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 show the arguments passed to a function
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 some environments without processes,
1822 @code{run} jumps to the start of your program. Other targets,
1823 like @samp{remote}, are always running. If you get an error
1824 message like this one:
1827 The "remote" target does not support "run".
1828 Try "help target" or "continue".
1832 then use @code{continue} to run your program. You may need @code{load}
1833 first (@pxref{load}).
1835 The execution of a program is affected by certain information it
1836 receives from its superior. @value{GDBN} provides ways to specify this
1837 information, which you must do @emph{before} starting your program. (You
1838 can change it after starting your program, but such changes only affect
1839 your program the next time you start it.) This information may be
1840 divided into four categories:
1843 @item The @emph{arguments.}
1844 Specify the arguments to give your program as the arguments of the
1845 @code{run} command. If a shell is available on your target, the shell
1846 is used to pass the arguments, so that you may use normal conventions
1847 (such as wildcard expansion or variable substitution) in describing
1849 In Unix systems, you can control which shell is used with the
1850 @code{SHELL} environment variable.
1851 @xref{Arguments, ,Your Program's Arguments}.
1853 @item The @emph{environment.}
1854 Your program normally inherits its environment from @value{GDBN}, but you can
1855 use the @value{GDBN} commands @code{set environment} and @code{unset
1856 environment} to change parts of the environment that affect
1857 your program. @xref{Environment, ,Your Program's Environment}.
1859 @item The @emph{working directory.}
1860 Your program inherits its working directory from @value{GDBN}. You can set
1861 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1862 @xref{Working Directory, ,Your Program's Working Directory}.
1864 @item The @emph{standard input and output.}
1865 Your program normally uses the same device for standard input and
1866 standard output as @value{GDBN} is using. You can redirect input and output
1867 in the @code{run} command line, or you can use the @code{tty} command to
1868 set a different device for your program.
1869 @xref{Input/Output, ,Your Program's Input and Output}.
1872 @emph{Warning:} While input and output redirection work, you cannot use
1873 pipes to pass the output of the program you are debugging to another
1874 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1878 When you issue the @code{run} command, your program begins to execute
1879 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1880 of how to arrange for your program to stop. Once your program has
1881 stopped, you may call functions in your program, using the @code{print}
1882 or @code{call} commands. @xref{Data, ,Examining Data}.
1884 If the modification time of your symbol file has changed since the last
1885 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1886 table, and reads it again. When it does this, @value{GDBN} tries to retain
1887 your current breakpoints.
1892 @cindex run to main procedure
1893 The name of the main procedure can vary from language to language.
1894 With C or C@t{++}, the main procedure name is always @code{main}, but
1895 other languages such as Ada do not require a specific name for their
1896 main procedure. The debugger provides a convenient way to start the
1897 execution of the program and to stop at the beginning of the main
1898 procedure, depending on the language used.
1900 The @samp{start} command does the equivalent of setting a temporary
1901 breakpoint at the beginning of the main procedure and then invoking
1902 the @samp{run} command.
1904 @cindex elaboration phase
1905 Some programs contain an @dfn{elaboration} phase where some startup code is
1906 executed before the main procedure is called. This depends on the
1907 languages used to write your program. In C@t{++}, for instance,
1908 constructors for static and global objects are executed before
1909 @code{main} is called. It is therefore possible that the debugger stops
1910 before reaching the main procedure. However, the temporary breakpoint
1911 will remain to halt execution.
1913 Specify the arguments to give to your program as arguments to the
1914 @samp{start} command. These arguments will be given verbatim to the
1915 underlying @samp{run} command. Note that the same arguments will be
1916 reused if no argument is provided during subsequent calls to
1917 @samp{start} or @samp{run}.
1919 It is sometimes necessary to debug the program during elaboration. In
1920 these cases, using the @code{start} command would stop the execution of
1921 your program too late, as the program would have already completed the
1922 elaboration phase. Under these circumstances, insert breakpoints in your
1923 elaboration code before running your program.
1925 @kindex set exec-wrapper
1926 @item set exec-wrapper @var{wrapper}
1927 @itemx show exec-wrapper
1928 @itemx unset exec-wrapper
1929 When @samp{exec-wrapper} is set, the specified wrapper is used to
1930 launch programs for debugging. @value{GDBN} starts your program
1931 with a shell command of the form @kbd{exec @var{wrapper}
1932 @var{program}}. Quoting is added to @var{program} and its
1933 arguments, but not to @var{wrapper}, so you should add quotes if
1934 appropriate for your shell. The wrapper runs until it executes
1935 your program, and then @value{GDBN} takes control.
1937 You can use any program that eventually calls @code{execve} with
1938 its arguments as a wrapper. Several standard Unix utilities do
1939 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1940 with @code{exec "$@@"} will also work.
1942 For example, you can use @code{env} to pass an environment variable to
1943 the debugged program, without setting the variable in your shell's
1947 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1951 This command is available when debugging locally on most targets, excluding
1952 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
1957 @section Your Program's Arguments
1959 @cindex arguments (to your program)
1960 The arguments to your program can be specified by the arguments of the
1962 They are passed to a shell, which expands wildcard characters and
1963 performs redirection of I/O, and thence to your program. Your
1964 @code{SHELL} environment variable (if it exists) specifies what shell
1965 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1966 the default shell (@file{/bin/sh} on Unix).
1968 On non-Unix systems, the program is usually invoked directly by
1969 @value{GDBN}, which emulates I/O redirection via the appropriate system
1970 calls, and the wildcard characters are expanded by the startup code of
1971 the program, not by the shell.
1973 @code{run} with no arguments uses the same arguments used by the previous
1974 @code{run}, or those set by the @code{set args} command.
1979 Specify the arguments to be used the next time your program is run. If
1980 @code{set args} has no arguments, @code{run} executes your program
1981 with no arguments. Once you have run your program with arguments,
1982 using @code{set args} before the next @code{run} is the only way to run
1983 it again without arguments.
1987 Show the arguments to give your program when it is started.
1991 @section Your Program's Environment
1993 @cindex environment (of your program)
1994 The @dfn{environment} consists of a set of environment variables and
1995 their values. Environment variables conventionally record such things as
1996 your user name, your home directory, your terminal type, and your search
1997 path for programs to run. Usually you set up environment variables with
1998 the shell and they are inherited by all the other programs you run. When
1999 debugging, it can be useful to try running your program with a modified
2000 environment without having to start @value{GDBN} over again.
2004 @item path @var{directory}
2005 Add @var{directory} to the front of the @code{PATH} environment variable
2006 (the search path for executables) that will be passed to your program.
2007 The value of @code{PATH} used by @value{GDBN} does not change.
2008 You may specify several directory names, separated by whitespace or by a
2009 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2010 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2011 is moved to the front, so it is searched sooner.
2013 You can use the string @samp{$cwd} to refer to whatever is the current
2014 working directory at the time @value{GDBN} searches the path. If you
2015 use @samp{.} instead, it refers to the directory where you executed the
2016 @code{path} command. @value{GDBN} replaces @samp{.} in the
2017 @var{directory} argument (with the current path) before adding
2018 @var{directory} to the search path.
2019 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2020 @c document that, since repeating it would be a no-op.
2024 Display the list of search paths for executables (the @code{PATH}
2025 environment variable).
2027 @kindex show environment
2028 @item show environment @r{[}@var{varname}@r{]}
2029 Print the value of environment variable @var{varname} to be given to
2030 your program when it starts. If you do not supply @var{varname},
2031 print the names and values of all environment variables to be given to
2032 your program. You can abbreviate @code{environment} as @code{env}.
2034 @kindex set environment
2035 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2036 Set environment variable @var{varname} to @var{value}. The value
2037 changes for your program only, not for @value{GDBN} itself. @var{value} may
2038 be any string; the values of environment variables are just strings, and
2039 any interpretation is supplied by your program itself. The @var{value}
2040 parameter is optional; if it is eliminated, the variable is set to a
2042 @c "any string" here does not include leading, trailing
2043 @c blanks. Gnu asks: does anyone care?
2045 For example, this command:
2052 tells the debugged program, when subsequently run, that its user is named
2053 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2054 are not actually required.)
2056 @kindex unset environment
2057 @item unset environment @var{varname}
2058 Remove variable @var{varname} from the environment to be passed to your
2059 program. This is different from @samp{set env @var{varname} =};
2060 @code{unset environment} removes the variable from the environment,
2061 rather than assigning it an empty value.
2064 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2066 by your @code{SHELL} environment variable if it exists (or
2067 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2068 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2069 @file{.bashrc} for BASH---any variables you set in that file affect
2070 your program. You may wish to move setting of environment variables to
2071 files that are only run when you sign on, such as @file{.login} or
2074 @node Working Directory
2075 @section Your Program's Working Directory
2077 @cindex working directory (of your program)
2078 Each time you start your program with @code{run}, it inherits its
2079 working directory from the current working directory of @value{GDBN}.
2080 The @value{GDBN} working directory is initially whatever it inherited
2081 from its parent process (typically the shell), but you can specify a new
2082 working directory in @value{GDBN} with the @code{cd} command.
2084 The @value{GDBN} working directory also serves as a default for the commands
2085 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2090 @cindex change working directory
2091 @item cd @var{directory}
2092 Set the @value{GDBN} working directory to @var{directory}.
2096 Print the @value{GDBN} working directory.
2099 It is generally impossible to find the current working directory of
2100 the process being debugged (since a program can change its directory
2101 during its run). If you work on a system where @value{GDBN} is
2102 configured with the @file{/proc} support, you can use the @code{info
2103 proc} command (@pxref{SVR4 Process Information}) to find out the
2104 current working directory of the debuggee.
2107 @section Your Program's Input and Output
2112 By default, the program you run under @value{GDBN} does input and output to
2113 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2114 to its own terminal modes to interact with you, but it records the terminal
2115 modes your program was using and switches back to them when you continue
2116 running your program.
2119 @kindex info terminal
2121 Displays information recorded by @value{GDBN} about the terminal modes your
2125 You can redirect your program's input and/or output using shell
2126 redirection with the @code{run} command. For example,
2133 starts your program, diverting its output to the file @file{outfile}.
2136 @cindex controlling terminal
2137 Another way to specify where your program should do input and output is
2138 with the @code{tty} command. This command accepts a file name as
2139 argument, and causes this file to be the default for future @code{run}
2140 commands. It also resets the controlling terminal for the child
2141 process, for future @code{run} commands. For example,
2148 directs that processes started with subsequent @code{run} commands
2149 default to do input and output on the terminal @file{/dev/ttyb} and have
2150 that as their controlling terminal.
2152 An explicit redirection in @code{run} overrides the @code{tty} command's
2153 effect on the input/output device, but not its effect on the controlling
2156 When you use the @code{tty} command or redirect input in the @code{run}
2157 command, only the input @emph{for your program} is affected. The input
2158 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2159 for @code{set inferior-tty}.
2161 @cindex inferior tty
2162 @cindex set inferior controlling terminal
2163 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2164 display the name of the terminal that will be used for future runs of your
2168 @item set inferior-tty /dev/ttyb
2169 @kindex set inferior-tty
2170 Set the tty for the program being debugged to /dev/ttyb.
2172 @item show inferior-tty
2173 @kindex show inferior-tty
2174 Show the current tty for the program being debugged.
2178 @section Debugging an Already-running Process
2183 @item attach @var{process-id}
2184 This command attaches to a running process---one that was started
2185 outside @value{GDBN}. (@code{info files} shows your active
2186 targets.) The command takes as argument a process ID. The usual way to
2187 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2188 or with the @samp{jobs -l} shell command.
2190 @code{attach} does not repeat if you press @key{RET} a second time after
2191 executing the command.
2194 To use @code{attach}, your program must be running in an environment
2195 which supports processes; for example, @code{attach} does not work for
2196 programs on bare-board targets that lack an operating system. You must
2197 also have permission to send the process a signal.
2199 When you use @code{attach}, the debugger finds the program running in
2200 the process first by looking in the current working directory, then (if
2201 the program is not found) by using the source file search path
2202 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2203 the @code{file} command to load the program. @xref{Files, ,Commands to
2206 The first thing @value{GDBN} does after arranging to debug the specified
2207 process is to stop it. You can examine and modify an attached process
2208 with all the @value{GDBN} commands that are ordinarily available when
2209 you start processes with @code{run}. You can insert breakpoints; you
2210 can step and continue; you can modify storage. If you would rather the
2211 process continue running, you may use the @code{continue} command after
2212 attaching @value{GDBN} to the process.
2217 When you have finished debugging the attached process, you can use the
2218 @code{detach} command to release it from @value{GDBN} control. Detaching
2219 the process continues its execution. After the @code{detach} command,
2220 that process and @value{GDBN} become completely independent once more, and you
2221 are ready to @code{attach} another process or start one with @code{run}.
2222 @code{detach} does not repeat if you press @key{RET} again after
2223 executing the command.
2226 If you exit @value{GDBN} while you have an attached process, you detach
2227 that process. If you use the @code{run} command, you kill that process.
2228 By default, @value{GDBN} asks for confirmation if you try to do either of these
2229 things; you can control whether or not you need to confirm by using the
2230 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2234 @section Killing the Child Process
2239 Kill the child process in which your program is running under @value{GDBN}.
2242 This command is useful if you wish to debug a core dump instead of a
2243 running process. @value{GDBN} ignores any core dump file while your program
2246 On some operating systems, a program cannot be executed outside @value{GDBN}
2247 while you have breakpoints set on it inside @value{GDBN}. You can use the
2248 @code{kill} command in this situation to permit running your program
2249 outside the debugger.
2251 The @code{kill} command is also useful if you wish to recompile and
2252 relink your program, since on many systems it is impossible to modify an
2253 executable file while it is running in a process. In this case, when you
2254 next type @code{run}, @value{GDBN} notices that the file has changed, and
2255 reads the symbol table again (while trying to preserve your current
2256 breakpoint settings).
2259 @section Debugging Programs with Multiple Threads
2261 @cindex threads of execution
2262 @cindex multiple threads
2263 @cindex switching threads
2264 In some operating systems, such as HP-UX and Solaris, a single program
2265 may have more than one @dfn{thread} of execution. The precise semantics
2266 of threads differ from one operating system to another, but in general
2267 the threads of a single program are akin to multiple processes---except
2268 that they share one address space (that is, they can all examine and
2269 modify the same variables). On the other hand, each thread has its own
2270 registers and execution stack, and perhaps private memory.
2272 @value{GDBN} provides these facilities for debugging multi-thread
2276 @item automatic notification of new threads
2277 @item @samp{thread @var{threadno}}, a command to switch among threads
2278 @item @samp{info threads}, a command to inquire about existing threads
2279 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2280 a command to apply a command to a list of threads
2281 @item thread-specific breakpoints
2282 @item @samp{set print thread-events}, which controls printing of
2283 messages on thread start and exit.
2287 @emph{Warning:} These facilities are not yet available on every
2288 @value{GDBN} configuration where the operating system supports threads.
2289 If your @value{GDBN} does not support threads, these commands have no
2290 effect. For example, a system without thread support shows no output
2291 from @samp{info threads}, and always rejects the @code{thread} command,
2295 (@value{GDBP}) info threads
2296 (@value{GDBP}) thread 1
2297 Thread ID 1 not known. Use the "info threads" command to
2298 see the IDs of currently known threads.
2300 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2301 @c doesn't support threads"?
2304 @cindex focus of debugging
2305 @cindex current thread
2306 The @value{GDBN} thread debugging facility allows you to observe all
2307 threads while your program runs---but whenever @value{GDBN} takes
2308 control, one thread in particular is always the focus of debugging.
2309 This thread is called the @dfn{current thread}. Debugging commands show
2310 program information from the perspective of the current thread.
2312 @cindex @code{New} @var{systag} message
2313 @cindex thread identifier (system)
2314 @c FIXME-implementors!! It would be more helpful if the [New...] message
2315 @c included GDB's numeric thread handle, so you could just go to that
2316 @c thread without first checking `info threads'.
2317 Whenever @value{GDBN} detects a new thread in your program, it displays
2318 the target system's identification for the thread with a message in the
2319 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2320 whose form varies depending on the particular system. For example, on
2321 @sc{gnu}/Linux, you might see
2324 [New Thread 46912507313328 (LWP 25582)]
2328 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2329 the @var{systag} is simply something like @samp{process 368}, with no
2332 @c FIXME!! (1) Does the [New...] message appear even for the very first
2333 @c thread of a program, or does it only appear for the
2334 @c second---i.e.@: when it becomes obvious we have a multithread
2336 @c (2) *Is* there necessarily a first thread always? Or do some
2337 @c multithread systems permit starting a program with multiple
2338 @c threads ab initio?
2340 @cindex thread number
2341 @cindex thread identifier (GDB)
2342 For debugging purposes, @value{GDBN} associates its own thread
2343 number---always a single integer---with each thread in your program.
2346 @kindex info threads
2348 Display a summary of all threads currently in your
2349 program. @value{GDBN} displays for each thread (in this order):
2353 the thread number assigned by @value{GDBN}
2356 the target system's thread identifier (@var{systag})
2359 the current stack frame summary for that thread
2363 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2364 indicates the current thread.
2368 @c end table here to get a little more width for example
2371 (@value{GDBP}) info threads
2372 3 process 35 thread 27 0x34e5 in sigpause ()
2373 2 process 35 thread 23 0x34e5 in sigpause ()
2374 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2380 @cindex debugging multithreaded programs (on HP-UX)
2381 @cindex thread identifier (GDB), on HP-UX
2382 For debugging purposes, @value{GDBN} associates its own thread
2383 number---a small integer assigned in thread-creation order---with each
2384 thread in your program.
2386 @cindex @code{New} @var{systag} message, on HP-UX
2387 @cindex thread identifier (system), on HP-UX
2388 @c FIXME-implementors!! It would be more helpful if the [New...] message
2389 @c included GDB's numeric thread handle, so you could just go to that
2390 @c thread without first checking `info threads'.
2391 Whenever @value{GDBN} detects a new thread in your program, it displays
2392 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2393 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2394 whose form varies depending on the particular system. For example, on
2398 [New thread 2 (system thread 26594)]
2402 when @value{GDBN} notices a new thread.
2405 @kindex info threads (HP-UX)
2407 Display a summary of all threads currently in your
2408 program. @value{GDBN} displays for each thread (in this order):
2411 @item the thread number assigned by @value{GDBN}
2413 @item the target system's thread identifier (@var{systag})
2415 @item the current stack frame summary for that thread
2419 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2420 indicates the current thread.
2424 @c end table here to get a little more width for example
2427 (@value{GDBP}) info threads
2428 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2430 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2431 from /usr/lib/libc.2
2432 1 system thread 27905 0x7b003498 in _brk () \@*
2433 from /usr/lib/libc.2
2436 On Solaris, you can display more information about user threads with a
2437 Solaris-specific command:
2440 @item maint info sol-threads
2441 @kindex maint info sol-threads
2442 @cindex thread info (Solaris)
2443 Display info on Solaris user threads.
2447 @kindex thread @var{threadno}
2448 @item thread @var{threadno}
2449 Make thread number @var{threadno} the current thread. The command
2450 argument @var{threadno} is the internal @value{GDBN} thread number, as
2451 shown in the first field of the @samp{info threads} display.
2452 @value{GDBN} responds by displaying the system identifier of the thread
2453 you selected, and its current stack frame summary:
2456 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2457 (@value{GDBP}) thread 2
2458 [Switching to process 35 thread 23]
2459 0x34e5 in sigpause ()
2463 As with the @samp{[New @dots{}]} message, the form of the text after
2464 @samp{Switching to} depends on your system's conventions for identifying
2467 @kindex thread apply
2468 @cindex apply command to several threads
2469 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2470 The @code{thread apply} command allows you to apply the named
2471 @var{command} to one or more threads. Specify the numbers of the
2472 threads that you want affected with the command argument
2473 @var{threadno}. It can be a single thread number, one of the numbers
2474 shown in the first field of the @samp{info threads} display; or it
2475 could be a range of thread numbers, as in @code{2-4}. To apply a
2476 command to all threads, type @kbd{thread apply all @var{command}}.
2478 @kindex set print thread-events
2479 @cindex print messages on thread start and exit
2480 @item set print thread-events
2481 @itemx set print thread-events on
2482 @itemx set print thread-events off
2483 The @code{set print thread-events} command allows you to enable or
2484 disable printing of messages when @value{GDBN} notices that new threads have
2485 started or that threads have exited. By default, these messages will
2486 be printed if detection of these events is supported by the target.
2487 Note that these messages cannot be disabled on all targets.
2489 @kindex show print thread-events
2490 @item show print thread-events
2491 Show whether messages will be printed when @value{GDBN} detects that threads
2492 have started and exited.
2495 @cindex automatic thread selection
2496 @cindex switching threads automatically
2497 @cindex threads, automatic switching
2498 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2499 signal, it automatically selects the thread where that breakpoint or
2500 signal happened. @value{GDBN} alerts you to the context switch with a
2501 message of the form @samp{[Switching to @var{systag}]} to identify the
2504 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2505 more information about how @value{GDBN} behaves when you stop and start
2506 programs with multiple threads.
2508 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2509 watchpoints in programs with multiple threads.
2512 @section Debugging Programs with Multiple Processes
2514 @cindex fork, debugging programs which call
2515 @cindex multiple processes
2516 @cindex processes, multiple
2517 On most systems, @value{GDBN} has no special support for debugging
2518 programs which create additional processes using the @code{fork}
2519 function. When a program forks, @value{GDBN} will continue to debug the
2520 parent process and the child process will run unimpeded. If you have
2521 set a breakpoint in any code which the child then executes, the child
2522 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2523 will cause it to terminate.
2525 However, if you want to debug the child process there is a workaround
2526 which isn't too painful. Put a call to @code{sleep} in the code which
2527 the child process executes after the fork. It may be useful to sleep
2528 only if a certain environment variable is set, or a certain file exists,
2529 so that the delay need not occur when you don't want to run @value{GDBN}
2530 on the child. While the child is sleeping, use the @code{ps} program to
2531 get its process ID. Then tell @value{GDBN} (a new invocation of
2532 @value{GDBN} if you are also debugging the parent process) to attach to
2533 the child process (@pxref{Attach}). From that point on you can debug
2534 the child process just like any other process which you attached to.
2536 On some systems, @value{GDBN} provides support for debugging programs that
2537 create additional processes using the @code{fork} or @code{vfork} functions.
2538 Currently, the only platforms with this feature are HP-UX (11.x and later
2539 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2541 By default, when a program forks, @value{GDBN} will continue to debug
2542 the parent process and the child process will run unimpeded.
2544 If you want to follow the child process instead of the parent process,
2545 use the command @w{@code{set follow-fork-mode}}.
2548 @kindex set follow-fork-mode
2549 @item set follow-fork-mode @var{mode}
2550 Set the debugger response to a program call of @code{fork} or
2551 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2552 process. The @var{mode} argument can be:
2556 The original process is debugged after a fork. The child process runs
2557 unimpeded. This is the default.
2560 The new process is debugged after a fork. The parent process runs
2565 @kindex show follow-fork-mode
2566 @item show follow-fork-mode
2567 Display the current debugger response to a @code{fork} or @code{vfork} call.
2570 @cindex debugging multiple processes
2571 On Linux, if you want to debug both the parent and child processes, use the
2572 command @w{@code{set detach-on-fork}}.
2575 @kindex set detach-on-fork
2576 @item set detach-on-fork @var{mode}
2577 Tells gdb whether to detach one of the processes after a fork, or
2578 retain debugger control over them both.
2582 The child process (or parent process, depending on the value of
2583 @code{follow-fork-mode}) will be detached and allowed to run
2584 independently. This is the default.
2587 Both processes will be held under the control of @value{GDBN}.
2588 One process (child or parent, depending on the value of
2589 @code{follow-fork-mode}) is debugged as usual, while the other
2594 @kindex show detach-on-fork
2595 @item show detach-on-fork
2596 Show whether detach-on-fork mode is on/off.
2599 If you choose to set @samp{detach-on-fork} mode off, then
2600 @value{GDBN} will retain control of all forked processes (including
2601 nested forks). You can list the forked processes under the control of
2602 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2603 from one fork to another by using the @w{@code{fork}} command.
2608 Print a list of all forked processes under the control of @value{GDBN}.
2609 The listing will include a fork id, a process id, and the current
2610 position (program counter) of the process.
2612 @kindex fork @var{fork-id}
2613 @item fork @var{fork-id}
2614 Make fork number @var{fork-id} the current process. The argument
2615 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2616 as shown in the first field of the @samp{info forks} display.
2618 @kindex process @var{process-id}
2619 @item process @var{process-id}
2620 Make process number @var{process-id} the current process. The
2621 argument @var{process-id} must be one that is listed in the output of
2626 To quit debugging one of the forked processes, you can either detach
2627 from it by using the @w{@code{detach fork}} command (allowing it to
2628 run independently), or delete (and kill) it using the
2629 @w{@code{delete fork}} command.
2632 @kindex detach fork @var{fork-id}
2633 @item detach fork @var{fork-id}
2634 Detach from the process identified by @value{GDBN} fork number
2635 @var{fork-id}, and remove it from the fork list. The process will be
2636 allowed to run independently.
2638 @kindex delete fork @var{fork-id}
2639 @item delete fork @var{fork-id}
2640 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2641 and remove it from the fork list.
2645 If you ask to debug a child process and a @code{vfork} is followed by an
2646 @code{exec}, @value{GDBN} executes the new target up to the first
2647 breakpoint in the new target. If you have a breakpoint set on
2648 @code{main} in your original program, the breakpoint will also be set on
2649 the child process's @code{main}.
2651 When a child process is spawned by @code{vfork}, you cannot debug the
2652 child or parent until an @code{exec} call completes.
2654 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2655 call executes, the new target restarts. To restart the parent process,
2656 use the @code{file} command with the parent executable name as its
2659 You can use the @code{catch} command to make @value{GDBN} stop whenever
2660 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2661 Catchpoints, ,Setting Catchpoints}.
2663 @node Checkpoint/Restart
2664 @section Setting a @emph{Bookmark} to Return to Later
2669 @cindex snapshot of a process
2670 @cindex rewind program state
2672 On certain operating systems@footnote{Currently, only
2673 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2674 program's state, called a @dfn{checkpoint}, and come back to it
2677 Returning to a checkpoint effectively undoes everything that has
2678 happened in the program since the @code{checkpoint} was saved. This
2679 includes changes in memory, registers, and even (within some limits)
2680 system state. Effectively, it is like going back in time to the
2681 moment when the checkpoint was saved.
2683 Thus, if you're stepping thru a program and you think you're
2684 getting close to the point where things go wrong, you can save
2685 a checkpoint. Then, if you accidentally go too far and miss
2686 the critical statement, instead of having to restart your program
2687 from the beginning, you can just go back to the checkpoint and
2688 start again from there.
2690 This can be especially useful if it takes a lot of time or
2691 steps to reach the point where you think the bug occurs.
2693 To use the @code{checkpoint}/@code{restart} method of debugging:
2698 Save a snapshot of the debugged program's current execution state.
2699 The @code{checkpoint} command takes no arguments, but each checkpoint
2700 is assigned a small integer id, similar to a breakpoint id.
2702 @kindex info checkpoints
2703 @item info checkpoints
2704 List the checkpoints that have been saved in the current debugging
2705 session. For each checkpoint, the following information will be
2712 @item Source line, or label
2715 @kindex restart @var{checkpoint-id}
2716 @item restart @var{checkpoint-id}
2717 Restore the program state that was saved as checkpoint number
2718 @var{checkpoint-id}. All program variables, registers, stack frames
2719 etc.@: will be returned to the values that they had when the checkpoint
2720 was saved. In essence, gdb will ``wind back the clock'' to the point
2721 in time when the checkpoint was saved.
2723 Note that breakpoints, @value{GDBN} variables, command history etc.
2724 are not affected by restoring a checkpoint. In general, a checkpoint
2725 only restores things that reside in the program being debugged, not in
2728 @kindex delete checkpoint @var{checkpoint-id}
2729 @item delete checkpoint @var{checkpoint-id}
2730 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2734 Returning to a previously saved checkpoint will restore the user state
2735 of the program being debugged, plus a significant subset of the system
2736 (OS) state, including file pointers. It won't ``un-write'' data from
2737 a file, but it will rewind the file pointer to the previous location,
2738 so that the previously written data can be overwritten. For files
2739 opened in read mode, the pointer will also be restored so that the
2740 previously read data can be read again.
2742 Of course, characters that have been sent to a printer (or other
2743 external device) cannot be ``snatched back'', and characters received
2744 from eg.@: a serial device can be removed from internal program buffers,
2745 but they cannot be ``pushed back'' into the serial pipeline, ready to
2746 be received again. Similarly, the actual contents of files that have
2747 been changed cannot be restored (at this time).
2749 However, within those constraints, you actually can ``rewind'' your
2750 program to a previously saved point in time, and begin debugging it
2751 again --- and you can change the course of events so as to debug a
2752 different execution path this time.
2754 @cindex checkpoints and process id
2755 Finally, there is one bit of internal program state that will be
2756 different when you return to a checkpoint --- the program's process
2757 id. Each checkpoint will have a unique process id (or @var{pid}),
2758 and each will be different from the program's original @var{pid}.
2759 If your program has saved a local copy of its process id, this could
2760 potentially pose a problem.
2762 @subsection A Non-obvious Benefit of Using Checkpoints
2764 On some systems such as @sc{gnu}/Linux, address space randomization
2765 is performed on new processes for security reasons. This makes it
2766 difficult or impossible to set a breakpoint, or watchpoint, on an
2767 absolute address if you have to restart the program, since the
2768 absolute location of a symbol will change from one execution to the
2771 A checkpoint, however, is an @emph{identical} copy of a process.
2772 Therefore if you create a checkpoint at (eg.@:) the start of main,
2773 and simply return to that checkpoint instead of restarting the
2774 process, you can avoid the effects of address randomization and
2775 your symbols will all stay in the same place.
2778 @chapter Stopping and Continuing
2780 The principal purposes of using a debugger are so that you can stop your
2781 program before it terminates; or so that, if your program runs into
2782 trouble, you can investigate and find out why.
2784 Inside @value{GDBN}, your program may stop for any of several reasons,
2785 such as a signal, a breakpoint, or reaching a new line after a
2786 @value{GDBN} command such as @code{step}. You may then examine and
2787 change variables, set new breakpoints or remove old ones, and then
2788 continue execution. Usually, the messages shown by @value{GDBN} provide
2789 ample explanation of the status of your program---but you can also
2790 explicitly request this information at any time.
2793 @kindex info program
2795 Display information about the status of your program: whether it is
2796 running or not, what process it is, and why it stopped.
2800 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2801 * Continuing and Stepping:: Resuming execution
2803 * Thread Stops:: Stopping and starting multi-thread programs
2807 @section Breakpoints, Watchpoints, and Catchpoints
2810 A @dfn{breakpoint} makes your program stop whenever a certain point in
2811 the program is reached. For each breakpoint, you can add conditions to
2812 control in finer detail whether your program stops. You can set
2813 breakpoints with the @code{break} command and its variants (@pxref{Set
2814 Breaks, ,Setting Breakpoints}), to specify the place where your program
2815 should stop by line number, function name or exact address in the
2818 On some systems, you can set breakpoints in shared libraries before
2819 the executable is run. There is a minor limitation on HP-UX systems:
2820 you must wait until the executable is run in order to set breakpoints
2821 in shared library routines that are not called directly by the program
2822 (for example, routines that are arguments in a @code{pthread_create}
2826 @cindex data breakpoints
2827 @cindex memory tracing
2828 @cindex breakpoint on memory address
2829 @cindex breakpoint on variable modification
2830 A @dfn{watchpoint} is a special breakpoint that stops your program
2831 when the value of an expression changes. The expression may be a value
2832 of a variable, or it could involve values of one or more variables
2833 combined by operators, such as @samp{a + b}. This is sometimes called
2834 @dfn{data breakpoints}. You must use a different command to set
2835 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2836 from that, you can manage a watchpoint like any other breakpoint: you
2837 enable, disable, and delete both breakpoints and watchpoints using the
2840 You can arrange to have values from your program displayed automatically
2841 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2845 @cindex breakpoint on events
2846 A @dfn{catchpoint} is another special breakpoint that stops your program
2847 when a certain kind of event occurs, such as the throwing of a C@t{++}
2848 exception or the loading of a library. As with watchpoints, you use a
2849 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2850 Catchpoints}), but aside from that, you can manage a catchpoint like any
2851 other breakpoint. (To stop when your program receives a signal, use the
2852 @code{handle} command; see @ref{Signals, ,Signals}.)
2854 @cindex breakpoint numbers
2855 @cindex numbers for breakpoints
2856 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2857 catchpoint when you create it; these numbers are successive integers
2858 starting with one. In many of the commands for controlling various
2859 features of breakpoints you use the breakpoint number to say which
2860 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2861 @dfn{disabled}; if disabled, it has no effect on your program until you
2864 @cindex breakpoint ranges
2865 @cindex ranges of breakpoints
2866 Some @value{GDBN} commands accept a range of breakpoints on which to
2867 operate. A breakpoint range is either a single breakpoint number, like
2868 @samp{5}, or two such numbers, in increasing order, separated by a
2869 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2870 all breakpoints in that range are operated on.
2873 * Set Breaks:: Setting breakpoints
2874 * Set Watchpoints:: Setting watchpoints
2875 * Set Catchpoints:: Setting catchpoints
2876 * Delete Breaks:: Deleting breakpoints
2877 * Disabling:: Disabling breakpoints
2878 * Conditions:: Break conditions
2879 * Break Commands:: Breakpoint command lists
2880 * Error in Breakpoints:: ``Cannot insert breakpoints''
2881 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2885 @subsection Setting Breakpoints
2887 @c FIXME LMB what does GDB do if no code on line of breakpt?
2888 @c consider in particular declaration with/without initialization.
2890 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2893 @kindex b @r{(@code{break})}
2894 @vindex $bpnum@r{, convenience variable}
2895 @cindex latest breakpoint
2896 Breakpoints are set with the @code{break} command (abbreviated
2897 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2898 number of the breakpoint you've set most recently; see @ref{Convenience
2899 Vars,, Convenience Variables}, for a discussion of what you can do with
2900 convenience variables.
2903 @item break @var{location}
2904 Set a breakpoint at the given @var{location}, which can specify a
2905 function name, a line number, or an address of an instruction.
2906 (@xref{Specify Location}, for a list of all the possible ways to
2907 specify a @var{location}.) The breakpoint will stop your program just
2908 before it executes any of the code in the specified @var{location}.
2910 When using source languages that permit overloading of symbols, such as
2911 C@t{++}, a function name may refer to more than one possible place to break.
2912 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
2916 When called without any arguments, @code{break} sets a breakpoint at
2917 the next instruction to be executed in the selected stack frame
2918 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2919 innermost, this makes your program stop as soon as control
2920 returns to that frame. This is similar to the effect of a
2921 @code{finish} command in the frame inside the selected frame---except
2922 that @code{finish} does not leave an active breakpoint. If you use
2923 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2924 the next time it reaches the current location; this may be useful
2927 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2928 least one instruction has been executed. If it did not do this, you
2929 would be unable to proceed past a breakpoint without first disabling the
2930 breakpoint. This rule applies whether or not the breakpoint already
2931 existed when your program stopped.
2933 @item break @dots{} if @var{cond}
2934 Set a breakpoint with condition @var{cond}; evaluate the expression
2935 @var{cond} each time the breakpoint is reached, and stop only if the
2936 value is nonzero---that is, if @var{cond} evaluates as true.
2937 @samp{@dots{}} stands for one of the possible arguments described
2938 above (or no argument) specifying where to break. @xref{Conditions,
2939 ,Break Conditions}, for more information on breakpoint conditions.
2942 @item tbreak @var{args}
2943 Set a breakpoint enabled only for one stop. @var{args} are the
2944 same as for the @code{break} command, and the breakpoint is set in the same
2945 way, but the breakpoint is automatically deleted after the first time your
2946 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2949 @cindex hardware breakpoints
2950 @item hbreak @var{args}
2951 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2952 @code{break} command and the breakpoint is set in the same way, but the
2953 breakpoint requires hardware support and some target hardware may not
2954 have this support. The main purpose of this is EPROM/ROM code
2955 debugging, so you can set a breakpoint at an instruction without
2956 changing the instruction. This can be used with the new trap-generation
2957 provided by SPARClite DSU and most x86-based targets. These targets
2958 will generate traps when a program accesses some data or instruction
2959 address that is assigned to the debug registers. However the hardware
2960 breakpoint registers can take a limited number of breakpoints. For
2961 example, on the DSU, only two data breakpoints can be set at a time, and
2962 @value{GDBN} will reject this command if more than two are used. Delete
2963 or disable unused hardware breakpoints before setting new ones
2964 (@pxref{Disabling, ,Disabling Breakpoints}).
2965 @xref{Conditions, ,Break Conditions}.
2966 For remote targets, you can restrict the number of hardware
2967 breakpoints @value{GDBN} will use, see @ref{set remote
2968 hardware-breakpoint-limit}.
2971 @item thbreak @var{args}
2972 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2973 are the same as for the @code{hbreak} command and the breakpoint is set in
2974 the same way. However, like the @code{tbreak} command,
2975 the breakpoint is automatically deleted after the
2976 first time your program stops there. Also, like the @code{hbreak}
2977 command, the breakpoint requires hardware support and some target hardware
2978 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2979 See also @ref{Conditions, ,Break Conditions}.
2982 @cindex regular expression
2983 @cindex breakpoints in functions matching a regexp
2984 @cindex set breakpoints in many functions
2985 @item rbreak @var{regex}
2986 Set breakpoints on all functions matching the regular expression
2987 @var{regex}. This command sets an unconditional breakpoint on all
2988 matches, printing a list of all breakpoints it set. Once these
2989 breakpoints are set, they are treated just like the breakpoints set with
2990 the @code{break} command. You can delete them, disable them, or make
2991 them conditional the same way as any other breakpoint.
2993 The syntax of the regular expression is the standard one used with tools
2994 like @file{grep}. Note that this is different from the syntax used by
2995 shells, so for instance @code{foo*} matches all functions that include
2996 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2997 @code{.*} leading and trailing the regular expression you supply, so to
2998 match only functions that begin with @code{foo}, use @code{^foo}.
3000 @cindex non-member C@t{++} functions, set breakpoint in
3001 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3002 breakpoints on overloaded functions that are not members of any special
3005 @cindex set breakpoints on all functions
3006 The @code{rbreak} command can be used to set breakpoints in
3007 @strong{all} the functions in a program, like this:
3010 (@value{GDBP}) rbreak .
3013 @kindex info breakpoints
3014 @cindex @code{$_} and @code{info breakpoints}
3015 @item info breakpoints @r{[}@var{n}@r{]}
3016 @itemx info break @r{[}@var{n}@r{]}
3017 @itemx info watchpoints @r{[}@var{n}@r{]}
3018 Print a table of all breakpoints, watchpoints, and catchpoints set and
3019 not deleted. Optional argument @var{n} means print information only
3020 about the specified breakpoint (or watchpoint or catchpoint). For
3021 each breakpoint, following columns are printed:
3024 @item Breakpoint Numbers
3026 Breakpoint, watchpoint, or catchpoint.
3028 Whether the breakpoint is marked to be disabled or deleted when hit.
3029 @item Enabled or Disabled
3030 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3031 that are not enabled.
3033 Where the breakpoint is in your program, as a memory address. For a
3034 pending breakpoint whose address is not yet known, this field will
3035 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3036 library that has the symbol or line referred by breakpoint is loaded.
3037 See below for details. A breakpoint with several locations will
3038 have @samp{<MULTIPLE>} in this field---see below for details.
3040 Where the breakpoint is in the source for your program, as a file and
3041 line number. For a pending breakpoint, the original string passed to
3042 the breakpoint command will be listed as it cannot be resolved until
3043 the appropriate shared library is loaded in the future.
3047 If a breakpoint is conditional, @code{info break} shows the condition on
3048 the line following the affected breakpoint; breakpoint commands, if any,
3049 are listed after that. A pending breakpoint is allowed to have a condition
3050 specified for it. The condition is not parsed for validity until a shared
3051 library is loaded that allows the pending breakpoint to resolve to a
3055 @code{info break} with a breakpoint
3056 number @var{n} as argument lists only that breakpoint. The
3057 convenience variable @code{$_} and the default examining-address for
3058 the @code{x} command are set to the address of the last breakpoint
3059 listed (@pxref{Memory, ,Examining Memory}).
3062 @code{info break} displays a count of the number of times the breakpoint
3063 has been hit. This is especially useful in conjunction with the
3064 @code{ignore} command. You can ignore a large number of breakpoint
3065 hits, look at the breakpoint info to see how many times the breakpoint
3066 was hit, and then run again, ignoring one less than that number. This
3067 will get you quickly to the last hit of that breakpoint.
3070 @value{GDBN} allows you to set any number of breakpoints at the same place in
3071 your program. There is nothing silly or meaningless about this. When
3072 the breakpoints are conditional, this is even useful
3073 (@pxref{Conditions, ,Break Conditions}).
3075 @cindex multiple locations, breakpoints
3076 @cindex breakpoints, multiple locations
3077 It is possible that a breakpoint corresponds to several locations
3078 in your program. Examples of this situation are:
3082 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3083 instances of the function body, used in different cases.
3086 For a C@t{++} template function, a given line in the function can
3087 correspond to any number of instantiations.
3090 For an inlined function, a given source line can correspond to
3091 several places where that function is inlined.
3094 In all those cases, @value{GDBN} will insert a breakpoint at all
3095 the relevant locations@footnote{
3096 As of this writing, multiple-location breakpoints work only if there's
3097 line number information for all the locations. This means that they
3098 will generally not work in system libraries, unless you have debug
3099 info with line numbers for them.}.
3101 A breakpoint with multiple locations is displayed in the breakpoint
3102 table using several rows---one header row, followed by one row for
3103 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3104 address column. The rows for individual locations contain the actual
3105 addresses for locations, and show the functions to which those
3106 locations belong. The number column for a location is of the form
3107 @var{breakpoint-number}.@var{location-number}.
3112 Num Type Disp Enb Address What
3113 1 breakpoint keep y <MULTIPLE>
3115 breakpoint already hit 1 time
3116 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3117 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3120 Each location can be individually enabled or disabled by passing
3121 @var{breakpoint-number}.@var{location-number} as argument to the
3122 @code{enable} and @code{disable} commands. Note that you cannot
3123 delete the individual locations from the list, you can only delete the
3124 entire list of locations that belong to their parent breakpoint (with
3125 the @kbd{delete @var{num}} command, where @var{num} is the number of
3126 the parent breakpoint, 1 in the above example). Disabling or enabling
3127 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3128 that belong to that breakpoint.
3130 @cindex pending breakpoints
3131 It's quite common to have a breakpoint inside a shared library.
3132 Shared libraries can be loaded and unloaded explicitly,
3133 and possibly repeatedly, as the program is executed. To support
3134 this use case, @value{GDBN} updates breakpoint locations whenever
3135 any shared library is loaded or unloaded. Typically, you would
3136 set a breakpoint in a shared library at the beginning of your
3137 debugging session, when the library is not loaded, and when the
3138 symbols from the library are not available. When you try to set
3139 breakpoint, @value{GDBN} will ask you if you want to set
3140 a so called @dfn{pending breakpoint}---breakpoint whose address
3141 is not yet resolved.
3143 After the program is run, whenever a new shared library is loaded,
3144 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3145 shared library contains the symbol or line referred to by some
3146 pending breakpoint, that breakpoint is resolved and becomes an
3147 ordinary breakpoint. When a library is unloaded, all breakpoints
3148 that refer to its symbols or source lines become pending again.
3150 This logic works for breakpoints with multiple locations, too. For
3151 example, if you have a breakpoint in a C@t{++} template function, and
3152 a newly loaded shared library has an instantiation of that template,
3153 a new location is added to the list of locations for the breakpoint.
3155 Except for having unresolved address, pending breakpoints do not
3156 differ from regular breakpoints. You can set conditions or commands,
3157 enable and disable them and perform other breakpoint operations.
3159 @value{GDBN} provides some additional commands for controlling what
3160 happens when the @samp{break} command cannot resolve breakpoint
3161 address specification to an address:
3163 @kindex set breakpoint pending
3164 @kindex show breakpoint pending
3166 @item set breakpoint pending auto
3167 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3168 location, it queries you whether a pending breakpoint should be created.
3170 @item set breakpoint pending on
3171 This indicates that an unrecognized breakpoint location should automatically
3172 result in a pending breakpoint being created.
3174 @item set breakpoint pending off
3175 This indicates that pending breakpoints are not to be created. Any
3176 unrecognized breakpoint location results in an error. This setting does
3177 not affect any pending breakpoints previously created.
3179 @item show breakpoint pending
3180 Show the current behavior setting for creating pending breakpoints.
3183 The settings above only affect the @code{break} command and its
3184 variants. Once breakpoint is set, it will be automatically updated
3185 as shared libraries are loaded and unloaded.
3187 @cindex automatic hardware breakpoints
3188 For some targets, @value{GDBN} can automatically decide if hardware or
3189 software breakpoints should be used, depending on whether the
3190 breakpoint address is read-only or read-write. This applies to
3191 breakpoints set with the @code{break} command as well as to internal
3192 breakpoints set by commands like @code{next} and @code{finish}. For
3193 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3196 You can control this automatic behaviour with the following commands::
3198 @kindex set breakpoint auto-hw
3199 @kindex show breakpoint auto-hw
3201 @item set breakpoint auto-hw on
3202 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3203 will try to use the target memory map to decide if software or hardware
3204 breakpoint must be used.
3206 @item set breakpoint auto-hw off
3207 This indicates @value{GDBN} should not automatically select breakpoint
3208 type. If the target provides a memory map, @value{GDBN} will warn when
3209 trying to set software breakpoint at a read-only address.
3212 @value{GDBN} normally implements breakpoints by replacing the program code
3213 at the breakpoint address with a special instruction, which, when
3214 executed, given control to the debugger. By default, the program
3215 code is so modified only when the program is resumed. As soon as
3216 the program stops, @value{GDBN} restores the original instructions. This
3217 behaviour guards against leaving breakpoints inserted in the
3218 target should gdb abrubptly disconnect. However, with slow remote
3219 targets, inserting and removing breakpoint can reduce the performance.
3220 This behavior can be controlled with the following commands::
3222 @kindex set breakpoint always-inserted
3223 @kindex show breakpoint always-inserted
3225 @item set breakpoint always-inserted off
3226 This is the default behaviour. All breakpoints, including newly added
3227 by the user, are inserted in the target only when the target is
3228 resumed. All breakpoints are removed from the target when it stops.
3230 @item set breakpoint always-inserted on
3231 Causes all breakpoints to be inserted in the target at all times. If
3232 the user adds a new breakpoint, or changes an existing breakpoint, the
3233 breakpoints in the target are updated immediately. A breakpoint is
3234 removed from the target only when breakpoint itself is removed.
3237 @cindex negative breakpoint numbers
3238 @cindex internal @value{GDBN} breakpoints
3239 @value{GDBN} itself sometimes sets breakpoints in your program for
3240 special purposes, such as proper handling of @code{longjmp} (in C
3241 programs). These internal breakpoints are assigned negative numbers,
3242 starting with @code{-1}; @samp{info breakpoints} does not display them.
3243 You can see these breakpoints with the @value{GDBN} maintenance command
3244 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3247 @node Set Watchpoints
3248 @subsection Setting Watchpoints
3250 @cindex setting watchpoints
3251 You can use a watchpoint to stop execution whenever the value of an
3252 expression changes, without having to predict a particular place where
3253 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3254 The expression may be as simple as the value of a single variable, or
3255 as complex as many variables combined by operators. Examples include:
3259 A reference to the value of a single variable.
3262 An address cast to an appropriate data type. For example,
3263 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3264 address (assuming an @code{int} occupies 4 bytes).
3267 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3268 expression can use any operators valid in the program's native
3269 language (@pxref{Languages}).
3272 You can set a watchpoint on an expression even if the expression can
3273 not be evaluated yet. For instance, you can set a watchpoint on
3274 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3275 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3276 the expression produces a valid value. If the expression becomes
3277 valid in some other way than changing a variable (e.g.@: if the memory
3278 pointed to by @samp{*global_ptr} becomes readable as the result of a
3279 @code{malloc} call), @value{GDBN} may not stop until the next time
3280 the expression changes.
3282 @cindex software watchpoints
3283 @cindex hardware watchpoints
3284 Depending on your system, watchpoints may be implemented in software or
3285 hardware. @value{GDBN} does software watchpointing by single-stepping your
3286 program and testing the variable's value each time, which is hundreds of
3287 times slower than normal execution. (But this may still be worth it, to
3288 catch errors where you have no clue what part of your program is the
3291 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3292 x86-based targets, @value{GDBN} includes support for hardware
3293 watchpoints, which do not slow down the running of your program.
3297 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3298 Set a watchpoint for an expression. @value{GDBN} will break when the
3299 expression @var{expr} is written into by the program and its value
3300 changes. The simplest (and the most popular) use of this command is
3301 to watch the value of a single variable:
3304 (@value{GDBP}) watch foo
3307 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3308 clause, @value{GDBN} breaks only when the thread identified by
3309 @var{threadnum} changes the value of @var{expr}. If any other threads
3310 change the value of @var{expr}, @value{GDBN} will not break. Note
3311 that watchpoints restricted to a single thread in this way only work
3312 with Hardware Watchpoints.
3315 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3316 Set a watchpoint that will break when the value of @var{expr} is read
3320 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3321 Set a watchpoint that will break when @var{expr} is either read from
3322 or written into by the program.
3324 @kindex info watchpoints @r{[}@var{n}@r{]}
3325 @item info watchpoints
3326 This command prints a list of watchpoints, breakpoints, and catchpoints;
3327 it is the same as @code{info break} (@pxref{Set Breaks}).
3330 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3331 watchpoints execute very quickly, and the debugger reports a change in
3332 value at the exact instruction where the change occurs. If @value{GDBN}
3333 cannot set a hardware watchpoint, it sets a software watchpoint, which
3334 executes more slowly and reports the change in value at the next
3335 @emph{statement}, not the instruction, after the change occurs.
3337 @cindex use only software watchpoints
3338 You can force @value{GDBN} to use only software watchpoints with the
3339 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3340 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3341 the underlying system supports them. (Note that hardware-assisted
3342 watchpoints that were set @emph{before} setting
3343 @code{can-use-hw-watchpoints} to zero will still use the hardware
3344 mechanism of watching expression values.)
3347 @item set can-use-hw-watchpoints
3348 @kindex set can-use-hw-watchpoints
3349 Set whether or not to use hardware watchpoints.
3351 @item show can-use-hw-watchpoints
3352 @kindex show can-use-hw-watchpoints
3353 Show the current mode of using hardware watchpoints.
3356 For remote targets, you can restrict the number of hardware
3357 watchpoints @value{GDBN} will use, see @ref{set remote
3358 hardware-breakpoint-limit}.
3360 When you issue the @code{watch} command, @value{GDBN} reports
3363 Hardware watchpoint @var{num}: @var{expr}
3367 if it was able to set a hardware watchpoint.
3369 Currently, the @code{awatch} and @code{rwatch} commands can only set
3370 hardware watchpoints, because accesses to data that don't change the
3371 value of the watched expression cannot be detected without examining
3372 every instruction as it is being executed, and @value{GDBN} does not do
3373 that currently. If @value{GDBN} finds that it is unable to set a
3374 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3375 will print a message like this:
3378 Expression cannot be implemented with read/access watchpoint.
3381 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3382 data type of the watched expression is wider than what a hardware
3383 watchpoint on the target machine can handle. For example, some systems
3384 can only watch regions that are up to 4 bytes wide; on such systems you
3385 cannot set hardware watchpoints for an expression that yields a
3386 double-precision floating-point number (which is typically 8 bytes
3387 wide). As a work-around, it might be possible to break the large region
3388 into a series of smaller ones and watch them with separate watchpoints.
3390 If you set too many hardware watchpoints, @value{GDBN} might be unable
3391 to insert all of them when you resume the execution of your program.
3392 Since the precise number of active watchpoints is unknown until such
3393 time as the program is about to be resumed, @value{GDBN} might not be
3394 able to warn you about this when you set the watchpoints, and the
3395 warning will be printed only when the program is resumed:
3398 Hardware watchpoint @var{num}: Could not insert watchpoint
3402 If this happens, delete or disable some of the watchpoints.
3404 Watching complex expressions that reference many variables can also
3405 exhaust the resources available for hardware-assisted watchpoints.
3406 That's because @value{GDBN} needs to watch every variable in the
3407 expression with separately allocated resources.
3409 If you call a function interactively using @code{print} or @code{call},
3410 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3411 kind of breakpoint or the call completes.
3413 @value{GDBN} automatically deletes watchpoints that watch local
3414 (automatic) variables, or expressions that involve such variables, when
3415 they go out of scope, that is, when the execution leaves the block in
3416 which these variables were defined. In particular, when the program
3417 being debugged terminates, @emph{all} local variables go out of scope,
3418 and so only watchpoints that watch global variables remain set. If you
3419 rerun the program, you will need to set all such watchpoints again. One
3420 way of doing that would be to set a code breakpoint at the entry to the
3421 @code{main} function and when it breaks, set all the watchpoints.
3423 @cindex watchpoints and threads
3424 @cindex threads and watchpoints
3425 In multi-threaded programs, watchpoints will detect changes to the
3426 watched expression from every thread.
3429 @emph{Warning:} In multi-threaded programs, software watchpoints
3430 have only limited usefulness. If @value{GDBN} creates a software
3431 watchpoint, it can only watch the value of an expression @emph{in a
3432 single thread}. If you are confident that the expression can only
3433 change due to the current thread's activity (and if you are also
3434 confident that no other thread can become current), then you can use
3435 software watchpoints as usual. However, @value{GDBN} may not notice
3436 when a non-current thread's activity changes the expression. (Hardware
3437 watchpoints, in contrast, watch an expression in all threads.)
3440 @xref{set remote hardware-watchpoint-limit}.
3442 @node Set Catchpoints
3443 @subsection Setting Catchpoints
3444 @cindex catchpoints, setting
3445 @cindex exception handlers
3446 @cindex event handling
3448 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3449 kinds of program events, such as C@t{++} exceptions or the loading of a
3450 shared library. Use the @code{catch} command to set a catchpoint.
3454 @item catch @var{event}
3455 Stop when @var{event} occurs. @var{event} can be any of the following:
3458 @cindex stop on C@t{++} exceptions
3459 The throwing of a C@t{++} exception.
3462 The catching of a C@t{++} exception.
3465 @cindex Ada exception catching
3466 @cindex catch Ada exceptions
3467 An Ada exception being raised. If an exception name is specified
3468 at the end of the command (eg @code{catch exception Program_Error}),
3469 the debugger will stop only when this specific exception is raised.
3470 Otherwise, the debugger stops execution when any Ada exception is raised.
3472 @item exception unhandled
3473 An exception that was raised but is not handled by the program.
3476 A failed Ada assertion.
3479 @cindex break on fork/exec
3480 A call to @code{exec}. This is currently only available for HP-UX
3484 A call to @code{fork}. This is currently only available for HP-UX
3488 A call to @code{vfork}. This is currently only available for HP-UX
3492 @itemx load @var{libname}
3493 @cindex break on load/unload of shared library
3494 The dynamic loading of any shared library, or the loading of the library
3495 @var{libname}. This is currently only available for HP-UX.
3498 @itemx unload @var{libname}
3499 The unloading of any dynamically loaded shared library, or the unloading
3500 of the library @var{libname}. This is currently only available for HP-UX.
3503 @item tcatch @var{event}
3504 Set a catchpoint that is enabled only for one stop. The catchpoint is
3505 automatically deleted after the first time the event is caught.
3509 Use the @code{info break} command to list the current catchpoints.
3511 There are currently some limitations to C@t{++} exception handling
3512 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3516 If you call a function interactively, @value{GDBN} normally returns
3517 control to you when the function has finished executing. If the call
3518 raises an exception, however, the call may bypass the mechanism that
3519 returns control to you and cause your program either to abort or to
3520 simply continue running until it hits a breakpoint, catches a signal
3521 that @value{GDBN} is listening for, or exits. This is the case even if
3522 you set a catchpoint for the exception; catchpoints on exceptions are
3523 disabled within interactive calls.
3526 You cannot raise an exception interactively.
3529 You cannot install an exception handler interactively.
3532 @cindex raise exceptions
3533 Sometimes @code{catch} is not the best way to debug exception handling:
3534 if you need to know exactly where an exception is raised, it is better to
3535 stop @emph{before} the exception handler is called, since that way you
3536 can see the stack before any unwinding takes place. If you set a
3537 breakpoint in an exception handler instead, it may not be easy to find
3538 out where the exception was raised.
3540 To stop just before an exception handler is called, you need some
3541 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3542 raised by calling a library function named @code{__raise_exception}
3543 which has the following ANSI C interface:
3546 /* @var{addr} is where the exception identifier is stored.
3547 @var{id} is the exception identifier. */
3548 void __raise_exception (void **addr, void *id);
3552 To make the debugger catch all exceptions before any stack
3553 unwinding takes place, set a breakpoint on @code{__raise_exception}
3554 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3556 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3557 that depends on the value of @var{id}, you can stop your program when
3558 a specific exception is raised. You can use multiple conditional
3559 breakpoints to stop your program when any of a number of exceptions are
3564 @subsection Deleting Breakpoints
3566 @cindex clearing breakpoints, watchpoints, catchpoints
3567 @cindex deleting breakpoints, watchpoints, catchpoints
3568 It is often necessary to eliminate a breakpoint, watchpoint, or
3569 catchpoint once it has done its job and you no longer want your program
3570 to stop there. This is called @dfn{deleting} the breakpoint. A
3571 breakpoint that has been deleted no longer exists; it is forgotten.
3573 With the @code{clear} command you can delete breakpoints according to
3574 where they are in your program. With the @code{delete} command you can
3575 delete individual breakpoints, watchpoints, or catchpoints by specifying
3576 their breakpoint numbers.
3578 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3579 automatically ignores breakpoints on the first instruction to be executed
3580 when you continue execution without changing the execution address.
3585 Delete any breakpoints at the next instruction to be executed in the
3586 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3587 the innermost frame is selected, this is a good way to delete a
3588 breakpoint where your program just stopped.
3590 @item clear @var{location}
3591 Delete any breakpoints set at the specified @var{location}.
3592 @xref{Specify Location}, for the various forms of @var{location}; the
3593 most useful ones are listed below:
3596 @item clear @var{function}
3597 @itemx clear @var{filename}:@var{function}
3598 Delete any breakpoints set at entry to the named @var{function}.
3600 @item clear @var{linenum}
3601 @itemx clear @var{filename}:@var{linenum}
3602 Delete any breakpoints set at or within the code of the specified
3603 @var{linenum} of the specified @var{filename}.
3606 @cindex delete breakpoints
3608 @kindex d @r{(@code{delete})}
3609 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3610 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3611 ranges specified as arguments. If no argument is specified, delete all
3612 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3613 confirm off}). You can abbreviate this command as @code{d}.
3617 @subsection Disabling Breakpoints
3619 @cindex enable/disable a breakpoint
3620 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3621 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3622 it had been deleted, but remembers the information on the breakpoint so
3623 that you can @dfn{enable} it again later.
3625 You disable and enable breakpoints, watchpoints, and catchpoints with
3626 the @code{enable} and @code{disable} commands, optionally specifying one
3627 or more breakpoint numbers as arguments. Use @code{info break} or
3628 @code{info watch} to print a list of breakpoints, watchpoints, and
3629 catchpoints if you do not know which numbers to use.
3631 Disabling and enabling a breakpoint that has multiple locations
3632 affects all of its locations.
3634 A breakpoint, watchpoint, or catchpoint can have any of four different
3635 states of enablement:
3639 Enabled. The breakpoint stops your program. A breakpoint set
3640 with the @code{break} command starts out in this state.
3642 Disabled. The breakpoint has no effect on your program.
3644 Enabled once. The breakpoint stops your program, but then becomes
3647 Enabled for deletion. The breakpoint stops your program, but
3648 immediately after it does so it is deleted permanently. A breakpoint
3649 set with the @code{tbreak} command starts out in this state.
3652 You can use the following commands to enable or disable breakpoints,
3653 watchpoints, and catchpoints:
3657 @kindex dis @r{(@code{disable})}
3658 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3659 Disable the specified breakpoints---or all breakpoints, if none are
3660 listed. A disabled breakpoint has no effect but is not forgotten. All
3661 options such as ignore-counts, conditions and commands are remembered in
3662 case the breakpoint is enabled again later. You may abbreviate
3663 @code{disable} as @code{dis}.
3666 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3667 Enable the specified breakpoints (or all defined breakpoints). They
3668 become effective once again in stopping your program.
3670 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3671 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3672 of these breakpoints immediately after stopping your program.
3674 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3675 Enable the specified breakpoints to work once, then die. @value{GDBN}
3676 deletes any of these breakpoints as soon as your program stops there.
3677 Breakpoints set by the @code{tbreak} command start out in this state.
3680 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3681 @c confusing: tbreak is also initially enabled.
3682 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3683 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3684 subsequently, they become disabled or enabled only when you use one of
3685 the commands above. (The command @code{until} can set and delete a
3686 breakpoint of its own, but it does not change the state of your other
3687 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3691 @subsection Break Conditions
3692 @cindex conditional breakpoints
3693 @cindex breakpoint conditions
3695 @c FIXME what is scope of break condition expr? Context where wanted?
3696 @c in particular for a watchpoint?
3697 The simplest sort of breakpoint breaks every time your program reaches a
3698 specified place. You can also specify a @dfn{condition} for a
3699 breakpoint. A condition is just a Boolean expression in your
3700 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3701 a condition evaluates the expression each time your program reaches it,
3702 and your program stops only if the condition is @emph{true}.
3704 This is the converse of using assertions for program validation; in that
3705 situation, you want to stop when the assertion is violated---that is,
3706 when the condition is false. In C, if you want to test an assertion expressed
3707 by the condition @var{assert}, you should set the condition
3708 @samp{! @var{assert}} on the appropriate breakpoint.
3710 Conditions are also accepted for watchpoints; you may not need them,
3711 since a watchpoint is inspecting the value of an expression anyhow---but
3712 it might be simpler, say, to just set a watchpoint on a variable name,
3713 and specify a condition that tests whether the new value is an interesting
3716 Break conditions can have side effects, and may even call functions in
3717 your program. This can be useful, for example, to activate functions
3718 that log program progress, or to use your own print functions to
3719 format special data structures. The effects are completely predictable
3720 unless there is another enabled breakpoint at the same address. (In
3721 that case, @value{GDBN} might see the other breakpoint first and stop your
3722 program without checking the condition of this one.) Note that
3723 breakpoint commands are usually more convenient and flexible than break
3725 purpose of performing side effects when a breakpoint is reached
3726 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3728 Break conditions can be specified when a breakpoint is set, by using
3729 @samp{if} in the arguments to the @code{break} command. @xref{Set
3730 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3731 with the @code{condition} command.
3733 You can also use the @code{if} keyword with the @code{watch} command.
3734 The @code{catch} command does not recognize the @code{if} keyword;
3735 @code{condition} is the only way to impose a further condition on a
3740 @item condition @var{bnum} @var{expression}
3741 Specify @var{expression} as the break condition for breakpoint,
3742 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3743 breakpoint @var{bnum} stops your program only if the value of
3744 @var{expression} is true (nonzero, in C). When you use
3745 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3746 syntactic correctness, and to determine whether symbols in it have
3747 referents in the context of your breakpoint. If @var{expression} uses
3748 symbols not referenced in the context of the breakpoint, @value{GDBN}
3749 prints an error message:
3752 No symbol "foo" in current context.
3757 not actually evaluate @var{expression} at the time the @code{condition}
3758 command (or a command that sets a breakpoint with a condition, like
3759 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3761 @item condition @var{bnum}
3762 Remove the condition from breakpoint number @var{bnum}. It becomes
3763 an ordinary unconditional breakpoint.
3766 @cindex ignore count (of breakpoint)
3767 A special case of a breakpoint condition is to stop only when the
3768 breakpoint has been reached a certain number of times. This is so
3769 useful that there is a special way to do it, using the @dfn{ignore
3770 count} of the breakpoint. Every breakpoint has an ignore count, which
3771 is an integer. Most of the time, the ignore count is zero, and
3772 therefore has no effect. But if your program reaches a breakpoint whose
3773 ignore count is positive, then instead of stopping, it just decrements
3774 the ignore count by one and continues. As a result, if the ignore count
3775 value is @var{n}, the breakpoint does not stop the next @var{n} times
3776 your program reaches it.
3780 @item ignore @var{bnum} @var{count}
3781 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3782 The next @var{count} times the breakpoint is reached, your program's
3783 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3786 To make the breakpoint stop the next time it is reached, specify
3789 When you use @code{continue} to resume execution of your program from a
3790 breakpoint, you can specify an ignore count directly as an argument to
3791 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3792 Stepping,,Continuing and Stepping}.
3794 If a breakpoint has a positive ignore count and a condition, the
3795 condition is not checked. Once the ignore count reaches zero,
3796 @value{GDBN} resumes checking the condition.
3798 You could achieve the effect of the ignore count with a condition such
3799 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3800 is decremented each time. @xref{Convenience Vars, ,Convenience
3804 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3807 @node Break Commands
3808 @subsection Breakpoint Command Lists
3810 @cindex breakpoint commands
3811 You can give any breakpoint (or watchpoint or catchpoint) a series of
3812 commands to execute when your program stops due to that breakpoint. For
3813 example, you might want to print the values of certain expressions, or
3814 enable other breakpoints.
3818 @kindex end@r{ (breakpoint commands)}
3819 @item commands @r{[}@var{bnum}@r{]}
3820 @itemx @dots{} @var{command-list} @dots{}
3822 Specify a list of commands for breakpoint number @var{bnum}. The commands
3823 themselves appear on the following lines. Type a line containing just
3824 @code{end} to terminate the commands.
3826 To remove all commands from a breakpoint, type @code{commands} and
3827 follow it immediately with @code{end}; that is, give no commands.
3829 With no @var{bnum} argument, @code{commands} refers to the last
3830 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3831 recently encountered).
3834 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3835 disabled within a @var{command-list}.
3837 You can use breakpoint commands to start your program up again. Simply
3838 use the @code{continue} command, or @code{step}, or any other command
3839 that resumes execution.
3841 Any other commands in the command list, after a command that resumes
3842 execution, are ignored. This is because any time you resume execution
3843 (even with a simple @code{next} or @code{step}), you may encounter
3844 another breakpoint---which could have its own command list, leading to
3845 ambiguities about which list to execute.
3848 If the first command you specify in a command list is @code{silent}, the
3849 usual message about stopping at a breakpoint is not printed. This may
3850 be desirable for breakpoints that are to print a specific message and
3851 then continue. If none of the remaining commands print anything, you
3852 see no sign that the breakpoint was reached. @code{silent} is
3853 meaningful only at the beginning of a breakpoint command list.
3855 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3856 print precisely controlled output, and are often useful in silent
3857 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3859 For example, here is how you could use breakpoint commands to print the
3860 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3866 printf "x is %d\n",x
3871 One application for breakpoint commands is to compensate for one bug so
3872 you can test for another. Put a breakpoint just after the erroneous line
3873 of code, give it a condition to detect the case in which something
3874 erroneous has been done, and give it commands to assign correct values
3875 to any variables that need them. End with the @code{continue} command
3876 so that your program does not stop, and start with the @code{silent}
3877 command so that no output is produced. Here is an example:
3888 @c @ifclear BARETARGET
3889 @node Error in Breakpoints
3890 @subsection ``Cannot insert breakpoints''
3892 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3894 Under some operating systems, breakpoints cannot be used in a program if
3895 any other process is running that program. In this situation,
3896 attempting to run or continue a program with a breakpoint causes
3897 @value{GDBN} to print an error message:
3900 Cannot insert breakpoints.
3901 The same program may be running in another process.
3904 When this happens, you have three ways to proceed:
3908 Remove or disable the breakpoints, then continue.
3911 Suspend @value{GDBN}, and copy the file containing your program to a new
3912 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3913 that @value{GDBN} should run your program under that name.
3914 Then start your program again.
3917 Relink your program so that the text segment is nonsharable, using the
3918 linker option @samp{-N}. The operating system limitation may not apply
3919 to nonsharable executables.
3923 A similar message can be printed if you request too many active
3924 hardware-assisted breakpoints and watchpoints:
3926 @c FIXME: the precise wording of this message may change; the relevant
3927 @c source change is not committed yet (Sep 3, 1999).
3929 Stopped; cannot insert breakpoints.
3930 You may have requested too many hardware breakpoints and watchpoints.
3934 This message is printed when you attempt to resume the program, since
3935 only then @value{GDBN} knows exactly how many hardware breakpoints and
3936 watchpoints it needs to insert.
3938 When this message is printed, you need to disable or remove some of the
3939 hardware-assisted breakpoints and watchpoints, and then continue.
3941 @node Breakpoint-related Warnings
3942 @subsection ``Breakpoint address adjusted...''
3943 @cindex breakpoint address adjusted
3945 Some processor architectures place constraints on the addresses at
3946 which breakpoints may be placed. For architectures thus constrained,
3947 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3948 with the constraints dictated by the architecture.
3950 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3951 a VLIW architecture in which a number of RISC-like instructions may be
3952 bundled together for parallel execution. The FR-V architecture
3953 constrains the location of a breakpoint instruction within such a
3954 bundle to the instruction with the lowest address. @value{GDBN}
3955 honors this constraint by adjusting a breakpoint's address to the
3956 first in the bundle.
3958 It is not uncommon for optimized code to have bundles which contain
3959 instructions from different source statements, thus it may happen that
3960 a breakpoint's address will be adjusted from one source statement to
3961 another. Since this adjustment may significantly alter @value{GDBN}'s
3962 breakpoint related behavior from what the user expects, a warning is
3963 printed when the breakpoint is first set and also when the breakpoint
3966 A warning like the one below is printed when setting a breakpoint
3967 that's been subject to address adjustment:
3970 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3973 Such warnings are printed both for user settable and @value{GDBN}'s
3974 internal breakpoints. If you see one of these warnings, you should
3975 verify that a breakpoint set at the adjusted address will have the
3976 desired affect. If not, the breakpoint in question may be removed and
3977 other breakpoints may be set which will have the desired behavior.
3978 E.g., it may be sufficient to place the breakpoint at a later
3979 instruction. A conditional breakpoint may also be useful in some
3980 cases to prevent the breakpoint from triggering too often.
3982 @value{GDBN} will also issue a warning when stopping at one of these
3983 adjusted breakpoints:
3986 warning: Breakpoint 1 address previously adjusted from 0x00010414
3990 When this warning is encountered, it may be too late to take remedial
3991 action except in cases where the breakpoint is hit earlier or more
3992 frequently than expected.
3994 @node Continuing and Stepping
3995 @section Continuing and Stepping
3999 @cindex resuming execution
4000 @dfn{Continuing} means resuming program execution until your program
4001 completes normally. In contrast, @dfn{stepping} means executing just
4002 one more ``step'' of your program, where ``step'' may mean either one
4003 line of source code, or one machine instruction (depending on what
4004 particular command you use). Either when continuing or when stepping,
4005 your program may stop even sooner, due to a breakpoint or a signal. (If
4006 it stops due to a signal, you may want to use @code{handle}, or use
4007 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4011 @kindex c @r{(@code{continue})}
4012 @kindex fg @r{(resume foreground execution)}
4013 @item continue @r{[}@var{ignore-count}@r{]}
4014 @itemx c @r{[}@var{ignore-count}@r{]}
4015 @itemx fg @r{[}@var{ignore-count}@r{]}
4016 Resume program execution, at the address where your program last stopped;
4017 any breakpoints set at that address are bypassed. The optional argument
4018 @var{ignore-count} allows you to specify a further number of times to
4019 ignore a breakpoint at this location; its effect is like that of
4020 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4022 The argument @var{ignore-count} is meaningful only when your program
4023 stopped due to a breakpoint. At other times, the argument to
4024 @code{continue} is ignored.
4026 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4027 debugged program is deemed to be the foreground program) are provided
4028 purely for convenience, and have exactly the same behavior as
4032 To resume execution at a different place, you can use @code{return}
4033 (@pxref{Returning, ,Returning from a Function}) to go back to the
4034 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4035 Different Address}) to go to an arbitrary location in your program.
4037 A typical technique for using stepping is to set a breakpoint
4038 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4039 beginning of the function or the section of your program where a problem
4040 is believed to lie, run your program until it stops at that breakpoint,
4041 and then step through the suspect area, examining the variables that are
4042 interesting, until you see the problem happen.
4046 @kindex s @r{(@code{step})}
4048 Continue running your program until control reaches a different source
4049 line, then stop it and return control to @value{GDBN}. This command is
4050 abbreviated @code{s}.
4053 @c "without debugging information" is imprecise; actually "without line
4054 @c numbers in the debugging information". (gcc -g1 has debugging info but
4055 @c not line numbers). But it seems complex to try to make that
4056 @c distinction here.
4057 @emph{Warning:} If you use the @code{step} command while control is
4058 within a function that was compiled without debugging information,
4059 execution proceeds until control reaches a function that does have
4060 debugging information. Likewise, it will not step into a function which
4061 is compiled without debugging information. To step through functions
4062 without debugging information, use the @code{stepi} command, described
4066 The @code{step} command only stops at the first instruction of a source
4067 line. This prevents the multiple stops that could otherwise occur in
4068 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4069 to stop if a function that has debugging information is called within
4070 the line. In other words, @code{step} @emph{steps inside} any functions
4071 called within the line.
4073 Also, the @code{step} command only enters a function if there is line
4074 number information for the function. Otherwise it acts like the
4075 @code{next} command. This avoids problems when using @code{cc -gl}
4076 on MIPS machines. Previously, @code{step} entered subroutines if there
4077 was any debugging information about the routine.
4079 @item step @var{count}
4080 Continue running as in @code{step}, but do so @var{count} times. If a
4081 breakpoint is reached, or a signal not related to stepping occurs before
4082 @var{count} steps, stepping stops right away.
4085 @kindex n @r{(@code{next})}
4086 @item next @r{[}@var{count}@r{]}
4087 Continue to the next source line in the current (innermost) stack frame.
4088 This is similar to @code{step}, but function calls that appear within
4089 the line of code are executed without stopping. Execution stops when
4090 control reaches a different line of code at the original stack level
4091 that was executing when you gave the @code{next} command. This command
4092 is abbreviated @code{n}.
4094 An argument @var{count} is a repeat count, as for @code{step}.
4097 @c FIX ME!! Do we delete this, or is there a way it fits in with
4098 @c the following paragraph? --- Vctoria
4100 @c @code{next} within a function that lacks debugging information acts like
4101 @c @code{step}, but any function calls appearing within the code of the
4102 @c function are executed without stopping.
4104 The @code{next} command only stops at the first instruction of a
4105 source line. This prevents multiple stops that could otherwise occur in
4106 @code{switch} statements, @code{for} loops, etc.
4108 @kindex set step-mode
4110 @cindex functions without line info, and stepping
4111 @cindex stepping into functions with no line info
4112 @itemx set step-mode on
4113 The @code{set step-mode on} command causes the @code{step} command to
4114 stop at the first instruction of a function which contains no debug line
4115 information rather than stepping over it.
4117 This is useful in cases where you may be interested in inspecting the
4118 machine instructions of a function which has no symbolic info and do not
4119 want @value{GDBN} to automatically skip over this function.
4121 @item set step-mode off
4122 Causes the @code{step} command to step over any functions which contains no
4123 debug information. This is the default.
4125 @item show step-mode
4126 Show whether @value{GDBN} will stop in or step over functions without
4127 source line debug information.
4131 Continue running until just after function in the selected stack frame
4132 returns. Print the returned value (if any).
4134 Contrast this with the @code{return} command (@pxref{Returning,
4135 ,Returning from a Function}).
4138 @kindex u @r{(@code{until})}
4139 @cindex run until specified location
4142 Continue running until a source line past the current line, in the
4143 current stack frame, is reached. This command is used to avoid single
4144 stepping through a loop more than once. It is like the @code{next}
4145 command, except that when @code{until} encounters a jump, it
4146 automatically continues execution until the program counter is greater
4147 than the address of the jump.
4149 This means that when you reach the end of a loop after single stepping
4150 though it, @code{until} makes your program continue execution until it
4151 exits the loop. In contrast, a @code{next} command at the end of a loop
4152 simply steps back to the beginning of the loop, which forces you to step
4153 through the next iteration.
4155 @code{until} always stops your program if it attempts to exit the current
4158 @code{until} may produce somewhat counterintuitive results if the order
4159 of machine code does not match the order of the source lines. For
4160 example, in the following excerpt from a debugging session, the @code{f}
4161 (@code{frame}) command shows that execution is stopped at line
4162 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4166 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4168 (@value{GDBP}) until
4169 195 for ( ; argc > 0; NEXTARG) @{
4172 This happened because, for execution efficiency, the compiler had
4173 generated code for the loop closure test at the end, rather than the
4174 start, of the loop---even though the test in a C @code{for}-loop is
4175 written before the body of the loop. The @code{until} command appeared
4176 to step back to the beginning of the loop when it advanced to this
4177 expression; however, it has not really gone to an earlier
4178 statement---not in terms of the actual machine code.
4180 @code{until} with no argument works by means of single
4181 instruction stepping, and hence is slower than @code{until} with an
4184 @item until @var{location}
4185 @itemx u @var{location}
4186 Continue running your program until either the specified location is
4187 reached, or the current stack frame returns. @var{location} is any of
4188 the forms described in @ref{Specify Location}.
4189 This form of the command uses temporary breakpoints, and
4190 hence is quicker than @code{until} without an argument. The specified
4191 location is actually reached only if it is in the current frame. This
4192 implies that @code{until} can be used to skip over recursive function
4193 invocations. For instance in the code below, if the current location is
4194 line @code{96}, issuing @code{until 99} will execute the program up to
4195 line @code{99} in the same invocation of factorial, i.e., after the inner
4196 invocations have returned.
4199 94 int factorial (int value)
4201 96 if (value > 1) @{
4202 97 value *= factorial (value - 1);
4209 @kindex advance @var{location}
4210 @itemx advance @var{location}
4211 Continue running the program up to the given @var{location}. An argument is
4212 required, which should be of one of the forms described in
4213 @ref{Specify Location}.
4214 Execution will also stop upon exit from the current stack
4215 frame. This command is similar to @code{until}, but @code{advance} will
4216 not skip over recursive function calls, and the target location doesn't
4217 have to be in the same frame as the current one.
4221 @kindex si @r{(@code{stepi})}
4223 @itemx stepi @var{arg}
4225 Execute one machine instruction, then stop and return to the debugger.
4227 It is often useful to do @samp{display/i $pc} when stepping by machine
4228 instructions. This makes @value{GDBN} automatically display the next
4229 instruction to be executed, each time your program stops. @xref{Auto
4230 Display,, Automatic Display}.
4232 An argument is a repeat count, as in @code{step}.
4236 @kindex ni @r{(@code{nexti})}
4238 @itemx nexti @var{arg}
4240 Execute one machine instruction, but if it is a function call,
4241 proceed until the function returns.
4243 An argument is a repeat count, as in @code{next}.
4250 A signal is an asynchronous event that can happen in a program. The
4251 operating system defines the possible kinds of signals, and gives each
4252 kind a name and a number. For example, in Unix @code{SIGINT} is the
4253 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4254 @code{SIGSEGV} is the signal a program gets from referencing a place in
4255 memory far away from all the areas in use; @code{SIGALRM} occurs when
4256 the alarm clock timer goes off (which happens only if your program has
4257 requested an alarm).
4259 @cindex fatal signals
4260 Some signals, including @code{SIGALRM}, are a normal part of the
4261 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4262 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4263 program has not specified in advance some other way to handle the signal.
4264 @code{SIGINT} does not indicate an error in your program, but it is normally
4265 fatal so it can carry out the purpose of the interrupt: to kill the program.
4267 @value{GDBN} has the ability to detect any occurrence of a signal in your
4268 program. You can tell @value{GDBN} in advance what to do for each kind of
4271 @cindex handling signals
4272 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4273 @code{SIGALRM} be silently passed to your program
4274 (so as not to interfere with their role in the program's functioning)
4275 but to stop your program immediately whenever an error signal happens.
4276 You can change these settings with the @code{handle} command.
4279 @kindex info signals
4283 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4284 handle each one. You can use this to see the signal numbers of all
4285 the defined types of signals.
4287 @item info signals @var{sig}
4288 Similar, but print information only about the specified signal number.
4290 @code{info handle} is an alias for @code{info signals}.
4293 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4294 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4295 can be the number of a signal or its name (with or without the
4296 @samp{SIG} at the beginning); a list of signal numbers of the form
4297 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4298 known signals. Optional arguments @var{keywords}, described below,
4299 say what change to make.
4303 The keywords allowed by the @code{handle} command can be abbreviated.
4304 Their full names are:
4308 @value{GDBN} should not stop your program when this signal happens. It may
4309 still print a message telling you that the signal has come in.
4312 @value{GDBN} should stop your program when this signal happens. This implies
4313 the @code{print} keyword as well.
4316 @value{GDBN} should print a message when this signal happens.
4319 @value{GDBN} should not mention the occurrence of the signal at all. This
4320 implies the @code{nostop} keyword as well.
4324 @value{GDBN} should allow your program to see this signal; your program
4325 can handle the signal, or else it may terminate if the signal is fatal
4326 and not handled. @code{pass} and @code{noignore} are synonyms.
4330 @value{GDBN} should not allow your program to see this signal.
4331 @code{nopass} and @code{ignore} are synonyms.
4335 When a signal stops your program, the signal is not visible to the
4337 continue. Your program sees the signal then, if @code{pass} is in
4338 effect for the signal in question @emph{at that time}. In other words,
4339 after @value{GDBN} reports a signal, you can use the @code{handle}
4340 command with @code{pass} or @code{nopass} to control whether your
4341 program sees that signal when you continue.
4343 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4344 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4345 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4348 You can also use the @code{signal} command to prevent your program from
4349 seeing a signal, or cause it to see a signal it normally would not see,
4350 or to give it any signal at any time. For example, if your program stopped
4351 due to some sort of memory reference error, you might store correct
4352 values into the erroneous variables and continue, hoping to see more
4353 execution; but your program would probably terminate immediately as
4354 a result of the fatal signal once it saw the signal. To prevent this,
4355 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4359 @section Stopping and Starting Multi-thread Programs
4361 When your program has multiple threads (@pxref{Threads,, Debugging
4362 Programs with Multiple Threads}), you can choose whether to set
4363 breakpoints on all threads, or on a particular thread.
4366 @cindex breakpoints and threads
4367 @cindex thread breakpoints
4368 @kindex break @dots{} thread @var{threadno}
4369 @item break @var{linespec} thread @var{threadno}
4370 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4371 @var{linespec} specifies source lines; there are several ways of
4372 writing them (@pxref{Specify Location}), but the effect is always to
4373 specify some source line.
4375 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4376 to specify that you only want @value{GDBN} to stop the program when a
4377 particular thread reaches this breakpoint. @var{threadno} is one of the
4378 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4379 column of the @samp{info threads} display.
4381 If you do not specify @samp{thread @var{threadno}} when you set a
4382 breakpoint, the breakpoint applies to @emph{all} threads of your
4385 You can use the @code{thread} qualifier on conditional breakpoints as
4386 well; in this case, place @samp{thread @var{threadno}} before the
4387 breakpoint condition, like this:
4390 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4395 @cindex stopped threads
4396 @cindex threads, stopped
4397 Whenever your program stops under @value{GDBN} for any reason,
4398 @emph{all} threads of execution stop, not just the current thread. This
4399 allows you to examine the overall state of the program, including
4400 switching between threads, without worrying that things may change
4403 @cindex thread breakpoints and system calls
4404 @cindex system calls and thread breakpoints
4405 @cindex premature return from system calls
4406 There is an unfortunate side effect. If one thread stops for a
4407 breakpoint, or for some other reason, and another thread is blocked in a
4408 system call, then the system call may return prematurely. This is a
4409 consequence of the interaction between multiple threads and the signals
4410 that @value{GDBN} uses to implement breakpoints and other events that
4413 To handle this problem, your program should check the return value of
4414 each system call and react appropriately. This is good programming
4417 For example, do not write code like this:
4423 The call to @code{sleep} will return early if a different thread stops
4424 at a breakpoint or for some other reason.
4426 Instead, write this:
4431 unslept = sleep (unslept);
4434 A system call is allowed to return early, so the system is still
4435 conforming to its specification. But @value{GDBN} does cause your
4436 multi-threaded program to behave differently than it would without
4439 Also, @value{GDBN} uses internal breakpoints in the thread library to
4440 monitor certain events such as thread creation and thread destruction.
4441 When such an event happens, a system call in another thread may return
4442 prematurely, even though your program does not appear to stop.
4444 @cindex continuing threads
4445 @cindex threads, continuing
4446 Conversely, whenever you restart the program, @emph{all} threads start
4447 executing. @emph{This is true even when single-stepping} with commands
4448 like @code{step} or @code{next}.
4450 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4451 Since thread scheduling is up to your debugging target's operating
4452 system (not controlled by @value{GDBN}), other threads may
4453 execute more than one statement while the current thread completes a
4454 single step. Moreover, in general other threads stop in the middle of a
4455 statement, rather than at a clean statement boundary, when the program
4458 You might even find your program stopped in another thread after
4459 continuing or even single-stepping. This happens whenever some other
4460 thread runs into a breakpoint, a signal, or an exception before the
4461 first thread completes whatever you requested.
