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
2241 @item @samp{set print thread-events}, which controls printing of
2242 messages on thread start and exit.
2246 @emph{Warning:} These facilities are not yet available on every
2247 @value{GDBN} configuration where the operating system supports threads.
2248 If your @value{GDBN} does not support threads, these commands have no
2249 effect. For example, a system without thread support shows no output
2250 from @samp{info threads}, and always rejects the @code{thread} command,
2254 (@value{GDBP}) info threads
2255 (@value{GDBP}) thread 1
2256 Thread ID 1 not known. Use the "info threads" command to
2257 see the IDs of currently known threads.
2259 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2260 @c doesn't support threads"?
2263 @cindex focus of debugging
2264 @cindex current thread
2265 The @value{GDBN} thread debugging facility allows you to observe all
2266 threads while your program runs---but whenever @value{GDBN} takes
2267 control, one thread in particular is always the focus of debugging.
2268 This thread is called the @dfn{current thread}. Debugging commands show
2269 program information from the perspective of the current thread.
2271 @cindex @code{New} @var{systag} message
2272 @cindex thread identifier (system)
2273 @c FIXME-implementors!! It would be more helpful if the [New...] message
2274 @c included GDB's numeric thread handle, so you could just go to that
2275 @c thread without first checking `info threads'.
2276 Whenever @value{GDBN} detects a new thread in your program, it displays
2277 the target system's identification for the thread with a message in the
2278 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2279 whose form varies depending on the particular system. For example, on
2280 @sc{gnu}/Linux, you might see
2283 [New Thread 46912507313328 (LWP 25582)]
2287 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2288 the @var{systag} is simply something like @samp{process 368}, with no
2291 @c FIXME!! (1) Does the [New...] message appear even for the very first
2292 @c thread of a program, or does it only appear for the
2293 @c second---i.e.@: when it becomes obvious we have a multithread
2295 @c (2) *Is* there necessarily a first thread always? Or do some
2296 @c multithread systems permit starting a program with multiple
2297 @c threads ab initio?
2299 @cindex thread number
2300 @cindex thread identifier (GDB)
2301 For debugging purposes, @value{GDBN} associates its own thread
2302 number---always a single integer---with each thread in your program.
2305 @kindex info threads
2307 Display a summary of all threads currently in your
2308 program. @value{GDBN} displays for each thread (in this order):
2312 the thread number assigned by @value{GDBN}
2315 the target system's thread identifier (@var{systag})
2318 the current stack frame summary for that thread
2322 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2323 indicates the current thread.
2327 @c end table here to get a little more width for example
2330 (@value{GDBP}) info threads
2331 3 process 35 thread 27 0x34e5 in sigpause ()
2332 2 process 35 thread 23 0x34e5 in sigpause ()
2333 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2339 @cindex debugging multithreaded programs (on HP-UX)
2340 @cindex thread identifier (GDB), on HP-UX
2341 For debugging purposes, @value{GDBN} associates its own thread
2342 number---a small integer assigned in thread-creation order---with each
2343 thread in your program.
2345 @cindex @code{New} @var{systag} message, on HP-UX
2346 @cindex thread identifier (system), on HP-UX
2347 @c FIXME-implementors!! It would be more helpful if the [New...] message
2348 @c included GDB's numeric thread handle, so you could just go to that
2349 @c thread without first checking `info threads'.
2350 Whenever @value{GDBN} detects a new thread in your program, it displays
2351 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2352 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2353 whose form varies depending on the particular system. For example, on
2357 [New thread 2 (system thread 26594)]
2361 when @value{GDBN} notices a new thread.
2364 @kindex info threads (HP-UX)
2366 Display a summary of all threads currently in your
2367 program. @value{GDBN} displays for each thread (in this order):
2370 @item the thread number assigned by @value{GDBN}
2372 @item the target system's thread identifier (@var{systag})
2374 @item the current stack frame summary for that thread
2378 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2379 indicates the current thread.
2383 @c end table here to get a little more width for example
2386 (@value{GDBP}) info threads
2387 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2389 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2390 from /usr/lib/libc.2
2391 1 system thread 27905 0x7b003498 in _brk () \@*
2392 from /usr/lib/libc.2
2395 On Solaris, you can display more information about user threads with a
2396 Solaris-specific command:
2399 @item maint info sol-threads
2400 @kindex maint info sol-threads
2401 @cindex thread info (Solaris)
2402 Display info on Solaris user threads.
2406 @kindex thread @var{threadno}
2407 @item thread @var{threadno}
2408 Make thread number @var{threadno} the current thread. The command
2409 argument @var{threadno} is the internal @value{GDBN} thread number, as
2410 shown in the first field of the @samp{info threads} display.
2411 @value{GDBN} responds by displaying the system identifier of the thread
2412 you selected, and its current stack frame summary:
2415 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2416 (@value{GDBP}) thread 2
2417 [Switching to process 35 thread 23]
2418 0x34e5 in sigpause ()
2422 As with the @samp{[New @dots{}]} message, the form of the text after
2423 @samp{Switching to} depends on your system's conventions for identifying
2426 @kindex thread apply
2427 @cindex apply command to several threads
2428 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2429 The @code{thread apply} command allows you to apply the named
2430 @var{command} to one or more threads. Specify the numbers of the
2431 threads that you want affected with the command argument
2432 @var{threadno}. It can be a single thread number, one of the numbers
2433 shown in the first field of the @samp{info threads} display; or it
2434 could be a range of thread numbers, as in @code{2-4}. To apply a
2435 command to all threads, type @kbd{thread apply all @var{command}}.
2437 @kindex set print thread-events
2438 @cindex print messages on thread start and exit
2439 @item set print thread-events
2440 @itemx set print thread-events on
2441 @itemx set print thread-events off
2442 The @code{set print thread-events} command allows you to enable or
2443 disable printing of messages when @value{GDBN} notices that new threads have
2444 started or that threads have exited. By default, these messages will
2445 be printed if detection of these events is supported by the target.
2446 Note that these messages cannot be disabled on all targets.
2448 @kindex show print thread-events
2449 @item show print thread-events
2450 Show whether messages will be printed when @value{GDBN} detects that threads
2451 have started and exited.
2454 @cindex automatic thread selection
2455 @cindex switching threads automatically
2456 @cindex threads, automatic switching
2457 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2458 signal, it automatically selects the thread where that breakpoint or
2459 signal happened. @value{GDBN} alerts you to the context switch with a
2460 message of the form @samp{[Switching to @var{systag}]} to identify the
2463 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2464 more information about how @value{GDBN} behaves when you stop and start
2465 programs with multiple threads.
2467 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2468 watchpoints in programs with multiple threads.
2471 @section Debugging Programs with Multiple Processes
2473 @cindex fork, debugging programs which call
2474 @cindex multiple processes
2475 @cindex processes, multiple
2476 On most systems, @value{GDBN} has no special support for debugging
2477 programs which create additional processes using the @code{fork}
2478 function. When a program forks, @value{GDBN} will continue to debug the
2479 parent process and the child process will run unimpeded. If you have
2480 set a breakpoint in any code which the child then executes, the child
2481 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2482 will cause it to terminate.
2484 However, if you want to debug the child process there is a workaround
2485 which isn't too painful. Put a call to @code{sleep} in the code which
2486 the child process executes after the fork. It may be useful to sleep
2487 only if a certain environment variable is set, or a certain file exists,
2488 so that the delay need not occur when you don't want to run @value{GDBN}
2489 on the child. While the child is sleeping, use the @code{ps} program to
2490 get its process ID. Then tell @value{GDBN} (a new invocation of
2491 @value{GDBN} if you are also debugging the parent process) to attach to
2492 the child process (@pxref{Attach}). From that point on you can debug
2493 the child process just like any other process which you attached to.
2495 On some systems, @value{GDBN} provides support for debugging programs that
2496 create additional processes using the @code{fork} or @code{vfork} functions.
2497 Currently, the only platforms with this feature are HP-UX (11.x and later
2498 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2500 By default, when a program forks, @value{GDBN} will continue to debug
2501 the parent process and the child process will run unimpeded.
2503 If you want to follow the child process instead of the parent process,
2504 use the command @w{@code{set follow-fork-mode}}.
2507 @kindex set follow-fork-mode
2508 @item set follow-fork-mode @var{mode}
2509 Set the debugger response to a program call of @code{fork} or
2510 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2511 process. The @var{mode} argument can be:
2515 The original process is debugged after a fork. The child process runs
2516 unimpeded. This is the default.
2519 The new process is debugged after a fork. The parent process runs
2524 @kindex show follow-fork-mode
2525 @item show follow-fork-mode
2526 Display the current debugger response to a @code{fork} or @code{vfork} call.
2529 @cindex debugging multiple processes
2530 On Linux, if you want to debug both the parent and child processes, use the
2531 command @w{@code{set detach-on-fork}}.
2534 @kindex set detach-on-fork
2535 @item set detach-on-fork @var{mode}
2536 Tells gdb whether to detach one of the processes after a fork, or
2537 retain debugger control over them both.
2541 The child process (or parent process, depending on the value of
2542 @code{follow-fork-mode}) will be detached and allowed to run
2543 independently. This is the default.
2546 Both processes will be held under the control of @value{GDBN}.
2547 One process (child or parent, depending on the value of
2548 @code{follow-fork-mode}) is debugged as usual, while the other
2553 @kindex show detach-on-follow
2554 @item show detach-on-follow
2555 Show whether detach-on-follow mode is on/off.
2558 If you choose to set @var{detach-on-follow} mode off, then
2559 @value{GDBN} will retain control of all forked processes (including
2560 nested forks). You can list the forked processes under the control of
2561 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2562 from one fork to another by using the @w{@code{fork}} command.
2567 Print a list of all forked processes under the control of @value{GDBN}.
2568 The listing will include a fork id, a process id, and the current
2569 position (program counter) of the process.
2572 @kindex fork @var{fork-id}
2573 @item fork @var{fork-id}
2574 Make fork number @var{fork-id} the current process. The argument
2575 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2576 as shown in the first field of the @samp{info forks} display.
2580 To quit debugging one of the forked processes, you can either detach
2581 from it by using the @w{@code{detach fork}} command (allowing it to
2582 run independently), or delete (and kill) it using the
2583 @w{@code{delete fork}} command.
2586 @kindex detach fork @var{fork-id}
2587 @item detach fork @var{fork-id}
2588 Detach from the process identified by @value{GDBN} fork number
2589 @var{fork-id}, and remove it from the fork list. The process will be
2590 allowed to run independently.
2592 @kindex delete fork @var{fork-id}
2593 @item delete fork @var{fork-id}
2594 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2595 and remove it from the fork list.
2599 If you ask to debug a child process and a @code{vfork} is followed by an
2600 @code{exec}, @value{GDBN} executes the new target up to the first
2601 breakpoint in the new target. If you have a breakpoint set on
2602 @code{main} in your original program, the breakpoint will also be set on
2603 the child process's @code{main}.
2605 When a child process is spawned by @code{vfork}, you cannot debug the
2606 child or parent until an @code{exec} call completes.
2608 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2609 call executes, the new target restarts. To restart the parent process,
2610 use the @code{file} command with the parent executable name as its
2613 You can use the @code{catch} command to make @value{GDBN} stop whenever
2614 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2615 Catchpoints, ,Setting Catchpoints}.
2617 @node Checkpoint/Restart
2618 @section Setting a @emph{Bookmark} to Return to Later
2623 @cindex snapshot of a process
2624 @cindex rewind program state
2626 On certain operating systems@footnote{Currently, only
2627 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2628 program's state, called a @dfn{checkpoint}, and come back to it
2631 Returning to a checkpoint effectively undoes everything that has
2632 happened in the program since the @code{checkpoint} was saved. This
2633 includes changes in memory, registers, and even (within some limits)
2634 system state. Effectively, it is like going back in time to the
2635 moment when the checkpoint was saved.
2637 Thus, if you're stepping thru a program and you think you're
2638 getting close to the point where things go wrong, you can save
2639 a checkpoint. Then, if you accidentally go too far and miss
2640 the critical statement, instead of having to restart your program
2641 from the beginning, you can just go back to the checkpoint and
2642 start again from there.
2644 This can be especially useful if it takes a lot of time or
2645 steps to reach the point where you think the bug occurs.
2647 To use the @code{checkpoint}/@code{restart} method of debugging:
2652 Save a snapshot of the debugged program's current execution state.
2653 The @code{checkpoint} command takes no arguments, but each checkpoint
2654 is assigned a small integer id, similar to a breakpoint id.
2656 @kindex info checkpoints
2657 @item info checkpoints
2658 List the checkpoints that have been saved in the current debugging
2659 session. For each checkpoint, the following information will be
2666 @item Source line, or label
2669 @kindex restart @var{checkpoint-id}
2670 @item restart @var{checkpoint-id}
2671 Restore the program state that was saved as checkpoint number
2672 @var{checkpoint-id}. All program variables, registers, stack frames
2673 etc.@: will be returned to the values that they had when the checkpoint
2674 was saved. In essence, gdb will ``wind back the clock'' to the point
2675 in time when the checkpoint was saved.
2677 Note that breakpoints, @value{GDBN} variables, command history etc.
2678 are not affected by restoring a checkpoint. In general, a checkpoint
2679 only restores things that reside in the program being debugged, not in
2682 @kindex delete checkpoint @var{checkpoint-id}
2683 @item delete checkpoint @var{checkpoint-id}
2684 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2688 Returning to a previously saved checkpoint will restore the user state
2689 of the program being debugged, plus a significant subset of the system
2690 (OS) state, including file pointers. It won't ``un-write'' data from
2691 a file, but it will rewind the file pointer to the previous location,
2692 so that the previously written data can be overwritten. For files
2693 opened in read mode, the pointer will also be restored so that the
2694 previously read data can be read again.
2696 Of course, characters that have been sent to a printer (or other
2697 external device) cannot be ``snatched back'', and characters received
2698 from eg.@: a serial device can be removed from internal program buffers,
2699 but they cannot be ``pushed back'' into the serial pipeline, ready to
2700 be received again. Similarly, the actual contents of files that have
2701 been changed cannot be restored (at this time).
2703 However, within those constraints, you actually can ``rewind'' your
2704 program to a previously saved point in time, and begin debugging it
2705 again --- and you can change the course of events so as to debug a
2706 different execution path this time.
2708 @cindex checkpoints and process id
2709 Finally, there is one bit of internal program state that will be
2710 different when you return to a checkpoint --- the program's process
2711 id. Each checkpoint will have a unique process id (or @var{pid}),
2712 and each will be different from the program's original @var{pid}.
2713 If your program has saved a local copy of its process id, this could
2714 potentially pose a problem.
2716 @subsection A Non-obvious Benefit of Using Checkpoints
2718 On some systems such as @sc{gnu}/Linux, address space randomization
2719 is performed on new processes for security reasons. This makes it
2720 difficult or impossible to set a breakpoint, or watchpoint, on an
2721 absolute address if you have to restart the program, since the
2722 absolute location of a symbol will change from one execution to the
2725 A checkpoint, however, is an @emph{identical} copy of a process.
2726 Therefore if you create a checkpoint at (eg.@:) the start of main,
2727 and simply return to that checkpoint instead of restarting the
2728 process, you can avoid the effects of address randomization and
2729 your symbols will all stay in the same place.
2732 @chapter Stopping and Continuing
2734 The principal purposes of using a debugger are so that you can stop your
2735 program before it terminates; or so that, if your program runs into
2736 trouble, you can investigate and find out why.
2738 Inside @value{GDBN}, your program may stop for any of several reasons,
2739 such as a signal, a breakpoint, or reaching a new line after a
2740 @value{GDBN} command such as @code{step}. You may then examine and
2741 change variables, set new breakpoints or remove old ones, and then
2742 continue execution. Usually, the messages shown by @value{GDBN} provide
2743 ample explanation of the status of your program---but you can also
2744 explicitly request this information at any time.
2747 @kindex info program
2749 Display information about the status of your program: whether it is
2750 running or not, what process it is, and why it stopped.
2754 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2755 * Continuing and Stepping:: Resuming execution
2757 * Thread Stops:: Stopping and starting multi-thread programs
2761 @section Breakpoints, Watchpoints, and Catchpoints
2764 A @dfn{breakpoint} makes your program stop whenever a certain point in
2765 the program is reached. For each breakpoint, you can add conditions to
2766 control in finer detail whether your program stops. You can set
2767 breakpoints with the @code{break} command and its variants (@pxref{Set
2768 Breaks, ,Setting Breakpoints}), to specify the place where your program
2769 should stop by line number, function name or exact address in the
2772 On some systems, you can set breakpoints in shared libraries before
2773 the executable is run. There is a minor limitation on HP-UX systems:
2774 you must wait until the executable is run in order to set breakpoints
2775 in shared library routines that are not called directly by the program
2776 (for example, routines that are arguments in a @code{pthread_create}
2780 @cindex data breakpoints
2781 @cindex memory tracing
2782 @cindex breakpoint on memory address
2783 @cindex breakpoint on variable modification
2784 A @dfn{watchpoint} is a special breakpoint that stops your program
2785 when the value of an expression changes. The expression may be a value
2786 of a variable, or it could involve values of one or more variables
2787 combined by operators, such as @samp{a + b}. This is sometimes called
2788 @dfn{data breakpoints}. You must use a different command to set
2789 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2790 from that, you can manage a watchpoint like any other breakpoint: you
2791 enable, disable, and delete both breakpoints and watchpoints using the
2794 You can arrange to have values from your program displayed automatically
2795 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2799 @cindex breakpoint on events
2800 A @dfn{catchpoint} is another special breakpoint that stops your program
2801 when a certain kind of event occurs, such as the throwing of a C@t{++}
2802 exception or the loading of a library. As with watchpoints, you use a
2803 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2804 Catchpoints}), but aside from that, you can manage a catchpoint like any
2805 other breakpoint. (To stop when your program receives a signal, use the
2806 @code{handle} command; see @ref{Signals, ,Signals}.)
2808 @cindex breakpoint numbers
2809 @cindex numbers for breakpoints
2810 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2811 catchpoint when you create it; these numbers are successive integers
2812 starting with one. In many of the commands for controlling various
2813 features of breakpoints you use the breakpoint number to say which
2814 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2815 @dfn{disabled}; if disabled, it has no effect on your program until you
2818 @cindex breakpoint ranges
2819 @cindex ranges of breakpoints
2820 Some @value{GDBN} commands accept a range of breakpoints on which to
2821 operate. A breakpoint range is either a single breakpoint number, like
2822 @samp{5}, or two such numbers, in increasing order, separated by a
2823 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2824 all breakpoints in that range are operated on.
2827 * Set Breaks:: Setting breakpoints
2828 * Set Watchpoints:: Setting watchpoints
2829 * Set Catchpoints:: Setting catchpoints
2830 * Delete Breaks:: Deleting breakpoints
2831 * Disabling:: Disabling breakpoints
2832 * Conditions:: Break conditions
2833 * Break Commands:: Breakpoint command lists
2834 * Breakpoint Menus:: Breakpoint menus
2835 * Error in Breakpoints:: ``Cannot insert breakpoints''
2836 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2840 @subsection Setting Breakpoints
2842 @c FIXME LMB what does GDB do if no code on line of breakpt?
2843 @c consider in particular declaration with/without initialization.
2845 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2848 @kindex b @r{(@code{break})}
2849 @vindex $bpnum@r{, convenience variable}
2850 @cindex latest breakpoint
2851 Breakpoints are set with the @code{break} command (abbreviated
2852 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2853 number of the breakpoint you've set most recently; see @ref{Convenience
2854 Vars,, Convenience Variables}, for a discussion of what you can do with
2855 convenience variables.
2858 @item break @var{location}
2859 Set a breakpoint at the given @var{location}, which can specify a
2860 function name, a line number, or an address of an instruction.
2861 (@xref{Specify Location}, for a list of all the possible ways to
2862 specify a @var{location}.) The breakpoint will stop your program just
2863 before it executes any of the code in the specified @var{location}.
2865 When using source languages that permit overloading of symbols, such as
2866 C@t{++}, a function name may refer to more than one possible place to break.
2867 @xref{Breakpoint Menus,,Breakpoint Menus}, for a discussion of that situation.
2870 When called without any arguments, @code{break} sets a breakpoint at
2871 the next instruction to be executed in the selected stack frame
2872 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2873 innermost, this makes your program stop as soon as control
2874 returns to that frame. This is similar to the effect of a
2875 @code{finish} command in the frame inside the selected frame---except
2876 that @code{finish} does not leave an active breakpoint. If you use
2877 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2878 the next time it reaches the current location; this may be useful
2881 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2882 least one instruction has been executed. If it did not do this, you
2883 would be unable to proceed past a breakpoint without first disabling the
2884 breakpoint. This rule applies whether or not the breakpoint already
2885 existed when your program stopped.
2887 @item break @dots{} if @var{cond}
2888 Set a breakpoint with condition @var{cond}; evaluate the expression
2889 @var{cond} each time the breakpoint is reached, and stop only if the
2890 value is nonzero---that is, if @var{cond} evaluates as true.
2891 @samp{@dots{}} stands for one of the possible arguments described
2892 above (or no argument) specifying where to break. @xref{Conditions,
2893 ,Break Conditions}, for more information on breakpoint conditions.
2896 @item tbreak @var{args}
2897 Set a breakpoint enabled only for one stop. @var{args} are the
2898 same as for the @code{break} command, and the breakpoint is set in the same
2899 way, but the breakpoint is automatically deleted after the first time your
2900 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2903 @cindex hardware breakpoints
2904 @item hbreak @var{args}
2905 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2906 @code{break} command and the breakpoint is set in the same way, but the
2907 breakpoint requires hardware support and some target hardware may not
2908 have this support. The main purpose of this is EPROM/ROM code
2909 debugging, so you can set a breakpoint at an instruction without
2910 changing the instruction. This can be used with the new trap-generation
2911 provided by SPARClite DSU and most x86-based targets. These targets
2912 will generate traps when a program accesses some data or instruction
2913 address that is assigned to the debug registers. However the hardware
2914 breakpoint registers can take a limited number of breakpoints. For
2915 example, on the DSU, only two data breakpoints can be set at a time, and
2916 @value{GDBN} will reject this command if more than two are used. Delete
2917 or disable unused hardware breakpoints before setting new ones
2918 (@pxref{Disabling, ,Disabling Breakpoints}).
2919 @xref{Conditions, ,Break Conditions}.
2920 For remote targets, you can restrict the number of hardware
2921 breakpoints @value{GDBN} will use, see @ref{set remote
2922 hardware-breakpoint-limit}.
2925 @item thbreak @var{args}
2926 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2927 are the same as for the @code{hbreak} command and the breakpoint is set in
2928 the same way. However, like the @code{tbreak} command,
2929 the breakpoint is automatically deleted after the
2930 first time your program stops there. Also, like the @code{hbreak}
2931 command, the breakpoint requires hardware support and some target hardware
2932 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2933 See also @ref{Conditions, ,Break Conditions}.
2936 @cindex regular expression
2937 @cindex breakpoints in functions matching a regexp
2938 @cindex set breakpoints in many functions
2939 @item rbreak @var{regex}
2940 Set breakpoints on all functions matching the regular expression
2941 @var{regex}. This command sets an unconditional breakpoint on all
2942 matches, printing a list of all breakpoints it set. Once these
2943 breakpoints are set, they are treated just like the breakpoints set with
2944 the @code{break} command. You can delete them, disable them, or make
2945 them conditional the same way as any other breakpoint.
2947 The syntax of the regular expression is the standard one used with tools
2948 like @file{grep}. Note that this is different from the syntax used by
2949 shells, so for instance @code{foo*} matches all functions that include
2950 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2951 @code{.*} leading and trailing the regular expression you supply, so to
2952 match only functions that begin with @code{foo}, use @code{^foo}.
2954 @cindex non-member C@t{++} functions, set breakpoint in
2955 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2956 breakpoints on overloaded functions that are not members of any special
2959 @cindex set breakpoints on all functions
2960 The @code{rbreak} command can be used to set breakpoints in
2961 @strong{all} the functions in a program, like this:
2964 (@value{GDBP}) rbreak .
2967 @kindex info breakpoints
2968 @cindex @code{$_} and @code{info breakpoints}
2969 @item info breakpoints @r{[}@var{n}@r{]}
2970 @itemx info break @r{[}@var{n}@r{]}
2971 @itemx info watchpoints @r{[}@var{n}@r{]}
2972 Print a table of all breakpoints, watchpoints, and catchpoints set and
2973 not deleted. Optional argument @var{n} means print information only
2974 about the specified breakpoint (or watchpoint or catchpoint). For
2975 each breakpoint, following columns are printed:
2978 @item Breakpoint Numbers
2980 Breakpoint, watchpoint, or catchpoint.
2982 Whether the breakpoint is marked to be disabled or deleted when hit.
2983 @item Enabled or Disabled
2984 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2985 that are not enabled. An optional @samp{(p)} suffix marks pending
2986 breakpoints---breakpoints for which address is either not yet
2987 resolved, pending load of a shared library, or for which address was
2988 in a shared library that was since unloaded. Such breakpoint won't
2989 fire until a shared library that has the symbol or line referred by
2990 breakpoint is loaded. See below for details.
2992 Where the breakpoint is in your program, as a memory address. For a
2993 pending breakpoint whose address is not yet known, this field will
2994 contain @samp{<PENDING>}. A breakpoint with several locations will
2995 have @samp{<MULTIPLE>} in this field---see below for details.
2997 Where the breakpoint is in the source for your program, as a file and
2998 line number. For a pending breakpoint, the original string passed to
2999 the breakpoint command will be listed as it cannot be resolved until
3000 the appropriate shared library is loaded in the future.
3004 If a breakpoint is conditional, @code{info break} shows the condition on
3005 the line following the affected breakpoint; breakpoint commands, if any,
3006 are listed after that. A pending breakpoint is allowed to have a condition
3007 specified for it. The condition is not parsed for validity until a shared
3008 library is loaded that allows the pending breakpoint to resolve to a
3012 @code{info break} with a breakpoint
3013 number @var{n} as argument lists only that breakpoint. The
3014 convenience variable @code{$_} and the default examining-address for
3015 the @code{x} command are set to the address of the last breakpoint
3016 listed (@pxref{Memory, ,Examining Memory}).
3019 @code{info break} displays a count of the number of times the breakpoint
3020 has been hit. This is especially useful in conjunction with the
3021 @code{ignore} command. You can ignore a large number of breakpoint
3022 hits, look at the breakpoint info to see how many times the breakpoint
3023 was hit, and then run again, ignoring one less than that number. This
3024 will get you quickly to the last hit of that breakpoint.
3027 @value{GDBN} allows you to set any number of breakpoints at the same place in
3028 your program. There is nothing silly or meaningless about this. When
3029 the breakpoints are conditional, this is even useful
3030 (@pxref{Conditions, ,Break Conditions}).
3032 It is possible that a breakpoint corresponds to several locations
3033 in your program. Examples of this situation are:
3038 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3039 instances of the function body, used in different cases.
3042 For a C@t{++} template function, a given line in the function can
3043 correspond to any number of instantiations.
3046 For an inlined function, a given source line can correspond to
3047 several places where that function is inlined.
3051 In all those cases, @value{GDBN} will insert a breakpoint at all
3052 the relevant locations.
3054 A breakpoint with multiple locations is displayed in the breakpoint
3055 table using several rows---one header row, followed by one row for
3056 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3057 address column. The rows for individual locations contain the actual
3058 addresses for locations, and show the functions to which those
3059 locations belong. The number column for a location is of the form
3060 @var{breakpoint-number}.@var{location-number}.
3065 Num Type Disp Enb Address What
3066 1 breakpoint keep y <MULTIPLE>
3068 breakpoint already hit 1 time
3069 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3070 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3073 Each location can be individually enabled or disabled by passing
3074 @var{breakpoint-number}.@var{location-number} as argument to the
3075 @code{enable} and @code{disable} commands. Note that you cannot
3076 delete the individual locations from the list, you can only delete the
3077 entire list of locations that belong to their parent breakpoint (with
3078 the @kbd{delete @var{num}} command, where @var{num} is the number of
3079 the parent breakpoint, 1 in the above example). Disabling or enabling
3080 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3081 that belong to that breakpoint.
3083 @cindex pending breakpoints
3084 It's quite common to have a breakpoint inside a shared library.
3085 Shared libraries can be loaded and unloaded explicitly,
3086 and possibly repeatedly, as the program is executed. To support
3087 this use case, @value{GDBN} updates breakpoint locations whenever
3088 any shared library is loaded or unloaded. Typically, you would
3089 set a breakpoint in a shared library at the beginning of your
3090 debugging session, when the library is not loaded, and when the
3091 symbols from the library are not available. When you try to set
3092 breakpoint, @value{GDBN} will ask you if you want to set
3093 a so called @dfn{pending breakpoint}---breakpoint whose address
3094 is not yet resolved.
3096 After the program is run, whenever a new shared library is loaded,
3097 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3098 shared library contains the symbol or line referred to by some
3099 pending breakpoint, that breakpoint is resolved and becomes an
3100 ordinary breakpoint. When a library is unloaded, all breakpoints
3101 that refer to its symbols or source lines become pending again.
3103 This logic works for breakpoints with multiple locations, too. For
3104 example, if you have a breakpoint in a C@t{++} template function, and
3105 a newly loaded shared library has an instantiation of that template,
3106 a new location is added to the list of locations for the breakpoint.
3108 Except for having unresolved address, pending breakpoints do not
3109 differ from regular breakpoints. You can set conditions or commands,
3110 enable and disable them and perform other breakpoint operations.
3112 @value{GDBN} provides some additional commands for controlling what
3113 happens when the @samp{break} command cannot resolve breakpoint
3114 address specification to an address:
3116 @kindex set breakpoint pending
3117 @kindex show breakpoint pending
3119 @item set breakpoint pending auto
3120 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3121 location, it queries you whether a pending breakpoint should be created.
3123 @item set breakpoint pending on
3124 This indicates that an unrecognized breakpoint location should automatically
3125 result in a pending breakpoint being created.
3127 @item set breakpoint pending off
3128 This indicates that pending breakpoints are not to be created. Any
3129 unrecognized breakpoint location results in an error. This setting does
3130 not affect any pending breakpoints previously created.
3132 @item show breakpoint pending
3133 Show the current behavior setting for creating pending breakpoints.
3136 The settings above only affect the @code{break} command and its
3137 variants. Once breakpoint is set, it will be automatically updated
3138 as shared libraries are loaded and unloaded.
3140 @cindex automatic hardware breakpoints
3141 For some targets, @value{GDBN} can automatically decide if hardware or
3142 software breakpoints should be used, depending on whether the
3143 breakpoint address is read-only or read-write. This applies to
3144 breakpoints set with the @code{break} command as well as to internal
3145 breakpoints set by commands like @code{next} and @code{finish}. For
3146 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3149 You can control this automatic behaviour with the following commands::
3151 @kindex set breakpoint auto-hw
3152 @kindex show breakpoint auto-hw
3154 @item set breakpoint auto-hw on
3155 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3156 will try to use the target memory map to decide if software or hardware
3157 breakpoint must be used.
3159 @item set breakpoint auto-hw off
3160 This indicates @value{GDBN} should not automatically select breakpoint
3161 type. If the target provides a memory map, @value{GDBN} will warn when
3162 trying to set software breakpoint at a read-only address.
3166 @cindex negative breakpoint numbers
3167 @cindex internal @value{GDBN} breakpoints
3168 @value{GDBN} itself sometimes sets breakpoints in your program for
3169 special purposes, such as proper handling of @code{longjmp} (in C
3170 programs). These internal breakpoints are assigned negative numbers,
3171 starting with @code{-1}; @samp{info breakpoints} does not display them.
3172 You can see these breakpoints with the @value{GDBN} maintenance command
3173 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3176 @node Set Watchpoints
3177 @subsection Setting Watchpoints
3179 @cindex setting watchpoints
3180 You can use a watchpoint to stop execution whenever the value of an
3181 expression changes, without having to predict a particular place where
3182 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3183 The expression may be as simple as the value of a single variable, or
3184 as complex as many variables combined by operators. Examples include:
3188 A reference to the value of a single variable.
3191 An address cast to an appropriate data type. For example,
3192 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3193 address (assuming an @code{int} occupies 4 bytes).
3196 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3197 expression can use any operators valid in the program's native
3198 language (@pxref{Languages}).
3201 @cindex software watchpoints
3202 @cindex hardware watchpoints
3203 Depending on your system, watchpoints may be implemented in software or
3204 hardware. @value{GDBN} does software watchpointing by single-stepping your
3205 program and testing the variable's value each time, which is hundreds of
3206 times slower than normal execution. (But this may still be worth it, to
3207 catch errors where you have no clue what part of your program is the
3210 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3211 x86-based targets, @value{GDBN} includes support for hardware
3212 watchpoints, which do not slow down the running of your program.
3216 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3217 Set a watchpoint for an expression. @value{GDBN} will break when the
3218 expression @var{expr} is written into by the program and its value
3219 changes. The simplest (and the most popular) use of this command is
3220 to watch the value of a single variable:
3223 (@value{GDBP}) watch foo
3226 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3227 clause, @value{GDBN} breaks only when the thread identified by
3228 @var{threadnum} changes the value of @var{expr}. If any other threads
3229 change the value of @var{expr}, @value{GDBN} will not break. Note
3230 that watchpoints restricted to a single thread in this way only work
3231 with Hardware Watchpoints.
3234 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3235 Set a watchpoint that will break when the value of @var{expr} is read
3239 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3240 Set a watchpoint that will break when @var{expr} is either read from
3241 or written into by the program.
3243 @kindex info watchpoints @r{[}@var{n}@r{]}
3244 @item info watchpoints
3245 This command prints a list of watchpoints, breakpoints, and catchpoints;
3246 it is the same as @code{info break} (@pxref{Set Breaks}).
3249 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3250 watchpoints execute very quickly, and the debugger reports a change in
3251 value at the exact instruction where the change occurs. If @value{GDBN}
3252 cannot set a hardware watchpoint, it sets a software watchpoint, which
3253 executes more slowly and reports the change in value at the next
3254 @emph{statement}, not the instruction, after the change occurs.
3256 @cindex use only software watchpoints
3257 You can force @value{GDBN} to use only software watchpoints with the
3258 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3259 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3260 the underlying system supports them. (Note that hardware-assisted
3261 watchpoints that were set @emph{before} setting
3262 @code{can-use-hw-watchpoints} to zero will still use the hardware
3263 mechanism of watching expression values.)
3266 @item set can-use-hw-watchpoints
3267 @kindex set can-use-hw-watchpoints
3268 Set whether or not to use hardware watchpoints.
3270 @item show can-use-hw-watchpoints
3271 @kindex show can-use-hw-watchpoints
3272 Show the current mode of using hardware watchpoints.
3275 For remote targets, you can restrict the number of hardware
3276 watchpoints @value{GDBN} will use, see @ref{set remote
3277 hardware-breakpoint-limit}.
3279 When you issue the @code{watch} command, @value{GDBN} reports
3282 Hardware watchpoint @var{num}: @var{expr}
3286 if it was able to set a hardware watchpoint.
3288 Currently, the @code{awatch} and @code{rwatch} commands can only set
3289 hardware watchpoints, because accesses to data that don't change the
3290 value of the watched expression cannot be detected without examining
3291 every instruction as it is being executed, and @value{GDBN} does not do
3292 that currently. If @value{GDBN} finds that it is unable to set a
3293 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3294 will print a message like this:
3297 Expression cannot be implemented with read/access watchpoint.
3300 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3301 data type of the watched expression is wider than what a hardware
3302 watchpoint on the target machine can handle. For example, some systems
3303 can only watch regions that are up to 4 bytes wide; on such systems you
3304 cannot set hardware watchpoints for an expression that yields a
3305 double-precision floating-point number (which is typically 8 bytes
3306 wide). As a work-around, it might be possible to break the large region
3307 into a series of smaller ones and watch them with separate watchpoints.
3309 If you set too many hardware watchpoints, @value{GDBN} might be unable
3310 to insert all of them when you resume the execution of your program.
3311 Since the precise number of active watchpoints is unknown until such
3312 time as the program is about to be resumed, @value{GDBN} might not be
3313 able to warn you about this when you set the watchpoints, and the
3314 warning will be printed only when the program is resumed:
3317 Hardware watchpoint @var{num}: Could not insert watchpoint
3321 If this happens, delete or disable some of the watchpoints.
3323 Watching complex expressions that reference many variables can also
3324 exhaust the resources available for hardware-assisted watchpoints.
3325 That's because @value{GDBN} needs to watch every variable in the
3326 expression with separately allocated resources.
3328 The SPARClite DSU will generate traps when a program accesses some data
3329 or instruction address that is assigned to the debug registers. For the
3330 data addresses, DSU facilitates the @code{watch} command. However the
3331 hardware breakpoint registers can only take two data watchpoints, and
3332 both watchpoints must be the same kind. For example, you can set two
3333 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3334 @strong{or} two with @code{awatch} commands, but you cannot set one
3335 watchpoint with one command and the other with a different command.
3336 @value{GDBN} will reject the command if you try to mix watchpoints.
3337 Delete or disable unused watchpoint commands before setting new ones.
3339 If you call a function interactively using @code{print} or @code{call},
3340 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3341 kind of breakpoint or the call completes.
3343 @value{GDBN} automatically deletes watchpoints that watch local
3344 (automatic) variables, or expressions that involve such variables, when
3345 they go out of scope, that is, when the execution leaves the block in
3346 which these variables were defined. In particular, when the program
3347 being debugged terminates, @emph{all} local variables go out of scope,
3348 and so only watchpoints that watch global variables remain set. If you
3349 rerun the program, you will need to set all such watchpoints again. One
3350 way of doing that would be to set a code breakpoint at the entry to the
3351 @code{main} function and when it breaks, set all the watchpoints.
3353 @cindex watchpoints and threads
3354 @cindex threads and watchpoints
3355 In multi-threaded programs, watchpoints will detect changes to the
3356 watched expression from every thread.
3359 @emph{Warning:} In multi-threaded programs, software watchpoints
3360 have only limited usefulness. If @value{GDBN} creates a software
3361 watchpoint, it can only watch the value of an expression @emph{in a
3362 single thread}. If you are confident that the expression can only
3363 change due to the current thread's activity (and if you are also
3364 confident that no other thread can become current), then you can use
3365 software watchpoints as usual. However, @value{GDBN} may not notice
3366 when a non-current thread's activity changes the expression. (Hardware
3367 watchpoints, in contrast, watch an expression in all threads.)
3370 @xref{set remote hardware-watchpoint-limit}.
3372 @node Set Catchpoints
3373 @subsection Setting Catchpoints
3374 @cindex catchpoints, setting
3375 @cindex exception handlers
3376 @cindex event handling
3378 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3379 kinds of program events, such as C@t{++} exceptions or the loading of a
3380 shared library. Use the @code{catch} command to set a catchpoint.
3384 @item catch @var{event}
3385 Stop when @var{event} occurs. @var{event} can be any of the following:
3388 @cindex stop on C@t{++} exceptions
3389 The throwing of a C@t{++} exception.
3392 The catching of a C@t{++} exception.
3395 @cindex Ada exception catching
3396 @cindex catch Ada exceptions
3397 An Ada exception being raised. If an exception name is specified
3398 at the end of the command (eg @code{catch exception Program_Error}),
3399 the debugger will stop only when this specific exception is raised.
3400 Otherwise, the debugger stops execution when any Ada exception is raised.
3402 @item exception unhandled
3403 An exception that was raised but is not handled by the program.
3406 A failed Ada assertion.
3409 @cindex break on fork/exec
3410 A call to @code{exec}. This is currently only available for HP-UX.
3413 A call to @code{fork}. This is currently only available for HP-UX.
3416 A call to @code{vfork}. This is currently only available for HP-UX.
3419 @itemx load @var{libname}
3420 @cindex break on load/unload of shared library
3421 The dynamic loading of any shared library, or the loading of the library
3422 @var{libname}. This is currently only available for HP-UX.
3425 @itemx unload @var{libname}
3426 The unloading of any dynamically loaded shared library, or the unloading
3427 of the library @var{libname}. This is currently only available for HP-UX.
3430 @item tcatch @var{event}
3431 Set a catchpoint that is enabled only for one stop. The catchpoint is
3432 automatically deleted after the first time the event is caught.
3436 Use the @code{info break} command to list the current catchpoints.
3438 There are currently some limitations to C@t{++} exception handling
3439 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3443 If you call a function interactively, @value{GDBN} normally returns
3444 control to you when the function has finished executing. If the call
3445 raises an exception, however, the call may bypass the mechanism that
3446 returns control to you and cause your program either to abort or to
3447 simply continue running until it hits a breakpoint, catches a signal
3448 that @value{GDBN} is listening for, or exits. This is the case even if
3449 you set a catchpoint for the exception; catchpoints on exceptions are
3450 disabled within interactive calls.
3453 You cannot raise an exception interactively.
3456 You cannot install an exception handler interactively.
3459 @cindex raise exceptions
3460 Sometimes @code{catch} is not the best way to debug exception handling:
3461 if you need to know exactly where an exception is raised, it is better to
3462 stop @emph{before} the exception handler is called, since that way you
3463 can see the stack before any unwinding takes place. If you set a
3464 breakpoint in an exception handler instead, it may not be easy to find
3465 out where the exception was raised.
3467 To stop just before an exception handler is called, you need some
3468 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3469 raised by calling a library function named @code{__raise_exception}
3470 which has the following ANSI C interface:
3473 /* @var{addr} is where the exception identifier is stored.
3474 @var{id} is the exception identifier. */
3475 void __raise_exception (void **addr, void *id);
3479 To make the debugger catch all exceptions before any stack
3480 unwinding takes place, set a breakpoint on @code{__raise_exception}
3481 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3483 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3484 that depends on the value of @var{id}, you can stop your program when
3485 a specific exception is raised. You can use multiple conditional
3486 breakpoints to stop your program when any of a number of exceptions are
3491 @subsection Deleting Breakpoints
3493 @cindex clearing breakpoints, watchpoints, catchpoints
3494 @cindex deleting breakpoints, watchpoints, catchpoints
3495 It is often necessary to eliminate a breakpoint, watchpoint, or
3496 catchpoint once it has done its job and you no longer want your program
3497 to stop there. This is called @dfn{deleting} the breakpoint. A
3498 breakpoint that has been deleted no longer exists; it is forgotten.
3500 With the @code{clear} command you can delete breakpoints according to
3501 where they are in your program. With the @code{delete} command you can
3502 delete individual breakpoints, watchpoints, or catchpoints by specifying
3503 their breakpoint numbers.
3505 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3506 automatically ignores breakpoints on the first instruction to be executed
3507 when you continue execution without changing the execution address.
3512 Delete any breakpoints at the next instruction to be executed in the
3513 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3514 the innermost frame is selected, this is a good way to delete a
3515 breakpoint where your program just stopped.
3517 @item clear @var{location}
3518 Delete any breakpoints set at the specified @var{location}.
3519 @xref{Specify Location}, for the various forms of @var{location}; the
3520 most useful ones are listed below:
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}.
3533 @cindex delete breakpoints
3535 @kindex d @r{(@code{delete})}
3536 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3537 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3538 ranges specified as arguments. If no argument is specified, delete all
3539 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3540 confirm off}). You can abbreviate this command as @code{d}.
3544 @subsection Disabling Breakpoints
3546 @cindex enable/disable a breakpoint
3547 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3548 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3549 it had been deleted, but remembers the information on the breakpoint so
3550 that you can @dfn{enable} it again later.
3552 You disable and enable breakpoints, watchpoints, and catchpoints with
3553 the @code{enable} and @code{disable} commands, optionally specifying one
3554 or more breakpoint numbers as arguments. Use @code{info break} or
3555 @code{info watch} to print a list of breakpoints, watchpoints, and
3556 catchpoints if you do not know which numbers to use.
3558 Disabling and enabling a breakpoint that has multiple locations
3559 affects all of its locations.
3561 A breakpoint, watchpoint, or catchpoint can have any of four different
3562 states of enablement:
3566 Enabled. The breakpoint stops your program. A breakpoint set
3567 with the @code{break} command starts out in this state.
3569 Disabled. The breakpoint has no effect on your program.
3571 Enabled once. The breakpoint stops your program, but then becomes
3574 Enabled for deletion. The breakpoint stops your program, but
3575 immediately after it does so it is deleted permanently. A breakpoint
3576 set with the @code{tbreak} command starts out in this state.
3579 You can use the following commands to enable or disable breakpoints,
3580 watchpoints, and catchpoints:
3584 @kindex dis @r{(@code{disable})}
3585 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3586 Disable the specified breakpoints---or all breakpoints, if none are
3587 listed. A disabled breakpoint has no effect but is not forgotten. All
3588 options such as ignore-counts, conditions and commands are remembered in
3589 case the breakpoint is enabled again later. You may abbreviate
3590 @code{disable} as @code{dis}.
3593 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3594 Enable the specified breakpoints (or all defined breakpoints). They
3595 become effective once again in stopping your program.
3597 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3598 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3599 of these breakpoints immediately after stopping your program.
3601 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3602 Enable the specified breakpoints to work once, then die. @value{GDBN}
3603 deletes any of these breakpoints as soon as your program stops there.
3604 Breakpoints set by the @code{tbreak} command start out in this state.
3607 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3608 @c confusing: tbreak is also initially enabled.
3609 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3610 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3611 subsequently, they become disabled or enabled only when you use one of
3612 the commands above. (The command @code{until} can set and delete a
3613 breakpoint of its own, but it does not change the state of your other
3614 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3618 @subsection Break Conditions
3619 @cindex conditional breakpoints
3620 @cindex breakpoint conditions
3622 @c FIXME what is scope of break condition expr? Context where wanted?
3623 @c in particular for a watchpoint?
3624 The simplest sort of breakpoint breaks every time your program reaches a
3625 specified place. You can also specify a @dfn{condition} for a
3626 breakpoint. A condition is just a Boolean expression in your
3627 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3628 a condition evaluates the expression each time your program reaches it,
3629 and your program stops only if the condition is @emph{true}.
3631 This is the converse of using assertions for program validation; in that
3632 situation, you want to stop when the assertion is violated---that is,
3633 when the condition is false. In C, if you want to test an assertion expressed
3634 by the condition @var{assert}, you should set the condition
3635 @samp{! @var{assert}} on the appropriate breakpoint.
3637 Conditions are also accepted for watchpoints; you may not need them,
3638 since a watchpoint is inspecting the value of an expression anyhow---but
3639 it might be simpler, say, to just set a watchpoint on a variable name,
3640 and specify a condition that tests whether the new value is an interesting
3643 Break conditions can have side effects, and may even call functions in
3644 your program. This can be useful, for example, to activate functions
3645 that log program progress, or to use your own print functions to
3646 format special data structures. The effects are completely predictable
3647 unless there is another enabled breakpoint at the same address. (In
3648 that case, @value{GDBN} might see the other breakpoint first and stop your
3649 program without checking the condition of this one.) Note that
3650 breakpoint commands are usually more convenient and flexible than break
3652 purpose of performing side effects when a breakpoint is reached
3653 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3655 Break conditions can be specified when a breakpoint is set, by using
3656 @samp{if} in the arguments to the @code{break} command. @xref{Set
3657 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3658 with the @code{condition} command.
3660 You can also use the @code{if} keyword with the @code{watch} command.
3661 The @code{catch} command does not recognize the @code{if} keyword;
3662 @code{condition} is the only way to impose a further condition on a
3667 @item condition @var{bnum} @var{expression}
3668 Specify @var{expression} as the break condition for breakpoint,
3669 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3670 breakpoint @var{bnum} stops your program only if the value of
3671 @var{expression} is true (nonzero, in C). When you use
3672 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3673 syntactic correctness, and to determine whether symbols in it have
3674 referents in the context of your breakpoint. If @var{expression} uses
3675 symbols not referenced in the context of the breakpoint, @value{GDBN}
3676 prints an error message:
3679 No symbol "foo" in current context.
3684 not actually evaluate @var{expression} at the time the @code{condition}
3685 command (or a command that sets a breakpoint with a condition, like
3686 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3688 @item condition @var{bnum}
3689 Remove the condition from breakpoint number @var{bnum}. It becomes
3690 an ordinary unconditional breakpoint.
3693 @cindex ignore count (of breakpoint)
3694 A special case of a breakpoint condition is to stop only when the
3695 breakpoint has been reached a certain number of times. This is so
3696 useful that there is a special way to do it, using the @dfn{ignore
3697 count} of the breakpoint. Every breakpoint has an ignore count, which
3698 is an integer. Most of the time, the ignore count is zero, and
3699 therefore has no effect. But if your program reaches a breakpoint whose
3700 ignore count is positive, then instead of stopping, it just decrements
3701 the ignore count by one and continues. As a result, if the ignore count
3702 value is @var{n}, the breakpoint does not stop the next @var{n} times
3703 your program reaches it.
3707 @item ignore @var{bnum} @var{count}
3708 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3709 The next @var{count} times the breakpoint is reached, your program's
3710 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3713 To make the breakpoint stop the next time it is reached, specify
3716 When you use @code{continue} to resume execution of your program from a
3717 breakpoint, you can specify an ignore count directly as an argument to
3718 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3719 Stepping,,Continuing and Stepping}.
3721 If a breakpoint has a positive ignore count and a condition, the
3722 condition is not checked. Once the ignore count reaches zero,
3723 @value{GDBN} resumes checking the condition.
3725 You could achieve the effect of the ignore count with a condition such
3726 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3727 is decremented each time. @xref{Convenience Vars, ,Convenience
3731 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3734 @node Break Commands
3735 @subsection Breakpoint Command Lists
3737 @cindex breakpoint commands
3738 You can give any breakpoint (or watchpoint or catchpoint) a series of
3739 commands to execute when your program stops due to that breakpoint. For
3740 example, you might want to print the values of certain expressions, or
3741 enable other breakpoints.
3745 @kindex end@r{ (breakpoint commands)}
3746 @item commands @r{[}@var{bnum}@r{]}
3747 @itemx @dots{} @var{command-list} @dots{}
3749 Specify a list of commands for breakpoint number @var{bnum}. The commands
3750 themselves appear on the following lines. Type a line containing just
3751 @code{end} to terminate the commands.
3753 To remove all commands from a breakpoint, type @code{commands} and
3754 follow it immediately with @code{end}; that is, give no commands.
3756 With no @var{bnum} argument, @code{commands} refers to the last
3757 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3758 recently encountered).
3761 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3762 disabled within a @var{command-list}.
3764 You can use breakpoint commands to start your program up again. Simply
3765 use the @code{continue} command, or @code{step}, or any other command
3766 that resumes execution.
3768 Any other commands in the command list, after a command that resumes
3769 execution, are ignored. This is because any time you resume execution
3770 (even with a simple @code{next} or @code{step}), you may encounter
3771 another breakpoint---which could have its own command list, leading to
3772 ambiguities about which list to execute.
3775 If the first command you specify in a command list is @code{silent}, the
3776 usual message about stopping at a breakpoint is not printed. This may
3777 be desirable for breakpoints that are to print a specific message and
3778 then continue. If none of the remaining commands print anything, you
3779 see no sign that the breakpoint was reached. @code{silent} is
3780 meaningful only at the beginning of a breakpoint command list.
3782 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3783 print precisely controlled output, and are often useful in silent
3784 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3786 For example, here is how you could use breakpoint commands to print the
3787 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3793 printf "x is %d\n",x
3798 One application for breakpoint commands is to compensate for one bug so
3799 you can test for another. Put a breakpoint just after the erroneous line
3800 of code, give it a condition to detect the case in which something
3801 erroneous has been done, and give it commands to assign correct values
3802 to any variables that need them. End with the @code{continue} command
3803 so that your program does not stop, and start with the @code{silent}
3804 command so that no output is produced. Here is an example:
3815 @node Breakpoint Menus
3816 @subsection Breakpoint Menus
3818 @cindex symbol overloading
3820 Some programming languages (notably C@t{++} and Objective-C) permit a
3821 single function name
3822 to be defined several times, for application in different contexts.
3823 This is called @dfn{overloading}. When a function name is overloaded,
3824 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3825 a breakpoint. You can use explicit signature of the function, as in
3826 @samp{break @var{function}(@var{types})}, to specify which
3827 particular version of the function you want. Otherwise, @value{GDBN} offers
3828 you a menu of numbered choices for different possible breakpoints, and
3829 waits for your selection with the prompt @samp{>}. The first two
3830 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3831 sets a breakpoint at each definition of @var{function}, and typing
3832 @kbd{0} aborts the @code{break} command without setting any new
3835 For example, the following session excerpt shows an attempt to set a
3836 breakpoint at the overloaded symbol @code{String::after}.
3837 We choose three particular definitions of that function name:
3839 @c FIXME! This is likely to change to show arg type lists, at least
3842 (@value{GDBP}) b String::after
3845 [2] file:String.cc; line number:867
3846 [3] file:String.cc; line number:860
3847 [4] file:String.cc; line number:875
3848 [5] file:String.cc; line number:853
3849 [6] file:String.cc; line number:846
3850 [7] file:String.cc; line number:735
3852 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3853 Breakpoint 2 at 0xb344: file String.cc, line 875.
3854 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3855 Multiple breakpoints were set.
3856 Use the "delete" command to delete unwanted
3862 @c @ifclear BARETARGET
3863 @node Error in Breakpoints
3864 @subsection ``Cannot insert breakpoints''
3866 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3868 Under some operating systems, breakpoints cannot be used in a program if
3869 any other process is running that program. In this situation,
3870 attempting to run or continue a program with a breakpoint causes
3871 @value{GDBN} to print an error message:
3874 Cannot insert breakpoints.
3875 The same program may be running in another process.
3878 When this happens, you have three ways to proceed:
3882 Remove or disable the breakpoints, then continue.
3885 Suspend @value{GDBN}, and copy the file containing your program to a new
3886 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3887 that @value{GDBN} should run your program under that name.
3888 Then start your program again.
3891 Relink your program so that the text segment is nonsharable, using the
3892 linker option @samp{-N}. The operating system limitation may not apply
3893 to nonsharable executables.
3897 A similar message can be printed if you request too many active
3898 hardware-assisted breakpoints and watchpoints:
3900 @c FIXME: the precise wording of this message may change; the relevant
3901 @c source change is not committed yet (Sep 3, 1999).
3903 Stopped; cannot insert breakpoints.
3904 You may have requested too many hardware breakpoints and watchpoints.
3908 This message is printed when you attempt to resume the program, since
3909 only then @value{GDBN} knows exactly how many hardware breakpoints and
3910 watchpoints it needs to insert.
3912 When this message is printed, you need to disable or remove some of the
3913 hardware-assisted breakpoints and watchpoints, and then continue.
3915 @node Breakpoint-related Warnings
3916 @subsection ``Breakpoint address adjusted...''
3917 @cindex breakpoint address adjusted
3919 Some processor architectures place constraints on the addresses at
3920 which breakpoints may be placed. For architectures thus constrained,
3921 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3922 with the constraints dictated by the architecture.
3924 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3925 a VLIW architecture in which a number of RISC-like instructions may be
3926 bundled together for parallel execution. The FR-V architecture
3927 constrains the location of a breakpoint instruction within such a
3928 bundle to the instruction with the lowest address. @value{GDBN}
3929 honors this constraint by adjusting a breakpoint's address to the
3930 first in the bundle.
3932 It is not uncommon for optimized code to have bundles which contain
3933 instructions from different source statements, thus it may happen that
3934 a breakpoint's address will be adjusted from one source statement to
3935 another. Since this adjustment may significantly alter @value{GDBN}'s
3936 breakpoint related behavior from what the user expects, a warning is
3937 printed when the breakpoint is first set and also when the breakpoint
3940 A warning like the one below is printed when setting a breakpoint
3941 that's been subject to address adjustment:
3944 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3947 Such warnings are printed both for user settable and @value{GDBN}'s
3948 internal breakpoints. If you see one of these warnings, you should
3949 verify that a breakpoint set at the adjusted address will have the
3950 desired affect. If not, the breakpoint in question may be removed and
3951 other breakpoints may be set which will have the desired behavior.
3952 E.g., it may be sufficient to place the breakpoint at a later
3953 instruction. A conditional breakpoint may also be useful in some
3954 cases to prevent the breakpoint from triggering too often.
3956 @value{GDBN} will also issue a warning when stopping at one of these
3957 adjusted breakpoints:
3960 warning: Breakpoint 1 address previously adjusted from 0x00010414
3964 When this warning is encountered, it may be too late to take remedial
3965 action except in cases where the breakpoint is hit earlier or more
3966 frequently than expected.
3968 @node Continuing and Stepping
3969 @section Continuing and Stepping
3973 @cindex resuming execution
3974 @dfn{Continuing} means resuming program execution until your program
3975 completes normally. In contrast, @dfn{stepping} means executing just
3976 one more ``step'' of your program, where ``step'' may mean either one
3977 line of source code, or one machine instruction (depending on what
3978 particular command you use). Either when continuing or when stepping,
3979 your program may stop even sooner, due to a breakpoint or a signal. (If
3980 it stops due to a signal, you may want to use @code{handle}, or use
3981 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3985 @kindex c @r{(@code{continue})}
3986 @kindex fg @r{(resume foreground execution)}
3987 @item continue @r{[}@var{ignore-count}@r{]}
3988 @itemx c @r{[}@var{ignore-count}@r{]}
3989 @itemx fg @r{[}@var{ignore-count}@r{]}
3990 Resume program execution, at the address where your program last stopped;
3991 any breakpoints set at that address are bypassed. The optional argument
3992 @var{ignore-count} allows you to specify a further number of times to
3993 ignore a breakpoint at this location; its effect is like that of
3994 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
3996 The argument @var{ignore-count} is meaningful only when your program
3997 stopped due to a breakpoint. At other times, the argument to
3998 @code{continue} is ignored.
4000 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4001 debugged program is deemed to be the foreground program) are provided
4002 purely for convenience, and have exactly the same behavior as
4006 To resume execution at a different place, you can use @code{return}
4007 (@pxref{Returning, ,Returning from a Function}) to go back to the
4008 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4009 Different Address}) to go to an arbitrary location in your program.
4011 A typical technique for using stepping is to set a breakpoint
4012 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4013 beginning of the function or the section of your program where a problem
4014 is believed to lie, run your program until it stops at that breakpoint,
4015 and then step through the suspect area, examining the variables that are
4016 interesting, until you see the problem happen.
4020 @kindex s @r{(@code{step})}
4022 Continue running your program until control reaches a different source
4023 line, then stop it and return control to @value{GDBN}. This command is
4024 abbreviated @code{s}.
4027 @c "without debugging information" is imprecise; actually "without line
4028 @c numbers in the debugging information". (gcc -g1 has debugging info but
4029 @c not line numbers). But it seems complex to try to make that
4030 @c distinction here.
4031 @emph{Warning:} If you use the @code{step} command while control is
4032 within a function that was compiled without debugging information,
4033 execution proceeds until control reaches a function that does have
4034 debugging information. Likewise, it will not step into a function which
4035 is compiled without debugging information. To step through functions
4036 without debugging information, use the @code{stepi} command, described
4040 The @code{step} command only stops at the first instruction of a source
4041 line. This prevents the multiple stops that could otherwise occur in
4042 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4043 to stop if a function that has debugging information is called within
4044 the line. In other words, @code{step} @emph{steps inside} any functions
4045 called within the line.
4047 Also, the @code{step} command only enters a function if there is line
4048 number information for the function. Otherwise it acts like the
4049 @code{next} command. This avoids problems when using @code{cc -gl}
4050 on MIPS machines. Previously, @code{step} entered subroutines if there
4051 was any debugging information about the routine.
4053 @item step @var{count}
4054 Continue running as in @code{step}, but do so @var{count} times. If a
4055 breakpoint is reached, or a signal not related to stepping occurs before
4056 @var{count} steps, stepping stops right away.
4059 @kindex n @r{(@code{next})}
4060 @item next @r{[}@var{count}@r{]}
4061 Continue to the next source line in the current (innermost) stack frame.
4062 This is similar to @code{step}, but function calls that appear within
4063 the line of code are executed without stopping. Execution stops when
4064 control reaches a different line of code at the original stack level
4065 that was executing when you gave the @code{next} command. This command
4066 is abbreviated @code{n}.
4068 An argument @var{count} is a repeat count, as for @code{step}.
4071 @c FIX ME!! Do we delete this, or is there a way it fits in with
4072 @c the following paragraph? --- Vctoria
4074 @c @code{next} within a function that lacks debugging information acts like
4075 @c @code{step}, but any function calls appearing within the code of the
4076 @c function are executed without stopping.
4078 The @code{next} command only stops at the first instruction of a
4079 source line. This prevents multiple stops that could otherwise occur in
4080 @code{switch} statements, @code{for} loops, etc.
4082 @kindex set step-mode
4084 @cindex functions without line info, and stepping
4085 @cindex stepping into functions with no line info
4086 @itemx set step-mode on
4087 The @code{set step-mode on} command causes the @code{step} command to
4088 stop at the first instruction of a function which contains no debug line
4089 information rather than stepping over it.
4091 This is useful in cases where you may be interested in inspecting the
4092 machine instructions of a function which has no symbolic info and do not
4093 want @value{GDBN} to automatically skip over this function.
4095 @item set step-mode off
4096 Causes the @code{step} command to step over any functions which contains no
4097 debug information. This is the default.
4099 @item show step-mode
4100 Show whether @value{GDBN} will stop in or step over functions without
4101 source line debug information.
4105 Continue running until just after function in the selected stack frame
4106 returns. Print the returned value (if any).
4108 Contrast this with the @code{return} command (@pxref{Returning,
4109 ,Returning from a Function}).
4112 @kindex u @r{(@code{until})}
4113 @cindex run until specified location
4116 Continue running until a source line past the current line, in the
4117 current stack frame, is reached. This command is used to avoid single
4118 stepping through a loop more than once. It is like the @code{next}
4119 command, except that when @code{until} encounters a jump, it
4120 automatically continues execution until the program counter is greater
4121 than the address of the jump.
4123 This means that when you reach the end of a loop after single stepping
4124 though it, @code{until} makes your program continue execution until it
4125 exits the loop. In contrast, a @code{next} command at the end of a loop
4126 simply steps back to the beginning of the loop, which forces you to step
4127 through the next iteration.
4129 @code{until} always stops your program if it attempts to exit the current
4132 @code{until} may produce somewhat counterintuitive results if the order
4133 of machine code does not match the order of the source lines. For
4134 example, in the following excerpt from a debugging session, the @code{f}
4135 (@code{frame}) command shows that execution is stopped at line
4136 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4140 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4142 (@value{GDBP}) until
4143 195 for ( ; argc > 0; NEXTARG) @{
4146 This happened because, for execution efficiency, the compiler had
4147 generated code for the loop closure test at the end, rather than the
4148 start, of the loop---even though the test in a C @code{for}-loop is
4149 written before the body of the loop. The @code{until} command appeared
4150 to step back to the beginning of the loop when it advanced to this
4151 expression; however, it has not really gone to an earlier
4152 statement---not in terms of the actual machine code.
4154 @code{until} with no argument works by means of single
4155 instruction stepping, and hence is slower than @code{until} with an
4158 @item until @var{location}
4159 @itemx u @var{location}
4160 Continue running your program until either the specified location is
4161 reached, or the current stack frame returns. @var{location} is any of
4162 the forms described in @ref{Specify Location}.
4163 This form of the command uses temporary breakpoints, and
4164 hence is quicker than @code{until} without an argument. The specified
4165 location is actually reached only if it is in the current frame. This
4166 implies that @code{until} can be used to skip over recursive function
4167 invocations. For instance in the code below, if the current location is
4168 line @code{96}, issuing @code{until 99} will execute the program up to
4169 line @code{99} in the same invocation of factorial, i.e., after the inner
4170 invocations have returned.
4173 94 int factorial (int value)
4175 96 if (value > 1) @{
4176 97 value *= factorial (value - 1);
4183 @kindex advance @var{location}
4184 @itemx advance @var{location}
4185 Continue running the program up to the given @var{location}. An argument is
4186 required, which should be of one of the forms described in
4187 @ref{Specify Location}.
4188 Execution will also stop upon exit from the current stack
4189 frame. This command is similar to @code{until}, but @code{advance} will
4190 not skip over recursive function calls, and the target location doesn't
4191 have to be in the same frame as the current one.
4195 @kindex si @r{(@code{stepi})}
4197 @itemx stepi @var{arg}
4199 Execute one machine instruction, then stop and return to the debugger.
4201 It is often useful to do @samp{display/i $pc} when stepping by machine
4202 instructions. This makes @value{GDBN} automatically display the next
4203 instruction to be executed, each time your program stops. @xref{Auto
4204 Display,, Automatic Display}.
4206 An argument is a repeat count, as in @code{step}.
4210 @kindex ni @r{(@code{nexti})}
4212 @itemx nexti @var{arg}
4214 Execute one machine instruction, but if it is a function call,
4215 proceed until the function returns.
4217 An argument is a repeat count, as in @code{next}.
4224 A signal is an asynchronous event that can happen in a program. The
4225 operating system defines the possible kinds of signals, and gives each
4226 kind a name and a number. For example, in Unix @code{SIGINT} is the
4227 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4228 @code{SIGSEGV} is the signal a program gets from referencing a place in
4229 memory far away from all the areas in use; @code{SIGALRM} occurs when
4230 the alarm clock timer goes off (which happens only if your program has
4231 requested an alarm).
4233 @cindex fatal signals
4234 Some signals, including @code{SIGALRM}, are a normal part of the
4235 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4236 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4237 program has not specified in advance some other way to handle the signal.
4238 @code{SIGINT} does not indicate an error in your program, but it is normally
4239 fatal so it can carry out the purpose of the interrupt: to kill the program.
4241 @value{GDBN} has the ability to detect any occurrence of a signal in your
4242 program. You can tell @value{GDBN} in advance what to do for each kind of
4245 @cindex handling signals
4246 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4247 @code{SIGALRM} be silently passed to your program
4248 (so as not to interfere with their role in the program's functioning)
4249 but to stop your program immediately whenever an error signal happens.
4250 You can change these settings with the @code{handle} command.
4253 @kindex info signals
4257 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4258 handle each one. You can use this to see the signal numbers of all
4259 the defined types of signals.
4261 @item info signals @var{sig}
4262 Similar, but print information only about the specified signal number.
4264 @code{info handle} is an alias for @code{info signals}.
4267 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4268 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4269 can be the number of a signal or its name (with or without the
4270 @samp{SIG} at the beginning); a list of signal numbers of the form
4271 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4272 known signals. Optional arguments @var{keywords}, described below,
4273 say what change to make.
4277 The keywords allowed by the @code{handle} command can be abbreviated.
4278 Their full names are:
4282 @value{GDBN} should not stop your program when this signal happens. It may
4283 still print a message telling you that the signal has come in.
4286 @value{GDBN} should stop your program when this signal happens. This implies
4287 the @code{print} keyword as well.
4290 @value{GDBN} should print a message when this signal happens.
4293 @value{GDBN} should not mention the occurrence of the signal at all. This
4294 implies the @code{nostop} keyword as well.
4298 @value{GDBN} should allow your program to see this signal; your program
4299 can handle the signal, or else it may terminate if the signal is fatal
4300 and not handled. @code{pass} and @code{noignore} are synonyms.
4304 @value{GDBN} should not allow your program to see this signal.
4305 @code{nopass} and @code{ignore} are synonyms.
4309 When a signal stops your program, the signal is not visible to the
4311 continue. Your program sees the signal then, if @code{pass} is in
4312 effect for the signal in question @emph{at that time}. In other words,
4313 after @value{GDBN} reports a signal, you can use the @code{handle}
4314 command with @code{pass} or @code{nopass} to control whether your
4315 program sees that signal when you continue.
4317 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4318 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4319 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4322 You can also use the @code{signal} command to prevent your program from
4323 seeing a signal, or cause it to see a signal it normally would not see,
4324 or to give it any signal at any time. For example, if your program stopped
4325 due to some sort of memory reference error, you might store correct
4326 values into the erroneous variables and continue, hoping to see more
4327 execution; but your program would probably terminate immediately as
4328 a result of the fatal signal once it saw the signal. To prevent this,
4329 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4333 @section Stopping and Starting Multi-thread Programs
4335 When your program has multiple threads (@pxref{Threads,, Debugging
4336 Programs with Multiple Threads}), you can choose whether to set
4337 breakpoints on all threads, or on a particular thread.
4340 @cindex breakpoints and threads
4341 @cindex thread breakpoints
4342 @kindex break @dots{} thread @var{threadno}
4343 @item break @var{linespec} thread @var{threadno}
4344 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4345 @var{linespec} specifies source lines; there are several ways of
4346 writing them (@pxref{Specify Location}), but the effect is always to
4347 specify some source line.
4349 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4350 to specify that you only want @value{GDBN} to stop the program when a
4351 particular thread reaches this breakpoint. @var{threadno} is one of the
4352 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4353 column of the @samp{info threads} display.
4355 If you do not specify @samp{thread @var{threadno}} when you set a
4356 breakpoint, the breakpoint applies to @emph{all} threads of your
4359 You can use the @code{thread} qualifier on conditional breakpoints as
4360 well; in this case, place @samp{thread @var{threadno}} before the
4361 breakpoint condition, like this:
4364 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4369 @cindex stopped threads
4370 @cindex threads, stopped
4371 Whenever your program stops under @value{GDBN} for any reason,
4372 @emph{all} threads of execution stop, not just the current thread. This
4373 allows you to examine the overall state of the program, including
4374 switching between threads, without worrying that things may change
4377 @cindex thread breakpoints and system calls
4378 @cindex system calls and thread breakpoints
4379 @cindex premature return from system calls
4380 There is an unfortunate side effect. If one thread stops for a
4381 breakpoint, or for some other reason, and another thread is blocked in a
4382 system call, then the system call may return prematurely. This is a
4383 consequence of the interaction between multiple threads and the signals
4384 that @value{GDBN} uses to implement breakpoints and other events that
4387 To handle this problem, your program should check the return value of
4388 each system call and react appropriately. This is good programming
4391 For example, do not write code like this:
4397 The call to @code{sleep} will return early if a different thread stops
4398 at a breakpoint or for some other reason.
4400 Instead, write this:
4405 unslept = sleep (unslept);
4408 A system call is allowed to return early, so the system is still
4409 conforming to its specification. But @value{GDBN} does cause your
4410 multi-threaded program to behave differently than it would without
4413 Also, @value{GDBN} uses internal breakpoints in the thread library to
4414 monitor certain events such as thread creation and thread destruction.
4415 When such an event happens, a system call in another thread may return
4416 prematurely, even though your program does not appear to stop.
4418 @cindex continuing threads
4419 @cindex threads, continuing
4420 Conversely, whenever you restart the program, @emph{all} threads start
4421 executing. @emph{This is true even when single-stepping} with commands
4422 like @code{step} or @code{next}.
4424 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4425 Since thread scheduling is up to your debugging target's operating
4426 system (not controlled by @value{GDBN}), other threads may
4427 execute more than one statement while the current thread completes a
4428 single step. Moreover, in general other threads stop in the middle of a
4429 statement, rather than at a clean statement boundary, when the program
4432 You might even find your program stopped in another thread after
4433 continuing or even single-stepping. This happens whenever some other
4434 thread runs into a breakpoint, a signal, or an exception before the
4435 first thread completes whatever you requested.
4437 On some OSes, you can lock the OS scheduler and thus allow only a single
4441 @item set scheduler-locking @var{mode}
4442 @cindex scheduler locking mode
4443 @cindex lock scheduler
4444 Set the scheduler locking mode. If it is @code{off}, then there is no
4445 locking and any thread may run at any time. If @code{on}, then only the
4446 current thread may run when the inferior is resumed. The @code{step}
4447 mode optimizes for single-stepping. It stops other threads from
4448 ``seizing the prompt'' by preempting the current thread while you are
4449 stepping. Other threads will only rarely (or never) get a chance to run
4450 when you step. They are more likely to run when you @samp{next} over a
4451 function call, and they are completely free to run when you use commands
4452 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4453 thread hits a breakpoint during its timeslice, they will never steal the
4454 @value{GDBN} prompt away from the thread that you are debugging.
4456 @item show scheduler-locking
4457 Display the current scheduler locking mode.
4462 @chapter Examining the Stack
4464 When your program has stopped, the first thing you need to know is where it
4465 stopped and how it got there.
4468 Each time your program performs a function call, information about the call
4470 That information includes the location of the call in your program,
4471 the arguments of the call,
4472 and the local variables of the function being called.
4473 The information is saved in a block of data called a @dfn{stack frame}.
4474 The stack frames are allocated in a region of memory called the @dfn{call
4477 When your program stops, the @value{GDBN} commands for examining the
4478 stack allow you to see all of this information.
4480 @cindex selected frame
4481 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4482 @value{GDBN} commands refer implicitly to the selected frame. In
4483 particular, whenever you ask @value{GDBN} for the value of a variable in
4484 your program, the value is found in the selected frame. There are
4485 special @value{GDBN} commands to select whichever frame you are
4486 interested in. @xref{Selection, ,Selecting a Frame}.
4488 When your program stops, @value{GDBN} automatically selects the
4489 currently executing frame and describes it briefly, similar to the
4490 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4493 * Frames:: Stack frames
4494 * Backtrace:: Backtraces
4495 * Selection:: Selecting a frame
4496 * Frame Info:: Information on a frame
4501 @section Stack Frames
4503 @cindex frame, definition
4505 The call stack is divided up into contiguous pieces called @dfn{stack
4506 frames}, or @dfn{frames} for short; each frame is the data associated
4507 with one call to one function. The frame contains the arguments given
4508 to the function, the function's local variables, and the address at
4509 which the function is executing.
4511 @cindex initial frame
4512 @cindex outermost frame
4513 @cindex innermost frame
4514 When your program is started, the stack has only one frame, that of the
4515 function @code{main}. This is called the @dfn{initial} frame or the
4516 @dfn{outermost} frame. Each time a function is called, a new frame is
4517 made. Each time a function returns, the frame for that function invocation
4518 is eliminated. If a function is recursive, there can be many frames for
4519 the same function. The frame for the function in which execution is
4520 actually occurring is called the @dfn{innermost} frame. This is the most
4521 recently created of all the stack frames that still exist.
4523 @cindex frame pointer
4524 Inside your program, stack frames are identified by their addresses. A
4525 stack frame consists of many bytes, each of which has its own address; each
4526 kind of computer has a convention for choosing one byte whose
4527 address serves as the address of the frame. Usually this address is kept
4528 in a register called the @dfn{frame pointer register}
4529 (@pxref{Registers, $fp}) while execution is going on in that frame.
4531 @cindex frame number
4532 @value{GDBN} assigns numbers to all existing stack frames, starting with
4533 zero for the innermost frame, one for the frame that called it,
4534 and so on upward. These numbers do not really exist in your program;
4535 they are assigned by @value{GDBN} to give you a way of designating stack
4536 frames in @value{GDBN} commands.
4538 @c The -fomit-frame-pointer below perennially causes hbox overflow
4539 @c underflow problems.
4540 @cindex frameless execution
4541 Some compilers provide a way to compile functions so that they operate
4542 without stack frames. (For example, the @value{NGCC} option
4544 @samp{-fomit-frame-pointer}
4546 generates functions without a frame.)
4547 This is occasionally done with heavily used library functions to save
4548 the frame setup time. @value{GDBN} has limited facilities for dealing
4549 with these function invocations. If the innermost function invocation
4550 has no stack frame, @value{GDBN} nevertheless regards it as though
4551 it had a separate frame, which is numbered zero as usual, allowing
4552 correct tracing of the function call chain. However, @value{GDBN} has
4553 no provision for frameless functions elsewhere in the stack.
4556 @kindex frame@r{, command}
4557 @cindex current stack frame
4558 @item frame @var{args}
4559 The @code{frame} command allows you to move from one stack frame to another,
4560 and to print the stack frame you select. @var{args} may be either the
4561 address of the frame or the stack frame number. Without an argument,
4562 @code{frame} prints the current stack frame.
4564 @kindex select-frame
4565 @cindex selecting frame silently
4567 The @code{select-frame} command allows you to move from one stack frame
4568 to another without printing the frame. This is the silent version of
4576 @cindex call stack traces
4577 A backtrace is a summary of how your program got where it is. It shows one
4578 line per frame, for many frames, starting with the currently executing
4579 frame (frame zero), followed by its caller (frame one), and on up the
4584 @kindex bt @r{(@code{backtrace})}
4587 Print a backtrace of the entire stack: one line per frame for all
4588 frames in the stack.
4590 You can stop the backtrace at any time by typing the system interrupt
4591 character, normally @kbd{Ctrl-c}.
4593 @item backtrace @var{n}
4595 Similar, but print only the innermost @var{n} frames.
4597 @item backtrace -@var{n}
4599 Similar, but print only the outermost @var{n} frames.
4601 @item backtrace full
4603 @itemx bt full @var{n}
4604 @itemx bt full -@var{n}
4605 Print the values of the local variables also. @var{n} specifies the
4606 number of frames to print, as described above.
4611 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4612 are additional aliases for @code{backtrace}.
4614 @cindex multiple threads, backtrace
4615 In a multi-threaded program, @value{GDBN} by default shows the
4616 backtrace only for the current thread. To display the backtrace for
4617 several or all of the threads, use the command @code{thread apply}
4618 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4619 apply all backtrace}, @value{GDBN} will display the backtrace for all
4620 the threads; this is handy when you debug a core dump of a
4621 multi-threaded program.
4623 Each line in the backtrace shows the frame number and the function name.
4624 The program counter value is also shown---unless you use @code{set
4625 print address off}. The backtrace also shows the source file name and
4626 line number, as well as the arguments to the function. The program
4627 counter value is omitted if it is at the beginning of the code for that
4630 Here is an example of a backtrace. It was made with the command
4631 @samp{bt 3}, so it shows the innermost three frames.
4635 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4637 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4638 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4640 (More stack frames follow...)
4645 The display for frame zero does not begin with a program counter
4646 value, indicating that your program has stopped at the beginning of the
4647 code for line @code{993} of @code{builtin.c}.
4649 @cindex value optimized out, in backtrace
4650 @cindex function call arguments, optimized out
4651 If your program was compiled with optimizations, some compilers will
4652 optimize away arguments passed to functions if those arguments are
4653 never used after the call. Such optimizations generate code that
4654 passes arguments through registers, but doesn't store those arguments
4655 in the stack frame. @value{GDBN} has no way of displaying such
4656 arguments in stack frames other than the innermost one. Here's what
4657 such a backtrace might look like:
4661 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4663 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4664 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4666 (More stack frames follow...)
4671 The values of arguments that were not saved in their stack frames are
4672 shown as @samp{<value optimized out>}.
4674 If you need to display the values of such optimized-out arguments,
4675 either deduce that from other variables whose values depend on the one
4676 you are interested in, or recompile without optimizations.
4678 @cindex backtrace beyond @code{main} function
4679 @cindex program entry point
4680 @cindex startup code, and backtrace
4681 Most programs have a standard user entry point---a place where system
4682 libraries and startup code transition into user code. For C this is
4683 @code{main}@footnote{
4684 Note that embedded programs (the so-called ``free-standing''
4685 environment) are not required to have a @code{main} function as the
4686 entry point. They could even have multiple entry points.}.
4687 When @value{GDBN} finds the entry function in a backtrace
4688 it will terminate the backtrace, to avoid tracing into highly
4689 system-specific (and generally uninteresting) code.
4691 If you need to examine the startup code, or limit the number of levels
4692 in a backtrace, you can change this behavior:
4695 @item set backtrace past-main
4696 @itemx set backtrace past-main on
4697 @kindex set backtrace
4698 Backtraces will continue past the user entry point.
4700 @item set backtrace past-main off
4701 Backtraces will stop when they encounter the user entry point. This is the
4704 @item show backtrace past-main
4705 @kindex show backtrace
4706 Display the current user entry point backtrace policy.
4708 @item set backtrace past-entry
4709 @itemx set backtrace past-entry on
4710 Backtraces will continue past the internal entry point of an application.
4711 This entry point is encoded by the linker when the application is built,
4712 and is likely before the user entry point @code{main} (or equivalent) is called.
4714 @item set backtrace past-entry off
4715 Backtraces will stop when they encounter the internal entry point of an
4716 application. This is the default.
4718 @item show backtrace past-entry
4719 Display the current internal entry point backtrace policy.
4721 @item set backtrace limit @var{n}
4722 @itemx set backtrace limit 0
4723 @cindex backtrace limit
4724 Limit the backtrace to @var{n} levels. A value of zero means
4727 @item show backtrace limit
4728 Display the current limit on backtrace levels.
4732 @section Selecting a Frame
4734 Most commands for examining the stack and other data in your program work on
4735 whichever stack frame is selected at the moment. Here are the commands for
4736 selecting a stack frame; all of them finish by printing a brief description
4737 of the stack frame just selected.
4740 @kindex frame@r{, selecting}
4741 @kindex f @r{(@code{frame})}
4744 Select frame number @var{n}. Recall that frame zero is the innermost
4745 (currently executing) frame, frame one is the frame that called the
4746 innermost one, and so on. The highest-numbered frame is the one for
4749 @item frame @var{addr}
4751 Select the frame at address @var{addr}. This is useful mainly if the
4752 chaining of stack frames has been damaged by a bug, making it
4753 impossible for @value{GDBN} to assign numbers properly to all frames. In
4754 addition, this can be useful when your program has multiple stacks and
4755 switches between them.
4757 On the SPARC architecture, @code{frame} needs two addresses to
4758 select an arbitrary frame: a frame pointer and a stack pointer.
4760 On the MIPS and Alpha architecture, it needs two addresses: a stack
4761 pointer and a program counter.
4763 On the 29k architecture, it needs three addresses: a register stack
4764 pointer, a program counter, and a memory stack pointer.
4768 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4769 advances toward the outermost frame, to higher frame numbers, to frames
4770 that have existed longer. @var{n} defaults to one.
4773 @kindex do @r{(@code{down})}
4775 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4776 advances toward the innermost frame, to lower frame numbers, to frames
4777 that were created more recently. @var{n} defaults to one. You may
4778 abbreviate @code{down} as @code{do}.
