an example that will make the program follow a certain path
22281 through the code. If you do not send us the example, we will not be able
22282 to construct one, so we will not be able to verify that the bug is fixed.
22284 And if we cannot understand what bug you are trying to fix, or why your
22285 patch should be an improvement, we will not install it. A test case will
22286 help us to understand.
22289 A guess about what the bug is or what it depends on.
22291 Such guesses are usually wrong. Even we cannot guess right about such
22292 things without first using the debugger to find the facts.
22295 @c The readline documentation is distributed with the readline code
22296 @c and consists of the two following files:
22298 @c inc-hist.texinfo
22299 @c Use -I with makeinfo to point to the appropriate directory,
22300 @c environment var TEXINPUTS with TeX.
22301 @include rluser.texi
22302 @include inc-hist.texinfo
22305 @node Formatting Documentation
22306 @appendix Formatting Documentation
22308 @cindex @value{GDBN} reference card
22309 @cindex reference card
22310 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22311 for printing with PostScript or Ghostscript, in the @file{gdb}
22312 subdirectory of the main source directory@footnote{In
22313 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22314 release.}. If you can use PostScript or Ghostscript with your printer,
22315 you can print the reference card immediately with @file{refcard.ps}.
22317 The release also includes the source for the reference card. You
22318 can format it, using @TeX{}, by typing:
22324 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22325 mode on US ``letter'' size paper;
22326 that is, on a sheet 11 inches wide by 8.5 inches
22327 high. You will need to specify this form of printing as an option to
22328 your @sc{dvi} output program.
22330 @cindex documentation
22332 All the documentation for @value{GDBN} comes as part of the machine-readable
22333 distribution. The documentation is written in Texinfo format, which is
22334 a documentation system that uses a single source file to produce both
22335 on-line information and a printed manual. You can use one of the Info
22336 formatting commands to create the on-line version of the documentation
22337 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22339 @value{GDBN} includes an already formatted copy of the on-line Info
22340 version of this manual in the @file{gdb} subdirectory. The main Info
22341 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22342 subordinate files matching @samp{gdb.info*} in the same directory. If
22343 necessary, you can print out these files, or read them with any editor;
22344 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22345 Emacs or the standalone @code{info} program, available as part of the
22346 @sc{gnu} Texinfo distribution.
22348 If you want to format these Info files yourself, you need one of the
22349 Info formatting programs, such as @code{texinfo-format-buffer} or
22352 If you have @code{makeinfo} installed, and are in the top level
22353 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22354 version @value{GDBVN}), you can make the Info file by typing:
22361 If you want to typeset and print copies of this manual, you need @TeX{},
22362 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22363 Texinfo definitions file.
22365 @TeX{} is a typesetting program; it does not print files directly, but
22366 produces output files called @sc{dvi} files. To print a typeset
22367 document, you need a program to print @sc{dvi} files. If your system
22368 has @TeX{} installed, chances are it has such a program. The precise
22369 command to use depends on your system; @kbd{lpr -d} is common; another
22370 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22371 require a file name without any extension or a @samp{.dvi} extension.
22373 @TeX{} also requires a macro definitions file called
22374 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22375 written in Texinfo format. On its own, @TeX{} cannot either read or
22376 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22377 and is located in the @file{gdb-@var{version-number}/texinfo}
22380 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22381 typeset and print this manual. First switch to the @file{gdb}
22382 subdirectory of the main source directory (for example, to
22383 @file{gdb-@value{GDBVN}/gdb}) and type:
22389 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22391 @node Installing GDB
22392 @appendix Installing @value{GDBN}
22393 @cindex installation
22396 * Requirements:: Requirements for building @value{GDBN}
22397 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22398 * Separate Objdir:: Compiling @value{GDBN} in another directory
22399 * Config Names:: Specifying names for hosts and targets
22400 * Configure Options:: Summary of options for configure
22404 @section Requirements for Building @value{GDBN}
22405 @cindex building @value{GDBN}, requirements for
22407 Building @value{GDBN} requires various tools and packages to be available.
22408 Other packages will be used only if they are found.
22410 @heading Tools/Packages Necessary for Building @value{GDBN}
22412 @item ISO C90 compiler
22413 @value{GDBN} is written in ISO C90. It should be buildable with any
22414 working C90 compiler, e.g.@: GCC.
22418 @heading Tools/Packages Optional for Building @value{GDBN}
22422 @value{GDBN} can use the Expat XML parsing library. This library may be
22423 included with your operating system distribution; if it is not, you
22424 can get the latest version from @url{http://expat.sourceforge.net}.
22425 The @file{configure} script will search for this library in several
22426 standard locations; if it is installed in an unusual path, you can
22427 use the @option{--with-libexpat-prefix} option to specify its location.
22433 Remote protocol memory maps (@pxref{Memory Map Format})
22435 Target descriptions (@pxref{Target Descriptions})
22437 Remote shared library lists (@pxref{Library List Format})
22439 MS-Windows shared libraries (@pxref{Shared Libraries})
22444 @node Running Configure
22445 @section Invoking the @value{GDBN} @file{configure} Script
22446 @cindex configuring @value{GDBN}
22447 @value{GDBN} comes with a @file{configure} script that automates the process
22448 of preparing @value{GDBN} for installation; you can then use @code{make} to
22449 build the @code{gdb} program.
22451 @c irrelevant in info file; it's as current as the code it lives with.
22452 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22453 look at the @file{README} file in the sources; we may have improved the
22454 installation procedures since publishing this manual.}
22457 The @value{GDBN} distribution includes all the source code you need for
22458 @value{GDBN} in a single directory, whose name is usually composed by
22459 appending the version number to @samp{gdb}.
22461 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22462 @file{gdb-@value{GDBVN}} directory. That directory contains:
22465 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22466 script for configuring @value{GDBN} and all its supporting libraries
22468 @item gdb-@value{GDBVN}/gdb
22469 the source specific to @value{GDBN} itself
22471 @item gdb-@value{GDBVN}/bfd
22472 source for the Binary File Descriptor library
22474 @item gdb-@value{GDBVN}/include
22475 @sc{gnu} include files
22477 @item gdb-@value{GDBVN}/libiberty
22478 source for the @samp{-liberty} free software library
22480 @item gdb-@value{GDBVN}/opcodes
22481 source for the library of opcode tables and disassemblers
22483 @item gdb-@value{GDBVN}/readline
22484 source for the @sc{gnu} command-line interface
22486 @item gdb-@value{GDBVN}/glob
22487 source for the @sc{gnu} filename pattern-matching subroutine
22489 @item gdb-@value{GDBVN}/mmalloc
22490 source for the @sc{gnu} memory-mapped malloc package
22493 The simplest way to configure and build @value{GDBN} is to run @file{configure}
22494 from the @file{gdb-@var{version-number}} source directory, which in
22495 this example is the @file{gdb-@value{GDBVN}} directory.
22497 First switch to the @file{gdb-@var{version-number}} source directory
22498 if you are not already in it; then run @file{configure}. Pass the
22499 identifier for the platform on which @value{GDBN} will run as an
22505 cd gdb-@value{GDBVN}
22506 ./configure @var{host}
22511 where @var{host} is an identifier such as @samp{sun4} or
22512 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22513 (You can often leave off @var{host}; @file{configure} tries to guess the
22514 correct value by examining your system.)
22516 Running @samp{configure @var{host}} and then running @code{make} builds the
22517 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22518 libraries, then @code{gdb} itself. The configured source files, and the
22519 binaries, are left in the corresponding source directories.
22522 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22523 system does not recognize this automatically when you run a different
22524 shell, you may need to run @code{sh} on it explicitly:
22527 sh configure @var{host}
22530 If you run @file{configure} from a directory that contains source
22531 directories for multiple libraries or programs, such as the
22532 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
22534 creates configuration files for every directory level underneath (unless
22535 you tell it not to, with the @samp{--norecursion} option).
22537 You should run the @file{configure} script from the top directory in the
22538 source tree, the @file{gdb-@var{version-number}} directory. If you run
22539 @file{configure} from one of the subdirectories, you will configure only
22540 that subdirectory. That is usually not what you want. In particular,
22541 if you run the first @file{configure} from the @file{gdb} subdirectory
22542 of the @file{gdb-@var{version-number}} directory, you will omit the
22543 configuration of @file{bfd}, @file{readline}, and other sibling
22544 directories of the @file{gdb} subdirectory. This leads to build errors
22545 about missing include files such as @file{bfd/bfd.h}.
22547 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22548 However, you should make sure that the shell on your path (named by
22549 the @samp{SHELL} environment variable) is publicly readable. Remember
22550 that @value{GDBN} uses the shell to start your program---some systems refuse to
22551 let @value{GDBN} debug child processes whose programs are not readable.
22553 @node Separate Objdir
22554 @section Compiling @value{GDBN} in Another Directory
22556 If you want to run @value{GDBN} versions for several host or target machines,
22557 you need a different @code{gdb} compiled for each combination of
22558 host and target. @file{configure} is designed to make this easy by
22559 allowing you to generate each configuration in a separate subdirectory,
22560 rather than in the source directory. If your @code{make} program
22561 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22562 @code{make} in each of these directories builds the @code{gdb}
22563 program specified there.
22565 To build @code{gdb} in a separate directory, run @file{configure}
22566 with the @samp{--srcdir} option to specify where to find the source.
22567 (You also need to specify a path to find @file{configure}
22568 itself from your working directory. If the path to @file{configure}
22569 would be the same as the argument to @samp{--srcdir}, you can leave out
22570 the @samp{--srcdir} option; it is assumed.)
22572 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22573 separate directory for a Sun 4 like this:
22577 cd gdb-@value{GDBVN}
22580 ../gdb-@value{GDBVN}/configure sun4
22585 When @file{configure} builds a configuration using a remote source
22586 directory, it creates a tree for the binaries with the same structure
22587 (and using the same names) as the tree under the source directory. In
22588 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22589 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22590 @file{gdb-sun4/gdb}.
22592 Make sure that your path to the @file{configure} script has just one
22593 instance of @file{gdb} in it. If your path to @file{configure} looks
22594 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22595 one subdirectory of @value{GDBN}, not the whole package. This leads to
22596 build errors about missing include files such as @file{bfd/bfd.h}.
22598 One popular reason to build several @value{GDBN} configurations in separate
22599 directories is to configure @value{GDBN} for cross-compiling (where
22600 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22601 programs that run on another machine---the @dfn{target}).
22602 You specify a cross-debugging target by
22603 giving the @samp{--target=@var{target}} option to @file{configure}.
22605 When you run @code{make} to build a program or library, you must run
22606 it in a configured directory---whatever directory you were in when you
22607 called @file{configure} (or one of its subdirectories).
22609 The @code{Makefile} that @file{configure} generates in each source
22610 directory also runs recursively. If you type @code{make} in a source
22611 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22612 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22613 will build all the required libraries, and then build GDB.
22615 When you have multiple hosts or targets configured in separate
22616 directories, you can run @code{make} on them in parallel (for example,
22617 if they are NFS-mounted on each of the hosts); they will not interfere
22621 @section Specifying Names for Hosts and Targets
22623 The specifications used for hosts and targets in the @file{configure}
22624 script are based on a three-part naming scheme, but some short predefined
22625 aliases are also supported. The full naming scheme encodes three pieces
22626 of information in the following pattern:
22629 @var{architecture}-@var{vendor}-@var{os}
22632 For example, you can use the alias @code{sun4} as a @var{host} argument,
22633 or as the value for @var{target} in a @code{--target=@var{target}}
22634 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22636 The @file{configure} script accompanying @value{GDBN} does not provide
22637 any query facility to list all supported host and target names or
22638 aliases. @file{configure} calls the Bourne shell script
22639 @code{config.sub} to map abbreviations to full names; you can read the
22640 script, if you wish, or you can use it to test your guesses on
22641 abbreviations---for example:
22644 % sh config.sub i386-linux
22646 % sh config.sub alpha-linux
22647 alpha-unknown-linux-gnu
22648 % sh config.sub hp9k700
22650 % sh config.sub sun4
22651 sparc-sun-sunos4.1.1
22652 % sh config.sub sun3
22653 m68k-sun-sunos4.1.1
22654 % sh config.sub i986v
22655 Invalid configuration `i986v': machine `i986v' not recognized
22659 @code{config.sub} is also distributed in the @value{GDBN} source
22660 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22662 @node Configure Options
22663 @section @file{configure} Options
22665 Here is a summary of the @file{configure} options and arguments that
22666 are most often useful for building @value{GDBN}. @file{configure} also has
22667 several other options not listed here. @inforef{What Configure
22668 Does,,configure.info}, for a full explanation of @file{configure}.
22671 configure @r{[}--help@r{]}
22672 @r{[}--prefix=@var{dir}@r{]}
22673 @r{[}--exec-prefix=@var{dir}@r{]}
22674 @r{[}--srcdir=@var{dirname}@r{]}
22675 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22676 @r{[}--target=@var{target}@r{]}
22681 You may introduce options with a single @samp{-} rather than
22682 @samp{--} if you prefer; but you may abbreviate option names if you use
22687 Display a quick summary of how to invoke @file{configure}.
22689 @item --prefix=@var{dir}
22690 Configure the source to install programs and files under directory
22693 @item --exec-prefix=@var{dir}
22694 Configure the source to install programs under directory
22697 @c avoid splitting the warning from the explanation:
22699 @item --srcdir=@var{dirname}
22700 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22701 @code{make} that implements the @code{VPATH} feature.}@*
22702 Use this option to make configurations in directories separate from the
22703 @value{GDBN} source directories. Among other things, you can use this to
22704 build (or maintain) several configurations simultaneously, in separate
22705 directories. @file{configure} writes configuration-specific files in
22706 the current directory, but arranges for them to use the source in the
22707 directory @var{dirname}. @file{configure} creates directories under
22708 the working directory in parallel to the source directories below
22711 @item --norecursion
22712 Configure only the directory level where @file{configure} is executed; do not
22713 propagate configuration to subdirectories.
22715 @item --target=@var{target}
22716 Configure @value{GDBN} for cross-debugging programs running on the specified
22717 @var{target}. Without this option, @value{GDBN} is configured to debug
22718 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22720 There is no convenient way to generate a list of all available targets.
22722 @item @var{host} @dots{}
22723 Configure @value{GDBN} to run on the specified @var{host}.
22725 There is no convenient way to generate a list of all available hosts.
22728 There are many other options available as well, but they are generally
22729 needed for special purposes only.
