1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
66 this GNU Manual. Buying copies from GNU Press supports the FSF in
67 developing GNU and promoting software freedom.''
71 @title Debugging with @value{GDBN}
72 @subtitle The @sc{gnu} Source-Level Debugger
74 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
75 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
79 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
80 \hfill {\it Debugging with @value{GDBN}}\par
81 \hfill \TeX{}info \texinfoversion\par
85 @vskip 0pt plus 1filll
86 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
87 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
88 Free Software Foundation, Inc.
90 Published by the Free Software Foundation @*
91 51 Franklin Street, Fifth Floor,
92 Boston, MA 02110-1301, USA@*
95 Permission is granted to copy, distribute and/or modify this document
96 under the terms of the GNU Free Documentation License, Version 1.1 or
97 any later version published by the Free Software Foundation; with the
98 Invariant Sections being ``Free Software'' and ``Free Software Needs
99 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
100 and with the Back-Cover Texts as in (a) below.
102 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
103 this GNU Manual. Buying copies from GNU Press supports the FSF in
104 developing GNU and promoting software freedom.''
106 This edition of the GDB manual is dedicated to the memory of Fred
107 Fish. Fred was a long-standing contributor to GDB and to Free
108 software in general. We will miss him.
113 @node Top, Summary, (dir), (dir)
115 @top Debugging with @value{GDBN}
117 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
119 This is the @value{EDITION} Edition, for @value{GDBN} Version
122 Copyright (C) 1988-2006 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Stack:: Examining the stack
137 * Source:: Examining source files
138 * Data:: Examining data
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Sequences:: Canned sequences of commands
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
159 * GDB Bugs:: Reporting bugs in @value{GDBN}
161 * Command Line Editing:: Command Line Editing
162 * Using History Interactively:: Using History Interactively
163 * Formatting Documentation:: How to format and print @value{GDBN} documentation
164 * Installing GDB:: Installing GDB
165 * Maintenance Commands:: Maintenance Commands
166 * Remote Protocol:: GDB Remote Serial Protocol
167 * Agent Expressions:: The GDB Agent Expression Mechanism
168 * Target Descriptions:: How targets can describe themselves to
170 * Copying:: GNU General Public License says
171 how you can copy and share GDB
172 * GNU Free Documentation License:: The license for this documentation
181 @unnumbered Summary of @value{GDBN}
183 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
184 going on ``inside'' another program while it executes---or what another
185 program was doing at the moment it crashed.
187 @value{GDBN} can do four main kinds of things (plus other things in support of
188 these) to help you catch bugs in the act:
192 Start your program, specifying anything that might affect its behavior.
195 Make your program stop on specified conditions.
198 Examine what has happened, when your program has stopped.
201 Change things in your program, so you can experiment with correcting the
202 effects of one bug and go on to learn about another.
205 You can use @value{GDBN} to debug programs written in C and C@t{++}.
206 For more information, see @ref{Supported Languages,,Supported Languages}.
207 For more information, see @ref{C,,C and C++}.
210 Support for Modula-2 is partial. For information on Modula-2, see
211 @ref{Modula-2,,Modula-2}.
214 Debugging Pascal programs which use sets, subranges, file variables, or
215 nested functions does not currently work. @value{GDBN} does not support
216 entering expressions, printing values, or similar features using Pascal
220 @value{GDBN} can be used to debug programs written in Fortran, although
221 it may be necessary to refer to some variables with a trailing
224 @value{GDBN} can be used to debug programs written in Objective-C,
225 using either the Apple/NeXT or the GNU Objective-C runtime.
228 * Free Software:: Freely redistributable software
229 * Contributors:: Contributors to GDB
233 @unnumberedsec Free Software
235 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
236 General Public License
237 (GPL). The GPL gives you the freedom to copy or adapt a licensed
238 program---but every person getting a copy also gets with it the
239 freedom to modify that copy (which means that they must get access to
240 the source code), and the freedom to distribute further copies.
241 Typical software companies use copyrights to limit your freedoms; the
242 Free Software Foundation uses the GPL to preserve these freedoms.
244 Fundamentally, the General Public License is a license which says that
245 you have these freedoms and that you cannot take these freedoms away
248 @unnumberedsec Free Software Needs Free Documentation
250 The biggest deficiency in the free software community today is not in
251 the software---it is the lack of good free documentation that we can
252 include with the free software. Many of our most important
253 programs do not come with free reference manuals and free introductory
254 texts. Documentation is an essential part of any software package;
255 when an important free software package does not come with a free
256 manual and a free tutorial, that is a major gap. We have many such
259 Consider Perl, for instance. The tutorial manuals that people
260 normally use are non-free. How did this come about? Because the
261 authors of those manuals published them with restrictive terms---no
262 copying, no modification, source files not available---which exclude
263 them from the free software world.
265 That wasn't the first time this sort of thing happened, and it was far
266 from the last. Many times we have heard a GNU user eagerly describe a
267 manual that he is writing, his intended contribution to the community,
268 only to learn that he had ruined everything by signing a publication
269 contract to make it non-free.
271 Free documentation, like free software, is a matter of freedom, not
272 price. The problem with the non-free manual is not that publishers
273 charge a price for printed copies---that in itself is fine. (The Free
274 Software Foundation sells printed copies of manuals, too.) The
275 problem is the restrictions on the use of the manual. Free manuals
276 are available in source code form, and give you permission to copy and
277 modify. Non-free manuals do not allow this.
279 The criteria of freedom for a free manual are roughly the same as for
280 free software. Redistribution (including the normal kinds of
281 commercial redistribution) must be permitted, so that the manual can
282 accompany every copy of the program, both on-line and on paper.
284 Permission for modification of the technical content is crucial too.
285 When people modify the software, adding or changing features, if they
286 are conscientious they will change the manual too---so they can
287 provide accurate and clear documentation for the modified program. A
288 manual that leaves you no choice but to write a new manual to document
289 a changed version of the program is not really available to our
292 Some kinds of limits on the way modification is handled are
293 acceptable. For example, requirements to preserve the original
294 author's copyright notice, the distribution terms, or the list of
295 authors, are ok. It is also no problem to require modified versions
296 to include notice that they were modified. Even entire sections that
297 may not be deleted or changed are acceptable, as long as they deal
298 with nontechnical topics (like this one). These kinds of restrictions
299 are acceptable because they don't obstruct the community's normal use
302 However, it must be possible to modify all the @emph{technical}
303 content of the manual, and then distribute the result in all the usual
304 media, through all the usual channels. Otherwise, the restrictions
305 obstruct the use of the manual, it is not free, and we need another
306 manual to replace it.
308 Please spread the word about this issue. Our community continues to
309 lose manuals to proprietary publishing. If we spread the word that
310 free software needs free reference manuals and free tutorials, perhaps
311 the next person who wants to contribute by writing documentation will
312 realize, before it is too late, that only free manuals contribute to
313 the free software community.
315 If you are writing documentation, please insist on publishing it under
316 the GNU Free Documentation License or another free documentation
317 license. Remember that this decision requires your approval---you
318 don't have to let the publisher decide. Some commercial publishers
319 will use a free license if you insist, but they will not propose the
320 option; it is up to you to raise the issue and say firmly that this is
321 what you want. If the publisher you are dealing with refuses, please
322 try other publishers. If you're not sure whether a proposed license
323 is free, write to @email{licensing@@gnu.org}.
325 You can encourage commercial publishers to sell more free, copylefted
326 manuals and tutorials by buying them, and particularly by buying
327 copies from the publishers that paid for their writing or for major
328 improvements. Meanwhile, try to avoid buying non-free documentation
329 at all. Check the distribution terms of a manual before you buy it,
330 and insist that whoever seeks your business must respect your freedom.
331 Check the history of the book, and try to reward the publishers that
332 have paid or pay the authors to work on it.
334 The Free Software Foundation maintains a list of free documentation
335 published by other publishers, at
336 @url{http://www.fsf.org/doc/other-free-books.html}.
339 @unnumberedsec Contributors to @value{GDBN}
341 Richard Stallman was the original author of @value{GDBN}, and of many
342 other @sc{gnu} programs. Many others have contributed to its
343 development. This section attempts to credit major contributors. One
344 of the virtues of free software is that everyone is free to contribute
345 to it; with regret, we cannot actually acknowledge everyone here. The
346 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
347 blow-by-blow account.
349 Changes much prior to version 2.0 are lost in the mists of time.
352 @emph{Plea:} Additions to this section are particularly welcome. If you
353 or your friends (or enemies, to be evenhanded) have been unfairly
354 omitted from this list, we would like to add your names!
357 So that they may not regard their many labors as thankless, we
358 particularly thank those who shepherded @value{GDBN} through major
360 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
361 Jim Blandy (release 4.18);
362 Jason Molenda (release 4.17);
363 Stan Shebs (release 4.14);
364 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
365 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
366 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
367 Jim Kingdon (releases 3.5, 3.4, and 3.3);
368 and Randy Smith (releases 3.2, 3.1, and 3.0).
370 Richard Stallman, assisted at various times by Peter TerMaat, Chris
371 Hanson, and Richard Mlynarik, handled releases through 2.8.
373 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
374 in @value{GDBN}, with significant additional contributions from Per
375 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
376 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
377 much general update work leading to release 3.0).
379 @value{GDBN} uses the BFD subroutine library to examine multiple
380 object-file formats; BFD was a joint project of David V.
381 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
383 David Johnson wrote the original COFF support; Pace Willison did
384 the original support for encapsulated COFF.
386 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
388 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
389 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
391 Jean-Daniel Fekete contributed Sun 386i support.
392 Chris Hanson improved the HP9000 support.
393 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
394 David Johnson contributed Encore Umax support.
395 Jyrki Kuoppala contributed Altos 3068 support.
396 Jeff Law contributed HP PA and SOM support.
397 Keith Packard contributed NS32K support.
398 Doug Rabson contributed Acorn Risc Machine support.
399 Bob Rusk contributed Harris Nighthawk CX-UX support.
400 Chris Smith contributed Convex support (and Fortran debugging).
401 Jonathan Stone contributed Pyramid support.
402 Michael Tiemann contributed SPARC support.
403 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
404 Pace Willison contributed Intel 386 support.
405 Jay Vosburgh contributed Symmetry support.
406 Marko Mlinar contributed OpenRISC 1000 support.
408 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
410 Rich Schaefer and Peter Schauer helped with support of SunOS shared
413 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
414 about several machine instruction sets.
416 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
417 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
418 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
419 and RDI targets, respectively.
421 Brian Fox is the author of the readline libraries providing
422 command-line editing and command history.
424 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
425 Modula-2 support, and contributed the Languages chapter of this manual.
427 Fred Fish wrote most of the support for Unix System Vr4.
428 He also enhanced the command-completion support to cover C@t{++} overloaded
431 Hitachi America (now Renesas America), Ltd. sponsored the support for
432 H8/300, H8/500, and Super-H processors.
434 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
436 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
439 Toshiba sponsored the support for the TX39 Mips processor.
441 Matsushita sponsored the support for the MN10200 and MN10300 processors.
443 Fujitsu sponsored the support for SPARClite and FR30 processors.
445 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
448 Michael Snyder added support for tracepoints.
450 Stu Grossman wrote gdbserver.
452 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
453 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
455 The following people at the Hewlett-Packard Company contributed
456 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
457 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
458 compiler, and the Text User Interface (nee Terminal User Interface):
459 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
460 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
461 provided HP-specific information in this manual.
463 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
464 Robert Hoehne made significant contributions to the DJGPP port.
466 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
467 development since 1991. Cygnus engineers who have worked on @value{GDBN}
468 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
469 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
470 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
471 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
472 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
473 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
474 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
475 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
476 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
477 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
478 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
479 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
480 Zuhn have made contributions both large and small.
482 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
483 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
485 Jim Blandy added support for preprocessor macros, while working for Red
488 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
489 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
490 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
491 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
492 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
493 with the migration of old architectures to this new framework.
495 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
496 unwinder framework, this consisting of a fresh new design featuring
497 frame IDs, independent frame sniffers, and the sentinel frame. Mark
498 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
499 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
500 trad unwinders. The architecture-specific changes, each involving a
501 complete rewrite of the architecture's frame code, were carried out by
502 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
503 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
504 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
505 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
508 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
509 Tensilica, Inc.@: contributed support for Xtensa processors. Others
510 who have worked on the Xtensa port of @value{GDBN} in the past include
511 Steve Tjiang, John Newlin, and Scott Foehner.
514 @chapter A Sample @value{GDBN} Session
516 You can use this manual at your leisure to read all about @value{GDBN}.
517 However, a handful of commands are enough to get started using the
518 debugger. This chapter illustrates those commands.
521 In this sample session, we emphasize user input like this: @b{input},
522 to make it easier to pick out from the surrounding output.
525 @c FIXME: this example may not be appropriate for some configs, where
526 @c FIXME...primary interest is in remote use.
528 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
529 processor) exhibits the following bug: sometimes, when we change its
530 quote strings from the default, the commands used to capture one macro
531 definition within another stop working. In the following short @code{m4}
532 session, we define a macro @code{foo} which expands to @code{0000}; we
533 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
534 same thing. However, when we change the open quote string to
535 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
536 procedure fails to define a new synonym @code{baz}:
545 @b{define(bar,defn(`foo'))}
549 @b{changequote(<QUOTE>,<UNQUOTE>)}
551 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
554 m4: End of input: 0: fatal error: EOF in string
558 Let us use @value{GDBN} to try to see what is going on.
561 $ @b{@value{GDBP} m4}
562 @c FIXME: this falsifies the exact text played out, to permit smallbook
563 @c FIXME... format to come out better.
564 @value{GDBN} is free software and you are welcome to distribute copies
565 of it under certain conditions; type "show copying" to see
567 There is absolutely no warranty for @value{GDBN}; type "show warranty"
570 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
575 @value{GDBN} reads only enough symbol data to know where to find the
576 rest when needed; as a result, the first prompt comes up very quickly.
577 We now tell @value{GDBN} to use a narrower display width than usual, so
578 that examples fit in this manual.
581 (@value{GDBP}) @b{set width 70}
585 We need to see how the @code{m4} built-in @code{changequote} works.
586 Having looked at the source, we know the relevant subroutine is
587 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
588 @code{break} command.
591 (@value{GDBP}) @b{break m4_changequote}
592 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
596 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
597 control; as long as control does not reach the @code{m4_changequote}
598 subroutine, the program runs as usual:
601 (@value{GDBP}) @b{run}
602 Starting program: /work/Editorial/gdb/gnu/m4/m4
610 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
611 suspends execution of @code{m4}, displaying information about the
612 context where it stops.
615 @b{changequote(<QUOTE>,<UNQUOTE>)}
617 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
619 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
623 Now we use the command @code{n} (@code{next}) to advance execution to
624 the next line of the current function.
628 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
633 @code{set_quotes} looks like a promising subroutine. We can go into it
634 by using the command @code{s} (@code{step}) instead of @code{next}.
635 @code{step} goes to the next line to be executed in @emph{any}
636 subroutine, so it steps into @code{set_quotes}.
640 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
642 530 if (lquote != def_lquote)
646 The display that shows the subroutine where @code{m4} is now
647 suspended (and its arguments) is called a stack frame display. It
648 shows a summary of the stack. We can use the @code{backtrace}
649 command (which can also be spelled @code{bt}), to see where we are
650 in the stack as a whole: the @code{backtrace} command displays a
651 stack frame for each active subroutine.
654 (@value{GDBP}) @b{bt}
655 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
657 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
659 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
660 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
662 #4 0x79dc in expand_input () at macro.c:40
663 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
667 We step through a few more lines to see what happens. The first two
668 times, we can use @samp{s}; the next two times we use @code{n} to avoid
669 falling into the @code{xstrdup} subroutine.
673 0x3b5c 532 if (rquote != def_rquote)
675 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
676 def_lquote : xstrdup(lq);
678 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
681 538 len_lquote = strlen(rquote);
685 The last line displayed looks a little odd; we can examine the variables
686 @code{lquote} and @code{rquote} to see if they are in fact the new left
687 and right quotes we specified. We use the command @code{p}
688 (@code{print}) to see their values.
691 (@value{GDBP}) @b{p lquote}
692 $1 = 0x35d40 "<QUOTE>"
693 (@value{GDBP}) @b{p rquote}
694 $2 = 0x35d50 "<UNQUOTE>"
698 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
699 To look at some context, we can display ten lines of source
700 surrounding the current line with the @code{l} (@code{list}) command.
706 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
708 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
711 538 len_lquote = strlen(rquote);
712 539 len_rquote = strlen(lquote);
719 Let us step past the two lines that set @code{len_lquote} and
720 @code{len_rquote}, and then examine the values of those variables.
724 539 len_rquote = strlen(lquote);
727 (@value{GDBP}) @b{p len_lquote}
729 (@value{GDBP}) @b{p len_rquote}
734 That certainly looks wrong, assuming @code{len_lquote} and
735 @code{len_rquote} are meant to be the lengths of @code{lquote} and
736 @code{rquote} respectively. We can set them to better values using
737 the @code{p} command, since it can print the value of
738 any expression---and that expression can include subroutine calls and
742 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
744 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
749 Is that enough to fix the problem of using the new quotes with the
750 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
751 executing with the @code{c} (@code{continue}) command, and then try the
752 example that caused trouble initially:
758 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
765 Success! The new quotes now work just as well as the default ones. The
766 problem seems to have been just the two typos defining the wrong
767 lengths. We allow @code{m4} exit by giving it an EOF as input:
771 Program exited normally.
775 The message @samp{Program exited normally.} is from @value{GDBN}; it
776 indicates @code{m4} has finished executing. We can end our @value{GDBN}
777 session with the @value{GDBN} @code{quit} command.
780 (@value{GDBP}) @b{quit}
784 @chapter Getting In and Out of @value{GDBN}
786 This chapter discusses how to start @value{GDBN}, and how to get out of it.
790 type @samp{@value{GDBP}} to start @value{GDBN}.
792 type @kbd{quit} or @kbd{Ctrl-d} to exit.
796 * Invoking GDB:: How to start @value{GDBN}
797 * Quitting GDB:: How to quit @value{GDBN}
798 * Shell Commands:: How to use shell commands inside @value{GDBN}
799 * Logging Output:: How to log @value{GDBN}'s output to a file
803 @section Invoking @value{GDBN}
805 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
806 @value{GDBN} reads commands from the terminal until you tell it to exit.
808 You can also run @code{@value{GDBP}} with a variety of arguments and options,
809 to specify more of your debugging environment at the outset.
811 The command-line options described here are designed
812 to cover a variety of situations; in some environments, some of these
813 options may effectively be unavailable.
815 The most usual way to start @value{GDBN} is with one argument,
816 specifying an executable program:
819 @value{GDBP} @var{program}
823 You can also start with both an executable program and a core file
827 @value{GDBP} @var{program} @var{core}
830 You can, instead, specify a process ID as a second argument, if you want
831 to debug a running process:
834 @value{GDBP} @var{program} 1234
838 would attach @value{GDBN} to process @code{1234} (unless you also have a file
839 named @file{1234}; @value{GDBN} does check for a core file first).
841 Taking advantage of the second command-line argument requires a fairly
842 complete operating system; when you use @value{GDBN} as a remote
843 debugger attached to a bare board, there may not be any notion of
844 ``process'', and there is often no way to get a core dump. @value{GDBN}
845 will warn you if it is unable to attach or to read core dumps.
847 You can optionally have @code{@value{GDBP}} pass any arguments after the
848 executable file to the inferior using @code{--args}. This option stops
851 @value{GDBP} --args gcc -O2 -c foo.c
853 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
854 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
856 You can run @code{@value{GDBP}} without printing the front material, which describes
857 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
864 You can further control how @value{GDBN} starts up by using command-line
865 options. @value{GDBN} itself can remind you of the options available.
875 to display all available options and briefly describe their use
876 (@samp{@value{GDBP} -h} is a shorter equivalent).
878 All options and command line arguments you give are processed
879 in sequential order. The order makes a difference when the
880 @samp{-x} option is used.
884 * File Options:: Choosing files
885 * Mode Options:: Choosing modes
886 * Startup:: What @value{GDBN} does during startup
890 @subsection Choosing Files
892 When @value{GDBN} starts, it reads any arguments other than options as
893 specifying an executable file and core file (or process ID). This is
894 the same as if the arguments were specified by the @samp{-se} and
895 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
896 first argument that does not have an associated option flag as
897 equivalent to the @samp{-se} option followed by that argument; and the
898 second argument that does not have an associated option flag, if any, as
899 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
900 If the second argument begins with a decimal digit, @value{GDBN} will
901 first attempt to attach to it as a process, and if that fails, attempt
902 to open it as a corefile. If you have a corefile whose name begins with
903 a digit, you can prevent @value{GDBN} from treating it as a pid by
904 prefixing it with @file{./}, e.g.@: @file{./12345}.
906 If @value{GDBN} has not been configured to included core file support,
907 such as for most embedded targets, then it will complain about a second
908 argument and ignore it.
910 Many options have both long and short forms; both are shown in the
911 following list. @value{GDBN} also recognizes the long forms if you truncate
912 them, so long as enough of the option is present to be unambiguous.
913 (If you prefer, you can flag option arguments with @samp{--} rather
914 than @samp{-}, though we illustrate the more usual convention.)
916 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
917 @c way, both those who look for -foo and --foo in the index, will find
921 @item -symbols @var{file}
923 @cindex @code{--symbols}
925 Read symbol table from file @var{file}.
927 @item -exec @var{file}
929 @cindex @code{--exec}
931 Use file @var{file} as the executable file to execute when appropriate,
932 and for examining pure data in conjunction with a core dump.
936 Read symbol table from file @var{file} and use it as the executable
939 @item -core @var{file}
941 @cindex @code{--core}
943 Use file @var{file} as a core dump to examine.
945 @item -pid @var{number}
946 @itemx -p @var{number}
949 Connect to process ID @var{number}, as with the @code{attach} command.
951 @item -command @var{file}
953 @cindex @code{--command}
955 Execute @value{GDBN} commands from file @var{file}. @xref{Command
956 Files,, Command files}.
958 @item -eval-command @var{command}
959 @itemx -ex @var{command}
960 @cindex @code{--eval-command}
962 Execute a single @value{GDBN} command.
964 This option may be used multiple times to call multiple commands. It may
965 also be interleaved with @samp{-command} as required.
968 @value{GDBP} -ex 'target sim' -ex 'load' \
969 -x setbreakpoints -ex 'run' a.out
972 @item -directory @var{directory}
973 @itemx -d @var{directory}
974 @cindex @code{--directory}
976 Add @var{directory} to the path to search for source and script files.
980 @cindex @code{--readnow}
982 Read each symbol file's entire symbol table immediately, rather than
983 the default, which is to read it incrementally as it is needed.
984 This makes startup slower, but makes future operations faster.
989 @subsection Choosing Modes
991 You can run @value{GDBN} in various alternative modes---for example, in
992 batch mode or quiet mode.
999 Do not execute commands found in any initialization files. Normally,
1000 @value{GDBN} executes the commands in these files after all the command
1001 options and arguments have been processed. @xref{Command Files,,Command
1007 @cindex @code{--quiet}
1008 @cindex @code{--silent}
1010 ``Quiet''. Do not print the introductory and copyright messages. These
1011 messages are also suppressed in batch mode.
1014 @cindex @code{--batch}
1015 Run in batch mode. Exit with status @code{0} after processing all the
1016 command files specified with @samp{-x} (and all commands from
1017 initialization files, if not inhibited with @samp{-n}). Exit with
1018 nonzero status if an error occurs in executing the @value{GDBN} commands
1019 in the command files.
1021 Batch mode may be useful for running @value{GDBN} as a filter, for
1022 example to download and run a program on another computer; in order to
1023 make this more useful, the message
1026 Program exited normally.
1030 (which is ordinarily issued whenever a program running under
1031 @value{GDBN} control terminates) is not issued when running in batch
1035 @cindex @code{--batch-silent}
1036 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1037 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1038 unaffected). This is much quieter than @samp{-silent} and would be useless
1039 for an interactive session.
1041 This is particularly useful when using targets that give @samp{Loading section}
1042 messages, for example.
1044 Note that targets that give their output via @value{GDBN}, as opposed to
1045 writing directly to @code{stdout}, will also be made silent.
1047 @item -return-child-result
1048 @cindex @code{--return-child-result}
1049 The return code from @value{GDBN} will be the return code from the child
1050 process (the process being debugged), with the following exceptions:
1054 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1055 internal error. In this case the exit code is the same as it would have been
1056 without @samp{-return-child-result}.
1058 The user quits with an explicit value. E.g., @samp{quit 1}.
1060 The child process never runs, or is not allowed to terminate, in which case
1061 the exit code will be -1.
1064 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1065 when @value{GDBN} is being used as a remote program loader or simulator
1070 @cindex @code{--nowindows}
1072 ``No windows''. If @value{GDBN} comes with a graphical user interface
1073 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1074 interface. If no GUI is available, this option has no effect.
1078 @cindex @code{--windows}
1080 If @value{GDBN} includes a GUI, then this option requires it to be
1083 @item -cd @var{directory}
1085 Run @value{GDBN} using @var{directory} as its working directory,
1086 instead of the current directory.
1090 @cindex @code{--fullname}
1092 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1093 subprocess. It tells @value{GDBN} to output the full file name and line
1094 number in a standard, recognizable fashion each time a stack frame is
1095 displayed (which includes each time your program stops). This
1096 recognizable format looks like two @samp{\032} characters, followed by
1097 the file name, line number and character position separated by colons,
1098 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1099 @samp{\032} characters as a signal to display the source code for the
1103 @cindex @code{--epoch}
1104 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1105 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1106 routines so as to allow Epoch to display values of expressions in a
1109 @item -annotate @var{level}
1110 @cindex @code{--annotate}
1111 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1112 effect is identical to using @samp{set annotate @var{level}}
1113 (@pxref{Annotations}). The annotation @var{level} controls how much
1114 information @value{GDBN} prints together with its prompt, values of
1115 expressions, source lines, and other types of output. Level 0 is the
1116 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1117 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1118 that control @value{GDBN}, and level 2 has been deprecated.
1120 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1124 @cindex @code{--args}
1125 Change interpretation of command line so that arguments following the
1126 executable file are passed as command line arguments to the inferior.
1127 This option stops option processing.
1129 @item -baud @var{bps}
1131 @cindex @code{--baud}
1133 Set the line speed (baud rate or bits per second) of any serial
1134 interface used by @value{GDBN} for remote debugging.
1136 @item -l @var{timeout}
1138 Set the timeout (in seconds) of any communication used by @value{GDBN}
1139 for remote debugging.
1141 @item -tty @var{device}
1142 @itemx -t @var{device}
1143 @cindex @code{--tty}
1145 Run using @var{device} for your program's standard input and output.
1146 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1148 @c resolve the situation of these eventually
1150 @cindex @code{--tui}
1151 Activate the @dfn{Text User Interface} when starting. The Text User
1152 Interface manages several text windows on the terminal, showing
1153 source, assembly, registers and @value{GDBN} command outputs
1154 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1155 Text User Interface can be enabled by invoking the program
1156 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1157 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1160 @c @cindex @code{--xdb}
1161 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1162 @c For information, see the file @file{xdb_trans.html}, which is usually
1163 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1166 @item -interpreter @var{interp}
1167 @cindex @code{--interpreter}
1168 Use the interpreter @var{interp} for interface with the controlling
1169 program or device. This option is meant to be set by programs which
1170 communicate with @value{GDBN} using it as a back end.
1171 @xref{Interpreters, , Command Interpreters}.
1173 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1174 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1175 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1176 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1177 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1178 @sc{gdb/mi} interfaces are no longer supported.
1181 @cindex @code{--write}
1182 Open the executable and core files for both reading and writing. This
1183 is equivalent to the @samp{set write on} command inside @value{GDBN}
1187 @cindex @code{--statistics}
1188 This option causes @value{GDBN} to print statistics about time and
1189 memory usage after it completes each command and returns to the prompt.
1192 @cindex @code{--version}
1193 This option causes @value{GDBN} to print its version number and
1194 no-warranty blurb, and exit.
1199 @subsection What @value{GDBN} Does During Startup
1200 @cindex @value{GDBN} startup
1202 Here's the description of what @value{GDBN} does during session startup:
1206 Sets up the command interpreter as specified by the command line
1207 (@pxref{Mode Options, interpreter}).
1211 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1212 DOS/Windows systems, the home directory is the one pointed to by the
1213 @code{HOME} environment variable.} and executes all the commands in
1217 Processes command line options and operands.
1220 Reads and executes the commands from init file (if any) in the current
1221 working directory. This is only done if the current directory is
1222 different from your home directory. Thus, you can have more than one
1223 init file, one generic in your home directory, and another, specific
1224 to the program you are debugging, in the directory where you invoke
1228 Reads command files specified by the @samp{-x} option. @xref{Command
1229 Files}, for more details about @value{GDBN} command files.
1232 Reads the command history recorded in the @dfn{history file}.
1233 @xref{Command History}, for more details about the command history and the
1234 files where @value{GDBN} records it.
1237 Init files use the same syntax as @dfn{command files} (@pxref{Command
1238 Files}) and are processed by @value{GDBN} in the same way. The init
1239 file in your home directory can set options (such as @samp{set
1240 complaints}) that affect subsequent processing of command line options
1241 and operands. Init files are not executed if you use the @samp{-nx}
1242 option (@pxref{Mode Options, ,Choosing Modes}).
1244 @cindex init file name
1245 @cindex @file{.gdbinit}
1246 @cindex @file{gdb.ini}
1247 The @value{GDBN} init files are normally called @file{.gdbinit}.
1248 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1249 the limitations of file names imposed by DOS filesystems. The Windows
1250 ports of @value{GDBN} use the standard name, but if they find a
1251 @file{gdb.ini} file, they warn you about that and suggest to rename
1252 the file to the standard name.
1256 @section Quitting @value{GDBN}
1257 @cindex exiting @value{GDBN}
1258 @cindex leaving @value{GDBN}
1261 @kindex quit @r{[}@var{expression}@r{]}
1262 @kindex q @r{(@code{quit})}
1263 @item quit @r{[}@var{expression}@r{]}
1265 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1266 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1267 do not supply @var{expression}, @value{GDBN} will terminate normally;
1268 otherwise it will terminate using the result of @var{expression} as the
1273 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1274 terminates the action of any @value{GDBN} command that is in progress and
1275 returns to @value{GDBN} command level. It is safe to type the interrupt
1276 character at any time because @value{GDBN} does not allow it to take effect
1277 until a time when it is safe.
1279 If you have been using @value{GDBN} to control an attached process or
1280 device, you can release it with the @code{detach} command
1281 (@pxref{Attach, ,Debugging an Already-running Process}).
1283 @node Shell Commands
1284 @section Shell Commands
1286 If you need to execute occasional shell commands during your
1287 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1288 just use the @code{shell} command.
1292 @cindex shell escape
1293 @item shell @var{command string}
1294 Invoke a standard shell to execute @var{command string}.
1295 If it exists, the environment variable @code{SHELL} determines which
1296 shell to run. Otherwise @value{GDBN} uses the default shell
1297 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1300 The utility @code{make} is often needed in development environments.
1301 You do not have to use the @code{shell} command for this purpose in
1306 @cindex calling make
1307 @item make @var{make-args}
1308 Execute the @code{make} program with the specified
1309 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1312 @node Logging Output
1313 @section Logging Output
1314 @cindex logging @value{GDBN} output
1315 @cindex save @value{GDBN} output to a file
1317 You may want to save the output of @value{GDBN} commands to a file.
1318 There are several commands to control @value{GDBN}'s logging.
1322 @item set logging on
1324 @item set logging off
1326 @cindex logging file name
1327 @item set logging file @var{file}
1328 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1329 @item set logging overwrite [on|off]
1330 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1331 you want @code{set logging on} to overwrite the logfile instead.
1332 @item set logging redirect [on|off]
1333 By default, @value{GDBN} output will go to both the terminal and the logfile.
1334 Set @code{redirect} if you want output to go only to the log file.
1335 @kindex show logging
1337 Show the current values of the logging settings.
1341 @chapter @value{GDBN} Commands
1343 You can abbreviate a @value{GDBN} command to the first few letters of the command
1344 name, if that abbreviation is unambiguous; and you can repeat certain
1345 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1346 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1347 show you the alternatives available, if there is more than one possibility).
1350 * Command Syntax:: How to give commands to @value{GDBN}
1351 * Completion:: Command completion
1352 * Help:: How to ask @value{GDBN} for help
1355 @node Command Syntax
1356 @section Command Syntax
1358 A @value{GDBN} command is a single line of input. There is no limit on
1359 how long it can be. It starts with a command name, which is followed by
1360 arguments whose meaning depends on the command name. For example, the
1361 command @code{step} accepts an argument which is the number of times to
1362 step, as in @samp{step 5}. You can also use the @code{step} command
1363 with no arguments. Some commands do not allow any arguments.
1365 @cindex abbreviation
1366 @value{GDBN} command names may always be truncated if that abbreviation is
1367 unambiguous. Other possible command abbreviations are listed in the
1368 documentation for individual commands. In some cases, even ambiguous
1369 abbreviations are allowed; for example, @code{s} is specially defined as
1370 equivalent to @code{step} even though there are other commands whose
1371 names start with @code{s}. You can test abbreviations by using them as
1372 arguments to the @code{help} command.
1374 @cindex repeating commands
1375 @kindex RET @r{(repeat last command)}
1376 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1377 repeat the previous command. Certain commands (for example, @code{run})
1378 will not repeat this way; these are commands whose unintentional
1379 repetition might cause trouble and which you are unlikely to want to
1380 repeat. User-defined commands can disable this feature; see
1381 @ref{Define, dont-repeat}.
1383 The @code{list} and @code{x} commands, when you repeat them with
1384 @key{RET}, construct new arguments rather than repeating
1385 exactly as typed. This permits easy scanning of source or memory.
1387 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1388 output, in a way similar to the common utility @code{more}
1389 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1390 @key{RET} too many in this situation, @value{GDBN} disables command
1391 repetition after any command that generates this sort of display.
1393 @kindex # @r{(a comment)}
1395 Any text from a @kbd{#} to the end of the line is a comment; it does
1396 nothing. This is useful mainly in command files (@pxref{Command
1397 Files,,Command Files}).
1399 @cindex repeating command sequences
1400 @kindex Ctrl-o @r{(operate-and-get-next)}
1401 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1402 commands. This command accepts the current line, like @key{RET}, and
1403 then fetches the next line relative to the current line from the history
1407 @section Command Completion
1410 @cindex word completion
1411 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1412 only one possibility; it can also show you what the valid possibilities
1413 are for the next word in a command, at any time. This works for @value{GDBN}
1414 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1416 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1417 of a word. If there is only one possibility, @value{GDBN} fills in the
1418 word, and waits for you to finish the command (or press @key{RET} to
1419 enter it). For example, if you type
1421 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1422 @c complete accuracy in these examples; space introduced for clarity.
1423 @c If texinfo enhancements make it unnecessary, it would be nice to
1424 @c replace " @key" by "@key" in the following...
1426 (@value{GDBP}) info bre @key{TAB}
1430 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1431 the only @code{info} subcommand beginning with @samp{bre}:
1434 (@value{GDBP}) info breakpoints
1438 You can either press @key{RET} at this point, to run the @code{info
1439 breakpoints} command, or backspace and enter something else, if
1440 @samp{breakpoints} does not look like the command you expected. (If you
1441 were sure you wanted @code{info breakpoints} in the first place, you
1442 might as well just type @key{RET} immediately after @samp{info bre},
1443 to exploit command abbreviations rather than command completion).
1445 If there is more than one possibility for the next word when you press
1446 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1447 characters and try again, or just press @key{TAB} a second time;
1448 @value{GDBN} displays all the possible completions for that word. For
1449 example, you might want to set a breakpoint on a subroutine whose name
1450 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1451 just sounds the bell. Typing @key{TAB} again displays all the
1452 function names in your program that begin with those characters, for
1456 (@value{GDBP}) b make_ @key{TAB}
1457 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1458 make_a_section_from_file make_environ
1459 make_abs_section make_function_type
1460 make_blockvector make_pointer_type
1461 make_cleanup make_reference_type
1462 make_command make_symbol_completion_list
1463 (@value{GDBP}) b make_
1467 After displaying the available possibilities, @value{GDBN} copies your
1468 partial input (@samp{b make_} in the example) so you can finish the
1471 If you just want to see the list of alternatives in the first place, you
1472 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1473 means @kbd{@key{META} ?}. You can type this either by holding down a
1474 key designated as the @key{META} shift on your keyboard (if there is
1475 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1477 @cindex quotes in commands
1478 @cindex completion of quoted strings
1479 Sometimes the string you need, while logically a ``word'', may contain
1480 parentheses or other characters that @value{GDBN} normally excludes from
1481 its notion of a word. To permit word completion to work in this
1482 situation, you may enclose words in @code{'} (single quote marks) in
1483 @value{GDBN} commands.
1485 The most likely situation where you might need this is in typing the
1486 name of a C@t{++} function. This is because C@t{++} allows function
1487 overloading (multiple definitions of the same function, distinguished
1488 by argument type). For example, when you want to set a breakpoint you
1489 may need to distinguish whether you mean the version of @code{name}
1490 that takes an @code{int} parameter, @code{name(int)}, or the version
1491 that takes a @code{float} parameter, @code{name(float)}. To use the
1492 word-completion facilities in this situation, type a single quote
1493 @code{'} at the beginning of the function name. This alerts
1494 @value{GDBN} that it may need to consider more information than usual
1495 when you press @key{TAB} or @kbd{M-?} to request word completion:
1498 (@value{GDBP}) b 'bubble( @kbd{M-?}
1499 bubble(double,double) bubble(int,int)
1500 (@value{GDBP}) b 'bubble(
1503 In some cases, @value{GDBN} can tell that completing a name requires using
1504 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1505 completing as much as it can) if you do not type the quote in the first
1509 (@value{GDBP}) b bub @key{TAB}
1510 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1511 (@value{GDBP}) b 'bubble(
1515 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1516 you have not yet started typing the argument list when you ask for
1517 completion on an overloaded symbol.
1519 For more information about overloaded functions, see @ref{C Plus Plus
1520 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1521 overload-resolution off} to disable overload resolution;
1522 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1526 @section Getting Help
1527 @cindex online documentation
1530 You can always ask @value{GDBN} itself for information on its commands,
1531 using the command @code{help}.
1534 @kindex h @r{(@code{help})}
1537 You can use @code{help} (abbreviated @code{h}) with no arguments to
1538 display a short list of named classes of commands:
1542 List of classes of commands:
1544 aliases -- Aliases of other commands
1545 breakpoints -- Making program stop at certain points
1546 data -- Examining data
1547 files -- Specifying and examining files
1548 internals -- Maintenance commands
1549 obscure -- Obscure features
1550 running -- Running the program
1551 stack -- Examining the stack
1552 status -- Status inquiries
1553 support -- Support facilities
1554 tracepoints -- Tracing of program execution without
1555 stopping the program
1556 user-defined -- User-defined commands
1558 Type "help" followed by a class name for a list of
1559 commands in that class.
1560 Type "help" followed by command name for full
1562 Command name abbreviations are allowed if unambiguous.
1565 @c the above line break eliminates huge line overfull...
1567 @item help @var{class}
1568 Using one of the general help classes as an argument, you can get a
1569 list of the individual commands in that class. For example, here is the
1570 help display for the class @code{status}:
1573 (@value{GDBP}) help status
1578 @c Line break in "show" line falsifies real output, but needed
1579 @c to fit in smallbook page size.
1580 info -- Generic command for showing things
1581 about the program being debugged
1582 show -- Generic command for showing things
1585 Type "help" followed by command name for full
1587 Command name abbreviations are allowed if unambiguous.
1591 @item help @var{command}
1592 With a command name as @code{help} argument, @value{GDBN} displays a
1593 short paragraph on how to use that command.
1596 @item apropos @var{args}
1597 The @code{apropos} command searches through all of the @value{GDBN}
1598 commands, and their documentation, for the regular expression specified in
1599 @var{args}. It prints out all matches found. For example:
1610 set symbol-reloading -- Set dynamic symbol table reloading
1611 multiple times in one run
1612 show symbol-reloading -- Show dynamic symbol table reloading
1613 multiple times in one run
1618 @item complete @var{args}
1619 The @code{complete @var{args}} command lists all the possible completions
1620 for the beginning of a command. Use @var{args} to specify the beginning of the
1621 command you want completed. For example:
1627 @noindent results in:
1638 @noindent This is intended for use by @sc{gnu} Emacs.
1641 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1642 and @code{show} to inquire about the state of your program, or the state
1643 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1644 manual introduces each of them in the appropriate context. The listings
1645 under @code{info} and under @code{show} in the Index point to
1646 all the sub-commands. @xref{Index}.
1651 @kindex i @r{(@code{info})}
1653 This command (abbreviated @code{i}) is for describing the state of your
1654 program. For example, you can show the arguments passed to a function
1655 with @code{info args}, list the registers currently in use with @code{info
1656 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1657 You can get a complete list of the @code{info} sub-commands with
1658 @w{@code{help info}}.
1662 You can assign the result of an expression to an environment variable with
1663 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1664 @code{set prompt $}.
1668 In contrast to @code{info}, @code{show} is for describing the state of
1669 @value{GDBN} itself.
1670 You can change most of the things you can @code{show}, by using the
1671 related command @code{set}; for example, you can control what number
1672 system is used for displays with @code{set radix}, or simply inquire
1673 which is currently in use with @code{show radix}.
1676 To display all the settable parameters and their current
1677 values, you can use @code{show} with no arguments; you may also use
1678 @code{info set}. Both commands produce the same display.
1679 @c FIXME: "info set" violates the rule that "info" is for state of
1680 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1681 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1685 Here are three miscellaneous @code{show} subcommands, all of which are
1686 exceptional in lacking corresponding @code{set} commands:
1689 @kindex show version
1690 @cindex @value{GDBN} version number
1692 Show what version of @value{GDBN} is running. You should include this
1693 information in @value{GDBN} bug-reports. If multiple versions of
1694 @value{GDBN} are in use at your site, you may need to determine which
1695 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1696 commands are introduced, and old ones may wither away. Also, many
1697 system vendors ship variant versions of @value{GDBN}, and there are
1698 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1699 The version number is the same as the one announced when you start
1702 @kindex show copying
1703 @kindex info copying
1704 @cindex display @value{GDBN} copyright
1707 Display information about permission for copying @value{GDBN}.
1709 @kindex show warranty
1710 @kindex info warranty
1712 @itemx info warranty
1713 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1714 if your version of @value{GDBN} comes with one.
1719 @chapter Running Programs Under @value{GDBN}
1721 When you run a program under @value{GDBN}, you must first generate
1722 debugging information when you compile it.
1724 You may start @value{GDBN} with its arguments, if any, in an environment
1725 of your choice. If you are doing native debugging, you may redirect
1726 your program's input and output, debug an already running process, or
1727 kill a child process.
1730 * Compilation:: Compiling for debugging
1731 * Starting:: Starting your program
1732 * Arguments:: Your program's arguments
1733 * Environment:: Your program's environment
1735 * Working Directory:: Your program's working directory
1736 * Input/Output:: Your program's input and output
1737 * Attach:: Debugging an already-running process
1738 * Kill Process:: Killing the child process
1740 * Threads:: Debugging programs with multiple threads
1741 * Processes:: Debugging programs with multiple processes
1742 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1746 @section Compiling for Debugging
1748 In order to debug a program effectively, you need to generate
1749 debugging information when you compile it. This debugging information
1750 is stored in the object file; it describes the data type of each
1751 variable or function and the correspondence between source line numbers
1752 and addresses in the executable code.
1754 To request debugging information, specify the @samp{-g} option when you run
1757 Programs that are to be shipped to your customers are compiled with
1758 optimizations, using the @samp{-O} compiler option. However, many
1759 compilers are unable to handle the @samp{-g} and @samp{-O} options
1760 together. Using those compilers, you cannot generate optimized
1761 executables containing debugging information.
1763 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1764 without @samp{-O}, making it possible to debug optimized code. We
1765 recommend that you @emph{always} use @samp{-g} whenever you compile a
1766 program. You may think your program is correct, but there is no sense
1767 in pushing your luck.
1769 @cindex optimized code, debugging
1770 @cindex debugging optimized code
1771 When you debug a program compiled with @samp{-g -O}, remember that the
1772 optimizer is rearranging your code; the debugger shows you what is
1773 really there. Do not be too surprised when the execution path does not
1774 exactly match your source file! An extreme example: if you define a
1775 variable, but never use it, @value{GDBN} never sees that
1776 variable---because the compiler optimizes it out of existence.
1778 Some things do not work as well with @samp{-g -O} as with just
1779 @samp{-g}, particularly on machines with instruction scheduling. If in
1780 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1781 please report it to us as a bug (including a test case!).
1782 @xref{Variables}, for more information about debugging optimized code.
1784 Older versions of the @sc{gnu} C compiler permitted a variant option
1785 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1786 format; if your @sc{gnu} C compiler has this option, do not use it.
1788 @value{GDBN} knows about preprocessor macros and can show you their
1789 expansion (@pxref{Macros}). Most compilers do not include information
1790 about preprocessor macros in the debugging information if you specify
1791 the @option{-g} flag alone, because this information is rather large.
1792 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1793 provides macro information if you specify the options
1794 @option{-gdwarf-2} and @option{-g3}; the former option requests
1795 debugging information in the Dwarf 2 format, and the latter requests
1796 ``extra information''. In the future, we hope to find more compact
1797 ways to represent macro information, so that it can be included with
1802 @section Starting your Program
1808 @kindex r @r{(@code{run})}
1811 Use the @code{run} command to start your program under @value{GDBN}.
1812 You must first specify the program name (except on VxWorks) with an
1813 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1814 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1815 (@pxref{Files, ,Commands to Specify Files}).
1819 If you are running your program in an execution environment that
1820 supports processes, @code{run} creates an inferior process and makes
1821 that process run your program. In some environments without processes,
1822 @code{run} jumps to the start of your program. Other targets,
1823 like @samp{remote}, are always running. If you get an error
1824 message like this one:
1827 The "remote" target does not support "run".
1828 Try "help target" or "continue".
1832 then use @code{continue} to run your program. You may need @code{load}
1833 first (@pxref{load}).
1835 The execution of a program is affected by certain information it
1836 receives from its superior. @value{GDBN} provides ways to specify this
1837 information, which you must do @emph{before} starting your program. (You
1838 can change it after starting your program, but such changes only affect
1839 your program the next time you start it.) This information may be
1840 divided into four categories:
1843 @item The @emph{arguments.}
1844 Specify the arguments to give your program as the arguments of the
1845 @code{run} command. If a shell is available on your target, the shell
1846 is used to pass the arguments, so that you may use normal conventions
1847 (such as wildcard expansion or variable substitution) in describing
1849 In Unix systems, you can control which shell is used with the
1850 @code{SHELL} environment variable.
1851 @xref{Arguments, ,Your Program's Arguments}.
1853 @item The @emph{environment.}
1854 Your program normally inherits its environment from @value{GDBN}, but you can
1855 use the @value{GDBN} commands @code{set environment} and @code{unset
1856 environment} to change parts of the environment that affect
1857 your program. @xref{Environment, ,Your Program's Environment}.
1859 @item The @emph{working directory.}
1860 Your program inherits its working directory from @value{GDBN}. You can set
1861 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1862 @xref{Working Directory, ,Your Program's Working Directory}.
1864 @item The @emph{standard input and output.}
1865 Your program normally uses the same device for standard input and
1866 standard output as @value{GDBN} is using. You can redirect input and output
1867 in the @code{run} command line, or you can use the @code{tty} command to
1868 set a different device for your program.
1869 @xref{Input/Output, ,Your Program's Input and Output}.
1872 @emph{Warning:} While input and output redirection work, you cannot use
1873 pipes to pass the output of the program you are debugging to another
1874 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1878 When you issue the @code{run} command, your program begins to execute
1879 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1880 of how to arrange for your program to stop. Once your program has
1881 stopped, you may call functions in your program, using the @code{print}
1882 or @code{call} commands. @xref{Data, ,Examining Data}.
1884 If the modification time of your symbol file has changed since the last
1885 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1886 table, and reads it again. When it does this, @value{GDBN} tries to retain
1887 your current breakpoints.
1892 @cindex run to main procedure
1893 The name of the main procedure can vary from language to language.
1894 With C or C@t{++}, the main procedure name is always @code{main}, but
1895 other languages such as Ada do not require a specific name for their
1896 main procedure. The debugger provides a convenient way to start the
1897 execution of the program and to stop at the beginning of the main
1898 procedure, depending on the language used.
1900 The @samp{start} command does the equivalent of setting a temporary
1901 breakpoint at the beginning of the main procedure and then invoking
1902 the @samp{run} command.
1904 @cindex elaboration phase
1905 Some programs contain an @dfn{elaboration} phase where some startup code is
1906 executed before the main procedure is called. This depends on the
1907 languages used to write your program. In C@t{++}, for instance,
1908 constructors for static and global objects are executed before
1909 @code{main} is called. It is therefore possible that the debugger stops
1910 before reaching the main procedure. However, the temporary breakpoint
1911 will remain to halt execution.
1913 Specify the arguments to give to your program as arguments to the
1914 @samp{start} command. These arguments will be given verbatim to the
1915 underlying @samp{run} command. Note that the same arguments will be
1916 reused if no argument is provided during subsequent calls to
1917 @samp{start} or @samp{run}.
1919 It is sometimes necessary to debug the program during elaboration. In
1920 these cases, using the @code{start} command would stop the execution of
1921 your program too late, as the program would have already completed the
1922 elaboration phase. Under these circumstances, insert breakpoints in your
1923 elaboration code before running your program.
1925 @kindex set exec-wrapper
1926 @item set exec-wrapper @var{wrapper}
1927 @itemx show exec-wrapper
1928 @itemx unset exec-wrapper
1929 When @samp{exec-wrapper} is set, the specified wrapper is used to
1930 launch programs for debugging. @value{GDBN} starts your program
1931 with a shell command of the form @kbd{exec @var{wrapper}
1932 @var{program}}. Quoting is added to @var{program} and its
1933 arguments, but not to @var{wrapper}, so you should add quotes if
1934 appropriate for your shell. The wrapper runs until it executes
1935 your program, and then @value{GDBN} takes control.
1937 You can use any program that eventually calls @code{execve} with
1938 its arguments as a wrapper. Several standard Unix utilities do
1939 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1940 with @code{exec "$@@"} will also work.
1942 For example, you can use @code{env} to pass an environment variable to
1943 the debugged program, without setting the variable in your shell's
1947 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1951 This command is available when debugging locally on most targets, excluding
1952 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
1957 @section Your Program's Arguments
1959 @cindex arguments (to your program)
1960 The arguments to your program can be specified by the arguments of the
1962 They are passed to a shell, which expands wildcard characters and
1963 performs redirection of I/O, and thence to your program. Your
1964 @code{SHELL} environment variable (if it exists) specifies what shell
1965 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1966 the default shell (@file{/bin/sh} on Unix).
1968 On non-Unix systems, the program is usually invoked directly by
1969 @value{GDBN}, which emulates I/O redirection via the appropriate system
1970 calls, and the wildcard characters are expanded by the startup code of
1971 the program, not by the shell.
1973 @code{run} with no arguments uses the same arguments used by the previous
1974 @code{run}, or those set by the @code{set args} command.
1979 Specify the arguments to be used the next time your program is run. If
1980 @code{set args} has no arguments, @code{run} executes your program
1981 with no arguments. Once you have run your program with arguments,
1982 using @code{set args} before the next @code{run} is the only way to run
1983 it again without arguments.
1987 Show the arguments to give your program when it is started.
1991 @section Your Program's Environment
1993 @cindex environment (of your program)
1994 The @dfn{environment} consists of a set of environment variables and
1995 their values. Environment variables conventionally record such things as
1996 your user name, your home directory, your terminal type, and your search
1997 path for programs to run. Usually you set up environment variables with
1998 the shell and they are inherited by all the other programs you run. When
1999 debugging, it can be useful to try running your program with a modified
2000 environment without having to start @value{GDBN} over again.
2004 @item path @var{directory}
2005 Add @var{directory} to the front of the @code{PATH} environment variable
2006 (the search path for executables) that will be passed to your program.
2007 The value of @code{PATH} used by @value{GDBN} does not change.
2008 You may specify several directory names, separated by whitespace or by a
2009 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2010 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2011 is moved to the front, so it is searched sooner.
2013 You can use the string @samp{$cwd} to refer to whatever is the current
2014 working directory at the time @value{GDBN} searches the path. If you
2015 use @samp{.} instead, it refers to the directory where you executed the
2016 @code{path} command. @value{GDBN} replaces @samp{.} in the
2017 @var{directory} argument (with the current path) before adding
2018 @var{directory} to the search path.
2019 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2020 @c document that, since repeating it would be a no-op.
2024 Display the list of search paths for executables (the @code{PATH}
2025 environment variable).
2027 @kindex show environment
2028 @item show environment @r{[}@var{varname}@r{]}
2029 Print the value of environment variable @var{varname} to be given to
2030 your program when it starts. If you do not supply @var{varname},
2031 print the names and values of all environment variables to be given to
2032 your program. You can abbreviate @code{environment} as @code{env}.
2034 @kindex set environment
2035 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2036 Set environment variable @var{varname} to @var{value}. The value
2037 changes for your program only, not for @value{GDBN} itself. @var{value} may
2038 be any string; the values of environment variables are just strings, and
2039 any interpretation is supplied by your program itself. The @var{value}
2040 parameter is optional; if it is eliminated, the variable is set to a
2042 @c "any string" here does not include leading, trailing
2043 @c blanks. Gnu asks: does anyone care?
2045 For example, this command:
2052 tells the debugged program, when subsequently run, that its user is named
2053 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2054 are not actually required.)
2056 @kindex unset environment
2057 @item unset environment @var{varname}
2058 Remove variable @var{varname} from the environment to be passed to your
2059 program. This is different from @samp{set env @var{varname} =};
2060 @code{unset environment} removes the variable from the environment,
2061 rather than assigning it an empty value.
2064 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2066 by your @code{SHELL} environment variable if it exists (or
2067 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2068 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2069 @file{.bashrc} for BASH---any variables you set in that file affect
2070 your program. You may wish to move setting of environment variables to
2071 files that are only run when you sign on, such as @file{.login} or
2074 @node Working Directory
2075 @section Your Program's Working Directory
2077 @cindex working directory (of your program)
2078 Each time you start your program with @code{run}, it inherits its
2079 working directory from the current working directory of @value{GDBN}.
2080 The @value{GDBN} working directory is initially whatever it inherited
2081 from its parent process (typically the shell), but you can specify a new
2082 working directory in @value{GDBN} with the @code{cd} command.
2084 The @value{GDBN} working directory also serves as a default for the commands
2085 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2090 @cindex change working directory
2091 @item cd @var{directory}
2092 Set the @value{GDBN} working directory to @var{directory}.
2096 Print the @value{GDBN} working directory.
2099 It is generally impossible to find the current working directory of
2100 the process being debugged (since a program can change its directory
2101 during its run). If you work on a system where @value{GDBN} is
2102 configured with the @file{/proc} support, you can use the @code{info
2103 proc} command (@pxref{SVR4 Process Information}) to find out the
2104 current working directory of the debuggee.
2107 @section Your Program's Input and Output
2112 By default, the program you run under @value{GDBN} does input and output to
2113 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2114 to its own terminal modes to interact with you, but it records the terminal
2115 modes your program was using and switches back to them when you continue
2116 running your program.
2119 @kindex info terminal
2121 Displays information recorded by @value{GDBN} about the terminal modes your
2125 You can redirect your program's input and/or output using shell
2126 redirection with the @code{run} command. For example,
2133 starts your program, diverting its output to the file @file{outfile}.
2136 @cindex controlling terminal
2137 Another way to specify where your program should do input and output is
2138 with the @code{tty} command. This command accepts a file name as
2139 argument, and causes this file to be the default for future @code{run}
2140 commands. It also resets the controlling terminal for the child
2141 process, for future @code{run} commands. For example,
2148 directs that processes started with subsequent @code{run} commands
2149 default to do input and output on the terminal @file{/dev/ttyb} and have
2150 that as their controlling terminal.
2152 An explicit redirection in @code{run} overrides the @code{tty} command's
2153 effect on the input/output device, but not its effect on the controlling
2156 When you use the @code{tty} command or redirect input in the @code{run}
2157 command, only the input @emph{for your program} is affected. The input
2158 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2159 for @code{set inferior-tty}.
2161 @cindex inferior tty
2162 @cindex set inferior controlling terminal
2163 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2164 display the name of the terminal that will be used for future runs of your
2168 @item set inferior-tty /dev/ttyb
2169 @kindex set inferior-tty
2170 Set the tty for the program being debugged to /dev/ttyb.
2172 @item show inferior-tty
2173 @kindex show inferior-tty
2174 Show the current tty for the program being debugged.
2178 @section Debugging an Already-running Process
2183 @item attach @var{process-id}
2184 This command attaches to a running process---one that was started
2185 outside @value{GDBN}. (@code{info files} shows your active
2186 targets.) The command takes as argument a process ID. The usual way to
2187 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2188 or with the @samp{jobs -l} shell command.
2190 @code{attach} does not repeat if you press @key{RET} a second time after
2191 executing the command.
2194 To use @code{attach}, your program must be running in an environment
2195 which supports processes; for example, @code{attach} does not work for
2196 programs on bare-board targets that lack an operating system. You must
2197 also have permission to send the process a signal.
2199 When you use @code{attach}, the debugger finds the program running in
2200 the process first by looking in the current working directory, then (if
2201 the program is not found) by using the source file search path
2202 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2203 the @code{file} command to load the program. @xref{Files, ,Commands to
2206 The first thing @value{GDBN} does after arranging to debug the specified
2207 process is to stop it. You can examine and modify an attached process
2208 with all the @value{GDBN} commands that are ordinarily available when
2209 you start processes with @code{run}. You can insert breakpoints; you
2210 can step and continue; you can modify storage. If you would rather the
2211 process continue running, you may use the @code{continue} command after
2212 attaching @value{GDBN} to the process.
2217 When you have finished debugging the attached process, you can use the
2218 @code{detach} command to release it from @value{GDBN} control. Detaching
2219 the process continues its execution. After the @code{detach} command,
2220 that process and @value{GDBN} become completely independent once more, and you
2221 are ready to @code{attach} another process or start one with @code{run}.
2222 @code{detach} does not repeat if you press @key{RET} again after
2223 executing the command.
2226 If you exit @value{GDBN} while you have an attached process, you detach
2227 that process. If you use the @code{run} command, you kill that process.
2228 By default, @value{GDBN} asks for confirmation if you try to do either of these
2229 things; you can control whether or not you need to confirm by using the
2230 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2234 @section Killing the Child Process
2239 Kill the child process in which your program is running under @value{GDBN}.
2242 This command is useful if you wish to debug a core dump instead of a
2243 running process. @value{GDBN} ignores any core dump file while your program
2246 On some operating systems, a program cannot be executed outside @value{GDBN}
2247 while you have breakpoints set on it inside @value{GDBN}. You can use the
2248 @code{kill} command in this situation to permit running your program
2249 outside the debugger.
2251 The @code{kill} command is also useful if you wish to recompile and
2252 relink your program, since on many systems it is impossible to modify an
2253 executable file while it is running in a process. In this case, when you
2254 next type @code{run}, @value{GDBN} notices that the file has changed, and
2255 reads the symbol table again (while trying to preserve your current
2256 breakpoint settings).
2259 @section Debugging Programs with Multiple Threads
2261 @cindex threads of execution
2262 @cindex multiple threads
2263 @cindex switching threads
2264 In some operating systems, such as HP-UX and Solaris, a single program
2265 may have more than one @dfn{thread} of execution. The precise semantics
2266 of threads differ from one operating system to another, but in general
2267 the threads of a single program are akin to multiple processes---except
2268 that they share one address space (that is, they can all examine and
2269 modify the same variables). On the other hand, each thread has its own
2270 registers and execution stack, and perhaps private memory.
2272 @value{GDBN} provides these facilities for debugging multi-thread
2276 @item automatic notification of new threads
2277 @item @samp{thread @var{threadno}}, a command to switch among threads
2278 @item @samp{info threads}, a command to inquire about existing threads
2279 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2280 a command to apply a command to a list of threads
2281 @item thread-specific breakpoints
2282 @item @samp{set print thread-events}, which controls printing of
2283 messages on thread start and exit.
2287 @emph{Warning:} These facilities are not yet available on every
2288 @value{GDBN} configuration where the operating system supports threads.
2289 If your @value{GDBN} does not support threads, these commands have no
2290 effect. For example, a system without thread support shows no output
2291 from @samp{info threads}, and always rejects the @code{thread} command,
2295 (@value{GDBP}) info threads
2296 (@value{GDBP}) thread 1
2297 Thread ID 1 not known. Use the "info threads" command to
2298 see the IDs of currently known threads.
2300 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2301 @c doesn't support threads"?
2304 @cindex focus of debugging
2305 @cindex current thread
2306 The @value{GDBN} thread debugging facility allows you to observe all
2307 threads while your program runs---but whenever @value{GDBN} takes
2308 control, one thread in particular is always the focus of debugging.
2309 This thread is called the @dfn{current thread}. Debugging commands show
2310 program information from the perspective of the current thread.
2312 @cindex @code{New} @var{systag} message
2313 @cindex thread identifier (system)
2314 @c FIXME-implementors!! It would be more helpful if the [New...] message
2315 @c included GDB's numeric thread handle, so you could just go to that
2316 @c thread without first checking `info threads'.
2317 Whenever @value{GDBN} detects a new thread in your program, it displays
2318 the target system's identification for the thread with a message in the
2319 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2320 whose form varies depending on the particular system. For example, on
2321 @sc{gnu}/Linux, you might see
2324 [New Thread 46912507313328 (LWP 25582)]
2328 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2329 the @var{systag} is simply something like @samp{process 368}, with no
2332 @c FIXME!! (1) Does the [New...] message appear even for the very first
2333 @c thread of a program, or does it only appear for the
2334 @c second---i.e.@: when it becomes obvious we have a multithread
2336 @c (2) *Is* there necessarily a first thread always? Or do some
2337 @c multithread systems permit starting a program with multiple
2338 @c threads ab initio?
2340 @cindex thread number
2341 @cindex thread identifier (GDB)
2342 For debugging purposes, @value{GDBN} associates its own thread
2343 number---always a single integer---with each thread in your program.
2346 @kindex info threads
2348 Display a summary of all threads currently in your
2349 program. @value{GDBN} displays for each thread (in this order):
2353 the thread number assigned by @value{GDBN}
2356 the target system's thread identifier (@var{systag})
2359 the current stack frame summary for that thread
2363 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2364 indicates the current thread.
2368 @c end table here to get a little more width for example
2371 (@value{GDBP}) info threads
2372 3 process 35 thread 27 0x34e5 in sigpause ()
2373 2 process 35 thread 23 0x34e5 in sigpause ()
2374 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2380 @cindex debugging multithreaded programs (on HP-UX)
2381 @cindex thread identifier (GDB), on HP-UX
2382 For debugging purposes, @value{GDBN} associates its own thread
2383 number---a small integer assigned in thread-creation order---with each
2384 thread in your program.
2386 @cindex @code{New} @var{systag} message, on HP-UX
2387 @cindex thread identifier (system), on HP-UX
2388 @c FIXME-implementors!! It would be more helpful if the [New...] message
2389 @c included GDB's numeric thread handle, so you could just go to that
2390 @c thread without first checking `info threads'.
2391 Whenever @value{GDBN} detects a new thread in your program, it displays
2392 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2393 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2394 whose form varies depending on the particular system. For example, on
2398 [New thread 2 (system thread 26594)]
2402 when @value{GDBN} notices a new thread.
2405 @kindex info threads (HP-UX)
2407 Display a summary of all threads currently in your
2408 program. @value{GDBN} displays for each thread (in this order):
2411 @item the thread number assigned by @value{GDBN}
2413 @item the target system's thread identifier (@var{systag})
2415 @item the current stack frame summary for that thread
2419 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2420 indicates the current thread.
2424 @c end table here to get a little more width for example
2427 (@value{GDBP}) info threads
2428 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2430 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2431 from /usr/lib/libc.2
2432 1 system thread 27905 0x7b003498 in _brk () \@*
2433 from /usr/lib/libc.2
2436 On Solaris, you can display more information about user threads with a
2437 Solaris-specific command:
2440 @item maint info sol-threads
2441 @kindex maint info sol-threads
2442 @cindex thread info (Solaris)
2443 Display info on Solaris user threads.
2447 @kindex thread @var{threadno}
2448 @item thread @var{threadno}
2449 Make thread number @var{threadno} the current thread. The command
2450 argument @var{threadno} is the internal @value{GDBN} thread number, as
2451 shown in the first field of the @samp{info threads} display.
2452 @value{GDBN} responds by displaying the system identifier of the thread
2453 you selected, and its current stack frame summary:
2456 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2457 (@value{GDBP}) thread 2
2458 [Switching to process 35 thread 23]
2459 0x34e5 in sigpause ()
2463 As with the @samp{[New @dots{}]} message, the form of the text after
2464 @samp{Switching to} depends on your system's conventions for identifying
2467 @kindex thread apply
2468 @cindex apply command to several threads
2469 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2470 The @code{thread apply} command allows you to apply the named
2471 @var{command} to one or more threads. Specify the numbers of the
2472 threads that you want affected with the command argument
2473 @var{threadno}. It can be a single thread number, one of the numbers
2474 shown in the first field of the @samp{info threads} display; or it
2475 could be a range of thread numbers, as in @code{2-4}. To apply a
2476 command to all threads, type @kbd{thread apply all @var{command}}.
2478 @kindex set print thread-events
2479 @cindex print messages on thread start and exit
2480 @item set print thread-events
2481 @itemx set print thread-events on
2482 @itemx set print thread-events off
2483 The @code{set print thread-events} command allows you to enable or
2484 disable printing of messages when @value{GDBN} notices that new threads have
2485 started or that threads have exited. By default, these messages will
2486 be printed if detection of these events is supported by the target.
2487 Note that these messages cannot be disabled on all targets.
2489 @kindex show print thread-events
2490 @item show print thread-events
2491 Show whether messages will be printed when @value{GDBN} detects that threads
2492 have started and exited.
2495 @cindex automatic thread selection
2496 @cindex switching threads automatically
2497 @cindex threads, automatic switching
2498 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2499 signal, it automatically selects the thread where that breakpoint or
2500 signal happened. @value{GDBN} alerts you to the context switch with a
2501 message of the form @samp{[Switching to @var{systag}]} to identify the
2504 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2505 more information about how @value{GDBN} behaves when you stop and start
2506 programs with multiple threads.
2508 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2509 watchpoints in programs with multiple threads.
2512 @section Debugging Programs with Multiple Processes
2514 @cindex fork, debugging programs which call
2515 @cindex multiple processes
2516 @cindex processes, multiple
2517 On most systems, @value{GDBN} has no special support for debugging
2518 programs which create additional processes using the @code{fork}
2519 function. When a program forks, @value{GDBN} will continue to debug the
2520 parent process and the child process will run unimpeded. If you have
2521 set a breakpoint in any code which the child then executes, the child
2522 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2523 will cause it to terminate.
2525 However, if you want to debug the child process there is a workaround
2526 which isn't too painful. Put a call to @code{sleep} in the code which
2527 the child process executes after the fork. It may be useful to sleep
2528 only if a certain environment variable is set, or a certain file exists,
2529 so that the delay need not occur when you don't want to run @value{GDBN}
2530 on the child. While the child is sleeping, use the @code{ps} program to
2531 get its process ID. Then tell @value{GDBN} (a new invocation of
2532 @value{GDBN} if you are also debugging the parent process) to attach to
2533 the child process (@pxref{Attach}). From that point on you can debug
2534 the child process just like any other process which you attached to.
2536 On some systems, @value{GDBN} provides support for debugging programs that
2537 create additional processes using the @code{fork} or @code{vfork} functions.
2538 Currently, the only platforms with this feature are HP-UX (11.x and later
2539 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2541 By default, when a program forks, @value{GDBN} will continue to debug
2542 the parent process and the child process will run unimpeded.
2544 If you want to follow the child process instead of the parent process,
2545 use the command @w{@code{set follow-fork-mode}}.
2548 @kindex set follow-fork-mode
2549 @item set follow-fork-mode @var{mode}
2550 Set the debugger response to a program call of @code{fork} or
2551 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2552 process. The @var{mode} argument can be:
2556 The original process is debugged after a fork. The child process runs
2557 unimpeded. This is the default.
2560 The new process is debugged after a fork. The parent process runs
2565 @kindex show follow-fork-mode
2566 @item show follow-fork-mode
2567 Display the current debugger response to a @code{fork} or @code{vfork} call.
2570 @cindex debugging multiple processes
2571 On Linux, if you want to debug both the parent and child processes, use the
2572 command @w{@code{set detach-on-fork}}.
2575 @kindex set detach-on-fork
2576 @item set detach-on-fork @var{mode}
2577 Tells gdb whether to detach one of the processes after a fork, or
2578 retain debugger control over them both.
2582 The child process (or parent process, depending on the value of
2583 @code{follow-fork-mode}) will be detached and allowed to run
2584 independently. This is the default.
2587 Both processes will be held under the control of @value{GDBN}.
2588 One process (child or parent, depending on the value of
2589 @code{follow-fork-mode}) is debugged as usual, while the other
2594 @kindex show detach-on-fork
2595 @item show detach-on-fork
2596 Show whether detach-on-fork mode is on/off.
2599 If you choose to set @samp{detach-on-fork} mode off, then
2600 @value{GDBN} will retain control of all forked processes (including
2601 nested forks). You can list the forked processes under the control of
2602 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2603 from one fork to another by using the @w{@code{fork}} command.
2608 Print a list of all forked processes under the control of @value{GDBN}.
2609 The listing will include a fork id, a process id, and the current
2610 position (program counter) of the process.
2612 @kindex fork @var{fork-id}
2613 @item fork @var{fork-id}
2614 Make fork number @var{fork-id} the current process. The argument
2615 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2616 as shown in the first field of the @samp{info forks} display.
2618 @kindex process @var{process-id}
2619 @item process @var{process-id}
2620 Make process number @var{process-id} the current process. The
2621 argument @var{process-id} must be one that is listed in the output of
2626 To quit debugging one of the forked processes, you can either detach
2627 from it by using the @w{@code{detach fork}} command (allowing it to
2628 run independently), or delete (and kill) it using the
2629 @w{@code{delete fork}} command.
2632 @kindex detach fork @var{fork-id}
2633 @item detach fork @var{fork-id}
2634 Detach from the process identified by @value{GDBN} fork number
2635 @var{fork-id}, and remove it from the fork list. The process will be
2636 allowed to run independently.
2638 @kindex delete fork @var{fork-id}
2639 @item delete fork @var{fork-id}
2640 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2641 and remove it from the fork list.
2645 If you ask to debug a child process and a @code{vfork} is followed by an
2646 @code{exec}, @value{GDBN} executes the new target up to the first
2647 breakpoint in the new target. If you have a breakpoint set on
2648 @code{main} in your original program, the breakpoint will also be set on
2649 the child process's @code{main}.
2651 When a child process is spawned by @code{vfork}, you cannot debug the
2652 child or parent until an @code{exec} call completes.
2654 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2655 call executes, the new target restarts. To restart the parent process,
2656 use the @code{file} command with the parent executable name as its
2659 You can use the @code{catch} command to make @value{GDBN} stop whenever
2660 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2661 Catchpoints, ,Setting Catchpoints}.
2663 @node Checkpoint/Restart
2664 @section Setting a @emph{Bookmark} to Return to Later
2669 @cindex snapshot of a process
2670 @cindex rewind program state
2672 On certain operating systems@footnote{Currently, only
2673 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2674 program's state, called a @dfn{checkpoint}, and come back to it
2677 Returning to a checkpoint effectively undoes everything that has
2678 happened in the program since the @code{checkpoint} was saved. This
2679 includes changes in memory, registers, and even (within some limits)
2680 system state. Effectively, it is like going back in time to the
2681 moment when the checkpoint was saved.
2683 Thus, if you're stepping thru a program and you think you're
2684 getting close to the point where things go wrong, you can save
2685 a checkpoint. Then, if you accidentally go too far and miss
2686 the critical statement, instead of having to restart your program
2687 from the beginning, you can just go back to the checkpoint and
2688 start again from there.
2690 This can be especially useful if it takes a lot of time or
2691 steps to reach the point where you think the bug occurs.
2693 To use the @code{checkpoint}/@code{restart} method of debugging:
2698 Save a snapshot of the debugged program's current execution state.
2699 The @code{checkpoint} command takes no arguments, but each checkpoint
2700 is assigned a small integer id, similar to a breakpoint id.