4781 All of these commands end by printing two lines of output describing the
4782 frame. The first line shows the frame number, the function name, the
4783 arguments, and the source file and line number of execution in that
4784 frame. The second line shows the text of that source line.
4792 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4794 10 read_input_file (argv[i]);
4798 After such a printout, the @code{list} command with no arguments
4799 prints ten lines centered on the point of execution in the frame.
4800 You can also edit the program at the point of execution with your favorite
4801 editing program by typing @code{edit}.
4802 @xref{List, ,Printing Source Lines},
4806 @kindex down-silently
4808 @item up-silently @var{n}
4809 @itemx down-silently @var{n}
4810 These two commands are variants of @code{up} and @code{down},
4811 respectively; they differ in that they do their work silently, without
4812 causing display of the new frame. They are intended primarily for use
4813 in @value{GDBN} command scripts, where the output might be unnecessary and
4818 @section Information About a Frame
4820 There are several other commands to print information about the selected
4826 When used without any argument, this command does not change which
4827 frame is selected, but prints a brief description of the currently
4828 selected stack frame. It can be abbreviated @code{f}. With an
4829 argument, this command is used to select a stack frame.
4830 @xref{Selection, ,Selecting a Frame}.
4833 @kindex info f @r{(@code{info frame})}
4836 This command prints a verbose description of the selected stack frame,
4841 the address of the frame
4843 the address of the next frame down (called by this frame)
4845 the address of the next frame up (caller of this frame)
4847 the language in which the source code corresponding to this frame is written
4849 the address of the frame's arguments
4851 the address of the frame's local variables
4853 the program counter saved in it (the address of execution in the caller frame)
4855 which registers were saved in the frame
4858 @noindent The verbose description is useful when
4859 something has gone wrong that has made the stack format fail to fit
4860 the usual conventions.
4862 @item info frame @var{addr}
4863 @itemx info f @var{addr}
4864 Print a verbose description of the frame at address @var{addr}, without
4865 selecting that frame. The selected frame remains unchanged by this
4866 command. This requires the same kind of address (more than one for some
4867 architectures) that you specify in the @code{frame} command.
4868 @xref{Selection, ,Selecting a Frame}.
4872 Print the arguments of the selected frame, each on a separate line.
4876 Print the local variables of the selected frame, each on a separate
4877 line. These are all variables (declared either static or automatic)
4878 accessible at the point of execution of the selected frame.
4881 @cindex catch exceptions, list active handlers
4882 @cindex exception handlers, how to list
4884 Print a list of all the exception handlers that are active in the
4885 current stack frame at the current point of execution. To see other
4886 exception handlers, visit the associated frame (using the @code{up},
4887 @code{down}, or @code{frame} commands); then type @code{info catch}.
4888 @xref{Set Catchpoints, , Setting Catchpoints}.
4894 @chapter Examining Source Files
4896 @value{GDBN} can print parts of your program's source, since the debugging
4897 information recorded in the program tells @value{GDBN} what source files were
4898 used to build it. When your program stops, @value{GDBN} spontaneously prints
4899 the line where it stopped. Likewise, when you select a stack frame
4900 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4901 execution in that frame has stopped. You can print other portions of
4902 source files by explicit command.
4904 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4905 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4906 @value{GDBN} under @sc{gnu} Emacs}.
4909 * List:: Printing source lines
4910 * Specify Location:: How to specify code locations
4911 * Edit:: Editing source files
4912 * Search:: Searching source files
4913 * Source Path:: Specifying source directories
4914 * Machine Code:: Source and machine code
4918 @section Printing Source Lines
4921 @kindex l @r{(@code{list})}
4922 To print lines from a source file, use the @code{list} command
4923 (abbreviated @code{l}). By default, ten lines are printed.
4924 There are several ways to specify what part of the file you want to
4925 print; see @ref{Specify Location}, for the full list.
4927 Here are the forms of the @code{list} command most commonly used:
4930 @item list @var{linenum}
4931 Print lines centered around line number @var{linenum} in the
4932 current source file.
4934 @item list @var{function}
4935 Print lines centered around the beginning of function
4939 Print more lines. If the last lines printed were printed with a
4940 @code{list} command, this prints lines following the last lines
4941 printed; however, if the last line printed was a solitary line printed
4942 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4943 Stack}), this prints lines centered around that line.
4946 Print lines just before the lines last printed.
4949 @cindex @code{list}, how many lines to display
4950 By default, @value{GDBN} prints ten source lines with any of these forms of
4951 the @code{list} command. You can change this using @code{set listsize}:
4954 @kindex set listsize
4955 @item set listsize @var{count}
4956 Make the @code{list} command display @var{count} source lines (unless
4957 the @code{list} argument explicitly specifies some other number).
4959 @kindex show listsize
4961 Display the number of lines that @code{list} prints.
4964 Repeating a @code{list} command with @key{RET} discards the argument,
4965 so it is equivalent to typing just @code{list}. This is more useful
4966 than listing the same lines again. An exception is made for an
4967 argument of @samp{-}; that argument is preserved in repetition so that
4968 each repetition moves up in the source file.
4970 In general, the @code{list} command expects you to supply zero, one or two
4971 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4972 of writing them (@pxref{Specify Location}), but the effect is always
4973 to specify some source line.
4975 Here is a complete description of the possible arguments for @code{list}:
4978 @item list @var{linespec}
4979 Print lines centered around the line specified by @var{linespec}.
4981 @item list @var{first},@var{last}
4982 Print lines from @var{first} to @var{last}. Both arguments are
4983 linespecs. When a @code{list} command has two linespecs, and the
4984 source file of the second linespec is omitted, this refers to
4985 the same source file as the first linespec.
4987 @item list ,@var{last}
4988 Print lines ending with @var{last}.
4990 @item list @var{first},
4991 Print lines starting with @var{first}.
4994 Print lines just after the lines last printed.
4997 Print lines just before the lines last printed.
5000 As described in the preceding table.
5003 @node Specify Location
5004 @section Specifying a Location
5005 @cindex specifying location
5008 Several @value{GDBN} commands accept arguments that specify a location
5009 of your program's code. Since @value{GDBN} is a source-level
5010 debugger, a location usually specifies some line in the source code;
5011 for that reason, locations are also known as @dfn{linespecs}.
5013 Here are all the different ways of specifying a code location that
5014 @value{GDBN} understands:
5018 Specifies the line number @var{linenum} of the current source file.
5021 @itemx +@var{offset}
5022 Specifies the line @var{offset} lines before or after the @dfn{current
5023 line}. For the @code{list} command, the current line is the last one
5024 printed; for the breakpoint commands, this is the line at which
5025 execution stopped in the currently selected @dfn{stack frame}
5026 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5027 used as the second of the two linespecs in a @code{list} command,
5028 this specifies the line @var{offset} lines up or down from the first
5031 @item @var{filename}:@var{linenum}
5032 Specifies the line @var{linenum} in the source file @var{filename}.
5034 @item @var{function}
5035 Specifies the line that begins the body of the function @var{function}.
5036 For example, in C, this is the line with the open brace.
5038 @item @var{filename}:@var{function}
5039 Specifies the line that begins the body of the function @var{function}
5040 in the file @var{filename}. You only need the file name with a
5041 function name to avoid ambiguity when there are identically named
5042 functions in different source files.
5044 @item *@var{address}
5045 Specifies the program address @var{address}. For line-oriented
5046 commands, such as @code{list} and @code{edit}, this specifies a source
5047 line that contains @var{address}. For @code{break} and other
5048 breakpoint oriented commands, this can be used to set breakpoints in
5049 parts of your program which do not have debugging information or
5052 Here @var{address} may be any expression valid in the current working
5053 language (@pxref{Languages, working language}) that specifies a code
5054 address. In addition, as a convenience, @value{GDBN} extends the
5055 semantics of expressions used in locations to cover the situations
5056 that frequently happen during debugging. Here are the various forms
5060 @item @var{expression}
5061 Any expression valid in the current working language.
5063 @item @var{funcaddr}
5064 An address of a function or procedure derived from its name. In C,
5065 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5066 simply the function's name @var{function} (and actually a special case
5067 of a valid expression). In Pascal and Modula-2, this is
5068 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5069 (although the Pascal form also works).
5071 This form specifies the address of the function's first instruction,
5072 before the stack frame and arguments have been set up.
5074 @item '@var{filename}'::@var{funcaddr}
5075 Like @var{funcaddr} above, but also specifies the name of the source
5076 file explicitly. This is useful if the name of the function does not
5077 specify the function unambiguously, e.g., if there are several
5078 functions with identical names in different source files.
5085 @section Editing Source Files
5086 @cindex editing source files
5089 @kindex e @r{(@code{edit})}
5090 To edit the lines in a source file, use the @code{edit} command.
5091 The editing program of your choice
5092 is invoked with the current line set to
5093 the active line in the program.
5094 Alternatively, there are several ways to specify what part of the file you
5095 want to print if you want to see other parts of the program:
5098 @item edit @var{location}
5099 Edit the source file specified by @code{location}. Editing starts at
5100 that @var{location}, e.g., at the specified source line of the
5101 specified file. @xref{Specify Location}, for all the possible forms
5102 of the @var{location} argument; here are the forms of the @code{edit}
5103 command most commonly used:
5106 @item edit @var{number}
5107 Edit the current source file with @var{number} as the active line number.
5109 @item edit @var{function}
5110 Edit the file containing @var{function} at the beginning of its definition.
5115 @subsection Choosing your Editor
5116 You can customize @value{GDBN} to use any editor you want
5118 The only restriction is that your editor (say @code{ex}), recognizes the
5119 following command-line syntax:
5121 ex +@var{number} file
5123 The optional numeric value +@var{number} specifies the number of the line in
5124 the file where to start editing.}.
5125 By default, it is @file{@value{EDITOR}}, but you can change this
5126 by setting the environment variable @code{EDITOR} before using
5127 @value{GDBN}. For example, to configure @value{GDBN} to use the
5128 @code{vi} editor, you could use these commands with the @code{sh} shell:
5134 or in the @code{csh} shell,
5136 setenv EDITOR /usr/bin/vi
5141 @section Searching Source Files
5142 @cindex searching source files
5144 There are two commands for searching through the current source file for a
5149 @kindex forward-search
5150 @item forward-search @var{regexp}
5151 @itemx search @var{regexp}
5152 The command @samp{forward-search @var{regexp}} checks each line,
5153 starting with the one following the last line listed, for a match for
5154 @var{regexp}. It lists the line that is found. You can use the
5155 synonym @samp{search @var{regexp}} or abbreviate the command name as
5158 @kindex reverse-search
5159 @item reverse-search @var{regexp}
5160 The command @samp{reverse-search @var{regexp}} checks each line, starting
5161 with the one before the last line listed and going backward, for a match
5162 for @var{regexp}. It lists the line that is found. You can abbreviate
5163 this command as @code{rev}.
5167 @section Specifying Source Directories
5170 @cindex directories for source files
5171 Executable programs sometimes do not record the directories of the source
5172 files from which they were compiled, just the names. Even when they do,
5173 the directories could be moved between the compilation and your debugging
5174 session. @value{GDBN} has a list of directories to search for source files;
5175 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5176 it tries all the directories in the list, in the order they are present
5177 in the list, until it finds a file with the desired name.
5179 For example, suppose an executable references the file
5180 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5181 @file{/mnt/cross}. The file is first looked up literally; if this
5182 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5183 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5184 message is printed. @value{GDBN} does not look up the parts of the
5185 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5186 Likewise, the subdirectories of the source path are not searched: if
5187 the source path is @file{/mnt/cross}, and the binary refers to
5188 @file{foo.c}, @value{GDBN} would not find it under
5189 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5191 Plain file names, relative file names with leading directories, file
5192 names containing dots, etc.@: are all treated as described above; for
5193 instance, if the source path is @file{/mnt/cross}, and the source file
5194 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5195 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5196 that---@file{/mnt/cross/foo.c}.
5198 Note that the executable search path is @emph{not} used to locate the
5201 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5202 any information it has cached about where source files are found and where
5203 each line is in the file.
5207 When you start @value{GDBN}, its source path includes only @samp{cdir}
5208 and @samp{cwd}, in that order.
5209 To add other directories, use the @code{directory} command.
5211 The search path is used to find both program source files and @value{GDBN}
5212 script files (read using the @samp{-command} option and @samp{source} command).
5214 In addition to the source path, @value{GDBN} provides a set of commands
5215 that manage a list of source path substitution rules. A @dfn{substitution
5216 rule} specifies how to rewrite source directories stored in the program's
5217 debug information in case the sources were moved to a different
5218 directory between compilation and debugging. A rule is made of
5219 two strings, the first specifying what needs to be rewritten in
5220 the path, and the second specifying how it should be rewritten.
5221 In @ref{set substitute-path}, we name these two parts @var{from} and
5222 @var{to} respectively. @value{GDBN} does a simple string replacement
5223 of @var{from} with @var{to} at the start of the directory part of the
5224 source file name, and uses that result instead of the original file
5225 name to look up the sources.
5227 Using the previous example, suppose the @file{foo-1.0} tree has been
5228 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5229 @value{GDBN} to replace @file{/usr/src} in all source path names with
5230 @file{/mnt/cross}. The first lookup will then be
5231 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5232 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5233 substitution rule, use the @code{set substitute-path} command
5234 (@pxref{set substitute-path}).
5236 To avoid unexpected substitution results, a rule is applied only if the
5237 @var{from} part of the directory name ends at a directory separator.
5238 For instance, a rule substituting @file{/usr/source} into
5239 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5240 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5241 is applied only at the beginning of the directory name, this rule will
5242 not be applied to @file{/root/usr/source/baz.c} either.
5244 In many cases, you can achieve the same result using the @code{directory}
5245 command. However, @code{set substitute-path} can be more efficient in
5246 the case where the sources are organized in a complex tree with multiple
5247 subdirectories. With the @code{directory} command, you need to add each
5248 subdirectory of your project. If you moved the entire tree while
5249 preserving its internal organization, then @code{set substitute-path}
5250 allows you to direct the debugger to all the sources with one single
5253 @code{set substitute-path} is also more than just a shortcut command.
5254 The source path is only used if the file at the original location no
5255 longer exists. On the other hand, @code{set substitute-path} modifies
5256 the debugger behavior to look at the rewritten location instead. So, if
5257 for any reason a source file that is not relevant to your executable is
5258 located at the original location, a substitution rule is the only
5259 method available to point @value{GDBN} at the new location.
5262 @item directory @var{dirname} @dots{}
5263 @item dir @var{dirname} @dots{}
5264 Add directory @var{dirname} to the front of the source path. Several
5265 directory names may be given to this command, separated by @samp{:}
5266 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5267 part of absolute file names) or
5268 whitespace. You may specify a directory that is already in the source
5269 path; this moves it forward, so @value{GDBN} searches it sooner.
5273 @vindex $cdir@r{, convenience variable}
5274 @vindex $cwd@r{, convenience variable}
5275 @cindex compilation directory
5276 @cindex current directory
5277 @cindex working directory
5278 @cindex directory, current
5279 @cindex directory, compilation
5280 You can use the string @samp{$cdir} to refer to the compilation
5281 directory (if one is recorded), and @samp{$cwd} to refer to the current
5282 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5283 tracks the current working directory as it changes during your @value{GDBN}
5284 session, while the latter is immediately expanded to the current
5285 directory at the time you add an entry to the source path.
5288 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5290 @c RET-repeat for @code{directory} is explicitly disabled, but since
5291 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5293 @item show directories
5294 @kindex show directories
5295 Print the source path: show which directories it contains.
5297 @anchor{set substitute-path}
5298 @item set substitute-path @var{from} @var{to}
5299 @kindex set substitute-path
5300 Define a source path substitution rule, and add it at the end of the
5301 current list of existing substitution rules. If a rule with the same
5302 @var{from} was already defined, then the old rule is also deleted.
5304 For example, if the file @file{/foo/bar/baz.c} was moved to
5305 @file{/mnt/cross/baz.c}, then the command
5308 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5312 will tell @value{GDBN} to replace @samp{/usr/src} with
5313 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5314 @file{baz.c} even though it was moved.
5316 In the case when more than one substitution rule have been defined,
5317 the rules are evaluated one by one in the order where they have been
5318 defined. The first one matching, if any, is selected to perform
5321 For instance, if we had entered the following commands:
5324 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5325 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5329 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5330 @file{/mnt/include/defs.h} by using the first rule. However, it would
5331 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5332 @file{/mnt/src/lib/foo.c}.
5335 @item unset substitute-path [path]
5336 @kindex unset substitute-path
5337 If a path is specified, search the current list of substitution rules
5338 for a rule that would rewrite that path. Delete that rule if found.
5339 A warning is emitted by the debugger if no rule could be found.
5341 If no path is specified, then all substitution rules are deleted.
5343 @item show substitute-path [path]
5344 @kindex show substitute-path
5345 If a path is specified, then print the source path substitution rule
5346 which would rewrite that path, if any.
5348 If no path is specified, then print all existing source path substitution
5353 If your source path is cluttered with directories that are no longer of
5354 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5355 versions of source. You can correct the situation as follows:
5359 Use @code{directory} with no argument to reset the source path to its default value.
5362 Use @code{directory} with suitable arguments to reinstall the
5363 directories you want in the source path. You can add all the
5364 directories in one command.
5368 @section Source and Machine Code
5369 @cindex source line and its code address
5371 You can use the command @code{info line} to map source lines to program
5372 addresses (and vice versa), and the command @code{disassemble} to display
5373 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5374 mode, the @code{info line} command causes the arrow to point to the
5375 line specified. Also, @code{info line} prints addresses in symbolic form as
5380 @item info line @var{linespec}
5381 Print the starting and ending addresses of the compiled code for
5382 source line @var{linespec}. You can specify source lines in any of
5383 the ways documented in @ref{Specify Location}.
5386 For example, we can use @code{info line} to discover the location of
5387 the object code for the first line of function
5388 @code{m4_changequote}:
5390 @c FIXME: I think this example should also show the addresses in
5391 @c symbolic form, as they usually would be displayed.
5393 (@value{GDBP}) info line m4_changequote
5394 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5398 @cindex code address and its source line
5399 We can also inquire (using @code{*@var{addr}} as the form for
5400 @var{linespec}) what source line covers a particular address:
5402 (@value{GDBP}) info line *0x63ff
5403 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5406 @cindex @code{$_} and @code{info line}
5407 @cindex @code{x} command, default address
5408 @kindex x@r{(examine), and} info line
5409 After @code{info line}, the default address for the @code{x} command
5410 is changed to the starting address of the line, so that @samp{x/i} is
5411 sufficient to begin examining the machine code (@pxref{Memory,
5412 ,Examining Memory}). Also, this address is saved as the value of the
5413 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5418 @cindex assembly instructions
5419 @cindex instructions, assembly
5420 @cindex machine instructions
5421 @cindex listing machine instructions
5423 This specialized command dumps a range of memory as machine
5424 instructions. The default memory range is the function surrounding the
5425 program counter of the selected frame. A single argument to this
5426 command is a program counter value; @value{GDBN} dumps the function
5427 surrounding this value. Two arguments specify a range of addresses
5428 (first inclusive, second exclusive) to dump.
5431 The following example shows the disassembly of a range of addresses of
5432 HP PA-RISC 2.0 code:
5435 (@value{GDBP}) disas 0x32c4 0x32e4
5436 Dump of assembler code from 0x32c4 to 0x32e4:
5437 0x32c4 <main+204>: addil 0,dp
5438 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5439 0x32cc <main+212>: ldil 0x3000,r31
5440 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5441 0x32d4 <main+220>: ldo 0(r31),rp
5442 0x32d8 <main+224>: addil -0x800,dp
5443 0x32dc <main+228>: ldo 0x588(r1),r26
5444 0x32e0 <main+232>: ldil 0x3000,r31
5445 End of assembler dump.
5448 Some architectures have more than one commonly-used set of instruction
5449 mnemonics or other syntax.
5451 For programs that were dynamically linked and use shared libraries,
5452 instructions that call functions or branch to locations in the shared
5453 libraries might show a seemingly bogus location---it's actually a
5454 location of the relocation table. On some architectures, @value{GDBN}
5455 might be able to resolve these to actual function names.
5458 @kindex set disassembly-flavor
5459 @cindex Intel disassembly flavor
5460 @cindex AT&T disassembly flavor
5461 @item set disassembly-flavor @var{instruction-set}
5462 Select the instruction set to use when disassembling the
5463 program via the @code{disassemble} or @code{x/i} commands.
5465 Currently this command is only defined for the Intel x86 family. You
5466 can set @var{instruction-set} to either @code{intel} or @code{att}.
5467 The default is @code{att}, the AT&T flavor used by default by Unix
5468 assemblers for x86-based targets.
5470 @kindex show disassembly-flavor
5471 @item show disassembly-flavor
5472 Show the current setting of the disassembly flavor.
5477 @chapter Examining Data
5479 @cindex printing data
5480 @cindex examining data
5483 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5484 @c document because it is nonstandard... Under Epoch it displays in a
5485 @c different window or something like that.
5486 The usual way to examine data in your program is with the @code{print}
5487 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5488 evaluates and prints the value of an expression of the language your
5489 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5490 Different Languages}).
5493 @item print @var{expr}
5494 @itemx print /@var{f} @var{expr}
5495 @var{expr} is an expression (in the source language). By default the
5496 value of @var{expr} is printed in a format appropriate to its data type;
5497 you can choose a different format by specifying @samp{/@var{f}}, where
5498 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5502 @itemx print /@var{f}
5503 @cindex reprint the last value
5504 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5505 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5506 conveniently inspect the same value in an alternative format.
5509 A more low-level way of examining data is with the @code{x} command.
5510 It examines data in memory at a specified address and prints it in a
5511 specified format. @xref{Memory, ,Examining Memory}.
5513 If you are interested in information about types, or about how the
5514 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5515 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5519 * Expressions:: Expressions
5520 * Variables:: Program variables
5521 * Arrays:: Artificial arrays
5522 * Output Formats:: Output formats
5523 * Memory:: Examining memory
5524 * Auto Display:: Automatic display
5525 * Print Settings:: Print settings
5526 * Value History:: Value history
5527 * Convenience Vars:: Convenience variables
5528 * Registers:: Registers
5529 * Floating Point Hardware:: Floating point hardware
5530 * Vector Unit:: Vector Unit
5531 * OS Information:: Auxiliary data provided by operating system
5532 * Memory Region Attributes:: Memory region attributes
5533 * Dump/Restore Files:: Copy between memory and a file
5534 * Core File Generation:: Cause a program dump its core
5535 * Character Sets:: Debugging programs that use a different
5536 character set than GDB does
5537 * Caching Remote Data:: Data caching for remote targets
5541 @section Expressions
5544 @code{print} and many other @value{GDBN} commands accept an expression and
5545 compute its value. Any kind of constant, variable or operator defined
5546 by the programming language you are using is valid in an expression in
5547 @value{GDBN}. This includes conditional expressions, function calls,
5548 casts, and string constants. It also includes preprocessor macros, if
5549 you compiled your program to include this information; see
5552 @cindex arrays in expressions
5553 @value{GDBN} supports array constants in expressions input by
5554 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5555 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5556 memory that is @code{malloc}ed in the target program.
5558 Because C is so widespread, most of the expressions shown in examples in
5559 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5560 Languages}, for information on how to use expressions in other
5563 In this section, we discuss operators that you can use in @value{GDBN}
5564 expressions regardless of your programming language.
5566 @cindex casts, in expressions
5567 Casts are supported in all languages, not just in C, because it is so
5568 useful to cast a number into a pointer in order to examine a structure
5569 at that address in memory.
5570 @c FIXME: casts supported---Mod2 true?
5572 @value{GDBN} supports these operators, in addition to those common
5573 to programming languages:
5577 @samp{@@} is a binary operator for treating parts of memory as arrays.
5578 @xref{Arrays, ,Artificial Arrays}, for more information.
5581 @samp{::} allows you to specify a variable in terms of the file or
5582 function where it is defined. @xref{Variables, ,Program Variables}.
5584 @cindex @{@var{type}@}
5585 @cindex type casting memory
5586 @cindex memory, viewing as typed object
5587 @cindex casts, to view memory
5588 @item @{@var{type}@} @var{addr}
5589 Refers to an object of type @var{type} stored at address @var{addr} in
5590 memory. @var{addr} may be any expression whose value is an integer or
5591 pointer (but parentheses are required around binary operators, just as in
5592 a cast). This construct is allowed regardless of what kind of data is
5593 normally supposed to reside at @var{addr}.
5597 @section Program Variables
5599 The most common kind of expression to use is the name of a variable
5602 Variables in expressions are understood in the selected stack frame
5603 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5607 global (or file-static)
5614 visible according to the scope rules of the
5615 programming language from the point of execution in that frame
5618 @noindent This means that in the function
5633 you can examine and use the variable @code{a} whenever your program is
5634 executing within the function @code{foo}, but you can only use or
5635 examine the variable @code{b} while your program is executing inside
5636 the block where @code{b} is declared.
5638 @cindex variable name conflict
5639 There is an exception: you can refer to a variable or function whose
5640 scope is a single source file even if the current execution point is not
5641 in this file. But it is possible to have more than one such variable or
5642 function with the same name (in different source files). If that
5643 happens, referring to that name has unpredictable effects. If you wish,
5644 you can specify a static variable in a particular function or file,
5645 using the colon-colon (@code{::}) notation:
5647 @cindex colon-colon, context for variables/functions
5649 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5650 @cindex @code{::}, context for variables/functions
5653 @var{file}::@var{variable}
5654 @var{function}::@var{variable}
5658 Here @var{file} or @var{function} is the name of the context for the
5659 static @var{variable}. In the case of file names, you can use quotes to
5660 make sure @value{GDBN} parses the file name as a single word---for example,
5661 to print a global value of @code{x} defined in @file{f2.c}:
5664 (@value{GDBP}) p 'f2.c'::x
5667 @cindex C@t{++} scope resolution
5668 This use of @samp{::} is very rarely in conflict with the very similar
5669 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5670 scope resolution operator in @value{GDBN} expressions.
5671 @c FIXME: Um, so what happens in one of those rare cases where it's in
5674 @cindex wrong values
5675 @cindex variable values, wrong
5676 @cindex function entry/exit, wrong values of variables
5677 @cindex optimized code, wrong values of variables
5679 @emph{Warning:} Occasionally, a local variable may appear to have the
5680 wrong value at certain points in a function---just after entry to a new
5681 scope, and just before exit.
5683 You may see this problem when you are stepping by machine instructions.
5684 This is because, on most machines, it takes more than one instruction to
5685 set up a stack frame (including local variable definitions); if you are
5686 stepping by machine instructions, variables may appear to have the wrong
5687 values until the stack frame is completely built. On exit, it usually
5688 also takes more than one machine instruction to destroy a stack frame;
5689 after you begin stepping through that group of instructions, local
5690 variable definitions may be gone.
5692 This may also happen when the compiler does significant optimizations.
5693 To be sure of always seeing accurate values, turn off all optimization
5696 @cindex ``No symbol "foo" in current context''
5697 Another possible effect of compiler optimizations is to optimize
5698 unused variables out of existence, or assign variables to registers (as
5699 opposed to memory addresses). Depending on the support for such cases
5700 offered by the debug info format used by the compiler, @value{GDBN}
5701 might not be able to display values for such local variables. If that
5702 happens, @value{GDBN} will print a message like this:
5705 No symbol "foo" in current context.
5708 To solve such problems, either recompile without optimizations, or use a
5709 different debug info format, if the compiler supports several such
5710 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5711 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5712 produces debug info in a format that is superior to formats such as
5713 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5714 an effective form for debug info. @xref{Debugging Options,,Options
5715 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5716 Compiler Collection (GCC)}.
5717 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5718 that are best suited to C@t{++} programs.
5720 If you ask to print an object whose contents are unknown to
5721 @value{GDBN}, e.g., because its data type is not completely specified
5722 by the debug information, @value{GDBN} will say @samp{<incomplete
5723 type>}. @xref{Symbols, incomplete type}, for more about this.
5725 Strings are identified as arrays of @code{char} values without specified
5726 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5727 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5728 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5729 defines literal string type @code{"char"} as @code{char} without a sign.
5734 signed char var1[] = "A";
5737 You get during debugging
5742 $2 = @{65 'A', 0 '\0'@}
5746 @section Artificial Arrays
5748 @cindex artificial array
5750 @kindex @@@r{, referencing memory as an array}
5751 It is often useful to print out several successive objects of the
5752 same type in memory; a section of an array, or an array of
5753 dynamically determined size for which only a pointer exists in the
5756 You can do this by referring to a contiguous span of memory as an
5757 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5758 operand of @samp{@@} should be the first element of the desired array
5759 and be an individual object. The right operand should be the desired length
5760 of the array. The result is an array value whose elements are all of
5761 the type of the left argument. The first element is actually the left
5762 argument; the second element comes from bytes of memory immediately
5763 following those that hold the first element, and so on. Here is an
5764 example. If a program says
5767 int *array = (int *) malloc (len * sizeof (int));
5771 you can print the contents of @code{array} with
5777 The left operand of @samp{@@} must reside in memory. Array values made
5778 with @samp{@@} in this way behave just like other arrays in terms of
5779 subscripting, and are coerced to pointers when used in expressions.
5780 Artificial arrays most often appear in expressions via the value history
5781 (@pxref{Value History, ,Value History}), after printing one out.
5783 Another way to create an artificial array is to use a cast.
5784 This re-interprets a value as if it were an array.
5785 The value need not be in memory:
5787 (@value{GDBP}) p/x (short[2])0x12345678
5788 $1 = @{0x1234, 0x5678@}
5791 As a convenience, if you leave the array length out (as in
5792 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5793 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5795 (@value{GDBP}) p/x (short[])0x12345678
5796 $2 = @{0x1234, 0x5678@}
5799 Sometimes the artificial array mechanism is not quite enough; in
5800 moderately complex data structures, the elements of interest may not
5801 actually be adjacent---for example, if you are interested in the values
5802 of pointers in an array. One useful work-around in this situation is
5803 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5804 Variables}) as a counter in an expression that prints the first
5805 interesting value, and then repeat that expression via @key{RET}. For
5806 instance, suppose you have an array @code{dtab} of pointers to
5807 structures, and you are interested in the values of a field @code{fv}
5808 in each structure. Here is an example of what you might type:
5818 @node Output Formats
5819 @section Output Formats
5821 @cindex formatted output
5822 @cindex output formats
5823 By default, @value{GDBN} prints a value according to its data type. Sometimes
5824 this is not what you want. For example, you might want to print a number
5825 in hex, or a pointer in decimal. Or you might want to view data in memory
5826 at a certain address as a character string or as an instruction. To do
5827 these things, specify an @dfn{output format} when you print a value.
5829 The simplest use of output formats is to say how to print a value
5830 already computed. This is done by starting the arguments of the
5831 @code{print} command with a slash and a format letter. The format
5832 letters supported are:
5836 Regard the bits of the value as an integer, and print the integer in
5840 Print as integer in signed decimal.
5843 Print as integer in unsigned decimal.
5846 Print as integer in octal.
5849 Print as integer in binary. The letter @samp{t} stands for ``two''.
5850 @footnote{@samp{b} cannot be used because these format letters are also
5851 used with the @code{x} command, where @samp{b} stands for ``byte'';
5852 see @ref{Memory,,Examining Memory}.}
5855 @cindex unknown address, locating
5856 @cindex locate address
5857 Print as an address, both absolute in hexadecimal and as an offset from
5858 the nearest preceding symbol. You can use this format used to discover
5859 where (in what function) an unknown address is located:
5862 (@value{GDBP}) p/a 0x54320
5863 $3 = 0x54320 <_initialize_vx+396>
5867 The command @code{info symbol 0x54320} yields similar results.
5868 @xref{Symbols, info symbol}.
5871 Regard as an integer and print it as a character constant. This
5872 prints both the numerical value and its character representation. The
5873 character representation is replaced with the octal escape @samp{\nnn}
5874 for characters outside the 7-bit @sc{ascii} range.
5876 Without this format, @value{GDBN} displays @code{char},
5877 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
5878 constants. Single-byte members of vectors are displayed as integer
5882 Regard the bits of the value as a floating point number and print
5883 using typical floating point syntax.
5886 @cindex printing strings
5887 @cindex printing byte arrays
5888 Regard as a string, if possible. With this format, pointers to single-byte
5889 data are displayed as null-terminated strings and arrays of single-byte data
5890 are displayed as fixed-length strings. Other values are displayed in their
5893 Without this format, @value{GDBN} displays pointers to and arrays of
5894 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
5895 strings. Single-byte members of a vector are displayed as an integer
5899 For example, to print the program counter in hex (@pxref{Registers}), type
5906 Note that no space is required before the slash; this is because command
5907 names in @value{GDBN} cannot contain a slash.
5909 To reprint the last value in the value history with a different format,
5910 you can use the @code{print} command with just a format and no
5911 expression. For example, @samp{p/x} reprints the last value in hex.
5914 @section Examining Memory
5916 You can use the command @code{x} (for ``examine'') to examine memory in
5917 any of several formats, independently of your program's data types.
5919 @cindex examining memory
5921 @kindex x @r{(examine memory)}
5922 @item x/@var{nfu} @var{addr}
5925 Use the @code{x} command to examine memory.
5928 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5929 much memory to display and how to format it; @var{addr} is an
5930 expression giving the address where you want to start displaying memory.
5931 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5932 Several commands set convenient defaults for @var{addr}.
5935 @item @var{n}, the repeat count
5936 The repeat count is a decimal integer; the default is 1. It specifies
5937 how much memory (counting by units @var{u}) to display.
5938 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5941 @item @var{f}, the display format
5942 The display format is one of the formats used by @code{print}
5943 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5944 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
5945 The default is @samp{x} (hexadecimal) initially. The default changes
5946 each time you use either @code{x} or @code{print}.
5948 @item @var{u}, the unit size
5949 The unit size is any of
5955 Halfwords (two bytes).
5957 Words (four bytes). This is the initial default.
5959 Giant words (eight bytes).
5962 Each time you specify a unit size with @code{x}, that size becomes the
5963 default unit the next time you use @code{x}. (For the @samp{s} and
5964 @samp{i} formats, the unit size is ignored and is normally not written.)
5966 @item @var{addr}, starting display address
5967 @var{addr} is the address where you want @value{GDBN} to begin displaying
5968 memory. The expression need not have a pointer value (though it may);
5969 it is always interpreted as an integer address of a byte of memory.
5970 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5971 @var{addr} is usually just after the last address examined---but several
5972 other commands also set the default address: @code{info breakpoints} (to
5973 the address of the last breakpoint listed), @code{info line} (to the
5974 starting address of a line), and @code{print} (if you use it to display
5975 a value from memory).
5978 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5979 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5980 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5981 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5982 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5984 Since the letters indicating unit sizes are all distinct from the
5985 letters specifying output formats, you do not have to remember whether
5986 unit size or format comes first; either order works. The output
5987 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5988 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5990 Even though the unit size @var{u} is ignored for the formats @samp{s}
5991 and @samp{i}, you might still want to use a count @var{n}; for example,
5992 @samp{3i} specifies that you want to see three machine instructions,
5993 including any operands. For convenience, especially when used with
5994 the @code{display} command, the @samp{i} format also prints branch delay
5995 slot instructions, if any, beyond the count specified, which immediately
5996 follow the last instruction that is within the count. The command
5997 @code{disassemble} gives an alternative way of inspecting machine
5998 instructions; see @ref{Machine Code,,Source and Machine Code}.
6000 All the defaults for the arguments to @code{x} are designed to make it
6001 easy to continue scanning memory with minimal specifications each time
6002 you use @code{x}. For example, after you have inspected three machine
6003 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6004 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6005 the repeat count @var{n} is used again; the other arguments default as
6006 for successive uses of @code{x}.
6008 @cindex @code{$_}, @code{$__}, and value history
6009 The addresses and contents printed by the @code{x} command are not saved
6010 in the value history because there is often too much of them and they
6011 would get in the way. Instead, @value{GDBN} makes these values available for
6012 subsequent use in expressions as values of the convenience variables
6013 @code{$_} and @code{$__}. After an @code{x} command, the last address
6014 examined is available for use in expressions in the convenience variable
6015 @code{$_}. The contents of that address, as examined, are available in
6016 the convenience variable @code{$__}.
6018 If the @code{x} command has a repeat count, the address and contents saved
6019 are from the last memory unit printed; this is not the same as the last
6020 address printed if several units were printed on the last line of output.
6022 @cindex remote memory comparison
6023 @cindex verify remote memory image
6024 When you are debugging a program running on a remote target machine
6025 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6026 remote machine's memory against the executable file you downloaded to
6027 the target. The @code{compare-sections} command is provided for such
6031 @kindex compare-sections
6032 @item compare-sections @r{[}@var{section-name}@r{]}
6033 Compare the data of a loadable section @var{section-name} in the
6034 executable file of the program being debugged with the same section in
6035 the remote machine's memory, and report any mismatches. With no
6036 arguments, compares all loadable sections. This command's
6037 availability depends on the target's support for the @code{"qCRC"}
6042 @section Automatic Display
6043 @cindex automatic display
6044 @cindex display of expressions
6046 If you find that you want to print the value of an expression frequently
6047 (to see how it changes), you might want to add it to the @dfn{automatic
6048 display list} so that @value{GDBN} prints its value each time your program stops.
6049 Each expression added to the list is given a number to identify it;
6050 to remove an expression from the list, you specify that number.
6051 The automatic display looks like this:
6055 3: bar[5] = (struct hack *) 0x3804
6059 This display shows item numbers, expressions and their current values. As with
6060 displays you request manually using @code{x} or @code{print}, you can
6061 specify the output format you prefer; in fact, @code{display} decides
6062 whether to use @code{print} or @code{x} depending your format
6063 specification---it uses @code{x} if you specify either the @samp{i}
6064 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6068 @item display @var{expr}
6069 Add the expression @var{expr} to the list of expressions to display
6070 each time your program stops. @xref{Expressions, ,Expressions}.
6072 @code{display} does not repeat if you press @key{RET} again after using it.
6074 @item display/@var{fmt} @var{expr}
6075 For @var{fmt} specifying only a display format and not a size or
6076 count, add the expression @var{expr} to the auto-display list but
6077 arrange to display it each time in the specified format @var{fmt}.
6078 @xref{Output Formats,,Output Formats}.
6080 @item display/@var{fmt} @var{addr}
6081 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6082 number of units, add the expression @var{addr} as a memory address to
6083 be examined each time your program stops. Examining means in effect
6084 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6087 For example, @samp{display/i $pc} can be helpful, to see the machine
6088 instruction about to be executed each time execution stops (@samp{$pc}
6089 is a common name for the program counter; @pxref{Registers, ,Registers}).
6092 @kindex delete display
6094 @item undisplay @var{dnums}@dots{}
6095 @itemx delete display @var{dnums}@dots{}
6096 Remove item numbers @var{dnums} from the list of expressions to display.
6098 @code{undisplay} does not repeat if you press @key{RET} after using it.
6099 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6101 @kindex disable display
6102 @item disable display @var{dnums}@dots{}
6103 Disable the display of item numbers @var{dnums}. A disabled display
6104 item is not printed automatically, but is not forgotten. It may be
6105 enabled again later.
6107 @kindex enable display
6108 @item enable display @var{dnums}@dots{}
6109 Enable display of item numbers @var{dnums}. It becomes effective once
6110 again in auto display of its expression, until you specify otherwise.
6113 Display the current values of the expressions on the list, just as is
6114 done when your program stops.
6116 @kindex info display
6118 Print the list of expressions previously set up to display
6119 automatically, each one with its item number, but without showing the
6120 values. This includes disabled expressions, which are marked as such.
6121 It also includes expressions which would not be displayed right now
6122 because they refer to automatic variables not currently available.
6125 @cindex display disabled out of scope
6126 If a display expression refers to local variables, then it does not make
6127 sense outside the lexical context for which it was set up. Such an
6128 expression is disabled when execution enters a context where one of its
6129 variables is not defined. For example, if you give the command
6130 @code{display last_char} while inside a function with an argument
6131 @code{last_char}, @value{GDBN} displays this argument while your program
6132 continues to stop inside that function. When it stops elsewhere---where
6133 there is no variable @code{last_char}---the display is disabled
6134 automatically. The next time your program stops where @code{last_char}
6135 is meaningful, you can enable the display expression once again.
6137 @node Print Settings
6138 @section Print Settings
6140 @cindex format options
6141 @cindex print settings
6142 @value{GDBN} provides the following ways to control how arrays, structures,
6143 and symbols are printed.
6146 These settings are useful for debugging programs in any language:
6150 @item set print address
6151 @itemx set print address on
6152 @cindex print/don't print memory addresses
6153 @value{GDBN} prints memory addresses showing the location of stack
6154 traces, structure values, pointer values, breakpoints, and so forth,
6155 even when it also displays the contents of those addresses. The default
6156 is @code{on}. For example, this is what a stack frame display looks like with
6157 @code{set print address on}:
6162 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6164 530 if (lquote != def_lquote)
6168 @item set print address off
6169 Do not print addresses when displaying their contents. For example,
6170 this is the same stack frame displayed with @code{set print address off}:
6174 (@value{GDBP}) set print addr off
6176 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6177 530 if (lquote != def_lquote)
6181 You can use @samp{set print address off} to eliminate all machine
6182 dependent displays from the @value{GDBN} interface. For example, with
6183 @code{print address off}, you should get the same text for backtraces on
6184 all machines---whether or not they involve pointer arguments.
6187 @item show print address
6188 Show whether or not addresses are to be printed.
6191 When @value{GDBN} prints a symbolic address, it normally prints the
6192 closest earlier symbol plus an offset. If that symbol does not uniquely
6193 identify the address (for example, it is a name whose scope is a single
6194 source file), you may need to clarify. One way to do this is with
6195 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6196 you can set @value{GDBN} to print the source file and line number when
6197 it prints a symbolic address:
6200 @item set print symbol-filename on
6201 @cindex source file and line of a symbol
6202 @cindex symbol, source file and line
6203 Tell @value{GDBN} to print the source file name and line number of a
6204 symbol in the symbolic form of an address.
6206 @item set print symbol-filename off
6207 Do not print source file name and line number of a symbol. This is the
6210 @item show print symbol-filename
6211 Show whether or not @value{GDBN} will print the source file name and
6212 line number of a symbol in the symbolic form of an address.
6215 Another situation where it is helpful to show symbol filenames and line
6216 numbers is when disassembling code; @value{GDBN} shows you the line
6217 number and source file that corresponds to each instruction.
6219 Also, you may wish to see the symbolic form only if the address being
6220 printed is reasonably close to the closest earlier symbol:
6223 @item set print max-symbolic-offset @var{max-offset}
6224 @cindex maximum value for offset of closest symbol
6225 Tell @value{GDBN} to only display the symbolic form of an address if the
6226 offset between the closest earlier symbol and the address is less than
6227 @var{max-offset}. The default is 0, which tells @value{GDBN}
6228 to always print the symbolic form of an address if any symbol precedes it.
6230 @item show print max-symbolic-offset
6231 Ask how large the maximum offset is that @value{GDBN} prints in a
6235 @cindex wild pointer, interpreting
6236 @cindex pointer, finding referent
6237 If you have a pointer and you are not sure where it points, try
6238 @samp{set print symbol-filename on}. Then you can determine the name
6239 and source file location of the variable where it points, using
6240 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6241 For example, here @value{GDBN} shows that a variable @code{ptt} points
6242 at another variable @code{t}, defined in @file{hi2.c}:
6245 (@value{GDBP}) set print symbol-filename on
6246 (@value{GDBP}) p/a ptt
6247 $4 = 0xe008 <t in hi2.c>
6251 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6252 does not show the symbol name and filename of the referent, even with
6253 the appropriate @code{set print} options turned on.
6256 Other settings control how different kinds of objects are printed:
6259 @item set print array
6260 @itemx set print array on
6261 @cindex pretty print arrays
6262 Pretty print arrays. This format is more convenient to read,
6263 but uses more space. The default is off.
6265 @item set print array off
6266 Return to compressed format for arrays.
6268 @item show print array
6269 Show whether compressed or pretty format is selected for displaying
6272 @cindex print array indexes
6273 @item set print array-indexes
6274 @itemx set print array-indexes on
6275 Print the index of each element when displaying arrays. May be more
6276 convenient to locate a given element in the array or quickly find the
6277 index of a given element in that printed array. The default is off.
6279 @item set print array-indexes off
6280 Stop printing element indexes when displaying arrays.
6282 @item show print array-indexes
6283 Show whether the index of each element is printed when displaying
6286 @item set print elements @var{number-of-elements}
6287 @cindex number of array elements to print
6288 @cindex limit on number of printed array elements
6289 Set a limit on how many elements of an array @value{GDBN} will print.
6290 If @value{GDBN} is printing a large array, it stops printing after it has
6291 printed the number of elements set by the @code{set print elements} command.
6292 This limit also applies to the display of strings.
6293 When @value{GDBN} starts, this limit is set to 200.
6294 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6296 @item show print elements
6297 Display the number of elements of a large array that @value{GDBN} will print.
6298 If the number is 0, then the printing is unlimited.
6300 @item set print frame-arguments @var{value}
6301 @cindex printing frame argument values
6302 @cindex print all frame argument values
6303 @cindex print frame argument values for scalars only
6304 @cindex do not print frame argument values
6305 This command allows to control how the values of arguments are printed
6306 when the debugger prints a frame (@pxref{Frames}). The possible
6311 The values of all arguments are printed. This is the default.
6314 Print the value of an argument only if it is a scalar. The value of more
6315 complex arguments such as arrays, structures, unions, etc, is replaced
6316 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6319 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6324 None of the argument values are printed. Instead, the value of each argument
6325 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6328 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6333 By default, all argument values are always printed. But this command
6334 can be useful in several cases. For instance, it can be used to reduce
6335 the amount of information printed in each frame, making the backtrace
6336 more readable. Also, this command can be used to improve performance
6337 when displaying Ada frames, because the computation of large arguments
6338 can sometimes be CPU-intensive, especiallly in large applications.
6339 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6340 avoids this computation, thus speeding up the display of each Ada frame.
6342 @item show print frame-arguments
6343 Show how the value of arguments should be displayed when printing a frame.
6345 @item set print repeats
6346 @cindex repeated array elements
6347 Set the threshold for suppressing display of repeated array
6348 elements. When the number of consecutive identical elements of an
6349 array exceeds the threshold, @value{GDBN} prints the string
6350 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6351 identical repetitions, instead of displaying the identical elements
6352 themselves. Setting the threshold to zero will cause all elements to
6353 be individually printed. The default threshold is 10.
6355 @item show print repeats
6356 Display the current threshold for printing repeated identical
6359 @item set print null-stop
6360 @cindex @sc{null} elements in arrays
6361 Cause @value{GDBN} to stop printing the characters of an array when the first
6362 @sc{null} is encountered. This is useful when large arrays actually
6363 contain only short strings.
6366 @item show print null-stop
6367 Show whether @value{GDBN} stops printing an array on the first
6368 @sc{null} character.
6370 @item set print pretty on
6371 @cindex print structures in indented form
6372 @cindex indentation in structure display
6373 Cause @value{GDBN} to print structures in an indented format with one member
6374 per line, like this:
6389 @item set print pretty off
6390 Cause @value{GDBN} to print structures in a compact format, like this:
6394 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6395 meat = 0x54 "Pork"@}
6400 This is the default format.
6402 @item show print pretty
6403 Show which format @value{GDBN} is using to print structures.
6405 @item set print sevenbit-strings on
6406 @cindex eight-bit characters in strings
6407 @cindex octal escapes in strings
6408 Print using only seven-bit characters; if this option is set,
6409 @value{GDBN} displays any eight-bit characters (in strings or
6410 character values) using the notation @code{\}@var{nnn}. This setting is
6411 best if you are working in English (@sc{ascii}) and you use the
6412 high-order bit of characters as a marker or ``meta'' bit.
6414 @item set print sevenbit-strings off
6415 Print full eight-bit characters. This allows the use of more
6416 international character sets, and is the default.
6418 @item show print sevenbit-strings
6419 Show whether or not @value{GDBN} is printing only seven-bit characters.
6421 @item set print union on
6422 @cindex unions in structures, printing
6423 Tell @value{GDBN} to print unions which are contained in structures
6424 and other unions. This is the default setting.
6426 @item set print union off
6427 Tell @value{GDBN} not to print unions which are contained in
6428 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6431 @item show print union
6432 Ask @value{GDBN} whether or not it will print unions which are contained in
6433 structures and other unions.
6435 For example, given the declarations
6438 typedef enum @{Tree, Bug@} Species;
6439 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6440 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6451 struct thing foo = @{Tree, @{Acorn@}@};
6455 with @code{set print union on} in effect @samp{p foo} would print
6458 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6462 and with @code{set print union off} in effect it would print
6465 $1 = @{it = Tree, form = @{...@}@}
6469 @code{set print union} affects programs written in C-like languages
6475 These settings are of interest when debugging C@t{++} programs:
6478 @cindex demangling C@t{++} names
6479 @item set print demangle
6480 @itemx set print demangle on
6481 Print C@t{++} names in their source form rather than in the encoded
6482 (``mangled'') form passed to the assembler and linker for type-safe
6483 linkage. The default is on.
6485 @item show print demangle
6486 Show whether C@t{++} names are printed in mangled or demangled form.
6488 @item set print asm-demangle
6489 @itemx set print asm-demangle on
6490 Print C@t{++} names in their source form rather than their mangled form, even
6491 in assembler code printouts such as instruction disassemblies.
6494 @item show print asm-demangle
6495 Show whether C@t{++} names in assembly listings are printed in mangled
6498 @cindex C@t{++} symbol decoding style
6499 @cindex symbol decoding style, C@t{++}
6500 @kindex set demangle-style
6501 @item set demangle-style @var{style}
6502 Choose among several encoding schemes used by different compilers to
6503 represent C@t{++} names. The choices for @var{style} are currently:
6507 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6510 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6511 This is the default.
6514 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6517 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6520 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6521 @strong{Warning:} this setting alone is not sufficient to allow
6522 debugging @code{cfront}-generated executables. @value{GDBN} would
6523 require further enhancement to permit that.
6526 If you omit @var{style}, you will see a list of possible formats.
6528 @item show demangle-style
6529 Display the encoding style currently in use for decoding C@t{++} symbols.
6531 @item set print object
6532 @itemx set print object on
6533 @cindex derived type of an object, printing
6534 @cindex display derived types
6535 When displaying a pointer to an object, identify the @emph{actual}
6536 (derived) type of the object rather than the @emph{declared} type, using
6537 the virtual function table.
6539 @item set print object off
6540 Display only the declared type of objects, without reference to the
6541 virtual function table. This is the default setting.
6543 @item show print object
6544 Show whether actual, or declared, object types are displayed.
6546 @item set print static-members
6547 @itemx set print static-members on
6548 @cindex static members of C@t{++} objects
6549 Print static members when displaying a C@t{++} object. The default is on.
6551 @item set print static-members off
6552 Do not print static members when displaying a C@t{++} object.
6554 @item show print static-members
6555 Show whether C@t{++} static members are printed or not.
6557 @item set print pascal_static-members
6558 @itemx set print pascal_static-members on
6559 @cindex static members of Pascal objects
6560 @cindex Pascal objects, static members display
6561 Print static members when displaying a Pascal object. The default is on.
6563 @item set print pascal_static-members off
6564 Do not print static members when displaying a Pascal object.
6566 @item show print pascal_static-members
6567 Show whether Pascal static members are printed or not.
6569 @c These don't work with HP ANSI C++ yet.
6570 @item set print vtbl
6571 @itemx set print vtbl on
6572 @cindex pretty print C@t{++} virtual function tables
6573 @cindex virtual functions (C@t{++}) display
6574 @cindex VTBL display
6575 Pretty print C@t{++} virtual function tables. The default is off.
6576 (The @code{vtbl} commands do not work on programs compiled with the HP
6577 ANSI C@t{++} compiler (@code{aCC}).)
6579 @item set print vtbl off
6580 Do not pretty print C@t{++} virtual function tables.
6582 @item show print vtbl
6583 Show whether C@t{++} virtual function tables are pretty printed, or not.
6587 @section Value History
6589 @cindex value history
6590 @cindex history of values printed by @value{GDBN}
6591 Values printed by the @code{print} command are saved in the @value{GDBN}
6592 @dfn{value history}. This allows you to refer to them in other expressions.
6593 Values are kept until the symbol table is re-read or discarded
6594 (for example with the @code{file} or @code{symbol-file} commands).
6595 When the symbol table changes, the value history is discarded,
6596 since the values may contain pointers back to the types defined in the
6601 @cindex history number
6602 The values printed are given @dfn{history numbers} by which you can
6603 refer to them. These are successive integers starting with one.
6604 @code{print} shows you the history number assigned to a value by
6605 printing @samp{$@var{num} = } before the value; here @var{num} is the
6608 To refer to any previous value, use @samp{$} followed by the value's
6609 history number. The way @code{print} labels its output is designed to
6610 remind you of this. Just @code{$} refers to the most recent value in
6611 the history, and @code{$$} refers to the value before that.
6612 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6613 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6614 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6616 For example, suppose you have just printed a pointer to a structure and
6617 want to see the contents of the structure. It suffices to type
6623 If you have a chain of structures where the component @code{next} points
6624 to the next one, you can print the contents of the next one with this:
6631 You can print successive links in the chain by repeating this
6632 command---which you can do by just typing @key{RET}.
6634 Note that the history records values, not expressions. If the value of
6635 @code{x} is 4 and you type these commands:
6643 then the value recorded in the value history by the @code{print} command
6644 remains 4 even though the value of @code{x} has changed.
6649 Print the last ten values in the value history, with their item numbers.
6650 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6651 values} does not change the history.
6653 @item show values @var{n}
6654 Print ten history values centered on history item number @var{n}.
6657 Print ten history values just after the values last printed. If no more
6658 values are available, @code{show values +} produces no display.
6661 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6662 same effect as @samp{show values +}.
6664 @node Convenience Vars
6665 @section Convenience Variables
6667 @cindex convenience variables
6668 @cindex user-defined variables
6669 @value{GDBN} provides @dfn{convenience variables} that you can use within
6670 @value{GDBN} to hold on to a value and refer to it later. These variables
6671 exist entirely within @value{GDBN}; they are not part of your program, and
6672 setting a convenience variable has no direct effect on further execution
6673 of your program. That is why you can use them freely.
6675 Convenience variables are prefixed with @samp{$}. Any name preceded by
6676 @samp{$} can be used for a convenience variable, unless it is one of
6677 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6678 (Value history references, in contrast, are @emph{numbers} preceded
6679 by @samp{$}. @xref{Value History, ,Value History}.)
6681 You can save a value in a convenience variable with an assignment
6682 expression, just as you would set a variable in your program.
6686 set $foo = *object_ptr
6690 would save in @code{$foo} the value contained in the object pointed to by
6693 Using a convenience variable for the first time creates it, but its
6694 value is @code{void} until you assign a new value. You can alter the
6695 value with another assignment at any time.
6697 Convenience variables have no fixed types. You can assign a convenience
6698 variable any type of value, including structures and arrays, even if
6699 that variable already has a value of a different type. The convenience
6700 variable, when used as an expression, has the type of its current value.
6703 @kindex show convenience
6704 @cindex show all user variables
6705 @item show convenience
6706 Print a list of convenience variables used so far, and their values.
6707 Abbreviated @code{show conv}.
6709 @kindex init-if-undefined
6710 @cindex convenience variables, initializing
6711 @item init-if-undefined $@var{variable} = @var{expression}
6712 Set a convenience variable if it has not already been set. This is useful
6713 for user-defined commands that keep some state. It is similar, in concept,
6714 to using local static variables with initializers in C (except that
6715 convenience variables are global). It can also be used to allow users to
6716 override default values used in a command script.
6718 If the variable is already defined then the expression is not evaluated so
6719 any side-effects do not occur.
6722 One of the ways to use a convenience variable is as a counter to be
6723 incremented or a pointer to be advanced. For example, to print
6724 a field from successive elements of an array of structures:
6728 print bar[$i++]->contents
6732 Repeat that command by typing @key{RET}.
6734 Some convenience variables are created automatically by @value{GDBN} and given
6735 values likely to be useful.
6738 @vindex $_@r{, convenience variable}
6740 The variable @code{$_} is automatically set by the @code{x} command to
6741 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6742 commands which provide a default address for @code{x} to examine also
6743 set @code{$_} to that address; these commands include @code{info line}
6744 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6745 except when set by the @code{x} command, in which case it is a pointer
6746 to the type of @code{$__}.
6748 @vindex $__@r{, convenience variable}
6750 The variable @code{$__} is automatically set by the @code{x} command
6751 to the value found in the last address examined. Its type is chosen
6752 to match the format in which the data was printed.
6755 @vindex $_exitcode@r{, convenience variable}
6756 The variable @code{$_exitcode} is automatically set to the exit code when
6757 the program being debugged terminates.
6760 On HP-UX systems, if you refer to a function or variable name that
6761 begins with a dollar sign, @value{GDBN} searches for a user or system
6762 name first, before it searches for a convenience variable.
6768 You can refer to machine register contents, in expressions, as variables
6769 with names starting with @samp{$}. The names of registers are different
6770 for each machine; use @code{info registers} to see the names used on
6774 @kindex info registers
6775 @item info registers
6776 Print the names and values of all registers except floating-point
6777 and vector registers (in the selected stack frame).
6779 @kindex info all-registers
6780 @cindex floating point registers
6781 @item info all-registers
6782 Print the names and values of all registers, including floating-point
6783 and vector registers (in the selected stack frame).
6785 @item info registers @var{regname} @dots{}
6786 Print the @dfn{relativized} value of each specified register @var{regname}.
6787 As discussed in detail below, register values are normally relative to
6788 the selected stack frame. @var{regname} may be any register name valid on
6789 the machine you are using, with or without the initial @samp{$}.
6792 @cindex stack pointer register
6793 @cindex program counter register
6794 @cindex process status register
6795 @cindex frame pointer register
6796 @cindex standard registers
6797 @value{GDBN} has four ``standard'' register names that are available (in
6798 expressions) on most machines---whenever they do not conflict with an
6799 architecture's canonical mnemonics for registers. The register names
6800 @code{$pc} and @code{$sp} are used for the program counter register and
6801 the stack pointer. @code{$fp} is used for a register that contains a
6802 pointer to the current stack frame, and @code{$ps} is used for a
6803 register that contains the processor status. For example,
6804 you could print the program counter in hex with
6811 or print the instruction to be executed next with
6818 or add four to the stack pointer@footnote{This is a way of removing
6819 one word from the stack, on machines where stacks grow downward in
6820 memory (most machines, nowadays). This assumes that the innermost
6821 stack frame is selected; setting @code{$sp} is not allowed when other
6822 stack frames are selected. To pop entire frames off the stack,
6823 regardless of machine architecture, use @code{return};
6824 see @ref{Returning, ,Returning from a Function}.} with
6830 Whenever possible, these four standard register names are available on
6831 your machine even though the machine has different canonical mnemonics,
6832 so long as there is no conflict. The @code{info registers} command
6833 shows the canonical names. For example, on the SPARC, @code{info
6834 registers} displays the processor status register as @code{$psr} but you
6835 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6836 is an alias for the @sc{eflags} register.
6838 @value{GDBN} always considers the contents of an ordinary register as an
6839 integer when the register is examined in this way. Some machines have
6840 special registers which can hold nothing but floating point; these
6841 registers are considered to have floating point values. There is no way
6842 to refer to the contents of an ordinary register as floating point value
6843 (although you can @emph{print} it as a floating point value with
6844 @samp{print/f $@var{regname}}).
6846 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6847 means that the data format in which the register contents are saved by
6848 the operating system is not the same one that your program normally
6849 sees. For example, the registers of the 68881 floating point
6850 coprocessor are always saved in ``extended'' (raw) format, but all C
6851 programs expect to work with ``double'' (virtual) format. In such
6852 cases, @value{GDBN} normally works with the virtual format only (the format
6853 that makes sense for your program), but the @code{info registers} command
6854 prints the data in both formats.
6856 @cindex SSE registers (x86)
6857 @cindex MMX registers (x86)
6858 Some machines have special registers whose contents can be interpreted
6859 in several different ways. For example, modern x86-based machines
6860 have SSE and MMX registers that can hold several values packed
6861 together in several different formats. @value{GDBN} refers to such
6862 registers in @code{struct} notation:
6865 (@value{GDBP}) print $xmm1
6867 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6868 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6869 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6870 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6871 v4_int32 = @{0, 20657912, 11, 13@},
6872 v2_int64 = @{88725056443645952, 55834574859@},
6873 uint128 = 0x0000000d0000000b013b36f800000000
6878 To set values of such registers, you need to tell @value{GDBN} which
6879 view of the register you wish to change, as if you were assigning
6880 value to a @code{struct} member:
6883 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6886 Normally, register values are relative to the selected stack frame
6887 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
6888 value that the register would contain if all stack frames farther in
6889 were exited and their saved registers restored. In order to see the
6890 true contents of hardware registers, you must select the innermost
6891 frame (with @samp{frame 0}).
6893 However, @value{GDBN} must deduce where registers are saved, from the machine
6894 code generated by your compiler. If some registers are not saved, or if
6895 @value{GDBN} is unable to locate the saved registers, the selected stack
6896 frame makes no difference.
6898 @node Floating Point Hardware
6899 @section Floating Point Hardware
6900 @cindex floating point
6902 Depending on the configuration, @value{GDBN} may be able to give
6903 you more information about the status of the floating point hardware.
6908 Display hardware-dependent information about the floating
6909 point unit. The exact contents and layout vary depending on the
6910 floating point chip. Currently, @samp{info float} is supported on
6911 the ARM and x86 machines.
6915 @section Vector Unit
6918 Depending on the configuration, @value{GDBN} may be able to give you
6919 more information about the status of the vector unit.
6924 Display information about the vector unit. The exact contents and
6925 layout vary depending on the hardware.
6928 @node OS Information
6929 @section Operating System Auxiliary Information
6930 @cindex OS information
6932 @value{GDBN} provides interfaces to useful OS facilities that can help
6933 you debug your program.
6935 @cindex @code{ptrace} system call
6936 @cindex @code{struct user} contents
6937 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6938 machines), it interfaces with the inferior via the @code{ptrace}
6939 system call. The operating system creates a special sata structure,
6940 called @code{struct user}, for this interface. You can use the
6941 command @code{info udot} to display the contents of this data
6947 Display the contents of the @code{struct user} maintained by the OS
6948 kernel for the program being debugged. @value{GDBN} displays the
6949 contents of @code{struct user} as a list of hex numbers, similar to
6950 the @code{examine} command.
6953 @cindex auxiliary vector
6954 @cindex vector, auxiliary
6955 Some operating systems supply an @dfn{auxiliary vector} to programs at
6956 startup. This is akin to the arguments and environment that you
6957 specify for a program, but contains a system-dependent variety of
6958 binary values that tell system libraries important details about the
6959 hardware, operating system, and process. Each value's purpose is
6960 identified by an integer tag; the meanings are well-known but system-specific.
6961 Depending on the configuration and operating system facilities,
6962 @value{GDBN} may be able to show you this information. For remote
6963 targets, this functionality may further depend on the remote stub's
6964 support of the @samp{qXfer:auxv:read} packet, see
6965 @ref{qXfer auxiliary vector read}.
6970 Display the auxiliary vector of the inferior, which can be either a
6971 live process or a core dump file. @value{GDBN} prints each tag value
6972 numerically, and also shows names and text descriptions for recognized
6973 tags. Some values in the vector are numbers, some bit masks, and some
6974 pointers to strings or other data. @value{GDBN} displays each value in the
6975 most appropriate form for a recognized tag, and in hexadecimal for
6976 an unrecognized tag.
6980 @node Memory Region Attributes
6981 @section Memory Region Attributes
6982 @cindex memory region attributes
6984 @dfn{Memory region attributes} allow you to describe special handling
6985 required by regions of your target's memory. @value{GDBN} uses
6986 attributes to determine whether to allow certain types of memory
6987 accesses; whether to use specific width accesses; and whether to cache
6988 target memory. By default the description of memory regions is
6989 fetched from the target (if the current target supports this), but the
6990 user can override the fetched regions.
6992 Defined memory regions can be individually enabled and disabled. When a
6993 memory region is disabled, @value{GDBN} uses the default attributes when
6994 accessing memory in that region. Similarly, if no memory regions have
6995 been defined, @value{GDBN} uses the default attributes when accessing
6998 When a memory region is defined, it is given a number to identify it;
6999 to enable, disable, or remove a memory region, you specify that number.
7003 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7004 Define a memory region bounded by @var{lower} and @var{upper} with
7005 attributes @var{attributes}@dots{}, and add it to the list of regions
7006 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7007 case: it is treated as the target's maximum memory address.
7008 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7011 Discard any user changes to the memory regions and use target-supplied
7012 regions, if available, or no regions if the target does not support.
7015 @item delete mem @var{nums}@dots{}
7016 Remove memory regions @var{nums}@dots{} from the list of regions
7017 monitored by @value{GDBN}.
7020 @item disable mem @var{nums}@dots{}
7021 Disable monitoring of memory regions @var{nums}@dots{}.
7022 A disabled memory region is not forgotten.
7023 It may be enabled again later.
7026 @item enable mem @var{nums}@dots{}
7027 Enable monitoring of memory regions @var{nums}@dots{}.
7031 Print a table of all defined memory regions, with the following columns
7035 @item Memory Region Number
7036 @item Enabled or Disabled.
7037 Enabled memory regions are marked with @samp{y}.
7038 Disabled memory regions are marked with @samp{n}.
7041 The address defining the inclusive lower bound of the memory region.
7044 The address defining the exclusive upper bound of the memory region.
7047 The list of attributes set for this memory region.
7052 @subsection Attributes
7054 @subsubsection Memory Access Mode
7055 The access mode attributes set whether @value{GDBN} may make read or
7056 write accesses to a memory region.
7058 While these attributes prevent @value{GDBN} from performing invalid
7059 memory accesses, they do nothing to prevent the target system, I/O DMA,
7060 etc.@: from accessing memory.
7064 Memory is read only.
7066 Memory is write only.
7068 Memory is read/write. This is the default.
7071 @subsubsection Memory Access Size
7072 The access size attribute tells @value{GDBN} to use specific sized
7073 accesses in the memory region. Often memory mapped device registers
7074 require specific sized accesses. If no access size attribute is
7075 specified, @value{GDBN} may use accesses of any size.
7079 Use 8 bit memory accesses.
7081 Use 16 bit memory accesses.
7083 Use 32 bit memory accesses.
7085 Use 64 bit memory accesses.
7088 @c @subsubsection Hardware/Software Breakpoints
7089 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7090 @c will use hardware or software breakpoints for the internal breakpoints
7091 @c used by the step, next, finish, until, etc. commands.
7095 @c Always use hardware breakpoints
7096 @c @item swbreak (default)
7099 @subsubsection Data Cache
7100 The data cache attributes set whether @value{GDBN} will cache target
7101 memory. While this generally improves performance by reducing debug
7102 protocol overhead, it can lead to incorrect results because @value{GDBN}
7103 does not know about volatile variables or memory mapped device
7108 Enable @value{GDBN} to cache target memory.
7110 Disable @value{GDBN} from caching target memory. This is the default.
7113 @subsection Memory Access Checking
7114 @value{GDBN} can be instructed to refuse accesses to memory that is
7115 not explicitly described. This can be useful if accessing such
7116 regions has undesired effects for a specific target, or to provide
7117 better error checking. The following commands control this behaviour.
7120 @kindex set mem inaccessible-by-default
7121 @item set mem inaccessible-by-default [on|off]
7122 If @code{on} is specified, make @value{GDBN} treat memory not
7123 explicitly described by the memory ranges as non-existent and refuse accesses
7124 to such memory. The checks are only performed if there's at least one
7125 memory range defined. If @code{off} is specified, make @value{GDBN}
7126 treat the memory not explicitly described by the memory ranges as RAM.
7127 The default value is @code{on}.
7128 @kindex show mem inaccessible-by-default
7129 @item show mem inaccessible-by-default
7130 Show the current handling of accesses to unknown memory.
7134 @c @subsubsection Memory Write Verification
7135 @c The memory write verification attributes set whether @value{GDBN}
7136 @c will re-reads data after each write to verify the write was successful.
7140 @c @item noverify (default)
7143 @node Dump/Restore Files
7144 @section Copy Between Memory and a File
7145 @cindex dump/restore files
7146 @cindex append data to a file
7147 @cindex dump data to a file
7148 @cindex restore data from a file
7150 You can use the commands @code{dump}, @code{append}, and
7151 @code{restore} to copy data between target memory and a file. The
7152 @code{dump} and @code{append} commands write data to a file, and the
7153 @code{restore} command reads data from a file back into the inferior's
7154 memory. Files may be in binary, Motorola S-record, Intel hex, or
7155 Tektronix Hex format; however, @value{GDBN} can only append to binary
7161 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7162 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7163 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7164 or the value of @var{expr}, to @var{filename} in the given format.
7166 The @var{format} parameter may be any one of:
7173 Motorola S-record format.
7175 Tektronix Hex format.
7178 @value{GDBN} uses the same definitions of these formats as the
7179 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7180 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7184 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7185 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7186 Append the contents of memory from @var{start_addr} to @var{end_addr},
7187 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7188 (@value{GDBN} can only append data to files in raw binary form.)
7191 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7192 Restore the contents of file @var{filename} into memory. The
7193 @code{restore} command can automatically recognize any known @sc{bfd}
7194 file format, except for raw binary. To restore a raw binary file you
7195 must specify the optional keyword @code{binary} after the filename.
7197 If @var{bias} is non-zero, its value will be added to the addresses
7198 contained in the file. Binary files always start at address zero, so
7199 they will be restored at address @var{bias}. Other bfd files have
7200 a built-in location; they will be restored at offset @var{bias}
7203 If @var{start} and/or @var{end} are non-zero, then only data between
7204 file offset @var{start} and file offset @var{end} will be restored.
7205 These offsets are relative to the addresses in the file, before
7206 the @var{bias} argument is applied.
7210 @node Core File Generation
7211 @section How to Produce a Core File from Your Program
7212 @cindex dump core from inferior
7214 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7215 image of a running process and its process status (register values
7216 etc.). Its primary use is post-mortem debugging of a program that
7217 crashed while it ran outside a debugger. A program that crashes
7218 automatically produces a core file, unless this feature is disabled by
7219 the user. @xref{Files}, for information on invoking @value{GDBN} in
7220 the post-mortem debugging mode.
7222 Occasionally, you may wish to produce a core file of the program you
7223 are debugging in order to preserve a snapshot of its state.
7224 @value{GDBN} has a special command for that.
7228 @kindex generate-core-file
7229 @item generate-core-file [@var{file}]
7230 @itemx gcore [@var{file}]
7231 Produce a core dump of the inferior process. The optional argument
7232 @var{file} specifies the file name where to put the core dump. If not
7233 specified, the file name defaults to @file{core.@var{pid}}, where
7234 @var{pid} is the inferior process ID.
7236 Note that this command is implemented only for some systems (as of
7237 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7240 @node Character Sets
7241 @section Character Sets
7242 @cindex character sets
7244 @cindex translating between character sets
7245 @cindex host character set
7246 @cindex target character set
7248 If the program you are debugging uses a different character set to
7249 represent characters and strings than the one @value{GDBN} uses itself,
7250 @value{GDBN} can automatically translate between the character sets for
7251 you. The character set @value{GDBN} uses we call the @dfn{host
7252 character set}; the one the inferior program uses we call the
7253 @dfn{target character set}.
7255 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7256 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7257 remote protocol (@pxref{Remote Debugging}) to debug a program
7258 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7259 then the host character set is Latin-1, and the target character set is
7260 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7261 target-charset EBCDIC-US}, then @value{GDBN} translates between
7262 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7263 character and string literals in expressions.
7265 @value{GDBN} has no way to automatically recognize which character set
7266 the inferior program uses; you must tell it, using the @code{set
7267 target-charset} command, described below.
7269 Here are the commands for controlling @value{GDBN}'s character set
7273 @item set target-charset @var{charset}
7274 @kindex set target-charset
7275 Set the current target character set to @var{charset}. We list the
7276 character set names @value{GDBN} recognizes below, but if you type
7277 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7278 list the target character sets it supports.
7282 @item set host-charset @var{charset}
7283 @kindex set host-charset
7284 Set the current host character set to @var{charset}.
7286 By default, @value{GDBN} uses a host character set appropriate to the
7287 system it is running on; you can override that default using the
7288 @code{set host-charset} command.
7290 @value{GDBN} can only use certain character sets as its host character
7291 set. We list the character set names @value{GDBN} recognizes below, and
7292 indicate which can be host character sets, but if you type
7293 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7294 list the host character sets it supports.
7296 @item set charset @var{charset}
7298 Set the current host and target character sets to @var{charset}. As
7299 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7300 @value{GDBN} will list the name of the character sets that can be used
7301 for both host and target.
7305 @kindex show charset
7306 Show the names of the current host and target charsets.
7308 @itemx show host-charset
7309 @kindex show host-charset
7310 Show the name of the current host charset.
7312 @itemx show target-charset
7313 @kindex show target-charset
7314 Show the name of the current target charset.
7318 @value{GDBN} currently includes support for the following character
7324 @cindex ASCII character set
7325 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7329 @cindex ISO 8859-1 character set
7330 @cindex ISO Latin 1 character set
7331 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7332 characters needed for French, German, and Spanish. @value{GDBN} can use
7333 this as its host character set.
7337 @cindex EBCDIC character set
7338 @cindex IBM1047 character set
7339 Variants of the @sc{ebcdic} character set, used on some of IBM's
7340 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7341 @value{GDBN} cannot use these as its host character set.
7345 Note that these are all single-byte character sets. More work inside
7346 @value{GDBN} is needed to support multi-byte or variable-width character
7347 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7349 Here is an example of @value{GDBN}'s character set support in action.
7350 Assume that the following source code has been placed in the file
7351 @file{charset-test.c}:
7357 = @{72, 101, 108, 108, 111, 44, 32, 119,
7358 111, 114, 108, 100, 33, 10, 0@};
7359 char ibm1047_hello[]
7360 = @{200, 133, 147, 147, 150, 107, 64, 166,
7361 150, 153, 147, 132, 90, 37, 0@};
7365 printf ("Hello, world!\n");
7369 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7370 containing the string @samp{Hello, world!} followed by a newline,
7371 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7373 We compile the program, and invoke the debugger on it:
7376 $ gcc -g charset-test.c -o charset-test
7377 $ gdb -nw charset-test
7378 GNU gdb 2001-12-19-cvs
7379 Copyright 2001 Free Software Foundation, Inc.
7384 We can use the @code{show charset} command to see what character sets
7385 @value{GDBN} is currently using to interpret and display characters and
7389 (@value{GDBP}) show charset
7390 The current host and target character set is `ISO-8859-1'.
7394 For the sake of printing this manual, let's use @sc{ascii} as our
7395 initial character set:
7397 (@value{GDBP}) set charset ASCII
7398 (@value{GDBP}) show charset
7399 The current host and target character set is `ASCII'.
7403 Let's assume that @sc{ascii} is indeed the correct character set for our
7404 host system --- in other words, let's assume that if @value{GDBN} prints
7405 characters using the @sc{ascii} character set, our terminal will display
7406 them properly. Since our current target character set is also
7407 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7410 (@value{GDBP}) print ascii_hello
7411 $1 = 0x401698 "Hello, world!\n"
7412 (@value{GDBP}) print ascii_hello[0]
7417 @value{GDBN} uses the target character set for character and string
7418 literals you use in expressions:
7421 (@value{GDBP}) print '+'
7426 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7429 @value{GDBN} relies on the user to tell it which character set the
7430 target program uses. If we print @code{ibm1047_hello} while our target
7431 character set is still @sc{ascii}, we get jibberish:
7434 (@value{GDBP}) print ibm1047_hello
7435 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7436 (@value{GDBP}) print ibm1047_hello[0]
7441 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7442 @value{GDBN} tells us the character sets it supports:
7445 (@value{GDBP}) set target-charset
7446 ASCII EBCDIC-US IBM1047 ISO-8859-1
7447 (@value{GDBP}) set target-charset
7450 We can select @sc{ibm1047} as our target character set, and examine the
7451 program's strings again. Now the @sc{ascii} string is wrong, but
7452 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7453 target character set, @sc{ibm1047}, to the host character set,
7454 @sc{ascii}, and they display correctly:
7457 (@value{GDBP}) set target-charset IBM1047
7458 (@value{GDBP}) show charset
7459 The current host character set is `ASCII'.
7460 The current target character set is `IBM1047'.
7461 (@value{GDBP}) print ascii_hello
7462 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7463 (@value{GDBP}) print ascii_hello[0]
7465 (@value{GDBP}) print ibm1047_hello
7466 $8 = 0x4016a8 "Hello, world!\n"
7467 (@value{GDBP}) print ibm1047_hello[0]
7472 As above, @value{GDBN} uses the target character set for character and
7473 string literals you use in expressions:
7476 (@value{GDBP}) print '+'
7481 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7484 @node Caching Remote Data
7485 @section Caching Data of Remote Targets
7486 @cindex caching data of remote targets
7488 @value{GDBN} can cache data exchanged between the debugger and a
7489 remote target (@pxref{Remote Debugging}). Such caching generally improves
7490 performance, because it reduces the overhead of the remote protocol by
7491 bundling memory reads and writes into large chunks. Unfortunately,
7492 @value{GDBN} does not currently know anything about volatile
7493 registers, and thus data caching will produce incorrect results when
7494 volatile registers are in use.
7497 @kindex set remotecache
7498 @item set remotecache on
7499 @itemx set remotecache off
7500 Set caching state for remote targets. When @code{ON}, use data
7501 caching. By default, this option is @code{OFF}.
7503 @kindex show remotecache
7504 @item show remotecache
7505 Show the current state of data caching for remote targets.
7509 Print the information about the data cache performance. The
7510 information displayed includes: the dcache width and depth; and for
7511 each cache line, how many times it was referenced, and its data and
7512 state (dirty, bad, ok, etc.). This command is useful for debugging
7513 the data cache operation.
7518 @chapter C Preprocessor Macros
7520 Some languages, such as C and C@t{++}, provide a way to define and invoke
7521 ``preprocessor macros'' which expand into strings of tokens.
7522 @value{GDBN} can evaluate expressions containing macro invocations, show
7523 the result of macro expansion, and show a macro's definition, including
7524 where it was defined.
7526 You may need to compile your program specially to provide @value{GDBN}
7527 with information about preprocessor macros. Most compilers do not
7528 include macros in their debugging information, even when you compile
7529 with the @option{-g} flag. @xref{Compilation}.
7531 A program may define a macro at one point, remove that definition later,
7532 and then provide a different definition after that. Thus, at different
7533 points in the program, a macro may have different definitions, or have
7534 no definition at all. If there is a current stack frame, @value{GDBN}
7535 uses the macros in scope at that frame's source code line. Otherwise,
7536 @value{GDBN} uses the macros in scope at the current listing location;
7539 At the moment, @value{GDBN} does not support the @code{##}
7540 token-splicing operator, the @code{#} stringification operator, or
7541 variable-arity macros.
7543 Whenever @value{GDBN} evaluates an expression, it always expands any
7544 macro invocations present in the expression. @value{GDBN} also provides
7545 the following commands for working with macros explicitly.
7549 @kindex macro expand
7550 @cindex macro expansion, showing the results of preprocessor
7551 @cindex preprocessor macro expansion, showing the results of
7552 @cindex expanding preprocessor macros
7553 @item macro expand @var{expression}
7554 @itemx macro exp @var{expression}
7555 Show the results of expanding all preprocessor macro invocations in
7556 @var{expression}. Since @value{GDBN} simply expands macros, but does
7557 not parse the result, @var{expression} need not be a valid expression;
7558 it can be any string of tokens.
7561 @item macro expand-once @var{expression}
7562 @itemx macro exp1 @var{expression}
7563 @cindex expand macro once
7564 @i{(This command is not yet implemented.)} Show the results of
7565 expanding those preprocessor macro invocations that appear explicitly in
7566 @var{expression}. Macro invocations appearing in that expansion are
7567 left unchanged. This command allows you to see the effect of a
7568 particular macro more clearly, without being confused by further
7569 expansions. Since @value{GDBN} simply expands macros, but does not
7570 parse the result, @var{expression} need not be a valid expression; it
7571 can be any string of tokens.
7574 @cindex macro definition, showing
7575 @cindex definition, showing a macro's
7576 @item info macro @var{macro}
7577 Show the definition of the macro named @var{macro}, and describe the
7578 source location where that definition was established.
7580 @kindex macro define
7581 @cindex user-defined macros
7582 @cindex defining macros interactively
7583 @cindex macros, user-defined
7584 @item macro define @var{macro} @var{replacement-list}
7585 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7586 @i{(This command is not yet implemented.)} Introduce a definition for a
7587 preprocessor macro named @var{macro}, invocations of which are replaced
7588 by the tokens given in @var{replacement-list}. The first form of this
7589 command defines an ``object-like'' macro, which takes no arguments; the
7590 second form defines a ``function-like'' macro, which takes the arguments
7591 given in @var{arglist}.
7593 A definition introduced by this command is in scope in every expression
7594 evaluated in @value{GDBN}, until it is removed with the @command{macro
7595 undef} command, described below. The definition overrides all
7596 definitions for @var{macro} present in the program being debugged, as
7597 well as any previous user-supplied definition.
7600 @item macro undef @var{macro}
7601 @i{(This command is not yet implemented.)} Remove any user-supplied
7602 definition for the macro named @var{macro}. This command only affects
7603 definitions provided with the @command{macro define} command, described
7604 above; it cannot remove definitions present in the program being
7609 @i{(This command is not yet implemented.)} List all the macros
7610 defined using the @code{macro define} command.
