1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
66 this GNU Manual. Buying copies from GNU Press supports the FSF in
67 developing GNU and promoting software freedom.''
71 @title Debugging with @value{GDBN}
72 @subtitle The @sc{gnu} Source-Level Debugger
74 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
75 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
79 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
80 \hfill {\it Debugging with @value{GDBN}}\par
81 \hfill \TeX{}info \texinfoversion\par
85 @vskip 0pt plus 1filll
86 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
87 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
88 Free Software Foundation, Inc.
90 Published by the Free Software Foundation @*
91 51 Franklin Street, Fifth Floor,
92 Boston, MA 02110-1301, USA@*
95 Permission is granted to copy, distribute and/or modify this document
96 under the terms of the GNU Free Documentation License, Version 1.1 or
97 any later version published by the Free Software Foundation; with the
98 Invariant Sections being ``Free Software'' and ``Free Software Needs
99 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
100 and with the Back-Cover Texts as in (a) below.
102 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
103 this GNU Manual. Buying copies from GNU Press supports the FSF in
104 developing GNU and promoting software freedom.''
106 This edition of the GDB manual is dedicated to the memory of Fred
107 Fish. Fred was a long-standing contributor to GDB and to Free
108 software in general. We will miss him.
113 @node Top, Summary, (dir), (dir)
115 @top Debugging with @value{GDBN}
117 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
119 This is the @value{EDITION} Edition, for @value{GDBN} Version
122 Copyright (C) 1988-2006 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Stack:: Examining the stack
137 * Source:: Examining source files
138 * Data:: Examining data
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Sequences:: Canned sequences of commands
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
159 * GDB Bugs:: Reporting bugs in @value{GDBN}
161 * Command Line Editing:: Command Line Editing
162 * Using History Interactively:: Using History Interactively
163 * Formatting Documentation:: How to format and print @value{GDBN} documentation
164 * Installing GDB:: Installing GDB
165 * Maintenance Commands:: Maintenance Commands
166 * Remote Protocol:: GDB Remote Serial Protocol
167 * Agent Expressions:: The GDB Agent Expression Mechanism
168 * Target Descriptions:: How targets can describe themselves to
170 * Copying:: GNU General Public License says
171 how you can copy and share GDB
172 * GNU Free Documentation License:: The license for this documentation
181 @unnumbered Summary of @value{GDBN}
183 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
184 going on ``inside'' another program while it executes---or what another
185 program was doing at the moment it crashed.
187 @value{GDBN} can do four main kinds of things (plus other things in support of
188 these) to help you catch bugs in the act:
192 Start your program, specifying anything that might affect its behavior.
195 Make your program stop on specified conditions.
198 Examine what has happened, when your program has stopped.
201 Change things in your program, so you can experiment with correcting the
202 effects of one bug and go on to learn about another.
205 You can use @value{GDBN} to debug programs written in C and C@t{++}.
206 For more information, see @ref{Supported Languages,,Supported Languages}.
207 For more information, see @ref{C,,C and C++}.
210 Support for Modula-2 is partial. For information on Modula-2, see
211 @ref{Modula-2,,Modula-2}.
214 Debugging Pascal programs which use sets, subranges, file variables, or
215 nested functions does not currently work. @value{GDBN} does not support
216 entering expressions, printing values, or similar features using Pascal
220 @value{GDBN} can be used to debug programs written in Fortran, although
221 it may be necessary to refer to some variables with a trailing
224 @value{GDBN} can be used to debug programs written in Objective-C,
225 using either the Apple/NeXT or the GNU Objective-C runtime.
228 * Free Software:: Freely redistributable software
229 * Contributors:: Contributors to GDB
233 @unnumberedsec Free Software
235 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
236 General Public License
237 (GPL). The GPL gives you the freedom to copy or adapt a licensed
238 program---but every person getting a copy also gets with it the
239 freedom to modify that copy (which means that they must get access to
240 the source code), and the freedom to distribute further copies.
241 Typical software companies use copyrights to limit your freedoms; the
242 Free Software Foundation uses the GPL to preserve these freedoms.
244 Fundamentally, the General Public License is a license which says that
245 you have these freedoms and that you cannot take these freedoms away
248 @unnumberedsec Free Software Needs Free Documentation
250 The biggest deficiency in the free software community today is not in
251 the software---it is the lack of good free documentation that we can
252 include with the free software. Many of our most important
253 programs do not come with free reference manuals and free introductory
254 texts. Documentation is an essential part of any software package;
255 when an important free software package does not come with a free
256 manual and a free tutorial, that is a major gap. We have many such
259 Consider Perl, for instance. The tutorial manuals that people
260 normally use are non-free. How did this come about? Because the
261 authors of those manuals published them with restrictive terms---no
262 copying, no modification, source files not available---which exclude
263 them from the free software world.
265 That wasn't the first time this sort of thing happened, and it was far
266 from the last. Many times we have heard a GNU user eagerly describe a
267 manual that he is writing, his intended contribution to the community,
268 only to learn that he had ruined everything by signing a publication
269 contract to make it non-free.
271 Free documentation, like free software, is a matter of freedom, not
272 price. The problem with the non-free manual is not that publishers
273 charge a price for printed copies---that in itself is fine. (The Free
274 Software Foundation sells printed copies of manuals, too.) The
275 problem is the restrictions on the use of the manual. Free manuals
276 are available in source code form, and give you permission to copy and
277 modify. Non-free manuals do not allow this.
279 The criteria of freedom for a free manual are roughly the same as for
280 free software. Redistribution (including the normal kinds of
281 commercial redistribution) must be permitted, so that the manual can
282 accompany every copy of the program, both on-line and on paper.
284 Permission for modification of the technical content is crucial too.
285 When people modify the software, adding or changing features, if they
286 are conscientious they will change the manual too---so they can
287 provide accurate and clear documentation for the modified program. A
288 manual that leaves you no choice but to write a new manual to document
289 a changed version of the program is not really available to our
292 Some kinds of limits on the way modification is handled are
293 acceptable. For example, requirements to preserve the original
294 author's copyright notice, the distribution terms, or the list of
295 authors, are ok. It is also no problem to require modified versions
296 to include notice that they were modified. Even entire sections that
297 may not be deleted or changed are acceptable, as long as they deal
298 with nontechnical topics (like this one). These kinds of restrictions
299 are acceptable because they don't obstruct the community's normal use
302 However, it must be possible to modify all the @emph{technical}
303 content of the manual, and then distribute the result in all the usual
304 media, through all the usual channels. Otherwise, the restrictions
305 obstruct the use of the manual, it is not free, and we need another
306 manual to replace it.
308 Please spread the word about this issue. Our community continues to
309 lose manuals to proprietary publishing. If we spread the word that
310 free software needs free reference manuals and free tutorials, perhaps
311 the next person who wants to contribute by writing documentation will
312 realize, before it is too late, that only free manuals contribute to
313 the free software community.
315 If you are writing documentation, please insist on publishing it under
316 the GNU Free Documentation License or another free documentation
317 license. Remember that this decision requires your approval---you
318 don't have to let the publisher decide. Some commercial publishers
319 will use a free license if you insist, but they will not propose the
320 option; it is up to you to raise the issue and say firmly that this is
321 what you want. If the publisher you are dealing with refuses, please
322 try other publishers. If you're not sure whether a proposed license
323 is free, write to @email{licensing@@gnu.org}.
325 You can encourage commercial publishers to sell more free, copylefted
326 manuals and tutorials by buying them, and particularly by buying
327 copies from the publishers that paid for their writing or for major
328 improvements. Meanwhile, try to avoid buying non-free documentation
329 at all. Check the distribution terms of a manual before you buy it,
330 and insist that whoever seeks your business must respect your freedom.
331 Check the history of the book, and try to reward the publishers that
332 have paid or pay the authors to work on it.
334 The Free Software Foundation maintains a list of free documentation
335 published by other publishers, at
336 @url{http://www.fsf.org/doc/other-free-books.html}.
339 @unnumberedsec Contributors to @value{GDBN}
341 Richard Stallman was the original author of @value{GDBN}, and of many
342 other @sc{gnu} programs. Many others have contributed to its
343 development. This section attempts to credit major contributors. One
344 of the virtues of free software is that everyone is free to contribute
345 to it; with regret, we cannot actually acknowledge everyone here. The
346 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
347 blow-by-blow account.
349 Changes much prior to version 2.0 are lost in the mists of time.
352 @emph{Plea:} Additions to this section are particularly welcome. If you
353 or your friends (or enemies, to be evenhanded) have been unfairly
354 omitted from this list, we would like to add your names!
357 So that they may not regard their many labors as thankless, we
358 particularly thank those who shepherded @value{GDBN} through major
360 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
361 Jim Blandy (release 4.18);
362 Jason Molenda (release 4.17);
363 Stan Shebs (release 4.14);
364 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
365 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
366 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
367 Jim Kingdon (releases 3.5, 3.4, and 3.3);
368 and Randy Smith (releases 3.2, 3.1, and 3.0).
370 Richard Stallman, assisted at various times by Peter TerMaat, Chris
371 Hanson, and Richard Mlynarik, handled releases through 2.8.
373 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
374 in @value{GDBN}, with significant additional contributions from Per
375 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
376 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
377 much general update work leading to release 3.0).
379 @value{GDBN} uses the BFD subroutine library to examine multiple
380 object-file formats; BFD was a joint project of David V.
381 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
383 David Johnson wrote the original COFF support; Pace Willison did
384 the original support for encapsulated COFF.
386 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
388 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
389 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
391 Jean-Daniel Fekete contributed Sun 386i support.
392 Chris Hanson improved the HP9000 support.
393 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
394 David Johnson contributed Encore Umax support.
395 Jyrki Kuoppala contributed Altos 3068 support.
396 Jeff Law contributed HP PA and SOM support.
397 Keith Packard contributed NS32K support.
398 Doug Rabson contributed Acorn Risc Machine support.
399 Bob Rusk contributed Harris Nighthawk CX-UX support.
400 Chris Smith contributed Convex support (and Fortran debugging).
401 Jonathan Stone contributed Pyramid support.
402 Michael Tiemann contributed SPARC support.
403 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
404 Pace Willison contributed Intel 386 support.
405 Jay Vosburgh contributed Symmetry support.
406 Marko Mlinar contributed OpenRISC 1000 support.
408 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
410 Rich Schaefer and Peter Schauer helped with support of SunOS shared
413 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
414 about several machine instruction sets.
416 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
417 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
418 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
419 and RDI targets, respectively.
421 Brian Fox is the author of the readline libraries providing
422 command-line editing and command history.
424 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
425 Modula-2 support, and contributed the Languages chapter of this manual.
427 Fred Fish wrote most of the support for Unix System Vr4.
428 He also enhanced the command-completion support to cover C@t{++} overloaded
431 Hitachi America (now Renesas America), Ltd. sponsored the support for
432 H8/300, H8/500, and Super-H processors.
434 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
436 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
439 Toshiba sponsored the support for the TX39 Mips processor.
441 Matsushita sponsored the support for the MN10200 and MN10300 processors.
443 Fujitsu sponsored the support for SPARClite and FR30 processors.
445 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
448 Michael Snyder added support for tracepoints.
450 Stu Grossman wrote gdbserver.
452 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
453 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
455 The following people at the Hewlett-Packard Company contributed
456 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
457 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
458 compiler, and the Text User Interface (nee Terminal User Interface):
459 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
460 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
461 provided HP-specific information in this manual.
463 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
464 Robert Hoehne made significant contributions to the DJGPP port.
466 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
467 development since 1991. Cygnus engineers who have worked on @value{GDBN}
468 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
469 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
470 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
471 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
472 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
473 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
474 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
475 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
476 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
477 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
478 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
479 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
480 Zuhn have made contributions both large and small.
482 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
483 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
485 Jim Blandy added support for preprocessor macros, while working for Red
488 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
489 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
490 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
491 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
492 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
493 with the migration of old architectures to this new framework.
495 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
496 unwinder framework, this consisting of a fresh new design featuring
497 frame IDs, independent frame sniffers, and the sentinel frame. Mark
498 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
499 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
500 trad unwinders. The architecture-specific changes, each involving a
501 complete rewrite of the architecture's frame code, were carried out by
502 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
503 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
504 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
505 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
508 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
509 Tensilica, Inc.@: contributed support for Xtensa processors. Others
510 who have worked on the Xtensa port of @value{GDBN} in the past include
511 Steve Tjiang, John Newlin, and Scott Foehner.
514 @chapter A Sample @value{GDBN} Session
516 You can use this manual at your leisure to read all about @value{GDBN}.
517 However, a handful of commands are enough to get started using the
518 debugger. This chapter illustrates those commands.
521 In this sample session, we emphasize user input like this: @b{input},
522 to make it easier to pick out from the surrounding output.
525 @c FIXME: this example may not be appropriate for some configs, where
526 @c FIXME...primary interest is in remote use.
528 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
529 processor) exhibits the following bug: sometimes, when we change its
530 quote strings from the default, the commands used to capture one macro
531 definition within another stop working. In the following short @code{m4}
532 session, we define a macro @code{foo} which expands to @code{0000}; we
533 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
534 same thing. However, when we change the open quote string to
535 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
536 procedure fails to define a new synonym @code{baz}:
545 @b{define(bar,defn(`foo'))}
549 @b{changequote(<QUOTE>,<UNQUOTE>)}
551 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
554 m4: End of input: 0: fatal error: EOF in string
558 Let us use @value{GDBN} to try to see what is going on.
561 $ @b{@value{GDBP} m4}
562 @c FIXME: this falsifies the exact text played out, to permit smallbook
563 @c FIXME... format to come out better.
564 @value{GDBN} is free software and you are welcome to distribute copies
565 of it under certain conditions; type "show copying" to see
567 There is absolutely no warranty for @value{GDBN}; type "show warranty"
570 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
575 @value{GDBN} reads only enough symbol data to know where to find the
576 rest when needed; as a result, the first prompt comes up very quickly.
577 We now tell @value{GDBN} to use a narrower display width than usual, so
578 that examples fit in this manual.
581 (@value{GDBP}) @b{set width 70}
585 We need to see how the @code{m4} built-in @code{changequote} works.
586 Having looked at the source, we know the relevant subroutine is
587 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
588 @code{break} command.
591 (@value{GDBP}) @b{break m4_changequote}
592 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
596 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
597 control; as long as control does not reach the @code{m4_changequote}
598 subroutine, the program runs as usual:
601 (@value{GDBP}) @b{run}
602 Starting program: /work/Editorial/gdb/gnu/m4/m4
610 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
611 suspends execution of @code{m4}, displaying information about the
612 context where it stops.
615 @b{changequote(<QUOTE>,<UNQUOTE>)}
617 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
619 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
623 Now we use the command @code{n} (@code{next}) to advance execution to
624 the next line of the current function.
628 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
633 @code{set_quotes} looks like a promising subroutine. We can go into it
634 by using the command @code{s} (@code{step}) instead of @code{next}.
635 @code{step} goes to the next line to be executed in @emph{any}
636 subroutine, so it steps into @code{set_quotes}.
640 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
642 530 if (lquote != def_lquote)
646 The display that shows the subroutine where @code{m4} is now
647 suspended (and its arguments) is called a stack frame display. It
648 shows a summary of the stack. We can use the @code{backtrace}
649 command (which can also be spelled @code{bt}), to see where we are
650 in the stack as a whole: the @code{backtrace} command displays a
651 stack frame for each active subroutine.
654 (@value{GDBP}) @b{bt}
655 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
657 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
659 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
660 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
662 #4 0x79dc in expand_input () at macro.c:40
663 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
667 We step through a few more lines to see what happens. The first two
668 times, we can use @samp{s}; the next two times we use @code{n} to avoid
669 falling into the @code{xstrdup} subroutine.
673 0x3b5c 532 if (rquote != def_rquote)
675 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
676 def_lquote : xstrdup(lq);
678 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
681 538 len_lquote = strlen(rquote);
685 The last line displayed looks a little odd; we can examine the variables
686 @code{lquote} and @code{rquote} to see if they are in fact the new left
687 and right quotes we specified. We use the command @code{p}
688 (@code{print}) to see their values.
691 (@value{GDBP}) @b{p lquote}
692 $1 = 0x35d40 "<QUOTE>"
693 (@value{GDBP}) @b{p rquote}
694 $2 = 0x35d50 "<UNQUOTE>"
698 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
699 To look at some context, we can display ten lines of source
700 surrounding the current line with the @code{l} (@code{list}) command.
706 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
708 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
711 538 len_lquote = strlen(rquote);
712 539 len_rquote = strlen(lquote);
719 Let us step past the two lines that set @code{len_lquote} and
720 @code{len_rquote}, and then examine the values of those variables.
724 539 len_rquote = strlen(lquote);
727 (@value{GDBP}) @b{p len_lquote}
729 (@value{GDBP}) @b{p len_rquote}
734 That certainly looks wrong, assuming @code{len_lquote} and
735 @code{len_rquote} are meant to be the lengths of @code{lquote} and
736 @code{rquote} respectively. We can set them to better values using
737 the @code{p} command, since it can print the value of
738 any expression---and that expression can include subroutine calls and
742 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
744 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
749 Is that enough to fix the problem of using the new quotes with the
750 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
751 executing with the @code{c} (@code{continue}) command, and then try the
752 example that caused trouble initially:
758 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
765 Success! The new quotes now work just as well as the default ones. The
766 problem seems to have been just the two typos defining the wrong
767 lengths. We allow @code{m4} exit by giving it an EOF as input:
771 Program exited normally.
775 The message @samp{Program exited normally.} is from @value{GDBN}; it
776 indicates @code{m4} has finished executing. We can end our @value{GDBN}
777 session with the @value{GDBN} @code{quit} command.
780 (@value{GDBP}) @b{quit}
784 @chapter Getting In and Out of @value{GDBN}
786 This chapter discusses how to start @value{GDBN}, and how to get out of it.
790 type @samp{@value{GDBP}} to start @value{GDBN}.
792 type @kbd{quit} or @kbd{Ctrl-d} to exit.
796 * Invoking GDB:: How to start @value{GDBN}
797 * Quitting GDB:: How to quit @value{GDBN}
798 * Shell Commands:: How to use shell commands inside @value{GDBN}
799 * Logging Output:: How to log @value{GDBN}'s output to a file
803 @section Invoking @value{GDBN}
805 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
806 @value{GDBN} reads commands from the terminal until you tell it to exit.
808 You can also run @code{@value{GDBP}} with a variety of arguments and options,
809 to specify more of your debugging environment at the outset.
811 The command-line options described here are designed
812 to cover a variety of situations; in some environments, some of these
813 options may effectively be unavailable.
815 The most usual way to start @value{GDBN} is with one argument,
816 specifying an executable program:
819 @value{GDBP} @var{program}
823 You can also start with both an executable program and a core file
827 @value{GDBP} @var{program} @var{core}
830 You can, instead, specify a process ID as a second argument, if you want
831 to debug a running process:
834 @value{GDBP} @var{program} 1234
838 would attach @value{GDBN} to process @code{1234} (unless you also have a file
839 named @file{1234}; @value{GDBN} does check for a core file first).
841 Taking advantage of the second command-line argument requires a fairly
842 complete operating system; when you use @value{GDBN} as a remote
843 debugger attached to a bare board, there may not be any notion of
844 ``process'', and there is often no way to get a core dump. @value{GDBN}
845 will warn you if it is unable to attach or to read core dumps.
847 You can optionally have @code{@value{GDBP}} pass any arguments after the
848 executable file to the inferior using @code{--args}. This option stops
851 @value{GDBP} --args gcc -O2 -c foo.c
853 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
854 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
856 You can run @code{@value{GDBP}} without printing the front material, which describes
857 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
864 You can further control how @value{GDBN} starts up by using command-line
865 options. @value{GDBN} itself can remind you of the options available.
875 to display all available options and briefly describe their use
876 (@samp{@value{GDBP} -h} is a shorter equivalent).
878 All options and command line arguments you give are processed
879 in sequential order. The order makes a difference when the
880 @samp{-x} option is used.
884 * File Options:: Choosing files
885 * Mode Options:: Choosing modes
886 * Startup:: What @value{GDBN} does during startup
890 @subsection Choosing Files
892 When @value{GDBN} starts, it reads any arguments other than options as
893 specifying an executable file and core file (or process ID). This is
894 the same as if the arguments were specified by the @samp{-se} and
895 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
896 first argument that does not have an associated option flag as
897 equivalent to the @samp{-se} option followed by that argument; and the
898 second argument that does not have an associated option flag, if any, as
899 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
900 If the second argument begins with a decimal digit, @value{GDBN} will
901 first attempt to attach to it as a process, and if that fails, attempt
902 to open it as a corefile. If you have a corefile whose name begins with
903 a digit, you can prevent @value{GDBN} from treating it as a pid by
904 prefixing it with @file{./}, e.g.@: @file{./12345}.
906 If @value{GDBN} has not been configured to included core file support,
907 such as for most embedded targets, then it will complain about a second
908 argument and ignore it.
910 Many options have both long and short forms; both are shown in the
911 following list. @value{GDBN} also recognizes the long forms if you truncate
912 them, so long as enough of the option is present to be unambiguous.
913 (If you prefer, you can flag option arguments with @samp{--} rather
914 than @samp{-}, though we illustrate the more usual convention.)
916 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
917 @c way, both those who look for -foo and --foo in the index, will find
921 @item -symbols @var{file}
923 @cindex @code{--symbols}
925 Read symbol table from file @var{file}.
927 @item -exec @var{file}
929 @cindex @code{--exec}
931 Use file @var{file} as the executable file to execute when appropriate,
932 and for examining pure data in conjunction with a core dump.
936 Read symbol table from file @var{file} and use it as the executable
939 @item -core @var{file}
941 @cindex @code{--core}
943 Use file @var{file} as a core dump to examine.
945 @item -pid @var{number}
946 @itemx -p @var{number}
949 Connect to process ID @var{number}, as with the @code{attach} command.
951 @item -command @var{file}
953 @cindex @code{--command}
955 Execute @value{GDBN} commands from file @var{file}. @xref{Command
956 Files,, Command files}.
958 @item -eval-command @var{command}
959 @itemx -ex @var{command}
960 @cindex @code{--eval-command}
962 Execute a single @value{GDBN} command.
964 This option may be used multiple times to call multiple commands. It may
965 also be interleaved with @samp{-command} as required.
968 @value{GDBP} -ex 'target sim' -ex 'load' \
969 -x setbreakpoints -ex 'run' a.out
972 @item -directory @var{directory}
973 @itemx -d @var{directory}
974 @cindex @code{--directory}
976 Add @var{directory} to the path to search for source and script files.
980 @cindex @code{--readnow}
982 Read each symbol file's entire symbol table immediately, rather than
983 the default, which is to read it incrementally as it is needed.
984 This makes startup slower, but makes future operations faster.
989 @subsection Choosing Modes
991 You can run @value{GDBN} in various alternative modes---for example, in
992 batch mode or quiet mode.
999 Do not execute commands found in any initialization files. Normally,
1000 @value{GDBN} executes the commands in these files after all the command
1001 options and arguments have been processed. @xref{Command Files,,Command
1007 @cindex @code{--quiet}
1008 @cindex @code{--silent}
1010 ``Quiet''. Do not print the introductory and copyright messages. These
1011 messages are also suppressed in batch mode.
1014 @cindex @code{--batch}
1015 Run in batch mode. Exit with status @code{0} after processing all the
1016 command files specified with @samp{-x} (and all commands from
1017 initialization files, if not inhibited with @samp{-n}). Exit with
1018 nonzero status if an error occurs in executing the @value{GDBN} commands
1019 in the command files.
1021 Batch mode may be useful for running @value{GDBN} as a filter, for
1022 example to download and run a program on another computer; in order to
1023 make this more useful, the message
1026 Program exited normally.
1030 (which is ordinarily issued whenever a program running under
1031 @value{GDBN} control terminates) is not issued when running in batch
1035 @cindex @code{--batch-silent}
1036 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1037 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1038 unaffected). This is much quieter than @samp{-silent} and would be useless
1039 for an interactive session.
1041 This is particularly useful when using targets that give @samp{Loading section}
1042 messages, for example.
1044 Note that targets that give their output via @value{GDBN}, as opposed to
1045 writing directly to @code{stdout}, will also be made silent.
1047 @item -return-child-result
1048 @cindex @code{--return-child-result}
1049 The return code from @value{GDBN} will be the return code from the child
1050 process (the process being debugged), with the following exceptions:
1054 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1055 internal error. In this case the exit code is the same as it would have been
1056 without @samp{-return-child-result}.
1058 The user quits with an explicit value. E.g., @samp{quit 1}.
1060 The child process never runs, or is not allowed to terminate, in which case
1061 the exit code will be -1.
1064 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1065 when @value{GDBN} is being used as a remote program loader or simulator
1070 @cindex @code{--nowindows}
1072 ``No windows''. If @value{GDBN} comes with a graphical user interface
1073 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1074 interface. If no GUI is available, this option has no effect.
1078 @cindex @code{--windows}
1080 If @value{GDBN} includes a GUI, then this option requires it to be
1083 @item -cd @var{directory}
1085 Run @value{GDBN} using @var{directory} as its working directory,
1086 instead of the current directory.
1090 @cindex @code{--fullname}
1092 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1093 subprocess. It tells @value{GDBN} to output the full file name and line
1094 number in a standard, recognizable fashion each time a stack frame is
1095 displayed (which includes each time your program stops). This
1096 recognizable format looks like two @samp{\032} characters, followed by
1097 the file name, line number and character position separated by colons,
1098 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1099 @samp{\032} characters as a signal to display the source code for the
1103 @cindex @code{--epoch}
1104 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1105 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1106 routines so as to allow Epoch to display values of expressions in a
1109 @item -annotate @var{level}
1110 @cindex @code{--annotate}
1111 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1112 effect is identical to using @samp{set annotate @var{level}}
1113 (@pxref{Annotations}). The annotation @var{level} controls how much
1114 information @value{GDBN} prints together with its prompt, values of
1115 expressions, source lines, and other types of output. Level 0 is the
1116 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1117 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1118 that control @value{GDBN}, and level 2 has been deprecated.
1120 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1124 @cindex @code{--args}
1125 Change interpretation of command line so that arguments following the
1126 executable file are passed as command line arguments to the inferior.
1127 This option stops option processing.
1129 @item -baud @var{bps}
1131 @cindex @code{--baud}
1133 Set the line speed (baud rate or bits per second) of any serial
1134 interface used by @value{GDBN} for remote debugging.
1136 @item -l @var{timeout}
1138 Set the timeout (in seconds) of any communication used by @value{GDBN}
1139 for remote debugging.
1141 @item -tty @var{device}
1142 @itemx -t @var{device}
1143 @cindex @code{--tty}
1145 Run using @var{device} for your program's standard input and output.
1146 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1148 @c resolve the situation of these eventually
1150 @cindex @code{--tui}
1151 Activate the @dfn{Text User Interface} when starting. The Text User
1152 Interface manages several text windows on the terminal, showing
1153 source, assembly, registers and @value{GDBN} command outputs
1154 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1155 Text User Interface can be enabled by invoking the program
1156 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1157 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1160 @c @cindex @code{--xdb}
1161 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1162 @c For information, see the file @file{xdb_trans.html}, which is usually
1163 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1166 @item -interpreter @var{interp}
1167 @cindex @code{--interpreter}
1168 Use the interpreter @var{interp} for interface with the controlling
1169 program or device. This option is meant to be set by programs which
1170 communicate with @value{GDBN} using it as a back end.
1171 @xref{Interpreters, , Command Interpreters}.
1173 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1174 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1175 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1176 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1177 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1178 @sc{gdb/mi} interfaces are no longer supported.
1181 @cindex @code{--write}
1182 Open the executable and core files for both reading and writing. This
1183 is equivalent to the @samp{set write on} command inside @value{GDBN}
1187 @cindex @code{--statistics}
1188 This option causes @value{GDBN} to print statistics about time and
1189 memory usage after it completes each command and returns to the prompt.
1192 @cindex @code{--version}
1193 This option causes @value{GDBN} to print its version number and
1194 no-warranty blurb, and exit.
1199 @subsection What @value{GDBN} Does During Startup
1200 @cindex @value{GDBN} startup
1202 Here's the description of what @value{GDBN} does during session startup:
1206 Sets up the command interpreter as specified by the command line
1207 (@pxref{Mode Options, interpreter}).
1211 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1212 DOS/Windows systems, the home directory is the one pointed to by the
1213 @code{HOME} environment variable.} and executes all the commands in
1217 Processes command line options and operands.
1220 Reads and executes the commands from init file (if any) in the current
1221 working directory. This is only done if the current directory is
1222 different from your home directory. Thus, you can have more than one
1223 init file, one generic in your home directory, and another, specific
1224 to the program you are debugging, in the directory where you invoke
1228 Reads command files specified by the @samp{-x} option. @xref{Command
1229 Files}, for more details about @value{GDBN} command files.
1232 Reads the command history recorded in the @dfn{history file}.
1233 @xref{Command History}, for more details about the command history and the
1234 files where @value{GDBN} records it.
1237 Init files use the same syntax as @dfn{command files} (@pxref{Command
1238 Files}) and are processed by @value{GDBN} in the same way. The init
1239 file in your home directory can set options (such as @samp{set
1240 complaints}) that affect subsequent processing of command line options
1241 and operands. Init files are not executed if you use the @samp{-nx}
1242 option (@pxref{Mode Options, ,Choosing Modes}).
1244 @cindex init file name
1245 @cindex @file{.gdbinit}
1246 @cindex @file{gdb.ini}
1247 The @value{GDBN} init files are normally called @file{.gdbinit}.
1248 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1249 the limitations of file names imposed by DOS filesystems. The Windows
1250 ports of @value{GDBN} use the standard name, but if they find a
1251 @file{gdb.ini} file, they warn you about that and suggest to rename
1252 the file to the standard name.
1256 @section Quitting @value{GDBN}
1257 @cindex exiting @value{GDBN}
1258 @cindex leaving @value{GDBN}
1261 @kindex quit @r{[}@var{expression}@r{]}
1262 @kindex q @r{(@code{quit})}
1263 @item quit @r{[}@var{expression}@r{]}
1265 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1266 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1267 do not supply @var{expression}, @value{GDBN} will terminate normally;
1268 otherwise it will terminate using the result of @var{expression} as the
1273 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1274 terminates the action of any @value{GDBN} command that is in progress and
1275 returns to @value{GDBN} command level. It is safe to type the interrupt
1276 character at any time because @value{GDBN} does not allow it to take effect
1277 until a time when it is safe.
1279 If you have been using @value{GDBN} to control an attached process or
1280 device, you can release it with the @code{detach} command
1281 (@pxref{Attach, ,Debugging an Already-running Process}).
1283 @node Shell Commands
1284 @section Shell Commands
1286 If you need to execute occasional shell commands during your
1287 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1288 just use the @code{shell} command.
1292 @cindex shell escape
1293 @item shell @var{command string}
1294 Invoke a standard shell to execute @var{command string}.
1295 If it exists, the environment variable @code{SHELL} determines which
1296 shell to run. Otherwise @value{GDBN} uses the default shell
1297 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1300 The utility @code{make} is often needed in development environments.
1301 You do not have to use the @code{shell} command for this purpose in
1306 @cindex calling make
1307 @item make @var{make-args}
1308 Execute the @code{make} program with the specified
1309 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1312 @node Logging Output
1313 @section Logging Output
1314 @cindex logging @value{GDBN} output
1315 @cindex save @value{GDBN} output to a file
1317 You may want to save the output of @value{GDBN} commands to a file.
1318 There are several commands to control @value{GDBN}'s logging.
1322 @item set logging on
1324 @item set logging off
1326 @cindex logging file name
1327 @item set logging file @var{file}
1328 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1329 @item set logging overwrite [on|off]
1330 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1331 you want @code{set logging on} to overwrite the logfile instead.
1332 @item set logging redirect [on|off]
1333 By default, @value{GDBN} output will go to both the terminal and the logfile.
1334 Set @code{redirect} if you want output to go only to the log file.
1335 @kindex show logging
1337 Show the current values of the logging settings.
1341 @chapter @value{GDBN} Commands
1343 You can abbreviate a @value{GDBN} command to the first few letters of the command
1344 name, if that abbreviation is unambiguous; and you can repeat certain
1345 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1346 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1347 show you the alternatives available, if there is more than one possibility).
1350 * Command Syntax:: How to give commands to @value{GDBN}
1351 * Completion:: Command completion
1352 * Help:: How to ask @value{GDBN} for help
1355 @node Command Syntax
1356 @section Command Syntax
1358 A @value{GDBN} command is a single line of input. There is no limit on
1359 how long it can be. It starts with a command name, which is followed by
1360 arguments whose meaning depends on the command name. For example, the
1361 command @code{step} accepts an argument which is the number of times to
1362 step, as in @samp{step 5}. You can also use the @code{step} command
1363 with no arguments. Some commands do not allow any arguments.
1365 @cindex abbreviation
1366 @value{GDBN} command names may always be truncated if that abbreviation is
1367 unambiguous. Other possible command abbreviations are listed in the
1368 documentation for individual commands. In some cases, even ambiguous
1369 abbreviations are allowed; for example, @code{s} is specially defined as
1370 equivalent to @code{step} even though there are other commands whose
1371 names start with @code{s}. You can test abbreviations by using them as
1372 arguments to the @code{help} command.
1374 @cindex repeating commands
1375 @kindex RET @r{(repeat last command)}
1376 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1377 repeat the previous command. Certain commands (for example, @code{run})
1378 will not repeat this way; these are commands whose unintentional
1379 repetition might cause trouble and which you are unlikely to want to
1380 repeat. User-defined commands can disable this feature; see
1381 @ref{Define, dont-repeat}.
1383 The @code{list} and @code{x} commands, when you repeat them with
1384 @key{RET}, construct new arguments rather than repeating
1385 exactly as typed. This permits easy scanning of source or memory.
1387 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1388 output, in a way similar to the common utility @code{more}
1389 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1390 @key{RET} too many in this situation, @value{GDBN} disables command
1391 repetition after any command that generates this sort of display.
1393 @kindex # @r{(a comment)}
1395 Any text from a @kbd{#} to the end of the line is a comment; it does
1396 nothing. This is useful mainly in command files (@pxref{Command
1397 Files,,Command Files}).
1399 @cindex repeating command sequences
1400 @kindex Ctrl-o @r{(operate-and-get-next)}
1401 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1402 commands. This command accepts the current line, like @key{RET}, and
1403 then fetches the next line relative to the current line from the history
1407 @section Command Completion
1410 @cindex word completion
1411 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1412 only one possibility; it can also show you what the valid possibilities
1413 are for the next word in a command, at any time. This works for @value{GDBN}
1414 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1416 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1417 of a word. If there is only one possibility, @value{GDBN} fills in the
1418 word, and waits for you to finish the command (or press @key{RET} to
1419 enter it). For example, if you type
1421 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1422 @c complete accuracy in these examples; space introduced for clarity.
1423 @c If texinfo enhancements make it unnecessary, it would be nice to
1424 @c replace " @key" by "@key" in the following...
1426 (@value{GDBP}) info bre @key{TAB}
1430 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1431 the only @code{info} subcommand beginning with @samp{bre}:
1434 (@value{GDBP}) info breakpoints
1438 You can either press @key{RET} at this point, to run the @code{info
1439 breakpoints} command, or backspace and enter something else, if
1440 @samp{breakpoints} does not look like the command you expected. (If you
1441 were sure you wanted @code{info breakpoints} in the first place, you
1442 might as well just type @key{RET} immediately after @samp{info bre},
1443 to exploit command abbreviations rather than command completion).
1445 If there is more than one possibility for the next word when you press
1446 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1447 characters and try again, or just press @key{TAB} a second time;
1448 @value{GDBN} displays all the possible completions for that word. For
1449 example, you might want to set a breakpoint on a subroutine whose name
1450 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1451 just sounds the bell. Typing @key{TAB} again displays all the
1452 function names in your program that begin with those characters, for
1456 (@value{GDBP}) b make_ @key{TAB}
1457 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1458 make_a_section_from_file make_environ
1459 make_abs_section make_function_type
1460 make_blockvector make_pointer_type
1461 make_cleanup make_reference_type
1462 make_command make_symbol_completion_list
1463 (@value{GDBP}) b make_
1467 After displaying the available possibilities, @value{GDBN} copies your
1468 partial input (@samp{b make_} in the example) so you can finish the
1471 If you just want to see the list of alternatives in the first place, you
1472 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1473 means @kbd{@key{META} ?}. You can type this either by holding down a
1474 key designated as the @key{META} shift on your keyboard (if there is
1475 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1477 @cindex quotes in commands
1478 @cindex completion of quoted strings
1479 Sometimes the string you need, while logically a ``word'', may contain
1480 parentheses or other characters that @value{GDBN} normally excludes from
1481 its notion of a word. To permit word completion to work in this
1482 situation, you may enclose words in @code{'} (single quote marks) in
1483 @value{GDBN} commands.
1485 The most likely situation where you might need this is in typing the
1486 name of a C@t{++} function. This is because C@t{++} allows function
1487 overloading (multiple definitions of the same function, distinguished
1488 by argument type). For example, when you want to set a breakpoint you
1489 may need to distinguish whether you mean the version of @code{name}
1490 that takes an @code{int} parameter, @code{name(int)}, or the version
1491 that takes a @code{float} parameter, @code{name(float)}. To use the
1492 word-completion facilities in this situation, type a single quote
1493 @code{'} at the beginning of the function name. This alerts
1494 @value{GDBN} that it may need to consider more information than usual
1495 when you press @key{TAB} or @kbd{M-?} to request word completion:
1498 (@value{GDBP}) b 'bubble( @kbd{M-?}
1499 bubble(double,double) bubble(int,int)
1500 (@value{GDBP}) b 'bubble(
1503 In some cases, @value{GDBN} can tell that completing a name requires using
1504 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1505 completing as much as it can) if you do not type the quote in the first
1509 (@value{GDBP}) b bub @key{TAB}
1510 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1511 (@value{GDBP}) b 'bubble(
1515 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1516 you have not yet started typing the argument list when you ask for
1517 completion on an overloaded symbol.
1519 For more information about overloaded functions, see @ref{C Plus Plus
1520 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1521 overload-resolution off} to disable overload resolution;
1522 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1526 @section Getting Help
1527 @cindex online documentation
1530 You can always ask @value{GDBN} itself for information on its commands,
1531 using the command @code{help}.
1534 @kindex h @r{(@code{help})}
1537 You can use @code{help} (abbreviated @code{h}) with no arguments to
1538 display a short list of named classes of commands:
1542 List of classes of commands:
1544 aliases -- Aliases of other commands
1545 breakpoints -- Making program stop at certain points
1546 data -- Examining data
1547 files -- Specifying and examining files
1548 internals -- Maintenance commands
1549 obscure -- Obscure features
1550 running -- Running the program
1551 stack -- Examining the stack
1552 status -- Status inquiries
1553 support -- Support facilities
1554 tracepoints -- Tracing of program execution without
1555 stopping the program
1556 user-defined -- User-defined commands
1558 Type "help" followed by a class name for a list of
1559 commands in that class.
1560 Type "help" followed by command name for full
1562 Command name abbreviations are allowed if unambiguous.
1565 @c the above line break eliminates huge line overfull...
1567 @item help @var{class}
1568 Using one of the general help classes as an argument, you can get a
1569 list of the individual commands in that class. For example, here is the
1570 help display for the class @code{status}:
1573 (@value{GDBP}) help status
1578 @c Line break in "show" line falsifies real output, but needed
1579 @c to fit in smallbook page size.
1580 info -- Generic command for showing things
1581 about the program being debugged
1582 show -- Generic command for showing things
1585 Type "help" followed by command name for full
1587 Command name abbreviations are allowed if unambiguous.
1591 @item help @var{command}
1592 With a command name as @code{help} argument, @value{GDBN} displays a
1593 short paragraph on how to use that command.
1596 @item apropos @var{args}
1597 The @code{apropos} command searches through all of the @value{GDBN}
1598 commands, and their documentation, for the regular expression specified in
1599 @var{args}. It prints out all matches found. For example:
1610 set symbol-reloading -- Set dynamic symbol table reloading
1611 multiple times in one run
1612 show symbol-reloading -- Show dynamic symbol table reloading
1613 multiple times in one run
1618 @item complete @var{args}
1619 The @code{complete @var{args}} command lists all the possible completions
1620 for the beginning of a command. Use @var{args} to specify the beginning of the
1621 command you want completed. For example:
1627 @noindent results in:
1638 @noindent This is intended for use by @sc{gnu} Emacs.
1641 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1642 and @code{show} to inquire about the state of your program, or the state
1643 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1644 manual introduces each of them in the appropriate context. The listings
1645 under @code{info} and under @code{show} in the Index point to
1646 all the sub-commands. @xref{Index}.
1651 @kindex i @r{(@code{info})}
1653 This command (abbreviated @code{i}) is for describing the state of your
1654 program. For example, you can list the arguments given to your program
1655 with @code{info args}, list the registers currently in use with @code{info
1656 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1657 You can get a complete list of the @code{info} sub-commands with
1658 @w{@code{help info}}.
1662 You can assign the result of an expression to an environment variable with
1663 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1664 @code{set prompt $}.
1668 In contrast to @code{info}, @code{show} is for describing the state of
1669 @value{GDBN} itself.
1670 You can change most of the things you can @code{show}, by using the
1671 related command @code{set}; for example, you can control what number
1672 system is used for displays with @code{set radix}, or simply inquire
1673 which is currently in use with @code{show radix}.
1676 To display all the settable parameters and their current
1677 values, you can use @code{show} with no arguments; you may also use
1678 @code{info set}. Both commands produce the same display.
1679 @c FIXME: "info set" violates the rule that "info" is for state of
1680 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1681 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1685 Here are three miscellaneous @code{show} subcommands, all of which are
1686 exceptional in lacking corresponding @code{set} commands:
1689 @kindex show version
1690 @cindex @value{GDBN} version number
1692 Show what version of @value{GDBN} is running. You should include this
1693 information in @value{GDBN} bug-reports. If multiple versions of
1694 @value{GDBN} are in use at your site, you may need to determine which
1695 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1696 commands are introduced, and old ones may wither away. Also, many
1697 system vendors ship variant versions of @value{GDBN}, and there are
1698 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1699 The version number is the same as the one announced when you start
1702 @kindex show copying
1703 @kindex info copying
1704 @cindex display @value{GDBN} copyright
1707 Display information about permission for copying @value{GDBN}.
1709 @kindex show warranty
1710 @kindex info warranty
1712 @itemx info warranty
1713 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1714 if your version of @value{GDBN} comes with one.
1719 @chapter Running Programs Under @value{GDBN}
1721 When you run a program under @value{GDBN}, you must first generate
1722 debugging information when you compile it.
1724 You may start @value{GDBN} with its arguments, if any, in an environment
1725 of your choice. If you are doing native debugging, you may redirect
1726 your program's input and output, debug an already running process, or
1727 kill a child process.
1730 * Compilation:: Compiling for debugging
1731 * Starting:: Starting your program
1732 * Arguments:: Your program's arguments
1733 * Environment:: Your program's environment
1735 * Working Directory:: Your program's working directory
1736 * Input/Output:: Your program's input and output
1737 * Attach:: Debugging an already-running process
1738 * Kill Process:: Killing the child process
1740 * Threads:: Debugging programs with multiple threads
1741 * Processes:: Debugging programs with multiple processes
1742 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1746 @section Compiling for Debugging
1748 In order to debug a program effectively, you need to generate
1749 debugging information when you compile it. This debugging information
1750 is stored in the object file; it describes the data type of each
1751 variable or function and the correspondence between source line numbers
1752 and addresses in the executable code.
1754 To request debugging information, specify the @samp{-g} option when you run
1757 Programs that are to be shipped to your customers are compiled with
1758 optimizations, using the @samp{-O} compiler option. However, many
1759 compilers are unable to handle the @samp{-g} and @samp{-O} options
1760 together. Using those compilers, you cannot generate optimized
1761 executables containing debugging information.
1763 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1764 without @samp{-O}, making it possible to debug optimized code. We
1765 recommend that you @emph{always} use @samp{-g} whenever you compile a
1766 program. You may think your program is correct, but there is no sense
1767 in pushing your luck.
1769 @cindex optimized code, debugging
1770 @cindex debugging optimized code
1771 When you debug a program compiled with @samp{-g -O}, remember that the
1772 optimizer is rearranging your code; the debugger shows you what is
1773 really there. Do not be too surprised when the execution path does not
1774 exactly match your source file! An extreme example: if you define a
1775 variable, but never use it, @value{GDBN} never sees that
1776 variable---because the compiler optimizes it out of existence.
1778 Some things do not work as well with @samp{-g -O} as with just
1779 @samp{-g}, particularly on machines with instruction scheduling. If in
1780 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1781 please report it to us as a bug (including a test case!).
1782 @xref{Variables}, for more information about debugging optimized code.
1784 Older versions of the @sc{gnu} C compiler permitted a variant option
1785 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1786 format; if your @sc{gnu} C compiler has this option, do not use it.
1788 @value{GDBN} knows about preprocessor macros and can show you their
1789 expansion (@pxref{Macros}). Most compilers do not include information
1790 about preprocessor macros in the debugging information if you specify
1791 the @option{-g} flag alone, because this information is rather large.
1792 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1793 provides macro information if you specify the options
1794 @option{-gdwarf-2} and @option{-g3}; the former option requests
1795 debugging information in the Dwarf 2 format, and the latter requests
1796 ``extra information''. In the future, we hope to find more compact
1797 ways to represent macro information, so that it can be included with
1802 @section Starting your Program
1808 @kindex r @r{(@code{run})}
1811 Use the @code{run} command to start your program under @value{GDBN}.
1812 You must first specify the program name (except on VxWorks) with an
1813 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1814 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1815 (@pxref{Files, ,Commands to Specify Files}).
1819 If you are running your program in an execution environment that
1820 supports processes, @code{run} creates an inferior process and makes
1821 that process run your program. (In environments without processes,
1822 @code{run} jumps to the start of your program.)
1824 The execution of a program is affected by certain information it
1825 receives from its superior. @value{GDBN} provides ways to specify this
1826 information, which you must do @emph{before} starting your program. (You
1827 can change it after starting your program, but such changes only affect
1828 your program the next time you start it.) This information may be
1829 divided into four categories:
1832 @item The @emph{arguments.}
1833 Specify the arguments to give your program as the arguments of the
1834 @code{run} command. If a shell is available on your target, the shell
1835 is used to pass the arguments, so that you may use normal conventions
1836 (such as wildcard expansion or variable substitution) in describing
1838 In Unix systems, you can control which shell is used with the
1839 @code{SHELL} environment variable.
1840 @xref{Arguments, ,Your Program's Arguments}.
1842 @item The @emph{environment.}
1843 Your program normally inherits its environment from @value{GDBN}, but you can
1844 use the @value{GDBN} commands @code{set environment} and @code{unset
1845 environment} to change parts of the environment that affect
1846 your program. @xref{Environment, ,Your Program's Environment}.
1848 @item The @emph{working directory.}
1849 Your program inherits its working directory from @value{GDBN}. You can set
1850 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1851 @xref{Working Directory, ,Your Program's Working Directory}.
1853 @item The @emph{standard input and output.}
1854 Your program normally uses the same device for standard input and
1855 standard output as @value{GDBN} is using. You can redirect input and output
1856 in the @code{run} command line, or you can use the @code{tty} command to
1857 set a different device for your program.
1858 @xref{Input/Output, ,Your Program's Input and Output}.
1861 @emph{Warning:} While input and output redirection work, you cannot use
1862 pipes to pass the output of the program you are debugging to another
1863 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1867 When you issue the @code{run} command, your program begins to execute
1868 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1869 of how to arrange for your program to stop. Once your program has
1870 stopped, you may call functions in your program, using the @code{print}
1871 or @code{call} commands. @xref{Data, ,Examining Data}.
1873 If the modification time of your symbol file has changed since the last
1874 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1875 table, and reads it again. When it does this, @value{GDBN} tries to retain
1876 your current breakpoints.
1881 @cindex run to main procedure
1882 The name of the main procedure can vary from language to language.
1883 With C or C@t{++}, the main procedure name is always @code{main}, but
1884 other languages such as Ada do not require a specific name for their
1885 main procedure. The debugger provides a convenient way to start the
1886 execution of the program and to stop at the beginning of the main
1887 procedure, depending on the language used.
1889 The @samp{start} command does the equivalent of setting a temporary
1890 breakpoint at the beginning of the main procedure and then invoking
1891 the @samp{run} command.
1893 @cindex elaboration phase
1894 Some programs contain an @dfn{elaboration} phase where some startup code is
1895 executed before the main procedure is called. This depends on the
1896 languages used to write your program. In C@t{++}, for instance,
1897 constructors for static and global objects are executed before
1898 @code{main} is called. It is therefore possible that the debugger stops
1899 before reaching the main procedure. However, the temporary breakpoint
1900 will remain to halt execution.
1902 Specify the arguments to give to your program as arguments to the
1903 @samp{start} command. These arguments will be given verbatim to the
1904 underlying @samp{run} command. Note that the same arguments will be
1905 reused if no argument is provided during subsequent calls to
1906 @samp{start} or @samp{run}.
1908 It is sometimes necessary to debug the program during elaboration. In
1909 these cases, using the @code{start} command would stop the execution of
1910 your program too late, as the program would have already completed the
1911 elaboration phase. Under these circumstances, insert breakpoints in your
1912 elaboration code before running your program.
1916 @section Your Program's Arguments
1918 @cindex arguments (to your program)
1919 The arguments to your program can be specified by the arguments of the
1921 They are passed to a shell, which expands wildcard characters and
1922 performs redirection of I/O, and thence to your program. Your
1923 @code{SHELL} environment variable (if it exists) specifies what shell
1924 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1925 the default shell (@file{/bin/sh} on Unix).
1927 On non-Unix systems, the program is usually invoked directly by
1928 @value{GDBN}, which emulates I/O redirection via the appropriate system
1929 calls, and the wildcard characters are expanded by the startup code of
1930 the program, not by the shell.
1932 @code{run} with no arguments uses the same arguments used by the previous
1933 @code{run}, or those set by the @code{set args} command.
1938 Specify the arguments to be used the next time your program is run. If
1939 @code{set args} has no arguments, @code{run} executes your program
1940 with no arguments. Once you have run your program with arguments,
1941 using @code{set args} before the next @code{run} is the only way to run
1942 it again without arguments.
1946 Show the arguments to give your program when it is started.
1950 @section Your Program's Environment
1952 @cindex environment (of your program)
1953 The @dfn{environment} consists of a set of environment variables and
1954 their values. Environment variables conventionally record such things as
1955 your user name, your home directory, your terminal type, and your search
1956 path for programs to run. Usually you set up environment variables with
1957 the shell and they are inherited by all the other programs you run. When
1958 debugging, it can be useful to try running your program with a modified
1959 environment without having to start @value{GDBN} over again.
1963 @item path @var{directory}
1964 Add @var{directory} to the front of the @code{PATH} environment variable
1965 (the search path for executables) that will be passed to your program.
1966 The value of @code{PATH} used by @value{GDBN} does not change.
1967 You may specify several directory names, separated by whitespace or by a
1968 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1969 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1970 is moved to the front, so it is searched sooner.
1972 You can use the string @samp{$cwd} to refer to whatever is the current
1973 working directory at the time @value{GDBN} searches the path. If you
1974 use @samp{.} instead, it refers to the directory where you executed the
1975 @code{path} command. @value{GDBN} replaces @samp{.} in the
1976 @var{directory} argument (with the current path) before adding
1977 @var{directory} to the search path.
1978 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1979 @c document that, since repeating it would be a no-op.
1983 Display the list of search paths for executables (the @code{PATH}
1984 environment variable).
1986 @kindex show environment
1987 @item show environment @r{[}@var{varname}@r{]}
1988 Print the value of environment variable @var{varname} to be given to
1989 your program when it starts. If you do not supply @var{varname},
1990 print the names and values of all environment variables to be given to
1991 your program. You can abbreviate @code{environment} as @code{env}.
1993 @kindex set environment
1994 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1995 Set environment variable @var{varname} to @var{value}. The value
1996 changes for your program only, not for @value{GDBN} itself. @var{value} may
1997 be any string; the values of environment variables are just strings, and
1998 any interpretation is supplied by your program itself. The @var{value}
1999 parameter is optional; if it is eliminated, the variable is set to a
2001 @c "any string" here does not include leading, trailing
2002 @c blanks. Gnu asks: does anyone care?
2004 For example, this command:
2011 tells the debugged program, when subsequently run, that its user is named
2012 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2013 are not actually required.)
2015 @kindex unset environment
2016 @item unset environment @var{varname}
2017 Remove variable @var{varname} from the environment to be passed to your
2018 program. This is different from @samp{set env @var{varname} =};
2019 @code{unset environment} removes the variable from the environment,
2020 rather than assigning it an empty value.
2023 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2025 by your @code{SHELL} environment variable if it exists (or
2026 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2027 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2028 @file{.bashrc} for BASH---any variables you set in that file affect
2029 your program. You may wish to move setting of environment variables to
2030 files that are only run when you sign on, such as @file{.login} or
2033 @node Working Directory
2034 @section Your Program's Working Directory
2036 @cindex working directory (of your program)
2037 Each time you start your program with @code{run}, it inherits its
2038 working directory from the current working directory of @value{GDBN}.
2039 The @value{GDBN} working directory is initially whatever it inherited
2040 from its parent process (typically the shell), but you can specify a new
2041 working directory in @value{GDBN} with the @code{cd} command.
2043 The @value{GDBN} working directory also serves as a default for the commands
2044 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2049 @cindex change working directory
2050 @item cd @var{directory}
2051 Set the @value{GDBN} working directory to @var{directory}.
2055 Print the @value{GDBN} working directory.
2058 It is generally impossible to find the current working directory of
2059 the process being debugged (since a program can change its directory
2060 during its run). If you work on a system where @value{GDBN} is
2061 configured with the @file{/proc} support, you can use the @code{info
2062 proc} command (@pxref{SVR4 Process Information}) to find out the
2063 current working directory of the debuggee.
2066 @section Your Program's Input and Output
2071 By default, the program you run under @value{GDBN} does input and output to
2072 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2073 to its own terminal modes to interact with you, but it records the terminal
2074 modes your program was using and switches back to them when you continue
2075 running your program.
2078 @kindex info terminal
2080 Displays information recorded by @value{GDBN} about the terminal modes your
2084 You can redirect your program's input and/or output using shell
2085 redirection with the @code{run} command. For example,
2092 starts your program, diverting its output to the file @file{outfile}.
2095 @cindex controlling terminal
2096 Another way to specify where your program should do input and output is
2097 with the @code{tty} command. This command accepts a file name as
2098 argument, and causes this file to be the default for future @code{run}
2099 commands. It also resets the controlling terminal for the child
2100 process, for future @code{run} commands. For example,
2107 directs that processes started with subsequent @code{run} commands
2108 default to do input and output on the terminal @file{/dev/ttyb} and have
2109 that as their controlling terminal.
2111 An explicit redirection in @code{run} overrides the @code{tty} command's
2112 effect on the input/output device, but not its effect on the controlling
2115 When you use the @code{tty} command or redirect input in the @code{run}
2116 command, only the input @emph{for your program} is affected. The input
2117 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2118 for @code{set inferior-tty}.
2120 @cindex inferior tty
2121 @cindex set inferior controlling terminal
2122 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2123 display the name of the terminal that will be used for future runs of your
2127 @item set inferior-tty /dev/ttyb
2128 @kindex set inferior-tty
2129 Set the tty for the program being debugged to /dev/ttyb.
2131 @item show inferior-tty
2132 @kindex show inferior-tty
2133 Show the current tty for the program being debugged.
2137 @section Debugging an Already-running Process
2142 @item attach @var{process-id}
2143 This command attaches to a running process---one that was started
2144 outside @value{GDBN}. (@code{info files} shows your active
2145 targets.) The command takes as argument a process ID. The usual way to
2146 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2147 or with the @samp{jobs -l} shell command.
2149 @code{attach} does not repeat if you press @key{RET} a second time after
2150 executing the command.
2153 To use @code{attach}, your program must be running in an environment
2154 which supports processes; for example, @code{attach} does not work for
2155 programs on bare-board targets that lack an operating system. You must
2156 also have permission to send the process a signal.
2158 When you use @code{attach}, the debugger finds the program running in
2159 the process first by looking in the current working directory, then (if
2160 the program is not found) by using the source file search path
2161 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2162 the @code{file} command to load the program. @xref{Files, ,Commands to
2165 The first thing @value{GDBN} does after arranging to debug the specified
2166 process is to stop it. You can examine and modify an attached process
2167 with all the @value{GDBN} commands that are ordinarily available when
2168 you start processes with @code{run}. You can insert breakpoints; you
2169 can step and continue; you can modify storage. If you would rather the
2170 process continue running, you may use the @code{continue} command after
2171 attaching @value{GDBN} to the process.
2176 When you have finished debugging the attached process, you can use the
2177 @code{detach} command to release it from @value{GDBN} control. Detaching
2178 the process continues its execution. After the @code{detach} command,
2179 that process and @value{GDBN} become completely independent once more, and you
2180 are ready to @code{attach} another process or start one with @code{run}.
2181 @code{detach} does not repeat if you press @key{RET} again after
2182 executing the command.
2185 If you exit @value{GDBN} while you have an attached process, you detach
2186 that process. If you use the @code{run} command, you kill that process.
2187 By default, @value{GDBN} asks for confirmation if you try to do either of these
2188 things; you can control whether or not you need to confirm by using the
2189 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2193 @section Killing the Child Process
2198 Kill the child process in which your program is running under @value{GDBN}.
2201 This command is useful if you wish to debug a core dump instead of a
2202 running process. @value{GDBN} ignores any core dump file while your program
2205 On some operating systems, a program cannot be executed outside @value{GDBN}
2206 while you have breakpoints set on it inside @value{GDBN}. You can use the
2207 @code{kill} command in this situation to permit running your program
2208 outside the debugger.
2210 The @code{kill} command is also useful if you wish to recompile and
2211 relink your program, since on many systems it is impossible to modify an
2212 executable file while it is running in a process. In this case, when you
2213 next type @code{run}, @value{GDBN} notices that the file has changed, and
2214 reads the symbol table again (while trying to preserve your current
2215 breakpoint settings).
2218 @section Debugging Programs with Multiple Threads
2220 @cindex threads of execution
2221 @cindex multiple threads
2222 @cindex switching threads
2223 In some operating systems, such as HP-UX and Solaris, a single program
2224 may have more than one @dfn{thread} of execution. The precise semantics
2225 of threads differ from one operating system to another, but in general
2226 the threads of a single program are akin to multiple processes---except
2227 that they share one address space (that is, they can all examine and
2228 modify the same variables). On the other hand, each thread has its own
2229 registers and execution stack, and perhaps private memory.
2231 @value{GDBN} provides these facilities for debugging multi-thread
2235 @item automatic notification of new threads
2236 @item @samp{thread @var{threadno}}, a command to switch among threads
2237 @item @samp{info threads}, a command to inquire about existing threads
2238 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2239 a command to apply a command to a list of threads
2240 @item thread-specific breakpoints
2244 @emph{Warning:} These facilities are not yet available on every
2245 @value{GDBN} configuration where the operating system supports threads.
2246 If your @value{GDBN} does not support threads, these commands have no
2247 effect. For example, a system without thread support shows no output
2248 from @samp{info threads}, and always rejects the @code{thread} command,
2252 (@value{GDBP}) info threads
2253 (@value{GDBP}) thread 1
2254 Thread ID 1 not known. Use the "info threads" command to
2255 see the IDs of currently known threads.
2257 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2258 @c doesn't support threads"?
2261 @cindex focus of debugging
2262 @cindex current thread
2263 The @value{GDBN} thread debugging facility allows you to observe all
2264 threads while your program runs---but whenever @value{GDBN} takes
2265 control, one thread in particular is always the focus of debugging.
2266 This thread is called the @dfn{current thread}. Debugging commands show
2267 program information from the perspective of the current thread.
2269 @cindex @code{New} @var{systag} message
2270 @cindex thread identifier (system)
2271 @c FIXME-implementors!! It would be more helpful if the [New...] message
2272 @c included GDB's numeric thread handle, so you could just go to that
2273 @c thread without first checking `info threads'.
2274 Whenever @value{GDBN} detects a new thread in your program, it displays
2275 the target system's identification for the thread with a message in the
2276 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2277 whose form varies depending on the particular system. For example, on
2278 @sc{gnu}/Linux, you might see
2281 [New Thread 46912507313328 (LWP 25582)]
2285 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2286 the @var{systag} is simply something like @samp{process 368}, with no
2289 @c FIXME!! (1) Does the [New...] message appear even for the very first
2290 @c thread of a program, or does it only appear for the
2291 @c second---i.e.@: when it becomes obvious we have a multithread
2293 @c (2) *Is* there necessarily a first thread always? Or do some
2294 @c multithread systems permit starting a program with multiple
2295 @c threads ab initio?
2297 @cindex thread number
2298 @cindex thread identifier (GDB)
2299 For debugging purposes, @value{GDBN} associates its own thread
2300 number---always a single integer---with each thread in your program.
2303 @kindex info threads
2305 Display a summary of all threads currently in your
2306 program. @value{GDBN} displays for each thread (in this order):
2310 the thread number assigned by @value{GDBN}
2313 the target system's thread identifier (@var{systag})
2316 the current stack frame summary for that thread
2320 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2321 indicates the current thread.
2325 @c end table here to get a little more width for example
2328 (@value{GDBP}) info threads
2329 3 process 35 thread 27 0x34e5 in sigpause ()
2330 2 process 35 thread 23 0x34e5 in sigpause ()
2331 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2337 @cindex debugging multithreaded programs (on HP-UX)
2338 @cindex thread identifier (GDB), on HP-UX
2339 For debugging purposes, @value{GDBN} associates its own thread
2340 number---a small integer assigned in thread-creation order---with each
2341 thread in your program.
2343 @cindex @code{New} @var{systag} message, on HP-UX
2344 @cindex thread identifier (system), on HP-UX
2345 @c FIXME-implementors!! It would be more helpful if the [New...] message
2346 @c included GDB's numeric thread handle, so you could just go to that
2347 @c thread without first checking `info threads'.
2348 Whenever @value{GDBN} detects a new thread in your program, it displays
2349 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2350 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2351 whose form varies depending on the particular system. For example, on
2355 [New thread 2 (system thread 26594)]
2359 when @value{GDBN} notices a new thread.
2362 @kindex info threads (HP-UX)
2364 Display a summary of all threads currently in your
2365 program. @value{GDBN} displays for each thread (in this order):
2368 @item the thread number assigned by @value{GDBN}
2370 @item the target system's thread identifier (@var{systag})
2372 @item the current stack frame summary for that thread
2376 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2377 indicates the current thread.
2381 @c end table here to get a little more width for example
2384 (@value{GDBP}) info threads
2385 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2387 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2388 from /usr/lib/libc.2
2389 1 system thread 27905 0x7b003498 in _brk () \@*
2390 from /usr/lib/libc.2
2393 On Solaris, you can display more information about user threads with a
2394 Solaris-specific command:
2397 @item maint info sol-threads
2398 @kindex maint info sol-threads
2399 @cindex thread info (Solaris)
2400 Display info on Solaris user threads.
2404 @kindex thread @var{threadno}
2405 @item thread @var{threadno}
2406 Make thread number @var{threadno} the current thread. The command
2407 argument @var{threadno} is the internal @value{GDBN} thread number, as
2408 shown in the first field of the @samp{info threads} display.
2409 @value{GDBN} responds by displaying the system identifier of the thread
2410 you selected, and its current stack frame summary:
2413 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2414 (@value{GDBP}) thread 2
2415 [Switching to process 35 thread 23]
2416 0x34e5 in sigpause ()
2420 As with the @samp{[New @dots{}]} message, the form of the text after
2421 @samp{Switching to} depends on your system's conventions for identifying
2424 @kindex thread apply
2425 @cindex apply command to several threads
2426 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2427 The @code{thread apply} command allows you to apply the named
2428 @var{command} to one or more threads. Specify the numbers of the
2429 threads that you want affected with the command argument
2430 @var{threadno}. It can be a single thread number, one of the numbers
2431 shown in the first field of the @samp{info threads} display; or it
2432 could be a range of thread numbers, as in @code{2-4}. To apply a
2433 command to all threads, type @kbd{thread apply all @var{command}}.
2436 @cindex automatic thread selection
2437 @cindex switching threads automatically
2438 @cindex threads, automatic switching
2439 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2440 signal, it automatically selects the thread where that breakpoint or
2441 signal happened. @value{GDBN} alerts you to the context switch with a
2442 message of the form @samp{[Switching to @var{systag}]} to identify the
2445 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2446 more information about how @value{GDBN} behaves when you stop and start
2447 programs with multiple threads.
2449 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2450 watchpoints in programs with multiple threads.
2453 @section Debugging Programs with Multiple Processes
2455 @cindex fork, debugging programs which call
2456 @cindex multiple processes
2457 @cindex processes, multiple
2458 On most systems, @value{GDBN} has no special support for debugging
2459 programs which create additional processes using the @code{fork}
2460 function. When a program forks, @value{GDBN} will continue to debug the
2461 parent process and the child process will run unimpeded. If you have
2462 set a breakpoint in any code which the child then executes, the child
2463 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2464 will cause it to terminate.
2466 However, if you want to debug the child process there is a workaround
2467 which isn't too painful. Put a call to @code{sleep} in the code which
2468 the child process executes after the fork. It may be useful to sleep
2469 only if a certain environment variable is set, or a certain file exists,
2470 so that the delay need not occur when you don't want to run @value{GDBN}
2471 on the child. While the child is sleeping, use the @code{ps} program to
2472 get its process ID. Then tell @value{GDBN} (a new invocation of
2473 @value{GDBN} if you are also debugging the parent process) to attach to
2474 the child process (@pxref{Attach}). From that point on you can debug
2475 the child process just like any other process which you attached to.
2477 On some systems, @value{GDBN} provides support for debugging programs that
2478 create additional processes using the @code{fork} or @code{vfork} functions.
2479 Currently, the only platforms with this feature are HP-UX (11.x and later
2480 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2482 By default, when a program forks, @value{GDBN} will continue to debug
2483 the parent process and the child process will run unimpeded.
2485 If you want to follow the child process instead of the parent process,
2486 use the command @w{@code{set follow-fork-mode}}.
2489 @kindex set follow-fork-mode
2490 @item set follow-fork-mode @var{mode}
2491 Set the debugger response to a program call of @code{fork} or
2492 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2493 process. The @var{mode} argument can be:
2497 The original process is debugged after a fork. The child process runs
2498 unimpeded. This is the default.
2501 The new process is debugged after a fork. The parent process runs
2506 @kindex show follow-fork-mode
2507 @item show follow-fork-mode
2508 Display the current debugger response to a @code{fork} or @code{vfork} call.
2511 @cindex debugging multiple processes
2512 On Linux, if you want to debug both the parent and child processes, use the
2513 command @w{@code{set detach-on-fork}}.
2516 @kindex set detach-on-fork
2517 @item set detach-on-fork @var{mode}
2518 Tells gdb whether to detach one of the processes after a fork, or
2519 retain debugger control over them both.
2523 The child process (or parent process, depending on the value of
2524 @code{follow-fork-mode}) will be detached and allowed to run
2525 independently. This is the default.
2528 Both processes will be held under the control of @value{GDBN}.
2529 One process (child or parent, depending on the value of
2530 @code{follow-fork-mode}) is debugged as usual, while the other
2535 @kindex show detach-on-follow
2536 @item show detach-on-follow
2537 Show whether detach-on-follow mode is on/off.
2540 If you choose to set @var{detach-on-follow} mode off, then
2541 @value{GDBN} will retain control of all forked processes (including
2542 nested forks). You can list the forked processes under the control of
2543 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2544 from one fork to another by using the @w{@code{fork}} command.
2549 Print a list of all forked processes under the control of @value{GDBN}.
2550 The listing will include a fork id, a process id, and the current
2551 position (program counter) of the process.
2554 @kindex fork @var{fork-id}
2555 @item fork @var{fork-id}
2556 Make fork number @var{fork-id} the current process. The argument
2557 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2558 as shown in the first field of the @samp{info forks} display.
2562 To quit debugging one of the forked processes, you can either detach
2563 from it by using the @w{@code{detach fork}} command (allowing it to
2564 run independently), or delete (and kill) it using the
2565 @w{@code{delete fork}} command.
2568 @kindex detach fork @var{fork-id}
2569 @item detach fork @var{fork-id}
2570 Detach from the process identified by @value{GDBN} fork number
2571 @var{fork-id}, and remove it from the fork list. The process will be
2572 allowed to run independently.
2574 @kindex delete fork @var{fork-id}
2575 @item delete fork @var{fork-id}
2576 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2577 and remove it from the fork list.
2581 If you ask to debug a child process and a @code{vfork} is followed by an
2582 @code{exec}, @value{GDBN} executes the new target up to the first
2583 breakpoint in the new target. If you have a breakpoint set on
2584 @code{main} in your original program, the breakpoint will also be set on
2585 the child process's @code{main}.
2587 When a child process is spawned by @code{vfork}, you cannot debug the
2588 child or parent until an @code{exec} call completes.
2590 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2591 call executes, the new target restarts. To restart the parent process,
2592 use the @code{file} command with the parent executable name as its
2595 You can use the @code{catch} command to make @value{GDBN} stop whenever
2596 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2597 Catchpoints, ,Setting Catchpoints}.
2599 @node Checkpoint/Restart
2600 @section Setting a @emph{Bookmark} to Return to Later
2605 @cindex snapshot of a process
2606 @cindex rewind program state
2608 On certain operating systems@footnote{Currently, only
2609 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2610 program's state, called a @dfn{checkpoint}, and come back to it
2613 Returning to a checkpoint effectively undoes everything that has
2614 happened in the program since the @code{checkpoint} was saved. This
2615 includes changes in memory, registers, and even (within some limits)
2616 system state. Effectively, it is like going back in time to the
2617 moment when the checkpoint was saved.
2619 Thus, if you're stepping thru a program and you think you're
2620 getting close to the point where things go wrong, you can save
2621 a checkpoint. Then, if you accidentally go too far and miss
2622 the critical statement, instead of having to restart your program
2623 from the beginning, you can just go back to the checkpoint and
2624 start again from there.
2626 This can be especially useful if it takes a lot of time or
2627 steps to reach the point where you think the bug occurs.
2629 To use the @code{checkpoint}/@code{restart} method of debugging:
2634 Save a snapshot of the debugged program's current execution state.
2635 The @code{checkpoint} command takes no arguments, but each checkpoint
2636 is assigned a small integer id, similar to a breakpoint id.
2638 @kindex info checkpoints
2639 @item info checkpoints
2640 List the checkpoints that have been saved in the current debugging
2641 session. For each checkpoint, the following information will be
2648 @item Source line, or label
2651 @kindex restart @var{checkpoint-id}
2652 @item restart @var{checkpoint-id}
2653 Restore the program state that was saved as checkpoint number
2654 @var{checkpoint-id}. All program variables, registers, stack frames
2655 etc.@: will be returned to the values that they had when the checkpoint
2656 was saved. In essence, gdb will ``wind back the clock'' to the point
2657 in time when the checkpoint was saved.
2659 Note that breakpoints, @value{GDBN} variables, command history etc.
2660 are not affected by restoring a checkpoint. In general, a checkpoint
2661 only restores things that reside in the program being debugged, not in
2664 @kindex delete checkpoint @var{checkpoint-id}
2665 @item delete checkpoint @var{checkpoint-id}
2666 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2670 Returning to a previously saved checkpoint will restore the user state
2671 of the program being debugged, plus a significant subset of the system
2672 (OS) state, including file pointers. It won't ``un-write'' data from
2673 a file, but it will rewind the file pointer to the previous location,
2674 so that the previously written data can be overwritten. For files
2675 opened in read mode, the pointer will also be restored so that the
2676 previously read data can be read again.
2678 Of course, characters that have been sent to a printer (or other
2679 external device) cannot be ``snatched back'', and characters received
2680 from eg.@: a serial device can be removed from internal program buffers,
2681 but they cannot be ``pushed back'' into the serial pipeline, ready to
2682 be received again. Similarly, the actual contents of files that have
2683 been changed cannot be restored (at this time).
2685 However, within those constraints, you actually can ``rewind'' your
2686 program to a previously saved point in time, and begin debugging it
2687 again --- and you can change the course of events so as to debug a
2688 different execution path this time.
2690 @cindex checkpoints and process id
2691 Finally, there is one bit of internal program state that will be
2692 different when you return to a checkpoint --- the program's process
2693 id. Each checkpoint will have a unique process id (or @var{pid}),
2694 and each will be different from the program's original @var{pid}.
2695 If your program has saved a local copy of its process id, this could
2696 potentially pose a problem.
2698 @subsection A Non-obvious Benefit of Using Checkpoints
2700 On some systems such as @sc{gnu}/Linux, address space randomization
2701 is performed on new processes for security reasons. This makes it
2702 difficult or impossible to set a breakpoint, or watchpoint, on an
2703 absolute address if you have to restart the program, since the
2704 absolute location of a symbol will change from one execution to the
2707 A checkpoint, however, is an @emph{identical} copy of a process.
2708 Therefore if you create a checkpoint at (eg.@:) the start of main,
2709 and simply return to that checkpoint instead of restarting the
2710 process, you can avoid the effects of address randomization and
2711 your symbols will all stay in the same place.
2714 @chapter Stopping and Continuing
2716 The principal purposes of using a debugger are so that you can stop your
2717 program before it terminates; or so that, if your program runs into
2718 trouble, you can investigate and find out why.
2720 Inside @value{GDBN}, your program may stop for any of several reasons,
2721 such as a signal, a breakpoint, or reaching a new line after a
2722 @value{GDBN} command such as @code{step}. You may then examine and
2723 change variables, set new breakpoints or remove old ones, and then
2724 continue execution. Usually, the messages shown by @value{GDBN} provide
2725 ample explanation of the status of your program---but you can also
2726 explicitly request this information at any time.
2729 @kindex info program
2731 Display information about the status of your program: whether it is
2732 running or not, what process it is, and why it stopped.
2736 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2737 * Continuing and Stepping:: Resuming execution
2739 * Thread Stops:: Stopping and starting multi-thread programs
2743 @section Breakpoints, Watchpoints, and Catchpoints
2746 A @dfn{breakpoint} makes your program stop whenever a certain point in
2747 the program is reached. For each breakpoint, you can add conditions to
2748 control in finer detail whether your program stops. You can set
2749 breakpoints with the @code{break} command and its variants (@pxref{Set
2750 Breaks, ,Setting Breakpoints}), to specify the place where your program
2751 should stop by line number, function name or exact address in the
2754 On some systems, you can set breakpoints in shared libraries before
2755 the executable is run. There is a minor limitation on HP-UX systems:
2756 you must wait until the executable is run in order to set breakpoints
2757 in shared library routines that are not called directly by the program
2758 (for example, routines that are arguments in a @code{pthread_create}
2762 @cindex data breakpoints
2763 @cindex memory tracing
2764 @cindex breakpoint on memory address
2765 @cindex breakpoint on variable modification
2766 A @dfn{watchpoint} is a special breakpoint that stops your program
2767 when the value of an expression changes. The expression may be a value
2768 of a variable, or it could involve values of one or more variables
2769 combined by operators, such as @samp{a + b}. This is sometimes called
2770 @dfn{data breakpoints}. You must use a different command to set
2771 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2772 from that, you can manage a watchpoint like any other breakpoint: you
2773 enable, disable, and delete both breakpoints and watchpoints using the
2776 You can arrange to have values from your program displayed automatically
2777 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2781 @cindex breakpoint on events
2782 A @dfn{catchpoint} is another special breakpoint that stops your program
2783 when a certain kind of event occurs, such as the throwing of a C@t{++}
2784 exception or the loading of a library. As with watchpoints, you use a
2785 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2786 Catchpoints}), but aside from that, you can manage a catchpoint like any
2787 other breakpoint. (To stop when your program receives a signal, use the
2788 @code{handle} command; see @ref{Signals, ,Signals}.)
2790 @cindex breakpoint numbers
2791 @cindex numbers for breakpoints
2792 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2793 catchpoint when you create it; these numbers are successive integers
2794 starting with one. In many of the commands for controlling various
2795 features of breakpoints you use the breakpoint number to say which
2796 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2797 @dfn{disabled}; if disabled, it has no effect on your program until you
2800 @cindex breakpoint ranges
2801 @cindex ranges of breakpoints
2802 Some @value{GDBN} commands accept a range of breakpoints on which to
2803 operate. A breakpoint range is either a single breakpoint number, like
2804 @samp{5}, or two such numbers, in increasing order, separated by a
2805 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2806 all breakpoints in that range are operated on.
2809 * Set Breaks:: Setting breakpoints
2810 * Set Watchpoints:: Setting watchpoints
2811 * Set Catchpoints:: Setting catchpoints
2812 * Delete Breaks:: Deleting breakpoints
2813 * Disabling:: Disabling breakpoints
2814 * Conditions:: Break conditions
2815 * Break Commands:: Breakpoint command lists
2816 * Breakpoint Menus:: Breakpoint menus
2817 * Error in Breakpoints:: ``Cannot insert breakpoints''
2818 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2822 @subsection Setting Breakpoints
2824 @c FIXME LMB what does GDB do if no code on line of breakpt?
2825 @c consider in particular declaration with/without initialization.
2827 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2830 @kindex b @r{(@code{break})}
2831 @vindex $bpnum@r{, convenience variable}
2832 @cindex latest breakpoint
2833 Breakpoints are set with the @code{break} command (abbreviated
2834 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2835 number of the breakpoint you've set most recently; see @ref{Convenience
2836 Vars,, Convenience Variables}, for a discussion of what you can do with
2837 convenience variables.
2840 @item break @var{location}
2841 Set a breakpoint at the given @var{location}, which can specify a
2842 function name, a line number, or an address of an instruction.
2843 (@xref{Specify Location}, for a list of all the possible ways to
2844 specify a @var{location}.) The breakpoint will stop your program just
2845 before it executes any of the code in the specified @var{location}.
2847 When using source languages that permit overloading of symbols, such as
2848 C@t{++}, a function name may refer to more than one possible place to break.
2849 @xref{Breakpoint Menus,,Breakpoint Menus}, for a discussion of that situation.
2852 When called without any arguments, @code{break} sets a breakpoint at
2853 the next instruction to be executed in the selected stack frame
2854 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2855 innermost, this makes your program stop as soon as control
2856 returns to that frame. This is similar to the effect of a
2857 @code{finish} command in the frame inside the selected frame---except
2858 that @code{finish} does not leave an active breakpoint. If you use
2859 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2860 the next time it reaches the current location; this may be useful
2863 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2864 least one instruction has been executed. If it did not do this, you
2865 would be unable to proceed past a breakpoint without first disabling the
2866 breakpoint. This rule applies whether or not the breakpoint already
2867 existed when your program stopped.
2869 @item break @dots{} if @var{cond}
2870 Set a breakpoint with condition @var{cond}; evaluate the expression
2871 @var{cond} each time the breakpoint is reached, and stop only if the
2872 value is nonzero---that is, if @var{cond} evaluates as true.
2873 @samp{@dots{}} stands for one of the possible arguments described
2874 above (or no argument) specifying where to break. @xref{Conditions,
2875 ,Break Conditions}, for more information on breakpoint conditions.
2878 @item tbreak @var{args}
2879 Set a breakpoint enabled only for one stop. @var{args} are the
2880 same as for the @code{break} command, and the breakpoint is set in the same
2881 way, but the breakpoint is automatically deleted after the first time your
2882 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2885 @cindex hardware breakpoints
2886 @item hbreak @var{args}
2887 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2888 @code{break} command and the breakpoint is set in the same way, but the
2889 breakpoint requires hardware support and some target hardware may not
2890 have this support. The main purpose of this is EPROM/ROM code
2891 debugging, so you can set a breakpoint at an instruction without
2892 changing the instruction. This can be used with the new trap-generation
2893 provided by SPARClite DSU and most x86-based targets. These targets
2894 will generate traps when a program accesses some data or instruction
2895 address that is assigned to the debug registers. However the hardware
2896 breakpoint registers can take a limited number of breakpoints. For
2897 example, on the DSU, only two data breakpoints can be set at a time, and
2898 @value{GDBN} will reject this command if more than two are used. Delete
2899 or disable unused hardware breakpoints before setting new ones
2900 (@pxref{Disabling, ,Disabling Breakpoints}).
2901 @xref{Conditions, ,Break Conditions}.
2902 For remote targets, you can restrict the number of hardware
2903 breakpoints @value{GDBN} will use, see @ref{set remote
2904 hardware-breakpoint-limit}.
2907 @item thbreak @var{args}
2908 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2909 are the same as for the @code{hbreak} command and the breakpoint is set in
2910 the same way. However, like the @code{tbreak} command,
2911 the breakpoint is automatically deleted after the
2912 first time your program stops there. Also, like the @code{hbreak}
2913 command, the breakpoint requires hardware support and some target hardware
2914 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2915 See also @ref{Conditions, ,Break Conditions}.
2918 @cindex regular expression
2919 @cindex breakpoints in functions matching a regexp
2920 @cindex set breakpoints in many functions
2921 @item rbreak @var{regex}
2922 Set breakpoints on all functions matching the regular expression
2923 @var{regex}. This command sets an unconditional breakpoint on all
2924 matches, printing a list of all breakpoints it set. Once these
2925 breakpoints are set, they are treated just like the breakpoints set with
2926 the @code{break} command. You can delete them, disable them, or make
2927 them conditional the same way as any other breakpoint.
2929 The syntax of the regular expression is the standard one used with tools
2930 like @file{grep}. Note that this is different from the syntax used by
2931 shells, so for instance @code{foo*} matches all functions that include
2932 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2933 @code{.*} leading and trailing the regular expression you supply, so to
2934 match only functions that begin with @code{foo}, use @code{^foo}.
2936 @cindex non-member C@t{++} functions, set breakpoint in
2937 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2938 breakpoints on overloaded functions that are not members of any special
2941 @cindex set breakpoints on all functions
2942 The @code{rbreak} command can be used to set breakpoints in
2943 @strong{all} the functions in a program, like this:
2946 (@value{GDBP}) rbreak .
2949 @kindex info breakpoints
2950 @cindex @code{$_} and @code{info breakpoints}
2951 @item info breakpoints @r{[}@var{n}@r{]}
2952 @itemx info break @r{[}@var{n}@r{]}
2953 @itemx info watchpoints @r{[}@var{n}@r{]}
2954 Print a table of all breakpoints, watchpoints, and catchpoints set and
2955 not deleted. Optional argument @var{n} means print information only
2956 about the specified breakpoint (or watchpoint or catchpoint). For
2957 each breakpoint, following columns are printed:
2960 @item Breakpoint Numbers
2962 Breakpoint, watchpoint, or catchpoint.
2964 Whether the breakpoint is marked to be disabled or deleted when hit.
2965 @item Enabled or Disabled
2966 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2967 that are not enabled. An optional @samp{(p)} suffix marks pending
2968 breakpoints---breakpoints for which address is either not yet
2969 resolved, pending load of a shared library, or for which address was
2970 in a shared library that was since unloaded. Such breakpoint won't
2971 fire until a shared library that has the symbol or line referred by
2972 breakpoint is loaded. See below for details.
2974 Where the breakpoint is in your program, as a memory address. For a
2975 pending breakpoint whose address is not yet known, this field will
2976 contain @samp{<PENDING>}. A breakpoint with several locations will
2977 have @samp{<MULTIPLE>} in this field---see below for details.
2979 Where the breakpoint is in the source for your program, as a file and
2980 line number. For a pending breakpoint, the original string passed to
2981 the breakpoint command will be listed as it cannot be resolved until
2982 the appropriate shared library is loaded in the future.
2986 If a breakpoint is conditional, @code{info break} shows the condition on
2987 the line following the affected breakpoint; breakpoint commands, if any,
2988 are listed after that. A pending breakpoint is allowed to have a condition
2989 specified for it. The condition is not parsed for validity until a shared
2990 library is loaded that allows the pending breakpoint to resolve to a
2994 @code{info break} with a breakpoint
2995 number @var{n} as argument lists only that breakpoint. The
2996 convenience variable @code{$_} and the default examining-address for
2997 the @code{x} command are set to the address of the last breakpoint
2998 listed (@pxref{Memory, ,Examining Memory}).
3001 @code{info break} displays a count of the number of times the breakpoint
3002 has been hit. This is especially useful in conjunction with the
3003 @code{ignore} command. You can ignore a large number of breakpoint
3004 hits, look at the breakpoint info to see how many times the breakpoint
3005 was hit, and then run again, ignoring one less than that number. This
3006 will get you quickly to the last hit of that breakpoint.
3009 @value{GDBN} allows you to set any number of breakpoints at the same place in
3010 your program. There is nothing silly or meaningless about this. When
3011 the breakpoints are conditional, this is even useful
3012 (@pxref{Conditions, ,Break Conditions}).
3014 It is possible that a breakpoint corresponds to several locations
3015 in your program. Examples of this situation are:
3020 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3021 instances of the function body, used in different cases.
3024 For a C@t{++} template function, a given line in the function can
3025 correspond to any number of instantiations.
3028 For an inlined function, a given source line can correspond to
3029 several places where that function is inlined.
3033 In all those cases, @value{GDBN} will insert a breakpoint at all
3034 the relevant locations.
3036 A breakpoint with multiple locations is displayed in the breakpoint
3037 table using several rows---one header row, followed by one row for
3038 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3039 address column. The rows for individual locations contain the actual
3040 addresses for locations, and show the functions to which those
3041 locations belong. The number column for a location is of the form
3042 @var{breakpoint-number}.@var{location-number}.
3047 Num Type Disp Enb Address What
3048 1 breakpoint keep y <MULTIPLE>
3050 breakpoint already hit 1 time
3051 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3052 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3055 Each location can be individually enabled or disabled by passing
3056 @var{breakpoint-number}.@var{location-number} as argument to the
3057 @code{enable} and @code{disable} commands. Note that you cannot
3058 delete the individual locations from the list, you can only delete the
3059 entire list of locations that belong to their parent breakpoint (with
3060 the @kbd{delete @var{num}} command, where @var{num} is the number of
3061 the parent breakpoint, 1 in the above example). Disabling or enabling
3062 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3063 that belong to that breakpoint.
3065 @cindex pending breakpoints
3066 It's quite common to have a breakpoint inside a shared library.
3067 Shared libraries can be loaded and unloaded explicitly,
3068 and possibly repeatedly, as the program is executed. To support
3069 this use case, @value{GDBN} updates breakpoint locations whenever
3070 any shared library is loaded or unloaded. Typically, you would
3071 set a breakpoint in a shared library at the beginning of your
3072 debugging session, when the library is not loaded, and when the
3073 symbols from the library are not available. When you try to set
3074 breakpoint, @value{GDBN} will ask you if you want to set
3075 a so called @dfn{pending breakpoint}---breakpoint whose address
3076 is not yet resolved.
3078 After the program is run, whenever a new shared library is loaded,
3079 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3080 shared library contains the symbol or line referred to by some
3081 pending breakpoint, that breakpoint is resolved and becomes an
3082 ordinary breakpoint. When a library is unloaded, all breakpoints
3083 that refer to its symbols or source lines become pending again.
3085 This logic works for breakpoints with multiple locations, too. For
3086 example, if you have a breakpoint in a C@t{++} template function, and
3087 a newly loaded shared library has an instantiation of that template,
3088 a new location is added to the list of locations for the breakpoint.
3090 Except for having unresolved address, pending breakpoints do not
3091 differ from regular breakpoints. You can set conditions or commands,
3092 enable and disable them and perform other breakpoint operations.
3094 @value{GDBN} provides some additional commands for controlling what
3095 happens when the @samp{break} command cannot resolve breakpoint
3096 address specification to an address:
3098 @kindex set breakpoint pending
3099 @kindex show breakpoint pending
3101 @item set breakpoint pending auto
3102 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3103 location, it queries you whether a pending breakpoint should be created.
3105 @item set breakpoint pending on
3106 This indicates that an unrecognized breakpoint location should automatically
3107 result in a pending breakpoint being created.
3109 @item set breakpoint pending off
3110 This indicates that pending breakpoints are not to be created. Any
3111 unrecognized breakpoint location results in an error. This setting does
3112 not affect any pending breakpoints previously created.
3114 @item show breakpoint pending
3115 Show the current behavior setting for creating pending breakpoints.
3118 The settings above only affect the @code{break} command and its
3119 variants. Once breakpoint is set, it will be automatically updated
3120 as shared libraries are loaded and unloaded.
3122 @cindex automatic hardware breakpoints
3123 For some targets, @value{GDBN} can automatically decide if hardware or
3124 software breakpoints should be used, depending on whether the
3125 breakpoint address is read-only or read-write. This applies to
3126 breakpoints set with the @code{break} command as well as to internal
3127 breakpoints set by commands like @code{next} and @code{finish}. For
3128 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3131 You can control this automatic behaviour with the following commands::
3133 @kindex set breakpoint auto-hw
3134 @kindex show breakpoint auto-hw
3136 @item set breakpoint auto-hw on
3137 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3138 will try to use the target memory map to decide if software or hardware
3139 breakpoint must be used.