22731 @node Maintenance Commands
22732 @appendix Maintenance Commands
22733 @cindex maintenance commands
22734 @cindex internal commands
22736 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22737 includes a number of commands intended for @value{GDBN} developers,
22738 that are not documented elsewhere in this manual. These commands are
22739 provided here for reference. (For commands that turn on debugging
22740 messages, see @ref{Debugging Output}.)
22743 @kindex maint agent
22744 @item maint agent @var{expression}
22745 Translate the given @var{expression} into remote agent bytecodes.
22746 This command is useful for debugging the Agent Expression mechanism
22747 (@pxref{Agent Expressions}).
22749 @kindex maint info breakpoints
22750 @item @anchor{maint info breakpoints}maint info breakpoints
22751 Using the same format as @samp{info breakpoints}, display both the
22752 breakpoints you've set explicitly, and those @value{GDBN} is using for
22753 internal purposes. Internal breakpoints are shown with negative
22754 breakpoint numbers. The type column identifies what kind of breakpoint
22759 Normal, explicitly set breakpoint.
22762 Normal, explicitly set watchpoint.
22765 Internal breakpoint, used to handle correctly stepping through
22766 @code{longjmp} calls.
22768 @item longjmp resume
22769 Internal breakpoint at the target of a @code{longjmp}.
22772 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22775 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22778 Shared library events.
22782 @kindex maint check-symtabs
22783 @item maint check-symtabs
22784 Check the consistency of psymtabs and symtabs.
22786 @kindex maint cplus first_component
22787 @item maint cplus first_component @var{name}
22788 Print the first C@t{++} class/namespace component of @var{name}.
22790 @kindex maint cplus namespace
22791 @item maint cplus namespace
22792 Print the list of possible C@t{++} namespaces.
22794 @kindex maint demangle
22795 @item maint demangle @var{name}
22796 Demangle a C@t{++} or Objective-C mangled @var{name}.
22798 @kindex maint deprecate
22799 @kindex maint undeprecate
22800 @cindex deprecated commands
22801 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22802 @itemx maint undeprecate @var{command}
22803 Deprecate or undeprecate the named @var{command}. Deprecated commands
22804 cause @value{GDBN} to issue a warning when you use them. The optional
22805 argument @var{replacement} says which newer command should be used in
22806 favor of the deprecated one; if it is given, @value{GDBN} will mention
22807 the replacement as part of the warning.
22809 @kindex maint dump-me
22810 @item maint dump-me
22811 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22812 Cause a fatal signal in the debugger and force it to dump its core.
22813 This is supported only on systems which support aborting a program
22814 with the @code{SIGQUIT} signal.
22816 @kindex maint internal-error
22817 @kindex maint internal-warning
22818 @item maint internal-error @r{[}@var{message-text}@r{]}
22819 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22820 Cause @value{GDBN} to call the internal function @code{internal_error}
22821 or @code{internal_warning} and hence behave as though an internal error
22822 or internal warning has been detected. In addition to reporting the
22823 internal problem, these functions give the user the opportunity to
22824 either quit @value{GDBN} or create a core file of the current
22825 @value{GDBN} session.
22827 These commands take an optional parameter @var{message-text} that is
22828 used as the text of the error or warning message.
22830 Here's an example of using @code{internal-error}:
22833 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22834 @dots{}/maint.c:121: internal-error: testing, 1, 2
22835 A problem internal to GDB has been detected. Further
22836 debugging may prove unreliable.
22837 Quit this debugging session? (y or n) @kbd{n}
22838 Create a core file? (y or n) @kbd{n}
22842 @kindex maint packet
22843 @item maint packet @var{text}
22844 If @value{GDBN} is talking to an inferior via the serial protocol,
22845 then this command sends the string @var{text} to the inferior, and
22846 displays the response packet. @value{GDBN} supplies the initial
22847 @samp{$} character, the terminating @samp{#} character, and the
22850 @kindex maint print architecture
22851 @item maint print architecture @r{[}@var{file}@r{]}
22852 Print the entire architecture configuration. The optional argument
22853 @var{file} names the file where the output goes.
22855 @kindex maint print c-tdesc
22856 @item maint print c-tdesc
22857 Print the current target description (@pxref{Target Descriptions}) as
22858 a C source file. The created source file can be used in @value{GDBN}
22859 when an XML parser is not available to parse the description.
22861 @kindex maint print dummy-frames
22862 @item maint print dummy-frames
22863 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22866 (@value{GDBP}) @kbd{b add}
22868 (@value{GDBP}) @kbd{print add(2,3)}
22869 Breakpoint 2, add (a=2, b=3) at @dots{}
22871 The program being debugged stopped while in a function called from GDB.
22873 (@value{GDBP}) @kbd{maint print dummy-frames}
22874 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22875 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22876 call_lo=0x01014000 call_hi=0x01014001
22880 Takes an optional file parameter.
22882 @kindex maint print registers
22883 @kindex maint print raw-registers
22884 @kindex maint print cooked-registers
22885 @kindex maint print register-groups
22886 @item maint print registers @r{[}@var{file}@r{]}
22887 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22888 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22889 @itemx maint print register-groups @r{[}@var{file}@r{]}
22890 Print @value{GDBN}'s internal register data structures.
22892 The command @code{maint print raw-registers} includes the contents of
22893 the raw register cache; the command @code{maint print cooked-registers}
22894 includes the (cooked) value of all registers; and the command
22895 @code{maint print register-groups} includes the groups that each
22896 register is a member of. @xref{Registers,, Registers, gdbint,
22897 @value{GDBN} Internals}.
22899 These commands take an optional parameter, a file name to which to
22900 write the information.
22902 @kindex maint print reggroups
22903 @item maint print reggroups @r{[}@var{file}@r{]}
22904 Print @value{GDBN}'s internal register group data structures. The
22905 optional argument @var{file} tells to what file to write the
22908 The register groups info looks like this:
22911 (@value{GDBP}) @kbd{maint print reggroups}
22924 This command forces @value{GDBN} to flush its internal register cache.
22926 @kindex maint print objfiles
22927 @cindex info for known object files
22928 @item maint print objfiles
22929 Print a dump of all known object files. For each object file, this
22930 command prints its name, address in memory, and all of its psymtabs
22933 @kindex maint print statistics
22934 @cindex bcache statistics
22935 @item maint print statistics
22936 This command prints, for each object file in the program, various data
22937 about that object file followed by the byte cache (@dfn{bcache})
22938 statistics for the object file. The objfile data includes the number
22939 of minimal, partial, full, and stabs symbols, the number of types
22940 defined by the objfile, the number of as yet unexpanded psym tables,
22941 the number of line tables and string tables, and the amount of memory
22942 used by the various tables. The bcache statistics include the counts,
22943 sizes, and counts of duplicates of all and unique objects, max,
22944 average, and median entry size, total memory used and its overhead and
22945 savings, and various measures of the hash table size and chain
22948 @kindex maint print target-stack
22949 @cindex target stack description
22950 @item maint print target-stack
22951 A @dfn{target} is an interface between the debugger and a particular
22952 kind of file or process. Targets can be stacked in @dfn{strata},
22953 so that more than one target can potentially respond to a request.
22954 In particular, memory accesses will walk down the stack of targets
22955 until they find a target that is interested in handling that particular
22958 This command prints a short description of each layer that was pushed on
22959 the @dfn{target stack}, starting from the top layer down to the bottom one.
22961 @kindex maint print type
22962 @cindex type chain of a data type
22963 @item maint print type @var{expr}
22964 Print the type chain for a type specified by @var{expr}. The argument
22965 can be either a type name or a symbol. If it is a symbol, the type of
22966 that symbol is described. The type chain produced by this command is
22967 a recursive definition of the data type as stored in @value{GDBN}'s
22968 data structures, including its flags and contained types.
22970 @kindex maint set dwarf2 max-cache-age
22971 @kindex maint show dwarf2 max-cache-age
22972 @item maint set dwarf2 max-cache-age
22973 @itemx maint show dwarf2 max-cache-age
22974 Control the DWARF 2 compilation unit cache.
22976 @cindex DWARF 2 compilation units cache
22977 In object files with inter-compilation-unit references, such as those
22978 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22979 reader needs to frequently refer to previously read compilation units.
22980 This setting controls how long a compilation unit will remain in the
22981 cache if it is not referenced. A higher limit means that cached
22982 compilation units will be stored in memory longer, and more total
22983 memory will be used. Setting it to zero disables caching, which will
22984 slow down @value{GDBN} startup, but reduce memory consumption.
22986 @kindex maint set profile
22987 @kindex maint show profile
22988 @cindex profiling GDB
22989 @item maint set profile
22990 @itemx maint show profile
22991 Control profiling of @value{GDBN}.
22993 Profiling will be disabled until you use the @samp{maint set profile}
22994 command to enable it. When you enable profiling, the system will begin
22995 collecting timing and execution count data; when you disable profiling or
22996 exit @value{GDBN}, the results will be written to a log file. Remember that
22997 if you use profiling, @value{GDBN} will overwrite the profiling log file
22998 (often called @file{gmon.out}). If you have a record of important profiling
22999 data in a @file{gmon.out} file, be sure to move it to a safe location.
23001 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
23002 compiled with the @samp{-pg} compiler option.
23004 @kindex maint show-debug-regs
23005 @cindex x86 hardware debug registers
23006 @item maint show-debug-regs
23007 Control whether to show variables that mirror the x86 hardware debug
23008 registers. Use @code{ON} to enable, @code{OFF} to disable. If
23009 enabled, the debug registers values are shown when @value{GDBN} inserts or
23010 removes a hardware breakpoint or watchpoint, and when the inferior
23011 triggers a hardware-assisted breakpoint or watchpoint.
23013 @kindex maint space
23014 @cindex memory used by commands
23016 Control whether to display memory usage for each command. If set to a
23017 nonzero value, @value{GDBN} will display how much memory each command
23018 took, following the command's own output. This can also be requested
23019 by invoking @value{GDBN} with the @option{--statistics} command-line
23020 switch (@pxref{Mode Options}).
23023 @cindex time of command execution
23025 Control whether to display the execution time for each command. If
23026 set to a nonzero value, @value{GDBN} will display how much time it
23027 took to execute each command, following the command's own output.
23028 This can also be requested by invoking @value{GDBN} with the
23029 @option{--statistics} command-line switch (@pxref{Mode Options}).
23031 @kindex maint translate-address
23032 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
23033 Find the symbol stored at the location specified by the address
23034 @var{addr} and an optional section name @var{section}. If found,
23035 @value{GDBN} prints the name of the closest symbol and an offset from
23036 the symbol's location to the specified address. This is similar to
23037 the @code{info address} command (@pxref{Symbols}), except that this
23038 command also allows to find symbols in other sections.
23042 The following command is useful for non-interactive invocations of
23043 @value{GDBN}, such as in the test suite.
23046 @item set watchdog @var{nsec}
23047 @kindex set watchdog
23048 @cindex watchdog timer
23049 @cindex timeout for commands
23050 Set the maximum number of seconds @value{GDBN} will wait for the
23051 target operation to finish. If this time expires, @value{GDBN}
23052 reports and error and the command is aborted.
23054 @item show watchdog
23055 Show the current setting of the target wait timeout.
23058 @node Remote Protocol
23059 @appendix @value{GDBN} Remote Serial Protocol
23064 * Stop Reply Packets::
23065 * General Query Packets::
23066 * Register Packet Format::
23067 * Tracepoint Packets::
23068 * Host I/O Packets::
23071 * File-I/O Remote Protocol Extension::
23072 * Library List Format::
23073 * Memory Map Format::
23079 There may be occasions when you need to know something about the
23080 protocol---for example, if there is only one serial port to your target
23081 machine, you might want your program to do something special if it
23082 recognizes a packet meant for @value{GDBN}.
23084 In the examples below, @samp{->} and @samp{<-} are used to indicate
23085 transmitted and received data, respectively.
23087 @cindex protocol, @value{GDBN} remote serial
23088 @cindex serial protocol, @value{GDBN} remote
23089 @cindex remote serial protocol
23090 All @value{GDBN} commands and responses (other than acknowledgments) are
23091 sent as a @var{packet}. A @var{packet} is introduced with the character
23092 @samp{$}, the actual @var{packet-data}, and the terminating character
23093 @samp{#} followed by a two-digit @var{checksum}:
23096 @code{$}@var{packet-data}@code{#}@var{checksum}
23100 @cindex checksum, for @value{GDBN} remote
23102 The two-digit @var{checksum} is computed as the modulo 256 sum of all
23103 characters between the leading @samp{$} and the trailing @samp{#} (an
23104 eight bit unsigned checksum).
23106 Implementors should note that prior to @value{GDBN} 5.0 the protocol
23107 specification also included an optional two-digit @var{sequence-id}:
23110 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
23113 @cindex sequence-id, for @value{GDBN} remote
23115 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
23116 has never output @var{sequence-id}s. Stubs that handle packets added
23117 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
23119 @cindex acknowledgment, for @value{GDBN} remote
23120 When either the host or the target machine receives a packet, the first
23121 response expected is an acknowledgment: either @samp{+} (to indicate
23122 the package was received correctly) or @samp{-} (to request
23126 -> @code{$}@var{packet-data}@code{#}@var{checksum}
23131 The host (@value{GDBN}) sends @var{command}s, and the target (the
23132 debugging stub incorporated in your program) sends a @var{response}. In
23133 the case of step and continue @var{command}s, the response is only sent
23134 when the operation has completed (the target has again stopped).
23136 @var{packet-data} consists of a sequence of characters with the
23137 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
23140 @cindex remote protocol, field separator
23141 Fields within the packet should be separated using @samp{,} @samp{;} or
23142 @samp{:}. Except where otherwise noted all numbers are represented in
23143 @sc{hex} with leading zeros suppressed.
23145 Implementors should note that prior to @value{GDBN} 5.0, the character
23146 @samp{:} could not appear as the third character in a packet (as it
23147 would potentially conflict with the @var{sequence-id}).
23149 @cindex remote protocol, binary data
23150 @anchor{Binary Data}
23151 Binary data in most packets is encoded either as two hexadecimal
23152 digits per byte of binary data. This allowed the traditional remote
23153 protocol to work over connections which were only seven-bit clean.
23154 Some packets designed more recently assume an eight-bit clean
23155 connection, and use a more efficient encoding to send and receive
23158 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
23159 as an escape character. Any escaped byte is transmitted as the escape
23160 character followed by the original character XORed with @code{0x20}.