7613 @cindex macros, example of debugging with
7614 Here is a transcript showing the above commands in action. First, we
7615 show our source files:
7623 #define ADD(x) (M + x)
7628 printf ("Hello, world!\n");
7630 printf ("We're so creative.\n");
7632 printf ("Goodbye, world!\n");
7639 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7640 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7641 compiler includes information about preprocessor macros in the debugging
7645 $ gcc -gdwarf-2 -g3 sample.c -o sample
7649 Now, we start @value{GDBN} on our sample program:
7653 GNU gdb 2002-05-06-cvs
7654 Copyright 2002 Free Software Foundation, Inc.
7655 GDB is free software, @dots{}
7659 We can expand macros and examine their definitions, even when the
7660 program is not running. @value{GDBN} uses the current listing position
7661 to decide which macro definitions are in scope:
7664 (@value{GDBP}) list main
7667 5 #define ADD(x) (M + x)
7672 10 printf ("Hello, world!\n");
7674 12 printf ("We're so creative.\n");
7675 (@value{GDBP}) info macro ADD
7676 Defined at /home/jimb/gdb/macros/play/sample.c:5
7677 #define ADD(x) (M + x)
7678 (@value{GDBP}) info macro Q
7679 Defined at /home/jimb/gdb/macros/play/sample.h:1
7680 included at /home/jimb/gdb/macros/play/sample.c:2
7682 (@value{GDBP}) macro expand ADD(1)
7683 expands to: (42 + 1)
7684 (@value{GDBP}) macro expand-once ADD(1)
7685 expands to: once (M + 1)
7689 In the example above, note that @command{macro expand-once} expands only
7690 the macro invocation explicit in the original text --- the invocation of
7691 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7692 which was introduced by @code{ADD}.
7694 Once the program is running, @value{GDBN} uses the macro definitions in
7695 force at the source line of the current stack frame:
7698 (@value{GDBP}) break main
7699 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7701 Starting program: /home/jimb/gdb/macros/play/sample
7703 Breakpoint 1, main () at sample.c:10
7704 10 printf ("Hello, world!\n");
7708 At line 10, the definition of the macro @code{N} at line 9 is in force:
7711 (@value{GDBP}) info macro N
7712 Defined at /home/jimb/gdb/macros/play/sample.c:9
7714 (@value{GDBP}) macro expand N Q M
7716 (@value{GDBP}) print N Q M
7721 As we step over directives that remove @code{N}'s definition, and then
7722 give it a new definition, @value{GDBN} finds the definition (or lack
7723 thereof) in force at each point:
7728 12 printf ("We're so creative.\n");
7729 (@value{GDBP}) info macro N
7730 The symbol `N' has no definition as a C/C++ preprocessor macro
7731 at /home/jimb/gdb/macros/play/sample.c:12
7734 14 printf ("Goodbye, world!\n");
7735 (@value{GDBP}) info macro N
7736 Defined at /home/jimb/gdb/macros/play/sample.c:13
7738 (@value{GDBP}) macro expand N Q M
7739 expands to: 1729 < 42
7740 (@value{GDBP}) print N Q M
7747 @chapter Tracepoints
7748 @c This chapter is based on the documentation written by Michael
7749 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7752 In some applications, it is not feasible for the debugger to interrupt
7753 the program's execution long enough for the developer to learn
7754 anything helpful about its behavior. If the program's correctness
7755 depends on its real-time behavior, delays introduced by a debugger
7756 might cause the program to change its behavior drastically, or perhaps
7757 fail, even when the code itself is correct. It is useful to be able
7758 to observe the program's behavior without interrupting it.
7760 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7761 specify locations in the program, called @dfn{tracepoints}, and
7762 arbitrary expressions to evaluate when those tracepoints are reached.
7763 Later, using the @code{tfind} command, you can examine the values
7764 those expressions had when the program hit the tracepoints. The
7765 expressions may also denote objects in memory---structures or arrays,
7766 for example---whose values @value{GDBN} should record; while visiting
7767 a particular tracepoint, you may inspect those objects as if they were
7768 in memory at that moment. However, because @value{GDBN} records these
7769 values without interacting with you, it can do so quickly and
7770 unobtrusively, hopefully not disturbing the program's behavior.
7772 The tracepoint facility is currently available only for remote
7773 targets. @xref{Targets}. In addition, your remote target must know
7774 how to collect trace data. This functionality is implemented in the
7775 remote stub; however, none of the stubs distributed with @value{GDBN}
7776 support tracepoints as of this writing. The format of the remote
7777 packets used to implement tracepoints are described in @ref{Tracepoint
7780 This chapter describes the tracepoint commands and features.
7784 * Analyze Collected Data::
7785 * Tracepoint Variables::
7788 @node Set Tracepoints
7789 @section Commands to Set Tracepoints
7791 Before running such a @dfn{trace experiment}, an arbitrary number of
7792 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7793 tracepoint has a number assigned to it by @value{GDBN}. Like with
7794 breakpoints, tracepoint numbers are successive integers starting from
7795 one. Many of the commands associated with tracepoints take the
7796 tracepoint number as their argument, to identify which tracepoint to
7799 For each tracepoint, you can specify, in advance, some arbitrary set
7800 of data that you want the target to collect in the trace buffer when
7801 it hits that tracepoint. The collected data can include registers,
7802 local variables, or global data. Later, you can use @value{GDBN}
7803 commands to examine the values these data had at the time the
7806 This section describes commands to set tracepoints and associated
7807 conditions and actions.
7810 * Create and Delete Tracepoints::
7811 * Enable and Disable Tracepoints::
7812 * Tracepoint Passcounts::
7813 * Tracepoint Actions::
7814 * Listing Tracepoints::
7815 * Starting and Stopping Trace Experiments::
7818 @node Create and Delete Tracepoints
7819 @subsection Create and Delete Tracepoints
7822 @cindex set tracepoint
7825 The @code{trace} command is very similar to the @code{break} command.
7826 Its argument can be a source line, a function name, or an address in
7827 the target program. @xref{Set Breaks}. The @code{trace} command
7828 defines a tracepoint, which is a point in the target program where the
7829 debugger will briefly stop, collect some data, and then allow the
7830 program to continue. Setting a tracepoint or changing its commands
7831 doesn't take effect until the next @code{tstart} command; thus, you
7832 cannot change the tracepoint attributes once a trace experiment is
7835 Here are some examples of using the @code{trace} command:
7838 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7840 (@value{GDBP}) @b{trace +2} // 2 lines forward
7842 (@value{GDBP}) @b{trace my_function} // first source line of function
7844 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7846 (@value{GDBP}) @b{trace *0x2117c4} // an address
7850 You can abbreviate @code{trace} as @code{tr}.
7853 @cindex last tracepoint number
7854 @cindex recent tracepoint number
7855 @cindex tracepoint number
7856 The convenience variable @code{$tpnum} records the tracepoint number
7857 of the most recently set tracepoint.
7859 @kindex delete tracepoint
7860 @cindex tracepoint deletion
7861 @item delete tracepoint @r{[}@var{num}@r{]}
7862 Permanently delete one or more tracepoints. With no argument, the
7863 default is to delete all tracepoints.
7868 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7870 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7874 You can abbreviate this command as @code{del tr}.
7877 @node Enable and Disable Tracepoints
7878 @subsection Enable and Disable Tracepoints
7881 @kindex disable tracepoint
7882 @item disable tracepoint @r{[}@var{num}@r{]}
7883 Disable tracepoint @var{num}, or all tracepoints if no argument
7884 @var{num} is given. A disabled tracepoint will have no effect during
7885 the next trace experiment, but it is not forgotten. You can re-enable
7886 a disabled tracepoint using the @code{enable tracepoint} command.
7888 @kindex enable tracepoint
7889 @item enable tracepoint @r{[}@var{num}@r{]}
7890 Enable tracepoint @var{num}, or all tracepoints. The enabled
7891 tracepoints will become effective the next time a trace experiment is
7895 @node Tracepoint Passcounts
7896 @subsection Tracepoint Passcounts
7900 @cindex tracepoint pass count
7901 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7902 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7903 automatically stop a trace experiment. If a tracepoint's passcount is
7904 @var{n}, then the trace experiment will be automatically stopped on
7905 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7906 @var{num} is not specified, the @code{passcount} command sets the
7907 passcount of the most recently defined tracepoint. If no passcount is
7908 given, the trace experiment will run until stopped explicitly by the
7914 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7915 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7917 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7918 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7919 (@value{GDBP}) @b{trace foo}
7920 (@value{GDBP}) @b{pass 3}
7921 (@value{GDBP}) @b{trace bar}
7922 (@value{GDBP}) @b{pass 2}
7923 (@value{GDBP}) @b{trace baz}
7924 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7925 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7926 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7927 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7931 @node Tracepoint Actions
7932 @subsection Tracepoint Action Lists
7936 @cindex tracepoint actions
7937 @item actions @r{[}@var{num}@r{]}
7938 This command will prompt for a list of actions to be taken when the
7939 tracepoint is hit. If the tracepoint number @var{num} is not
7940 specified, this command sets the actions for the one that was most
7941 recently defined (so that you can define a tracepoint and then say
7942 @code{actions} without bothering about its number). You specify the
7943 actions themselves on the following lines, one action at a time, and
7944 terminate the actions list with a line containing just @code{end}. So
7945 far, the only defined actions are @code{collect} and
7946 @code{while-stepping}.
7948 @cindex remove actions from a tracepoint
7949 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7950 and follow it immediately with @samp{end}.
7953 (@value{GDBP}) @b{collect @var{data}} // collect some data
7955 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7957 (@value{GDBP}) @b{end} // signals the end of actions.
7960 In the following example, the action list begins with @code{collect}
7961 commands indicating the things to be collected when the tracepoint is
7962 hit. Then, in order to single-step and collect additional data
7963 following the tracepoint, a @code{while-stepping} command is used,
7964 followed by the list of things to be collected while stepping. The
7965 @code{while-stepping} command is terminated by its own separate
7966 @code{end} command. Lastly, the action list is terminated by an
7970 (@value{GDBP}) @b{trace foo}
7971 (@value{GDBP}) @b{actions}
7972 Enter actions for tracepoint 1, one per line:
7981 @kindex collect @r{(tracepoints)}
7982 @item collect @var{expr1}, @var{expr2}, @dots{}
7983 Collect values of the given expressions when the tracepoint is hit.
7984 This command accepts a comma-separated list of any valid expressions.
7985 In addition to global, static, or local variables, the following
7986 special arguments are supported:
7990 collect all registers
7993 collect all function arguments
7996 collect all local variables.
7999 You can give several consecutive @code{collect} commands, each one
8000 with a single argument, or one @code{collect} command with several
8001 arguments separated by commas: the effect is the same.
8003 The command @code{info scope} (@pxref{Symbols, info scope}) is
8004 particularly useful for figuring out what data to collect.
8006 @kindex while-stepping @r{(tracepoints)}
8007 @item while-stepping @var{n}
8008 Perform @var{n} single-step traces after the tracepoint, collecting
8009 new data at each step. The @code{while-stepping} command is
8010 followed by the list of what to collect while stepping (followed by
8011 its own @code{end} command):
8015 > collect $regs, myglobal
8021 You may abbreviate @code{while-stepping} as @code{ws} or
8025 @node Listing Tracepoints
8026 @subsection Listing Tracepoints
8029 @kindex info tracepoints
8031 @cindex information about tracepoints
8032 @item info tracepoints @r{[}@var{num}@r{]}
8033 Display information about the tracepoint @var{num}. If you don't specify
8034 a tracepoint number, displays information about all the tracepoints
8035 defined so far. For each tracepoint, the following information is
8042 whether it is enabled or disabled
8046 its passcount as given by the @code{passcount @var{n}} command
8048 its step count as given by the @code{while-stepping @var{n}} command
8050 where in the source files is the tracepoint set
8052 its action list as given by the @code{actions} command
8056 (@value{GDBP}) @b{info trace}
8057 Num Enb Address PassC StepC What
8058 1 y 0x002117c4 0 0 <gdb_asm>
8059 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8060 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8065 This command can be abbreviated @code{info tp}.
8068 @node Starting and Stopping Trace Experiments
8069 @subsection Starting and Stopping Trace Experiments
8073 @cindex start a new trace experiment
8074 @cindex collected data discarded
8076 This command takes no arguments. It starts the trace experiment, and
8077 begins collecting data. This has the side effect of discarding all
8078 the data collected in the trace buffer during the previous trace
8082 @cindex stop a running trace experiment
8084 This command takes no arguments. It ends the trace experiment, and
8085 stops collecting data.
8087 @strong{Note}: a trace experiment and data collection may stop
8088 automatically if any tracepoint's passcount is reached
8089 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8092 @cindex status of trace data collection
8093 @cindex trace experiment, status of
8095 This command displays the status of the current trace data
8099 Here is an example of the commands we described so far:
8102 (@value{GDBP}) @b{trace gdb_c_test}
8103 (@value{GDBP}) @b{actions}
8104 Enter actions for tracepoint #1, one per line.
8105 > collect $regs,$locals,$args
8110 (@value{GDBP}) @b{tstart}
8111 [time passes @dots{}]
8112 (@value{GDBP}) @b{tstop}
8116 @node Analyze Collected Data
8117 @section Using the Collected Data
8119 After the tracepoint experiment ends, you use @value{GDBN} commands
8120 for examining the trace data. The basic idea is that each tracepoint
8121 collects a trace @dfn{snapshot} every time it is hit and another
8122 snapshot every time it single-steps. All these snapshots are
8123 consecutively numbered from zero and go into a buffer, and you can
8124 examine them later. The way you examine them is to @dfn{focus} on a
8125 specific trace snapshot. When the remote stub is focused on a trace
8126 snapshot, it will respond to all @value{GDBN} requests for memory and
8127 registers by reading from the buffer which belongs to that snapshot,
8128 rather than from @emph{real} memory or registers of the program being
8129 debugged. This means that @strong{all} @value{GDBN} commands
8130 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8131 behave as if we were currently debugging the program state as it was
8132 when the tracepoint occurred. Any requests for data that are not in
8133 the buffer will fail.
8136 * tfind:: How to select a trace snapshot
8137 * tdump:: How to display all data for a snapshot
8138 * save-tracepoints:: How to save tracepoints for a future run
8142 @subsection @code{tfind @var{n}}
8145 @cindex select trace snapshot
8146 @cindex find trace snapshot
8147 The basic command for selecting a trace snapshot from the buffer is
8148 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8149 counting from zero. If no argument @var{n} is given, the next
8150 snapshot is selected.
8152 Here are the various forms of using the @code{tfind} command.
8156 Find the first snapshot in the buffer. This is a synonym for
8157 @code{tfind 0} (since 0 is the number of the first snapshot).
8160 Stop debugging trace snapshots, resume @emph{live} debugging.
8163 Same as @samp{tfind none}.
8166 No argument means find the next trace snapshot.
8169 Find the previous trace snapshot before the current one. This permits
8170 retracing earlier steps.
8172 @item tfind tracepoint @var{num}
8173 Find the next snapshot associated with tracepoint @var{num}. Search
8174 proceeds forward from the last examined trace snapshot. If no
8175 argument @var{num} is given, it means find the next snapshot collected
8176 for the same tracepoint as the current snapshot.
8178 @item tfind pc @var{addr}
8179 Find the next snapshot associated with the value @var{addr} of the
8180 program counter. Search proceeds forward from the last examined trace
8181 snapshot. If no argument @var{addr} is given, it means find the next
8182 snapshot with the same value of PC as the current snapshot.
8184 @item tfind outside @var{addr1}, @var{addr2}
8185 Find the next snapshot whose PC is outside the given range of
8188 @item tfind range @var{addr1}, @var{addr2}
8189 Find the next snapshot whose PC is between @var{addr1} and
8190 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8192 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8193 Find the next snapshot associated with the source line @var{n}. If
8194 the optional argument @var{file} is given, refer to line @var{n} in
8195 that source file. Search proceeds forward from the last examined
8196 trace snapshot. If no argument @var{n} is given, it means find the
8197 next line other than the one currently being examined; thus saying
8198 @code{tfind line} repeatedly can appear to have the same effect as
8199 stepping from line to line in a @emph{live} debugging session.
8202 The default arguments for the @code{tfind} commands are specifically
8203 designed to make it easy to scan through the trace buffer. For
8204 instance, @code{tfind} with no argument selects the next trace
8205 snapshot, and @code{tfind -} with no argument selects the previous
8206 trace snapshot. So, by giving one @code{tfind} command, and then
8207 simply hitting @key{RET} repeatedly you can examine all the trace
8208 snapshots in order. Or, by saying @code{tfind -} and then hitting
8209 @key{RET} repeatedly you can examine the snapshots in reverse order.
8210 The @code{tfind line} command with no argument selects the snapshot
8211 for the next source line executed. The @code{tfind pc} command with
8212 no argument selects the next snapshot with the same program counter
8213 (PC) as the current frame. The @code{tfind tracepoint} command with
8214 no argument selects the next trace snapshot collected by the same
8215 tracepoint as the current one.
8217 In addition to letting you scan through the trace buffer manually,
8218 these commands make it easy to construct @value{GDBN} scripts that
8219 scan through the trace buffer and print out whatever collected data
8220 you are interested in. Thus, if we want to examine the PC, FP, and SP
8221 registers from each trace frame in the buffer, we can say this:
8224 (@value{GDBP}) @b{tfind start}
8225 (@value{GDBP}) @b{while ($trace_frame != -1)}
8226 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8227 $trace_frame, $pc, $sp, $fp
8231 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8232 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8233 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8234 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8235 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8236 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8237 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8238 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8239 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8240 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8241 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8244 Or, if we want to examine the variable @code{X} at each source line in
8248 (@value{GDBP}) @b{tfind start}
8249 (@value{GDBP}) @b{while ($trace_frame != -1)}
8250 > printf "Frame %d, X == %d\n", $trace_frame, X
8260 @subsection @code{tdump}
8262 @cindex dump all data collected at tracepoint
8263 @cindex tracepoint data, display
8265 This command takes no arguments. It prints all the data collected at
8266 the current trace snapshot.
8269 (@value{GDBP}) @b{trace 444}
8270 (@value{GDBP}) @b{actions}
8271 Enter actions for tracepoint #2, one per line:
8272 > collect $regs, $locals, $args, gdb_long_test
8275 (@value{GDBP}) @b{tstart}
8277 (@value{GDBP}) @b{tfind line 444}
8278 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8280 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8282 (@value{GDBP}) @b{tdump}
8283 Data collected at tracepoint 2, trace frame 1:
8284 d0 0xc4aa0085 -995491707
8288 d4 0x71aea3d 119204413
8293 a1 0x3000668 50333288
8296 a4 0x3000698 50333336
8298 fp 0x30bf3c 0x30bf3c
8299 sp 0x30bf34 0x30bf34
8301 pc 0x20b2c8 0x20b2c8
8305 p = 0x20e5b4 "gdb-test"
8312 gdb_long_test = 17 '\021'
8317 @node save-tracepoints
8318 @subsection @code{save-tracepoints @var{filename}}
8319 @kindex save-tracepoints
8320 @cindex save tracepoints for future sessions
8322 This command saves all current tracepoint definitions together with
8323 their actions and passcounts, into a file @file{@var{filename}}
8324 suitable for use in a later debugging session. To read the saved
8325 tracepoint definitions, use the @code{source} command (@pxref{Command
8328 @node Tracepoint Variables
8329 @section Convenience Variables for Tracepoints
8330 @cindex tracepoint variables
8331 @cindex convenience variables for tracepoints
8334 @vindex $trace_frame
8335 @item (int) $trace_frame
8336 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8337 snapshot is selected.
8340 @item (int) $tracepoint
8341 The tracepoint for the current trace snapshot.
8344 @item (int) $trace_line
8345 The line number for the current trace snapshot.
8348 @item (char []) $trace_file
8349 The source file for the current trace snapshot.
8352 @item (char []) $trace_func
8353 The name of the function containing @code{$tracepoint}.
8356 Note: @code{$trace_file} is not suitable for use in @code{printf},
8357 use @code{output} instead.
8359 Here's a simple example of using these convenience variables for
8360 stepping through all the trace snapshots and printing some of their
8364 (@value{GDBP}) @b{tfind start}
8366 (@value{GDBP}) @b{while $trace_frame != -1}
8367 > output $trace_file
8368 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8374 @chapter Debugging Programs That Use Overlays
8377 If your program is too large to fit completely in your target system's
8378 memory, you can sometimes use @dfn{overlays} to work around this
8379 problem. @value{GDBN} provides some support for debugging programs that
8383 * How Overlays Work:: A general explanation of overlays.
8384 * Overlay Commands:: Managing overlays in @value{GDBN}.
8385 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8386 mapped by asking the inferior.
8387 * Overlay Sample Program:: A sample program using overlays.
8390 @node How Overlays Work
8391 @section How Overlays Work
8392 @cindex mapped overlays
8393 @cindex unmapped overlays
8394 @cindex load address, overlay's
8395 @cindex mapped address
8396 @cindex overlay area
8398 Suppose you have a computer whose instruction address space is only 64
8399 kilobytes long, but which has much more memory which can be accessed by
8400 other means: special instructions, segment registers, or memory
8401 management hardware, for example. Suppose further that you want to
8402 adapt a program which is larger than 64 kilobytes to run on this system.
8404 One solution is to identify modules of your program which are relatively
8405 independent, and need not call each other directly; call these modules
8406 @dfn{overlays}. Separate the overlays from the main program, and place
8407 their machine code in the larger memory. Place your main program in
8408 instruction memory, but leave at least enough space there to hold the
8409 largest overlay as well.
8411 Now, to call a function located in an overlay, you must first copy that
8412 overlay's machine code from the large memory into the space set aside
8413 for it in the instruction memory, and then jump to its entry point
8416 @c NB: In the below the mapped area's size is greater or equal to the
8417 @c size of all overlays. This is intentional to remind the developer
8418 @c that overlays don't necessarily need to be the same size.
8422 Data Instruction Larger
8423 Address Space Address Space Address Space
8424 +-----------+ +-----------+ +-----------+
8426 +-----------+ +-----------+ +-----------+<-- overlay 1
8427 | program | | main | .----| overlay 1 | load address
8428 | variables | | program | | +-----------+
8429 | and heap | | | | | |
8430 +-----------+ | | | +-----------+<-- overlay 2
8431 | | +-----------+ | | | load address
8432 +-----------+ | | | .-| overlay 2 |
8434 mapped --->+-----------+ | | +-----------+
8436 | overlay | <-' | | |
8437 | area | <---' +-----------+<-- overlay 3
8438 | | <---. | | load address
8439 +-----------+ `--| overlay 3 |
8446 @anchor{A code overlay}A code overlay
8450 The diagram (@pxref{A code overlay}) shows a system with separate data
8451 and instruction address spaces. To map an overlay, the program copies
8452 its code from the larger address space to the instruction address space.
8453 Since the overlays shown here all use the same mapped address, only one
8454 may be mapped at a time. For a system with a single address space for
8455 data and instructions, the diagram would be similar, except that the
8456 program variables and heap would share an address space with the main
8457 program and the overlay area.
8459 An overlay loaded into instruction memory and ready for use is called a
8460 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8461 instruction memory. An overlay not present (or only partially present)
8462 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8463 is its address in the larger memory. The mapped address is also called
8464 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8465 called the @dfn{load memory address}, or @dfn{LMA}.
8467 Unfortunately, overlays are not a completely transparent way to adapt a
8468 program to limited instruction memory. They introduce a new set of
8469 global constraints you must keep in mind as you design your program:
8474 Before calling or returning to a function in an overlay, your program
8475 must make sure that overlay is actually mapped. Otherwise, the call or
8476 return will transfer control to the right address, but in the wrong
8477 overlay, and your program will probably crash.
8480 If the process of mapping an overlay is expensive on your system, you
8481 will need to choose your overlays carefully to minimize their effect on
8482 your program's performance.
8485 The executable file you load onto your system must contain each
8486 overlay's instructions, appearing at the overlay's load address, not its
8487 mapped address. However, each overlay's instructions must be relocated
8488 and its symbols defined as if the overlay were at its mapped address.
8489 You can use GNU linker scripts to specify different load and relocation
8490 addresses for pieces of your program; see @ref{Overlay Description,,,
8491 ld.info, Using ld: the GNU linker}.
8494 The procedure for loading executable files onto your system must be able
8495 to load their contents into the larger address space as well as the
8496 instruction and data spaces.
8500 The overlay system described above is rather simple, and could be
8501 improved in many ways:
8506 If your system has suitable bank switch registers or memory management
8507 hardware, you could use those facilities to make an overlay's load area
8508 contents simply appear at their mapped address in instruction space.
8509 This would probably be faster than copying the overlay to its mapped
8510 area in the usual way.
8513 If your overlays are small enough, you could set aside more than one
8514 overlay area, and have more than one overlay mapped at a time.
8517 You can use overlays to manage data, as well as instructions. In
8518 general, data overlays are even less transparent to your design than
8519 code overlays: whereas code overlays only require care when you call or
8520 return to functions, data overlays require care every time you access
8521 the data. Also, if you change the contents of a data overlay, you
8522 must copy its contents back out to its load address before you can copy a
8523 different data overlay into the same mapped area.
8528 @node Overlay Commands
8529 @section Overlay Commands
8531 To use @value{GDBN}'s overlay support, each overlay in your program must
8532 correspond to a separate section of the executable file. The section's
8533 virtual memory address and load memory address must be the overlay's
8534 mapped and load addresses. Identifying overlays with sections allows
8535 @value{GDBN} to determine the appropriate address of a function or
8536 variable, depending on whether the overlay is mapped or not.
8538 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8539 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8544 Disable @value{GDBN}'s overlay support. When overlay support is
8545 disabled, @value{GDBN} assumes that all functions and variables are
8546 always present at their mapped addresses. By default, @value{GDBN}'s
8547 overlay support is disabled.
8549 @item overlay manual
8550 @cindex manual overlay debugging
8551 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8552 relies on you to tell it which overlays are mapped, and which are not,
8553 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8554 commands described below.
8556 @item overlay map-overlay @var{overlay}
8557 @itemx overlay map @var{overlay}
8558 @cindex map an overlay
8559 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8560 be the name of the object file section containing the overlay. When an
8561 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8562 functions and variables at their mapped addresses. @value{GDBN} assumes
8563 that any other overlays whose mapped ranges overlap that of
8564 @var{overlay} are now unmapped.
8566 @item overlay unmap-overlay @var{overlay}
8567 @itemx overlay unmap @var{overlay}
8568 @cindex unmap an overlay
8569 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8570 must be the name of the object file section containing the overlay.
8571 When an overlay is unmapped, @value{GDBN} assumes it can find the
8572 overlay's functions and variables at their load addresses.
8575 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8576 consults a data structure the overlay manager maintains in the inferior
8577 to see which overlays are mapped. For details, see @ref{Automatic
8580 @item overlay load-target
8582 @cindex reloading the overlay table
8583 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8584 re-reads the table @value{GDBN} automatically each time the inferior
8585 stops, so this command should only be necessary if you have changed the
8586 overlay mapping yourself using @value{GDBN}. This command is only
8587 useful when using automatic overlay debugging.
8589 @item overlay list-overlays
8591 @cindex listing mapped overlays
8592 Display a list of the overlays currently mapped, along with their mapped
8593 addresses, load addresses, and sizes.
8597 Normally, when @value{GDBN} prints a code address, it includes the name
8598 of the function the address falls in:
8601 (@value{GDBP}) print main
8602 $3 = @{int ()@} 0x11a0 <main>
8605 When overlay debugging is enabled, @value{GDBN} recognizes code in
8606 unmapped overlays, and prints the names of unmapped functions with
8607 asterisks around them. For example, if @code{foo} is a function in an
8608 unmapped overlay, @value{GDBN} prints it this way:
8611 (@value{GDBP}) overlay list
8612 No sections are mapped.
8613 (@value{GDBP}) print foo
8614 $5 = @{int (int)@} 0x100000 <*foo*>
8617 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8621 (@value{GDBP}) overlay list
8622 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8623 mapped at 0x1016 - 0x104a
8624 (@value{GDBP}) print foo
8625 $6 = @{int (int)@} 0x1016 <foo>
8628 When overlay debugging is enabled, @value{GDBN} can find the correct
8629 address for functions and variables in an overlay, whether or not the
8630 overlay is mapped. This allows most @value{GDBN} commands, like
8631 @code{break} and @code{disassemble}, to work normally, even on unmapped
8632 code. However, @value{GDBN}'s breakpoint support has some limitations:
8636 @cindex breakpoints in overlays
8637 @cindex overlays, setting breakpoints in
8638 You can set breakpoints in functions in unmapped overlays, as long as
8639 @value{GDBN} can write to the overlay at its load address.
8641 @value{GDBN} can not set hardware or simulator-based breakpoints in
8642 unmapped overlays. However, if you set a breakpoint at the end of your
8643 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8644 you are using manual overlay management), @value{GDBN} will re-set its
8645 breakpoints properly.
8649 @node Automatic Overlay Debugging
8650 @section Automatic Overlay Debugging
8651 @cindex automatic overlay debugging
8653 @value{GDBN} can automatically track which overlays are mapped and which
8654 are not, given some simple co-operation from the overlay manager in the
8655 inferior. If you enable automatic overlay debugging with the
8656 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8657 looks in the inferior's memory for certain variables describing the
8658 current state of the overlays.
8660 Here are the variables your overlay manager must define to support
8661 @value{GDBN}'s automatic overlay debugging:
8665 @item @code{_ovly_table}:
8666 This variable must be an array of the following structures:
8671 /* The overlay's mapped address. */
8674 /* The size of the overlay, in bytes. */
8677 /* The overlay's load address. */
8680 /* Non-zero if the overlay is currently mapped;
8682 unsigned long mapped;
8686 @item @code{_novlys}:
8687 This variable must be a four-byte signed integer, holding the total
8688 number of elements in @code{_ovly_table}.
8692 To decide whether a particular overlay is mapped or not, @value{GDBN}
8693 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8694 @code{lma} members equal the VMA and LMA of the overlay's section in the
8695 executable file. When @value{GDBN} finds a matching entry, it consults
8696 the entry's @code{mapped} member to determine whether the overlay is
8699 In addition, your overlay manager may define a function called
8700 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8701 will silently set a breakpoint there. If the overlay manager then
8702 calls this function whenever it has changed the overlay table, this
8703 will enable @value{GDBN} to accurately keep track of which overlays
8704 are in program memory, and update any breakpoints that may be set
8705 in overlays. This will allow breakpoints to work even if the
8706 overlays are kept in ROM or other non-writable memory while they
8707 are not being executed.
8709 @node Overlay Sample Program
8710 @section Overlay Sample Program
8711 @cindex overlay example program
8713 When linking a program which uses overlays, you must place the overlays
8714 at their load addresses, while relocating them to run at their mapped
8715 addresses. To do this, you must write a linker script (@pxref{Overlay
8716 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8717 since linker scripts are specific to a particular host system, target
8718 architecture, and target memory layout, this manual cannot provide
8719 portable sample code demonstrating @value{GDBN}'s overlay support.
8721 However, the @value{GDBN} source distribution does contain an overlaid
8722 program, with linker scripts for a few systems, as part of its test
8723 suite. The program consists of the following files from
8724 @file{gdb/testsuite/gdb.base}:
8728 The main program file.
8730 A simple overlay manager, used by @file{overlays.c}.
8735 Overlay modules, loaded and used by @file{overlays.c}.
8738 Linker scripts for linking the test program on the @code{d10v-elf}
8739 and @code{m32r-elf} targets.
8742 You can build the test program using the @code{d10v-elf} GCC
8743 cross-compiler like this:
8746 $ d10v-elf-gcc -g -c overlays.c
8747 $ d10v-elf-gcc -g -c ovlymgr.c
8748 $ d10v-elf-gcc -g -c foo.c
8749 $ d10v-elf-gcc -g -c bar.c
8750 $ d10v-elf-gcc -g -c baz.c
8751 $ d10v-elf-gcc -g -c grbx.c
8752 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8753 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8756 The build process is identical for any other architecture, except that
8757 you must substitute the appropriate compiler and linker script for the
8758 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8762 @chapter Using @value{GDBN} with Different Languages
8765 Although programming languages generally have common aspects, they are
8766 rarely expressed in the same manner. For instance, in ANSI C,
8767 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8768 Modula-2, it is accomplished by @code{p^}. Values can also be
8769 represented (and displayed) differently. Hex numbers in C appear as
8770 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8772 @cindex working language
8773 Language-specific information is built into @value{GDBN} for some languages,
8774 allowing you to express operations like the above in your program's
8775 native language, and allowing @value{GDBN} to output values in a manner
8776 consistent with the syntax of your program's native language. The
8777 language you use to build expressions is called the @dfn{working
8781 * Setting:: Switching between source languages
8782 * Show:: Displaying the language
8783 * Checks:: Type and range checks
8784 * Supported Languages:: Supported languages
8785 * Unsupported Languages:: Unsupported languages
8789 @section Switching Between Source Languages
8791 There are two ways to control the working language---either have @value{GDBN}
8792 set it automatically, or select it manually yourself. You can use the
8793 @code{set language} command for either purpose. On startup, @value{GDBN}
8794 defaults to setting the language automatically. The working language is
8795 used to determine how expressions you type are interpreted, how values
8798 In addition to the working language, every source file that
8799 @value{GDBN} knows about has its own working language. For some object
8800 file formats, the compiler might indicate which language a particular
8801 source file is in. However, most of the time @value{GDBN} infers the
8802 language from the name of the file. The language of a source file
8803 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8804 show each frame appropriately for its own language. There is no way to
8805 set the language of a source file from within @value{GDBN}, but you can
8806 set the language associated with a filename extension. @xref{Show, ,
8807 Displaying the Language}.
8809 This is most commonly a problem when you use a program, such
8810 as @code{cfront} or @code{f2c}, that generates C but is written in
8811 another language. In that case, make the
8812 program use @code{#line} directives in its C output; that way
8813 @value{GDBN} will know the correct language of the source code of the original
8814 program, and will display that source code, not the generated C code.
8817 * Filenames:: Filename extensions and languages.
8818 * Manually:: Setting the working language manually
8819 * Automatically:: Having @value{GDBN} infer the source language
8823 @subsection List of Filename Extensions and Languages
8825 If a source file name ends in one of the following extensions, then
8826 @value{GDBN} infers that its language is the one indicated.
8847 Objective-C source file
8854 Modula-2 source file
8858 Assembler source file. This actually behaves almost like C, but
8859 @value{GDBN} does not skip over function prologues when stepping.
8862 In addition, you may set the language associated with a filename
8863 extension. @xref{Show, , Displaying the Language}.
8866 @subsection Setting the Working Language
8868 If you allow @value{GDBN} to set the language automatically,
8869 expressions are interpreted the same way in your debugging session and
8872 @kindex set language
8873 If you wish, you may set the language manually. To do this, issue the
8874 command @samp{set language @var{lang}}, where @var{lang} is the name of
8876 @code{c} or @code{modula-2}.
8877 For a list of the supported languages, type @samp{set language}.
8879 Setting the language manually prevents @value{GDBN} from updating the working
8880 language automatically. This can lead to confusion if you try
8881 to debug a program when the working language is not the same as the
8882 source language, when an expression is acceptable to both
8883 languages---but means different things. For instance, if the current
8884 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8892 might not have the effect you intended. In C, this means to add
8893 @code{b} and @code{c} and place the result in @code{a}. The result
8894 printed would be the value of @code{a}. In Modula-2, this means to compare
8895 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8898 @subsection Having @value{GDBN} Infer the Source Language
8900 To have @value{GDBN} set the working language automatically, use
8901 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8902 then infers the working language. That is, when your program stops in a
8903 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8904 working language to the language recorded for the function in that
8905 frame. If the language for a frame is unknown (that is, if the function
8906 or block corresponding to the frame was defined in a source file that
8907 does not have a recognized extension), the current working language is
8908 not changed, and @value{GDBN} issues a warning.
8910 This may not seem necessary for most programs, which are written
8911 entirely in one source language. However, program modules and libraries
8912 written in one source language can be used by a main program written in
8913 a different source language. Using @samp{set language auto} in this
8914 case frees you from having to set the working language manually.
8917 @section Displaying the Language
8919 The following commands help you find out which language is the
8920 working language, and also what language source files were written in.
8924 @kindex show language
8925 Display the current working language. This is the
8926 language you can use with commands such as @code{print} to
8927 build and compute expressions that may involve variables in your program.
8930 @kindex info frame@r{, show the source language}
8931 Display the source language for this frame. This language becomes the
8932 working language if you use an identifier from this frame.
8933 @xref{Frame Info, ,Information about a Frame}, to identify the other
8934 information listed here.
8937 @kindex info source@r{, show the source language}
8938 Display the source language of this source file.
8939 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8940 information listed here.
8943 In unusual circumstances, you may have source files with extensions
8944 not in the standard list. You can then set the extension associated
8945 with a language explicitly:
8948 @item set extension-language @var{ext} @var{language}
8949 @kindex set extension-language
8950 Tell @value{GDBN} that source files with extension @var{ext} are to be
8951 assumed as written in the source language @var{language}.
8953 @item info extensions
8954 @kindex info extensions
8955 List all the filename extensions and the associated languages.
8959 @section Type and Range Checking
8962 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8963 checking are included, but they do not yet have any effect. This
8964 section documents the intended facilities.
8966 @c FIXME remove warning when type/range code added
8968 Some languages are designed to guard you against making seemingly common
8969 errors through a series of compile- and run-time checks. These include
8970 checking the type of arguments to functions and operators, and making
8971 sure mathematical overflows are caught at run time. Checks such as
8972 these help to ensure a program's correctness once it has been compiled
8973 by eliminating type mismatches, and providing active checks for range
8974 errors when your program is running.
8976 @value{GDBN} can check for conditions like the above if you wish.
8977 Although @value{GDBN} does not check the statements in your program,
8978 it can check expressions entered directly into @value{GDBN} for
8979 evaluation via the @code{print} command, for example. As with the
8980 working language, @value{GDBN} can also decide whether or not to check
8981 automatically based on your program's source language.
8982 @xref{Supported Languages, ,Supported Languages}, for the default
8983 settings of supported languages.
8986 * Type Checking:: An overview of type checking
8987 * Range Checking:: An overview of range checking
8990 @cindex type checking
8991 @cindex checks, type
8993 @subsection An Overview of Type Checking
8995 Some languages, such as Modula-2, are strongly typed, meaning that the
8996 arguments to operators and functions have to be of the correct type,
8997 otherwise an error occurs. These checks prevent type mismatch
8998 errors from ever causing any run-time problems. For example,
9006 The second example fails because the @code{CARDINAL} 1 is not
9007 type-compatible with the @code{REAL} 2.3.
9009 For the expressions you use in @value{GDBN} commands, you can tell the
9010 @value{GDBN} type checker to skip checking;
9011 to treat any mismatches as errors and abandon the expression;
9012 or to only issue warnings when type mismatches occur,
9013 but evaluate the expression anyway. When you choose the last of
9014 these, @value{GDBN} evaluates expressions like the second example above, but
9015 also issues a warning.
9017 Even if you turn type checking off, there may be other reasons
9018 related to type that prevent @value{GDBN} from evaluating an expression.
9019 For instance, @value{GDBN} does not know how to add an @code{int} and
9020 a @code{struct foo}. These particular type errors have nothing to do
9021 with the language in use, and usually arise from expressions, such as
9022 the one described above, which make little sense to evaluate anyway.
9024 Each language defines to what degree it is strict about type. For
9025 instance, both Modula-2 and C require the arguments to arithmetical
9026 operators to be numbers. In C, enumerated types and pointers can be
9027 represented as numbers, so that they are valid arguments to mathematical
9028 operators. @xref{Supported Languages, ,Supported Languages}, for further
9029 details on specific languages.
9031 @value{GDBN} provides some additional commands for controlling the type checker:
9033 @kindex set check type
9034 @kindex show check type
9036 @item set check type auto
9037 Set type checking on or off based on the current working language.
9038 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9041 @item set check type on
9042 @itemx set check type off
9043 Set type checking on or off, overriding the default setting for the
9044 current working language. Issue a warning if the setting does not
9045 match the language default. If any type mismatches occur in
9046 evaluating an expression while type checking is on, @value{GDBN} prints a
9047 message and aborts evaluation of the expression.
9049 @item set check type warn
9050 Cause the type checker to issue warnings, but to always attempt to
9051 evaluate the expression. Evaluating the expression may still
9052 be impossible for other reasons. For example, @value{GDBN} cannot add
9053 numbers and structures.
9056 Show the current setting of the type checker, and whether or not @value{GDBN}
9057 is setting it automatically.
9060 @cindex range checking
9061 @cindex checks, range
9062 @node Range Checking
9063 @subsection An Overview of Range Checking
9065 In some languages (such as Modula-2), it is an error to exceed the
9066 bounds of a type; this is enforced with run-time checks. Such range
9067 checking is meant to ensure program correctness by making sure
9068 computations do not overflow, or indices on an array element access do
9069 not exceed the bounds of the array.
9071 For expressions you use in @value{GDBN} commands, you can tell
9072 @value{GDBN} to treat range errors in one of three ways: ignore them,
9073 always treat them as errors and abandon the expression, or issue
9074 warnings but evaluate the expression anyway.
9076 A range error can result from numerical overflow, from exceeding an
9077 array index bound, or when you type a constant that is not a member
9078 of any type. Some languages, however, do not treat overflows as an
9079 error. In many implementations of C, mathematical overflow causes the
9080 result to ``wrap around'' to lower values---for example, if @var{m} is
9081 the largest integer value, and @var{s} is the smallest, then
9084 @var{m} + 1 @result{} @var{s}
9087 This, too, is specific to individual languages, and in some cases
9088 specific to individual compilers or machines. @xref{Supported Languages, ,
9089 Supported Languages}, for further details on specific languages.
9091 @value{GDBN} provides some additional commands for controlling the range checker:
9093 @kindex set check range
9094 @kindex show check range
9096 @item set check range auto
9097 Set range checking on or off based on the current working language.
9098 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9101 @item set check range on
9102 @itemx set check range off
9103 Set range checking on or off, overriding the default setting for the
9104 current working language. A warning is issued if the setting does not
9105 match the language default. If a range error occurs and range checking is on,
9106 then a message is printed and evaluation of the expression is aborted.
9108 @item set check range warn
9109 Output messages when the @value{GDBN} range checker detects a range error,
9110 but attempt to evaluate the expression anyway. Evaluating the
9111 expression may still be impossible for other reasons, such as accessing
9112 memory that the process does not own (a typical example from many Unix
9116 Show the current setting of the range checker, and whether or not it is
9117 being set automatically by @value{GDBN}.
9120 @node Supported Languages
9121 @section Supported Languages
9123 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9124 assembly, Modula-2, and Ada.
9125 @c This is false ...
9126 Some @value{GDBN} features may be used in expressions regardless of the
9127 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9128 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9129 ,Expressions}) can be used with the constructs of any supported
9132 The following sections detail to what degree each source language is
9133 supported by @value{GDBN}. These sections are not meant to be language
9134 tutorials or references, but serve only as a reference guide to what the
9135 @value{GDBN} expression parser accepts, and what input and output
9136 formats should look like for different languages. There are many good
9137 books written on each of these languages; please look to these for a
9138 language reference or tutorial.
9142 * Objective-C:: Objective-C
9145 * Modula-2:: Modula-2
9150 @subsection C and C@t{++}
9152 @cindex C and C@t{++}
9153 @cindex expressions in C or C@t{++}
9155 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9156 to both languages. Whenever this is the case, we discuss those languages
9160 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9161 @cindex @sc{gnu} C@t{++}
9162 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9163 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9164 effectively, you must compile your C@t{++} programs with a supported
9165 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9166 compiler (@code{aCC}).
9168 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9169 format; if it doesn't work on your system, try the stabs+ debugging
9170 format. You can select those formats explicitly with the @code{g++}
9171 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9172 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9173 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9176 * C Operators:: C and C@t{++} operators
9177 * C Constants:: C and C@t{++} constants
9178 * C Plus Plus Expressions:: C@t{++} expressions
9179 * C Defaults:: Default settings for C and C@t{++}
9180 * C Checks:: C and C@t{++} type and range checks
9181 * Debugging C:: @value{GDBN} and C
9182 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9183 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9187 @subsubsection C and C@t{++} Operators
9189 @cindex C and C@t{++} operators
9191 Operators must be defined on values of specific types. For instance,
9192 @code{+} is defined on numbers, but not on structures. Operators are
9193 often defined on groups of types.
9195 For the purposes of C and C@t{++}, the following definitions hold:
9200 @emph{Integral types} include @code{int} with any of its storage-class
9201 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9204 @emph{Floating-point types} include @code{float}, @code{double}, and
9205 @code{long double} (if supported by the target platform).
9208 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9211 @emph{Scalar types} include all of the above.
9216 The following operators are supported. They are listed here
9217 in order of increasing precedence:
9221 The comma or sequencing operator. Expressions in a comma-separated list
9222 are evaluated from left to right, with the result of the entire
9223 expression being the last expression evaluated.
9226 Assignment. The value of an assignment expression is the value
9227 assigned. Defined on scalar types.
9230 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9231 and translated to @w{@code{@var{a} = @var{a op b}}}.
9232 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9233 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9234 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9237 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9238 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9242 Logical @sc{or}. Defined on integral types.
9245 Logical @sc{and}. Defined on integral types.
9248 Bitwise @sc{or}. Defined on integral types.
9251 Bitwise exclusive-@sc{or}. Defined on integral types.
9254 Bitwise @sc{and}. Defined on integral types.
9257 Equality and inequality. Defined on scalar types. The value of these
9258 expressions is 0 for false and non-zero for true.
9260 @item <@r{, }>@r{, }<=@r{, }>=
9261 Less than, greater than, less than or equal, greater than or equal.
9262 Defined on scalar types. The value of these expressions is 0 for false
9263 and non-zero for true.
9266 left shift, and right shift. Defined on integral types.
9269 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9272 Addition and subtraction. Defined on integral types, floating-point types and
9275 @item *@r{, }/@r{, }%
9276 Multiplication, division, and modulus. Multiplication and division are
9277 defined on integral and floating-point types. Modulus is defined on
9281 Increment and decrement. When appearing before a variable, the
9282 operation is performed before the variable is used in an expression;
9283 when appearing after it, the variable's value is used before the
9284 operation takes place.
9287 Pointer dereferencing. Defined on pointer types. Same precedence as
9291 Address operator. Defined on variables. Same precedence as @code{++}.
9293 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9294 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9295 to examine the address
9296 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9300 Negative. Defined on integral and floating-point types. Same
9301 precedence as @code{++}.
9304 Logical negation. Defined on integral types. Same precedence as
9308 Bitwise complement operator. Defined on integral types. Same precedence as
9313 Structure member, and pointer-to-structure member. For convenience,
9314 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9315 pointer based on the stored type information.
9316 Defined on @code{struct} and @code{union} data.
9319 Dereferences of pointers to members.
9322 Array indexing. @code{@var{a}[@var{i}]} is defined as
9323 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9326 Function parameter list. Same precedence as @code{->}.
9329 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9330 and @code{class} types.
9333 Doubled colons also represent the @value{GDBN} scope operator
9334 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9338 If an operator is redefined in the user code, @value{GDBN} usually
9339 attempts to invoke the redefined version instead of using the operator's
9343 @subsubsection C and C@t{++} Constants
9345 @cindex C and C@t{++} constants
9347 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9352 Integer constants are a sequence of digits. Octal constants are
9353 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9354 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9355 @samp{l}, specifying that the constant should be treated as a
9359 Floating point constants are a sequence of digits, followed by a decimal
9360 point, followed by a sequence of digits, and optionally followed by an
9361 exponent. An exponent is of the form:
9362 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9363 sequence of digits. The @samp{+} is optional for positive exponents.
9364 A floating-point constant may also end with a letter @samp{f} or
9365 @samp{F}, specifying that the constant should be treated as being of
9366 the @code{float} (as opposed to the default @code{double}) type; or with
9367 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9371 Enumerated constants consist of enumerated identifiers, or their
9372 integral equivalents.
9375 Character constants are a single character surrounded by single quotes
9376 (@code{'}), or a number---the ordinal value of the corresponding character
9377 (usually its @sc{ascii} value). Within quotes, the single character may
9378 be represented by a letter or by @dfn{escape sequences}, which are of
9379 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9380 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9381 @samp{@var{x}} is a predefined special character---for example,
9382 @samp{\n} for newline.
9385 String constants are a sequence of character constants surrounded by
9386 double quotes (@code{"}). Any valid character constant (as described
9387 above) may appear. Double quotes within the string must be preceded by
9388 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9392 Pointer constants are an integral value. You can also write pointers
9393 to constants using the C operator @samp{&}.
9396 Array constants are comma-separated lists surrounded by braces @samp{@{}
9397 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9398 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9399 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9402 @node C Plus Plus Expressions
9403 @subsubsection C@t{++} Expressions
9405 @cindex expressions in C@t{++}
9406 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9408 @cindex debugging C@t{++} programs
9409 @cindex C@t{++} compilers
9410 @cindex debug formats and C@t{++}
9411 @cindex @value{NGCC} and C@t{++}
9413 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9414 proper compiler and the proper debug format. Currently, @value{GDBN}
9415 works best when debugging C@t{++} code that is compiled with
9416 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9417 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9418 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9419 stabs+ as their default debug format, so you usually don't need to
9420 specify a debug format explicitly. Other compilers and/or debug formats
9421 are likely to work badly or not at all when using @value{GDBN} to debug
9427 @cindex member functions
9429 Member function calls are allowed; you can use expressions like
9432 count = aml->GetOriginal(x, y)
9435 @vindex this@r{, inside C@t{++} member functions}
9436 @cindex namespace in C@t{++}
9438 While a member function is active (in the selected stack frame), your
9439 expressions have the same namespace available as the member function;
9440 that is, @value{GDBN} allows implicit references to the class instance
9441 pointer @code{this} following the same rules as C@t{++}.
9443 @cindex call overloaded functions
9444 @cindex overloaded functions, calling
9445 @cindex type conversions in C@t{++}
9447 You can call overloaded functions; @value{GDBN} resolves the function
9448 call to the right definition, with some restrictions. @value{GDBN} does not
9449 perform overload resolution involving user-defined type conversions,
9450 calls to constructors, or instantiations of templates that do not exist
9451 in the program. It also cannot handle ellipsis argument lists or
9454 It does perform integral conversions and promotions, floating-point
9455 promotions, arithmetic conversions, pointer conversions, conversions of
9456 class objects to base classes, and standard conversions such as those of
9457 functions or arrays to pointers; it requires an exact match on the
9458 number of function arguments.
9460 Overload resolution is always performed, unless you have specified
9461 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9462 ,@value{GDBN} Features for C@t{++}}.
9464 You must specify @code{set overload-resolution off} in order to use an
9465 explicit function signature to call an overloaded function, as in
9467 p 'foo(char,int)'('x', 13)
9470 The @value{GDBN} command-completion facility can simplify this;
9471 see @ref{Completion, ,Command Completion}.
9473 @cindex reference declarations
9475 @value{GDBN} understands variables declared as C@t{++} references; you can use
9476 them in expressions just as you do in C@t{++} source---they are automatically
9479 In the parameter list shown when @value{GDBN} displays a frame, the values of
9480 reference variables are not displayed (unlike other variables); this
9481 avoids clutter, since references are often used for large structures.
9482 The @emph{address} of a reference variable is always shown, unless
9483 you have specified @samp{set print address off}.
9486 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9487 expressions can use it just as expressions in your program do. Since
9488 one scope may be defined in another, you can use @code{::} repeatedly if
9489 necessary, for example in an expression like
9490 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9491 resolving name scope by reference to source files, in both C and C@t{++}
9492 debugging (@pxref{Variables, ,Program Variables}).
9495 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9496 calling virtual functions correctly, printing out virtual bases of
9497 objects, calling functions in a base subobject, casting objects, and
9498 invoking user-defined operators.
9501 @subsubsection C and C@t{++} Defaults
9503 @cindex C and C@t{++} defaults
9505 If you allow @value{GDBN} to set type and range checking automatically, they
9506 both default to @code{off} whenever the working language changes to
9507 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9508 selects the working language.
9510 If you allow @value{GDBN} to set the language automatically, it
9511 recognizes source files whose names end with @file{.c}, @file{.C}, or
9512 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9513 these files, it sets the working language to C or C@t{++}.
9514 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9515 for further details.
9517 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9518 @c unimplemented. If (b) changes, it might make sense to let this node
9519 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9522 @subsubsection C and C@t{++} Type and Range Checks
9524 @cindex C and C@t{++} checks
9526 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9527 is not used. However, if you turn type checking on, @value{GDBN}
9528 considers two variables type equivalent if:
9532 The two variables are structured and have the same structure, union, or
9536 The two variables have the same type name, or types that have been
9537 declared equivalent through @code{typedef}.
9540 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9543 The two @code{struct}, @code{union}, or @code{enum} variables are
9544 declared in the same declaration. (Note: this may not be true for all C
9549 Range checking, if turned on, is done on mathematical operations. Array
9550 indices are not checked, since they are often used to index a pointer
9551 that is not itself an array.
9554 @subsubsection @value{GDBN} and C
9556 The @code{set print union} and @code{show print union} commands apply to
9557 the @code{union} type. When set to @samp{on}, any @code{union} that is
9558 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9559 appears as @samp{@{...@}}.
9561 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9562 with pointers and a memory allocation function. @xref{Expressions,
9565 @node Debugging C Plus Plus
9566 @subsubsection @value{GDBN} Features for C@t{++}
9568 @cindex commands for C@t{++}
9570 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9571 designed specifically for use with C@t{++}. Here is a summary:
9574 @cindex break in overloaded functions
9575 @item @r{breakpoint menus}
9576 When you want a breakpoint in a function whose name is overloaded,
9577 @value{GDBN} breakpoint menus help you specify which function definition
9578 you want. @xref{Breakpoint Menus,,Breakpoint Menus}.
9580 @cindex overloading in C@t{++}
9581 @item rbreak @var{regex}
9582 Setting breakpoints using regular expressions is helpful for setting
9583 breakpoints on overloaded functions that are not members of any special
9585 @xref{Set Breaks, ,Setting Breakpoints}.
9587 @cindex C@t{++} exception handling
9590 Debug C@t{++} exception handling using these commands. @xref{Set
9591 Catchpoints, , Setting Catchpoints}.
9594 @item ptype @var{typename}
9595 Print inheritance relationships as well as other information for type
9597 @xref{Symbols, ,Examining the Symbol Table}.
9599 @cindex C@t{++} symbol display
9600 @item set print demangle
9601 @itemx show print demangle
9602 @itemx set print asm-demangle
9603 @itemx show print asm-demangle
9604 Control whether C@t{++} symbols display in their source form, both when
9605 displaying code as C@t{++} source and when displaying disassemblies.
9606 @xref{Print Settings, ,Print Settings}.
9608 @item set print object
9609 @itemx show print object
9610 Choose whether to print derived (actual) or declared types of objects.
9611 @xref{Print Settings, ,Print Settings}.
9613 @item set print vtbl
9614 @itemx show print vtbl
9615 Control the format for printing virtual function tables.
9616 @xref{Print Settings, ,Print Settings}.
9617 (The @code{vtbl} commands do not work on programs compiled with the HP
9618 ANSI C@t{++} compiler (@code{aCC}).)
9620 @kindex set overload-resolution
9621 @cindex overloaded functions, overload resolution
9622 @item set overload-resolution on
9623 Enable overload resolution for C@t{++} expression evaluation. The default
9624 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9625 and searches for a function whose signature matches the argument types,
9626 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9627 Expressions, ,C@t{++} Expressions}, for details).
9628 If it cannot find a match, it emits a message.
9630 @item set overload-resolution off
9631 Disable overload resolution for C@t{++} expression evaluation. For
9632 overloaded functions that are not class member functions, @value{GDBN}
9633 chooses the first function of the specified name that it finds in the
9634 symbol table, whether or not its arguments are of the correct type. For
9635 overloaded functions that are class member functions, @value{GDBN}
9636 searches for a function whose signature @emph{exactly} matches the
9639 @kindex show overload-resolution
9640 @item show overload-resolution
9641 Show the current setting of overload resolution.
9643 @item @r{Overloaded symbol names}
9644 You can specify a particular definition of an overloaded symbol, using
9645 the same notation that is used to declare such symbols in C@t{++}: type
9646 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9647 also use the @value{GDBN} command-line word completion facilities to list the
9648 available choices, or to finish the type list for you.
9649 @xref{Completion,, Command Completion}, for details on how to do this.
9652 @node Decimal Floating Point
9653 @subsubsection Decimal Floating Point format
9654 @cindex decimal floating point format
9656 @value{GDBN} can examine, set and perform computations with numbers in
9657 decimal floating point format, which in the C language correspond to the
9658 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
9659 specified by the extension to support decimal floating-point arithmetic.
9661 There are two encodings in use, depending on the architecture: BID (Binary
9662 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
9663 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
9666 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
9667 to manipulate decimal floating point numbers, it is not possible to convert
9668 (using a cast, for example) integers wider than 32-bit to decimal float.
9670 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
9671 point computations, error checking in decimal float operations ignores
9672 underflow, overflow and divide by zero exceptions.
9675 @subsection Objective-C
9678 This section provides information about some commands and command
9679 options that are useful for debugging Objective-C code. See also
9680 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9681 few more commands specific to Objective-C support.
9684 * Method Names in Commands::
9685 * The Print Command with Objective-C::
9688 @node Method Names in Commands
9689 @subsubsection Method Names in Commands
9691 The following commands have been extended to accept Objective-C method
9692 names as line specifications:
9694 @kindex clear@r{, and Objective-C}
9695 @kindex break@r{, and Objective-C}
9696 @kindex info line@r{, and Objective-C}
9697 @kindex jump@r{, and Objective-C}
9698 @kindex list@r{, and Objective-C}
9702 @item @code{info line}
9707 A fully qualified Objective-C method name is specified as
9710 -[@var{Class} @var{methodName}]
9713 where the minus sign is used to indicate an instance method and a
9714 plus sign (not shown) is used to indicate a class method. The class
9715 name @var{Class} and method name @var{methodName} are enclosed in
9716 brackets, similar to the way messages are specified in Objective-C
9717 source code. For example, to set a breakpoint at the @code{create}
9718 instance method of class @code{Fruit} in the program currently being
9722 break -[Fruit create]
9725 To list ten program lines around the @code{initialize} class method,
9729 list +[NSText initialize]
9732 In the current version of @value{GDBN}, the plus or minus sign is
9733 required. In future versions of @value{GDBN}, the plus or minus
9734 sign will be optional, but you can use it to narrow the search. It
9735 is also possible to specify just a method name:
9741 You must specify the complete method name, including any colons. If
9742 your program's source files contain more than one @code{create} method,
9743 you'll be presented with a numbered list of classes that implement that
9744 method. Indicate your choice by number, or type @samp{0} to exit if
9747 As another example, to clear a breakpoint established at the
9748 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9751 clear -[NSWindow makeKeyAndOrderFront:]
9754 @node The Print Command with Objective-C
9755 @subsubsection The Print Command With Objective-C
9756 @cindex Objective-C, print objects
9757 @kindex print-object
9758 @kindex po @r{(@code{print-object})}
9760 The print command has also been extended to accept methods. For example:
9763 print -[@var{object} hash]
9766 @cindex print an Objective-C object description
9767 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9769 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9770 and print the result. Also, an additional command has been added,
9771 @code{print-object} or @code{po} for short, which is meant to print
9772 the description of an object. However, this command may only work
9773 with certain Objective-C libraries that have a particular hook
9774 function, @code{_NSPrintForDebugger}, defined.
9778 @cindex Fortran-specific support in @value{GDBN}
9780 @value{GDBN} can be used to debug programs written in Fortran, but it
9781 currently supports only the features of Fortran 77 language.
9783 @cindex trailing underscore, in Fortran symbols
9784 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9785 among them) append an underscore to the names of variables and
9786 functions. When you debug programs compiled by those compilers, you
9787 will need to refer to variables and functions with a trailing
9791 * Fortran Operators:: Fortran operators and expressions
9792 * Fortran Defaults:: Default settings for Fortran
9793 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
9796 @node Fortran Operators
9797 @subsubsection Fortran Operators and Expressions
9799 @cindex Fortran operators and expressions
9801 Operators must be defined on values of specific types. For instance,
9802 @code{+} is defined on numbers, but not on characters or other non-
9803 arithmetic types. Operators are often defined on groups of types.
9807 The exponentiation operator. It raises the first operand to the power
9811 The range operator. Normally used in the form of array(low:high) to
9812 represent a section of array.
9815 @node Fortran Defaults
9816 @subsubsection Fortran Defaults
9818 @cindex Fortran Defaults
9820 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9821 default uses case-insensitive matches for Fortran symbols. You can
9822 change that with the @samp{set case-insensitive} command, see
9823 @ref{Symbols}, for the details.
9825 @node Special Fortran Commands
9826 @subsubsection Special Fortran Commands
9828 @cindex Special Fortran commands
9830 @value{GDBN} has some commands to support Fortran-specific features,
9831 such as displaying common blocks.
9834 @cindex @code{COMMON} blocks, Fortran
9836 @item info common @r{[}@var{common-name}@r{]}
9837 This command prints the values contained in the Fortran @code{COMMON}
9838 block whose name is @var{common-name}. With no argument, the names of
9839 all @code{COMMON} blocks visible at the current program location are
9846 @cindex Pascal support in @value{GDBN}, limitations
9847 Debugging Pascal programs which use sets, subranges, file variables, or
9848 nested functions does not currently work. @value{GDBN} does not support
9849 entering expressions, printing values, or similar features using Pascal
9852 The Pascal-specific command @code{set print pascal_static-members}
9853 controls whether static members of Pascal objects are displayed.
9854 @xref{Print Settings, pascal_static-members}.
9857 @subsection Modula-2
9859 @cindex Modula-2, @value{GDBN} support
9861 The extensions made to @value{GDBN} to support Modula-2 only support
9862 output from the @sc{gnu} Modula-2 compiler (which is currently being
9863 developed). Other Modula-2 compilers are not currently supported, and
9864 attempting to debug executables produced by them is most likely
9865 to give an error as @value{GDBN} reads in the executable's symbol
9868 @cindex expressions in Modula-2
9870 * M2 Operators:: Built-in operators
9871 * Built-In Func/Proc:: Built-in functions and procedures
9872 * M2 Constants:: Modula-2 constants
9873 * M2 Types:: Modula-2 types
9874 * M2 Defaults:: Default settings for Modula-2
9875 * Deviations:: Deviations from standard Modula-2
9876 * M2 Checks:: Modula-2 type and range checks
9877 * M2 Scope:: The scope operators @code{::} and @code{.}
9878 * GDB/M2:: @value{GDBN} and Modula-2
9882 @subsubsection Operators
9883 @cindex Modula-2 operators
9885 Operators must be defined on values of specific types. For instance,
9886 @code{+} is defined on numbers, but not on structures. Operators are
9887 often defined on groups of types. For the purposes of Modula-2, the
9888 following definitions hold:
9893 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9897 @emph{Character types} consist of @code{CHAR} and its subranges.
9900 @emph{Floating-point types} consist of @code{REAL}.
9903 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9907 @emph{Scalar types} consist of all of the above.
9910 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9913 @emph{Boolean types} consist of @code{BOOLEAN}.
9917 The following operators are supported, and appear in order of
9918 increasing precedence:
9922 Function argument or array index separator.
9925 Assignment. The value of @var{var} @code{:=} @var{value} is
9929 Less than, greater than on integral, floating-point, or enumerated
9933 Less than or equal to, greater than or equal to
9934 on integral, floating-point and enumerated types, or set inclusion on
9935 set types. Same precedence as @code{<}.
9937 @item =@r{, }<>@r{, }#
9938 Equality and two ways of expressing inequality, valid on scalar types.
9939 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9940 available for inequality, since @code{#} conflicts with the script
9944 Set membership. Defined on set types and the types of their members.
9945 Same precedence as @code{<}.
9948 Boolean disjunction. Defined on boolean types.
9951 Boolean conjunction. Defined on boolean types.
9954 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9957 Addition and subtraction on integral and floating-point types, or union
9958 and difference on set types.
9961 Multiplication on integral and floating-point types, or set intersection
9965 Division on floating-point types, or symmetric set difference on set
9966 types. Same precedence as @code{*}.
9969 Integer division and remainder. Defined on integral types. Same
9970 precedence as @code{*}.
9973 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9976 Pointer dereferencing. Defined on pointer types.
9979 Boolean negation. Defined on boolean types. Same precedence as
9983 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9984 precedence as @code{^}.
9987 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9990 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9994 @value{GDBN} and Modula-2 scope operators.
9998 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9999 treats the use of the operator @code{IN}, or the use of operators
10000 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10001 @code{<=}, and @code{>=} on sets as an error.
10005 @node Built-In Func/Proc
10006 @subsubsection Built-in Functions and Procedures
10007 @cindex Modula-2 built-ins
10009 Modula-2 also makes available several built-in procedures and functions.
10010 In describing these, the following metavariables are used:
10015 represents an @code{ARRAY} variable.
10018 represents a @code{CHAR} constant or variable.
10021 represents a variable or constant of integral type.
10024 represents an identifier that belongs to a set. Generally used in the
10025 same function with the metavariable @var{s}. The type of @var{s} should
10026 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10029 represents a variable or constant of integral or floating-point type.
10032 represents a variable or constant of floating-point type.
10038 represents a variable.
10041 represents a variable or constant of one of many types. See the
10042 explanation of the function for details.
10045 All Modula-2 built-in procedures also return a result, described below.
10049 Returns the absolute value of @var{n}.
10052 If @var{c} is a lower case letter, it returns its upper case
10053 equivalent, otherwise it returns its argument.
10056 Returns the character whose ordinal value is @var{i}.
10059 Decrements the value in the variable @var{v} by one. Returns the new value.
10061 @item DEC(@var{v},@var{i})
10062 Decrements the value in the variable @var{v} by @var{i}. Returns the
10065 @item EXCL(@var{m},@var{s})
10066 Removes the element @var{m} from the set @var{s}. Returns the new
10069 @item FLOAT(@var{i})
10070 Returns the floating point equivalent of the integer @var{i}.
10072 @item HIGH(@var{a})
10073 Returns the index of the last member of @var{a}.
10076 Increments the value in the variable @var{v} by one. Returns the new value.
10078 @item INC(@var{v},@var{i})
10079 Increments the value in the variable @var{v} by @var{i}. Returns the
10082 @item INCL(@var{m},@var{s})
10083 Adds the element @var{m} to the set @var{s} if it is not already
10084 there. Returns the new set.
10087 Returns the maximum value of the type @var{t}.
10090 Returns the minimum value of the type @var{t}.
10093 Returns boolean TRUE if @var{i} is an odd number.
10096 Returns the ordinal value of its argument. For example, the ordinal
10097 value of a character is its @sc{ascii} value (on machines supporting the
10098 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10099 integral, character and enumerated types.
10101 @item SIZE(@var{x})
10102 Returns the size of its argument. @var{x} can be a variable or a type.
10104 @item TRUNC(@var{r})
10105 Returns the integral part of @var{r}.
10107 @item TSIZE(@var{x})
10108 Returns the size of its argument. @var{x} can be a variable or a type.
10110 @item VAL(@var{t},@var{i})
10111 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10115 @emph{Warning:} Sets and their operations are not yet supported, so
10116 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10120 @cindex Modula-2 constants
10122 @subsubsection Constants
10124 @value{GDBN} allows you to express the constants of Modula-2 in the following
10130 Integer constants are simply a sequence of digits. When used in an
10131 expression, a constant is interpreted to be type-compatible with the
10132 rest of the expression. Hexadecimal integers are specified by a
10133 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10136 Floating point constants appear as a sequence of digits, followed by a
10137 decimal point and another sequence of digits. An optional exponent can
10138 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10139 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10140 digits of the floating point constant must be valid decimal (base 10)
10144 Character constants consist of a single character enclosed by a pair of
10145 like quotes, either single (@code{'}) or double (@code{"}). They may
10146 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10147 followed by a @samp{C}.
10150 String constants consist of a sequence of characters enclosed by a
10151 pair of like quotes, either single (@code{'}) or double (@code{"}).
10152 Escape sequences in the style of C are also allowed. @xref{C
10153 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10157 Enumerated constants consist of an enumerated identifier.
10160 Boolean constants consist of the identifiers @code{TRUE} and
10164 Pointer constants consist of integral values only.
10167 Set constants are not yet supported.
10171 @subsubsection Modula-2 Types
10172 @cindex Modula-2 types
10174 Currently @value{GDBN} can print the following data types in Modula-2
10175 syntax: array types, record types, set types, pointer types, procedure
10176 types, enumerated types, subrange types and base types. You can also
10177 print the contents of variables declared using these type.
10178 This section gives a number of simple source code examples together with
10179 sample @value{GDBN} sessions.
10181 The first example contains the following section of code:
10190 and you can request @value{GDBN} to interrogate the type and value of
10191 @code{r} and @code{s}.
10194 (@value{GDBP}) print s
10196 (@value{GDBP}) ptype s
10198 (@value{GDBP}) print r
10200 (@value{GDBP}) ptype r
10205 Likewise if your source code declares @code{s} as:
10209 s: SET ['A'..'Z'] ;
10213 then you may query the type of @code{s} by:
10216 (@value{GDBP}) ptype s
10217 type = SET ['A'..'Z']
10221 Note that at present you cannot interactively manipulate set
10222 expressions using the debugger.
10224 The following example shows how you might declare an array in Modula-2
10225 and how you can interact with @value{GDBN} to print its type and contents:
10229 s: ARRAY [-10..10] OF CHAR ;
10233 (@value{GDBP}) ptype s
10234 ARRAY [-10..10] OF CHAR
10237 Note that the array handling is not yet complete and although the type
10238 is printed correctly, expression handling still assumes that all
10239 arrays have a lower bound of zero and not @code{-10} as in the example
10242 Here are some more type related Modula-2 examples:
10246 colour = (blue, red, yellow, green) ;
10247 t = [blue..yellow] ;
10255 The @value{GDBN} interaction shows how you can query the data type
10256 and value of a variable.
10259 (@value{GDBP}) print s
10261 (@value{GDBP}) ptype t
10262 type = [blue..yellow]
10266 In this example a Modula-2 array is declared and its contents
10267 displayed. Observe that the contents are written in the same way as
10268 their @code{C} counterparts.
10272 s: ARRAY [1..5] OF CARDINAL ;
10278 (@value{GDBP}) print s
10279 $1 = @{1, 0, 0, 0, 0@}
10280 (@value{GDBP}) ptype s
10281 type = ARRAY [1..5] OF CARDINAL
10284 The Modula-2 language interface to @value{GDBN} also understands
10285 pointer types as shown in this example:
10289 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10296 and you can request that @value{GDBN} describes the type of @code{s}.
10299 (@value{GDBP}) ptype s
10300 type = POINTER TO ARRAY [1..5] OF CARDINAL
10303 @value{GDBN} handles compound types as we can see in this example.
10304 Here we combine array types, record types, pointer types and subrange
10315 myarray = ARRAY myrange OF CARDINAL ;
10316 myrange = [-2..2] ;
10318 s: POINTER TO ARRAY myrange OF foo ;
10322 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10326 (@value{GDBP}) ptype s
10327 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10330 f3 : ARRAY [-2..2] OF CARDINAL;
10335 @subsubsection Modula-2 Defaults
10336 @cindex Modula-2 defaults
10338 If type and range checking are set automatically by @value{GDBN}, they
10339 both default to @code{on} whenever the working language changes to
10340 Modula-2. This happens regardless of whether you or @value{GDBN}
10341 selected the working language.
10343 If you allow @value{GDBN} to set the language automatically, then entering
10344 code compiled from a file whose name ends with @file{.mod} sets the
10345 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10346 Infer the Source Language}, for further details.
10349 @subsubsection Deviations from Standard Modula-2
10350 @cindex Modula-2, deviations from
10352 A few changes have been made to make Modula-2 programs easier to debug.
10353 This is done primarily via loosening its type strictness:
10357 Unlike in standard Modula-2, pointer constants can be formed by
10358 integers. This allows you to modify pointer variables during
10359 debugging. (In standard Modula-2, the actual address contained in a
10360 pointer variable is hidden from you; it can only be modified
10361 through direct assignment to another pointer variable or expression that
10362 returned a pointer.)
10365 C escape sequences can be used in strings and characters to represent
10366 non-printable characters. @value{GDBN} prints out strings with these
10367 escape sequences embedded. Single non-printable characters are
10368 printed using the @samp{CHR(@var{nnn})} format.
10371 The assignment operator (@code{:=}) returns the value of its right-hand
10375 All built-in procedures both modify @emph{and} return their argument.
10379 @subsubsection Modula-2 Type and Range Checks
10380 @cindex Modula-2 checks
10383 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10386 @c FIXME remove warning when type/range checks added
10388 @value{GDBN} considers two Modula-2 variables type equivalent if:
10392 They are of types that have been declared equivalent via a @code{TYPE
10393 @var{t1} = @var{t2}} statement
10396 They have been declared on the same line. (Note: This is true of the
10397 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10400 As long as type checking is enabled, any attempt to combine variables
10401 whose types are not equivalent is an error.
10403 Range checking is done on all mathematical operations, assignment, array
10404 index bounds, and all built-in functions and procedures.
10407 @subsubsection The Scope Operators @code{::} and @code{.}
10409 @cindex @code{.}, Modula-2 scope operator
10410 @cindex colon, doubled as scope operator
10412 @vindex colon-colon@r{, in Modula-2}
10413 @c Info cannot handle :: but TeX can.
10416 @vindex ::@r{, in Modula-2}
10419 There are a few subtle differences between the Modula-2 scope operator
10420 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10425 @var{module} . @var{id}
10426 @var{scope} :: @var{id}
10430 where @var{scope} is the name of a module or a procedure,
10431 @var{module} the name of a module, and @var{id} is any declared
10432 identifier within your program, except another module.
10434 Using the @code{::} operator makes @value{GDBN} search the scope
10435 specified by @var{scope} for the identifier @var{id}. If it is not
10436 found in the specified scope, then @value{GDBN} searches all scopes
10437 enclosing the one specified by @var{scope}.
10439 Using the @code{.} operator makes @value{GDBN} search the current scope for
10440 the identifier specified by @var{id} that was imported from the
10441 definition module specified by @var{module}. With this operator, it is
10442 an error if the identifier @var{id} was not imported from definition
10443 module @var{module}, or if @var{id} is not an identifier in
10447 @subsubsection @value{GDBN} and Modula-2
10449 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10450 Five subcommands of @code{set print} and @code{show print} apply
10451 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10452 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10453 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10454 analogue in Modula-2.
10456 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10457 with any language, is not useful with Modula-2. Its
10458 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10459 created in Modula-2 as they can in C or C@t{++}. However, because an
10460 address can be specified by an integral constant, the construct
10461 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10463 @cindex @code{#} in Modula-2
10464 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10465 interpreted as the beginning of a comment. Use @code{<>} instead.
10471 The extensions made to @value{GDBN} for Ada only support
10472 output from the @sc{gnu} Ada (GNAT) compiler.
10473 Other Ada compilers are not currently supported, and
10474 attempting to debug executables produced by them is most likely
10478 @cindex expressions in Ada
10480 * Ada Mode Intro:: General remarks on the Ada syntax
10481 and semantics supported by Ada mode
10483 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10484 * Additions to Ada:: Extensions of the Ada expression syntax.
10485 * Stopping Before Main Program:: Debugging the program during elaboration.
10486 * Ada Glitches:: Known peculiarities of Ada mode.
10489 @node Ada Mode Intro
10490 @subsubsection Introduction
10491 @cindex Ada mode, general
10493 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10494 syntax, with some extensions.
10495 The philosophy behind the design of this subset is
10499 That @value{GDBN} should provide basic literals and access to operations for
10500 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10501 leaving more sophisticated computations to subprograms written into the
10502 program (which therefore may be called from @value{GDBN}).
10505 That type safety and strict adherence to Ada language restrictions
10506 are not particularly important to the @value{GDBN} user.
10509 That brevity is important to the @value{GDBN} user.
10512 Thus, for brevity, the debugger acts as if there were
10513 implicit @code{with} and @code{use} clauses in effect for all user-written
10514 packages, making it unnecessary to fully qualify most names with
10515 their packages, regardless of context. Where this causes ambiguity,
10516 @value{GDBN} asks the user's intent.
10518 The debugger will start in Ada mode if it detects an Ada main program.
10519 As for other languages, it will enter Ada mode when stopped in a program that
10520 was translated from an Ada source file.
10522 While in Ada mode, you may use `@t{--}' for comments. This is useful
10523 mostly for documenting command files. The standard @value{GDBN} comment
10524 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10525 middle (to allow based literals).
10527 The debugger supports limited overloading. Given a subprogram call in which
10528 the function symbol has multiple definitions, it will use the number of
10529 actual parameters and some information about their types to attempt to narrow
10530 the set of definitions. It also makes very limited use of context, preferring
10531 procedures to functions in the context of the @code{call} command, and
10532 functions to procedures elsewhere.
10534 @node Omissions from Ada
10535 @subsubsection Omissions from Ada
10536 @cindex Ada, omissions from
10538 Here are the notable omissions from the subset:
10542 Only a subset of the attributes are supported:
10546 @t{'First}, @t{'Last}, and @t{'Length}
10547 on array objects (not on types and subtypes).
10550 @t{'Min} and @t{'Max}.
10553 @t{'Pos} and @t{'Val}.
10559 @t{'Range} on array objects (not subtypes), but only as the right
10560 operand of the membership (@code{in}) operator.
10563 @t{'Access}, @t{'Unchecked_Access}, and
10564 @t{'Unrestricted_Access} (a GNAT extension).
10572 @code{Characters.Latin_1} are not available and
10573 concatenation is not implemented. Thus, escape characters in strings are
10574 not currently available.
10577 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10578 equality of representations. They will generally work correctly
10579 for strings and arrays whose elements have integer or enumeration types.
10580 They may not work correctly for arrays whose element
10581 types have user-defined equality, for arrays of real values
10582 (in particular, IEEE-conformant floating point, because of negative
10583 zeroes and NaNs), and for arrays whose elements contain unused bits with
10584 indeterminate values.
10587 The other component-by-component array operations (@code{and}, @code{or},
10588 @code{xor}, @code{not}, and relational tests other than equality)
10589 are not implemented.
10592 @cindex array aggregates (Ada)
10593 @cindex record aggregates (Ada)
10594 @cindex aggregates (Ada)
10595 There is limited support for array and record aggregates. They are
10596 permitted only on the right sides of assignments, as in these examples:
10599 set An_Array := (1, 2, 3, 4, 5, 6)
10600 set An_Array := (1, others => 0)
10601 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10602 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10603 set A_Record := (1, "Peter", True);
10604 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10608 discriminant's value by assigning an aggregate has an
10609 undefined effect if that discriminant is used within the record.
10610 However, you can first modify discriminants by directly assigning to
10611 them (which normally would not be allowed in Ada), and then performing an
10612 aggregate assignment. For example, given a variable @code{A_Rec}
10613 declared to have a type such as:
10616 type Rec (Len : Small_Integer := 0) is record
10618 Vals : IntArray (1 .. Len);
10622 you can assign a value with a different size of @code{Vals} with two
10627 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10630 As this example also illustrates, @value{GDBN} is very loose about the usual
10631 rules concerning aggregates. You may leave out some of the
10632 components of an array or record aggregate (such as the @code{Len}
10633 component in the assignment to @code{A_Rec} above); they will retain their
10634 original values upon assignment. You may freely use dynamic values as
10635 indices in component associations. You may even use overlapping or
10636 redundant component associations, although which component values are
10637 assigned in such cases is not defined.
10640 Calls to dispatching subprograms are not implemented.
10643 The overloading algorithm is much more limited (i.e., less selective)
10644 than that of real Ada. It makes only limited use of the context in
10645 which a subexpression appears to resolve its meaning, and it is much
10646 looser in its rules for allowing type matches. As a result, some
10647 function calls will be ambiguous, and the user will be asked to choose
10648 the proper resolution.
10651 The @code{new} operator is not implemented.
10654 Entry calls are not implemented.
10657 Aside from printing, arithmetic operations on the native VAX floating-point
10658 formats are not supported.
10661 It is not possible to slice a packed array.
10664 @node Additions to Ada
10665 @subsubsection Additions to Ada
10666 @cindex Ada, deviations from
10668 As it does for other languages, @value{GDBN} makes certain generic
10669 extensions to Ada (@pxref{Expressions}):
10673 If the expression @var{E} is a variable residing in memory (typically
10674 a local variable or array element) and @var{N} is a positive integer,
10675 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10676 @var{N}-1 adjacent variables following it in memory as an array. In
10677 Ada, this operator is generally not necessary, since its prime use is
10678 in displaying parts of an array, and slicing will usually do this in
10679 Ada. However, there are occasional uses when debugging programs in
10680 which certain debugging information has been optimized away.
10683 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10684 appears in function or file @var{B}.'' When @var{B} is a file name,
10685 you must typically surround it in single quotes.
10688 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10689 @var{type} that appears at address @var{addr}.''
10692 A name starting with @samp{$} is a convenience variable
10693 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10696 In addition, @value{GDBN} provides a few other shortcuts and outright
10697 additions specific to Ada:
10701 The assignment statement is allowed as an expression, returning
10702 its right-hand operand as its value. Thus, you may enter
10706 print A(tmp := y + 1)
10710 The semicolon is allowed as an ``operator,'' returning as its value
10711 the value of its right-hand operand.
10712 This allows, for example,
10713 complex conditional breaks:
10717 condition 1 (report(i); k += 1; A(k) > 100)
10721 Rather than use catenation and symbolic character names to introduce special
10722 characters into strings, one may instead use a special bracket notation,
10723 which is also used to print strings. A sequence of characters of the form
10724 @samp{["@var{XX}"]} within a string or character literal denotes the
10725 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10726 sequence of characters @samp{["""]} also denotes a single quotation mark
10727 in strings. For example,
10729 "One line.["0a"]Next line.["0a"]"
10732 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10736 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10737 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10745 When printing arrays, @value{GDBN} uses positional notation when the
10746 array has a lower bound of 1, and uses a modified named notation otherwise.