4463 On some OSes, you can lock the OS scheduler and thus allow only a single
4467 @item set scheduler-locking @var{mode}
4468 @cindex scheduler locking mode
4469 @cindex lock scheduler
4470 Set the scheduler locking mode. If it is @code{off}, then there is no
4471 locking and any thread may run at any time. If @code{on}, then only the
4472 current thread may run when the inferior is resumed. The @code{step}
4473 mode optimizes for single-stepping. It stops other threads from
4474 ``seizing the prompt'' by preempting the current thread while you are
4475 stepping. Other threads will only rarely (or never) get a chance to run
4476 when you step. They are more likely to run when you @samp{next} over a
4477 function call, and they are completely free to run when you use commands
4478 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4479 thread hits a breakpoint during its timeslice, they will never steal the
4480 @value{GDBN} prompt away from the thread that you are debugging.
4482 @item show scheduler-locking
4483 Display the current scheduler locking mode.
4488 @chapter Examining the Stack
4490 When your program has stopped, the first thing you need to know is where it
4491 stopped and how it got there.
4494 Each time your program performs a function call, information about the call
4496 That information includes the location of the call in your program,
4497 the arguments of the call,
4498 and the local variables of the function being called.
4499 The information is saved in a block of data called a @dfn{stack frame}.
4500 The stack frames are allocated in a region of memory called the @dfn{call
4503 When your program stops, the @value{GDBN} commands for examining the
4504 stack allow you to see all of this information.
4506 @cindex selected frame
4507 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4508 @value{GDBN} commands refer implicitly to the selected frame. In
4509 particular, whenever you ask @value{GDBN} for the value of a variable in
4510 your program, the value is found in the selected frame. There are
4511 special @value{GDBN} commands to select whichever frame you are
4512 interested in. @xref{Selection, ,Selecting a Frame}.
4514 When your program stops, @value{GDBN} automatically selects the
4515 currently executing frame and describes it briefly, similar to the
4516 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4519 * Frames:: Stack frames
4520 * Backtrace:: Backtraces
4521 * Selection:: Selecting a frame
4522 * Frame Info:: Information on a frame
4527 @section Stack Frames
4529 @cindex frame, definition
4531 The call stack is divided up into contiguous pieces called @dfn{stack
4532 frames}, or @dfn{frames} for short; each frame is the data associated
4533 with one call to one function. The frame contains the arguments given
4534 to the function, the function's local variables, and the address at
4535 which the function is executing.
4537 @cindex initial frame
4538 @cindex outermost frame
4539 @cindex innermost frame
4540 When your program is started, the stack has only one frame, that of the
4541 function @code{main}. This is called the @dfn{initial} frame or the
4542 @dfn{outermost} frame. Each time a function is called, a new frame is
4543 made. Each time a function returns, the frame for that function invocation
4544 is eliminated. If a function is recursive, there can be many frames for
4545 the same function. The frame for the function in which execution is
4546 actually occurring is called the @dfn{innermost} frame. This is the most
4547 recently created of all the stack frames that still exist.
4549 @cindex frame pointer
4550 Inside your program, stack frames are identified by their addresses. A
4551 stack frame consists of many bytes, each of which has its own address; each
4552 kind of computer has a convention for choosing one byte whose
4553 address serves as the address of the frame. Usually this address is kept
4554 in a register called the @dfn{frame pointer register}
4555 (@pxref{Registers, $fp}) while execution is going on in that frame.
4557 @cindex frame number
4558 @value{GDBN} assigns numbers to all existing stack frames, starting with
4559 zero for the innermost frame, one for the frame that called it,
4560 and so on upward. These numbers do not really exist in your program;
4561 they are assigned by @value{GDBN} to give you a way of designating stack
4562 frames in @value{GDBN} commands.
4564 @c The -fomit-frame-pointer below perennially causes hbox overflow
4565 @c underflow problems.
4566 @cindex frameless execution
4567 Some compilers provide a way to compile functions so that they operate
4568 without stack frames. (For example, the @value{NGCC} option
4570 @samp{-fomit-frame-pointer}
4572 generates functions without a frame.)
4573 This is occasionally done with heavily used library functions to save
4574 the frame setup time. @value{GDBN} has limited facilities for dealing
4575 with these function invocations. If the innermost function invocation
4576 has no stack frame, @value{GDBN} nevertheless regards it as though
4577 it had a separate frame, which is numbered zero as usual, allowing
4578 correct tracing of the function call chain. However, @value{GDBN} has
4579 no provision for frameless functions elsewhere in the stack.
4582 @kindex frame@r{, command}
4583 @cindex current stack frame
4584 @item frame @var{args}
4585 The @code{frame} command allows you to move from one stack frame to another,
4586 and to print the stack frame you select. @var{args} may be either the
4587 address of the frame or the stack frame number. Without an argument,
4588 @code{frame} prints the current stack frame.
4590 @kindex select-frame
4591 @cindex selecting frame silently
4593 The @code{select-frame} command allows you to move from one stack frame
4594 to another without printing the frame. This is the silent version of
4602 @cindex call stack traces
4603 A backtrace is a summary of how your program got where it is. It shows one
4604 line per frame, for many frames, starting with the currently executing
4605 frame (frame zero), followed by its caller (frame one), and on up the
4610 @kindex bt @r{(@code{backtrace})}
4613 Print a backtrace of the entire stack: one line per frame for all
4614 frames in the stack.
4616 You can stop the backtrace at any time by typing the system interrupt
4617 character, normally @kbd{Ctrl-c}.
4619 @item backtrace @var{n}
4621 Similar, but print only the innermost @var{n} frames.
4623 @item backtrace -@var{n}
4625 Similar, but print only the outermost @var{n} frames.
4627 @item backtrace full
4629 @itemx bt full @var{n}
4630 @itemx bt full -@var{n}
4631 Print the values of the local variables also. @var{n} specifies the
4632 number of frames to print, as described above.
4637 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4638 are additional aliases for @code{backtrace}.
4640 @cindex multiple threads, backtrace
4641 In a multi-threaded program, @value{GDBN} by default shows the
4642 backtrace only for the current thread. To display the backtrace for
4643 several or all of the threads, use the command @code{thread apply}
4644 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4645 apply all backtrace}, @value{GDBN} will display the backtrace for all
4646 the threads; this is handy when you debug a core dump of a
4647 multi-threaded program.
4649 Each line in the backtrace shows the frame number and the function name.
4650 The program counter value is also shown---unless you use @code{set
4651 print address off}. The backtrace also shows the source file name and
4652 line number, as well as the arguments to the function. The program
4653 counter value is omitted if it is at the beginning of the code for that
4656 Here is an example of a backtrace. It was made with the command
4657 @samp{bt 3}, so it shows the innermost three frames.
4661 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4663 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4664 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4666 (More stack frames follow...)
4671 The display for frame zero does not begin with a program counter
4672 value, indicating that your program has stopped at the beginning of the
4673 code for line @code{993} of @code{builtin.c}.
4675 @cindex value optimized out, in backtrace
4676 @cindex function call arguments, optimized out
4677 If your program was compiled with optimizations, some compilers will
4678 optimize away arguments passed to functions if those arguments are
4679 never used after the call. Such optimizations generate code that
4680 passes arguments through registers, but doesn't store those arguments
4681 in the stack frame. @value{GDBN} has no way of displaying such
4682 arguments in stack frames other than the innermost one. Here's what
4683 such a backtrace might look like:
4687 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4689 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4690 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4692 (More stack frames follow...)
4697 The values of arguments that were not saved in their stack frames are
4698 shown as @samp{<value optimized out>}.
4700 If you need to display the values of such optimized-out arguments,
4701 either deduce that from other variables whose values depend on the one
4702 you are interested in, or recompile without optimizations.
4704 @cindex backtrace beyond @code{main} function
4705 @cindex program entry point
4706 @cindex startup code, and backtrace
4707 Most programs have a standard user entry point---a place where system
4708 libraries and startup code transition into user code. For C this is
4709 @code{main}@footnote{
4710 Note that embedded programs (the so-called ``free-standing''
4711 environment) are not required to have a @code{main} function as the
4712 entry point. They could even have multiple entry points.}.
4713 When @value{GDBN} finds the entry function in a backtrace
4714 it will terminate the backtrace, to avoid tracing into highly
4715 system-specific (and generally uninteresting) code.
4717 If you need to examine the startup code, or limit the number of levels
4718 in a backtrace, you can change this behavior:
4721 @item set backtrace past-main
4722 @itemx set backtrace past-main on
4723 @kindex set backtrace
4724 Backtraces will continue past the user entry point.
4726 @item set backtrace past-main off
4727 Backtraces will stop when they encounter the user entry point. This is the
4730 @item show backtrace past-main
4731 @kindex show backtrace
4732 Display the current user entry point backtrace policy.
4734 @item set backtrace past-entry
4735 @itemx set backtrace past-entry on
4736 Backtraces will continue past the internal entry point of an application.
4737 This entry point is encoded by the linker when the application is built,
4738 and is likely before the user entry point @code{main} (or equivalent) is called.
4740 @item set backtrace past-entry off
4741 Backtraces will stop when they encounter the internal entry point of an
4742 application. This is the default.
4744 @item show backtrace past-entry
4745 Display the current internal entry point backtrace policy.
4747 @item set backtrace limit @var{n}
4748 @itemx set backtrace limit 0
4749 @cindex backtrace limit
4750 Limit the backtrace to @var{n} levels. A value of zero means
4753 @item show backtrace limit
4754 Display the current limit on backtrace levels.
4758 @section Selecting a Frame
4760 Most commands for examining the stack and other data in your program work on
4761 whichever stack frame is selected at the moment. Here are the commands for
4762 selecting a stack frame; all of them finish by printing a brief description
4763 of the stack frame just selected.
4766 @kindex frame@r{, selecting}
4767 @kindex f @r{(@code{frame})}
4770 Select frame number @var{n}. Recall that frame zero is the innermost
4771 (currently executing) frame, frame one is the frame that called the
4772 innermost one, and so on. The highest-numbered frame is the one for
4775 @item frame @var{addr}
4777 Select the frame at address @var{addr}. This is useful mainly if the
4778 chaining of stack frames has been damaged by a bug, making it
4779 impossible for @value{GDBN} to assign numbers properly to all frames. In
4780 addition, this can be useful when your program has multiple stacks and
4781 switches between them.
4783 On the SPARC architecture, @code{frame} needs two addresses to
4784 select an arbitrary frame: a frame pointer and a stack pointer.
4786 On the MIPS and Alpha architecture, it needs two addresses: a stack
4787 pointer and a program counter.
4789 On the 29k architecture, it needs three addresses: a register stack
4790 pointer, a program counter, and a memory stack pointer.
4794 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4795 advances toward the outermost frame, to higher frame numbers, to frames
4796 that have existed longer. @var{n} defaults to one.
4799 @kindex do @r{(@code{down})}
4801 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4802 advances toward the innermost frame, to lower frame numbers, to frames
4803 that were created more recently. @var{n} defaults to one. You may
4804 abbreviate @code{down} as @code{do}.
4807 All of these commands end by printing two lines of output describing the
4808 frame. The first line shows the frame number, the function name, the
4809 arguments, and the source file and line number of execution in that
4810 frame. The second line shows the text of that source line.
4818 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4820 10 read_input_file (argv[i]);
4824 After such a printout, the @code{list} command with no arguments
4825 prints ten lines centered on the point of execution in the frame.
4826 You can also edit the program at the point of execution with your favorite
4827 editing program by typing @code{edit}.
4828 @xref{List, ,Printing Source Lines},
4832 @kindex down-silently
4834 @item up-silently @var{n}
4835 @itemx down-silently @var{n}
4836 These two commands are variants of @code{up} and @code{down},
4837 respectively; they differ in that they do their work silently, without
4838 causing display of the new frame. They are intended primarily for use
4839 in @value{GDBN} command scripts, where the output might be unnecessary and
4844 @section Information About a Frame
4846 There are several other commands to print information about the selected
4852 When used without any argument, this command does not change which
4853 frame is selected, but prints a brief description of the currently
4854 selected stack frame. It can be abbreviated @code{f}. With an
4855 argument, this command is used to select a stack frame.
4856 @xref{Selection, ,Selecting a Frame}.
4859 @kindex info f @r{(@code{info frame})}
4862 This command prints a verbose description of the selected stack frame,
4867 the address of the frame
4869 the address of the next frame down (called by this frame)
4871 the address of the next frame up (caller of this frame)
4873 the language in which the source code corresponding to this frame is written
4875 the address of the frame's arguments
4877 the address of the frame's local variables
4879 the program counter saved in it (the address of execution in the caller frame)
4881 which registers were saved in the frame
4884 @noindent The verbose description is useful when
4885 something has gone wrong that has made the stack format fail to fit
4886 the usual conventions.
4888 @item info frame @var{addr}
4889 @itemx info f @var{addr}
4890 Print a verbose description of the frame at address @var{addr}, without
4891 selecting that frame. The selected frame remains unchanged by this
4892 command. This requires the same kind of address (more than one for some
4893 architectures) that you specify in the @code{frame} command.
4894 @xref{Selection, ,Selecting a Frame}.
4898 Print the arguments of the selected frame, each on a separate line.
4902 Print the local variables of the selected frame, each on a separate
4903 line. These are all variables (declared either static or automatic)
4904 accessible at the point of execution of the selected frame.
4907 @cindex catch exceptions, list active handlers
4908 @cindex exception handlers, how to list
4910 Print a list of all the exception handlers that are active in the
4911 current stack frame at the current point of execution. To see other
4912 exception handlers, visit the associated frame (using the @code{up},
4913 @code{down}, or @code{frame} commands); then type @code{info catch}.
4914 @xref{Set Catchpoints, , Setting Catchpoints}.
4920 @chapter Examining Source Files
4922 @value{GDBN} can print parts of your program's source, since the debugging
4923 information recorded in the program tells @value{GDBN} what source files were
4924 used to build it. When your program stops, @value{GDBN} spontaneously prints
4925 the line where it stopped. Likewise, when you select a stack frame
4926 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4927 execution in that frame has stopped. You can print other portions of
4928 source files by explicit command.
4930 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4931 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4932 @value{GDBN} under @sc{gnu} Emacs}.
4935 * List:: Printing source lines
4936 * Specify Location:: How to specify code locations
4937 * Edit:: Editing source files
4938 * Search:: Searching source files
4939 * Source Path:: Specifying source directories
4940 * Machine Code:: Source and machine code
4944 @section Printing Source Lines
4947 @kindex l @r{(@code{list})}
4948 To print lines from a source file, use the @code{list} command
4949 (abbreviated @code{l}). By default, ten lines are printed.
4950 There are several ways to specify what part of the file you want to
4951 print; see @ref{Specify Location}, for the full list.
4953 Here are the forms of the @code{list} command most commonly used:
4956 @item list @var{linenum}
4957 Print lines centered around line number @var{linenum} in the
4958 current source file.
4960 @item list @var{function}
4961 Print lines centered around the beginning of function
4965 Print more lines. If the last lines printed were printed with a
4966 @code{list} command, this prints lines following the last lines
4967 printed; however, if the last line printed was a solitary line printed
4968 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4969 Stack}), this prints lines centered around that line.
4972 Print lines just before the lines last printed.
4975 @cindex @code{list}, how many lines to display
4976 By default, @value{GDBN} prints ten source lines with any of these forms of
4977 the @code{list} command. You can change this using @code{set listsize}:
4980 @kindex set listsize
4981 @item set listsize @var{count}
4982 Make the @code{list} command display @var{count} source lines (unless
4983 the @code{list} argument explicitly specifies some other number).
4985 @kindex show listsize
4987 Display the number of lines that @code{list} prints.
4990 Repeating a @code{list} command with @key{RET} discards the argument,
4991 so it is equivalent to typing just @code{list}. This is more useful
4992 than listing the same lines again. An exception is made for an
4993 argument of @samp{-}; that argument is preserved in repetition so that
4994 each repetition moves up in the source file.
4996 In general, the @code{list} command expects you to supply zero, one or two
4997 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4998 of writing them (@pxref{Specify Location}), but the effect is always
4999 to specify some source line.
5001 Here is a complete description of the possible arguments for @code{list}:
5004 @item list @var{linespec}
5005 Print lines centered around the line specified by @var{linespec}.
5007 @item list @var{first},@var{last}
5008 Print lines from @var{first} to @var{last}. Both arguments are
5009 linespecs. When a @code{list} command has two linespecs, and the
5010 source file of the second linespec is omitted, this refers to
5011 the same source file as the first linespec.
5013 @item list ,@var{last}
5014 Print lines ending with @var{last}.
5016 @item list @var{first},
5017 Print lines starting with @var{first}.
5020 Print lines just after the lines last printed.
5023 Print lines just before the lines last printed.
5026 As described in the preceding table.
5029 @node Specify Location
5030 @section Specifying a Location
5031 @cindex specifying location
5034 Several @value{GDBN} commands accept arguments that specify a location
5035 of your program's code. Since @value{GDBN} is a source-level
5036 debugger, a location usually specifies some line in the source code;
5037 for that reason, locations are also known as @dfn{linespecs}.
5039 Here are all the different ways of specifying a code location that
5040 @value{GDBN} understands:
5044 Specifies the line number @var{linenum} of the current source file.
5047 @itemx +@var{offset}
5048 Specifies the line @var{offset} lines before or after the @dfn{current
5049 line}. For the @code{list} command, the current line is the last one
5050 printed; for the breakpoint commands, this is the line at which
5051 execution stopped in the currently selected @dfn{stack frame}
5052 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5053 used as the second of the two linespecs in a @code{list} command,
5054 this specifies the line @var{offset} lines up or down from the first
5057 @item @var{filename}:@var{linenum}
5058 Specifies the line @var{linenum} in the source file @var{filename}.
5060 @item @var{function}
5061 Specifies the line that begins the body of the function @var{function}.
5062 For example, in C, this is the line with the open brace.
5064 @item @var{filename}:@var{function}
5065 Specifies the line that begins the body of the function @var{function}
5066 in the file @var{filename}. You only need the file name with a
5067 function name to avoid ambiguity when there are identically named
5068 functions in different source files.
5070 @item *@var{address}
5071 Specifies the program address @var{address}. For line-oriented
5072 commands, such as @code{list} and @code{edit}, this specifies a source
5073 line that contains @var{address}. For @code{break} and other
5074 breakpoint oriented commands, this can be used to set breakpoints in
5075 parts of your program which do not have debugging information or
5078 Here @var{address} may be any expression valid in the current working
5079 language (@pxref{Languages, working language}) that specifies a code
5080 address. In addition, as a convenience, @value{GDBN} extends the
5081 semantics of expressions used in locations to cover the situations
5082 that frequently happen during debugging. Here are the various forms
5086 @item @var{expression}
5087 Any expression valid in the current working language.
5089 @item @var{funcaddr}
5090 An address of a function or procedure derived from its name. In C,
5091 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5092 simply the function's name @var{function} (and actually a special case
5093 of a valid expression). In Pascal and Modula-2, this is
5094 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5095 (although the Pascal form also works).
5097 This form specifies the address of the function's first instruction,
5098 before the stack frame and arguments have been set up.
5100 @item '@var{filename}'::@var{funcaddr}
5101 Like @var{funcaddr} above, but also specifies the name of the source
5102 file explicitly. This is useful if the name of the function does not
5103 specify the function unambiguously, e.g., if there are several
5104 functions with identical names in different source files.
5111 @section Editing Source Files
5112 @cindex editing source files
5115 @kindex e @r{(@code{edit})}
5116 To edit the lines in a source file, use the @code{edit} command.
5117 The editing program of your choice
5118 is invoked with the current line set to
5119 the active line in the program.
5120 Alternatively, there are several ways to specify what part of the file you
5121 want to print if you want to see other parts of the program:
5124 @item edit @var{location}
5125 Edit the source file specified by @code{location}. Editing starts at
5126 that @var{location}, e.g., at the specified source line of the
5127 specified file. @xref{Specify Location}, for all the possible forms
5128 of the @var{location} argument; here are the forms of the @code{edit}
5129 command most commonly used:
5132 @item edit @var{number}
5133 Edit the current source file with @var{number} as the active line number.
5135 @item edit @var{function}
5136 Edit the file containing @var{function} at the beginning of its definition.
5141 @subsection Choosing your Editor
5142 You can customize @value{GDBN} to use any editor you want
5144 The only restriction is that your editor (say @code{ex}), recognizes the
5145 following command-line syntax:
5147 ex +@var{number} file
5149 The optional numeric value +@var{number} specifies the number of the line in
5150 the file where to start editing.}.
5151 By default, it is @file{@value{EDITOR}}, but you can change this
5152 by setting the environment variable @code{EDITOR} before using
5153 @value{GDBN}. For example, to configure @value{GDBN} to use the
5154 @code{vi} editor, you could use these commands with the @code{sh} shell:
5160 or in the @code{csh} shell,
5162 setenv EDITOR /usr/bin/vi
5167 @section Searching Source Files
5168 @cindex searching source files
5170 There are two commands for searching through the current source file for a
5175 @kindex forward-search
5176 @item forward-search @var{regexp}
5177 @itemx search @var{regexp}
5178 The command @samp{forward-search @var{regexp}} checks each line,
5179 starting with the one following the last line listed, for a match for
5180 @var{regexp}. It lists the line that is found. You can use the
5181 synonym @samp{search @var{regexp}} or abbreviate the command name as
5184 @kindex reverse-search
5185 @item reverse-search @var{regexp}
5186 The command @samp{reverse-search @var{regexp}} checks each line, starting
5187 with the one before the last line listed and going backward, for a match
5188 for @var{regexp}. It lists the line that is found. You can abbreviate
5189 this command as @code{rev}.
5193 @section Specifying Source Directories
5196 @cindex directories for source files
5197 Executable programs sometimes do not record the directories of the source
5198 files from which they were compiled, just the names. Even when they do,
5199 the directories could be moved between the compilation and your debugging
5200 session. @value{GDBN} has a list of directories to search for source files;
5201 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5202 it tries all the directories in the list, in the order they are present
5203 in the list, until it finds a file with the desired name.
5205 For example, suppose an executable references the file
5206 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5207 @file{/mnt/cross}. The file is first looked up literally; if this
5208 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5209 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5210 message is printed. @value{GDBN} does not look up the parts of the
5211 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5212 Likewise, the subdirectories of the source path are not searched: if
5213 the source path is @file{/mnt/cross}, and the binary refers to
5214 @file{foo.c}, @value{GDBN} would not find it under
5215 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5217 Plain file names, relative file names with leading directories, file
5218 names containing dots, etc.@: are all treated as described above; for
5219 instance, if the source path is @file{/mnt/cross}, and the source file
5220 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5221 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5222 that---@file{/mnt/cross/foo.c}.
5224 Note that the executable search path is @emph{not} used to locate the
5227 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5228 any information it has cached about where source files are found and where
5229 each line is in the file.
5233 When you start @value{GDBN}, its source path includes only @samp{cdir}
5234 and @samp{cwd}, in that order.
5235 To add other directories, use the @code{directory} command.
5237 The search path is used to find both program source files and @value{GDBN}
5238 script files (read using the @samp{-command} option and @samp{source} command).
5240 In addition to the source path, @value{GDBN} provides a set of commands
5241 that manage a list of source path substitution rules. A @dfn{substitution
5242 rule} specifies how to rewrite source directories stored in the program's
5243 debug information in case the sources were moved to a different
5244 directory between compilation and debugging. A rule is made of
5245 two strings, the first specifying what needs to be rewritten in
5246 the path, and the second specifying how it should be rewritten.
5247 In @ref{set substitute-path}, we name these two parts @var{from} and
5248 @var{to} respectively. @value{GDBN} does a simple string replacement
5249 of @var{from} with @var{to} at the start of the directory part of the
5250 source file name, and uses that result instead of the original file
5251 name to look up the sources.
5253 Using the previous example, suppose the @file{foo-1.0} tree has been
5254 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5255 @value{GDBN} to replace @file{/usr/src} in all source path names with
5256 @file{/mnt/cross}. The first lookup will then be
5257 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5258 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5259 substitution rule, use the @code{set substitute-path} command
5260 (@pxref{set substitute-path}).
5262 To avoid unexpected substitution results, a rule is applied only if the
5263 @var{from} part of the directory name ends at a directory separator.
5264 For instance, a rule substituting @file{/usr/source} into
5265 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5266 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5267 is applied only at the beginning of the directory name, this rule will
5268 not be applied to @file{/root/usr/source/baz.c} either.
5270 In many cases, you can achieve the same result using the @code{directory}
5271 command. However, @code{set substitute-path} can be more efficient in
5272 the case where the sources are organized in a complex tree with multiple
5273 subdirectories. With the @code{directory} command, you need to add each
5274 subdirectory of your project. If you moved the entire tree while
5275 preserving its internal organization, then @code{set substitute-path}
5276 allows you to direct the debugger to all the sources with one single
5279 @code{set substitute-path} is also more than just a shortcut command.
5280 The source path is only used if the file at the original location no
5281 longer exists. On the other hand, @code{set substitute-path} modifies
5282 the debugger behavior to look at the rewritten location instead. So, if
5283 for any reason a source file that is not relevant to your executable is
5284 located at the original location, a substitution rule is the only
5285 method available to point @value{GDBN} at the new location.
5288 @item directory @var{dirname} @dots{}
5289 @item dir @var{dirname} @dots{}
5290 Add directory @var{dirname} to the front of the source path. Several
5291 directory names may be given to this command, separated by @samp{:}
5292 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5293 part of absolute file names) or
5294 whitespace. You may specify a directory that is already in the source
5295 path; this moves it forward, so @value{GDBN} searches it sooner.
5299 @vindex $cdir@r{, convenience variable}
5300 @vindex $cwd@r{, convenience variable}
5301 @cindex compilation directory
5302 @cindex current directory
5303 @cindex working directory
5304 @cindex directory, current
5305 @cindex directory, compilation
5306 You can use the string @samp{$cdir} to refer to the compilation
5307 directory (if one is recorded), and @samp{$cwd} to refer to the current
5308 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5309 tracks the current working directory as it changes during your @value{GDBN}
5310 session, while the latter is immediately expanded to the current
5311 directory at the time you add an entry to the source path.
5314 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5316 @c RET-repeat for @code{directory} is explicitly disabled, but since
5317 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5319 @item show directories
5320 @kindex show directories
5321 Print the source path: show which directories it contains.
5323 @anchor{set substitute-path}
5324 @item set substitute-path @var{from} @var{to}
5325 @kindex set substitute-path
5326 Define a source path substitution rule, and add it at the end of the
5327 current list of existing substitution rules. If a rule with the same
5328 @var{from} was already defined, then the old rule is also deleted.
5330 For example, if the file @file{/foo/bar/baz.c} was moved to
5331 @file{/mnt/cross/baz.c}, then the command
5334 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5338 will tell @value{GDBN} to replace @samp{/usr/src} with
5339 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5340 @file{baz.c} even though it was moved.
5342 In the case when more than one substitution rule have been defined,
5343 the rules are evaluated one by one in the order where they have been
5344 defined. The first one matching, if any, is selected to perform
5347 For instance, if we had entered the following commands:
5350 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5351 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5355 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5356 @file{/mnt/include/defs.h} by using the first rule. However, it would
5357 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5358 @file{/mnt/src/lib/foo.c}.
5361 @item unset substitute-path [path]
5362 @kindex unset substitute-path
5363 If a path is specified, search the current list of substitution rules
5364 for a rule that would rewrite that path. Delete that rule if found.
5365 A warning is emitted by the debugger if no rule could be found.
5367 If no path is specified, then all substitution rules are deleted.
5369 @item show substitute-path [path]
5370 @kindex show substitute-path
5371 If a path is specified, then print the source path substitution rule
5372 which would rewrite that path, if any.
5374 If no path is specified, then print all existing source path substitution
5379 If your source path is cluttered with directories that are no longer of
5380 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5381 versions of source. You can correct the situation as follows:
5385 Use @code{directory} with no argument to reset the source path to its default value.
5388 Use @code{directory} with suitable arguments to reinstall the
5389 directories you want in the source path. You can add all the
5390 directories in one command.
5394 @section Source and Machine Code
5395 @cindex source line and its code address
5397 You can use the command @code{info line} to map source lines to program
5398 addresses (and vice versa), and the command @code{disassemble} to display
5399 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5400 mode, the @code{info line} command causes the arrow to point to the
5401 line specified. Also, @code{info line} prints addresses in symbolic form as
5406 @item info line @var{linespec}
5407 Print the starting and ending addresses of the compiled code for
5408 source line @var{linespec}. You can specify source lines in any of
5409 the ways documented in @ref{Specify Location}.
5412 For example, we can use @code{info line} to discover the location of
5413 the object code for the first line of function
5414 @code{m4_changequote}:
5416 @c FIXME: I think this example should also show the addresses in
5417 @c symbolic form, as they usually would be displayed.
5419 (@value{GDBP}) info line m4_changequote
5420 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5424 @cindex code address and its source line
5425 We can also inquire (using @code{*@var{addr}} as the form for
5426 @var{linespec}) what source line covers a particular address:
5428 (@value{GDBP}) info line *0x63ff
5429 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5432 @cindex @code{$_} and @code{info line}
5433 @cindex @code{x} command, default address
5434 @kindex x@r{(examine), and} info line
5435 After @code{info line}, the default address for the @code{x} command
5436 is changed to the starting address of the line, so that @samp{x/i} is
5437 sufficient to begin examining the machine code (@pxref{Memory,
5438 ,Examining Memory}). Also, this address is saved as the value of the
5439 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5444 @cindex assembly instructions
5445 @cindex instructions, assembly
5446 @cindex machine instructions
5447 @cindex listing machine instructions
5449 This specialized command dumps a range of memory as machine
5450 instructions. The default memory range is the function surrounding the
5451 program counter of the selected frame. A single argument to this
5452 command is a program counter value; @value{GDBN} dumps the function
5453 surrounding this value. Two arguments specify a range of addresses
5454 (first inclusive, second exclusive) to dump.
5457 The following example shows the disassembly of a range of addresses of
5458 HP PA-RISC 2.0 code:
5461 (@value{GDBP}) disas 0x32c4 0x32e4
5462 Dump of assembler code from 0x32c4 to 0x32e4:
5463 0x32c4 <main+204>: addil 0,dp
5464 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5465 0x32cc <main+212>: ldil 0x3000,r31
5466 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5467 0x32d4 <main+220>: ldo 0(r31),rp
5468 0x32d8 <main+224>: addil -0x800,dp
5469 0x32dc <main+228>: ldo 0x588(r1),r26
5470 0x32e0 <main+232>: ldil 0x3000,r31
5471 End of assembler dump.
5474 Some architectures have more than one commonly-used set of instruction
5475 mnemonics or other syntax.
5477 For programs that were dynamically linked and use shared libraries,
5478 instructions that call functions or branch to locations in the shared
5479 libraries might show a seemingly bogus location---it's actually a
5480 location of the relocation table. On some architectures, @value{GDBN}
5481 might be able to resolve these to actual function names.
5484 @kindex set disassembly-flavor
5485 @cindex Intel disassembly flavor
5486 @cindex AT&T disassembly flavor
5487 @item set disassembly-flavor @var{instruction-set}
5488 Select the instruction set to use when disassembling the
5489 program via the @code{disassemble} or @code{x/i} commands.
5491 Currently this command is only defined for the Intel x86 family. You
5492 can set @var{instruction-set} to either @code{intel} or @code{att}.
5493 The default is @code{att}, the AT&T flavor used by default by Unix
5494 assemblers for x86-based targets.
5496 @kindex show disassembly-flavor
5497 @item show disassembly-flavor
5498 Show the current setting of the disassembly flavor.
5503 @chapter Examining Data
5505 @cindex printing data
5506 @cindex examining data
5509 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5510 @c document because it is nonstandard... Under Epoch it displays in a
5511 @c different window or something like that.
5512 The usual way to examine data in your program is with the @code{print}
5513 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5514 evaluates and prints the value of an expression of the language your
5515 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5516 Different Languages}).
5519 @item print @var{expr}
5520 @itemx print /@var{f} @var{expr}
5521 @var{expr} is an expression (in the source language). By default the
5522 value of @var{expr} is printed in a format appropriate to its data type;
5523 you can choose a different format by specifying @samp{/@var{f}}, where
5524 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5528 @itemx print /@var{f}
5529 @cindex reprint the last value
5530 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5531 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5532 conveniently inspect the same value in an alternative format.
5535 A more low-level way of examining data is with the @code{x} command.
5536 It examines data in memory at a specified address and prints it in a
5537 specified format. @xref{Memory, ,Examining Memory}.
5539 If you are interested in information about types, or about how the
5540 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5541 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5545 * Expressions:: Expressions
5546 * Ambiguous Expressions:: Ambiguous Expressions
5547 * Variables:: Program variables
5548 * Arrays:: Artificial arrays
5549 * Output Formats:: Output formats
5550 * Memory:: Examining memory
5551 * Auto Display:: Automatic display
5552 * Print Settings:: Print settings
5553 * Value History:: Value history
5554 * Convenience Vars:: Convenience variables
5555 * Registers:: Registers
5556 * Floating Point Hardware:: Floating point hardware
5557 * Vector Unit:: Vector Unit
5558 * OS Information:: Auxiliary data provided by operating system
5559 * Memory Region Attributes:: Memory region attributes
5560 * Dump/Restore Files:: Copy between memory and a file
5561 * Core File Generation:: Cause a program dump its core
5562 * Character Sets:: Debugging programs that use a different
5563 character set than GDB does
5564 * Caching Remote Data:: Data caching for remote targets
5568 @section Expressions
5571 @code{print} and many other @value{GDBN} commands accept an expression and
5572 compute its value. Any kind of constant, variable or operator defined
5573 by the programming language you are using is valid in an expression in
5574 @value{GDBN}. This includes conditional expressions, function calls,
5575 casts, and string constants. It also includes preprocessor macros, if
5576 you compiled your program to include this information; see
5579 @cindex arrays in expressions
5580 @value{GDBN} supports array constants in expressions input by
5581 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5582 you can use the command @code{print @{1, 2, 3@}} to create an array
5583 of three integers. If you pass an array to a function or assign it
5584 to a program variable, @value{GDBN} copies the array to memory that
5585 is @code{malloc}ed in the target program.
5587 Because C is so widespread, most of the expressions shown in examples in
5588 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5589 Languages}, for information on how to use expressions in other
5592 In this section, we discuss operators that you can use in @value{GDBN}
5593 expressions regardless of your programming language.
5595 @cindex casts, in expressions
5596 Casts are supported in all languages, not just in C, because it is so
5597 useful to cast a number into a pointer in order to examine a structure
5598 at that address in memory.
5599 @c FIXME: casts supported---Mod2 true?
5601 @value{GDBN} supports these operators, in addition to those common
5602 to programming languages:
5606 @samp{@@} is a binary operator for treating parts of memory as arrays.
5607 @xref{Arrays, ,Artificial Arrays}, for more information.
5610 @samp{::} allows you to specify a variable in terms of the file or
5611 function where it is defined. @xref{Variables, ,Program Variables}.
5613 @cindex @{@var{type}@}
5614 @cindex type casting memory
5615 @cindex memory, viewing as typed object
5616 @cindex casts, to view memory
5617 @item @{@var{type}@} @var{addr}
5618 Refers to an object of type @var{type} stored at address @var{addr} in
5619 memory. @var{addr} may be any expression whose value is an integer or
5620 pointer (but parentheses are required around binary operators, just as in
5621 a cast). This construct is allowed regardless of what kind of data is
5622 normally supposed to reside at @var{addr}.
5625 @node Ambiguous Expressions
5626 @section Ambiguous Expressions
5627 @cindex ambiguous expressions
5629 Expressions can sometimes contain some ambiguous elements. For instance,
5630 some programming languages (notably Ada, C@t{++} and Objective-C) permit
5631 a single function name to be defined several times, for application in
5632 different contexts. This is called @dfn{overloading}. Another example
5633 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
5634 templates and is typically instantiated several times, resulting in
5635 the same function name being defined in different contexts.
5637 In some cases and depending on the language, it is possible to adjust
5638 the expression to remove the ambiguity. For instance in C@t{++}, you
5639 can specify the signature of the function you want to break on, as in
5640 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
5641 qualified name of your function often makes the expression unambiguous
5644 When an ambiguity that needs to be resolved is detected, the debugger
5645 has the capability to display a menu of numbered choices for each
5646 possibility, and then waits for the selection with the prompt @samp{>}.
5647 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
5648 aborts the current command. If the command in which the expression was
5649 used allows more than one choice to be selected, the next option in the
5650 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
5653 For example, the following session excerpt shows an attempt to set a
5654 breakpoint at the overloaded symbol @code{String::after}.
5655 We choose three particular definitions of that function name:
5657 @c FIXME! This is likely to change to show arg type lists, at least
5660 (@value{GDBP}) b String::after
5663 [2] file:String.cc; line number:867
5664 [3] file:String.cc; line number:860
5665 [4] file:String.cc; line number:875
5666 [5] file:String.cc; line number:853
5667 [6] file:String.cc; line number:846
5668 [7] file:String.cc; line number:735
5670 Breakpoint 1 at 0xb26c: file String.cc, line 867.
5671 Breakpoint 2 at 0xb344: file String.cc, line 875.
5672 Breakpoint 3 at 0xafcc: file String.cc, line 846.
5673 Multiple breakpoints were set.
5674 Use the "delete" command to delete unwanted
5681 @kindex set multiple-symbols
5682 @item set multiple-symbols @var{mode}
5683 @cindex multiple-symbols menu
5685 This option allows you to adjust the debugger behavior when an expression
5688 By default, @var{mode} is set to @code{all}. If the command with which
5689 the expression is used allows more than one choice, then @value{GDBN}
5690 automatically selects all possible choices. For instance, inserting
5691 a breakpoint on a function using an ambiguous name results in a breakpoint
5692 inserted on each possible match. However, if a unique choice must be made,
5693 then @value{GDBN} uses the menu to help you disambiguate the expression.
5694 For instance, printing the address of an overloaded function will result
5695 in the use of the menu.
5697 When @var{mode} is set to @code{ask}, the debugger always uses the menu
5698 when an ambiguity is detected.
5700 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
5701 an error due to the ambiguity and the command is aborted.
5703 @kindex show multiple-symbols
5704 @item show multiple-symbols
5705 Show the current value of the @code{multiple-symbols} setting.
5709 @section Program Variables
5711 The most common kind of expression to use is the name of a variable
5714 Variables in expressions are understood in the selected stack frame
5715 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5719 global (or file-static)
5726 visible according to the scope rules of the
5727 programming language from the point of execution in that frame
5730 @noindent This means that in the function
5745 you can examine and use the variable @code{a} whenever your program is
5746 executing within the function @code{foo}, but you can only use or
5747 examine the variable @code{b} while your program is executing inside
5748 the block where @code{b} is declared.
5750 @cindex variable name conflict
5751 There is an exception: you can refer to a variable or function whose
5752 scope is a single source file even if the current execution point is not
5753 in this file. But it is possible to have more than one such variable or
5754 function with the same name (in different source files). If that
5755 happens, referring to that name has unpredictable effects. If you wish,
5756 you can specify a static variable in a particular function or file,
5757 using the colon-colon (@code{::}) notation:
5759 @cindex colon-colon, context for variables/functions
5761 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5762 @cindex @code{::}, context for variables/functions
5765 @var{file}::@var{variable}
5766 @var{function}::@var{variable}
5770 Here @var{file} or @var{function} is the name of the context for the
5771 static @var{variable}. In the case of file names, you can use quotes to
5772 make sure @value{GDBN} parses the file name as a single word---for example,
5773 to print a global value of @code{x} defined in @file{f2.c}:
5776 (@value{GDBP}) p 'f2.c'::x
5779 @cindex C@t{++} scope resolution
5780 This use of @samp{::} is very rarely in conflict with the very similar
5781 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5782 scope resolution operator in @value{GDBN} expressions.
5783 @c FIXME: Um, so what happens in one of those rare cases where it's in
5786 @cindex wrong values
5787 @cindex variable values, wrong
5788 @cindex function entry/exit, wrong values of variables
5789 @cindex optimized code, wrong values of variables
5791 @emph{Warning:} Occasionally, a local variable may appear to have the
5792 wrong value at certain points in a function---just after entry to a new
5793 scope, and just before exit.
5795 You may see this problem when you are stepping by machine instructions.
5796 This is because, on most machines, it takes more than one instruction to
5797 set up a stack frame (including local variable definitions); if you are
5798 stepping by machine instructions, variables may appear to have the wrong
5799 values until the stack frame is completely built. On exit, it usually
5800 also takes more than one machine instruction to destroy a stack frame;
5801 after you begin stepping through that group of instructions, local
5802 variable definitions may be gone.
5804 This may also happen when the compiler does significant optimizations.
5805 To be sure of always seeing accurate values, turn off all optimization
5808 @cindex ``No symbol "foo" in current context''
5809 Another possible effect of compiler optimizations is to optimize
5810 unused variables out of existence, or assign variables to registers (as
5811 opposed to memory addresses). Depending on the support for such cases
5812 offered by the debug info format used by the compiler, @value{GDBN}
5813 might not be able to display values for such local variables. If that
5814 happens, @value{GDBN} will print a message like this:
5817 No symbol "foo" in current context.
5820 To solve such problems, either recompile without optimizations, or use a
5821 different debug info format, if the compiler supports several such
5822 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5823 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5824 produces debug info in a format that is superior to formats such as
5825 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5826 an effective form for debug info. @xref{Debugging Options,,Options
5827 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5828 Compiler Collection (GCC)}.
5829 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5830 that are best suited to C@t{++} programs.
5832 If you ask to print an object whose contents are unknown to
5833 @value{GDBN}, e.g., because its data type is not completely specified
5834 by the debug information, @value{GDBN} will say @samp{<incomplete
5835 type>}. @xref{Symbols, incomplete type}, for more about this.
5837 Strings are identified as arrays of @code{char} values without specified
5838 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5839 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5840 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5841 defines literal string type @code{"char"} as @code{char} without a sign.
5846 signed char var1[] = "A";
5849 You get during debugging
5854 $2 = @{65 'A', 0 '\0'@}
5858 @section Artificial Arrays
5860 @cindex artificial array
5862 @kindex @@@r{, referencing memory as an array}
5863 It is often useful to print out several successive objects of the
5864 same type in memory; a section of an array, or an array of
5865 dynamically determined size for which only a pointer exists in the
5868 You can do this by referring to a contiguous span of memory as an
5869 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5870 operand of @samp{@@} should be the first element of the desired array
5871 and be an individual object. The right operand should be the desired length
5872 of the array. The result is an array value whose elements are all of
5873 the type of the left argument. The first element is actually the left
5874 argument; the second element comes from bytes of memory immediately
5875 following those that hold the first element, and so on. Here is an
5876 example. If a program says
5879 int *array = (int *) malloc (len * sizeof (int));
5883 you can print the contents of @code{array} with
5889 The left operand of @samp{@@} must reside in memory. Array values made
5890 with @samp{@@} in this way behave just like other arrays in terms of
5891 subscripting, and are coerced to pointers when used in expressions.
5892 Artificial arrays most often appear in expressions via the value history
5893 (@pxref{Value History, ,Value History}), after printing one out.
5895 Another way to create an artificial array is to use a cast.
5896 This re-interprets a value as if it were an array.
5897 The value need not be in memory:
5899 (@value{GDBP}) p/x (short[2])0x12345678
5900 $1 = @{0x1234, 0x5678@}
5903 As a convenience, if you leave the array length out (as in
5904 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5905 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5907 (@value{GDBP}) p/x (short[])0x12345678
5908 $2 = @{0x1234, 0x5678@}
5911 Sometimes the artificial array mechanism is not quite enough; in
5912 moderately complex data structures, the elements of interest may not
5913 actually be adjacent---for example, if you are interested in the values
5914 of pointers in an array. One useful work-around in this situation is
5915 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5916 Variables}) as a counter in an expression that prints the first
5917 interesting value, and then repeat that expression via @key{RET}. For
5918 instance, suppose you have an array @code{dtab} of pointers to
5919 structures, and you are interested in the values of a field @code{fv}
5920 in each structure. Here is an example of what you might type:
5930 @node Output Formats
5931 @section Output Formats
5933 @cindex formatted output
5934 @cindex output formats
5935 By default, @value{GDBN} prints a value according to its data type. Sometimes
5936 this is not what you want. For example, you might want to print a number
5937 in hex, or a pointer in decimal. Or you might want to view data in memory
5938 at a certain address as a character string or as an instruction. To do
5939 these things, specify an @dfn{output format} when you print a value.
5941 The simplest use of output formats is to say how to print a value
5942 already computed. This is done by starting the arguments of the
5943 @code{print} command with a slash and a format letter. The format
5944 letters supported are:
5948 Regard the bits of the value as an integer, and print the integer in
5952 Print as integer in signed decimal.
5955 Print as integer in unsigned decimal.
5958 Print as integer in octal.
5961 Print as integer in binary. The letter @samp{t} stands for ``two''.
5962 @footnote{@samp{b} cannot be used because these format letters are also
5963 used with the @code{x} command, where @samp{b} stands for ``byte'';
5964 see @ref{Memory,,Examining Memory}.}
5967 @cindex unknown address, locating
5968 @cindex locate address
5969 Print as an address, both absolute in hexadecimal and as an offset from
5970 the nearest preceding symbol. You can use this format used to discover
5971 where (in what function) an unknown address is located:
5974 (@value{GDBP}) p/a 0x54320
5975 $3 = 0x54320 <_initialize_vx+396>
5979 The command @code{info symbol 0x54320} yields similar results.
5980 @xref{Symbols, info symbol}.
5983 Regard as an integer and print it as a character constant. This
5984 prints both the numerical value and its character representation. The
5985 character representation is replaced with the octal escape @samp{\nnn}
5986 for characters outside the 7-bit @sc{ascii} range.
5988 Without this format, @value{GDBN} displays @code{char},
5989 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
5990 constants. Single-byte members of vectors are displayed as integer
5994 Regard the bits of the value as a floating point number and print
5995 using typical floating point syntax.
5998 @cindex printing strings
5999 @cindex printing byte arrays
6000 Regard as a string, if possible. With this format, pointers to single-byte
6001 data are displayed as null-terminated strings and arrays of single-byte data
6002 are displayed as fixed-length strings. Other values are displayed in their
6005 Without this format, @value{GDBN} displays pointers to and arrays of
6006 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6007 strings. Single-byte members of a vector are displayed as an integer
6011 For example, to print the program counter in hex (@pxref{Registers}), type
6018 Note that no space is required before the slash; this is because command
6019 names in @value{GDBN} cannot contain a slash.
6021 To reprint the last value in the value history with a different format,
6022 you can use the @code{print} command with just a format and no
6023 expression. For example, @samp{p/x} reprints the last value in hex.
6026 @section Examining Memory
6028 You can use the command @code{x} (for ``examine'') to examine memory in
6029 any of several formats, independently of your program's data types.
6031 @cindex examining memory
6033 @kindex x @r{(examine memory)}
6034 @item x/@var{nfu} @var{addr}
6037 Use the @code{x} command to examine memory.
6040 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6041 much memory to display and how to format it; @var{addr} is an
6042 expression giving the address where you want to start displaying memory.
6043 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6044 Several commands set convenient defaults for @var{addr}.
6047 @item @var{n}, the repeat count
6048 The repeat count is a decimal integer; the default is 1. It specifies
6049 how much memory (counting by units @var{u}) to display.
6050 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6053 @item @var{f}, the display format
6054 The display format is one of the formats used by @code{print}
6055 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6056 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6057 The default is @samp{x} (hexadecimal) initially. The default changes
6058 each time you use either @code{x} or @code{print}.
6060 @item @var{u}, the unit size
6061 The unit size is any of
6067 Halfwords (two bytes).
6069 Words (four bytes). This is the initial default.
6071 Giant words (eight bytes).
6074 Each time you specify a unit size with @code{x}, that size becomes the
6075 default unit the next time you use @code{x}. (For the @samp{s} and
6076 @samp{i} formats, the unit size is ignored and is normally not written.)
6078 @item @var{addr}, starting display address
6079 @var{addr} is the address where you want @value{GDBN} to begin displaying
6080 memory. The expression need not have a pointer value (though it may);
6081 it is always interpreted as an integer address of a byte of memory.
6082 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6083 @var{addr} is usually just after the last address examined---but several
6084 other commands also set the default address: @code{info breakpoints} (to
6085 the address of the last breakpoint listed), @code{info line} (to the
6086 starting address of a line), and @code{print} (if you use it to display
6087 a value from memory).
6090 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6091 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6092 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6093 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6094 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6096 Since the letters indicating unit sizes are all distinct from the
6097 letters specifying output formats, you do not have to remember whether
6098 unit size or format comes first; either order works. The output
6099 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6100 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6102 Even though the unit size @var{u} is ignored for the formats @samp{s}
6103 and @samp{i}, you might still want to use a count @var{n}; for example,
6104 @samp{3i} specifies that you want to see three machine instructions,
6105 including any operands. For convenience, especially when used with
6106 the @code{display} command, the @samp{i} format also prints branch delay
6107 slot instructions, if any, beyond the count specified, which immediately
6108 follow the last instruction that is within the count. The command
6109 @code{disassemble} gives an alternative way of inspecting machine
6110 instructions; see @ref{Machine Code,,Source and Machine Code}.
6112 All the defaults for the arguments to @code{x} are designed to make it
6113 easy to continue scanning memory with minimal specifications each time
6114 you use @code{x}. For example, after you have inspected three machine
6115 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6116 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6117 the repeat count @var{n} is used again; the other arguments default as
6118 for successive uses of @code{x}.
6120 @cindex @code{$_}, @code{$__}, and value history
6121 The addresses and contents printed by the @code{x} command are not saved
6122 in the value history because there is often too much of them and they
6123 would get in the way. Instead, @value{GDBN} makes these values available for
6124 subsequent use in expressions as values of the convenience variables
6125 @code{$_} and @code{$__}. After an @code{x} command, the last address
6126 examined is available for use in expressions in the convenience variable
6127 @code{$_}. The contents of that address, as examined, are available in
6128 the convenience variable @code{$__}.
6130 If the @code{x} command has a repeat count, the address and contents saved
6131 are from the last memory unit printed; this is not the same as the last
6132 address printed if several units were printed on the last line of output.
6134 @cindex remote memory comparison
6135 @cindex verify remote memory image
6136 When you are debugging a program running on a remote target machine
6137 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6138 remote machine's memory against the executable file you downloaded to
6139 the target. The @code{compare-sections} command is provided for such
6143 @kindex compare-sections
6144 @item compare-sections @r{[}@var{section-name}@r{]}
6145 Compare the data of a loadable section @var{section-name} in the
6146 executable file of the program being debugged with the same section in
6147 the remote machine's memory, and report any mismatches. With no
6148 arguments, compares all loadable sections. This command's
6149 availability depends on the target's support for the @code{"qCRC"}
6154 @section Automatic Display
6155 @cindex automatic display
6156 @cindex display of expressions
6158 If you find that you want to print the value of an expression frequently
6159 (to see how it changes), you might want to add it to the @dfn{automatic
6160 display list} so that @value{GDBN} prints its value each time your program stops.
6161 Each expression added to the list is given a number to identify it;
6162 to remove an expression from the list, you specify that number.
6163 The automatic display looks like this:
6167 3: bar[5] = (struct hack *) 0x3804
6171 This display shows item numbers, expressions and their current values. As with
6172 displays you request manually using @code{x} or @code{print}, you can
6173 specify the output format you prefer; in fact, @code{display} decides
6174 whether to use @code{print} or @code{x} depending your format
6175 specification---it uses @code{x} if you specify either the @samp{i}
6176 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6180 @item display @var{expr}
6181 Add the expression @var{expr} to the list of expressions to display
6182 each time your program stops. @xref{Expressions, ,Expressions}.
6184 @code{display} does not repeat if you press @key{RET} again after using it.
6186 @item display/@var{fmt} @var{expr}
6187 For @var{fmt} specifying only a display format and not a size or
6188 count, add the expression @var{expr} to the auto-display list but
6189 arrange to display it each time in the specified format @var{fmt}.
6190 @xref{Output Formats,,Output Formats}.
6192 @item display/@var{fmt} @var{addr}
6193 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6194 number of units, add the expression @var{addr} as a memory address to
6195 be examined each time your program stops. Examining means in effect
6196 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6199 For example, @samp{display/i $pc} can be helpful, to see the machine
6200 instruction about to be executed each time execution stops (@samp{$pc}
6201 is a common name for the program counter; @pxref{Registers, ,Registers}).
6204 @kindex delete display
6206 @item undisplay @var{dnums}@dots{}
6207 @itemx delete display @var{dnums}@dots{}
6208 Remove item numbers @var{dnums} from the list of expressions to display.
6210 @code{undisplay} does not repeat if you press @key{RET} after using it.
6211 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6213 @kindex disable display
6214 @item disable display @var{dnums}@dots{}
6215 Disable the display of item numbers @var{dnums}. A disabled display
6216 item is not printed automatically, but is not forgotten. It may be
6217 enabled again later.
6219 @kindex enable display
6220 @item enable display @var{dnums}@dots{}
6221 Enable display of item numbers @var{dnums}. It becomes effective once
6222 again in auto display of its expression, until you specify otherwise.
6225 Display the current values of the expressions on the list, just as is
6226 done when your program stops.
6228 @kindex info display
6230 Print the list of expressions previously set up to display
6231 automatically, each one with its item number, but without showing the
6232 values. This includes disabled expressions, which are marked as such.
6233 It also includes expressions which would not be displayed right now
6234 because they refer to automatic variables not currently available.
6237 @cindex display disabled out of scope
6238 If a display expression refers to local variables, then it does not make
6239 sense outside the lexical context for which it was set up. Such an
6240 expression is disabled when execution enters a context where one of its
6241 variables is not defined. For example, if you give the command
6242 @code{display last_char} while inside a function with an argument
6243 @code{last_char}, @value{GDBN} displays this argument while your program
6244 continues to stop inside that function. When it stops elsewhere---where
6245 there is no variable @code{last_char}---the display is disabled
6246 automatically. The next time your program stops where @code{last_char}
6247 is meaningful, you can enable the display expression once again.
6249 @node Print Settings
6250 @section Print Settings
6252 @cindex format options
6253 @cindex print settings
6254 @value{GDBN} provides the following ways to control how arrays, structures,
6255 and symbols are printed.
6258 These settings are useful for debugging programs in any language:
6262 @item set print address
6263 @itemx set print address on
6264 @cindex print/don't print memory addresses
6265 @value{GDBN} prints memory addresses showing the location of stack
6266 traces, structure values, pointer values, breakpoints, and so forth,
6267 even when it also displays the contents of those addresses. The default
6268 is @code{on}. For example, this is what a stack frame display looks like with
6269 @code{set print address on}:
6274 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6276 530 if (lquote != def_lquote)
6280 @item set print address off
6281 Do not print addresses when displaying their contents. For example,
6282 this is the same stack frame displayed with @code{set print address off}:
6286 (@value{GDBP}) set print addr off
6288 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6289 530 if (lquote != def_lquote)
6293 You can use @samp{set print address off} to eliminate all machine
6294 dependent displays from the @value{GDBN} interface. For example, with
6295 @code{print address off}, you should get the same text for backtraces on
6296 all machines---whether or not they involve pointer arguments.
6299 @item show print address
6300 Show whether or not addresses are to be printed.
6303 When @value{GDBN} prints a symbolic address, it normally prints the
6304 closest earlier symbol plus an offset. If that symbol does not uniquely
6305 identify the address (for example, it is a name whose scope is a single
6306 source file), you may need to clarify. One way to do this is with
6307 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6308 you can set @value{GDBN} to print the source file and line number when
6309 it prints a symbolic address:
6312 @item set print symbol-filename on
6313 @cindex source file and line of a symbol
6314 @cindex symbol, source file and line
6315 Tell @value{GDBN} to print the source file name and line number of a
6316 symbol in the symbolic form of an address.
6318 @item set print symbol-filename off
6319 Do not print source file name and line number of a symbol. This is the
6322 @item show print symbol-filename
6323 Show whether or not @value{GDBN} will print the source file name and
6324 line number of a symbol in the symbolic form of an address.
6327 Another situation where it is helpful to show symbol filenames and line
6328 numbers is when disassembling code; @value{GDBN} shows you the line
6329 number and source file that corresponds to each instruction.
6331 Also, you may wish to see the symbolic form only if the address being
6332 printed is reasonably close to the closest earlier symbol:
6335 @item set print max-symbolic-offset @var{max-offset}
6336 @cindex maximum value for offset of closest symbol
6337 Tell @value{GDBN} to only display the symbolic form of an address if the
6338 offset between the closest earlier symbol and the address is less than
6339 @var{max-offset}. The default is 0, which tells @value{GDBN}
6340 to always print the symbolic form of an address if any symbol precedes it.
6342 @item show print max-symbolic-offset
6343 Ask how large the maximum offset is that @value{GDBN} prints in a
6347 @cindex wild pointer, interpreting
6348 @cindex pointer, finding referent
6349 If you have a pointer and you are not sure where it points, try
6350 @samp{set print symbol-filename on}. Then you can determine the name
6351 and source file location of the variable where it points, using
6352 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6353 For example, here @value{GDBN} shows that a variable @code{ptt} points
6354 at another variable @code{t}, defined in @file{hi2.c}:
6357 (@value{GDBP}) set print symbol-filename on
6358 (@value{GDBP}) p/a ptt
6359 $4 = 0xe008 <t in hi2.c>
6363 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6364 does not show the symbol name and filename of the referent, even with
6365 the appropriate @code{set print} options turned on.
6368 Other settings control how different kinds of objects are printed:
6371 @item set print array
6372 @itemx set print array on
6373 @cindex pretty print arrays
6374 Pretty print arrays. This format is more convenient to read,
6375 but uses more space. The default is off.
6377 @item set print array off
6378 Return to compressed format for arrays.
6380 @item show print array
6381 Show whether compressed or pretty format is selected for displaying
6384 @cindex print array indexes
6385 @item set print array-indexes
6386 @itemx set print array-indexes on
6387 Print the index of each element when displaying arrays. May be more
6388 convenient to locate a given element in the array or quickly find the
6389 index of a given element in that printed array. The default is off.
6391 @item set print array-indexes off
6392 Stop printing element indexes when displaying arrays.
6394 @item show print array-indexes
6395 Show whether the index of each element is printed when displaying
6398 @item set print elements @var{number-of-elements}
6399 @cindex number of array elements to print
6400 @cindex limit on number of printed array elements
6401 Set a limit on how many elements of an array @value{GDBN} will print.
6402 If @value{GDBN} is printing a large array, it stops printing after it has
6403 printed the number of elements set by the @code{set print elements} command.
6404 This limit also applies to the display of strings.
6405 When @value{GDBN} starts, this limit is set to 200.
6406 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6408 @item show print elements
6409 Display the number of elements of a large array that @value{GDBN} will print.
6410 If the number is 0, then the printing is unlimited.
6412 @item set print frame-arguments @var{value}
6413 @cindex printing frame argument values
6414 @cindex print all frame argument values
6415 @cindex print frame argument values for scalars only
6416 @cindex do not print frame argument values
6417 This command allows to control how the values of arguments are printed
6418 when the debugger prints a frame (@pxref{Frames}). The possible
6423 The values of all arguments are printed. This is the default.
6426 Print the value of an argument only if it is a scalar. The value of more
6427 complex arguments such as arrays, structures, unions, etc, is replaced
6428 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6431 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6436 None of the argument values are printed. Instead, the value of each argument
6437 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6440 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6445 By default, all argument values are always printed. But this command
6446 can be useful in several cases. For instance, it can be used to reduce
6447 the amount of information printed in each frame, making the backtrace
6448 more readable. Also, this command can be used to improve performance
6449 when displaying Ada frames, because the computation of large arguments
6450 can sometimes be CPU-intensive, especiallly in large applications.
6451 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6452 avoids this computation, thus speeding up the display of each Ada frame.
6454 @item show print frame-arguments
6455 Show how the value of arguments should be displayed when printing a frame.
6457 @item set print repeats
6458 @cindex repeated array elements
6459 Set the threshold for suppressing display of repeated array
6460 elements. When the number of consecutive identical elements of an
6461 array exceeds the threshold, @value{GDBN} prints the string
6462 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6463 identical repetitions, instead of displaying the identical elements
6464 themselves. Setting the threshold to zero will cause all elements to
6465 be individually printed. The default threshold is 10.
6467 @item show print repeats
6468 Display the current threshold for printing repeated identical
6471 @item set print null-stop
6472 @cindex @sc{null} elements in arrays
6473 Cause @value{GDBN} to stop printing the characters of an array when the first
6474 @sc{null} is encountered. This is useful when large arrays actually
6475 contain only short strings.
6478 @item show print null-stop
6479 Show whether @value{GDBN} stops printing an array on the first
6480 @sc{null} character.
6482 @item set print pretty on
6483 @cindex print structures in indented form
6484 @cindex indentation in structure display
6485 Cause @value{GDBN} to print structures in an indented format with one member
6486 per line, like this:
6501 @item set print pretty off
6502 Cause @value{GDBN} to print structures in a compact format, like this:
6506 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6507 meat = 0x54 "Pork"@}
6512 This is the default format.
6514 @item show print pretty
6515 Show which format @value{GDBN} is using to print structures.
6517 @item set print sevenbit-strings on
6518 @cindex eight-bit characters in strings
6519 @cindex octal escapes in strings
6520 Print using only seven-bit characters; if this option is set,
6521 @value{GDBN} displays any eight-bit characters (in strings or
6522 character values) using the notation @code{\}@var{nnn}. This setting is
6523 best if you are working in English (@sc{ascii}) and you use the
6524 high-order bit of characters as a marker or ``meta'' bit.
6526 @item set print sevenbit-strings off
6527 Print full eight-bit characters. This allows the use of more
6528 international character sets, and is the default.
6530 @item show print sevenbit-strings
6531 Show whether or not @value{GDBN} is printing only seven-bit characters.
6533 @item set print union on
6534 @cindex unions in structures, printing
6535 Tell @value{GDBN} to print unions which are contained in structures
6536 and other unions. This is the default setting.
6538 @item set print union off
6539 Tell @value{GDBN} not to print unions which are contained in
6540 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6543 @item show print union
6544 Ask @value{GDBN} whether or not it will print unions which are contained in
6545 structures and other unions.
6547 For example, given the declarations
6550 typedef enum @{Tree, Bug@} Species;
6551 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6552 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6563 struct thing foo = @{Tree, @{Acorn@}@};
6567 with @code{set print union on} in effect @samp{p foo} would print
6570 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6574 and with @code{set print union off} in effect it would print
6577 $1 = @{it = Tree, form = @{...@}@}
6581 @code{set print union} affects programs written in C-like languages
6587 These settings are of interest when debugging C@t{++} programs:
6590 @cindex demangling C@t{++} names
6591 @item set print demangle
6592 @itemx set print demangle on
6593 Print C@t{++} names in their source form rather than in the encoded
6594 (``mangled'') form passed to the assembler and linker for type-safe
6595 linkage. The default is on.
6597 @item show print demangle
6598 Show whether C@t{++} names are printed in mangled or demangled form.
6600 @item set print asm-demangle
6601 @itemx set print asm-demangle on
6602 Print C@t{++} names in their source form rather than their mangled form, even
6603 in assembler code printouts such as instruction disassemblies.
6606 @item show print asm-demangle
6607 Show whether C@t{++} names in assembly listings are printed in mangled
6610 @cindex C@t{++} symbol decoding style
6611 @cindex symbol decoding style, C@t{++}
6612 @kindex set demangle-style
6613 @item set demangle-style @var{style}
6614 Choose among several encoding schemes used by different compilers to
6615 represent C@t{++} names. The choices for @var{style} are currently:
6619 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6622 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6623 This is the default.
6626 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6629 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6632 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6633 @strong{Warning:} this setting alone is not sufficient to allow
6634 debugging @code{cfront}-generated executables. @value{GDBN} would
6635 require further enhancement to permit that.
6638 If you omit @var{style}, you will see a list of possible formats.
6640 @item show demangle-style
6641 Display the encoding style currently in use for decoding C@t{++} symbols.
6643 @item set print object
6644 @itemx set print object on
6645 @cindex derived type of an object, printing
6646 @cindex display derived types
6647 When displaying a pointer to an object, identify the @emph{actual}
6648 (derived) type of the object rather than the @emph{declared} type, using
6649 the virtual function table.
6651 @item set print object off
6652 Display only the declared type of objects, without reference to the
6653 virtual function table. This is the default setting.
6655 @item show print object
6656 Show whether actual, or declared, object types are displayed.
6658 @item set print static-members
6659 @itemx set print static-members on
6660 @cindex static members of C@t{++} objects
6661 Print static members when displaying a C@t{++} object. The default is on.
6663 @item set print static-members off
6664 Do not print static members when displaying a C@t{++} object.
6666 @item show print static-members
6667 Show whether C@t{++} static members are printed or not.
6669 @item set print pascal_static-members
6670 @itemx set print pascal_static-members on
6671 @cindex static members of Pascal objects
6672 @cindex Pascal objects, static members display
6673 Print static members when displaying a Pascal object. The default is on.
6675 @item set print pascal_static-members off
6676 Do not print static members when displaying a Pascal object.
6678 @item show print pascal_static-members
6679 Show whether Pascal static members are printed or not.
6681 @c These don't work with HP ANSI C++ yet.
6682 @item set print vtbl
6683 @itemx set print vtbl on
6684 @cindex pretty print C@t{++} virtual function tables
6685 @cindex virtual functions (C@t{++}) display
6686 @cindex VTBL display
6687 Pretty print C@t{++} virtual function tables. The default is off.
6688 (The @code{vtbl} commands do not work on programs compiled with the HP
6689 ANSI C@t{++} compiler (@code{aCC}).)
6691 @item set print vtbl off
6692 Do not pretty print C@t{++} virtual function tables.
6694 @item show print vtbl
6695 Show whether C@t{++} virtual function tables are pretty printed, or not.
6699 @section Value History
6701 @cindex value history
6702 @cindex history of values printed by @value{GDBN}
6703 Values printed by the @code{print} command are saved in the @value{GDBN}
6704 @dfn{value history}. This allows you to refer to them in other expressions.
6705 Values are kept until the symbol table is re-read or discarded
6706 (for example with the @code{file} or @code{symbol-file} commands).
6707 When the symbol table changes, the value history is discarded,
6708 since the values may contain pointers back to the types defined in the
6713 @cindex history number
6714 The values printed are given @dfn{history numbers} by which you can
6715 refer to them. These are successive integers starting with one.
6716 @code{print} shows you the history number assigned to a value by
6717 printing @samp{$@var{num} = } before the value; here @var{num} is the
6720 To refer to any previous value, use @samp{$} followed by the value's
6721 history number. The way @code{print} labels its output is designed to
6722 remind you of this. Just @code{$} refers to the most recent value in
6723 the history, and @code{$$} refers to the value before that.
6724 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6725 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6726 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6728 For example, suppose you have just printed a pointer to a structure and
6729 want to see the contents of the structure. It suffices to type
6735 If you have a chain of structures where the component @code{next} points
6736 to the next one, you can print the contents of the next one with this:
6743 You can print successive links in the chain by repeating this
6744 command---which you can do by just typing @key{RET}.
6746 Note that the history records values, not expressions. If the value of
6747 @code{x} is 4 and you type these commands:
6755 then the value recorded in the value history by the @code{print} command
6756 remains 4 even though the value of @code{x} has changed.
6761 Print the last ten values in the value history, with their item numbers.
6762 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6763 values} does not change the history.
6765 @item show values @var{n}
6766 Print ten history values centered on history item number @var{n}.
6769 Print ten history values just after the values last printed. If no more
6770 values are available, @code{show values +} produces no display.
6773 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6774 same effect as @samp{show values +}.
6776 @node Convenience Vars
6777 @section Convenience Variables
6779 @cindex convenience variables
6780 @cindex user-defined variables
6781 @value{GDBN} provides @dfn{convenience variables} that you can use within
6782 @value{GDBN} to hold on to a value and refer to it later. These variables
6783 exist entirely within @value{GDBN}; they are not part of your program, and
6784 setting a convenience variable has no direct effect on further execution
6785 of your program. That is why you can use them freely.
6787 Convenience variables are prefixed with @samp{$}. Any name preceded by
6788 @samp{$} can be used for a convenience variable, unless it is one of
6789 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6790 (Value history references, in contrast, are @emph{numbers} preceded
6791 by @samp{$}. @xref{Value History, ,Value History}.)
6793 You can save a value in a convenience variable with an assignment
6794 expression, just as you would set a variable in your program.
6798 set $foo = *object_ptr
6802 would save in @code{$foo} the value contained in the object pointed to by
6805 Using a convenience variable for the first time creates it, but its
6806 value is @code{void} until you assign a new value. You can alter the
6807 value with another assignment at any time.
6809 Convenience variables have no fixed types. You can assign a convenience
6810 variable any type of value, including structures and arrays, even if
6811 that variable already has a value of a different type. The convenience
6812 variable, when used as an expression, has the type of its current value.
6815 @kindex show convenience
6816 @cindex show all user variables
6817 @item show convenience
6818 Print a list of convenience variables used so far, and their values.
6819 Abbreviated @code{show conv}.
6821 @kindex init-if-undefined
6822 @cindex convenience variables, initializing
6823 @item init-if-undefined $@var{variable} = @var{expression}
6824 Set a convenience variable if it has not already been set. This is useful
6825 for user-defined commands that keep some state. It is similar, in concept,
6826 to using local static variables with initializers in C (except that
6827 convenience variables are global). It can also be used to allow users to
6828 override default values used in a command script.
6830 If the variable is already defined then the expression is not evaluated so
6831 any side-effects do not occur.
6834 One of the ways to use a convenience variable is as a counter to be
6835 incremented or a pointer to be advanced. For example, to print
6836 a field from successive elements of an array of structures:
6840 print bar[$i++]->contents
6844 Repeat that command by typing @key{RET}.
6846 Some convenience variables are created automatically by @value{GDBN} and given
6847 values likely to be useful.
6850 @vindex $_@r{, convenience variable}
6852 The variable @code{$_} is automatically set by the @code{x} command to
6853 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6854 commands which provide a default address for @code{x} to examine also
6855 set @code{$_} to that address; these commands include @code{info line}
6856 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6857 except when set by the @code{x} command, in which case it is a pointer
6858 to the type of @code{$__}.
6860 @vindex $__@r{, convenience variable}
6862 The variable @code{$__} is automatically set by the @code{x} command
6863 to the value found in the last address examined. Its type is chosen
6864 to match the format in which the data was printed.
6867 @vindex $_exitcode@r{, convenience variable}
6868 The variable @code{$_exitcode} is automatically set to the exit code when
6869 the program being debugged terminates.
6872 On HP-UX systems, if you refer to a function or variable name that
6873 begins with a dollar sign, @value{GDBN} searches for a user or system
6874 name first, before it searches for a convenience variable.
6880 You can refer to machine register contents, in expressions, as variables
6881 with names starting with @samp{$}. The names of registers are different
6882 for each machine; use @code{info registers} to see the names used on
6886 @kindex info registers
6887 @item info registers
6888 Print the names and values of all registers except floating-point
6889 and vector registers (in the selected stack frame).
6891 @kindex info all-registers
6892 @cindex floating point registers
6893 @item info all-registers
6894 Print the names and values of all registers, including floating-point
6895 and vector registers (in the selected stack frame).
6897 @item info registers @var{regname} @dots{}
6898 Print the @dfn{relativized} value of each specified register @var{regname}.
6899 As discussed in detail below, register values are normally relative to
6900 the selected stack frame. @var{regname} may be any register name valid on
6901 the machine you are using, with or without the initial @samp{$}.
6904 @cindex stack pointer register
6905 @cindex program counter register
6906 @cindex process status register
6907 @cindex frame pointer register
6908 @cindex standard registers
6909 @value{GDBN} has four ``standard'' register names that are available (in
6910 expressions) on most machines---whenever they do not conflict with an
6911 architecture's canonical mnemonics for registers. The register names
6912 @code{$pc} and @code{$sp} are used for the program counter register and
6913 the stack pointer. @code{$fp} is used for a register that contains a
6914 pointer to the current stack frame, and @code{$ps} is used for a
6915 register that contains the processor status. For example,
6916 you could print the program counter in hex with
6923 or print the instruction to be executed next with
6930 or add four to the stack pointer@footnote{This is a way of removing
6931 one word from the stack, on machines where stacks grow downward in
6932 memory (most machines, nowadays). This assumes that the innermost
6933 stack frame is selected; setting @code{$sp} is not allowed when other
6934 stack frames are selected. To pop entire frames off the stack,
6935 regardless of machine architecture, use @code{return};
6936 see @ref{Returning, ,Returning from a Function}.} with
6942 Whenever possible, these four standard register names are available on
6943 your machine even though the machine has different canonical mnemonics,
6944 so long as there is no conflict. The @code{info registers} command
6945 shows the canonical names. For example, on the SPARC, @code{info
6946 registers} displays the processor status register as @code{$psr} but you
6947 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6948 is an alias for the @sc{eflags} register.
6950 @value{GDBN} always considers the contents of an ordinary register as an
6951 integer when the register is examined in this way. Some machines have
6952 special registers which can hold nothing but floating point; these
6953 registers are considered to have floating point values. There is no way
6954 to refer to the contents of an ordinary register as floating point value
6955 (although you can @emph{print} it as a floating point value with
6956 @samp{print/f $@var{regname}}).
6958 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6959 means that the data format in which the register contents are saved by
6960 the operating system is not the same one that your program normally
6961 sees. For example, the registers of the 68881 floating point
6962 coprocessor are always saved in ``extended'' (raw) format, but all C
6963 programs expect to work with ``double'' (virtual) format. In such
6964 cases, @value{GDBN} normally works with the virtual format only (the format
6965 that makes sense for your program), but the @code{info registers} command
6966 prints the data in both formats.
6968 @cindex SSE registers (x86)
6969 @cindex MMX registers (x86)
6970 Some machines have special registers whose contents can be interpreted
6971 in several different ways. For example, modern x86-based machines
6972 have SSE and MMX registers that can hold several values packed
6973 together in several different formats. @value{GDBN} refers to such
6974 registers in @code{struct} notation:
6977 (@value{GDBP}) print $xmm1
6979 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6980 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6981 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6982 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6983 v4_int32 = @{0, 20657912, 11, 13@},
6984 v2_int64 = @{88725056443645952, 55834574859@},
6985 uint128 = 0x0000000d0000000b013b36f800000000
6990 To set values of such registers, you need to tell @value{GDBN} which
6991 view of the register you wish to change, as if you were assigning
6992 value to a @code{struct} member:
6995 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6998 Normally, register values are relative to the selected stack frame
6999 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7000 value that the register would contain if all stack frames farther in
7001 were exited and their saved registers restored. In order to see the
7002 true contents of hardware registers, you must select the innermost
7003 frame (with @samp{frame 0}).
7005 However, @value{GDBN} must deduce where registers are saved, from the machine
7006 code generated by your compiler. If some registers are not saved, or if
7007 @value{GDBN} is unable to locate the saved registers, the selected stack
7008 frame makes no difference.
7010 @node Floating Point Hardware
7011 @section Floating Point Hardware
7012 @cindex floating point
7014 Depending on the configuration, @value{GDBN} may be able to give
7015 you more information about the status of the floating point hardware.
7020 Display hardware-dependent information about the floating
7021 point unit. The exact contents and layout vary depending on the
7022 floating point chip. Currently, @samp{info float} is supported on
7023 the ARM and x86 machines.
7027 @section Vector Unit
7030 Depending on the configuration, @value{GDBN} may be able to give you
7031 more information about the status of the vector unit.
7036 Display information about the vector unit. The exact contents and
7037 layout vary depending on the hardware.
7040 @node OS Information
7041 @section Operating System Auxiliary Information
7042 @cindex OS information
7044 @value{GDBN} provides interfaces to useful OS facilities that can help
7045 you debug your program.
7047 @cindex @code{ptrace} system call
7048 @cindex @code{struct user} contents
7049 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7050 machines), it interfaces with the inferior via the @code{ptrace}
7051 system call. The operating system creates a special sata structure,
7052 called @code{struct user}, for this interface. You can use the
7053 command @code{info udot} to display the contents of this data
7059 Display the contents of the @code{struct user} maintained by the OS
7060 kernel for the program being debugged. @value{GDBN} displays the
7061 contents of @code{struct user} as a list of hex numbers, similar to
7062 the @code{examine} command.
7065 @cindex auxiliary vector
7066 @cindex vector, auxiliary
7067 Some operating systems supply an @dfn{auxiliary vector} to programs at
7068 startup. This is akin to the arguments and environment that you
7069 specify for a program, but contains a system-dependent variety of
7070 binary values that tell system libraries important details about the
7071 hardware, operating system, and process. Each value's purpose is
7072 identified by an integer tag; the meanings are well-known but system-specific.
7073 Depending on the configuration and operating system facilities,
7074 @value{GDBN} may be able to show you this information. For remote
7075 targets, this functionality may further depend on the remote stub's
7076 support of the @samp{qXfer:auxv:read} packet, see
7077 @ref{qXfer auxiliary vector read}.
7082 Display the auxiliary vector of the inferior, which can be either a
7083 live process or a core dump file. @value{GDBN} prints each tag value
7084 numerically, and also shows names and text descriptions for recognized
7085 tags. Some values in the vector are numbers, some bit masks, and some
7086 pointers to strings or other data. @value{GDBN} displays each value in the
7087 most appropriate form for a recognized tag, and in hexadecimal for
7088 an unrecognized tag.
7092 @node Memory Region Attributes
7093 @section Memory Region Attributes
7094 @cindex memory region attributes
7096 @dfn{Memory region attributes} allow you to describe special handling
7097 required by regions of your target's memory. @value{GDBN} uses
7098 attributes to determine whether to allow certain types of memory
7099 accesses; whether to use specific width accesses; and whether to cache
7100 target memory. By default the description of memory regions is
7101 fetched from the target (if the current target supports this), but the
7102 user can override the fetched regions.
7104 Defined memory regions can be individually enabled and disabled. When a
7105 memory region is disabled, @value{GDBN} uses the default attributes when
7106 accessing memory in that region. Similarly, if no memory regions have
7107 been defined, @value{GDBN} uses the default attributes when accessing
7110 When a memory region is defined, it is given a number to identify it;
7111 to enable, disable, or remove a memory region, you specify that number.
7115 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7116 Define a memory region bounded by @var{lower} and @var{upper} with
7117 attributes @var{attributes}@dots{}, and add it to the list of regions
7118 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7119 case: it is treated as the target's maximum memory address.
7120 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7123 Discard any user changes to the memory regions and use target-supplied
7124 regions, if available, or no regions if the target does not support.
7127 @item delete mem @var{nums}@dots{}
7128 Remove memory regions @var{nums}@dots{} from the list of regions
7129 monitored by @value{GDBN}.
7132 @item disable mem @var{nums}@dots{}
7133 Disable monitoring of memory regions @var{nums}@dots{}.
7134 A disabled memory region is not forgotten.
7135 It may be enabled again later.
7138 @item enable mem @var{nums}@dots{}
7139 Enable monitoring of memory regions @var{nums}@dots{}.
7143 Print a table of all defined memory regions, with the following columns
7147 @item Memory Region Number
7148 @item Enabled or Disabled.
7149 Enabled memory regions are marked with @samp{y}.
7150 Disabled memory regions are marked with @samp{n}.
7153 The address defining the inclusive lower bound of the memory region.
7156 The address defining the exclusive upper bound of the memory region.
7159 The list of attributes set for this memory region.
7164 @subsection Attributes
7166 @subsubsection Memory Access Mode
7167 The access mode attributes set whether @value{GDBN} may make read or
7168 write accesses to a memory region.
7170 While these attributes prevent @value{GDBN} from performing invalid
7171 memory accesses, they do nothing to prevent the target system, I/O DMA,
7172 etc.@: from accessing memory.
7176 Memory is read only.
7178 Memory is write only.
7180 Memory is read/write. This is the default.
7183 @subsubsection Memory Access Size
7184 The access size attribute tells @value{GDBN} to use specific sized
7185 accesses in the memory region. Often memory mapped device registers
7186 require specific sized accesses. If no access size attribute is
7187 specified, @value{GDBN} may use accesses of any size.
7191 Use 8 bit memory accesses.
7193 Use 16 bit memory accesses.
7195 Use 32 bit memory accesses.
7197 Use 64 bit memory accesses.
7200 @c @subsubsection Hardware/Software Breakpoints
7201 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7202 @c will use hardware or software breakpoints for the internal breakpoints
7203 @c used by the step, next, finish, until, etc. commands.
7207 @c Always use hardware breakpoints
7208 @c @item swbreak (default)
7211 @subsubsection Data Cache
7212 The data cache attributes set whether @value{GDBN} will cache target
7213 memory. While this generally improves performance by reducing debug
7214 protocol overhead, it can lead to incorrect results because @value{GDBN}
7215 does not know about volatile variables or memory mapped device
7220 Enable @value{GDBN} to cache target memory.
7222 Disable @value{GDBN} from caching target memory. This is the default.
7225 @subsection Memory Access Checking
7226 @value{GDBN} can be instructed to refuse accesses to memory that is
7227 not explicitly described. This can be useful if accessing such
7228 regions has undesired effects for a specific target, or to provide
7229 better error checking. The following commands control this behaviour.
7232 @kindex set mem inaccessible-by-default
7233 @item set mem inaccessible-by-default [on|off]
7234 If @code{on} is specified, make @value{GDBN} treat memory not
7235 explicitly described by the memory ranges as non-existent and refuse accesses
7236 to such memory. The checks are only performed if there's at least one
7237 memory range defined. If @code{off} is specified, make @value{GDBN}
7238 treat the memory not explicitly described by the memory ranges as RAM.
7239 The default value is @code{on}.
7240 @kindex show mem inaccessible-by-default
7241 @item show mem inaccessible-by-default
7242 Show the current handling of accesses to unknown memory.
7246 @c @subsubsection Memory Write Verification
7247 @c The memory write verification attributes set whether @value{GDBN}
7248 @c will re-reads data after each write to verify the write was successful.
7252 @c @item noverify (default)
7255 @node Dump/Restore Files
7256 @section Copy Between Memory and a File
7257 @cindex dump/restore files
7258 @cindex append data to a file
7259 @cindex dump data to a file
7260 @cindex restore data from a file
7262 You can use the commands @code{dump}, @code{append}, and
7263 @code{restore} to copy data between target memory and a file. The
7264 @code{dump} and @code{append} commands write data to a file, and the
7265 @code{restore} command reads data from a file back into the inferior's
7266 memory. Files may be in binary, Motorola S-record, Intel hex, or
7267 Tektronix Hex format; however, @value{GDBN} can only append to binary
7273 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7274 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7275 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7276 or the value of @var{expr}, to @var{filename} in the given format.
7278 The @var{format} parameter may be any one of:
7285 Motorola S-record format.
7287 Tektronix Hex format.
7290 @value{GDBN} uses the same definitions of these formats as the
7291 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7292 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7296 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7297 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7298 Append the contents of memory from @var{start_addr} to @var{end_addr},
7299 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7300 (@value{GDBN} can only append data to files in raw binary form.)
7303 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7304 Restore the contents of file @var{filename} into memory. The
7305 @code{restore} command can automatically recognize any known @sc{bfd}
7306 file format, except for raw binary. To restore a raw binary file you
7307 must specify the optional keyword @code{binary} after the filename.
7309 If @var{bias} is non-zero, its value will be added to the addresses
7310 contained in the file. Binary files always start at address zero, so
7311 they will be restored at address @var{bias}. Other bfd files have
7312 a built-in location; they will be restored at offset @var{bias}
7315 If @var{start} and/or @var{end} are non-zero, then only data between
7316 file offset @var{start} and file offset @var{end} will be restored.
7317 These offsets are relative to the addresses in the file, before
7318 the @var{bias} argument is applied.
7322 @node Core File Generation
7323 @section How to Produce a Core File from Your Program
7324 @cindex dump core from inferior
7326 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7327 image of a running process and its process status (register values
7328 etc.). Its primary use is post-mortem debugging of a program that
7329 crashed while it ran outside a debugger. A program that crashes
7330 automatically produces a core file, unless this feature is disabled by
7331 the user. @xref{Files}, for information on invoking @value{GDBN} in
7332 the post-mortem debugging mode.
7334 Occasionally, you may wish to produce a core file of the program you
7335 are debugging in order to preserve a snapshot of its state.
7336 @value{GDBN} has a special command for that.
7340 @kindex generate-core-file
7341 @item generate-core-file [@var{file}]
7342 @itemx gcore [@var{file}]
7343 Produce a core dump of the inferior process. The optional argument
7344 @var{file} specifies the file name where to put the core dump. If not
7345 specified, the file name defaults to @file{core.@var{pid}}, where
7346 @var{pid} is the inferior process ID.
7348 Note that this command is implemented only for some systems (as of
7349 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7352 @node Character Sets
7353 @section Character Sets
7354 @cindex character sets
7356 @cindex translating between character sets
7357 @cindex host character set
7358 @cindex target character set
7360 If the program you are debugging uses a different character set to
7361 represent characters and strings than the one @value{GDBN} uses itself,
7362 @value{GDBN} can automatically translate between the character sets for
7363 you. The character set @value{GDBN} uses we call the @dfn{host
7364 character set}; the one the inferior program uses we call the
7365 @dfn{target character set}.
7367 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7368 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7369 remote protocol (@pxref{Remote Debugging}) to debug a program
7370 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7371 then the host character set is Latin-1, and the target character set is
7372 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7373 target-charset EBCDIC-US}, then @value{GDBN} translates between
7374 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7375 character and string literals in expressions.