23161 For example, the byte @code{0x7d} would be transmitted as the two
23162 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
23163 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
23164 @samp{@}}) must always be escaped. Responses sent by the stub
23165 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
23166 is not interpreted as the start of a run-length encoded sequence
23169 Response @var{data} can be run-length encoded to save space.
23170 Run-length encoding replaces runs of identical characters with one
23171 instance of the repeated character, followed by a @samp{*} and a
23172 repeat count. The repeat count is itself sent encoded, to avoid
23173 binary characters in @var{data}: a value of @var{n} is sent as
23174 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
23175 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
23176 code 32) for a repeat count of 3. (This is because run-length
23177 encoding starts to win for counts 3 or more.) Thus, for example,
23178 @samp{0* } is a run-length encoding of ``0000'': the space character
23179 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
23182 The printable characters @samp{#} and @samp{$} or with a numeric value
23183 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
23184 seven repeats (@samp{$}) can be expanded using a repeat count of only
23185 five (@samp{"}). For example, @samp{00000000} can be encoded as
23188 The error response returned for some packets includes a two character
23189 error number. That number is not well defined.
23191 @cindex empty response, for unsupported packets
23192 For any @var{command} not supported by the stub, an empty response
23193 (@samp{$#00}) should be returned. That way it is possible to extend the
23194 protocol. A newer @value{GDBN} can tell if a packet is supported based
23197 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
23198 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
23204 The following table provides a complete list of all currently defined
23205 @var{command}s and their corresponding response @var{data}.
23206 @xref{File-I/O Remote Protocol Extension}, for details about the File
23207 I/O extension of the remote protocol.
23209 Each packet's description has a template showing the packet's overall
23210 syntax, followed by an explanation of the packet's meaning. We
23211 include spaces in some of the templates for clarity; these are not
23212 part of the packet's syntax. No @value{GDBN} packet uses spaces to
23213 separate its components. For example, a template like @samp{foo
23214 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
23215 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
23216 @var{baz}. @value{GDBN} does not transmit a space character between the
23217 @samp{foo} and the @var{bar}, or between the @var{bar} and the
23220 Note that all packet forms beginning with an upper- or lower-case
23221 letter, other than those described here, are reserved for future use.
23223 Here are the packet descriptions.
23228 @cindex @samp{!} packet
23229 Enable extended mode. In extended mode, the remote server is made
23230 persistent. The @samp{R} packet is used to restart the program being
23236 The remote target both supports and has enabled extended mode.
23240 @cindex @samp{?} packet
23241 Indicate the reason the target halted. The reply is the same as for
23245 @xref{Stop Reply Packets}, for the reply specifications.
23247 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
23248 @cindex @samp{A} packet
23249 Initialized @code{argv[]} array passed into program. @var{arglen}
23250 specifies the number of bytes in the hex encoded byte stream
23251 @var{arg}. See @code{gdbserver} for more details.
23256 The arguments were set.
23262 @cindex @samp{b} packet
23263 (Don't use this packet; its behavior is not well-defined.)
23264 Change the serial line speed to @var{baud}.
23266 JTC: @emph{When does the transport layer state change? When it's
23267 received, or after the ACK is transmitted. In either case, there are
23268 problems if the command or the acknowledgment packet is dropped.}
23270 Stan: @emph{If people really wanted to add something like this, and get
23271 it working for the first time, they ought to modify ser-unix.c to send
23272 some kind of out-of-band message to a specially-setup stub and have the
23273 switch happen "in between" packets, so that from remote protocol's point
23274 of view, nothing actually happened.}
23276 @item B @var{addr},@var{mode}
23277 @cindex @samp{B} packet
23278 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23279 breakpoint at @var{addr}.
23281 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23282 (@pxref{insert breakpoint or watchpoint packet}).
23284 @item c @r{[}@var{addr}@r{]}
23285 @cindex @samp{c} packet
23286 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23287 resume at current address.
23290 @xref{Stop Reply Packets}, for the reply specifications.
23292 @item C @var{sig}@r{[};@var{addr}@r{]}
23293 @cindex @samp{C} packet
23294 Continue with signal @var{sig} (hex signal number). If
23295 @samp{;@var{addr}} is omitted, resume at same address.
23298 @xref{Stop Reply Packets}, for the reply specifications.
23301 @cindex @samp{d} packet
23304 Don't use this packet; instead, define a general set packet
23305 (@pxref{General Query Packets}).
23308 @cindex @samp{D} packet
23309 Detach @value{GDBN} from the remote system. Sent to the remote target
23310 before @value{GDBN} disconnects via the @code{detach} command.
23320 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23321 @cindex @samp{F} packet
23322 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23323 This is part of the File-I/O protocol extension. @xref{File-I/O
23324 Remote Protocol Extension}, for the specification.
23327 @anchor{read registers packet}
23328 @cindex @samp{g} packet
23329 Read general registers.
23333 @item @var{XX@dots{}}
23334 Each byte of register data is described by two hex digits. The bytes
23335 with the register are transmitted in target byte order. The size of
23336 each register and their position within the @samp{g} packet are
23337 determined by the @value{GDBN} internal gdbarch functions
23338 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
23339 specification of several standard @samp{g} packets is specified below.
23344 @item G @var{XX@dots{}}
23345 @cindex @samp{G} packet
23346 Write general registers. @xref{read registers packet}, for a
23347 description of the @var{XX@dots{}} data.
23357 @item H @var{c} @var{t}
23358 @cindex @samp{H} packet
23359 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23360 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23361 should be @samp{c} for step and continue operations, @samp{g} for other
23362 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23363 the threads, a thread number, or @samp{0} which means pick any thread.
23374 @c 'H': How restrictive (or permissive) is the thread model. If a
23375 @c thread is selected and stopped, are other threads allowed
23376 @c to continue to execute? As I mentioned above, I think the
23377 @c semantics of each command when a thread is selected must be
23378 @c described. For example:
23380 @c 'g': If the stub supports threads and a specific thread is
23381 @c selected, returns the register block from that thread;
23382 @c otherwise returns current registers.
23384 @c 'G' If the stub supports threads and a specific thread is
23385 @c selected, sets the registers of the register block of
23386 @c that thread; otherwise sets current registers.
23388 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23389 @anchor{cycle step packet}
23390 @cindex @samp{i} packet
23391 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23392 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23393 step starting at that address.
23396 @cindex @samp{I} packet
23397 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23401 @cindex @samp{k} packet
23404 FIXME: @emph{There is no description of how to operate when a specific
23405 thread context has been selected (i.e.@: does 'k' kill only that
23408 @item m @var{addr},@var{length}
23409 @cindex @samp{m} packet
23410 Read @var{length} bytes of memory starting at address @var{addr}.
23411 Note that @var{addr} may not be aligned to any particular boundary.
23413 The stub need not use any particular size or alignment when gathering
23414 data from memory for the response; even if @var{addr} is word-aligned
23415 and @var{length} is a multiple of the word size, the stub is free to
23416 use byte accesses, or not. For this reason, this packet may not be
23417 suitable for accessing memory-mapped I/O devices.
23418 @cindex alignment of remote memory accesses
23419 @cindex size of remote memory accesses
23420 @cindex memory, alignment and size of remote accesses
23424 @item @var{XX@dots{}}
23425 Memory contents; each byte is transmitted as a two-digit hexadecimal
23426 number. The reply may contain fewer bytes than requested if the
23427 server was able to read only part of the region of memory.
23432 @item M @var{addr},@var{length}:@var{XX@dots{}}
23433 @cindex @samp{M} packet
23434 Write @var{length} bytes of memory starting at address @var{addr}.
23435 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23436 hexadecimal number.
23443 for an error (this includes the case where only part of the data was
23448 @cindex @samp{p} packet
23449 Read the value of register @var{n}; @var{n} is in hex.
23450 @xref{read registers packet}, for a description of how the returned
23451 register value is encoded.
23455 @item @var{XX@dots{}}
23456 the register's value
23460 Indicating an unrecognized @var{query}.
23463 @item P @var{n@dots{}}=@var{r@dots{}}
23464 @anchor{write register packet}
23465 @cindex @samp{P} packet
23466 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23467 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23468 digits for each byte in the register (target byte order).
23478 @item q @var{name} @var{params}@dots{}
23479 @itemx Q @var{name} @var{params}@dots{}
23480 @cindex @samp{q} packet
23481 @cindex @samp{Q} packet
23482 General query (@samp{q}) and set (@samp{Q}). These packets are
23483 described fully in @ref{General Query Packets}.
23486 @cindex @samp{r} packet
23487 Reset the entire system.
23489 Don't use this packet; use the @samp{R} packet instead.
23492 @cindex @samp{R} packet
23493 Restart the program being debugged. @var{XX}, while needed, is ignored.
23494 This packet is only available in extended mode.
23496 The @samp{R} packet has no reply.
23498 @item s @r{[}@var{addr}@r{]}
23499 @cindex @samp{s} packet
23500 Single step. @var{addr} is the address at which to resume. If
23501 @var{addr} is omitted, resume at same address.
23504 @xref{Stop Reply Packets}, for the reply specifications.
23506 @item S @var{sig}@r{[};@var{addr}@r{]}
23507 @anchor{step with signal packet}
23508 @cindex @samp{S} packet
23509 Step with signal. This is analogous to the @samp{C} packet, but
23510 requests a single-step, rather than a normal resumption of execution.
23513 @xref{Stop Reply Packets}, for the reply specifications.
23515 @item t @var{addr}:@var{PP},@var{MM}
23516 @cindex @samp{t} packet
23517 Search backwards starting at address @var{addr} for a match with pattern
23518 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23519 @var{addr} must be at least 3 digits.
23522 @cindex @samp{T} packet
23523 Find out if the thread XX is alive.
23528 thread is still alive
23534 Packets starting with @samp{v} are identified by a multi-letter name,
23535 up to the first @samp{;} or @samp{?} (or the end of the packet).
23537 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23538 @cindex @samp{vCont} packet
23539 Resume the inferior, specifying different actions for each thread.
23540 If an action is specified with no @var{tid}, then it is applied to any
23541 threads that don't have a specific action specified; if no default action is
23542 specified then other threads should remain stopped. Specifying multiple
23543 default actions is an error; specifying no actions is also an error.
23544 Thread IDs are specified in hexadecimal. Currently supported actions are:
23550 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23554 Step with signal @var{sig}. @var{sig} should be two hex digits.
23557 The optional @var{addr} argument normally associated with these packets is
23558 not supported in @samp{vCont}.
23561 @xref{Stop Reply Packets}, for the reply specifications.
23564 @cindex @samp{vCont?} packet
23565 Request a list of actions supported by the @samp{vCont} packet.
23569 @item vCont@r{[};@var{action}@dots{}@r{]}
23570 The @samp{vCont} packet is supported. Each @var{action} is a supported
23571 command in the @samp{vCont} packet.
23573 The @samp{vCont} packet is not supported.
23576 @item vFile:@var{operation}:@var{parameter}@dots{}
23577 @cindex @samp{vFile} packet
23578 Perform a file operation on the target system. For details,
23579 see @ref{Host I/O Packets}.
23581 @item vFlashErase:@var{addr},@var{length}
23582 @cindex @samp{vFlashErase} packet
23583 Direct the stub to erase @var{length} bytes of flash starting at
23584 @var{addr}. The region may enclose any number of flash blocks, but
23585 its start and end must fall on block boundaries, as indicated by the
23586 flash block size appearing in the memory map (@pxref{Memory Map
23587 Format}). @value{GDBN} groups flash memory programming operations
23588 together, and sends a @samp{vFlashDone} request after each group; the
23589 stub is allowed to delay erase operation until the @samp{vFlashDone}
23590 packet is received.
23600 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23601 @cindex @samp{vFlashWrite} packet
23602 Direct the stub to write data to flash address @var{addr}. The data
23603 is passed in binary form using the same encoding as for the @samp{X}
23604 packet (@pxref{Binary Data}). The memory ranges specified by
23605 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23606 not overlap, and must appear in order of increasing addresses
23607 (although @samp{vFlashErase} packets for higher addresses may already
23608 have been received; the ordering is guaranteed only between
23609 @samp{vFlashWrite} packets). If a packet writes to an address that was
23610 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23611 target-specific method, the results are unpredictable.
23619 for vFlashWrite addressing non-flash memory
23625 @cindex @samp{vFlashDone} packet
23626 Indicate to the stub that flash programming operation is finished.
23627 The stub is permitted to delay or batch the effects of a group of
23628 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23629 @samp{vFlashDone} packet is received. The contents of the affected
23630 regions of flash memory are unpredictable until the @samp{vFlashDone}
23631 request is completed.
23633 @item X @var{addr},@var{length}:@var{XX@dots{}}
23635 @cindex @samp{X} packet
23636 Write data to memory, where the data is transmitted in binary.
23637 @var{addr} is address, @var{length} is number of bytes,
23638 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23648 @item z @var{type},@var{addr},@var{length}
23649 @itemx Z @var{type},@var{addr},@var{length}
23650 @anchor{insert breakpoint or watchpoint packet}
23651 @cindex @samp{z} packet
23652 @cindex @samp{Z} packets
23653 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23654 watchpoint starting at address @var{address} and covering the next
23655 @var{length} bytes.
23657 Each breakpoint and watchpoint packet @var{type} is documented
23660 @emph{Implementation notes: A remote target shall return an empty string
23661 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23662 remote target shall support either both or neither of a given
23663 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23664 avoid potential problems with duplicate packets, the operations should
23665 be implemented in an idempotent way.}
23667 @item z0,@var{addr},@var{length}
23668 @itemx Z0,@var{addr},@var{length}
23669 @cindex @samp{z0} packet
23670 @cindex @samp{Z0} packet
23671 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23672 @var{addr} of size @var{length}.
23674 A memory breakpoint is implemented by replacing the instruction at
23675 @var{addr} with a software breakpoint or trap instruction. The
23676 @var{length} is used by targets that indicates the size of the
23677 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23678 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23680 @emph{Implementation note: It is possible for a target to copy or move
23681 code that contains memory breakpoints (e.g., when implementing
23682 overlays). The behavior of this packet, in the presence of such a
23683 target, is not defined.}
23695 @item z1,@var{addr},@var{length}
23696 @itemx Z1,@var{addr},@var{length}
23697 @cindex @samp{z1} packet
23698 @cindex @samp{Z1} packet
23699 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23700 address @var{addr} of size @var{length}.
23702 A hardware breakpoint is implemented using a mechanism that is not
23703 dependant on being able to modify the target's memory.