10747 For example, a one-dimensional array of three integers with a lower bound
10748 of 3 might print as
10755 That is, in contrast to valid Ada, only the first component has a @code{=>}
10759 You may abbreviate attributes in expressions with any unique,
10760 multi-character subsequence of
10761 their names (an exact match gets preference).
10762 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10763 in place of @t{a'length}.
10766 @cindex quoting Ada internal identifiers
10767 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10768 to lower case. The GNAT compiler uses upper-case characters for
10769 some of its internal identifiers, which are normally of no interest to users.
10770 For the rare occasions when you actually have to look at them,
10771 enclose them in angle brackets to avoid the lower-case mapping.
10774 @value{GDBP} print <JMPBUF_SAVE>[0]
10778 Printing an object of class-wide type or dereferencing an
10779 access-to-class-wide value will display all the components of the object's
10780 specific type (as indicated by its run-time tag). Likewise, component
10781 selection on such a value will operate on the specific type of the
10786 @node Stopping Before Main Program
10787 @subsubsection Stopping at the Very Beginning
10789 @cindex breakpointing Ada elaboration code
10790 It is sometimes necessary to debug the program during elaboration, and
10791 before reaching the main procedure.
10792 As defined in the Ada Reference
10793 Manual, the elaboration code is invoked from a procedure called
10794 @code{adainit}. To run your program up to the beginning of
10795 elaboration, simply use the following two commands:
10796 @code{tbreak adainit} and @code{run}.
10799 @subsubsection Known Peculiarities of Ada Mode
10800 @cindex Ada, problems
10802 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10803 we know of several problems with and limitations of Ada mode in
10805 some of which will be fixed with planned future releases of the debugger
10806 and the GNU Ada compiler.
10810 Currently, the debugger
10811 has insufficient information to determine whether certain pointers represent
10812 pointers to objects or the objects themselves.
10813 Thus, the user may have to tack an extra @code{.all} after an expression
10814 to get it printed properly.
10817 Static constants that the compiler chooses not to materialize as objects in
10818 storage are invisible to the debugger.
10821 Named parameter associations in function argument lists are ignored (the
10822 argument lists are treated as positional).
10825 Many useful library packages are currently invisible to the debugger.
10828 Fixed-point arithmetic, conversions, input, and output is carried out using
10829 floating-point arithmetic, and may give results that only approximate those on
10833 The type of the @t{'Address} attribute may not be @code{System.Address}.
10836 The GNAT compiler never generates the prefix @code{Standard} for any of
10837 the standard symbols defined by the Ada language. @value{GDBN} knows about
10838 this: it will strip the prefix from names when you use it, and will never
10839 look for a name you have so qualified among local symbols, nor match against
10840 symbols in other packages or subprograms. If you have
10841 defined entities anywhere in your program other than parameters and
10842 local variables whose simple names match names in @code{Standard},
10843 GNAT's lack of qualification here can cause confusion. When this happens,
10844 you can usually resolve the confusion
10845 by qualifying the problematic names with package
10846 @code{Standard} explicitly.
10849 @node Unsupported Languages
10850 @section Unsupported Languages
10852 @cindex unsupported languages
10853 @cindex minimal language
10854 In addition to the other fully-supported programming languages,
10855 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10856 It does not represent a real programming language, but provides a set
10857 of capabilities close to what the C or assembly languages provide.
10858 This should allow most simple operations to be performed while debugging
10859 an application that uses a language currently not supported by @value{GDBN}.
10861 If the language is set to @code{auto}, @value{GDBN} will automatically
10862 select this language if the current frame corresponds to an unsupported
10866 @chapter Examining the Symbol Table
10868 The commands described in this chapter allow you to inquire about the
10869 symbols (names of variables, functions and types) defined in your
10870 program. This information is inherent in the text of your program and
10871 does not change as your program executes. @value{GDBN} finds it in your
10872 program's symbol table, in the file indicated when you started @value{GDBN}
10873 (@pxref{File Options, ,Choosing Files}), or by one of the
10874 file-management commands (@pxref{Files, ,Commands to Specify Files}).
10876 @cindex symbol names
10877 @cindex names of symbols
10878 @cindex quoting names
10879 Occasionally, you may need to refer to symbols that contain unusual
10880 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10881 most frequent case is in referring to static variables in other
10882 source files (@pxref{Variables,,Program Variables}). File names
10883 are recorded in object files as debugging symbols, but @value{GDBN} would
10884 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10885 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10886 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10893 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10896 @cindex case-insensitive symbol names
10897 @cindex case sensitivity in symbol names
10898 @kindex set case-sensitive
10899 @item set case-sensitive on
10900 @itemx set case-sensitive off
10901 @itemx set case-sensitive auto
10902 Normally, when @value{GDBN} looks up symbols, it matches their names
10903 with case sensitivity determined by the current source language.
10904 Occasionally, you may wish to control that. The command @code{set
10905 case-sensitive} lets you do that by specifying @code{on} for
10906 case-sensitive matches or @code{off} for case-insensitive ones. If
10907 you specify @code{auto}, case sensitivity is reset to the default
10908 suitable for the source language. The default is case-sensitive
10909 matches for all languages except for Fortran, for which the default is
10910 case-insensitive matches.
10912 @kindex show case-sensitive
10913 @item show case-sensitive
10914 This command shows the current setting of case sensitivity for symbols
10917 @kindex info address
10918 @cindex address of a symbol
10919 @item info address @var{symbol}
10920 Describe where the data for @var{symbol} is stored. For a register
10921 variable, this says which register it is kept in. For a non-register
10922 local variable, this prints the stack-frame offset at which the variable
10925 Note the contrast with @samp{print &@var{symbol}}, which does not work
10926 at all for a register variable, and for a stack local variable prints
10927 the exact address of the current instantiation of the variable.
10929 @kindex info symbol
10930 @cindex symbol from address
10931 @cindex closest symbol and offset for an address
10932 @item info symbol @var{addr}
10933 Print the name of a symbol which is stored at the address @var{addr}.
10934 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10935 nearest symbol and an offset from it:
10938 (@value{GDBP}) info symbol 0x54320
10939 _initialize_vx + 396 in section .text
10943 This is the opposite of the @code{info address} command. You can use
10944 it to find out the name of a variable or a function given its address.
10947 @item whatis [@var{arg}]
10948 Print the data type of @var{arg}, which can be either an expression or
10949 a data type. With no argument, print the data type of @code{$}, the
10950 last value in the value history. If @var{arg} is an expression, it is
10951 not actually evaluated, and any side-effecting operations (such as
10952 assignments or function calls) inside it do not take place. If
10953 @var{arg} is a type name, it may be the name of a type or typedef, or
10954 for C code it may have the form @samp{class @var{class-name}},
10955 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10956 @samp{enum @var{enum-tag}}.
10957 @xref{Expressions, ,Expressions}.
10960 @item ptype [@var{arg}]
10961 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10962 detailed description of the type, instead of just the name of the type.
10963 @xref{Expressions, ,Expressions}.
10965 For example, for this variable declaration:
10968 struct complex @{double real; double imag;@} v;
10972 the two commands give this output:
10976 (@value{GDBP}) whatis v
10977 type = struct complex
10978 (@value{GDBP}) ptype v
10979 type = struct complex @{
10987 As with @code{whatis}, using @code{ptype} without an argument refers to
10988 the type of @code{$}, the last value in the value history.
10990 @cindex incomplete type
10991 Sometimes, programs use opaque data types or incomplete specifications
10992 of complex data structure. If the debug information included in the
10993 program does not allow @value{GDBN} to display a full declaration of
10994 the data type, it will say @samp{<incomplete type>}. For example,
10995 given these declarations:
10999 struct foo *fooptr;
11003 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11006 (@value{GDBP}) ptype foo
11007 $1 = <incomplete type>
11011 ``Incomplete type'' is C terminology for data types that are not
11012 completely specified.
11015 @item info types @var{regexp}
11017 Print a brief description of all types whose names match the regular
11018 expression @var{regexp} (or all types in your program, if you supply
11019 no argument). Each complete typename is matched as though it were a
11020 complete line; thus, @samp{i type value} gives information on all
11021 types in your program whose names include the string @code{value}, but
11022 @samp{i type ^value$} gives information only on types whose complete
11023 name is @code{value}.
11025 This command differs from @code{ptype} in two ways: first, like
11026 @code{whatis}, it does not print a detailed description; second, it
11027 lists all source files where a type is defined.
11030 @cindex local variables
11031 @item info scope @var{location}
11032 List all the variables local to a particular scope. This command
11033 accepts a @var{location} argument---a function name, a source line, or
11034 an address preceded by a @samp{*}, and prints all the variables local
11035 to the scope defined by that location. (@xref{Specify Location}, for
11036 details about supported forms of @var{location}.) For example:
11039 (@value{GDBP}) @b{info scope command_line_handler}
11040 Scope for command_line_handler:
11041 Symbol rl is an argument at stack/frame offset 8, length 4.
11042 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11043 Symbol linelength is in static storage at address 0x150a1c, length 4.
11044 Symbol p is a local variable in register $esi, length 4.
11045 Symbol p1 is a local variable in register $ebx, length 4.
11046 Symbol nline is a local variable in register $edx, length 4.
11047 Symbol repeat is a local variable at frame offset -8, length 4.
11051 This command is especially useful for determining what data to collect
11052 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11055 @kindex info source
11057 Show information about the current source file---that is, the source file for
11058 the function containing the current point of execution:
11061 the name of the source file, and the directory containing it,
11063 the directory it was compiled in,
11065 its length, in lines,
11067 which programming language it is written in,
11069 whether the executable includes debugging information for that file, and
11070 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11072 whether the debugging information includes information about
11073 preprocessor macros.
11077 @kindex info sources
11079 Print the names of all source files in your program for which there is
11080 debugging information, organized into two lists: files whose symbols
11081 have already been read, and files whose symbols will be read when needed.
11083 @kindex info functions
11084 @item info functions
11085 Print the names and data types of all defined functions.
11087 @item info functions @var{regexp}
11088 Print the names and data types of all defined functions
11089 whose names contain a match for regular expression @var{regexp}.
11090 Thus, @samp{info fun step} finds all functions whose names
11091 include @code{step}; @samp{info fun ^step} finds those whose names
11092 start with @code{step}. If a function name contains characters
11093 that conflict with the regular expression language (e.g.@:
11094 @samp{operator*()}), they may be quoted with a backslash.
11096 @kindex info variables
11097 @item info variables
11098 Print the names and data types of all variables that are declared
11099 outside of functions (i.e.@: excluding local variables).
11101 @item info variables @var{regexp}
11102 Print the names and data types of all variables (except for local
11103 variables) whose names contain a match for regular expression
11106 @kindex info classes
11107 @cindex Objective-C, classes and selectors
11109 @itemx info classes @var{regexp}
11110 Display all Objective-C classes in your program, or
11111 (with the @var{regexp} argument) all those matching a particular regular
11114 @kindex info selectors
11115 @item info selectors
11116 @itemx info selectors @var{regexp}
11117 Display all Objective-C selectors in your program, or
11118 (with the @var{regexp} argument) all those matching a particular regular
11122 This was never implemented.
11123 @kindex info methods
11125 @itemx info methods @var{regexp}
11126 The @code{info methods} command permits the user to examine all defined
11127 methods within C@t{++} program, or (with the @var{regexp} argument) a
11128 specific set of methods found in the various C@t{++} classes. Many
11129 C@t{++} classes provide a large number of methods. Thus, the output
11130 from the @code{ptype} command can be overwhelming and hard to use. The
11131 @code{info-methods} command filters the methods, printing only those
11132 which match the regular-expression @var{regexp}.
11135 @cindex reloading symbols
11136 Some systems allow individual object files that make up your program to
11137 be replaced without stopping and restarting your program. For example,
11138 in VxWorks you can simply recompile a defective object file and keep on
11139 running. If you are running on one of these systems, you can allow
11140 @value{GDBN} to reload the symbols for automatically relinked modules:
11143 @kindex set symbol-reloading
11144 @item set symbol-reloading on
11145 Replace symbol definitions for the corresponding source file when an
11146 object file with a particular name is seen again.
11148 @item set symbol-reloading off
11149 Do not replace symbol definitions when encountering object files of the
11150 same name more than once. This is the default state; if you are not
11151 running on a system that permits automatic relinking of modules, you
11152 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11153 may discard symbols when linking large programs, that may contain
11154 several modules (from different directories or libraries) with the same
11157 @kindex show symbol-reloading
11158 @item show symbol-reloading
11159 Show the current @code{on} or @code{off} setting.
11162 @cindex opaque data types
11163 @kindex set opaque-type-resolution
11164 @item set opaque-type-resolution on
11165 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11166 declared as a pointer to a @code{struct}, @code{class}, or
11167 @code{union}---for example, @code{struct MyType *}---that is used in one
11168 source file although the full declaration of @code{struct MyType} is in
11169 another source file. The default is on.
11171 A change in the setting of this subcommand will not take effect until
11172 the next time symbols for a file are loaded.
11174 @item set opaque-type-resolution off
11175 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11176 is printed as follows:
11178 @{<no data fields>@}
11181 @kindex show opaque-type-resolution
11182 @item show opaque-type-resolution
11183 Show whether opaque types are resolved or not.
11185 @kindex maint print symbols
11186 @cindex symbol dump
11187 @kindex maint print psymbols
11188 @cindex partial symbol dump
11189 @item maint print symbols @var{filename}
11190 @itemx maint print psymbols @var{filename}
11191 @itemx maint print msymbols @var{filename}
11192 Write a dump of debugging symbol data into the file @var{filename}.
11193 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11194 symbols with debugging data are included. If you use @samp{maint print
11195 symbols}, @value{GDBN} includes all the symbols for which it has already
11196 collected full details: that is, @var{filename} reflects symbols for
11197 only those files whose symbols @value{GDBN} has read. You can use the
11198 command @code{info sources} to find out which files these are. If you
11199 use @samp{maint print psymbols} instead, the dump shows information about
11200 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11201 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11202 @samp{maint print msymbols} dumps just the minimal symbol information
11203 required for each object file from which @value{GDBN} has read some symbols.
11204 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11205 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11207 @kindex maint info symtabs
11208 @kindex maint info psymtabs
11209 @cindex listing @value{GDBN}'s internal symbol tables
11210 @cindex symbol tables, listing @value{GDBN}'s internal
11211 @cindex full symbol tables, listing @value{GDBN}'s internal
11212 @cindex partial symbol tables, listing @value{GDBN}'s internal
11213 @item maint info symtabs @r{[} @var{regexp} @r{]}
11214 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11216 List the @code{struct symtab} or @code{struct partial_symtab}
11217 structures whose names match @var{regexp}. If @var{regexp} is not
11218 given, list them all. The output includes expressions which you can
11219 copy into a @value{GDBN} debugging this one to examine a particular
11220 structure in more detail. For example:
11223 (@value{GDBP}) maint info psymtabs dwarf2read
11224 @{ objfile /home/gnu/build/gdb/gdb
11225 ((struct objfile *) 0x82e69d0)
11226 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11227 ((struct partial_symtab *) 0x8474b10)
11230 text addresses 0x814d3c8 -- 0x8158074
11231 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11232 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11233 dependencies (none)
11236 (@value{GDBP}) maint info symtabs
11240 We see that there is one partial symbol table whose filename contains
11241 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11242 and we see that @value{GDBN} has not read in any symtabs yet at all.
11243 If we set a breakpoint on a function, that will cause @value{GDBN} to
11244 read the symtab for the compilation unit containing that function:
11247 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11248 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11250 (@value{GDBP}) maint info symtabs
11251 @{ objfile /home/gnu/build/gdb/gdb
11252 ((struct objfile *) 0x82e69d0)
11253 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11254 ((struct symtab *) 0x86c1f38)
11257 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11258 linetable ((struct linetable *) 0x8370fa0)
11259 debugformat DWARF 2
11268 @chapter Altering Execution
11270 Once you think you have found an error in your program, you might want to
11271 find out for certain whether correcting the apparent error would lead to
11272 correct results in the rest of the run. You can find the answer by
11273 experiment, using the @value{GDBN} features for altering execution of the
11276 For example, you can store new values into variables or memory
11277 locations, give your program a signal, restart it at a different
11278 address, or even return prematurely from a function.
11281 * Assignment:: Assignment to variables
11282 * Jumping:: Continuing at a different address
11283 * Signaling:: Giving your program a signal
11284 * Returning:: Returning from a function
11285 * Calling:: Calling your program's functions
11286 * Patching:: Patching your program
11290 @section Assignment to Variables
11293 @cindex setting variables
11294 To alter the value of a variable, evaluate an assignment expression.
11295 @xref{Expressions, ,Expressions}. For example,
11302 stores the value 4 into the variable @code{x}, and then prints the
11303 value of the assignment expression (which is 4).
11304 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11305 information on operators in supported languages.
11307 @kindex set variable
11308 @cindex variables, setting
11309 If you are not interested in seeing the value of the assignment, use the
11310 @code{set} command instead of the @code{print} command. @code{set} is
11311 really the same as @code{print} except that the expression's value is
11312 not printed and is not put in the value history (@pxref{Value History,
11313 ,Value History}). The expression is evaluated only for its effects.
11315 If the beginning of the argument string of the @code{set} command
11316 appears identical to a @code{set} subcommand, use the @code{set
11317 variable} command instead of just @code{set}. This command is identical
11318 to @code{set} except for its lack of subcommands. For example, if your
11319 program has a variable @code{width}, you get an error if you try to set
11320 a new value with just @samp{set width=13}, because @value{GDBN} has the
11321 command @code{set width}:
11324 (@value{GDBP}) whatis width
11326 (@value{GDBP}) p width
11328 (@value{GDBP}) set width=47
11329 Invalid syntax in expression.
11333 The invalid expression, of course, is @samp{=47}. In
11334 order to actually set the program's variable @code{width}, use
11337 (@value{GDBP}) set var width=47
11340 Because the @code{set} command has many subcommands that can conflict
11341 with the names of program variables, it is a good idea to use the
11342 @code{set variable} command instead of just @code{set}. For example, if
11343 your program has a variable @code{g}, you run into problems if you try
11344 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11345 the command @code{set gnutarget}, abbreviated @code{set g}:
11349 (@value{GDBP}) whatis g
11353 (@value{GDBP}) set g=4
11357 The program being debugged has been started already.
11358 Start it from the beginning? (y or n) y
11359 Starting program: /home/smith/cc_progs/a.out
11360 "/home/smith/cc_progs/a.out": can't open to read symbols:
11361 Invalid bfd target.
11362 (@value{GDBP}) show g
11363 The current BFD target is "=4".
11368 The program variable @code{g} did not change, and you silently set the
11369 @code{gnutarget} to an invalid value. In order to set the variable
11373 (@value{GDBP}) set var g=4
11376 @value{GDBN} allows more implicit conversions in assignments than C; you can
11377 freely store an integer value into a pointer variable or vice versa,
11378 and you can convert any structure to any other structure that is the
11379 same length or shorter.
11380 @comment FIXME: how do structs align/pad in these conversions?
11381 @comment /doc@cygnus.com 18dec1990
11383 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11384 construct to generate a value of specified type at a specified address
11385 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11386 to memory location @code{0x83040} as an integer (which implies a certain size
11387 and representation in memory), and
11390 set @{int@}0x83040 = 4
11394 stores the value 4 into that memory location.
11397 @section Continuing at a Different Address
11399 Ordinarily, when you continue your program, you do so at the place where
11400 it stopped, with the @code{continue} command. You can instead continue at
11401 an address of your own choosing, with the following commands:
11405 @item jump @var{linespec}
11406 @itemx jump @var{location}
11407 Resume execution at line @var{linespec} or at address given by
11408 @var{location}. Execution stops again immediately if there is a
11409 breakpoint there. @xref{Specify Location}, for a description of the
11410 different forms of @var{linespec} and @var{location}. It is common
11411 practice to use the @code{tbreak} command in conjunction with
11412 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
11414 The @code{jump} command does not change the current stack frame, or
11415 the stack pointer, or the contents of any memory location or any
11416 register other than the program counter. If line @var{linespec} is in
11417 a different function from the one currently executing, the results may
11418 be bizarre if the two functions expect different patterns of arguments or
11419 of local variables. For this reason, the @code{jump} command requests
11420 confirmation if the specified line is not in the function currently
11421 executing. However, even bizarre results are predictable if you are
11422 well acquainted with the machine-language code of your program.
11425 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11426 On many systems, you can get much the same effect as the @code{jump}
11427 command by storing a new value into the register @code{$pc}. The
11428 difference is that this does not start your program running; it only
11429 changes the address of where it @emph{will} run when you continue. For
11437 makes the next @code{continue} command or stepping command execute at
11438 address @code{0x485}, rather than at the address where your program stopped.
11439 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11441 The most common occasion to use the @code{jump} command is to back
11442 up---perhaps with more breakpoints set---over a portion of a program
11443 that has already executed, in order to examine its execution in more
11448 @section Giving your Program a Signal
11449 @cindex deliver a signal to a program
11453 @item signal @var{signal}
11454 Resume execution where your program stopped, but immediately give it the
11455 signal @var{signal}. @var{signal} can be the name or the number of a
11456 signal. For example, on many systems @code{signal 2} and @code{signal
11457 SIGINT} are both ways of sending an interrupt signal.
11459 Alternatively, if @var{signal} is zero, continue execution without
11460 giving a signal. This is useful when your program stopped on account of
11461 a signal and would ordinary see the signal when resumed with the
11462 @code{continue} command; @samp{signal 0} causes it to resume without a
11465 @code{signal} does not repeat when you press @key{RET} a second time
11466 after executing the command.
11470 Invoking the @code{signal} command is not the same as invoking the
11471 @code{kill} utility from the shell. Sending a signal with @code{kill}
11472 causes @value{GDBN} to decide what to do with the signal depending on
11473 the signal handling tables (@pxref{Signals}). The @code{signal} command
11474 passes the signal directly to your program.
11478 @section Returning from a Function
11481 @cindex returning from a function
11484 @itemx return @var{expression}
11485 You can cancel execution of a function call with the @code{return}
11486 command. If you give an
11487 @var{expression} argument, its value is used as the function's return
11491 When you use @code{return}, @value{GDBN} discards the selected stack frame
11492 (and all frames within it). You can think of this as making the
11493 discarded frame return prematurely. If you wish to specify a value to
11494 be returned, give that value as the argument to @code{return}.
11496 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11497 Frame}), and any other frames inside of it, leaving its caller as the
11498 innermost remaining frame. That frame becomes selected. The
11499 specified value is stored in the registers used for returning values
11502 The @code{return} command does not resume execution; it leaves the
11503 program stopped in the state that would exist if the function had just
11504 returned. In contrast, the @code{finish} command (@pxref{Continuing
11505 and Stepping, ,Continuing and Stepping}) resumes execution until the
11506 selected stack frame returns naturally.
11509 @section Calling Program Functions
11512 @cindex calling functions
11513 @cindex inferior functions, calling
11514 @item print @var{expr}
11515 Evaluate the expression @var{expr} and display the resulting value.
11516 @var{expr} may include calls to functions in the program being
11520 @item call @var{expr}
11521 Evaluate the expression @var{expr} without displaying @code{void}
11524 You can use this variant of the @code{print} command if you want to
11525 execute a function from your program that does not return anything
11526 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11527 with @code{void} returned values that @value{GDBN} will otherwise
11528 print. If the result is not void, it is printed and saved in the
11532 It is possible for the function you call via the @code{print} or
11533 @code{call} command to generate a signal (e.g., if there's a bug in
11534 the function, or if you passed it incorrect arguments). What happens
11535 in that case is controlled by the @code{set unwindonsignal} command.
11538 @item set unwindonsignal
11539 @kindex set unwindonsignal
11540 @cindex unwind stack in called functions
11541 @cindex call dummy stack unwinding
11542 Set unwinding of the stack if a signal is received while in a function
11543 that @value{GDBN} called in the program being debugged. If set to on,
11544 @value{GDBN} unwinds the stack it created for the call and restores
11545 the context to what it was before the call. If set to off (the
11546 default), @value{GDBN} stops in the frame where the signal was
11549 @item show unwindonsignal
11550 @kindex show unwindonsignal
11551 Show the current setting of stack unwinding in the functions called by
11555 @cindex weak alias functions
11556 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11557 for another function. In such case, @value{GDBN} might not pick up
11558 the type information, including the types of the function arguments,
11559 which causes @value{GDBN} to call the inferior function incorrectly.
11560 As a result, the called function will function erroneously and may
11561 even crash. A solution to that is to use the name of the aliased
11565 @section Patching Programs
11567 @cindex patching binaries
11568 @cindex writing into executables
11569 @cindex writing into corefiles
11571 By default, @value{GDBN} opens the file containing your program's
11572 executable code (or the corefile) read-only. This prevents accidental
11573 alterations to machine code; but it also prevents you from intentionally
11574 patching your program's binary.
11576 If you'd like to be able to patch the binary, you can specify that
11577 explicitly with the @code{set write} command. For example, you might
11578 want to turn on internal debugging flags, or even to make emergency
11584 @itemx set write off
11585 If you specify @samp{set write on}, @value{GDBN} opens executable and
11586 core files for both reading and writing; if you specify @samp{set write
11587 off} (the default), @value{GDBN} opens them read-only.
11589 If you have already loaded a file, you must load it again (using the
11590 @code{exec-file} or @code{core-file} command) after changing @code{set
11591 write}, for your new setting to take effect.
11595 Display whether executable files and core files are opened for writing
11596 as well as reading.
11600 @chapter @value{GDBN} Files
11602 @value{GDBN} needs to know the file name of the program to be debugged,
11603 both in order to read its symbol table and in order to start your
11604 program. To debug a core dump of a previous run, you must also tell
11605 @value{GDBN} the name of the core dump file.
11608 * Files:: Commands to specify files
11609 * Separate Debug Files:: Debugging information in separate files
11610 * Symbol Errors:: Errors reading symbol files
11614 @section Commands to Specify Files
11616 @cindex symbol table
11617 @cindex core dump file
11619 You may want to specify executable and core dump file names. The usual
11620 way to do this is at start-up time, using the arguments to
11621 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11622 Out of @value{GDBN}}).
11624 Occasionally it is necessary to change to a different file during a
11625 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11626 specify a file you want to use. Or you are debugging a remote target
11627 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11628 Program}). In these situations the @value{GDBN} commands to specify
11629 new files are useful.
11632 @cindex executable file
11634 @item file @var{filename}
11635 Use @var{filename} as the program to be debugged. It is read for its
11636 symbols and for the contents of pure memory. It is also the program
11637 executed when you use the @code{run} command. If you do not specify a
11638 directory and the file is not found in the @value{GDBN} working directory,
11639 @value{GDBN} uses the environment variable @code{PATH} as a list of
11640 directories to search, just as the shell does when looking for a program
11641 to run. You can change the value of this variable, for both @value{GDBN}
11642 and your program, using the @code{path} command.
11644 @cindex unlinked object files
11645 @cindex patching object files
11646 You can load unlinked object @file{.o} files into @value{GDBN} using
11647 the @code{file} command. You will not be able to ``run'' an object
11648 file, but you can disassemble functions and inspect variables. Also,
11649 if the underlying BFD functionality supports it, you could use
11650 @kbd{gdb -write} to patch object files using this technique. Note
11651 that @value{GDBN} can neither interpret nor modify relocations in this
11652 case, so branches and some initialized variables will appear to go to
11653 the wrong place. But this feature is still handy from time to time.
11656 @code{file} with no argument makes @value{GDBN} discard any information it
11657 has on both executable file and the symbol table.
11660 @item exec-file @r{[} @var{filename} @r{]}
11661 Specify that the program to be run (but not the symbol table) is found
11662 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11663 if necessary to locate your program. Omitting @var{filename} means to
11664 discard information on the executable file.
11666 @kindex symbol-file
11667 @item symbol-file @r{[} @var{filename} @r{]}
11668 Read symbol table information from file @var{filename}. @code{PATH} is
11669 searched when necessary. Use the @code{file} command to get both symbol
11670 table and program to run from the same file.
11672 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11673 program's symbol table.
11675 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11676 some breakpoints and auto-display expressions. This is because they may
11677 contain pointers to the internal data recording symbols and data types,
11678 which are part of the old symbol table data being discarded inside
11681 @code{symbol-file} does not repeat if you press @key{RET} again after
11684 When @value{GDBN} is configured for a particular environment, it
11685 understands debugging information in whatever format is the standard
11686 generated for that environment; you may use either a @sc{gnu} compiler, or
11687 other compilers that adhere to the local conventions.
11688 Best results are usually obtained from @sc{gnu} compilers; for example,
11689 using @code{@value{NGCC}} you can generate debugging information for
11692 For most kinds of object files, with the exception of old SVR3 systems
11693 using COFF, the @code{symbol-file} command does not normally read the
11694 symbol table in full right away. Instead, it scans the symbol table
11695 quickly to find which source files and which symbols are present. The
11696 details are read later, one source file at a time, as they are needed.
11698 The purpose of this two-stage reading strategy is to make @value{GDBN}
11699 start up faster. For the most part, it is invisible except for
11700 occasional pauses while the symbol table details for a particular source
11701 file are being read. (The @code{set verbose} command can turn these
11702 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11703 Warnings and Messages}.)
11705 We have not implemented the two-stage strategy for COFF yet. When the
11706 symbol table is stored in COFF format, @code{symbol-file} reads the
11707 symbol table data in full right away. Note that ``stabs-in-COFF''
11708 still does the two-stage strategy, since the debug info is actually
11712 @cindex reading symbols immediately
11713 @cindex symbols, reading immediately
11714 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11715 @itemx file @var{filename} @r{[} -readnow @r{]}
11716 You can override the @value{GDBN} two-stage strategy for reading symbol
11717 tables by using the @samp{-readnow} option with any of the commands that
11718 load symbol table information, if you want to be sure @value{GDBN} has the
11719 entire symbol table available.
11721 @c FIXME: for now no mention of directories, since this seems to be in
11722 @c flux. 13mar1992 status is that in theory GDB would look either in
11723 @c current dir or in same dir as myprog; but issues like competing
11724 @c GDB's, or clutter in system dirs, mean that in practice right now
11725 @c only current dir is used. FFish says maybe a special GDB hierarchy
11726 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11730 @item core-file @r{[}@var{filename}@r{]}
11732 Specify the whereabouts of a core dump file to be used as the ``contents
11733 of memory''. Traditionally, core files contain only some parts of the
11734 address space of the process that generated them; @value{GDBN} can access the
11735 executable file itself for other parts.
11737 @code{core-file} with no argument specifies that no core file is
11740 Note that the core file is ignored when your program is actually running
11741 under @value{GDBN}. So, if you have been running your program and you
11742 wish to debug a core file instead, you must kill the subprocess in which
11743 the program is running. To do this, use the @code{kill} command
11744 (@pxref{Kill Process, ,Killing the Child Process}).
11746 @kindex add-symbol-file
11747 @cindex dynamic linking
11748 @item add-symbol-file @var{filename} @var{address}
11749 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11750 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11751 The @code{add-symbol-file} command reads additional symbol table
11752 information from the file @var{filename}. You would use this command
11753 when @var{filename} has been dynamically loaded (by some other means)
11754 into the program that is running. @var{address} should be the memory
11755 address at which the file has been loaded; @value{GDBN} cannot figure
11756 this out for itself. You can additionally specify an arbitrary number
11757 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11758 section name and base address for that section. You can specify any
11759 @var{address} as an expression.
11761 The symbol table of the file @var{filename} is added to the symbol table
11762 originally read with the @code{symbol-file} command. You can use the
11763 @code{add-symbol-file} command any number of times; the new symbol data
11764 thus read keeps adding to the old. To discard all old symbol data
11765 instead, use the @code{symbol-file} command without any arguments.
11767 @cindex relocatable object files, reading symbols from
11768 @cindex object files, relocatable, reading symbols from
11769 @cindex reading symbols from relocatable object files
11770 @cindex symbols, reading from relocatable object files
11771 @cindex @file{.o} files, reading symbols from
11772 Although @var{filename} is typically a shared library file, an
11773 executable file, or some other object file which has been fully
11774 relocated for loading into a process, you can also load symbolic
11775 information from relocatable @file{.o} files, as long as:
11779 the file's symbolic information refers only to linker symbols defined in
11780 that file, not to symbols defined by other object files,
11782 every section the file's symbolic information refers to has actually
11783 been loaded into the inferior, as it appears in the file, and
11785 you can determine the address at which every section was loaded, and
11786 provide these to the @code{add-symbol-file} command.
11790 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11791 relocatable files into an already running program; such systems
11792 typically make the requirements above easy to meet. However, it's
11793 important to recognize that many native systems use complex link
11794 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11795 assembly, for example) that make the requirements difficult to meet. In
11796 general, one cannot assume that using @code{add-symbol-file} to read a
11797 relocatable object file's symbolic information will have the same effect
11798 as linking the relocatable object file into the program in the normal
11801 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11803 @kindex add-symbol-file-from-memory
11804 @cindex @code{syscall DSO}
11805 @cindex load symbols from memory
11806 @item add-symbol-file-from-memory @var{address}
11807 Load symbols from the given @var{address} in a dynamically loaded
11808 object file whose image is mapped directly into the inferior's memory.
11809 For example, the Linux kernel maps a @code{syscall DSO} into each
11810 process's address space; this DSO provides kernel-specific code for
11811 some system calls. The argument can be any expression whose
11812 evaluation yields the address of the file's shared object file header.
11813 For this command to work, you must have used @code{symbol-file} or
11814 @code{exec-file} commands in advance.
11816 @kindex add-shared-symbol-files
11818 @item add-shared-symbol-files @var{library-file}
11819 @itemx assf @var{library-file}
11820 The @code{add-shared-symbol-files} command can currently be used only
11821 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11822 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11823 @value{GDBN} automatically looks for shared libraries, however if
11824 @value{GDBN} does not find yours, you can invoke
11825 @code{add-shared-symbol-files}. It takes one argument: the shared
11826 library's file name. @code{assf} is a shorthand alias for
11827 @code{add-shared-symbol-files}.
11830 @item section @var{section} @var{addr}
11831 The @code{section} command changes the base address of the named
11832 @var{section} of the exec file to @var{addr}. This can be used if the
11833 exec file does not contain section addresses, (such as in the
11834 @code{a.out} format), or when the addresses specified in the file
11835 itself are wrong. Each section must be changed separately. The
11836 @code{info files} command, described below, lists all the sections and
11840 @kindex info target
11843 @code{info files} and @code{info target} are synonymous; both print the
11844 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11845 including the names of the executable and core dump files currently in
11846 use by @value{GDBN}, and the files from which symbols were loaded. The
11847 command @code{help target} lists all possible targets rather than
11850 @kindex maint info sections
11851 @item maint info sections
11852 Another command that can give you extra information about program sections
11853 is @code{maint info sections}. In addition to the section information
11854 displayed by @code{info files}, this command displays the flags and file
11855 offset of each section in the executable and core dump files. In addition,
11856 @code{maint info sections} provides the following command options (which
11857 may be arbitrarily combined):
11861 Display sections for all loaded object files, including shared libraries.
11862 @item @var{sections}
11863 Display info only for named @var{sections}.
11864 @item @var{section-flags}
11865 Display info only for sections for which @var{section-flags} are true.
11866 The section flags that @value{GDBN} currently knows about are:
11869 Section will have space allocated in the process when loaded.
11870 Set for all sections except those containing debug information.
11872 Section will be loaded from the file into the child process memory.
11873 Set for pre-initialized code and data, clear for @code{.bss} sections.
11875 Section needs to be relocated before loading.
11877 Section cannot be modified by the child process.
11879 Section contains executable code only.
11881 Section contains data only (no executable code).
11883 Section will reside in ROM.
11885 Section contains data for constructor/destructor lists.
11887 Section is not empty.
11889 An instruction to the linker to not output the section.
11890 @item COFF_SHARED_LIBRARY
11891 A notification to the linker that the section contains
11892 COFF shared library information.
11894 Section contains common symbols.
11897 @kindex set trust-readonly-sections
11898 @cindex read-only sections
11899 @item set trust-readonly-sections on
11900 Tell @value{GDBN} that readonly sections in your object file
11901 really are read-only (i.e.@: that their contents will not change).
11902 In that case, @value{GDBN} can fetch values from these sections
11903 out of the object file, rather than from the target program.
11904 For some targets (notably embedded ones), this can be a significant
11905 enhancement to debugging performance.
11907 The default is off.
11909 @item set trust-readonly-sections off
11910 Tell @value{GDBN} not to trust readonly sections. This means that
11911 the contents of the section might change while the program is running,
11912 and must therefore be fetched from the target when needed.
11914 @item show trust-readonly-sections
11915 Show the current setting of trusting readonly sections.
11918 All file-specifying commands allow both absolute and relative file names
11919 as arguments. @value{GDBN} always converts the file name to an absolute file
11920 name and remembers it that way.
11922 @cindex shared libraries
11923 @anchor{Shared Libraries}
11924 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11925 and IBM RS/6000 AIX shared libraries.
11927 On MS-Windows @value{GDBN} must be linked with the Expat library to support
11928 shared libraries. @xref{Expat}.
11930 @value{GDBN} automatically loads symbol definitions from shared libraries
11931 when you use the @code{run} command, or when you examine a core file.
11932 (Before you issue the @code{run} command, @value{GDBN} does not understand
11933 references to a function in a shared library, however---unless you are
11934 debugging a core file).
11936 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11937 automatically loads the symbols at the time of the @code{shl_load} call.
11939 @c FIXME: some @value{GDBN} release may permit some refs to undef
11940 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11941 @c FIXME...lib; check this from time to time when updating manual
11943 There are times, however, when you may wish to not automatically load
11944 symbol definitions from shared libraries, such as when they are
11945 particularly large or there are many of them.
11947 To control the automatic loading of shared library symbols, use the
11951 @kindex set auto-solib-add
11952 @item set auto-solib-add @var{mode}
11953 If @var{mode} is @code{on}, symbols from all shared object libraries
11954 will be loaded automatically when the inferior begins execution, you
11955 attach to an independently started inferior, or when the dynamic linker
11956 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11957 is @code{off}, symbols must be loaded manually, using the
11958 @code{sharedlibrary} command. The default value is @code{on}.
11960 @cindex memory used for symbol tables
11961 If your program uses lots of shared libraries with debug info that
11962 takes large amounts of memory, you can decrease the @value{GDBN}
11963 memory footprint by preventing it from automatically loading the
11964 symbols from shared libraries. To that end, type @kbd{set
11965 auto-solib-add off} before running the inferior, then load each
11966 library whose debug symbols you do need with @kbd{sharedlibrary
11967 @var{regexp}}, where @var{regexp} is a regular expression that matches
11968 the libraries whose symbols you want to be loaded.
11970 @kindex show auto-solib-add
11971 @item show auto-solib-add
11972 Display the current autoloading mode.
11975 @cindex load shared library
11976 To explicitly load shared library symbols, use the @code{sharedlibrary}
11980 @kindex info sharedlibrary
11983 @itemx info sharedlibrary
11984 Print the names of the shared libraries which are currently loaded.
11986 @kindex sharedlibrary
11988 @item sharedlibrary @var{regex}
11989 @itemx share @var{regex}
11990 Load shared object library symbols for files matching a
11991 Unix regular expression.
11992 As with files loaded automatically, it only loads shared libraries
11993 required by your program for a core file or after typing @code{run}. If
11994 @var{regex} is omitted all shared libraries required by your program are
11997 @item nosharedlibrary
11998 @kindex nosharedlibrary
11999 @cindex unload symbols from shared libraries
12000 Unload all shared object library symbols. This discards all symbols
12001 that have been loaded from all shared libraries. Symbols from shared
12002 libraries that were loaded by explicit user requests are not
12006 Sometimes you may wish that @value{GDBN} stops and gives you control
12007 when any of shared library events happen. Use the @code{set
12008 stop-on-solib-events} command for this:
12011 @item set stop-on-solib-events
12012 @kindex set stop-on-solib-events
12013 This command controls whether @value{GDBN} should give you control
12014 when the dynamic linker notifies it about some shared library event.
12015 The most common event of interest is loading or unloading of a new
12018 @item show stop-on-solib-events
12019 @kindex show stop-on-solib-events
12020 Show whether @value{GDBN} stops and gives you control when shared
12021 library events happen.
12024 Shared libraries are also supported in many cross or remote debugging
12025 configurations. A copy of the target's libraries need to be present on the
12026 host system; they need to be the same as the target libraries, although the
12027 copies on the target can be stripped as long as the copies on the host are
12030 @cindex where to look for shared libraries
12031 For remote debugging, you need to tell @value{GDBN} where the target
12032 libraries are, so that it can load the correct copies---otherwise, it
12033 may try to load the host's libraries. @value{GDBN} has two variables
12034 to specify the search directories for target libraries.
12037 @cindex prefix for shared library file names
12038 @cindex system root, alternate
12039 @kindex set solib-absolute-prefix
12040 @kindex set sysroot
12041 @item set sysroot @var{path}
12042 Use @var{path} as the system root for the program being debugged. Any
12043 absolute shared library paths will be prefixed with @var{path}; many
12044 runtime loaders store the absolute paths to the shared library in the
12045 target program's memory. If you use @code{set sysroot} to find shared
12046 libraries, they need to be laid out in the same way that they are on
12047 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12050 The @code{set solib-absolute-prefix} command is an alias for @code{set
12053 @cindex default system root
12054 @cindex @samp{--with-sysroot}
12055 You can set the default system root by using the configure-time
12056 @samp{--with-sysroot} option. If the system root is inside
12057 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12058 @samp{--exec-prefix}), then the default system root will be updated
12059 automatically if the installed @value{GDBN} is moved to a new
12062 @kindex show sysroot
12064 Display the current shared library prefix.
12066 @kindex set solib-search-path
12067 @item set solib-search-path @var{path}
12068 If this variable is set, @var{path} is a colon-separated list of
12069 directories to search for shared libraries. @samp{solib-search-path}
12070 is used after @samp{sysroot} fails to locate the library, or if the
12071 path to the library is relative instead of absolute. If you want to
12072 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12073 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12074 finding your host's libraries. @samp{sysroot} is preferred; setting
12075 it to a nonexistent directory may interfere with automatic loading
12076 of shared library symbols.
12078 @kindex show solib-search-path
12079 @item show solib-search-path
12080 Display the current shared library search path.
12084 @node Separate Debug Files
12085 @section Debugging Information in Separate Files
12086 @cindex separate debugging information files
12087 @cindex debugging information in separate files
12088 @cindex @file{.debug} subdirectories
12089 @cindex debugging information directory, global
12090 @cindex global debugging information directory
12091 @cindex build ID, and separate debugging files
12092 @cindex @file{.build-id} directory
12094 @value{GDBN} allows you to put a program's debugging information in a
12095 file separate from the executable itself, in a way that allows
12096 @value{GDBN} to find and load the debugging information automatically.
12097 Since debugging information can be very large---sometimes larger
12098 than the executable code itself---some systems distribute debugging
12099 information for their executables in separate files, which users can
12100 install only when they need to debug a problem.
12102 @value{GDBN} supports two ways of specifying the separate debug info
12107 The executable contains a @dfn{debug link} that specifies the name of
12108 the separate debug info file. The separate debug file's name is
12109 usually @file{@var{executable}.debug}, where @var{executable} is the
12110 name of the corresponding executable file without leading directories
12111 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12112 debug link specifies a CRC32 checksum for the debug file, which
12113 @value{GDBN} uses to validate that the executable and the debug file
12114 came from the same build.
12117 The executable contains a @dfn{build ID}, a unique bit string that is
12118 also present in the corresponding debug info file. (This is supported
12119 only on some operating systems, notably those which use the ELF format
12120 for binary files and the @sc{gnu} Binutils.) For more details about
12121 this feature, see the description of the @option{--build-id}
12122 command-line option in @ref{Options, , Command Line Options, ld.info,
12123 The GNU Linker}. The debug info file's name is not specified
12124 explicitly by the build ID, but can be computed from the build ID, see
12128 Depending on the way the debug info file is specified, @value{GDBN}
12129 uses two different methods of looking for the debug file:
12133 For the ``debug link'' method, @value{GDBN} looks up the named file in
12134 the directory of the executable file, then in a subdirectory of that
12135 directory named @file{.debug}, and finally under the global debug
12136 directory, in a subdirectory whose name is identical to the leading
12137 directories of the executable's absolute file name.
12140 For the ``build ID'' method, @value{GDBN} looks in the
12141 @file{.build-id} subdirectory of the global debug directory for a file
12142 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12143 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12144 are the rest of the bit string. (Real build ID strings are 32 or more
12145 hex characters, not 10.)
12148 So, for example, suppose you ask @value{GDBN} to debug
12149 @file{/usr/bin/ls}, which has a debug link that specifies the
12150 file @file{ls.debug}, and a build ID whose value in hex is
12151 @code{abcdef1234}. If the global debug directory is
12152 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12153 debug information files, in the indicated order:
12157 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12159 @file{/usr/bin/ls.debug}
12161 @file{/usr/bin/.debug/ls.debug}
12163 @file{/usr/lib/debug/usr/bin/ls.debug}.
12166 You can set the global debugging info directory's name, and view the
12167 name @value{GDBN} is currently using.
12171 @kindex set debug-file-directory
12172 @item set debug-file-directory @var{directory}
12173 Set the directory which @value{GDBN} searches for separate debugging
12174 information files to @var{directory}.
12176 @kindex show debug-file-directory
12177 @item show debug-file-directory
12178 Show the directory @value{GDBN} searches for separate debugging
12183 @cindex @code{.gnu_debuglink} sections
12184 @cindex debug link sections
12185 A debug link is a special section of the executable file named
12186 @code{.gnu_debuglink}. The section must contain:
12190 A filename, with any leading directory components removed, followed by
12193 zero to three bytes of padding, as needed to reach the next four-byte
12194 boundary within the section, and
12196 a four-byte CRC checksum, stored in the same endianness used for the
12197 executable file itself. The checksum is computed on the debugging
12198 information file's full contents by the function given below, passing
12199 zero as the @var{crc} argument.
12202 Any executable file format can carry a debug link, as long as it can
12203 contain a section named @code{.gnu_debuglink} with the contents
12206 @cindex @code{.note.gnu.build-id} sections
12207 @cindex build ID sections
12208 The build ID is a special section in the executable file (and in other
12209 ELF binary files that @value{GDBN} may consider). This section is
12210 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12211 It contains unique identification for the built files---the ID remains
12212 the same across multiple builds of the same build tree. The default
12213 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12214 content for the build ID string. The same section with an identical
12215 value is present in the original built binary with symbols, in its
12216 stripped variant, and in the separate debugging information file.
12218 The debugging information file itself should be an ordinary
12219 executable, containing a full set of linker symbols, sections, and
12220 debugging information. The sections of the debugging information file
12221 should have the same names, addresses, and sizes as the original file,
12222 but they need not contain any data---much like a @code{.bss} section
12223 in an ordinary executable.
12225 The @sc{gnu} binary utilities (Binutils) package includes the
12226 @samp{objcopy} utility that can produce
12227 the separated executable / debugging information file pairs using the
12228 following commands:
12231 @kbd{objcopy --only-keep-debug foo foo.debug}
12236 These commands remove the debugging
12237 information from the executable file @file{foo} and place it in the file
12238 @file{foo.debug}. You can use the first, second or both methods to link the
12243 The debug link method needs the following additional command to also leave
12244 behind a debug link in @file{foo}:
12247 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12250 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12251 a version of the @code{strip} command such that the command @kbd{strip foo -f
12252 foo.debug} has the same functionality as the two @code{objcopy} commands and
12253 the @code{ln -s} command above, together.
12256 Build ID gets embedded into the main executable using @code{ld --build-id} or
12257 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12258 compatibility fixes for debug files separation are present in @sc{gnu} binary
12259 utilities (Binutils) package since version 2.18.
12264 Since there are many different ways to compute CRC's for the debug
12265 link (different polynomials, reversals, byte ordering, etc.), the
12266 simplest way to describe the CRC used in @code{.gnu_debuglink}
12267 sections is to give the complete code for a function that computes it:
12269 @kindex gnu_debuglink_crc32
12272 gnu_debuglink_crc32 (unsigned long crc,
12273 unsigned char *buf, size_t len)
12275 static const unsigned long crc32_table[256] =
12277 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12278 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12279 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12280 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12281 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12282 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12283 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12284 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12285 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12286 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12287 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12288 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12289 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12290 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12291 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12292 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12293 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12294 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12295 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12296 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12297 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12298 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12299 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12300 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12301 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12302 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12303 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12304 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12305 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12306 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12307 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12308 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12309 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12310 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12311 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12312 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12313 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12314 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12315 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12316 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12317 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12318 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12319 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12320 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12321 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12322 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12323 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12324 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12325 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12326 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12327 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12330 unsigned char *end;
12332 crc = ~crc & 0xffffffff;
12333 for (end = buf + len; buf < end; ++buf)
12334 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12335 return ~crc & 0xffffffff;
12340 This computation does not apply to the ``build ID'' method.
12343 @node Symbol Errors
12344 @section Errors Reading Symbol Files
12346 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12347 such as symbol types it does not recognize, or known bugs in compiler
12348 output. By default, @value{GDBN} does not notify you of such problems, since
12349 they are relatively common and primarily of interest to people
12350 debugging compilers. If you are interested in seeing information
12351 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12352 only one message about each such type of problem, no matter how many
12353 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12354 to see how many times the problems occur, with the @code{set
12355 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12358 The messages currently printed, and their meanings, include:
12361 @item inner block not inside outer block in @var{symbol}
12363 The symbol information shows where symbol scopes begin and end
12364 (such as at the start of a function or a block of statements). This
12365 error indicates that an inner scope block is not fully contained
12366 in its outer scope blocks.
12368 @value{GDBN} circumvents the problem by treating the inner block as if it had
12369 the same scope as the outer block. In the error message, @var{symbol}
12370 may be shown as ``@code{(don't know)}'' if the outer block is not a
12373 @item block at @var{address} out of order
12375 The symbol information for symbol scope blocks should occur in
12376 order of increasing addresses. This error indicates that it does not
12379 @value{GDBN} does not circumvent this problem, and has trouble
12380 locating symbols in the source file whose symbols it is reading. (You
12381 can often determine what source file is affected by specifying
12382 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12385 @item bad block start address patched
12387 The symbol information for a symbol scope block has a start address
12388 smaller than the address of the preceding source line. This is known
12389 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12391 @value{GDBN} circumvents the problem by treating the symbol scope block as
12392 starting on the previous source line.
12394 @item bad string table offset in symbol @var{n}
12397 Symbol number @var{n} contains a pointer into the string table which is
12398 larger than the size of the string table.
12400 @value{GDBN} circumvents the problem by considering the symbol to have the
12401 name @code{foo}, which may cause other problems if many symbols end up
12404 @item unknown symbol type @code{0x@var{nn}}
12406 The symbol information contains new data types that @value{GDBN} does
12407 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12408 uncomprehended information, in hexadecimal.
12410 @value{GDBN} circumvents the error by ignoring this symbol information.
12411 This usually allows you to debug your program, though certain symbols
12412 are not accessible. If you encounter such a problem and feel like
12413 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12414 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12415 and examine @code{*bufp} to see the symbol.
12417 @item stub type has NULL name
12419 @value{GDBN} could not find the full definition for a struct or class.
12421 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12422 The symbol information for a C@t{++} member function is missing some
12423 information that recent versions of the compiler should have output for
12426 @item info mismatch between compiler and debugger
12428 @value{GDBN} could not parse a type specification output by the compiler.
12433 @chapter Specifying a Debugging Target
12435 @cindex debugging target
12436 A @dfn{target} is the execution environment occupied by your program.
12438 Often, @value{GDBN} runs in the same host environment as your program;
12439 in that case, the debugging target is specified as a side effect when
12440 you use the @code{file} or @code{core} commands. When you need more
12441 flexibility---for example, running @value{GDBN} on a physically separate
12442 host, or controlling a standalone system over a serial port or a
12443 realtime system over a TCP/IP connection---you can use the @code{target}
12444 command to specify one of the target types configured for @value{GDBN}
12445 (@pxref{Target Commands, ,Commands for Managing Targets}).
12447 @cindex target architecture
12448 It is possible to build @value{GDBN} for several different @dfn{target
12449 architectures}. When @value{GDBN} is built like that, you can choose
12450 one of the available architectures with the @kbd{set architecture}
12454 @kindex set architecture
12455 @kindex show architecture
12456 @item set architecture @var{arch}
12457 This command sets the current target architecture to @var{arch}. The
12458 value of @var{arch} can be @code{"auto"}, in addition to one of the
12459 supported architectures.
12461 @item show architecture
12462 Show the current target architecture.
12464 @item set processor
12466 @kindex set processor
12467 @kindex show processor
12468 These are alias commands for, respectively, @code{set architecture}
12469 and @code{show architecture}.
12473 * Active Targets:: Active targets
12474 * Target Commands:: Commands for managing targets
12475 * Byte Order:: Choosing target byte order
12478 @node Active Targets
12479 @section Active Targets
12481 @cindex stacking targets
12482 @cindex active targets
12483 @cindex multiple targets
12485 There are three classes of targets: processes, core files, and
12486 executable files. @value{GDBN} can work concurrently on up to three
12487 active targets, one in each class. This allows you to (for example)
12488 start a process and inspect its activity without abandoning your work on
12491 For example, if you execute @samp{gdb a.out}, then the executable file
12492 @code{a.out} is the only active target. If you designate a core file as
12493 well---presumably from a prior run that crashed and coredumped---then
12494 @value{GDBN} has two active targets and uses them in tandem, looking
12495 first in the corefile target, then in the executable file, to satisfy
12496 requests for memory addresses. (Typically, these two classes of target
12497 are complementary, since core files contain only a program's
12498 read-write memory---variables and so on---plus machine status, while
12499 executable files contain only the program text and initialized data.)
12501 When you type @code{run}, your executable file becomes an active process
12502 target as well. When a process target is active, all @value{GDBN}
12503 commands requesting memory addresses refer to that target; addresses in
12504 an active core file or executable file target are obscured while the
12505 process target is active.
12507 Use the @code{core-file} and @code{exec-file} commands to select a new
12508 core file or executable target (@pxref{Files, ,Commands to Specify
12509 Files}). To specify as a target a process that is already running, use
12510 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12513 @node Target Commands
12514 @section Commands for Managing Targets
12517 @item target @var{type} @var{parameters}
12518 Connects the @value{GDBN} host environment to a target machine or
12519 process. A target is typically a protocol for talking to debugging
12520 facilities. You use the argument @var{type} to specify the type or
12521 protocol of the target machine.
12523 Further @var{parameters} are interpreted by the target protocol, but
12524 typically include things like device names or host names to connect
12525 with, process numbers, and baud rates.
12527 The @code{target} command does not repeat if you press @key{RET} again
12528 after executing the command.
12530 @kindex help target
12532 Displays the names of all targets available. To display targets
12533 currently selected, use either @code{info target} or @code{info files}
12534 (@pxref{Files, ,Commands to Specify Files}).
12536 @item help target @var{name}
12537 Describe a particular target, including any parameters necessary to
12540 @kindex set gnutarget
12541 @item set gnutarget @var{args}
12542 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12543 knows whether it is reading an @dfn{executable},
12544 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12545 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12546 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12549 @emph{Warning:} To specify a file format with @code{set gnutarget},
12550 you must know the actual BFD name.
12554 @xref{Files, , Commands to Specify Files}.
12556 @kindex show gnutarget
12557 @item show gnutarget
12558 Use the @code{show gnutarget} command to display what file format
12559 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12560 @value{GDBN} will determine the file format for each file automatically,
12561 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12564 @cindex common targets
12565 Here are some common targets (available, or not, depending on the GDB
12570 @item target exec @var{program}
12571 @cindex executable file target
12572 An executable file. @samp{target exec @var{program}} is the same as
12573 @samp{exec-file @var{program}}.
12575 @item target core @var{filename}
12576 @cindex core dump file target
12577 A core dump file. @samp{target core @var{filename}} is the same as
12578 @samp{core-file @var{filename}}.
12580 @item target remote @var{medium}
12581 @cindex remote target
12582 A remote system connected to @value{GDBN} via a serial line or network
12583 connection. This command tells @value{GDBN} to use its own remote
12584 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12586 For example, if you have a board connected to @file{/dev/ttya} on the
12587 machine running @value{GDBN}, you could say:
12590 target remote /dev/ttya
12593 @code{target remote} supports the @code{load} command. This is only
12594 useful if you have some other way of getting the stub to the target
12595 system, and you can put it somewhere in memory where it won't get
12596 clobbered by the download.
12599 @cindex built-in simulator target
12600 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12608 works; however, you cannot assume that a specific memory map, device
12609 drivers, or even basic I/O is available, although some simulators do
12610 provide these. For info about any processor-specific simulator details,
12611 see the appropriate section in @ref{Embedded Processors, ,Embedded
12616 Some configurations may include these targets as well:
12620 @item target nrom @var{dev}
12621 @cindex NetROM ROM emulator target
12622 NetROM ROM emulator. This target only supports downloading.
12626 Different targets are available on different configurations of @value{GDBN};
12627 your configuration may have more or fewer targets.
12629 Many remote targets require you to download the executable's code once
12630 you've successfully established a connection. You may wish to control
12631 various aspects of this process.
12636 @kindex set hash@r{, for remote monitors}
12637 @cindex hash mark while downloading
12638 This command controls whether a hash mark @samp{#} is displayed while
12639 downloading a file to the remote monitor. If on, a hash mark is
12640 displayed after each S-record is successfully downloaded to the
12644 @kindex show hash@r{, for remote monitors}
12645 Show the current status of displaying the hash mark.
12647 @item set debug monitor
12648 @kindex set debug monitor
12649 @cindex display remote monitor communications
12650 Enable or disable display of communications messages between
12651 @value{GDBN} and the remote monitor.
12653 @item show debug monitor
12654 @kindex show debug monitor
12655 Show the current status of displaying communications between
12656 @value{GDBN} and the remote monitor.
12661 @kindex load @var{filename}
12662 @item load @var{filename}
12663 Depending on what remote debugging facilities are configured into
12664 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12665 is meant to make @var{filename} (an executable) available for debugging
12666 on the remote system---by downloading, or dynamic linking, for example.
12667 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12668 the @code{add-symbol-file} command.
12670 If your @value{GDBN} does not have a @code{load} command, attempting to
12671 execute it gets the error message ``@code{You can't do that when your
12672 target is @dots{}}''
12674 The file is loaded at whatever address is specified in the executable.
12675 For some object file formats, you can specify the load address when you
12676 link the program; for other formats, like a.out, the object file format
12677 specifies a fixed address.
12678 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12680 Depending on the remote side capabilities, @value{GDBN} may be able to
12681 load programs into flash memory.
12683 @code{load} does not repeat if you press @key{RET} again after using it.
12687 @section Choosing Target Byte Order
12689 @cindex choosing target byte order
12690 @cindex target byte order
12692 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12693 offer the ability to run either big-endian or little-endian byte
12694 orders. Usually the executable or symbol will include a bit to
12695 designate the endian-ness, and you will not need to worry about
12696 which to use. However, you may still find it useful to adjust
12697 @value{GDBN}'s idea of processor endian-ness manually.
12701 @item set endian big
12702 Instruct @value{GDBN} to assume the target is big-endian.
12704 @item set endian little
12705 Instruct @value{GDBN} to assume the target is little-endian.
12707 @item set endian auto
12708 Instruct @value{GDBN} to use the byte order associated with the
12712 Display @value{GDBN}'s current idea of the target byte order.
12716 Note that these commands merely adjust interpretation of symbolic
12717 data on the host, and that they have absolutely no effect on the
12721 @node Remote Debugging
12722 @chapter Debugging Remote Programs
12723 @cindex remote debugging
12725 If you are trying to debug a program running on a machine that cannot run
12726 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12727 For example, you might use remote debugging on an operating system kernel,
12728 or on a small system which does not have a general purpose operating system
12729 powerful enough to run a full-featured debugger.
12731 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12732 to make this work with particular debugging targets. In addition,
12733 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12734 but not specific to any particular target system) which you can use if you
12735 write the remote stubs---the code that runs on the remote system to
12736 communicate with @value{GDBN}.
12738 Other remote targets may be available in your
12739 configuration of @value{GDBN}; use @code{help target} to list them.
12742 * Connecting:: Connecting to a remote target
12743 * File Transfer:: Sending files to a remote system
12744 * Server:: Using the gdbserver program
12745 * Remote Configuration:: Remote configuration
12746 * Remote Stub:: Implementing a remote stub
12750 @section Connecting to a Remote Target
12752 On the @value{GDBN} host machine, you will need an unstripped copy of
12753 your program, since @value{GDBN} needs symbol and debugging information.
12754 Start up @value{GDBN} as usual, using the name of the local copy of your
12755 program as the first argument.
12757 @cindex @code{target remote}
12758 @value{GDBN} can communicate with the target over a serial line, or
12759 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12760 each case, @value{GDBN} uses the same protocol for debugging your
12761 program; only the medium carrying the debugging packets varies. The
12762 @code{target remote} command establishes a connection to the target.
12763 Its arguments indicate which medium to use:
12767 @item target remote @var{serial-device}
12768 @cindex serial line, @code{target remote}
12769 Use @var{serial-device} to communicate with the target. For example,
12770 to use a serial line connected to the device named @file{/dev/ttyb}:
12773 target remote /dev/ttyb
12776 If you're using a serial line, you may want to give @value{GDBN} the
12777 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12778 (@pxref{Remote Configuration, set remotebaud}) before the
12779 @code{target} command.
12781 @item target remote @code{@var{host}:@var{port}}
12782 @itemx target remote @code{tcp:@var{host}:@var{port}}
12783 @cindex @acronym{TCP} port, @code{target remote}
12784 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12785 The @var{host} may be either a host name or a numeric @acronym{IP}
12786 address; @var{port} must be a decimal number. The @var{host} could be
12787 the target machine itself, if it is directly connected to the net, or
12788 it might be a terminal server which in turn has a serial line to the
12791 For example, to connect to port 2828 on a terminal server named
12795 target remote manyfarms:2828
12798 If your remote target is actually running on the same machine as your
12799 debugger session (e.g.@: a simulator for your target running on the
12800 same host), you can omit the hostname. For example, to connect to
12801 port 1234 on your local machine:
12804 target remote :1234
12808 Note that the colon is still required here.
12810 @item target remote @code{udp:@var{host}:@var{port}}
12811 @cindex @acronym{UDP} port, @code{target remote}
12812 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12813 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12816 target remote udp:manyfarms:2828
12819 When using a @acronym{UDP} connection for remote debugging, you should
12820 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12821 can silently drop packets on busy or unreliable networks, which will
12822 cause havoc with your debugging session.
12824 @item target remote | @var{command}
12825 @cindex pipe, @code{target remote} to
12826 Run @var{command} in the background and communicate with it using a
12827 pipe. The @var{command} is a shell command, to be parsed and expanded
12828 by the system's command shell, @code{/bin/sh}; it should expect remote
12829 protocol packets on its standard input, and send replies on its
12830 standard output. You could use this to run a stand-alone simulator
12831 that speaks the remote debugging protocol, to make net connections
12832 using programs like @code{ssh}, or for other similar tricks.
12834 If @var{command} closes its standard output (perhaps by exiting),
12835 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12836 program has already exited, this will have no effect.)
12840 Once the connection has been established, you can use all the usual
12841 commands to examine and change data and to step and continue the
12844 @cindex interrupting remote programs
12845 @cindex remote programs, interrupting
12846 Whenever @value{GDBN} is waiting for the remote program, if you type the
12847 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12848 program. This may or may not succeed, depending in part on the hardware
12849 and the serial drivers the remote system uses. If you type the
12850 interrupt character once again, @value{GDBN} displays this prompt:
12853 Interrupted while waiting for the program.
12854 Give up (and stop debugging it)? (y or n)
12857 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12858 (If you decide you want to try again later, you can use @samp{target
12859 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12860 goes back to waiting.
12863 @kindex detach (remote)
12865 When you have finished debugging the remote program, you can use the
12866 @code{detach} command to release it from @value{GDBN} control.
12867 Detaching from the target normally resumes its execution, but the results
12868 will depend on your particular remote stub. After the @code{detach}
12869 command, @value{GDBN} is free to connect to another target.
12873 The @code{disconnect} command behaves like @code{detach}, except that
12874 the target is generally not resumed. It will wait for @value{GDBN}
12875 (this instance or another one) to connect and continue debugging. After
12876 the @code{disconnect} command, @value{GDBN} is again free to connect to
12879 @cindex send command to remote monitor
12880 @cindex extend @value{GDBN} for remote targets
12881 @cindex add new commands for external monitor
12883 @item monitor @var{cmd}
12884 This command allows you to send arbitrary commands directly to the
12885 remote monitor. Since @value{GDBN} doesn't care about the commands it
12886 sends like this, this command is the way to extend @value{GDBN}---you
12887 can add new commands that only the external monitor will understand
12891 @node File Transfer
12892 @section Sending files to a remote system
12893 @cindex remote target, file transfer
12894 @cindex file transfer
12895 @cindex sending files to remote systems
12897 Some remote targets offer the ability to transfer files over the same
12898 connection used to communicate with @value{GDBN}. This is convenient
12899 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
12900 running @code{gdbserver} over a network interface. For other targets,
12901 e.g.@: embedded devices with only a single serial port, this may be
12902 the only way to upload or download files.
12904 Not all remote targets support these commands.
12908 @item remote put @var{hostfile} @var{targetfile}
12909 Copy file @var{hostfile} from the host system (the machine running
12910 @value{GDBN}) to @var{targetfile} on the target system.
12913 @item remote get @var{targetfile} @var{hostfile}
12914 Copy file @var{targetfile} from the target system to @var{hostfile}
12915 on the host system.
12917 @kindex remote delete
12918 @item remote delete @var{targetfile}
12919 Delete @var{targetfile} from the target system.
12924 @section Using the @code{gdbserver} Program
12927 @cindex remote connection without stubs
12928 @code{gdbserver} is a control program for Unix-like systems, which
12929 allows you to connect your program with a remote @value{GDBN} via
12930 @code{target remote}---but without linking in the usual debugging stub.
12932 @code{gdbserver} is not a complete replacement for the debugging stubs,
12933 because it requires essentially the same operating-system facilities
12934 that @value{GDBN} itself does. In fact, a system that can run
12935 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12936 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12937 because it is a much smaller program than @value{GDBN} itself. It is
12938 also easier to port than all of @value{GDBN}, so you may be able to get
12939 started more quickly on a new system by using @code{gdbserver}.
12940 Finally, if you develop code for real-time systems, you may find that
12941 the tradeoffs involved in real-time operation make it more convenient to
12942 do as much development work as possible on another system, for example
12943 by cross-compiling. You can use @code{gdbserver} to make a similar
12944 choice for debugging.
12946 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12947 or a TCP connection, using the standard @value{GDBN} remote serial
12951 @item On the target machine,
12952 you need to have a copy of the program you want to debug.
12953 @code{gdbserver} does not need your program's symbol table, so you can
12954 strip the program if necessary to save space. @value{GDBN} on the host
12955 system does all the symbol handling.
12957 To use the server, you must tell it how to communicate with @value{GDBN};
12958 the name of your program; and the arguments for your program. The usual
12962 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12965 @var{comm} is either a device name (to use a serial line) or a TCP
12966 hostname and portnumber. For example, to debug Emacs with the argument
12967 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12971 target> gdbserver /dev/com1 emacs foo.txt
12974 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12977 To use a TCP connection instead of a serial line:
12980 target> gdbserver host:2345 emacs foo.txt
12983 The only difference from the previous example is the first argument,
12984 specifying that you are communicating with the host @value{GDBN} via
12985 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12986 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12987 (Currently, the @samp{host} part is ignored.) You can choose any number
12988 you want for the port number as long as it does not conflict with any
12989 TCP ports already in use on the target system (for example, @code{23} is
12990 reserved for @code{telnet}).@footnote{If you choose a port number that
12991 conflicts with another service, @code{gdbserver} prints an error message
12992 and exits.} You must use the same port number with the host @value{GDBN}
12993 @code{target remote} command.
12995 On some targets, @code{gdbserver} can also attach to running programs.
12996 This is accomplished via the @code{--attach} argument. The syntax is:
12999 target> gdbserver @var{comm} --attach @var{pid}
13002 @var{pid} is the process ID of a currently running process. It isn't necessary
13003 to point @code{gdbserver} at a binary for the running process.
13006 @cindex attach to a program by name
13007 You can debug processes by name instead of process ID if your target has the
13008 @code{pidof} utility:
13011 target> gdbserver @var{comm} --attach `pidof @var{program}`
13014 In case more than one copy of @var{program} is running, or @var{program}
13015 has multiple threads, most versions of @code{pidof} support the
13016 @code{-s} option to only return the first process ID.
13018 @item On the host machine,
13019 first make sure you have the necessary symbol files. Load symbols for
13020 your application using the @code{file} command before you connect. Use
13021 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
13022 was compiled with the correct sysroot using @code{--with-system-root}).
13024 The symbol file and target libraries must exactly match the executable
13025 and libraries on the target, with one exception: the files on the host
13026 system should not be stripped, even if the files on the target system
13027 are. Mismatched or missing files will lead to confusing results
13028 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
13029 files may also prevent @code{gdbserver} from debugging multi-threaded
13032 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
13033 For TCP connections, you must start up @code{gdbserver} prior to using
13034 the @code{target remote} command. Otherwise you may get an error whose
13035 text depends on the host system, but which usually looks something like
13036 @samp{Connection refused}. You don't need to use the @code{load}
13037 command in @value{GDBN} when using @code{gdbserver}, since the program is
13038 already on the target.
13042 @subsection Monitor Commands for @code{gdbserver}
13043 @cindex monitor commands, for @code{gdbserver}
13045 During a @value{GDBN} session using @code{gdbserver}, you can use the
13046 @code{monitor} command to send special requests to @code{gdbserver}.
13047 Here are the available commands; they are only of interest when
13048 debugging @value{GDBN} or @code{gdbserver}.
13052 List the available monitor commands.
13054 @item monitor set debug 0
13055 @itemx monitor set debug 1
13056 Disable or enable general debugging messages.
13058 @item monitor set remote-debug 0
13059 @itemx monitor set remote-debug 1
13060 Disable or enable specific debugging messages associated with the remote
13061 protocol (@pxref{Remote Protocol}).
13065 @node Remote Configuration
13066 @section Remote Configuration
13069 @kindex show remote
13070 This section documents the configuration options available when
13071 debugging remote programs. For the options related to the File I/O
13072 extensions of the remote protocol, see @ref{system,
13073 system-call-allowed}.
13076 @item set remoteaddresssize @var{bits}
13077 @cindex address size for remote targets
13078 @cindex bits in remote address
13079 Set the maximum size of address in a memory packet to the specified
13080 number of bits. @value{GDBN} will mask off the address bits above
13081 that number, when it passes addresses to the remote target. The
13082 default value is the number of bits in the target's address.
13084 @item show remoteaddresssize
13085 Show the current value of remote address size in bits.
13087 @item set remotebaud @var{n}
13088 @cindex baud rate for remote targets
13089 Set the baud rate for the remote serial I/O to @var{n} baud. The
13090 value is used to set the speed of the serial port used for debugging
13093 @item show remotebaud
13094 Show the current speed of the remote connection.
13096 @item set remotebreak
13097 @cindex interrupt remote programs
13098 @cindex BREAK signal instead of Ctrl-C
13099 @anchor{set remotebreak}
13100 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13101 when you type @kbd{Ctrl-c} to interrupt the program running
13102 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13103 character instead. The default is off, since most remote systems
13104 expect to see @samp{Ctrl-C} as the interrupt signal.
13106 @item show remotebreak
13107 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13108 interrupt the remote program.
13110 @item set remoteflow on
13111 @itemx set remoteflow off
13112 @kindex set remoteflow
13113 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13114 on the serial port used to communicate to the remote target.
13116 @item show remoteflow
13117 @kindex show remoteflow
13118 Show the current setting of hardware flow control.
13120 @item set remotelogbase @var{base}
13121 Set the base (a.k.a.@: radix) of logging serial protocol
13122 communications to @var{base}. Supported values of @var{base} are:
13123 @code{ascii}, @code{octal}, and @code{hex}. The default is
13126 @item show remotelogbase
13127 Show the current setting of the radix for logging remote serial
13130 @item set remotelogfile @var{file}
13131 @cindex record serial communications on file
13132 Record remote serial communications on the named @var{file}. The
13133 default is not to record at all.
13135 @item show remotelogfile.
13136 Show the current setting of the file name on which to record the
13137 serial communications.
13139 @item set remotetimeout @var{num}
13140 @cindex timeout for serial communications
13141 @cindex remote timeout
13142 Set the timeout limit to wait for the remote target to respond to
13143 @var{num} seconds. The default is 2 seconds.
13145 @item show remotetimeout
13146 Show the current number of seconds to wait for the remote target
13149 @cindex limit hardware breakpoints and watchpoints
13150 @cindex remote target, limit break- and watchpoints
13151 @anchor{set remote hardware-watchpoint-limit}
13152 @anchor{set remote hardware-breakpoint-limit}
13153 @item set remote hardware-watchpoint-limit @var{limit}
13154 @itemx set remote hardware-breakpoint-limit @var{limit}
13155 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13156 watchpoints. A limit of -1, the default, is treated as unlimited.
13159 @cindex remote packets, enabling and disabling
13160 The @value{GDBN} remote protocol autodetects the packets supported by
13161 your debugging stub. If you need to override the autodetection, you
13162 can use these commands to enable or disable individual packets. Each
13163 packet can be set to @samp{on} (the remote target supports this
13164 packet), @samp{off} (the remote target does not support this packet),
13165 or @samp{auto} (detect remote target support for this packet). They
13166 all default to @samp{auto}. For more information about each packet,
13167 see @ref{Remote Protocol}.
13169 During normal use, you should not have to use any of these commands.
13170 If you do, that may be a bug in your remote debugging stub, or a bug
13171 in @value{GDBN}. You may want to report the problem to the
13172 @value{GDBN} developers.
13174 For each packet @var{name}, the command to enable or disable the
13175 packet is @code{set remote @var{name}-packet}. The available settings
13178 @multitable @columnfractions 0.28 0.32 0.25
13181 @tab Related Features
13183 @item @code{fetch-register}
13185 @tab @code{info registers}
13187 @item @code{set-register}
13191 @item @code{binary-download}
13193 @tab @code{load}, @code{set}
13195 @item @code{read-aux-vector}
13196 @tab @code{qXfer:auxv:read}
13197 @tab @code{info auxv}
13199 @item @code{symbol-lookup}
13200 @tab @code{qSymbol}
13201 @tab Detecting multiple threads
13203 @item @code{verbose-resume}
13205 @tab Stepping or resuming multiple threads
13207 @item @code{software-breakpoint}
13211 @item @code{hardware-breakpoint}
13215 @item @code{write-watchpoint}
13219 @item @code{read-watchpoint}
13223 @item @code{access-watchpoint}
13227 @item @code{target-features}
13228 @tab @code{qXfer:features:read}
13229 @tab @code{set architecture}
13231 @item @code{library-info}
13232 @tab @code{qXfer:libraries:read}
13233 @tab @code{info sharedlibrary}
13235 @item @code{memory-map}
13236 @tab @code{qXfer:memory-map:read}
13237 @tab @code{info mem}
13239 @item @code{read-spu-object}
13240 @tab @code{qXfer:spu:read}
13241 @tab @code{info spu}
13243 @item @code{write-spu-object}
13244 @tab @code{qXfer:spu:write}
13245 @tab @code{info spu}
13247 @item @code{get-thread-local-@*storage-address}
13248 @tab @code{qGetTLSAddr}
13249 @tab Displaying @code{__thread} variables
13251 @item @code{supported-packets}
13252 @tab @code{qSupported}
13253 @tab Remote communications parameters
13255 @item @code{pass-signals}
13256 @tab @code{QPassSignals}
13257 @tab @code{handle @var{signal}}
13259 @item @code{hostio-close-packet}
13260 @tab @code{vFile:close}
13261 @tab @code{remote get}, @code{remote put}
13263 @item @code{hostio-open-packet}
13264 @tab @code{vFile:open}
13265 @tab @code{remote get}, @code{remote put}
13267 @item @code{hostio-pread-packet}
13268 @tab @code{vFile:pread}
13269 @tab @code{remote get}, @code{remote put}
13271 @item @code{hostio-pwrite-packet}
13272 @tab @code{vFile:pwrite}
13273 @tab @code{remote get}, @code{remote put}
13275 @item @code{hostio-unlink-packet}
13276 @tab @code{vFile:unlink}
13277 @tab @code{remote delete}
13281 @section Implementing a Remote Stub
13283 @cindex debugging stub, example
13284 @cindex remote stub, example
13285 @cindex stub example, remote debugging
13286 The stub files provided with @value{GDBN} implement the target side of the
13287 communication protocol, and the @value{GDBN} side is implemented in the
13288 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13289 these subroutines to communicate, and ignore the details. (If you're
13290 implementing your own stub file, you can still ignore the details: start
13291 with one of the existing stub files. @file{sparc-stub.c} is the best
13292 organized, and therefore the easiest to read.)
13294 @cindex remote serial debugging, overview
13295 To debug a program running on another machine (the debugging
13296 @dfn{target} machine), you must first arrange for all the usual
13297 prerequisites for the program to run by itself. For example, for a C
13302 A startup routine to set up the C runtime environment; these usually
13303 have a name like @file{crt0}. The startup routine may be supplied by
13304 your hardware supplier, or you may have to write your own.
13307 A C subroutine library to support your program's
13308 subroutine calls, notably managing input and output.
13311 A way of getting your program to the other machine---for example, a
13312 download program. These are often supplied by the hardware
13313 manufacturer, but you may have to write your own from hardware
13317 The next step is to arrange for your program to use a serial port to
13318 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13319 machine). In general terms, the scheme looks like this:
13323 @value{GDBN} already understands how to use this protocol; when everything
13324 else is set up, you can simply use the @samp{target remote} command
13325 (@pxref{Targets,,Specifying a Debugging Target}).
13327 @item On the target,
13328 you must link with your program a few special-purpose subroutines that
13329 implement the @value{GDBN} remote serial protocol. The file containing these
13330 subroutines is called a @dfn{debugging stub}.
13332 On certain remote targets, you can use an auxiliary program
13333 @code{gdbserver} instead of linking a stub into your program.
13334 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13337 The debugging stub is specific to the architecture of the remote
13338 machine; for example, use @file{sparc-stub.c} to debug programs on
13341 @cindex remote serial stub list
13342 These working remote stubs are distributed with @value{GDBN}:
13347 @cindex @file{i386-stub.c}
13350 For Intel 386 and compatible architectures.
13353 @cindex @file{m68k-stub.c}
13354 @cindex Motorola 680x0
13356 For Motorola 680x0 architectures.
13359 @cindex @file{sh-stub.c}
13362 For Renesas SH architectures.
13365 @cindex @file{sparc-stub.c}
13367 For @sc{sparc} architectures.
13369 @item sparcl-stub.c
13370 @cindex @file{sparcl-stub.c}
13373 For Fujitsu @sc{sparclite} architectures.
13377 The @file{README} file in the @value{GDBN} distribution may list other
13378 recently added stubs.
13381 * Stub Contents:: What the stub can do for you
13382 * Bootstrapping:: What you must do for the stub
13383 * Debug Session:: Putting it all together
13386 @node Stub Contents
13387 @subsection What the Stub Can Do for You
13389 @cindex remote serial stub
13390 The debugging stub for your architecture supplies these three
13394 @item set_debug_traps
13395 @findex set_debug_traps
13396 @cindex remote serial stub, initialization
13397 This routine arranges for @code{handle_exception} to run when your
13398 program stops. You must call this subroutine explicitly near the
13399 beginning of your program.
13401 @item handle_exception
13402 @findex handle_exception
13403 @cindex remote serial stub, main routine
13404 This is the central workhorse, but your program never calls it
13405 explicitly---the setup code arranges for @code{handle_exception} to
13406 run when a trap is triggered.
13408 @code{handle_exception} takes control when your program stops during
13409 execution (for example, on a breakpoint), and mediates communications
13410 with @value{GDBN} on the host machine. This is where the communications
13411 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13412 representative on the target machine. It begins by sending summary
13413 information on the state of your program, then continues to execute,
13414 retrieving and transmitting any information @value{GDBN} needs, until you
13415 execute a @value{GDBN} command that makes your program resume; at that point,
13416 @code{handle_exception} returns control to your own code on the target
13420 @cindex @code{breakpoint} subroutine, remote
13421 Use this auxiliary subroutine to make your program contain a
13422 breakpoint. Depending on the particular situation, this may be the only
13423 way for @value{GDBN} to get control. For instance, if your target
13424 machine has some sort of interrupt button, you won't need to call this;
13425 pressing the interrupt button transfers control to
13426 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13427 simply receiving characters on the serial port may also trigger a trap;
13428 again, in that situation, you don't need to call @code{breakpoint} from
13429 your own program---simply running @samp{target remote} from the host
13430 @value{GDBN} session gets control.
13432 Call @code{breakpoint} if none of these is true, or if you simply want
13433 to make certain your program stops at a predetermined point for the
13434 start of your debugging session.
13437 @node Bootstrapping
13438 @subsection What You Must Do for the Stub
13440 @cindex remote stub, support routines
13441 The debugging stubs that come with @value{GDBN} are set up for a particular
13442 chip architecture, but they have no information about the rest of your
13443 debugging target machine.
13445 First of all you need to tell the stub how to communicate with the
13449 @item int getDebugChar()
13450 @findex getDebugChar
13451 Write this subroutine to read a single character from the serial port.
13452 It may be identical to @code{getchar} for your target system; a
13453 different name is used to allow you to distinguish the two if you wish.
13455 @item void putDebugChar(int)
13456 @findex putDebugChar
13457 Write this subroutine to write a single character to the serial port.
13458 It may be identical to @code{putchar} for your target system; a
13459 different name is used to allow you to distinguish the two if you wish.