2702 @kindex info checkpoints
2703 @item info checkpoints
2704 List the checkpoints that have been saved in the current debugging
2705 session. For each checkpoint, the following information will be
2712 @item Source line, or label
2715 @kindex restart @var{checkpoint-id}
2716 @item restart @var{checkpoint-id}
2717 Restore the program state that was saved as checkpoint number
2718 @var{checkpoint-id}. All program variables, registers, stack frames
2719 etc.@: will be returned to the values that they had when the checkpoint
2720 was saved. In essence, gdb will ``wind back the clock'' to the point
2721 in time when the checkpoint was saved.
2723 Note that breakpoints, @value{GDBN} variables, command history etc.
2724 are not affected by restoring a checkpoint. In general, a checkpoint
2725 only restores things that reside in the program being debugged, not in
2728 @kindex delete checkpoint @var{checkpoint-id}
2729 @item delete checkpoint @var{checkpoint-id}
2730 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2734 Returning to a previously saved checkpoint will restore the user state
2735 of the program being debugged, plus a significant subset of the system
2736 (OS) state, including file pointers. It won't ``un-write'' data from
2737 a file, but it will rewind the file pointer to the previous location,
2738 so that the previously written data can be overwritten. For files
2739 opened in read mode, the pointer will also be restored so that the
2740 previously read data can be read again.
2742 Of course, characters that have been sent to a printer (or other
2743 external device) cannot be ``snatched back'', and characters received
2744 from eg.@: a serial device can be removed from internal program buffers,
2745 but they cannot be ``pushed back'' into the serial pipeline, ready to
2746 be received again. Similarly, the actual contents of files that have
2747 been changed cannot be restored (at this time).
2749 However, within those constraints, you actually can ``rewind'' your
2750 program to a previously saved point in time, and begin debugging it
2751 again --- and you can change the course of events so as to debug a
2752 different execution path this time.
2754 @cindex checkpoints and process id
2755 Finally, there is one bit of internal program state that will be
2756 different when you return to a checkpoint --- the program's process
2757 id. Each checkpoint will have a unique process id (or @var{pid}),
2758 and each will be different from the program's original @var{pid}.
2759 If your program has saved a local copy of its process id, this could
2760 potentially pose a problem.
2762 @subsection A Non-obvious Benefit of Using Checkpoints
2764 On some systems such as @sc{gnu}/Linux, address space randomization
2765 is performed on new processes for security reasons. This makes it
2766 difficult or impossible to set a breakpoint, or watchpoint, on an
2767 absolute address if you have to restart the program, since the
2768 absolute location of a symbol will change from one execution to the
2771 A checkpoint, however, is an @emph{identical} copy of a process.
2772 Therefore if you create a checkpoint at (eg.@:) the start of main,
2773 and simply return to that checkpoint instead of restarting the
2774 process, you can avoid the effects of address randomization and
2775 your symbols will all stay in the same place.
2778 @chapter Stopping and Continuing
2780 The principal purposes of using a debugger are so that you can stop your
2781 program before it terminates; or so that, if your program runs into
2782 trouble, you can investigate and find out why.
2784 Inside @value{GDBN}, your program may stop for any of several reasons,
2785 such as a signal, a breakpoint, or reaching a new line after a
2786 @value{GDBN} command such as @code{step}. You may then examine and
2787 change variables, set new breakpoints or remove old ones, and then
2788 continue execution. Usually, the messages shown by @value{GDBN} provide
2789 ample explanation of the status of your program---but you can also
2790 explicitly request this information at any time.
2793 @kindex info program
2795 Display information about the status of your program: whether it is
2796 running or not, what process it is, and why it stopped.
2800 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2801 * Continuing and Stepping:: Resuming execution
2803 * Thread Stops:: Stopping and starting multi-thread programs
2807 @section Breakpoints, Watchpoints, and Catchpoints
2810 A @dfn{breakpoint} makes your program stop whenever a certain point in
2811 the program is reached. For each breakpoint, you can add conditions to
2812 control in finer detail whether your program stops. You can set
2813 breakpoints with the @code{break} command and its variants (@pxref{Set
2814 Breaks, ,Setting Breakpoints}), to specify the place where your program
2815 should stop by line number, function name or exact address in the
2818 On some systems, you can set breakpoints in shared libraries before
2819 the executable is run. There is a minor limitation on HP-UX systems:
2820 you must wait until the executable is run in order to set breakpoints
2821 in shared library routines that are not called directly by the program
2822 (for example, routines that are arguments in a @code{pthread_create}
2826 @cindex data breakpoints
2827 @cindex memory tracing
2828 @cindex breakpoint on memory address
2829 @cindex breakpoint on variable modification
2830 A @dfn{watchpoint} is a special breakpoint that stops your program
2831 when the value of an expression changes. The expression may be a value
2832 of a variable, or it could involve values of one or more variables
2833 combined by operators, such as @samp{a + b}. This is sometimes called
2834 @dfn{data breakpoints}. You must use a different command to set
2835 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2836 from that, you can manage a watchpoint like any other breakpoint: you
2837 enable, disable, and delete both breakpoints and watchpoints using the
2840 You can arrange to have values from your program displayed automatically
2841 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2845 @cindex breakpoint on events
2846 A @dfn{catchpoint} is another special breakpoint that stops your program
2847 when a certain kind of event occurs, such as the throwing of a C@t{++}
2848 exception or the loading of a library. As with watchpoints, you use a
2849 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2850 Catchpoints}), but aside from that, you can manage a catchpoint like any
2851 other breakpoint. (To stop when your program receives a signal, use the
2852 @code{handle} command; see @ref{Signals, ,Signals}.)
2854 @cindex breakpoint numbers
2855 @cindex numbers for breakpoints
2856 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2857 catchpoint when you create it; these numbers are successive integers
2858 starting with one. In many of the commands for controlling various
2859 features of breakpoints you use the breakpoint number to say which
2860 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2861 @dfn{disabled}; if disabled, it has no effect on your program until you
2864 @cindex breakpoint ranges
2865 @cindex ranges of breakpoints
2866 Some @value{GDBN} commands accept a range of breakpoints on which to
2867 operate. A breakpoint range is either a single breakpoint number, like
2868 @samp{5}, or two such numbers, in increasing order, separated by a
2869 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2870 all breakpoints in that range are operated on.
2873 * Set Breaks:: Setting breakpoints
2874 * Set Watchpoints:: Setting watchpoints
2875 * Set Catchpoints:: Setting catchpoints
2876 * Delete Breaks:: Deleting breakpoints
2877 * Disabling:: Disabling breakpoints
2878 * Conditions:: Break conditions
2879 * Break Commands:: Breakpoint command lists
2880 * Error in Breakpoints:: ``Cannot insert breakpoints''
2881 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2885 @subsection Setting Breakpoints
2887 @c FIXME LMB what does GDB do if no code on line of breakpt?
2888 @c consider in particular declaration with/without initialization.
2890 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2893 @kindex b @r{(@code{break})}
2894 @vindex $bpnum@r{, convenience variable}
2895 @cindex latest breakpoint
2896 Breakpoints are set with the @code{break} command (abbreviated
2897 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2898 number of the breakpoint you've set most recently; see @ref{Convenience
2899 Vars,, Convenience Variables}, for a discussion of what you can do with
2900 convenience variables.
2903 @item break @var{location}
2904 Set a breakpoint at the given @var{location}, which can specify a
2905 function name, a line number, or an address of an instruction.
2906 (@xref{Specify Location}, for a list of all the possible ways to
2907 specify a @var{location}.) The breakpoint will stop your program just
2908 before it executes any of the code in the specified @var{location}.
2910 When using source languages that permit overloading of symbols, such as
2911 C@t{++}, a function name may refer to more than one possible place to break.
2912 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
2916 When called without any arguments, @code{break} sets a breakpoint at
2917 the next instruction to be executed in the selected stack frame
2918 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2919 innermost, this makes your program stop as soon as control
2920 returns to that frame. This is similar to the effect of a
2921 @code{finish} command in the frame inside the selected frame---except
2922 that @code{finish} does not leave an active breakpoint. If you use
2923 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2924 the next time it reaches the current location; this may be useful
2927 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2928 least one instruction has been executed. If it did not do this, you
2929 would be unable to proceed past a breakpoint without first disabling the
2930 breakpoint. This rule applies whether or not the breakpoint already
2931 existed when your program stopped.
2933 @item break @dots{} if @var{cond}
2934 Set a breakpoint with condition @var{cond}; evaluate the expression
2935 @var{cond} each time the breakpoint is reached, and stop only if the
2936 value is nonzero---that is, if @var{cond} evaluates as true.
2937 @samp{@dots{}} stands for one of the possible arguments described
2938 above (or no argument) specifying where to break. @xref{Conditions,
2939 ,Break Conditions}, for more information on breakpoint conditions.
2942 @item tbreak @var{args}
2943 Set a breakpoint enabled only for one stop. @var{args} are the
2944 same as for the @code{break} command, and the breakpoint is set in the same
2945 way, but the breakpoint is automatically deleted after the first time your
2946 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2949 @cindex hardware breakpoints
2950 @item hbreak @var{args}
2951 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2952 @code{break} command and the breakpoint is set in the same way, but the
2953 breakpoint requires hardware support and some target hardware may not
2954 have this support. The main purpose of this is EPROM/ROM code
2955 debugging, so you can set a breakpoint at an instruction without
2956 changing the instruction. This can be used with the new trap-generation
2957 provided by SPARClite DSU and most x86-based targets. These targets
2958 will generate traps when a program accesses some data or instruction
2959 address that is assigned to the debug registers. However the hardware
2960 breakpoint registers can take a limited number of breakpoints. For
2961 example, on the DSU, only two data breakpoints can be set at a time, and
2962 @value{GDBN} will reject this command if more than two are used. Delete
2963 or disable unused hardware breakpoints before setting new ones
2964 (@pxref{Disabling, ,Disabling Breakpoints}).
2965 @xref{Conditions, ,Break Conditions}.
2966 For remote targets, you can restrict the number of hardware
2967 breakpoints @value{GDBN} will use, see @ref{set remote
2968 hardware-breakpoint-limit}.
2971 @item thbreak @var{args}
2972 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2973 are the same as for the @code{hbreak} command and the breakpoint is set in
2974 the same way. However, like the @code{tbreak} command,
2975 the breakpoint is automatically deleted after the
2976 first time your program stops there. Also, like the @code{hbreak}
2977 command, the breakpoint requires hardware support and some target hardware
2978 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2979 See also @ref{Conditions, ,Break Conditions}.
2982 @cindex regular expression
2983 @cindex breakpoints in functions matching a regexp
2984 @cindex set breakpoints in many functions
2985 @item rbreak @var{regex}
2986 Set breakpoints on all functions matching the regular expression
2987 @var{regex}. This command sets an unconditional breakpoint on all
2988 matches, printing a list of all breakpoints it set. Once these
2989 breakpoints are set, they are treated just like the breakpoints set with
2990 the @code{break} command. You can delete them, disable them, or make
2991 them conditional the same way as any other breakpoint.
2993 The syntax of the regular expression is the standard one used with tools
2994 like @file{grep}. Note that this is different from the syntax used by
2995 shells, so for instance @code{foo*} matches all functions that include
2996 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2997 @code{.*} leading and trailing the regular expression you supply, so to
2998 match only functions that begin with @code{foo}, use @code{^foo}.
3000 @cindex non-member C@t{++} functions, set breakpoint in
3001 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3002 breakpoints on overloaded functions that are not members of any special
3005 @cindex set breakpoints on all functions
3006 The @code{rbreak} command can be used to set breakpoints in
3007 @strong{all} the functions in a program, like this:
3010 (@value{GDBP}) rbreak .
3013 @kindex info breakpoints
3014 @cindex @code{$_} and @code{info breakpoints}
3015 @item info breakpoints @r{[}@var{n}@r{]}
3016 @itemx info break @r{[}@var{n}@r{]}
3017 @itemx info watchpoints @r{[}@var{n}@r{]}
3018 Print a table of all breakpoints, watchpoints, and catchpoints set and
3019 not deleted. Optional argument @var{n} means print information only
3020 about the specified breakpoint (or watchpoint or catchpoint). For
3021 each breakpoint, following columns are printed:
3024 @item Breakpoint Numbers
3026 Breakpoint, watchpoint, or catchpoint.
3028 Whether the breakpoint is marked to be disabled or deleted when hit.
3029 @item Enabled or Disabled
3030 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3031 that are not enabled.
3033 Where the breakpoint is in your program, as a memory address. For a
3034 pending breakpoint whose address is not yet known, this field will
3035 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3036 library that has the symbol or line referred by breakpoint is loaded.
3037 See below for details. A breakpoint with several locations will
3038 have @samp{<MULTIPLE>} in this field---see below for details.
3040 Where the breakpoint is in the source for your program, as a file and
3041 line number. For a pending breakpoint, the original string passed to
3042 the breakpoint command will be listed as it cannot be resolved until
3043 the appropriate shared library is loaded in the future.
3047 If a breakpoint is conditional, @code{info break} shows the condition on
3048 the line following the affected breakpoint; breakpoint commands, if any,
3049 are listed after that. A pending breakpoint is allowed to have a condition
3050 specified for it. The condition is not parsed for validity until a shared
3051 library is loaded that allows the pending breakpoint to resolve to a
3055 @code{info break} with a breakpoint
3056 number @var{n} as argument lists only that breakpoint. The
3057 convenience variable @code{$_} and the default examining-address for
3058 the @code{x} command are set to the address of the last breakpoint
3059 listed (@pxref{Memory, ,Examining Memory}).
3062 @code{info break} displays a count of the number of times the breakpoint
3063 has been hit. This is especially useful in conjunction with the
3064 @code{ignore} command. You can ignore a large number of breakpoint
3065 hits, look at the breakpoint info to see how many times the breakpoint
3066 was hit, and then run again, ignoring one less than that number. This
3067 will get you quickly to the last hit of that breakpoint.
3070 @value{GDBN} allows you to set any number of breakpoints at the same place in
3071 your program. There is nothing silly or meaningless about this. When
3072 the breakpoints are conditional, this is even useful
3073 (@pxref{Conditions, ,Break Conditions}).
3075 It is possible that a breakpoint corresponds to several locations
3076 in your program. Examples of this situation are:
3081 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3082 instances of the function body, used in different cases.
3085 For a C@t{++} template function, a given line in the function can
3086 correspond to any number of instantiations.
3089 For an inlined function, a given source line can correspond to
3090 several places where that function is inlined.
3094 In all those cases, @value{GDBN} will insert a breakpoint at all
3095 the relevant locations.
3097 A breakpoint with multiple locations is displayed in the breakpoint
3098 table using several rows---one header row, followed by one row for
3099 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3100 address column. The rows for individual locations contain the actual
3101 addresses for locations, and show the functions to which those
3102 locations belong. The number column for a location is of the form
3103 @var{breakpoint-number}.@var{location-number}.
3108 Num Type Disp Enb Address What
3109 1 breakpoint keep y <MULTIPLE>
3111 breakpoint already hit 1 time
3112 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3113 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3116 Each location can be individually enabled or disabled by passing
3117 @var{breakpoint-number}.@var{location-number} as argument to the
3118 @code{enable} and @code{disable} commands. Note that you cannot
3119 delete the individual locations from the list, you can only delete the
3120 entire list of locations that belong to their parent breakpoint (with
3121 the @kbd{delete @var{num}} command, where @var{num} is the number of
3122 the parent breakpoint, 1 in the above example). Disabling or enabling
3123 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3124 that belong to that breakpoint.
3126 @cindex pending breakpoints
3127 It's quite common to have a breakpoint inside a shared library.
3128 Shared libraries can be loaded and unloaded explicitly,
3129 and possibly repeatedly, as the program is executed. To support
3130 this use case, @value{GDBN} updates breakpoint locations whenever
3131 any shared library is loaded or unloaded. Typically, you would
3132 set a breakpoint in a shared library at the beginning of your
3133 debugging session, when the library is not loaded, and when the
3134 symbols from the library are not available. When you try to set
3135 breakpoint, @value{GDBN} will ask you if you want to set
3136 a so called @dfn{pending breakpoint}---breakpoint whose address
3137 is not yet resolved.
3139 After the program is run, whenever a new shared library is loaded,
3140 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3141 shared library contains the symbol or line referred to by some
3142 pending breakpoint, that breakpoint is resolved and becomes an
3143 ordinary breakpoint. When a library is unloaded, all breakpoints
3144 that refer to its symbols or source lines become pending again.
3146 This logic works for breakpoints with multiple locations, too. For
3147 example, if you have a breakpoint in a C@t{++} template function, and
3148 a newly loaded shared library has an instantiation of that template,
3149 a new location is added to the list of locations for the breakpoint.
3151 Except for having unresolved address, pending breakpoints do not
3152 differ from regular breakpoints. You can set conditions or commands,
3153 enable and disable them and perform other breakpoint operations.
3155 @value{GDBN} provides some additional commands for controlling what
3156 happens when the @samp{break} command cannot resolve breakpoint
3157 address specification to an address:
3159 @kindex set breakpoint pending
3160 @kindex show breakpoint pending
3162 @item set breakpoint pending auto
3163 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3164 location, it queries you whether a pending breakpoint should be created.
3166 @item set breakpoint pending on
3167 This indicates that an unrecognized breakpoint location should automatically
3168 result in a pending breakpoint being created.
3170 @item set breakpoint pending off
3171 This indicates that pending breakpoints are not to be created. Any
3172 unrecognized breakpoint location results in an error. This setting does
3173 not affect any pending breakpoints previously created.
3175 @item show breakpoint pending
3176 Show the current behavior setting for creating pending breakpoints.
3179 The settings above only affect the @code{break} command and its
3180 variants. Once breakpoint is set, it will be automatically updated
3181 as shared libraries are loaded and unloaded.
3183 @cindex automatic hardware breakpoints
3184 For some targets, @value{GDBN} can automatically decide if hardware or
3185 software breakpoints should be used, depending on whether the
3186 breakpoint address is read-only or read-write. This applies to
3187 breakpoints set with the @code{break} command as well as to internal
3188 breakpoints set by commands like @code{next} and @code{finish}. For
3189 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3192 You can control this automatic behaviour with the following commands::
3194 @kindex set breakpoint auto-hw
3195 @kindex show breakpoint auto-hw
3197 @item set breakpoint auto-hw on
3198 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3199 will try to use the target memory map to decide if software or hardware
3200 breakpoint must be used.
3202 @item set breakpoint auto-hw off
3203 This indicates @value{GDBN} should not automatically select breakpoint
3204 type. If the target provides a memory map, @value{GDBN} will warn when
3205 trying to set software breakpoint at a read-only address.
3209 @cindex negative breakpoint numbers
3210 @cindex internal @value{GDBN} breakpoints
3211 @value{GDBN} itself sometimes sets breakpoints in your program for
3212 special purposes, such as proper handling of @code{longjmp} (in C
3213 programs). These internal breakpoints are assigned negative numbers,
3214 starting with @code{-1}; @samp{info breakpoints} does not display them.
3215 You can see these breakpoints with the @value{GDBN} maintenance command
3216 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3219 @node Set Watchpoints
3220 @subsection Setting Watchpoints
3222 @cindex setting watchpoints
3223 You can use a watchpoint to stop execution whenever the value of an
3224 expression changes, without having to predict a particular place where
3225 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3226 The expression may be as simple as the value of a single variable, or
3227 as complex as many variables combined by operators. Examples include:
3231 A reference to the value of a single variable.
3234 An address cast to an appropriate data type. For example,
3235 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3236 address (assuming an @code{int} occupies 4 bytes).
3239 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3240 expression can use any operators valid in the program's native
3241 language (@pxref{Languages}).
3244 You can set a watchpoint on an expression even if the expression can
3245 not be evaluated yet. For instance, you can set a watchpoint on
3246 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3247 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3248 the expression produces a valid value. If the expression becomes
3249 valid in some other way than changing a variable (e.g.@: if the memory
3250 pointed to by @samp{*global_ptr} becomes readable as the result of a
3251 @code{malloc} call), @value{GDBN} may not stop until the next time
3252 the expression changes.
3254 @cindex software watchpoints
3255 @cindex hardware watchpoints
3256 Depending on your system, watchpoints may be implemented in software or
3257 hardware. @value{GDBN} does software watchpointing by single-stepping your
3258 program and testing the variable's value each time, which is hundreds of
3259 times slower than normal execution. (But this may still be worth it, to
3260 catch errors where you have no clue what part of your program is the
3263 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3264 x86-based targets, @value{GDBN} includes support for hardware
3265 watchpoints, which do not slow down the running of your program.
3269 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3270 Set a watchpoint for an expression. @value{GDBN} will break when the
3271 expression @var{expr} is written into by the program and its value
3272 changes. The simplest (and the most popular) use of this command is
3273 to watch the value of a single variable:
3276 (@value{GDBP}) watch foo
3279 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3280 clause, @value{GDBN} breaks only when the thread identified by
3281 @var{threadnum} changes the value of @var{expr}. If any other threads
3282 change the value of @var{expr}, @value{GDBN} will not break. Note
3283 that watchpoints restricted to a single thread in this way only work
3284 with Hardware Watchpoints.
3287 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3288 Set a watchpoint that will break when the value of @var{expr} is read
3292 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3293 Set a watchpoint that will break when @var{expr} is either read from
3294 or written into by the program.
3296 @kindex info watchpoints @r{[}@var{n}@r{]}
3297 @item info watchpoints
3298 This command prints a list of watchpoints, breakpoints, and catchpoints;
3299 it is the same as @code{info break} (@pxref{Set Breaks}).
3302 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3303 watchpoints execute very quickly, and the debugger reports a change in
3304 value at the exact instruction where the change occurs. If @value{GDBN}
3305 cannot set a hardware watchpoint, it sets a software watchpoint, which
3306 executes more slowly and reports the change in value at the next
3307 @emph{statement}, not the instruction, after the change occurs.
3309 @cindex use only software watchpoints
3310 You can force @value{GDBN} to use only software watchpoints with the
3311 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3312 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3313 the underlying system supports them. (Note that hardware-assisted
3314 watchpoints that were set @emph{before} setting
3315 @code{can-use-hw-watchpoints} to zero will still use the hardware
3316 mechanism of watching expression values.)
3319 @item set can-use-hw-watchpoints
3320 @kindex set can-use-hw-watchpoints
3321 Set whether or not to use hardware watchpoints.
3323 @item show can-use-hw-watchpoints
3324 @kindex show can-use-hw-watchpoints
3325 Show the current mode of using hardware watchpoints.
3328 For remote targets, you can restrict the number of hardware
3329 watchpoints @value{GDBN} will use, see @ref{set remote
3330 hardware-breakpoint-limit}.
3332 When you issue the @code{watch} command, @value{GDBN} reports
3335 Hardware watchpoint @var{num}: @var{expr}
3339 if it was able to set a hardware watchpoint.
3341 Currently, the @code{awatch} and @code{rwatch} commands can only set
3342 hardware watchpoints, because accesses to data that don't change the
3343 value of the watched expression cannot be detected without examining
3344 every instruction as it is being executed, and @value{GDBN} does not do
3345 that currently. If @value{GDBN} finds that it is unable to set a
3346 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3347 will print a message like this:
3350 Expression cannot be implemented with read/access watchpoint.
3353 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3354 data type of the watched expression is wider than what a hardware
3355 watchpoint on the target machine can handle. For example, some systems
3356 can only watch regions that are up to 4 bytes wide; on such systems you
3357 cannot set hardware watchpoints for an expression that yields a
3358 double-precision floating-point number (which is typically 8 bytes
3359 wide). As a work-around, it might be possible to break the large region
3360 into a series of smaller ones and watch them with separate watchpoints.
3362 If you set too many hardware watchpoints, @value{GDBN} might be unable
3363 to insert all of them when you resume the execution of your program.
3364 Since the precise number of active watchpoints is unknown until such
3365 time as the program is about to be resumed, @value{GDBN} might not be
3366 able to warn you about this when you set the watchpoints, and the
3367 warning will be printed only when the program is resumed:
3370 Hardware watchpoint @var{num}: Could not insert watchpoint
3374 If this happens, delete or disable some of the watchpoints.
3376 Watching complex expressions that reference many variables can also
3377 exhaust the resources available for hardware-assisted watchpoints.
3378 That's because @value{GDBN} needs to watch every variable in the
3379 expression with separately allocated resources.
3381 If you call a function interactively using @code{print} or @code{call},
3382 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3383 kind of breakpoint or the call completes.
3385 @value{GDBN} automatically deletes watchpoints that watch local
3386 (automatic) variables, or expressions that involve such variables, when
3387 they go out of scope, that is, when the execution leaves the block in
3388 which these variables were defined. In particular, when the program
3389 being debugged terminates, @emph{all} local variables go out of scope,
3390 and so only watchpoints that watch global variables remain set. If you
3391 rerun the program, you will need to set all such watchpoints again. One
3392 way of doing that would be to set a code breakpoint at the entry to the
3393 @code{main} function and when it breaks, set all the watchpoints.
3395 @cindex watchpoints and threads
3396 @cindex threads and watchpoints
3397 In multi-threaded programs, watchpoints will detect changes to the
3398 watched expression from every thread.
3401 @emph{Warning:} In multi-threaded programs, software watchpoints
3402 have only limited usefulness. If @value{GDBN} creates a software
3403 watchpoint, it can only watch the value of an expression @emph{in a
3404 single thread}. If you are confident that the expression can only
3405 change due to the current thread's activity (and if you are also
3406 confident that no other thread can become current), then you can use
3407 software watchpoints as usual. However, @value{GDBN} may not notice
3408 when a non-current thread's activity changes the expression. (Hardware
3409 watchpoints, in contrast, watch an expression in all threads.)
3412 @xref{set remote hardware-watchpoint-limit}.
3414 @node Set Catchpoints
3415 @subsection Setting Catchpoints
3416 @cindex catchpoints, setting
3417 @cindex exception handlers
3418 @cindex event handling
3420 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3421 kinds of program events, such as C@t{++} exceptions or the loading of a
3422 shared library. Use the @code{catch} command to set a catchpoint.
3426 @item catch @var{event}
3427 Stop when @var{event} occurs. @var{event} can be any of the following:
3430 @cindex stop on C@t{++} exceptions
3431 The throwing of a C@t{++} exception.
3434 The catching of a C@t{++} exception.
3437 @cindex Ada exception catching
3438 @cindex catch Ada exceptions
3439 An Ada exception being raised. If an exception name is specified
3440 at the end of the command (eg @code{catch exception Program_Error}),
3441 the debugger will stop only when this specific exception is raised.
3442 Otherwise, the debugger stops execution when any Ada exception is raised.
3444 @item exception unhandled
3445 An exception that was raised but is not handled by the program.
3448 A failed Ada assertion.
3451 @cindex break on fork/exec
3452 A call to @code{exec}. This is currently only available for HP-UX
3456 A call to @code{fork}. This is currently only available for HP-UX
3460 A call to @code{vfork}. This is currently only available for HP-UX
3464 @itemx load @var{libname}
3465 @cindex break on load/unload of shared library
3466 The dynamic loading of any shared library, or the loading of the library
3467 @var{libname}. This is currently only available for HP-UX.
3470 @itemx unload @var{libname}
3471 The unloading of any dynamically loaded shared library, or the unloading
3472 of the library @var{libname}. This is currently only available for HP-UX.
3475 @item tcatch @var{event}
3476 Set a catchpoint that is enabled only for one stop. The catchpoint is
3477 automatically deleted after the first time the event is caught.
3481 Use the @code{info break} command to list the current catchpoints.
3483 There are currently some limitations to C@t{++} exception handling
3484 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3488 If you call a function interactively, @value{GDBN} normally returns
3489 control to you when the function has finished executing. If the call
3490 raises an exception, however, the call may bypass the mechanism that
3491 returns control to you and cause your program either to abort or to
3492 simply continue running until it hits a breakpoint, catches a signal
3493 that @value{GDBN} is listening for, or exits. This is the case even if
3494 you set a catchpoint for the exception; catchpoints on exceptions are
3495 disabled within interactive calls.
3498 You cannot raise an exception interactively.
3501 You cannot install an exception handler interactively.
3504 @cindex raise exceptions
3505 Sometimes @code{catch} is not the best way to debug exception handling:
3506 if you need to know exactly where an exception is raised, it is better to
3507 stop @emph{before} the exception handler is called, since that way you
3508 can see the stack before any unwinding takes place. If you set a
3509 breakpoint in an exception handler instead, it may not be easy to find
3510 out where the exception was raised.
3512 To stop just before an exception handler is called, you need some
3513 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3514 raised by calling a library function named @code{__raise_exception}
3515 which has the following ANSI C interface:
3518 /* @var{addr} is where the exception identifier is stored.
3519 @var{id} is the exception identifier. */
3520 void __raise_exception (void **addr, void *id);
3524 To make the debugger catch all exceptions before any stack
3525 unwinding takes place, set a breakpoint on @code{__raise_exception}
3526 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3528 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3529 that depends on the value of @var{id}, you can stop your program when
3530 a specific exception is raised. You can use multiple conditional
3531 breakpoints to stop your program when any of a number of exceptions are
3536 @subsection Deleting Breakpoints
3538 @cindex clearing breakpoints, watchpoints, catchpoints
3539 @cindex deleting breakpoints, watchpoints, catchpoints
3540 It is often necessary to eliminate a breakpoint, watchpoint, or
3541 catchpoint once it has done its job and you no longer want your program
3542 to stop there. This is called @dfn{deleting} the breakpoint. A
3543 breakpoint that has been deleted no longer exists; it is forgotten.
3545 With the @code{clear} command you can delete breakpoints according to
3546 where they are in your program. With the @code{delete} command you can
3547 delete individual breakpoints, watchpoints, or catchpoints by specifying
3548 their breakpoint numbers.
3550 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3551 automatically ignores breakpoints on the first instruction to be executed
3552 when you continue execution without changing the execution address.
3557 Delete any breakpoints at the next instruction to be executed in the
3558 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3559 the innermost frame is selected, this is a good way to delete a
3560 breakpoint where your program just stopped.
3562 @item clear @var{location}
3563 Delete any breakpoints set at the specified @var{location}.
3564 @xref{Specify Location}, for the various forms of @var{location}; the
3565 most useful ones are listed below:
3568 @item clear @var{function}
3569 @itemx clear @var{filename}:@var{function}
3570 Delete any breakpoints set at entry to the named @var{function}.
3572 @item clear @var{linenum}
3573 @itemx clear @var{filename}:@var{linenum}
3574 Delete any breakpoints set at or within the code of the specified
3575 @var{linenum} of the specified @var{filename}.
3578 @cindex delete breakpoints
3580 @kindex d @r{(@code{delete})}
3581 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3582 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3583 ranges specified as arguments. If no argument is specified, delete all
3584 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3585 confirm off}). You can abbreviate this command as @code{d}.
3589 @subsection Disabling Breakpoints
3591 @cindex enable/disable a breakpoint
3592 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3593 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3594 it had been deleted, but remembers the information on the breakpoint so
3595 that you can @dfn{enable} it again later.
3597 You disable and enable breakpoints, watchpoints, and catchpoints with
3598 the @code{enable} and @code{disable} commands, optionally specifying one
3599 or more breakpoint numbers as arguments. Use @code{info break} or
3600 @code{info watch} to print a list of breakpoints, watchpoints, and
3601 catchpoints if you do not know which numbers to use.
3603 Disabling and enabling a breakpoint that has multiple locations
3604 affects all of its locations.
3606 A breakpoint, watchpoint, or catchpoint can have any of four different
3607 states of enablement:
3611 Enabled. The breakpoint stops your program. A breakpoint set
3612 with the @code{break} command starts out in this state.
3614 Disabled. The breakpoint has no effect on your program.
3616 Enabled once. The breakpoint stops your program, but then becomes
3619 Enabled for deletion. The breakpoint stops your program, but
3620 immediately after it does so it is deleted permanently. A breakpoint
3621 set with the @code{tbreak} command starts out in this state.
3624 You can use the following commands to enable or disable breakpoints,
3625 watchpoints, and catchpoints:
3629 @kindex dis @r{(@code{disable})}
3630 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3631 Disable the specified breakpoints---or all breakpoints, if none are
3632 listed. A disabled breakpoint has no effect but is not forgotten. All
3633 options such as ignore-counts, conditions and commands are remembered in
3634 case the breakpoint is enabled again later. You may abbreviate
3635 @code{disable} as @code{dis}.
3638 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3639 Enable the specified breakpoints (or all defined breakpoints). They
3640 become effective once again in stopping your program.
3642 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3643 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3644 of these breakpoints immediately after stopping your program.
3646 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3647 Enable the specified breakpoints to work once, then die. @value{GDBN}
3648 deletes any of these breakpoints as soon as your program stops there.
3649 Breakpoints set by the @code{tbreak} command start out in this state.
3652 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3653 @c confusing: tbreak is also initially enabled.
3654 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3655 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3656 subsequently, they become disabled or enabled only when you use one of
3657 the commands above. (The command @code{until} can set and delete a
3658 breakpoint of its own, but it does not change the state of your other
3659 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3663 @subsection Break Conditions
3664 @cindex conditional breakpoints
3665 @cindex breakpoint conditions
3667 @c FIXME what is scope of break condition expr? Context where wanted?
3668 @c in particular for a watchpoint?
3669 The simplest sort of breakpoint breaks every time your program reaches a
3670 specified place. You can also specify a @dfn{condition} for a
3671 breakpoint. A condition is just a Boolean expression in your
3672 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3673 a condition evaluates the expression each time your program reaches it,
3674 and your program stops only if the condition is @emph{true}.
3676 This is the converse of using assertions for program validation; in that
3677 situation, you want to stop when the assertion is violated---that is,
3678 when the condition is false. In C, if you want to test an assertion expressed
3679 by the condition @var{assert}, you should set the condition
3680 @samp{! @var{assert}} on the appropriate breakpoint.
3682 Conditions are also accepted for watchpoints; you may not need them,
3683 since a watchpoint is inspecting the value of an expression anyhow---but
3684 it might be simpler, say, to just set a watchpoint on a variable name,
3685 and specify a condition that tests whether the new value is an interesting
3688 Break conditions can have side effects, and may even call functions in
3689 your program. This can be useful, for example, to activate functions
3690 that log program progress, or to use your own print functions to
3691 format special data structures. The effects are completely predictable
3692 unless there is another enabled breakpoint at the same address. (In
3693 that case, @value{GDBN} might see the other breakpoint first and stop your
3694 program without checking the condition of this one.) Note that
3695 breakpoint commands are usually more convenient and flexible than break
3697 purpose of performing side effects when a breakpoint is reached
3698 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3700 Break conditions can be specified when a breakpoint is set, by using
3701 @samp{if} in the arguments to the @code{break} command. @xref{Set
3702 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3703 with the @code{condition} command.
3705 You can also use the @code{if} keyword with the @code{watch} command.
3706 The @code{catch} command does not recognize the @code{if} keyword;
3707 @code{condition} is the only way to impose a further condition on a
3712 @item condition @var{bnum} @var{expression}
3713 Specify @var{expression} as the break condition for breakpoint,
3714 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3715 breakpoint @var{bnum} stops your program only if the value of
3716 @var{expression} is true (nonzero, in C). When you use
3717 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3718 syntactic correctness, and to determine whether symbols in it have
3719 referents in the context of your breakpoint. If @var{expression} uses
3720 symbols not referenced in the context of the breakpoint, @value{GDBN}
3721 prints an error message:
3724 No symbol "foo" in current context.
3729 not actually evaluate @var{expression} at the time the @code{condition}
3730 command (or a command that sets a breakpoint with a condition, like
3731 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3733 @item condition @var{bnum}
3734 Remove the condition from breakpoint number @var{bnum}. It becomes
3735 an ordinary unconditional breakpoint.
3738 @cindex ignore count (of breakpoint)
3739 A special case of a breakpoint condition is to stop only when the
3740 breakpoint has been reached a certain number of times. This is so
3741 useful that there is a special way to do it, using the @dfn{ignore
3742 count} of the breakpoint. Every breakpoint has an ignore count, which
3743 is an integer. Most of the time, the ignore count is zero, and
3744 therefore has no effect. But if your program reaches a breakpoint whose
3745 ignore count is positive, then instead of stopping, it just decrements
3746 the ignore count by one and continues. As a result, if the ignore count
3747 value is @var{n}, the breakpoint does not stop the next @var{n} times
3748 your program reaches it.
3752 @item ignore @var{bnum} @var{count}
3753 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3754 The next @var{count} times the breakpoint is reached, your program's
3755 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3758 To make the breakpoint stop the next time it is reached, specify
3761 When you use @code{continue} to resume execution of your program from a
3762 breakpoint, you can specify an ignore count directly as an argument to
3763 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3764 Stepping,,Continuing and Stepping}.
3766 If a breakpoint has a positive ignore count and a condition, the
3767 condition is not checked. Once the ignore count reaches zero,
3768 @value{GDBN} resumes checking the condition.
3770 You could achieve the effect of the ignore count with a condition such
3771 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3772 is decremented each time. @xref{Convenience Vars, ,Convenience
3776 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3779 @node Break Commands
3780 @subsection Breakpoint Command Lists
3782 @cindex breakpoint commands
3783 You can give any breakpoint (or watchpoint or catchpoint) a series of
3784 commands to execute when your program stops due to that breakpoint. For
3785 example, you might want to print the values of certain expressions, or
3786 enable other breakpoints.
3790 @kindex end@r{ (breakpoint commands)}
3791 @item commands @r{[}@var{bnum}@r{]}
3792 @itemx @dots{} @var{command-list} @dots{}
3794 Specify a list of commands for breakpoint number @var{bnum}. The commands
3795 themselves appear on the following lines. Type a line containing just
3796 @code{end} to terminate the commands.
3798 To remove all commands from a breakpoint, type @code{commands} and
3799 follow it immediately with @code{end}; that is, give no commands.
3801 With no @var{bnum} argument, @code{commands} refers to the last
3802 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3803 recently encountered).
3806 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3807 disabled within a @var{command-list}.
3809 You can use breakpoint commands to start your program up again. Simply
3810 use the @code{continue} command, or @code{step}, or any other command
3811 that resumes execution.
3813 Any other commands in the command list, after a command that resumes
3814 execution, are ignored. This is because any time you resume execution
3815 (even with a simple @code{next} or @code{step}), you may encounter
3816 another breakpoint---which could have its own command list, leading to
3817 ambiguities about which list to execute.
3820 If the first command you specify in a command list is @code{silent}, the
3821 usual message about stopping at a breakpoint is not printed. This may
3822 be desirable for breakpoints that are to print a specific message and
3823 then continue. If none of the remaining commands print anything, you
3824 see no sign that the breakpoint was reached. @code{silent} is
3825 meaningful only at the beginning of a breakpoint command list.
3827 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3828 print precisely controlled output, and are often useful in silent
3829 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3831 For example, here is how you could use breakpoint commands to print the
3832 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3838 printf "x is %d\n",x
3843 One application for breakpoint commands is to compensate for one bug so
3844 you can test for another. Put a breakpoint just after the erroneous line
3845 of code, give it a condition to detect the case in which something
3846 erroneous has been done, and give it commands to assign correct values
3847 to any variables that need them. End with the @code{continue} command
3848 so that your program does not stop, and start with the @code{silent}
3849 command so that no output is produced. Here is an example:
3860 @c @ifclear BARETARGET
3861 @node Error in Breakpoints
3862 @subsection ``Cannot insert breakpoints''
3864 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3866 Under some operating systems, breakpoints cannot be used in a program if
3867 any other process is running that program. In this situation,
3868 attempting to run or continue a program with a breakpoint causes
3869 @value{GDBN} to print an error message:
3872 Cannot insert breakpoints.
3873 The same program may be running in another process.
3876 When this happens, you have three ways to proceed:
3880 Remove or disable the breakpoints, then continue.
3883 Suspend @value{GDBN}, and copy the file containing your program to a new
3884 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3885 that @value{GDBN} should run your program under that name.
3886 Then start your program again.
3889 Relink your program so that the text segment is nonsharable, using the
3890 linker option @samp{-N}. The operating system limitation may not apply
3891 to nonsharable executables.
3895 A similar message can be printed if you request too many active
3896 hardware-assisted breakpoints and watchpoints:
3898 @c FIXME: the precise wording of this message may change; the relevant
3899 @c source change is not committed yet (Sep 3, 1999).
3901 Stopped; cannot insert breakpoints.
3902 You may have requested too many hardware breakpoints and watchpoints.
3906 This message is printed when you attempt to resume the program, since
3907 only then @value{GDBN} knows exactly how many hardware breakpoints and
3908 watchpoints it needs to insert.
3910 When this message is printed, you need to disable or remove some of the
3911 hardware-assisted breakpoints and watchpoints, and then continue.
3913 @node Breakpoint-related Warnings
3914 @subsection ``Breakpoint address adjusted...''
3915 @cindex breakpoint address adjusted
3917 Some processor architectures place constraints on the addresses at
3918 which breakpoints may be placed. For architectures thus constrained,
3919 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3920 with the constraints dictated by the architecture.
3922 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3923 a VLIW architecture in which a number of RISC-like instructions may be
3924 bundled together for parallel execution. The FR-V architecture
3925 constrains the location of a breakpoint instruction within such a
3926 bundle to the instruction with the lowest address. @value{GDBN}
3927 honors this constraint by adjusting a breakpoint's address to the
3928 first in the bundle.
3930 It is not uncommon for optimized code to have bundles which contain
3931 instructions from different source statements, thus it may happen that
3932 a breakpoint's address will be adjusted from one source statement to
3933 another. Since this adjustment may significantly alter @value{GDBN}'s
3934 breakpoint related behavior from what the user expects, a warning is
3935 printed when the breakpoint is first set and also when the breakpoint
3938 A warning like the one below is printed when setting a breakpoint
3939 that's been subject to address adjustment:
3942 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3945 Such warnings are printed both for user settable and @value{GDBN}'s
3946 internal breakpoints. If you see one of these warnings, you should
3947 verify that a breakpoint set at the adjusted address will have the
3948 desired affect. If not, the breakpoint in question may be removed and
3949 other breakpoints may be set which will have the desired behavior.
3950 E.g., it may be sufficient to place the breakpoint at a later
3951 instruction. A conditional breakpoint may also be useful in some
3952 cases to prevent the breakpoint from triggering too often.
3954 @value{GDBN} will also issue a warning when stopping at one of these
3955 adjusted breakpoints:
3958 warning: Breakpoint 1 address previously adjusted from 0x00010414
3962 When this warning is encountered, it may be too late to take remedial
3963 action except in cases where the breakpoint is hit earlier or more
3964 frequently than expected.
3966 @node Continuing and Stepping
3967 @section Continuing and Stepping
3971 @cindex resuming execution
3972 @dfn{Continuing} means resuming program execution until your program
3973 completes normally. In contrast, @dfn{stepping} means executing just
3974 one more ``step'' of your program, where ``step'' may mean either one
3975 line of source code, or one machine instruction (depending on what
3976 particular command you use). Either when continuing or when stepping,
3977 your program may stop even sooner, due to a breakpoint or a signal. (If
3978 it stops due to a signal, you may want to use @code{handle}, or use
3979 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3983 @kindex c @r{(@code{continue})}
3984 @kindex fg @r{(resume foreground execution)}
3985 @item continue @r{[}@var{ignore-count}@r{]}
3986 @itemx c @r{[}@var{ignore-count}@r{]}
3987 @itemx fg @r{[}@var{ignore-count}@r{]}
3988 Resume program execution, at the address where your program last stopped;
3989 any breakpoints set at that address are bypassed. The optional argument
3990 @var{ignore-count} allows you to specify a further number of times to
3991 ignore a breakpoint at this location; its effect is like that of
3992 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
3994 The argument @var{ignore-count} is meaningful only when your program
3995 stopped due to a breakpoint. At other times, the argument to
3996 @code{continue} is ignored.
3998 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3999 debugged program is deemed to be the foreground program) are provided
4000 purely for convenience, and have exactly the same behavior as
4004 To resume execution at a different place, you can use @code{return}
4005 (@pxref{Returning, ,Returning from a Function}) to go back to the
4006 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4007 Different Address}) to go to an arbitrary location in your program.
4009 A typical technique for using stepping is to set a breakpoint
4010 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4011 beginning of the function or the section of your program where a problem
4012 is believed to lie, run your program until it stops at that breakpoint,
4013 and then step through the suspect area, examining the variables that are
4014 interesting, until you see the problem happen.
4018 @kindex s @r{(@code{step})}
4020 Continue running your program until control reaches a different source
4021 line, then stop it and return control to @value{GDBN}. This command is
4022 abbreviated @code{s}.
4025 @c "without debugging information" is imprecise; actually "without line
4026 @c numbers in the debugging information". (gcc -g1 has debugging info but
4027 @c not line numbers). But it seems complex to try to make that
4028 @c distinction here.
4029 @emph{Warning:} If you use the @code{step} command while control is
4030 within a function that was compiled without debugging information,
4031 execution proceeds until control reaches a function that does have
4032 debugging information. Likewise, it will not step into a function which
4033 is compiled without debugging information. To step through functions
4034 without debugging information, use the @code{stepi} command, described
4038 The @code{step} command only stops at the first instruction of a source
4039 line. This prevents the multiple stops that could otherwise occur in
4040 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4041 to stop if a function that has debugging information is called within
4042 the line. In other words, @code{step} @emph{steps inside} any functions
4043 called within the line.
4045 Also, the @code{step} command only enters a function if there is line
4046 number information for the function. Otherwise it acts like the
4047 @code{next} command. This avoids problems when using @code{cc -gl}
4048 on MIPS machines. Previously, @code{step} entered subroutines if there
4049 was any debugging information about the routine.
4051 @item step @var{count}
4052 Continue running as in @code{step}, but do so @var{count} times. If a
4053 breakpoint is reached, or a signal not related to stepping occurs before
4054 @var{count} steps, stepping stops right away.
4057 @kindex n @r{(@code{next})}
4058 @item next @r{[}@var{count}@r{]}
4059 Continue to the next source line in the current (innermost) stack frame.
4060 This is similar to @code{step}, but function calls that appear within
4061 the line of code are executed without stopping. Execution stops when
4062 control reaches a different line of code at the original stack level
4063 that was executing when you gave the @code{next} command. This command
4064 is abbreviated @code{n}.
4066 An argument @var{count} is a repeat count, as for @code{step}.
4069 @c FIX ME!! Do we delete this, or is there a way it fits in with
4070 @c the following paragraph? --- Vctoria
4072 @c @code{next} within a function that lacks debugging information acts like
4073 @c @code{step}, but any function calls appearing within the code of the
4074 @c function are executed without stopping.
4076 The @code{next} command only stops at the first instruction of a
4077 source line. This prevents multiple stops that could otherwise occur in
4078 @code{switch} statements, @code{for} loops, etc.
4080 @kindex set step-mode
4082 @cindex functions without line info, and stepping
4083 @cindex stepping into functions with no line info
4084 @itemx set step-mode on
4085 The @code{set step-mode on} command causes the @code{step} command to
4086 stop at the first instruction of a function which contains no debug line
4087 information rather than stepping over it.
4089 This is useful in cases where you may be interested in inspecting the
4090 machine instructions of a function which has no symbolic info and do not
4091 want @value{GDBN} to automatically skip over this function.
4093 @item set step-mode off
4094 Causes the @code{step} command to step over any functions which contains no
4095 debug information. This is the default.
4097 @item show step-mode
4098 Show whether @value{GDBN} will stop in or step over functions without
4099 source line debug information.
4103 Continue running until just after function in the selected stack frame
4104 returns. Print the returned value (if any).
4106 Contrast this with the @code{return} command (@pxref{Returning,
4107 ,Returning from a Function}).
4110 @kindex u @r{(@code{until})}
4111 @cindex run until specified location
4114 Continue running until a source line past the current line, in the
4115 current stack frame, is reached. This command is used to avoid single
4116 stepping through a loop more than once. It is like the @code{next}
4117 command, except that when @code{until} encounters a jump, it
4118 automatically continues execution until the program counter is greater
4119 than the address of the jump.
4121 This means that when you reach the end of a loop after single stepping
4122 though it, @code{until} makes your program continue execution until it
4123 exits the loop. In contrast, a @code{next} command at the end of a loop
4124 simply steps back to the beginning of the loop, which forces you to step
4125 through the next iteration.
4127 @code{until} always stops your program if it attempts to exit the current
4130 @code{until} may produce somewhat counterintuitive results if the order
4131 of machine code does not match the order of the source lines. For
4132 example, in the following excerpt from a debugging session, the @code{f}
4133 (@code{frame}) command shows that execution is stopped at line
4134 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4138 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4140 (@value{GDBP}) until
4141 195 for ( ; argc > 0; NEXTARG) @{
4144 This happened because, for execution efficiency, the compiler had
4145 generated code for the loop closure test at the end, rather than the
4146 start, of the loop---even though the test in a C @code{for}-loop is
4147 written before the body of the loop. The @code{until} command appeared
4148 to step back to the beginning of the loop when it advanced to this
4149 expression; however, it has not really gone to an earlier
4150 statement---not in terms of the actual machine code.
4152 @code{until} with no argument works by means of single
4153 instruction stepping, and hence is slower than @code{until} with an
4156 @item until @var{location}
4157 @itemx u @var{location}
4158 Continue running your program until either the specified location is
4159 reached, or the current stack frame returns. @var{location} is any of
4160 the forms described in @ref{Specify Location}.
4161 This form of the command uses temporary breakpoints, and
4162 hence is quicker than @code{until} without an argument. The specified
4163 location is actually reached only if it is in the current frame. This
4164 implies that @code{until} can be used to skip over recursive function
4165 invocations. For instance in the code below, if the current location is
4166 line @code{96}, issuing @code{until 99} will execute the program up to
4167 line @code{99} in the same invocation of factorial, i.e., after the inner
4168 invocations have returned.
4171 94 int factorial (int value)
4173 96 if (value > 1) @{
4174 97 value *= factorial (value - 1);
4181 @kindex advance @var{location}
4182 @itemx advance @var{location}
4183 Continue running the program up to the given @var{location}. An argument is
4184 required, which should be of one of the forms described in
4185 @ref{Specify Location}.
4186 Execution will also stop upon exit from the current stack
4187 frame. This command is similar to @code{until}, but @code{advance} will
4188 not skip over recursive function calls, and the target location doesn't
4189 have to be in the same frame as the current one.
4193 @kindex si @r{(@code{stepi})}
4195 @itemx stepi @var{arg}
4197 Execute one machine instruction, then stop and return to the debugger.
4199 It is often useful to do @samp{display/i $pc} when stepping by machine
4200 instructions. This makes @value{GDBN} automatically display the next
4201 instruction to be executed, each time your program stops. @xref{Auto
4202 Display,, Automatic Display}.
4204 An argument is a repeat count, as in @code{step}.
4208 @kindex ni @r{(@code{nexti})}
4210 @itemx nexti @var{arg}
4212 Execute one machine instruction, but if it is a function call,
4213 proceed until the function returns.
4215 An argument is a repeat count, as in @code{next}.
4222 A signal is an asynchronous event that can happen in a program. The
4223 operating system defines the possible kinds of signals, and gives each
4224 kind a name and a number. For example, in Unix @code{SIGINT} is the
4225 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4226 @code{SIGSEGV} is the signal a program gets from referencing a place in
4227 memory far away from all the areas in use; @code{SIGALRM} occurs when
4228 the alarm clock timer goes off (which happens only if your program has
4229 requested an alarm).
4231 @cindex fatal signals
4232 Some signals, including @code{SIGALRM}, are a normal part of the
4233 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4234 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4235 program has not specified in advance some other way to handle the signal.
4236 @code{SIGINT} does not indicate an error in your program, but it is normally
4237 fatal so it can carry out the purpose of the interrupt: to kill the program.
4239 @value{GDBN} has the ability to detect any occurrence of a signal in your
4240 program. You can tell @value{GDBN} in advance what to do for each kind of
4243 @cindex handling signals
4244 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4245 @code{SIGALRM} be silently passed to your program
4246 (so as not to interfere with their role in the program's functioning)
4247 but to stop your program immediately whenever an error signal happens.
4248 You can change these settings with the @code{handle} command.
4251 @kindex info signals
4255 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4256 handle each one. You can use this to see the signal numbers of all
4257 the defined types of signals.
4259 @item info signals @var{sig}
4260 Similar, but print information only about the specified signal number.
4262 @code{info handle} is an alias for @code{info signals}.
4265 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4266 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4267 can be the number of a signal or its name (with or without the
4268 @samp{SIG} at the beginning); a list of signal numbers of the form
4269 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4270 known signals. Optional arguments @var{keywords}, described below,
4271 say what change to make.
4275 The keywords allowed by the @code{handle} command can be abbreviated.
4276 Their full names are:
4280 @value{GDBN} should not stop your program when this signal happens. It may
4281 still print a message telling you that the signal has come in.
4284 @value{GDBN} should stop your program when this signal happens. This implies
4285 the @code{print} keyword as well.
4288 @value{GDBN} should print a message when this signal happens.
4291 @value{GDBN} should not mention the occurrence of the signal at all. This
4292 implies the @code{nostop} keyword as well.
4296 @value{GDBN} should allow your program to see this signal; your program
4297 can handle the signal, or else it may terminate if the signal is fatal
4298 and not handled. @code{pass} and @code{noignore} are synonyms.
4302 @value{GDBN} should not allow your program to see this signal.
4303 @code{nopass} and @code{ignore} are synonyms.
4307 When a signal stops your program, the signal is not visible to the
4309 continue. Your program sees the signal then, if @code{pass} is in
4310 effect for the signal in question @emph{at that time}. In other words,
4311 after @value{GDBN} reports a signal, you can use the @code{handle}
4312 command with @code{pass} or @code{nopass} to control whether your
4313 program sees that signal when you continue.
4315 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4316 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4317 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4320 You can also use the @code{signal} command to prevent your program from
4321 seeing a signal, or cause it to see a signal it normally would not see,
4322 or to give it any signal at any time. For example, if your program stopped
4323 due to some sort of memory reference error, you might store correct
4324 values into the erroneous variables and continue, hoping to see more
4325 execution; but your program would probably terminate immediately as
4326 a result of the fatal signal once it saw the signal. To prevent this,
4327 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4331 @section Stopping and Starting Multi-thread Programs
4333 When your program has multiple threads (@pxref{Threads,, Debugging
4334 Programs with Multiple Threads}), you can choose whether to set
4335 breakpoints on all threads, or on a particular thread.
4338 @cindex breakpoints and threads
4339 @cindex thread breakpoints
4340 @kindex break @dots{} thread @var{threadno}
4341 @item break @var{linespec} thread @var{threadno}
4342 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4343 @var{linespec} specifies source lines; there are several ways of
4344 writing them (@pxref{Specify Location}), but the effect is always to
4345 specify some source line.
4347 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4348 to specify that you only want @value{GDBN} to stop the program when a
4349 particular thread reaches this breakpoint. @var{threadno} is one of the
4350 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4351 column of the @samp{info threads} display.
4353 If you do not specify @samp{thread @var{threadno}} when you set a
4354 breakpoint, the breakpoint applies to @emph{all} threads of your
4357 You can use the @code{thread} qualifier on conditional breakpoints as
4358 well; in this case, place @samp{thread @var{threadno}} before the
4359 breakpoint condition, like this:
4362 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4367 @cindex stopped threads
4368 @cindex threads, stopped
4369 Whenever your program stops under @value{GDBN} for any reason,
4370 @emph{all} threads of execution stop, not just the current thread. This
4371 allows you to examine the overall state of the program, including
4372 switching between threads, without worrying that things may change
4375 @cindex thread breakpoints and system calls
4376 @cindex system calls and thread breakpoints
4377 @cindex premature return from system calls
4378 There is an unfortunate side effect. If one thread stops for a
4379 breakpoint, or for some other reason, and another thread is blocked in a
4380 system call, then the system call may return prematurely. This is a
4381 consequence of the interaction between multiple threads and the signals
4382 that @value{GDBN} uses to implement breakpoints and other events that
4385 To handle this problem, your program should check the return value of
4386 each system call and react appropriately. This is good programming
4389 For example, do not write code like this:
4395 The call to @code{sleep} will return early if a different thread stops
4396 at a breakpoint or for some other reason.
4398 Instead, write this:
4403 unslept = sleep (unslept);
4406 A system call is allowed to return early, so the system is still
4407 conforming to its specification. But @value{GDBN} does cause your
4408 multi-threaded program to behave differently than it would without
4411 Also, @value{GDBN} uses internal breakpoints in the thread library to
4412 monitor certain events such as thread creation and thread destruction.
4413 When such an event happens, a system call in another thread may return
4414 prematurely, even though your program does not appear to stop.
4416 @cindex continuing threads
4417 @cindex threads, continuing
4418 Conversely, whenever you restart the program, @emph{all} threads start
4419 executing. @emph{This is true even when single-stepping} with commands
4420 like @code{step} or @code{next}.
4422 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4423 Since thread scheduling is up to your debugging target's operating
4424 system (not controlled by @value{GDBN}), other threads may
4425 execute more than one statement while the current thread completes a
4426 single step. Moreover, in general other threads stop in the middle of a
4427 statement, rather than at a clean statement boundary, when the program
4430 You might even find your program stopped in another thread after
4431 continuing or even single-stepping. This happens whenever some other
4432 thread runs into a breakpoint, a signal, or an exception before the
4433 first thread completes whatever you requested.
4435 On some OSes, you can lock the OS scheduler and thus allow only a single
4439 @item set scheduler-locking @var{mode}
4440 @cindex scheduler locking mode
4441 @cindex lock scheduler
4442 Set the scheduler locking mode. If it is @code{off}, then there is no
4443 locking and any thread may run at any time. If @code{on}, then only the
4444 current thread may run when the inferior is resumed. The @code{step}
4445 mode optimizes for single-stepping. It stops other threads from
4446 ``seizing the prompt'' by preempting the current thread while you are
4447 stepping. Other threads will only rarely (or never) get a chance to run
4448 when you step. They are more likely to run when you @samp{next} over a
4449 function call, and they are completely free to run when you use commands
4450 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4451 thread hits a breakpoint during its timeslice, they will never steal the
4452 @value{GDBN} prompt away from the thread that you are debugging.
4454 @item show scheduler-locking
4455 Display the current scheduler locking mode.
4460 @chapter Examining the Stack
4462 When your program has stopped, the first thing you need to know is where it
4463 stopped and how it got there.
4466 Each time your program performs a function call, information about the call
4468 That information includes the location of the call in your program,
4469 the arguments of the call,
4470 and the local variables of the function being called.
4471 The information is saved in a block of data called a @dfn{stack frame}.
4472 The stack frames are allocated in a region of memory called the @dfn{call
4475 When your program stops, the @value{GDBN} commands for examining the
4476 stack allow you to see all of this information.
4478 @cindex selected frame
4479 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4480 @value{GDBN} commands refer implicitly to the selected frame. In
4481 particular, whenever you ask @value{GDBN} for the value of a variable in
4482 your program, the value is found in the selected frame. There are
4483 special @value{GDBN} commands to select whichever frame you are
4484 interested in. @xref{Selection, ,Selecting a Frame}.
4486 When your program stops, @value{GDBN} automatically selects the
4487 currently executing frame and describes it briefly, similar to the
4488 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4491 * Frames:: Stack frames
4492 * Backtrace:: Backtraces
4493 * Selection:: Selecting a frame
4494 * Frame Info:: Information on a frame
4499 @section Stack Frames
4501 @cindex frame, definition
4503 The call stack is divided up into contiguous pieces called @dfn{stack
4504 frames}, or @dfn{frames} for short; each frame is the data associated
4505 with one call to one function. The frame contains the arguments given
4506 to the function, the function's local variables, and the address at
4507 which the function is executing.
4509 @cindex initial frame
4510 @cindex outermost frame
4511 @cindex innermost frame
4512 When your program is started, the stack has only one frame, that of the
4513 function @code{main}. This is called the @dfn{initial} frame or the
4514 @dfn{outermost} frame. Each time a function is called, a new frame is
4515 made. Each time a function returns, the frame for that function invocation
4516 is eliminated. If a function is recursive, there can be many frames for
4517 the same function. The frame for the function in which execution is
4518 actually occurring is called the @dfn{innermost} frame. This is the most
4519 recently created of all the stack frames that still exist.
4521 @cindex frame pointer
4522 Inside your program, stack frames are identified by their addresses. A
4523 stack frame consists of many bytes, each of which has its own address; each
4524 kind of computer has a convention for choosing one byte whose
4525 address serves as the address of the frame. Usually this address is kept
4526 in a register called the @dfn{frame pointer register}
4527 (@pxref{Registers, $fp}) while execution is going on in that frame.
4529 @cindex frame number
4530 @value{GDBN} assigns numbers to all existing stack frames, starting with
4531 zero for the innermost frame, one for the frame that called it,
4532 and so on upward. These numbers do not really exist in your program;
4533 they are assigned by @value{GDBN} to give you a way of designating stack
4534 frames in @value{GDBN} commands.
4536 @c The -fomit-frame-pointer below perennially causes hbox overflow
4537 @c underflow problems.
4538 @cindex frameless execution
4539 Some compilers provide a way to compile functions so that they operate
4540 without stack frames. (For example, the @value{NGCC} option
4542 @samp{-fomit-frame-pointer}
4544 generates functions without a frame.)
4545 This is occasionally done with heavily used library functions to save
4546 the frame setup time. @value{GDBN} has limited facilities for dealing
4547 with these function invocations. If the innermost function invocation
4548 has no stack frame, @value{GDBN} nevertheless regards it as though
4549 it had a separate frame, which is numbered zero as usual, allowing
4550 correct tracing of the function call chain. However, @value{GDBN} has
4551 no provision for frameless functions elsewhere in the stack.
4554 @kindex frame@r{, command}
4555 @cindex current stack frame
4556 @item frame @var{args}
4557 The @code{frame} command allows you to move from one stack frame to another,
4558 and to print the stack frame you select. @var{args} may be either the
4559 address of the frame or the stack frame number. Without an argument,
4560 @code{frame} prints the current stack frame.
4562 @kindex select-frame
4563 @cindex selecting frame silently
4565 The @code{select-frame} command allows you to move from one stack frame
4566 to another without printing the frame. This is the silent version of
4574 @cindex call stack traces
4575 A backtrace is a summary of how your program got where it is. It shows one
4576 line per frame, for many frames, starting with the currently executing
4577 frame (frame zero), followed by its caller (frame one), and on up the
4582 @kindex bt @r{(@code{backtrace})}
4585 Print a backtrace of the entire stack: one line per frame for all
4586 frames in the stack.
4588 You can stop the backtrace at any time by typing the system interrupt
4589 character, normally @kbd{Ctrl-c}.
4591 @item backtrace @var{n}
4593 Similar, but print only the innermost @var{n} frames.
4595 @item backtrace -@var{n}
4597 Similar, but print only the outermost @var{n} frames.
4599 @item backtrace full
4601 @itemx bt full @var{n}
4602 @itemx bt full -@var{n}
4603 Print the values of the local variables also. @var{n} specifies the
4604 number of frames to print, as described above.
4609 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4610 are additional aliases for @code{backtrace}.
4612 @cindex multiple threads, backtrace
4613 In a multi-threaded program, @value{GDBN} by default shows the
4614 backtrace only for the current thread. To display the backtrace for
4615 several or all of the threads, use the command @code{thread apply}
4616 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4617 apply all backtrace}, @value{GDBN} will display the backtrace for all
4618 the threads; this is handy when you debug a core dump of a
4619 multi-threaded program.
4621 Each line in the backtrace shows the frame number and the function name.
4622 The program counter value is also shown---unless you use @code{set
4623 print address off}. The backtrace also shows the source file name and
4624 line number, as well as the arguments to the function. The program
4625 counter value is omitted if it is at the beginning of the code for that
4628 Here is an example of a backtrace. It was made with the command
4629 @samp{bt 3}, so it shows the innermost three frames.
4633 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4635 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4636 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4638 (More stack frames follow...)
4643 The display for frame zero does not begin with a program counter
4644 value, indicating that your program has stopped at the beginning of the
4645 code for line @code{993} of @code{builtin.c}.
4647 @cindex value optimized out, in backtrace
4648 @cindex function call arguments, optimized out
4649 If your program was compiled with optimizations, some compilers will
4650 optimize away arguments passed to functions if those arguments are
4651 never used after the call. Such optimizations generate code that
4652 passes arguments through registers, but doesn't store those arguments
4653 in the stack frame. @value{GDBN} has no way of displaying such
4654 arguments in stack frames other than the innermost one. Here's what
4655 such a backtrace might look like:
4659 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4661 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4662 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4664 (More stack frames follow...)
4669 The values of arguments that were not saved in their stack frames are
4670 shown as @samp{<value optimized out>}.
4672 If you need to display the values of such optimized-out arguments,
4673 either deduce that from other variables whose values depend on the one
4674 you are interested in, or recompile without optimizations.
4676 @cindex backtrace beyond @code{main} function
4677 @cindex program entry point
4678 @cindex startup code, and backtrace
4679 Most programs have a standard user entry point---a place where system
4680 libraries and startup code transition into user code. For C this is
4681 @code{main}@footnote{
4682 Note that embedded programs (the so-called ``free-standing''
4683 environment) are not required to have a @code{main} function as the
4684 entry point. They could even have multiple entry points.}.
4685 When @value{GDBN} finds the entry function in a backtrace
4686 it will terminate the backtrace, to avoid tracing into highly
4687 system-specific (and generally uninteresting) code.
4689 If you need to examine the startup code, or limit the number of levels
4690 in a backtrace, you can change this behavior:
4693 @item set backtrace past-main
4694 @itemx set backtrace past-main on
4695 @kindex set backtrace
4696 Backtraces will continue past the user entry point.
4698 @item set backtrace past-main off
4699 Backtraces will stop when they encounter the user entry point. This is the
4702 @item show backtrace past-main
4703 @kindex show backtrace
4704 Display the current user entry point backtrace policy.
4706 @item set backtrace past-entry
4707 @itemx set backtrace past-entry on
4708 Backtraces will continue past the internal entry point of an application.
4709 This entry point is encoded by the linker when the application is built,
4710 and is likely before the user entry point @code{main} (or equivalent) is called.
4712 @item set backtrace past-entry off
4713 Backtraces will stop when they encounter the internal entry point of an
4714 application. This is the default.
4716 @item show backtrace past-entry
4717 Display the current internal entry point backtrace policy.
4719 @item set backtrace limit @var{n}
4720 @itemx set backtrace limit 0
4721 @cindex backtrace limit
4722 Limit the backtrace to @var{n} levels. A value of zero means
4725 @item show backtrace limit
4726 Display the current limit on backtrace levels.
4730 @section Selecting a Frame
4732 Most commands for examining the stack and other data in your program work on
4733 whichever stack frame is selected at the moment. Here are the commands for
4734 selecting a stack frame; all of them finish by printing a brief description
4735 of the stack frame just selected.
4738 @kindex frame@r{, selecting}
4739 @kindex f @r{(@code{frame})}
4742 Select frame number @var{n}. Recall that frame zero is the innermost
4743 (currently executing) frame, frame one is the frame that called the
4744 innermost one, and so on. The highest-numbered frame is the one for
4747 @item frame @var{addr}
4749 Select the frame at address @var{addr}. This is useful mainly if the
4750 chaining of stack frames has been damaged by a bug, making it
4751 impossible for @value{GDBN} to assign numbers properly to all frames. In
4752 addition, this can be useful when your program has multiple stacks and
4753 switches between them.
4755 On the SPARC architecture, @code{frame} needs two addresses to
4756 select an arbitrary frame: a frame pointer and a stack pointer.
4758 On the MIPS and Alpha architecture, it needs two addresses: a stack
4759 pointer and a program counter.
4761 On the 29k architecture, it needs three addresses: a register stack
4762 pointer, a program counter, and a memory stack pointer.
4766 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4767 advances toward the outermost frame, to higher frame numbers, to frames
4768 that have existed longer. @var{n} defaults to one.
4771 @kindex do @r{(@code{down})}
4773 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4774 advances toward the innermost frame, to lower frame numbers, to frames
4775 that were created more recently. @var{n} defaults to one. You may
4776 abbreviate @code{down} as @code{do}.
4779 All of these commands end by printing two lines of output describing the
4780 frame. The first line shows the frame number, the function name, the
4781 arguments, and the source file and line number of execution in that
4782 frame. The second line shows the text of that source line.
4790 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4792 10 read_input_file (argv[i]);
4796 After such a printout, the @code{list} command with no arguments
4797 prints ten lines centered on the point of execution in the frame.
4798 You can also edit the program at the point of execution with your favorite
4799 editing program by typing @code{edit}.
4800 @xref{List, ,Printing Source Lines},
4804 @kindex down-silently
4806 @item up-silently @var{n}
4807 @itemx down-silently @var{n}
4808 These two commands are variants of @code{up} and @code{down},
4809 respectively; they differ in that they do their work silently, without
4810 causing display of the new frame. They are intended primarily for use
4811 in @value{GDBN} command scripts, where the output might be unnecessary and
4816 @section Information About a Frame
4818 There are several other commands to print information about the selected
4824 When used without any argument, this command does not change which
4825 frame is selected, but prints a brief description of the currently
4826 selected stack frame. It can be abbreviated @code{f}. With an
4827 argument, this command is used to select a stack frame.
4828 @xref{Selection, ,Selecting a Frame}.
4831 @kindex info f @r{(@code{info frame})}
4834 This command prints a verbose description of the selected stack frame,
4839 the address of the frame
4841 the address of the next frame down (called by this frame)
4843 the address of the next frame up (caller of this frame)
4845 the language in which the source code corresponding to this frame is written
4847 the address of the frame's arguments
4849 the address of the frame's local variables
4851 the program counter saved in it (the address of execution in the caller frame)
4853 which registers were saved in the frame
4856 @noindent The verbose description is useful when
4857 something has gone wrong that has made the stack format fail to fit
4858 the usual conventions.
4860 @item info frame @var{addr}
4861 @itemx info f @var{addr}
4862 Print a verbose description of the frame at address @var{addr}, without
4863 selecting that frame. The selected frame remains unchanged by this
4864 command. This requires the same kind of address (more than one for some
4865 architectures) that you specify in the @code{frame} command.
4866 @xref{Selection, ,Selecting a Frame}.
4870 Print the arguments of the selected frame, each on a separate line.
4874 Print the local variables of the selected frame, each on a separate
4875 line. These are all variables (declared either static or automatic)
4876 accessible at the point of execution of the selected frame.
4879 @cindex catch exceptions, list active handlers
4880 @cindex exception handlers, how to list
4882 Print a list of all the exception handlers that are active in the
4883 current stack frame at the current point of execution. To see other
4884 exception handlers, visit the associated frame (using the @code{up},
4885 @code{down}, or @code{frame} commands); then type @code{info catch}.
4886 @xref{Set Catchpoints, , Setting Catchpoints}.
4892 @chapter Examining Source Files
4894 @value{GDBN} can print parts of your program's source, since the debugging
4895 information recorded in the program tells @value{GDBN} what source files were
4896 used to build it. When your program stops, @value{GDBN} spontaneously prints
4897 the line where it stopped. Likewise, when you select a stack frame
4898 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4899 execution in that frame has stopped. You can print other portions of
4900 source files by explicit command.
4902 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4903 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4904 @value{GDBN} under @sc{gnu} Emacs}.
4907 * List:: Printing source lines
4908 * Specify Location:: How to specify code locations
4909 * Edit:: Editing source files
4910 * Search:: Searching source files
4911 * Source Path:: Specifying source directories
4912 * Machine Code:: Source and machine code
4916 @section Printing Source Lines
4919 @kindex l @r{(@code{list})}
4920 To print lines from a source file, use the @code{list} command
4921 (abbreviated @code{l}). By default, ten lines are printed.
4922 There are several ways to specify what part of the file you want to
4923 print; see @ref{Specify Location}, for the full list.
4925 Here are the forms of the @code{list} command most commonly used:
4928 @item list @var{linenum}
4929 Print lines centered around line number @var{linenum} in the
4930 current source file.
4932 @item list @var{function}
4933 Print lines centered around the beginning of function
4937 Print more lines. If the last lines printed were printed with a
4938 @code{list} command, this prints lines following the last lines
4939 printed; however, if the last line printed was a solitary line printed
4940 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4941 Stack}), this prints lines centered around that line.
4944 Print lines just before the lines last printed.
4947 @cindex @code{list}, how many lines to display
4948 By default, @value{GDBN} prints ten source lines with any of these forms of
4949 the @code{list} command. You can change this using @code{set listsize}:
4952 @kindex set listsize
4953 @item set listsize @var{count}
4954 Make the @code{list} command display @var{count} source lines (unless
4955 the @code{list} argument explicitly specifies some other number).