23705 @emph{Implementation note: A hardware breakpoint is not affected by code
23718 @item z2,@var{addr},@var{length}
23719 @itemx Z2,@var{addr},@var{length}
23720 @cindex @samp{z2} packet
23721 @cindex @samp{Z2} packet
23722 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23734 @item z3,@var{addr},@var{length}
23735 @itemx Z3,@var{addr},@var{length}
23736 @cindex @samp{z3} packet
23737 @cindex @samp{Z3} packet
23738 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23750 @item z4,@var{addr},@var{length}
23751 @itemx Z4,@var{addr},@var{length}
23752 @cindex @samp{z4} packet
23753 @cindex @samp{Z4} packet
23754 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23768 @node Stop Reply Packets
23769 @section Stop Reply Packets
23770 @cindex stop reply packets
23772 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23773 receive any of the below as a reply. In the case of the @samp{C},
23774 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23775 when the target halts. In the below the exact meaning of @dfn{signal
23776 number} is defined by the header @file{include/gdb/signals.h} in the
23777 @value{GDBN} source code.
23779 As in the description of request packets, we include spaces in the
23780 reply templates for clarity; these are not part of the reply packet's
23781 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23787 The program received signal number @var{AA} (a two-digit hexadecimal
23788 number). This is equivalent to a @samp{T} response with no
23789 @var{n}:@var{r} pairs.
23791 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23792 @cindex @samp{T} packet reply
23793 The program received signal number @var{AA} (a two-digit hexadecimal
23794 number). This is equivalent to an @samp{S} response, except that the
23795 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23796 and other information directly in the stop reply packet, reducing
23797 round-trip latency. Single-step and breakpoint traps are reported
23798 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23802 If @var{n} is a hexadecimal number, it is a register number, and the
23803 corresponding @var{r} gives that register's value. @var{r} is a
23804 series of bytes in target byte order, with each byte given by a
23805 two-digit hex number.
23808 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23812 If @var{n} is a recognized @dfn{stop reason}, it describes a more
23813 specific event that stopped the target. The currently defined stop
23814 reasons are listed below. @var{aa} should be @samp{05}, the trap
23815 signal. At most one stop reason should be present.
23818 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23819 and go on to the next; this allows us to extend the protocol in the
23823 The currently defined stop reasons are:
23829 The packet indicates a watchpoint hit, and @var{r} is the data address, in
23832 @cindex shared library events, remote reply
23834 The packet indicates that the loaded libraries have changed.
23835 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
23836 list of loaded libraries. @var{r} is ignored.
23840 The process exited, and @var{AA} is the exit status. This is only
23841 applicable to certain targets.
23844 The process terminated with signal @var{AA}.
23846 @item O @var{XX}@dots{}
23847 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23848 written as the program's console output. This can happen at any time
23849 while the program is running and the debugger should continue to wait
23850 for @samp{W}, @samp{T}, etc.
23852 @item F @var{call-id},@var{parameter}@dots{}
23853 @var{call-id} is the identifier which says which host system call should
23854 be called. This is just the name of the function. Translation into the
23855 correct system call is only applicable as it's defined in @value{GDBN}.
23856 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
23859 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23860 this very system call.
23862 The target replies with this packet when it expects @value{GDBN} to
23863 call a host system call on behalf of the target. @value{GDBN} replies
23864 with an appropriate @samp{F} packet and keeps up waiting for the next
23865 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23866 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
23867 Protocol Extension}, for more details.
23871 @node General Query Packets
23872 @section General Query Packets
23873 @cindex remote query requests
23875 Packets starting with @samp{q} are @dfn{general query packets};
23876 packets starting with @samp{Q} are @dfn{general set packets}. General
23877 query and set packets are a semi-unified form for retrieving and
23878 sending information to and from the stub.
23880 The initial letter of a query or set packet is followed by a name
23881 indicating what sort of thing the packet applies to. For example,
23882 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23883 definitions with the stub. These packet names follow some
23888 The name must not contain commas, colons or semicolons.
23890 Most @value{GDBN} query and set packets have a leading upper case
23893 The names of custom vendor packets should use a company prefix, in
23894 lower case, followed by a period. For example, packets designed at
23895 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23896 foos) or @samp{Qacme.bar} (for setting bars).
23899 The name of a query or set packet should be separated from any
23900 parameters by a @samp{:}; the parameters themselves should be
23901 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23902 full packet name, and check for a separator or the end of the packet,
23903 in case two packet names share a common prefix. New packets should not begin
23904 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23905 packets predate these conventions, and have arguments without any terminator
23906 for the packet name; we suspect they are in widespread use in places that
23907 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23908 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23911 Like the descriptions of the other packets, each description here
23912 has a template showing the packet's overall syntax, followed by an
23913 explanation of the packet's meaning. We include spaces in some of the
23914 templates for clarity; these are not part of the packet's syntax. No
23915 @value{GDBN} packet uses spaces to separate its components.
23917 Here are the currently defined query and set packets:
23922 @cindex current thread, remote request
23923 @cindex @samp{qC} packet
23924 Return the current thread id.
23929 Where @var{pid} is an unsigned hexadecimal process id.
23930 @item @r{(anything else)}
23931 Any other reply implies the old pid.
23934 @item qCRC:@var{addr},@var{length}
23935 @cindex CRC of memory block, remote request
23936 @cindex @samp{qCRC} packet
23937 Compute the CRC checksum of a block of memory.
23941 An error (such as memory fault)
23942 @item C @var{crc32}
23943 The specified memory region's checksum is @var{crc32}.
23947 @itemx qsThreadInfo
23948 @cindex list active threads, remote request
23949 @cindex @samp{qfThreadInfo} packet
23950 @cindex @samp{qsThreadInfo} packet
23951 Obtain a list of all active thread ids from the target (OS). Since there
23952 may be too many active threads to fit into one reply packet, this query
23953 works iteratively: it may require more than one query/reply sequence to
23954 obtain the entire list of threads. The first query of the sequence will
23955 be the @samp{qfThreadInfo} query; subsequent queries in the
23956 sequence will be the @samp{qsThreadInfo} query.
23958 NOTE: This packet replaces the @samp{qL} query (see below).
23964 @item m @var{id},@var{id}@dots{}
23965 a comma-separated list of thread ids
23967 (lower case letter @samp{L}) denotes end of list.
23970 In response to each query, the target will reply with a list of one or
23971 more thread ids, in big-endian unsigned hex, separated by commas.
23972 @value{GDBN} will respond to each reply with a request for more thread
23973 ids (using the @samp{qs} form of the query), until the target responds
23974 with @samp{l} (lower-case el, for @dfn{last}).
23976 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23977 @cindex get thread-local storage address, remote request
23978 @cindex @samp{qGetTLSAddr} packet
23979 Fetch the address associated with thread local storage specified
23980 by @var{thread-id}, @var{offset}, and @var{lm}.
23982 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23983 thread for which to fetch the TLS address.
23985 @var{offset} is the (big endian, hex encoded) offset associated with the
23986 thread local variable. (This offset is obtained from the debug
23987 information associated with the variable.)
23989 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
23990 the load module associated with the thread local storage. For example,
23991 a @sc{gnu}/Linux system will pass the link map address of the shared
23992 object associated with the thread local storage under consideration.
23993 Other operating environments may choose to represent the load module
23994 differently, so the precise meaning of this parameter will vary.
23998 @item @var{XX}@dots{}
23999 Hex encoded (big endian) bytes representing the address of the thread
24000 local storage requested.
24003 An error occurred. @var{nn} are hex digits.
24006 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
24009 @item qL @var{startflag} @var{threadcount} @var{nextthread}
24010 Obtain thread information from RTOS. Where: @var{startflag} (one hex
24011 digit) is one to indicate the first query and zero to indicate a
24012 subsequent query; @var{threadcount} (two hex digits) is the maximum
24013 number of threads the response packet can contain; and @var{nextthread}
24014 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
24015 returned in the response as @var{argthread}.
24017 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
24021 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
24022 Where: @var{count} (two hex digits) is the number of threads being
24023 returned; @var{done} (one hex digit) is zero to indicate more threads
24024 and one indicates no further threads; @var{argthreadid} (eight hex
24025 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
24026 is a sequence of thread IDs from the target. @var{threadid} (eight hex
24027 digits). See @code{remote.c:parse_threadlist_response()}.
24031 @cindex section offsets, remote request
24032 @cindex @samp{qOffsets} packet
24033 Get section offsets that the target used when relocating the downloaded
24038 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
24039 Relocate the @code{Text} section by @var{xxx} from its original address.
24040 Relocate the @code{Data} section by @var{yyy} from its original address.
24041 If the object file format provides segment information (e.g.@: @sc{elf}
24042 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
24043 segments by the supplied offsets.
24045 @emph{Note: while a @code{Bss} offset may be included in the response,
24046 @value{GDBN} ignores this and instead applies the @code{Data} offset
24047 to the @code{Bss} section.}
24049 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
24050 Relocate the first segment of the object file, which conventionally
24051 contains program code, to a starting address of @var{xxx}. If
24052 @samp{DataSeg} is specified, relocate the second segment, which
24053 conventionally contains modifiable data, to a starting address of
24054 @var{yyy}. @value{GDBN} will report an error if the object file
24055 does not contain segment information, or does not contain at least
24056 as many segments as mentioned in the reply. Extra segments are
24057 kept at fixed offsets relative to the last relocated segment.
24060 @item qP @var{mode} @var{threadid}
24061 @cindex thread information, remote request
24062 @cindex @samp{qP} packet
24063 Returns information on @var{threadid}. Where: @var{mode} is a hex
24064 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
24066 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
24069 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
24071 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
24072 @cindex pass signals to inferior, remote request
24073 @cindex @samp{QPassSignals} packet
24074 @anchor{QPassSignals}
24075 Each listed @var{signal} should be passed directly to the inferior process.
24076 Signals are numbered identically to continue packets and stop replies
24077 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
24078 strictly greater than the previous item. These signals do not need to stop
24079 the inferior, or be reported to @value{GDBN}. All other signals should be
24080 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
24081 combine; any earlier @samp{QPassSignals} list is completely replaced by the
24082 new list. This packet improves performance when using @samp{handle
24083 @var{signal} nostop noprint pass}.
24088 The request succeeded.
24091 An error occurred. @var{nn} are hex digits.
24094 An empty reply indicates that @samp{QPassSignals} is not supported by
24098 Use of this packet is controlled by the @code{set remote pass-signals}
24099 command (@pxref{Remote Configuration, set remote pass-signals}).
24100 This packet is not probed by default; the remote stub must request it,
24101 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24103 @item qRcmd,@var{command}
24104 @cindex execute remote command, remote request
24105 @cindex @samp{qRcmd} packet
24106 @var{command} (hex encoded) is passed to the local interpreter for
24107 execution. Invalid commands should be reported using the output
24108 string. Before the final result packet, the target may also respond
24109 with a number of intermediate @samp{O@var{output}} console output
24110 packets. @emph{Implementors should note that providing access to a
24111 stubs's interpreter may have security implications}.
24116 A command response with no output.
24118 A command response with the hex encoded output string @var{OUTPUT}.
24120 Indicate a badly formed request.
24122 An empty reply indicates that @samp{qRcmd} is not recognized.
24125 (Note that the @code{qRcmd} packet's name is separated from the
24126 command by a @samp{,}, not a @samp{:}, contrary to the naming
24127 conventions above. Please don't use this packet as a model for new
24130 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
24131 @cindex supported packets, remote query
24132 @cindex features of the remote protocol
24133 @cindex @samp{qSupported} packet
24134 @anchor{qSupported}
24135 Tell the remote stub about features supported by @value{GDBN}, and
24136 query the stub for features it supports. This packet allows
24137 @value{GDBN} and the remote stub to take advantage of each others'
24138 features. @samp{qSupported} also consolidates multiple feature probes
24139 at startup, to improve @value{GDBN} performance---a single larger
24140 packet performs better than multiple smaller probe packets on
24141 high-latency links. Some features may enable behavior which must not
24142 be on by default, e.g.@: because it would confuse older clients or
24143 stubs. Other features may describe packets which could be
24144 automatically probed for, but are not. These features must be
24145 reported before @value{GDBN} will use them. This ``default
24146 unsupported'' behavior is not appropriate for all packets, but it
24147 helps to keep the initial connection time under control with new
24148 versions of @value{GDBN} which support increasing numbers of packets.
24152 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
24153 The stub supports or does not support each returned @var{stubfeature},
24154 depending on the form of each @var{stubfeature} (see below for the
24157 An empty reply indicates that @samp{qSupported} is not recognized,
24158 or that no features needed to be reported to @value{GDBN}.
24161 The allowed forms for each feature (either a @var{gdbfeature} in the
24162 @samp{qSupported} packet, or a @var{stubfeature} in the response)
24166 @item @var{name}=@var{value}
24167 The remote protocol feature @var{name} is supported, and associated
24168 with the specified @var{value}. The format of @var{value} depends
24169 on the feature, but it must not include a semicolon.
24171 The remote protocol feature @var{name} is supported, and does not
24172 need an associated value.
24174 The remote protocol feature @var{name} is not supported.
24176 The remote protocol feature @var{name} may be supported, and
24177 @value{GDBN} should auto-detect support in some other way when it is
24178 needed. This form will not be used for @var{gdbfeature} notifications,
24179 but may be used for @var{stubfeature} responses.
24182 Whenever the stub receives a @samp{qSupported} request, the
24183 supplied set of @value{GDBN} features should override any previous
24184 request. This allows @value{GDBN} to put the stub in a known
24185 state, even if the stub had previously been communicating with
24186 a different version of @value{GDBN}.
24188 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
24189 are defined yet. Stubs should ignore any unknown values for
24190 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
24191 packet supports receiving packets of unlimited length (earlier
24192 versions of @value{GDBN} may reject overly long responses). Values
24193 for @var{gdbfeature} may be defined in the future to let the stub take
24194 advantage of new features in @value{GDBN}, e.g.@: incompatible
24195 improvements in the remote protocol---support for unlimited length
24196 responses would be a @var{gdbfeature} example, if it were not implied by
24197 the @samp{qSupported} query. The stub's reply should be independent
24198 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
24199 describes all the features it supports, and then the stub replies with
24200 all the features it supports.
24202 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
24203 responses, as long as each response uses one of the standard forms.
24205 Some features are flags. A stub which supports a flag feature
24206 should respond with a @samp{+} form response. Other features
24207 require values, and the stub should respond with an @samp{=}
24210 Each feature has a default value, which @value{GDBN} will use if
24211 @samp{qSupported} is not available or if the feature is not mentioned
24212 in the @samp{qSupported} response. The default values are fixed; a
24213 stub is free to omit any feature responses that match the defaults.