7377 @value{GDBN} has no way to automatically recognize which character set
7378 the inferior program uses; you must tell it, using the @code{set
7379 target-charset} command, described below.
7381 Here are the commands for controlling @value{GDBN}'s character set
7385 @item set target-charset @var{charset}
7386 @kindex set target-charset
7387 Set the current target character set to @var{charset}. We list the
7388 character set names @value{GDBN} recognizes below, but if you type
7389 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7390 list the target character sets it supports.
7394 @item set host-charset @var{charset}
7395 @kindex set host-charset
7396 Set the current host character set to @var{charset}.
7398 By default, @value{GDBN} uses a host character set appropriate to the
7399 system it is running on; you can override that default using the
7400 @code{set host-charset} command.
7402 @value{GDBN} can only use certain character sets as its host character
7403 set. We list the character set names @value{GDBN} recognizes below, and
7404 indicate which can be host character sets, but if you type
7405 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7406 list the host character sets it supports.
7408 @item set charset @var{charset}
7410 Set the current host and target character sets to @var{charset}. As
7411 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7412 @value{GDBN} will list the name of the character sets that can be used
7413 for both host and target.
7417 @kindex show charset
7418 Show the names of the current host and target charsets.
7420 @itemx show host-charset
7421 @kindex show host-charset
7422 Show the name of the current host charset.
7424 @itemx show target-charset
7425 @kindex show target-charset
7426 Show the name of the current target charset.
7430 @value{GDBN} currently includes support for the following character
7436 @cindex ASCII character set
7437 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7441 @cindex ISO 8859-1 character set
7442 @cindex ISO Latin 1 character set
7443 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7444 characters needed for French, German, and Spanish. @value{GDBN} can use
7445 this as its host character set.
7449 @cindex EBCDIC character set
7450 @cindex IBM1047 character set
7451 Variants of the @sc{ebcdic} character set, used on some of IBM's
7452 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7453 @value{GDBN} cannot use these as its host character set.
7457 Note that these are all single-byte character sets. More work inside
7458 @value{GDBN} is needed to support multi-byte or variable-width character
7459 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7461 Here is an example of @value{GDBN}'s character set support in action.
7462 Assume that the following source code has been placed in the file
7463 @file{charset-test.c}:
7469 = @{72, 101, 108, 108, 111, 44, 32, 119,
7470 111, 114, 108, 100, 33, 10, 0@};
7471 char ibm1047_hello[]
7472 = @{200, 133, 147, 147, 150, 107, 64, 166,
7473 150, 153, 147, 132, 90, 37, 0@};
7477 printf ("Hello, world!\n");
7481 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7482 containing the string @samp{Hello, world!} followed by a newline,
7483 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7485 We compile the program, and invoke the debugger on it:
7488 $ gcc -g charset-test.c -o charset-test
7489 $ gdb -nw charset-test
7490 GNU gdb 2001-12-19-cvs
7491 Copyright 2001 Free Software Foundation, Inc.
7496 We can use the @code{show charset} command to see what character sets
7497 @value{GDBN} is currently using to interpret and display characters and
7501 (@value{GDBP}) show charset
7502 The current host and target character set is `ISO-8859-1'.
7506 For the sake of printing this manual, let's use @sc{ascii} as our
7507 initial character set:
7509 (@value{GDBP}) set charset ASCII
7510 (@value{GDBP}) show charset
7511 The current host and target character set is `ASCII'.
7515 Let's assume that @sc{ascii} is indeed the correct character set for our
7516 host system --- in other words, let's assume that if @value{GDBN} prints
7517 characters using the @sc{ascii} character set, our terminal will display
7518 them properly. Since our current target character set is also
7519 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7522 (@value{GDBP}) print ascii_hello
7523 $1 = 0x401698 "Hello, world!\n"
7524 (@value{GDBP}) print ascii_hello[0]
7529 @value{GDBN} uses the target character set for character and string
7530 literals you use in expressions:
7533 (@value{GDBP}) print '+'
7538 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7541 @value{GDBN} relies on the user to tell it which character set the
7542 target program uses. If we print @code{ibm1047_hello} while our target
7543 character set is still @sc{ascii}, we get jibberish:
7546 (@value{GDBP}) print ibm1047_hello
7547 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7548 (@value{GDBP}) print ibm1047_hello[0]
7553 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7554 @value{GDBN} tells us the character sets it supports:
7557 (@value{GDBP}) set target-charset
7558 ASCII EBCDIC-US IBM1047 ISO-8859-1
7559 (@value{GDBP}) set target-charset
7562 We can select @sc{ibm1047} as our target character set, and examine the
7563 program's strings again. Now the @sc{ascii} string is wrong, but
7564 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7565 target character set, @sc{ibm1047}, to the host character set,
7566 @sc{ascii}, and they display correctly:
7569 (@value{GDBP}) set target-charset IBM1047
7570 (@value{GDBP}) show charset
7571 The current host character set is `ASCII'.
7572 The current target character set is `IBM1047'.
7573 (@value{GDBP}) print ascii_hello
7574 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7575 (@value{GDBP}) print ascii_hello[0]
7577 (@value{GDBP}) print ibm1047_hello
7578 $8 = 0x4016a8 "Hello, world!\n"
7579 (@value{GDBP}) print ibm1047_hello[0]
7584 As above, @value{GDBN} uses the target character set for character and
7585 string literals you use in expressions:
7588 (@value{GDBP}) print '+'
7593 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7596 @node Caching Remote Data
7597 @section Caching Data of Remote Targets
7598 @cindex caching data of remote targets
7600 @value{GDBN} can cache data exchanged between the debugger and a
7601 remote target (@pxref{Remote Debugging}). Such caching generally improves
7602 performance, because it reduces the overhead of the remote protocol by
7603 bundling memory reads and writes into large chunks. Unfortunately,
7604 @value{GDBN} does not currently know anything about volatile
7605 registers, and thus data caching will produce incorrect results when
7606 volatile registers are in use.
7609 @kindex set remotecache
7610 @item set remotecache on
7611 @itemx set remotecache off
7612 Set caching state for remote targets. When @code{ON}, use data
7613 caching. By default, this option is @code{OFF}.
7615 @kindex show remotecache
7616 @item show remotecache
7617 Show the current state of data caching for remote targets.
7621 Print the information about the data cache performance. The
7622 information displayed includes: the dcache width and depth; and for
7623 each cache line, how many times it was referenced, and its data and
7624 state (dirty, bad, ok, etc.). This command is useful for debugging
7625 the data cache operation.
7630 @chapter C Preprocessor Macros
7632 Some languages, such as C and C@t{++}, provide a way to define and invoke
7633 ``preprocessor macros'' which expand into strings of tokens.
7634 @value{GDBN} can evaluate expressions containing macro invocations, show
7635 the result of macro expansion, and show a macro's definition, including
7636 where it was defined.
7638 You may need to compile your program specially to provide @value{GDBN}
7639 with information about preprocessor macros. Most compilers do not
7640 include macros in their debugging information, even when you compile
7641 with the @option{-g} flag. @xref{Compilation}.
7643 A program may define a macro at one point, remove that definition later,
7644 and then provide a different definition after that. Thus, at different
7645 points in the program, a macro may have different definitions, or have
7646 no definition at all. If there is a current stack frame, @value{GDBN}
7647 uses the macros in scope at that frame's source code line. Otherwise,
7648 @value{GDBN} uses the macros in scope at the current listing location;
7651 At the moment, @value{GDBN} does not support the @code{##}
7652 token-splicing operator, the @code{#} stringification operator, or
7653 variable-arity macros.
7655 Whenever @value{GDBN} evaluates an expression, it always expands any
7656 macro invocations present in the expression. @value{GDBN} also provides
7657 the following commands for working with macros explicitly.
7661 @kindex macro expand
7662 @cindex macro expansion, showing the results of preprocessor
7663 @cindex preprocessor macro expansion, showing the results of
7664 @cindex expanding preprocessor macros
7665 @item macro expand @var{expression}
7666 @itemx macro exp @var{expression}
7667 Show the results of expanding all preprocessor macro invocations in
7668 @var{expression}. Since @value{GDBN} simply expands macros, but does
7669 not parse the result, @var{expression} need not be a valid expression;
7670 it can be any string of tokens.
7673 @item macro expand-once @var{expression}
7674 @itemx macro exp1 @var{expression}
7675 @cindex expand macro once
7676 @i{(This command is not yet implemented.)} Show the results of
7677 expanding those preprocessor macro invocations that appear explicitly in
7678 @var{expression}. Macro invocations appearing in that expansion are
7679 left unchanged. This command allows you to see the effect of a
7680 particular macro more clearly, without being confused by further
7681 expansions. Since @value{GDBN} simply expands macros, but does not
7682 parse the result, @var{expression} need not be a valid expression; it
7683 can be any string of tokens.
7686 @cindex macro definition, showing
7687 @cindex definition, showing a macro's
7688 @item info macro @var{macro}
7689 Show the definition of the macro named @var{macro}, and describe the
7690 source location where that definition was established.
7692 @kindex macro define
7693 @cindex user-defined macros
7694 @cindex defining macros interactively
7695 @cindex macros, user-defined
7696 @item macro define @var{macro} @var{replacement-list}
7697 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7698 @i{(This command is not yet implemented.)} Introduce a definition for a
7699 preprocessor macro named @var{macro}, invocations of which are replaced
7700 by the tokens given in @var{replacement-list}. The first form of this
7701 command defines an ``object-like'' macro, which takes no arguments; the
7702 second form defines a ``function-like'' macro, which takes the arguments
7703 given in @var{arglist}.
7705 A definition introduced by this command is in scope in every expression
7706 evaluated in @value{GDBN}, until it is removed with the @command{macro
7707 undef} command, described below. The definition overrides all
7708 definitions for @var{macro} present in the program being debugged, as
7709 well as any previous user-supplied definition.
7712 @item macro undef @var{macro}
7713 @i{(This command is not yet implemented.)} Remove any user-supplied
7714 definition for the macro named @var{macro}. This command only affects
7715 definitions provided with the @command{macro define} command, described
7716 above; it cannot remove definitions present in the program being
7721 @i{(This command is not yet implemented.)} List all the macros
7722 defined using the @code{macro define} command.
7725 @cindex macros, example of debugging with
7726 Here is a transcript showing the above commands in action. First, we
7727 show our source files:
7735 #define ADD(x) (M + x)
7740 printf ("Hello, world!\n");
7742 printf ("We're so creative.\n");
7744 printf ("Goodbye, world!\n");
7751 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7752 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7753 compiler includes information about preprocessor macros in the debugging
7757 $ gcc -gdwarf-2 -g3 sample.c -o sample
7761 Now, we start @value{GDBN} on our sample program:
7765 GNU gdb 2002-05-06-cvs
7766 Copyright 2002 Free Software Foundation, Inc.
7767 GDB is free software, @dots{}
7771 We can expand macros and examine their definitions, even when the
7772 program is not running. @value{GDBN} uses the current listing position
7773 to decide which macro definitions are in scope:
7776 (@value{GDBP}) list main
7779 5 #define ADD(x) (M + x)
7784 10 printf ("Hello, world!\n");
7786 12 printf ("We're so creative.\n");
7787 (@value{GDBP}) info macro ADD
7788 Defined at /home/jimb/gdb/macros/play/sample.c:5
7789 #define ADD(x) (M + x)
7790 (@value{GDBP}) info macro Q
7791 Defined at /home/jimb/gdb/macros/play/sample.h:1
7792 included at /home/jimb/gdb/macros/play/sample.c:2
7794 (@value{GDBP}) macro expand ADD(1)
7795 expands to: (42 + 1)
7796 (@value{GDBP}) macro expand-once ADD(1)
7797 expands to: once (M + 1)
7801 In the example above, note that @command{macro expand-once} expands only
7802 the macro invocation explicit in the original text --- the invocation of
7803 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7804 which was introduced by @code{ADD}.
7806 Once the program is running, @value{GDBN} uses the macro definitions in
7807 force at the source line of the current stack frame:
7810 (@value{GDBP}) break main
7811 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7813 Starting program: /home/jimb/gdb/macros/play/sample
7815 Breakpoint 1, main () at sample.c:10
7816 10 printf ("Hello, world!\n");
7820 At line 10, the definition of the macro @code{N} at line 9 is in force:
7823 (@value{GDBP}) info macro N
7824 Defined at /home/jimb/gdb/macros/play/sample.c:9
7826 (@value{GDBP}) macro expand N Q M
7828 (@value{GDBP}) print N Q M
7833 As we step over directives that remove @code{N}'s definition, and then
7834 give it a new definition, @value{GDBN} finds the definition (or lack
7835 thereof) in force at each point:
7840 12 printf ("We're so creative.\n");
7841 (@value{GDBP}) info macro N
7842 The symbol `N' has no definition as a C/C++ preprocessor macro
7843 at /home/jimb/gdb/macros/play/sample.c:12
7846 14 printf ("Goodbye, world!\n");
7847 (@value{GDBP}) info macro N
7848 Defined at /home/jimb/gdb/macros/play/sample.c:13
7850 (@value{GDBP}) macro expand N Q M
7851 expands to: 1729 < 42
7852 (@value{GDBP}) print N Q M
7859 @chapter Tracepoints
7860 @c This chapter is based on the documentation written by Michael
7861 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7864 In some applications, it is not feasible for the debugger to interrupt
7865 the program's execution long enough for the developer to learn
7866 anything helpful about its behavior. If the program's correctness
7867 depends on its real-time behavior, delays introduced by a debugger
7868 might cause the program to change its behavior drastically, or perhaps
7869 fail, even when the code itself is correct. It is useful to be able
7870 to observe the program's behavior without interrupting it.
7872 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7873 specify locations in the program, called @dfn{tracepoints}, and
7874 arbitrary expressions to evaluate when those tracepoints are reached.
7875 Later, using the @code{tfind} command, you can examine the values
7876 those expressions had when the program hit the tracepoints. The
7877 expressions may also denote objects in memory---structures or arrays,
7878 for example---whose values @value{GDBN} should record; while visiting
7879 a particular tracepoint, you may inspect those objects as if they were
7880 in memory at that moment. However, because @value{GDBN} records these
7881 values without interacting with you, it can do so quickly and
7882 unobtrusively, hopefully not disturbing the program's behavior.
7884 The tracepoint facility is currently available only for remote
7885 targets. @xref{Targets}. In addition, your remote target must know
7886 how to collect trace data. This functionality is implemented in the
7887 remote stub; however, none of the stubs distributed with @value{GDBN}
7888 support tracepoints as of this writing. The format of the remote
7889 packets used to implement tracepoints are described in @ref{Tracepoint
7892 This chapter describes the tracepoint commands and features.
7896 * Analyze Collected Data::
7897 * Tracepoint Variables::
7900 @node Set Tracepoints
7901 @section Commands to Set Tracepoints
7903 Before running such a @dfn{trace experiment}, an arbitrary number of
7904 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7905 tracepoint has a number assigned to it by @value{GDBN}. Like with
7906 breakpoints, tracepoint numbers are successive integers starting from
7907 one. Many of the commands associated with tracepoints take the
7908 tracepoint number as their argument, to identify which tracepoint to
7911 For each tracepoint, you can specify, in advance, some arbitrary set
7912 of data that you want the target to collect in the trace buffer when
7913 it hits that tracepoint. The collected data can include registers,
7914 local variables, or global data. Later, you can use @value{GDBN}
7915 commands to examine the values these data had at the time the
7918 This section describes commands to set tracepoints and associated
7919 conditions and actions.
7922 * Create and Delete Tracepoints::
7923 * Enable and Disable Tracepoints::
7924 * Tracepoint Passcounts::
7925 * Tracepoint Actions::
7926 * Listing Tracepoints::
7927 * Starting and Stopping Trace Experiments::
7930 @node Create and Delete Tracepoints
7931 @subsection Create and Delete Tracepoints
7934 @cindex set tracepoint
7937 The @code{trace} command is very similar to the @code{break} command.
7938 Its argument can be a source line, a function name, or an address in
7939 the target program. @xref{Set Breaks}. The @code{trace} command
7940 defines a tracepoint, which is a point in the target program where the
7941 debugger will briefly stop, collect some data, and then allow the
7942 program to continue. Setting a tracepoint or changing its commands
7943 doesn't take effect until the next @code{tstart} command; thus, you
7944 cannot change the tracepoint attributes once a trace experiment is
7947 Here are some examples of using the @code{trace} command:
7950 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7952 (@value{GDBP}) @b{trace +2} // 2 lines forward
7954 (@value{GDBP}) @b{trace my_function} // first source line of function
7956 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7958 (@value{GDBP}) @b{trace *0x2117c4} // an address
7962 You can abbreviate @code{trace} as @code{tr}.
7965 @cindex last tracepoint number
7966 @cindex recent tracepoint number
7967 @cindex tracepoint number
7968 The convenience variable @code{$tpnum} records the tracepoint number
7969 of the most recently set tracepoint.
7971 @kindex delete tracepoint
7972 @cindex tracepoint deletion
7973 @item delete tracepoint @r{[}@var{num}@r{]}
7974 Permanently delete one or more tracepoints. With no argument, the
7975 default is to delete all tracepoints.
7980 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7982 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7986 You can abbreviate this command as @code{del tr}.
7989 @node Enable and Disable Tracepoints
7990 @subsection Enable and Disable Tracepoints
7993 @kindex disable tracepoint
7994 @item disable tracepoint @r{[}@var{num}@r{]}
7995 Disable tracepoint @var{num}, or all tracepoints if no argument
7996 @var{num} is given. A disabled tracepoint will have no effect during
7997 the next trace experiment, but it is not forgotten. You can re-enable
7998 a disabled tracepoint using the @code{enable tracepoint} command.
8000 @kindex enable tracepoint
8001 @item enable tracepoint @r{[}@var{num}@r{]}
8002 Enable tracepoint @var{num}, or all tracepoints. The enabled
8003 tracepoints will become effective the next time a trace experiment is
8007 @node Tracepoint Passcounts
8008 @subsection Tracepoint Passcounts
8012 @cindex tracepoint pass count
8013 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8014 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8015 automatically stop a trace experiment. If a tracepoint's passcount is
8016 @var{n}, then the trace experiment will be automatically stopped on
8017 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8018 @var{num} is not specified, the @code{passcount} command sets the
8019 passcount of the most recently defined tracepoint. If no passcount is
8020 given, the trace experiment will run until stopped explicitly by the
8026 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8027 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8029 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8030 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8031 (@value{GDBP}) @b{trace foo}
8032 (@value{GDBP}) @b{pass 3}
8033 (@value{GDBP}) @b{trace bar}
8034 (@value{GDBP}) @b{pass 2}
8035 (@value{GDBP}) @b{trace baz}
8036 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8037 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8038 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8039 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8043 @node Tracepoint Actions
8044 @subsection Tracepoint Action Lists
8048 @cindex tracepoint actions
8049 @item actions @r{[}@var{num}@r{]}
8050 This command will prompt for a list of actions to be taken when the
8051 tracepoint is hit. If the tracepoint number @var{num} is not
8052 specified, this command sets the actions for the one that was most
8053 recently defined (so that you can define a tracepoint and then say
8054 @code{actions} without bothering about its number). You specify the
8055 actions themselves on the following lines, one action at a time, and
8056 terminate the actions list with a line containing just @code{end}. So
8057 far, the only defined actions are @code{collect} and
8058 @code{while-stepping}.
8060 @cindex remove actions from a tracepoint
8061 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8062 and follow it immediately with @samp{end}.
8065 (@value{GDBP}) @b{collect @var{data}} // collect some data
8067 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8069 (@value{GDBP}) @b{end} // signals the end of actions.
8072 In the following example, the action list begins with @code{collect}
8073 commands indicating the things to be collected when the tracepoint is
8074 hit. Then, in order to single-step and collect additional data
8075 following the tracepoint, a @code{while-stepping} command is used,
8076 followed by the list of things to be collected while stepping. The
8077 @code{while-stepping} command is terminated by its own separate
8078 @code{end} command. Lastly, the action list is terminated by an
8082 (@value{GDBP}) @b{trace foo}
8083 (@value{GDBP}) @b{actions}
8084 Enter actions for tracepoint 1, one per line:
8093 @kindex collect @r{(tracepoints)}
8094 @item collect @var{expr1}, @var{expr2}, @dots{}
8095 Collect values of the given expressions when the tracepoint is hit.
8096 This command accepts a comma-separated list of any valid expressions.
8097 In addition to global, static, or local variables, the following
8098 special arguments are supported:
8102 collect all registers
8105 collect all function arguments
8108 collect all local variables.
8111 You can give several consecutive @code{collect} commands, each one
8112 with a single argument, or one @code{collect} command with several
8113 arguments separated by commas: the effect is the same.
8115 The command @code{info scope} (@pxref{Symbols, info scope}) is
8116 particularly useful for figuring out what data to collect.
8118 @kindex while-stepping @r{(tracepoints)}
8119 @item while-stepping @var{n}
8120 Perform @var{n} single-step traces after the tracepoint, collecting
8121 new data at each step. The @code{while-stepping} command is
8122 followed by the list of what to collect while stepping (followed by
8123 its own @code{end} command):
8127 > collect $regs, myglobal
8133 You may abbreviate @code{while-stepping} as @code{ws} or
8137 @node Listing Tracepoints
8138 @subsection Listing Tracepoints
8141 @kindex info tracepoints
8143 @cindex information about tracepoints
8144 @item info tracepoints @r{[}@var{num}@r{]}
8145 Display information about the tracepoint @var{num}. If you don't specify
8146 a tracepoint number, displays information about all the tracepoints
8147 defined so far. For each tracepoint, the following information is
8154 whether it is enabled or disabled
8158 its passcount as given by the @code{passcount @var{n}} command
8160 its step count as given by the @code{while-stepping @var{n}} command
8162 where in the source files is the tracepoint set
8164 its action list as given by the @code{actions} command
8168 (@value{GDBP}) @b{info trace}
8169 Num Enb Address PassC StepC What
8170 1 y 0x002117c4 0 0 <gdb_asm>
8171 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8172 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8177 This command can be abbreviated @code{info tp}.
8180 @node Starting and Stopping Trace Experiments
8181 @subsection Starting and Stopping Trace Experiments
8185 @cindex start a new trace experiment
8186 @cindex collected data discarded
8188 This command takes no arguments. It starts the trace experiment, and
8189 begins collecting data. This has the side effect of discarding all
8190 the data collected in the trace buffer during the previous trace
8194 @cindex stop a running trace experiment
8196 This command takes no arguments. It ends the trace experiment, and
8197 stops collecting data.
8199 @strong{Note}: a trace experiment and data collection may stop
8200 automatically if any tracepoint's passcount is reached
8201 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8204 @cindex status of trace data collection
8205 @cindex trace experiment, status of
8207 This command displays the status of the current trace data
8211 Here is an example of the commands we described so far:
8214 (@value{GDBP}) @b{trace gdb_c_test}
8215 (@value{GDBP}) @b{actions}
8216 Enter actions for tracepoint #1, one per line.
8217 > collect $regs,$locals,$args
8222 (@value{GDBP}) @b{tstart}
8223 [time passes @dots{}]
8224 (@value{GDBP}) @b{tstop}
8228 @node Analyze Collected Data
8229 @section Using the Collected Data
8231 After the tracepoint experiment ends, you use @value{GDBN} commands
8232 for examining the trace data. The basic idea is that each tracepoint
8233 collects a trace @dfn{snapshot} every time it is hit and another
8234 snapshot every time it single-steps. All these snapshots are
8235 consecutively numbered from zero and go into a buffer, and you can
8236 examine them later. The way you examine them is to @dfn{focus} on a
8237 specific trace snapshot. When the remote stub is focused on a trace
8238 snapshot, it will respond to all @value{GDBN} requests for memory and
8239 registers by reading from the buffer which belongs to that snapshot,
8240 rather than from @emph{real} memory or registers of the program being
8241 debugged. This means that @strong{all} @value{GDBN} commands
8242 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8243 behave as if we were currently debugging the program state as it was
8244 when the tracepoint occurred. Any requests for data that are not in
8245 the buffer will fail.
8248 * tfind:: How to select a trace snapshot
8249 * tdump:: How to display all data for a snapshot
8250 * save-tracepoints:: How to save tracepoints for a future run
8254 @subsection @code{tfind @var{n}}
8257 @cindex select trace snapshot
8258 @cindex find trace snapshot
8259 The basic command for selecting a trace snapshot from the buffer is
8260 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8261 counting from zero. If no argument @var{n} is given, the next
8262 snapshot is selected.
8264 Here are the various forms of using the @code{tfind} command.
8268 Find the first snapshot in the buffer. This is a synonym for
8269 @code{tfind 0} (since 0 is the number of the first snapshot).
8272 Stop debugging trace snapshots, resume @emph{live} debugging.
8275 Same as @samp{tfind none}.
8278 No argument means find the next trace snapshot.
8281 Find the previous trace snapshot before the current one. This permits
8282 retracing earlier steps.
8284 @item tfind tracepoint @var{num}
8285 Find the next snapshot associated with tracepoint @var{num}. Search
8286 proceeds forward from the last examined trace snapshot. If no
8287 argument @var{num} is given, it means find the next snapshot collected
8288 for the same tracepoint as the current snapshot.
8290 @item tfind pc @var{addr}
8291 Find the next snapshot associated with the value @var{addr} of the
8292 program counter. Search proceeds forward from the last examined trace
8293 snapshot. If no argument @var{addr} is given, it means find the next
8294 snapshot with the same value of PC as the current snapshot.
8296 @item tfind outside @var{addr1}, @var{addr2}
8297 Find the next snapshot whose PC is outside the given range of
8300 @item tfind range @var{addr1}, @var{addr2}
8301 Find the next snapshot whose PC is between @var{addr1} and
8302 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8304 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8305 Find the next snapshot associated with the source line @var{n}. If
8306 the optional argument @var{file} is given, refer to line @var{n} in
8307 that source file. Search proceeds forward from the last examined
8308 trace snapshot. If no argument @var{n} is given, it means find the
8309 next line other than the one currently being examined; thus saying
8310 @code{tfind line} repeatedly can appear to have the same effect as
8311 stepping from line to line in a @emph{live} debugging session.
8314 The default arguments for the @code{tfind} commands are specifically
8315 designed to make it easy to scan through the trace buffer. For
8316 instance, @code{tfind} with no argument selects the next trace
8317 snapshot, and @code{tfind -} with no argument selects the previous
8318 trace snapshot. So, by giving one @code{tfind} command, and then
8319 simply hitting @key{RET} repeatedly you can examine all the trace
8320 snapshots in order. Or, by saying @code{tfind -} and then hitting
8321 @key{RET} repeatedly you can examine the snapshots in reverse order.
8322 The @code{tfind line} command with no argument selects the snapshot
8323 for the next source line executed. The @code{tfind pc} command with
8324 no argument selects the next snapshot with the same program counter
8325 (PC) as the current frame. The @code{tfind tracepoint} command with
8326 no argument selects the next trace snapshot collected by the same
8327 tracepoint as the current one.
8329 In addition to letting you scan through the trace buffer manually,
8330 these commands make it easy to construct @value{GDBN} scripts that
8331 scan through the trace buffer and print out whatever collected data
8332 you are interested in. Thus, if we want to examine the PC, FP, and SP
8333 registers from each trace frame in the buffer, we can say this:
8336 (@value{GDBP}) @b{tfind start}
8337 (@value{GDBP}) @b{while ($trace_frame != -1)}
8338 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8339 $trace_frame, $pc, $sp, $fp
8343 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8344 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8345 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8346 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8347 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8348 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8349 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8350 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8351 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8352 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8353 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8356 Or, if we want to examine the variable @code{X} at each source line in
8360 (@value{GDBP}) @b{tfind start}
8361 (@value{GDBP}) @b{while ($trace_frame != -1)}
8362 > printf "Frame %d, X == %d\n", $trace_frame, X
8372 @subsection @code{tdump}
8374 @cindex dump all data collected at tracepoint
8375 @cindex tracepoint data, display
8377 This command takes no arguments. It prints all the data collected at
8378 the current trace snapshot.
8381 (@value{GDBP}) @b{trace 444}
8382 (@value{GDBP}) @b{actions}
8383 Enter actions for tracepoint #2, one per line:
8384 > collect $regs, $locals, $args, gdb_long_test
8387 (@value{GDBP}) @b{tstart}
8389 (@value{GDBP}) @b{tfind line 444}
8390 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8392 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8394 (@value{GDBP}) @b{tdump}
8395 Data collected at tracepoint 2, trace frame 1:
8396 d0 0xc4aa0085 -995491707
8400 d4 0x71aea3d 119204413
8405 a1 0x3000668 50333288
8408 a4 0x3000698 50333336
8410 fp 0x30bf3c 0x30bf3c
8411 sp 0x30bf34 0x30bf34
8413 pc 0x20b2c8 0x20b2c8
8417 p = 0x20e5b4 "gdb-test"
8424 gdb_long_test = 17 '\021'
8429 @node save-tracepoints
8430 @subsection @code{save-tracepoints @var{filename}}
8431 @kindex save-tracepoints
8432 @cindex save tracepoints for future sessions
8434 This command saves all current tracepoint definitions together with
8435 their actions and passcounts, into a file @file{@var{filename}}
8436 suitable for use in a later debugging session. To read the saved
8437 tracepoint definitions, use the @code{source} command (@pxref{Command
8440 @node Tracepoint Variables
8441 @section Convenience Variables for Tracepoints
8442 @cindex tracepoint variables
8443 @cindex convenience variables for tracepoints
8446 @vindex $trace_frame
8447 @item (int) $trace_frame
8448 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8449 snapshot is selected.
8452 @item (int) $tracepoint
8453 The tracepoint for the current trace snapshot.
8456 @item (int) $trace_line
8457 The line number for the current trace snapshot.
8460 @item (char []) $trace_file
8461 The source file for the current trace snapshot.
8464 @item (char []) $trace_func
8465 The name of the function containing @code{$tracepoint}.
8468 Note: @code{$trace_file} is not suitable for use in @code{printf},
8469 use @code{output} instead.
8471 Here's a simple example of using these convenience variables for
8472 stepping through all the trace snapshots and printing some of their
8476 (@value{GDBP}) @b{tfind start}
8478 (@value{GDBP}) @b{while $trace_frame != -1}
8479 > output $trace_file
8480 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8486 @chapter Debugging Programs That Use Overlays
8489 If your program is too large to fit completely in your target system's
8490 memory, you can sometimes use @dfn{overlays} to work around this
8491 problem. @value{GDBN} provides some support for debugging programs that
8495 * How Overlays Work:: A general explanation of overlays.
8496 * Overlay Commands:: Managing overlays in @value{GDBN}.
8497 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8498 mapped by asking the inferior.
8499 * Overlay Sample Program:: A sample program using overlays.
8502 @node How Overlays Work
8503 @section How Overlays Work
8504 @cindex mapped overlays
8505 @cindex unmapped overlays
8506 @cindex load address, overlay's
8507 @cindex mapped address
8508 @cindex overlay area
8510 Suppose you have a computer whose instruction address space is only 64
8511 kilobytes long, but which has much more memory which can be accessed by
8512 other means: special instructions, segment registers, or memory
8513 management hardware, for example. Suppose further that you want to
8514 adapt a program which is larger than 64 kilobytes to run on this system.
8516 One solution is to identify modules of your program which are relatively
8517 independent, and need not call each other directly; call these modules
8518 @dfn{overlays}. Separate the overlays from the main program, and place
8519 their machine code in the larger memory. Place your main program in
8520 instruction memory, but leave at least enough space there to hold the
8521 largest overlay as well.
8523 Now, to call a function located in an overlay, you must first copy that
8524 overlay's machine code from the large memory into the space set aside
8525 for it in the instruction memory, and then jump to its entry point
8528 @c NB: In the below the mapped area's size is greater or equal to the
8529 @c size of all overlays. This is intentional to remind the developer
8530 @c that overlays don't necessarily need to be the same size.
8534 Data Instruction Larger
8535 Address Space Address Space Address Space
8536 +-----------+ +-----------+ +-----------+
8538 +-----------+ +-----------+ +-----------+<-- overlay 1
8539 | program | | main | .----| overlay 1 | load address
8540 | variables | | program | | +-----------+
8541 | and heap | | | | | |
8542 +-----------+ | | | +-----------+<-- overlay 2
8543 | | +-----------+ | | | load address
8544 +-----------+ | | | .-| overlay 2 |
8546 mapped --->+-----------+ | | +-----------+
8548 | overlay | <-' | | |
8549 | area | <---' +-----------+<-- overlay 3
8550 | | <---. | | load address
8551 +-----------+ `--| overlay 3 |
8558 @anchor{A code overlay}A code overlay
8562 The diagram (@pxref{A code overlay}) shows a system with separate data
8563 and instruction address spaces. To map an overlay, the program copies
8564 its code from the larger address space to the instruction address space.
8565 Since the overlays shown here all use the same mapped address, only one
8566 may be mapped at a time. For a system with a single address space for
8567 data and instructions, the diagram would be similar, except that the
8568 program variables and heap would share an address space with the main
8569 program and the overlay area.
8571 An overlay loaded into instruction memory and ready for use is called a
8572 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8573 instruction memory. An overlay not present (or only partially present)
8574 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8575 is its address in the larger memory. The mapped address is also called
8576 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8577 called the @dfn{load memory address}, or @dfn{LMA}.
8579 Unfortunately, overlays are not a completely transparent way to adapt a
8580 program to limited instruction memory. They introduce a new set of
8581 global constraints you must keep in mind as you design your program:
8586 Before calling or returning to a function in an overlay, your program
8587 must make sure that overlay is actually mapped. Otherwise, the call or
8588 return will transfer control to the right address, but in the wrong
8589 overlay, and your program will probably crash.
8592 If the process of mapping an overlay is expensive on your system, you
8593 will need to choose your overlays carefully to minimize their effect on
8594 your program's performance.
8597 The executable file you load onto your system must contain each
8598 overlay's instructions, appearing at the overlay's load address, not its
8599 mapped address. However, each overlay's instructions must be relocated
8600 and its symbols defined as if the overlay were at its mapped address.
8601 You can use GNU linker scripts to specify different load and relocation
8602 addresses for pieces of your program; see @ref{Overlay Description,,,
8603 ld.info, Using ld: the GNU linker}.
8606 The procedure for loading executable files onto your system must be able
8607 to load their contents into the larger address space as well as the
8608 instruction and data spaces.
8612 The overlay system described above is rather simple, and could be
8613 improved in many ways:
8618 If your system has suitable bank switch registers or memory management
8619 hardware, you could use those facilities to make an overlay's load area
8620 contents simply appear at their mapped address in instruction space.
8621 This would probably be faster than copying the overlay to its mapped
8622 area in the usual way.
8625 If your overlays are small enough, you could set aside more than one
8626 overlay area, and have more than one overlay mapped at a time.
8629 You can use overlays to manage data, as well as instructions. In
8630 general, data overlays are even less transparent to your design than
8631 code overlays: whereas code overlays only require care when you call or
8632 return to functions, data overlays require care every time you access
8633 the data. Also, if you change the contents of a data overlay, you
8634 must copy its contents back out to its load address before you can copy a
8635 different data overlay into the same mapped area.
8640 @node Overlay Commands
8641 @section Overlay Commands
8643 To use @value{GDBN}'s overlay support, each overlay in your program must
8644 correspond to a separate section of the executable file. The section's
8645 virtual memory address and load memory address must be the overlay's
8646 mapped and load addresses. Identifying overlays with sections allows
8647 @value{GDBN} to determine the appropriate address of a function or
8648 variable, depending on whether the overlay is mapped or not.
8650 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8651 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8656 Disable @value{GDBN}'s overlay support. When overlay support is
8657 disabled, @value{GDBN} assumes that all functions and variables are
8658 always present at their mapped addresses. By default, @value{GDBN}'s
8659 overlay support is disabled.
8661 @item overlay manual
8662 @cindex manual overlay debugging
8663 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8664 relies on you to tell it which overlays are mapped, and which are not,
8665 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8666 commands described below.
8668 @item overlay map-overlay @var{overlay}
8669 @itemx overlay map @var{overlay}
8670 @cindex map an overlay
8671 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8672 be the name of the object file section containing the overlay. When an
8673 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8674 functions and variables at their mapped addresses. @value{GDBN} assumes
8675 that any other overlays whose mapped ranges overlap that of
8676 @var{overlay} are now unmapped.
8678 @item overlay unmap-overlay @var{overlay}
8679 @itemx overlay unmap @var{overlay}
8680 @cindex unmap an overlay
8681 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8682 must be the name of the object file section containing the overlay.
8683 When an overlay is unmapped, @value{GDBN} assumes it can find the
8684 overlay's functions and variables at their load addresses.
8687 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8688 consults a data structure the overlay manager maintains in the inferior
8689 to see which overlays are mapped. For details, see @ref{Automatic
8692 @item overlay load-target
8694 @cindex reloading the overlay table
8695 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8696 re-reads the table @value{GDBN} automatically each time the inferior
8697 stops, so this command should only be necessary if you have changed the
8698 overlay mapping yourself using @value{GDBN}. This command is only
8699 useful when using automatic overlay debugging.
8701 @item overlay list-overlays
8703 @cindex listing mapped overlays
8704 Display a list of the overlays currently mapped, along with their mapped
8705 addresses, load addresses, and sizes.
8709 Normally, when @value{GDBN} prints a code address, it includes the name
8710 of the function the address falls in:
8713 (@value{GDBP}) print main
8714 $3 = @{int ()@} 0x11a0 <main>
8717 When overlay debugging is enabled, @value{GDBN} recognizes code in
8718 unmapped overlays, and prints the names of unmapped functions with
8719 asterisks around them. For example, if @code{foo} is a function in an
8720 unmapped overlay, @value{GDBN} prints it this way:
8723 (@value{GDBP}) overlay list
8724 No sections are mapped.
8725 (@value{GDBP}) print foo
8726 $5 = @{int (int)@} 0x100000 <*foo*>
8729 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8733 (@value{GDBP}) overlay list
8734 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8735 mapped at 0x1016 - 0x104a
8736 (@value{GDBP}) print foo
8737 $6 = @{int (int)@} 0x1016 <foo>
8740 When overlay debugging is enabled, @value{GDBN} can find the correct
8741 address for functions and variables in an overlay, whether or not the
8742 overlay is mapped. This allows most @value{GDBN} commands, like
8743 @code{break} and @code{disassemble}, to work normally, even on unmapped
8744 code. However, @value{GDBN}'s breakpoint support has some limitations:
8748 @cindex breakpoints in overlays
8749 @cindex overlays, setting breakpoints in
8750 You can set breakpoints in functions in unmapped overlays, as long as
8751 @value{GDBN} can write to the overlay at its load address.
8753 @value{GDBN} can not set hardware or simulator-based breakpoints in
8754 unmapped overlays. However, if you set a breakpoint at the end of your
8755 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8756 you are using manual overlay management), @value{GDBN} will re-set its
8757 breakpoints properly.
8761 @node Automatic Overlay Debugging
8762 @section Automatic Overlay Debugging
8763 @cindex automatic overlay debugging
8765 @value{GDBN} can automatically track which overlays are mapped and which
8766 are not, given some simple co-operation from the overlay manager in the
8767 inferior. If you enable automatic overlay debugging with the
8768 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8769 looks in the inferior's memory for certain variables describing the
8770 current state of the overlays.
8772 Here are the variables your overlay manager must define to support
8773 @value{GDBN}'s automatic overlay debugging:
8777 @item @code{_ovly_table}:
8778 This variable must be an array of the following structures:
8783 /* The overlay's mapped address. */
8786 /* The size of the overlay, in bytes. */
8789 /* The overlay's load address. */
8792 /* Non-zero if the overlay is currently mapped;
8794 unsigned long mapped;
8798 @item @code{_novlys}:
8799 This variable must be a four-byte signed integer, holding the total
8800 number of elements in @code{_ovly_table}.
8804 To decide whether a particular overlay is mapped or not, @value{GDBN}
8805 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8806 @code{lma} members equal the VMA and LMA of the overlay's section in the
8807 executable file. When @value{GDBN} finds a matching entry, it consults
8808 the entry's @code{mapped} member to determine whether the overlay is
8811 In addition, your overlay manager may define a function called
8812 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8813 will silently set a breakpoint there. If the overlay manager then
8814 calls this function whenever it has changed the overlay table, this
8815 will enable @value{GDBN} to accurately keep track of which overlays
8816 are in program memory, and update any breakpoints that may be set
8817 in overlays. This will allow breakpoints to work even if the
8818 overlays are kept in ROM or other non-writable memory while they
8819 are not being executed.
8821 @node Overlay Sample Program
8822 @section Overlay Sample Program
8823 @cindex overlay example program
8825 When linking a program which uses overlays, you must place the overlays
8826 at their load addresses, while relocating them to run at their mapped
8827 addresses. To do this, you must write a linker script (@pxref{Overlay
8828 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8829 since linker scripts are specific to a particular host system, target
8830 architecture, and target memory layout, this manual cannot provide
8831 portable sample code demonstrating @value{GDBN}'s overlay support.
8833 However, the @value{GDBN} source distribution does contain an overlaid
8834 program, with linker scripts for a few systems, as part of its test
8835 suite. The program consists of the following files from
8836 @file{gdb/testsuite/gdb.base}:
8840 The main program file.
8842 A simple overlay manager, used by @file{overlays.c}.
8847 Overlay modules, loaded and used by @file{overlays.c}.
8850 Linker scripts for linking the test program on the @code{d10v-elf}
8851 and @code{m32r-elf} targets.
8854 You can build the test program using the @code{d10v-elf} GCC
8855 cross-compiler like this:
8858 $ d10v-elf-gcc -g -c overlays.c
8859 $ d10v-elf-gcc -g -c ovlymgr.c
8860 $ d10v-elf-gcc -g -c foo.c
8861 $ d10v-elf-gcc -g -c bar.c
8862 $ d10v-elf-gcc -g -c baz.c
8863 $ d10v-elf-gcc -g -c grbx.c
8864 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8865 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8868 The build process is identical for any other architecture, except that
8869 you must substitute the appropriate compiler and linker script for the
8870 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8874 @chapter Using @value{GDBN} with Different Languages
8877 Although programming languages generally have common aspects, they are
8878 rarely expressed in the same manner. For instance, in ANSI C,
8879 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8880 Modula-2, it is accomplished by @code{p^}. Values can also be
8881 represented (and displayed) differently. Hex numbers in C appear as
8882 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8884 @cindex working language
8885 Language-specific information is built into @value{GDBN} for some languages,
8886 allowing you to express operations like the above in your program's
8887 native language, and allowing @value{GDBN} to output values in a manner
8888 consistent with the syntax of your program's native language. The
8889 language you use to build expressions is called the @dfn{working
8893 * Setting:: Switching between source languages
8894 * Show:: Displaying the language
8895 * Checks:: Type and range checks
8896 * Supported Languages:: Supported languages
8897 * Unsupported Languages:: Unsupported languages
8901 @section Switching Between Source Languages
8903 There are two ways to control the working language---either have @value{GDBN}
8904 set it automatically, or select it manually yourself. You can use the
8905 @code{set language} command for either purpose. On startup, @value{GDBN}
8906 defaults to setting the language automatically. The working language is
8907 used to determine how expressions you type are interpreted, how values
8910 In addition to the working language, every source file that
8911 @value{GDBN} knows about has its own working language. For some object
8912 file formats, the compiler might indicate which language a particular
8913 source file is in. However, most of the time @value{GDBN} infers the
8914 language from the name of the file. The language of a source file
8915 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8916 show each frame appropriately for its own language. There is no way to
8917 set the language of a source file from within @value{GDBN}, but you can
8918 set the language associated with a filename extension. @xref{Show, ,
8919 Displaying the Language}.
8921 This is most commonly a problem when you use a program, such
8922 as @code{cfront} or @code{f2c}, that generates C but is written in
8923 another language. In that case, make the
8924 program use @code{#line} directives in its C output; that way
8925 @value{GDBN} will know the correct language of the source code of the original
8926 program, and will display that source code, not the generated C code.
8929 * Filenames:: Filename extensions and languages.
8930 * Manually:: Setting the working language manually
8931 * Automatically:: Having @value{GDBN} infer the source language
8935 @subsection List of Filename Extensions and Languages
8937 If a source file name ends in one of the following extensions, then
8938 @value{GDBN} infers that its language is the one indicated.
8959 Objective-C source file
8966 Modula-2 source file
8970 Assembler source file. This actually behaves almost like C, but
8971 @value{GDBN} does not skip over function prologues when stepping.
8974 In addition, you may set the language associated with a filename
8975 extension. @xref{Show, , Displaying the Language}.
8978 @subsection Setting the Working Language
8980 If you allow @value{GDBN} to set the language automatically,
8981 expressions are interpreted the same way in your debugging session and
8984 @kindex set language
8985 If you wish, you may set the language manually. To do this, issue the
8986 command @samp{set language @var{lang}}, where @var{lang} is the name of
8988 @code{c} or @code{modula-2}.
8989 For a list of the supported languages, type @samp{set language}.
8991 Setting the language manually prevents @value{GDBN} from updating the working
8992 language automatically. This can lead to confusion if you try
8993 to debug a program when the working language is not the same as the
8994 source language, when an expression is acceptable to both
8995 languages---but means different things. For instance, if the current
8996 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9004 might not have the effect you intended. In C, this means to add
9005 @code{b} and @code{c} and place the result in @code{a}. The result
9006 printed would be the value of @code{a}. In Modula-2, this means to compare
9007 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9010 @subsection Having @value{GDBN} Infer the Source Language
9012 To have @value{GDBN} set the working language automatically, use
9013 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9014 then infers the working language. That is, when your program stops in a
9015 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9016 working language to the language recorded for the function in that
9017 frame. If the language for a frame is unknown (that is, if the function
9018 or block corresponding to the frame was defined in a source file that
9019 does not have a recognized extension), the current working language is
9020 not changed, and @value{GDBN} issues a warning.
9022 This may not seem necessary for most programs, which are written
9023 entirely in one source language. However, program modules and libraries
9024 written in one source language can be used by a main program written in
9025 a different source language. Using @samp{set language auto} in this
9026 case frees you from having to set the working language manually.
9029 @section Displaying the Language
9031 The following commands help you find out which language is the
9032 working language, and also what language source files were written in.
9036 @kindex show language
9037 Display the current working language. This is the
9038 language you can use with commands such as @code{print} to
9039 build and compute expressions that may involve variables in your program.
9042 @kindex info frame@r{, show the source language}
9043 Display the source language for this frame. This language becomes the
9044 working language if you use an identifier from this frame.
9045 @xref{Frame Info, ,Information about a Frame}, to identify the other
9046 information listed here.
9049 @kindex info source@r{, show the source language}
9050 Display the source language of this source file.
9051 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9052 information listed here.
9055 In unusual circumstances, you may have source files with extensions
9056 not in the standard list. You can then set the extension associated
9057 with a language explicitly:
9060 @item set extension-language @var{ext} @var{language}
9061 @kindex set extension-language
9062 Tell @value{GDBN} that source files with extension @var{ext} are to be
9063 assumed as written in the source language @var{language}.
9065 @item info extensions
9066 @kindex info extensions
9067 List all the filename extensions and the associated languages.
9071 @section Type and Range Checking
9074 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9075 checking are included, but they do not yet have any effect. This
9076 section documents the intended facilities.
9078 @c FIXME remove warning when type/range code added
9080 Some languages are designed to guard you against making seemingly common
9081 errors through a series of compile- and run-time checks. These include
9082 checking the type of arguments to functions and operators, and making
9083 sure mathematical overflows are caught at run time. Checks such as
9084 these help to ensure a program's correctness once it has been compiled
9085 by eliminating type mismatches, and providing active checks for range
9086 errors when your program is running.
9088 @value{GDBN} can check for conditions like the above if you wish.
9089 Although @value{GDBN} does not check the statements in your program,
9090 it can check expressions entered directly into @value{GDBN} for
9091 evaluation via the @code{print} command, for example. As with the
9092 working language, @value{GDBN} can also decide whether or not to check
9093 automatically based on your program's source language.
9094 @xref{Supported Languages, ,Supported Languages}, for the default
9095 settings of supported languages.
9098 * Type Checking:: An overview of type checking
9099 * Range Checking:: An overview of range checking
9102 @cindex type checking
9103 @cindex checks, type
9105 @subsection An Overview of Type Checking
9107 Some languages, such as Modula-2, are strongly typed, meaning that the
9108 arguments to operators and functions have to be of the correct type,
9109 otherwise an error occurs. These checks prevent type mismatch
9110 errors from ever causing any run-time problems. For example,
9118 The second example fails because the @code{CARDINAL} 1 is not
9119 type-compatible with the @code{REAL} 2.3.
9121 For the expressions you use in @value{GDBN} commands, you can tell the
9122 @value{GDBN} type checker to skip checking;
9123 to treat any mismatches as errors and abandon the expression;
9124 or to only issue warnings when type mismatches occur,
9125 but evaluate the expression anyway. When you choose the last of
9126 these, @value{GDBN} evaluates expressions like the second example above, but
9127 also issues a warning.
9129 Even if you turn type checking off, there may be other reasons
9130 related to type that prevent @value{GDBN} from evaluating an expression.
9131 For instance, @value{GDBN} does not know how to add an @code{int} and
9132 a @code{struct foo}. These particular type errors have nothing to do
9133 with the language in use, and usually arise from expressions, such as
9134 the one described above, which make little sense to evaluate anyway.
9136 Each language defines to what degree it is strict about type. For
9137 instance, both Modula-2 and C require the arguments to arithmetical
9138 operators to be numbers. In C, enumerated types and pointers can be
9139 represented as numbers, so that they are valid arguments to mathematical
9140 operators. @xref{Supported Languages, ,Supported Languages}, for further
9141 details on specific languages.
9143 @value{GDBN} provides some additional commands for controlling the type checker:
9145 @kindex set check type
9146 @kindex show check type
9148 @item set check type auto
9149 Set type checking on or off based on the current working language.
9150 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9153 @item set check type on
9154 @itemx set check type off
9155 Set type checking on or off, overriding the default setting for the
9156 current working language. Issue a warning if the setting does not
9157 match the language default. If any type mismatches occur in
9158 evaluating an expression while type checking is on, @value{GDBN} prints a
9159 message and aborts evaluation of the expression.
9161 @item set check type warn
9162 Cause the type checker to issue warnings, but to always attempt to
9163 evaluate the expression. Evaluating the expression may still
9164 be impossible for other reasons. For example, @value{GDBN} cannot add
9165 numbers and structures.
9168 Show the current setting of the type checker, and whether or not @value{GDBN}
9169 is setting it automatically.
9172 @cindex range checking
9173 @cindex checks, range
9174 @node Range Checking
9175 @subsection An Overview of Range Checking
9177 In some languages (such as Modula-2), it is an error to exceed the
9178 bounds of a type; this is enforced with run-time checks. Such range
9179 checking is meant to ensure program correctness by making sure
9180 computations do not overflow, or indices on an array element access do
9181 not exceed the bounds of the array.
9183 For expressions you use in @value{GDBN} commands, you can tell
9184 @value{GDBN} to treat range errors in one of three ways: ignore them,
9185 always treat them as errors and abandon the expression, or issue
9186 warnings but evaluate the expression anyway.
9188 A range error can result from numerical overflow, from exceeding an
9189 array index bound, or when you type a constant that is not a member
9190 of any type. Some languages, however, do not treat overflows as an
9191 error. In many implementations of C, mathematical overflow causes the
9192 result to ``wrap around'' to lower values---for example, if @var{m} is
9193 the largest integer value, and @var{s} is the smallest, then
9196 @var{m} + 1 @result{} @var{s}
9199 This, too, is specific to individual languages, and in some cases
9200 specific to individual compilers or machines. @xref{Supported Languages, ,
9201 Supported Languages}, for further details on specific languages.
9203 @value{GDBN} provides some additional commands for controlling the range checker:
9205 @kindex set check range
9206 @kindex show check range
9208 @item set check range auto
9209 Set range checking on or off based on the current working language.
9210 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9213 @item set check range on
9214 @itemx set check range off
9215 Set range checking on or off, overriding the default setting for the
9216 current working language. A warning is issued if the setting does not
9217 match the language default. If a range error occurs and range checking is on,
9218 then a message is printed and evaluation of the expression is aborted.
9220 @item set check range warn
9221 Output messages when the @value{GDBN} range checker detects a range error,
9222 but attempt to evaluate the expression anyway. Evaluating the
9223 expression may still be impossible for other reasons, such as accessing
9224 memory that the process does not own (a typical example from many Unix
9228 Show the current setting of the range checker, and whether or not it is
9229 being set automatically by @value{GDBN}.
9232 @node Supported Languages
9233 @section Supported Languages
9235 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9236 assembly, Modula-2, and Ada.
9237 @c This is false ...
9238 Some @value{GDBN} features may be used in expressions regardless of the
9239 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9240 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9241 ,Expressions}) can be used with the constructs of any supported
9244 The following sections detail to what degree each source language is
9245 supported by @value{GDBN}. These sections are not meant to be language
9246 tutorials or references, but serve only as a reference guide to what the
9247 @value{GDBN} expression parser accepts, and what input and output
9248 formats should look like for different languages. There are many good
9249 books written on each of these languages; please look to these for a
9250 language reference or tutorial.
9254 * Objective-C:: Objective-C
9257 * Modula-2:: Modula-2
9262 @subsection C and C@t{++}
9264 @cindex C and C@t{++}
9265 @cindex expressions in C or C@t{++}
9267 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9268 to both languages. Whenever this is the case, we discuss those languages
9272 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9273 @cindex @sc{gnu} C@t{++}
9274 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9275 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9276 effectively, you must compile your C@t{++} programs with a supported
9277 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9278 compiler (@code{aCC}).
9280 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9281 format; if it doesn't work on your system, try the stabs+ debugging
9282 format. You can select those formats explicitly with the @code{g++}
9283 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9284 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9285 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9288 * C Operators:: C and C@t{++} operators
9289 * C Constants:: C and C@t{++} constants
9290 * C Plus Plus Expressions:: C@t{++} expressions
9291 * C Defaults:: Default settings for C and C@t{++}
9292 * C Checks:: C and C@t{++} type and range checks
9293 * Debugging C:: @value{GDBN} and C
9294 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9295 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9299 @subsubsection C and C@t{++} Operators
9301 @cindex C and C@t{++} operators
9303 Operators must be defined on values of specific types. For instance,
9304 @code{+} is defined on numbers, but not on structures. Operators are
9305 often defined on groups of types.
9307 For the purposes of C and C@t{++}, the following definitions hold:
9312 @emph{Integral types} include @code{int} with any of its storage-class
9313 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9316 @emph{Floating-point types} include @code{float}, @code{double}, and
9317 @code{long double} (if supported by the target platform).
9320 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9323 @emph{Scalar types} include all of the above.
9328 The following operators are supported. They are listed here
9329 in order of increasing precedence:
9333 The comma or sequencing operator. Expressions in a comma-separated list
9334 are evaluated from left to right, with the result of the entire
9335 expression being the last expression evaluated.
9338 Assignment. The value of an assignment expression is the value
9339 assigned. Defined on scalar types.
9342 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9343 and translated to @w{@code{@var{a} = @var{a op b}}}.
9344 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9345 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9346 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9349 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9350 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9354 Logical @sc{or}. Defined on integral types.
9357 Logical @sc{and}. Defined on integral types.
9360 Bitwise @sc{or}. Defined on integral types.
9363 Bitwise exclusive-@sc{or}. Defined on integral types.
9366 Bitwise @sc{and}. Defined on integral types.
9369 Equality and inequality. Defined on scalar types. The value of these
9370 expressions is 0 for false and non-zero for true.
9372 @item <@r{, }>@r{, }<=@r{, }>=
9373 Less than, greater than, less than or equal, greater than or equal.
9374 Defined on scalar types. The value of these expressions is 0 for false
9375 and non-zero for true.
9378 left shift, and right shift. Defined on integral types.
9381 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9384 Addition and subtraction. Defined on integral types, floating-point types and
9387 @item *@r{, }/@r{, }%
9388 Multiplication, division, and modulus. Multiplication and division are
9389 defined on integral and floating-point types. Modulus is defined on
9393 Increment and decrement. When appearing before a variable, the
9394 operation is performed before the variable is used in an expression;
9395 when appearing after it, the variable's value is used before the
9396 operation takes place.
9399 Pointer dereferencing. Defined on pointer types. Same precedence as
9403 Address operator. Defined on variables. Same precedence as @code{++}.
9405 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9406 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9407 to examine the address
9408 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9412 Negative. Defined on integral and floating-point types. Same
9413 precedence as @code{++}.
9416 Logical negation. Defined on integral types. Same precedence as
9420 Bitwise complement operator. Defined on integral types. Same precedence as
9425 Structure member, and pointer-to-structure member. For convenience,
9426 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9427 pointer based on the stored type information.
9428 Defined on @code{struct} and @code{union} data.
9431 Dereferences of pointers to members.
9434 Array indexing. @code{@var{a}[@var{i}]} is defined as
9435 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9438 Function parameter list. Same precedence as @code{->}.
9441 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9442 and @code{class} types.
9445 Doubled colons also represent the @value{GDBN} scope operator
9446 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9450 If an operator is redefined in the user code, @value{GDBN} usually
9451 attempts to invoke the redefined version instead of using the operator's
9455 @subsubsection C and C@t{++} Constants
9457 @cindex C and C@t{++} constants
9459 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9464 Integer constants are a sequence of digits. Octal constants are
9465 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9466 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9467 @samp{l}, specifying that the constant should be treated as a
9471 Floating point constants are a sequence of digits, followed by a decimal
9472 point, followed by a sequence of digits, and optionally followed by an
9473 exponent. An exponent is of the form:
9474 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9475 sequence of digits. The @samp{+} is optional for positive exponents.
9476 A floating-point constant may also end with a letter @samp{f} or
9477 @samp{F}, specifying that the constant should be treated as being of
9478 the @code{float} (as opposed to the default @code{double}) type; or with
9479 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9483 Enumerated constants consist of enumerated identifiers, or their
9484 integral equivalents.
9487 Character constants are a single character surrounded by single quotes
9488 (@code{'}), or a number---the ordinal value of the corresponding character
9489 (usually its @sc{ascii} value). Within quotes, the single character may
9490 be represented by a letter or by @dfn{escape sequences}, which are of
9491 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9492 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9493 @samp{@var{x}} is a predefined special character---for example,
9494 @samp{\n} for newline.
9497 String constants are a sequence of character constants surrounded by
9498 double quotes (@code{"}). Any valid character constant (as described
9499 above) may appear. Double quotes within the string must be preceded by
9500 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9504 Pointer constants are an integral value. You can also write pointers
9505 to constants using the C operator @samp{&}.
9508 Array constants are comma-separated lists surrounded by braces @samp{@{}
9509 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9510 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9511 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9514 @node C Plus Plus Expressions
9515 @subsubsection C@t{++} Expressions
9517 @cindex expressions in C@t{++}
9518 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9520 @cindex debugging C@t{++} programs
9521 @cindex C@t{++} compilers
9522 @cindex debug formats and C@t{++}
9523 @cindex @value{NGCC} and C@t{++}
9525 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9526 proper compiler and the proper debug format. Currently, @value{GDBN}
9527 works best when debugging C@t{++} code that is compiled with
9528 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9529 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9530 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9531 stabs+ as their default debug format, so you usually don't need to
9532 specify a debug format explicitly. Other compilers and/or debug formats
9533 are likely to work badly or not at all when using @value{GDBN} to debug
9539 @cindex member functions
9541 Member function calls are allowed; you can use expressions like
9544 count = aml->GetOriginal(x, y)
9547 @vindex this@r{, inside C@t{++} member functions}
9548 @cindex namespace in C@t{++}
9550 While a member function is active (in the selected stack frame), your
9551 expressions have the same namespace available as the member function;
9552 that is, @value{GDBN} allows implicit references to the class instance
9553 pointer @code{this} following the same rules as C@t{++}.
9555 @cindex call overloaded functions
9556 @cindex overloaded functions, calling
9557 @cindex type conversions in C@t{++}
9559 You can call overloaded functions; @value{GDBN} resolves the function
9560 call to the right definition, with some restrictions. @value{GDBN} does not
9561 perform overload resolution involving user-defined type conversions,
9562 calls to constructors, or instantiations of templates that do not exist
9563 in the program. It also cannot handle ellipsis argument lists or
9566 It does perform integral conversions and promotions, floating-point
9567 promotions, arithmetic conversions, pointer conversions, conversions of
9568 class objects to base classes, and standard conversions such as those of
9569 functions or arrays to pointers; it requires an exact match on the
9570 number of function arguments.
9572 Overload resolution is always performed, unless you have specified
9573 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9574 ,@value{GDBN} Features for C@t{++}}.
9576 You must specify @code{set overload-resolution off} in order to use an
9577 explicit function signature to call an overloaded function, as in
9579 p 'foo(char,int)'('x', 13)
9582 The @value{GDBN} command-completion facility can simplify this;
9583 see @ref{Completion, ,Command Completion}.
9585 @cindex reference declarations
9587 @value{GDBN} understands variables declared as C@t{++} references; you can use
9588 them in expressions just as you do in C@t{++} source---they are automatically
9591 In the parameter list shown when @value{GDBN} displays a frame, the values of
9592 reference variables are not displayed (unlike other variables); this
9593 avoids clutter, since references are often used for large structures.
9594 The @emph{address} of a reference variable is always shown, unless
9595 you have specified @samp{set print address off}.
9598 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9599 expressions can use it just as expressions in your program do. Since
9600 one scope may be defined in another, you can use @code{::} repeatedly if
9601 necessary, for example in an expression like
9602 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9603 resolving name scope by reference to source files, in both C and C@t{++}
9604 debugging (@pxref{Variables, ,Program Variables}).
9607 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9608 calling virtual functions correctly, printing out virtual bases of
9609 objects, calling functions in a base subobject, casting objects, and
9610 invoking user-defined operators.
9613 @subsubsection C and C@t{++} Defaults
9615 @cindex C and C@t{++} defaults
9617 If you allow @value{GDBN} to set type and range checking automatically, they
9618 both default to @code{off} whenever the working language changes to
9619 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9620 selects the working language.
9622 If you allow @value{GDBN} to set the language automatically, it
9623 recognizes source files whose names end with @file{.c}, @file{.C}, or
9624 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9625 these files, it sets the working language to C or C@t{++}.
9626 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9627 for further details.
9629 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9630 @c unimplemented. If (b) changes, it might make sense to let this node
9631 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9634 @subsubsection C and C@t{++} Type and Range Checks
9636 @cindex C and C@t{++} checks
9638 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9639 is not used. However, if you turn type checking on, @value{GDBN}
9640 considers two variables type equivalent if:
9644 The two variables are structured and have the same structure, union, or
9648 The two variables have the same type name, or types that have been
9649 declared equivalent through @code{typedef}.
9652 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9655 The two @code{struct}, @code{union}, or @code{enum} variables are
9656 declared in the same declaration. (Note: this may not be true for all C
9661 Range checking, if turned on, is done on mathematical operations. Array
9662 indices are not checked, since they are often used to index a pointer
9663 that is not itself an array.
9666 @subsubsection @value{GDBN} and C
9668 The @code{set print union} and @code{show print union} commands apply to
9669 the @code{union} type. When set to @samp{on}, any @code{union} that is
9670 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9671 appears as @samp{@{...@}}.
9673 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9674 with pointers and a memory allocation function. @xref{Expressions,
9677 @node Debugging C Plus Plus
9678 @subsubsection @value{GDBN} Features for C@t{++}
9680 @cindex commands for C@t{++}
9682 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9683 designed specifically for use with C@t{++}. Here is a summary:
9686 @cindex break in overloaded functions
9687 @item @r{breakpoint menus}
9688 When you want a breakpoint in a function whose name is overloaded,
9689 @value{GDBN} has the capability to display a menu of possible breakpoint
9690 locations to help you specify which function definition you want.
9691 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
9693 @cindex overloading in C@t{++}
9694 @item rbreak @var{regex}
9695 Setting breakpoints using regular expressions is helpful for setting
9696 breakpoints on overloaded functions that are not members of any special
9698 @xref{Set Breaks, ,Setting Breakpoints}.
9700 @cindex C@t{++} exception handling
9703 Debug C@t{++} exception handling using these commands. @xref{Set
9704 Catchpoints, , Setting Catchpoints}.
9707 @item ptype @var{typename}
9708 Print inheritance relationships as well as other information for type
9710 @xref{Symbols, ,Examining the Symbol Table}.
9712 @cindex C@t{++} symbol display
9713 @item set print demangle
9714 @itemx show print demangle
9715 @itemx set print asm-demangle
9716 @itemx show print asm-demangle
9717 Control whether C@t{++} symbols display in their source form, both when
9718 displaying code as C@t{++} source and when displaying disassemblies.
9719 @xref{Print Settings, ,Print Settings}.
9721 @item set print object
9722 @itemx show print object
9723 Choose whether to print derived (actual) or declared types of objects.
9724 @xref{Print Settings, ,Print Settings}.
9726 @item set print vtbl
9727 @itemx show print vtbl
9728 Control the format for printing virtual function tables.
9729 @xref{Print Settings, ,Print Settings}.
9730 (The @code{vtbl} commands do not work on programs compiled with the HP
9731 ANSI C@t{++} compiler (@code{aCC}).)
9733 @kindex set overload-resolution
9734 @cindex overloaded functions, overload resolution
9735 @item set overload-resolution on
9736 Enable overload resolution for C@t{++} expression evaluation. The default
9737 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9738 and searches for a function whose signature matches the argument types,
9739 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9740 Expressions, ,C@t{++} Expressions}, for details).
9741 If it cannot find a match, it emits a message.
9743 @item set overload-resolution off
9744 Disable overload resolution for C@t{++} expression evaluation. For
9745 overloaded functions that are not class member functions, @value{GDBN}
9746 chooses the first function of the specified name that it finds in the
9747 symbol table, whether or not its arguments are of the correct type. For
9748 overloaded functions that are class member functions, @value{GDBN}
9749 searches for a function whose signature @emph{exactly} matches the
9752 @kindex show overload-resolution
9753 @item show overload-resolution
9754 Show the current setting of overload resolution.
9756 @item @r{Overloaded symbol names}
9757 You can specify a particular definition of an overloaded symbol, using
9758 the same notation that is used to declare such symbols in C@t{++}: type
9759 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9760 also use the @value{GDBN} command-line word completion facilities to list the
9761 available choices, or to finish the type list for you.
9762 @xref{Completion,, Command Completion}, for details on how to do this.
9765 @node Decimal Floating Point
9766 @subsubsection Decimal Floating Point format
9767 @cindex decimal floating point format
9769 @value{GDBN} can examine, set and perform computations with numbers in
9770 decimal floating point format, which in the C language correspond to the
9771 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
9772 specified by the extension to support decimal floating-point arithmetic.
9774 There are two encodings in use, depending on the architecture: BID (Binary
9775 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
9776 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
9779 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
9780 to manipulate decimal floating point numbers, it is not possible to convert
9781 (using a cast, for example) integers wider than 32-bit to decimal float.
9783 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
9784 point computations, error checking in decimal float operations ignores
9785 underflow, overflow and divide by zero exceptions.
9787 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
9788 to inspect @code{_Decimal128} values stored in floating point registers. See
9789 @ref{PowerPC,,PowerPC} for more details.
9792 @subsection Objective-C
9795 This section provides information about some commands and command
9796 options that are useful for debugging Objective-C code. See also
9797 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9798 few more commands specific to Objective-C support.
9801 * Method Names in Commands::
9802 * The Print Command with Objective-C::
9805 @node Method Names in Commands
9806 @subsubsection Method Names in Commands
9808 The following commands have been extended to accept Objective-C method
9809 names as line specifications:
9811 @kindex clear@r{, and Objective-C}
9812 @kindex break@r{, and Objective-C}
9813 @kindex info line@r{, and Objective-C}
9814 @kindex jump@r{, and Objective-C}
9815 @kindex list@r{, and Objective-C}
9819 @item @code{info line}
9824 A fully qualified Objective-C method name is specified as
9827 -[@var{Class} @var{methodName}]
9830 where the minus sign is used to indicate an instance method and a
9831 plus sign (not shown) is used to indicate a class method. The class
9832 name @var{Class} and method name @var{methodName} are enclosed in
9833 brackets, similar to the way messages are specified in Objective-C
9834 source code. For example, to set a breakpoint at the @code{create}
9835 instance method of class @code{Fruit} in the program currently being
9839 break -[Fruit create]
9842 To list ten program lines around the @code{initialize} class method,
9846 list +[NSText initialize]
9849 In the current version of @value{GDBN}, the plus or minus sign is
9850 required. In future versions of @value{GDBN}, the plus or minus
9851 sign will be optional, but you can use it to narrow the search. It
9852 is also possible to specify just a method name:
9858 You must specify the complete method name, including any colons. If
9859 your program's source files contain more than one @code{create} method,
9860 you'll be presented with a numbered list of classes that implement that
9861 method. Indicate your choice by number, or type @samp{0} to exit if
9864 As another example, to clear a breakpoint established at the
9865 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9868 clear -[NSWindow makeKeyAndOrderFront:]
9871 @node The Print Command with Objective-C
9872 @subsubsection The Print Command With Objective-C
9873 @cindex Objective-C, print objects
9874 @kindex print-object
9875 @kindex po @r{(@code{print-object})}
9877 The print command has also been extended to accept methods. For example:
9880 print -[@var{object} hash]
9883 @cindex print an Objective-C object description
9884 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9886 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9887 and print the result. Also, an additional command has been added,
9888 @code{print-object} or @code{po} for short, which is meant to print
9889 the description of an object. However, this command may only work
9890 with certain Objective-C libraries that have a particular hook
9891 function, @code{_NSPrintForDebugger}, defined.
9895 @cindex Fortran-specific support in @value{GDBN}
9897 @value{GDBN} can be used to debug programs written in Fortran, but it
9898 currently supports only the features of Fortran 77 language.
9900 @cindex trailing underscore, in Fortran symbols
9901 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9902 among them) append an underscore to the names of variables and
9903 functions. When you debug programs compiled by those compilers, you
9904 will need to refer to variables and functions with a trailing
9908 * Fortran Operators:: Fortran operators and expressions
9909 * Fortran Defaults:: Default settings for Fortran
9910 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
9913 @node Fortran Operators
9914 @subsubsection Fortran Operators and Expressions
9916 @cindex Fortran operators and expressions
9918 Operators must be defined on values of specific types. For instance,
9919 @code{+} is defined on numbers, but not on characters or other non-
9920 arithmetic types. Operators are often defined on groups of types.
9924 The exponentiation operator. It raises the first operand to the power
9928 The range operator. Normally used in the form of array(low:high) to
9929 represent a section of array.
9932 The access component operator. Normally used to access elements in derived
9933 types. Also suitable for unions. As unions aren't part of regular Fortran,
9934 this can only happen when accessing a register that uses a gdbarch-defined
9938 @node Fortran Defaults
9939 @subsubsection Fortran Defaults
9941 @cindex Fortran Defaults
9943 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9944 default uses case-insensitive matches for Fortran symbols. You can
9945 change that with the @samp{set case-insensitive} command, see
9946 @ref{Symbols}, for the details.
9948 @node Special Fortran Commands
9949 @subsubsection Special Fortran Commands
9951 @cindex Special Fortran commands
9953 @value{GDBN} has some commands to support Fortran-specific features,
9954 such as displaying common blocks.
9957 @cindex @code{COMMON} blocks, Fortran
9959 @item info common @r{[}@var{common-name}@r{]}
9960 This command prints the values contained in the Fortran @code{COMMON}
9961 block whose name is @var{common-name}. With no argument, the names of
9962 all @code{COMMON} blocks visible at the current program location are
9969 @cindex Pascal support in @value{GDBN}, limitations
9970 Debugging Pascal programs which use sets, subranges, file variables, or
9971 nested functions does not currently work. @value{GDBN} does not support
9972 entering expressions, printing values, or similar features using Pascal
9975 The Pascal-specific command @code{set print pascal_static-members}
9976 controls whether static members of Pascal objects are displayed.
9977 @xref{Print Settings, pascal_static-members}.
9980 @subsection Modula-2
9982 @cindex Modula-2, @value{GDBN} support
9984 The extensions made to @value{GDBN} to support Modula-2 only support
9985 output from the @sc{gnu} Modula-2 compiler (which is currently being
9986 developed). Other Modula-2 compilers are not currently supported, and
9987 attempting to debug executables produced by them is most likely
9988 to give an error as @value{GDBN} reads in the executable's symbol
9991 @cindex expressions in Modula-2
9993 * M2 Operators:: Built-in operators
9994 * Built-In Func/Proc:: Built-in functions and procedures
9995 * M2 Constants:: Modula-2 constants
9996 * M2 Types:: Modula-2 types
9997 * M2 Defaults:: Default settings for Modula-2
9998 * Deviations:: Deviations from standard Modula-2
9999 * M2 Checks:: Modula-2 type and range checks
10000 * M2 Scope:: The scope operators @code{::} and @code{.}
10001 * GDB/M2:: @value{GDBN} and Modula-2
10005 @subsubsection Operators
10006 @cindex Modula-2 operators
10008 Operators must be defined on values of specific types. For instance,
10009 @code{+} is defined on numbers, but not on structures. Operators are
10010 often defined on groups of types. For the purposes of Modula-2, the
10011 following definitions hold:
10016 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10020 @emph{Character types} consist of @code{CHAR} and its subranges.
10023 @emph{Floating-point types} consist of @code{REAL}.
10026 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10030 @emph{Scalar types} consist of all of the above.
10033 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10036 @emph{Boolean types} consist of @code{BOOLEAN}.
10040 The following operators are supported, and appear in order of
10041 increasing precedence:
10045 Function argument or array index separator.
10048 Assignment. The value of @var{var} @code{:=} @var{value} is
10052 Less than, greater than on integral, floating-point, or enumerated
10056 Less than or equal to, greater than or equal to
10057 on integral, floating-point and enumerated types, or set inclusion on
10058 set types. Same precedence as @code{<}.
10060 @item =@r{, }<>@r{, }#
10061 Equality and two ways of expressing inequality, valid on scalar types.
10062 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10063 available for inequality, since @code{#} conflicts with the script
10067 Set membership. Defined on set types and the types of their members.
10068 Same precedence as @code{<}.
10071 Boolean disjunction. Defined on boolean types.
10074 Boolean conjunction. Defined on boolean types.
10077 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10080 Addition and subtraction on integral and floating-point types, or union
10081 and difference on set types.
10084 Multiplication on integral and floating-point types, or set intersection
10088 Division on floating-point types, or symmetric set difference on set
10089 types. Same precedence as @code{*}.
10092 Integer division and remainder. Defined on integral types. Same
10093 precedence as @code{*}.
10096 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10099 Pointer dereferencing. Defined on pointer types.
10102 Boolean negation. Defined on boolean types. Same precedence as
10106 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10107 precedence as @code{^}.
10110 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10113 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10117 @value{GDBN} and Modula-2 scope operators.
10121 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10122 treats the use of the operator @code{IN}, or the use of operators
10123 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10124 @code{<=}, and @code{>=} on sets as an error.
10128 @node Built-In Func/Proc
10129 @subsubsection Built-in Functions and Procedures
10130 @cindex Modula-2 built-ins
10132 Modula-2 also makes available several built-in procedures and functions.
10133 In describing these, the following metavariables are used:
10138 represents an @code{ARRAY} variable.
10141 represents a @code{CHAR} constant or variable.
10144 represents a variable or constant of integral type.
10147 represents an identifier that belongs to a set. Generally used in the
10148 same function with the metavariable @var{s}. The type of @var{s} should
10149 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10152 represents a variable or constant of integral or floating-point type.
10155 represents a variable or constant of floating-point type.
10161 represents a variable.
10164 represents a variable or constant of one of many types. See the
10165 explanation of the function for details.
10168 All Modula-2 built-in procedures also return a result, described below.
10172 Returns the absolute value of @var{n}.
10175 If @var{c} is a lower case letter, it returns its upper case
10176 equivalent, otherwise it returns its argument.
10179 Returns the character whose ordinal value is @var{i}.
10182 Decrements the value in the variable @var{v} by one. Returns the new value.
10184 @item DEC(@var{v},@var{i})
10185 Decrements the value in the variable @var{v} by @var{i}. Returns the
10188 @item EXCL(@var{m},@var{s})
10189 Removes the element @var{m} from the set @var{s}. Returns the new
10192 @item FLOAT(@var{i})
10193 Returns the floating point equivalent of the integer @var{i}.
10195 @item HIGH(@var{a})
10196 Returns the index of the last member of @var{a}.
10199 Increments the value in the variable @var{v} by one. Returns the new value.
10201 @item INC(@var{v},@var{i})
10202 Increments the value in the variable @var{v} by @var{i}. Returns the
10205 @item INCL(@var{m},@var{s})
10206 Adds the element @var{m} to the set @var{s} if it is not already
10207 there. Returns the new set.
10210 Returns the maximum value of the type @var{t}.
10213 Returns the minimum value of the type @var{t}.
10216 Returns boolean TRUE if @var{i} is an odd number.
10219 Returns the ordinal value of its argument. For example, the ordinal
10220 value of a character is its @sc{ascii} value (on machines supporting the
10221 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10222 integral, character and enumerated types.
10224 @item SIZE(@var{x})
10225 Returns the size of its argument. @var{x} can be a variable or a type.
10227 @item TRUNC(@var{r})
10228 Returns the integral part of @var{r}.
10230 @item TSIZE(@var{x})
10231 Returns the size of its argument. @var{x} can be a variable or a type.
10233 @item VAL(@var{t},@var{i})
10234 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10238 @emph{Warning:} Sets and their operations are not yet supported, so
10239 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10243 @cindex Modula-2 constants
10245 @subsubsection Constants
10247 @value{GDBN} allows you to express the constants of Modula-2 in the following
10253 Integer constants are simply a sequence of digits. When used in an
10254 expression, a constant is interpreted to be type-compatible with the
10255 rest of the expression. Hexadecimal integers are specified by a
10256 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10259 Floating point constants appear as a sequence of digits, followed by a
10260 decimal point and another sequence of digits. An optional exponent can
10261 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10262 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10263 digits of the floating point constant must be valid decimal (base 10)
10267 Character constants consist of a single character enclosed by a pair of
10268 like quotes, either single (@code{'}) or double (@code{"}). They may
10269 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10270 followed by a @samp{C}.
10273 String constants consist of a sequence of characters enclosed by a
10274 pair of like quotes, either single (@code{'}) or double (@code{"}).
10275 Escape sequences in the style of C are also allowed. @xref{C
10276 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10280 Enumerated constants consist of an enumerated identifier.
10283 Boolean constants consist of the identifiers @code{TRUE} and
10287 Pointer constants consist of integral values only.
10290 Set constants are not yet supported.
10294 @subsubsection Modula-2 Types
10295 @cindex Modula-2 types
10297 Currently @value{GDBN} can print the following data types in Modula-2
10298 syntax: array types, record types, set types, pointer types, procedure
10299 types, enumerated types, subrange types and base types. You can also
10300 print the contents of variables declared using these type.
10301 This section gives a number of simple source code examples together with
10302 sample @value{GDBN} sessions.
10304 The first example contains the following section of code:
10313 and you can request @value{GDBN} to interrogate the type and value of
10314 @code{r} and @code{s}.
10317 (@value{GDBP}) print s
10319 (@value{GDBP}) ptype s
10321 (@value{GDBP}) print r
10323 (@value{GDBP}) ptype r
10328 Likewise if your source code declares @code{s} as:
10332 s: SET ['A'..'Z'] ;
10336 then you may query the type of @code{s} by:
10339 (@value{GDBP}) ptype s
10340 type = SET ['A'..'Z']
10344 Note that at present you cannot interactively manipulate set
10345 expressions using the debugger.
10347 The following example shows how you might declare an array in Modula-2
10348 and how you can interact with @value{GDBN} to print its type and contents:
10352 s: ARRAY [-10..10] OF CHAR ;
10356 (@value{GDBP}) ptype s
10357 ARRAY [-10..10] OF CHAR
10360 Note that the array handling is not yet complete and although the type
10361 is printed correctly, expression handling still assumes that all
10362 arrays have a lower bound of zero and not @code{-10} as in the example
10365 Here are some more type related Modula-2 examples:
10369 colour = (blue, red, yellow, green) ;
10370 t = [blue..yellow] ;
10378 The @value{GDBN} interaction shows how you can query the data type
10379 and value of a variable.
10382 (@value{GDBP}) print s
10384 (@value{GDBP}) ptype t
10385 type = [blue..yellow]
10389 In this example a Modula-2 array is declared and its contents
10390 displayed. Observe that the contents are written in the same way as
10391 their @code{C} counterparts.
10395 s: ARRAY [1..5] OF CARDINAL ;
10401 (@value{GDBP}) print s
10402 $1 = @{1, 0, 0, 0, 0@}
10403 (@value{GDBP}) ptype s
10404 type = ARRAY [1..5] OF CARDINAL
10407 The Modula-2 language interface to @value{GDBN} also understands
10408 pointer types as shown in this example:
10412 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10419 and you can request that @value{GDBN} describes the type of @code{s}.
10422 (@value{GDBP}) ptype s
10423 type = POINTER TO ARRAY [1..5] OF CARDINAL
10426 @value{GDBN} handles compound types as we can see in this example.
10427 Here we combine array types, record types, pointer types and subrange
10438 myarray = ARRAY myrange OF CARDINAL ;
10439 myrange = [-2..2] ;
10441 s: POINTER TO ARRAY myrange OF foo ;
10445 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10449 (@value{GDBP}) ptype s
10450 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10453 f3 : ARRAY [-2..2] OF CARDINAL;
10458 @subsubsection Modula-2 Defaults
10459 @cindex Modula-2 defaults
10461 If type and range checking are set automatically by @value{GDBN}, they
10462 both default to @code{on} whenever the working language changes to
10463 Modula-2. This happens regardless of whether you or @value{GDBN}
10464 selected the working language.
10466 If you allow @value{GDBN} to set the language automatically, then entering
10467 code compiled from a file whose name ends with @file{.mod} sets the
10468 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10469 Infer the Source Language}, for further details.
10472 @subsubsection Deviations from Standard Modula-2
10473 @cindex Modula-2, deviations from
10475 A few changes have been made to make Modula-2 programs easier to debug.
10476 This is done primarily via loosening its type strictness:
10480 Unlike in standard Modula-2, pointer constants can be formed by
10481 integers. This allows you to modify pointer variables during
10482 debugging. (In standard Modula-2, the actual address contained in a
10483 pointer variable is hidden from you; it can only be modified
10484 through direct assignment to another pointer variable or expression that
10485 returned a pointer.)
10488 C escape sequences can be used in strings and characters to represent
10489 non-printable characters. @value{GDBN} prints out strings with these
10490 escape sequences embedded. Single non-printable characters are
10491 printed using the @samp{CHR(@var{nnn})} format.
10494 The assignment operator (@code{:=}) returns the value of its right-hand
10498 All built-in procedures both modify @emph{and} return their argument.
10502 @subsubsection Modula-2 Type and Range Checks
10503 @cindex Modula-2 checks
10506 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10509 @c FIXME remove warning when type/range checks added
10511 @value{GDBN} considers two Modula-2 variables type equivalent if:
10515 They are of types that have been declared equivalent via a @code{TYPE
10516 @var{t1} = @var{t2}} statement
10519 They have been declared on the same line. (Note: This is true of the
10520 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10523 As long as type checking is enabled, any attempt to combine variables
10524 whose types are not equivalent is an error.
10526 Range checking is done on all mathematical operations, assignment, array
10527 index bounds, and all built-in functions and procedures.
10530 @subsubsection The Scope Operators @code{::} and @code{.}
10532 @cindex @code{.}, Modula-2 scope operator
10533 @cindex colon, doubled as scope operator
10535 @vindex colon-colon@r{, in Modula-2}
10536 @c Info cannot handle :: but TeX can.
10539 @vindex ::@r{, in Modula-2}
10542 There are a few subtle differences between the Modula-2 scope operator
10543 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10548 @var{module} . @var{id}
10549 @var{scope} :: @var{id}
10553 where @var{scope} is the name of a module or a procedure,
10554 @var{module} the name of a module, and @var{id} is any declared
10555 identifier within your program, except another module.
10557 Using the @code{::} operator makes @value{GDBN} search the scope
10558 specified by @var{scope} for the identifier @var{id}. If it is not
10559 found in the specified scope, then @value{GDBN} searches all scopes
10560 enclosing the one specified by @var{scope}.
10562 Using the @code{.} operator makes @value{GDBN} search the current scope for
10563 the identifier specified by @var{id} that was imported from the
10564 definition module specified by @var{module}. With this operator, it is
10565 an error if the identifier @var{id} was not imported from definition
10566 module @var{module}, or if @var{id} is not an identifier in
10570 @subsubsection @value{GDBN} and Modula-2
10572 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10573 Five subcommands of @code{set print} and @code{show print} apply
10574 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10575 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10576 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10577 analogue in Modula-2.
10579 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10580 with any language, is not useful with Modula-2. Its
10581 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10582 created in Modula-2 as they can in C or C@t{++}. However, because an
10583 address can be specified by an integral constant, the construct
10584 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10586 @cindex @code{#} in Modula-2
10587 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10588 interpreted as the beginning of a comment. Use @code{<>} instead.
10594 The extensions made to @value{GDBN} for Ada only support
10595 output from the @sc{gnu} Ada (GNAT) compiler.