4957 @kindex show listsize
4959 Display the number of lines that @code{list} prints.
4962 Repeating a @code{list} command with @key{RET} discards the argument,
4963 so it is equivalent to typing just @code{list}. This is more useful
4964 than listing the same lines again. An exception is made for an
4965 argument of @samp{-}; that argument is preserved in repetition so that
4966 each repetition moves up in the source file.
4968 In general, the @code{list} command expects you to supply zero, one or two
4969 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4970 of writing them (@pxref{Specify Location}), but the effect is always
4971 to specify some source line.
4973 Here is a complete description of the possible arguments for @code{list}:
4976 @item list @var{linespec}
4977 Print lines centered around the line specified by @var{linespec}.
4979 @item list @var{first},@var{last}
4980 Print lines from @var{first} to @var{last}. Both arguments are
4981 linespecs. When a @code{list} command has two linespecs, and the
4982 source file of the second linespec is omitted, this refers to
4983 the same source file as the first linespec.
4985 @item list ,@var{last}
4986 Print lines ending with @var{last}.
4988 @item list @var{first},
4989 Print lines starting with @var{first}.
4992 Print lines just after the lines last printed.
4995 Print lines just before the lines last printed.
4998 As described in the preceding table.
5001 @node Specify Location
5002 @section Specifying a Location
5003 @cindex specifying location
5006 Several @value{GDBN} commands accept arguments that specify a location
5007 of your program's code. Since @value{GDBN} is a source-level
5008 debugger, a location usually specifies some line in the source code;
5009 for that reason, locations are also known as @dfn{linespecs}.
5011 Here are all the different ways of specifying a code location that
5012 @value{GDBN} understands:
5016 Specifies the line number @var{linenum} of the current source file.
5019 @itemx +@var{offset}
5020 Specifies the line @var{offset} lines before or after the @dfn{current
5021 line}. For the @code{list} command, the current line is the last one
5022 printed; for the breakpoint commands, this is the line at which
5023 execution stopped in the currently selected @dfn{stack frame}
5024 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5025 used as the second of the two linespecs in a @code{list} command,
5026 this specifies the line @var{offset} lines up or down from the first
5029 @item @var{filename}:@var{linenum}
5030 Specifies the line @var{linenum} in the source file @var{filename}.
5032 @item @var{function}
5033 Specifies the line that begins the body of the function @var{function}.
5034 For example, in C, this is the line with the open brace.
5036 @item @var{filename}:@var{function}
5037 Specifies the line that begins the body of the function @var{function}
5038 in the file @var{filename}. You only need the file name with a
5039 function name to avoid ambiguity when there are identically named
5040 functions in different source files.
5042 @item *@var{address}
5043 Specifies the program address @var{address}. For line-oriented
5044 commands, such as @code{list} and @code{edit}, this specifies a source
5045 line that contains @var{address}. For @code{break} and other
5046 breakpoint oriented commands, this can be used to set breakpoints in
5047 parts of your program which do not have debugging information or
5050 Here @var{address} may be any expression valid in the current working
5051 language (@pxref{Languages, working language}) that specifies a code
5052 address. In addition, as a convenience, @value{GDBN} extends the
5053 semantics of expressions used in locations to cover the situations
5054 that frequently happen during debugging. Here are the various forms
5058 @item @var{expression}
5059 Any expression valid in the current working language.
5061 @item @var{funcaddr}
5062 An address of a function or procedure derived from its name. In C,
5063 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5064 simply the function's name @var{function} (and actually a special case
5065 of a valid expression). In Pascal and Modula-2, this is
5066 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5067 (although the Pascal form also works).
5069 This form specifies the address of the function's first instruction,
5070 before the stack frame and arguments have been set up.
5072 @item '@var{filename}'::@var{funcaddr}
5073 Like @var{funcaddr} above, but also specifies the name of the source
5074 file explicitly. This is useful if the name of the function does not
5075 specify the function unambiguously, e.g., if there are several
5076 functions with identical names in different source files.
5083 @section Editing Source Files
5084 @cindex editing source files
5087 @kindex e @r{(@code{edit})}
5088 To edit the lines in a source file, use the @code{edit} command.
5089 The editing program of your choice
5090 is invoked with the current line set to
5091 the active line in the program.
5092 Alternatively, there are several ways to specify what part of the file you
5093 want to print if you want to see other parts of the program:
5096 @item edit @var{location}
5097 Edit the source file specified by @code{location}. Editing starts at
5098 that @var{location}, e.g., at the specified source line of the
5099 specified file. @xref{Specify Location}, for all the possible forms
5100 of the @var{location} argument; here are the forms of the @code{edit}
5101 command most commonly used:
5104 @item edit @var{number}
5105 Edit the current source file with @var{number} as the active line number.
5107 @item edit @var{function}
5108 Edit the file containing @var{function} at the beginning of its definition.
5113 @subsection Choosing your Editor
5114 You can customize @value{GDBN} to use any editor you want
5116 The only restriction is that your editor (say @code{ex}), recognizes the
5117 following command-line syntax:
5119 ex +@var{number} file
5121 The optional numeric value +@var{number} specifies the number of the line in
5122 the file where to start editing.}.
5123 By default, it is @file{@value{EDITOR}}, but you can change this
5124 by setting the environment variable @code{EDITOR} before using
5125 @value{GDBN}. For example, to configure @value{GDBN} to use the
5126 @code{vi} editor, you could use these commands with the @code{sh} shell:
5132 or in the @code{csh} shell,
5134 setenv EDITOR /usr/bin/vi
5139 @section Searching Source Files
5140 @cindex searching source files
5142 There are two commands for searching through the current source file for a
5147 @kindex forward-search
5148 @item forward-search @var{regexp}
5149 @itemx search @var{regexp}
5150 The command @samp{forward-search @var{regexp}} checks each line,
5151 starting with the one following the last line listed, for a match for
5152 @var{regexp}. It lists the line that is found. You can use the
5153 synonym @samp{search @var{regexp}} or abbreviate the command name as
5156 @kindex reverse-search
5157 @item reverse-search @var{regexp}
5158 The command @samp{reverse-search @var{regexp}} checks each line, starting
5159 with the one before the last line listed and going backward, for a match
5160 for @var{regexp}. It lists the line that is found. You can abbreviate
5161 this command as @code{rev}.
5165 @section Specifying Source Directories
5168 @cindex directories for source files
5169 Executable programs sometimes do not record the directories of the source
5170 files from which they were compiled, just the names. Even when they do,
5171 the directories could be moved between the compilation and your debugging
5172 session. @value{GDBN} has a list of directories to search for source files;
5173 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5174 it tries all the directories in the list, in the order they are present
5175 in the list, until it finds a file with the desired name.
5177 For example, suppose an executable references the file
5178 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5179 @file{/mnt/cross}. The file is first looked up literally; if this
5180 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5181 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5182 message is printed. @value{GDBN} does not look up the parts of the
5183 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5184 Likewise, the subdirectories of the source path are not searched: if
5185 the source path is @file{/mnt/cross}, and the binary refers to
5186 @file{foo.c}, @value{GDBN} would not find it under
5187 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5189 Plain file names, relative file names with leading directories, file
5190 names containing dots, etc.@: are all treated as described above; for
5191 instance, if the source path is @file{/mnt/cross}, and the source file
5192 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5193 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5194 that---@file{/mnt/cross/foo.c}.
5196 Note that the executable search path is @emph{not} used to locate the
5199 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5200 any information it has cached about where source files are found and where
5201 each line is in the file.
5205 When you start @value{GDBN}, its source path includes only @samp{cdir}
5206 and @samp{cwd}, in that order.
5207 To add other directories, use the @code{directory} command.
5209 The search path is used to find both program source files and @value{GDBN}
5210 script files (read using the @samp{-command} option and @samp{source} command).
5212 In addition to the source path, @value{GDBN} provides a set of commands
5213 that manage a list of source path substitution rules. A @dfn{substitution
5214 rule} specifies how to rewrite source directories stored in the program's
5215 debug information in case the sources were moved to a different
5216 directory between compilation and debugging. A rule is made of
5217 two strings, the first specifying what needs to be rewritten in
5218 the path, and the second specifying how it should be rewritten.
5219 In @ref{set substitute-path}, we name these two parts @var{from} and
5220 @var{to} respectively. @value{GDBN} does a simple string replacement
5221 of @var{from} with @var{to} at the start of the directory part of the
5222 source file name, and uses that result instead of the original file
5223 name to look up the sources.
5225 Using the previous example, suppose the @file{foo-1.0} tree has been
5226 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5227 @value{GDBN} to replace @file{/usr/src} in all source path names with
5228 @file{/mnt/cross}. The first lookup will then be
5229 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5230 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5231 substitution rule, use the @code{set substitute-path} command
5232 (@pxref{set substitute-path}).
5234 To avoid unexpected substitution results, a rule is applied only if the
5235 @var{from} part of the directory name ends at a directory separator.
5236 For instance, a rule substituting @file{/usr/source} into
5237 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5238 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5239 is applied only at the beginning of the directory name, this rule will
5240 not be applied to @file{/root/usr/source/baz.c} either.
5242 In many cases, you can achieve the same result using the @code{directory}
5243 command. However, @code{set substitute-path} can be more efficient in
5244 the case where the sources are organized in a complex tree with multiple
5245 subdirectories. With the @code{directory} command, you need to add each
5246 subdirectory of your project. If you moved the entire tree while
5247 preserving its internal organization, then @code{set substitute-path}
5248 allows you to direct the debugger to all the sources with one single
5251 @code{set substitute-path} is also more than just a shortcut command.
5252 The source path is only used if the file at the original location no
5253 longer exists. On the other hand, @code{set substitute-path} modifies
5254 the debugger behavior to look at the rewritten location instead. So, if
5255 for any reason a source file that is not relevant to your executable is
5256 located at the original location, a substitution rule is the only
5257 method available to point @value{GDBN} at the new location.
5260 @item directory @var{dirname} @dots{}
5261 @item dir @var{dirname} @dots{}
5262 Add directory @var{dirname} to the front of the source path. Several
5263 directory names may be given to this command, separated by @samp{:}
5264 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5265 part of absolute file names) or
5266 whitespace. You may specify a directory that is already in the source
5267 path; this moves it forward, so @value{GDBN} searches it sooner.
5271 @vindex $cdir@r{, convenience variable}
5272 @vindex $cwd@r{, convenience variable}
5273 @cindex compilation directory
5274 @cindex current directory
5275 @cindex working directory
5276 @cindex directory, current
5277 @cindex directory, compilation
5278 You can use the string @samp{$cdir} to refer to the compilation
5279 directory (if one is recorded), and @samp{$cwd} to refer to the current
5280 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5281 tracks the current working directory as it changes during your @value{GDBN}
5282 session, while the latter is immediately expanded to the current
5283 directory at the time you add an entry to the source path.
5286 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5288 @c RET-repeat for @code{directory} is explicitly disabled, but since
5289 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5291 @item show directories
5292 @kindex show directories
5293 Print the source path: show which directories it contains.
5295 @anchor{set substitute-path}
5296 @item set substitute-path @var{from} @var{to}
5297 @kindex set substitute-path
5298 Define a source path substitution rule, and add it at the end of the
5299 current list of existing substitution rules. If a rule with the same
5300 @var{from} was already defined, then the old rule is also deleted.
5302 For example, if the file @file{/foo/bar/baz.c} was moved to
5303 @file{/mnt/cross/baz.c}, then the command
5306 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5310 will tell @value{GDBN} to replace @samp{/usr/src} with
5311 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5312 @file{baz.c} even though it was moved.
5314 In the case when more than one substitution rule have been defined,
5315 the rules are evaluated one by one in the order where they have been
5316 defined. The first one matching, if any, is selected to perform
5319 For instance, if we had entered the following commands:
5322 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5323 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5327 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5328 @file{/mnt/include/defs.h} by using the first rule. However, it would
5329 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5330 @file{/mnt/src/lib/foo.c}.
5333 @item unset substitute-path [path]
5334 @kindex unset substitute-path
5335 If a path is specified, search the current list of substitution rules
5336 for a rule that would rewrite that path. Delete that rule if found.
5337 A warning is emitted by the debugger if no rule could be found.
5339 If no path is specified, then all substitution rules are deleted.
5341 @item show substitute-path [path]
5342 @kindex show substitute-path
5343 If a path is specified, then print the source path substitution rule
5344 which would rewrite that path, if any.
5346 If no path is specified, then print all existing source path substitution
5351 If your source path is cluttered with directories that are no longer of
5352 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5353 versions of source. You can correct the situation as follows:
5357 Use @code{directory} with no argument to reset the source path to its default value.
5360 Use @code{directory} with suitable arguments to reinstall the
5361 directories you want in the source path. You can add all the
5362 directories in one command.
5366 @section Source and Machine Code
5367 @cindex source line and its code address
5369 You can use the command @code{info line} to map source lines to program
5370 addresses (and vice versa), and the command @code{disassemble} to display
5371 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5372 mode, the @code{info line} command causes the arrow to point to the
5373 line specified. Also, @code{info line} prints addresses in symbolic form as
5378 @item info line @var{linespec}
5379 Print the starting and ending addresses of the compiled code for
5380 source line @var{linespec}. You can specify source lines in any of
5381 the ways documented in @ref{Specify Location}.
5384 For example, we can use @code{info line} to discover the location of
5385 the object code for the first line of function
5386 @code{m4_changequote}:
5388 @c FIXME: I think this example should also show the addresses in
5389 @c symbolic form, as they usually would be displayed.
5391 (@value{GDBP}) info line m4_changequote
5392 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5396 @cindex code address and its source line
5397 We can also inquire (using @code{*@var{addr}} as the form for
5398 @var{linespec}) what source line covers a particular address:
5400 (@value{GDBP}) info line *0x63ff
5401 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5404 @cindex @code{$_} and @code{info line}
5405 @cindex @code{x} command, default address
5406 @kindex x@r{(examine), and} info line
5407 After @code{info line}, the default address for the @code{x} command
5408 is changed to the starting address of the line, so that @samp{x/i} is
5409 sufficient to begin examining the machine code (@pxref{Memory,
5410 ,Examining Memory}). Also, this address is saved as the value of the
5411 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5416 @cindex assembly instructions
5417 @cindex instructions, assembly
5418 @cindex machine instructions
5419 @cindex listing machine instructions
5421 This specialized command dumps a range of memory as machine
5422 instructions. The default memory range is the function surrounding the
5423 program counter of the selected frame. A single argument to this
5424 command is a program counter value; @value{GDBN} dumps the function
5425 surrounding this value. Two arguments specify a range of addresses
5426 (first inclusive, second exclusive) to dump.
5429 The following example shows the disassembly of a range of addresses of
5430 HP PA-RISC 2.0 code:
5433 (@value{GDBP}) disas 0x32c4 0x32e4
5434 Dump of assembler code from 0x32c4 to 0x32e4:
5435 0x32c4 <main+204>: addil 0,dp
5436 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5437 0x32cc <main+212>: ldil 0x3000,r31
5438 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5439 0x32d4 <main+220>: ldo 0(r31),rp
5440 0x32d8 <main+224>: addil -0x800,dp
5441 0x32dc <main+228>: ldo 0x588(r1),r26
5442 0x32e0 <main+232>: ldil 0x3000,r31
5443 End of assembler dump.
5446 Some architectures have more than one commonly-used set of instruction
5447 mnemonics or other syntax.
5449 For programs that were dynamically linked and use shared libraries,
5450 instructions that call functions or branch to locations in the shared
5451 libraries might show a seemingly bogus location---it's actually a
5452 location of the relocation table. On some architectures, @value{GDBN}
5453 might be able to resolve these to actual function names.
5456 @kindex set disassembly-flavor
5457 @cindex Intel disassembly flavor
5458 @cindex AT&T disassembly flavor
5459 @item set disassembly-flavor @var{instruction-set}
5460 Select the instruction set to use when disassembling the
5461 program via the @code{disassemble} or @code{x/i} commands.
5463 Currently this command is only defined for the Intel x86 family. You
5464 can set @var{instruction-set} to either @code{intel} or @code{att}.
5465 The default is @code{att}, the AT&T flavor used by default by Unix
5466 assemblers for x86-based targets.
5468 @kindex show disassembly-flavor
5469 @item show disassembly-flavor
5470 Show the current setting of the disassembly flavor.
5475 @chapter Examining Data
5477 @cindex printing data
5478 @cindex examining data
5481 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5482 @c document because it is nonstandard... Under Epoch it displays in a
5483 @c different window or something like that.
5484 The usual way to examine data in your program is with the @code{print}
5485 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5486 evaluates and prints the value of an expression of the language your
5487 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5488 Different Languages}).
5491 @item print @var{expr}
5492 @itemx print /@var{f} @var{expr}
5493 @var{expr} is an expression (in the source language). By default the
5494 value of @var{expr} is printed in a format appropriate to its data type;
5495 you can choose a different format by specifying @samp{/@var{f}}, where
5496 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5500 @itemx print /@var{f}
5501 @cindex reprint the last value
5502 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5503 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5504 conveniently inspect the same value in an alternative format.
5507 A more low-level way of examining data is with the @code{x} command.
5508 It examines data in memory at a specified address and prints it in a
5509 specified format. @xref{Memory, ,Examining Memory}.
5511 If you are interested in information about types, or about how the
5512 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5513 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5517 * Expressions:: Expressions
5518 * Ambiguous Expressions:: Ambiguous Expressions
5519 * Variables:: Program variables
5520 * Arrays:: Artificial arrays
5521 * Output Formats:: Output formats
5522 * Memory:: Examining memory
5523 * Auto Display:: Automatic display
5524 * Print Settings:: Print settings
5525 * Value History:: Value history
5526 * Convenience Vars:: Convenience variables
5527 * Registers:: Registers
5528 * Floating Point Hardware:: Floating point hardware
5529 * Vector Unit:: Vector Unit
5530 * OS Information:: Auxiliary data provided by operating system
5531 * Memory Region Attributes:: Memory region attributes
5532 * Dump/Restore Files:: Copy between memory and a file
5533 * Core File Generation:: Cause a program dump its core
5534 * Character Sets:: Debugging programs that use a different
5535 character set than GDB does
5536 * Caching Remote Data:: Data caching for remote targets
5540 @section Expressions
5543 @code{print} and many other @value{GDBN} commands accept an expression and
5544 compute its value. Any kind of constant, variable or operator defined
5545 by the programming language you are using is valid in an expression in
5546 @value{GDBN}. This includes conditional expressions, function calls,
5547 casts, and string constants. It also includes preprocessor macros, if
5548 you compiled your program to include this information; see
5551 @cindex arrays in expressions
5552 @value{GDBN} supports array constants in expressions input by
5553 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5554 you can use the command @code{print @{1, 2, 3@}} to create an array
5555 of three integers. If you pass an array to a function or assign it
5556 to a program variable, @value{GDBN} copies the array to memory that
5557 is @code{malloc}ed in the target program.
5559 Because C is so widespread, most of the expressions shown in examples in
5560 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5561 Languages}, for information on how to use expressions in other
5564 In this section, we discuss operators that you can use in @value{GDBN}
5565 expressions regardless of your programming language.
5567 @cindex casts, in expressions
5568 Casts are supported in all languages, not just in C, because it is so
5569 useful to cast a number into a pointer in order to examine a structure
5570 at that address in memory.
5571 @c FIXME: casts supported---Mod2 true?
5573 @value{GDBN} supports these operators, in addition to those common
5574 to programming languages:
5578 @samp{@@} is a binary operator for treating parts of memory as arrays.
5579 @xref{Arrays, ,Artificial Arrays}, for more information.
5582 @samp{::} allows you to specify a variable in terms of the file or
5583 function where it is defined. @xref{Variables, ,Program Variables}.
5585 @cindex @{@var{type}@}
5586 @cindex type casting memory
5587 @cindex memory, viewing as typed object
5588 @cindex casts, to view memory
5589 @item @{@var{type}@} @var{addr}
5590 Refers to an object of type @var{type} stored at address @var{addr} in
5591 memory. @var{addr} may be any expression whose value is an integer or
5592 pointer (but parentheses are required around binary operators, just as in
5593 a cast). This construct is allowed regardless of what kind of data is
5594 normally supposed to reside at @var{addr}.
5597 @node Ambiguous Expressions
5598 @section Ambiguous Expressions
5599 @cindex ambiguous expressions
5601 Expressions can sometimes contain some ambiguous elements. For instance,
5602 some programming languages (notably Ada, C@t{++} and Objective-C) permit
5603 a single function name to be defined several times, for application in
5604 different contexts. This is called @dfn{overloading}. Another example
5605 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
5606 templates and is typically instantiated several times, resulting in
5607 the same function name being defined in different contexts.
5609 In some cases and depending on the language, it is possible to adjust
5610 the expression to remove the ambiguity. For instance in C@t{++}, you
5611 can specify the signature of the function you want to break on, as in
5612 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
5613 qualified name of your function often makes the expression unambiguous
5616 When an ambiguity that needs to be resolved is detected, the debugger
5617 has the capability to display a menu of numbered choices for each
5618 possibility, and then waits for the selection with the prompt @samp{>}.
5619 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
5620 aborts the current command. If the command in which the expression was
5621 used allows more than one choice to be selected, the next option in the
5622 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
5625 For example, the following session excerpt shows an attempt to set a
5626 breakpoint at the overloaded symbol @code{String::after}.
5627 We choose three particular definitions of that function name:
5629 @c FIXME! This is likely to change to show arg type lists, at least
5632 (@value{GDBP}) b String::after
5635 [2] file:String.cc; line number:867
5636 [3] file:String.cc; line number:860
5637 [4] file:String.cc; line number:875
5638 [5] file:String.cc; line number:853
5639 [6] file:String.cc; line number:846
5640 [7] file:String.cc; line number:735
5642 Breakpoint 1 at 0xb26c: file String.cc, line 867.
5643 Breakpoint 2 at 0xb344: file String.cc, line 875.
5644 Breakpoint 3 at 0xafcc: file String.cc, line 846.
5645 Multiple breakpoints were set.
5646 Use the "delete" command to delete unwanted
5653 @kindex set multiple-symbols
5654 @item set multiple-symbols @var{mode}
5655 @cindex multiple-symbols menu
5657 This option allows you to adjust the debugger behavior when an expression
5660 By default, @var{mode} is set to @code{all}. If the command with which
5661 the expression is used allows more than one choice, then @value{GDBN}
5662 automatically selects all possible choices. For instance, inserting
5663 a breakpoint on a function using an ambiguous name results in a breakpoint
5664 inserted on each possible match. However, if a unique choice must be made,
5665 then @value{GDBN} uses the menu to help you disambiguate the expression.
5666 For instance, printing the address of an overloaded function will result
5667 in the use of the menu.
5669 When @var{mode} is set to @code{ask}, the debugger always uses the menu
5670 when an ambiguity is detected.
5672 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
5673 an error due to the ambiguity and the command is aborted.
5675 @kindex show multiple-symbols
5676 @item show multiple-symbols
5677 Show the current value of the @code{multiple-symbols} setting.
5681 @section Program Variables
5683 The most common kind of expression to use is the name of a variable
5686 Variables in expressions are understood in the selected stack frame
5687 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5691 global (or file-static)
5698 visible according to the scope rules of the
5699 programming language from the point of execution in that frame
5702 @noindent This means that in the function
5717 you can examine and use the variable @code{a} whenever your program is
5718 executing within the function @code{foo}, but you can only use or
5719 examine the variable @code{b} while your program is executing inside
5720 the block where @code{b} is declared.
5722 @cindex variable name conflict
5723 There is an exception: you can refer to a variable or function whose
5724 scope is a single source file even if the current execution point is not
5725 in this file. But it is possible to have more than one such variable or
5726 function with the same name (in different source files). If that
5727 happens, referring to that name has unpredictable effects. If you wish,
5728 you can specify a static variable in a particular function or file,
5729 using the colon-colon (@code{::}) notation:
5731 @cindex colon-colon, context for variables/functions
5733 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5734 @cindex @code{::}, context for variables/functions
5737 @var{file}::@var{variable}
5738 @var{function}::@var{variable}
5742 Here @var{file} or @var{function} is the name of the context for the
5743 static @var{variable}. In the case of file names, you can use quotes to
5744 make sure @value{GDBN} parses the file name as a single word---for example,
5745 to print a global value of @code{x} defined in @file{f2.c}:
5748 (@value{GDBP}) p 'f2.c'::x
5751 @cindex C@t{++} scope resolution
5752 This use of @samp{::} is very rarely in conflict with the very similar
5753 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5754 scope resolution operator in @value{GDBN} expressions.
5755 @c FIXME: Um, so what happens in one of those rare cases where it's in
5758 @cindex wrong values
5759 @cindex variable values, wrong
5760 @cindex function entry/exit, wrong values of variables
5761 @cindex optimized code, wrong values of variables
5763 @emph{Warning:} Occasionally, a local variable may appear to have the
5764 wrong value at certain points in a function---just after entry to a new
5765 scope, and just before exit.
5767 You may see this problem when you are stepping by machine instructions.
5768 This is because, on most machines, it takes more than one instruction to
5769 set up a stack frame (including local variable definitions); if you are
5770 stepping by machine instructions, variables may appear to have the wrong
5771 values until the stack frame is completely built. On exit, it usually
5772 also takes more than one machine instruction to destroy a stack frame;
5773 after you begin stepping through that group of instructions, local
5774 variable definitions may be gone.
5776 This may also happen when the compiler does significant optimizations.
5777 To be sure of always seeing accurate values, turn off all optimization
5780 @cindex ``No symbol "foo" in current context''
5781 Another possible effect of compiler optimizations is to optimize
5782 unused variables out of existence, or assign variables to registers (as
5783 opposed to memory addresses). Depending on the support for such cases
5784 offered by the debug info format used by the compiler, @value{GDBN}
5785 might not be able to display values for such local variables. If that
5786 happens, @value{GDBN} will print a message like this:
5789 No symbol "foo" in current context.
5792 To solve such problems, either recompile without optimizations, or use a
5793 different debug info format, if the compiler supports several such
5794 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5795 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5796 produces debug info in a format that is superior to formats such as
5797 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5798 an effective form for debug info. @xref{Debugging Options,,Options
5799 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5800 Compiler Collection (GCC)}.
5801 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5802 that are best suited to C@t{++} programs.
5804 If you ask to print an object whose contents are unknown to
5805 @value{GDBN}, e.g., because its data type is not completely specified
5806 by the debug information, @value{GDBN} will say @samp{<incomplete
5807 type>}. @xref{Symbols, incomplete type}, for more about this.
5809 Strings are identified as arrays of @code{char} values without specified
5810 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5811 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5812 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5813 defines literal string type @code{"char"} as @code{char} without a sign.
5818 signed char var1[] = "A";
5821 You get during debugging
5826 $2 = @{65 'A', 0 '\0'@}
5830 @section Artificial Arrays
5832 @cindex artificial array
5834 @kindex @@@r{, referencing memory as an array}
5835 It is often useful to print out several successive objects of the
5836 same type in memory; a section of an array, or an array of
5837 dynamically determined size for which only a pointer exists in the
5840 You can do this by referring to a contiguous span of memory as an
5841 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5842 operand of @samp{@@} should be the first element of the desired array
5843 and be an individual object. The right operand should be the desired length
5844 of the array. The result is an array value whose elements are all of
5845 the type of the left argument. The first element is actually the left
5846 argument; the second element comes from bytes of memory immediately
5847 following those that hold the first element, and so on. Here is an
5848 example. If a program says
5851 int *array = (int *) malloc (len * sizeof (int));
5855 you can print the contents of @code{array} with
5861 The left operand of @samp{@@} must reside in memory. Array values made
5862 with @samp{@@} in this way behave just like other arrays in terms of
5863 subscripting, and are coerced to pointers when used in expressions.
5864 Artificial arrays most often appear in expressions via the value history
5865 (@pxref{Value History, ,Value History}), after printing one out.
5867 Another way to create an artificial array is to use a cast.
5868 This re-interprets a value as if it were an array.
5869 The value need not be in memory:
5871 (@value{GDBP}) p/x (short[2])0x12345678
5872 $1 = @{0x1234, 0x5678@}
5875 As a convenience, if you leave the array length out (as in
5876 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5877 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5879 (@value{GDBP}) p/x (short[])0x12345678
5880 $2 = @{0x1234, 0x5678@}
5883 Sometimes the artificial array mechanism is not quite enough; in
5884 moderately complex data structures, the elements of interest may not
5885 actually be adjacent---for example, if you are interested in the values
5886 of pointers in an array. One useful work-around in this situation is
5887 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5888 Variables}) as a counter in an expression that prints the first
5889 interesting value, and then repeat that expression via @key{RET}. For
5890 instance, suppose you have an array @code{dtab} of pointers to
5891 structures, and you are interested in the values of a field @code{fv}
5892 in each structure. Here is an example of what you might type:
5902 @node Output Formats
5903 @section Output Formats
5905 @cindex formatted output
5906 @cindex output formats
5907 By default, @value{GDBN} prints a value according to its data type. Sometimes
5908 this is not what you want. For example, you might want to print a number
5909 in hex, or a pointer in decimal. Or you might want to view data in memory
5910 at a certain address as a character string or as an instruction. To do
5911 these things, specify an @dfn{output format} when you print a value.
5913 The simplest use of output formats is to say how to print a value
5914 already computed. This is done by starting the arguments of the
5915 @code{print} command with a slash and a format letter. The format
5916 letters supported are:
5920 Regard the bits of the value as an integer, and print the integer in
5924 Print as integer in signed decimal.
5927 Print as integer in unsigned decimal.
5930 Print as integer in octal.
5933 Print as integer in binary. The letter @samp{t} stands for ``two''.
5934 @footnote{@samp{b} cannot be used because these format letters are also
5935 used with the @code{x} command, where @samp{b} stands for ``byte'';
5936 see @ref{Memory,,Examining Memory}.}
5939 @cindex unknown address, locating
5940 @cindex locate address
5941 Print as an address, both absolute in hexadecimal and as an offset from
5942 the nearest preceding symbol. You can use this format used to discover
5943 where (in what function) an unknown address is located:
5946 (@value{GDBP}) p/a 0x54320
5947 $3 = 0x54320 <_initialize_vx+396>
5951 The command @code{info symbol 0x54320} yields similar results.
5952 @xref{Symbols, info symbol}.
5955 Regard as an integer and print it as a character constant. This
5956 prints both the numerical value and its character representation. The
5957 character representation is replaced with the octal escape @samp{\nnn}
5958 for characters outside the 7-bit @sc{ascii} range.
5960 Without this format, @value{GDBN} displays @code{char},
5961 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
5962 constants. Single-byte members of vectors are displayed as integer
5966 Regard the bits of the value as a floating point number and print
5967 using typical floating point syntax.
5970 @cindex printing strings
5971 @cindex printing byte arrays
5972 Regard as a string, if possible. With this format, pointers to single-byte
5973 data are displayed as null-terminated strings and arrays of single-byte data
5974 are displayed as fixed-length strings. Other values are displayed in their
5977 Without this format, @value{GDBN} displays pointers to and arrays of
5978 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
5979 strings. Single-byte members of a vector are displayed as an integer
5983 For example, to print the program counter in hex (@pxref{Registers}), type
5990 Note that no space is required before the slash; this is because command
5991 names in @value{GDBN} cannot contain a slash.
5993 To reprint the last value in the value history with a different format,
5994 you can use the @code{print} command with just a format and no
5995 expression. For example, @samp{p/x} reprints the last value in hex.
5998 @section Examining Memory
6000 You can use the command @code{x} (for ``examine'') to examine memory in
6001 any of several formats, independently of your program's data types.
6003 @cindex examining memory
6005 @kindex x @r{(examine memory)}
6006 @item x/@var{nfu} @var{addr}
6009 Use the @code{x} command to examine memory.
6012 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6013 much memory to display and how to format it; @var{addr} is an
6014 expression giving the address where you want to start displaying memory.
6015 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6016 Several commands set convenient defaults for @var{addr}.
6019 @item @var{n}, the repeat count
6020 The repeat count is a decimal integer; the default is 1. It specifies
6021 how much memory (counting by units @var{u}) to display.
6022 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6025 @item @var{f}, the display format
6026 The display format is one of the formats used by @code{print}
6027 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6028 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6029 The default is @samp{x} (hexadecimal) initially. The default changes
6030 each time you use either @code{x} or @code{print}.
6032 @item @var{u}, the unit size
6033 The unit size is any of
6039 Halfwords (two bytes).
6041 Words (four bytes). This is the initial default.
6043 Giant words (eight bytes).
6046 Each time you specify a unit size with @code{x}, that size becomes the
6047 default unit the next time you use @code{x}. (For the @samp{s} and
6048 @samp{i} formats, the unit size is ignored and is normally not written.)
6050 @item @var{addr}, starting display address
6051 @var{addr} is the address where you want @value{GDBN} to begin displaying
6052 memory. The expression need not have a pointer value (though it may);
6053 it is always interpreted as an integer address of a byte of memory.
6054 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6055 @var{addr} is usually just after the last address examined---but several
6056 other commands also set the default address: @code{info breakpoints} (to
6057 the address of the last breakpoint listed), @code{info line} (to the
6058 starting address of a line), and @code{print} (if you use it to display
6059 a value from memory).
6062 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6063 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6064 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6065 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6066 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6068 Since the letters indicating unit sizes are all distinct from the
6069 letters specifying output formats, you do not have to remember whether
6070 unit size or format comes first; either order works. The output
6071 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6072 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6074 Even though the unit size @var{u} is ignored for the formats @samp{s}
6075 and @samp{i}, you might still want to use a count @var{n}; for example,
6076 @samp{3i} specifies that you want to see three machine instructions,
6077 including any operands. For convenience, especially when used with
6078 the @code{display} command, the @samp{i} format also prints branch delay
6079 slot instructions, if any, beyond the count specified, which immediately
6080 follow the last instruction that is within the count. The command
6081 @code{disassemble} gives an alternative way of inspecting machine
6082 instructions; see @ref{Machine Code,,Source and Machine Code}.
6084 All the defaults for the arguments to @code{x} are designed to make it
6085 easy to continue scanning memory with minimal specifications each time
6086 you use @code{x}. For example, after you have inspected three machine
6087 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6088 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6089 the repeat count @var{n} is used again; the other arguments default as
6090 for successive uses of @code{x}.
6092 @cindex @code{$_}, @code{$__}, and value history
6093 The addresses and contents printed by the @code{x} command are not saved
6094 in the value history because there is often too much of them and they
6095 would get in the way. Instead, @value{GDBN} makes these values available for
6096 subsequent use in expressions as values of the convenience variables
6097 @code{$_} and @code{$__}. After an @code{x} command, the last address
6098 examined is available for use in expressions in the convenience variable
6099 @code{$_}. The contents of that address, as examined, are available in
6100 the convenience variable @code{$__}.
6102 If the @code{x} command has a repeat count, the address and contents saved
6103 are from the last memory unit printed; this is not the same as the last
6104 address printed if several units were printed on the last line of output.
6106 @cindex remote memory comparison
6107 @cindex verify remote memory image
6108 When you are debugging a program running on a remote target machine
6109 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6110 remote machine's memory against the executable file you downloaded to
6111 the target. The @code{compare-sections} command is provided for such
6115 @kindex compare-sections
6116 @item compare-sections @r{[}@var{section-name}@r{]}
6117 Compare the data of a loadable section @var{section-name} in the
6118 executable file of the program being debugged with the same section in
6119 the remote machine's memory, and report any mismatches. With no
6120 arguments, compares all loadable sections. This command's
6121 availability depends on the target's support for the @code{"qCRC"}
6126 @section Automatic Display
6127 @cindex automatic display
6128 @cindex display of expressions
6130 If you find that you want to print the value of an expression frequently
6131 (to see how it changes), you might want to add it to the @dfn{automatic
6132 display list} so that @value{GDBN} prints its value each time your program stops.
6133 Each expression added to the list is given a number to identify it;
6134 to remove an expression from the list, you specify that number.
6135 The automatic display looks like this:
6139 3: bar[5] = (struct hack *) 0x3804
6143 This display shows item numbers, expressions and their current values. As with
6144 displays you request manually using @code{x} or @code{print}, you can
6145 specify the output format you prefer; in fact, @code{display} decides
6146 whether to use @code{print} or @code{x} depending your format
6147 specification---it uses @code{x} if you specify either the @samp{i}
6148 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6152 @item display @var{expr}
6153 Add the expression @var{expr} to the list of expressions to display
6154 each time your program stops. @xref{Expressions, ,Expressions}.
6156 @code{display} does not repeat if you press @key{RET} again after using it.
6158 @item display/@var{fmt} @var{expr}
6159 For @var{fmt} specifying only a display format and not a size or
6160 count, add the expression @var{expr} to the auto-display list but
6161 arrange to display it each time in the specified format @var{fmt}.
6162 @xref{Output Formats,,Output Formats}.
6164 @item display/@var{fmt} @var{addr}
6165 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6166 number of units, add the expression @var{addr} as a memory address to
6167 be examined each time your program stops. Examining means in effect
6168 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6171 For example, @samp{display/i $pc} can be helpful, to see the machine
6172 instruction about to be executed each time execution stops (@samp{$pc}
6173 is a common name for the program counter; @pxref{Registers, ,Registers}).
6176 @kindex delete display
6178 @item undisplay @var{dnums}@dots{}
6179 @itemx delete display @var{dnums}@dots{}
6180 Remove item numbers @var{dnums} from the list of expressions to display.
6182 @code{undisplay} does not repeat if you press @key{RET} after using it.
6183 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6185 @kindex disable display
6186 @item disable display @var{dnums}@dots{}
6187 Disable the display of item numbers @var{dnums}. A disabled display
6188 item is not printed automatically, but is not forgotten. It may be
6189 enabled again later.
6191 @kindex enable display
6192 @item enable display @var{dnums}@dots{}
6193 Enable display of item numbers @var{dnums}. It becomes effective once
6194 again in auto display of its expression, until you specify otherwise.
6197 Display the current values of the expressions on the list, just as is
6198 done when your program stops.
6200 @kindex info display
6202 Print the list of expressions previously set up to display
6203 automatically, each one with its item number, but without showing the
6204 values. This includes disabled expressions, which are marked as such.
6205 It also includes expressions which would not be displayed right now
6206 because they refer to automatic variables not currently available.
6209 @cindex display disabled out of scope
6210 If a display expression refers to local variables, then it does not make
6211 sense outside the lexical context for which it was set up. Such an
6212 expression is disabled when execution enters a context where one of its
6213 variables is not defined. For example, if you give the command
6214 @code{display last_char} while inside a function with an argument
6215 @code{last_char}, @value{GDBN} displays this argument while your program
6216 continues to stop inside that function. When it stops elsewhere---where
6217 there is no variable @code{last_char}---the display is disabled
6218 automatically. The next time your program stops where @code{last_char}
6219 is meaningful, you can enable the display expression once again.
6221 @node Print Settings
6222 @section Print Settings
6224 @cindex format options
6225 @cindex print settings
6226 @value{GDBN} provides the following ways to control how arrays, structures,
6227 and symbols are printed.
6230 These settings are useful for debugging programs in any language:
6234 @item set print address
6235 @itemx set print address on
6236 @cindex print/don't print memory addresses
6237 @value{GDBN} prints memory addresses showing the location of stack
6238 traces, structure values, pointer values, breakpoints, and so forth,
6239 even when it also displays the contents of those addresses. The default
6240 is @code{on}. For example, this is what a stack frame display looks like with
6241 @code{set print address on}:
6246 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6248 530 if (lquote != def_lquote)
6252 @item set print address off
6253 Do not print addresses when displaying their contents. For example,
6254 this is the same stack frame displayed with @code{set print address off}:
6258 (@value{GDBP}) set print addr off
6260 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6261 530 if (lquote != def_lquote)
6265 You can use @samp{set print address off} to eliminate all machine
6266 dependent displays from the @value{GDBN} interface. For example, with
6267 @code{print address off}, you should get the same text for backtraces on
6268 all machines---whether or not they involve pointer arguments.
6271 @item show print address
6272 Show whether or not addresses are to be printed.
6275 When @value{GDBN} prints a symbolic address, it normally prints the
6276 closest earlier symbol plus an offset. If that symbol does not uniquely
6277 identify the address (for example, it is a name whose scope is a single
6278 source file), you may need to clarify. One way to do this is with
6279 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6280 you can set @value{GDBN} to print the source file and line number when
6281 it prints a symbolic address:
6284 @item set print symbol-filename on
6285 @cindex source file and line of a symbol
6286 @cindex symbol, source file and line
6287 Tell @value{GDBN} to print the source file name and line number of a
6288 symbol in the symbolic form of an address.
6290 @item set print symbol-filename off
6291 Do not print source file name and line number of a symbol. This is the
6294 @item show print symbol-filename
6295 Show whether or not @value{GDBN} will print the source file name and
6296 line number of a symbol in the symbolic form of an address.
6299 Another situation where it is helpful to show symbol filenames and line
6300 numbers is when disassembling code; @value{GDBN} shows you the line
6301 number and source file that corresponds to each instruction.
6303 Also, you may wish to see the symbolic form only if the address being
6304 printed is reasonably close to the closest earlier symbol:
6307 @item set print max-symbolic-offset @var{max-offset}
6308 @cindex maximum value for offset of closest symbol
6309 Tell @value{GDBN} to only display the symbolic form of an address if the
6310 offset between the closest earlier symbol and the address is less than
6311 @var{max-offset}. The default is 0, which tells @value{GDBN}
6312 to always print the symbolic form of an address if any symbol precedes it.
6314 @item show print max-symbolic-offset
6315 Ask how large the maximum offset is that @value{GDBN} prints in a
6319 @cindex wild pointer, interpreting
6320 @cindex pointer, finding referent
6321 If you have a pointer and you are not sure where it points, try
6322 @samp{set print symbol-filename on}. Then you can determine the name
6323 and source file location of the variable where it points, using
6324 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6325 For example, here @value{GDBN} shows that a variable @code{ptt} points
6326 at another variable @code{t}, defined in @file{hi2.c}:
6329 (@value{GDBP}) set print symbol-filename on
6330 (@value{GDBP}) p/a ptt
6331 $4 = 0xe008 <t in hi2.c>
6335 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6336 does not show the symbol name and filename of the referent, even with
6337 the appropriate @code{set print} options turned on.
6340 Other settings control how different kinds of objects are printed:
6343 @item set print array
6344 @itemx set print array on
6345 @cindex pretty print arrays
6346 Pretty print arrays. This format is more convenient to read,
6347 but uses more space. The default is off.
6349 @item set print array off
6350 Return to compressed format for arrays.
6352 @item show print array
6353 Show whether compressed or pretty format is selected for displaying
6356 @cindex print array indexes
6357 @item set print array-indexes
6358 @itemx set print array-indexes on
6359 Print the index of each element when displaying arrays. May be more
6360 convenient to locate a given element in the array or quickly find the
6361 index of a given element in that printed array. The default is off.
6363 @item set print array-indexes off
6364 Stop printing element indexes when displaying arrays.
6366 @item show print array-indexes
6367 Show whether the index of each element is printed when displaying
6370 @item set print elements @var{number-of-elements}
6371 @cindex number of array elements to print
6372 @cindex limit on number of printed array elements
6373 Set a limit on how many elements of an array @value{GDBN} will print.
6374 If @value{GDBN} is printing a large array, it stops printing after it has
6375 printed the number of elements set by the @code{set print elements} command.
6376 This limit also applies to the display of strings.
6377 When @value{GDBN} starts, this limit is set to 200.
6378 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6380 @item show print elements
6381 Display the number of elements of a large array that @value{GDBN} will print.
6382 If the number is 0, then the printing is unlimited.
6384 @item set print frame-arguments @var{value}
6385 @cindex printing frame argument values
6386 @cindex print all frame argument values
6387 @cindex print frame argument values for scalars only
6388 @cindex do not print frame argument values
6389 This command allows to control how the values of arguments are printed
6390 when the debugger prints a frame (@pxref{Frames}). The possible
6395 The values of all arguments are printed. This is the default.
6398 Print the value of an argument only if it is a scalar. The value of more
6399 complex arguments such as arrays, structures, unions, etc, is replaced
6400 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6403 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6408 None of the argument values are printed. Instead, the value of each argument
6409 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6412 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6417 By default, all argument values are always printed. But this command
6418 can be useful in several cases. For instance, it can be used to reduce
6419 the amount of information printed in each frame, making the backtrace
6420 more readable. Also, this command can be used to improve performance
6421 when displaying Ada frames, because the computation of large arguments
6422 can sometimes be CPU-intensive, especiallly in large applications.
6423 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6424 avoids this computation, thus speeding up the display of each Ada frame.
6426 @item show print frame-arguments
6427 Show how the value of arguments should be displayed when printing a frame.
6429 @item set print repeats
6430 @cindex repeated array elements
6431 Set the threshold for suppressing display of repeated array
6432 elements. When the number of consecutive identical elements of an
6433 array exceeds the threshold, @value{GDBN} prints the string
6434 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6435 identical repetitions, instead of displaying the identical elements
6436 themselves. Setting the threshold to zero will cause all elements to
6437 be individually printed. The default threshold is 10.
6439 @item show print repeats
6440 Display the current threshold for printing repeated identical
6443 @item set print null-stop
6444 @cindex @sc{null} elements in arrays
6445 Cause @value{GDBN} to stop printing the characters of an array when the first
6446 @sc{null} is encountered. This is useful when large arrays actually
6447 contain only short strings.
6450 @item show print null-stop
6451 Show whether @value{GDBN} stops printing an array on the first
6452 @sc{null} character.
6454 @item set print pretty on
6455 @cindex print structures in indented form
6456 @cindex indentation in structure display
6457 Cause @value{GDBN} to print structures in an indented format with one member
6458 per line, like this:
6473 @item set print pretty off
6474 Cause @value{GDBN} to print structures in a compact format, like this:
6478 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6479 meat = 0x54 "Pork"@}
6484 This is the default format.
6486 @item show print pretty
6487 Show which format @value{GDBN} is using to print structures.
6489 @item set print sevenbit-strings on
6490 @cindex eight-bit characters in strings
6491 @cindex octal escapes in strings
6492 Print using only seven-bit characters; if this option is set,
6493 @value{GDBN} displays any eight-bit characters (in strings or
6494 character values) using the notation @code{\}@var{nnn}. This setting is
6495 best if you are working in English (@sc{ascii}) and you use the
6496 high-order bit of characters as a marker or ``meta'' bit.
6498 @item set print sevenbit-strings off
6499 Print full eight-bit characters. This allows the use of more
6500 international character sets, and is the default.
6502 @item show print sevenbit-strings
6503 Show whether or not @value{GDBN} is printing only seven-bit characters.
6505 @item set print union on
6506 @cindex unions in structures, printing
6507 Tell @value{GDBN} to print unions which are contained in structures
6508 and other unions. This is the default setting.
6510 @item set print union off
6511 Tell @value{GDBN} not to print unions which are contained in
6512 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6515 @item show print union
6516 Ask @value{GDBN} whether or not it will print unions which are contained in
6517 structures and other unions.
6519 For example, given the declarations
6522 typedef enum @{Tree, Bug@} Species;
6523 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6524 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6535 struct thing foo = @{Tree, @{Acorn@}@};
6539 with @code{set print union on} in effect @samp{p foo} would print
6542 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6546 and with @code{set print union off} in effect it would print
6549 $1 = @{it = Tree, form = @{...@}@}
6553 @code{set print union} affects programs written in C-like languages
6559 These settings are of interest when debugging C@t{++} programs:
6562 @cindex demangling C@t{++} names
6563 @item set print demangle
6564 @itemx set print demangle on
6565 Print C@t{++} names in their source form rather than in the encoded
6566 (``mangled'') form passed to the assembler and linker for type-safe
6567 linkage. The default is on.
6569 @item show print demangle
6570 Show whether C@t{++} names are printed in mangled or demangled form.
6572 @item set print asm-demangle
6573 @itemx set print asm-demangle on
6574 Print C@t{++} names in their source form rather than their mangled form, even
6575 in assembler code printouts such as instruction disassemblies.
6578 @item show print asm-demangle
6579 Show whether C@t{++} names in assembly listings are printed in mangled
6582 @cindex C@t{++} symbol decoding style
6583 @cindex symbol decoding style, C@t{++}
6584 @kindex set demangle-style
6585 @item set demangle-style @var{style}
6586 Choose among several encoding schemes used by different compilers to
6587 represent C@t{++} names. The choices for @var{style} are currently:
6591 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6594 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6595 This is the default.
6598 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6601 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6604 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6605 @strong{Warning:} this setting alone is not sufficient to allow
6606 debugging @code{cfront}-generated executables. @value{GDBN} would
6607 require further enhancement to permit that.
6610 If you omit @var{style}, you will see a list of possible formats.
6612 @item show demangle-style
6613 Display the encoding style currently in use for decoding C@t{++} symbols.
6615 @item set print object
6616 @itemx set print object on
6617 @cindex derived type of an object, printing
6618 @cindex display derived types
6619 When displaying a pointer to an object, identify the @emph{actual}
6620 (derived) type of the object rather than the @emph{declared} type, using
6621 the virtual function table.
6623 @item set print object off
6624 Display only the declared type of objects, without reference to the
6625 virtual function table. This is the default setting.
6627 @item show print object
6628 Show whether actual, or declared, object types are displayed.
6630 @item set print static-members
6631 @itemx set print static-members on
6632 @cindex static members of C@t{++} objects
6633 Print static members when displaying a C@t{++} object. The default is on.
6635 @item set print static-members off
6636 Do not print static members when displaying a C@t{++} object.
6638 @item show print static-members
6639 Show whether C@t{++} static members are printed or not.
6641 @item set print pascal_static-members
6642 @itemx set print pascal_static-members on
6643 @cindex static members of Pascal objects
6644 @cindex Pascal objects, static members display
6645 Print static members when displaying a Pascal object. The default is on.
6647 @item set print pascal_static-members off
6648 Do not print static members when displaying a Pascal object.
6650 @item show print pascal_static-members
6651 Show whether Pascal static members are printed or not.
6653 @c These don't work with HP ANSI C++ yet.
6654 @item set print vtbl
6655 @itemx set print vtbl on
6656 @cindex pretty print C@t{++} virtual function tables
6657 @cindex virtual functions (C@t{++}) display
6658 @cindex VTBL display
6659 Pretty print C@t{++} virtual function tables. The default is off.
6660 (The @code{vtbl} commands do not work on programs compiled with the HP
6661 ANSI C@t{++} compiler (@code{aCC}).)
6663 @item set print vtbl off
6664 Do not pretty print C@t{++} virtual function tables.
6666 @item show print vtbl
6667 Show whether C@t{++} virtual function tables are pretty printed, or not.
6671 @section Value History
6673 @cindex value history
6674 @cindex history of values printed by @value{GDBN}
6675 Values printed by the @code{print} command are saved in the @value{GDBN}
6676 @dfn{value history}. This allows you to refer to them in other expressions.
6677 Values are kept until the symbol table is re-read or discarded
6678 (for example with the @code{file} or @code{symbol-file} commands).
6679 When the symbol table changes, the value history is discarded,
6680 since the values may contain pointers back to the types defined in the
6685 @cindex history number
6686 The values printed are given @dfn{history numbers} by which you can
6687 refer to them. These are successive integers starting with one.
6688 @code{print} shows you the history number assigned to a value by
6689 printing @samp{$@var{num} = } before the value; here @var{num} is the
6692 To refer to any previous value, use @samp{$} followed by the value's
6693 history number. The way @code{print} labels its output is designed to
6694 remind you of this. Just @code{$} refers to the most recent value in
6695 the history, and @code{$$} refers to the value before that.
6696 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6697 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6698 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6700 For example, suppose you have just printed a pointer to a structure and
6701 want to see the contents of the structure. It suffices to type
6707 If you have a chain of structures where the component @code{next} points
6708 to the next one, you can print the contents of the next one with this:
6715 You can print successive links in the chain by repeating this
6716 command---which you can do by just typing @key{RET}.
6718 Note that the history records values, not expressions. If the value of
6719 @code{x} is 4 and you type these commands:
6727 then the value recorded in the value history by the @code{print} command
6728 remains 4 even though the value of @code{x} has changed.
6733 Print the last ten values in the value history, with their item numbers.
6734 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6735 values} does not change the history.
6737 @item show values @var{n}
6738 Print ten history values centered on history item number @var{n}.
6741 Print ten history values just after the values last printed. If no more
6742 values are available, @code{show values +} produces no display.
6745 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6746 same effect as @samp{show values +}.
6748 @node Convenience Vars
6749 @section Convenience Variables
6751 @cindex convenience variables
6752 @cindex user-defined variables
6753 @value{GDBN} provides @dfn{convenience variables} that you can use within
6754 @value{GDBN} to hold on to a value and refer to it later. These variables
6755 exist entirely within @value{GDBN}; they are not part of your program, and
6756 setting a convenience variable has no direct effect on further execution
6757 of your program. That is why you can use them freely.
6759 Convenience variables are prefixed with @samp{$}. Any name preceded by
6760 @samp{$} can be used for a convenience variable, unless it is one of
6761 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6762 (Value history references, in contrast, are @emph{numbers} preceded
6763 by @samp{$}. @xref{Value History, ,Value History}.)
6765 You can save a value in a convenience variable with an assignment
6766 expression, just as you would set a variable in your program.
6770 set $foo = *object_ptr
6774 would save in @code{$foo} the value contained in the object pointed to by
6777 Using a convenience variable for the first time creates it, but its
6778 value is @code{void} until you assign a new value. You can alter the
6779 value with another assignment at any time.
6781 Convenience variables have no fixed types. You can assign a convenience
6782 variable any type of value, including structures and arrays, even if
6783 that variable already has a value of a different type. The convenience
6784 variable, when used as an expression, has the type of its current value.
6787 @kindex show convenience
6788 @cindex show all user variables
6789 @item show convenience
6790 Print a list of convenience variables used so far, and their values.
6791 Abbreviated @code{show conv}.
6793 @kindex init-if-undefined
6794 @cindex convenience variables, initializing
6795 @item init-if-undefined $@var{variable} = @var{expression}
6796 Set a convenience variable if it has not already been set. This is useful
6797 for user-defined commands that keep some state. It is similar, in concept,
6798 to using local static variables with initializers in C (except that
6799 convenience variables are global). It can also be used to allow users to
6800 override default values used in a command script.
6802 If the variable is already defined then the expression is not evaluated so
6803 any side-effects do not occur.
6806 One of the ways to use a convenience variable is as a counter to be
6807 incremented or a pointer to be advanced. For example, to print
6808 a field from successive elements of an array of structures:
6812 print bar[$i++]->contents
6816 Repeat that command by typing @key{RET}.
6818 Some convenience variables are created automatically by @value{GDBN} and given
6819 values likely to be useful.
6822 @vindex $_@r{, convenience variable}
6824 The variable @code{$_} is automatically set by the @code{x} command to
6825 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6826 commands which provide a default address for @code{x} to examine also
6827 set @code{$_} to that address; these commands include @code{info line}
6828 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6829 except when set by the @code{x} command, in which case it is a pointer
6830 to the type of @code{$__}.
6832 @vindex $__@r{, convenience variable}
6834 The variable @code{$__} is automatically set by the @code{x} command
6835 to the value found in the last address examined. Its type is chosen
6836 to match the format in which the data was printed.
6839 @vindex $_exitcode@r{, convenience variable}
6840 The variable @code{$_exitcode} is automatically set to the exit code when
6841 the program being debugged terminates.
6844 On HP-UX systems, if you refer to a function or variable name that
6845 begins with a dollar sign, @value{GDBN} searches for a user or system
6846 name first, before it searches for a convenience variable.
6852 You can refer to machine register contents, in expressions, as variables
6853 with names starting with @samp{$}. The names of registers are different
6854 for each machine; use @code{info registers} to see the names used on
6858 @kindex info registers
6859 @item info registers
6860 Print the names and values of all registers except floating-point
6861 and vector registers (in the selected stack frame).
6863 @kindex info all-registers
6864 @cindex floating point registers
6865 @item info all-registers
6866 Print the names and values of all registers, including floating-point
6867 and vector registers (in the selected stack frame).
6869 @item info registers @var{regname} @dots{}
6870 Print the @dfn{relativized} value of each specified register @var{regname}.
6871 As discussed in detail below, register values are normally relative to
6872 the selected stack frame. @var{regname} may be any register name valid on
6873 the machine you are using, with or without the initial @samp{$}.
6876 @cindex stack pointer register
6877 @cindex program counter register
6878 @cindex process status register
6879 @cindex frame pointer register
6880 @cindex standard registers
6881 @value{GDBN} has four ``standard'' register names that are available (in
6882 expressions) on most machines---whenever they do not conflict with an
6883 architecture's canonical mnemonics for registers. The register names
6884 @code{$pc} and @code{$sp} are used for the program counter register and
6885 the stack pointer. @code{$fp} is used for a register that contains a
6886 pointer to the current stack frame, and @code{$ps} is used for a
6887 register that contains the processor status. For example,
6888 you could print the program counter in hex with
6895 or print the instruction to be executed next with
6902 or add four to the stack pointer@footnote{This is a way of removing
6903 one word from the stack, on machines where stacks grow downward in
6904 memory (most machines, nowadays). This assumes that the innermost
6905 stack frame is selected; setting @code{$sp} is not allowed when other
6906 stack frames are selected. To pop entire frames off the stack,
6907 regardless of machine architecture, use @code{return};
6908 see @ref{Returning, ,Returning from a Function}.} with
6914 Whenever possible, these four standard register names are available on
6915 your machine even though the machine has different canonical mnemonics,
6916 so long as there is no conflict. The @code{info registers} command
6917 shows the canonical names. For example, on the SPARC, @code{info
6918 registers} displays the processor status register as @code{$psr} but you
6919 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6920 is an alias for the @sc{eflags} register.
6922 @value{GDBN} always considers the contents of an ordinary register as an
6923 integer when the register is examined in this way. Some machines have
6924 special registers which can hold nothing but floating point; these
6925 registers are considered to have floating point values. There is no way
6926 to refer to the contents of an ordinary register as floating point value
6927 (although you can @emph{print} it as a floating point value with
6928 @samp{print/f $@var{regname}}).
6930 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6931 means that the data format in which the register contents are saved by
6932 the operating system is not the same one that your program normally
6933 sees. For example, the registers of the 68881 floating point
6934 coprocessor are always saved in ``extended'' (raw) format, but all C
6935 programs expect to work with ``double'' (virtual) format. In such
6936 cases, @value{GDBN} normally works with the virtual format only (the format
6937 that makes sense for your program), but the @code{info registers} command
6938 prints the data in both formats.
6940 @cindex SSE registers (x86)
6941 @cindex MMX registers (x86)
6942 Some machines have special registers whose contents can be interpreted
6943 in several different ways. For example, modern x86-based machines
6944 have SSE and MMX registers that can hold several values packed
6945 together in several different formats. @value{GDBN} refers to such
6946 registers in @code{struct} notation:
6949 (@value{GDBP}) print $xmm1
6951 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6952 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6953 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6954 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6955 v4_int32 = @{0, 20657912, 11, 13@},
6956 v2_int64 = @{88725056443645952, 55834574859@},
6957 uint128 = 0x0000000d0000000b013b36f800000000
6962 To set values of such registers, you need to tell @value{GDBN} which
6963 view of the register you wish to change, as if you were assigning
6964 value to a @code{struct} member:
6967 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6970 Normally, register values are relative to the selected stack frame
6971 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
6972 value that the register would contain if all stack frames farther in
6973 were exited and their saved registers restored. In order to see the
6974 true contents of hardware registers, you must select the innermost
6975 frame (with @samp{frame 0}).
6977 However, @value{GDBN} must deduce where registers are saved, from the machine
6978 code generated by your compiler. If some registers are not saved, or if
6979 @value{GDBN} is unable to locate the saved registers, the selected stack
6980 frame makes no difference.
6982 @node Floating Point Hardware
6983 @section Floating Point Hardware
6984 @cindex floating point
6986 Depending on the configuration, @value{GDBN} may be able to give
6987 you more information about the status of the floating point hardware.
6992 Display hardware-dependent information about the floating
6993 point unit. The exact contents and layout vary depending on the
6994 floating point chip. Currently, @samp{info float} is supported on
6995 the ARM and x86 machines.
6999 @section Vector Unit
7002 Depending on the configuration, @value{GDBN} may be able to give you
7003 more information about the status of the vector unit.
7008 Display information about the vector unit. The exact contents and
7009 layout vary depending on the hardware.
7012 @node OS Information
7013 @section Operating System Auxiliary Information
7014 @cindex OS information
7016 @value{GDBN} provides interfaces to useful OS facilities that can help
7017 you debug your program.
7019 @cindex @code{ptrace} system call
7020 @cindex @code{struct user} contents
7021 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7022 machines), it interfaces with the inferior via the @code{ptrace}
7023 system call. The operating system creates a special sata structure,
7024 called @code{struct user}, for this interface. You can use the
7025 command @code{info udot} to display the contents of this data
7031 Display the contents of the @code{struct user} maintained by the OS
7032 kernel for the program being debugged. @value{GDBN} displays the
7033 contents of @code{struct user} as a list of hex numbers, similar to
7034 the @code{examine} command.
7037 @cindex auxiliary vector
7038 @cindex vector, auxiliary
7039 Some operating systems supply an @dfn{auxiliary vector} to programs at
7040 startup. This is akin to the arguments and environment that you
7041 specify for a program, but contains a system-dependent variety of
7042 binary values that tell system libraries important details about the
7043 hardware, operating system, and process. Each value's purpose is
7044 identified by an integer tag; the meanings are well-known but system-specific.
7045 Depending on the configuration and operating system facilities,
7046 @value{GDBN} may be able to show you this information. For remote
7047 targets, this functionality may further depend on the remote stub's
7048 support of the @samp{qXfer:auxv:read} packet, see
7049 @ref{qXfer auxiliary vector read}.
7054 Display the auxiliary vector of the inferior, which can be either a
7055 live process or a core dump file. @value{GDBN} prints each tag value
7056 numerically, and also shows names and text descriptions for recognized
7057 tags. Some values in the vector are numbers, some bit masks, and some
7058 pointers to strings or other data. @value{GDBN} displays each value in the
7059 most appropriate form for a recognized tag, and in hexadecimal for
7060 an unrecognized tag.
7064 @node Memory Region Attributes
7065 @section Memory Region Attributes
7066 @cindex memory region attributes
7068 @dfn{Memory region attributes} allow you to describe special handling
7069 required by regions of your target's memory. @value{GDBN} uses
7070 attributes to determine whether to allow certain types of memory
7071 accesses; whether to use specific width accesses; and whether to cache
7072 target memory. By default the description of memory regions is
7073 fetched from the target (if the current target supports this), but the
7074 user can override the fetched regions.
7076 Defined memory regions can be individually enabled and disabled. When a
7077 memory region is disabled, @value{GDBN} uses the default attributes when
7078 accessing memory in that region. Similarly, if no memory regions have
7079 been defined, @value{GDBN} uses the default attributes when accessing
7082 When a memory region is defined, it is given a number to identify it;
7083 to enable, disable, or remove a memory region, you specify that number.
7087 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7088 Define a memory region bounded by @var{lower} and @var{upper} with
7089 attributes @var{attributes}@dots{}, and add it to the list of regions
7090 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7091 case: it is treated as the target's maximum memory address.
7092 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7095 Discard any user changes to the memory regions and use target-supplied
7096 regions, if available, or no regions if the target does not support.
7099 @item delete mem @var{nums}@dots{}
7100 Remove memory regions @var{nums}@dots{} from the list of regions
7101 monitored by @value{GDBN}.
7104 @item disable mem @var{nums}@dots{}
7105 Disable monitoring of memory regions @var{nums}@dots{}.
7106 A disabled memory region is not forgotten.
7107 It may be enabled again later.
7110 @item enable mem @var{nums}@dots{}
7111 Enable monitoring of memory regions @var{nums}@dots{}.
7115 Print a table of all defined memory regions, with the following columns
7119 @item Memory Region Number
7120 @item Enabled or Disabled.
7121 Enabled memory regions are marked with @samp{y}.
7122 Disabled memory regions are marked with @samp{n}.
7125 The address defining the inclusive lower bound of the memory region.
7128 The address defining the exclusive upper bound of the memory region.
7131 The list of attributes set for this memory region.
7136 @subsection Attributes
7138 @subsubsection Memory Access Mode
7139 The access mode attributes set whether @value{GDBN} may make read or
7140 write accesses to a memory region.
7142 While these attributes prevent @value{GDBN} from performing invalid
7143 memory accesses, they do nothing to prevent the target system, I/O DMA,
7144 etc.@: from accessing memory.
7148 Memory is read only.
7150 Memory is write only.
7152 Memory is read/write. This is the default.
7155 @subsubsection Memory Access Size
7156 The access size attribute tells @value{GDBN} to use specific sized
7157 accesses in the memory region. Often memory mapped device registers
7158 require specific sized accesses. If no access size attribute is
7159 specified, @value{GDBN} may use accesses of any size.
7163 Use 8 bit memory accesses.
7165 Use 16 bit memory accesses.
7167 Use 32 bit memory accesses.
7169 Use 64 bit memory accesses.
7172 @c @subsubsection Hardware/Software Breakpoints
7173 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7174 @c will use hardware or software breakpoints for the internal breakpoints
7175 @c used by the step, next, finish, until, etc. commands.
7179 @c Always use hardware breakpoints
7180 @c @item swbreak (default)
7183 @subsubsection Data Cache
7184 The data cache attributes set whether @value{GDBN} will cache target
7185 memory. While this generally improves performance by reducing debug
7186 protocol overhead, it can lead to incorrect results because @value{GDBN}
7187 does not know about volatile variables or memory mapped device
7192 Enable @value{GDBN} to cache target memory.
7194 Disable @value{GDBN} from caching target memory. This is the default.
7197 @subsection Memory Access Checking
7198 @value{GDBN} can be instructed to refuse accesses to memory that is
7199 not explicitly described. This can be useful if accessing such
7200 regions has undesired effects for a specific target, or to provide
7201 better error checking. The following commands control this behaviour.
7204 @kindex set mem inaccessible-by-default
7205 @item set mem inaccessible-by-default [on|off]
7206 If @code{on} is specified, make @value{GDBN} treat memory not
7207 explicitly described by the memory ranges as non-existent and refuse accesses
7208 to such memory. The checks are only performed if there's at least one
7209 memory range defined. If @code{off} is specified, make @value{GDBN}
7210 treat the memory not explicitly described by the memory ranges as RAM.
7211 The default value is @code{on}.
7212 @kindex show mem inaccessible-by-default
7213 @item show mem inaccessible-by-default
7214 Show the current handling of accesses to unknown memory.
7218 @c @subsubsection Memory Write Verification
7219 @c The memory write verification attributes set whether @value{GDBN}
7220 @c will re-reads data after each write to verify the write was successful.
7224 @c @item noverify (default)
7227 @node Dump/Restore Files
7228 @section Copy Between Memory and a File
7229 @cindex dump/restore files
7230 @cindex append data to a file
7231 @cindex dump data to a file
7232 @cindex restore data from a file
7234 You can use the commands @code{dump}, @code{append}, and
7235 @code{restore} to copy data between target memory and a file. The
7236 @code{dump} and @code{append} commands write data to a file, and the
7237 @code{restore} command reads data from a file back into the inferior's
7238 memory. Files may be in binary, Motorola S-record, Intel hex, or
7239 Tektronix Hex format; however, @value{GDBN} can only append to binary
7245 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7246 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7247 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7248 or the value of @var{expr}, to @var{filename} in the given format.
7250 The @var{format} parameter may be any one of:
7257 Motorola S-record format.
7259 Tektronix Hex format.
7262 @value{GDBN} uses the same definitions of these formats as the
7263 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7264 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7268 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7269 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7270 Append the contents of memory from @var{start_addr} to @var{end_addr},
7271 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7272 (@value{GDBN} can only append data to files in raw binary form.)
7275 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7276 Restore the contents of file @var{filename} into memory. The
7277 @code{restore} command can automatically recognize any known @sc{bfd}
7278 file format, except for raw binary. To restore a raw binary file you
7279 must specify the optional keyword @code{binary} after the filename.
7281 If @var{bias} is non-zero, its value will be added to the addresses
7282 contained in the file. Binary files always start at address zero, so
7283 they will be restored at address @var{bias}. Other bfd files have
7284 a built-in location; they will be restored at offset @var{bias}
7287 If @var{start} and/or @var{end} are non-zero, then only data between
7288 file offset @var{start} and file offset @var{end} will be restored.
7289 These offsets are relative to the addresses in the file, before
7290 the @var{bias} argument is applied.
7294 @node Core File Generation
7295 @section How to Produce a Core File from Your Program
7296 @cindex dump core from inferior
7298 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7299 image of a running process and its process status (register values
7300 etc.). Its primary use is post-mortem debugging of a program that
7301 crashed while it ran outside a debugger. A program that crashes
7302 automatically produces a core file, unless this feature is disabled by
7303 the user. @xref{Files}, for information on invoking @value{GDBN} in
7304 the post-mortem debugging mode.
7306 Occasionally, you may wish to produce a core file of the program you
7307 are debugging in order to preserve a snapshot of its state.
7308 @value{GDBN} has a special command for that.
7312 @kindex generate-core-file
7313 @item generate-core-file [@var{file}]
7314 @itemx gcore [@var{file}]
7315 Produce a core dump of the inferior process. The optional argument
7316 @var{file} specifies the file name where to put the core dump. If not
7317 specified, the file name defaults to @file{core.@var{pid}}, where
7318 @var{pid} is the inferior process ID.
7320 Note that this command is implemented only for some systems (as of
7321 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7324 @node Character Sets
7325 @section Character Sets
7326 @cindex character sets
7328 @cindex translating between character sets
7329 @cindex host character set
7330 @cindex target character set
7332 If the program you are debugging uses a different character set to
7333 represent characters and strings than the one @value{GDBN} uses itself,
7334 @value{GDBN} can automatically translate between the character sets for
7335 you. The character set @value{GDBN} uses we call the @dfn{host
7336 character set}; the one the inferior program uses we call the
7337 @dfn{target character set}.
7339 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7340 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7341 remote protocol (@pxref{Remote Debugging}) to debug a program
7342 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7343 then the host character set is Latin-1, and the target character set is
7344 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7345 target-charset EBCDIC-US}, then @value{GDBN} translates between
7346 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7347 character and string literals in expressions.
7349 @value{GDBN} has no way to automatically recognize which character set
7350 the inferior program uses; you must tell it, using the @code{set
7351 target-charset} command, described below.
7353 Here are the commands for controlling @value{GDBN}'s character set
7357 @item set target-charset @var{charset}
7358 @kindex set target-charset
7359 Set the current target character set to @var{charset}. We list the
7360 character set names @value{GDBN} recognizes below, but if you type
7361 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7362 list the target character sets it supports.
7366 @item set host-charset @var{charset}
7367 @kindex set host-charset
7368 Set the current host character set to @var{charset}.
7370 By default, @value{GDBN} uses a host character set appropriate to the
7371 system it is running on; you can override that default using the
7372 @code{set host-charset} command.
7374 @value{GDBN} can only use certain character sets as its host character
7375 set. We list the character set names @value{GDBN} recognizes below, and
7376 indicate which can be host character sets, but if you type
7377 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7378 list the host character sets it supports.
7380 @item set charset @var{charset}
7382 Set the current host and target character sets to @var{charset}. As
7383 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7384 @value{GDBN} will list the name of the character sets that can be used
7385 for both host and target.
7389 @kindex show charset
7390 Show the names of the current host and target charsets.
7392 @itemx show host-charset
7393 @kindex show host-charset
7394 Show the name of the current host charset.
7396 @itemx show target-charset
7397 @kindex show target-charset
7398 Show the name of the current target charset.
7402 @value{GDBN} currently includes support for the following character
7408 @cindex ASCII character set
7409 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7413 @cindex ISO 8859-1 character set
7414 @cindex ISO Latin 1 character set
7415 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7416 characters needed for French, German, and Spanish. @value{GDBN} can use
7417 this as its host character set.
7421 @cindex EBCDIC character set
7422 @cindex IBM1047 character set
7423 Variants of the @sc{ebcdic} character set, used on some of IBM's
7424 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7425 @value{GDBN} cannot use these as its host character set.
7429 Note that these are all single-byte character sets. More work inside
7430 @value{GDBN} is needed to support multi-byte or variable-width character
7431 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7433 Here is an example of @value{GDBN}'s character set support in action.