3141 @item set breakpoint auto-hw off
3142 This indicates @value{GDBN} should not automatically select breakpoint
3143 type. If the target provides a memory map, @value{GDBN} will warn when
3144 trying to set software breakpoint at a read-only address.
3148 @cindex negative breakpoint numbers
3149 @cindex internal @value{GDBN} breakpoints
3150 @value{GDBN} itself sometimes sets breakpoints in your program for
3151 special purposes, such as proper handling of @code{longjmp} (in C
3152 programs). These internal breakpoints are assigned negative numbers,
3153 starting with @code{-1}; @samp{info breakpoints} does not display them.
3154 You can see these breakpoints with the @value{GDBN} maintenance command
3155 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3158 @node Set Watchpoints
3159 @subsection Setting Watchpoints
3161 @cindex setting watchpoints
3162 You can use a watchpoint to stop execution whenever the value of an
3163 expression changes, without having to predict a particular place where
3164 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3165 The expression may be as simple as the value of a single variable, or
3166 as complex as many variables combined by operators. Examples include:
3170 A reference to the value of a single variable.
3173 An address cast to an appropriate data type. For example,
3174 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3175 address (assuming an @code{int} occupies 4 bytes).
3178 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3179 expression can use any operators valid in the program's native
3180 language (@pxref{Languages}).
3183 @cindex software watchpoints
3184 @cindex hardware watchpoints
3185 Depending on your system, watchpoints may be implemented in software or
3186 hardware. @value{GDBN} does software watchpointing by single-stepping your
3187 program and testing the variable's value each time, which is hundreds of
3188 times slower than normal execution. (But this may still be worth it, to
3189 catch errors where you have no clue what part of your program is the
3192 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3193 x86-based targets, @value{GDBN} includes support for hardware
3194 watchpoints, which do not slow down the running of your program.
3198 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3199 Set a watchpoint for an expression. @value{GDBN} will break when the
3200 expression @var{expr} is written into by the program and its value
3201 changes. The simplest (and the most popular) use of this command is
3202 to watch the value of a single variable:
3205 (@value{GDBP}) watch foo
3208 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3209 clause, @value{GDBN} breaks only when the thread identified by
3210 @var{threadnum} changes the value of @var{expr}. If any other threads
3211 change the value of @var{expr}, @value{GDBN} will not break. Note
3212 that watchpoints restricted to a single thread in this way only work
3213 with Hardware Watchpoints.
3216 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3217 Set a watchpoint that will break when the value of @var{expr} is read
3221 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3222 Set a watchpoint that will break when @var{expr} is either read from
3223 or written into by the program.
3225 @kindex info watchpoints @r{[}@var{n}@r{]}
3226 @item info watchpoints
3227 This command prints a list of watchpoints, breakpoints, and catchpoints;
3228 it is the same as @code{info break} (@pxref{Set Breaks}).
3231 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3232 watchpoints execute very quickly, and the debugger reports a change in
3233 value at the exact instruction where the change occurs. If @value{GDBN}
3234 cannot set a hardware watchpoint, it sets a software watchpoint, which
3235 executes more slowly and reports the change in value at the next
3236 @emph{statement}, not the instruction, after the change occurs.
3238 @cindex use only software watchpoints
3239 You can force @value{GDBN} to use only software watchpoints with the
3240 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3241 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3242 the underlying system supports them. (Note that hardware-assisted
3243 watchpoints that were set @emph{before} setting
3244 @code{can-use-hw-watchpoints} to zero will still use the hardware
3245 mechanism of watching expression values.)
3248 @item set can-use-hw-watchpoints
3249 @kindex set can-use-hw-watchpoints
3250 Set whether or not to use hardware watchpoints.
3252 @item show can-use-hw-watchpoints
3253 @kindex show can-use-hw-watchpoints
3254 Show the current mode of using hardware watchpoints.
3257 For remote targets, you can restrict the number of hardware
3258 watchpoints @value{GDBN} will use, see @ref{set remote
3259 hardware-breakpoint-limit}.
3261 When you issue the @code{watch} command, @value{GDBN} reports
3264 Hardware watchpoint @var{num}: @var{expr}
3268 if it was able to set a hardware watchpoint.
3270 Currently, the @code{awatch} and @code{rwatch} commands can only set
3271 hardware watchpoints, because accesses to data that don't change the
3272 value of the watched expression cannot be detected without examining
3273 every instruction as it is being executed, and @value{GDBN} does not do
3274 that currently. If @value{GDBN} finds that it is unable to set a
3275 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3276 will print a message like this:
3279 Expression cannot be implemented with read/access watchpoint.
3282 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3283 data type of the watched expression is wider than what a hardware
3284 watchpoint on the target machine can handle. For example, some systems
3285 can only watch regions that are up to 4 bytes wide; on such systems you
3286 cannot set hardware watchpoints for an expression that yields a
3287 double-precision floating-point number (which is typically 8 bytes
3288 wide). As a work-around, it might be possible to break the large region
3289 into a series of smaller ones and watch them with separate watchpoints.
3291 If you set too many hardware watchpoints, @value{GDBN} might be unable
3292 to insert all of them when you resume the execution of your program.
3293 Since the precise number of active watchpoints is unknown until such
3294 time as the program is about to be resumed, @value{GDBN} might not be
3295 able to warn you about this when you set the watchpoints, and the
3296 warning will be printed only when the program is resumed:
3299 Hardware watchpoint @var{num}: Could not insert watchpoint
3303 If this happens, delete or disable some of the watchpoints.
3305 Watching complex expressions that reference many variables can also
3306 exhaust the resources available for hardware-assisted watchpoints.
3307 That's because @value{GDBN} needs to watch every variable in the
3308 expression with separately allocated resources.
3310 The SPARClite DSU will generate traps when a program accesses some data
3311 or instruction address that is assigned to the debug registers. For the
3312 data addresses, DSU facilitates the @code{watch} command. However the
3313 hardware breakpoint registers can only take two data watchpoints, and
3314 both watchpoints must be the same kind. For example, you can set two
3315 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3316 @strong{or} two with @code{awatch} commands, but you cannot set one
3317 watchpoint with one command and the other with a different command.
3318 @value{GDBN} will reject the command if you try to mix watchpoints.
3319 Delete or disable unused watchpoint commands before setting new ones.
3321 If you call a function interactively using @code{print} or @code{call},
3322 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3323 kind of breakpoint or the call completes.
3325 @value{GDBN} automatically deletes watchpoints that watch local
3326 (automatic) variables, or expressions that involve such variables, when
3327 they go out of scope, that is, when the execution leaves the block in
3328 which these variables were defined. In particular, when the program
3329 being debugged terminates, @emph{all} local variables go out of scope,
3330 and so only watchpoints that watch global variables remain set. If you
3331 rerun the program, you will need to set all such watchpoints again. One
3332 way of doing that would be to set a code breakpoint at the entry to the
3333 @code{main} function and when it breaks, set all the watchpoints.
3335 @cindex watchpoints and threads
3336 @cindex threads and watchpoints
3337 In multi-threaded programs, watchpoints will detect changes to the
3338 watched expression from every thread.
3341 @emph{Warning:} In multi-threaded programs, software watchpoints
3342 have only limited usefulness. If @value{GDBN} creates a software
3343 watchpoint, it can only watch the value of an expression @emph{in a
3344 single thread}. If you are confident that the expression can only
3345 change due to the current thread's activity (and if you are also
3346 confident that no other thread can become current), then you can use
3347 software watchpoints as usual. However, @value{GDBN} may not notice
3348 when a non-current thread's activity changes the expression. (Hardware
3349 watchpoints, in contrast, watch an expression in all threads.)
3352 @xref{set remote hardware-watchpoint-limit}.
3354 @node Set Catchpoints
3355 @subsection Setting Catchpoints
3356 @cindex catchpoints, setting
3357 @cindex exception handlers
3358 @cindex event handling
3360 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3361 kinds of program events, such as C@t{++} exceptions or the loading of a
3362 shared library. Use the @code{catch} command to set a catchpoint.
3366 @item catch @var{event}
3367 Stop when @var{event} occurs. @var{event} can be any of the following:
3370 @cindex stop on C@t{++} exceptions
3371 The throwing of a C@t{++} exception.
3374 The catching of a C@t{++} exception.
3377 @cindex Ada exception catching
3378 @cindex catch Ada exceptions
3379 An Ada exception being raised. If an exception name is specified
3380 at the end of the command (eg @code{catch exception Program_Error}),
3381 the debugger will stop only when this specific exception is raised.
3382 Otherwise, the debugger stops execution when any Ada exception is raised.
3384 @item exception unhandled
3385 An exception that was raised but is not handled by the program.
3388 A failed Ada assertion.
3391 @cindex break on fork/exec
3392 A call to @code{exec}. This is currently only available for HP-UX.
3395 A call to @code{fork}. This is currently only available for HP-UX.
3398 A call to @code{vfork}. This is currently only available for HP-UX.
3401 @itemx load @var{libname}
3402 @cindex break on load/unload of shared library
3403 The dynamic loading of any shared library, or the loading of the library
3404 @var{libname}. This is currently only available for HP-UX.
3407 @itemx unload @var{libname}
3408 The unloading of any dynamically loaded shared library, or the unloading
3409 of the library @var{libname}. This is currently only available for HP-UX.
3412 @item tcatch @var{event}
3413 Set a catchpoint that is enabled only for one stop. The catchpoint is
3414 automatically deleted after the first time the event is caught.
3418 Use the @code{info break} command to list the current catchpoints.
3420 There are currently some limitations to C@t{++} exception handling
3421 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3425 If you call a function interactively, @value{GDBN} normally returns
3426 control to you when the function has finished executing. If the call
3427 raises an exception, however, the call may bypass the mechanism that
3428 returns control to you and cause your program either to abort or to
3429 simply continue running until it hits a breakpoint, catches a signal
3430 that @value{GDBN} is listening for, or exits. This is the case even if
3431 you set a catchpoint for the exception; catchpoints on exceptions are
3432 disabled within interactive calls.
3435 You cannot raise an exception interactively.
3438 You cannot install an exception handler interactively.
3441 @cindex raise exceptions
3442 Sometimes @code{catch} is not the best way to debug exception handling:
3443 if you need to know exactly where an exception is raised, it is better to
3444 stop @emph{before} the exception handler is called, since that way you
3445 can see the stack before any unwinding takes place. If you set a
3446 breakpoint in an exception handler instead, it may not be easy to find
3447 out where the exception was raised.
3449 To stop just before an exception handler is called, you need some
3450 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3451 raised by calling a library function named @code{__raise_exception}
3452 which has the following ANSI C interface:
3455 /* @var{addr} is where the exception identifier is stored.
3456 @var{id} is the exception identifier. */
3457 void __raise_exception (void **addr, void *id);
3461 To make the debugger catch all exceptions before any stack
3462 unwinding takes place, set a breakpoint on @code{__raise_exception}
3463 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3465 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3466 that depends on the value of @var{id}, you can stop your program when
3467 a specific exception is raised. You can use multiple conditional
3468 breakpoints to stop your program when any of a number of exceptions are
3473 @subsection Deleting Breakpoints
3475 @cindex clearing breakpoints, watchpoints, catchpoints
3476 @cindex deleting breakpoints, watchpoints, catchpoints
3477 It is often necessary to eliminate a breakpoint, watchpoint, or
3478 catchpoint once it has done its job and you no longer want your program
3479 to stop there. This is called @dfn{deleting} the breakpoint. A
3480 breakpoint that has been deleted no longer exists; it is forgotten.
3482 With the @code{clear} command you can delete breakpoints according to
3483 where they are in your program. With the @code{delete} command you can
3484 delete individual breakpoints, watchpoints, or catchpoints by specifying
3485 their breakpoint numbers.
3487 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3488 automatically ignores breakpoints on the first instruction to be executed
3489 when you continue execution without changing the execution address.
3494 Delete any breakpoints at the next instruction to be executed in the
3495 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3496 the innermost frame is selected, this is a good way to delete a
3497 breakpoint where your program just stopped.
3499 @item clear @var{location}
3500 Delete any breakpoints set at the specified @var{location}.
3501 @xref{Specify Location}, for the various forms of @var{location}; the
3502 most useful ones are listed below:
3505 @item clear @var{function}
3506 @itemx clear @var{filename}:@var{function}
3507 Delete any breakpoints set at entry to the named @var{function}.
3509 @item clear @var{linenum}
3510 @itemx clear @var{filename}:@var{linenum}
3511 Delete any breakpoints set at or within the code of the specified
3512 @var{linenum} of the specified @var{filename}.
3515 @cindex delete breakpoints
3517 @kindex d @r{(@code{delete})}
3518 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3519 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3520 ranges specified as arguments. If no argument is specified, delete all
3521 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3522 confirm off}). You can abbreviate this command as @code{d}.
3526 @subsection Disabling Breakpoints
3528 @cindex enable/disable a breakpoint
3529 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3530 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3531 it had been deleted, but remembers the information on the breakpoint so
3532 that you can @dfn{enable} it again later.
3534 You disable and enable breakpoints, watchpoints, and catchpoints with
3535 the @code{enable} and @code{disable} commands, optionally specifying one
3536 or more breakpoint numbers as arguments. Use @code{info break} or
3537 @code{info watch} to print a list of breakpoints, watchpoints, and
3538 catchpoints if you do not know which numbers to use.
3540 Disabling and enabling a breakpoint that has multiple locations
3541 affects all of its locations.
3543 A breakpoint, watchpoint, or catchpoint can have any of four different
3544 states of enablement:
3548 Enabled. The breakpoint stops your program. A breakpoint set
3549 with the @code{break} command starts out in this state.
3551 Disabled. The breakpoint has no effect on your program.
3553 Enabled once. The breakpoint stops your program, but then becomes
3556 Enabled for deletion. The breakpoint stops your program, but
3557 immediately after it does so it is deleted permanently. A breakpoint
3558 set with the @code{tbreak} command starts out in this state.
3561 You can use the following commands to enable or disable breakpoints,
3562 watchpoints, and catchpoints:
3566 @kindex dis @r{(@code{disable})}
3567 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3568 Disable the specified breakpoints---or all breakpoints, if none are
3569 listed. A disabled breakpoint has no effect but is not forgotten. All
3570 options such as ignore-counts, conditions and commands are remembered in
3571 case the breakpoint is enabled again later. You may abbreviate
3572 @code{disable} as @code{dis}.
3575 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3576 Enable the specified breakpoints (or all defined breakpoints). They
3577 become effective once again in stopping your program.
3579 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3580 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3581 of these breakpoints immediately after stopping your program.
3583 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3584 Enable the specified breakpoints to work once, then die. @value{GDBN}
3585 deletes any of these breakpoints as soon as your program stops there.
3586 Breakpoints set by the @code{tbreak} command start out in this state.
3589 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3590 @c confusing: tbreak is also initially enabled.
3591 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3592 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3593 subsequently, they become disabled or enabled only when you use one of
3594 the commands above. (The command @code{until} can set and delete a
3595 breakpoint of its own, but it does not change the state of your other
3596 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3600 @subsection Break Conditions
3601 @cindex conditional breakpoints
3602 @cindex breakpoint conditions
3604 @c FIXME what is scope of break condition expr? Context where wanted?
3605 @c in particular for a watchpoint?
3606 The simplest sort of breakpoint breaks every time your program reaches a
3607 specified place. You can also specify a @dfn{condition} for a
3608 breakpoint. A condition is just a Boolean expression in your
3609 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3610 a condition evaluates the expression each time your program reaches it,
3611 and your program stops only if the condition is @emph{true}.
3613 This is the converse of using assertions for program validation; in that
3614 situation, you want to stop when the assertion is violated---that is,
3615 when the condition is false. In C, if you want to test an assertion expressed
3616 by the condition @var{assert}, you should set the condition
3617 @samp{! @var{assert}} on the appropriate breakpoint.
3619 Conditions are also accepted for watchpoints; you may not need them,
3620 since a watchpoint is inspecting the value of an expression anyhow---but
3621 it might be simpler, say, to just set a watchpoint on a variable name,
3622 and specify a condition that tests whether the new value is an interesting
3625 Break conditions can have side effects, and may even call functions in
3626 your program. This can be useful, for example, to activate functions
3627 that log program progress, or to use your own print functions to
3628 format special data structures. The effects are completely predictable
3629 unless there is another enabled breakpoint at the same address. (In
3630 that case, @value{GDBN} might see the other breakpoint first and stop your
3631 program without checking the condition of this one.) Note that
3632 breakpoint commands are usually more convenient and flexible than break
3634 purpose of performing side effects when a breakpoint is reached
3635 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3637 Break conditions can be specified when a breakpoint is set, by using
3638 @samp{if} in the arguments to the @code{break} command. @xref{Set
3639 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3640 with the @code{condition} command.
3642 You can also use the @code{if} keyword with the @code{watch} command.
3643 The @code{catch} command does not recognize the @code{if} keyword;
3644 @code{condition} is the only way to impose a further condition on a
3649 @item condition @var{bnum} @var{expression}
3650 Specify @var{expression} as the break condition for breakpoint,
3651 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3652 breakpoint @var{bnum} stops your program only if the value of
3653 @var{expression} is true (nonzero, in C). When you use
3654 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3655 syntactic correctness, and to determine whether symbols in it have
3656 referents in the context of your breakpoint. If @var{expression} uses
3657 symbols not referenced in the context of the breakpoint, @value{GDBN}
3658 prints an error message:
3661 No symbol "foo" in current context.
3666 not actually evaluate @var{expression} at the time the @code{condition}
3667 command (or a command that sets a breakpoint with a condition, like
3668 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3670 @item condition @var{bnum}
3671 Remove the condition from breakpoint number @var{bnum}. It becomes
3672 an ordinary unconditional breakpoint.
3675 @cindex ignore count (of breakpoint)
3676 A special case of a breakpoint condition is to stop only when the
3677 breakpoint has been reached a certain number of times. This is so
3678 useful that there is a special way to do it, using the @dfn{ignore
3679 count} of the breakpoint. Every breakpoint has an ignore count, which
3680 is an integer. Most of the time, the ignore count is zero, and
3681 therefore has no effect. But if your program reaches a breakpoint whose
3682 ignore count is positive, then instead of stopping, it just decrements
3683 the ignore count by one and continues. As a result, if the ignore count
3684 value is @var{n}, the breakpoint does not stop the next @var{n} times
3685 your program reaches it.
3689 @item ignore @var{bnum} @var{count}
3690 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3691 The next @var{count} times the breakpoint is reached, your program's
3692 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3695 To make the breakpoint stop the next time it is reached, specify
3698 When you use @code{continue} to resume execution of your program from a
3699 breakpoint, you can specify an ignore count directly as an argument to
3700 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3701 Stepping,,Continuing and Stepping}.
3703 If a breakpoint has a positive ignore count and a condition, the
3704 condition is not checked. Once the ignore count reaches zero,
3705 @value{GDBN} resumes checking the condition.
3707 You could achieve the effect of the ignore count with a condition such
3708 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3709 is decremented each time. @xref{Convenience Vars, ,Convenience
3713 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3716 @node Break Commands
3717 @subsection Breakpoint Command Lists
3719 @cindex breakpoint commands
3720 You can give any breakpoint (or watchpoint or catchpoint) a series of
3721 commands to execute when your program stops due to that breakpoint. For
3722 example, you might want to print the values of certain expressions, or
3723 enable other breakpoints.
3727 @kindex end@r{ (breakpoint commands)}
3728 @item commands @r{[}@var{bnum}@r{]}
3729 @itemx @dots{} @var{command-list} @dots{}
3731 Specify a list of commands for breakpoint number @var{bnum}. The commands
3732 themselves appear on the following lines. Type a line containing just
3733 @code{end} to terminate the commands.
3735 To remove all commands from a breakpoint, type @code{commands} and
3736 follow it immediately with @code{end}; that is, give no commands.
3738 With no @var{bnum} argument, @code{commands} refers to the last
3739 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3740 recently encountered).
3743 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3744 disabled within a @var{command-list}.
3746 You can use breakpoint commands to start your program up again. Simply
3747 use the @code{continue} command, or @code{step}, or any other command
3748 that resumes execution.
3750 Any other commands in the command list, after a command that resumes
3751 execution, are ignored. This is because any time you resume execution
3752 (even with a simple @code{next} or @code{step}), you may encounter
3753 another breakpoint---which could have its own command list, leading to
3754 ambiguities about which list to execute.
3757 If the first command you specify in a command list is @code{silent}, the
3758 usual message about stopping at a breakpoint is not printed. This may
3759 be desirable for breakpoints that are to print a specific message and
3760 then continue. If none of the remaining commands print anything, you
3761 see no sign that the breakpoint was reached. @code{silent} is
3762 meaningful only at the beginning of a breakpoint command list.
3764 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3765 print precisely controlled output, and are often useful in silent
3766 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3768 For example, here is how you could use breakpoint commands to print the
3769 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3775 printf "x is %d\n",x
3780 One application for breakpoint commands is to compensate for one bug so
3781 you can test for another. Put a breakpoint just after the erroneous line
3782 of code, give it a condition to detect the case in which something
3783 erroneous has been done, and give it commands to assign correct values
3784 to any variables that need them. End with the @code{continue} command
3785 so that your program does not stop, and start with the @code{silent}
3786 command so that no output is produced. Here is an example:
3797 @node Breakpoint Menus
3798 @subsection Breakpoint Menus
3800 @cindex symbol overloading
3802 Some programming languages (notably C@t{++} and Objective-C) permit a
3803 single function name
3804 to be defined several times, for application in different contexts.
3805 This is called @dfn{overloading}. When a function name is overloaded,
3806 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3807 a breakpoint. You can use explicit signature of the function, as in
3808 @samp{break @var{function}(@var{types})}, to specify which
3809 particular version of the function you want. Otherwise, @value{GDBN} offers
3810 you a menu of numbered choices for different possible breakpoints, and
3811 waits for your selection with the prompt @samp{>}. The first two
3812 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3813 sets a breakpoint at each definition of @var{function}, and typing
3814 @kbd{0} aborts the @code{break} command without setting any new
3817 For example, the following session excerpt shows an attempt to set a
3818 breakpoint at the overloaded symbol @code{String::after}.
3819 We choose three particular definitions of that function name:
3821 @c FIXME! This is likely to change to show arg type lists, at least
3824 (@value{GDBP}) b String::after
3827 [2] file:String.cc; line number:867
3828 [3] file:String.cc; line number:860
3829 [4] file:String.cc; line number:875
3830 [5] file:String.cc; line number:853
3831 [6] file:String.cc; line number:846
3832 [7] file:String.cc; line number:735
3834 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3835 Breakpoint 2 at 0xb344: file String.cc, line 875.
3836 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3837 Multiple breakpoints were set.
3838 Use the "delete" command to delete unwanted
3844 @c @ifclear BARETARGET
3845 @node Error in Breakpoints
3846 @subsection ``Cannot insert breakpoints''
3848 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3850 Under some operating systems, breakpoints cannot be used in a program if
3851 any other process is running that program. In this situation,
3852 attempting to run or continue a program with a breakpoint causes
3853 @value{GDBN} to print an error message:
3856 Cannot insert breakpoints.
3857 The same program may be running in another process.
3860 When this happens, you have three ways to proceed:
3864 Remove or disable the breakpoints, then continue.
3867 Suspend @value{GDBN}, and copy the file containing your program to a new
3868 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3869 that @value{GDBN} should run your program under that name.
3870 Then start your program again.
3873 Relink your program so that the text segment is nonsharable, using the
3874 linker option @samp{-N}. The operating system limitation may not apply
3875 to nonsharable executables.
3879 A similar message can be printed if you request too many active
3880 hardware-assisted breakpoints and watchpoints:
3882 @c FIXME: the precise wording of this message may change; the relevant
3883 @c source change is not committed yet (Sep 3, 1999).
3885 Stopped; cannot insert breakpoints.
3886 You may have requested too many hardware breakpoints and watchpoints.
3890 This message is printed when you attempt to resume the program, since
3891 only then @value{GDBN} knows exactly how many hardware breakpoints and
3892 watchpoints it needs to insert.
3894 When this message is printed, you need to disable or remove some of the
3895 hardware-assisted breakpoints and watchpoints, and then continue.
3897 @node Breakpoint-related Warnings
3898 @subsection ``Breakpoint address adjusted...''
3899 @cindex breakpoint address adjusted
3901 Some processor architectures place constraints on the addresses at
3902 which breakpoints may be placed. For architectures thus constrained,
3903 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3904 with the constraints dictated by the architecture.
3906 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3907 a VLIW architecture in which a number of RISC-like instructions may be
3908 bundled together for parallel execution. The FR-V architecture
3909 constrains the location of a breakpoint instruction within such a
3910 bundle to the instruction with the lowest address. @value{GDBN}
3911 honors this constraint by adjusting a breakpoint's address to the
3912 first in the bundle.
3914 It is not uncommon for optimized code to have bundles which contain
3915 instructions from different source statements, thus it may happen that
3916 a breakpoint's address will be adjusted from one source statement to
3917 another. Since this adjustment may significantly alter @value{GDBN}'s
3918 breakpoint related behavior from what the user expects, a warning is
3919 printed when the breakpoint is first set and also when the breakpoint
3922 A warning like the one below is printed when setting a breakpoint
3923 that's been subject to address adjustment:
3926 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3929 Such warnings are printed both for user settable and @value{GDBN}'s
3930 internal breakpoints. If you see one of these warnings, you should
3931 verify that a breakpoint set at the adjusted address will have the
3932 desired affect. If not, the breakpoint in question may be removed and
3933 other breakpoints may be set which will have the desired behavior.
3934 E.g., it may be sufficient to place the breakpoint at a later
3935 instruction. A conditional breakpoint may also be useful in some
3936 cases to prevent the breakpoint from triggering too often.
3938 @value{GDBN} will also issue a warning when stopping at one of these
3939 adjusted breakpoints:
3942 warning: Breakpoint 1 address previously adjusted from 0x00010414
3946 When this warning is encountered, it may be too late to take remedial
3947 action except in cases where the breakpoint is hit earlier or more
3948 frequently than expected.
3950 @node Continuing and Stepping
3951 @section Continuing and Stepping
3955 @cindex resuming execution
3956 @dfn{Continuing} means resuming program execution until your program
3957 completes normally. In contrast, @dfn{stepping} means executing just
3958 one more ``step'' of your program, where ``step'' may mean either one
3959 line of source code, or one machine instruction (depending on what
3960 particular command you use). Either when continuing or when stepping,
3961 your program may stop even sooner, due to a breakpoint or a signal. (If
3962 it stops due to a signal, you may want to use @code{handle}, or use
3963 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3967 @kindex c @r{(@code{continue})}
3968 @kindex fg @r{(resume foreground execution)}
3969 @item continue @r{[}@var{ignore-count}@r{]}
3970 @itemx c @r{[}@var{ignore-count}@r{]}
3971 @itemx fg @r{[}@var{ignore-count}@r{]}
3972 Resume program execution, at the address where your program last stopped;
3973 any breakpoints set at that address are bypassed. The optional argument
3974 @var{ignore-count} allows you to specify a further number of times to
3975 ignore a breakpoint at this location; its effect is like that of
3976 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
3978 The argument @var{ignore-count} is meaningful only when your program
3979 stopped due to a breakpoint. At other times, the argument to
3980 @code{continue} is ignored.
3982 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3983 debugged program is deemed to be the foreground program) are provided
3984 purely for convenience, and have exactly the same behavior as
3988 To resume execution at a different place, you can use @code{return}
3989 (@pxref{Returning, ,Returning from a Function}) to go back to the
3990 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3991 Different Address}) to go to an arbitrary location in your program.
3993 A typical technique for using stepping is to set a breakpoint
3994 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
3995 beginning of the function or the section of your program where a problem
3996 is believed to lie, run your program until it stops at that breakpoint,
3997 and then step through the suspect area, examining the variables that are
3998 interesting, until you see the problem happen.
4002 @kindex s @r{(@code{step})}
4004 Continue running your program until control reaches a different source
4005 line, then stop it and return control to @value{GDBN}. This command is
4006 abbreviated @code{s}.
4009 @c "without debugging information" is imprecise; actually "without line
4010 @c numbers in the debugging information". (gcc -g1 has debugging info but
4011 @c not line numbers). But it seems complex to try to make that
4012 @c distinction here.
4013 @emph{Warning:} If you use the @code{step} command while control is
4014 within a function that was compiled without debugging information,
4015 execution proceeds until control reaches a function that does have
4016 debugging information. Likewise, it will not step into a function which
4017 is compiled without debugging information. To step through functions
4018 without debugging information, use the @code{stepi} command, described
4022 The @code{step} command only stops at the first instruction of a source
4023 line. This prevents the multiple stops that could otherwise occur in
4024 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4025 to stop if a function that has debugging information is called within
4026 the line. In other words, @code{step} @emph{steps inside} any functions
4027 called within the line.
4029 Also, the @code{step} command only enters a function if there is line
4030 number information for the function. Otherwise it acts like the
4031 @code{next} command. This avoids problems when using @code{cc -gl}
4032 on MIPS machines. Previously, @code{step} entered subroutines if there
4033 was any debugging information about the routine.
4035 @item step @var{count}
4036 Continue running as in @code{step}, but do so @var{count} times. If a
4037 breakpoint is reached, or a signal not related to stepping occurs before
4038 @var{count} steps, stepping stops right away.
4041 @kindex n @r{(@code{next})}
4042 @item next @r{[}@var{count}@r{]}
4043 Continue to the next source line in the current (innermost) stack frame.
4044 This is similar to @code{step}, but function calls that appear within
4045 the line of code are executed without stopping. Execution stops when
4046 control reaches a different line of code at the original stack level
4047 that was executing when you gave the @code{next} command. This command
4048 is abbreviated @code{n}.
4050 An argument @var{count} is a repeat count, as for @code{step}.
4053 @c FIX ME!! Do we delete this, or is there a way it fits in with
4054 @c the following paragraph? --- Vctoria
4056 @c @code{next} within a function that lacks debugging information acts like
4057 @c @code{step}, but any function calls appearing within the code of the
4058 @c function are executed without stopping.
4060 The @code{next} command only stops at the first instruction of a
4061 source line. This prevents multiple stops that could otherwise occur in
4062 @code{switch} statements, @code{for} loops, etc.
4064 @kindex set step-mode
4066 @cindex functions without line info, and stepping
4067 @cindex stepping into functions with no line info
4068 @itemx set step-mode on
4069 The @code{set step-mode on} command causes the @code{step} command to
4070 stop at the first instruction of a function which contains no debug line
4071 information rather than stepping over it.
4073 This is useful in cases where you may be interested in inspecting the
4074 machine instructions of a function which has no symbolic info and do not
4075 want @value{GDBN} to automatically skip over this function.
4077 @item set step-mode off
4078 Causes the @code{step} command to step over any functions which contains no
4079 debug information. This is the default.
4081 @item show step-mode
4082 Show whether @value{GDBN} will stop in or step over functions without
4083 source line debug information.
4087 Continue running until just after function in the selected stack frame
4088 returns. Print the returned value (if any).
4090 Contrast this with the @code{return} command (@pxref{Returning,
4091 ,Returning from a Function}).
4094 @kindex u @r{(@code{until})}
4095 @cindex run until specified location
4098 Continue running until a source line past the current line, in the
4099 current stack frame, is reached. This command is used to avoid single
4100 stepping through a loop more than once. It is like the @code{next}
4101 command, except that when @code{until} encounters a jump, it
4102 automatically continues execution until the program counter is greater
4103 than the address of the jump.
4105 This means that when you reach the end of a loop after single stepping
4106 though it, @code{until} makes your program continue execution until it
4107 exits the loop. In contrast, a @code{next} command at the end of a loop
4108 simply steps back to the beginning of the loop, which forces you to step
4109 through the next iteration.
4111 @code{until} always stops your program if it attempts to exit the current
4114 @code{until} may produce somewhat counterintuitive results if the order
4115 of machine code does not match the order of the source lines. For
4116 example, in the following excerpt from a debugging session, the @code{f}
4117 (@code{frame}) command shows that execution is stopped at line
4118 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4122 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4124 (@value{GDBP}) until
4125 195 for ( ; argc > 0; NEXTARG) @{
4128 This happened because, for execution efficiency, the compiler had
4129 generated code for the loop closure test at the end, rather than the
4130 start, of the loop---even though the test in a C @code{for}-loop is
4131 written before the body of the loop. The @code{until} command appeared
4132 to step back to the beginning of the loop when it advanced to this
4133 expression; however, it has not really gone to an earlier
4134 statement---not in terms of the actual machine code.
4136 @code{until} with no argument works by means of single
4137 instruction stepping, and hence is slower than @code{until} with an
4140 @item until @var{location}
4141 @itemx u @var{location}
4142 Continue running your program until either the specified location is
4143 reached, or the current stack frame returns. @var{location} is any of
4144 the forms described in @ref{Specify Location}.
4145 This form of the command uses temporary breakpoints, and
4146 hence is quicker than @code{until} without an argument. The specified
4147 location is actually reached only if it is in the current frame. This
4148 implies that @code{until} can be used to skip over recursive function
4149 invocations. For instance in the code below, if the current location is
4150 line @code{96}, issuing @code{until 99} will execute the program up to
4151 line @code{99} in the same invocation of factorial, i.e., after the inner
4152 invocations have returned.
4155 94 int factorial (int value)
4157 96 if (value > 1) @{
4158 97 value *= factorial (value - 1);
4165 @kindex advance @var{location}
4166 @itemx advance @var{location}
4167 Continue running the program up to the given @var{location}. An argument is
4168 required, which should be of one of the forms described in
4169 @ref{Specify Location}.
4170 Execution will also stop upon exit from the current stack
4171 frame. This command is similar to @code{until}, but @code{advance} will
4172 not skip over recursive function calls, and the target location doesn't
4173 have to be in the same frame as the current one.
4177 @kindex si @r{(@code{stepi})}
4179 @itemx stepi @var{arg}
4181 Execute one machine instruction, then stop and return to the debugger.
4183 It is often useful to do @samp{display/i $pc} when stepping by machine
4184 instructions. This makes @value{GDBN} automatically display the next
4185 instruction to be executed, each time your program stops. @xref{Auto
4186 Display,, Automatic Display}.
4188 An argument is a repeat count, as in @code{step}.
4192 @kindex ni @r{(@code{nexti})}
4194 @itemx nexti @var{arg}
4196 Execute one machine instruction, but if it is a function call,
4197 proceed until the function returns.
4199 An argument is a repeat count, as in @code{next}.
4206 A signal is an asynchronous event that can happen in a program. The
4207 operating system defines the possible kinds of signals, and gives each
4208 kind a name and a number. For example, in Unix @code{SIGINT} is the
4209 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4210 @code{SIGSEGV} is the signal a program gets from referencing a place in
4211 memory far away from all the areas in use; @code{SIGALRM} occurs when
4212 the alarm clock timer goes off (which happens only if your program has
4213 requested an alarm).
4215 @cindex fatal signals
4216 Some signals, including @code{SIGALRM}, are a normal part of the
4217 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4218 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4219 program has not specified in advance some other way to handle the signal.
4220 @code{SIGINT} does not indicate an error in your program, but it is normally
4221 fatal so it can carry out the purpose of the interrupt: to kill the program.
4223 @value{GDBN} has the ability to detect any occurrence of a signal in your
4224 program. You can tell @value{GDBN} in advance what to do for each kind of
4227 @cindex handling signals
4228 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4229 @code{SIGALRM} be silently passed to your program
4230 (so as not to interfere with their role in the program's functioning)
4231 but to stop your program immediately whenever an error signal happens.
4232 You can change these settings with the @code{handle} command.
4235 @kindex info signals
4239 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4240 handle each one. You can use this to see the signal numbers of all
4241 the defined types of signals.
4243 @item info signals @var{sig}
4244 Similar, but print information only about the specified signal number.
4246 @code{info handle} is an alias for @code{info signals}.
4249 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4250 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4251 can be the number of a signal or its name (with or without the
4252 @samp{SIG} at the beginning); a list of signal numbers of the form
4253 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4254 known signals. Optional arguments @var{keywords}, described below,
4255 say what change to make.
4259 The keywords allowed by the @code{handle} command can be abbreviated.
4260 Their full names are:
4264 @value{GDBN} should not stop your program when this signal happens. It may
4265 still print a message telling you that the signal has come in.
4268 @value{GDBN} should stop your program when this signal happens. This implies
4269 the @code{print} keyword as well.
4272 @value{GDBN} should print a message when this signal happens.
4275 @value{GDBN} should not mention the occurrence of the signal at all. This
4276 implies the @code{nostop} keyword as well.
4280 @value{GDBN} should allow your program to see this signal; your program
4281 can handle the signal, or else it may terminate if the signal is fatal
4282 and not handled. @code{pass} and @code{noignore} are synonyms.
4286 @value{GDBN} should not allow your program to see this signal.
4287 @code{nopass} and @code{ignore} are synonyms.
4291 When a signal stops your program, the signal is not visible to the
4293 continue. Your program sees the signal then, if @code{pass} is in
4294 effect for the signal in question @emph{at that time}. In other words,
4295 after @value{GDBN} reports a signal, you can use the @code{handle}
4296 command with @code{pass} or @code{nopass} to control whether your
4297 program sees that signal when you continue.
4299 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4300 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4301 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4304 You can also use the @code{signal} command to prevent your program from
4305 seeing a signal, or cause it to see a signal it normally would not see,
4306 or to give it any signal at any time. For example, if your program stopped
4307 due to some sort of memory reference error, you might store correct
4308 values into the erroneous variables and continue, hoping to see more
4309 execution; but your program would probably terminate immediately as
4310 a result of the fatal signal once it saw the signal. To prevent this,
4311 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4315 @section Stopping and Starting Multi-thread Programs
4317 When your program has multiple threads (@pxref{Threads,, Debugging
4318 Programs with Multiple Threads}), you can choose whether to set
4319 breakpoints on all threads, or on a particular thread.
4322 @cindex breakpoints and threads
4323 @cindex thread breakpoints
4324 @kindex break @dots{} thread @var{threadno}
4325 @item break @var{linespec} thread @var{threadno}
4326 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4327 @var{linespec} specifies source lines; there are several ways of
4328 writing them (@pxref{Specify Location}), but the effect is always to
4329 specify some source line.
4331 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4332 to specify that you only want @value{GDBN} to stop the program when a
4333 particular thread reaches this breakpoint. @var{threadno} is one of the
4334 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4335 column of the @samp{info threads} display.
4337 If you do not specify @samp{thread @var{threadno}} when you set a
4338 breakpoint, the breakpoint applies to @emph{all} threads of your
4341 You can use the @code{thread} qualifier on conditional breakpoints as
4342 well; in this case, place @samp{thread @var{threadno}} before the
4343 breakpoint condition, like this:
4346 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4351 @cindex stopped threads
4352 @cindex threads, stopped
4353 Whenever your program stops under @value{GDBN} for any reason,
4354 @emph{all} threads of execution stop, not just the current thread. This
4355 allows you to examine the overall state of the program, including
4356 switching between threads, without worrying that things may change
4359 @cindex thread breakpoints and system calls
4360 @cindex system calls and thread breakpoints
4361 @cindex premature return from system calls
4362 There is an unfortunate side effect. If one thread stops for a
4363 breakpoint, or for some other reason, and another thread is blocked in a
4364 system call, then the system call may return prematurely. This is a
4365 consequence of the interaction between multiple threads and the signals
4366 that @value{GDBN} uses to implement breakpoints and other events that
4369 To handle this problem, your program should check the return value of
4370 each system call and react appropriately. This is good programming
4373 For example, do not write code like this:
4379 The call to @code{sleep} will return early if a different thread stops
4380 at a breakpoint or for some other reason.
4382 Instead, write this:
4387 unslept = sleep (unslept);
4390 A system call is allowed to return early, so the system is still
4391 conforming to its specification. But @value{GDBN} does cause your
4392 multi-threaded program to behave differently than it would without
4395 Also, @value{GDBN} uses internal breakpoints in the thread library to
4396 monitor certain events such as thread creation and thread destruction.
4397 When such an event happens, a system call in another thread may return
4398 prematurely, even though your program does not appear to stop.
4400 @cindex continuing threads
4401 @cindex threads, continuing
4402 Conversely, whenever you restart the program, @emph{all} threads start
4403 executing. @emph{This is true even when single-stepping} with commands
4404 like @code{step} or @code{next}.
4406 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4407 Since thread scheduling is up to your debugging target's operating
4408 system (not controlled by @value{GDBN}), other threads may
4409 execute more than one statement while the current thread completes a
4410 single step. Moreover, in general other threads stop in the middle of a
4411 statement, rather than at a clean statement boundary, when the program
4414 You might even find your program stopped in another thread after
4415 continuing or even single-stepping. This happens whenever some other
4416 thread runs into a breakpoint, a signal, or an exception before the
4417 first thread completes whatever you requested.
4419 On some OSes, you can lock the OS scheduler and thus allow only a single
4423 @item set scheduler-locking @var{mode}
4424 @cindex scheduler locking mode
4425 @cindex lock scheduler
4426 Set the scheduler locking mode. If it is @code{off}, then there is no
4427 locking and any thread may run at any time. If @code{on}, then only the
4428 current thread may run when the inferior is resumed. The @code{step}
4429 mode optimizes for single-stepping. It stops other threads from
4430 ``seizing the prompt'' by preempting the current thread while you are
4431 stepping. Other threads will only rarely (or never) get a chance to run
4432 when you step. They are more likely to run when you @samp{next} over a
4433 function call, and they are completely free to run when you use commands
4434 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4435 thread hits a breakpoint during its timeslice, they will never steal the
4436 @value{GDBN} prompt away from the thread that you are debugging.
4438 @item show scheduler-locking
4439 Display the current scheduler locking mode.
4444 @chapter Examining the Stack
4446 When your program has stopped, the first thing you need to know is where it
4447 stopped and how it got there.
4450 Each time your program performs a function call, information about the call
4452 That information includes the location of the call in your program,
4453 the arguments of the call,
4454 and the local variables of the function being called.
4455 The information is saved in a block of data called a @dfn{stack frame}.
4456 The stack frames are allocated in a region of memory called the @dfn{call
4459 When your program stops, the @value{GDBN} commands for examining the
4460 stack allow you to see all of this information.
4462 @cindex selected frame
4463 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4464 @value{GDBN} commands refer implicitly to the selected frame. In
4465 particular, whenever you ask @value{GDBN} for the value of a variable in
4466 your program, the value is found in the selected frame. There are
4467 special @value{GDBN} commands to select whichever frame you are
4468 interested in. @xref{Selection, ,Selecting a Frame}.
4470 When your program stops, @value{GDBN} automatically selects the
4471 currently executing frame and describes it briefly, similar to the
4472 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4475 * Frames:: Stack frames
4476 * Backtrace:: Backtraces
4477 * Selection:: Selecting a frame
4478 * Frame Info:: Information on a frame
4483 @section Stack Frames
4485 @cindex frame, definition
4487 The call stack is divided up into contiguous pieces called @dfn{stack
4488 frames}, or @dfn{frames} for short; each frame is the data associated
4489 with one call to one function. The frame contains the arguments given
4490 to the function, the function's local variables, and the address at
4491 which the function is executing.
4493 @cindex initial frame
4494 @cindex outermost frame
4495 @cindex innermost frame
4496 When your program is started, the stack has only one frame, that of the
4497 function @code{main}. This is called the @dfn{initial} frame or the
4498 @dfn{outermost} frame. Each time a function is called, a new frame is
4499 made. Each time a function returns, the frame for that function invocation
4500 is eliminated. If a function is recursive, there can be many frames for
4501 the same function. The frame for the function in which execution is
4502 actually occurring is called the @dfn{innermost} frame. This is the most
4503 recently created of all the stack frames that still exist.
4505 @cindex frame pointer
4506 Inside your program, stack frames are identified by their addresses. A
4507 stack frame consists of many bytes, each of which has its own address; each
4508 kind of computer has a convention for choosing one byte whose
4509 address serves as the address of the frame. Usually this address is kept
4510 in a register called the @dfn{frame pointer register}
4511 (@pxref{Registers, $fp}) while execution is going on in that frame.
4513 @cindex frame number
4514 @value{GDBN} assigns numbers to all existing stack frames, starting with
4515 zero for the innermost frame, one for the frame that called it,
4516 and so on upward. These numbers do not really exist in your program;
4517 they are assigned by @value{GDBN} to give you a way of designating stack
4518 frames in @value{GDBN} commands.
4520 @c The -fomit-frame-pointer below perennially causes hbox overflow
4521 @c underflow problems.
4522 @cindex frameless execution
4523 Some compilers provide a way to compile functions so that they operate
4524 without stack frames. (For example, the @value{NGCC} option
4526 @samp{-fomit-frame-pointer}
4528 generates functions without a frame.)
4529 This is occasionally done with heavily used library functions to save
4530 the frame setup time. @value{GDBN} has limited facilities for dealing
4531 with these function invocations. If the innermost function invocation
4532 has no stack frame, @value{GDBN} nevertheless regards it as though
4533 it had a separate frame, which is numbered zero as usual, allowing
4534 correct tracing of the function call chain. However, @value{GDBN} has
4535 no provision for frameless functions elsewhere in the stack.
4538 @kindex frame@r{, command}
4539 @cindex current stack frame
4540 @item frame @var{args}
4541 The @code{frame} command allows you to move from one stack frame to another,
4542 and to print the stack frame you select. @var{args} may be either the
4543 address of the frame or the stack frame number. Without an argument,
4544 @code{frame} prints the current stack frame.
4546 @kindex select-frame
4547 @cindex selecting frame silently
4549 The @code{select-frame} command allows you to move from one stack frame
4550 to another without printing the frame. This is the silent version of
4558 @cindex call stack traces
4559 A backtrace is a summary of how your program got where it is. It shows one
4560 line per frame, for many frames, starting with the currently executing
4561 frame (frame zero), followed by its caller (frame one), and on up the
4566 @kindex bt @r{(@code{backtrace})}
4569 Print a backtrace of the entire stack: one line per frame for all
4570 frames in the stack.
4572 You can stop the backtrace at any time by typing the system interrupt
4573 character, normally @kbd{Ctrl-c}.
4575 @item backtrace @var{n}
4577 Similar, but print only the innermost @var{n} frames.
4579 @item backtrace -@var{n}
4581 Similar, but print only the outermost @var{n} frames.
4583 @item backtrace full
4585 @itemx bt full @var{n}
4586 @itemx bt full -@var{n}
4587 Print the values of the local variables also. @var{n} specifies the
4588 number of frames to print, as described above.
4593 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4594 are additional aliases for @code{backtrace}.
4596 @cindex multiple threads, backtrace
4597 In a multi-threaded program, @value{GDBN} by default shows the
4598 backtrace only for the current thread. To display the backtrace for
4599 several or all of the threads, use the command @code{thread apply}
4600 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4601 apply all backtrace}, @value{GDBN} will display the backtrace for all
4602 the threads; this is handy when you debug a core dump of a
4603 multi-threaded program.
4605 Each line in the backtrace shows the frame number and the function name.
4606 The program counter value is also shown---unless you use @code{set
4607 print address off}. The backtrace also shows the source file name and
4608 line number, as well as the arguments to the function. The program
4609 counter value is omitted if it is at the beginning of the code for that
4612 Here is an example of a backtrace. It was made with the command
4613 @samp{bt 3}, so it shows the innermost three frames.
4617 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4619 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4620 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4622 (More stack frames follow...)
4627 The display for frame zero does not begin with a program counter
4628 value, indicating that your program has stopped at the beginning of the
4629 code for line @code{993} of @code{builtin.c}.
4631 @cindex value optimized out, in backtrace
4632 @cindex function call arguments, optimized out
4633 If your program was compiled with optimizations, some compilers will
4634 optimize away arguments passed to functions if those arguments are
4635 never used after the call. Such optimizations generate code that
4636 passes arguments through registers, but doesn't store those arguments
4637 in the stack frame. @value{GDBN} has no way of displaying such
4638 arguments in stack frames other than the innermost one. Here's what
4639 such a backtrace might look like:
4643 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4645 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4646 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4648 (More stack frames follow...)
4653 The values of arguments that were not saved in their stack frames are
4654 shown as @samp{<value optimized out>}.
4656 If you need to display the values of such optimized-out arguments,
4657 either deduce that from other variables whose values depend on the one
4658 you are interested in, or recompile without optimizations.
4660 @cindex backtrace beyond @code{main} function
4661 @cindex program entry point
4662 @cindex startup code, and backtrace
4663 Most programs have a standard user entry point---a place where system
4664 libraries and startup code transition into user code. For C this is
4665 @code{main}@footnote{
4666 Note that embedded programs (the so-called ``free-standing''
4667 environment) are not required to have a @code{main} function as the
4668 entry point. They could even have multiple entry points.}.
4669 When @value{GDBN} finds the entry function in a backtrace
4670 it will terminate the backtrace, to avoid tracing into highly
4671 system-specific (and generally uninteresting) code.
4673 If you need to examine the startup code, or limit the number of levels
4674 in a backtrace, you can change this behavior:
4677 @item set backtrace past-main
4678 @itemx set backtrace past-main on
4679 @kindex set backtrace
4680 Backtraces will continue past the user entry point.
4682 @item set backtrace past-main off
4683 Backtraces will stop when they encounter the user entry point. This is the
4686 @item show backtrace past-main
4687 @kindex show backtrace
4688 Display the current user entry point backtrace policy.
4690 @item set backtrace past-entry
4691 @itemx set backtrace past-entry on
4692 Backtraces will continue past the internal entry point of an application.
4693 This entry point is encoded by the linker when the application is built,
4694 and is likely before the user entry point @code{main} (or equivalent) is called.
4696 @item set backtrace past-entry off
4697 Backtraces will stop when they encounter the internal entry point of an
4698 application. This is the default.
4700 @item show backtrace past-entry
4701 Display the current internal entry point backtrace policy.
4703 @item set backtrace limit @var{n}
4704 @itemx set backtrace limit 0
4705 @cindex backtrace limit
4706 Limit the backtrace to @var{n} levels. A value of zero means
4709 @item show backtrace limit
4710 Display the current limit on backtrace levels.
4714 @section Selecting a Frame
4716 Most commands for examining the stack and other data in your program work on
4717 whichever stack frame is selected at the moment. Here are the commands for
4718 selecting a stack frame; all of them finish by printing a brief description
4719 of the stack frame just selected.
4722 @kindex frame@r{, selecting}
4723 @kindex f @r{(@code{frame})}
4726 Select frame number @var{n}. Recall that frame zero is the innermost
4727 (currently executing) frame, frame one is the frame that called the
4728 innermost one, and so on. The highest-numbered frame is the one for
4731 @item frame @var{addr}
4733 Select the frame at address @var{addr}. This is useful mainly if the
4734 chaining of stack frames has been damaged by a bug, making it
4735 impossible for @value{GDBN} to assign numbers properly to all frames. In
4736 addition, this can be useful when your program has multiple stacks and
4737 switches between them.
4739 On the SPARC architecture, @code{frame} needs two addresses to
4740 select an arbitrary frame: a frame pointer and a stack pointer.
4742 On the MIPS and Alpha architecture, it needs two addresses: a stack
4743 pointer and a program counter.
4745 On the 29k architecture, it needs three addresses: a register stack
4746 pointer, a program counter, and a memory stack pointer.
4750 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4751 advances toward the outermost frame, to higher frame numbers, to frames
4752 that have existed longer. @var{n} defaults to one.
4755 @kindex do @r{(@code{down})}
4757 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4758 advances toward the innermost frame, to lower frame numbers, to frames
4759 that were created more recently. @var{n} defaults to one. You may
4760 abbreviate @code{down} as @code{do}.
4763 All of these commands end by printing two lines of output describing the
4764 frame. The first line shows the frame number, the function name, the
4765 arguments, and the source file and line number of execution in that
4766 frame. The second line shows the text of that source line.
4774 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4776 10 read_input_file (argv[i]);
4780 After such a printout, the @code{list} command with no arguments
4781 prints ten lines centered on the point of execution in the frame.
4782 You can also edit the program at the point of execution with your favorite
4783 editing program by typing @code{edit}.
4784 @xref{List, ,Printing Source Lines},
4788 @kindex down-silently
4790 @item up-silently @var{n}
4791 @itemx down-silently @var{n}
4792 These two commands are variants of @code{up} and @code{down},
4793 respectively; they differ in that they do their work silently, without
4794 causing display of the new frame. They are intended primarily for use
4795 in @value{GDBN} command scripts, where the output might be unnecessary and
4800 @section Information About a Frame
4802 There are several other commands to print information about the selected
4808 When used without any argument, this command does not change which
4809 frame is selected, but prints a brief description of the currently
4810 selected stack frame. It can be abbreviated @code{f}. With an
4811 argument, this command is used to select a stack frame.
4812 @xref{Selection, ,Selecting a Frame}.
4815 @kindex info f @r{(@code{info frame})}
4818 This command prints a verbose description of the selected stack frame,
4823 the address of the frame
4825 the address of the next frame down (called by this frame)
4827 the address of the next frame up (caller of this frame)
4829 the language in which the source code corresponding to this frame is written
4831 the address of the frame's arguments
4833 the address of the frame's local variables
4835 the program counter saved in it (the address of execution in the caller frame)
4837 which registers were saved in the frame
4840 @noindent The verbose description is useful when
4841 something has gone wrong that has made the stack format fail to fit
4842 the usual conventions.
4844 @item info frame @var{addr}
4845 @itemx info f @var{addr}
4846 Print a verbose description of the frame at address @var{addr}, without
4847 selecting that frame. The selected frame remains unchanged by this
4848 command. This requires the same kind of address (more than one for some
4849 architectures) that you specify in the @code{frame} command.
4850 @xref{Selection, ,Selecting a Frame}.
4854 Print the arguments of the selected frame, each on a separate line.
4858 Print the local variables of the selected frame, each on a separate
4859 line. These are all variables (declared either static or automatic)
4860 accessible at the point of execution of the selected frame.
4863 @cindex catch exceptions, list active handlers
4864 @cindex exception handlers, how to list
4866 Print a list of all the exception handlers that are active in the
4867 current stack frame at the current point of execution. To see other
4868 exception handlers, visit the associated frame (using the @code{up},
4869 @code{down}, or @code{frame} commands); then type @code{info catch}.
4870 @xref{Set Catchpoints, , Setting Catchpoints}.
4876 @chapter Examining Source Files
4878 @value{GDBN} can print parts of your program's source, since the debugging
4879 information recorded in the program tells @value{GDBN} what source files were
4880 used to build it. When your program stops, @value{GDBN} spontaneously prints
4881 the line where it stopped. Likewise, when you select a stack frame
4882 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4883 execution in that frame has stopped. You can print other portions of
4884 source files by explicit command.
4886 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4887 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4888 @value{GDBN} under @sc{gnu} Emacs}.
4891 * List:: Printing source lines
4892 * Specify Location:: How to specify code locations
4893 * Edit:: Editing source files
4894 * Search:: Searching source files
4895 * Source Path:: Specifying source directories
4896 * Machine Code:: Source and machine code
4900 @section Printing Source Lines
4903 @kindex l @r{(@code{list})}
4904 To print lines from a source file, use the @code{list} command
4905 (abbreviated @code{l}). By default, ten lines are printed.
4906 There are several ways to specify what part of the file you want to
4907 print; see @ref{Specify Location}, for the full list.
4909 Here are the forms of the @code{list} command most commonly used:
4912 @item list @var{linenum}
4913 Print lines centered around line number @var{linenum} in the
4914 current source file.
4916 @item list @var{function}
4917 Print lines centered around the beginning of function
4921 Print more lines. If the last lines printed were printed with a
4922 @code{list} command, this prints lines following the last lines
4923 printed; however, if the last line printed was a solitary line printed
4924 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4925 Stack}), this prints lines centered around that line.
4928 Print lines just before the lines last printed.
4931 @cindex @code{list}, how many lines to display
4932 By default, @value{GDBN} prints ten source lines with any of these forms of
4933 the @code{list} command. You can change this using @code{set listsize}:
4936 @kindex set listsize
4937 @item set listsize @var{count}
4938 Make the @code{list} command display @var{count} source lines (unless
4939 the @code{list} argument explicitly specifies some other number).
4941 @kindex show listsize
4943 Display the number of lines that @code{list} prints.
4946 Repeating a @code{list} command with @key{RET} discards the argument,
4947 so it is equivalent to typing just @code{list}. This is more useful
4948 than listing the same lines again. An exception is made for an
4949 argument of @samp{-}; that argument is preserved in repetition so that
4950 each repetition moves up in the source file.
4952 In general, the @code{list} command expects you to supply zero, one or two
4953 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4954 of writing them (@pxref{Specify Location}), but the effect is always
4955 to specify some source line.
4957 Here is a complete description of the possible arguments for @code{list}:
4960 @item list @var{linespec}
4961 Print lines centered around the line specified by @var{linespec}.
4963 @item list @var{first},@var{last}
4964 Print lines from @var{first} to @var{last}. Both arguments are
4965 linespecs. When a @code{list} command has two linespecs, and the
4966 source file of the second linespec is omitted, this refers to
4967 the same source file as the first linespec.
4969 @item list ,@var{last}
4970 Print lines ending with @var{last}.
4972 @item list @var{first},
4973 Print lines starting with @var{first}.
4976 Print lines just after the lines last printed.
4979 Print lines just before the lines last printed.
4982 As described in the preceding table.
4985 @node Specify Location
4986 @section Specifying a Location
4987 @cindex specifying location
4990 Several @value{GDBN} commands accept arguments that specify a location
4991 of your program's code. Since @value{GDBN} is a source-level
4992 debugger, a location usually specifies some line in the source code;
4993 for that reason, locations are also known as @dfn{linespecs}.
4995 Here are all the different ways of specifying a code location that
4996 @value{GDBN} understands:
5000 Specifies the line number @var{linenum} of the current source file.
5003 @itemx +@var{offset}
5004 Specifies the line @var{offset} lines before or after the @dfn{current
5005 line}. For the @code{list} command, the current line is the last one
5006 printed; for the breakpoint commands, this is the line at which
5007 execution stopped in the currently selected @dfn{stack frame}
5008 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5009 used as the second of the two linespecs in a @code{list} command,
5010 this specifies the line @var{offset} lines up or down from the first
5013 @item @var{filename}:@var{linenum}
5014 Specifies the line @var{linenum} in the source file @var{filename}.
5016 @item @var{function}
5017 Specifies the line that begins the body of the function @var{function}.
5018 For example, in C, this is the line with the open brace.
5020 @item @var{filename}:@var{function}
5021 Specifies the line that begins the body of the function @var{function}
5022 in the file @var{filename}. You only need the file name with a
5023 function name to avoid ambiguity when there are identically named
5024 functions in different source files.
5026 @item *@var{address}
5027 Specifies the program address @var{address}. For line-oriented
5028 commands, such as @code{list} and @code{edit}, this specifies a source
5029 line that contains @var{address}. For @code{break} and other
5030 breakpoint oriented commands, this can be used to set breakpoints in
5031 parts of your program which do not have debugging information or
5034 Here @var{address} may be any expression valid in the current working
5035 language (@pxref{Languages, working language}) that specifies a code
5036 address. As a convenience, @value{GDBN} extends the semantics of
5037 expressions used in locations to cover the situations that frequently
5038 happen during debugging. Here are the various forms of @var{address}:
5041 @item @var{expression}
5042 Any expression valid in the current working language.
5044 @item @var{funcaddr}
5045 An address of a function or procedure derived from its name. In C,
5046 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5047 simply the function's name @var{function} (and actually a special case
5048 of a valid expression). In Pascal and Modula-2, this is
5049 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5050 (although the Pascal form also works).
5052 This form specifies the address of the function's first instruction,
5053 before the stack frame and arguments have been set up.
5055 @item '@var{filename}'::@var{funcaddr}
5056 Like @var{funcaddr} above, but also specifies the name of the source
5057 file explicitly. This is useful if the name of the function does not
5058 specify the function unambiguously, e.g., if there are several
5059 functions with identical names in different source files.
5066 @section Editing Source Files
5067 @cindex editing source files
5070 @kindex e @r{(@code{edit})}
5071 To edit the lines in a source file, use the @code{edit} command.
5072 The editing program of your choice
5073 is invoked with the current line set to
5074 the active line in the program.
5075 Alternatively, there are several ways to specify what part of the file you
5076 want to print if you want to see other parts of the program:
5079 @item edit @var{location}
5080 Edit the source file specified by @code{location}. Editing starts at
5081 that @var{location}, e.g., at the specified source line of the
5082 specified file. @xref{Specify Location}, for all the possible forms
5083 of the @var{location} argument; here are the forms of the @code{edit}
5084 command most commonly used:
5087 @item edit @var{number}
5088 Edit the current source file with @var{number} as the active line number.
5090 @item edit @var{function}
5091 Edit the file containing @var{function} at the beginning of its definition.
5096 @subsection Choosing your Editor
5097 You can customize @value{GDBN} to use any editor you want
5099 The only restriction is that your editor (say @code{ex}), recognizes the
5100 following command-line syntax:
5102 ex +@var{number} file
5104 The optional numeric value +@var{number} specifies the number of the line in
5105 the file where to start editing.}.
5106 By default, it is @file{@value{EDITOR}}, but you can change this
5107 by setting the environment variable @code{EDITOR} before using
5108 @value{GDBN}. For example, to configure @value{GDBN} to use the
5109 @code{vi} editor, you could use these commands with the @code{sh} shell:
5115 or in the @code{csh} shell,
5117 setenv EDITOR /usr/bin/vi
5122 @section Searching Source Files
5123 @cindex searching source files
5125 There are two commands for searching through the current source file for a
5130 @kindex forward-search
5131 @item forward-search @var{regexp}
5132 @itemx search @var{regexp}
5133 The command @samp{forward-search @var{regexp}} checks each line,
5134 starting with the one following the last line listed, for a match for
5135 @var{regexp}. It lists the line that is found. You can use the
5136 synonym @samp{search @var{regexp}} or abbreviate the command name as
5139 @kindex reverse-search
5140 @item reverse-search @var{regexp}
5141 The command @samp{reverse-search @var{regexp}} checks each line, starting
5142 with the one before the last line listed and going backward, for a match
5143 for @var{regexp}. It lists the line that is found. You can abbreviate
5144 this command as @code{rev}.
5148 @section Specifying Source Directories
5151 @cindex directories for source files
5152 Executable programs sometimes do not record the directories of the source
5153 files from which they were compiled, just the names. Even when they do,
5154 the directories could be moved between the compilation and your debugging
5155 session. @value{GDBN} has a list of directories to search for source files;
5156 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5157 it tries all the directories in the list, in the order they are present
5158 in the list, until it finds a file with the desired name.
5160 For example, suppose an executable references the file
5161 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5162 @file{/mnt/cross}. The file is first looked up literally; if this
5163 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5164 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5165 message is printed. @value{GDBN} does not look up the parts of the
5166 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5167 Likewise, the subdirectories of the source path are not searched: if
5168 the source path is @file{/mnt/cross}, and the binary refers to
5169 @file{foo.c}, @value{GDBN} would not find it under
5170 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5172 Plain file names, relative file names with leading directories, file
5173 names containing dots, etc.@: are all treated as described above; for
5174 instance, if the source path is @file{/mnt/cross}, and the source file
5175 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5176 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5177 that---@file{/mnt/cross/foo.c}.
5179 Note that the executable search path is @emph{not} used to locate the
5182 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5183 any information it has cached about where source files are found and where
5184 each line is in the file.
5188 When you start @value{GDBN}, its source path includes only @samp{cdir}
5189 and @samp{cwd}, in that order.
5190 To add other directories, use the @code{directory} command.
5192 The search path is used to find both program source files and @value{GDBN}
5193 script files (read using the @samp{-command} option and @samp{source} command).
5195 In addition to the source path, @value{GDBN} provides a set of commands
5196 that manage a list of source path substitution rules. A @dfn{substitution
5197 rule} specifies how to rewrite source directories stored in the program's
5198 debug information in case the sources were moved to a different
5199 directory between compilation and debugging. A rule is made of
5200 two strings, the first specifying what needs to be rewritten in
5201 the path, and the second specifying how it should be rewritten.
5202 In @ref{set substitute-path}, we name these two parts @var{from} and
5203 @var{to} respectively. @value{GDBN} does a simple string replacement
5204 of @var{from} with @var{to} at the start of the directory part of the
5205 source file name, and uses that result instead of the original file
5206 name to look up the sources.
5208 Using the previous example, suppose the @file{foo-1.0} tree has been
5209 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5210 @value{GDBN} to replace @file{/usr/src} in all source path names with
5211 @file{/mnt/cross}. The first lookup will then be
5212 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5213 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5214 substitution rule, use the @code{set substitute-path} command
5215 (@pxref{set substitute-path}).
5217 To avoid unexpected substitution results, a rule is applied only if the
5218 @var{from} part of the directory name ends at a directory separator.
5219 For instance, a rule substituting @file{/usr/source} into
5220 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5221 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5222 is applied only at the beginning of the directory name, this rule will
5223 not be applied to @file{/root/usr/source/baz.c} either.
5225 In many cases, you can achieve the same result using the @code{directory}
5226 command. However, @code{set substitute-path} can be more efficient in
5227 the case where the sources are organized in a complex tree with multiple
5228 subdirectories. With the @code{directory} command, you need to add each
5229 subdirectory of your project. If you moved the entire tree while
5230 preserving its internal organization, then @code{set substitute-path}
5231 allows you to direct the debugger to all the sources with one single
5234 @code{set substitute-path} is also more than just a shortcut command.
5235 The source path is only used if the file at the original location no
5236 longer exists. On the other hand, @code{set substitute-path} modifies
5237 the debugger behavior to look at the rewritten location instead. So, if
5238 for any reason a source file that is not relevant to your executable is
5239 located at the original location, a substitution rule is the only
5240 method available to point @value{GDBN} at the new location.
5243 @item directory @var{dirname} @dots{}
5244 @item dir @var{dirname} @dots{}
5245 Add directory @var{dirname} to the front of the source path. Several
5246 directory names may be given to this command, separated by @samp{:}
5247 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5248 part of absolute file names) or
5249 whitespace. You may specify a directory that is already in the source
5250 path; this moves it forward, so @value{GDBN} searches it sooner.
5254 @vindex $cdir@r{, convenience variable}
5255 @vindex $cwd@r{, convenience variable}
5256 @cindex compilation directory
5257 @cindex current directory
5258 @cindex working directory
5259 @cindex directory, current
5260 @cindex directory, compilation
5261 You can use the string @samp{$cdir} to refer to the compilation
5262 directory (if one is recorded), and @samp{$cwd} to refer to the current
5263 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5264 tracks the current working directory as it changes during your @value{GDBN}
5265 session, while the latter is immediately expanded to the current
5266 directory at the time you add an entry to the source path.
5269 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5271 @c RET-repeat for @code{directory} is explicitly disabled, but since
5272 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5274 @item show directories
5275 @kindex show directories
5276 Print the source path: show which directories it contains.
5278 @anchor{set substitute-path}
5279 @item set substitute-path @var{from} @var{to}
5280 @kindex set substitute-path
5281 Define a source path substitution rule, and add it at the end of the
5282 current list of existing substitution rules. If a rule with the same
5283 @var{from} was already defined, then the old rule is also deleted.
5285 For example, if the file @file{/foo/bar/baz.c} was moved to
5286 @file{/mnt/cross/baz.c}, then the command
5289 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5293 will tell @value{GDBN} to replace @samp{/usr/src} with
5294 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5295 @file{baz.c} even though it was moved.
5297 In the case when more than one substitution rule have been defined,
5298 the rules are evaluated one by one in the order where they have been
5299 defined. The first one matching, if any, is selected to perform
5302 For instance, if we had entered the following commands:
5305 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5306 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5310 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5311 @file{/mnt/include/defs.h} by using the first rule. However, it would
5312 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5313 @file{/mnt/src/lib/foo.c}.
5316 @item unset substitute-path [path]
5317 @kindex unset substitute-path
5318 If a path is specified, search the current list of substitution rules
5319 for a rule that would rewrite that path. Delete that rule if found.
5320 A warning is emitted by the debugger if no rule could be found.
5322 If no path is specified, then all substitution rules are deleted.
5324 @item show substitute-path [path]
5325 @kindex show substitute-path
5326 If a path is specified, then print the source path substitution rule
5327 which would rewrite that path, if any.
5329 If no path is specified, then print all existing source path substitution
5334 If your source path is cluttered with directories that are no longer of
5335 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5336 versions of source. You can correct the situation as follows:
5340 Use @code{directory} with no argument to reset the source path to its default value.
5343 Use @code{directory} with suitable arguments to reinstall the
5344 directories you want in the source path. You can add all the
5345 directories in one command.
5349 @section Source and Machine Code
5350 @cindex source line and its code address
5352 You can use the command @code{info line} to map source lines to program
5353 addresses (and vice versa), and the command @code{disassemble} to display
5354 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5355 mode, the @code{info line} command causes the arrow to point to the
5356 line specified. Also, @code{info line} prints addresses in symbolic form as
5361 @item info line @var{linespec}
5362 Print the starting and ending addresses of the compiled code for
5363 source line @var{linespec}. You can specify source lines in any of
5364 the ways documented in @ref{Specify Location}.
5367 For example, we can use @code{info line} to discover the location of
5368 the object code for the first line of function
5369 @code{m4_changequote}:
5371 @c FIXME: I think this example should also show the addresses in
5372 @c symbolic form, as they usually would be displayed.
5374 (@value{GDBP}) info line m4_changequote
5375 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5379 @cindex code address and its source line
5380 We can also inquire (using @code{*@var{addr}} as the form for
5381 @var{linespec}) what source line covers a particular address:
5383 (@value{GDBP}) info line *0x63ff
5384 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5387 @cindex @code{$_} and @code{info line}
5388 @cindex @code{x} command, default address
5389 @kindex x@r{(examine), and} info line
5390 After @code{info line}, the default address for the @code{x} command
5391 is changed to the starting address of the line, so that @samp{x/i} is
5392 sufficient to begin examining the machine code (@pxref{Memory,
5393 ,Examining Memory}). Also, this address is saved as the value of the
5394 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5399 @cindex assembly instructions
5400 @cindex instructions, assembly
5401 @cindex machine instructions
5402 @cindex listing machine instructions
5404 This specialized command dumps a range of memory as machine
5405 instructions. The default memory range is the function surrounding the
5406 program counter of the selected frame. A single argument to this
5407 command is a program counter value; @value{GDBN} dumps the function
5408 surrounding this value. Two arguments specify a range of addresses
5409 (first inclusive, second exclusive) to dump.
5412 The following example shows the disassembly of a range of addresses of
5413 HP PA-RISC 2.0 code:
5416 (@value{GDBP}) disas 0x32c4 0x32e4
5417 Dump of assembler code from 0x32c4 to 0x32e4:
5418 0x32c4 <main+204>: addil 0,dp
5419 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5420 0x32cc <main+212>: ldil 0x3000,r31
5421 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5422 0x32d4 <main+220>: ldo 0(r31),rp
5423 0x32d8 <main+224>: addil -0x800,dp
5424 0x32dc <main+228>: ldo 0x588(r1),r26
5425 0x32e0 <main+232>: ldil 0x3000,r31
5426 End of assembler dump.
5429 Some architectures have more than one commonly-used set of instruction
5430 mnemonics or other syntax.
5432 For programs that were dynamically linked and use shared libraries,
5433 instructions that call functions or branch to locations in the shared
5434 libraries might show a seemingly bogus location---it's actually a
5435 location of the relocation table. On some architectures, @value{GDBN}
5436 might be able to resolve these to actual function names.
5439 @kindex set disassembly-flavor
5440 @cindex Intel disassembly flavor
5441 @cindex AT&T disassembly flavor
5442 @item set disassembly-flavor @var{instruction-set}
5443 Select the instruction set to use when disassembling the
5444 program via the @code{disassemble} or @code{x/i} commands.
5446 Currently this command is only defined for the Intel x86 family. You
5447 can set @var{instruction-set} to either @code{intel} or @code{att}.
5448 The default is @code{att}, the AT&T flavor used by default by Unix
5449 assemblers for x86-based targets.
5451 @kindex show disassembly-flavor
5452 @item show disassembly-flavor
5453 Show the current setting of the disassembly flavor.
5458 @chapter Examining Data
5460 @cindex printing data
5461 @cindex examining data
5464 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5465 @c document because it is nonstandard... Under Epoch it displays in a
5466 @c different window or something like that.
5467 The usual way to examine data in your program is with the @code{print}
5468 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5469 evaluates and prints the value of an expression of the language your
5470 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5471 Different Languages}).
5474 @item print @var{expr}
5475 @itemx print /@var{f} @var{expr}
5476 @var{expr} is an expression (in the source language). By default the
5477 value of @var{expr} is printed in a format appropriate to its data type;
5478 you can choose a different format by specifying @samp{/@var{f}}, where
5479 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5483 @itemx print /@var{f}
5484 @cindex reprint the last value
5485 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5486 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5487 conveniently inspect the same value in an alternative format.
5490 A more low-level way of examining data is with the @code{x} command.
5491 It examines data in memory at a specified address and prints it in a
5492 specified format. @xref{Memory, ,Examining Memory}.
5494 If you are interested in information about types, or about how the
5495 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5496 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5500 * Expressions:: Expressions
5501 * Variables:: Program variables
5502 * Arrays:: Artificial arrays
5503 * Output Formats:: Output formats
5504 * Memory:: Examining memory
5505 * Auto Display:: Automatic display
5506 * Print Settings:: Print settings
5507 * Value History:: Value history
5508 * Convenience Vars:: Convenience variables
5509 * Registers:: Registers
5510 * Floating Point Hardware:: Floating point hardware
5511 * Vector Unit:: Vector Unit
5512 * OS Information:: Auxiliary data provided by operating system
5513 * Memory Region Attributes:: Memory region attributes
5514 * Dump/Restore Files:: Copy between memory and a file
5515 * Core File Generation:: Cause a program dump its core
5516 * Character Sets:: Debugging programs that use a different
5517 character set than GDB does
5518 * Caching Remote Data:: Data caching for remote targets
5522 @section Expressions
5525 @code{print} and many other @value{GDBN} commands accept an expression and
5526 compute its value. Any kind of constant, variable or operator defined
5527 by the programming language you are using is valid in an expression in
5528 @value{GDBN}. This includes conditional expressions, function calls,
5529 casts, and string constants. It also includes preprocessor macros, if
5530 you compiled your program to include this information; see
5533 @cindex arrays in expressions
5534 @value{GDBN} supports array constants in expressions input by
5535 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5536 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5537 memory that is @code{malloc}ed in the target program.
5539 Because C is so widespread, most of the expressions shown in examples in
5540 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5541 Languages}, for information on how to use expressions in other
5544 In this section, we discuss operators that you can use in @value{GDBN}
5545 expressions regardless of your programming language.
5547 @cindex casts, in expressions
5548 Casts are supported in all languages, not just in C, because it is so
5549 useful to cast a number into a pointer in order to examine a structure
5550 at that address in memory.
5551 @c FIXME: casts supported---Mod2 true?
5553 @value{GDBN} supports these operators, in addition to those common
5554 to programming languages:
5558 @samp{@@} is a binary operator for treating parts of memory as arrays.
5559 @xref{Arrays, ,Artificial Arrays}, for more information.
5562 @samp{::} allows you to specify a variable in terms of the file or
5563 function where it is defined. @xref{Variables, ,Program Variables}.
5565 @cindex @{@var{type}@}
5566 @cindex type casting memory
5567 @cindex memory, viewing as typed object
5568 @cindex casts, to view memory
5569 @item @{@var{type}@} @var{addr}
5570 Refers to an object of type @var{type} stored at address @var{addr} in
5571 memory. @var{addr} may be any expression whose value is an integer or
5572 pointer (but parentheses are required around binary operators, just as in
5573 a cast). This construct is allowed regardless of what kind of data is
5574 normally supposed to reside at @var{addr}.
5578 @section Program Variables
5580 The most common kind of expression to use is the name of a variable
5583 Variables in expressions are understood in the selected stack frame
5584 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5588 global (or file-static)
5595 visible according to the scope rules of the
5596 programming language from the point of execution in that frame
5599 @noindent This means that in the function
5614 you can examine and use the variable @code{a} whenever your program is
5615 executing within the function @code{foo}, but you can only use or
5616 examine the variable @code{b} while your program is executing inside
5617 the block where @code{b} is declared.
5619 @cindex variable name conflict
5620 There is an exception: you can refer to a variable or function whose
5621 scope is a single source file even if the current execution point is not
5622 in this file. But it is possible to have more than one such variable or
5623 function with the same name (in different source files). If that
5624 happens, referring to that name has unpredictable effects. If you wish,
5625 you can specify a static variable in a particular function or file,
5626 using the colon-colon (@code{::}) notation:
5628 @cindex colon-colon, context for variables/functions
5630 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5631 @cindex @code{::}, context for variables/functions
5634 @var{file}::@var{variable}
5635 @var{function}::@var{variable}
5639 Here @var{file} or @var{function} is the name of the context for the
5640 static @var{variable}. In the case of file names, you can use quotes to
5641 make sure @value{GDBN} parses the file name as a single word---for example,
5642 to print a global value of @code{x} defined in @file{f2.c}:
5645 (@value{GDBP}) p 'f2.c'::x
5648 @cindex C@t{++} scope resolution
5649 This use of @samp{::} is very rarely in conflict with the very similar
5650 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5651 scope resolution operator in @value{GDBN} expressions.
5652 @c FIXME: Um, so what happens in one of those rare cases where it's in
5655 @cindex wrong values
5656 @cindex variable values, wrong
5657 @cindex function entry/exit, wrong values of variables
5658 @cindex optimized code, wrong values of variables
5660 @emph{Warning:} Occasionally, a local variable may appear to have the
5661 wrong value at certain points in a function---just after entry to a new
5662 scope, and just before exit.
5664 You may see this problem when you are stepping by machine instructions.
5665 This is because, on most machines, it takes more than one instruction to
5666 set up a stack frame (including local variable definitions); if you are
5667 stepping by machine instructions, variables may appear to have the wrong
5668 values until the stack frame is completely built. On exit, it usually
5669 also takes more than one machine instruction to destroy a stack frame;
5670 after you begin stepping through that group of instructions, local
5671 variable definitions may be gone.
5673 This may also happen when the compiler does significant optimizations.
5674 To be sure of always seeing accurate values, turn off all optimization
5677 @cindex ``No symbol "foo" in current context''
5678 Another possible effect of compiler optimizations is to optimize
5679 unused variables out of existence, or assign variables to registers (as
5680 opposed to memory addresses). Depending on the support for such cases
5681 offered by the debug info format used by the compiler, @value{GDBN}
5682 might not be able to display values for such local variables. If that
5683 happens, @value{GDBN} will print a message like this:
5686 No symbol "foo" in current context.
5689 To solve such problems, either recompile without optimizations, or use a
5690 different debug info format, if the compiler supports several such
5691 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5692 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5693 produces debug info in a format that is superior to formats such as
5694 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5695 an effective form for debug info. @xref{Debugging Options,,Options
5696 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5697 Compiler Collection (GCC)}.
5698 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5699 that are best suited to C@t{++} programs.
5701 If you ask to print an object whose contents are unknown to
5702 @value{GDBN}, e.g., because its data type is not completely specified
5703 by the debug information, @value{GDBN} will say @samp{<incomplete
5704 type>}. @xref{Symbols, incomplete type}, for more about this.
5706 Strings are identified as arrays of @code{char} values without specified
5707 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5708 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5709 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5710 defines literal string type @code{"char"} as @code{char} without a sign.
5715 signed char var1[] = "A";
5718 You get during debugging
5723 $2 = @{65 'A', 0 '\0'@}
5727 @section Artificial Arrays
5729 @cindex artificial array
5731 @kindex @@@r{, referencing memory as an array}
5732 It is often useful to print out several successive objects of the
5733 same type in memory; a section of an array, or an array of
5734 dynamically determined size for which only a pointer exists in the
5737 You can do this by referring to a contiguous span of memory as an
5738 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5739 operand of @samp{@@} should be the first element of the desired array
5740 and be an individual object. The right operand should be the desired length
5741 of the array. The result is an array value whose elements are all of
5742 the type of the left argument. The first element is actually the left
5743 argument; the second element comes from bytes of memory immediately
5744 following those that hold the first element, and so on. Here is an
5745 example. If a program says
5748 int *array = (int *) malloc (len * sizeof (int));
5752 you can print the contents of @code{array} with
5758 The left operand of @samp{@@} must reside in memory. Array values made
5759 with @samp{@@} in this way behave just like other arrays in terms of
5760 subscripting, and are coerced to pointers when used in expressions.
5761 Artificial arrays most often appear in expressions via the value history
5762 (@pxref{Value History, ,Value History}), after printing one out.
5764 Another way to create an artificial array is to use a cast.
5765 This re-interprets a value as if it were an array.
5766 The value need not be in memory:
5768 (@value{GDBP}) p/x (short[2])0x12345678
5769 $1 = @{0x1234, 0x5678@}
5772 As a convenience, if you leave the array length out (as in
5773 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5774 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5776 (@value{GDBP}) p/x (short[])0x12345678
5777 $2 = @{0x1234, 0x5678@}
5780 Sometimes the artificial array mechanism is not quite enough; in
5781 moderately complex data structures, the elements of interest may not
5782 actually be adjacent---for example, if you are interested in the values
5783 of pointers in an array. One useful work-around in this situation is
5784 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5785 Variables}) as a counter in an expression that prints the first
5786 interesting value, and then repeat that expression via @key{RET}. For
5787 instance, suppose you have an array @code{dtab} of pointers to
5788 structures, and you are interested in the values of a field @code{fv}
5789 in each structure. Here is an example of what you might type:
5799 @node Output Formats
5800 @section Output Formats
5802 @cindex formatted output
5803 @cindex output formats
5804 By default, @value{GDBN} prints a value according to its data type. Sometimes
5805 this is not what you want. For example, you might want to print a number
5806 in hex, or a pointer in decimal. Or you might want to view data in memory
5807 at a certain address as a character string or as an instruction. To do
5808 these things, specify an @dfn{output format} when you print a value.
5810 The simplest use of output formats is to say how to print a value
5811 already computed. This is done by starting the arguments of the
5812 @code{print} command with a slash and a format letter. The format
5813 letters supported are:
5817 Regard the bits of the value as an integer, and print the integer in
5821 Print as integer in signed decimal.
5824 Print as integer in unsigned decimal.
5827 Print as integer in octal.
5830 Print as integer in binary. The letter @samp{t} stands for ``two''.
5831 @footnote{@samp{b} cannot be used because these format letters are also
5832 used with the @code{x} command, where @samp{b} stands for ``byte'';
5833 see @ref{Memory,,Examining Memory}.}
5836 @cindex unknown address, locating
5837 @cindex locate address
5838 Print as an address, both absolute in hexadecimal and as an offset from
5839 the nearest preceding symbol. You can use this format used to discover
5840 where (in what function) an unknown address is located:
5843 (@value{GDBP}) p/a 0x54320
5844 $3 = 0x54320 <_initialize_vx+396>
5848 The command @code{info symbol 0x54320} yields similar results.
5849 @xref{Symbols, info symbol}.
5852 Regard as an integer and print it as a character constant. This
5853 prints both the numerical value and its character representation. The
5854 character representation is replaced with the octal escape @samp{\nnn}
5855 for characters outside the 7-bit @sc{ascii} range.
5857 Without this format, @value{GDBN} displays @code{char},
5858 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
5859 constants. Single-byte members of vectors are displayed as integer
5863 Regard the bits of the value as a floating point number and print
5864 using typical floating point syntax.
5867 @cindex printing strings
5868 @cindex printing byte arrays
5869 Regard as a string, if possible. With this format, pointers to single-byte
5870 data are displayed as null-terminated strings and arrays of single-byte data
5871 are displayed as fixed-length strings. Other values are displayed in their
5874 Without this format, @value{GDBN} displays pointers to and arrays of
5875 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
5876 strings. Single-byte members of a vector are displayed as an integer
5880 For example, to print the program counter in hex (@pxref{Registers}), type
5887 Note that no space is required before the slash; this is because command
5888 names in @value{GDBN} cannot contain a slash.
5890 To reprint the last value in the value history with a different format,
5891 you can use the @code{print} command with just a format and no
5892 expression. For example, @samp{p/x} reprints the last value in hex.
5895 @section Examining Memory
5897 You can use the command @code{x} (for ``examine'') to examine memory in
5898 any of several formats, independently of your program's data types.
5900 @cindex examining memory
5902 @kindex x @r{(examine memory)}
5903 @item x/@var{nfu} @var{addr}
5906 Use the @code{x} command to examine memory.
5909 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5910 much memory to display and how to format it; @var{addr} is an
5911 expression giving the address where you want to start displaying memory.
5912 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5913 Several commands set convenient defaults for @var{addr}.
5916 @item @var{n}, the repeat count
5917 The repeat count is a decimal integer; the default is 1. It specifies
5918 how much memory (counting by units @var{u}) to display.
5919 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5922 @item @var{f}, the display format
5923 The display format is one of the formats used by @code{print}
5924 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5925 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
5926 The default is @samp{x} (hexadecimal) initially. The default changes
5927 each time you use either @code{x} or @code{print}.
5929 @item @var{u}, the unit size
5930 The unit size is any of
5936 Halfwords (two bytes).
5938 Words (four bytes). This is the initial default.
5940 Giant words (eight bytes).
5943 Each time you specify a unit size with @code{x}, that size becomes the
5944 default unit the next time you use @code{x}. (For the @samp{s} and
5945 @samp{i} formats, the unit size is ignored and is normally not written.)
5947 @item @var{addr}, starting display address
5948 @var{addr} is the address where you want @value{GDBN} to begin displaying
5949 memory. The expression need not have a pointer value (though it may);
5950 it is always interpreted as an integer address of a byte of memory.
5951 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5952 @var{addr} is usually just after the last address examined---but several
5953 other commands also set the default address: @code{info breakpoints} (to
5954 the address of the last breakpoint listed), @code{info line} (to the
5955 starting address of a line), and @code{print} (if you use it to display
5956 a value from memory).
5959 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5960 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5961 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5962 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5963 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5965 Since the letters indicating unit sizes are all distinct from the
5966 letters specifying output formats, you do not have to remember whether
5967 unit size or format comes first; either order works. The output
5968 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5969 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5971 Even though the unit size @var{u} is ignored for the formats @samp{s}
5972 and @samp{i}, you might still want to use a count @var{n}; for example,
5973 @samp{3i} specifies that you want to see three machine instructions,
5974 including any operands. For convenience, especially when used with
5975 the @code{display} command, the @samp{i} format also prints branch delay
5976 slot instructions, if any, beyond the count specified, which immediately
5977 follow the last instruction that is within the count. The command
5978 @code{disassemble} gives an alternative way of inspecting machine
5979 instructions; see @ref{Machine Code,,Source and Machine Code}.
5981 All the defaults for the arguments to @code{x} are designed to make it
5982 easy to continue scanning memory with minimal specifications each time
5983 you use @code{x}. For example, after you have inspected three machine
5984 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5985 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5986 the repeat count @var{n} is used again; the other arguments default as
5987 for successive uses of @code{x}.
5989 @cindex @code{$_}, @code{$__}, and value history
5990 The addresses and contents printed by the @code{x} command are not saved
5991 in the value history because there is often too much of them and they
5992 would get in the way. Instead, @value{GDBN} makes these values available for
5993 subsequent use in expressions as values of the convenience variables
5994 @code{$_} and @code{$__}. After an @code{x} command, the last address
5995 examined is available for use in expressions in the convenience variable
5996 @code{$_}. The contents of that address, as examined, are available in
5997 the convenience variable @code{$__}.
5999 If the @code{x} command has a repeat count, the address and contents saved
6000 are from the last memory unit printed; this is not the same as the last
6001 address printed if several units were printed on the last line of output.
6003 @cindex remote memory comparison
6004 @cindex verify remote memory image
6005 When you are debugging a program running on a remote target machine
6006 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6007 remote machine's memory against the executable file you downloaded to
6008 the target. The @code{compare-sections} command is provided for such
6012 @kindex compare-sections
6013 @item compare-sections @r{[}@var{section-name}@r{]}
6014 Compare the data of a loadable section @var{section-name} in the
6015 executable file of the program being debugged with the same section in
6016 the remote machine's memory, and report any mismatches. With no
6017 arguments, compares all loadable sections. This command's
6018 availability depends on the target's support for the @code{"qCRC"}
6023 @section Automatic Display
6024 @cindex automatic display
6025 @cindex display of expressions
6027 If you find that you want to print the value of an expression frequently
6028 (to see how it changes), you might want to add it to the @dfn{automatic
6029 display list} so that @value{GDBN} prints its value each time your program stops.
6030 Each expression added to the list is given a number to identify it;
6031 to remove an expression from the list, you specify that number.
6032 The automatic display looks like this:
6036 3: bar[5] = (struct hack *) 0x3804
6040 This display shows item numbers, expressions and their current values. As with
6041 displays you request manually using @code{x} or @code{print}, you can
6042 specify the output format you prefer; in fact, @code{display} decides
6043 whether to use @code{print} or @code{x} depending your format
6044 specification---it uses @code{x} if you specify either the @samp{i}
6045 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6049 @item display @var{expr}
6050 Add the expression @var{expr} to the list of expressions to display
6051 each time your program stops. @xref{Expressions, ,Expressions}.
6053 @code{display} does not repeat if you press @key{RET} again after using it.