24215 Not all features can be probed, but for those which can, the probing
24216 mechanism is useful: in some cases, a stub's internal
24217 architecture may not allow the protocol layer to know some information
24218 about the underlying target in advance. This is especially common in
24219 stubs which may be configured for multiple targets.
24221 These are the currently defined stub features and their properties:
24223 @multitable @columnfractions 0.35 0.2 0.12 0.2
24224 @c NOTE: The first row should be @headitem, but we do not yet require
24225 @c a new enough version of Texinfo (4.7) to use @headitem.
24227 @tab Value Required
24231 @item @samp{PacketSize}
24236 @item @samp{qXfer:auxv:read}
24241 @item @samp{qXfer:features:read}
24246 @item @samp{qXfer:libraries:read}
24251 @item @samp{qXfer:memory-map:read}
24256 @item @samp{qXfer:spu:read}
24261 @item @samp{qXfer:spu:write}
24266 @item @samp{QPassSignals}
24273 These are the currently defined stub features, in more detail:
24276 @cindex packet size, remote protocol
24277 @item PacketSize=@var{bytes}
24278 The remote stub can accept packets up to at least @var{bytes} in
24279 length. @value{GDBN} will send packets up to this size for bulk
24280 transfers, and will never send larger packets. This is a limit on the
24281 data characters in the packet, including the frame and checksum.
24282 There is no trailing NUL byte in a remote protocol packet; if the stub
24283 stores packets in a NUL-terminated format, it should allow an extra
24284 byte in its buffer for the NUL. If this stub feature is not supported,
24285 @value{GDBN} guesses based on the size of the @samp{g} packet response.
24287 @item qXfer:auxv:read
24288 The remote stub understands the @samp{qXfer:auxv:read} packet
24289 (@pxref{qXfer auxiliary vector read}).
24291 @item qXfer:features:read
24292 The remote stub understands the @samp{qXfer:features:read} packet
24293 (@pxref{qXfer target description read}).
24295 @item qXfer:libraries:read
24296 The remote stub understands the @samp{qXfer:libraries:read} packet
24297 (@pxref{qXfer library list read}).
24299 @item qXfer:memory-map:read
24300 The remote stub understands the @samp{qXfer:memory-map:read} packet
24301 (@pxref{qXfer memory map read}).
24303 @item qXfer:spu:read
24304 The remote stub understands the @samp{qXfer:spu:read} packet
24305 (@pxref{qXfer spu read}).
24307 @item qXfer:spu:write
24308 The remote stub understands the @samp{qXfer:spu:write} packet
24309 (@pxref{qXfer spu write}).
24312 The remote stub understands the @samp{QPassSignals} packet
24313 (@pxref{QPassSignals}).
24318 @cindex symbol lookup, remote request
24319 @cindex @samp{qSymbol} packet
24320 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24321 requests. Accept requests from the target for the values of symbols.
24326 The target does not need to look up any (more) symbols.
24327 @item qSymbol:@var{sym_name}
24328 The target requests the value of symbol @var{sym_name} (hex encoded).
24329 @value{GDBN} may provide the value by using the
24330 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24334 @item qSymbol:@var{sym_value}:@var{sym_name}
24335 Set the value of @var{sym_name} to @var{sym_value}.
24337 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24338 target has previously requested.
24340 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24341 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24347 The target does not need to look up any (more) symbols.
24348 @item qSymbol:@var{sym_name}
24349 The target requests the value of a new symbol @var{sym_name} (hex
24350 encoded). @value{GDBN} will continue to supply the values of symbols
24351 (if available), until the target ceases to request them.
24356 @xref{Tracepoint Packets}.
24358 @item qThreadExtraInfo,@var{id}
24359 @cindex thread attributes info, remote request
24360 @cindex @samp{qThreadExtraInfo} packet
24361 Obtain a printable string description of a thread's attributes from
24362 the target OS. @var{id} is a thread-id in big-endian hex. This
24363 string may contain anything that the target OS thinks is interesting
24364 for @value{GDBN} to tell the user about the thread. The string is
24365 displayed in @value{GDBN}'s @code{info threads} display. Some
24366 examples of possible thread extra info strings are @samp{Runnable}, or
24367 @samp{Blocked on Mutex}.
24371 @item @var{XX}@dots{}
24372 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
24373 comprising the printable string containing the extra information about
24374 the thread's attributes.
24377 (Note that the @code{qThreadExtraInfo} packet's name is separated from
24378 the command by a @samp{,}, not a @samp{:}, contrary to the naming
24379 conventions above. Please don't use this packet as a model for new
24387 @xref{Tracepoint Packets}.
24389 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
24390 @cindex read special object, remote request
24391 @cindex @samp{qXfer} packet
24392 @anchor{qXfer read}
24393 Read uninterpreted bytes from the target's special data area
24394 identified by the keyword @var{object}. Request @var{length} bytes
24395 starting at @var{offset} bytes into the data. The content and
24396 encoding of @var{annex} is specific to @var{object}; it can supply
24397 additional details about what data to access.
24399 Here are the specific requests of this form defined so far. All
24400 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
24401 formats, listed below.
24404 @item qXfer:auxv:read::@var{offset},@var{length}
24405 @anchor{qXfer auxiliary vector read}
24406 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
24407 auxiliary vector}. Note @var{annex} must be empty.
24409 This packet is not probed by default; the remote stub must request it,
24410 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24412 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
24413 @anchor{qXfer target description read}
24414 Access the @dfn{target description}. @xref{Target Descriptions}. The
24415 annex specifies which XML document to access. The main description is
24416 always loaded from the @samp{target.xml} annex.
24418 This packet is not probed by default; the remote stub must request it,
24419 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24421 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
24422 @anchor{qXfer library list read}
24423 Access the target's list of loaded libraries. @xref{Library List Format}.
24424 The annex part of the generic @samp{qXfer} packet must be empty
24425 (@pxref{qXfer read}).
24427 Targets which maintain a list of libraries in the program's memory do
24428 not need to implement this packet; it is designed for platforms where
24429 the operating system manages the list of loaded libraries.
24431 This packet is not probed by default; the remote stub must request it,
24432 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24434 @item qXfer:memory-map:read::@var{offset},@var{length}
24435 @anchor{qXfer memory map read}
24436 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
24437 annex part of the generic @samp{qXfer} packet must be empty
24438 (@pxref{qXfer read}).
24440 This packet is not probed by default; the remote stub must request it,
24441 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24443 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
24444 @anchor{qXfer spu read}
24445 Read contents of an @code{spufs} file on the target system. The
24446 annex specifies which file to read; it must be of the form
24447 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24448 in the target process, and @var{name} identifes the @code{spufs} file
24449 in that context to be accessed.
24451 This packet is not probed by default; the remote stub must request it,
24452 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24458 Data @var{data} (@pxref{Binary Data}) has been read from the
24459 target. There may be more data at a higher address (although
24460 it is permitted to return @samp{m} even for the last valid
24461 block of data, as long as at least one byte of data was read).
24462 @var{data} may have fewer bytes than the @var{length} in the
24466 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24467 There is no more data to be read. @var{data} may have fewer bytes
24468 than the @var{length} in the request.
24471 The @var{offset} in the request is at the end of the data.
24472 There is no more data to be read.
24475 The request was malformed, or @var{annex} was invalid.
24478 The offset was invalid, or there was an error encountered reading the data.
24479 @var{nn} is a hex-encoded @code{errno} value.
24482 An empty reply indicates the @var{object} string was not recognized by
24483 the stub, or that the object does not support reading.
24486 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24487 @cindex write data into object, remote request
24488 Write uninterpreted bytes into the target's special data area
24489 identified by the keyword @var{object}, starting at @var{offset} bytes
24490 into the data. @var{data}@dots{} is the binary-encoded data
24491 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24492 is specific to @var{object}; it can supply additional details about what data
24495 Here are the specific requests of this form defined so far. All
24496 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
24497 formats, listed below.
24500 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24501 @anchor{qXfer spu write}
24502 Write @var{data} to an @code{spufs} file on the target system. The
24503 annex specifies which file to write; it must be of the form
24504 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24505 in the target process, and @var{name} identifes the @code{spufs} file
24506 in that context to be accessed.
24508 This packet is not probed by default; the remote stub must request it,
24509 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24515 @var{nn} (hex encoded) is the number of bytes written.
24516 This may be fewer bytes than supplied in the request.
24519 The request was malformed, or @var{annex} was invalid.
24522 The offset was invalid, or there was an error encountered writing the data.
24523 @var{nn} is a hex-encoded @code{errno} value.
24526 An empty reply indicates the @var{object} string was not
24527 recognized by the stub, or that the object does not support writing.
24530 @item qXfer:@var{object}:@var{operation}:@dots{}
24531 Requests of this form may be added in the future. When a stub does
24532 not recognize the @var{object} keyword, or its support for
24533 @var{object} does not recognize the @var{operation} keyword, the stub
24534 must respond with an empty packet.
24538 @node Register Packet Format
24539 @section Register Packet Format
24541 The following @code{g}/@code{G} packets have previously been defined.
24542 In the below, some thirty-two bit registers are transferred as
24543 sixty-four bits. Those registers should be zero/sign extended (which?)
24544 to fill the space allocated. Register bytes are transferred in target
24545 byte order. The two nibbles within a register byte are transferred
24546 most-significant - least-significant.
24552 All registers are transferred as thirty-two bit quantities in the order:
24553 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24554 registers; fsr; fir; fp.
24558 All registers are transferred as sixty-four bit quantities (including
24559 thirty-two bit registers such as @code{sr}). The ordering is the same
24564 @node Tracepoint Packets
24565 @section Tracepoint Packets
24566 @cindex tracepoint packets
24567 @cindex packets, tracepoint
24569 Here we describe the packets @value{GDBN} uses to implement
24570 tracepoints (@pxref{Tracepoints}).
24574 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24575 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24576 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24577 the tracepoint is disabled. @var{step} is the tracepoint's step
24578 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24579 present, further @samp{QTDP} packets will follow to specify this
24580 tracepoint's actions.
24585 The packet was understood and carried out.
24587 The packet was not recognized.
24590 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24591 Define actions to be taken when a tracepoint is hit. @var{n} and
24592 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24593 this tracepoint. This packet may only be sent immediately after
24594 another @samp{QTDP} packet that ended with a @samp{-}. If the
24595 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24596 specifying more actions for this tracepoint.
24598 In the series of action packets for a given tracepoint, at most one
24599 can have an @samp{S} before its first @var{action}. If such a packet
24600 is sent, it and the following packets define ``while-stepping''
24601 actions. Any prior packets define ordinary actions --- that is, those
24602 taken when the tracepoint is first hit. If no action packet has an
24603 @samp{S}, then all the packets in the series specify ordinary
24604 tracepoint actions.
24606 The @samp{@var{action}@dots{}} portion of the packet is a series of
24607 actions, concatenated without separators. Each action has one of the
24613 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24614 a hexadecimal number whose @var{i}'th bit is set if register number
24615 @var{i} should be collected. (The least significant bit is numbered
24616 zero.) Note that @var{mask} may be any number of digits long; it may
24617 not fit in a 32-bit word.
24619 @item M @var{basereg},@var{offset},@var{len}
24620 Collect @var{len} bytes of memory starting at the address in register
24621 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24622 @samp{-1}, then the range has a fixed address: @var{offset} is the
24623 address of the lowest byte to collect. The @var{basereg},
24624 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24625 values (the @samp{-1} value for @var{basereg} is a special case).
24627 @item X @var{len},@var{expr}
24628 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24629 it directs. @var{expr} is an agent expression, as described in
24630 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24631 two-digit hex number in the packet; @var{len} is the number of bytes
24632 in the expression (and thus one-half the number of hex digits in the
24637 Any number of actions may be packed together in a single @samp{QTDP}
24638 packet, as long as the packet does not exceed the maximum packet
24639 length (400 bytes, for many stubs). There may be only one @samp{R}
24640 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24641 actions. Any registers referred to by @samp{M} and @samp{X} actions
24642 must be collected by a preceding @samp{R} action. (The
24643 ``while-stepping'' actions are treated as if they were attached to a
24644 separate tracepoint, as far as these restrictions are concerned.)
24649 The packet was understood and carried out.
24651 The packet was not recognized.
24654 @item QTFrame:@var{n}
24655 Select the @var{n}'th tracepoint frame from the buffer, and use the
24656 register and memory contents recorded there to answer subsequent
24657 request packets from @value{GDBN}.
24659 A successful reply from the stub indicates that the stub has found the
24660 requested frame. The response is a series of parts, concatenated
24661 without separators, describing the frame we selected. Each part has
24662 one of the following forms:
24666 The selected frame is number @var{n} in the trace frame buffer;
24667 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24668 was no frame matching the criteria in the request packet.
24671 The selected trace frame records a hit of tracepoint number @var{t};
24672 @var{t} is a hexadecimal number.
24676 @item QTFrame:pc:@var{addr}
24677 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24678 currently selected frame whose PC is @var{addr};
24679 @var{addr} is a hexadecimal number.
24681 @item QTFrame:tdp:@var{t}
24682 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24683 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24684 is a hexadecimal number.
24686 @item QTFrame:range:@var{start}:@var{end}
24687 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24688 currently selected frame whose PC is between @var{start} (inclusive)
24689 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24692 @item QTFrame:outside:@var{start}:@var{end}
24693 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24694 frame @emph{outside} the given range of addresses.
24697 Begin the tracepoint experiment. Begin collecting data from tracepoint
24698 hits in the trace frame buffer.
24701 End the tracepoint experiment. Stop collecting trace frames.
24704 Clear the table of tracepoints, and empty the trace frame buffer.
24706 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24707 Establish the given ranges of memory as ``transparent''. The stub
24708 will answer requests for these ranges from memory's current contents,
24709 if they were not collected as part of the tracepoint hit.
24711 @value{GDBN} uses this to mark read-only regions of memory, like those
24712 containing program code. Since these areas never change, they should
24713 still have the same contents they did when the tracepoint was hit, so
24714 there's no reason for the stub to refuse to provide their contents.
24717 Ask the stub if there is a trace experiment running right now.
24722 There is no trace experiment running.
24724 There is a trace experiment running.
24730 @node Host I/O Packets
24731 @section Host I/O Packets
24732 @cindex Host I/O, remote protocol
24733 @cindex file transfer, remote protocol
24735 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
24736 operations on the far side of a remote link. For example, Host I/O is
24737 used to upload and download files to a remote target with its own
24738 filesystem. Host I/O uses the same constant values and data structure
24739 layout as the target-initiated File-I/O protocol. However, the
24740 Host I/O packets are structured differently. The target-initiated
24741 protocol relies on target memory to store parameters and buffers.