10596 Other Ada compilers are not currently supported, and
10597 attempting to debug executables produced by them is most likely
10601 @cindex expressions in Ada
10603 * Ada Mode Intro:: General remarks on the Ada syntax
10604 and semantics supported by Ada mode
10606 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10607 * Additions to Ada:: Extensions of the Ada expression syntax.
10608 * Stopping Before Main Program:: Debugging the program during elaboration.
10609 * Ada Glitches:: Known peculiarities of Ada mode.
10612 @node Ada Mode Intro
10613 @subsubsection Introduction
10614 @cindex Ada mode, general
10616 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10617 syntax, with some extensions.
10618 The philosophy behind the design of this subset is
10622 That @value{GDBN} should provide basic literals and access to operations for
10623 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10624 leaving more sophisticated computations to subprograms written into the
10625 program (which therefore may be called from @value{GDBN}).
10628 That type safety and strict adherence to Ada language restrictions
10629 are not particularly important to the @value{GDBN} user.
10632 That brevity is important to the @value{GDBN} user.
10635 Thus, for brevity, the debugger acts as if there were
10636 implicit @code{with} and @code{use} clauses in effect for all user-written
10637 packages, making it unnecessary to fully qualify most names with
10638 their packages, regardless of context. Where this causes ambiguity,
10639 @value{GDBN} asks the user's intent.
10641 The debugger will start in Ada mode if it detects an Ada main program.
10642 As for other languages, it will enter Ada mode when stopped in a program that
10643 was translated from an Ada source file.
10645 While in Ada mode, you may use `@t{--}' for comments. This is useful
10646 mostly for documenting command files. The standard @value{GDBN} comment
10647 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10648 middle (to allow based literals).
10650 The debugger supports limited overloading. Given a subprogram call in which
10651 the function symbol has multiple definitions, it will use the number of
10652 actual parameters and some information about their types to attempt to narrow
10653 the set of definitions. It also makes very limited use of context, preferring
10654 procedures to functions in the context of the @code{call} command, and
10655 functions to procedures elsewhere.
10657 @node Omissions from Ada
10658 @subsubsection Omissions from Ada
10659 @cindex Ada, omissions from
10661 Here are the notable omissions from the subset:
10665 Only a subset of the attributes are supported:
10669 @t{'First}, @t{'Last}, and @t{'Length}
10670 on array objects (not on types and subtypes).
10673 @t{'Min} and @t{'Max}.
10676 @t{'Pos} and @t{'Val}.
10682 @t{'Range} on array objects (not subtypes), but only as the right
10683 operand of the membership (@code{in}) operator.
10686 @t{'Access}, @t{'Unchecked_Access}, and
10687 @t{'Unrestricted_Access} (a GNAT extension).
10695 @code{Characters.Latin_1} are not available and
10696 concatenation is not implemented. Thus, escape characters in strings are
10697 not currently available.
10700 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10701 equality of representations. They will generally work correctly
10702 for strings and arrays whose elements have integer or enumeration types.
10703 They may not work correctly for arrays whose element
10704 types have user-defined equality, for arrays of real values
10705 (in particular, IEEE-conformant floating point, because of negative
10706 zeroes and NaNs), and for arrays whose elements contain unused bits with
10707 indeterminate values.
10710 The other component-by-component array operations (@code{and}, @code{or},
10711 @code{xor}, @code{not}, and relational tests other than equality)
10712 are not implemented.
10715 @cindex array aggregates (Ada)
10716 @cindex record aggregates (Ada)
10717 @cindex aggregates (Ada)
10718 There is limited support for array and record aggregates. They are
10719 permitted only on the right sides of assignments, as in these examples:
10722 set An_Array := (1, 2, 3, 4, 5, 6)
10723 set An_Array := (1, others => 0)
10724 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10725 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10726 set A_Record := (1, "Peter", True);
10727 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10731 discriminant's value by assigning an aggregate has an
10732 undefined effect if that discriminant is used within the record.
10733 However, you can first modify discriminants by directly assigning to
10734 them (which normally would not be allowed in Ada), and then performing an
10735 aggregate assignment. For example, given a variable @code{A_Rec}
10736 declared to have a type such as:
10739 type Rec (Len : Small_Integer := 0) is record
10741 Vals : IntArray (1 .. Len);
10745 you can assign a value with a different size of @code{Vals} with two
10750 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10753 As this example also illustrates, @value{GDBN} is very loose about the usual
10754 rules concerning aggregates. You may leave out some of the
10755 components of an array or record aggregate (such as the @code{Len}
10756 component in the assignment to @code{A_Rec} above); they will retain their
10757 original values upon assignment. You may freely use dynamic values as
10758 indices in component associations. You may even use overlapping or
10759 redundant component associations, although which component values are
10760 assigned in such cases is not defined.
10763 Calls to dispatching subprograms are not implemented.
10766 The overloading algorithm is much more limited (i.e., less selective)
10767 than that of real Ada. It makes only limited use of the context in
10768 which a subexpression appears to resolve its meaning, and it is much
10769 looser in its rules for allowing type matches. As a result, some
10770 function calls will be ambiguous, and the user will be asked to choose
10771 the proper resolution.
10774 The @code{new} operator is not implemented.
10777 Entry calls are not implemented.
10780 Aside from printing, arithmetic operations on the native VAX floating-point
10781 formats are not supported.
10784 It is not possible to slice a packed array.
10787 @node Additions to Ada
10788 @subsubsection Additions to Ada
10789 @cindex Ada, deviations from
10791 As it does for other languages, @value{GDBN} makes certain generic
10792 extensions to Ada (@pxref{Expressions}):
10796 If the expression @var{E} is a variable residing in memory (typically
10797 a local variable or array element) and @var{N} is a positive integer,
10798 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10799 @var{N}-1 adjacent variables following it in memory as an array. In
10800 Ada, this operator is generally not necessary, since its prime use is
10801 in displaying parts of an array, and slicing will usually do this in
10802 Ada. However, there are occasional uses when debugging programs in
10803 which certain debugging information has been optimized away.
10806 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10807 appears in function or file @var{B}.'' When @var{B} is a file name,
10808 you must typically surround it in single quotes.
10811 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10812 @var{type} that appears at address @var{addr}.''
10815 A name starting with @samp{$} is a convenience variable
10816 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10819 In addition, @value{GDBN} provides a few other shortcuts and outright
10820 additions specific to Ada:
10824 The assignment statement is allowed as an expression, returning
10825 its right-hand operand as its value. Thus, you may enter
10829 print A(tmp := y + 1)
10833 The semicolon is allowed as an ``operator,'' returning as its value
10834 the value of its right-hand operand.
10835 This allows, for example,
10836 complex conditional breaks:
10840 condition 1 (report(i); k += 1; A(k) > 100)
10844 Rather than use catenation and symbolic character names to introduce special
10845 characters into strings, one may instead use a special bracket notation,
10846 which is also used to print strings. A sequence of characters of the form
10847 @samp{["@var{XX}"]} within a string or character literal denotes the
10848 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10849 sequence of characters @samp{["""]} also denotes a single quotation mark
10850 in strings. For example,
10852 "One line.["0a"]Next line.["0a"]"
10855 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10859 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10860 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10868 When printing arrays, @value{GDBN} uses positional notation when the
10869 array has a lower bound of 1, and uses a modified named notation otherwise.
10870 For example, a one-dimensional array of three integers with a lower bound
10871 of 3 might print as
10878 That is, in contrast to valid Ada, only the first component has a @code{=>}
10882 You may abbreviate attributes in expressions with any unique,
10883 multi-character subsequence of
10884 their names (an exact match gets preference).
10885 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10886 in place of @t{a'length}.
10889 @cindex quoting Ada internal identifiers
10890 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10891 to lower case. The GNAT compiler uses upper-case characters for
10892 some of its internal identifiers, which are normally of no interest to users.
10893 For the rare occasions when you actually have to look at them,
10894 enclose them in angle brackets to avoid the lower-case mapping.
10897 @value{GDBP} print <JMPBUF_SAVE>[0]
10901 Printing an object of class-wide type or dereferencing an
10902 access-to-class-wide value will display all the components of the object's
10903 specific type (as indicated by its run-time tag). Likewise, component
10904 selection on such a value will operate on the specific type of the
10909 @node Stopping Before Main Program
10910 @subsubsection Stopping at the Very Beginning
10912 @cindex breakpointing Ada elaboration code
10913 It is sometimes necessary to debug the program during elaboration, and
10914 before reaching the main procedure.
10915 As defined in the Ada Reference
10916 Manual, the elaboration code is invoked from a procedure called
10917 @code{adainit}. To run your program up to the beginning of
10918 elaboration, simply use the following two commands:
10919 @code{tbreak adainit} and @code{run}.
10922 @subsubsection Known Peculiarities of Ada Mode
10923 @cindex Ada, problems
10925 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10926 we know of several problems with and limitations of Ada mode in
10928 some of which will be fixed with planned future releases of the debugger
10929 and the GNU Ada compiler.
10933 Currently, the debugger
10934 has insufficient information to determine whether certain pointers represent
10935 pointers to objects or the objects themselves.
10936 Thus, the user may have to tack an extra @code{.all} after an expression
10937 to get it printed properly.
10940 Static constants that the compiler chooses not to materialize as objects in
10941 storage are invisible to the debugger.
10944 Named parameter associations in function argument lists are ignored (the
10945 argument lists are treated as positional).
10948 Many useful library packages are currently invisible to the debugger.
10951 Fixed-point arithmetic, conversions, input, and output is carried out using
10952 floating-point arithmetic, and may give results that only approximate those on
10956 The type of the @t{'Address} attribute may not be @code{System.Address}.
10959 The GNAT compiler never generates the prefix @code{Standard} for any of
10960 the standard symbols defined by the Ada language. @value{GDBN} knows about
10961 this: it will strip the prefix from names when you use it, and will never
10962 look for a name you have so qualified among local symbols, nor match against
10963 symbols in other packages or subprograms. If you have
10964 defined entities anywhere in your program other than parameters and
10965 local variables whose simple names match names in @code{Standard},
10966 GNAT's lack of qualification here can cause confusion. When this happens,
10967 you can usually resolve the confusion
10968 by qualifying the problematic names with package
10969 @code{Standard} explicitly.
10972 @node Unsupported Languages
10973 @section Unsupported Languages
10975 @cindex unsupported languages
10976 @cindex minimal language
10977 In addition to the other fully-supported programming languages,
10978 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10979 It does not represent a real programming language, but provides a set
10980 of capabilities close to what the C or assembly languages provide.
10981 This should allow most simple operations to be performed while debugging
10982 an application that uses a language currently not supported by @value{GDBN}.
10984 If the language is set to @code{auto}, @value{GDBN} will automatically
10985 select this language if the current frame corresponds to an unsupported
10989 @chapter Examining the Symbol Table
10991 The commands described in this chapter allow you to inquire about the
10992 symbols (names of variables, functions and types) defined in your
10993 program. This information is inherent in the text of your program and
10994 does not change as your program executes. @value{GDBN} finds it in your
10995 program's symbol table, in the file indicated when you started @value{GDBN}
10996 (@pxref{File Options, ,Choosing Files}), or by one of the
10997 file-management commands (@pxref{Files, ,Commands to Specify Files}).
10999 @cindex symbol names
11000 @cindex names of symbols
11001 @cindex quoting names
11002 Occasionally, you may need to refer to symbols that contain unusual
11003 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11004 most frequent case is in referring to static variables in other
11005 source files (@pxref{Variables,,Program Variables}). File names
11006 are recorded in object files as debugging symbols, but @value{GDBN} would
11007 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11008 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11009 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11016 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11019 @cindex case-insensitive symbol names
11020 @cindex case sensitivity in symbol names
11021 @kindex set case-sensitive
11022 @item set case-sensitive on
11023 @itemx set case-sensitive off
11024 @itemx set case-sensitive auto
11025 Normally, when @value{GDBN} looks up symbols, it matches their names
11026 with case sensitivity determined by the current source language.
11027 Occasionally, you may wish to control that. The command @code{set
11028 case-sensitive} lets you do that by specifying @code{on} for
11029 case-sensitive matches or @code{off} for case-insensitive ones. If
11030 you specify @code{auto}, case sensitivity is reset to the default
11031 suitable for the source language. The default is case-sensitive
11032 matches for all languages except for Fortran, for which the default is
11033 case-insensitive matches.
11035 @kindex show case-sensitive
11036 @item show case-sensitive
11037 This command shows the current setting of case sensitivity for symbols
11040 @kindex info address
11041 @cindex address of a symbol
11042 @item info address @var{symbol}
11043 Describe where the data for @var{symbol} is stored. For a register
11044 variable, this says which register it is kept in. For a non-register
11045 local variable, this prints the stack-frame offset at which the variable
11048 Note the contrast with @samp{print &@var{symbol}}, which does not work
11049 at all for a register variable, and for a stack local variable prints
11050 the exact address of the current instantiation of the variable.
11052 @kindex info symbol
11053 @cindex symbol from address
11054 @cindex closest symbol and offset for an address
11055 @item info symbol @var{addr}
11056 Print the name of a symbol which is stored at the address @var{addr}.
11057 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11058 nearest symbol and an offset from it:
11061 (@value{GDBP}) info symbol 0x54320
11062 _initialize_vx + 396 in section .text
11066 This is the opposite of the @code{info address} command. You can use
11067 it to find out the name of a variable or a function given its address.
11070 @item whatis [@var{arg}]
11071 Print the data type of @var{arg}, which can be either an expression or
11072 a data type. With no argument, print the data type of @code{$}, the
11073 last value in the value history. If @var{arg} is an expression, it is
11074 not actually evaluated, and any side-effecting operations (such as
11075 assignments or function calls) inside it do not take place. If
11076 @var{arg} is a type name, it may be the name of a type or typedef, or
11077 for C code it may have the form @samp{class @var{class-name}},
11078 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11079 @samp{enum @var{enum-tag}}.
11080 @xref{Expressions, ,Expressions}.
11083 @item ptype [@var{arg}]
11084 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11085 detailed description of the type, instead of just the name of the type.
11086 @xref{Expressions, ,Expressions}.
11088 For example, for this variable declaration:
11091 struct complex @{double real; double imag;@} v;
11095 the two commands give this output:
11099 (@value{GDBP}) whatis v
11100 type = struct complex
11101 (@value{GDBP}) ptype v
11102 type = struct complex @{
11110 As with @code{whatis}, using @code{ptype} without an argument refers to
11111 the type of @code{$}, the last value in the value history.
11113 @cindex incomplete type
11114 Sometimes, programs use opaque data types or incomplete specifications
11115 of complex data structure. If the debug information included in the
11116 program does not allow @value{GDBN} to display a full declaration of
11117 the data type, it will say @samp{<incomplete type>}. For example,
11118 given these declarations:
11122 struct foo *fooptr;
11126 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11129 (@value{GDBP}) ptype foo
11130 $1 = <incomplete type>
11134 ``Incomplete type'' is C terminology for data types that are not
11135 completely specified.
11138 @item info types @var{regexp}
11140 Print a brief description of all types whose names match the regular
11141 expression @var{regexp} (or all types in your program, if you supply
11142 no argument). Each complete typename is matched as though it were a
11143 complete line; thus, @samp{i type value} gives information on all
11144 types in your program whose names include the string @code{value}, but
11145 @samp{i type ^value$} gives information only on types whose complete
11146 name is @code{value}.
11148 This command differs from @code{ptype} in two ways: first, like
11149 @code{whatis}, it does not print a detailed description; second, it
11150 lists all source files where a type is defined.
11153 @cindex local variables
11154 @item info scope @var{location}
11155 List all the variables local to a particular scope. This command
11156 accepts a @var{location} argument---a function name, a source line, or
11157 an address preceded by a @samp{*}, and prints all the variables local
11158 to the scope defined by that location. (@xref{Specify Location}, for
11159 details about supported forms of @var{location}.) For example:
11162 (@value{GDBP}) @b{info scope command_line_handler}
11163 Scope for command_line_handler:
11164 Symbol rl is an argument at stack/frame offset 8, length 4.
11165 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11166 Symbol linelength is in static storage at address 0x150a1c, length 4.
11167 Symbol p is a local variable in register $esi, length 4.
11168 Symbol p1 is a local variable in register $ebx, length 4.
11169 Symbol nline is a local variable in register $edx, length 4.
11170 Symbol repeat is a local variable at frame offset -8, length 4.
11174 This command is especially useful for determining what data to collect
11175 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11178 @kindex info source
11180 Show information about the current source file---that is, the source file for
11181 the function containing the current point of execution:
11184 the name of the source file, and the directory containing it,
11186 the directory it was compiled in,
11188 its length, in lines,
11190 which programming language it is written in,
11192 whether the executable includes debugging information for that file, and
11193 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11195 whether the debugging information includes information about
11196 preprocessor macros.
11200 @kindex info sources
11202 Print the names of all source files in your program for which there is
11203 debugging information, organized into two lists: files whose symbols
11204 have already been read, and files whose symbols will be read when needed.
11206 @kindex info functions
11207 @item info functions
11208 Print the names and data types of all defined functions.
11210 @item info functions @var{regexp}
11211 Print the names and data types of all defined functions
11212 whose names contain a match for regular expression @var{regexp}.
11213 Thus, @samp{info fun step} finds all functions whose names
11214 include @code{step}; @samp{info fun ^step} finds those whose names
11215 start with @code{step}. If a function name contains characters
11216 that conflict with the regular expression language (e.g.@:
11217 @samp{operator*()}), they may be quoted with a backslash.
11219 @kindex info variables
11220 @item info variables
11221 Print the names and data types of all variables that are declared
11222 outside of functions (i.e.@: excluding local variables).
11224 @item info variables @var{regexp}
11225 Print the names and data types of all variables (except for local
11226 variables) whose names contain a match for regular expression
11229 @kindex info classes
11230 @cindex Objective-C, classes and selectors
11232 @itemx info classes @var{regexp}
11233 Display all Objective-C classes in your program, or
11234 (with the @var{regexp} argument) all those matching a particular regular
11237 @kindex info selectors
11238 @item info selectors
11239 @itemx info selectors @var{regexp}
11240 Display all Objective-C selectors in your program, or
11241 (with the @var{regexp} argument) all those matching a particular regular
11245 This was never implemented.
11246 @kindex info methods
11248 @itemx info methods @var{regexp}
11249 The @code{info methods} command permits the user to examine all defined
11250 methods within C@t{++} program, or (with the @var{regexp} argument) a
11251 specific set of methods found in the various C@t{++} classes. Many
11252 C@t{++} classes provide a large number of methods. Thus, the output
11253 from the @code{ptype} command can be overwhelming and hard to use. The
11254 @code{info-methods} command filters the methods, printing only those
11255 which match the regular-expression @var{regexp}.
11258 @cindex reloading symbols
11259 Some systems allow individual object files that make up your program to
11260 be replaced without stopping and restarting your program. For example,
11261 in VxWorks you can simply recompile a defective object file and keep on
11262 running. If you are running on one of these systems, you can allow
11263 @value{GDBN} to reload the symbols for automatically relinked modules:
11266 @kindex set symbol-reloading
11267 @item set symbol-reloading on
11268 Replace symbol definitions for the corresponding source file when an
11269 object file with a particular name is seen again.
11271 @item set symbol-reloading off
11272 Do not replace symbol definitions when encountering object files of the
11273 same name more than once. This is the default state; if you are not
11274 running on a system that permits automatic relinking of modules, you
11275 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11276 may discard symbols when linking large programs, that may contain
11277 several modules (from different directories or libraries) with the same
11280 @kindex show symbol-reloading
11281 @item show symbol-reloading
11282 Show the current @code{on} or @code{off} setting.
11285 @cindex opaque data types
11286 @kindex set opaque-type-resolution
11287 @item set opaque-type-resolution on
11288 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11289 declared as a pointer to a @code{struct}, @code{class}, or
11290 @code{union}---for example, @code{struct MyType *}---that is used in one
11291 source file although the full declaration of @code{struct MyType} is in
11292 another source file. The default is on.
11294 A change in the setting of this subcommand will not take effect until
11295 the next time symbols for a file are loaded.
11297 @item set opaque-type-resolution off
11298 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11299 is printed as follows:
11301 @{<no data fields>@}
11304 @kindex show opaque-type-resolution
11305 @item show opaque-type-resolution
11306 Show whether opaque types are resolved or not.
11308 @kindex maint print symbols
11309 @cindex symbol dump
11310 @kindex maint print psymbols
11311 @cindex partial symbol dump
11312 @item maint print symbols @var{filename}
11313 @itemx maint print psymbols @var{filename}
11314 @itemx maint print msymbols @var{filename}
11315 Write a dump of debugging symbol data into the file @var{filename}.
11316 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11317 symbols with debugging data are included. If you use @samp{maint print
11318 symbols}, @value{GDBN} includes all the symbols for which it has already
11319 collected full details: that is, @var{filename} reflects symbols for
11320 only those files whose symbols @value{GDBN} has read. You can use the
11321 command @code{info sources} to find out which files these are. If you
11322 use @samp{maint print psymbols} instead, the dump shows information about
11323 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11324 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11325 @samp{maint print msymbols} dumps just the minimal symbol information
11326 required for each object file from which @value{GDBN} has read some symbols.
11327 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11328 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11330 @kindex maint info symtabs
11331 @kindex maint info psymtabs
11332 @cindex listing @value{GDBN}'s internal symbol tables
11333 @cindex symbol tables, listing @value{GDBN}'s internal
11334 @cindex full symbol tables, listing @value{GDBN}'s internal
11335 @cindex partial symbol tables, listing @value{GDBN}'s internal
11336 @item maint info symtabs @r{[} @var{regexp} @r{]}
11337 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11339 List the @code{struct symtab} or @code{struct partial_symtab}
11340 structures whose names match @var{regexp}. If @var{regexp} is not
11341 given, list them all. The output includes expressions which you can
11342 copy into a @value{GDBN} debugging this one to examine a particular
11343 structure in more detail. For example:
11346 (@value{GDBP}) maint info psymtabs dwarf2read
11347 @{ objfile /home/gnu/build/gdb/gdb
11348 ((struct objfile *) 0x82e69d0)
11349 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11350 ((struct partial_symtab *) 0x8474b10)
11353 text addresses 0x814d3c8 -- 0x8158074
11354 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11355 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11356 dependencies (none)
11359 (@value{GDBP}) maint info symtabs
11363 We see that there is one partial symbol table whose filename contains
11364 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11365 and we see that @value{GDBN} has not read in any symtabs yet at all.
11366 If we set a breakpoint on a function, that will cause @value{GDBN} to
11367 read the symtab for the compilation unit containing that function:
11370 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11371 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11373 (@value{GDBP}) maint info symtabs
11374 @{ objfile /home/gnu/build/gdb/gdb
11375 ((struct objfile *) 0x82e69d0)
11376 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11377 ((struct symtab *) 0x86c1f38)
11380 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11381 linetable ((struct linetable *) 0x8370fa0)
11382 debugformat DWARF 2
11391 @chapter Altering Execution
11393 Once you think you have found an error in your program, you might want to
11394 find out for certain whether correcting the apparent error would lead to
11395 correct results in the rest of the run. You can find the answer by
11396 experiment, using the @value{GDBN} features for altering execution of the
11399 For example, you can store new values into variables or memory
11400 locations, give your program a signal, restart it at a different
11401 address, or even return prematurely from a function.
11404 * Assignment:: Assignment to variables
11405 * Jumping:: Continuing at a different address
11406 * Signaling:: Giving your program a signal
11407 * Returning:: Returning from a function
11408 * Calling:: Calling your program's functions
11409 * Patching:: Patching your program
11413 @section Assignment to Variables
11416 @cindex setting variables
11417 To alter the value of a variable, evaluate an assignment expression.
11418 @xref{Expressions, ,Expressions}. For example,
11425 stores the value 4 into the variable @code{x}, and then prints the
11426 value of the assignment expression (which is 4).
11427 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11428 information on operators in supported languages.
11430 @kindex set variable
11431 @cindex variables, setting
11432 If you are not interested in seeing the value of the assignment, use the
11433 @code{set} command instead of the @code{print} command. @code{set} is
11434 really the same as @code{print} except that the expression's value is
11435 not printed and is not put in the value history (@pxref{Value History,
11436 ,Value History}). The expression is evaluated only for its effects.
11438 If the beginning of the argument string of the @code{set} command
11439 appears identical to a @code{set} subcommand, use the @code{set
11440 variable} command instead of just @code{set}. This command is identical
11441 to @code{set} except for its lack of subcommands. For example, if your
11442 program has a variable @code{width}, you get an error if you try to set
11443 a new value with just @samp{set width=13}, because @value{GDBN} has the
11444 command @code{set width}:
11447 (@value{GDBP}) whatis width
11449 (@value{GDBP}) p width
11451 (@value{GDBP}) set width=47
11452 Invalid syntax in expression.
11456 The invalid expression, of course, is @samp{=47}. In
11457 order to actually set the program's variable @code{width}, use
11460 (@value{GDBP}) set var width=47
11463 Because the @code{set} command has many subcommands that can conflict
11464 with the names of program variables, it is a good idea to use the
11465 @code{set variable} command instead of just @code{set}. For example, if
11466 your program has a variable @code{g}, you run into problems if you try
11467 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11468 the command @code{set gnutarget}, abbreviated @code{set g}:
11472 (@value{GDBP}) whatis g
11476 (@value{GDBP}) set g=4
11480 The program being debugged has been started already.
11481 Start it from the beginning? (y or n) y
11482 Starting program: /home/smith/cc_progs/a.out
11483 "/home/smith/cc_progs/a.out": can't open to read symbols:
11484 Invalid bfd target.
11485 (@value{GDBP}) show g
11486 The current BFD target is "=4".
11491 The program variable @code{g} did not change, and you silently set the
11492 @code{gnutarget} to an invalid value. In order to set the variable
11496 (@value{GDBP}) set var g=4
11499 @value{GDBN} allows more implicit conversions in assignments than C; you can
11500 freely store an integer value into a pointer variable or vice versa,
11501 and you can convert any structure to any other structure that is the
11502 same length or shorter.
11503 @comment FIXME: how do structs align/pad in these conversions?
11504 @comment /doc@cygnus.com 18dec1990
11506 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11507 construct to generate a value of specified type at a specified address
11508 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11509 to memory location @code{0x83040} as an integer (which implies a certain size
11510 and representation in memory), and
11513 set @{int@}0x83040 = 4
11517 stores the value 4 into that memory location.
11520 @section Continuing at a Different Address
11522 Ordinarily, when you continue your program, you do so at the place where
11523 it stopped, with the @code{continue} command. You can instead continue at
11524 an address of your own choosing, with the following commands:
11528 @item jump @var{linespec}
11529 @itemx jump @var{location}
11530 Resume execution at line @var{linespec} or at address given by
11531 @var{location}. Execution stops again immediately if there is a
11532 breakpoint there. @xref{Specify Location}, for a description of the
11533 different forms of @var{linespec} and @var{location}. It is common
11534 practice to use the @code{tbreak} command in conjunction with
11535 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
11537 The @code{jump} command does not change the current stack frame, or
11538 the stack pointer, or the contents of any memory location or any
11539 register other than the program counter. If line @var{linespec} is in
11540 a different function from the one currently executing, the results may
11541 be bizarre if the two functions expect different patterns of arguments or
11542 of local variables. For this reason, the @code{jump} command requests
11543 confirmation if the specified line is not in the function currently
11544 executing. However, even bizarre results are predictable if you are
11545 well acquainted with the machine-language code of your program.
11548 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11549 On many systems, you can get much the same effect as the @code{jump}
11550 command by storing a new value into the register @code{$pc}. The
11551 difference is that this does not start your program running; it only
11552 changes the address of where it @emph{will} run when you continue. For
11560 makes the next @code{continue} command or stepping command execute at
11561 address @code{0x485}, rather than at the address where your program stopped.
11562 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11564 The most common occasion to use the @code{jump} command is to back
11565 up---perhaps with more breakpoints set---over a portion of a program
11566 that has already executed, in order to examine its execution in more
11571 @section Giving your Program a Signal
11572 @cindex deliver a signal to a program
11576 @item signal @var{signal}
11577 Resume execution where your program stopped, but immediately give it the
11578 signal @var{signal}. @var{signal} can be the name or the number of a
11579 signal. For example, on many systems @code{signal 2} and @code{signal
11580 SIGINT} are both ways of sending an interrupt signal.
11582 Alternatively, if @var{signal} is zero, continue execution without
11583 giving a signal. This is useful when your program stopped on account of
11584 a signal and would ordinary see the signal when resumed with the
11585 @code{continue} command; @samp{signal 0} causes it to resume without a
11588 @code{signal} does not repeat when you press @key{RET} a second time
11589 after executing the command.
11593 Invoking the @code{signal} command is not the same as invoking the
11594 @code{kill} utility from the shell. Sending a signal with @code{kill}
11595 causes @value{GDBN} to decide what to do with the signal depending on
11596 the signal handling tables (@pxref{Signals}). The @code{signal} command
11597 passes the signal directly to your program.
11601 @section Returning from a Function
11604 @cindex returning from a function
11607 @itemx return @var{expression}
11608 You can cancel execution of a function call with the @code{return}
11609 command. If you give an
11610 @var{expression} argument, its value is used as the function's return
11614 When you use @code{return}, @value{GDBN} discards the selected stack frame
11615 (and all frames within it). You can think of this as making the
11616 discarded frame return prematurely. If you wish to specify a value to
11617 be returned, give that value as the argument to @code{return}.
11619 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11620 Frame}), and any other frames inside of it, leaving its caller as the
11621 innermost remaining frame. That frame becomes selected. The
11622 specified value is stored in the registers used for returning values
11625 The @code{return} command does not resume execution; it leaves the
11626 program stopped in the state that would exist if the function had just
11627 returned. In contrast, the @code{finish} command (@pxref{Continuing
11628 and Stepping, ,Continuing and Stepping}) resumes execution until the
11629 selected stack frame returns naturally.
11632 @section Calling Program Functions
11635 @cindex calling functions
11636 @cindex inferior functions, calling
11637 @item print @var{expr}
11638 Evaluate the expression @var{expr} and display the resulting value.
11639 @var{expr} may include calls to functions in the program being
11643 @item call @var{expr}
11644 Evaluate the expression @var{expr} without displaying @code{void}
11647 You can use this variant of the @code{print} command if you want to
11648 execute a function from your program that does not return anything
11649 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11650 with @code{void} returned values that @value{GDBN} will otherwise
11651 print. If the result is not void, it is printed and saved in the
11655 It is possible for the function you call via the @code{print} or
11656 @code{call} command to generate a signal (e.g., if there's a bug in
11657 the function, or if you passed it incorrect arguments). What happens
11658 in that case is controlled by the @code{set unwindonsignal} command.
11661 @item set unwindonsignal
11662 @kindex set unwindonsignal
11663 @cindex unwind stack in called functions
11664 @cindex call dummy stack unwinding
11665 Set unwinding of the stack if a signal is received while in a function
11666 that @value{GDBN} called in the program being debugged. If set to on,
11667 @value{GDBN} unwinds the stack it created for the call and restores
11668 the context to what it was before the call. If set to off (the
11669 default), @value{GDBN} stops in the frame where the signal was
11672 @item show unwindonsignal
11673 @kindex show unwindonsignal
11674 Show the current setting of stack unwinding in the functions called by
11678 @cindex weak alias functions
11679 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11680 for another function. In such case, @value{GDBN} might not pick up
11681 the type information, including the types of the function arguments,
11682 which causes @value{GDBN} to call the inferior function incorrectly.
11683 As a result, the called function will function erroneously and may
11684 even crash. A solution to that is to use the name of the aliased
11688 @section Patching Programs
11690 @cindex patching binaries
11691 @cindex writing into executables
11692 @cindex writing into corefiles
11694 By default, @value{GDBN} opens the file containing your program's
11695 executable code (or the corefile) read-only. This prevents accidental
11696 alterations to machine code; but it also prevents you from intentionally
11697 patching your program's binary.
11699 If you'd like to be able to patch the binary, you can specify that
11700 explicitly with the @code{set write} command. For example, you might
11701 want to turn on internal debugging flags, or even to make emergency
11707 @itemx set write off
11708 If you specify @samp{set write on}, @value{GDBN} opens executable and
11709 core files for both reading and writing; if you specify @samp{set write
11710 off} (the default), @value{GDBN} opens them read-only.
11712 If you have already loaded a file, you must load it again (using the
11713 @code{exec-file} or @code{core-file} command) after changing @code{set
11714 write}, for your new setting to take effect.
11718 Display whether executable files and core files are opened for writing
11719 as well as reading.
11723 @chapter @value{GDBN} Files
11725 @value{GDBN} needs to know the file name of the program to be debugged,
11726 both in order to read its symbol table and in order to start your
11727 program. To debug a core dump of a previous run, you must also tell
11728 @value{GDBN} the name of the core dump file.
11731 * Files:: Commands to specify files
11732 * Separate Debug Files:: Debugging information in separate files
11733 * Symbol Errors:: Errors reading symbol files
11737 @section Commands to Specify Files
11739 @cindex symbol table
11740 @cindex core dump file
11742 You may want to specify executable and core dump file names. The usual
11743 way to do this is at start-up time, using the arguments to
11744 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11745 Out of @value{GDBN}}).
11747 Occasionally it is necessary to change to a different file during a
11748 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11749 specify a file you want to use. Or you are debugging a remote target
11750 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11751 Program}). In these situations the @value{GDBN} commands to specify
11752 new files are useful.
11755 @cindex executable file
11757 @item file @var{filename}
11758 Use @var{filename} as the program to be debugged. It is read for its
11759 symbols and for the contents of pure memory. It is also the program
11760 executed when you use the @code{run} command. If you do not specify a
11761 directory and the file is not found in the @value{GDBN} working directory,
11762 @value{GDBN} uses the environment variable @code{PATH} as a list of
11763 directories to search, just as the shell does when looking for a program
11764 to run. You can change the value of this variable, for both @value{GDBN}
11765 and your program, using the @code{path} command.
11767 @cindex unlinked object files
11768 @cindex patching object files
11769 You can load unlinked object @file{.o} files into @value{GDBN} using
11770 the @code{file} command. You will not be able to ``run'' an object
11771 file, but you can disassemble functions and inspect variables. Also,
11772 if the underlying BFD functionality supports it, you could use
11773 @kbd{gdb -write} to patch object files using this technique. Note
11774 that @value{GDBN} can neither interpret nor modify relocations in this
11775 case, so branches and some initialized variables will appear to go to
11776 the wrong place. But this feature is still handy from time to time.
11779 @code{file} with no argument makes @value{GDBN} discard any information it
11780 has on both executable file and the symbol table.
11783 @item exec-file @r{[} @var{filename} @r{]}
11784 Specify that the program to be run (but not the symbol table) is found
11785 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11786 if necessary to locate your program. Omitting @var{filename} means to
11787 discard information on the executable file.
11789 @kindex symbol-file
11790 @item symbol-file @r{[} @var{filename} @r{]}
11791 Read symbol table information from file @var{filename}. @code{PATH} is
11792 searched when necessary. Use the @code{file} command to get both symbol
11793 table and program to run from the same file.
11795 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11796 program's symbol table.
11798 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11799 some breakpoints and auto-display expressions. This is because they may
11800 contain pointers to the internal data recording symbols and data types,
11801 which are part of the old symbol table data being discarded inside
11804 @code{symbol-file} does not repeat if you press @key{RET} again after
11807 When @value{GDBN} is configured for a particular environment, it
11808 understands debugging information in whatever format is the standard
11809 generated for that environment; you may use either a @sc{gnu} compiler, or
11810 other compilers that adhere to the local conventions.
11811 Best results are usually obtained from @sc{gnu} compilers; for example,
11812 using @code{@value{NGCC}} you can generate debugging information for
11815 For most kinds of object files, with the exception of old SVR3 systems
11816 using COFF, the @code{symbol-file} command does not normally read the
11817 symbol table in full right away. Instead, it scans the symbol table
11818 quickly to find which source files and which symbols are present. The
11819 details are read later, one source file at a time, as they are needed.
11821 The purpose of this two-stage reading strategy is to make @value{GDBN}
11822 start up faster. For the most part, it is invisible except for
11823 occasional pauses while the symbol table details for a particular source
11824 file are being read. (The @code{set verbose} command can turn these
11825 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11826 Warnings and Messages}.)
11828 We have not implemented the two-stage strategy for COFF yet. When the
11829 symbol table is stored in COFF format, @code{symbol-file} reads the
11830 symbol table data in full right away. Note that ``stabs-in-COFF''
11831 still does the two-stage strategy, since the debug info is actually
11835 @cindex reading symbols immediately
11836 @cindex symbols, reading immediately
11837 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11838 @itemx file @var{filename} @r{[} -readnow @r{]}
11839 You can override the @value{GDBN} two-stage strategy for reading symbol
11840 tables by using the @samp{-readnow} option with any of the commands that
11841 load symbol table information, if you want to be sure @value{GDBN} has the
11842 entire symbol table available.
11844 @c FIXME: for now no mention of directories, since this seems to be in
11845 @c flux. 13mar1992 status is that in theory GDB would look either in
11846 @c current dir or in same dir as myprog; but issues like competing
11847 @c GDB's, or clutter in system dirs, mean that in practice right now
11848 @c only current dir is used. FFish says maybe a special GDB hierarchy
11849 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11853 @item core-file @r{[}@var{filename}@r{]}
11855 Specify the whereabouts of a core dump file to be used as the ``contents
11856 of memory''. Traditionally, core files contain only some parts of the
11857 address space of the process that generated them; @value{GDBN} can access the
11858 executable file itself for other parts.
11860 @code{core-file} with no argument specifies that no core file is
11863 Note that the core file is ignored when your program is actually running
11864 under @value{GDBN}. So, if you have been running your program and you
11865 wish to debug a core file instead, you must kill the subprocess in which
11866 the program is running. To do this, use the @code{kill} command
11867 (@pxref{Kill Process, ,Killing the Child Process}).
11869 @kindex add-symbol-file
11870 @cindex dynamic linking
11871 @item add-symbol-file @var{filename} @var{address}
11872 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11873 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11874 The @code{add-symbol-file} command reads additional symbol table
11875 information from the file @var{filename}. You would use this command
11876 when @var{filename} has been dynamically loaded (by some other means)
11877 into the program that is running. @var{address} should be the memory
11878 address at which the file has been loaded; @value{GDBN} cannot figure
11879 this out for itself. You can additionally specify an arbitrary number
11880 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11881 section name and base address for that section. You can specify any
11882 @var{address} as an expression.
11884 The symbol table of the file @var{filename} is added to the symbol table
11885 originally read with the @code{symbol-file} command. You can use the
11886 @code{add-symbol-file} command any number of times; the new symbol data
11887 thus read keeps adding to the old. To discard all old symbol data
11888 instead, use the @code{symbol-file} command without any arguments.
11890 @cindex relocatable object files, reading symbols from
11891 @cindex object files, relocatable, reading symbols from
11892 @cindex reading symbols from relocatable object files
11893 @cindex symbols, reading from relocatable object files
11894 @cindex @file{.o} files, reading symbols from
11895 Although @var{filename} is typically a shared library file, an
11896 executable file, or some other object file which has been fully
11897 relocated for loading into a process, you can also load symbolic
11898 information from relocatable @file{.o} files, as long as:
11902 the file's symbolic information refers only to linker symbols defined in
11903 that file, not to symbols defined by other object files,
11905 every section the file's symbolic information refers to has actually
11906 been loaded into the inferior, as it appears in the file, and
11908 you can determine the address at which every section was loaded, and
11909 provide these to the @code{add-symbol-file} command.
11913 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11914 relocatable files into an already running program; such systems
11915 typically make the requirements above easy to meet. However, it's
11916 important to recognize that many native systems use complex link
11917 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11918 assembly, for example) that make the requirements difficult to meet. In
11919 general, one cannot assume that using @code{add-symbol-file} to read a
11920 relocatable object file's symbolic information will have the same effect
11921 as linking the relocatable object file into the program in the normal
11924 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11926 @kindex add-symbol-file-from-memory
11927 @cindex @code{syscall DSO}
11928 @cindex load symbols from memory
11929 @item add-symbol-file-from-memory @var{address}
11930 Load symbols from the given @var{address} in a dynamically loaded
11931 object file whose image is mapped directly into the inferior's memory.
11932 For example, the Linux kernel maps a @code{syscall DSO} into each
11933 process's address space; this DSO provides kernel-specific code for
11934 some system calls. The argument can be any expression whose
11935 evaluation yields the address of the file's shared object file header.
11936 For this command to work, you must have used @code{symbol-file} or
11937 @code{exec-file} commands in advance.
11939 @kindex add-shared-symbol-files
11941 @item add-shared-symbol-files @var{library-file}
11942 @itemx assf @var{library-file}
11943 The @code{add-shared-symbol-files} command can currently be used only
11944 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11945 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11946 @value{GDBN} automatically looks for shared libraries, however if
11947 @value{GDBN} does not find yours, you can invoke
11948 @code{add-shared-symbol-files}. It takes one argument: the shared
11949 library's file name. @code{assf} is a shorthand alias for
11950 @code{add-shared-symbol-files}.
11953 @item section @var{section} @var{addr}
11954 The @code{section} command changes the base address of the named
11955 @var{section} of the exec file to @var{addr}. This can be used if the
11956 exec file does not contain section addresses, (such as in the
11957 @code{a.out} format), or when the addresses specified in the file
11958 itself are wrong. Each section must be changed separately. The
11959 @code{info files} command, described below, lists all the sections and
11963 @kindex info target
11966 @code{info files} and @code{info target} are synonymous; both print the
11967 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11968 including the names of the executable and core dump files currently in
11969 use by @value{GDBN}, and the files from which symbols were loaded. The
11970 command @code{help target} lists all possible targets rather than
11973 @kindex maint info sections
11974 @item maint info sections
11975 Another command that can give you extra information about program sections
11976 is @code{maint info sections}. In addition to the section information
11977 displayed by @code{info files}, this command displays the flags and file
11978 offset of each section in the executable and core dump files. In addition,
11979 @code{maint info sections} provides the following command options (which
11980 may be arbitrarily combined):
11984 Display sections for all loaded object files, including shared libraries.
11985 @item @var{sections}
11986 Display info only for named @var{sections}.
11987 @item @var{section-flags}
11988 Display info only for sections for which @var{section-flags} are true.
11989 The section flags that @value{GDBN} currently knows about are:
11992 Section will have space allocated in the process when loaded.
11993 Set for all sections except those containing debug information.
11995 Section will be loaded from the file into the child process memory.
11996 Set for pre-initialized code and data, clear for @code{.bss} sections.
11998 Section needs to be relocated before loading.
12000 Section cannot be modified by the child process.
12002 Section contains executable code only.
12004 Section contains data only (no executable code).
12006 Section will reside in ROM.
12008 Section contains data for constructor/destructor lists.
12010 Section is not empty.
12012 An instruction to the linker to not output the section.
12013 @item COFF_SHARED_LIBRARY
12014 A notification to the linker that the section contains
12015 COFF shared library information.
12017 Section contains common symbols.
12020 @kindex set trust-readonly-sections
12021 @cindex read-only sections
12022 @item set trust-readonly-sections on
12023 Tell @value{GDBN} that readonly sections in your object file
12024 really are read-only (i.e.@: that their contents will not change).
12025 In that case, @value{GDBN} can fetch values from these sections
12026 out of the object file, rather than from the target program.
12027 For some targets (notably embedded ones), this can be a significant
12028 enhancement to debugging performance.
12030 The default is off.
12032 @item set trust-readonly-sections off
12033 Tell @value{GDBN} not to trust readonly sections. This means that
12034 the contents of the section might change while the program is running,
12035 and must therefore be fetched from the target when needed.
12037 @item show trust-readonly-sections
12038 Show the current setting of trusting readonly sections.
12041 All file-specifying commands allow both absolute and relative file names
12042 as arguments. @value{GDBN} always converts the file name to an absolute file
12043 name and remembers it that way.
12045 @cindex shared libraries
12046 @anchor{Shared Libraries}
12047 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12048 and IBM RS/6000 AIX shared libraries.
12050 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12051 shared libraries. @xref{Expat}.
12053 @value{GDBN} automatically loads symbol definitions from shared libraries
12054 when you use the @code{run} command, or when you examine a core file.
12055 (Before you issue the @code{run} command, @value{GDBN} does not understand
12056 references to a function in a shared library, however---unless you are
12057 debugging a core file).
12059 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12060 automatically loads the symbols at the time of the @code{shl_load} call.
12062 @c FIXME: some @value{GDBN} release may permit some refs to undef
12063 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12064 @c FIXME...lib; check this from time to time when updating manual
12066 There are times, however, when you may wish to not automatically load
12067 symbol definitions from shared libraries, such as when they are
12068 particularly large or there are many of them.
12070 To control the automatic loading of shared library symbols, use the
12074 @kindex set auto-solib-add
12075 @item set auto-solib-add @var{mode}
12076 If @var{mode} is @code{on}, symbols from all shared object libraries
12077 will be loaded automatically when the inferior begins execution, you
12078 attach to an independently started inferior, or when the dynamic linker
12079 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12080 is @code{off}, symbols must be loaded manually, using the
12081 @code{sharedlibrary} command. The default value is @code{on}.
12083 @cindex memory used for symbol tables
12084 If your program uses lots of shared libraries with debug info that
12085 takes large amounts of memory, you can decrease the @value{GDBN}
12086 memory footprint by preventing it from automatically loading the
12087 symbols from shared libraries. To that end, type @kbd{set
12088 auto-solib-add off} before running the inferior, then load each
12089 library whose debug symbols you do need with @kbd{sharedlibrary
12090 @var{regexp}}, where @var{regexp} is a regular expression that matches
12091 the libraries whose symbols you want to be loaded.
12093 @kindex show auto-solib-add
12094 @item show auto-solib-add
12095 Display the current autoloading mode.
12098 @cindex load shared library
12099 To explicitly load shared library symbols, use the @code{sharedlibrary}
12103 @kindex info sharedlibrary
12106 @itemx info sharedlibrary
12107 Print the names of the shared libraries which are currently loaded.
12109 @kindex sharedlibrary
12111 @item sharedlibrary @var{regex}
12112 @itemx share @var{regex}
12113 Load shared object library symbols for files matching a
12114 Unix regular expression.
12115 As with files loaded automatically, it only loads shared libraries
12116 required by your program for a core file or after typing @code{run}. If
12117 @var{regex} is omitted all shared libraries required by your program are
12120 @item nosharedlibrary
12121 @kindex nosharedlibrary
12122 @cindex unload symbols from shared libraries
12123 Unload all shared object library symbols. This discards all symbols
12124 that have been loaded from all shared libraries. Symbols from shared
12125 libraries that were loaded by explicit user requests are not
12129 Sometimes you may wish that @value{GDBN} stops and gives you control
12130 when any of shared library events happen. Use the @code{set
12131 stop-on-solib-events} command for this:
12134 @item set stop-on-solib-events
12135 @kindex set stop-on-solib-events
12136 This command controls whether @value{GDBN} should give you control
12137 when the dynamic linker notifies it about some shared library event.
12138 The most common event of interest is loading or unloading of a new
12141 @item show stop-on-solib-events
12142 @kindex show stop-on-solib-events
12143 Show whether @value{GDBN} stops and gives you control when shared
12144 library events happen.
12147 Shared libraries are also supported in many cross or remote debugging
12148 configurations. A copy of the target's libraries need to be present on the
12149 host system; they need to be the same as the target libraries, although the
12150 copies on the target can be stripped as long as the copies on the host are
12153 @cindex where to look for shared libraries
12154 For remote debugging, you need to tell @value{GDBN} where the target
12155 libraries are, so that it can load the correct copies---otherwise, it
12156 may try to load the host's libraries. @value{GDBN} has two variables
12157 to specify the search directories for target libraries.
12160 @cindex prefix for shared library file names
12161 @cindex system root, alternate
12162 @kindex set solib-absolute-prefix
12163 @kindex set sysroot
12164 @item set sysroot @var{path}
12165 Use @var{path} as the system root for the program being debugged. Any
12166 absolute shared library paths will be prefixed with @var{path}; many
12167 runtime loaders store the absolute paths to the shared library in the
12168 target program's memory. If you use @code{set sysroot} to find shared
12169 libraries, they need to be laid out in the same way that they are on
12170 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12173 The @code{set solib-absolute-prefix} command is an alias for @code{set
12176 @cindex default system root
12177 @cindex @samp{--with-sysroot}
12178 You can set the default system root by using the configure-time
12179 @samp{--with-sysroot} option. If the system root is inside
12180 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12181 @samp{--exec-prefix}), then the default system root will be updated
12182 automatically if the installed @value{GDBN} is moved to a new
12185 @kindex show sysroot
12187 Display the current shared library prefix.
12189 @kindex set solib-search-path
12190 @item set solib-search-path @var{path}
12191 If this variable is set, @var{path} is a colon-separated list of
12192 directories to search for shared libraries. @samp{solib-search-path}
12193 is used after @samp{sysroot} fails to locate the library, or if the
12194 path to the library is relative instead of absolute. If you want to
12195 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12196 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12197 finding your host's libraries. @samp{sysroot} is preferred; setting
12198 it to a nonexistent directory may interfere with automatic loading
12199 of shared library symbols.
12201 @kindex show solib-search-path
12202 @item show solib-search-path
12203 Display the current shared library search path.
12207 @node Separate Debug Files
12208 @section Debugging Information in Separate Files
12209 @cindex separate debugging information files
12210 @cindex debugging information in separate files
12211 @cindex @file{.debug} subdirectories
12212 @cindex debugging information directory, global
12213 @cindex global debugging information directory
12214 @cindex build ID, and separate debugging files
12215 @cindex @file{.build-id} directory
12217 @value{GDBN} allows you to put a program's debugging information in a
12218 file separate from the executable itself, in a way that allows
12219 @value{GDBN} to find and load the debugging information automatically.
12220 Since debugging information can be very large---sometimes larger
12221 than the executable code itself---some systems distribute debugging
12222 information for their executables in separate files, which users can
12223 install only when they need to debug a problem.
12225 @value{GDBN} supports two ways of specifying the separate debug info
12230 The executable contains a @dfn{debug link} that specifies the name of
12231 the separate debug info file. The separate debug file's name is
12232 usually @file{@var{executable}.debug}, where @var{executable} is the
12233 name of the corresponding executable file without leading directories
12234 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12235 debug link specifies a CRC32 checksum for the debug file, which
12236 @value{GDBN} uses to validate that the executable and the debug file
12237 came from the same build.
12240 The executable contains a @dfn{build ID}, a unique bit string that is
12241 also present in the corresponding debug info file. (This is supported
12242 only on some operating systems, notably those which use the ELF format
12243 for binary files and the @sc{gnu} Binutils.) For more details about
12244 this feature, see the description of the @option{--build-id}
12245 command-line option in @ref{Options, , Command Line Options, ld.info,
12246 The GNU Linker}. The debug info file's name is not specified
12247 explicitly by the build ID, but can be computed from the build ID, see
12251 Depending on the way the debug info file is specified, @value{GDBN}
12252 uses two different methods of looking for the debug file:
12256 For the ``debug link'' method, @value{GDBN} looks up the named file in
12257 the directory of the executable file, then in a subdirectory of that
12258 directory named @file{.debug}, and finally under the global debug
12259 directory, in a subdirectory whose name is identical to the leading
12260 directories of the executable's absolute file name.
12263 For the ``build ID'' method, @value{GDBN} looks in the
12264 @file{.build-id} subdirectory of the global debug directory for a file
12265 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12266 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12267 are the rest of the bit string. (Real build ID strings are 32 or more
12268 hex characters, not 10.)
12271 So, for example, suppose you ask @value{GDBN} to debug
12272 @file{/usr/bin/ls}, which has a debug link that specifies the
12273 file @file{ls.debug}, and a build ID whose value in hex is
12274 @code{abcdef1234}. If the global debug directory is
12275 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12276 debug information files, in the indicated order:
12280 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12282 @file{/usr/bin/ls.debug}
12284 @file{/usr/bin/.debug/ls.debug}
12286 @file{/usr/lib/debug/usr/bin/ls.debug}.
12289 You can set the global debugging info directory's name, and view the
12290 name @value{GDBN} is currently using.
12294 @kindex set debug-file-directory
12295 @item set debug-file-directory @var{directory}
12296 Set the directory which @value{GDBN} searches for separate debugging
12297 information files to @var{directory}.
12299 @kindex show debug-file-directory
12300 @item show debug-file-directory
12301 Show the directory @value{GDBN} searches for separate debugging
12306 @cindex @code{.gnu_debuglink} sections
12307 @cindex debug link sections
12308 A debug link is a special section of the executable file named
12309 @code{.gnu_debuglink}. The section must contain:
12313 A filename, with any leading directory components removed, followed by
12316 zero to three bytes of padding, as needed to reach the next four-byte
12317 boundary within the section, and
12319 a four-byte CRC checksum, stored in the same endianness used for the
12320 executable file itself. The checksum is computed on the debugging
12321 information file's full contents by the function given below, passing
12322 zero as the @var{crc} argument.
12325 Any executable file format can carry a debug link, as long as it can
12326 contain a section named @code{.gnu_debuglink} with the contents
12329 @cindex @code{.note.gnu.build-id} sections
12330 @cindex build ID sections
12331 The build ID is a special section in the executable file (and in other
12332 ELF binary files that @value{GDBN} may consider). This section is
12333 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12334 It contains unique identification for the built files---the ID remains
12335 the same across multiple builds of the same build tree. The default
12336 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12337 content for the build ID string. The same section with an identical
12338 value is present in the original built binary with symbols, in its
12339 stripped variant, and in the separate debugging information file.
12341 The debugging information file itself should be an ordinary
12342 executable, containing a full set of linker symbols, sections, and
12343 debugging information. The sections of the debugging information file
12344 should have the same names, addresses, and sizes as the original file,
12345 but they need not contain any data---much like a @code{.bss} section
12346 in an ordinary executable.
12348 The @sc{gnu} binary utilities (Binutils) package includes the
12349 @samp{objcopy} utility that can produce
12350 the separated executable / debugging information file pairs using the
12351 following commands:
12354 @kbd{objcopy --only-keep-debug foo foo.debug}
12359 These commands remove the debugging
12360 information from the executable file @file{foo} and place it in the file
12361 @file{foo.debug}. You can use the first, second or both methods to link the
12366 The debug link method needs the following additional command to also leave
12367 behind a debug link in @file{foo}:
12370 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12373 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12374 a version of the @code{strip} command such that the command @kbd{strip foo -f
12375 foo.debug} has the same functionality as the two @code{objcopy} commands and
12376 the @code{ln -s} command above, together.
12379 Build ID gets embedded into the main executable using @code{ld --build-id} or
12380 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12381 compatibility fixes for debug files separation are present in @sc{gnu} binary
12382 utilities (Binutils) package since version 2.18.
12387 Since there are many different ways to compute CRC's for the debug
12388 link (different polynomials, reversals, byte ordering, etc.), the
12389 simplest way to describe the CRC used in @code{.gnu_debuglink}
12390 sections is to give the complete code for a function that computes it:
12392 @kindex gnu_debuglink_crc32
12395 gnu_debuglink_crc32 (unsigned long crc,
12396 unsigned char *buf, size_t len)
12398 static const unsigned long crc32_table[256] =
12400 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12401 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12402 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12403 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12404 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12405 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12406 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12407 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12408 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12409 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12410 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12411 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12412 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12413 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12414 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12415 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12416 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12417 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12418 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12419 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12420 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12421 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12422 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12423 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12424 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12425 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12426 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12427 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12428 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12429 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12430 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12431 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12432 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12433 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12434 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12435 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12436 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12437 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12438 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12439 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12440 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12441 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12442 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12443 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12444 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12445 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12446 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12447 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12448 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12449 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12450 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12453 unsigned char *end;
12455 crc = ~crc & 0xffffffff;
12456 for (end = buf + len; buf < end; ++buf)
12457 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12458 return ~crc & 0xffffffff;
12463 This computation does not apply to the ``build ID'' method.
12466 @node Symbol Errors
12467 @section Errors Reading Symbol Files
12469 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12470 such as symbol types it does not recognize, or known bugs in compiler
12471 output. By default, @value{GDBN} does not notify you of such problems, since
12472 they are relatively common and primarily of interest to people
12473 debugging compilers. If you are interested in seeing information
12474 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12475 only one message about each such type of problem, no matter how many
12476 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12477 to see how many times the problems occur, with the @code{set
12478 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12481 The messages currently printed, and their meanings, include:
12484 @item inner block not inside outer block in @var{symbol}
12486 The symbol information shows where symbol scopes begin and end
12487 (such as at the start of a function or a block of statements). This
12488 error indicates that an inner scope block is not fully contained
12489 in its outer scope blocks.
12491 @value{GDBN} circumvents the problem by treating the inner block as if it had
12492 the same scope as the outer block. In the error message, @var{symbol}
12493 may be shown as ``@code{(don't know)}'' if the outer block is not a
12496 @item block at @var{address} out of order
12498 The symbol information for symbol scope blocks should occur in
12499 order of increasing addresses. This error indicates that it does not
12502 @value{GDBN} does not circumvent this problem, and has trouble
12503 locating symbols in the source file whose symbols it is reading. (You
12504 can often determine what source file is affected by specifying
12505 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12508 @item bad block start address patched
12510 The symbol information for a symbol scope block has a start address
12511 smaller than the address of the preceding source line. This is known
12512 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12514 @value{GDBN} circumvents the problem by treating the symbol scope block as
12515 starting on the previous source line.
12517 @item bad string table offset in symbol @var{n}
12520 Symbol number @var{n} contains a pointer into the string table which is
12521 larger than the size of the string table.
12523 @value{GDBN} circumvents the problem by considering the symbol to have the
12524 name @code{foo}, which may cause other problems if many symbols end up
12527 @item unknown symbol type @code{0x@var{nn}}
12529 The symbol information contains new data types that @value{GDBN} does
12530 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12531 uncomprehended information, in hexadecimal.
12533 @value{GDBN} circumvents the error by ignoring this symbol information.
12534 This usually allows you to debug your program, though certain symbols
12535 are not accessible. If you encounter such a problem and feel like
12536 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12537 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12538 and examine @code{*bufp} to see the symbol.
12540 @item stub type has NULL name
12542 @value{GDBN} could not find the full definition for a struct or class.
12544 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12545 The symbol information for a C@t{++} member function is missing some
12546 information that recent versions of the compiler should have output for
12549 @item info mismatch between compiler and debugger
12551 @value{GDBN} could not parse a type specification output by the compiler.
12556 @chapter Specifying a Debugging Target
12558 @cindex debugging target
12559 A @dfn{target} is the execution environment occupied by your program.
12561 Often, @value{GDBN} runs in the same host environment as your program;
12562 in that case, the debugging target is specified as a side effect when
12563 you use the @code{file} or @code{core} commands. When you need more
12564 flexibility---for example, running @value{GDBN} on a physically separate
12565 host, or controlling a standalone system over a serial port or a
12566 realtime system over a TCP/IP connection---you can use the @code{target}
12567 command to specify one of the target types configured for @value{GDBN}
12568 (@pxref{Target Commands, ,Commands for Managing Targets}).
12570 @cindex target architecture
12571 It is possible to build @value{GDBN} for several different @dfn{target
12572 architectures}. When @value{GDBN} is built like that, you can choose
12573 one of the available architectures with the @kbd{set architecture}
12577 @kindex set architecture
12578 @kindex show architecture
12579 @item set architecture @var{arch}
12580 This command sets the current target architecture to @var{arch}. The
12581 value of @var{arch} can be @code{"auto"}, in addition to one of the
12582 supported architectures.
12584 @item show architecture
12585 Show the current target architecture.
12587 @item set processor
12589 @kindex set processor
12590 @kindex show processor
12591 These are alias commands for, respectively, @code{set architecture}
12592 and @code{show architecture}.
12596 * Active Targets:: Active targets
12597 * Target Commands:: Commands for managing targets
12598 * Byte Order:: Choosing target byte order
12601 @node Active Targets
12602 @section Active Targets
12604 @cindex stacking targets
12605 @cindex active targets
12606 @cindex multiple targets
12608 There are three classes of targets: processes, core files, and
12609 executable files. @value{GDBN} can work concurrently on up to three
12610 active targets, one in each class. This allows you to (for example)
12611 start a process and inspect its activity without abandoning your work on
12614 For example, if you execute @samp{gdb a.out}, then the executable file
12615 @code{a.out} is the only active target. If you designate a core file as
12616 well---presumably from a prior run that crashed and coredumped---then
12617 @value{GDBN} has two active targets and uses them in tandem, looking
12618 first in the corefile target, then in the executable file, to satisfy
12619 requests for memory addresses. (Typically, these two classes of target
12620 are complementary, since core files contain only a program's
12621 read-write memory---variables and so on---plus machine status, while
12622 executable files contain only the program text and initialized data.)
12624 When you type @code{run}, your executable file becomes an active process
12625 target as well. When a process target is active, all @value{GDBN}
12626 commands requesting memory addresses refer to that target; addresses in
12627 an active core file or executable file target are obscured while the
12628 process target is active.
12630 Use the @code{core-file} and @code{exec-file} commands to select a new
12631 core file or executable target (@pxref{Files, ,Commands to Specify
12632 Files}). To specify as a target a process that is already running, use
12633 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12636 @node Target Commands
12637 @section Commands for Managing Targets
12640 @item target @var{type} @var{parameters}
12641 Connects the @value{GDBN} host environment to a target machine or
12642 process. A target is typically a protocol for talking to debugging
12643 facilities. You use the argument @var{type} to specify the type or
12644 protocol of the target machine.
12646 Further @var{parameters} are interpreted by the target protocol, but
12647 typically include things like device names or host names to connect
12648 with, process numbers, and baud rates.
12650 The @code{target} command does not repeat if you press @key{RET} again
12651 after executing the command.
12653 @kindex help target
12655 Displays the names of all targets available. To display targets
12656 currently selected, use either @code{info target} or @code{info files}
12657 (@pxref{Files, ,Commands to Specify Files}).
12659 @item help target @var{name}
12660 Describe a particular target, including any parameters necessary to
12663 @kindex set gnutarget
12664 @item set gnutarget @var{args}
12665 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12666 knows whether it is reading an @dfn{executable},
12667 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12668 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12669 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12672 @emph{Warning:} To specify a file format with @code{set gnutarget},
12673 you must know the actual BFD name.
12677 @xref{Files, , Commands to Specify Files}.
12679 @kindex show gnutarget
12680 @item show gnutarget
12681 Use the @code{show gnutarget} command to display what file format
12682 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12683 @value{GDBN} will determine the file format for each file automatically,
12684 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12687 @cindex common targets
12688 Here are some common targets (available, or not, depending on the GDB
12693 @item target exec @var{program}
12694 @cindex executable file target
12695 An executable file. @samp{target exec @var{program}} is the same as
12696 @samp{exec-file @var{program}}.
12698 @item target core @var{filename}
12699 @cindex core dump file target
12700 A core dump file. @samp{target core @var{filename}} is the same as
12701 @samp{core-file @var{filename}}.
12703 @item target remote @var{medium}
12704 @cindex remote target
12705 A remote system connected to @value{GDBN} via a serial line or network
12706 connection. This command tells @value{GDBN} to use its own remote
12707 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12709 For example, if you have a board connected to @file{/dev/ttya} on the
12710 machine running @value{GDBN}, you could say:
12713 target remote /dev/ttya
12716 @code{target remote} supports the @code{load} command. This is only
12717 useful if you have some other way of getting the stub to the target
12718 system, and you can put it somewhere in memory where it won't get
12719 clobbered by the download.
12722 @cindex built-in simulator target
12723 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12731 works; however, you cannot assume that a specific memory map, device
12732 drivers, or even basic I/O is available, although some simulators do
12733 provide these. For info about any processor-specific simulator details,
12734 see the appropriate section in @ref{Embedded Processors, ,Embedded
12739 Some configurations may include these targets as well:
12743 @item target nrom @var{dev}
12744 @cindex NetROM ROM emulator target
12745 NetROM ROM emulator. This target only supports downloading.
12749 Different targets are available on different configurations of @value{GDBN};
12750 your configuration may have more or fewer targets.
12752 Many remote targets require you to download the executable's code once
12753 you've successfully established a connection. You may wish to control
12754 various aspects of this process.
12759 @kindex set hash@r{, for remote monitors}
12760 @cindex hash mark while downloading
12761 This command controls whether a hash mark @samp{#} is displayed while
12762 downloading a file to the remote monitor. If on, a hash mark is
12763 displayed after each S-record is successfully downloaded to the
12767 @kindex show hash@r{, for remote monitors}
12768 Show the current status of displaying the hash mark.
12770 @item set debug monitor
12771 @kindex set debug monitor
12772 @cindex display remote monitor communications
12773 Enable or disable display of communications messages between
12774 @value{GDBN} and the remote monitor.
12776 @item show debug monitor
12777 @kindex show debug monitor
12778 Show the current status of displaying communications between
12779 @value{GDBN} and the remote monitor.
12784 @kindex load @var{filename}
12785 @item load @var{filename}
12787 Depending on what remote debugging facilities are configured into
12788 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12789 is meant to make @var{filename} (an executable) available for debugging
12790 on the remote system---by downloading, or dynamic linking, for example.
12791 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12792 the @code{add-symbol-file} command.
12794 If your @value{GDBN} does not have a @code{load} command, attempting to
12795 execute it gets the error message ``@code{You can't do that when your
12796 target is @dots{}}''
12798 The file is loaded at whatever address is specified in the executable.
12799 For some object file formats, you can specify the load address when you
12800 link the program; for other formats, like a.out, the object file format
12801 specifies a fixed address.
12802 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12804 Depending on the remote side capabilities, @value{GDBN} may be able to
12805 load programs into flash memory.
12807 @code{load} does not repeat if you press @key{RET} again after using it.
12811 @section Choosing Target Byte Order
12813 @cindex choosing target byte order
12814 @cindex target byte order
12816 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12817 offer the ability to run either big-endian or little-endian byte
12818 orders. Usually the executable or symbol will include a bit to
12819 designate the endian-ness, and you will not need to worry about
12820 which to use. However, you may still find it useful to adjust
12821 @value{GDBN}'s idea of processor endian-ness manually.
12825 @item set endian big
12826 Instruct @value{GDBN} to assume the target is big-endian.
12828 @item set endian little
12829 Instruct @value{GDBN} to assume the target is little-endian.
12831 @item set endian auto
12832 Instruct @value{GDBN} to use the byte order associated with the
12836 Display @value{GDBN}'s current idea of the target byte order.
12840 Note that these commands merely adjust interpretation of symbolic
12841 data on the host, and that they have absolutely no effect on the
12845 @node Remote Debugging
12846 @chapter Debugging Remote Programs
12847 @cindex remote debugging
12849 If you are trying to debug a program running on a machine that cannot run
12850 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12851 For example, you might use remote debugging on an operating system kernel,
12852 or on a small system which does not have a general purpose operating system
12853 powerful enough to run a full-featured debugger.
12855 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12856 to make this work with particular debugging targets. In addition,
12857 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12858 but not specific to any particular target system) which you can use if you
12859 write the remote stubs---the code that runs on the remote system to
12860 communicate with @value{GDBN}.
12862 Other remote targets may be available in your
12863 configuration of @value{GDBN}; use @code{help target} to list them.
12866 * Connecting:: Connecting to a remote target
12867 * File Transfer:: Sending files to a remote system
12868 * Server:: Using the gdbserver program
12869 * Remote Configuration:: Remote configuration
12870 * Remote Stub:: Implementing a remote stub
12874 @section Connecting to a Remote Target
12876 On the @value{GDBN} host machine, you will need an unstripped copy of
12877 your program, since @value{GDBN} needs symbol and debugging information.
12878 Start up @value{GDBN} as usual, using the name of the local copy of your
12879 program as the first argument.
12881 @cindex @code{target remote}
12882 @value{GDBN} can communicate with the target over a serial line, or
12883 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12884 each case, @value{GDBN} uses the same protocol for debugging your
12885 program; only the medium carrying the debugging packets varies. The
12886 @code{target remote} command establishes a connection to the target.
12887 Its arguments indicate which medium to use:
12891 @item target remote @var{serial-device}
12892 @cindex serial line, @code{target remote}
12893 Use @var{serial-device} to communicate with the target. For example,
12894 to use a serial line connected to the device named @file{/dev/ttyb}:
12897 target remote /dev/ttyb
12900 If you're using a serial line, you may want to give @value{GDBN} the
12901 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12902 (@pxref{Remote Configuration, set remotebaud}) before the
12903 @code{target} command.
12905 @item target remote @code{@var{host}:@var{port}}
12906 @itemx target remote @code{tcp:@var{host}:@var{port}}
12907 @cindex @acronym{TCP} port, @code{target remote}
12908 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12909 The @var{host} may be either a host name or a numeric @acronym{IP}
12910 address; @var{port} must be a decimal number. The @var{host} could be
12911 the target machine itself, if it is directly connected to the net, or
12912 it might be a terminal server which in turn has a serial line to the
12915 For example, to connect to port 2828 on a terminal server named
12919 target remote manyfarms:2828
12922 If your remote target is actually running on the same machine as your
12923 debugger session (e.g.@: a simulator for your target running on the
12924 same host), you can omit the hostname. For example, to connect to
12925 port 1234 on your local machine:
12928 target remote :1234
12932 Note that the colon is still required here.
12934 @item target remote @code{udp:@var{host}:@var{port}}
12935 @cindex @acronym{UDP} port, @code{target remote}
12936 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12937 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12940 target remote udp:manyfarms:2828
12943 When using a @acronym{UDP} connection for remote debugging, you should
12944 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12945 can silently drop packets on busy or unreliable networks, which will
12946 cause havoc with your debugging session.
12948 @item target remote | @var{command}
12949 @cindex pipe, @code{target remote} to
12950 Run @var{command} in the background and communicate with it using a
12951 pipe. The @var{command} is a shell command, to be parsed and expanded
12952 by the system's command shell, @code{/bin/sh}; it should expect remote
12953 protocol packets on its standard input, and send replies on its
12954 standard output. You could use this to run a stand-alone simulator
12955 that speaks the remote debugging protocol, to make net connections
12956 using programs like @code{ssh}, or for other similar tricks.
12958 If @var{command} closes its standard output (perhaps by exiting),
12959 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12960 program has already exited, this will have no effect.)
12964 Once the connection has been established, you can use all the usual
12965 commands to examine and change data. The remote program is already
12966 running; you can use @kbd{step} and @kbd{continue}, and you do not
12967 need to use @kbd{run}.
12969 @cindex interrupting remote programs
12970 @cindex remote programs, interrupting
12971 Whenever @value{GDBN} is waiting for the remote program, if you type the
12972 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12973 program. This may or may not succeed, depending in part on the hardware
12974 and the serial drivers the remote system uses. If you type the
12975 interrupt character once again, @value{GDBN} displays this prompt:
12978 Interrupted while waiting for the program.
12979 Give up (and stop debugging it)? (y or n)
12982 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12983 (If you decide you want to try again later, you can use @samp{target
12984 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12985 goes back to waiting.
12988 @kindex detach (remote)
12990 When you have finished debugging the remote program, you can use the
12991 @code{detach} command to release it from @value{GDBN} control.
12992 Detaching from the target normally resumes its execution, but the results
12993 will depend on your particular remote stub. After the @code{detach}
12994 command, @value{GDBN} is free to connect to another target.
12998 The @code{disconnect} command behaves like @code{detach}, except that
12999 the target is generally not resumed. It will wait for @value{GDBN}
13000 (this instance or another one) to connect and continue debugging. After
13001 the @code{disconnect} command, @value{GDBN} is again free to connect to
13004 @cindex send command to remote monitor
13005 @cindex extend @value{GDBN} for remote targets
13006 @cindex add new commands for external monitor
13008 @item monitor @var{cmd}
13009 This command allows you to send arbitrary commands directly to the
13010 remote monitor. Since @value{GDBN} doesn't care about the commands it
13011 sends like this, this command is the way to extend @value{GDBN}---you
13012 can add new commands that only the external monitor will understand
13016 @node File Transfer
13017 @section Sending files to a remote system
13018 @cindex remote target, file transfer
13019 @cindex file transfer
13020 @cindex sending files to remote systems
13022 Some remote targets offer the ability to transfer files over the same
13023 connection used to communicate with @value{GDBN}. This is convenient
13024 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13025 running @code{gdbserver} over a network interface. For other targets,
13026 e.g.@: embedded devices with only a single serial port, this may be
13027 the only way to upload or download files.
13029 Not all remote targets support these commands.
13033 @item remote put @var{hostfile} @var{targetfile}
13034 Copy file @var{hostfile} from the host system (the machine running
13035 @value{GDBN}) to @var{targetfile} on the target system.
13038 @item remote get @var{targetfile} @var{hostfile}
13039 Copy file @var{targetfile} from the target system to @var{hostfile}
13040 on the host system.
13042 @kindex remote delete
13043 @item remote delete @var{targetfile}
13044 Delete @var{targetfile} from the target system.
13049 @section Using the @code{gdbserver} Program
13052 @cindex remote connection without stubs
13053 @code{gdbserver} is a control program for Unix-like systems, which
13054 allows you to connect your program with a remote @value{GDBN} via
13055 @code{target remote}---but without linking in the usual debugging stub.
13057 @code{gdbserver} is not a complete replacement for the debugging stubs,
13058 because it requires essentially the same operating-system facilities
13059 that @value{GDBN} itself does. In fact, a system that can run
13060 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13061 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13062 because it is a much smaller program than @value{GDBN} itself. It is
13063 also easier to port than all of @value{GDBN}, so you may be able to get
13064 started more quickly on a new system by using @code{gdbserver}.
13065 Finally, if you develop code for real-time systems, you may find that
13066 the tradeoffs involved in real-time operation make it more convenient to
13067 do as much development work as possible on another system, for example
13068 by cross-compiling. You can use @code{gdbserver} to make a similar
13069 choice for debugging.
13071 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13072 or a TCP connection, using the standard @value{GDBN} remote serial
13076 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13077 Do not run @code{gdbserver} connected to any public network; a
13078 @value{GDBN} connection to @code{gdbserver} provides access to the
13079 target system with the same privileges as the user running
13083 @subsection Running @code{gdbserver}
13084 @cindex arguments, to @code{gdbserver}
13086 Run @code{gdbserver} on the target system. You need a copy of the
13087 program you want to debug, including any libraries it requires.
13088 @code{gdbserver} does not need your program's symbol table, so you can
13089 strip the program if necessary to save space. @value{GDBN} on the host
13090 system does all the symbol handling.
13092 To use the server, you must tell it how to communicate with @value{GDBN};
13093 the name of your program; and the arguments for your program. The usual
13097 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13100 @var{comm} is either a device name (to use a serial line) or a TCP
13101 hostname and portnumber. For example, to debug Emacs with the argument
13102 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13106 target> gdbserver /dev/com1 emacs foo.txt
13109 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13112 To use a TCP connection instead of a serial line:
13115 target> gdbserver host:2345 emacs foo.txt
13118 The only difference from the previous example is the first argument,
13119 specifying that you are communicating with the host @value{GDBN} via
13120 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13121 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13122 (Currently, the @samp{host} part is ignored.) You can choose any number
13123 you want for the port number as long as it does not conflict with any
13124 TCP ports already in use on the target system (for example, @code{23} is
13125 reserved for @code{telnet}).@footnote{If you choose a port number that
13126 conflicts with another service, @code{gdbserver} prints an error message
13127 and exits.} You must use the same port number with the host @value{GDBN}
13128 @code{target remote} command.
13130 @subsubsection Attaching to a Running Program
13132 On some targets, @code{gdbserver} can also attach to running programs.
13133 This is accomplished via the @code{--attach} argument. The syntax is:
13136 target> gdbserver --attach @var{comm} @var{pid}
13139 @var{pid} is the process ID of a currently running process. It isn't necessary
13140 to point @code{gdbserver} at a binary for the running process.
13143 @cindex attach to a program by name
13144 You can debug processes by name instead of process ID if your target has the
13145 @code{pidof} utility:
13148 target> gdbserver --attach @var{comm} `pidof @var{program}`
13151 In case more than one copy of @var{program} is running, or @var{program}
13152 has multiple threads, most versions of @code{pidof} support the
13153 @code{-s} option to only return the first process ID.
13155 @subsubsection Multi-Process Mode for @code{gdbserver}
13156 @cindex gdbserver, multiple processes
13157 @cindex multiple processes with gdbserver
13159 When you connect to @code{gdbserver} using @code{target remote},
13160 @code{gdbserver} debugs the specified program only once. When the
13161 program exits, or you detach from it, @value{GDBN} closes the connection
13162 and @code{gdbserver} exits.
13164 If you connect using @kbd{target extended-remote}, @code{gdbserver}
13165 enters multi-process mode. When the debugged program exits, or you
13166 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
13167 though no program is running. The @code{run} and @code{attach}
13168 commands instruct @code{gdbserver} to run or attach to a new program.
13169 The @code{run} command uses @code{set remote exec-file} (@pxref{set
13170 remote exec-file}) to select the program to run. Command line
13171 arguments are supported, except for wildcard expansion and I/O
13172 redirection (@pxref{Arguments}).
13174 To start @code{gdbserver} without supplying an initial command to run
13175 or process ID to attach, use the @option{--multi} command line option.
13176 Then you can connect using @kbd{target extended-remote} and start
13177 the program you want to debug.
13179 @code{gdbserver} does not automatically exit in multi-process mode.
13180 You can terminate it by using @code{monitor exit}
13181 (@pxref{Monitor Commands for gdbserver}).
13183 @subsubsection Other Command-Line Arguments for @code{gdbserver}
13185 You can include @option{--debug} on the @code{gdbserver} command line.
13186 @code{gdbserver} will display extra status information about the debugging
13187 process. This option is intended for @code{gdbserver} development and
13188 for bug reports to the developers.
13190 The @option{--wrapper} option specifies a wrapper to launch programs
13191 for debugging. The option should be followed by the name of the
13192 wrapper, then any command-line arguments to pass to the wrapper, then
13193 @kbd{--} indicating the end of the wrapper arguments.
13195 @code{gdbserver} runs the specified wrapper program with a combined
13196 command line including the wrapper arguments, then the name of the
13197 program to debug, then any arguments to the program. The wrapper
13198 runs until it executes your program, and then @value{GDBN} gains control.
13200 You can use any program that eventually calls @code{execve} with
13201 its arguments as a wrapper. Several standard Unix utilities do
13202 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
13203 with @code{exec "$@@"} will also work.
13205 For example, you can use @code{env} to pass an environment variable to
13206 the debugged program, without setting the variable in @code{gdbserver}'s
13210 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
13213 @subsection Connecting to @code{gdbserver}
13215 Run @value{GDBN} on the host system.
13217 First make sure you have the necessary symbol files. Load symbols for
13218 your application using the @code{file} command before you connect. Use
13219 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
13220 was compiled with the correct sysroot using @code{--with-sysroot}).
13222 The symbol file and target libraries must exactly match the executable
13223 and libraries on the target, with one exception: the files on the host
13224 system should not be stripped, even if the files on the target system
13225 are. Mismatched or missing files will lead to confusing results
13226 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
13227 files may also prevent @code{gdbserver} from debugging multi-threaded
13230 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
13231 For TCP connections, you must start up @code{gdbserver} prior to using
13232 the @code{target remote} command. Otherwise you may get an error whose
13233 text depends on the host system, but which usually looks something like
13234 @samp{Connection refused}. Don't use the @code{load}
13235 command in @value{GDBN} when using @code{gdbserver}, since the program is
13236 already on the target.
13238 @subsection Monitor Commands for @code{gdbserver}
13239 @cindex monitor commands, for @code{gdbserver}
13240 @anchor{Monitor Commands for gdbserver}
13242 During a @value{GDBN} session using @code{gdbserver}, you can use the
13243 @code{monitor} command to send special requests to @code{gdbserver}.
13244 Here are the available commands.
13248 List the available monitor commands.
13250 @item monitor set debug 0
13251 @itemx monitor set debug 1
13252 Disable or enable general debugging messages.
13254 @item monitor set remote-debug 0
13255 @itemx monitor set remote-debug 1
13256 Disable or enable specific debugging messages associated with the remote
13257 protocol (@pxref{Remote Protocol}).
13260 Tell gdbserver to exit immediately. This command should be followed by
13261 @code{disconnect} to close the debugging session. @code{gdbserver} will
13262 detach from any attached processes and kill any processes it created.
13263 Use @code{monitor exit} to terminate @code{gdbserver} at the end
13264 of a multi-process mode debug session.
13268 @node Remote Configuration
13269 @section Remote Configuration
13272 @kindex show remote
13273 This section documents the configuration options available when
13274 debugging remote programs. For the options related to the File I/O
13275 extensions of the remote protocol, see @ref{system,
13276 system-call-allowed}.
13279 @item set remoteaddresssize @var{bits}
13280 @cindex address size for remote targets
13281 @cindex bits in remote address
13282 Set the maximum size of address in a memory packet to the specified
13283 number of bits. @value{GDBN} will mask off the address bits above
13284 that number, when it passes addresses to the remote target. The
13285 default value is the number of bits in the target's address.
13287 @item show remoteaddresssize
13288 Show the current value of remote address size in bits.
13290 @item set remotebaud @var{n}
13291 @cindex baud rate for remote targets
13292 Set the baud rate for the remote serial I/O to @var{n} baud. The
13293 value is used to set the speed of the serial port used for debugging
13296 @item show remotebaud
13297 Show the current speed of the remote connection.
13299 @item set remotebreak
13300 @cindex interrupt remote programs
13301 @cindex BREAK signal instead of Ctrl-C
13302 @anchor{set remotebreak}
13303 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13304 when you type @kbd{Ctrl-c} to interrupt the program running
13305 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13306 character instead. The default is off, since most remote systems
13307 expect to see @samp{Ctrl-C} as the interrupt signal.
13309 @item show remotebreak
13310 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13311 interrupt the remote program.
13313 @item set remoteflow on
13314 @itemx set remoteflow off
13315 @kindex set remoteflow
13316 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13317 on the serial port used to communicate to the remote target.
13319 @item show remoteflow
13320 @kindex show remoteflow
13321 Show the current setting of hardware flow control.
13323 @item set remotelogbase @var{base}
13324 Set the base (a.k.a.@: radix) of logging serial protocol
13325 communications to @var{base}. Supported values of @var{base} are:
13326 @code{ascii}, @code{octal}, and @code{hex}. The default is
13329 @item show remotelogbase
13330 Show the current setting of the radix for logging remote serial
13333 @item set remotelogfile @var{file}
13334 @cindex record serial communications on file
13335 Record remote serial communications on the named @var{file}. The
13336 default is not to record at all.
13338 @item show remotelogfile.
13339 Show the current setting of the file name on which to record the
13340 serial communications.
13342 @item set remotetimeout @var{num}
13343 @cindex timeout for serial communications
13344 @cindex remote timeout
13345 Set the timeout limit to wait for the remote target to respond to
13346 @var{num} seconds. The default is 2 seconds.
13348 @item show remotetimeout
13349 Show the current number of seconds to wait for the remote target
13352 @cindex limit hardware breakpoints and watchpoints
13353 @cindex remote target, limit break- and watchpoints
13354 @anchor{set remote hardware-watchpoint-limit}
13355 @anchor{set remote hardware-breakpoint-limit}
13356 @item set remote hardware-watchpoint-limit @var{limit}
13357 @itemx set remote hardware-breakpoint-limit @var{limit}
13358 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13359 watchpoints. A limit of -1, the default, is treated as unlimited.
13361 @item set remote exec-file @var{filename}
13362 @itemx show remote exec-file
13363 @anchor{set remote exec-file}
13364 @cindex executable file, for remote target
13365 Select the file used for @code{run} with @code{target
13366 extended-remote}. This should be set to a filename valid on the
13367 target system. If it is not set, the target will use a default
13368 filename (e.g.@: the last program run).
13371 @cindex remote packets, enabling and disabling
13372 The @value{GDBN} remote protocol autodetects the packets supported by
13373 your debugging stub. If you need to override the autodetection, you
13374 can use these commands to enable or disable individual packets. Each
13375 packet can be set to @samp{on} (the remote target supports this
13376 packet), @samp{off} (the remote target does not support this packet),
13377 or @samp{auto} (detect remote target support for this packet). They
13378 all default to @samp{auto}. For more information about each packet,
13379 see @ref{Remote Protocol}.
13381 During normal use, you should not have to use any of these commands.
13382 If you do, that may be a bug in your remote debugging stub, or a bug
13383 in @value{GDBN}. You may want to report the problem to the
13384 @value{GDBN} developers.