6055 @item display/@var{fmt} @var{expr}
6056 For @var{fmt} specifying only a display format and not a size or
6057 count, add the expression @var{expr} to the auto-display list but
6058 arrange to display it each time in the specified format @var{fmt}.
6059 @xref{Output Formats,,Output Formats}.
6061 @item display/@var{fmt} @var{addr}
6062 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6063 number of units, add the expression @var{addr} as a memory address to
6064 be examined each time your program stops. Examining means in effect
6065 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6068 For example, @samp{display/i $pc} can be helpful, to see the machine
6069 instruction about to be executed each time execution stops (@samp{$pc}
6070 is a common name for the program counter; @pxref{Registers, ,Registers}).
6073 @kindex delete display
6075 @item undisplay @var{dnums}@dots{}
6076 @itemx delete display @var{dnums}@dots{}
6077 Remove item numbers @var{dnums} from the list of expressions to display.
6079 @code{undisplay} does not repeat if you press @key{RET} after using it.
6080 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6082 @kindex disable display
6083 @item disable display @var{dnums}@dots{}
6084 Disable the display of item numbers @var{dnums}. A disabled display
6085 item is not printed automatically, but is not forgotten. It may be
6086 enabled again later.
6088 @kindex enable display
6089 @item enable display @var{dnums}@dots{}
6090 Enable display of item numbers @var{dnums}. It becomes effective once
6091 again in auto display of its expression, until you specify otherwise.
6094 Display the current values of the expressions on the list, just as is
6095 done when your program stops.
6097 @kindex info display
6099 Print the list of expressions previously set up to display
6100 automatically, each one with its item number, but without showing the
6101 values. This includes disabled expressions, which are marked as such.
6102 It also includes expressions which would not be displayed right now
6103 because they refer to automatic variables not currently available.
6106 @cindex display disabled out of scope
6107 If a display expression refers to local variables, then it does not make
6108 sense outside the lexical context for which it was set up. Such an
6109 expression is disabled when execution enters a context where one of its
6110 variables is not defined. For example, if you give the command
6111 @code{display last_char} while inside a function with an argument
6112 @code{last_char}, @value{GDBN} displays this argument while your program
6113 continues to stop inside that function. When it stops elsewhere---where
6114 there is no variable @code{last_char}---the display is disabled
6115 automatically. The next time your program stops where @code{last_char}
6116 is meaningful, you can enable the display expression once again.
6118 @node Print Settings
6119 @section Print Settings
6121 @cindex format options
6122 @cindex print settings
6123 @value{GDBN} provides the following ways to control how arrays, structures,
6124 and symbols are printed.
6127 These settings are useful for debugging programs in any language:
6131 @item set print address
6132 @itemx set print address on
6133 @cindex print/don't print memory addresses
6134 @value{GDBN} prints memory addresses showing the location of stack
6135 traces, structure values, pointer values, breakpoints, and so forth,
6136 even when it also displays the contents of those addresses. The default
6137 is @code{on}. For example, this is what a stack frame display looks like with
6138 @code{set print address on}:
6143 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6145 530 if (lquote != def_lquote)
6149 @item set print address off
6150 Do not print addresses when displaying their contents. For example,
6151 this is the same stack frame displayed with @code{set print address off}:
6155 (@value{GDBP}) set print addr off
6157 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6158 530 if (lquote != def_lquote)
6162 You can use @samp{set print address off} to eliminate all machine
6163 dependent displays from the @value{GDBN} interface. For example, with
6164 @code{print address off}, you should get the same text for backtraces on
6165 all machines---whether or not they involve pointer arguments.
6168 @item show print address
6169 Show whether or not addresses are to be printed.
6172 When @value{GDBN} prints a symbolic address, it normally prints the
6173 closest earlier symbol plus an offset. If that symbol does not uniquely
6174 identify the address (for example, it is a name whose scope is a single
6175 source file), you may need to clarify. One way to do this is with
6176 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6177 you can set @value{GDBN} to print the source file and line number when
6178 it prints a symbolic address:
6181 @item set print symbol-filename on
6182 @cindex source file and line of a symbol
6183 @cindex symbol, source file and line
6184 Tell @value{GDBN} to print the source file name and line number of a
6185 symbol in the symbolic form of an address.
6187 @item set print symbol-filename off
6188 Do not print source file name and line number of a symbol. This is the
6191 @item show print symbol-filename
6192 Show whether or not @value{GDBN} will print the source file name and
6193 line number of a symbol in the symbolic form of an address.
6196 Another situation where it is helpful to show symbol filenames and line
6197 numbers is when disassembling code; @value{GDBN} shows you the line
6198 number and source file that corresponds to each instruction.
6200 Also, you may wish to see the symbolic form only if the address being
6201 printed is reasonably close to the closest earlier symbol:
6204 @item set print max-symbolic-offset @var{max-offset}
6205 @cindex maximum value for offset of closest symbol
6206 Tell @value{GDBN} to only display the symbolic form of an address if the
6207 offset between the closest earlier symbol and the address is less than
6208 @var{max-offset}. The default is 0, which tells @value{GDBN}
6209 to always print the symbolic form of an address if any symbol precedes it.
6211 @item show print max-symbolic-offset
6212 Ask how large the maximum offset is that @value{GDBN} prints in a
6216 @cindex wild pointer, interpreting
6217 @cindex pointer, finding referent
6218 If you have a pointer and you are not sure where it points, try
6219 @samp{set print symbol-filename on}. Then you can determine the name
6220 and source file location of the variable where it points, using
6221 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6222 For example, here @value{GDBN} shows that a variable @code{ptt} points
6223 at another variable @code{t}, defined in @file{hi2.c}:
6226 (@value{GDBP}) set print symbol-filename on
6227 (@value{GDBP}) p/a ptt
6228 $4 = 0xe008 <t in hi2.c>
6232 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6233 does not show the symbol name and filename of the referent, even with
6234 the appropriate @code{set print} options turned on.
6237 Other settings control how different kinds of objects are printed:
6240 @item set print array
6241 @itemx set print array on
6242 @cindex pretty print arrays
6243 Pretty print arrays. This format is more convenient to read,
6244 but uses more space. The default is off.
6246 @item set print array off
6247 Return to compressed format for arrays.
6249 @item show print array
6250 Show whether compressed or pretty format is selected for displaying
6253 @cindex print array indexes
6254 @item set print array-indexes
6255 @itemx set print array-indexes on
6256 Print the index of each element when displaying arrays. May be more
6257 convenient to locate a given element in the array or quickly find the
6258 index of a given element in that printed array. The default is off.
6260 @item set print array-indexes off
6261 Stop printing element indexes when displaying arrays.
6263 @item show print array-indexes
6264 Show whether the index of each element is printed when displaying
6267 @item set print elements @var{number-of-elements}
6268 @cindex number of array elements to print
6269 @cindex limit on number of printed array elements
6270 Set a limit on how many elements of an array @value{GDBN} will print.
6271 If @value{GDBN} is printing a large array, it stops printing after it has
6272 printed the number of elements set by the @code{set print elements} command.
6273 This limit also applies to the display of strings.
6274 When @value{GDBN} starts, this limit is set to 200.
6275 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6277 @item show print elements
6278 Display the number of elements of a large array that @value{GDBN} will print.
6279 If the number is 0, then the printing is unlimited.
6281 @item set print frame-arguments @var{value}
6282 @cindex printing frame argument values
6283 @cindex print all frame argument values
6284 @cindex print frame argument values for scalars only
6285 @cindex do not print frame argument values
6286 This command allows to control how the values of arguments are printed
6287 when the debugger prints a frame (@pxref{Frames}). The possible
6292 The values of all arguments are printed. This is the default.
6295 Print the value of an argument only if it is a scalar. The value of more
6296 complex arguments such as arrays, structures, unions, etc, is replaced
6297 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6300 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6305 None of the argument values are printed. Instead, the value of each argument
6306 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6309 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6314 By default, all argument values are always printed. But this command
6315 can be useful in several cases. For instance, it can be used to reduce
6316 the amount of information printed in each frame, making the backtrace
6317 more readable. Also, this command can be used to improve performance
6318 when displaying Ada frames, because the computation of large arguments
6319 can sometimes be CPU-intensive, especiallly in large applications.
6320 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6321 avoids this computation, thus speeding up the display of each Ada frame.
6323 @item show print frame-arguments
6324 Show how the value of arguments should be displayed when printing a frame.
6326 @item set print repeats
6327 @cindex repeated array elements
6328 Set the threshold for suppressing display of repeated array
6329 elements. When the number of consecutive identical elements of an
6330 array exceeds the threshold, @value{GDBN} prints the string
6331 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6332 identical repetitions, instead of displaying the identical elements
6333 themselves. Setting the threshold to zero will cause all elements to
6334 be individually printed. The default threshold is 10.
6336 @item show print repeats
6337 Display the current threshold for printing repeated identical
6340 @item set print null-stop
6341 @cindex @sc{null} elements in arrays
6342 Cause @value{GDBN} to stop printing the characters of an array when the first
6343 @sc{null} is encountered. This is useful when large arrays actually
6344 contain only short strings.
6347 @item show print null-stop
6348 Show whether @value{GDBN} stops printing an array on the first
6349 @sc{null} character.
6351 @item set print pretty on
6352 @cindex print structures in indented form
6353 @cindex indentation in structure display
6354 Cause @value{GDBN} to print structures in an indented format with one member
6355 per line, like this:
6370 @item set print pretty off
6371 Cause @value{GDBN} to print structures in a compact format, like this:
6375 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6376 meat = 0x54 "Pork"@}
6381 This is the default format.
6383 @item show print pretty
6384 Show which format @value{GDBN} is using to print structures.
6386 @item set print sevenbit-strings on
6387 @cindex eight-bit characters in strings
6388 @cindex octal escapes in strings
6389 Print using only seven-bit characters; if this option is set,
6390 @value{GDBN} displays any eight-bit characters (in strings or
6391 character values) using the notation @code{\}@var{nnn}. This setting is
6392 best if you are working in English (@sc{ascii}) and you use the
6393 high-order bit of characters as a marker or ``meta'' bit.
6395 @item set print sevenbit-strings off
6396 Print full eight-bit characters. This allows the use of more
6397 international character sets, and is the default.
6399 @item show print sevenbit-strings
6400 Show whether or not @value{GDBN} is printing only seven-bit characters.
6402 @item set print union on
6403 @cindex unions in structures, printing
6404 Tell @value{GDBN} to print unions which are contained in structures
6405 and other unions. This is the default setting.
6407 @item set print union off
6408 Tell @value{GDBN} not to print unions which are contained in
6409 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6412 @item show print union
6413 Ask @value{GDBN} whether or not it will print unions which are contained in
6414 structures and other unions.
6416 For example, given the declarations
6419 typedef enum @{Tree, Bug@} Species;
6420 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6421 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6432 struct thing foo = @{Tree, @{Acorn@}@};
6436 with @code{set print union on} in effect @samp{p foo} would print
6439 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6443 and with @code{set print union off} in effect it would print
6446 $1 = @{it = Tree, form = @{...@}@}
6450 @code{set print union} affects programs written in C-like languages
6456 These settings are of interest when debugging C@t{++} programs:
6459 @cindex demangling C@t{++} names
6460 @item set print demangle
6461 @itemx set print demangle on
6462 Print C@t{++} names in their source form rather than in the encoded
6463 (``mangled'') form passed to the assembler and linker for type-safe
6464 linkage. The default is on.
6466 @item show print demangle
6467 Show whether C@t{++} names are printed in mangled or demangled form.
6469 @item set print asm-demangle
6470 @itemx set print asm-demangle on
6471 Print C@t{++} names in their source form rather than their mangled form, even
6472 in assembler code printouts such as instruction disassemblies.
6475 @item show print asm-demangle
6476 Show whether C@t{++} names in assembly listings are printed in mangled
6479 @cindex C@t{++} symbol decoding style
6480 @cindex symbol decoding style, C@t{++}
6481 @kindex set demangle-style
6482 @item set demangle-style @var{style}
6483 Choose among several encoding schemes used by different compilers to
6484 represent C@t{++} names. The choices for @var{style} are currently:
6488 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6491 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6492 This is the default.
6495 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6498 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6501 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6502 @strong{Warning:} this setting alone is not sufficient to allow
6503 debugging @code{cfront}-generated executables. @value{GDBN} would
6504 require further enhancement to permit that.
6507 If you omit @var{style}, you will see a list of possible formats.
6509 @item show demangle-style
6510 Display the encoding style currently in use for decoding C@t{++} symbols.
6512 @item set print object
6513 @itemx set print object on
6514 @cindex derived type of an object, printing
6515 @cindex display derived types
6516 When displaying a pointer to an object, identify the @emph{actual}
6517 (derived) type of the object rather than the @emph{declared} type, using
6518 the virtual function table.
6520 @item set print object off
6521 Display only the declared type of objects, without reference to the
6522 virtual function table. This is the default setting.
6524 @item show print object
6525 Show whether actual, or declared, object types are displayed.
6527 @item set print static-members
6528 @itemx set print static-members on
6529 @cindex static members of C@t{++} objects
6530 Print static members when displaying a C@t{++} object. The default is on.
6532 @item set print static-members off
6533 Do not print static members when displaying a C@t{++} object.
6535 @item show print static-members
6536 Show whether C@t{++} static members are printed or not.
6538 @item set print pascal_static-members
6539 @itemx set print pascal_static-members on
6540 @cindex static members of Pascal objects
6541 @cindex Pascal objects, static members display
6542 Print static members when displaying a Pascal object. The default is on.
6544 @item set print pascal_static-members off
6545 Do not print static members when displaying a Pascal object.
6547 @item show print pascal_static-members
6548 Show whether Pascal static members are printed or not.
6550 @c These don't work with HP ANSI C++ yet.
6551 @item set print vtbl
6552 @itemx set print vtbl on
6553 @cindex pretty print C@t{++} virtual function tables
6554 @cindex virtual functions (C@t{++}) display
6555 @cindex VTBL display
6556 Pretty print C@t{++} virtual function tables. The default is off.
6557 (The @code{vtbl} commands do not work on programs compiled with the HP
6558 ANSI C@t{++} compiler (@code{aCC}).)
6560 @item set print vtbl off
6561 Do not pretty print C@t{++} virtual function tables.
6563 @item show print vtbl
6564 Show whether C@t{++} virtual function tables are pretty printed, or not.
6568 @section Value History
6570 @cindex value history
6571 @cindex history of values printed by @value{GDBN}
6572 Values printed by the @code{print} command are saved in the @value{GDBN}
6573 @dfn{value history}. This allows you to refer to them in other expressions.
6574 Values are kept until the symbol table is re-read or discarded
6575 (for example with the @code{file} or @code{symbol-file} commands).
6576 When the symbol table changes, the value history is discarded,
6577 since the values may contain pointers back to the types defined in the
6582 @cindex history number
6583 The values printed are given @dfn{history numbers} by which you can
6584 refer to them. These are successive integers starting with one.
6585 @code{print} shows you the history number assigned to a value by
6586 printing @samp{$@var{num} = } before the value; here @var{num} is the
6589 To refer to any previous value, use @samp{$} followed by the value's
6590 history number. The way @code{print} labels its output is designed to
6591 remind you of this. Just @code{$} refers to the most recent value in
6592 the history, and @code{$$} refers to the value before that.
6593 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6594 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6595 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6597 For example, suppose you have just printed a pointer to a structure and
6598 want to see the contents of the structure. It suffices to type
6604 If you have a chain of structures where the component @code{next} points
6605 to the next one, you can print the contents of the next one with this:
6612 You can print successive links in the chain by repeating this
6613 command---which you can do by just typing @key{RET}.
6615 Note that the history records values, not expressions. If the value of
6616 @code{x} is 4 and you type these commands:
6624 then the value recorded in the value history by the @code{print} command
6625 remains 4 even though the value of @code{x} has changed.
6630 Print the last ten values in the value history, with their item numbers.
6631 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6632 values} does not change the history.
6634 @item show values @var{n}
6635 Print ten history values centered on history item number @var{n}.
6638 Print ten history values just after the values last printed. If no more
6639 values are available, @code{show values +} produces no display.
6642 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6643 same effect as @samp{show values +}.
6645 @node Convenience Vars
6646 @section Convenience Variables
6648 @cindex convenience variables
6649 @cindex user-defined variables
6650 @value{GDBN} provides @dfn{convenience variables} that you can use within
6651 @value{GDBN} to hold on to a value and refer to it later. These variables
6652 exist entirely within @value{GDBN}; they are not part of your program, and
6653 setting a convenience variable has no direct effect on further execution
6654 of your program. That is why you can use them freely.
6656 Convenience variables are prefixed with @samp{$}. Any name preceded by
6657 @samp{$} can be used for a convenience variable, unless it is one of
6658 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6659 (Value history references, in contrast, are @emph{numbers} preceded
6660 by @samp{$}. @xref{Value History, ,Value History}.)
6662 You can save a value in a convenience variable with an assignment
6663 expression, just as you would set a variable in your program.
6667 set $foo = *object_ptr
6671 would save in @code{$foo} the value contained in the object pointed to by
6674 Using a convenience variable for the first time creates it, but its
6675 value is @code{void} until you assign a new value. You can alter the
6676 value with another assignment at any time.
6678 Convenience variables have no fixed types. You can assign a convenience
6679 variable any type of value, including structures and arrays, even if
6680 that variable already has a value of a different type. The convenience
6681 variable, when used as an expression, has the type of its current value.
6684 @kindex show convenience
6685 @cindex show all user variables
6686 @item show convenience
6687 Print a list of convenience variables used so far, and their values.
6688 Abbreviated @code{show conv}.
6690 @kindex init-if-undefined
6691 @cindex convenience variables, initializing
6692 @item init-if-undefined $@var{variable} = @var{expression}
6693 Set a convenience variable if it has not already been set. This is useful
6694 for user-defined commands that keep some state. It is similar, in concept,
6695 to using local static variables with initializers in C (except that
6696 convenience variables are global). It can also be used to allow users to
6697 override default values used in a command script.
6699 If the variable is already defined then the expression is not evaluated so
6700 any side-effects do not occur.
6703 One of the ways to use a convenience variable is as a counter to be
6704 incremented or a pointer to be advanced. For example, to print
6705 a field from successive elements of an array of structures:
6709 print bar[$i++]->contents
6713 Repeat that command by typing @key{RET}.
6715 Some convenience variables are created automatically by @value{GDBN} and given
6716 values likely to be useful.
6719 @vindex $_@r{, convenience variable}
6721 The variable @code{$_} is automatically set by the @code{x} command to
6722 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6723 commands which provide a default address for @code{x} to examine also
6724 set @code{$_} to that address; these commands include @code{info line}
6725 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6726 except when set by the @code{x} command, in which case it is a pointer
6727 to the type of @code{$__}.
6729 @vindex $__@r{, convenience variable}
6731 The variable @code{$__} is automatically set by the @code{x} command
6732 to the value found in the last address examined. Its type is chosen
6733 to match the format in which the data was printed.
6736 @vindex $_exitcode@r{, convenience variable}
6737 The variable @code{$_exitcode} is automatically set to the exit code when
6738 the program being debugged terminates.
6741 On HP-UX systems, if you refer to a function or variable name that
6742 begins with a dollar sign, @value{GDBN} searches for a user or system
6743 name first, before it searches for a convenience variable.
6749 You can refer to machine register contents, in expressions, as variables
6750 with names starting with @samp{$}. The names of registers are different
6751 for each machine; use @code{info registers} to see the names used on
6755 @kindex info registers
6756 @item info registers
6757 Print the names and values of all registers except floating-point
6758 and vector registers (in the selected stack frame).
6760 @kindex info all-registers
6761 @cindex floating point registers
6762 @item info all-registers
6763 Print the names and values of all registers, including floating-point
6764 and vector registers (in the selected stack frame).
6766 @item info registers @var{regname} @dots{}
6767 Print the @dfn{relativized} value of each specified register @var{regname}.
6768 As discussed in detail below, register values are normally relative to
6769 the selected stack frame. @var{regname} may be any register name valid on
6770 the machine you are using, with or without the initial @samp{$}.
6773 @cindex stack pointer register
6774 @cindex program counter register
6775 @cindex process status register
6776 @cindex frame pointer register
6777 @cindex standard registers
6778 @value{GDBN} has four ``standard'' register names that are available (in
6779 expressions) on most machines---whenever they do not conflict with an
6780 architecture's canonical mnemonics for registers. The register names
6781 @code{$pc} and @code{$sp} are used for the program counter register and
6782 the stack pointer. @code{$fp} is used for a register that contains a
6783 pointer to the current stack frame, and @code{$ps} is used for a
6784 register that contains the processor status. For example,
6785 you could print the program counter in hex with
6792 or print the instruction to be executed next with
6799 or add four to the stack pointer@footnote{This is a way of removing
6800 one word from the stack, on machines where stacks grow downward in
6801 memory (most machines, nowadays). This assumes that the innermost
6802 stack frame is selected; setting @code{$sp} is not allowed when other
6803 stack frames are selected. To pop entire frames off the stack,
6804 regardless of machine architecture, use @code{return};
6805 see @ref{Returning, ,Returning from a Function}.} with
6811 Whenever possible, these four standard register names are available on
6812 your machine even though the machine has different canonical mnemonics,
6813 so long as there is no conflict. The @code{info registers} command
6814 shows the canonical names. For example, on the SPARC, @code{info
6815 registers} displays the processor status register as @code{$psr} but you
6816 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6817 is an alias for the @sc{eflags} register.
6819 @value{GDBN} always considers the contents of an ordinary register as an
6820 integer when the register is examined in this way. Some machines have
6821 special registers which can hold nothing but floating point; these
6822 registers are considered to have floating point values. There is no way
6823 to refer to the contents of an ordinary register as floating point value
6824 (although you can @emph{print} it as a floating point value with
6825 @samp{print/f $@var{regname}}).
6827 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6828 means that the data format in which the register contents are saved by
6829 the operating system is not the same one that your program normally
6830 sees. For example, the registers of the 68881 floating point
6831 coprocessor are always saved in ``extended'' (raw) format, but all C
6832 programs expect to work with ``double'' (virtual) format. In such
6833 cases, @value{GDBN} normally works with the virtual format only (the format
6834 that makes sense for your program), but the @code{info registers} command
6835 prints the data in both formats.
6837 @cindex SSE registers (x86)
6838 @cindex MMX registers (x86)
6839 Some machines have special registers whose contents can be interpreted
6840 in several different ways. For example, modern x86-based machines
6841 have SSE and MMX registers that can hold several values packed
6842 together in several different formats. @value{GDBN} refers to such
6843 registers in @code{struct} notation:
6846 (@value{GDBP}) print $xmm1
6848 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6849 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6850 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6851 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6852 v4_int32 = @{0, 20657912, 11, 13@},
6853 v2_int64 = @{88725056443645952, 55834574859@},
6854 uint128 = 0x0000000d0000000b013b36f800000000
6859 To set values of such registers, you need to tell @value{GDBN} which
6860 view of the register you wish to change, as if you were assigning
6861 value to a @code{struct} member:
6864 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6867 Normally, register values are relative to the selected stack frame
6868 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
6869 value that the register would contain if all stack frames farther in
6870 were exited and their saved registers restored. In order to see the
6871 true contents of hardware registers, you must select the innermost
6872 frame (with @samp{frame 0}).
6874 However, @value{GDBN} must deduce where registers are saved, from the machine
6875 code generated by your compiler. If some registers are not saved, or if
6876 @value{GDBN} is unable to locate the saved registers, the selected stack
6877 frame makes no difference.
6879 @node Floating Point Hardware
6880 @section Floating Point Hardware
6881 @cindex floating point
6883 Depending on the configuration, @value{GDBN} may be able to give
6884 you more information about the status of the floating point hardware.
6889 Display hardware-dependent information about the floating
6890 point unit. The exact contents and layout vary depending on the
6891 floating point chip. Currently, @samp{info float} is supported on
6892 the ARM and x86 machines.
6896 @section Vector Unit
6899 Depending on the configuration, @value{GDBN} may be able to give you
6900 more information about the status of the vector unit.
6905 Display information about the vector unit. The exact contents and
6906 layout vary depending on the hardware.
6909 @node OS Information
6910 @section Operating System Auxiliary Information
6911 @cindex OS information
6913 @value{GDBN} provides interfaces to useful OS facilities that can help
6914 you debug your program.
6916 @cindex @code{ptrace} system call
6917 @cindex @code{struct user} contents
6918 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6919 machines), it interfaces with the inferior via the @code{ptrace}
6920 system call. The operating system creates a special sata structure,
6921 called @code{struct user}, for this interface. You can use the
6922 command @code{info udot} to display the contents of this data
6928 Display the contents of the @code{struct user} maintained by the OS
6929 kernel for the program being debugged. @value{GDBN} displays the
6930 contents of @code{struct user} as a list of hex numbers, similar to
6931 the @code{examine} command.
6934 @cindex auxiliary vector
6935 @cindex vector, auxiliary
6936 Some operating systems supply an @dfn{auxiliary vector} to programs at
6937 startup. This is akin to the arguments and environment that you
6938 specify for a program, but contains a system-dependent variety of
6939 binary values that tell system libraries important details about the
6940 hardware, operating system, and process. Each value's purpose is
6941 identified by an integer tag; the meanings are well-known but system-specific.
6942 Depending on the configuration and operating system facilities,
6943 @value{GDBN} may be able to show you this information. For remote
6944 targets, this functionality may further depend on the remote stub's
6945 support of the @samp{qXfer:auxv:read} packet, see
6946 @ref{qXfer auxiliary vector read}.
6951 Display the auxiliary vector of the inferior, which can be either a
6952 live process or a core dump file. @value{GDBN} prints each tag value
6953 numerically, and also shows names and text descriptions for recognized
6954 tags. Some values in the vector are numbers, some bit masks, and some
6955 pointers to strings or other data. @value{GDBN} displays each value in the
6956 most appropriate form for a recognized tag, and in hexadecimal for
6957 an unrecognized tag.
6961 @node Memory Region Attributes
6962 @section Memory Region Attributes
6963 @cindex memory region attributes
6965 @dfn{Memory region attributes} allow you to describe special handling
6966 required by regions of your target's memory. @value{GDBN} uses
6967 attributes to determine whether to allow certain types of memory
6968 accesses; whether to use specific width accesses; and whether to cache
6969 target memory. By default the description of memory regions is
6970 fetched from the target (if the current target supports this), but the
6971 user can override the fetched regions.
6973 Defined memory regions can be individually enabled and disabled. When a
6974 memory region is disabled, @value{GDBN} uses the default attributes when
6975 accessing memory in that region. Similarly, if no memory regions have
6976 been defined, @value{GDBN} uses the default attributes when accessing
6979 When a memory region is defined, it is given a number to identify it;
6980 to enable, disable, or remove a memory region, you specify that number.
6984 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6985 Define a memory region bounded by @var{lower} and @var{upper} with
6986 attributes @var{attributes}@dots{}, and add it to the list of regions
6987 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6988 case: it is treated as the target's maximum memory address.
6989 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6992 Discard any user changes to the memory regions and use target-supplied
6993 regions, if available, or no regions if the target does not support.
6996 @item delete mem @var{nums}@dots{}
6997 Remove memory regions @var{nums}@dots{} from the list of regions
6998 monitored by @value{GDBN}.
7001 @item disable mem @var{nums}@dots{}
7002 Disable monitoring of memory regions @var{nums}@dots{}.
7003 A disabled memory region is not forgotten.
7004 It may be enabled again later.
7007 @item enable mem @var{nums}@dots{}
7008 Enable monitoring of memory regions @var{nums}@dots{}.
7012 Print a table of all defined memory regions, with the following columns
7016 @item Memory Region Number
7017 @item Enabled or Disabled.
7018 Enabled memory regions are marked with @samp{y}.
7019 Disabled memory regions are marked with @samp{n}.
7022 The address defining the inclusive lower bound of the memory region.
7025 The address defining the exclusive upper bound of the memory region.
7028 The list of attributes set for this memory region.
7033 @subsection Attributes
7035 @subsubsection Memory Access Mode
7036 The access mode attributes set whether @value{GDBN} may make read or
7037 write accesses to a memory region.
7039 While these attributes prevent @value{GDBN} from performing invalid
7040 memory accesses, they do nothing to prevent the target system, I/O DMA,
7041 etc.@: from accessing memory.
7045 Memory is read only.
7047 Memory is write only.
7049 Memory is read/write. This is the default.
7052 @subsubsection Memory Access Size
7053 The access size attribute tells @value{GDBN} to use specific sized
7054 accesses in the memory region. Often memory mapped device registers
7055 require specific sized accesses. If no access size attribute is
7056 specified, @value{GDBN} may use accesses of any size.
7060 Use 8 bit memory accesses.
7062 Use 16 bit memory accesses.
7064 Use 32 bit memory accesses.
7066 Use 64 bit memory accesses.
7069 @c @subsubsection Hardware/Software Breakpoints
7070 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7071 @c will use hardware or software breakpoints for the internal breakpoints
7072 @c used by the step, next, finish, until, etc. commands.
7076 @c Always use hardware breakpoints
7077 @c @item swbreak (default)
7080 @subsubsection Data Cache
7081 The data cache attributes set whether @value{GDBN} will cache target
7082 memory. While this generally improves performance by reducing debug
7083 protocol overhead, it can lead to incorrect results because @value{GDBN}
7084 does not know about volatile variables or memory mapped device
7089 Enable @value{GDBN} to cache target memory.
7091 Disable @value{GDBN} from caching target memory. This is the default.
7094 @subsection Memory Access Checking
7095 @value{GDBN} can be instructed to refuse accesses to memory that is
7096 not explicitly described. This can be useful if accessing such
7097 regions has undesired effects for a specific target, or to provide
7098 better error checking. The following commands control this behaviour.
7101 @kindex set mem inaccessible-by-default
7102 @item set mem inaccessible-by-default [on|off]
7103 If @code{on} is specified, make @value{GDBN} treat memory not
7104 explicitly described by the memory ranges as non-existent and refuse accesses
7105 to such memory. The checks are only performed if there's at least one
7106 memory range defined. If @code{off} is specified, make @value{GDBN}
7107 treat the memory not explicitly described by the memory ranges as RAM.
7108 The default value is @code{on}.
7109 @kindex show mem inaccessible-by-default
7110 @item show mem inaccessible-by-default
7111 Show the current handling of accesses to unknown memory.
7115 @c @subsubsection Memory Write Verification
7116 @c The memory write verification attributes set whether @value{GDBN}
7117 @c will re-reads data after each write to verify the write was successful.
7121 @c @item noverify (default)
7124 @node Dump/Restore Files
7125 @section Copy Between Memory and a File
7126 @cindex dump/restore files
7127 @cindex append data to a file
7128 @cindex dump data to a file
7129 @cindex restore data from a file
7131 You can use the commands @code{dump}, @code{append}, and
7132 @code{restore} to copy data between target memory and a file. The
7133 @code{dump} and @code{append} commands write data to a file, and the
7134 @code{restore} command reads data from a file back into the inferior's
7135 memory. Files may be in binary, Motorola S-record, Intel hex, or
7136 Tektronix Hex format; however, @value{GDBN} can only append to binary
7142 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7143 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7144 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7145 or the value of @var{expr}, to @var{filename} in the given format.
7147 The @var{format} parameter may be any one of:
7154 Motorola S-record format.
7156 Tektronix Hex format.
7159 @value{GDBN} uses the same definitions of these formats as the
7160 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7161 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7165 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7166 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7167 Append the contents of memory from @var{start_addr} to @var{end_addr},
7168 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7169 (@value{GDBN} can only append data to files in raw binary form.)
7172 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7173 Restore the contents of file @var{filename} into memory. The
7174 @code{restore} command can automatically recognize any known @sc{bfd}
7175 file format, except for raw binary. To restore a raw binary file you
7176 must specify the optional keyword @code{binary} after the filename.
7178 If @var{bias} is non-zero, its value will be added to the addresses
7179 contained in the file. Binary files always start at address zero, so
7180 they will be restored at address @var{bias}. Other bfd files have
7181 a built-in location; they will be restored at offset @var{bias}
7184 If @var{start} and/or @var{end} are non-zero, then only data between
7185 file offset @var{start} and file offset @var{end} will be restored.
7186 These offsets are relative to the addresses in the file, before
7187 the @var{bias} argument is applied.
7191 @node Core File Generation
7192 @section How to Produce a Core File from Your Program
7193 @cindex dump core from inferior
7195 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7196 image of a running process and its process status (register values
7197 etc.). Its primary use is post-mortem debugging of a program that
7198 crashed while it ran outside a debugger. A program that crashes
7199 automatically produces a core file, unless this feature is disabled by
7200 the user. @xref{Files}, for information on invoking @value{GDBN} in
7201 the post-mortem debugging mode.
7203 Occasionally, you may wish to produce a core file of the program you
7204 are debugging in order to preserve a snapshot of its state.
7205 @value{GDBN} has a special command for that.
7209 @kindex generate-core-file
7210 @item generate-core-file [@var{file}]
7211 @itemx gcore [@var{file}]
7212 Produce a core dump of the inferior process. The optional argument
7213 @var{file} specifies the file name where to put the core dump. If not
7214 specified, the file name defaults to @file{core.@var{pid}}, where
7215 @var{pid} is the inferior process ID.
7217 Note that this command is implemented only for some systems (as of
7218 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7221 @node Character Sets
7222 @section Character Sets
7223 @cindex character sets
7225 @cindex translating between character sets
7226 @cindex host character set
7227 @cindex target character set
7229 If the program you are debugging uses a different character set to
7230 represent characters and strings than the one @value{GDBN} uses itself,
7231 @value{GDBN} can automatically translate between the character sets for
7232 you. The character set @value{GDBN} uses we call the @dfn{host
7233 character set}; the one the inferior program uses we call the
7234 @dfn{target character set}.
7236 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7237 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7238 remote protocol (@pxref{Remote Debugging}) to debug a program
7239 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7240 then the host character set is Latin-1, and the target character set is
7241 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7242 target-charset EBCDIC-US}, then @value{GDBN} translates between
7243 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7244 character and string literals in expressions.
7246 @value{GDBN} has no way to automatically recognize which character set
7247 the inferior program uses; you must tell it, using the @code{set
7248 target-charset} command, described below.
7250 Here are the commands for controlling @value{GDBN}'s character set
7254 @item set target-charset @var{charset}
7255 @kindex set target-charset
7256 Set the current target character set to @var{charset}. We list the
7257 character set names @value{GDBN} recognizes below, but if you type
7258 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7259 list the target character sets it supports.
7263 @item set host-charset @var{charset}
7264 @kindex set host-charset
7265 Set the current host character set to @var{charset}.
7267 By default, @value{GDBN} uses a host character set appropriate to the
7268 system it is running on; you can override that default using the
7269 @code{set host-charset} command.
7271 @value{GDBN} can only use certain character sets as its host character
7272 set. We list the character set names @value{GDBN} recognizes below, and
7273 indicate which can be host character sets, but if you type
7274 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7275 list the host character sets it supports.
7277 @item set charset @var{charset}
7279 Set the current host and target character sets to @var{charset}. As
7280 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7281 @value{GDBN} will list the name of the character sets that can be used
7282 for both host and target.
7286 @kindex show charset
7287 Show the names of the current host and target charsets.
7289 @itemx show host-charset
7290 @kindex show host-charset
7291 Show the name of the current host charset.
7293 @itemx show target-charset
7294 @kindex show target-charset
7295 Show the name of the current target charset.
7299 @value{GDBN} currently includes support for the following character
7305 @cindex ASCII character set
7306 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7310 @cindex ISO 8859-1 character set
7311 @cindex ISO Latin 1 character set
7312 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7313 characters needed for French, German, and Spanish. @value{GDBN} can use
7314 this as its host character set.
7318 @cindex EBCDIC character set
7319 @cindex IBM1047 character set
7320 Variants of the @sc{ebcdic} character set, used on some of IBM's
7321 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7322 @value{GDBN} cannot use these as its host character set.
7326 Note that these are all single-byte character sets. More work inside
7327 @value{GDBN} is needed to support multi-byte or variable-width character
7328 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7330 Here is an example of @value{GDBN}'s character set support in action.
7331 Assume that the following source code has been placed in the file
7332 @file{charset-test.c}:
7338 = @{72, 101, 108, 108, 111, 44, 32, 119,
7339 111, 114, 108, 100, 33, 10, 0@};
7340 char ibm1047_hello[]
7341 = @{200, 133, 147, 147, 150, 107, 64, 166,
7342 150, 153, 147, 132, 90, 37, 0@};
7346 printf ("Hello, world!\n");
7350 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7351 containing the string @samp{Hello, world!} followed by a newline,
7352 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7354 We compile the program, and invoke the debugger on it:
7357 $ gcc -g charset-test.c -o charset-test
7358 $ gdb -nw charset-test
7359 GNU gdb 2001-12-19-cvs
7360 Copyright 2001 Free Software Foundation, Inc.
7365 We can use the @code{show charset} command to see what character sets
7366 @value{GDBN} is currently using to interpret and display characters and
7370 (@value{GDBP}) show charset
7371 The current host and target character set is `ISO-8859-1'.
7375 For the sake of printing this manual, let's use @sc{ascii} as our
7376 initial character set:
7378 (@value{GDBP}) set charset ASCII
7379 (@value{GDBP}) show charset
7380 The current host and target character set is `ASCII'.
7384 Let's assume that @sc{ascii} is indeed the correct character set for our
7385 host system --- in other words, let's assume that if @value{GDBN} prints
7386 characters using the @sc{ascii} character set, our terminal will display
7387 them properly. Since our current target character set is also
7388 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7391 (@value{GDBP}) print ascii_hello
7392 $1 = 0x401698 "Hello, world!\n"
7393 (@value{GDBP}) print ascii_hello[0]
7398 @value{GDBN} uses the target character set for character and string
7399 literals you use in expressions:
7402 (@value{GDBP}) print '+'
7407 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7410 @value{GDBN} relies on the user to tell it which character set the
7411 target program uses. If we print @code{ibm1047_hello} while our target
7412 character set is still @sc{ascii}, we get jibberish:
7415 (@value{GDBP}) print ibm1047_hello
7416 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7417 (@value{GDBP}) print ibm1047_hello[0]
7422 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7423 @value{GDBN} tells us the character sets it supports:
7426 (@value{GDBP}) set target-charset
7427 ASCII EBCDIC-US IBM1047 ISO-8859-1
7428 (@value{GDBP}) set target-charset
7431 We can select @sc{ibm1047} as our target character set, and examine the
7432 program's strings again. Now the @sc{ascii} string is wrong, but
7433 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7434 target character set, @sc{ibm1047}, to the host character set,
7435 @sc{ascii}, and they display correctly:
7438 (@value{GDBP}) set target-charset IBM1047
7439 (@value{GDBP}) show charset
7440 The current host character set is `ASCII'.
7441 The current target character set is `IBM1047'.
7442 (@value{GDBP}) print ascii_hello
7443 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7444 (@value{GDBP}) print ascii_hello[0]
7446 (@value{GDBP}) print ibm1047_hello
7447 $8 = 0x4016a8 "Hello, world!\n"
7448 (@value{GDBP}) print ibm1047_hello[0]
7453 As above, @value{GDBN} uses the target character set for character and
7454 string literals you use in expressions:
7457 (@value{GDBP}) print '+'
7462 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7465 @node Caching Remote Data
7466 @section Caching Data of Remote Targets
7467 @cindex caching data of remote targets
7469 @value{GDBN} can cache data exchanged between the debugger and a
7470 remote target (@pxref{Remote Debugging}). Such caching generally improves
7471 performance, because it reduces the overhead of the remote protocol by
7472 bundling memory reads and writes into large chunks. Unfortunately,
7473 @value{GDBN} does not currently know anything about volatile
7474 registers, and thus data caching will produce incorrect results when
7475 volatile registers are in use.
7478 @kindex set remotecache
7479 @item set remotecache on
7480 @itemx set remotecache off
7481 Set caching state for remote targets. When @code{ON}, use data
7482 caching. By default, this option is @code{OFF}.
7484 @kindex show remotecache
7485 @item show remotecache
7486 Show the current state of data caching for remote targets.
7490 Print the information about the data cache performance. The
7491 information displayed includes: the dcache width and depth; and for
7492 each cache line, how many times it was referenced, and its data and
7493 state (dirty, bad, ok, etc.). This command is useful for debugging
7494 the data cache operation.
7499 @chapter C Preprocessor Macros
7501 Some languages, such as C and C@t{++}, provide a way to define and invoke
7502 ``preprocessor macros'' which expand into strings of tokens.
7503 @value{GDBN} can evaluate expressions containing macro invocations, show
7504 the result of macro expansion, and show a macro's definition, including
7505 where it was defined.
7507 You may need to compile your program specially to provide @value{GDBN}
7508 with information about preprocessor macros. Most compilers do not
7509 include macros in their debugging information, even when you compile
7510 with the @option{-g} flag. @xref{Compilation}.
7512 A program may define a macro at one point, remove that definition later,
7513 and then provide a different definition after that. Thus, at different
7514 points in the program, a macro may have different definitions, or have
7515 no definition at all. If there is a current stack frame, @value{GDBN}
7516 uses the macros in scope at that frame's source code line. Otherwise,
7517 @value{GDBN} uses the macros in scope at the current listing location;
7520 At the moment, @value{GDBN} does not support the @code{##}
7521 token-splicing operator, the @code{#} stringification operator, or
7522 variable-arity macros.
7524 Whenever @value{GDBN} evaluates an expression, it always expands any
7525 macro invocations present in the expression. @value{GDBN} also provides
7526 the following commands for working with macros explicitly.
7530 @kindex macro expand
7531 @cindex macro expansion, showing the results of preprocessor
7532 @cindex preprocessor macro expansion, showing the results of
7533 @cindex expanding preprocessor macros
7534 @item macro expand @var{expression}
7535 @itemx macro exp @var{expression}
7536 Show the results of expanding all preprocessor macro invocations in
7537 @var{expression}. Since @value{GDBN} simply expands macros, but does
7538 not parse the result, @var{expression} need not be a valid expression;
7539 it can be any string of tokens.
7542 @item macro expand-once @var{expression}
7543 @itemx macro exp1 @var{expression}
7544 @cindex expand macro once
7545 @i{(This command is not yet implemented.)} Show the results of
7546 expanding those preprocessor macro invocations that appear explicitly in
7547 @var{expression}. Macro invocations appearing in that expansion are
7548 left unchanged. This command allows you to see the effect of a
7549 particular macro more clearly, without being confused by further
7550 expansions. Since @value{GDBN} simply expands macros, but does not
7551 parse the result, @var{expression} need not be a valid expression; it
7552 can be any string of tokens.
7555 @cindex macro definition, showing
7556 @cindex definition, showing a macro's
7557 @item info macro @var{macro}
7558 Show the definition of the macro named @var{macro}, and describe the
7559 source location where that definition was established.
7561 @kindex macro define
7562 @cindex user-defined macros
7563 @cindex defining macros interactively
7564 @cindex macros, user-defined
7565 @item macro define @var{macro} @var{replacement-list}
7566 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7567 @i{(This command is not yet implemented.)} Introduce a definition for a
7568 preprocessor macro named @var{macro}, invocations of which are replaced
7569 by the tokens given in @var{replacement-list}. The first form of this
7570 command defines an ``object-like'' macro, which takes no arguments; the
7571 second form defines a ``function-like'' macro, which takes the arguments
7572 given in @var{arglist}.
7574 A definition introduced by this command is in scope in every expression
7575 evaluated in @value{GDBN}, until it is removed with the @command{macro
7576 undef} command, described below. The definition overrides all
7577 definitions for @var{macro} present in the program being debugged, as
7578 well as any previous user-supplied definition.
7581 @item macro undef @var{macro}
7582 @i{(This command is not yet implemented.)} Remove any user-supplied
7583 definition for the macro named @var{macro}. This command only affects
7584 definitions provided with the @command{macro define} command, described
7585 above; it cannot remove definitions present in the program being
7590 @i{(This command is not yet implemented.)} List all the macros
7591 defined using the @code{macro define} command.
7594 @cindex macros, example of debugging with
7595 Here is a transcript showing the above commands in action. First, we
7596 show our source files:
7604 #define ADD(x) (M + x)
7609 printf ("Hello, world!\n");
7611 printf ("We're so creative.\n");
7613 printf ("Goodbye, world!\n");
7620 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7621 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7622 compiler includes information about preprocessor macros in the debugging
7626 $ gcc -gdwarf-2 -g3 sample.c -o sample
7630 Now, we start @value{GDBN} on our sample program:
7634 GNU gdb 2002-05-06-cvs
7635 Copyright 2002 Free Software Foundation, Inc.
7636 GDB is free software, @dots{}
7640 We can expand macros and examine their definitions, even when the
7641 program is not running. @value{GDBN} uses the current listing position
7642 to decide which macro definitions are in scope:
7645 (@value{GDBP}) list main
7648 5 #define ADD(x) (M + x)
7653 10 printf ("Hello, world!\n");
7655 12 printf ("We're so creative.\n");
7656 (@value{GDBP}) info macro ADD
7657 Defined at /home/jimb/gdb/macros/play/sample.c:5
7658 #define ADD(x) (M + x)
7659 (@value{GDBP}) info macro Q
7660 Defined at /home/jimb/gdb/macros/play/sample.h:1
7661 included at /home/jimb/gdb/macros/play/sample.c:2
7663 (@value{GDBP}) macro expand ADD(1)
7664 expands to: (42 + 1)
7665 (@value{GDBP}) macro expand-once ADD(1)
7666 expands to: once (M + 1)
7670 In the example above, note that @command{macro expand-once} expands only
7671 the macro invocation explicit in the original text --- the invocation of
7672 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7673 which was introduced by @code{ADD}.
7675 Once the program is running, @value{GDBN} uses the macro definitions in
7676 force at the source line of the current stack frame:
7679 (@value{GDBP}) break main
7680 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7682 Starting program: /home/jimb/gdb/macros/play/sample
7684 Breakpoint 1, main () at sample.c:10
7685 10 printf ("Hello, world!\n");
7689 At line 10, the definition of the macro @code{N} at line 9 is in force:
7692 (@value{GDBP}) info macro N
7693 Defined at /home/jimb/gdb/macros/play/sample.c:9
7695 (@value{GDBP}) macro expand N Q M
7697 (@value{GDBP}) print N Q M
7702 As we step over directives that remove @code{N}'s definition, and then
7703 give it a new definition, @value{GDBN} finds the definition (or lack
7704 thereof) in force at each point:
7709 12 printf ("We're so creative.\n");
7710 (@value{GDBP}) info macro N
7711 The symbol `N' has no definition as a C/C++ preprocessor macro
7712 at /home/jimb/gdb/macros/play/sample.c:12
7715 14 printf ("Goodbye, world!\n");
7716 (@value{GDBP}) info macro N
7717 Defined at /home/jimb/gdb/macros/play/sample.c:13
7719 (@value{GDBP}) macro expand N Q M
7720 expands to: 1729 < 42
7721 (@value{GDBP}) print N Q M
7728 @chapter Tracepoints
7729 @c This chapter is based on the documentation written by Michael
7730 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7733 In some applications, it is not feasible for the debugger to interrupt
7734 the program's execution long enough for the developer to learn
7735 anything helpful about its behavior. If the program's correctness
7736 depends on its real-time behavior, delays introduced by a debugger
7737 might cause the program to change its behavior drastically, or perhaps
7738 fail, even when the code itself is correct. It is useful to be able
7739 to observe the program's behavior without interrupting it.
7741 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7742 specify locations in the program, called @dfn{tracepoints}, and
7743 arbitrary expressions to evaluate when those tracepoints are reached.
7744 Later, using the @code{tfind} command, you can examine the values
7745 those expressions had when the program hit the tracepoints. The
7746 expressions may also denote objects in memory---structures or arrays,
7747 for example---whose values @value{GDBN} should record; while visiting
7748 a particular tracepoint, you may inspect those objects as if they were
7749 in memory at that moment. However, because @value{GDBN} records these
7750 values without interacting with you, it can do so quickly and
7751 unobtrusively, hopefully not disturbing the program's behavior.
7753 The tracepoint facility is currently available only for remote
7754 targets. @xref{Targets}. In addition, your remote target must know
7755 how to collect trace data. This functionality is implemented in the
7756 remote stub; however, none of the stubs distributed with @value{GDBN}
7757 support tracepoints as of this writing. The format of the remote
7758 packets used to implement tracepoints are described in @ref{Tracepoint
7761 This chapter describes the tracepoint commands and features.
7765 * Analyze Collected Data::
7766 * Tracepoint Variables::
7769 @node Set Tracepoints
7770 @section Commands to Set Tracepoints
7772 Before running such a @dfn{trace experiment}, an arbitrary number of
7773 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7774 tracepoint has a number assigned to it by @value{GDBN}. Like with
7775 breakpoints, tracepoint numbers are successive integers starting from
7776 one. Many of the commands associated with tracepoints take the
7777 tracepoint number as their argument, to identify which tracepoint to
7780 For each tracepoint, you can specify, in advance, some arbitrary set
7781 of data that you want the target to collect in the trace buffer when
7782 it hits that tracepoint. The collected data can include registers,
7783 local variables, or global data. Later, you can use @value{GDBN}
7784 commands to examine the values these data had at the time the
7787 This section describes commands to set tracepoints and associated
7788 conditions and actions.
7791 * Create and Delete Tracepoints::
7792 * Enable and Disable Tracepoints::
7793 * Tracepoint Passcounts::
7794 * Tracepoint Actions::
7795 * Listing Tracepoints::
7796 * Starting and Stopping Trace Experiments::
7799 @node Create and Delete Tracepoints
7800 @subsection Create and Delete Tracepoints
7803 @cindex set tracepoint
7806 The @code{trace} command is very similar to the @code{break} command.
7807 Its argument can be a source line, a function name, or an address in
7808 the target program. @xref{Set Breaks}. The @code{trace} command
7809 defines a tracepoint, which is a point in the target program where the
7810 debugger will briefly stop, collect some data, and then allow the
7811 program to continue. Setting a tracepoint or changing its commands
7812 doesn't take effect until the next @code{tstart} command; thus, you
7813 cannot change the tracepoint attributes once a trace experiment is
7816 Here are some examples of using the @code{trace} command:
7819 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7821 (@value{GDBP}) @b{trace +2} // 2 lines forward
7823 (@value{GDBP}) @b{trace my_function} // first source line of function
7825 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7827 (@value{GDBP}) @b{trace *0x2117c4} // an address
7831 You can abbreviate @code{trace} as @code{tr}.
7834 @cindex last tracepoint number
7835 @cindex recent tracepoint number
7836 @cindex tracepoint number
7837 The convenience variable @code{$tpnum} records the tracepoint number
7838 of the most recently set tracepoint.
7840 @kindex delete tracepoint
7841 @cindex tracepoint deletion
7842 @item delete tracepoint @r{[}@var{num}@r{]}
7843 Permanently delete one or more tracepoints. With no argument, the
7844 default is to delete all tracepoints.
7849 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7851 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7855 You can abbreviate this command as @code{del tr}.
7858 @node Enable and Disable Tracepoints
7859 @subsection Enable and Disable Tracepoints
7862 @kindex disable tracepoint
7863 @item disable tracepoint @r{[}@var{num}@r{]}
7864 Disable tracepoint @var{num}, or all tracepoints if no argument
7865 @var{num} is given. A disabled tracepoint will have no effect during
7866 the next trace experiment, but it is not forgotten. You can re-enable
7867 a disabled tracepoint using the @code{enable tracepoint} command.
7869 @kindex enable tracepoint
7870 @item enable tracepoint @r{[}@var{num}@r{]}
7871 Enable tracepoint @var{num}, or all tracepoints. The enabled
7872 tracepoints will become effective the next time a trace experiment is
7876 @node Tracepoint Passcounts
7877 @subsection Tracepoint Passcounts
7881 @cindex tracepoint pass count
7882 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7883 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7884 automatically stop a trace experiment. If a tracepoint's passcount is
7885 @var{n}, then the trace experiment will be automatically stopped on
7886 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7887 @var{num} is not specified, the @code{passcount} command sets the
7888 passcount of the most recently defined tracepoint. If no passcount is
7889 given, the trace experiment will run until stopped explicitly by the
7895 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7896 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7898 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7899 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7900 (@value{GDBP}) @b{trace foo}
7901 (@value{GDBP}) @b{pass 3}
7902 (@value{GDBP}) @b{trace bar}
7903 (@value{GDBP}) @b{pass 2}
7904 (@value{GDBP}) @b{trace baz}
7905 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7906 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7907 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7908 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7912 @node Tracepoint Actions
7913 @subsection Tracepoint Action Lists
7917 @cindex tracepoint actions
7918 @item actions @r{[}@var{num}@r{]}
7919 This command will prompt for a list of actions to be taken when the
7920 tracepoint is hit. If the tracepoint number @var{num} is not
7921 specified, this command sets the actions for the one that was most
7922 recently defined (so that you can define a tracepoint and then say
7923 @code{actions} without bothering about its number). You specify the
7924 actions themselves on the following lines, one action at a time, and
7925 terminate the actions list with a line containing just @code{end}. So
7926 far, the only defined actions are @code{collect} and
7927 @code{while-stepping}.
7929 @cindex remove actions from a tracepoint
7930 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7931 and follow it immediately with @samp{end}.
7934 (@value{GDBP}) @b{collect @var{data}} // collect some data
7936 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7938 (@value{GDBP}) @b{end} // signals the end of actions.
7941 In the following example, the action list begins with @code{collect}
7942 commands indicating the things to be collected when the tracepoint is
7943 hit. Then, in order to single-step and collect additional data
7944 following the tracepoint, a @code{while-stepping} command is used,
7945 followed by the list of things to be collected while stepping. The
7946 @code{while-stepping} command is terminated by its own separate
7947 @code{end} command. Lastly, the action list is terminated by an
7951 (@value{GDBP}) @b{trace foo}
7952 (@value{GDBP}) @b{actions}
7953 Enter actions for tracepoint 1, one per line:
7962 @kindex collect @r{(tracepoints)}
7963 @item collect @var{expr1}, @var{expr2}, @dots{}
7964 Collect values of the given expressions when the tracepoint is hit.
7965 This command accepts a comma-separated list of any valid expressions.
7966 In addition to global, static, or local variables, the following
7967 special arguments are supported:
7971 collect all registers
7974 collect all function arguments
7977 collect all local variables.
7980 You can give several consecutive @code{collect} commands, each one
7981 with a single argument, or one @code{collect} command with several
7982 arguments separated by commas: the effect is the same.
7984 The command @code{info scope} (@pxref{Symbols, info scope}) is
7985 particularly useful for figuring out what data to collect.
7987 @kindex while-stepping @r{(tracepoints)}
7988 @item while-stepping @var{n}
7989 Perform @var{n} single-step traces after the tracepoint, collecting
7990 new data at each step. The @code{while-stepping} command is
7991 followed by the list of what to collect while stepping (followed by
7992 its own @code{end} command):
7996 > collect $regs, myglobal
8002 You may abbreviate @code{while-stepping} as @code{ws} or
8006 @node Listing Tracepoints
8007 @subsection Listing Tracepoints
8010 @kindex info tracepoints
8012 @cindex information about tracepoints
8013 @item info tracepoints @r{[}@var{num}@r{]}
8014 Display information about the tracepoint @var{num}. If you don't specify
8015 a tracepoint number, displays information about all the tracepoints
8016 defined so far. For each tracepoint, the following information is
8023 whether it is enabled or disabled
8027 its passcount as given by the @code{passcount @var{n}} command
8029 its step count as given by the @code{while-stepping @var{n}} command
8031 where in the source files is the tracepoint set
8033 its action list as given by the @code{actions} command
8037 (@value{GDBP}) @b{info trace}
8038 Num Enb Address PassC StepC What
8039 1 y 0x002117c4 0 0 <gdb_asm>
8040 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8041 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8046 This command can be abbreviated @code{info tp}.
8049 @node Starting and Stopping Trace Experiments
8050 @subsection Starting and Stopping Trace Experiments
8054 @cindex start a new trace experiment
8055 @cindex collected data discarded
8057 This command takes no arguments. It starts the trace experiment, and
8058 begins collecting data. This has the side effect of discarding all
8059 the data collected in the trace buffer during the previous trace
8063 @cindex stop a running trace experiment
8065 This command takes no arguments. It ends the trace experiment, and
8066 stops collecting data.
8068 @strong{Note}: a trace experiment and data collection may stop
8069 automatically if any tracepoint's passcount is reached
8070 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8073 @cindex status of trace data collection
8074 @cindex trace experiment, status of
8076 This command displays the status of the current trace data
8080 Here is an example of the commands we described so far:
8083 (@value{GDBP}) @b{trace gdb_c_test}
8084 (@value{GDBP}) @b{actions}
8085 Enter actions for tracepoint #1, one per line.
8086 > collect $regs,$locals,$args
8091 (@value{GDBP}) @b{tstart}
8092 [time passes @dots{}]
8093 (@value{GDBP}) @b{tstop}
8097 @node Analyze Collected Data
8098 @section Using the Collected Data
8100 After the tracepoint experiment ends, you use @value{GDBN} commands
8101 for examining the trace data. The basic idea is that each tracepoint
8102 collects a trace @dfn{snapshot} every time it is hit and another
8103 snapshot every time it single-steps. All these snapshots are
8104 consecutively numbered from zero and go into a buffer, and you can
8105 examine them later. The way you examine them is to @dfn{focus} on a
8106 specific trace snapshot. When the remote stub is focused on a trace
8107 snapshot, it will respond to all @value{GDBN} requests for memory and
8108 registers by reading from the buffer which belongs to that snapshot,
8109 rather than from @emph{real} memory or registers of the program being
8110 debugged. This means that @strong{all} @value{GDBN} commands
8111 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8112 behave as if we were currently debugging the program state as it was
8113 when the tracepoint occurred. Any requests for data that are not in
8114 the buffer will fail.
8117 * tfind:: How to select a trace snapshot
8118 * tdump:: How to display all data for a snapshot
8119 * save-tracepoints:: How to save tracepoints for a future run
8123 @subsection @code{tfind @var{n}}
8126 @cindex select trace snapshot
8127 @cindex find trace snapshot
8128 The basic command for selecting a trace snapshot from the buffer is
8129 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8130 counting from zero. If no argument @var{n} is given, the next
8131 snapshot is selected.
8133 Here are the various forms of using the @code{tfind} command.
8137 Find the first snapshot in the buffer. This is a synonym for
8138 @code{tfind 0} (since 0 is the number of the first snapshot).
8141 Stop debugging trace snapshots, resume @emph{live} debugging.
8144 Same as @samp{tfind none}.
8147 No argument means find the next trace snapshot.
8150 Find the previous trace snapshot before the current one. This permits
8151 retracing earlier steps.
8153 @item tfind tracepoint @var{num}
8154 Find the next snapshot associated with tracepoint @var{num}. Search
8155 proceeds forward from the last examined trace snapshot. If no
8156 argument @var{num} is given, it means find the next snapshot collected
8157 for the same tracepoint as the current snapshot.
8159 @item tfind pc @var{addr}
8160 Find the next snapshot associated with the value @var{addr} of the
8161 program counter. Search proceeds forward from the last examined trace
8162 snapshot. If no argument @var{addr} is given, it means find the next
8163 snapshot with the same value of PC as the current snapshot.
8165 @item tfind outside @var{addr1}, @var{addr2}
8166 Find the next snapshot whose PC is outside the given range of
8169 @item tfind range @var{addr1}, @var{addr2}
8170 Find the next snapshot whose PC is between @var{addr1} and
8171 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8173 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8174 Find the next snapshot associated with the source line @var{n}. If
8175 the optional argument @var{file} is given, refer to line @var{n} in
8176 that source file. Search proceeds forward from the last examined
8177 trace snapshot. If no argument @var{n} is given, it means find the
8178 next line other than the one currently being examined; thus saying
8179 @code{tfind line} repeatedly can appear to have the same effect as
8180 stepping from line to line in a @emph{live} debugging session.
8183 The default arguments for the @code{tfind} commands are specifically
8184 designed to make it easy to scan through the trace buffer. For
8185 instance, @code{tfind} with no argument selects the next trace
8186 snapshot, and @code{tfind -} with no argument selects the previous
8187 trace snapshot. So, by giving one @code{tfind} command, and then
8188 simply hitting @key{RET} repeatedly you can examine all the trace
8189 snapshots in order. Or, by saying @code{tfind -} and then hitting
8190 @key{RET} repeatedly you can examine the snapshots in reverse order.
8191 The @code{tfind line} command with no argument selects the snapshot
8192 for the next source line executed. The @code{tfind pc} command with
8193 no argument selects the next snapshot with the same program counter
8194 (PC) as the current frame. The @code{tfind tracepoint} command with
8195 no argument selects the next trace snapshot collected by the same
8196 tracepoint as the current one.
8198 In addition to letting you scan through the trace buffer manually,
8199 these commands make it easy to construct @value{GDBN} scripts that
8200 scan through the trace buffer and print out whatever collected data
8201 you are interested in. Thus, if we want to examine the PC, FP, and SP
8202 registers from each trace frame in the buffer, we can say this:
8205 (@value{GDBP}) @b{tfind start}
8206 (@value{GDBP}) @b{while ($trace_frame != -1)}
8207 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8208 $trace_frame, $pc, $sp, $fp
8212 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8213 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8214 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8215 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8216 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8217 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8218 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8219 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8220 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8221 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8222 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8225 Or, if we want to examine the variable @code{X} at each source line in
8229 (@value{GDBP}) @b{tfind start}
8230 (@value{GDBP}) @b{while ($trace_frame != -1)}
8231 > printf "Frame %d, X == %d\n", $trace_frame, X
8241 @subsection @code{tdump}
8243 @cindex dump all data collected at tracepoint
8244 @cindex tracepoint data, display
8246 This command takes no arguments. It prints all the data collected at
8247 the current trace snapshot.
8250 (@value{GDBP}) @b{trace 444}
8251 (@value{GDBP}) @b{actions}
8252 Enter actions for tracepoint #2, one per line:
8253 > collect $regs, $locals, $args, gdb_long_test
8256 (@value{GDBP}) @b{tstart}
8258 (@value{GDBP}) @b{tfind line 444}
8259 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8261 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8263 (@value{GDBP}) @b{tdump}
8264 Data collected at tracepoint 2, trace frame 1:
8265 d0 0xc4aa0085 -995491707
8269 d4 0x71aea3d 119204413
8274 a1 0x3000668 50333288
8277 a4 0x3000698 50333336
8279 fp 0x30bf3c 0x30bf3c
8280 sp 0x30bf34 0x30bf34
8282 pc 0x20b2c8 0x20b2c8
8286 p = 0x20e5b4 "gdb-test"
8293 gdb_long_test = 17 '\021'
8298 @node save-tracepoints
8299 @subsection @code{save-tracepoints @var{filename}}
8300 @kindex save-tracepoints
8301 @cindex save tracepoints for future sessions
8303 This command saves all current tracepoint definitions together with
8304 their actions and passcounts, into a file @file{@var{filename}}
8305 suitable for use in a later debugging session. To read the saved
8306 tracepoint definitions, use the @code{source} command (@pxref{Command
8309 @node Tracepoint Variables
8310 @section Convenience Variables for Tracepoints
8311 @cindex tracepoint variables
8312 @cindex convenience variables for tracepoints
8315 @vindex $trace_frame
8316 @item (int) $trace_frame
8317 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8318 snapshot is selected.
8321 @item (int) $tracepoint
8322 The tracepoint for the current trace snapshot.
8325 @item (int) $trace_line
8326 The line number for the current trace snapshot.
8329 @item (char []) $trace_file
8330 The source file for the current trace snapshot.
8333 @item (char []) $trace_func
8334 The name of the function containing @code{$tracepoint}.
8337 Note: @code{$trace_file} is not suitable for use in @code{printf},
8338 use @code{output} instead.
8340 Here's a simple example of using these convenience variables for
8341 stepping through all the trace snapshots and printing some of their
8345 (@value{GDBP}) @b{tfind start}
8347 (@value{GDBP}) @b{while $trace_frame != -1}
8348 > output $trace_file
8349 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8355 @chapter Debugging Programs That Use Overlays
8358 If your program is too large to fit completely in your target system's
8359 memory, you can sometimes use @dfn{overlays} to work around this
8360 problem. @value{GDBN} provides some support for debugging programs that
8364 * How Overlays Work:: A general explanation of overlays.
8365 * Overlay Commands:: Managing overlays in @value{GDBN}.
8366 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8367 mapped by asking the inferior.
8368 * Overlay Sample Program:: A sample program using overlays.
8371 @node How Overlays Work
8372 @section How Overlays Work
8373 @cindex mapped overlays
8374 @cindex unmapped overlays
8375 @cindex load address, overlay's
8376 @cindex mapped address
8377 @cindex overlay area
8379 Suppose you have a computer whose instruction address space is only 64
8380 kilobytes long, but which has much more memory which can be accessed by
8381 other means: special instructions, segment registers, or memory
8382 management hardware, for example. Suppose further that you want to
8383 adapt a program which is larger than 64 kilobytes to run on this system.
8385 One solution is to identify modules of your program which are relatively
8386 independent, and need not call each other directly; call these modules
8387 @dfn{overlays}. Separate the overlays from the main program, and place
8388 their machine code in the larger memory. Place your main program in
8389 instruction memory, but leave at least enough space there to hold the
8390 largest overlay as well.
8392 Now, to call a function located in an overlay, you must first copy that
8393 overlay's machine code from the large memory into the space set aside
8394 for it in the instruction memory, and then jump to its entry point
8397 @c NB: In the below the mapped area's size is greater or equal to the
8398 @c size of all overlays. This is intentional to remind the developer
8399 @c that overlays don't necessarily need to be the same size.
8403 Data Instruction Larger
8404 Address Space Address Space Address Space
8405 +-----------+ +-----------+ +-----------+
8407 +-----------+ +-----------+ +-----------+<-- overlay 1
8408 | program | | main | .----| overlay 1 | load address
8409 | variables | | program | | +-----------+
8410 | and heap | | | | | |
8411 +-----------+ | | | +-----------+<-- overlay 2
8412 | | +-----------+ | | | load address
8413 +-----------+ | | | .-| overlay 2 |
8415 mapped --->+-----------+ | | +-----------+
8417 | overlay | <-' | | |
8418 | area | <---' +-----------+<-- overlay 3
8419 | | <---. | | load address
8420 +-----------+ `--| overlay 3 |
8427 @anchor{A code overlay}A code overlay
8431 The diagram (@pxref{A code overlay}) shows a system with separate data
8432 and instruction address spaces. To map an overlay, the program copies
8433 its code from the larger address space to the instruction address space.
8434 Since the overlays shown here all use the same mapped address, only one
8435 may be mapped at a time. For a system with a single address space for
8436 data and instructions, the diagram would be similar, except that the
8437 program variables and heap would share an address space with the main
8438 program and the overlay area.
8440 An overlay loaded into instruction memory and ready for use is called a
8441 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8442 instruction memory. An overlay not present (or only partially present)
8443 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8444 is its address in the larger memory. The mapped address is also called
8445 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8446 called the @dfn{load memory address}, or @dfn{LMA}.
8448 Unfortunately, overlays are not a completely transparent way to adapt a
8449 program to limited instruction memory. They introduce a new set of
8450 global constraints you must keep in mind as you design your program:
8455 Before calling or returning to a function in an overlay, your program
8456 must make sure that overlay is actually mapped. Otherwise, the call or
8457 return will transfer control to the right address, but in the wrong
8458 overlay, and your program will probably crash.
8461 If the process of mapping an overlay is expensive on your system, you
8462 will need to choose your overlays carefully to minimize their effect on
8463 your program's performance.
8466 The executable file you load onto your system must contain each
8467 overlay's instructions, appearing at the overlay's load address, not its
8468 mapped address. However, each overlay's instructions must be relocated
8469 and its symbols defined as if the overlay were at its mapped address.
8470 You can use GNU linker scripts to specify different load and relocation
8471 addresses for pieces of your program; see @ref{Overlay Description,,,
8472 ld.info, Using ld: the GNU linker}.
8475 The procedure for loading executable files onto your system must be able
8476 to load their contents into the larger address space as well as the
8477 instruction and data spaces.
8481 The overlay system described above is rather simple, and could be
8482 improved in many ways:
8487 If your system has suitable bank switch registers or memory management
8488 hardware, you could use those facilities to make an overlay's load area
8489 contents simply appear at their mapped address in instruction space.
8490 This would probably be faster than copying the overlay to its mapped
8491 area in the usual way.
8494 If your overlays are small enough, you could set aside more than one
8495 overlay area, and have more than one overlay mapped at a time.
8498 You can use overlays to manage data, as well as instructions. In
8499 general, data overlays are even less transparent to your design than
8500 code overlays: whereas code overlays only require care when you call or
8501 return to functions, data overlays require care every time you access
8502 the data. Also, if you change the contents of a data overlay, you
8503 must copy its contents back out to its load address before you can copy a
8504 different data overlay into the same mapped area.
8509 @node Overlay Commands
8510 @section Overlay Commands
8512 To use @value{GDBN}'s overlay support, each overlay in your program must
8513 correspond to a separate section of the executable file. The section's
8514 virtual memory address and load memory address must be the overlay's
8515 mapped and load addresses. Identifying overlays with sections allows
8516 @value{GDBN} to determine the appropriate address of a function or
8517 variable, depending on whether the overlay is mapped or not.
8519 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8520 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8525 Disable @value{GDBN}'s overlay support. When overlay support is
8526 disabled, @value{GDBN} assumes that all functions and variables are
8527 always present at their mapped addresses. By default, @value{GDBN}'s
8528 overlay support is disabled.
8530 @item overlay manual
8531 @cindex manual overlay debugging
8532 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8533 relies on you to tell it which overlays are mapped, and which are not,
8534 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8535 commands described below.
8537 @item overlay map-overlay @var{overlay}
8538 @itemx overlay map @var{overlay}
8539 @cindex map an overlay
8540 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8541 be the name of the object file section containing the overlay. When an
8542 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8543 functions and variables at their mapped addresses. @value{GDBN} assumes
8544 that any other overlays whose mapped ranges overlap that of
8545 @var{overlay} are now unmapped.
8547 @item overlay unmap-overlay @var{overlay}
8548 @itemx overlay unmap @var{overlay}
8549 @cindex unmap an overlay
8550 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8551 must be the name of the object file section containing the overlay.
8552 When an overlay is unmapped, @value{GDBN} assumes it can find the
8553 overlay's functions and variables at their load addresses.
8556 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8557 consults a data structure the overlay manager maintains in the inferior
8558 to see which overlays are mapped. For details, see @ref{Automatic
8561 @item overlay load-target
8563 @cindex reloading the overlay table
8564 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8565 re-reads the table @value{GDBN} automatically each time the inferior
8566 stops, so this command should only be necessary if you have changed the
8567 overlay mapping yourself using @value{GDBN}. This command is only
8568 useful when using automatic overlay debugging.
8570 @item overlay list-overlays
8572 @cindex listing mapped overlays
8573 Display a list of the overlays currently mapped, along with their mapped
8574 addresses, load addresses, and sizes.
8578 Normally, when @value{GDBN} prints a code address, it includes the name
8579 of the function the address falls in:
8582 (@value{GDBP}) print main
8583 $3 = @{int ()@} 0x11a0 <main>
8586 When overlay debugging is enabled, @value{GDBN} recognizes code in
8587 unmapped overlays, and prints the names of unmapped functions with
8588 asterisks around them. For example, if @code{foo} is a function in an
8589 unmapped overlay, @value{GDBN} prints it this way:
8592 (@value{GDBP}) overlay list
8593 No sections are mapped.
8594 (@value{GDBP}) print foo
8595 $5 = @{int (int)@} 0x100000 <*foo*>
8598 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8602 (@value{GDBP}) overlay list
8603 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8604 mapped at 0x1016 - 0x104a
8605 (@value{GDBP}) print foo
8606 $6 = @{int (int)@} 0x1016 <foo>
8609 When overlay debugging is enabled, @value{GDBN} can find the correct
8610 address for functions and variables in an overlay, whether or not the
8611 overlay is mapped. This allows most @value{GDBN} commands, like
8612 @code{break} and @code{disassemble}, to work normally, even on unmapped
8613 code. However, @value{GDBN}'s breakpoint support has some limitations:
8617 @cindex breakpoints in overlays
8618 @cindex overlays, setting breakpoints in
8619 You can set breakpoints in functions in unmapped overlays, as long as
8620 @value{GDBN} can write to the overlay at its load address.
8622 @value{GDBN} can not set hardware or simulator-based breakpoints in
8623 unmapped overlays. However, if you set a breakpoint at the end of your
8624 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8625 you are using manual overlay management), @value{GDBN} will re-set its
8626 breakpoints properly.
8630 @node Automatic Overlay Debugging
8631 @section Automatic Overlay Debugging
8632 @cindex automatic overlay debugging
8634 @value{GDBN} can automatically track which overlays are mapped and which
8635 are not, given some simple co-operation from the overlay manager in the
8636 inferior. If you enable automatic overlay debugging with the
8637 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8638 looks in the inferior's memory for certain variables describing the
8639 current state of the overlays.
8641 Here are the variables your overlay manager must define to support
8642 @value{GDBN}'s automatic overlay debugging:
8646 @item @code{_ovly_table}:
8647 This variable must be an array of the following structures:
8652 /* The overlay's mapped address. */
8655 /* The size of the overlay, in bytes. */
8658 /* The overlay's load address. */
8661 /* Non-zero if the overlay is currently mapped;
8663 unsigned long mapped;
8667 @item @code{_novlys}:
8668 This variable must be a four-byte signed integer, holding the total
8669 number of elements in @code{_ovly_table}.
8673 To decide whether a particular overlay is mapped or not, @value{GDBN}
8674 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8675 @code{lma} members equal the VMA and LMA of the overlay's section in the
8676 executable file. When @value{GDBN} finds a matching entry, it consults
8677 the entry's @code{mapped} member to determine whether the overlay is
8680 In addition, your overlay manager may define a function called
8681 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8682 will silently set a breakpoint there. If the overlay manager then
8683 calls this function whenever it has changed the overlay table, this
8684 will enable @value{GDBN} to accurately keep track of which overlays
8685 are in program memory, and update any breakpoints that may be set
8686 in overlays. This will allow breakpoints to work even if the
8687 overlays are kept in ROM or other non-writable memory while they
8688 are not being executed.
8690 @node Overlay Sample Program
8691 @section Overlay Sample Program
8692 @cindex overlay example program
8694 When linking a program which uses overlays, you must place the overlays
8695 at their load addresses, while relocating them to run at their mapped
8696 addresses. To do this, you must write a linker script (@pxref{Overlay
8697 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8698 since linker scripts are specific to a particular host system, target
8699 architecture, and target memory layout, this manual cannot provide
8700 portable sample code demonstrating @value{GDBN}'s overlay support.
8702 However, the @value{GDBN} source distribution does contain an overlaid
8703 program, with linker scripts for a few systems, as part of its test
8704 suite. The program consists of the following files from
8705 @file{gdb/testsuite/gdb.base}:
8709 The main program file.
8711 A simple overlay manager, used by @file{overlays.c}.
8716 Overlay modules, loaded and used by @file{overlays.c}.
8719 Linker scripts for linking the test program on the @code{d10v-elf}
8720 and @code{m32r-elf} targets.
8723 You can build the test program using the @code{d10v-elf} GCC
8724 cross-compiler like this:
8727 $ d10v-elf-gcc -g -c overlays.c
8728 $ d10v-elf-gcc -g -c ovlymgr.c
8729 $ d10v-elf-gcc -g -c foo.c
8730 $ d10v-elf-gcc -g -c bar.c
8731 $ d10v-elf-gcc -g -c baz.c
8732 $ d10v-elf-gcc -g -c grbx.c
8733 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8734 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8737 The build process is identical for any other architecture, except that
8738 you must substitute the appropriate compiler and linker script for the
8739 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8743 @chapter Using @value{GDBN} with Different Languages
8746 Although programming languages generally have common aspects, they are
8747 rarely expressed in the same manner. For instance, in ANSI C,
8748 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8749 Modula-2, it is accomplished by @code{p^}. Values can also be
8750 represented (and displayed) differently. Hex numbers in C appear as
8751 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8753 @cindex working language
8754 Language-specific information is built into @value{GDBN} for some languages,
8755 allowing you to express operations like the above in your program's
8756 native language, and allowing @value{GDBN} to output values in a manner
8757 consistent with the syntax of your program's native language. The
8758 language you use to build expressions is called the @dfn{working
8762 * Setting:: Switching between source languages
8763 * Show:: Displaying the language
8764 * Checks:: Type and range checks
8765 * Supported Languages:: Supported languages
8766 * Unsupported Languages:: Unsupported languages
8770 @section Switching Between Source Languages
8772 There are two ways to control the working language---either have @value{GDBN}
8773 set it automatically, or select it manually yourself. You can use the
8774 @code{set language} command for either purpose. On startup, @value{GDBN}
8775 defaults to setting the language automatically. The working language is
8776 used to determine how expressions you type are interpreted, how values
8779 In addition to the working language, every source file that
8780 @value{GDBN} knows about has its own working language. For some object
8781 file formats, the compiler might indicate which language a particular
8782 source file is in. However, most of the time @value{GDBN} infers the
8783 language from the name of the file. The language of a source file
8784 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8785 show each frame appropriately for its own language. There is no way to
8786 set the language of a source file from within @value{GDBN}, but you can
8787 set the language associated with a filename extension. @xref{Show, ,
8788 Displaying the Language}.
8790 This is most commonly a problem when you use a program, such
8791 as @code{cfront} or @code{f2c}, that generates C but is written in
8792 another language. In that case, make the
8793 program use @code{#line} directives in its C output; that way
8794 @value{GDBN} will know the correct language of the source code of the original
8795 program, and will display that source code, not the generated C code.
8798 * Filenames:: Filename extensions and languages.
8799 * Manually:: Setting the working language manually
8800 * Automatically:: Having @value{GDBN} infer the source language
8804 @subsection List of Filename Extensions and Languages
8806 If a source file name ends in one of the following extensions, then
8807 @value{GDBN} infers that its language is the one indicated.
8828 Objective-C source file
8835 Modula-2 source file
8839 Assembler source file. This actually behaves almost like C, but
8840 @value{GDBN} does not skip over function prologues when stepping.
8843 In addition, you may set the language associated with a filename
8844 extension. @xref{Show, , Displaying the Language}.
8847 @subsection Setting the Working Language
8849 If you allow @value{GDBN} to set the language automatically,
8850 expressions are interpreted the same way in your debugging session and
8853 @kindex set language
8854 If you wish, you may set the language manually. To do this, issue the
8855 command @samp{set language @var{lang}}, where @var{lang} is the name of
8857 @code{c} or @code{modula-2}.
8858 For a list of the supported languages, type @samp{set language}.
8860 Setting the language manually prevents @value{GDBN} from updating the working
8861 language automatically. This can lead to confusion if you try
8862 to debug a program when the working language is not the same as the
8863 source language, when an expression is acceptable to both
8864 languages---but means different things. For instance, if the current
8865 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8873 might not have the effect you intended. In C, this means to add
8874 @code{b} and @code{c} and place the result in @code{a}. The result
8875 printed would be the value of @code{a}. In Modula-2, this means to compare
8876 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8879 @subsection Having @value{GDBN} Infer the Source Language
8881 To have @value{GDBN} set the working language automatically, use
8882 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8883 then infers the working language. That is, when your program stops in a
8884 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8885 working language to the language recorded for the function in that
8886 frame. If the language for a frame is unknown (that is, if the function
8887 or block corresponding to the frame was defined in a source file that
8888 does not have a recognized extension), the current working language is
8889 not changed, and @value{GDBN} issues a warning.
8891 This may not seem necessary for most programs, which are written
8892 entirely in one source language. However, program modules and libraries
8893 written in one source language can be used by a main program written in
8894 a different source language. Using @samp{set language auto} in this
8895 case frees you from having to set the working language manually.
8898 @section Displaying the Language
8900 The following commands help you find out which language is the
8901 working language, and also what language source files were written in.
8905 @kindex show language
8906 Display the current working language. This is the
8907 language you can use with commands such as @code{print} to
8908 build and compute expressions that may involve variables in your program.
8911 @kindex info frame@r{, show the source language}
8912 Display the source language for this frame. This language becomes the
8913 working language if you use an identifier from this frame.
8914 @xref{Frame Info, ,Information about a Frame}, to identify the other
8915 information listed here.
8918 @kindex info source@r{, show the source language}
8919 Display the source language of this source file.
8920 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8921 information listed here.
8924 In unusual circumstances, you may have source files with extensions
8925 not in the standard list. You can then set the extension associated
8926 with a language explicitly:
8929 @item set extension-language @var{ext} @var{language}
8930 @kindex set extension-language
8931 Tell @value{GDBN} that source files with extension @var{ext} are to be
8932 assumed as written in the source language @var{language}.
8934 @item info extensions
8935 @kindex info extensions
8936 List all the filename extensions and the associated languages.
8940 @section Type and Range Checking
8943 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8944 checking are included, but they do not yet have any effect. This
8945 section documents the intended facilities.
8947 @c FIXME remove warning when type/range code added
8949 Some languages are designed to guard you against making seemingly common
8950 errors through a series of compile- and run-time checks. These include
8951 checking the type of arguments to functions and operators, and making
8952 sure mathematical overflows are caught at run time. Checks such as
8953 these help to ensure a program's correctness once it has been compiled
8954 by eliminating type mismatches, and providing active checks for range
8955 errors when your program is running.
8957 @value{GDBN} can check for conditions like the above if you wish.
8958 Although @value{GDBN} does not check the statements in your program,
8959 it can check expressions entered directly into @value{GDBN} for
8960 evaluation via the @code{print} command, for example. As with the
8961 working language, @value{GDBN} can also decide whether or not to check
8962 automatically based on your program's source language.
8963 @xref{Supported Languages, ,Supported Languages}, for the default
8964 settings of supported languages.
8967 * Type Checking:: An overview of type checking
8968 * Range Checking:: An overview of range checking
8971 @cindex type checking
8972 @cindex checks, type
8974 @subsection An Overview of Type Checking
8976 Some languages, such as Modula-2, are strongly typed, meaning that the
8977 arguments to operators and functions have to be of the correct type,
8978 otherwise an error occurs. These checks prevent type mismatch
8979 errors from ever causing any run-time problems. For example,
8987 The second example fails because the @code{CARDINAL} 1 is not
8988 type-compatible with the @code{REAL} 2.3.
8990 For the expressions you use in @value{GDBN} commands, you can tell the
8991 @value{GDBN} type checker to skip checking;
8992 to treat any mismatches as errors and abandon the expression;
8993 or to only issue warnings when type mismatches occur,
8994 but evaluate the expression anyway. When you choose the last of
8995 these, @value{GDBN} evaluates expressions like the second example above, but
8996 also issues a warning.
8998 Even if you turn type checking off, there may be other reasons
8999 related to type that prevent @value{GDBN} from evaluating an expression.
9000 For instance, @value{GDBN} does not know how to add an @code{int} and
9001 a @code{struct foo}. These particular type errors have nothing to do
9002 with the language in use, and usually arise from expressions, such as
9003 the one described above, which make little sense to evaluate anyway.
9005 Each language defines to what degree it is strict about type. For
9006 instance, both Modula-2 and C require the arguments to arithmetical
9007 operators to be numbers. In C, enumerated types and pointers can be
9008 represented as numbers, so that they are valid arguments to mathematical
9009 operators. @xref{Supported Languages, ,Supported Languages}, for further
9010 details on specific languages.
9012 @value{GDBN} provides some additional commands for controlling the type checker:
9014 @kindex set check type
9015 @kindex show check type
9017 @item set check type auto
9018 Set type checking on or off based on the current working language.
9019 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9022 @item set check type on
9023 @itemx set check type off
9024 Set type checking on or off, overriding the default setting for the
9025 current working language. Issue a warning if the setting does not
9026 match the language default. If any type mismatches occur in
9027 evaluating an expression while type checking is on, @value{GDBN} prints a
9028 message and aborts evaluation of the expression.
9030 @item set check type warn
9031 Cause the type checker to issue warnings, but to always attempt to
9032 evaluate the expression. Evaluating the expression may still
9033 be impossible for other reasons. For example, @value{GDBN} cannot add
9034 numbers and structures.
9037 Show the current setting of the type checker, and whether or not @value{GDBN}
9038 is setting it automatically.
9041 @cindex range checking
9042 @cindex checks, range
9043 @node Range Checking
9044 @subsection An Overview of Range Checking
9046 In some languages (such as Modula-2), it is an error to exceed the
9047 bounds of a type; this is enforced with run-time checks. Such range
9048 checking is meant to ensure program correctness by making sure
9049 computations do not overflow, or indices on an array element access do
9050 not exceed the bounds of the array.
9052 For expressions you use in @value{GDBN} commands, you can tell
9053 @value{GDBN} to treat range errors in one of three ways: ignore them,
9054 always treat them as errors and abandon the expression, or issue
9055 warnings but evaluate the expression anyway.
9057 A range error can result from numerical overflow, from exceeding an
9058 array index bound, or when you type a constant that is not a member
9059 of any type. Some languages, however, do not treat overflows as an
9060 error. In many implementations of C, mathematical overflow causes the
9061 result to ``wrap around'' to lower values---for example, if @var{m} is
9062 the largest integer value, and @var{s} is the smallest, then
9065 @var{m} + 1 @result{} @var{s}
9068 This, too, is specific to individual languages, and in some cases
9069 specific to individual compilers or machines. @xref{Supported Languages, ,
9070 Supported Languages}, for further details on specific languages.
9072 @value{GDBN} provides some additional commands for controlling the range checker:
9074 @kindex set check range
9075 @kindex show check range
9077 @item set check range auto
9078 Set range checking on or off based on the current working language.
9079 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9082 @item set check range on
9083 @itemx set check range off
9084 Set range checking on or off, overriding the default setting for the
9085 current working language. A warning is issued if the setting does not
9086 match the language default. If a range error occurs and range checking is on,
9087 then a message is printed and evaluation of the expression is aborted.
9089 @item set check range warn
9090 Output messages when the @value{GDBN} range checker detects a range error,
9091 but attempt to evaluate the expression anyway. Evaluating the
9092 expression may still be impossible for other reasons, such as accessing
9093 memory that the process does not own (a typical example from many Unix
9097 Show the current setting of the range checker, and whether or not it is
9098 being set automatically by @value{GDBN}.
9101 @node Supported Languages
9102 @section Supported Languages
9104 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9105 assembly, Modula-2, and Ada.
9106 @c This is false ...
9107 Some @value{GDBN} features may be used in expressions regardless of the
9108 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9109 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9110 ,Expressions}) can be used with the constructs of any supported
9113 The following sections detail to what degree each source language is
9114 supported by @value{GDBN}. These sections are not meant to be language
9115 tutorials or references, but serve only as a reference guide to what the
9116 @value{GDBN} expression parser accepts, and what input and output
9117 formats should look like for different languages. There are many good
9118 books written on each of these languages; please look to these for a
9119 language reference or tutorial.
9123 * Objective-C:: Objective-C
9126 * Modula-2:: Modula-2
9131 @subsection C and C@t{++}
9133 @cindex C and C@t{++}
9134 @cindex expressions in C or C@t{++}
9136 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9137 to both languages. Whenever this is the case, we discuss those languages
9141 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9142 @cindex @sc{gnu} C@t{++}
9143 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9144 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9145 effectively, you must compile your C@t{++} programs with a supported
9146 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9147 compiler (@code{aCC}).
9149 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9150 format; if it doesn't work on your system, try the stabs+ debugging
9151 format. You can select those formats explicitly with the @code{g++}
9152 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9153 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9154 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9157 * C Operators:: C and C@t{++} operators
9158 * C Constants:: C and C@t{++} constants
9159 * C Plus Plus Expressions:: C@t{++} expressions
9160 * C Defaults:: Default settings for C and C@t{++}
9161 * C Checks:: C and C@t{++} type and range checks
9162 * Debugging C:: @value{GDBN} and C
9163 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9164 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9168 @subsubsection C and C@t{++} Operators
9170 @cindex C and C@t{++} operators
9172 Operators must be defined on values of specific types. For instance,
9173 @code{+} is defined on numbers, but not on structures. Operators are
9174 often defined on groups of types.
9176 For the purposes of C and C@t{++}, the following definitions hold:
9181 @emph{Integral types} include @code{int} with any of its storage-class
9182 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9185 @emph{Floating-point types} include @code{float}, @code{double}, and
9186 @code{long double} (if supported by the target platform).
9189 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9192 @emph{Scalar types} include all of the above.
9197 The following operators are supported. They are listed here
9198 in order of increasing precedence:
9202 The comma or sequencing operator. Expressions in a comma-separated list
9203 are evaluated from left to right, with the result of the entire
9204 expression being the last expression evaluated.
9207 Assignment. The value of an assignment expression is the value
9208 assigned. Defined on scalar types.
9211 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9212 and translated to @w{@code{@var{a} = @var{a op b}}}.
9213 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9214 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9215 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9218 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9219 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9223 Logical @sc{or}. Defined on integral types.
9226 Logical @sc{and}. Defined on integral types.
9229 Bitwise @sc{or}. Defined on integral types.
9232 Bitwise exclusive-@sc{or}. Defined on integral types.
9235 Bitwise @sc{and}. Defined on integral types.
9238 Equality and inequality. Defined on scalar types. The value of these
9239 expressions is 0 for false and non-zero for true.