13462 @cindex control C, and remote debugging
13463 @cindex interrupting remote targets
13464 If you want @value{GDBN} to be able to stop your program while it is
13465 running, you need to use an interrupt-driven serial driver, and arrange
13466 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13467 character). That is the character which @value{GDBN} uses to tell the
13468 remote system to stop.
13470 Getting the debugging target to return the proper status to @value{GDBN}
13471 probably requires changes to the standard stub; one quick and dirty way
13472 is to just execute a breakpoint instruction (the ``dirty'' part is that
13473 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13475 Other routines you need to supply are:
13478 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13479 @findex exceptionHandler
13480 Write this function to install @var{exception_address} in the exception
13481 handling tables. You need to do this because the stub does not have any
13482 way of knowing what the exception handling tables on your target system
13483 are like (for example, the processor's table might be in @sc{rom},
13484 containing entries which point to a table in @sc{ram}).
13485 @var{exception_number} is the exception number which should be changed;
13486 its meaning is architecture-dependent (for example, different numbers
13487 might represent divide by zero, misaligned access, etc). When this
13488 exception occurs, control should be transferred directly to
13489 @var{exception_address}, and the processor state (stack, registers,
13490 and so on) should be just as it is when a processor exception occurs. So if
13491 you want to use a jump instruction to reach @var{exception_address}, it
13492 should be a simple jump, not a jump to subroutine.
13494 For the 386, @var{exception_address} should be installed as an interrupt
13495 gate so that interrupts are masked while the handler runs. The gate
13496 should be at privilege level 0 (the most privileged level). The
13497 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13498 help from @code{exceptionHandler}.
13500 @item void flush_i_cache()
13501 @findex flush_i_cache
13502 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13503 instruction cache, if any, on your target machine. If there is no
13504 instruction cache, this subroutine may be a no-op.
13506 On target machines that have instruction caches, @value{GDBN} requires this
13507 function to make certain that the state of your program is stable.
13511 You must also make sure this library routine is available:
13514 @item void *memset(void *, int, int)
13516 This is the standard library function @code{memset} that sets an area of
13517 memory to a known value. If you have one of the free versions of
13518 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13519 either obtain it from your hardware manufacturer, or write your own.
13522 If you do not use the GNU C compiler, you may need other standard
13523 library subroutines as well; this varies from one stub to another,
13524 but in general the stubs are likely to use any of the common library
13525 subroutines which @code{@value{NGCC}} generates as inline code.
13528 @node Debug Session
13529 @subsection Putting it All Together
13531 @cindex remote serial debugging summary
13532 In summary, when your program is ready to debug, you must follow these
13537 Make sure you have defined the supporting low-level routines
13538 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13540 @code{getDebugChar}, @code{putDebugChar},
13541 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13545 Insert these lines near the top of your program:
13553 For the 680x0 stub only, you need to provide a variable called
13554 @code{exceptionHook}. Normally you just use:
13557 void (*exceptionHook)() = 0;
13561 but if before calling @code{set_debug_traps}, you set it to point to a
13562 function in your program, that function is called when
13563 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13564 error). The function indicated by @code{exceptionHook} is called with
13565 one parameter: an @code{int} which is the exception number.
13568 Compile and link together: your program, the @value{GDBN} debugging stub for
13569 your target architecture, and the supporting subroutines.
13572 Make sure you have a serial connection between your target machine and
13573 the @value{GDBN} host, and identify the serial port on the host.
13576 @c The "remote" target now provides a `load' command, so we should
13577 @c document that. FIXME.
13578 Download your program to your target machine (or get it there by
13579 whatever means the manufacturer provides), and start it.
13582 Start @value{GDBN} on the host, and connect to the target
13583 (@pxref{Connecting,,Connecting to a Remote Target}).
13587 @node Configurations
13588 @chapter Configuration-Specific Information
13590 While nearly all @value{GDBN} commands are available for all native and
13591 cross versions of the debugger, there are some exceptions. This chapter
13592 describes things that are only available in certain configurations.
13594 There are three major categories of configurations: native
13595 configurations, where the host and target are the same, embedded
13596 operating system configurations, which are usually the same for several
13597 different processor architectures, and bare embedded processors, which
13598 are quite different from each other.
13603 * Embedded Processors::
13610 This section describes details specific to particular native
13615 * BSD libkvm Interface:: Debugging BSD kernel memory images
13616 * SVR4 Process Information:: SVR4 process information
13617 * DJGPP Native:: Features specific to the DJGPP port
13618 * Cygwin Native:: Features specific to the Cygwin port
13619 * Hurd Native:: Features specific to @sc{gnu} Hurd
13620 * Neutrino:: Features specific to QNX Neutrino
13626 On HP-UX systems, if you refer to a function or variable name that
13627 begins with a dollar sign, @value{GDBN} searches for a user or system
13628 name first, before it searches for a convenience variable.
13631 @node BSD libkvm Interface
13632 @subsection BSD libkvm Interface
13635 @cindex kernel memory image
13636 @cindex kernel crash dump
13638 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13639 interface that provides a uniform interface for accessing kernel virtual
13640 memory images, including live systems and crash dumps. @value{GDBN}
13641 uses this interface to allow you to debug live kernels and kernel crash
13642 dumps on many native BSD configurations. This is implemented as a
13643 special @code{kvm} debugging target. For debugging a live system, load
13644 the currently running kernel into @value{GDBN} and connect to the
13648 (@value{GDBP}) @b{target kvm}
13651 For debugging crash dumps, provide the file name of the crash dump as an
13655 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13658 Once connected to the @code{kvm} target, the following commands are
13664 Set current context from the @dfn{Process Control Block} (PCB) address.
13667 Set current context from proc address. This command isn't available on
13668 modern FreeBSD systems.
13671 @node SVR4 Process Information
13672 @subsection SVR4 Process Information
13674 @cindex examine process image
13675 @cindex process info via @file{/proc}
13677 Many versions of SVR4 and compatible systems provide a facility called
13678 @samp{/proc} that can be used to examine the image of a running
13679 process using file-system subroutines. If @value{GDBN} is configured
13680 for an operating system with this facility, the command @code{info
13681 proc} is available to report information about the process running
13682 your program, or about any process running on your system. @code{info
13683 proc} works only on SVR4 systems that include the @code{procfs} code.
13684 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13685 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13691 @itemx info proc @var{process-id}
13692 Summarize available information about any running process. If a
13693 process ID is specified by @var{process-id}, display information about
13694 that process; otherwise display information about the program being
13695 debugged. The summary includes the debugged process ID, the command
13696 line used to invoke it, its current working directory, and its
13697 executable file's absolute file name.
13699 On some systems, @var{process-id} can be of the form
13700 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13701 within a process. If the optional @var{pid} part is missing, it means
13702 a thread from the process being debugged (the leading @samp{/} still
13703 needs to be present, or else @value{GDBN} will interpret the number as
13704 a process ID rather than a thread ID).
13706 @item info proc mappings
13707 @cindex memory address space mappings
13708 Report the memory address space ranges accessible in the program, with
13709 information on whether the process has read, write, or execute access
13710 rights to each range. On @sc{gnu}/Linux systems, each memory range
13711 includes the object file which is mapped to that range, instead of the
13712 memory access rights to that range.
13714 @item info proc stat
13715 @itemx info proc status
13716 @cindex process detailed status information
13717 These subcommands are specific to @sc{gnu}/Linux systems. They show
13718 the process-related information, including the user ID and group ID;
13719 how many threads are there in the process; its virtual memory usage;
13720 the signals that are pending, blocked, and ignored; its TTY; its
13721 consumption of system and user time; its stack size; its @samp{nice}
13722 value; etc. For more information, see the @samp{proc} man page
13723 (type @kbd{man 5 proc} from your shell prompt).
13725 @item info proc all
13726 Show all the information about the process described under all of the
13727 above @code{info proc} subcommands.
13730 @comment These sub-options of 'info proc' were not included when
13731 @comment procfs.c was re-written. Keep their descriptions around
13732 @comment against the day when someone finds the time to put them back in.
13733 @kindex info proc times
13734 @item info proc times
13735 Starting time, user CPU time, and system CPU time for your program and
13738 @kindex info proc id
13740 Report on the process IDs related to your program: its own process ID,
13741 the ID of its parent, the process group ID, and the session ID.
13744 @item set procfs-trace
13745 @kindex set procfs-trace
13746 @cindex @code{procfs} API calls
13747 This command enables and disables tracing of @code{procfs} API calls.
13749 @item show procfs-trace
13750 @kindex show procfs-trace
13751 Show the current state of @code{procfs} API call tracing.
13753 @item set procfs-file @var{file}
13754 @kindex set procfs-file
13755 Tell @value{GDBN} to write @code{procfs} API trace to the named
13756 @var{file}. @value{GDBN} appends the trace info to the previous
13757 contents of the file. The default is to display the trace on the
13760 @item show procfs-file
13761 @kindex show procfs-file
13762 Show the file to which @code{procfs} API trace is written.
13764 @item proc-trace-entry
13765 @itemx proc-trace-exit
13766 @itemx proc-untrace-entry
13767 @itemx proc-untrace-exit
13768 @kindex proc-trace-entry
13769 @kindex proc-trace-exit
13770 @kindex proc-untrace-entry
13771 @kindex proc-untrace-exit
13772 These commands enable and disable tracing of entries into and exits
13773 from the @code{syscall} interface.
13776 @kindex info pidlist
13777 @cindex process list, QNX Neutrino
13778 For QNX Neutrino only, this command displays the list of all the
13779 processes and all the threads within each process.
13782 @kindex info meminfo
13783 @cindex mapinfo list, QNX Neutrino
13784 For QNX Neutrino only, this command displays the list of all mapinfos.
13788 @subsection Features for Debugging @sc{djgpp} Programs
13789 @cindex @sc{djgpp} debugging
13790 @cindex native @sc{djgpp} debugging
13791 @cindex MS-DOS-specific commands
13794 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13795 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13796 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13797 top of real-mode DOS systems and their emulations.
13799 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13800 defines a few commands specific to the @sc{djgpp} port. This
13801 subsection describes those commands.
13806 This is a prefix of @sc{djgpp}-specific commands which print
13807 information about the target system and important OS structures.
13810 @cindex MS-DOS system info
13811 @cindex free memory information (MS-DOS)
13812 @item info dos sysinfo
13813 This command displays assorted information about the underlying
13814 platform: the CPU type and features, the OS version and flavor, the
13815 DPMI version, and the available conventional and DPMI memory.
13820 @cindex segment descriptor tables
13821 @cindex descriptor tables display
13823 @itemx info dos ldt
13824 @itemx info dos idt
13825 These 3 commands display entries from, respectively, Global, Local,
13826 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13827 tables are data structures which store a descriptor for each segment
13828 that is currently in use. The segment's selector is an index into a
13829 descriptor table; the table entry for that index holds the
13830 descriptor's base address and limit, and its attributes and access
13833 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13834 segment (used for both data and the stack), and a DOS segment (which
13835 allows access to DOS/BIOS data structures and absolute addresses in
13836 conventional memory). However, the DPMI host will usually define
13837 additional segments in order to support the DPMI environment.
13839 @cindex garbled pointers
13840 These commands allow to display entries from the descriptor tables.
13841 Without an argument, all entries from the specified table are
13842 displayed. An argument, which should be an integer expression, means
13843 display a single entry whose index is given by the argument. For
13844 example, here's a convenient way to display information about the
13845 debugged program's data segment:
13848 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13849 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13853 This comes in handy when you want to see whether a pointer is outside
13854 the data segment's limit (i.e.@: @dfn{garbled}).
13856 @cindex page tables display (MS-DOS)
13858 @itemx info dos pte
13859 These two commands display entries from, respectively, the Page
13860 Directory and the Page Tables. Page Directories and Page Tables are
13861 data structures which control how virtual memory addresses are mapped
13862 into physical addresses. A Page Table includes an entry for every
13863 page of memory that is mapped into the program's address space; there
13864 may be several Page Tables, each one holding up to 4096 entries. A
13865 Page Directory has up to 4096 entries, one each for every Page Table
13866 that is currently in use.
13868 Without an argument, @kbd{info dos pde} displays the entire Page
13869 Directory, and @kbd{info dos pte} displays all the entries in all of
13870 the Page Tables. An argument, an integer expression, given to the
13871 @kbd{info dos pde} command means display only that entry from the Page
13872 Directory table. An argument given to the @kbd{info dos pte} command
13873 means display entries from a single Page Table, the one pointed to by
13874 the specified entry in the Page Directory.
13876 @cindex direct memory access (DMA) on MS-DOS
13877 These commands are useful when your program uses @dfn{DMA} (Direct
13878 Memory Access), which needs physical addresses to program the DMA
13881 These commands are supported only with some DPMI servers.
13883 @cindex physical address from linear address
13884 @item info dos address-pte @var{addr}
13885 This command displays the Page Table entry for a specified linear
13886 address. The argument @var{addr} is a linear address which should
13887 already have the appropriate segment's base address added to it,
13888 because this command accepts addresses which may belong to @emph{any}
13889 segment. For example, here's how to display the Page Table entry for
13890 the page where a variable @code{i} is stored:
13893 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13894 @exdent @code{Page Table entry for address 0x11a00d30:}
13895 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13899 This says that @code{i} is stored at offset @code{0xd30} from the page
13900 whose physical base address is @code{0x02698000}, and shows all the
13901 attributes of that page.
13903 Note that you must cast the addresses of variables to a @code{char *},
13904 since otherwise the value of @code{__djgpp_base_address}, the base
13905 address of all variables and functions in a @sc{djgpp} program, will
13906 be added using the rules of C pointer arithmetics: if @code{i} is
13907 declared an @code{int}, @value{GDBN} will add 4 times the value of
13908 @code{__djgpp_base_address} to the address of @code{i}.
13910 Here's another example, it displays the Page Table entry for the
13914 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13915 @exdent @code{Page Table entry for address 0x29110:}
13916 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13920 (The @code{+ 3} offset is because the transfer buffer's address is the
13921 3rd member of the @code{_go32_info_block} structure.) The output
13922 clearly shows that this DPMI server maps the addresses in conventional
13923 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13924 linear (@code{0x29110}) addresses are identical.
13926 This command is supported only with some DPMI servers.
13929 @cindex DOS serial data link, remote debugging
13930 In addition to native debugging, the DJGPP port supports remote
13931 debugging via a serial data link. The following commands are specific
13932 to remote serial debugging in the DJGPP port of @value{GDBN}.
13935 @kindex set com1base
13936 @kindex set com1irq
13937 @kindex set com2base
13938 @kindex set com2irq
13939 @kindex set com3base
13940 @kindex set com3irq
13941 @kindex set com4base
13942 @kindex set com4irq
13943 @item set com1base @var{addr}
13944 This command sets the base I/O port address of the @file{COM1} serial
13947 @item set com1irq @var{irq}
13948 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13949 for the @file{COM1} serial port.
13951 There are similar commands @samp{set com2base}, @samp{set com3irq},
13952 etc.@: for setting the port address and the @code{IRQ} lines for the
13955 @kindex show com1base
13956 @kindex show com1irq
13957 @kindex show com2base
13958 @kindex show com2irq
13959 @kindex show com3base
13960 @kindex show com3irq
13961 @kindex show com4base
13962 @kindex show com4irq
13963 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13964 display the current settings of the base address and the @code{IRQ}
13965 lines used by the COM ports.
13968 @kindex info serial
13969 @cindex DOS serial port status
13970 This command prints the status of the 4 DOS serial ports. For each
13971 port, it prints whether it's active or not, its I/O base address and
13972 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13973 counts of various errors encountered so far.
13977 @node Cygwin Native
13978 @subsection Features for Debugging MS Windows PE Executables
13979 @cindex MS Windows debugging
13980 @cindex native Cygwin debugging
13981 @cindex Cygwin-specific commands
13983 @value{GDBN} supports native debugging of MS Windows programs, including
13984 DLLs with and without symbolic debugging information. There are various
13985 additional Cygwin-specific commands, described in this section.
13986 Working with DLLs that have no debugging symbols is described in
13987 @ref{Non-debug DLL Symbols}.
13992 This is a prefix of MS Windows-specific commands which print
13993 information about the target system and important OS structures.
13995 @item info w32 selector
13996 This command displays information returned by
13997 the Win32 API @code{GetThreadSelectorEntry} function.
13998 It takes an optional argument that is evaluated to
13999 a long value to give the information about this given selector.
14000 Without argument, this command displays information
14001 about the six segment registers.
14005 This is a Cygwin-specific alias of @code{info shared}.
14007 @kindex dll-symbols
14009 This command loads symbols from a dll similarly to
14010 add-sym command but without the need to specify a base address.
14012 @kindex set cygwin-exceptions
14013 @cindex debugging the Cygwin DLL
14014 @cindex Cygwin DLL, debugging
14015 @item set cygwin-exceptions @var{mode}
14016 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
14017 happen inside the Cygwin DLL. If @var{mode} is @code{off},
14018 @value{GDBN} will delay recognition of exceptions, and may ignore some
14019 exceptions which seem to be caused by internal Cygwin DLL
14020 ``bookkeeping''. This option is meant primarily for debugging the
14021 Cygwin DLL itself; the default value is @code{off} to avoid annoying
14022 @value{GDBN} users with false @code{SIGSEGV} signals.
14024 @kindex show cygwin-exceptions
14025 @item show cygwin-exceptions
14026 Displays whether @value{GDBN} will break on exceptions that happen
14027 inside the Cygwin DLL itself.
14029 @kindex set new-console
14030 @item set new-console @var{mode}
14031 If @var{mode} is @code{on} the debuggee will
14032 be started in a new console on next start.
14033 If @var{mode} is @code{off}i, the debuggee will
14034 be started in the same console as the debugger.
14036 @kindex show new-console
14037 @item show new-console
14038 Displays whether a new console is used
14039 when the debuggee is started.
14041 @kindex set new-group
14042 @item set new-group @var{mode}
14043 This boolean value controls whether the debuggee should
14044 start a new group or stay in the same group as the debugger.
14045 This affects the way the Windows OS handles
14048 @kindex show new-group
14049 @item show new-group
14050 Displays current value of new-group boolean.
14052 @kindex set debugevents
14053 @item set debugevents
14054 This boolean value adds debug output concerning kernel events related
14055 to the debuggee seen by the debugger. This includes events that
14056 signal thread and process creation and exit, DLL loading and
14057 unloading, console interrupts, and debugging messages produced by the
14058 Windows @code{OutputDebugString} API call.
14060 @kindex set debugexec
14061 @item set debugexec
14062 This boolean value adds debug output concerning execute events
14063 (such as resume thread) seen by the debugger.
14065 @kindex set debugexceptions
14066 @item set debugexceptions
14067 This boolean value adds debug output concerning exceptions in the
14068 debuggee seen by the debugger.
14070 @kindex set debugmemory
14071 @item set debugmemory
14072 This boolean value adds debug output concerning debuggee memory reads
14073 and writes by the debugger.
14077 This boolean values specifies whether the debuggee is called
14078 via a shell or directly (default value is on).
14082 Displays if the debuggee will be started with a shell.
14087 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14090 @node Non-debug DLL Symbols
14091 @subsubsection Support for DLLs without Debugging Symbols
14092 @cindex DLLs with no debugging symbols
14093 @cindex Minimal symbols and DLLs
14095 Very often on windows, some of the DLLs that your program relies on do
14096 not include symbolic debugging information (for example,
14097 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14098 symbols in a DLL, it relies on the minimal amount of symbolic
14099 information contained in the DLL's export table. This section
14100 describes working with such symbols, known internally to @value{GDBN} as
14101 ``minimal symbols''.
14103 Note that before the debugged program has started execution, no DLLs
14104 will have been loaded. The easiest way around this problem is simply to
14105 start the program --- either by setting a breakpoint or letting the
14106 program run once to completion. It is also possible to force
14107 @value{GDBN} to load a particular DLL before starting the executable ---
14108 see the shared library information in @ref{Files}, or the
14109 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14110 explicitly loading symbols from a DLL with no debugging information will
14111 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14112 which may adversely affect symbol lookup performance.
14114 @subsubsection DLL Name Prefixes
14116 In keeping with the naming conventions used by the Microsoft debugging
14117 tools, DLL export symbols are made available with a prefix based on the
14118 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14119 also entered into the symbol table, so @code{CreateFileA} is often
14120 sufficient. In some cases there will be name clashes within a program
14121 (particularly if the executable itself includes full debugging symbols)
14122 necessitating the use of the fully qualified name when referring to the
14123 contents of the DLL. Use single-quotes around the name to avoid the
14124 exclamation mark (``!'') being interpreted as a language operator.
14126 Note that the internal name of the DLL may be all upper-case, even
14127 though the file name of the DLL is lower-case, or vice-versa. Since
14128 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14129 some confusion. If in doubt, try the @code{info functions} and
14130 @code{info variables} commands or even @code{maint print msymbols}
14131 (@pxref{Symbols}). Here's an example:
14134 (@value{GDBP}) info function CreateFileA
14135 All functions matching regular expression "CreateFileA":
14137 Non-debugging symbols:
14138 0x77e885f4 CreateFileA
14139 0x77e885f4 KERNEL32!CreateFileA
14143 (@value{GDBP}) info function !
14144 All functions matching regular expression "!":
14146 Non-debugging symbols:
14147 0x6100114c cygwin1!__assert
14148 0x61004034 cygwin1!_dll_crt0@@0
14149 0x61004240 cygwin1!dll_crt0(per_process *)
14153 @subsubsection Working with Minimal Symbols
14155 Symbols extracted from a DLL's export table do not contain very much
14156 type information. All that @value{GDBN} can do is guess whether a symbol
14157 refers to a function or variable depending on the linker section that
14158 contains the symbol. Also note that the actual contents of the memory
14159 contained in a DLL are not available unless the program is running. This
14160 means that you cannot examine the contents of a variable or disassemble
14161 a function within a DLL without a running program.
14163 Variables are generally treated as pointers and dereferenced
14164 automatically. For this reason, it is often necessary to prefix a
14165 variable name with the address-of operator (``&'') and provide explicit
14166 type information in the command. Here's an example of the type of
14170 (@value{GDBP}) print 'cygwin1!__argv'
14175 (@value{GDBP}) x 'cygwin1!__argv'
14176 0x10021610: "\230y\""
14179 And two possible solutions:
14182 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14183 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14187 (@value{GDBP}) x/2x &'cygwin1!__argv'
14188 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14189 (@value{GDBP}) x/x 0x10021608
14190 0x10021608: 0x0022fd98
14191 (@value{GDBP}) x/s 0x0022fd98
14192 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14195 Setting a break point within a DLL is possible even before the program
14196 starts execution. However, under these circumstances, @value{GDBN} can't
14197 examine the initial instructions of the function in order to skip the
14198 function's frame set-up code. You can work around this by using ``*&''
14199 to set the breakpoint at a raw memory address:
14202 (@value{GDBP}) break *&'python22!PyOS_Readline'
14203 Breakpoint 1 at 0x1e04eff0
14206 The author of these extensions is not entirely convinced that setting a
14207 break point within a shared DLL like @file{kernel32.dll} is completely
14211 @subsection Commands Specific to @sc{gnu} Hurd Systems
14212 @cindex @sc{gnu} Hurd debugging
14214 This subsection describes @value{GDBN} commands specific to the
14215 @sc{gnu} Hurd native debugging.
14220 @kindex set signals@r{, Hurd command}
14221 @kindex set sigs@r{, Hurd command}
14222 This command toggles the state of inferior signal interception by
14223 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14224 affected by this command. @code{sigs} is a shorthand alias for
14229 @kindex show signals@r{, Hurd command}
14230 @kindex show sigs@r{, Hurd command}
14231 Show the current state of intercepting inferior's signals.
14233 @item set signal-thread
14234 @itemx set sigthread
14235 @kindex set signal-thread
14236 @kindex set sigthread
14237 This command tells @value{GDBN} which thread is the @code{libc} signal
14238 thread. That thread is run when a signal is delivered to a running
14239 process. @code{set sigthread} is the shorthand alias of @code{set
14242 @item show signal-thread
14243 @itemx show sigthread
14244 @kindex show signal-thread
14245 @kindex show sigthread
14246 These two commands show which thread will run when the inferior is
14247 delivered a signal.
14250 @kindex set stopped@r{, Hurd command}
14251 This commands tells @value{GDBN} that the inferior process is stopped,
14252 as with the @code{SIGSTOP} signal. The stopped process can be
14253 continued by delivering a signal to it.
14256 @kindex show stopped@r{, Hurd command}
14257 This command shows whether @value{GDBN} thinks the debuggee is
14260 @item set exceptions
14261 @kindex set exceptions@r{, Hurd command}
14262 Use this command to turn off trapping of exceptions in the inferior.
14263 When exception trapping is off, neither breakpoints nor
14264 single-stepping will work. To restore the default, set exception
14267 @item show exceptions
14268 @kindex show exceptions@r{, Hurd command}
14269 Show the current state of trapping exceptions in the inferior.
14271 @item set task pause
14272 @kindex set task@r{, Hurd commands}
14273 @cindex task attributes (@sc{gnu} Hurd)
14274 @cindex pause current task (@sc{gnu} Hurd)
14275 This command toggles task suspension when @value{GDBN} has control.
14276 Setting it to on takes effect immediately, and the task is suspended
14277 whenever @value{GDBN} gets control. Setting it to off will take
14278 effect the next time the inferior is continued. If this option is set
14279 to off, you can use @code{set thread default pause on} or @code{set
14280 thread pause on} (see below) to pause individual threads.
14282 @item show task pause
14283 @kindex show task@r{, Hurd commands}
14284 Show the current state of task suspension.
14286 @item set task detach-suspend-count
14287 @cindex task suspend count
14288 @cindex detach from task, @sc{gnu} Hurd
14289 This command sets the suspend count the task will be left with when
14290 @value{GDBN} detaches from it.
14292 @item show task detach-suspend-count
14293 Show the suspend count the task will be left with when detaching.
14295 @item set task exception-port
14296 @itemx set task excp
14297 @cindex task exception port, @sc{gnu} Hurd
14298 This command sets the task exception port to which @value{GDBN} will
14299 forward exceptions. The argument should be the value of the @dfn{send
14300 rights} of the task. @code{set task excp} is a shorthand alias.
14302 @item set noninvasive
14303 @cindex noninvasive task options
14304 This command switches @value{GDBN} to a mode that is the least
14305 invasive as far as interfering with the inferior is concerned. This
14306 is the same as using @code{set task pause}, @code{set exceptions}, and
14307 @code{set signals} to values opposite to the defaults.
14309 @item info send-rights
14310 @itemx info receive-rights
14311 @itemx info port-rights
14312 @itemx info port-sets
14313 @itemx info dead-names
14316 @cindex send rights, @sc{gnu} Hurd
14317 @cindex receive rights, @sc{gnu} Hurd
14318 @cindex port rights, @sc{gnu} Hurd
14319 @cindex port sets, @sc{gnu} Hurd
14320 @cindex dead names, @sc{gnu} Hurd
14321 These commands display information about, respectively, send rights,
14322 receive rights, port rights, port sets, and dead names of a task.
14323 There are also shorthand aliases: @code{info ports} for @code{info
14324 port-rights} and @code{info psets} for @code{info port-sets}.
14326 @item set thread pause
14327 @kindex set thread@r{, Hurd command}
14328 @cindex thread properties, @sc{gnu} Hurd
14329 @cindex pause current thread (@sc{gnu} Hurd)
14330 This command toggles current thread suspension when @value{GDBN} has
14331 control. Setting it to on takes effect immediately, and the current
14332 thread is suspended whenever @value{GDBN} gets control. Setting it to
14333 off will take effect the next time the inferior is continued.
14334 Normally, this command has no effect, since when @value{GDBN} has
14335 control, the whole task is suspended. However, if you used @code{set
14336 task pause off} (see above), this command comes in handy to suspend
14337 only the current thread.
14339 @item show thread pause
14340 @kindex show thread@r{, Hurd command}
14341 This command shows the state of current thread suspension.
14343 @item set thread run
14344 This command sets whether the current thread is allowed to run.
14346 @item show thread run
14347 Show whether the current thread is allowed to run.
14349 @item set thread detach-suspend-count
14350 @cindex thread suspend count, @sc{gnu} Hurd
14351 @cindex detach from thread, @sc{gnu} Hurd
14352 This command sets the suspend count @value{GDBN} will leave on a
14353 thread when detaching. This number is relative to the suspend count
14354 found by @value{GDBN} when it notices the thread; use @code{set thread
14355 takeover-suspend-count} to force it to an absolute value.
14357 @item show thread detach-suspend-count
14358 Show the suspend count @value{GDBN} will leave on the thread when
14361 @item set thread exception-port
14362 @itemx set thread excp
14363 Set the thread exception port to which to forward exceptions. This
14364 overrides the port set by @code{set task exception-port} (see above).
14365 @code{set thread excp} is the shorthand alias.
14367 @item set thread takeover-suspend-count
14368 Normally, @value{GDBN}'s thread suspend counts are relative to the
14369 value @value{GDBN} finds when it notices each thread. This command
14370 changes the suspend counts to be absolute instead.
14372 @item set thread default
14373 @itemx show thread default
14374 @cindex thread default settings, @sc{gnu} Hurd
14375 Each of the above @code{set thread} commands has a @code{set thread
14376 default} counterpart (e.g., @code{set thread default pause}, @code{set
14377 thread default exception-port}, etc.). The @code{thread default}
14378 variety of commands sets the default thread properties for all
14379 threads; you can then change the properties of individual threads with
14380 the non-default commands.
14385 @subsection QNX Neutrino
14386 @cindex QNX Neutrino
14388 @value{GDBN} provides the following commands specific to the QNX
14392 @item set debug nto-debug
14393 @kindex set debug nto-debug
14394 When set to on, enables debugging messages specific to the QNX
14397 @item show debug nto-debug
14398 @kindex show debug nto-debug
14399 Show the current state of QNX Neutrino messages.
14404 @section Embedded Operating Systems
14406 This section describes configurations involving the debugging of
14407 embedded operating systems that are available for several different
14411 * VxWorks:: Using @value{GDBN} with VxWorks
14414 @value{GDBN} includes the ability to debug programs running on
14415 various real-time operating systems.
14418 @subsection Using @value{GDBN} with VxWorks
14424 @kindex target vxworks
14425 @item target vxworks @var{machinename}
14426 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14427 is the target system's machine name or IP address.
14431 On VxWorks, @code{load} links @var{filename} dynamically on the
14432 current target system as well as adding its symbols in @value{GDBN}.
14434 @value{GDBN} enables developers to spawn and debug tasks running on networked
14435 VxWorks targets from a Unix host. Already-running tasks spawned from
14436 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14437 both the Unix host and on the VxWorks target. The program
14438 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14439 installed with the name @code{vxgdb}, to distinguish it from a
14440 @value{GDBN} for debugging programs on the host itself.)
14443 @item VxWorks-timeout @var{args}
14444 @kindex vxworks-timeout
14445 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14446 This option is set by the user, and @var{args} represents the number of
14447 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14448 your VxWorks target is a slow software simulator or is on the far side
14449 of a thin network line.
14452 The following information on connecting to VxWorks was current when
14453 this manual was produced; newer releases of VxWorks may use revised
14456 @findex INCLUDE_RDB
14457 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14458 to include the remote debugging interface routines in the VxWorks
14459 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14460 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14461 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14462 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14463 information on configuring and remaking VxWorks, see the manufacturer's
14465 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14467 Once you have included @file{rdb.a} in your VxWorks system image and set
14468 your Unix execution search path to find @value{GDBN}, you are ready to
14469 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14470 @code{vxgdb}, depending on your installation).
14472 @value{GDBN} comes up showing the prompt:
14479 * VxWorks Connection:: Connecting to VxWorks
14480 * VxWorks Download:: VxWorks download
14481 * VxWorks Attach:: Running tasks
14484 @node VxWorks Connection
14485 @subsubsection Connecting to VxWorks
14487 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14488 network. To connect to a target whose host name is ``@code{tt}'', type:
14491 (vxgdb) target vxworks tt
14495 @value{GDBN} displays messages like these:
14498 Attaching remote machine across net...
14503 @value{GDBN} then attempts to read the symbol tables of any object modules
14504 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14505 these files by searching the directories listed in the command search
14506 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14507 to find an object file, it displays a message such as:
14510 prog.o: No such file or directory.
14513 When this happens, add the appropriate directory to the search path with
14514 the @value{GDBN} command @code{path}, and execute the @code{target}
14517 @node VxWorks Download
14518 @subsubsection VxWorks Download
14520 @cindex download to VxWorks
14521 If you have connected to the VxWorks target and you want to debug an
14522 object that has not yet been loaded, you can use the @value{GDBN}
14523 @code{load} command to download a file from Unix to VxWorks
14524 incrementally. The object file given as an argument to the @code{load}
14525 command is actually opened twice: first by the VxWorks target in order
14526 to download the code, then by @value{GDBN} in order to read the symbol
14527 table. This can lead to problems if the current working directories on
14528 the two systems differ. If both systems have NFS mounted the same
14529 filesystems, you can avoid these problems by using absolute paths.
14530 Otherwise, it is simplest to set the working directory on both systems
14531 to the directory in which the object file resides, and then to reference
14532 the file by its name, without any path. For instance, a program
14533 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14534 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14535 program, type this on VxWorks:
14538 -> cd "@var{vxpath}/vw/demo/rdb"
14542 Then, in @value{GDBN}, type:
14545 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14546 (vxgdb) load prog.o
14549 @value{GDBN} displays a response similar to this:
14552 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14555 You can also use the @code{load} command to reload an object module
14556 after editing and recompiling the corresponding source file. Note that
14557 this makes @value{GDBN} delete all currently-defined breakpoints,
14558 auto-displays, and convenience variables, and to clear the value
14559 history. (This is necessary in order to preserve the integrity of
14560 debugger's data structures that reference the target system's symbol
14563 @node VxWorks Attach
14564 @subsubsection Running Tasks
14566 @cindex running VxWorks tasks
14567 You can also attach to an existing task using the @code{attach} command as
14571 (vxgdb) attach @var{task}
14575 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14576 or suspended when you attach to it. Running tasks are suspended at
14577 the time of attachment.
14579 @node Embedded Processors
14580 @section Embedded Processors
14582 This section goes into details specific to particular embedded
14585 @cindex send command to simulator
14586 Whenever a specific embedded processor has a simulator, @value{GDBN}
14587 allows to send an arbitrary command to the simulator.
14590 @item sim @var{command}
14591 @kindex sim@r{, a command}
14592 Send an arbitrary @var{command} string to the simulator. Consult the
14593 documentation for the specific simulator in use for information about
14594 acceptable commands.
14600 * M32R/D:: Renesas M32R/D
14601 * M68K:: Motorola M68K
14602 * MIPS Embedded:: MIPS Embedded
14603 * OpenRISC 1000:: OpenRisc 1000
14604 * PA:: HP PA Embedded
14605 * PowerPC:: PowerPC
14606 * Sparclet:: Tsqware Sparclet
14607 * Sparclite:: Fujitsu Sparclite
14608 * Z8000:: Zilog Z8000
14611 * Super-H:: Renesas Super-H
14620 @item target rdi @var{dev}
14621 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14622 use this target to communicate with both boards running the Angel
14623 monitor, or with the EmbeddedICE JTAG debug device.
14626 @item target rdp @var{dev}
14631 @value{GDBN} provides the following ARM-specific commands:
14634 @item set arm disassembler
14636 This commands selects from a list of disassembly styles. The
14637 @code{"std"} style is the standard style.
14639 @item show arm disassembler
14641 Show the current disassembly style.
14643 @item set arm apcs32
14644 @cindex ARM 32-bit mode
14645 This command toggles ARM operation mode between 32-bit and 26-bit.
14647 @item show arm apcs32
14648 Display the current usage of the ARM 32-bit mode.
14650 @item set arm fpu @var{fputype}
14651 This command sets the ARM floating-point unit (FPU) type. The
14652 argument @var{fputype} can be one of these:
14656 Determine the FPU type by querying the OS ABI.
14658 Software FPU, with mixed-endian doubles on little-endian ARM
14661 GCC-compiled FPA co-processor.
14663 Software FPU with pure-endian doubles.
14669 Show the current type of the FPU.
14672 This command forces @value{GDBN} to use the specified ABI.
14675 Show the currently used ABI.
14677 @item set debug arm
14678 Toggle whether to display ARM-specific debugging messages from the ARM
14679 target support subsystem.
14681 @item show debug arm
14682 Show whether ARM-specific debugging messages are enabled.
14685 The following commands are available when an ARM target is debugged
14686 using the RDI interface:
14689 @item rdilogfile @r{[}@var{file}@r{]}
14691 @cindex ADP (Angel Debugger Protocol) logging
14692 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14693 With an argument, sets the log file to the specified @var{file}. With
14694 no argument, show the current log file name. The default log file is
14697 @item rdilogenable @r{[}@var{arg}@r{]}
14698 @kindex rdilogenable
14699 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14700 enables logging, with an argument 0 or @code{"no"} disables it. With
14701 no arguments displays the current setting. When logging is enabled,
14702 ADP packets exchanged between @value{GDBN} and the RDI target device
14703 are logged to a file.
14705 @item set rdiromatzero
14706 @kindex set rdiromatzero
14707 @cindex ROM at zero address, RDI
14708 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14709 vector catching is disabled, so that zero address can be used. If off
14710 (the default), vector catching is enabled. For this command to take
14711 effect, it needs to be invoked prior to the @code{target rdi} command.
14713 @item show rdiromatzero
14714 @kindex show rdiromatzero
14715 Show the current setting of ROM at zero address.
14717 @item set rdiheartbeat
14718 @kindex set rdiheartbeat
14719 @cindex RDI heartbeat
14720 Enable or disable RDI heartbeat packets. It is not recommended to
14721 turn on this option, since it confuses ARM and EPI JTAG interface, as
14722 well as the Angel monitor.
14724 @item show rdiheartbeat
14725 @kindex show rdiheartbeat
14726 Show the setting of RDI heartbeat packets.
14731 @subsection Renesas M32R/D and M32R/SDI
14734 @kindex target m32r
14735 @item target m32r @var{dev}
14736 Renesas M32R/D ROM monitor.
14738 @kindex target m32rsdi
14739 @item target m32rsdi @var{dev}
14740 Renesas M32R SDI server, connected via parallel port to the board.
14743 The following @value{GDBN} commands are specific to the M32R monitor:
14746 @item set download-path @var{path}
14747 @kindex set download-path
14748 @cindex find downloadable @sc{srec} files (M32R)
14749 Set the default path for finding downloadable @sc{srec} files.
14751 @item show download-path
14752 @kindex show download-path
14753 Show the default path for downloadable @sc{srec} files.
14755 @item set board-address @var{addr}
14756 @kindex set board-address
14757 @cindex M32-EVA target board address
14758 Set the IP address for the M32R-EVA target board.
14760 @item show board-address
14761 @kindex show board-address
14762 Show the current IP address of the target board.
14764 @item set server-address @var{addr}
14765 @kindex set server-address
14766 @cindex download server address (M32R)
14767 Set the IP address for the download server, which is the @value{GDBN}'s
14770 @item show server-address
14771 @kindex show server-address
14772 Display the IP address of the download server.
14774 @item upload @r{[}@var{file}@r{]}
14775 @kindex upload@r{, M32R}
14776 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14777 upload capability. If no @var{file} argument is given, the current
14778 executable file is uploaded.
14780 @item tload @r{[}@var{file}@r{]}
14781 @kindex tload@r{, M32R}
14782 Test the @code{upload} command.
14785 The following commands are available for M32R/SDI:
14790 @cindex reset SDI connection, M32R
14791 This command resets the SDI connection.
14795 This command shows the SDI connection status.
14798 @kindex debug_chaos
14799 @cindex M32R/Chaos debugging
14800 Instructs the remote that M32R/Chaos debugging is to be used.
14802 @item use_debug_dma
14803 @kindex use_debug_dma
14804 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14807 @kindex use_mon_code
14808 Instructs the remote to use the MON_CODE method of accessing memory.
14811 @kindex use_ib_break
14812 Instructs the remote to set breakpoints by IB break.
14814 @item use_dbt_break
14815 @kindex use_dbt_break
14816 Instructs the remote to set breakpoints by DBT.
14822 The Motorola m68k configuration includes ColdFire support, and a
14823 target command for the following ROM monitor.
14827 @kindex target dbug
14828 @item target dbug @var{dev}
14829 dBUG ROM monitor for Motorola ColdFire.
14833 @node MIPS Embedded
14834 @subsection MIPS Embedded
14836 @cindex MIPS boards
14837 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14838 MIPS board attached to a serial line. This is available when
14839 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14842 Use these @value{GDBN} commands to specify the connection to your target board:
14845 @item target mips @var{port}
14846 @kindex target mips @var{port}
14847 To run a program on the board, start up @code{@value{GDBP}} with the
14848 name of your program as the argument. To connect to the board, use the
14849 command @samp{target mips @var{port}}, where @var{port} is the name of
14850 the serial port connected to the board. If the program has not already
14851 been downloaded to the board, you may use the @code{load} command to
14852 download it. You can then use all the usual @value{GDBN} commands.
14854 For example, this sequence connects to the target board through a serial
14855 port, and loads and runs a program called @var{prog} through the
14859 host$ @value{GDBP} @var{prog}
14860 @value{GDBN} is free software and @dots{}
14861 (@value{GDBP}) target mips /dev/ttyb
14862 (@value{GDBP}) load @var{prog}
14866 @item target mips @var{hostname}:@var{portnumber}
14867 On some @value{GDBN} host configurations, you can specify a TCP
14868 connection (for instance, to a serial line managed by a terminal
14869 concentrator) instead of a serial port, using the syntax
14870 @samp{@var{hostname}:@var{portnumber}}.
14872 @item target pmon @var{port}
14873 @kindex target pmon @var{port}
14876 @item target ddb @var{port}
14877 @kindex target ddb @var{port}
14878 NEC's DDB variant of PMON for Vr4300.
14880 @item target lsi @var{port}
14881 @kindex target lsi @var{port}
14882 LSI variant of PMON.
14884 @kindex target r3900
14885 @item target r3900 @var{dev}
14886 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14888 @kindex target array
14889 @item target array @var{dev}
14890 Array Tech LSI33K RAID controller board.
14896 @value{GDBN} also supports these special commands for MIPS targets:
14899 @item set mipsfpu double
14900 @itemx set mipsfpu single
14901 @itemx set mipsfpu none
14902 @itemx set mipsfpu auto
14903 @itemx show mipsfpu
14904 @kindex set mipsfpu
14905 @kindex show mipsfpu
14906 @cindex MIPS remote floating point
14907 @cindex floating point, MIPS remote
14908 If your target board does not support the MIPS floating point
14909 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14910 need this, you may wish to put the command in your @value{GDBN} init
14911 file). This tells @value{GDBN} how to find the return value of
14912 functions which return floating point values. It also allows
14913 @value{GDBN} to avoid saving the floating point registers when calling
14914 functions on the board. If you are using a floating point coprocessor
14915 with only single precision floating point support, as on the @sc{r4650}
14916 processor, use the command @samp{set mipsfpu single}. The default
14917 double precision floating point coprocessor may be selected using
14918 @samp{set mipsfpu double}.
14920 In previous versions the only choices were double precision or no
14921 floating point, so @samp{set mipsfpu on} will select double precision
14922 and @samp{set mipsfpu off} will select no floating point.
14924 As usual, you can inquire about the @code{mipsfpu} variable with
14925 @samp{show mipsfpu}.
14927 @item set timeout @var{seconds}
14928 @itemx set retransmit-timeout @var{seconds}
14929 @itemx show timeout
14930 @itemx show retransmit-timeout
14931 @cindex @code{timeout}, MIPS protocol
14932 @cindex @code{retransmit-timeout}, MIPS protocol
14933 @kindex set timeout
14934 @kindex show timeout
14935 @kindex set retransmit-timeout
14936 @kindex show retransmit-timeout
14937 You can control the timeout used while waiting for a packet, in the MIPS
14938 remote protocol, with the @code{set timeout @var{seconds}} command. The
14939 default is 5 seconds. Similarly, you can control the timeout used while
14940 waiting for an acknowledgement of a packet with the @code{set
14941 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14942 You can inspect both values with @code{show timeout} and @code{show
14943 retransmit-timeout}. (These commands are @emph{only} available when
14944 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14946 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14947 is waiting for your program to stop. In that case, @value{GDBN} waits
14948 forever because it has no way of knowing how long the program is going
14949 to run before stopping.
14951 @item set syn-garbage-limit @var{num}
14952 @kindex set syn-garbage-limit@r{, MIPS remote}
14953 @cindex synchronize with remote MIPS target
14954 Limit the maximum number of characters @value{GDBN} should ignore when
14955 it tries to synchronize with the remote target. The default is 10
14956 characters. Setting the limit to -1 means there's no limit.
14958 @item show syn-garbage-limit
14959 @kindex show syn-garbage-limit@r{, MIPS remote}
14960 Show the current limit on the number of characters to ignore when
14961 trying to synchronize with the remote system.
14963 @item set monitor-prompt @var{prompt}
14964 @kindex set monitor-prompt@r{, MIPS remote}
14965 @cindex remote monitor prompt
14966 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14967 remote monitor. The default depends on the target:
14977 @item show monitor-prompt
14978 @kindex show monitor-prompt@r{, MIPS remote}
14979 Show the current strings @value{GDBN} expects as the prompt from the
14982 @item set monitor-warnings
14983 @kindex set monitor-warnings@r{, MIPS remote}
14984 Enable or disable monitor warnings about hardware breakpoints. This
14985 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14986 display warning messages whose codes are returned by the @code{lsi}
14987 PMON monitor for breakpoint commands.
14989 @item show monitor-warnings
14990 @kindex show monitor-warnings@r{, MIPS remote}
14991 Show the current setting of printing monitor warnings.
14993 @item pmon @var{command}
14994 @kindex pmon@r{, MIPS remote}
14995 @cindex send PMON command
14996 This command allows sending an arbitrary @var{command} string to the
14997 monitor. The monitor must be in debug mode for this to work.
15000 @node OpenRISC 1000
15001 @subsection OpenRISC 1000
15002 @cindex OpenRISC 1000
15004 @cindex or1k boards
15005 See OR1k Architecture document (@uref{www.opencores.org}) for more information
15006 about platform and commands.
15010 @kindex target jtag
15011 @item target jtag jtag://@var{host}:@var{port}
15013 Connects to remote JTAG server.
15014 JTAG remote server can be either an or1ksim or JTAG server,
15015 connected via parallel port to the board.
15017 Example: @code{target jtag jtag://localhost:9999}
15020 @item or1ksim @var{command}
15021 If connected to @code{or1ksim} OpenRISC 1000 Architectural
15022 Simulator, proprietary commands can be executed.
15024 @kindex info or1k spr
15025 @item info or1k spr
15026 Displays spr groups.
15028 @item info or1k spr @var{group}
15029 @itemx info or1k spr @var{groupno}
15030 Displays register names in selected group.
15032 @item info or1k spr @var{group} @var{register}
15033 @itemx info or1k spr @var{register}
15034 @itemx info or1k spr @var{groupno} @var{registerno}
15035 @itemx info or1k spr @var{registerno}
15036 Shows information about specified spr register.
15039 @item spr @var{group} @var{register} @var{value}
15040 @itemx spr @var{register @var{value}}
15041 @itemx spr @var{groupno} @var{registerno @var{value}}
15042 @itemx spr @var{registerno @var{value}}
15043 Writes @var{value} to specified spr register.
15046 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15047 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15048 program execution and is thus much faster. Hardware breakpoints/watchpoint
15049 triggers can be set using:
15052 Load effective address/data
15054 Store effective address/data
15056 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15061 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15062 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15064 @code{htrace} commands:
15065 @cindex OpenRISC 1000 htrace
15068 @item hwatch @var{conditional}
15069 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15070 or Data. For example:
15072 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15074 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15078 Display information about current HW trace configuration.
15080 @item htrace trigger @var{conditional}
15081 Set starting criteria for HW trace.
15083 @item htrace qualifier @var{conditional}
15084 Set acquisition qualifier for HW trace.
15086 @item htrace stop @var{conditional}
15087 Set HW trace stopping criteria.
15089 @item htrace record [@var{data}]*
15090 Selects the data to be recorded, when qualifier is met and HW trace was
15093 @item htrace enable
15094 @itemx htrace disable
15095 Enables/disables the HW trace.
15097 @item htrace rewind [@var{filename}]
15098 Clears currently recorded trace data.
15100 If filename is specified, new trace file is made and any newly collected data
15101 will be written there.
15103 @item htrace print [@var{start} [@var{len}]]
15104 Prints trace buffer, using current record configuration.
15106 @item htrace mode continuous
15107 Set continuous trace mode.
15109 @item htrace mode suspend
15110 Set suspend trace mode.
15115 @subsection PowerPC
15117 @value{GDBN} provides the following PowerPC-specific commands:
15120 @kindex set powerpc
15121 @item set powerpc soft-float
15122 @itemx show powerpc soft-float
15123 Force @value{GDBN} to use (or not use) a software floating point calling
15124 convention. By default, @value{GDBN} selects the calling convention based
15125 on the selected architecture and the provided executable file.
15127 @item set powerpc vector-abi
15128 @itemx show powerpc vector-abi
15129 Force @value{GDBN} to use the specified calling convention for vector
15130 arguments and return values. The valid options are @samp{auto};
15131 @samp{generic}, to avoid vector registers even if they are present;
15132 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15133 registers. By default, @value{GDBN} selects the calling convention
15134 based on the selected architecture and the provided executable file.
15136 @kindex target dink32
15137 @item target dink32 @var{dev}
15138 DINK32 ROM monitor.
15140 @kindex target ppcbug
15141 @item target ppcbug @var{dev}
15142 @kindex target ppcbug1
15143 @item target ppcbug1 @var{dev}
15144 PPCBUG ROM monitor for PowerPC.
15147 @item target sds @var{dev}
15148 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15151 @cindex SDS protocol
15152 The following commands specific to the SDS protocol are supported
15156 @item set sdstimeout @var{nsec}
15157 @kindex set sdstimeout
15158 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15159 default is 2 seconds.
15161 @item show sdstimeout
15162 @kindex show sdstimeout
15163 Show the current value of the SDS timeout.
15165 @item sds @var{command}
15166 @kindex sds@r{, a command}
15167 Send the specified @var{command} string to the SDS monitor.
15172 @subsection HP PA Embedded
15176 @kindex target op50n
15177 @item target op50n @var{dev}
15178 OP50N monitor, running on an OKI HPPA board.
15180 @kindex target w89k
15181 @item target w89k @var{dev}
15182 W89K monitor, running on a Winbond HPPA board.
15187 @subsection Tsqware Sparclet
15191 @value{GDBN} enables developers to debug tasks running on
15192 Sparclet targets from a Unix host.
15193 @value{GDBN} uses code that runs on
15194 both the Unix host and on the Sparclet target. The program
15195 @code{@value{GDBP}} is installed and executed on the Unix host.
15198 @item remotetimeout @var{args}
15199 @kindex remotetimeout
15200 @value{GDBN} supports the option @code{remotetimeout}.
15201 This option is set by the user, and @var{args} represents the number of
15202 seconds @value{GDBN} waits for responses.
15205 @cindex compiling, on Sparclet
15206 When compiling for debugging, include the options @samp{-g} to get debug
15207 information and @samp{-Ttext} to relocate the program to where you wish to
15208 load it on the target. You may also want to add the options @samp{-n} or
15209 @samp{-N} in order to reduce the size of the sections. Example:
15212 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15215 You can use @code{objdump} to verify that the addresses are what you intended:
15218 sparclet-aout-objdump --headers --syms prog
15221 @cindex running, on Sparclet
15223 your Unix execution search path to find @value{GDBN}, you are ready to
15224 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15225 (or @code{sparclet-aout-gdb}, depending on your installation).
15227 @value{GDBN} comes up showing the prompt:
15234 * Sparclet File:: Setting the file to debug
15235 * Sparclet Connection:: Connecting to Sparclet
15236 * Sparclet Download:: Sparclet download
15237 * Sparclet Execution:: Running and debugging
15240 @node Sparclet File
15241 @subsubsection Setting File to Debug
15243 The @value{GDBN} command @code{file} lets you choose with program to debug.
15246 (gdbslet) file prog
15250 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15251 @value{GDBN} locates
15252 the file by searching the directories listed in the command search
15254 If the file was compiled with debug information (option @samp{-g}), source
15255 files will be searched as well.
15256 @value{GDBN} locates
15257 the source files by searching the directories listed in the directory search
15258 path (@pxref{Environment, ,Your Program's Environment}).
15260 to find a file, it displays a message such as:
15263 prog: No such file or directory.
15266 When this happens, add the appropriate directories to the search paths with
15267 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15268 @code{target} command again.
15270 @node Sparclet Connection
15271 @subsubsection Connecting to Sparclet
15273 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15274 To connect to a target on serial port ``@code{ttya}'', type:
15277 (gdbslet) target sparclet /dev/ttya
15278 Remote target sparclet connected to /dev/ttya
15279 main () at ../prog.c:3
15283 @value{GDBN} displays messages like these:
15289 @node Sparclet Download
15290 @subsubsection Sparclet Download
15292 @cindex download to Sparclet
15293 Once connected to the Sparclet target,
15294 you can use the @value{GDBN}
15295 @code{load} command to download the file from the host to the target.
15296 The file name and load offset should be given as arguments to the @code{load}
15298 Since the file format is aout, the program must be loaded to the starting
15299 address. You can use @code{objdump} to find out what this value is. The load
15300 offset is an offset which is added to the VMA (virtual memory address)
15301 of each of the file's sections.
15302 For instance, if the program
15303 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15304 and bss at 0x12010170, in @value{GDBN}, type:
15307 (gdbslet) load prog 0x12010000
15308 Loading section .text, size 0xdb0 vma 0x12010000
15311 If the code is loaded at a different address then what the program was linked
15312 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15313 to tell @value{GDBN} where to map the symbol table.
15315 @node Sparclet Execution
15316 @subsubsection Running and Debugging
15318 @cindex running and debugging Sparclet programs
15319 You can now begin debugging the task using @value{GDBN}'s execution control
15320 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15321 manual for the list of commands.
15325 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15327 Starting program: prog
15328 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15329 3 char *symarg = 0;
15331 4 char *execarg = "hello!";
15336 @subsection Fujitsu Sparclite
15340 @kindex target sparclite
15341 @item target sparclite @var{dev}
15342 Fujitsu sparclite boards, used only for the purpose of loading.
15343 You must use an additional command to debug the program.
15344 For example: target remote @var{dev} using @value{GDBN} standard
15350 @subsection Zilog Z8000
15353 @cindex simulator, Z8000
15354 @cindex Zilog Z8000 simulator
15356 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15359 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15360 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15361 segmented variant). The simulator recognizes which architecture is
15362 appropriate by inspecting the object code.
15365 @item target sim @var{args}
15367 @kindex target sim@r{, with Z8000}
15368 Debug programs on a simulated CPU. If the simulator supports setup
15369 options, specify them via @var{args}.
15373 After specifying this target, you can debug programs for the simulated
15374 CPU in the same style as programs for your host computer; use the
15375 @code{file} command to load a new program image, the @code{run} command
15376 to run your program, and so on.
15378 As well as making available all the usual machine registers
15379 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15380 additional items of information as specially named registers:
15385 Counts clock-ticks in the simulator.
15388 Counts instructions run in the simulator.
15391 Execution time in 60ths of a second.
15395 You can refer to these values in @value{GDBN} expressions with the usual
15396 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15397 conditional breakpoint that suspends only after at least 5000
15398 simulated clock ticks.
15401 @subsection Atmel AVR
15404 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15405 following AVR-specific commands:
15408 @item info io_registers
15409 @kindex info io_registers@r{, AVR}
15410 @cindex I/O registers (Atmel AVR)
15411 This command displays information about the AVR I/O registers. For
15412 each register, @value{GDBN} prints its number and value.
15419 When configured for debugging CRIS, @value{GDBN} provides the
15420 following CRIS-specific commands:
15423 @item set cris-version @var{ver}
15424 @cindex CRIS version
15425 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15426 The CRIS version affects register names and sizes. This command is useful in
15427 case autodetection of the CRIS version fails.
15429 @item show cris-version
15430 Show the current CRIS version.
15432 @item set cris-dwarf2-cfi
15433 @cindex DWARF-2 CFI and CRIS
15434 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15435 Change to @samp{off} when using @code{gcc-cris} whose version is below
15438 @item show cris-dwarf2-cfi
15439 Show the current state of using DWARF-2 CFI.
15441 @item set cris-mode @var{mode}
15443 Set the current CRIS mode to @var{mode}. It should only be changed when
15444 debugging in guru mode, in which case it should be set to
15445 @samp{guru} (the default is @samp{normal}).
15447 @item show cris-mode
15448 Show the current CRIS mode.
15452 @subsection Renesas Super-H
15455 For the Renesas Super-H processor, @value{GDBN} provides these
15460 @kindex regs@r{, Super-H}
15461 Show the values of all Super-H registers.
15465 @node Architectures
15466 @section Architectures
15468 This section describes characteristics of architectures that affect
15469 all uses of @value{GDBN} with the architecture, both native and cross.
15476 * HPPA:: HP PA architecture
15477 * SPU:: Cell Broadband Engine SPU architecture
15481 @subsection x86 Architecture-specific Issues
15484 @item set struct-convention @var{mode}
15485 @kindex set struct-convention
15486 @cindex struct return convention
15487 @cindex struct/union returned in registers
15488 Set the convention used by the inferior to return @code{struct}s and
15489 @code{union}s from functions to @var{mode}. Possible values of
15490 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15491 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15492 are returned on the stack, while @code{"reg"} means that a
15493 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15494 be returned in a register.
15496 @item show struct-convention
15497 @kindex show struct-convention
15498 Show the current setting of the convention to return @code{struct}s
15507 @kindex set rstack_high_address
15508 @cindex AMD 29K register stack
15509 @cindex register stack, AMD29K
15510 @item set rstack_high_address @var{address}
15511 On AMD 29000 family processors, registers are saved in a separate
15512 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15513 extent of this stack. Normally, @value{GDBN} just assumes that the
15514 stack is ``large enough''. This may result in @value{GDBN} referencing
15515 memory locations that do not exist. If necessary, you can get around
15516 this problem by specifying the ending address of the register stack with
15517 the @code{set rstack_high_address} command. The argument should be an
15518 address, which you probably want to precede with @samp{0x} to specify in
15521 @kindex show rstack_high_address
15522 @item show rstack_high_address
15523 Display the current limit of the register stack, on AMD 29000 family
15531 See the following section.
15536 @cindex stack on Alpha
15537 @cindex stack on MIPS
15538 @cindex Alpha stack
15540 Alpha- and MIPS-based computers use an unusual stack frame, which
15541 sometimes requires @value{GDBN} to search backward in the object code to
15542 find the beginning of a function.
15544 @cindex response time, MIPS debugging
15545 To improve response time (especially for embedded applications, where
15546 @value{GDBN} may be restricted to a slow serial line for this search)
15547 you may want to limit the size of this search, using one of these
15551 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15552 @item set heuristic-fence-post @var{limit}
15553 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15554 search for the beginning of a function. A value of @var{0} (the
15555 default) means there is no limit. However, except for @var{0}, the
15556 larger the limit the more bytes @code{heuristic-fence-post} must search
15557 and therefore the longer it takes to run. You should only need to use
15558 this command when debugging a stripped executable.
15560 @item show heuristic-fence-post
15561 Display the current limit.
15565 These commands are available @emph{only} when @value{GDBN} is configured
15566 for debugging programs on Alpha or MIPS processors.
15568 Several MIPS-specific commands are available when debugging MIPS
15572 @item set mips abi @var{arg}
15573 @kindex set mips abi
15574 @cindex set ABI for MIPS
15575 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15576 values of @var{arg} are:
15580 The default ABI associated with the current binary (this is the
15591 @item show mips abi
15592 @kindex show mips abi
15593 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15596 @itemx show mipsfpu
15597 @xref{MIPS Embedded, set mipsfpu}.
15599 @item set mips mask-address @var{arg}
15600 @kindex set mips mask-address
15601 @cindex MIPS addresses, masking
15602 This command determines whether the most-significant 32 bits of 64-bit
15603 MIPS addresses are masked off. The argument @var{arg} can be
15604 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15605 setting, which lets @value{GDBN} determine the correct value.
15607 @item show mips mask-address
15608 @kindex show mips mask-address
15609 Show whether the upper 32 bits of MIPS addresses are masked off or
15612 @item set remote-mips64-transfers-32bit-regs
15613 @kindex set remote-mips64-transfers-32bit-regs
15614 This command controls compatibility with 64-bit MIPS targets that
15615 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15616 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15617 and 64 bits for other registers, set this option to @samp{on}.
15619 @item show remote-mips64-transfers-32bit-regs
15620 @kindex show remote-mips64-transfers-32bit-regs
15621 Show the current setting of compatibility with older MIPS 64 targets.
15623 @item set debug mips
15624 @kindex set debug mips
15625 This command turns on and off debugging messages for the MIPS-specific
15626 target code in @value{GDBN}.
15628 @item show debug mips
15629 @kindex show debug mips
15630 Show the current setting of MIPS debugging messages.
15636 @cindex HPPA support
15638 When @value{GDBN} is debugging the HP PA architecture, it provides the
15639 following special commands:
15642 @item set debug hppa
15643 @kindex set debug hppa
15644 This command determines whether HPPA architecture-specific debugging
15645 messages are to be displayed.
15647 @item show debug hppa
15648 Show whether HPPA debugging messages are displayed.
15650 @item maint print unwind @var{address}
15651 @kindex maint print unwind@r{, HPPA}
15652 This command displays the contents of the unwind table entry at the
15653 given @var{address}.
15659 @subsection Cell Broadband Engine SPU architecture
15660 @cindex Cell Broadband Engine
15663 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
15664 it provides the following special commands:
15667 @item info spu event
15669 Display SPU event facility status. Shows current event mask
15670 and pending event status.
15672 @item info spu signal
15673 Display SPU signal notification facility status. Shows pending
15674 signal-control word and signal notification mode of both signal
15675 notification channels.
15677 @item info spu mailbox
15678 Display SPU mailbox facility status. Shows all pending entries,
15679 in order of processing, in each of the SPU Write Outbound,
15680 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
15683 Display MFC DMA status. Shows all pending commands in the MFC
15684 DMA queue. For each entry, opcode, tag, class IDs, effective
15685 and local store addresses and transfer size are shown.
15687 @item info spu proxydma
15688 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
15689 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
15690 and local store addresses and transfer size are shown.
15695 @node Controlling GDB
15696 @chapter Controlling @value{GDBN}
15698 You can alter the way @value{GDBN} interacts with you by using the
15699 @code{set} command. For commands controlling how @value{GDBN} displays
15700 data, see @ref{Print Settings, ,Print Settings}. Other settings are
15705 * Editing:: Command editing
15706 * Command History:: Command history
15707 * Screen Size:: Screen size
15708 * Numbers:: Numbers
15709 * ABI:: Configuring the current ABI
15710 * Messages/Warnings:: Optional warnings and messages
15711 * Debugging Output:: Optional messages about internal happenings
15719 @value{GDBN} indicates its readiness to read a command by printing a string
15720 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15721 can change the prompt string with the @code{set prompt} command. For
15722 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15723 the prompt in one of the @value{GDBN} sessions so that you can always tell
15724 which one you are talking to.
15726 @emph{Note:} @code{set prompt} does not add a space for you after the
15727 prompt you set. This allows you to set a prompt which ends in a space
15728 or a prompt that does not.
15732 @item set prompt @var{newprompt}
15733 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15735 @kindex show prompt
15737 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15741 @section Command Editing
15743 @cindex command line editing
15745 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15746 @sc{gnu} library provides consistent behavior for programs which provide a
15747 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15748 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15749 substitution, and a storage and recall of command history across
15750 debugging sessions.
15752 You may control the behavior of command line editing in @value{GDBN} with the
15753 command @code{set}.
15756 @kindex set editing
15759 @itemx set editing on
15760 Enable command line editing (enabled by default).
15762 @item set editing off
15763 Disable command line editing.
15765 @kindex show editing
15767 Show whether command line editing is enabled.
15770 @xref{Command Line Editing}, for more details about the Readline
15771 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15772 encouraged to read that chapter.
15774 @node Command History
15775 @section Command History
15776 @cindex command history
15778 @value{GDBN} can keep track of the commands you type during your
15779 debugging sessions, so that you can be certain of precisely what
15780 happened. Use these commands to manage the @value{GDBN} command
15783 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15784 package, to provide the history facility. @xref{Using History
15785 Interactively}, for the detailed description of the History library.
15787 To issue a command to @value{GDBN} without affecting certain aspects of
15788 the state which is seen by users, prefix it with @samp{server }
15789 (@pxref{Server Prefix}). This
15790 means that this command will not affect the command history, nor will it
15791 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15792 pressed on a line by itself.
15794 @cindex @code{server}, command prefix
15795 The server prefix does not affect the recording of values into the value
15796 history; to print a value without recording it into the value history,
15797 use the @code{output} command instead of the @code{print} command.
15799 Here is the description of @value{GDBN} commands related to command
15803 @cindex history substitution
15804 @cindex history file
15805 @kindex set history filename
15806 @cindex @env{GDBHISTFILE}, environment variable
15807 @item set history filename @var{fname}
15808 Set the name of the @value{GDBN} command history file to @var{fname}.
15809 This is the file where @value{GDBN} reads an initial command history
15810 list, and where it writes the command history from this session when it
15811 exits. You can access this list through history expansion or through
15812 the history command editing characters listed below. This file defaults
15813 to the value of the environment variable @code{GDBHISTFILE}, or to
15814 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15817 @cindex save command history
15818 @kindex set history save
15819 @item set history save
15820 @itemx set history save on
15821 Record command history in a file, whose name may be specified with the
15822 @code{set history filename} command. By default, this option is disabled.
15824 @item set history save off
15825 Stop recording command history in a file.
15827 @cindex history size
15828 @kindex set history size
15829 @cindex @env{HISTSIZE}, environment variable
15830 @item set history size @var{size}
15831 Set the number of commands which @value{GDBN} keeps in its history list.
15832 This defaults to the value of the environment variable
15833 @code{HISTSIZE}, or to 256 if this variable is not set.
15836 History expansion assigns special meaning to the character @kbd{!}.
15837 @xref{Event Designators}, for more details.
15839 @cindex history expansion, turn on/off
15840 Since @kbd{!} is also the logical not operator in C, history expansion
15841 is off by default. If you decide to enable history expansion with the
15842 @code{set history expansion on} command, you may sometimes need to
15843 follow @kbd{!} (when it is used as logical not, in an expression) with
15844 a space or a tab to prevent it from being expanded. The readline
15845 history facilities do not attempt substitution on the strings
15846 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15848 The commands to control history expansion are:
15851 @item set history expansion on
15852 @itemx set history expansion
15853 @kindex set history expansion
15854 Enable history expansion. History expansion is off by default.
15856 @item set history expansion off
15857 Disable history expansion.
15860 @kindex show history
15862 @itemx show history filename
15863 @itemx show history save
15864 @itemx show history size
15865 @itemx show history expansion
15866 These commands display the state of the @value{GDBN} history parameters.
15867 @code{show history} by itself displays all four states.
15872 @kindex show commands
15873 @cindex show last commands
15874 @cindex display command history
15875 @item show commands
15876 Display the last ten commands in the command history.
15878 @item show commands @var{n}
15879 Print ten commands centered on command number @var{n}.
15881 @item show commands +
15882 Print ten commands just after the commands last printed.
15886 @section Screen Size
15887 @cindex size of screen
15888 @cindex pauses in output
15890 Certain commands to @value{GDBN} may produce large amounts of
15891 information output to the screen. To help you read all of it,
15892 @value{GDBN} pauses and asks you for input at the end of each page of
15893 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15894 to discard the remaining output. Also, the screen width setting
15895 determines when to wrap lines of output. Depending on what is being
15896 printed, @value{GDBN} tries to break the line at a readable place,
15897 rather than simply letting it overflow onto the following line.
15899 Normally @value{GDBN} knows the size of the screen from the terminal
15900 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15901 together with the value of the @code{TERM} environment variable and the
15902 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15903 you can override it with the @code{set height} and @code{set
15910 @kindex show height
15911 @item set height @var{lpp}
15913 @itemx set width @var{cpl}
15915 These @code{set} commands specify a screen height of @var{lpp} lines and
15916 a screen width of @var{cpl} characters. The associated @code{show}
15917 commands display the current settings.
15919 If you specify a height of zero lines, @value{GDBN} does not pause during
15920 output no matter how long the output is. This is useful if output is to a
15921 file or to an editor buffer.
15923 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15924 from wrapping its output.
15926 @item set pagination on
15927 @itemx set pagination off
15928 @kindex set pagination
15929 Turn the output pagination on or off; the default is on. Turning
15930 pagination off is the alternative to @code{set height 0}.
15932 @item show pagination
15933 @kindex show pagination
15934 Show the current pagination mode.
15939 @cindex number representation
15940 @cindex entering numbers
15942 You can always enter numbers in octal, decimal, or hexadecimal in
15943 @value{GDBN} by the usual conventions: octal numbers begin with
15944 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15945 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15946 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15947 10; likewise, the default display for numbers---when no particular
15948 format is specified---is base 10. You can change the default base for
15949 both input and output with the commands described below.
15952 @kindex set input-radix
15953 @item set input-radix @var{base}
15954 Set the default base for numeric input. Supported choices
15955 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15956 specified either unambiguously or using the current input radix; for
15960 set input-radix 012
15961 set input-radix 10.
15962 set input-radix 0xa
15966 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15967 leaves the input radix unchanged, no matter what it was, since
15968 @samp{10}, being without any leading or trailing signs of its base, is
15969 interpreted in the current radix. Thus, if the current radix is 16,
15970 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15973 @kindex set output-radix
15974 @item set output-radix @var{base}
15975 Set the default base for numeric display. Supported choices
15976 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15977 specified either unambiguously or using the current input radix.
15979 @kindex show input-radix
15980 @item show input-radix
15981 Display the current default base for numeric input.
15983 @kindex show output-radix
15984 @item show output-radix
15985 Display the current default base for numeric display.
15987 @item set radix @r{[}@var{base}@r{]}
15991 These commands set and show the default base for both input and output
15992 of numbers. @code{set radix} sets the radix of input and output to
15993 the same base; without an argument, it resets the radix back to its
15994 default value of 10.
15999 @section Configuring the Current ABI
16001 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
16002 application automatically. However, sometimes you need to override its
16003 conclusions. Use these commands to manage @value{GDBN}'s view of the
16010 One @value{GDBN} configuration can debug binaries for multiple operating
16011 system targets, either via remote debugging or native emulation.
16012 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
16013 but you can override its conclusion using the @code{set osabi} command.
16014 One example where this is useful is in debugging of binaries which use
16015 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16016 not have the same identifying marks that the standard C library for your
16021 Show the OS ABI currently in use.
16024 With no argument, show the list of registered available OS ABI's.
16026 @item set osabi @var{abi}
16027 Set the current OS ABI to @var{abi}.
16030 @cindex float promotion
16032 Generally, the way that an argument of type @code{float} is passed to a
16033 function depends on whether the function is prototyped. For a prototyped
16034 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16035 according to the architecture's convention for @code{float}. For unprototyped
16036 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16037 @code{double} and then passed.
16039 Unfortunately, some forms of debug information do not reliably indicate whether
16040 a function is prototyped. If @value{GDBN} calls a function that is not marked
16041 as prototyped, it consults @kbd{set coerce-float-to-double}.
16044 @kindex set coerce-float-to-double
16045 @item set coerce-float-to-double
16046 @itemx set coerce-float-to-double on
16047 Arguments of type @code{float} will be promoted to @code{double} when passed
16048 to an unprototyped function. This is the default setting.
16050 @item set coerce-float-to-double off
16051 Arguments of type @code{float} will be passed directly to unprototyped
16054 @kindex show coerce-float-to-double
16055 @item show coerce-float-to-double
16056 Show the current setting of promoting @code{float} to @code{double}.
16060 @kindex show cp-abi
16061 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16062 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16063 used to build your application. @value{GDBN} only fully supports
16064 programs with a single C@t{++} ABI; if your program contains code using
16065 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16066 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16067 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16068 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16069 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16070 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16075 Show the C@t{++} ABI currently in use.
16078 With no argument, show the list of supported C@t{++} ABI's.
16080 @item set cp-abi @var{abi}
16081 @itemx set cp-abi auto
16082 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16085 @node Messages/Warnings
16086 @section Optional Warnings and Messages
16088 @cindex verbose operation
16089 @cindex optional warnings
16090 By default, @value{GDBN} is silent about its inner workings. If you are
16091 running on a slow machine, you may want to use the @code{set verbose}
16092 command. This makes @value{GDBN} tell you when it does a lengthy
16093 internal operation, so you will not think it has crashed.
16095 Currently, the messages controlled by @code{set verbose} are those
16096 which announce that the symbol table for a source file is being read;
16097 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16100 @kindex set verbose
16101 @item set verbose on
16102 Enables @value{GDBN} output of certain informational messages.
16104 @item set verbose off
16105 Disables @value{GDBN} output of certain informational messages.
16107 @kindex show verbose
16109 Displays whether @code{set verbose} is on or off.
16112 By default, if @value{GDBN} encounters bugs in the symbol table of an
16113 object file, it is silent; but if you are debugging a compiler, you may
16114 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16119 @kindex set complaints
16120 @item set complaints @var{limit}
16121 Permits @value{GDBN} to output @var{limit} complaints about each type of
16122 unusual symbols before becoming silent about the problem. Set
16123 @var{limit} to zero to suppress all complaints; set it to a large number
16124 to prevent complaints from being suppressed.
16126 @kindex show complaints
16127 @item show complaints
16128 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16132 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16133 lot of stupid questions to confirm certain commands. For example, if
16134 you try to run a program which is already running:
16138 The program being debugged has been started already.
16139 Start it from the beginning? (y or n)
16142 If you are willing to unflinchingly face the consequences of your own
16143 commands, you can disable this ``feature'':
16147 @kindex set confirm
16149 @cindex confirmation
16150 @cindex stupid questions
16151 @item set confirm off
16152 Disables confirmation requests.
16154 @item set confirm on
16155 Enables confirmation requests (the default).
16157 @kindex show confirm
16159 Displays state of confirmation requests.
16163 @cindex command tracing
16164 If you need to debug user-defined commands or sourced files you may find it
16165 useful to enable @dfn{command tracing}. In this mode each command will be
16166 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16167 quantity denoting the call depth of each command.
16170 @kindex set trace-commands
16171 @cindex command scripts, debugging
16172 @item set trace-commands on
16173 Enable command tracing.
16174 @item set trace-commands off
16175 Disable command tracing.
16176 @item show trace-commands
16177 Display the current state of command tracing.
16180 @node Debugging Output
16181 @section Optional Messages about Internal Happenings
16182 @cindex optional debugging messages
16184 @value{GDBN} has commands that enable optional debugging messages from
16185 various @value{GDBN} subsystems; normally these commands are of
16186 interest to @value{GDBN} maintainers, or when reporting a bug. This
16187 section documents those commands.
16190 @kindex set exec-done-display
16191 @item set exec-done-display
16192 Turns on or off the notification of asynchronous commands'
16193 completion. When on, @value{GDBN} will print a message when an
16194 asynchronous command finishes its execution. The default is off.
16195 @kindex show exec-done-display
16196 @item show exec-done-display
16197 Displays the current setting of asynchronous command completion
16200 @cindex gdbarch debugging info
16201 @cindex architecture debugging info
16202 @item set debug arch
16203 Turns on or off display of gdbarch debugging info. The default is off
16205 @item show debug arch
16206 Displays the current state of displaying gdbarch debugging info.
16207 @item set debug aix-thread
16208 @cindex AIX threads
16209 Display debugging messages about inner workings of the AIX thread
16211 @item show debug aix-thread
16212 Show the current state of AIX thread debugging info display.
16213 @item set debug event
16214 @cindex event debugging info
16215 Turns on or off display of @value{GDBN} event debugging info. The
16217 @item show debug event
16218 Displays the current state of displaying @value{GDBN} event debugging
16220 @item set debug expression
16221 @cindex expression debugging info
16222 Turns on or off display of debugging info about @value{GDBN}
16223 expression parsing. The default is off.
16224 @item show debug expression
16225 Displays the current state of displaying debugging info about
16226 @value{GDBN} expression parsing.
16227 @item set debug frame
16228 @cindex frame debugging info
16229 Turns on or off display of @value{GDBN} frame debugging info. The
16231 @item show debug frame
16232 Displays the current state of displaying @value{GDBN} frame debugging
16234 @item set debug infrun
16235 @cindex inferior debugging info
16236 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16237 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16238 for implementing operations such as single-stepping the inferior.
16239 @item show debug infrun
16240 Displays the current state of @value{GDBN} inferior debugging.
16241 @item set debug lin-lwp
16242 @cindex @sc{gnu}/Linux LWP debug messages
16243 @cindex Linux lightweight processes
16244 Turns on or off debugging messages from the Linux LWP debug support.
16245 @item show debug lin-lwp
16246 Show the current state of Linux LWP debugging messages.
16247 @item set debug observer
16248 @cindex observer debugging info
16249 Turns on or off display of @value{GDBN} observer debugging. This
16250 includes info such as the notification of observable events.
16251 @item show debug observer
16252 Displays the current state of observer debugging.
16253 @item set debug overload
16254 @cindex C@t{++} overload debugging info
16255 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16256 info. This includes info such as ranking of functions, etc. The default
16258 @item show debug overload
16259 Displays the current state of displaying @value{GDBN} C@t{++} overload
16261 @cindex packets, reporting on stdout
16262 @cindex serial connections, debugging
16263 @cindex debug remote protocol
16264 @cindex remote protocol debugging
16265 @cindex display remote packets
16266 @item set debug remote
16267 Turns on or off display of reports on all packets sent back and forth across
16268 the serial line to the remote machine. The info is printed on the
16269 @value{GDBN} standard output stream. The default is off.
16270 @item show debug remote
16271 Displays the state of display of remote packets.
16272 @item set debug serial
16273 Turns on or off display of @value{GDBN} serial debugging info. The
16275 @item show debug serial
16276 Displays the current state of displaying @value{GDBN} serial debugging
16278 @item set debug solib-frv
16279 @cindex FR-V shared-library debugging
16280 Turns on or off debugging messages for FR-V shared-library code.
16281 @item show debug solib-frv
16282 Display the current state of FR-V shared-library code debugging
16284 @item set debug target
16285 @cindex target debugging info
16286 Turns on or off display of @value{GDBN} target debugging info. This info
16287 includes what is going on at the target level of GDB, as it happens. The
16288 default is 0. Set it to 1 to track events, and to 2 to also track the
16289 value of large memory transfers. Changes to this flag do not take effect
16290 until the next time you connect to a target or use the @code{run} command.
16291 @item show debug target
16292 Displays the current state of displaying @value{GDBN} target debugging
16294 @item set debugvarobj
16295 @cindex variable object debugging info
16296 Turns on or off display of @value{GDBN} variable object debugging
16297 info. The default is off.
16298 @item show debugvarobj
16299 Displays the current state of displaying @value{GDBN} variable object
16301 @item set debug xml
16302 @cindex XML parser debugging
16303 Turns on or off debugging messages for built-in XML parsers.
16304 @item show debug xml
16305 Displays the current state of XML debugging messages.
16309 @chapter Canned Sequences of Commands
16311 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16312 Command Lists}), @value{GDBN} provides two ways to store sequences of
16313 commands for execution as a unit: user-defined commands and command
16317 * Define:: How to define your own commands
16318 * Hooks:: Hooks for user-defined commands
16319 * Command Files:: How to write scripts of commands to be stored in a file
16320 * Output:: Commands for controlled output
16324 @section User-defined Commands
16326 @cindex user-defined command
16327 @cindex arguments, to user-defined commands
16328 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16329 which you assign a new name as a command. This is done with the
16330 @code{define} command. User commands may accept up to 10 arguments
16331 separated by whitespace. Arguments are accessed within the user command
16332 via @code{$arg0@dots{}$arg9}. A trivial example:
16336 print $arg0 + $arg1 + $arg2
16341 To execute the command use:
16348 This defines the command @code{adder}, which prints the sum of
16349 its three arguments. Note the arguments are text substitutions, so they may
16350 reference variables, use complex expressions, or even perform inferior
16353 @cindex argument count in user-defined commands
16354 @cindex how many arguments (user-defined commands)
16355 In addition, @code{$argc} may be used to find out how many arguments have
16356 been passed. This expands to a number in the range 0@dots{}10.
16361 print $arg0 + $arg1
16364 print $arg0 + $arg1 + $arg2
16372 @item define @var{commandname}
16373 Define a command named @var{commandname}. If there is already a command
16374 by that name, you are asked to confirm that you want to redefine it.
16376 The definition of the command is made up of other @value{GDBN} command lines,
16377 which are given following the @code{define} command. The end of these
16378 commands is marked by a line containing @code{end}.
16381 @kindex end@r{ (user-defined commands)}
16382 @item document @var{commandname}
16383 Document the user-defined command @var{commandname}, so that it can be
16384 accessed by @code{help}. The command @var{commandname} must already be
16385 defined. This command reads lines of documentation just as @code{define}
16386 reads the lines of the command definition, ending with @code{end}.
16387 After the @code{document} command is finished, @code{help} on command
16388 @var{commandname} displays the documentation you have written.
16390 You may use the @code{document} command again to change the
16391 documentation of a command. Redefining the command with @code{define}
16392 does not change the documentation.
16394 @kindex dont-repeat
16395 @cindex don't repeat command
16397 Used inside a user-defined command, this tells @value{GDBN} that this
16398 command should not be repeated when the user hits @key{RET}
16399 (@pxref{Command Syntax, repeat last command}).
16401 @kindex help user-defined
16402 @item help user-defined
16403 List all user-defined commands, with the first line of the documentation
16408 @itemx show user @var{commandname}
16409 Display the @value{GDBN} commands used to define @var{commandname} (but
16410 not its documentation). If no @var{commandname} is given, display the
16411 definitions for all user-defined commands.