24742 Host I/O requests are initiated by @value{GDBN}, and the
24743 target's memory is not involved. @xref{File-I/O Remote Protocol
24744 Extension}, for more details on the target-initiated protocol.
24746 The Host I/O request packets all encode a single operation along with
24747 its arguments. They have this format:
24751 @item vFile:@var{operation}: @var{parameter}@dots{}
24752 @var{operation} is the name of the particular request; the target
24753 should compare the entire packet name up to the second colon when checking
24754 for a supported operation. The format of @var{parameter} depends on
24755 the operation. Numbers are always passed in hexadecimal. Negative
24756 numbers have an explicit minus sign (i.e.@: two's complement is not
24757 used). Strings (e.g.@: filenames) are encoded as a series of
24758 hexadecimal bytes. The last argument to a system call may be a
24759 buffer of escaped binary data (@pxref{Binary Data}).
24763 The valid responses to Host I/O packets are:
24767 @item F @var{result} [, @var{errno}] [; @var{attachment}]
24768 @var{result} is the integer value returned by this operation, usually
24769 non-negative for success and -1 for errors. If an error has occured,
24770 @var{errno} will be included in the result. @var{errno} will have a
24771 value defined by the File-I/O protocol (@pxref{Errno Values}). For
24772 operations which return data, @var{attachment} supplies the data as a
24773 binary buffer. Binary buffers in response packets are escaped in the
24774 normal way (@pxref{Binary Data}). See the individual packet
24775 documentation for the interpretation of @var{result} and
24779 An empty response indicates that this operation is not recognized.
24783 These are the supported Host I/O operations:
24786 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
24787 Open a file at @var{pathname} and return a file descriptor for it, or
24788 return -1 if an error occurs. @var{pathname} is a string,
24789 @var{flags} is an integer indicating a mask of open flags
24790 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
24791 of mode bits to use if the file is created (@pxref{mode_t Values}).
24792 @xref{open}, for details of the open flags and mode values.
24794 @item vFile:close: @var{fd}
24795 Close the open file corresponding to @var{fd} and return 0, or
24796 -1 if an error occurs.
24798 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
24799 Read data from the open file corresponding to @var{fd}. Up to
24800 @var{count} bytes will be read from the file, starting at @var{offset}
24801 relative to the start of the file. The target may read fewer bytes;
24802 common reasons include packet size limits and an end-of-file
24803 condition. The number of bytes read is returned. Zero should only be
24804 returned for a successful read at the end of the file, or if
24805 @var{count} was zero.
24807 The data read should be returned as a binary attachment on success.
24808 If zero bytes were read, the response should include an empty binary
24809 attachment (i.e.@: a trailing semicolon). The return value is the
24810 number of target bytes read; the binary attachment may be longer if
24811 some characters were escaped.
24813 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
24814 Write @var{data} (a binary buffer) to the open file corresponding
24815 to @var{fd}. Start the write at @var{offset} from the start of the
24816 file. Unlike many @code{write} system calls, there is no
24817 separate @var{count} argument; the length of @var{data} in the
24818 packet is used. @samp{vFile:write} returns the number of bytes written,
24819 which may be shorter than the length of @var{data}, or -1 if an
24822 @item vFile:unlink: @var{pathname}
24823 Delete the file at @var{pathname} on the target. Return 0,
24824 or -1 if an error occurs. @var{pathname} is a string.
24829 @section Interrupts
24830 @cindex interrupts (remote protocol)
24832 When a program on the remote target is running, @value{GDBN} may
24833 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24834 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24835 setting (@pxref{set remotebreak}).
24837 The precise meaning of @code{BREAK} is defined by the transport
24838 mechanism and may, in fact, be undefined. @value{GDBN} does
24839 not currently define a @code{BREAK} mechanism for any of the network
24842 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24843 transport mechanisms. It is represented by sending the single byte
24844 @code{0x03} without any of the usual packet overhead described in
24845 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24846 transmitted as part of a packet, it is considered to be packet data
24847 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24848 (@pxref{X packet}), used for binary downloads, may include an unescaped
24849 @code{0x03} as part of its packet.
24851 Stubs are not required to recognize these interrupt mechanisms and the
24852 precise meaning associated with receipt of the interrupt is
24853 implementation defined. If the stub is successful at interrupting the
24854 running program, it is expected that it will send one of the Stop
24855 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24856 of successfully stopping the program. Interrupts received while the
24857 program is stopped will be discarded.
24862 Example sequence of a target being re-started. Notice how the restart
24863 does not get any direct output:
24868 @emph{target restarts}
24871 <- @code{T001:1234123412341234}
24875 Example sequence of a target being stepped by a single instruction:
24878 -> @code{G1445@dots{}}
24883 <- @code{T001:1234123412341234}
24887 <- @code{1455@dots{}}
24891 @node File-I/O Remote Protocol Extension
24892 @section File-I/O Remote Protocol Extension
24893 @cindex File-I/O remote protocol extension
24896 * File-I/O Overview::
24897 * Protocol Basics::
24898 * The F Request Packet::
24899 * The F Reply Packet::
24900 * The Ctrl-C Message::
24902 * List of Supported Calls::
24903 * Protocol-specific Representation of Datatypes::
24905 * File-I/O Examples::
24908 @node File-I/O Overview
24909 @subsection File-I/O Overview
24910 @cindex file-i/o overview
24912 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24913 target to use the host's file system and console I/O to perform various
24914 system calls. System calls on the target system are translated into a
24915 remote protocol packet to the host system, which then performs the needed
24916 actions and returns a response packet to the target system.
24917 This simulates file system operations even on targets that lack file systems.
24919 The protocol is defined to be independent of both the host and target systems.
24920 It uses its own internal representation of datatypes and values. Both
24921 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24922 translating the system-dependent value representations into the internal
24923 protocol representations when data is transmitted.
24925 The communication is synchronous. A system call is possible only when
24926 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24927 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24928 the target is stopped to allow deterministic access to the target's
24929 memory. Therefore File-I/O is not interruptible by target signals. On
24930 the other hand, it is possible to interrupt File-I/O by a user interrupt
24931 (@samp{Ctrl-C}) within @value{GDBN}.
24933 The target's request to perform a host system call does not finish
24934 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24935 after finishing the system call, the target returns to continuing the
24936 previous activity (continue, step). No additional continue or step
24937 request from @value{GDBN} is required.
24940 (@value{GDBP}) continue
24941 <- target requests 'system call X'
24942 target is stopped, @value{GDBN} executes system call
24943 -> @value{GDBN} returns result
24944 ... target continues, @value{GDBN} returns to wait for the target
24945 <- target hits breakpoint and sends a Txx packet
24948 The protocol only supports I/O on the console and to regular files on
24949 the host file system. Character or block special devices, pipes,
24950 named pipes, sockets or any other communication method on the host
24951 system are not supported by this protocol.
24953 @node Protocol Basics
24954 @subsection Protocol Basics
24955 @cindex protocol basics, file-i/o
24957 The File-I/O protocol uses the @code{F} packet as the request as well
24958 as reply packet. Since a File-I/O system call can only occur when
24959 @value{GDBN} is waiting for a response from the continuing or stepping target,
24960 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24961 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24962 This @code{F} packet contains all information needed to allow @value{GDBN}
24963 to call the appropriate host system call:
24967 A unique identifier for the requested system call.
24970 All parameters to the system call. Pointers are given as addresses
24971 in the target memory address space. Pointers to strings are given as
24972 pointer/length pair. Numerical values are given as they are.
24973 Numerical control flags are given in a protocol-specific representation.
24977 At this point, @value{GDBN} has to perform the following actions.
24981 If the parameters include pointer values to data needed as input to a
24982 system call, @value{GDBN} requests this data from the target with a
24983 standard @code{m} packet request. This additional communication has to be
24984 expected by the target implementation and is handled as any other @code{m}
24988 @value{GDBN} translates all value from protocol representation to host
24989 representation as needed. Datatypes are coerced into the host types.
24992 @value{GDBN} calls the system call.
24995 It then coerces datatypes back to protocol representation.
24998 If the system call is expected to return data in buffer space specified
24999 by pointer parameters to the call, the data is transmitted to the
25000 target using a @code{M} or @code{X} packet. This packet has to be expected
25001 by the target implementation and is handled as any other @code{M} or @code{X}
25006 Eventually @value{GDBN} replies with another @code{F} packet which contains all
25007 necessary information for the target to continue. This at least contains
25014 @code{errno}, if has been changed by the system call.
25021 After having done the needed type and value coercion, the target continues
25022 the latest continue or step action.
25024 @node The F Request Packet
25025 @subsection The @code{F} Request Packet
25026 @cindex file-i/o request packet
25027 @cindex @code{F} request packet
25029 The @code{F} request packet has the following format:
25032 @item F@var{call-id},@var{parameter@dots{}}
25034 @var{call-id} is the identifier to indicate the host system call to be called.
25035 This is just the name of the function.
25037 @var{parameter@dots{}} are the parameters to the system call.
25038 Parameters are hexadecimal integer values, either the actual values in case
25039 of scalar datatypes, pointers to target buffer space in case of compound
25040 datatypes and unspecified memory areas, or pointer/length pairs in case
25041 of string parameters. These are appended to the @var{call-id} as a
25042 comma-delimited list. All values are transmitted in ASCII
25043 string representation, pointer/length pairs separated by a slash.
25049 @node The F Reply Packet
25050 @subsection The @code{F} Reply Packet
25051 @cindex file-i/o reply packet
25052 @cindex @code{F} reply packet
25054 The @code{F} reply packet has the following format:
25058 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
25060 @var{retcode} is the return code of the system call as hexadecimal value.
25062 @var{errno} is the @code{errno} set by the call, in protocol-specific
25064 This parameter can be omitted if the call was successful.
25066 @var{Ctrl-C flag} is only sent if the user requested a break. In this
25067 case, @var{errno} must be sent as well, even if the call was successful.
25068 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
25075 or, if the call was interrupted before the host call has been performed:
25082 assuming 4 is the protocol-specific representation of @code{EINTR}.
25087 @node The Ctrl-C Message
25088 @subsection The @samp{Ctrl-C} Message
25089 @cindex ctrl-c message, in file-i/o protocol
25091 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
25092 reply packet (@pxref{The F Reply Packet}),
25093 the target should behave as if it had
25094 gotten a break message. The meaning for the target is ``system call
25095 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
25096 (as with a break message) and return to @value{GDBN} with a @code{T02}
25099 It's important for the target to know in which
25100 state the system call was interrupted. There are two possible cases:
25104 The system call hasn't been performed on the host yet.
25107 The system call on the host has been finished.
25111 These two states can be distinguished by the target by the value of the
25112 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
25113 call hasn't been performed. This is equivalent to the @code{EINTR} handling
25114 on POSIX systems. In any other case, the target may presume that the
25115 system call has been finished --- successfully or not --- and should behave
25116 as if the break message arrived right after the system call.
25118 @value{GDBN} must behave reliably. If the system call has not been called
25119 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
25120 @code{errno} in the packet. If the system call on the host has been finished
25121 before the user requests a break, the full action must be finished by
25122 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
25123 The @code{F} packet may only be sent when either nothing has happened
25124 or the full action has been completed.
25127 @subsection Console I/O
25128 @cindex console i/o as part of file-i/o
25130 By default and if not explicitly closed by the target system, the file
25131 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
25132 on the @value{GDBN} console is handled as any other file output operation
25133 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
25134 by @value{GDBN} so that after the target read request from file descriptor
25135 0 all following typing is buffered until either one of the following
25140 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
25142 system call is treated as finished.
25145 The user presses @key{RET}. This is treated as end of input with a trailing
25149 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
25150 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
25154 If the user has typed more characters than fit in the buffer given to
25155 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
25156 either another @code{read(0, @dots{})} is requested by the target, or debugging
25157 is stopped at the user's request.
25160 @node List of Supported Calls
25161 @subsection List of Supported Calls
25162 @cindex list of supported file-i/o calls
25179 @unnumberedsubsubsec open
25180 @cindex open, file-i/o system call
25185 int open(const char *pathname, int flags);
25186 int open(const char *pathname, int flags, mode_t mode);
25190 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
25193 @var{flags} is the bitwise @code{OR} of the following values:
25197 If the file does not exist it will be created. The host
25198 rules apply as far as file ownership and time stamps
25202 When used with @code{O_CREAT}, if the file already exists it is
25203 an error and open() fails.
25206 If the file already exists and the open mode allows
25207 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
25208 truncated to zero length.
25211 The file is opened in append mode.
25214 The file is opened for reading only.
25217 The file is opened for writing only.
25220 The file is opened for reading and writing.
25224 Other bits are silently ignored.
25228 @var{mode} is the bitwise @code{OR} of the following values:
25232 User has read permission.
25235 User has write permission.
25238 Group has read permission.
25241 Group has write permission.
25244 Others have read permission.
25247 Others have write permission.
25251 Other bits are silently ignored.
25254 @item Return value:
25255 @code{open} returns the new file descriptor or -1 if an error
25262 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
25265 @var{pathname} refers to a directory.
25268 The requested access is not allowed.
25271 @var{pathname} was too long.
25274 A directory component in @var{pathname} does not exist.
25277 @var{pathname} refers to a device, pipe, named pipe or socket.
25280 @var{pathname} refers to a file on a read-only filesystem and
25281 write access was requested.
25284 @var{pathname} is an invalid pointer value.
25287 No space on device to create the file.
25290 The process already has the maximum number of files open.
25293 The limit on the total number of files open on the system
25297 The call was interrupted by the user.
25303 @unnumberedsubsubsec close
25304 @cindex close, file-i/o system call
25313 @samp{Fclose,@var{fd}}
25315 @item Return value:
25316 @code{close} returns zero on success, or -1 if an error occurred.
25322 @var{fd} isn't a valid open file descriptor.
25325 The call was interrupted by the user.
25331 @unnumberedsubsubsec read
25332 @cindex read, file-i/o system call
25337 int read(int fd, void *buf, unsigned int count);
25341 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
25343 @item Return value:
25344 On success, the number of bytes read is returned.
25345 Zero indicates end of file. If count is zero, read
25346 returns zero as well. On error, -1 is returned.
25352 @var{fd} is not a valid file descriptor or is not open for
25356 @var{bufptr} is an invalid pointer value.
25359 The call was interrupted by the user.
25365 @unnumberedsubsubsec write
25366 @cindex write, file-i/o system call
25371 int write(int fd, const void *buf, unsigned int count);
25375 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
25377 @item Return value:
25378 On success, the number of bytes written are returned.
25379 Zero indicates nothing was written. On error, -1
25386 @var{fd} is not a valid file descriptor or is not open for
25390 @var{bufptr} is an invalid pointer value.