13386 For each packet @var{name}, the command to enable or disable the
13387 packet is @code{set remote @var{name}-packet}. The available settings
13390 @multitable @columnfractions 0.28 0.32 0.25
13393 @tab Related Features
13395 @item @code{fetch-register}
13397 @tab @code{info registers}
13399 @item @code{set-register}
13403 @item @code{binary-download}
13405 @tab @code{load}, @code{set}
13407 @item @code{read-aux-vector}
13408 @tab @code{qXfer:auxv:read}
13409 @tab @code{info auxv}
13411 @item @code{symbol-lookup}
13412 @tab @code{qSymbol}
13413 @tab Detecting multiple threads
13415 @item @code{attach}
13416 @tab @code{vAttach}
13419 @item @code{verbose-resume}
13421 @tab Stepping or resuming multiple threads
13427 @item @code{software-breakpoint}
13431 @item @code{hardware-breakpoint}
13435 @item @code{write-watchpoint}
13439 @item @code{read-watchpoint}
13443 @item @code{access-watchpoint}
13447 @item @code{target-features}
13448 @tab @code{qXfer:features:read}
13449 @tab @code{set architecture}
13451 @item @code{library-info}
13452 @tab @code{qXfer:libraries:read}
13453 @tab @code{info sharedlibrary}
13455 @item @code{memory-map}
13456 @tab @code{qXfer:memory-map:read}
13457 @tab @code{info mem}
13459 @item @code{read-spu-object}
13460 @tab @code{qXfer:spu:read}
13461 @tab @code{info spu}
13463 @item @code{write-spu-object}
13464 @tab @code{qXfer:spu:write}
13465 @tab @code{info spu}
13467 @item @code{get-thread-local-@*storage-address}
13468 @tab @code{qGetTLSAddr}
13469 @tab Displaying @code{__thread} variables
13471 @item @code{supported-packets}
13472 @tab @code{qSupported}
13473 @tab Remote communications parameters
13475 @item @code{pass-signals}
13476 @tab @code{QPassSignals}
13477 @tab @code{handle @var{signal}}
13479 @item @code{hostio-close-packet}
13480 @tab @code{vFile:close}
13481 @tab @code{remote get}, @code{remote put}
13483 @item @code{hostio-open-packet}
13484 @tab @code{vFile:open}
13485 @tab @code{remote get}, @code{remote put}
13487 @item @code{hostio-pread-packet}
13488 @tab @code{vFile:pread}
13489 @tab @code{remote get}, @code{remote put}
13491 @item @code{hostio-pwrite-packet}
13492 @tab @code{vFile:pwrite}
13493 @tab @code{remote get}, @code{remote put}
13495 @item @code{hostio-unlink-packet}
13496 @tab @code{vFile:unlink}
13497 @tab @code{remote delete}
13501 @section Implementing a Remote Stub
13503 @cindex debugging stub, example
13504 @cindex remote stub, example
13505 @cindex stub example, remote debugging
13506 The stub files provided with @value{GDBN} implement the target side of the
13507 communication protocol, and the @value{GDBN} side is implemented in the
13508 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13509 these subroutines to communicate, and ignore the details. (If you're
13510 implementing your own stub file, you can still ignore the details: start
13511 with one of the existing stub files. @file{sparc-stub.c} is the best
13512 organized, and therefore the easiest to read.)
13514 @cindex remote serial debugging, overview
13515 To debug a program running on another machine (the debugging
13516 @dfn{target} machine), you must first arrange for all the usual
13517 prerequisites for the program to run by itself. For example, for a C
13522 A startup routine to set up the C runtime environment; these usually
13523 have a name like @file{crt0}. The startup routine may be supplied by
13524 your hardware supplier, or you may have to write your own.
13527 A C subroutine library to support your program's
13528 subroutine calls, notably managing input and output.
13531 A way of getting your program to the other machine---for example, a
13532 download program. These are often supplied by the hardware
13533 manufacturer, but you may have to write your own from hardware
13537 The next step is to arrange for your program to use a serial port to
13538 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13539 machine). In general terms, the scheme looks like this:
13543 @value{GDBN} already understands how to use this protocol; when everything
13544 else is set up, you can simply use the @samp{target remote} command
13545 (@pxref{Targets,,Specifying a Debugging Target}).
13547 @item On the target,
13548 you must link with your program a few special-purpose subroutines that
13549 implement the @value{GDBN} remote serial protocol. The file containing these
13550 subroutines is called a @dfn{debugging stub}.
13552 On certain remote targets, you can use an auxiliary program
13553 @code{gdbserver} instead of linking a stub into your program.
13554 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13557 The debugging stub is specific to the architecture of the remote
13558 machine; for example, use @file{sparc-stub.c} to debug programs on
13561 @cindex remote serial stub list
13562 These working remote stubs are distributed with @value{GDBN}:
13567 @cindex @file{i386-stub.c}
13570 For Intel 386 and compatible architectures.
13573 @cindex @file{m68k-stub.c}
13574 @cindex Motorola 680x0
13576 For Motorola 680x0 architectures.
13579 @cindex @file{sh-stub.c}
13582 For Renesas SH architectures.
13585 @cindex @file{sparc-stub.c}
13587 For @sc{sparc} architectures.
13589 @item sparcl-stub.c
13590 @cindex @file{sparcl-stub.c}
13593 For Fujitsu @sc{sparclite} architectures.
13597 The @file{README} file in the @value{GDBN} distribution may list other
13598 recently added stubs.
13601 * Stub Contents:: What the stub can do for you
13602 * Bootstrapping:: What you must do for the stub
13603 * Debug Session:: Putting it all together
13606 @node Stub Contents
13607 @subsection What the Stub Can Do for You
13609 @cindex remote serial stub
13610 The debugging stub for your architecture supplies these three
13614 @item set_debug_traps
13615 @findex set_debug_traps
13616 @cindex remote serial stub, initialization
13617 This routine arranges for @code{handle_exception} to run when your
13618 program stops. You must call this subroutine explicitly near the
13619 beginning of your program.
13621 @item handle_exception
13622 @findex handle_exception
13623 @cindex remote serial stub, main routine
13624 This is the central workhorse, but your program never calls it
13625 explicitly---the setup code arranges for @code{handle_exception} to
13626 run when a trap is triggered.
13628 @code{handle_exception} takes control when your program stops during
13629 execution (for example, on a breakpoint), and mediates communications
13630 with @value{GDBN} on the host machine. This is where the communications
13631 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13632 representative on the target machine. It begins by sending summary
13633 information on the state of your program, then continues to execute,
13634 retrieving and transmitting any information @value{GDBN} needs, until you
13635 execute a @value{GDBN} command that makes your program resume; at that point,
13636 @code{handle_exception} returns control to your own code on the target
13640 @cindex @code{breakpoint} subroutine, remote
13641 Use this auxiliary subroutine to make your program contain a
13642 breakpoint. Depending on the particular situation, this may be the only
13643 way for @value{GDBN} to get control. For instance, if your target
13644 machine has some sort of interrupt button, you won't need to call this;
13645 pressing the interrupt button transfers control to
13646 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13647 simply receiving characters on the serial port may also trigger a trap;
13648 again, in that situation, you don't need to call @code{breakpoint} from
13649 your own program---simply running @samp{target remote} from the host
13650 @value{GDBN} session gets control.
13652 Call @code{breakpoint} if none of these is true, or if you simply want
13653 to make certain your program stops at a predetermined point for the
13654 start of your debugging session.
13657 @node Bootstrapping
13658 @subsection What You Must Do for the Stub
13660 @cindex remote stub, support routines
13661 The debugging stubs that come with @value{GDBN} are set up for a particular
13662 chip architecture, but they have no information about the rest of your
13663 debugging target machine.
13665 First of all you need to tell the stub how to communicate with the
13669 @item int getDebugChar()
13670 @findex getDebugChar
13671 Write this subroutine to read a single character from the serial port.
13672 It may be identical to @code{getchar} for your target system; a
13673 different name is used to allow you to distinguish the two if you wish.
13675 @item void putDebugChar(int)
13676 @findex putDebugChar
13677 Write this subroutine to write a single character to the serial port.
13678 It may be identical to @code{putchar} for your target system; a
13679 different name is used to allow you to distinguish the two if you wish.
13682 @cindex control C, and remote debugging
13683 @cindex interrupting remote targets
13684 If you want @value{GDBN} to be able to stop your program while it is
13685 running, you need to use an interrupt-driven serial driver, and arrange
13686 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13687 character). That is the character which @value{GDBN} uses to tell the
13688 remote system to stop.
13690 Getting the debugging target to return the proper status to @value{GDBN}
13691 probably requires changes to the standard stub; one quick and dirty way
13692 is to just execute a breakpoint instruction (the ``dirty'' part is that
13693 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13695 Other routines you need to supply are:
13698 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13699 @findex exceptionHandler
13700 Write this function to install @var{exception_address} in the exception
13701 handling tables. You need to do this because the stub does not have any
13702 way of knowing what the exception handling tables on your target system
13703 are like (for example, the processor's table might be in @sc{rom},
13704 containing entries which point to a table in @sc{ram}).
13705 @var{exception_number} is the exception number which should be changed;
13706 its meaning is architecture-dependent (for example, different numbers
13707 might represent divide by zero, misaligned access, etc). When this
13708 exception occurs, control should be transferred directly to
13709 @var{exception_address}, and the processor state (stack, registers,
13710 and so on) should be just as it is when a processor exception occurs. So if
13711 you want to use a jump instruction to reach @var{exception_address}, it
13712 should be a simple jump, not a jump to subroutine.
13714 For the 386, @var{exception_address} should be installed as an interrupt
13715 gate so that interrupts are masked while the handler runs. The gate
13716 should be at privilege level 0 (the most privileged level). The
13717 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13718 help from @code{exceptionHandler}.
13720 @item void flush_i_cache()
13721 @findex flush_i_cache
13722 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13723 instruction cache, if any, on your target machine. If there is no
13724 instruction cache, this subroutine may be a no-op.
13726 On target machines that have instruction caches, @value{GDBN} requires this
13727 function to make certain that the state of your program is stable.
13731 You must also make sure this library routine is available:
13734 @item void *memset(void *, int, int)
13736 This is the standard library function @code{memset} that sets an area of
13737 memory to a known value. If you have one of the free versions of
13738 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13739 either obtain it from your hardware manufacturer, or write your own.
13742 If you do not use the GNU C compiler, you may need other standard
13743 library subroutines as well; this varies from one stub to another,
13744 but in general the stubs are likely to use any of the common library
13745 subroutines which @code{@value{NGCC}} generates as inline code.
13748 @node Debug Session
13749 @subsection Putting it All Together
13751 @cindex remote serial debugging summary
13752 In summary, when your program is ready to debug, you must follow these
13757 Make sure you have defined the supporting low-level routines
13758 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13760 @code{getDebugChar}, @code{putDebugChar},
13761 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13765 Insert these lines near the top of your program:
13773 For the 680x0 stub only, you need to provide a variable called
13774 @code{exceptionHook}. Normally you just use:
13777 void (*exceptionHook)() = 0;
13781 but if before calling @code{set_debug_traps}, you set it to point to a
13782 function in your program, that function is called when
13783 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13784 error). The function indicated by @code{exceptionHook} is called with
13785 one parameter: an @code{int} which is the exception number.
13788 Compile and link together: your program, the @value{GDBN} debugging stub for
13789 your target architecture, and the supporting subroutines.
13792 Make sure you have a serial connection between your target machine and
13793 the @value{GDBN} host, and identify the serial port on the host.
13796 @c The "remote" target now provides a `load' command, so we should
13797 @c document that. FIXME.
13798 Download your program to your target machine (or get it there by
13799 whatever means the manufacturer provides), and start it.
13802 Start @value{GDBN} on the host, and connect to the target
13803 (@pxref{Connecting,,Connecting to a Remote Target}).
13807 @node Configurations
13808 @chapter Configuration-Specific Information
13810 While nearly all @value{GDBN} commands are available for all native and
13811 cross versions of the debugger, there are some exceptions. This chapter
13812 describes things that are only available in certain configurations.
13814 There are three major categories of configurations: native
13815 configurations, where the host and target are the same, embedded
13816 operating system configurations, which are usually the same for several
13817 different processor architectures, and bare embedded processors, which
13818 are quite different from each other.
13823 * Embedded Processors::
13830 This section describes details specific to particular native
13835 * BSD libkvm Interface:: Debugging BSD kernel memory images
13836 * SVR4 Process Information:: SVR4 process information
13837 * DJGPP Native:: Features specific to the DJGPP port
13838 * Cygwin Native:: Features specific to the Cygwin port
13839 * Hurd Native:: Features specific to @sc{gnu} Hurd
13840 * Neutrino:: Features specific to QNX Neutrino
13846 On HP-UX systems, if you refer to a function or variable name that
13847 begins with a dollar sign, @value{GDBN} searches for a user or system
13848 name first, before it searches for a convenience variable.
13851 @node BSD libkvm Interface
13852 @subsection BSD libkvm Interface
13855 @cindex kernel memory image
13856 @cindex kernel crash dump
13858 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13859 interface that provides a uniform interface for accessing kernel virtual
13860 memory images, including live systems and crash dumps. @value{GDBN}
13861 uses this interface to allow you to debug live kernels and kernel crash
13862 dumps on many native BSD configurations. This is implemented as a
13863 special @code{kvm} debugging target. For debugging a live system, load
13864 the currently running kernel into @value{GDBN} and connect to the
13868 (@value{GDBP}) @b{target kvm}
13871 For debugging crash dumps, provide the file name of the crash dump as an
13875 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13878 Once connected to the @code{kvm} target, the following commands are
13884 Set current context from the @dfn{Process Control Block} (PCB) address.
13887 Set current context from proc address. This command isn't available on
13888 modern FreeBSD systems.
13891 @node SVR4 Process Information
13892 @subsection SVR4 Process Information
13894 @cindex examine process image
13895 @cindex process info via @file{/proc}
13897 Many versions of SVR4 and compatible systems provide a facility called
13898 @samp{/proc} that can be used to examine the image of a running
13899 process using file-system subroutines. If @value{GDBN} is configured
13900 for an operating system with this facility, the command @code{info
13901 proc} is available to report information about the process running
13902 your program, or about any process running on your system. @code{info
13903 proc} works only on SVR4 systems that include the @code{procfs} code.
13904 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13905 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13911 @itemx info proc @var{process-id}
13912 Summarize available information about any running process. If a
13913 process ID is specified by @var{process-id}, display information about
13914 that process; otherwise display information about the program being
13915 debugged. The summary includes the debugged process ID, the command
13916 line used to invoke it, its current working directory, and its
13917 executable file's absolute file name.
13919 On some systems, @var{process-id} can be of the form
13920 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13921 within a process. If the optional @var{pid} part is missing, it means
13922 a thread from the process being debugged (the leading @samp{/} still
13923 needs to be present, or else @value{GDBN} will interpret the number as
13924 a process ID rather than a thread ID).
13926 @item info proc mappings
13927 @cindex memory address space mappings
13928 Report the memory address space ranges accessible in the program, with
13929 information on whether the process has read, write, or execute access
13930 rights to each range. On @sc{gnu}/Linux systems, each memory range
13931 includes the object file which is mapped to that range, instead of the
13932 memory access rights to that range.
13934 @item info proc stat
13935 @itemx info proc status
13936 @cindex process detailed status information
13937 These subcommands are specific to @sc{gnu}/Linux systems. They show
13938 the process-related information, including the user ID and group ID;
13939 how many threads are there in the process; its virtual memory usage;
13940 the signals that are pending, blocked, and ignored; its TTY; its
13941 consumption of system and user time; its stack size; its @samp{nice}
13942 value; etc. For more information, see the @samp{proc} man page
13943 (type @kbd{man 5 proc} from your shell prompt).
13945 @item info proc all
13946 Show all the information about the process described under all of the
13947 above @code{info proc} subcommands.
13950 @comment These sub-options of 'info proc' were not included when
13951 @comment procfs.c was re-written. Keep their descriptions around
13952 @comment against the day when someone finds the time to put them back in.
13953 @kindex info proc times
13954 @item info proc times
13955 Starting time, user CPU time, and system CPU time for your program and
13958 @kindex info proc id
13960 Report on the process IDs related to your program: its own process ID,
13961 the ID of its parent, the process group ID, and the session ID.
13964 @item set procfs-trace
13965 @kindex set procfs-trace
13966 @cindex @code{procfs} API calls
13967 This command enables and disables tracing of @code{procfs} API calls.
13969 @item show procfs-trace
13970 @kindex show procfs-trace
13971 Show the current state of @code{procfs} API call tracing.
13973 @item set procfs-file @var{file}
13974 @kindex set procfs-file
13975 Tell @value{GDBN} to write @code{procfs} API trace to the named
13976 @var{file}. @value{GDBN} appends the trace info to the previous
13977 contents of the file. The default is to display the trace on the
13980 @item show procfs-file
13981 @kindex show procfs-file
13982 Show the file to which @code{procfs} API trace is written.
13984 @item proc-trace-entry
13985 @itemx proc-trace-exit
13986 @itemx proc-untrace-entry
13987 @itemx proc-untrace-exit
13988 @kindex proc-trace-entry
13989 @kindex proc-trace-exit
13990 @kindex proc-untrace-entry
13991 @kindex proc-untrace-exit
13992 These commands enable and disable tracing of entries into and exits
13993 from the @code{syscall} interface.
13996 @kindex info pidlist
13997 @cindex process list, QNX Neutrino
13998 For QNX Neutrino only, this command displays the list of all the
13999 processes and all the threads within each process.
14002 @kindex info meminfo
14003 @cindex mapinfo list, QNX Neutrino
14004 For QNX Neutrino only, this command displays the list of all mapinfos.
14008 @subsection Features for Debugging @sc{djgpp} Programs
14009 @cindex @sc{djgpp} debugging
14010 @cindex native @sc{djgpp} debugging
14011 @cindex MS-DOS-specific commands
14014 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14015 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14016 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14017 top of real-mode DOS systems and their emulations.
14019 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14020 defines a few commands specific to the @sc{djgpp} port. This
14021 subsection describes those commands.
14026 This is a prefix of @sc{djgpp}-specific commands which print
14027 information about the target system and important OS structures.
14030 @cindex MS-DOS system info
14031 @cindex free memory information (MS-DOS)
14032 @item info dos sysinfo
14033 This command displays assorted information about the underlying
14034 platform: the CPU type and features, the OS version and flavor, the
14035 DPMI version, and the available conventional and DPMI memory.
14040 @cindex segment descriptor tables
14041 @cindex descriptor tables display
14043 @itemx info dos ldt
14044 @itemx info dos idt
14045 These 3 commands display entries from, respectively, Global, Local,
14046 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14047 tables are data structures which store a descriptor for each segment
14048 that is currently in use. The segment's selector is an index into a
14049 descriptor table; the table entry for that index holds the
14050 descriptor's base address and limit, and its attributes and access
14053 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14054 segment (used for both data and the stack), and a DOS segment (which
14055 allows access to DOS/BIOS data structures and absolute addresses in
14056 conventional memory). However, the DPMI host will usually define
14057 additional segments in order to support the DPMI environment.
14059 @cindex garbled pointers
14060 These commands allow to display entries from the descriptor tables.
14061 Without an argument, all entries from the specified table are
14062 displayed. An argument, which should be an integer expression, means
14063 display a single entry whose index is given by the argument. For
14064 example, here's a convenient way to display information about the
14065 debugged program's data segment:
14068 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14069 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14073 This comes in handy when you want to see whether a pointer is outside
14074 the data segment's limit (i.e.@: @dfn{garbled}).
14076 @cindex page tables display (MS-DOS)
14078 @itemx info dos pte
14079 These two commands display entries from, respectively, the Page
14080 Directory and the Page Tables. Page Directories and Page Tables are
14081 data structures which control how virtual memory addresses are mapped
14082 into physical addresses. A Page Table includes an entry for every
14083 page of memory that is mapped into the program's address space; there
14084 may be several Page Tables, each one holding up to 4096 entries. A
14085 Page Directory has up to 4096 entries, one each for every Page Table
14086 that is currently in use.
14088 Without an argument, @kbd{info dos pde} displays the entire Page
14089 Directory, and @kbd{info dos pte} displays all the entries in all of
14090 the Page Tables. An argument, an integer expression, given to the
14091 @kbd{info dos pde} command means display only that entry from the Page
14092 Directory table. An argument given to the @kbd{info dos pte} command
14093 means display entries from a single Page Table, the one pointed to by
14094 the specified entry in the Page Directory.
14096 @cindex direct memory access (DMA) on MS-DOS
14097 These commands are useful when your program uses @dfn{DMA} (Direct
14098 Memory Access), which needs physical addresses to program the DMA
14101 These commands are supported only with some DPMI servers.
14103 @cindex physical address from linear address
14104 @item info dos address-pte @var{addr}
14105 This command displays the Page Table entry for a specified linear
14106 address. The argument @var{addr} is a linear address which should
14107 already have the appropriate segment's base address added to it,
14108 because this command accepts addresses which may belong to @emph{any}
14109 segment. For example, here's how to display the Page Table entry for
14110 the page where a variable @code{i} is stored:
14113 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14114 @exdent @code{Page Table entry for address 0x11a00d30:}
14115 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14119 This says that @code{i} is stored at offset @code{0xd30} from the page
14120 whose physical base address is @code{0x02698000}, and shows all the
14121 attributes of that page.
14123 Note that you must cast the addresses of variables to a @code{char *},
14124 since otherwise the value of @code{__djgpp_base_address}, the base
14125 address of all variables and functions in a @sc{djgpp} program, will
14126 be added using the rules of C pointer arithmetics: if @code{i} is
14127 declared an @code{int}, @value{GDBN} will add 4 times the value of
14128 @code{__djgpp_base_address} to the address of @code{i}.
14130 Here's another example, it displays the Page Table entry for the
14134 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14135 @exdent @code{Page Table entry for address 0x29110:}
14136 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14140 (The @code{+ 3} offset is because the transfer buffer's address is the
14141 3rd member of the @code{_go32_info_block} structure.) The output
14142 clearly shows that this DPMI server maps the addresses in conventional
14143 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
14144 linear (@code{0x29110}) addresses are identical.
14146 This command is supported only with some DPMI servers.
14149 @cindex DOS serial data link, remote debugging
14150 In addition to native debugging, the DJGPP port supports remote
14151 debugging via a serial data link. The following commands are specific
14152 to remote serial debugging in the DJGPP port of @value{GDBN}.
14155 @kindex set com1base
14156 @kindex set com1irq
14157 @kindex set com2base
14158 @kindex set com2irq
14159 @kindex set com3base
14160 @kindex set com3irq
14161 @kindex set com4base
14162 @kindex set com4irq
14163 @item set com1base @var{addr}
14164 This command sets the base I/O port address of the @file{COM1} serial
14167 @item set com1irq @var{irq}
14168 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
14169 for the @file{COM1} serial port.
14171 There are similar commands @samp{set com2base}, @samp{set com3irq},
14172 etc.@: for setting the port address and the @code{IRQ} lines for the
14175 @kindex show com1base
14176 @kindex show com1irq
14177 @kindex show com2base
14178 @kindex show com2irq
14179 @kindex show com3base
14180 @kindex show com3irq
14181 @kindex show com4base
14182 @kindex show com4irq
14183 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
14184 display the current settings of the base address and the @code{IRQ}
14185 lines used by the COM ports.
14188 @kindex info serial
14189 @cindex DOS serial port status
14190 This command prints the status of the 4 DOS serial ports. For each
14191 port, it prints whether it's active or not, its I/O base address and
14192 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
14193 counts of various errors encountered so far.
14197 @node Cygwin Native
14198 @subsection Features for Debugging MS Windows PE Executables
14199 @cindex MS Windows debugging
14200 @cindex native Cygwin debugging
14201 @cindex Cygwin-specific commands
14203 @value{GDBN} supports native debugging of MS Windows programs, including
14204 DLLs with and without symbolic debugging information. There are various
14205 additional Cygwin-specific commands, described in this section.
14206 Working with DLLs that have no debugging symbols is described in
14207 @ref{Non-debug DLL Symbols}.
14212 This is a prefix of MS Windows-specific commands which print
14213 information about the target system and important OS structures.
14215 @item info w32 selector
14216 This command displays information returned by
14217 the Win32 API @code{GetThreadSelectorEntry} function.
14218 It takes an optional argument that is evaluated to
14219 a long value to give the information about this given selector.
14220 Without argument, this command displays information
14221 about the six segment registers.
14225 This is a Cygwin-specific alias of @code{info shared}.
14227 @kindex dll-symbols
14229 This command loads symbols from a dll similarly to
14230 add-sym command but without the need to specify a base address.
14232 @kindex set cygwin-exceptions
14233 @cindex debugging the Cygwin DLL
14234 @cindex Cygwin DLL, debugging
14235 @item set cygwin-exceptions @var{mode}
14236 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
14237 happen inside the Cygwin DLL. If @var{mode} is @code{off},
14238 @value{GDBN} will delay recognition of exceptions, and may ignore some
14239 exceptions which seem to be caused by internal Cygwin DLL
14240 ``bookkeeping''. This option is meant primarily for debugging the
14241 Cygwin DLL itself; the default value is @code{off} to avoid annoying
14242 @value{GDBN} users with false @code{SIGSEGV} signals.
14244 @kindex show cygwin-exceptions
14245 @item show cygwin-exceptions
14246 Displays whether @value{GDBN} will break on exceptions that happen
14247 inside the Cygwin DLL itself.
14249 @kindex set new-console
14250 @item set new-console @var{mode}
14251 If @var{mode} is @code{on} the debuggee will
14252 be started in a new console on next start.
14253 If @var{mode} is @code{off}i, the debuggee will
14254 be started in the same console as the debugger.
14256 @kindex show new-console
14257 @item show new-console
14258 Displays whether a new console is used
14259 when the debuggee is started.
14261 @kindex set new-group
14262 @item set new-group @var{mode}
14263 This boolean value controls whether the debuggee should
14264 start a new group or stay in the same group as the debugger.
14265 This affects the way the Windows OS handles
14268 @kindex show new-group
14269 @item show new-group
14270 Displays current value of new-group boolean.
14272 @kindex set debugevents
14273 @item set debugevents
14274 This boolean value adds debug output concerning kernel events related
14275 to the debuggee seen by the debugger. This includes events that
14276 signal thread and process creation and exit, DLL loading and
14277 unloading, console interrupts, and debugging messages produced by the
14278 Windows @code{OutputDebugString} API call.
14280 @kindex set debugexec
14281 @item set debugexec
14282 This boolean value adds debug output concerning execute events
14283 (such as resume thread) seen by the debugger.
14285 @kindex set debugexceptions
14286 @item set debugexceptions
14287 This boolean value adds debug output concerning exceptions in the
14288 debuggee seen by the debugger.
14290 @kindex set debugmemory
14291 @item set debugmemory
14292 This boolean value adds debug output concerning debuggee memory reads
14293 and writes by the debugger.
14297 This boolean values specifies whether the debuggee is called
14298 via a shell or directly (default value is on).
14302 Displays if the debuggee will be started with a shell.
14307 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14310 @node Non-debug DLL Symbols
14311 @subsubsection Support for DLLs without Debugging Symbols
14312 @cindex DLLs with no debugging symbols
14313 @cindex Minimal symbols and DLLs
14315 Very often on windows, some of the DLLs that your program relies on do
14316 not include symbolic debugging information (for example,
14317 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14318 symbols in a DLL, it relies on the minimal amount of symbolic
14319 information contained in the DLL's export table. This section
14320 describes working with such symbols, known internally to @value{GDBN} as
14321 ``minimal symbols''.
14323 Note that before the debugged program has started execution, no DLLs
14324 will have been loaded. The easiest way around this problem is simply to
14325 start the program --- either by setting a breakpoint or letting the
14326 program run once to completion. It is also possible to force
14327 @value{GDBN} to load a particular DLL before starting the executable ---
14328 see the shared library information in @ref{Files}, or the
14329 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14330 explicitly loading symbols from a DLL with no debugging information will
14331 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14332 which may adversely affect symbol lookup performance.
14334 @subsubsection DLL Name Prefixes
14336 In keeping with the naming conventions used by the Microsoft debugging
14337 tools, DLL export symbols are made available with a prefix based on the
14338 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14339 also entered into the symbol table, so @code{CreateFileA} is often
14340 sufficient. In some cases there will be name clashes within a program
14341 (particularly if the executable itself includes full debugging symbols)
14342 necessitating the use of the fully qualified name when referring to the
14343 contents of the DLL. Use single-quotes around the name to avoid the
14344 exclamation mark (``!'') being interpreted as a language operator.
14346 Note that the internal name of the DLL may be all upper-case, even
14347 though the file name of the DLL is lower-case, or vice-versa. Since
14348 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14349 some confusion. If in doubt, try the @code{info functions} and
14350 @code{info variables} commands or even @code{maint print msymbols}
14351 (@pxref{Symbols}). Here's an example:
14354 (@value{GDBP}) info function CreateFileA
14355 All functions matching regular expression "CreateFileA":
14357 Non-debugging symbols:
14358 0x77e885f4 CreateFileA
14359 0x77e885f4 KERNEL32!CreateFileA
14363 (@value{GDBP}) info function !
14364 All functions matching regular expression "!":
14366 Non-debugging symbols:
14367 0x6100114c cygwin1!__assert
14368 0x61004034 cygwin1!_dll_crt0@@0
14369 0x61004240 cygwin1!dll_crt0(per_process *)
14373 @subsubsection Working with Minimal Symbols
14375 Symbols extracted from a DLL's export table do not contain very much
14376 type information. All that @value{GDBN} can do is guess whether a symbol
14377 refers to a function or variable depending on the linker section that
14378 contains the symbol. Also note that the actual contents of the memory
14379 contained in a DLL are not available unless the program is running. This
14380 means that you cannot examine the contents of a variable or disassemble
14381 a function within a DLL without a running program.
14383 Variables are generally treated as pointers and dereferenced
14384 automatically. For this reason, it is often necessary to prefix a
14385 variable name with the address-of operator (``&'') and provide explicit
14386 type information in the command. Here's an example of the type of
14390 (@value{GDBP}) print 'cygwin1!__argv'
14395 (@value{GDBP}) x 'cygwin1!__argv'
14396 0x10021610: "\230y\""
14399 And two possible solutions:
14402 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14403 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14407 (@value{GDBP}) x/2x &'cygwin1!__argv'
14408 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14409 (@value{GDBP}) x/x 0x10021608
14410 0x10021608: 0x0022fd98
14411 (@value{GDBP}) x/s 0x0022fd98
14412 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14415 Setting a break point within a DLL is possible even before the program
14416 starts execution. However, under these circumstances, @value{GDBN} can't
14417 examine the initial instructions of the function in order to skip the
14418 function's frame set-up code. You can work around this by using ``*&''
14419 to set the breakpoint at a raw memory address:
14422 (@value{GDBP}) break *&'python22!PyOS_Readline'
14423 Breakpoint 1 at 0x1e04eff0
14426 The author of these extensions is not entirely convinced that setting a
14427 break point within a shared DLL like @file{kernel32.dll} is completely
14431 @subsection Commands Specific to @sc{gnu} Hurd Systems
14432 @cindex @sc{gnu} Hurd debugging
14434 This subsection describes @value{GDBN} commands specific to the
14435 @sc{gnu} Hurd native debugging.
14440 @kindex set signals@r{, Hurd command}
14441 @kindex set sigs@r{, Hurd command}
14442 This command toggles the state of inferior signal interception by
14443 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14444 affected by this command. @code{sigs} is a shorthand alias for
14449 @kindex show signals@r{, Hurd command}
14450 @kindex show sigs@r{, Hurd command}
14451 Show the current state of intercepting inferior's signals.
14453 @item set signal-thread
14454 @itemx set sigthread
14455 @kindex set signal-thread
14456 @kindex set sigthread
14457 This command tells @value{GDBN} which thread is the @code{libc} signal
14458 thread. That thread is run when a signal is delivered to a running
14459 process. @code{set sigthread} is the shorthand alias of @code{set
14462 @item show signal-thread
14463 @itemx show sigthread
14464 @kindex show signal-thread
14465 @kindex show sigthread
14466 These two commands show which thread will run when the inferior is
14467 delivered a signal.
14470 @kindex set stopped@r{, Hurd command}
14471 This commands tells @value{GDBN} that the inferior process is stopped,
14472 as with the @code{SIGSTOP} signal. The stopped process can be
14473 continued by delivering a signal to it.
14476 @kindex show stopped@r{, Hurd command}
14477 This command shows whether @value{GDBN} thinks the debuggee is
14480 @item set exceptions
14481 @kindex set exceptions@r{, Hurd command}
14482 Use this command to turn off trapping of exceptions in the inferior.
14483 When exception trapping is off, neither breakpoints nor
14484 single-stepping will work. To restore the default, set exception
14487 @item show exceptions
14488 @kindex show exceptions@r{, Hurd command}
14489 Show the current state of trapping exceptions in the inferior.
14491 @item set task pause
14492 @kindex set task@r{, Hurd commands}
14493 @cindex task attributes (@sc{gnu} Hurd)
14494 @cindex pause current task (@sc{gnu} Hurd)
14495 This command toggles task suspension when @value{GDBN} has control.
14496 Setting it to on takes effect immediately, and the task is suspended
14497 whenever @value{GDBN} gets control. Setting it to off will take
14498 effect the next time the inferior is continued. If this option is set
14499 to off, you can use @code{set thread default pause on} or @code{set
14500 thread pause on} (see below) to pause individual threads.
14502 @item show task pause
14503 @kindex show task@r{, Hurd commands}
14504 Show the current state of task suspension.
14506 @item set task detach-suspend-count
14507 @cindex task suspend count
14508 @cindex detach from task, @sc{gnu} Hurd
14509 This command sets the suspend count the task will be left with when
14510 @value{GDBN} detaches from it.
14512 @item show task detach-suspend-count
14513 Show the suspend count the task will be left with when detaching.
14515 @item set task exception-port
14516 @itemx set task excp
14517 @cindex task exception port, @sc{gnu} Hurd
14518 This command sets the task exception port to which @value{GDBN} will
14519 forward exceptions. The argument should be the value of the @dfn{send
14520 rights} of the task. @code{set task excp} is a shorthand alias.
14522 @item set noninvasive
14523 @cindex noninvasive task options
14524 This command switches @value{GDBN} to a mode that is the least
14525 invasive as far as interfering with the inferior is concerned. This
14526 is the same as using @code{set task pause}, @code{set exceptions}, and
14527 @code{set signals} to values opposite to the defaults.
14529 @item info send-rights
14530 @itemx info receive-rights
14531 @itemx info port-rights
14532 @itemx info port-sets
14533 @itemx info dead-names
14536 @cindex send rights, @sc{gnu} Hurd
14537 @cindex receive rights, @sc{gnu} Hurd
14538 @cindex port rights, @sc{gnu} Hurd
14539 @cindex port sets, @sc{gnu} Hurd
14540 @cindex dead names, @sc{gnu} Hurd
14541 These commands display information about, respectively, send rights,
14542 receive rights, port rights, port sets, and dead names of a task.
14543 There are also shorthand aliases: @code{info ports} for @code{info
14544 port-rights} and @code{info psets} for @code{info port-sets}.
14546 @item set thread pause
14547 @kindex set thread@r{, Hurd command}
14548 @cindex thread properties, @sc{gnu} Hurd
14549 @cindex pause current thread (@sc{gnu} Hurd)
14550 This command toggles current thread suspension when @value{GDBN} has
14551 control. Setting it to on takes effect immediately, and the current
14552 thread is suspended whenever @value{GDBN} gets control. Setting it to
14553 off will take effect the next time the inferior is continued.
14554 Normally, this command has no effect, since when @value{GDBN} has
14555 control, the whole task is suspended. However, if you used @code{set
14556 task pause off} (see above), this command comes in handy to suspend
14557 only the current thread.
14559 @item show thread pause
14560 @kindex show thread@r{, Hurd command}
14561 This command shows the state of current thread suspension.
14563 @item set thread run
14564 This command sets whether the current thread is allowed to run.
14566 @item show thread run
14567 Show whether the current thread is allowed to run.
14569 @item set thread detach-suspend-count
14570 @cindex thread suspend count, @sc{gnu} Hurd
14571 @cindex detach from thread, @sc{gnu} Hurd
14572 This command sets the suspend count @value{GDBN} will leave on a
14573 thread when detaching. This number is relative to the suspend count
14574 found by @value{GDBN} when it notices the thread; use @code{set thread
14575 takeover-suspend-count} to force it to an absolute value.
14577 @item show thread detach-suspend-count
14578 Show the suspend count @value{GDBN} will leave on the thread when
14581 @item set thread exception-port
14582 @itemx set thread excp
14583 Set the thread exception port to which to forward exceptions. This
14584 overrides the port set by @code{set task exception-port} (see above).
14585 @code{set thread excp} is the shorthand alias.
14587 @item set thread takeover-suspend-count
14588 Normally, @value{GDBN}'s thread suspend counts are relative to the
14589 value @value{GDBN} finds when it notices each thread. This command
14590 changes the suspend counts to be absolute instead.
14592 @item set thread default
14593 @itemx show thread default
14594 @cindex thread default settings, @sc{gnu} Hurd
14595 Each of the above @code{set thread} commands has a @code{set thread
14596 default} counterpart (e.g., @code{set thread default pause}, @code{set
14597 thread default exception-port}, etc.). The @code{thread default}
14598 variety of commands sets the default thread properties for all
14599 threads; you can then change the properties of individual threads with
14600 the non-default commands.
14605 @subsection QNX Neutrino
14606 @cindex QNX Neutrino
14608 @value{GDBN} provides the following commands specific to the QNX
14612 @item set debug nto-debug
14613 @kindex set debug nto-debug
14614 When set to on, enables debugging messages specific to the QNX
14617 @item show debug nto-debug
14618 @kindex show debug nto-debug
14619 Show the current state of QNX Neutrino messages.
14624 @section Embedded Operating Systems
14626 This section describes configurations involving the debugging of
14627 embedded operating systems that are available for several different
14631 * VxWorks:: Using @value{GDBN} with VxWorks
14634 @value{GDBN} includes the ability to debug programs running on
14635 various real-time operating systems.
14638 @subsection Using @value{GDBN} with VxWorks
14644 @kindex target vxworks
14645 @item target vxworks @var{machinename}
14646 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14647 is the target system's machine name or IP address.
14651 On VxWorks, @code{load} links @var{filename} dynamically on the
14652 current target system as well as adding its symbols in @value{GDBN}.
14654 @value{GDBN} enables developers to spawn and debug tasks running on networked
14655 VxWorks targets from a Unix host. Already-running tasks spawned from
14656 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14657 both the Unix host and on the VxWorks target. The program
14658 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14659 installed with the name @code{vxgdb}, to distinguish it from a
14660 @value{GDBN} for debugging programs on the host itself.)
14663 @item VxWorks-timeout @var{args}
14664 @kindex vxworks-timeout
14665 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14666 This option is set by the user, and @var{args} represents the number of
14667 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14668 your VxWorks target is a slow software simulator or is on the far side
14669 of a thin network line.
14672 The following information on connecting to VxWorks was current when
14673 this manual was produced; newer releases of VxWorks may use revised
14676 @findex INCLUDE_RDB
14677 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14678 to include the remote debugging interface routines in the VxWorks
14679 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14680 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14681 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14682 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14683 information on configuring and remaking VxWorks, see the manufacturer's
14685 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14687 Once you have included @file{rdb.a} in your VxWorks system image and set
14688 your Unix execution search path to find @value{GDBN}, you are ready to
14689 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14690 @code{vxgdb}, depending on your installation).
14692 @value{GDBN} comes up showing the prompt:
14699 * VxWorks Connection:: Connecting to VxWorks
14700 * VxWorks Download:: VxWorks download
14701 * VxWorks Attach:: Running tasks
14704 @node VxWorks Connection
14705 @subsubsection Connecting to VxWorks
14707 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14708 network. To connect to a target whose host name is ``@code{tt}'', type:
14711 (vxgdb) target vxworks tt
14715 @value{GDBN} displays messages like these:
14718 Attaching remote machine across net...
14723 @value{GDBN} then attempts to read the symbol tables of any object modules
14724 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14725 these files by searching the directories listed in the command search
14726 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14727 to find an object file, it displays a message such as:
14730 prog.o: No such file or directory.
14733 When this happens, add the appropriate directory to the search path with
14734 the @value{GDBN} command @code{path}, and execute the @code{target}
14737 @node VxWorks Download
14738 @subsubsection VxWorks Download
14740 @cindex download to VxWorks
14741 If you have connected to the VxWorks target and you want to debug an
14742 object that has not yet been loaded, you can use the @value{GDBN}
14743 @code{load} command to download a file from Unix to VxWorks
14744 incrementally. The object file given as an argument to the @code{load}
14745 command is actually opened twice: first by the VxWorks target in order
14746 to download the code, then by @value{GDBN} in order to read the symbol
14747 table. This can lead to problems if the current working directories on
14748 the two systems differ. If both systems have NFS mounted the same
14749 filesystems, you can avoid these problems by using absolute paths.
14750 Otherwise, it is simplest to set the working directory on both systems
14751 to the directory in which the object file resides, and then to reference
14752 the file by its name, without any path. For instance, a program
14753 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14754 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14755 program, type this on VxWorks:
14758 -> cd "@var{vxpath}/vw/demo/rdb"
14762 Then, in @value{GDBN}, type:
14765 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14766 (vxgdb) load prog.o
14769 @value{GDBN} displays a response similar to this:
14772 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14775 You can also use the @code{load} command to reload an object module
14776 after editing and recompiling the corresponding source file. Note that
14777 this makes @value{GDBN} delete all currently-defined breakpoints,
14778 auto-displays, and convenience variables, and to clear the value
14779 history. (This is necessary in order to preserve the integrity of
14780 debugger's data structures that reference the target system's symbol
14783 @node VxWorks Attach
14784 @subsubsection Running Tasks
14786 @cindex running VxWorks tasks
14787 You can also attach to an existing task using the @code{attach} command as
14791 (vxgdb) attach @var{task}
14795 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14796 or suspended when you attach to it. Running tasks are suspended at
14797 the time of attachment.
14799 @node Embedded Processors
14800 @section Embedded Processors
14802 This section goes into details specific to particular embedded
14805 @cindex send command to simulator
14806 Whenever a specific embedded processor has a simulator, @value{GDBN}
14807 allows to send an arbitrary command to the simulator.
14810 @item sim @var{command}
14811 @kindex sim@r{, a command}
14812 Send an arbitrary @var{command} string to the simulator. Consult the
14813 documentation for the specific simulator in use for information about
14814 acceptable commands.
14820 * M32R/D:: Renesas M32R/D
14821 * M68K:: Motorola M68K
14822 * MIPS Embedded:: MIPS Embedded
14823 * OpenRISC 1000:: OpenRisc 1000
14824 * PA:: HP PA Embedded
14825 * PowerPC Embedded:: PowerPC Embedded
14826 * Sparclet:: Tsqware Sparclet
14827 * Sparclite:: Fujitsu Sparclite
14828 * Z8000:: Zilog Z8000
14831 * Super-H:: Renesas Super-H
14840 @item target rdi @var{dev}
14841 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14842 use this target to communicate with both boards running the Angel
14843 monitor, or with the EmbeddedICE JTAG debug device.
14846 @item target rdp @var{dev}
14851 @value{GDBN} provides the following ARM-specific commands:
14854 @item set arm disassembler
14856 This commands selects from a list of disassembly styles. The
14857 @code{"std"} style is the standard style.
14859 @item show arm disassembler
14861 Show the current disassembly style.
14863 @item set arm apcs32
14864 @cindex ARM 32-bit mode
14865 This command toggles ARM operation mode between 32-bit and 26-bit.
14867 @item show arm apcs32
14868 Display the current usage of the ARM 32-bit mode.
14870 @item set arm fpu @var{fputype}
14871 This command sets the ARM floating-point unit (FPU) type. The
14872 argument @var{fputype} can be one of these:
14876 Determine the FPU type by querying the OS ABI.
14878 Software FPU, with mixed-endian doubles on little-endian ARM
14881 GCC-compiled FPA co-processor.
14883 Software FPU with pure-endian doubles.
14889 Show the current type of the FPU.
14892 This command forces @value{GDBN} to use the specified ABI.
14895 Show the currently used ABI.
14897 @item set debug arm
14898 Toggle whether to display ARM-specific debugging messages from the ARM
14899 target support subsystem.
14901 @item show debug arm
14902 Show whether ARM-specific debugging messages are enabled.
14905 The following commands are available when an ARM target is debugged
14906 using the RDI interface:
14909 @item rdilogfile @r{[}@var{file}@r{]}
14911 @cindex ADP (Angel Debugger Protocol) logging
14912 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14913 With an argument, sets the log file to the specified @var{file}. With
14914 no argument, show the current log file name. The default log file is
14917 @item rdilogenable @r{[}@var{arg}@r{]}
14918 @kindex rdilogenable
14919 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14920 enables logging, with an argument 0 or @code{"no"} disables it. With
14921 no arguments displays the current setting. When logging is enabled,
14922 ADP packets exchanged between @value{GDBN} and the RDI target device
14923 are logged to a file.
14925 @item set rdiromatzero
14926 @kindex set rdiromatzero
14927 @cindex ROM at zero address, RDI
14928 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14929 vector catching is disabled, so that zero address can be used. If off
14930 (the default), vector catching is enabled. For this command to take
14931 effect, it needs to be invoked prior to the @code{target rdi} command.
14933 @item show rdiromatzero
14934 @kindex show rdiromatzero
14935 Show the current setting of ROM at zero address.
14937 @item set rdiheartbeat
14938 @kindex set rdiheartbeat
14939 @cindex RDI heartbeat
14940 Enable or disable RDI heartbeat packets. It is not recommended to
14941 turn on this option, since it confuses ARM and EPI JTAG interface, as
14942 well as the Angel monitor.
14944 @item show rdiheartbeat
14945 @kindex show rdiheartbeat
14946 Show the setting of RDI heartbeat packets.
14951 @subsection Renesas M32R/D and M32R/SDI
14954 @kindex target m32r
14955 @item target m32r @var{dev}
14956 Renesas M32R/D ROM monitor.
14958 @kindex target m32rsdi
14959 @item target m32rsdi @var{dev}
14960 Renesas M32R SDI server, connected via parallel port to the board.
14963 The following @value{GDBN} commands are specific to the M32R monitor:
14966 @item set download-path @var{path}
14967 @kindex set download-path
14968 @cindex find downloadable @sc{srec} files (M32R)
14969 Set the default path for finding downloadable @sc{srec} files.
14971 @item show download-path
14972 @kindex show download-path
14973 Show the default path for downloadable @sc{srec} files.
14975 @item set board-address @var{addr}
14976 @kindex set board-address
14977 @cindex M32-EVA target board address
14978 Set the IP address for the M32R-EVA target board.
14980 @item show board-address
14981 @kindex show board-address
14982 Show the current IP address of the target board.
14984 @item set server-address @var{addr}
14985 @kindex set server-address
14986 @cindex download server address (M32R)
14987 Set the IP address for the download server, which is the @value{GDBN}'s
14990 @item show server-address
14991 @kindex show server-address
14992 Display the IP address of the download server.
14994 @item upload @r{[}@var{file}@r{]}
14995 @kindex upload@r{, M32R}
14996 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14997 upload capability. If no @var{file} argument is given, the current
14998 executable file is uploaded.
15000 @item tload @r{[}@var{file}@r{]}
15001 @kindex tload@r{, M32R}
15002 Test the @code{upload} command.
15005 The following commands are available for M32R/SDI:
15010 @cindex reset SDI connection, M32R
15011 This command resets the SDI connection.
15015 This command shows the SDI connection status.
15018 @kindex debug_chaos
15019 @cindex M32R/Chaos debugging
15020 Instructs the remote that M32R/Chaos debugging is to be used.
15022 @item use_debug_dma
15023 @kindex use_debug_dma
15024 Instructs the remote to use the DEBUG_DMA method of accessing memory.
15027 @kindex use_mon_code
15028 Instructs the remote to use the MON_CODE method of accessing memory.
15031 @kindex use_ib_break
15032 Instructs the remote to set breakpoints by IB break.
15034 @item use_dbt_break
15035 @kindex use_dbt_break
15036 Instructs the remote to set breakpoints by DBT.
15042 The Motorola m68k configuration includes ColdFire support, and a
15043 target command for the following ROM monitor.
15047 @kindex target dbug
15048 @item target dbug @var{dev}
15049 dBUG ROM monitor for Motorola ColdFire.
15053 @node MIPS Embedded
15054 @subsection MIPS Embedded
15056 @cindex MIPS boards
15057 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15058 MIPS board attached to a serial line. This is available when
15059 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15062 Use these @value{GDBN} commands to specify the connection to your target board:
15065 @item target mips @var{port}
15066 @kindex target mips @var{port}
15067 To run a program on the board, start up @code{@value{GDBP}} with the
15068 name of your program as the argument. To connect to the board, use the
15069 command @samp{target mips @var{port}}, where @var{port} is the name of
15070 the serial port connected to the board. If the program has not already
15071 been downloaded to the board, you may use the @code{load} command to
15072 download it. You can then use all the usual @value{GDBN} commands.
15074 For example, this sequence connects to the target board through a serial
15075 port, and loads and runs a program called @var{prog} through the
15079 host$ @value{GDBP} @var{prog}
15080 @value{GDBN} is free software and @dots{}
15081 (@value{GDBP}) target mips /dev/ttyb
15082 (@value{GDBP}) load @var{prog}
15086 @item target mips @var{hostname}:@var{portnumber}
15087 On some @value{GDBN} host configurations, you can specify a TCP
15088 connection (for instance, to a serial line managed by a terminal
15089 concentrator) instead of a serial port, using the syntax
15090 @samp{@var{hostname}:@var{portnumber}}.
15092 @item target pmon @var{port}
15093 @kindex target pmon @var{port}
15096 @item target ddb @var{port}
15097 @kindex target ddb @var{port}
15098 NEC's DDB variant of PMON for Vr4300.
15100 @item target lsi @var{port}
15101 @kindex target lsi @var{port}
15102 LSI variant of PMON.
15104 @kindex target r3900
15105 @item target r3900 @var{dev}
15106 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
15108 @kindex target array
15109 @item target array @var{dev}
15110 Array Tech LSI33K RAID controller board.
15116 @value{GDBN} also supports these special commands for MIPS targets:
15119 @item set mipsfpu double
15120 @itemx set mipsfpu single
15121 @itemx set mipsfpu none
15122 @itemx set mipsfpu auto
15123 @itemx show mipsfpu
15124 @kindex set mipsfpu
15125 @kindex show mipsfpu
15126 @cindex MIPS remote floating point
15127 @cindex floating point, MIPS remote
15128 If your target board does not support the MIPS floating point
15129 coprocessor, you should use the command @samp{set mipsfpu none} (if you
15130 need this, you may wish to put the command in your @value{GDBN} init
15131 file). This tells @value{GDBN} how to find the return value of
15132 functions which return floating point values. It also allows
15133 @value{GDBN} to avoid saving the floating point registers when calling
15134 functions on the board. If you are using a floating point coprocessor
15135 with only single precision floating point support, as on the @sc{r4650}
15136 processor, use the command @samp{set mipsfpu single}. The default
15137 double precision floating point coprocessor may be selected using
15138 @samp{set mipsfpu double}.
15140 In previous versions the only choices were double precision or no
15141 floating point, so @samp{set mipsfpu on} will select double precision
15142 and @samp{set mipsfpu off} will select no floating point.
15144 As usual, you can inquire about the @code{mipsfpu} variable with
15145 @samp{show mipsfpu}.
15147 @item set timeout @var{seconds}
15148 @itemx set retransmit-timeout @var{seconds}
15149 @itemx show timeout
15150 @itemx show retransmit-timeout
15151 @cindex @code{timeout}, MIPS protocol
15152 @cindex @code{retransmit-timeout}, MIPS protocol
15153 @kindex set timeout
15154 @kindex show timeout
15155 @kindex set retransmit-timeout
15156 @kindex show retransmit-timeout
15157 You can control the timeout used while waiting for a packet, in the MIPS
15158 remote protocol, with the @code{set timeout @var{seconds}} command. The
15159 default is 5 seconds. Similarly, you can control the timeout used while
15160 waiting for an acknowledgement of a packet with the @code{set
15161 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
15162 You can inspect both values with @code{show timeout} and @code{show
15163 retransmit-timeout}. (These commands are @emph{only} available when
15164 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
15166 The timeout set by @code{set timeout} does not apply when @value{GDBN}
15167 is waiting for your program to stop. In that case, @value{GDBN} waits
15168 forever because it has no way of knowing how long the program is going
15169 to run before stopping.
15171 @item set syn-garbage-limit @var{num}
15172 @kindex set syn-garbage-limit@r{, MIPS remote}
15173 @cindex synchronize with remote MIPS target
15174 Limit the maximum number of characters @value{GDBN} should ignore when
15175 it tries to synchronize with the remote target. The default is 10
15176 characters. Setting the limit to -1 means there's no limit.
15178 @item show syn-garbage-limit
15179 @kindex show syn-garbage-limit@r{, MIPS remote}
15180 Show the current limit on the number of characters to ignore when
15181 trying to synchronize with the remote system.
15183 @item set monitor-prompt @var{prompt}
15184 @kindex set monitor-prompt@r{, MIPS remote}
15185 @cindex remote monitor prompt
15186 Tell @value{GDBN} to expect the specified @var{prompt} string from the
15187 remote monitor. The default depends on the target:
15197 @item show monitor-prompt
15198 @kindex show monitor-prompt@r{, MIPS remote}
15199 Show the current strings @value{GDBN} expects as the prompt from the
15202 @item set monitor-warnings
15203 @kindex set monitor-warnings@r{, MIPS remote}
15204 Enable or disable monitor warnings about hardware breakpoints. This
15205 has effect only for the @code{lsi} target. When on, @value{GDBN} will
15206 display warning messages whose codes are returned by the @code{lsi}
15207 PMON monitor for breakpoint commands.
15209 @item show monitor-warnings
15210 @kindex show monitor-warnings@r{, MIPS remote}
15211 Show the current setting of printing monitor warnings.
15213 @item pmon @var{command}
15214 @kindex pmon@r{, MIPS remote}
15215 @cindex send PMON command
15216 This command allows sending an arbitrary @var{command} string to the
15217 monitor. The monitor must be in debug mode for this to work.
15220 @node OpenRISC 1000
15221 @subsection OpenRISC 1000
15222 @cindex OpenRISC 1000
15224 @cindex or1k boards
15225 See OR1k Architecture document (@uref{www.opencores.org}) for more information
15226 about platform and commands.
15230 @kindex target jtag
15231 @item target jtag jtag://@var{host}:@var{port}
15233 Connects to remote JTAG server.
15234 JTAG remote server can be either an or1ksim or JTAG server,
15235 connected via parallel port to the board.
15237 Example: @code{target jtag jtag://localhost:9999}
15240 @item or1ksim @var{command}
15241 If connected to @code{or1ksim} OpenRISC 1000 Architectural
15242 Simulator, proprietary commands can be executed.
15244 @kindex info or1k spr
15245 @item info or1k spr
15246 Displays spr groups.
15248 @item info or1k spr @var{group}
15249 @itemx info or1k spr @var{groupno}
15250 Displays register names in selected group.
15252 @item info or1k spr @var{group} @var{register}
15253 @itemx info or1k spr @var{register}
15254 @itemx info or1k spr @var{groupno} @var{registerno}
15255 @itemx info or1k spr @var{registerno}
15256 Shows information about specified spr register.
15259 @item spr @var{group} @var{register} @var{value}
15260 @itemx spr @var{register @var{value}}
15261 @itemx spr @var{groupno} @var{registerno @var{value}}
15262 @itemx spr @var{registerno @var{value}}
15263 Writes @var{value} to specified spr register.
15266 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15267 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15268 program execution and is thus much faster. Hardware breakpoints/watchpoint
15269 triggers can be set using:
15272 Load effective address/data
15274 Store effective address/data
15276 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15281 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15282 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15284 @code{htrace} commands:
15285 @cindex OpenRISC 1000 htrace
15288 @item hwatch @var{conditional}
15289 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15290 or Data. For example:
15292 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15294 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15298 Display information about current HW trace configuration.
15300 @item htrace trigger @var{conditional}
15301 Set starting criteria for HW trace.
15303 @item htrace qualifier @var{conditional}
15304 Set acquisition qualifier for HW trace.
15306 @item htrace stop @var{conditional}
15307 Set HW trace stopping criteria.
15309 @item htrace record [@var{data}]*
15310 Selects the data to be recorded, when qualifier is met and HW trace was
15313 @item htrace enable
15314 @itemx htrace disable
15315 Enables/disables the HW trace.
15317 @item htrace rewind [@var{filename}]
15318 Clears currently recorded trace data.
15320 If filename is specified, new trace file is made and any newly collected data
15321 will be written there.
15323 @item htrace print [@var{start} [@var{len}]]
15324 Prints trace buffer, using current record configuration.
15326 @item htrace mode continuous
15327 Set continuous trace mode.
15329 @item htrace mode suspend
15330 Set suspend trace mode.
15334 @node PowerPC Embedded
15335 @subsection PowerPC Embedded
15337 @value{GDBN} provides the following PowerPC-specific commands:
15340 @kindex set powerpc
15341 @item set powerpc soft-float
15342 @itemx show powerpc soft-float
15343 Force @value{GDBN} to use (or not use) a software floating point calling
15344 convention. By default, @value{GDBN} selects the calling convention based
15345 on the selected architecture and the provided executable file.
15347 @item set powerpc vector-abi
15348 @itemx show powerpc vector-abi
15349 Force @value{GDBN} to use the specified calling convention for vector
15350 arguments and return values. The valid options are @samp{auto};
15351 @samp{generic}, to avoid vector registers even if they are present;
15352 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15353 registers. By default, @value{GDBN} selects the calling convention
15354 based on the selected architecture and the provided executable file.
15356 @kindex target dink32
15357 @item target dink32 @var{dev}
15358 DINK32 ROM monitor.
15360 @kindex target ppcbug
15361 @item target ppcbug @var{dev}
15362 @kindex target ppcbug1
15363 @item target ppcbug1 @var{dev}
15364 PPCBUG ROM monitor for PowerPC.
15367 @item target sds @var{dev}
15368 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15371 @cindex SDS protocol
15372 The following commands specific to the SDS protocol are supported
15376 @item set sdstimeout @var{nsec}
15377 @kindex set sdstimeout
15378 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15379 default is 2 seconds.
15381 @item show sdstimeout
15382 @kindex show sdstimeout
15383 Show the current value of the SDS timeout.
15385 @item sds @var{command}
15386 @kindex sds@r{, a command}
15387 Send the specified @var{command} string to the SDS monitor.
15392 @subsection HP PA Embedded
15396 @kindex target op50n
15397 @item target op50n @var{dev}
15398 OP50N monitor, running on an OKI HPPA board.
15400 @kindex target w89k
15401 @item target w89k @var{dev}
15402 W89K monitor, running on a Winbond HPPA board.
15407 @subsection Tsqware Sparclet
15411 @value{GDBN} enables developers to debug tasks running on
15412 Sparclet targets from a Unix host.
15413 @value{GDBN} uses code that runs on
15414 both the Unix host and on the Sparclet target. The program
15415 @code{@value{GDBP}} is installed and executed on the Unix host.
15418 @item remotetimeout @var{args}
15419 @kindex remotetimeout
15420 @value{GDBN} supports the option @code{remotetimeout}.
15421 This option is set by the user, and @var{args} represents the number of
15422 seconds @value{GDBN} waits for responses.
15425 @cindex compiling, on Sparclet
15426 When compiling for debugging, include the options @samp{-g} to get debug
15427 information and @samp{-Ttext} to relocate the program to where you wish to
15428 load it on the target. You may also want to add the options @samp{-n} or
15429 @samp{-N} in order to reduce the size of the sections. Example:
15432 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15435 You can use @code{objdump} to verify that the addresses are what you intended:
15438 sparclet-aout-objdump --headers --syms prog
15441 @cindex running, on Sparclet
15443 your Unix execution search path to find @value{GDBN}, you are ready to
15444 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15445 (or @code{sparclet-aout-gdb}, depending on your installation).
15447 @value{GDBN} comes up showing the prompt:
15454 * Sparclet File:: Setting the file to debug
15455 * Sparclet Connection:: Connecting to Sparclet
15456 * Sparclet Download:: Sparclet download
15457 * Sparclet Execution:: Running and debugging
15460 @node Sparclet File
15461 @subsubsection Setting File to Debug
15463 The @value{GDBN} command @code{file} lets you choose with program to debug.
15466 (gdbslet) file prog
15470 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15471 @value{GDBN} locates
15472 the file by searching the directories listed in the command search
15474 If the file was compiled with debug information (option @samp{-g}), source
15475 files will be searched as well.
15476 @value{GDBN} locates
15477 the source files by searching the directories listed in the directory search
15478 path (@pxref{Environment, ,Your Program's Environment}).
15480 to find a file, it displays a message such as:
15483 prog: No such file or directory.
15486 When this happens, add the appropriate directories to the search paths with
15487 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15488 @code{target} command again.
15490 @node Sparclet Connection
15491 @subsubsection Connecting to Sparclet
15493 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15494 To connect to a target on serial port ``@code{ttya}'', type:
15497 (gdbslet) target sparclet /dev/ttya
15498 Remote target sparclet connected to /dev/ttya
15499 main () at ../prog.c:3
15503 @value{GDBN} displays messages like these:
15509 @node Sparclet Download
15510 @subsubsection Sparclet Download
15512 @cindex download to Sparclet
15513 Once connected to the Sparclet target,
15514 you can use the @value{GDBN}
15515 @code{load} command to download the file from the host to the target.
15516 The file name and load offset should be given as arguments to the @code{load}
15518 Since the file format is aout, the program must be loaded to the starting
15519 address. You can use @code{objdump} to find out what this value is. The load
15520 offset is an offset which is added to the VMA (virtual memory address)
15521 of each of the file's sections.
15522 For instance, if the program
15523 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15524 and bss at 0x12010170, in @value{GDBN}, type:
15527 (gdbslet) load prog 0x12010000
15528 Loading section .text, size 0xdb0 vma 0x12010000
15531 If the code is loaded at a different address then what the program was linked
15532 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15533 to tell @value{GDBN} where to map the symbol table.
15535 @node Sparclet Execution
15536 @subsubsection Running and Debugging
15538 @cindex running and debugging Sparclet programs
15539 You can now begin debugging the task using @value{GDBN}'s execution control
15540 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15541 manual for the list of commands.
15545 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15547 Starting program: prog
15548 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15549 3 char *symarg = 0;
15551 4 char *execarg = "hello!";
15556 @subsection Fujitsu Sparclite
15560 @kindex target sparclite
15561 @item target sparclite @var{dev}
15562 Fujitsu sparclite boards, used only for the purpose of loading.
15563 You must use an additional command to debug the program.
15564 For example: target remote @var{dev} using @value{GDBN} standard
15570 @subsection Zilog Z8000
15573 @cindex simulator, Z8000
15574 @cindex Zilog Z8000 simulator
15576 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15579 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15580 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15581 segmented variant). The simulator recognizes which architecture is
15582 appropriate by inspecting the object code.
15585 @item target sim @var{args}
15587 @kindex target sim@r{, with Z8000}
15588 Debug programs on a simulated CPU. If the simulator supports setup
15589 options, specify them via @var{args}.
15593 After specifying this target, you can debug programs for the simulated
15594 CPU in the same style as programs for your host computer; use the
15595 @code{file} command to load a new program image, the @code{run} command
15596 to run your program, and so on.
15598 As well as making available all the usual machine registers
15599 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15600 additional items of information as specially named registers:
15605 Counts clock-ticks in the simulator.
15608 Counts instructions run in the simulator.
15611 Execution time in 60ths of a second.
15615 You can refer to these values in @value{GDBN} expressions with the usual
15616 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15617 conditional breakpoint that suspends only after at least 5000
15618 simulated clock ticks.
15621 @subsection Atmel AVR
15624 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15625 following AVR-specific commands:
15628 @item info io_registers
15629 @kindex info io_registers@r{, AVR}
15630 @cindex I/O registers (Atmel AVR)
15631 This command displays information about the AVR I/O registers. For
15632 each register, @value{GDBN} prints its number and value.
15639 When configured for debugging CRIS, @value{GDBN} provides the
15640 following CRIS-specific commands:
15643 @item set cris-version @var{ver}
15644 @cindex CRIS version
15645 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15646 The CRIS version affects register names and sizes. This command is useful in
15647 case autodetection of the CRIS version fails.
15649 @item show cris-version
15650 Show the current CRIS version.
15652 @item set cris-dwarf2-cfi
15653 @cindex DWARF-2 CFI and CRIS
15654 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15655 Change to @samp{off} when using @code{gcc-cris} whose version is below
15658 @item show cris-dwarf2-cfi
15659 Show the current state of using DWARF-2 CFI.
15661 @item set cris-mode @var{mode}
15663 Set the current CRIS mode to @var{mode}. It should only be changed when
15664 debugging in guru mode, in which case it should be set to
15665 @samp{guru} (the default is @samp{normal}).
15667 @item show cris-mode
15668 Show the current CRIS mode.
15672 @subsection Renesas Super-H
15675 For the Renesas Super-H processor, @value{GDBN} provides these
15680 @kindex regs@r{, Super-H}
15681 Show the values of all Super-H registers.
15683 @item set sh calling-convention @var{convention}
15684 @kindex set sh calling-convention
15685 Set the calling-convention used when calling functions from @value{GDBN}.
15686 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
15687 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
15688 convention. If the DWARF-2 information of the called function specifies
15689 that the function follows the Renesas calling convention, the function
15690 is called using the Renesas calling convention. If the calling convention
15691 is set to @samp{renesas}, the Renesas calling convention is always used,
15692 regardless of the DWARF-2 information. This can be used to override the
15693 default of @samp{gcc} if debug information is missing, or the compiler
15694 does not emit the DWARF-2 calling convention entry for a function.
15696 @item show sh calling-convention
15697 @kindex show sh calling-convention
15698 Show the current calling convention setting.
15703 @node Architectures
15704 @section Architectures
15706 This section describes characteristics of architectures that affect
15707 all uses of @value{GDBN} with the architecture, both native and cross.
15714 * HPPA:: HP PA architecture
15715 * SPU:: Cell Broadband Engine SPU architecture
15720 @subsection x86 Architecture-specific Issues
15723 @item set struct-convention @var{mode}
15724 @kindex set struct-convention
15725 @cindex struct return convention
15726 @cindex struct/union returned in registers
15727 Set the convention used by the inferior to return @code{struct}s and
15728 @code{union}s from functions to @var{mode}. Possible values of
15729 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15730 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15731 are returned on the stack, while @code{"reg"} means that a
15732 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15733 be returned in a register.
15735 @item show struct-convention
15736 @kindex show struct-convention
15737 Show the current setting of the convention to return @code{struct}s
15746 @kindex set rstack_high_address
15747 @cindex AMD 29K register stack
15748 @cindex register stack, AMD29K
15749 @item set rstack_high_address @var{address}
15750 On AMD 29000 family processors, registers are saved in a separate
15751 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15752 extent of this stack. Normally, @value{GDBN} just assumes that the
15753 stack is ``large enough''. This may result in @value{GDBN} referencing
15754 memory locations that do not exist. If necessary, you can get around
15755 this problem by specifying the ending address of the register stack with
15756 the @code{set rstack_high_address} command. The argument should be an
15757 address, which you probably want to precede with @samp{0x} to specify in
15760 @kindex show rstack_high_address
15761 @item show rstack_high_address
15762 Display the current limit of the register stack, on AMD 29000 family
15770 See the following section.
15775 @cindex stack on Alpha
15776 @cindex stack on MIPS
15777 @cindex Alpha stack
15779 Alpha- and MIPS-based computers use an unusual stack frame, which
15780 sometimes requires @value{GDBN} to search backward in the object code to
15781 find the beginning of a function.
15783 @cindex response time, MIPS debugging
15784 To improve response time (especially for embedded applications, where
15785 @value{GDBN} may be restricted to a slow serial line for this search)
15786 you may want to limit the size of this search, using one of these
15790 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15791 @item set heuristic-fence-post @var{limit}
15792 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15793 search for the beginning of a function. A value of @var{0} (the
15794 default) means there is no limit. However, except for @var{0}, the
15795 larger the limit the more bytes @code{heuristic-fence-post} must search
15796 and therefore the longer it takes to run. You should only need to use
15797 this command when debugging a stripped executable.
15799 @item show heuristic-fence-post
15800 Display the current limit.
15804 These commands are available @emph{only} when @value{GDBN} is configured
15805 for debugging programs on Alpha or MIPS processors.
15807 Several MIPS-specific commands are available when debugging MIPS
15811 @item set mips abi @var{arg}
15812 @kindex set mips abi
15813 @cindex set ABI for MIPS
15814 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15815 values of @var{arg} are:
15819 The default ABI associated with the current binary (this is the
15830 @item show mips abi
15831 @kindex show mips abi
15832 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15835 @itemx show mipsfpu
15836 @xref{MIPS Embedded, set mipsfpu}.
15838 @item set mips mask-address @var{arg}
15839 @kindex set mips mask-address
15840 @cindex MIPS addresses, masking
15841 This command determines whether the most-significant 32 bits of 64-bit
15842 MIPS addresses are masked off. The argument @var{arg} can be
15843 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15844 setting, which lets @value{GDBN} determine the correct value.
15846 @item show mips mask-address
15847 @kindex show mips mask-address
15848 Show whether the upper 32 bits of MIPS addresses are masked off or
15851 @item set remote-mips64-transfers-32bit-regs
15852 @kindex set remote-mips64-transfers-32bit-regs
15853 This command controls compatibility with 64-bit MIPS targets that
15854 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15855 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15856 and 64 bits for other registers, set this option to @samp{on}.
15858 @item show remote-mips64-transfers-32bit-regs
15859 @kindex show remote-mips64-transfers-32bit-regs
15860 Show the current setting of compatibility with older MIPS 64 targets.
15862 @item set debug mips
15863 @kindex set debug mips
15864 This command turns on and off debugging messages for the MIPS-specific
15865 target code in @value{GDBN}.
15867 @item show debug mips
15868 @kindex show debug mips
15869 Show the current setting of MIPS debugging messages.
15875 @cindex HPPA support
15877 When @value{GDBN} is debugging the HP PA architecture, it provides the
15878 following special commands:
15881 @item set debug hppa
15882 @kindex set debug hppa
15883 This command determines whether HPPA architecture-specific debugging
15884 messages are to be displayed.
15886 @item show debug hppa
15887 Show whether HPPA debugging messages are displayed.
15889 @item maint print unwind @var{address}
15890 @kindex maint print unwind@r{, HPPA}
15891 This command displays the contents of the unwind table entry at the
15892 given @var{address}.
15898 @subsection Cell Broadband Engine SPU architecture
15899 @cindex Cell Broadband Engine
15902 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
15903 it provides the following special commands:
15906 @item info spu event
15908 Display SPU event facility status. Shows current event mask
15909 and pending event status.
15911 @item info spu signal
15912 Display SPU signal notification facility status. Shows pending
15913 signal-control word and signal notification mode of both signal
15914 notification channels.
15916 @item info spu mailbox
15917 Display SPU mailbox facility status. Shows all pending entries,
15918 in order of processing, in each of the SPU Write Outbound,
15919 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
15922 Display MFC DMA status. Shows all pending commands in the MFC
15923 DMA queue. For each entry, opcode, tag, class IDs, effective
15924 and local store addresses and transfer size are shown.
15926 @item info spu proxydma
15927 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
15928 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
15929 and local store addresses and transfer size are shown.
15934 @subsection PowerPC
15935 @cindex PowerPC architecture
15937 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
15938 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
15939 numbers stored in the floating point registers. These values must be stored
15940 in two consecutive registers, always starting at an even register like
15941 @code{f0} or @code{f2}.
15943 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
15944 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
15945 @code{f2} and @code{f3} for @code{$dl1} and so on.
15948 @node Controlling GDB
15949 @chapter Controlling @value{GDBN}
15951 You can alter the way @value{GDBN} interacts with you by using the
15952 @code{set} command. For commands controlling how @value{GDBN} displays
15953 data, see @ref{Print Settings, ,Print Settings}. Other settings are
15958 * Editing:: Command editing
15959 * Command History:: Command history
15960 * Screen Size:: Screen size
15961 * Numbers:: Numbers
15962 * ABI:: Configuring the current ABI
15963 * Messages/Warnings:: Optional warnings and messages
15964 * Debugging Output:: Optional messages about internal happenings
15972 @value{GDBN} indicates its readiness to read a command by printing a string
15973 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15974 can change the prompt string with the @code{set prompt} command. For
15975 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15976 the prompt in one of the @value{GDBN} sessions so that you can always tell
15977 which one you are talking to.
15979 @emph{Note:} @code{set prompt} does not add a space for you after the
15980 prompt you set. This allows you to set a prompt which ends in a space
15981 or a prompt that does not.
15985 @item set prompt @var{newprompt}
15986 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15988 @kindex show prompt
15990 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15994 @section Command Editing
15996 @cindex command line editing
15998 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15999 @sc{gnu} library provides consistent behavior for programs which provide a
16000 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16001 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16002 substitution, and a storage and recall of command history across
16003 debugging sessions.
16005 You may control the behavior of command line editing in @value{GDBN} with the
16006 command @code{set}.
16009 @kindex set editing
16012 @itemx set editing on
16013 Enable command line editing (enabled by default).
16015 @item set editing off
16016 Disable command line editing.
16018 @kindex show editing
16020 Show whether command line editing is enabled.
16023 @xref{Command Line Editing}, for more details about the Readline
16024 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
16025 encouraged to read that chapter.
16027 @node Command History
16028 @section Command History
16029 @cindex command history
16031 @value{GDBN} can keep track of the commands you type during your
16032 debugging sessions, so that you can be certain of precisely what
16033 happened. Use these commands to manage the @value{GDBN} command
16036 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
16037 package, to provide the history facility. @xref{Using History
16038 Interactively}, for the detailed description of the History library.
16040 To issue a command to @value{GDBN} without affecting certain aspects of
16041 the state which is seen by users, prefix it with @samp{server }
16042 (@pxref{Server Prefix}). This
16043 means that this command will not affect the command history, nor will it
16044 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
16045 pressed on a line by itself.
16047 @cindex @code{server}, command prefix
16048 The server prefix does not affect the recording of values into the value
16049 history; to print a value without recording it into the value history,
16050 use the @code{output} command instead of the @code{print} command.
16052 Here is the description of @value{GDBN} commands related to command
16056 @cindex history substitution
16057 @cindex history file
16058 @kindex set history filename
16059 @cindex @env{GDBHISTFILE}, environment variable
16060 @item set history filename @var{fname}
16061 Set the name of the @value{GDBN} command history file to @var{fname}.
16062 This is the file where @value{GDBN} reads an initial command history
16063 list, and where it writes the command history from this session when it
16064 exits. You can access this list through history expansion or through
16065 the history command editing characters listed below. This file defaults
16066 to the value of the environment variable @code{GDBHISTFILE}, or to
16067 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16070 @cindex save command history
16071 @kindex set history save
16072 @item set history save
16073 @itemx set history save on
16074 Record command history in a file, whose name may be specified with the
16075 @code{set history filename} command. By default, this option is disabled.
16077 @item set history save off
16078 Stop recording command history in a file.
16080 @cindex history size
16081 @kindex set history size
16082 @cindex @env{HISTSIZE}, environment variable
16083 @item set history size @var{size}
16084 Set the number of commands which @value{GDBN} keeps in its history list.
16085 This defaults to the value of the environment variable
16086 @code{HISTSIZE}, or to 256 if this variable is not set.
16089 History expansion assigns special meaning to the character @kbd{!}.
16090 @xref{Event Designators}, for more details.
16092 @cindex history expansion, turn on/off
16093 Since @kbd{!} is also the logical not operator in C, history expansion
16094 is off by default. If you decide to enable history expansion with the
16095 @code{set history expansion on} command, you may sometimes need to
16096 follow @kbd{!} (when it is used as logical not, in an expression) with
16097 a space or a tab to prevent it from being expanded. The readline
16098 history facilities do not attempt substitution on the strings
16099 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
16101 The commands to control history expansion are:
16104 @item set history expansion on
16105 @itemx set history expansion
16106 @kindex set history expansion
16107 Enable history expansion. History expansion is off by default.
16109 @item set history expansion off
16110 Disable history expansion.
16113 @kindex show history
16115 @itemx show history filename
16116 @itemx show history save
16117 @itemx show history size
16118 @itemx show history expansion
16119 These commands display the state of the @value{GDBN} history parameters.
16120 @code{show history} by itself displays all four states.
16125 @kindex show commands
16126 @cindex show last commands
16127 @cindex display command history
16128 @item show commands
16129 Display the last ten commands in the command history.
16131 @item show commands @var{n}
16132 Print ten commands centered on command number @var{n}.
16134 @item show commands +
16135 Print ten commands just after the commands last printed.
16139 @section Screen Size
16140 @cindex size of screen
16141 @cindex pauses in output
16143 Certain commands to @value{GDBN} may produce large amounts of
16144 information output to the screen. To help you read all of it,
16145 @value{GDBN} pauses and asks you for input at the end of each page of
16146 output. Type @key{RET} when you want to continue the output, or @kbd{q}
16147 to discard the remaining output. Also, the screen width setting
16148 determines when to wrap lines of output. Depending on what is being
16149 printed, @value{GDBN} tries to break the line at a readable place,
16150 rather than simply letting it overflow onto the following line.
16152 Normally @value{GDBN} knows the size of the screen from the terminal
16153 driver software. For example, on Unix @value{GDBN} uses the termcap data base
16154 together with the value of the @code{TERM} environment variable and the
16155 @code{stty rows} and @code{stty cols} settings. If this is not correct,
16156 you can override it with the @code{set height} and @code{set
16163 @kindex show height
16164 @item set height @var{lpp}
16166 @itemx set width @var{cpl}
16168 These @code{set} commands specify a screen height of @var{lpp} lines and
16169 a screen width of @var{cpl} characters. The associated @code{show}
16170 commands display the current settings.
16172 If you specify a height of zero lines, @value{GDBN} does not pause during
16173 output no matter how long the output is. This is useful if output is to a
16174 file or to an editor buffer.
16176 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
16177 from wrapping its output.
16179 @item set pagination on
16180 @itemx set pagination off
16181 @kindex set pagination
16182 Turn the output pagination on or off; the default is on. Turning
16183 pagination off is the alternative to @code{set height 0}.
16185 @item show pagination
16186 @kindex show pagination
16187 Show the current pagination mode.
16192 @cindex number representation
16193 @cindex entering numbers
16195 You can always enter numbers in octal, decimal, or hexadecimal in
16196 @value{GDBN} by the usual conventions: octal numbers begin with
16197 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
16198 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
16199 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
16200 10; likewise, the default display for numbers---when no particular
16201 format is specified---is base 10. You can change the default base for
16202 both input and output with the commands described below.
16205 @kindex set input-radix
16206 @item set input-radix @var{base}
16207 Set the default base for numeric input. Supported choices
16208 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16209 specified either unambiguously or using the current input radix; for
16213 set input-radix 012
16214 set input-radix 10.
16215 set input-radix 0xa
16219 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
16220 leaves the input radix unchanged, no matter what it was, since
16221 @samp{10}, being without any leading or trailing signs of its base, is
16222 interpreted in the current radix. Thus, if the current radix is 16,
16223 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
16226 @kindex set output-radix
16227 @item set output-radix @var{base}
16228 Set the default base for numeric display. Supported choices
16229 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16230 specified either unambiguously or using the current input radix.
16232 @kindex show input-radix
16233 @item show input-radix
16234 Display the current default base for numeric input.
16236 @kindex show output-radix
16237 @item show output-radix
16238 Display the current default base for numeric display.
16240 @item set radix @r{[}@var{base}@r{]}
16244 These commands set and show the default base for both input and output
16245 of numbers. @code{set radix} sets the radix of input and output to
16246 the same base; without an argument, it resets the radix back to its
16247 default value of 10.
16252 @section Configuring the Current ABI
16254 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
16255 application automatically. However, sometimes you need to override its
16256 conclusions. Use these commands to manage @value{GDBN}'s view of the
16263 One @value{GDBN} configuration can debug binaries for multiple operating
16264 system targets, either via remote debugging or native emulation.
16265 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
16266 but you can override its conclusion using the @code{set osabi} command.
16267 One example where this is useful is in debugging of binaries which use
16268 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16269 not have the same identifying marks that the standard C library for your
16274 Show the OS ABI currently in use.
16277 With no argument, show the list of registered available OS ABI's.
16279 @item set osabi @var{abi}
16280 Set the current OS ABI to @var{abi}.
16283 @cindex float promotion
16285 Generally, the way that an argument of type @code{float} is passed to a
16286 function depends on whether the function is prototyped. For a prototyped
16287 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16288 according to the architecture's convention for @code{float}. For unprototyped
16289 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16290 @code{double} and then passed.
16292 Unfortunately, some forms of debug information do not reliably indicate whether
16293 a function is prototyped. If @value{GDBN} calls a function that is not marked
16294 as prototyped, it consults @kbd{set coerce-float-to-double}.
16297 @kindex set coerce-float-to-double
16298 @item set coerce-float-to-double
16299 @itemx set coerce-float-to-double on
16300 Arguments of type @code{float} will be promoted to @code{double} when passed
16301 to an unprototyped function. This is the default setting.
16303 @item set coerce-float-to-double off
16304 Arguments of type @code{float} will be passed directly to unprototyped
16307 @kindex show coerce-float-to-double
16308 @item show coerce-float-to-double
16309 Show the current setting of promoting @code{float} to @code{double}.
16313 @kindex show cp-abi
16314 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16315 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16316 used to build your application. @value{GDBN} only fully supports
16317 programs with a single C@t{++} ABI; if your program contains code using
16318 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16319 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16320 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16321 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16322 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16323 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16328 Show the C@t{++} ABI currently in use.
16331 With no argument, show the list of supported C@t{++} ABI's.
16333 @item set cp-abi @var{abi}
16334 @itemx set cp-abi auto
16335 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16338 @node Messages/Warnings
16339 @section Optional Warnings and Messages
16341 @cindex verbose operation
16342 @cindex optional warnings
16343 By default, @value{GDBN} is silent about its inner workings. If you are
16344 running on a slow machine, you may want to use the @code{set verbose}
16345 command. This makes @value{GDBN} tell you when it does a lengthy
16346 internal operation, so you will not think it has crashed.
16348 Currently, the messages controlled by @code{set verbose} are those
16349 which announce that the symbol table for a source file is being read;
16350 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16353 @kindex set verbose
16354 @item set verbose on
16355 Enables @value{GDBN} output of certain informational messages.
16357 @item set verbose off
16358 Disables @value{GDBN} output of certain informational messages.
16360 @kindex show verbose
16362 Displays whether @code{set verbose} is on or off.
16365 By default, if @value{GDBN} encounters bugs in the symbol table of an
16366 object file, it is silent; but if you are debugging a compiler, you may
16367 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16372 @kindex set complaints
16373 @item set complaints @var{limit}
16374 Permits @value{GDBN} to output @var{limit} complaints about each type of
16375 unusual symbols before becoming silent about the problem. Set
16376 @var{limit} to zero to suppress all complaints; set it to a large number
16377 to prevent complaints from being suppressed.
16379 @kindex show complaints
16380 @item show complaints
16381 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16385 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16386 lot of stupid questions to confirm certain commands. For example, if
16387 you try to run a program which is already running:
16391 The program being debugged has been started already.
16392 Start it from the beginning? (y or n)
16395 If you are willing to unflinchingly face the consequences of your own
16396 commands, you can disable this ``feature'':
16400 @kindex set confirm
16402 @cindex confirmation
16403 @cindex stupid questions
16404 @item set confirm off
16405 Disables confirmation requests.
16407 @item set confirm on
16408 Enables confirmation requests (the default).
16410 @kindex show confirm
16412 Displays state of confirmation requests.
16416 @cindex command tracing
16417 If you need to debug user-defined commands or sourced files you may find it
16418 useful to enable @dfn{command tracing}. In this mode each command will be
16419 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16420 quantity denoting the call depth of each command.
16423 @kindex set trace-commands
16424 @cindex command scripts, debugging
16425 @item set trace-commands on
16426 Enable command tracing.
16427 @item set trace-commands off
16428 Disable command tracing.
16429 @item show trace-commands
16430 Display the current state of command tracing.
16433 @node Debugging Output
16434 @section Optional Messages about Internal Happenings
16435 @cindex optional debugging messages
16437 @value{GDBN} has commands that enable optional debugging messages from
16438 various @value{GDBN} subsystems; normally these commands are of
16439 interest to @value{GDBN} maintainers, or when reporting a bug. This
16440 section documents those commands.
16443 @kindex set exec-done-display
16444 @item set exec-done-display
16445 Turns on or off the notification of asynchronous commands'
16446 completion. When on, @value{GDBN} will print a message when an
16447 asynchronous command finishes its execution. The default is off.
16448 @kindex show exec-done-display
16449 @item show exec-done-display
16450 Displays the current setting of asynchronous command completion
16453 @cindex gdbarch debugging info
16454 @cindex architecture debugging info
16455 @item set debug arch
16456 Turns on or off display of gdbarch debugging info. The default is off
16458 @item show debug arch
16459 Displays the current state of displaying gdbarch debugging info.
16460 @item set debug aix-thread
16461 @cindex AIX threads
16462 Display debugging messages about inner workings of the AIX thread
16464 @item show debug aix-thread
16465 Show the current state of AIX thread debugging info display.
16466 @item set debug event
16467 @cindex event debugging info
16468 Turns on or off display of @value{GDBN} event debugging info. The
16470 @item show debug event
16471 Displays the current state of displaying @value{GDBN} event debugging
16473 @item set debug expression
16474 @cindex expression debugging info
16475 Turns on or off display of debugging info about @value{GDBN}
16476 expression parsing. The default is off.
16477 @item show debug expression
16478 Displays the current state of displaying debugging info about
16479 @value{GDBN} expression parsing.
16480 @item set debug frame
16481 @cindex frame debugging info
16482 Turns on or off display of @value{GDBN} frame debugging info. The
16484 @item show debug frame
16485 Displays the current state of displaying @value{GDBN} frame debugging
16487 @item set debug infrun
16488 @cindex inferior debugging info
16489 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16490 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16491 for implementing operations such as single-stepping the inferior.