9241 @item <@r{, }>@r{, }<=@r{, }>=
9242 Less than, greater than, less than or equal, greater than or equal.
9243 Defined on scalar types. The value of these expressions is 0 for false
9244 and non-zero for true.
9247 left shift, and right shift. Defined on integral types.
9250 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9253 Addition and subtraction. Defined on integral types, floating-point types and
9256 @item *@r{, }/@r{, }%
9257 Multiplication, division, and modulus. Multiplication and division are
9258 defined on integral and floating-point types. Modulus is defined on
9262 Increment and decrement. When appearing before a variable, the
9263 operation is performed before the variable is used in an expression;
9264 when appearing after it, the variable's value is used before the
9265 operation takes place.
9268 Pointer dereferencing. Defined on pointer types. Same precedence as
9272 Address operator. Defined on variables. Same precedence as @code{++}.
9274 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9275 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9276 to examine the address
9277 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9281 Negative. Defined on integral and floating-point types. Same
9282 precedence as @code{++}.
9285 Logical negation. Defined on integral types. Same precedence as
9289 Bitwise complement operator. Defined on integral types. Same precedence as
9294 Structure member, and pointer-to-structure member. For convenience,
9295 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9296 pointer based on the stored type information.
9297 Defined on @code{struct} and @code{union} data.
9300 Dereferences of pointers to members.
9303 Array indexing. @code{@var{a}[@var{i}]} is defined as
9304 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9307 Function parameter list. Same precedence as @code{->}.
9310 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9311 and @code{class} types.
9314 Doubled colons also represent the @value{GDBN} scope operator
9315 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9319 If an operator is redefined in the user code, @value{GDBN} usually
9320 attempts to invoke the redefined version instead of using the operator's
9324 @subsubsection C and C@t{++} Constants
9326 @cindex C and C@t{++} constants
9328 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9333 Integer constants are a sequence of digits. Octal constants are
9334 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9335 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9336 @samp{l}, specifying that the constant should be treated as a
9340 Floating point constants are a sequence of digits, followed by a decimal
9341 point, followed by a sequence of digits, and optionally followed by an
9342 exponent. An exponent is of the form:
9343 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9344 sequence of digits. The @samp{+} is optional for positive exponents.
9345 A floating-point constant may also end with a letter @samp{f} or
9346 @samp{F}, specifying that the constant should be treated as being of
9347 the @code{float} (as opposed to the default @code{double}) type; or with
9348 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9352 Enumerated constants consist of enumerated identifiers, or their
9353 integral equivalents.
9356 Character constants are a single character surrounded by single quotes
9357 (@code{'}), or a number---the ordinal value of the corresponding character
9358 (usually its @sc{ascii} value). Within quotes, the single character may
9359 be represented by a letter or by @dfn{escape sequences}, which are of
9360 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9361 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9362 @samp{@var{x}} is a predefined special character---for example,
9363 @samp{\n} for newline.
9366 String constants are a sequence of character constants surrounded by
9367 double quotes (@code{"}). Any valid character constant (as described
9368 above) may appear. Double quotes within the string must be preceded by
9369 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9373 Pointer constants are an integral value. You can also write pointers
9374 to constants using the C operator @samp{&}.
9377 Array constants are comma-separated lists surrounded by braces @samp{@{}
9378 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9379 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9380 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9383 @node C Plus Plus Expressions
9384 @subsubsection C@t{++} Expressions
9386 @cindex expressions in C@t{++}
9387 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9389 @cindex debugging C@t{++} programs
9390 @cindex C@t{++} compilers
9391 @cindex debug formats and C@t{++}
9392 @cindex @value{NGCC} and C@t{++}
9394 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9395 proper compiler and the proper debug format. Currently, @value{GDBN}
9396 works best when debugging C@t{++} code that is compiled with
9397 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9398 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9399 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9400 stabs+ as their default debug format, so you usually don't need to
9401 specify a debug format explicitly. Other compilers and/or debug formats
9402 are likely to work badly or not at all when using @value{GDBN} to debug
9408 @cindex member functions
9410 Member function calls are allowed; you can use expressions like
9413 count = aml->GetOriginal(x, y)
9416 @vindex this@r{, inside C@t{++} member functions}
9417 @cindex namespace in C@t{++}
9419 While a member function is active (in the selected stack frame), your
9420 expressions have the same namespace available as the member function;
9421 that is, @value{GDBN} allows implicit references to the class instance
9422 pointer @code{this} following the same rules as C@t{++}.
9424 @cindex call overloaded functions
9425 @cindex overloaded functions, calling
9426 @cindex type conversions in C@t{++}
9428 You can call overloaded functions; @value{GDBN} resolves the function
9429 call to the right definition, with some restrictions. @value{GDBN} does not
9430 perform overload resolution involving user-defined type conversions,
9431 calls to constructors, or instantiations of templates that do not exist
9432 in the program. It also cannot handle ellipsis argument lists or
9435 It does perform integral conversions and promotions, floating-point
9436 promotions, arithmetic conversions, pointer conversions, conversions of
9437 class objects to base classes, and standard conversions such as those of
9438 functions or arrays to pointers; it requires an exact match on the
9439 number of function arguments.
9441 Overload resolution is always performed, unless you have specified
9442 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9443 ,@value{GDBN} Features for C@t{++}}.
9445 You must specify @code{set overload-resolution off} in order to use an
9446 explicit function signature to call an overloaded function, as in
9448 p 'foo(char,int)'('x', 13)
9451 The @value{GDBN} command-completion facility can simplify this;
9452 see @ref{Completion, ,Command Completion}.
9454 @cindex reference declarations
9456 @value{GDBN} understands variables declared as C@t{++} references; you can use
9457 them in expressions just as you do in C@t{++} source---they are automatically
9460 In the parameter list shown when @value{GDBN} displays a frame, the values of
9461 reference variables are not displayed (unlike other variables); this
9462 avoids clutter, since references are often used for large structures.
9463 The @emph{address} of a reference variable is always shown, unless
9464 you have specified @samp{set print address off}.
9467 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9468 expressions can use it just as expressions in your program do. Since
9469 one scope may be defined in another, you can use @code{::} repeatedly if
9470 necessary, for example in an expression like
9471 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9472 resolving name scope by reference to source files, in both C and C@t{++}
9473 debugging (@pxref{Variables, ,Program Variables}).
9476 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9477 calling virtual functions correctly, printing out virtual bases of
9478 objects, calling functions in a base subobject, casting objects, and
9479 invoking user-defined operators.
9482 @subsubsection C and C@t{++} Defaults
9484 @cindex C and C@t{++} defaults
9486 If you allow @value{GDBN} to set type and range checking automatically, they
9487 both default to @code{off} whenever the working language changes to
9488 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9489 selects the working language.
9491 If you allow @value{GDBN} to set the language automatically, it
9492 recognizes source files whose names end with @file{.c}, @file{.C}, or
9493 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9494 these files, it sets the working language to C or C@t{++}.
9495 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9496 for further details.
9498 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9499 @c unimplemented. If (b) changes, it might make sense to let this node
9500 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9503 @subsubsection C and C@t{++} Type and Range Checks
9505 @cindex C and C@t{++} checks
9507 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9508 is not used. However, if you turn type checking on, @value{GDBN}
9509 considers two variables type equivalent if:
9513 The two variables are structured and have the same structure, union, or
9517 The two variables have the same type name, or types that have been
9518 declared equivalent through @code{typedef}.
9521 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9524 The two @code{struct}, @code{union}, or @code{enum} variables are
9525 declared in the same declaration. (Note: this may not be true for all C
9530 Range checking, if turned on, is done on mathematical operations. Array
9531 indices are not checked, since they are often used to index a pointer
9532 that is not itself an array.
9535 @subsubsection @value{GDBN} and C
9537 The @code{set print union} and @code{show print union} commands apply to
9538 the @code{union} type. When set to @samp{on}, any @code{union} that is
9539 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9540 appears as @samp{@{...@}}.
9542 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9543 with pointers and a memory allocation function. @xref{Expressions,
9546 @node Debugging C Plus Plus
9547 @subsubsection @value{GDBN} Features for C@t{++}
9549 @cindex commands for C@t{++}
9551 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9552 designed specifically for use with C@t{++}. Here is a summary:
9555 @cindex break in overloaded functions
9556 @item @r{breakpoint menus}
9557 When you want a breakpoint in a function whose name is overloaded,
9558 @value{GDBN} breakpoint menus help you specify which function definition
9559 you want. @xref{Breakpoint Menus,,Breakpoint Menus}.
9561 @cindex overloading in C@t{++}
9562 @item rbreak @var{regex}
9563 Setting breakpoints using regular expressions is helpful for setting
9564 breakpoints on overloaded functions that are not members of any special
9566 @xref{Set Breaks, ,Setting Breakpoints}.
9568 @cindex C@t{++} exception handling
9571 Debug C@t{++} exception handling using these commands. @xref{Set
9572 Catchpoints, , Setting Catchpoints}.
9575 @item ptype @var{typename}
9576 Print inheritance relationships as well as other information for type
9578 @xref{Symbols, ,Examining the Symbol Table}.
9580 @cindex C@t{++} symbol display
9581 @item set print demangle
9582 @itemx show print demangle
9583 @itemx set print asm-demangle
9584 @itemx show print asm-demangle
9585 Control whether C@t{++} symbols display in their source form, both when
9586 displaying code as C@t{++} source and when displaying disassemblies.
9587 @xref{Print Settings, ,Print Settings}.
9589 @item set print object
9590 @itemx show print object
9591 Choose whether to print derived (actual) or declared types of objects.
9592 @xref{Print Settings, ,Print Settings}.
9594 @item set print vtbl
9595 @itemx show print vtbl
9596 Control the format for printing virtual function tables.
9597 @xref{Print Settings, ,Print Settings}.
9598 (The @code{vtbl} commands do not work on programs compiled with the HP
9599 ANSI C@t{++} compiler (@code{aCC}).)
9601 @kindex set overload-resolution
9602 @cindex overloaded functions, overload resolution
9603 @item set overload-resolution on
9604 Enable overload resolution for C@t{++} expression evaluation. The default
9605 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9606 and searches for a function whose signature matches the argument types,
9607 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9608 Expressions, ,C@t{++} Expressions}, for details).
9609 If it cannot find a match, it emits a message.
9611 @item set overload-resolution off
9612 Disable overload resolution for C@t{++} expression evaluation. For
9613 overloaded functions that are not class member functions, @value{GDBN}
9614 chooses the first function of the specified name that it finds in the
9615 symbol table, whether or not its arguments are of the correct type. For
9616 overloaded functions that are class member functions, @value{GDBN}
9617 searches for a function whose signature @emph{exactly} matches the
9620 @kindex show overload-resolution
9621 @item show overload-resolution
9622 Show the current setting of overload resolution.
9624 @item @r{Overloaded symbol names}
9625 You can specify a particular definition of an overloaded symbol, using
9626 the same notation that is used to declare such symbols in C@t{++}: type
9627 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9628 also use the @value{GDBN} command-line word completion facilities to list the
9629 available choices, or to finish the type list for you.
9630 @xref{Completion,, Command Completion}, for details on how to do this.
9633 @node Decimal Floating Point
9634 @subsubsection Decimal Floating Point format
9635 @cindex decimal floating point format
9637 @value{GDBN} can examine, set and perform computations with numbers in
9638 decimal floating point format, which in the C language correspond to the
9639 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
9640 specified by the extension to support decimal floating-point arithmetic.
9642 There are two encodings in use, depending on the architecture: BID (Binary
9643 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
9644 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
9647 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
9648 to manipulate decimal floating point numbers, it is not possible to convert
9649 (using a cast, for example) integers wider than 32-bit to decimal float.
9651 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
9652 point computations, error checking in decimal float operations ignores
9653 underflow, overflow and divide by zero exceptions.
9656 @subsection Objective-C
9659 This section provides information about some commands and command
9660 options that are useful for debugging Objective-C code. See also
9661 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9662 few more commands specific to Objective-C support.
9665 * Method Names in Commands::
9666 * The Print Command with Objective-C::
9669 @node Method Names in Commands
9670 @subsubsection Method Names in Commands
9672 The following commands have been extended to accept Objective-C method
9673 names as line specifications:
9675 @kindex clear@r{, and Objective-C}
9676 @kindex break@r{, and Objective-C}
9677 @kindex info line@r{, and Objective-C}
9678 @kindex jump@r{, and Objective-C}
9679 @kindex list@r{, and Objective-C}
9683 @item @code{info line}
9688 A fully qualified Objective-C method name is specified as
9691 -[@var{Class} @var{methodName}]
9694 where the minus sign is used to indicate an instance method and a
9695 plus sign (not shown) is used to indicate a class method. The class
9696 name @var{Class} and method name @var{methodName} are enclosed in
9697 brackets, similar to the way messages are specified in Objective-C
9698 source code. For example, to set a breakpoint at the @code{create}
9699 instance method of class @code{Fruit} in the program currently being
9703 break -[Fruit create]
9706 To list ten program lines around the @code{initialize} class method,
9710 list +[NSText initialize]
9713 In the current version of @value{GDBN}, the plus or minus sign is
9714 required. In future versions of @value{GDBN}, the plus or minus
9715 sign will be optional, but you can use it to narrow the search. It
9716 is also possible to specify just a method name:
9722 You must specify the complete method name, including any colons. If
9723 your program's source files contain more than one @code{create} method,
9724 you'll be presented with a numbered list of classes that implement that
9725 method. Indicate your choice by number, or type @samp{0} to exit if
9728 As another example, to clear a breakpoint established at the
9729 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9732 clear -[NSWindow makeKeyAndOrderFront:]
9735 @node The Print Command with Objective-C
9736 @subsubsection The Print Command With Objective-C
9737 @cindex Objective-C, print objects
9738 @kindex print-object
9739 @kindex po @r{(@code{print-object})}
9741 The print command has also been extended to accept methods. For example:
9744 print -[@var{object} hash]
9747 @cindex print an Objective-C object description
9748 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9750 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9751 and print the result. Also, an additional command has been added,
9752 @code{print-object} or @code{po} for short, which is meant to print
9753 the description of an object. However, this command may only work
9754 with certain Objective-C libraries that have a particular hook
9755 function, @code{_NSPrintForDebugger}, defined.
9759 @cindex Fortran-specific support in @value{GDBN}
9761 @value{GDBN} can be used to debug programs written in Fortran, but it
9762 currently supports only the features of Fortran 77 language.
9764 @cindex trailing underscore, in Fortran symbols
9765 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9766 among them) append an underscore to the names of variables and
9767 functions. When you debug programs compiled by those compilers, you
9768 will need to refer to variables and functions with a trailing
9772 * Fortran Operators:: Fortran operators and expressions
9773 * Fortran Defaults:: Default settings for Fortran
9774 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
9777 @node Fortran Operators
9778 @subsubsection Fortran Operators and Expressions
9780 @cindex Fortran operators and expressions
9782 Operators must be defined on values of specific types. For instance,
9783 @code{+} is defined on numbers, but not on characters or other non-
9784 arithmetic types. Operators are often defined on groups of types.
9788 The exponentiation operator. It raises the first operand to the power
9792 The range operator. Normally used in the form of array(low:high) to
9793 represent a section of array.
9796 @node Fortran Defaults
9797 @subsubsection Fortran Defaults
9799 @cindex Fortran Defaults
9801 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9802 default uses case-insensitive matches for Fortran symbols. You can
9803 change that with the @samp{set case-insensitive} command, see
9804 @ref{Symbols}, for the details.
9806 @node Special Fortran Commands
9807 @subsubsection Special Fortran Commands
9809 @cindex Special Fortran commands
9811 @value{GDBN} has some commands to support Fortran-specific features,
9812 such as displaying common blocks.
9815 @cindex @code{COMMON} blocks, Fortran
9817 @item info common @r{[}@var{common-name}@r{]}
9818 This command prints the values contained in the Fortran @code{COMMON}
9819 block whose name is @var{common-name}. With no argument, the names of
9820 all @code{COMMON} blocks visible at the current program location are
9827 @cindex Pascal support in @value{GDBN}, limitations
9828 Debugging Pascal programs which use sets, subranges, file variables, or
9829 nested functions does not currently work. @value{GDBN} does not support
9830 entering expressions, printing values, or similar features using Pascal
9833 The Pascal-specific command @code{set print pascal_static-members}
9834 controls whether static members of Pascal objects are displayed.
9835 @xref{Print Settings, pascal_static-members}.
9838 @subsection Modula-2
9840 @cindex Modula-2, @value{GDBN} support
9842 The extensions made to @value{GDBN} to support Modula-2 only support
9843 output from the @sc{gnu} Modula-2 compiler (which is currently being
9844 developed). Other Modula-2 compilers are not currently supported, and
9845 attempting to debug executables produced by them is most likely
9846 to give an error as @value{GDBN} reads in the executable's symbol
9849 @cindex expressions in Modula-2
9851 * M2 Operators:: Built-in operators
9852 * Built-In Func/Proc:: Built-in functions and procedures
9853 * M2 Constants:: Modula-2 constants
9854 * M2 Types:: Modula-2 types
9855 * M2 Defaults:: Default settings for Modula-2
9856 * Deviations:: Deviations from standard Modula-2
9857 * M2 Checks:: Modula-2 type and range checks
9858 * M2 Scope:: The scope operators @code{::} and @code{.}
9859 * GDB/M2:: @value{GDBN} and Modula-2
9863 @subsubsection Operators
9864 @cindex Modula-2 operators
9866 Operators must be defined on values of specific types. For instance,
9867 @code{+} is defined on numbers, but not on structures. Operators are
9868 often defined on groups of types. For the purposes of Modula-2, the
9869 following definitions hold:
9874 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9878 @emph{Character types} consist of @code{CHAR} and its subranges.
9881 @emph{Floating-point types} consist of @code{REAL}.
9884 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9888 @emph{Scalar types} consist of all of the above.
9891 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9894 @emph{Boolean types} consist of @code{BOOLEAN}.
9898 The following operators are supported, and appear in order of
9899 increasing precedence:
9903 Function argument or array index separator.
9906 Assignment. The value of @var{var} @code{:=} @var{value} is
9910 Less than, greater than on integral, floating-point, or enumerated
9914 Less than or equal to, greater than or equal to
9915 on integral, floating-point and enumerated types, or set inclusion on
9916 set types. Same precedence as @code{<}.
9918 @item =@r{, }<>@r{, }#
9919 Equality and two ways of expressing inequality, valid on scalar types.
9920 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9921 available for inequality, since @code{#} conflicts with the script
9925 Set membership. Defined on set types and the types of their members.
9926 Same precedence as @code{<}.
9929 Boolean disjunction. Defined on boolean types.
9932 Boolean conjunction. Defined on boolean types.
9935 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9938 Addition and subtraction on integral and floating-point types, or union
9939 and difference on set types.
9942 Multiplication on integral and floating-point types, or set intersection
9946 Division on floating-point types, or symmetric set difference on set
9947 types. Same precedence as @code{*}.
9950 Integer division and remainder. Defined on integral types. Same
9951 precedence as @code{*}.
9954 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9957 Pointer dereferencing. Defined on pointer types.
9960 Boolean negation. Defined on boolean types. Same precedence as
9964 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9965 precedence as @code{^}.
9968 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9971 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9975 @value{GDBN} and Modula-2 scope operators.
9979 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9980 treats the use of the operator @code{IN}, or the use of operators
9981 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9982 @code{<=}, and @code{>=} on sets as an error.
9986 @node Built-In Func/Proc
9987 @subsubsection Built-in Functions and Procedures
9988 @cindex Modula-2 built-ins
9990 Modula-2 also makes available several built-in procedures and functions.
9991 In describing these, the following metavariables are used:
9996 represents an @code{ARRAY} variable.
9999 represents a @code{CHAR} constant or variable.
10002 represents a variable or constant of integral type.
10005 represents an identifier that belongs to a set. Generally used in the
10006 same function with the metavariable @var{s}. The type of @var{s} should
10007 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10010 represents a variable or constant of integral or floating-point type.
10013 represents a variable or constant of floating-point type.
10019 represents a variable.
10022 represents a variable or constant of one of many types. See the
10023 explanation of the function for details.
10026 All Modula-2 built-in procedures also return a result, described below.
10030 Returns the absolute value of @var{n}.
10033 If @var{c} is a lower case letter, it returns its upper case
10034 equivalent, otherwise it returns its argument.
10037 Returns the character whose ordinal value is @var{i}.
10040 Decrements the value in the variable @var{v} by one. Returns the new value.
10042 @item DEC(@var{v},@var{i})
10043 Decrements the value in the variable @var{v} by @var{i}. Returns the
10046 @item EXCL(@var{m},@var{s})
10047 Removes the element @var{m} from the set @var{s}. Returns the new
10050 @item FLOAT(@var{i})
10051 Returns the floating point equivalent of the integer @var{i}.
10053 @item HIGH(@var{a})
10054 Returns the index of the last member of @var{a}.
10057 Increments the value in the variable @var{v} by one. Returns the new value.
10059 @item INC(@var{v},@var{i})
10060 Increments the value in the variable @var{v} by @var{i}. Returns the
10063 @item INCL(@var{m},@var{s})
10064 Adds the element @var{m} to the set @var{s} if it is not already
10065 there. Returns the new set.
10068 Returns the maximum value of the type @var{t}.
10071 Returns the minimum value of the type @var{t}.
10074 Returns boolean TRUE if @var{i} is an odd number.
10077 Returns the ordinal value of its argument. For example, the ordinal
10078 value of a character is its @sc{ascii} value (on machines supporting the
10079 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10080 integral, character and enumerated types.
10082 @item SIZE(@var{x})
10083 Returns the size of its argument. @var{x} can be a variable or a type.
10085 @item TRUNC(@var{r})
10086 Returns the integral part of @var{r}.
10088 @item TSIZE(@var{x})
10089 Returns the size of its argument. @var{x} can be a variable or a type.
10091 @item VAL(@var{t},@var{i})
10092 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10096 @emph{Warning:} Sets and their operations are not yet supported, so
10097 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10101 @cindex Modula-2 constants
10103 @subsubsection Constants
10105 @value{GDBN} allows you to express the constants of Modula-2 in the following
10111 Integer constants are simply a sequence of digits. When used in an
10112 expression, a constant is interpreted to be type-compatible with the
10113 rest of the expression. Hexadecimal integers are specified by a
10114 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10117 Floating point constants appear as a sequence of digits, followed by a
10118 decimal point and another sequence of digits. An optional exponent can
10119 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10120 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10121 digits of the floating point constant must be valid decimal (base 10)
10125 Character constants consist of a single character enclosed by a pair of
10126 like quotes, either single (@code{'}) or double (@code{"}). They may
10127 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10128 followed by a @samp{C}.
10131 String constants consist of a sequence of characters enclosed by a
10132 pair of like quotes, either single (@code{'}) or double (@code{"}).
10133 Escape sequences in the style of C are also allowed. @xref{C
10134 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10138 Enumerated constants consist of an enumerated identifier.
10141 Boolean constants consist of the identifiers @code{TRUE} and
10145 Pointer constants consist of integral values only.
10148 Set constants are not yet supported.
10152 @subsubsection Modula-2 Types
10153 @cindex Modula-2 types
10155 Currently @value{GDBN} can print the following data types in Modula-2
10156 syntax: array types, record types, set types, pointer types, procedure
10157 types, enumerated types, subrange types and base types. You can also
10158 print the contents of variables declared using these type.
10159 This section gives a number of simple source code examples together with
10160 sample @value{GDBN} sessions.
10162 The first example contains the following section of code:
10171 and you can request @value{GDBN} to interrogate the type and value of
10172 @code{r} and @code{s}.
10175 (@value{GDBP}) print s
10177 (@value{GDBP}) ptype s
10179 (@value{GDBP}) print r
10181 (@value{GDBP}) ptype r
10186 Likewise if your source code declares @code{s} as:
10190 s: SET ['A'..'Z'] ;
10194 then you may query the type of @code{s} by:
10197 (@value{GDBP}) ptype s
10198 type = SET ['A'..'Z']
10202 Note that at present you cannot interactively manipulate set
10203 expressions using the debugger.
10205 The following example shows how you might declare an array in Modula-2
10206 and how you can interact with @value{GDBN} to print its type and contents:
10210 s: ARRAY [-10..10] OF CHAR ;
10214 (@value{GDBP}) ptype s
10215 ARRAY [-10..10] OF CHAR
10218 Note that the array handling is not yet complete and although the type
10219 is printed correctly, expression handling still assumes that all
10220 arrays have a lower bound of zero and not @code{-10} as in the example
10223 Here are some more type related Modula-2 examples:
10227 colour = (blue, red, yellow, green) ;
10228 t = [blue..yellow] ;
10236 The @value{GDBN} interaction shows how you can query the data type
10237 and value of a variable.
10240 (@value{GDBP}) print s
10242 (@value{GDBP}) ptype t
10243 type = [blue..yellow]
10247 In this example a Modula-2 array is declared and its contents
10248 displayed. Observe that the contents are written in the same way as
10249 their @code{C} counterparts.
10253 s: ARRAY [1..5] OF CARDINAL ;
10259 (@value{GDBP}) print s
10260 $1 = @{1, 0, 0, 0, 0@}
10261 (@value{GDBP}) ptype s
10262 type = ARRAY [1..5] OF CARDINAL
10265 The Modula-2 language interface to @value{GDBN} also understands
10266 pointer types as shown in this example:
10270 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10277 and you can request that @value{GDBN} describes the type of @code{s}.
10280 (@value{GDBP}) ptype s
10281 type = POINTER TO ARRAY [1..5] OF CARDINAL
10284 @value{GDBN} handles compound types as we can see in this example.
10285 Here we combine array types, record types, pointer types and subrange
10296 myarray = ARRAY myrange OF CARDINAL ;
10297 myrange = [-2..2] ;
10299 s: POINTER TO ARRAY myrange OF foo ;
10303 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10307 (@value{GDBP}) ptype s
10308 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10311 f3 : ARRAY [-2..2] OF CARDINAL;
10316 @subsubsection Modula-2 Defaults
10317 @cindex Modula-2 defaults
10319 If type and range checking are set automatically by @value{GDBN}, they
10320 both default to @code{on} whenever the working language changes to
10321 Modula-2. This happens regardless of whether you or @value{GDBN}
10322 selected the working language.
10324 If you allow @value{GDBN} to set the language automatically, then entering
10325 code compiled from a file whose name ends with @file{.mod} sets the
10326 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10327 Infer the Source Language}, for further details.
10330 @subsubsection Deviations from Standard Modula-2
10331 @cindex Modula-2, deviations from
10333 A few changes have been made to make Modula-2 programs easier to debug.
10334 This is done primarily via loosening its type strictness:
10338 Unlike in standard Modula-2, pointer constants can be formed by
10339 integers. This allows you to modify pointer variables during
10340 debugging. (In standard Modula-2, the actual address contained in a
10341 pointer variable is hidden from you; it can only be modified
10342 through direct assignment to another pointer variable or expression that
10343 returned a pointer.)
10346 C escape sequences can be used in strings and characters to represent
10347 non-printable characters. @value{GDBN} prints out strings with these
10348 escape sequences embedded. Single non-printable characters are
10349 printed using the @samp{CHR(@var{nnn})} format.
10352 The assignment operator (@code{:=}) returns the value of its right-hand
10356 All built-in procedures both modify @emph{and} return their argument.
10360 @subsubsection Modula-2 Type and Range Checks
10361 @cindex Modula-2 checks
10364 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10367 @c FIXME remove warning when type/range checks added
10369 @value{GDBN} considers two Modula-2 variables type equivalent if:
10373 They are of types that have been declared equivalent via a @code{TYPE
10374 @var{t1} = @var{t2}} statement
10377 They have been declared on the same line. (Note: This is true of the
10378 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10381 As long as type checking is enabled, any attempt to combine variables
10382 whose types are not equivalent is an error.
10384 Range checking is done on all mathematical operations, assignment, array
10385 index bounds, and all built-in functions and procedures.
10388 @subsubsection The Scope Operators @code{::} and @code{.}
10390 @cindex @code{.}, Modula-2 scope operator
10391 @cindex colon, doubled as scope operator
10393 @vindex colon-colon@r{, in Modula-2}
10394 @c Info cannot handle :: but TeX can.
10397 @vindex ::@r{, in Modula-2}
10400 There are a few subtle differences between the Modula-2 scope operator
10401 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10406 @var{module} . @var{id}
10407 @var{scope} :: @var{id}
10411 where @var{scope} is the name of a module or a procedure,
10412 @var{module} the name of a module, and @var{id} is any declared
10413 identifier within your program, except another module.
10415 Using the @code{::} operator makes @value{GDBN} search the scope
10416 specified by @var{scope} for the identifier @var{id}. If it is not
10417 found in the specified scope, then @value{GDBN} searches all scopes
10418 enclosing the one specified by @var{scope}.
10420 Using the @code{.} operator makes @value{GDBN} search the current scope for
10421 the identifier specified by @var{id} that was imported from the
10422 definition module specified by @var{module}. With this operator, it is
10423 an error if the identifier @var{id} was not imported from definition
10424 module @var{module}, or if @var{id} is not an identifier in
10428 @subsubsection @value{GDBN} and Modula-2
10430 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10431 Five subcommands of @code{set print} and @code{show print} apply
10432 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10433 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10434 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10435 analogue in Modula-2.
10437 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10438 with any language, is not useful with Modula-2. Its
10439 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10440 created in Modula-2 as they can in C or C@t{++}. However, because an
10441 address can be specified by an integral constant, the construct
10442 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10444 @cindex @code{#} in Modula-2
10445 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10446 interpreted as the beginning of a comment. Use @code{<>} instead.
10452 The extensions made to @value{GDBN} for Ada only support
10453 output from the @sc{gnu} Ada (GNAT) compiler.
10454 Other Ada compilers are not currently supported, and
10455 attempting to debug executables produced by them is most likely
10459 @cindex expressions in Ada
10461 * Ada Mode Intro:: General remarks on the Ada syntax
10462 and semantics supported by Ada mode
10464 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10465 * Additions to Ada:: Extensions of the Ada expression syntax.
10466 * Stopping Before Main Program:: Debugging the program during elaboration.
10467 * Ada Glitches:: Known peculiarities of Ada mode.
10470 @node Ada Mode Intro
10471 @subsubsection Introduction
10472 @cindex Ada mode, general
10474 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10475 syntax, with some extensions.
10476 The philosophy behind the design of this subset is
10480 That @value{GDBN} should provide basic literals and access to operations for
10481 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10482 leaving more sophisticated computations to subprograms written into the
10483 program (which therefore may be called from @value{GDBN}).
10486 That type safety and strict adherence to Ada language restrictions
10487 are not particularly important to the @value{GDBN} user.
10490 That brevity is important to the @value{GDBN} user.
10493 Thus, for brevity, the debugger acts as if there were
10494 implicit @code{with} and @code{use} clauses in effect for all user-written
10495 packages, making it unnecessary to fully qualify most names with
10496 their packages, regardless of context. Where this causes ambiguity,
10497 @value{GDBN} asks the user's intent.
10499 The debugger will start in Ada mode if it detects an Ada main program.
10500 As for other languages, it will enter Ada mode when stopped in a program that
10501 was translated from an Ada source file.
10503 While in Ada mode, you may use `@t{--}' for comments. This is useful
10504 mostly for documenting command files. The standard @value{GDBN} comment
10505 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10506 middle (to allow based literals).
10508 The debugger supports limited overloading. Given a subprogram call in which
10509 the function symbol has multiple definitions, it will use the number of
10510 actual parameters and some information about their types to attempt to narrow
10511 the set of definitions. It also makes very limited use of context, preferring
10512 procedures to functions in the context of the @code{call} command, and
10513 functions to procedures elsewhere.
10515 @node Omissions from Ada
10516 @subsubsection Omissions from Ada
10517 @cindex Ada, omissions from
10519 Here are the notable omissions from the subset:
10523 Only a subset of the attributes are supported:
10527 @t{'First}, @t{'Last}, and @t{'Length}
10528 on array objects (not on types and subtypes).
10531 @t{'Min} and @t{'Max}.
10534 @t{'Pos} and @t{'Val}.
10540 @t{'Range} on array objects (not subtypes), but only as the right
10541 operand of the membership (@code{in}) operator.
10544 @t{'Access}, @t{'Unchecked_Access}, and
10545 @t{'Unrestricted_Access} (a GNAT extension).
10553 @code{Characters.Latin_1} are not available and
10554 concatenation is not implemented. Thus, escape characters in strings are
10555 not currently available.
10558 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10559 equality of representations. They will generally work correctly
10560 for strings and arrays whose elements have integer or enumeration types.
10561 They may not work correctly for arrays whose element
10562 types have user-defined equality, for arrays of real values
10563 (in particular, IEEE-conformant floating point, because of negative
10564 zeroes and NaNs), and for arrays whose elements contain unused bits with
10565 indeterminate values.
10568 The other component-by-component array operations (@code{and}, @code{or},
10569 @code{xor}, @code{not}, and relational tests other than equality)
10570 are not implemented.
10573 @cindex array aggregates (Ada)
10574 @cindex record aggregates (Ada)
10575 @cindex aggregates (Ada)
10576 There is limited support for array and record aggregates. They are
10577 permitted only on the right sides of assignments, as in these examples:
10580 set An_Array := (1, 2, 3, 4, 5, 6)
10581 set An_Array := (1, others => 0)
10582 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10583 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10584 set A_Record := (1, "Peter", True);
10585 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10589 discriminant's value by assigning an aggregate has an
10590 undefined effect if that discriminant is used within the record.
10591 However, you can first modify discriminants by directly assigning to
10592 them (which normally would not be allowed in Ada), and then performing an
10593 aggregate assignment. For example, given a variable @code{A_Rec}
10594 declared to have a type such as:
10597 type Rec (Len : Small_Integer := 0) is record
10599 Vals : IntArray (1 .. Len);
10603 you can assign a value with a different size of @code{Vals} with two
10608 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10611 As this example also illustrates, @value{GDBN} is very loose about the usual
10612 rules concerning aggregates. You may leave out some of the
10613 components of an array or record aggregate (such as the @code{Len}
10614 component in the assignment to @code{A_Rec} above); they will retain their
10615 original values upon assignment. You may freely use dynamic values as
10616 indices in component associations. You may even use overlapping or
10617 redundant component associations, although which component values are
10618 assigned in such cases is not defined.
10621 Calls to dispatching subprograms are not implemented.
10624 The overloading algorithm is much more limited (i.e., less selective)
10625 than that of real Ada. It makes only limited use of the context in
10626 which a subexpression appears to resolve its meaning, and it is much
10627 looser in its rules for allowing type matches. As a result, some
10628 function calls will be ambiguous, and the user will be asked to choose
10629 the proper resolution.
10632 The @code{new} operator is not implemented.
10635 Entry calls are not implemented.
10638 Aside from printing, arithmetic operations on the native VAX floating-point
10639 formats are not supported.
10642 It is not possible to slice a packed array.
10645 @node Additions to Ada
10646 @subsubsection Additions to Ada
10647 @cindex Ada, deviations from
10649 As it does for other languages, @value{GDBN} makes certain generic
10650 extensions to Ada (@pxref{Expressions}):
10654 If the expression @var{E} is a variable residing in memory (typically
10655 a local variable or array element) and @var{N} is a positive integer,
10656 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10657 @var{N}-1 adjacent variables following it in memory as an array. In
10658 Ada, this operator is generally not necessary, since its prime use is
10659 in displaying parts of an array, and slicing will usually do this in
10660 Ada. However, there are occasional uses when debugging programs in
10661 which certain debugging information has been optimized away.
10664 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10665 appears in function or file @var{B}.'' When @var{B} is a file name,
10666 you must typically surround it in single quotes.
10669 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10670 @var{type} that appears at address @var{addr}.''
10673 A name starting with @samp{$} is a convenience variable
10674 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10677 In addition, @value{GDBN} provides a few other shortcuts and outright
10678 additions specific to Ada:
10682 The assignment statement is allowed as an expression, returning
10683 its right-hand operand as its value. Thus, you may enter
10687 print A(tmp := y + 1)
10691 The semicolon is allowed as an ``operator,'' returning as its value
10692 the value of its right-hand operand.
10693 This allows, for example,
10694 complex conditional breaks:
10698 condition 1 (report(i); k += 1; A(k) > 100)
10702 Rather than use catenation and symbolic character names to introduce special
10703 characters into strings, one may instead use a special bracket notation,
10704 which is also used to print strings. A sequence of characters of the form
10705 @samp{["@var{XX}"]} within a string or character literal denotes the
10706 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10707 sequence of characters @samp{["""]} also denotes a single quotation mark
10708 in strings. For example,
10710 "One line.["0a"]Next line.["0a"]"
10713 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10717 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10718 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10726 When printing arrays, @value{GDBN} uses positional notation when the
10727 array has a lower bound of 1, and uses a modified named notation otherwise.
10728 For example, a one-dimensional array of three integers with a lower bound
10729 of 3 might print as
10736 That is, in contrast to valid Ada, only the first component has a @code{=>}
10740 You may abbreviate attributes in expressions with any unique,
10741 multi-character subsequence of
10742 their names (an exact match gets preference).
10743 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10744 in place of @t{a'length}.
10747 @cindex quoting Ada internal identifiers
10748 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10749 to lower case. The GNAT compiler uses upper-case characters for
10750 some of its internal identifiers, which are normally of no interest to users.
10751 For the rare occasions when you actually have to look at them,
10752 enclose them in angle brackets to avoid the lower-case mapping.
10755 @value{GDBP} print <JMPBUF_SAVE>[0]
10759 Printing an object of class-wide type or dereferencing an
10760 access-to-class-wide value will display all the components of the object's
10761 specific type (as indicated by its run-time tag). Likewise, component
10762 selection on such a value will operate on the specific type of the
10767 @node Stopping Before Main Program
10768 @subsubsection Stopping at the Very Beginning
10770 @cindex breakpointing Ada elaboration code
10771 It is sometimes necessary to debug the program during elaboration, and
10772 before reaching the main procedure.
10773 As defined in the Ada Reference
10774 Manual, the elaboration code is invoked from a procedure called
10775 @code{adainit}. To run your program up to the beginning of
10776 elaboration, simply use the following two commands:
10777 @code{tbreak adainit} and @code{run}.
10780 @subsubsection Known Peculiarities of Ada Mode
10781 @cindex Ada, problems
10783 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10784 we know of several problems with and limitations of Ada mode in
10786 some of which will be fixed with planned future releases of the debugger
10787 and the GNU Ada compiler.
10791 Currently, the debugger
10792 has insufficient information to determine whether certain pointers represent
10793 pointers to objects or the objects themselves.
10794 Thus, the user may have to tack an extra @code{.all} after an expression
10795 to get it printed properly.
10798 Static constants that the compiler chooses not to materialize as objects in
10799 storage are invisible to the debugger.
10802 Named parameter associations in function argument lists are ignored (the
10803 argument lists are treated as positional).
10806 Many useful library packages are currently invisible to the debugger.
10809 Fixed-point arithmetic, conversions, input, and output is carried out using
10810 floating-point arithmetic, and may give results that only approximate those on
10814 The type of the @t{'Address} attribute may not be @code{System.Address}.
10817 The GNAT compiler never generates the prefix @code{Standard} for any of
10818 the standard symbols defined by the Ada language. @value{GDBN} knows about
10819 this: it will strip the prefix from names when you use it, and will never
10820 look for a name you have so qualified among local symbols, nor match against
10821 symbols in other packages or subprograms. If you have
10822 defined entities anywhere in your program other than parameters and
10823 local variables whose simple names match names in @code{Standard},
10824 GNAT's lack of qualification here can cause confusion. When this happens,
10825 you can usually resolve the confusion
10826 by qualifying the problematic names with package
10827 @code{Standard} explicitly.
10830 @node Unsupported Languages
10831 @section Unsupported Languages
10833 @cindex unsupported languages
10834 @cindex minimal language
10835 In addition to the other fully-supported programming languages,
10836 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10837 It does not represent a real programming language, but provides a set
10838 of capabilities close to what the C or assembly languages provide.
10839 This should allow most simple operations to be performed while debugging
10840 an application that uses a language currently not supported by @value{GDBN}.
10842 If the language is set to @code{auto}, @value{GDBN} will automatically
10843 select this language if the current frame corresponds to an unsupported
10847 @chapter Examining the Symbol Table
10849 The commands described in this chapter allow you to inquire about the
10850 symbols (names of variables, functions and types) defined in your
10851 program. This information is inherent in the text of your program and
10852 does not change as your program executes. @value{GDBN} finds it in your
10853 program's symbol table, in the file indicated when you started @value{GDBN}
10854 (@pxref{File Options, ,Choosing Files}), or by one of the
10855 file-management commands (@pxref{Files, ,Commands to Specify Files}).
10857 @cindex symbol names
10858 @cindex names of symbols
10859 @cindex quoting names
10860 Occasionally, you may need to refer to symbols that contain unusual
10861 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10862 most frequent case is in referring to static variables in other
10863 source files (@pxref{Variables,,Program Variables}). File names
10864 are recorded in object files as debugging symbols, but @value{GDBN} would
10865 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10866 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10867 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10874 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10877 @cindex case-insensitive symbol names
10878 @cindex case sensitivity in symbol names
10879 @kindex set case-sensitive
10880 @item set case-sensitive on
10881 @itemx set case-sensitive off
10882 @itemx set case-sensitive auto
10883 Normally, when @value{GDBN} looks up symbols, it matches their names
10884 with case sensitivity determined by the current source language.
10885 Occasionally, you may wish to control that. The command @code{set
10886 case-sensitive} lets you do that by specifying @code{on} for
10887 case-sensitive matches or @code{off} for case-insensitive ones. If
10888 you specify @code{auto}, case sensitivity is reset to the default
10889 suitable for the source language. The default is case-sensitive
10890 matches for all languages except for Fortran, for which the default is
10891 case-insensitive matches.
10893 @kindex show case-sensitive
10894 @item show case-sensitive
10895 This command shows the current setting of case sensitivity for symbols
10898 @kindex info address
10899 @cindex address of a symbol
10900 @item info address @var{symbol}
10901 Describe where the data for @var{symbol} is stored. For a register
10902 variable, this says which register it is kept in. For a non-register
10903 local variable, this prints the stack-frame offset at which the variable
10906 Note the contrast with @samp{print &@var{symbol}}, which does not work
10907 at all for a register variable, and for a stack local variable prints
10908 the exact address of the current instantiation of the variable.
10910 @kindex info symbol
10911 @cindex symbol from address
10912 @cindex closest symbol and offset for an address
10913 @item info symbol @var{addr}
10914 Print the name of a symbol which is stored at the address @var{addr}.
10915 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10916 nearest symbol and an offset from it:
10919 (@value{GDBP}) info symbol 0x54320
10920 _initialize_vx + 396 in section .text
10924 This is the opposite of the @code{info address} command. You can use
10925 it to find out the name of a variable or a function given its address.
10928 @item whatis [@var{arg}]
10929 Print the data type of @var{arg}, which can be either an expression or
10930 a data type. With no argument, print the data type of @code{$}, the
10931 last value in the value history. If @var{arg} is an expression, it is
10932 not actually evaluated, and any side-effecting operations (such as
10933 assignments or function calls) inside it do not take place. If
10934 @var{arg} is a type name, it may be the name of a type or typedef, or
10935 for C code it may have the form @samp{class @var{class-name}},
10936 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10937 @samp{enum @var{enum-tag}}.
10938 @xref{Expressions, ,Expressions}.
10941 @item ptype [@var{arg}]
10942 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10943 detailed description of the type, instead of just the name of the type.
10944 @xref{Expressions, ,Expressions}.
10946 For example, for this variable declaration:
10949 struct complex @{double real; double imag;@} v;
10953 the two commands give this output:
10957 (@value{GDBP}) whatis v
10958 type = struct complex
10959 (@value{GDBP}) ptype v
10960 type = struct complex @{
10968 As with @code{whatis}, using @code{ptype} without an argument refers to
10969 the type of @code{$}, the last value in the value history.
10971 @cindex incomplete type
10972 Sometimes, programs use opaque data types or incomplete specifications
10973 of complex data structure. If the debug information included in the
10974 program does not allow @value{GDBN} to display a full declaration of
10975 the data type, it will say @samp{<incomplete type>}. For example,
10976 given these declarations:
10980 struct foo *fooptr;
10984 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10987 (@value{GDBP}) ptype foo
10988 $1 = <incomplete type>
10992 ``Incomplete type'' is C terminology for data types that are not
10993 completely specified.
10996 @item info types @var{regexp}
10998 Print a brief description of all types whose names match the regular
10999 expression @var{regexp} (or all types in your program, if you supply
11000 no argument). Each complete typename is matched as though it were a
11001 complete line; thus, @samp{i type value} gives information on all
11002 types in your program whose names include the string @code{value}, but
11003 @samp{i type ^value$} gives information only on types whose complete
11004 name is @code{value}.
11006 This command differs from @code{ptype} in two ways: first, like
11007 @code{whatis}, it does not print a detailed description; second, it
11008 lists all source files where a type is defined.
11011 @cindex local variables
11012 @item info scope @var{location}
11013 List all the variables local to a particular scope. This command
11014 accepts a @var{location} argument---a function name, a source line, or
11015 an address preceded by a @samp{*}, and prints all the variables local
11016 to the scope defined by that location. (@xref{Specify Location}, for
11017 details about supported forms of @var{location}.) For example:
11020 (@value{GDBP}) @b{info scope command_line_handler}
11021 Scope for command_line_handler:
11022 Symbol rl is an argument at stack/frame offset 8, length 4.
11023 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11024 Symbol linelength is in static storage at address 0x150a1c, length 4.
11025 Symbol p is a local variable in register $esi, length 4.
11026 Symbol p1 is a local variable in register $ebx, length 4.
11027 Symbol nline is a local variable in register $edx, length 4.
11028 Symbol repeat is a local variable at frame offset -8, length 4.
11032 This command is especially useful for determining what data to collect
11033 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11036 @kindex info source
11038 Show information about the current source file---that is, the source file for
11039 the function containing the current point of execution:
11042 the name of the source file, and the directory containing it,
11044 the directory it was compiled in,
11046 its length, in lines,
11048 which programming language it is written in,
11050 whether the executable includes debugging information for that file, and
11051 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11053 whether the debugging information includes information about
11054 preprocessor macros.
11058 @kindex info sources
11060 Print the names of all source files in your program for which there is
11061 debugging information, organized into two lists: files whose symbols
11062 have already been read, and files whose symbols will be read when needed.
11064 @kindex info functions
11065 @item info functions
11066 Print the names and data types of all defined functions.
11068 @item info functions @var{regexp}
11069 Print the names and data types of all defined functions
11070 whose names contain a match for regular expression @var{regexp}.
11071 Thus, @samp{info fun step} finds all functions whose names
11072 include @code{step}; @samp{info fun ^step} finds those whose names
11073 start with @code{step}. If a function name contains characters
11074 that conflict with the regular expression language (e.g.@:
11075 @samp{operator*()}), they may be quoted with a backslash.
11077 @kindex info variables
11078 @item info variables
11079 Print the names and data types of all variables that are declared
11080 outside of functions (i.e.@: excluding local variables).
11082 @item info variables @var{regexp}
11083 Print the names and data types of all variables (except for local
11084 variables) whose names contain a match for regular expression
11087 @kindex info classes
11088 @cindex Objective-C, classes and selectors
11090 @itemx info classes @var{regexp}
11091 Display all Objective-C classes in your program, or
11092 (with the @var{regexp} argument) all those matching a particular regular
11095 @kindex info selectors
11096 @item info selectors
11097 @itemx info selectors @var{regexp}
11098 Display all Objective-C selectors in your program, or
11099 (with the @var{regexp} argument) all those matching a particular regular
11103 This was never implemented.
11104 @kindex info methods
11106 @itemx info methods @var{regexp}
11107 The @code{info methods} command permits the user to examine all defined
11108 methods within C@t{++} program, or (with the @var{regexp} argument) a
11109 specific set of methods found in the various C@t{++} classes. Many
11110 C@t{++} classes provide a large number of methods. Thus, the output
11111 from the @code{ptype} command can be overwhelming and hard to use. The
11112 @code{info-methods} command filters the methods, printing only those
11113 which match the regular-expression @var{regexp}.
11116 @cindex reloading symbols
11117 Some systems allow individual object files that make up your program to
11118 be replaced without stopping and restarting your program. For example,
11119 in VxWorks you can simply recompile a defective object file and keep on
11120 running. If you are running on one of these systems, you can allow
11121 @value{GDBN} to reload the symbols for automatically relinked modules:
11124 @kindex set symbol-reloading
11125 @item set symbol-reloading on
11126 Replace symbol definitions for the corresponding source file when an
11127 object file with a particular name is seen again.
11129 @item set symbol-reloading off
11130 Do not replace symbol definitions when encountering object files of the
11131 same name more than once. This is the default state; if you are not
11132 running on a system that permits automatic relinking of modules, you
11133 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11134 may discard symbols when linking large programs, that may contain
11135 several modules (from different directories or libraries) with the same
11138 @kindex show symbol-reloading
11139 @item show symbol-reloading
11140 Show the current @code{on} or @code{off} setting.
11143 @cindex opaque data types
11144 @kindex set opaque-type-resolution
11145 @item set opaque-type-resolution on
11146 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11147 declared as a pointer to a @code{struct}, @code{class}, or
11148 @code{union}---for example, @code{struct MyType *}---that is used in one
11149 source file although the full declaration of @code{struct MyType} is in
11150 another source file. The default is on.
11152 A change in the setting of this subcommand will not take effect until
11153 the next time symbols for a file are loaded.
11155 @item set opaque-type-resolution off
11156 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11157 is printed as follows:
11159 @{<no data fields>@}
11162 @kindex show opaque-type-resolution
11163 @item show opaque-type-resolution
11164 Show whether opaque types are resolved or not.
11166 @kindex maint print symbols
11167 @cindex symbol dump
11168 @kindex maint print psymbols
11169 @cindex partial symbol dump
11170 @item maint print symbols @var{filename}
11171 @itemx maint print psymbols @var{filename}
11172 @itemx maint print msymbols @var{filename}
11173 Write a dump of debugging symbol data into the file @var{filename}.
11174 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11175 symbols with debugging data are included. If you use @samp{maint print
11176 symbols}, @value{GDBN} includes all the symbols for which it has already
11177 collected full details: that is, @var{filename} reflects symbols for
11178 only those files whose symbols @value{GDBN} has read. You can use the
11179 command @code{info sources} to find out which files these are. If you
11180 use @samp{maint print psymbols} instead, the dump shows information about
11181 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11182 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11183 @samp{maint print msymbols} dumps just the minimal symbol information
11184 required for each object file from which @value{GDBN} has read some symbols.
11185 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11186 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11188 @kindex maint info symtabs
11189 @kindex maint info psymtabs
11190 @cindex listing @value{GDBN}'s internal symbol tables
11191 @cindex symbol tables, listing @value{GDBN}'s internal
11192 @cindex full symbol tables, listing @value{GDBN}'s internal
11193 @cindex partial symbol tables, listing @value{GDBN}'s internal
11194 @item maint info symtabs @r{[} @var{regexp} @r{]}
11195 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11197 List the @code{struct symtab} or @code{struct partial_symtab}
11198 structures whose names match @var{regexp}. If @var{regexp} is not
11199 given, list them all. The output includes expressions which you can
11200 copy into a @value{GDBN} debugging this one to examine a particular
11201 structure in more detail. For example:
11204 (@value{GDBP}) maint info psymtabs dwarf2read
11205 @{ objfile /home/gnu/build/gdb/gdb
11206 ((struct objfile *) 0x82e69d0)
11207 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11208 ((struct partial_symtab *) 0x8474b10)
11211 text addresses 0x814d3c8 -- 0x8158074
11212 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11213 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11214 dependencies (none)
11217 (@value{GDBP}) maint info symtabs
11221 We see that there is one partial symbol table whose filename contains
11222 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11223 and we see that @value{GDBN} has not read in any symtabs yet at all.
11224 If we set a breakpoint on a function, that will cause @value{GDBN} to
11225 read the symtab for the compilation unit containing that function:
11228 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11229 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11231 (@value{GDBP}) maint info symtabs
11232 @{ objfile /home/gnu/build/gdb/gdb
11233 ((struct objfile *) 0x82e69d0)
11234 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11235 ((struct symtab *) 0x86c1f38)
11238 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11239 linetable ((struct linetable *) 0x8370fa0)
11240 debugformat DWARF 2
11249 @chapter Altering Execution
11251 Once you think you have found an error in your program, you might want to
11252 find out for certain whether correcting the apparent error would lead to
11253 correct results in the rest of the run. You can find the answer by
11254 experiment, using the @value{GDBN} features for altering execution of the
11257 For example, you can store new values into variables or memory
11258 locations, give your program a signal, restart it at a different
11259 address, or even return prematurely from a function.
11262 * Assignment:: Assignment to variables
11263 * Jumping:: Continuing at a different address
11264 * Signaling:: Giving your program a signal
11265 * Returning:: Returning from a function
11266 * Calling:: Calling your program's functions
11267 * Patching:: Patching your program
11271 @section Assignment to Variables
11274 @cindex setting variables
11275 To alter the value of a variable, evaluate an assignment expression.
11276 @xref{Expressions, ,Expressions}. For example,
11283 stores the value 4 into the variable @code{x}, and then prints the
11284 value of the assignment expression (which is 4).
11285 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11286 information on operators in supported languages.
11288 @kindex set variable
11289 @cindex variables, setting
11290 If you are not interested in seeing the value of the assignment, use the
11291 @code{set} command instead of the @code{print} command. @code{set} is
11292 really the same as @code{print} except that the expression's value is
11293 not printed and is not put in the value history (@pxref{Value History,
11294 ,Value History}). The expression is evaluated only for its effects.
11296 If the beginning of the argument string of the @code{set} command
11297 appears identical to a @code{set} subcommand, use the @code{set
11298 variable} command instead of just @code{set}. This command is identical
11299 to @code{set} except for its lack of subcommands. For example, if your
11300 program has a variable @code{width}, you get an error if you try to set
11301 a new value with just @samp{set width=13}, because @value{GDBN} has the
11302 command @code{set width}:
11305 (@value{GDBP}) whatis width
11307 (@value{GDBP}) p width
11309 (@value{GDBP}) set width=47
11310 Invalid syntax in expression.
11314 The invalid expression, of course, is @samp{=47}. In
11315 order to actually set the program's variable @code{width}, use
11318 (@value{GDBP}) set var width=47
11321 Because the @code{set} command has many subcommands that can conflict
11322 with the names of program variables, it is a good idea to use the
11323 @code{set variable} command instead of just @code{set}. For example, if
11324 your program has a variable @code{g}, you run into problems if you try
11325 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11326 the command @code{set gnutarget}, abbreviated @code{set g}:
11330 (@value{GDBP}) whatis g
11334 (@value{GDBP}) set g=4
11338 The program being debugged has been started already.
11339 Start it from the beginning? (y or n) y
11340 Starting program: /home/smith/cc_progs/a.out
11341 "/home/smith/cc_progs/a.out": can't open to read symbols:
11342 Invalid bfd target.
11343 (@value{GDBP}) show g
11344 The current BFD target is "=4".
11349 The program variable @code{g} did not change, and you silently set the
11350 @code{gnutarget} to an invalid value. In order to set the variable
11354 (@value{GDBP}) set var g=4
11357 @value{GDBN} allows more implicit conversions in assignments than C; you can
11358 freely store an integer value into a pointer variable or vice versa,
11359 and you can convert any structure to any other structure that is the
11360 same length or shorter.
11361 @comment FIXME: how do structs align/pad in these conversions?
11362 @comment /doc@cygnus.com 18dec1990
11364 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11365 construct to generate a value of specified type at a specified address
11366 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11367 to memory location @code{0x83040} as an integer (which implies a certain size
11368 and representation in memory), and
11371 set @{int@}0x83040 = 4
11375 stores the value 4 into that memory location.
11378 @section Continuing at a Different Address
11380 Ordinarily, when you continue your program, you do so at the place where
11381 it stopped, with the @code{continue} command. You can instead continue at
11382 an address of your own choosing, with the following commands:
11386 @item jump @var{linespec}
11387 @itemx jump @var{location}
11388 Resume execution at line @var{linespec} or at address given by
11389 @var{location}. Execution stops again immediately if there is a
11390 breakpoint there. @xref{Specify Location}, for a description of the
11391 different forms of @var{linespec} and @var{location}. It is common
11392 practice to use the @code{tbreak} command in conjunction with
11393 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
11395 The @code{jump} command does not change the current stack frame, or
11396 the stack pointer, or the contents of any memory location or any
11397 register other than the program counter. If line @var{linespec} is in
11398 a different function from the one currently executing, the results may
11399 be bizarre if the two functions expect different patterns of arguments or
11400 of local variables. For this reason, the @code{jump} command requests
11401 confirmation if the specified line is not in the function currently
11402 executing. However, even bizarre results are predictable if you are
11403 well acquainted with the machine-language code of your program.
11406 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11407 On many systems, you can get much the same effect as the @code{jump}
11408 command by storing a new value into the register @code{$pc}. The
11409 difference is that this does not start your program running; it only
11410 changes the address of where it @emph{will} run when you continue. For
11418 makes the next @code{continue} command or stepping command execute at
11419 address @code{0x485}, rather than at the address where your program stopped.
11420 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11422 The most common occasion to use the @code{jump} command is to back
11423 up---perhaps with more breakpoints set---over a portion of a program
11424 that has already executed, in order to examine its execution in more
11429 @section Giving your Program a Signal
11430 @cindex deliver a signal to a program
11434 @item signal @var{signal}
11435 Resume execution where your program stopped, but immediately give it the
11436 signal @var{signal}. @var{signal} can be the name or the number of a
11437 signal. For example, on many systems @code{signal 2} and @code{signal
11438 SIGINT} are both ways of sending an interrupt signal.
11440 Alternatively, if @var{signal} is zero, continue execution without
11441 giving a signal. This is useful when your program stopped on account of
11442 a signal and would ordinary see the signal when resumed with the
11443 @code{continue} command; @samp{signal 0} causes it to resume without a
11446 @code{signal} does not repeat when you press @key{RET} a second time
11447 after executing the command.
11451 Invoking the @code{signal} command is not the same as invoking the
11452 @code{kill} utility from the shell. Sending a signal with @code{kill}
11453 causes @value{GDBN} to decide what to do with the signal depending on
11454 the signal handling tables (@pxref{Signals}). The @code{signal} command
11455 passes the signal directly to your program.
11459 @section Returning from a Function
11462 @cindex returning from a function
11465 @itemx return @var{expression}
11466 You can cancel execution of a function call with the @code{return}
11467 command. If you give an
11468 @var{expression} argument, its value is used as the function's return
11472 When you use @code{return}, @value{GDBN} discards the selected stack frame
11473 (and all frames within it). You can think of this as making the
11474 discarded frame return prematurely. If you wish to specify a value to
11475 be returned, give that value as the argument to @code{return}.
11477 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11478 Frame}), and any other frames inside of it, leaving its caller as the
11479 innermost remaining frame. That frame becomes selected. The
11480 specified value is stored in the registers used for returning values
11483 The @code{return} command does not resume execution; it leaves the
11484 program stopped in the state that would exist if the function had just
11485 returned. In contrast, the @code{finish} command (@pxref{Continuing
11486 and Stepping, ,Continuing and Stepping}) resumes execution until the
11487 selected stack frame returns naturally.
11490 @section Calling Program Functions
11493 @cindex calling functions
11494 @cindex inferior functions, calling
11495 @item print @var{expr}
11496 Evaluate the expression @var{expr} and display the resulting value.
11497 @var{expr} may include calls to functions in the program being
11501 @item call @var{expr}
11502 Evaluate the expression @var{expr} without displaying @code{void}
11505 You can use this variant of the @code{print} command if you want to
11506 execute a function from your program that does not return anything
11507 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11508 with @code{void} returned values that @value{GDBN} will otherwise
11509 print. If the result is not void, it is printed and saved in the
11513 It is possible for the function you call via the @code{print} or
11514 @code{call} command to generate a signal (e.g., if there's a bug in
11515 the function, or if you passed it incorrect arguments). What happens
11516 in that case is controlled by the @code{set unwindonsignal} command.
11519 @item set unwindonsignal
11520 @kindex set unwindonsignal
11521 @cindex unwind stack in called functions
11522 @cindex call dummy stack unwinding
11523 Set unwinding of the stack if a signal is received while in a function
11524 that @value{GDBN} called in the program being debugged. If set to on,
11525 @value{GDBN} unwinds the stack it created for the call and restores
11526 the context to what it was before the call. If set to off (the
11527 default), @value{GDBN} stops in the frame where the signal was
11530 @item show unwindonsignal
11531 @kindex show unwindonsignal
11532 Show the current setting of stack unwinding in the functions called by
11536 @cindex weak alias functions
11537 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11538 for another function. In such case, @value{GDBN} might not pick up
11539 the type information, including the types of the function arguments,
11540 which causes @value{GDBN} to call the inferior function incorrectly.
11541 As a result, the called function will function erroneously and may
11542 even crash. A solution to that is to use the name of the aliased
11546 @section Patching Programs
11548 @cindex patching binaries
11549 @cindex writing into executables
11550 @cindex writing into corefiles
11552 By default, @value{GDBN} opens the file containing your program's
11553 executable code (or the corefile) read-only. This prevents accidental
11554 alterations to machine code; but it also prevents you from intentionally
11555 patching your program's binary.
11557 If you'd like to be able to patch the binary, you can specify that
11558 explicitly with the @code{set write} command. For example, you might
11559 want to turn on internal debugging flags, or even to make emergency
11565 @itemx set write off
11566 If you specify @samp{set write on}, @value{GDBN} opens executable and
11567 core files for both reading and writing; if you specify @samp{set write
11568 off} (the default), @value{GDBN} opens them read-only.
11570 If you have already loaded a file, you must load it again (using the
11571 @code{exec-file} or @code{core-file} command) after changing @code{set
11572 write}, for your new setting to take effect.
11576 Display whether executable files and core files are opened for writing
11577 as well as reading.
11581 @chapter @value{GDBN} Files
11583 @value{GDBN} needs to know the file name of the program to be debugged,
11584 both in order to read its symbol table and in order to start your
11585 program. To debug a core dump of a previous run, you must also tell
11586 @value{GDBN} the name of the core dump file.
11589 * Files:: Commands to specify files
11590 * Separate Debug Files:: Debugging information in separate files
11591 * Symbol Errors:: Errors reading symbol files
11595 @section Commands to Specify Files
11597 @cindex symbol table
11598 @cindex core dump file
11600 You may want to specify executable and core dump file names. The usual
11601 way to do this is at start-up time, using the arguments to
11602 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11603 Out of @value{GDBN}}).
11605 Occasionally it is necessary to change to a different file during a
11606 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11607 specify a file you want to use. Or you are debugging a remote target
11608 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11609 Program}). In these situations the @value{GDBN} commands to specify
11610 new files are useful.
11613 @cindex executable file
11615 @item file @var{filename}
11616 Use @var{filename} as the program to be debugged. It is read for its
11617 symbols and for the contents of pure memory. It is also the program
11618 executed when you use the @code{run} command. If you do not specify a
11619 directory and the file is not found in the @value{GDBN} working directory,
11620 @value{GDBN} uses the environment variable @code{PATH} as a list of
11621 directories to search, just as the shell does when looking for a program
11622 to run. You can change the value of this variable, for both @value{GDBN}
11623 and your program, using the @code{path} command.
11625 @cindex unlinked object files
11626 @cindex patching object files
11627 You can load unlinked object @file{.o} files into @value{GDBN} using
11628 the @code{file} command. You will not be able to ``run'' an object
11629 file, but you can disassemble functions and inspect variables. Also,
11630 if the underlying BFD functionality supports it, you could use
11631 @kbd{gdb -write} to patch object files using this technique. Note
11632 that @value{GDBN} can neither interpret nor modify relocations in this
11633 case, so branches and some initialized variables will appear to go to
11634 the wrong place. But this feature is still handy from time to time.
11637 @code{file} with no argument makes @value{GDBN} discard any information it
11638 has on both executable file and the symbol table.
11641 @item exec-file @r{[} @var{filename} @r{]}
11642 Specify that the program to be run (but not the symbol table) is found
11643 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11644 if necessary to locate your program. Omitting @var{filename} means to
11645 discard information on the executable file.
11647 @kindex symbol-file
11648 @item symbol-file @r{[} @var{filename} @r{]}
11649 Read symbol table information from file @var{filename}. @code{PATH} is
11650 searched when necessary. Use the @code{file} command to get both symbol
11651 table and program to run from the same file.
11653 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11654 program's symbol table.
11656 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11657 some breakpoints and auto-display expressions. This is because they may
11658 contain pointers to the internal data recording symbols and data types,
11659 which are part of the old symbol table data being discarded inside
11662 @code{symbol-file} does not repeat if you press @key{RET} again after
11665 When @value{GDBN} is configured for a particular environment, it
11666 understands debugging information in whatever format is the standard
11667 generated for that environment; you may use either a @sc{gnu} compiler, or
11668 other compilers that adhere to the local conventions.
11669 Best results are usually obtained from @sc{gnu} compilers; for example,
11670 using @code{@value{NGCC}} you can generate debugging information for
11673 For most kinds of object files, with the exception of old SVR3 systems
11674 using COFF, the @code{symbol-file} command does not normally read the
11675 symbol table in full right away. Instead, it scans the symbol table
11676 quickly to find which source files and which symbols are present. The
11677 details are read later, one source file at a time, as they are needed.
11679 The purpose of this two-stage reading strategy is to make @value{GDBN}
11680 start up faster. For the most part, it is invisible except for
11681 occasional pauses while the symbol table details for a particular source
11682 file are being read. (The @code{set verbose} command can turn these
11683 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11684 Warnings and Messages}.)
11686 We have not implemented the two-stage strategy for COFF yet. When the
11687 symbol table is stored in COFF format, @code{symbol-file} reads the
11688 symbol table data in full right away. Note that ``stabs-in-COFF''
11689 still does the two-stage strategy, since the debug info is actually
11693 @cindex reading symbols immediately
11694 @cindex symbols, reading immediately
11695 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11696 @itemx file @var{filename} @r{[} -readnow @r{]}
11697 You can override the @value{GDBN} two-stage strategy for reading symbol
11698 tables by using the @samp{-readnow} option with any of the commands that
11699 load symbol table information, if you want to be sure @value{GDBN} has the
11700 entire symbol table available.
11702 @c FIXME: for now no mention of directories, since this seems to be in
11703 @c flux. 13mar1992 status is that in theory GDB would look either in
11704 @c current dir or in same dir as myprog; but issues like competing
11705 @c GDB's, or clutter in system dirs, mean that in practice right now
11706 @c only current dir is used. FFish says maybe a special GDB hierarchy
11707 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11711 @item core-file @r{[}@var{filename}@r{]}
11713 Specify the whereabouts of a core dump file to be used as the ``contents
11714 of memory''. Traditionally, core files contain only some parts of the
11715 address space of the process that generated them; @value{GDBN} can access the
11716 executable file itself for other parts.
11718 @code{core-file} with no argument specifies that no core file is
11721 Note that the core file is ignored when your program is actually running
11722 under @value{GDBN}. So, if you have been running your program and you
11723 wish to debug a core file instead, you must kill the subprocess in which
11724 the program is running. To do this, use the @code{kill} command
11725 (@pxref{Kill Process, ,Killing the Child Process}).
11727 @kindex add-symbol-file
11728 @cindex dynamic linking
11729 @item add-symbol-file @var{filename} @var{address}
11730 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11731 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11732 The @code{add-symbol-file} command reads additional symbol table
11733 information from the file @var{filename}. You would use this command
11734 when @var{filename} has been dynamically loaded (by some other means)
11735 into the program that is running. @var{address} should be the memory
11736 address at which the file has been loaded; @value{GDBN} cannot figure
11737 this out for itself. You can additionally specify an arbitrary number
11738 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11739 section name and base address for that section. You can specify any
11740 @var{address} as an expression.
11742 The symbol table of the file @var{filename} is added to the symbol table
11743 originally read with the @code{symbol-file} command. You can use the
11744 @code{add-symbol-file} command any number of times; the new symbol data
11745 thus read keeps adding to the old. To discard all old symbol data
11746 instead, use the @code{symbol-file} command without any arguments.
11748 @cindex relocatable object files, reading symbols from
11749 @cindex object files, relocatable, reading symbols from
11750 @cindex reading symbols from relocatable object files
11751 @cindex symbols, reading from relocatable object files
11752 @cindex @file{.o} files, reading symbols from
11753 Although @var{filename} is typically a shared library file, an
11754 executable file, or some other object file which has been fully
11755 relocated for loading into a process, you can also load symbolic
11756 information from relocatable @file{.o} files, as long as:
11760 the file's symbolic information refers only to linker symbols defined in
11761 that file, not to symbols defined by other object files,
11763 every section the file's symbolic information refers to has actually
11764 been loaded into the inferior, as it appears in the file, and
11766 you can determine the address at which every section was loaded, and
11767 provide these to the @code{add-symbol-file} command.
11771 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11772 relocatable files into an already running program; such systems
11773 typically make the requirements above easy to meet. However, it's
11774 important to recognize that many native systems use complex link
11775 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11776 assembly, for example) that make the requirements difficult to meet. In
11777 general, one cannot assume that using @code{add-symbol-file} to read a
11778 relocatable object file's symbolic information will have the same effect
11779 as linking the relocatable object file into the program in the normal
11782 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11784 @kindex add-symbol-file-from-memory
11785 @cindex @code{syscall DSO}
11786 @cindex load symbols from memory
11787 @item add-symbol-file-from-memory @var{address}
11788 Load symbols from the given @var{address} in a dynamically loaded
11789 object file whose image is mapped directly into the inferior's memory.
11790 For example, the Linux kernel maps a @code{syscall DSO} into each
11791 process's address space; this DSO provides kernel-specific code for
11792 some system calls. The argument can be any expression whose
11793 evaluation yields the address of the file's shared object file header.
11794 For this command to work, you must have used @code{symbol-file} or
11795 @code{exec-file} commands in advance.
11797 @kindex add-shared-symbol-files
11799 @item add-shared-symbol-files @var{library-file}
11800 @itemx assf @var{library-file}
11801 The @code{add-shared-symbol-files} command can currently be used only
11802 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11803 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11804 @value{GDBN} automatically looks for shared libraries, however if
11805 @value{GDBN} does not find yours, you can invoke
11806 @code{add-shared-symbol-files}. It takes one argument: the shared
11807 library's file name. @code{assf} is a shorthand alias for
11808 @code{add-shared-symbol-files}.
11811 @item section @var{section} @var{addr}
11812 The @code{section} command changes the base address of the named
11813 @var{section} of the exec file to @var{addr}. This can be used if the
11814 exec file does not contain section addresses, (such as in the
11815 @code{a.out} format), or when the addresses specified in the file
11816 itself are wrong. Each section must be changed separately. The
11817 @code{info files} command, described below, lists all the sections and
11821 @kindex info target
11824 @code{info files} and @code{info target} are synonymous; both print the
11825 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11826 including the names of the executable and core dump files currently in
11827 use by @value{GDBN}, and the files from which symbols were loaded. The
11828 command @code{help target} lists all possible targets rather than
11831 @kindex maint info sections
11832 @item maint info sections
11833 Another command that can give you extra information about program sections
11834 is @code{maint info sections}. In addition to the section information
11835 displayed by @code{info files}, this command displays the flags and file
11836 offset of each section in the executable and core dump files. In addition,
11837 @code{maint info sections} provides the following command options (which
11838 may be arbitrarily combined):
11842 Display sections for all loaded object files, including shared libraries.
11843 @item @var{sections}
11844 Display info only for named @var{sections}.
11845 @item @var{section-flags}
11846 Display info only for sections for which @var{section-flags} are true.
11847 The section flags that @value{GDBN} currently knows about are:
11850 Section will have space allocated in the process when loaded.
11851 Set for all sections except those containing debug information.
11853 Section will be loaded from the file into the child process memory.
11854 Set for pre-initialized code and data, clear for @code{.bss} sections.
11856 Section needs to be relocated before loading.
11858 Section cannot be modified by the child process.
11860 Section contains executable code only.
11862 Section contains data only (no executable code).
11864 Section will reside in ROM.
11866 Section contains data for constructor/destructor lists.
11868 Section is not empty.
11870 An instruction to the linker to not output the section.
11871 @item COFF_SHARED_LIBRARY
11872 A notification to the linker that the section contains
11873 COFF shared library information.
11875 Section contains common symbols.
11878 @kindex set trust-readonly-sections
11879 @cindex read-only sections
11880 @item set trust-readonly-sections on
11881 Tell @value{GDBN} that readonly sections in your object file
11882 really are read-only (i.e.@: that their contents will not change).
11883 In that case, @value{GDBN} can fetch values from these sections
11884 out of the object file, rather than from the target program.
11885 For some targets (notably embedded ones), this can be a significant
11886 enhancement to debugging performance.
11888 The default is off.
11890 @item set trust-readonly-sections off
11891 Tell @value{GDBN} not to trust readonly sections. This means that
11892 the contents of the section might change while the program is running,
11893 and must therefore be fetched from the target when needed.
11895 @item show trust-readonly-sections
11896 Show the current setting of trusting readonly sections.
11899 All file-specifying commands allow both absolute and relative file names
11900 as arguments. @value{GDBN} always converts the file name to an absolute file
11901 name and remembers it that way.
11903 @cindex shared libraries
11904 @anchor{Shared Libraries}
11905 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11906 and IBM RS/6000 AIX shared libraries.
11908 On MS-Windows @value{GDBN} must be linked with the Expat library to support
11909 shared libraries. @xref{Expat}.
11911 @value{GDBN} automatically loads symbol definitions from shared libraries
11912 when you use the @code{run} command, or when you examine a core file.
11913 (Before you issue the @code{run} command, @value{GDBN} does not understand
11914 references to a function in a shared library, however---unless you are
11915 debugging a core file).
11917 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11918 automatically loads the symbols at the time of the @code{shl_load} call.
11920 @c FIXME: some @value{GDBN} release may permit some refs to undef
11921 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11922 @c FIXME...lib; check this from time to time when updating manual
11924 There are times, however, when you may wish to not automatically load
11925 symbol definitions from shared libraries, such as when they are
11926 particularly large or there are many of them.
11928 To control the automatic loading of shared library symbols, use the
11932 @kindex set auto-solib-add
11933 @item set auto-solib-add @var{mode}
11934 If @var{mode} is @code{on}, symbols from all shared object libraries
11935 will be loaded automatically when the inferior begins execution, you
11936 attach to an independently started inferior, or when the dynamic linker
11937 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11938 is @code{off}, symbols must be loaded manually, using the
11939 @code{sharedlibrary} command. The default value is @code{on}.
11941 @cindex memory used for symbol tables
11942 If your program uses lots of shared libraries with debug info that
11943 takes large amounts of memory, you can decrease the @value{GDBN}
11944 memory footprint by preventing it from automatically loading the
11945 symbols from shared libraries. To that end, type @kbd{set
11946 auto-solib-add off} before running the inferior, then load each
11947 library whose debug symbols you do need with @kbd{sharedlibrary
11948 @var{regexp}}, where @var{regexp} is a regular expression that matches
11949 the libraries whose symbols you want to be loaded.
11951 @kindex show auto-solib-add
11952 @item show auto-solib-add
11953 Display the current autoloading mode.
11956 @cindex load shared library
11957 To explicitly load shared library symbols, use the @code{sharedlibrary}
11961 @kindex info sharedlibrary
11964 @itemx info sharedlibrary
11965 Print the names of the shared libraries which are currently loaded.
11967 @kindex sharedlibrary
11969 @item sharedlibrary @var{regex}
11970 @itemx share @var{regex}
11971 Load shared object library symbols for files matching a
11972 Unix regular expression.
11973 As with files loaded automatically, it only loads shared libraries
11974 required by your program for a core file or after typing @code{run}. If
11975 @var{regex} is omitted all shared libraries required by your program are
11978 @item nosharedlibrary
11979 @kindex nosharedlibrary
11980 @cindex unload symbols from shared libraries
11981 Unload all shared object library symbols. This discards all symbols
11982 that have been loaded from all shared libraries. Symbols from shared
11983 libraries that were loaded by explicit user requests are not
11987 Sometimes you may wish that @value{GDBN} stops and gives you control
11988 when any of shared library events happen. Use the @code{set
11989 stop-on-solib-events} command for this:
11992 @item set stop-on-solib-events
11993 @kindex set stop-on-solib-events
11994 This command controls whether @value{GDBN} should give you control
11995 when the dynamic linker notifies it about some shared library event.
11996 The most common event of interest is loading or unloading of a new
11999 @item show stop-on-solib-events
12000 @kindex show stop-on-solib-events
12001 Show whether @value{GDBN} stops and gives you control when shared
12002 library events happen.
12005 Shared libraries are also supported in many cross or remote debugging
12006 configurations. A copy of the target's libraries need to be present on the
12007 host system; they need to be the same as the target libraries, although the
12008 copies on the target can be stripped as long as the copies on the host are
12011 @cindex where to look for shared libraries
12012 For remote debugging, you need to tell @value{GDBN} where the target
12013 libraries are, so that it can load the correct copies---otherwise, it
12014 may try to load the host's libraries. @value{GDBN} has two variables
12015 to specify the search directories for target libraries.
12018 @cindex prefix for shared library file names
12019 @cindex system root, alternate
12020 @kindex set solib-absolute-prefix
12021 @kindex set sysroot
12022 @item set sysroot @var{path}
12023 Use @var{path} as the system root for the program being debugged. Any
12024 absolute shared library paths will be prefixed with @var{path}; many
12025 runtime loaders store the absolute paths to the shared library in the
12026 target program's memory. If you use @code{set sysroot} to find shared
12027 libraries, they need to be laid out in the same way that they are on
12028 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12031 The @code{set solib-absolute-prefix} command is an alias for @code{set
12034 @cindex default system root
12035 @cindex @samp{--with-sysroot}
12036 You can set the default system root by using the configure-time
12037 @samp{--with-sysroot} option. If the system root is inside
12038 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12039 @samp{--exec-prefix}), then the default system root will be updated
12040 automatically if the installed @value{GDBN} is moved to a new
12043 @kindex show sysroot
12045 Display the current shared library prefix.
12047 @kindex set solib-search-path
12048 @item set solib-search-path @var{path}
12049 If this variable is set, @var{path} is a colon-separated list of
12050 directories to search for shared libraries. @samp{solib-search-path}
12051 is used after @samp{sysroot} fails to locate the library, or if the
12052 path to the library is relative instead of absolute. If you want to
12053 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12054 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12055 finding your host's libraries. @samp{sysroot} is preferred; setting
12056 it to a nonexistent directory may interfere with automatic loading
12057 of shared library symbols.
12059 @kindex show solib-search-path
12060 @item show solib-search-path
12061 Display the current shared library search path.
12065 @node Separate Debug Files
12066 @section Debugging Information in Separate Files
12067 @cindex separate debugging information files
12068 @cindex debugging information in separate files
12069 @cindex @file{.debug} subdirectories
12070 @cindex debugging information directory, global
12071 @cindex global debugging information directory
12072 @cindex build ID, and separate debugging files
12073 @cindex @file{.build-id} directory
12075 @value{GDBN} allows you to put a program's debugging information in a
12076 file separate from the executable itself, in a way that allows
12077 @value{GDBN} to find and load the debugging information automatically.
12078 Since debugging information can be very large---sometimes larger
12079 than the executable code itself---some systems distribute debugging
12080 information for their executables in separate files, which users can
12081 install only when they need to debug a problem.
12083 @value{GDBN} supports two ways of specifying the separate debug info
12088 The executable contains a @dfn{debug link} that specifies the name of
12089 the separate debug info file. The separate debug file's name is
12090 usually @file{@var{executable}.debug}, where @var{executable} is the
12091 name of the corresponding executable file without leading directories
12092 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12093 debug link specifies a CRC32 checksum for the debug file, which
12094 @value{GDBN} uses to validate that the executable and the debug file
12095 came from the same build.
12098 The executable contains a @dfn{build ID}, a unique bit string that is
12099 also present in the corresponding debug info file. (This is supported
12100 only on some operating systems, notably those which use the ELF format
12101 for binary files and the @sc{gnu} Binutils.) For more details about
12102 this feature, see the description of the @option{--build-id}
12103 command-line option in @ref{Options, , Command Line Options, ld.info,
12104 The GNU Linker}. The debug info file's name is not specified
12105 explicitly by the build ID, but can be computed from the build ID, see
12109 Depending on the way the debug info file is specified, @value{GDBN}
12110 uses two different methods of looking for the debug file:
12114 For the ``debug link'' method, @value{GDBN} looks up the named file in
12115 the directory of the executable file, then in a subdirectory of that
12116 directory named @file{.debug}, and finally under the global debug
12117 directory, in a subdirectory whose name is identical to the leading
12118 directories of the executable's absolute file name.
12121 For the ``build ID'' method, @value{GDBN} looks in the
12122 @file{.build-id} subdirectory of the global debug directory for a file
12123 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12124 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12125 are the rest of the bit string. (Real build ID strings are 32 or more
12126 hex characters, not 10.)
12129 So, for example, suppose you ask @value{GDBN} to debug
12130 @file{/usr/bin/ls}, which has a debug link that specifies the
12131 file @file{ls.debug}, and a build ID whose value in hex is
12132 @code{abcdef1234}. If the global debug directory is
12133 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12134 debug information files, in the indicated order:
12138 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12140 @file{/usr/bin/ls.debug}
12142 @file{/usr/bin/.debug/ls.debug}
12144 @file{/usr/lib/debug/usr/bin/ls.debug}.
12147 You can set the global debugging info directory's name, and view the
12148 name @value{GDBN} is currently using.
12152 @kindex set debug-file-directory
12153 @item set debug-file-directory @var{directory}
12154 Set the directory which @value{GDBN} searches for separate debugging
12155 information files to @var{directory}.
12157 @kindex show debug-file-directory
12158 @item show debug-file-directory
12159 Show the directory @value{GDBN} searches for separate debugging
12164 @cindex @code{.gnu_debuglink} sections
12165 @cindex debug link sections
12166 A debug link is a special section of the executable file named
12167 @code{.gnu_debuglink}. The section must contain:
12171 A filename, with any leading directory components removed, followed by
12174 zero to three bytes of padding, as needed to reach the next four-byte
12175 boundary within the section, and
12177 a four-byte CRC checksum, stored in the same endianness used for the
12178 executable file itself. The checksum is computed on the debugging
12179 information file's full contents by the function given below, passing
12180 zero as the @var{crc} argument.
12183 Any executable file format can carry a debug link, as long as it can
12184 contain a section named @code{.gnu_debuglink} with the contents
12187 @cindex @code{.note.gnu.build-id} sections
12188 @cindex build ID sections
12189 The build ID is a special section in the executable file (and in other
12190 ELF binary files that @value{GDBN} may consider). This section is
12191 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12192 It contains unique identification for the built files---the ID remains
12193 the same across multiple builds of the same build tree. The default
12194 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12195 content for the build ID string. The same section with an identical
12196 value is present in the original built binary with symbols, in its
12197 stripped variant, and in the separate debugging information file.
12199 The debugging information file itself should be an ordinary
12200 executable, containing a full set of linker symbols, sections, and
12201 debugging information. The sections of the debugging information file
12202 should have the same names, addresses, and sizes as the original file,
12203 but they need not contain any data---much like a @code{.bss} section
12204 in an ordinary executable.
12206 The @sc{gnu} binary utilities (Binutils) package includes the
12207 @samp{objcopy} utility that can produce
12208 the separated executable / debugging information file pairs using the
12209 following commands:
12212 @kbd{objcopy --only-keep-debug foo foo.debug}
12217 These commands remove the debugging
12218 information from the executable file @file{foo} and place it in the file
12219 @file{foo.debug}. You can use the first, second or both methods to link the
12224 The debug link method needs the following additional command to also leave
12225 behind a debug link in @file{foo}:
12228 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12231 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12232 a version of the @code{strip} command such that the command @kbd{strip foo -f
12233 foo.debug} has the same functionality as the two @code{objcopy} commands and
12234 the @code{ln -s} command above, together.
12237 Build ID gets embedded into the main executable using @code{ld --build-id} or
12238 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12239 compatibility fixes for debug files separation are present in @sc{gnu} binary
12240 utilities (Binutils) package since version 2.18.
12245 Since there are many different ways to compute CRC's for the debug
12246 link (different polynomials, reversals, byte ordering, etc.), the
12247 simplest way to describe the CRC used in @code{.gnu_debuglink}
12248 sections is to give the complete code for a function that computes it:
12250 @kindex gnu_debuglink_crc32
12253 gnu_debuglink_crc32 (unsigned long crc,
12254 unsigned char *buf, size_t len)
12256 static const unsigned long crc32_table[256] =
12258 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12259 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12260 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12261 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12262 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12263 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12264 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12265 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12266 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12267 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12268 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12269 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12270 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12271 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12272 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12273 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12274 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12275 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12276 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12277 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12278 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12279 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12280 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12281 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12282 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12283 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12284 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12285 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12286 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12287 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12288 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12289 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12290 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12291 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12292 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12293 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12294 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12295 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12296 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12297 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12298 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12299 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12300 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12301 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12302 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12303 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12304 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12305 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12306 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12307 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12308 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12311 unsigned char *end;
12313 crc = ~crc & 0xffffffff;
12314 for (end = buf + len; buf < end; ++buf)
12315 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12316 return ~crc & 0xffffffff;
12321 This computation does not apply to the ``build ID'' method.
12324 @node Symbol Errors
12325 @section Errors Reading Symbol Files
12327 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12328 such as symbol types it does not recognize, or known bugs in compiler
12329 output. By default, @value{GDBN} does not notify you of such problems, since
12330 they are relatively common and primarily of interest to people
12331 debugging compilers. If you are interested in seeing information
12332 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12333 only one message about each such type of problem, no matter how many
12334 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12335 to see how many times the problems occur, with the @code{set
12336 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12339 The messages currently printed, and their meanings, include:
12342 @item inner block not inside outer block in @var{symbol}
12344 The symbol information shows where symbol scopes begin and end
12345 (such as at the start of a function or a block of statements). This
12346 error indicates that an inner scope block is not fully contained
12347 in its outer scope blocks.
12349 @value{GDBN} circumvents the problem by treating the inner block as if it had
12350 the same scope as the outer block. In the error message, @var{symbol}
12351 may be shown as ``@code{(don't know)}'' if the outer block is not a
12354 @item block at @var{address} out of order
12356 The symbol information for symbol scope blocks should occur in
12357 order of increasing addresses. This error indicates that it does not
12360 @value{GDBN} does not circumvent this problem, and has trouble
12361 locating symbols in the source file whose symbols it is reading. (You
12362 can often determine what source file is affected by specifying
12363 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12366 @item bad block start address patched
12368 The symbol information for a symbol scope block has a start address
12369 smaller than the address of the preceding source line. This is known
12370 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12372 @value{GDBN} circumvents the problem by treating the symbol scope block as
12373 starting on the previous source line.
12375 @item bad string table offset in symbol @var{n}
12378 Symbol number @var{n} contains a pointer into the string table which is
12379 larger than the size of the string table.
12381 @value{GDBN} circumvents the problem by considering the symbol to have the
12382 name @code{foo}, which may cause other problems if many symbols end up
12385 @item unknown symbol type @code{0x@var{nn}}
12387 The symbol information contains new data types that @value{GDBN} does
12388 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12389 uncomprehended information, in hexadecimal.
12391 @value{GDBN} circumvents the error by ignoring this symbol information.
12392 This usually allows you to debug your program, though certain symbols
12393 are not accessible. If you encounter such a problem and feel like
12394 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12395 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12396 and examine @code{*bufp} to see the symbol.
12398 @item stub type has NULL name
12400 @value{GDBN} could not find the full definition for a struct or class.
12402 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12403 The symbol information for a C@t{++} member function is missing some
12404 information that recent versions of the compiler should have output for
12407 @item info mismatch between compiler and debugger
12409 @value{GDBN} could not parse a type specification output by the compiler.
12414 @chapter Specifying a Debugging Target
12416 @cindex debugging target
12417 A @dfn{target} is the execution environment occupied by your program.
12419 Often, @value{GDBN} runs in the same host environment as your program;
12420 in that case, the debugging target is specified as a side effect when
12421 you use the @code{file} or @code{core} commands. When you need more
12422 flexibility---for example, running @value{GDBN} on a physically separate
12423 host, or controlling a standalone system over a serial port or a
12424 realtime system over a TCP/IP connection---you can use the @code{target}
12425 command to specify one of the target types configured for @value{GDBN}
12426 (@pxref{Target Commands, ,Commands for Managing Targets}).
12428 @cindex target architecture
12429 It is possible to build @value{GDBN} for several different @dfn{target
12430 architectures}. When @value{GDBN} is built like that, you can choose
12431 one of the available architectures with the @kbd{set architecture}
12435 @kindex set architecture
12436 @kindex show architecture
12437 @item set architecture @var{arch}
12438 This command sets the current target architecture to @var{arch}. The
12439 value of @var{arch} can be @code{"auto"}, in addition to one of the
12440 supported architectures.
12442 @item show architecture
12443 Show the current target architecture.
12445 @item set processor
12447 @kindex set processor
12448 @kindex show processor
12449 These are alias commands for, respectively, @code{set architecture}
12450 and @code{show architecture}.