16413 @cindex infinite recursion in user-defined commands
16414 @kindex show max-user-call-depth
16415 @kindex set max-user-call-depth
16416 @item show max-user-call-depth
16417 @itemx set max-user-call-depth
16418 The value of @code{max-user-call-depth} controls how many recursion
16419 levels are allowed in user-defined commands before @value{GDBN} suspects an
16420 infinite recursion and aborts the command.
16423 In addition to the above commands, user-defined commands frequently
16424 use control flow commands, described in @ref{Command Files}.
16426 When user-defined commands are executed, the
16427 commands of the definition are not printed. An error in any command
16428 stops execution of the user-defined command.
16430 If used interactively, commands that would ask for confirmation proceed
16431 without asking when used inside a user-defined command. Many @value{GDBN}
16432 commands that normally print messages to say what they are doing omit the
16433 messages when used in a user-defined command.
16436 @section User-defined Command Hooks
16437 @cindex command hooks
16438 @cindex hooks, for commands
16439 @cindex hooks, pre-command
16442 You may define @dfn{hooks}, which are a special kind of user-defined
16443 command. Whenever you run the command @samp{foo}, if the user-defined
16444 command @samp{hook-foo} exists, it is executed (with no arguments)
16445 before that command.
16447 @cindex hooks, post-command
16449 A hook may also be defined which is run after the command you executed.
16450 Whenever you run the command @samp{foo}, if the user-defined command
16451 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16452 that command. Post-execution hooks may exist simultaneously with
16453 pre-execution hooks, for the same command.
16455 It is valid for a hook to call the command which it hooks. If this
16456 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16458 @c It would be nice if hookpost could be passed a parameter indicating
16459 @c if the command it hooks executed properly or not. FIXME!
16461 @kindex stop@r{, a pseudo-command}
16462 In addition, a pseudo-command, @samp{stop} exists. Defining
16463 (@samp{hook-stop}) makes the associated commands execute every time
16464 execution stops in your program: before breakpoint commands are run,
16465 displays are printed, or the stack frame is printed.
16467 For example, to ignore @code{SIGALRM} signals while
16468 single-stepping, but treat them normally during normal execution,
16473 handle SIGALRM nopass
16477 handle SIGALRM pass
16480 define hook-continue
16481 handle SIGALRM pass
16485 As a further example, to hook at the beginning and end of the @code{echo}
16486 command, and to add extra text to the beginning and end of the message,
16494 define hookpost-echo
16498 (@value{GDBP}) echo Hello World
16499 <<<---Hello World--->>>
16504 You can define a hook for any single-word command in @value{GDBN}, but
16505 not for command aliases; you should define a hook for the basic command
16506 name, e.g.@: @code{backtrace} rather than @code{bt}.
16507 @c FIXME! So how does Joe User discover whether a command is an alias
16509 If an error occurs during the execution of your hook, execution of
16510 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16511 (before the command that you actually typed had a chance to run).
16513 If you try to define a hook which does not match any known command, you
16514 get a warning from the @code{define} command.
16516 @node Command Files
16517 @section Command Files
16519 @cindex command files
16520 @cindex scripting commands
16521 A command file for @value{GDBN} is a text file made of lines that are
16522 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16523 also be included. An empty line in a command file does nothing; it
16524 does not mean to repeat the last command, as it would from the
16527 You can request the execution of a command file with the @code{source}
16532 @cindex execute commands from a file
16533 @item source [@code{-v}] @var{filename}
16534 Execute the command file @var{filename}.
16537 The lines in a command file are generally executed sequentially,
16538 unless the order of execution is changed by one of the
16539 @emph{flow-control commands} described below. The commands are not
16540 printed as they are executed. An error in any command terminates
16541 execution of the command file and control is returned to the console.
16543 @value{GDBN} searches for @var{filename} in the current directory and then
16544 on the search path (specified with the @samp{directory} command).
16546 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16547 each command as it is executed. The option must be given before
16548 @var{filename}, and is interpreted as part of the filename anywhere else.
16550 Commands that would ask for confirmation if used interactively proceed
16551 without asking when used in a command file. Many @value{GDBN} commands that
16552 normally print messages to say what they are doing omit the messages
16553 when called from command files.
16555 @value{GDBN} also accepts command input from standard input. In this
16556 mode, normal output goes to standard output and error output goes to
16557 standard error. Errors in a command file supplied on standard input do
16558 not terminate execution of the command file---execution continues with
16562 gdb < cmds > log 2>&1
16565 (The syntax above will vary depending on the shell used.) This example
16566 will execute commands from the file @file{cmds}. All output and errors
16567 would be directed to @file{log}.
16569 Since commands stored on command files tend to be more general than
16570 commands typed interactively, they frequently need to deal with
16571 complicated situations, such as different or unexpected values of
16572 variables and symbols, changes in how the program being debugged is
16573 built, etc. @value{GDBN} provides a set of flow-control commands to
16574 deal with these complexities. Using these commands, you can write
16575 complex scripts that loop over data structures, execute commands
16576 conditionally, etc.
16583 This command allows to include in your script conditionally executed
16584 commands. The @code{if} command takes a single argument, which is an
16585 expression to evaluate. It is followed by a series of commands that
16586 are executed only if the expression is true (its value is nonzero).
16587 There can then optionally be an @code{else} line, followed by a series
16588 of commands that are only executed if the expression was false. The
16589 end of the list is marked by a line containing @code{end}.
16593 This command allows to write loops. Its syntax is similar to
16594 @code{if}: the command takes a single argument, which is an expression
16595 to evaluate, and must be followed by the commands to execute, one per
16596 line, terminated by an @code{end}. These commands are called the
16597 @dfn{body} of the loop. The commands in the body of @code{while} are
16598 executed repeatedly as long as the expression evaluates to true.
16602 This command exits the @code{while} loop in whose body it is included.
16603 Execution of the script continues after that @code{while}s @code{end}
16606 @kindex loop_continue
16607 @item loop_continue
16608 This command skips the execution of the rest of the body of commands
16609 in the @code{while} loop in whose body it is included. Execution
16610 branches to the beginning of the @code{while} loop, where it evaluates
16611 the controlling expression.
16613 @kindex end@r{ (if/else/while commands)}
16615 Terminate the block of commands that are the body of @code{if},
16616 @code{else}, or @code{while} flow-control commands.
16621 @section Commands for Controlled Output
16623 During the execution of a command file or a user-defined command, normal
16624 @value{GDBN} output is suppressed; the only output that appears is what is
16625 explicitly printed by the commands in the definition. This section
16626 describes three commands useful for generating exactly the output you
16631 @item echo @var{text}
16632 @c I do not consider backslash-space a standard C escape sequence
16633 @c because it is not in ANSI.
16634 Print @var{text}. Nonprinting characters can be included in
16635 @var{text} using C escape sequences, such as @samp{\n} to print a
16636 newline. @strong{No newline is printed unless you specify one.}
16637 In addition to the standard C escape sequences, a backslash followed
16638 by a space stands for a space. This is useful for displaying a
16639 string with spaces at the beginning or the end, since leading and
16640 trailing spaces are otherwise trimmed from all arguments.
16641 To print @samp{@w{ }and foo =@w{ }}, use the command
16642 @samp{echo \@w{ }and foo = \@w{ }}.
16644 A backslash at the end of @var{text} can be used, as in C, to continue
16645 the command onto subsequent lines. For example,
16648 echo This is some text\n\
16649 which is continued\n\
16650 onto several lines.\n
16653 produces the same output as
16656 echo This is some text\n
16657 echo which is continued\n
16658 echo onto several lines.\n
16662 @item output @var{expression}
16663 Print the value of @var{expression} and nothing but that value: no
16664 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16665 value history either. @xref{Expressions, ,Expressions}, for more information
16668 @item output/@var{fmt} @var{expression}
16669 Print the value of @var{expression} in format @var{fmt}. You can use
16670 the same formats as for @code{print}. @xref{Output Formats,,Output
16671 Formats}, for more information.
16674 @item printf @var{template}, @var{expressions}@dots{}
16675 Print the values of one or more @var{expressions} under the control of
16676 the string @var{template}. To print several values, make
16677 @var{expressions} be a comma-separated list of individual expressions,
16678 which may be either numbers or pointers. Their values are printed as
16679 specified by @var{template}, exactly as a C program would do by
16680 executing the code below:
16683 printf (@var{template}, @var{expressions}@dots{});
16686 As in @code{C} @code{printf}, ordinary characters in @var{template}
16687 are printed verbatim, while @dfn{conversion specification} introduced
16688 by the @samp{%} character cause subsequent @var{expressions} to be
16689 evaluated, their values converted and formatted according to type and
16690 style information encoded in the conversion specifications, and then
16693 For example, you can print two values in hex like this:
16696 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16699 @code{printf} supports all the standard @code{C} conversion
16700 specifications, including the flags and modifiers between the @samp{%}
16701 character and the conversion letter, with the following exceptions:
16705 The argument-ordering modifiers, such as @samp{2$}, are not supported.
16708 The modifier @samp{*} is not supported for specifying precision or
16712 The @samp{'} flag (for separation of digits into groups according to
16713 @code{LC_NUMERIC'}) is not supported.
16716 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
16720 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
16723 The conversion letters @samp{a} and @samp{A} are not supported.
16727 Note that the @samp{ll} type modifier is supported only if the
16728 underlying @code{C} implementation used to build @value{GDBN} supports
16729 the @code{long long int} type, and the @samp{L} type modifier is
16730 supported only if @code{long double} type is available.
16732 As in @code{C}, @code{printf} supports simple backslash-escape
16733 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
16734 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
16735 single character. Octal and hexadecimal escape sequences are not
16738 Additionally, @code{printf} supports conversion specifications for DFP
16739 (@dfn{Decimal Floating Point}) types using the following length modifiers
16740 together with a floating point specifier.
16745 @samp{H} for printing @code{Decimal32} types.
16748 @samp{D} for printing @code{Decimal64} types.
16751 @samp{DD} for printing @code{Decimal128} types.
16754 If the underlying @code{C} implementation used to build @value{GDBN} has
16755 support for the three length modifiers for DFP types, other modifiers
16756 such as width and precision will also be available for @value{GDBN} to use.
16758 In case there is no such @code{C} support, no additional modifiers will be
16759 available and the value will be printed in the standard way.
16761 Here's an example of printing DFP types using the above conversion letters:
16763 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
16769 @chapter Command Interpreters
16770 @cindex command interpreters
16772 @value{GDBN} supports multiple command interpreters, and some command
16773 infrastructure to allow users or user interface writers to switch
16774 between interpreters or run commands in other interpreters.
16776 @value{GDBN} currently supports two command interpreters, the console
16777 interpreter (sometimes called the command-line interpreter or @sc{cli})
16778 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16779 describes both of these interfaces in great detail.
16781 By default, @value{GDBN} will start with the console interpreter.
16782 However, the user may choose to start @value{GDBN} with another
16783 interpreter by specifying the @option{-i} or @option{--interpreter}
16784 startup options. Defined interpreters include:
16788 @cindex console interpreter
16789 The traditional console or command-line interpreter. This is the most often
16790 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16791 @value{GDBN} will use this interpreter.
16794 @cindex mi interpreter
16795 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16796 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16797 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16801 @cindex mi2 interpreter
16802 The current @sc{gdb/mi} interface.
16805 @cindex mi1 interpreter
16806 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16810 @cindex invoke another interpreter
16811 The interpreter being used by @value{GDBN} may not be dynamically
16812 switched at runtime. Although possible, this could lead to a very
16813 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16814 enters the command "interpreter-set console" in a console view,
16815 @value{GDBN} would switch to using the console interpreter, rendering
16816 the IDE inoperable!
16818 @kindex interpreter-exec
16819 Although you may only choose a single interpreter at startup, you may execute
16820 commands in any interpreter from the current interpreter using the appropriate
16821 command. If you are running the console interpreter, simply use the
16822 @code{interpreter-exec} command:
16825 interpreter-exec mi "-data-list-register-names"
16828 @sc{gdb/mi} has a similar command, although it is only available in versions of
16829 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16832 @chapter @value{GDBN} Text User Interface
16834 @cindex Text User Interface
16837 * TUI Overview:: TUI overview
16838 * TUI Keys:: TUI key bindings
16839 * TUI Single Key Mode:: TUI single key mode
16840 * TUI Commands:: TUI-specific commands
16841 * TUI Configuration:: TUI configuration variables
16844 The @value{GDBN} Text User Interface (TUI) is a terminal
16845 interface which uses the @code{curses} library to show the source
16846 file, the assembly output, the program registers and @value{GDBN}
16847 commands in separate text windows. The TUI mode is supported only
16848 on platforms where a suitable version of the @code{curses} library
16851 @pindex @value{GDBTUI}
16852 The TUI mode is enabled by default when you invoke @value{GDBN} as
16853 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
16854 You can also switch in and out of TUI mode while @value{GDBN} runs by
16855 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
16856 @xref{TUI Keys, ,TUI Key Bindings}.
16859 @section TUI Overview
16861 In TUI mode, @value{GDBN} can display several text windows:
16865 This window is the @value{GDBN} command window with the @value{GDBN}
16866 prompt and the @value{GDBN} output. The @value{GDBN} input is still
16867 managed using readline.
16870 The source window shows the source file of the program. The current
16871 line and active breakpoints are displayed in this window.
16874 The assembly window shows the disassembly output of the program.
16877 This window shows the processor registers. Registers are highlighted
16878 when their values change.
16881 The source and assembly windows show the current program position
16882 by highlighting the current line and marking it with a @samp{>} marker.
16883 Breakpoints are indicated with two markers. The first marker
16884 indicates the breakpoint type:
16888 Breakpoint which was hit at least once.
16891 Breakpoint which was never hit.
16894 Hardware breakpoint which was hit at least once.
16897 Hardware breakpoint which was never hit.
16900 The second marker indicates whether the breakpoint is enabled or not:
16904 Breakpoint is enabled.
16907 Breakpoint is disabled.
16910 The source, assembly and register windows are updated when the current
16911 thread changes, when the frame changes, or when the program counter
16914 These windows are not all visible at the same time. The command
16915 window is always visible. The others can be arranged in several
16926 source and assembly,
16929 source and registers, or
16932 assembly and registers.
16935 A status line above the command window shows the following information:
16939 Indicates the current @value{GDBN} target.
16940 (@pxref{Targets, ,Specifying a Debugging Target}).
16943 Gives the current process or thread number.
16944 When no process is being debugged, this field is set to @code{No process}.
16947 Gives the current function name for the selected frame.
16948 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16949 When there is no symbol corresponding to the current program counter,
16950 the string @code{??} is displayed.
16953 Indicates the current line number for the selected frame.
16954 When the current line number is not known, the string @code{??} is displayed.
16957 Indicates the current program counter address.
16961 @section TUI Key Bindings
16962 @cindex TUI key bindings
16964 The TUI installs several key bindings in the readline keymaps
16965 (@pxref{Command Line Editing}). The following key bindings
16966 are installed for both TUI mode and the @value{GDBN} standard mode.
16975 Enter or leave the TUI mode. When leaving the TUI mode,
16976 the curses window management stops and @value{GDBN} operates using
16977 its standard mode, writing on the terminal directly. When reentering
16978 the TUI mode, control is given back to the curses windows.
16979 The screen is then refreshed.
16983 Use a TUI layout with only one window. The layout will
16984 either be @samp{source} or @samp{assembly}. When the TUI mode
16985 is not active, it will switch to the TUI mode.
16987 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16991 Use a TUI layout with at least two windows. When the current
16992 layout already has two windows, the next layout with two windows is used.
16993 When a new layout is chosen, one window will always be common to the
16994 previous layout and the new one.
16996 Think of it as the Emacs @kbd{C-x 2} binding.
17000 Change the active window. The TUI associates several key bindings
17001 (like scrolling and arrow keys) with the active window. This command
17002 gives the focus to the next TUI window.
17004 Think of it as the Emacs @kbd{C-x o} binding.
17008 Switch in and out of the TUI SingleKey mode that binds single
17009 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
17012 The following key bindings only work in the TUI mode:
17017 Scroll the active window one page up.
17021 Scroll the active window one page down.
17025 Scroll the active window one line up.
17029 Scroll the active window one line down.
17033 Scroll the active window one column left.
17037 Scroll the active window one column right.
17041 Refresh the screen.
17044 Because the arrow keys scroll the active window in the TUI mode, they
17045 are not available for their normal use by readline unless the command
17046 window has the focus. When another window is active, you must use
17047 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
17048 and @kbd{C-f} to control the command window.
17050 @node TUI Single Key Mode
17051 @section TUI Single Key Mode
17052 @cindex TUI single key mode
17054 The TUI also provides a @dfn{SingleKey} mode, which binds several
17055 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
17056 switch into this mode, where the following key bindings are used:
17059 @kindex c @r{(SingleKey TUI key)}
17063 @kindex d @r{(SingleKey TUI key)}
17067 @kindex f @r{(SingleKey TUI key)}
17071 @kindex n @r{(SingleKey TUI key)}
17075 @kindex q @r{(SingleKey TUI key)}
17077 exit the SingleKey mode.
17079 @kindex r @r{(SingleKey TUI key)}
17083 @kindex s @r{(SingleKey TUI key)}
17087 @kindex u @r{(SingleKey TUI key)}
17091 @kindex v @r{(SingleKey TUI key)}
17095 @kindex w @r{(SingleKey TUI key)}
17100 Other keys temporarily switch to the @value{GDBN} command prompt.
17101 The key that was pressed is inserted in the editing buffer so that
17102 it is possible to type most @value{GDBN} commands without interaction
17103 with the TUI SingleKey mode. Once the command is entered the TUI
17104 SingleKey mode is restored. The only way to permanently leave
17105 this mode is by typing @kbd{q} or @kbd{C-x s}.
17109 @section TUI-specific Commands
17110 @cindex TUI commands
17112 The TUI has specific commands to control the text windows.
17113 These commands are always available, even when @value{GDBN} is not in
17114 the TUI mode. When @value{GDBN} is in the standard mode, most
17115 of these commands will automatically switch to the TUI mode.
17120 List and give the size of all displayed windows.
17124 Display the next layout.
17127 Display the previous layout.
17130 Display the source window only.
17133 Display the assembly window only.
17136 Display the source and assembly window.
17139 Display the register window together with the source or assembly window.
17143 Make the next window active for scrolling.
17146 Make the previous window active for scrolling.
17149 Make the source window active for scrolling.
17152 Make the assembly window active for scrolling.
17155 Make the register window active for scrolling.
17158 Make the command window active for scrolling.
17162 Refresh the screen. This is similar to typing @kbd{C-L}.
17164 @item tui reg float
17166 Show the floating point registers in the register window.
17168 @item tui reg general
17169 Show the general registers in the register window.
17172 Show the next register group. The list of register groups as well as
17173 their order is target specific. The predefined register groups are the
17174 following: @code{general}, @code{float}, @code{system}, @code{vector},
17175 @code{all}, @code{save}, @code{restore}.
17177 @item tui reg system
17178 Show the system registers in the register window.
17182 Update the source window and the current execution point.
17184 @item winheight @var{name} +@var{count}
17185 @itemx winheight @var{name} -@var{count}
17187 Change the height of the window @var{name} by @var{count}
17188 lines. Positive counts increase the height, while negative counts
17191 @item tabset @var{nchars}
17193 Set the width of tab stops to be @var{nchars} characters.
17196 @node TUI Configuration
17197 @section TUI Configuration Variables
17198 @cindex TUI configuration variables
17200 Several configuration variables control the appearance of TUI windows.
17203 @item set tui border-kind @var{kind}
17204 @kindex set tui border-kind
17205 Select the border appearance for the source, assembly and register windows.
17206 The possible values are the following:
17209 Use a space character to draw the border.
17212 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
17215 Use the Alternate Character Set to draw the border. The border is
17216 drawn using character line graphics if the terminal supports them.
17219 @item set tui border-mode @var{mode}
17220 @kindex set tui border-mode
17221 @itemx set tui active-border-mode @var{mode}
17222 @kindex set tui active-border-mode
17223 Select the display attributes for the borders of the inactive windows
17224 or the active window. The @var{mode} can be one of the following:
17227 Use normal attributes to display the border.
17233 Use reverse video mode.
17236 Use half bright mode.
17238 @item half-standout
17239 Use half bright and standout mode.
17242 Use extra bright or bold mode.
17244 @item bold-standout
17245 Use extra bright or bold and standout mode.
17250 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17253 @cindex @sc{gnu} Emacs
17254 A special interface allows you to use @sc{gnu} Emacs to view (and
17255 edit) the source files for the program you are debugging with
17258 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17259 executable file you want to debug as an argument. This command starts
17260 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17261 created Emacs buffer.
17262 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17264 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17269 All ``terminal'' input and output goes through an Emacs buffer, called
17272 This applies both to @value{GDBN} commands and their output, and to the input
17273 and output done by the program you are debugging.
17275 This is useful because it means that you can copy the text of previous
17276 commands and input them again; you can even use parts of the output
17279 All the facilities of Emacs' Shell mode are available for interacting
17280 with your program. In particular, you can send signals the usual
17281 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17285 @value{GDBN} displays source code through Emacs.
17287 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17288 source file for that frame and puts an arrow (@samp{=>}) at the
17289 left margin of the current line. Emacs uses a separate buffer for
17290 source display, and splits the screen to show both your @value{GDBN} session
17293 Explicit @value{GDBN} @code{list} or search commands still produce output as
17294 usual, but you probably have no reason to use them from Emacs.
17297 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17298 a graphical mode, enabled by default, which provides further buffers
17299 that can control the execution and describe the state of your program.
17300 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17302 If you specify an absolute file name when prompted for the @kbd{M-x
17303 gdb} argument, then Emacs sets your current working directory to where
17304 your program resides. If you only specify the file name, then Emacs
17305 sets your current working directory to to the directory associated
17306 with the previous buffer. In this case, @value{GDBN} may find your
17307 program by searching your environment's @code{PATH} variable, but on
17308 some operating systems it might not find the source. So, although the
17309 @value{GDBN} input and output session proceeds normally, the auxiliary
17310 buffer does not display the current source and line of execution.
17312 The initial working directory of @value{GDBN} is printed on the top
17313 line of the GUD buffer and this serves as a default for the commands
17314 that specify files for @value{GDBN} to operate on. @xref{Files,
17315 ,Commands to Specify Files}.
17317 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17318 need to call @value{GDBN} by a different name (for example, if you
17319 keep several configurations around, with different names) you can
17320 customize the Emacs variable @code{gud-gdb-command-name} to run the
17323 In the GUD buffer, you can use these special Emacs commands in
17324 addition to the standard Shell mode commands:
17328 Describe the features of Emacs' GUD Mode.
17331 Execute to another source line, like the @value{GDBN} @code{step} command; also
17332 update the display window to show the current file and location.
17335 Execute to next source line in this function, skipping all function
17336 calls, like the @value{GDBN} @code{next} command. Then update the display window
17337 to show the current file and location.
17340 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17341 display window accordingly.
17344 Execute until exit from the selected stack frame, like the @value{GDBN}
17345 @code{finish} command.
17348 Continue execution of your program, like the @value{GDBN} @code{continue}
17352 Go up the number of frames indicated by the numeric argument
17353 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17354 like the @value{GDBN} @code{up} command.
17357 Go down the number of frames indicated by the numeric argument, like the
17358 @value{GDBN} @code{down} command.
17361 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17362 tells @value{GDBN} to set a breakpoint on the source line point is on.
17364 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17365 separate frame which shows a backtrace when the GUD buffer is current.
17366 Move point to any frame in the stack and type @key{RET} to make it
17367 become the current frame and display the associated source in the
17368 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17369 selected frame become the current one. In graphical mode, the
17370 speedbar displays watch expressions.
17372 If you accidentally delete the source-display buffer, an easy way to get
17373 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17374 request a frame display; when you run under Emacs, this recreates
17375 the source buffer if necessary to show you the context of the current
17378 The source files displayed in Emacs are in ordinary Emacs buffers
17379 which are visiting the source files in the usual way. You can edit
17380 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17381 communicates with Emacs in terms of line numbers. If you add or
17382 delete lines from the text, the line numbers that @value{GDBN} knows cease
17383 to correspond properly with the code.
17385 A more detailed description of Emacs' interaction with @value{GDBN} is
17386 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17389 @c The following dropped because Epoch is nonstandard. Reactivate
17390 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17392 @kindex Emacs Epoch environment
17396 Version 18 of @sc{gnu} Emacs has a built-in window system
17397 called the @code{epoch}
17398 environment. Users of this environment can use a new command,
17399 @code{inspect} which performs identically to @code{print} except that
17400 each value is printed in its own window.
17405 @chapter The @sc{gdb/mi} Interface
17407 @unnumberedsec Function and Purpose
17409 @cindex @sc{gdb/mi}, its purpose
17410 @sc{gdb/mi} is a line based machine oriented text interface to
17411 @value{GDBN} and is activated by specifying using the
17412 @option{--interpreter} command line option (@pxref{Mode Options}). It
17413 is specifically intended to support the development of systems which
17414 use the debugger as just one small component of a larger system.
17416 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17417 in the form of a reference manual.
17419 Note that @sc{gdb/mi} is still under construction, so some of the
17420 features described below are incomplete and subject to change
17421 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17423 @unnumberedsec Notation and Terminology
17425 @cindex notational conventions, for @sc{gdb/mi}
17426 This chapter uses the following notation:
17430 @code{|} separates two alternatives.
17433 @code{[ @var{something} ]} indicates that @var{something} is optional:
17434 it may or may not be given.
17437 @code{( @var{group} )*} means that @var{group} inside the parentheses
17438 may repeat zero or more times.
17441 @code{( @var{group} )+} means that @var{group} inside the parentheses
17442 may repeat one or more times.
17445 @code{"@var{string}"} means a literal @var{string}.
17449 @heading Dependencies
17453 * GDB/MI Command Syntax::
17454 * GDB/MI Compatibility with CLI::
17455 * GDB/MI Development and Front Ends::
17456 * GDB/MI Output Records::
17457 * GDB/MI Simple Examples::
17458 * GDB/MI Command Description Format::
17459 * GDB/MI Breakpoint Commands::
17460 * GDB/MI Program Context::
17461 * GDB/MI Thread Commands::
17462 * GDB/MI Program Execution::
17463 * GDB/MI Stack Manipulation::
17464 * GDB/MI Variable Objects::
17465 * GDB/MI Data Manipulation::
17466 * GDB/MI Tracepoint Commands::
17467 * GDB/MI Symbol Query::
17468 * GDB/MI File Commands::
17470 * GDB/MI Kod Commands::
17471 * GDB/MI Memory Overlay Commands::
17472 * GDB/MI Signal Handling Commands::
17474 * GDB/MI Target Manipulation::
17475 * GDB/MI File Transfer Commands::
17476 * GDB/MI Miscellaneous Commands::
17479 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17480 @node GDB/MI Command Syntax
17481 @section @sc{gdb/mi} Command Syntax
17484 * GDB/MI Input Syntax::
17485 * GDB/MI Output Syntax::
17488 @node GDB/MI Input Syntax
17489 @subsection @sc{gdb/mi} Input Syntax
17491 @cindex input syntax for @sc{gdb/mi}
17492 @cindex @sc{gdb/mi}, input syntax
17494 @item @var{command} @expansion{}
17495 @code{@var{cli-command} | @var{mi-command}}
17497 @item @var{cli-command} @expansion{}
17498 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17499 @var{cli-command} is any existing @value{GDBN} CLI command.
17501 @item @var{mi-command} @expansion{}
17502 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17503 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17505 @item @var{token} @expansion{}
17506 "any sequence of digits"
17508 @item @var{option} @expansion{}
17509 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17511 @item @var{parameter} @expansion{}
17512 @code{@var{non-blank-sequence} | @var{c-string}}
17514 @item @var{operation} @expansion{}
17515 @emph{any of the operations described in this chapter}
17517 @item @var{non-blank-sequence} @expansion{}
17518 @emph{anything, provided it doesn't contain special characters such as
17519 "-", @var{nl}, """ and of course " "}
17521 @item @var{c-string} @expansion{}
17522 @code{""" @var{seven-bit-iso-c-string-content} """}
17524 @item @var{nl} @expansion{}
17533 The CLI commands are still handled by the @sc{mi} interpreter; their
17534 output is described below.
17537 The @code{@var{token}}, when present, is passed back when the command
17541 Some @sc{mi} commands accept optional arguments as part of the parameter
17542 list. Each option is identified by a leading @samp{-} (dash) and may be
17543 followed by an optional argument parameter. Options occur first in the
17544 parameter list and can be delimited from normal parameters using
17545 @samp{--} (this is useful when some parameters begin with a dash).
17552 We want easy access to the existing CLI syntax (for debugging).
17555 We want it to be easy to spot a @sc{mi} operation.
17558 @node GDB/MI Output Syntax
17559 @subsection @sc{gdb/mi} Output Syntax
17561 @cindex output syntax of @sc{gdb/mi}
17562 @cindex @sc{gdb/mi}, output syntax
17563 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17564 followed, optionally, by a single result record. This result record
17565 is for the most recent command. The sequence of output records is
17566 terminated by @samp{(gdb)}.
17568 If an input command was prefixed with a @code{@var{token}} then the
17569 corresponding output for that command will also be prefixed by that same
17573 @item @var{output} @expansion{}
17574 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17576 @item @var{result-record} @expansion{}
17577 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17579 @item @var{out-of-band-record} @expansion{}
17580 @code{@var{async-record} | @var{stream-record}}
17582 @item @var{async-record} @expansion{}
17583 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17585 @item @var{exec-async-output} @expansion{}
17586 @code{[ @var{token} ] "*" @var{async-output}}
17588 @item @var{status-async-output} @expansion{}
17589 @code{[ @var{token} ] "+" @var{async-output}}
17591 @item @var{notify-async-output} @expansion{}
17592 @code{[ @var{token} ] "=" @var{async-output}}
17594 @item @var{async-output} @expansion{}
17595 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17597 @item @var{result-class} @expansion{}
17598 @code{"done" | "running" | "connected" | "error" | "exit"}
17600 @item @var{async-class} @expansion{}
17601 @code{"stopped" | @var{others}} (where @var{others} will be added
17602 depending on the needs---this is still in development).
17604 @item @var{result} @expansion{}
17605 @code{ @var{variable} "=" @var{value}}
17607 @item @var{variable} @expansion{}
17608 @code{ @var{string} }
17610 @item @var{value} @expansion{}
17611 @code{ @var{const} | @var{tuple} | @var{list} }
17613 @item @var{const} @expansion{}
17614 @code{@var{c-string}}
17616 @item @var{tuple} @expansion{}
17617 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17619 @item @var{list} @expansion{}
17620 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17621 @var{result} ( "," @var{result} )* "]" }
17623 @item @var{stream-record} @expansion{}
17624 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17626 @item @var{console-stream-output} @expansion{}
17627 @code{"~" @var{c-string}}
17629 @item @var{target-stream-output} @expansion{}
17630 @code{"@@" @var{c-string}}
17632 @item @var{log-stream-output} @expansion{}
17633 @code{"&" @var{c-string}}
17635 @item @var{nl} @expansion{}
17638 @item @var{token} @expansion{}
17639 @emph{any sequence of digits}.
17647 All output sequences end in a single line containing a period.
17650 The @code{@var{token}} is from the corresponding request. If an execution
17651 command is interrupted by the @samp{-exec-interrupt} command, the
17652 @var{token} associated with the @samp{*stopped} message is the one of the
17653 original execution command, not the one of the interrupt command.
17656 @cindex status output in @sc{gdb/mi}
17657 @var{status-async-output} contains on-going status information about the
17658 progress of a slow operation. It can be discarded. All status output is
17659 prefixed by @samp{+}.
17662 @cindex async output in @sc{gdb/mi}
17663 @var{exec-async-output} contains asynchronous state change on the target
17664 (stopped, started, disappeared). All async output is prefixed by
17668 @cindex notify output in @sc{gdb/mi}
17669 @var{notify-async-output} contains supplementary information that the
17670 client should handle (e.g., a new breakpoint information). All notify
17671 output is prefixed by @samp{=}.
17674 @cindex console output in @sc{gdb/mi}
17675 @var{console-stream-output} is output that should be displayed as is in the
17676 console. It is the textual response to a CLI command. All the console
17677 output is prefixed by @samp{~}.
17680 @cindex target output in @sc{gdb/mi}
17681 @var{target-stream-output} is the output produced by the target program.
17682 All the target output is prefixed by @samp{@@}.
17685 @cindex log output in @sc{gdb/mi}
17686 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17687 instance messages that should be displayed as part of an error log. All
17688 the log output is prefixed by @samp{&}.
17691 @cindex list output in @sc{gdb/mi}
17692 New @sc{gdb/mi} commands should only output @var{lists} containing
17698 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17699 details about the various output records.
17701 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17702 @node GDB/MI Compatibility with CLI
17703 @section @sc{gdb/mi} Compatibility with CLI
17705 @cindex compatibility, @sc{gdb/mi} and CLI
17706 @cindex @sc{gdb/mi}, compatibility with CLI
17708 For the developers convenience CLI commands can be entered directly,
17709 but there may be some unexpected behaviour. For example, commands
17710 that query the user will behave as if the user replied yes, breakpoint
17711 command lists are not executed and some CLI commands, such as
17712 @code{if}, @code{when} and @code{define}, prompt for further input with
17713 @samp{>}, which is not valid MI output.
17715 This feature may be removed at some stage in the future and it is
17716 recommended that front ends use the @code{-interpreter-exec} command
17717 (@pxref{-interpreter-exec}).
17719 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17720 @node GDB/MI Development and Front Ends
17721 @section @sc{gdb/mi} Development and Front Ends
17722 @cindex @sc{gdb/mi} development
17724 The application which takes the MI output and presents the state of the
17725 program being debugged to the user is called a @dfn{front end}.
17727 Although @sc{gdb/mi} is still incomplete, it is currently being used
17728 by a variety of front ends to @value{GDBN}. This makes it difficult
17729 to introduce new functionality without breaking existing usage. This
17730 section tries to minimize the problems by describing how the protocol
17733 Some changes in MI need not break a carefully designed front end, and
17734 for these the MI version will remain unchanged. The following is a
17735 list of changes that may occur within one level, so front ends should
17736 parse MI output in a way that can handle them:
17740 New MI commands may be added.
17743 New fields may be added to the output of any MI command.
17746 The range of values for fields with specified values, e.g.,
17747 @code{in_scope} (@pxref{-var-update}) may be extended.
17749 @c The format of field's content e.g type prefix, may change so parse it
17750 @c at your own risk. Yes, in general?
17752 @c The order of fields may change? Shouldn't really matter but it might
17753 @c resolve inconsistencies.
17756 If the changes are likely to break front ends, the MI version level
17757 will be increased by one. This will allow the front end to parse the
17758 output according to the MI version. Apart from mi0, new versions of
17759 @value{GDBN} will not support old versions of MI and it will be the
17760 responsibility of the front end to work with the new one.
17762 @c Starting with mi3, add a new command -mi-version that prints the MI
17765 The best way to avoid unexpected changes in MI that might break your front
17766 end is to make your project known to @value{GDBN} developers and
17767 follow development on @email{gdb@@sourceware.org} and
17768 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17769 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17770 Group, which has the aim of creating a more general MI protocol
17771 called Debugger Machine Interface (DMI) that will become a standard
17772 for all debuggers, not just @value{GDBN}.
17773 @cindex mailing lists
17775 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17776 @node GDB/MI Output Records
17777 @section @sc{gdb/mi} Output Records
17780 * GDB/MI Result Records::
17781 * GDB/MI Stream Records::
17782 * GDB/MI Out-of-band Records::
17785 @node GDB/MI Result Records
17786 @subsection @sc{gdb/mi} Result Records
17788 @cindex result records in @sc{gdb/mi}
17789 @cindex @sc{gdb/mi}, result records
17790 In addition to a number of out-of-band notifications, the response to a
17791 @sc{gdb/mi} command includes one of the following result indications:
17795 @item "^done" [ "," @var{results} ]
17796 The synchronous operation was successful, @code{@var{results}} are the return
17801 @c Is this one correct? Should it be an out-of-band notification?
17802 The asynchronous operation was successfully started. The target is
17807 @value{GDBN} has connected to a remote target.
17809 @item "^error" "," @var{c-string}
17811 The operation failed. The @code{@var{c-string}} contains the corresponding
17816 @value{GDBN} has terminated.
17820 @node GDB/MI Stream Records
17821 @subsection @sc{gdb/mi} Stream Records
17823 @cindex @sc{gdb/mi}, stream records
17824 @cindex stream records in @sc{gdb/mi}
17825 @value{GDBN} internally maintains a number of output streams: the console, the
17826 target, and the log. The output intended for each of these streams is
17827 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17829 Each stream record begins with a unique @dfn{prefix character} which
17830 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17831 Syntax}). In addition to the prefix, each stream record contains a
17832 @code{@var{string-output}}. This is either raw text (with an implicit new
17833 line) or a quoted C string (which does not contain an implicit newline).
17836 @item "~" @var{string-output}
17837 The console output stream contains text that should be displayed in the
17838 CLI console window. It contains the textual responses to CLI commands.
17840 @item "@@" @var{string-output}
17841 The target output stream contains any textual output from the running
17842 target. This is only present when GDB's event loop is truly
17843 asynchronous, which is currently only the case for remote targets.
17845 @item "&" @var{string-output}
17846 The log stream contains debugging messages being produced by @value{GDBN}'s
17850 @node GDB/MI Out-of-band Records
17851 @subsection @sc{gdb/mi} Out-of-band Records
17853 @cindex out-of-band records in @sc{gdb/mi}
17854 @cindex @sc{gdb/mi}, out-of-band records
17855 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17856 additional changes that have occurred. Those changes can either be a
17857 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17858 target activity (e.g., target stopped).
17860 The following is a preliminary list of possible out-of-band records.
17861 In particular, the @var{exec-async-output} records.
17864 @item *stopped,reason="@var{reason}"
17867 @var{reason} can be one of the following:
17870 @item breakpoint-hit
17871 A breakpoint was reached.
17872 @item watchpoint-trigger
17873 A watchpoint was triggered.
17874 @item read-watchpoint-trigger
17875 A read watchpoint was triggered.
17876 @item access-watchpoint-trigger
17877 An access watchpoint was triggered.
17878 @item function-finished
17879 An -exec-finish or similar CLI command was accomplished.
17880 @item location-reached
17881 An -exec-until or similar CLI command was accomplished.
17882 @item watchpoint-scope
17883 A watchpoint has gone out of scope.
17884 @item end-stepping-range
17885 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17886 similar CLI command was accomplished.
17887 @item exited-signalled
17888 The inferior exited because of a signal.
17890 The inferior exited.
17891 @item exited-normally
17892 The inferior exited normally.
17893 @item signal-received
17894 A signal was received by the inferior.
17898 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17899 @node GDB/MI Simple Examples
17900 @section Simple Examples of @sc{gdb/mi} Interaction
17901 @cindex @sc{gdb/mi}, simple examples
17903 This subsection presents several simple examples of interaction using
17904 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17905 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17906 the output received from @sc{gdb/mi}.
17908 Note the line breaks shown in the examples are here only for
17909 readability, they don't appear in the real output.
17911 @subheading Setting a Breakpoint
17913 Setting a breakpoint generates synchronous output which contains detailed
17914 information of the breakpoint.
17917 -> -break-insert main
17918 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17919 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17920 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17924 @subheading Program Execution
17926 Program execution generates asynchronous records and MI gives the
17927 reason that execution stopped.
17933 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17934 frame=@{addr="0x08048564",func="main",
17935 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17936 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17941 <- *stopped,reason="exited-normally"
17945 @subheading Quitting @value{GDBN}
17947 Quitting @value{GDBN} just prints the result class @samp{^exit}.
17955 @subheading A Bad Command
17957 Here's what happens if you pass a non-existent command:
17961 <- ^error,msg="Undefined MI command: rubbish"
17966 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17967 @node GDB/MI Command Description Format
17968 @section @sc{gdb/mi} Command Description Format
17970 The remaining sections describe blocks of commands. Each block of
17971 commands is laid out in a fashion similar to this section.
17973 @subheading Motivation
17975 The motivation for this collection of commands.
17977 @subheading Introduction
17979 A brief introduction to this collection of commands as a whole.
17981 @subheading Commands
17983 For each command in the block, the following is described:
17985 @subsubheading Synopsis
17988 -command @var{args}@dots{}
17991 @subsubheading Result
17993 @subsubheading @value{GDBN} Command
17995 The corresponding @value{GDBN} CLI command(s), if any.
17997 @subsubheading Example
17999 Example(s) formatted for readability. Some of the described commands have
18000 not been implemented yet and these are labeled N.A.@: (not available).
18003 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18004 @node GDB/MI Breakpoint Commands
18005 @section @sc{gdb/mi} Breakpoint Commands
18007 @cindex breakpoint commands for @sc{gdb/mi}
18008 @cindex @sc{gdb/mi}, breakpoint commands
18009 This section documents @sc{gdb/mi} commands for manipulating
18012 @subheading The @code{-break-after} Command
18013 @findex -break-after
18015 @subsubheading Synopsis
18018 -break-after @var{number} @var{count}
18021 The breakpoint number @var{number} is not in effect until it has been
18022 hit @var{count} times. To see how this is reflected in the output of
18023 the @samp{-break-list} command, see the description of the
18024 @samp{-break-list} command below.
18026 @subsubheading @value{GDBN} Command
18028 The corresponding @value{GDBN} command is @samp{ignore}.
18030 @subsubheading Example
18035 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
18036 fullname="/home/foo/hello.c",line="5",times="0"@}
18043 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18044 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18045 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18046 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18047 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18048 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18049 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18050 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18051 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18052 line="5",times="0",ignore="3"@}]@}
18057 @subheading The @code{-break-catch} Command
18058 @findex -break-catch
18060 @subheading The @code{-break-commands} Command
18061 @findex -break-commands
18065 @subheading The @code{-break-condition} Command
18066 @findex -break-condition
18068 @subsubheading Synopsis
18071 -break-condition @var{number} @var{expr}
18074 Breakpoint @var{number} will stop the program only if the condition in
18075 @var{expr} is true. The condition becomes part of the
18076 @samp{-break-list} output (see the description of the @samp{-break-list}
18079 @subsubheading @value{GDBN} Command
18081 The corresponding @value{GDBN} command is @samp{condition}.
18083 @subsubheading Example
18087 -break-condition 1 1
18091 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18092 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18093 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18094 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18095 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18096 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18097 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18098 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18099 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18100 line="5",cond="1",times="0",ignore="3"@}]@}
18104 @subheading The @code{-break-delete} Command
18105 @findex -break-delete
18107 @subsubheading Synopsis
18110 -break-delete ( @var{breakpoint} )+
18113 Delete the breakpoint(s) whose number(s) are specified in the argument
18114 list. This is obviously reflected in the breakpoint list.
18116 @subsubheading @value{GDBN} Command
18118 The corresponding @value{GDBN} command is @samp{delete}.
18120 @subsubheading Example
18128 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18129 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18130 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18131 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18132 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18133 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18134 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18139 @subheading The @code{-break-disable} Command
18140 @findex -break-disable
18142 @subsubheading Synopsis
18145 -break-disable ( @var{breakpoint} )+
18148 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18149 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18151 @subsubheading @value{GDBN} Command
18153 The corresponding @value{GDBN} command is @samp{disable}.
18155 @subsubheading Example
18163 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18164 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18165 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18166 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18167 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18168 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18169 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18170 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18171 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18172 line="5",times="0"@}]@}
18176 @subheading The @code{-break-enable} Command
18177 @findex -break-enable
18179 @subsubheading Synopsis
18182 -break-enable ( @var{breakpoint} )+
18185 Enable (previously disabled) @var{breakpoint}(s).
18187 @subsubheading @value{GDBN} Command
18189 The corresponding @value{GDBN} command is @samp{enable}.
18191 @subsubheading Example
18199 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18200 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18201 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18202 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18203 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18204 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18205 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18206 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18207 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18208 line="5",times="0"@}]@}
18212 @subheading The @code{-break-info} Command
18213 @findex -break-info
18215 @subsubheading Synopsis
18218 -break-info @var{breakpoint}
18222 Get information about a single breakpoint.
18224 @subsubheading @value{GDBN} Command
18226 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18228 @subsubheading Example
18231 @subheading The @code{-break-insert} Command
18232 @findex -break-insert
18234 @subsubheading Synopsis
18237 -break-insert [ -t ] [ -h ] [ -f ]
18238 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18239 [ -p @var{thread} ] [ @var{location} ]
18243 If specified, @var{location}, can be one of:
18250 @item filename:linenum
18251 @item filename:function
18255 The possible optional parameters of this command are:
18259 Insert a temporary breakpoint.
18261 Insert a hardware breakpoint.
18262 @item -c @var{condition}
18263 Make the breakpoint conditional on @var{condition}.
18264 @item -i @var{ignore-count}
18265 Initialize the @var{ignore-count}.
18267 If @var{location} cannot be parsed (for example if it
18268 refers to unknown files or functions), create a pending
18269 breakpoint. Without this flag, @value{GDBN} will report
18270 an error, and won't create a breakpoint, if @var{location}
18274 @subsubheading Result
18276 The result is in the form:
18279 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18280 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18281 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18282 times="@var{times}"@}
18286 where @var{number} is the @value{GDBN} number for this breakpoint,
18287 @var{funcname} is the name of the function where the breakpoint was
18288 inserted, @var{filename} is the name of the source file which contains
18289 this function, @var{lineno} is the source line number within that file
18290 and @var{times} the number of times that the breakpoint has been hit
18291 (always 0 for -break-insert but may be greater for -break-info or -break-list
18292 which use the same output).
18294 Note: this format is open to change.
18295 @c An out-of-band breakpoint instead of part of the result?
18297 @subsubheading @value{GDBN} Command
18299 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18300 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18302 @subsubheading Example
18307 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18308 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18310 -break-insert -t foo
18311 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18312 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18315 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18316 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18317 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18318 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18319 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18320 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18321 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18322 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18323 addr="0x0001072c", func="main",file="recursive2.c",
18324 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18325 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18326 addr="0x00010774",func="foo",file="recursive2.c",
18327 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18329 -break-insert -r foo.*
18330 ~int foo(int, int);
18331 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18332 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18336 @subheading The @code{-break-list} Command
18337 @findex -break-list
18339 @subsubheading Synopsis
18345 Displays the list of inserted breakpoints, showing the following fields:
18349 number of the breakpoint
18351 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18353 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18356 is the breakpoint enabled or no: @samp{y} or @samp{n}
18358 memory location at which the breakpoint is set
18360 logical location of the breakpoint, expressed by function name, file
18363 number of times the breakpoint has been hit
18366 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18367 @code{body} field is an empty list.
18369 @subsubheading @value{GDBN} Command
18371 The corresponding @value{GDBN} command is @samp{info break}.
18373 @subsubheading Example
18378 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18379 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18380 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18381 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18382 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18383 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18384 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18385 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18386 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18387 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18388 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18389 line="13",times="0"@}]@}
18393 Here's an example of the result when there are no breakpoints:
18398 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18399 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18400 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18401 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18402 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18403 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18404 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18409 @subheading The @code{-break-watch} Command
18410 @findex -break-watch
18412 @subsubheading Synopsis
18415 -break-watch [ -a | -r ]
18418 Create a watchpoint. With the @samp{-a} option it will create an
18419 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18420 read from or on a write to the memory location. With the @samp{-r}
18421 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18422 trigger only when the memory location is accessed for reading. Without
18423 either of the options, the watchpoint created is a regular watchpoint,
18424 i.e., it will trigger when the memory location is accessed for writing.
18425 @xref{Set Watchpoints, , Setting Watchpoints}.
18427 Note that @samp{-break-list} will report a single list of watchpoints and
18428 breakpoints inserted.
18430 @subsubheading @value{GDBN} Command
18432 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18435 @subsubheading Example
18437 Setting a watchpoint on a variable in the @code{main} function:
18442 ^done,wpt=@{number="2",exp="x"@}
18447 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18448 value=@{old="-268439212",new="55"@},
18449 frame=@{func="main",args=[],file="recursive2.c",
18450 fullname="/home/foo/bar/recursive2.c",line="5"@}
18454 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18455 the program execution twice: first for the variable changing value, then
18456 for the watchpoint going out of scope.
18461 ^done,wpt=@{number="5",exp="C"@}
18466 *stopped,reason="watchpoint-trigger",
18467 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18468 frame=@{func="callee4",args=[],
18469 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18470 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18475 *stopped,reason="watchpoint-scope",wpnum="5",
18476 frame=@{func="callee3",args=[@{name="strarg",
18477 value="0x11940 \"A string argument.\""@}],
18478 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18479 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18483 Listing breakpoints and watchpoints, at different points in the program
18484 execution. Note that once the watchpoint goes out of scope, it is
18490 ^done,wpt=@{number="2",exp="C"@}
18493 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18494 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18495 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18496 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18497 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18498 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18499 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18500 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18501 addr="0x00010734",func="callee4",
18502 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18503 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18504 bkpt=@{number="2",type="watchpoint",disp="keep",
18505 enabled="y",addr="",what="C",times="0"@}]@}
18510 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18511 value=@{old="-276895068",new="3"@},
18512 frame=@{func="callee4",args=[],
18513 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18514 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18517 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18518 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18519 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18520 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18521 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18522 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18523 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18524 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18525 addr="0x00010734",func="callee4",
18526 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18527 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18528 bkpt=@{number="2",type="watchpoint",disp="keep",
18529 enabled="y",addr="",what="C",times="-5"@}]@}
18533 ^done,reason="watchpoint-scope",wpnum="2",
18534 frame=@{func="callee3",args=[@{name="strarg",
18535 value="0x11940 \"A string argument.\""@}],
18536 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18537 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18540 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18541 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18542 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18543 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18544 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18545 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18546 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18547 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18548 addr="0x00010734",func="callee4",
18549 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18550 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18555 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18556 @node GDB/MI Program Context
18557 @section @sc{gdb/mi} Program Context
18559 @subheading The @code{-exec-arguments} Command
18560 @findex -exec-arguments
18563 @subsubheading Synopsis
18566 -exec-arguments @var{args}
18569 Set the inferior program arguments, to be used in the next
18572 @subsubheading @value{GDBN} Command
18574 The corresponding @value{GDBN} command is @samp{set args}.
18576 @subsubheading Example
18579 Don't have one around.
18582 @subheading The @code{-exec-show-arguments} Command
18583 @findex -exec-show-arguments
18585 @subsubheading Synopsis
18588 -exec-show-arguments
18591 Print the arguments of the program.
18593 @subsubheading @value{GDBN} Command
18595 The corresponding @value{GDBN} command is @samp{show args}.
18597 @subsubheading Example
18601 @subheading The @code{-environment-cd} Command
18602 @findex -environment-cd
18604 @subsubheading Synopsis
18607 -environment-cd @var{pathdir}
18610 Set @value{GDBN}'s working directory.
18612 @subsubheading @value{GDBN} Command
18614 The corresponding @value{GDBN} command is @samp{cd}.
18616 @subsubheading Example
18620 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18626 @subheading The @code{-environment-directory} Command
18627 @findex -environment-directory
18629 @subsubheading Synopsis
18632 -environment-directory [ -r ] [ @var{pathdir} ]+
18635 Add directories @var{pathdir} to beginning of search path for source files.
18636 If the @samp{-r} option is used, the search path is reset to the default
18637 search path. If directories @var{pathdir} are supplied in addition to the
18638 @samp{-r} option, the search path is first reset and then addition
18640 Multiple directories may be specified, separated by blanks. Specifying
18641 multiple directories in a single command
18642 results in the directories added to the beginning of the
18643 search path in the same order they were presented in the command.
18644 If blanks are needed as
18645 part of a directory name, double-quotes should be used around
18646 the name. In the command output, the path will show up separated
18647 by the system directory-separator character. The directory-separator
18648 character must not be used
18649 in any directory name.
18650 If no directories are specified, the current search path is displayed.
18652 @subsubheading @value{GDBN} Command
18654 The corresponding @value{GDBN} command is @samp{dir}.
18656 @subsubheading Example
18660 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18661 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18663 -environment-directory ""
18664 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18666 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18667 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18669 -environment-directory -r
18670 ^done,source-path="$cdir:$cwd"
18675 @subheading The @code{-environment-path} Command
18676 @findex -environment-path
18678 @subsubheading Synopsis
18681 -environment-path [ -r ] [ @var{pathdir} ]+
18684 Add directories @var{pathdir} to beginning of search path for object files.
18685 If the @samp{-r} option is used, the search path is reset to the original
18686 search path that existed at gdb start-up. If directories @var{pathdir} are
18687 supplied in addition to the
18688 @samp{-r} option, the search path is first reset and then addition
18690 Multiple directories may be specified, separated by blanks. Specifying
18691 multiple directories in a single command
18692 results in the directories added to the beginning of the
18693 search path in the same order they were presented in the command.
18694 If blanks are needed as
18695 part of a directory name, double-quotes should be used around
18696 the name. In the command output, the path will show up separated
18697 by the system directory-separator character. The directory-separator
18698 character must not be used
18699 in any directory name.
18700 If no directories are specified, the current path is displayed.
18703 @subsubheading @value{GDBN} Command
18705 The corresponding @value{GDBN} command is @samp{path}.
18707 @subsubheading Example
18712 ^done,path="/usr/bin"
18714 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18715 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18717 -environment-path -r /usr/local/bin
18718 ^done,path="/usr/local/bin:/usr/bin"
18723 @subheading The @code{-environment-pwd} Command
18724 @findex -environment-pwd
18726 @subsubheading Synopsis
18732 Show the current working directory.
18734 @subsubheading @value{GDBN} Command
18736 The corresponding @value{GDBN} command is @samp{pwd}.
18738 @subsubheading Example
18743 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18747 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18748 @node GDB/MI Thread Commands
18749 @section @sc{gdb/mi} Thread Commands
18752 @subheading The @code{-thread-info} Command
18753 @findex -thread-info
18755 @subsubheading Synopsis
18761 @subsubheading @value{GDBN} Command
18765 @subsubheading Example
18769 @subheading The @code{-thread-list-all-threads} Command
18770 @findex -thread-list-all-threads
18772 @subsubheading Synopsis
18775 -thread-list-all-threads
18778 @subsubheading @value{GDBN} Command
18780 The equivalent @value{GDBN} command is @samp{info threads}.
18782 @subsubheading Example
18786 @subheading The @code{-thread-list-ids} Command
18787 @findex -thread-list-ids
18789 @subsubheading Synopsis
18795 Produces a list of the currently known @value{GDBN} thread ids. At the
18796 end of the list it also prints the total number of such threads.
18798 @subsubheading @value{GDBN} Command
18800 Part of @samp{info threads} supplies the same information.
18802 @subsubheading Example
18804 No threads present, besides the main process:
18809 ^done,thread-ids=@{@},number-of-threads="0"
18819 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18820 number-of-threads="3"
18825 @subheading The @code{-thread-select} Command
18826 @findex -thread-select
18828 @subsubheading Synopsis
18831 -thread-select @var{threadnum}
18834 Make @var{threadnum} the current thread. It prints the number of the new
18835 current thread, and the topmost frame for that thread.
18837 @subsubheading @value{GDBN} Command
18839 The corresponding @value{GDBN} command is @samp{thread}.
18841 @subsubheading Example
18848 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18849 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18853 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18854 number-of-threads="3"
18857 ^done,new-thread-id="3",
18858 frame=@{level="0",func="vprintf",
18859 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18860 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18864 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18865 @node GDB/MI Program Execution
18866 @section @sc{gdb/mi} Program Execution
18868 These are the asynchronous commands which generate the out-of-band
18869 record @samp{*stopped}. Currently @value{GDBN} only really executes
18870 asynchronously with remote targets and this interaction is mimicked in
18873 @subheading The @code{-exec-continue} Command
18874 @findex -exec-continue
18876 @subsubheading Synopsis
18882 Resumes the execution of the inferior program until a breakpoint is
18883 encountered, or until the inferior exits.
18885 @subsubheading @value{GDBN} Command
18887 The corresponding @value{GDBN} corresponding is @samp{continue}.
18889 @subsubheading Example
18896 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18897 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18902 @subheading The @code{-exec-finish} Command
18903 @findex -exec-finish
18905 @subsubheading Synopsis
18911 Resumes the execution of the inferior program until the current
18912 function is exited. Displays the results returned by the function.
18914 @subsubheading @value{GDBN} Command
18916 The corresponding @value{GDBN} command is @samp{finish}.
18918 @subsubheading Example
18920 Function returning @code{void}.
18927 *stopped,reason="function-finished",frame=@{func="main",args=[],
18928 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18932 Function returning other than @code{void}. The name of the internal
18933 @value{GDBN} variable storing the result is printed, together with the
18940 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18941 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18942 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18943 gdb-result-var="$1",return-value="0"
18948 @subheading The @code{-exec-interrupt} Command
18949 @findex -exec-interrupt
18951 @subsubheading Synopsis
18957 Interrupts the background execution of the target. Note how the token
18958 associated with the stop message is the one for the execution command
18959 that has been interrupted. The token for the interrupt itself only
18960 appears in the @samp{^done} output. If the user is trying to
18961 interrupt a non-running program, an error message will be printed.
18963 @subsubheading @value{GDBN} Command
18965 The corresponding @value{GDBN} command is @samp{interrupt}.
18967 @subsubheading Example
18978 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18979 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18980 fullname="/home/foo/bar/try.c",line="13"@}
18985 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18990 @subheading The @code{-exec-next} Command
18993 @subsubheading Synopsis
18999 Resumes execution of the inferior program, stopping when the beginning
19000 of the next source line is reached.
19002 @subsubheading @value{GDBN} Command
19004 The corresponding @value{GDBN} command is @samp{next}.
19006 @subsubheading Example
19012 *stopped,reason="end-stepping-range",line="8",file="hello.c"
19017 @subheading The @code{-exec-next-instruction} Command
19018 @findex -exec-next-instruction
19020 @subsubheading Synopsis
19023 -exec-next-instruction
19026 Executes one machine instruction. If the instruction is a function
19027 call, continues until the function returns. If the program stops at an
19028 instruction in the middle of a source line, the address will be
19031 @subsubheading @value{GDBN} Command
19033 The corresponding @value{GDBN} command is @samp{nexti}.
19035 @subsubheading Example
19039 -exec-next-instruction
19043 *stopped,reason="end-stepping-range",
19044 addr="0x000100d4",line="5",file="hello.c"
19049 @subheading The @code{-exec-return} Command
19050 @findex -exec-return
19052 @subsubheading Synopsis
19058 Makes current function return immediately. Doesn't execute the inferior.
19059 Displays the new current frame.
19061 @subsubheading @value{GDBN} Command
19063 The corresponding @value{GDBN} command is @samp{return}.
19065 @subsubheading Example
19069 200-break-insert callee4
19070 200^done,bkpt=@{number="1",addr="0x00010734",
19071 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19076 000*stopped,reason="breakpoint-hit",bkptno="1",
19077 frame=@{func="callee4",args=[],
19078 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19079 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19085 111^done,frame=@{level="0",func="callee3",
19086 args=[@{name="strarg",
19087 value="0x11940 \"A string argument.\""@}],
19088 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19089 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19094 @subheading The @code{-exec-run} Command
19097 @subsubheading Synopsis
19103 Starts execution of the inferior from the beginning. The inferior
19104 executes until either a breakpoint is encountered or the program
19105 exits. In the latter case the output will include an exit code, if
19106 the program has exited exceptionally.
19108 @subsubheading @value{GDBN} Command
19110 The corresponding @value{GDBN} command is @samp{run}.
19112 @subsubheading Examples
19117 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19122 *stopped,reason="breakpoint-hit",bkptno="1",
19123 frame=@{func="main",args=[],file="recursive2.c",
19124 fullname="/home/foo/bar/recursive2.c",line="4"@}
19129 Program exited normally:
19137 *stopped,reason="exited-normally"
19142 Program exited exceptionally:
19150 *stopped,reason="exited",exit-code="01"
19154 Another way the program can terminate is if it receives a signal such as
19155 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19159 *stopped,reason="exited-signalled",signal-name="SIGINT",
19160 signal-meaning="Interrupt"
19164 @c @subheading -exec-signal
19167 @subheading The @code{-exec-step} Command
19170 @subsubheading Synopsis
19176 Resumes execution of the inferior program, stopping when the beginning
19177 of the next source line is reached, if the next source line is not a
19178 function call. If it is, stop at the first instruction of the called
19181 @subsubheading @value{GDBN} Command
19183 The corresponding @value{GDBN} command is @samp{step}.
19185 @subsubheading Example
19187 Stepping into a function:
19193 *stopped,reason="end-stepping-range",
19194 frame=@{func="foo",args=[@{name="a",value="10"@},
19195 @{name="b",value="0"@}],file="recursive2.c",
19196 fullname="/home/foo/bar/recursive2.c",line="11"@}
19206 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19211 @subheading The @code{-exec-step-instruction} Command
19212 @findex -exec-step-instruction
19214 @subsubheading Synopsis
19217 -exec-step-instruction
19220 Resumes the inferior which executes one machine instruction. The
19221 output, once @value{GDBN} has stopped, will vary depending on whether
19222 we have stopped in the middle of a source line or not. In the former
19223 case, the address at which the program stopped will be printed as
19226 @subsubheading @value{GDBN} Command
19228 The corresponding @value{GDBN} command is @samp{stepi}.
19230 @subsubheading Example
19234 -exec-step-instruction
19238 *stopped,reason="end-stepping-range",
19239 frame=@{func="foo",args=[],file="try.c",
19240 fullname="/home/foo/bar/try.c",line="10"@}
19242 -exec-step-instruction
19246 *stopped,reason="end-stepping-range",
19247 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19248 fullname="/home/foo/bar/try.c",line="10"@}
19253 @subheading The @code{-exec-until} Command
19254 @findex -exec-until
19256 @subsubheading Synopsis
19259 -exec-until [ @var{location} ]
19262 Executes the inferior until the @var{location} specified in the
19263 argument is reached. If there is no argument, the inferior executes
19264 until a source line greater than the current one is reached. The
19265 reason for stopping in this case will be @samp{location-reached}.
19267 @subsubheading @value{GDBN} Command
19269 The corresponding @value{GDBN} command is @samp{until}.
19271 @subsubheading Example
19275 -exec-until recursive2.c:6
19279 *stopped,reason="location-reached",frame=@{func="main",args=[],
19280 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19285 @subheading -file-clear
19286 Is this going away????
19289 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19290 @node GDB/MI Stack Manipulation
19291 @section @sc{gdb/mi} Stack Manipulation Commands
19294 @subheading The @code{-stack-info-frame} Command
19295 @findex -stack-info-frame
19297 @subsubheading Synopsis
19303 Get info on the selected frame.
19305 @subsubheading @value{GDBN} Command
19307 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19308 (without arguments).
19310 @subsubheading Example
19315 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19316 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19317 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19321 @subheading The @code{-stack-info-depth} Command
19322 @findex -stack-info-depth
19324 @subsubheading Synopsis
19327 -stack-info-depth [ @var{max-depth} ]
19330 Return the depth of the stack. If the integer argument @var{max-depth}
19331 is specified, do not count beyond @var{max-depth} frames.
19333 @subsubheading @value{GDBN} Command
19335 There's no equivalent @value{GDBN} command.
19337 @subsubheading Example
19339 For a stack with frame levels 0 through 11:
19346 -stack-info-depth 4
19349 -stack-info-depth 12
19352 -stack-info-depth 11
19355 -stack-info-depth 13
19360 @subheading The @code{-stack-list-arguments} Command
19361 @findex -stack-list-arguments
19363 @subsubheading Synopsis
19366 -stack-list-arguments @var{show-values}
19367 [ @var{low-frame} @var{high-frame} ]
19370 Display a list of the arguments for the frames between @var{low-frame}
19371 and @var{high-frame} (inclusive). If @var{low-frame} and
19372 @var{high-frame} are not provided, list the arguments for the whole
19373 call stack. If the two arguments are equal, show the single frame
19374 at the corresponding level. It is an error if @var{low-frame} is
19375 larger than the actual number of frames. On the other hand,
19376 @var{high-frame} may be larger than the actual number of frames, in
19377 which case only existing frames will be returned.
19379 The @var{show-values} argument must have a value of 0 or 1. A value of
19380 0 means that only the names of the arguments are listed, a value of 1
19381 means that both names and values of the arguments are printed.
19383 @subsubheading @value{GDBN} Command
19385 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19386 @samp{gdb_get_args} command which partially overlaps with the
19387 functionality of @samp{-stack-list-arguments}.
19389 @subsubheading Example
19396 frame=@{level="0",addr="0x00010734",func="callee4",
19397 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19398 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19399 frame=@{level="1",addr="0x0001076c",func="callee3",
19400 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19401 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19402 frame=@{level="2",addr="0x0001078c",func="callee2",
19403 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19404 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19405 frame=@{level="3",addr="0x000107b4",func="callee1",
19406 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19407 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19408 frame=@{level="4",addr="0x000107e0",func="main",
19409 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19410 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19412 -stack-list-arguments 0
19415 frame=@{level="0",args=[]@},
19416 frame=@{level="1",args=[name="strarg"]@},
19417 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19418 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19419 frame=@{level="4",args=[]@}]
19421 -stack-list-arguments 1
19424 frame=@{level="0",args=[]@},
19426 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19427 frame=@{level="2",args=[
19428 @{name="intarg",value="2"@},
19429 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19430 @{frame=@{level="3",args=[
19431 @{name="intarg",value="2"@},
19432 @{name="strarg",value="0x11940 \"A string argument.\""@},
19433 @{name="fltarg",value="3.5"@}]@},
19434 frame=@{level="4",args=[]@}]
19436 -stack-list-arguments 0 2 2
19437 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19439 -stack-list-arguments 1 2 2
19440 ^done,stack-args=[frame=@{level="2",
19441 args=[@{name="intarg",value="2"@},
19442 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19446 @c @subheading -stack-list-exception-handlers
19449 @subheading The @code{-stack-list-frames} Command
19450 @findex -stack-list-frames
19452 @subsubheading Synopsis
19455 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19458 List the frames currently on the stack. For each frame it displays the
19463 The frame number, 0 being the topmost frame, i.e., the innermost function.
19465 The @code{$pc} value for that frame.
19469 File name of the source file where the function lives.
19471 Line number corresponding to the @code{$pc}.
19474 If invoked without arguments, this command prints a backtrace for the
19475 whole stack. If given two integer arguments, it shows the frames whose
19476 levels are between the two arguments (inclusive). If the two arguments
19477 are equal, it shows the single frame at the corresponding level. It is
19478 an error if @var{low-frame} is larger than the actual number of
19479 frames. On the other hand, @var{high-frame} may be larger than the
19480 actual number of frames, in which case only existing frames will be returned.
19482 @subsubheading @value{GDBN} Command
19484 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19486 @subsubheading Example
19488 Full stack backtrace:
19494 [frame=@{level="0",addr="0x0001076c",func="foo",
19495 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19496 frame=@{level="1",addr="0x000107a4",func="foo",
19497 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19498 frame=@{level="2",addr="0x000107a4",func="foo",
19499 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19500 frame=@{level="3",addr="0x000107a4",func="foo",
19501 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19502 frame=@{level="4",addr="0x000107a4",func="foo",
19503 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19504 frame=@{level="5",addr="0x000107a4",func="foo",
19505 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19506 frame=@{level="6",addr="0x000107a4",func="foo",
19507 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19508 frame=@{level="7",addr="0x000107a4",func="foo",
19509 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19510 frame=@{level="8",addr="0x000107a4",func="foo",
19511 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19512 frame=@{level="9",addr="0x000107a4",func="foo",
19513 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19514 frame=@{level="10",addr="0x000107a4",func="foo",
19515 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19516 frame=@{level="11",addr="0x00010738",func="main",
19517 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19521 Show frames between @var{low_frame} and @var{high_frame}:
19525 -stack-list-frames 3 5
19527 [frame=@{level="3",addr="0x000107a4",func="foo",
19528 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19529 frame=@{level="4",addr="0x000107a4",func="foo",
19530 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19531 frame=@{level="5",addr="0x000107a4",func="foo",
19532 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19536 Show a single frame:
19540 -stack-list-frames 3 3
19542 [frame=@{level="3",addr="0x000107a4",func="foo",
19543 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19548 @subheading The @code{-stack-list-locals} Command
19549 @findex -stack-list-locals
19551 @subsubheading Synopsis
19554 -stack-list-locals @var{print-values}
19557 Display the local variable names for the selected frame. If
19558 @var{print-values} is 0 or @code{--no-values}, print only the names of
19559 the variables; if it is 1 or @code{--all-values}, print also their
19560 values; and if it is 2 or @code{--simple-values}, print the name,
19561 type and value for simple data types and the name and type for arrays,
19562 structures and unions. In this last case, a frontend can immediately
19563 display the value of simple data types and create variable objects for
19564 other data types when the user wishes to explore their values in
19567 @subsubheading @value{GDBN} Command
19569 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19571 @subsubheading Example
19575 -stack-list-locals 0
19576 ^done,locals=[name="A",name="B",name="C"]
19578 -stack-list-locals --all-values
19579 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19580 @{name="C",value="@{1, 2, 3@}"@}]
19581 -stack-list-locals --simple-values
19582 ^done,locals=[@{name="A",type="int",value="1"@},
19583 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19588 @subheading The @code{-stack-select-frame} Command
19589 @findex -stack-select-frame
19591 @subsubheading Synopsis
19594 -stack-select-frame @var{framenum}
19597 Change the selected frame. Select a different frame @var{framenum} on
19600 @subsubheading @value{GDBN} Command
19602 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19603 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19605 @subsubheading Example
19609 -stack-select-frame 2
19614 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19615 @node GDB/MI Variable Objects
19616 @section @sc{gdb/mi} Variable Objects
19620 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19622 For the implementation of a variable debugger window (locals, watched
19623 expressions, etc.), we are proposing the adaptation of the existing code
19624 used by @code{Insight}.
19626 The two main reasons for that are:
19630 It has been proven in practice (it is already on its second generation).
19633 It will shorten development time (needless to say how important it is
19637 The original interface was designed to be used by Tcl code, so it was
19638 slightly changed so it could be used through @sc{gdb/mi}. This section
19639 describes the @sc{gdb/mi} operations that will be available and gives some
19640 hints about their use.
19642 @emph{Note}: In addition to the set of operations described here, we
19643 expect the @sc{gui} implementation of a variable window to require, at
19644 least, the following operations:
19647 @item @code{-gdb-show} @code{output-radix}
19648 @item @code{-stack-list-arguments}
19649 @item @code{-stack-list-locals}
19650 @item @code{-stack-select-frame}
19655 @subheading Introduction to Variable Objects
19657 @cindex variable objects in @sc{gdb/mi}
19659 Variable objects are "object-oriented" MI interface for examining and
19660 changing values of expressions. Unlike some other MI interfaces that
19661 work with expressions, variable objects are specifically designed for
19662 simple and efficient presentation in the frontend. A variable object
19663 is identified by string name. When a variable object is created, the
19664 frontend specifies the expression for that variable object. The
19665 expression can be a simple variable, or it can be an arbitrary complex
19666 expression, and can even involve CPU registers. After creating a
19667 variable object, the frontend can invoke other variable object
19668 operations---for example to obtain or change the value of a variable
19669 object, or to change display format.
19671 Variable objects have hierarchical tree structure. Any variable object
19672 that corresponds to a composite type, such as structure in C, has
19673 a number of child variable objects, for example corresponding to each
19674 element of a structure. A child variable object can itself have
19675 children, recursively. Recursion ends when we reach
19676 leaf variable objects, which always have built-in types. Child variable
19677 objects are created only by explicit request, so if a frontend
19678 is not interested in the children of a particular variable object, no
19679 child will be created.
19681 For a leaf variable object it is possible to obtain its value as a
19682 string, or set the value from a string. String value can be also
19683 obtained for a non-leaf variable object, but it's generally a string
19684 that only indicates the type of the object, and does not list its
19685 contents. Assignment to a non-leaf variable object is not allowed.
19687 A frontend does not need to read the values of all variable objects each time
19688 the program stops. Instead, MI provides an update command that lists all
19689 variable objects whose values has changed since the last update
19690 operation. This considerably reduces the amount of data that must
19691 be transferred to the frontend. As noted above, children variable
19692 objects are created on demand, and only leaf variable objects have a
19693 real value. As result, gdb will read target memory only for leaf
19694 variables that frontend has created.
19696 The automatic update is not always desirable. For example, a frontend
19697 might want to keep a value of some expression for future reference,
19698 and never update it. For another example, fetching memory is
19699 relatively slow for embedded targets, so a frontend might want
19700 to disable automatic update for the variables that are either not
19701 visible on the screen, or ``closed''. This is possible using so
19702 called ``frozen variable objects''. Such variable objects are never
19703 implicitly updated.
19705 The following is the complete set of @sc{gdb/mi} operations defined to
19706 access this functionality:
19708 @multitable @columnfractions .4 .6
19709 @item @strong{Operation}
19710 @tab @strong{Description}
19712 @item @code{-var-create}
19713 @tab create a variable object
19714 @item @code{-var-delete}
19715 @tab delete the variable object and/or its children
19716 @item @code{-var-set-format}
19717 @tab set the display format of this variable
19718 @item @code{-var-show-format}
19719 @tab show the display format of this variable
19720 @item @code{-var-info-num-children}
19721 @tab tells how many children this object has
19722 @item @code{-var-list-children}
19723 @tab return a list of the object's children
19724 @item @code{-var-info-type}
19725 @tab show the type of this variable object
19726 @item @code{-var-info-expression}
19727 @tab print parent-relative expression that this variable object represents
19728 @item @code{-var-info-path-expression}
19729 @tab print full expression that this variable object represents
19730 @item @code{-var-show-attributes}
19731 @tab is this variable editable? does it exist here?
19732 @item @code{-var-evaluate-expression}
19733 @tab get the value of this variable
19734 @item @code{-var-assign}
19735 @tab set the value of this variable
19736 @item @code{-var-update}
19737 @tab update the variable and its children
19738 @item @code{-var-set-frozen}
19739 @tab set frozeness attribute
19742 In the next subsection we describe each operation in detail and suggest
19743 how it can be used.
19745 @subheading Description And Use of Operations on Variable Objects
19747 @subheading The @code{-var-create} Command
19748 @findex -var-create
19750 @subsubheading Synopsis
19753 -var-create @{@var{name} | "-"@}
19754 @{@var{frame-addr} | "*"@} @var{expression}
19757 This operation creates a variable object, which allows the monitoring of
19758 a variable, the result of an expression, a memory cell or a CPU
19761 The @var{name} parameter is the string by which the object can be
19762 referenced. It must be unique. If @samp{-} is specified, the varobj
19763 system will generate a string ``varNNNNNN'' automatically. It will be
19764 unique provided that one does not specify @var{name} on that format.
19765 The command fails if a duplicate name is found.
19767 The frame under which the expression should be evaluated can be
19768 specified by @var{frame-addr}. A @samp{*} indicates that the current
19769 frame should be used.
19771 @var{expression} is any expression valid on the current language set (must not
19772 begin with a @samp{*}), or one of the following:
19776 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19779 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19782 @samp{$@var{regname}} --- a CPU register name
19785 @subsubheading Result
19787 This operation returns the name, number of children and the type of the
19788 object created. Type is returned as a string as the ones generated by
19789 the @value{GDBN} CLI:
19792 name="@var{name}",numchild="N",type="@var{type}"
19796 @subheading The @code{-var-delete} Command
19797 @findex -var-delete
19799 @subsubheading Synopsis
19802 -var-delete [ -c ] @var{name}
19805 Deletes a previously created variable object and all of its children.
19806 With the @samp{-c} option, just deletes the children.
19808 Returns an error if the object @var{name} is not found.
19811 @subheading The @code{-var-set-format} Command
19812 @findex -var-set-format
19814 @subsubheading Synopsis
19817 -var-set-format @var{name} @var{format-spec}
19820 Sets the output format for the value of the object @var{name} to be
19823 The syntax for the @var{format-spec} is as follows:
19826 @var{format-spec} @expansion{}
19827 @{binary | decimal | hexadecimal | octal | natural@}
19830 The natural format is the default format choosen automatically
19831 based on the variable type (like decimal for an @code{int}, hex
19832 for pointers, etc.).
19834 For a variable with children, the format is set only on the
19835 variable itself, and the children are not affected.
19837 @subheading The @code{-var-show-format} Command
19838 @findex -var-show-format
19840 @subsubheading Synopsis
19843 -var-show-format @var{name}
19846 Returns the format used to display the value of the object @var{name}.
19849 @var{format} @expansion{}
19854 @subheading The @code{-var-info-num-children} Command
19855 @findex -var-info-num-children
19857 @subsubheading Synopsis
19860 -var-info-num-children @var{name}
19863 Returns the number of children of a variable object @var{name}:
19870 @subheading The @code{-var-list-children} Command
19871 @findex -var-list-children
19873 @subsubheading Synopsis
19876 -var-list-children [@var{print-values}] @var{name}
19878 @anchor{-var-list-children}
19880 Return a list of the children of the specified variable object and
19881 create variable objects for them, if they do not already exist. With
19882 a single argument or if @var{print-values} has a value for of 0 or
19883 @code{--no-values}, print only the names of the variables; if
19884 @var{print-values} is 1 or @code{--all-values}, also print their
19885 values; and if it is 2 or @code{--simple-values} print the name and
19886 value for simple data types and just the name for arrays, structures
19889 @subsubheading Example
19893 -var-list-children n
19894 ^done,numchild=@var{n},children=[@{name=@var{name},
19895 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19897 -var-list-children --all-values n
19898 ^done,numchild=@var{n},children=[@{name=@var{name},
19899 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19903 @subheading The @code{-var-info-type} Command
19904 @findex -var-info-type
19906 @subsubheading Synopsis
19909 -var-info-type @var{name}
19912 Returns the type of the specified variable @var{name}. The type is
19913 returned as a string in the same format as it is output by the
19917 type=@var{typename}
19921 @subheading The @code{-var-info-expression} Command
19922 @findex -var-info-expression
19924 @subsubheading Synopsis
19927 -var-info-expression @var{name}
19930 Returns a string that is suitable for presenting this
19931 variable object in user interface. The string is generally
19932 not valid expression in the current language, and cannot be evaluated.
19934 For example, if @code{a} is an array, and variable object
19935 @code{A} was created for @code{a}, then we'll get this output:
19938 (gdb) -var-info-expression A.1
19939 ^done,lang="C",exp="1"
19943 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
19945 Note that the output of the @code{-var-list-children} command also
19946 includes those expressions, so the @code{-var-info-expression} command
19949 @subheading The @code{-var-info-path-expression} Command
19950 @findex -var-info-path-expression
19952 @subsubheading Synopsis
19955 -var-info-path-expression @var{name}
19958 Returns an expression that can be evaluated in the current
19959 context and will yield the same value that a variable object has.
19960 Compare this with the @code{-var-info-expression} command, which
19961 result can be used only for UI presentation. Typical use of
19962 the @code{-var-info-path-expression} command is creating a
19963 watchpoint from a variable object.
19965 For example, suppose @code{C} is a C@t{++} class, derived from class
19966 @code{Base}, and that the @code{Base} class has a member called
19967 @code{m_size}. Assume a variable @code{c} is has the type of
19968 @code{C} and a variable object @code{C} was created for variable
19969 @code{c}. Then, we'll get this output:
19971 (gdb) -var-info-path-expression C.Base.public.m_size
19972 ^done,path_expr=((Base)c).m_size)
19975 @subheading The @code{-var-show-attributes} Command
19976 @findex -var-show-attributes
19978 @subsubheading Synopsis
19981 -var-show-attributes @var{name}
19984 List attributes of the specified variable object @var{name}:
19987 status=@var{attr} [ ( ,@var{attr} )* ]
19991 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19993 @subheading The @code{-var-evaluate-expression} Command
19994 @findex -var-evaluate-expression
19996 @subsubheading Synopsis
19999 -var-evaluate-expression @var{name}
20002 Evaluates the expression that is represented by the specified variable
20003 object and returns its value as a string. The format of the
20004 string can be changed using the @code{-var-set-format} command.
20010 Note that one must invoke @code{-var-list-children} for a variable
20011 before the value of a child variable can be evaluated.
20013 @subheading The @code{-var-assign} Command
20014 @findex -var-assign
20016 @subsubheading Synopsis
20019 -var-assign @var{name} @var{expression}
20022 Assigns the value of @var{expression} to the variable object specified
20023 by @var{name}. The object must be @samp{editable}. If the variable's
20024 value is altered by the assign, the variable will show up in any
20025 subsequent @code{-var-update} list.
20027 @subsubheading Example
20035 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20039 @subheading The @code{-var-update} Command
20040 @findex -var-update
20042 @subsubheading Synopsis
20045 -var-update [@var{print-values}] @{@var{name} | "*"@}
20048 Reevaluate the expressions corresponding to the variable object
20049 @var{name} and all its direct and indirect children, and return the
20050 list of variable objects whose values have changed; @var{name} must
20051 be a root variable object. Here, ``changed'' means that the result of
20052 @code{-var-evaluate-expression} before and after the
20053 @code{-var-update} is different. If @samp{*} is used as the variable
20054 object names, all existing variable objects are updated, except
20055 for frozen ones (@pxref{-var-set-frozen}). The option
20056 @var{print-values} determines whether both names and values, or just
20057 names are printed. The possible values of this options are the same
20058 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
20059 recommended to use the @samp{--all-values} option, to reduce the
20060 number of MI commands needed on each program stop.