16492 @item show debug infrun
16493 Displays the current state of @value{GDBN} inferior debugging.
16494 @item set debug lin-lwp
16495 @cindex @sc{gnu}/Linux LWP debug messages
16496 @cindex Linux lightweight processes
16497 Turns on or off debugging messages from the Linux LWP debug support.
16498 @item show debug lin-lwp
16499 Show the current state of Linux LWP debugging messages.
16500 @item set debug lin-lwp-async
16501 @cindex @sc{gnu}/Linux LWP async debug messages
16502 @cindex Linux lightweight processes
16503 Turns on or off debugging messages from the Linux LWP async debug support.
16504 @item show debug lin-lwp-async
16505 Show the current state of Linux LWP async debugging messages.
16506 @item set debug observer
16507 @cindex observer debugging info
16508 Turns on or off display of @value{GDBN} observer debugging. This
16509 includes info such as the notification of observable events.
16510 @item show debug observer
16511 Displays the current state of observer debugging.
16512 @item set debug overload
16513 @cindex C@t{++} overload debugging info
16514 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16515 info. This includes info such as ranking of functions, etc. The default
16517 @item show debug overload
16518 Displays the current state of displaying @value{GDBN} C@t{++} overload
16520 @cindex packets, reporting on stdout
16521 @cindex serial connections, debugging
16522 @cindex debug remote protocol
16523 @cindex remote protocol debugging
16524 @cindex display remote packets
16525 @item set debug remote
16526 Turns on or off display of reports on all packets sent back and forth across
16527 the serial line to the remote machine. The info is printed on the
16528 @value{GDBN} standard output stream. The default is off.
16529 @item show debug remote
16530 Displays the state of display of remote packets.
16531 @item set debug serial
16532 Turns on or off display of @value{GDBN} serial debugging info. The
16534 @item show debug serial
16535 Displays the current state of displaying @value{GDBN} serial debugging
16537 @item set debug solib-frv
16538 @cindex FR-V shared-library debugging
16539 Turns on or off debugging messages for FR-V shared-library code.
16540 @item show debug solib-frv
16541 Display the current state of FR-V shared-library code debugging
16543 @item set debug target
16544 @cindex target debugging info
16545 Turns on or off display of @value{GDBN} target debugging info. This info
16546 includes what is going on at the target level of GDB, as it happens. The
16547 default is 0. Set it to 1 to track events, and to 2 to also track the
16548 value of large memory transfers. Changes to this flag do not take effect
16549 until the next time you connect to a target or use the @code{run} command.
16550 @item show debug target
16551 Displays the current state of displaying @value{GDBN} target debugging
16553 @item set debug timestamp
16554 @cindex timestampping debugging info
16555 Turns on or off display of timestamps with @value{GDBN} debugging info.
16556 When enabled, seconds and microseconds are displayed before each debugging
16558 @item show debug timestamp
16559 Displays the current state of displaying timestamps with @value{GDBN}
16561 @item set debugvarobj
16562 @cindex variable object debugging info
16563 Turns on or off display of @value{GDBN} variable object debugging
16564 info. The default is off.
16565 @item show debugvarobj
16566 Displays the current state of displaying @value{GDBN} variable object
16568 @item set debug xml
16569 @cindex XML parser debugging
16570 Turns on or off debugging messages for built-in XML parsers.
16571 @item show debug xml
16572 Displays the current state of XML debugging messages.
16576 @chapter Canned Sequences of Commands
16578 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16579 Command Lists}), @value{GDBN} provides two ways to store sequences of
16580 commands for execution as a unit: user-defined commands and command
16584 * Define:: How to define your own commands
16585 * Hooks:: Hooks for user-defined commands
16586 * Command Files:: How to write scripts of commands to be stored in a file
16587 * Output:: Commands for controlled output
16591 @section User-defined Commands
16593 @cindex user-defined command
16594 @cindex arguments, to user-defined commands
16595 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16596 which you assign a new name as a command. This is done with the
16597 @code{define} command. User commands may accept up to 10 arguments
16598 separated by whitespace. Arguments are accessed within the user command
16599 via @code{$arg0@dots{}$arg9}. A trivial example:
16603 print $arg0 + $arg1 + $arg2
16608 To execute the command use:
16615 This defines the command @code{adder}, which prints the sum of
16616 its three arguments. Note the arguments are text substitutions, so they may
16617 reference variables, use complex expressions, or even perform inferior
16620 @cindex argument count in user-defined commands
16621 @cindex how many arguments (user-defined commands)
16622 In addition, @code{$argc} may be used to find out how many arguments have
16623 been passed. This expands to a number in the range 0@dots{}10.
16628 print $arg0 + $arg1
16631 print $arg0 + $arg1 + $arg2
16639 @item define @var{commandname}
16640 Define a command named @var{commandname}. If there is already a command
16641 by that name, you are asked to confirm that you want to redefine it.
16643 The definition of the command is made up of other @value{GDBN} command lines,
16644 which are given following the @code{define} command. The end of these
16645 commands is marked by a line containing @code{end}.
16648 @kindex end@r{ (user-defined commands)}
16649 @item document @var{commandname}
16650 Document the user-defined command @var{commandname}, so that it can be
16651 accessed by @code{help}. The command @var{commandname} must already be
16652 defined. This command reads lines of documentation just as @code{define}
16653 reads the lines of the command definition, ending with @code{end}.
16654 After the @code{document} command is finished, @code{help} on command
16655 @var{commandname} displays the documentation you have written.
16657 You may use the @code{document} command again to change the
16658 documentation of a command. Redefining the command with @code{define}
16659 does not change the documentation.
16661 @kindex dont-repeat
16662 @cindex don't repeat command
16664 Used inside a user-defined command, this tells @value{GDBN} that this
16665 command should not be repeated when the user hits @key{RET}
16666 (@pxref{Command Syntax, repeat last command}).
16668 @kindex help user-defined
16669 @item help user-defined
16670 List all user-defined commands, with the first line of the documentation
16675 @itemx show user @var{commandname}
16676 Display the @value{GDBN} commands used to define @var{commandname} (but
16677 not its documentation). If no @var{commandname} is given, display the
16678 definitions for all user-defined commands.
16680 @cindex infinite recursion in user-defined commands
16681 @kindex show max-user-call-depth
16682 @kindex set max-user-call-depth
16683 @item show max-user-call-depth
16684 @itemx set max-user-call-depth
16685 The value of @code{max-user-call-depth} controls how many recursion
16686 levels are allowed in user-defined commands before @value{GDBN} suspects an
16687 infinite recursion and aborts the command.
16690 In addition to the above commands, user-defined commands frequently
16691 use control flow commands, described in @ref{Command Files}.
16693 When user-defined commands are executed, the
16694 commands of the definition are not printed. An error in any command
16695 stops execution of the user-defined command.
16697 If used interactively, commands that would ask for confirmation proceed
16698 without asking when used inside a user-defined command. Many @value{GDBN}
16699 commands that normally print messages to say what they are doing omit the
16700 messages when used in a user-defined command.
16703 @section User-defined Command Hooks
16704 @cindex command hooks
16705 @cindex hooks, for commands
16706 @cindex hooks, pre-command
16709 You may define @dfn{hooks}, which are a special kind of user-defined
16710 command. Whenever you run the command @samp{foo}, if the user-defined
16711 command @samp{hook-foo} exists, it is executed (with no arguments)
16712 before that command.
16714 @cindex hooks, post-command
16716 A hook may also be defined which is run after the command you executed.
16717 Whenever you run the command @samp{foo}, if the user-defined command
16718 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16719 that command. Post-execution hooks may exist simultaneously with
16720 pre-execution hooks, for the same command.
16722 It is valid for a hook to call the command which it hooks. If this
16723 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16725 @c It would be nice if hookpost could be passed a parameter indicating
16726 @c if the command it hooks executed properly or not. FIXME!
16728 @kindex stop@r{, a pseudo-command}
16729 In addition, a pseudo-command, @samp{stop} exists. Defining
16730 (@samp{hook-stop}) makes the associated commands execute every time
16731 execution stops in your program: before breakpoint commands are run,
16732 displays are printed, or the stack frame is printed.
16734 For example, to ignore @code{SIGALRM} signals while
16735 single-stepping, but treat them normally during normal execution,
16740 handle SIGALRM nopass
16744 handle SIGALRM pass
16747 define hook-continue
16748 handle SIGALRM pass
16752 As a further example, to hook at the beginning and end of the @code{echo}
16753 command, and to add extra text to the beginning and end of the message,
16761 define hookpost-echo
16765 (@value{GDBP}) echo Hello World
16766 <<<---Hello World--->>>
16771 You can define a hook for any single-word command in @value{GDBN}, but
16772 not for command aliases; you should define a hook for the basic command
16773 name, e.g.@: @code{backtrace} rather than @code{bt}.
16774 @c FIXME! So how does Joe User discover whether a command is an alias
16776 If an error occurs during the execution of your hook, execution of
16777 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16778 (before the command that you actually typed had a chance to run).
16780 If you try to define a hook which does not match any known command, you
16781 get a warning from the @code{define} command.
16783 @node Command Files
16784 @section Command Files
16786 @cindex command files
16787 @cindex scripting commands
16788 A command file for @value{GDBN} is a text file made of lines that are
16789 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16790 also be included. An empty line in a command file does nothing; it
16791 does not mean to repeat the last command, as it would from the
16794 You can request the execution of a command file with the @code{source}
16799 @cindex execute commands from a file
16800 @item source [@code{-v}] @var{filename}
16801 Execute the command file @var{filename}.
16804 The lines in a command file are generally executed sequentially,
16805 unless the order of execution is changed by one of the
16806 @emph{flow-control commands} described below. The commands are not
16807 printed as they are executed. An error in any command terminates
16808 execution of the command file and control is returned to the console.
16810 @value{GDBN} searches for @var{filename} in the current directory and then
16811 on the search path (specified with the @samp{directory} command).
16813 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16814 each command as it is executed. The option must be given before
16815 @var{filename}, and is interpreted as part of the filename anywhere else.
16817 Commands that would ask for confirmation if used interactively proceed
16818 without asking when used in a command file. Many @value{GDBN} commands that
16819 normally print messages to say what they are doing omit the messages
16820 when called from command files.
16822 @value{GDBN} also accepts command input from standard input. In this
16823 mode, normal output goes to standard output and error output goes to
16824 standard error. Errors in a command file supplied on standard input do
16825 not terminate execution of the command file---execution continues with
16829 gdb < cmds > log 2>&1
16832 (The syntax above will vary depending on the shell used.) This example
16833 will execute commands from the file @file{cmds}. All output and errors
16834 would be directed to @file{log}.
16836 Since commands stored on command files tend to be more general than
16837 commands typed interactively, they frequently need to deal with
16838 complicated situations, such as different or unexpected values of
16839 variables and symbols, changes in how the program being debugged is
16840 built, etc. @value{GDBN} provides a set of flow-control commands to
16841 deal with these complexities. Using these commands, you can write
16842 complex scripts that loop over data structures, execute commands
16843 conditionally, etc.
16850 This command allows to include in your script conditionally executed
16851 commands. The @code{if} command takes a single argument, which is an
16852 expression to evaluate. It is followed by a series of commands that
16853 are executed only if the expression is true (its value is nonzero).
16854 There can then optionally be an @code{else} line, followed by a series
16855 of commands that are only executed if the expression was false. The
16856 end of the list is marked by a line containing @code{end}.
16860 This command allows to write loops. Its syntax is similar to
16861 @code{if}: the command takes a single argument, which is an expression
16862 to evaluate, and must be followed by the commands to execute, one per
16863 line, terminated by an @code{end}. These commands are called the
16864 @dfn{body} of the loop. The commands in the body of @code{while} are
16865 executed repeatedly as long as the expression evaluates to true.
16869 This command exits the @code{while} loop in whose body it is included.
16870 Execution of the script continues after that @code{while}s @code{end}
16873 @kindex loop_continue
16874 @item loop_continue
16875 This command skips the execution of the rest of the body of commands
16876 in the @code{while} loop in whose body it is included. Execution
16877 branches to the beginning of the @code{while} loop, where it evaluates
16878 the controlling expression.
16880 @kindex end@r{ (if/else/while commands)}
16882 Terminate the block of commands that are the body of @code{if},
16883 @code{else}, or @code{while} flow-control commands.
16888 @section Commands for Controlled Output
16890 During the execution of a command file or a user-defined command, normal
16891 @value{GDBN} output is suppressed; the only output that appears is what is
16892 explicitly printed by the commands in the definition. This section
16893 describes three commands useful for generating exactly the output you
16898 @item echo @var{text}
16899 @c I do not consider backslash-space a standard C escape sequence
16900 @c because it is not in ANSI.
16901 Print @var{text}. Nonprinting characters can be included in
16902 @var{text} using C escape sequences, such as @samp{\n} to print a
16903 newline. @strong{No newline is printed unless you specify one.}
16904 In addition to the standard C escape sequences, a backslash followed
16905 by a space stands for a space. This is useful for displaying a
16906 string with spaces at the beginning or the end, since leading and
16907 trailing spaces are otherwise trimmed from all arguments.
16908 To print @samp{@w{ }and foo =@w{ }}, use the command
16909 @samp{echo \@w{ }and foo = \@w{ }}.
16911 A backslash at the end of @var{text} can be used, as in C, to continue
16912 the command onto subsequent lines. For example,
16915 echo This is some text\n\
16916 which is continued\n\
16917 onto several lines.\n
16920 produces the same output as
16923 echo This is some text\n
16924 echo which is continued\n
16925 echo onto several lines.\n
16929 @item output @var{expression}
16930 Print the value of @var{expression} and nothing but that value: no
16931 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16932 value history either. @xref{Expressions, ,Expressions}, for more information
16935 @item output/@var{fmt} @var{expression}
16936 Print the value of @var{expression} in format @var{fmt}. You can use
16937 the same formats as for @code{print}. @xref{Output Formats,,Output
16938 Formats}, for more information.
16941 @item printf @var{template}, @var{expressions}@dots{}
16942 Print the values of one or more @var{expressions} under the control of
16943 the string @var{template}. To print several values, make
16944 @var{expressions} be a comma-separated list of individual expressions,
16945 which may be either numbers or pointers. Their values are printed as
16946 specified by @var{template}, exactly as a C program would do by
16947 executing the code below:
16950 printf (@var{template}, @var{expressions}@dots{});
16953 As in @code{C} @code{printf}, ordinary characters in @var{template}
16954 are printed verbatim, while @dfn{conversion specification} introduced
16955 by the @samp{%} character cause subsequent @var{expressions} to be
16956 evaluated, their values converted and formatted according to type and
16957 style information encoded in the conversion specifications, and then
16960 For example, you can print two values in hex like this:
16963 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16966 @code{printf} supports all the standard @code{C} conversion
16967 specifications, including the flags and modifiers between the @samp{%}
16968 character and the conversion letter, with the following exceptions:
16972 The argument-ordering modifiers, such as @samp{2$}, are not supported.
16975 The modifier @samp{*} is not supported for specifying precision or
16979 The @samp{'} flag (for separation of digits into groups according to
16980 @code{LC_NUMERIC'}) is not supported.
16983 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
16987 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
16990 The conversion letters @samp{a} and @samp{A} are not supported.
16994 Note that the @samp{ll} type modifier is supported only if the
16995 underlying @code{C} implementation used to build @value{GDBN} supports
16996 the @code{long long int} type, and the @samp{L} type modifier is
16997 supported only if @code{long double} type is available.
16999 As in @code{C}, @code{printf} supports simple backslash-escape
17000 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
17001 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
17002 single character. Octal and hexadecimal escape sequences are not
17005 Additionally, @code{printf} supports conversion specifications for DFP
17006 (@dfn{Decimal Floating Point}) types using the following length modifiers
17007 together with a floating point specifier.
17012 @samp{H} for printing @code{Decimal32} types.
17015 @samp{D} for printing @code{Decimal64} types.
17018 @samp{DD} for printing @code{Decimal128} types.
17021 If the underlying @code{C} implementation used to build @value{GDBN} has
17022 support for the three length modifiers for DFP types, other modifiers
17023 such as width and precision will also be available for @value{GDBN} to use.
17025 In case there is no such @code{C} support, no additional modifiers will be
17026 available and the value will be printed in the standard way.
17028 Here's an example of printing DFP types using the above conversion letters:
17030 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
17036 @chapter Command Interpreters
17037 @cindex command interpreters
17039 @value{GDBN} supports multiple command interpreters, and some command
17040 infrastructure to allow users or user interface writers to switch
17041 between interpreters or run commands in other interpreters.
17043 @value{GDBN} currently supports two command interpreters, the console
17044 interpreter (sometimes called the command-line interpreter or @sc{cli})
17045 and the machine interface interpreter (or @sc{gdb/mi}). This manual
17046 describes both of these interfaces in great detail.
17048 By default, @value{GDBN} will start with the console interpreter.
17049 However, the user may choose to start @value{GDBN} with another
17050 interpreter by specifying the @option{-i} or @option{--interpreter}
17051 startup options. Defined interpreters include:
17055 @cindex console interpreter
17056 The traditional console or command-line interpreter. This is the most often
17057 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
17058 @value{GDBN} will use this interpreter.
17061 @cindex mi interpreter
17062 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
17063 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
17064 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
17068 @cindex mi2 interpreter
17069 The current @sc{gdb/mi} interface.
17072 @cindex mi1 interpreter
17073 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
17077 @cindex invoke another interpreter
17078 The interpreter being used by @value{GDBN} may not be dynamically
17079 switched at runtime. Although possible, this could lead to a very
17080 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
17081 enters the command "interpreter-set console" in a console view,
17082 @value{GDBN} would switch to using the console interpreter, rendering
17083 the IDE inoperable!
17085 @kindex interpreter-exec
17086 Although you may only choose a single interpreter at startup, you may execute
17087 commands in any interpreter from the current interpreter using the appropriate
17088 command. If you are running the console interpreter, simply use the
17089 @code{interpreter-exec} command:
17092 interpreter-exec mi "-data-list-register-names"
17095 @sc{gdb/mi} has a similar command, although it is only available in versions of
17096 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
17099 @chapter @value{GDBN} Text User Interface
17101 @cindex Text User Interface
17104 * TUI Overview:: TUI overview
17105 * TUI Keys:: TUI key bindings
17106 * TUI Single Key Mode:: TUI single key mode
17107 * TUI Commands:: TUI-specific commands
17108 * TUI Configuration:: TUI configuration variables
17111 The @value{GDBN} Text User Interface (TUI) is a terminal
17112 interface which uses the @code{curses} library to show the source
17113 file, the assembly output, the program registers and @value{GDBN}
17114 commands in separate text windows. The TUI mode is supported only
17115 on platforms where a suitable version of the @code{curses} library
17118 @pindex @value{GDBTUI}
17119 The TUI mode is enabled by default when you invoke @value{GDBN} as
17120 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
17121 You can also switch in and out of TUI mode while @value{GDBN} runs by
17122 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
17123 @xref{TUI Keys, ,TUI Key Bindings}.
17126 @section TUI Overview
17128 In TUI mode, @value{GDBN} can display several text windows:
17132 This window is the @value{GDBN} command window with the @value{GDBN}
17133 prompt and the @value{GDBN} output. The @value{GDBN} input is still
17134 managed using readline.
17137 The source window shows the source file of the program. The current
17138 line and active breakpoints are displayed in this window.
17141 The assembly window shows the disassembly output of the program.
17144 This window shows the processor registers. Registers are highlighted
17145 when their values change.
17148 The source and assembly windows show the current program position
17149 by highlighting the current line and marking it with a @samp{>} marker.
17150 Breakpoints are indicated with two markers. The first marker
17151 indicates the breakpoint type:
17155 Breakpoint which was hit at least once.
17158 Breakpoint which was never hit.
17161 Hardware breakpoint which was hit at least once.
17164 Hardware breakpoint which was never hit.
17167 The second marker indicates whether the breakpoint is enabled or not:
17171 Breakpoint is enabled.
17174 Breakpoint is disabled.
17177 The source, assembly and register windows are updated when the current
17178 thread changes, when the frame changes, or when the program counter
17181 These windows are not all visible at the same time. The command
17182 window is always visible. The others can be arranged in several
17193 source and assembly,
17196 source and registers, or
17199 assembly and registers.
17202 A status line above the command window shows the following information:
17206 Indicates the current @value{GDBN} target.
17207 (@pxref{Targets, ,Specifying a Debugging Target}).
17210 Gives the current process or thread number.
17211 When no process is being debugged, this field is set to @code{No process}.
17214 Gives the current function name for the selected frame.
17215 The name is demangled if demangling is turned on (@pxref{Print Settings}).
17216 When there is no symbol corresponding to the current program counter,
17217 the string @code{??} is displayed.
17220 Indicates the current line number for the selected frame.
17221 When the current line number is not known, the string @code{??} is displayed.
17224 Indicates the current program counter address.
17228 @section TUI Key Bindings
17229 @cindex TUI key bindings
17231 The TUI installs several key bindings in the readline keymaps
17232 (@pxref{Command Line Editing}). The following key bindings
17233 are installed for both TUI mode and the @value{GDBN} standard mode.
17242 Enter or leave the TUI mode. When leaving the TUI mode,
17243 the curses window management stops and @value{GDBN} operates using
17244 its standard mode, writing on the terminal directly. When reentering
17245 the TUI mode, control is given back to the curses windows.
17246 The screen is then refreshed.
17250 Use a TUI layout with only one window. The layout will
17251 either be @samp{source} or @samp{assembly}. When the TUI mode
17252 is not active, it will switch to the TUI mode.
17254 Think of this key binding as the Emacs @kbd{C-x 1} binding.
17258 Use a TUI layout with at least two windows. When the current
17259 layout already has two windows, the next layout with two windows is used.
17260 When a new layout is chosen, one window will always be common to the
17261 previous layout and the new one.
17263 Think of it as the Emacs @kbd{C-x 2} binding.
17267 Change the active window. The TUI associates several key bindings
17268 (like scrolling and arrow keys) with the active window. This command
17269 gives the focus to the next TUI window.
17271 Think of it as the Emacs @kbd{C-x o} binding.
17275 Switch in and out of the TUI SingleKey mode that binds single
17276 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
17279 The following key bindings only work in the TUI mode:
17284 Scroll the active window one page up.
17288 Scroll the active window one page down.
17292 Scroll the active window one line up.
17296 Scroll the active window one line down.
17300 Scroll the active window one column left.
17304 Scroll the active window one column right.
17308 Refresh the screen.
17311 Because the arrow keys scroll the active window in the TUI mode, they
17312 are not available for their normal use by readline unless the command
17313 window has the focus. When another window is active, you must use
17314 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
17315 and @kbd{C-f} to control the command window.
17317 @node TUI Single Key Mode
17318 @section TUI Single Key Mode
17319 @cindex TUI single key mode
17321 The TUI also provides a @dfn{SingleKey} mode, which binds several
17322 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
17323 switch into this mode, where the following key bindings are used:
17326 @kindex c @r{(SingleKey TUI key)}
17330 @kindex d @r{(SingleKey TUI key)}
17334 @kindex f @r{(SingleKey TUI key)}
17338 @kindex n @r{(SingleKey TUI key)}
17342 @kindex q @r{(SingleKey TUI key)}
17344 exit the SingleKey mode.
17346 @kindex r @r{(SingleKey TUI key)}
17350 @kindex s @r{(SingleKey TUI key)}
17354 @kindex u @r{(SingleKey TUI key)}
17358 @kindex v @r{(SingleKey TUI key)}
17362 @kindex w @r{(SingleKey TUI key)}
17367 Other keys temporarily switch to the @value{GDBN} command prompt.
17368 The key that was pressed is inserted in the editing buffer so that
17369 it is possible to type most @value{GDBN} commands without interaction
17370 with the TUI SingleKey mode. Once the command is entered the TUI
17371 SingleKey mode is restored. The only way to permanently leave
17372 this mode is by typing @kbd{q} or @kbd{C-x s}.
17376 @section TUI-specific Commands
17377 @cindex TUI commands
17379 The TUI has specific commands to control the text windows.
17380 These commands are always available, even when @value{GDBN} is not in
17381 the TUI mode. When @value{GDBN} is in the standard mode, most
17382 of these commands will automatically switch to the TUI mode.
17387 List and give the size of all displayed windows.
17391 Display the next layout.
17394 Display the previous layout.
17397 Display the source window only.
17400 Display the assembly window only.
17403 Display the source and assembly window.
17406 Display the register window together with the source or assembly window.
17410 Make the next window active for scrolling.
17413 Make the previous window active for scrolling.
17416 Make the source window active for scrolling.
17419 Make the assembly window active for scrolling.
17422 Make the register window active for scrolling.
17425 Make the command window active for scrolling.
17429 Refresh the screen. This is similar to typing @kbd{C-L}.
17431 @item tui reg float
17433 Show the floating point registers in the register window.
17435 @item tui reg general
17436 Show the general registers in the register window.
17439 Show the next register group. The list of register groups as well as
17440 their order is target specific. The predefined register groups are the
17441 following: @code{general}, @code{float}, @code{system}, @code{vector},
17442 @code{all}, @code{save}, @code{restore}.
17444 @item tui reg system
17445 Show the system registers in the register window.
17449 Update the source window and the current execution point.
17451 @item winheight @var{name} +@var{count}
17452 @itemx winheight @var{name} -@var{count}
17454 Change the height of the window @var{name} by @var{count}
17455 lines. Positive counts increase the height, while negative counts
17458 @item tabset @var{nchars}
17460 Set the width of tab stops to be @var{nchars} characters.
17463 @node TUI Configuration
17464 @section TUI Configuration Variables
17465 @cindex TUI configuration variables
17467 Several configuration variables control the appearance of TUI windows.
17470 @item set tui border-kind @var{kind}
17471 @kindex set tui border-kind
17472 Select the border appearance for the source, assembly and register windows.
17473 The possible values are the following:
17476 Use a space character to draw the border.
17479 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
17482 Use the Alternate Character Set to draw the border. The border is
17483 drawn using character line graphics if the terminal supports them.
17486 @item set tui border-mode @var{mode}
17487 @kindex set tui border-mode
17488 @itemx set tui active-border-mode @var{mode}
17489 @kindex set tui active-border-mode
17490 Select the display attributes for the borders of the inactive windows
17491 or the active window. The @var{mode} can be one of the following:
17494 Use normal attributes to display the border.
17500 Use reverse video mode.
17503 Use half bright mode.
17505 @item half-standout
17506 Use half bright and standout mode.
17509 Use extra bright or bold mode.
17511 @item bold-standout
17512 Use extra bright or bold and standout mode.
17517 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17520 @cindex @sc{gnu} Emacs
17521 A special interface allows you to use @sc{gnu} Emacs to view (and
17522 edit) the source files for the program you are debugging with
17525 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17526 executable file you want to debug as an argument. This command starts
17527 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17528 created Emacs buffer.
17529 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17531 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17536 All ``terminal'' input and output goes through an Emacs buffer, called
17539 This applies both to @value{GDBN} commands and their output, and to the input
17540 and output done by the program you are debugging.
17542 This is useful because it means that you can copy the text of previous
17543 commands and input them again; you can even use parts of the output
17546 All the facilities of Emacs' Shell mode are available for interacting
17547 with your program. In particular, you can send signals the usual
17548 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17552 @value{GDBN} displays source code through Emacs.
17554 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17555 source file for that frame and puts an arrow (@samp{=>}) at the
17556 left margin of the current line. Emacs uses a separate buffer for
17557 source display, and splits the screen to show both your @value{GDBN} session
17560 Explicit @value{GDBN} @code{list} or search commands still produce output as
17561 usual, but you probably have no reason to use them from Emacs.
17564 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17565 a graphical mode, enabled by default, which provides further buffers
17566 that can control the execution and describe the state of your program.
17567 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17569 If you specify an absolute file name when prompted for the @kbd{M-x
17570 gdb} argument, then Emacs sets your current working directory to where
17571 your program resides. If you only specify the file name, then Emacs
17572 sets your current working directory to to the directory associated
17573 with the previous buffer. In this case, @value{GDBN} may find your
17574 program by searching your environment's @code{PATH} variable, but on
17575 some operating systems it might not find the source. So, although the
17576 @value{GDBN} input and output session proceeds normally, the auxiliary
17577 buffer does not display the current source and line of execution.
17579 The initial working directory of @value{GDBN} is printed on the top
17580 line of the GUD buffer and this serves as a default for the commands
17581 that specify files for @value{GDBN} to operate on. @xref{Files,
17582 ,Commands to Specify Files}.
17584 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17585 need to call @value{GDBN} by a different name (for example, if you
17586 keep several configurations around, with different names) you can
17587 customize the Emacs variable @code{gud-gdb-command-name} to run the
17590 In the GUD buffer, you can use these special Emacs commands in
17591 addition to the standard Shell mode commands:
17595 Describe the features of Emacs' GUD Mode.
17598 Execute to another source line, like the @value{GDBN} @code{step} command; also
17599 update the display window to show the current file and location.
17602 Execute to next source line in this function, skipping all function
17603 calls, like the @value{GDBN} @code{next} command. Then update the display window
17604 to show the current file and location.
17607 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17608 display window accordingly.
17611 Execute until exit from the selected stack frame, like the @value{GDBN}
17612 @code{finish} command.
17615 Continue execution of your program, like the @value{GDBN} @code{continue}
17619 Go up the number of frames indicated by the numeric argument
17620 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17621 like the @value{GDBN} @code{up} command.
17624 Go down the number of frames indicated by the numeric argument, like the
17625 @value{GDBN} @code{down} command.
17628 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17629 tells @value{GDBN} to set a breakpoint on the source line point is on.
17631 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17632 separate frame which shows a backtrace when the GUD buffer is current.
17633 Move point to any frame in the stack and type @key{RET} to make it
17634 become the current frame and display the associated source in the
17635 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17636 selected frame become the current one. In graphical mode, the
17637 speedbar displays watch expressions.
17639 If you accidentally delete the source-display buffer, an easy way to get
17640 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17641 request a frame display; when you run under Emacs, this recreates
17642 the source buffer if necessary to show you the context of the current
17645 The source files displayed in Emacs are in ordinary Emacs buffers
17646 which are visiting the source files in the usual way. You can edit
17647 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17648 communicates with Emacs in terms of line numbers. If you add or
17649 delete lines from the text, the line numbers that @value{GDBN} knows cease
17650 to correspond properly with the code.
17652 A more detailed description of Emacs' interaction with @value{GDBN} is
17653 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17656 @c The following dropped because Epoch is nonstandard. Reactivate
17657 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17659 @kindex Emacs Epoch environment
17663 Version 18 of @sc{gnu} Emacs has a built-in window system
17664 called the @code{epoch}
17665 environment. Users of this environment can use a new command,
17666 @code{inspect} which performs identically to @code{print} except that
17667 each value is printed in its own window.
17672 @chapter The @sc{gdb/mi} Interface
17674 @unnumberedsec Function and Purpose
17676 @cindex @sc{gdb/mi}, its purpose
17677 @sc{gdb/mi} is a line based machine oriented text interface to
17678 @value{GDBN} and is activated by specifying using the
17679 @option{--interpreter} command line option (@pxref{Mode Options}). It
17680 is specifically intended to support the development of systems which
17681 use the debugger as just one small component of a larger system.
17683 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17684 in the form of a reference manual.
17686 Note that @sc{gdb/mi} is still under construction, so some of the
17687 features described below are incomplete and subject to change
17688 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17690 @unnumberedsec Notation and Terminology
17692 @cindex notational conventions, for @sc{gdb/mi}
17693 This chapter uses the following notation:
17697 @code{|} separates two alternatives.
17700 @code{[ @var{something} ]} indicates that @var{something} is optional:
17701 it may or may not be given.
17704 @code{( @var{group} )*} means that @var{group} inside the parentheses
17705 may repeat zero or more times.
17708 @code{( @var{group} )+} means that @var{group} inside the parentheses
17709 may repeat one or more times.
17712 @code{"@var{string}"} means a literal @var{string}.
17716 @heading Dependencies
17720 * GDB/MI Command Syntax::
17721 * GDB/MI Compatibility with CLI::
17722 * GDB/MI Development and Front Ends::
17723 * GDB/MI Output Records::
17724 * GDB/MI Simple Examples::
17725 * GDB/MI Command Description Format::
17726 * GDB/MI Breakpoint Commands::
17727 * GDB/MI Program Context::
17728 * GDB/MI Thread Commands::
17729 * GDB/MI Program Execution::
17730 * GDB/MI Stack Manipulation::
17731 * GDB/MI Variable Objects::
17732 * GDB/MI Data Manipulation::
17733 * GDB/MI Tracepoint Commands::
17734 * GDB/MI Symbol Query::
17735 * GDB/MI File Commands::
17737 * GDB/MI Kod Commands::
17738 * GDB/MI Memory Overlay Commands::
17739 * GDB/MI Signal Handling Commands::
17741 * GDB/MI Target Manipulation::
17742 * GDB/MI File Transfer Commands::
17743 * GDB/MI Miscellaneous Commands::
17746 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17747 @node GDB/MI Command Syntax
17748 @section @sc{gdb/mi} Command Syntax
17751 * GDB/MI Input Syntax::
17752 * GDB/MI Output Syntax::
17755 @node GDB/MI Input Syntax
17756 @subsection @sc{gdb/mi} Input Syntax
17758 @cindex input syntax for @sc{gdb/mi}
17759 @cindex @sc{gdb/mi}, input syntax
17761 @item @var{command} @expansion{}
17762 @code{@var{cli-command} | @var{mi-command}}
17764 @item @var{cli-command} @expansion{}
17765 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17766 @var{cli-command} is any existing @value{GDBN} CLI command.
17768 @item @var{mi-command} @expansion{}
17769 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17770 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17772 @item @var{token} @expansion{}
17773 "any sequence of digits"
17775 @item @var{option} @expansion{}
17776 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17778 @item @var{parameter} @expansion{}
17779 @code{@var{non-blank-sequence} | @var{c-string}}
17781 @item @var{operation} @expansion{}
17782 @emph{any of the operations described in this chapter}
17784 @item @var{non-blank-sequence} @expansion{}
17785 @emph{anything, provided it doesn't contain special characters such as
17786 "-", @var{nl}, """ and of course " "}
17788 @item @var{c-string} @expansion{}
17789 @code{""" @var{seven-bit-iso-c-string-content} """}
17791 @item @var{nl} @expansion{}
17800 The CLI commands are still handled by the @sc{mi} interpreter; their
17801 output is described below.
17804 The @code{@var{token}}, when present, is passed back when the command
17808 Some @sc{mi} commands accept optional arguments as part of the parameter
17809 list. Each option is identified by a leading @samp{-} (dash) and may be
17810 followed by an optional argument parameter. Options occur first in the
17811 parameter list and can be delimited from normal parameters using
17812 @samp{--} (this is useful when some parameters begin with a dash).
17819 We want easy access to the existing CLI syntax (for debugging).
17822 We want it to be easy to spot a @sc{mi} operation.
17825 @node GDB/MI Output Syntax
17826 @subsection @sc{gdb/mi} Output Syntax
17828 @cindex output syntax of @sc{gdb/mi}
17829 @cindex @sc{gdb/mi}, output syntax
17830 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17831 followed, optionally, by a single result record. This result record
17832 is for the most recent command. The sequence of output records is
17833 terminated by @samp{(gdb)}.
17835 If an input command was prefixed with a @code{@var{token}} then the
17836 corresponding output for that command will also be prefixed by that same
17840 @item @var{output} @expansion{}
17841 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17843 @item @var{result-record} @expansion{}
17844 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17846 @item @var{out-of-band-record} @expansion{}
17847 @code{@var{async-record} | @var{stream-record}}
17849 @item @var{async-record} @expansion{}
17850 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17852 @item @var{exec-async-output} @expansion{}
17853 @code{[ @var{token} ] "*" @var{async-output}}
17855 @item @var{status-async-output} @expansion{}
17856 @code{[ @var{token} ] "+" @var{async-output}}
17858 @item @var{notify-async-output} @expansion{}
17859 @code{[ @var{token} ] "=" @var{async-output}}
17861 @item @var{async-output} @expansion{}
17862 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17864 @item @var{result-class} @expansion{}
17865 @code{"done" | "running" | "connected" | "error" | "exit"}
17867 @item @var{async-class} @expansion{}
17868 @code{"stopped" | @var{others}} (where @var{others} will be added
17869 depending on the needs---this is still in development).
17871 @item @var{result} @expansion{}
17872 @code{ @var{variable} "=" @var{value}}
17874 @item @var{variable} @expansion{}
17875 @code{ @var{string} }
17877 @item @var{value} @expansion{}
17878 @code{ @var{const} | @var{tuple} | @var{list} }
17880 @item @var{const} @expansion{}
17881 @code{@var{c-string}}
17883 @item @var{tuple} @expansion{}
17884 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17886 @item @var{list} @expansion{}
17887 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17888 @var{result} ( "," @var{result} )* "]" }
17890 @item @var{stream-record} @expansion{}
17891 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17893 @item @var{console-stream-output} @expansion{}
17894 @code{"~" @var{c-string}}
17896 @item @var{target-stream-output} @expansion{}
17897 @code{"@@" @var{c-string}}
17899 @item @var{log-stream-output} @expansion{}
17900 @code{"&" @var{c-string}}
17902 @item @var{nl} @expansion{}
17905 @item @var{token} @expansion{}
17906 @emph{any sequence of digits}.
17914 All output sequences end in a single line containing a period.
17917 The @code{@var{token}} is from the corresponding request. If an execution
17918 command is interrupted by the @samp{-exec-interrupt} command, the
17919 @var{token} associated with the @samp{*stopped} message is the one of the
17920 original execution command, not the one of the interrupt command.
17923 @cindex status output in @sc{gdb/mi}
17924 @var{status-async-output} contains on-going status information about the
17925 progress of a slow operation. It can be discarded. All status output is
17926 prefixed by @samp{+}.
17929 @cindex async output in @sc{gdb/mi}
17930 @var{exec-async-output} contains asynchronous state change on the target
17931 (stopped, started, disappeared). All async output is prefixed by
17935 @cindex notify output in @sc{gdb/mi}
17936 @var{notify-async-output} contains supplementary information that the
17937 client should handle (e.g., a new breakpoint information). All notify
17938 output is prefixed by @samp{=}.
17941 @cindex console output in @sc{gdb/mi}
17942 @var{console-stream-output} is output that should be displayed as is in the
17943 console. It is the textual response to a CLI command. All the console
17944 output is prefixed by @samp{~}.
17947 @cindex target output in @sc{gdb/mi}
17948 @var{target-stream-output} is the output produced by the target program.
17949 All the target output is prefixed by @samp{@@}.
17952 @cindex log output in @sc{gdb/mi}
17953 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17954 instance messages that should be displayed as part of an error log. All
17955 the log output is prefixed by @samp{&}.
17958 @cindex list output in @sc{gdb/mi}
17959 New @sc{gdb/mi} commands should only output @var{lists} containing
17965 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17966 details about the various output records.
17968 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17969 @node GDB/MI Compatibility with CLI
17970 @section @sc{gdb/mi} Compatibility with CLI
17972 @cindex compatibility, @sc{gdb/mi} and CLI
17973 @cindex @sc{gdb/mi}, compatibility with CLI
17975 For the developers convenience CLI commands can be entered directly,
17976 but there may be some unexpected behaviour. For example, commands
17977 that query the user will behave as if the user replied yes, breakpoint
17978 command lists are not executed and some CLI commands, such as
17979 @code{if}, @code{when} and @code{define}, prompt for further input with
17980 @samp{>}, which is not valid MI output.
17982 This feature may be removed at some stage in the future and it is
17983 recommended that front ends use the @code{-interpreter-exec} command
17984 (@pxref{-interpreter-exec}).
17986 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17987 @node GDB/MI Development and Front Ends
17988 @section @sc{gdb/mi} Development and Front Ends
17989 @cindex @sc{gdb/mi} development
17991 The application which takes the MI output and presents the state of the
17992 program being debugged to the user is called a @dfn{front end}.
17994 Although @sc{gdb/mi} is still incomplete, it is currently being used
17995 by a variety of front ends to @value{GDBN}. This makes it difficult
17996 to introduce new functionality without breaking existing usage. This
17997 section tries to minimize the problems by describing how the protocol
18000 Some changes in MI need not break a carefully designed front end, and
18001 for these the MI version will remain unchanged. The following is a
18002 list of changes that may occur within one level, so front ends should
18003 parse MI output in a way that can handle them:
18007 New MI commands may be added.
18010 New fields may be added to the output of any MI command.
18013 The range of values for fields with specified values, e.g.,
18014 @code{in_scope} (@pxref{-var-update}) may be extended.
18016 @c The format of field's content e.g type prefix, may change so parse it
18017 @c at your own risk. Yes, in general?
18019 @c The order of fields may change? Shouldn't really matter but it might
18020 @c resolve inconsistencies.
18023 If the changes are likely to break front ends, the MI version level
18024 will be increased by one. This will allow the front end to parse the
18025 output according to the MI version. Apart from mi0, new versions of
18026 @value{GDBN} will not support old versions of MI and it will be the
18027 responsibility of the front end to work with the new one.
18029 @c Starting with mi3, add a new command -mi-version that prints the MI
18032 The best way to avoid unexpected changes in MI that might break your front
18033 end is to make your project known to @value{GDBN} developers and
18034 follow development on @email{gdb@@sourceware.org} and
18035 @email{gdb-patches@@sourceware.org}. There is also the mailing list
18036 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
18037 Group, which has the aim of creating a more general MI protocol
18038 called Debugger Machine Interface (DMI) that will become a standard
18039 for all debuggers, not just @value{GDBN}.
18040 @cindex mailing lists
18042 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18043 @node GDB/MI Output Records
18044 @section @sc{gdb/mi} Output Records
18047 * GDB/MI Result Records::
18048 * GDB/MI Stream Records::
18049 * GDB/MI Out-of-band Records::
18052 @node GDB/MI Result Records
18053 @subsection @sc{gdb/mi} Result Records
18055 @cindex result records in @sc{gdb/mi}
18056 @cindex @sc{gdb/mi}, result records
18057 In addition to a number of out-of-band notifications, the response to a
18058 @sc{gdb/mi} command includes one of the following result indications:
18062 @item "^done" [ "," @var{results} ]
18063 The synchronous operation was successful, @code{@var{results}} are the return
18068 @c Is this one correct? Should it be an out-of-band notification?
18069 The asynchronous operation was successfully started. The target is
18074 @value{GDBN} has connected to a remote target.
18076 @item "^error" "," @var{c-string}
18078 The operation failed. The @code{@var{c-string}} contains the corresponding
18083 @value{GDBN} has terminated.
18087 @node GDB/MI Stream Records
18088 @subsection @sc{gdb/mi} Stream Records
18090 @cindex @sc{gdb/mi}, stream records
18091 @cindex stream records in @sc{gdb/mi}
18092 @value{GDBN} internally maintains a number of output streams: the console, the
18093 target, and the log. The output intended for each of these streams is
18094 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
18096 Each stream record begins with a unique @dfn{prefix character} which
18097 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
18098 Syntax}). In addition to the prefix, each stream record contains a
18099 @code{@var{string-output}}. This is either raw text (with an implicit new
18100 line) or a quoted C string (which does not contain an implicit newline).
18103 @item "~" @var{string-output}
18104 The console output stream contains text that should be displayed in the
18105 CLI console window. It contains the textual responses to CLI commands.
18107 @item "@@" @var{string-output}
18108 The target output stream contains any textual output from the running
18109 target. This is only present when GDB's event loop is truly
18110 asynchronous, which is currently only the case for remote targets.
18112 @item "&" @var{string-output}
18113 The log stream contains debugging messages being produced by @value{GDBN}'s
18117 @node GDB/MI Out-of-band Records
18118 @subsection @sc{gdb/mi} Out-of-band Records
18120 @cindex out-of-band records in @sc{gdb/mi}
18121 @cindex @sc{gdb/mi}, out-of-band records
18122 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
18123 additional changes that have occurred. Those changes can either be a
18124 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
18125 target activity (e.g., target stopped).
18127 The following is a preliminary list of possible out-of-band records.
18128 In particular, the @var{exec-async-output} records.
18131 @item *stopped,reason="@var{reason}"
18134 @var{reason} can be one of the following:
18137 @item breakpoint-hit
18138 A breakpoint was reached.
18139 @item watchpoint-trigger
18140 A watchpoint was triggered.
18141 @item read-watchpoint-trigger
18142 A read watchpoint was triggered.
18143 @item access-watchpoint-trigger
18144 An access watchpoint was triggered.
18145 @item function-finished
18146 An -exec-finish or similar CLI command was accomplished.
18147 @item location-reached
18148 An -exec-until or similar CLI command was accomplished.
18149 @item watchpoint-scope
18150 A watchpoint has gone out of scope.
18151 @item end-stepping-range
18152 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
18153 similar CLI command was accomplished.
18154 @item exited-signalled
18155 The inferior exited because of a signal.
18157 The inferior exited.
18158 @item exited-normally
18159 The inferior exited normally.
18160 @item signal-received
18161 A signal was received by the inferior.
18165 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18166 @node GDB/MI Simple Examples
18167 @section Simple Examples of @sc{gdb/mi} Interaction
18168 @cindex @sc{gdb/mi}, simple examples
18170 This subsection presents several simple examples of interaction using
18171 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
18172 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
18173 the output received from @sc{gdb/mi}.
18175 Note the line breaks shown in the examples are here only for
18176 readability, they don't appear in the real output.
18178 @subheading Setting a Breakpoint
18180 Setting a breakpoint generates synchronous output which contains detailed
18181 information of the breakpoint.
18184 -> -break-insert main
18185 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18186 enabled="y",addr="0x08048564",func="main",file="myprog.c",
18187 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
18191 @subheading Program Execution
18193 Program execution generates asynchronous records and MI gives the
18194 reason that execution stopped.
18200 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
18201 frame=@{addr="0x08048564",func="main",
18202 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
18203 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
18208 <- *stopped,reason="exited-normally"
18212 @subheading Quitting @value{GDBN}
18214 Quitting @value{GDBN} just prints the result class @samp{^exit}.
18222 @subheading A Bad Command
18224 Here's what happens if you pass a non-existent command:
18228 <- ^error,msg="Undefined MI command: rubbish"
18233 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18234 @node GDB/MI Command Description Format
18235 @section @sc{gdb/mi} Command Description Format
18237 The remaining sections describe blocks of commands. Each block of
18238 commands is laid out in a fashion similar to this section.
18240 @subheading Motivation
18242 The motivation for this collection of commands.
18244 @subheading Introduction
18246 A brief introduction to this collection of commands as a whole.
18248 @subheading Commands
18250 For each command in the block, the following is described:
18252 @subsubheading Synopsis
18255 -command @var{args}@dots{}
18258 @subsubheading Result
18260 @subsubheading @value{GDBN} Command
18262 The corresponding @value{GDBN} CLI command(s), if any.
18264 @subsubheading Example
18266 Example(s) formatted for readability. Some of the described commands have
18267 not been implemented yet and these are labeled N.A.@: (not available).
18270 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18271 @node GDB/MI Breakpoint Commands
18272 @section @sc{gdb/mi} Breakpoint Commands
18274 @cindex breakpoint commands for @sc{gdb/mi}
18275 @cindex @sc{gdb/mi}, breakpoint commands
18276 This section documents @sc{gdb/mi} commands for manipulating
18279 @subheading The @code{-break-after} Command
18280 @findex -break-after
18282 @subsubheading Synopsis
18285 -break-after @var{number} @var{count}
18288 The breakpoint number @var{number} is not in effect until it has been
18289 hit @var{count} times. To see how this is reflected in the output of
18290 the @samp{-break-list} command, see the description of the
18291 @samp{-break-list} command below.
18293 @subsubheading @value{GDBN} Command
18295 The corresponding @value{GDBN} command is @samp{ignore}.
18297 @subsubheading Example
18302 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18303 enabled="y",addr="0x000100d0",func="main",file="hello.c",
18304 fullname="/home/foo/hello.c",line="5",times="0"@}
18311 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18312 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18313 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18314 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18315 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18316 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18317 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18318 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18319 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18320 line="5",times="0",ignore="3"@}]@}
18325 @subheading The @code{-break-catch} Command
18326 @findex -break-catch
18328 @subheading The @code{-break-commands} Command
18329 @findex -break-commands
18333 @subheading The @code{-break-condition} Command
18334 @findex -break-condition
18336 @subsubheading Synopsis
18339 -break-condition @var{number} @var{expr}
18342 Breakpoint @var{number} will stop the program only if the condition in
18343 @var{expr} is true. The condition becomes part of the
18344 @samp{-break-list} output (see the description of the @samp{-break-list}
18347 @subsubheading @value{GDBN} Command
18349 The corresponding @value{GDBN} command is @samp{condition}.
18351 @subsubheading Example
18355 -break-condition 1 1
18359 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18360 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18361 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18362 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18363 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18364 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18365 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18366 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18367 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18368 line="5",cond="1",times="0",ignore="3"@}]@}
18372 @subheading The @code{-break-delete} Command
18373 @findex -break-delete
18375 @subsubheading Synopsis
18378 -break-delete ( @var{breakpoint} )+
18381 Delete the breakpoint(s) whose number(s) are specified in the argument
18382 list. This is obviously reflected in the breakpoint list.
18384 @subsubheading @value{GDBN} Command
18386 The corresponding @value{GDBN} command is @samp{delete}.
18388 @subsubheading Example
18396 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18397 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18398 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18399 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18400 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18401 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18402 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18407 @subheading The @code{-break-disable} Command
18408 @findex -break-disable
18410 @subsubheading Synopsis
18413 -break-disable ( @var{breakpoint} )+
18416 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18417 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18419 @subsubheading @value{GDBN} Command
18421 The corresponding @value{GDBN} command is @samp{disable}.
18423 @subsubheading Example
18431 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18432 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18433 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18434 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18435 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18436 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18437 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18438 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18439 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18440 line="5",times="0"@}]@}
18444 @subheading The @code{-break-enable} Command
18445 @findex -break-enable
18447 @subsubheading Synopsis
18450 -break-enable ( @var{breakpoint} )+
18453 Enable (previously disabled) @var{breakpoint}(s).
18455 @subsubheading @value{GDBN} Command
18457 The corresponding @value{GDBN} command is @samp{enable}.
18459 @subsubheading Example
18467 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18468 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18469 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18470 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18471 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18472 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18473 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18474 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18475 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18476 line="5",times="0"@}]@}
18480 @subheading The @code{-break-info} Command
18481 @findex -break-info
18483 @subsubheading Synopsis
18486 -break-info @var{breakpoint}
18490 Get information about a single breakpoint.
18492 @subsubheading @value{GDBN} Command
18494 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18496 @subsubheading Example
18499 @subheading The @code{-break-insert} Command
18500 @findex -break-insert
18502 @subsubheading Synopsis
18505 -break-insert [ -t ] [ -h ] [ -f ]
18506 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18507 [ -p @var{thread} ] [ @var{location} ]
18511 If specified, @var{location}, can be one of:
18518 @item filename:linenum
18519 @item filename:function
18523 The possible optional parameters of this command are:
18527 Insert a temporary breakpoint.
18529 Insert a hardware breakpoint.
18530 @item -c @var{condition}
18531 Make the breakpoint conditional on @var{condition}.
18532 @item -i @var{ignore-count}
18533 Initialize the @var{ignore-count}.
18535 If @var{location} cannot be parsed (for example if it
18536 refers to unknown files or functions), create a pending
18537 breakpoint. Without this flag, @value{GDBN} will report
18538 an error, and won't create a breakpoint, if @var{location}
18542 @subsubheading Result
18544 The result is in the form:
18547 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18548 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18549 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18550 times="@var{times}"@}
18554 where @var{number} is the @value{GDBN} number for this breakpoint,
18555 @var{funcname} is the name of the function where the breakpoint was
18556 inserted, @var{filename} is the name of the source file which contains
18557 this function, @var{lineno} is the source line number within that file
18558 and @var{times} the number of times that the breakpoint has been hit
18559 (always 0 for -break-insert but may be greater for -break-info or -break-list
18560 which use the same output).
18562 Note: this format is open to change.
18563 @c An out-of-band breakpoint instead of part of the result?
18565 @subsubheading @value{GDBN} Command
18567 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18568 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18570 @subsubheading Example
18575 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18576 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18578 -break-insert -t foo
18579 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18580 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18583 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18584 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18585 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18586 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18587 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18588 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18589 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18590 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18591 addr="0x0001072c", func="main",file="recursive2.c",
18592 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18593 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18594 addr="0x00010774",func="foo",file="recursive2.c",
18595 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18597 -break-insert -r foo.*
18598 ~int foo(int, int);
18599 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18600 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18604 @subheading The @code{-break-list} Command
18605 @findex -break-list
18607 @subsubheading Synopsis
18613 Displays the list of inserted breakpoints, showing the following fields:
18617 number of the breakpoint
18619 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18621 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18624 is the breakpoint enabled or no: @samp{y} or @samp{n}
18626 memory location at which the breakpoint is set
18628 logical location of the breakpoint, expressed by function name, file
18631 number of times the breakpoint has been hit
18634 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18635 @code{body} field is an empty list.
18637 @subsubheading @value{GDBN} Command
18639 The corresponding @value{GDBN} command is @samp{info break}.
18641 @subsubheading Example
18646 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18647 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18648 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18649 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18650 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18651 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18652 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18653 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18654 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18655 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18656 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18657 line="13",times="0"@}]@}
18661 Here's an example of the result when there are no breakpoints:
18666 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18667 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18668 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18669 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18670 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18671 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18672 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18677 @subheading The @code{-break-watch} Command
18678 @findex -break-watch
18680 @subsubheading Synopsis
18683 -break-watch [ -a | -r ]
18686 Create a watchpoint. With the @samp{-a} option it will create an
18687 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18688 read from or on a write to the memory location. With the @samp{-r}
18689 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18690 trigger only when the memory location is accessed for reading. Without
18691 either of the options, the watchpoint created is a regular watchpoint,
18692 i.e., it will trigger when the memory location is accessed for writing.
18693 @xref{Set Watchpoints, , Setting Watchpoints}.
18695 Note that @samp{-break-list} will report a single list of watchpoints and
18696 breakpoints inserted.
18698 @subsubheading @value{GDBN} Command
18700 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18703 @subsubheading Example
18705 Setting a watchpoint on a variable in the @code{main} function:
18710 ^done,wpt=@{number="2",exp="x"@}
18715 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18716 value=@{old="-268439212",new="55"@},
18717 frame=@{func="main",args=[],file="recursive2.c",
18718 fullname="/home/foo/bar/recursive2.c",line="5"@}
18722 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18723 the program execution twice: first for the variable changing value, then
18724 for the watchpoint going out of scope.
18729 ^done,wpt=@{number="5",exp="C"@}
18734 *stopped,reason="watchpoint-trigger",
18735 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18736 frame=@{func="callee4",args=[],
18737 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18738 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18743 *stopped,reason="watchpoint-scope",wpnum="5",
18744 frame=@{func="callee3",args=[@{name="strarg",
18745 value="0x11940 \"A string argument.\""@}],
18746 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18747 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18751 Listing breakpoints and watchpoints, at different points in the program
18752 execution. Note that once the watchpoint goes out of scope, it is
18758 ^done,wpt=@{number="2",exp="C"@}
18761 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18762 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18763 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18764 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18765 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18766 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18767 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18768 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18769 addr="0x00010734",func="callee4",
18770 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18771 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18772 bkpt=@{number="2",type="watchpoint",disp="keep",
18773 enabled="y",addr="",what="C",times="0"@}]@}
18778 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18779 value=@{old="-276895068",new="3"@},
18780 frame=@{func="callee4",args=[],
18781 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18782 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18785 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18786 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18787 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18788 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18789 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18790 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18791 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18792 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18793 addr="0x00010734",func="callee4",
18794 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18795 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18796 bkpt=@{number="2",type="watchpoint",disp="keep",
18797 enabled="y",addr="",what="C",times="-5"@}]@}
18801 ^done,reason="watchpoint-scope",wpnum="2",
18802 frame=@{func="callee3",args=[@{name="strarg",
18803 value="0x11940 \"A string argument.\""@}],
18804 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18805 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18808 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18809 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18810 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18811 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18812 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18813 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18814 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18815 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18816 addr="0x00010734",func="callee4",
18817 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18818 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18823 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18824 @node GDB/MI Program Context
18825 @section @sc{gdb/mi} Program Context
18827 @subheading The @code{-exec-arguments} Command
18828 @findex -exec-arguments
18831 @subsubheading Synopsis
18834 -exec-arguments @var{args}
18837 Set the inferior program arguments, to be used in the next
18840 @subsubheading @value{GDBN} Command
18842 The corresponding @value{GDBN} command is @samp{set args}.
18844 @subsubheading Example
18847 Don't have one around.
18850 @subheading The @code{-exec-show-arguments} Command
18851 @findex -exec-show-arguments
18853 @subsubheading Synopsis
18856 -exec-show-arguments
18859 Print the arguments of the program.
18861 @subsubheading @value{GDBN} Command
18863 The corresponding @value{GDBN} command is @samp{show args}.
18865 @subsubheading Example
18869 @subheading The @code{-environment-cd} Command
18870 @findex -environment-cd
18872 @subsubheading Synopsis
18875 -environment-cd @var{pathdir}
18878 Set @value{GDBN}'s working directory.
18880 @subsubheading @value{GDBN} Command
18882 The corresponding @value{GDBN} command is @samp{cd}.
18884 @subsubheading Example
18888 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18894 @subheading The @code{-environment-directory} Command
18895 @findex -environment-directory
18897 @subsubheading Synopsis
18900 -environment-directory [ -r ] [ @var{pathdir} ]+
18903 Add directories @var{pathdir} to beginning of search path for source files.
18904 If the @samp{-r} option is used, the search path is reset to the default
18905 search path. If directories @var{pathdir} are supplied in addition to the
18906 @samp{-r} option, the search path is first reset and then addition
18908 Multiple directories may be specified, separated by blanks. Specifying
18909 multiple directories in a single command
18910 results in the directories added to the beginning of the
18911 search path in the same order they were presented in the command.
18912 If blanks are needed as
18913 part of a directory name, double-quotes should be used around
18914 the name. In the command output, the path will show up separated
18915 by the system directory-separator character. The directory-separator
18916 character must not be used
18917 in any directory name.
18918 If no directories are specified, the current search path is displayed.
18920 @subsubheading @value{GDBN} Command
18922 The corresponding @value{GDBN} command is @samp{dir}.
18924 @subsubheading Example
18928 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18929 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18931 -environment-directory ""
18932 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18934 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18935 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18937 -environment-directory -r
18938 ^done,source-path="$cdir:$cwd"
18943 @subheading The @code{-environment-path} Command
18944 @findex -environment-path
18946 @subsubheading Synopsis
18949 -environment-path [ -r ] [ @var{pathdir} ]+
18952 Add directories @var{pathdir} to beginning of search path for object files.
18953 If the @samp{-r} option is used, the search path is reset to the original
18954 search path that existed at gdb start-up. If directories @var{pathdir} are
18955 supplied in addition to the
18956 @samp{-r} option, the search path is first reset and then addition
18958 Multiple directories may be specified, separated by blanks. Specifying
18959 multiple directories in a single command
18960 results in the directories added to the beginning of the
18961 search path in the same order they were presented in the command.
18962 If blanks are needed as
18963 part of a directory name, double-quotes should be used around
18964 the name. In the command output, the path will show up separated
18965 by the system directory-separator character. The directory-separator
18966 character must not be used
18967 in any directory name.
18968 If no directories are specified, the current path is displayed.
18971 @subsubheading @value{GDBN} Command
18973 The corresponding @value{GDBN} command is @samp{path}.
18975 @subsubheading Example
18980 ^done,path="/usr/bin"
18982 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18983 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18985 -environment-path -r /usr/local/bin
18986 ^done,path="/usr/local/bin:/usr/bin"
18991 @subheading The @code{-environment-pwd} Command
18992 @findex -environment-pwd
18994 @subsubheading Synopsis
19000 Show the current working directory.
19002 @subsubheading @value{GDBN} Command
19004 The corresponding @value{GDBN} command is @samp{pwd}.
19006 @subsubheading Example
19011 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
19015 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19016 @node GDB/MI Thread Commands
19017 @section @sc{gdb/mi} Thread Commands
19020 @subheading The @code{-thread-info} Command
19021 @findex -thread-info
19023 @subsubheading Synopsis
19026 -thread-info [ @var{thread-id} ]
19029 Reports information about either a specific thread, if
19030 the @var{thread-id} parameter is present, or about all
19031 threads. When printing information about all threads,
19032 also reports the current thread.
19034 @subsubheading @value{GDBN} Command
19036 The @samp{info thread} command prints the same information
19039 @subsubheading Example
19044 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
19045 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},
19046 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
19047 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
19048 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}@}],
19049 current-thread-id="1"
19053 @subheading The @code{-thread-list-ids} Command
19054 @findex -thread-list-ids
19056 @subsubheading Synopsis
19062 Produces a list of the currently known @value{GDBN} thread ids. At the
19063 end of the list it also prints the total number of such threads.
19065 @subsubheading @value{GDBN} Command
19067 Part of @samp{info threads} supplies the same information.
19069 @subsubheading Example
19071 No threads present, besides the main process:
19076 ^done,thread-ids=@{@},number-of-threads="0"
19086 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19087 number-of-threads="3"
19092 @subheading The @code{-thread-select} Command
19093 @findex -thread-select
19095 @subsubheading Synopsis
19098 -thread-select @var{threadnum}
19101 Make @var{threadnum} the current thread. It prints the number of the new
19102 current thread, and the topmost frame for that thread.
19104 @subsubheading @value{GDBN} Command
19106 The corresponding @value{GDBN} command is @samp{thread}.
19108 @subsubheading Example
19115 *stopped,reason="end-stepping-range",thread-id="2",line="187",
19116 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
19120 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19121 number-of-threads="3"
19124 ^done,new-thread-id="3",
19125 frame=@{level="0",func="vprintf",
19126 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
19127 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
19131 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19132 @node GDB/MI Program Execution
19133 @section @sc{gdb/mi} Program Execution
19135 These are the asynchronous commands which generate the out-of-band
19136 record @samp{*stopped}. Currently @value{GDBN} only really executes
19137 asynchronously with remote targets and this interaction is mimicked in
19140 @subheading The @code{-exec-continue} Command
19141 @findex -exec-continue
19143 @subsubheading Synopsis
19149 Resumes the execution of the inferior program until a breakpoint is
19150 encountered, or until the inferior exits.
19152 @subsubheading @value{GDBN} Command
19154 The corresponding @value{GDBN} corresponding is @samp{continue}.
19156 @subsubheading Example
19163 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
19164 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
19170 @subheading The @code{-exec-finish} Command
19171 @findex -exec-finish
19173 @subsubheading Synopsis
19179 Resumes the execution of the inferior program until the current
19180 function is exited. Displays the results returned by the function.
19182 @subsubheading @value{GDBN} Command
19184 The corresponding @value{GDBN} command is @samp{finish}.
19186 @subsubheading Example
19188 Function returning @code{void}.
19195 *stopped,reason="function-finished",frame=@{func="main",args=[],
19196 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
19200 Function returning other than @code{void}. The name of the internal
19201 @value{GDBN} variable storing the result is printed, together with the
19208 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
19209 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
19210 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19211 gdb-result-var="$1",return-value="0"
19216 @subheading The @code{-exec-interrupt} Command
19217 @findex -exec-interrupt
19219 @subsubheading Synopsis
19225 Interrupts the background execution of the target. Note how the token
19226 associated with the stop message is the one for the execution command
19227 that has been interrupted. The token for the interrupt itself only
19228 appears in the @samp{^done} output. If the user is trying to
19229 interrupt a non-running program, an error message will be printed.
19231 @subsubheading @value{GDBN} Command
19233 The corresponding @value{GDBN} command is @samp{interrupt}.
19235 @subsubheading Example
19246 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
19247 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
19248 fullname="/home/foo/bar/try.c",line="13"@}
19253 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
19258 @subheading The @code{-exec-next} Command
19261 @subsubheading Synopsis
19267 Resumes execution of the inferior program, stopping when the beginning
19268 of the next source line is reached.
19270 @subsubheading @value{GDBN} Command
19272 The corresponding @value{GDBN} command is @samp{next}.
19274 @subsubheading Example
19280 *stopped,reason="end-stepping-range",line="8",file="hello.c"
19285 @subheading The @code{-exec-next-instruction} Command
19286 @findex -exec-next-instruction
19288 @subsubheading Synopsis
19291 -exec-next-instruction
19294 Executes one machine instruction. If the instruction is a function
19295 call, continues until the function returns. If the program stops at an
19296 instruction in the middle of a source line, the address will be
19299 @subsubheading @value{GDBN} Command
19301 The corresponding @value{GDBN} command is @samp{nexti}.
19303 @subsubheading Example
19307 -exec-next-instruction
19311 *stopped,reason="end-stepping-range",
19312 addr="0x000100d4",line="5",file="hello.c"
19317 @subheading The @code{-exec-return} Command
19318 @findex -exec-return
19320 @subsubheading Synopsis
19326 Makes current function return immediately. Doesn't execute the inferior.
19327 Displays the new current frame.
19329 @subsubheading @value{GDBN} Command
19331 The corresponding @value{GDBN} command is @samp{return}.
19333 @subsubheading Example
19337 200-break-insert callee4
19338 200^done,bkpt=@{number="1",addr="0x00010734",
19339 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19344 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
19345 frame=@{func="callee4",args=[],
19346 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19347 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19353 111^done,frame=@{level="0",func="callee3",
19354 args=[@{name="strarg",
19355 value="0x11940 \"A string argument.\""@}],
19356 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19357 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19362 @subheading The @code{-exec-run} Command
19365 @subsubheading Synopsis
19371 Starts execution of the inferior from the beginning. The inferior
19372 executes until either a breakpoint is encountered or the program
19373 exits. In the latter case the output will include an exit code, if
19374 the program has exited exceptionally.
19376 @subsubheading @value{GDBN} Command
19378 The corresponding @value{GDBN} command is @samp{run}.
19380 @subsubheading Examples
19385 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19390 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
19391 frame=@{func="main",args=[],file="recursive2.c",
19392 fullname="/home/foo/bar/recursive2.c",line="4"@}
19397 Program exited normally:
19405 *stopped,reason="exited-normally"
19410 Program exited exceptionally:
19418 *stopped,reason="exited",exit-code="01"
19422 Another way the program can terminate is if it receives a signal such as
19423 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19427 *stopped,reason="exited-signalled",signal-name="SIGINT",
19428 signal-meaning="Interrupt"
19432 @c @subheading -exec-signal
19435 @subheading The @code{-exec-step} Command
19438 @subsubheading Synopsis
19444 Resumes execution of the inferior program, stopping when the beginning
19445 of the next source line is reached, if the next source line is not a
19446 function call. If it is, stop at the first instruction of the called
19449 @subsubheading @value{GDBN} Command
19451 The corresponding @value{GDBN} command is @samp{step}.
19453 @subsubheading Example
19455 Stepping into a function:
19461 *stopped,reason="end-stepping-range",
19462 frame=@{func="foo",args=[@{name="a",value="10"@},
19463 @{name="b",value="0"@}],file="recursive2.c",
19464 fullname="/home/foo/bar/recursive2.c",line="11"@}
19474 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19479 @subheading The @code{-exec-step-instruction} Command
19480 @findex -exec-step-instruction
19482 @subsubheading Synopsis
19485 -exec-step-instruction
19488 Resumes the inferior which executes one machine instruction. The
19489 output, once @value{GDBN} has stopped, will vary depending on whether
19490 we have stopped in the middle of a source line or not. In the former
19491 case, the address at which the program stopped will be printed as
19494 @subsubheading @value{GDBN} Command
19496 The corresponding @value{GDBN} command is @samp{stepi}.
19498 @subsubheading Example
19502 -exec-step-instruction
19506 *stopped,reason="end-stepping-range",
19507 frame=@{func="foo",args=[],file="try.c",
19508 fullname="/home/foo/bar/try.c",line="10"@}
19510 -exec-step-instruction
19514 *stopped,reason="end-stepping-range",
19515 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19516 fullname="/home/foo/bar/try.c",line="10"@}
19521 @subheading The @code{-exec-until} Command
19522 @findex -exec-until
19524 @subsubheading Synopsis
19527 -exec-until [ @var{location} ]
19530 Executes the inferior until the @var{location} specified in the
19531 argument is reached. If there is no argument, the inferior executes
19532 until a source line greater than the current one is reached. The
19533 reason for stopping in this case will be @samp{location-reached}.
19535 @subsubheading @value{GDBN} Command
19537 The corresponding @value{GDBN} command is @samp{until}.
19539 @subsubheading Example
19543 -exec-until recursive2.c:6
19547 *stopped,reason="location-reached",frame=@{func="main",args=[],
19548 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19553 @subheading -file-clear
19554 Is this going away????
19557 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19558 @node GDB/MI Stack Manipulation
19559 @section @sc{gdb/mi} Stack Manipulation Commands
19562 @subheading The @code{-stack-info-frame} Command
19563 @findex -stack-info-frame
19565 @subsubheading Synopsis
19571 Get info on the selected frame.
19573 @subsubheading @value{GDBN} Command
19575 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19576 (without arguments).
19578 @subsubheading Example
19583 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19584 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19585 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19589 @subheading The @code{-stack-info-depth} Command
19590 @findex -stack-info-depth
19592 @subsubheading Synopsis
19595 -stack-info-depth [ @var{max-depth} ]
19598 Return the depth of the stack. If the integer argument @var{max-depth}
19599 is specified, do not count beyond @var{max-depth} frames.
19601 @subsubheading @value{GDBN} Command
19603 There's no equivalent @value{GDBN} command.
19605 @subsubheading Example
19607 For a stack with frame levels 0 through 11:
19614 -stack-info-depth 4
19617 -stack-info-depth 12
19620 -stack-info-depth 11
19623 -stack-info-depth 13
19628 @subheading The @code{-stack-list-arguments} Command
19629 @findex -stack-list-arguments
19631 @subsubheading Synopsis
19634 -stack-list-arguments @var{show-values}
19635 [ @var{low-frame} @var{high-frame} ]
19638 Display a list of the arguments for the frames between @var{low-frame}
19639 and @var{high-frame} (inclusive). If @var{low-frame} and
19640 @var{high-frame} are not provided, list the arguments for the whole
19641 call stack. If the two arguments are equal, show the single frame
19642 at the corresponding level. It is an error if @var{low-frame} is
19643 larger than the actual number of frames. On the other hand,
19644 @var{high-frame} may be larger than the actual number of frames, in
19645 which case only existing frames will be returned.
19647 The @var{show-values} argument must have a value of 0 or 1. A value of
19648 0 means that only the names of the arguments are listed, a value of 1
19649 means that both names and values of the arguments are printed.
19651 @subsubheading @value{GDBN} Command
19653 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19654 @samp{gdb_get_args} command which partially overlaps with the
19655 functionality of @samp{-stack-list-arguments}.
19657 @subsubheading Example
19664 frame=@{level="0",addr="0x00010734",func="callee4",
19665 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19666 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19667 frame=@{level="1",addr="0x0001076c",func="callee3",
19668 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19669 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19670 frame=@{level="2",addr="0x0001078c",func="callee2",
19671 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19672 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19673 frame=@{level="3",addr="0x000107b4",func="callee1",
19674 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19675 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19676 frame=@{level="4",addr="0x000107e0",func="main",
19677 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19678 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19680 -stack-list-arguments 0
19683 frame=@{level="0",args=[]@},
19684 frame=@{level="1",args=[name="strarg"]@},
19685 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19686 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19687 frame=@{level="4",args=[]@}]
19689 -stack-list-arguments 1
19692 frame=@{level="0",args=[]@},
19694 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19695 frame=@{level="2",args=[
19696 @{name="intarg",value="2"@},
19697 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19698 @{frame=@{level="3",args=[
19699 @{name="intarg",value="2"@},
19700 @{name="strarg",value="0x11940 \"A string argument.\""@},
19701 @{name="fltarg",value="3.5"@}]@},
19702 frame=@{level="4",args=[]@}]
19704 -stack-list-arguments 0 2 2
19705 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19707 -stack-list-arguments 1 2 2
19708 ^done,stack-args=[frame=@{level="2",
19709 args=[@{name="intarg",value="2"@},
19710 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19714 @c @subheading -stack-list-exception-handlers
19717 @subheading The @code{-stack-list-frames} Command
19718 @findex -stack-list-frames
19720 @subsubheading Synopsis
19723 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19726 List the frames currently on the stack. For each frame it displays the
19731 The frame number, 0 being the topmost frame, i.e., the innermost function.
19733 The @code{$pc} value for that frame.
19737 File name of the source file where the function lives.
19739 Line number corresponding to the @code{$pc}.
19742 If invoked without arguments, this command prints a backtrace for the
19743 whole stack. If given two integer arguments, it shows the frames whose
19744 levels are between the two arguments (inclusive). If the two arguments
19745 are equal, it shows the single frame at the corresponding level. It is
19746 an error if @var{low-frame} is larger than the actual number of
19747 frames. On the other hand, @var{high-frame} may be larger than the
19748 actual number of frames, in which case only existing frames will be returned.
19750 @subsubheading @value{GDBN} Command
19752 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19754 @subsubheading Example
19756 Full stack backtrace:
19762 [frame=@{level="0",addr="0x0001076c",func="foo",
19763 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19764 frame=@{level="1",addr="0x000107a4",func="foo",
19765 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19766 frame=@{level="2",addr="0x000107a4",func="foo",
19767 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19768 frame=@{level="3",addr="0x000107a4",func="foo",
19769 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19770 frame=@{level="4",addr="0x000107a4",func="foo",
19771 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19772 frame=@{level="5",addr="0x000107a4",func="foo",
19773 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19774 frame=@{level="6",addr="0x000107a4",func="foo",
19775 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19776 frame=@{level="7",addr="0x000107a4",func="foo",
19777 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19778 frame=@{level="8",addr="0x000107a4",func="foo",
19779 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19780 frame=@{level="9",addr="0x000107a4",func="foo",
19781 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19782 frame=@{level="10",addr="0x000107a4",func="foo",
19783 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19784 frame=@{level="11",addr="0x00010738",func="main",
19785 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19789 Show frames between @var{low_frame} and @var{high_frame}:
19793 -stack-list-frames 3 5
19795 [frame=@{level="3",addr="0x000107a4",func="foo",
19796 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19797 frame=@{level="4",addr="0x000107a4",func="foo",
19798 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19799 frame=@{level="5",addr="0x000107a4",func="foo",
19800 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19804 Show a single frame:
19808 -stack-list-frames 3 3
19810 [frame=@{level="3",addr="0x000107a4",func="foo",
19811 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19816 @subheading The @code{-stack-list-locals} Command
19817 @findex -stack-list-locals
19819 @subsubheading Synopsis
19822 -stack-list-locals @var{print-values}
19825 Display the local variable names for the selected frame. If
19826 @var{print-values} is 0 or @code{--no-values}, print only the names of
19827 the variables; if it is 1 or @code{--all-values}, print also their
19828 values; and if it is 2 or @code{--simple-values}, print the name,
19829 type and value for simple data types and the name and type for arrays,
19830 structures and unions. In this last case, a frontend can immediately
19831 display the value of simple data types and create variable objects for
19832 other data types when the user wishes to explore their values in
19835 @subsubheading @value{GDBN} Command
19837 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19839 @subsubheading Example
19843 -stack-list-locals 0
19844 ^done,locals=[name="A",name="B",name="C"]
19846 -stack-list-locals --all-values
19847 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19848 @{name="C",value="@{1, 2, 3@}"@}]
19849 -stack-list-locals --simple-values
19850 ^done,locals=[@{name="A",type="int",value="1"@},
19851 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19856 @subheading The @code{-stack-select-frame} Command
19857 @findex -stack-select-frame
19859 @subsubheading Synopsis
19862 -stack-select-frame @var{framenum}
19865 Change the selected frame. Select a different frame @var{framenum} on
19868 @subsubheading @value{GDBN} Command
19870 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19871 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19873 @subsubheading Example
19877 -stack-select-frame 2
19882 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19883 @node GDB/MI Variable Objects
19884 @section @sc{gdb/mi} Variable Objects
19888 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19890 For the implementation of a variable debugger window (locals, watched
19891 expressions, etc.), we are proposing the adaptation of the existing code
19892 used by @code{Insight}.
19894 The two main reasons for that are:
19898 It has been proven in practice (it is already on its second generation).
19901 It will shorten development time (needless to say how important it is
19905 The original interface was designed to be used by Tcl code, so it was
19906 slightly changed so it could be used through @sc{gdb/mi}. This section
19907 describes the @sc{gdb/mi} operations that will be available and gives some
19908 hints about their use.
19910 @emph{Note}: In addition to the set of operations described here, we
19911 expect the @sc{gui} implementation of a variable window to require, at
19912 least, the following operations:
19915 @item @code{-gdb-show} @code{output-radix}
19916 @item @code{-stack-list-arguments}
19917 @item @code{-stack-list-locals}
19918 @item @code{-stack-select-frame}
19923 @subheading Introduction to Variable Objects
19925 @cindex variable objects in @sc{gdb/mi}
19927 Variable objects are "object-oriented" MI interface for examining and
19928 changing values of expressions. Unlike some other MI interfaces that
19929 work with expressions, variable objects are specifically designed for
19930 simple and efficient presentation in the frontend. A variable object
19931 is identified by string name. When a variable object is created, the
19932 frontend specifies the expression for that variable object. The
19933 expression can be a simple variable, or it can be an arbitrary complex
19934 expression, and can even involve CPU registers. After creating a
19935 variable object, the frontend can invoke other variable object
19936 operations---for example to obtain or change the value of a variable
19937 object, or to change display format.
19939 Variable objects have hierarchical tree structure. Any variable object
19940 that corresponds to a composite type, such as structure in C, has
19941 a number of child variable objects, for example corresponding to each
19942 element of a structure. A child variable object can itself have
19943 children, recursively. Recursion ends when we reach
19944 leaf variable objects, which always have built-in types. Child variable
19945 objects are created only by explicit request, so if a frontend
19946 is not interested in the children of a particular variable object, no
19947 child will be created.
19949 For a leaf variable object it is possible to obtain its value as a
19950 string, or set the value from a string. String value can be also
19951 obtained for a non-leaf variable object, but it's generally a string
19952 that only indicates the type of the object, and does not list its
19953 contents. Assignment to a non-leaf variable object is not allowed.
19955 A frontend does not need to read the values of all variable objects each time
19956 the program stops. Instead, MI provides an update command that lists all
19957 variable objects whose values has changed since the last update
19958 operation. This considerably reduces the amount of data that must
19959 be transferred to the frontend. As noted above, children variable
19960 objects are created on demand, and only leaf variable objects have a
19961 real value. As result, gdb will read target memory only for leaf
19962 variables that frontend has created.
19964 The automatic update is not always desirable. For example, a frontend
19965 might want to keep a value of some expression for future reference,
19966 and never update it. For another example, fetching memory is
19967 relatively slow for embedded targets, so a frontend might want
19968 to disable automatic update for the variables that are either not
19969 visible on the screen, or ``closed''. This is possible using so
19970 called ``frozen variable objects''. Such variable objects are never
19971 implicitly updated.
19973 The following is the complete set of @sc{gdb/mi} operations defined to
19974 access this functionality:
19976 @multitable @columnfractions .4 .6
19977 @item @strong{Operation}
19978 @tab @strong{Description}
19980 @item @code{-var-create}
19981 @tab create a variable object
19982 @item @code{-var-delete}
19983 @tab delete the variable object and/or its children
19984 @item @code{-var-set-format}
19985 @tab set the display format of this variable
19986 @item @code{-var-show-format}
19987 @tab show the display format of this variable
19988 @item @code{-var-info-num-children}
19989 @tab tells how many children this object has
19990 @item @code{-var-list-children}
19991 @tab return a list of the object's children
19992 @item @code{-var-info-type}
19993 @tab show the type of this variable object
19994 @item @code{-var-info-expression}
19995 @tab print parent-relative expression that this variable object represents
19996 @item @code{-var-info-path-expression}
19997 @tab print full expression that this variable object represents
19998 @item @code{-var-show-attributes}
19999 @tab is this variable editable? does it exist here?
20000 @item @code{-var-evaluate-expression}
20001 @tab get the value of this variable
20002 @item @code{-var-assign}
20003 @tab set the value of this variable
20004 @item @code{-var-update}
20005 @tab update the variable and its children
20006 @item @code{-var-set-frozen}
20007 @tab set frozeness attribute
20010 In the next subsection we describe each operation in detail and suggest
20011 how it can be used.
20013 @subheading Description And Use of Operations on Variable Objects
20015 @subheading The @code{-var-create} Command
20016 @findex -var-create
20018 @subsubheading Synopsis
20021 -var-create @{@var{name} | "-"@}
20022 @{@var{frame-addr} | "*"@} @var{expression}
20025 This operation creates a variable object, which allows the monitoring of
20026 a variable, the result of an expression, a memory cell or a CPU
20029 The @var{name} parameter is the string by which the object can be
20030 referenced. It must be unique. If @samp{-} is specified, the varobj
20031 system will generate a string ``varNNNNNN'' automatically. It will be
20032 unique provided that one does not specify @var{name} on that format.
20033 The command fails if a duplicate name is found.
20035 The frame under which the expression should be evaluated can be
20036 specified by @var{frame-addr}. A @samp{*} indicates that the current
20037 frame should be used.
20039 @var{expression} is any expression valid on the current language set (must not
20040 begin with a @samp{*}), or one of the following:
20044 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20047 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20050 @samp{$@var{regname}} --- a CPU register name
20053 @subsubheading Result
20055 This operation returns the name, number of children and the type of the
20056 object created. Type is returned as a string as the ones generated by
20057 the @value{GDBN} CLI:
20060 name="@var{name}",numchild="N",type="@var{type}"
20064 @subheading The @code{-var-delete} Command
20065 @findex -var-delete
20067 @subsubheading Synopsis
20070 -var-delete [ -c ] @var{name}
20073 Deletes a previously created variable object and all of its children.
20074 With the @samp{-c} option, just deletes the children.
20076 Returns an error if the object @var{name} is not found.
20079 @subheading The @code{-var-set-format} Command
20080 @findex -var-set-format
20082 @subsubheading Synopsis
20085 -var-set-format @var{name} @var{format-spec}
20088 Sets the output format for the value of the object @var{name} to be
20091 @anchor{-var-set-format}
20092 The syntax for the @var{format-spec} is as follows:
20095 @var{format-spec} @expansion{}
20096 @{binary | decimal | hexadecimal | octal | natural@}
20099 The natural format is the default format choosen automatically
20100 based on the variable type (like decimal for an @code{int}, hex
20101 for pointers, etc.).
20103 For a variable with children, the format is set only on the
20104 variable itself, and the children are not affected.
20106 @subheading The @code{-var-show-format} Command
20107 @findex -var-show-format
20109 @subsubheading Synopsis
20112 -var-show-format @var{name}
20115 Returns the format used to display the value of the object @var{name}.
20118 @var{format} @expansion{}
20123 @subheading The @code{-var-info-num-children} Command
20124 @findex -var-info-num-children
20126 @subsubheading Synopsis
20129 -var-info-num-children @var{name}
20132 Returns the number of children of a variable object @var{name}:
20139 @subheading The @code{-var-list-children} Command
20140 @findex -var-list-children
20142 @subsubheading Synopsis
20145 -var-list-children [@var{print-values}] @var{name}
20147 @anchor{-var-list-children}
20149 Return a list of the children of the specified variable object and
20150 create variable objects for them, if they do not already exist. With
20151 a single argument or if @var{print-values} has a value for of 0 or
20152 @code{--no-values}, print only the names of the variables; if
20153 @var{print-values} is 1 or @code{--all-values}, also print their
20154 values; and if it is 2 or @code{--simple-values} print the name and
20155 value for simple data types and just the name for arrays, structures
20158 @subsubheading Example
20162 -var-list-children n
20163 ^done,numchild=@var{n},children=[@{name=@var{name},
20164 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20166 -var-list-children --all-values n
20167 ^done,numchild=@var{n},children=[@{name=@var{name},
20168 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20172 @subheading The @code{-var-info-type} Command
20173 @findex -var-info-type
20175 @subsubheading Synopsis
20178 -var-info-type @var{name}
20181 Returns the type of the specified variable @var{name}. The type is
20182 returned as a string in the same format as it is output by the
20186 type=@var{typename}
20190 @subheading The @code{-var-info-expression} Command
20191 @findex -var-info-expression
20193 @subsubheading Synopsis
20196 -var-info-expression @var{name}
20199 Returns a string that is suitable for presenting this
20200 variable object in user interface. The string is generally
20201 not valid expression in the current language, and cannot be evaluated.
20203 For example, if @code{a} is an array, and variable object
20204 @code{A} was created for @code{a}, then we'll get this output:
20207 (gdb) -var-info-expression A.1
20208 ^done,lang="C",exp="1"
20212 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
20214 Note that the output of the @code{-var-list-children} command also
20215 includes those expressions, so the @code{-var-info-expression} command
20218 @subheading The @code{-var-info-path-expression} Command
20219 @findex -var-info-path-expression
20221 @subsubheading Synopsis
20224 -var-info-path-expression @var{name}
20227 Returns an expression that can be evaluated in the current
20228 context and will yield the same value that a variable object has.
20229 Compare this with the @code{-var-info-expression} command, which
20230 result can be used only for UI presentation. Typical use of
20231 the @code{-var-info-path-expression} command is creating a
20232 watchpoint from a variable object.