25393 An attempt was made to write a file that exceeds the
25394 host-specific maximum file size allowed.
25397 No space on device to write the data.
25400 The call was interrupted by the user.
25406 @unnumberedsubsubsec lseek
25407 @cindex lseek, file-i/o system call
25412 long lseek (int fd, long offset, int flag);
25416 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
25418 @var{flag} is one of:
25422 The offset is set to @var{offset} bytes.
25425 The offset is set to its current location plus @var{offset}
25429 The offset is set to the size of the file plus @var{offset}
25433 @item Return value:
25434 On success, the resulting unsigned offset in bytes from
25435 the beginning of the file is returned. Otherwise, a
25436 value of -1 is returned.
25442 @var{fd} is not a valid open file descriptor.
25445 @var{fd} is associated with the @value{GDBN} console.
25448 @var{flag} is not a proper value.
25451 The call was interrupted by the user.
25457 @unnumberedsubsubsec rename
25458 @cindex rename, file-i/o system call
25463 int rename(const char *oldpath, const char *newpath);
25467 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
25469 @item Return value:
25470 On success, zero is returned. On error, -1 is returned.
25476 @var{newpath} is an existing directory, but @var{oldpath} is not a
25480 @var{newpath} is a non-empty directory.
25483 @var{oldpath} or @var{newpath} is a directory that is in use by some
25487 An attempt was made to make a directory a subdirectory
25491 A component used as a directory in @var{oldpath} or new
25492 path is not a directory. Or @var{oldpath} is a directory
25493 and @var{newpath} exists but is not a directory.
25496 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
25499 No access to the file or the path of the file.
25503 @var{oldpath} or @var{newpath} was too long.
25506 A directory component in @var{oldpath} or @var{newpath} does not exist.
25509 The file is on a read-only filesystem.
25512 The device containing the file has no room for the new
25516 The call was interrupted by the user.
25522 @unnumberedsubsubsec unlink
25523 @cindex unlink, file-i/o system call
25528 int unlink(const char *pathname);
25532 @samp{Funlink,@var{pathnameptr}/@var{len}}
25534 @item Return value:
25535 On success, zero is returned. On error, -1 is returned.
25541 No access to the file or the path of the file.
25544 The system does not allow unlinking of directories.
25547 The file @var{pathname} cannot be unlinked because it's
25548 being used by another process.
25551 @var{pathnameptr} is an invalid pointer value.
25554 @var{pathname} was too long.
25557 A directory component in @var{pathname} does not exist.
25560 A component of the path is not a directory.
25563 The file is on a read-only filesystem.
25566 The call was interrupted by the user.
25572 @unnumberedsubsubsec stat/fstat
25573 @cindex fstat, file-i/o system call
25574 @cindex stat, file-i/o system call
25579 int stat(const char *pathname, struct stat *buf);
25580 int fstat(int fd, struct stat *buf);
25584 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25585 @samp{Ffstat,@var{fd},@var{bufptr}}
25587 @item Return value:
25588 On success, zero is returned. On error, -1 is returned.
25594 @var{fd} is not a valid open file.
25597 A directory component in @var{pathname} does not exist or the
25598 path is an empty string.
25601 A component of the path is not a directory.
25604 @var{pathnameptr} is an invalid pointer value.
25607 No access to the file or the path of the file.
25610 @var{pathname} was too long.
25613 The call was interrupted by the user.
25619 @unnumberedsubsubsec gettimeofday
25620 @cindex gettimeofday, file-i/o system call
25625 int gettimeofday(struct timeval *tv, void *tz);
25629 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25631 @item Return value:
25632 On success, 0 is returned, -1 otherwise.
25638 @var{tz} is a non-NULL pointer.
25641 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25647 @unnumberedsubsubsec isatty
25648 @cindex isatty, file-i/o system call
25653 int isatty(int fd);
25657 @samp{Fisatty,@var{fd}}
25659 @item Return value:
25660 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
25666 The call was interrupted by the user.
25671 Note that the @code{isatty} call is treated as a special case: it returns
25672 1 to the target if the file descriptor is attached
25673 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
25674 would require implementing @code{ioctl} and would be more complex than
25679 @unnumberedsubsubsec system
25680 @cindex system, file-i/o system call
25685 int system(const char *command);
25689 @samp{Fsystem,@var{commandptr}/@var{len}}
25691 @item Return value:
25692 If @var{len} is zero, the return value indicates whether a shell is
25693 available. A zero return value indicates a shell is not available.
25694 For non-zero @var{len}, the value returned is -1 on error and the
25695 return status of the command otherwise. Only the exit status of the
25696 command is returned, which is extracted from the host's @code{system}
25697 return value by calling @code{WEXITSTATUS(retval)}. In case
25698 @file{/bin/sh} could not be executed, 127 is returned.
25704 The call was interrupted by the user.
25709 @value{GDBN} takes over the full task of calling the necessary host calls
25710 to perform the @code{system} call. The return value of @code{system} on
25711 the host is simplified before it's returned
25712 to the target. Any termination signal information from the child process
25713 is discarded, and the return value consists
25714 entirely of the exit status of the called command.
25716 Due to security concerns, the @code{system} call is by default refused
25717 by @value{GDBN}. The user has to allow this call explicitly with the
25718 @code{set remote system-call-allowed 1} command.
25721 @item set remote system-call-allowed
25722 @kindex set remote system-call-allowed
25723 Control whether to allow the @code{system} calls in the File I/O
25724 protocol for the remote target. The default is zero (disabled).
25726 @item show remote system-call-allowed
25727 @kindex show remote system-call-allowed
25728 Show whether the @code{system} calls are allowed in the File I/O
25732 @node Protocol-specific Representation of Datatypes
25733 @subsection Protocol-specific Representation of Datatypes
25734 @cindex protocol-specific representation of datatypes, in file-i/o protocol
25737 * Integral Datatypes::
25739 * Memory Transfer::
25744 @node Integral Datatypes
25745 @unnumberedsubsubsec Integral Datatypes
25746 @cindex integral datatypes, in file-i/o protocol
25748 The integral datatypes used in the system calls are @code{int},
25749 @code{unsigned int}, @code{long}, @code{unsigned long},
25750 @code{mode_t}, and @code{time_t}.
25752 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25753 implemented as 32 bit values in this protocol.
25755 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25757 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25758 in @file{limits.h}) to allow range checking on host and target.
25760 @code{time_t} datatypes are defined as seconds since the Epoch.
25762 All integral datatypes transferred as part of a memory read or write of a
25763 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25766 @node Pointer Values
25767 @unnumberedsubsubsec Pointer Values
25768 @cindex pointer values, in file-i/o protocol
25770 Pointers to target data are transmitted as they are. An exception
25771 is made for pointers to buffers for which the length isn't
25772 transmitted as part of the function call, namely strings. Strings
25773 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25780 which is a pointer to data of length 18 bytes at position 0x1aaf.
25781 The length is defined as the full string length in bytes, including
25782 the trailing null byte. For example, the string @code{"hello world"}
25783 at address 0x123456 is transmitted as
25789 @node Memory Transfer
25790 @unnumberedsubsubsec Memory Transfer
25791 @cindex memory transfer, in file-i/o protocol
25793 Structured data which is transferred using a memory read or write (for
25794 example, a @code{struct stat}) is expected to be in a protocol-specific format
25795 with all scalar multibyte datatypes being big endian. Translation to
25796 this representation needs to be done both by the target before the @code{F}
25797 packet is sent, and by @value{GDBN} before
25798 it transfers memory to the target. Transferred pointers to structured
25799 data should point to the already-coerced data at any time.
25803 @unnumberedsubsubsec struct stat
25804 @cindex struct stat, in file-i/o protocol
25806 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25807 is defined as follows:
25811 unsigned int st_dev; /* device */
25812 unsigned int st_ino; /* inode */
25813 mode_t st_mode; /* protection */
25814 unsigned int st_nlink; /* number of hard links */
25815 unsigned int st_uid; /* user ID of owner */
25816 unsigned int st_gid; /* group ID of owner */
25817 unsigned int st_rdev; /* device type (if inode device) */
25818 unsigned long st_size; /* total size, in bytes */
25819 unsigned long st_blksize; /* blocksize for filesystem I/O */
25820 unsigned long st_blocks; /* number of blocks allocated */
25821 time_t st_atime; /* time of last access */
25822 time_t st_mtime; /* time of last modification */
25823 time_t st_ctime; /* time of last change */
25827 The integral datatypes conform to the definitions given in the
25828 appropriate section (see @ref{Integral Datatypes}, for details) so this
25829 structure is of size 64 bytes.
25831 The values of several fields have a restricted meaning and/or
25837 A value of 0 represents a file, 1 the console.
25840 No valid meaning for the target. Transmitted unchanged.
25843 Valid mode bits are described in @ref{Constants}. Any other
25844 bits have currently no meaning for the target.
25849 No valid meaning for the target. Transmitted unchanged.
25854 These values have a host and file system dependent
25855 accuracy. Especially on Windows hosts, the file system may not
25856 support exact timing values.
25859 The target gets a @code{struct stat} of the above representation and is
25860 responsible for coercing it to the target representation before
25863 Note that due to size differences between the host, target, and protocol
25864 representations of @code{struct stat} members, these members could eventually
25865 get truncated on the target.
25867 @node struct timeval
25868 @unnumberedsubsubsec struct timeval
25869 @cindex struct timeval, in file-i/o protocol
25871 The buffer of type @code{struct timeval} used by the File-I/O protocol
25872 is defined as follows:
25876 time_t tv_sec; /* second */
25877 long tv_usec; /* microsecond */
25881 The integral datatypes conform to the definitions given in the
25882 appropriate section (see @ref{Integral Datatypes}, for details) so this
25883 structure is of size 8 bytes.
25886 @subsection Constants
25887 @cindex constants, in file-i/o protocol
25889 The following values are used for the constants inside of the
25890 protocol. @value{GDBN} and target are responsible for translating these
25891 values before and after the call as needed.
25902 @unnumberedsubsubsec Open Flags
25903 @cindex open flags, in file-i/o protocol
25905 All values are given in hexadecimal representation.
25917 @node mode_t Values
25918 @unnumberedsubsubsec mode_t Values
25919 @cindex mode_t values, in file-i/o protocol
25921 All values are given in octal representation.
25938 @unnumberedsubsubsec Errno Values
25939 @cindex errno values, in file-i/o protocol
25941 All values are given in decimal representation.
25966 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25967 any error value not in the list of supported error numbers.
25970 @unnumberedsubsubsec Lseek Flags
25971 @cindex lseek flags, in file-i/o protocol
25980 @unnumberedsubsubsec Limits
25981 @cindex limits, in file-i/o protocol
25983 All values are given in decimal representation.
25986 INT_MIN -2147483648
25988 UINT_MAX 4294967295
25989 LONG_MIN -9223372036854775808
25990 LONG_MAX 9223372036854775807
25991 ULONG_MAX 18446744073709551615
25994 @node File-I/O Examples
25995 @subsection File-I/O Examples
25996 @cindex file-i/o examples
25998 Example sequence of a write call, file descriptor 3, buffer is at target
25999 address 0x1234, 6 bytes should be written:
26002 <- @code{Fwrite,3,1234,6}
26003 @emph{request memory read from target}
26006 @emph{return "6 bytes written"}
26010 Example sequence of a read call, file descriptor 3, buffer is at target
26011 address 0x1234, 6 bytes should be read:
26014 <- @code{Fread,3,1234,6}
26015 @emph{request memory write to target}
26016 -> @code{X1234,6:XXXXXX}
26017 @emph{return "6 bytes read"}
26021 Example sequence of a read call, call fails on the host due to invalid
26022 file descriptor (@code{EBADF}):
26025 <- @code{Fread,3,1234,6}
26029 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
26033 <- @code{Fread,3,1234,6}
26038 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
26042 <- @code{Fread,3,1234,6}
26043 -> @code{X1234,6:XXXXXX}
26047 @node Library List Format
26048 @section Library List Format
26049 @cindex library list format, remote protocol
26051 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
26052 same process as your application to manage libraries. In this case,
26053 @value{GDBN} can use the loader's symbol table and normal memory
26054 operations to maintain a list of shared libraries. On other
26055 platforms, the operating system manages loaded libraries.
26056 @value{GDBN} can not retrieve the list of currently loaded libraries
26057 through memory operations, so it uses the @samp{qXfer:libraries:read}
26058 packet (@pxref{qXfer library list read}) instead. The remote stub
26059 queries the target's operating system and reports which libraries
26062 The @samp{qXfer:libraries:read} packet returns an XML document which
26063 lists loaded libraries and their offsets. Each library has an
26064 associated name and one or more segment base addresses, which report
26065 where the library was loaded in memory. The segment bases are start
26066 addresses, not relocation offsets; they do not depend on the library's
26067 link-time base addresses.
26069 @value{GDBN} must be linked with the Expat library to support XML
26070 library lists. @xref{Expat}.
26072 A simple memory map, with one loaded library relocated by a single
26073 offset, looks like this:
26077 <library name="/lib/libc.so.6">
26078 <segment address="0x10000000"/>
26083 The format of a library list is described by this DTD:
26086 <!-- library-list: Root element with versioning -->
26087 <!ELEMENT library-list (library)*>
26088 <!ATTLIST library-list version CDATA #FIXED "1.0">
26089 <!ELEMENT library (segment)*>
26090 <!ATTLIST library name CDATA #REQUIRED>
26091 <!ELEMENT segment EMPTY>
26092 <!ATTLIST segment address CDATA #REQUIRED>
26095 @node Memory Map Format
26096 @section Memory Map Format
26097 @cindex memory map format
26099 To be able to write into flash memory, @value{GDBN} needs to obtain a
26100 memory map from the target. This section describes the format of the
26103 The memory map is obtained using the @samp{qXfer:memory-map:read}
26104 (@pxref{qXfer memory map read}) packet and is an XML document that
26105 lists memory regions.
26107 @value{GDBN} must be linked with the Expat library to support XML
26108 memory maps. @xref{Expat}.