12454 * Active Targets:: Active targets
12455 * Target Commands:: Commands for managing targets
12456 * Byte Order:: Choosing target byte order
12459 @node Active Targets
12460 @section Active Targets
12462 @cindex stacking targets
12463 @cindex active targets
12464 @cindex multiple targets
12466 There are three classes of targets: processes, core files, and
12467 executable files. @value{GDBN} can work concurrently on up to three
12468 active targets, one in each class. This allows you to (for example)
12469 start a process and inspect its activity without abandoning your work on
12472 For example, if you execute @samp{gdb a.out}, then the executable file
12473 @code{a.out} is the only active target. If you designate a core file as
12474 well---presumably from a prior run that crashed and coredumped---then
12475 @value{GDBN} has two active targets and uses them in tandem, looking
12476 first in the corefile target, then in the executable file, to satisfy
12477 requests for memory addresses. (Typically, these two classes of target
12478 are complementary, since core files contain only a program's
12479 read-write memory---variables and so on---plus machine status, while
12480 executable files contain only the program text and initialized data.)
12482 When you type @code{run}, your executable file becomes an active process
12483 target as well. When a process target is active, all @value{GDBN}
12484 commands requesting memory addresses refer to that target; addresses in
12485 an active core file or executable file target are obscured while the
12486 process target is active.
12488 Use the @code{core-file} and @code{exec-file} commands to select a new
12489 core file or executable target (@pxref{Files, ,Commands to Specify
12490 Files}). To specify as a target a process that is already running, use
12491 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12494 @node Target Commands
12495 @section Commands for Managing Targets
12498 @item target @var{type} @var{parameters}
12499 Connects the @value{GDBN} host environment to a target machine or
12500 process. A target is typically a protocol for talking to debugging
12501 facilities. You use the argument @var{type} to specify the type or
12502 protocol of the target machine.
12504 Further @var{parameters} are interpreted by the target protocol, but
12505 typically include things like device names or host names to connect
12506 with, process numbers, and baud rates.
12508 The @code{target} command does not repeat if you press @key{RET} again
12509 after executing the command.
12511 @kindex help target
12513 Displays the names of all targets available. To display targets
12514 currently selected, use either @code{info target} or @code{info files}
12515 (@pxref{Files, ,Commands to Specify Files}).
12517 @item help target @var{name}
12518 Describe a particular target, including any parameters necessary to
12521 @kindex set gnutarget
12522 @item set gnutarget @var{args}
12523 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12524 knows whether it is reading an @dfn{executable},
12525 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12526 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12527 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12530 @emph{Warning:} To specify a file format with @code{set gnutarget},
12531 you must know the actual BFD name.
12535 @xref{Files, , Commands to Specify Files}.
12537 @kindex show gnutarget
12538 @item show gnutarget
12539 Use the @code{show gnutarget} command to display what file format
12540 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12541 @value{GDBN} will determine the file format for each file automatically,
12542 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12545 @cindex common targets
12546 Here are some common targets (available, or not, depending on the GDB
12551 @item target exec @var{program}
12552 @cindex executable file target
12553 An executable file. @samp{target exec @var{program}} is the same as
12554 @samp{exec-file @var{program}}.
12556 @item target core @var{filename}
12557 @cindex core dump file target
12558 A core dump file. @samp{target core @var{filename}} is the same as
12559 @samp{core-file @var{filename}}.
12561 @item target remote @var{medium}
12562 @cindex remote target
12563 A remote system connected to @value{GDBN} via a serial line or network
12564 connection. This command tells @value{GDBN} to use its own remote
12565 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12567 For example, if you have a board connected to @file{/dev/ttya} on the
12568 machine running @value{GDBN}, you could say:
12571 target remote /dev/ttya
12574 @code{target remote} supports the @code{load} command. This is only
12575 useful if you have some other way of getting the stub to the target
12576 system, and you can put it somewhere in memory where it won't get
12577 clobbered by the download.
12580 @cindex built-in simulator target
12581 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12589 works; however, you cannot assume that a specific memory map, device
12590 drivers, or even basic I/O is available, although some simulators do
12591 provide these. For info about any processor-specific simulator details,
12592 see the appropriate section in @ref{Embedded Processors, ,Embedded
12597 Some configurations may include these targets as well:
12601 @item target nrom @var{dev}
12602 @cindex NetROM ROM emulator target
12603 NetROM ROM emulator. This target only supports downloading.
12607 Different targets are available on different configurations of @value{GDBN};
12608 your configuration may have more or fewer targets.
12610 Many remote targets require you to download the executable's code once
12611 you've successfully established a connection. You may wish to control
12612 various aspects of this process.
12617 @kindex set hash@r{, for remote monitors}
12618 @cindex hash mark while downloading
12619 This command controls whether a hash mark @samp{#} is displayed while
12620 downloading a file to the remote monitor. If on, a hash mark is
12621 displayed after each S-record is successfully downloaded to the
12625 @kindex show hash@r{, for remote monitors}
12626 Show the current status of displaying the hash mark.
12628 @item set debug monitor
12629 @kindex set debug monitor
12630 @cindex display remote monitor communications
12631 Enable or disable display of communications messages between
12632 @value{GDBN} and the remote monitor.
12634 @item show debug monitor
12635 @kindex show debug monitor
12636 Show the current status of displaying communications between
12637 @value{GDBN} and the remote monitor.
12642 @kindex load @var{filename}
12643 @item load @var{filename}
12644 Depending on what remote debugging facilities are configured into
12645 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12646 is meant to make @var{filename} (an executable) available for debugging
12647 on the remote system---by downloading, or dynamic linking, for example.
12648 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12649 the @code{add-symbol-file} command.
12651 If your @value{GDBN} does not have a @code{load} command, attempting to
12652 execute it gets the error message ``@code{You can't do that when your
12653 target is @dots{}}''
12655 The file is loaded at whatever address is specified in the executable.
12656 For some object file formats, you can specify the load address when you
12657 link the program; for other formats, like a.out, the object file format
12658 specifies a fixed address.
12659 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12661 Depending on the remote side capabilities, @value{GDBN} may be able to
12662 load programs into flash memory.
12664 @code{load} does not repeat if you press @key{RET} again after using it.
12668 @section Choosing Target Byte Order
12670 @cindex choosing target byte order
12671 @cindex target byte order
12673 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12674 offer the ability to run either big-endian or little-endian byte
12675 orders. Usually the executable or symbol will include a bit to
12676 designate the endian-ness, and you will not need to worry about
12677 which to use. However, you may still find it useful to adjust
12678 @value{GDBN}'s idea of processor endian-ness manually.
12682 @item set endian big
12683 Instruct @value{GDBN} to assume the target is big-endian.
12685 @item set endian little
12686 Instruct @value{GDBN} to assume the target is little-endian.
12688 @item set endian auto
12689 Instruct @value{GDBN} to use the byte order associated with the
12693 Display @value{GDBN}'s current idea of the target byte order.
12697 Note that these commands merely adjust interpretation of symbolic
12698 data on the host, and that they have absolutely no effect on the
12702 @node Remote Debugging
12703 @chapter Debugging Remote Programs
12704 @cindex remote debugging
12706 If you are trying to debug a program running on a machine that cannot run
12707 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12708 For example, you might use remote debugging on an operating system kernel,
12709 or on a small system which does not have a general purpose operating system
12710 powerful enough to run a full-featured debugger.
12712 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12713 to make this work with particular debugging targets. In addition,
12714 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12715 but not specific to any particular target system) which you can use if you
12716 write the remote stubs---the code that runs on the remote system to
12717 communicate with @value{GDBN}.
12719 Other remote targets may be available in your
12720 configuration of @value{GDBN}; use @code{help target} to list them.
12723 * Connecting:: Connecting to a remote target
12724 * File Transfer:: Sending files to a remote system
12725 * Server:: Using the gdbserver program
12726 * Remote Configuration:: Remote configuration
12727 * Remote Stub:: Implementing a remote stub
12731 @section Connecting to a Remote Target
12733 On the @value{GDBN} host machine, you will need an unstripped copy of
12734 your program, since @value{GDBN} needs symbol and debugging information.
12735 Start up @value{GDBN} as usual, using the name of the local copy of your
12736 program as the first argument.
12738 @cindex @code{target remote}
12739 @value{GDBN} can communicate with the target over a serial line, or
12740 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12741 each case, @value{GDBN} uses the same protocol for debugging your
12742 program; only the medium carrying the debugging packets varies. The
12743 @code{target remote} command establishes a connection to the target.
12744 Its arguments indicate which medium to use:
12748 @item target remote @var{serial-device}
12749 @cindex serial line, @code{target remote}
12750 Use @var{serial-device} to communicate with the target. For example,
12751 to use a serial line connected to the device named @file{/dev/ttyb}:
12754 target remote /dev/ttyb
12757 If you're using a serial line, you may want to give @value{GDBN} the
12758 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12759 (@pxref{Remote Configuration, set remotebaud}) before the
12760 @code{target} command.
12762 @item target remote @code{@var{host}:@var{port}}
12763 @itemx target remote @code{tcp:@var{host}:@var{port}}
12764 @cindex @acronym{TCP} port, @code{target remote}
12765 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12766 The @var{host} may be either a host name or a numeric @acronym{IP}
12767 address; @var{port} must be a decimal number. The @var{host} could be
12768 the target machine itself, if it is directly connected to the net, or
12769 it might be a terminal server which in turn has a serial line to the
12772 For example, to connect to port 2828 on a terminal server named
12776 target remote manyfarms:2828
12779 If your remote target is actually running on the same machine as your
12780 debugger session (e.g.@: a simulator for your target running on the
12781 same host), you can omit the hostname. For example, to connect to
12782 port 1234 on your local machine:
12785 target remote :1234
12789 Note that the colon is still required here.
12791 @item target remote @code{udp:@var{host}:@var{port}}
12792 @cindex @acronym{UDP} port, @code{target remote}
12793 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12794 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12797 target remote udp:manyfarms:2828
12800 When using a @acronym{UDP} connection for remote debugging, you should
12801 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12802 can silently drop packets on busy or unreliable networks, which will
12803 cause havoc with your debugging session.
12805 @item target remote | @var{command}
12806 @cindex pipe, @code{target remote} to
12807 Run @var{command} in the background and communicate with it using a
12808 pipe. The @var{command} is a shell command, to be parsed and expanded
12809 by the system's command shell, @code{/bin/sh}; it should expect remote
12810 protocol packets on its standard input, and send replies on its
12811 standard output. You could use this to run a stand-alone simulator
12812 that speaks the remote debugging protocol, to make net connections
12813 using programs like @code{ssh}, or for other similar tricks.
12815 If @var{command} closes its standard output (perhaps by exiting),
12816 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12817 program has already exited, this will have no effect.)
12821 Once the connection has been established, you can use all the usual
12822 commands to examine and change data and to step and continue the
12825 @cindex interrupting remote programs
12826 @cindex remote programs, interrupting
12827 Whenever @value{GDBN} is waiting for the remote program, if you type the
12828 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12829 program. This may or may not succeed, depending in part on the hardware
12830 and the serial drivers the remote system uses. If you type the
12831 interrupt character once again, @value{GDBN} displays this prompt:
12834 Interrupted while waiting for the program.
12835 Give up (and stop debugging it)? (y or n)
12838 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12839 (If you decide you want to try again later, you can use @samp{target
12840 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12841 goes back to waiting.
12844 @kindex detach (remote)
12846 When you have finished debugging the remote program, you can use the
12847 @code{detach} command to release it from @value{GDBN} control.
12848 Detaching from the target normally resumes its execution, but the results
12849 will depend on your particular remote stub. After the @code{detach}
12850 command, @value{GDBN} is free to connect to another target.
12854 The @code{disconnect} command behaves like @code{detach}, except that
12855 the target is generally not resumed. It will wait for @value{GDBN}
12856 (this instance or another one) to connect and continue debugging. After
12857 the @code{disconnect} command, @value{GDBN} is again free to connect to
12860 @cindex send command to remote monitor
12861 @cindex extend @value{GDBN} for remote targets
12862 @cindex add new commands for external monitor
12864 @item monitor @var{cmd}
12865 This command allows you to send arbitrary commands directly to the
12866 remote monitor. Since @value{GDBN} doesn't care about the commands it
12867 sends like this, this command is the way to extend @value{GDBN}---you
12868 can add new commands that only the external monitor will understand
12872 @node File Transfer
12873 @section Sending files to a remote system
12874 @cindex remote target, file transfer
12875 @cindex file transfer
12876 @cindex sending files to remote systems
12878 Some remote targets offer the ability to transfer files over the same
12879 connection used to communicate with @value{GDBN}. This is convenient
12880 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
12881 running @code{gdbserver} over a network interface. For other targets,
12882 e.g.@: embedded devices with only a single serial port, this may be
12883 the only way to upload or download files.
12885 Not all remote targets support these commands.
12889 @item remote put @var{hostfile} @var{targetfile}
12890 Copy file @var{hostfile} from the host system (the machine running
12891 @value{GDBN}) to @var{targetfile} on the target system.
12894 @item remote get @var{targetfile} @var{hostfile}
12895 Copy file @var{targetfile} from the target system to @var{hostfile}
12896 on the host system.
12898 @kindex remote delete
12899 @item remote delete @var{targetfile}
12900 Delete @var{targetfile} from the target system.
12905 @section Using the @code{gdbserver} Program
12908 @cindex remote connection without stubs
12909 @code{gdbserver} is a control program for Unix-like systems, which
12910 allows you to connect your program with a remote @value{GDBN} via
12911 @code{target remote}---but without linking in the usual debugging stub.
12913 @code{gdbserver} is not a complete replacement for the debugging stubs,
12914 because it requires essentially the same operating-system facilities
12915 that @value{GDBN} itself does. In fact, a system that can run
12916 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12917 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12918 because it is a much smaller program than @value{GDBN} itself. It is
12919 also easier to port than all of @value{GDBN}, so you may be able to get
12920 started more quickly on a new system by using @code{gdbserver}.
12921 Finally, if you develop code for real-time systems, you may find that
12922 the tradeoffs involved in real-time operation make it more convenient to
12923 do as much development work as possible on another system, for example
12924 by cross-compiling. You can use @code{gdbserver} to make a similar
12925 choice for debugging.
12927 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12928 or a TCP connection, using the standard @value{GDBN} remote serial
12932 @item On the target machine,
12933 you need to have a copy of the program you want to debug.
12934 @code{gdbserver} does not need your program's symbol table, so you can
12935 strip the program if necessary to save space. @value{GDBN} on the host
12936 system does all the symbol handling.
12938 To use the server, you must tell it how to communicate with @value{GDBN};
12939 the name of your program; and the arguments for your program. The usual
12943 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12946 @var{comm} is either a device name (to use a serial line) or a TCP
12947 hostname and portnumber. For example, to debug Emacs with the argument
12948 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12952 target> gdbserver /dev/com1 emacs foo.txt
12955 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12958 To use a TCP connection instead of a serial line:
12961 target> gdbserver host:2345 emacs foo.txt
12964 The only difference from the previous example is the first argument,
12965 specifying that you are communicating with the host @value{GDBN} via
12966 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12967 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12968 (Currently, the @samp{host} part is ignored.) You can choose any number
12969 you want for the port number as long as it does not conflict with any
12970 TCP ports already in use on the target system (for example, @code{23} is
12971 reserved for @code{telnet}).@footnote{If you choose a port number that
12972 conflicts with another service, @code{gdbserver} prints an error message
12973 and exits.} You must use the same port number with the host @value{GDBN}
12974 @code{target remote} command.
12976 On some targets, @code{gdbserver} can also attach to running programs.
12977 This is accomplished via the @code{--attach} argument. The syntax is:
12980 target> gdbserver @var{comm} --attach @var{pid}
12983 @var{pid} is the process ID of a currently running process. It isn't necessary
12984 to point @code{gdbserver} at a binary for the running process.
12987 @cindex attach to a program by name
12988 You can debug processes by name instead of process ID if your target has the
12989 @code{pidof} utility:
12992 target> gdbserver @var{comm} --attach `pidof @var{program}`
12995 In case more than one copy of @var{program} is running, or @var{program}
12996 has multiple threads, most versions of @code{pidof} support the
12997 @code{-s} option to only return the first process ID.
12999 @item On the host machine,
13000 first make sure you have the necessary symbol files. Load symbols for
13001 your application using the @code{file} command before you connect. Use
13002 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
13003 was compiled with the correct sysroot using @code{--with-system-root}).
13005 The symbol file and target libraries must exactly match the executable
13006 and libraries on the target, with one exception: the files on the host
13007 system should not be stripped, even if the files on the target system
13008 are. Mismatched or missing files will lead to confusing results
13009 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
13010 files may also prevent @code{gdbserver} from debugging multi-threaded
13013 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
13014 For TCP connections, you must start up @code{gdbserver} prior to using
13015 the @code{target remote} command. Otherwise you may get an error whose
13016 text depends on the host system, but which usually looks something like
13017 @samp{Connection refused}. You don't need to use the @code{load}
13018 command in @value{GDBN} when using @code{gdbserver}, since the program is
13019 already on the target.
13023 @subsection Monitor Commands for @code{gdbserver}
13024 @cindex monitor commands, for @code{gdbserver}
13026 During a @value{GDBN} session using @code{gdbserver}, you can use the
13027 @code{monitor} command to send special requests to @code{gdbserver}.
13028 Here are the available commands; they are only of interest when
13029 debugging @value{GDBN} or @code{gdbserver}.
13033 List the available monitor commands.
13035 @item monitor set debug 0
13036 @itemx monitor set debug 1
13037 Disable or enable general debugging messages.
13039 @item monitor set remote-debug 0
13040 @itemx monitor set remote-debug 1
13041 Disable or enable specific debugging messages associated with the remote
13042 protocol (@pxref{Remote Protocol}).
13046 @node Remote Configuration
13047 @section Remote Configuration
13050 @kindex show remote
13051 This section documents the configuration options available when
13052 debugging remote programs. For the options related to the File I/O
13053 extensions of the remote protocol, see @ref{system,
13054 system-call-allowed}.
13057 @item set remoteaddresssize @var{bits}
13058 @cindex address size for remote targets
13059 @cindex bits in remote address
13060 Set the maximum size of address in a memory packet to the specified
13061 number of bits. @value{GDBN} will mask off the address bits above
13062 that number, when it passes addresses to the remote target. The
13063 default value is the number of bits in the target's address.
13065 @item show remoteaddresssize
13066 Show the current value of remote address size in bits.
13068 @item set remotebaud @var{n}
13069 @cindex baud rate for remote targets
13070 Set the baud rate for the remote serial I/O to @var{n} baud. The
13071 value is used to set the speed of the serial port used for debugging
13074 @item show remotebaud
13075 Show the current speed of the remote connection.
13077 @item set remotebreak
13078 @cindex interrupt remote programs
13079 @cindex BREAK signal instead of Ctrl-C
13080 @anchor{set remotebreak}
13081 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13082 when you type @kbd{Ctrl-c} to interrupt the program running
13083 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13084 character instead. The default is off, since most remote systems
13085 expect to see @samp{Ctrl-C} as the interrupt signal.
13087 @item show remotebreak
13088 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13089 interrupt the remote program.
13091 @item set remoteflow on
13092 @itemx set remoteflow off
13093 @kindex set remoteflow
13094 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13095 on the serial port used to communicate to the remote target.
13097 @item show remoteflow
13098 @kindex show remoteflow
13099 Show the current setting of hardware flow control.
13101 @item set remotelogbase @var{base}
13102 Set the base (a.k.a.@: radix) of logging serial protocol
13103 communications to @var{base}. Supported values of @var{base} are:
13104 @code{ascii}, @code{octal}, and @code{hex}. The default is
13107 @item show remotelogbase
13108 Show the current setting of the radix for logging remote serial
13111 @item set remotelogfile @var{file}
13112 @cindex record serial communications on file
13113 Record remote serial communications on the named @var{file}. The
13114 default is not to record at all.
13116 @item show remotelogfile.
13117 Show the current setting of the file name on which to record the
13118 serial communications.
13120 @item set remotetimeout @var{num}
13121 @cindex timeout for serial communications
13122 @cindex remote timeout
13123 Set the timeout limit to wait for the remote target to respond to
13124 @var{num} seconds. The default is 2 seconds.
13126 @item show remotetimeout
13127 Show the current number of seconds to wait for the remote target
13130 @cindex limit hardware breakpoints and watchpoints
13131 @cindex remote target, limit break- and watchpoints
13132 @anchor{set remote hardware-watchpoint-limit}
13133 @anchor{set remote hardware-breakpoint-limit}
13134 @item set remote hardware-watchpoint-limit @var{limit}
13135 @itemx set remote hardware-breakpoint-limit @var{limit}
13136 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13137 watchpoints. A limit of -1, the default, is treated as unlimited.
13140 @cindex remote packets, enabling and disabling
13141 The @value{GDBN} remote protocol autodetects the packets supported by
13142 your debugging stub. If you need to override the autodetection, you
13143 can use these commands to enable or disable individual packets. Each
13144 packet can be set to @samp{on} (the remote target supports this
13145 packet), @samp{off} (the remote target does not support this packet),
13146 or @samp{auto} (detect remote target support for this packet). They
13147 all default to @samp{auto}. For more information about each packet,
13148 see @ref{Remote Protocol}.
13150 During normal use, you should not have to use any of these commands.
13151 If you do, that may be a bug in your remote debugging stub, or a bug
13152 in @value{GDBN}. You may want to report the problem to the
13153 @value{GDBN} developers.
13155 For each packet @var{name}, the command to enable or disable the
13156 packet is @code{set remote @var{name}-packet}. The available settings
13159 @multitable @columnfractions 0.28 0.32 0.25
13162 @tab Related Features
13164 @item @code{fetch-register}
13166 @tab @code{info registers}
13168 @item @code{set-register}
13172 @item @code{binary-download}
13174 @tab @code{load}, @code{set}
13176 @item @code{read-aux-vector}
13177 @tab @code{qXfer:auxv:read}
13178 @tab @code{info auxv}
13180 @item @code{symbol-lookup}
13181 @tab @code{qSymbol}
13182 @tab Detecting multiple threads
13184 @item @code{verbose-resume}
13186 @tab Stepping or resuming multiple threads
13188 @item @code{software-breakpoint}
13192 @item @code{hardware-breakpoint}
13196 @item @code{write-watchpoint}
13200 @item @code{read-watchpoint}
13204 @item @code{access-watchpoint}
13208 @item @code{target-features}
13209 @tab @code{qXfer:features:read}
13210 @tab @code{set architecture}
13212 @item @code{library-info}
13213 @tab @code{qXfer:libraries:read}
13214 @tab @code{info sharedlibrary}
13216 @item @code{memory-map}
13217 @tab @code{qXfer:memory-map:read}
13218 @tab @code{info mem}
13220 @item @code{read-spu-object}
13221 @tab @code{qXfer:spu:read}
13222 @tab @code{info spu}
13224 @item @code{write-spu-object}
13225 @tab @code{qXfer:spu:write}
13226 @tab @code{info spu}
13228 @item @code{get-thread-local-@*storage-address}
13229 @tab @code{qGetTLSAddr}
13230 @tab Displaying @code{__thread} variables
13232 @item @code{supported-packets}
13233 @tab @code{qSupported}
13234 @tab Remote communications parameters
13236 @item @code{pass-signals}
13237 @tab @code{QPassSignals}
13238 @tab @code{handle @var{signal}}
13240 @item @code{hostio-close-packet}
13241 @tab @code{vFile:close}
13242 @tab @code{remote get}, @code{remote put}
13244 @item @code{hostio-open-packet}
13245 @tab @code{vFile:open}
13246 @tab @code{remote get}, @code{remote put}
13248 @item @code{hostio-pread-packet}
13249 @tab @code{vFile:pread}
13250 @tab @code{remote get}, @code{remote put}
13252 @item @code{hostio-pwrite-packet}
13253 @tab @code{vFile:pwrite}
13254 @tab @code{remote get}, @code{remote put}
13256 @item @code{hostio-unlink-packet}
13257 @tab @code{vFile:unlink}
13258 @tab @code{remote delete}
13262 @section Implementing a Remote Stub
13264 @cindex debugging stub, example
13265 @cindex remote stub, example
13266 @cindex stub example, remote debugging
13267 The stub files provided with @value{GDBN} implement the target side of the
13268 communication protocol, and the @value{GDBN} side is implemented in the
13269 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13270 these subroutines to communicate, and ignore the details. (If you're
13271 implementing your own stub file, you can still ignore the details: start
13272 with one of the existing stub files. @file{sparc-stub.c} is the best
13273 organized, and therefore the easiest to read.)
13275 @cindex remote serial debugging, overview
13276 To debug a program running on another machine (the debugging
13277 @dfn{target} machine), you must first arrange for all the usual
13278 prerequisites for the program to run by itself. For example, for a C
13283 A startup routine to set up the C runtime environment; these usually
13284 have a name like @file{crt0}. The startup routine may be supplied by
13285 your hardware supplier, or you may have to write your own.
13288 A C subroutine library to support your program's
13289 subroutine calls, notably managing input and output.
13292 A way of getting your program to the other machine---for example, a
13293 download program. These are often supplied by the hardware
13294 manufacturer, but you may have to write your own from hardware
13298 The next step is to arrange for your program to use a serial port to
13299 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13300 machine). In general terms, the scheme looks like this:
13304 @value{GDBN} already understands how to use this protocol; when everything
13305 else is set up, you can simply use the @samp{target remote} command
13306 (@pxref{Targets,,Specifying a Debugging Target}).
13308 @item On the target,
13309 you must link with your program a few special-purpose subroutines that
13310 implement the @value{GDBN} remote serial protocol. The file containing these
13311 subroutines is called a @dfn{debugging stub}.
13313 On certain remote targets, you can use an auxiliary program
13314 @code{gdbserver} instead of linking a stub into your program.
13315 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13318 The debugging stub is specific to the architecture of the remote
13319 machine; for example, use @file{sparc-stub.c} to debug programs on
13322 @cindex remote serial stub list
13323 These working remote stubs are distributed with @value{GDBN}:
13328 @cindex @file{i386-stub.c}
13331 For Intel 386 and compatible architectures.
13334 @cindex @file{m68k-stub.c}
13335 @cindex Motorola 680x0
13337 For Motorola 680x0 architectures.
13340 @cindex @file{sh-stub.c}
13343 For Renesas SH architectures.
13346 @cindex @file{sparc-stub.c}
13348 For @sc{sparc} architectures.
13350 @item sparcl-stub.c
13351 @cindex @file{sparcl-stub.c}
13354 For Fujitsu @sc{sparclite} architectures.
13358 The @file{README} file in the @value{GDBN} distribution may list other
13359 recently added stubs.
13362 * Stub Contents:: What the stub can do for you
13363 * Bootstrapping:: What you must do for the stub
13364 * Debug Session:: Putting it all together
13367 @node Stub Contents
13368 @subsection What the Stub Can Do for You
13370 @cindex remote serial stub
13371 The debugging stub for your architecture supplies these three
13375 @item set_debug_traps
13376 @findex set_debug_traps
13377 @cindex remote serial stub, initialization
13378 This routine arranges for @code{handle_exception} to run when your
13379 program stops. You must call this subroutine explicitly near the
13380 beginning of your program.
13382 @item handle_exception
13383 @findex handle_exception
13384 @cindex remote serial stub, main routine
13385 This is the central workhorse, but your program never calls it
13386 explicitly---the setup code arranges for @code{handle_exception} to
13387 run when a trap is triggered.
13389 @code{handle_exception} takes control when your program stops during
13390 execution (for example, on a breakpoint), and mediates communications
13391 with @value{GDBN} on the host machine. This is where the communications
13392 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13393 representative on the target machine. It begins by sending summary
13394 information on the state of your program, then continues to execute,
13395 retrieving and transmitting any information @value{GDBN} needs, until you
13396 execute a @value{GDBN} command that makes your program resume; at that point,
13397 @code{handle_exception} returns control to your own code on the target
13401 @cindex @code{breakpoint} subroutine, remote
13402 Use this auxiliary subroutine to make your program contain a
13403 breakpoint. Depending on the particular situation, this may be the only
13404 way for @value{GDBN} to get control. For instance, if your target
13405 machine has some sort of interrupt button, you won't need to call this;
13406 pressing the interrupt button transfers control to
13407 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13408 simply receiving characters on the serial port may also trigger a trap;
13409 again, in that situation, you don't need to call @code{breakpoint} from
13410 your own program---simply running @samp{target remote} from the host
13411 @value{GDBN} session gets control.
13413 Call @code{breakpoint} if none of these is true, or if you simply want
13414 to make certain your program stops at a predetermined point for the
13415 start of your debugging session.
13418 @node Bootstrapping
13419 @subsection What You Must Do for the Stub
13421 @cindex remote stub, support routines
13422 The debugging stubs that come with @value{GDBN} are set up for a particular
13423 chip architecture, but they have no information about the rest of your
13424 debugging target machine.
13426 First of all you need to tell the stub how to communicate with the
13430 @item int getDebugChar()
13431 @findex getDebugChar
13432 Write this subroutine to read a single character from the serial port.
13433 It may be identical to @code{getchar} for your target system; a
13434 different name is used to allow you to distinguish the two if you wish.
13436 @item void putDebugChar(int)
13437 @findex putDebugChar
13438 Write this subroutine to write a single character to the serial port.
13439 It may be identical to @code{putchar} for your target system; a
13440 different name is used to allow you to distinguish the two if you wish.
13443 @cindex control C, and remote debugging
13444 @cindex interrupting remote targets
13445 If you want @value{GDBN} to be able to stop your program while it is
13446 running, you need to use an interrupt-driven serial driver, and arrange
13447 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13448 character). That is the character which @value{GDBN} uses to tell the
13449 remote system to stop.
13451 Getting the debugging target to return the proper status to @value{GDBN}
13452 probably requires changes to the standard stub; one quick and dirty way
13453 is to just execute a breakpoint instruction (the ``dirty'' part is that
13454 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13456 Other routines you need to supply are:
13459 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13460 @findex exceptionHandler
13461 Write this function to install @var{exception_address} in the exception
13462 handling tables. You need to do this because the stub does not have any
13463 way of knowing what the exception handling tables on your target system
13464 are like (for example, the processor's table might be in @sc{rom},
13465 containing entries which point to a table in @sc{ram}).
13466 @var{exception_number} is the exception number which should be changed;
13467 its meaning is architecture-dependent (for example, different numbers
13468 might represent divide by zero, misaligned access, etc). When this
13469 exception occurs, control should be transferred directly to
13470 @var{exception_address}, and the processor state (stack, registers,
13471 and so on) should be just as it is when a processor exception occurs. So if
13472 you want to use a jump instruction to reach @var{exception_address}, it
13473 should be a simple jump, not a jump to subroutine.
13475 For the 386, @var{exception_address} should be installed as an interrupt
13476 gate so that interrupts are masked while the handler runs. The gate
13477 should be at privilege level 0 (the most privileged level). The
13478 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13479 help from @code{exceptionHandler}.
13481 @item void flush_i_cache()
13482 @findex flush_i_cache
13483 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13484 instruction cache, if any, on your target machine. If there is no
13485 instruction cache, this subroutine may be a no-op.
13487 On target machines that have instruction caches, @value{GDBN} requires this
13488 function to make certain that the state of your program is stable.
13492 You must also make sure this library routine is available:
13495 @item void *memset(void *, int, int)
13497 This is the standard library function @code{memset} that sets an area of
13498 memory to a known value. If you have one of the free versions of
13499 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13500 either obtain it from your hardware manufacturer, or write your own.
13503 If you do not use the GNU C compiler, you may need other standard
13504 library subroutines as well; this varies from one stub to another,
13505 but in general the stubs are likely to use any of the common library
13506 subroutines which @code{@value{NGCC}} generates as inline code.
13509 @node Debug Session
13510 @subsection Putting it All Together
13512 @cindex remote serial debugging summary
13513 In summary, when your program is ready to debug, you must follow these
13518 Make sure you have defined the supporting low-level routines
13519 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13521 @code{getDebugChar}, @code{putDebugChar},
13522 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13526 Insert these lines near the top of your program:
13534 For the 680x0 stub only, you need to provide a variable called
13535 @code{exceptionHook}. Normally you just use:
13538 void (*exceptionHook)() = 0;
13542 but if before calling @code{set_debug_traps}, you set it to point to a
13543 function in your program, that function is called when
13544 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13545 error). The function indicated by @code{exceptionHook} is called with
13546 one parameter: an @code{int} which is the exception number.
13549 Compile and link together: your program, the @value{GDBN} debugging stub for
13550 your target architecture, and the supporting subroutines.
13553 Make sure you have a serial connection between your target machine and
13554 the @value{GDBN} host, and identify the serial port on the host.
13557 @c The "remote" target now provides a `load' command, so we should
13558 @c document that. FIXME.
13559 Download your program to your target machine (or get it there by
13560 whatever means the manufacturer provides), and start it.
13563 Start @value{GDBN} on the host, and connect to the target
13564 (@pxref{Connecting,,Connecting to a Remote Target}).
13568 @node Configurations
13569 @chapter Configuration-Specific Information
13571 While nearly all @value{GDBN} commands are available for all native and
13572 cross versions of the debugger, there are some exceptions. This chapter
13573 describes things that are only available in certain configurations.
13575 There are three major categories of configurations: native
13576 configurations, where the host and target are the same, embedded
13577 operating system configurations, which are usually the same for several
13578 different processor architectures, and bare embedded processors, which
13579 are quite different from each other.
13584 * Embedded Processors::
13591 This section describes details specific to particular native
13596 * BSD libkvm Interface:: Debugging BSD kernel memory images
13597 * SVR4 Process Information:: SVR4 process information
13598 * DJGPP Native:: Features specific to the DJGPP port
13599 * Cygwin Native:: Features specific to the Cygwin port
13600 * Hurd Native:: Features specific to @sc{gnu} Hurd
13601 * Neutrino:: Features specific to QNX Neutrino
13607 On HP-UX systems, if you refer to a function or variable name that
13608 begins with a dollar sign, @value{GDBN} searches for a user or system
13609 name first, before it searches for a convenience variable.
13612 @node BSD libkvm Interface
13613 @subsection BSD libkvm Interface
13616 @cindex kernel memory image
13617 @cindex kernel crash dump
13619 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13620 interface that provides a uniform interface for accessing kernel virtual
13621 memory images, including live systems and crash dumps. @value{GDBN}
13622 uses this interface to allow you to debug live kernels and kernel crash
13623 dumps on many native BSD configurations. This is implemented as a
13624 special @code{kvm} debugging target. For debugging a live system, load
13625 the currently running kernel into @value{GDBN} and connect to the
13629 (@value{GDBP}) @b{target kvm}
13632 For debugging crash dumps, provide the file name of the crash dump as an
13636 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13639 Once connected to the @code{kvm} target, the following commands are
13645 Set current context from the @dfn{Process Control Block} (PCB) address.
13648 Set current context from proc address. This command isn't available on
13649 modern FreeBSD systems.
13652 @node SVR4 Process Information
13653 @subsection SVR4 Process Information
13655 @cindex examine process image
13656 @cindex process info via @file{/proc}
13658 Many versions of SVR4 and compatible systems provide a facility called
13659 @samp{/proc} that can be used to examine the image of a running
13660 process using file-system subroutines. If @value{GDBN} is configured
13661 for an operating system with this facility, the command @code{info
13662 proc} is available to report information about the process running
13663 your program, or about any process running on your system. @code{info
13664 proc} works only on SVR4 systems that include the @code{procfs} code.
13665 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13666 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13672 @itemx info proc @var{process-id}
13673 Summarize available information about any running process. If a
13674 process ID is specified by @var{process-id}, display information about
13675 that process; otherwise display information about the program being
13676 debugged. The summary includes the debugged process ID, the command
13677 line used to invoke it, its current working directory, and its
13678 executable file's absolute file name.
13680 On some systems, @var{process-id} can be of the form
13681 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13682 within a process. If the optional @var{pid} part is missing, it means
13683 a thread from the process being debugged (the leading @samp{/} still
13684 needs to be present, or else @value{GDBN} will interpret the number as
13685 a process ID rather than a thread ID).
13687 @item info proc mappings
13688 @cindex memory address space mappings
13689 Report the memory address space ranges accessible in the program, with
13690 information on whether the process has read, write, or execute access
13691 rights to each range. On @sc{gnu}/Linux systems, each memory range
13692 includes the object file which is mapped to that range, instead of the
13693 memory access rights to that range.
13695 @item info proc stat
13696 @itemx info proc status
13697 @cindex process detailed status information
13698 These subcommands are specific to @sc{gnu}/Linux systems. They show
13699 the process-related information, including the user ID and group ID;
13700 how many threads are there in the process; its virtual memory usage;
13701 the signals that are pending, blocked, and ignored; its TTY; its
13702 consumption of system and user time; its stack size; its @samp{nice}
13703 value; etc. For more information, see the @samp{proc} man page
13704 (type @kbd{man 5 proc} from your shell prompt).
13706 @item info proc all
13707 Show all the information about the process described under all of the
13708 above @code{info proc} subcommands.
13711 @comment These sub-options of 'info proc' were not included when
13712 @comment procfs.c was re-written. Keep their descriptions around
13713 @comment against the day when someone finds the time to put them back in.
13714 @kindex info proc times
13715 @item info proc times
13716 Starting time, user CPU time, and system CPU time for your program and
13719 @kindex info proc id
13721 Report on the process IDs related to your program: its own process ID,
13722 the ID of its parent, the process group ID, and the session ID.
13725 @item set procfs-trace
13726 @kindex set procfs-trace
13727 @cindex @code{procfs} API calls
13728 This command enables and disables tracing of @code{procfs} API calls.
13730 @item show procfs-trace
13731 @kindex show procfs-trace
13732 Show the current state of @code{procfs} API call tracing.
13734 @item set procfs-file @var{file}
13735 @kindex set procfs-file
13736 Tell @value{GDBN} to write @code{procfs} API trace to the named
13737 @var{file}. @value{GDBN} appends the trace info to the previous
13738 contents of the file. The default is to display the trace on the
13741 @item show procfs-file
13742 @kindex show procfs-file
13743 Show the file to which @code{procfs} API trace is written.
13745 @item proc-trace-entry
13746 @itemx proc-trace-exit
13747 @itemx proc-untrace-entry
13748 @itemx proc-untrace-exit
13749 @kindex proc-trace-entry
13750 @kindex proc-trace-exit
13751 @kindex proc-untrace-entry
13752 @kindex proc-untrace-exit
13753 These commands enable and disable tracing of entries into and exits
13754 from the @code{syscall} interface.
13757 @kindex info pidlist
13758 @cindex process list, QNX Neutrino
13759 For QNX Neutrino only, this command displays the list of all the
13760 processes and all the threads within each process.
13763 @kindex info meminfo
13764 @cindex mapinfo list, QNX Neutrino
13765 For QNX Neutrino only, this command displays the list of all mapinfos.
13769 @subsection Features for Debugging @sc{djgpp} Programs
13770 @cindex @sc{djgpp} debugging
13771 @cindex native @sc{djgpp} debugging
13772 @cindex MS-DOS-specific commands
13775 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13776 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13777 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13778 top of real-mode DOS systems and their emulations.
13780 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13781 defines a few commands specific to the @sc{djgpp} port. This
13782 subsection describes those commands.
13787 This is a prefix of @sc{djgpp}-specific commands which print
13788 information about the target system and important OS structures.
13791 @cindex MS-DOS system info
13792 @cindex free memory information (MS-DOS)
13793 @item info dos sysinfo
13794 This command displays assorted information about the underlying
13795 platform: the CPU type and features, the OS version and flavor, the
13796 DPMI version, and the available conventional and DPMI memory.
13801 @cindex segment descriptor tables
13802 @cindex descriptor tables display
13804 @itemx info dos ldt
13805 @itemx info dos idt
13806 These 3 commands display entries from, respectively, Global, Local,
13807 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13808 tables are data structures which store a descriptor for each segment
13809 that is currently in use. The segment's selector is an index into a
13810 descriptor table; the table entry for that index holds the
13811 descriptor's base address and limit, and its attributes and access
13814 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13815 segment (used for both data and the stack), and a DOS segment (which
13816 allows access to DOS/BIOS data structures and absolute addresses in
13817 conventional memory). However, the DPMI host will usually define
13818 additional segments in order to support the DPMI environment.
13820 @cindex garbled pointers
13821 These commands allow to display entries from the descriptor tables.
13822 Without an argument, all entries from the specified table are
13823 displayed. An argument, which should be an integer expression, means
13824 display a single entry whose index is given by the argument. For
13825 example, here's a convenient way to display information about the
13826 debugged program's data segment:
13829 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13830 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13834 This comes in handy when you want to see whether a pointer is outside
13835 the data segment's limit (i.e.@: @dfn{garbled}).
13837 @cindex page tables display (MS-DOS)
13839 @itemx info dos pte
13840 These two commands display entries from, respectively, the Page
13841 Directory and the Page Tables. Page Directories and Page Tables are
13842 data structures which control how virtual memory addresses are mapped
13843 into physical addresses. A Page Table includes an entry for every
13844 page of memory that is mapped into the program's address space; there
13845 may be several Page Tables, each one holding up to 4096 entries. A
13846 Page Directory has up to 4096 entries, one each for every Page Table
13847 that is currently in use.
13849 Without an argument, @kbd{info dos pde} displays the entire Page
13850 Directory, and @kbd{info dos pte} displays all the entries in all of
13851 the Page Tables. An argument, an integer expression, given to the
13852 @kbd{info dos pde} command means display only that entry from the Page
13853 Directory table. An argument given to the @kbd{info dos pte} command
13854 means display entries from a single Page Table, the one pointed to by
13855 the specified entry in the Page Directory.
13857 @cindex direct memory access (DMA) on MS-DOS
13858 These commands are useful when your program uses @dfn{DMA} (Direct
13859 Memory Access), which needs physical addresses to program the DMA
13862 These commands are supported only with some DPMI servers.
13864 @cindex physical address from linear address
13865 @item info dos address-pte @var{addr}
13866 This command displays the Page Table entry for a specified linear
13867 address. The argument @var{addr} is a linear address which should
13868 already have the appropriate segment's base address added to it,
13869 because this command accepts addresses which may belong to @emph{any}
13870 segment. For example, here's how to display the Page Table entry for
13871 the page where a variable @code{i} is stored:
13874 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13875 @exdent @code{Page Table entry for address 0x11a00d30:}
13876 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13880 This says that @code{i} is stored at offset @code{0xd30} from the page
13881 whose physical base address is @code{0x02698000}, and shows all the
13882 attributes of that page.
13884 Note that you must cast the addresses of variables to a @code{char *},
13885 since otherwise the value of @code{__djgpp_base_address}, the base
13886 address of all variables and functions in a @sc{djgpp} program, will
13887 be added using the rules of C pointer arithmetics: if @code{i} is
13888 declared an @code{int}, @value{GDBN} will add 4 times the value of
13889 @code{__djgpp_base_address} to the address of @code{i}.
13891 Here's another example, it displays the Page Table entry for the
13895 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13896 @exdent @code{Page Table entry for address 0x29110:}
13897 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13901 (The @code{+ 3} offset is because the transfer buffer's address is the
13902 3rd member of the @code{_go32_info_block} structure.) The output
13903 clearly shows that this DPMI server maps the addresses in conventional
13904 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13905 linear (@code{0x29110}) addresses are identical.
13907 This command is supported only with some DPMI servers.
13910 @cindex DOS serial data link, remote debugging
13911 In addition to native debugging, the DJGPP port supports remote
13912 debugging via a serial data link. The following commands are specific
13913 to remote serial debugging in the DJGPP port of @value{GDBN}.
13916 @kindex set com1base
13917 @kindex set com1irq
13918 @kindex set com2base
13919 @kindex set com2irq
13920 @kindex set com3base
13921 @kindex set com3irq
13922 @kindex set com4base
13923 @kindex set com4irq
13924 @item set com1base @var{addr}
13925 This command sets the base I/O port address of the @file{COM1} serial
13928 @item set com1irq @var{irq}
13929 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13930 for the @file{COM1} serial port.
13932 There are similar commands @samp{set com2base}, @samp{set com3irq},
13933 etc.@: for setting the port address and the @code{IRQ} lines for the
13936 @kindex show com1base
13937 @kindex show com1irq
13938 @kindex show com2base
13939 @kindex show com2irq
13940 @kindex show com3base
13941 @kindex show com3irq
13942 @kindex show com4base
13943 @kindex show com4irq
13944 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13945 display the current settings of the base address and the @code{IRQ}
13946 lines used by the COM ports.
13949 @kindex info serial
13950 @cindex DOS serial port status
13951 This command prints the status of the 4 DOS serial ports. For each
13952 port, it prints whether it's active or not, its I/O base address and
13953 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13954 counts of various errors encountered so far.
13958 @node Cygwin Native
13959 @subsection Features for Debugging MS Windows PE Executables
13960 @cindex MS Windows debugging
13961 @cindex native Cygwin debugging
13962 @cindex Cygwin-specific commands
13964 @value{GDBN} supports native debugging of MS Windows programs, including
13965 DLLs with and without symbolic debugging information. There are various
13966 additional Cygwin-specific commands, described in this section.
13967 Working with DLLs that have no debugging symbols is described in
13968 @ref{Non-debug DLL Symbols}.
13973 This is a prefix of MS Windows-specific commands which print
13974 information about the target system and important OS structures.
13976 @item info w32 selector
13977 This command displays information returned by
13978 the Win32 API @code{GetThreadSelectorEntry} function.
13979 It takes an optional argument that is evaluated to
13980 a long value to give the information about this given selector.
13981 Without argument, this command displays information
13982 about the six segment registers.
13986 This is a Cygwin-specific alias of @code{info shared}.
13988 @kindex dll-symbols
13990 This command loads symbols from a dll similarly to
13991 add-sym command but without the need to specify a base address.
13993 @kindex set cygwin-exceptions
13994 @cindex debugging the Cygwin DLL
13995 @cindex Cygwin DLL, debugging
13996 @item set cygwin-exceptions @var{mode}
13997 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13998 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13999 @value{GDBN} will delay recognition of exceptions, and may ignore some
14000 exceptions which seem to be caused by internal Cygwin DLL
14001 ``bookkeeping''. This option is meant primarily for debugging the
14002 Cygwin DLL itself; the default value is @code{off} to avoid annoying
14003 @value{GDBN} users with false @code{SIGSEGV} signals.
14005 @kindex show cygwin-exceptions
14006 @item show cygwin-exceptions
14007 Displays whether @value{GDBN} will break on exceptions that happen
14008 inside the Cygwin DLL itself.
14010 @kindex set new-console
14011 @item set new-console @var{mode}
14012 If @var{mode} is @code{on} the debuggee will
14013 be started in a new console on next start.
14014 If @var{mode} is @code{off}i, the debuggee will
14015 be started in the same console as the debugger.
14017 @kindex show new-console
14018 @item show new-console
14019 Displays whether a new console is used
14020 when the debuggee is started.
14022 @kindex set new-group
14023 @item set new-group @var{mode}
14024 This boolean value controls whether the debuggee should
14025 start a new group or stay in the same group as the debugger.
14026 This affects the way the Windows OS handles
14029 @kindex show new-group
14030 @item show new-group
14031 Displays current value of new-group boolean.
14033 @kindex set debugevents
14034 @item set debugevents
14035 This boolean value adds debug output concerning kernel events related
14036 to the debuggee seen by the debugger. This includes events that
14037 signal thread and process creation and exit, DLL loading and
14038 unloading, console interrupts, and debugging messages produced by the
14039 Windows @code{OutputDebugString} API call.
14041 @kindex set debugexec
14042 @item set debugexec
14043 This boolean value adds debug output concerning execute events
14044 (such as resume thread) seen by the debugger.
14046 @kindex set debugexceptions
14047 @item set debugexceptions
14048 This boolean value adds debug output concerning exceptions in the
14049 debuggee seen by the debugger.
14051 @kindex set debugmemory
14052 @item set debugmemory
14053 This boolean value adds debug output concerning debuggee memory reads
14054 and writes by the debugger.
14058 This boolean values specifies whether the debuggee is called
14059 via a shell or directly (default value is on).
14063 Displays if the debuggee will be started with a shell.
14068 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14071 @node Non-debug DLL Symbols
14072 @subsubsection Support for DLLs without Debugging Symbols
14073 @cindex DLLs with no debugging symbols
14074 @cindex Minimal symbols and DLLs
14076 Very often on windows, some of the DLLs that your program relies on do
14077 not include symbolic debugging information (for example,
14078 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14079 symbols in a DLL, it relies on the minimal amount of symbolic
14080 information contained in the DLL's export table. This section
14081 describes working with such symbols, known internally to @value{GDBN} as
14082 ``minimal symbols''.
14084 Note that before the debugged program has started execution, no DLLs
14085 will have been loaded. The easiest way around this problem is simply to
14086 start the program --- either by setting a breakpoint or letting the
14087 program run once to completion. It is also possible to force
14088 @value{GDBN} to load a particular DLL before starting the executable ---
14089 see the shared library information in @ref{Files}, or the
14090 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14091 explicitly loading symbols from a DLL with no debugging information will
14092 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14093 which may adversely affect symbol lookup performance.
14095 @subsubsection DLL Name Prefixes
14097 In keeping with the naming conventions used by the Microsoft debugging
14098 tools, DLL export symbols are made available with a prefix based on the
14099 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14100 also entered into the symbol table, so @code{CreateFileA} is often
14101 sufficient. In some cases there will be name clashes within a program
14102 (particularly if the executable itself includes full debugging symbols)
14103 necessitating the use of the fully qualified name when referring to the
14104 contents of the DLL. Use single-quotes around the name to avoid the
14105 exclamation mark (``!'') being interpreted as a language operator.
14107 Note that the internal name of the DLL may be all upper-case, even
14108 though the file name of the DLL is lower-case, or vice-versa. Since
14109 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14110 some confusion. If in doubt, try the @code{info functions} and
14111 @code{info variables} commands or even @code{maint print msymbols}
14112 (@pxref{Symbols}). Here's an example:
14115 (@value{GDBP}) info function CreateFileA
14116 All functions matching regular expression "CreateFileA":
14118 Non-debugging symbols:
14119 0x77e885f4 CreateFileA
14120 0x77e885f4 KERNEL32!CreateFileA
14124 (@value{GDBP}) info function !
14125 All functions matching regular expression "!":
14127 Non-debugging symbols:
14128 0x6100114c cygwin1!__assert
14129 0x61004034 cygwin1!_dll_crt0@@0
14130 0x61004240 cygwin1!dll_crt0(per_process *)
14134 @subsubsection Working with Minimal Symbols
14136 Symbols extracted from a DLL's export table do not contain very much
14137 type information. All that @value{GDBN} can do is guess whether a symbol
14138 refers to a function or variable depending on the linker section that
14139 contains the symbol. Also note that the actual contents of the memory
14140 contained in a DLL are not available unless the program is running. This
14141 means that you cannot examine the contents of a variable or disassemble
14142 a function within a DLL without a running program.
14144 Variables are generally treated as pointers and dereferenced
14145 automatically. For this reason, it is often necessary to prefix a
14146 variable name with the address-of operator (``&'') and provide explicit
14147 type information in the command. Here's an example of the type of
14151 (@value{GDBP}) print 'cygwin1!__argv'
14156 (@value{GDBP}) x 'cygwin1!__argv'
14157 0x10021610: "\230y\""
14160 And two possible solutions:
14163 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14164 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14168 (@value{GDBP}) x/2x &'cygwin1!__argv'
14169 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14170 (@value{GDBP}) x/x 0x10021608
14171 0x10021608: 0x0022fd98
14172 (@value{GDBP}) x/s 0x0022fd98
14173 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14176 Setting a break point within a DLL is possible even before the program
14177 starts execution. However, under these circumstances, @value{GDBN} can't
14178 examine the initial instructions of the function in order to skip the
14179 function's frame set-up code. You can work around this by using ``*&''
14180 to set the breakpoint at a raw memory address:
14183 (@value{GDBP}) break *&'python22!PyOS_Readline'
14184 Breakpoint 1 at 0x1e04eff0
14187 The author of these extensions is not entirely convinced that setting a
14188 break point within a shared DLL like @file{kernel32.dll} is completely
14192 @subsection Commands Specific to @sc{gnu} Hurd Systems
14193 @cindex @sc{gnu} Hurd debugging
14195 This subsection describes @value{GDBN} commands specific to the
14196 @sc{gnu} Hurd native debugging.
14201 @kindex set signals@r{, Hurd command}
14202 @kindex set sigs@r{, Hurd command}
14203 This command toggles the state of inferior signal interception by
14204 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14205 affected by this command. @code{sigs} is a shorthand alias for
14210 @kindex show signals@r{, Hurd command}
14211 @kindex show sigs@r{, Hurd command}
14212 Show the current state of intercepting inferior's signals.
14214 @item set signal-thread
14215 @itemx set sigthread
14216 @kindex set signal-thread
14217 @kindex set sigthread
14218 This command tells @value{GDBN} which thread is the @code{libc} signal
14219 thread. That thread is run when a signal is delivered to a running
14220 process. @code{set sigthread} is the shorthand alias of @code{set
14223 @item show signal-thread
14224 @itemx show sigthread
14225 @kindex show signal-thread
14226 @kindex show sigthread
14227 These two commands show which thread will run when the inferior is
14228 delivered a signal.
14231 @kindex set stopped@r{, Hurd command}
14232 This commands tells @value{GDBN} that the inferior process is stopped,
14233 as with the @code{SIGSTOP} signal. The stopped process can be
14234 continued by delivering a signal to it.
14237 @kindex show stopped@r{, Hurd command}
14238 This command shows whether @value{GDBN} thinks the debuggee is
14241 @item set exceptions
14242 @kindex set exceptions@r{, Hurd command}
14243 Use this command to turn off trapping of exceptions in the inferior.
14244 When exception trapping is off, neither breakpoints nor
14245 single-stepping will work. To restore the default, set exception
14248 @item show exceptions
14249 @kindex show exceptions@r{, Hurd command}
14250 Show the current state of trapping exceptions in the inferior.
14252 @item set task pause
14253 @kindex set task@r{, Hurd commands}
14254 @cindex task attributes (@sc{gnu} Hurd)
14255 @cindex pause current task (@sc{gnu} Hurd)
14256 This command toggles task suspension when @value{GDBN} has control.
14257 Setting it to on takes effect immediately, and the task is suspended
14258 whenever @value{GDBN} gets control. Setting it to off will take
14259 effect the next time the inferior is continued. If this option is set
14260 to off, you can use @code{set thread default pause on} or @code{set
14261 thread pause on} (see below) to pause individual threads.
14263 @item show task pause
14264 @kindex show task@r{, Hurd commands}
14265 Show the current state of task suspension.
14267 @item set task detach-suspend-count
14268 @cindex task suspend count
14269 @cindex detach from task, @sc{gnu} Hurd
14270 This command sets the suspend count the task will be left with when
14271 @value{GDBN} detaches from it.
14273 @item show task detach-suspend-count
14274 Show the suspend count the task will be left with when detaching.
14276 @item set task exception-port
14277 @itemx set task excp
14278 @cindex task exception port, @sc{gnu} Hurd
14279 This command sets the task exception port to which @value{GDBN} will
14280 forward exceptions. The argument should be the value of the @dfn{send
14281 rights} of the task. @code{set task excp} is a shorthand alias.
14283 @item set noninvasive
14284 @cindex noninvasive task options
14285 This command switches @value{GDBN} to a mode that is the least
14286 invasive as far as interfering with the inferior is concerned. This
14287 is the same as using @code{set task pause}, @code{set exceptions}, and
14288 @code{set signals} to values opposite to the defaults.
14290 @item info send-rights
14291 @itemx info receive-rights
14292 @itemx info port-rights
14293 @itemx info port-sets
14294 @itemx info dead-names
14297 @cindex send rights, @sc{gnu} Hurd
14298 @cindex receive rights, @sc{gnu} Hurd
14299 @cindex port rights, @sc{gnu} Hurd
14300 @cindex port sets, @sc{gnu} Hurd
14301 @cindex dead names, @sc{gnu} Hurd
14302 These commands display information about, respectively, send rights,
14303 receive rights, port rights, port sets, and dead names of a task.
14304 There are also shorthand aliases: @code{info ports} for @code{info
14305 port-rights} and @code{info psets} for @code{info port-sets}.
14307 @item set thread pause
14308 @kindex set thread@r{, Hurd command}
14309 @cindex thread properties, @sc{gnu} Hurd
14310 @cindex pause current thread (@sc{gnu} Hurd)
14311 This command toggles current thread suspension when @value{GDBN} has
14312 control. Setting it to on takes effect immediately, and the current
14313 thread is suspended whenever @value{GDBN} gets control. Setting it to
14314 off will take effect the next time the inferior is continued.
14315 Normally, this command has no effect, since when @value{GDBN} has
14316 control, the whole task is suspended. However, if you used @code{set
14317 task pause off} (see above), this command comes in handy to suspend
14318 only the current thread.
14320 @item show thread pause
14321 @kindex show thread@r{, Hurd command}
14322 This command shows the state of current thread suspension.
14324 @item set thread run
14325 This command sets whether the current thread is allowed to run.
14327 @item show thread run
14328 Show whether the current thread is allowed to run.
14330 @item set thread detach-suspend-count
14331 @cindex thread suspend count, @sc{gnu} Hurd
14332 @cindex detach from thread, @sc{gnu} Hurd
14333 This command sets the suspend count @value{GDBN} will leave on a
14334 thread when detaching. This number is relative to the suspend count
14335 found by @value{GDBN} when it notices the thread; use @code{set thread
14336 takeover-suspend-count} to force it to an absolute value.
14338 @item show thread detach-suspend-count
14339 Show the suspend count @value{GDBN} will leave on the thread when
14342 @item set thread exception-port
14343 @itemx set thread excp
14344 Set the thread exception port to which to forward exceptions. This
14345 overrides the port set by @code{set task exception-port} (see above).
14346 @code{set thread excp} is the shorthand alias.
14348 @item set thread takeover-suspend-count
14349 Normally, @value{GDBN}'s thread suspend counts are relative to the
14350 value @value{GDBN} finds when it notices each thread. This command
14351 changes the suspend counts to be absolute instead.
14353 @item set thread default
14354 @itemx show thread default
14355 @cindex thread default settings, @sc{gnu} Hurd
14356 Each of the above @code{set thread} commands has a @code{set thread
14357 default} counterpart (e.g., @code{set thread default pause}, @code{set
14358 thread default exception-port}, etc.). The @code{thread default}
14359 variety of commands sets the default thread properties for all
14360 threads; you can then change the properties of individual threads with
14361 the non-default commands.
14366 @subsection QNX Neutrino
14367 @cindex QNX Neutrino
14369 @value{GDBN} provides the following commands specific to the QNX
14373 @item set debug nto-debug
14374 @kindex set debug nto-debug
14375 When set to on, enables debugging messages specific to the QNX
14378 @item show debug nto-debug
14379 @kindex show debug nto-debug
14380 Show the current state of QNX Neutrino messages.
14385 @section Embedded Operating Systems
14387 This section describes configurations involving the debugging of
14388 embedded operating systems that are available for several different
14392 * VxWorks:: Using @value{GDBN} with VxWorks
14395 @value{GDBN} includes the ability to debug programs running on
14396 various real-time operating systems.
14399 @subsection Using @value{GDBN} with VxWorks
14405 @kindex target vxworks
14406 @item target vxworks @var{machinename}
14407 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14408 is the target system's machine name or IP address.
14412 On VxWorks, @code{load} links @var{filename} dynamically on the
14413 current target system as well as adding its symbols in @value{GDBN}.
14415 @value{GDBN} enables developers to spawn and debug tasks running on networked
14416 VxWorks targets from a Unix host. Already-running tasks spawned from
14417 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14418 both the Unix host and on the VxWorks target. The program
14419 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14420 installed with the name @code{vxgdb}, to distinguish it from a
14421 @value{GDBN} for debugging programs on the host itself.)
14424 @item VxWorks-timeout @var{args}
14425 @kindex vxworks-timeout
14426 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14427 This option is set by the user, and @var{args} represents the number of
14428 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14429 your VxWorks target is a slow software simulator or is on the far side
14430 of a thin network line.
14433 The following information on connecting to VxWorks was current when
14434 this manual was produced; newer releases of VxWorks may use revised
14437 @findex INCLUDE_RDB
14438 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14439 to include the remote debugging interface routines in the VxWorks
14440 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14441 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14442 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14443 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14444 information on configuring and remaking VxWorks, see the manufacturer's
14446 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14448 Once you have included @file{rdb.a} in your VxWorks system image and set
14449 your Unix execution search path to find @value{GDBN}, you are ready to
14450 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14451 @code{vxgdb}, depending on your installation).
14453 @value{GDBN} comes up showing the prompt:
14460 * VxWorks Connection:: Connecting to VxWorks
14461 * VxWorks Download:: VxWorks download
14462 * VxWorks Attach:: Running tasks
14465 @node VxWorks Connection
14466 @subsubsection Connecting to VxWorks
14468 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14469 network. To connect to a target whose host name is ``@code{tt}'', type:
14472 (vxgdb) target vxworks tt
14476 @value{GDBN} displays messages like these:
14479 Attaching remote machine across net...
14484 @value{GDBN} then attempts to read the symbol tables of any object modules
14485 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14486 these files by searching the directories listed in the command search
14487 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14488 to find an object file, it displays a message such as:
14491 prog.o: No such file or directory.
14494 When this happens, add the appropriate directory to the search path with
14495 the @value{GDBN} command @code{path}, and execute the @code{target}
14498 @node VxWorks Download
14499 @subsubsection VxWorks Download
14501 @cindex download to VxWorks
14502 If you have connected to the VxWorks target and you want to debug an
14503 object that has not yet been loaded, you can use the @value{GDBN}
14504 @code{load} command to download a file from Unix to VxWorks
14505 incrementally. The object file given as an argument to the @code{load}
14506 command is actually opened twice: first by the VxWorks target in order
14507 to download the code, then by @value{GDBN} in order to read the symbol
14508 table. This can lead to problems if the current working directories on
14509 the two systems differ. If both systems have NFS mounted the same
14510 filesystems, you can avoid these problems by using absolute paths.
14511 Otherwise, it is simplest to set the working directory on both systems
14512 to the directory in which the object file resides, and then to reference
14513 the file by its name, without any path. For instance, a program
14514 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14515 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14516 program, type this on VxWorks:
14519 -> cd "@var{vxpath}/vw/demo/rdb"
14523 Then, in @value{GDBN}, type:
14526 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14527 (vxgdb) load prog.o
14530 @value{GDBN} displays a response similar to this:
14533 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14536 You can also use the @code{load} command to reload an object module
14537 after editing and recompiling the corresponding source file. Note that
14538 this makes @value{GDBN} delete all currently-defined breakpoints,
14539 auto-displays, and convenience variables, and to clear the value
14540 history. (This is necessary in order to preserve the integrity of
14541 debugger's data structures that reference the target system's symbol
14544 @node VxWorks Attach
14545 @subsubsection Running Tasks
14547 @cindex running VxWorks tasks
14548 You can also attach to an existing task using the @code{attach} command as
14552 (vxgdb) attach @var{task}
14556 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14557 or suspended when you attach to it. Running tasks are suspended at
14558 the time of attachment.
14560 @node Embedded Processors
14561 @section Embedded Processors
14563 This section goes into details specific to particular embedded
14566 @cindex send command to simulator
14567 Whenever a specific embedded processor has a simulator, @value{GDBN}
14568 allows to send an arbitrary command to the simulator.
14571 @item sim @var{command}
14572 @kindex sim@r{, a command}
14573 Send an arbitrary @var{command} string to the simulator. Consult the
14574 documentation for the specific simulator in use for information about
14575 acceptable commands.
14581 * M32R/D:: Renesas M32R/D
14582 * M68K:: Motorola M68K
14583 * MIPS Embedded:: MIPS Embedded
14584 * OpenRISC 1000:: OpenRisc 1000
14585 * PA:: HP PA Embedded
14586 * PowerPC:: PowerPC
14587 * Sparclet:: Tsqware Sparclet
14588 * Sparclite:: Fujitsu Sparclite
14589 * Z8000:: Zilog Z8000
14592 * Super-H:: Renesas Super-H
14601 @item target rdi @var{dev}
14602 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14603 use this target to communicate with both boards running the Angel
14604 monitor, or with the EmbeddedICE JTAG debug device.
14607 @item target rdp @var{dev}
14612 @value{GDBN} provides the following ARM-specific commands:
14615 @item set arm disassembler
14617 This commands selects from a list of disassembly styles. The
14618 @code{"std"} style is the standard style.
14620 @item show arm disassembler
14622 Show the current disassembly style.
14624 @item set arm apcs32
14625 @cindex ARM 32-bit mode
14626 This command toggles ARM operation mode between 32-bit and 26-bit.
14628 @item show arm apcs32
14629 Display the current usage of the ARM 32-bit mode.
14631 @item set arm fpu @var{fputype}
14632 This command sets the ARM floating-point unit (FPU) type. The
14633 argument @var{fputype} can be one of these:
14637 Determine the FPU type by querying the OS ABI.
14639 Software FPU, with mixed-endian doubles on little-endian ARM
14642 GCC-compiled FPA co-processor.
14644 Software FPU with pure-endian doubles.
14650 Show the current type of the FPU.
14653 This command forces @value{GDBN} to use the specified ABI.
14656 Show the currently used ABI.
14658 @item set debug arm
14659 Toggle whether to display ARM-specific debugging messages from the ARM
14660 target support subsystem.
14662 @item show debug arm
14663 Show whether ARM-specific debugging messages are enabled.
14666 The following commands are available when an ARM target is debugged
14667 using the RDI interface:
14670 @item rdilogfile @r{[}@var{file}@r{]}
14672 @cindex ADP (Angel Debugger Protocol) logging
14673 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14674 With an argument, sets the log file to the specified @var{file}. With
14675 no argument, show the current log file name. The default log file is
14678 @item rdilogenable @r{[}@var{arg}@r{]}
14679 @kindex rdilogenable
14680 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14681 enables logging, with an argument 0 or @code{"no"} disables it. With
14682 no arguments displays the current setting. When logging is enabled,
14683 ADP packets exchanged between @value{GDBN} and the RDI target device
14684 are logged to a file.
14686 @item set rdiromatzero
14687 @kindex set rdiromatzero
14688 @cindex ROM at zero address, RDI
14689 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14690 vector catching is disabled, so that zero address can be used. If off
14691 (the default), vector catching is enabled. For this command to take
14692 effect, it needs to be invoked prior to the @code{target rdi} command.
14694 @item show rdiromatzero
14695 @kindex show rdiromatzero
14696 Show the current setting of ROM at zero address.
14698 @item set rdiheartbeat
14699 @kindex set rdiheartbeat
14700 @cindex RDI heartbeat
14701 Enable or disable RDI heartbeat packets. It is not recommended to
14702 turn on this option, since it confuses ARM and EPI JTAG interface, as
14703 well as the Angel monitor.
14705 @item show rdiheartbeat
14706 @kindex show rdiheartbeat
14707 Show the setting of RDI heartbeat packets.
14712 @subsection Renesas M32R/D and M32R/SDI
14715 @kindex target m32r
14716 @item target m32r @var{dev}
14717 Renesas M32R/D ROM monitor.
14719 @kindex target m32rsdi
14720 @item target m32rsdi @var{dev}
14721 Renesas M32R SDI server, connected via parallel port to the board.
14724 The following @value{GDBN} commands are specific to the M32R monitor:
14727 @item set download-path @var{path}
14728 @kindex set download-path
14729 @cindex find downloadable @sc{srec} files (M32R)
14730 Set the default path for finding downloadable @sc{srec} files.
14732 @item show download-path
14733 @kindex show download-path
14734 Show the default path for downloadable @sc{srec} files.
14736 @item set board-address @var{addr}
14737 @kindex set board-address
14738 @cindex M32-EVA target board address
14739 Set the IP address for the M32R-EVA target board.
14741 @item show board-address
14742 @kindex show board-address
14743 Show the current IP address of the target board.
14745 @item set server-address @var{addr}
14746 @kindex set server-address
14747 @cindex download server address (M32R)
14748 Set the IP address for the download server, which is the @value{GDBN}'s
14751 @item show server-address
14752 @kindex show server-address
14753 Display the IP address of the download server.
14755 @item upload @r{[}@var{file}@r{]}
14756 @kindex upload@r{, M32R}
14757 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14758 upload capability. If no @var{file} argument is given, the current
14759 executable file is uploaded.
14761 @item tload @r{[}@var{file}@r{]}
14762 @kindex tload@r{, M32R}
14763 Test the @code{upload} command.
14766 The following commands are available for M32R/SDI:
14771 @cindex reset SDI connection, M32R
14772 This command resets the SDI connection.
14776 This command shows the SDI connection status.
14779 @kindex debug_chaos
14780 @cindex M32R/Chaos debugging
14781 Instructs the remote that M32R/Chaos debugging is to be used.
14783 @item use_debug_dma
14784 @kindex use_debug_dma
14785 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14788 @kindex use_mon_code
14789 Instructs the remote to use the MON_CODE method of accessing memory.
14792 @kindex use_ib_break
14793 Instructs the remote to set breakpoints by IB break.
14795 @item use_dbt_break
14796 @kindex use_dbt_break
14797 Instructs the remote to set breakpoints by DBT.
14803 The Motorola m68k configuration includes ColdFire support, and a
14804 target command for the following ROM monitor.
14808 @kindex target dbug
14809 @item target dbug @var{dev}
14810 dBUG ROM monitor for Motorola ColdFire.
14814 @node MIPS Embedded
14815 @subsection MIPS Embedded
14817 @cindex MIPS boards
14818 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14819 MIPS board attached to a serial line. This is available when
14820 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14823 Use these @value{GDBN} commands to specify the connection to your target board:
14826 @item target mips @var{port}
14827 @kindex target mips @var{port}
14828 To run a program on the board, start up @code{@value{GDBP}} with the
14829 name of your program as the argument. To connect to the board, use the
14830 command @samp{target mips @var{port}}, where @var{port} is the name of
14831 the serial port connected to the board. If the program has not already
14832 been downloaded to the board, you may use the @code{load} command to
14833 download it. You can then use all the usual @value{GDBN} commands.
14835 For example, this sequence connects to the target board through a serial
14836 port, and loads and runs a program called @var{prog} through the
14840 host$ @value{GDBP} @var{prog}
14841 @value{GDBN} is free software and @dots{}
14842 (@value{GDBP}) target mips /dev/ttyb
14843 (@value{GDBP}) load @var{prog}
14847 @item target mips @var{hostname}:@var{portnumber}
14848 On some @value{GDBN} host configurations, you can specify a TCP
14849 connection (for instance, to a serial line managed by a terminal
14850 concentrator) instead of a serial port, using the syntax
14851 @samp{@var{hostname}:@var{portnumber}}.
14853 @item target pmon @var{port}
14854 @kindex target pmon @var{port}
14857 @item target ddb @var{port}
14858 @kindex target ddb @var{port}
14859 NEC's DDB variant of PMON for Vr4300.
14861 @item target lsi @var{port}
14862 @kindex target lsi @var{port}
14863 LSI variant of PMON.
14865 @kindex target r3900
14866 @item target r3900 @var{dev}
14867 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14869 @kindex target array
14870 @item target array @var{dev}
14871 Array Tech LSI33K RAID controller board.
14877 @value{GDBN} also supports these special commands for MIPS targets:
14880 @item set mipsfpu double
14881 @itemx set mipsfpu single
14882 @itemx set mipsfpu none
14883 @itemx set mipsfpu auto
14884 @itemx show mipsfpu
14885 @kindex set mipsfpu
14886 @kindex show mipsfpu
14887 @cindex MIPS remote floating point
14888 @cindex floating point, MIPS remote
14889 If your target board does not support the MIPS floating point
14890 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14891 need this, you may wish to put the command in your @value{GDBN} init
14892 file). This tells @value{GDBN} how to find the return value of
14893 functions which return floating point values. It also allows
14894 @value{GDBN} to avoid saving the floating point registers when calling
14895 functions on the board. If you are using a floating point coprocessor
14896 with only single precision floating point support, as on the @sc{r4650}
14897 processor, use the command @samp{set mipsfpu single}. The default
14898 double precision floating point coprocessor may be selected using
14899 @samp{set mipsfpu double}.
14901 In previous versions the only choices were double precision or no
14902 floating point, so @samp{set mipsfpu on} will select double precision
14903 and @samp{set mipsfpu off} will select no floating point.
14905 As usual, you can inquire about the @code{mipsfpu} variable with
14906 @samp{show mipsfpu}.
14908 @item set timeout @var{seconds}
14909 @itemx set retransmit-timeout @var{seconds}
14910 @itemx show timeout
14911 @itemx show retransmit-timeout
14912 @cindex @code{timeout}, MIPS protocol
14913 @cindex @code{retransmit-timeout}, MIPS protocol
14914 @kindex set timeout
14915 @kindex show timeout
14916 @kindex set retransmit-timeout
14917 @kindex show retransmit-timeout
14918 You can control the timeout used while waiting for a packet, in the MIPS
14919 remote protocol, with the @code{set timeout @var{seconds}} command. The
14920 default is 5 seconds. Similarly, you can control the timeout used while
14921 waiting for an acknowledgement of a packet with the @code{set
14922 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14923 You can inspect both values with @code{show timeout} and @code{show
14924 retransmit-timeout}. (These commands are @emph{only} available when
14925 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14927 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14928 is waiting for your program to stop. In that case, @value{GDBN} waits
14929 forever because it has no way of knowing how long the program is going
14930 to run before stopping.
14932 @item set syn-garbage-limit @var{num}
14933 @kindex set syn-garbage-limit@r{, MIPS remote}
14934 @cindex synchronize with remote MIPS target
14935 Limit the maximum number of characters @value{GDBN} should ignore when
14936 it tries to synchronize with the remote target. The default is 10
14937 characters. Setting the limit to -1 means there's no limit.
14939 @item show syn-garbage-limit
14940 @kindex show syn-garbage-limit@r{, MIPS remote}
14941 Show the current limit on the number of characters to ignore when
14942 trying to synchronize with the remote system.
14944 @item set monitor-prompt @var{prompt}
14945 @kindex set monitor-prompt@r{, MIPS remote}
14946 @cindex remote monitor prompt
14947 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14948 remote monitor. The default depends on the target:
14958 @item show monitor-prompt
14959 @kindex show monitor-prompt@r{, MIPS remote}
14960 Show the current strings @value{GDBN} expects as the prompt from the
14963 @item set monitor-warnings
14964 @kindex set monitor-warnings@r{, MIPS remote}
14965 Enable or disable monitor warnings about hardware breakpoints. This
14966 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14967 display warning messages whose codes are returned by the @code{lsi}
14968 PMON monitor for breakpoint commands.
14970 @item show monitor-warnings
14971 @kindex show monitor-warnings@r{, MIPS remote}
14972 Show the current setting of printing monitor warnings.
14974 @item pmon @var{command}
14975 @kindex pmon@r{, MIPS remote}
14976 @cindex send PMON command
14977 This command allows sending an arbitrary @var{command} string to the
14978 monitor. The monitor must be in debug mode for this to work.
14981 @node OpenRISC 1000
14982 @subsection OpenRISC 1000
14983 @cindex OpenRISC 1000
14985 @cindex or1k boards
14986 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14987 about platform and commands.
14991 @kindex target jtag
14992 @item target jtag jtag://@var{host}:@var{port}
14994 Connects to remote JTAG server.
14995 JTAG remote server can be either an or1ksim or JTAG server,
14996 connected via parallel port to the board.
14998 Example: @code{target jtag jtag://localhost:9999}
15001 @item or1ksim @var{command}
15002 If connected to @code{or1ksim} OpenRISC 1000 Architectural
15003 Simulator, proprietary commands can be executed.
15005 @kindex info or1k spr
15006 @item info or1k spr
15007 Displays spr groups.
15009 @item info or1k spr @var{group}
15010 @itemx info or1k spr @var{groupno}
15011 Displays register names in selected group.
15013 @item info or1k spr @var{group} @var{register}
15014 @itemx info or1k spr @var{register}
15015 @itemx info or1k spr @var{groupno} @var{registerno}
15016 @itemx info or1k spr @var{registerno}
15017 Shows information about specified spr register.
15020 @item spr @var{group} @var{register} @var{value}
15021 @itemx spr @var{register @var{value}}
15022 @itemx spr @var{groupno} @var{registerno @var{value}}
15023 @itemx spr @var{registerno @var{value}}
15024 Writes @var{value} to specified spr register.
15027 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15028 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15029 program execution and is thus much faster. Hardware breakpoints/watchpoint
15030 triggers can be set using:
15033 Load effective address/data
15035 Store effective address/data
15037 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15042 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15043 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15045 @code{htrace} commands:
15046 @cindex OpenRISC 1000 htrace
15049 @item hwatch @var{conditional}
15050 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15051 or Data. For example:
15053 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15055 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15059 Display information about current HW trace configuration.
15061 @item htrace trigger @var{conditional}
15062 Set starting criteria for HW trace.
15064 @item htrace qualifier @var{conditional}
15065 Set acquisition qualifier for HW trace.
15067 @item htrace stop @var{conditional}
15068 Set HW trace stopping criteria.
15070 @item htrace record [@var{data}]*
15071 Selects the data to be recorded, when qualifier is met and HW trace was
15074 @item htrace enable
15075 @itemx htrace disable
15076 Enables/disables the HW trace.
15078 @item htrace rewind [@var{filename}]
15079 Clears currently recorded trace data.
15081 If filename is specified, new trace file is made and any newly collected data
15082 will be written there.
15084 @item htrace print [@var{start} [@var{len}]]
15085 Prints trace buffer, using current record configuration.
15087 @item htrace mode continuous
15088 Set continuous trace mode.
15090 @item htrace mode suspend
15091 Set suspend trace mode.
15096 @subsection PowerPC
15098 @value{GDBN} provides the following PowerPC-specific commands:
15101 @kindex set powerpc
15102 @item set powerpc soft-float
15103 @itemx show powerpc soft-float
15104 Force @value{GDBN} to use (or not use) a software floating point calling
15105 convention. By default, @value{GDBN} selects the calling convention based
15106 on the selected architecture and the provided executable file.
15108 @item set powerpc vector-abi
15109 @itemx show powerpc vector-abi
15110 Force @value{GDBN} to use the specified calling convention for vector
15111 arguments and return values. The valid options are @samp{auto};
15112 @samp{generic}, to avoid vector registers even if they are present;
15113 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15114 registers. By default, @value{GDBN} selects the calling convention
15115 based on the selected architecture and the provided executable file.
15117 @kindex target dink32
15118 @item target dink32 @var{dev}
15119 DINK32 ROM monitor.
15121 @kindex target ppcbug
15122 @item target ppcbug @var{dev}
15123 @kindex target ppcbug1
15124 @item target ppcbug1 @var{dev}
15125 PPCBUG ROM monitor for PowerPC.
15128 @item target sds @var{dev}
15129 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15132 @cindex SDS protocol
15133 The following commands specific to the SDS protocol are supported
15137 @item set sdstimeout @var{nsec}
15138 @kindex set sdstimeout
15139 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15140 default is 2 seconds.
15142 @item show sdstimeout
15143 @kindex show sdstimeout
15144 Show the current value of the SDS timeout.
15146 @item sds @var{command}
15147 @kindex sds@r{, a command}
15148 Send the specified @var{command} string to the SDS monitor.
15153 @subsection HP PA Embedded
15157 @kindex target op50n
15158 @item target op50n @var{dev}
15159 OP50N monitor, running on an OKI HPPA board.
15161 @kindex target w89k
15162 @item target w89k @var{dev}
15163 W89K monitor, running on a Winbond HPPA board.
15168 @subsection Tsqware Sparclet
15172 @value{GDBN} enables developers to debug tasks running on
15173 Sparclet targets from a Unix host.
15174 @value{GDBN} uses code that runs on
15175 both the Unix host and on the Sparclet target. The program
15176 @code{@value{GDBP}} is installed and executed on the Unix host.
15179 @item remotetimeout @var{args}
15180 @kindex remotetimeout
15181 @value{GDBN} supports the option @code{remotetimeout}.
15182 This option is set by the user, and @var{args} represents the number of
15183 seconds @value{GDBN} waits for responses.
15186 @cindex compiling, on Sparclet
15187 When compiling for debugging, include the options @samp{-g} to get debug
15188 information and @samp{-Ttext} to relocate the program to where you wish to
15189 load it on the target. You may also want to add the options @samp{-n} or
15190 @samp{-N} in order to reduce the size of the sections. Example:
15193 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15196 You can use @code{objdump} to verify that the addresses are what you intended:
15199 sparclet-aout-objdump --headers --syms prog
15202 @cindex running, on Sparclet
15204 your Unix execution search path to find @value{GDBN}, you are ready to
15205 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15206 (or @code{sparclet-aout-gdb}, depending on your installation).
15208 @value{GDBN} comes up showing the prompt:
15215 * Sparclet File:: Setting the file to debug
15216 * Sparclet Connection:: Connecting to Sparclet
15217 * Sparclet Download:: Sparclet download
15218 * Sparclet Execution:: Running and debugging
15221 @node Sparclet File
15222 @subsubsection Setting File to Debug
15224 The @value{GDBN} command @code{file} lets you choose with program to debug.
15227 (gdbslet) file prog
15231 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15232 @value{GDBN} locates
15233 the file by searching the directories listed in the command search
15235 If the file was compiled with debug information (option @samp{-g}), source
15236 files will be searched as well.
15237 @value{GDBN} locates
15238 the source files by searching the directories listed in the directory search
15239 path (@pxref{Environment, ,Your Program's Environment}).
15241 to find a file, it displays a message such as:
15244 prog: No such file or directory.
15247 When this happens, add the appropriate directories to the search paths with
15248 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15249 @code{target} command again.
15251 @node Sparclet Connection
15252 @subsubsection Connecting to Sparclet
15254 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15255 To connect to a target on serial port ``@code{ttya}'', type:
15258 (gdbslet) target sparclet /dev/ttya
15259 Remote target sparclet connected to /dev/ttya
15260 main () at ../prog.c:3
15264 @value{GDBN} displays messages like these:
15270 @node Sparclet Download
15271 @subsubsection Sparclet Download
15273 @cindex download to Sparclet
15274 Once connected to the Sparclet target,
15275 you can use the @value{GDBN}
15276 @code{load} command to download the file from the host to the target.
15277 The file name and load offset should be given as arguments to the @code{load}
15279 Since the file format is aout, the program must be loaded to the starting
15280 address. You can use @code{objdump} to find out what this value is. The load
15281 offset is an offset which is added to the VMA (virtual memory address)
15282 of each of the file's sections.
15283 For instance, if the program
15284 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15285 and bss at 0x12010170, in @value{GDBN}, type:
15288 (gdbslet) load prog 0x12010000
15289 Loading section .text, size 0xdb0 vma 0x12010000
15292 If the code is loaded at a different address then what the program was linked
15293 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15294 to tell @value{GDBN} where to map the symbol table.
15296 @node Sparclet Execution
15297 @subsubsection Running and Debugging
15299 @cindex running and debugging Sparclet programs
15300 You can now begin debugging the task using @value{GDBN}'s execution control
15301 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15302 manual for the list of commands.
15306 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15308 Starting program: prog
15309 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15310 3 char *symarg = 0;
15312 4 char *execarg = "hello!";
15317 @subsection Fujitsu Sparclite
15321 @kindex target sparclite
15322 @item target sparclite @var{dev}
15323 Fujitsu sparclite boards, used only for the purpose of loading.
15324 You must use an additional command to debug the program.
15325 For example: target remote @var{dev} using @value{GDBN} standard
15331 @subsection Zilog Z8000
15334 @cindex simulator, Z8000
15335 @cindex Zilog Z8000 simulator
15337 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15340 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15341 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15342 segmented variant). The simulator recognizes which architecture is
15343 appropriate by inspecting the object code.
15346 @item target sim @var{args}
15348 @kindex target sim@r{, with Z8000}
15349 Debug programs on a simulated CPU. If the simulator supports setup
15350 options, specify them via @var{args}.
15354 After specifying this target, you can debug programs for the simulated
15355 CPU in the same style as programs for your host computer; use the
15356 @code{file} command to load a new program image, the @code{run} command
15357 to run your program, and so on.
15359 As well as making available all the usual machine registers
15360 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15361 additional items of information as specially named registers:
15366 Counts clock-ticks in the simulator.
15369 Counts instructions run in the simulator.
15372 Execution time in 60ths of a second.
15376 You can refer to these values in @value{GDBN} expressions with the usual
15377 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15378 conditional breakpoint that suspends only after at least 5000
15379 simulated clock ticks.
15382 @subsection Atmel AVR
15385 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15386 following AVR-specific commands:
15389 @item info io_registers
15390 @kindex info io_registers@r{, AVR}
15391 @cindex I/O registers (Atmel AVR)
15392 This command displays information about the AVR I/O registers. For
15393 each register, @value{GDBN} prints its number and value.
15400 When configured for debugging CRIS, @value{GDBN} provides the
15401 following CRIS-specific commands:
15404 @item set cris-version @var{ver}
15405 @cindex CRIS version
15406 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15407 The CRIS version affects register names and sizes. This command is useful in
15408 case autodetection of the CRIS version fails.
15410 @item show cris-version
15411 Show the current CRIS version.
15413 @item set cris-dwarf2-cfi
15414 @cindex DWARF-2 CFI and CRIS
15415 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15416 Change to @samp{off} when using @code{gcc-cris} whose version is below
15419 @item show cris-dwarf2-cfi
15420 Show the current state of using DWARF-2 CFI.
15422 @item set cris-mode @var{mode}
15424 Set the current CRIS mode to @var{mode}. It should only be changed when
15425 debugging in guru mode, in which case it should be set to
15426 @samp{guru} (the default is @samp{normal}).
15428 @item show cris-mode
15429 Show the current CRIS mode.
15433 @subsection Renesas Super-H
15436 For the Renesas Super-H processor, @value{GDBN} provides these
15441 @kindex regs@r{, Super-H}
15442 Show the values of all Super-H registers.
15446 @node Architectures
15447 @section Architectures
15449 This section describes characteristics of architectures that affect
15450 all uses of @value{GDBN} with the architecture, both native and cross.
15457 * HPPA:: HP PA architecture
15458 * SPU:: Cell Broadband Engine SPU architecture
15462 @subsection x86 Architecture-specific Issues
15465 @item set struct-convention @var{mode}
15466 @kindex set struct-convention
15467 @cindex struct return convention
15468 @cindex struct/union returned in registers
15469 Set the convention used by the inferior to return @code{struct}s and
15470 @code{union}s from functions to @var{mode}. Possible values of
15471 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15472 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15473 are returned on the stack, while @code{"reg"} means that a
15474 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15475 be returned in a register.
15477 @item show struct-convention
15478 @kindex show struct-convention
15479 Show the current setting of the convention to return @code{struct}s
15488 @kindex set rstack_high_address
15489 @cindex AMD 29K register stack
15490 @cindex register stack, AMD29K
15491 @item set rstack_high_address @var{address}
15492 On AMD 29000 family processors, registers are saved in a separate
15493 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15494 extent of this stack. Normally, @value{GDBN} just assumes that the
15495 stack is ``large enough''. This may result in @value{GDBN} referencing
15496 memory locations that do not exist. If necessary, you can get around
15497 this problem by specifying the ending address of the register stack with
15498 the @code{set rstack_high_address} command. The argument should be an
15499 address, which you probably want to precede with @samp{0x} to specify in
15502 @kindex show rstack_high_address
15503 @item show rstack_high_address
15504 Display the current limit of the register stack, on AMD 29000 family
15512 See the following section.
15517 @cindex stack on Alpha
15518 @cindex stack on MIPS
15519 @cindex Alpha stack
15521 Alpha- and MIPS-based computers use an unusual stack frame, which
15522 sometimes requires @value{GDBN} to search backward in the object code to
15523 find the beginning of a function.
15525 @cindex response time, MIPS debugging
15526 To improve response time (especially for embedded applications, where
15527 @value{GDBN} may be restricted to a slow serial line for this search)
15528 you may want to limit the size of this search, using one of these
15532 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15533 @item set heuristic-fence-post @var{limit}
15534 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15535 search for the beginning of a function. A value of @var{0} (the
15536 default) means there is no limit. However, except for @var{0}, the
15537 larger the limit the more bytes @code{heuristic-fence-post} must search
15538 and therefore the longer it takes to run. You should only need to use
15539 this command when debugging a stripped executable.
15541 @item show heuristic-fence-post
15542 Display the current limit.
15546 These commands are available @emph{only} when @value{GDBN} is configured
15547 for debugging programs on Alpha or MIPS processors.
15549 Several MIPS-specific commands are available when debugging MIPS
15553 @item set mips abi @var{arg}
15554 @kindex set mips abi
15555 @cindex set ABI for MIPS
15556 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15557 values of @var{arg} are:
15561 The default ABI associated with the current binary (this is the
15572 @item show mips abi
15573 @kindex show mips abi
15574 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15577 @itemx show mipsfpu
15578 @xref{MIPS Embedded, set mipsfpu}.