20234 For example, suppose @code{C} is a C@t{++} class, derived from class
20235 @code{Base}, and that the @code{Base} class has a member called
20236 @code{m_size}. Assume a variable @code{c} is has the type of
20237 @code{C} and a variable object @code{C} was created for variable
20238 @code{c}. Then, we'll get this output:
20240 (gdb) -var-info-path-expression C.Base.public.m_size
20241 ^done,path_expr=((Base)c).m_size)
20244 @subheading The @code{-var-show-attributes} Command
20245 @findex -var-show-attributes
20247 @subsubheading Synopsis
20250 -var-show-attributes @var{name}
20253 List attributes of the specified variable object @var{name}:
20256 status=@var{attr} [ ( ,@var{attr} )* ]
20260 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20262 @subheading The @code{-var-evaluate-expression} Command
20263 @findex -var-evaluate-expression
20265 @subsubheading Synopsis
20268 -var-evaluate-expression [-f @var{format-spec}] @var{name}
20271 Evaluates the expression that is represented by the specified variable
20272 object and returns its value as a string. The format of the string
20273 can be specified with the @samp{-f} option. The possible values of
20274 this option are the same as for @code{-var-set-format}
20275 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
20276 the current display format will be used. The current display format
20277 can be changed using the @code{-var-set-format} command.
20283 Note that one must invoke @code{-var-list-children} for a variable
20284 before the value of a child variable can be evaluated.
20286 @subheading The @code{-var-assign} Command
20287 @findex -var-assign
20289 @subsubheading Synopsis
20292 -var-assign @var{name} @var{expression}
20295 Assigns the value of @var{expression} to the variable object specified
20296 by @var{name}. The object must be @samp{editable}. If the variable's
20297 value is altered by the assign, the variable will show up in any
20298 subsequent @code{-var-update} list.
20300 @subsubheading Example
20308 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20312 @subheading The @code{-var-update} Command
20313 @findex -var-update
20315 @subsubheading Synopsis
20318 -var-update [@var{print-values}] @{@var{name} | "*"@}
20321 Reevaluate the expressions corresponding to the variable object
20322 @var{name} and all its direct and indirect children, and return the
20323 list of variable objects whose values have changed; @var{name} must
20324 be a root variable object. Here, ``changed'' means that the result of
20325 @code{-var-evaluate-expression} before and after the
20326 @code{-var-update} is different. If @samp{*} is used as the variable
20327 object names, all existing variable objects are updated, except
20328 for frozen ones (@pxref{-var-set-frozen}). The option
20329 @var{print-values} determines whether both names and values, or just
20330 names are printed. The possible values of this option are the same
20331 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
20332 recommended to use the @samp{--all-values} option, to reduce the
20333 number of MI commands needed on each program stop.
20336 @subsubheading Example
20343 -var-update --all-values var1
20344 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20345 type_changed="false"@}]
20349 @anchor{-var-update}
20350 The field in_scope may take three values:
20354 The variable object's current value is valid.
20357 The variable object does not currently hold a valid value but it may
20358 hold one in the future if its associated expression comes back into
20362 The variable object no longer holds a valid value.
20363 This can occur when the executable file being debugged has changed,
20364 either through recompilation or by using the @value{GDBN} @code{file}
20365 command. The front end should normally choose to delete these variable
20369 In the future new values may be added to this list so the front should
20370 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
20372 @subheading The @code{-var-set-frozen} Command
20373 @findex -var-set-frozen
20374 @anchor{-var-set-frozen}
20376 @subsubheading Synopsis
20379 -var-set-frozen @var{name} @var{flag}
20382 Set the frozenness flag on the variable object @var{name}. The
20383 @var{flag} parameter should be either @samp{1} to make the variable
20384 frozen or @samp{0} to make it unfrozen. If a variable object is
20385 frozen, then neither itself, nor any of its children, are
20386 implicitly updated by @code{-var-update} of
20387 a parent variable or by @code{-var-update *}. Only
20388 @code{-var-update} of the variable itself will update its value and
20389 values of its children. After a variable object is unfrozen, it is
20390 implicitly updated by all subsequent @code{-var-update} operations.
20391 Unfreezing a variable does not update it, only subsequent
20392 @code{-var-update} does.
20394 @subsubheading Example
20398 -var-set-frozen V 1
20404 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20405 @node GDB/MI Data Manipulation
20406 @section @sc{gdb/mi} Data Manipulation
20408 @cindex data manipulation, in @sc{gdb/mi}
20409 @cindex @sc{gdb/mi}, data manipulation
20410 This section describes the @sc{gdb/mi} commands that manipulate data:
20411 examine memory and registers, evaluate expressions, etc.
20413 @c REMOVED FROM THE INTERFACE.
20414 @c @subheading -data-assign
20415 @c Change the value of a program variable. Plenty of side effects.
20416 @c @subsubheading GDB Command
20418 @c @subsubheading Example
20421 @subheading The @code{-data-disassemble} Command
20422 @findex -data-disassemble
20424 @subsubheading Synopsis
20428 [ -s @var{start-addr} -e @var{end-addr} ]
20429 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20437 @item @var{start-addr}
20438 is the beginning address (or @code{$pc})
20439 @item @var{end-addr}
20441 @item @var{filename}
20442 is the name of the file to disassemble
20443 @item @var{linenum}
20444 is the line number to disassemble around
20446 is the number of disassembly lines to be produced. If it is -1,
20447 the whole function will be disassembled, in case no @var{end-addr} is
20448 specified. If @var{end-addr} is specified as a non-zero value, and
20449 @var{lines} is lower than the number of disassembly lines between
20450 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20451 displayed; if @var{lines} is higher than the number of lines between
20452 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20455 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20459 @subsubheading Result
20461 The output for each instruction is composed of four fields:
20470 Note that whatever included in the instruction field, is not manipulated
20471 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20473 @subsubheading @value{GDBN} Command
20475 There's no direct mapping from this command to the CLI.
20477 @subsubheading Example
20479 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20483 -data-disassemble -s $pc -e "$pc + 20" -- 0
20486 @{address="0x000107c0",func-name="main",offset="4",
20487 inst="mov 2, %o0"@},
20488 @{address="0x000107c4",func-name="main",offset="8",
20489 inst="sethi %hi(0x11800), %o2"@},
20490 @{address="0x000107c8",func-name="main",offset="12",
20491 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20492 @{address="0x000107cc",func-name="main",offset="16",
20493 inst="sethi %hi(0x11800), %o2"@},
20494 @{address="0x000107d0",func-name="main",offset="20",
20495 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20499 Disassemble the whole @code{main} function. Line 32 is part of
20503 -data-disassemble -f basics.c -l 32 -- 0
20505 @{address="0x000107bc",func-name="main",offset="0",
20506 inst="save %sp, -112, %sp"@},
20507 @{address="0x000107c0",func-name="main",offset="4",
20508 inst="mov 2, %o0"@},
20509 @{address="0x000107c4",func-name="main",offset="8",
20510 inst="sethi %hi(0x11800), %o2"@},
20512 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20513 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20517 Disassemble 3 instructions from the start of @code{main}:
20521 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20523 @{address="0x000107bc",func-name="main",offset="0",
20524 inst="save %sp, -112, %sp"@},
20525 @{address="0x000107c0",func-name="main",offset="4",
20526 inst="mov 2, %o0"@},
20527 @{address="0x000107c4",func-name="main",offset="8",
20528 inst="sethi %hi(0x11800), %o2"@}]
20532 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20536 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20538 src_and_asm_line=@{line="31",
20539 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20540 testsuite/gdb.mi/basics.c",line_asm_insn=[
20541 @{address="0x000107bc",func-name="main",offset="0",
20542 inst="save %sp, -112, %sp"@}]@},
20543 src_and_asm_line=@{line="32",
20544 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20545 testsuite/gdb.mi/basics.c",line_asm_insn=[
20546 @{address="0x000107c0",func-name="main",offset="4",
20547 inst="mov 2, %o0"@},
20548 @{address="0x000107c4",func-name="main",offset="8",
20549 inst="sethi %hi(0x11800), %o2"@}]@}]
20554 @subheading The @code{-data-evaluate-expression} Command
20555 @findex -data-evaluate-expression
20557 @subsubheading Synopsis
20560 -data-evaluate-expression @var{expr}
20563 Evaluate @var{expr} as an expression. The expression could contain an
20564 inferior function call. The function call will execute synchronously.
20565 If the expression contains spaces, it must be enclosed in double quotes.
20567 @subsubheading @value{GDBN} Command
20569 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20570 @samp{call}. In @code{gdbtk} only, there's a corresponding
20571 @samp{gdb_eval} command.
20573 @subsubheading Example
20575 In the following example, the numbers that precede the commands are the
20576 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20577 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20581 211-data-evaluate-expression A
20584 311-data-evaluate-expression &A
20585 311^done,value="0xefffeb7c"
20587 411-data-evaluate-expression A+3
20590 511-data-evaluate-expression "A + 3"
20596 @subheading The @code{-data-list-changed-registers} Command
20597 @findex -data-list-changed-registers
20599 @subsubheading Synopsis
20602 -data-list-changed-registers
20605 Display a list of the registers that have changed.
20607 @subsubheading @value{GDBN} Command
20609 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20610 has the corresponding command @samp{gdb_changed_register_list}.
20612 @subsubheading Example
20614 On a PPC MBX board:
20622 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
20623 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
20626 -data-list-changed-registers
20627 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20628 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20629 "24","25","26","27","28","30","31","64","65","66","67","69"]
20634 @subheading The @code{-data-list-register-names} Command
20635 @findex -data-list-register-names
20637 @subsubheading Synopsis
20640 -data-list-register-names [ ( @var{regno} )+ ]
20643 Show a list of register names for the current target. If no arguments
20644 are given, it shows a list of the names of all the registers. If
20645 integer numbers are given as arguments, it will print a list of the
20646 names of the registers corresponding to the arguments. To ensure
20647 consistency between a register name and its number, the output list may
20648 include empty register names.
20650 @subsubheading @value{GDBN} Command
20652 @value{GDBN} does not have a command which corresponds to
20653 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20654 corresponding command @samp{gdb_regnames}.
20656 @subsubheading Example
20658 For the PPC MBX board:
20661 -data-list-register-names
20662 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20663 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20664 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20665 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20666 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20667 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20668 "", "pc","ps","cr","lr","ctr","xer"]
20670 -data-list-register-names 1 2 3
20671 ^done,register-names=["r1","r2","r3"]
20675 @subheading The @code{-data-list-register-values} Command
20676 @findex -data-list-register-values
20678 @subsubheading Synopsis
20681 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20684 Display the registers' contents. @var{fmt} is the format according to
20685 which the registers' contents are to be returned, followed by an optional
20686 list of numbers specifying the registers to display. A missing list of
20687 numbers indicates that the contents of all the registers must be returned.
20689 Allowed formats for @var{fmt} are:
20706 @subsubheading @value{GDBN} Command
20708 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20709 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20711 @subsubheading Example
20713 For a PPC MBX board (note: line breaks are for readability only, they
20714 don't appear in the actual output):
20718 -data-list-register-values r 64 65
20719 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20720 @{number="65",value="0x00029002"@}]
20722 -data-list-register-values x
20723 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20724 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20725 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20726 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20727 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20728 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20729 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20730 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20731 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20732 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20733 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20734 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20735 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20736 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20737 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20738 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20739 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20740 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20741 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20742 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20743 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20744 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20745 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20746 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20747 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20748 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20749 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20750 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20751 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20752 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20753 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20754 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20755 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20756 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20757 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20758 @{number="69",value="0x20002b03"@}]
20763 @subheading The @code{-data-read-memory} Command
20764 @findex -data-read-memory
20766 @subsubheading Synopsis
20769 -data-read-memory [ -o @var{byte-offset} ]
20770 @var{address} @var{word-format} @var{word-size}
20771 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20778 @item @var{address}
20779 An expression specifying the address of the first memory word to be
20780 read. Complex expressions containing embedded white space should be
20781 quoted using the C convention.
20783 @item @var{word-format}
20784 The format to be used to print the memory words. The notation is the
20785 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20788 @item @var{word-size}
20789 The size of each memory word in bytes.
20791 @item @var{nr-rows}
20792 The number of rows in the output table.
20794 @item @var{nr-cols}
20795 The number of columns in the output table.
20798 If present, indicates that each row should include an @sc{ascii} dump. The
20799 value of @var{aschar} is used as a padding character when a byte is not a
20800 member of the printable @sc{ascii} character set (printable @sc{ascii}
20801 characters are those whose code is between 32 and 126, inclusively).
20803 @item @var{byte-offset}
20804 An offset to add to the @var{address} before fetching memory.
20807 This command displays memory contents as a table of @var{nr-rows} by
20808 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20809 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20810 (returned as @samp{total-bytes}). Should less than the requested number
20811 of bytes be returned by the target, the missing words are identified
20812 using @samp{N/A}. The number of bytes read from the target is returned
20813 in @samp{nr-bytes} and the starting address used to read memory in
20816 The address of the next/previous row or page is available in
20817 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20820 @subsubheading @value{GDBN} Command
20822 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20823 @samp{gdb_get_mem} memory read command.
20825 @subsubheading Example
20827 Read six bytes of memory starting at @code{bytes+6} but then offset by
20828 @code{-6} bytes. Format as three rows of two columns. One byte per
20829 word. Display each word in hex.
20833 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20834 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20835 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20836 prev-page="0x0000138a",memory=[
20837 @{addr="0x00001390",data=["0x00","0x01"]@},
20838 @{addr="0x00001392",data=["0x02","0x03"]@},
20839 @{addr="0x00001394",data=["0x04","0x05"]@}]
20843 Read two bytes of memory starting at address @code{shorts + 64} and
20844 display as a single word formatted in decimal.
20848 5-data-read-memory shorts+64 d 2 1 1
20849 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20850 next-row="0x00001512",prev-row="0x0000150e",
20851 next-page="0x00001512",prev-page="0x0000150e",memory=[
20852 @{addr="0x00001510",data=["128"]@}]
20856 Read thirty two bytes of memory starting at @code{bytes+16} and format
20857 as eight rows of four columns. Include a string encoding with @samp{x}
20858 used as the non-printable character.
20862 4-data-read-memory bytes+16 x 1 8 4 x
20863 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20864 next-row="0x000013c0",prev-row="0x0000139c",
20865 next-page="0x000013c0",prev-page="0x00001380",memory=[
20866 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20867 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20868 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20869 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20870 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20871 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20872 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20873 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20877 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20878 @node GDB/MI Tracepoint Commands
20879 @section @sc{gdb/mi} Tracepoint Commands
20881 The tracepoint commands are not yet implemented.
20883 @c @subheading -trace-actions
20885 @c @subheading -trace-delete
20887 @c @subheading -trace-disable
20889 @c @subheading -trace-dump
20891 @c @subheading -trace-enable
20893 @c @subheading -trace-exists
20895 @c @subheading -trace-find
20897 @c @subheading -trace-frame-number
20899 @c @subheading -trace-info
20901 @c @subheading -trace-insert
20903 @c @subheading -trace-list
20905 @c @subheading -trace-pass-count
20907 @c @subheading -trace-save
20909 @c @subheading -trace-start
20911 @c @subheading -trace-stop
20914 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20915 @node GDB/MI Symbol Query
20916 @section @sc{gdb/mi} Symbol Query Commands
20919 @subheading The @code{-symbol-info-address} Command
20920 @findex -symbol-info-address
20922 @subsubheading Synopsis
20925 -symbol-info-address @var{symbol}
20928 Describe where @var{symbol} is stored.
20930 @subsubheading @value{GDBN} Command
20932 The corresponding @value{GDBN} command is @samp{info address}.
20934 @subsubheading Example
20938 @subheading The @code{-symbol-info-file} Command
20939 @findex -symbol-info-file
20941 @subsubheading Synopsis
20947 Show the file for the symbol.
20949 @subsubheading @value{GDBN} Command
20951 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20952 @samp{gdb_find_file}.
20954 @subsubheading Example
20958 @subheading The @code{-symbol-info-function} Command
20959 @findex -symbol-info-function
20961 @subsubheading Synopsis
20964 -symbol-info-function
20967 Show which function the symbol lives in.
20969 @subsubheading @value{GDBN} Command
20971 @samp{gdb_get_function} in @code{gdbtk}.
20973 @subsubheading Example
20977 @subheading The @code{-symbol-info-line} Command
20978 @findex -symbol-info-line
20980 @subsubheading Synopsis
20986 Show the core addresses of the code for a source line.
20988 @subsubheading @value{GDBN} Command
20990 The corresponding @value{GDBN} command is @samp{info line}.
20991 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20993 @subsubheading Example
20997 @subheading The @code{-symbol-info-symbol} Command
20998 @findex -symbol-info-symbol
21000 @subsubheading Synopsis
21003 -symbol-info-symbol @var{addr}
21006 Describe what symbol is at location @var{addr}.
21008 @subsubheading @value{GDBN} Command
21010 The corresponding @value{GDBN} command is @samp{info symbol}.
21012 @subsubheading Example
21016 @subheading The @code{-symbol-list-functions} Command
21017 @findex -symbol-list-functions
21019 @subsubheading Synopsis
21022 -symbol-list-functions
21025 List the functions in the executable.
21027 @subsubheading @value{GDBN} Command
21029 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
21030 @samp{gdb_search} in @code{gdbtk}.
21032 @subsubheading Example
21036 @subheading The @code{-symbol-list-lines} Command
21037 @findex -symbol-list-lines
21039 @subsubheading Synopsis
21042 -symbol-list-lines @var{filename}
21045 Print the list of lines that contain code and their associated program
21046 addresses for the given source filename. The entries are sorted in
21047 ascending PC order.
21049 @subsubheading @value{GDBN} Command
21051 There is no corresponding @value{GDBN} command.
21053 @subsubheading Example
21056 -symbol-list-lines basics.c
21057 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
21062 @subheading The @code{-symbol-list-types} Command
21063 @findex -symbol-list-types
21065 @subsubheading Synopsis
21071 List all the type names.
21073 @subsubheading @value{GDBN} Command
21075 The corresponding commands are @samp{info types} in @value{GDBN},
21076 @samp{gdb_search} in @code{gdbtk}.
21078 @subsubheading Example
21082 @subheading The @code{-symbol-list-variables} Command
21083 @findex -symbol-list-variables
21085 @subsubheading Synopsis
21088 -symbol-list-variables
21091 List all the global and static variable names.
21093 @subsubheading @value{GDBN} Command
21095 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
21097 @subsubheading Example
21101 @subheading The @code{-symbol-locate} Command
21102 @findex -symbol-locate
21104 @subsubheading Synopsis
21110 @subsubheading @value{GDBN} Command
21112 @samp{gdb_loc} in @code{gdbtk}.
21114 @subsubheading Example
21118 @subheading The @code{-symbol-type} Command
21119 @findex -symbol-type
21121 @subsubheading Synopsis
21124 -symbol-type @var{variable}
21127 Show type of @var{variable}.
21129 @subsubheading @value{GDBN} Command
21131 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
21132 @samp{gdb_obj_variable}.
21134 @subsubheading Example
21138 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21139 @node GDB/MI File Commands
21140 @section @sc{gdb/mi} File Commands
21142 This section describes the GDB/MI commands to specify executable file names
21143 and to read in and obtain symbol table information.
21145 @subheading The @code{-file-exec-and-symbols} Command
21146 @findex -file-exec-and-symbols
21148 @subsubheading Synopsis
21151 -file-exec-and-symbols @var{file}
21154 Specify the executable file to be debugged. This file is the one from
21155 which the symbol table is also read. If no file is specified, the
21156 command clears the executable and symbol information. If breakpoints
21157 are set when using this command with no arguments, @value{GDBN} will produce
21158 error messages. Otherwise, no output is produced, except a completion
21161 @subsubheading @value{GDBN} Command
21163 The corresponding @value{GDBN} command is @samp{file}.
21165 @subsubheading Example
21169 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21175 @subheading The @code{-file-exec-file} Command
21176 @findex -file-exec-file
21178 @subsubheading Synopsis
21181 -file-exec-file @var{file}
21184 Specify the executable file to be debugged. Unlike
21185 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
21186 from this file. If used without argument, @value{GDBN} clears the information
21187 about the executable file. No output is produced, except a completion
21190 @subsubheading @value{GDBN} Command
21192 The corresponding @value{GDBN} command is @samp{exec-file}.
21194 @subsubheading Example
21198 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21204 @subheading The @code{-file-list-exec-sections} Command
21205 @findex -file-list-exec-sections
21207 @subsubheading Synopsis
21210 -file-list-exec-sections
21213 List the sections of the current executable file.
21215 @subsubheading @value{GDBN} Command
21217 The @value{GDBN} command @samp{info file} shows, among the rest, the same
21218 information as this command. @code{gdbtk} has a corresponding command
21219 @samp{gdb_load_info}.
21221 @subsubheading Example
21225 @subheading The @code{-file-list-exec-source-file} Command
21226 @findex -file-list-exec-source-file
21228 @subsubheading Synopsis
21231 -file-list-exec-source-file
21234 List the line number, the current source file, and the absolute path
21235 to the current source file for the current executable. The macro
21236 information field has a value of @samp{1} or @samp{0} depending on
21237 whether or not the file includes preprocessor macro information.
21239 @subsubheading @value{GDBN} Command
21241 The @value{GDBN} equivalent is @samp{info source}
21243 @subsubheading Example
21247 123-file-list-exec-source-file
21248 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
21253 @subheading The @code{-file-list-exec-source-files} Command
21254 @findex -file-list-exec-source-files
21256 @subsubheading Synopsis
21259 -file-list-exec-source-files
21262 List the source files for the current executable.
21264 It will always output the filename, but only when @value{GDBN} can find
21265 the absolute file name of a source file, will it output the fullname.
21267 @subsubheading @value{GDBN} Command
21269 The @value{GDBN} equivalent is @samp{info sources}.
21270 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
21272 @subsubheading Example
21275 -file-list-exec-source-files
21277 @{file=foo.c,fullname=/home/foo.c@},
21278 @{file=/home/bar.c,fullname=/home/bar.c@},
21279 @{file=gdb_could_not_find_fullpath.c@}]
21283 @subheading The @code{-file-list-shared-libraries} Command
21284 @findex -file-list-shared-libraries
21286 @subsubheading Synopsis
21289 -file-list-shared-libraries
21292 List the shared libraries in the program.
21294 @subsubheading @value{GDBN} Command
21296 The corresponding @value{GDBN} command is @samp{info shared}.
21298 @subsubheading Example
21302 @subheading The @code{-file-list-symbol-files} Command
21303 @findex -file-list-symbol-files
21305 @subsubheading Synopsis
21308 -file-list-symbol-files
21313 @subsubheading @value{GDBN} Command
21315 The corresponding @value{GDBN} command is @samp{info file} (part of it).
21317 @subsubheading Example
21321 @subheading The @code{-file-symbol-file} Command
21322 @findex -file-symbol-file
21324 @subsubheading Synopsis
21327 -file-symbol-file @var{file}
21330 Read symbol table info from the specified @var{file} argument. When
21331 used without arguments, clears @value{GDBN}'s symbol table info. No output is
21332 produced, except for a completion notification.
21334 @subsubheading @value{GDBN} Command
21336 The corresponding @value{GDBN} command is @samp{symbol-file}.
21338 @subsubheading Example
21342 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21348 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21349 @node GDB/MI Memory Overlay Commands
21350 @section @sc{gdb/mi} Memory Overlay Commands
21352 The memory overlay commands are not implemented.
21354 @c @subheading -overlay-auto
21356 @c @subheading -overlay-list-mapping-state
21358 @c @subheading -overlay-list-overlays
21360 @c @subheading -overlay-map
21362 @c @subheading -overlay-off
21364 @c @subheading -overlay-on
21366 @c @subheading -overlay-unmap
21368 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21369 @node GDB/MI Signal Handling Commands
21370 @section @sc{gdb/mi} Signal Handling Commands
21372 Signal handling commands are not implemented.
21374 @c @subheading -signal-handle
21376 @c @subheading -signal-list-handle-actions
21378 @c @subheading -signal-list-signal-types
21382 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21383 @node GDB/MI Target Manipulation
21384 @section @sc{gdb/mi} Target Manipulation Commands
21387 @subheading The @code{-target-attach} Command
21388 @findex -target-attach
21390 @subsubheading Synopsis
21393 -target-attach @var{pid} | @var{file}
21396 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
21398 @subsubheading @value{GDBN} Command
21400 The corresponding @value{GDBN} command is @samp{attach}.
21402 @subsubheading Example
21406 @subheading The @code{-target-compare-sections} Command
21407 @findex -target-compare-sections
21409 @subsubheading Synopsis
21412 -target-compare-sections [ @var{section} ]
21415 Compare data of section @var{section} on target to the exec file.
21416 Without the argument, all sections are compared.
21418 @subsubheading @value{GDBN} Command
21420 The @value{GDBN} equivalent is @samp{compare-sections}.
21422 @subsubheading Example
21426 @subheading The @code{-target-detach} Command
21427 @findex -target-detach
21429 @subsubheading Synopsis
21435 Detach from the remote target which normally resumes its execution.
21438 @subsubheading @value{GDBN} Command
21440 The corresponding @value{GDBN} command is @samp{detach}.
21442 @subsubheading Example
21452 @subheading The @code{-target-disconnect} Command
21453 @findex -target-disconnect
21455 @subsubheading Synopsis
21461 Disconnect from the remote target. There's no output and the target is
21462 generally not resumed.
21464 @subsubheading @value{GDBN} Command
21466 The corresponding @value{GDBN} command is @samp{disconnect}.
21468 @subsubheading Example
21478 @subheading The @code{-target-download} Command
21479 @findex -target-download
21481 @subsubheading Synopsis
21487 Loads the executable onto the remote target.
21488 It prints out an update message every half second, which includes the fields:
21492 The name of the section.
21494 The size of what has been sent so far for that section.
21496 The size of the section.
21498 The total size of what was sent so far (the current and the previous sections).
21500 The size of the overall executable to download.
21504 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21505 @sc{gdb/mi} Output Syntax}).
21507 In addition, it prints the name and size of the sections, as they are
21508 downloaded. These messages include the following fields:
21512 The name of the section.
21514 The size of the section.
21516 The size of the overall executable to download.
21520 At the end, a summary is printed.
21522 @subsubheading @value{GDBN} Command
21524 The corresponding @value{GDBN} command is @samp{load}.
21526 @subsubheading Example
21528 Note: each status message appears on a single line. Here the messages
21529 have been broken down so that they can fit onto a page.
21534 +download,@{section=".text",section-size="6668",total-size="9880"@}
21535 +download,@{section=".text",section-sent="512",section-size="6668",
21536 total-sent="512",total-size="9880"@}
21537 +download,@{section=".text",section-sent="1024",section-size="6668",
21538 total-sent="1024",total-size="9880"@}
21539 +download,@{section=".text",section-sent="1536",section-size="6668",
21540 total-sent="1536",total-size="9880"@}
21541 +download,@{section=".text",section-sent="2048",section-size="6668",
21542 total-sent="2048",total-size="9880"@}
21543 +download,@{section=".text",section-sent="2560",section-size="6668",
21544 total-sent="2560",total-size="9880"@}
21545 +download,@{section=".text",section-sent="3072",section-size="6668",
21546 total-sent="3072",total-size="9880"@}
21547 +download,@{section=".text",section-sent="3584",section-size="6668",
21548 total-sent="3584",total-size="9880"@}
21549 +download,@{section=".text",section-sent="4096",section-size="6668",
21550 total-sent="4096",total-size="9880"@}
21551 +download,@{section=".text",section-sent="4608",section-size="6668",
21552 total-sent="4608",total-size="9880"@}
21553 +download,@{section=".text",section-sent="5120",section-size="6668",
21554 total-sent="5120",total-size="9880"@}
21555 +download,@{section=".text",section-sent="5632",section-size="6668",
21556 total-sent="5632",total-size="9880"@}
21557 +download,@{section=".text",section-sent="6144",section-size="6668",
21558 total-sent="6144",total-size="9880"@}
21559 +download,@{section=".text",section-sent="6656",section-size="6668",
21560 total-sent="6656",total-size="9880"@}
21561 +download,@{section=".init",section-size="28",total-size="9880"@}
21562 +download,@{section=".fini",section-size="28",total-size="9880"@}
21563 +download,@{section=".data",section-size="3156",total-size="9880"@}
21564 +download,@{section=".data",section-sent="512",section-size="3156",
21565 total-sent="7236",total-size="9880"@}
21566 +download,@{section=".data",section-sent="1024",section-size="3156",
21567 total-sent="7748",total-size="9880"@}
21568 +download,@{section=".data",section-sent="1536",section-size="3156",
21569 total-sent="8260",total-size="9880"@}
21570 +download,@{section=".data",section-sent="2048",section-size="3156",
21571 total-sent="8772",total-size="9880"@}
21572 +download,@{section=".data",section-sent="2560",section-size="3156",
21573 total-sent="9284",total-size="9880"@}
21574 +download,@{section=".data",section-sent="3072",section-size="3156",
21575 total-sent="9796",total-size="9880"@}
21576 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21582 @subheading The @code{-target-exec-status} Command
21583 @findex -target-exec-status
21585 @subsubheading Synopsis
21588 -target-exec-status
21591 Provide information on the state of the target (whether it is running or
21592 not, for instance).
21594 @subsubheading @value{GDBN} Command
21596 There's no equivalent @value{GDBN} command.
21598 @subsubheading Example
21602 @subheading The @code{-target-list-available-targets} Command
21603 @findex -target-list-available-targets
21605 @subsubheading Synopsis
21608 -target-list-available-targets
21611 List the possible targets to connect to.
21613 @subsubheading @value{GDBN} Command
21615 The corresponding @value{GDBN} command is @samp{help target}.
21617 @subsubheading Example
21621 @subheading The @code{-target-list-current-targets} Command
21622 @findex -target-list-current-targets
21624 @subsubheading Synopsis
21627 -target-list-current-targets
21630 Describe the current target.
21632 @subsubheading @value{GDBN} Command
21634 The corresponding information is printed by @samp{info file} (among
21637 @subsubheading Example
21641 @subheading The @code{-target-list-parameters} Command
21642 @findex -target-list-parameters
21644 @subsubheading Synopsis
21647 -target-list-parameters
21652 @subsubheading @value{GDBN} Command
21656 @subsubheading Example
21660 @subheading The @code{-target-select} Command
21661 @findex -target-select
21663 @subsubheading Synopsis
21666 -target-select @var{type} @var{parameters @dots{}}
21669 Connect @value{GDBN} to the remote target. This command takes two args:
21673 The type of target, for instance @samp{async}, @samp{remote}, etc.
21674 @item @var{parameters}
21675 Device names, host names and the like. @xref{Target Commands, ,
21676 Commands for Managing Targets}, for more details.
21679 The output is a connection notification, followed by the address at
21680 which the target program is, in the following form:
21683 ^connected,addr="@var{address}",func="@var{function name}",
21684 args=[@var{arg list}]
21687 @subsubheading @value{GDBN} Command
21689 The corresponding @value{GDBN} command is @samp{target}.
21691 @subsubheading Example
21695 -target-select async /dev/ttya
21696 ^connected,addr="0xfe00a300",func="??",args=[]
21700 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21701 @node GDB/MI File Transfer Commands
21702 @section @sc{gdb/mi} File Transfer Commands
21705 @subheading The @code{-target-file-put} Command
21706 @findex -target-file-put
21708 @subsubheading Synopsis
21711 -target-file-put @var{hostfile} @var{targetfile}
21714 Copy file @var{hostfile} from the host system (the machine running
21715 @value{GDBN}) to @var{targetfile} on the target system.
21717 @subsubheading @value{GDBN} Command
21719 The corresponding @value{GDBN} command is @samp{remote put}.
21721 @subsubheading Example
21725 -target-file-put localfile remotefile
21731 @subheading The @code{-target-file-put} Command
21732 @findex -target-file-get
21734 @subsubheading Synopsis
21737 -target-file-get @var{targetfile} @var{hostfile}
21740 Copy file @var{targetfile} from the target system to @var{hostfile}
21741 on the host system.
21743 @subsubheading @value{GDBN} Command
21745 The corresponding @value{GDBN} command is @samp{remote get}.
21747 @subsubheading Example
21751 -target-file-get remotefile localfile
21757 @subheading The @code{-target-file-delete} Command
21758 @findex -target-file-delete
21760 @subsubheading Synopsis
21763 -target-file-delete @var{targetfile}
21766 Delete @var{targetfile} from the target system.
21768 @subsubheading @value{GDBN} Command
21770 The corresponding @value{GDBN} command is @samp{remote delete}.
21772 @subsubheading Example
21776 -target-file-delete remotefile
21782 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21783 @node GDB/MI Miscellaneous Commands
21784 @section Miscellaneous @sc{gdb/mi} Commands
21786 @c @subheading -gdb-complete
21788 @subheading The @code{-gdb-exit} Command
21791 @subsubheading Synopsis
21797 Exit @value{GDBN} immediately.
21799 @subsubheading @value{GDBN} Command
21801 Approximately corresponds to @samp{quit}.
21803 @subsubheading Example
21812 @subheading The @code{-exec-abort} Command
21813 @findex -exec-abort
21815 @subsubheading Synopsis
21821 Kill the inferior running program.
21823 @subsubheading @value{GDBN} Command
21825 The corresponding @value{GDBN} command is @samp{kill}.
21827 @subsubheading Example
21831 @subheading The @code{-gdb-set} Command
21834 @subsubheading Synopsis
21840 Set an internal @value{GDBN} variable.
21841 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21843 @subsubheading @value{GDBN} Command
21845 The corresponding @value{GDBN} command is @samp{set}.
21847 @subsubheading Example
21857 @subheading The @code{-gdb-show} Command
21860 @subsubheading Synopsis
21866 Show the current value of a @value{GDBN} variable.
21868 @subsubheading @value{GDBN} Command
21870 The corresponding @value{GDBN} command is @samp{show}.
21872 @subsubheading Example
21881 @c @subheading -gdb-source
21884 @subheading The @code{-gdb-version} Command
21885 @findex -gdb-version
21887 @subsubheading Synopsis
21893 Show version information for @value{GDBN}. Used mostly in testing.
21895 @subsubheading @value{GDBN} Command
21897 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21898 default shows this information when you start an interactive session.
21900 @subsubheading Example
21902 @c This example modifies the actual output from GDB to avoid overfull
21908 ~Copyright 2000 Free Software Foundation, Inc.
21909 ~GDB is free software, covered by the GNU General Public License, and
21910 ~you are welcome to change it and/or distribute copies of it under
21911 ~ certain conditions.
21912 ~Type "show copying" to see the conditions.
21913 ~There is absolutely no warranty for GDB. Type "show warranty" for
21915 ~This GDB was configured as
21916 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21921 @subheading The @code{-list-features} Command
21922 @findex -list-features
21924 Returns a list of particular features of the MI protocol that
21925 this version of gdb implements. A feature can be a command,
21926 or a new field in an output of some command, or even an
21927 important bugfix. While a frontend can sometimes detect presence
21928 of a feature at runtime, it is easier to perform detection at debugger
21931 The command returns a list of strings, with each string naming an
21932 available feature. Each returned string is just a name, it does not
21933 have any internal structure. The list of possible feature names
21939 (gdb) -list-features
21940 ^done,result=["feature1","feature2"]
21943 The current list of features is:
21947 @samp{frozen-varobjs}---indicates presence of the
21948 @code{-var-set-frozen} command, as well as possible presense of the
21949 @code{frozen} field in the output of @code{-varobj-create}.
21951 @samp{pending-breakpoints}---indicates presence of the @code{-f}
21952 option to the @code{-break-insert} command.
21954 @samp{thread-info}---indicates presence of the @code{-thread-info} command.
21958 @subheading The @code{-interpreter-exec} Command
21959 @findex -interpreter-exec
21961 @subheading Synopsis
21964 -interpreter-exec @var{interpreter} @var{command}
21966 @anchor{-interpreter-exec}
21968 Execute the specified @var{command} in the given @var{interpreter}.
21970 @subheading @value{GDBN} Command
21972 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21974 @subheading Example
21978 -interpreter-exec console "break main"
21979 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21980 &"During symbol reading, bad structure-type format.\n"
21981 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21986 @subheading The @code{-inferior-tty-set} Command
21987 @findex -inferior-tty-set
21989 @subheading Synopsis
21992 -inferior-tty-set /dev/pts/1
21995 Set terminal for future runs of the program being debugged.
21997 @subheading @value{GDBN} Command
21999 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
22001 @subheading Example
22005 -inferior-tty-set /dev/pts/1
22010 @subheading The @code{-inferior-tty-show} Command
22011 @findex -inferior-tty-show
22013 @subheading Synopsis
22019 Show terminal for future runs of program being debugged.
22021 @subheading @value{GDBN} Command
22023 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
22025 @subheading Example
22029 -inferior-tty-set /dev/pts/1
22033 ^done,inferior_tty_terminal="/dev/pts/1"
22037 @subheading The @code{-enable-timings} Command
22038 @findex -enable-timings
22040 @subheading Synopsis
22043 -enable-timings [yes | no]
22046 Toggle the printing of the wallclock, user and system times for an MI
22047 command as a field in its output. This command is to help frontend
22048 developers optimize the performance of their code. No argument is
22049 equivalent to @samp{yes}.
22051 @subheading @value{GDBN} Command
22055 @subheading Example
22063 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22064 addr="0x080484ed",func="main",file="myprog.c",
22065 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
22066 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
22074 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22075 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
22076 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
22077 fullname="/home/nickrob/myprog.c",line="73"@}
22082 @chapter @value{GDBN} Annotations
22084 This chapter describes annotations in @value{GDBN}. Annotations were
22085 designed to interface @value{GDBN} to graphical user interfaces or other
22086 similar programs which want to interact with @value{GDBN} at a
22087 relatively high level.
22089 The annotation mechanism has largely been superseded by @sc{gdb/mi}
22093 This is Edition @value{EDITION}, @value{DATE}.
22097 * Annotations Overview:: What annotations are; the general syntax.
22098 * Server Prefix:: Issuing a command without affecting user state.
22099 * Prompting:: Annotations marking @value{GDBN}'s need for input.
22100 * Errors:: Annotations for error messages.
22101 * Invalidation:: Some annotations describe things now invalid.
22102 * Annotations for Running::
22103 Whether the program is running, how it stopped, etc.
22104 * Source Annotations:: Annotations describing source code.
22107 @node Annotations Overview
22108 @section What is an Annotation?
22109 @cindex annotations
22111 Annotations start with a newline character, two @samp{control-z}
22112 characters, and the name of the annotation. If there is no additional
22113 information associated with this annotation, the name of the annotation
22114 is followed immediately by a newline. If there is additional
22115 information, the name of the annotation is followed by a space, the
22116 additional information, and a newline. The additional information
22117 cannot contain newline characters.
22119 Any output not beginning with a newline and two @samp{control-z}
22120 characters denotes literal output from @value{GDBN}. Currently there is
22121 no need for @value{GDBN} to output a newline followed by two
22122 @samp{control-z} characters, but if there was such a need, the
22123 annotations could be extended with an @samp{escape} annotation which
22124 means those three characters as output.
22126 The annotation @var{level}, which is specified using the
22127 @option{--annotate} command line option (@pxref{Mode Options}), controls
22128 how much information @value{GDBN} prints together with its prompt,
22129 values of expressions, source lines, and other types of output. Level 0
22130 is for no annotations, level 1 is for use when @value{GDBN} is run as a
22131 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
22132 for programs that control @value{GDBN}, and level 2 annotations have
22133 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
22134 Interface, annotate, GDB's Obsolete Annotations}).
22137 @kindex set annotate
22138 @item set annotate @var{level}
22139 The @value{GDBN} command @code{set annotate} sets the level of
22140 annotations to the specified @var{level}.
22142 @item show annotate
22143 @kindex show annotate
22144 Show the current annotation level.
22147 This chapter describes level 3 annotations.
22149 A simple example of starting up @value{GDBN} with annotations is:
22152 $ @kbd{gdb --annotate=3}
22154 Copyright 2003 Free Software Foundation, Inc.
22155 GDB is free software, covered by the GNU General Public License,
22156 and you are welcome to change it and/or distribute copies of it
22157 under certain conditions.
22158 Type "show copying" to see the conditions.
22159 There is absolutely no warranty for GDB. Type "show warranty"
22161 This GDB was configured as "i386-pc-linux-gnu"
22172 Here @samp{quit} is input to @value{GDBN}; the rest is output from
22173 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
22174 denotes a @samp{control-z} character) are annotations; the rest is
22175 output from @value{GDBN}.
22177 @node Server Prefix
22178 @section The Server Prefix
22179 @cindex server prefix
22181 If you prefix a command with @samp{server } then it will not affect
22182 the command history, nor will it affect @value{GDBN}'s notion of which
22183 command to repeat if @key{RET} is pressed on a line by itself. This
22184 means that commands can be run behind a user's back by a front-end in
22185 a transparent manner.
22187 The server prefix does not affect the recording of values into the value
22188 history; to print a value without recording it into the value history,
22189 use the @code{output} command instead of the @code{print} command.
22192 @section Annotation for @value{GDBN} Input
22194 @cindex annotations for prompts
22195 When @value{GDBN} prompts for input, it annotates this fact so it is possible
22196 to know when to send output, when the output from a given command is
22199 Different kinds of input each have a different @dfn{input type}. Each
22200 input type has three annotations: a @code{pre-} annotation, which
22201 denotes the beginning of any prompt which is being output, a plain
22202 annotation, which denotes the end of the prompt, and then a @code{post-}
22203 annotation which denotes the end of any echo which may (or may not) be
22204 associated with the input. For example, the @code{prompt} input type
22205 features the following annotations:
22213 The input types are
22216 @findex pre-prompt annotation
22217 @findex prompt annotation
22218 @findex post-prompt annotation
22220 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
22222 @findex pre-commands annotation
22223 @findex commands annotation
22224 @findex post-commands annotation
22226 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
22227 command. The annotations are repeated for each command which is input.
22229 @findex pre-overload-choice annotation
22230 @findex overload-choice annotation
22231 @findex post-overload-choice annotation
22232 @item overload-choice
22233 When @value{GDBN} wants the user to select between various overloaded functions.
22235 @findex pre-query annotation
22236 @findex query annotation
22237 @findex post-query annotation
22239 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
22241 @findex pre-prompt-for-continue annotation
22242 @findex prompt-for-continue annotation
22243 @findex post-prompt-for-continue annotation
22244 @item prompt-for-continue
22245 When @value{GDBN} is asking the user to press return to continue. Note: Don't
22246 expect this to work well; instead use @code{set height 0} to disable
22247 prompting. This is because the counting of lines is buggy in the
22248 presence of annotations.
22253 @cindex annotations for errors, warnings and interrupts
22255 @findex quit annotation
22260 This annotation occurs right before @value{GDBN} responds to an interrupt.
22262 @findex error annotation
22267 This annotation occurs right before @value{GDBN} responds to an error.
22269 Quit and error annotations indicate that any annotations which @value{GDBN} was
22270 in the middle of may end abruptly. For example, if a
22271 @code{value-history-begin} annotation is followed by a @code{error}, one
22272 cannot expect to receive the matching @code{value-history-end}. One
22273 cannot expect not to receive it either, however; an error annotation
22274 does not necessarily mean that @value{GDBN} is immediately returning all the way
22277 @findex error-begin annotation
22278 A quit or error annotation may be preceded by
22284 Any output between that and the quit or error annotation is the error
22287 Warning messages are not yet annotated.
22288 @c If we want to change that, need to fix warning(), type_error(),
22289 @c range_error(), and possibly other places.
22292 @section Invalidation Notices
22294 @cindex annotations for invalidation messages
22295 The following annotations say that certain pieces of state may have
22299 @findex frames-invalid annotation
22300 @item ^Z^Zframes-invalid
22302 The frames (for example, output from the @code{backtrace} command) may
22305 @findex breakpoints-invalid annotation
22306 @item ^Z^Zbreakpoints-invalid
22308 The breakpoints may have changed. For example, the user just added or
22309 deleted a breakpoint.
22312 @node Annotations for Running
22313 @section Running the Program
22314 @cindex annotations for running programs
22316 @findex starting annotation
22317 @findex stopping annotation
22318 When the program starts executing due to a @value{GDBN} command such as
22319 @code{step} or @code{continue},
22325 is output. When the program stops,
22331 is output. Before the @code{stopped} annotation, a variety of
22332 annotations describe how the program stopped.
22335 @findex exited annotation
22336 @item ^Z^Zexited @var{exit-status}
22337 The program exited, and @var{exit-status} is the exit status (zero for
22338 successful exit, otherwise nonzero).
22340 @findex signalled annotation
22341 @findex signal-name annotation
22342 @findex signal-name-end annotation
22343 @findex signal-string annotation
22344 @findex signal-string-end annotation
22345 @item ^Z^Zsignalled
22346 The program exited with a signal. After the @code{^Z^Zsignalled}, the
22347 annotation continues:
22353 ^Z^Zsignal-name-end
22357 ^Z^Zsignal-string-end
22362 where @var{name} is the name of the signal, such as @code{SIGILL} or
22363 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
22364 as @code{Illegal Instruction} or @code{Segmentation fault}.
22365 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
22366 user's benefit and have no particular format.
22368 @findex signal annotation
22370 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
22371 just saying that the program received the signal, not that it was
22372 terminated with it.
22374 @findex breakpoint annotation
22375 @item ^Z^Zbreakpoint @var{number}
22376 The program hit breakpoint number @var{number}.
22378 @findex watchpoint annotation
22379 @item ^Z^Zwatchpoint @var{number}
22380 The program hit watchpoint number @var{number}.
22383 @node Source Annotations
22384 @section Displaying Source
22385 @cindex annotations for source display
22387 @findex source annotation
22388 The following annotation is used instead of displaying source code:
22391 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
22394 where @var{filename} is an absolute file name indicating which source
22395 file, @var{line} is the line number within that file (where 1 is the
22396 first line in the file), @var{character} is the character position
22397 within the file (where 0 is the first character in the file) (for most
22398 debug formats this will necessarily point to the beginning of a line),
22399 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
22400 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
22401 @var{addr} is the address in the target program associated with the
22402 source which is being displayed. @var{addr} is in the form @samp{0x}
22403 followed by one or more lowercase hex digits (note that this does not
22404 depend on the language).
22407 @chapter Reporting Bugs in @value{GDBN}
22408 @cindex bugs in @value{GDBN}
22409 @cindex reporting bugs in @value{GDBN}
22411 Your bug reports play an essential role in making @value{GDBN} reliable.
22413 Reporting a bug may help you by bringing a solution to your problem, or it
22414 may not. But in any case the principal function of a bug report is to help
22415 the entire community by making the next version of @value{GDBN} work better. Bug
22416 reports are your contribution to the maintenance of @value{GDBN}.
22418 In order for a bug report to serve its purpose, you must include the
22419 information that enables us to fix the bug.
22422 * Bug Criteria:: Have you found a bug?
22423 * Bug Reporting:: How to report bugs
22427 @section Have You Found a Bug?
22428 @cindex bug criteria
22430 If you are not sure whether you have found a bug, here are some guidelines:
22433 @cindex fatal signal
22434 @cindex debugger crash
22435 @cindex crash of debugger
22437 If the debugger gets a fatal signal, for any input whatever, that is a
22438 @value{GDBN} bug. Reliable debuggers never crash.
22440 @cindex error on valid input
22442 If @value{GDBN} produces an error message for valid input, that is a
22443 bug. (Note that if you're cross debugging, the problem may also be
22444 somewhere in the connection to the target.)
22446 @cindex invalid input
22448 If @value{GDBN} does not produce an error message for invalid input,
22449 that is a bug. However, you should note that your idea of
22450 ``invalid input'' might be our idea of ``an extension'' or ``support
22451 for traditional practice''.
22454 If you are an experienced user of debugging tools, your suggestions
22455 for improvement of @value{GDBN} are welcome in any case.
22458 @node Bug Reporting
22459 @section How to Report Bugs
22460 @cindex bug reports
22461 @cindex @value{GDBN} bugs, reporting
22463 A number of companies and individuals offer support for @sc{gnu} products.
22464 If you obtained @value{GDBN} from a support organization, we recommend you
22465 contact that organization first.
22467 You can find contact information for many support companies and
22468 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
22470 @c should add a web page ref...
22472 In any event, we also recommend that you submit bug reports for
22473 @value{GDBN}. The preferred method is to submit them directly using
22474 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
22475 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
22478 @strong{Do not send bug reports to @samp{info-gdb}, or to
22479 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
22480 not want to receive bug reports. Those that do have arranged to receive
22483 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
22484 serves as a repeater. The mailing list and the newsgroup carry exactly
22485 the same messages. Often people think of posting bug reports to the
22486 newsgroup instead of mailing them. This appears to work, but it has one
22487 problem which can be crucial: a newsgroup posting often lacks a mail
22488 path back to the sender. Thus, if we need to ask for more information,
22489 we may be unable to reach you. For this reason, it is better to send
22490 bug reports to the mailing list.
22492 The fundamental principle of reporting bugs usefully is this:
22493 @strong{report all the facts}. If you are not sure whether to state a
22494 fact or leave it out, state it!
22496 Often people omit facts because they think they know what causes the
22497 problem and assume that some details do not matter. Thus, you might
22498 assume that the name of the variable you use in an example does not matter.
22499 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
22500 stray memory reference which happens to fetch from the location where that
22501 name is stored in memory; perhaps, if the name were different, the contents
22502 of that location would fool the debugger into doing the right thing despite
22503 the bug. Play it safe and give a specific, complete example. That is the
22504 easiest thing for you to do, and the most helpful.
22506 Keep in mind that the purpose of a bug report is to enable us to fix the
22507 bug. It may be that the bug has been reported previously, but neither
22508 you nor we can know that unless your bug report is complete and
22511 Sometimes people give a few sketchy facts and ask, ``Does this ring a
22512 bell?'' Those bug reports are useless, and we urge everyone to
22513 @emph{refuse to respond to them} except to chide the sender to report
22516 To enable us to fix the bug, you should include all these things:
22520 The version of @value{GDBN}. @value{GDBN} announces it if you start
22521 with no arguments; you can also print it at any time using @code{show
22524 Without this, we will not know whether there is any point in looking for
22525 the bug in the current version of @value{GDBN}.
22528 The type of machine you are using, and the operating system name and
22532 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
22533 ``@value{GCC}--2.8.1''.
22536 What compiler (and its version) was used to compile the program you are
22537 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
22538 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
22539 to get this information; for other compilers, see the documentation for
22543 The command arguments you gave the compiler to compile your example and
22544 observe the bug. For example, did you use @samp{-O}? To guarantee
22545 you will not omit something important, list them all. A copy of the
22546 Makefile (or the output from make) is sufficient.
22548 If we were to try to guess the arguments, we would probably guess wrong
22549 and then we might not encounter the bug.
22552 A complete input script, and all necessary source files, that will
22556 A description of what behavior you observe that you believe is
22557 incorrect. For example, ``It gets a fatal signal.''
22559 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
22560 will certainly notice it. But if the bug is incorrect output, we might
22561 not notice unless it is glaringly wrong. You might as well not give us
22562 a chance to make a mistake.
22564 Even if the problem you experience is a fatal signal, you should still
22565 say so explicitly. Suppose something strange is going on, such as, your
22566 copy of @value{GDBN} is out of synch, or you have encountered a bug in
22567 the C library on your system. (This has happened!) Your copy might
22568 crash and ours would not. If you told us to expect a crash, then when
22569 ours fails to crash, we would know that the bug was not happening for
22570 us. If you had not told us to expect a crash, then we would not be able
22571 to draw any conclusion from our observations.
22574 @cindex recording a session script
22575 To collect all this information, you can use a session recording program
22576 such as @command{script}, which is available on many Unix systems.
22577 Just run your @value{GDBN} session inside @command{script} and then
22578 include the @file{typescript} file with your bug report.
22580 Another way to record a @value{GDBN} session is to run @value{GDBN}
22581 inside Emacs and then save the entire buffer to a file.
22584 If you wish to suggest changes to the @value{GDBN} source, send us context
22585 diffs. If you even discuss something in the @value{GDBN} source, refer to
22586 it by context, not by line number.
22588 The line numbers in our development sources will not match those in your
22589 sources. Your line numbers would convey no useful information to us.
22593 Here are some things that are not necessary:
22597 A description of the envelope of the bug.
22599 Often people who encounter a bug spend a lot of time investigating
22600 which changes to the input file will make the bug go away and which
22601 changes will not affect it.
22603 This is often time consuming and not very useful, because the way we
22604 will find the bug is by running a single example under the debugger
22605 with breakpoints, not by pure deduction from a series of examples.
22606 We recommend that you save your time for something else.
22608 Of course, if you can find a simpler example to report @emph{instead}
22609 of the original one, that is a convenience for us. Errors in the
22610 output will be easier to spot, running under the debugger will take
22611 less time, and so on.
22613 However, simplification is not vital; if you do not want to do this,
22614 report the bug anyway and send us the entire test case you used.
22617 A patch for the bug.
22619 A patch for the bug does help us if it is a good one. But do not omit
22620 the necessary information, such as the test case, on the assumption that
22621 a patch is all we need. We might see problems with your patch and decide
22622 to fix the problem another way, or we might not understand it at all.
22624 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22625 construct an example that will make the program follow a certain path
22626 through the code. If you do not send us the example, we will not be able
22627 to construct one, so we will not be able to verify that the bug is fixed.
22629 And if we cannot understand what bug you are trying to fix, or why your
22630 patch should be an improvement, we will not install it. A test case will
22631 help us to understand.
22634 A guess about what the bug is or what it depends on.
22636 Such guesses are usually wrong. Even we cannot guess right about such
22637 things without first using the debugger to find the facts.
22640 @c The readline documentation is distributed with the readline code
22641 @c and consists of the two following files:
22643 @c inc-hist.texinfo
22644 @c Use -I with makeinfo to point to the appropriate directory,
22645 @c environment var TEXINPUTS with TeX.
22646 @include rluser.texi
22647 @include inc-hist.texinfo
22650 @node Formatting Documentation
22651 @appendix Formatting Documentation
22653 @cindex @value{GDBN} reference card
22654 @cindex reference card
22655 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22656 for printing with PostScript or Ghostscript, in the @file{gdb}
22657 subdirectory of the main source directory@footnote{In
22658 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22659 release.}. If you can use PostScript or Ghostscript with your printer,
22660 you can print the reference card immediately with @file{refcard.ps}.
22662 The release also includes the source for the reference card. You
22663 can format it, using @TeX{}, by typing:
22669 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22670 mode on US ``letter'' size paper;
22671 that is, on a sheet 11 inches wide by 8.5 inches
22672 high. You will need to specify this form of printing as an option to
22673 your @sc{dvi} output program.
22675 @cindex documentation
22677 All the documentation for @value{GDBN} comes as part of the machine-readable
22678 distribution. The documentation is written in Texinfo format, which is
22679 a documentation system that uses a single source file to produce both
22680 on-line information and a printed manual. You can use one of the Info
22681 formatting commands to create the on-line version of the documentation
22682 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22684 @value{GDBN} includes an already formatted copy of the on-line Info
22685 version of this manual in the @file{gdb} subdirectory. The main Info
22686 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22687 subordinate files matching @samp{gdb.info*} in the same directory. If
22688 necessary, you can print out these files, or read them with any editor;
22689 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22690 Emacs or the standalone @code{info} program, available as part of the
22691 @sc{gnu} Texinfo distribution.
22693 If you want to format these Info files yourself, you need one of the
22694 Info formatting programs, such as @code{texinfo-format-buffer} or
22697 If you have @code{makeinfo} installed, and are in the top level
22698 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22699 version @value{GDBVN}), you can make the Info file by typing:
22706 If you want to typeset and print copies of this manual, you need @TeX{},
22707 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22708 Texinfo definitions file.
22710 @TeX{} is a typesetting program; it does not print files directly, but
22711 produces output files called @sc{dvi} files. To print a typeset
22712 document, you need a program to print @sc{dvi} files. If your system
22713 has @TeX{} installed, chances are it has such a program. The precise
22714 command to use depends on your system; @kbd{lpr -d} is common; another
22715 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22716 require a file name without any extension or a @samp{.dvi} extension.
22718 @TeX{} also requires a macro definitions file called
22719 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22720 written in Texinfo format. On its own, @TeX{} cannot either read or
22721 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22722 and is located in the @file{gdb-@var{version-number}/texinfo}
22725 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22726 typeset and print this manual. First switch to the @file{gdb}
22727 subdirectory of the main source directory (for example, to
22728 @file{gdb-@value{GDBVN}/gdb}) and type:
22734 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22736 @node Installing GDB
22737 @appendix Installing @value{GDBN}
22738 @cindex installation
22741 * Requirements:: Requirements for building @value{GDBN}
22742 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22743 * Separate Objdir:: Compiling @value{GDBN} in another directory
22744 * Config Names:: Specifying names for hosts and targets
22745 * Configure Options:: Summary of options for configure
22749 @section Requirements for Building @value{GDBN}
22750 @cindex building @value{GDBN}, requirements for
22752 Building @value{GDBN} requires various tools and packages to be available.
22753 Other packages will be used only if they are found.
22755 @heading Tools/Packages Necessary for Building @value{GDBN}
22757 @item ISO C90 compiler
22758 @value{GDBN} is written in ISO C90. It should be buildable with any
22759 working C90 compiler, e.g.@: GCC.
22763 @heading Tools/Packages Optional for Building @value{GDBN}
22767 @value{GDBN} can use the Expat XML parsing library. This library may be
22768 included with your operating system distribution; if it is not, you
22769 can get the latest version from @url{http://expat.sourceforge.net}.
22770 The @file{configure} script will search for this library in several
22771 standard locations; if it is installed in an unusual path, you can
22772 use the @option{--with-libexpat-prefix} option to specify its location.
22778 Remote protocol memory maps (@pxref{Memory Map Format})
22780 Target descriptions (@pxref{Target Descriptions})
22782 Remote shared library lists (@pxref{Library List Format})
22784 MS-Windows shared libraries (@pxref{Shared Libraries})
22788 @cindex compressed debug sections
22789 @value{GDBN} will use the @samp{zlib} library, if available, to read
22790 compressed debug sections. Some linkers, such as GNU gold, are capable
22791 of producing binaries with compressed debug sections. If @value{GDBN}
22792 is compiled with @samp{zlib}, it will be able to read the debug
22793 information in such binaries.
22795 The @samp{zlib} library is likely included with your operating system
22796 distribution; if it is not, you can get the latest version from
22797 @url{http://zlib.net}.
22801 @node Running Configure
22802 @section Invoking the @value{GDBN} @file{configure} Script
22803 @cindex configuring @value{GDBN}
22804 @value{GDBN} comes with a @file{configure} script that automates the process
22805 of preparing @value{GDBN} for installation; you can then use @code{make} to
22806 build the @code{gdb} program.
22808 @c irrelevant in info file; it's as current as the code it lives with.
22809 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22810 look at the @file{README} file in the sources; we may have improved the
22811 installation procedures since publishing this manual.}
22814 The @value{GDBN} distribution includes all the source code you need for
22815 @value{GDBN} in a single directory, whose name is usually composed by
22816 appending the version number to @samp{gdb}.
22818 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22819 @file{gdb-@value{GDBVN}} directory. That directory contains:
22822 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22823 script for configuring @value{GDBN} and all its supporting libraries
22825 @item gdb-@value{GDBVN}/gdb
22826 the source specific to @value{GDBN} itself
22828 @item gdb-@value{GDBVN}/bfd
22829 source for the Binary File Descriptor library
22831 @item gdb-@value{GDBVN}/include
22832 @sc{gnu} include files
22834 @item gdb-@value{GDBVN}/libiberty
22835 source for the @samp{-liberty} free software library
22837 @item gdb-@value{GDBVN}/opcodes
22838 source for the library of opcode tables and disassemblers
22840 @item gdb-@value{GDBVN}/readline
22841 source for the @sc{gnu} command-line interface
22843 @item gdb-@value{GDBVN}/glob
22844 source for the @sc{gnu} filename pattern-matching subroutine
22846 @item gdb-@value{GDBVN}/mmalloc
22847 source for the @sc{gnu} memory-mapped malloc package
22850 The simplest way to configure and build @value{GDBN} is to run @file{configure}
22851 from the @file{gdb-@var{version-number}} source directory, which in
22852 this example is the @file{gdb-@value{GDBVN}} directory.
22854 First switch to the @file{gdb-@var{version-number}} source directory
22855 if you are not already in it; then run @file{configure}. Pass the
22856 identifier for the platform on which @value{GDBN} will run as an
22862 cd gdb-@value{GDBVN}
22863 ./configure @var{host}
22868 where @var{host} is an identifier such as @samp{sun4} or
22869 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22870 (You can often leave off @var{host}; @file{configure} tries to guess the
22871 correct value by examining your system.)
22873 Running @samp{configure @var{host}} and then running @code{make} builds the
22874 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22875 libraries, then @code{gdb} itself. The configured source files, and the
22876 binaries, are left in the corresponding source directories.
22879 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22880 system does not recognize this automatically when you run a different
22881 shell, you may need to run @code{sh} on it explicitly:
22884 sh configure @var{host}
22887 If you run @file{configure} from a directory that contains source
22888 directories for multiple libraries or programs, such as the
22889 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
22891 creates configuration files for every directory level underneath (unless
22892 you tell it not to, with the @samp{--norecursion} option).
22894 You should run the @file{configure} script from the top directory in the
22895 source tree, the @file{gdb-@var{version-number}} directory. If you run
22896 @file{configure} from one of the subdirectories, you will configure only
22897 that subdirectory. That is usually not what you want. In particular,
22898 if you run the first @file{configure} from the @file{gdb} subdirectory
22899 of the @file{gdb-@var{version-number}} directory, you will omit the
22900 configuration of @file{bfd}, @file{readline}, and other sibling
22901 directories of the @file{gdb} subdirectory. This leads to build errors
22902 about missing include files such as @file{bfd/bfd.h}.
22904 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22905 However, you should make sure that the shell on your path (named by
22906 the @samp{SHELL} environment variable) is publicly readable. Remember
22907 that @value{GDBN} uses the shell to start your program---some systems refuse to
22908 let @value{GDBN} debug child processes whose programs are not readable.
22910 @node Separate Objdir
22911 @section Compiling @value{GDBN} in Another Directory
22913 If you want to run @value{GDBN} versions for several host or target machines,
22914 you need a different @code{gdb} compiled for each combination of
22915 host and target. @file{configure} is designed to make this easy by
22916 allowing you to generate each configuration in a separate subdirectory,
22917 rather than in the source directory. If your @code{make} program
22918 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22919 @code{make} in each of these directories builds the @code{gdb}
22920 program specified there.
22922 To build @code{gdb} in a separate directory, run @file{configure}
22923 with the @samp{--srcdir} option to specify where to find the source.
22924 (You also need to specify a path to find @file{configure}
22925 itself from your working directory. If the path to @file{configure}
22926 would be the same as the argument to @samp{--srcdir}, you can leave out
22927 the @samp{--srcdir} option; it is assumed.)
22929 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22930 separate directory for a Sun 4 like this:
22934 cd gdb-@value{GDBVN}
22937 ../gdb-@value{GDBVN}/configure sun4
22942 When @file{configure} builds a configuration using a remote source
22943 directory, it creates a tree for the binaries with the same structure
22944 (and using the same names) as the tree under the source directory. In
22945 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22946 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22947 @file{gdb-sun4/gdb}.
22949 Make sure that your path to the @file{configure} script has just one
22950 instance of @file{gdb} in it. If your path to @file{configure} looks
22951 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22952 one subdirectory of @value{GDBN}, not the whole package. This leads to
22953 build errors about missing include files such as @file{bfd/bfd.h}.
22955 One popular reason to build several @value{GDBN} configurations in separate
22956 directories is to configure @value{GDBN} for cross-compiling (where
22957 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22958 programs that run on another machine---the @dfn{target}).
22959 You specify a cross-debugging target by
22960 giving the @samp{--target=@var{target}} option to @file{configure}.
22962 When you run @code{make} to build a program or library, you must run
22963 it in a configured directory---whatever directory you were in when you
22964 called @file{configure} (or one of its subdirectories).
22966 The @code{Makefile} that @file{configure} generates in each source
22967 directory also runs recursively. If you type @code{make} in a source
22968 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22969 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22970 will build all the required libraries, and then build GDB.
22972 When you have multiple hosts or targets configured in separate
22973 directories, you can run @code{make} on them in parallel (for example,
22974 if they are NFS-mounted on each of the hosts); they will not interfere
22978 @section Specifying Names for Hosts and Targets
22980 The specifications used for hosts and targets in the @file{configure}
22981 script are based on a three-part naming scheme, but some short predefined
22982 aliases are also supported. The full naming scheme encodes three pieces
22983 of information in the following pattern:
22986 @var{architecture}-@var{vendor}-@var{os}
22989 For example, you can use the alias @code{sun4} as a @var{host} argument,
22990 or as the value for @var{target} in a @code{--target=@var{target}}
22991 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22993 The @file{configure} script accompanying @value{GDBN} does not provide
22994 any query facility to list all supported host and target names or
22995 aliases. @file{configure} calls the Bourne shell script
22996 @code{config.sub} to map abbreviations to full names; you can read the
22997 script, if you wish, or you can use it to test your guesses on
22998 abbreviations---for example:
23001 % sh config.sub i386-linux
23003 % sh config.sub alpha-linux
23004 alpha-unknown-linux-gnu
23005 % sh config.sub hp9k700
23007 % sh config.sub sun4
23008 sparc-sun-sunos4.1.1
23009 % sh config.sub sun3
23010 m68k-sun-sunos4.1.1
23011 % sh config.sub i986v
23012 Invalid configuration `i986v': machine `i986v' not recognized
23016 @code{config.sub} is also distributed in the @value{GDBN} source
23017 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
23019 @node Configure Options
23020 @section @file{configure} Options
23022 Here is a summary of the @file{configure} options and arguments that
23023 are most often useful for building @value{GDBN}. @file{configure} also has
23024 several other options not listed here. @inforef{What Configure
23025 Does,,configure.info}, for a full explanation of @file{configure}.
23028 configure @r{[}--help@r{]}
23029 @r{[}--prefix=@var{dir}@r{]}
23030 @r{[}--exec-prefix=@var{dir}@r{]}
23031 @r{[}--srcdir=@var{dirname}@r{]}
23032 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
23033 @r{[}--target=@var{target}@r{]}
23038 You may introduce options with a single @samp{-} rather than
23039 @samp{--} if you prefer; but you may abbreviate option names if you use
23044 Display a quick summary of how to invoke @file{configure}.
23046 @item --prefix=@var{dir}
23047 Configure the source to install programs and files under directory
23050 @item --exec-prefix=@var{dir}
23051 Configure the source to install programs under directory
23054 @c avoid splitting the warning from the explanation:
23056 @item --srcdir=@var{dirname}
23057 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
23058 @code{make} that implements the @code{VPATH} feature.}@*
23059 Use this option to make configurations in directories separate from the
23060 @value{GDBN} source directories. Among other things, you can use this to
23061 build (or maintain) several configurations simultaneously, in separate
23062 directories. @file{configure} writes configuration-specific files in
23063 the current directory, but arranges for them to use the source in the
23064 directory @var{dirname}. @file{configure} creates directories under
23065 the working directory in parallel to the source directories below
23068 @item --norecursion
23069 Configure only the directory level where @file{configure} is executed; do not
23070 propagate configuration to subdirectories.
23072 @item --target=@var{target}
23073 Configure @value{GDBN} for cross-debugging programs running on the specified
23074 @var{target}. Without this option, @value{GDBN} is configured to debug
23075 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
23077 There is no convenient way to generate a list of all available targets.
23079 @item @var{host} @dots{}
23080 Configure @value{GDBN} to run on the specified @var{host}.
23082 There is no convenient way to generate a list of all available hosts.
23085 There are many other options available as well, but they are generally
23086 needed for special purposes only.
23088 @node Maintenance Commands
23089 @appendix Maintenance Commands
23090 @cindex maintenance commands
23091 @cindex internal commands
23093 In addition to commands intended for @value{GDBN} users, @value{GDBN}
23094 includes a number of commands intended for @value{GDBN} developers,
23095 that are not documented elsewhere in this manual. These commands are
23096 provided here for reference. (For commands that turn on debugging
23097 messages, see @ref{Debugging Output}.)
23100 @kindex maint agent
23101 @item maint agent @var{expression}
23102 Translate the given @var{expression} into remote agent bytecodes.
23103 This command is useful for debugging the Agent Expression mechanism
23104 (@pxref{Agent Expressions}).
23106 @kindex maint info breakpoints
23107 @item @anchor{maint info breakpoints}maint info breakpoints
23108 Using the same format as @samp{info breakpoints}, display both the
23109 breakpoints you've set explicitly, and those @value{GDBN} is using for
23110 internal purposes. Internal breakpoints are shown with negative
23111 breakpoint numbers. The type column identifies what kind of breakpoint
23116 Normal, explicitly set breakpoint.
23119 Normal, explicitly set watchpoint.
23122 Internal breakpoint, used to handle correctly stepping through
23123 @code{longjmp} calls.
23125 @item longjmp resume
23126 Internal breakpoint at the target of a @code{longjmp}.
23129 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
23132 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
23135 Shared library events.
23139 @kindex maint check-symtabs
23140 @item maint check-symtabs
23141 Check the consistency of psymtabs and symtabs.
23143 @kindex maint cplus first_component
23144 @item maint cplus first_component @var{name}
23145 Print the first C@t{++} class/namespace component of @var{name}.
23147 @kindex maint cplus namespace
23148 @item maint cplus namespace
23149 Print the list of possible C@t{++} namespaces.
23151 @kindex maint demangle
23152 @item maint demangle @var{name}
23153 Demangle a C@t{++} or Objective-C mangled @var{name}.
23155 @kindex maint deprecate
23156 @kindex maint undeprecate
23157 @cindex deprecated commands
23158 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
23159 @itemx maint undeprecate @var{command}
23160 Deprecate or undeprecate the named @var{command}. Deprecated commands
23161 cause @value{GDBN} to issue a warning when you use them. The optional
23162 argument @var{replacement} says which newer command should be used in
23163 favor of the deprecated one; if it is given, @value{GDBN} will mention
23164 the replacement as part of the warning.
23166 @kindex maint dump-me
23167 @item maint dump-me
23168 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
23169 Cause a fatal signal in the debugger and force it to dump its core.
23170 This is supported only on systems which support aborting a program
23171 with the @code{SIGQUIT} signal.
23173 @kindex maint internal-error
23174 @kindex maint internal-warning
23175 @item maint internal-error @r{[}@var{message-text}@r{]}
23176 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
23177 Cause @value{GDBN} to call the internal function @code{internal_error}
23178 or @code{internal_warning} and hence behave as though an internal error
23179 or internal warning has been detected. In addition to reporting the
23180 internal problem, these functions give the user the opportunity to
23181 either quit @value{GDBN} or create a core file of the current
23182 @value{GDBN} session.
23184 These commands take an optional parameter @var{message-text} that is
23185 used as the text of the error or warning message.
23187 Here's an example of using @code{internal-error}:
23190 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
23191 @dots{}/maint.c:121: internal-error: testing, 1, 2
23192 A problem internal to GDB has been detected. Further
23193 debugging may prove unreliable.
23194 Quit this debugging session? (y or n) @kbd{n}
23195 Create a core file? (y or n) @kbd{n}
23199 @kindex maint packet
23200 @item maint packet @var{text}
23201 If @value{GDBN} is talking to an inferior via the serial protocol,
23202 then this command sends the string @var{text} to the inferior, and
23203 displays the response packet. @value{GDBN} supplies the initial
23204 @samp{$} character, the terminating @samp{#} character, and the
23207 @kindex maint print architecture
23208 @item maint print architecture @r{[}@var{file}@r{]}
23209 Print the entire architecture configuration. The optional argument
23210 @var{file} names the file where the output goes.
23212 @kindex maint print c-tdesc
23213 @item maint print c-tdesc
23214 Print the current target description (@pxref{Target Descriptions}) as
23215 a C source file. The created source file can be used in @value{GDBN}
23216 when an XML parser is not available to parse the description.
23218 @kindex maint print dummy-frames
23219 @item maint print dummy-frames
23220 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
23223 (@value{GDBP}) @kbd{b add}
23225 (@value{GDBP}) @kbd{print add(2,3)}
23226 Breakpoint 2, add (a=2, b=3) at @dots{}
23228 The program being debugged stopped while in a function called from GDB.
23230 (@value{GDBP}) @kbd{maint print dummy-frames}
23231 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
23232 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
23233 call_lo=0x01014000 call_hi=0x01014001
23237 Takes an optional file parameter.
23239 @kindex maint print registers
23240 @kindex maint print raw-registers
23241 @kindex maint print cooked-registers
23242 @kindex maint print register-groups
23243 @item maint print registers @r{[}@var{file}@r{]}
23244 @itemx maint print raw-registers @r{[}@var{file}@r{]}
23245 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
23246 @itemx maint print register-groups @r{[}@var{file}@r{]}
23247 Print @value{GDBN}'s internal register data structures.
23249 The command @code{maint print raw-registers} includes the contents of
23250 the raw register cache; the command @code{maint print cooked-registers}
23251 includes the (cooked) value of all registers; and the command
23252 @code{maint print register-groups} includes the groups that each
23253 register is a member of. @xref{Registers,, Registers, gdbint,
23254 @value{GDBN} Internals}.
23256 These commands take an optional parameter, a file name to which to
23257 write the information.
23259 @kindex maint print reggroups
23260 @item maint print reggroups @r{[}@var{file}@r{]}
23261 Print @value{GDBN}'s internal register group data structures. The
23262 optional argument @var{file} tells to what file to write the
23265 The register groups info looks like this:
23268 (@value{GDBP}) @kbd{maint print reggroups}
23281 This command forces @value{GDBN} to flush its internal register cache.
23283 @kindex maint print objfiles
23284 @cindex info for known object files
23285 @item maint print objfiles
23286 Print a dump of all known object files. For each object file, this
23287 command prints its name, address in memory, and all of its psymtabs
23290 @kindex maint print statistics
23291 @cindex bcache statistics
23292 @item maint print statistics
23293 This command prints, for each object file in the program, various data
23294 about that object file followed by the byte cache (@dfn{bcache})
23295 statistics for the object file. The objfile data includes the number
23296 of minimal, partial, full, and stabs symbols, the number of types
23297 defined by the objfile, the number of as yet unexpanded psym tables,
23298 the number of line tables and string tables, and the amount of memory
23299 used by the various tables. The bcache statistics include the counts,
23300 sizes, and counts of duplicates of all and unique objects, max,
23301 average, and median entry size, total memory used and its overhead and
23302 savings, and various measures of the hash table size and chain
23305 @kindex maint print target-stack
23306 @cindex target stack description
23307 @item maint print target-stack
23308 A @dfn{target} is an interface between the debugger and a particular
23309 kind of file or process. Targets can be stacked in @dfn{strata},
23310 so that more than one target can potentially respond to a request.
23311 In particular, memory accesses will walk down the stack of targets
23312 until they find a target that is interested in handling that particular
23315 This command prints a short description of each layer that was pushed on
23316 the @dfn{target stack}, starting from the top layer down to the bottom one.
23318 @kindex maint print type
23319 @cindex type chain of a data type
23320 @item maint print type @var{expr}
23321 Print the type chain for a type specified by @var{expr}. The argument
23322 can be either a type name or a symbol. If it is a symbol, the type of
23323 that symbol is described. The type chain produced by this command is
23324 a recursive definition of the data type as stored in @value{GDBN}'s
23325 data structures, including its flags and contained types.
23327 @kindex maint set dwarf2 max-cache-age
23328 @kindex maint show dwarf2 max-cache-age
23329 @item maint set dwarf2 max-cache-age
23330 @itemx maint show dwarf2 max-cache-age
23331 Control the DWARF 2 compilation unit cache.
23333 @cindex DWARF 2 compilation units cache
23334 In object files with inter-compilation-unit references, such as those
23335 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
23336 reader needs to frequently refer to previously read compilation units.
23337 This setting controls how long a compilation unit will remain in the
23338 cache if it is not referenced. A higher limit means that cached
23339 compilation units will be stored in memory longer, and more total
23340 memory will be used. Setting it to zero disables caching, which will
23341 slow down @value{GDBN} startup, but reduce memory consumption.
23343 @kindex maint set profile
23344 @kindex maint show profile
23345 @cindex profiling GDB
23346 @item maint set profile
23347 @itemx maint show profile
23348 Control profiling of @value{GDBN}.
23350 Profiling will be disabled until you use the @samp{maint set profile}
23351 command to enable it. When you enable profiling, the system will begin
23352 collecting timing and execution count data; when you disable profiling or
23353 exit @value{GDBN}, the results will be written to a log file. Remember that
23354 if you use profiling, @value{GDBN} will overwrite the profiling log file
23355 (often called @file{gmon.out}). If you have a record of important profiling
23356 data in a @file{gmon.out} file, be sure to move it to a safe location.
23358 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
23359 compiled with the @samp{-pg} compiler option.
23361 @kindex maint set linux-async
23362 @kindex maint show linux-async
23363 @cindex asynchronous support
23364 @item maint set linux-async
23365 @itemx maint show linux-async
23366 Control the GNU/Linux native asynchronous support of @value{GDBN}.
23368 GNU/Linux native asynchronous support will be disabled until you use
23369 the @samp{maint set linux-async} command to enable it.
23371 @kindex maint show-debug-regs
23372 @cindex x86 hardware debug registers
23373 @item maint show-debug-regs
23374 Control whether to show variables that mirror the x86 hardware debug
23375 registers. Use @code{ON} to enable, @code{OFF} to disable. If
23376 enabled, the debug registers values are shown when @value{GDBN} inserts or
23377 removes a hardware breakpoint or watchpoint, and when the inferior
23378 triggers a hardware-assisted breakpoint or watchpoint.
23380 @kindex maint space
23381 @cindex memory used by commands
23383 Control whether to display memory usage for each command. If set to a
23384 nonzero value, @value{GDBN} will display how much memory each command
23385 took, following the command's own output. This can also be requested
23386 by invoking @value{GDBN} with the @option{--statistics} command-line
23387 switch (@pxref{Mode Options}).
23390 @cindex time of command execution
23392 Control whether to display the execution time for each command. If
23393 set to a nonzero value, @value{GDBN} will display how much time it
23394 took to execute each command, following the command's own output.
23395 This can also be requested by invoking @value{GDBN} with the
23396 @option{--statistics} command-line switch (@pxref{Mode Options}).
23398 @kindex maint translate-address
23399 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
23400 Find the symbol stored at the location specified by the address
23401 @var{addr} and an optional section name @var{section}. If found,
23402 @value{GDBN} prints the name of the closest symbol and an offset from
23403 the symbol's location to the specified address. This is similar to
23404 the @code{info address} command (@pxref{Symbols}), except that this
23405 command also allows to find symbols in other sections.
23409 The following command is useful for non-interactive invocations of
23410 @value{GDBN}, such as in the test suite.
23413 @item set watchdog @var{nsec}
23414 @kindex set watchdog
23415 @cindex watchdog timer
23416 @cindex timeout for commands
23417 Set the maximum number of seconds @value{GDBN} will wait for the
23418 target operation to finish. If this time expires, @value{GDBN}
23419 reports and error and the command is aborted.
23421 @item show watchdog
23422 Show the current setting of the target wait timeout.
23425 @node Remote Protocol
23426 @appendix @value{GDBN} Remote Serial Protocol
23431 * Stop Reply Packets::
23432 * General Query Packets::
23433 * Register Packet Format::
23434 * Tracepoint Packets::
23435 * Host I/O Packets::
23438 * File-I/O Remote Protocol Extension::
23439 * Library List Format::
23440 * Memory Map Format::
23446 There may be occasions when you need to know something about the
23447 protocol---for example, if there is only one serial port to your target
23448 machine, you might want your program to do something special if it
23449 recognizes a packet meant for @value{GDBN}.
23451 In the examples below, @samp{->} and @samp{<-} are used to indicate
23452 transmitted and received data, respectively.
23454 @cindex protocol, @value{GDBN} remote serial
23455 @cindex serial protocol, @value{GDBN} remote
23456 @cindex remote serial protocol
23457 All @value{GDBN} commands and responses (other than acknowledgments) are
23458 sent as a @var{packet}. A @var{packet} is introduced with the character
23459 @samp{$}, the actual @var{packet-data}, and the terminating character
23460 @samp{#} followed by a two-digit @var{checksum}:
23463 @code{$}@var{packet-data}@code{#}@var{checksum}
23467 @cindex checksum, for @value{GDBN} remote
23469 The two-digit @var{checksum} is computed as the modulo 256 sum of all
23470 characters between the leading @samp{$} and the trailing @samp{#} (an
23471 eight bit unsigned checksum).
23473 Implementors should note that prior to @value{GDBN} 5.0 the protocol
23474 specification also included an optional two-digit @var{sequence-id}:
23477 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
23480 @cindex sequence-id, for @value{GDBN} remote
23482 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
23483 has never output @var{sequence-id}s. Stubs that handle packets added
23484 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
23486 @cindex acknowledgment, for @value{GDBN} remote
23487 When either the host or the target machine receives a packet, the first
23488 response expected is an acknowledgment: either @samp{+} (to indicate
23489 the package was received correctly) or @samp{-} (to request
23493 -> @code{$}@var{packet-data}@code{#}@var{checksum}
23498 The host (@value{GDBN}) sends @var{command}s, and the target (the
23499 debugging stub incorporated in your program) sends a @var{response}. In
23500 the case of step and continue @var{command}s, the response is only sent
23501 when the operation has completed (the target has again stopped).
23503 @var{packet-data} consists of a sequence of characters with the
23504 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
23507 @cindex remote protocol, field separator
23508 Fields within the packet should be separated using @samp{,} @samp{;} or
23509 @samp{:}. Except where otherwise noted all numbers are represented in
23510 @sc{hex} with leading zeros suppressed.
23512 Implementors should note that prior to @value{GDBN} 5.0, the character
23513 @samp{:} could not appear as the third character in a packet (as it
23514 would potentially conflict with the @var{sequence-id}).
23516 @cindex remote protocol, binary data
23517 @anchor{Binary Data}
23518 Binary data in most packets is encoded either as two hexadecimal
23519 digits per byte of binary data. This allowed the traditional remote
23520 protocol to work over connections which were only seven-bit clean.
23521 Some packets designed more recently assume an eight-bit clean
23522 connection, and use a more efficient encoding to send and receive
23525 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
23526 as an escape character. Any escaped byte is transmitted as the escape
23527 character followed by the original character XORed with @code{0x20}.
23528 For example, the byte @code{0x7d} would be transmitted as the two
23529 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
23530 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
23531 @samp{@}}) must always be escaped. Responses sent by the stub
23532 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
23533 is not interpreted as the start of a run-length encoded sequence
23536 Response @var{data} can be run-length encoded to save space.
23537 Run-length encoding replaces runs of identical characters with one
23538 instance of the repeated character, followed by a @samp{*} and a
23539 repeat count. The repeat count is itself sent encoded, to avoid
23540 binary characters in @var{data}: a value of @var{n} is sent as
23541 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
23542 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
23543 code 32) for a repeat count of 3. (This is because run-length
23544 encoding starts to win for counts 3 or more.) Thus, for example,
23545 @samp{0* } is a run-length encoding of ``0000'': the space character
23546 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
23549 The printable characters @samp{#} and @samp{$} or with a numeric value
23550 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
23551 seven repeats (@samp{$}) can be expanded using a repeat count of only
23552 five (@samp{"}). For example, @samp{00000000} can be encoded as
23555 The error response returned for some packets includes a two character
23556 error number. That number is not well defined.
23558 @cindex empty response, for unsupported packets
23559 For any @var{command} not supported by the stub, an empty response
23560 (@samp{$#00}) should be returned. That way it is possible to extend the
23561 protocol. A newer @value{GDBN} can tell if a packet is supported based
23564 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
23565 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
23571 The following table provides a complete list of all currently defined
23572 @var{command}s and their corresponding response @var{data}.
23573 @xref{File-I/O Remote Protocol Extension}, for details about the File
23574 I/O extension of the remote protocol.
23576 Each packet's description has a template showing the packet's overall
23577 syntax, followed by an explanation of the packet's meaning. We
23578 include spaces in some of the templates for clarity; these are not
23579 part of the packet's syntax. No @value{GDBN} packet uses spaces to
23580 separate its components. For example, a template like @samp{foo
23581 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
23582 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
23583 @var{baz}. @value{GDBN} does not transmit a space character between the
23584 @samp{foo} and the @var{bar}, or between the @var{bar} and the
23587 Note that all packet forms beginning with an upper- or lower-case
23588 letter, other than those described here, are reserved for future use.
23590 Here are the packet descriptions.
23595 @cindex @samp{!} packet
23596 @anchor{extended mode}
23597 Enable extended mode. In extended mode, the remote server is made
23598 persistent. The @samp{R} packet is used to restart the program being
23604 The remote target both supports and has enabled extended mode.
23608 @cindex @samp{?} packet
23609 Indicate the reason the target halted. The reply is the same as for
23613 @xref{Stop Reply Packets}, for the reply specifications.
23615 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
23616 @cindex @samp{A} packet
23617 Initialized @code{argv[]} array passed into program. @var{arglen}
23618 specifies the number of bytes in the hex encoded byte stream
23619 @var{arg}. See @code{gdbserver} for more details.
23624 The arguments were set.
23630 @cindex @samp{b} packet
23631 (Don't use this packet; its behavior is not well-defined.)
23632 Change the serial line speed to @var{baud}.
23634 JTC: @emph{When does the transport layer state change? When it's
23635 received, or after the ACK is transmitted. In either case, there are
23636 problems if the command or the acknowledgment packet is dropped.}
23638 Stan: @emph{If people really wanted to add something like this, and get
23639 it working for the first time, they ought to modify ser-unix.c to send
23640 some kind of out-of-band message to a specially-setup stub and have the
23641 switch happen "in between" packets, so that from remote protocol's point
23642 of view, nothing actually happened.}
23644 @item B @var{addr},@var{mode}
23645 @cindex @samp{B} packet
23646 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23647 breakpoint at @var{addr}.