7434 Assume that the following source code has been placed in the file
7435 @file{charset-test.c}:
7441 = @{72, 101, 108, 108, 111, 44, 32, 119,
7442 111, 114, 108, 100, 33, 10, 0@};
7443 char ibm1047_hello[]
7444 = @{200, 133, 147, 147, 150, 107, 64, 166,
7445 150, 153, 147, 132, 90, 37, 0@};
7449 printf ("Hello, world!\n");
7453 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7454 containing the string @samp{Hello, world!} followed by a newline,
7455 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7457 We compile the program, and invoke the debugger on it:
7460 $ gcc -g charset-test.c -o charset-test
7461 $ gdb -nw charset-test
7462 GNU gdb 2001-12-19-cvs
7463 Copyright 2001 Free Software Foundation, Inc.
7468 We can use the @code{show charset} command to see what character sets
7469 @value{GDBN} is currently using to interpret and display characters and
7473 (@value{GDBP}) show charset
7474 The current host and target character set is `ISO-8859-1'.
7478 For the sake of printing this manual, let's use @sc{ascii} as our
7479 initial character set:
7481 (@value{GDBP}) set charset ASCII
7482 (@value{GDBP}) show charset
7483 The current host and target character set is `ASCII'.
7487 Let's assume that @sc{ascii} is indeed the correct character set for our
7488 host system --- in other words, let's assume that if @value{GDBN} prints
7489 characters using the @sc{ascii} character set, our terminal will display
7490 them properly. Since our current target character set is also
7491 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7494 (@value{GDBP}) print ascii_hello
7495 $1 = 0x401698 "Hello, world!\n"
7496 (@value{GDBP}) print ascii_hello[0]
7501 @value{GDBN} uses the target character set for character and string
7502 literals you use in expressions:
7505 (@value{GDBP}) print '+'
7510 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7513 @value{GDBN} relies on the user to tell it which character set the
7514 target program uses. If we print @code{ibm1047_hello} while our target
7515 character set is still @sc{ascii}, we get jibberish:
7518 (@value{GDBP}) print ibm1047_hello
7519 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7520 (@value{GDBP}) print ibm1047_hello[0]
7525 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7526 @value{GDBN} tells us the character sets it supports:
7529 (@value{GDBP}) set target-charset
7530 ASCII EBCDIC-US IBM1047 ISO-8859-1
7531 (@value{GDBP}) set target-charset
7534 We can select @sc{ibm1047} as our target character set, and examine the
7535 program's strings again. Now the @sc{ascii} string is wrong, but
7536 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7537 target character set, @sc{ibm1047}, to the host character set,
7538 @sc{ascii}, and they display correctly:
7541 (@value{GDBP}) set target-charset IBM1047
7542 (@value{GDBP}) show charset
7543 The current host character set is `ASCII'.
7544 The current target character set is `IBM1047'.
7545 (@value{GDBP}) print ascii_hello
7546 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7547 (@value{GDBP}) print ascii_hello[0]
7549 (@value{GDBP}) print ibm1047_hello
7550 $8 = 0x4016a8 "Hello, world!\n"
7551 (@value{GDBP}) print ibm1047_hello[0]
7556 As above, @value{GDBN} uses the target character set for character and
7557 string literals you use in expressions:
7560 (@value{GDBP}) print '+'
7565 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7568 @node Caching Remote Data
7569 @section Caching Data of Remote Targets
7570 @cindex caching data of remote targets
7572 @value{GDBN} can cache data exchanged between the debugger and a
7573 remote target (@pxref{Remote Debugging}). Such caching generally improves
7574 performance, because it reduces the overhead of the remote protocol by
7575 bundling memory reads and writes into large chunks. Unfortunately,
7576 @value{GDBN} does not currently know anything about volatile
7577 registers, and thus data caching will produce incorrect results when
7578 volatile registers are in use.
7581 @kindex set remotecache
7582 @item set remotecache on
7583 @itemx set remotecache off
7584 Set caching state for remote targets. When @code{ON}, use data
7585 caching. By default, this option is @code{OFF}.
7587 @kindex show remotecache
7588 @item show remotecache
7589 Show the current state of data caching for remote targets.
7593 Print the information about the data cache performance. The
7594 information displayed includes: the dcache width and depth; and for
7595 each cache line, how many times it was referenced, and its data and
7596 state (dirty, bad, ok, etc.). This command is useful for debugging
7597 the data cache operation.
7602 @chapter C Preprocessor Macros
7604 Some languages, such as C and C@t{++}, provide a way to define and invoke
7605 ``preprocessor macros'' which expand into strings of tokens.
7606 @value{GDBN} can evaluate expressions containing macro invocations, show
7607 the result of macro expansion, and show a macro's definition, including
7608 where it was defined.
7610 You may need to compile your program specially to provide @value{GDBN}
7611 with information about preprocessor macros. Most compilers do not
7612 include macros in their debugging information, even when you compile
7613 with the @option{-g} flag. @xref{Compilation}.
7615 A program may define a macro at one point, remove that definition later,
7616 and then provide a different definition after that. Thus, at different
7617 points in the program, a macro may have different definitions, or have
7618 no definition at all. If there is a current stack frame, @value{GDBN}
7619 uses the macros in scope at that frame's source code line. Otherwise,
7620 @value{GDBN} uses the macros in scope at the current listing location;
7623 At the moment, @value{GDBN} does not support the @code{##}
7624 token-splicing operator, the @code{#} stringification operator, or
7625 variable-arity macros.
7627 Whenever @value{GDBN} evaluates an expression, it always expands any
7628 macro invocations present in the expression. @value{GDBN} also provides
7629 the following commands for working with macros explicitly.
7633 @kindex macro expand
7634 @cindex macro expansion, showing the results of preprocessor
7635 @cindex preprocessor macro expansion, showing the results of
7636 @cindex expanding preprocessor macros
7637 @item macro expand @var{expression}
7638 @itemx macro exp @var{expression}
7639 Show the results of expanding all preprocessor macro invocations in
7640 @var{expression}. Since @value{GDBN} simply expands macros, but does
7641 not parse the result, @var{expression} need not be a valid expression;
7642 it can be any string of tokens.
7645 @item macro expand-once @var{expression}
7646 @itemx macro exp1 @var{expression}
7647 @cindex expand macro once
7648 @i{(This command is not yet implemented.)} Show the results of
7649 expanding those preprocessor macro invocations that appear explicitly in
7650 @var{expression}. Macro invocations appearing in that expansion are
7651 left unchanged. This command allows you to see the effect of a
7652 particular macro more clearly, without being confused by further
7653 expansions. Since @value{GDBN} simply expands macros, but does not
7654 parse the result, @var{expression} need not be a valid expression; it
7655 can be any string of tokens.
7658 @cindex macro definition, showing
7659 @cindex definition, showing a macro's
7660 @item info macro @var{macro}
7661 Show the definition of the macro named @var{macro}, and describe the
7662 source location where that definition was established.
7664 @kindex macro define
7665 @cindex user-defined macros
7666 @cindex defining macros interactively
7667 @cindex macros, user-defined
7668 @item macro define @var{macro} @var{replacement-list}
7669 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7670 @i{(This command is not yet implemented.)} Introduce a definition for a
7671 preprocessor macro named @var{macro}, invocations of which are replaced
7672 by the tokens given in @var{replacement-list}. The first form of this
7673 command defines an ``object-like'' macro, which takes no arguments; the
7674 second form defines a ``function-like'' macro, which takes the arguments
7675 given in @var{arglist}.
7677 A definition introduced by this command is in scope in every expression
7678 evaluated in @value{GDBN}, until it is removed with the @command{macro
7679 undef} command, described below. The definition overrides all
7680 definitions for @var{macro} present in the program being debugged, as
7681 well as any previous user-supplied definition.
7684 @item macro undef @var{macro}
7685 @i{(This command is not yet implemented.)} Remove any user-supplied
7686 definition for the macro named @var{macro}. This command only affects
7687 definitions provided with the @command{macro define} command, described
7688 above; it cannot remove definitions present in the program being
7693 @i{(This command is not yet implemented.)} List all the macros
7694 defined using the @code{macro define} command.
7697 @cindex macros, example of debugging with
7698 Here is a transcript showing the above commands in action. First, we
7699 show our source files:
7707 #define ADD(x) (M + x)
7712 printf ("Hello, world!\n");
7714 printf ("We're so creative.\n");
7716 printf ("Goodbye, world!\n");
7723 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7724 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7725 compiler includes information about preprocessor macros in the debugging
7729 $ gcc -gdwarf-2 -g3 sample.c -o sample
7733 Now, we start @value{GDBN} on our sample program:
7737 GNU gdb 2002-05-06-cvs
7738 Copyright 2002 Free Software Foundation, Inc.
7739 GDB is free software, @dots{}
7743 We can expand macros and examine their definitions, even when the
7744 program is not running. @value{GDBN} uses the current listing position
7745 to decide which macro definitions are in scope:
7748 (@value{GDBP}) list main
7751 5 #define ADD(x) (M + x)
7756 10 printf ("Hello, world!\n");
7758 12 printf ("We're so creative.\n");
7759 (@value{GDBP}) info macro ADD
7760 Defined at /home/jimb/gdb/macros/play/sample.c:5
7761 #define ADD(x) (M + x)
7762 (@value{GDBP}) info macro Q
7763 Defined at /home/jimb/gdb/macros/play/sample.h:1
7764 included at /home/jimb/gdb/macros/play/sample.c:2
7766 (@value{GDBP}) macro expand ADD(1)
7767 expands to: (42 + 1)
7768 (@value{GDBP}) macro expand-once ADD(1)
7769 expands to: once (M + 1)
7773 In the example above, note that @command{macro expand-once} expands only
7774 the macro invocation explicit in the original text --- the invocation of
7775 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7776 which was introduced by @code{ADD}.
7778 Once the program is running, @value{GDBN} uses the macro definitions in
7779 force at the source line of the current stack frame:
7782 (@value{GDBP}) break main
7783 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7785 Starting program: /home/jimb/gdb/macros/play/sample
7787 Breakpoint 1, main () at sample.c:10
7788 10 printf ("Hello, world!\n");
7792 At line 10, the definition of the macro @code{N} at line 9 is in force:
7795 (@value{GDBP}) info macro N
7796 Defined at /home/jimb/gdb/macros/play/sample.c:9
7798 (@value{GDBP}) macro expand N Q M
7800 (@value{GDBP}) print N Q M
7805 As we step over directives that remove @code{N}'s definition, and then
7806 give it a new definition, @value{GDBN} finds the definition (or lack
7807 thereof) in force at each point:
7812 12 printf ("We're so creative.\n");
7813 (@value{GDBP}) info macro N
7814 The symbol `N' has no definition as a C/C++ preprocessor macro
7815 at /home/jimb/gdb/macros/play/sample.c:12
7818 14 printf ("Goodbye, world!\n");
7819 (@value{GDBP}) info macro N
7820 Defined at /home/jimb/gdb/macros/play/sample.c:13
7822 (@value{GDBP}) macro expand N Q M
7823 expands to: 1729 < 42
7824 (@value{GDBP}) print N Q M
7831 @chapter Tracepoints
7832 @c This chapter is based on the documentation written by Michael
7833 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7836 In some applications, it is not feasible for the debugger to interrupt
7837 the program's execution long enough for the developer to learn
7838 anything helpful about its behavior. If the program's correctness
7839 depends on its real-time behavior, delays introduced by a debugger
7840 might cause the program to change its behavior drastically, or perhaps
7841 fail, even when the code itself is correct. It is useful to be able
7842 to observe the program's behavior without interrupting it.
7844 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7845 specify locations in the program, called @dfn{tracepoints}, and
7846 arbitrary expressions to evaluate when those tracepoints are reached.
7847 Later, using the @code{tfind} command, you can examine the values
7848 those expressions had when the program hit the tracepoints. The
7849 expressions may also denote objects in memory---structures or arrays,
7850 for example---whose values @value{GDBN} should record; while visiting
7851 a particular tracepoint, you may inspect those objects as if they were
7852 in memory at that moment. However, because @value{GDBN} records these
7853 values without interacting with you, it can do so quickly and
7854 unobtrusively, hopefully not disturbing the program's behavior.
7856 The tracepoint facility is currently available only for remote
7857 targets. @xref{Targets}. In addition, your remote target must know
7858 how to collect trace data. This functionality is implemented in the
7859 remote stub; however, none of the stubs distributed with @value{GDBN}
7860 support tracepoints as of this writing. The format of the remote
7861 packets used to implement tracepoints are described in @ref{Tracepoint
7864 This chapter describes the tracepoint commands and features.
7868 * Analyze Collected Data::
7869 * Tracepoint Variables::
7872 @node Set Tracepoints
7873 @section Commands to Set Tracepoints
7875 Before running such a @dfn{trace experiment}, an arbitrary number of
7876 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7877 tracepoint has a number assigned to it by @value{GDBN}. Like with
7878 breakpoints, tracepoint numbers are successive integers starting from
7879 one. Many of the commands associated with tracepoints take the
7880 tracepoint number as their argument, to identify which tracepoint to
7883 For each tracepoint, you can specify, in advance, some arbitrary set
7884 of data that you want the target to collect in the trace buffer when
7885 it hits that tracepoint. The collected data can include registers,
7886 local variables, or global data. Later, you can use @value{GDBN}
7887 commands to examine the values these data had at the time the
7890 This section describes commands to set tracepoints and associated
7891 conditions and actions.
7894 * Create and Delete Tracepoints::
7895 * Enable and Disable Tracepoints::
7896 * Tracepoint Passcounts::
7897 * Tracepoint Actions::
7898 * Listing Tracepoints::
7899 * Starting and Stopping Trace Experiments::
7902 @node Create and Delete Tracepoints
7903 @subsection Create and Delete Tracepoints
7906 @cindex set tracepoint
7909 The @code{trace} command is very similar to the @code{break} command.
7910 Its argument can be a source line, a function name, or an address in
7911 the target program. @xref{Set Breaks}. The @code{trace} command
7912 defines a tracepoint, which is a point in the target program where the
7913 debugger will briefly stop, collect some data, and then allow the
7914 program to continue. Setting a tracepoint or changing its commands
7915 doesn't take effect until the next @code{tstart} command; thus, you
7916 cannot change the tracepoint attributes once a trace experiment is
7919 Here are some examples of using the @code{trace} command:
7922 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7924 (@value{GDBP}) @b{trace +2} // 2 lines forward
7926 (@value{GDBP}) @b{trace my_function} // first source line of function
7928 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7930 (@value{GDBP}) @b{trace *0x2117c4} // an address
7934 You can abbreviate @code{trace} as @code{tr}.
7937 @cindex last tracepoint number
7938 @cindex recent tracepoint number
7939 @cindex tracepoint number
7940 The convenience variable @code{$tpnum} records the tracepoint number
7941 of the most recently set tracepoint.
7943 @kindex delete tracepoint
7944 @cindex tracepoint deletion
7945 @item delete tracepoint @r{[}@var{num}@r{]}
7946 Permanently delete one or more tracepoints. With no argument, the
7947 default is to delete all tracepoints.
7952 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7954 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7958 You can abbreviate this command as @code{del tr}.
7961 @node Enable and Disable Tracepoints
7962 @subsection Enable and Disable Tracepoints
7965 @kindex disable tracepoint
7966 @item disable tracepoint @r{[}@var{num}@r{]}
7967 Disable tracepoint @var{num}, or all tracepoints if no argument
7968 @var{num} is given. A disabled tracepoint will have no effect during
7969 the next trace experiment, but it is not forgotten. You can re-enable
7970 a disabled tracepoint using the @code{enable tracepoint} command.
7972 @kindex enable tracepoint
7973 @item enable tracepoint @r{[}@var{num}@r{]}
7974 Enable tracepoint @var{num}, or all tracepoints. The enabled
7975 tracepoints will become effective the next time a trace experiment is
7979 @node Tracepoint Passcounts
7980 @subsection Tracepoint Passcounts
7984 @cindex tracepoint pass count
7985 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7986 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7987 automatically stop a trace experiment. If a tracepoint's passcount is
7988 @var{n}, then the trace experiment will be automatically stopped on
7989 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7990 @var{num} is not specified, the @code{passcount} command sets the
7991 passcount of the most recently defined tracepoint. If no passcount is
7992 given, the trace experiment will run until stopped explicitly by the
7998 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7999 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8001 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8002 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8003 (@value{GDBP}) @b{trace foo}
8004 (@value{GDBP}) @b{pass 3}
8005 (@value{GDBP}) @b{trace bar}
8006 (@value{GDBP}) @b{pass 2}
8007 (@value{GDBP}) @b{trace baz}
8008 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8009 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8010 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8011 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8015 @node Tracepoint Actions
8016 @subsection Tracepoint Action Lists
8020 @cindex tracepoint actions
8021 @item actions @r{[}@var{num}@r{]}
8022 This command will prompt for a list of actions to be taken when the
8023 tracepoint is hit. If the tracepoint number @var{num} is not
8024 specified, this command sets the actions for the one that was most
8025 recently defined (so that you can define a tracepoint and then say
8026 @code{actions} without bothering about its number). You specify the
8027 actions themselves on the following lines, one action at a time, and
8028 terminate the actions list with a line containing just @code{end}. So
8029 far, the only defined actions are @code{collect} and
8030 @code{while-stepping}.
8032 @cindex remove actions from a tracepoint
8033 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8034 and follow it immediately with @samp{end}.
8037 (@value{GDBP}) @b{collect @var{data}} // collect some data
8039 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8041 (@value{GDBP}) @b{end} // signals the end of actions.
8044 In the following example, the action list begins with @code{collect}
8045 commands indicating the things to be collected when the tracepoint is
8046 hit. Then, in order to single-step and collect additional data
8047 following the tracepoint, a @code{while-stepping} command is used,
8048 followed by the list of things to be collected while stepping. The
8049 @code{while-stepping} command is terminated by its own separate
8050 @code{end} command. Lastly, the action list is terminated by an
8054 (@value{GDBP}) @b{trace foo}
8055 (@value{GDBP}) @b{actions}
8056 Enter actions for tracepoint 1, one per line:
8065 @kindex collect @r{(tracepoints)}
8066 @item collect @var{expr1}, @var{expr2}, @dots{}
8067 Collect values of the given expressions when the tracepoint is hit.
8068 This command accepts a comma-separated list of any valid expressions.
8069 In addition to global, static, or local variables, the following
8070 special arguments are supported:
8074 collect all registers
8077 collect all function arguments
8080 collect all local variables.
8083 You can give several consecutive @code{collect} commands, each one
8084 with a single argument, or one @code{collect} command with several
8085 arguments separated by commas: the effect is the same.
8087 The command @code{info scope} (@pxref{Symbols, info scope}) is
8088 particularly useful for figuring out what data to collect.
8090 @kindex while-stepping @r{(tracepoints)}
8091 @item while-stepping @var{n}
8092 Perform @var{n} single-step traces after the tracepoint, collecting
8093 new data at each step. The @code{while-stepping} command is
8094 followed by the list of what to collect while stepping (followed by
8095 its own @code{end} command):
8099 > collect $regs, myglobal
8105 You may abbreviate @code{while-stepping} as @code{ws} or
8109 @node Listing Tracepoints
8110 @subsection Listing Tracepoints
8113 @kindex info tracepoints
8115 @cindex information about tracepoints
8116 @item info tracepoints @r{[}@var{num}@r{]}
8117 Display information about the tracepoint @var{num}. If you don't specify
8118 a tracepoint number, displays information about all the tracepoints
8119 defined so far. For each tracepoint, the following information is
8126 whether it is enabled or disabled
8130 its passcount as given by the @code{passcount @var{n}} command
8132 its step count as given by the @code{while-stepping @var{n}} command
8134 where in the source files is the tracepoint set
8136 its action list as given by the @code{actions} command
8140 (@value{GDBP}) @b{info trace}
8141 Num Enb Address PassC StepC What
8142 1 y 0x002117c4 0 0 <gdb_asm>
8143 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8144 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8149 This command can be abbreviated @code{info tp}.
8152 @node Starting and Stopping Trace Experiments
8153 @subsection Starting and Stopping Trace Experiments
8157 @cindex start a new trace experiment
8158 @cindex collected data discarded
8160 This command takes no arguments. It starts the trace experiment, and
8161 begins collecting data. This has the side effect of discarding all
8162 the data collected in the trace buffer during the previous trace
8166 @cindex stop a running trace experiment
8168 This command takes no arguments. It ends the trace experiment, and
8169 stops collecting data.
8171 @strong{Note}: a trace experiment and data collection may stop
8172 automatically if any tracepoint's passcount is reached
8173 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8176 @cindex status of trace data collection
8177 @cindex trace experiment, status of
8179 This command displays the status of the current trace data
8183 Here is an example of the commands we described so far:
8186 (@value{GDBP}) @b{trace gdb_c_test}
8187 (@value{GDBP}) @b{actions}
8188 Enter actions for tracepoint #1, one per line.
8189 > collect $regs,$locals,$args
8194 (@value{GDBP}) @b{tstart}
8195 [time passes @dots{}]
8196 (@value{GDBP}) @b{tstop}
8200 @node Analyze Collected Data
8201 @section Using the Collected Data
8203 After the tracepoint experiment ends, you use @value{GDBN} commands
8204 for examining the trace data. The basic idea is that each tracepoint
8205 collects a trace @dfn{snapshot} every time it is hit and another
8206 snapshot every time it single-steps. All these snapshots are
8207 consecutively numbered from zero and go into a buffer, and you can
8208 examine them later. The way you examine them is to @dfn{focus} on a
8209 specific trace snapshot. When the remote stub is focused on a trace
8210 snapshot, it will respond to all @value{GDBN} requests for memory and
8211 registers by reading from the buffer which belongs to that snapshot,
8212 rather than from @emph{real} memory or registers of the program being
8213 debugged. This means that @strong{all} @value{GDBN} commands
8214 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8215 behave as if we were currently debugging the program state as it was
8216 when the tracepoint occurred. Any requests for data that are not in
8217 the buffer will fail.
8220 * tfind:: How to select a trace snapshot
8221 * tdump:: How to display all data for a snapshot
8222 * save-tracepoints:: How to save tracepoints for a future run
8226 @subsection @code{tfind @var{n}}
8229 @cindex select trace snapshot
8230 @cindex find trace snapshot
8231 The basic command for selecting a trace snapshot from the buffer is
8232 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8233 counting from zero. If no argument @var{n} is given, the next
8234 snapshot is selected.
8236 Here are the various forms of using the @code{tfind} command.
8240 Find the first snapshot in the buffer. This is a synonym for
8241 @code{tfind 0} (since 0 is the number of the first snapshot).
8244 Stop debugging trace snapshots, resume @emph{live} debugging.
8247 Same as @samp{tfind none}.
8250 No argument means find the next trace snapshot.
8253 Find the previous trace snapshot before the current one. This permits
8254 retracing earlier steps.
8256 @item tfind tracepoint @var{num}
8257 Find the next snapshot associated with tracepoint @var{num}. Search
8258 proceeds forward from the last examined trace snapshot. If no
8259 argument @var{num} is given, it means find the next snapshot collected
8260 for the same tracepoint as the current snapshot.
8262 @item tfind pc @var{addr}
8263 Find the next snapshot associated with the value @var{addr} of the
8264 program counter. Search proceeds forward from the last examined trace
8265 snapshot. If no argument @var{addr} is given, it means find the next
8266 snapshot with the same value of PC as the current snapshot.
8268 @item tfind outside @var{addr1}, @var{addr2}
8269 Find the next snapshot whose PC is outside the given range of
8272 @item tfind range @var{addr1}, @var{addr2}
8273 Find the next snapshot whose PC is between @var{addr1} and
8274 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8276 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8277 Find the next snapshot associated with the source line @var{n}. If
8278 the optional argument @var{file} is given, refer to line @var{n} in
8279 that source file. Search proceeds forward from the last examined
8280 trace snapshot. If no argument @var{n} is given, it means find the
8281 next line other than the one currently being examined; thus saying
8282 @code{tfind line} repeatedly can appear to have the same effect as
8283 stepping from line to line in a @emph{live} debugging session.
8286 The default arguments for the @code{tfind} commands are specifically
8287 designed to make it easy to scan through the trace buffer. For
8288 instance, @code{tfind} with no argument selects the next trace
8289 snapshot, and @code{tfind -} with no argument selects the previous
8290 trace snapshot. So, by giving one @code{tfind} command, and then
8291 simply hitting @key{RET} repeatedly you can examine all the trace
8292 snapshots in order. Or, by saying @code{tfind -} and then hitting
8293 @key{RET} repeatedly you can examine the snapshots in reverse order.
8294 The @code{tfind line} command with no argument selects the snapshot
8295 for the next source line executed. The @code{tfind pc} command with
8296 no argument selects the next snapshot with the same program counter
8297 (PC) as the current frame. The @code{tfind tracepoint} command with
8298 no argument selects the next trace snapshot collected by the same
8299 tracepoint as the current one.
8301 In addition to letting you scan through the trace buffer manually,
8302 these commands make it easy to construct @value{GDBN} scripts that
8303 scan through the trace buffer and print out whatever collected data
8304 you are interested in. Thus, if we want to examine the PC, FP, and SP
8305 registers from each trace frame in the buffer, we can say this:
8308 (@value{GDBP}) @b{tfind start}
8309 (@value{GDBP}) @b{while ($trace_frame != -1)}
8310 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8311 $trace_frame, $pc, $sp, $fp
8315 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8316 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8317 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8318 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8319 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8320 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8321 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8322 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8323 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8324 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8325 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8328 Or, if we want to examine the variable @code{X} at each source line in
8332 (@value{GDBP}) @b{tfind start}
8333 (@value{GDBP}) @b{while ($trace_frame != -1)}
8334 > printf "Frame %d, X == %d\n", $trace_frame, X
8344 @subsection @code{tdump}
8346 @cindex dump all data collected at tracepoint
8347 @cindex tracepoint data, display
8349 This command takes no arguments. It prints all the data collected at
8350 the current trace snapshot.
8353 (@value{GDBP}) @b{trace 444}
8354 (@value{GDBP}) @b{actions}
8355 Enter actions for tracepoint #2, one per line:
8356 > collect $regs, $locals, $args, gdb_long_test
8359 (@value{GDBP}) @b{tstart}
8361 (@value{GDBP}) @b{tfind line 444}
8362 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8364 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8366 (@value{GDBP}) @b{tdump}
8367 Data collected at tracepoint 2, trace frame 1:
8368 d0 0xc4aa0085 -995491707
8372 d4 0x71aea3d 119204413
8377 a1 0x3000668 50333288
8380 a4 0x3000698 50333336
8382 fp 0x30bf3c 0x30bf3c
8383 sp 0x30bf34 0x30bf34
8385 pc 0x20b2c8 0x20b2c8
8389 p = 0x20e5b4 "gdb-test"
8396 gdb_long_test = 17 '\021'
8401 @node save-tracepoints
8402 @subsection @code{save-tracepoints @var{filename}}
8403 @kindex save-tracepoints
8404 @cindex save tracepoints for future sessions
8406 This command saves all current tracepoint definitions together with
8407 their actions and passcounts, into a file @file{@var{filename}}
8408 suitable for use in a later debugging session. To read the saved
8409 tracepoint definitions, use the @code{source} command (@pxref{Command
8412 @node Tracepoint Variables
8413 @section Convenience Variables for Tracepoints
8414 @cindex tracepoint variables
8415 @cindex convenience variables for tracepoints
8418 @vindex $trace_frame
8419 @item (int) $trace_frame
8420 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8421 snapshot is selected.
8424 @item (int) $tracepoint
8425 The tracepoint for the current trace snapshot.
8428 @item (int) $trace_line
8429 The line number for the current trace snapshot.
8432 @item (char []) $trace_file
8433 The source file for the current trace snapshot.
8436 @item (char []) $trace_func
8437 The name of the function containing @code{$tracepoint}.
8440 Note: @code{$trace_file} is not suitable for use in @code{printf},
8441 use @code{output} instead.
8443 Here's a simple example of using these convenience variables for
8444 stepping through all the trace snapshots and printing some of their
8448 (@value{GDBP}) @b{tfind start}
8450 (@value{GDBP}) @b{while $trace_frame != -1}
8451 > output $trace_file
8452 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8458 @chapter Debugging Programs That Use Overlays
8461 If your program is too large to fit completely in your target system's
8462 memory, you can sometimes use @dfn{overlays} to work around this
8463 problem. @value{GDBN} provides some support for debugging programs that
8467 * How Overlays Work:: A general explanation of overlays.
8468 * Overlay Commands:: Managing overlays in @value{GDBN}.
8469 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8470 mapped by asking the inferior.
8471 * Overlay Sample Program:: A sample program using overlays.
8474 @node How Overlays Work
8475 @section How Overlays Work
8476 @cindex mapped overlays
8477 @cindex unmapped overlays
8478 @cindex load address, overlay's
8479 @cindex mapped address
8480 @cindex overlay area
8482 Suppose you have a computer whose instruction address space is only 64
8483 kilobytes long, but which has much more memory which can be accessed by
8484 other means: special instructions, segment registers, or memory
8485 management hardware, for example. Suppose further that you want to
8486 adapt a program which is larger than 64 kilobytes to run on this system.
8488 One solution is to identify modules of your program which are relatively
8489 independent, and need not call each other directly; call these modules
8490 @dfn{overlays}. Separate the overlays from the main program, and place
8491 their machine code in the larger memory. Place your main program in
8492 instruction memory, but leave at least enough space there to hold the
8493 largest overlay as well.
8495 Now, to call a function located in an overlay, you must first copy that
8496 overlay's machine code from the large memory into the space set aside
8497 for it in the instruction memory, and then jump to its entry point
8500 @c NB: In the below the mapped area's size is greater or equal to the
8501 @c size of all overlays. This is intentional to remind the developer
8502 @c that overlays don't necessarily need to be the same size.
8506 Data Instruction Larger
8507 Address Space Address Space Address Space
8508 +-----------+ +-----------+ +-----------+
8510 +-----------+ +-----------+ +-----------+<-- overlay 1
8511 | program | | main | .----| overlay 1 | load address
8512 | variables | | program | | +-----------+
8513 | and heap | | | | | |
8514 +-----------+ | | | +-----------+<-- overlay 2
8515 | | +-----------+ | | | load address
8516 +-----------+ | | | .-| overlay 2 |
8518 mapped --->+-----------+ | | +-----------+
8520 | overlay | <-' | | |
8521 | area | <---' +-----------+<-- overlay 3
8522 | | <---. | | load address
8523 +-----------+ `--| overlay 3 |
8530 @anchor{A code overlay}A code overlay
8534 The diagram (@pxref{A code overlay}) shows a system with separate data
8535 and instruction address spaces. To map an overlay, the program copies
8536 its code from the larger address space to the instruction address space.
8537 Since the overlays shown here all use the same mapped address, only one
8538 may be mapped at a time. For a system with a single address space for
8539 data and instructions, the diagram would be similar, except that the
8540 program variables and heap would share an address space with the main
8541 program and the overlay area.
8543 An overlay loaded into instruction memory and ready for use is called a
8544 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8545 instruction memory. An overlay not present (or only partially present)
8546 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8547 is its address in the larger memory. The mapped address is also called
8548 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8549 called the @dfn{load memory address}, or @dfn{LMA}.
8551 Unfortunately, overlays are not a completely transparent way to adapt a
8552 program to limited instruction memory. They introduce a new set of
8553 global constraints you must keep in mind as you design your program:
8558 Before calling or returning to a function in an overlay, your program
8559 must make sure that overlay is actually mapped. Otherwise, the call or
8560 return will transfer control to the right address, but in the wrong
8561 overlay, and your program will probably crash.
8564 If the process of mapping an overlay is expensive on your system, you
8565 will need to choose your overlays carefully to minimize their effect on
8566 your program's performance.
8569 The executable file you load onto your system must contain each
8570 overlay's instructions, appearing at the overlay's load address, not its
8571 mapped address. However, each overlay's instructions must be relocated
8572 and its symbols defined as if the overlay were at its mapped address.
8573 You can use GNU linker scripts to specify different load and relocation
8574 addresses for pieces of your program; see @ref{Overlay Description,,,
8575 ld.info, Using ld: the GNU linker}.
8578 The procedure for loading executable files onto your system must be able
8579 to load their contents into the larger address space as well as the
8580 instruction and data spaces.
8584 The overlay system described above is rather simple, and could be
8585 improved in many ways:
8590 If your system has suitable bank switch registers or memory management
8591 hardware, you could use those facilities to make an overlay's load area
8592 contents simply appear at their mapped address in instruction space.
8593 This would probably be faster than copying the overlay to its mapped
8594 area in the usual way.
8597 If your overlays are small enough, you could set aside more than one
8598 overlay area, and have more than one overlay mapped at a time.
8601 You can use overlays to manage data, as well as instructions. In
8602 general, data overlays are even less transparent to your design than
8603 code overlays: whereas code overlays only require care when you call or
8604 return to functions, data overlays require care every time you access
8605 the data. Also, if you change the contents of a data overlay, you
8606 must copy its contents back out to its load address before you can copy a
8607 different data overlay into the same mapped area.
8612 @node Overlay Commands
8613 @section Overlay Commands
8615 To use @value{GDBN}'s overlay support, each overlay in your program must
8616 correspond to a separate section of the executable file. The section's
8617 virtual memory address and load memory address must be the overlay's
8618 mapped and load addresses. Identifying overlays with sections allows
8619 @value{GDBN} to determine the appropriate address of a function or
8620 variable, depending on whether the overlay is mapped or not.
8622 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8623 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8628 Disable @value{GDBN}'s overlay support. When overlay support is
8629 disabled, @value{GDBN} assumes that all functions and variables are
8630 always present at their mapped addresses. By default, @value{GDBN}'s
8631 overlay support is disabled.
8633 @item overlay manual
8634 @cindex manual overlay debugging
8635 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8636 relies on you to tell it which overlays are mapped, and which are not,
8637 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8638 commands described below.
8640 @item overlay map-overlay @var{overlay}
8641 @itemx overlay map @var{overlay}
8642 @cindex map an overlay
8643 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8644 be the name of the object file section containing the overlay. When an
8645 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8646 functions and variables at their mapped addresses. @value{GDBN} assumes
8647 that any other overlays whose mapped ranges overlap that of
8648 @var{overlay} are now unmapped.
8650 @item overlay unmap-overlay @var{overlay}
8651 @itemx overlay unmap @var{overlay}
8652 @cindex unmap an overlay
8653 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8654 must be the name of the object file section containing the overlay.
8655 When an overlay is unmapped, @value{GDBN} assumes it can find the
8656 overlay's functions and variables at their load addresses.
8659 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8660 consults a data structure the overlay manager maintains in the inferior
8661 to see which overlays are mapped. For details, see @ref{Automatic
8664 @item overlay load-target
8666 @cindex reloading the overlay table
8667 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8668 re-reads the table @value{GDBN} automatically each time the inferior
8669 stops, so this command should only be necessary if you have changed the
8670 overlay mapping yourself using @value{GDBN}. This command is only
8671 useful when using automatic overlay debugging.
8673 @item overlay list-overlays
8675 @cindex listing mapped overlays
8676 Display a list of the overlays currently mapped, along with their mapped
8677 addresses, load addresses, and sizes.
8681 Normally, when @value{GDBN} prints a code address, it includes the name
8682 of the function the address falls in:
8685 (@value{GDBP}) print main
8686 $3 = @{int ()@} 0x11a0 <main>
8689 When overlay debugging is enabled, @value{GDBN} recognizes code in
8690 unmapped overlays, and prints the names of unmapped functions with
8691 asterisks around them. For example, if @code{foo} is a function in an
8692 unmapped overlay, @value{GDBN} prints it this way:
8695 (@value{GDBP}) overlay list
8696 No sections are mapped.
8697 (@value{GDBP}) print foo
8698 $5 = @{int (int)@} 0x100000 <*foo*>
8701 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8705 (@value{GDBP}) overlay list
8706 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8707 mapped at 0x1016 - 0x104a
8708 (@value{GDBP}) print foo
8709 $6 = @{int (int)@} 0x1016 <foo>
8712 When overlay debugging is enabled, @value{GDBN} can find the correct
8713 address for functions and variables in an overlay, whether or not the
8714 overlay is mapped. This allows most @value{GDBN} commands, like
8715 @code{break} and @code{disassemble}, to work normally, even on unmapped
8716 code. However, @value{GDBN}'s breakpoint support has some limitations:
8720 @cindex breakpoints in overlays
8721 @cindex overlays, setting breakpoints in
8722 You can set breakpoints in functions in unmapped overlays, as long as
8723 @value{GDBN} can write to the overlay at its load address.
8725 @value{GDBN} can not set hardware or simulator-based breakpoints in
8726 unmapped overlays. However, if you set a breakpoint at the end of your
8727 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8728 you are using manual overlay management), @value{GDBN} will re-set its
8729 breakpoints properly.
8733 @node Automatic Overlay Debugging
8734 @section Automatic Overlay Debugging
8735 @cindex automatic overlay debugging
8737 @value{GDBN} can automatically track which overlays are mapped and which
8738 are not, given some simple co-operation from the overlay manager in the
8739 inferior. If you enable automatic overlay debugging with the
8740 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8741 looks in the inferior's memory for certain variables describing the
8742 current state of the overlays.
8744 Here are the variables your overlay manager must define to support
8745 @value{GDBN}'s automatic overlay debugging:
8749 @item @code{_ovly_table}:
8750 This variable must be an array of the following structures:
8755 /* The overlay's mapped address. */
8758 /* The size of the overlay, in bytes. */
8761 /* The overlay's load address. */
8764 /* Non-zero if the overlay is currently mapped;
8766 unsigned long mapped;
8770 @item @code{_novlys}:
8771 This variable must be a four-byte signed integer, holding the total
8772 number of elements in @code{_ovly_table}.
8776 To decide whether a particular overlay is mapped or not, @value{GDBN}
8777 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8778 @code{lma} members equal the VMA and LMA of the overlay's section in the
8779 executable file. When @value{GDBN} finds a matching entry, it consults
8780 the entry's @code{mapped} member to determine whether the overlay is
8783 In addition, your overlay manager may define a function called
8784 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8785 will silently set a breakpoint there. If the overlay manager then
8786 calls this function whenever it has changed the overlay table, this
8787 will enable @value{GDBN} to accurately keep track of which overlays
8788 are in program memory, and update any breakpoints that may be set
8789 in overlays. This will allow breakpoints to work even if the
8790 overlays are kept in ROM or other non-writable memory while they
8791 are not being executed.
8793 @node Overlay Sample Program
8794 @section Overlay Sample Program
8795 @cindex overlay example program
8797 When linking a program which uses overlays, you must place the overlays
8798 at their load addresses, while relocating them to run at their mapped
8799 addresses. To do this, you must write a linker script (@pxref{Overlay
8800 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8801 since linker scripts are specific to a particular host system, target
8802 architecture, and target memory layout, this manual cannot provide
8803 portable sample code demonstrating @value{GDBN}'s overlay support.
8805 However, the @value{GDBN} source distribution does contain an overlaid
8806 program, with linker scripts for a few systems, as part of its test
8807 suite. The program consists of the following files from
8808 @file{gdb/testsuite/gdb.base}:
8812 The main program file.
8814 A simple overlay manager, used by @file{overlays.c}.
8819 Overlay modules, loaded and used by @file{overlays.c}.
8822 Linker scripts for linking the test program on the @code{d10v-elf}
8823 and @code{m32r-elf} targets.
8826 You can build the test program using the @code{d10v-elf} GCC
8827 cross-compiler like this:
8830 $ d10v-elf-gcc -g -c overlays.c
8831 $ d10v-elf-gcc -g -c ovlymgr.c
8832 $ d10v-elf-gcc -g -c foo.c
8833 $ d10v-elf-gcc -g -c bar.c
8834 $ d10v-elf-gcc -g -c baz.c
8835 $ d10v-elf-gcc -g -c grbx.c
8836 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8837 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8840 The build process is identical for any other architecture, except that
8841 you must substitute the appropriate compiler and linker script for the
8842 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8846 @chapter Using @value{GDBN} with Different Languages
8849 Although programming languages generally have common aspects, they are
8850 rarely expressed in the same manner. For instance, in ANSI C,
8851 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8852 Modula-2, it is accomplished by @code{p^}. Values can also be
8853 represented (and displayed) differently. Hex numbers in C appear as
8854 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8856 @cindex working language
8857 Language-specific information is built into @value{GDBN} for some languages,
8858 allowing you to express operations like the above in your program's
8859 native language, and allowing @value{GDBN} to output values in a manner
8860 consistent with the syntax of your program's native language. The
8861 language you use to build expressions is called the @dfn{working
8865 * Setting:: Switching between source languages
8866 * Show:: Displaying the language
8867 * Checks:: Type and range checks
8868 * Supported Languages:: Supported languages
8869 * Unsupported Languages:: Unsupported languages
8873 @section Switching Between Source Languages
8875 There are two ways to control the working language---either have @value{GDBN}
8876 set it automatically, or select it manually yourself. You can use the
8877 @code{set language} command for either purpose. On startup, @value{GDBN}
8878 defaults to setting the language automatically. The working language is
8879 used to determine how expressions you type are interpreted, how values
8882 In addition to the working language, every source file that
8883 @value{GDBN} knows about has its own working language. For some object
8884 file formats, the compiler might indicate which language a particular
8885 source file is in. However, most of the time @value{GDBN} infers the
8886 language from the name of the file. The language of a source file
8887 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8888 show each frame appropriately for its own language. There is no way to
8889 set the language of a source file from within @value{GDBN}, but you can
8890 set the language associated with a filename extension. @xref{Show, ,
8891 Displaying the Language}.
8893 This is most commonly a problem when you use a program, such
8894 as @code{cfront} or @code{f2c}, that generates C but is written in
8895 another language. In that case, make the
8896 program use @code{#line} directives in its C output; that way
8897 @value{GDBN} will know the correct language of the source code of the original
8898 program, and will display that source code, not the generated C code.
8901 * Filenames:: Filename extensions and languages.
8902 * Manually:: Setting the working language manually
8903 * Automatically:: Having @value{GDBN} infer the source language
8907 @subsection List of Filename Extensions and Languages
8909 If a source file name ends in one of the following extensions, then
8910 @value{GDBN} infers that its language is the one indicated.
8931 Objective-C source file
8938 Modula-2 source file
8942 Assembler source file. This actually behaves almost like C, but
8943 @value{GDBN} does not skip over function prologues when stepping.
8946 In addition, you may set the language associated with a filename
8947 extension. @xref{Show, , Displaying the Language}.
8950 @subsection Setting the Working Language
8952 If you allow @value{GDBN} to set the language automatically,
8953 expressions are interpreted the same way in your debugging session and
8956 @kindex set language
8957 If you wish, you may set the language manually. To do this, issue the
8958 command @samp{set language @var{lang}}, where @var{lang} is the name of
8960 @code{c} or @code{modula-2}.
8961 For a list of the supported languages, type @samp{set language}.
8963 Setting the language manually prevents @value{GDBN} from updating the working
8964 language automatically. This can lead to confusion if you try
8965 to debug a program when the working language is not the same as the
8966 source language, when an expression is acceptable to both
8967 languages---but means different things. For instance, if the current
8968 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8976 might not have the effect you intended. In C, this means to add
8977 @code{b} and @code{c} and place the result in @code{a}. The result
8978 printed would be the value of @code{a}. In Modula-2, this means to compare
8979 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8982 @subsection Having @value{GDBN} Infer the Source Language
8984 To have @value{GDBN} set the working language automatically, use
8985 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8986 then infers the working language. That is, when your program stops in a
8987 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8988 working language to the language recorded for the function in that
8989 frame. If the language for a frame is unknown (that is, if the function
8990 or block corresponding to the frame was defined in a source file that
8991 does not have a recognized extension), the current working language is
8992 not changed, and @value{GDBN} issues a warning.
8994 This may not seem necessary for most programs, which are written
8995 entirely in one source language. However, program modules and libraries
8996 written in one source language can be used by a main program written in
8997 a different source language. Using @samp{set language auto} in this
8998 case frees you from having to set the working language manually.
9001 @section Displaying the Language
9003 The following commands help you find out which language is the
9004 working language, and also what language source files were written in.
9008 @kindex show language
9009 Display the current working language. This is the
9010 language you can use with commands such as @code{print} to
9011 build and compute expressions that may involve variables in your program.
9014 @kindex info frame@r{, show the source language}
9015 Display the source language for this frame. This language becomes the
9016 working language if you use an identifier from this frame.
9017 @xref{Frame Info, ,Information about a Frame}, to identify the other
9018 information listed here.
9021 @kindex info source@r{, show the source language}
9022 Display the source language of this source file.
9023 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9024 information listed here.
9027 In unusual circumstances, you may have source files with extensions
9028 not in the standard list. You can then set the extension associated
9029 with a language explicitly:
9032 @item set extension-language @var{ext} @var{language}
9033 @kindex set extension-language
9034 Tell @value{GDBN} that source files with extension @var{ext} are to be
9035 assumed as written in the source language @var{language}.
9037 @item info extensions
9038 @kindex info extensions
9039 List all the filename extensions and the associated languages.
9043 @section Type and Range Checking
9046 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9047 checking are included, but they do not yet have any effect. This
9048 section documents the intended facilities.
9050 @c FIXME remove warning when type/range code added
9052 Some languages are designed to guard you against making seemingly common
9053 errors through a series of compile- and run-time checks. These include
9054 checking the type of arguments to functions and operators, and making
9055 sure mathematical overflows are caught at run time. Checks such as
9056 these help to ensure a program's correctness once it has been compiled
9057 by eliminating type mismatches, and providing active checks for range
9058 errors when your program is running.
9060 @value{GDBN} can check for conditions like the above if you wish.
9061 Although @value{GDBN} does not check the statements in your program,
9062 it can check expressions entered directly into @value{GDBN} for
9063 evaluation via the @code{print} command, for example. As with the
9064 working language, @value{GDBN} can also decide whether or not to check
9065 automatically based on your program's source language.
9066 @xref{Supported Languages, ,Supported Languages}, for the default
9067 settings of supported languages.
9070 * Type Checking:: An overview of type checking
9071 * Range Checking:: An overview of range checking
9074 @cindex type checking
9075 @cindex checks, type
9077 @subsection An Overview of Type Checking
9079 Some languages, such as Modula-2, are strongly typed, meaning that the
9080 arguments to operators and functions have to be of the correct type,
9081 otherwise an error occurs. These checks prevent type mismatch
9082 errors from ever causing any run-time problems. For example,
9090 The second example fails because the @code{CARDINAL} 1 is not
9091 type-compatible with the @code{REAL} 2.3.
9093 For the expressions you use in @value{GDBN} commands, you can tell the
9094 @value{GDBN} type checker to skip checking;
9095 to treat any mismatches as errors and abandon the expression;
9096 or to only issue warnings when type mismatches occur,
9097 but evaluate the expression anyway. When you choose the last of
9098 these, @value{GDBN} evaluates expressions like the second example above, but
9099 also issues a warning.
9101 Even if you turn type checking off, there may be other reasons
9102 related to type that prevent @value{GDBN} from evaluating an expression.
9103 For instance, @value{GDBN} does not know how to add an @code{int} and
9104 a @code{struct foo}. These particular type errors have nothing to do
9105 with the language in use, and usually arise from expressions, such as
9106 the one described above, which make little sense to evaluate anyway.
9108 Each language defines to what degree it is strict about type. For
9109 instance, both Modula-2 and C require the arguments to arithmetical
9110 operators to be numbers. In C, enumerated types and pointers can be
9111 represented as numbers, so that they are valid arguments to mathematical
9112 operators. @xref{Supported Languages, ,Supported Languages}, for further
9113 details on specific languages.
9115 @value{GDBN} provides some additional commands for controlling the type checker:
9117 @kindex set check type
9118 @kindex show check type
9120 @item set check type auto
9121 Set type checking on or off based on the current working language.
9122 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9125 @item set check type on
9126 @itemx set check type off
9127 Set type checking on or off, overriding the default setting for the
9128 current working language. Issue a warning if the setting does not
9129 match the language default. If any type mismatches occur in
9130 evaluating an expression while type checking is on, @value{GDBN} prints a
9131 message and aborts evaluation of the expression.
9133 @item set check type warn
9134 Cause the type checker to issue warnings, but to always attempt to
9135 evaluate the expression. Evaluating the expression may still
9136 be impossible for other reasons. For example, @value{GDBN} cannot add
9137 numbers and structures.
9140 Show the current setting of the type checker, and whether or not @value{GDBN}
9141 is setting it automatically.
9144 @cindex range checking
9145 @cindex checks, range
9146 @node Range Checking
9147 @subsection An Overview of Range Checking
9149 In some languages (such as Modula-2), it is an error to exceed the
9150 bounds of a type; this is enforced with run-time checks. Such range
9151 checking is meant to ensure program correctness by making sure
9152 computations do not overflow, or indices on an array element access do
9153 not exceed the bounds of the array.
9155 For expressions you use in @value{GDBN} commands, you can tell
9156 @value{GDBN} to treat range errors in one of three ways: ignore them,
9157 always treat them as errors and abandon the expression, or issue
9158 warnings but evaluate the expression anyway.
9160 A range error can result from numerical overflow, from exceeding an
9161 array index bound, or when you type a constant that is not a member
9162 of any type. Some languages, however, do not treat overflows as an
9163 error. In many implementations of C, mathematical overflow causes the
9164 result to ``wrap around'' to lower values---for example, if @var{m} is
9165 the largest integer value, and @var{s} is the smallest, then
9168 @var{m} + 1 @result{} @var{s}
9171 This, too, is specific to individual languages, and in some cases
9172 specific to individual compilers or machines. @xref{Supported Languages, ,
9173 Supported Languages}, for further details on specific languages.
9175 @value{GDBN} provides some additional commands for controlling the range checker:
9177 @kindex set check range
9178 @kindex show check range
9180 @item set check range auto
9181 Set range checking on or off based on the current working language.
9182 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9185 @item set check range on
9186 @itemx set check range off
9187 Set range checking on or off, overriding the default setting for the
9188 current working language. A warning is issued if the setting does not
9189 match the language default. If a range error occurs and range checking is on,
9190 then a message is printed and evaluation of the expression is aborted.
9192 @item set check range warn
9193 Output messages when the @value{GDBN} range checker detects a range error,
9194 but attempt to evaluate the expression anyway. Evaluating the
9195 expression may still be impossible for other reasons, such as accessing
9196 memory that the process does not own (a typical example from many Unix
9200 Show the current setting of the range checker, and whether or not it is
9201 being set automatically by @value{GDBN}.
9204 @node Supported Languages
9205 @section Supported Languages
9207 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9208 assembly, Modula-2, and Ada.
9209 @c This is false ...
9210 Some @value{GDBN} features may be used in expressions regardless of the
9211 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9212 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9213 ,Expressions}) can be used with the constructs of any supported
9216 The following sections detail to what degree each source language is
9217 supported by @value{GDBN}. These sections are not meant to be language
9218 tutorials or references, but serve only as a reference guide to what the
9219 @value{GDBN} expression parser accepts, and what input and output
9220 formats should look like for different languages. There are many good
9221 books written on each of these languages; please look to these for a
9222 language reference or tutorial.
9226 * Objective-C:: Objective-C
9229 * Modula-2:: Modula-2
9234 @subsection C and C@t{++}
9236 @cindex C and C@t{++}
9237 @cindex expressions in C or C@t{++}
9239 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9240 to both languages. Whenever this is the case, we discuss those languages
9244 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9245 @cindex @sc{gnu} C@t{++}
9246 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9247 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9248 effectively, you must compile your C@t{++} programs with a supported
9249 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9250 compiler (@code{aCC}).
9252 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9253 format; if it doesn't work on your system, try the stabs+ debugging
9254 format. You can select those formats explicitly with the @code{g++}
9255 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9256 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9257 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9260 * C Operators:: C and C@t{++} operators
9261 * C Constants:: C and C@t{++} constants
9262 * C Plus Plus Expressions:: C@t{++} expressions
9263 * C Defaults:: Default settings for C and C@t{++}
9264 * C Checks:: C and C@t{++} type and range checks
9265 * Debugging C:: @value{GDBN} and C
9266 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9267 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9271 @subsubsection C and C@t{++} Operators
9273 @cindex C and C@t{++} operators
9275 Operators must be defined on values of specific types. For instance,
9276 @code{+} is defined on numbers, but not on structures. Operators are
9277 often defined on groups of types.
9279 For the purposes of C and C@t{++}, the following definitions hold:
9284 @emph{Integral types} include @code{int} with any of its storage-class
9285 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9288 @emph{Floating-point types} include @code{float}, @code{double}, and
9289 @code{long double} (if supported by the target platform).
9292 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9295 @emph{Scalar types} include all of the above.
9300 The following operators are supported. They are listed here
9301 in order of increasing precedence:
9305 The comma or sequencing operator. Expressions in a comma-separated list
9306 are evaluated from left to right, with the result of the entire
9307 expression being the last expression evaluated.
9310 Assignment. The value of an assignment expression is the value
9311 assigned. Defined on scalar types.
9314 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9315 and translated to @w{@code{@var{a} = @var{a op b}}}.
9316 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9317 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9318 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9321 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9322 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9326 Logical @sc{or}. Defined on integral types.
9329 Logical @sc{and}. Defined on integral types.
9332 Bitwise @sc{or}. Defined on integral types.
9335 Bitwise exclusive-@sc{or}. Defined on integral types.
9338 Bitwise @sc{and}. Defined on integral types.
9341 Equality and inequality. Defined on scalar types. The value of these
9342 expressions is 0 for false and non-zero for true.
9344 @item <@r{, }>@r{, }<=@r{, }>=
9345 Less than, greater than, less than or equal, greater than or equal.
9346 Defined on scalar types. The value of these expressions is 0 for false
9347 and non-zero for true.
9350 left shift, and right shift. Defined on integral types.
9353 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9356 Addition and subtraction. Defined on integral types, floating-point types and
9359 @item *@r{, }/@r{, }%
9360 Multiplication, division, and modulus. Multiplication and division are
9361 defined on integral and floating-point types. Modulus is defined on
9365 Increment and decrement. When appearing before a variable, the
9366 operation is performed before the variable is used in an expression;
9367 when appearing after it, the variable's value is used before the
9368 operation takes place.
9371 Pointer dereferencing. Defined on pointer types. Same precedence as
9375 Address operator. Defined on variables. Same precedence as @code{++}.
9377 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9378 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9379 to examine the address
9380 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9384 Negative. Defined on integral and floating-point types. Same
9385 precedence as @code{++}.
9388 Logical negation. Defined on integral types. Same precedence as
9392 Bitwise complement operator. Defined on integral types. Same precedence as
9397 Structure member, and pointer-to-structure member. For convenience,
9398 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9399 pointer based on the stored type information.
9400 Defined on @code{struct} and @code{union} data.
9403 Dereferences of pointers to members.
9406 Array indexing. @code{@var{a}[@var{i}]} is defined as
9407 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9410 Function parameter list. Same precedence as @code{->}.
9413 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9414 and @code{class} types.
9417 Doubled colons also represent the @value{GDBN} scope operator
9418 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9422 If an operator is redefined in the user code, @value{GDBN} usually
9423 attempts to invoke the redefined version instead of using the operator's
9427 @subsubsection C and C@t{++} Constants
9429 @cindex C and C@t{++} constants
9431 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9436 Integer constants are a sequence of digits. Octal constants are
9437 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9438 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9439 @samp{l}, specifying that the constant should be treated as a
9443 Floating point constants are a sequence of digits, followed by a decimal
9444 point, followed by a sequence of digits, and optionally followed by an
9445 exponent. An exponent is of the form:
9446 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9447 sequence of digits. The @samp{+} is optional for positive exponents.
9448 A floating-point constant may also end with a letter @samp{f} or
9449 @samp{F}, specifying that the constant should be treated as being of
9450 the @code{float} (as opposed to the default @code{double}) type; or with
9451 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9455 Enumerated constants consist of enumerated identifiers, or their
9456 integral equivalents.
9459 Character constants are a single character surrounded by single quotes
9460 (@code{'}), or a number---the ordinal value of the corresponding character
9461 (usually its @sc{ascii} value). Within quotes, the single character may
9462 be represented by a letter or by @dfn{escape sequences}, which are of
9463 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9464 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9465 @samp{@var{x}} is a predefined special character---for example,
9466 @samp{\n} for newline.
9469 String constants are a sequence of character constants surrounded by
9470 double quotes (@code{"}). Any valid character constant (as described
9471 above) may appear. Double quotes within the string must be preceded by
9472 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9476 Pointer constants are an integral value. You can also write pointers
9477 to constants using the C operator @samp{&}.
9480 Array constants are comma-separated lists surrounded by braces @samp{@{}
9481 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9482 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9483 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9486 @node C Plus Plus Expressions
9487 @subsubsection C@t{++} Expressions
9489 @cindex expressions in C@t{++}
9490 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9492 @cindex debugging C@t{++} programs
9493 @cindex C@t{++} compilers
9494 @cindex debug formats and C@t{++}
9495 @cindex @value{NGCC} and C@t{++}
9497 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9498 proper compiler and the proper debug format. Currently, @value{GDBN}
9499 works best when debugging C@t{++} code that is compiled with
9500 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9501 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9502 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9503 stabs+ as their default debug format, so you usually don't need to
9504 specify a debug format explicitly. Other compilers and/or debug formats
9505 are likely to work badly or not at all when using @value{GDBN} to debug
9511 @cindex member functions
9513 Member function calls are allowed; you can use expressions like
9516 count = aml->GetOriginal(x, y)
9519 @vindex this@r{, inside C@t{++} member functions}
9520 @cindex namespace in C@t{++}
9522 While a member function is active (in the selected stack frame), your
9523 expressions have the same namespace available as the member function;
9524 that is, @value{GDBN} allows implicit references to the class instance
9525 pointer @code{this} following the same rules as C@t{++}.
9527 @cindex call overloaded functions
9528 @cindex overloaded functions, calling
9529 @cindex type conversions in C@t{++}
9531 You can call overloaded functions; @value{GDBN} resolves the function
9532 call to the right definition, with some restrictions. @value{GDBN} does not
9533 perform overload resolution involving user-defined type conversions,
9534 calls to constructors, or instantiations of templates that do not exist
9535 in the program. It also cannot handle ellipsis argument lists or
9538 It does perform integral conversions and promotions, floating-point
9539 promotions, arithmetic conversions, pointer conversions, conversions of
9540 class objects to base classes, and standard conversions such as those of
9541 functions or arrays to pointers; it requires an exact match on the
9542 number of function arguments.
9544 Overload resolution is always performed, unless you have specified
9545 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9546 ,@value{GDBN} Features for C@t{++}}.
9548 You must specify @code{set overload-resolution off} in order to use an
9549 explicit function signature to call an overloaded function, as in
9551 p 'foo(char,int)'('x', 13)
9554 The @value{GDBN} command-completion facility can simplify this;
9555 see @ref{Completion, ,Command Completion}.
9557 @cindex reference declarations
9559 @value{GDBN} understands variables declared as C@t{++} references; you can use
9560 them in expressions just as you do in C@t{++} source---they are automatically
9563 In the parameter list shown when @value{GDBN} displays a frame, the values of
9564 reference variables are not displayed (unlike other variables); this
9565 avoids clutter, since references are often used for large structures.
9566 The @emph{address} of a reference variable is always shown, unless
9567 you have specified @samp{set print address off}.
9570 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9571 expressions can use it just as expressions in your program do. Since
9572 one scope may be defined in another, you can use @code{::} repeatedly if
9573 necessary, for example in an expression like
9574 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9575 resolving name scope by reference to source files, in both C and C@t{++}
9576 debugging (@pxref{Variables, ,Program Variables}).
9579 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9580 calling virtual functions correctly, printing out virtual bases of
9581 objects, calling functions in a base subobject, casting objects, and
9582 invoking user-defined operators.
9585 @subsubsection C and C@t{++} Defaults
9587 @cindex C and C@t{++} defaults
9589 If you allow @value{GDBN} to set type and range checking automatically, they
9590 both default to @code{off} whenever the working language changes to
9591 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9592 selects the working language.
9594 If you allow @value{GDBN} to set the language automatically, it
9595 recognizes source files whose names end with @file{.c}, @file{.C}, or
9596 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9597 these files, it sets the working language to C or C@t{++}.
9598 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9599 for further details.
9601 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9602 @c unimplemented. If (b) changes, it might make sense to let this node
9603 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9606 @subsubsection C and C@t{++} Type and Range Checks
9608 @cindex C and C@t{++} checks
9610 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9611 is not used. However, if you turn type checking on, @value{GDBN}
9612 considers two variables type equivalent if:
9616 The two variables are structured and have the same structure, union, or
9620 The two variables have the same type name, or types that have been
9621 declared equivalent through @code{typedef}.
9624 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9627 The two @code{struct}, @code{union}, or @code{enum} variables are
9628 declared in the same declaration. (Note: this may not be true for all C
9633 Range checking, if turned on, is done on mathematical operations. Array
9634 indices are not checked, since they are often used to index a pointer
9635 that is not itself an array.
9638 @subsubsection @value{GDBN} and C
9640 The @code{set print union} and @code{show print union} commands apply to
9641 the @code{union} type. When set to @samp{on}, any @code{union} that is
9642 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9643 appears as @samp{@{...@}}.
9645 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9646 with pointers and a memory allocation function. @xref{Expressions,
9649 @node Debugging C Plus Plus
9650 @subsubsection @value{GDBN} Features for C@t{++}
9652 @cindex commands for C@t{++}
9654 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9655 designed specifically for use with C@t{++}. Here is a summary:
9658 @cindex break in overloaded functions
9659 @item @r{breakpoint menus}
9660 When you want a breakpoint in a function whose name is overloaded,
9661 @value{GDBN} has the capability to display a menu of possible breakpoint
9662 locations to help you specify which function definition you want.
9663 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
9665 @cindex overloading in C@t{++}
9666 @item rbreak @var{regex}
9667 Setting breakpoints using regular expressions is helpful for setting
9668 breakpoints on overloaded functions that are not members of any special
9670 @xref{Set Breaks, ,Setting Breakpoints}.
9672 @cindex C@t{++} exception handling
9675 Debug C@t{++} exception handling using these commands. @xref{Set
9676 Catchpoints, , Setting Catchpoints}.
9679 @item ptype @var{typename}
9680 Print inheritance relationships as well as other information for type
9682 @xref{Symbols, ,Examining the Symbol Table}.
9684 @cindex C@t{++} symbol display
9685 @item set print demangle
9686 @itemx show print demangle
9687 @itemx set print asm-demangle
9688 @itemx show print asm-demangle
9689 Control whether C@t{++} symbols display in their source form, both when
9690 displaying code as C@t{++} source and when displaying disassemblies.
9691 @xref{Print Settings, ,Print Settings}.
9693 @item set print object
9694 @itemx show print object
9695 Choose whether to print derived (actual) or declared types of objects.
9696 @xref{Print Settings, ,Print Settings}.
9698 @item set print vtbl
9699 @itemx show print vtbl
9700 Control the format for printing virtual function tables.
9701 @xref{Print Settings, ,Print Settings}.
9702 (The @code{vtbl} commands do not work on programs compiled with the HP
9703 ANSI C@t{++} compiler (@code{aCC}).)
9705 @kindex set overload-resolution
9706 @cindex overloaded functions, overload resolution
9707 @item set overload-resolution on
9708 Enable overload resolution for C@t{++} expression evaluation. The default
9709 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9710 and searches for a function whose signature matches the argument types,
9711 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9712 Expressions, ,C@t{++} Expressions}, for details).
9713 If it cannot find a match, it emits a message.
9715 @item set overload-resolution off
9716 Disable overload resolution for C@t{++} expression evaluation. For
9717 overloaded functions that are not class member functions, @value{GDBN}
9718 chooses the first function of the specified name that it finds in the
9719 symbol table, whether or not its arguments are of the correct type. For
9720 overloaded functions that are class member functions, @value{GDBN}
9721 searches for a function whose signature @emph{exactly} matches the
9724 @kindex show overload-resolution
9725 @item show overload-resolution
9726 Show the current setting of overload resolution.
9728 @item @r{Overloaded symbol names}
9729 You can specify a particular definition of an overloaded symbol, using
9730 the same notation that is used to declare such symbols in C@t{++}: type
9731 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9732 also use the @value{GDBN} command-line word completion facilities to list the
9733 available choices, or to finish the type list for you.
9734 @xref{Completion,, Command Completion}, for details on how to do this.
9737 @node Decimal Floating Point
9738 @subsubsection Decimal Floating Point format
9739 @cindex decimal floating point format
9741 @value{GDBN} can examine, set and perform computations with numbers in
9742 decimal floating point format, which in the C language correspond to the
9743 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
9744 specified by the extension to support decimal floating-point arithmetic.
9746 There are two encodings in use, depending on the architecture: BID (Binary
9747 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
9748 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
9751 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
9752 to manipulate decimal floating point numbers, it is not possible to convert
9753 (using a cast, for example) integers wider than 32-bit to decimal float.
9755 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
9756 point computations, error checking in decimal float operations ignores
9757 underflow, overflow and divide by zero exceptions.
9759 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
9760 to inspect @code{_Decimal128} values stored in floating point registers. See
9761 @ref{PowerPC,,PowerPC} for more details.
9764 @subsection Objective-C
9767 This section provides information about some commands and command
9768 options that are useful for debugging Objective-C code. See also
9769 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9770 few more commands specific to Objective-C support.
9773 * Method Names in Commands::
9774 * The Print Command with Objective-C::
9777 @node Method Names in Commands
9778 @subsubsection Method Names in Commands
9780 The following commands have been extended to accept Objective-C method
9781 names as line specifications:
9783 @kindex clear@r{, and Objective-C}
9784 @kindex break@r{, and Objective-C}
9785 @kindex info line@r{, and Objective-C}
9786 @kindex jump@r{, and Objective-C}
9787 @kindex list@r{, and Objective-C}
9791 @item @code{info line}
9796 A fully qualified Objective-C method name is specified as
9799 -[@var{Class} @var{methodName}]
9802 where the minus sign is used to indicate an instance method and a
9803 plus sign (not shown) is used to indicate a class method. The class
9804 name @var{Class} and method name @var{methodName} are enclosed in
9805 brackets, similar to the way messages are specified in Objective-C
9806 source code. For example, to set a breakpoint at the @code{create}
9807 instance method of class @code{Fruit} in the program currently being
9811 break -[Fruit create]
9814 To list ten program lines around the @code{initialize} class method,
9818 list +[NSText initialize]
9821 In the current version of @value{GDBN}, the plus or minus sign is
9822 required. In future versions of @value{GDBN}, the plus or minus
9823 sign will be optional, but you can use it to narrow the search. It
9824 is also possible to specify just a method name:
9830 You must specify the complete method name, including any colons. If
9831 your program's source files contain more than one @code{create} method,
9832 you'll be presented with a numbered list of classes that implement that
9833 method. Indicate your choice by number, or type @samp{0} to exit if
9836 As another example, to clear a breakpoint established at the
9837 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9840 clear -[NSWindow makeKeyAndOrderFront:]
9843 @node The Print Command with Objective-C
9844 @subsubsection The Print Command With Objective-C
9845 @cindex Objective-C, print objects
9846 @kindex print-object
9847 @kindex po @r{(@code{print-object})}
9849 The print command has also been extended to accept methods. For example:
9852 print -[@var{object} hash]
9855 @cindex print an Objective-C object description
9856 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9858 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9859 and print the result. Also, an additional command has been added,
9860 @code{print-object} or @code{po} for short, which is meant to print
9861 the description of an object. However, this command may only work
9862 with certain Objective-C libraries that have a particular hook
9863 function, @code{_NSPrintForDebugger}, defined.
9867 @cindex Fortran-specific support in @value{GDBN}
9869 @value{GDBN} can be used to debug programs written in Fortran, but it
9870 currently supports only the features of Fortran 77 language.
9872 @cindex trailing underscore, in Fortran symbols
9873 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9874 among them) append an underscore to the names of variables and
9875 functions. When you debug programs compiled by those compilers, you
9876 will need to refer to variables and functions with a trailing
9880 * Fortran Operators:: Fortran operators and expressions
9881 * Fortran Defaults:: Default settings for Fortran
9882 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
9885 @node Fortran Operators
9886 @subsubsection Fortran Operators and Expressions
9888 @cindex Fortran operators and expressions
9890 Operators must be defined on values of specific types. For instance,
9891 @code{+} is defined on numbers, but not on characters or other non-
9892 arithmetic types. Operators are often defined on groups of types.
9896 The exponentiation operator. It raises the first operand to the power
9900 The range operator. Normally used in the form of array(low:high) to
9901 represent a section of array.
9904 @node Fortran Defaults
9905 @subsubsection Fortran Defaults
9907 @cindex Fortran Defaults
9909 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9910 default uses case-insensitive matches for Fortran symbols. You can
9911 change that with the @samp{set case-insensitive} command, see
9912 @ref{Symbols}, for the details.
9914 @node Special Fortran Commands
9915 @subsubsection Special Fortran Commands
9917 @cindex Special Fortran commands
9919 @value{GDBN} has some commands to support Fortran-specific features,
9920 such as displaying common blocks.
9923 @cindex @code{COMMON} blocks, Fortran
9925 @item info common @r{[}@var{common-name}@r{]}
9926 This command prints the values contained in the Fortran @code{COMMON}
9927 block whose name is @var{common-name}. With no argument, the names of
9928 all @code{COMMON} blocks visible at the current program location are
9935 @cindex Pascal support in @value{GDBN}, limitations
9936 Debugging Pascal programs which use sets, subranges, file variables, or
9937 nested functions does not currently work. @value{GDBN} does not support
9938 entering expressions, printing values, or similar features using Pascal
9941 The Pascal-specific command @code{set print pascal_static-members}
9942 controls whether static members of Pascal objects are displayed.
9943 @xref{Print Settings, pascal_static-members}.
9946 @subsection Modula-2
9948 @cindex Modula-2, @value{GDBN} support
9950 The extensions made to @value{GDBN} to support Modula-2 only support
9951 output from the @sc{gnu} Modula-2 compiler (which is currently being
9952 developed). Other Modula-2 compilers are not currently supported, and
9953 attempting to debug executables produced by them is most likely
9954 to give an error as @value{GDBN} reads in the executable's symbol
9957 @cindex expressions in Modula-2
9959 * M2 Operators:: Built-in operators
9960 * Built-In Func/Proc:: Built-in functions and procedures
9961 * M2 Constants:: Modula-2 constants
9962 * M2 Types:: Modula-2 types
9963 * M2 Defaults:: Default settings for Modula-2
9964 * Deviations:: Deviations from standard Modula-2
9965 * M2 Checks:: Modula-2 type and range checks
9966 * M2 Scope:: The scope operators @code{::} and @code{.}
9967 * GDB/M2:: @value{GDBN} and Modula-2
9971 @subsubsection Operators
9972 @cindex Modula-2 operators
9974 Operators must be defined on values of specific types. For instance,
9975 @code{+} is defined on numbers, but not on structures. Operators are
9976 often defined on groups of types. For the purposes of Modula-2, the
9977 following definitions hold:
9982 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9986 @emph{Character types} consist of @code{CHAR} and its subranges.
9989 @emph{Floating-point types} consist of @code{REAL}.
9992 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9996 @emph{Scalar types} consist of all of the above.
9999 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10002 @emph{Boolean types} consist of @code{BOOLEAN}.
10006 The following operators are supported, and appear in order of
10007 increasing precedence:
10011 Function argument or array index separator.
10014 Assignment. The value of @var{var} @code{:=} @var{value} is
10018 Less than, greater than on integral, floating-point, or enumerated
10022 Less than or equal to, greater than or equal to
10023 on integral, floating-point and enumerated types, or set inclusion on
10024 set types. Same precedence as @code{<}.
10026 @item =@r{, }<>@r{, }#
10027 Equality and two ways of expressing inequality, valid on scalar types.
10028 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10029 available for inequality, since @code{#} conflicts with the script
10033 Set membership. Defined on set types and the types of their members.
10034 Same precedence as @code{<}.
10037 Boolean disjunction. Defined on boolean types.
10040 Boolean conjunction. Defined on boolean types.
10043 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10046 Addition and subtraction on integral and floating-point types, or union
10047 and difference on set types.
10050 Multiplication on integral and floating-point types, or set intersection
10054 Division on floating-point types, or symmetric set difference on set
10055 types. Same precedence as @code{*}.
10058 Integer division and remainder. Defined on integral types. Same
10059 precedence as @code{*}.
10062 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10065 Pointer dereferencing. Defined on pointer types.
10068 Boolean negation. Defined on boolean types. Same precedence as
10072 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10073 precedence as @code{^}.
10076 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10079 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10083 @value{GDBN} and Modula-2 scope operators.
10087 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10088 treats the use of the operator @code{IN}, or the use of operators
10089 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10090 @code{<=}, and @code{>=} on sets as an error.
10094 @node Built-In Func/Proc
10095 @subsubsection Built-in Functions and Procedures
10096 @cindex Modula-2 built-ins
10098 Modula-2 also makes available several built-in procedures and functions.
10099 In describing these, the following metavariables are used:
10104 represents an @code{ARRAY} variable.