20063 @subsubheading Example
20070 -var-update --all-values var1
20071 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20072 type_changed="false"@}]
20076 @anchor{-var-update}
20077 The field in_scope may take three values:
20081 The variable object's current value is valid.
20084 The variable object does not currently hold a valid value but it may
20085 hold one in the future if its associated expression comes back into
20089 The variable object no longer holds a valid value.
20090 This can occur when the executable file being debugged has changed,
20091 either through recompilation or by using the @value{GDBN} @code{file}
20092 command. The front end should normally choose to delete these variable
20096 In the future new values may be added to this list so the front should
20097 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
20099 @subheading The @code{-var-set-frozen} Command
20100 @findex -var-set-frozen
20101 @anchor{-var-set-frozen}
20103 @subsubheading Synopsis
20106 -var-set-frozen @var{name} @var{flag}
20109 Set the frozenness flag on the variable object @var{name}. The
20110 @var{flag} parameter should be either @samp{1} to make the variable
20111 frozen or @samp{0} to make it unfrozen. If a variable object is
20112 frozen, then neither itself, nor any of its children, are
20113 implicitly updated by @code{-var-update} of
20114 a parent variable or by @code{-var-update *}. Only
20115 @code{-var-update} of the variable itself will update its value and
20116 values of its children. After a variable object is unfrozen, it is
20117 implicitly updated by all subsequent @code{-var-update} operations.
20118 Unfreezing a variable does not update it, only subsequent
20119 @code{-var-update} does.
20121 @subsubheading Example
20125 -var-set-frozen V 1
20131 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20132 @node GDB/MI Data Manipulation
20133 @section @sc{gdb/mi} Data Manipulation
20135 @cindex data manipulation, in @sc{gdb/mi}
20136 @cindex @sc{gdb/mi}, data manipulation
20137 This section describes the @sc{gdb/mi} commands that manipulate data:
20138 examine memory and registers, evaluate expressions, etc.
20140 @c REMOVED FROM THE INTERFACE.
20141 @c @subheading -data-assign
20142 @c Change the value of a program variable. Plenty of side effects.
20143 @c @subsubheading GDB Command
20145 @c @subsubheading Example
20148 @subheading The @code{-data-disassemble} Command
20149 @findex -data-disassemble
20151 @subsubheading Synopsis
20155 [ -s @var{start-addr} -e @var{end-addr} ]
20156 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20164 @item @var{start-addr}
20165 is the beginning address (or @code{$pc})
20166 @item @var{end-addr}
20168 @item @var{filename}
20169 is the name of the file to disassemble
20170 @item @var{linenum}
20171 is the line number to disassemble around
20173 is the number of disassembly lines to be produced. If it is -1,
20174 the whole function will be disassembled, in case no @var{end-addr} is
20175 specified. If @var{end-addr} is specified as a non-zero value, and
20176 @var{lines} is lower than the number of disassembly lines between
20177 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20178 displayed; if @var{lines} is higher than the number of lines between
20179 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20182 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20186 @subsubheading Result
20188 The output for each instruction is composed of four fields:
20197 Note that whatever included in the instruction field, is not manipulated
20198 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20200 @subsubheading @value{GDBN} Command
20202 There's no direct mapping from this command to the CLI.
20204 @subsubheading Example
20206 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20210 -data-disassemble -s $pc -e "$pc + 20" -- 0
20213 @{address="0x000107c0",func-name="main",offset="4",
20214 inst="mov 2, %o0"@},
20215 @{address="0x000107c4",func-name="main",offset="8",
20216 inst="sethi %hi(0x11800), %o2"@},
20217 @{address="0x000107c8",func-name="main",offset="12",
20218 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20219 @{address="0x000107cc",func-name="main",offset="16",
20220 inst="sethi %hi(0x11800), %o2"@},
20221 @{address="0x000107d0",func-name="main",offset="20",
20222 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20226 Disassemble the whole @code{main} function. Line 32 is part of
20230 -data-disassemble -f basics.c -l 32 -- 0
20232 @{address="0x000107bc",func-name="main",offset="0",
20233 inst="save %sp, -112, %sp"@},
20234 @{address="0x000107c0",func-name="main",offset="4",
20235 inst="mov 2, %o0"@},
20236 @{address="0x000107c4",func-name="main",offset="8",
20237 inst="sethi %hi(0x11800), %o2"@},
20239 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20240 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20244 Disassemble 3 instructions from the start of @code{main}:
20248 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20250 @{address="0x000107bc",func-name="main",offset="0",
20251 inst="save %sp, -112, %sp"@},
20252 @{address="0x000107c0",func-name="main",offset="4",
20253 inst="mov 2, %o0"@},
20254 @{address="0x000107c4",func-name="main",offset="8",
20255 inst="sethi %hi(0x11800), %o2"@}]
20259 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20263 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20265 src_and_asm_line=@{line="31",
20266 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20267 testsuite/gdb.mi/basics.c",line_asm_insn=[
20268 @{address="0x000107bc",func-name="main",offset="0",
20269 inst="save %sp, -112, %sp"@}]@},
20270 src_and_asm_line=@{line="32",
20271 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20272 testsuite/gdb.mi/basics.c",line_asm_insn=[
20273 @{address="0x000107c0",func-name="main",offset="4",
20274 inst="mov 2, %o0"@},
20275 @{address="0x000107c4",func-name="main",offset="8",
20276 inst="sethi %hi(0x11800), %o2"@}]@}]
20281 @subheading The @code{-data-evaluate-expression} Command
20282 @findex -data-evaluate-expression
20284 @subsubheading Synopsis
20287 -data-evaluate-expression @var{expr}
20290 Evaluate @var{expr} as an expression. The expression could contain an
20291 inferior function call. The function call will execute synchronously.
20292 If the expression contains spaces, it must be enclosed in double quotes.
20294 @subsubheading @value{GDBN} Command
20296 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20297 @samp{call}. In @code{gdbtk} only, there's a corresponding
20298 @samp{gdb_eval} command.
20300 @subsubheading Example
20302 In the following example, the numbers that precede the commands are the
20303 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20304 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20308 211-data-evaluate-expression A
20311 311-data-evaluate-expression &A
20312 311^done,value="0xefffeb7c"
20314 411-data-evaluate-expression A+3
20317 511-data-evaluate-expression "A + 3"
20323 @subheading The @code{-data-list-changed-registers} Command
20324 @findex -data-list-changed-registers
20326 @subsubheading Synopsis
20329 -data-list-changed-registers
20332 Display a list of the registers that have changed.
20334 @subsubheading @value{GDBN} Command
20336 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20337 has the corresponding command @samp{gdb_changed_register_list}.
20339 @subsubheading Example
20341 On a PPC MBX board:
20349 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20350 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20352 -data-list-changed-registers
20353 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20354 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20355 "24","25","26","27","28","30","31","64","65","66","67","69"]
20360 @subheading The @code{-data-list-register-names} Command
20361 @findex -data-list-register-names
20363 @subsubheading Synopsis
20366 -data-list-register-names [ ( @var{regno} )+ ]
20369 Show a list of register names for the current target. If no arguments
20370 are given, it shows a list of the names of all the registers. If
20371 integer numbers are given as arguments, it will print a list of the
20372 names of the registers corresponding to the arguments. To ensure
20373 consistency between a register name and its number, the output list may
20374 include empty register names.
20376 @subsubheading @value{GDBN} Command
20378 @value{GDBN} does not have a command which corresponds to
20379 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20380 corresponding command @samp{gdb_regnames}.
20382 @subsubheading Example
20384 For the PPC MBX board:
20387 -data-list-register-names
20388 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20389 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20390 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20391 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20392 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20393 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20394 "", "pc","ps","cr","lr","ctr","xer"]
20396 -data-list-register-names 1 2 3
20397 ^done,register-names=["r1","r2","r3"]
20401 @subheading The @code{-data-list-register-values} Command
20402 @findex -data-list-register-values
20404 @subsubheading Synopsis
20407 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20410 Display the registers' contents. @var{fmt} is the format according to
20411 which the registers' contents are to be returned, followed by an optional
20412 list of numbers specifying the registers to display. A missing list of
20413 numbers indicates that the contents of all the registers must be returned.
20415 Allowed formats for @var{fmt} are:
20432 @subsubheading @value{GDBN} Command
20434 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20435 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20437 @subsubheading Example
20439 For a PPC MBX board (note: line breaks are for readability only, they
20440 don't appear in the actual output):
20444 -data-list-register-values r 64 65
20445 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20446 @{number="65",value="0x00029002"@}]
20448 -data-list-register-values x
20449 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20450 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20451 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20452 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20453 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20454 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20455 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20456 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20457 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20458 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20459 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20460 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20461 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20462 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20463 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20464 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20465 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20466 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20467 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20468 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20469 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20470 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20471 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20472 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20473 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20474 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20475 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20476 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20477 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20478 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20479 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20480 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20481 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20482 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20483 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20484 @{number="69",value="0x20002b03"@}]
20489 @subheading The @code{-data-read-memory} Command
20490 @findex -data-read-memory
20492 @subsubheading Synopsis
20495 -data-read-memory [ -o @var{byte-offset} ]
20496 @var{address} @var{word-format} @var{word-size}
20497 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20504 @item @var{address}
20505 An expression specifying the address of the first memory word to be
20506 read. Complex expressions containing embedded white space should be
20507 quoted using the C convention.
20509 @item @var{word-format}
20510 The format to be used to print the memory words. The notation is the
20511 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20514 @item @var{word-size}
20515 The size of each memory word in bytes.
20517 @item @var{nr-rows}
20518 The number of rows in the output table.
20520 @item @var{nr-cols}
20521 The number of columns in the output table.
20524 If present, indicates that each row should include an @sc{ascii} dump. The
20525 value of @var{aschar} is used as a padding character when a byte is not a
20526 member of the printable @sc{ascii} character set (printable @sc{ascii}
20527 characters are those whose code is between 32 and 126, inclusively).
20529 @item @var{byte-offset}
20530 An offset to add to the @var{address} before fetching memory.
20533 This command displays memory contents as a table of @var{nr-rows} by
20534 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20535 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20536 (returned as @samp{total-bytes}). Should less than the requested number
20537 of bytes be returned by the target, the missing words are identified
20538 using @samp{N/A}. The number of bytes read from the target is returned
20539 in @samp{nr-bytes} and the starting address used to read memory in
20542 The address of the next/previous row or page is available in
20543 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20546 @subsubheading @value{GDBN} Command
20548 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20549 @samp{gdb_get_mem} memory read command.
20551 @subsubheading Example
20553 Read six bytes of memory starting at @code{bytes+6} but then offset by
20554 @code{-6} bytes. Format as three rows of two columns. One byte per
20555 word. Display each word in hex.
20559 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20560 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20561 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20562 prev-page="0x0000138a",memory=[
20563 @{addr="0x00001390",data=["0x00","0x01"]@},
20564 @{addr="0x00001392",data=["0x02","0x03"]@},
20565 @{addr="0x00001394",data=["0x04","0x05"]@}]
20569 Read two bytes of memory starting at address @code{shorts + 64} and
20570 display as a single word formatted in decimal.
20574 5-data-read-memory shorts+64 d 2 1 1
20575 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20576 next-row="0x00001512",prev-row="0x0000150e",
20577 next-page="0x00001512",prev-page="0x0000150e",memory=[
20578 @{addr="0x00001510",data=["128"]@}]
20582 Read thirty two bytes of memory starting at @code{bytes+16} and format
20583 as eight rows of four columns. Include a string encoding with @samp{x}
20584 used as the non-printable character.
20588 4-data-read-memory bytes+16 x 1 8 4 x
20589 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20590 next-row="0x000013c0",prev-row="0x0000139c",
20591 next-page="0x000013c0",prev-page="0x00001380",memory=[
20592 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20593 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20594 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20595 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20596 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20597 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20598 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20599 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20603 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20604 @node GDB/MI Tracepoint Commands
20605 @section @sc{gdb/mi} Tracepoint Commands
20607 The tracepoint commands are not yet implemented.
20609 @c @subheading -trace-actions
20611 @c @subheading -trace-delete
20613 @c @subheading -trace-disable
20615 @c @subheading -trace-dump
20617 @c @subheading -trace-enable
20619 @c @subheading -trace-exists
20621 @c @subheading -trace-find
20623 @c @subheading -trace-frame-number
20625 @c @subheading -trace-info
20627 @c @subheading -trace-insert
20629 @c @subheading -trace-list
20631 @c @subheading -trace-pass-count
20633 @c @subheading -trace-save
20635 @c @subheading -trace-start
20637 @c @subheading -trace-stop
20640 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20641 @node GDB/MI Symbol Query
20642 @section @sc{gdb/mi} Symbol Query Commands
20645 @subheading The @code{-symbol-info-address} Command
20646 @findex -symbol-info-address
20648 @subsubheading Synopsis
20651 -symbol-info-address @var{symbol}
20654 Describe where @var{symbol} is stored.
20656 @subsubheading @value{GDBN} Command
20658 The corresponding @value{GDBN} command is @samp{info address}.
20660 @subsubheading Example
20664 @subheading The @code{-symbol-info-file} Command
20665 @findex -symbol-info-file
20667 @subsubheading Synopsis
20673 Show the file for the symbol.
20675 @subsubheading @value{GDBN} Command
20677 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20678 @samp{gdb_find_file}.
20680 @subsubheading Example
20684 @subheading The @code{-symbol-info-function} Command
20685 @findex -symbol-info-function
20687 @subsubheading Synopsis
20690 -symbol-info-function
20693 Show which function the symbol lives in.
20695 @subsubheading @value{GDBN} Command
20697 @samp{gdb_get_function} in @code{gdbtk}.
20699 @subsubheading Example
20703 @subheading The @code{-symbol-info-line} Command
20704 @findex -symbol-info-line
20706 @subsubheading Synopsis
20712 Show the core addresses of the code for a source line.
20714 @subsubheading @value{GDBN} Command
20716 The corresponding @value{GDBN} command is @samp{info line}.
20717 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20719 @subsubheading Example
20723 @subheading The @code{-symbol-info-symbol} Command
20724 @findex -symbol-info-symbol
20726 @subsubheading Synopsis
20729 -symbol-info-symbol @var{addr}
20732 Describe what symbol is at location @var{addr}.
20734 @subsubheading @value{GDBN} Command
20736 The corresponding @value{GDBN} command is @samp{info symbol}.
20738 @subsubheading Example
20742 @subheading The @code{-symbol-list-functions} Command
20743 @findex -symbol-list-functions
20745 @subsubheading Synopsis
20748 -symbol-list-functions
20751 List the functions in the executable.
20753 @subsubheading @value{GDBN} Command
20755 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20756 @samp{gdb_search} in @code{gdbtk}.
20758 @subsubheading Example
20762 @subheading The @code{-symbol-list-lines} Command
20763 @findex -symbol-list-lines
20765 @subsubheading Synopsis
20768 -symbol-list-lines @var{filename}
20771 Print the list of lines that contain code and their associated program
20772 addresses for the given source filename. The entries are sorted in
20773 ascending PC order.
20775 @subsubheading @value{GDBN} Command
20777 There is no corresponding @value{GDBN} command.
20779 @subsubheading Example
20782 -symbol-list-lines basics.c
20783 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20788 @subheading The @code{-symbol-list-types} Command
20789 @findex -symbol-list-types
20791 @subsubheading Synopsis
20797 List all the type names.
20799 @subsubheading @value{GDBN} Command
20801 The corresponding commands are @samp{info types} in @value{GDBN},
20802 @samp{gdb_search} in @code{gdbtk}.
20804 @subsubheading Example
20808 @subheading The @code{-symbol-list-variables} Command
20809 @findex -symbol-list-variables
20811 @subsubheading Synopsis
20814 -symbol-list-variables
20817 List all the global and static variable names.
20819 @subsubheading @value{GDBN} Command
20821 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20823 @subsubheading Example
20827 @subheading The @code{-symbol-locate} Command
20828 @findex -symbol-locate
20830 @subsubheading Synopsis
20836 @subsubheading @value{GDBN} Command
20838 @samp{gdb_loc} in @code{gdbtk}.
20840 @subsubheading Example
20844 @subheading The @code{-symbol-type} Command
20845 @findex -symbol-type
20847 @subsubheading Synopsis
20850 -symbol-type @var{variable}
20853 Show type of @var{variable}.
20855 @subsubheading @value{GDBN} Command
20857 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20858 @samp{gdb_obj_variable}.
20860 @subsubheading Example
20864 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20865 @node GDB/MI File Commands
20866 @section @sc{gdb/mi} File Commands
20868 This section describes the GDB/MI commands to specify executable file names
20869 and to read in and obtain symbol table information.
20871 @subheading The @code{-file-exec-and-symbols} Command
20872 @findex -file-exec-and-symbols
20874 @subsubheading Synopsis
20877 -file-exec-and-symbols @var{file}
20880 Specify the executable file to be debugged. This file is the one from
20881 which the symbol table is also read. If no file is specified, the
20882 command clears the executable and symbol information. If breakpoints
20883 are set when using this command with no arguments, @value{GDBN} will produce
20884 error messages. Otherwise, no output is produced, except a completion
20887 @subsubheading @value{GDBN} Command
20889 The corresponding @value{GDBN} command is @samp{file}.
20891 @subsubheading Example
20895 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20901 @subheading The @code{-file-exec-file} Command
20902 @findex -file-exec-file
20904 @subsubheading Synopsis
20907 -file-exec-file @var{file}
20910 Specify the executable file to be debugged. Unlike
20911 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20912 from this file. If used without argument, @value{GDBN} clears the information
20913 about the executable file. No output is produced, except a completion
20916 @subsubheading @value{GDBN} Command
20918 The corresponding @value{GDBN} command is @samp{exec-file}.
20920 @subsubheading Example
20924 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20930 @subheading The @code{-file-list-exec-sections} Command
20931 @findex -file-list-exec-sections
20933 @subsubheading Synopsis
20936 -file-list-exec-sections
20939 List the sections of the current executable file.
20941 @subsubheading @value{GDBN} Command
20943 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20944 information as this command. @code{gdbtk} has a corresponding command
20945 @samp{gdb_load_info}.
20947 @subsubheading Example
20951 @subheading The @code{-file-list-exec-source-file} Command
20952 @findex -file-list-exec-source-file
20954 @subsubheading Synopsis
20957 -file-list-exec-source-file
20960 List the line number, the current source file, and the absolute path
20961 to the current source file for the current executable.
20963 @subsubheading @value{GDBN} Command
20965 The @value{GDBN} equivalent is @samp{info source}
20967 @subsubheading Example
20971 123-file-list-exec-source-file
20972 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20977 @subheading The @code{-file-list-exec-source-files} Command
20978 @findex -file-list-exec-source-files
20980 @subsubheading Synopsis
20983 -file-list-exec-source-files
20986 List the source files for the current executable.
20988 It will always output the filename, but only when @value{GDBN} can find
20989 the absolute file name of a source file, will it output the fullname.
20991 @subsubheading @value{GDBN} Command
20993 The @value{GDBN} equivalent is @samp{info sources}.
20994 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20996 @subsubheading Example
20999 -file-list-exec-source-files
21001 @{file=foo.c,fullname=/home/foo.c@},
21002 @{file=/home/bar.c,fullname=/home/bar.c@},
21003 @{file=gdb_could_not_find_fullpath.c@}]
21007 @subheading The @code{-file-list-shared-libraries} Command
21008 @findex -file-list-shared-libraries
21010 @subsubheading Synopsis
21013 -file-list-shared-libraries
21016 List the shared libraries in the program.
21018 @subsubheading @value{GDBN} Command
21020 The corresponding @value{GDBN} command is @samp{info shared}.
21022 @subsubheading Example
21026 @subheading The @code{-file-list-symbol-files} Command
21027 @findex -file-list-symbol-files
21029 @subsubheading Synopsis
21032 -file-list-symbol-files
21037 @subsubheading @value{GDBN} Command
21039 The corresponding @value{GDBN} command is @samp{info file} (part of it).
21041 @subsubheading Example
21045 @subheading The @code{-file-symbol-file} Command
21046 @findex -file-symbol-file
21048 @subsubheading Synopsis
21051 -file-symbol-file @var{file}
21054 Read symbol table info from the specified @var{file} argument. When
21055 used without arguments, clears @value{GDBN}'s symbol table info. No output is
21056 produced, except for a completion notification.
21058 @subsubheading @value{GDBN} Command
21060 The corresponding @value{GDBN} command is @samp{symbol-file}.
21062 @subsubheading Example
21066 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21072 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21073 @node GDB/MI Memory Overlay Commands
21074 @section @sc{gdb/mi} Memory Overlay Commands
21076 The memory overlay commands are not implemented.
21078 @c @subheading -overlay-auto
21080 @c @subheading -overlay-list-mapping-state
21082 @c @subheading -overlay-list-overlays
21084 @c @subheading -overlay-map
21086 @c @subheading -overlay-off
21088 @c @subheading -overlay-on
21090 @c @subheading -overlay-unmap
21092 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21093 @node GDB/MI Signal Handling Commands
21094 @section @sc{gdb/mi} Signal Handling Commands
21096 Signal handling commands are not implemented.
21098 @c @subheading -signal-handle
21100 @c @subheading -signal-list-handle-actions
21102 @c @subheading -signal-list-signal-types
21106 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21107 @node GDB/MI Target Manipulation
21108 @section @sc{gdb/mi} Target Manipulation Commands
21111 @subheading The @code{-target-attach} Command
21112 @findex -target-attach
21114 @subsubheading Synopsis
21117 -target-attach @var{pid} | @var{file}
21120 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
21122 @subsubheading @value{GDBN} Command
21124 The corresponding @value{GDBN} command is @samp{attach}.
21126 @subsubheading Example
21130 @subheading The @code{-target-compare-sections} Command
21131 @findex -target-compare-sections
21133 @subsubheading Synopsis
21136 -target-compare-sections [ @var{section} ]
21139 Compare data of section @var{section} on target to the exec file.
21140 Without the argument, all sections are compared.
21142 @subsubheading @value{GDBN} Command
21144 The @value{GDBN} equivalent is @samp{compare-sections}.
21146 @subsubheading Example
21150 @subheading The @code{-target-detach} Command
21151 @findex -target-detach
21153 @subsubheading Synopsis
21159 Detach from the remote target which normally resumes its execution.
21162 @subsubheading @value{GDBN} Command
21164 The corresponding @value{GDBN} command is @samp{detach}.
21166 @subsubheading Example
21176 @subheading The @code{-target-disconnect} Command
21177 @findex -target-disconnect
21179 @subsubheading Synopsis
21185 Disconnect from the remote target. There's no output and the target is
21186 generally not resumed.
21188 @subsubheading @value{GDBN} Command
21190 The corresponding @value{GDBN} command is @samp{disconnect}.
21192 @subsubheading Example
21202 @subheading The @code{-target-download} Command
21203 @findex -target-download
21205 @subsubheading Synopsis
21211 Loads the executable onto the remote target.
21212 It prints out an update message every half second, which includes the fields:
21216 The name of the section.
21218 The size of what has been sent so far for that section.
21220 The size of the section.
21222 The total size of what was sent so far (the current and the previous sections).
21224 The size of the overall executable to download.
21228 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21229 @sc{gdb/mi} Output Syntax}).
21231 In addition, it prints the name and size of the sections, as they are
21232 downloaded. These messages include the following fields:
21236 The name of the section.
21238 The size of the section.
21240 The size of the overall executable to download.
21244 At the end, a summary is printed.
21246 @subsubheading @value{GDBN} Command
21248 The corresponding @value{GDBN} command is @samp{load}.
21250 @subsubheading Example
21252 Note: each status message appears on a single line. Here the messages
21253 have been broken down so that they can fit onto a page.
21258 +download,@{section=".text",section-size="6668",total-size="9880"@}
21259 +download,@{section=".text",section-sent="512",section-size="6668",
21260 total-sent="512",total-size="9880"@}
21261 +download,@{section=".text",section-sent="1024",section-size="6668",
21262 total-sent="1024",total-size="9880"@}
21263 +download,@{section=".text",section-sent="1536",section-size="6668",
21264 total-sent="1536",total-size="9880"@}
21265 +download,@{section=".text",section-sent="2048",section-size="6668",
21266 total-sent="2048",total-size="9880"@}
21267 +download,@{section=".text",section-sent="2560",section-size="6668",
21268 total-sent="2560",total-size="9880"@}
21269 +download,@{section=".text",section-sent="3072",section-size="6668",
21270 total-sent="3072",total-size="9880"@}
21271 +download,@{section=".text",section-sent="3584",section-size="6668",
21272 total-sent="3584",total-size="9880"@}
21273 +download,@{section=".text",section-sent="4096",section-size="6668",
21274 total-sent="4096",total-size="9880"@}
21275 +download,@{section=".text",section-sent="4608",section-size="6668",
21276 total-sent="4608",total-size="9880"@}
21277 +download,@{section=".text",section-sent="5120",section-size="6668",
21278 total-sent="5120",total-size="9880"@}
21279 +download,@{section=".text",section-sent="5632",section-size="6668",
21280 total-sent="5632",total-size="9880"@}
21281 +download,@{section=".text",section-sent="6144",section-size="6668",
21282 total-sent="6144",total-size="9880"@}
21283 +download,@{section=".text",section-sent="6656",section-size="6668",
21284 total-sent="6656",total-size="9880"@}
21285 +download,@{section=".init",section-size="28",total-size="9880"@}
21286 +download,@{section=".fini",section-size="28",total-size="9880"@}
21287 +download,@{section=".data",section-size="3156",total-size="9880"@}
21288 +download,@{section=".data",section-sent="512",section-size="3156",
21289 total-sent="7236",total-size="9880"@}
21290 +download,@{section=".data",section-sent="1024",section-size="3156",
21291 total-sent="7748",total-size="9880"@}
21292 +download,@{section=".data",section-sent="1536",section-size="3156",
21293 total-sent="8260",total-size="9880"@}
21294 +download,@{section=".data",section-sent="2048",section-size="3156",
21295 total-sent="8772",total-size="9880"@}
21296 +download,@{section=".data",section-sent="2560",section-size="3156",
21297 total-sent="9284",total-size="9880"@}
21298 +download,@{section=".data",section-sent="3072",section-size="3156",
21299 total-sent="9796",total-size="9880"@}
21300 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21306 @subheading The @code{-target-exec-status} Command
21307 @findex -target-exec-status
21309 @subsubheading Synopsis
21312 -target-exec-status
21315 Provide information on the state of the target (whether it is running or
21316 not, for instance).
21318 @subsubheading @value{GDBN} Command
21320 There's no equivalent @value{GDBN} command.
21322 @subsubheading Example
21326 @subheading The @code{-target-list-available-targets} Command
21327 @findex -target-list-available-targets
21329 @subsubheading Synopsis
21332 -target-list-available-targets
21335 List the possible targets to connect to.
21337 @subsubheading @value{GDBN} Command
21339 The corresponding @value{GDBN} command is @samp{help target}.
21341 @subsubheading Example
21345 @subheading The @code{-target-list-current-targets} Command
21346 @findex -target-list-current-targets
21348 @subsubheading Synopsis
21351 -target-list-current-targets
21354 Describe the current target.
21356 @subsubheading @value{GDBN} Command
21358 The corresponding information is printed by @samp{info file} (among
21361 @subsubheading Example
21365 @subheading The @code{-target-list-parameters} Command
21366 @findex -target-list-parameters
21368 @subsubheading Synopsis
21371 -target-list-parameters
21376 @subsubheading @value{GDBN} Command
21380 @subsubheading Example
21384 @subheading The @code{-target-select} Command
21385 @findex -target-select
21387 @subsubheading Synopsis
21390 -target-select @var{type} @var{parameters @dots{}}
21393 Connect @value{GDBN} to the remote target. This command takes two args:
21397 The type of target, for instance @samp{async}, @samp{remote}, etc.
21398 @item @var{parameters}
21399 Device names, host names and the like. @xref{Target Commands, ,
21400 Commands for Managing Targets}, for more details.
21403 The output is a connection notification, followed by the address at
21404 which the target program is, in the following form:
21407 ^connected,addr="@var{address}",func="@var{function name}",
21408 args=[@var{arg list}]
21411 @subsubheading @value{GDBN} Command
21413 The corresponding @value{GDBN} command is @samp{target}.
21415 @subsubheading Example
21419 -target-select async /dev/ttya
21420 ^connected,addr="0xfe00a300",func="??",args=[]
21424 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21425 @node GDB/MI File Transfer Commands
21426 @section @sc{gdb/mi} File Transfer Commands
21429 @subheading The @code{-target-file-put} Command
21430 @findex -target-file-put
21432 @subsubheading Synopsis
21435 -target-file-put @var{hostfile} @var{targetfile}
21438 Copy file @var{hostfile} from the host system (the machine running
21439 @value{GDBN}) to @var{targetfile} on the target system.
21441 @subsubheading @value{GDBN} Command
21443 The corresponding @value{GDBN} command is @samp{remote put}.
21445 @subsubheading Example
21449 -target-file-put localfile remotefile
21455 @subheading The @code{-target-file-put} Command
21456 @findex -target-file-get
21458 @subsubheading Synopsis
21461 -target-file-get @var{targetfile} @var{hostfile}
21464 Copy file @var{targetfile} from the target system to @var{hostfile}
21465 on the host system.
21467 @subsubheading @value{GDBN} Command
21469 The corresponding @value{GDBN} command is @samp{remote get}.
21471 @subsubheading Example
21475 -target-file-get remotefile localfile
21481 @subheading The @code{-target-file-delete} Command
21482 @findex -target-file-delete
21484 @subsubheading Synopsis
21487 -target-file-delete @var{targetfile}
21490 Delete @var{targetfile} from the target system.
21492 @subsubheading @value{GDBN} Command
21494 The corresponding @value{GDBN} command is @samp{remote delete}.
21496 @subsubheading Example
21500 -target-file-delete remotefile
21506 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21507 @node GDB/MI Miscellaneous Commands
21508 @section Miscellaneous @sc{gdb/mi} Commands
21510 @c @subheading -gdb-complete
21512 @subheading The @code{-gdb-exit} Command
21515 @subsubheading Synopsis
21521 Exit @value{GDBN} immediately.
21523 @subsubheading @value{GDBN} Command
21525 Approximately corresponds to @samp{quit}.
21527 @subsubheading Example
21536 @subheading The @code{-exec-abort} Command
21537 @findex -exec-abort
21539 @subsubheading Synopsis
21545 Kill the inferior running program.
21547 @subsubheading @value{GDBN} Command
21549 The corresponding @value{GDBN} command is @samp{kill}.
21551 @subsubheading Example
21555 @subheading The @code{-gdb-set} Command
21558 @subsubheading Synopsis
21564 Set an internal @value{GDBN} variable.
21565 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21567 @subsubheading @value{GDBN} Command
21569 The corresponding @value{GDBN} command is @samp{set}.
21571 @subsubheading Example
21581 @subheading The @code{-gdb-show} Command
21584 @subsubheading Synopsis
21590 Show the current value of a @value{GDBN} variable.
21592 @subsubheading @value{GDBN} Command
21594 The corresponding @value{GDBN} command is @samp{show}.
21596 @subsubheading Example
21605 @c @subheading -gdb-source
21608 @subheading The @code{-gdb-version} Command
21609 @findex -gdb-version
21611 @subsubheading Synopsis
21617 Show version information for @value{GDBN}. Used mostly in testing.
21619 @subsubheading @value{GDBN} Command
21621 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21622 default shows this information when you start an interactive session.
21624 @subsubheading Example
21626 @c This example modifies the actual output from GDB to avoid overfull
21632 ~Copyright 2000 Free Software Foundation, Inc.
21633 ~GDB is free software, covered by the GNU General Public License, and
21634 ~you are welcome to change it and/or distribute copies of it under
21635 ~ certain conditions.
21636 ~Type "show copying" to see the conditions.
21637 ~There is absolutely no warranty for GDB. Type "show warranty" for
21639 ~This GDB was configured as
21640 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21645 @subheading The @code{-list-features} Command
21646 @findex -list-features
21648 Returns a list of particular features of the MI protocol that
21649 this version of gdb implements. A feature can be a command,
21650 or a new field in an output of some command, or even an
21651 important bugfix. While a frontend can sometimes detect presence
21652 of a feature at runtime, it is easier to perform detection at debugger
21655 The command returns a list of strings, with each string naming an
21656 available feature. Each returned string is just a name, it does not
21657 have any internal structure. The list of possible feature names
21663 (gdb) -list-features
21664 ^done,result=["feature1","feature2"]
21667 The current list of features is:
21671 @samp{frozen-varobjs}---indicates presence of the
21672 @code{-var-set-frozen} command, as well as possible presense of the
21673 @code{frozen} field in the output of @code{-varobj-create}.
21675 @samp{pending-breakpoints}---indicates presence of the @code{-f}
21676 option to the @code{-break-insert} command.
21680 @subheading The @code{-interpreter-exec} Command
21681 @findex -interpreter-exec
21683 @subheading Synopsis
21686 -interpreter-exec @var{interpreter} @var{command}
21688 @anchor{-interpreter-exec}
21690 Execute the specified @var{command} in the given @var{interpreter}.
21692 @subheading @value{GDBN} Command
21694 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21696 @subheading Example
21700 -interpreter-exec console "break main"
21701 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21702 &"During symbol reading, bad structure-type format.\n"
21703 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21708 @subheading The @code{-inferior-tty-set} Command
21709 @findex -inferior-tty-set
21711 @subheading Synopsis
21714 -inferior-tty-set /dev/pts/1
21717 Set terminal for future runs of the program being debugged.
21719 @subheading @value{GDBN} Command
21721 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21723 @subheading Example
21727 -inferior-tty-set /dev/pts/1
21732 @subheading The @code{-inferior-tty-show} Command
21733 @findex -inferior-tty-show
21735 @subheading Synopsis
21741 Show terminal for future runs of program being debugged.
21743 @subheading @value{GDBN} Command
21745 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21747 @subheading Example
21751 -inferior-tty-set /dev/pts/1
21755 ^done,inferior_tty_terminal="/dev/pts/1"
21759 @subheading The @code{-enable-timings} Command
21760 @findex -enable-timings
21762 @subheading Synopsis
21765 -enable-timings [yes | no]
21768 Toggle the printing of the wallclock, user and system times for an MI
21769 command as a field in its output. This command is to help frontend
21770 developers optimize the performance of their code. No argument is
21771 equivalent to @samp{yes}.
21773 @subheading @value{GDBN} Command
21777 @subheading Example
21785 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21786 addr="0x080484ed",func="main",file="myprog.c",
21787 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
21788 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
21796 *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
21797 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
21798 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
21799 fullname="/home/nickrob/myprog.c",line="73"@}
21804 @chapter @value{GDBN} Annotations
21806 This chapter describes annotations in @value{GDBN}. Annotations were
21807 designed to interface @value{GDBN} to graphical user interfaces or other
21808 similar programs which want to interact with @value{GDBN} at a
21809 relatively high level.
21811 The annotation mechanism has largely been superseded by @sc{gdb/mi}
21815 This is Edition @value{EDITION}, @value{DATE}.
21819 * Annotations Overview:: What annotations are; the general syntax.
21820 * Server Prefix:: Issuing a command without affecting user state.
21821 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21822 * Errors:: Annotations for error messages.
21823 * Invalidation:: Some annotations describe things now invalid.
21824 * Annotations for Running::
21825 Whether the program is running, how it stopped, etc.
21826 * Source Annotations:: Annotations describing source code.
21829 @node Annotations Overview
21830 @section What is an Annotation?
21831 @cindex annotations
21833 Annotations start with a newline character, two @samp{control-z}
21834 characters, and the name of the annotation. If there is no additional
21835 information associated with this annotation, the name of the annotation
21836 is followed immediately by a newline. If there is additional
21837 information, the name of the annotation is followed by a space, the
21838 additional information, and a newline. The additional information
21839 cannot contain newline characters.
21841 Any output not beginning with a newline and two @samp{control-z}
21842 characters denotes literal output from @value{GDBN}. Currently there is
21843 no need for @value{GDBN} to output a newline followed by two
21844 @samp{control-z} characters, but if there was such a need, the
21845 annotations could be extended with an @samp{escape} annotation which
21846 means those three characters as output.
21848 The annotation @var{level}, which is specified using the
21849 @option{--annotate} command line option (@pxref{Mode Options}), controls
21850 how much information @value{GDBN} prints together with its prompt,
21851 values of expressions, source lines, and other types of output. Level 0
21852 is for no annotations, level 1 is for use when @value{GDBN} is run as a
21853 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21854 for programs that control @value{GDBN}, and level 2 annotations have
21855 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21856 Interface, annotate, GDB's Obsolete Annotations}).
21859 @kindex set annotate
21860 @item set annotate @var{level}
21861 The @value{GDBN} command @code{set annotate} sets the level of
21862 annotations to the specified @var{level}.
21864 @item show annotate
21865 @kindex show annotate
21866 Show the current annotation level.
21869 This chapter describes level 3 annotations.
21871 A simple example of starting up @value{GDBN} with annotations is:
21874 $ @kbd{gdb --annotate=3}
21876 Copyright 2003 Free Software Foundation, Inc.
21877 GDB is free software, covered by the GNU General Public License,
21878 and you are welcome to change it and/or distribute copies of it
21879 under certain conditions.
21880 Type "show copying" to see the conditions.
21881 There is absolutely no warranty for GDB. Type "show warranty"
21883 This GDB was configured as "i386-pc-linux-gnu"
21894 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21895 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21896 denotes a @samp{control-z} character) are annotations; the rest is
21897 output from @value{GDBN}.
21899 @node Server Prefix
21900 @section The Server Prefix
21901 @cindex server prefix
21903 If you prefix a command with @samp{server } then it will not affect
21904 the command history, nor will it affect @value{GDBN}'s notion of which
21905 command to repeat if @key{RET} is pressed on a line by itself. This
21906 means that commands can be run behind a user's back by a front-end in
21907 a transparent manner.
21909 The server prefix does not affect the recording of values into the value
21910 history; to print a value without recording it into the value history,
21911 use the @code{output} command instead of the @code{print} command.
21914 @section Annotation for @value{GDBN} Input
21916 @cindex annotations for prompts
21917 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21918 to know when to send output, when the output from a given command is
21921 Different kinds of input each have a different @dfn{input type}. Each
21922 input type has three annotations: a @code{pre-} annotation, which
21923 denotes the beginning of any prompt which is being output, a plain
21924 annotation, which denotes the end of the prompt, and then a @code{post-}
21925 annotation which denotes the end of any echo which may (or may not) be
21926 associated with the input. For example, the @code{prompt} input type
21927 features the following annotations:
21935 The input types are
21938 @findex pre-prompt annotation
21939 @findex prompt annotation
21940 @findex post-prompt annotation
21942 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21944 @findex pre-commands annotation
21945 @findex commands annotation
21946 @findex post-commands annotation
21948 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21949 command. The annotations are repeated for each command which is input.
21951 @findex pre-overload-choice annotation
21952 @findex overload-choice annotation
21953 @findex post-overload-choice annotation
21954 @item overload-choice
21955 When @value{GDBN} wants the user to select between various overloaded functions.
21957 @findex pre-query annotation
21958 @findex query annotation
21959 @findex post-query annotation
21961 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21963 @findex pre-prompt-for-continue annotation
21964 @findex prompt-for-continue annotation
21965 @findex post-prompt-for-continue annotation
21966 @item prompt-for-continue
21967 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21968 expect this to work well; instead use @code{set height 0} to disable
21969 prompting. This is because the counting of lines is buggy in the
21970 presence of annotations.
21975 @cindex annotations for errors, warnings and interrupts
21977 @findex quit annotation
21982 This annotation occurs right before @value{GDBN} responds to an interrupt.
21984 @findex error annotation
21989 This annotation occurs right before @value{GDBN} responds to an error.
21991 Quit and error annotations indicate that any annotations which @value{GDBN} was
21992 in the middle of may end abruptly. For example, if a
21993 @code{value-history-begin} annotation is followed by a @code{error}, one
21994 cannot expect to receive the matching @code{value-history-end}. One
21995 cannot expect not to receive it either, however; an error annotation
21996 does not necessarily mean that @value{GDBN} is immediately returning all the way
21999 @findex error-begin annotation
22000 A quit or error annotation may be preceded by
22006 Any output between that and the quit or error annotation is the error
22009 Warning messages are not yet annotated.
22010 @c If we want to change that, need to fix warning(), type_error(),
22011 @c range_error(), and possibly other places.
22014 @section Invalidation Notices
22016 @cindex annotations for invalidation messages
22017 The following annotations say that certain pieces of state may have
22021 @findex frames-invalid annotation
22022 @item ^Z^Zframes-invalid
22024 The frames (for example, output from the @code{backtrace} command) may
22027 @findex breakpoints-invalid annotation
22028 @item ^Z^Zbreakpoints-invalid
22030 The breakpoints may have changed. For example, the user just added or
22031 deleted a breakpoint.
22034 @node Annotations for Running
22035 @section Running the Program
22036 @cindex annotations for running programs
22038 @findex starting annotation
22039 @findex stopping annotation
22040 When the program starts executing due to a @value{GDBN} command such as
22041 @code{step} or @code{continue},
22047 is output. When the program stops,
22053 is output. Before the @code{stopped} annotation, a variety of
22054 annotations describe how the program stopped.
22057 @findex exited annotation
22058 @item ^Z^Zexited @var{exit-status}
22059 The program exited, and @var{exit-status} is the exit status (zero for
22060 successful exit, otherwise nonzero).
22062 @findex signalled annotation
22063 @findex signal-name annotation
22064 @findex signal-name-end annotation
22065 @findex signal-string annotation
22066 @findex signal-string-end annotation
22067 @item ^Z^Zsignalled
22068 The program exited with a signal. After the @code{^Z^Zsignalled}, the
22069 annotation continues:
22075 ^Z^Zsignal-name-end
22079 ^Z^Zsignal-string-end
22084 where @var{name} is the name of the signal, such as @code{SIGILL} or
22085 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
22086 as @code{Illegal Instruction} or @code{Segmentation fault}.
22087 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
22088 user's benefit and have no particular format.
22090 @findex signal annotation
22092 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
22093 just saying that the program received the signal, not that it was
22094 terminated with it.
22096 @findex breakpoint annotation
22097 @item ^Z^Zbreakpoint @var{number}
22098 The program hit breakpoint number @var{number}.
22100 @findex watchpoint annotation
22101 @item ^Z^Zwatchpoint @var{number}
22102 The program hit watchpoint number @var{number}.
22105 @node Source Annotations
22106 @section Displaying Source
22107 @cindex annotations for source display
22109 @findex source annotation
22110 The following annotation is used instead of displaying source code:
22113 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
22116 where @var{filename} is an absolute file name indicating which source
22117 file, @var{line} is the line number within that file (where 1 is the
22118 first line in the file), @var{character} is the character position
22119 within the file (where 0 is the first character in the file) (for most
22120 debug formats this will necessarily point to the beginning of a line),
22121 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
22122 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
22123 @var{addr} is the address in the target program associated with the
22124 source which is being displayed. @var{addr} is in the form @samp{0x}
22125 followed by one or more lowercase hex digits (note that this does not
22126 depend on the language).
22129 @chapter Reporting Bugs in @value{GDBN}
22130 @cindex bugs in @value{GDBN}
22131 @cindex reporting bugs in @value{GDBN}
22133 Your bug reports play an essential role in making @value{GDBN} reliable.
22135 Reporting a bug may help you by bringing a solution to your problem, or it
22136 may not. But in any case the principal function of a bug report is to help
22137 the entire community by making the next version of @value{GDBN} work better. Bug
22138 reports are your contribution to the maintenance of @value{GDBN}.
22140 In order for a bug report to serve its purpose, you must include the
22141 information that enables us to fix the bug.
22144 * Bug Criteria:: Have you found a bug?
22145 * Bug Reporting:: How to report bugs
22149 @section Have You Found a Bug?
22150 @cindex bug criteria
22152 If you are not sure whether you have found a bug, here are some guidelines:
22155 @cindex fatal signal
22156 @cindex debugger crash
22157 @cindex crash of debugger
22159 If the debugger gets a fatal signal, for any input whatever, that is a
22160 @value{GDBN} bug. Reliable debuggers never crash.
22162 @cindex error on valid input
22164 If @value{GDBN} produces an error message for valid input, that is a
22165 bug. (Note that if you're cross debugging, the problem may also be
22166 somewhere in the connection to the target.)
22168 @cindex invalid input
22170 If @value{GDBN} does not produce an error message for invalid input,
22171 that is a bug. However, you should note that your idea of
22172 ``invalid input'' might be our idea of ``an extension'' or ``support
22173 for traditional practice''.
22176 If you are an experienced user of debugging tools, your suggestions
22177 for improvement of @value{GDBN} are welcome in any case.
22180 @node Bug Reporting
22181 @section How to Report Bugs
22182 @cindex bug reports
22183 @cindex @value{GDBN} bugs, reporting
22185 A number of companies and individuals offer support for @sc{gnu} products.
22186 If you obtained @value{GDBN} from a support organization, we recommend you
22187 contact that organization first.
22189 You can find contact information for many support companies and
22190 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
22192 @c should add a web page ref...
22194 In any event, we also recommend that you submit bug reports for
22195 @value{GDBN}. The preferred method is to submit them directly using
22196 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
22197 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
22200 @strong{Do not send bug reports to @samp{info-gdb}, or to
22201 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
22202 not want to receive bug reports. Those that do have arranged to receive
22205 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
22206 serves as a repeater. The mailing list and the newsgroup carry exactly
22207 the same messages. Often people think of posting bug reports to the
22208 newsgroup instead of mailing them. This appears to work, but it has one
22209 problem which can be crucial: a newsgroup posting often lacks a mail
22210 path back to the sender. Thus, if we need to ask for more information,
22211 we may be unable to reach you. For this reason, it is better to send
22212 bug reports to the mailing list.
22214 The fundamental principle of reporting bugs usefully is this:
22215 @strong{report all the facts}. If you are not sure whether to state a
22216 fact or leave it out, state it!
22218 Often people omit facts because they think they know what causes the
22219 problem and assume that some details do not matter. Thus, you might
22220 assume that the name of the variable you use in an example does not matter.
22221 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
22222 stray memory reference which happens to fetch from the location where that
22223 name is stored in memory; perhaps, if the name were different, the contents
22224 of that location would fool the debugger into doing the right thing despite
22225 the bug. Play it safe and give a specific, complete example. That is the
22226 easiest thing for you to do, and the most helpful.
22228 Keep in mind that the purpose of a bug report is to enable us to fix the
22229 bug. It may be that the bug has been reported previously, but neither
22230 you nor we can know that unless your bug report is complete and
22233 Sometimes people give a few sketchy facts and ask, ``Does this ring a
22234 bell?'' Those bug reports are useless, and we urge everyone to
22235 @emph{refuse to respond to them} except to chide the sender to report
22238 To enable us to fix the bug, you should include all these things:
22242 The version of @value{GDBN}. @value{GDBN} announces it if you start
22243 with no arguments; you can also print it at any time using @code{show
22246 Without this, we will not know whether there is any point in looking for
22247 the bug in the current version of @value{GDBN}.
22250 The type of machine you are using, and the operating system name and
22254 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
22255 ``@value{GCC}--2.8.1''.
22258 What compiler (and its version) was used to compile the program you are
22259 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
22260 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
22261 to get this information; for other compilers, see the documentation for
22265 The command arguments you gave the compiler to compile your example and
22266 observe the bug. For example, did you use @samp{-O}? To guarantee
22267 you will not omit something important, list them all. A copy of the
22268 Makefile (or the output from make) is sufficient.
22270 If we were to try to guess the arguments, we would probably guess wrong
22271 and then we might not encounter the bug.
22274 A complete input script, and all necessary source files, that will
22278 A description of what behavior you observe that you believe is
22279 incorrect. For example, ``It gets a fatal signal.''
22281 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
22282 will certainly notice it. But if the bug is incorrect output, we might
22283 not notice unless it is glaringly wrong. You might as well not give us
22284 a chance to make a mistake.
22286 Even if the problem you experience is a fatal signal, you should still
22287 say so explicitly. Suppose something strange is going on, such as, your
22288 copy of @value{GDBN} is out of synch, or you have encountered a bug in
22289 the C library on your system. (This has happened!) Your copy might
22290 crash and ours would not. If you told us to expect a crash, then when
22291 ours fails to crash, we would know that the bug was not happening for
22292 us. If you had not told us to expect a crash, then we would not be able
22293 to draw any conclusion from our observations.
22296 @cindex recording a session script
22297 To collect all this information, you can use a session recording program
22298 such as @command{script}, which is available on many Unix systems.
22299 Just run your @value{GDBN} session inside @command{script} and then
22300 include the @file{typescript} file with your bug report.
22302 Another way to record a @value{GDBN} session is to run @value{GDBN}
22303 inside Emacs and then save the entire buffer to a file.
22306 If you wish to suggest changes to the @value{GDBN} source, send us context
22307 diffs. If you even discuss something in the @value{GDBN} source, refer to
22308 it by context, not by line number.
22310 The line numbers in our development sources will not match those in your
22311 sources. Your line numbers would convey no useful information to us.
22315 Here are some things that are not necessary:
22319 A description of the envelope of the bug.
22321 Often people who encounter a bug spend a lot of time investigating
22322 which changes to the input file will make the bug go away and which
22323 changes will not affect it.
22325 This is often time consuming and not very useful, because the way we
22326 will find the bug is by running a single example under the debugger
22327 with breakpoints, not by pure deduction from a series of examples.
22328 We recommend that you save your time for something else.
22330 Of course, if you can find a simpler example to report @emph{instead}
22331 of the original one, that is a convenience for us. Errors in the
22332 output will be easier to spot, running under the debugger will take
22333 less time, and so on.
22335 However, simplification is not vital; if you do not want to do this,
22336 report the bug anyway and send us the entire test case you used.
22339 A patch for the bug.
22341 A patch for the bug does help us if it is a good one. But do not omit
22342 the necessary information, such as the test case, on the assumption that
22343 a patch is all we need. We might see problems with your patch and decide
22344 to fix the problem another way, or we might not understand it at all.
22346 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22347 construct an example that will make the program follow a certain path
22348 through the code. If you do not send us the example, we will not be able
22349 to construct one, so we will not be able to verify that the bug is fixed.
22351 And if we cannot understand what bug you are trying to fix, or why your
22352 patch should be an improvement, we will not install it. A test case will
22353 help us to understand.
22356 A guess about what the bug is or what it depends on.
22358 Such guesses are usually wrong. Even we cannot guess right about such
22359 things without first using the debugger to find the facts.
22362 @c The readline documentation is distributed with the readline code
22363 @c and consists of the two following files:
22365 @c inc-hist.texinfo
22366 @c Use -I with makeinfo to point to the appropriate directory,
22367 @c environment var TEXINPUTS with TeX.
22368 @include rluser.texi
22369 @include inc-hist.texinfo
22372 @node Formatting Documentation
22373 @appendix Formatting Documentation
22375 @cindex @value{GDBN} reference card
22376 @cindex reference card
22377 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22378 for printing with PostScript or Ghostscript, in the @file{gdb}
22379 subdirectory of the main source directory@footnote{In
22380 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22381 release.}. If you can use PostScript or Ghostscript with your printer,
22382 you can print the reference card immediately with @file{refcard.ps}.
22384 The release also includes the source for the reference card. You
22385 can format it, using @TeX{}, by typing:
22391 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22392 mode on US ``letter'' size paper;
22393 that is, on a sheet 11 inches wide by 8.5 inches
22394 high. You will need to specify this form of printing as an option to
22395 your @sc{dvi} output program.
22397 @cindex documentation
22399 All the documentation for @value{GDBN} comes as part of the machine-readable
22400 distribution. The documentation is written in Texinfo format, which is
22401 a documentation system that uses a single source file to produce both
22402 on-line information and a printed manual. You can use one of the Info
22403 formatting commands to create the on-line version of the documentation
22404 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22406 @value{GDBN} includes an already formatted copy of the on-line Info
22407 version of this manual in the @file{gdb} subdirectory. The main Info
22408 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22409 subordinate files matching @samp{gdb.info*} in the same directory. If
22410 necessary, you can print out these files, or read them with any editor;
22411 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22412 Emacs or the standalone @code{info} program, available as part of the
22413 @sc{gnu} Texinfo distribution.
22415 If you want to format these Info files yourself, you need one of the
22416 Info formatting programs, such as @code{texinfo-format-buffer} or
22419 If you have @code{makeinfo} installed, and are in the top level
22420 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22421 version @value{GDBVN}), you can make the Info file by typing:
22428 If you want to typeset and print copies of this manual, you need @TeX{},
22429 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22430 Texinfo definitions file.
22432 @TeX{} is a typesetting program; it does not print files directly, but
22433 produces output files called @sc{dvi} files. To print a typeset
22434 document, you need a program to print @sc{dvi} files. If your system
22435 has @TeX{} installed, chances are it has such a program. The precise
22436 command to use depends on your system; @kbd{lpr -d} is common; another
22437 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22438 require a file name without any extension or a @samp{.dvi} extension.
22440 @TeX{} also requires a macro definitions file called
22441 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22442 written in Texinfo format. On its own, @TeX{} cannot either read or
22443 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22444 and is located in the @file{gdb-@var{version-number}/texinfo}
22447 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22448 typeset and print this manual. First switch to the @file{gdb}
22449 subdirectory of the main source directory (for example, to
22450 @file{gdb-@value{GDBVN}/gdb}) and type:
22456 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22458 @node Installing GDB
22459 @appendix Installing @value{GDBN}
22460 @cindex installation
22463 * Requirements:: Requirements for building @value{GDBN}
22464 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22465 * Separate Objdir:: Compiling @value{GDBN} in another directory
22466 * Config Names:: Specifying names for hosts and targets
22467 * Configure Options:: Summary of options for configure
22471 @section Requirements for Building @value{GDBN}
22472 @cindex building @value{GDBN}, requirements for
22474 Building @value{GDBN} requires various tools and packages to be available.
22475 Other packages will be used only if they are found.
22477 @heading Tools/Packages Necessary for Building @value{GDBN}
22479 @item ISO C90 compiler
22480 @value{GDBN} is written in ISO C90. It should be buildable with any
22481 working C90 compiler, e.g.@: GCC.
22485 @heading Tools/Packages Optional for Building @value{GDBN}
22489 @value{GDBN} can use the Expat XML parsing library. This library may be
22490 included with your operating system distribution; if it is not, you
22491 can get the latest version from @url{http://expat.sourceforge.net}.
22492 The @file{configure} script will search for this library in several
22493 standard locations; if it is installed in an unusual path, you can
22494 use the @option{--with-libexpat-prefix} option to specify its location.
22500 Remote protocol memory maps (@pxref{Memory Map Format})
22502 Target descriptions (@pxref{Target Descriptions})
22504 Remote shared library lists (@pxref{Library List Format})
22506 MS-Windows shared libraries (@pxref{Shared Libraries})
22511 @node Running Configure
22512 @section Invoking the @value{GDBN} @file{configure} Script
22513 @cindex configuring @value{GDBN}
22514 @value{GDBN} comes with a @file{configure} script that automates the process
22515 of preparing @value{GDBN} for installation; you can then use @code{make} to
22516 build the @code{gdb} program.
22518 @c irrelevant in info file; it's as current as the code it lives with.
22519 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22520 look at the @file{README} file in the sources; we may have improved the
22521 installation procedures since publishing this manual.}
22524 The @value{GDBN} distribution includes all the source code you need for
22525 @value{GDBN} in a single directory, whose name is usually composed by
22526 appending the version number to @samp{gdb}.
22528 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22529 @file{gdb-@value{GDBVN}} directory. That directory contains:
22532 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22533 script for configuring @value{GDBN} and all its supporting libraries
22535 @item gdb-@value{GDBVN}/gdb
22536 the source specific to @value{GDBN} itself
22538 @item gdb-@value{GDBVN}/bfd
22539 source for the Binary File Descriptor library
22541 @item gdb-@value{GDBVN}/include
22542 @sc{gnu} include files
22544 @item gdb-@value{GDBVN}/libiberty
22545 source for the @samp{-liberty} free software library
22547 @item gdb-@value{GDBVN}/opcodes
22548 source for the library of opcode tables and disassemblers
22550 @item gdb-@value{GDBVN}/readline
22551 source for the @sc{gnu} command-line interface
22553 @item gdb-@value{GDBVN}/glob
22554 source for the @sc{gnu} filename pattern-matching subroutine
22556 @item gdb-@value{GDBVN}/mmalloc
22557 source for the @sc{gnu} memory-mapped malloc package
22560 The simplest way to configure and build @value{GDBN} is to run @file{configure}
22561 from the @file{gdb-@var{version-number}} source directory, which in
22562 this example is the @file{gdb-@value{GDBVN}} directory.
22564 First switch to the @file{gdb-@var{version-number}} source directory
22565 if you are not already in it; then run @file{configure}. Pass the
22566 identifier for the platform on which @value{GDBN} will run as an
22572 cd gdb-@value{GDBVN}
22573 ./configure @var{host}
22578 where @var{host} is an identifier such as @samp{sun4} or
22579 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22580 (You can often leave off @var{host}; @file{configure} tries to guess the
22581 correct value by examining your system.)
22583 Running @samp{configure @var{host}} and then running @code{make} builds the
22584 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22585 libraries, then @code{gdb} itself. The configured source files, and the
22586 binaries, are left in the corresponding source directories.
22589 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22590 system does not recognize this automatically when you run a different
22591 shell, you may need to run @code{sh} on it explicitly:
22594 sh configure @var{host}
22597 If you run @file{configure} from a directory that contains source
22598 directories for multiple libraries or programs, such as the
22599 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
22601 creates configuration files for every directory level underneath (unless
22602 you tell it not to, with the @samp{--norecursion} option).
22604 You should run the @file{configure} script from the top directory in the
22605 source tree, the @file{gdb-@var{version-number}} directory. If you run
22606 @file{configure} from one of the subdirectories, you will configure only
22607 that subdirectory. That is usually not what you want. In particular,
22608 if you run the first @file{configure} from the @file{gdb} subdirectory
22609 of the @file{gdb-@var{version-number}} directory, you will omit the
22610 configuration of @file{bfd}, @file{readline}, and other sibling
22611 directories of the @file{gdb} subdirectory. This leads to build errors
22612 about missing include files such as @file{bfd/bfd.h}.
22614 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22615 However, you should make sure that the shell on your path (named by
22616 the @samp{SHELL} environment variable) is publicly readable. Remember
22617 that @value{GDBN} uses the shell to start your program---some systems refuse to
22618 let @value{GDBN} debug child processes whose programs are not readable.
22620 @node Separate Objdir
22621 @section Compiling @value{GDBN} in Another Directory
22623 If you want to run @value{GDBN} versions for several host or target machines,
22624 you need a different @code{gdb} compiled for each combination of
22625 host and target. @file{configure} is designed to make this easy by
22626 allowing you to generate each configuration in a separate subdirectory,
22627 rather than in the source directory. If your @code{make} program
22628 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22629 @code{make} in each of these directories builds the @code{gdb}
22630 program specified there.
22632 To build @code{gdb} in a separate directory, run @file{configure}
22633 with the @samp{--srcdir} option to specify where to find the source.
22634 (You also need to specify a path to find @file{configure}
22635 itself from your working directory. If the path to @file{configure}
22636 would be the same as the argument to @samp{--srcdir}, you can leave out
22637 the @samp{--srcdir} option; it is assumed.)
22639 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22640 separate directory for a Sun 4 like this:
22644 cd gdb-@value{GDBVN}
22647 ../gdb-@value{GDBVN}/configure sun4
22652 When @file{configure} builds a configuration using a remote source
22653 directory, it creates a tree for the binaries with the same structure
22654 (and using the same names) as the tree under the source directory. In
22655 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22656 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22657 @file{gdb-sun4/gdb}.
22659 Make sure that your path to the @file{configure} script has just one
22660 instance of @file{gdb} in it. If your path to @file{configure} looks
22661 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22662 one subdirectory of @value{GDBN}, not the whole package. This leads to
22663 build errors about missing include files such as @file{bfd/bfd.h}.
22665 One popular reason to build several @value{GDBN} configurations in separate
22666 directories is to configure @value{GDBN} for cross-compiling (where
22667 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22668 programs that run on another machine---the @dfn{target}).
22669 You specify a cross-debugging target by
22670 giving the @samp{--target=@var{target}} option to @file{configure}.
22672 When you run @code{make} to build a program or library, you must run
22673 it in a configured directory---whatever directory you were in when you
22674 called @file{configure} (or one of its subdirectories).
22676 The @code{Makefile} that @file{configure} generates in each source
22677 directory also runs recursively. If you type @code{make} in a source
22678 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22679 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22680 will build all the required libraries, and then build GDB.
22682 When you have multiple hosts or targets configured in separate
22683 directories, you can run @code{make} on them in parallel (for example,
22684 if they are NFS-mounted on each of the hosts); they will not interfere
22688 @section Specifying Names for Hosts and Targets
22690 The specifications used for hosts and targets in the @file{configure}
22691 script are based on a three-part naming scheme, but some short predefined
22692 aliases are also supported. The full naming scheme encodes three pieces
22693 of information in the following pattern:
22696 @var{architecture}-@var{vendor}-@var{os}
22699 For example, you can use the alias @code{sun4} as a @var{host} argument,
22700 or as the value for @var{target} in a @code{--target=@var{target}}
22701 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22703 The @file{configure} script accompanying @value{GDBN} does not provide
22704 any query facility to list all supported host and target names or
22705 aliases. @file{configure} calls the Bourne shell script
22706 @code{config.sub} to map abbreviations to full names; you can read the
22707 script, if you wish, or you can use it to test your guesses on
22708 abbreviations---for example:
22711 % sh config.sub i386-linux
22713 % sh config.sub alpha-linux
22714 alpha-unknown-linux-gnu
22715 % sh config.sub hp9k700
22717 % sh config.sub sun4
22718 sparc-sun-sunos4.1.1
22719 % sh config.sub sun3
22720 m68k-sun-sunos4.1.1
22721 % sh config.sub i986v
22722 Invalid configuration `i986v': machine `i986v' not recognized
22726 @code{config.sub} is also distributed in the @value{GDBN} source
22727 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22729 @node Configure Options
22730 @section @file{configure} Options
22732 Here is a summary of the @file{configure} options and arguments that
22733 are most often useful for building @value{GDBN}. @file{configure} also has
22734 several other options not listed here. @inforef{What Configure
22735 Does,,configure.info}, for a full explanation of @file{configure}.
22738 configure @r{[}--help@r{]}
22739 @r{[}--prefix=@var{dir}@r{]}
22740 @r{[}--exec-prefix=@var{dir}@r{]}
22741 @r{[}--srcdir=@var{dirname}@r{]}
22742 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22743 @r{[}--target=@var{target}@r{]}
22748 You may introduce options with a single @samp{-} rather than
22749 @samp{--} if you prefer; but you may abbreviate option names if you use
22754 Display a quick summary of how to invoke @file{configure}.
22756 @item --prefix=@var{dir}
22757 Configure the source to install programs and files under directory
22760 @item --exec-prefix=@var{dir}
22761 Configure the source to install programs under directory
22764 @c avoid splitting the warning from the explanation:
22766 @item --srcdir=@var{dirname}
22767 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22768 @code{make} that implements the @code{VPATH} feature.}@*
22769 Use this option to make configurations in directories separate from the
22770 @value{GDBN} source directories. Among other things, you can use this to
22771 build (or maintain) several configurations simultaneously, in separate
22772 directories. @file{configure} writes configuration-specific files in
22773 the current directory, but arranges for them to use the source in the
22774 directory @var{dirname}. @file{configure} creates directories under
22775 the working directory in parallel to the source directories below
22778 @item --norecursion
22779 Configure only the directory level where @file{configure} is executed; do not
22780 propagate configuration to subdirectories.
22782 @item --target=@var{target}
22783 Configure @value{GDBN} for cross-debugging programs running on the specified
22784 @var{target}. Without this option, @value{GDBN} is configured to debug
22785 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22787 There is no convenient way to generate a list of all available targets.
22789 @item @var{host} @dots{}
22790 Configure @value{GDBN} to run on the specified @var{host}.
22792 There is no convenient way to generate a list of all available hosts.
22795 There are many other options available as well, but they are generally
22796 needed for special purposes only.
22798 @node Maintenance Commands
22799 @appendix Maintenance Commands
22800 @cindex maintenance commands
22801 @cindex internal commands
22803 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22804 includes a number of commands intended for @value{GDBN} developers,
22805 that are not documented elsewhere in this manual. These commands are
22806 provided here for reference. (For commands that turn on debugging
22807 messages, see @ref{Debugging Output}.)
22810 @kindex maint agent
22811 @item maint agent @var{expression}
22812 Translate the given @var{expression} into remote agent bytecodes.
22813 This command is useful for debugging the Agent Expression mechanism
22814 (@pxref{Agent Expressions}).
22816 @kindex maint info breakpoints
22817 @item @anchor{maint info breakpoints}maint info breakpoints
22818 Using the same format as @samp{info breakpoints}, display both the
22819 breakpoints you've set explicitly, and those @value{GDBN} is using for
22820 internal purposes. Internal breakpoints are shown with negative
22821 breakpoint numbers. The type column identifies what kind of breakpoint
22826 Normal, explicitly set breakpoint.
22829 Normal, explicitly set watchpoint.
22832 Internal breakpoint, used to handle correctly stepping through
22833 @code{longjmp} calls.
22835 @item longjmp resume
22836 Internal breakpoint at the target of a @code{longjmp}.
22839 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22842 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22845 Shared library events.
22849 @kindex maint check-symtabs
22850 @item maint check-symtabs
22851 Check the consistency of psymtabs and symtabs.
22853 @kindex maint cplus first_component
22854 @item maint cplus first_component @var{name}
22855 Print the first C@t{++} class/namespace component of @var{name}.
22857 @kindex maint cplus namespace
22858 @item maint cplus namespace
22859 Print the list of possible C@t{++} namespaces.
22861 @kindex maint demangle
22862 @item maint demangle @var{name}
22863 Demangle a C@t{++} or Objective-C mangled @var{name}.
22865 @kindex maint deprecate
22866 @kindex maint undeprecate
22867 @cindex deprecated commands
22868 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22869 @itemx maint undeprecate @var{command}
22870 Deprecate or undeprecate the named @var{command}. Deprecated commands
22871 cause @value{GDBN} to issue a warning when you use them. The optional
22872 argument @var{replacement} says which newer command should be used in
22873 favor of the deprecated one; if it is given, @value{GDBN} will mention
22874 the replacement as part of the warning.
22876 @kindex maint dump-me
22877 @item maint dump-me
22878 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22879 Cause a fatal signal in the debugger and force it to dump its core.
22880 This is supported only on systems which support aborting a program
22881 with the @code{SIGQUIT} signal.
22883 @kindex maint internal-error
22884 @kindex maint internal-warning
22885 @item maint internal-error @r{[}@var{message-text}@r{]}
22886 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22887 Cause @value{GDBN} to call the internal function @code{internal_error}
22888 or @code{internal_warning} and hence behave as though an internal error
22889 or internal warning has been detected. In addition to reporting the
22890 internal problem, these functions give the user the opportunity to
22891 either quit @value{GDBN} or create a core file of the current
22892 @value{GDBN} session.
22894 These commands take an optional parameter @var{message-text} that is
22895 used as the text of the error or warning message.
22897 Here's an example of using @code{internal-error}:
22900 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22901 @dots{}/maint.c:121: internal-error: testing, 1, 2
22902 A problem internal to GDB has been detected. Further
22903 debugging may prove unreliable.
22904 Quit this debugging session? (y or n) @kbd{n}
22905 Create a core file? (y or n) @kbd{n}
22909 @kindex maint packet
22910 @item maint packet @var{text}
22911 If @value{GDBN} is talking to an inferior via the serial protocol,
22912 then this command sends the string @var{text} to the inferior, and
22913 displays the response packet. @value{GDBN} supplies the initial
22914 @samp{$} character, the terminating @samp{#} character, and the
22917 @kindex maint print architecture
22918 @item maint print architecture @r{[}@var{file}@r{]}
22919 Print the entire architecture configuration. The optional argument
22920 @var{file} names the file where the output goes.
22922 @kindex maint print c-tdesc
22923 @item maint print c-tdesc
22924 Print the current target description (@pxref{Target Descriptions}) as
22925 a C source file. The created source file can be used in @value{GDBN}
22926 when an XML parser is not available to parse the description.
22928 @kindex maint print dummy-frames
22929 @item maint print dummy-frames
22930 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22933 (@value{GDBP}) @kbd{b add}
22935 (@value{GDBP}) @kbd{print add(2,3)}
22936 Breakpoint 2, add (a=2, b=3) at @dots{}
22938 The program being debugged stopped while in a function called from GDB.
22940 (@value{GDBP}) @kbd{maint print dummy-frames}
22941 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22942 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22943 call_lo=0x01014000 call_hi=0x01014001
22947 Takes an optional file parameter.
22949 @kindex maint print registers
22950 @kindex maint print raw-registers
22951 @kindex maint print cooked-registers
22952 @kindex maint print register-groups
22953 @item maint print registers @r{[}@var{file}@r{]}
22954 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22955 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22956 @itemx maint print register-groups @r{[}@var{file}@r{]}
22957 Print @value{GDBN}'s internal register data structures.
22959 The command @code{maint print raw-registers} includes the contents of
22960 the raw register cache; the command @code{maint print cooked-registers}
22961 includes the (cooked) value of all registers; and the command
22962 @code{maint print register-groups} includes the groups that each
22963 register is a member of. @xref{Registers,, Registers, gdbint,
22964 @value{GDBN} Internals}.
22966 These commands take an optional parameter, a file name to which to
22967 write the information.
22969 @kindex maint print reggroups
22970 @item maint print reggroups @r{[}@var{file}@r{]}
22971 Print @value{GDBN}'s internal register group data structures. The
22972 optional argument @var{file} tells to what file to write the
22975 The register groups info looks like this:
22978 (@value{GDBP}) @kbd{maint print reggroups}
22991 This command forces @value{GDBN} to flush its internal register cache.
22993 @kindex maint print objfiles
22994 @cindex info for known object files
22995 @item maint print objfiles
22996 Print a dump of all known object files. For each object file, this
22997 command prints its name, address in memory, and all of its psymtabs
23000 @kindex maint print statistics
23001 @cindex bcache statistics
23002 @item maint print statistics
23003 This command prints, for each object file in the program, various data
23004 about that object file followed by the byte cache (@dfn{bcache})
23005 statistics for the object file. The objfile data includes the number
23006 of minimal, partial, full, and stabs symbols, the number of types
23007 defined by the objfile, the number of as yet unexpanded psym tables,
23008 the number of line tables and string tables, and the amount of memory
23009 used by the various tables. The bcache statistics include the counts,
23010 sizes, and counts of duplicates of all and unique objects, max,
23011 average, and median entry size, total memory used and its overhead and
23012 savings, and various measures of the hash table size and chain
23015 @kindex maint print target-stack
23016 @cindex target stack description
23017 @item maint print target-stack
23018 A @dfn{target} is an interface between the debugger and a particular
23019 kind of file or process. Targets can be stacked in @dfn{strata},
23020 so that more than one target can potentially respond to a request.
23021 In particular, memory accesses will walk down the stack of targets
23022 until they find a target that is interested in handling that particular
23025 This command prints a short description of each layer that was pushed on
23026 the @dfn{target stack}, starting from the top layer down to the bottom one.
23028 @kindex maint print type
23029 @cindex type chain of a data type
23030 @item maint print type @var{expr}
23031 Print the type chain for a type specified by @var{expr}. The argument
23032 can be either a type name or a symbol. If it is a symbol, the type of
23033 that symbol is described. The type chain produced by this command is
23034 a recursive definition of the data type as stored in @value{GDBN}'s
23035 data structures, including its flags and contained types.
23037 @kindex maint set dwarf2 max-cache-age
23038 @kindex maint show dwarf2 max-cache-age
23039 @item maint set dwarf2 max-cache-age
23040 @itemx maint show dwarf2 max-cache-age
23041 Control the DWARF 2 compilation unit cache.
23043 @cindex DWARF 2 compilation units cache
23044 In object files with inter-compilation-unit references, such as those
23045 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
23046 reader needs to frequently refer to previously read compilation units.
23047 This setting controls how long a compilation unit will remain in the
23048 cache if it is not referenced. A higher limit means that cached
23049 compilation units will be stored in memory longer, and more total
23050 memory will be used. Setting it to zero disables caching, which will
23051 slow down @value{GDBN} startup, but reduce memory consumption.
23053 @kindex maint set profile
23054 @kindex maint show profile
23055 @cindex profiling GDB
23056 @item maint set profile
23057 @itemx maint show profile
23058 Control profiling of @value{GDBN}.
23060 Profiling will be disabled until you use the @samp{maint set profile}
23061 command to enable it. When you enable profiling, the system will begin
23062 collecting timing and execution count data; when you disable profiling or
23063 exit @value{GDBN}, the results will be written to a log file. Remember that
23064 if you use profiling, @value{GDBN} will overwrite the profiling log file
23065 (often called @file{gmon.out}). If you have a record of important profiling
23066 data in a @file{gmon.out} file, be sure to move it to a safe location.
23068 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
23069 compiled with the @samp{-pg} compiler option.
23071 @kindex maint show-debug-regs
23072 @cindex x86 hardware debug registers
23073 @item maint show-debug-regs
23074 Control whether to show variables that mirror the x86 hardware debug
23075 registers. Use @code{ON} to enable, @code{OFF} to disable. If
23076 enabled, the debug registers values are shown when @value{GDBN} inserts or
23077 removes a hardware breakpoint or watchpoint, and when the inferior
23078 triggers a hardware-assisted breakpoint or watchpoint.
23080 @kindex maint space
23081 @cindex memory used by commands
23083 Control whether to display memory usage for each command. If set to a
23084 nonzero value, @value{GDBN} will display how much memory each command
23085 took, following the command's own output. This can also be requested
23086 by invoking @value{GDBN} with the @option{--statistics} command-line
23087 switch (@pxref{Mode Options}).
23090 @cindex time of command execution
23092 Control whether to display the execution time for each command. If
23093 set to a nonzero value, @value{GDBN} will display how much time it
23094 took to execute each command, following the command's own output.
23095 This can also be requested by invoking @value{GDBN} with the
23096 @option{--statistics} command-line switch (@pxref{Mode Options}).
23098 @kindex maint translate-address
23099 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
23100 Find the symbol stored at the location specified by the address
23101 @var{addr} and an optional section name @var{section}. If found,
23102 @value{GDBN} prints the name of the closest symbol and an offset from
23103 the symbol's location to the specified address. This is similar to
23104 the @code{info address} command (@pxref{Symbols}), except that this
23105 command also allows to find symbols in other sections.
23109 The following command is useful for non-interactive invocations of
23110 @value{GDBN}, such as in the test suite.
23113 @item set watchdog @var{nsec}
23114 @kindex set watchdog
23115 @cindex watchdog timer
23116 @cindex timeout for commands
23117 Set the maximum number of seconds @value{GDBN} will wait for the
23118 target operation to finish. If this time expires, @value{GDBN}
23119 reports and error and the command is aborted.
23121 @item show watchdog
23122 Show the current setting of the target wait timeout.
23125 @node Remote Protocol
23126 @appendix @value{GDBN} Remote Serial Protocol
23131 * Stop Reply Packets::
23132 * General Query Packets::
23133 * Register Packet Format::
23134 * Tracepoint Packets::
23135 * Host I/O Packets::
23138 * File-I/O Remote Protocol Extension::
23139 * Library List Format::
23140 * Memory Map Format::
23146 There may be occasions when you need to know something about the
23147 protocol---for example, if there is only one serial port to your target
23148 machine, you might want your program to do something special if it
23149 recognizes a packet meant for @value{GDBN}.
23151 In the examples below, @samp{->} and @samp{<-} are used to indicate
23152 transmitted and received data, respectively.
23154 @cindex protocol, @value{GDBN} remote serial
23155 @cindex serial protocol, @value{GDBN} remote
23156 @cindex remote serial protocol
23157 All @value{GDBN} commands and responses (other than acknowledgments) are
23158 sent as a @var{packet}. A @var{packet} is introduced with the character
23159 @samp{$}, the actual @var{packet-data}, and the terminating character
23160 @samp{#} followed by a two-digit @var{checksum}:
23163 @code{$}@var{packet-data}@code{#}@var{checksum}
23167 @cindex checksum, for @value{GDBN} remote
23169 The two-digit @var{checksum} is computed as the modulo 256 sum of all
23170 characters between the leading @samp{$} and the trailing @samp{#} (an
23171 eight bit unsigned checksum).
23173 Implementors should note that prior to @value{GDBN} 5.0 the protocol
23174 specification also included an optional two-digit @var{sequence-id}:
23177 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
23180 @cindex sequence-id, for @value{GDBN} remote
23182 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
23183 has never output @var{sequence-id}s. Stubs that handle packets added
23184 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
23186 @cindex acknowledgment, for @value{GDBN} remote
23187 When either the host or the target machine receives a packet, the first
23188 response expected is an acknowledgment: either @samp{+} (to indicate
23189 the package was received correctly) or @samp{-} (to request
23193 -> @code{$}@var{packet-data}@code{#}@var{checksum}
23198 The host (@value{GDBN}) sends @var{command}s, and the target (the
23199 debugging stub incorporated in your program) sends a @var{response}. In
23200 the case of step and continue @var{command}s, the response is only sent
23201 when the operation has completed (the target has again stopped).
23203 @var{packet-data} consists of a sequence of characters with the
23204 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
23207 @cindex remote protocol, field separator
23208 Fields within the packet should be separated using @samp{,} @samp{;} or
23209 @samp{:}. Except where otherwise noted all numbers are represented in
23210 @sc{hex} with leading zeros suppressed.
23212 Implementors should note that prior to @value{GDBN} 5.0, the character
23213 @samp{:} could not appear as the third character in a packet (as it
23214 would potentially conflict with the @var{sequence-id}).
23216 @cindex remote protocol, binary data
23217 @anchor{Binary Data}
23218 Binary data in most packets is encoded either as two hexadecimal
23219 digits per byte of binary data. This allowed the traditional remote
23220 protocol to work over connections which were only seven-bit clean.
23221 Some packets designed more recently assume an eight-bit clean
23222 connection, and use a more efficient encoding to send and receive
23225 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
23226 as an escape character. Any escaped byte is transmitted as the escape
23227 character followed by the original character XORed with @code{0x20}.
23228 For example, the byte @code{0x7d} would be transmitted as the two
23229 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
23230 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
23231 @samp{@}}) must always be escaped. Responses sent by the stub
23232 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
23233 is not interpreted as the start of a run-length encoded sequence
23236 Response @var{data} can be run-length encoded to save space.
23237 Run-length encoding replaces runs of identical characters with one
23238 instance of the repeated character, followed by a @samp{*} and a
23239 repeat count. The repeat count is itself sent encoded, to avoid
23240 binary characters in @var{data}: a value of @var{n} is sent as
23241 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
23242 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
23243 code 32) for a repeat count of 3. (This is because run-length
23244 encoding starts to win for counts 3 or more.) Thus, for example,
23245 @samp{0* } is a run-length encoding of ``0000'': the space character
23246 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
23249 The printable characters @samp{#} and @samp{$} or with a numeric value
23250 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
23251 seven repeats (@samp{$}) can be expanded using a repeat count of only
23252 five (@samp{"}). For example, @samp{00000000} can be encoded as
23255 The error response returned for some packets includes a two character
23256 error number. That number is not well defined.
23258 @cindex empty response, for unsupported packets
23259 For any @var{command} not supported by the stub, an empty response
23260 (@samp{$#00}) should be returned. That way it is possible to extend the
23261 protocol. A newer @value{GDBN} can tell if a packet is supported based
23264 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
23265 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
23271 The following table provides a complete list of all currently defined
23272 @var{command}s and their corresponding response @var{data}.
23273 @xref{File-I/O Remote Protocol Extension}, for details about the File
23274 I/O extension of the remote protocol.
23276 Each packet's description has a template showing the packet's overall
23277 syntax, followed by an explanation of the packet's meaning. We
23278 include spaces in some of the templates for clarity; these are not
23279 part of the packet's syntax. No @value{GDBN} packet uses spaces to
23280 separate its components. For example, a template like @samp{foo
23281 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
23282 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
23283 @var{baz}. @value{GDBN} does not transmit a space character between the
23284 @samp{foo} and the @var{bar}, or between the @var{bar} and the
23287 Note that all packet forms beginning with an upper- or lower-case
23288 letter, other than those described here, are reserved for future use.
23290 Here are the packet descriptions.
23295 @cindex @samp{!} packet
23296 Enable extended mode. In extended mode, the remote server is made
23297 persistent. The @samp{R} packet is used to restart the program being
23303 The remote target both supports and has enabled extended mode.
23307 @cindex @samp{?} packet
23308 Indicate the reason the target halted. The reply is the same as for
23312 @xref{Stop Reply Packets}, for the reply specifications.
23314 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
23315 @cindex @samp{A} packet
23316 Initialized @code{argv[]} array passed into program. @var{arglen}
23317 specifies the number of bytes in the hex encoded byte stream
23318 @var{arg}. See @code{gdbserver} for more details.
23323 The arguments were set.
23329 @cindex @samp{b} packet
23330 (Don't use this packet; its behavior is not well-defined.)
23331 Change the serial line speed to @var{baud}.
23333 JTC: @emph{When does the transport layer state change? When it's
23334 received, or after the ACK is transmitted. In either case, there are
23335 problems if the command or the acknowledgment packet is dropped.}
23337 Stan: @emph{If people really wanted to add something like this, and get
23338 it working for the first time, they ought to modify ser-unix.c to send
23339 some kind of out-of-band message to a specially-setup stub and have the
23340 switch happen "in between" packets, so that from remote protocol's point
23341 of view, nothing actually happened.}
23343 @item B @var{addr},@var{mode}
23344 @cindex @samp{B} packet
23345 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23346 breakpoint at @var{addr}.
23348 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23349 (@pxref{insert breakpoint or watchpoint packet}).
23351 @item c @r{[}@var{addr}@r{]}
23352 @cindex @samp{c} packet
23353 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23354 resume at current address.
23357 @xref{Stop Reply Packets}, for the reply specifications.
23359 @item C @var{sig}@r{[};@var{addr}@r{]}
23360 @cindex @samp{C} packet
23361 Continue with signal @var{sig} (hex signal number). If
23362 @samp{;@var{addr}} is omitted, resume at same address.
23365 @xref{Stop Reply Packets}, for the reply specifications.