23649 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23650 (@pxref{insert breakpoint or watchpoint packet}).
23652 @item c @r{[}@var{addr}@r{]}
23653 @cindex @samp{c} packet
23654 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23655 resume at current address.
23658 @xref{Stop Reply Packets}, for the reply specifications.
23660 @item C @var{sig}@r{[};@var{addr}@r{]}
23661 @cindex @samp{C} packet
23662 Continue with signal @var{sig} (hex signal number). If
23663 @samp{;@var{addr}} is omitted, resume at same address.
23666 @xref{Stop Reply Packets}, for the reply specifications.
23669 @cindex @samp{d} packet
23672 Don't use this packet; instead, define a general set packet
23673 (@pxref{General Query Packets}).
23676 @cindex @samp{D} packet
23677 Detach @value{GDBN} from the remote system. Sent to the remote target
23678 before @value{GDBN} disconnects via the @code{detach} command.
23688 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23689 @cindex @samp{F} packet
23690 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23691 This is part of the File-I/O protocol extension. @xref{File-I/O
23692 Remote Protocol Extension}, for the specification.
23695 @anchor{read registers packet}
23696 @cindex @samp{g} packet
23697 Read general registers.
23701 @item @var{XX@dots{}}
23702 Each byte of register data is described by two hex digits. The bytes
23703 with the register are transmitted in target byte order. The size of
23704 each register and their position within the @samp{g} packet are
23705 determined by the @value{GDBN} internal gdbarch functions
23706 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
23707 specification of several standard @samp{g} packets is specified below.
23712 @item G @var{XX@dots{}}
23713 @cindex @samp{G} packet
23714 Write general registers. @xref{read registers packet}, for a
23715 description of the @var{XX@dots{}} data.
23725 @item H @var{c} @var{t}
23726 @cindex @samp{H} packet
23727 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23728 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23729 should be @samp{c} for step and continue operations, @samp{g} for other
23730 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23731 the threads, a thread number, or @samp{0} which means pick any thread.
23742 @c 'H': How restrictive (or permissive) is the thread model. If a
23743 @c thread is selected and stopped, are other threads allowed
23744 @c to continue to execute? As I mentioned above, I think the
23745 @c semantics of each command when a thread is selected must be
23746 @c described. For example:
23748 @c 'g': If the stub supports threads and a specific thread is
23749 @c selected, returns the register block from that thread;
23750 @c otherwise returns current registers.
23752 @c 'G' If the stub supports threads and a specific thread is
23753 @c selected, sets the registers of the register block of
23754 @c that thread; otherwise sets current registers.
23756 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23757 @anchor{cycle step packet}
23758 @cindex @samp{i} packet
23759 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23760 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23761 step starting at that address.
23764 @cindex @samp{I} packet
23765 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23769 @cindex @samp{k} packet
23772 FIXME: @emph{There is no description of how to operate when a specific
23773 thread context has been selected (i.e.@: does 'k' kill only that
23776 @item m @var{addr},@var{length}
23777 @cindex @samp{m} packet
23778 Read @var{length} bytes of memory starting at address @var{addr}.
23779 Note that @var{addr} may not be aligned to any particular boundary.
23781 The stub need not use any particular size or alignment when gathering
23782 data from memory for the response; even if @var{addr} is word-aligned
23783 and @var{length} is a multiple of the word size, the stub is free to
23784 use byte accesses, or not. For this reason, this packet may not be
23785 suitable for accessing memory-mapped I/O devices.
23786 @cindex alignment of remote memory accesses
23787 @cindex size of remote memory accesses
23788 @cindex memory, alignment and size of remote accesses
23792 @item @var{XX@dots{}}
23793 Memory contents; each byte is transmitted as a two-digit hexadecimal
23794 number. The reply may contain fewer bytes than requested if the
23795 server was able to read only part of the region of memory.
23800 @item M @var{addr},@var{length}:@var{XX@dots{}}
23801 @cindex @samp{M} packet
23802 Write @var{length} bytes of memory starting at address @var{addr}.
23803 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23804 hexadecimal number.
23811 for an error (this includes the case where only part of the data was
23816 @cindex @samp{p} packet
23817 Read the value of register @var{n}; @var{n} is in hex.
23818 @xref{read registers packet}, for a description of how the returned
23819 register value is encoded.
23823 @item @var{XX@dots{}}
23824 the register's value
23828 Indicating an unrecognized @var{query}.
23831 @item P @var{n@dots{}}=@var{r@dots{}}
23832 @anchor{write register packet}
23833 @cindex @samp{P} packet
23834 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23835 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23836 digits for each byte in the register (target byte order).
23846 @item q @var{name} @var{params}@dots{}
23847 @itemx Q @var{name} @var{params}@dots{}
23848 @cindex @samp{q} packet
23849 @cindex @samp{Q} packet
23850 General query (@samp{q}) and set (@samp{Q}). These packets are
23851 described fully in @ref{General Query Packets}.
23854 @cindex @samp{r} packet
23855 Reset the entire system.
23857 Don't use this packet; use the @samp{R} packet instead.
23860 @cindex @samp{R} packet
23861 Restart the program being debugged. @var{XX}, while needed, is ignored.
23862 This packet is only available in extended mode (@pxref{extended mode}).
23864 The @samp{R} packet has no reply.
23866 @item s @r{[}@var{addr}@r{]}
23867 @cindex @samp{s} packet
23868 Single step. @var{addr} is the address at which to resume. If
23869 @var{addr} is omitted, resume at same address.
23872 @xref{Stop Reply Packets}, for the reply specifications.
23874 @item S @var{sig}@r{[};@var{addr}@r{]}
23875 @anchor{step with signal packet}
23876 @cindex @samp{S} packet
23877 Step with signal. This is analogous to the @samp{C} packet, but
23878 requests a single-step, rather than a normal resumption of execution.
23881 @xref{Stop Reply Packets}, for the reply specifications.
23883 @item t @var{addr}:@var{PP},@var{MM}
23884 @cindex @samp{t} packet
23885 Search backwards starting at address @var{addr} for a match with pattern
23886 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23887 @var{addr} must be at least 3 digits.
23890 @cindex @samp{T} packet
23891 Find out if the thread XX is alive.
23896 thread is still alive
23902 Packets starting with @samp{v} are identified by a multi-letter name,
23903 up to the first @samp{;} or @samp{?} (or the end of the packet).
23905 @item vAttach;@var{pid}
23906 @cindex @samp{vAttach} packet
23907 Attach to a new process with the specified process ID. @var{pid} is a
23908 hexadecimal integer identifying the process. If the stub is currently
23909 controlling a process, it is killed. The attached process is stopped.
23911 This packet is only available in extended mode (@pxref{extended mode}).
23917 @item @r{Any stop packet}
23918 for success (@pxref{Stop Reply Packets})
23921 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23922 @cindex @samp{vCont} packet
23923 Resume the inferior, specifying different actions for each thread.
23924 If an action is specified with no @var{tid}, then it is applied to any
23925 threads that don't have a specific action specified; if no default action is
23926 specified then other threads should remain stopped. Specifying multiple
23927 default actions is an error; specifying no actions is also an error.
23928 Thread IDs are specified in hexadecimal. Currently supported actions are:
23934 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23938 Step with signal @var{sig}. @var{sig} should be two hex digits.
23941 The optional @var{addr} argument normally associated with these packets is
23942 not supported in @samp{vCont}.
23945 @xref{Stop Reply Packets}, for the reply specifications.
23948 @cindex @samp{vCont?} packet
23949 Request a list of actions supported by the @samp{vCont} packet.
23953 @item vCont@r{[};@var{action}@dots{}@r{]}
23954 The @samp{vCont} packet is supported. Each @var{action} is a supported
23955 command in the @samp{vCont} packet.
23957 The @samp{vCont} packet is not supported.
23960 @item vFile:@var{operation}:@var{parameter}@dots{}
23961 @cindex @samp{vFile} packet
23962 Perform a file operation on the target system. For details,
23963 see @ref{Host I/O Packets}.
23965 @item vFlashErase:@var{addr},@var{length}
23966 @cindex @samp{vFlashErase} packet
23967 Direct the stub to erase @var{length} bytes of flash starting at
23968 @var{addr}. The region may enclose any number of flash blocks, but
23969 its start and end must fall on block boundaries, as indicated by the
23970 flash block size appearing in the memory map (@pxref{Memory Map
23971 Format}). @value{GDBN} groups flash memory programming operations
23972 together, and sends a @samp{vFlashDone} request after each group; the
23973 stub is allowed to delay erase operation until the @samp{vFlashDone}
23974 packet is received.
23984 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23985 @cindex @samp{vFlashWrite} packet
23986 Direct the stub to write data to flash address @var{addr}. The data
23987 is passed in binary form using the same encoding as for the @samp{X}
23988 packet (@pxref{Binary Data}). The memory ranges specified by
23989 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23990 not overlap, and must appear in order of increasing addresses
23991 (although @samp{vFlashErase} packets for higher addresses may already
23992 have been received; the ordering is guaranteed only between
23993 @samp{vFlashWrite} packets). If a packet writes to an address that was
23994 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23995 target-specific method, the results are unpredictable.
24003 for vFlashWrite addressing non-flash memory
24009 @cindex @samp{vFlashDone} packet
24010 Indicate to the stub that flash programming operation is finished.
24011 The stub is permitted to delay or batch the effects of a group of
24012 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
24013 @samp{vFlashDone} packet is received. The contents of the affected
24014 regions of flash memory are unpredictable until the @samp{vFlashDone}
24015 request is completed.
24017 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
24018 @cindex @samp{vRun} packet
24019 Run the program @var{filename}, passing it each @var{argument} on its
24020 command line. The file and arguments are hex-encoded strings. If
24021 @var{filename} is an empty string, the stub may use a default program
24022 (e.g.@: the last program run). The program is created in the stopped
24023 state. If the stub is currently controlling a process, it is killed.
24025 This packet is only available in extended mode (@pxref{extended mode}).
24031 @item @r{Any stop packet}
24032 for success (@pxref{Stop Reply Packets})
24035 @item X @var{addr},@var{length}:@var{XX@dots{}}
24037 @cindex @samp{X} packet
24038 Write data to memory, where the data is transmitted in binary.
24039 @var{addr} is address, @var{length} is number of bytes,
24040 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
24050 @item z @var{type},@var{addr},@var{length}
24051 @itemx Z @var{type},@var{addr},@var{length}
24052 @anchor{insert breakpoint or watchpoint packet}
24053 @cindex @samp{z} packet
24054 @cindex @samp{Z} packets
24055 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
24056 watchpoint starting at address @var{address} and covering the next
24057 @var{length} bytes.
24059 Each breakpoint and watchpoint packet @var{type} is documented
24062 @emph{Implementation notes: A remote target shall return an empty string
24063 for an unrecognized breakpoint or watchpoint packet @var{type}. A
24064 remote target shall support either both or neither of a given
24065 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
24066 avoid potential problems with duplicate packets, the operations should
24067 be implemented in an idempotent way.}
24069 @item z0,@var{addr},@var{length}
24070 @itemx Z0,@var{addr},@var{length}
24071 @cindex @samp{z0} packet
24072 @cindex @samp{Z0} packet
24073 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
24074 @var{addr} of size @var{length}.
24076 A memory breakpoint is implemented by replacing the instruction at
24077 @var{addr} with a software breakpoint or trap instruction. The
24078 @var{length} is used by targets that indicates the size of the
24079 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
24080 @sc{mips} can insert either a 2 or 4 byte breakpoint).
24082 @emph{Implementation note: It is possible for a target to copy or move
24083 code that contains memory breakpoints (e.g., when implementing
24084 overlays). The behavior of this packet, in the presence of such a
24085 target, is not defined.}
24097 @item z1,@var{addr},@var{length}
24098 @itemx Z1,@var{addr},@var{length}
24099 @cindex @samp{z1} packet
24100 @cindex @samp{Z1} packet
24101 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
24102 address @var{addr} of size @var{length}.
24104 A hardware breakpoint is implemented using a mechanism that is not
24105 dependant on being able to modify the target's memory.
24107 @emph{Implementation note: A hardware breakpoint is not affected by code
24120 @item z2,@var{addr},@var{length}
24121 @itemx Z2,@var{addr},@var{length}
24122 @cindex @samp{z2} packet
24123 @cindex @samp{Z2} packet
24124 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
24136 @item z3,@var{addr},@var{length}
24137 @itemx Z3,@var{addr},@var{length}
24138 @cindex @samp{z3} packet
24139 @cindex @samp{Z3} packet
24140 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
24152 @item z4,@var{addr},@var{length}
24153 @itemx Z4,@var{addr},@var{length}
24154 @cindex @samp{z4} packet
24155 @cindex @samp{Z4} packet
24156 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
24170 @node Stop Reply Packets
24171 @section Stop Reply Packets
24172 @cindex stop reply packets
24174 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
24175 receive any of the below as a reply. In the case of the @samp{C},
24176 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
24177 when the target halts. In the below the exact meaning of @dfn{signal
24178 number} is defined by the header @file{include/gdb/signals.h} in the
24179 @value{GDBN} source code.
24181 As in the description of request packets, we include spaces in the
24182 reply templates for clarity; these are not part of the reply packet's
24183 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
24189 The program received signal number @var{AA} (a two-digit hexadecimal
24190 number). This is equivalent to a @samp{T} response with no
24191 @var{n}:@var{r} pairs.
24193 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
24194 @cindex @samp{T} packet reply
24195 The program received signal number @var{AA} (a two-digit hexadecimal
24196 number). This is equivalent to an @samp{S} response, except that the
24197 @samp{@var{n}:@var{r}} pairs can carry values of important registers
24198 and other information directly in the stop reply packet, reducing
24199 round-trip latency. Single-step and breakpoint traps are reported
24200 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
24204 If @var{n} is a hexadecimal number, it is a register number, and the
24205 corresponding @var{r} gives that register's value. @var{r} is a
24206 series of bytes in target byte order, with each byte given by a
24207 two-digit hex number.
24210 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
24214 If @var{n} is a recognized @dfn{stop reason}, it describes a more
24215 specific event that stopped the target. The currently defined stop
24216 reasons are listed below. @var{aa} should be @samp{05}, the trap
24217 signal. At most one stop reason should be present.
24220 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
24221 and go on to the next; this allows us to extend the protocol in the
24225 The currently defined stop reasons are:
24231 The packet indicates a watchpoint hit, and @var{r} is the data address, in
24234 @cindex shared library events, remote reply
24236 The packet indicates that the loaded libraries have changed.
24237 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
24238 list of loaded libraries. @var{r} is ignored.
24242 The process exited, and @var{AA} is the exit status. This is only
24243 applicable to certain targets.
24246 The process terminated with signal @var{AA}.
24248 @item O @var{XX}@dots{}
24249 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
24250 written as the program's console output. This can happen at any time
24251 while the program is running and the debugger should continue to wait
24252 for @samp{W}, @samp{T}, etc.
24254 @item F @var{call-id},@var{parameter}@dots{}
24255 @var{call-id} is the identifier which says which host system call should
24256 be called. This is just the name of the function. Translation into the
24257 correct system call is only applicable as it's defined in @value{GDBN}.
24258 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
24261 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
24262 this very system call.
24264 The target replies with this packet when it expects @value{GDBN} to
24265 call a host system call on behalf of the target. @value{GDBN} replies
24266 with an appropriate @samp{F} packet and keeps up waiting for the next
24267 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
24268 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
24269 Protocol Extension}, for more details.
24273 @node General Query Packets
24274 @section General Query Packets
24275 @cindex remote query requests
24277 Packets starting with @samp{q} are @dfn{general query packets};
24278 packets starting with @samp{Q} are @dfn{general set packets}. General
24279 query and set packets are a semi-unified form for retrieving and
24280 sending information to and from the stub.
24282 The initial letter of a query or set packet is followed by a name
24283 indicating what sort of thing the packet applies to. For example,
24284 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
24285 definitions with the stub. These packet names follow some
24290 The name must not contain commas, colons or semicolons.
24292 Most @value{GDBN} query and set packets have a leading upper case
24295 The names of custom vendor packets should use a company prefix, in
24296 lower case, followed by a period. For example, packets designed at
24297 the Acme Corporation might begin with @samp{qacme.foo} (for querying
24298 foos) or @samp{Qacme.bar} (for setting bars).
24301 The name of a query or set packet should be separated from any
24302 parameters by a @samp{:}; the parameters themselves should be
24303 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
24304 full packet name, and check for a separator or the end of the packet,
24305 in case two packet names share a common prefix. New packets should not begin
24306 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
24307 packets predate these conventions, and have arguments without any terminator
24308 for the packet name; we suspect they are in widespread use in places that
24309 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
24310 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
24313 Like the descriptions of the other packets, each description here
24314 has a template showing the packet's overall syntax, followed by an
24315 explanation of the packet's meaning. We include spaces in some of the
24316 templates for clarity; these are not part of the packet's syntax. No
24317 @value{GDBN} packet uses spaces to separate its components.
24319 Here are the currently defined query and set packets:
24324 @cindex current thread, remote request
24325 @cindex @samp{qC} packet
24326 Return the current thread id.
24331 Where @var{pid} is an unsigned hexadecimal process id.
24332 @item @r{(anything else)}
24333 Any other reply implies the old pid.
24336 @item qCRC:@var{addr},@var{length}
24337 @cindex CRC of memory block, remote request
24338 @cindex @samp{qCRC} packet
24339 Compute the CRC checksum of a block of memory.
24343 An error (such as memory fault)
24344 @item C @var{crc32}
24345 The specified memory region's checksum is @var{crc32}.
24349 @itemx qsThreadInfo
24350 @cindex list active threads, remote request
24351 @cindex @samp{qfThreadInfo} packet
24352 @cindex @samp{qsThreadInfo} packet
24353 Obtain a list of all active thread ids from the target (OS). Since there
24354 may be too many active threads to fit into one reply packet, this query
24355 works iteratively: it may require more than one query/reply sequence to
24356 obtain the entire list of threads. The first query of the sequence will
24357 be the @samp{qfThreadInfo} query; subsequent queries in the
24358 sequence will be the @samp{qsThreadInfo} query.
24360 NOTE: This packet replaces the @samp{qL} query (see below).
24366 @item m @var{id},@var{id}@dots{}
24367 a comma-separated list of thread ids
24369 (lower case letter @samp{L}) denotes end of list.
24372 In response to each query, the target will reply with a list of one or
24373 more thread ids, in big-endian unsigned hex, separated by commas.
24374 @value{GDBN} will respond to each reply with a request for more thread
24375 ids (using the @samp{qs} form of the query), until the target responds
24376 with @samp{l} (lower-case el, for @dfn{last}).
24378 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
24379 @cindex get thread-local storage address, remote request
24380 @cindex @samp{qGetTLSAddr} packet
24381 Fetch the address associated with thread local storage specified
24382 by @var{thread-id}, @var{offset}, and @var{lm}.
24384 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
24385 thread for which to fetch the TLS address.
24387 @var{offset} is the (big endian, hex encoded) offset associated with the
24388 thread local variable. (This offset is obtained from the debug
24389 information associated with the variable.)
24391 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
24392 the load module associated with the thread local storage. For example,
24393 a @sc{gnu}/Linux system will pass the link map address of the shared
24394 object associated with the thread local storage under consideration.
24395 Other operating environments may choose to represent the load module
24396 differently, so the precise meaning of this parameter will vary.
24400 @item @var{XX}@dots{}
24401 Hex encoded (big endian) bytes representing the address of the thread
24402 local storage requested.
24405 An error occurred. @var{nn} are hex digits.
24408 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
24411 @item qL @var{startflag} @var{threadcount} @var{nextthread}
24412 Obtain thread information from RTOS. Where: @var{startflag} (one hex
24413 digit) is one to indicate the first query and zero to indicate a
24414 subsequent query; @var{threadcount} (two hex digits) is the maximum
24415 number of threads the response packet can contain; and @var{nextthread}
24416 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
24417 returned in the response as @var{argthread}.
24419 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
24423 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
24424 Where: @var{count} (two hex digits) is the number of threads being
24425 returned; @var{done} (one hex digit) is zero to indicate more threads
24426 and one indicates no further threads; @var{argthreadid} (eight hex
24427 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
24428 is a sequence of thread IDs from the target. @var{threadid} (eight hex
24429 digits). See @code{remote.c:parse_threadlist_response()}.
24433 @cindex section offsets, remote request
24434 @cindex @samp{qOffsets} packet
24435 Get section offsets that the target used when relocating the downloaded
24440 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
24441 Relocate the @code{Text} section by @var{xxx} from its original address.
24442 Relocate the @code{Data} section by @var{yyy} from its original address.
24443 If the object file format provides segment information (e.g.@: @sc{elf}
24444 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
24445 segments by the supplied offsets.
24447 @emph{Note: while a @code{Bss} offset may be included in the response,
24448 @value{GDBN} ignores this and instead applies the @code{Data} offset
24449 to the @code{Bss} section.}
24451 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
24452 Relocate the first segment of the object file, which conventionally
24453 contains program code, to a starting address of @var{xxx}. If
24454 @samp{DataSeg} is specified, relocate the second segment, which
24455 conventionally contains modifiable data, to a starting address of
24456 @var{yyy}. @value{GDBN} will report an error if the object file
24457 does not contain segment information, or does not contain at least
24458 as many segments as mentioned in the reply. Extra segments are
24459 kept at fixed offsets relative to the last relocated segment.
24462 @item qP @var{mode} @var{threadid}
24463 @cindex thread information, remote request
24464 @cindex @samp{qP} packet
24465 Returns information on @var{threadid}. Where: @var{mode} is a hex
24466 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
24468 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
24471 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
24473 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
24474 @cindex pass signals to inferior, remote request
24475 @cindex @samp{QPassSignals} packet
24476 @anchor{QPassSignals}
24477 Each listed @var{signal} should be passed directly to the inferior process.
24478 Signals are numbered identically to continue packets and stop replies
24479 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
24480 strictly greater than the previous item. These signals do not need to stop
24481 the inferior, or be reported to @value{GDBN}. All other signals should be
24482 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
24483 combine; any earlier @samp{QPassSignals} list is completely replaced by the
24484 new list. This packet improves performance when using @samp{handle
24485 @var{signal} nostop noprint pass}.
24490 The request succeeded.
24493 An error occurred. @var{nn} are hex digits.
24496 An empty reply indicates that @samp{QPassSignals} is not supported by
24500 Use of this packet is controlled by the @code{set remote pass-signals}
24501 command (@pxref{Remote Configuration, set remote pass-signals}).
24502 This packet is not probed by default; the remote stub must request it,
24503 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24505 @item qRcmd,@var{command}
24506 @cindex execute remote command, remote request
24507 @cindex @samp{qRcmd} packet
24508 @var{command} (hex encoded) is passed to the local interpreter for
24509 execution. Invalid commands should be reported using the output
24510 string. Before the final result packet, the target may also respond
24511 with a number of intermediate @samp{O@var{output}} console output
24512 packets. @emph{Implementors should note that providing access to a
24513 stubs's interpreter may have security implications}.
24518 A command response with no output.
24520 A command response with the hex encoded output string @var{OUTPUT}.
24522 Indicate a badly formed request.
24524 An empty reply indicates that @samp{qRcmd} is not recognized.
24527 (Note that the @code{qRcmd} packet's name is separated from the
24528 command by a @samp{,}, not a @samp{:}, contrary to the naming
24529 conventions above. Please don't use this packet as a model for new
24532 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
24533 @cindex supported packets, remote query
24534 @cindex features of the remote protocol
24535 @cindex @samp{qSupported} packet
24536 @anchor{qSupported}
24537 Tell the remote stub about features supported by @value{GDBN}, and
24538 query the stub for features it supports. This packet allows
24539 @value{GDBN} and the remote stub to take advantage of each others'
24540 features. @samp{qSupported} also consolidates multiple feature probes
24541 at startup, to improve @value{GDBN} performance---a single larger
24542 packet performs better than multiple smaller probe packets on
24543 high-latency links. Some features may enable behavior which must not
24544 be on by default, e.g.@: because it would confuse older clients or
24545 stubs. Other features may describe packets which could be
24546 automatically probed for, but are not. These features must be
24547 reported before @value{GDBN} will use them. This ``default
24548 unsupported'' behavior is not appropriate for all packets, but it
24549 helps to keep the initial connection time under control with new
24550 versions of @value{GDBN} which support increasing numbers of packets.
24554 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
24555 The stub supports or does not support each returned @var{stubfeature},
24556 depending on the form of each @var{stubfeature} (see below for the
24559 An empty reply indicates that @samp{qSupported} is not recognized,
24560 or that no features needed to be reported to @value{GDBN}.
24563 The allowed forms for each feature (either a @var{gdbfeature} in the
24564 @samp{qSupported} packet, or a @var{stubfeature} in the response)
24568 @item @var{name}=@var{value}
24569 The remote protocol feature @var{name} is supported, and associated
24570 with the specified @var{value}. The format of @var{value} depends
24571 on the feature, but it must not include a semicolon.
24573 The remote protocol feature @var{name} is supported, and does not
24574 need an associated value.
24576 The remote protocol feature @var{name} is not supported.
24578 The remote protocol feature @var{name} may be supported, and
24579 @value{GDBN} should auto-detect support in some other way when it is
24580 needed. This form will not be used for @var{gdbfeature} notifications,
24581 but may be used for @var{stubfeature} responses.
24584 Whenever the stub receives a @samp{qSupported} request, the
24585 supplied set of @value{GDBN} features should override any previous
24586 request. This allows @value{GDBN} to put the stub in a known
24587 state, even if the stub had previously been communicating with
24588 a different version of @value{GDBN}.
24590 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
24591 are defined yet. Stubs should ignore any unknown values for
24592 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
24593 packet supports receiving packets of unlimited length (earlier
24594 versions of @value{GDBN} may reject overly long responses). Values
24595 for @var{gdbfeature} may be defined in the future to let the stub take
24596 advantage of new features in @value{GDBN}, e.g.@: incompatible
24597 improvements in the remote protocol---support for unlimited length
24598 responses would be a @var{gdbfeature} example, if it were not implied by
24599 the @samp{qSupported} query. The stub's reply should be independent
24600 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
24601 describes all the features it supports, and then the stub replies with
24602 all the features it supports.
24604 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
24605 responses, as long as each response uses one of the standard forms.
24607 Some features are flags. A stub which supports a flag feature
24608 should respond with a @samp{+} form response. Other features
24609 require values, and the stub should respond with an @samp{=}
24612 Each feature has a default value, which @value{GDBN} will use if
24613 @samp{qSupported} is not available or if the feature is not mentioned
24614 in the @samp{qSupported} response. The default values are fixed; a
24615 stub is free to omit any feature responses that match the defaults.
24617 Not all features can be probed, but for those which can, the probing
24618 mechanism is useful: in some cases, a stub's internal
24619 architecture may not allow the protocol layer to know some information
24620 about the underlying target in advance. This is especially common in
24621 stubs which may be configured for multiple targets.
24623 These are the currently defined stub features and their properties:
24625 @multitable @columnfractions 0.35 0.2 0.12 0.2
24626 @c NOTE: The first row should be @headitem, but we do not yet require
24627 @c a new enough version of Texinfo (4.7) to use @headitem.
24629 @tab Value Required
24633 @item @samp{PacketSize}
24638 @item @samp{qXfer:auxv:read}
24643 @item @samp{qXfer:features:read}
24648 @item @samp{qXfer:libraries:read}
24653 @item @samp{qXfer:memory-map:read}
24658 @item @samp{qXfer:spu:read}
24663 @item @samp{qXfer:spu:write}
24668 @item @samp{QPassSignals}
24675 These are the currently defined stub features, in more detail:
24678 @cindex packet size, remote protocol
24679 @item PacketSize=@var{bytes}
24680 The remote stub can accept packets up to at least @var{bytes} in
24681 length. @value{GDBN} will send packets up to this size for bulk
24682 transfers, and will never send larger packets. This is a limit on the
24683 data characters in the packet, including the frame and checksum.
24684 There is no trailing NUL byte in a remote protocol packet; if the stub
24685 stores packets in a NUL-terminated format, it should allow an extra
24686 byte in its buffer for the NUL. If this stub feature is not supported,
24687 @value{GDBN} guesses based on the size of the @samp{g} packet response.
24689 @item qXfer:auxv:read
24690 The remote stub understands the @samp{qXfer:auxv:read} packet
24691 (@pxref{qXfer auxiliary vector read}).
24693 @item qXfer:features:read
24694 The remote stub understands the @samp{qXfer:features:read} packet
24695 (@pxref{qXfer target description read}).
24697 @item qXfer:libraries:read
24698 The remote stub understands the @samp{qXfer:libraries:read} packet
24699 (@pxref{qXfer library list read}).
24701 @item qXfer:memory-map:read
24702 The remote stub understands the @samp{qXfer:memory-map:read} packet
24703 (@pxref{qXfer memory map read}).
24705 @item qXfer:spu:read
24706 The remote stub understands the @samp{qXfer:spu:read} packet
24707 (@pxref{qXfer spu read}).
24709 @item qXfer:spu:write
24710 The remote stub understands the @samp{qXfer:spu:write} packet
24711 (@pxref{qXfer spu write}).
24714 The remote stub understands the @samp{QPassSignals} packet
24715 (@pxref{QPassSignals}).
24720 @cindex symbol lookup, remote request
24721 @cindex @samp{qSymbol} packet
24722 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24723 requests. Accept requests from the target for the values of symbols.
24728 The target does not need to look up any (more) symbols.
24729 @item qSymbol:@var{sym_name}
24730 The target requests the value of symbol @var{sym_name} (hex encoded).
24731 @value{GDBN} may provide the value by using the
24732 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24736 @item qSymbol:@var{sym_value}:@var{sym_name}
24737 Set the value of @var{sym_name} to @var{sym_value}.
24739 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24740 target has previously requested.
24742 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24743 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24749 The target does not need to look up any (more) symbols.
24750 @item qSymbol:@var{sym_name}
24751 The target requests the value of a new symbol @var{sym_name} (hex
24752 encoded). @value{GDBN} will continue to supply the values of symbols
24753 (if available), until the target ceases to request them.
24758 @xref{Tracepoint Packets}.
24760 @item qThreadExtraInfo,@var{id}
24761 @cindex thread attributes info, remote request
24762 @cindex @samp{qThreadExtraInfo} packet
24763 Obtain a printable string description of a thread's attributes from
24764 the target OS. @var{id} is a thread-id in big-endian hex. This
24765 string may contain anything that the target OS thinks is interesting
24766 for @value{GDBN} to tell the user about the thread. The string is
24767 displayed in @value{GDBN}'s @code{info threads} display. Some
24768 examples of possible thread extra info strings are @samp{Runnable}, or
24769 @samp{Blocked on Mutex}.
24773 @item @var{XX}@dots{}
24774 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
24775 comprising the printable string containing the extra information about
24776 the thread's attributes.
24779 (Note that the @code{qThreadExtraInfo} packet's name is separated from
24780 the command by a @samp{,}, not a @samp{:}, contrary to the naming
24781 conventions above. Please don't use this packet as a model for new
24789 @xref{Tracepoint Packets}.
24791 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
24792 @cindex read special object, remote request
24793 @cindex @samp{qXfer} packet
24794 @anchor{qXfer read}
24795 Read uninterpreted bytes from the target's special data area
24796 identified by the keyword @var{object}. Request @var{length} bytes
24797 starting at @var{offset} bytes into the data. The content and
24798 encoding of @var{annex} is specific to @var{object}; it can supply
24799 additional details about what data to access.
24801 Here are the specific requests of this form defined so far. All
24802 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
24803 formats, listed below.
24806 @item qXfer:auxv:read::@var{offset},@var{length}
24807 @anchor{qXfer auxiliary vector read}
24808 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
24809 auxiliary vector}. Note @var{annex} must be empty.
24811 This packet is not probed by default; the remote stub must request it,
24812 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24814 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
24815 @anchor{qXfer target description read}
24816 Access the @dfn{target description}. @xref{Target Descriptions}. The
24817 annex specifies which XML document to access. The main description is
24818 always loaded from the @samp{target.xml} annex.
24820 This packet is not probed by default; the remote stub must request it,
24821 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24823 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
24824 @anchor{qXfer library list read}
24825 Access the target's list of loaded libraries. @xref{Library List Format}.
24826 The annex part of the generic @samp{qXfer} packet must be empty
24827 (@pxref{qXfer read}).
24829 Targets which maintain a list of libraries in the program's memory do
24830 not need to implement this packet; it is designed for platforms where
24831 the operating system manages the list of loaded libraries.
24833 This packet is not probed by default; the remote stub must request it,
24834 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24836 @item qXfer:memory-map:read::@var{offset},@var{length}
24837 @anchor{qXfer memory map read}
24838 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
24839 annex part of the generic @samp{qXfer} packet must be empty
24840 (@pxref{qXfer read}).
24842 This packet is not probed by default; the remote stub must request it,
24843 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24845 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
24846 @anchor{qXfer spu read}
24847 Read contents of an @code{spufs} file on the target system. The
24848 annex specifies which file to read; it must be of the form
24849 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24850 in the target process, and @var{name} identifes the @code{spufs} file
24851 in that context to be accessed.
24853 This packet is not probed by default; the remote stub must request it,
24854 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24860 Data @var{data} (@pxref{Binary Data}) has been read from the
24861 target. There may be more data at a higher address (although
24862 it is permitted to return @samp{m} even for the last valid
24863 block of data, as long as at least one byte of data was read).
24864 @var{data} may have fewer bytes than the @var{length} in the
24868 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24869 There is no more data to be read. @var{data} may have fewer bytes
24870 than the @var{length} in the request.
24873 The @var{offset} in the request is at the end of the data.
24874 There is no more data to be read.
24877 The request was malformed, or @var{annex} was invalid.
24880 The offset was invalid, or there was an error encountered reading the data.
24881 @var{nn} is a hex-encoded @code{errno} value.
24884 An empty reply indicates the @var{object} string was not recognized by
24885 the stub, or that the object does not support reading.
24888 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24889 @cindex write data into object, remote request
24890 Write uninterpreted bytes into the target's special data area
24891 identified by the keyword @var{object}, starting at @var{offset} bytes
24892 into the data. @var{data}@dots{} is the binary-encoded data
24893 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24894 is specific to @var{object}; it can supply additional details about what data
24897 Here are the specific requests of this form defined so far. All
24898 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
24899 formats, listed below.
24902 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24903 @anchor{qXfer spu write}
24904 Write @var{data} to an @code{spufs} file on the target system. The
24905 annex specifies which file to write; it must be of the form
24906 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24907 in the target process, and @var{name} identifes the @code{spufs} file
24908 in that context to be accessed.
24910 This packet is not probed by default; the remote stub must request it,
24911 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24917 @var{nn} (hex encoded) is the number of bytes written.
24918 This may be fewer bytes than supplied in the request.
24921 The request was malformed, or @var{annex} was invalid.
24924 The offset was invalid, or there was an error encountered writing the data.
24925 @var{nn} is a hex-encoded @code{errno} value.
24928 An empty reply indicates the @var{object} string was not
24929 recognized by the stub, or that the object does not support writing.
24932 @item qXfer:@var{object}:@var{operation}:@dots{}
24933 Requests of this form may be added in the future. When a stub does
24934 not recognize the @var{object} keyword, or its support for
24935 @var{object} does not recognize the @var{operation} keyword, the stub
24936 must respond with an empty packet.
24940 @node Register Packet Format
24941 @section Register Packet Format
24943 The following @code{g}/@code{G} packets have previously been defined.
24944 In the below, some thirty-two bit registers are transferred as
24945 sixty-four bits. Those registers should be zero/sign extended (which?)
24946 to fill the space allocated. Register bytes are transferred in target
24947 byte order. The two nibbles within a register byte are transferred
24948 most-significant - least-significant.
24954 All registers are transferred as thirty-two bit quantities in the order:
24955 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24956 registers; fsr; fir; fp.
24960 All registers are transferred as sixty-four bit quantities (including
24961 thirty-two bit registers such as @code{sr}). The ordering is the same
24966 @node Tracepoint Packets
24967 @section Tracepoint Packets
24968 @cindex tracepoint packets
24969 @cindex packets, tracepoint
24971 Here we describe the packets @value{GDBN} uses to implement
24972 tracepoints (@pxref{Tracepoints}).
24976 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24977 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24978 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24979 the tracepoint is disabled. @var{step} is the tracepoint's step
24980 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24981 present, further @samp{QTDP} packets will follow to specify this
24982 tracepoint's actions.
24987 The packet was understood and carried out.
24989 The packet was not recognized.
24992 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24993 Define actions to be taken when a tracepoint is hit. @var{n} and
24994 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24995 this tracepoint. This packet may only be sent immediately after
24996 another @samp{QTDP} packet that ended with a @samp{-}. If the
24997 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24998 specifying more actions for this tracepoint.
25000 In the series of action packets for a given tracepoint, at most one
25001 can have an @samp{S} before its first @var{action}. If such a packet
25002 is sent, it and the following packets define ``while-stepping''
25003 actions. Any prior packets define ordinary actions --- that is, those
25004 taken when the tracepoint is first hit. If no action packet has an
25005 @samp{S}, then all the packets in the series specify ordinary
25006 tracepoint actions.
25008 The @samp{@var{action}@dots{}} portion of the packet is a series of
25009 actions, concatenated without separators. Each action has one of the
25015 Collect the registers whose bits are set in @var{mask}. @var{mask} is
25016 a hexadecimal number whose @var{i}'th bit is set if register number
25017 @var{i} should be collected. (The least significant bit is numbered
25018 zero.) Note that @var{mask} may be any number of digits long; it may
25019 not fit in a 32-bit word.
25021 @item M @var{basereg},@var{offset},@var{len}
25022 Collect @var{len} bytes of memory starting at the address in register
25023 number @var{basereg}, plus @var{offset}. If @var{basereg} is
25024 @samp{-1}, then the range has a fixed address: @var{offset} is the
25025 address of the lowest byte to collect. The @var{basereg},
25026 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
25027 values (the @samp{-1} value for @var{basereg} is a special case).
25029 @item X @var{len},@var{expr}
25030 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
25031 it directs. @var{expr} is an agent expression, as described in
25032 @ref{Agent Expressions}. Each byte of the expression is encoded as a
25033 two-digit hex number in the packet; @var{len} is the number of bytes
25034 in the expression (and thus one-half the number of hex digits in the
25039 Any number of actions may be packed together in a single @samp{QTDP}
25040 packet, as long as the packet does not exceed the maximum packet
25041 length (400 bytes, for many stubs). There may be only one @samp{R}
25042 action per tracepoint, and it must precede any @samp{M} or @samp{X}
25043 actions. Any registers referred to by @samp{M} and @samp{X} actions
25044 must be collected by a preceding @samp{R} action. (The
25045 ``while-stepping'' actions are treated as if they were attached to a
25046 separate tracepoint, as far as these restrictions are concerned.)
25051 The packet was understood and carried out.
25053 The packet was not recognized.
25056 @item QTFrame:@var{n}
25057 Select the @var{n}'th tracepoint frame from the buffer, and use the
25058 register and memory contents recorded there to answer subsequent
25059 request packets from @value{GDBN}.
25061 A successful reply from the stub indicates that the stub has found the
25062 requested frame. The response is a series of parts, concatenated
25063 without separators, describing the frame we selected. Each part has
25064 one of the following forms:
25068 The selected frame is number @var{n} in the trace frame buffer;
25069 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
25070 was no frame matching the criteria in the request packet.
25073 The selected trace frame records a hit of tracepoint number @var{t};
25074 @var{t} is a hexadecimal number.
25078 @item QTFrame:pc:@var{addr}
25079 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25080 currently selected frame whose PC is @var{addr};
25081 @var{addr} is a hexadecimal number.
25083 @item QTFrame:tdp:@var{t}
25084 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25085 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
25086 is a hexadecimal number.
25088 @item QTFrame:range:@var{start}:@var{end}
25089 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25090 currently selected frame whose PC is between @var{start} (inclusive)
25091 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
25094 @item QTFrame:outside:@var{start}:@var{end}
25095 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
25096 frame @emph{outside} the given range of addresses.
25099 Begin the tracepoint experiment. Begin collecting data from tracepoint
25100 hits in the trace frame buffer.
25103 End the tracepoint experiment. Stop collecting trace frames.
25106 Clear the table of tracepoints, and empty the trace frame buffer.
25108 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
25109 Establish the given ranges of memory as ``transparent''. The stub
25110 will answer requests for these ranges from memory's current contents,
25111 if they were not collected as part of the tracepoint hit.
25113 @value{GDBN} uses this to mark read-only regions of memory, like those
25114 containing program code. Since these areas never change, they should
25115 still have the same contents they did when the tracepoint was hit, so
25116 there's no reason for the stub to refuse to provide their contents.
25119 Ask the stub if there is a trace experiment running right now.
25124 There is no trace experiment running.
25126 There is a trace experiment running.
25132 @node Host I/O Packets
25133 @section Host I/O Packets
25134 @cindex Host I/O, remote protocol
25135 @cindex file transfer, remote protocol
25137 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
25138 operations on the far side of a remote link. For example, Host I/O is
25139 used to upload and download files to a remote target with its own
25140 filesystem. Host I/O uses the same constant values and data structure
25141 layout as the target-initiated File-I/O protocol. However, the
25142 Host I/O packets are structured differently. The target-initiated
25143 protocol relies on target memory to store parameters and buffers.
25144 Host I/O requests are initiated by @value{GDBN}, and the
25145 target's memory is not involved. @xref{File-I/O Remote Protocol
25146 Extension}, for more details on the target-initiated protocol.
25148 The Host I/O request packets all encode a single operation along with
25149 its arguments. They have this format:
25153 @item vFile:@var{operation}: @var{parameter}@dots{}
25154 @var{operation} is the name of the particular request; the target
25155 should compare the entire packet name up to the second colon when checking
25156 for a supported operation. The format of @var{parameter} depends on
25157 the operation. Numbers are always passed in hexadecimal. Negative
25158 numbers have an explicit minus sign (i.e.@: two's complement is not
25159 used). Strings (e.g.@: filenames) are encoded as a series of
25160 hexadecimal bytes. The last argument to a system call may be a
25161 buffer of escaped binary data (@pxref{Binary Data}).
25165 The valid responses to Host I/O packets are:
25169 @item F @var{result} [, @var{errno}] [; @var{attachment}]
25170 @var{result} is the integer value returned by this operation, usually
25171 non-negative for success and -1 for errors. If an error has occured,
25172 @var{errno} will be included in the result. @var{errno} will have a
25173 value defined by the File-I/O protocol (@pxref{Errno Values}). For
25174 operations which return data, @var{attachment} supplies the data as a
25175 binary buffer. Binary buffers in response packets are escaped in the
25176 normal way (@pxref{Binary Data}). See the individual packet
25177 documentation for the interpretation of @var{result} and
25181 An empty response indicates that this operation is not recognized.
25185 These are the supported Host I/O operations:
25188 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
25189 Open a file at @var{pathname} and return a file descriptor for it, or
25190 return -1 if an error occurs. @var{pathname} is a string,
25191 @var{flags} is an integer indicating a mask of open flags
25192 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
25193 of mode bits to use if the file is created (@pxref{mode_t Values}).
25194 @xref{open}, for details of the open flags and mode values.
25196 @item vFile:close: @var{fd}
25197 Close the open file corresponding to @var{fd} and return 0, or
25198 -1 if an error occurs.
25200 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
25201 Read data from the open file corresponding to @var{fd}. Up to
25202 @var{count} bytes will be read from the file, starting at @var{offset}
25203 relative to the start of the file. The target may read fewer bytes;
25204 common reasons include packet size limits and an end-of-file
25205 condition. The number of bytes read is returned. Zero should only be
25206 returned for a successful read at the end of the file, or if
25207 @var{count} was zero.
25209 The data read should be returned as a binary attachment on success.
25210 If zero bytes were read, the response should include an empty binary
25211 attachment (i.e.@: a trailing semicolon). The return value is the
25212 number of target bytes read; the binary attachment may be longer if
25213 some characters were escaped.
25215 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
25216 Write @var{data} (a binary buffer) to the open file corresponding
25217 to @var{fd}. Start the write at @var{offset} from the start of the
25218 file. Unlike many @code{write} system calls, there is no
25219 separate @var{count} argument; the length of @var{data} in the
25220 packet is used. @samp{vFile:write} returns the number of bytes written,
25221 which may be shorter than the length of @var{data}, or -1 if an
25224 @item vFile:unlink: @var{pathname}
25225 Delete the file at @var{pathname} on the target. Return 0,
25226 or -1 if an error occurs. @var{pathname} is a string.
25231 @section Interrupts
25232 @cindex interrupts (remote protocol)
25234 When a program on the remote target is running, @value{GDBN} may
25235 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
25236 control of which is specified via @value{GDBN}'s @samp{remotebreak}
25237 setting (@pxref{set remotebreak}).
25239 The precise meaning of @code{BREAK} is defined by the transport
25240 mechanism and may, in fact, be undefined. @value{GDBN} does
25241 not currently define a @code{BREAK} mechanism for any of the network
25244 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
25245 transport mechanisms. It is represented by sending the single byte
25246 @code{0x03} without any of the usual packet overhead described in
25247 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
25248 transmitted as part of a packet, it is considered to be packet data
25249 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
25250 (@pxref{X packet}), used for binary downloads, may include an unescaped
25251 @code{0x03} as part of its packet.
25253 Stubs are not required to recognize these interrupt mechanisms and the
25254 precise meaning associated with receipt of the interrupt is
25255 implementation defined. If the stub is successful at interrupting the
25256 running program, it is expected that it will send one of the Stop
25257 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
25258 of successfully stopping the program. Interrupts received while the
25259 program is stopped will be discarded.
25264 Example sequence of a target being re-started. Notice how the restart
25265 does not get any direct output:
25270 @emph{target restarts}
25273 <- @code{T001:1234123412341234}
25277 Example sequence of a target being stepped by a single instruction:
25280 -> @code{G1445@dots{}}
25285 <- @code{T001:1234123412341234}
25289 <- @code{1455@dots{}}
25293 @node File-I/O Remote Protocol Extension
25294 @section File-I/O Remote Protocol Extension
25295 @cindex File-I/O remote protocol extension
25298 * File-I/O Overview::
25299 * Protocol Basics::
25300 * The F Request Packet::
25301 * The F Reply Packet::
25302 * The Ctrl-C Message::
25304 * List of Supported Calls::
25305 * Protocol-specific Representation of Datatypes::
25307 * File-I/O Examples::
25310 @node File-I/O Overview
25311 @subsection File-I/O Overview
25312 @cindex file-i/o overview
25314 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
25315 target to use the host's file system and console I/O to perform various
25316 system calls. System calls on the target system are translated into a
25317 remote protocol packet to the host system, which then performs the needed
25318 actions and returns a response packet to the target system.
25319 This simulates file system operations even on targets that lack file systems.
25321 The protocol is defined to be independent of both the host and target systems.
25322 It uses its own internal representation of datatypes and values. Both
25323 @value{GDBN} and the target's @value{GDBN} stub are responsible for
25324 translating the system-dependent value representations into the internal
25325 protocol representations when data is transmitted.
25327 The communication is synchronous. A system call is possible only when
25328 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
25329 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
25330 the target is stopped to allow deterministic access to the target's
25331 memory. Therefore File-I/O is not interruptible by target signals. On
25332 the other hand, it is possible to interrupt File-I/O by a user interrupt
25333 (@samp{Ctrl-C}) within @value{GDBN}.
25335 The target's request to perform a host system call does not finish
25336 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
25337 after finishing the system call, the target returns to continuing the
25338 previous activity (continue, step). No additional continue or step
25339 request from @value{GDBN} is required.
25342 (@value{GDBP}) continue
25343 <- target requests 'system call X'
25344 target is stopped, @value{GDBN} executes system call
25345 -> @value{GDBN} returns result
25346 ... target continues, @value{GDBN} returns to wait for the target
25347 <- target hits breakpoint and sends a Txx packet
25350 The protocol only supports I/O on the console and to regular files on
25351 the host file system. Character or block special devices, pipes,
25352 named pipes, sockets or any other communication method on the host
25353 system are not supported by this protocol.
25355 @node Protocol Basics
25356 @subsection Protocol Basics
25357 @cindex protocol basics, file-i/o
25359 The File-I/O protocol uses the @code{F} packet as the request as well
25360 as reply packet. Since a File-I/O system call can only occur when
25361 @value{GDBN} is waiting for a response from the continuing or stepping target,
25362 the File-I/O request is a reply that @value{GDBN} has to expect as a result
25363 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
25364 This @code{F} packet contains all information needed to allow @value{GDBN}
25365 to call the appropriate host system call:
25369 A unique identifier for the requested system call.
25372 All parameters to the system call. Pointers are given as addresses
25373 in the target memory address space. Pointers to strings are given as
25374 pointer/length pair. Numerical values are given as they are.
25375 Numerical control flags are given in a protocol-specific representation.
25379 At this point, @value{GDBN} has to perform the following actions.
25383 If the parameters include pointer values to data needed as input to a
25384 system call, @value{GDBN} requests this data from the target with a
25385 standard @code{m} packet request. This additional communication has to be
25386 expected by the target implementation and is handled as any other @code{m}
25390 @value{GDBN} translates all value from protocol representation to host
25391 representation as needed. Datatypes are coerced into the host types.
25394 @value{GDBN} calls the system call.
25397 It then coerces datatypes back to protocol representation.
25400 If the system call is expected to return data in buffer space specified
25401 by pointer parameters to the call, the data is transmitted to the
25402 target using a @code{M} or @code{X} packet. This packet has to be expected
25403 by the target implementation and is handled as any other @code{M} or @code{X}
25408 Eventually @value{GDBN} replies with another @code{F} packet which contains all
25409 necessary information for the target to continue. This at least contains
25416 @code{errno}, if has been changed by the system call.
25423 After having done the needed type and value coercion, the target continues
25424 the latest continue or step action.
25426 @node The F Request Packet
25427 @subsection The @code{F} Request Packet
25428 @cindex file-i/o request packet
25429 @cindex @code{F} request packet
25431 The @code{F} request packet has the following format:
25434 @item F@var{call-id},@var{parameter@dots{}}
25436 @var{call-id} is the identifier to indicate the host system call to be called.
25437 This is just the name of the function.
25439 @var{parameter@dots{}} are the parameters to the system call.
25440 Parameters are hexadecimal integer values, either the actual values in case
25441 of scalar datatypes, pointers to target buffer space in case of compound
25442 datatypes and unspecified memory areas, or pointer/length pairs in case
25443 of string parameters. These are appended to the @var{call-id} as a
25444 comma-delimited list. All values are transmitted in ASCII
25445 string representation, pointer/length pairs separated by a slash.
25451 @node The F Reply Packet
25452 @subsection The @code{F} Reply Packet
25453 @cindex file-i/o reply packet
25454 @cindex @code{F} reply packet
25456 The @code{F} reply packet has the following format:
25460 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
25462 @var{retcode} is the return code of the system call as hexadecimal value.
25464 @var{errno} is the @code{errno} set by the call, in protocol-specific
25466 This parameter can be omitted if the call was successful.
25468 @var{Ctrl-C flag} is only sent if the user requested a break. In this
25469 case, @var{errno} must be sent as well, even if the call was successful.
25470 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
25477 or, if the call was interrupted before the host call has been performed:
25484 assuming 4 is the protocol-specific representation of @code{EINTR}.
25489 @node The Ctrl-C Message
25490 @subsection The @samp{Ctrl-C} Message
25491 @cindex ctrl-c message, in file-i/o protocol
25493 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
25494 reply packet (@pxref{The F Reply Packet}),
25495 the target should behave as if it had
25496 gotten a break message. The meaning for the target is ``system call
25497 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
25498 (as with a break message) and return to @value{GDBN} with a @code{T02}
25501 It's important for the target to know in which
25502 state the system call was interrupted. There are two possible cases:
25506 The system call hasn't been performed on the host yet.
25509 The system call on the host has been finished.
25513 These two states can be distinguished by the target by the value of the
25514 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
25515 call hasn't been performed. This is equivalent to the @code{EINTR} handling
25516 on POSIX systems. In any other case, the target may presume that the
25517 system call has been finished --- successfully or not --- and should behave
25518 as if the break message arrived right after the system call.
25520 @value{GDBN} must behave reliably. If the system call has not been called
25521 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
25522 @code{errno} in the packet. If the system call on the host has been finished
25523 before the user requests a break, the full action must be finished by
25524 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
25525 The @code{F} packet may only be sent when either nothing has happened
25526 or the full action has been completed.
25529 @subsection Console I/O
25530 @cindex console i/o as part of file-i/o
25532 By default and if not explicitly closed by the target system, the file
25533 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
25534 on the @value{GDBN} console is handled as any other file output operation
25535 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
25536 by @value{GDBN} so that after the target read request from file descriptor
25537 0 all following typing is buffered until either one of the following
25542 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
25544 system call is treated as finished.
25547 The user presses @key{RET}. This is treated as end of input with a trailing
25551 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
25552 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
25556 If the user has typed more characters than fit in the buffer given to
25557 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
25558 either another @code{read(0, @dots{})} is requested by the target, or debugging
25559 is stopped at the user's request.
25562 @node List of Supported Calls
25563 @subsection List of Supported Calls
25564 @cindex list of supported file-i/o calls
25581 @unnumberedsubsubsec open
25582 @cindex open, file-i/o system call
25587 int open(const char *pathname, int flags);
25588 int open(const char *pathname, int flags, mode_t mode);
25592 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
25595 @var{flags} is the bitwise @code{OR} of the following values:
25599 If the file does not exist it will be created. The host
25600 rules apply as far as file ownership and time stamps
25604 When used with @code{O_CREAT}, if the file already exists it is
25605 an error and open() fails.
25608 If the file already exists and the open mode allows
25609 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
25610 truncated to zero length.
25613 The file is opened in append mode.
25616 The file is opened for reading only.
25619 The file is opened for writing only.
25622 The file is opened for reading and writing.
25626 Other bits are silently ignored.
25630 @var{mode} is the bitwise @code{OR} of the following values:
25634 User has read permission.
25637 User has write permission.
25640 Group has read permission.
25643 Group has write permission.
25646 Others have read permission.
25649 Others have write permission.
25653 Other bits are silently ignored.
25656 @item Return value:
25657 @code{open} returns the new file descriptor or -1 if an error
25664 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
25667 @var{pathname} refers to a directory.
25670 The requested access is not allowed.
25673 @var{pathname} was too long.
25676 A directory component in @var{pathname} does not exist.
25679 @var{pathname} refers to a device, pipe, named pipe or socket.
25682 @var{pathname} refers to a file on a read-only filesystem and
25683 write access was requested.
25686 @var{pathname} is an invalid pointer value.
25689 No space on device to create the file.
25692 The process already has the maximum number of files open.
25695 The limit on the total number of files open on the system
25699 The call was interrupted by the user.
25705 @unnumberedsubsubsec close
25706 @cindex close, file-i/o system call
25715 @samp{Fclose,@var{fd}}
25717 @item Return value:
25718 @code{close} returns zero on success, or -1 if an error occurred.
25724 @var{fd} isn't a valid open file descriptor.
25727 The call was interrupted by the user.
25733 @unnumberedsubsubsec read
25734 @cindex read, file-i/o system call
25739 int read(int fd, void *buf, unsigned int count);
25743 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
25745 @item Return value:
25746 On success, the number of bytes read is returned.
25747 Zero indicates end of file. If count is zero, read
25748 returns zero as well. On error, -1 is returned.
25754 @var{fd} is not a valid file descriptor or is not open for
25758 @var{bufptr} is an invalid pointer value.
25761 The call was interrupted by the user.
25767 @unnumberedsubsubsec write
25768 @cindex write, file-i/o system call
25773 int write(int fd, const void *buf, unsigned int count);
25777 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
25779 @item Return value:
25780 On success, the number of bytes written are returned.
25781 Zero indicates nothing was written. On error, -1
25788 @var{fd} is not a valid file descriptor or is not open for
25792 @var{bufptr} is an invalid pointer value.
25795 An attempt was made to write a file that exceeds the
25796 host-specific maximum file size allowed.
25799 No space on device to write the data.
25802 The call was interrupted by the user.
25808 @unnumberedsubsubsec lseek
25809 @cindex lseek, file-i/o system call
25814 long lseek (int fd, long offset, int flag);
25818 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
25820 @var{flag} is one of:
25824 The offset is set to @var{offset} bytes.
25827 The offset is set to its current location plus @var{offset}
25831 The offset is set to the size of the file plus @var{offset}
25835 @item Return value:
25836 On success, the resulting unsigned offset in bytes from
25837 the beginning of the file is returned. Otherwise, a
25838 value of -1 is returned.
25844 @var{fd} is not a valid open file descriptor.
25847 @var{fd} is associated with the @value{GDBN} console.
25850 @var{flag} is not a proper value.
25853 The call was interrupted by the user.
25859 @unnumberedsubsubsec rename
25860 @cindex rename, file-i/o system call
25865 int rename(const char *oldpath, const char *newpath);
25869 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
25871 @item Return value:
25872 On success, zero is returned. On error, -1 is returned.
25878 @var{newpath} is an existing directory, but @var{oldpath} is not a
25882 @var{newpath} is a non-empty directory.
25885 @var{oldpath} or @var{newpath} is a directory that is in use by some
25889 An attempt was made to make a directory a subdirectory
25893 A component used as a directory in @var{oldpath} or new
25894 path is not a directory. Or @var{oldpath} is a directory
25895 and @var{newpath} exists but is not a directory.
25898 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
25901 No access to the file or the path of the file.
25905 @var{oldpath} or @var{newpath} was too long.
25908 A directory component in @var{oldpath} or @var{newpath} does not exist.
25911 The file is on a read-only filesystem.
25914 The device containing the file has no room for the new
25918 The call was interrupted by the user.
25924 @unnumberedsubsubsec unlink
25925 @cindex unlink, file-i/o system call
25930 int unlink(const char *pathname);
25934 @samp{Funlink,@var{pathnameptr}/@var{len}}
25936 @item Return value:
25937 On success, zero is returned. On error, -1 is returned.
25943 No access to the file or the path of the file.
25946 The system does not allow unlinking of directories.
25949 The file @var{pathname} cannot be unlinked because it's
25950 being used by another process.
25953 @var{pathnameptr} is an invalid pointer value.
25956 @var{pathname} was too long.
25959 A directory component in @var{pathname} does not exist.
25962 A component of the path is not a directory.
25965 The file is on a read-only filesystem.
25968 The call was interrupted by the user.
25974 @unnumberedsubsubsec stat/fstat
25975 @cindex fstat, file-i/o system call
25976 @cindex stat, file-i/o system call
25981 int stat(const char *pathname, struct stat *buf);
25982 int fstat(int fd, struct stat *buf);
25986 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25987 @samp{Ffstat,@var{fd},@var{bufptr}}
25989 @item Return value:
25990 On success, zero is returned. On error, -1 is returned.
25996 @var{fd} is not a valid open file.
25999 A directory component in @var{pathname} does not exist or the
26000 path is an empty string.
26003 A component of the path is not a directory.
26006 @var{pathnameptr} is an invalid pointer value.
26009 No access to the file or the path of the file.
26012 @var{pathname} was too long.
26015 The call was interrupted by the user.
26021 @unnumberedsubsubsec gettimeofday
26022 @cindex gettimeofday, file-i/o system call
26027 int gettimeofday(struct timeval *tv, void *tz);
26031 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
26033 @item Return value:
26034 On success, 0 is returned, -1 otherwise.
26040 @var{tz} is a non-NULL pointer.
26043 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
26049 @unnumberedsubsubsec isatty
26050 @cindex isatty, file-i/o system call
26055 int isatty(int fd);
26059 @samp{Fisatty,@var{fd}}
26061 @item Return value:
26062 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
26068 The call was interrupted by the user.
26073 Note that the @code{isatty} call is treated as a special case: it returns
26074 1 to the target if the file descriptor is attached
26075 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
26076 would require implementing @code{ioctl} and would be more complex than
26081 @unnumberedsubsubsec system
26082 @cindex system, file-i/o system call
26087 int system(const char *command);
26091 @samp{Fsystem,@var{commandptr}/@var{len}}
26093 @item Return value:
26094 If @var{len} is zero, the return value indicates whether a shell is
26095 available. A zero return value indicates a shell is not available.
26096 For non-zero @var{len}, the value returned is -1 on error and the
26097 return status of the command otherwise. Only the exit status of the
26098 command is returned, which is extracted from the host's @code{system}
26099 return value by calling @code{WEXITSTATUS(retval)}. In case
26100 @file{/bin/sh} could not be executed, 127 is returned.
26106 The call was interrupted by the user.
26111 @value{GDBN} takes over the full task of calling the necessary host calls
26112 to perform the @code{system} call. The return value of @code{system} on
26113 the host is simplified before it's returned
26114 to the target. Any termination signal information from the child process
26115 is discarded, and the return value consists
26116 entirely of the exit status of the called command.
26118 Due to security concerns, the @code{system} call is by default refused
26119 by @value{GDBN}. The user has to allow this call explicitly with the
26120 @code{set remote system-call-allowed 1} command.
26123 @item set remote system-call-allowed
26124 @kindex set remote system-call-allowed
26125 Control whether to allow the @code{system} calls in the File I/O
26126 protocol for the remote target. The default is zero (disabled).
26128 @item show remote system-call-allowed
26129 @kindex show remote system-call-allowed
26130 Show whether the @code{system} calls are allowed in the File I/O
26134 @node Protocol-specific Representation of Datatypes
26135 @subsection Protocol-specific Representation of Datatypes
26136 @cindex protocol-specific representation of datatypes, in file-i/o protocol
26139 * Integral Datatypes::
26141 * Memory Transfer::
26146 @node Integral Datatypes
26147 @unnumberedsubsubsec Integral Datatypes
26148 @cindex integral datatypes, in file-i/o protocol
26150 The integral datatypes used in the system calls are @code{int},
26151 @code{unsigned int}, @code{long}, @code{unsigned long},
26152 @code{mode_t}, and @code{time_t}.
26154 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
26155 implemented as 32 bit values in this protocol.
26157 @code{long} and @code{unsigned long} are implemented as 64 bit types.
26159 @xref{Limits}, for corresponding MIN and MAX values (similar to those
26160 in @file{limits.h}) to allow range checking on host and target.
26162 @code{time_t} datatypes are defined as seconds since the Epoch.
26164 All integral datatypes transferred as part of a memory read or write of a
26165 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
26168 @node Pointer Values
26169 @unnumberedsubsubsec Pointer Values
26170 @cindex pointer values, in file-i/o protocol
26172 Pointers to target data are transmitted as they are. An exception
26173 is made for pointers to buffers for which the length isn't
26174 transmitted as part of the function call, namely strings. Strings
26175 are transmitted as a pointer/length pair, both as hex values, e.g.@:
26182 which is a pointer to data of length 18 bytes at position 0x1aaf.
26183 The length is defined as the full string length in bytes, including
26184 the trailing null byte. For example, the string @code{"hello world"}
26185 at address 0x123456 is transmitted as
26191 @node Memory Transfer
26192 @unnumberedsubsubsec Memory Transfer
26193 @cindex memory transfer, in file-i/o protocol
26195 Structured data which is transferred using a memory read or write (for
26196 example, a @code{struct stat}) is expected to be in a protocol-specific format
26197 with all scalar multibyte datatypes being big endian. Translation to
26198 this representation needs to be done both by the target before the @code{F}
26199 packet is sent, and by @value{GDBN} before
26200 it transfers memory to the target. Transferred pointers to structured
26201 data should point to the already-coerced data at any time.
26205 @unnumberedsubsubsec struct stat
26206 @cindex struct stat, in file-i/o protocol
26208 The buffer of type @code{struct stat} used by the target and @value{GDBN}
26209 is defined as follows:
26213 unsigned int st_dev; /* device */
26214 unsigned int st_ino; /* inode */
26215 mode_t st_mode; /* protection */
26216 unsigned int st_nlink; /* number of hard links */
26217 unsigned int st_uid; /* user ID of owner */
26218 unsigned int st_gid; /* group ID of owner */
26219 unsigned int st_rdev; /* device type (if inode device) */
26220 unsigned long st_size; /* total size, in bytes */
26221 unsigned long st_blksize; /* blocksize for filesystem I/O */
26222 unsigned long st_blocks; /* number of blocks allocated */
26223 time_t st_atime; /* time of last access */
26224 time_t st_mtime; /* time of last modification */
26225 time_t st_ctime; /* time of last change */
26229 The integral datatypes conform to the definitions given in the
26230 appropriate section (see @ref{Integral Datatypes}, for details) so this
26231 structure is of size 64 bytes.
26233 The values of several fields have a restricted meaning and/or
26239 A value of 0 represents a file, 1 the console.
26242 No valid meaning for the target. Transmitted unchanged.
26245 Valid mode bits are described in @ref{Constants}. Any other
26246 bits have currently no meaning for the target.
26251 No valid meaning for the target. Transmitted unchanged.
26256 These values have a host and file system dependent
26257 accuracy. Especially on Windows hosts, the file system may not
26258 support exact timing values.
26261 The target gets a @code{struct stat} of the above representation and is
26262 responsible for coercing it to the target representation before
26265 Note that due to size differences between the host, target, and protocol
26266 representations of @code{struct stat} members, these members could eventually
26267 get truncated on the target.
26269 @node struct timeval
26270 @unnumberedsubsubsec struct timeval
26271 @cindex struct timeval, in file-i/o protocol
26273 The buffer of type @code{struct timeval} used by the File-I/O protocol
26274 is defined as follows:
26278 time_t tv_sec; /* second */
26279 long tv_usec; /* microsecond */
26283 The integral datatypes conform to the definitions given in the
26284 appropriate section (see @ref{Integral Datatypes}, for details) so this
26285 structure is of size 8 bytes.
26288 @subsection Constants
26289 @cindex constants, in file-i/o protocol
26291 The following values are used for the constants inside of the
26292 protocol. @value{GDBN} and target are responsible for translating these
26293 values before and after the call as needed.
26304 @unnumberedsubsubsec Open Flags
26305 @cindex open flags, in file-i/o protocol
26307 All values are given in hexadecimal representation.
26319 @node mode_t Values
26320 @unnumberedsubsubsec mode_t Values
26321 @cindex mode_t values, in file-i/o protocol
26323 All values are given in octal representation.
26340 @unnumberedsubsubsec Errno Values
26341 @cindex errno values, in file-i/o protocol
26343 All values are given in decimal representation.
26368 @code{EUNKNOWN} is used as a fallback error value if a host system returns
26369 any error value not in the list of supported error numbers.
26372 @unnumberedsubsubsec Lseek Flags
26373 @cindex lseek flags, in file-i/o protocol
26382 @unnumberedsubsubsec Limits
26383 @cindex limits, in file-i/o protocol
26385 All values are given in decimal representation.
26388 INT_MIN -2147483648
26390 UINT_MAX 4294967295
26391 LONG_MIN -9223372036854775808
26392 LONG_MAX 9223372036854775807
26393 ULONG_MAX 18446744073709551615
26396 @node File-I/O Examples
26397 @subsection File-I/O Examples
26398 @cindex file-i/o examples
26400 Example sequence of a write call, file descriptor 3, buffer is at target
26401 address 0x1234, 6 bytes should be written:
26404 <- @code{Fwrite,3,1234,6}
26405 @emph{request memory read from target}
26408 @emph{return "6 bytes written"}
26412 Example sequence of a read call, file descriptor 3, buffer is at target
26413 address 0x1234, 6 bytes should be read:
26416 <- @code{Fread,3,1234,6}
26417 @emph{request memory write to target}
26418 -> @code{X1234,6:XXXXXX}
26419 @emph{return "6 bytes read"}
26423 Example sequence of a read call, call fails on the host due to invalid
26424 file descriptor (@code{EBADF}):
26427 <- @code{Fread,3,1234,6}
26431 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
26435 <- @code{Fread,3,1234,6}
26440 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
26444 <- @code{Fread,3,1234,6}
26445 -> @code{X1234,6:XXXXXX}
26449 @node Library List Format
26450 @section Library List Format
26451 @cindex library list format, remote protocol
26453 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
26454 same process as your application to manage libraries. In this case,
26455 @value{GDBN} can use the loader's symbol table and normal memory
26456 operations to maintain a list of shared libraries. On other
26457 platforms, the operating system manages loaded libraries.
26458 @value{GDBN} can not retrieve the list of currently loaded libraries
26459 through memory operations, so it uses the @samp{qXfer:libraries:read}
26460 packet (@pxref{qXfer library list read}) instead. The remote stub
26461 queries the target's operating system and reports which libraries
26464 The @samp{qXfer:libraries:read} packet returns an XML document which
26465 lists loaded libraries and their offsets. Each library has an
26466 associated name and one or more segment or section base addresses,
26467 which report where the library was loaded in memory.
26469 For the common case of libraries that are fully linked binaries, the
26470 library should have a list of segments. If the target supports
26471 dynamic linking of a relocatable object file, its library XML element
26472 should instead include a list of allocated sections. The segment or
26473 section bases are start addresses, not relocation offsets; they do not
26474 depend on the library's link-time base addresses.
26476 @value{GDBN} must be linked with the Expat library to support XML
26477 library lists. @xref{Expat}.
26479 A simple memory map, with one loaded library relocated by a single
26480 offset, looks like this:
26484 <library name="/lib/libc.so.6">
26485 <segment address="0x10000000"/>
26490 Another simple memory map, with one loaded library with three
26491 allocated sections (.text, .data, .bss), looks like this:
26495 <library name="sharedlib.o">
26496 <section address="0x10000000"/>
26497 <section address="0x20000000"/>
26498 <section address="0x30000000"/>
26503 The format of a library list is described by this DTD:
26506 <!-- library-list: Root element with versioning -->
26507 <!ELEMENT library-list (library)*>
26508 <!ATTLIST library-list version CDATA #FIXED "1.0">
26509 <!ELEMENT library (segment*, section*)>
26510 <!ATTLIST library name CDATA #REQUIRED>
26511 <!ELEMENT segment EMPTY>
26512 <!ATTLIST segment address CDATA #REQUIRED>
26513 <!ELEMENT section EMPTY>
26514 <!ATTLIST section address CDATA #REQUIRED>
26517 In addition, segments and section descriptors cannot be mixed within a
26518 single library element, and you must supply at least one segment or
26519 section for each library.
26521 @node Memory Map Format
26522 @section Memory Map Format
26523 @cindex memory map format
26525 To be able to write into flash memory, @value{GDBN} needs to obtain a
26526 memory map from the target. This section describes the format of the
26529 The memory map is obtained using the @samp{qXfer:memory-map:read}
26530 (@pxref{qXfer memory map read}) packet and is an XML document that
26531 lists memory regions.
26533 @value{GDBN} must be linked with the Expat library to support XML
26534 memory maps. @xref{Expat}.
26536 The top-level structure of the document is shown below:
26539 <?xml version="1.0"?>
26540 <!DOCTYPE memory-map
26541 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
26542 "http://sourceware.org/gdb/gdb-memory-map.dtd">
26548 Each region can be either:
26553 A region of RAM starting at @var{addr} and extending for @var{length}
26557 <memory type="ram" start="@var{addr}" length="@var{length}"/>
26562 A region of read-only memory:
26565 <memory type="rom" start="@var{addr}" length="@var{length}"/>
26570 A region of flash memory, with erasure blocks @var{blocksize}
26574 <memory type="flash" start="@var{addr}" length="@var{length}">
26575 <property name="blocksize">@var{blocksize}</property>
26581 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
26582 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
26583 packets to write to addresses in such ranges.
26585 The formal DTD for memory map format is given below:
26588 <!-- ................................................... -->
26589 <!-- Memory Map XML DTD ................................ -->
26590 <!-- File: memory-map.dtd .............................. -->
26591 <!-- .................................... .............. -->
26592 <!-- memory-map.dtd -->
26593 <!-- memory-map: Root element with versioning -->
26594 <!ELEMENT memory-map (memory | property)>
26595 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
26596 <!ELEMENT memory (property)>
26597 <!-- memory: Specifies a memory region,
26598 and its type, or device. -->
26599 <!ATTLIST memory type CDATA #REQUIRED
26600 start CDATA #REQUIRED
26601 length CDATA #REQUIRED
26602 device CDATA #IMPLIED>
26603 <!-- property: Generic attribute tag -->
26604 <!ELEMENT property (#PCDATA | property)*>
26605 <!ATTLIST property name CDATA #REQUIRED>
26608 @include agentexpr.texi
26610 @node Target Descriptions
26611 @appendix Target Descriptions
26612 @cindex target descriptions
26614 @strong{Warning:} target descriptions are still under active development,
26615 and the contents and format may change between @value{GDBN} releases.
26616 The format is expected to stabilize in the future.
26618 One of the challenges of using @value{GDBN} to debug embedded systems
26619 is that there are so many minor variants of each processor
26620 architecture in use. It is common practice for vendors to start with
26621 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
26622 and then make changes to adapt it to a particular market niche. Some
26623 architectures have hundreds of variants, available from dozens of
26624 vendors. This leads to a number of problems:
26628 With so many different customized processors, it is difficult for
26629 the @value{GDBN} maintainers to keep up with the changes.
26631 Since individual variants may have short lifetimes or limited
26632 audiences, it may not be worthwhile to carry information about every
26633 variant in the @value{GDBN} source tree.
26635 When @value{GDBN} does support the architecture of the embedded system
26636 at hand, the task of finding the correct architecture name to give the
26637 @command{set architecture} command can be error-prone.
26640 To address these problems, the @value{GDBN} remote protocol allows a
26641 target system to not only identify itself to @value{GDBN}, but to
26642 actually describe its own features. This lets @value{GDBN} support
26643 processor variants it has never seen before --- to the extent that the
26644 descriptions are accurate, and that @value{GDBN} understands them.
26646 @value{GDBN} must be linked with the Expat library to support XML
26647 target descriptions. @xref{Expat}.
26650 * Retrieving Descriptions:: How descriptions are fetched from a target.
26651 * Target Description Format:: The contents of a target description.
26652 * Predefined Target Types:: Standard types available for target
26654 * Standard Target Features:: Features @value{GDBN} knows about.
26657 @node Retrieving Descriptions
26658 @section Retrieving Descriptions
26660 Target descriptions can be read from the target automatically, or
26661 specified by the user manually. The default behavior is to read the
26662 description from the target. @value{GDBN} retrieves it via the remote
26663 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
26664 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
26665 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
26666 XML document, of the form described in @ref{Target Description
26669 Alternatively, you can specify a file to read for the target description.
26670 If a file is set, the target will not be queried. The commands to
26671 specify a file are:
26674 @cindex set tdesc filename
26675 @item set tdesc filename @var{path}
26676 Read the target description from @var{path}.
26678 @cindex unset tdesc filename
26679 @item unset tdesc filename
26680 Do not read the XML target description from a file. @value{GDBN}
26681 will use the description supplied by the current target.
26683 @cindex show tdesc filename
26684 @item show tdesc filename
26685 Show the filename to read for a target description, if any.
26689 @node Target Description Format
26690 @section Target Description Format
26691 @cindex target descriptions, XML format
26693 A target description annex is an @uref{http://www.w3.org/XML/, XML}
26694 document which complies with the Document Type Definition provided in
26695 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
26696 means you can use generally available tools like @command{xmllint} to
26697 check that your feature descriptions are well-formed and valid.
26698 However, to help people unfamiliar with XML write descriptions for
26699 their targets, we also describe the grammar here.
26701 Target descriptions can identify the architecture of the remote target
26702 and (for some architectures) provide information about custom register
26703 sets. @value{GDBN} can use this information to autoconfigure for your
26704 target, or to warn you if you connect to an unsupported target.
26706 Here is a simple target description:
26709 <target version="1.0">
26710 <architecture>i386:x86-64</architecture>
26715 This minimal description only says that the target uses
26716 the x86-64 architecture.
26718 A target description has the following overall form, with [ ] marking
26719 optional elements and @dots{} marking repeatable elements. The elements
26720 are explained further below.
26723 <?xml version="1.0"?>
26724 <!DOCTYPE target SYSTEM "gdb-target.dtd">
26725 <target version="1.0">
26726 @r{[}@var{architecture}@r{]}
26727 @r{[}@var{feature}@dots{}@r{]}
26732 The description is generally insensitive to whitespace and line
26733 breaks, under the usual common-sense rules. The XML version
26734 declaration and document type declaration can generally be omitted
26735 (@value{GDBN} does not require them), but specifying them may be
26736 useful for XML validation tools. The @samp{version} attribute for
26737 @samp{<target>} may also be omitted, but we recommend
26738 including it; if future versions of @value{GDBN} use an incompatible
26739 revision of @file{gdb-target.dtd}, they will detect and report
26740 the version mismatch.
26742 @subsection Inclusion
26743 @cindex target descriptions, inclusion
26746 @cindex <xi:include>
26749 It can sometimes be valuable to split a target description up into
26750 several different annexes, either for organizational purposes, or to
26751 share files between different possible target descriptions. You can
26752 divide a description into multiple files by replacing any element of
26753 the target description with an inclusion directive of the form:
26756 <xi:include href="@var{document}"/>
26760 When @value{GDBN} encounters an element of this form, it will retrieve
26761 the named XML @var{document}, and replace the inclusion directive with
26762 the contents of that document. If the current description was read
26763 using @samp{qXfer}, then so will be the included document;
26764 @var{document} will be interpreted as the name of an annex. If the
26765 current description was read from a file, @value{GDBN} will look for
26766 @var{document} as a file in the same directory where it found the
26767 original description.
26769 @subsection Architecture
26770 @cindex <architecture>
26772 An @samp{<architecture>} element has this form:
26775 <architecture>@var{arch}</architecture>
26778 @var{arch} is an architecture name from the same selection
26779 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
26780 Debugging Target}).
26782 @subsection Features
26785 Each @samp{<feature>} describes some logical portion of the target
26786 system. Features are currently used to describe available CPU
26787 registers and the types of their contents. A @samp{<feature>} element
26791 <feature name="@var{name}">
26792 @r{[}@var{type}@dots{}@r{]}
26798 Each feature's name should be unique within the description. The name
26799 of a feature does not matter unless @value{GDBN} has some special
26800 knowledge of the contents of that feature; if it does, the feature
26801 should have its standard name. @xref{Standard Target Features}.
26805 Any register's value is a collection of bits which @value{GDBN} must
26806 interpret. The default interpretation is a two's complement integer,
26807 but other types can be requested by name in the register description.
26808 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
26809 Target Types}), and the description can define additional composite types.
26811 Each type element must have an @samp{id} attribute, which gives
26812 a unique (within the containing @samp{<feature>}) name to the type.
26813 Types must be defined before they are used.
26816 Some targets offer vector registers, which can be treated as arrays
26817 of scalar elements. These types are written as @samp{<vector>} elements,
26818 specifying the array element type, @var{type}, and the number of elements,
26822 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
26826 If a register's value is usefully viewed in multiple ways, define it
26827 with a union type containing the useful representations. The
26828 @samp{<union>} element contains one or more @samp{<field>} elements,
26829 each of which has a @var{name} and a @var{type}:
26832 <union id="@var{id}">
26833 <field name="@var{name}" type="@var{type}"/>
26838 @subsection Registers
26841 Each register is represented as an element with this form:
26844 <reg name="@var{name}"
26845 bitsize="@var{size}"
26846 @r{[}regnum="@var{num}"@r{]}
26847 @r{[}save-restore="@var{save-restore}"@r{]}
26848 @r{[}type="@var{type}"@r{]}
26849 @r{[}group="@var{group}"@r{]}/>
26853 The components are as follows:
26858 The register's name; it must be unique within the target description.
26861 The register's size, in bits.
26864 The register's number. If omitted, a register's number is one greater
26865 than that of the previous register (either in the current feature or in
26866 a preceeding feature); the first register in the target description
26867 defaults to zero. This register number is used to read or write
26868 the register; e.g.@: it is used in the remote @code{p} and @code{P}
26869 packets, and registers appear in the @code{g} and @code{G} packets
26870 in order of increasing register number.
26873 Whether the register should be preserved across inferior function
26874 calls; this must be either @code{yes} or @code{no}. The default is
26875 @code{yes}, which is appropriate for most registers except for
26876 some system control registers; this is not related to the target's
26880 The type of the register. @var{type} may be a predefined type, a type
26881 defined in the current feature, or one of the special types @code{int}
26882 and @code{float}. @code{int} is an integer type of the correct size
26883 for @var{bitsize}, and @code{float} is a floating point type (in the
26884 architecture's normal floating point format) of the correct size for
26885 @var{bitsize}. The default is @code{int}.
26888 The register group to which this register belongs. @var{group} must
26889 be either @code{general}, @code{float}, or @code{vector}. If no
26890 @var{group} is specified, @value{GDBN} will not display the register
26891 in @code{info registers}.
26895 @node Predefined Target Types
26896 @section Predefined Target Types
26897 @cindex target descriptions, predefined types
26899 Type definitions in the self-description can build up composite types
26900 from basic building blocks, but can not define fundamental types. Instead,
26901 standard identifiers are provided by @value{GDBN} for the fundamental
26902 types. The currently supported types are:
26911 Signed integer types holding the specified number of bits.
26918 Unsigned integer types holding the specified number of bits.
26922 Pointers to unspecified code and data. The program counter and
26923 any dedicated return address register may be marked as code
26924 pointers; printing a code pointer converts it into a symbolic
26925 address. The stack pointer and any dedicated address registers
26926 may be marked as data pointers.
26929 Single precision IEEE floating point.
26932 Double precision IEEE floating point.
26935 The 12-byte extended precision format used by ARM FPA registers.
26939 @node Standard Target Features
26940 @section Standard Target Features
26941 @cindex target descriptions, standard features
26943 A target description must contain either no registers or all the
26944 target's registers. If the description contains no registers, then
26945 @value{GDBN} will assume a default register layout, selected based on
26946 the architecture. If the description contains any registers, the
26947 default layout will not be used; the standard registers must be
26948 described in the target description, in such a way that @value{GDBN}
26949 can recognize them.
26951 This is accomplished by giving specific names to feature elements
26952 which contain standard registers. @value{GDBN} will look for features
26953 with those names and verify that they contain the expected registers;
26954 if any known feature is missing required registers, or if any required
26955 feature is missing, @value{GDBN} will reject the target
26956 description. You can add additional registers to any of the
26957 standard features --- @value{GDBN} will display them just as if
26958 they were added to an unrecognized feature.
26960 This section lists the known features and their expected contents.
26961 Sample XML documents for these features are included in the
26962 @value{GDBN} source tree, in the directory @file{gdb/features}.
26964 Names recognized by @value{GDBN} should include the name of the
26965 company or organization which selected the name, and the overall
26966 architecture to which the feature applies; so e.g.@: the feature
26967 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
26969 The names of registers are not case sensitive for the purpose
26970 of recognizing standard features, but @value{GDBN} will only display
26971 registers using the capitalization used in the description.
26977 * PowerPC Features::
26982 @subsection ARM Features
26983 @cindex target descriptions, ARM features
26985 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
26986 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
26987 @samp{lr}, @samp{pc}, and @samp{cpsr}.
26989 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
26990 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
26992 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
26993 it should contain at least registers @samp{wR0} through @samp{wR15} and
26994 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
26995 @samp{wCSSF}, and @samp{wCASF} registers are optional.
26997 @node MIPS Features
26998 @subsection MIPS Features
26999 @cindex target descriptions, MIPS features
27001 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
27002 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
27003 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
27006 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
27007 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
27008 registers. They may be 32-bit or 64-bit depending on the target.
27010 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
27011 it may be optional in a future version of @value{GDBN}. It should
27012 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
27013 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
27015 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
27016 contain a single register, @samp{restart}, which is used by the
27017 Linux kernel to control restartable syscalls.
27019 @node M68K Features
27020 @subsection M68K Features
27021 @cindex target descriptions, M68K features
27024 @item @samp{org.gnu.gdb.m68k.core}
27025 @itemx @samp{org.gnu.gdb.coldfire.core}
27026 @itemx @samp{org.gnu.gdb.fido.core}
27027 One of those features must be always present.
27028 The feature that is present determines which flavor of m86k is
27029 used. The feature that is present should contain registers
27030 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
27031 @samp{sp}, @samp{ps} and @samp{pc}.
27033 @item @samp{org.gnu.gdb.coldfire.fp}
27034 This feature is optional. If present, it should contain registers
27035 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
27039 @node PowerPC Features
27040 @subsection PowerPC Features
27041 @cindex target descriptions, PowerPC features
27043 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
27044 targets. It should contain registers @samp{r0} through @samp{r31},
27045 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
27046 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
27048 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
27049 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
27051 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
27052 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
27055 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
27056 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
27057 @samp{spefscr}. SPE targets should provide 32-bit registers in
27058 @samp{org.gnu.gdb.power.core} and provide the upper halves in
27059 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
27060 these to present registers @samp{ev0} through @samp{ev31} to the
27075 % I think something like @colophon should be in texinfo. In the
27077 \long\def\colophon{\hbox to0pt{}\vfill
27078 \centerline{The body of this manual is set in}
27079 \centerline{\fontname\tenrm,}
27080 \centerline{with headings in {\bf\fontname\tenbf}}
27081 \centerline{and examples in {\tt\fontname\tentt}.}
27082 \centerline{{\it\fontname\tenit\/},}
27083 \centerline{{\bf\fontname\tenbf}, and}
27084 \centerline{{\sl\fontname\tensl\/}}
27085 \centerline{are used for emphasis.}\vfill}
27087 % Blame: doc@cygnus.com, 1991.