15580 @item set mips mask-address @var{arg}
15581 @kindex set mips mask-address
15582 @cindex MIPS addresses, masking
15583 This command determines whether the most-significant 32 bits of 64-bit
15584 MIPS addresses are masked off. The argument @var{arg} can be
15585 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15586 setting, which lets @value{GDBN} determine the correct value.
15588 @item show mips mask-address
15589 @kindex show mips mask-address
15590 Show whether the upper 32 bits of MIPS addresses are masked off or
15593 @item set remote-mips64-transfers-32bit-regs
15594 @kindex set remote-mips64-transfers-32bit-regs
15595 This command controls compatibility with 64-bit MIPS targets that
15596 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15597 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15598 and 64 bits for other registers, set this option to @samp{on}.
15600 @item show remote-mips64-transfers-32bit-regs
15601 @kindex show remote-mips64-transfers-32bit-regs
15602 Show the current setting of compatibility with older MIPS 64 targets.
15604 @item set debug mips
15605 @kindex set debug mips
15606 This command turns on and off debugging messages for the MIPS-specific
15607 target code in @value{GDBN}.
15609 @item show debug mips
15610 @kindex show debug mips
15611 Show the current setting of MIPS debugging messages.
15617 @cindex HPPA support
15619 When @value{GDBN} is debugging the HP PA architecture, it provides the
15620 following special commands:
15623 @item set debug hppa
15624 @kindex set debug hppa
15625 This command determines whether HPPA architecture-specific debugging
15626 messages are to be displayed.
15628 @item show debug hppa
15629 Show whether HPPA debugging messages are displayed.
15631 @item maint print unwind @var{address}
15632 @kindex maint print unwind@r{, HPPA}
15633 This command displays the contents of the unwind table entry at the
15634 given @var{address}.
15640 @subsection Cell Broadband Engine SPU architecture
15641 @cindex Cell Broadband Engine
15644 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
15645 it provides the following special commands:
15648 @item info spu event
15650 Display SPU event facility status. Shows current event mask
15651 and pending event status.
15653 @item info spu signal
15654 Display SPU signal notification facility status. Shows pending
15655 signal-control word and signal notification mode of both signal
15656 notification channels.
15658 @item info spu mailbox
15659 Display SPU mailbox facility status. Shows all pending entries,
15660 in order of processing, in each of the SPU Write Outbound,
15661 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
15664 Display MFC DMA status. Shows all pending commands in the MFC
15665 DMA queue. For each entry, opcode, tag, class IDs, effective
15666 and local store addresses and transfer size are shown.
15668 @item info spu proxydma
15669 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
15670 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
15671 and local store addresses and transfer size are shown.
15676 @node Controlling GDB
15677 @chapter Controlling @value{GDBN}
15679 You can alter the way @value{GDBN} interacts with you by using the
15680 @code{set} command. For commands controlling how @value{GDBN} displays
15681 data, see @ref{Print Settings, ,Print Settings}. Other settings are
15686 * Editing:: Command editing
15687 * Command History:: Command history
15688 * Screen Size:: Screen size
15689 * Numbers:: Numbers
15690 * ABI:: Configuring the current ABI
15691 * Messages/Warnings:: Optional warnings and messages
15692 * Debugging Output:: Optional messages about internal happenings
15700 @value{GDBN} indicates its readiness to read a command by printing a string
15701 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15702 can change the prompt string with the @code{set prompt} command. For
15703 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15704 the prompt in one of the @value{GDBN} sessions so that you can always tell
15705 which one you are talking to.
15707 @emph{Note:} @code{set prompt} does not add a space for you after the
15708 prompt you set. This allows you to set a prompt which ends in a space
15709 or a prompt that does not.
15713 @item set prompt @var{newprompt}
15714 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15716 @kindex show prompt
15718 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15722 @section Command Editing
15724 @cindex command line editing
15726 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15727 @sc{gnu} library provides consistent behavior for programs which provide a
15728 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15729 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15730 substitution, and a storage and recall of command history across
15731 debugging sessions.
15733 You may control the behavior of command line editing in @value{GDBN} with the
15734 command @code{set}.
15737 @kindex set editing
15740 @itemx set editing on
15741 Enable command line editing (enabled by default).
15743 @item set editing off
15744 Disable command line editing.
15746 @kindex show editing
15748 Show whether command line editing is enabled.
15751 @xref{Command Line Editing}, for more details about the Readline
15752 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15753 encouraged to read that chapter.
15755 @node Command History
15756 @section Command History
15757 @cindex command history
15759 @value{GDBN} can keep track of the commands you type during your
15760 debugging sessions, so that you can be certain of precisely what
15761 happened. Use these commands to manage the @value{GDBN} command
15764 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15765 package, to provide the history facility. @xref{Using History
15766 Interactively}, for the detailed description of the History library.
15768 To issue a command to @value{GDBN} without affecting certain aspects of
15769 the state which is seen by users, prefix it with @samp{server }
15770 (@pxref{Server Prefix}). This
15771 means that this command will not affect the command history, nor will it
15772 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15773 pressed on a line by itself.
15775 @cindex @code{server}, command prefix
15776 The server prefix does not affect the recording of values into the value
15777 history; to print a value without recording it into the value history,
15778 use the @code{output} command instead of the @code{print} command.
15780 Here is the description of @value{GDBN} commands related to command
15784 @cindex history substitution
15785 @cindex history file
15786 @kindex set history filename
15787 @cindex @env{GDBHISTFILE}, environment variable
15788 @item set history filename @var{fname}
15789 Set the name of the @value{GDBN} command history file to @var{fname}.
15790 This is the file where @value{GDBN} reads an initial command history
15791 list, and where it writes the command history from this session when it
15792 exits. You can access this list through history expansion or through
15793 the history command editing characters listed below. This file defaults
15794 to the value of the environment variable @code{GDBHISTFILE}, or to
15795 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15798 @cindex save command history
15799 @kindex set history save
15800 @item set history save
15801 @itemx set history save on
15802 Record command history in a file, whose name may be specified with the
15803 @code{set history filename} command. By default, this option is disabled.
15805 @item set history save off
15806 Stop recording command history in a file.
15808 @cindex history size
15809 @kindex set history size
15810 @cindex @env{HISTSIZE}, environment variable
15811 @item set history size @var{size}
15812 Set the number of commands which @value{GDBN} keeps in its history list.
15813 This defaults to the value of the environment variable
15814 @code{HISTSIZE}, or to 256 if this variable is not set.
15817 History expansion assigns special meaning to the character @kbd{!}.
15818 @xref{Event Designators}, for more details.
15820 @cindex history expansion, turn on/off
15821 Since @kbd{!} is also the logical not operator in C, history expansion
15822 is off by default. If you decide to enable history expansion with the
15823 @code{set history expansion on} command, you may sometimes need to
15824 follow @kbd{!} (when it is used as logical not, in an expression) with
15825 a space or a tab to prevent it from being expanded. The readline
15826 history facilities do not attempt substitution on the strings
15827 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15829 The commands to control history expansion are:
15832 @item set history expansion on
15833 @itemx set history expansion
15834 @kindex set history expansion
15835 Enable history expansion. History expansion is off by default.
15837 @item set history expansion off
15838 Disable history expansion.
15841 @kindex show history
15843 @itemx show history filename
15844 @itemx show history save
15845 @itemx show history size
15846 @itemx show history expansion
15847 These commands display the state of the @value{GDBN} history parameters.
15848 @code{show history} by itself displays all four states.
15853 @kindex show commands
15854 @cindex show last commands
15855 @cindex display command history
15856 @item show commands
15857 Display the last ten commands in the command history.
15859 @item show commands @var{n}
15860 Print ten commands centered on command number @var{n}.
15862 @item show commands +
15863 Print ten commands just after the commands last printed.
15867 @section Screen Size
15868 @cindex size of screen
15869 @cindex pauses in output
15871 Certain commands to @value{GDBN} may produce large amounts of
15872 information output to the screen. To help you read all of it,
15873 @value{GDBN} pauses and asks you for input at the end of each page of
15874 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15875 to discard the remaining output. Also, the screen width setting
15876 determines when to wrap lines of output. Depending on what is being
15877 printed, @value{GDBN} tries to break the line at a readable place,
15878 rather than simply letting it overflow onto the following line.
15880 Normally @value{GDBN} knows the size of the screen from the terminal
15881 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15882 together with the value of the @code{TERM} environment variable and the
15883 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15884 you can override it with the @code{set height} and @code{set
15891 @kindex show height
15892 @item set height @var{lpp}
15894 @itemx set width @var{cpl}
15896 These @code{set} commands specify a screen height of @var{lpp} lines and
15897 a screen width of @var{cpl} characters. The associated @code{show}
15898 commands display the current settings.
15900 If you specify a height of zero lines, @value{GDBN} does not pause during
15901 output no matter how long the output is. This is useful if output is to a
15902 file or to an editor buffer.
15904 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15905 from wrapping its output.
15907 @item set pagination on
15908 @itemx set pagination off
15909 @kindex set pagination
15910 Turn the output pagination on or off; the default is on. Turning
15911 pagination off is the alternative to @code{set height 0}.
15913 @item show pagination
15914 @kindex show pagination
15915 Show the current pagination mode.
15920 @cindex number representation
15921 @cindex entering numbers
15923 You can always enter numbers in octal, decimal, or hexadecimal in
15924 @value{GDBN} by the usual conventions: octal numbers begin with
15925 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15926 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15927 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15928 10; likewise, the default display for numbers---when no particular
15929 format is specified---is base 10. You can change the default base for
15930 both input and output with the commands described below.
15933 @kindex set input-radix
15934 @item set input-radix @var{base}
15935 Set the default base for numeric input. Supported choices
15936 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15937 specified either unambiguously or using the current input radix; for
15941 set input-radix 012
15942 set input-radix 10.
15943 set input-radix 0xa
15947 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15948 leaves the input radix unchanged, no matter what it was, since
15949 @samp{10}, being without any leading or trailing signs of its base, is
15950 interpreted in the current radix. Thus, if the current radix is 16,
15951 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15954 @kindex set output-radix
15955 @item set output-radix @var{base}
15956 Set the default base for numeric display. Supported choices
15957 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15958 specified either unambiguously or using the current input radix.
15960 @kindex show input-radix
15961 @item show input-radix
15962 Display the current default base for numeric input.
15964 @kindex show output-radix
15965 @item show output-radix
15966 Display the current default base for numeric display.
15968 @item set radix @r{[}@var{base}@r{]}
15972 These commands set and show the default base for both input and output
15973 of numbers. @code{set radix} sets the radix of input and output to
15974 the same base; without an argument, it resets the radix back to its
15975 default value of 10.
15980 @section Configuring the Current ABI
15982 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15983 application automatically. However, sometimes you need to override its
15984 conclusions. Use these commands to manage @value{GDBN}'s view of the
15991 One @value{GDBN} configuration can debug binaries for multiple operating
15992 system targets, either via remote debugging or native emulation.
15993 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15994 but you can override its conclusion using the @code{set osabi} command.
15995 One example where this is useful is in debugging of binaries which use
15996 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15997 not have the same identifying marks that the standard C library for your
16002 Show the OS ABI currently in use.
16005 With no argument, show the list of registered available OS ABI's.
16007 @item set osabi @var{abi}
16008 Set the current OS ABI to @var{abi}.
16011 @cindex float promotion
16013 Generally, the way that an argument of type @code{float} is passed to a
16014 function depends on whether the function is prototyped. For a prototyped
16015 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16016 according to the architecture's convention for @code{float}. For unprototyped
16017 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16018 @code{double} and then passed.
16020 Unfortunately, some forms of debug information do not reliably indicate whether
16021 a function is prototyped. If @value{GDBN} calls a function that is not marked
16022 as prototyped, it consults @kbd{set coerce-float-to-double}.
16025 @kindex set coerce-float-to-double
16026 @item set coerce-float-to-double
16027 @itemx set coerce-float-to-double on
16028 Arguments of type @code{float} will be promoted to @code{double} when passed
16029 to an unprototyped function. This is the default setting.
16031 @item set coerce-float-to-double off
16032 Arguments of type @code{float} will be passed directly to unprototyped
16035 @kindex show coerce-float-to-double
16036 @item show coerce-float-to-double
16037 Show the current setting of promoting @code{float} to @code{double}.
16041 @kindex show cp-abi
16042 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16043 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16044 used to build your application. @value{GDBN} only fully supports
16045 programs with a single C@t{++} ABI; if your program contains code using
16046 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16047 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16048 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16049 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16050 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16051 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16056 Show the C@t{++} ABI currently in use.
16059 With no argument, show the list of supported C@t{++} ABI's.
16061 @item set cp-abi @var{abi}
16062 @itemx set cp-abi auto
16063 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16066 @node Messages/Warnings
16067 @section Optional Warnings and Messages
16069 @cindex verbose operation
16070 @cindex optional warnings
16071 By default, @value{GDBN} is silent about its inner workings. If you are
16072 running on a slow machine, you may want to use the @code{set verbose}
16073 command. This makes @value{GDBN} tell you when it does a lengthy
16074 internal operation, so you will not think it has crashed.
16076 Currently, the messages controlled by @code{set verbose} are those
16077 which announce that the symbol table for a source file is being read;
16078 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16081 @kindex set verbose
16082 @item set verbose on
16083 Enables @value{GDBN} output of certain informational messages.
16085 @item set verbose off
16086 Disables @value{GDBN} output of certain informational messages.
16088 @kindex show verbose
16090 Displays whether @code{set verbose} is on or off.
16093 By default, if @value{GDBN} encounters bugs in the symbol table of an
16094 object file, it is silent; but if you are debugging a compiler, you may
16095 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16100 @kindex set complaints
16101 @item set complaints @var{limit}
16102 Permits @value{GDBN} to output @var{limit} complaints about each type of
16103 unusual symbols before becoming silent about the problem. Set
16104 @var{limit} to zero to suppress all complaints; set it to a large number
16105 to prevent complaints from being suppressed.
16107 @kindex show complaints
16108 @item show complaints
16109 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16113 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16114 lot of stupid questions to confirm certain commands. For example, if
16115 you try to run a program which is already running:
16119 The program being debugged has been started already.
16120 Start it from the beginning? (y or n)
16123 If you are willing to unflinchingly face the consequences of your own
16124 commands, you can disable this ``feature'':
16128 @kindex set confirm
16130 @cindex confirmation
16131 @cindex stupid questions
16132 @item set confirm off
16133 Disables confirmation requests.
16135 @item set confirm on
16136 Enables confirmation requests (the default).
16138 @kindex show confirm
16140 Displays state of confirmation requests.
16144 @cindex command tracing
16145 If you need to debug user-defined commands or sourced files you may find it
16146 useful to enable @dfn{command tracing}. In this mode each command will be
16147 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16148 quantity denoting the call depth of each command.
16151 @kindex set trace-commands
16152 @cindex command scripts, debugging
16153 @item set trace-commands on
16154 Enable command tracing.
16155 @item set trace-commands off
16156 Disable command tracing.
16157 @item show trace-commands
16158 Display the current state of command tracing.
16161 @node Debugging Output
16162 @section Optional Messages about Internal Happenings
16163 @cindex optional debugging messages
16165 @value{GDBN} has commands that enable optional debugging messages from
16166 various @value{GDBN} subsystems; normally these commands are of
16167 interest to @value{GDBN} maintainers, or when reporting a bug. This
16168 section documents those commands.
16171 @kindex set exec-done-display
16172 @item set exec-done-display
16173 Turns on or off the notification of asynchronous commands'
16174 completion. When on, @value{GDBN} will print a message when an
16175 asynchronous command finishes its execution. The default is off.
16176 @kindex show exec-done-display
16177 @item show exec-done-display
16178 Displays the current setting of asynchronous command completion
16181 @cindex gdbarch debugging info
16182 @cindex architecture debugging info
16183 @item set debug arch
16184 Turns on or off display of gdbarch debugging info. The default is off
16186 @item show debug arch
16187 Displays the current state of displaying gdbarch debugging info.
16188 @item set debug aix-thread
16189 @cindex AIX threads
16190 Display debugging messages about inner workings of the AIX thread
16192 @item show debug aix-thread
16193 Show the current state of AIX thread debugging info display.
16194 @item set debug event
16195 @cindex event debugging info
16196 Turns on or off display of @value{GDBN} event debugging info. The
16198 @item show debug event
16199 Displays the current state of displaying @value{GDBN} event debugging
16201 @item set debug expression
16202 @cindex expression debugging info
16203 Turns on or off display of debugging info about @value{GDBN}
16204 expression parsing. The default is off.
16205 @item show debug expression
16206 Displays the current state of displaying debugging info about
16207 @value{GDBN} expression parsing.
16208 @item set debug frame
16209 @cindex frame debugging info
16210 Turns on or off display of @value{GDBN} frame debugging info. The
16212 @item show debug frame
16213 Displays the current state of displaying @value{GDBN} frame debugging
16215 @item set debug infrun
16216 @cindex inferior debugging info
16217 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16218 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16219 for implementing operations such as single-stepping the inferior.
16220 @item show debug infrun
16221 Displays the current state of @value{GDBN} inferior debugging.
16222 @item set debug lin-lwp
16223 @cindex @sc{gnu}/Linux LWP debug messages
16224 @cindex Linux lightweight processes
16225 Turns on or off debugging messages from the Linux LWP debug support.
16226 @item show debug lin-lwp
16227 Show the current state of Linux LWP debugging messages.
16228 @item set debug observer
16229 @cindex observer debugging info
16230 Turns on or off display of @value{GDBN} observer debugging. This
16231 includes info such as the notification of observable events.
16232 @item show debug observer
16233 Displays the current state of observer debugging.
16234 @item set debug overload
16235 @cindex C@t{++} overload debugging info
16236 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16237 info. This includes info such as ranking of functions, etc. The default
16239 @item show debug overload
16240 Displays the current state of displaying @value{GDBN} C@t{++} overload
16242 @cindex packets, reporting on stdout
16243 @cindex serial connections, debugging
16244 @cindex debug remote protocol
16245 @cindex remote protocol debugging
16246 @cindex display remote packets
16247 @item set debug remote
16248 Turns on or off display of reports on all packets sent back and forth across
16249 the serial line to the remote machine. The info is printed on the
16250 @value{GDBN} standard output stream. The default is off.
16251 @item show debug remote
16252 Displays the state of display of remote packets.
16253 @item set debug serial
16254 Turns on or off display of @value{GDBN} serial debugging info. The
16256 @item show debug serial
16257 Displays the current state of displaying @value{GDBN} serial debugging
16259 @item set debug solib-frv
16260 @cindex FR-V shared-library debugging
16261 Turns on or off debugging messages for FR-V shared-library code.
16262 @item show debug solib-frv
16263 Display the current state of FR-V shared-library code debugging
16265 @item set debug target
16266 @cindex target debugging info
16267 Turns on or off display of @value{GDBN} target debugging info. This info
16268 includes what is going on at the target level of GDB, as it happens. The
16269 default is 0. Set it to 1 to track events, and to 2 to also track the
16270 value of large memory transfers. Changes to this flag do not take effect
16271 until the next time you connect to a target or use the @code{run} command.
16272 @item show debug target
16273 Displays the current state of displaying @value{GDBN} target debugging
16275 @item set debugvarobj
16276 @cindex variable object debugging info
16277 Turns on or off display of @value{GDBN} variable object debugging
16278 info. The default is off.
16279 @item show debugvarobj
16280 Displays the current state of displaying @value{GDBN} variable object
16282 @item set debug xml
16283 @cindex XML parser debugging
16284 Turns on or off debugging messages for built-in XML parsers.
16285 @item show debug xml
16286 Displays the current state of XML debugging messages.
16290 @chapter Canned Sequences of Commands
16292 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16293 Command Lists}), @value{GDBN} provides two ways to store sequences of
16294 commands for execution as a unit: user-defined commands and command
16298 * Define:: How to define your own commands
16299 * Hooks:: Hooks for user-defined commands
16300 * Command Files:: How to write scripts of commands to be stored in a file
16301 * Output:: Commands for controlled output
16305 @section User-defined Commands
16307 @cindex user-defined command
16308 @cindex arguments, to user-defined commands
16309 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16310 which you assign a new name as a command. This is done with the
16311 @code{define} command. User commands may accept up to 10 arguments
16312 separated by whitespace. Arguments are accessed within the user command
16313 via @code{$arg0@dots{}$arg9}. A trivial example:
16317 print $arg0 + $arg1 + $arg2
16322 To execute the command use:
16329 This defines the command @code{adder}, which prints the sum of
16330 its three arguments. Note the arguments are text substitutions, so they may
16331 reference variables, use complex expressions, or even perform inferior
16334 @cindex argument count in user-defined commands
16335 @cindex how many arguments (user-defined commands)
16336 In addition, @code{$argc} may be used to find out how many arguments have
16337 been passed. This expands to a number in the range 0@dots{}10.
16342 print $arg0 + $arg1
16345 print $arg0 + $arg1 + $arg2
16353 @item define @var{commandname}
16354 Define a command named @var{commandname}. If there is already a command
16355 by that name, you are asked to confirm that you want to redefine it.
16357 The definition of the command is made up of other @value{GDBN} command lines,
16358 which are given following the @code{define} command. The end of these
16359 commands is marked by a line containing @code{end}.
16362 @kindex end@r{ (user-defined commands)}
16363 @item document @var{commandname}
16364 Document the user-defined command @var{commandname}, so that it can be
16365 accessed by @code{help}. The command @var{commandname} must already be
16366 defined. This command reads lines of documentation just as @code{define}
16367 reads the lines of the command definition, ending with @code{end}.
16368 After the @code{document} command is finished, @code{help} on command
16369 @var{commandname} displays the documentation you have written.
16371 You may use the @code{document} command again to change the
16372 documentation of a command. Redefining the command with @code{define}
16373 does not change the documentation.
16375 @kindex dont-repeat
16376 @cindex don't repeat command
16378 Used inside a user-defined command, this tells @value{GDBN} that this
16379 command should not be repeated when the user hits @key{RET}
16380 (@pxref{Command Syntax, repeat last command}).
16382 @kindex help user-defined
16383 @item help user-defined
16384 List all user-defined commands, with the first line of the documentation
16389 @itemx show user @var{commandname}
16390 Display the @value{GDBN} commands used to define @var{commandname} (but
16391 not its documentation). If no @var{commandname} is given, display the
16392 definitions for all user-defined commands.
16394 @cindex infinite recursion in user-defined commands
16395 @kindex show max-user-call-depth
16396 @kindex set max-user-call-depth
16397 @item show max-user-call-depth
16398 @itemx set max-user-call-depth
16399 The value of @code{max-user-call-depth} controls how many recursion
16400 levels are allowed in user-defined commands before @value{GDBN} suspects an
16401 infinite recursion and aborts the command.
16404 In addition to the above commands, user-defined commands frequently
16405 use control flow commands, described in @ref{Command Files}.
16407 When user-defined commands are executed, the
16408 commands of the definition are not printed. An error in any command
16409 stops execution of the user-defined command.
16411 If used interactively, commands that would ask for confirmation proceed
16412 without asking when used inside a user-defined command. Many @value{GDBN}
16413 commands that normally print messages to say what they are doing omit the
16414 messages when used in a user-defined command.
16417 @section User-defined Command Hooks
16418 @cindex command hooks
16419 @cindex hooks, for commands
16420 @cindex hooks, pre-command
16423 You may define @dfn{hooks}, which are a special kind of user-defined
16424 command. Whenever you run the command @samp{foo}, if the user-defined
16425 command @samp{hook-foo} exists, it is executed (with no arguments)
16426 before that command.
16428 @cindex hooks, post-command
16430 A hook may also be defined which is run after the command you executed.
16431 Whenever you run the command @samp{foo}, if the user-defined command
16432 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16433 that command. Post-execution hooks may exist simultaneously with
16434 pre-execution hooks, for the same command.
16436 It is valid for a hook to call the command which it hooks. If this
16437 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16439 @c It would be nice if hookpost could be passed a parameter indicating
16440 @c if the command it hooks executed properly or not. FIXME!
16442 @kindex stop@r{, a pseudo-command}
16443 In addition, a pseudo-command, @samp{stop} exists. Defining
16444 (@samp{hook-stop}) makes the associated commands execute every time
16445 execution stops in your program: before breakpoint commands are run,
16446 displays are printed, or the stack frame is printed.
16448 For example, to ignore @code{SIGALRM} signals while
16449 single-stepping, but treat them normally during normal execution,
16454 handle SIGALRM nopass
16458 handle SIGALRM pass
16461 define hook-continue
16462 handle SIGALRM pass
16466 As a further example, to hook at the beginning and end of the @code{echo}
16467 command, and to add extra text to the beginning and end of the message,
16475 define hookpost-echo
16479 (@value{GDBP}) echo Hello World
16480 <<<---Hello World--->>>
16485 You can define a hook for any single-word command in @value{GDBN}, but
16486 not for command aliases; you should define a hook for the basic command
16487 name, e.g.@: @code{backtrace} rather than @code{bt}.
16488 @c FIXME! So how does Joe User discover whether a command is an alias
16490 If an error occurs during the execution of your hook, execution of
16491 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16492 (before the command that you actually typed had a chance to run).
16494 If you try to define a hook which does not match any known command, you
16495 get a warning from the @code{define} command.
16497 @node Command Files
16498 @section Command Files
16500 @cindex command files
16501 @cindex scripting commands
16502 A command file for @value{GDBN} is a text file made of lines that are
16503 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16504 also be included. An empty line in a command file does nothing; it
16505 does not mean to repeat the last command, as it would from the
16508 You can request the execution of a command file with the @code{source}
16513 @cindex execute commands from a file
16514 @item source [@code{-v}] @var{filename}
16515 Execute the command file @var{filename}.
16518 The lines in a command file are generally executed sequentially,
16519 unless the order of execution is changed by one of the
16520 @emph{flow-control commands} described below. The commands are not
16521 printed as they are executed. An error in any command terminates
16522 execution of the command file and control is returned to the console.
16524 @value{GDBN} searches for @var{filename} in the current directory and then
16525 on the search path (specified with the @samp{directory} command).
16527 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16528 each command as it is executed. The option must be given before
16529 @var{filename}, and is interpreted as part of the filename anywhere else.
16531 Commands that would ask for confirmation if used interactively proceed
16532 without asking when used in a command file. Many @value{GDBN} commands that
16533 normally print messages to say what they are doing omit the messages
16534 when called from command files.
16536 @value{GDBN} also accepts command input from standard input. In this
16537 mode, normal output goes to standard output and error output goes to
16538 standard error. Errors in a command file supplied on standard input do
16539 not terminate execution of the command file---execution continues with
16543 gdb < cmds > log 2>&1
16546 (The syntax above will vary depending on the shell used.) This example
16547 will execute commands from the file @file{cmds}. All output and errors
16548 would be directed to @file{log}.
16550 Since commands stored on command files tend to be more general than
16551 commands typed interactively, they frequently need to deal with
16552 complicated situations, such as different or unexpected values of
16553 variables and symbols, changes in how the program being debugged is
16554 built, etc. @value{GDBN} provides a set of flow-control commands to
16555 deal with these complexities. Using these commands, you can write
16556 complex scripts that loop over data structures, execute commands
16557 conditionally, etc.
16564 This command allows to include in your script conditionally executed
16565 commands. The @code{if} command takes a single argument, which is an
16566 expression to evaluate. It is followed by a series of commands that
16567 are executed only if the expression is true (its value is nonzero).
16568 There can then optionally be an @code{else} line, followed by a series
16569 of commands that are only executed if the expression was false. The
16570 end of the list is marked by a line containing @code{end}.
16574 This command allows to write loops. Its syntax is similar to
16575 @code{if}: the command takes a single argument, which is an expression
16576 to evaluate, and must be followed by the commands to execute, one per
16577 line, terminated by an @code{end}. These commands are called the
16578 @dfn{body} of the loop. The commands in the body of @code{while} are
16579 executed repeatedly as long as the expression evaluates to true.
16583 This command exits the @code{while} loop in whose body it is included.
16584 Execution of the script continues after that @code{while}s @code{end}
16587 @kindex loop_continue
16588 @item loop_continue
16589 This command skips the execution of the rest of the body of commands
16590 in the @code{while} loop in whose body it is included. Execution
16591 branches to the beginning of the @code{while} loop, where it evaluates
16592 the controlling expression.
16594 @kindex end@r{ (if/else/while commands)}
16596 Terminate the block of commands that are the body of @code{if},
16597 @code{else}, or @code{while} flow-control commands.
16602 @section Commands for Controlled Output
16604 During the execution of a command file or a user-defined command, normal
16605 @value{GDBN} output is suppressed; the only output that appears is what is
16606 explicitly printed by the commands in the definition. This section
16607 describes three commands useful for generating exactly the output you
16612 @item echo @var{text}
16613 @c I do not consider backslash-space a standard C escape sequence
16614 @c because it is not in ANSI.
16615 Print @var{text}. Nonprinting characters can be included in
16616 @var{text} using C escape sequences, such as @samp{\n} to print a
16617 newline. @strong{No newline is printed unless you specify one.}
16618 In addition to the standard C escape sequences, a backslash followed
16619 by a space stands for a space. This is useful for displaying a
16620 string with spaces at the beginning or the end, since leading and
16621 trailing spaces are otherwise trimmed from all arguments.
16622 To print @samp{@w{ }and foo =@w{ }}, use the command
16623 @samp{echo \@w{ }and foo = \@w{ }}.
16625 A backslash at the end of @var{text} can be used, as in C, to continue
16626 the command onto subsequent lines. For example,
16629 echo This is some text\n\
16630 which is continued\n\
16631 onto several lines.\n
16634 produces the same output as
16637 echo This is some text\n
16638 echo which is continued\n
16639 echo onto several lines.\n
16643 @item output @var{expression}
16644 Print the value of @var{expression} and nothing but that value: no
16645 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16646 value history either. @xref{Expressions, ,Expressions}, for more information
16649 @item output/@var{fmt} @var{expression}
16650 Print the value of @var{expression} in format @var{fmt}. You can use
16651 the same formats as for @code{print}. @xref{Output Formats,,Output
16652 Formats}, for more information.
16655 @item printf @var{template}, @var{expressions}@dots{}
16656 Print the values of one or more @var{expressions} under the control of
16657 the string @var{template}. To print several values, make
16658 @var{expressions} be a comma-separated list of individual expressions,
16659 which may be either numbers or pointers. Their values are printed as
16660 specified by @var{template}, exactly as a C program would do by
16661 executing the code below:
16664 printf (@var{template}, @var{expressions}@dots{});
16667 As in @code{C} @code{printf}, ordinary characters in @var{template}
16668 are printed verbatim, while @dfn{conversion specification} introduced
16669 by the @samp{%} character cause subsequent @var{expressions} to be
16670 evaluated, their values converted and formatted according to type and
16671 style information encoded in the conversion specifications, and then
16674 For example, you can print two values in hex like this:
16677 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16680 @code{printf} supports all the standard @code{C} conversion
16681 specifications, including the flags and modifiers between the @samp{%}
16682 character and the conversion letter, with the following exceptions:
16686 The argument-ordering modifiers, such as @samp{2$}, are not supported.
16689 The modifier @samp{*} is not supported for specifying precision or
16693 The @samp{'} flag (for separation of digits into groups according to
16694 @code{LC_NUMERIC'}) is not supported.
16697 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
16701 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
16704 The conversion letters @samp{a} and @samp{A} are not supported.
16708 Note that the @samp{ll} type modifier is supported only if the
16709 underlying @code{C} implementation used to build @value{GDBN} supports
16710 the @code{long long int} type, and the @samp{L} type modifier is
16711 supported only if @code{long double} type is available.
16713 As in @code{C}, @code{printf} supports simple backslash-escape
16714 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
16715 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
16716 single character. Octal and hexadecimal escape sequences are not
16719 Additionally, @code{printf} supports conversion specifications for DFP
16720 (@dfn{Decimal Floating Point}) types using the following length modifiers
16721 together with a floating point specifier.
16726 @samp{H} for printing @code{Decimal32} types.
16729 @samp{D} for printing @code{Decimal64} types.
16732 @samp{DD} for printing @code{Decimal128} types.
16735 If the underlying @code{C} implementation used to build @value{GDBN} has
16736 support for the three length modifiers for DFP types, other modifiers
16737 such as width and precision will also be available for @value{GDBN} to use.
16739 In case there is no such @code{C} support, no additional modifiers will be
16740 available and the value will be printed in the standard way.
16742 Here's an example of printing DFP types using the above conversion letters:
16744 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
16750 @chapter Command Interpreters
16751 @cindex command interpreters
16753 @value{GDBN} supports multiple command interpreters, and some command
16754 infrastructure to allow users or user interface writers to switch
16755 between interpreters or run commands in other interpreters.
16757 @value{GDBN} currently supports two command interpreters, the console
16758 interpreter (sometimes called the command-line interpreter or @sc{cli})
16759 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16760 describes both of these interfaces in great detail.
16762 By default, @value{GDBN} will start with the console interpreter.
16763 However, the user may choose to start @value{GDBN} with another
16764 interpreter by specifying the @option{-i} or @option{--interpreter}
16765 startup options. Defined interpreters include:
16769 @cindex console interpreter
16770 The traditional console or command-line interpreter. This is the most often
16771 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16772 @value{GDBN} will use this interpreter.
16775 @cindex mi interpreter
16776 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16777 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16778 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16782 @cindex mi2 interpreter
16783 The current @sc{gdb/mi} interface.
16786 @cindex mi1 interpreter
16787 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16791 @cindex invoke another interpreter
16792 The interpreter being used by @value{GDBN} may not be dynamically
16793 switched at runtime. Although possible, this could lead to a very
16794 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16795 enters the command "interpreter-set console" in a console view,
16796 @value{GDBN} would switch to using the console interpreter, rendering
16797 the IDE inoperable!
16799 @kindex interpreter-exec
16800 Although you may only choose a single interpreter at startup, you may execute
16801 commands in any interpreter from the current interpreter using the appropriate
16802 command. If you are running the console interpreter, simply use the
16803 @code{interpreter-exec} command:
16806 interpreter-exec mi "-data-list-register-names"
16809 @sc{gdb/mi} has a similar command, although it is only available in versions of
16810 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16813 @chapter @value{GDBN} Text User Interface
16815 @cindex Text User Interface
16818 * TUI Overview:: TUI overview
16819 * TUI Keys:: TUI key bindings
16820 * TUI Single Key Mode:: TUI single key mode
16821 * TUI Commands:: TUI-specific commands
16822 * TUI Configuration:: TUI configuration variables
16825 The @value{GDBN} Text User Interface (TUI) is a terminal
16826 interface which uses the @code{curses} library to show the source
16827 file, the assembly output, the program registers and @value{GDBN}
16828 commands in separate text windows. The TUI mode is supported only
16829 on platforms where a suitable version of the @code{curses} library
16832 @pindex @value{GDBTUI}
16833 The TUI mode is enabled by default when you invoke @value{GDBN} as
16834 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
16835 You can also switch in and out of TUI mode while @value{GDBN} runs by
16836 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
16837 @xref{TUI Keys, ,TUI Key Bindings}.
16840 @section TUI Overview
16842 In TUI mode, @value{GDBN} can display several text windows:
16846 This window is the @value{GDBN} command window with the @value{GDBN}
16847 prompt and the @value{GDBN} output. The @value{GDBN} input is still
16848 managed using readline.
16851 The source window shows the source file of the program. The current
16852 line and active breakpoints are displayed in this window.
16855 The assembly window shows the disassembly output of the program.
16858 This window shows the processor registers. Registers are highlighted
16859 when their values change.
16862 The source and assembly windows show the current program position
16863 by highlighting the current line and marking it with a @samp{>} marker.
16864 Breakpoints are indicated with two markers. The first marker
16865 indicates the breakpoint type:
16869 Breakpoint which was hit at least once.
16872 Breakpoint which was never hit.
16875 Hardware breakpoint which was hit at least once.
16878 Hardware breakpoint which was never hit.
16881 The second marker indicates whether the breakpoint is enabled or not:
16885 Breakpoint is enabled.
16888 Breakpoint is disabled.
16891 The source, assembly and register windows are updated when the current
16892 thread changes, when the frame changes, or when the program counter
16895 These windows are not all visible at the same time. The command
16896 window is always visible. The others can be arranged in several
16907 source and assembly,
16910 source and registers, or
16913 assembly and registers.
16916 A status line above the command window shows the following information:
16920 Indicates the current @value{GDBN} target.
16921 (@pxref{Targets, ,Specifying a Debugging Target}).
16924 Gives the current process or thread number.
16925 When no process is being debugged, this field is set to @code{No process}.
16928 Gives the current function name for the selected frame.
16929 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16930 When there is no symbol corresponding to the current program counter,
16931 the string @code{??} is displayed.
16934 Indicates the current line number for the selected frame.
16935 When the current line number is not known, the string @code{??} is displayed.
16938 Indicates the current program counter address.
16942 @section TUI Key Bindings
16943 @cindex TUI key bindings
16945 The TUI installs several key bindings in the readline keymaps
16946 (@pxref{Command Line Editing}). The following key bindings
16947 are installed for both TUI mode and the @value{GDBN} standard mode.
16956 Enter or leave the TUI mode. When leaving the TUI mode,
16957 the curses window management stops and @value{GDBN} operates using
16958 its standard mode, writing on the terminal directly. When reentering
16959 the TUI mode, control is given back to the curses windows.
16960 The screen is then refreshed.
16964 Use a TUI layout with only one window. The layout will
16965 either be @samp{source} or @samp{assembly}. When the TUI mode
16966 is not active, it will switch to the TUI mode.
16968 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16972 Use a TUI layout with at least two windows. When the current
16973 layout already has two windows, the next layout with two windows is used.
16974 When a new layout is chosen, one window will always be common to the
16975 previous layout and the new one.
16977 Think of it as the Emacs @kbd{C-x 2} binding.
16981 Change the active window. The TUI associates several key bindings
16982 (like scrolling and arrow keys) with the active window. This command
16983 gives the focus to the next TUI window.
16985 Think of it as the Emacs @kbd{C-x o} binding.
16989 Switch in and out of the TUI SingleKey mode that binds single
16990 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
16993 The following key bindings only work in the TUI mode:
16998 Scroll the active window one page up.
17002 Scroll the active window one page down.
17006 Scroll the active window one line up.
17010 Scroll the active window one line down.
17014 Scroll the active window one column left.
17018 Scroll the active window one column right.
17022 Refresh the screen.
17025 Because the arrow keys scroll the active window in the TUI mode, they
17026 are not available for their normal use by readline unless the command
17027 window has the focus. When another window is active, you must use
17028 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
17029 and @kbd{C-f} to control the command window.
17031 @node TUI Single Key Mode
17032 @section TUI Single Key Mode
17033 @cindex TUI single key mode
17035 The TUI also provides a @dfn{SingleKey} mode, which binds several
17036 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
17037 switch into this mode, where the following key bindings are used:
17040 @kindex c @r{(SingleKey TUI key)}
17044 @kindex d @r{(SingleKey TUI key)}
17048 @kindex f @r{(SingleKey TUI key)}
17052 @kindex n @r{(SingleKey TUI key)}
17056 @kindex q @r{(SingleKey TUI key)}
17058 exit the SingleKey mode.
17060 @kindex r @r{(SingleKey TUI key)}
17064 @kindex s @r{(SingleKey TUI key)}
17068 @kindex u @r{(SingleKey TUI key)}
17072 @kindex v @r{(SingleKey TUI key)}
17076 @kindex w @r{(SingleKey TUI key)}
17081 Other keys temporarily switch to the @value{GDBN} command prompt.
17082 The key that was pressed is inserted in the editing buffer so that
17083 it is possible to type most @value{GDBN} commands without interaction
17084 with the TUI SingleKey mode. Once the command is entered the TUI
17085 SingleKey mode is restored. The only way to permanently leave
17086 this mode is by typing @kbd{q} or @kbd{C-x s}.
17090 @section TUI-specific Commands
17091 @cindex TUI commands
17093 The TUI has specific commands to control the text windows.
17094 These commands are always available, even when @value{GDBN} is not in
17095 the TUI mode. When @value{GDBN} is in the standard mode, most
17096 of these commands will automatically switch to the TUI mode.
17101 List and give the size of all displayed windows.
17105 Display the next layout.
17108 Display the previous layout.
17111 Display the source window only.
17114 Display the assembly window only.
17117 Display the source and assembly window.
17120 Display the register window together with the source or assembly window.
17124 Make the next window active for scrolling.
17127 Make the previous window active for scrolling.
17130 Make the source window active for scrolling.
17133 Make the assembly window active for scrolling.
17136 Make the register window active for scrolling.
17139 Make the command window active for scrolling.
17143 Refresh the screen. This is similar to typing @kbd{C-L}.
17145 @item tui reg float
17147 Show the floating point registers in the register window.
17149 @item tui reg general
17150 Show the general registers in the register window.
17153 Show the next register group. The list of register groups as well as
17154 their order is target specific. The predefined register groups are the
17155 following: @code{general}, @code{float}, @code{system}, @code{vector},
17156 @code{all}, @code{save}, @code{restore}.
17158 @item tui reg system
17159 Show the system registers in the register window.
17163 Update the source window and the current execution point.
17165 @item winheight @var{name} +@var{count}
17166 @itemx winheight @var{name} -@var{count}
17168 Change the height of the window @var{name} by @var{count}
17169 lines. Positive counts increase the height, while negative counts
17172 @item tabset @var{nchars}
17174 Set the width of tab stops to be @var{nchars} characters.
17177 @node TUI Configuration
17178 @section TUI Configuration Variables
17179 @cindex TUI configuration variables
17181 Several configuration variables control the appearance of TUI windows.
17184 @item set tui border-kind @var{kind}
17185 @kindex set tui border-kind
17186 Select the border appearance for the source, assembly and register windows.
17187 The possible values are the following:
17190 Use a space character to draw the border.
17193 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
17196 Use the Alternate Character Set to draw the border. The border is
17197 drawn using character line graphics if the terminal supports them.
17200 @item set tui border-mode @var{mode}
17201 @kindex set tui border-mode
17202 @itemx set tui active-border-mode @var{mode}
17203 @kindex set tui active-border-mode
17204 Select the display attributes for the borders of the inactive windows
17205 or the active window. The @var{mode} can be one of the following:
17208 Use normal attributes to display the border.
17214 Use reverse video mode.
17217 Use half bright mode.
17219 @item half-standout
17220 Use half bright and standout mode.
17223 Use extra bright or bold mode.
17225 @item bold-standout
17226 Use extra bright or bold and standout mode.
17231 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17234 @cindex @sc{gnu} Emacs
17235 A special interface allows you to use @sc{gnu} Emacs to view (and
17236 edit) the source files for the program you are debugging with
17239 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17240 executable file you want to debug as an argument. This command starts
17241 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17242 created Emacs buffer.
17243 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17245 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17250 All ``terminal'' input and output goes through an Emacs buffer, called
17253 This applies both to @value{GDBN} commands and their output, and to the input
17254 and output done by the program you are debugging.
17256 This is useful because it means that you can copy the text of previous
17257 commands and input them again; you can even use parts of the output
17260 All the facilities of Emacs' Shell mode are available for interacting
17261 with your program. In particular, you can send signals the usual
17262 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17266 @value{GDBN} displays source code through Emacs.
17268 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17269 source file for that frame and puts an arrow (@samp{=>}) at the
17270 left margin of the current line. Emacs uses a separate buffer for
17271 source display, and splits the screen to show both your @value{GDBN} session
17274 Explicit @value{GDBN} @code{list} or search commands still produce output as
17275 usual, but you probably have no reason to use them from Emacs.
17278 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17279 a graphical mode, enabled by default, which provides further buffers
17280 that can control the execution and describe the state of your program.
17281 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17283 If you specify an absolute file name when prompted for the @kbd{M-x
17284 gdb} argument, then Emacs sets your current working directory to where
17285 your program resides. If you only specify the file name, then Emacs
17286 sets your current working directory to to the directory associated
17287 with the previous buffer. In this case, @value{GDBN} may find your
17288 program by searching your environment's @code{PATH} variable, but on
17289 some operating systems it might not find the source. So, although the
17290 @value{GDBN} input and output session proceeds normally, the auxiliary
17291 buffer does not display the current source and line of execution.
17293 The initial working directory of @value{GDBN} is printed on the top
17294 line of the GUD buffer and this serves as a default for the commands
17295 that specify files for @value{GDBN} to operate on. @xref{Files,
17296 ,Commands to Specify Files}.
17298 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17299 need to call @value{GDBN} by a different name (for example, if you
17300 keep several configurations around, with different names) you can
17301 customize the Emacs variable @code{gud-gdb-command-name} to run the
17304 In the GUD buffer, you can use these special Emacs commands in
17305 addition to the standard Shell mode commands:
17309 Describe the features of Emacs' GUD Mode.
17312 Execute to another source line, like the @value{GDBN} @code{step} command; also
17313 update the display window to show the current file and location.
17316 Execute to next source line in this function, skipping all function
17317 calls, like the @value{GDBN} @code{next} command. Then update the display window
17318 to show the current file and location.
17321 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17322 display window accordingly.
17325 Execute until exit from the selected stack frame, like the @value{GDBN}
17326 @code{finish} command.
17329 Continue execution of your program, like the @value{GDBN} @code{continue}
17333 Go up the number of frames indicated by the numeric argument
17334 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17335 like the @value{GDBN} @code{up} command.
17338 Go down the number of frames indicated by the numeric argument, like the
17339 @value{GDBN} @code{down} command.
17342 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17343 tells @value{GDBN} to set a breakpoint on the source line point is on.
17345 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17346 separate frame which shows a backtrace when the GUD buffer is current.
17347 Move point to any frame in the stack and type @key{RET} to make it
17348 become the current frame and display the associated source in the
17349 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17350 selected frame become the current one. In graphical mode, the
17351 speedbar displays watch expressions.
17353 If you accidentally delete the source-display buffer, an easy way to get
17354 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17355 request a frame display; when you run under Emacs, this recreates
17356 the source buffer if necessary to show you the context of the current
17359 The source files displayed in Emacs are in ordinary Emacs buffers
17360 which are visiting the source files in the usual way. You can edit
17361 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17362 communicates with Emacs in terms of line numbers. If you add or
17363 delete lines from the text, the line numbers that @value{GDBN} knows cease
17364 to correspond properly with the code.
17366 A more detailed description of Emacs' interaction with @value{GDBN} is
17367 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17370 @c The following dropped because Epoch is nonstandard. Reactivate
17371 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17373 @kindex Emacs Epoch environment
17377 Version 18 of @sc{gnu} Emacs has a built-in window system
17378 called the @code{epoch}
17379 environment. Users of this environment can use a new command,
17380 @code{inspect} which performs identically to @code{print} except that
17381 each value is printed in its own window.
17386 @chapter The @sc{gdb/mi} Interface
17388 @unnumberedsec Function and Purpose
17390 @cindex @sc{gdb/mi}, its purpose
17391 @sc{gdb/mi} is a line based machine oriented text interface to
17392 @value{GDBN} and is activated by specifying using the
17393 @option{--interpreter} command line option (@pxref{Mode Options}). It
17394 is specifically intended to support the development of systems which
17395 use the debugger as just one small component of a larger system.
17397 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17398 in the form of a reference manual.
17400 Note that @sc{gdb/mi} is still under construction, so some of the
17401 features described below are incomplete and subject to change
17402 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17404 @unnumberedsec Notation and Terminology
17406 @cindex notational conventions, for @sc{gdb/mi}
17407 This chapter uses the following notation:
17411 @code{|} separates two alternatives.
17414 @code{[ @var{something} ]} indicates that @var{something} is optional:
17415 it may or may not be given.
17418 @code{( @var{group} )*} means that @var{group} inside the parentheses
17419 may repeat zero or more times.
17422 @code{( @var{group} )+} means that @var{group} inside the parentheses
17423 may repeat one or more times.
17426 @code{"@var{string}"} means a literal @var{string}.
17430 @heading Dependencies
17434 * GDB/MI Command Syntax::
17435 * GDB/MI Compatibility with CLI::
17436 * GDB/MI Development and Front Ends::
17437 * GDB/MI Output Records::
17438 * GDB/MI Simple Examples::
17439 * GDB/MI Command Description Format::
17440 * GDB/MI Breakpoint Commands::
17441 * GDB/MI Program Context::
17442 * GDB/MI Thread Commands::
17443 * GDB/MI Program Execution::
17444 * GDB/MI Stack Manipulation::
17445 * GDB/MI Variable Objects::
17446 * GDB/MI Data Manipulation::
17447 * GDB/MI Tracepoint Commands::
17448 * GDB/MI Symbol Query::
17449 * GDB/MI File Commands::
17451 * GDB/MI Kod Commands::
17452 * GDB/MI Memory Overlay Commands::
17453 * GDB/MI Signal Handling Commands::
17455 * GDB/MI Target Manipulation::
17456 * GDB/MI File Transfer Commands::
17457 * GDB/MI Miscellaneous Commands::
17460 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17461 @node GDB/MI Command Syntax
17462 @section @sc{gdb/mi} Command Syntax
17465 * GDB/MI Input Syntax::
17466 * GDB/MI Output Syntax::
17469 @node GDB/MI Input Syntax
17470 @subsection @sc{gdb/mi} Input Syntax
17472 @cindex input syntax for @sc{gdb/mi}
17473 @cindex @sc{gdb/mi}, input syntax
17475 @item @var{command} @expansion{}
17476 @code{@var{cli-command} | @var{mi-command}}
17478 @item @var{cli-command} @expansion{}
17479 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17480 @var{cli-command} is any existing @value{GDBN} CLI command.
17482 @item @var{mi-command} @expansion{}
17483 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17484 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17486 @item @var{token} @expansion{}
17487 "any sequence of digits"
17489 @item @var{option} @expansion{}
17490 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17492 @item @var{parameter} @expansion{}
17493 @code{@var{non-blank-sequence} | @var{c-string}}
17495 @item @var{operation} @expansion{}
17496 @emph{any of the operations described in this chapter}
17498 @item @var{non-blank-sequence} @expansion{}
17499 @emph{anything, provided it doesn't contain special characters such as
17500 "-", @var{nl}, """ and of course " "}
17502 @item @var{c-string} @expansion{}
17503 @code{""" @var{seven-bit-iso-c-string-content} """}
17505 @item @var{nl} @expansion{}
17514 The CLI commands are still handled by the @sc{mi} interpreter; their
17515 output is described below.
17518 The @code{@var{token}}, when present, is passed back when the command
17522 Some @sc{mi} commands accept optional arguments as part of the parameter
17523 list. Each option is identified by a leading @samp{-} (dash) and may be
17524 followed by an optional argument parameter. Options occur first in the
17525 parameter list and can be delimited from normal parameters using
17526 @samp{--} (this is useful when some parameters begin with a dash).
17533 We want easy access to the existing CLI syntax (for debugging).
17536 We want it to be easy to spot a @sc{mi} operation.
17539 @node GDB/MI Output Syntax
17540 @subsection @sc{gdb/mi} Output Syntax
17542 @cindex output syntax of @sc{gdb/mi}
17543 @cindex @sc{gdb/mi}, output syntax
17544 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17545 followed, optionally, by a single result record. This result record
17546 is for the most recent command. The sequence of output records is
17547 terminated by @samp{(gdb)}.
17549 If an input command was prefixed with a @code{@var{token}} then the
17550 corresponding output for that command will also be prefixed by that same
17554 @item @var{output} @expansion{}
17555 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17557 @item @var{result-record} @expansion{}
17558 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17560 @item @var{out-of-band-record} @expansion{}
17561 @code{@var{async-record} | @var{stream-record}}
17563 @item @var{async-record} @expansion{}
17564 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17566 @item @var{exec-async-output} @expansion{}
17567 @code{[ @var{token} ] "*" @var{async-output}}
17569 @item @var{status-async-output} @expansion{}
17570 @code{[ @var{token} ] "+" @var{async-output}}
17572 @item @var{notify-async-output} @expansion{}
17573 @code{[ @var{token} ] "=" @var{async-output}}
17575 @item @var{async-output} @expansion{}
17576 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17578 @item @var{result-class} @expansion{}
17579 @code{"done" | "running" | "connected" | "error" | "exit"}
17581 @item @var{async-class} @expansion{}
17582 @code{"stopped" | @var{others}} (where @var{others} will be added
17583 depending on the needs---this is still in development).
17585 @item @var{result} @expansion{}
17586 @code{ @var{variable} "=" @var{value}}
17588 @item @var{variable} @expansion{}
17589 @code{ @var{string} }
17591 @item @var{value} @expansion{}
17592 @code{ @var{const} | @var{tuple} | @var{list} }
17594 @item @var{const} @expansion{}
17595 @code{@var{c-string}}
17597 @item @var{tuple} @expansion{}
17598 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17600 @item @var{list} @expansion{}
17601 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17602 @var{result} ( "," @var{result} )* "]" }
17604 @item @var{stream-record} @expansion{}
17605 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17607 @item @var{console-stream-output} @expansion{}
17608 @code{"~" @var{c-string}}
17610 @item @var{target-stream-output} @expansion{}
17611 @code{"@@" @var{c-string}}
17613 @item @var{log-stream-output} @expansion{}
17614 @code{"&" @var{c-string}}
17616 @item @var{nl} @expansion{}
17619 @item @var{token} @expansion{}
17620 @emph{any sequence of digits}.
17628 All output sequences end in a single line containing a period.
17631 The @code{@var{token}} is from the corresponding request. If an execution
17632 command is interrupted by the @samp{-exec-interrupt} command, the
17633 @var{token} associated with the @samp{*stopped} message is the one of the
17634 original execution command, not the one of the interrupt command.
17637 @cindex status output in @sc{gdb/mi}
17638 @var{status-async-output} contains on-going status information about the
17639 progress of a slow operation. It can be discarded. All status output is
17640 prefixed by @samp{+}.
17643 @cindex async output in @sc{gdb/mi}
17644 @var{exec-async-output} contains asynchronous state change on the target
17645 (stopped, started, disappeared). All async output is prefixed by
17649 @cindex notify output in @sc{gdb/mi}
17650 @var{notify-async-output} contains supplementary information that the
17651 client should handle (e.g., a new breakpoint information). All notify
17652 output is prefixed by @samp{=}.
17655 @cindex console output in @sc{gdb/mi}
17656 @var{console-stream-output} is output that should be displayed as is in the
17657 console. It is the textual response to a CLI command. All the console
17658 output is prefixed by @samp{~}.
17661 @cindex target output in @sc{gdb/mi}
17662 @var{target-stream-output} is the output produced by the target program.
17663 All the target output is prefixed by @samp{@@}.
17666 @cindex log output in @sc{gdb/mi}
17667 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17668 instance messages that should be displayed as part of an error log. All
17669 the log output is prefixed by @samp{&}.
17672 @cindex list output in @sc{gdb/mi}
17673 New @sc{gdb/mi} commands should only output @var{lists} containing
17679 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17680 details about the various output records.
17682 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17683 @node GDB/MI Compatibility with CLI
17684 @section @sc{gdb/mi} Compatibility with CLI
17686 @cindex compatibility, @sc{gdb/mi} and CLI
17687 @cindex @sc{gdb/mi}, compatibility with CLI
17689 For the developers convenience CLI commands can be entered directly,
17690 but there may be some unexpected behaviour. For example, commands
17691 that query the user will behave as if the user replied yes, breakpoint
17692 command lists are not executed and some CLI commands, such as
17693 @code{if}, @code{when} and @code{define}, prompt for further input with
17694 @samp{>}, which is not valid MI output.
17696 This feature may be removed at some stage in the future and it is
17697 recommended that front ends use the @code{-interpreter-exec} command
17698 (@pxref{-interpreter-exec}).
17700 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17701 @node GDB/MI Development and Front Ends
17702 @section @sc{gdb/mi} Development and Front Ends
17703 @cindex @sc{gdb/mi} development
17705 The application which takes the MI output and presents the state of the
17706 program being debugged to the user is called a @dfn{front end}.
17708 Although @sc{gdb/mi} is still incomplete, it is currently being used
17709 by a variety of front ends to @value{GDBN}. This makes it difficult
17710 to introduce new functionality without breaking existing usage. This
17711 section tries to minimize the problems by describing how the protocol
17714 Some changes in MI need not break a carefully designed front end, and
17715 for these the MI version will remain unchanged. The following is a
17716 list of changes that may occur within one level, so front ends should
17717 parse MI output in a way that can handle them:
17721 New MI commands may be added.
17724 New fields may be added to the output of any MI command.
17727 The range of values for fields with specified values, e.g.,
17728 @code{in_scope} (@pxref{-var-update}) may be extended.
17730 @c The format of field's content e.g type prefix, may change so parse it
17731 @c at your own risk. Yes, in general?
17733 @c The order of fields may change? Shouldn't really matter but it might
17734 @c resolve inconsistencies.
17737 If the changes are likely to break front ends, the MI version level
17738 will be increased by one. This will allow the front end to parse the
17739 output according to the MI version. Apart from mi0, new versions of
17740 @value{GDBN} will not support old versions of MI and it will be the
17741 responsibility of the front end to work with the new one.
17743 @c Starting with mi3, add a new command -mi-version that prints the MI
17746 The best way to avoid unexpected changes in MI that might break your front
17747 end is to make your project known to @value{GDBN} developers and
17748 follow development on @email{gdb@@sourceware.org} and
17749 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17750 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17751 Group, which has the aim of creating a more general MI protocol
17752 called Debugger Machine Interface (DMI) that will become a standard
17753 for all debuggers, not just @value{GDBN}.
17754 @cindex mailing lists
17756 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17757 @node GDB/MI Output Records
17758 @section @sc{gdb/mi} Output Records
17761 * GDB/MI Result Records::
17762 * GDB/MI Stream Records::
17763 * GDB/MI Out-of-band Records::
17766 @node GDB/MI Result Records
17767 @subsection @sc{gdb/mi} Result Records
17769 @cindex result records in @sc{gdb/mi}
17770 @cindex @sc{gdb/mi}, result records
17771 In addition to a number of out-of-band notifications, the response to a
17772 @sc{gdb/mi} command includes one of the following result indications:
17776 @item "^done" [ "," @var{results} ]
17777 The synchronous operation was successful, @code{@var{results}} are the return
17782 @c Is this one correct? Should it be an out-of-band notification?
17783 The asynchronous operation was successfully started. The target is
17788 @value{GDBN} has connected to a remote target.
17790 @item "^error" "," @var{c-string}
17792 The operation failed. The @code{@var{c-string}} contains the corresponding
17797 @value{GDBN} has terminated.
17801 @node GDB/MI Stream Records
17802 @subsection @sc{gdb/mi} Stream Records
17804 @cindex @sc{gdb/mi}, stream records
17805 @cindex stream records in @sc{gdb/mi}
17806 @value{GDBN} internally maintains a number of output streams: the console, the
17807 target, and the log. The output intended for each of these streams is
17808 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17810 Each stream record begins with a unique @dfn{prefix character} which
17811 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17812 Syntax}). In addition to the prefix, each stream record contains a
17813 @code{@var{string-output}}. This is either raw text (with an implicit new
17814 line) or a quoted C string (which does not contain an implicit newline).
17817 @item "~" @var{string-output}
17818 The console output stream contains text that should be displayed in the
17819 CLI console window. It contains the textual responses to CLI commands.
17821 @item "@@" @var{string-output}
17822 The target output stream contains any textual output from the running
17823 target. This is only present when GDB's event loop is truly
17824 asynchronous, which is currently only the case for remote targets.
17826 @item "&" @var{string-output}
17827 The log stream contains debugging messages being produced by @value{GDBN}'s
17831 @node GDB/MI Out-of-band Records
17832 @subsection @sc{gdb/mi} Out-of-band Records
17834 @cindex out-of-band records in @sc{gdb/mi}
17835 @cindex @sc{gdb/mi}, out-of-band records
17836 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17837 additional changes that have occurred. Those changes can either be a
17838 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17839 target activity (e.g., target stopped).
17841 The following is a preliminary list of possible out-of-band records.
17842 In particular, the @var{exec-async-output} records.
17845 @item *stopped,reason="@var{reason}"
17848 @var{reason} can be one of the following:
17851 @item breakpoint-hit
17852 A breakpoint was reached.
17853 @item watchpoint-trigger
17854 A watchpoint was triggered.
17855 @item read-watchpoint-trigger
17856 A read watchpoint was triggered.
17857 @item access-watchpoint-trigger
17858 An access watchpoint was triggered.
17859 @item function-finished
17860 An -exec-finish or similar CLI command was accomplished.
17861 @item location-reached
17862 An -exec-until or similar CLI command was accomplished.
17863 @item watchpoint-scope
17864 A watchpoint has gone out of scope.
17865 @item end-stepping-range
17866 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17867 similar CLI command was accomplished.
17868 @item exited-signalled
17869 The inferior exited because of a signal.
17871 The inferior exited.
17872 @item exited-normally
17873 The inferior exited normally.
17874 @item signal-received
17875 A signal was received by the inferior.
17879 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17880 @node GDB/MI Simple Examples
17881 @section Simple Examples of @sc{gdb/mi} Interaction
17882 @cindex @sc{gdb/mi}, simple examples
17884 This subsection presents several simple examples of interaction using
17885 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17886 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17887 the output received from @sc{gdb/mi}.
17889 Note the line breaks shown in the examples are here only for
17890 readability, they don't appear in the real output.
17892 @subheading Setting a Breakpoint
17894 Setting a breakpoint generates synchronous output which contains detailed
17895 information of the breakpoint.
17898 -> -break-insert main
17899 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17900 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17901 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17905 @subheading Program Execution
17907 Program execution generates asynchronous records and MI gives the
17908 reason that execution stopped.
17914 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17915 frame=@{addr="0x08048564",func="main",
17916 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17917 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17922 <- *stopped,reason="exited-normally"
17926 @subheading Quitting @value{GDBN}
17928 Quitting @value{GDBN} just prints the result class @samp{^exit}.
17936 @subheading A Bad Command
17938 Here's what happens if you pass a non-existent command:
17942 <- ^error,msg="Undefined MI command: rubbish"
17947 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17948 @node GDB/MI Command Description Format
17949 @section @sc{gdb/mi} Command Description Format
17951 The remaining sections describe blocks of commands. Each block of
17952 commands is laid out in a fashion similar to this section.
17954 @subheading Motivation
17956 The motivation for this collection of commands.
17958 @subheading Introduction
17960 A brief introduction to this collection of commands as a whole.
17962 @subheading Commands
17964 For each command in the block, the following is described:
17966 @subsubheading Synopsis
17969 -command @var{args}@dots{}
17972 @subsubheading Result
17974 @subsubheading @value{GDBN} Command
17976 The corresponding @value{GDBN} CLI command(s), if any.
17978 @subsubheading Example
17980 Example(s) formatted for readability. Some of the described commands have
17981 not been implemented yet and these are labeled N.A.@: (not available).
17984 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17985 @node GDB/MI Breakpoint Commands
17986 @section @sc{gdb/mi} Breakpoint Commands
17988 @cindex breakpoint commands for @sc{gdb/mi}
17989 @cindex @sc{gdb/mi}, breakpoint commands
17990 This section documents @sc{gdb/mi} commands for manipulating
17993 @subheading The @code{-break-after} Command
17994 @findex -break-after
17996 @subsubheading Synopsis
17999 -break-after @var{number} @var{count}
18002 The breakpoint number @var{number} is not in effect until it has been
18003 hit @var{count} times. To see how this is reflected in the output of
18004 the @samp{-break-list} command, see the description of the
18005 @samp{-break-list} command below.
18007 @subsubheading @value{GDBN} Command
18009 The corresponding @value{GDBN} command is @samp{ignore}.
18011 @subsubheading Example
18016 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
18017 fullname="/home/foo/hello.c",line="5",times="0"@}
18024 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18025 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18026 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18027 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18028 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18029 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18030 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18031 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18032 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18033 line="5",times="0",ignore="3"@}]@}
18038 @subheading The @code{-break-catch} Command
18039 @findex -break-catch
18041 @subheading The @code{-break-commands} Command
18042 @findex -break-commands
18046 @subheading The @code{-break-condition} Command
18047 @findex -break-condition
18049 @subsubheading Synopsis
18052 -break-condition @var{number} @var{expr}
18055 Breakpoint @var{number} will stop the program only if the condition in
18056 @var{expr} is true. The condition becomes part of the
18057 @samp{-break-list} output (see the description of the @samp{-break-list}
18060 @subsubheading @value{GDBN} Command
18062 The corresponding @value{GDBN} command is @samp{condition}.
18064 @subsubheading Example
18068 -break-condition 1 1
18072 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18073 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18074 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18075 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18076 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18077 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18078 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18079 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18080 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18081 line="5",cond="1",times="0",ignore="3"@}]@}
18085 @subheading The @code{-break-delete} Command
18086 @findex -break-delete
18088 @subsubheading Synopsis
18091 -break-delete ( @var{breakpoint} )+
18094 Delete the breakpoint(s) whose number(s) are specified in the argument
18095 list. This is obviously reflected in the breakpoint list.
18097 @subsubheading @value{GDBN} Command
18099 The corresponding @value{GDBN} command is @samp{delete}.
18101 @subsubheading Example
18109 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18110 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18111 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18112 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18113 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18114 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18115 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18120 @subheading The @code{-break-disable} Command
18121 @findex -break-disable
18123 @subsubheading Synopsis
18126 -break-disable ( @var{breakpoint} )+
18129 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18130 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18132 @subsubheading @value{GDBN} Command
18134 The corresponding @value{GDBN} command is @samp{disable}.
18136 @subsubheading Example
18144 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18145 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18146 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18147 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18148 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18149 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18150 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18151 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18152 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18153 line="5",times="0"@}]@}
18157 @subheading The @code{-break-enable} Command
18158 @findex -break-enable
18160 @subsubheading Synopsis
18163 -break-enable ( @var{breakpoint} )+
18166 Enable (previously disabled) @var{breakpoint}(s).
18168 @subsubheading @value{GDBN} Command
18170 The corresponding @value{GDBN} command is @samp{enable}.
18172 @subsubheading Example
18180 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18181 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18182 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18183 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18184 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18185 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18186 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18187 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18188 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18189 line="5",times="0"@}]@}
18193 @subheading The @code{-break-info} Command
18194 @findex -break-info
18196 @subsubheading Synopsis
18199 -break-info @var{breakpoint}
18203 Get information about a single breakpoint.
18205 @subsubheading @value{GDBN} Command
18207 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18209 @subsubheading Example
18212 @subheading The @code{-break-insert} Command
18213 @findex -break-insert
18215 @subsubheading Synopsis
18218 -break-insert [ -t ] [ -h ] [ -f ]
18219 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18220 [ -p @var{thread} ] [ @var{location} ]
18224 If specified, @var{location}, can be one of:
18231 @item filename:linenum
18232 @item filename:function
18236 The possible optional parameters of this command are:
18240 Insert a temporary breakpoint.
18242 Insert a hardware breakpoint.
18243 @item -c @var{condition}
18244 Make the breakpoint conditional on @var{condition}.
18245 @item -i @var{ignore-count}
18246 Initialize the @var{ignore-count}.
18248 If @var{location} cannot be parsed (for example if it
18249 refers to unknown files or functions), create a pending
18250 breakpoint. Without this flag, @value{GDBN} will report
18251 an error, and won't create a breakpoint, if @var{location}
18255 @subsubheading Result
18257 The result is in the form:
18260 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18261 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18262 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18263 times="@var{times}"@}
18267 where @var{number} is the @value{GDBN} number for this breakpoint,
18268 @var{funcname} is the name of the function where the breakpoint was
18269 inserted, @var{filename} is the name of the source file which contains
18270 this function, @var{lineno} is the source line number within that file
18271 and @var{times} the number of times that the breakpoint has been hit
18272 (always 0 for -break-insert but may be greater for -break-info or -break-list
18273 which use the same output).
18275 Note: this format is open to change.
18276 @c An out-of-band breakpoint instead of part of the result?
18278 @subsubheading @value{GDBN} Command
18280 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18281 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18283 @subsubheading Example
18288 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18289 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18291 -break-insert -t foo
18292 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18293 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18296 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18297 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18298 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18299 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18300 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18301 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18302 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18303 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18304 addr="0x0001072c", func="main",file="recursive2.c",
18305 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18306 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18307 addr="0x00010774",func="foo",file="recursive2.c",
18308 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18310 -break-insert -r foo.*
18311 ~int foo(int, int);
18312 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18313 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18317 @subheading The @code{-break-list} Command
18318 @findex -break-list
18320 @subsubheading Synopsis
18326 Displays the list of inserted breakpoints, showing the following fields:
18330 number of the breakpoint
18332 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18334 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18337 is the breakpoint enabled or no: @samp{y} or @samp{n}
18339 memory location at which the breakpoint is set
18341 logical location of the breakpoint, expressed by function name, file
18344 number of times the breakpoint has been hit
18347 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18348 @code{body} field is an empty list.
18350 @subsubheading @value{GDBN} Command
18352 The corresponding @value{GDBN} command is @samp{info break}.
18354 @subsubheading Example
18359 ^done,BreakpointTable=@{nr_rows="2",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",line="5",times="0"@},
18368 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18369 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18370 line="13",times="0"@}]@}
18374 Here's an example of the result when there are no breakpoints:
18379 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18380 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18381 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18382 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18383 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18384 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18385 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18390 @subheading The @code{-break-watch} Command
18391 @findex -break-watch
18393 @subsubheading Synopsis
18396 -break-watch [ -a | -r ]
18399 Create a watchpoint. With the @samp{-a} option it will create an
18400 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18401 read from or on a write to the memory location. With the @samp{-r}
18402 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18403 trigger only when the memory location is accessed for reading. Without
18404 either of the options, the watchpoint created is a regular watchpoint,
18405 i.e., it will trigger when the memory location is accessed for writing.
18406 @xref{Set Watchpoints, , Setting Watchpoints}.
18408 Note that @samp{-break-list} will report a single list of watchpoints and
18409 breakpoints inserted.
18411 @subsubheading @value{GDBN} Command
18413 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18416 @subsubheading Example
18418 Setting a watchpoint on a variable in the @code{main} function:
18423 ^done,wpt=@{number="2",exp="x"@}
18428 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18429 value=@{old="-268439212",new="55"@},
18430 frame=@{func="main",args=[],file="recursive2.c",
18431 fullname="/home/foo/bar/recursive2.c",line="5"@}
18435 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18436 the program execution twice: first for the variable changing value, then
18437 for the watchpoint going out of scope.
18442 ^done,wpt=@{number="5",exp="C"@}
18447 *stopped,reason="watchpoint-trigger",
18448 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18449 frame=@{func="callee4",args=[],
18450 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18451 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18456 *stopped,reason="watchpoint-scope",wpnum="5",
18457 frame=@{func="callee3",args=[@{name="strarg",
18458 value="0x11940 \"A string argument.\""@}],
18459 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18460 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18464 Listing breakpoints and watchpoints, at different points in the program
18465 execution. Note that once the watchpoint goes out of scope, it is
18471 ^done,wpt=@{number="2",exp="C"@}
18474 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18475 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18476 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18477 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18478 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18479 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18480 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18481 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18482 addr="0x00010734",func="callee4",
18483 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18484 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18485 bkpt=@{number="2",type="watchpoint",disp="keep",
18486 enabled="y",addr="",what="C",times="0"@}]@}
18491 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18492 value=@{old="-276895068",new="3"@},
18493 frame=@{func="callee4",args=[],
18494 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18495 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18498 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18499 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18500 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18501 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18502 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18503 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18504 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18505 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18506 addr="0x00010734",func="callee4",
18507 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18508 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18509 bkpt=@{number="2",type="watchpoint",disp="keep",
18510 enabled="y",addr="",what="C",times="-5"@}]@}
18514 ^done,reason="watchpoint-scope",wpnum="2",
18515 frame=@{func="callee3",args=[@{name="strarg",
18516 value="0x11940 \"A string argument.\""@}],
18517 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18518 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18521 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18522 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18523 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18524 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18525 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18526 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18527 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18528 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18529 addr="0x00010734",func="callee4",
18530 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18531 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18536 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18537 @node GDB/MI Program Context
18538 @section @sc{gdb/mi} Program Context
18540 @subheading The @code{-exec-arguments} Command
18541 @findex -exec-arguments
18544 @subsubheading Synopsis
18547 -exec-arguments @var{args}
18550 Set the inferior program arguments, to be used in the next
18553 @subsubheading @value{GDBN} Command
18555 The corresponding @value{GDBN} command is @samp{set args}.
18557 @subsubheading Example
18560 Don't have one around.
18563 @subheading The @code{-exec-show-arguments} Command
18564 @findex -exec-show-arguments
18566 @subsubheading Synopsis
18569 -exec-show-arguments
18572 Print the arguments of the program.
18574 @subsubheading @value{GDBN} Command
18576 The corresponding @value{GDBN} command is @samp{show args}.
18578 @subsubheading Example
18582 @subheading The @code{-environment-cd} Command
18583 @findex -environment-cd
18585 @subsubheading Synopsis
18588 -environment-cd @var{pathdir}
18591 Set @value{GDBN}'s working directory.
18593 @subsubheading @value{GDBN} Command
18595 The corresponding @value{GDBN} command is @samp{cd}.
18597 @subsubheading Example
18601 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18607 @subheading The @code{-environment-directory} Command
18608 @findex -environment-directory
18610 @subsubheading Synopsis
18613 -environment-directory [ -r ] [ @var{pathdir} ]+
18616 Add directories @var{pathdir} to beginning of search path for source files.
18617 If the @samp{-r} option is used, the search path is reset to the default
18618 search path. If directories @var{pathdir} are supplied in addition to the
18619 @samp{-r} option, the search path is first reset and then addition
18621 Multiple directories may be specified, separated by blanks. Specifying
18622 multiple directories in a single command
18623 results in the directories added to the beginning of the
18624 search path in the same order they were presented in the command.
18625 If blanks are needed as
18626 part of a directory name, double-quotes should be used around
18627 the name. In the command output, the path will show up separated
18628 by the system directory-separator character. The directory-separator
18629 character must not be used
18630 in any directory name.
18631 If no directories are specified, the current search path is displayed.
18633 @subsubheading @value{GDBN} Command
18635 The corresponding @value{GDBN} command is @samp{dir}.
18637 @subsubheading Example
18641 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18642 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18644 -environment-directory ""
18645 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18647 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18648 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18650 -environment-directory -r
18651 ^done,source-path="$cdir:$cwd"
18656 @subheading The @code{-environment-path} Command
18657 @findex -environment-path
18659 @subsubheading Synopsis
18662 -environment-path [ -r ] [ @var{pathdir} ]+
18665 Add directories @var{pathdir} to beginning of search path for object files.
18666 If the @samp{-r} option is used, the search path is reset to the original
18667 search path that existed at gdb start-up. If directories @var{pathdir} are
18668 supplied in addition to the
18669 @samp{-r} option, the search path is first reset and then addition
18671 Multiple directories may be specified, separated by blanks. Specifying
18672 multiple directories in a single command
18673 results in the directories added to the beginning of the
18674 search path in the same order they were presented in the command.
18675 If blanks are needed as
18676 part of a directory name, double-quotes should be used around
18677 the name. In the command output, the path will show up separated
18678 by the system directory-separator character. The directory-separator
18679 character must not be used
18680 in any directory name.
18681 If no directories are specified, the current path is displayed.
18684 @subsubheading @value{GDBN} Command
18686 The corresponding @value{GDBN} command is @samp{path}.
18688 @subsubheading Example
18693 ^done,path="/usr/bin"
18695 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18696 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18698 -environment-path -r /usr/local/bin
18699 ^done,path="/usr/local/bin:/usr/bin"
18704 @subheading The @code{-environment-pwd} Command
18705 @findex -environment-pwd
18707 @subsubheading Synopsis
18713 Show the current working directory.
18715 @subsubheading @value{GDBN} Command
18717 The corresponding @value{GDBN} command is @samp{pwd}.
18719 @subsubheading Example
18724 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18728 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18729 @node GDB/MI Thread Commands
18730 @section @sc{gdb/mi} Thread Commands
18733 @subheading The @code{-thread-info} Command
18734 @findex -thread-info
18736 @subsubheading Synopsis
18742 @subsubheading @value{GDBN} Command
18746 @subsubheading Example
18750 @subheading The @code{-thread-list-all-threads} Command
18751 @findex -thread-list-all-threads
18753 @subsubheading Synopsis
18756 -thread-list-all-threads
18759 @subsubheading @value{GDBN} Command
18761 The equivalent @value{GDBN} command is @samp{info threads}.
18763 @subsubheading Example
18767 @subheading The @code{-thread-list-ids} Command
18768 @findex -thread-list-ids
18770 @subsubheading Synopsis
18776 Produces a list of the currently known @value{GDBN} thread ids. At the
18777 end of the list it also prints the total number of such threads.
18779 @subsubheading @value{GDBN} Command
18781 Part of @samp{info threads} supplies the same information.
18783 @subsubheading Example
18785 No threads present, besides the main process:
18790 ^done,thread-ids=@{@},number-of-threads="0"
18800 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18801 number-of-threads="3"
18806 @subheading The @code{-thread-select} Command
18807 @findex -thread-select
18809 @subsubheading Synopsis
18812 -thread-select @var{threadnum}
18815 Make @var{threadnum} the current thread. It prints the number of the new
18816 current thread, and the topmost frame for that thread.
18818 @subsubheading @value{GDBN} Command
18820 The corresponding @value{GDBN} command is @samp{thread}.
18822 @subsubheading Example
18829 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18830 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18834 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18835 number-of-threads="3"
18838 ^done,new-thread-id="3",
18839 frame=@{level="0",func="vprintf",
18840 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18841 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18845 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18846 @node GDB/MI Program Execution
18847 @section @sc{gdb/mi} Program Execution
18849 These are the asynchronous commands which generate the out-of-band
18850 record @samp{*stopped}. Currently @value{GDBN} only really executes
18851 asynchronously with remote targets and this interaction is mimicked in
18854 @subheading The @code{-exec-continue} Command
18855 @findex -exec-continue
18857 @subsubheading Synopsis
18863 Resumes the execution of the inferior program until a breakpoint is
18864 encountered, or until the inferior exits.
18866 @subsubheading @value{GDBN} Command
18868 The corresponding @value{GDBN} corresponding is @samp{continue}.
18870 @subsubheading Example
18877 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18878 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18883 @subheading The @code{-exec-finish} Command
18884 @findex -exec-finish
18886 @subsubheading Synopsis
18892 Resumes the execution of the inferior program until the current
18893 function is exited. Displays the results returned by the function.
18895 @subsubheading @value{GDBN} Command
18897 The corresponding @value{GDBN} command is @samp{finish}.
18899 @subsubheading Example
18901 Function returning @code{void}.
18908 *stopped,reason="function-finished",frame=@{func="main",args=[],
18909 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18913 Function returning other than @code{void}. The name of the internal
18914 @value{GDBN} variable storing the result is printed, together with the
18921 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18922 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18923 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18924 gdb-result-var="$1",return-value="0"
18929 @subheading The @code{-exec-interrupt} Command
18930 @findex -exec-interrupt
18932 @subsubheading Synopsis
18938 Interrupts the background execution of the target. Note how the token
18939 associated with the stop message is the one for the execution command
18940 that has been interrupted. The token for the interrupt itself only
18941 appears in the @samp{^done} output. If the user is trying to
18942 interrupt a non-running program, an error message will be printed.
18944 @subsubheading @value{GDBN} Command
18946 The corresponding @value{GDBN} command is @samp{interrupt}.
18948 @subsubheading Example
18959 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18960 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18961 fullname="/home/foo/bar/try.c",line="13"@}
18966 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18971 @subheading The @code{-exec-next} Command
18974 @subsubheading Synopsis
18980 Resumes execution of the inferior program, stopping when the beginning
18981 of the next source line is reached.
18983 @subsubheading @value{GDBN} Command
18985 The corresponding @value{GDBN} command is @samp{next}.
18987 @subsubheading Example
18993 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18998 @subheading The @code{-exec-next-instruction} Command
18999 @findex -exec-next-instruction
19001 @subsubheading Synopsis
19004 -exec-next-instruction
19007 Executes one machine instruction. If the instruction is a function
19008 call, continues until the function returns. If the program stops at an
19009 instruction in the middle of a source line, the address will be
19012 @subsubheading @value{GDBN} Command
19014 The corresponding @value{GDBN} command is @samp{nexti}.
19016 @subsubheading Example
19020 -exec-next-instruction
19024 *stopped,reason="end-stepping-range",
19025 addr="0x000100d4",line="5",file="hello.c"
19030 @subheading The @code{-exec-return} Command
19031 @findex -exec-return
19033 @subsubheading Synopsis
19039 Makes current function return immediately. Doesn't execute the inferior.
19040 Displays the new current frame.
19042 @subsubheading @value{GDBN} Command
19044 The corresponding @value{GDBN} command is @samp{return}.
19046 @subsubheading Example
19050 200-break-insert callee4
19051 200^done,bkpt=@{number="1",addr="0x00010734",
19052 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19057 000*stopped,reason="breakpoint-hit",bkptno="1",
19058 frame=@{func="callee4",args=[],
19059 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19060 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19066 111^done,frame=@{level="0",func="callee3",
19067 args=[@{name="strarg",
19068 value="0x11940 \"A string argument.\""@}],
19069 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19070 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19075 @subheading The @code{-exec-run} Command
19078 @subsubheading Synopsis
19084 Starts execution of the inferior from the beginning. The inferior
19085 executes until either a breakpoint is encountered or the program
19086 exits. In the latter case the output will include an exit code, if
19087 the program has exited exceptionally.
19089 @subsubheading @value{GDBN} Command
19091 The corresponding @value{GDBN} command is @samp{run}.
19093 @subsubheading Examples
19098 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19103 *stopped,reason="breakpoint-hit",bkptno="1",
19104 frame=@{func="main",args=[],file="recursive2.c",
19105 fullname="/home/foo/bar/recursive2.c",line="4"@}
19110 Program exited normally:
19118 *stopped,reason="exited-normally"
19123 Program exited exceptionally:
19131 *stopped,reason="exited",exit-code="01"
19135 Another way the program can terminate is if it receives a signal such as
19136 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19140 *stopped,reason="exited-signalled",signal-name="SIGINT",
19141 signal-meaning="Interrupt"
19145 @c @subheading -exec-signal
19148 @subheading The @code{-exec-step} Command
19151 @subsubheading Synopsis
19157 Resumes execution of the inferior program, stopping when the beginning
19158 of the next source line is reached, if the next source line is not a
19159 function call. If it is, stop at the first instruction of the called
19162 @subsubheading @value{GDBN} Command
19164 The corresponding @value{GDBN} command is @samp{step}.
19166 @subsubheading Example
19168 Stepping into a function:
19174 *stopped,reason="end-stepping-range",
19175 frame=@{func="foo",args=[@{name="a",value="10"@},
19176 @{name="b",value="0"@}],file="recursive2.c",
19177 fullname="/home/foo/bar/recursive2.c",line="11"@}
19187 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19192 @subheading The @code{-exec-step-instruction} Command
19193 @findex -exec-step-instruction
19195 @subsubheading Synopsis
19198 -exec-step-instruction
19201 Resumes the inferior which executes one machine instruction. The
19202 output, once @value{GDBN} has stopped, will vary depending on whether
19203 we have stopped in the middle of a source line or not. In the former
19204 case, the address at which the program stopped will be printed as
19207 @subsubheading @value{GDBN} Command
19209 The corresponding @value{GDBN} command is @samp{stepi}.
19211 @subsubheading Example
19215 -exec-step-instruction
19219 *stopped,reason="end-stepping-range",
19220 frame=@{func="foo",args=[],file="try.c",
19221 fullname="/home/foo/bar/try.c",line="10"@}
19223 -exec-step-instruction
19227 *stopped,reason="end-stepping-range",
19228 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19229 fullname="/home/foo/bar/try.c",line="10"@}
19234 @subheading The @code{-exec-until} Command
19235 @findex -exec-until
19237 @subsubheading Synopsis
19240 -exec-until [ @var{location} ]
19243 Executes the inferior until the @var{location} specified in the
19244 argument is reached. If there is no argument, the inferior executes
19245 until a source line greater than the current one is reached. The
19246 reason for stopping in this case will be @samp{location-reached}.
19248 @subsubheading @value{GDBN} Command
19250 The corresponding @value{GDBN} command is @samp{until}.
19252 @subsubheading Example
19256 -exec-until recursive2.c:6
19260 *stopped,reason="location-reached",frame=@{func="main",args=[],
19261 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19266 @subheading -file-clear
19267 Is this going away????
19270 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19271 @node GDB/MI Stack Manipulation
19272 @section @sc{gdb/mi} Stack Manipulation Commands
19275 @subheading The @code{-stack-info-frame} Command
19276 @findex -stack-info-frame
19278 @subsubheading Synopsis
19284 Get info on the selected frame.
19286 @subsubheading @value{GDBN} Command
19288 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19289 (without arguments).
19291 @subsubheading Example
19296 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19297 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19298 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19302 @subheading The @code{-stack-info-depth} Command
19303 @findex -stack-info-depth
19305 @subsubheading Synopsis
19308 -stack-info-depth [ @var{max-depth} ]
19311 Return the depth of the stack. If the integer argument @var{max-depth}
19312 is specified, do not count beyond @var{max-depth} frames.
19314 @subsubheading @value{GDBN} Command
19316 There's no equivalent @value{GDBN} command.
19318 @subsubheading Example
19320 For a stack with frame levels 0 through 11:
19327 -stack-info-depth 4
19330 -stack-info-depth 12
19333 -stack-info-depth 11
19336 -stack-info-depth 13
19341 @subheading The @code{-stack-list-arguments} Command
19342 @findex -stack-list-arguments
19344 @subsubheading Synopsis
19347 -stack-list-arguments @var{show-values}
19348 [ @var{low-frame} @var{high-frame} ]
19351 Display a list of the arguments for the frames between @var{low-frame}
19352 and @var{high-frame} (inclusive). If @var{low-frame} and
19353 @var{high-frame} are not provided, list the arguments for the whole
19354 call stack. If the two arguments are equal, show the single frame
19355 at the corresponding level. It is an error if @var{low-frame} is
19356 larger than the actual number of frames. On the other hand,
19357 @var{high-frame} may be larger than the actual number of frames, in
19358 which case only existing frames will be returned.
19360 The @var{show-values} argument must have a value of 0 or 1. A value of
19361 0 means that only the names of the arguments are listed, a value of 1
19362 means that both names and values of the arguments are printed.
19364 @subsubheading @value{GDBN} Command
19366 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19367 @samp{gdb_get_args} command which partially overlaps with the
19368 functionality of @samp{-stack-list-arguments}.
19370 @subsubheading Example
19377 frame=@{level="0",addr="0x00010734",func="callee4",
19378 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19379 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19380 frame=@{level="1",addr="0x0001076c",func="callee3",
19381 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19382 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19383 frame=@{level="2",addr="0x0001078c",func="callee2",
19384 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19385 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19386 frame=@{level="3",addr="0x000107b4",func="callee1",
19387 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19388 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19389 frame=@{level="4",addr="0x000107e0",func="main",
19390 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19391 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19393 -stack-list-arguments 0
19396 frame=@{level="0",args=[]@},
19397 frame=@{level="1",args=[name="strarg"]@},
19398 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19399 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19400 frame=@{level="4",args=[]@}]
19402 -stack-list-arguments 1
19405 frame=@{level="0",args=[]@},
19407 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19408 frame=@{level="2",args=[
19409 @{name="intarg",value="2"@},
19410 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19411 @{frame=@{level="3",args=[
19412 @{name="intarg",value="2"@},
19413 @{name="strarg",value="0x11940 \"A string argument.\""@},
19414 @{name="fltarg",value="3.5"@}]@},
19415 frame=@{level="4",args=[]@}]
19417 -stack-list-arguments 0 2 2
19418 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19420 -stack-list-arguments 1 2 2
19421 ^done,stack-args=[frame=@{level="2",
19422 args=[@{name="intarg",value="2"@},
19423 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19427 @c @subheading -stack-list-exception-handlers
19430 @subheading The @code{-stack-list-frames} Command
19431 @findex -stack-list-frames
19433 @subsubheading Synopsis
19436 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19439 List the frames currently on the stack. For each frame it displays the
19444 The frame number, 0 being the topmost frame, i.e., the innermost function.
19446 The @code{$pc} value for that frame.
19450 File name of the source file where the function lives.
19452 Line number corresponding to the @code{$pc}.
19455 If invoked without arguments, this command prints a backtrace for the
19456 whole stack. If given two integer arguments, it shows the frames whose
19457 levels are between the two arguments (inclusive). If the two arguments
19458 are equal, it shows the single frame at the corresponding level. It is
19459 an error if @var{low-frame} is larger than the actual number of
19460 frames. On the other hand, @var{high-frame} may be larger than the
19461 actual number of frames, in which case only existing frames will be returned.