10107 represents a @code{CHAR} constant or variable.
10110 represents a variable or constant of integral type.
10113 represents an identifier that belongs to a set. Generally used in the
10114 same function with the metavariable @var{s}. The type of @var{s} should
10115 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10118 represents a variable or constant of integral or floating-point type.
10121 represents a variable or constant of floating-point type.
10127 represents a variable.
10130 represents a variable or constant of one of many types. See the
10131 explanation of the function for details.
10134 All Modula-2 built-in procedures also return a result, described below.
10138 Returns the absolute value of @var{n}.
10141 If @var{c} is a lower case letter, it returns its upper case
10142 equivalent, otherwise it returns its argument.
10145 Returns the character whose ordinal value is @var{i}.
10148 Decrements the value in the variable @var{v} by one. Returns the new value.
10150 @item DEC(@var{v},@var{i})
10151 Decrements the value in the variable @var{v} by @var{i}. Returns the
10154 @item EXCL(@var{m},@var{s})
10155 Removes the element @var{m} from the set @var{s}. Returns the new
10158 @item FLOAT(@var{i})
10159 Returns the floating point equivalent of the integer @var{i}.
10161 @item HIGH(@var{a})
10162 Returns the index of the last member of @var{a}.
10165 Increments the value in the variable @var{v} by one. Returns the new value.
10167 @item INC(@var{v},@var{i})
10168 Increments the value in the variable @var{v} by @var{i}. Returns the
10171 @item INCL(@var{m},@var{s})
10172 Adds the element @var{m} to the set @var{s} if it is not already
10173 there. Returns the new set.
10176 Returns the maximum value of the type @var{t}.
10179 Returns the minimum value of the type @var{t}.
10182 Returns boolean TRUE if @var{i} is an odd number.
10185 Returns the ordinal value of its argument. For example, the ordinal
10186 value of a character is its @sc{ascii} value (on machines supporting the
10187 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10188 integral, character and enumerated types.
10190 @item SIZE(@var{x})
10191 Returns the size of its argument. @var{x} can be a variable or a type.
10193 @item TRUNC(@var{r})
10194 Returns the integral part of @var{r}.
10196 @item TSIZE(@var{x})
10197 Returns the size of its argument. @var{x} can be a variable or a type.
10199 @item VAL(@var{t},@var{i})
10200 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10204 @emph{Warning:} Sets and their operations are not yet supported, so
10205 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10209 @cindex Modula-2 constants
10211 @subsubsection Constants
10213 @value{GDBN} allows you to express the constants of Modula-2 in the following
10219 Integer constants are simply a sequence of digits. When used in an
10220 expression, a constant is interpreted to be type-compatible with the
10221 rest of the expression. Hexadecimal integers are specified by a
10222 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10225 Floating point constants appear as a sequence of digits, followed by a
10226 decimal point and another sequence of digits. An optional exponent can
10227 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10228 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10229 digits of the floating point constant must be valid decimal (base 10)
10233 Character constants consist of a single character enclosed by a pair of
10234 like quotes, either single (@code{'}) or double (@code{"}). They may
10235 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10236 followed by a @samp{C}.
10239 String constants consist of a sequence of characters enclosed by a
10240 pair of like quotes, either single (@code{'}) or double (@code{"}).
10241 Escape sequences in the style of C are also allowed. @xref{C
10242 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10246 Enumerated constants consist of an enumerated identifier.
10249 Boolean constants consist of the identifiers @code{TRUE} and
10253 Pointer constants consist of integral values only.
10256 Set constants are not yet supported.
10260 @subsubsection Modula-2 Types
10261 @cindex Modula-2 types
10263 Currently @value{GDBN} can print the following data types in Modula-2
10264 syntax: array types, record types, set types, pointer types, procedure
10265 types, enumerated types, subrange types and base types. You can also
10266 print the contents of variables declared using these type.
10267 This section gives a number of simple source code examples together with
10268 sample @value{GDBN} sessions.
10270 The first example contains the following section of code:
10279 and you can request @value{GDBN} to interrogate the type and value of
10280 @code{r} and @code{s}.
10283 (@value{GDBP}) print s
10285 (@value{GDBP}) ptype s
10287 (@value{GDBP}) print r
10289 (@value{GDBP}) ptype r
10294 Likewise if your source code declares @code{s} as:
10298 s: SET ['A'..'Z'] ;
10302 then you may query the type of @code{s} by:
10305 (@value{GDBP}) ptype s
10306 type = SET ['A'..'Z']
10310 Note that at present you cannot interactively manipulate set
10311 expressions using the debugger.
10313 The following example shows how you might declare an array in Modula-2
10314 and how you can interact with @value{GDBN} to print its type and contents:
10318 s: ARRAY [-10..10] OF CHAR ;
10322 (@value{GDBP}) ptype s
10323 ARRAY [-10..10] OF CHAR
10326 Note that the array handling is not yet complete and although the type
10327 is printed correctly, expression handling still assumes that all
10328 arrays have a lower bound of zero and not @code{-10} as in the example
10331 Here are some more type related Modula-2 examples:
10335 colour = (blue, red, yellow, green) ;
10336 t = [blue..yellow] ;
10344 The @value{GDBN} interaction shows how you can query the data type
10345 and value of a variable.
10348 (@value{GDBP}) print s
10350 (@value{GDBP}) ptype t
10351 type = [blue..yellow]
10355 In this example a Modula-2 array is declared and its contents
10356 displayed. Observe that the contents are written in the same way as
10357 their @code{C} counterparts.
10361 s: ARRAY [1..5] OF CARDINAL ;
10367 (@value{GDBP}) print s
10368 $1 = @{1, 0, 0, 0, 0@}
10369 (@value{GDBP}) ptype s
10370 type = ARRAY [1..5] OF CARDINAL
10373 The Modula-2 language interface to @value{GDBN} also understands
10374 pointer types as shown in this example:
10378 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10385 and you can request that @value{GDBN} describes the type of @code{s}.
10388 (@value{GDBP}) ptype s
10389 type = POINTER TO ARRAY [1..5] OF CARDINAL
10392 @value{GDBN} handles compound types as we can see in this example.
10393 Here we combine array types, record types, pointer types and subrange
10404 myarray = ARRAY myrange OF CARDINAL ;
10405 myrange = [-2..2] ;
10407 s: POINTER TO ARRAY myrange OF foo ;
10411 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10415 (@value{GDBP}) ptype s
10416 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10419 f3 : ARRAY [-2..2] OF CARDINAL;
10424 @subsubsection Modula-2 Defaults
10425 @cindex Modula-2 defaults
10427 If type and range checking are set automatically by @value{GDBN}, they
10428 both default to @code{on} whenever the working language changes to
10429 Modula-2. This happens regardless of whether you or @value{GDBN}
10430 selected the working language.
10432 If you allow @value{GDBN} to set the language automatically, then entering
10433 code compiled from a file whose name ends with @file{.mod} sets the
10434 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10435 Infer the Source Language}, for further details.
10438 @subsubsection Deviations from Standard Modula-2
10439 @cindex Modula-2, deviations from
10441 A few changes have been made to make Modula-2 programs easier to debug.
10442 This is done primarily via loosening its type strictness:
10446 Unlike in standard Modula-2, pointer constants can be formed by
10447 integers. This allows you to modify pointer variables during
10448 debugging. (In standard Modula-2, the actual address contained in a
10449 pointer variable is hidden from you; it can only be modified
10450 through direct assignment to another pointer variable or expression that
10451 returned a pointer.)
10454 C escape sequences can be used in strings and characters to represent
10455 non-printable characters. @value{GDBN} prints out strings with these
10456 escape sequences embedded. Single non-printable characters are
10457 printed using the @samp{CHR(@var{nnn})} format.
10460 The assignment operator (@code{:=}) returns the value of its right-hand
10464 All built-in procedures both modify @emph{and} return their argument.
10468 @subsubsection Modula-2 Type and Range Checks
10469 @cindex Modula-2 checks
10472 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10475 @c FIXME remove warning when type/range checks added
10477 @value{GDBN} considers two Modula-2 variables type equivalent if:
10481 They are of types that have been declared equivalent via a @code{TYPE
10482 @var{t1} = @var{t2}} statement
10485 They have been declared on the same line. (Note: This is true of the
10486 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10489 As long as type checking is enabled, any attempt to combine variables
10490 whose types are not equivalent is an error.
10492 Range checking is done on all mathematical operations, assignment, array
10493 index bounds, and all built-in functions and procedures.
10496 @subsubsection The Scope Operators @code{::} and @code{.}
10498 @cindex @code{.}, Modula-2 scope operator
10499 @cindex colon, doubled as scope operator
10501 @vindex colon-colon@r{, in Modula-2}
10502 @c Info cannot handle :: but TeX can.
10505 @vindex ::@r{, in Modula-2}
10508 There are a few subtle differences between the Modula-2 scope operator
10509 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10514 @var{module} . @var{id}
10515 @var{scope} :: @var{id}
10519 where @var{scope} is the name of a module or a procedure,
10520 @var{module} the name of a module, and @var{id} is any declared
10521 identifier within your program, except another module.
10523 Using the @code{::} operator makes @value{GDBN} search the scope
10524 specified by @var{scope} for the identifier @var{id}. If it is not
10525 found in the specified scope, then @value{GDBN} searches all scopes
10526 enclosing the one specified by @var{scope}.
10528 Using the @code{.} operator makes @value{GDBN} search the current scope for
10529 the identifier specified by @var{id} that was imported from the
10530 definition module specified by @var{module}. With this operator, it is
10531 an error if the identifier @var{id} was not imported from definition
10532 module @var{module}, or if @var{id} is not an identifier in
10536 @subsubsection @value{GDBN} and Modula-2
10538 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10539 Five subcommands of @code{set print} and @code{show print} apply
10540 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10541 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10542 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10543 analogue in Modula-2.
10545 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10546 with any language, is not useful with Modula-2. Its
10547 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10548 created in Modula-2 as they can in C or C@t{++}. However, because an
10549 address can be specified by an integral constant, the construct
10550 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10552 @cindex @code{#} in Modula-2
10553 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10554 interpreted as the beginning of a comment. Use @code{<>} instead.
10560 The extensions made to @value{GDBN} for Ada only support
10561 output from the @sc{gnu} Ada (GNAT) compiler.
10562 Other Ada compilers are not currently supported, and
10563 attempting to debug executables produced by them is most likely
10567 @cindex expressions in Ada
10569 * Ada Mode Intro:: General remarks on the Ada syntax
10570 and semantics supported by Ada mode
10572 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10573 * Additions to Ada:: Extensions of the Ada expression syntax.
10574 * Stopping Before Main Program:: Debugging the program during elaboration.
10575 * Ada Glitches:: Known peculiarities of Ada mode.
10578 @node Ada Mode Intro
10579 @subsubsection Introduction
10580 @cindex Ada mode, general
10582 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10583 syntax, with some extensions.
10584 The philosophy behind the design of this subset is
10588 That @value{GDBN} should provide basic literals and access to operations for
10589 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10590 leaving more sophisticated computations to subprograms written into the
10591 program (which therefore may be called from @value{GDBN}).
10594 That type safety and strict adherence to Ada language restrictions
10595 are not particularly important to the @value{GDBN} user.
10598 That brevity is important to the @value{GDBN} user.
10601 Thus, for brevity, the debugger acts as if there were
10602 implicit @code{with} and @code{use} clauses in effect for all user-written
10603 packages, making it unnecessary to fully qualify most names with
10604 their packages, regardless of context. Where this causes ambiguity,
10605 @value{GDBN} asks the user's intent.
10607 The debugger will start in Ada mode if it detects an Ada main program.
10608 As for other languages, it will enter Ada mode when stopped in a program that
10609 was translated from an Ada source file.
10611 While in Ada mode, you may use `@t{--}' for comments. This is useful
10612 mostly for documenting command files. The standard @value{GDBN} comment
10613 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10614 middle (to allow based literals).
10616 The debugger supports limited overloading. Given a subprogram call in which
10617 the function symbol has multiple definitions, it will use the number of
10618 actual parameters and some information about their types to attempt to narrow
10619 the set of definitions. It also makes very limited use of context, preferring
10620 procedures to functions in the context of the @code{call} command, and
10621 functions to procedures elsewhere.
10623 @node Omissions from Ada
10624 @subsubsection Omissions from Ada
10625 @cindex Ada, omissions from
10627 Here are the notable omissions from the subset:
10631 Only a subset of the attributes are supported:
10635 @t{'First}, @t{'Last}, and @t{'Length}
10636 on array objects (not on types and subtypes).
10639 @t{'Min} and @t{'Max}.
10642 @t{'Pos} and @t{'Val}.
10648 @t{'Range} on array objects (not subtypes), but only as the right
10649 operand of the membership (@code{in}) operator.
10652 @t{'Access}, @t{'Unchecked_Access}, and
10653 @t{'Unrestricted_Access} (a GNAT extension).
10661 @code{Characters.Latin_1} are not available and
10662 concatenation is not implemented. Thus, escape characters in strings are
10663 not currently available.
10666 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10667 equality of representations. They will generally work correctly
10668 for strings and arrays whose elements have integer or enumeration types.
10669 They may not work correctly for arrays whose element
10670 types have user-defined equality, for arrays of real values
10671 (in particular, IEEE-conformant floating point, because of negative
10672 zeroes and NaNs), and for arrays whose elements contain unused bits with
10673 indeterminate values.
10676 The other component-by-component array operations (@code{and}, @code{or},
10677 @code{xor}, @code{not}, and relational tests other than equality)
10678 are not implemented.
10681 @cindex array aggregates (Ada)
10682 @cindex record aggregates (Ada)
10683 @cindex aggregates (Ada)
10684 There is limited support for array and record aggregates. They are
10685 permitted only on the right sides of assignments, as in these examples:
10688 set An_Array := (1, 2, 3, 4, 5, 6)
10689 set An_Array := (1, others => 0)
10690 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10691 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10692 set A_Record := (1, "Peter", True);
10693 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10697 discriminant's value by assigning an aggregate has an
10698 undefined effect if that discriminant is used within the record.
10699 However, you can first modify discriminants by directly assigning to
10700 them (which normally would not be allowed in Ada), and then performing an
10701 aggregate assignment. For example, given a variable @code{A_Rec}
10702 declared to have a type such as:
10705 type Rec (Len : Small_Integer := 0) is record
10707 Vals : IntArray (1 .. Len);
10711 you can assign a value with a different size of @code{Vals} with two
10716 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10719 As this example also illustrates, @value{GDBN} is very loose about the usual
10720 rules concerning aggregates. You may leave out some of the
10721 components of an array or record aggregate (such as the @code{Len}
10722 component in the assignment to @code{A_Rec} above); they will retain their
10723 original values upon assignment. You may freely use dynamic values as
10724 indices in component associations. You may even use overlapping or
10725 redundant component associations, although which component values are
10726 assigned in such cases is not defined.
10729 Calls to dispatching subprograms are not implemented.
10732 The overloading algorithm is much more limited (i.e., less selective)
10733 than that of real Ada. It makes only limited use of the context in
10734 which a subexpression appears to resolve its meaning, and it is much
10735 looser in its rules for allowing type matches. As a result, some
10736 function calls will be ambiguous, and the user will be asked to choose
10737 the proper resolution.
10740 The @code{new} operator is not implemented.
10743 Entry calls are not implemented.
10746 Aside from printing, arithmetic operations on the native VAX floating-point
10747 formats are not supported.
10750 It is not possible to slice a packed array.
10753 @node Additions to Ada
10754 @subsubsection Additions to Ada
10755 @cindex Ada, deviations from
10757 As it does for other languages, @value{GDBN} makes certain generic
10758 extensions to Ada (@pxref{Expressions}):
10762 If the expression @var{E} is a variable residing in memory (typically
10763 a local variable or array element) and @var{N} is a positive integer,
10764 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10765 @var{N}-1 adjacent variables following it in memory as an array. In
10766 Ada, this operator is generally not necessary, since its prime use is
10767 in displaying parts of an array, and slicing will usually do this in
10768 Ada. However, there are occasional uses when debugging programs in
10769 which certain debugging information has been optimized away.
10772 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10773 appears in function or file @var{B}.'' When @var{B} is a file name,
10774 you must typically surround it in single quotes.
10777 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10778 @var{type} that appears at address @var{addr}.''
10781 A name starting with @samp{$} is a convenience variable
10782 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10785 In addition, @value{GDBN} provides a few other shortcuts and outright
10786 additions specific to Ada:
10790 The assignment statement is allowed as an expression, returning
10791 its right-hand operand as its value. Thus, you may enter
10795 print A(tmp := y + 1)
10799 The semicolon is allowed as an ``operator,'' returning as its value
10800 the value of its right-hand operand.
10801 This allows, for example,
10802 complex conditional breaks:
10806 condition 1 (report(i); k += 1; A(k) > 100)
10810 Rather than use catenation and symbolic character names to introduce special
10811 characters into strings, one may instead use a special bracket notation,
10812 which is also used to print strings. A sequence of characters of the form
10813 @samp{["@var{XX}"]} within a string or character literal denotes the
10814 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10815 sequence of characters @samp{["""]} also denotes a single quotation mark
10816 in strings. For example,
10818 "One line.["0a"]Next line.["0a"]"
10821 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10825 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10826 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10834 When printing arrays, @value{GDBN} uses positional notation when the
10835 array has a lower bound of 1, and uses a modified named notation otherwise.
10836 For example, a one-dimensional array of three integers with a lower bound
10837 of 3 might print as
10844 That is, in contrast to valid Ada, only the first component has a @code{=>}
10848 You may abbreviate attributes in expressions with any unique,
10849 multi-character subsequence of
10850 their names (an exact match gets preference).
10851 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10852 in place of @t{a'length}.
10855 @cindex quoting Ada internal identifiers
10856 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10857 to lower case. The GNAT compiler uses upper-case characters for
10858 some of its internal identifiers, which are normally of no interest to users.
10859 For the rare occasions when you actually have to look at them,
10860 enclose them in angle brackets to avoid the lower-case mapping.
10863 @value{GDBP} print <JMPBUF_SAVE>[0]
10867 Printing an object of class-wide type or dereferencing an
10868 access-to-class-wide value will display all the components of the object's
10869 specific type (as indicated by its run-time tag). Likewise, component
10870 selection on such a value will operate on the specific type of the
10875 @node Stopping Before Main Program
10876 @subsubsection Stopping at the Very Beginning
10878 @cindex breakpointing Ada elaboration code
10879 It is sometimes necessary to debug the program during elaboration, and
10880 before reaching the main procedure.
10881 As defined in the Ada Reference
10882 Manual, the elaboration code is invoked from a procedure called
10883 @code{adainit}. To run your program up to the beginning of
10884 elaboration, simply use the following two commands:
10885 @code{tbreak adainit} and @code{run}.
10888 @subsubsection Known Peculiarities of Ada Mode
10889 @cindex Ada, problems
10891 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10892 we know of several problems with and limitations of Ada mode in
10894 some of which will be fixed with planned future releases of the debugger
10895 and the GNU Ada compiler.
10899 Currently, the debugger
10900 has insufficient information to determine whether certain pointers represent
10901 pointers to objects or the objects themselves.
10902 Thus, the user may have to tack an extra @code{.all} after an expression
10903 to get it printed properly.
10906 Static constants that the compiler chooses not to materialize as objects in
10907 storage are invisible to the debugger.
10910 Named parameter associations in function argument lists are ignored (the
10911 argument lists are treated as positional).
10914 Many useful library packages are currently invisible to the debugger.
10917 Fixed-point arithmetic, conversions, input, and output is carried out using
10918 floating-point arithmetic, and may give results that only approximate those on
10922 The type of the @t{'Address} attribute may not be @code{System.Address}.
10925 The GNAT compiler never generates the prefix @code{Standard} for any of
10926 the standard symbols defined by the Ada language. @value{GDBN} knows about
10927 this: it will strip the prefix from names when you use it, and will never
10928 look for a name you have so qualified among local symbols, nor match against
10929 symbols in other packages or subprograms. If you have
10930 defined entities anywhere in your program other than parameters and
10931 local variables whose simple names match names in @code{Standard},
10932 GNAT's lack of qualification here can cause confusion. When this happens,
10933 you can usually resolve the confusion
10934 by qualifying the problematic names with package
10935 @code{Standard} explicitly.
10938 @node Unsupported Languages
10939 @section Unsupported Languages
10941 @cindex unsupported languages
10942 @cindex minimal language
10943 In addition to the other fully-supported programming languages,
10944 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10945 It does not represent a real programming language, but provides a set
10946 of capabilities close to what the C or assembly languages provide.
10947 This should allow most simple operations to be performed while debugging
10948 an application that uses a language currently not supported by @value{GDBN}.
10950 If the language is set to @code{auto}, @value{GDBN} will automatically
10951 select this language if the current frame corresponds to an unsupported
10955 @chapter Examining the Symbol Table
10957 The commands described in this chapter allow you to inquire about the
10958 symbols (names of variables, functions and types) defined in your
10959 program. This information is inherent in the text of your program and
10960 does not change as your program executes. @value{GDBN} finds it in your
10961 program's symbol table, in the file indicated when you started @value{GDBN}
10962 (@pxref{File Options, ,Choosing Files}), or by one of the
10963 file-management commands (@pxref{Files, ,Commands to Specify Files}).
10965 @cindex symbol names
10966 @cindex names of symbols
10967 @cindex quoting names
10968 Occasionally, you may need to refer to symbols that contain unusual
10969 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10970 most frequent case is in referring to static variables in other
10971 source files (@pxref{Variables,,Program Variables}). File names
10972 are recorded in object files as debugging symbols, but @value{GDBN} would
10973 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10974 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10975 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10982 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10985 @cindex case-insensitive symbol names
10986 @cindex case sensitivity in symbol names
10987 @kindex set case-sensitive
10988 @item set case-sensitive on
10989 @itemx set case-sensitive off
10990 @itemx set case-sensitive auto
10991 Normally, when @value{GDBN} looks up symbols, it matches their names
10992 with case sensitivity determined by the current source language.
10993 Occasionally, you may wish to control that. The command @code{set
10994 case-sensitive} lets you do that by specifying @code{on} for
10995 case-sensitive matches or @code{off} for case-insensitive ones. If
10996 you specify @code{auto}, case sensitivity is reset to the default
10997 suitable for the source language. The default is case-sensitive
10998 matches for all languages except for Fortran, for which the default is
10999 case-insensitive matches.
11001 @kindex show case-sensitive
11002 @item show case-sensitive
11003 This command shows the current setting of case sensitivity for symbols
11006 @kindex info address
11007 @cindex address of a symbol
11008 @item info address @var{symbol}
11009 Describe where the data for @var{symbol} is stored. For a register
11010 variable, this says which register it is kept in. For a non-register
11011 local variable, this prints the stack-frame offset at which the variable
11014 Note the contrast with @samp{print &@var{symbol}}, which does not work
11015 at all for a register variable, and for a stack local variable prints
11016 the exact address of the current instantiation of the variable.
11018 @kindex info symbol
11019 @cindex symbol from address
11020 @cindex closest symbol and offset for an address
11021 @item info symbol @var{addr}
11022 Print the name of a symbol which is stored at the address @var{addr}.
11023 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11024 nearest symbol and an offset from it:
11027 (@value{GDBP}) info symbol 0x54320
11028 _initialize_vx + 396 in section .text
11032 This is the opposite of the @code{info address} command. You can use
11033 it to find out the name of a variable or a function given its address.
11036 @item whatis [@var{arg}]
11037 Print the data type of @var{arg}, which can be either an expression or
11038 a data type. With no argument, print the data type of @code{$}, the
11039 last value in the value history. If @var{arg} is an expression, it is
11040 not actually evaluated, and any side-effecting operations (such as
11041 assignments or function calls) inside it do not take place. If
11042 @var{arg} is a type name, it may be the name of a type or typedef, or
11043 for C code it may have the form @samp{class @var{class-name}},
11044 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11045 @samp{enum @var{enum-tag}}.
11046 @xref{Expressions, ,Expressions}.
11049 @item ptype [@var{arg}]
11050 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11051 detailed description of the type, instead of just the name of the type.
11052 @xref{Expressions, ,Expressions}.
11054 For example, for this variable declaration:
11057 struct complex @{double real; double imag;@} v;
11061 the two commands give this output:
11065 (@value{GDBP}) whatis v
11066 type = struct complex
11067 (@value{GDBP}) ptype v
11068 type = struct complex @{
11076 As with @code{whatis}, using @code{ptype} without an argument refers to
11077 the type of @code{$}, the last value in the value history.
11079 @cindex incomplete type
11080 Sometimes, programs use opaque data types or incomplete specifications
11081 of complex data structure. If the debug information included in the
11082 program does not allow @value{GDBN} to display a full declaration of
11083 the data type, it will say @samp{<incomplete type>}. For example,
11084 given these declarations:
11088 struct foo *fooptr;
11092 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11095 (@value{GDBP}) ptype foo
11096 $1 = <incomplete type>
11100 ``Incomplete type'' is C terminology for data types that are not
11101 completely specified.
11104 @item info types @var{regexp}
11106 Print a brief description of all types whose names match the regular
11107 expression @var{regexp} (or all types in your program, if you supply
11108 no argument). Each complete typename is matched as though it were a
11109 complete line; thus, @samp{i type value} gives information on all
11110 types in your program whose names include the string @code{value}, but
11111 @samp{i type ^value$} gives information only on types whose complete
11112 name is @code{value}.
11114 This command differs from @code{ptype} in two ways: first, like
11115 @code{whatis}, it does not print a detailed description; second, it
11116 lists all source files where a type is defined.
11119 @cindex local variables
11120 @item info scope @var{location}
11121 List all the variables local to a particular scope. This command
11122 accepts a @var{location} argument---a function name, a source line, or
11123 an address preceded by a @samp{*}, and prints all the variables local
11124 to the scope defined by that location. (@xref{Specify Location}, for
11125 details about supported forms of @var{location}.) For example:
11128 (@value{GDBP}) @b{info scope command_line_handler}
11129 Scope for command_line_handler:
11130 Symbol rl is an argument at stack/frame offset 8, length 4.
11131 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11132 Symbol linelength is in static storage at address 0x150a1c, length 4.
11133 Symbol p is a local variable in register $esi, length 4.
11134 Symbol p1 is a local variable in register $ebx, length 4.
11135 Symbol nline is a local variable in register $edx, length 4.
11136 Symbol repeat is a local variable at frame offset -8, length 4.
11140 This command is especially useful for determining what data to collect
11141 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11144 @kindex info source
11146 Show information about the current source file---that is, the source file for
11147 the function containing the current point of execution:
11150 the name of the source file, and the directory containing it,
11152 the directory it was compiled in,
11154 its length, in lines,
11156 which programming language it is written in,
11158 whether the executable includes debugging information for that file, and
11159 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11161 whether the debugging information includes information about
11162 preprocessor macros.
11166 @kindex info sources
11168 Print the names of all source files in your program for which there is
11169 debugging information, organized into two lists: files whose symbols
11170 have already been read, and files whose symbols will be read when needed.
11172 @kindex info functions
11173 @item info functions
11174 Print the names and data types of all defined functions.
11176 @item info functions @var{regexp}
11177 Print the names and data types of all defined functions
11178 whose names contain a match for regular expression @var{regexp}.
11179 Thus, @samp{info fun step} finds all functions whose names
11180 include @code{step}; @samp{info fun ^step} finds those whose names
11181 start with @code{step}. If a function name contains characters
11182 that conflict with the regular expression language (e.g.@:
11183 @samp{operator*()}), they may be quoted with a backslash.
11185 @kindex info variables
11186 @item info variables
11187 Print the names and data types of all variables that are declared
11188 outside of functions (i.e.@: excluding local variables).
11190 @item info variables @var{regexp}
11191 Print the names and data types of all variables (except for local
11192 variables) whose names contain a match for regular expression
11195 @kindex info classes
11196 @cindex Objective-C, classes and selectors
11198 @itemx info classes @var{regexp}
11199 Display all Objective-C classes in your program, or
11200 (with the @var{regexp} argument) all those matching a particular regular
11203 @kindex info selectors
11204 @item info selectors
11205 @itemx info selectors @var{regexp}
11206 Display all Objective-C selectors in your program, or
11207 (with the @var{regexp} argument) all those matching a particular regular
11211 This was never implemented.
11212 @kindex info methods
11214 @itemx info methods @var{regexp}
11215 The @code{info methods} command permits the user to examine all defined
11216 methods within C@t{++} program, or (with the @var{regexp} argument) a
11217 specific set of methods found in the various C@t{++} classes. Many
11218 C@t{++} classes provide a large number of methods. Thus, the output
11219 from the @code{ptype} command can be overwhelming and hard to use. The
11220 @code{info-methods} command filters the methods, printing only those
11221 which match the regular-expression @var{regexp}.
11224 @cindex reloading symbols
11225 Some systems allow individual object files that make up your program to
11226 be replaced without stopping and restarting your program. For example,
11227 in VxWorks you can simply recompile a defective object file and keep on
11228 running. If you are running on one of these systems, you can allow
11229 @value{GDBN} to reload the symbols for automatically relinked modules:
11232 @kindex set symbol-reloading
11233 @item set symbol-reloading on
11234 Replace symbol definitions for the corresponding source file when an
11235 object file with a particular name is seen again.
11237 @item set symbol-reloading off
11238 Do not replace symbol definitions when encountering object files of the
11239 same name more than once. This is the default state; if you are not
11240 running on a system that permits automatic relinking of modules, you
11241 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11242 may discard symbols when linking large programs, that may contain
11243 several modules (from different directories or libraries) with the same
11246 @kindex show symbol-reloading
11247 @item show symbol-reloading
11248 Show the current @code{on} or @code{off} setting.
11251 @cindex opaque data types
11252 @kindex set opaque-type-resolution
11253 @item set opaque-type-resolution on
11254 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11255 declared as a pointer to a @code{struct}, @code{class}, or
11256 @code{union}---for example, @code{struct MyType *}---that is used in one
11257 source file although the full declaration of @code{struct MyType} is in
11258 another source file. The default is on.
11260 A change in the setting of this subcommand will not take effect until
11261 the next time symbols for a file are loaded.
11263 @item set opaque-type-resolution off
11264 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11265 is printed as follows:
11267 @{<no data fields>@}
11270 @kindex show opaque-type-resolution
11271 @item show opaque-type-resolution
11272 Show whether opaque types are resolved or not.
11274 @kindex maint print symbols
11275 @cindex symbol dump
11276 @kindex maint print psymbols
11277 @cindex partial symbol dump
11278 @item maint print symbols @var{filename}
11279 @itemx maint print psymbols @var{filename}
11280 @itemx maint print msymbols @var{filename}
11281 Write a dump of debugging symbol data into the file @var{filename}.
11282 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11283 symbols with debugging data are included. If you use @samp{maint print
11284 symbols}, @value{GDBN} includes all the symbols for which it has already
11285 collected full details: that is, @var{filename} reflects symbols for
11286 only those files whose symbols @value{GDBN} has read. You can use the
11287 command @code{info sources} to find out which files these are. If you
11288 use @samp{maint print psymbols} instead, the dump shows information about
11289 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11290 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11291 @samp{maint print msymbols} dumps just the minimal symbol information
11292 required for each object file from which @value{GDBN} has read some symbols.
11293 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11294 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11296 @kindex maint info symtabs
11297 @kindex maint info psymtabs
11298 @cindex listing @value{GDBN}'s internal symbol tables
11299 @cindex symbol tables, listing @value{GDBN}'s internal
11300 @cindex full symbol tables, listing @value{GDBN}'s internal
11301 @cindex partial symbol tables, listing @value{GDBN}'s internal
11302 @item maint info symtabs @r{[} @var{regexp} @r{]}
11303 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11305 List the @code{struct symtab} or @code{struct partial_symtab}
11306 structures whose names match @var{regexp}. If @var{regexp} is not
11307 given, list them all. The output includes expressions which you can
11308 copy into a @value{GDBN} debugging this one to examine a particular
11309 structure in more detail. For example:
11312 (@value{GDBP}) maint info psymtabs dwarf2read
11313 @{ objfile /home/gnu/build/gdb/gdb
11314 ((struct objfile *) 0x82e69d0)
11315 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11316 ((struct partial_symtab *) 0x8474b10)
11319 text addresses 0x814d3c8 -- 0x8158074
11320 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11321 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11322 dependencies (none)
11325 (@value{GDBP}) maint info symtabs
11329 We see that there is one partial symbol table whose filename contains
11330 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11331 and we see that @value{GDBN} has not read in any symtabs yet at all.
11332 If we set a breakpoint on a function, that will cause @value{GDBN} to
11333 read the symtab for the compilation unit containing that function:
11336 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11337 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11339 (@value{GDBP}) maint info symtabs
11340 @{ objfile /home/gnu/build/gdb/gdb
11341 ((struct objfile *) 0x82e69d0)
11342 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11343 ((struct symtab *) 0x86c1f38)
11346 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11347 linetable ((struct linetable *) 0x8370fa0)
11348 debugformat DWARF 2
11357 @chapter Altering Execution
11359 Once you think you have found an error in your program, you might want to
11360 find out for certain whether correcting the apparent error would lead to
11361 correct results in the rest of the run. You can find the answer by
11362 experiment, using the @value{GDBN} features for altering execution of the
11365 For example, you can store new values into variables or memory
11366 locations, give your program a signal, restart it at a different
11367 address, or even return prematurely from a function.
11370 * Assignment:: Assignment to variables
11371 * Jumping:: Continuing at a different address
11372 * Signaling:: Giving your program a signal
11373 * Returning:: Returning from a function
11374 * Calling:: Calling your program's functions
11375 * Patching:: Patching your program
11379 @section Assignment to Variables
11382 @cindex setting variables
11383 To alter the value of a variable, evaluate an assignment expression.
11384 @xref{Expressions, ,Expressions}. For example,
11391 stores the value 4 into the variable @code{x}, and then prints the
11392 value of the assignment expression (which is 4).
11393 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11394 information on operators in supported languages.
11396 @kindex set variable
11397 @cindex variables, setting
11398 If you are not interested in seeing the value of the assignment, use the
11399 @code{set} command instead of the @code{print} command. @code{set} is
11400 really the same as @code{print} except that the expression's value is
11401 not printed and is not put in the value history (@pxref{Value History,
11402 ,Value History}). The expression is evaluated only for its effects.
11404 If the beginning of the argument string of the @code{set} command
11405 appears identical to a @code{set} subcommand, use the @code{set
11406 variable} command instead of just @code{set}. This command is identical
11407 to @code{set} except for its lack of subcommands. For example, if your
11408 program has a variable @code{width}, you get an error if you try to set
11409 a new value with just @samp{set width=13}, because @value{GDBN} has the
11410 command @code{set width}:
11413 (@value{GDBP}) whatis width
11415 (@value{GDBP}) p width
11417 (@value{GDBP}) set width=47
11418 Invalid syntax in expression.
11422 The invalid expression, of course, is @samp{=47}. In
11423 order to actually set the program's variable @code{width}, use
11426 (@value{GDBP}) set var width=47
11429 Because the @code{set} command has many subcommands that can conflict
11430 with the names of program variables, it is a good idea to use the
11431 @code{set variable} command instead of just @code{set}. For example, if
11432 your program has a variable @code{g}, you run into problems if you try
11433 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11434 the command @code{set gnutarget}, abbreviated @code{set g}:
11438 (@value{GDBP}) whatis g
11442 (@value{GDBP}) set g=4
11446 The program being debugged has been started already.
11447 Start it from the beginning? (y or n) y
11448 Starting program: /home/smith/cc_progs/a.out
11449 "/home/smith/cc_progs/a.out": can't open to read symbols:
11450 Invalid bfd target.
11451 (@value{GDBP}) show g
11452 The current BFD target is "=4".
11457 The program variable @code{g} did not change, and you silently set the
11458 @code{gnutarget} to an invalid value. In order to set the variable
11462 (@value{GDBP}) set var g=4
11465 @value{GDBN} allows more implicit conversions in assignments than C; you can
11466 freely store an integer value into a pointer variable or vice versa,
11467 and you can convert any structure to any other structure that is the
11468 same length or shorter.
11469 @comment FIXME: how do structs align/pad in these conversions?
11470 @comment /doc@cygnus.com 18dec1990
11472 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11473 construct to generate a value of specified type at a specified address
11474 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11475 to memory location @code{0x83040} as an integer (which implies a certain size
11476 and representation in memory), and
11479 set @{int@}0x83040 = 4
11483 stores the value 4 into that memory location.
11486 @section Continuing at a Different Address
11488 Ordinarily, when you continue your program, you do so at the place where
11489 it stopped, with the @code{continue} command. You can instead continue at
11490 an address of your own choosing, with the following commands:
11494 @item jump @var{linespec}
11495 @itemx jump @var{location}
11496 Resume execution at line @var{linespec} or at address given by
11497 @var{location}. Execution stops again immediately if there is a
11498 breakpoint there. @xref{Specify Location}, for a description of the
11499 different forms of @var{linespec} and @var{location}. It is common
11500 practice to use the @code{tbreak} command in conjunction with
11501 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
11503 The @code{jump} command does not change the current stack frame, or
11504 the stack pointer, or the contents of any memory location or any
11505 register other than the program counter. If line @var{linespec} is in
11506 a different function from the one currently executing, the results may
11507 be bizarre if the two functions expect different patterns of arguments or
11508 of local variables. For this reason, the @code{jump} command requests
11509 confirmation if the specified line is not in the function currently
11510 executing. However, even bizarre results are predictable if you are
11511 well acquainted with the machine-language code of your program.
11514 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11515 On many systems, you can get much the same effect as the @code{jump}
11516 command by storing a new value into the register @code{$pc}. The
11517 difference is that this does not start your program running; it only
11518 changes the address of where it @emph{will} run when you continue. For
11526 makes the next @code{continue} command or stepping command execute at
11527 address @code{0x485}, rather than at the address where your program stopped.
11528 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11530 The most common occasion to use the @code{jump} command is to back
11531 up---perhaps with more breakpoints set---over a portion of a program
11532 that has already executed, in order to examine its execution in more
11537 @section Giving your Program a Signal
11538 @cindex deliver a signal to a program
11542 @item signal @var{signal}
11543 Resume execution where your program stopped, but immediately give it the
11544 signal @var{signal}. @var{signal} can be the name or the number of a
11545 signal. For example, on many systems @code{signal 2} and @code{signal
11546 SIGINT} are both ways of sending an interrupt signal.
11548 Alternatively, if @var{signal} is zero, continue execution without
11549 giving a signal. This is useful when your program stopped on account of
11550 a signal and would ordinary see the signal when resumed with the
11551 @code{continue} command; @samp{signal 0} causes it to resume without a
11554 @code{signal} does not repeat when you press @key{RET} a second time
11555 after executing the command.
11559 Invoking the @code{signal} command is not the same as invoking the
11560 @code{kill} utility from the shell. Sending a signal with @code{kill}
11561 causes @value{GDBN} to decide what to do with the signal depending on
11562 the signal handling tables (@pxref{Signals}). The @code{signal} command
11563 passes the signal directly to your program.
11567 @section Returning from a Function
11570 @cindex returning from a function
11573 @itemx return @var{expression}
11574 You can cancel execution of a function call with the @code{return}
11575 command. If you give an
11576 @var{expression} argument, its value is used as the function's return
11580 When you use @code{return}, @value{GDBN} discards the selected stack frame
11581 (and all frames within it). You can think of this as making the
11582 discarded frame return prematurely. If you wish to specify a value to
11583 be returned, give that value as the argument to @code{return}.
11585 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11586 Frame}), and any other frames inside of it, leaving its caller as the
11587 innermost remaining frame. That frame becomes selected. The
11588 specified value is stored in the registers used for returning values
11591 The @code{return} command does not resume execution; it leaves the
11592 program stopped in the state that would exist if the function had just
11593 returned. In contrast, the @code{finish} command (@pxref{Continuing
11594 and Stepping, ,Continuing and Stepping}) resumes execution until the
11595 selected stack frame returns naturally.
11598 @section Calling Program Functions
11601 @cindex calling functions
11602 @cindex inferior functions, calling
11603 @item print @var{expr}
11604 Evaluate the expression @var{expr} and display the resulting value.
11605 @var{expr} may include calls to functions in the program being
11609 @item call @var{expr}
11610 Evaluate the expression @var{expr} without displaying @code{void}
11613 You can use this variant of the @code{print} command if you want to
11614 execute a function from your program that does not return anything
11615 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11616 with @code{void} returned values that @value{GDBN} will otherwise
11617 print. If the result is not void, it is printed and saved in the
11621 It is possible for the function you call via the @code{print} or
11622 @code{call} command to generate a signal (e.g., if there's a bug in
11623 the function, or if you passed it incorrect arguments). What happens
11624 in that case is controlled by the @code{set unwindonsignal} command.
11627 @item set unwindonsignal
11628 @kindex set unwindonsignal
11629 @cindex unwind stack in called functions
11630 @cindex call dummy stack unwinding
11631 Set unwinding of the stack if a signal is received while in a function
11632 that @value{GDBN} called in the program being debugged. If set to on,
11633 @value{GDBN} unwinds the stack it created for the call and restores
11634 the context to what it was before the call. If set to off (the
11635 default), @value{GDBN} stops in the frame where the signal was
11638 @item show unwindonsignal
11639 @kindex show unwindonsignal
11640 Show the current setting of stack unwinding in the functions called by
11644 @cindex weak alias functions
11645 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11646 for another function. In such case, @value{GDBN} might not pick up
11647 the type information, including the types of the function arguments,
11648 which causes @value{GDBN} to call the inferior function incorrectly.
11649 As a result, the called function will function erroneously and may
11650 even crash. A solution to that is to use the name of the aliased
11654 @section Patching Programs
11656 @cindex patching binaries
11657 @cindex writing into executables
11658 @cindex writing into corefiles
11660 By default, @value{GDBN} opens the file containing your program's
11661 executable code (or the corefile) read-only. This prevents accidental
11662 alterations to machine code; but it also prevents you from intentionally
11663 patching your program's binary.
11665 If you'd like to be able to patch the binary, you can specify that
11666 explicitly with the @code{set write} command. For example, you might
11667 want to turn on internal debugging flags, or even to make emergency
11673 @itemx set write off
11674 If you specify @samp{set write on}, @value{GDBN} opens executable and
11675 core files for both reading and writing; if you specify @samp{set write
11676 off} (the default), @value{GDBN} opens them read-only.
11678 If you have already loaded a file, you must load it again (using the
11679 @code{exec-file} or @code{core-file} command) after changing @code{set
11680 write}, for your new setting to take effect.
11684 Display whether executable files and core files are opened for writing
11685 as well as reading.
11689 @chapter @value{GDBN} Files
11691 @value{GDBN} needs to know the file name of the program to be debugged,
11692 both in order to read its symbol table and in order to start your
11693 program. To debug a core dump of a previous run, you must also tell
11694 @value{GDBN} the name of the core dump file.
11697 * Files:: Commands to specify files
11698 * Separate Debug Files:: Debugging information in separate files
11699 * Symbol Errors:: Errors reading symbol files
11703 @section Commands to Specify Files
11705 @cindex symbol table
11706 @cindex core dump file
11708 You may want to specify executable and core dump file names. The usual
11709 way to do this is at start-up time, using the arguments to
11710 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11711 Out of @value{GDBN}}).
11713 Occasionally it is necessary to change to a different file during a
11714 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11715 specify a file you want to use. Or you are debugging a remote target
11716 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11717 Program}). In these situations the @value{GDBN} commands to specify
11718 new files are useful.
11721 @cindex executable file
11723 @item file @var{filename}
11724 Use @var{filename} as the program to be debugged. It is read for its
11725 symbols and for the contents of pure memory. It is also the program
11726 executed when you use the @code{run} command. If you do not specify a
11727 directory and the file is not found in the @value{GDBN} working directory,
11728 @value{GDBN} uses the environment variable @code{PATH} as a list of
11729 directories to search, just as the shell does when looking for a program
11730 to run. You can change the value of this variable, for both @value{GDBN}
11731 and your program, using the @code{path} command.
11733 @cindex unlinked object files
11734 @cindex patching object files
11735 You can load unlinked object @file{.o} files into @value{GDBN} using
11736 the @code{file} command. You will not be able to ``run'' an object
11737 file, but you can disassemble functions and inspect variables. Also,
11738 if the underlying BFD functionality supports it, you could use
11739 @kbd{gdb -write} to patch object files using this technique. Note
11740 that @value{GDBN} can neither interpret nor modify relocations in this
11741 case, so branches and some initialized variables will appear to go to
11742 the wrong place. But this feature is still handy from time to time.
11745 @code{file} with no argument makes @value{GDBN} discard any information it
11746 has on both executable file and the symbol table.
11749 @item exec-file @r{[} @var{filename} @r{]}
11750 Specify that the program to be run (but not the symbol table) is found
11751 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11752 if necessary to locate your program. Omitting @var{filename} means to
11753 discard information on the executable file.
11755 @kindex symbol-file
11756 @item symbol-file @r{[} @var{filename} @r{]}
11757 Read symbol table information from file @var{filename}. @code{PATH} is
11758 searched when necessary. Use the @code{file} command to get both symbol
11759 table and program to run from the same file.
11761 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11762 program's symbol table.
11764 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11765 some breakpoints and auto-display expressions. This is because they may
11766 contain pointers to the internal data recording symbols and data types,
11767 which are part of the old symbol table data being discarded inside
11770 @code{symbol-file} does not repeat if you press @key{RET} again after
11773 When @value{GDBN} is configured for a particular environment, it
11774 understands debugging information in whatever format is the standard
11775 generated for that environment; you may use either a @sc{gnu} compiler, or
11776 other compilers that adhere to the local conventions.
11777 Best results are usually obtained from @sc{gnu} compilers; for example,
11778 using @code{@value{NGCC}} you can generate debugging information for
11781 For most kinds of object files, with the exception of old SVR3 systems
11782 using COFF, the @code{symbol-file} command does not normally read the
11783 symbol table in full right away. Instead, it scans the symbol table
11784 quickly to find which source files and which symbols are present. The
11785 details are read later, one source file at a time, as they are needed.
11787 The purpose of this two-stage reading strategy is to make @value{GDBN}
11788 start up faster. For the most part, it is invisible except for
11789 occasional pauses while the symbol table details for a particular source
11790 file are being read. (The @code{set verbose} command can turn these
11791 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11792 Warnings and Messages}.)
11794 We have not implemented the two-stage strategy for COFF yet. When the
11795 symbol table is stored in COFF format, @code{symbol-file} reads the
11796 symbol table data in full right away. Note that ``stabs-in-COFF''
11797 still does the two-stage strategy, since the debug info is actually
11801 @cindex reading symbols immediately
11802 @cindex symbols, reading immediately
11803 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11804 @itemx file @var{filename} @r{[} -readnow @r{]}
11805 You can override the @value{GDBN} two-stage strategy for reading symbol
11806 tables by using the @samp{-readnow} option with any of the commands that
11807 load symbol table information, if you want to be sure @value{GDBN} has the
11808 entire symbol table available.
11810 @c FIXME: for now no mention of directories, since this seems to be in
11811 @c flux. 13mar1992 status is that in theory GDB would look either in
11812 @c current dir or in same dir as myprog; but issues like competing
11813 @c GDB's, or clutter in system dirs, mean that in practice right now
11814 @c only current dir is used. FFish says maybe a special GDB hierarchy
11815 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11819 @item core-file @r{[}@var{filename}@r{]}
11821 Specify the whereabouts of a core dump file to be used as the ``contents
11822 of memory''. Traditionally, core files contain only some parts of the
11823 address space of the process that generated them; @value{GDBN} can access the
11824 executable file itself for other parts.
11826 @code{core-file} with no argument specifies that no core file is
11829 Note that the core file is ignored when your program is actually running
11830 under @value{GDBN}. So, if you have been running your program and you
11831 wish to debug a core file instead, you must kill the subprocess in which
11832 the program is running. To do this, use the @code{kill} command
11833 (@pxref{Kill Process, ,Killing the Child Process}).
11835 @kindex add-symbol-file
11836 @cindex dynamic linking
11837 @item add-symbol-file @var{filename} @var{address}
11838 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11839 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11840 The @code{add-symbol-file} command reads additional symbol table
11841 information from the file @var{filename}. You would use this command
11842 when @var{filename} has been dynamically loaded (by some other means)
11843 into the program that is running. @var{address} should be the memory
11844 address at which the file has been loaded; @value{GDBN} cannot figure
11845 this out for itself. You can additionally specify an arbitrary number
11846 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11847 section name and base address for that section. You can specify any
11848 @var{address} as an expression.
11850 The symbol table of the file @var{filename} is added to the symbol table
11851 originally read with the @code{symbol-file} command. You can use the
11852 @code{add-symbol-file} command any number of times; the new symbol data
11853 thus read keeps adding to the old. To discard all old symbol data
11854 instead, use the @code{symbol-file} command without any arguments.
11856 @cindex relocatable object files, reading symbols from
11857 @cindex object files, relocatable, reading symbols from
11858 @cindex reading symbols from relocatable object files
11859 @cindex symbols, reading from relocatable object files
11860 @cindex @file{.o} files, reading symbols from
11861 Although @var{filename} is typically a shared library file, an
11862 executable file, or some other object file which has been fully
11863 relocated for loading into a process, you can also load symbolic
11864 information from relocatable @file{.o} files, as long as:
11868 the file's symbolic information refers only to linker symbols defined in
11869 that file, not to symbols defined by other object files,
11871 every section the file's symbolic information refers to has actually
11872 been loaded into the inferior, as it appears in the file, and
11874 you can determine the address at which every section was loaded, and
11875 provide these to the @code{add-symbol-file} command.
11879 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11880 relocatable files into an already running program; such systems
11881 typically make the requirements above easy to meet. However, it's
11882 important to recognize that many native systems use complex link
11883 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11884 assembly, for example) that make the requirements difficult to meet. In
11885 general, one cannot assume that using @code{add-symbol-file} to read a
11886 relocatable object file's symbolic information will have the same effect
11887 as linking the relocatable object file into the program in the normal
11890 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11892 @kindex add-symbol-file-from-memory
11893 @cindex @code{syscall DSO}
11894 @cindex load symbols from memory
11895 @item add-symbol-file-from-memory @var{address}
11896 Load symbols from the given @var{address} in a dynamically loaded
11897 object file whose image is mapped directly into the inferior's memory.
11898 For example, the Linux kernel maps a @code{syscall DSO} into each
11899 process's address space; this DSO provides kernel-specific code for
11900 some system calls. The argument can be any expression whose
11901 evaluation yields the address of the file's shared object file header.
11902 For this command to work, you must have used @code{symbol-file} or
11903 @code{exec-file} commands in advance.
11905 @kindex add-shared-symbol-files
11907 @item add-shared-symbol-files @var{library-file}
11908 @itemx assf @var{library-file}
11909 The @code{add-shared-symbol-files} command can currently be used only
11910 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11911 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11912 @value{GDBN} automatically looks for shared libraries, however if
11913 @value{GDBN} does not find yours, you can invoke
11914 @code{add-shared-symbol-files}. It takes one argument: the shared
11915 library's file name. @code{assf} is a shorthand alias for
11916 @code{add-shared-symbol-files}.
11919 @item section @var{section} @var{addr}
11920 The @code{section} command changes the base address of the named
11921 @var{section} of the exec file to @var{addr}. This can be used if the
11922 exec file does not contain section addresses, (such as in the
11923 @code{a.out} format), or when the addresses specified in the file
11924 itself are wrong. Each section must be changed separately. The
11925 @code{info files} command, described below, lists all the sections and
11929 @kindex info target
11932 @code{info files} and @code{info target} are synonymous; both print the
11933 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11934 including the names of the executable and core dump files currently in
11935 use by @value{GDBN}, and the files from which symbols were loaded. The
11936 command @code{help target} lists all possible targets rather than
11939 @kindex maint info sections
11940 @item maint info sections
11941 Another command that can give you extra information about program sections
11942 is @code{maint info sections}. In addition to the section information
11943 displayed by @code{info files}, this command displays the flags and file
11944 offset of each section in the executable and core dump files. In addition,
11945 @code{maint info sections} provides the following command options (which
11946 may be arbitrarily combined):
11950 Display sections for all loaded object files, including shared libraries.
11951 @item @var{sections}
11952 Display info only for named @var{sections}.
11953 @item @var{section-flags}
11954 Display info only for sections for which @var{section-flags} are true.
11955 The section flags that @value{GDBN} currently knows about are:
11958 Section will have space allocated in the process when loaded.
11959 Set for all sections except those containing debug information.
11961 Section will be loaded from the file into the child process memory.
11962 Set for pre-initialized code and data, clear for @code{.bss} sections.
11964 Section needs to be relocated before loading.
11966 Section cannot be modified by the child process.
11968 Section contains executable code only.
11970 Section contains data only (no executable code).
11972 Section will reside in ROM.
11974 Section contains data for constructor/destructor lists.
11976 Section is not empty.
11978 An instruction to the linker to not output the section.
11979 @item COFF_SHARED_LIBRARY
11980 A notification to the linker that the section contains
11981 COFF shared library information.
11983 Section contains common symbols.
11986 @kindex set trust-readonly-sections
11987 @cindex read-only sections
11988 @item set trust-readonly-sections on
11989 Tell @value{GDBN} that readonly sections in your object file
11990 really are read-only (i.e.@: that their contents will not change).
11991 In that case, @value{GDBN} can fetch values from these sections
11992 out of the object file, rather than from the target program.
11993 For some targets (notably embedded ones), this can be a significant
11994 enhancement to debugging performance.
11996 The default is off.
11998 @item set trust-readonly-sections off
11999 Tell @value{GDBN} not to trust readonly sections. This means that
12000 the contents of the section might change while the program is running,
12001 and must therefore be fetched from the target when needed.
12003 @item show trust-readonly-sections
12004 Show the current setting of trusting readonly sections.
12007 All file-specifying commands allow both absolute and relative file names
12008 as arguments. @value{GDBN} always converts the file name to an absolute file
12009 name and remembers it that way.
12011 @cindex shared libraries
12012 @anchor{Shared Libraries}
12013 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12014 and IBM RS/6000 AIX shared libraries.
12016 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12017 shared libraries. @xref{Expat}.
12019 @value{GDBN} automatically loads symbol definitions from shared libraries
12020 when you use the @code{run} command, or when you examine a core file.
12021 (Before you issue the @code{run} command, @value{GDBN} does not understand
12022 references to a function in a shared library, however---unless you are
12023 debugging a core file).
12025 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12026 automatically loads the symbols at the time of the @code{shl_load} call.
12028 @c FIXME: some @value{GDBN} release may permit some refs to undef
12029 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12030 @c FIXME...lib; check this from time to time when updating manual
12032 There are times, however, when you may wish to not automatically load
12033 symbol definitions from shared libraries, such as when they are
12034 particularly large or there are many of them.
12036 To control the automatic loading of shared library symbols, use the
12040 @kindex set auto-solib-add
12041 @item set auto-solib-add @var{mode}
12042 If @var{mode} is @code{on}, symbols from all shared object libraries
12043 will be loaded automatically when the inferior begins execution, you
12044 attach to an independently started inferior, or when the dynamic linker
12045 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12046 is @code{off}, symbols must be loaded manually, using the
12047 @code{sharedlibrary} command. The default value is @code{on}.
12049 @cindex memory used for symbol tables
12050 If your program uses lots of shared libraries with debug info that
12051 takes large amounts of memory, you can decrease the @value{GDBN}
12052 memory footprint by preventing it from automatically loading the
12053 symbols from shared libraries. To that end, type @kbd{set
12054 auto-solib-add off} before running the inferior, then load each
12055 library whose debug symbols you do need with @kbd{sharedlibrary
12056 @var{regexp}}, where @var{regexp} is a regular expression that matches
12057 the libraries whose symbols you want to be loaded.
12059 @kindex show auto-solib-add
12060 @item show auto-solib-add
12061 Display the current autoloading mode.
12064 @cindex load shared library
12065 To explicitly load shared library symbols, use the @code{sharedlibrary}
12069 @kindex info sharedlibrary
12072 @itemx info sharedlibrary
12073 Print the names of the shared libraries which are currently loaded.
12075 @kindex sharedlibrary
12077 @item sharedlibrary @var{regex}
12078 @itemx share @var{regex}
12079 Load shared object library symbols for files matching a
12080 Unix regular expression.
12081 As with files loaded automatically, it only loads shared libraries
12082 required by your program for a core file or after typing @code{run}. If
12083 @var{regex} is omitted all shared libraries required by your program are
12086 @item nosharedlibrary
12087 @kindex nosharedlibrary
12088 @cindex unload symbols from shared libraries
12089 Unload all shared object library symbols. This discards all symbols
12090 that have been loaded from all shared libraries. Symbols from shared
12091 libraries that were loaded by explicit user requests are not
12095 Sometimes you may wish that @value{GDBN} stops and gives you control
12096 when any of shared library events happen. Use the @code{set
12097 stop-on-solib-events} command for this:
12100 @item set stop-on-solib-events
12101 @kindex set stop-on-solib-events
12102 This command controls whether @value{GDBN} should give you control
12103 when the dynamic linker notifies it about some shared library event.
12104 The most common event of interest is loading or unloading of a new
12107 @item show stop-on-solib-events
12108 @kindex show stop-on-solib-events
12109 Show whether @value{GDBN} stops and gives you control when shared
12110 library events happen.
12113 Shared libraries are also supported in many cross or remote debugging
12114 configurations. A copy of the target's libraries need to be present on the
12115 host system; they need to be the same as the target libraries, although the
12116 copies on the target can be stripped as long as the copies on the host are
12119 @cindex where to look for shared libraries
12120 For remote debugging, you need to tell @value{GDBN} where the target
12121 libraries are, so that it can load the correct copies---otherwise, it
12122 may try to load the host's libraries. @value{GDBN} has two variables
12123 to specify the search directories for target libraries.
12126 @cindex prefix for shared library file names
12127 @cindex system root, alternate
12128 @kindex set solib-absolute-prefix
12129 @kindex set sysroot
12130 @item set sysroot @var{path}
12131 Use @var{path} as the system root for the program being debugged. Any
12132 absolute shared library paths will be prefixed with @var{path}; many
12133 runtime loaders store the absolute paths to the shared library in the
12134 target program's memory. If you use @code{set sysroot} to find shared
12135 libraries, they need to be laid out in the same way that they are on
12136 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12139 The @code{set solib-absolute-prefix} command is an alias for @code{set
12142 @cindex default system root
12143 @cindex @samp{--with-sysroot}
12144 You can set the default system root by using the configure-time
12145 @samp{--with-sysroot} option. If the system root is inside
12146 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12147 @samp{--exec-prefix}), then the default system root will be updated
12148 automatically if the installed @value{GDBN} is moved to a new
12151 @kindex show sysroot
12153 Display the current shared library prefix.
12155 @kindex set solib-search-path
12156 @item set solib-search-path @var{path}
12157 If this variable is set, @var{path} is a colon-separated list of
12158 directories to search for shared libraries. @samp{solib-search-path}
12159 is used after @samp{sysroot} fails to locate the library, or if the
12160 path to the library is relative instead of absolute. If you want to
12161 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12162 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12163 finding your host's libraries. @samp{sysroot} is preferred; setting
12164 it to a nonexistent directory may interfere with automatic loading
12165 of shared library symbols.
12167 @kindex show solib-search-path
12168 @item show solib-search-path
12169 Display the current shared library search path.
12173 @node Separate Debug Files
12174 @section Debugging Information in Separate Files
12175 @cindex separate debugging information files
12176 @cindex debugging information in separate files
12177 @cindex @file{.debug} subdirectories
12178 @cindex debugging information directory, global
12179 @cindex global debugging information directory
12180 @cindex build ID, and separate debugging files
12181 @cindex @file{.build-id} directory
12183 @value{GDBN} allows you to put a program's debugging information in a
12184 file separate from the executable itself, in a way that allows
12185 @value{GDBN} to find and load the debugging information automatically.
12186 Since debugging information can be very large---sometimes larger
12187 than the executable code itself---some systems distribute debugging
12188 information for their executables in separate files, which users can
12189 install only when they need to debug a problem.
12191 @value{GDBN} supports two ways of specifying the separate debug info
12196 The executable contains a @dfn{debug link} that specifies the name of
12197 the separate debug info file. The separate debug file's name is
12198 usually @file{@var{executable}.debug}, where @var{executable} is the
12199 name of the corresponding executable file without leading directories
12200 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12201 debug link specifies a CRC32 checksum for the debug file, which
12202 @value{GDBN} uses to validate that the executable and the debug file
12203 came from the same build.
12206 The executable contains a @dfn{build ID}, a unique bit string that is
12207 also present in the corresponding debug info file. (This is supported
12208 only on some operating systems, notably those which use the ELF format
12209 for binary files and the @sc{gnu} Binutils.) For more details about
12210 this feature, see the description of the @option{--build-id}
12211 command-line option in @ref{Options, , Command Line Options, ld.info,
12212 The GNU Linker}. The debug info file's name is not specified
12213 explicitly by the build ID, but can be computed from the build ID, see
12217 Depending on the way the debug info file is specified, @value{GDBN}
12218 uses two different methods of looking for the debug file:
12222 For the ``debug link'' method, @value{GDBN} looks up the named file in
12223 the directory of the executable file, then in a subdirectory of that
12224 directory named @file{.debug}, and finally under the global debug
12225 directory, in a subdirectory whose name is identical to the leading
12226 directories of the executable's absolute file name.
12229 For the ``build ID'' method, @value{GDBN} looks in the
12230 @file{.build-id} subdirectory of the global debug directory for a file
12231 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12232 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12233 are the rest of the bit string. (Real build ID strings are 32 or more
12234 hex characters, not 10.)
12237 So, for example, suppose you ask @value{GDBN} to debug
12238 @file{/usr/bin/ls}, which has a debug link that specifies the
12239 file @file{ls.debug}, and a build ID whose value in hex is
12240 @code{abcdef1234}. If the global debug directory is
12241 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12242 debug information files, in the indicated order:
12246 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12248 @file{/usr/bin/ls.debug}
12250 @file{/usr/bin/.debug/ls.debug}
12252 @file{/usr/lib/debug/usr/bin/ls.debug}.
12255 You can set the global debugging info directory's name, and view the
12256 name @value{GDBN} is currently using.
12260 @kindex set debug-file-directory
12261 @item set debug-file-directory @var{directory}
12262 Set the directory which @value{GDBN} searches for separate debugging
12263 information files to @var{directory}.
12265 @kindex show debug-file-directory
12266 @item show debug-file-directory
12267 Show the directory @value{GDBN} searches for separate debugging
12272 @cindex @code{.gnu_debuglink} sections
12273 @cindex debug link sections
12274 A debug link is a special section of the executable file named
12275 @code{.gnu_debuglink}. The section must contain:
12279 A filename, with any leading directory components removed, followed by
12282 zero to three bytes of padding, as needed to reach the next four-byte
12283 boundary within the section, and
12285 a four-byte CRC checksum, stored in the same endianness used for the
12286 executable file itself. The checksum is computed on the debugging
12287 information file's full contents by the function given below, passing
12288 zero as the @var{crc} argument.
12291 Any executable file format can carry a debug link, as long as it can
12292 contain a section named @code{.gnu_debuglink} with the contents
12295 @cindex @code{.note.gnu.build-id} sections
12296 @cindex build ID sections
12297 The build ID is a special section in the executable file (and in other
12298 ELF binary files that @value{GDBN} may consider). This section is
12299 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12300 It contains unique identification for the built files---the ID remains
12301 the same across multiple builds of the same build tree. The default
12302 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12303 content for the build ID string. The same section with an identical
12304 value is present in the original built binary with symbols, in its
12305 stripped variant, and in the separate debugging information file.
12307 The debugging information file itself should be an ordinary
12308 executable, containing a full set of linker symbols, sections, and
12309 debugging information. The sections of the debugging information file
12310 should have the same names, addresses, and sizes as the original file,
12311 but they need not contain any data---much like a @code{.bss} section
12312 in an ordinary executable.
12314 The @sc{gnu} binary utilities (Binutils) package includes the
12315 @samp{objcopy} utility that can produce
12316 the separated executable / debugging information file pairs using the
12317 following commands:
12320 @kbd{objcopy --only-keep-debug foo foo.debug}
12325 These commands remove the debugging
12326 information from the executable file @file{foo} and place it in the file
12327 @file{foo.debug}. You can use the first, second or both methods to link the
12332 The debug link method needs the following additional command to also leave
12333 behind a debug link in @file{foo}:
12336 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12339 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12340 a version of the @code{strip} command such that the command @kbd{strip foo -f
12341 foo.debug} has the same functionality as the two @code{objcopy} commands and
12342 the @code{ln -s} command above, together.
12345 Build ID gets embedded into the main executable using @code{ld --build-id} or
12346 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12347 compatibility fixes for debug files separation are present in @sc{gnu} binary
12348 utilities (Binutils) package since version 2.18.
12353 Since there are many different ways to compute CRC's for the debug
12354 link (different polynomials, reversals, byte ordering, etc.), the
12355 simplest way to describe the CRC used in @code{.gnu_debuglink}
12356 sections is to give the complete code for a function that computes it:
12358 @kindex gnu_debuglink_crc32
12361 gnu_debuglink_crc32 (unsigned long crc,
12362 unsigned char *buf, size_t len)
12364 static const unsigned long crc32_table[256] =
12366 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12367 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12368 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12369 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12370 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12371 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12372 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12373 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12374 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12375 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12376 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12377 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12378 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12379 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12380 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12381 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12382 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12383 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12384 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12385 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12386 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12387 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12388 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12389 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12390 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12391 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12392 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12393 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12394 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12395 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12396 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12397 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12398 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12399 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12400 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12401 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12402 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12403 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12404 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12405 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12406 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12407 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12408 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12409 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12410 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12411 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12412 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12413 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12414 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12415 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12416 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12419 unsigned char *end;
12421 crc = ~crc & 0xffffffff;
12422 for (end = buf + len; buf < end; ++buf)
12423 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12424 return ~crc & 0xffffffff;
12429 This computation does not apply to the ``build ID'' method.
12432 @node Symbol Errors
12433 @section Errors Reading Symbol Files
12435 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12436 such as symbol types it does not recognize, or known bugs in compiler
12437 output. By default, @value{GDBN} does not notify you of such problems, since
12438 they are relatively common and primarily of interest to people
12439 debugging compilers. If you are interested in seeing information
12440 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12441 only one message about each such type of problem, no matter how many
12442 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12443 to see how many times the problems occur, with the @code{set
12444 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12447 The messages currently printed, and their meanings, include:
12450 @item inner block not inside outer block in @var{symbol}
12452 The symbol information shows where symbol scopes begin and end
12453 (such as at the start of a function or a block of statements). This
12454 error indicates that an inner scope block is not fully contained
12455 in its outer scope blocks.
12457 @value{GDBN} circumvents the problem by treating the inner block as if it had
12458 the same scope as the outer block. In the error message, @var{symbol}
12459 may be shown as ``@code{(don't know)}'' if the outer block is not a
12462 @item block at @var{address} out of order
12464 The symbol information for symbol scope blocks should occur in
12465 order of increasing addresses. This error indicates that it does not
12468 @value{GDBN} does not circumvent this problem, and has trouble
12469 locating symbols in the source file whose symbols it is reading. (You
12470 can often determine what source file is affected by specifying
12471 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12474 @item bad block start address patched
12476 The symbol information for a symbol scope block has a start address
12477 smaller than the address of the preceding source line. This is known
12478 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12480 @value{GDBN} circumvents the problem by treating the symbol scope block as
12481 starting on the previous source line.
12483 @item bad string table offset in symbol @var{n}
12486 Symbol number @var{n} contains a pointer into the string table which is
12487 larger than the size of the string table.
12489 @value{GDBN} circumvents the problem by considering the symbol to have the
12490 name @code{foo}, which may cause other problems if many symbols end up
12493 @item unknown symbol type @code{0x@var{nn}}
12495 The symbol information contains new data types that @value{GDBN} does
12496 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12497 uncomprehended information, in hexadecimal.
12499 @value{GDBN} circumvents the error by ignoring this symbol information.
12500 This usually allows you to debug your program, though certain symbols
12501 are not accessible. If you encounter such a problem and feel like
12502 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12503 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12504 and examine @code{*bufp} to see the symbol.
12506 @item stub type has NULL name
12508 @value{GDBN} could not find the full definition for a struct or class.
12510 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12511 The symbol information for a C@t{++} member function is missing some
12512 information that recent versions of the compiler should have output for
12515 @item info mismatch between compiler and debugger
12517 @value{GDBN} could not parse a type specification output by the compiler.
12522 @chapter Specifying a Debugging Target
12524 @cindex debugging target
12525 A @dfn{target} is the execution environment occupied by your program.
12527 Often, @value{GDBN} runs in the same host environment as your program;
12528 in that case, the debugging target is specified as a side effect when
12529 you use the @code{file} or @code{core} commands. When you need more
12530 flexibility---for example, running @value{GDBN} on a physically separate
12531 host, or controlling a standalone system over a serial port or a
12532 realtime system over a TCP/IP connection---you can use the @code{target}
12533 command to specify one of the target types configured for @value{GDBN}
12534 (@pxref{Target Commands, ,Commands for Managing Targets}).
12536 @cindex target architecture
12537 It is possible to build @value{GDBN} for several different @dfn{target
12538 architectures}. When @value{GDBN} is built like that, you can choose
12539 one of the available architectures with the @kbd{set architecture}
12543 @kindex set architecture
12544 @kindex show architecture
12545 @item set architecture @var{arch}
12546 This command sets the current target architecture to @var{arch}. The
12547 value of @var{arch} can be @code{"auto"}, in addition to one of the
12548 supported architectures.
12550 @item show architecture
12551 Show the current target architecture.
12553 @item set processor
12555 @kindex set processor
12556 @kindex show processor
12557 These are alias commands for, respectively, @code{set architecture}
12558 and @code{show architecture}.
12562 * Active Targets:: Active targets
12563 * Target Commands:: Commands for managing targets
12564 * Byte Order:: Choosing target byte order
12567 @node Active Targets
12568 @section Active Targets
12570 @cindex stacking targets
12571 @cindex active targets
12572 @cindex multiple targets
12574 There are three classes of targets: processes, core files, and
12575 executable files. @value{GDBN} can work concurrently on up to three
12576 active targets, one in each class. This allows you to (for example)
12577 start a process and inspect its activity without abandoning your work on
12580 For example, if you execute @samp{gdb a.out}, then the executable file
12581 @code{a.out} is the only active target. If you designate a core file as
12582 well---presumably from a prior run that crashed and coredumped---then
12583 @value{GDBN} has two active targets and uses them in tandem, looking
12584 first in the corefile target, then in the executable file, to satisfy
12585 requests for memory addresses. (Typically, these two classes of target
12586 are complementary, since core files contain only a program's
12587 read-write memory---variables and so on---plus machine status, while
12588 executable files contain only the program text and initialized data.)
12590 When you type @code{run}, your executable file becomes an active process
12591 target as well. When a process target is active, all @value{GDBN}
12592 commands requesting memory addresses refer to that target; addresses in
12593 an active core file or executable file target are obscured while the
12594 process target is active.
12596 Use the @code{core-file} and @code{exec-file} commands to select a new
12597 core file or executable target (@pxref{Files, ,Commands to Specify
12598 Files}). To specify as a target a process that is already running, use
12599 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12602 @node Target Commands
12603 @section Commands for Managing Targets
12606 @item target @var{type} @var{parameters}
12607 Connects the @value{GDBN} host environment to a target machine or
12608 process. A target is typically a protocol for talking to debugging
12609 facilities. You use the argument @var{type} to specify the type or
12610 protocol of the target machine.
12612 Further @var{parameters} are interpreted by the target protocol, but
12613 typically include things like device names or host names to connect
12614 with, process numbers, and baud rates.
12616 The @code{target} command does not repeat if you press @key{RET} again
12617 after executing the command.
12619 @kindex help target
12621 Displays the names of all targets available. To display targets
12622 currently selected, use either @code{info target} or @code{info files}
12623 (@pxref{Files, ,Commands to Specify Files}).
12625 @item help target @var{name}
12626 Describe a particular target, including any parameters necessary to
12629 @kindex set gnutarget
12630 @item set gnutarget @var{args}
12631 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12632 knows whether it is reading an @dfn{executable},
12633 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12634 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12635 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12638 @emph{Warning:} To specify a file format with @code{set gnutarget},
12639 you must know the actual BFD name.
12643 @xref{Files, , Commands to Specify Files}.
12645 @kindex show gnutarget
12646 @item show gnutarget
12647 Use the @code{show gnutarget} command to display what file format
12648 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12649 @value{GDBN} will determine the file format for each file automatically,
12650 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12653 @cindex common targets
12654 Here are some common targets (available, or not, depending on the GDB
12659 @item target exec @var{program}
12660 @cindex executable file target
12661 An executable file. @samp{target exec @var{program}} is the same as
12662 @samp{exec-file @var{program}}.