23368 @cindex @samp{d} packet
23371 Don't use this packet; instead, define a general set packet
23372 (@pxref{General Query Packets}).
23375 @cindex @samp{D} packet
23376 Detach @value{GDBN} from the remote system. Sent to the remote target
23377 before @value{GDBN} disconnects via the @code{detach} command.
23387 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23388 @cindex @samp{F} packet
23389 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23390 This is part of the File-I/O protocol extension. @xref{File-I/O
23391 Remote Protocol Extension}, for the specification.
23394 @anchor{read registers packet}
23395 @cindex @samp{g} packet
23396 Read general registers.
23400 @item @var{XX@dots{}}
23401 Each byte of register data is described by two hex digits. The bytes
23402 with the register are transmitted in target byte order. The size of
23403 each register and their position within the @samp{g} packet are
23404 determined by the @value{GDBN} internal gdbarch functions
23405 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
23406 specification of several standard @samp{g} packets is specified below.
23411 @item G @var{XX@dots{}}
23412 @cindex @samp{G} packet
23413 Write general registers. @xref{read registers packet}, for a
23414 description of the @var{XX@dots{}} data.
23424 @item H @var{c} @var{t}
23425 @cindex @samp{H} packet
23426 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23427 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23428 should be @samp{c} for step and continue operations, @samp{g} for other
23429 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23430 the threads, a thread number, or @samp{0} which means pick any thread.
23441 @c 'H': How restrictive (or permissive) is the thread model. If a
23442 @c thread is selected and stopped, are other threads allowed
23443 @c to continue to execute? As I mentioned above, I think the
23444 @c semantics of each command when a thread is selected must be
23445 @c described. For example:
23447 @c 'g': If the stub supports threads and a specific thread is
23448 @c selected, returns the register block from that thread;
23449 @c otherwise returns current registers.
23451 @c 'G' If the stub supports threads and a specific thread is
23452 @c selected, sets the registers of the register block of
23453 @c that thread; otherwise sets current registers.
23455 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23456 @anchor{cycle step packet}
23457 @cindex @samp{i} packet
23458 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23459 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23460 step starting at that address.
23463 @cindex @samp{I} packet
23464 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23468 @cindex @samp{k} packet
23471 FIXME: @emph{There is no description of how to operate when a specific
23472 thread context has been selected (i.e.@: does 'k' kill only that
23475 @item m @var{addr},@var{length}
23476 @cindex @samp{m} packet
23477 Read @var{length} bytes of memory starting at address @var{addr}.
23478 Note that @var{addr} may not be aligned to any particular boundary.
23480 The stub need not use any particular size or alignment when gathering
23481 data from memory for the response; even if @var{addr} is word-aligned
23482 and @var{length} is a multiple of the word size, the stub is free to
23483 use byte accesses, or not. For this reason, this packet may not be
23484 suitable for accessing memory-mapped I/O devices.
23485 @cindex alignment of remote memory accesses
23486 @cindex size of remote memory accesses
23487 @cindex memory, alignment and size of remote accesses
23491 @item @var{XX@dots{}}
23492 Memory contents; each byte is transmitted as a two-digit hexadecimal
23493 number. The reply may contain fewer bytes than requested if the
23494 server was able to read only part of the region of memory.
23499 @item M @var{addr},@var{length}:@var{XX@dots{}}
23500 @cindex @samp{M} packet
23501 Write @var{length} bytes of memory starting at address @var{addr}.
23502 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23503 hexadecimal number.
23510 for an error (this includes the case where only part of the data was
23515 @cindex @samp{p} packet
23516 Read the value of register @var{n}; @var{n} is in hex.
23517 @xref{read registers packet}, for a description of how the returned
23518 register value is encoded.
23522 @item @var{XX@dots{}}
23523 the register's value
23527 Indicating an unrecognized @var{query}.
23530 @item P @var{n@dots{}}=@var{r@dots{}}
23531 @anchor{write register packet}
23532 @cindex @samp{P} packet
23533 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23534 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23535 digits for each byte in the register (target byte order).
23545 @item q @var{name} @var{params}@dots{}
23546 @itemx Q @var{name} @var{params}@dots{}
23547 @cindex @samp{q} packet
23548 @cindex @samp{Q} packet
23549 General query (@samp{q}) and set (@samp{Q}). These packets are
23550 described fully in @ref{General Query Packets}.
23553 @cindex @samp{r} packet
23554 Reset the entire system.
23556 Don't use this packet; use the @samp{R} packet instead.
23559 @cindex @samp{R} packet
23560 Restart the program being debugged. @var{XX}, while needed, is ignored.
23561 This packet is only available in extended mode.
23563 The @samp{R} packet has no reply.
23565 @item s @r{[}@var{addr}@r{]}
23566 @cindex @samp{s} packet
23567 Single step. @var{addr} is the address at which to resume. If
23568 @var{addr} is omitted, resume at same address.
23571 @xref{Stop Reply Packets}, for the reply specifications.
23573 @item S @var{sig}@r{[};@var{addr}@r{]}
23574 @anchor{step with signal packet}
23575 @cindex @samp{S} packet
23576 Step with signal. This is analogous to the @samp{C} packet, but
23577 requests a single-step, rather than a normal resumption of execution.
23580 @xref{Stop Reply Packets}, for the reply specifications.
23582 @item t @var{addr}:@var{PP},@var{MM}
23583 @cindex @samp{t} packet
23584 Search backwards starting at address @var{addr} for a match with pattern
23585 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23586 @var{addr} must be at least 3 digits.
23589 @cindex @samp{T} packet
23590 Find out if the thread XX is alive.
23595 thread is still alive
23601 Packets starting with @samp{v} are identified by a multi-letter name,
23602 up to the first @samp{;} or @samp{?} (or the end of the packet).
23604 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23605 @cindex @samp{vCont} packet
23606 Resume the inferior, specifying different actions for each thread.
23607 If an action is specified with no @var{tid}, then it is applied to any
23608 threads that don't have a specific action specified; if no default action is
23609 specified then other threads should remain stopped. Specifying multiple
23610 default actions is an error; specifying no actions is also an error.
23611 Thread IDs are specified in hexadecimal. Currently supported actions are:
23617 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23621 Step with signal @var{sig}. @var{sig} should be two hex digits.
23624 The optional @var{addr} argument normally associated with these packets is
23625 not supported in @samp{vCont}.
23628 @xref{Stop Reply Packets}, for the reply specifications.
23631 @cindex @samp{vCont?} packet
23632 Request a list of actions supported by the @samp{vCont} packet.
23636 @item vCont@r{[};@var{action}@dots{}@r{]}
23637 The @samp{vCont} packet is supported. Each @var{action} is a supported
23638 command in the @samp{vCont} packet.
23640 The @samp{vCont} packet is not supported.
23643 @item vFile:@var{operation}:@var{parameter}@dots{}
23644 @cindex @samp{vFile} packet
23645 Perform a file operation on the target system. For details,
23646 see @ref{Host I/O Packets}.
23648 @item vFlashErase:@var{addr},@var{length}
23649 @cindex @samp{vFlashErase} packet
23650 Direct the stub to erase @var{length} bytes of flash starting at
23651 @var{addr}. The region may enclose any number of flash blocks, but
23652 its start and end must fall on block boundaries, as indicated by the
23653 flash block size appearing in the memory map (@pxref{Memory Map
23654 Format}). @value{GDBN} groups flash memory programming operations
23655 together, and sends a @samp{vFlashDone} request after each group; the
23656 stub is allowed to delay erase operation until the @samp{vFlashDone}
23657 packet is received.
23667 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23668 @cindex @samp{vFlashWrite} packet
23669 Direct the stub to write data to flash address @var{addr}. The data
23670 is passed in binary form using the same encoding as for the @samp{X}
23671 packet (@pxref{Binary Data}). The memory ranges specified by
23672 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23673 not overlap, and must appear in order of increasing addresses
23674 (although @samp{vFlashErase} packets for higher addresses may already
23675 have been received; the ordering is guaranteed only between
23676 @samp{vFlashWrite} packets). If a packet writes to an address that was
23677 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23678 target-specific method, the results are unpredictable.
23686 for vFlashWrite addressing non-flash memory
23692 @cindex @samp{vFlashDone} packet
23693 Indicate to the stub that flash programming operation is finished.
23694 The stub is permitted to delay or batch the effects of a group of
23695 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23696 @samp{vFlashDone} packet is received. The contents of the affected
23697 regions of flash memory are unpredictable until the @samp{vFlashDone}
23698 request is completed.
23700 @item X @var{addr},@var{length}:@var{XX@dots{}}
23702 @cindex @samp{X} packet
23703 Write data to memory, where the data is transmitted in binary.
23704 @var{addr} is address, @var{length} is number of bytes,
23705 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23715 @item z @var{type},@var{addr},@var{length}
23716 @itemx Z @var{type},@var{addr},@var{length}
23717 @anchor{insert breakpoint or watchpoint packet}
23718 @cindex @samp{z} packet
23719 @cindex @samp{Z} packets
23720 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23721 watchpoint starting at address @var{address} and covering the next
23722 @var{length} bytes.
23724 Each breakpoint and watchpoint packet @var{type} is documented
23727 @emph{Implementation notes: A remote target shall return an empty string
23728 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23729 remote target shall support either both or neither of a given
23730 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23731 avoid potential problems with duplicate packets, the operations should
23732 be implemented in an idempotent way.}
23734 @item z0,@var{addr},@var{length}
23735 @itemx Z0,@var{addr},@var{length}
23736 @cindex @samp{z0} packet
23737 @cindex @samp{Z0} packet
23738 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23739 @var{addr} of size @var{length}.
23741 A memory breakpoint is implemented by replacing the instruction at
23742 @var{addr} with a software breakpoint or trap instruction. The
23743 @var{length} is used by targets that indicates the size of the
23744 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23745 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23747 @emph{Implementation note: It is possible for a target to copy or move
23748 code that contains memory breakpoints (e.g., when implementing
23749 overlays). The behavior of this packet, in the presence of such a
23750 target, is not defined.}
23762 @item z1,@var{addr},@var{length}
23763 @itemx Z1,@var{addr},@var{length}
23764 @cindex @samp{z1} packet
23765 @cindex @samp{Z1} packet
23766 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23767 address @var{addr} of size @var{length}.
23769 A hardware breakpoint is implemented using a mechanism that is not
23770 dependant on being able to modify the target's memory.
23772 @emph{Implementation note: A hardware breakpoint is not affected by code
23785 @item z2,@var{addr},@var{length}
23786 @itemx Z2,@var{addr},@var{length}
23787 @cindex @samp{z2} packet
23788 @cindex @samp{Z2} packet
23789 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23801 @item z3,@var{addr},@var{length}
23802 @itemx Z3,@var{addr},@var{length}
23803 @cindex @samp{z3} packet
23804 @cindex @samp{Z3} packet
23805 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23817 @item z4,@var{addr},@var{length}
23818 @itemx Z4,@var{addr},@var{length}
23819 @cindex @samp{z4} packet
23820 @cindex @samp{Z4} packet
23821 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23835 @node Stop Reply Packets
23836 @section Stop Reply Packets
23837 @cindex stop reply packets
23839 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23840 receive any of the below as a reply. In the case of the @samp{C},
23841 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23842 when the target halts. In the below the exact meaning of @dfn{signal
23843 number} is defined by the header @file{include/gdb/signals.h} in the
23844 @value{GDBN} source code.
23846 As in the description of request packets, we include spaces in the
23847 reply templates for clarity; these are not part of the reply packet's
23848 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23854 The program received signal number @var{AA} (a two-digit hexadecimal
23855 number). This is equivalent to a @samp{T} response with no
23856 @var{n}:@var{r} pairs.
23858 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23859 @cindex @samp{T} packet reply
23860 The program received signal number @var{AA} (a two-digit hexadecimal
23861 number). This is equivalent to an @samp{S} response, except that the
23862 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23863 and other information directly in the stop reply packet, reducing
23864 round-trip latency. Single-step and breakpoint traps are reported
23865 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23869 If @var{n} is a hexadecimal number, it is a register number, and the
23870 corresponding @var{r} gives that register's value. @var{r} is a
23871 series of bytes in target byte order, with each byte given by a
23872 two-digit hex number.
23875 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23879 If @var{n} is a recognized @dfn{stop reason}, it describes a more
23880 specific event that stopped the target. The currently defined stop
23881 reasons are listed below. @var{aa} should be @samp{05}, the trap
23882 signal. At most one stop reason should be present.
23885 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23886 and go on to the next; this allows us to extend the protocol in the
23890 The currently defined stop reasons are:
23896 The packet indicates a watchpoint hit, and @var{r} is the data address, in
23899 @cindex shared library events, remote reply
23901 The packet indicates that the loaded libraries have changed.
23902 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
23903 list of loaded libraries. @var{r} is ignored.
23907 The process exited, and @var{AA} is the exit status. This is only
23908 applicable to certain targets.
23911 The process terminated with signal @var{AA}.
23913 @item O @var{XX}@dots{}
23914 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23915 written as the program's console output. This can happen at any time
23916 while the program is running and the debugger should continue to wait
23917 for @samp{W}, @samp{T}, etc.
23919 @item F @var{call-id},@var{parameter}@dots{}
23920 @var{call-id} is the identifier which says which host system call should
23921 be called. This is just the name of the function. Translation into the
23922 correct system call is only applicable as it's defined in @value{GDBN}.
23923 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
23926 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23927 this very system call.
23929 The target replies with this packet when it expects @value{GDBN} to
23930 call a host system call on behalf of the target. @value{GDBN} replies
23931 with an appropriate @samp{F} packet and keeps up waiting for the next
23932 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23933 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
23934 Protocol Extension}, for more details.
23938 @node General Query Packets
23939 @section General Query Packets
23940 @cindex remote query requests
23942 Packets starting with @samp{q} are @dfn{general query packets};
23943 packets starting with @samp{Q} are @dfn{general set packets}. General
23944 query and set packets are a semi-unified form for retrieving and
23945 sending information to and from the stub.
23947 The initial letter of a query or set packet is followed by a name
23948 indicating what sort of thing the packet applies to. For example,
23949 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23950 definitions with the stub. These packet names follow some
23955 The name must not contain commas, colons or semicolons.
23957 Most @value{GDBN} query and set packets have a leading upper case
23960 The names of custom vendor packets should use a company prefix, in
23961 lower case, followed by a period. For example, packets designed at
23962 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23963 foos) or @samp{Qacme.bar} (for setting bars).
23966 The name of a query or set packet should be separated from any
23967 parameters by a @samp{:}; the parameters themselves should be
23968 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23969 full packet name, and check for a separator or the end of the packet,
23970 in case two packet names share a common prefix. New packets should not begin
23971 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23972 packets predate these conventions, and have arguments without any terminator
23973 for the packet name; we suspect they are in widespread use in places that
23974 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23975 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23978 Like the descriptions of the other packets, each description here
23979 has a template showing the packet's overall syntax, followed by an
23980 explanation of the packet's meaning. We include spaces in some of the
23981 templates for clarity; these are not part of the packet's syntax. No
23982 @value{GDBN} packet uses spaces to separate its components.
23984 Here are the currently defined query and set packets:
23989 @cindex current thread, remote request
23990 @cindex @samp{qC} packet
23991 Return the current thread id.
23996 Where @var{pid} is an unsigned hexadecimal process id.
23997 @item @r{(anything else)}
23998 Any other reply implies the old pid.
24001 @item qCRC:@var{addr},@var{length}
24002 @cindex CRC of memory block, remote request
24003 @cindex @samp{qCRC} packet
24004 Compute the CRC checksum of a block of memory.
24008 An error (such as memory fault)
24009 @item C @var{crc32}
24010 The specified memory region's checksum is @var{crc32}.
24014 @itemx qsThreadInfo
24015 @cindex list active threads, remote request
24016 @cindex @samp{qfThreadInfo} packet
24017 @cindex @samp{qsThreadInfo} packet
24018 Obtain a list of all active thread ids from the target (OS). Since there
24019 may be too many active threads to fit into one reply packet, this query
24020 works iteratively: it may require more than one query/reply sequence to
24021 obtain the entire list of threads. The first query of the sequence will
24022 be the @samp{qfThreadInfo} query; subsequent queries in the
24023 sequence will be the @samp{qsThreadInfo} query.
24025 NOTE: This packet replaces the @samp{qL} query (see below).
24031 @item m @var{id},@var{id}@dots{}
24032 a comma-separated list of thread ids
24034 (lower case letter @samp{L}) denotes end of list.
24037 In response to each query, the target will reply with a list of one or
24038 more thread ids, in big-endian unsigned hex, separated by commas.
24039 @value{GDBN} will respond to each reply with a request for more thread
24040 ids (using the @samp{qs} form of the query), until the target responds
24041 with @samp{l} (lower-case el, for @dfn{last}).
24043 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
24044 @cindex get thread-local storage address, remote request
24045 @cindex @samp{qGetTLSAddr} packet
24046 Fetch the address associated with thread local storage specified
24047 by @var{thread-id}, @var{offset}, and @var{lm}.
24049 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
24050 thread for which to fetch the TLS address.
24052 @var{offset} is the (big endian, hex encoded) offset associated with the
24053 thread local variable. (This offset is obtained from the debug
24054 information associated with the variable.)
24056 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
24057 the load module associated with the thread local storage. For example,
24058 a @sc{gnu}/Linux system will pass the link map address of the shared
24059 object associated with the thread local storage under consideration.
24060 Other operating environments may choose to represent the load module
24061 differently, so the precise meaning of this parameter will vary.
24065 @item @var{XX}@dots{}
24066 Hex encoded (big endian) bytes representing the address of the thread
24067 local storage requested.
24070 An error occurred. @var{nn} are hex digits.
24073 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
24076 @item qL @var{startflag} @var{threadcount} @var{nextthread}
24077 Obtain thread information from RTOS. Where: @var{startflag} (one hex
24078 digit) is one to indicate the first query and zero to indicate a
24079 subsequent query; @var{threadcount} (two hex digits) is the maximum
24080 number of threads the response packet can contain; and @var{nextthread}
24081 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
24082 returned in the response as @var{argthread}.
24084 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
24088 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
24089 Where: @var{count} (two hex digits) is the number of threads being
24090 returned; @var{done} (one hex digit) is zero to indicate more threads
24091 and one indicates no further threads; @var{argthreadid} (eight hex
24092 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
24093 is a sequence of thread IDs from the target. @var{threadid} (eight hex
24094 digits). See @code{remote.c:parse_threadlist_response()}.
24098 @cindex section offsets, remote request
24099 @cindex @samp{qOffsets} packet
24100 Get section offsets that the target used when relocating the downloaded
24105 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
24106 Relocate the @code{Text} section by @var{xxx} from its original address.
24107 Relocate the @code{Data} section by @var{yyy} from its original address.
24108 If the object file format provides segment information (e.g.@: @sc{elf}
24109 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
24110 segments by the supplied offsets.
24112 @emph{Note: while a @code{Bss} offset may be included in the response,
24113 @value{GDBN} ignores this and instead applies the @code{Data} offset
24114 to the @code{Bss} section.}
24116 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
24117 Relocate the first segment of the object file, which conventionally
24118 contains program code, to a starting address of @var{xxx}. If
24119 @samp{DataSeg} is specified, relocate the second segment, which
24120 conventionally contains modifiable data, to a starting address of
24121 @var{yyy}. @value{GDBN} will report an error if the object file
24122 does not contain segment information, or does not contain at least
24123 as many segments as mentioned in the reply. Extra segments are
24124 kept at fixed offsets relative to the last relocated segment.
24127 @item qP @var{mode} @var{threadid}
24128 @cindex thread information, remote request
24129 @cindex @samp{qP} packet
24130 Returns information on @var{threadid}. Where: @var{mode} is a hex
24131 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
24133 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
24136 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
24138 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
24139 @cindex pass signals to inferior, remote request
24140 @cindex @samp{QPassSignals} packet
24141 @anchor{QPassSignals}
24142 Each listed @var{signal} should be passed directly to the inferior process.
24143 Signals are numbered identically to continue packets and stop replies
24144 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
24145 strictly greater than the previous item. These signals do not need to stop
24146 the inferior, or be reported to @value{GDBN}. All other signals should be
24147 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
24148 combine; any earlier @samp{QPassSignals} list is completely replaced by the
24149 new list. This packet improves performance when using @samp{handle
24150 @var{signal} nostop noprint pass}.
24155 The request succeeded.
24158 An error occurred. @var{nn} are hex digits.
24161 An empty reply indicates that @samp{QPassSignals} is not supported by
24165 Use of this packet is controlled by the @code{set remote pass-signals}
24166 command (@pxref{Remote Configuration, set remote pass-signals}).
24167 This packet is not probed by default; the remote stub must request it,
24168 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24170 @item qRcmd,@var{command}
24171 @cindex execute remote command, remote request
24172 @cindex @samp{qRcmd} packet
24173 @var{command} (hex encoded) is passed to the local interpreter for
24174 execution. Invalid commands should be reported using the output
24175 string. Before the final result packet, the target may also respond
24176 with a number of intermediate @samp{O@var{output}} console output
24177 packets. @emph{Implementors should note that providing access to a
24178 stubs's interpreter may have security implications}.
24183 A command response with no output.
24185 A command response with the hex encoded output string @var{OUTPUT}.
24187 Indicate a badly formed request.
24189 An empty reply indicates that @samp{qRcmd} is not recognized.
24192 (Note that the @code{qRcmd} packet's name is separated from the
24193 command by a @samp{,}, not a @samp{:}, contrary to the naming
24194 conventions above. Please don't use this packet as a model for new
24197 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
24198 @cindex supported packets, remote query
24199 @cindex features of the remote protocol
24200 @cindex @samp{qSupported} packet
24201 @anchor{qSupported}
24202 Tell the remote stub about features supported by @value{GDBN}, and
24203 query the stub for features it supports. This packet allows
24204 @value{GDBN} and the remote stub to take advantage of each others'
24205 features. @samp{qSupported} also consolidates multiple feature probes
24206 at startup, to improve @value{GDBN} performance---a single larger
24207 packet performs better than multiple smaller probe packets on
24208 high-latency links. Some features may enable behavior which must not
24209 be on by default, e.g.@: because it would confuse older clients or
24210 stubs. Other features may describe packets which could be
24211 automatically probed for, but are not. These features must be
24212 reported before @value{GDBN} will use them. This ``default
24213 unsupported'' behavior is not appropriate for all packets, but it
24214 helps to keep the initial connection time under control with new
24215 versions of @value{GDBN} which support increasing numbers of packets.
24219 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
24220 The stub supports or does not support each returned @var{stubfeature},
24221 depending on the form of each @var{stubfeature} (see below for the
24224 An empty reply indicates that @samp{qSupported} is not recognized,
24225 or that no features needed to be reported to @value{GDBN}.
24228 The allowed forms for each feature (either a @var{gdbfeature} in the
24229 @samp{qSupported} packet, or a @var{stubfeature} in the response)
24233 @item @var{name}=@var{value}
24234 The remote protocol feature @var{name} is supported, and associated
24235 with the specified @var{value}. The format of @var{value} depends
24236 on the feature, but it must not include a semicolon.
24238 The remote protocol feature @var{name} is supported, and does not
24239 need an associated value.
24241 The remote protocol feature @var{name} is not supported.
24243 The remote protocol feature @var{name} may be supported, and
24244 @value{GDBN} should auto-detect support in some other way when it is
24245 needed. This form will not be used for @var{gdbfeature} notifications,
24246 but may be used for @var{stubfeature} responses.
24249 Whenever the stub receives a @samp{qSupported} request, the
24250 supplied set of @value{GDBN} features should override any previous
24251 request. This allows @value{GDBN} to put the stub in a known
24252 state, even if the stub had previously been communicating with
24253 a different version of @value{GDBN}.
24255 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
24256 are defined yet. Stubs should ignore any unknown values for
24257 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
24258 packet supports receiving packets of unlimited length (earlier
24259 versions of @value{GDBN} may reject overly long responses). Values
24260 for @var{gdbfeature} may be defined in the future to let the stub take
24261 advantage of new features in @value{GDBN}, e.g.@: incompatible
24262 improvements in the remote protocol---support for unlimited length
24263 responses would be a @var{gdbfeature} example, if it were not implied by
24264 the @samp{qSupported} query. The stub's reply should be independent
24265 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
24266 describes all the features it supports, and then the stub replies with
24267 all the features it supports.
24269 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
24270 responses, as long as each response uses one of the standard forms.
24272 Some features are flags. A stub which supports a flag feature
24273 should respond with a @samp{+} form response. Other features
24274 require values, and the stub should respond with an @samp{=}
24277 Each feature has a default value, which @value{GDBN} will use if
24278 @samp{qSupported} is not available or if the feature is not mentioned
24279 in the @samp{qSupported} response. The default values are fixed; a
24280 stub is free to omit any feature responses that match the defaults.
24282 Not all features can be probed, but for those which can, the probing
24283 mechanism is useful: in some cases, a stub's internal
24284 architecture may not allow the protocol layer to know some information
24285 about the underlying target in advance. This is especially common in
24286 stubs which may be configured for multiple targets.
24288 These are the currently defined stub features and their properties:
24290 @multitable @columnfractions 0.35 0.2 0.12 0.2
24291 @c NOTE: The first row should be @headitem, but we do not yet require
24292 @c a new enough version of Texinfo (4.7) to use @headitem.
24294 @tab Value Required
24298 @item @samp{PacketSize}
24303 @item @samp{qXfer:auxv:read}
24308 @item @samp{qXfer:features:read}
24313 @item @samp{qXfer:libraries:read}
24318 @item @samp{qXfer:memory-map:read}
24323 @item @samp{qXfer:spu:read}
24328 @item @samp{qXfer:spu:write}
24333 @item @samp{QPassSignals}
24340 These are the currently defined stub features, in more detail:
24343 @cindex packet size, remote protocol
24344 @item PacketSize=@var{bytes}
24345 The remote stub can accept packets up to at least @var{bytes} in
24346 length. @value{GDBN} will send packets up to this size for bulk
24347 transfers, and will never send larger packets. This is a limit on the
24348 data characters in the packet, including the frame and checksum.
24349 There is no trailing NUL byte in a remote protocol packet; if the stub
24350 stores packets in a NUL-terminated format, it should allow an extra
24351 byte in its buffer for the NUL. If this stub feature is not supported,
24352 @value{GDBN} guesses based on the size of the @samp{g} packet response.
24354 @item qXfer:auxv:read
24355 The remote stub understands the @samp{qXfer:auxv:read} packet
24356 (@pxref{qXfer auxiliary vector read}).
24358 @item qXfer:features:read
24359 The remote stub understands the @samp{qXfer:features:read} packet
24360 (@pxref{qXfer target description read}).
24362 @item qXfer:libraries:read
24363 The remote stub understands the @samp{qXfer:libraries:read} packet
24364 (@pxref{qXfer library list read}).
24366 @item qXfer:memory-map:read
24367 The remote stub understands the @samp{qXfer:memory-map:read} packet
24368 (@pxref{qXfer memory map read}).
24370 @item qXfer:spu:read
24371 The remote stub understands the @samp{qXfer:spu:read} packet
24372 (@pxref{qXfer spu read}).
24374 @item qXfer:spu:write
24375 The remote stub understands the @samp{qXfer:spu:write} packet
24376 (@pxref{qXfer spu write}).
24379 The remote stub understands the @samp{QPassSignals} packet
24380 (@pxref{QPassSignals}).
24385 @cindex symbol lookup, remote request
24386 @cindex @samp{qSymbol} packet
24387 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24388 requests. Accept requests from the target for the values of symbols.
24393 The target does not need to look up any (more) symbols.
24394 @item qSymbol:@var{sym_name}
24395 The target requests the value of symbol @var{sym_name} (hex encoded).
24396 @value{GDBN} may provide the value by using the
24397 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24401 @item qSymbol:@var{sym_value}:@var{sym_name}
24402 Set the value of @var{sym_name} to @var{sym_value}.
24404 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24405 target has previously requested.
24407 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24408 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24414 The target does not need to look up any (more) symbols.
24415 @item qSymbol:@var{sym_name}
24416 The target requests the value of a new symbol @var{sym_name} (hex
24417 encoded). @value{GDBN} will continue to supply the values of symbols
24418 (if available), until the target ceases to request them.
24423 @xref{Tracepoint Packets}.
24425 @item qThreadExtraInfo,@var{id}
24426 @cindex thread attributes info, remote request
24427 @cindex @samp{qThreadExtraInfo} packet
24428 Obtain a printable string description of a thread's attributes from
24429 the target OS. @var{id} is a thread-id in big-endian hex. This
24430 string may contain anything that the target OS thinks is interesting
24431 for @value{GDBN} to tell the user about the thread. The string is
24432 displayed in @value{GDBN}'s @code{info threads} display. Some
24433 examples of possible thread extra info strings are @samp{Runnable}, or
24434 @samp{Blocked on Mutex}.
24438 @item @var{XX}@dots{}
24439 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
24440 comprising the printable string containing the extra information about
24441 the thread's attributes.
24444 (Note that the @code{qThreadExtraInfo} packet's name is separated from
24445 the command by a @samp{,}, not a @samp{:}, contrary to the naming
24446 conventions above. Please don't use this packet as a model for new
24454 @xref{Tracepoint Packets}.
24456 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
24457 @cindex read special object, remote request
24458 @cindex @samp{qXfer} packet
24459 @anchor{qXfer read}
24460 Read uninterpreted bytes from the target's special data area
24461 identified by the keyword @var{object}. Request @var{length} bytes
24462 starting at @var{offset} bytes into the data. The content and
24463 encoding of @var{annex} is specific to @var{object}; it can supply
24464 additional details about what data to access.
24466 Here are the specific requests of this form defined so far. All
24467 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
24468 formats, listed below.
24471 @item qXfer:auxv:read::@var{offset},@var{length}
24472 @anchor{qXfer auxiliary vector read}
24473 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
24474 auxiliary vector}. Note @var{annex} must be empty.
24476 This packet is not probed by default; the remote stub must request it,
24477 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24479 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
24480 @anchor{qXfer target description read}
24481 Access the @dfn{target description}. @xref{Target Descriptions}. The
24482 annex specifies which XML document to access. The main description is
24483 always loaded from the @samp{target.xml} annex.
24485 This packet is not probed by default; the remote stub must request it,
24486 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24488 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
24489 @anchor{qXfer library list read}
24490 Access the target's list of loaded libraries. @xref{Library List Format}.
24491 The annex part of the generic @samp{qXfer} packet must be empty
24492 (@pxref{qXfer read}).
24494 Targets which maintain a list of libraries in the program's memory do
24495 not need to implement this packet; it is designed for platforms where
24496 the operating system manages the list of loaded libraries.
24498 This packet is not probed by default; the remote stub must request it,
24499 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24501 @item qXfer:memory-map:read::@var{offset},@var{length}
24502 @anchor{qXfer memory map read}
24503 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
24504 annex part of the generic @samp{qXfer} packet must be empty
24505 (@pxref{qXfer read}).
24507 This packet is not probed by default; the remote stub must request it,
24508 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24510 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
24511 @anchor{qXfer spu read}
24512 Read contents of an @code{spufs} file on the target system. The
24513 annex specifies which file to read; it must be of the form
24514 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24515 in the target process, and @var{name} identifes the @code{spufs} file
24516 in that context to be accessed.
24518 This packet is not probed by default; the remote stub must request it,
24519 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24525 Data @var{data} (@pxref{Binary Data}) has been read from the
24526 target. There may be more data at a higher address (although
24527 it is permitted to return @samp{m} even for the last valid
24528 block of data, as long as at least one byte of data was read).
24529 @var{data} may have fewer bytes than the @var{length} in the
24533 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24534 There is no more data to be read. @var{data} may have fewer bytes
24535 than the @var{length} in the request.
24538 The @var{offset} in the request is at the end of the data.
24539 There is no more data to be read.
24542 The request was malformed, or @var{annex} was invalid.
24545 The offset was invalid, or there was an error encountered reading the data.
24546 @var{nn} is a hex-encoded @code{errno} value.
24549 An empty reply indicates the @var{object} string was not recognized by
24550 the stub, or that the object does not support reading.
24553 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24554 @cindex write data into object, remote request
24555 Write uninterpreted bytes into the target's special data area
24556 identified by the keyword @var{object}, starting at @var{offset} bytes
24557 into the data. @var{data}@dots{} is the binary-encoded data
24558 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24559 is specific to @var{object}; it can supply additional details about what data
24562 Here are the specific requests of this form defined so far. All
24563 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
24564 formats, listed below.
24567 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24568 @anchor{qXfer spu write}
24569 Write @var{data} to an @code{spufs} file on the target system. The
24570 annex specifies which file to write; it must be of the form
24571 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24572 in the target process, and @var{name} identifes the @code{spufs} file
24573 in that context to be accessed.
24575 This packet is not probed by default; the remote stub must request it,
24576 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24582 @var{nn} (hex encoded) is the number of bytes written.
24583 This may be fewer bytes than supplied in the request.
24586 The request was malformed, or @var{annex} was invalid.
24589 The offset was invalid, or there was an error encountered writing the data.
24590 @var{nn} is a hex-encoded @code{errno} value.
24593 An empty reply indicates the @var{object} string was not
24594 recognized by the stub, or that the object does not support writing.
24597 @item qXfer:@var{object}:@var{operation}:@dots{}
24598 Requests of this form may be added in the future. When a stub does
24599 not recognize the @var{object} keyword, or its support for
24600 @var{object} does not recognize the @var{operation} keyword, the stub
24601 must respond with an empty packet.
24605 @node Register Packet Format
24606 @section Register Packet Format
24608 The following @code{g}/@code{G} packets have previously been defined.
24609 In the below, some thirty-two bit registers are transferred as
24610 sixty-four bits. Those registers should be zero/sign extended (which?)
24611 to fill the space allocated. Register bytes are transferred in target
24612 byte order. The two nibbles within a register byte are transferred
24613 most-significant - least-significant.
24619 All registers are transferred as thirty-two bit quantities in the order:
24620 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24621 registers; fsr; fir; fp.
24625 All registers are transferred as sixty-four bit quantities (including
24626 thirty-two bit registers such as @code{sr}). The ordering is the same
24631 @node Tracepoint Packets
24632 @section Tracepoint Packets
24633 @cindex tracepoint packets
24634 @cindex packets, tracepoint
24636 Here we describe the packets @value{GDBN} uses to implement
24637 tracepoints (@pxref{Tracepoints}).
24641 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24642 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24643 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24644 the tracepoint is disabled. @var{step} is the tracepoint's step
24645 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24646 present, further @samp{QTDP} packets will follow to specify this
24647 tracepoint's actions.
24652 The packet was understood and carried out.
24654 The packet was not recognized.
24657 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24658 Define actions to be taken when a tracepoint is hit. @var{n} and
24659 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24660 this tracepoint. This packet may only be sent immediately after
24661 another @samp{QTDP} packet that ended with a @samp{-}. If the
24662 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24663 specifying more actions for this tracepoint.
24665 In the series of action packets for a given tracepoint, at most one
24666 can have an @samp{S} before its first @var{action}. If such a packet
24667 is sent, it and the following packets define ``while-stepping''
24668 actions. Any prior packets define ordinary actions --- that is, those
24669 taken when the tracepoint is first hit. If no action packet has an
24670 @samp{S}, then all the packets in the series specify ordinary
24671 tracepoint actions.
24673 The @samp{@var{action}@dots{}} portion of the packet is a series of
24674 actions, concatenated without separators. Each action has one of the
24680 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24681 a hexadecimal number whose @var{i}'th bit is set if register number
24682 @var{i} should be collected. (The least significant bit is numbered
24683 zero.) Note that @var{mask} may be any number of digits long; it may
24684 not fit in a 32-bit word.
24686 @item M @var{basereg},@var{offset},@var{len}
24687 Collect @var{len} bytes of memory starting at the address in register
24688 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24689 @samp{-1}, then the range has a fixed address: @var{offset} is the
24690 address of the lowest byte to collect. The @var{basereg},
24691 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24692 values (the @samp{-1} value for @var{basereg} is a special case).
24694 @item X @var{len},@var{expr}
24695 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24696 it directs. @var{expr} is an agent expression, as described in
24697 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24698 two-digit hex number in the packet; @var{len} is the number of bytes
24699 in the expression (and thus one-half the number of hex digits in the
24704 Any number of actions may be packed together in a single @samp{QTDP}
24705 packet, as long as the packet does not exceed the maximum packet
24706 length (400 bytes, for many stubs). There may be only one @samp{R}
24707 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24708 actions. Any registers referred to by @samp{M} and @samp{X} actions
24709 must be collected by a preceding @samp{R} action. (The
24710 ``while-stepping'' actions are treated as if they were attached to a
24711 separate tracepoint, as far as these restrictions are concerned.)
24716 The packet was understood and carried out.
24718 The packet was not recognized.
24721 @item QTFrame:@var{n}
24722 Select the @var{n}'th tracepoint frame from the buffer, and use the
24723 register and memory contents recorded there to answer subsequent
24724 request packets from @value{GDBN}.
24726 A successful reply from the stub indicates that the stub has found the
24727 requested frame. The response is a series of parts, concatenated
24728 without separators, describing the frame we selected. Each part has
24729 one of the following forms:
24733 The selected frame is number @var{n} in the trace frame buffer;
24734 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24735 was no frame matching the criteria in the request packet.
24738 The selected trace frame records a hit of tracepoint number @var{t};
24739 @var{t} is a hexadecimal number.
24743 @item QTFrame:pc:@var{addr}
24744 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24745 currently selected frame whose PC is @var{addr};
24746 @var{addr} is a hexadecimal number.
24748 @item QTFrame:tdp:@var{t}
24749 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24750 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24751 is a hexadecimal number.
24753 @item QTFrame:range:@var{start}:@var{end}
24754 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24755 currently selected frame whose PC is between @var{start} (inclusive)
24756 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24759 @item QTFrame:outside:@var{start}:@var{end}
24760 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24761 frame @emph{outside} the given range of addresses.
24764 Begin the tracepoint experiment. Begin collecting data from tracepoint
24765 hits in the trace frame buffer.
24768 End the tracepoint experiment. Stop collecting trace frames.
24771 Clear the table of tracepoints, and empty the trace frame buffer.
24773 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24774 Establish the given ranges of memory as ``transparent''. The stub
24775 will answer requests for these ranges from memory's current contents,
24776 if they were not collected as part of the tracepoint hit.
24778 @value{GDBN} uses this to mark read-only regions of memory, like those
24779 containing program code. Since these areas never change, they should
24780 still have the same contents they did when the tracepoint was hit, so
24781 there's no reason for the stub to refuse to provide their contents.
24784 Ask the stub if there is a trace experiment running right now.
24789 There is no trace experiment running.
24791 There is a trace experiment running.
24797 @node Host I/O Packets
24798 @section Host I/O Packets
24799 @cindex Host I/O, remote protocol
24800 @cindex file transfer, remote protocol
24802 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
24803 operations on the far side of a remote link. For example, Host I/O is
24804 used to upload and download files to a remote target with its own
24805 filesystem. Host I/O uses the same constant values and data structure
24806 layout as the target-initiated File-I/O protocol. However, the
24807 Host I/O packets are structured differently. The target-initiated
24808 protocol relies on target memory to store parameters and buffers.
24809 Host I/O requests are initiated by @value{GDBN}, and the
24810 target's memory is not involved. @xref{File-I/O Remote Protocol
24811 Extension}, for more details on the target-initiated protocol.
24813 The Host I/O request packets all encode a single operation along with
24814 its arguments. They have this format:
24818 @item vFile:@var{operation}: @var{parameter}@dots{}
24819 @var{operation} is the name of the particular request; the target
24820 should compare the entire packet name up to the second colon when checking
24821 for a supported operation. The format of @var{parameter} depends on
24822 the operation. Numbers are always passed in hexadecimal. Negative
24823 numbers have an explicit minus sign (i.e.@: two's complement is not
24824 used). Strings (e.g.@: filenames) are encoded as a series of
24825 hexadecimal bytes. The last argument to a system call may be a
24826 buffer of escaped binary data (@pxref{Binary Data}).
24830 The valid responses to Host I/O packets are:
24834 @item F @var{result} [, @var{errno}] [; @var{attachment}]
24835 @var{result} is the integer value returned by this operation, usually
24836 non-negative for success and -1 for errors. If an error has occured,
24837 @var{errno} will be included in the result. @var{errno} will have a
24838 value defined by the File-I/O protocol (@pxref{Errno Values}). For
24839 operations which return data, @var{attachment} supplies the data as a
24840 binary buffer. Binary buffers in response packets are escaped in the
24841 normal way (@pxref{Binary Data}). See the individual packet
24842 documentation for the interpretation of @var{result} and
24846 An empty response indicates that this operation is not recognized.
24850 These are the supported Host I/O operations:
24853 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
24854 Open a file at @var{pathname} and return a file descriptor for it, or
24855 return -1 if an error occurs. @var{pathname} is a string,
24856 @var{flags} is an integer indicating a mask of open flags
24857 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
24858 of mode bits to use if the file is created (@pxref{mode_t Values}).
24859 @xref{open}, for details of the open flags and mode values.
24861 @item vFile:close: @var{fd}
24862 Close the open file corresponding to @var{fd} and return 0, or
24863 -1 if an error occurs.
24865 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
24866 Read data from the open file corresponding to @var{fd}. Up to
24867 @var{count} bytes will be read from the file, starting at @var{offset}
24868 relative to the start of the file. The target may read fewer bytes;
24869 common reasons include packet size limits and an end-of-file
24870 condition. The number of bytes read is returned. Zero should only be
24871 returned for a successful read at the end of the file, or if
24872 @var{count} was zero.
24874 The data read should be returned as a binary attachment on success.
24875 If zero bytes were read, the response should include an empty binary
24876 attachment (i.e.@: a trailing semicolon). The return value is the
24877 number of target bytes read; the binary attachment may be longer if
24878 some characters were escaped.
24880 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
24881 Write @var{data} (a binary buffer) to the open file corresponding
24882 to @var{fd}. Start the write at @var{offset} from the start of the
24883 file. Unlike many @code{write} system calls, there is no
24884 separate @var{count} argument; the length of @var{data} in the
24885 packet is used. @samp{vFile:write} returns the number of bytes written,
24886 which may be shorter than the length of @var{data}, or -1 if an
24889 @item vFile:unlink: @var{pathname}
24890 Delete the file at @var{pathname} on the target. Return 0,
24891 or -1 if an error occurs. @var{pathname} is a string.
24896 @section Interrupts
24897 @cindex interrupts (remote protocol)
24899 When a program on the remote target is running, @value{GDBN} may
24900 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24901 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24902 setting (@pxref{set remotebreak}).
24904 The precise meaning of @code{BREAK} is defined by the transport
24905 mechanism and may, in fact, be undefined. @value{GDBN} does
24906 not currently define a @code{BREAK} mechanism for any of the network
24909 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24910 transport mechanisms. It is represented by sending the single byte
24911 @code{0x03} without any of the usual packet overhead described in
24912 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24913 transmitted as part of a packet, it is considered to be packet data
24914 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24915 (@pxref{X packet}), used for binary downloads, may include an unescaped
24916 @code{0x03} as part of its packet.
24918 Stubs are not required to recognize these interrupt mechanisms and the
24919 precise meaning associated with receipt of the interrupt is
24920 implementation defined. If the stub is successful at interrupting the
24921 running program, it is expected that it will send one of the Stop
24922 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24923 of successfully stopping the program. Interrupts received while the
24924 program is stopped will be discarded.
24929 Example sequence of a target being re-started. Notice how the restart
24930 does not get any direct output:
24935 @emph{target restarts}
24938 <- @code{T001:1234123412341234}
24942 Example sequence of a target being stepped by a single instruction:
24945 -> @code{G1445@dots{}}
24950 <- @code{T001:1234123412341234}
24954 <- @code{1455@dots{}}
24958 @node File-I/O Remote Protocol Extension
24959 @section File-I/O Remote Protocol Extension
24960 @cindex File-I/O remote protocol extension
24963 * File-I/O Overview::
24964 * Protocol Basics::
24965 * The F Request Packet::
24966 * The F Reply Packet::
24967 * The Ctrl-C Message::
24969 * List of Supported Calls::
24970 * Protocol-specific Representation of Datatypes::
24972 * File-I/O Examples::
24975 @node File-I/O Overview
24976 @subsection File-I/O Overview
24977 @cindex file-i/o overview
24979 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24980 target to use the host's file system and console I/O to perform various
24981 system calls. System calls on the target system are translated into a
24982 remote protocol packet to the host system, which then performs the needed
24983 actions and returns a response packet to the target system.
24984 This simulates file system operations even on targets that lack file systems.
24986 The protocol is defined to be independent of both the host and target systems.
24987 It uses its own internal representation of datatypes and values. Both
24988 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24989 translating the system-dependent value representations into the internal
24990 protocol representations when data is transmitted.
24992 The communication is synchronous. A system call is possible only when
24993 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24994 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24995 the target is stopped to allow deterministic access to the target's
24996 memory. Therefore File-I/O is not interruptible by target signals. On
24997 the other hand, it is possible to interrupt File-I/O by a user interrupt
24998 (@samp{Ctrl-C}) within @value{GDBN}.
25000 The target's request to perform a host system call does not finish
25001 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
25002 after finishing the system call, the target returns to continuing the
25003 previous activity (continue, step). No additional continue or step
25004 request from @value{GDBN} is required.
25007 (@value{GDBP}) continue
25008 <- target requests 'system call X'
25009 target is stopped, @value{GDBN} executes system call
25010 -> @value{GDBN} returns result
25011 ... target continues, @value{GDBN} returns to wait for the target
25012 <- target hits breakpoint and sends a Txx packet
25015 The protocol only supports I/O on the console and to regular files on
25016 the host file system. Character or block special devices, pipes,
25017 named pipes, sockets or any other communication method on the host
25018 system are not supported by this protocol.
25020 @node Protocol Basics
25021 @subsection Protocol Basics
25022 @cindex protocol basics, file-i/o
25024 The File-I/O protocol uses the @code{F} packet as the request as well
25025 as reply packet. Since a File-I/O system call can only occur when
25026 @value{GDBN} is waiting for a response from the continuing or stepping target,
25027 the File-I/O request is a reply that @value{GDBN} has to expect as a result
25028 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
25029 This @code{F} packet contains all information needed to allow @value{GDBN}
25030 to call the appropriate host system call:
25034 A unique identifier for the requested system call.
25037 All parameters to the system call. Pointers are given as addresses
25038 in the target memory address space. Pointers to strings are given as
25039 pointer/length pair. Numerical values are given as they are.
25040 Numerical control flags are given in a protocol-specific representation.
25044 At this point, @value{GDBN} has to perform the following actions.
25048 If the parameters include pointer values to data needed as input to a
25049 system call, @value{GDBN} requests this data from the target with a
25050 standard @code{m} packet request. This additional communication has to be
25051 expected by the target implementation and is handled as any other @code{m}
25055 @value{GDBN} translates all value from protocol representation to host
25056 representation as needed. Datatypes are coerced into the host types.
25059 @value{GDBN} calls the system call.
25062 It then coerces datatypes back to protocol representation.
25065 If the system call is expected to return data in buffer space specified
25066 by pointer parameters to the call, the data is transmitted to the
25067 target using a @code{M} or @code{X} packet. This packet has to be expected
25068 by the target implementation and is handled as any other @code{M} or @code{X}
25073 Eventually @value{GDBN} replies with another @code{F} packet which contains all
25074 necessary information for the target to continue. This at least contains
25081 @code{errno}, if has been changed by the system call.
25088 After having done the needed type and value coercion, the target continues
25089 the latest continue or step action.
25091 @node The F Request Packet
25092 @subsection The @code{F} Request Packet
25093 @cindex file-i/o request packet
25094 @cindex @code{F} request packet
25096 The @code{F} request packet has the following format:
25099 @item F@var{call-id},@var{parameter@dots{}}
25101 @var{call-id} is the identifier to indicate the host system call to be called.
25102 This is just the name of the function.
25104 @var{parameter@dots{}} are the parameters to the system call.
25105 Parameters are hexadecimal integer values, either the actual values in case
25106 of scalar datatypes, pointers to target buffer space in case of compound
25107 datatypes and unspecified memory areas, or pointer/length pairs in case
25108 of string parameters. These are appended to the @var{call-id} as a
25109 comma-delimited list. All values are transmitted in ASCII
25110 string representation, pointer/length pairs separated by a slash.
25116 @node The F Reply Packet
25117 @subsection The @code{F} Reply Packet
25118 @cindex file-i/o reply packet
25119 @cindex @code{F} reply packet
25121 The @code{F} reply packet has the following format:
25125 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
25127 @var{retcode} is the return code of the system call as hexadecimal value.
25129 @var{errno} is the @code{errno} set by the call, in protocol-specific
25131 This parameter can be omitted if the call was successful.
25133 @var{Ctrl-C flag} is only sent if the user requested a break. In this
25134 case, @var{errno} must be sent as well, even if the call was successful.
25135 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
25142 or, if the call was interrupted before the host call has been performed:
25149 assuming 4 is the protocol-specific representation of @code{EINTR}.
25154 @node The Ctrl-C Message
25155 @subsection The @samp{Ctrl-C} Message
25156 @cindex ctrl-c message, in file-i/o protocol
25158 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
25159 reply packet (@pxref{The F Reply Packet}),
25160 the target should behave as if it had
25161 gotten a break message. The meaning for the target is ``system call
25162 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
25163 (as with a break message) and return to @value{GDBN} with a @code{T02}
25166 It's important for the target to know in which
25167 state the system call was interrupted. There are two possible cases:
25171 The system call hasn't been performed on the host yet.
25174 The system call on the host has been finished.
25178 These two states can be distinguished by the target by the value of the
25179 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
25180 call hasn't been performed. This is equivalent to the @code{EINTR} handling
25181 on POSIX systems. In any other case, the target may presume that the
25182 system call has been finished --- successfully or not --- and should behave
25183 as if the break message arrived right after the system call.
25185 @value{GDBN} must behave reliably. If the system call has not been called
25186 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
25187 @code{errno} in the packet. If the system call on the host has been finished
25188 before the user requests a break, the full action must be finished by
25189 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
25190 The @code{F} packet may only be sent when either nothing has happened
25191 or the full action has been completed.
25194 @subsection Console I/O
25195 @cindex console i/o as part of file-i/o
25197 By default and if not explicitly closed by the target system, the file
25198 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
25199 on the @value{GDBN} console is handled as any other file output operation
25200 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
25201 by @value{GDBN} so that after the target read request from file descriptor
25202 0 all following typing is buffered until either one of the following
25207 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
25209 system call is treated as finished.
25212 The user presses @key{RET}. This is treated as end of input with a trailing
25216 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
25217 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
25221 If the user has typed more characters than fit in the buffer given to
25222 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
25223 either another @code{read(0, @dots{})} is requested by the target, or debugging
25224 is stopped at the user's request.
25227 @node List of Supported Calls
25228 @subsection List of Supported Calls
25229 @cindex list of supported file-i/o calls
25246 @unnumberedsubsubsec open
25247 @cindex open, file-i/o system call
25252 int open(const char *pathname, int flags);
25253 int open(const char *pathname, int flags, mode_t mode);
25257 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
25260 @var{flags} is the bitwise @code{OR} of the following values:
25264 If the file does not exist it will be created. The host
25265 rules apply as far as file ownership and time stamps
25269 When used with @code{O_CREAT}, if the file already exists it is
25270 an error and open() fails.
25273 If the file already exists and the open mode allows
25274 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
25275 truncated to zero length.
25278 The file is opened in append mode.
25281 The file is opened for reading only.
25284 The file is opened for writing only.
25287 The file is opened for reading and writing.
25291 Other bits are silently ignored.
25295 @var{mode} is the bitwise @code{OR} of the following values:
25299 User has read permission.
25302 User has write permission.
25305 Group has read permission.
25308 Group has write permission.
25311 Others have read permission.
25314 Others have write permission.
25318 Other bits are silently ignored.
25321 @item Return value:
25322 @code{open} returns the new file descriptor or -1 if an error
25329 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
25332 @var{pathname} refers to a directory.
25335 The requested access is not allowed.
25338 @var{pathname} was too long.
25341 A directory component in @var{pathname} does not exist.
25344 @var{pathname} refers to a device, pipe, named pipe or socket.
25347 @var{pathname} refers to a file on a read-only filesystem and
25348 write access was requested.
25351 @var{pathname} is an invalid pointer value.
25354 No space on device to create the file.
25357 The process already has the maximum number of files open.
25360 The limit on the total number of files open on the system
25364 The call was interrupted by the user.
25370 @unnumberedsubsubsec close
25371 @cindex close, file-i/o system call
25380 @samp{Fclose,@var{fd}}
25382 @item Return value:
25383 @code{close} returns zero on success, or -1 if an error occurred.
25389 @var{fd} isn't a valid open file descriptor.
25392 The call was interrupted by the user.
25398 @unnumberedsubsubsec read
25399 @cindex read, file-i/o system call
25404 int read(int fd, void *buf, unsigned int count);
25408 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
25410 @item Return value:
25411 On success, the number of bytes read is returned.
25412 Zero indicates end of file. If count is zero, read
25413 returns zero as well. On error, -1 is returned.
25419 @var{fd} is not a valid file descriptor or is not open for
25423 @var{bufptr} is an invalid pointer value.
25426 The call was interrupted by the user.
25432 @unnumberedsubsubsec write
25433 @cindex write, file-i/o system call
25438 int write(int fd, const void *buf, unsigned int count);
25442 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
25444 @item Return value:
25445 On success, the number of bytes written are returned.
25446 Zero indicates nothing was written. On error, -1
25453 @var{fd} is not a valid file descriptor or is not open for
25457 @var{bufptr} is an invalid pointer value.
25460 An attempt was made to write a file that exceeds the
25461 host-specific maximum file size allowed.
25464 No space on device to write the data.
25467 The call was interrupted by the user.
25473 @unnumberedsubsubsec lseek
25474 @cindex lseek, file-i/o system call
25479 long lseek (int fd, long offset, int flag);
25483 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
25485 @var{flag} is one of:
25489 The offset is set to @var{offset} bytes.
25492 The offset is set to its current location plus @var{offset}
25496 The offset is set to the size of the file plus @var{offset}
25500 @item Return value:
25501 On success, the resulting unsigned offset in bytes from
25502 the beginning of the file is returned. Otherwise, a
25503 value of -1 is returned.
25509 @var{fd} is not a valid open file descriptor.
25512 @var{fd} is associated with the @value{GDBN} console.
25515 @var{flag} is not a proper value.
25518 The call was interrupted by the user.
25524 @unnumberedsubsubsec rename
25525 @cindex rename, file-i/o system call
25530 int rename(const char *oldpath, const char *newpath);
25534 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
25536 @item Return value:
25537 On success, zero is returned. On error, -1 is returned.
25543 @var{newpath} is an existing directory, but @var{oldpath} is not a
25547 @var{newpath} is a non-empty directory.
25550 @var{oldpath} or @var{newpath} is a directory that is in use by some
25554 An attempt was made to make a directory a subdirectory
25558 A component used as a directory in @var{oldpath} or new
25559 path is not a directory. Or @var{oldpath} is a directory
25560 and @var{newpath} exists but is not a directory.
25563 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
25566 No access to the file or the path of the file.
25570 @var{oldpath} or @var{newpath} was too long.
25573 A directory component in @var{oldpath} or @var{newpath} does not exist.
25576 The file is on a read-only filesystem.
25579 The device containing the file has no room for the new
25583 The call was interrupted by the user.
25589 @unnumberedsubsubsec unlink
25590 @cindex unlink, file-i/o system call
25595 int unlink(const char *pathname);
25599 @samp{Funlink,@var{pathnameptr}/@var{len}}
25601 @item Return value:
25602 On success, zero is returned. On error, -1 is returned.
25608 No access to the file or the path of the file.
25611 The system does not allow unlinking of directories.
25614 The file @var{pathname} cannot be unlinked because it's
25615 being used by another process.
25618 @var{pathnameptr} is an invalid pointer value.
25621 @var{pathname} was too long.
25624 A directory component in @var{pathname} does not exist.
25627 A component of the path is not a directory.
25630 The file is on a read-only filesystem.
25633 The call was interrupted by the user.
25639 @unnumberedsubsubsec stat/fstat
25640 @cindex fstat, file-i/o system call
25641 @cindex stat, file-i/o system call
25646 int stat(const char *pathname, struct stat *buf);
25647 int fstat(int fd, struct stat *buf);
25651 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25652 @samp{Ffstat,@var{fd},@var{bufptr}}
25654 @item Return value:
25655 On success, zero is returned. On error, -1 is returned.
25661 @var{fd} is not a valid open file.
25664 A directory component in @var{pathname} does not exist or the
25665 path is an empty string.
25668 A component of the path is not a directory.
25671 @var{pathnameptr} is an invalid pointer value.
25674 No access to the file or the path of the file.
25677 @var{pathname} was too long.
25680 The call was interrupted by the user.
25686 @unnumberedsubsubsec gettimeofday
25687 @cindex gettimeofday, file-i/o system call
25692 int gettimeofday(struct timeval *tv, void *tz);
25696 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25698 @item Return value:
25699 On success, 0 is returned, -1 otherwise.
25705 @var{tz} is a non-NULL pointer.
25708 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25714 @unnumberedsubsubsec isatty
25715 @cindex isatty, file-i/o system call
25720 int isatty(int fd);
25724 @samp{Fisatty,@var{fd}}
25726 @item Return value:
25727 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
25733 The call was interrupted by the user.
25738 Note that the @code{isatty} call is treated as a special case: it returns
25739 1 to the target if the file descriptor is attached
25740 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
25741 would require implementing @code{ioctl} and would be more complex than
25746 @unnumberedsubsubsec system
25747 @cindex system, file-i/o system call
25752 int system(const char *command);
25756 @samp{Fsystem,@var{commandptr}/@var{len}}
25758 @item Return value:
25759 If @var{len} is zero, the return value indicates whether a shell is
25760 available. A zero return value indicates a shell is not available.
25761 For non-zero @var{len}, the value returned is -1 on error and the
25762 return status of the command otherwise. Only the exit status of the
25763 command is returned, which is extracted from the host's @code{system}
25764 return value by calling @code{WEXITSTATUS(retval)}. In case
25765 @file{/bin/sh} could not be executed, 127 is returned.
25771 The call was interrupted by the user.
25776 @value{GDBN} takes over the full task of calling the necessary host calls
25777 to perform the @code{system} call. The return value of @code{system} on
25778 the host is simplified before it's returned
25779 to the target. Any termination signal information from the child process
25780 is discarded, and the return value consists
25781 entirely of the exit status of the called command.
25783 Due to security concerns, the @code{system} call is by default refused
25784 by @value{GDBN}. The user has to allow this call explicitly with the
25785 @code{set remote system-call-allowed 1} command.
25788 @item set remote system-call-allowed
25789 @kindex set remote system-call-allowed
25790 Control whether to allow the @code{system} calls in the File I/O
25791 protocol for the remote target. The default is zero (disabled).
25793 @item show remote system-call-allowed
25794 @kindex show remote system-call-allowed
25795 Show whether the @code{system} calls are allowed in the File I/O
25799 @node Protocol-specific Representation of Datatypes
25800 @subsection Protocol-specific Representation of Datatypes
25801 @cindex protocol-specific representation of datatypes, in file-i/o protocol
25804 * Integral Datatypes::
25806 * Memory Transfer::
25811 @node Integral Datatypes
25812 @unnumberedsubsubsec Integral Datatypes
25813 @cindex integral datatypes, in file-i/o protocol
25815 The integral datatypes used in the system calls are @code{int},
25816 @code{unsigned int}, @code{long}, @code{unsigned long},
25817 @code{mode_t}, and @code{time_t}.
25819 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25820 implemented as 32 bit values in this protocol.
25822 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25824 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25825 in @file{limits.h}) to allow range checking on host and target.
25827 @code{time_t} datatypes are defined as seconds since the Epoch.
25829 All integral datatypes transferred as part of a memory read or write of a
25830 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25833 @node Pointer Values
25834 @unnumberedsubsubsec Pointer Values
25835 @cindex pointer values, in file-i/o protocol
25837 Pointers to target data are transmitted as they are. An exception
25838 is made for pointers to buffers for which the length isn't
25839 transmitted as part of the function call, namely strings. Strings
25840 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25847 which is a pointer to data of length 18 bytes at position 0x1aaf.
25848 The length is defined as the full string length in bytes, including
25849 the trailing null byte. For example, the string @code{"hello world"}
25850 at address 0x123456 is transmitted as
25856 @node Memory Transfer
25857 @unnumberedsubsubsec Memory Transfer
25858 @cindex memory transfer, in file-i/o protocol
25860 Structured data which is transferred using a memory read or write (for
25861 example, a @code{struct stat}) is expected to be in a protocol-specific format
25862 with all scalar multibyte datatypes being big endian. Translation to
25863 this representation needs to be done both by the target before the @code{F}
25864 packet is sent, and by @value{GDBN} before
25865 it transfers memory to the target. Transferred pointers to structured
25866 data should point to the already-coerced data at any time.
25870 @unnumberedsubsubsec struct stat
25871 @cindex struct stat, in file-i/o protocol
25873 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25874 is defined as follows:
25878 unsigned int st_dev; /* device */
25879 unsigned int st_ino; /* inode */
25880 mode_t st_mode; /* protection */
25881 unsigned int st_nlink; /* number of hard links */
25882 unsigned int st_uid; /* user ID of owner */
25883 unsigned int st_gid; /* group ID of owner */
25884 unsigned int st_rdev; /* device type (if inode device) */
25885 unsigned long st_size; /* total size, in bytes */
25886 unsigned long st_blksize; /* blocksize for filesystem I/O */
25887 unsigned long st_blocks; /* number of blocks allocated */
25888 time_t st_atime; /* time of last access */
25889 time_t st_mtime; /* time of last modification */
25890 time_t st_ctime; /* time of last change */
25894 The integral datatypes conform to the definitions given in the
25895 appropriate section (see @ref{Integral Datatypes}, for details) so this
25896 structure is of size 64 bytes.
25898 The values of several fields have a restricted meaning and/or
25904 A value of 0 represents a file, 1 the console.
25907 No valid meaning for the target. Transmitted unchanged.
25910 Valid mode bits are described in @ref{Constants}. Any other
25911 bits have currently no meaning for the target.
25916 No valid meaning for the target. Transmitted unchanged.
25921 These values have a host and file system dependent
25922 accuracy. Especially on Windows hosts, the file system may not
25923 support exact timing values.
25926 The target gets a @code{struct stat} of the above representation and is
25927 responsible for coercing it to the target representation before
25930 Note that due to size differences between the host, target, and protocol
25931 representations of @code{struct stat} members, these members could eventually
25932 get truncated on the target.
25934 @node struct timeval
25935 @unnumberedsubsubsec struct timeval
25936 @cindex struct timeval, in file-i/o protocol
25938 The buffer of type @code{struct timeval} used by the File-I/O protocol
25939 is defined as follows:
25943 time_t tv_sec; /* second */
25944 long tv_usec; /* microsecond */
25948 The integral datatypes conform to the definitions given in the
25949 appropriate section (see @ref{Integral Datatypes}, for details) so this
25950 structure is of size 8 bytes.
25953 @subsection Constants
25954 @cindex constants, in file-i/o protocol
25956 The following values are used for the constants inside of the
25957 protocol. @value{GDBN} and target are responsible for translating these
25958 values before and after the call as needed.
25969 @unnumberedsubsubsec Open Flags
25970 @cindex open flags, in file-i/o protocol
25972 All values are given in hexadecimal representation.
25984 @node mode_t Values
25985 @unnumberedsubsubsec mode_t Values
25986 @cindex mode_t values, in file-i/o protocol
25988 All values are given in octal representation.
26005 @unnumberedsubsubsec Errno Values
26006 @cindex errno values, in file-i/o protocol
26008 All values are given in decimal representation.
26033 @code{EUNKNOWN} is used as a fallback error value if a host system returns
26034 any error value not in the list of supported error numbers.
26037 @unnumberedsubsubsec Lseek Flags
26038 @cindex lseek flags, in file-i/o protocol
26047 @unnumberedsubsubsec Limits
26048 @cindex limits, in file-i/o protocol
26050 All values are given in decimal representation.
26053 INT_MIN -2147483648
26055 UINT_MAX 4294967295
26056 LONG_MIN -9223372036854775808
26057 LONG_MAX 9223372036854775807
26058 ULONG_MAX 18446744073709551615
26061 @node File-I/O Examples
26062 @subsection File-I/O Examples
26063 @cindex file-i/o examples
26065 Example sequence of a write call, file descriptor 3, buffer is at target
26066 address 0x1234, 6 bytes should be written:
26069 <- @code{Fwrite,3,1234,6}
26070 @emph{request memory read from target}
26073 @emph{return "6 bytes written"}
26077 Example sequence of a read call, file descriptor 3, buffer is at target
26078 address 0x1234, 6 bytes should be read:
26081 <- @code{Fread,3,1234,6}
26082 @emph{request memory write to target}
26083 -> @code{X1234,6:XXXXXX}
26084 @emph{return "6 bytes read"}
26088 Example sequence of a read call, call fails on the host due to invalid
26089 file descriptor (@code{EBADF}):
26092 <- @code{Fread,3,1234,6}
26096 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
26100 <- @code{Fread,3,1234,6}
26105 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
26109 <- @code{Fread,3,1234,6}
26110 -> @code{X1234,6:XXXXXX}
26114 @node Library List Format
26115 @section Library List Format
26116 @cindex library list format, remote protocol
26118 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
26119 same process as your application to manage libraries. In this case,
26120 @value{GDBN} can use the loader's symbol table and normal memory
26121 operations to maintain a list of shared libraries. On other
26122 platforms, the operating system manages loaded libraries.
26123 @value{GDBN} can not retrieve the list of currently loaded libraries
26124 through memory operations, so it uses the @samp{qXfer:libraries:read}
26125 packet (@pxref{qXfer library list read}) instead. The remote stub
26126 queries the target's operating system and reports which libraries
26129 The @samp{qXfer:libraries:read} packet returns an XML document which
26130 lists loaded libraries and their offsets. Each library has an
26131 associated name and one or more segment base addresses, which report
26132 where the library was loaded in memory. The segment bases are start
26133 addresses, not relocation offsets; they do not depend on the library's
26134 link-time base addresses.
26136 @value{GDBN} must be linked with the Expat library to support XML
26137 library lists. @xref{Expat}.
26139 A simple memory map, with one loaded library relocated by a single
26140 offset, looks like this:
26144 <library name="/lib/libc.so.6">
26145 <segment address="0x10000000"/>
26150 The format of a library list is described by this DTD:
26153 <!-- library-list: Root element with versioning -->
26154 <!ELEMENT library-list (library)*>
26155 <!ATTLIST library-list version CDATA #FIXED "1.0">
26156 <!ELEMENT library (segment)*>
26157 <!ATTLIST library name CDATA #REQUIRED>
26158 <!ELEMENT segment EMPTY>
26159 <!ATTLIST segment address CDATA #REQUIRED>
26162 @node Memory Map Format
26163 @section Memory Map Format
26164 @cindex memory map format
26166 To be able to write into flash memory, @value{GDBN} needs to obtain a
26167 memory map from the target. This section describes the format of the
26170 The memory map is obtained using the @samp{qXfer:memory-map:read}
26171 (@pxref{qXfer memory map read}) packet and is an XML document that
26172 lists memory regions.
26174 @value{GDBN} must be linked with the Expat library to support XML
26175 memory maps. @xref{Expat}.
26177 The top-level structure of the document is shown below:
26180 <?xml version="1.0"?>
26181 <!DOCTYPE memory-map
26182 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
26183 "http://sourceware.org/gdb/gdb-memory-map.dtd">
26189 Each region can be either:
26194 A region of RAM starting at @var{addr} and extending for @var{length}
26198 <memory type="ram" start="@var{addr}" length="@var{length}"/>
26203 A region of read-only memory:
26206 <memory type="rom" start="@var{addr}" length="@var{length}"/>
26211 A region of flash memory, with erasure blocks @var{blocksize}
26215 <memory type="flash" start="@var{addr}" length="@var{length}">
26216 <property name="blocksize">@var{blocksize}</property>
26222 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
26223 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
26224 packets to write to addresses in such ranges.
26226 The formal DTD for memory map format is given below:
26229 <!-- ................................................... -->
26230 <!-- Memory Map XML DTD ................................ -->
26231 <!-- File: memory-map.dtd .............................. -->
26232 <!-- .................................... .............. -->
26233 <!-- memory-map.dtd -->
26234 <!-- memory-map: Root element with versioning -->
26235 <!ELEMENT memory-map (memory | property)>
26236 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
26237 <!ELEMENT memory (property)>
26238 <!-- memory: Specifies a memory region,
26239 and its type, or device. -->
26240 <!ATTLIST memory type CDATA #REQUIRED
26241 start CDATA #REQUIRED
26242 length CDATA #REQUIRED
26243 device CDATA #IMPLIED>
26244 <!-- property: Generic attribute tag -->
26245 <!ELEMENT property (#PCDATA | property)*>
26246 <!ATTLIST property name CDATA #REQUIRED>
26249 @include agentexpr.texi
26251 @node Target Descriptions
26252 @appendix Target Descriptions
26253 @cindex target descriptions
26255 @strong{Warning:} target descriptions are still under active development,
26256 and the contents and format may change between @value{GDBN} releases.
26257 The format is expected to stabilize in the future.
26259 One of the challenges of using @value{GDBN} to debug embedded systems
26260 is that there are so many minor variants of each processor
26261 architecture in use. It is common practice for vendors to start with
26262 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
26263 and then make changes to adapt it to a particular market niche. Some
26264 architectures have hundreds of variants, available from dozens of
26265 vendors. This leads to a number of problems:
26269 With so many different customized processors, it is difficult for
26270 the @value{GDBN} maintainers to keep up with the changes.
26272 Since individual variants may have short lifetimes or limited
26273 audiences, it may not be worthwhile to carry information about every
26274 variant in the @value{GDBN} source tree.
26276 When @value{GDBN} does support the architecture of the embedded system
26277 at hand, the task of finding the correct architecture name to give the
26278 @command{set architecture} command can be error-prone.
26281 To address these problems, the @value{GDBN} remote protocol allows a
26282 target system to not only identify itself to @value{GDBN}, but to
26283 actually describe its own features. This lets @value{GDBN} support
26284 processor variants it has never seen before --- to the extent that the
26285 descriptions are accurate, and that @value{GDBN} understands them.
26287 @value{GDBN} must be linked with the Expat library to support XML
26288 target descriptions. @xref{Expat}.
26291 * Retrieving Descriptions:: How descriptions are fetched from a target.
26292 * Target Description Format:: The contents of a target description.
26293 * Predefined Target Types:: Standard types available for target
26295 * Standard Target Features:: Features @value{GDBN} knows about.
26298 @node Retrieving Descriptions
26299 @section Retrieving Descriptions
26301 Target descriptions can be read from the target automatically, or
26302 specified by the user manually. The default behavior is to read the
26303 description from the target. @value{GDBN} retrieves it via the remote
26304 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
26305 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
26306 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
26307 XML document, of the form described in @ref{Target Description
26310 Alternatively, you can specify a file to read for the target description.
26311 If a file is set, the target will not be queried. The commands to
26312 specify a file are:
26315 @cindex set tdesc filename
26316 @item set tdesc filename @var{path}
26317 Read the target description from @var{path}.
26319 @cindex unset tdesc filename
26320 @item unset tdesc filename
26321 Do not read the XML target description from a file. @value{GDBN}
26322 will use the description supplied by the current target.
26324 @cindex show tdesc filename
26325 @item show tdesc filename
26326 Show the filename to read for a target description, if any.
26330 @node Target Description Format
26331 @section Target Description Format
26332 @cindex target descriptions, XML format
26334 A target description annex is an @uref{http://www.w3.org/XML/, XML}
26335 document which complies with the Document Type Definition provided in
26336 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
26337 means you can use generally available tools like @command{xmllint} to
26338 check that your feature descriptions are well-formed and valid.
26339 However, to help people unfamiliar with XML write descriptions for
26340 their targets, we also describe the grammar here.
26342 Target descriptions can identify the architecture of the remote target
26343 and (for some architectures) provide information about custom register
26344 sets. @value{GDBN} can use this information to autoconfigure for your
26345 target, or to warn you if you connect to an unsupported target.
26347 Here is a simple target description:
26350 <target version="1.0">
26351 <architecture>i386:x86-64</architecture>
26356 This minimal description only says that the target uses
26357 the x86-64 architecture.
26359 A target description has the following overall form, with [ ] marking
26360 optional elements and @dots{} marking repeatable elements. The elements
26361 are explained further below.
26364 <?xml version="1.0"?>
26365 <!DOCTYPE target SYSTEM "gdb-target.dtd">
26366 <target version="1.0">
26367 @r{[}@var{architecture}@r{]}
26368 @r{[}@var{feature}@dots{}@r{]}
26373 The description is generally insensitive to whitespace and line
26374 breaks, under the usual common-sense rules. The XML version
26375 declaration and document type declaration can generally be omitted
26376 (@value{GDBN} does not require them), but specifying them may be
26377 useful for XML validation tools. The @samp{version} attribute for
26378 @samp{<target>} may also be omitted, but we recommend
26379 including it; if future versions of @value{GDBN} use an incompatible
26380 revision of @file{gdb-target.dtd}, they will detect and report
26381 the version mismatch.
26383 @subsection Inclusion
26384 @cindex target descriptions, inclusion
26387 @cindex <xi:include>
26390 It can sometimes be valuable to split a target description up into
26391 several different annexes, either for organizational purposes, or to
26392 share files between different possible target descriptions. You can
26393 divide a description into multiple files by replacing any element of
26394 the target description with an inclusion directive of the form:
26397 <xi:include href="@var{document}"/>
26401 When @value{GDBN} encounters an element of this form, it will retrieve
26402 the named XML @var{document}, and replace the inclusion directive with
26403 the contents of that document. If the current description was read
26404 using @samp{qXfer}, then so will be the included document;
26405 @var{document} will be interpreted as the name of an annex. If the
26406 current description was read from a file, @value{GDBN} will look for
26407 @var{document} as a file in the same directory where it found the
26408 original description.
26410 @subsection Architecture
26411 @cindex <architecture>
26413 An @samp{<architecture>} element has this form:
26416 <architecture>@var{arch}</architecture>
26419 @var{arch} is an architecture name from the same selection
26420 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
26421 Debugging Target}).
26423 @subsection Features
26426 Each @samp{<feature>} describes some logical portion of the target
26427 system. Features are currently used to describe available CPU
26428 registers and the types of their contents. A @samp{<feature>} element
26432 <feature name="@var{name}">
26433 @r{[}@var{type}@dots{}@r{]}
26439 Each feature's name should be unique within the description. The name
26440 of a feature does not matter unless @value{GDBN} has some special
26441 knowledge of the contents of that feature; if it does, the feature
26442 should have its standard name. @xref{Standard Target Features}.
26446 Any register's value is a collection of bits which @value{GDBN} must
26447 interpret. The default interpretation is a two's complement integer,
26448 but other types can be requested by name in the register description.
26449 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
26450 Target Types}), and the description can define additional composite types.
26452 Each type element must have an @samp{id} attribute, which gives
26453 a unique (within the containing @samp{<feature>}) name to the type.
26454 Types must be defined before they are used.
26457 Some targets offer vector registers, which can be treated as arrays
26458 of scalar elements. These types are written as @samp{<vector>} elements,
26459 specifying the array element type, @var{type}, and the number of elements,
26463 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
26467 If a register's value is usefully viewed in multiple ways, define it
26468 with a union type containing the useful representations. The
26469 @samp{<union>} element contains one or more @samp{<field>} elements,
26470 each of which has a @var{name} and a @var{type}:
26473 <union id="@var{id}">
26474 <field name="@var{name}" type="@var{type}"/>
26479 @subsection Registers
26482 Each register is represented as an element with this form:
26485 <reg name="@var{name}"
26486 bitsize="@var{size}"
26487 @r{[}regnum="@var{num}"@r{]}
26488 @r{[}save-restore="@var{save-restore}"@r{]}
26489 @r{[}type="@var{type}"@r{]}
26490 @r{[}group="@var{group}"@r{]}/>
26494 The components are as follows:
26499 The register's name; it must be unique within the target description.
26502 The register's size, in bits.
26505 The register's number. If omitted, a register's number is one greater
26506 than that of the previous register (either in the current feature or in
26507 a preceeding feature); the first register in the target description
26508 defaults to zero. This register number is used to read or write
26509 the register; e.g.@: it is used in the remote @code{p} and @code{P}
26510 packets, and registers appear in the @code{g} and @code{G} packets
26511 in order of increasing register number.
26514 Whether the register should be preserved across inferior function
26515 calls; this must be either @code{yes} or @code{no}. The default is
26516 @code{yes}, which is appropriate for most registers except for
26517 some system control registers; this is not related to the target's
26521 The type of the register. @var{type} may be a predefined type, a type
26522 defined in the current feature, or one of the special types @code{int}
26523 and @code{float}. @code{int} is an integer type of the correct size
26524 for @var{bitsize}, and @code{float} is a floating point type (in the
26525 architecture's normal floating point format) of the correct size for
26526 @var{bitsize}. The default is @code{int}.
26529 The register group to which this register belongs. @var{group} must
26530 be either @code{general}, @code{float}, or @code{vector}. If no
26531 @var{group} is specified, @value{GDBN} will not display the register
26532 in @code{info registers}.
26536 @node Predefined Target Types
26537 @section Predefined Target Types
26538 @cindex target descriptions, predefined types
26540 Type definitions in the self-description can build up composite types
26541 from basic building blocks, but can not define fundamental types. Instead,
26542 standard identifiers are provided by @value{GDBN} for the fundamental
26543 types. The currently supported types are:
26552 Signed integer types holding the specified number of bits.
26559 Unsigned integer types holding the specified number of bits.
26563 Pointers to unspecified code and data. The program counter and
26564 any dedicated return address register may be marked as code
26565 pointers; printing a code pointer converts it into a symbolic
26566 address. The stack pointer and any dedicated address registers
26567 may be marked as data pointers.
26570 Single precision IEEE floating point.
26573 Double precision IEEE floating point.
26576 The 12-byte extended precision format used by ARM FPA registers.
26580 @node Standard Target Features
26581 @section Standard Target Features
26582 @cindex target descriptions, standard features
26584 A target description must contain either no registers or all the
26585 target's registers. If the description contains no registers, then
26586 @value{GDBN} will assume a default register layout, selected based on
26587 the architecture. If the description contains any registers, the
26588 default layout will not be used; the standard registers must be
26589 described in the target description, in such a way that @value{GDBN}
26590 can recognize them.
26592 This is accomplished by giving specific names to feature elements
26593 which contain standard registers. @value{GDBN} will look for features
26594 with those names and verify that they contain the expected registers;
26595 if any known feature is missing required registers, or if any required
26596 feature is missing, @value{GDBN} will reject the target
26597 description. You can add additional registers to any of the
26598 standard features --- @value{GDBN} will display them just as if
26599 they were added to an unrecognized feature.
26601 This section lists the known features and their expected contents.
26602 Sample XML documents for these features are included in the
26603 @value{GDBN} source tree, in the directory @file{gdb/features}.
26605 Names recognized by @value{GDBN} should include the name of the
26606 company or organization which selected the name, and the overall
26607 architecture to which the feature applies; so e.g.@: the feature
26608 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
26610 The names of registers are not case sensitive for the purpose
26611 of recognizing standard features, but @value{GDBN} will only display
26612 registers using the capitalization used in the description.
26621 @subsection ARM Features
26622 @cindex target descriptions, ARM features
26624 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
26625 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
26626 @samp{lr}, @samp{pc}, and @samp{cpsr}.
26628 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
26629 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
26631 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
26632 it should contain at least registers @samp{wR0} through @samp{wR15} and
26633 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
26634 @samp{wCSSF}, and @samp{wCASF} registers are optional.
26636 @subsection MIPS Features
26637 @cindex target descriptions, MIPS features
26639 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
26640 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
26641 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
26644 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
26645 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
26646 registers. They may be 32-bit or 64-bit depending on the target.
26648 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
26649 it may be optional in a future version of @value{GDBN}. It should
26650 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
26651 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
26653 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
26654 contain a single register, @samp{restart}, which is used by the
26655 Linux kernel to control restartable syscalls.
26657 @node M68K Features
26658 @subsection M68K Features
26659 @cindex target descriptions, M68K features
26662 @item @samp{org.gnu.gdb.m68k.core}
26663 @itemx @samp{org.gnu.gdb.coldfire.core}
26664 @itemx @samp{org.gnu.gdb.fido.core}
26665 One of those features must be always present.
26666 The feature that is present determines which flavor of m86k is
26667 used. The feature that is present should contain registers
26668 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
26669 @samp{sp}, @samp{ps} and @samp{pc}.
26671 @item @samp{org.gnu.gdb.coldfire.fp}
26672 This feature is optional. If present, it should contain registers
26673 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
26677 @subsection PowerPC Features
26678 @cindex target descriptions, PowerPC features
26680 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
26681 targets. It should contain registers @samp{r0} through @samp{r31},
26682 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
26683 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
26685 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
26686 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
26688 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
26689 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
26692 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
26693 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
26694 @samp{spefscr}. SPE targets should provide 32-bit registers in
26695 @samp{org.gnu.gdb.power.core} and provide the upper halves in
26696 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
26697 these to present registers @samp{ev0} through @samp{ev31} to the
26712 % I think something like @colophon should be in texinfo. In the
26714 \long\def\colophon{\hbox to0pt{}\vfill
26715 \centerline{The body of this manual is set in}
26716 \centerline{\fontname\tenrm,}
26717 \centerline{with headings in {\bf\fontname\tenbf}}
26718 \centerline{and examples in {\tt\fontname\tentt}.}
26719 \centerline{{\it\fontname\tenit\/},}
26720 \centerline{{\bf\fontname\tenbf}, and}
26721 \centerline{{\sl\fontname\tensl\/}}
26722 \centerline{are used for emphasis.}\vfill}
26724 % Blame: doc@cygnus.com, 1991.