19463 @subsubheading @value{GDBN} Command
19465 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19467 @subsubheading Example
19469 Full stack backtrace:
19475 [frame=@{level="0",addr="0x0001076c",func="foo",
19476 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19477 frame=@{level="1",addr="0x000107a4",func="foo",
19478 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19479 frame=@{level="2",addr="0x000107a4",func="foo",
19480 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19481 frame=@{level="3",addr="0x000107a4",func="foo",
19482 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19483 frame=@{level="4",addr="0x000107a4",func="foo",
19484 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19485 frame=@{level="5",addr="0x000107a4",func="foo",
19486 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19487 frame=@{level="6",addr="0x000107a4",func="foo",
19488 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19489 frame=@{level="7",addr="0x000107a4",func="foo",
19490 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19491 frame=@{level="8",addr="0x000107a4",func="foo",
19492 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19493 frame=@{level="9",addr="0x000107a4",func="foo",
19494 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19495 frame=@{level="10",addr="0x000107a4",func="foo",
19496 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19497 frame=@{level="11",addr="0x00010738",func="main",
19498 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19502 Show frames between @var{low_frame} and @var{high_frame}:
19506 -stack-list-frames 3 5
19508 [frame=@{level="3",addr="0x000107a4",func="foo",
19509 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19510 frame=@{level="4",addr="0x000107a4",func="foo",
19511 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19512 frame=@{level="5",addr="0x000107a4",func="foo",
19513 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19517 Show a single frame:
19521 -stack-list-frames 3 3
19523 [frame=@{level="3",addr="0x000107a4",func="foo",
19524 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19529 @subheading The @code{-stack-list-locals} Command
19530 @findex -stack-list-locals
19532 @subsubheading Synopsis
19535 -stack-list-locals @var{print-values}
19538 Display the local variable names for the selected frame. If
19539 @var{print-values} is 0 or @code{--no-values}, print only the names of
19540 the variables; if it is 1 or @code{--all-values}, print also their
19541 values; and if it is 2 or @code{--simple-values}, print the name,
19542 type and value for simple data types and the name and type for arrays,
19543 structures and unions. In this last case, a frontend can immediately
19544 display the value of simple data types and create variable objects for
19545 other data types when the user wishes to explore their values in
19548 @subsubheading @value{GDBN} Command
19550 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19552 @subsubheading Example
19556 -stack-list-locals 0
19557 ^done,locals=[name="A",name="B",name="C"]
19559 -stack-list-locals --all-values
19560 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19561 @{name="C",value="@{1, 2, 3@}"@}]
19562 -stack-list-locals --simple-values
19563 ^done,locals=[@{name="A",type="int",value="1"@},
19564 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19569 @subheading The @code{-stack-select-frame} Command
19570 @findex -stack-select-frame
19572 @subsubheading Synopsis
19575 -stack-select-frame @var{framenum}
19578 Change the selected frame. Select a different frame @var{framenum} on
19581 @subsubheading @value{GDBN} Command
19583 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19584 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19586 @subsubheading Example
19590 -stack-select-frame 2
19595 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19596 @node GDB/MI Variable Objects
19597 @section @sc{gdb/mi} Variable Objects
19601 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19603 For the implementation of a variable debugger window (locals, watched
19604 expressions, etc.), we are proposing the adaptation of the existing code
19605 used by @code{Insight}.
19607 The two main reasons for that are:
19611 It has been proven in practice (it is already on its second generation).
19614 It will shorten development time (needless to say how important it is
19618 The original interface was designed to be used by Tcl code, so it was
19619 slightly changed so it could be used through @sc{gdb/mi}. This section
19620 describes the @sc{gdb/mi} operations that will be available and gives some
19621 hints about their use.
19623 @emph{Note}: In addition to the set of operations described here, we
19624 expect the @sc{gui} implementation of a variable window to require, at
19625 least, the following operations:
19628 @item @code{-gdb-show} @code{output-radix}
19629 @item @code{-stack-list-arguments}
19630 @item @code{-stack-list-locals}
19631 @item @code{-stack-select-frame}
19636 @subheading Introduction to Variable Objects
19638 @cindex variable objects in @sc{gdb/mi}
19640 Variable objects are "object-oriented" MI interface for examining and
19641 changing values of expressions. Unlike some other MI interfaces that
19642 work with expressions, variable objects are specifically designed for
19643 simple and efficient presentation in the frontend. A variable object
19644 is identified by string name. When a variable object is created, the
19645 frontend specifies the expression for that variable object. The
19646 expression can be a simple variable, or it can be an arbitrary complex
19647 expression, and can even involve CPU registers. After creating a
19648 variable object, the frontend can invoke other variable object
19649 operations---for example to obtain or change the value of a variable
19650 object, or to change display format.
19652 Variable objects have hierarchical tree structure. Any variable object
19653 that corresponds to a composite type, such as structure in C, has
19654 a number of child variable objects, for example corresponding to each
19655 element of a structure. A child variable object can itself have
19656 children, recursively. Recursion ends when we reach
19657 leaf variable objects, which always have built-in types. Child variable
19658 objects are created only by explicit request, so if a frontend
19659 is not interested in the children of a particular variable object, no
19660 child will be created.
19662 For a leaf variable object it is possible to obtain its value as a
19663 string, or set the value from a string. String value can be also
19664 obtained for a non-leaf variable object, but it's generally a string
19665 that only indicates the type of the object, and does not list its
19666 contents. Assignment to a non-leaf variable object is not allowed.
19668 A frontend does not need to read the values of all variable objects each time
19669 the program stops. Instead, MI provides an update command that lists all
19670 variable objects whose values has changed since the last update
19671 operation. This considerably reduces the amount of data that must
19672 be transferred to the frontend. As noted above, children variable
19673 objects are created on demand, and only leaf variable objects have a
19674 real value. As result, gdb will read target memory only for leaf
19675 variables that frontend has created.
19677 The automatic update is not always desirable. For example, a frontend
19678 might want to keep a value of some expression for future reference,
19679 and never update it. For another example, fetching memory is
19680 relatively slow for embedded targets, so a frontend might want
19681 to disable automatic update for the variables that are either not
19682 visible on the screen, or ``closed''. This is possible using so
19683 called ``frozen variable objects''. Such variable objects are never
19684 implicitly updated.
19686 The following is the complete set of @sc{gdb/mi} operations defined to
19687 access this functionality:
19689 @multitable @columnfractions .4 .6
19690 @item @strong{Operation}
19691 @tab @strong{Description}
19693 @item @code{-var-create}
19694 @tab create a variable object
19695 @item @code{-var-delete}
19696 @tab delete the variable object and/or its children
19697 @item @code{-var-set-format}
19698 @tab set the display format of this variable
19699 @item @code{-var-show-format}
19700 @tab show the display format of this variable
19701 @item @code{-var-info-num-children}
19702 @tab tells how many children this object has
19703 @item @code{-var-list-children}
19704 @tab return a list of the object's children
19705 @item @code{-var-info-type}
19706 @tab show the type of this variable object
19707 @item @code{-var-info-expression}
19708 @tab print parent-relative expression that this variable object represents
19709 @item @code{-var-info-path-expression}
19710 @tab print full expression that this variable object represents
19711 @item @code{-var-show-attributes}
19712 @tab is this variable editable? does it exist here?
19713 @item @code{-var-evaluate-expression}
19714 @tab get the value of this variable
19715 @item @code{-var-assign}
19716 @tab set the value of this variable
19717 @item @code{-var-update}
19718 @tab update the variable and its children
19719 @item @code{-var-set-frozen}
19720 @tab set frozeness attribute
19723 In the next subsection we describe each operation in detail and suggest
19724 how it can be used.
19726 @subheading Description And Use of Operations on Variable Objects
19728 @subheading The @code{-var-create} Command
19729 @findex -var-create
19731 @subsubheading Synopsis
19734 -var-create @{@var{name} | "-"@}
19735 @{@var{frame-addr} | "*"@} @var{expression}
19738 This operation creates a variable object, which allows the monitoring of
19739 a variable, the result of an expression, a memory cell or a CPU
19742 The @var{name} parameter is the string by which the object can be
19743 referenced. It must be unique. If @samp{-} is specified, the varobj
19744 system will generate a string ``varNNNNNN'' automatically. It will be
19745 unique provided that one does not specify @var{name} on that format.
19746 The command fails if a duplicate name is found.
19748 The frame under which the expression should be evaluated can be
19749 specified by @var{frame-addr}. A @samp{*} indicates that the current
19750 frame should be used.
19752 @var{expression} is any expression valid on the current language set (must not
19753 begin with a @samp{*}), or one of the following:
19757 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19760 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19763 @samp{$@var{regname}} --- a CPU register name
19766 @subsubheading Result
19768 This operation returns the name, number of children and the type of the
19769 object created. Type is returned as a string as the ones generated by
19770 the @value{GDBN} CLI:
19773 name="@var{name}",numchild="N",type="@var{type}"
19777 @subheading The @code{-var-delete} Command
19778 @findex -var-delete
19780 @subsubheading Synopsis
19783 -var-delete [ -c ] @var{name}
19786 Deletes a previously created variable object and all of its children.
19787 With the @samp{-c} option, just deletes the children.
19789 Returns an error if the object @var{name} is not found.
19792 @subheading The @code{-var-set-format} Command
19793 @findex -var-set-format
19795 @subsubheading Synopsis
19798 -var-set-format @var{name} @var{format-spec}
19801 Sets the output format for the value of the object @var{name} to be
19804 The syntax for the @var{format-spec} is as follows:
19807 @var{format-spec} @expansion{}
19808 @{binary | decimal | hexadecimal | octal | natural@}
19811 The natural format is the default format choosen automatically
19812 based on the variable type (like decimal for an @code{int}, hex
19813 for pointers, etc.).
19815 For a variable with children, the format is set only on the
19816 variable itself, and the children are not affected.
19818 @subheading The @code{-var-show-format} Command
19819 @findex -var-show-format
19821 @subsubheading Synopsis
19824 -var-show-format @var{name}
19827 Returns the format used to display the value of the object @var{name}.
19830 @var{format} @expansion{}
19835 @subheading The @code{-var-info-num-children} Command
19836 @findex -var-info-num-children
19838 @subsubheading Synopsis
19841 -var-info-num-children @var{name}
19844 Returns the number of children of a variable object @var{name}:
19851 @subheading The @code{-var-list-children} Command
19852 @findex -var-list-children
19854 @subsubheading Synopsis
19857 -var-list-children [@var{print-values}] @var{name}
19859 @anchor{-var-list-children}
19861 Return a list of the children of the specified variable object and
19862 create variable objects for them, if they do not already exist. With
19863 a single argument or if @var{print-values} has a value for of 0 or
19864 @code{--no-values}, print only the names of the variables; if
19865 @var{print-values} is 1 or @code{--all-values}, also print their
19866 values; and if it is 2 or @code{--simple-values} print the name and
19867 value for simple data types and just the name for arrays, structures
19870 @subsubheading Example
19874 -var-list-children n
19875 ^done,numchild=@var{n},children=[@{name=@var{name},
19876 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19878 -var-list-children --all-values n
19879 ^done,numchild=@var{n},children=[@{name=@var{name},
19880 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19884 @subheading The @code{-var-info-type} Command
19885 @findex -var-info-type
19887 @subsubheading Synopsis
19890 -var-info-type @var{name}
19893 Returns the type of the specified variable @var{name}. The type is
19894 returned as a string in the same format as it is output by the
19898 type=@var{typename}
19902 @subheading The @code{-var-info-expression} Command
19903 @findex -var-info-expression
19905 @subsubheading Synopsis
19908 -var-info-expression @var{name}
19911 Returns a string that is suitable for presenting this
19912 variable object in user interface. The string is generally
19913 not valid expression in the current language, and cannot be evaluated.
19915 For example, if @code{a} is an array, and variable object
19916 @code{A} was created for @code{a}, then we'll get this output:
19919 (gdb) -var-info-expression A.1
19920 ^done,lang="C",exp="1"
19924 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
19926 Note that the output of the @code{-var-list-children} command also
19927 includes those expressions, so the @code{-var-info-expression} command
19930 @subheading The @code{-var-info-path-expression} Command
19931 @findex -var-info-path-expression
19933 @subsubheading Synopsis
19936 -var-info-path-expression @var{name}
19939 Returns an expression that can be evaluated in the current
19940 context and will yield the same value that a variable object has.
19941 Compare this with the @code{-var-info-expression} command, which
19942 result can be used only for UI presentation. Typical use of
19943 the @code{-var-info-path-expression} command is creating a
19944 watchpoint from a variable object.
19946 For example, suppose @code{C} is a C@t{++} class, derived from class
19947 @code{Base}, and that the @code{Base} class has a member called
19948 @code{m_size}. Assume a variable @code{c} is has the type of
19949 @code{C} and a variable object @code{C} was created for variable
19950 @code{c}. Then, we'll get this output:
19952 (gdb) -var-info-path-expression C.Base.public.m_size
19953 ^done,path_expr=((Base)c).m_size)
19956 @subheading The @code{-var-show-attributes} Command
19957 @findex -var-show-attributes
19959 @subsubheading Synopsis
19962 -var-show-attributes @var{name}
19965 List attributes of the specified variable object @var{name}:
19968 status=@var{attr} [ ( ,@var{attr} )* ]
19972 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19974 @subheading The @code{-var-evaluate-expression} Command
19975 @findex -var-evaluate-expression
19977 @subsubheading Synopsis
19980 -var-evaluate-expression @var{name}
19983 Evaluates the expression that is represented by the specified variable
19984 object and returns its value as a string. The format of the
19985 string can be changed using the @code{-var-set-format} command.
19991 Note that one must invoke @code{-var-list-children} for a variable
19992 before the value of a child variable can be evaluated.
19994 @subheading The @code{-var-assign} Command
19995 @findex -var-assign
19997 @subsubheading Synopsis
20000 -var-assign @var{name} @var{expression}
20003 Assigns the value of @var{expression} to the variable object specified
20004 by @var{name}. The object must be @samp{editable}. If the variable's
20005 value is altered by the assign, the variable will show up in any
20006 subsequent @code{-var-update} list.
20008 @subsubheading Example
20016 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20020 @subheading The @code{-var-update} Command
20021 @findex -var-update
20023 @subsubheading Synopsis
20026 -var-update [@var{print-values}] @{@var{name} | "*"@}
20029 Reevaluate the expressions corresponding to the variable object
20030 @var{name} and all its direct and indirect children, and return the
20031 list of variable objects whose values have changed; @var{name} must
20032 be a root variable object. Here, ``changed'' means that the result of
20033 @code{-var-evaluate-expression} before and after the
20034 @code{-var-update} is different. If @samp{*} is used as the variable
20035 object names, all existing variable objects are updated, except
20036 for frozen ones (@pxref{-var-set-frozen}). The option
20037 @var{print-values} determines whether both names and values, or just
20038 names are printed. The possible values of this options are the same
20039 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
20040 recommended to use the @samp{--all-values} option, to reduce the
20041 number of MI commands needed on each program stop.
20044 @subsubheading Example
20051 -var-update --all-values var1
20052 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20053 type_changed="false"@}]
20057 @anchor{-var-update}
20058 The field in_scope may take three values:
20062 The variable object's current value is valid.
20065 The variable object does not currently hold a valid value but it may
20066 hold one in the future if its associated expression comes back into
20070 The variable object no longer holds a valid value.
20071 This can occur when the executable file being debugged has changed,
20072 either through recompilation or by using the @value{GDBN} @code{file}
20073 command. The front end should normally choose to delete these variable
20077 In the future new values may be added to this list so the front should
20078 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
20080 @subheading The @code{-var-set-frozen} Command
20081 @findex -var-set-frozen
20082 @anchor{-var-set-frozen}
20084 @subsubheading Synopsis
20087 -var-set-frozen @var{name} @var{flag}
20090 Set the frozenness flag on the variable object @var{name}. The
20091 @var{flag} parameter should be either @samp{1} to make the variable
20092 frozen or @samp{0} to make it unfrozen. If a variable object is
20093 frozen, then neither itself, nor any of its children, are
20094 implicitly updated by @code{-var-update} of
20095 a parent variable or by @code{-var-update *}. Only
20096 @code{-var-update} of the variable itself will update its value and
20097 values of its children. After a variable object is unfrozen, it is
20098 implicitly updated by all subsequent @code{-var-update} operations.
20099 Unfreezing a variable does not update it, only subsequent
20100 @code{-var-update} does.
20102 @subsubheading Example
20106 -var-set-frozen V 1
20112 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20113 @node GDB/MI Data Manipulation
20114 @section @sc{gdb/mi} Data Manipulation
20116 @cindex data manipulation, in @sc{gdb/mi}
20117 @cindex @sc{gdb/mi}, data manipulation
20118 This section describes the @sc{gdb/mi} commands that manipulate data:
20119 examine memory and registers, evaluate expressions, etc.
20121 @c REMOVED FROM THE INTERFACE.
20122 @c @subheading -data-assign
20123 @c Change the value of a program variable. Plenty of side effects.
20124 @c @subsubheading GDB Command
20126 @c @subsubheading Example
20129 @subheading The @code{-data-disassemble} Command
20130 @findex -data-disassemble
20132 @subsubheading Synopsis
20136 [ -s @var{start-addr} -e @var{end-addr} ]
20137 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20145 @item @var{start-addr}
20146 is the beginning address (or @code{$pc})
20147 @item @var{end-addr}
20149 @item @var{filename}
20150 is the name of the file to disassemble
20151 @item @var{linenum}
20152 is the line number to disassemble around
20154 is the number of disassembly lines to be produced. If it is -1,
20155 the whole function will be disassembled, in case no @var{end-addr} is
20156 specified. If @var{end-addr} is specified as a non-zero value, and
20157 @var{lines} is lower than the number of disassembly lines between
20158 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20159 displayed; if @var{lines} is higher than the number of lines between
20160 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20163 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20167 @subsubheading Result
20169 The output for each instruction is composed of four fields:
20178 Note that whatever included in the instruction field, is not manipulated
20179 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20181 @subsubheading @value{GDBN} Command
20183 There's no direct mapping from this command to the CLI.
20185 @subsubheading Example
20187 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20191 -data-disassemble -s $pc -e "$pc + 20" -- 0
20194 @{address="0x000107c0",func-name="main",offset="4",
20195 inst="mov 2, %o0"@},
20196 @{address="0x000107c4",func-name="main",offset="8",
20197 inst="sethi %hi(0x11800), %o2"@},
20198 @{address="0x000107c8",func-name="main",offset="12",
20199 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20200 @{address="0x000107cc",func-name="main",offset="16",
20201 inst="sethi %hi(0x11800), %o2"@},
20202 @{address="0x000107d0",func-name="main",offset="20",
20203 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20207 Disassemble the whole @code{main} function. Line 32 is part of
20211 -data-disassemble -f basics.c -l 32 -- 0
20213 @{address="0x000107bc",func-name="main",offset="0",
20214 inst="save %sp, -112, %sp"@},
20215 @{address="0x000107c0",func-name="main",offset="4",
20216 inst="mov 2, %o0"@},
20217 @{address="0x000107c4",func-name="main",offset="8",
20218 inst="sethi %hi(0x11800), %o2"@},
20220 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20221 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20225 Disassemble 3 instructions from the start of @code{main}:
20229 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20231 @{address="0x000107bc",func-name="main",offset="0",
20232 inst="save %sp, -112, %sp"@},
20233 @{address="0x000107c0",func-name="main",offset="4",
20234 inst="mov 2, %o0"@},
20235 @{address="0x000107c4",func-name="main",offset="8",
20236 inst="sethi %hi(0x11800), %o2"@}]
20240 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20244 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20246 src_and_asm_line=@{line="31",
20247 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20248 testsuite/gdb.mi/basics.c",line_asm_insn=[
20249 @{address="0x000107bc",func-name="main",offset="0",
20250 inst="save %sp, -112, %sp"@}]@},
20251 src_and_asm_line=@{line="32",
20252 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20253 testsuite/gdb.mi/basics.c",line_asm_insn=[
20254 @{address="0x000107c0",func-name="main",offset="4",
20255 inst="mov 2, %o0"@},
20256 @{address="0x000107c4",func-name="main",offset="8",
20257 inst="sethi %hi(0x11800), %o2"@}]@}]
20262 @subheading The @code{-data-evaluate-expression} Command
20263 @findex -data-evaluate-expression
20265 @subsubheading Synopsis
20268 -data-evaluate-expression @var{expr}
20271 Evaluate @var{expr} as an expression. The expression could contain an
20272 inferior function call. The function call will execute synchronously.
20273 If the expression contains spaces, it must be enclosed in double quotes.
20275 @subsubheading @value{GDBN} Command
20277 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20278 @samp{call}. In @code{gdbtk} only, there's a corresponding
20279 @samp{gdb_eval} command.
20281 @subsubheading Example
20283 In the following example, the numbers that precede the commands are the
20284 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20285 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20289 211-data-evaluate-expression A
20292 311-data-evaluate-expression &A
20293 311^done,value="0xefffeb7c"
20295 411-data-evaluate-expression A+3
20298 511-data-evaluate-expression "A + 3"
20304 @subheading The @code{-data-list-changed-registers} Command
20305 @findex -data-list-changed-registers
20307 @subsubheading Synopsis
20310 -data-list-changed-registers
20313 Display a list of the registers that have changed.
20315 @subsubheading @value{GDBN} Command
20317 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20318 has the corresponding command @samp{gdb_changed_register_list}.
20320 @subsubheading Example
20322 On a PPC MBX board:
20330 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20331 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20333 -data-list-changed-registers
20334 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20335 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20336 "24","25","26","27","28","30","31","64","65","66","67","69"]
20341 @subheading The @code{-data-list-register-names} Command
20342 @findex -data-list-register-names
20344 @subsubheading Synopsis
20347 -data-list-register-names [ ( @var{regno} )+ ]
20350 Show a list of register names for the current target. If no arguments
20351 are given, it shows a list of the names of all the registers. If
20352 integer numbers are given as arguments, it will print a list of the
20353 names of the registers corresponding to the arguments. To ensure
20354 consistency between a register name and its number, the output list may
20355 include empty register names.
20357 @subsubheading @value{GDBN} Command
20359 @value{GDBN} does not have a command which corresponds to
20360 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20361 corresponding command @samp{gdb_regnames}.
20363 @subsubheading Example
20365 For the PPC MBX board:
20368 -data-list-register-names
20369 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20370 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20371 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20372 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20373 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20374 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20375 "", "pc","ps","cr","lr","ctr","xer"]
20377 -data-list-register-names 1 2 3
20378 ^done,register-names=["r1","r2","r3"]
20382 @subheading The @code{-data-list-register-values} Command
20383 @findex -data-list-register-values
20385 @subsubheading Synopsis
20388 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20391 Display the registers' contents. @var{fmt} is the format according to
20392 which the registers' contents are to be returned, followed by an optional
20393 list of numbers specifying the registers to display. A missing list of
20394 numbers indicates that the contents of all the registers must be returned.
20396 Allowed formats for @var{fmt} are:
20413 @subsubheading @value{GDBN} Command
20415 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20416 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20418 @subsubheading Example
20420 For a PPC MBX board (note: line breaks are for readability only, they
20421 don't appear in the actual output):
20425 -data-list-register-values r 64 65
20426 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20427 @{number="65",value="0x00029002"@}]
20429 -data-list-register-values x
20430 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20431 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20432 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20433 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20434 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20435 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20436 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20437 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20438 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20439 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20440 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20441 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20442 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20443 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20444 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20445 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20446 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20447 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20448 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20449 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20450 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20451 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20452 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20453 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20454 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20455 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20456 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20457 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20458 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20459 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20460 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20461 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20462 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20463 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20464 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20465 @{number="69",value="0x20002b03"@}]
20470 @subheading The @code{-data-read-memory} Command
20471 @findex -data-read-memory
20473 @subsubheading Synopsis
20476 -data-read-memory [ -o @var{byte-offset} ]
20477 @var{address} @var{word-format} @var{word-size}
20478 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20485 @item @var{address}
20486 An expression specifying the address of the first memory word to be
20487 read. Complex expressions containing embedded white space should be
20488 quoted using the C convention.
20490 @item @var{word-format}
20491 The format to be used to print the memory words. The notation is the
20492 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20495 @item @var{word-size}
20496 The size of each memory word in bytes.
20498 @item @var{nr-rows}
20499 The number of rows in the output table.
20501 @item @var{nr-cols}
20502 The number of columns in the output table.
20505 If present, indicates that each row should include an @sc{ascii} dump. The
20506 value of @var{aschar} is used as a padding character when a byte is not a
20507 member of the printable @sc{ascii} character set (printable @sc{ascii}
20508 characters are those whose code is between 32 and 126, inclusively).
20510 @item @var{byte-offset}
20511 An offset to add to the @var{address} before fetching memory.
20514 This command displays memory contents as a table of @var{nr-rows} by
20515 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20516 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20517 (returned as @samp{total-bytes}). Should less than the requested number
20518 of bytes be returned by the target, the missing words are identified
20519 using @samp{N/A}. The number of bytes read from the target is returned
20520 in @samp{nr-bytes} and the starting address used to read memory in
20523 The address of the next/previous row or page is available in
20524 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20527 @subsubheading @value{GDBN} Command
20529 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20530 @samp{gdb_get_mem} memory read command.
20532 @subsubheading Example
20534 Read six bytes of memory starting at @code{bytes+6} but then offset by
20535 @code{-6} bytes. Format as three rows of two columns. One byte per
20536 word. Display each word in hex.
20540 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20541 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20542 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20543 prev-page="0x0000138a",memory=[
20544 @{addr="0x00001390",data=["0x00","0x01"]@},
20545 @{addr="0x00001392",data=["0x02","0x03"]@},
20546 @{addr="0x00001394",data=["0x04","0x05"]@}]
20550 Read two bytes of memory starting at address @code{shorts + 64} and
20551 display as a single word formatted in decimal.
20555 5-data-read-memory shorts+64 d 2 1 1
20556 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20557 next-row="0x00001512",prev-row="0x0000150e",
20558 next-page="0x00001512",prev-page="0x0000150e",memory=[
20559 @{addr="0x00001510",data=["128"]@}]
20563 Read thirty two bytes of memory starting at @code{bytes+16} and format
20564 as eight rows of four columns. Include a string encoding with @samp{x}
20565 used as the non-printable character.
20569 4-data-read-memory bytes+16 x 1 8 4 x
20570 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20571 next-row="0x000013c0",prev-row="0x0000139c",
20572 next-page="0x000013c0",prev-page="0x00001380",memory=[
20573 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20574 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20575 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20576 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20577 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20578 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20579 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20580 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20584 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20585 @node GDB/MI Tracepoint Commands
20586 @section @sc{gdb/mi} Tracepoint Commands
20588 The tracepoint commands are not yet implemented.
20590 @c @subheading -trace-actions
20592 @c @subheading -trace-delete
20594 @c @subheading -trace-disable
20596 @c @subheading -trace-dump
20598 @c @subheading -trace-enable
20600 @c @subheading -trace-exists
20602 @c @subheading -trace-find
20604 @c @subheading -trace-frame-number
20606 @c @subheading -trace-info
20608 @c @subheading -trace-insert
20610 @c @subheading -trace-list
20612 @c @subheading -trace-pass-count
20614 @c @subheading -trace-save
20616 @c @subheading -trace-start
20618 @c @subheading -trace-stop
20621 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20622 @node GDB/MI Symbol Query
20623 @section @sc{gdb/mi} Symbol Query Commands
20626 @subheading The @code{-symbol-info-address} Command
20627 @findex -symbol-info-address
20629 @subsubheading Synopsis
20632 -symbol-info-address @var{symbol}
20635 Describe where @var{symbol} is stored.
20637 @subsubheading @value{GDBN} Command
20639 The corresponding @value{GDBN} command is @samp{info address}.
20641 @subsubheading Example
20645 @subheading The @code{-symbol-info-file} Command
20646 @findex -symbol-info-file
20648 @subsubheading Synopsis
20654 Show the file for the symbol.
20656 @subsubheading @value{GDBN} Command
20658 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20659 @samp{gdb_find_file}.
20661 @subsubheading Example
20665 @subheading The @code{-symbol-info-function} Command
20666 @findex -symbol-info-function
20668 @subsubheading Synopsis
20671 -symbol-info-function
20674 Show which function the symbol lives in.
20676 @subsubheading @value{GDBN} Command
20678 @samp{gdb_get_function} in @code{gdbtk}.
20680 @subsubheading Example
20684 @subheading The @code{-symbol-info-line} Command
20685 @findex -symbol-info-line
20687 @subsubheading Synopsis
20693 Show the core addresses of the code for a source line.
20695 @subsubheading @value{GDBN} Command
20697 The corresponding @value{GDBN} command is @samp{info line}.
20698 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20700 @subsubheading Example
20704 @subheading The @code{-symbol-info-symbol} Command
20705 @findex -symbol-info-symbol
20707 @subsubheading Synopsis
20710 -symbol-info-symbol @var{addr}
20713 Describe what symbol is at location @var{addr}.
20715 @subsubheading @value{GDBN} Command
20717 The corresponding @value{GDBN} command is @samp{info symbol}.
20719 @subsubheading Example
20723 @subheading The @code{-symbol-list-functions} Command
20724 @findex -symbol-list-functions
20726 @subsubheading Synopsis
20729 -symbol-list-functions
20732 List the functions in the executable.
20734 @subsubheading @value{GDBN} Command
20736 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20737 @samp{gdb_search} in @code{gdbtk}.
20739 @subsubheading Example
20743 @subheading The @code{-symbol-list-lines} Command
20744 @findex -symbol-list-lines
20746 @subsubheading Synopsis
20749 -symbol-list-lines @var{filename}
20752 Print the list of lines that contain code and their associated program
20753 addresses for the given source filename. The entries are sorted in
20754 ascending PC order.
20756 @subsubheading @value{GDBN} Command
20758 There is no corresponding @value{GDBN} command.
20760 @subsubheading Example
20763 -symbol-list-lines basics.c
20764 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20769 @subheading The @code{-symbol-list-types} Command
20770 @findex -symbol-list-types
20772 @subsubheading Synopsis
20778 List all the type names.
20780 @subsubheading @value{GDBN} Command
20782 The corresponding commands are @samp{info types} in @value{GDBN},
20783 @samp{gdb_search} in @code{gdbtk}.
20785 @subsubheading Example
20789 @subheading The @code{-symbol-list-variables} Command
20790 @findex -symbol-list-variables
20792 @subsubheading Synopsis
20795 -symbol-list-variables
20798 List all the global and static variable names.
20800 @subsubheading @value{GDBN} Command
20802 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20804 @subsubheading Example
20808 @subheading The @code{-symbol-locate} Command
20809 @findex -symbol-locate
20811 @subsubheading Synopsis
20817 @subsubheading @value{GDBN} Command
20819 @samp{gdb_loc} in @code{gdbtk}.
20821 @subsubheading Example
20825 @subheading The @code{-symbol-type} Command
20826 @findex -symbol-type
20828 @subsubheading Synopsis
20831 -symbol-type @var{variable}
20834 Show type of @var{variable}.
20836 @subsubheading @value{GDBN} Command
20838 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20839 @samp{gdb_obj_variable}.
20841 @subsubheading Example
20845 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20846 @node GDB/MI File Commands
20847 @section @sc{gdb/mi} File Commands
20849 This section describes the GDB/MI commands to specify executable file names
20850 and to read in and obtain symbol table information.
20852 @subheading The @code{-file-exec-and-symbols} Command
20853 @findex -file-exec-and-symbols
20855 @subsubheading Synopsis
20858 -file-exec-and-symbols @var{file}
20861 Specify the executable file to be debugged. This file is the one from
20862 which the symbol table is also read. If no file is specified, the
20863 command clears the executable and symbol information. If breakpoints
20864 are set when using this command with no arguments, @value{GDBN} will produce
20865 error messages. Otherwise, no output is produced, except a completion
20868 @subsubheading @value{GDBN} Command
20870 The corresponding @value{GDBN} command is @samp{file}.
20872 @subsubheading Example
20876 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20882 @subheading The @code{-file-exec-file} Command
20883 @findex -file-exec-file
20885 @subsubheading Synopsis
20888 -file-exec-file @var{file}
20891 Specify the executable file to be debugged. Unlike
20892 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20893 from this file. If used without argument, @value{GDBN} clears the information
20894 about the executable file. No output is produced, except a completion
20897 @subsubheading @value{GDBN} Command
20899 The corresponding @value{GDBN} command is @samp{exec-file}.
20901 @subsubheading Example
20905 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20911 @subheading The @code{-file-list-exec-sections} Command
20912 @findex -file-list-exec-sections
20914 @subsubheading Synopsis
20917 -file-list-exec-sections
20920 List the sections of the current executable file.
20922 @subsubheading @value{GDBN} Command
20924 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20925 information as this command. @code{gdbtk} has a corresponding command
20926 @samp{gdb_load_info}.
20928 @subsubheading Example
20932 @subheading The @code{-file-list-exec-source-file} Command
20933 @findex -file-list-exec-source-file
20935 @subsubheading Synopsis
20938 -file-list-exec-source-file
20941 List the line number, the current source file, and the absolute path
20942 to the current source file for the current executable.
20944 @subsubheading @value{GDBN} Command
20946 The @value{GDBN} equivalent is @samp{info source}
20948 @subsubheading Example
20952 123-file-list-exec-source-file
20953 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20958 @subheading The @code{-file-list-exec-source-files} Command
20959 @findex -file-list-exec-source-files
20961 @subsubheading Synopsis
20964 -file-list-exec-source-files
20967 List the source files for the current executable.
20969 It will always output the filename, but only when @value{GDBN} can find
20970 the absolute file name of a source file, will it output the fullname.
20972 @subsubheading @value{GDBN} Command
20974 The @value{GDBN} equivalent is @samp{info sources}.
20975 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20977 @subsubheading Example
20980 -file-list-exec-source-files
20982 @{file=foo.c,fullname=/home/foo.c@},
20983 @{file=/home/bar.c,fullname=/home/bar.c@},
20984 @{file=gdb_could_not_find_fullpath.c@}]
20988 @subheading The @code{-file-list-shared-libraries} Command
20989 @findex -file-list-shared-libraries
20991 @subsubheading Synopsis
20994 -file-list-shared-libraries
20997 List the shared libraries in the program.
20999 @subsubheading @value{GDBN} Command
21001 The corresponding @value{GDBN} command is @samp{info shared}.
21003 @subsubheading Example
21007 @subheading The @code{-file-list-symbol-files} Command
21008 @findex -file-list-symbol-files
21010 @subsubheading Synopsis
21013 -file-list-symbol-files
21018 @subsubheading @value{GDBN} Command
21020 The corresponding @value{GDBN} command is @samp{info file} (part of it).
21022 @subsubheading Example
21026 @subheading The @code{-file-symbol-file} Command
21027 @findex -file-symbol-file
21029 @subsubheading Synopsis
21032 -file-symbol-file @var{file}
21035 Read symbol table info from the specified @var{file} argument. When
21036 used without arguments, clears @value{GDBN}'s symbol table info. No output is
21037 produced, except for a completion notification.
21039 @subsubheading @value{GDBN} Command
21041 The corresponding @value{GDBN} command is @samp{symbol-file}.
21043 @subsubheading Example
21047 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21053 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21054 @node GDB/MI Memory Overlay Commands
21055 @section @sc{gdb/mi} Memory Overlay Commands
21057 The memory overlay commands are not implemented.
21059 @c @subheading -overlay-auto
21061 @c @subheading -overlay-list-mapping-state
21063 @c @subheading -overlay-list-overlays
21065 @c @subheading -overlay-map
21067 @c @subheading -overlay-off
21069 @c @subheading -overlay-on
21071 @c @subheading -overlay-unmap
21073 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21074 @node GDB/MI Signal Handling Commands
21075 @section @sc{gdb/mi} Signal Handling Commands
21077 Signal handling commands are not implemented.
21079 @c @subheading -signal-handle
21081 @c @subheading -signal-list-handle-actions
21083 @c @subheading -signal-list-signal-types
21087 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21088 @node GDB/MI Target Manipulation
21089 @section @sc{gdb/mi} Target Manipulation Commands
21092 @subheading The @code{-target-attach} Command
21093 @findex -target-attach
21095 @subsubheading Synopsis
21098 -target-attach @var{pid} | @var{file}
21101 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
21103 @subsubheading @value{GDBN} Command
21105 The corresponding @value{GDBN} command is @samp{attach}.
21107 @subsubheading Example
21111 @subheading The @code{-target-compare-sections} Command
21112 @findex -target-compare-sections
21114 @subsubheading Synopsis
21117 -target-compare-sections [ @var{section} ]
21120 Compare data of section @var{section} on target to the exec file.
21121 Without the argument, all sections are compared.
21123 @subsubheading @value{GDBN} Command
21125 The @value{GDBN} equivalent is @samp{compare-sections}.
21127 @subsubheading Example
21131 @subheading The @code{-target-detach} Command
21132 @findex -target-detach
21134 @subsubheading Synopsis
21140 Detach from the remote target which normally resumes its execution.
21143 @subsubheading @value{GDBN} Command
21145 The corresponding @value{GDBN} command is @samp{detach}.
21147 @subsubheading Example
21157 @subheading The @code{-target-disconnect} Command
21158 @findex -target-disconnect
21160 @subsubheading Synopsis
21166 Disconnect from the remote target. There's no output and the target is
21167 generally not resumed.
21169 @subsubheading @value{GDBN} Command
21171 The corresponding @value{GDBN} command is @samp{disconnect}.
21173 @subsubheading Example
21183 @subheading The @code{-target-download} Command
21184 @findex -target-download
21186 @subsubheading Synopsis
21192 Loads the executable onto the remote target.
21193 It prints out an update message every half second, which includes the fields:
21197 The name of the section.
21199 The size of what has been sent so far for that section.
21201 The size of the section.
21203 The total size of what was sent so far (the current and the previous sections).
21205 The size of the overall executable to download.
21209 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21210 @sc{gdb/mi} Output Syntax}).
21212 In addition, it prints the name and size of the sections, as they are
21213 downloaded. These messages include the following fields:
21217 The name of the section.
21219 The size of the section.
21221 The size of the overall executable to download.
21225 At the end, a summary is printed.
21227 @subsubheading @value{GDBN} Command
21229 The corresponding @value{GDBN} command is @samp{load}.
21231 @subsubheading Example
21233 Note: each status message appears on a single line. Here the messages
21234 have been broken down so that they can fit onto a page.
21239 +download,@{section=".text",section-size="6668",total-size="9880"@}
21240 +download,@{section=".text",section-sent="512",section-size="6668",
21241 total-sent="512",total-size="9880"@}
21242 +download,@{section=".text",section-sent="1024",section-size="6668",
21243 total-sent="1024",total-size="9880"@}
21244 +download,@{section=".text",section-sent="1536",section-size="6668",
21245 total-sent="1536",total-size="9880"@}
21246 +download,@{section=".text",section-sent="2048",section-size="6668",
21247 total-sent="2048",total-size="9880"@}
21248 +download,@{section=".text",section-sent="2560",section-size="6668",
21249 total-sent="2560",total-size="9880"@}
21250 +download,@{section=".text",section-sent="3072",section-size="6668",
21251 total-sent="3072",total-size="9880"@}
21252 +download,@{section=".text",section-sent="3584",section-size="6668",
21253 total-sent="3584",total-size="9880"@}
21254 +download,@{section=".text",section-sent="4096",section-size="6668",
21255 total-sent="4096",total-size="9880"@}
21256 +download,@{section=".text",section-sent="4608",section-size="6668",
21257 total-sent="4608",total-size="9880"@}
21258 +download,@{section=".text",section-sent="5120",section-size="6668",
21259 total-sent="5120",total-size="9880"@}
21260 +download,@{section=".text",section-sent="5632",section-size="6668",
21261 total-sent="5632",total-size="9880"@}
21262 +download,@{section=".text",section-sent="6144",section-size="6668",
21263 total-sent="6144",total-size="9880"@}
21264 +download,@{section=".text",section-sent="6656",section-size="6668",
21265 total-sent="6656",total-size="9880"@}
21266 +download,@{section=".init",section-size="28",total-size="9880"@}
21267 +download,@{section=".fini",section-size="28",total-size="9880"@}
21268 +download,@{section=".data",section-size="3156",total-size="9880"@}
21269 +download,@{section=".data",section-sent="512",section-size="3156",
21270 total-sent="7236",total-size="9880"@}
21271 +download,@{section=".data",section-sent="1024",section-size="3156",
21272 total-sent="7748",total-size="9880"@}
21273 +download,@{section=".data",section-sent="1536",section-size="3156",
21274 total-sent="8260",total-size="9880"@}
21275 +download,@{section=".data",section-sent="2048",section-size="3156",
21276 total-sent="8772",total-size="9880"@}
21277 +download,@{section=".data",section-sent="2560",section-size="3156",
21278 total-sent="9284",total-size="9880"@}
21279 +download,@{section=".data",section-sent="3072",section-size="3156",
21280 total-sent="9796",total-size="9880"@}
21281 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21287 @subheading The @code{-target-exec-status} Command
21288 @findex -target-exec-status
21290 @subsubheading Synopsis
21293 -target-exec-status
21296 Provide information on the state of the target (whether it is running or
21297 not, for instance).
21299 @subsubheading @value{GDBN} Command
21301 There's no equivalent @value{GDBN} command.
21303 @subsubheading Example
21307 @subheading The @code{-target-list-available-targets} Command
21308 @findex -target-list-available-targets
21310 @subsubheading Synopsis
21313 -target-list-available-targets
21316 List the possible targets to connect to.
21318 @subsubheading @value{GDBN} Command
21320 The corresponding @value{GDBN} command is @samp{help target}.
21322 @subsubheading Example
21326 @subheading The @code{-target-list-current-targets} Command
21327 @findex -target-list-current-targets
21329 @subsubheading Synopsis
21332 -target-list-current-targets
21335 Describe the current target.
21337 @subsubheading @value{GDBN} Command
21339 The corresponding information is printed by @samp{info file} (among
21342 @subsubheading Example
21346 @subheading The @code{-target-list-parameters} Command
21347 @findex -target-list-parameters
21349 @subsubheading Synopsis
21352 -target-list-parameters
21357 @subsubheading @value{GDBN} Command
21361 @subsubheading Example
21365 @subheading The @code{-target-select} Command
21366 @findex -target-select
21368 @subsubheading Synopsis
21371 -target-select @var{type} @var{parameters @dots{}}
21374 Connect @value{GDBN} to the remote target. This command takes two args:
21378 The type of target, for instance @samp{async}, @samp{remote}, etc.
21379 @item @var{parameters}
21380 Device names, host names and the like. @xref{Target Commands, ,
21381 Commands for Managing Targets}, for more details.
21384 The output is a connection notification, followed by the address at
21385 which the target program is, in the following form:
21388 ^connected,addr="@var{address}",func="@var{function name}",
21389 args=[@var{arg list}]
21392 @subsubheading @value{GDBN} Command
21394 The corresponding @value{GDBN} command is @samp{target}.
21396 @subsubheading Example
21400 -target-select async /dev/ttya
21401 ^connected,addr="0xfe00a300",func="??",args=[]
21405 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21406 @node GDB/MI File Transfer Commands
21407 @section @sc{gdb/mi} File Transfer Commands
21410 @subheading The @code{-target-file-put} Command
21411 @findex -target-file-put
21413 @subsubheading Synopsis
21416 -target-file-put @var{hostfile} @var{targetfile}
21419 Copy file @var{hostfile} from the host system (the machine running
21420 @value{GDBN}) to @var{targetfile} on the target system.
21422 @subsubheading @value{GDBN} Command
21424 The corresponding @value{GDBN} command is @samp{remote put}.
21426 @subsubheading Example
21430 -target-file-put localfile remotefile
21436 @subheading The @code{-target-file-put} Command
21437 @findex -target-file-get
21439 @subsubheading Synopsis
21442 -target-file-get @var{targetfile} @var{hostfile}
21445 Copy file @var{targetfile} from the target system to @var{hostfile}
21446 on the host system.
21448 @subsubheading @value{GDBN} Command
21450 The corresponding @value{GDBN} command is @samp{remote get}.
21452 @subsubheading Example
21456 -target-file-get remotefile localfile
21462 @subheading The @code{-target-file-delete} Command
21463 @findex -target-file-delete
21465 @subsubheading Synopsis
21468 -target-file-delete @var{targetfile}
21471 Delete @var{targetfile} from the target system.
21473 @subsubheading @value{GDBN} Command
21475 The corresponding @value{GDBN} command is @samp{remote delete}.
21477 @subsubheading Example
21481 -target-file-delete remotefile
21487 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21488 @node GDB/MI Miscellaneous Commands
21489 @section Miscellaneous @sc{gdb/mi} Commands
21491 @c @subheading -gdb-complete
21493 @subheading The @code{-gdb-exit} Command
21496 @subsubheading Synopsis
21502 Exit @value{GDBN} immediately.
21504 @subsubheading @value{GDBN} Command
21506 Approximately corresponds to @samp{quit}.
21508 @subsubheading Example
21517 @subheading The @code{-exec-abort} Command
21518 @findex -exec-abort
21520 @subsubheading Synopsis
21526 Kill the inferior running program.
21528 @subsubheading @value{GDBN} Command
21530 The corresponding @value{GDBN} command is @samp{kill}.
21532 @subsubheading Example
21536 @subheading The @code{-gdb-set} Command
21539 @subsubheading Synopsis
21545 Set an internal @value{GDBN} variable.
21546 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21548 @subsubheading @value{GDBN} Command
21550 The corresponding @value{GDBN} command is @samp{set}.
21552 @subsubheading Example
21562 @subheading The @code{-gdb-show} Command
21565 @subsubheading Synopsis
21571 Show the current value of a @value{GDBN} variable.
21573 @subsubheading @value{GDBN} Command
21575 The corresponding @value{GDBN} command is @samp{show}.
21577 @subsubheading Example
21586 @c @subheading -gdb-source
21589 @subheading The @code{-gdb-version} Command
21590 @findex -gdb-version
21592 @subsubheading Synopsis
21598 Show version information for @value{GDBN}. Used mostly in testing.
21600 @subsubheading @value{GDBN} Command
21602 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21603 default shows this information when you start an interactive session.
21605 @subsubheading Example
21607 @c This example modifies the actual output from GDB to avoid overfull
21613 ~Copyright 2000 Free Software Foundation, Inc.
21614 ~GDB is free software, covered by the GNU General Public License, and
21615 ~you are welcome to change it and/or distribute copies of it under
21616 ~ certain conditions.
21617 ~Type "show copying" to see the conditions.
21618 ~There is absolutely no warranty for GDB. Type "show warranty" for
21620 ~This GDB was configured as
21621 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21626 @subheading The @code{-list-features} Command
21627 @findex -list-features
21629 Returns a list of particular features of the MI protocol that
21630 this version of gdb implements. A feature can be a command,
21631 or a new field in an output of some command, or even an
21632 important bugfix. While a frontend can sometimes detect presence
21633 of a feature at runtime, it is easier to perform detection at debugger
21636 The command returns a list of strings, with each string naming an
21637 available feature. Each returned string is just a name, it does not
21638 have any internal structure. The list of possible feature names
21644 (gdb) -list-features
21645 ^done,result=["feature1","feature2"]
21648 The current list of features is:
21652 @samp{frozen-varobjs}---indicates presence of the
21653 @code{-var-set-frozen} command, as well as possible presense of the
21654 @code{frozen} field in the output of @code{-varobj-create}.
21656 @samp{pending-breakpoints}---indicates presence of the @code{-f}
21657 option to the @code{-break-insert} command.
21661 @subheading The @code{-interpreter-exec} Command
21662 @findex -interpreter-exec
21664 @subheading Synopsis
21667 -interpreter-exec @var{interpreter} @var{command}
21669 @anchor{-interpreter-exec}
21671 Execute the specified @var{command} in the given @var{interpreter}.
21673 @subheading @value{GDBN} Command
21675 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21677 @subheading Example
21681 -interpreter-exec console "break main"
21682 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21683 &"During symbol reading, bad structure-type format.\n"
21684 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21689 @subheading The @code{-inferior-tty-set} Command
21690 @findex -inferior-tty-set
21692 @subheading Synopsis
21695 -inferior-tty-set /dev/pts/1
21698 Set terminal for future runs of the program being debugged.
21700 @subheading @value{GDBN} Command
21702 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21704 @subheading Example
21708 -inferior-tty-set /dev/pts/1
21713 @subheading The @code{-inferior-tty-show} Command
21714 @findex -inferior-tty-show
21716 @subheading Synopsis
21722 Show terminal for future runs of program being debugged.
21724 @subheading @value{GDBN} Command
21726 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21728 @subheading Example
21732 -inferior-tty-set /dev/pts/1
21736 ^done,inferior_tty_terminal="/dev/pts/1"
21740 @subheading The @code{-enable-timings} Command
21741 @findex -enable-timings
21743 @subheading Synopsis
21746 -enable-timings [yes | no]
21749 Toggle the printing of the wallclock, user and system times for an MI
21750 command as a field in its output. This command is to help frontend
21751 developers optimize the performance of their code. No argument is
21752 equivalent to @samp{yes}.
21754 @subheading @value{GDBN} Command
21758 @subheading Example
21766 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21767 addr="0x080484ed",func="main",file="myprog.c",
21768 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
21769 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
21777 *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
21778 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
21779 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
21780 fullname="/home/nickrob/myprog.c",line="73"@}
21785 @chapter @value{GDBN} Annotations
21787 This chapter describes annotations in @value{GDBN}. Annotations were
21788 designed to interface @value{GDBN} to graphical user interfaces or other
21789 similar programs which want to interact with @value{GDBN} at a
21790 relatively high level.
21792 The annotation mechanism has largely been superseded by @sc{gdb/mi}
21796 This is Edition @value{EDITION}, @value{DATE}.
21800 * Annotations Overview:: What annotations are; the general syntax.
21801 * Server Prefix:: Issuing a command without affecting user state.
21802 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21803 * Errors:: Annotations for error messages.
21804 * Invalidation:: Some annotations describe things now invalid.
21805 * Annotations for Running::
21806 Whether the program is running, how it stopped, etc.
21807 * Source Annotations:: Annotations describing source code.
21810 @node Annotations Overview
21811 @section What is an Annotation?
21812 @cindex annotations
21814 Annotations start with a newline character, two @samp{control-z}
21815 characters, and the name of the annotation. If there is no additional
21816 information associated with this annotation, the name of the annotation
21817 is followed immediately by a newline. If there is additional
21818 information, the name of the annotation is followed by a space, the
21819 additional information, and a newline. The additional information
21820 cannot contain newline characters.
21822 Any output not beginning with a newline and two @samp{control-z}
21823 characters denotes literal output from @value{GDBN}. Currently there is
21824 no need for @value{GDBN} to output a newline followed by two
21825 @samp{control-z} characters, but if there was such a need, the
21826 annotations could be extended with an @samp{escape} annotation which
21827 means those three characters as output.
21829 The annotation @var{level}, which is specified using the
21830 @option{--annotate} command line option (@pxref{Mode Options}), controls
21831 how much information @value{GDBN} prints together with its prompt,
21832 values of expressions, source lines, and other types of output. Level 0
21833 is for no annotations, level 1 is for use when @value{GDBN} is run as a
21834 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21835 for programs that control @value{GDBN}, and level 2 annotations have
21836 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21837 Interface, annotate, GDB's Obsolete Annotations}).
21840 @kindex set annotate
21841 @item set annotate @var{level}
21842 The @value{GDBN} command @code{set annotate} sets the level of
21843 annotations to the specified @var{level}.
21845 @item show annotate
21846 @kindex show annotate
21847 Show the current annotation level.
21850 This chapter describes level 3 annotations.
21852 A simple example of starting up @value{GDBN} with annotations is:
21855 $ @kbd{gdb --annotate=3}
21857 Copyright 2003 Free Software Foundation, Inc.
21858 GDB is free software, covered by the GNU General Public License,
21859 and you are welcome to change it and/or distribute copies of it
21860 under certain conditions.
21861 Type "show copying" to see the conditions.
21862 There is absolutely no warranty for GDB. Type "show warranty"
21864 This GDB was configured as "i386-pc-linux-gnu"
21875 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21876 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21877 denotes a @samp{control-z} character) are annotations; the rest is
21878 output from @value{GDBN}.
21880 @node Server Prefix
21881 @section The Server Prefix
21882 @cindex server prefix
21884 If you prefix a command with @samp{server } then it will not affect
21885 the command history, nor will it affect @value{GDBN}'s notion of which
21886 command to repeat if @key{RET} is pressed on a line by itself. This
21887 means that commands can be run behind a user's back by a front-end in
21888 a transparent manner.
21890 The server prefix does not affect the recording of values into the value
21891 history; to print a value without recording it into the value history,
21892 use the @code{output} command instead of the @code{print} command.
21895 @section Annotation for @value{GDBN} Input
21897 @cindex annotations for prompts
21898 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21899 to know when to send output, when the output from a given command is
21902 Different kinds of input each have a different @dfn{input type}. Each
21903 input type has three annotations: a @code{pre-} annotation, which
21904 denotes the beginning of any prompt which is being output, a plain
21905 annotation, which denotes the end of the prompt, and then a @code{post-}
21906 annotation which denotes the end of any echo which may (or may not) be
21907 associated with the input. For example, the @code{prompt} input type
21908 features the following annotations:
21916 The input types are
21919 @findex pre-prompt annotation
21920 @findex prompt annotation
21921 @findex post-prompt annotation
21923 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21925 @findex pre-commands annotation
21926 @findex commands annotation
21927 @findex post-commands annotation
21929 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21930 command. The annotations are repeated for each command which is input.
21932 @findex pre-overload-choice annotation
21933 @findex overload-choice annotation
21934 @findex post-overload-choice annotation
21935 @item overload-choice
21936 When @value{GDBN} wants the user to select between various overloaded functions.
21938 @findex pre-query annotation
21939 @findex query annotation
21940 @findex post-query annotation
21942 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21944 @findex pre-prompt-for-continue annotation
21945 @findex prompt-for-continue annotation
21946 @findex post-prompt-for-continue annotation
21947 @item prompt-for-continue
21948 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21949 expect this to work well; instead use @code{set height 0} to disable
21950 prompting. This is because the counting of lines is buggy in the
21951 presence of annotations.
21956 @cindex annotations for errors, warnings and interrupts
21958 @findex quit annotation
21963 This annotation occurs right before @value{GDBN} responds to an interrupt.
21965 @findex error annotation
21970 This annotation occurs right before @value{GDBN} responds to an error.
21972 Quit and error annotations indicate that any annotations which @value{GDBN} was
21973 in the middle of may end abruptly. For example, if a
21974 @code{value-history-begin} annotation is followed by a @code{error}, one
21975 cannot expect to receive the matching @code{value-history-end}. One
21976 cannot expect not to receive it either, however; an error annotation
21977 does not necessarily mean that @value{GDBN} is immediately returning all the way
21980 @findex error-begin annotation
21981 A quit or error annotation may be preceded by
21987 Any output between that and the quit or error annotation is the error
21990 Warning messages are not yet annotated.
21991 @c If we want to change that, need to fix warning(), type_error(),
21992 @c range_error(), and possibly other places.
21995 @section Invalidation Notices
21997 @cindex annotations for invalidation messages
21998 The following annotations say that certain pieces of state may have
22002 @findex frames-invalid annotation
22003 @item ^Z^Zframes-invalid
22005 The frames (for example, output from the @code{backtrace} command) may
22008 @findex breakpoints-invalid annotation
22009 @item ^Z^Zbreakpoints-invalid
22011 The breakpoints may have changed. For example, the user just added or
22012 deleted a breakpoint.
22015 @node Annotations for Running
22016 @section Running the Program
22017 @cindex annotations for running programs
22019 @findex starting annotation
22020 @findex stopping annotation
22021 When the program starts executing due to a @value{GDBN} command such as
22022 @code{step} or @code{continue},
22028 is output. When the program stops,
22034 is output. Before the @code{stopped} annotation, a variety of
22035 annotations describe how the program stopped.
22038 @findex exited annotation
22039 @item ^Z^Zexited @var{exit-status}
22040 The program exited, and @var{exit-status} is the exit status (zero for
22041 successful exit, otherwise nonzero).
22043 @findex signalled annotation
22044 @findex signal-name annotation
22045 @findex signal-name-end annotation
22046 @findex signal-string annotation
22047 @findex signal-string-end annotation
22048 @item ^Z^Zsignalled
22049 The program exited with a signal. After the @code{^Z^Zsignalled}, the
22050 annotation continues:
22056 ^Z^Zsignal-name-end
22060 ^Z^Zsignal-string-end
22065 where @var{name} is the name of the signal, such as @code{SIGILL} or
22066 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
22067 as @code{Illegal Instruction} or @code{Segmentation fault}.
22068 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
22069 user's benefit and have no particular format.
22071 @findex signal annotation
22073 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
22074 just saying that the program received the signal, not that it was
22075 terminated with it.
22077 @findex breakpoint annotation
22078 @item ^Z^Zbreakpoint @var{number}
22079 The program hit breakpoint number @var{number}.
22081 @findex watchpoint annotation
22082 @item ^Z^Zwatchpoint @var{number}
22083 The program hit watchpoint number @var{number}.
22086 @node Source Annotations
22087 @section Displaying Source
22088 @cindex annotations for source display
22090 @findex source annotation
22091 The following annotation is used instead of displaying source code:
22094 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
22097 where @var{filename} is an absolute file name indicating which source
22098 file, @var{line} is the line number within that file (where 1 is the
22099 first line in the file), @var{character} is the character position
22100 within the file (where 0 is the first character in the file) (for most
22101 debug formats this will necessarily point to the beginning of a line),
22102 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
22103 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
22104 @var{addr} is the address in the target program associated with the
22105 source which is being displayed. @var{addr} is in the form @samp{0x}
22106 followed by one or more lowercase hex digits (note that this does not
22107 depend on the language).
22110 @chapter Reporting Bugs in @value{GDBN}
22111 @cindex bugs in @value{GDBN}
22112 @cindex reporting bugs in @value{GDBN}
22114 Your bug reports play an essential role in making @value{GDBN} reliable.
22116 Reporting a bug may help you by bringing a solution to your problem, or it
22117 may not. But in any case the principal function of a bug report is to help
22118 the entire community by making the next version of @value{GDBN} work better. Bug
22119 reports are your contribution to the maintenance of @value{GDBN}.
22121 In order for a bug report to serve its purpose, you must include the
22122 information that enables us to fix the bug.
22125 * Bug Criteria:: Have you found a bug?
22126 * Bug Reporting:: How to report bugs
22130 @section Have You Found a Bug?
22131 @cindex bug criteria
22133 If you are not sure whether you have found a bug, here are some guidelines:
22136 @cindex fatal signal
22137 @cindex debugger crash
22138 @cindex crash of debugger
22140 If the debugger gets a fatal signal, for any input whatever, that is a
22141 @value{GDBN} bug. Reliable debuggers never crash.
22143 @cindex error on valid input
22145 If @value{GDBN} produces an error message for valid input, that is a
22146 bug. (Note that if you're cross debugging, the problem may also be
22147 somewhere in the connection to the target.)
22149 @cindex invalid input
22151 If @value{GDBN} does not produce an error message for invalid input,
22152 that is a bug. However, you should note that your idea of
22153 ``invalid input'' might be our idea of ``an extension'' or ``support
22154 for traditional practice''.
22157 If you are an experienced user of debugging tools, your suggestions
22158 for improvement of @value{GDBN} are welcome in any case.
22161 @node Bug Reporting
22162 @section How to Report Bugs
22163 @cindex bug reports
22164 @cindex @value{GDBN} bugs, reporting
22166 A number of companies and individuals offer support for @sc{gnu} products.
22167 If you obtained @value{GDBN} from a support organization, we recommend you
22168 contact that organization first.
22170 You can find contact information for many support companies and
22171 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
22173 @c should add a web page ref...
22175 In any event, we also recommend that you submit bug reports for
22176 @value{GDBN}. The preferred method is to submit them directly using
22177 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
22178 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
22181 @strong{Do not send bug reports to @samp{info-gdb}, or to
22182 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
22183 not want to receive bug reports. Those that do have arranged to receive
22186 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
22187 serves as a repeater. The mailing list and the newsgroup carry exactly
22188 the same messages. Often people think of posting bug reports to the
22189 newsgroup instead of mailing them. This appears to work, but it has one
22190 problem which can be crucial: a newsgroup posting often lacks a mail
22191 path back to the sender. Thus, if we need to ask for more information,
22192 we may be unable to reach you. For this reason, it is better to send
22193 bug reports to the mailing list.
22195 The fundamental principle of reporting bugs usefully is this:
22196 @strong{report all the facts}. If you are not sure whether to state a
22197 fact or leave it out, state it!
22199 Often people omit facts because they think they know what causes the
22200 problem and assume that some details do not matter. Thus, you might
22201 assume that the name of the variable you use in an example does not matter.
22202 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
22203 stray memory reference which happens to fetch from the location where that
22204 name is stored in memory; perhaps, if the name were different, the contents
22205 of that location would fool the debugger into doing the right thing despite
22206 the bug. Play it safe and give a specific, complete example. That is the
22207 easiest thing for you to do, and the most helpful.
22209 Keep in mind that the purpose of a bug report is to enable us to fix the
22210 bug. It may be that the bug has been reported previously, but neither
22211 you nor we can know that unless your bug report is complete and
22214 Sometimes people give a few sketchy facts and ask, ``Does this ring a
22215 bell?'' Those bug reports are useless, and we urge everyone to
22216 @emph{refuse to respond to them} except to chide the sender to report
22219 To enable us to fix the bug, you should include all these things:
22223 The version of @value{GDBN}. @value{GDBN} announces it if you start
22224 with no arguments; you can also print it at any time using @code{show
22227 Without this, we will not know whether there is any point in looking for
22228 the bug in the current version of @value{GDBN}.
22231 The type of machine you are using, and the operating system name and
22235 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
22236 ``@value{GCC}--2.8.1''.
22239 What compiler (and its version) was used to compile the program you are
22240 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
22241 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
22242 to get this information; for other compilers, see the documentation for
22246 The command arguments you gave the compiler to compile your example and
22247 observe the bug. For example, did you use @samp{-O}? To guarantee
22248 you will not omit something important, list them all. A copy of the
22249 Makefile (or the output from make) is sufficient.
22251 If we were to try to guess the arguments, we would probably guess wrong
22252 and then we might not encounter the bug.
22255 A complete input script, and all necessary source files, that will
22259 A description of what behavior you observe that you believe is
22260 incorrect. For example, ``It gets a fatal signal.''
22262 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
22263 will certainly notice it. But if the bug is incorrect output, we might
22264 not notice unless it is glaringly wrong. You might as well not give us
22265 a chance to make a mistake.
22267 Even if the problem you experience is a fatal signal, you should still
22268 say so explicitly. Suppose something strange is going on, such as, your
22269 copy of @value{GDBN} is out of synch, or you have encountered a bug in
22270 the C library on your system. (This has happened!) Your copy might
22271 crash and ours would not. If you told us to expect a crash, then when
22272 ours fails to crash, we would know that the bug was not happening for
22273 us. If you had not told us to expect a crash, then we would not be able
22274 to draw any conclusion from our observations.
22277 @cindex recording a session script
22278 To collect all this information, you can use a session recording program
22279 such as @command{script}, which is available on many Unix systems.
22280 Just run your @value{GDBN} session inside @command{script} and then
22281 include the @file{typescript} file with your bug report.
22283 Another way to record a @value{GDBN} session is to run @value{GDBN}
22284 inside Emacs and then save the entire buffer to a file.
22287 If you wish to suggest changes to the @value{GDBN} source, send us context
22288 diffs. If you even discuss something in the @value{GDBN} source, refer to
22289 it by context, not by line number.
22291 The line numbers in our development sources will not match those in your
22292 sources. Your line numbers would convey no useful information to us.
22296 Here are some things that are not necessary:
22300 A description of the envelope of the bug.
22302 Often people who encounter a bug spend a lot of time investigating
22303 which changes to the input file will make the bug go away and which
22304 changes will not affect it.
22306 This is often time consuming and not very useful, because the way we
22307 will find the bug is by running a single example under the debugger
22308 with breakpoints, not by pure deduction from a series of examples.
22309 We recommend that you save your time for something else.
22311 Of course, if you can find a simpler example to report @emph{instead}
22312 of the original one, that is a convenience for us. Errors in the
22313 output will be easier to spot, running under the debugger will take
22314 less time, and so on.
22316 However, simplification is not vital; if you do not want to do this,
22317 report the bug anyway and send us the entire test case you used.
22320 A patch for the bug.
22322 A patch for the bug does help us if it is a good one. But do not omit
22323 the necessary information, such as the test case, on the assumption that
22324 a patch is all we need. We might see problems with your patch and decide
22325 to fix the problem another way, or we might not understand it at all.
22327 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22328 construct an example that will make the program follow a certain path
22329 through the code. If you do not send us the example, we will not be able
22330 to construct one, so we will not be able to verify that the bug is fixed.
22332 And if we cannot understand what bug you are trying to fix, or why your
22333 patch should be an improvement, we will not install it. A test case will
22334 help us to understand.
22337 A guess about what the bug is or what it depends on.
22339 Such guesses are usually wrong. Even we cannot guess right about such
22340 things without first using the debugger to find the facts.
22343 @c The readline documentation is distributed with the readline code
22344 @c and consists of the two following files:
22346 @c inc-hist.texinfo
22347 @c Use -I with makeinfo to point to the appropriate directory,
22348 @c environment var TEXINPUTS with TeX.
22349 @include rluser.texi
22350 @include inc-hist.texinfo
22353 @node Formatting Documentation
22354 @appendix Formatting Documentation
22356 @cindex @value{GDBN} reference card
22357 @cindex reference card
22358 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22359 for printing with PostScript or Ghostscript, in the @file{gdb}
22360 subdirectory of the main source directory@footnote{In
22361 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22362 release.}. If you can use PostScript or Ghostscript with your printer,
22363 you can print the reference card immediately with @file{refcard.ps}.
22365 The release also includes the source for the reference card. You
22366 can format it, using @TeX{}, by typing:
22372 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22373 mode on US ``letter'' size paper;
22374 that is, on a sheet 11 inches wide by 8.5 inches
22375 high. You will need to specify this form of printing as an option to
22376 your @sc{dvi} output program.
22378 @cindex documentation
22380 All the documentation for @value{GDBN} comes as part of the machine-readable
22381 distribution. The documentation is written in Texinfo format, which is
22382 a documentation system that uses a single source file to produce both
22383 on-line information and a printed manual. You can use one of the Info
22384 formatting commands to create the on-line version of the documentation
22385 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22387 @value{GDBN} includes an already formatted copy of the on-line Info
22388 version of this manual in the @file{gdb} subdirectory. The main Info
22389 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22390 subordinate files matching @samp{gdb.info*} in the same directory. If
22391 necessary, you can print out these files, or read them with any editor;
22392 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22393 Emacs or the standalone @code{info} program, available as part of the
22394 @sc{gnu} Texinfo distribution.
22396 If you want to format these Info files yourself, you need one of the
22397 Info formatting programs, such as @code{texinfo-format-buffer} or
22400 If you have @code{makeinfo} installed, and are in the top level
22401 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22402 version @value{GDBVN}), you can make the Info file by typing:
22409 If you want to typeset and print copies of this manual, you need @TeX{},
22410 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22411 Texinfo definitions file.
22413 @TeX{} is a typesetting program; it does not print files directly, but
22414 produces output files called @sc{dvi} files. To print a typeset
22415 document, you need a program to print @sc{dvi} files. If your system
22416 has @TeX{} installed, chances are it has such a program. The precise
22417 command to use depends on your system; @kbd{lpr -d} is common; another
22418 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22419 require a file name without any extension or a @samp{.dvi} extension.
22421 @TeX{} also requires a macro definitions file called
22422 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22423 written in Texinfo format. On its own, @TeX{} cannot either read or
22424 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22425 and is located in the @file{gdb-@var{version-number}/texinfo}
22428 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22429 typeset and print this manual. First switch to the @file{gdb}
22430 subdirectory of the main source directory (for example, to
22431 @file{gdb-@value{GDBVN}/gdb}) and type:
22437 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22439 @node Installing GDB
22440 @appendix Installing @value{GDBN}
22441 @cindex installation
22444 * Requirements:: Requirements for building @value{GDBN}
22445 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22446 * Separate Objdir:: Compiling @value{GDBN} in another directory
22447 * Config Names:: Specifying names for hosts and targets
22448 * Configure Options:: Summary of options for configure
22452 @section Requirements for Building @value{GDBN}
22453 @cindex building @value{GDBN}, requirements for
22455 Building @value{GDBN} requires various tools and packages to be available.
22456 Other packages will be used only if they are found.
22458 @heading Tools/Packages Necessary for Building @value{GDBN}
22460 @item ISO C90 compiler
22461 @value{GDBN} is written in ISO C90. It should be buildable with any
22462 working C90 compiler, e.g.@: GCC.
22466 @heading Tools/Packages Optional for Building @value{GDBN}
22470 @value{GDBN} can use the Expat XML parsing library. This library may be
22471 included with your operating system distribution; if it is not, you
22472 can get the latest version from @url{http://expat.sourceforge.net}.
22473 The @file{configure} script will search for this library in several
22474 standard locations; if it is installed in an unusual path, you can
22475 use the @option{--with-libexpat-prefix} option to specify its location.
22481 Remote protocol memory maps (@pxref{Memory Map Format})
22483 Target descriptions (@pxref{Target Descriptions})
22485 Remote shared library lists (@pxref{Library List Format})
22487 MS-Windows shared libraries (@pxref{Shared Libraries})
22492 @node Running Configure
22493 @section Invoking the @value{GDBN} @file{configure} Script
22494 @cindex configuring @value{GDBN}
22495 @value{GDBN} comes with a @file{configure} script that automates the process
22496 of preparing @value{GDBN} for installation; you can then use @code{make} to
22497 build the @code{gdb} program.
22499 @c irrelevant in info file; it's as current as the code it lives with.
22500 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22501 look at the @file{README} file in the sources; we may have improved the
22502 installation procedures since publishing this manual.}
22505 The @value{GDBN} distribution includes all the source code you need for
22506 @value{GDBN} in a single directory, whose name is usually composed by
22507 appending the version number to @samp{gdb}.
22509 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22510 @file{gdb-@value{GDBVN}} directory. That directory contains:
22513 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22514 script for configuring @value{GDBN} and all its supporting libraries
22516 @item gdb-@value{GDBVN}/gdb
22517 the source specific to @value{GDBN} itself
22519 @item gdb-@value{GDBVN}/bfd
22520 source for the Binary File Descriptor library
22522 @item gdb-@value{GDBVN}/include
22523 @sc{gnu} include files
22525 @item gdb-@value{GDBVN}/libiberty
22526 source for the @samp{-liberty} free software library
22528 @item gdb-@value{GDBVN}/opcodes
22529 source for the library of opcode tables and disassemblers
22531 @item gdb-@value{GDBVN}/readline
22532 source for the @sc{gnu} command-line interface
22534 @item gdb-@value{GDBVN}/glob
22535 source for the @sc{gnu} filename pattern-matching subroutine
22537 @item gdb-@value{GDBVN}/mmalloc
22538 source for the @sc{gnu} memory-mapped malloc package
22541 The simplest way to configure and build @value{GDBN} is to run @file{configure}
22542 from the @file{gdb-@var{version-number}} source directory, which in
22543 this example is the @file{gdb-@value{GDBVN}} directory.
22545 First switch to the @file{gdb-@var{version-number}} source directory
22546 if you are not already in it; then run @file{configure}. Pass the
22547 identifier for the platform on which @value{GDBN} will run as an
22553 cd gdb-@value{GDBVN}
22554 ./configure @var{host}
22559 where @var{host} is an identifier such as @samp{sun4} or
22560 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22561 (You can often leave off @var{host}; @file{configure} tries to guess the
22562 correct value by examining your system.)
22564 Running @samp{configure @var{host}} and then running @code{make} builds the
22565 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22566 libraries, then @code{gdb} itself. The configured source files, and the
22567 binaries, are left in the corresponding source directories.
22570 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22571 system does not recognize this automatically when you run a different
22572 shell, you may need to run @code{sh} on it explicitly:
22575 sh configure @var{host}
22578 If you run @file{configure} from a directory that contains source
22579 directories for multiple libraries or programs, such as the
22580 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
22582 creates configuration files for every directory level underneath (unless
22583 you tell it not to, with the @samp{--norecursion} option).
22585 You should run the @file{configure} script from the top directory in the
22586 source tree, the @file{gdb-@var{version-number}} directory. If you run
22587 @file{configure} from one of the subdirectories, you will configure only
22588 that subdirectory. That is usually not what you want. In particular,
22589 if you run the first @file{configure} from the @file{gdb} subdirectory
22590 of the @file{gdb-@var{version-number}} directory, you will omit the
22591 configuration of @file{bfd}, @file{readline}, and other sibling
22592 directories of the @file{gdb} subdirectory. This leads to build errors
22593 about missing include files such as @file{bfd/bfd.h}.
22595 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22596 However, you should make sure that the shell on your path (named by
22597 the @samp{SHELL} environment variable) is publicly readable. Remember
22598 that @value{GDBN} uses the shell to start your program---some systems refuse to
22599 let @value{GDBN} debug child processes whose programs are not readable.
22601 @node Separate Objdir
22602 @section Compiling @value{GDBN} in Another Directory
22604 If you want to run @value{GDBN} versions for several host or target machines,
22605 you need a different @code{gdb} compiled for each combination of
22606 host and target. @file{configure} is designed to make this easy by
22607 allowing you to generate each configuration in a separate subdirectory,
22608 rather than in the source directory. If your @code{make} program
22609 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22610 @code{make} in each of these directories builds the @code{gdb}
22611 program specified there.
22613 To build @code{gdb} in a separate directory, run @file{configure}
22614 with the @samp{--srcdir} option to specify where to find the source.
22615 (You also need to specify a path to find @file{configure}
22616 itself from your working directory. If the path to @file{configure}
22617 would be the same as the argument to @samp{--srcdir}, you can leave out
22618 the @samp{--srcdir} option; it is assumed.)
22620 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22621 separate directory for a Sun 4 like this:
22625 cd gdb-@value{GDBVN}
22628 ../gdb-@value{GDBVN}/configure sun4
22633 When @file{configure} builds a configuration using a remote source
22634 directory, it creates a tree for the binaries with the same structure
22635 (and using the same names) as the tree under the source directory. In
22636 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22637 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22638 @file{gdb-sun4/gdb}.
22640 Make sure that your path to the @file{configure} script has just one
22641 instance of @file{gdb} in it. If your path to @file{configure} looks
22642 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22643 one subdirectory of @value{GDBN}, not the whole package. This leads to
22644 build errors about missing include files such as @file{bfd/bfd.h}.
22646 One popular reason to build several @value{GDBN} configurations in separate
22647 directories is to configure @value{GDBN} for cross-compiling (where
22648 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22649 programs that run on another machine---the @dfn{target}).
22650 You specify a cross-debugging target by
22651 giving the @samp{--target=@var{target}} option to @file{configure}.
22653 When you run @code{make} to build a program or library, you must run
22654 it in a configured directory---whatever directory you were in when you
22655 called @file{configure} (or one of its subdirectories).
22657 The @code{Makefile} that @file{configure} generates in each source
22658 directory also runs recursively. If you type @code{make} in a source
22659 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22660 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22661 will build all the required libraries, and then build GDB.
22663 When you have multiple hosts or targets configured in separate
22664 directories, you can run @code{make} on them in parallel (for example,
22665 if they are NFS-mounted on each of the hosts); they will not interfere
22669 @section Specifying Names for Hosts and Targets
22671 The specifications used for hosts and targets in the @file{configure}
22672 script are based on a three-part naming scheme, but some short predefined
22673 aliases are also supported. The full naming scheme encodes three pieces
22674 of information in the following pattern:
22677 @var{architecture}-@var{vendor}-@var{os}
22680 For example, you can use the alias @code{sun4} as a @var{host} argument,
22681 or as the value for @var{target} in a @code{--target=@var{target}}
22682 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22684 The @file{configure} script accompanying @value{GDBN} does not provide
22685 any query facility to list all supported host and target names or
22686 aliases. @file{configure} calls the Bourne shell script
22687 @code{config.sub} to map abbreviations to full names; you can read the
22688 script, if you wish, or you can use it to test your guesses on
22689 abbreviations---for example:
22692 % sh config.sub i386-linux
22694 % sh config.sub alpha-linux
22695 alpha-unknown-linux-gnu
22696 % sh config.sub hp9k700
22698 % sh config.sub sun4
22699 sparc-sun-sunos4.1.1
22700 % sh config.sub sun3
22701 m68k-sun-sunos4.1.1
22702 % sh config.sub i986v
22703 Invalid configuration `i986v': machine `i986v' not recognized
22707 @code{config.sub} is also distributed in the @value{GDBN} source
22708 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22710 @node Configure Options
22711 @section @file{configure} Options
22713 Here is a summary of the @file{configure} options and arguments that
22714 are most often useful for building @value{GDBN}. @file{configure} also has
22715 several other options not listed here. @inforef{What Configure
22716 Does,,configure.info}, for a full explanation of @file{configure}.
22719 configure @r{[}--help@r{]}
22720 @r{[}--prefix=@var{dir}@r{]}
22721 @r{[}--exec-prefix=@var{dir}@r{]}
22722 @r{[}--srcdir=@var{dirname}@r{]}
22723 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22724 @r{[}--target=@var{target}@r{]}
22729 You may introduce options with a single @samp{-} rather than
22730 @samp{--} if you prefer; but you may abbreviate option names if you use
22735 Display a quick summary of how to invoke @file{configure}.
22737 @item --prefix=@var{dir}
22738 Configure the source to install programs and files under directory
22741 @item --exec-prefix=@var{dir}
22742 Configure the source to install programs under directory
22745 @c avoid splitting the warning from the explanation:
22747 @item --srcdir=@var{dirname}
22748 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22749 @code{make} that implements the @code{VPATH} feature.}@*
22750 Use this option to make configurations in directories separate from the
22751 @value{GDBN} source directories. Among other things, you can use this to
22752 build (or maintain) several configurations simultaneously, in separate
22753 directories. @file{configure} writes configuration-specific files in
22754 the current directory, but arranges for them to use the source in the
22755 directory @var{dirname}. @file{configure} creates directories under
22756 the working directory in parallel to the source directories below
22759 @item --norecursion
22760 Configure only the directory level where @file{configure} is executed; do not
22761 propagate configuration to subdirectories.
22763 @item --target=@var{target}
22764 Configure @value{GDBN} for cross-debugging programs running on the specified
22765 @var{target}. Without this option, @value{GDBN} is configured to debug
22766 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22768 There is no convenient way to generate a list of all available targets.
22770 @item @var{host} @dots{}
22771 Configure @value{GDBN} to run on the specified @var{host}.
22773 There is no convenient way to generate a list of all available hosts.
22776 There are many other options available as well, but they are generally
22777 needed for special purposes only.
22779 @node Maintenance Commands
22780 @appendix Maintenance Commands
22781 @cindex maintenance commands
22782 @cindex internal commands
22784 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22785 includes a number of commands intended for @value{GDBN} developers,
22786 that are not documented elsewhere in this manual. These commands are
22787 provided here for reference. (For commands that turn on debugging
22788 messages, see @ref{Debugging Output}.)
22791 @kindex maint agent
22792 @item maint agent @var{expression}
22793 Translate the given @var{expression} into remote agent bytecodes.
22794 This command is useful for debugging the Agent Expression mechanism
22795 (@pxref{Agent Expressions}).
22797 @kindex maint info breakpoints
22798 @item @anchor{maint info breakpoints}maint info breakpoints
22799 Using the same format as @samp{info breakpoints}, display both the
22800 breakpoints you've set explicitly, and those @value{GDBN} is using for
22801 internal purposes. Internal breakpoints are shown with negative
22802 breakpoint numbers. The type column identifies what kind of breakpoint
22807 Normal, explicitly set breakpoint.
22810 Normal, explicitly set watchpoint.
22813 Internal breakpoint, used to handle correctly stepping through
22814 @code{longjmp} calls.
22816 @item longjmp resume
22817 Internal breakpoint at the target of a @code{longjmp}.
22820 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22823 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22826 Shared library events.
22830 @kindex maint check-symtabs
22831 @item maint check-symtabs
22832 Check the consistency of psymtabs and symtabs.
22834 @kindex maint cplus first_component
22835 @item maint cplus first_component @var{name}
22836 Print the first C@t{++} class/namespace component of @var{name}.
22838 @kindex maint cplus namespace
22839 @item maint cplus namespace
22840 Print the list of possible C@t{++} namespaces.
22842 @kindex maint demangle
22843 @item maint demangle @var{name}
22844 Demangle a C@t{++} or Objective-C mangled @var{name}.
22846 @kindex maint deprecate
22847 @kindex maint undeprecate
22848 @cindex deprecated commands
22849 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22850 @itemx maint undeprecate @var{command}
22851 Deprecate or undeprecate the named @var{command}. Deprecated commands
22852 cause @value{GDBN} to issue a warning when you use them. The optional
22853 argument @var{replacement} says which newer command should be used in
22854 favor of the deprecated one; if it is given, @value{GDBN} will mention
22855 the replacement as part of the warning.
22857 @kindex maint dump-me
22858 @item maint dump-me
22859 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22860 Cause a fatal signal in the debugger and force it to dump its core.
22861 This is supported only on systems which support aborting a program
22862 with the @code{SIGQUIT} signal.
22864 @kindex maint internal-error
22865 @kindex maint internal-warning
22866 @item maint internal-error @r{[}@var{message-text}@r{]}
22867 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22868 Cause @value{GDBN} to call the internal function @code{internal_error}
22869 or @code{internal_warning} and hence behave as though an internal error
22870 or internal warning has been detected. In addition to reporting the
22871 internal problem, these functions give the user the opportunity to
22872 either quit @value{GDBN} or create a core file of the current
22873 @value{GDBN} session.
22875 These commands take an optional parameter @var{message-text} that is
22876 used as the text of the error or warning message.
22878 Here's an example of using @code{internal-error}:
22881 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22882 @dots{}/maint.c:121: internal-error: testing, 1, 2
22883 A problem internal to GDB has been detected. Further
22884 debugging may prove unreliable.
22885 Quit this debugging session? (y or n) @kbd{n}
22886 Create a core file? (y or n) @kbd{n}
22890 @kindex maint packet
22891 @item maint packet @var{text}
22892 If @value{GDBN} is talking to an inferior via the serial protocol,
22893 then this command sends the string @var{text} to the inferior, and
22894 displays the response packet. @value{GDBN} supplies the initial
22895 @samp{$} character, the terminating @samp{#} character, and the
22898 @kindex maint print architecture
22899 @item maint print architecture @r{[}@var{file}@r{]}
22900 Print the entire architecture configuration. The optional argument
22901 @var{file} names the file where the output goes.
22903 @kindex maint print c-tdesc
22904 @item maint print c-tdesc
22905 Print the current target description (@pxref{Target Descriptions}) as
22906 a C source file. The created source file can be used in @value{GDBN}
22907 when an XML parser is not available to parse the description.
22909 @kindex maint print dummy-frames
22910 @item maint print dummy-frames
22911 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22914 (@value{GDBP}) @kbd{b add}
22916 (@value{GDBP}) @kbd{print add(2,3)}
22917 Breakpoint 2, add (a=2, b=3) at @dots{}
22919 The program being debugged stopped while in a function called from GDB.
22921 (@value{GDBP}) @kbd{maint print dummy-frames}
22922 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22923 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22924 call_lo=0x01014000 call_hi=0x01014001
22928 Takes an optional file parameter.
22930 @kindex maint print registers
22931 @kindex maint print raw-registers
22932 @kindex maint print cooked-registers
22933 @kindex maint print register-groups
22934 @item maint print registers @r{[}@var{file}@r{]}
22935 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22936 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22937 @itemx maint print register-groups @r{[}@var{file}@r{]}
22938 Print @value{GDBN}'s internal register data structures.
22940 The command @code{maint print raw-registers} includes the contents of
22941 the raw register cache; the command @code{maint print cooked-registers}
22942 includes the (cooked) value of all registers; and the command
22943 @code{maint print register-groups} includes the groups that each
22944 register is a member of. @xref{Registers,, Registers, gdbint,
22945 @value{GDBN} Internals}.
22947 These commands take an optional parameter, a file name to which to
22948 write the information.
22950 @kindex maint print reggroups
22951 @item maint print reggroups @r{[}@var{file}@r{]}
22952 Print @value{GDBN}'s internal register group data structures. The
22953 optional argument @var{file} tells to what file to write the
22956 The register groups info looks like this:
22959 (@value{GDBP}) @kbd{maint print reggroups}
22972 This command forces @value{GDBN} to flush its internal register cache.
22974 @kindex maint print objfiles
22975 @cindex info for known object files
22976 @item maint print objfiles
22977 Print a dump of all known object files. For each object file, this
22978 command prints its name, address in memory, and all of its psymtabs
22981 @kindex maint print statistics
22982 @cindex bcache statistics
22983 @item maint print statistics
22984 This command prints, for each object file in the program, various data
22985 about that object file followed by the byte cache (@dfn{bcache})
22986 statistics for the object file. The objfile data includes the number
22987 of minimal, partial, full, and stabs symbols, the number of types
22988 defined by the objfile, the number of as yet unexpanded psym tables,
22989 the number of line tables and string tables, and the amount of memory
22990 used by the various tables. The bcache statistics include the counts,
22991 sizes, and counts of duplicates of all and unique objects, max,
22992 average, and median entry size, total memory used and its overhead and
22993 savings, and various measures of the hash table size and chain
22996 @kindex maint print target-stack
22997 @cindex target stack description
22998 @item maint print target-stack
22999 A @dfn{target} is an interface between the debugger and a particular
23000 kind of file or process. Targets can be stacked in @dfn{strata},
23001 so that more than one target can potentially respond to a request.
23002 In particular, memory accesses will walk down the stack of targets
23003 until they find a target that is interested in handling that particular
23006 This command prints a short description of each layer that was pushed on
23007 the @dfn{target stack}, starting from the top layer down to the bottom one.
23009 @kindex maint print type
23010 @cindex type chain of a data type
23011 @item maint print type @var{expr}
23012 Print the type chain for a type specified by @var{expr}. The argument
23013 can be either a type name or a symbol. If it is a symbol, the type of
23014 that symbol is described. The type chain produced by this command is
23015 a recursive definition of the data type as stored in @value{GDBN}'s
23016 data structures, including its flags and contained types.
23018 @kindex maint set dwarf2 max-cache-age
23019 @kindex maint show dwarf2 max-cache-age
23020 @item maint set dwarf2 max-cache-age
23021 @itemx maint show dwarf2 max-cache-age
23022 Control the DWARF 2 compilation unit cache.
23024 @cindex DWARF 2 compilation units cache
23025 In object files with inter-compilation-unit references, such as those
23026 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
23027 reader needs to frequently refer to previously read compilation units.
23028 This setting controls how long a compilation unit will remain in the
23029 cache if it is not referenced. A higher limit means that cached
23030 compilation units will be stored in memory longer, and more total
23031 memory will be used. Setting it to zero disables caching, which will
23032 slow down @value{GDBN} startup, but reduce memory consumption.
23034 @kindex maint set profile
23035 @kindex maint show profile
23036 @cindex profiling GDB
23037 @item maint set profile
23038 @itemx maint show profile
23039 Control profiling of @value{GDBN}.
23041 Profiling will be disabled until you use the @samp{maint set profile}
23042 command to enable it. When you enable profiling, the system will begin
23043 collecting timing and execution count data; when you disable profiling or
23044 exit @value{GDBN}, the results will be written to a log file. Remember that
23045 if you use profiling, @value{GDBN} will overwrite the profiling log file
23046 (often called @file{gmon.out}). If you have a record of important profiling
23047 data in a @file{gmon.out} file, be sure to move it to a safe location.
23049 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
23050 compiled with the @samp{-pg} compiler option.
23052 @kindex maint show-debug-regs
23053 @cindex x86 hardware debug registers
23054 @item maint show-debug-regs
23055 Control whether to show variables that mirror the x86 hardware debug
23056 registers. Use @code{ON} to enable, @code{OFF} to disable. If
23057 enabled, the debug registers values are shown when @value{GDBN} inserts or
23058 removes a hardware breakpoint or watchpoint, and when the inferior
23059 triggers a hardware-assisted breakpoint or watchpoint.
23061 @kindex maint space
23062 @cindex memory used by commands
23064 Control whether to display memory usage for each command. If set to a
23065 nonzero value, @value{GDBN} will display how much memory each command
23066 took, following the command's own output. This can also be requested
23067 by invoking @value{GDBN} with the @option{--statistics} command-line
23068 switch (@pxref{Mode Options}).
23071 @cindex time of command execution
23073 Control whether to display the execution time for each command. If
23074 set to a nonzero value, @value{GDBN} will display how much time it
23075 took to execute each command, following the command's own output.
23076 This can also be requested by invoking @value{GDBN} with the
23077 @option{--statistics} command-line switch (@pxref{Mode Options}).
23079 @kindex maint translate-address
23080 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
23081 Find the symbol stored at the location specified by the address
23082 @var{addr} and an optional section name @var{section}. If found,
23083 @value{GDBN} prints the name of the closest symbol and an offset from
23084 the symbol's location to the specified address. This is similar to
23085 the @code{info address} command (@pxref{Symbols}), except that this
23086 command also allows to find symbols in other sections.
23090 The following command is useful for non-interactive invocations of
23091 @value{GDBN}, such as in the test suite.
23094 @item set watchdog @var{nsec}
23095 @kindex set watchdog
23096 @cindex watchdog timer
23097 @cindex timeout for commands
23098 Set the maximum number of seconds @value{GDBN} will wait for the
23099 target operation to finish. If this time expires, @value{GDBN}
23100 reports and error and the command is aborted.