26110 The top-level structure of the document is shown below:
26113 <?xml version="1.0"?>
26114 <!DOCTYPE memory-map
26115 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
26116 "http://sourceware.org/gdb/gdb-memory-map.dtd">
26122 Each region can be either:
26127 A region of RAM starting at @var{addr} and extending for @var{length}
26131 <memory type="ram" start="@var{addr}" length="@var{length}"/>
26136 A region of read-only memory:
26139 <memory type="rom" start="@var{addr}" length="@var{length}"/>
26144 A region of flash memory, with erasure blocks @var{blocksize}
26148 <memory type="flash" start="@var{addr}" length="@var{length}">
26149 <property name="blocksize">@var{blocksize}</property>
26155 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
26156 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
26157 packets to write to addresses in such ranges.
26159 The formal DTD for memory map format is given below:
26162 <!-- ................................................... -->
26163 <!-- Memory Map XML DTD ................................ -->
26164 <!-- File: memory-map.dtd .............................. -->
26165 <!-- .................................... .............. -->
26166 <!-- memory-map.dtd -->
26167 <!-- memory-map: Root element with versioning -->
26168 <!ELEMENT memory-map (memory | property)>
26169 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
26170 <!ELEMENT memory (property)>
26171 <!-- memory: Specifies a memory region,
26172 and its type, or device. -->
26173 <!ATTLIST memory type CDATA #REQUIRED
26174 start CDATA #REQUIRED
26175 length CDATA #REQUIRED
26176 device CDATA #IMPLIED>
26177 <!-- property: Generic attribute tag -->
26178 <!ELEMENT property (#PCDATA | property)*>
26179 <!ATTLIST property name CDATA #REQUIRED>
26182 @include agentexpr.texi
26184 @node Target Descriptions
26185 @appendix Target Descriptions
26186 @cindex target descriptions
26188 @strong{Warning:} target descriptions are still under active development,
26189 and the contents and format may change between @value{GDBN} releases.
26190 The format is expected to stabilize in the future.
26192 One of the challenges of using @value{GDBN} to debug embedded systems
26193 is that there are so many minor variants of each processor
26194 architecture in use. It is common practice for vendors to start with
26195 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
26196 and then make changes to adapt it to a particular market niche. Some
26197 architectures have hundreds of variants, available from dozens of
26198 vendors. This leads to a number of problems:
26202 With so many different customized processors, it is difficult for
26203 the @value{GDBN} maintainers to keep up with the changes.
26205 Since individual variants may have short lifetimes or limited
26206 audiences, it may not be worthwhile to carry information about every
26207 variant in the @value{GDBN} source tree.
26209 When @value{GDBN} does support the architecture of the embedded system
26210 at hand, the task of finding the correct architecture name to give the
26211 @command{set architecture} command can be error-prone.
26214 To address these problems, the @value{GDBN} remote protocol allows a
26215 target system to not only identify itself to @value{GDBN}, but to
26216 actually describe its own features. This lets @value{GDBN} support
26217 processor variants it has never seen before --- to the extent that the
26218 descriptions are accurate, and that @value{GDBN} understands them.
26220 @value{GDBN} must be linked with the Expat library to support XML
26221 target descriptions. @xref{Expat}.
26224 * Retrieving Descriptions:: How descriptions are fetched from a target.
26225 * Target Description Format:: The contents of a target description.
26226 * Predefined Target Types:: Standard types available for target
26228 * Standard Target Features:: Features @value{GDBN} knows about.
26231 @node Retrieving Descriptions
26232 @section Retrieving Descriptions
26234 Target descriptions can be read from the target automatically, or
26235 specified by the user manually. The default behavior is to read the
26236 description from the target. @value{GDBN} retrieves it via the remote
26237 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
26238 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
26239 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
26240 XML document, of the form described in @ref{Target Description
26243 Alternatively, you can specify a file to read for the target description.
26244 If a file is set, the target will not be queried. The commands to
26245 specify a file are:
26248 @cindex set tdesc filename
26249 @item set tdesc filename @var{path}
26250 Read the target description from @var{path}.
26252 @cindex unset tdesc filename
26253 @item unset tdesc filename
26254 Do not read the XML target description from a file. @value{GDBN}
26255 will use the description supplied by the current target.
26257 @cindex show tdesc filename
26258 @item show tdesc filename
26259 Show the filename to read for a target description, if any.
26263 @node Target Description Format
26264 @section Target Description Format
26265 @cindex target descriptions, XML format
26267 A target description annex is an @uref{http://www.w3.org/XML/, XML}
26268 document which complies with the Document Type Definition provided in
26269 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
26270 means you can use generally available tools like @command{xmllint} to
26271 check that your feature descriptions are well-formed and valid.
26272 However, to help people unfamiliar with XML write descriptions for
26273 their targets, we also describe the grammar here.
26275 Target descriptions can identify the architecture of the remote target
26276 and (for some architectures) provide information about custom register
26277 sets. @value{GDBN} can use this information to autoconfigure for your
26278 target, or to warn you if you connect to an unsupported target.
26280 Here is a simple target description:
26283 <target version="1.0">
26284 <architecture>i386:x86-64</architecture>
26289 This minimal description only says that the target uses
26290 the x86-64 architecture.
26292 A target description has the following overall form, with [ ] marking
26293 optional elements and @dots{} marking repeatable elements. The elements
26294 are explained further below.
26297 <?xml version="1.0"?>
26298 <!DOCTYPE target SYSTEM "gdb-target.dtd">
26299 <target version="1.0">
26300 @r{[}@var{architecture}@r{]}
26301 @r{[}@var{feature}@dots{}@r{]}
26306 The description is generally insensitive to whitespace and line
26307 breaks, under the usual common-sense rules. The XML version
26308 declaration and document type declaration can generally be omitted
26309 (@value{GDBN} does not require them), but specifying them may be
26310 useful for XML validation tools. The @samp{version} attribute for
26311 @samp{<target>} may also be omitted, but we recommend
26312 including it; if future versions of @value{GDBN} use an incompatible
26313 revision of @file{gdb-target.dtd}, they will detect and report
26314 the version mismatch.
26316 @subsection Inclusion
26317 @cindex target descriptions, inclusion
26320 @cindex <xi:include>
26323 It can sometimes be valuable to split a target description up into
26324 several different annexes, either for organizational purposes, or to
26325 share files between different possible target descriptions. You can
26326 divide a description into multiple files by replacing any element of
26327 the target description with an inclusion directive of the form:
26330 <xi:include href="@var{document}"/>
26334 When @value{GDBN} encounters an element of this form, it will retrieve
26335 the named XML @var{document}, and replace the inclusion directive with
26336 the contents of that document. If the current description was read
26337 using @samp{qXfer}, then so will be the included document;
26338 @var{document} will be interpreted as the name of an annex. If the
26339 current description was read from a file, @value{GDBN} will look for
26340 @var{document} as a file in the same directory where it found the
26341 original description.
26343 @subsection Architecture
26344 @cindex <architecture>
26346 An @samp{<architecture>} element has this form:
26349 <architecture>@var{arch}</architecture>
26352 @var{arch} is an architecture name from the same selection
26353 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
26354 Debugging Target}).
26356 @subsection Features
26359 Each @samp{<feature>} describes some logical portion of the target
26360 system. Features are currently used to describe available CPU
26361 registers and the types of their contents. A @samp{<feature>} element
26365 <feature name="@var{name}">
26366 @r{[}@var{type}@dots{}@r{]}
26372 Each feature's name should be unique within the description. The name
26373 of a feature does not matter unless @value{GDBN} has some special
26374 knowledge of the contents of that feature; if it does, the feature
26375 should have its standard name. @xref{Standard Target Features}.
26379 Any register's value is a collection of bits which @value{GDBN} must
26380 interpret. The default interpretation is a two's complement integer,
26381 but other types can be requested by name in the register description.
26382 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
26383 Target Types}), and the description can define additional composite types.
26385 Each type element must have an @samp{id} attribute, which gives
26386 a unique (within the containing @samp{<feature>}) name to the type.
26387 Types must be defined before they are used.
26390 Some targets offer vector registers, which can be treated as arrays
26391 of scalar elements. These types are written as @samp{<vector>} elements,
26392 specifying the array element type, @var{type}, and the number of elements,
26396 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
26400 If a register's value is usefully viewed in multiple ways, define it
26401 with a union type containing the useful representations. The
26402 @samp{<union>} element contains one or more @samp{<field>} elements,
26403 each of which has a @var{name} and a @var{type}:
26406 <union id="@var{id}">
26407 <field name="@var{name}" type="@var{type}"/>
26412 @subsection Registers
26415 Each register is represented as an element with this form:
26418 <reg name="@var{name}"
26419 bitsize="@var{size}"
26420 @r{[}regnum="@var{num}"@r{]}
26421 @r{[}save-restore="@var{save-restore}"@r{]}
26422 @r{[}type="@var{type}"@r{]}
26423 @r{[}group="@var{group}"@r{]}/>
26427 The components are as follows:
26432 The register's name; it must be unique within the target description.
26435 The register's size, in bits.
26438 The register's number. If omitted, a register's number is one greater
26439 than that of the previous register (either in the current feature or in
26440 a preceeding feature); the first register in the target description
26441 defaults to zero. This register number is used to read or write
26442 the register; e.g.@: it is used in the remote @code{p} and @code{P}
26443 packets, and registers appear in the @code{g} and @code{G} packets
26444 in order of increasing register number.
26447 Whether the register should be preserved across inferior function
26448 calls; this must be either @code{yes} or @code{no}. The default is
26449 @code{yes}, which is appropriate for most registers except for
26450 some system control registers; this is not related to the target's
26454 The type of the register. @var{type} may be a predefined type, a type
26455 defined in the current feature, or one of the special types @code{int}
26456 and @code{float}. @code{int} is an integer type of the correct size
26457 for @var{bitsize}, and @code{float} is a floating point type (in the
26458 architecture's normal floating point format) of the correct size for
26459 @var{bitsize}. The default is @code{int}.
26462 The register group to which this register belongs. @var{group} must
26463 be either @code{general}, @code{float}, or @code{vector}. If no
26464 @var{group} is specified, @value{GDBN} will not display the register
26465 in @code{info registers}.
26469 @node Predefined Target Types
26470 @section Predefined Target Types
26471 @cindex target descriptions, predefined types
26473 Type definitions in the self-description can build up composite types
26474 from basic building blocks, but can not define fundamental types. Instead,
26475 standard identifiers are provided by @value{GDBN} for the fundamental
26476 types. The currently supported types are:
26485 Signed integer types holding the specified number of bits.
26492 Unsigned integer types holding the specified number of bits.
26496 Pointers to unspecified code and data. The program counter and
26497 any dedicated return address register may be marked as code
26498 pointers; printing a code pointer converts it into a symbolic
26499 address. The stack pointer and any dedicated address registers
26500 may be marked as data pointers.
26503 Single precision IEEE floating point.
26506 Double precision IEEE floating point.
26509 The 12-byte extended precision format used by ARM FPA registers.
26513 @node Standard Target Features
26514 @section Standard Target Features
26515 @cindex target descriptions, standard features
26517 A target description must contain either no registers or all the
26518 target's registers. If the description contains no registers, then
26519 @value{GDBN} will assume a default register layout, selected based on
26520 the architecture. If the description contains any registers, the
26521 default layout will not be used; the standard registers must be
26522 described in the target description, in such a way that @value{GDBN}
26523 can recognize them.
26525 This is accomplished by giving specific names to feature elements
26526 which contain standard registers. @value{GDBN} will look for features
26527 with those names and verify that they contain the expected registers;
26528 if any known feature is missing required registers, or if any required
26529 feature is missing, @value{GDBN} will reject the target
26530 description. You can add additional registers to any of the
26531 standard features --- @value{GDBN} will display them just as if
26532 they were added to an unrecognized feature.
26534 This section lists the known features and their expected contents.
26535 Sample XML documents for these features are included in the
26536 @value{GDBN} source tree, in the directory @file{gdb/features}.
26538 Names recognized by @value{GDBN} should include the name of the
26539 company or organization which selected the name, and the overall
26540 architecture to which the feature applies; so e.g.@: the feature
26541 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
26543 The names of registers are not case sensitive for the purpose
26544 of recognizing standard features, but @value{GDBN} will only display
26545 registers using the capitalization used in the description.
26554 @subsection ARM Features
26555 @cindex target descriptions, ARM features
26557 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
26558 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
26559 @samp{lr}, @samp{pc}, and @samp{cpsr}.
26561 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
26562 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
26564 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
26565 it should contain at least registers @samp{wR0} through @samp{wR15} and
26566 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
26567 @samp{wCSSF}, and @samp{wCASF} registers are optional.
26569 @subsection MIPS Features
26570 @cindex target descriptions, MIPS features
26572 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
26573 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
26574 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
26577 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
26578 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
26579 registers. They may be 32-bit or 64-bit depending on the target.
26581 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
26582 it may be optional in a future version of @value{GDBN}. It should
26583 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
26584 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
26586 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
26587 contain a single register, @samp{restart}, which is used by the
26588 Linux kernel to control restartable syscalls.
26590 @node M68K Features
26591 @subsection M68K Features
26592 @cindex target descriptions, M68K features
26595 @item @samp{org.gnu.gdb.m68k.core}
26596 @itemx @samp{org.gnu.gdb.coldfire.core}
26597 @itemx @samp{org.gnu.gdb.fido.core}
26598 One of those features must be always present.
26599 The feature that is present determines which flavor of m86k is
26600 used. The feature that is present should contain registers
26601 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
26602 @samp{sp}, @samp{ps} and @samp{pc}.
26604 @item @samp{org.gnu.gdb.coldfire.fp}
26605 This feature is optional. If present, it should contain registers
26606 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
26610 @subsection PowerPC Features
26611 @cindex target descriptions, PowerPC features
26613 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
26614 targets. It should contain registers @samp{r0} through @samp{r31},
26615 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
26616 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
26618 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
26619 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
26621 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
26622 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
26625 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
26626 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
26627 @samp{spefscr}. SPE targets should provide 32-bit registers in
26628 @samp{org.gnu.gdb.power.core} and provide the upper halves in
26629 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
26630 these to present registers @samp{ev0} through @samp{ev31} to the
26645 % I think something like @colophon should be in texinfo. In the
26647 \long\def\colophon{\hbox to0pt{}\vfill
26648 \centerline{The body of this manual is set in}
26649 \centerline{\fontname\tenrm,}
26650 \centerline{with headings in {\bf\fontname\tenbf}}
26651 \centerline{and examples in {\tt\fontname\tentt}.}
26652 \centerline{{\it\fontname\tenit\/},}
26653 \centerline{{\bf\fontname\tenbf}, and}
26654 \centerline{{\sl\fontname\tensl\/}}
26655 \centerline{are used for emphasis.}\vfill}
26657 % Blame: doc@cygnus.com, 1991.