12664 @item target core @var{filename}
12665 @cindex core dump file target
12666 A core dump file. @samp{target core @var{filename}} is the same as
12667 @samp{core-file @var{filename}}.
12669 @item target remote @var{medium}
12670 @cindex remote target
12671 A remote system connected to @value{GDBN} via a serial line or network
12672 connection. This command tells @value{GDBN} to use its own remote
12673 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12675 For example, if you have a board connected to @file{/dev/ttya} on the
12676 machine running @value{GDBN}, you could say:
12679 target remote /dev/ttya
12682 @code{target remote} supports the @code{load} command. This is only
12683 useful if you have some other way of getting the stub to the target
12684 system, and you can put it somewhere in memory where it won't get
12685 clobbered by the download.
12688 @cindex built-in simulator target
12689 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12697 works; however, you cannot assume that a specific memory map, device
12698 drivers, or even basic I/O is available, although some simulators do
12699 provide these. For info about any processor-specific simulator details,
12700 see the appropriate section in @ref{Embedded Processors, ,Embedded
12705 Some configurations may include these targets as well:
12709 @item target nrom @var{dev}
12710 @cindex NetROM ROM emulator target
12711 NetROM ROM emulator. This target only supports downloading.
12715 Different targets are available on different configurations of @value{GDBN};
12716 your configuration may have more or fewer targets.
12718 Many remote targets require you to download the executable's code once
12719 you've successfully established a connection. You may wish to control
12720 various aspects of this process.
12725 @kindex set hash@r{, for remote monitors}
12726 @cindex hash mark while downloading
12727 This command controls whether a hash mark @samp{#} is displayed while
12728 downloading a file to the remote monitor. If on, a hash mark is
12729 displayed after each S-record is successfully downloaded to the
12733 @kindex show hash@r{, for remote monitors}
12734 Show the current status of displaying the hash mark.
12736 @item set debug monitor
12737 @kindex set debug monitor
12738 @cindex display remote monitor communications
12739 Enable or disable display of communications messages between
12740 @value{GDBN} and the remote monitor.
12742 @item show debug monitor
12743 @kindex show debug monitor
12744 Show the current status of displaying communications between
12745 @value{GDBN} and the remote monitor.
12750 @kindex load @var{filename}
12751 @item load @var{filename}
12753 Depending on what remote debugging facilities are configured into
12754 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12755 is meant to make @var{filename} (an executable) available for debugging
12756 on the remote system---by downloading, or dynamic linking, for example.
12757 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12758 the @code{add-symbol-file} command.
12760 If your @value{GDBN} does not have a @code{load} command, attempting to
12761 execute it gets the error message ``@code{You can't do that when your
12762 target is @dots{}}''
12764 The file is loaded at whatever address is specified in the executable.
12765 For some object file formats, you can specify the load address when you
12766 link the program; for other formats, like a.out, the object file format
12767 specifies a fixed address.
12768 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12770 Depending on the remote side capabilities, @value{GDBN} may be able to
12771 load programs into flash memory.
12773 @code{load} does not repeat if you press @key{RET} again after using it.
12777 @section Choosing Target Byte Order
12779 @cindex choosing target byte order
12780 @cindex target byte order
12782 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12783 offer the ability to run either big-endian or little-endian byte
12784 orders. Usually the executable or symbol will include a bit to
12785 designate the endian-ness, and you will not need to worry about
12786 which to use. However, you may still find it useful to adjust
12787 @value{GDBN}'s idea of processor endian-ness manually.
12791 @item set endian big
12792 Instruct @value{GDBN} to assume the target is big-endian.
12794 @item set endian little
12795 Instruct @value{GDBN} to assume the target is little-endian.
12797 @item set endian auto
12798 Instruct @value{GDBN} to use the byte order associated with the
12802 Display @value{GDBN}'s current idea of the target byte order.
12806 Note that these commands merely adjust interpretation of symbolic
12807 data on the host, and that they have absolutely no effect on the
12811 @node Remote Debugging
12812 @chapter Debugging Remote Programs
12813 @cindex remote debugging
12815 If you are trying to debug a program running on a machine that cannot run
12816 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12817 For example, you might use remote debugging on an operating system kernel,
12818 or on a small system which does not have a general purpose operating system
12819 powerful enough to run a full-featured debugger.
12821 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12822 to make this work with particular debugging targets. In addition,
12823 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12824 but not specific to any particular target system) which you can use if you
12825 write the remote stubs---the code that runs on the remote system to
12826 communicate with @value{GDBN}.
12828 Other remote targets may be available in your
12829 configuration of @value{GDBN}; use @code{help target} to list them.
12832 * Connecting:: Connecting to a remote target
12833 * File Transfer:: Sending files to a remote system
12834 * Server:: Using the gdbserver program
12835 * Remote Configuration:: Remote configuration
12836 * Remote Stub:: Implementing a remote stub
12840 @section Connecting to a Remote Target
12842 On the @value{GDBN} host machine, you will need an unstripped copy of
12843 your program, since @value{GDBN} needs symbol and debugging information.
12844 Start up @value{GDBN} as usual, using the name of the local copy of your
12845 program as the first argument.
12847 @cindex @code{target remote}
12848 @value{GDBN} can communicate with the target over a serial line, or
12849 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12850 each case, @value{GDBN} uses the same protocol for debugging your
12851 program; only the medium carrying the debugging packets varies. The
12852 @code{target remote} command establishes a connection to the target.
12853 Its arguments indicate which medium to use:
12857 @item target remote @var{serial-device}
12858 @cindex serial line, @code{target remote}
12859 Use @var{serial-device} to communicate with the target. For example,
12860 to use a serial line connected to the device named @file{/dev/ttyb}:
12863 target remote /dev/ttyb
12866 If you're using a serial line, you may want to give @value{GDBN} the
12867 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12868 (@pxref{Remote Configuration, set remotebaud}) before the
12869 @code{target} command.
12871 @item target remote @code{@var{host}:@var{port}}
12872 @itemx target remote @code{tcp:@var{host}:@var{port}}
12873 @cindex @acronym{TCP} port, @code{target remote}
12874 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12875 The @var{host} may be either a host name or a numeric @acronym{IP}
12876 address; @var{port} must be a decimal number. The @var{host} could be
12877 the target machine itself, if it is directly connected to the net, or
12878 it might be a terminal server which in turn has a serial line to the
12881 For example, to connect to port 2828 on a terminal server named
12885 target remote manyfarms:2828
12888 If your remote target is actually running on the same machine as your
12889 debugger session (e.g.@: a simulator for your target running on the
12890 same host), you can omit the hostname. For example, to connect to
12891 port 1234 on your local machine:
12894 target remote :1234
12898 Note that the colon is still required here.
12900 @item target remote @code{udp:@var{host}:@var{port}}
12901 @cindex @acronym{UDP} port, @code{target remote}
12902 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12903 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12906 target remote udp:manyfarms:2828
12909 When using a @acronym{UDP} connection for remote debugging, you should
12910 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12911 can silently drop packets on busy or unreliable networks, which will
12912 cause havoc with your debugging session.
12914 @item target remote | @var{command}
12915 @cindex pipe, @code{target remote} to
12916 Run @var{command} in the background and communicate with it using a
12917 pipe. The @var{command} is a shell command, to be parsed and expanded
12918 by the system's command shell, @code{/bin/sh}; it should expect remote
12919 protocol packets on its standard input, and send replies on its
12920 standard output. You could use this to run a stand-alone simulator
12921 that speaks the remote debugging protocol, to make net connections
12922 using programs like @code{ssh}, or for other similar tricks.
12924 If @var{command} closes its standard output (perhaps by exiting),
12925 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12926 program has already exited, this will have no effect.)
12930 Once the connection has been established, you can use all the usual
12931 commands to examine and change data. The remote program is already
12932 running; you can use @kbd{step} and @kbd{continue}, and you do not
12933 need to use @kbd{run}.
12935 @cindex interrupting remote programs
12936 @cindex remote programs, interrupting
12937 Whenever @value{GDBN} is waiting for the remote program, if you type the
12938 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12939 program. This may or may not succeed, depending in part on the hardware
12940 and the serial drivers the remote system uses. If you type the
12941 interrupt character once again, @value{GDBN} displays this prompt:
12944 Interrupted while waiting for the program.
12945 Give up (and stop debugging it)? (y or n)
12948 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12949 (If you decide you want to try again later, you can use @samp{target
12950 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12951 goes back to waiting.
12954 @kindex detach (remote)
12956 When you have finished debugging the remote program, you can use the
12957 @code{detach} command to release it from @value{GDBN} control.
12958 Detaching from the target normally resumes its execution, but the results
12959 will depend on your particular remote stub. After the @code{detach}
12960 command, @value{GDBN} is free to connect to another target.
12964 The @code{disconnect} command behaves like @code{detach}, except that
12965 the target is generally not resumed. It will wait for @value{GDBN}
12966 (this instance or another one) to connect and continue debugging. After
12967 the @code{disconnect} command, @value{GDBN} is again free to connect to
12970 @cindex send command to remote monitor
12971 @cindex extend @value{GDBN} for remote targets
12972 @cindex add new commands for external monitor
12974 @item monitor @var{cmd}
12975 This command allows you to send arbitrary commands directly to the
12976 remote monitor. Since @value{GDBN} doesn't care about the commands it
12977 sends like this, this command is the way to extend @value{GDBN}---you
12978 can add new commands that only the external monitor will understand
12982 @node File Transfer
12983 @section Sending files to a remote system
12984 @cindex remote target, file transfer
12985 @cindex file transfer
12986 @cindex sending files to remote systems
12988 Some remote targets offer the ability to transfer files over the same
12989 connection used to communicate with @value{GDBN}. This is convenient
12990 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
12991 running @code{gdbserver} over a network interface. For other targets,
12992 e.g.@: embedded devices with only a single serial port, this may be
12993 the only way to upload or download files.
12995 Not all remote targets support these commands.
12999 @item remote put @var{hostfile} @var{targetfile}
13000 Copy file @var{hostfile} from the host system (the machine running
13001 @value{GDBN}) to @var{targetfile} on the target system.
13004 @item remote get @var{targetfile} @var{hostfile}
13005 Copy file @var{targetfile} from the target system to @var{hostfile}
13006 on the host system.
13008 @kindex remote delete
13009 @item remote delete @var{targetfile}
13010 Delete @var{targetfile} from the target system.
13015 @section Using the @code{gdbserver} Program
13018 @cindex remote connection without stubs
13019 @code{gdbserver} is a control program for Unix-like systems, which
13020 allows you to connect your program with a remote @value{GDBN} via
13021 @code{target remote}---but without linking in the usual debugging stub.
13023 @code{gdbserver} is not a complete replacement for the debugging stubs,
13024 because it requires essentially the same operating-system facilities
13025 that @value{GDBN} itself does. In fact, a system that can run
13026 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13027 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13028 because it is a much smaller program than @value{GDBN} itself. It is
13029 also easier to port than all of @value{GDBN}, so you may be able to get
13030 started more quickly on a new system by using @code{gdbserver}.
13031 Finally, if you develop code for real-time systems, you may find that
13032 the tradeoffs involved in real-time operation make it more convenient to
13033 do as much development work as possible on another system, for example
13034 by cross-compiling. You can use @code{gdbserver} to make a similar
13035 choice for debugging.
13037 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13038 or a TCP connection, using the standard @value{GDBN} remote serial
13042 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13043 Do not run @code{gdbserver} connected to any public network; a
13044 @value{GDBN} connection to @code{gdbserver} provides access to the
13045 target system with the same privileges as the user running
13049 @subsection Running @code{gdbserver}
13050 @cindex arguments, to @code{gdbserver}
13052 Run @code{gdbserver} on the target system. You need a copy of the
13053 program you want to debug, including any libraries it requires.
13054 @code{gdbserver} does not need your program's symbol table, so you can
13055 strip the program if necessary to save space. @value{GDBN} on the host
13056 system does all the symbol handling.
13058 To use the server, you must tell it how to communicate with @value{GDBN};
13059 the name of your program; and the arguments for your program. The usual
13063 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13066 @var{comm} is either a device name (to use a serial line) or a TCP
13067 hostname and portnumber. For example, to debug Emacs with the argument
13068 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13072 target> gdbserver /dev/com1 emacs foo.txt
13075 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13078 To use a TCP connection instead of a serial line:
13081 target> gdbserver host:2345 emacs foo.txt
13084 The only difference from the previous example is the first argument,
13085 specifying that you are communicating with the host @value{GDBN} via
13086 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13087 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13088 (Currently, the @samp{host} part is ignored.) You can choose any number
13089 you want for the port number as long as it does not conflict with any
13090 TCP ports already in use on the target system (for example, @code{23} is
13091 reserved for @code{telnet}).@footnote{If you choose a port number that
13092 conflicts with another service, @code{gdbserver} prints an error message
13093 and exits.} You must use the same port number with the host @value{GDBN}
13094 @code{target remote} command.
13096 @subsubsection Attaching to a Running Program
13098 On some targets, @code{gdbserver} can also attach to running programs.
13099 This is accomplished via the @code{--attach} argument. The syntax is:
13102 target> gdbserver --attach @var{comm} @var{pid}
13105 @var{pid} is the process ID of a currently running process. It isn't necessary
13106 to point @code{gdbserver} at a binary for the running process.
13109 @cindex attach to a program by name
13110 You can debug processes by name instead of process ID if your target has the
13111 @code{pidof} utility:
13114 target> gdbserver --attach @var{comm} `pidof @var{program}`
13117 In case more than one copy of @var{program} is running, or @var{program}
13118 has multiple threads, most versions of @code{pidof} support the
13119 @code{-s} option to only return the first process ID.
13121 @subsubsection Multi-Process Mode for @code{gdbserver}
13122 @cindex gdbserver, multiple processes
13123 @cindex multiple processes with gdbserver
13125 When you connect to @code{gdbserver} using @code{target remote},
13126 @code{gdbserver} debugs the specified program only once. When the
13127 program exits, or you detach from it, @value{GDBN} closes the connection
13128 and @code{gdbserver} exits.
13130 If you connect using @kbd{target extended-remote}, @code{gdbserver}
13131 enters multi-process mode. When the debugged program exits, or you
13132 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
13133 though no program is running. The @code{run} and @code{attach}
13134 commands instruct @code{gdbserver} to run or attach to a new program.
13135 The @code{run} command uses @code{set remote exec-file} (@pxref{set
13136 remote exec-file}) to select the program to run. Command line
13137 arguments are supported, except for wildcard expansion and I/O
13138 redirection (@pxref{Arguments}).
13140 To start @code{gdbserver} without supplying an initial command to run
13141 or process ID to attach, use the @option{--multi} command line option.
13142 Then you can connect using @kbd{target extended-remote} and start
13143 the program you want to debug.
13145 @code{gdbserver} does not automatically exit in multi-process mode.
13146 You can terminate it by using @code{monitor exit}
13147 (@pxref{Monitor Commands for gdbserver}).
13149 @subsubsection Other Command-Line Arguments for @code{gdbserver}
13151 You can include @option{--debug} on the @code{gdbserver} command line.
13152 @code{gdbserver} will display extra status information about the debugging
13153 process. This option is intended for @code{gdbserver} development and
13154 for bug reports to the developers.
13156 The @option{--wrapper} option specifies a wrapper to launch programs
13157 for debugging. The option should be followed by the name of the
13158 wrapper, then any command-line arguments to pass to the wrapper, then
13159 @kbd{--} indicating the end of the wrapper arguments.
13161 @code{gdbserver} runs the specified wrapper program with a combined
13162 command line including the wrapper arguments, then the name of the
13163 program to debug, then any arguments to the program. The wrapper
13164 runs until it executes your program, and then @value{GDBN} gains control.
13166 You can use any program that eventually calls @code{execve} with
13167 its arguments as a wrapper. Several standard Unix utilities do
13168 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
13169 with @code{exec "$@@"} will also work.
13171 For example, you can use @code{env} to pass an environment variable to
13172 the debugged program, without setting the variable in @code{gdbserver}'s
13176 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
13179 @subsection Connecting to @code{gdbserver}
13181 Run @value{GDBN} on the host system.
13183 First make sure you have the necessary symbol files. Load symbols for
13184 your application using the @code{file} command before you connect. Use
13185 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
13186 was compiled with the correct sysroot using @code{--with-sysroot}).
13188 The symbol file and target libraries must exactly match the executable
13189 and libraries on the target, with one exception: the files on the host
13190 system should not be stripped, even if the files on the target system
13191 are. Mismatched or missing files will lead to confusing results
13192 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
13193 files may also prevent @code{gdbserver} from debugging multi-threaded
13196 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
13197 For TCP connections, you must start up @code{gdbserver} prior to using
13198 the @code{target remote} command. Otherwise you may get an error whose
13199 text depends on the host system, but which usually looks something like
13200 @samp{Connection refused}. Don't use the @code{load}
13201 command in @value{GDBN} when using @code{gdbserver}, since the program is
13202 already on the target.
13204 @subsection Monitor Commands for @code{gdbserver}
13205 @cindex monitor commands, for @code{gdbserver}
13206 @anchor{Monitor Commands for gdbserver}
13208 During a @value{GDBN} session using @code{gdbserver}, you can use the
13209 @code{monitor} command to send special requests to @code{gdbserver}.
13210 Here are the available commands.
13214 List the available monitor commands.
13216 @item monitor set debug 0
13217 @itemx monitor set debug 1
13218 Disable or enable general debugging messages.
13220 @item monitor set remote-debug 0
13221 @itemx monitor set remote-debug 1
13222 Disable or enable specific debugging messages associated with the remote
13223 protocol (@pxref{Remote Protocol}).
13226 Tell gdbserver to exit immediately. This command should be followed by
13227 @code{disconnect} to close the debugging session. @code{gdbserver} will
13228 detach from any attached processes and kill any processes it created.
13229 Use @code{monitor exit} to terminate @code{gdbserver} at the end
13230 of a multi-process mode debug session.
13234 @node Remote Configuration
13235 @section Remote Configuration
13238 @kindex show remote
13239 This section documents the configuration options available when
13240 debugging remote programs. For the options related to the File I/O
13241 extensions of the remote protocol, see @ref{system,
13242 system-call-allowed}.
13245 @item set remoteaddresssize @var{bits}
13246 @cindex address size for remote targets
13247 @cindex bits in remote address
13248 Set the maximum size of address in a memory packet to the specified
13249 number of bits. @value{GDBN} will mask off the address bits above
13250 that number, when it passes addresses to the remote target. The
13251 default value is the number of bits in the target's address.
13253 @item show remoteaddresssize
13254 Show the current value of remote address size in bits.
13256 @item set remotebaud @var{n}
13257 @cindex baud rate for remote targets
13258 Set the baud rate for the remote serial I/O to @var{n} baud. The
13259 value is used to set the speed of the serial port used for debugging
13262 @item show remotebaud
13263 Show the current speed of the remote connection.
13265 @item set remotebreak
13266 @cindex interrupt remote programs
13267 @cindex BREAK signal instead of Ctrl-C
13268 @anchor{set remotebreak}
13269 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13270 when you type @kbd{Ctrl-c} to interrupt the program running
13271 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13272 character instead. The default is off, since most remote systems
13273 expect to see @samp{Ctrl-C} as the interrupt signal.
13275 @item show remotebreak
13276 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13277 interrupt the remote program.
13279 @item set remoteflow on
13280 @itemx set remoteflow off
13281 @kindex set remoteflow
13282 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13283 on the serial port used to communicate to the remote target.
13285 @item show remoteflow
13286 @kindex show remoteflow
13287 Show the current setting of hardware flow control.
13289 @item set remotelogbase @var{base}
13290 Set the base (a.k.a.@: radix) of logging serial protocol
13291 communications to @var{base}. Supported values of @var{base} are:
13292 @code{ascii}, @code{octal}, and @code{hex}. The default is
13295 @item show remotelogbase
13296 Show the current setting of the radix for logging remote serial
13299 @item set remotelogfile @var{file}
13300 @cindex record serial communications on file
13301 Record remote serial communications on the named @var{file}. The
13302 default is not to record at all.
13304 @item show remotelogfile.
13305 Show the current setting of the file name on which to record the
13306 serial communications.
13308 @item set remotetimeout @var{num}
13309 @cindex timeout for serial communications
13310 @cindex remote timeout
13311 Set the timeout limit to wait for the remote target to respond to
13312 @var{num} seconds. The default is 2 seconds.
13314 @item show remotetimeout
13315 Show the current number of seconds to wait for the remote target
13318 @cindex limit hardware breakpoints and watchpoints
13319 @cindex remote target, limit break- and watchpoints
13320 @anchor{set remote hardware-watchpoint-limit}
13321 @anchor{set remote hardware-breakpoint-limit}
13322 @item set remote hardware-watchpoint-limit @var{limit}
13323 @itemx set remote hardware-breakpoint-limit @var{limit}
13324 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13325 watchpoints. A limit of -1, the default, is treated as unlimited.
13327 @item set remote exec-file @var{filename}
13328 @itemx show remote exec-file
13329 @anchor{set remote exec-file}
13330 @cindex executable file, for remote target
13331 Select the file used for @code{run} with @code{target
13332 extended-remote}. This should be set to a filename valid on the
13333 target system. If it is not set, the target will use a default
13334 filename (e.g.@: the last program run).
13337 @cindex remote packets, enabling and disabling
13338 The @value{GDBN} remote protocol autodetects the packets supported by
13339 your debugging stub. If you need to override the autodetection, you
13340 can use these commands to enable or disable individual packets. Each
13341 packet can be set to @samp{on} (the remote target supports this
13342 packet), @samp{off} (the remote target does not support this packet),
13343 or @samp{auto} (detect remote target support for this packet). They
13344 all default to @samp{auto}. For more information about each packet,
13345 see @ref{Remote Protocol}.
13347 During normal use, you should not have to use any of these commands.
13348 If you do, that may be a bug in your remote debugging stub, or a bug
13349 in @value{GDBN}. You may want to report the problem to the
13350 @value{GDBN} developers.
13352 For each packet @var{name}, the command to enable or disable the
13353 packet is @code{set remote @var{name}-packet}. The available settings
13356 @multitable @columnfractions 0.28 0.32 0.25
13359 @tab Related Features
13361 @item @code{fetch-register}
13363 @tab @code{info registers}
13365 @item @code{set-register}
13369 @item @code{binary-download}
13371 @tab @code{load}, @code{set}
13373 @item @code{read-aux-vector}
13374 @tab @code{qXfer:auxv:read}
13375 @tab @code{info auxv}
13377 @item @code{symbol-lookup}
13378 @tab @code{qSymbol}
13379 @tab Detecting multiple threads
13381 @item @code{attach}
13382 @tab @code{vAttach}
13385 @item @code{verbose-resume}
13387 @tab Stepping or resuming multiple threads
13393 @item @code{software-breakpoint}
13397 @item @code{hardware-breakpoint}
13401 @item @code{write-watchpoint}
13405 @item @code{read-watchpoint}
13409 @item @code{access-watchpoint}
13413 @item @code{target-features}
13414 @tab @code{qXfer:features:read}
13415 @tab @code{set architecture}
13417 @item @code{library-info}
13418 @tab @code{qXfer:libraries:read}
13419 @tab @code{info sharedlibrary}
13421 @item @code{memory-map}
13422 @tab @code{qXfer:memory-map:read}
13423 @tab @code{info mem}
13425 @item @code{read-spu-object}
13426 @tab @code{qXfer:spu:read}
13427 @tab @code{info spu}
13429 @item @code{write-spu-object}
13430 @tab @code{qXfer:spu:write}
13431 @tab @code{info spu}
13433 @item @code{get-thread-local-@*storage-address}
13434 @tab @code{qGetTLSAddr}
13435 @tab Displaying @code{__thread} variables
13437 @item @code{supported-packets}
13438 @tab @code{qSupported}
13439 @tab Remote communications parameters
13441 @item @code{pass-signals}
13442 @tab @code{QPassSignals}
13443 @tab @code{handle @var{signal}}
13445 @item @code{hostio-close-packet}
13446 @tab @code{vFile:close}
13447 @tab @code{remote get}, @code{remote put}
13449 @item @code{hostio-open-packet}
13450 @tab @code{vFile:open}
13451 @tab @code{remote get}, @code{remote put}
13453 @item @code{hostio-pread-packet}
13454 @tab @code{vFile:pread}
13455 @tab @code{remote get}, @code{remote put}
13457 @item @code{hostio-pwrite-packet}
13458 @tab @code{vFile:pwrite}
13459 @tab @code{remote get}, @code{remote put}
13461 @item @code{hostio-unlink-packet}
13462 @tab @code{vFile:unlink}
13463 @tab @code{remote delete}
13467 @section Implementing a Remote Stub
13469 @cindex debugging stub, example
13470 @cindex remote stub, example
13471 @cindex stub example, remote debugging
13472 The stub files provided with @value{GDBN} implement the target side of the
13473 communication protocol, and the @value{GDBN} side is implemented in the
13474 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13475 these subroutines to communicate, and ignore the details. (If you're
13476 implementing your own stub file, you can still ignore the details: start
13477 with one of the existing stub files. @file{sparc-stub.c} is the best
13478 organized, and therefore the easiest to read.)
13480 @cindex remote serial debugging, overview
13481 To debug a program running on another machine (the debugging
13482 @dfn{target} machine), you must first arrange for all the usual
13483 prerequisites for the program to run by itself. For example, for a C
13488 A startup routine to set up the C runtime environment; these usually
13489 have a name like @file{crt0}. The startup routine may be supplied by
13490 your hardware supplier, or you may have to write your own.
13493 A C subroutine library to support your program's
13494 subroutine calls, notably managing input and output.
13497 A way of getting your program to the other machine---for example, a
13498 download program. These are often supplied by the hardware
13499 manufacturer, but you may have to write your own from hardware
13503 The next step is to arrange for your program to use a serial port to
13504 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13505 machine). In general terms, the scheme looks like this:
13509 @value{GDBN} already understands how to use this protocol; when everything
13510 else is set up, you can simply use the @samp{target remote} command
13511 (@pxref{Targets,,Specifying a Debugging Target}).
13513 @item On the target,
13514 you must link with your program a few special-purpose subroutines that
13515 implement the @value{GDBN} remote serial protocol. The file containing these
13516 subroutines is called a @dfn{debugging stub}.
13518 On certain remote targets, you can use an auxiliary program
13519 @code{gdbserver} instead of linking a stub into your program.
13520 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13523 The debugging stub is specific to the architecture of the remote
13524 machine; for example, use @file{sparc-stub.c} to debug programs on
13527 @cindex remote serial stub list
13528 These working remote stubs are distributed with @value{GDBN}:
13533 @cindex @file{i386-stub.c}
13536 For Intel 386 and compatible architectures.
13539 @cindex @file{m68k-stub.c}
13540 @cindex Motorola 680x0
13542 For Motorola 680x0 architectures.
13545 @cindex @file{sh-stub.c}
13548 For Renesas SH architectures.
13551 @cindex @file{sparc-stub.c}
13553 For @sc{sparc} architectures.
13555 @item sparcl-stub.c
13556 @cindex @file{sparcl-stub.c}
13559 For Fujitsu @sc{sparclite} architectures.
13563 The @file{README} file in the @value{GDBN} distribution may list other
13564 recently added stubs.
13567 * Stub Contents:: What the stub can do for you
13568 * Bootstrapping:: What you must do for the stub
13569 * Debug Session:: Putting it all together
13572 @node Stub Contents
13573 @subsection What the Stub Can Do for You
13575 @cindex remote serial stub
13576 The debugging stub for your architecture supplies these three
13580 @item set_debug_traps
13581 @findex set_debug_traps
13582 @cindex remote serial stub, initialization
13583 This routine arranges for @code{handle_exception} to run when your
13584 program stops. You must call this subroutine explicitly near the
13585 beginning of your program.
13587 @item handle_exception
13588 @findex handle_exception
13589 @cindex remote serial stub, main routine
13590 This is the central workhorse, but your program never calls it
13591 explicitly---the setup code arranges for @code{handle_exception} to
13592 run when a trap is triggered.
13594 @code{handle_exception} takes control when your program stops during
13595 execution (for example, on a breakpoint), and mediates communications
13596 with @value{GDBN} on the host machine. This is where the communications
13597 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13598 representative on the target machine. It begins by sending summary
13599 information on the state of your program, then continues to execute,
13600 retrieving and transmitting any information @value{GDBN} needs, until you
13601 execute a @value{GDBN} command that makes your program resume; at that point,
13602 @code{handle_exception} returns control to your own code on the target
13606 @cindex @code{breakpoint} subroutine, remote
13607 Use this auxiliary subroutine to make your program contain a
13608 breakpoint. Depending on the particular situation, this may be the only
13609 way for @value{GDBN} to get control. For instance, if your target
13610 machine has some sort of interrupt button, you won't need to call this;
13611 pressing the interrupt button transfers control to
13612 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13613 simply receiving characters on the serial port may also trigger a trap;
13614 again, in that situation, you don't need to call @code{breakpoint} from
13615 your own program---simply running @samp{target remote} from the host
13616 @value{GDBN} session gets control.
13618 Call @code{breakpoint} if none of these is true, or if you simply want
13619 to make certain your program stops at a predetermined point for the
13620 start of your debugging session.
13623 @node Bootstrapping
13624 @subsection What You Must Do for the Stub
13626 @cindex remote stub, support routines
13627 The debugging stubs that come with @value{GDBN} are set up for a particular
13628 chip architecture, but they have no information about the rest of your
13629 debugging target machine.
13631 First of all you need to tell the stub how to communicate with the
13635 @item int getDebugChar()
13636 @findex getDebugChar
13637 Write this subroutine to read a single character from the serial port.
13638 It may be identical to @code{getchar} for your target system; a
13639 different name is used to allow you to distinguish the two if you wish.
13641 @item void putDebugChar(int)
13642 @findex putDebugChar
13643 Write this subroutine to write a single character to the serial port.
13644 It may be identical to @code{putchar} for your target system; a
13645 different name is used to allow you to distinguish the two if you wish.
13648 @cindex control C, and remote debugging
13649 @cindex interrupting remote targets
13650 If you want @value{GDBN} to be able to stop your program while it is
13651 running, you need to use an interrupt-driven serial driver, and arrange
13652 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13653 character). That is the character which @value{GDBN} uses to tell the
13654 remote system to stop.
13656 Getting the debugging target to return the proper status to @value{GDBN}
13657 probably requires changes to the standard stub; one quick and dirty way
13658 is to just execute a breakpoint instruction (the ``dirty'' part is that
13659 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13661 Other routines you need to supply are:
13664 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13665 @findex exceptionHandler
13666 Write this function to install @var{exception_address} in the exception
13667 handling tables. You need to do this because the stub does not have any
13668 way of knowing what the exception handling tables on your target system
13669 are like (for example, the processor's table might be in @sc{rom},
13670 containing entries which point to a table in @sc{ram}).
13671 @var{exception_number} is the exception number which should be changed;
13672 its meaning is architecture-dependent (for example, different numbers
13673 might represent divide by zero, misaligned access, etc). When this
13674 exception occurs, control should be transferred directly to
13675 @var{exception_address}, and the processor state (stack, registers,
13676 and so on) should be just as it is when a processor exception occurs. So if
13677 you want to use a jump instruction to reach @var{exception_address}, it
13678 should be a simple jump, not a jump to subroutine.
13680 For the 386, @var{exception_address} should be installed as an interrupt
13681 gate so that interrupts are masked while the handler runs. The gate
13682 should be at privilege level 0 (the most privileged level). The
13683 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13684 help from @code{exceptionHandler}.
13686 @item void flush_i_cache()
13687 @findex flush_i_cache
13688 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13689 instruction cache, if any, on your target machine. If there is no
13690 instruction cache, this subroutine may be a no-op.
13692 On target machines that have instruction caches, @value{GDBN} requires this
13693 function to make certain that the state of your program is stable.
13697 You must also make sure this library routine is available:
13700 @item void *memset(void *, int, int)
13702 This is the standard library function @code{memset} that sets an area of
13703 memory to a known value. If you have one of the free versions of
13704 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13705 either obtain it from your hardware manufacturer, or write your own.
13708 If you do not use the GNU C compiler, you may need other standard
13709 library subroutines as well; this varies from one stub to another,
13710 but in general the stubs are likely to use any of the common library
13711 subroutines which @code{@value{NGCC}} generates as inline code.
13714 @node Debug Session
13715 @subsection Putting it All Together
13717 @cindex remote serial debugging summary
13718 In summary, when your program is ready to debug, you must follow these
13723 Make sure you have defined the supporting low-level routines
13724 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13726 @code{getDebugChar}, @code{putDebugChar},
13727 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13731 Insert these lines near the top of your program:
13739 For the 680x0 stub only, you need to provide a variable called
13740 @code{exceptionHook}. Normally you just use:
13743 void (*exceptionHook)() = 0;
13747 but if before calling @code{set_debug_traps}, you set it to point to a
13748 function in your program, that function is called when
13749 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13750 error). The function indicated by @code{exceptionHook} is called with
13751 one parameter: an @code{int} which is the exception number.
13754 Compile and link together: your program, the @value{GDBN} debugging stub for
13755 your target architecture, and the supporting subroutines.
13758 Make sure you have a serial connection between your target machine and
13759 the @value{GDBN} host, and identify the serial port on the host.
13762 @c The "remote" target now provides a `load' command, so we should
13763 @c document that. FIXME.
13764 Download your program to your target machine (or get it there by
13765 whatever means the manufacturer provides), and start it.
13768 Start @value{GDBN} on the host, and connect to the target
13769 (@pxref{Connecting,,Connecting to a Remote Target}).
13773 @node Configurations
13774 @chapter Configuration-Specific Information
13776 While nearly all @value{GDBN} commands are available for all native and
13777 cross versions of the debugger, there are some exceptions. This chapter
13778 describes things that are only available in certain configurations.
13780 There are three major categories of configurations: native
13781 configurations, where the host and target are the same, embedded
13782 operating system configurations, which are usually the same for several
13783 different processor architectures, and bare embedded processors, which
13784 are quite different from each other.
13789 * Embedded Processors::
13796 This section describes details specific to particular native
13801 * BSD libkvm Interface:: Debugging BSD kernel memory images
13802 * SVR4 Process Information:: SVR4 process information
13803 * DJGPP Native:: Features specific to the DJGPP port
13804 * Cygwin Native:: Features specific to the Cygwin port
13805 * Hurd Native:: Features specific to @sc{gnu} Hurd
13806 * Neutrino:: Features specific to QNX Neutrino
13812 On HP-UX systems, if you refer to a function or variable name that
13813 begins with a dollar sign, @value{GDBN} searches for a user or system
13814 name first, before it searches for a convenience variable.
13817 @node BSD libkvm Interface
13818 @subsection BSD libkvm Interface
13821 @cindex kernel memory image
13822 @cindex kernel crash dump
13824 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13825 interface that provides a uniform interface for accessing kernel virtual
13826 memory images, including live systems and crash dumps. @value{GDBN}
13827 uses this interface to allow you to debug live kernels and kernel crash
13828 dumps on many native BSD configurations. This is implemented as a
13829 special @code{kvm} debugging target. For debugging a live system, load
13830 the currently running kernel into @value{GDBN} and connect to the
13834 (@value{GDBP}) @b{target kvm}
13837 For debugging crash dumps, provide the file name of the crash dump as an
13841 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13844 Once connected to the @code{kvm} target, the following commands are
13850 Set current context from the @dfn{Process Control Block} (PCB) address.
13853 Set current context from proc address. This command isn't available on
13854 modern FreeBSD systems.
13857 @node SVR4 Process Information
13858 @subsection SVR4 Process Information
13860 @cindex examine process image
13861 @cindex process info via @file{/proc}
13863 Many versions of SVR4 and compatible systems provide a facility called
13864 @samp{/proc} that can be used to examine the image of a running
13865 process using file-system subroutines. If @value{GDBN} is configured
13866 for an operating system with this facility, the command @code{info
13867 proc} is available to report information about the process running
13868 your program, or about any process running on your system. @code{info
13869 proc} works only on SVR4 systems that include the @code{procfs} code.
13870 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13871 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13877 @itemx info proc @var{process-id}
13878 Summarize available information about any running process. If a
13879 process ID is specified by @var{process-id}, display information about
13880 that process; otherwise display information about the program being
13881 debugged. The summary includes the debugged process ID, the command
13882 line used to invoke it, its current working directory, and its
13883 executable file's absolute file name.
13885 On some systems, @var{process-id} can be of the form
13886 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13887 within a process. If the optional @var{pid} part is missing, it means
13888 a thread from the process being debugged (the leading @samp{/} still
13889 needs to be present, or else @value{GDBN} will interpret the number as
13890 a process ID rather than a thread ID).
13892 @item info proc mappings
13893 @cindex memory address space mappings
13894 Report the memory address space ranges accessible in the program, with
13895 information on whether the process has read, write, or execute access
13896 rights to each range. On @sc{gnu}/Linux systems, each memory range
13897 includes the object file which is mapped to that range, instead of the
13898 memory access rights to that range.
13900 @item info proc stat
13901 @itemx info proc status
13902 @cindex process detailed status information
13903 These subcommands are specific to @sc{gnu}/Linux systems. They show
13904 the process-related information, including the user ID and group ID;
13905 how many threads are there in the process; its virtual memory usage;
13906 the signals that are pending, blocked, and ignored; its TTY; its
13907 consumption of system and user time; its stack size; its @samp{nice}
13908 value; etc. For more information, see the @samp{proc} man page
13909 (type @kbd{man 5 proc} from your shell prompt).
13911 @item info proc all
13912 Show all the information about the process described under all of the
13913 above @code{info proc} subcommands.
13916 @comment These sub-options of 'info proc' were not included when
13917 @comment procfs.c was re-written. Keep their descriptions around
13918 @comment against the day when someone finds the time to put them back in.
13919 @kindex info proc times
13920 @item info proc times
13921 Starting time, user CPU time, and system CPU time for your program and
13924 @kindex info proc id
13926 Report on the process IDs related to your program: its own process ID,
13927 the ID of its parent, the process group ID, and the session ID.
13930 @item set procfs-trace
13931 @kindex set procfs-trace
13932 @cindex @code{procfs} API calls
13933 This command enables and disables tracing of @code{procfs} API calls.
13935 @item show procfs-trace
13936 @kindex show procfs-trace
13937 Show the current state of @code{procfs} API call tracing.
13939 @item set procfs-file @var{file}
13940 @kindex set procfs-file
13941 Tell @value{GDBN} to write @code{procfs} API trace to the named
13942 @var{file}. @value{GDBN} appends the trace info to the previous
13943 contents of the file. The default is to display the trace on the
13946 @item show procfs-file
13947 @kindex show procfs-file
13948 Show the file to which @code{procfs} API trace is written.
13950 @item proc-trace-entry
13951 @itemx proc-trace-exit
13952 @itemx proc-untrace-entry
13953 @itemx proc-untrace-exit
13954 @kindex proc-trace-entry
13955 @kindex proc-trace-exit
13956 @kindex proc-untrace-entry
13957 @kindex proc-untrace-exit
13958 These commands enable and disable tracing of entries into and exits
13959 from the @code{syscall} interface.
13962 @kindex info pidlist
13963 @cindex process list, QNX Neutrino
13964 For QNX Neutrino only, this command displays the list of all the
13965 processes and all the threads within each process.
13968 @kindex info meminfo
13969 @cindex mapinfo list, QNX Neutrino
13970 For QNX Neutrino only, this command displays the list of all mapinfos.
13974 @subsection Features for Debugging @sc{djgpp} Programs
13975 @cindex @sc{djgpp} debugging
13976 @cindex native @sc{djgpp} debugging
13977 @cindex MS-DOS-specific commands
13980 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13981 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13982 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13983 top of real-mode DOS systems and their emulations.
13985 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13986 defines a few commands specific to the @sc{djgpp} port. This
13987 subsection describes those commands.
13992 This is a prefix of @sc{djgpp}-specific commands which print
13993 information about the target system and important OS structures.
13996 @cindex MS-DOS system info
13997 @cindex free memory information (MS-DOS)
13998 @item info dos sysinfo
13999 This command displays assorted information about the underlying
14000 platform: the CPU type and features, the OS version and flavor, the
14001 DPMI version, and the available conventional and DPMI memory.
14006 @cindex segment descriptor tables
14007 @cindex descriptor tables display
14009 @itemx info dos ldt
14010 @itemx info dos idt
14011 These 3 commands display entries from, respectively, Global, Local,
14012 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14013 tables are data structures which store a descriptor for each segment
14014 that is currently in use. The segment's selector is an index into a
14015 descriptor table; the table entry for that index holds the
14016 descriptor's base address and limit, and its attributes and access
14019 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14020 segment (used for both data and the stack), and a DOS segment (which
14021 allows access to DOS/BIOS data structures and absolute addresses in
14022 conventional memory). However, the DPMI host will usually define
14023 additional segments in order to support the DPMI environment.
14025 @cindex garbled pointers
14026 These commands allow to display entries from the descriptor tables.
14027 Without an argument, all entries from the specified table are
14028 displayed. An argument, which should be an integer expression, means
14029 display a single entry whose index is given by the argument. For
14030 example, here's a convenient way to display information about the
14031 debugged program's data segment:
14034 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14035 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14039 This comes in handy when you want to see whether a pointer is outside
14040 the data segment's limit (i.e.@: @dfn{garbled}).
14042 @cindex page tables display (MS-DOS)
14044 @itemx info dos pte
14045 These two commands display entries from, respectively, the Page
14046 Directory and the Page Tables. Page Directories and Page Tables are
14047 data structures which control how virtual memory addresses are mapped
14048 into physical addresses. A Page Table includes an entry for every
14049 page of memory that is mapped into the program's address space; there
14050 may be several Page Tables, each one holding up to 4096 entries. A
14051 Page Directory has up to 4096 entries, one each for every Page Table
14052 that is currently in use.
14054 Without an argument, @kbd{info dos pde} displays the entire Page
14055 Directory, and @kbd{info dos pte} displays all the entries in all of
14056 the Page Tables. An argument, an integer expression, given to the
14057 @kbd{info dos pde} command means display only that entry from the Page
14058 Directory table. An argument given to the @kbd{info dos pte} command
14059 means display entries from a single Page Table, the one pointed to by
14060 the specified entry in the Page Directory.
14062 @cindex direct memory access (DMA) on MS-DOS
14063 These commands are useful when your program uses @dfn{DMA} (Direct
14064 Memory Access), which needs physical addresses to program the DMA
14067 These commands are supported only with some DPMI servers.
14069 @cindex physical address from linear address
14070 @item info dos address-pte @var{addr}
14071 This command displays the Page Table entry for a specified linear
14072 address. The argument @var{addr} is a linear address which should
14073 already have the appropriate segment's base address added to it,
14074 because this command accepts addresses which may belong to @emph{any}
14075 segment. For example, here's how to display the Page Table entry for
14076 the page where a variable @code{i} is stored:
14079 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14080 @exdent @code{Page Table entry for address 0x11a00d30:}
14081 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14085 This says that @code{i} is stored at offset @code{0xd30} from the page
14086 whose physical base address is @code{0x02698000}, and shows all the
14087 attributes of that page.
14089 Note that you must cast the addresses of variables to a @code{char *},
14090 since otherwise the value of @code{__djgpp_base_address}, the base
14091 address of all variables and functions in a @sc{djgpp} program, will
14092 be added using the rules of C pointer arithmetics: if @code{i} is
14093 declared an @code{int}, @value{GDBN} will add 4 times the value of
14094 @code{__djgpp_base_address} to the address of @code{i}.
14096 Here's another example, it displays the Page Table entry for the
14100 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14101 @exdent @code{Page Table entry for address 0x29110:}
14102 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14106 (The @code{+ 3} offset is because the transfer buffer's address is the
14107 3rd member of the @code{_go32_info_block} structure.) The output
14108 clearly shows that this DPMI server maps the addresses in conventional
14109 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
14110 linear (@code{0x29110}) addresses are identical.
14112 This command is supported only with some DPMI servers.
14115 @cindex DOS serial data link, remote debugging
14116 In addition to native debugging, the DJGPP port supports remote
14117 debugging via a serial data link. The following commands are specific
14118 to remote serial debugging in the DJGPP port of @value{GDBN}.
14121 @kindex set com1base
14122 @kindex set com1irq
14123 @kindex set com2base
14124 @kindex set com2irq
14125 @kindex set com3base
14126 @kindex set com3irq
14127 @kindex set com4base
14128 @kindex set com4irq
14129 @item set com1base @var{addr}
14130 This command sets the base I/O port address of the @file{COM1} serial
14133 @item set com1irq @var{irq}
14134 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
14135 for the @file{COM1} serial port.
14137 There are similar commands @samp{set com2base}, @samp{set com3irq},
14138 etc.@: for setting the port address and the @code{IRQ} lines for the
14141 @kindex show com1base
14142 @kindex show com1irq
14143 @kindex show com2base
14144 @kindex show com2irq
14145 @kindex show com3base
14146 @kindex show com3irq
14147 @kindex show com4base
14148 @kindex show com4irq
14149 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
14150 display the current settings of the base address and the @code{IRQ}
14151 lines used by the COM ports.
14154 @kindex info serial
14155 @cindex DOS serial port status
14156 This command prints the status of the 4 DOS serial ports. For each
14157 port, it prints whether it's active or not, its I/O base address and
14158 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
14159 counts of various errors encountered so far.
14163 @node Cygwin Native
14164 @subsection Features for Debugging MS Windows PE Executables
14165 @cindex MS Windows debugging
14166 @cindex native Cygwin debugging
14167 @cindex Cygwin-specific commands
14169 @value{GDBN} supports native debugging of MS Windows programs, including
14170 DLLs with and without symbolic debugging information. There are various
14171 additional Cygwin-specific commands, described in this section.
14172 Working with DLLs that have no debugging symbols is described in
14173 @ref{Non-debug DLL Symbols}.
14178 This is a prefix of MS Windows-specific commands which print
14179 information about the target system and important OS structures.
14181 @item info w32 selector
14182 This command displays information returned by
14183 the Win32 API @code{GetThreadSelectorEntry} function.
14184 It takes an optional argument that is evaluated to
14185 a long value to give the information about this given selector.
14186 Without argument, this command displays information
14187 about the six segment registers.
14191 This is a Cygwin-specific alias of @code{info shared}.
14193 @kindex dll-symbols
14195 This command loads symbols from a dll similarly to
14196 add-sym command but without the need to specify a base address.
14198 @kindex set cygwin-exceptions
14199 @cindex debugging the Cygwin DLL
14200 @cindex Cygwin DLL, debugging
14201 @item set cygwin-exceptions @var{mode}
14202 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
14203 happen inside the Cygwin DLL. If @var{mode} is @code{off},
14204 @value{GDBN} will delay recognition of exceptions, and may ignore some
14205 exceptions which seem to be caused by internal Cygwin DLL
14206 ``bookkeeping''. This option is meant primarily for debugging the
14207 Cygwin DLL itself; the default value is @code{off} to avoid annoying
14208 @value{GDBN} users with false @code{SIGSEGV} signals.
14210 @kindex show cygwin-exceptions
14211 @item show cygwin-exceptions
14212 Displays whether @value{GDBN} will break on exceptions that happen
14213 inside the Cygwin DLL itself.
14215 @kindex set new-console
14216 @item set new-console @var{mode}
14217 If @var{mode} is @code{on} the debuggee will
14218 be started in a new console on next start.
14219 If @var{mode} is @code{off}i, the debuggee will
14220 be started in the same console as the debugger.
14222 @kindex show new-console
14223 @item show new-console
14224 Displays whether a new console is used
14225 when the debuggee is started.
14227 @kindex set new-group
14228 @item set new-group @var{mode}
14229 This boolean value controls whether the debuggee should
14230 start a new group or stay in the same group as the debugger.
14231 This affects the way the Windows OS handles
14234 @kindex show new-group
14235 @item show new-group
14236 Displays current value of new-group boolean.
14238 @kindex set debugevents
14239 @item set debugevents
14240 This boolean value adds debug output concerning kernel events related
14241 to the debuggee seen by the debugger. This includes events that
14242 signal thread and process creation and exit, DLL loading and
14243 unloading, console interrupts, and debugging messages produced by the
14244 Windows @code{OutputDebugString} API call.
14246 @kindex set debugexec
14247 @item set debugexec
14248 This boolean value adds debug output concerning execute events
14249 (such as resume thread) seen by the debugger.
14251 @kindex set debugexceptions
14252 @item set debugexceptions
14253 This boolean value adds debug output concerning exceptions in the
14254 debuggee seen by the debugger.
14256 @kindex set debugmemory
14257 @item set debugmemory
14258 This boolean value adds debug output concerning debuggee memory reads
14259 and writes by the debugger.
14263 This boolean values specifies whether the debuggee is called
14264 via a shell or directly (default value is on).
14268 Displays if the debuggee will be started with a shell.
14273 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14276 @node Non-debug DLL Symbols
14277 @subsubsection Support for DLLs without Debugging Symbols
14278 @cindex DLLs with no debugging symbols
14279 @cindex Minimal symbols and DLLs
14281 Very often on windows, some of the DLLs that your program relies on do
14282 not include symbolic debugging information (for example,
14283 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14284 symbols in a DLL, it relies on the minimal amount of symbolic
14285 information contained in the DLL's export table. This section
14286 describes working with such symbols, known internally to @value{GDBN} as
14287 ``minimal symbols''.
14289 Note that before the debugged program has started execution, no DLLs
14290 will have been loaded. The easiest way around this problem is simply to
14291 start the program --- either by setting a breakpoint or letting the
14292 program run once to completion. It is also possible to force
14293 @value{GDBN} to load a particular DLL before starting the executable ---
14294 see the shared library information in @ref{Files}, or the
14295 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14296 explicitly loading symbols from a DLL with no debugging information will
14297 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14298 which may adversely affect symbol lookup performance.
14300 @subsubsection DLL Name Prefixes
14302 In keeping with the naming conventions used by the Microsoft debugging
14303 tools, DLL export symbols are made available with a prefix based on the
14304 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14305 also entered into the symbol table, so @code{CreateFileA} is often
14306 sufficient. In some cases there will be name clashes within a program
14307 (particularly if the executable itself includes full debugging symbols)
14308 necessitating the use of the fully qualified name when referring to the
14309 contents of the DLL. Use single-quotes around the name to avoid the
14310 exclamation mark (``!'') being interpreted as a language operator.
14312 Note that the internal name of the DLL may be all upper-case, even
14313 though the file name of the DLL is lower-case, or vice-versa. Since
14314 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14315 some confusion. If in doubt, try the @code{info functions} and
14316 @code{info variables} commands or even @code{maint print msymbols}
14317 (@pxref{Symbols}). Here's an example:
14320 (@value{GDBP}) info function CreateFileA
14321 All functions matching regular expression "CreateFileA":
14323 Non-debugging symbols:
14324 0x77e885f4 CreateFileA
14325 0x77e885f4 KERNEL32!CreateFileA
14329 (@value{GDBP}) info function !
14330 All functions matching regular expression "!":
14332 Non-debugging symbols:
14333 0x6100114c cygwin1!__assert
14334 0x61004034 cygwin1!_dll_crt0@@0
14335 0x61004240 cygwin1!dll_crt0(per_process *)
14339 @subsubsection Working with Minimal Symbols
14341 Symbols extracted from a DLL's export table do not contain very much
14342 type information. All that @value{GDBN} can do is guess whether a symbol
14343 refers to a function or variable depending on the linker section that
14344 contains the symbol. Also note that the actual contents of the memory
14345 contained in a DLL are not available unless the program is running. This
14346 means that you cannot examine the contents of a variable or disassemble
14347 a function within a DLL without a running program.
14349 Variables are generally treated as pointers and dereferenced
14350 automatically. For this reason, it is often necessary to prefix a
14351 variable name with the address-of operator (``&'') and provide explicit
14352 type information in the command. Here's an example of the type of
14356 (@value{GDBP}) print 'cygwin1!__argv'
14361 (@value{GDBP}) x 'cygwin1!__argv'
14362 0x10021610: "\230y\""
14365 And two possible solutions:
14368 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14369 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14373 (@value{GDBP}) x/2x &'cygwin1!__argv'
14374 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14375 (@value{GDBP}) x/x 0x10021608
14376 0x10021608: 0x0022fd98
14377 (@value{GDBP}) x/s 0x0022fd98
14378 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14381 Setting a break point within a DLL is possible even before the program
14382 starts execution. However, under these circumstances, @value{GDBN} can't
14383 examine the initial instructions of the function in order to skip the
14384 function's frame set-up code. You can work around this by using ``*&''
14385 to set the breakpoint at a raw memory address:
14388 (@value{GDBP}) break *&'python22!PyOS_Readline'
14389 Breakpoint 1 at 0x1e04eff0
14392 The author of these extensions is not entirely convinced that setting a
14393 break point within a shared DLL like @file{kernel32.dll} is completely
14397 @subsection Commands Specific to @sc{gnu} Hurd Systems
14398 @cindex @sc{gnu} Hurd debugging
14400 This subsection describes @value{GDBN} commands specific to the
14401 @sc{gnu} Hurd native debugging.
14406 @kindex set signals@r{, Hurd command}
14407 @kindex set sigs@r{, Hurd command}
14408 This command toggles the state of inferior signal interception by
14409 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14410 affected by this command. @code{sigs} is a shorthand alias for
14415 @kindex show signals@r{, Hurd command}
14416 @kindex show sigs@r{, Hurd command}
14417 Show the current state of intercepting inferior's signals.
14419 @item set signal-thread
14420 @itemx set sigthread
14421 @kindex set signal-thread
14422 @kindex set sigthread
14423 This command tells @value{GDBN} which thread is the @code{libc} signal
14424 thread. That thread is run when a signal is delivered to a running
14425 process. @code{set sigthread} is the shorthand alias of @code{set
14428 @item show signal-thread
14429 @itemx show sigthread
14430 @kindex show signal-thread
14431 @kindex show sigthread
14432 These two commands show which thread will run when the inferior is
14433 delivered a signal.
14436 @kindex set stopped@r{, Hurd command}
14437 This commands tells @value{GDBN} that the inferior process is stopped,
14438 as with the @code{SIGSTOP} signal. The stopped process can be
14439 continued by delivering a signal to it.
14442 @kindex show stopped@r{, Hurd command}
14443 This command shows whether @value{GDBN} thinks the debuggee is
14446 @item set exceptions
14447 @kindex set exceptions@r{, Hurd command}
14448 Use this command to turn off trapping of exceptions in the inferior.
14449 When exception trapping is off, neither breakpoints nor
14450 single-stepping will work. To restore the default, set exception
14453 @item show exceptions
14454 @kindex show exceptions@r{, Hurd command}
14455 Show the current state of trapping exceptions in the inferior.
14457 @item set task pause
14458 @kindex set task@r{, Hurd commands}
14459 @cindex task attributes (@sc{gnu} Hurd)
14460 @cindex pause current task (@sc{gnu} Hurd)
14461 This command toggles task suspension when @value{GDBN} has control.
14462 Setting it to on takes effect immediately, and the task is suspended
14463 whenever @value{GDBN} gets control. Setting it to off will take
14464 effect the next time the inferior is continued. If this option is set
14465 to off, you can use @code{set thread default pause on} or @code{set
14466 thread pause on} (see below) to pause individual threads.
14468 @item show task pause
14469 @kindex show task@r{, Hurd commands}
14470 Show the current state of task suspension.
14472 @item set task detach-suspend-count
14473 @cindex task suspend count
14474 @cindex detach from task, @sc{gnu} Hurd
14475 This command sets the suspend count the task will be left with when
14476 @value{GDBN} detaches from it.
14478 @item show task detach-suspend-count
14479 Show the suspend count the task will be left with when detaching.
14481 @item set task exception-port
14482 @itemx set task excp
14483 @cindex task exception port, @sc{gnu} Hurd
14484 This command sets the task exception port to which @value{GDBN} will
14485 forward exceptions. The argument should be the value of the @dfn{send
14486 rights} of the task. @code{set task excp} is a shorthand alias.
14488 @item set noninvasive
14489 @cindex noninvasive task options
14490 This command switches @value{GDBN} to a mode that is the least
14491 invasive as far as interfering with the inferior is concerned. This
14492 is the same as using @code{set task pause}, @code{set exceptions}, and
14493 @code{set signals} to values opposite to the defaults.
14495 @item info send-rights
14496 @itemx info receive-rights
14497 @itemx info port-rights
14498 @itemx info port-sets
14499 @itemx info dead-names
14502 @cindex send rights, @sc{gnu} Hurd
14503 @cindex receive rights, @sc{gnu} Hurd
14504 @cindex port rights, @sc{gnu} Hurd
14505 @cindex port sets, @sc{gnu} Hurd
14506 @cindex dead names, @sc{gnu} Hurd
14507 These commands display information about, respectively, send rights,
14508 receive rights, port rights, port sets, and dead names of a task.
14509 There are also shorthand aliases: @code{info ports} for @code{info
14510 port-rights} and @code{info psets} for @code{info port-sets}.
14512 @item set thread pause
14513 @kindex set thread@r{, Hurd command}
14514 @cindex thread properties, @sc{gnu} Hurd
14515 @cindex pause current thread (@sc{gnu} Hurd)
14516 This command toggles current thread suspension when @value{GDBN} has
14517 control. Setting it to on takes effect immediately, and the current
14518 thread is suspended whenever @value{GDBN} gets control. Setting it to
14519 off will take effect the next time the inferior is continued.
14520 Normally, this command has no effect, since when @value{GDBN} has
14521 control, the whole task is suspended. However, if you used @code{set
14522 task pause off} (see above), this command comes in handy to suspend
14523 only the current thread.
14525 @item show thread pause
14526 @kindex show thread@r{, Hurd command}
14527 This command shows the state of current thread suspension.
14529 @item set thread run
14530 This command sets whether the current thread is allowed to run.
14532 @item show thread run
14533 Show whether the current thread is allowed to run.
14535 @item set thread detach-suspend-count
14536 @cindex thread suspend count, @sc{gnu} Hurd
14537 @cindex detach from thread, @sc{gnu} Hurd
14538 This command sets the suspend count @value{GDBN} will leave on a
14539 thread when detaching. This number is relative to the suspend count
14540 found by @value{GDBN} when it notices the thread; use @code{set thread
14541 takeover-suspend-count} to force it to an absolute value.
14543 @item show thread detach-suspend-count
14544 Show the suspend count @value{GDBN} will leave on the thread when
14547 @item set thread exception-port
14548 @itemx set thread excp
14549 Set the thread exception port to which to forward exceptions. This
14550 overrides the port set by @code{set task exception-port} (see above).
14551 @code{set thread excp} is the shorthand alias.
14553 @item set thread takeover-suspend-count
14554 Normally, @value{GDBN}'s thread suspend counts are relative to the
14555 value @value{GDBN} finds when it notices each thread. This command
14556 changes the suspend counts to be absolute instead.
14558 @item set thread default
14559 @itemx show thread default
14560 @cindex thread default settings, @sc{gnu} Hurd
14561 Each of the above @code{set thread} commands has a @code{set thread
14562 default} counterpart (e.g., @code{set thread default pause}, @code{set
14563 thread default exception-port}, etc.). The @code{thread default}
14564 variety of commands sets the default thread properties for all
14565 threads; you can then change the properties of individual threads with
14566 the non-default commands.
14571 @subsection QNX Neutrino
14572 @cindex QNX Neutrino
14574 @value{GDBN} provides the following commands specific to the QNX
14578 @item set debug nto-debug
14579 @kindex set debug nto-debug
14580 When set to on, enables debugging messages specific to the QNX
14583 @item show debug nto-debug
14584 @kindex show debug nto-debug
14585 Show the current state of QNX Neutrino messages.
14590 @section Embedded Operating Systems
14592 This section describes configurations involving the debugging of
14593 embedded operating systems that are available for several different
14597 * VxWorks:: Using @value{GDBN} with VxWorks
14600 @value{GDBN} includes the ability to debug programs running on
14601 various real-time operating systems.
14604 @subsection Using @value{GDBN} with VxWorks
14610 @kindex target vxworks
14611 @item target vxworks @var{machinename}
14612 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14613 is the target system's machine name or IP address.
14617 On VxWorks, @code{load} links @var{filename} dynamically on the
14618 current target system as well as adding its symbols in @value{GDBN}.
14620 @value{GDBN} enables developers to spawn and debug tasks running on networked
14621 VxWorks targets from a Unix host. Already-running tasks spawned from
14622 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14623 both the Unix host and on the VxWorks target. The program
14624 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14625 installed with the name @code{vxgdb}, to distinguish it from a
14626 @value{GDBN} for debugging programs on the host itself.)
14629 @item VxWorks-timeout @var{args}
14630 @kindex vxworks-timeout
14631 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14632 This option is set by the user, and @var{args} represents the number of
14633 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14634 your VxWorks target is a slow software simulator or is on the far side
14635 of a thin network line.
14638 The following information on connecting to VxWorks was current when
14639 this manual was produced; newer releases of VxWorks may use revised
14642 @findex INCLUDE_RDB
14643 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14644 to include the remote debugging interface routines in the VxWorks
14645 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14646 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14647 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14648 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14649 information on configuring and remaking VxWorks, see the manufacturer's
14651 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14653 Once you have included @file{rdb.a} in your VxWorks system image and set
14654 your Unix execution search path to find @value{GDBN}, you are ready to
14655 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14656 @code{vxgdb}, depending on your installation).
14658 @value{GDBN} comes up showing the prompt:
14665 * VxWorks Connection:: Connecting to VxWorks
14666 * VxWorks Download:: VxWorks download
14667 * VxWorks Attach:: Running tasks
14670 @node VxWorks Connection
14671 @subsubsection Connecting to VxWorks
14673 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14674 network. To connect to a target whose host name is ``@code{tt}'', type:
14677 (vxgdb) target vxworks tt
14681 @value{GDBN} displays messages like these:
14684 Attaching remote machine across net...
14689 @value{GDBN} then attempts to read the symbol tables of any object modules
14690 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14691 these files by searching the directories listed in the command search
14692 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14693 to find an object file, it displays a message such as:
14696 prog.o: No such file or directory.
14699 When this happens, add the appropriate directory to the search path with
14700 the @value{GDBN} command @code{path}, and execute the @code{target}
14703 @node VxWorks Download
14704 @subsubsection VxWorks Download
14706 @cindex download to VxWorks
14707 If you have connected to the VxWorks target and you want to debug an
14708 object that has not yet been loaded, you can use the @value{GDBN}
14709 @code{load} command to download a file from Unix to VxWorks
14710 incrementally. The object file given as an argument to the @code{load}
14711 command is actually opened twice: first by the VxWorks target in order
14712 to download the code, then by @value{GDBN} in order to read the symbol
14713 table. This can lead to problems if the current working directories on
14714 the two systems differ. If both systems have NFS mounted the same
14715 filesystems, you can avoid these problems by using absolute paths.
14716 Otherwise, it is simplest to set the working directory on both systems
14717 to the directory in which the object file resides, and then to reference
14718 the file by its name, without any path. For instance, a program
14719 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14720 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14721 program, type this on VxWorks:
14724 -> cd "@var{vxpath}/vw/demo/rdb"
14728 Then, in @value{GDBN}, type:
14731 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14732 (vxgdb) load prog.o
14735 @value{GDBN} displays a response similar to this:
14738 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14741 You can also use the @code{load} command to reload an object module
14742 after editing and recompiling the corresponding source file. Note that
14743 this makes @value{GDBN} delete all currently-defined breakpoints,
14744 auto-displays, and convenience variables, and to clear the value
14745 history. (This is necessary in order to preserve the integrity of
14746 debugger's data structures that reference the target system's symbol
14749 @node VxWorks Attach
14750 @subsubsection Running Tasks
14752 @cindex running VxWorks tasks
14753 You can also attach to an existing task using the @code{attach} command as
14757 (vxgdb) attach @var{task}
14761 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14762 or suspended when you attach to it. Running tasks are suspended at
14763 the time of attachment.
14765 @node Embedded Processors
14766 @section Embedded Processors
14768 This section goes into details specific to particular embedded
14771 @cindex send command to simulator
14772 Whenever a specific embedded processor has a simulator, @value{GDBN}
14773 allows to send an arbitrary command to the simulator.
14776 @item sim @var{command}
14777 @kindex sim@r{, a command}
14778 Send an arbitrary @var{command} string to the simulator. Consult the
14779 documentation for the specific simulator in use for information about
14780 acceptable commands.
14786 * M32R/D:: Renesas M32R/D
14787 * M68K:: Motorola M68K
14788 * MIPS Embedded:: MIPS Embedded
14789 * OpenRISC 1000:: OpenRisc 1000
14790 * PA:: HP PA Embedded
14791 * PowerPC Embedded:: PowerPC Embedded
14792 * Sparclet:: Tsqware Sparclet
14793 * Sparclite:: Fujitsu Sparclite
14794 * Z8000:: Zilog Z8000
14797 * Super-H:: Renesas Super-H
14806 @item target rdi @var{dev}
14807 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14808 use this target to communicate with both boards running the Angel
14809 monitor, or with the EmbeddedICE JTAG debug device.
14812 @item target rdp @var{dev}
14817 @value{GDBN} provides the following ARM-specific commands:
14820 @item set arm disassembler
14822 This commands selects from a list of disassembly styles. The
14823 @code{"std"} style is the standard style.
14825 @item show arm disassembler
14827 Show the current disassembly style.
14829 @item set arm apcs32
14830 @cindex ARM 32-bit mode
14831 This command toggles ARM operation mode between 32-bit and 26-bit.
14833 @item show arm apcs32
14834 Display the current usage of the ARM 32-bit mode.
14836 @item set arm fpu @var{fputype}
14837 This command sets the ARM floating-point unit (FPU) type. The
14838 argument @var{fputype} can be one of these:
14842 Determine the FPU type by querying the OS ABI.
14844 Software FPU, with mixed-endian doubles on little-endian ARM
14847 GCC-compiled FPA co-processor.
14849 Software FPU with pure-endian doubles.
14855 Show the current type of the FPU.
14858 This command forces @value{GDBN} to use the specified ABI.
14861 Show the currently used ABI.
14863 @item set debug arm
14864 Toggle whether to display ARM-specific debugging messages from the ARM
14865 target support subsystem.
14867 @item show debug arm
14868 Show whether ARM-specific debugging messages are enabled.
14871 The following commands are available when an ARM target is debugged
14872 using the RDI interface:
14875 @item rdilogfile @r{[}@var{file}@r{]}
14877 @cindex ADP (Angel Debugger Protocol) logging
14878 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14879 With an argument, sets the log file to the specified @var{file}. With
14880 no argument, show the current log file name. The default log file is
14883 @item rdilogenable @r{[}@var{arg}@r{]}
14884 @kindex rdilogenable
14885 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14886 enables logging, with an argument 0 or @code{"no"} disables it. With
14887 no arguments displays the current setting. When logging is enabled,
14888 ADP packets exchanged between @value{GDBN} and the RDI target device
14889 are logged to a file.
14891 @item set rdiromatzero
14892 @kindex set rdiromatzero
14893 @cindex ROM at zero address, RDI
14894 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14895 vector catching is disabled, so that zero address can be used. If off
14896 (the default), vector catching is enabled. For this command to take
14897 effect, it needs to be invoked prior to the @code{target rdi} command.
14899 @item show rdiromatzero
14900 @kindex show rdiromatzero
14901 Show the current setting of ROM at zero address.
14903 @item set rdiheartbeat
14904 @kindex set rdiheartbeat
14905 @cindex RDI heartbeat
14906 Enable or disable RDI heartbeat packets. It is not recommended to
14907 turn on this option, since it confuses ARM and EPI JTAG interface, as
14908 well as the Angel monitor.
14910 @item show rdiheartbeat
14911 @kindex show rdiheartbeat
14912 Show the setting of RDI heartbeat packets.
14917 @subsection Renesas M32R/D and M32R/SDI
14920 @kindex target m32r
14921 @item target m32r @var{dev}
14922 Renesas M32R/D ROM monitor.
14924 @kindex target m32rsdi
14925 @item target m32rsdi @var{dev}
14926 Renesas M32R SDI server, connected via parallel port to the board.
14929 The following @value{GDBN} commands are specific to the M32R monitor:
14932 @item set download-path @var{path}
14933 @kindex set download-path
14934 @cindex find downloadable @sc{srec} files (M32R)
14935 Set the default path for finding downloadable @sc{srec} files.
14937 @item show download-path
14938 @kindex show download-path
14939 Show the default path for downloadable @sc{srec} files.
14941 @item set board-address @var{addr}
14942 @kindex set board-address
14943 @cindex M32-EVA target board address
14944 Set the IP address for the M32R-EVA target board.
14946 @item show board-address
14947 @kindex show board-address
14948 Show the current IP address of the target board.
14950 @item set server-address @var{addr}
14951 @kindex set server-address
14952 @cindex download server address (M32R)
14953 Set the IP address for the download server, which is the @value{GDBN}'s
14956 @item show server-address
14957 @kindex show server-address
14958 Display the IP address of the download server.
14960 @item upload @r{[}@var{file}@r{]}
14961 @kindex upload@r{, M32R}
14962 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14963 upload capability. If no @var{file} argument is given, the current
14964 executable file is uploaded.
14966 @item tload @r{[}@var{file}@r{]}
14967 @kindex tload@r{, M32R}
14968 Test the @code{upload} command.
14971 The following commands are available for M32R/SDI:
14976 @cindex reset SDI connection, M32R
14977 This command resets the SDI connection.
14981 This command shows the SDI connection status.
14984 @kindex debug_chaos
14985 @cindex M32R/Chaos debugging
14986 Instructs the remote that M32R/Chaos debugging is to be used.
14988 @item use_debug_dma
14989 @kindex use_debug_dma
14990 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14993 @kindex use_mon_code
14994 Instructs the remote to use the MON_CODE method of accessing memory.
14997 @kindex use_ib_break
14998 Instructs the remote to set breakpoints by IB break.
15000 @item use_dbt_break
15001 @kindex use_dbt_break
15002 Instructs the remote to set breakpoints by DBT.
15008 The Motorola m68k configuration includes ColdFire support, and a
15009 target command for the following ROM monitor.
15013 @kindex target dbug
15014 @item target dbug @var{dev}
15015 dBUG ROM monitor for Motorola ColdFire.
15019 @node MIPS Embedded
15020 @subsection MIPS Embedded
15022 @cindex MIPS boards
15023 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15024 MIPS board attached to a serial line. This is available when
15025 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15028 Use these @value{GDBN} commands to specify the connection to your target board:
15031 @item target mips @var{port}
15032 @kindex target mips @var{port}
15033 To run a program on the board, start up @code{@value{GDBP}} with the
15034 name of your program as the argument. To connect to the board, use the
15035 command @samp{target mips @var{port}}, where @var{port} is the name of
15036 the serial port connected to the board. If the program has not already
15037 been downloaded to the board, you may use the @code{load} command to
15038 download it. You can then use all the usual @value{GDBN} commands.
15040 For example, this sequence connects to the target board through a serial
15041 port, and loads and runs a program called @var{prog} through the
15045 host$ @value{GDBP} @var{prog}
15046 @value{GDBN} is free software and @dots{}
15047 (@value{GDBP}) target mips /dev/ttyb
15048 (@value{GDBP}) load @var{prog}
15052 @item target mips @var{hostname}:@var{portnumber}
15053 On some @value{GDBN} host configurations, you can specify a TCP
15054 connection (for instance, to a serial line managed by a terminal
15055 concentrator) instead of a serial port, using the syntax
15056 @samp{@var{hostname}:@var{portnumber}}.
15058 @item target pmon @var{port}
15059 @kindex target pmon @var{port}
15062 @item target ddb @var{port}
15063 @kindex target ddb @var{port}
15064 NEC's DDB variant of PMON for Vr4300.
15066 @item target lsi @var{port}
15067 @kindex target lsi @var{port}
15068 LSI variant of PMON.
15070 @kindex target r3900
15071 @item target r3900 @var{dev}
15072 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
15074 @kindex target array
15075 @item target array @var{dev}
15076 Array Tech LSI33K RAID controller board.
15082 @value{GDBN} also supports these special commands for MIPS targets:
15085 @item set mipsfpu double
15086 @itemx set mipsfpu single
15087 @itemx set mipsfpu none
15088 @itemx set mipsfpu auto
15089 @itemx show mipsfpu
15090 @kindex set mipsfpu
15091 @kindex show mipsfpu
15092 @cindex MIPS remote floating point
15093 @cindex floating point, MIPS remote
15094 If your target board does not support the MIPS floating point
15095 coprocessor, you should use the command @samp{set mipsfpu none} (if you
15096 need this, you may wish to put the command in your @value{GDBN} init
15097 file). This tells @value{GDBN} how to find the return value of
15098 functions which return floating point values. It also allows
15099 @value{GDBN} to avoid saving the floating point registers when calling
15100 functions on the board. If you are using a floating point coprocessor
15101 with only single precision floating point support, as on the @sc{r4650}
15102 processor, use the command @samp{set mipsfpu single}. The default
15103 double precision floating point coprocessor may be selected using
15104 @samp{set mipsfpu double}.