23102 @item show watchdog
23103 Show the current setting of the target wait timeout.
23106 @node Remote Protocol
23107 @appendix @value{GDBN} Remote Serial Protocol
23112 * Stop Reply Packets::
23113 * General Query Packets::
23114 * Register Packet Format::
23115 * Tracepoint Packets::
23116 * Host I/O Packets::
23119 * File-I/O Remote Protocol Extension::
23120 * Library List Format::
23121 * Memory Map Format::
23127 There may be occasions when you need to know something about the
23128 protocol---for example, if there is only one serial port to your target
23129 machine, you might want your program to do something special if it
23130 recognizes a packet meant for @value{GDBN}.
23132 In the examples below, @samp{->} and @samp{<-} are used to indicate
23133 transmitted and received data, respectively.
23135 @cindex protocol, @value{GDBN} remote serial
23136 @cindex serial protocol, @value{GDBN} remote
23137 @cindex remote serial protocol
23138 All @value{GDBN} commands and responses (other than acknowledgments) are
23139 sent as a @var{packet}. A @var{packet} is introduced with the character
23140 @samp{$}, the actual @var{packet-data}, and the terminating character
23141 @samp{#} followed by a two-digit @var{checksum}:
23144 @code{$}@var{packet-data}@code{#}@var{checksum}
23148 @cindex checksum, for @value{GDBN} remote
23150 The two-digit @var{checksum} is computed as the modulo 256 sum of all
23151 characters between the leading @samp{$} and the trailing @samp{#} (an
23152 eight bit unsigned checksum).
23154 Implementors should note that prior to @value{GDBN} 5.0 the protocol
23155 specification also included an optional two-digit @var{sequence-id}:
23158 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
23161 @cindex sequence-id, for @value{GDBN} remote
23163 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
23164 has never output @var{sequence-id}s. Stubs that handle packets added
23165 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
23167 @cindex acknowledgment, for @value{GDBN} remote
23168 When either the host or the target machine receives a packet, the first
23169 response expected is an acknowledgment: either @samp{+} (to indicate
23170 the package was received correctly) or @samp{-} (to request
23174 -> @code{$}@var{packet-data}@code{#}@var{checksum}
23179 The host (@value{GDBN}) sends @var{command}s, and the target (the
23180 debugging stub incorporated in your program) sends a @var{response}. In
23181 the case of step and continue @var{command}s, the response is only sent
23182 when the operation has completed (the target has again stopped).
23184 @var{packet-data} consists of a sequence of characters with the
23185 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
23188 @cindex remote protocol, field separator
23189 Fields within the packet should be separated using @samp{,} @samp{;} or
23190 @samp{:}. Except where otherwise noted all numbers are represented in
23191 @sc{hex} with leading zeros suppressed.
23193 Implementors should note that prior to @value{GDBN} 5.0, the character
23194 @samp{:} could not appear as the third character in a packet (as it
23195 would potentially conflict with the @var{sequence-id}).
23197 @cindex remote protocol, binary data
23198 @anchor{Binary Data}
23199 Binary data in most packets is encoded either as two hexadecimal
23200 digits per byte of binary data. This allowed the traditional remote
23201 protocol to work over connections which were only seven-bit clean.
23202 Some packets designed more recently assume an eight-bit clean
23203 connection, and use a more efficient encoding to send and receive
23206 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
23207 as an escape character. Any escaped byte is transmitted as the escape
23208 character followed by the original character XORed with @code{0x20}.
23209 For example, the byte @code{0x7d} would be transmitted as the two
23210 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
23211 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
23212 @samp{@}}) must always be escaped. Responses sent by the stub
23213 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
23214 is not interpreted as the start of a run-length encoded sequence
23217 Response @var{data} can be run-length encoded to save space.
23218 Run-length encoding replaces runs of identical characters with one
23219 instance of the repeated character, followed by a @samp{*} and a
23220 repeat count. The repeat count is itself sent encoded, to avoid
23221 binary characters in @var{data}: a value of @var{n} is sent as
23222 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
23223 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
23224 code 32) for a repeat count of 3. (This is because run-length
23225 encoding starts to win for counts 3 or more.) Thus, for example,
23226 @samp{0* } is a run-length encoding of ``0000'': the space character
23227 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
23230 The printable characters @samp{#} and @samp{$} or with a numeric value
23231 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
23232 seven repeats (@samp{$}) can be expanded using a repeat count of only
23233 five (@samp{"}). For example, @samp{00000000} can be encoded as
23236 The error response returned for some packets includes a two character
23237 error number. That number is not well defined.
23239 @cindex empty response, for unsupported packets
23240 For any @var{command} not supported by the stub, an empty response
23241 (@samp{$#00}) should be returned. That way it is possible to extend the
23242 protocol. A newer @value{GDBN} can tell if a packet is supported based
23245 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
23246 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
23252 The following table provides a complete list of all currently defined
23253 @var{command}s and their corresponding response @var{data}.
23254 @xref{File-I/O Remote Protocol Extension}, for details about the File
23255 I/O extension of the remote protocol.
23257 Each packet's description has a template showing the packet's overall
23258 syntax, followed by an explanation of the packet's meaning. We
23259 include spaces in some of the templates for clarity; these are not
23260 part of the packet's syntax. No @value{GDBN} packet uses spaces to
23261 separate its components. For example, a template like @samp{foo
23262 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
23263 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
23264 @var{baz}. @value{GDBN} does not transmit a space character between the
23265 @samp{foo} and the @var{bar}, or between the @var{bar} and the
23268 Note that all packet forms beginning with an upper- or lower-case
23269 letter, other than those described here, are reserved for future use.
23271 Here are the packet descriptions.
23276 @cindex @samp{!} packet
23277 Enable extended mode. In extended mode, the remote server is made
23278 persistent. The @samp{R} packet is used to restart the program being
23284 The remote target both supports and has enabled extended mode.
23288 @cindex @samp{?} packet
23289 Indicate the reason the target halted. The reply is the same as for
23293 @xref{Stop Reply Packets}, for the reply specifications.
23295 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
23296 @cindex @samp{A} packet
23297 Initialized @code{argv[]} array passed into program. @var{arglen}
23298 specifies the number of bytes in the hex encoded byte stream
23299 @var{arg}. See @code{gdbserver} for more details.
23304 The arguments were set.
23310 @cindex @samp{b} packet
23311 (Don't use this packet; its behavior is not well-defined.)
23312 Change the serial line speed to @var{baud}.
23314 JTC: @emph{When does the transport layer state change? When it's
23315 received, or after the ACK is transmitted. In either case, there are
23316 problems if the command or the acknowledgment packet is dropped.}
23318 Stan: @emph{If people really wanted to add something like this, and get
23319 it working for the first time, they ought to modify ser-unix.c to send
23320 some kind of out-of-band message to a specially-setup stub and have the
23321 switch happen "in between" packets, so that from remote protocol's point
23322 of view, nothing actually happened.}
23324 @item B @var{addr},@var{mode}
23325 @cindex @samp{B} packet
23326 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23327 breakpoint at @var{addr}.
23329 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23330 (@pxref{insert breakpoint or watchpoint packet}).
23332 @item c @r{[}@var{addr}@r{]}
23333 @cindex @samp{c} packet
23334 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23335 resume at current address.
23338 @xref{Stop Reply Packets}, for the reply specifications.
23340 @item C @var{sig}@r{[};@var{addr}@r{]}
23341 @cindex @samp{C} packet
23342 Continue with signal @var{sig} (hex signal number). If
23343 @samp{;@var{addr}} is omitted, resume at same address.
23346 @xref{Stop Reply Packets}, for the reply specifications.
23349 @cindex @samp{d} packet
23352 Don't use this packet; instead, define a general set packet
23353 (@pxref{General Query Packets}).
23356 @cindex @samp{D} packet
23357 Detach @value{GDBN} from the remote system. Sent to the remote target
23358 before @value{GDBN} disconnects via the @code{detach} command.
23368 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23369 @cindex @samp{F} packet
23370 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23371 This is part of the File-I/O protocol extension. @xref{File-I/O
23372 Remote Protocol Extension}, for the specification.
23375 @anchor{read registers packet}
23376 @cindex @samp{g} packet
23377 Read general registers.
23381 @item @var{XX@dots{}}
23382 Each byte of register data is described by two hex digits. The bytes
23383 with the register are transmitted in target byte order. The size of
23384 each register and their position within the @samp{g} packet are
23385 determined by the @value{GDBN} internal gdbarch functions
23386 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
23387 specification of several standard @samp{g} packets is specified below.
23392 @item G @var{XX@dots{}}
23393 @cindex @samp{G} packet
23394 Write general registers. @xref{read registers packet}, for a
23395 description of the @var{XX@dots{}} data.
23405 @item H @var{c} @var{t}
23406 @cindex @samp{H} packet
23407 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23408 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23409 should be @samp{c} for step and continue operations, @samp{g} for other
23410 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23411 the threads, a thread number, or @samp{0} which means pick any thread.
23422 @c 'H': How restrictive (or permissive) is the thread model. If a
23423 @c thread is selected and stopped, are other threads allowed
23424 @c to continue to execute? As I mentioned above, I think the
23425 @c semantics of each command when a thread is selected must be
23426 @c described. For example:
23428 @c 'g': If the stub supports threads and a specific thread is
23429 @c selected, returns the register block from that thread;
23430 @c otherwise returns current registers.
23432 @c 'G' If the stub supports threads and a specific thread is
23433 @c selected, sets the registers of the register block of
23434 @c that thread; otherwise sets current registers.
23436 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23437 @anchor{cycle step packet}
23438 @cindex @samp{i} packet
23439 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23440 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23441 step starting at that address.
23444 @cindex @samp{I} packet
23445 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23449 @cindex @samp{k} packet
23452 FIXME: @emph{There is no description of how to operate when a specific
23453 thread context has been selected (i.e.@: does 'k' kill only that
23456 @item m @var{addr},@var{length}
23457 @cindex @samp{m} packet
23458 Read @var{length} bytes of memory starting at address @var{addr}.
23459 Note that @var{addr} may not be aligned to any particular boundary.
23461 The stub need not use any particular size or alignment when gathering
23462 data from memory for the response; even if @var{addr} is word-aligned
23463 and @var{length} is a multiple of the word size, the stub is free to
23464 use byte accesses, or not. For this reason, this packet may not be
23465 suitable for accessing memory-mapped I/O devices.
23466 @cindex alignment of remote memory accesses
23467 @cindex size of remote memory accesses
23468 @cindex memory, alignment and size of remote accesses
23472 @item @var{XX@dots{}}
23473 Memory contents; each byte is transmitted as a two-digit hexadecimal
23474 number. The reply may contain fewer bytes than requested if the
23475 server was able to read only part of the region of memory.
23480 @item M @var{addr},@var{length}:@var{XX@dots{}}
23481 @cindex @samp{M} packet
23482 Write @var{length} bytes of memory starting at address @var{addr}.
23483 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23484 hexadecimal number.
23491 for an error (this includes the case where only part of the data was
23496 @cindex @samp{p} packet
23497 Read the value of register @var{n}; @var{n} is in hex.
23498 @xref{read registers packet}, for a description of how the returned
23499 register value is encoded.
23503 @item @var{XX@dots{}}
23504 the register's value
23508 Indicating an unrecognized @var{query}.
23511 @item P @var{n@dots{}}=@var{r@dots{}}
23512 @anchor{write register packet}
23513 @cindex @samp{P} packet
23514 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23515 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23516 digits for each byte in the register (target byte order).
23526 @item q @var{name} @var{params}@dots{}
23527 @itemx Q @var{name} @var{params}@dots{}
23528 @cindex @samp{q} packet
23529 @cindex @samp{Q} packet
23530 General query (@samp{q}) and set (@samp{Q}). These packets are
23531 described fully in @ref{General Query Packets}.
23534 @cindex @samp{r} packet
23535 Reset the entire system.
23537 Don't use this packet; use the @samp{R} packet instead.
23540 @cindex @samp{R} packet
23541 Restart the program being debugged. @var{XX}, while needed, is ignored.
23542 This packet is only available in extended mode.
23544 The @samp{R} packet has no reply.
23546 @item s @r{[}@var{addr}@r{]}
23547 @cindex @samp{s} packet
23548 Single step. @var{addr} is the address at which to resume. If
23549 @var{addr} is omitted, resume at same address.
23552 @xref{Stop Reply Packets}, for the reply specifications.
23554 @item S @var{sig}@r{[};@var{addr}@r{]}
23555 @anchor{step with signal packet}
23556 @cindex @samp{S} packet
23557 Step with signal. This is analogous to the @samp{C} packet, but
23558 requests a single-step, rather than a normal resumption of execution.
23561 @xref{Stop Reply Packets}, for the reply specifications.
23563 @item t @var{addr}:@var{PP},@var{MM}
23564 @cindex @samp{t} packet
23565 Search backwards starting at address @var{addr} for a match with pattern
23566 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23567 @var{addr} must be at least 3 digits.
23570 @cindex @samp{T} packet
23571 Find out if the thread XX is alive.
23576 thread is still alive
23582 Packets starting with @samp{v} are identified by a multi-letter name,
23583 up to the first @samp{;} or @samp{?} (or the end of the packet).
23585 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23586 @cindex @samp{vCont} packet
23587 Resume the inferior, specifying different actions for each thread.
23588 If an action is specified with no @var{tid}, then it is applied to any
23589 threads that don't have a specific action specified; if no default action is
23590 specified then other threads should remain stopped. Specifying multiple
23591 default actions is an error; specifying no actions is also an error.
23592 Thread IDs are specified in hexadecimal. Currently supported actions are:
23598 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23602 Step with signal @var{sig}. @var{sig} should be two hex digits.
23605 The optional @var{addr} argument normally associated with these packets is
23606 not supported in @samp{vCont}.
23609 @xref{Stop Reply Packets}, for the reply specifications.
23612 @cindex @samp{vCont?} packet
23613 Request a list of actions supported by the @samp{vCont} packet.
23617 @item vCont@r{[};@var{action}@dots{}@r{]}
23618 The @samp{vCont} packet is supported. Each @var{action} is a supported
23619 command in the @samp{vCont} packet.
23621 The @samp{vCont} packet is not supported.
23624 @item vFile:@var{operation}:@var{parameter}@dots{}
23625 @cindex @samp{vFile} packet
23626 Perform a file operation on the target system. For details,
23627 see @ref{Host I/O Packets}.
23629 @item vFlashErase:@var{addr},@var{length}
23630 @cindex @samp{vFlashErase} packet
23631 Direct the stub to erase @var{length} bytes of flash starting at
23632 @var{addr}. The region may enclose any number of flash blocks, but
23633 its start and end must fall on block boundaries, as indicated by the
23634 flash block size appearing in the memory map (@pxref{Memory Map
23635 Format}). @value{GDBN} groups flash memory programming operations
23636 together, and sends a @samp{vFlashDone} request after each group; the
23637 stub is allowed to delay erase operation until the @samp{vFlashDone}
23638 packet is received.
23648 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23649 @cindex @samp{vFlashWrite} packet
23650 Direct the stub to write data to flash address @var{addr}. The data
23651 is passed in binary form using the same encoding as for the @samp{X}
23652 packet (@pxref{Binary Data}). The memory ranges specified by
23653 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23654 not overlap, and must appear in order of increasing addresses
23655 (although @samp{vFlashErase} packets for higher addresses may already
23656 have been received; the ordering is guaranteed only between
23657 @samp{vFlashWrite} packets). If a packet writes to an address that was
23658 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23659 target-specific method, the results are unpredictable.
23667 for vFlashWrite addressing non-flash memory
23673 @cindex @samp{vFlashDone} packet
23674 Indicate to the stub that flash programming operation is finished.
23675 The stub is permitted to delay or batch the effects of a group of
23676 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23677 @samp{vFlashDone} packet is received. The contents of the affected
23678 regions of flash memory are unpredictable until the @samp{vFlashDone}
23679 request is completed.
23681 @item X @var{addr},@var{length}:@var{XX@dots{}}
23683 @cindex @samp{X} packet
23684 Write data to memory, where the data is transmitted in binary.
23685 @var{addr} is address, @var{length} is number of bytes,
23686 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23696 @item z @var{type},@var{addr},@var{length}
23697 @itemx Z @var{type},@var{addr},@var{length}
23698 @anchor{insert breakpoint or watchpoint packet}
23699 @cindex @samp{z} packet
23700 @cindex @samp{Z} packets
23701 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23702 watchpoint starting at address @var{address} and covering the next
23703 @var{length} bytes.
23705 Each breakpoint and watchpoint packet @var{type} is documented
23708 @emph{Implementation notes: A remote target shall return an empty string
23709 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23710 remote target shall support either both or neither of a given
23711 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23712 avoid potential problems with duplicate packets, the operations should
23713 be implemented in an idempotent way.}
23715 @item z0,@var{addr},@var{length}
23716 @itemx Z0,@var{addr},@var{length}
23717 @cindex @samp{z0} packet
23718 @cindex @samp{Z0} packet
23719 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23720 @var{addr} of size @var{length}.
23722 A memory breakpoint is implemented by replacing the instruction at
23723 @var{addr} with a software breakpoint or trap instruction. The
23724 @var{length} is used by targets that indicates the size of the
23725 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23726 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23728 @emph{Implementation note: It is possible for a target to copy or move
23729 code that contains memory breakpoints (e.g., when implementing
23730 overlays). The behavior of this packet, in the presence of such a
23731 target, is not defined.}
23743 @item z1,@var{addr},@var{length}
23744 @itemx Z1,@var{addr},@var{length}
23745 @cindex @samp{z1} packet
23746 @cindex @samp{Z1} packet
23747 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23748 address @var{addr} of size @var{length}.
23750 A hardware breakpoint is implemented using a mechanism that is not
23751 dependant on being able to modify the target's memory.
23753 @emph{Implementation note: A hardware breakpoint is not affected by code
23766 @item z2,@var{addr},@var{length}
23767 @itemx Z2,@var{addr},@var{length}
23768 @cindex @samp{z2} packet
23769 @cindex @samp{Z2} packet
23770 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23782 @item z3,@var{addr},@var{length}
23783 @itemx Z3,@var{addr},@var{length}
23784 @cindex @samp{z3} packet
23785 @cindex @samp{Z3} packet
23786 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23798 @item z4,@var{addr},@var{length}
23799 @itemx Z4,@var{addr},@var{length}
23800 @cindex @samp{z4} packet
23801 @cindex @samp{Z4} packet
23802 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23816 @node Stop Reply Packets
23817 @section Stop Reply Packets
23818 @cindex stop reply packets
23820 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23821 receive any of the below as a reply. In the case of the @samp{C},
23822 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23823 when the target halts. In the below the exact meaning of @dfn{signal
23824 number} is defined by the header @file{include/gdb/signals.h} in the
23825 @value{GDBN} source code.
23827 As in the description of request packets, we include spaces in the
23828 reply templates for clarity; these are not part of the reply packet's
23829 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23835 The program received signal number @var{AA} (a two-digit hexadecimal
23836 number). This is equivalent to a @samp{T} response with no
23837 @var{n}:@var{r} pairs.
23839 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23840 @cindex @samp{T} packet reply
23841 The program received signal number @var{AA} (a two-digit hexadecimal
23842 number). This is equivalent to an @samp{S} response, except that the
23843 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23844 and other information directly in the stop reply packet, reducing
23845 round-trip latency. Single-step and breakpoint traps are reported
23846 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23850 If @var{n} is a hexadecimal number, it is a register number, and the
23851 corresponding @var{r} gives that register's value. @var{r} is a
23852 series of bytes in target byte order, with each byte given by a
23853 two-digit hex number.
23856 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23860 If @var{n} is a recognized @dfn{stop reason}, it describes a more
23861 specific event that stopped the target. The currently defined stop
23862 reasons are listed below. @var{aa} should be @samp{05}, the trap
23863 signal. At most one stop reason should be present.
23866 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23867 and go on to the next; this allows us to extend the protocol in the
23871 The currently defined stop reasons are:
23877 The packet indicates a watchpoint hit, and @var{r} is the data address, in
23880 @cindex shared library events, remote reply
23882 The packet indicates that the loaded libraries have changed.
23883 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
23884 list of loaded libraries. @var{r} is ignored.
23888 The process exited, and @var{AA} is the exit status. This is only
23889 applicable to certain targets.
23892 The process terminated with signal @var{AA}.
23894 @item O @var{XX}@dots{}
23895 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23896 written as the program's console output. This can happen at any time
23897 while the program is running and the debugger should continue to wait
23898 for @samp{W}, @samp{T}, etc.
23900 @item F @var{call-id},@var{parameter}@dots{}
23901 @var{call-id} is the identifier which says which host system call should
23902 be called. This is just the name of the function. Translation into the
23903 correct system call is only applicable as it's defined in @value{GDBN}.
23904 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
23907 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23908 this very system call.
23910 The target replies with this packet when it expects @value{GDBN} to
23911 call a host system call on behalf of the target. @value{GDBN} replies
23912 with an appropriate @samp{F} packet and keeps up waiting for the next
23913 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23914 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
23915 Protocol Extension}, for more details.
23919 @node General Query Packets
23920 @section General Query Packets
23921 @cindex remote query requests
23923 Packets starting with @samp{q} are @dfn{general query packets};
23924 packets starting with @samp{Q} are @dfn{general set packets}. General
23925 query and set packets are a semi-unified form for retrieving and
23926 sending information to and from the stub.
23928 The initial letter of a query or set packet is followed by a name
23929 indicating what sort of thing the packet applies to. For example,
23930 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23931 definitions with the stub. These packet names follow some
23936 The name must not contain commas, colons or semicolons.
23938 Most @value{GDBN} query and set packets have a leading upper case
23941 The names of custom vendor packets should use a company prefix, in
23942 lower case, followed by a period. For example, packets designed at
23943 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23944 foos) or @samp{Qacme.bar} (for setting bars).
23947 The name of a query or set packet should be separated from any
23948 parameters by a @samp{:}; the parameters themselves should be
23949 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23950 full packet name, and check for a separator or the end of the packet,
23951 in case two packet names share a common prefix. New packets should not begin
23952 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23953 packets predate these conventions, and have arguments without any terminator
23954 for the packet name; we suspect they are in widespread use in places that
23955 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23956 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23959 Like the descriptions of the other packets, each description here
23960 has a template showing the packet's overall syntax, followed by an
23961 explanation of the packet's meaning. We include spaces in some of the
23962 templates for clarity; these are not part of the packet's syntax. No
23963 @value{GDBN} packet uses spaces to separate its components.
23965 Here are the currently defined query and set packets:
23970 @cindex current thread, remote request
23971 @cindex @samp{qC} packet
23972 Return the current thread id.
23977 Where @var{pid} is an unsigned hexadecimal process id.
23978 @item @r{(anything else)}
23979 Any other reply implies the old pid.
23982 @item qCRC:@var{addr},@var{length}
23983 @cindex CRC of memory block, remote request
23984 @cindex @samp{qCRC} packet
23985 Compute the CRC checksum of a block of memory.
23989 An error (such as memory fault)
23990 @item C @var{crc32}
23991 The specified memory region's checksum is @var{crc32}.
23995 @itemx qsThreadInfo
23996 @cindex list active threads, remote request
23997 @cindex @samp{qfThreadInfo} packet
23998 @cindex @samp{qsThreadInfo} packet
23999 Obtain a list of all active thread ids from the target (OS). Since there
24000 may be too many active threads to fit into one reply packet, this query
24001 works iteratively: it may require more than one query/reply sequence to
24002 obtain the entire list of threads. The first query of the sequence will
24003 be the @samp{qfThreadInfo} query; subsequent queries in the
24004 sequence will be the @samp{qsThreadInfo} query.
24006 NOTE: This packet replaces the @samp{qL} query (see below).
24012 @item m @var{id},@var{id}@dots{}
24013 a comma-separated list of thread ids
24015 (lower case letter @samp{L}) denotes end of list.
24018 In response to each query, the target will reply with a list of one or
24019 more thread ids, in big-endian unsigned hex, separated by commas.
24020 @value{GDBN} will respond to each reply with a request for more thread
24021 ids (using the @samp{qs} form of the query), until the target responds
24022 with @samp{l} (lower-case el, for @dfn{last}).
24024 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
24025 @cindex get thread-local storage address, remote request
24026 @cindex @samp{qGetTLSAddr} packet
24027 Fetch the address associated with thread local storage specified
24028 by @var{thread-id}, @var{offset}, and @var{lm}.
24030 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
24031 thread for which to fetch the TLS address.
24033 @var{offset} is the (big endian, hex encoded) offset associated with the
24034 thread local variable. (This offset is obtained from the debug
24035 information associated with the variable.)
24037 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
24038 the load module associated with the thread local storage. For example,
24039 a @sc{gnu}/Linux system will pass the link map address of the shared
24040 object associated with the thread local storage under consideration.
24041 Other operating environments may choose to represent the load module
24042 differently, so the precise meaning of this parameter will vary.
24046 @item @var{XX}@dots{}
24047 Hex encoded (big endian) bytes representing the address of the thread
24048 local storage requested.
24051 An error occurred. @var{nn} are hex digits.
24054 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
24057 @item qL @var{startflag} @var{threadcount} @var{nextthread}
24058 Obtain thread information from RTOS. Where: @var{startflag} (one hex
24059 digit) is one to indicate the first query and zero to indicate a
24060 subsequent query; @var{threadcount} (two hex digits) is the maximum
24061 number of threads the response packet can contain; and @var{nextthread}
24062 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
24063 returned in the response as @var{argthread}.
24065 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
24069 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
24070 Where: @var{count} (two hex digits) is the number of threads being
24071 returned; @var{done} (one hex digit) is zero to indicate more threads
24072 and one indicates no further threads; @var{argthreadid} (eight hex
24073 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
24074 is a sequence of thread IDs from the target. @var{threadid} (eight hex
24075 digits). See @code{remote.c:parse_threadlist_response()}.
24079 @cindex section offsets, remote request
24080 @cindex @samp{qOffsets} packet
24081 Get section offsets that the target used when relocating the downloaded
24086 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
24087 Relocate the @code{Text} section by @var{xxx} from its original address.
24088 Relocate the @code{Data} section by @var{yyy} from its original address.
24089 If the object file format provides segment information (e.g.@: @sc{elf}
24090 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
24091 segments by the supplied offsets.
24093 @emph{Note: while a @code{Bss} offset may be included in the response,
24094 @value{GDBN} ignores this and instead applies the @code{Data} offset
24095 to the @code{Bss} section.}
24097 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
24098 Relocate the first segment of the object file, which conventionally
24099 contains program code, to a starting address of @var{xxx}. If
24100 @samp{DataSeg} is specified, relocate the second segment, which
24101 conventionally contains modifiable data, to a starting address of
24102 @var{yyy}. @value{GDBN} will report an error if the object file
24103 does not contain segment information, or does not contain at least
24104 as many segments as mentioned in the reply. Extra segments are
24105 kept at fixed offsets relative to the last relocated segment.
24108 @item qP @var{mode} @var{threadid}
24109 @cindex thread information, remote request
24110 @cindex @samp{qP} packet
24111 Returns information on @var{threadid}. Where: @var{mode} is a hex
24112 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
24114 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
24117 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
24119 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
24120 @cindex pass signals to inferior, remote request
24121 @cindex @samp{QPassSignals} packet
24122 @anchor{QPassSignals}
24123 Each listed @var{signal} should be passed directly to the inferior process.
24124 Signals are numbered identically to continue packets and stop replies
24125 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
24126 strictly greater than the previous item. These signals do not need to stop
24127 the inferior, or be reported to @value{GDBN}. All other signals should be
24128 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
24129 combine; any earlier @samp{QPassSignals} list is completely replaced by the
24130 new list. This packet improves performance when using @samp{handle
24131 @var{signal} nostop noprint pass}.
24136 The request succeeded.
24139 An error occurred. @var{nn} are hex digits.
24142 An empty reply indicates that @samp{QPassSignals} is not supported by
24146 Use of this packet is controlled by the @code{set remote pass-signals}
24147 command (@pxref{Remote Configuration, set remote pass-signals}).
24148 This packet is not probed by default; the remote stub must request it,
24149 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24151 @item qRcmd,@var{command}
24152 @cindex execute remote command, remote request
24153 @cindex @samp{qRcmd} packet
24154 @var{command} (hex encoded) is passed to the local interpreter for
24155 execution. Invalid commands should be reported using the output
24156 string. Before the final result packet, the target may also respond
24157 with a number of intermediate @samp{O@var{output}} console output
24158 packets. @emph{Implementors should note that providing access to a
24159 stubs's interpreter may have security implications}.
24164 A command response with no output.
24166 A command response with the hex encoded output string @var{OUTPUT}.
24168 Indicate a badly formed request.
24170 An empty reply indicates that @samp{qRcmd} is not recognized.
24173 (Note that the @code{qRcmd} packet's name is separated from the
24174 command by a @samp{,}, not a @samp{:}, contrary to the naming
24175 conventions above. Please don't use this packet as a model for new
24178 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
24179 @cindex supported packets, remote query
24180 @cindex features of the remote protocol
24181 @cindex @samp{qSupported} packet
24182 @anchor{qSupported}
24183 Tell the remote stub about features supported by @value{GDBN}, and
24184 query the stub for features it supports. This packet allows
24185 @value{GDBN} and the remote stub to take advantage of each others'
24186 features. @samp{qSupported} also consolidates multiple feature probes
24187 at startup, to improve @value{GDBN} performance---a single larger
24188 packet performs better than multiple smaller probe packets on
24189 high-latency links. Some features may enable behavior which must not
24190 be on by default, e.g.@: because it would confuse older clients or
24191 stubs. Other features may describe packets which could be
24192 automatically probed for, but are not. These features must be
24193 reported before @value{GDBN} will use them. This ``default
24194 unsupported'' behavior is not appropriate for all packets, but it
24195 helps to keep the initial connection time under control with new
24196 versions of @value{GDBN} which support increasing numbers of packets.
24200 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
24201 The stub supports or does not support each returned @var{stubfeature},
24202 depending on the form of each @var{stubfeature} (see below for the
24205 An empty reply indicates that @samp{qSupported} is not recognized,
24206 or that no features needed to be reported to @value{GDBN}.
24209 The allowed forms for each feature (either a @var{gdbfeature} in the
24210 @samp{qSupported} packet, or a @var{stubfeature} in the response)
24214 @item @var{name}=@var{value}
24215 The remote protocol feature @var{name} is supported, and associated
24216 with the specified @var{value}. The format of @var{value} depends
24217 on the feature, but it must not include a semicolon.
24219 The remote protocol feature @var{name} is supported, and does not
24220 need an associated value.
24222 The remote protocol feature @var{name} is not supported.
24224 The remote protocol feature @var{name} may be supported, and
24225 @value{GDBN} should auto-detect support in some other way when it is
24226 needed. This form will not be used for @var{gdbfeature} notifications,
24227 but may be used for @var{stubfeature} responses.
24230 Whenever the stub receives a @samp{qSupported} request, the
24231 supplied set of @value{GDBN} features should override any previous
24232 request. This allows @value{GDBN} to put the stub in a known
24233 state, even if the stub had previously been communicating with
24234 a different version of @value{GDBN}.
24236 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
24237 are defined yet. Stubs should ignore any unknown values for
24238 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
24239 packet supports receiving packets of unlimited length (earlier
24240 versions of @value{GDBN} may reject overly long responses). Values
24241 for @var{gdbfeature} may be defined in the future to let the stub take
24242 advantage of new features in @value{GDBN}, e.g.@: incompatible
24243 improvements in the remote protocol---support for unlimited length
24244 responses would be a @var{gdbfeature} example, if it were not implied by
24245 the @samp{qSupported} query. The stub's reply should be independent
24246 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
24247 describes all the features it supports, and then the stub replies with
24248 all the features it supports.
24250 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
24251 responses, as long as each response uses one of the standard forms.
24253 Some features are flags. A stub which supports a flag feature
24254 should respond with a @samp{+} form response. Other features
24255 require values, and the stub should respond with an @samp{=}
24258 Each feature has a default value, which @value{GDBN} will use if
24259 @samp{qSupported} is not available or if the feature is not mentioned
24260 in the @samp{qSupported} response. The default values are fixed; a
24261 stub is free to omit any feature responses that match the defaults.
24263 Not all features can be probed, but for those which can, the probing
24264 mechanism is useful: in some cases, a stub's internal
24265 architecture may not allow the protocol layer to know some information
24266 about the underlying target in advance. This is especially common in
24267 stubs which may be configured for multiple targets.
24269 These are the currently defined stub features and their properties:
24271 @multitable @columnfractions 0.35 0.2 0.12 0.2
24272 @c NOTE: The first row should be @headitem, but we do not yet require
24273 @c a new enough version of Texinfo (4.7) to use @headitem.
24275 @tab Value Required
24279 @item @samp{PacketSize}
24284 @item @samp{qXfer:auxv:read}
24289 @item @samp{qXfer:features:read}
24294 @item @samp{qXfer:libraries:read}
24299 @item @samp{qXfer:memory-map:read}
24304 @item @samp{qXfer:spu:read}
24309 @item @samp{qXfer:spu:write}
24314 @item @samp{QPassSignals}
24321 These are the currently defined stub features, in more detail:
24324 @cindex packet size, remote protocol
24325 @item PacketSize=@var{bytes}
24326 The remote stub can accept packets up to at least @var{bytes} in
24327 length. @value{GDBN} will send packets up to this size for bulk
24328 transfers, and will never send larger packets. This is a limit on the
24329 data characters in the packet, including the frame and checksum.
24330 There is no trailing NUL byte in a remote protocol packet; if the stub
24331 stores packets in a NUL-terminated format, it should allow an extra
24332 byte in its buffer for the NUL. If this stub feature is not supported,
24333 @value{GDBN} guesses based on the size of the @samp{g} packet response.
24335 @item qXfer:auxv:read
24336 The remote stub understands the @samp{qXfer:auxv:read} packet
24337 (@pxref{qXfer auxiliary vector read}).
24339 @item qXfer:features:read
24340 The remote stub understands the @samp{qXfer:features:read} packet
24341 (@pxref{qXfer target description read}).
24343 @item qXfer:libraries:read
24344 The remote stub understands the @samp{qXfer:libraries:read} packet
24345 (@pxref{qXfer library list read}).
24347 @item qXfer:memory-map:read
24348 The remote stub understands the @samp{qXfer:memory-map:read} packet
24349 (@pxref{qXfer memory map read}).
24351 @item qXfer:spu:read
24352 The remote stub understands the @samp{qXfer:spu:read} packet
24353 (@pxref{qXfer spu read}).
24355 @item qXfer:spu:write
24356 The remote stub understands the @samp{qXfer:spu:write} packet
24357 (@pxref{qXfer spu write}).
24360 The remote stub understands the @samp{QPassSignals} packet
24361 (@pxref{QPassSignals}).
24366 @cindex symbol lookup, remote request
24367 @cindex @samp{qSymbol} packet
24368 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24369 requests. Accept requests from the target for the values of symbols.
24374 The target does not need to look up any (more) symbols.
24375 @item qSymbol:@var{sym_name}
24376 The target requests the value of symbol @var{sym_name} (hex encoded).
24377 @value{GDBN} may provide the value by using the
24378 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24382 @item qSymbol:@var{sym_value}:@var{sym_name}
24383 Set the value of @var{sym_name} to @var{sym_value}.
24385 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24386 target has previously requested.
24388 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24389 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24395 The target does not need to look up any (more) symbols.
24396 @item qSymbol:@var{sym_name}
24397 The target requests the value of a new symbol @var{sym_name} (hex
24398 encoded). @value{GDBN} will continue to supply the values of symbols
24399 (if available), until the target ceases to request them.
24404 @xref{Tracepoint Packets}.
24406 @item qThreadExtraInfo,@var{id}
24407 @cindex thread attributes info, remote request
24408 @cindex @samp{qThreadExtraInfo} packet
24409 Obtain a printable string description of a thread's attributes from
24410 the target OS. @var{id} is a thread-id in big-endian hex. This
24411 string may contain anything that the target OS thinks is interesting
24412 for @value{GDBN} to tell the user about the thread. The string is
24413 displayed in @value{GDBN}'s @code{info threads} display. Some
24414 examples of possible thread extra info strings are @samp{Runnable}, or
24415 @samp{Blocked on Mutex}.
24419 @item @var{XX}@dots{}
24420 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
24421 comprising the printable string containing the extra information about
24422 the thread's attributes.
24425 (Note that the @code{qThreadExtraInfo} packet's name is separated from
24426 the command by a @samp{,}, not a @samp{:}, contrary to the naming
24427 conventions above. Please don't use this packet as a model for new
24435 @xref{Tracepoint Packets}.
24437 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
24438 @cindex read special object, remote request
24439 @cindex @samp{qXfer} packet
24440 @anchor{qXfer read}
24441 Read uninterpreted bytes from the target's special data area
24442 identified by the keyword @var{object}. Request @var{length} bytes
24443 starting at @var{offset} bytes into the data. The content and
24444 encoding of @var{annex} is specific to @var{object}; it can supply
24445 additional details about what data to access.
24447 Here are the specific requests of this form defined so far. All
24448 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
24449 formats, listed below.
24452 @item qXfer:auxv:read::@var{offset},@var{length}
24453 @anchor{qXfer auxiliary vector read}
24454 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
24455 auxiliary vector}. Note @var{annex} must be empty.
24457 This packet is not probed by default; the remote stub must request it,
24458 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24460 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
24461 @anchor{qXfer target description read}
24462 Access the @dfn{target description}. @xref{Target Descriptions}. The
24463 annex specifies which XML document to access. The main description is
24464 always loaded from the @samp{target.xml} annex.
24466 This packet is not probed by default; the remote stub must request it,
24467 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24469 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
24470 @anchor{qXfer library list read}
24471 Access the target's list of loaded libraries. @xref{Library List Format}.
24472 The annex part of the generic @samp{qXfer} packet must be empty
24473 (@pxref{qXfer read}).
24475 Targets which maintain a list of libraries in the program's memory do
24476 not need to implement this packet; it is designed for platforms where
24477 the operating system manages the list of loaded libraries.
24479 This packet is not probed by default; the remote stub must request it,
24480 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24482 @item qXfer:memory-map:read::@var{offset},@var{length}
24483 @anchor{qXfer memory map read}
24484 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
24485 annex part of the generic @samp{qXfer} packet must be empty
24486 (@pxref{qXfer read}).
24488 This packet is not probed by default; the remote stub must request it,
24489 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24491 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
24492 @anchor{qXfer spu read}
24493 Read contents of an @code{spufs} file on the target system. The
24494 annex specifies which file to read; it must be of the form
24495 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24496 in the target process, and @var{name} identifes the @code{spufs} file
24497 in that context to be accessed.
24499 This packet is not probed by default; the remote stub must request it,
24500 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24506 Data @var{data} (@pxref{Binary Data}) has been read from the
24507 target. There may be more data at a higher address (although
24508 it is permitted to return @samp{m} even for the last valid
24509 block of data, as long as at least one byte of data was read).
24510 @var{data} may have fewer bytes than the @var{length} in the
24514 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24515 There is no more data to be read. @var{data} may have fewer bytes
24516 than the @var{length} in the request.
24519 The @var{offset} in the request is at the end of the data.
24520 There is no more data to be read.
24523 The request was malformed, or @var{annex} was invalid.
24526 The offset was invalid, or there was an error encountered reading the data.
24527 @var{nn} is a hex-encoded @code{errno} value.
24530 An empty reply indicates the @var{object} string was not recognized by
24531 the stub, or that the object does not support reading.
24534 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24535 @cindex write data into object, remote request
24536 Write uninterpreted bytes into the target's special data area
24537 identified by the keyword @var{object}, starting at @var{offset} bytes
24538 into the data. @var{data}@dots{} is the binary-encoded data
24539 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24540 is specific to @var{object}; it can supply additional details about what data
24543 Here are the specific requests of this form defined so far. All
24544 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
24545 formats, listed below.
24548 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24549 @anchor{qXfer spu write}
24550 Write @var{data} to an @code{spufs} file on the target system. The
24551 annex specifies which file to write; it must be of the form
24552 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24553 in the target process, and @var{name} identifes the @code{spufs} file
24554 in that context to be accessed.
24556 This packet is not probed by default; the remote stub must request it,
24557 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24563 @var{nn} (hex encoded) is the number of bytes written.
24564 This may be fewer bytes than supplied in the request.
24567 The request was malformed, or @var{annex} was invalid.
24570 The offset was invalid, or there was an error encountered writing the data.
24571 @var{nn} is a hex-encoded @code{errno} value.
24574 An empty reply indicates the @var{object} string was not
24575 recognized by the stub, or that the object does not support writing.
24578 @item qXfer:@var{object}:@var{operation}:@dots{}
24579 Requests of this form may be added in the future. When a stub does
24580 not recognize the @var{object} keyword, or its support for
24581 @var{object} does not recognize the @var{operation} keyword, the stub
24582 must respond with an empty packet.
24586 @node Register Packet Format
24587 @section Register Packet Format
24589 The following @code{g}/@code{G} packets have previously been defined.
24590 In the below, some thirty-two bit registers are transferred as
24591 sixty-four bits. Those registers should be zero/sign extended (which?)
24592 to fill the space allocated. Register bytes are transferred in target
24593 byte order. The two nibbles within a register byte are transferred
24594 most-significant - least-significant.
24600 All registers are transferred as thirty-two bit quantities in the order:
24601 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24602 registers; fsr; fir; fp.
24606 All registers are transferred as sixty-four bit quantities (including
24607 thirty-two bit registers such as @code{sr}). The ordering is the same
24612 @node Tracepoint Packets
24613 @section Tracepoint Packets
24614 @cindex tracepoint packets
24615 @cindex packets, tracepoint
24617 Here we describe the packets @value{GDBN} uses to implement
24618 tracepoints (@pxref{Tracepoints}).
24622 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24623 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24624 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24625 the tracepoint is disabled. @var{step} is the tracepoint's step
24626 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24627 present, further @samp{QTDP} packets will follow to specify this
24628 tracepoint's actions.
24633 The packet was understood and carried out.
24635 The packet was not recognized.
24638 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24639 Define actions to be taken when a tracepoint is hit. @var{n} and
24640 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24641 this tracepoint. This packet may only be sent immediately after
24642 another @samp{QTDP} packet that ended with a @samp{-}. If the
24643 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24644 specifying more actions for this tracepoint.
24646 In the series of action packets for a given tracepoint, at most one
24647 can have an @samp{S} before its first @var{action}. If such a packet
24648 is sent, it and the following packets define ``while-stepping''
24649 actions. Any prior packets define ordinary actions --- that is, those
24650 taken when the tracepoint is first hit. If no action packet has an
24651 @samp{S}, then all the packets in the series specify ordinary
24652 tracepoint actions.
24654 The @samp{@var{action}@dots{}} portion of the packet is a series of
24655 actions, concatenated without separators. Each action has one of the
24661 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24662 a hexadecimal number whose @var{i}'th bit is set if register number
24663 @var{i} should be collected. (The least significant bit is numbered
24664 zero.) Note that @var{mask} may be any number of digits long; it may
24665 not fit in a 32-bit word.
24667 @item M @var{basereg},@var{offset},@var{len}
24668 Collect @var{len} bytes of memory starting at the address in register
24669 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24670 @samp{-1}, then the range has a fixed address: @var{offset} is the
24671 address of the lowest byte to collect. The @var{basereg},
24672 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24673 values (the @samp{-1} value for @var{basereg} is a special case).
24675 @item X @var{len},@var{expr}
24676 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24677 it directs. @var{expr} is an agent expression, as described in
24678 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24679 two-digit hex number in the packet; @var{len} is the number of bytes
24680 in the expression (and thus one-half the number of hex digits in the
24685 Any number of actions may be packed together in a single @samp{QTDP}
24686 packet, as long as the packet does not exceed the maximum packet
24687 length (400 bytes, for many stubs). There may be only one @samp{R}
24688 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24689 actions. Any registers referred to by @samp{M} and @samp{X} actions
24690 must be collected by a preceding @samp{R} action. (The
24691 ``while-stepping'' actions are treated as if they were attached to a
24692 separate tracepoint, as far as these restrictions are concerned.)
24697 The packet was understood and carried out.
24699 The packet was not recognized.
24702 @item QTFrame:@var{n}
24703 Select the @var{n}'th tracepoint frame from the buffer, and use the
24704 register and memory contents recorded there to answer subsequent
24705 request packets from @value{GDBN}.
24707 A successful reply from the stub indicates that the stub has found the
24708 requested frame. The response is a series of parts, concatenated
24709 without separators, describing the frame we selected. Each part has
24710 one of the following forms:
24714 The selected frame is number @var{n} in the trace frame buffer;
24715 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24716 was no frame matching the criteria in the request packet.
24719 The selected trace frame records a hit of tracepoint number @var{t};
24720 @var{t} is a hexadecimal number.
24724 @item QTFrame:pc:@var{addr}
24725 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24726 currently selected frame whose PC is @var{addr};
24727 @var{addr} is a hexadecimal number.
24729 @item QTFrame:tdp:@var{t}
24730 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24731 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24732 is a hexadecimal number.
24734 @item QTFrame:range:@var{start}:@var{end}
24735 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24736 currently selected frame whose PC is between @var{start} (inclusive)
24737 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24740 @item QTFrame:outside:@var{start}:@var{end}
24741 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24742 frame @emph{outside} the given range of addresses.
24745 Begin the tracepoint experiment. Begin collecting data from tracepoint
24746 hits in the trace frame buffer.
24749 End the tracepoint experiment. Stop collecting trace frames.
24752 Clear the table of tracepoints, and empty the trace frame buffer.
24754 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24755 Establish the given ranges of memory as ``transparent''. The stub
24756 will answer requests for these ranges from memory's current contents,
24757 if they were not collected as part of the tracepoint hit.
24759 @value{GDBN} uses this to mark read-only regions of memory, like those
24760 containing program code. Since these areas never change, they should
24761 still have the same contents they did when the tracepoint was hit, so
24762 there's no reason for the stub to refuse to provide their contents.
24765 Ask the stub if there is a trace experiment running right now.
24770 There is no trace experiment running.
24772 There is a trace experiment running.
24778 @node Host I/O Packets
24779 @section Host I/O Packets
24780 @cindex Host I/O, remote protocol
24781 @cindex file transfer, remote protocol
24783 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
24784 operations on the far side of a remote link. For example, Host I/O is
24785 used to upload and download files to a remote target with its own
24786 filesystem. Host I/O uses the same constant values and data structure
24787 layout as the target-initiated File-I/O protocol. However, the
24788 Host I/O packets are structured differently. The target-initiated
24789 protocol relies on target memory to store parameters and buffers.
24790 Host I/O requests are initiated by @value{GDBN}, and the
24791 target's memory is not involved. @xref{File-I/O Remote Protocol
24792 Extension}, for more details on the target-initiated protocol.
24794 The Host I/O request packets all encode a single operation along with
24795 its arguments. They have this format:
24799 @item vFile:@var{operation}: @var{parameter}@dots{}
24800 @var{operation} is the name of the particular request; the target
24801 should compare the entire packet name up to the second colon when checking
24802 for a supported operation. The format of @var{parameter} depends on
24803 the operation. Numbers are always passed in hexadecimal. Negative
24804 numbers have an explicit minus sign (i.e.@: two's complement is not
24805 used). Strings (e.g.@: filenames) are encoded as a series of
24806 hexadecimal bytes. The last argument to a system call may be a
24807 buffer of escaped binary data (@pxref{Binary Data}).
24811 The valid responses to Host I/O packets are:
24815 @item F @var{result} [, @var{errno}] [; @var{attachment}]
24816 @var{result} is the integer value returned by this operation, usually
24817 non-negative for success and -1 for errors. If an error has occured,
24818 @var{errno} will be included in the result. @var{errno} will have a
24819 value defined by the File-I/O protocol (@pxref{Errno Values}). For
24820 operations which return data, @var{attachment} supplies the data as a
24821 binary buffer. Binary buffers in response packets are escaped in the
24822 normal way (@pxref{Binary Data}). See the individual packet
24823 documentation for the interpretation of @var{result} and
24827 An empty response indicates that this operation is not recognized.
24831 These are the supported Host I/O operations:
24834 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
24835 Open a file at @var{pathname} and return a file descriptor for it, or
24836 return -1 if an error occurs. @var{pathname} is a string,
24837 @var{flags} is an integer indicating a mask of open flags
24838 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
24839 of mode bits to use if the file is created (@pxref{mode_t Values}).
24840 @xref{open}, for details of the open flags and mode values.
24842 @item vFile:close: @var{fd}
24843 Close the open file corresponding to @var{fd} and return 0, or
24844 -1 if an error occurs.
24846 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
24847 Read data from the open file corresponding to @var{fd}. Up to
24848 @var{count} bytes will be read from the file, starting at @var{offset}
24849 relative to the start of the file. The target may read fewer bytes;
24850 common reasons include packet size limits and an end-of-file
24851 condition. The number of bytes read is returned. Zero should only be
24852 returned for a successful read at the end of the file, or if
24853 @var{count} was zero.
24855 The data read should be returned as a binary attachment on success.
24856 If zero bytes were read, the response should include an empty binary
24857 attachment (i.e.@: a trailing semicolon). The return value is the
24858 number of target bytes read; the binary attachment may be longer if
24859 some characters were escaped.
24861 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
24862 Write @var{data} (a binary buffer) to the open file corresponding
24863 to @var{fd}. Start the write at @var{offset} from the start of the
24864 file. Unlike many @code{write} system calls, there is no
24865 separate @var{count} argument; the length of @var{data} in the
24866 packet is used. @samp{vFile:write} returns the number of bytes written,
24867 which may be shorter than the length of @var{data}, or -1 if an
24870 @item vFile:unlink: @var{pathname}
24871 Delete the file at @var{pathname} on the target. Return 0,
24872 or -1 if an error occurs. @var{pathname} is a string.
24877 @section Interrupts
24878 @cindex interrupts (remote protocol)
24880 When a program on the remote target is running, @value{GDBN} may
24881 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24882 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24883 setting (@pxref{set remotebreak}).
24885 The precise meaning of @code{BREAK} is defined by the transport
24886 mechanism and may, in fact, be undefined. @value{GDBN} does
24887 not currently define a @code{BREAK} mechanism for any of the network
24890 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24891 transport mechanisms. It is represented by sending the single byte
24892 @code{0x03} without any of the usual packet overhead described in
24893 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24894 transmitted as part of a packet, it is considered to be packet data
24895 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24896 (@pxref{X packet}), used for binary downloads, may include an unescaped
24897 @code{0x03} as part of its packet.
24899 Stubs are not required to recognize these interrupt mechanisms and the
24900 precise meaning associated with receipt of the interrupt is
24901 implementation defined. If the stub is successful at interrupting the
24902 running program, it is expected that it will send one of the Stop
24903 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24904 of successfully stopping the program. Interrupts received while the
24905 program is stopped will be discarded.
24910 Example sequence of a target being re-started. Notice how the restart
24911 does not get any direct output:
24916 @emph{target restarts}
24919 <- @code{T001:1234123412341234}
24923 Example sequence of a target being stepped by a single instruction:
24926 -> @code{G1445@dots{}}
24931 <- @code{T001:1234123412341234}
24935 <- @code{1455@dots{}}
24939 @node File-I/O Remote Protocol Extension
24940 @section File-I/O Remote Protocol Extension
24941 @cindex File-I/O remote protocol extension
24944 * File-I/O Overview::
24945 * Protocol Basics::
24946 * The F Request Packet::
24947 * The F Reply Packet::
24948 * The Ctrl-C Message::
24950 * List of Supported Calls::
24951 * Protocol-specific Representation of Datatypes::
24953 * File-I/O Examples::
24956 @node File-I/O Overview
24957 @subsection File-I/O Overview
24958 @cindex file-i/o overview
24960 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24961 target to use the host's file system and console I/O to perform various
24962 system calls. System calls on the target system are translated into a
24963 remote protocol packet to the host system, which then performs the needed
24964 actions and returns a response packet to the target system.
24965 This simulates file system operations even on targets that lack file systems.
24967 The protocol is defined to be independent of both the host and target systems.
24968 It uses its own internal representation of datatypes and values. Both
24969 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24970 translating the system-dependent value representations into the internal
24971 protocol representations when data is transmitted.
24973 The communication is synchronous. A system call is possible only when
24974 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24975 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24976 the target is stopped to allow deterministic access to the target's
24977 memory. Therefore File-I/O is not interruptible by target signals. On
24978 the other hand, it is possible to interrupt File-I/O by a user interrupt
24979 (@samp{Ctrl-C}) within @value{GDBN}.
24981 The target's request to perform a host system call does not finish
24982 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24983 after finishing the system call, the target returns to continuing the
24984 previous activity (continue, step). No additional continue or step
24985 request from @value{GDBN} is required.
24988 (@value{GDBP}) continue
24989 <- target requests 'system call X'
24990 target is stopped, @value{GDBN} executes system call
24991 -> @value{GDBN} returns result
24992 ... target continues, @value{GDBN} returns to wait for the target
24993 <- target hits breakpoint and sends a Txx packet
24996 The protocol only supports I/O on the console and to regular files on
24997 the host file system. Character or block special devices, pipes,
24998 named pipes, sockets or any other communication method on the host
24999 system are not supported by this protocol.
25001 @node Protocol Basics
25002 @subsection Protocol Basics
25003 @cindex protocol basics, file-i/o
25005 The File-I/O protocol uses the @code{F} packet as the request as well
25006 as reply packet. Since a File-I/O system call can only occur when
25007 @value{GDBN} is waiting for a response from the continuing or stepping target,
25008 the File-I/O request is a reply that @value{GDBN} has to expect as a result
25009 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
25010 This @code{F} packet contains all information needed to allow @value{GDBN}
25011 to call the appropriate host system call:
25015 A unique identifier for the requested system call.
25018 All parameters to the system call. Pointers are given as addresses
25019 in the target memory address space. Pointers to strings are given as
25020 pointer/length pair. Numerical values are given as they are.
25021 Numerical control flags are given in a protocol-specific representation.
25025 At this point, @value{GDBN} has to perform the following actions.
25029 If the parameters include pointer values to data needed as input to a
25030 system call, @value{GDBN} requests this data from the target with a
25031 standard @code{m} packet request. This additional communication has to be
25032 expected by the target implementation and is handled as any other @code{m}
25036 @value{GDBN} translates all value from protocol representation to host
25037 representation as needed. Datatypes are coerced into the host types.
25040 @value{GDBN} calls the system call.
25043 It then coerces datatypes back to protocol representation.
25046 If the system call is expected to return data in buffer space specified
25047 by pointer parameters to the call, the data is transmitted to the
25048 target using a @code{M} or @code{X} packet. This packet has to be expected
25049 by the target implementation and is handled as any other @code{M} or @code{X}
25054 Eventually @value{GDBN} replies with another @code{F} packet which contains all
25055 necessary information for the target to continue. This at least contains
25062 @code{errno}, if has been changed by the system call.
25069 After having done the needed type and value coercion, the target continues
25070 the latest continue or step action.
25072 @node The F Request Packet
25073 @subsection The @code{F} Request Packet
25074 @cindex file-i/o request packet
25075 @cindex @code{F} request packet
25077 The @code{F} request packet has the following format:
25080 @item F@var{call-id},@var{parameter@dots{}}
25082 @var{call-id} is the identifier to indicate the host system call to be called.
25083 This is just the name of the function.
25085 @var{parameter@dots{}} are the parameters to the system call.
25086 Parameters are hexadecimal integer values, either the actual values in case
25087 of scalar datatypes, pointers to target buffer space in case of compound
25088 datatypes and unspecified memory areas, or pointer/length pairs in case
25089 of string parameters. These are appended to the @var{call-id} as a
25090 comma-delimited list. All values are transmitted in ASCII
25091 string representation, pointer/length pairs separated by a slash.
25097 @node The F Reply Packet
25098 @subsection The @code{F} Reply Packet
25099 @cindex file-i/o reply packet
25100 @cindex @code{F} reply packet
25102 The @code{F} reply packet has the following format:
25106 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
25108 @var{retcode} is the return code of the system call as hexadecimal value.
25110 @var{errno} is the @code{errno} set by the call, in protocol-specific
25112 This parameter can be omitted if the call was successful.
25114 @var{Ctrl-C flag} is only sent if the user requested a break. In this
25115 case, @var{errno} must be sent as well, even if the call was successful.
25116 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
25123 or, if the call was interrupted before the host call has been performed:
25130 assuming 4 is the protocol-specific representation of @code{EINTR}.
25135 @node The Ctrl-C Message
25136 @subsection The @samp{Ctrl-C} Message
25137 @cindex ctrl-c message, in file-i/o protocol
25139 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
25140 reply packet (@pxref{The F Reply Packet}),
25141 the target should behave as if it had
25142 gotten a break message. The meaning for the target is ``system call
25143 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
25144 (as with a break message) and return to @value{GDBN} with a @code{T02}
25147 It's important for the target to know in which
25148 state the system call was interrupted. There are two possible cases:
25152 The system call hasn't been performed on the host yet.
25155 The system call on the host has been finished.
25159 These two states can be distinguished by the target by the value of the
25160 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
25161 call hasn't been performed. This is equivalent to the @code{EINTR} handling
25162 on POSIX systems. In any other case, the target may presume that the
25163 system call has been finished --- successfully or not --- and should behave
25164 as if the break message arrived right after the system call.
25166 @value{GDBN} must behave reliably. If the system call has not been called
25167 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
25168 @code{errno} in the packet. If the system call on the host has been finished
25169 before the user requests a break, the full action must be finished by
25170 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
25171 The @code{F} packet may only be sent when either nothing has happened
25172 or the full action has been completed.
25175 @subsection Console I/O
25176 @cindex console i/o as part of file-i/o
25178 By default and if not explicitly closed by the target system, the file
25179 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
25180 on the @value{GDBN} console is handled as any other file output operation
25181 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
25182 by @value{GDBN} so that after the target read request from file descriptor
25183 0 all following typing is buffered until either one of the following
25188 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
25190 system call is treated as finished.
25193 The user presses @key{RET}. This is treated as end of input with a trailing
25197 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
25198 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
25202 If the user has typed more characters than fit in the buffer given to
25203 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
25204 either another @code{read(0, @dots{})} is requested by the target, or debugging
25205 is stopped at the user's request.
25208 @node List of Supported Calls
25209 @subsection List of Supported Calls
25210 @cindex list of supported file-i/o calls
25227 @unnumberedsubsubsec open
25228 @cindex open, file-i/o system call
25233 int open(const char *pathname, int flags);
25234 int open(const char *pathname, int flags, mode_t mode);
25238 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
25241 @var{flags} is the bitwise @code{OR} of the following values:
25245 If the file does not exist it will be created. The host
25246 rules apply as far as file ownership and time stamps
25250 When used with @code{O_CREAT}, if the file already exists it is
25251 an error and open() fails.
25254 If the file already exists and the open mode allows
25255 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
25256 truncated to zero length.
25259 The file is opened in append mode.
25262 The file is opened for reading only.
25265 The file is opened for writing only.
25268 The file is opened for reading and writing.
25272 Other bits are silently ignored.
25276 @var{mode} is the bitwise @code{OR} of the following values:
25280 User has read permission.
25283 User has write permission.
25286 Group has read permission.
25289 Group has write permission.
25292 Others have read permission.
25295 Others have write permission.
25299 Other bits are silently ignored.
25302 @item Return value:
25303 @code{open} returns the new file descriptor or -1 if an error
25310 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
25313 @var{pathname} refers to a directory.
25316 The requested access is not allowed.
25319 @var{pathname} was too long.
25322 A directory component in @var{pathname} does not exist.
25325 @var{pathname} refers to a device, pipe, named pipe or socket.
25328 @var{pathname} refers to a file on a read-only filesystem and
25329 write access was requested.
25332 @var{pathname} is an invalid pointer value.
25335 No space on device to create the file.
25338 The process already has the maximum number of files open.
25341 The limit on the total number of files open on the system
25345 The call was interrupted by the user.
25351 @unnumberedsubsubsec close
25352 @cindex close, file-i/o system call
25361 @samp{Fclose,@var{fd}}
25363 @item Return value:
25364 @code{close} returns zero on success, or -1 if an error occurred.
25370 @var{fd} isn't a valid open file descriptor.
25373 The call was interrupted by the user.
25379 @unnumberedsubsubsec read
25380 @cindex read, file-i/o system call
25385 int read(int fd, void *buf, unsigned int count);
25389 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
25391 @item Return value:
25392 On success, the number of bytes read is returned.
25393 Zero indicates end of file. If count is zero, read
25394 returns zero as well. On error, -1 is returned.
25400 @var{fd} is not a valid file descriptor or is not open for
25404 @var{bufptr} is an invalid pointer value.
25407 The call was interrupted by the user.
25413 @unnumberedsubsubsec write
25414 @cindex write, file-i/o system call
25419 int write(int fd, const void *buf, unsigned int count);
25423 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
25425 @item Return value:
25426 On success, the number of bytes written are returned.
25427 Zero indicates nothing was written. On error, -1
25434 @var{fd} is not a valid file descriptor or is not open for
25438 @var{bufptr} is an invalid pointer value.
25441 An attempt was made to write a file that exceeds the
25442 host-specific maximum file size allowed.
25445 No space on device to write the data.
25448 The call was interrupted by the user.
25454 @unnumberedsubsubsec lseek
25455 @cindex lseek, file-i/o system call
25460 long lseek (int fd, long offset, int flag);
25464 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
25466 @var{flag} is one of:
25470 The offset is set to @var{offset} bytes.
25473 The offset is set to its current location plus @var{offset}
25477 The offset is set to the size of the file plus @var{offset}
25481 @item Return value:
25482 On success, the resulting unsigned offset in bytes from
25483 the beginning of the file is returned. Otherwise, a
25484 value of -1 is returned.
25490 @var{fd} is not a valid open file descriptor.
25493 @var{fd} is associated with the @value{GDBN} console.
25496 @var{flag} is not a proper value.
25499 The call was interrupted by the user.
25505 @unnumberedsubsubsec rename
25506 @cindex rename, file-i/o system call
25511 int rename(const char *oldpath, const char *newpath);
25515 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
25517 @item Return value:
25518 On success, zero is returned. On error, -1 is returned.
25524 @var{newpath} is an existing directory, but @var{oldpath} is not a
25528 @var{newpath} is a non-empty directory.
25531 @var{oldpath} or @var{newpath} is a directory that is in use by some
25535 An attempt was made to make a directory a subdirectory
25539 A component used as a directory in @var{oldpath} or new
25540 path is not a directory. Or @var{oldpath} is a directory
25541 and @var{newpath} exists but is not a directory.
25544 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
25547 No access to the file or the path of the file.
25551 @var{oldpath} or @var{newpath} was too long.
25554 A directory component in @var{oldpath} or @var{newpath} does not exist.
25557 The file is on a read-only filesystem.
25560 The device containing the file has no room for the new
25564 The call was interrupted by the user.
25570 @unnumberedsubsubsec unlink
25571 @cindex unlink, file-i/o system call
25576 int unlink(const char *pathname);
25580 @samp{Funlink,@var{pathnameptr}/@var{len}}
25582 @item Return value:
25583 On success, zero is returned. On error, -1 is returned.
25589 No access to the file or the path of the file.
25592 The system does not allow unlinking of directories.
25595 The file @var{pathname} cannot be unlinked because it's
25596 being used by another process.
25599 @var{pathnameptr} is an invalid pointer value.
25602 @var{pathname} was too long.
25605 A directory component in @var{pathname} does not exist.
25608 A component of the path is not a directory.
25611 The file is on a read-only filesystem.
25614 The call was interrupted by the user.
25620 @unnumberedsubsubsec stat/fstat
25621 @cindex fstat, file-i/o system call
25622 @cindex stat, file-i/o system call
25627 int stat(const char *pathname, struct stat *buf);
25628 int fstat(int fd, struct stat *buf);
25632 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25633 @samp{Ffstat,@var{fd},@var{bufptr}}
25635 @item Return value:
25636 On success, zero is returned. On error, -1 is returned.
25642 @var{fd} is not a valid open file.
25645 A directory component in @var{pathname} does not exist or the
25646 path is an empty string.
25649 A component of the path is not a directory.
25652 @var{pathnameptr} is an invalid pointer value.
25655 No access to the file or the path of the file.
25658 @var{pathname} was too long.
25661 The call was interrupted by the user.
25667 @unnumberedsubsubsec gettimeofday
25668 @cindex gettimeofday, file-i/o system call
25673 int gettimeofday(struct timeval *tv, void *tz);
25677 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25679 @item Return value:
25680 On success, 0 is returned, -1 otherwise.
25686 @var{tz} is a non-NULL pointer.
25689 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25695 @unnumberedsubsubsec isatty
25696 @cindex isatty, file-i/o system call
25701 int isatty(int fd);
25705 @samp{Fisatty,@var{fd}}
25707 @item Return value:
25708 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
25714 The call was interrupted by the user.
25719 Note that the @code{isatty} call is treated as a special case: it returns
25720 1 to the target if the file descriptor is attached
25721 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
25722 would require implementing @code{ioctl} and would be more complex than
25727 @unnumberedsubsubsec system
25728 @cindex system, file-i/o system call
25733 int system(const char *command);
25737 @samp{Fsystem,@var{commandptr}/@var{len}}
25739 @item Return value:
25740 If @var{len} is zero, the return value indicates whether a shell is
25741 available. A zero return value indicates a shell is not available.
25742 For non-zero @var{len}, the value returned is -1 on error and the
25743 return status of the command otherwise. Only the exit status of the
25744 command is returned, which is extracted from the host's @code{system}
25745 return value by calling @code{WEXITSTATUS(retval)}. In case
25746 @file{/bin/sh} could not be executed, 127 is returned.
25752 The call was interrupted by the user.
25757 @value{GDBN} takes over the full task of calling the necessary host calls
25758 to perform the @code{system} call. The return value of @code{system} on
25759 the host is simplified before it's returned
25760 to the target. Any termination signal information from the child process
25761 is discarded, and the return value consists
25762 entirely of the exit status of the called command.
25764 Due to security concerns, the @code{system} call is by default refused
25765 by @value{GDBN}. The user has to allow this call explicitly with the
25766 @code{set remote system-call-allowed 1} command.
25769 @item set remote system-call-allowed
25770 @kindex set remote system-call-allowed
25771 Control whether to allow the @code{system} calls in the File I/O
25772 protocol for the remote target. The default is zero (disabled).
25774 @item show remote system-call-allowed
25775 @kindex show remote system-call-allowed
25776 Show whether the @code{system} calls are allowed in the File I/O
25780 @node Protocol-specific Representation of Datatypes
25781 @subsection Protocol-specific Representation of Datatypes
25782 @cindex protocol-specific representation of datatypes, in file-i/o protocol
25785 * Integral Datatypes::
25787 * Memory Transfer::
25792 @node Integral Datatypes
25793 @unnumberedsubsubsec Integral Datatypes
25794 @cindex integral datatypes, in file-i/o protocol
25796 The integral datatypes used in the system calls are @code{int},
25797 @code{unsigned int}, @code{long}, @code{unsigned long},
25798 @code{mode_t}, and @code{time_t}.
25800 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25801 implemented as 32 bit values in this protocol.
25803 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25805 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25806 in @file{limits.h}) to allow range checking on host and target.
25808 @code{time_t} datatypes are defined as seconds since the Epoch.
25810 All integral datatypes transferred as part of a memory read or write of a
25811 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25814 @node Pointer Values
25815 @unnumberedsubsubsec Pointer Values
25816 @cindex pointer values, in file-i/o protocol
25818 Pointers to target data are transmitted as they are. An exception
25819 is made for pointers to buffers for which the length isn't
25820 transmitted as part of the function call, namely strings. Strings
25821 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25828 which is a pointer to data of length 18 bytes at position 0x1aaf.
25829 The length is defined as the full string length in bytes, including
25830 the trailing null byte. For example, the string @code{"hello world"}
25831 at address 0x123456 is transmitted as
25837 @node Memory Transfer
25838 @unnumberedsubsubsec Memory Transfer
25839 @cindex memory transfer, in file-i/o protocol
25841 Structured data which is transferred using a memory read or write (for
25842 example, a @code{struct stat}) is expected to be in a protocol-specific format
25843 with all scalar multibyte datatypes being big endian. Translation to
25844 this representation needs to be done both by the target before the @code{F}
25845 packet is sent, and by @value{GDBN} before
25846 it transfers memory to the target. Transferred pointers to structured
25847 data should point to the already-coerced data at any time.
25851 @unnumberedsubsubsec struct stat
25852 @cindex struct stat, in file-i/o protocol
25854 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25855 is defined as follows:
25859 unsigned int st_dev; /* device */
25860 unsigned int st_ino; /* inode */
25861 mode_t st_mode; /* protection */
25862 unsigned int st_nlink; /* number of hard links */
25863 unsigned int st_uid; /* user ID of owner */
25864 unsigned int st_gid; /* group ID of owner */
25865 unsigned int st_rdev; /* device type (if inode device) */
25866 unsigned long st_size; /* total size, in bytes */
25867 unsigned long st_blksize; /* blocksize for filesystem I/O */
25868 unsigned long st_blocks; /* number of blocks allocated */
25869 time_t st_atime; /* time of last access */
25870 time_t st_mtime; /* time of last modification */
25871 time_t st_ctime; /* time of last change */
25875 The integral datatypes conform to the definitions given in the
25876 appropriate section (see @ref{Integral Datatypes}, for details) so this
25877 structure is of size 64 bytes.
25879 The values of several fields have a restricted meaning and/or
25885 A value of 0 represents a file, 1 the console.
25888 No valid meaning for the target. Transmitted unchanged.
25891 Valid mode bits are described in @ref{Constants}. Any other
25892 bits have currently no meaning for the target.
25897 No valid meaning for the target. Transmitted unchanged.
25902 These values have a host and file system dependent
25903 accuracy. Especially on Windows hosts, the file system may not
25904 support exact timing values.
25907 The target gets a @code{struct stat} of the above representation and is
25908 responsible for coercing it to the target representation before
25911 Note that due to size differences between the host, target, and protocol
25912 representations of @code{struct stat} members, these members could eventually
25913 get truncated on the target.
25915 @node struct timeval
25916 @unnumberedsubsubsec struct timeval
25917 @cindex struct timeval, in file-i/o protocol
25919 The buffer of type @code{struct timeval} used by the File-I/O protocol
25920 is defined as follows:
25924 time_t tv_sec; /* second */
25925 long tv_usec; /* microsecond */
25929 The integral datatypes conform to the definitions given in the
25930 appropriate section (see @ref{Integral Datatypes}, for details) so this
25931 structure is of size 8 bytes.
25934 @subsection Constants
25935 @cindex constants, in file-i/o protocol
25937 The following values are used for the constants inside of the
25938 protocol. @value{GDBN} and target are responsible for translating these
25939 values before and after the call as needed.
25950 @unnumberedsubsubsec Open Flags
25951 @cindex open flags, in file-i/o protocol
25953 All values are given in hexadecimal representation.
25965 @node mode_t Values
25966 @unnumberedsubsubsec mode_t Values
25967 @cindex mode_t values, in file-i/o protocol
25969 All values are given in octal representation.
25986 @unnumberedsubsubsec Errno Values
25987 @cindex errno values, in file-i/o protocol
25989 All values are given in decimal representation.
26014 @code{EUNKNOWN} is used as a fallback error value if a host system returns
26015 any error value not in the list of supported error numbers.
26018 @unnumberedsubsubsec Lseek Flags
26019 @cindex lseek flags, in file-i/o protocol
26028 @unnumberedsubsubsec Limits
26029 @cindex limits, in file-i/o protocol
26031 All values are given in decimal representation.
26034 INT_MIN -2147483648
26036 UINT_MAX 4294967295
26037 LONG_MIN -9223372036854775808
26038 LONG_MAX 9223372036854775807
26039 ULONG_MAX 18446744073709551615
26042 @node File-I/O Examples
26043 @subsection File-I/O Examples
26044 @cindex file-i/o examples
26046 Example sequence of a write call, file descriptor 3, buffer is at target
26047 address 0x1234, 6 bytes should be written:
26050 <- @code{Fwrite,3,1234,6}
26051 @emph{request memory read from target}
26054 @emph{return "6 bytes written"}
26058 Example sequence of a read call, file descriptor 3, buffer is at target
26059 address 0x1234, 6 bytes should be read:
26062 <- @code{Fread,3,1234,6}
26063 @emph{request memory write to target}
26064 -> @code{X1234,6:XXXXXX}
26065 @emph{return "6 bytes read"}
26069 Example sequence of a read call, call fails on the host due to invalid
26070 file descriptor (@code{EBADF}):
26073 <- @code{Fread,3,1234,6}
26077 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
26081 <- @code{Fread,3,1234,6}
26086 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
26090 <- @code{Fread,3,1234,6}
26091 -> @code{X1234,6:XXXXXX}
26095 @node Library List Format
26096 @section Library List Format
26097 @cindex library list format, remote protocol
26099 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
26100 same process as your application to manage libraries. In this case,
26101 @value{GDBN} can use the loader's symbol table and normal memory
26102 operations to maintain a list of shared libraries. On other
26103 platforms, the operating system manages loaded libraries.
26104 @value{GDBN} can not retrieve the list of currently loaded libraries
26105 through memory operations, so it uses the @samp{qXfer:libraries:read}
26106 packet (@pxref{qXfer library list read}) instead. The remote stub
26107 queries the target's operating system and reports which libraries
26110 The @samp{qXfer:libraries:read} packet returns an XML document which
26111 lists loaded libraries and their offsets. Each library has an
26112 associated name and one or more segment base addresses, which report
26113 where the library was loaded in memory. The segment bases are start
26114 addresses, not relocation offsets; they do not depend on the library's
26115 link-time base addresses.
26117 @value{GDBN} must be linked with the Expat library to support XML
26118 library lists. @xref{Expat}.
26120 A simple memory map, with one loaded library relocated by a single
26121 offset, looks like this:
26125 <library name="/lib/libc.so.6">
26126 <segment address="0x10000000"/>
26131 The format of a library list is described by this DTD:
26134 <!-- library-list: Root element with versioning -->
26135 <!ELEMENT library-list (library)*>
26136 <!ATTLIST library-list version CDATA #FIXED "1.0">
26137 <!ELEMENT library (segment)*>
26138 <!ATTLIST library name CDATA #REQUIRED>
26139 <!ELEMENT segment EMPTY>
26140 <!ATTLIST segment address CDATA #REQUIRED>
26143 @node Memory Map Format
26144 @section Memory Map Format
26145 @cindex memory map format
26147 To be able to write into flash memory, @value{GDBN} needs to obtain a
26148 memory map from the target. This section describes the format of the
26151 The memory map is obtained using the @samp{qXfer:memory-map:read}
26152 (@pxref{qXfer memory map read}) packet and is an XML document that
26153 lists memory regions.
26155 @value{GDBN} must be linked with the Expat library to support XML
26156 memory maps. @xref{Expat}.
26158 The top-level structure of the document is shown below:
26161 <?xml version="1.0"?>
26162 <!DOCTYPE memory-map
26163 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
26164 "http://sourceware.org/gdb/gdb-memory-map.dtd">
26170 Each region can be either:
26175 A region of RAM starting at @var{addr} and extending for @var{length}
26179 <memory type="ram" start="@var{addr}" length="@var{length}"/>
26184 A region of read-only memory:
26187 <memory type="rom" start="@var{addr}" length="@var{length}"/>
26192 A region of flash memory, with erasure blocks @var{blocksize}
26196 <memory type="flash" start="@var{addr}" length="@var{length}">
26197 <property name="blocksize">@var{blocksize}</property>
26203 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
26204 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
26205 packets to write to addresses in such ranges.
26207 The formal DTD for memory map format is given below:
26210 <!-- ................................................... -->
26211 <!-- Memory Map XML DTD ................................ -->
26212 <!-- File: memory-map.dtd .............................. -->
26213 <!-- .................................... .............. -->
26214 <!-- memory-map.dtd -->
26215 <!-- memory-map: Root element with versioning -->
26216 <!ELEMENT memory-map (memory | property)>
26217 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
26218 <!ELEMENT memory (property)>
26219 <!-- memory: Specifies a memory region,
26220 and its type, or device. -->
26221 <!ATTLIST memory type CDATA #REQUIRED
26222 start CDATA #REQUIRED
26223 length CDATA #REQUIRED
26224 device CDATA #IMPLIED>
26225 <!-- property: Generic attribute tag -->
26226 <!ELEMENT property (#PCDATA | property)*>
26227 <!ATTLIST property name CDATA #REQUIRED>
26230 @include agentexpr.texi
26232 @node Target Descriptions
26233 @appendix Target Descriptions
26234 @cindex target descriptions
26236 @strong{Warning:} target descriptions are still under active development,
26237 and the contents and format may change between @value{GDBN} releases.
26238 The format is expected to stabilize in the future.
26240 One of the challenges of using @value{GDBN} to debug embedded systems
26241 is that there are so many minor variants of each processor
26242 architecture in use. It is common practice for vendors to start with
26243 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
26244 and then make changes to adapt it to a particular market niche. Some
26245 architectures have hundreds of variants, available from dozens of
26246 vendors. This leads to a number of problems:
26250 With so many different customized processors, it is difficult for
26251 the @value{GDBN} maintainers to keep up with the changes.
26253 Since individual variants may have short lifetimes or limited
26254 audiences, it may not be worthwhile to carry information about every
26255 variant in the @value{GDBN} source tree.
26257 When @value{GDBN} does support the architecture of the embedded system
26258 at hand, the task of finding the correct architecture name to give the
26259 @command{set architecture} command can be error-prone.
26262 To address these problems, the @value{GDBN} remote protocol allows a
26263 target system to not only identify itself to @value{GDBN}, but to
26264 actually describe its own features. This lets @value{GDBN} support
26265 processor variants it has never seen before --- to the extent that the
26266 descriptions are accurate, and that @value{GDBN} understands them.
26268 @value{GDBN} must be linked with the Expat library to support XML
26269 target descriptions. @xref{Expat}.
26272 * Retrieving Descriptions:: How descriptions are fetched from a target.
26273 * Target Description Format:: The contents of a target description.
26274 * Predefined Target Types:: Standard types available for target
26276 * Standard Target Features:: Features @value{GDBN} knows about.
26279 @node Retrieving Descriptions
26280 @section Retrieving Descriptions
26282 Target descriptions can be read from the target automatically, or
26283 specified by the user manually. The default behavior is to read the
26284 description from the target. @value{GDBN} retrieves it via the remote
26285 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
26286 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
26287 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
26288 XML document, of the form described in @ref{Target Description
26291 Alternatively, you can specify a file to read for the target description.
26292 If a file is set, the target will not be queried. The commands to
26293 specify a file are:
26296 @cindex set tdesc filename
26297 @item set tdesc filename @var{path}
26298 Read the target description from @var{path}.
26300 @cindex unset tdesc filename
26301 @item unset tdesc filename
26302 Do not read the XML target description from a file. @value{GDBN}
26303 will use the description supplied by the current target.
26305 @cindex show tdesc filename
26306 @item show tdesc filename
26307 Show the filename to read for a target description, if any.
26311 @node Target Description Format
26312 @section Target Description Format
26313 @cindex target descriptions, XML format
26315 A target description annex is an @uref{http://www.w3.org/XML/, XML}
26316 document which complies with the Document Type Definition provided in
26317 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
26318 means you can use generally available tools like @command{xmllint} to
26319 check that your feature descriptions are well-formed and valid.
26320 However, to help people unfamiliar with XML write descriptions for
26321 their targets, we also describe the grammar here.
26323 Target descriptions can identify the architecture of the remote target
26324 and (for some architectures) provide information about custom register
26325 sets. @value{GDBN} can use this information to autoconfigure for your
26326 target, or to warn you if you connect to an unsupported target.
26328 Here is a simple target description:
26331 <target version="1.0">
26332 <architecture>i386:x86-64</architecture>
26337 This minimal description only says that the target uses
26338 the x86-64 architecture.
26340 A target description has the following overall form, with [ ] marking
26341 optional elements and @dots{} marking repeatable elements. The elements
26342 are explained further below.
26345 <?xml version="1.0"?>
26346 <!DOCTYPE target SYSTEM "gdb-target.dtd">
26347 <target version="1.0">
26348 @r{[}@var{architecture}@r{]}
26349 @r{[}@var{feature}@dots{}@r{]}
26354 The description is generally insensitive to whitespace and line
26355 breaks, under the usual common-sense rules. The XML version
26356 declaration and document type declaration can generally be omitted
26357 (@value{GDBN} does not require them), but specifying them may be
26358 useful for XML validation tools. The @samp{version} attribute for
26359 @samp{<target>} may also be omitted, but we recommend
26360 including it; if future versions of @value{GDBN} use an incompatible
26361 revision of @file{gdb-target.dtd}, they will detect and report
26362 the version mismatch.
26364 @subsection Inclusion
26365 @cindex target descriptions, inclusion
26368 @cindex <xi:include>
26371 It can sometimes be valuable to split a target description up into
26372 several different annexes, either for organizational purposes, or to
26373 share files between different possible target descriptions. You can
26374 divide a description into multiple files by replacing any element of
26375 the target description with an inclusion directive of the form:
26378 <xi:include href="@var{document}"/>
26382 When @value{GDBN} encounters an element of this form, it will retrieve
26383 the named XML @var{document}, and replace the inclusion directive with
26384 the contents of that document. If the current description was read
26385 using @samp{qXfer}, then so will be the included document;
26386 @var{document} will be interpreted as the name of an annex. If the
26387 current description was read from a file, @value{GDBN} will look for
26388 @var{document} as a file in the same directory where it found the
26389 original description.
26391 @subsection Architecture
26392 @cindex <architecture>
26394 An @samp{<architecture>} element has this form:
26397 <architecture>@var{arch}</architecture>
26400 @var{arch} is an architecture name from the same selection
26401 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
26402 Debugging Target}).
26404 @subsection Features
26407 Each @samp{<feature>} describes some logical portion of the target
26408 system. Features are currently used to describe available CPU
26409 registers and the types of their contents. A @samp{<feature>} element
26413 <feature name="@var{name}">
26414 @r{[}@var{type}@dots{}@r{]}
26420 Each feature's name should be unique within the description. The name
26421 of a feature does not matter unless @value{GDBN} has some special
26422 knowledge of the contents of that feature; if it does, the feature
26423 should have its standard name. @xref{Standard Target Features}.
26427 Any register's value is a collection of bits which @value{GDBN} must
26428 interpret. The default interpretation is a two's complement integer,
26429 but other types can be requested by name in the register description.
26430 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
26431 Target Types}), and the description can define additional composite types.
26433 Each type element must have an @samp{id} attribute, which gives
26434 a unique (within the containing @samp{<feature>}) name to the type.
26435 Types must be defined before they are used.
26438 Some targets offer vector registers, which can be treated as arrays
26439 of scalar elements. These types are written as @samp{<vector>} elements,
26440 specifying the array element type, @var{type}, and the number of elements,
26444 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
26448 If a register's value is usefully viewed in multiple ways, define it
26449 with a union type containing the useful representations. The
26450 @samp{<union>} element contains one or more @samp{<field>} elements,
26451 each of which has a @var{name} and a @var{type}:
26454 <union id="@var{id}">
26455 <field name="@var{name}" type="@var{type}"/>
26460 @subsection Registers
26463 Each register is represented as an element with this form:
26466 <reg name="@var{name}"
26467 bitsize="@var{size}"
26468 @r{[}regnum="@var{num}"@r{]}
26469 @r{[}save-restore="@var{save-restore}"@r{]}
26470 @r{[}type="@var{type}"@r{]}
26471 @r{[}group="@var{group}"@r{]}/>
26475 The components are as follows:
26480 The register's name; it must be unique within the target description.
26483 The register's size, in bits.
26486 The register's number. If omitted, a register's number is one greater
26487 than that of the previous register (either in the current feature or in
26488 a preceeding feature); the first register in the target description
26489 defaults to zero. This register number is used to read or write
26490 the register; e.g.@: it is used in the remote @code{p} and @code{P}
26491 packets, and registers appear in the @code{g} and @code{G} packets
26492 in order of increasing register number.
26495 Whether the register should be preserved across inferior function
26496 calls; this must be either @code{yes} or @code{no}. The default is
26497 @code{yes}, which is appropriate for most registers except for
26498 some system control registers; this is not related to the target's
26502 The type of the register. @var{type} may be a predefined type, a type
26503 defined in the current feature, or one of the special types @code{int}
26504 and @code{float}. @code{int} is an integer type of the correct size
26505 for @var{bitsize}, and @code{float} is a floating point type (in the
26506 architecture's normal floating point format) of the correct size for
26507 @var{bitsize}. The default is @code{int}.
26510 The register group to which this register belongs. @var{group} must
26511 be either @code{general}, @code{float}, or @code{vector}. If no
26512 @var{group} is specified, @value{GDBN} will not display the register
26513 in @code{info registers}.
26517 @node Predefined Target Types
26518 @section Predefined Target Types
26519 @cindex target descriptions, predefined types
26521 Type definitions in the self-description can build up composite types
26522 from basic building blocks, but can not define fundamental types. Instead,
26523 standard identifiers are provided by @value{GDBN} for the fundamental
26524 types. The currently supported types are:
26533 Signed integer types holding the specified number of bits.
26540 Unsigned integer types holding the specified number of bits.
26544 Pointers to unspecified code and data. The program counter and
26545 any dedicated return address register may be marked as code
26546 pointers; printing a code pointer converts it into a symbolic
26547 address. The stack pointer and any dedicated address registers
26548 may be marked as data pointers.
26551 Single precision IEEE floating point.
26554 Double precision IEEE floating point.
26557 The 12-byte extended precision format used by ARM FPA registers.
26561 @node Standard Target Features
26562 @section Standard Target Features
26563 @cindex target descriptions, standard features
26565 A target description must contain either no registers or all the
26566 target's registers. If the description contains no registers, then
26567 @value{GDBN} will assume a default register layout, selected based on
26568 the architecture. If the description contains any registers, the
26569 default layout will not be used; the standard registers must be
26570 described in the target description, in such a way that @value{GDBN}
26571 can recognize them.
26573 This is accomplished by giving specific names to feature elements
26574 which contain standard registers. @value{GDBN} will look for features
26575 with those names and verify that they contain the expected registers;
26576 if any known feature is missing required registers, or if any required
26577 feature is missing, @value{GDBN} will reject the target
26578 description. You can add additional registers to any of the
26579 standard features --- @value{GDBN} will display them just as if
26580 they were added to an unrecognized feature.
26582 This section lists the known features and their expected contents.
26583 Sample XML documents for these features are included in the
26584 @value{GDBN} source tree, in the directory @file{gdb/features}.
26586 Names recognized by @value{GDBN} should include the name of the
26587 company or organization which selected the name, and the overall
26588 architecture to which the feature applies; so e.g.@: the feature
26589 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
26591 The names of registers are not case sensitive for the purpose
26592 of recognizing standard features, but @value{GDBN} will only display
26593 registers using the capitalization used in the description.
26602 @subsection ARM Features
26603 @cindex target descriptions, ARM features
26605 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
26606 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
26607 @samp{lr}, @samp{pc}, and @samp{cpsr}.
26609 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
26610 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
26612 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
26613 it should contain at least registers @samp{wR0} through @samp{wR15} and
26614 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
26615 @samp{wCSSF}, and @samp{wCASF} registers are optional.
26617 @subsection MIPS Features
26618 @cindex target descriptions, MIPS features
26620 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
26621 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
26622 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
26625 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
26626 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
26627 registers. They may be 32-bit or 64-bit depending on the target.
26629 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
26630 it may be optional in a future version of @value{GDBN}. It should
26631 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
26632 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
26634 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
26635 contain a single register, @samp{restart}, which is used by the
26636 Linux kernel to control restartable syscalls.
26638 @node M68K Features
26639 @subsection M68K Features
26640 @cindex target descriptions, M68K features
26643 @item @samp{org.gnu.gdb.m68k.core}
26644 @itemx @samp{org.gnu.gdb.coldfire.core}
26645 @itemx @samp{org.gnu.gdb.fido.core}
26646 One of those features must be always present.
26647 The feature that is present determines which flavor of m86k is
26648 used. The feature that is present should contain registers
26649 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
26650 @samp{sp}, @samp{ps} and @samp{pc}.
26652 @item @samp{org.gnu.gdb.coldfire.fp}
26653 This feature is optional. If present, it should contain registers
26654 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
26658 @subsection PowerPC Features
26659 @cindex target descriptions, PowerPC features
26661 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
26662 targets. It should contain registers @samp{r0} through @samp{r31},
26663 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
26664 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
26666 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
26667 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
26669 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
26670 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
26673 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
26674 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
26675 @samp{spefscr}. SPE targets should provide 32-bit registers in
26676 @samp{org.gnu.gdb.power.core} and provide the upper halves in
26677 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
26678 these to present registers @samp{ev0} through @samp{ev31} to the
26693 % I think something like @colophon should be in texinfo. In the
26695 \long\def\colophon{\hbox to0pt{}\vfill
26696 \centerline{The body of this manual is set in}
26697 \centerline{\fontname\tenrm,}
26698 \centerline{with headings in {\bf\fontname\tenbf}}
26699 \centerline{and examples in {\tt\fontname\tentt}.}
26700 \centerline{{\it\fontname\tenit\/},}
26701 \centerline{{\bf\fontname\tenbf}, and}
26702 \centerline{{\sl\fontname\tensl\/}}
26703 \centerline{are used for emphasis.}\vfill}
26705 % Blame: doc@cygnus.com, 1991.