15106 In previous versions the only choices were double precision or no
15107 floating point, so @samp{set mipsfpu on} will select double precision
15108 and @samp{set mipsfpu off} will select no floating point.
15110 As usual, you can inquire about the @code{mipsfpu} variable with
15111 @samp{show mipsfpu}.
15113 @item set timeout @var{seconds}
15114 @itemx set retransmit-timeout @var{seconds}
15115 @itemx show timeout
15116 @itemx show retransmit-timeout
15117 @cindex @code{timeout}, MIPS protocol
15118 @cindex @code{retransmit-timeout}, MIPS protocol
15119 @kindex set timeout
15120 @kindex show timeout
15121 @kindex set retransmit-timeout
15122 @kindex show retransmit-timeout
15123 You can control the timeout used while waiting for a packet, in the MIPS
15124 remote protocol, with the @code{set timeout @var{seconds}} command. The
15125 default is 5 seconds. Similarly, you can control the timeout used while
15126 waiting for an acknowledgement of a packet with the @code{set
15127 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
15128 You can inspect both values with @code{show timeout} and @code{show
15129 retransmit-timeout}. (These commands are @emph{only} available when
15130 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
15132 The timeout set by @code{set timeout} does not apply when @value{GDBN}
15133 is waiting for your program to stop. In that case, @value{GDBN} waits
15134 forever because it has no way of knowing how long the program is going
15135 to run before stopping.
15137 @item set syn-garbage-limit @var{num}
15138 @kindex set syn-garbage-limit@r{, MIPS remote}
15139 @cindex synchronize with remote MIPS target
15140 Limit the maximum number of characters @value{GDBN} should ignore when
15141 it tries to synchronize with the remote target. The default is 10
15142 characters. Setting the limit to -1 means there's no limit.
15144 @item show syn-garbage-limit
15145 @kindex show syn-garbage-limit@r{, MIPS remote}
15146 Show the current limit on the number of characters to ignore when
15147 trying to synchronize with the remote system.
15149 @item set monitor-prompt @var{prompt}
15150 @kindex set monitor-prompt@r{, MIPS remote}
15151 @cindex remote monitor prompt
15152 Tell @value{GDBN} to expect the specified @var{prompt} string from the
15153 remote monitor. The default depends on the target:
15163 @item show monitor-prompt
15164 @kindex show monitor-prompt@r{, MIPS remote}
15165 Show the current strings @value{GDBN} expects as the prompt from the
15168 @item set monitor-warnings
15169 @kindex set monitor-warnings@r{, MIPS remote}
15170 Enable or disable monitor warnings about hardware breakpoints. This
15171 has effect only for the @code{lsi} target. When on, @value{GDBN} will
15172 display warning messages whose codes are returned by the @code{lsi}
15173 PMON monitor for breakpoint commands.
15175 @item show monitor-warnings
15176 @kindex show monitor-warnings@r{, MIPS remote}
15177 Show the current setting of printing monitor warnings.
15179 @item pmon @var{command}
15180 @kindex pmon@r{, MIPS remote}
15181 @cindex send PMON command
15182 This command allows sending an arbitrary @var{command} string to the
15183 monitor. The monitor must be in debug mode for this to work.
15186 @node OpenRISC 1000
15187 @subsection OpenRISC 1000
15188 @cindex OpenRISC 1000
15190 @cindex or1k boards
15191 See OR1k Architecture document (@uref{www.opencores.org}) for more information
15192 about platform and commands.
15196 @kindex target jtag
15197 @item target jtag jtag://@var{host}:@var{port}
15199 Connects to remote JTAG server.
15200 JTAG remote server can be either an or1ksim or JTAG server,
15201 connected via parallel port to the board.
15203 Example: @code{target jtag jtag://localhost:9999}
15206 @item or1ksim @var{command}
15207 If connected to @code{or1ksim} OpenRISC 1000 Architectural
15208 Simulator, proprietary commands can be executed.
15210 @kindex info or1k spr
15211 @item info or1k spr
15212 Displays spr groups.
15214 @item info or1k spr @var{group}
15215 @itemx info or1k spr @var{groupno}
15216 Displays register names in selected group.
15218 @item info or1k spr @var{group} @var{register}
15219 @itemx info or1k spr @var{register}
15220 @itemx info or1k spr @var{groupno} @var{registerno}
15221 @itemx info or1k spr @var{registerno}
15222 Shows information about specified spr register.
15225 @item spr @var{group} @var{register} @var{value}
15226 @itemx spr @var{register @var{value}}
15227 @itemx spr @var{groupno} @var{registerno @var{value}}
15228 @itemx spr @var{registerno @var{value}}
15229 Writes @var{value} to specified spr register.
15232 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15233 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15234 program execution and is thus much faster. Hardware breakpoints/watchpoint
15235 triggers can be set using:
15238 Load effective address/data
15240 Store effective address/data
15242 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15247 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15248 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15250 @code{htrace} commands:
15251 @cindex OpenRISC 1000 htrace
15254 @item hwatch @var{conditional}
15255 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15256 or Data. For example:
15258 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15260 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15264 Display information about current HW trace configuration.
15266 @item htrace trigger @var{conditional}
15267 Set starting criteria for HW trace.
15269 @item htrace qualifier @var{conditional}
15270 Set acquisition qualifier for HW trace.
15272 @item htrace stop @var{conditional}
15273 Set HW trace stopping criteria.
15275 @item htrace record [@var{data}]*
15276 Selects the data to be recorded, when qualifier is met and HW trace was
15279 @item htrace enable
15280 @itemx htrace disable
15281 Enables/disables the HW trace.
15283 @item htrace rewind [@var{filename}]
15284 Clears currently recorded trace data.
15286 If filename is specified, new trace file is made and any newly collected data
15287 will be written there.
15289 @item htrace print [@var{start} [@var{len}]]
15290 Prints trace buffer, using current record configuration.
15292 @item htrace mode continuous
15293 Set continuous trace mode.
15295 @item htrace mode suspend
15296 Set suspend trace mode.
15300 @node PowerPC Embedded
15301 @subsection PowerPC Embedded
15303 @value{GDBN} provides the following PowerPC-specific commands:
15306 @kindex set powerpc
15307 @item set powerpc soft-float
15308 @itemx show powerpc soft-float
15309 Force @value{GDBN} to use (or not use) a software floating point calling
15310 convention. By default, @value{GDBN} selects the calling convention based
15311 on the selected architecture and the provided executable file.
15313 @item set powerpc vector-abi
15314 @itemx show powerpc vector-abi
15315 Force @value{GDBN} to use the specified calling convention for vector
15316 arguments and return values. The valid options are @samp{auto};
15317 @samp{generic}, to avoid vector registers even if they are present;
15318 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15319 registers. By default, @value{GDBN} selects the calling convention
15320 based on the selected architecture and the provided executable file.
15322 @kindex target dink32
15323 @item target dink32 @var{dev}
15324 DINK32 ROM monitor.
15326 @kindex target ppcbug
15327 @item target ppcbug @var{dev}
15328 @kindex target ppcbug1
15329 @item target ppcbug1 @var{dev}
15330 PPCBUG ROM monitor for PowerPC.
15333 @item target sds @var{dev}
15334 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15337 @cindex SDS protocol
15338 The following commands specific to the SDS protocol are supported
15342 @item set sdstimeout @var{nsec}
15343 @kindex set sdstimeout
15344 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15345 default is 2 seconds.
15347 @item show sdstimeout
15348 @kindex show sdstimeout
15349 Show the current value of the SDS timeout.
15351 @item sds @var{command}
15352 @kindex sds@r{, a command}
15353 Send the specified @var{command} string to the SDS monitor.
15358 @subsection HP PA Embedded
15362 @kindex target op50n
15363 @item target op50n @var{dev}
15364 OP50N monitor, running on an OKI HPPA board.
15366 @kindex target w89k
15367 @item target w89k @var{dev}
15368 W89K monitor, running on a Winbond HPPA board.
15373 @subsection Tsqware Sparclet
15377 @value{GDBN} enables developers to debug tasks running on
15378 Sparclet targets from a Unix host.
15379 @value{GDBN} uses code that runs on
15380 both the Unix host and on the Sparclet target. The program
15381 @code{@value{GDBP}} is installed and executed on the Unix host.
15384 @item remotetimeout @var{args}
15385 @kindex remotetimeout
15386 @value{GDBN} supports the option @code{remotetimeout}.
15387 This option is set by the user, and @var{args} represents the number of
15388 seconds @value{GDBN} waits for responses.
15391 @cindex compiling, on Sparclet
15392 When compiling for debugging, include the options @samp{-g} to get debug
15393 information and @samp{-Ttext} to relocate the program to where you wish to
15394 load it on the target. You may also want to add the options @samp{-n} or
15395 @samp{-N} in order to reduce the size of the sections. Example:
15398 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15401 You can use @code{objdump} to verify that the addresses are what you intended:
15404 sparclet-aout-objdump --headers --syms prog
15407 @cindex running, on Sparclet
15409 your Unix execution search path to find @value{GDBN}, you are ready to
15410 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15411 (or @code{sparclet-aout-gdb}, depending on your installation).
15413 @value{GDBN} comes up showing the prompt:
15420 * Sparclet File:: Setting the file to debug
15421 * Sparclet Connection:: Connecting to Sparclet
15422 * Sparclet Download:: Sparclet download
15423 * Sparclet Execution:: Running and debugging
15426 @node Sparclet File
15427 @subsubsection Setting File to Debug
15429 The @value{GDBN} command @code{file} lets you choose with program to debug.
15432 (gdbslet) file prog
15436 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15437 @value{GDBN} locates
15438 the file by searching the directories listed in the command search
15440 If the file was compiled with debug information (option @samp{-g}), source
15441 files will be searched as well.
15442 @value{GDBN} locates
15443 the source files by searching the directories listed in the directory search
15444 path (@pxref{Environment, ,Your Program's Environment}).
15446 to find a file, it displays a message such as:
15449 prog: No such file or directory.
15452 When this happens, add the appropriate directories to the search paths with
15453 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15454 @code{target} command again.
15456 @node Sparclet Connection
15457 @subsubsection Connecting to Sparclet
15459 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15460 To connect to a target on serial port ``@code{ttya}'', type:
15463 (gdbslet) target sparclet /dev/ttya
15464 Remote target sparclet connected to /dev/ttya
15465 main () at ../prog.c:3
15469 @value{GDBN} displays messages like these:
15475 @node Sparclet Download
15476 @subsubsection Sparclet Download
15478 @cindex download to Sparclet
15479 Once connected to the Sparclet target,
15480 you can use the @value{GDBN}
15481 @code{load} command to download the file from the host to the target.
15482 The file name and load offset should be given as arguments to the @code{load}
15484 Since the file format is aout, the program must be loaded to the starting
15485 address. You can use @code{objdump} to find out what this value is. The load
15486 offset is an offset which is added to the VMA (virtual memory address)
15487 of each of the file's sections.
15488 For instance, if the program
15489 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15490 and bss at 0x12010170, in @value{GDBN}, type:
15493 (gdbslet) load prog 0x12010000
15494 Loading section .text, size 0xdb0 vma 0x12010000
15497 If the code is loaded at a different address then what the program was linked
15498 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15499 to tell @value{GDBN} where to map the symbol table.
15501 @node Sparclet Execution
15502 @subsubsection Running and Debugging
15504 @cindex running and debugging Sparclet programs
15505 You can now begin debugging the task using @value{GDBN}'s execution control
15506 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15507 manual for the list of commands.
15511 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15513 Starting program: prog
15514 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15515 3 char *symarg = 0;
15517 4 char *execarg = "hello!";
15522 @subsection Fujitsu Sparclite
15526 @kindex target sparclite
15527 @item target sparclite @var{dev}
15528 Fujitsu sparclite boards, used only for the purpose of loading.
15529 You must use an additional command to debug the program.
15530 For example: target remote @var{dev} using @value{GDBN} standard
15536 @subsection Zilog Z8000
15539 @cindex simulator, Z8000
15540 @cindex Zilog Z8000 simulator
15542 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15545 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15546 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15547 segmented variant). The simulator recognizes which architecture is
15548 appropriate by inspecting the object code.
15551 @item target sim @var{args}
15553 @kindex target sim@r{, with Z8000}
15554 Debug programs on a simulated CPU. If the simulator supports setup
15555 options, specify them via @var{args}.
15559 After specifying this target, you can debug programs for the simulated
15560 CPU in the same style as programs for your host computer; use the
15561 @code{file} command to load a new program image, the @code{run} command
15562 to run your program, and so on.
15564 As well as making available all the usual machine registers
15565 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15566 additional items of information as specially named registers:
15571 Counts clock-ticks in the simulator.
15574 Counts instructions run in the simulator.
15577 Execution time in 60ths of a second.
15581 You can refer to these values in @value{GDBN} expressions with the usual
15582 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15583 conditional breakpoint that suspends only after at least 5000
15584 simulated clock ticks.
15587 @subsection Atmel AVR
15590 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15591 following AVR-specific commands:
15594 @item info io_registers
15595 @kindex info io_registers@r{, AVR}
15596 @cindex I/O registers (Atmel AVR)
15597 This command displays information about the AVR I/O registers. For
15598 each register, @value{GDBN} prints its number and value.
15605 When configured for debugging CRIS, @value{GDBN} provides the
15606 following CRIS-specific commands:
15609 @item set cris-version @var{ver}
15610 @cindex CRIS version
15611 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15612 The CRIS version affects register names and sizes. This command is useful in
15613 case autodetection of the CRIS version fails.
15615 @item show cris-version
15616 Show the current CRIS version.
15618 @item set cris-dwarf2-cfi
15619 @cindex DWARF-2 CFI and CRIS
15620 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15621 Change to @samp{off} when using @code{gcc-cris} whose version is below
15624 @item show cris-dwarf2-cfi
15625 Show the current state of using DWARF-2 CFI.
15627 @item set cris-mode @var{mode}
15629 Set the current CRIS mode to @var{mode}. It should only be changed when
15630 debugging in guru mode, in which case it should be set to
15631 @samp{guru} (the default is @samp{normal}).
15633 @item show cris-mode
15634 Show the current CRIS mode.
15638 @subsection Renesas Super-H
15641 For the Renesas Super-H processor, @value{GDBN} provides these
15646 @kindex regs@r{, Super-H}
15647 Show the values of all Super-H registers.
15651 @node Architectures
15652 @section Architectures
15654 This section describes characteristics of architectures that affect
15655 all uses of @value{GDBN} with the architecture, both native and cross.
15662 * HPPA:: HP PA architecture
15663 * SPU:: Cell Broadband Engine SPU architecture
15668 @subsection x86 Architecture-specific Issues
15671 @item set struct-convention @var{mode}
15672 @kindex set struct-convention
15673 @cindex struct return convention
15674 @cindex struct/union returned in registers
15675 Set the convention used by the inferior to return @code{struct}s and
15676 @code{union}s from functions to @var{mode}. Possible values of
15677 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15678 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15679 are returned on the stack, while @code{"reg"} means that a
15680 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15681 be returned in a register.
15683 @item show struct-convention
15684 @kindex show struct-convention
15685 Show the current setting of the convention to return @code{struct}s
15694 @kindex set rstack_high_address
15695 @cindex AMD 29K register stack
15696 @cindex register stack, AMD29K
15697 @item set rstack_high_address @var{address}
15698 On AMD 29000 family processors, registers are saved in a separate
15699 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15700 extent of this stack. Normally, @value{GDBN} just assumes that the
15701 stack is ``large enough''. This may result in @value{GDBN} referencing
15702 memory locations that do not exist. If necessary, you can get around
15703 this problem by specifying the ending address of the register stack with
15704 the @code{set rstack_high_address} command. The argument should be an
15705 address, which you probably want to precede with @samp{0x} to specify in
15708 @kindex show rstack_high_address
15709 @item show rstack_high_address
15710 Display the current limit of the register stack, on AMD 29000 family
15718 See the following section.
15723 @cindex stack on Alpha
15724 @cindex stack on MIPS
15725 @cindex Alpha stack
15727 Alpha- and MIPS-based computers use an unusual stack frame, which
15728 sometimes requires @value{GDBN} to search backward in the object code to
15729 find the beginning of a function.
15731 @cindex response time, MIPS debugging
15732 To improve response time (especially for embedded applications, where
15733 @value{GDBN} may be restricted to a slow serial line for this search)
15734 you may want to limit the size of this search, using one of these
15738 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15739 @item set heuristic-fence-post @var{limit}
15740 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15741 search for the beginning of a function. A value of @var{0} (the
15742 default) means there is no limit. However, except for @var{0}, the
15743 larger the limit the more bytes @code{heuristic-fence-post} must search
15744 and therefore the longer it takes to run. You should only need to use
15745 this command when debugging a stripped executable.
15747 @item show heuristic-fence-post
15748 Display the current limit.
15752 These commands are available @emph{only} when @value{GDBN} is configured
15753 for debugging programs on Alpha or MIPS processors.
15755 Several MIPS-specific commands are available when debugging MIPS
15759 @item set mips abi @var{arg}
15760 @kindex set mips abi
15761 @cindex set ABI for MIPS
15762 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15763 values of @var{arg} are:
15767 The default ABI associated with the current binary (this is the
15778 @item show mips abi
15779 @kindex show mips abi
15780 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15783 @itemx show mipsfpu
15784 @xref{MIPS Embedded, set mipsfpu}.
15786 @item set mips mask-address @var{arg}
15787 @kindex set mips mask-address
15788 @cindex MIPS addresses, masking
15789 This command determines whether the most-significant 32 bits of 64-bit
15790 MIPS addresses are masked off. The argument @var{arg} can be
15791 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15792 setting, which lets @value{GDBN} determine the correct value.
15794 @item show mips mask-address
15795 @kindex show mips mask-address
15796 Show whether the upper 32 bits of MIPS addresses are masked off or
15799 @item set remote-mips64-transfers-32bit-regs
15800 @kindex set remote-mips64-transfers-32bit-regs
15801 This command controls compatibility with 64-bit MIPS targets that
15802 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15803 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15804 and 64 bits for other registers, set this option to @samp{on}.
15806 @item show remote-mips64-transfers-32bit-regs
15807 @kindex show remote-mips64-transfers-32bit-regs
15808 Show the current setting of compatibility with older MIPS 64 targets.
15810 @item set debug mips
15811 @kindex set debug mips
15812 This command turns on and off debugging messages for the MIPS-specific
15813 target code in @value{GDBN}.
15815 @item show debug mips
15816 @kindex show debug mips
15817 Show the current setting of MIPS debugging messages.
15823 @cindex HPPA support
15825 When @value{GDBN} is debugging the HP PA architecture, it provides the
15826 following special commands:
15829 @item set debug hppa
15830 @kindex set debug hppa
15831 This command determines whether HPPA architecture-specific debugging
15832 messages are to be displayed.
15834 @item show debug hppa
15835 Show whether HPPA debugging messages are displayed.
15837 @item maint print unwind @var{address}
15838 @kindex maint print unwind@r{, HPPA}
15839 This command displays the contents of the unwind table entry at the
15840 given @var{address}.
15846 @subsection Cell Broadband Engine SPU architecture
15847 @cindex Cell Broadband Engine
15850 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
15851 it provides the following special commands:
15854 @item info spu event
15856 Display SPU event facility status. Shows current event mask
15857 and pending event status.
15859 @item info spu signal
15860 Display SPU signal notification facility status. Shows pending
15861 signal-control word and signal notification mode of both signal
15862 notification channels.
15864 @item info spu mailbox
15865 Display SPU mailbox facility status. Shows all pending entries,
15866 in order of processing, in each of the SPU Write Outbound,
15867 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
15870 Display MFC DMA status. Shows all pending commands in the MFC
15871 DMA queue. For each entry, opcode, tag, class IDs, effective
15872 and local store addresses and transfer size are shown.
15874 @item info spu proxydma
15875 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
15876 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
15877 and local store addresses and transfer size are shown.
15882 @subsection PowerPC
15883 @cindex PowerPC architecture
15885 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
15886 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
15887 numbers stored in the floating point registers. These values must be stored
15888 in two consecutive registers, always starting at an even register like
15889 @code{f0} or @code{f2}.
15891 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
15892 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
15893 @code{f2} and @code{f3} for @code{$dl1} and so on.
15896 @node Controlling GDB
15897 @chapter Controlling @value{GDBN}
15899 You can alter the way @value{GDBN} interacts with you by using the
15900 @code{set} command. For commands controlling how @value{GDBN} displays
15901 data, see @ref{Print Settings, ,Print Settings}. Other settings are
15906 * Editing:: Command editing
15907 * Command History:: Command history
15908 * Screen Size:: Screen size
15909 * Numbers:: Numbers
15910 * ABI:: Configuring the current ABI
15911 * Messages/Warnings:: Optional warnings and messages
15912 * Debugging Output:: Optional messages about internal happenings
15920 @value{GDBN} indicates its readiness to read a command by printing a string
15921 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15922 can change the prompt string with the @code{set prompt} command. For
15923 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15924 the prompt in one of the @value{GDBN} sessions so that you can always tell
15925 which one you are talking to.
15927 @emph{Note:} @code{set prompt} does not add a space for you after the
15928 prompt you set. This allows you to set a prompt which ends in a space
15929 or a prompt that does not.
15933 @item set prompt @var{newprompt}
15934 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15936 @kindex show prompt
15938 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15942 @section Command Editing
15944 @cindex command line editing
15946 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15947 @sc{gnu} library provides consistent behavior for programs which provide a
15948 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15949 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15950 substitution, and a storage and recall of command history across
15951 debugging sessions.
15953 You may control the behavior of command line editing in @value{GDBN} with the
15954 command @code{set}.
15957 @kindex set editing
15960 @itemx set editing on
15961 Enable command line editing (enabled by default).
15963 @item set editing off
15964 Disable command line editing.
15966 @kindex show editing
15968 Show whether command line editing is enabled.
15971 @xref{Command Line Editing}, for more details about the Readline
15972 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15973 encouraged to read that chapter.
15975 @node Command History
15976 @section Command History
15977 @cindex command history
15979 @value{GDBN} can keep track of the commands you type during your
15980 debugging sessions, so that you can be certain of precisely what
15981 happened. Use these commands to manage the @value{GDBN} command
15984 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15985 package, to provide the history facility. @xref{Using History
15986 Interactively}, for the detailed description of the History library.
15988 To issue a command to @value{GDBN} without affecting certain aspects of
15989 the state which is seen by users, prefix it with @samp{server }
15990 (@pxref{Server Prefix}). This
15991 means that this command will not affect the command history, nor will it
15992 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15993 pressed on a line by itself.
15995 @cindex @code{server}, command prefix
15996 The server prefix does not affect the recording of values into the value
15997 history; to print a value without recording it into the value history,
15998 use the @code{output} command instead of the @code{print} command.
16000 Here is the description of @value{GDBN} commands related to command
16004 @cindex history substitution
16005 @cindex history file
16006 @kindex set history filename
16007 @cindex @env{GDBHISTFILE}, environment variable
16008 @item set history filename @var{fname}
16009 Set the name of the @value{GDBN} command history file to @var{fname}.
16010 This is the file where @value{GDBN} reads an initial command history
16011 list, and where it writes the command history from this session when it
16012 exits. You can access this list through history expansion or through
16013 the history command editing characters listed below. This file defaults
16014 to the value of the environment variable @code{GDBHISTFILE}, or to
16015 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16018 @cindex save command history
16019 @kindex set history save
16020 @item set history save
16021 @itemx set history save on
16022 Record command history in a file, whose name may be specified with the
16023 @code{set history filename} command. By default, this option is disabled.
16025 @item set history save off
16026 Stop recording command history in a file.
16028 @cindex history size
16029 @kindex set history size
16030 @cindex @env{HISTSIZE}, environment variable
16031 @item set history size @var{size}
16032 Set the number of commands which @value{GDBN} keeps in its history list.
16033 This defaults to the value of the environment variable
16034 @code{HISTSIZE}, or to 256 if this variable is not set.
16037 History expansion assigns special meaning to the character @kbd{!}.
16038 @xref{Event Designators}, for more details.
16040 @cindex history expansion, turn on/off
16041 Since @kbd{!} is also the logical not operator in C, history expansion
16042 is off by default. If you decide to enable history expansion with the
16043 @code{set history expansion on} command, you may sometimes need to
16044 follow @kbd{!} (when it is used as logical not, in an expression) with
16045 a space or a tab to prevent it from being expanded. The readline
16046 history facilities do not attempt substitution on the strings
16047 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
16049 The commands to control history expansion are:
16052 @item set history expansion on
16053 @itemx set history expansion
16054 @kindex set history expansion
16055 Enable history expansion. History expansion is off by default.
16057 @item set history expansion off
16058 Disable history expansion.
16061 @kindex show history
16063 @itemx show history filename
16064 @itemx show history save
16065 @itemx show history size
16066 @itemx show history expansion
16067 These commands display the state of the @value{GDBN} history parameters.
16068 @code{show history} by itself displays all four states.
16073 @kindex show commands
16074 @cindex show last commands
16075 @cindex display command history
16076 @item show commands
16077 Display the last ten commands in the command history.
16079 @item show commands @var{n}
16080 Print ten commands centered on command number @var{n}.
16082 @item show commands +
16083 Print ten commands just after the commands last printed.
16087 @section Screen Size
16088 @cindex size of screen
16089 @cindex pauses in output
16091 Certain commands to @value{GDBN} may produce large amounts of
16092 information output to the screen. To help you read all of it,
16093 @value{GDBN} pauses and asks you for input at the end of each page of
16094 output. Type @key{RET} when you want to continue the output, or @kbd{q}
16095 to discard the remaining output. Also, the screen width setting
16096 determines when to wrap lines of output. Depending on what is being
16097 printed, @value{GDBN} tries to break the line at a readable place,
16098 rather than simply letting it overflow onto the following line.
16100 Normally @value{GDBN} knows the size of the screen from the terminal
16101 driver software. For example, on Unix @value{GDBN} uses the termcap data base
16102 together with the value of the @code{TERM} environment variable and the
16103 @code{stty rows} and @code{stty cols} settings. If this is not correct,
16104 you can override it with the @code{set height} and @code{set
16111 @kindex show height
16112 @item set height @var{lpp}
16114 @itemx set width @var{cpl}
16116 These @code{set} commands specify a screen height of @var{lpp} lines and
16117 a screen width of @var{cpl} characters. The associated @code{show}
16118 commands display the current settings.
16120 If you specify a height of zero lines, @value{GDBN} does not pause during
16121 output no matter how long the output is. This is useful if output is to a
16122 file or to an editor buffer.
16124 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
16125 from wrapping its output.
16127 @item set pagination on
16128 @itemx set pagination off
16129 @kindex set pagination
16130 Turn the output pagination on or off; the default is on. Turning
16131 pagination off is the alternative to @code{set height 0}.
16133 @item show pagination
16134 @kindex show pagination
16135 Show the current pagination mode.
16140 @cindex number representation
16141 @cindex entering numbers
16143 You can always enter numbers in octal, decimal, or hexadecimal in
16144 @value{GDBN} by the usual conventions: octal numbers begin with
16145 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
16146 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
16147 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
16148 10; likewise, the default display for numbers---when no particular
16149 format is specified---is base 10. You can change the default base for
16150 both input and output with the commands described below.
16153 @kindex set input-radix
16154 @item set input-radix @var{base}
16155 Set the default base for numeric input. Supported choices
16156 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16157 specified either unambiguously or using the current input radix; for
16161 set input-radix 012
16162 set input-radix 10.
16163 set input-radix 0xa
16167 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
16168 leaves the input radix unchanged, no matter what it was, since
16169 @samp{10}, being without any leading or trailing signs of its base, is
16170 interpreted in the current radix. Thus, if the current radix is 16,
16171 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
16174 @kindex set output-radix
16175 @item set output-radix @var{base}
16176 Set the default base for numeric display. Supported choices
16177 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16178 specified either unambiguously or using the current input radix.
16180 @kindex show input-radix
16181 @item show input-radix
16182 Display the current default base for numeric input.
16184 @kindex show output-radix
16185 @item show output-radix
16186 Display the current default base for numeric display.
16188 @item set radix @r{[}@var{base}@r{]}
16192 These commands set and show the default base for both input and output
16193 of numbers. @code{set radix} sets the radix of input and output to
16194 the same base; without an argument, it resets the radix back to its
16195 default value of 10.
16200 @section Configuring the Current ABI
16202 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
16203 application automatically. However, sometimes you need to override its
16204 conclusions. Use these commands to manage @value{GDBN}'s view of the
16211 One @value{GDBN} configuration can debug binaries for multiple operating
16212 system targets, either via remote debugging or native emulation.
16213 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
16214 but you can override its conclusion using the @code{set osabi} command.
16215 One example where this is useful is in debugging of binaries which use
16216 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16217 not have the same identifying marks that the standard C library for your
16222 Show the OS ABI currently in use.
16225 With no argument, show the list of registered available OS ABI's.
16227 @item set osabi @var{abi}
16228 Set the current OS ABI to @var{abi}.
16231 @cindex float promotion
16233 Generally, the way that an argument of type @code{float} is passed to a
16234 function depends on whether the function is prototyped. For a prototyped
16235 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16236 according to the architecture's convention for @code{float}. For unprototyped
16237 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16238 @code{double} and then passed.
16240 Unfortunately, some forms of debug information do not reliably indicate whether
16241 a function is prototyped. If @value{GDBN} calls a function that is not marked
16242 as prototyped, it consults @kbd{set coerce-float-to-double}.
16245 @kindex set coerce-float-to-double
16246 @item set coerce-float-to-double
16247 @itemx set coerce-float-to-double on
16248 Arguments of type @code{float} will be promoted to @code{double} when passed
16249 to an unprototyped function. This is the default setting.
16251 @item set coerce-float-to-double off
16252 Arguments of type @code{float} will be passed directly to unprototyped
16255 @kindex show coerce-float-to-double
16256 @item show coerce-float-to-double
16257 Show the current setting of promoting @code{float} to @code{double}.
16261 @kindex show cp-abi
16262 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16263 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16264 used to build your application. @value{GDBN} only fully supports
16265 programs with a single C@t{++} ABI; if your program contains code using
16266 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16267 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16268 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16269 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16270 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16271 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16276 Show the C@t{++} ABI currently in use.
16279 With no argument, show the list of supported C@t{++} ABI's.
16281 @item set cp-abi @var{abi}
16282 @itemx set cp-abi auto
16283 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16286 @node Messages/Warnings
16287 @section Optional Warnings and Messages
16289 @cindex verbose operation
16290 @cindex optional warnings
16291 By default, @value{GDBN} is silent about its inner workings. If you are
16292 running on a slow machine, you may want to use the @code{set verbose}
16293 command. This makes @value{GDBN} tell you when it does a lengthy
16294 internal operation, so you will not think it has crashed.
16296 Currently, the messages controlled by @code{set verbose} are those
16297 which announce that the symbol table for a source file is being read;
16298 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16301 @kindex set verbose
16302 @item set verbose on
16303 Enables @value{GDBN} output of certain informational messages.
16305 @item set verbose off
16306 Disables @value{GDBN} output of certain informational messages.
16308 @kindex show verbose
16310 Displays whether @code{set verbose} is on or off.
16313 By default, if @value{GDBN} encounters bugs in the symbol table of an
16314 object file, it is silent; but if you are debugging a compiler, you may
16315 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16320 @kindex set complaints
16321 @item set complaints @var{limit}
16322 Permits @value{GDBN} to output @var{limit} complaints about each type of
16323 unusual symbols before becoming silent about the problem. Set
16324 @var{limit} to zero to suppress all complaints; set it to a large number
16325 to prevent complaints from being suppressed.
16327 @kindex show complaints
16328 @item show complaints
16329 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16333 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16334 lot of stupid questions to confirm certain commands. For example, if
16335 you try to run a program which is already running:
16339 The program being debugged has been started already.
16340 Start it from the beginning? (y or n)
16343 If you are willing to unflinchingly face the consequences of your own
16344 commands, you can disable this ``feature'':
16348 @kindex set confirm
16350 @cindex confirmation
16351 @cindex stupid questions
16352 @item set confirm off
16353 Disables confirmation requests.
16355 @item set confirm on
16356 Enables confirmation requests (the default).
16358 @kindex show confirm
16360 Displays state of confirmation requests.
16364 @cindex command tracing
16365 If you need to debug user-defined commands or sourced files you may find it
16366 useful to enable @dfn{command tracing}. In this mode each command will be
16367 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16368 quantity denoting the call depth of each command.
16371 @kindex set trace-commands
16372 @cindex command scripts, debugging
16373 @item set trace-commands on
16374 Enable command tracing.
16375 @item set trace-commands off
16376 Disable command tracing.
16377 @item show trace-commands
16378 Display the current state of command tracing.
16381 @node Debugging Output
16382 @section Optional Messages about Internal Happenings
16383 @cindex optional debugging messages
16385 @value{GDBN} has commands that enable optional debugging messages from
16386 various @value{GDBN} subsystems; normally these commands are of
16387 interest to @value{GDBN} maintainers, or when reporting a bug. This
16388 section documents those commands.
16391 @kindex set exec-done-display
16392 @item set exec-done-display
16393 Turns on or off the notification of asynchronous commands'
16394 completion. When on, @value{GDBN} will print a message when an
16395 asynchronous command finishes its execution. The default is off.
16396 @kindex show exec-done-display
16397 @item show exec-done-display
16398 Displays the current setting of asynchronous command completion
16401 @cindex gdbarch debugging info
16402 @cindex architecture debugging info
16403 @item set debug arch
16404 Turns on or off display of gdbarch debugging info. The default is off
16406 @item show debug arch
16407 Displays the current state of displaying gdbarch debugging info.
16408 @item set debug aix-thread
16409 @cindex AIX threads
16410 Display debugging messages about inner workings of the AIX thread
16412 @item show debug aix-thread
16413 Show the current state of AIX thread debugging info display.
16414 @item set debug event
16415 @cindex event debugging info
16416 Turns on or off display of @value{GDBN} event debugging info. The
16418 @item show debug event
16419 Displays the current state of displaying @value{GDBN} event debugging
16421 @item set debug expression
16422 @cindex expression debugging info
16423 Turns on or off display of debugging info about @value{GDBN}
16424 expression parsing. The default is off.
16425 @item show debug expression
16426 Displays the current state of displaying debugging info about
16427 @value{GDBN} expression parsing.
16428 @item set debug frame
16429 @cindex frame debugging info
16430 Turns on or off display of @value{GDBN} frame debugging info. The
16432 @item show debug frame
16433 Displays the current state of displaying @value{GDBN} frame debugging
16435 @item set debug infrun
16436 @cindex inferior debugging info
16437 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16438 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16439 for implementing operations such as single-stepping the inferior.
16440 @item show debug infrun
16441 Displays the current state of @value{GDBN} inferior debugging.
16442 @item set debug lin-lwp
16443 @cindex @sc{gnu}/Linux LWP debug messages
16444 @cindex Linux lightweight processes
16445 Turns on or off debugging messages from the Linux LWP debug support.
16446 @item show debug lin-lwp
16447 Show the current state of Linux LWP debugging messages.
16448 @item set debug lin-lwp-async
16449 @cindex @sc{gnu}/Linux LWP async debug messages
16450 @cindex Linux lightweight processes
16451 Turns on or off debugging messages from the Linux LWP async debug support.
16452 @item show debug lin-lwp-async
16453 Show the current state of Linux LWP async debugging messages.
16454 @item set debug observer
16455 @cindex observer debugging info
16456 Turns on or off display of @value{GDBN} observer debugging. This
16457 includes info such as the notification of observable events.
16458 @item show debug observer
16459 Displays the current state of observer debugging.
16460 @item set debug overload
16461 @cindex C@t{++} overload debugging info
16462 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16463 info. This includes info such as ranking of functions, etc. The default
16465 @item show debug overload
16466 Displays the current state of displaying @value{GDBN} C@t{++} overload
16468 @cindex packets, reporting on stdout
16469 @cindex serial connections, debugging
16470 @cindex debug remote protocol
16471 @cindex remote protocol debugging
16472 @cindex display remote packets
16473 @item set debug remote
16474 Turns on or off display of reports on all packets sent back and forth across
16475 the serial line to the remote machine. The info is printed on the
16476 @value{GDBN} standard output stream. The default is off.
16477 @item show debug remote
16478 Displays the state of display of remote packets.
16479 @item set debug serial
16480 Turns on or off display of @value{GDBN} serial debugging info. The
16482 @item show debug serial
16483 Displays the current state of displaying @value{GDBN} serial debugging
16485 @item set debug solib-frv
16486 @cindex FR-V shared-library debugging
16487 Turns on or off debugging messages for FR-V shared-library code.
16488 @item show debug solib-frv
16489 Display the current state of FR-V shared-library code debugging
16491 @item set debug target
16492 @cindex target debugging info
16493 Turns on or off display of @value{GDBN} target debugging info. This info
16494 includes what is going on at the target level of GDB, as it happens. The
16495 default is 0. Set it to 1 to track events, and to 2 to also track the
16496 value of large memory transfers. Changes to this flag do not take effect
16497 until the next time you connect to a target or use the @code{run} command.
16498 @item show debug target
16499 Displays the current state of displaying @value{GDBN} target debugging
16501 @item set debug timestamp
16502 @cindex timestampping debugging info
16503 Turns on or off display of timestamps with @value{GDBN} debugging info.
16504 When enabled, seconds and microseconds are displayed before each debugging
16506 @item show debug timestamp
16507 Displays the current state of displaying timestamps with @value{GDBN}
16509 @item set debugvarobj
16510 @cindex variable object debugging info
16511 Turns on or off display of @value{GDBN} variable object debugging
16512 info. The default is off.
16513 @item show debugvarobj
16514 Displays the current state of displaying @value{GDBN} variable object
16516 @item set debug xml
16517 @cindex XML parser debugging
16518 Turns on or off debugging messages for built-in XML parsers.
16519 @item show debug xml
16520 Displays the current state of XML debugging messages.
16524 @chapter Canned Sequences of Commands
16526 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16527 Command Lists}), @value{GDBN} provides two ways to store sequences of
16528 commands for execution as a unit: user-defined commands and command
16532 * Define:: How to define your own commands
16533 * Hooks:: Hooks for user-defined commands
16534 * Command Files:: How to write scripts of commands to be stored in a file
16535 * Output:: Commands for controlled output
16539 @section User-defined Commands
16541 @cindex user-defined command
16542 @cindex arguments, to user-defined commands
16543 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16544 which you assign a new name as a command. This is done with the
16545 @code{define} command. User commands may accept up to 10 arguments
16546 separated by whitespace. Arguments are accessed within the user command
16547 via @code{$arg0@dots{}$arg9}. A trivial example:
16551 print $arg0 + $arg1 + $arg2
16556 To execute the command use:
16563 This defines the command @code{adder}, which prints the sum of
16564 its three arguments. Note the arguments are text substitutions, so they may
16565 reference variables, use complex expressions, or even perform inferior
16568 @cindex argument count in user-defined commands
16569 @cindex how many arguments (user-defined commands)
16570 In addition, @code{$argc} may be used to find out how many arguments have
16571 been passed. This expands to a number in the range 0@dots{}10.
16576 print $arg0 + $arg1
16579 print $arg0 + $arg1 + $arg2
16587 @item define @var{commandname}
16588 Define a command named @var{commandname}. If there is already a command
16589 by that name, you are asked to confirm that you want to redefine it.
16591 The definition of the command is made up of other @value{GDBN} command lines,
16592 which are given following the @code{define} command. The end of these
16593 commands is marked by a line containing @code{end}.
16596 @kindex end@r{ (user-defined commands)}
16597 @item document @var{commandname}
16598 Document the user-defined command @var{commandname}, so that it can be
16599 accessed by @code{help}. The command @var{commandname} must already be
16600 defined. This command reads lines of documentation just as @code{define}
16601 reads the lines of the command definition, ending with @code{end}.
16602 After the @code{document} command is finished, @code{help} on command
16603 @var{commandname} displays the documentation you have written.
16605 You may use the @code{document} command again to change the
16606 documentation of a command. Redefining the command with @code{define}
16607 does not change the documentation.
16609 @kindex dont-repeat
16610 @cindex don't repeat command
16612 Used inside a user-defined command, this tells @value{GDBN} that this
16613 command should not be repeated when the user hits @key{RET}
16614 (@pxref{Command Syntax, repeat last command}).
16616 @kindex help user-defined
16617 @item help user-defined
16618 List all user-defined commands, with the first line of the documentation
16623 @itemx show user @var{commandname}
16624 Display the @value{GDBN} commands used to define @var{commandname} (but
16625 not its documentation). If no @var{commandname} is given, display the
16626 definitions for all user-defined commands.
16628 @cindex infinite recursion in user-defined commands
16629 @kindex show max-user-call-depth
16630 @kindex set max-user-call-depth
16631 @item show max-user-call-depth
16632 @itemx set max-user-call-depth
16633 The value of @code{max-user-call-depth} controls how many recursion
16634 levels are allowed in user-defined commands before @value{GDBN} suspects an
16635 infinite recursion and aborts the command.
16638 In addition to the above commands, user-defined commands frequently
16639 use control flow commands, described in @ref{Command Files}.
16641 When user-defined commands are executed, the
16642 commands of the definition are not printed. An error in any command
16643 stops execution of the user-defined command.
16645 If used interactively, commands that would ask for confirmation proceed
16646 without asking when used inside a user-defined command. Many @value{GDBN}
16647 commands that normally print messages to say what they are doing omit the
16648 messages when used in a user-defined command.
16651 @section User-defined Command Hooks
16652 @cindex command hooks
16653 @cindex hooks, for commands
16654 @cindex hooks, pre-command
16657 You may define @dfn{hooks}, which are a special kind of user-defined
16658 command. Whenever you run the command @samp{foo}, if the user-defined
16659 command @samp{hook-foo} exists, it is executed (with no arguments)
16660 before that command.
16662 @cindex hooks, post-command
16664 A hook may also be defined which is run after the command you executed.
16665 Whenever you run the command @samp{foo}, if the user-defined command
16666 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16667 that command. Post-execution hooks may exist simultaneously with
16668 pre-execution hooks, for the same command.
16670 It is valid for a hook to call the command which it hooks. If this
16671 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16673 @c It would be nice if hookpost could be passed a parameter indicating
16674 @c if the command it hooks executed properly or not. FIXME!
16676 @kindex stop@r{, a pseudo-command}
16677 In addition, a pseudo-command, @samp{stop} exists. Defining
16678 (@samp{hook-stop}) makes the associated commands execute every time
16679 execution stops in your program: before breakpoint commands are run,
16680 displays are printed, or the stack frame is printed.
16682 For example, to ignore @code{SIGALRM} signals while
16683 single-stepping, but treat them normally during normal execution,
16688 handle SIGALRM nopass
16692 handle SIGALRM pass
16695 define hook-continue
16696 handle SIGALRM pass
16700 As a further example, to hook at the beginning and end of the @code{echo}
16701 command, and to add extra text to the beginning and end of the message,
16709 define hookpost-echo
16713 (@value{GDBP}) echo Hello World
16714 <<<---Hello World--->>>
16719 You can define a hook for any single-word command in @value{GDBN}, but
16720 not for command aliases; you should define a hook for the basic command
16721 name, e.g.@: @code{backtrace} rather than @code{bt}.
16722 @c FIXME! So how does Joe User discover whether a command is an alias
16724 If an error occurs during the execution of your hook, execution of
16725 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16726 (before the command that you actually typed had a chance to run).
16728 If you try to define a hook which does not match any known command, you
16729 get a warning from the @code{define} command.
16731 @node Command Files
16732 @section Command Files
16734 @cindex command files
16735 @cindex scripting commands
16736 A command file for @value{GDBN} is a text file made of lines that are
16737 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16738 also be included. An empty line in a command file does nothing; it
16739 does not mean to repeat the last command, as it would from the
16742 You can request the execution of a command file with the @code{source}
16747 @cindex execute commands from a file
16748 @item source [@code{-v}] @var{filename}
16749 Execute the command file @var{filename}.
16752 The lines in a command file are generally executed sequentially,
16753 unless the order of execution is changed by one of the
16754 @emph{flow-control commands} described below. The commands are not
16755 printed as they are executed. An error in any command terminates
16756 execution of the command file and control is returned to the console.
16758 @value{GDBN} searches for @var{filename} in the current directory and then
16759 on the search path (specified with the @samp{directory} command).
16761 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16762 each command as it is executed. The option must be given before
16763 @var{filename}, and is interpreted as part of the filename anywhere else.
16765 Commands that would ask for confirmation if used interactively proceed
16766 without asking when used in a command file. Many @value{GDBN} commands that
16767 normally print messages to say what they are doing omit the messages
16768 when called from command files.
16770 @value{GDBN} also accepts command input from standard input. In this
16771 mode, normal output goes to standard output and error output goes to
16772 standard error. Errors in a command file supplied on standard input do
16773 not terminate execution of the command file---execution continues with
16777 gdb < cmds > log 2>&1
16780 (The syntax above will vary depending on the shell used.) This example
16781 will execute commands from the file @file{cmds}. All output and errors
16782 would be directed to @file{log}.
16784 Since commands stored on command files tend to be more general than
16785 commands typed interactively, they frequently need to deal with
16786 complicated situations, such as different or unexpected values of
16787 variables and symbols, changes in how the program being debugged is
16788 built, etc. @value{GDBN} provides a set of flow-control commands to
16789 deal with these complexities. Using these commands, you can write
16790 complex scripts that loop over data structures, execute commands
16791 conditionally, etc.
16798 This command allows to include in your script conditionally executed
16799 commands. The @code{if} command takes a single argument, which is an
16800 expression to evaluate. It is followed by a series of commands that
16801 are executed only if the expression is true (its value is nonzero).
16802 There can then optionally be an @code{else} line, followed by a series
16803 of commands that are only executed if the expression was false. The
16804 end of the list is marked by a line containing @code{end}.
16808 This command allows to write loops. Its syntax is similar to
16809 @code{if}: the command takes a single argument, which is an expression
16810 to evaluate, and must be followed by the commands to execute, one per
16811 line, terminated by an @code{end}. These commands are called the
16812 @dfn{body} of the loop. The commands in the body of @code{while} are
16813 executed repeatedly as long as the expression evaluates to true.
16817 This command exits the @code{while} loop in whose body it is included.
16818 Execution of the script continues after that @code{while}s @code{end}
16821 @kindex loop_continue
16822 @item loop_continue
16823 This command skips the execution of the rest of the body of commands
16824 in the @code{while} loop in whose body it is included. Execution
16825 branches to the beginning of the @code{while} loop, where it evaluates
16826 the controlling expression.
16828 @kindex end@r{ (if/else/while commands)}
16830 Terminate the block of commands that are the body of @code{if},
16831 @code{else}, or @code{while} flow-control commands.
16836 @section Commands for Controlled Output
16838 During the execution of a command file or a user-defined command, normal
16839 @value{GDBN} output is suppressed; the only output that appears is what is
16840 explicitly printed by the commands in the definition. This section
16841 describes three commands useful for generating exactly the output you
16846 @item echo @var{text}
16847 @c I do not consider backslash-space a standard C escape sequence
16848 @c because it is not in ANSI.
16849 Print @var{text}. Nonprinting characters can be included in
16850 @var{text} using C escape sequences, such as @samp{\n} to print a
16851 newline. @strong{No newline is printed unless you specify one.}
16852 In addition to the standard C escape sequences, a backslash followed
16853 by a space stands for a space. This is useful for displaying a
16854 string with spaces at the beginning or the end, since leading and
16855 trailing spaces are otherwise trimmed from all arguments.
16856 To print @samp{@w{ }and foo =@w{ }}, use the command
16857 @samp{echo \@w{ }and foo = \@w{ }}.
16859 A backslash at the end of @var{text} can be used, as in C, to continue
16860 the command onto subsequent lines. For example,
16863 echo This is some text\n\
16864 which is continued\n\
16865 onto several lines.\n
16868 produces the same output as
16871 echo This is some text\n
16872 echo which is continued\n
16873 echo onto several lines.\n
16877 @item output @var{expression}
16878 Print the value of @var{expression} and nothing but that value: no
16879 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16880 value history either. @xref{Expressions, ,Expressions}, for more information
16883 @item output/@var{fmt} @var{expression}
16884 Print the value of @var{expression} in format @var{fmt}. You can use
16885 the same formats as for @code{print}. @xref{Output Formats,,Output
16886 Formats}, for more information.
16889 @item printf @var{template}, @var{expressions}@dots{}
16890 Print the values of one or more @var{expressions} under the control of
16891 the string @var{template}. To print several values, make
16892 @var{expressions} be a comma-separated list of individual expressions,
16893 which may be either numbers or pointers. Their values are printed as
16894 specified by @var{template}, exactly as a C program would do by
16895 executing the code below:
16898 printf (@var{template}, @var{expressions}@dots{});
16901 As in @code{C} @code{printf}, ordinary characters in @var{template}
16902 are printed verbatim, while @dfn{conversion specification} introduced
16903 by the @samp{%} character cause subsequent @var{expressions} to be
16904 evaluated, their values converted and formatted according to type and
16905 style information encoded in the conversion specifications, and then
16908 For example, you can print two values in hex like this:
16911 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16914 @code{printf} supports all the standard @code{C} conversion
16915 specifications, including the flags and modifiers between the @samp{%}
16916 character and the conversion letter, with the following exceptions:
16920 The argument-ordering modifiers, such as @samp{2$}, are not supported.
16923 The modifier @samp{*} is not supported for specifying precision or
16927 The @samp{'} flag (for separation of digits into groups according to
16928 @code{LC_NUMERIC'}) is not supported.
16931 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
16935 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
16938 The conversion letters @samp{a} and @samp{A} are not supported.
16942 Note that the @samp{ll} type modifier is supported only if the
16943 underlying @code{C} implementation used to build @value{GDBN} supports
16944 the @code{long long int} type, and the @samp{L} type modifier is
16945 supported only if @code{long double} type is available.
16947 As in @code{C}, @code{printf} supports simple backslash-escape
16948 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
16949 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
16950 single character. Octal and hexadecimal escape sequences are not
16953 Additionally, @code{printf} supports conversion specifications for DFP
16954 (@dfn{Decimal Floating Point}) types using the following length modifiers
16955 together with a floating point specifier.
16960 @samp{H} for printing @code{Decimal32} types.
16963 @samp{D} for printing @code{Decimal64} types.
16966 @samp{DD} for printing @code{Decimal128} types.
16969 If the underlying @code{C} implementation used to build @value{GDBN} has
16970 support for the three length modifiers for DFP types, other modifiers
16971 such as width and precision will also be available for @value{GDBN} to use.
16973 In case there is no such @code{C} support, no additional modifiers will be
16974 available and the value will be printed in the standard way.
16976 Here's an example of printing DFP types using the above conversion letters:
16978 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
16984 @chapter Command Interpreters
16985 @cindex command interpreters
16987 @value{GDBN} supports multiple command interpreters, and some command
16988 infrastructure to allow users or user interface writers to switch
16989 between interpreters or run commands in other interpreters.
16991 @value{GDBN} currently supports two command interpreters, the console
16992 interpreter (sometimes called the command-line interpreter or @sc{cli})
16993 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16994 describes both of these interfaces in great detail.
16996 By default, @value{GDBN} will start with the console interpreter.
16997 However, the user may choose to start @value{GDBN} with another
16998 interpreter by specifying the @option{-i} or @option{--interpreter}
16999 startup options. Defined interpreters include:
17003 @cindex console interpreter
17004 The traditional console or command-line interpreter. This is the most often
17005 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
17006 @value{GDBN} will use this interpreter.
17009 @cindex mi interpreter
17010 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
17011 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
17012 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
17016 @cindex mi2 interpreter
17017 The current @sc{gdb/mi} interface.
17020 @cindex mi1 interpreter
17021 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
17025 @cindex invoke another interpreter
17026 The interpreter being used by @value{GDBN} may not be dynamically
17027 switched at runtime. Although possible, this could lead to a very
17028 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
17029 enters the command "interpreter-set console" in a console view,
17030 @value{GDBN} would switch to using the console interpreter, rendering
17031 the IDE inoperable!
17033 @kindex interpreter-exec
17034 Although you may only choose a single interpreter at startup, you may execute
17035 commands in any interpreter from the current interpreter using the appropriate
17036 command. If you are running the console interpreter, simply use the
17037 @code{interpreter-exec} command:
17040 interpreter-exec mi "-data-list-register-names"
17043 @sc{gdb/mi} has a similar command, although it is only available in versions of
17044 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
17047 @chapter @value{GDBN} Text User Interface
17049 @cindex Text User Interface
17052 * TUI Overview:: TUI overview
17053 * TUI Keys:: TUI key bindings
17054 * TUI Single Key Mode:: TUI single key mode
17055 * TUI Commands:: TUI-specific commands
17056 * TUI Configuration:: TUI configuration variables
17059 The @value{GDBN} Text User Interface (TUI) is a terminal
17060 interface which uses the @code{curses} library to show the source
17061 file, the assembly output, the program registers and @value{GDBN}
17062 commands in separate text windows. The TUI mode is supported only
17063 on platforms where a suitable version of the @code{curses} library
17066 @pindex @value{GDBTUI}
17067 The TUI mode is enabled by default when you invoke @value{GDBN} as
17068 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
17069 You can also switch in and out of TUI mode while @value{GDBN} runs by
17070 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
17071 @xref{TUI Keys, ,TUI Key Bindings}.
17074 @section TUI Overview
17076 In TUI mode, @value{GDBN} can display several text windows:
17080 This window is the @value{GDBN} command window with the @value{GDBN}
17081 prompt and the @value{GDBN} output. The @value{GDBN} input is still
17082 managed using readline.
17085 The source window shows the source file of the program. The current
17086 line and active breakpoints are displayed in this window.
17089 The assembly window shows the disassembly output of the program.
17092 This window shows the processor registers. Registers are highlighted
17093 when their values change.
17096 The source and assembly windows show the current program position
17097 by highlighting the current line and marking it with a @samp{>} marker.
17098 Breakpoints are indicated with two markers. The first marker
17099 indicates the breakpoint type:
17103 Breakpoint which was hit at least once.
17106 Breakpoint which was never hit.
17109 Hardware breakpoint which was hit at least once.
17112 Hardware breakpoint which was never hit.
17115 The second marker indicates whether the breakpoint is enabled or not:
17119 Breakpoint is enabled.
17122 Breakpoint is disabled.
17125 The source, assembly and register windows are updated when the current
17126 thread changes, when the frame changes, or when the program counter
17129 These windows are not all visible at the same time. The command
17130 window is always visible. The others can be arranged in several
17141 source and assembly,
17144 source and registers, or
17147 assembly and registers.
17150 A status line above the command window shows the following information:
17154 Indicates the current @value{GDBN} target.
17155 (@pxref{Targets, ,Specifying a Debugging Target}).
17158 Gives the current process or thread number.
17159 When no process is being debugged, this field is set to @code{No process}.
17162 Gives the current function name for the selected frame.
17163 The name is demangled if demangling is turned on (@pxref{Print Settings}).
17164 When there is no symbol corresponding to the current program counter,
17165 the string @code{??} is displayed.
17168 Indicates the current line number for the selected frame.
17169 When the current line number is not known, the string @code{??} is displayed.
17172 Indicates the current program counter address.
17176 @section TUI Key Bindings
17177 @cindex TUI key bindings
17179 The TUI installs several key bindings in the readline keymaps
17180 (@pxref{Command Line Editing}). The following key bindings
17181 are installed for both TUI mode and the @value{GDBN} standard mode.
17190 Enter or leave the TUI mode. When leaving the TUI mode,
17191 the curses window management stops and @value{GDBN} operates using
17192 its standard mode, writing on the terminal directly. When reentering
17193 the TUI mode, control is given back to the curses windows.
17194 The screen is then refreshed.
17198 Use a TUI layout with only one window. The layout will
17199 either be @samp{source} or @samp{assembly}. When the TUI mode
17200 is not active, it will switch to the TUI mode.
17202 Think of this key binding as the Emacs @kbd{C-x 1} binding.
17206 Use a TUI layout with at least two windows. When the current
17207 layout already has two windows, the next layout with two windows is used.
17208 When a new layout is chosen, one window will always be common to the
17209 previous layout and the new one.
17211 Think of it as the Emacs @kbd{C-x 2} binding.
17215 Change the active window. The TUI associates several key bindings
17216 (like scrolling and arrow keys) with the active window. This command
17217 gives the focus to the next TUI window.
17219 Think of it as the Emacs @kbd{C-x o} binding.
17223 Switch in and out of the TUI SingleKey mode that binds single
17224 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
17227 The following key bindings only work in the TUI mode:
17232 Scroll the active window one page up.
17236 Scroll the active window one page down.
17240 Scroll the active window one line up.
17244 Scroll the active window one line down.
17248 Scroll the active window one column left.
17252 Scroll the active window one column right.
17256 Refresh the screen.
17259 Because the arrow keys scroll the active window in the TUI mode, they
17260 are not available for their normal use by readline unless the command
17261 window has the focus. When another window is active, you must use
17262 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
17263 and @kbd{C-f} to control the command window.
17265 @node TUI Single Key Mode
17266 @section TUI Single Key Mode
17267 @cindex TUI single key mode
17269 The TUI also provides a @dfn{SingleKey} mode, which binds several
17270 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
17271 switch into this mode, where the following key bindings are used:
17274 @kindex c @r{(SingleKey TUI key)}
17278 @kindex d @r{(SingleKey TUI key)}
17282 @kindex f @r{(SingleKey TUI key)}
17286 @kindex n @r{(SingleKey TUI key)}
17290 @kindex q @r{(SingleKey TUI key)}
17292 exit the SingleKey mode.
17294 @kindex r @r{(SingleKey TUI key)}
17298 @kindex s @r{(SingleKey TUI key)}
17302 @kindex u @r{(SingleKey TUI key)}
17306 @kindex v @r{(SingleKey TUI key)}
17310 @kindex w @r{(SingleKey TUI key)}
17315 Other keys temporarily switch to the @value{GDBN} command prompt.
17316 The key that was pressed is inserted in the editing buffer so that
17317 it is possible to type most @value{GDBN} commands without interaction
17318 with the TUI SingleKey mode. Once the command is entered the TUI
17319 SingleKey mode is restored. The only way to permanently leave
17320 this mode is by typing @kbd{q} or @kbd{C-x s}.
17324 @section TUI-specific Commands
17325 @cindex TUI commands
17327 The TUI has specific commands to control the text windows.
17328 These commands are always available, even when @value{GDBN} is not in
17329 the TUI mode. When @value{GDBN} is in the standard mode, most
17330 of these commands will automatically switch to the TUI mode.
17335 List and give the size of all displayed windows.
17339 Display the next layout.
17342 Display the previous layout.
17345 Display the source window only.
17348 Display the assembly window only.
17351 Display the source and assembly window.
17354 Display the register window together with the source or assembly window.
17358 Make the next window active for scrolling.
17361 Make the previous window active for scrolling.
17364 Make the source window active for scrolling.
17367 Make the assembly window active for scrolling.
17370 Make the register window active for scrolling.
17373 Make the command window active for scrolling.
17377 Refresh the screen. This is similar to typing @kbd{C-L}.
17379 @item tui reg float
17381 Show the floating point registers in the register window.
17383 @item tui reg general
17384 Show the general registers in the register window.
17387 Show the next register group. The list of register groups as well as
17388 their order is target specific. The predefined register groups are the
17389 following: @code{general}, @code{float}, @code{system}, @code{vector},
17390 @code{all}, @code{save}, @code{restore}.
17392 @item tui reg system
17393 Show the system registers in the register window.
17397 Update the source window and the current execution point.
17399 @item winheight @var{name} +@var{count}
17400 @itemx winheight @var{name} -@var{count}
17402 Change the height of the window @var{name} by @var{count}
17403 lines. Positive counts increase the height, while negative counts
17406 @item tabset @var{nchars}
17408 Set the width of tab stops to be @var{nchars} characters.
17411 @node TUI Configuration
17412 @section TUI Configuration Variables
17413 @cindex TUI configuration variables
17415 Several configuration variables control the appearance of TUI windows.
17418 @item set tui border-kind @var{kind}
17419 @kindex set tui border-kind
17420 Select the border appearance for the source, assembly and register windows.
17421 The possible values are the following:
17424 Use a space character to draw the border.
17427 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
17430 Use the Alternate Character Set to draw the border. The border is
17431 drawn using character line graphics if the terminal supports them.
17434 @item set tui border-mode @var{mode}
17435 @kindex set tui border-mode
17436 @itemx set tui active-border-mode @var{mode}
17437 @kindex set tui active-border-mode
17438 Select the display attributes for the borders of the inactive windows
17439 or the active window. The @var{mode} can be one of the following:
17442 Use normal attributes to display the border.
17448 Use reverse video mode.
17451 Use half bright mode.
17453 @item half-standout
17454 Use half bright and standout mode.
17457 Use extra bright or bold mode.
17459 @item bold-standout
17460 Use extra bright or bold and standout mode.
17465 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17468 @cindex @sc{gnu} Emacs
17469 A special interface allows you to use @sc{gnu} Emacs to view (and
17470 edit) the source files for the program you are debugging with
17473 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17474 executable file you want to debug as an argument. This command starts
17475 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17476 created Emacs buffer.
17477 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17479 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17484 All ``terminal'' input and output goes through an Emacs buffer, called
17487 This applies both to @value{GDBN} commands and their output, and to the input
17488 and output done by the program you are debugging.
17490 This is useful because it means that you can copy the text of previous
17491 commands and input them again; you can even use parts of the output
17494 All the facilities of Emacs' Shell mode are available for interacting
17495 with your program. In particular, you can send signals the usual
17496 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17500 @value{GDBN} displays source code through Emacs.
17502 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17503 source file for that frame and puts an arrow (@samp{=>}) at the
17504 left margin of the current line. Emacs uses a separate buffer for
17505 source display, and splits the screen to show both your @value{GDBN} session
17508 Explicit @value{GDBN} @code{list} or search commands still produce output as
17509 usual, but you probably have no reason to use them from Emacs.
17512 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17513 a graphical mode, enabled by default, which provides further buffers
17514 that can control the execution and describe the state of your program.
17515 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17517 If you specify an absolute file name when prompted for the @kbd{M-x
17518 gdb} argument, then Emacs sets your current working directory to where
17519 your program resides. If you only specify the file name, then Emacs
17520 sets your current working directory to to the directory associated
17521 with the previous buffer. In this case, @value{GDBN} may find your
17522 program by searching your environment's @code{PATH} variable, but on
17523 some operating systems it might not find the source. So, although the
17524 @value{GDBN} input and output session proceeds normally, the auxiliary
17525 buffer does not display the current source and line of execution.
17527 The initial working directory of @value{GDBN} is printed on the top
17528 line of the GUD buffer and this serves as a default for the commands
17529 that specify files for @value{GDBN} to operate on. @xref{Files,
17530 ,Commands to Specify Files}.
17532 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17533 need to call @value{GDBN} by a different name (for example, if you
17534 keep several configurations around, with different names) you can
17535 customize the Emacs variable @code{gud-gdb-command-name} to run the
17538 In the GUD buffer, you can use these special Emacs commands in
17539 addition to the standard Shell mode commands:
17543 Describe the features of Emacs' GUD Mode.
17546 Execute to another source line, like the @value{GDBN} @code{step} command; also
17547 update the display window to show the current file and location.
17550 Execute to next source line in this function, skipping all function
17551 calls, like the @value{GDBN} @code{next} command. Then update the display window
17552 to show the current file and location.
17555 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17556 display window accordingly.
17559 Execute until exit from the selected stack frame, like the @value{GDBN}
17560 @code{finish} command.
17563 Continue execution of your program, like the @value{GDBN} @code{continue}
17567 Go up the number of frames indicated by the numeric argument
17568 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17569 like the @value{GDBN} @code{up} command.
17572 Go down the number of frames indicated by the numeric argument, like the
17573 @value{GDBN} @code{down} command.
17576 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17577 tells @value{GDBN} to set a breakpoint on the source line point is on.
17579 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17580 separate frame which shows a backtrace when the GUD buffer is current.
17581 Move point to any frame in the stack and type @key{RET} to make it
17582 become the current frame and display the associated source in the
17583 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17584 selected frame become the current one. In graphical mode, the
17585 speedbar displays watch expressions.
17587 If you accidentally delete the source-display buffer, an easy way to get
17588 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17589 request a frame display; when you run under Emacs, this recreates
17590 the source buffer if necessary to show you the context of the current
17593 The source files displayed in Emacs are in ordinary Emacs buffers
17594 which are visiting the source files in the usual way. You can edit
17595 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17596 communicates with Emacs in terms of line numbers. If you add or
17597 delete lines from the text, the line numbers that @value{GDBN} knows cease
17598 to correspond properly with the code.
17600 A more detailed description of Emacs' interaction with @value{GDBN} is
17601 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17604 @c The following dropped because Epoch is nonstandard. Reactivate
17605 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17607 @kindex Emacs Epoch environment
17611 Version 18 of @sc{gnu} Emacs has a built-in window system
17612 called the @code{epoch}
17613 environment. Users of this environment can use a new command,
17614 @code{inspect} which performs identically to @code{print} except that
17615 each value is printed in its own window.
17620 @chapter The @sc{gdb/mi} Interface
17622 @unnumberedsec Function and Purpose
17624 @cindex @sc{gdb/mi}, its purpose
17625 @sc{gdb/mi} is a line based machine oriented text interface to
17626 @value{GDBN} and is activated by specifying using the
17627 @option{--interpreter} command line option (@pxref{Mode Options}). It
17628 is specifically intended to support the development of systems which
17629 use the debugger as just one small component of a larger system.
17631 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17632 in the form of a reference manual.
17634 Note that @sc{gdb/mi} is still under construction, so some of the
17635 features described below are incomplete and subject to change
17636 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17638 @unnumberedsec Notation and Terminology
17640 @cindex notational conventions, for @sc{gdb/mi}
17641 This chapter uses the following notation:
17645 @code{|} separates two alternatives.
17648 @code{[ @var{something} ]} indicates that @var{something} is optional:
17649 it may or may not be given.
17652 @code{( @var{group} )*} means that @var{group} inside the parentheses
17653 may repeat zero or more times.
17656 @code{( @var{group} )+} means that @var{group} inside the parentheses
17657 may repeat one or more times.
17660 @code{"@var{string}"} means a literal @var{string}.
17664 @heading Dependencies
17668 * GDB/MI Command Syntax::
17669 * GDB/MI Compatibility with CLI::
17670 * GDB/MI Development and Front Ends::
17671 * GDB/MI Output Records::
17672 * GDB/MI Simple Examples::
17673 * GDB/MI Command Description Format::
17674 * GDB/MI Breakpoint Commands::
17675 * GDB/MI Program Context::
17676 * GDB/MI Thread Commands::
17677 * GDB/MI Program Execution::
17678 * GDB/MI Stack Manipulation::
17679 * GDB/MI Variable Objects::
17680 * GDB/MI Data Manipulation::
17681 * GDB/MI Tracepoint Commands::
17682 * GDB/MI Symbol Query::
17683 * GDB/MI File Commands::
17685 * GDB/MI Kod Commands::
17686 * GDB/MI Memory Overlay Commands::
17687 * GDB/MI Signal Handling Commands::
17689 * GDB/MI Target Manipulation::
17690 * GDB/MI File Transfer Commands::
17691 * GDB/MI Miscellaneous Commands::
17694 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17695 @node GDB/MI Command Syntax
17696 @section @sc{gdb/mi} Command Syntax
17699 * GDB/MI Input Syntax::
17700 * GDB/MI Output Syntax::
17703 @node GDB/MI Input Syntax
17704 @subsection @sc{gdb/mi} Input Syntax
17706 @cindex input syntax for @sc{gdb/mi}
17707 @cindex @sc{gdb/mi}, input syntax
17709 @item @var{command} @expansion{}
17710 @code{@var{cli-command} | @var{mi-command}}
17712 @item @var{cli-command} @expansion{}
17713 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17714 @var{cli-command} is any existing @value{GDBN} CLI command.
17716 @item @var{mi-command} @expansion{}
17717 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17718 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17720 @item @var{token} @expansion{}
17721 "any sequence of digits"
17723 @item @var{option} @expansion{}
17724 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17726 @item @var{parameter} @expansion{}
17727 @code{@var{non-blank-sequence} | @var{c-string}}
17729 @item @var{operation} @expansion{}
17730 @emph{any of the operations described in this chapter}
17732 @item @var{non-blank-sequence} @expansion{}
17733 @emph{anything, provided it doesn't contain special characters such as
17734 "-", @var{nl}, """ and of course " "}
17736 @item @var{c-string} @expansion{}
17737 @code{""" @var{seven-bit-iso-c-string-content} """}
17739 @item @var{nl} @expansion{}
17748 The CLI commands are still handled by the @sc{mi} interpreter; their
17749 output is described below.
17752 The @code{@var{token}}, when present, is passed back when the command
17756 Some @sc{mi} commands accept optional arguments as part of the parameter
17757 list. Each option is identified by a leading @samp{-} (dash) and may be
17758 followed by an optional argument parameter. Options occur first in the
17759 parameter list and can be delimited from normal parameters using
17760 @samp{--} (this is useful when some parameters begin with a dash).
17767 We want easy access to the existing CLI syntax (for debugging).
17770 We want it to be easy to spot a @sc{mi} operation.
17773 @node GDB/MI Output Syntax
17774 @subsection @sc{gdb/mi} Output Syntax
17776 @cindex output syntax of @sc{gdb/mi}
17777 @cindex @sc{gdb/mi}, output syntax
17778 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17779 followed, optionally, by a single result record. This result record
17780 is for the most recent command. The sequence of output records is
17781 terminated by @samp{(gdb)}.
17783 If an input command was prefixed with a @code{@var{token}} then the
17784 corresponding output for that command will also be prefixed by that same
17788 @item @var{output} @expansion{}
17789 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17791 @item @var{result-record} @expansion{}
17792 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17794 @item @var{out-of-band-record} @expansion{}
17795 @code{@var{async-record} | @var{stream-record}}
17797 @item @var{async-record} @expansion{}
17798 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17800 @item @var{exec-async-output} @expansion{}
17801 @code{[ @var{token} ] "*" @var{async-output}}
17803 @item @var{status-async-output} @expansion{}
17804 @code{[ @var{token} ] "+" @var{async-output}}
17806 @item @var{notify-async-output} @expansion{}
17807 @code{[ @var{token} ] "=" @var{async-output}}
17809 @item @var{async-output} @expansion{}
17810 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17812 @item @var{result-class} @expansion{}
17813 @code{"done" | "running" | "connected" | "error" | "exit"}
17815 @item @var{async-class} @expansion{}
17816 @code{"stopped" | @var{others}} (where @var{others} will be added
17817 depending on the needs---this is still in development).
17819 @item @var{result} @expansion{}
17820 @code{ @var{variable} "=" @var{value}}
17822 @item @var{variable} @expansion{}
17823 @code{ @var{string} }
17825 @item @var{value} @expansion{}
17826 @code{ @var{const} | @var{tuple} | @var{list} }
17828 @item @var{const} @expansion{}
17829 @code{@var{c-string}}
17831 @item @var{tuple} @expansion{}
17832 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17834 @item @var{list} @expansion{}
17835 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17836 @var{result} ( "," @var{result} )* "]" }
17838 @item @var{stream-record} @expansion{}
17839 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17841 @item @var{console-stream-output} @expansion{}
17842 @code{"~" @var{c-string}}
17844 @item @var{target-stream-output} @expansion{}
17845 @code{"@@" @var{c-string}}
17847 @item @var{log-stream-output} @expansion{}
17848 @code{"&" @var{c-string}}
17850 @item @var{nl} @expansion{}
17853 @item @var{token} @expansion{}
17854 @emph{any sequence of digits}.
17862 All output sequences end in a single line containing a period.
17865 The @code{@var{token}} is from the corresponding request. If an execution
17866 command is interrupted by the @samp{-exec-interrupt} command, the
17867 @var{token} associated with the @samp{*stopped} message is the one of the
17868 original execution command, not the one of the interrupt command.
17871 @cindex status output in @sc{gdb/mi}
17872 @var{status-async-output} contains on-going status information about the
17873 progress of a slow operation. It can be discarded. All status output is
17874 prefixed by @samp{+}.
17877 @cindex async output in @sc{gdb/mi}
17878 @var{exec-async-output} contains asynchronous state change on the target
17879 (stopped, started, disappeared). All async output is prefixed by
17883 @cindex notify output in @sc{gdb/mi}
17884 @var{notify-async-output} contains supplementary information that the
17885 client should handle (e.g., a new breakpoint information). All notify
17886 output is prefixed by @samp{=}.
17889 @cindex console output in @sc{gdb/mi}
17890 @var{console-stream-output} is output that should be displayed as is in the
17891 console. It is the textual response to a CLI command. All the console
17892 output is prefixed by @samp{~}.
17895 @cindex target output in @sc{gdb/mi}
17896 @var{target-stream-output} is the output produced by the target program.
17897 All the target output is prefixed by @samp{@@}.
17900 @cindex log output in @sc{gdb/mi}
17901 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17902 instance messages that should be displayed as part of an error log. All
17903 the log output is prefixed by @samp{&}.
17906 @cindex list output in @sc{gdb/mi}
17907 New @sc{gdb/mi} commands should only output @var{lists} containing
17913 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17914 details about the various output records.
17916 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17917 @node GDB/MI Compatibility with CLI
17918 @section @sc{gdb/mi} Compatibility with CLI
17920 @cindex compatibility, @sc{gdb/mi} and CLI
17921 @cindex @sc{gdb/mi}, compatibility with CLI
17923 For the developers convenience CLI commands can be entered directly,
17924 but there may be some unexpected behaviour. For example, commands
17925 that query the user will behave as if the user replied yes, breakpoint
17926 command lists are not executed and some CLI commands, such as
17927 @code{if}, @code{when} and @code{define}, prompt for further input with
17928 @samp{>}, which is not valid MI output.
17930 This feature may be removed at some stage in the future and it is
17931 recommended that front ends use the @code{-interpreter-exec} command
17932 (@pxref{-interpreter-exec}).
17934 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17935 @node GDB/MI Development and Front Ends
17936 @section @sc{gdb/mi} Development and Front Ends
17937 @cindex @sc{gdb/mi} development
17939 The application which takes the MI output and presents the state of the
17940 program being debugged to the user is called a @dfn{front end}.
17942 Although @sc{gdb/mi} is still incomplete, it is currently being used
17943 by a variety of front ends to @value{GDBN}. This makes it difficult
17944 to introduce new functionality without breaking existing usage. This
17945 section tries to minimize the problems by describing how the protocol
17948 Some changes in MI need not break a carefully designed front end, and
17949 for these the MI version will remain unchanged. The following is a
17950 list of changes that may occur within one level, so front ends should
17951 parse MI output in a way that can handle them:
17955 New MI commands may be added.
17958 New fields may be added to the output of any MI command.
17961 The range of values for fields with specified values, e.g.,
17962 @code{in_scope} (@pxref{-var-update}) may be extended.
17964 @c The format of field's content e.g type prefix, may change so parse it
17965 @c at your own risk. Yes, in general?
17967 @c The order of fields may change? Shouldn't really matter but it might
17968 @c resolve inconsistencies.
17971 If the changes are likely to break front ends, the MI version level
17972 will be increased by one. This will allow the front end to parse the
17973 output according to the MI version. Apart from mi0, new versions of
17974 @value{GDBN} will not support old versions of MI and it will be the
17975 responsibility of the front end to work with the new one.
17977 @c Starting with mi3, add a new command -mi-version that prints the MI
17980 The best way to avoid unexpected changes in MI that might break your front
17981 end is to make your project known to @value{GDBN} developers and
17982 follow development on @email{gdb@@sourceware.org} and
17983 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17984 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17985 Group, which has the aim of creating a more general MI protocol
17986 called Debugger Machine Interface (DMI) that will become a standard
17987 for all debuggers, not just @value{GDBN}.
17988 @cindex mailing lists
17990 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17991 @node GDB/MI Output Records
17992 @section @sc{gdb/mi} Output Records
17995 * GDB/MI Result Records::
17996 * GDB/MI Stream Records::
17997 * GDB/MI Out-of-band Records::
18000 @node GDB/MI Result Records
18001 @subsection @sc{gdb/mi} Result Records
18003 @cindex result records in @sc{gdb/mi}
18004 @cindex @sc{gdb/mi}, result records
18005 In addition to a number of out-of-band notifications, the response to a
18006 @sc{gdb/mi} command includes one of the following result indications:
18010 @item "^done" [ "," @var{results} ]
18011 The synchronous operation was successful, @code{@var{results}} are the return
18016 @c Is this one correct? Should it be an out-of-band notification?
18017 The asynchronous operation was successfully started. The target is
18022 @value{GDBN} has connected to a remote target.
18024 @item "^error" "," @var{c-string}
18026 The operation failed. The @code{@var{c-string}} contains the corresponding
18031 @value{GDBN} has terminated.
18035 @node GDB/MI Stream Records
18036 @subsection @sc{gdb/mi} Stream Records
18038 @cindex @sc{gdb/mi}, stream records
18039 @cindex stream records in @sc{gdb/mi}
18040 @value{GDBN} internally maintains a number of output streams: the console, the
18041 target, and the log. The output intended for each of these streams is
18042 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
18044 Each stream record begins with a unique @dfn{prefix character} which
18045 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
18046 Syntax}). In addition to the prefix, each stream record contains a
18047 @code{@var{string-output}}. This is either raw text (with an implicit new
18048 line) or a quoted C string (which does not contain an implicit newline).
18051 @item "~" @var{string-output}
18052 The console output stream contains text that should be displayed in the
18053 CLI console window. It contains the textual responses to CLI commands.
18055 @item "@@" @var{string-output}
18056 The target output stream contains any textual output from the running
18057 target. This is only present when GDB's event loop is truly
18058 asynchronous, which is currently only the case for remote targets.
18060 @item "&" @var{string-output}
18061 The log stream contains debugging messages being produced by @value{GDBN}'s
18065 @node GDB/MI Out-of-band Records
18066 @subsection @sc{gdb/mi} Out-of-band Records
18068 @cindex out-of-band records in @sc{gdb/mi}
18069 @cindex @sc{gdb/mi}, out-of-band records
18070 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
18071 additional changes that have occurred. Those changes can either be a
18072 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
18073 target activity (e.g., target stopped).
18075 The following is a preliminary list of possible out-of-band records.
18076 In particular, the @var{exec-async-output} records.
18079 @item *stopped,reason="@var{reason}"
18082 @var{reason} can be one of the following:
18085 @item breakpoint-hit
18086 A breakpoint was reached.
18087 @item watchpoint-trigger
18088 A watchpoint was triggered.
18089 @item read-watchpoint-trigger
18090 A read watchpoint was triggered.
18091 @item access-watchpoint-trigger
18092 An access watchpoint was triggered.
18093 @item function-finished
18094 An -exec-finish or similar CLI command was accomplished.
18095 @item location-reached
18096 An -exec-until or similar CLI command was accomplished.
18097 @item watchpoint-scope
18098 A watchpoint has gone out of scope.
18099 @item end-stepping-range
18100 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
18101 similar CLI command was accomplished.
18102 @item exited-signalled
18103 The inferior exited because of a signal.
18105 The inferior exited.
18106 @item exited-normally
18107 The inferior exited normally.
18108 @item signal-received
18109 A signal was received by the inferior.
18113 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18114 @node GDB/MI Simple Examples
18115 @section Simple Examples of @sc{gdb/mi} Interaction
18116 @cindex @sc{gdb/mi}, simple examples
18118 This subsection presents several simple examples of interaction using
18119 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
18120 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
18121 the output received from @sc{gdb/mi}.
18123 Note the line breaks shown in the examples are here only for
18124 readability, they don't appear in the real output.
18126 @subheading Setting a Breakpoint
18128 Setting a breakpoint generates synchronous output which contains detailed
18129 information of the breakpoint.
18132 -> -break-insert main
18133 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18134 enabled="y",addr="0x08048564",func="main",file="myprog.c",
18135 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
18139 @subheading Program Execution
18141 Program execution generates asynchronous records and MI gives the
18142 reason that execution stopped.
18148 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
18149 frame=@{addr="0x08048564",func="main",
18150 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
18151 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
18156 <- *stopped,reason="exited-normally"
18160 @subheading Quitting @value{GDBN}
18162 Quitting @value{GDBN} just prints the result class @samp{^exit}.
18170 @subheading A Bad Command
18172 Here's what happens if you pass a non-existent command:
18176 <- ^error,msg="Undefined MI command: rubbish"
18181 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18182 @node GDB/MI Command Description Format
18183 @section @sc{gdb/mi} Command Description Format
18185 The remaining sections describe blocks of commands. Each block of
18186 commands is laid out in a fashion similar to this section.
18188 @subheading Motivation
18190 The motivation for this collection of commands.
18192 @subheading Introduction
18194 A brief introduction to this collection of commands as a whole.
18196 @subheading Commands
18198 For each command in the block, the following is described:
18200 @subsubheading Synopsis
18203 -command @var{args}@dots{}
18206 @subsubheading Result
18208 @subsubheading @value{GDBN} Command
18210 The corresponding @value{GDBN} CLI command(s), if any.
18212 @subsubheading Example
18214 Example(s) formatted for readability. Some of the described commands have
18215 not been implemented yet and these are labeled N.A.@: (not available).
18218 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18219 @node GDB/MI Breakpoint Commands
18220 @section @sc{gdb/mi} Breakpoint Commands
18222 @cindex breakpoint commands for @sc{gdb/mi}
18223 @cindex @sc{gdb/mi}, breakpoint commands
18224 This section documents @sc{gdb/mi} commands for manipulating
18227 @subheading The @code{-break-after} Command
18228 @findex -break-after
18230 @subsubheading Synopsis
18233 -break-after @var{number} @var{count}
18236 The breakpoint number @var{number} is not in effect until it has been
18237 hit @var{count} times. To see how this is reflected in the output of
18238 the @samp{-break-list} command, see the description of the
18239 @samp{-break-list} command below.
18241 @subsubheading @value{GDBN} Command
18243 The corresponding @value{GDBN} command is @samp{ignore}.
18245 @subsubheading Example
18250 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18251 enabled="y",addr="0x000100d0",func="main",file="hello.c",
18252 fullname="/home/foo/hello.c",line="5",times="0"@}
18259 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18260 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18261 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18262 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18263 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18264 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18265 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18266 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18267 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18268 line="5",times="0",ignore="3"@}]@}
18273 @subheading The @code{-break-catch} Command
18274 @findex -break-catch
18276 @subheading The @code{-break-commands} Command
18277 @findex -break-commands
18281 @subheading The @code{-break-condition} Command
18282 @findex -break-condition
18284 @subsubheading Synopsis
18287 -break-condition @var{number} @var{expr}
18290 Breakpoint @var{number} will stop the program only if the condition in
18291 @var{expr} is true. The condition becomes part of the
18292 @samp{-break-list} output (see the description of the @samp{-break-list}
18295 @subsubheading @value{GDBN} Command
18297 The corresponding @value{GDBN} command is @samp{condition}.
18299 @subsubheading Example
18303 -break-condition 1 1
18307 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18308 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18309 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18310 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18311 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18312 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18313 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18314 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18315 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18316 line="5",cond="1",times="0",ignore="3"@}]@}
18320 @subheading The @code{-break-delete} Command
18321 @findex -break-delete
18323 @subsubheading Synopsis
18326 -break-delete ( @var{breakpoint} )+
18329 Delete the breakpoint(s) whose number(s) are specified in the argument
18330 list. This is obviously reflected in the breakpoint list.
18332 @subsubheading @value{GDBN} Command
18334 The corresponding @value{GDBN} command is @samp{delete}.
18336 @subsubheading Example
18344 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18345 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18346 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18347 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18348 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18349 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18350 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18355 @subheading The @code{-break-disable} Command
18356 @findex -break-disable
18358 @subsubheading Synopsis
18361 -break-disable ( @var{breakpoint} )+
18364 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18365 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18367 @subsubheading @value{GDBN} Command
18369 The corresponding @value{GDBN} command is @samp{disable}.
18371 @subsubheading Example
18379 ^done,BreakpointTable=@{nr_rows="1",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"@}],
18386 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18387 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18388 line="5",times="0"@}]@}
18392 @subheading The @code{-break-enable} Command
18393 @findex -break-enable
18395 @subsubheading Synopsis
18398 -break-enable ( @var{breakpoint} )+
18401 Enable (previously disabled) @var{breakpoint}(s).
18403 @subsubheading @value{GDBN} Command
18405 The corresponding @value{GDBN} command is @samp{enable}.
18407 @subsubheading Example
18415 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18416 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18417 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18418 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18419 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18420 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18421 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18422 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18423 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18424 line="5",times="0"@}]@}
18428 @subheading The @code{-break-info} Command
18429 @findex -break-info
18431 @subsubheading Synopsis
18434 -break-info @var{breakpoint}
18438 Get information about a single breakpoint.
18440 @subsubheading @value{GDBN} Command
18442 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18444 @subsubheading Example
18447 @subheading The @code{-break-insert} Command
18448 @findex -break-insert
18450 @subsubheading Synopsis
18453 -break-insert [ -t ] [ -h ] [ -f ]
18454 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18455 [ -p @var{thread} ] [ @var{location} ]
18459 If specified, @var{location}, can be one of:
18466 @item filename:linenum
18467 @item filename:function
18471 The possible optional parameters of this command are:
18475 Insert a temporary breakpoint.
18477 Insert a hardware breakpoint.
18478 @item -c @var{condition}
18479 Make the breakpoint conditional on @var{condition}.
18480 @item -i @var{ignore-count}
18481 Initialize the @var{ignore-count}.
18483 If @var{location} cannot be parsed (for example if it
18484 refers to unknown files or functions), create a pending
18485 breakpoint. Without this flag, @value{GDBN} will report
18486 an error, and won't create a breakpoint, if @var{location}
18490 @subsubheading Result
18492 The result is in the form:
18495 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18496 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18497 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18498 times="@var{times}"@}
18502 where @var{number} is the @value{GDBN} number for this breakpoint,
18503 @var{funcname} is the name of the function where the breakpoint was
18504 inserted, @var{filename} is the name of the source file which contains
18505 this function, @var{lineno} is the source line number within that file
18506 and @var{times} the number of times that the breakpoint has been hit
18507 (always 0 for -break-insert but may be greater for -break-info or -break-list
18508 which use the same output).
18510 Note: this format is open to change.
18511 @c An out-of-band breakpoint instead of part of the result?
18513 @subsubheading @value{GDBN} Command
18515 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18516 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18518 @subsubheading Example
18523 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18524 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18526 -break-insert -t foo
18527 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18528 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18531 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18532 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18533 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18534 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18535 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18536 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18537 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18538 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18539 addr="0x0001072c", func="main",file="recursive2.c",
18540 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18541 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18542 addr="0x00010774",func="foo",file="recursive2.c",
18543 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18545 -break-insert -r foo.*
18546 ~int foo(int, int);
18547 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18548 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18552 @subheading The @code{-break-list} Command
18553 @findex -break-list
18555 @subsubheading Synopsis
18561 Displays the list of inserted breakpoints, showing the following fields:
18565 number of the breakpoint
18567 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18569 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18572 is the breakpoint enabled or no: @samp{y} or @samp{n}
18574 memory location at which the breakpoint is set
18576 logical location of the breakpoint, expressed by function name, file
18579 number of times the breakpoint has been hit
18582 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18583 @code{body} field is an empty list.
18585 @subsubheading @value{GDBN} Command
18587 The corresponding @value{GDBN} command is @samp{info break}.
18589 @subsubheading Example
18594 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18595 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18596 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18597 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18598 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18599 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18600 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18601 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18602 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18603 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18604 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18605 line="13",times="0"@}]@}
18609 Here's an example of the result when there are no breakpoints:
18614 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18615 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18616 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18617 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18618 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18619 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18620 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18625 @subheading The @code{-break-watch} Command
18626 @findex -break-watch
18628 @subsubheading Synopsis
18631 -break-watch [ -a | -r ]
18634 Create a watchpoint. With the @samp{-a} option it will create an
18635 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18636 read from or on a write to the memory location. With the @samp{-r}
18637 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18638 trigger only when the memory location is accessed for reading. Without
18639 either of the options, the watchpoint created is a regular watchpoint,
18640 i.e., it will trigger when the memory location is accessed for writing.
18641 @xref{Set Watchpoints, , Setting Watchpoints}.
18643 Note that @samp{-break-list} will report a single list of watchpoints and
18644 breakpoints inserted.
18646 @subsubheading @value{GDBN} Command
18648 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18651 @subsubheading Example
18653 Setting a watchpoint on a variable in the @code{main} function:
18658 ^done,wpt=@{number="2",exp="x"@}
18663 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18664 value=@{old="-268439212",new="55"@},
18665 frame=@{func="main",args=[],file="recursive2.c",
18666 fullname="/home/foo/bar/recursive2.c",line="5"@}
18670 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18671 the program execution twice: first for the variable changing value, then
18672 for the watchpoint going out of scope.
18677 ^done,wpt=@{number="5",exp="C"@}
18682 *stopped,reason="watchpoint-trigger",
18683 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18684 frame=@{func="callee4",args=[],
18685 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18686 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18691 *stopped,reason="watchpoint-scope",wpnum="5",
18692 frame=@{func="callee3",args=[@{name="strarg",
18693 value="0x11940 \"A string argument.\""@}],
18694 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18695 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18699 Listing breakpoints and watchpoints, at different points in the program
18700 execution. Note that once the watchpoint goes out of scope, it is
18706 ^done,wpt=@{number="2",exp="C"@}
18709 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18710 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18711 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18712 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18713 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18714 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18715 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18716 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18717 addr="0x00010734",func="callee4",
18718 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18719 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18720 bkpt=@{number="2",type="watchpoint",disp="keep",
18721 enabled="y",addr="",what="C",times="0"@}]@}
18726 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18727 value=@{old="-276895068",new="3"@},
18728 frame=@{func="callee4",args=[],
18729 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18730 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18733 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18734 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18735 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18736 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18737 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18738 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18739 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18740 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18741 addr="0x00010734",func="callee4",
18742 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18743 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18744 bkpt=@{number="2",type="watchpoint",disp="keep",
18745 enabled="y",addr="",what="C",times="-5"@}]@}
18749 ^done,reason="watchpoint-scope",wpnum="2",
18750 frame=@{func="callee3",args=[@{name="strarg",
18751 value="0x11940 \"A string argument.\""@}],
18752 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18753 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18756 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18757 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18758 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18759 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18760 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18761 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18762 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18763 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18764 addr="0x00010734",func="callee4",
18765 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18766 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18771 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18772 @node GDB/MI Program Context
18773 @section @sc{gdb/mi} Program Context
18775 @subheading The @code{-exec-arguments} Command
18776 @findex -exec-arguments
18779 @subsubheading Synopsis
18782 -exec-arguments @var{args}
18785 Set the inferior program arguments, to be used in the next
18788 @subsubheading @value{GDBN} Command
18790 The corresponding @value{GDBN} command is @samp{set args}.
18792 @subsubheading Example
18795 Don't have one around.
18798 @subheading The @code{-exec-show-arguments} Command
18799 @findex -exec-show-arguments
18801 @subsubheading Synopsis
18804 -exec-show-arguments
18807 Print the arguments of the program.
18809 @subsubheading @value{GDBN} Command
18811 The corresponding @value{GDBN} command is @samp{show args}.
18813 @subsubheading Example
18817 @subheading The @code{-environment-cd} Command
18818 @findex -environment-cd
18820 @subsubheading Synopsis
18823 -environment-cd @var{pathdir}
18826 Set @value{GDBN}'s working directory.
18828 @subsubheading @value{GDBN} Command
18830 The corresponding @value{GDBN} command is @samp{cd}.
18832 @subsubheading Example
18836 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18842 @subheading The @code{-environment-directory} Command
18843 @findex -environment-directory
18845 @subsubheading Synopsis
18848 -environment-directory [ -r ] [ @var{pathdir} ]+
18851 Add directories @var{pathdir} to beginning of search path for source files.
18852 If the @samp{-r} option is used, the search path is reset to the default
18853 search path. If directories @var{pathdir} are supplied in addition to the
18854 @samp{-r} option, the search path is first reset and then addition
18856 Multiple directories may be specified, separated by blanks. Specifying
18857 multiple directories in a single command
18858 results in the directories added to the beginning of the
18859 search path in the same order they were presented in the command.
18860 If blanks are needed as
18861 part of a directory name, double-quotes should be used around
18862 the name. In the command output, the path will show up separated
18863 by the system directory-separator character. The directory-separator
18864 character must not be used
18865 in any directory name.
18866 If no directories are specified, the current search path is displayed.
18868 @subsubheading @value{GDBN} Command
18870 The corresponding @value{GDBN} command is @samp{dir}.
18872 @subsubheading Example
18876 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18877 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18879 -environment-directory ""
18880 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18882 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18883 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18885 -environment-directory -r
18886 ^done,source-path="$cdir:$cwd"
18891 @subheading The @code{-environment-path} Command
18892 @findex -environment-path
18894 @subsubheading Synopsis
18897 -environment-path [ -r ] [ @var{pathdir} ]+
18900 Add directories @var{pathdir} to beginning of search path for object files.
18901 If the @samp{-r} option is used, the search path is reset to the original
18902 search path that existed at gdb start-up. If directories @var{pathdir} are
18903 supplied in addition to the
18904 @samp{-r} option, the search path is first reset and then addition
18906 Multiple directories may be specified, separated by blanks. Specifying
18907 multiple directories in a single command
18908 results in the directories added to the beginning of the
18909 search path in the same order they were presented in the command.
18910 If blanks are needed as
18911 part of a directory name, double-quotes should be used around
18912 the name. In the command output, the path will show up separated
18913 by the system directory-separator character. The directory-separator
18914 character must not be used
18915 in any directory name.
18916 If no directories are specified, the current path is displayed.
18919 @subsubheading @value{GDBN} Command
18921 The corresponding @value{GDBN} command is @samp{path}.
18923 @subsubheading Example
18928 ^done,path="/usr/bin"
18930 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18931 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18933 -environment-path -r /usr/local/bin
18934 ^done,path="/usr/local/bin:/usr/bin"
18939 @subheading The @code{-environment-pwd} Command
18940 @findex -environment-pwd
18942 @subsubheading Synopsis
18948 Show the current working directory.
18950 @subsubheading @value{GDBN} Command
18952 The corresponding @value{GDBN} command is @samp{pwd}.
18954 @subsubheading Example
18959 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18963 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18964 @node GDB/MI Thread Commands
18965 @section @sc{gdb/mi} Thread Commands
18968 @subheading The @code{-thread-info} Command
18969 @findex -thread-info
18971 @subsubheading Synopsis
18974 -thread-info [ @var{thread-id} ]
18977 Reports information about either a specific thread, if
18978 the @var{thread-id} parameter is present, or about all
18979 threads. When printing information about all threads,
18980 also reports the current thread.
18982 @subsubheading @value{GDBN} Command
18984 The @samp{info thread} command prints the same information
18987 @subsubheading Example
18992 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
18993 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},
18994 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
18995 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
18996 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}@}],
18997 current-thread-id="1"
19001 @subheading The @code{-thread-list-ids} Command
19002 @findex -thread-list-ids
19004 @subsubheading Synopsis
19010 Produces a list of the currently known @value{GDBN} thread ids. At the
19011 end of the list it also prints the total number of such threads.
19013 @subsubheading @value{GDBN} Command
19015 Part of @samp{info threads} supplies the same information.
19017 @subsubheading Example
19019 No threads present, besides the main process:
19024 ^done,thread-ids=@{@},number-of-threads="0"
19034 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19035 number-of-threads="3"
19040 @subheading The @code{-thread-select} Command
19041 @findex -thread-select
19043 @subsubheading Synopsis
19046 -thread-select @var{threadnum}
19049 Make @var{threadnum} the current thread. It prints the number of the new
19050 current thread, and the topmost frame for that thread.
19052 @subsubheading @value{GDBN} Command
19054 The corresponding @value{GDBN} command is @samp{thread}.
19056 @subsubheading Example
19063 *stopped,reason="end-stepping-range",thread-id="2",line="187",
19064 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
19068 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19069 number-of-threads="3"
19072 ^done,new-thread-id="3",
19073 frame=@{level="0",func="vprintf",
19074 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
19075 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
19079 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19080 @node GDB/MI Program Execution
19081 @section @sc{gdb/mi} Program Execution
19083 These are the asynchronous commands which generate the out-of-band
19084 record @samp{*stopped}. Currently @value{GDBN} only really executes
19085 asynchronously with remote targets and this interaction is mimicked in
19088 @subheading The @code{-exec-continue} Command
19089 @findex -exec-continue
19091 @subsubheading Synopsis
19097 Resumes the execution of the inferior program until a breakpoint is
19098 encountered, or until the inferior exits.
19100 @subsubheading @value{GDBN} Command
19102 The corresponding @value{GDBN} corresponding is @samp{continue}.
19104 @subsubheading Example
19111 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
19112 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
19118 @subheading The @code{-exec-finish} Command
19119 @findex -exec-finish
19121 @subsubheading Synopsis
19127 Resumes the execution of the inferior program until the current
19128 function is exited. Displays the results returned by the function.
19130 @subsubheading @value{GDBN} Command
19132 The corresponding @value{GDBN} command is @samp{finish}.
19134 @subsubheading Example
19136 Function returning @code{void}.
19143 *stopped,reason="function-finished",frame=@{func="main",args=[],
19144 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
19148 Function returning other than @code{void}. The name of the internal
19149 @value{GDBN} variable storing the result is printed, together with the
19156 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
19157 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
19158 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19159 gdb-result-var="$1",return-value="0"
19164 @subheading The @code{-exec-interrupt} Command
19165 @findex -exec-interrupt
19167 @subsubheading Synopsis
19173 Interrupts the background execution of the target. Note how the token
19174 associated with the stop message is the one for the execution command
19175 that has been interrupted. The token for the interrupt itself only
19176 appears in the @samp{^done} output. If the user is trying to
19177 interrupt a non-running program, an error message will be printed.
19179 @subsubheading @value{GDBN} Command
19181 The corresponding @value{GDBN} command is @samp{interrupt}.
19183 @subsubheading Example
19194 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
19195 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
19196 fullname="/home/foo/bar/try.c",line="13"@}
19201 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
19206 @subheading The @code{-exec-next} Command
19209 @subsubheading Synopsis
19215 Resumes execution of the inferior program, stopping when the beginning
19216 of the next source line is reached.
19218 @subsubheading @value{GDBN} Command
19220 The corresponding @value{GDBN} command is @samp{next}.
19222 @subsubheading Example
19228 *stopped,reason="end-stepping-range",line="8",file="hello.c"
19233 @subheading The @code{-exec-next-instruction} Command
19234 @findex -exec-next-instruction
19236 @subsubheading Synopsis
19239 -exec-next-instruction
19242 Executes one machine instruction. If the instruction is a function
19243 call, continues until the function returns. If the program stops at an
19244 instruction in the middle of a source line, the address will be
19247 @subsubheading @value{GDBN} Command
19249 The corresponding @value{GDBN} command is @samp{nexti}.
19251 @subsubheading Example
19255 -exec-next-instruction
19259 *stopped,reason="end-stepping-range",
19260 addr="0x000100d4",line="5",file="hello.c"
19265 @subheading The @code{-exec-return} Command
19266 @findex -exec-return
19268 @subsubheading Synopsis
19274 Makes current function return immediately. Doesn't execute the inferior.
19275 Displays the new current frame.
19277 @subsubheading @value{GDBN} Command
19279 The corresponding @value{GDBN} command is @samp{return}.
19281 @subsubheading Example
19285 200-break-insert callee4
19286 200^done,bkpt=@{number="1",addr="0x00010734",
19287 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19292 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
19293 frame=@{func="callee4",args=[],
19294 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19295 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19301 111^done,frame=@{level="0",func="callee3",
19302 args=[@{name="strarg",
19303 value="0x11940 \"A string argument.\""@}],
19304 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19305 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19310 @subheading The @code{-exec-run} Command
19313 @subsubheading Synopsis
19319 Starts execution of the inferior from the beginning. The inferior
19320 executes until either a breakpoint is encountered or the program
19321 exits. In the latter case the output will include an exit code, if
19322 the program has exited exceptionally.
19324 @subsubheading @value{GDBN} Command
19326 The corresponding @value{GDBN} command is @samp{run}.
19328 @subsubheading Examples
19333 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19338 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
19339 frame=@{func="main",args=[],file="recursive2.c",
19340 fullname="/home/foo/bar/recursive2.c",line="4"@}
19345 Program exited normally:
19353 *stopped,reason="exited-normally"
19358 Program exited exceptionally:
19366 *stopped,reason="exited",exit-code="01"
19370 Another way the program can terminate is if it receives a signal such as
19371 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19375 *stopped,reason="exited-signalled",signal-name="SIGINT",
19376 signal-meaning="Interrupt"
19380 @c @subheading -exec-signal
19383 @subheading The @code{-exec-step} Command
19386 @subsubheading Synopsis
19392 Resumes execution of the inferior program, stopping when the beginning
19393 of the next source line is reached, if the next source line is not a
19394 function call. If it is, stop at the first instruction of the called
19397 @subsubheading @value{GDBN} Command
19399 The corresponding @value{GDBN} command is @samp{step}.
19401 @subsubheading Example
19403 Stepping into a function:
19409 *stopped,reason="end-stepping-range",
19410 frame=@{func="foo",args=[@{name="a",value="10"@},
19411 @{name="b",value="0"@}],file="recursive2.c",
19412 fullname="/home/foo/bar/recursive2.c",line="11"@}
19422 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19427 @subheading The @code{-exec-step-instruction} Command
19428 @findex -exec-step-instruction
19430 @subsubheading Synopsis
19433 -exec-step-instruction
19436 Resumes the inferior which executes one machine instruction. The
19437 output, once @value{GDBN} has stopped, will vary depending on whether
19438 we have stopped in the middle of a source line or not. In the former
19439 case, the address at which the program stopped will be printed as
19442 @subsubheading @value{GDBN} Command
19444 The corresponding @value{GDBN} command is @samp{stepi}.
19446 @subsubheading Example
19450 -exec-step-instruction
19454 *stopped,reason="end-stepping-range",
19455 frame=@{func="foo",args=[],file="try.c",
19456 fullname="/home/foo/bar/try.c",line="10"@}
19458 -exec-step-instruction
19462 *stopped,reason="end-stepping-range",
19463 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19464 fullname="/home/foo/bar/try.c",line="10"@}
19469 @subheading The @code{-exec-until} Command
19470 @findex -exec-until
19472 @subsubheading Synopsis
19475 -exec-until [ @var{location} ]
19478 Executes the inferior until the @var{location} specified in the
19479 argument is reached. If there is no argument, the inferior executes
19480 until a source line greater than the current one is reached. The
19481 reason for stopping in this case will be @samp{location-reached}.
19483 @subsubheading @value{GDBN} Command
19485 The corresponding @value{GDBN} command is @samp{until}.
19487 @subsubheading Example
19491 -exec-until recursive2.c:6
19495 *stopped,reason="location-reached",frame=@{func="main",args=[],
19496 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19501 @subheading -file-clear
19502 Is this going away????
19505 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19506 @node GDB/MI Stack Manipulation
19507 @section @sc{gdb/mi} Stack Manipulation Commands
19510 @subheading The @code{-stack-info-frame} Command
19511 @findex -stack-info-frame
19513 @subsubheading Synopsis
19519 Get info on the selected frame.
19521 @subsubheading @value{GDBN} Command
19523 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19524 (without arguments).
19526 @subsubheading Example
19531 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19532 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19533 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19537 @subheading The @code{-stack-info-depth} Command
19538 @findex -stack-info-depth
19540 @subsubheading Synopsis
19543 -stack-info-depth [ @var{max-depth} ]
19546 Return the depth of the stack. If the integer argument @var{max-depth}
19547 is specified, do not count beyond @var{max-depth} frames.
19549 @subsubheading @value{GDBN} Command
19551 There's no equivalent @value{GDBN} command.
19553 @subsubheading Example
19555 For a stack with frame levels 0 through 11:
19562 -stack-info-depth 4
19565 -stack-info-depth 12
19568 -stack-info-depth 11
19571 -stack-info-depth 13
19576 @subheading The @code{-stack-list-arguments} Command
19577 @findex -stack-list-arguments
19579 @subsubheading Synopsis
19582 -stack-list-arguments @var{show-values}
19583 [ @var{low-frame} @var{high-frame} ]
19586 Display a list of the arguments for the frames between @var{low-frame}
19587 and @var{high-frame} (inclusive). If @var{low-frame} and
19588 @var{high-frame} are not provided, list the arguments for the whole
19589 call stack. If the two arguments are equal, show the single frame
19590 at the corresponding level. It is an error if @var{low-frame} is
19591 larger than the actual number of frames. On the other hand,
19592 @var{high-frame} may be larger than the actual number of frames, in
19593 which case only existing frames will be returned.
19595 The @var{show-values} argument must have a value of 0 or 1. A value of
19596 0 means that only the names of the arguments are listed, a value of 1
19597 means that both names and values of the arguments are printed.
19599 @subsubheading @value{GDBN} Command
19601 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19602 @samp{gdb_get_args} command which partially overlaps with the
19603 functionality of @samp{-stack-list-arguments}.
19605 @subsubheading Example
19612 frame=@{level="0",addr="0x00010734",func="callee4",
19613 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19614 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19615 frame=@{level="1",addr="0x0001076c",func="callee3",
19616 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19617 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19618 frame=@{level="2",addr="0x0001078c",func="callee2",
19619 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19620 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19621 frame=@{level="3",addr="0x000107b4",func="callee1",
19622 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19623 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19624 frame=@{level="4",addr="0x000107e0",func="main",
19625 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19626 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19628 -stack-list-arguments 0
19631 frame=@{level="0",args=[]@},
19632 frame=@{level="1",args=[name="strarg"]@},
19633 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19634 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19635 frame=@{level="4",args=[]@}]
19637 -stack-list-arguments 1
19640 frame=@{level="0",args=[]@},
19642 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19643 frame=@{level="2",args=[
19644 @{name="intarg",value="2"@},
19645 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19646 @{frame=@{level="3",args=[
19647 @{name="intarg",value="2"@},
19648 @{name="strarg",value="0x11940 \"A string argument.\""@},
19649 @{name="fltarg",value="3.5"@}]@},
19650 frame=@{level="4",args=[]@}]
19652 -stack-list-arguments 0 2 2
19653 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19655 -stack-list-arguments 1 2 2
19656 ^done,stack-args=[frame=@{level="2",
19657 args=[@{name="intarg",value="2"@},
19658 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19662 @c @subheading -stack-list-exception-handlers
19665 @subheading The @code{-stack-list-frames} Command
19666 @findex -stack-list-frames
19668 @subsubheading Synopsis
19671 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19674 List the frames currently on the stack. For each frame it displays the
19679 The frame number, 0 being the topmost frame, i.e., the innermost function.
19681 The @code{$pc} value for that frame.
19685 File name of the source file where the function lives.
19687 Line number corresponding to the @code{$pc}.
19690 If invoked without arguments, this command prints a backtrace for the
19691 whole stack. If given two integer arguments, it shows the frames whose
19692 levels are between the two arguments (inclusive). If the two arguments
19693 are equal, it shows the single frame at the corresponding level. It is
19694 an error if @var{low-frame} is larger than the actual number of
19695 frames. On the other hand, @var{high-frame} may be larger than the
19696 actual number of frames, in which case only existing frames will be returned.
19698 @subsubheading @value{GDBN} Command
19700 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19702 @subsubheading Example
19704 Full stack backtrace:
19710 [frame=@{level="0",addr="0x0001076c",func="foo",
19711 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19712 frame=@{level="1",addr="0x000107a4",func="foo",
19713 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19714 frame=@{level="2",addr="0x000107a4",func="foo",
19715 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19716 frame=@{level="3",addr="0x000107a4",func="foo",
19717 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19718 frame=@{level="4",addr="0x000107a4",func="foo",
19719 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19720 frame=@{level="5",addr="0x000107a4",func="foo",
19721 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19722 frame=@{level="6",addr="0x000107a4",func="foo",
19723 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19724 frame=@{level="7",addr="0x000107a4",func="foo",
19725 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19726 frame=@{level="8",addr="0x000107a4",func="foo",
19727 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19728 frame=@{level="9",addr="0x000107a4",func="foo",
19729 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19730 frame=@{level="10",addr="0x000107a4",func="foo",
19731 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19732 frame=@{level="11",addr="0x00010738",func="main",
19733 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19737 Show frames between @var{low_frame} and @var{high_frame}:
19741 -stack-list-frames 3 5
19743 [frame=@{level="3",addr="0x000107a4",func="foo",
19744 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19745 frame=@{level="4",addr="0x000107a4",func="foo",
19746 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19747 frame=@{level="5",addr="0x000107a4",func="foo",
19748 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19752 Show a single frame:
19756 -stack-list-frames 3 3
19758 [frame=@{level="3",addr="0x000107a4",func="foo",
19759 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19764 @subheading The @code{-stack-list-locals} Command
19765 @findex -stack-list-locals
19767 @subsubheading Synopsis
19770 -stack-list-locals @var{print-values}
19773 Display the local variable names for the selected frame. If
19774 @var{print-values} is 0 or @code{--no-values}, print only the names of
19775 the variables; if it is 1 or @code{--all-values}, print also their
19776 values; and if it is 2 or @code{--simple-values}, print the name,
19777 type and value for simple data types and the name and type for arrays,
19778 structures and unions. In this last case, a frontend can immediately
19779 display the value of simple data types and create variable objects for
19780 other data types when the user wishes to explore their values in
19783 @subsubheading @value{GDBN} Command
19785 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19787 @subsubheading Example
19791 -stack-list-locals 0
19792 ^done,locals=[name="A",name="B",name="C"]
19794 -stack-list-locals --all-values
19795 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19796 @{name="C",value="@{1, 2, 3@}"@}]
19797 -stack-list-locals --simple-values
19798 ^done,locals=[@{name="A",type="int",value="1"@},
19799 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19804 @subheading The @code{-stack-select-frame} Command
19805 @findex -stack-select-frame
19807 @subsubheading Synopsis
19810 -stack-select-frame @var{framenum}
19813 Change the selected frame. Select a different frame @var{framenum} on
19816 @subsubheading @value{GDBN} Command
19818 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19819 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19821 @subsubheading Example
19825 -stack-select-frame 2
19830 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19831 @node GDB/MI Variable Objects
19832 @section @sc{gdb/mi} Variable Objects
19836 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19838 For the implementation of a variable debugger window (locals, watched
19839 expressions, etc.), we are proposing the adaptation of the existing code
19840 used by @code{Insight}.
19842 The two main reasons for that are:
19846 It has been proven in practice (it is already on its second generation).
19849 It will shorten development time (needless to say how important it is
19853 The original interface was designed to be used by Tcl code, so it was
19854 slightly changed so it could be used through @sc{gdb/mi}. This section
19855 describes the @sc{gdb/mi} operations that will be available and gives some
19856 hints about their use.
19858 @emph{Note}: In addition to the set of operations described here, we
19859 expect the @sc{gui} implementation of a variable window to require, at
19860 least, the following operations:
19863 @item @code{-gdb-show} @code{output-radix}
19864 @item @code{-stack-list-arguments}
19865 @item @code{-stack-list-locals}
19866 @item @code{-stack-select-frame}
19871 @subheading Introduction to Variable Objects
19873 @cindex variable objects in @sc{gdb/mi}
19875 Variable objects are "object-oriented" MI interface for examining and
19876 changing values of expressions. Unlike some other MI interfaces that
19877 work with expressions, variable objects are specifically designed for
19878 simple and efficient presentation in the frontend. A variable object
19879 is identified by string name. When a variable object is created, the
19880 frontend specifies the expression for that variable object. The
19881 expression can be a simple variable, or it can be an arbitrary complex
19882 expression, and can even involve CPU registers. After creating a
19883 variable object, the frontend can invoke other variable object
19884 operations---for example to obtain or change the value of a variable
19885 object, or to change display format.
19887 Variable objects have hierarchical tree structure. Any variable object
19888 that corresponds to a composite type, such as structure in C, has
19889 a number of child variable objects, for example corresponding to each
19890 element of a structure. A child variable object can itself have
19891 children, recursively. Recursion ends when we reach
19892 leaf variable objects, which always have built-in types. Child variable
19893 objects are created only by explicit request, so if a frontend
19894 is not interested in the children of a particular variable object, no
19895 child will be created.
19897 For a leaf variable object it is possible to obtain its value as a
19898 string, or set the value from a string. String value can be also
19899 obtained for a non-leaf variable object, but it's generally a string
19900 that only indicates the type of the object, and does not list its
19901 contents. Assignment to a non-leaf variable object is not allowed.
19903 A frontend does not need to read the values of all variable objects each time
19904 the program stops. Instead, MI provides an update command that lists all
19905 variable objects whose values has changed since the last update
19906 operation. This considerably reduces the amount of data that must
19907 be transferred to the frontend. As noted above, children variable
19908 objects are created on demand, and only leaf variable objects have a
19909 real value. As result, gdb will read target memory only for leaf
19910 variables that frontend has created.
19912 The automatic update is not always desirable. For example, a frontend
19913 might want to keep a value of some expression for future reference,
19914 and never update it. For another example, fetching memory is
19915 relatively slow for embedded targets, so a frontend might want
19916 to disable automatic update for the variables that are either not
19917 visible on the screen, or ``closed''. This is possible using so
19918 called ``frozen variable objects''. Such variable objects are never
19919 implicitly updated.
19921 The following is the complete set of @sc{gdb/mi} operations defined to
19922 access this functionality:
19924 @multitable @columnfractions .4 .6
19925 @item @strong{Operation}
19926 @tab @strong{Description}
19928 @item @code{-var-create}
19929 @tab create a variable object
19930 @item @code{-var-delete}
19931 @tab delete the variable object and/or its children
19932 @item @code{-var-set-format}
19933 @tab set the display format of this variable
19934 @item @code{-var-show-format}
19935 @tab show the display format of this variable
19936 @item @code{-var-info-num-children}
19937 @tab tells how many children this object has
19938 @item @code{-var-list-children}
19939 @tab return a list of the object's children
19940 @item @code{-var-info-type}
19941 @tab show the type of this variable object
19942 @item @code{-var-info-expression}
19943 @tab print parent-relative expression that this variable object represents
19944 @item @code{-var-info-path-expression}
19945 @tab print full expression that this variable object represents
19946 @item @code{-var-show-attributes}
19947 @tab is this variable editable? does it exist here?
19948 @item @code{-var-evaluate-expression}
19949 @tab get the value of this variable
19950 @item @code{-var-assign}
19951 @tab set the value of this variable
19952 @item @code{-var-update}
19953 @tab update the variable and its children
19954 @item @code{-var-set-frozen}
19955 @tab set frozeness attribute
19958 In the next subsection we describe each operation in detail and suggest
19959 how it can be used.
19961 @subheading Description And Use of Operations on Variable Objects
19963 @subheading The @code{-var-create} Command
19964 @findex -var-create
19966 @subsubheading Synopsis
19969 -var-create @{@var{name} | "-"@}
19970 @{@var{frame-addr} | "*"@} @var{expression}
19973 This operation creates a variable object, which allows the monitoring of
19974 a variable, the result of an expression, a memory cell or a CPU
19977 The @var{name} parameter is the string by which the object can be
19978 referenced. It must be unique. If @samp{-} is specified, the varobj
19979 system will generate a string ``varNNNNNN'' automatically. It will be
19980 unique provided that one does not specify @var{name} on that format.
19981 The command fails if a duplicate name is found.
19983 The frame under which the expression should be evaluated can be
19984 specified by @var{frame-addr}. A @samp{*} indicates that the current
19985 frame should be used.
19987 @var{expression} is any expression valid on the current language set (must not
19988 begin with a @samp{*}), or one of the following:
19992 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19995 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19998 @samp{$@var{regname}} --- a CPU register name
20001 @subsubheading Result
20003 This operation returns the name, number of children and the type of the
20004 object created. Type is returned as a string as the ones generated by
20005 the @value{GDBN} CLI:
20008 name="@var{name}",numchild="N",type="@var{type}"
20012 @subheading The @code{-var-delete} Command
20013 @findex -var-delete
20015 @subsubheading Synopsis
20018 -var-delete [ -c ] @var{name}
20021 Deletes a previously created variable object and all of its children.
20022 With the @samp{-c} option, just deletes the children.
20024 Returns an error if the object @var{name} is not found.
20027 @subheading The @code{-var-set-format} Command
20028 @findex -var-set-format
20030 @subsubheading Synopsis
20033 -var-set-format @var{name} @var{format-spec}
20036 Sets the output format for the value of the object @var{name} to be
20039 @anchor{-var-set-format}
20040 The syntax for the @var{format-spec} is as follows:
20043 @var{format-spec} @expansion{}
20044 @{binary | decimal | hexadecimal | octal | natural@}
20047 The natural format is the default format choosen automatically
20048 based on the variable type (like decimal for an @code{int}, hex
20049 for pointers, etc.).
20051 For a variable with children, the format is set only on the
20052 variable itself, and the children are not affected.
20054 @subheading The @code{-var-show-format} Command
20055 @findex -var-show-format
20057 @subsubheading Synopsis
20060 -var-show-format @var{name}
20063 Returns the format used to display the value of the object @var{name}.
20066 @var{format} @expansion{}
20071 @subheading The @code{-var-info-num-children} Command
20072 @findex -var-info-num-children
20074 @subsubheading Synopsis
20077 -var-info-num-children @var{name}
20080 Returns the number of children of a variable object @var{name}:
20087 @subheading The @code{-var-list-children} Command
20088 @findex -var-list-children
20090 @subsubheading Synopsis
20093 -var-list-children [@var{print-values}] @var{name}
20095 @anchor{-var-list-children}
20097 Return a list of the children of the specified variable object and
20098 create variable objects for them, if they do not already exist. With
20099 a single argument or if @var{print-values} has a value for of 0 or
20100 @code{--no-values}, print only the names of the variables; if
20101 @var{print-values} is 1 or @code{--all-values}, also print their
20102 values; and if it is 2 or @code{--simple-values} print the name and
20103 value for simple data types and just the name for arrays, structures
20106 @subsubheading Example
20110 -var-list-children n
20111 ^done,numchild=@var{n},children=[@{name=@var{name},
20112 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20114 -var-list-children --all-values n
20115 ^done,numchild=@var{n},children=[@{name=@var{name},
20116 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20120 @subheading The @code{-var-info-type} Command
20121 @findex -var-info-type
20123 @subsubheading Synopsis
20126 -var-info-type @var{name}
20129 Returns the type of the specified variable @var{name}. The type is
20130 returned as a string in the same format as it is output by the
20134 type=@var{typename}
20138 @subheading The @code{-var-info-expression} Command
20139 @findex -var-info-expression
20141 @subsubheading Synopsis
20144 -var-info-expression @var{name}
20147 Returns a string that is suitable for presenting this
20148 variable object in user interface. The string is generally
20149 not valid expression in the current language, and cannot be evaluated.
20151 For example, if @code{a} is an array, and variable object
20152 @code{A} was created for @code{a}, then we'll get this output:
20155 (gdb) -var-info-expression A.1
20156 ^done,lang="C",exp="1"
20160 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
20162 Note that the output of the @code{-var-list-children} command also
20163 includes those expressions, so the @code{-var-info-expression} command
20166 @subheading The @code{-var-info-path-expression} Command
20167 @findex -var-info-path-expression
20169 @subsubheading Synopsis
20172 -var-info-path-expression @var{name}
20175 Returns an expression that can be evaluated in the current
20176 context and will yield the same value that a variable object has.
20177 Compare this with the @code{-var-info-expression} command, which
20178 result can be used only for UI presentation. Typical use of
20179 the @code{-var-info-path-expression} command is creating a
20180 watchpoint from a variable object.
20182 For example, suppose @code{C} is a C@t{++} class, derived from class
20183 @code{Base}, and that the @code{Base} class has a member called
20184 @code{m_size}. Assume a variable @code{c} is has the type of
20185 @code{C} and a variable object @code{C} was created for variable
20186 @code{c}. Then, we'll get this output:
20188 (gdb) -var-info-path-expression C.Base.public.m_size
20189 ^done,path_expr=((Base)c).m_size)
20192 @subheading The @code{-var-show-attributes} Command
20193 @findex -var-show-attributes
20195 @subsubheading Synopsis
20198 -var-show-attributes @var{name}
20201 List attributes of the specified variable object @var{name}:
20204 status=@var{attr} [ ( ,@var{attr} )* ]
20208 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20210 @subheading The @code{-var-evaluate-expression} Command
20211 @findex -var-evaluate-expression
20213 @subsubheading Synopsis
20216 -var-evaluate-expression [-f @var{format-spec}] @var{name}
20219 Evaluates the expression that is represented by the specified variable
20220 object and returns its value as a string. The format of the string
20221 can be specified with the @samp{-f} option. The possible values of
20222 this option are the same as for @code{-var-set-format}
20223 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
20224 the current display format will be used. The current display format
20225 can be changed using the @code{-var-set-format} command.
20231 Note that one must invoke @code{-var-list-children} for a variable
20232 before the value of a child variable can be evaluated.
20234 @subheading The @code{-var-assign} Command
20235 @findex -var-assign
20237 @subsubheading Synopsis
20240 -var-assign @var{name} @var{expression}
20243 Assigns the value of @var{expression} to the variable object specified
20244 by @var{name}. The object must be @samp{editable}. If the variable's
20245 value is altered by the assign, the variable will show up in any
20246 subsequent @code{-var-update} list.
20248 @subsubheading Example
20256 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20260 @subheading The @code{-var-update} Command
20261 @findex -var-update
20263 @subsubheading Synopsis
20266 -var-update [@var{print-values}] @{@var{name} | "*"@}
20269 Reevaluate the expressions corresponding to the variable object
20270 @var{name} and all its direct and indirect children, and return the
20271 list of variable objects whose values have changed; @var{name} must
20272 be a root variable object. Here, ``changed'' means that the result of
20273 @code{-var-evaluate-expression} before and after the
20274 @code{-var-update} is different. If @samp{*} is used as the variable
20275 object names, all existing variable objects are updated, except
20276 for frozen ones (@pxref{-var-set-frozen}). The option
20277 @var{print-values} determines whether both names and values, or just
20278 names are printed. The possible values of this option are the same
20279 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
20280 recommended to use the @samp{--all-values} option, to reduce the
20281 number of MI commands needed on each program stop.
20284 @subsubheading Example
20291 -var-update --all-values var1
20292 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20293 type_changed="false"@}]
20297 @anchor{-var-update}
20298 The field in_scope may take three values:
20302 The variable object's current value is valid.
20305 The variable object does not currently hold a valid value but it may
20306 hold one in the future if its associated expression comes back into
20310 The variable object no longer holds a valid value.
20311 This can occur when the executable file being debugged has changed,
20312 either through recompilation or by using the @value{GDBN} @code{file}
20313 command. The front end should normally choose to delete these variable
20317 In the future new values may be added to this list so the front should
20318 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
20320 @subheading The @code{-var-set-frozen} Command
20321 @findex -var-set-frozen
20322 @anchor{-var-set-frozen}
20324 @subsubheading Synopsis
20327 -var-set-frozen @var{name} @var{flag}
20330 Set the frozenness flag on the variable object @var{name}. The
20331 @var{flag} parameter should be either @samp{1} to make the variable
20332 frozen or @samp{0} to make it unfrozen. If a variable object is
20333 frozen, then neither itself, nor any of its children, are
20334 implicitly updated by @code{-var-update} of
20335 a parent variable or by @code{-var-update *}. Only
20336 @code{-var-update} of the variable itself will update its value and
20337 values of its children. After a variable object is unfrozen, it is
20338 implicitly updated by all subsequent @code{-var-update} operations.
20339 Unfreezing a variable does not update it, only subsequent
20340 @code{-var-update} does.
20342 @subsubheading Example
20346 -var-set-frozen V 1
20352 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20353 @node GDB/MI Data Manipulation
20354 @section @sc{gdb/mi} Data Manipulation
20356 @cindex data manipulation, in @sc{gdb/mi}
20357 @cindex @sc{gdb/mi}, data manipulation
20358 This section describes the @sc{gdb/mi} commands that manipulate data:
20359 examine memory and registers, evaluate expressions, etc.
20361 @c REMOVED FROM THE INTERFACE.
20362 @c @subheading -data-assign
20363 @c Change the value of a program variable. Plenty of side effects.
20364 @c @subsubheading GDB Command
20366 @c @subsubheading Example
20369 @subheading The @code{-data-disassemble} Command
20370 @findex -data-disassemble
20372 @subsubheading Synopsis
20376 [ -s @var{start-addr} -e @var{end-addr} ]
20377 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20385 @item @var{start-addr}
20386 is the beginning address (or @code{$pc})
20387 @item @var{end-addr}
20389 @item @var{filename}
20390 is the name of the file to disassemble
20391 @item @var{linenum}
20392 is the line number to disassemble around
20394 is the number of disassembly lines to be produced. If it is -1,
20395 the whole function will be disassembled, in case no @var{end-addr} is
20396 specified. If @var{end-addr} is specified as a non-zero value, and
20397 @var{lines} is lower than the number of disassembly lines between
20398 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20399 displayed; if @var{lines} is higher than the number of lines between
20400 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20403 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20407 @subsubheading Result
20409 The output for each instruction is composed of four fields:
20418 Note that whatever included in the instruction field, is not manipulated
20419 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20421 @subsubheading @value{GDBN} Command
20423 There's no direct mapping from this command to the CLI.
20425 @subsubheading Example
20427 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20431 -data-disassemble -s $pc -e "$pc + 20" -- 0
20434 @{address="0x000107c0",func-name="main",offset="4",
20435 inst="mov 2, %o0"@},
20436 @{address="0x000107c4",func-name="main",offset="8",
20437 inst="sethi %hi(0x11800), %o2"@},
20438 @{address="0x000107c8",func-name="main",offset="12",
20439 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20440 @{address="0x000107cc",func-name="main",offset="16",
20441 inst="sethi %hi(0x11800), %o2"@},
20442 @{address="0x000107d0",func-name="main",offset="20",
20443 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20447 Disassemble the whole @code{main} function. Line 32 is part of
20451 -data-disassemble -f basics.c -l 32 -- 0
20453 @{address="0x000107bc",func-name="main",offset="0",
20454 inst="save %sp, -112, %sp"@},
20455 @{address="0x000107c0",func-name="main",offset="4",
20456 inst="mov 2, %o0"@},
20457 @{address="0x000107c4",func-name="main",offset="8",
20458 inst="sethi %hi(0x11800), %o2"@},
20460 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20461 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20465 Disassemble 3 instructions from the start of @code{main}:
20469 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20471 @{address="0x000107bc",func-name="main",offset="0",
20472 inst="save %sp, -112, %sp"@},
20473 @{address="0x000107c0",func-name="main",offset="4",
20474 inst="mov 2, %o0"@},
20475 @{address="0x000107c4",func-name="main",offset="8",
20476 inst="sethi %hi(0x11800), %o2"@}]
20480 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20484 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20486 src_and_asm_line=@{line="31",
20487 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20488 testsuite/gdb.mi/basics.c",line_asm_insn=[
20489 @{address="0x000107bc",func-name="main",offset="0",
20490 inst="save %sp, -112, %sp"@}]@},
20491 src_and_asm_line=@{line="32",
20492 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20493 testsuite/gdb.mi/basics.c",line_asm_insn=[
20494 @{address="0x000107c0",func-name="main",offset="4",
20495 inst="mov 2, %o0"@},
20496 @{address="0x000107c4",func-name="main",offset="8",
20497 inst="sethi %hi(0x11800), %o2"@}]@}]
20502 @subheading The @code{-data-evaluate-expression} Command
20503 @findex -data-evaluate-expression
20505 @subsubheading Synopsis
20508 -data-evaluate-expression @var{expr}
20511 Evaluate @var{expr} as an expression. The expression could contain an
20512 inferior function call. The function call will execute synchronously.
20513 If the expression contains spaces, it must be enclosed in double quotes.
20515 @subsubheading @value{GDBN} Command
20517 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20518 @samp{call}. In @code{gdbtk} only, there's a corresponding
20519 @samp{gdb_eval} command.
20521 @subsubheading Example
20523 In the following example, the numbers that precede the commands are the
20524 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20525 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20529 211-data-evaluate-expression A
20532 311-data-evaluate-expression &A
20533 311^done,value="0xefffeb7c"
20535 411-data-evaluate-expression A+3
20538 511-data-evaluate-expression "A + 3"
20544 @subheading The @code{-data-list-changed-registers} Command
20545 @findex -data-list-changed-registers
20547 @subsubheading Synopsis
20550 -data-list-changed-registers
20553 Display a list of the registers that have changed.
20555 @subsubheading @value{GDBN} Command
20557 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20558 has the corresponding command @samp{gdb_changed_register_list}.
20560 @subsubheading Example
20562 On a PPC MBX board:
20570 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
20571 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
20574 -data-list-changed-registers
20575 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20576 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20577 "24","25","26","27","28","30","31","64","65","66","67","69"]
20582 @subheading The @code{-data-list-register-names} Command
20583 @findex -data-list-register-names
20585 @subsubheading Synopsis
20588 -data-list-register-names [ ( @var{regno} )+ ]
20591 Show a list of register names for the current target. If no arguments
20592 are given, it shows a list of the names of all the registers. If
20593 integer numbers are given as arguments, it will print a list of the
20594 names of the registers corresponding to the arguments. To ensure
20595 consistency between a register name and its number, the output list may
20596 include empty register names.
20598 @subsubheading @value{GDBN} Command
20600 @value{GDBN} does not have a command which corresponds to
20601 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20602 corresponding command @samp{gdb_regnames}.
20604 @subsubheading Example
20606 For the PPC MBX board:
20609 -data-list-register-names
20610 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20611 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20612 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20613 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20614 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20615 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20616 "", "pc","ps","cr","lr","ctr","xer"]
20618 -data-list-register-names 1 2 3
20619 ^done,register-names=["r1","r2","r3"]
20623 @subheading The @code{-data-list-register-values} Command
20624 @findex -data-list-register-values
20626 @subsubheading Synopsis
20629 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20632 Display the registers' contents. @var{fmt} is the format according to
20633 which the registers' contents are to be returned, followed by an optional
20634 list of numbers specifying the registers to display. A missing list of
20635 numbers indicates that the contents of all the registers must be returned.
20637 Allowed formats for @var{fmt} are:
20654 @subsubheading @value{GDBN} Command
20656 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20657 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20659 @subsubheading Example
20661 For a PPC MBX board (note: line breaks are for readability only, they
20662 don't appear in the actual output):
20666 -data-list-register-values r 64 65
20667 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20668 @{number="65",value="0x00029002"@}]
20670 -data-list-register-values x
20671 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20672 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20673 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20674 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20675 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20676 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20677 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20678 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20679 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20680 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20681 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20682 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20683 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20684 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20685 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20686 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20687 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20688 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20689 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20690 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20691 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20692 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20693 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20694 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20695 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20696 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20697 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20698 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20699 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20700 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20701 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20702 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20703 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20704 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20705 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20706 @{number="69",value="0x20002b03"@}]
20711 @subheading The @code{-data-read-memory} Command
20712 @findex -data-read-memory
20714 @subsubheading Synopsis
20717 -data-read-memory [ -o @var{byte-offset} ]
20718 @var{address} @var{word-format} @var{word-size}
20719 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20726 @item @var{address}
20727 An expression specifying the address of the first memory word to be
20728 read. Complex expressions containing embedded white space should be
20729 quoted using the C convention.
20731 @item @var{word-format}
20732 The format to be used to print the memory words. The notation is the
20733 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20736 @item @var{word-size}
20737 The size of each memory word in bytes.
20739 @item @var{nr-rows}
20740 The number of rows in the output table.
20742 @item @var{nr-cols}
20743 The number of columns in the output table.
20746 If present, indicates that each row should include an @sc{ascii} dump. The
20747 value of @var{aschar} is used as a padding character when a byte is not a
20748 member of the printable @sc{ascii} character set (printable @sc{ascii}
20749 characters are those whose code is between 32 and 126, inclusively).
20751 @item @var{byte-offset}
20752 An offset to add to the @var{address} before fetching memory.
20755 This command displays memory contents as a table of @var{nr-rows} by
20756 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20757 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20758 (returned as @samp{total-bytes}). Should less than the requested number
20759 of bytes be returned by the target, the missing words are identified
20760 using @samp{N/A}. The number of bytes read from the target is returned
20761 in @samp{nr-bytes} and the starting address used to read memory in
20764 The address of the next/previous row or page is available in
20765 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20768 @subsubheading @value{GDBN} Command
20770 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20771 @samp{gdb_get_mem} memory read command.
20773 @subsubheading Example
20775 Read six bytes of memory starting at @code{bytes+6} but then offset by
20776 @code{-6} bytes. Format as three rows of two columns. One byte per
20777 word. Display each word in hex.
20781 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20782 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20783 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20784 prev-page="0x0000138a",memory=[
20785 @{addr="0x00001390",data=["0x00","0x01"]@},
20786 @{addr="0x00001392",data=["0x02","0x03"]@},
20787 @{addr="0x00001394",data=["0x04","0x05"]@}]
20791 Read two bytes of memory starting at address @code{shorts + 64} and
20792 display as a single word formatted in decimal.
20796 5-data-read-memory shorts+64 d 2 1 1
20797 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20798 next-row="0x00001512",prev-row="0x0000150e",
20799 next-page="0x00001512",prev-page="0x0000150e",memory=[
20800 @{addr="0x00001510",data=["128"]@}]
20804 Read thirty two bytes of memory starting at @code{bytes+16} and format
20805 as eight rows of four columns. Include a string encoding with @samp{x}
20806 used as the non-printable character.
20810 4-data-read-memory bytes+16 x 1 8 4 x
20811 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20812 next-row="0x000013c0",prev-row="0x0000139c",
20813 next-page="0x000013c0",prev-page="0x00001380",memory=[
20814 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20815 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20816 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20817 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20818 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20819 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20820 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20821 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20825 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20826 @node GDB/MI Tracepoint Commands
20827 @section @sc{gdb/mi} Tracepoint Commands
20829 The tracepoint commands are not yet implemented.
20831 @c @subheading -trace-actions
20833 @c @subheading -trace-delete
20835 @c @subheading -trace-disable
20837 @c @subheading -trace-dump
20839 @c @subheading -trace-enable
20841 @c @subheading -trace-exists
20843 @c @subheading -trace-find
20845 @c @subheading -trace-frame-number
20847 @c @subheading -trace-info
20849 @c @subheading -trace-insert
20851 @c @subheading -trace-list
20853 @c @subheading -trace-pass-count
20855 @c @subheading -trace-save
20857 @c @subheading -trace-start
20859 @c @subheading -trace-stop
20862 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20863 @node GDB/MI Symbol Query
20864 @section @sc{gdb/mi} Symbol Query Commands
20867 @subheading The @code{-symbol-info-address} Command
20868 @findex -symbol-info-address
20870 @subsubheading Synopsis
20873 -symbol-info-address @var{symbol}
20876 Describe where @var{symbol} is stored.
20878 @subsubheading @value{GDBN} Command
20880 The corresponding @value{GDBN} command is @samp{info address}.
20882 @subsubheading Example
20886 @subheading The @code{-symbol-info-file} Command
20887 @findex -symbol-info-file
20889 @subsubheading Synopsis
20895 Show the file for the symbol.
20897 @subsubheading @value{GDBN} Command
20899 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20900 @samp{gdb_find_file}.
20902 @subsubheading Example
20906 @subheading The @code{-symbol-info-function} Command
20907 @findex -symbol-info-function
20909 @subsubheading Synopsis
20912 -symbol-info-function
20915 Show which function the symbol lives in.
20917 @subsubheading @value{GDBN} Command
20919 @samp{gdb_get_function} in @code{gdbtk}.
20921 @subsubheading Example
20925 @subheading The @code{-symbol-info-line} Command
20926 @findex -symbol-info-line
20928 @subsubheading Synopsis
20934 Show the core addresses of the code for a source line.
20936 @subsubheading @value{GDBN} Command
20938 The corresponding @value{GDBN} command is @samp{info line}.
20939 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20941 @subsubheading Example
20945 @subheading The @code{-symbol-info-symbol} Command
20946 @findex -symbol-info-symbol
20948 @subsubheading Synopsis
20951 -symbol-info-symbol @var{addr}
20954 Describe what symbol is at location @var{addr}.
20956 @subsubheading @value{GDBN} Command
20958 The corresponding @value{GDBN} command is @samp{info symbol}.
20960 @subsubheading Example
20964 @subheading The @code{-symbol-list-functions} Command
20965 @findex -symbol-list-functions
20967 @subsubheading Synopsis
20970 -symbol-list-functions
20973 List the functions in the executable.
20975 @subsubheading @value{GDBN} Command
20977 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20978 @samp{gdb_search} in @code{gdbtk}.
20980 @subsubheading Example
20984 @subheading The @code{-symbol-list-lines} Command
20985 @findex -symbol-list-lines
20987 @subsubheading Synopsis
20990 -symbol-list-lines @var{filename}
20993 Print the list of lines that contain code and their associated program
20994 addresses for the given source filename. The entries are sorted in
20995 ascending PC order.
20997 @subsubheading @value{GDBN} Command
20999 There is no corresponding @value{GDBN} command.
21001 @subsubheading Example
21004 -symbol-list-lines basics.c
21005 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
21010 @subheading The @code{-symbol-list-types} Command
21011 @findex -symbol-list-types
21013 @subsubheading Synopsis
21019 List all the type names.
21021 @subsubheading @value{GDBN} Command
21023 The corresponding commands are @samp{info types} in @value{GDBN},
21024 @samp{gdb_search} in @code{gdbtk}.
21026 @subsubheading Example
21030 @subheading The @code{-symbol-list-variables} Command
21031 @findex -symbol-list-variables
21033 @subsubheading Synopsis
21036 -symbol-list-variables
21039 List all the global and static variable names.
21041 @subsubheading @value{GDBN} Command
21043 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
21045 @subsubheading Example
21049 @subheading The @code{-symbol-locate} Command
21050 @findex -symbol-locate
21052 @subsubheading Synopsis
21058 @subsubheading @value{GDBN} Command
21060 @samp{gdb_loc} in @code{gdbtk}.
21062 @subsubheading Example
21066 @subheading The @code{-symbol-type} Command
21067 @findex -symbol-type
21069 @subsubheading Synopsis
21072 -symbol-type @var{variable}
21075 Show type of @var{variable}.
21077 @subsubheading @value{GDBN} Command
21079 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
21080 @samp{gdb_obj_variable}.
21082 @subsubheading Example
21086 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21087 @node GDB/MI File Commands
21088 @section @sc{gdb/mi} File Commands
21090 This section describes the GDB/MI commands to specify executable file names
21091 and to read in and obtain symbol table information.
21093 @subheading The @code{-file-exec-and-symbols} Command
21094 @findex -file-exec-and-symbols
21096 @subsubheading Synopsis
21099 -file-exec-and-symbols @var{file}
21102 Specify the executable file to be debugged. This file is the one from
21103 which the symbol table is also read. If no file is specified, the
21104 command clears the executable and symbol information. If breakpoints
21105 are set when using this command with no arguments, @value{GDBN} will produce
21106 error messages. Otherwise, no output is produced, except a completion
21109 @subsubheading @value{GDBN} Command
21111 The corresponding @value{GDBN} command is @samp{file}.
21113 @subsubheading Example
21117 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21123 @subheading The @code{-file-exec-file} Command
21124 @findex -file-exec-file
21126 @subsubheading Synopsis
21129 -file-exec-file @var{file}
21132 Specify the executable file to be debugged. Unlike
21133 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
21134 from this file. If used without argument, @value{GDBN} clears the information
21135 about the executable file. No output is produced, except a completion
21138 @subsubheading @value{GDBN} Command
21140 The corresponding @value{GDBN} command is @samp{exec-file}.
21142 @subsubheading Example
21146 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21152 @subheading The @code{-file-list-exec-sections} Command
21153 @findex -file-list-exec-sections
21155 @subsubheading Synopsis
21158 -file-list-exec-sections
21161 List the sections of the current executable file.
21163 @subsubheading @value{GDBN} Command
21165 The @value{GDBN} command @samp{info file} shows, among the rest, the same
21166 information as this command. @code{gdbtk} has a corresponding command
21167 @samp{gdb_load_info}.
21169 @subsubheading Example
21173 @subheading The @code{-file-list-exec-source-file} Command
21174 @findex -file-list-exec-source-file
21176 @subsubheading Synopsis
21179 -file-list-exec-source-file
21182 List the line number, the current source file, and the absolute path
21183 to the current source file for the current executable. The macro
21184 information field has a value of @samp{1} or @samp{0} depending on
21185 whether or not the file includes preprocessor macro information.
21187 @subsubheading @value{GDBN} Command
21189 The @value{GDBN} equivalent is @samp{info source}
21191 @subsubheading Example
21195 123-file-list-exec-source-file
21196 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
21201 @subheading The @code{-file-list-exec-source-files} Command
21202 @findex -file-list-exec-source-files
21204 @subsubheading Synopsis
21207 -file-list-exec-source-files
21210 List the source files for the current executable.
21212 It will always output the filename, but only when @value{GDBN} can find
21213 the absolute file name of a source file, will it output the fullname.
21215 @subsubheading @value{GDBN} Command
21217 The @value{GDBN} equivalent is @samp{info sources}.
21218 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
21220 @subsubheading Example
21223 -file-list-exec-source-files
21225 @{file=foo.c,fullname=/home/foo.c@},
21226 @{file=/home/bar.c,fullname=/home/bar.c@},
21227 @{file=gdb_could_not_find_fullpath.c@}]
21231 @subheading The @code{-file-list-shared-libraries} Command
21232 @findex -file-list-shared-libraries
21234 @subsubheading Synopsis
21237 -file-list-shared-libraries
21240 List the shared libraries in the program.
21242 @subsubheading @value{GDBN} Command
21244 The corresponding @value{GDBN} command is @samp{info shared}.
21246 @subsubheading Example
21250 @subheading The @code{-file-list-symbol-files} Command
21251 @findex -file-list-symbol-files
21253 @subsubheading Synopsis
21256 -file-list-symbol-files
21261 @subsubheading @value{GDBN} Command
21263 The corresponding @value{GDBN} command is @samp{info file} (part of it).
21265 @subsubheading Example
21269 @subheading The @code{-file-symbol-file} Command
21270 @findex -file-symbol-file
21272 @subsubheading Synopsis
21275 -file-symbol-file @var{file}
21278 Read symbol table info from the specified @var{file} argument. When
21279 used without arguments, clears @value{GDBN}'s symbol table info. No output is
21280 produced, except for a completion notification.
21282 @subsubheading @value{GDBN} Command
21284 The corresponding @value{GDBN} command is @samp{symbol-file}.
21286 @subsubheading Example
21290 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21296 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21297 @node GDB/MI Memory Overlay Commands
21298 @section @sc{gdb/mi} Memory Overlay Commands
21300 The memory overlay commands are not implemented.
21302 @c @subheading -overlay-auto
21304 @c @subheading -overlay-list-mapping-state
21306 @c @subheading -overlay-list-overlays
21308 @c @subheading -overlay-map
21310 @c @subheading -overlay-off
21312 @c @subheading -overlay-on
21314 @c @subheading -overlay-unmap
21316 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21317 @node GDB/MI Signal Handling Commands
21318 @section @sc{gdb/mi} Signal Handling Commands
21320 Signal handling commands are not implemented.
21322 @c @subheading -signal-handle
21324 @c @subheading -signal-list-handle-actions
21326 @c @subheading -signal-list-signal-types
21330 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21331 @node GDB/MI Target Manipulation
21332 @section @sc{gdb/mi} Target Manipulation Commands
21335 @subheading The @code{-target-attach} Command
21336 @findex -target-attach
21338 @subsubheading Synopsis
21341 -target-attach @var{pid} | @var{file}
21344 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
21346 @subsubheading @value{GDBN} Command
21348 The corresponding @value{GDBN} command is @samp{attach}.
21350 @subsubheading Example
21354 @subheading The @code{-target-compare-sections} Command
21355 @findex -target-compare-sections
21357 @subsubheading Synopsis
21360 -target-compare-sections [ @var{section} ]
21363 Compare data of section @var{section} on target to the exec file.
21364 Without the argument, all sections are compared.
21366 @subsubheading @value{GDBN} Command
21368 The @value{GDBN} equivalent is @samp{compare-sections}.
21370 @subsubheading Example
21374 @subheading The @code{-target-detach} Command
21375 @findex -target-detach
21377 @subsubheading Synopsis
21383 Detach from the remote target which normally resumes its execution.
21386 @subsubheading @value{GDBN} Command
21388 The corresponding @value{GDBN} command is @samp{detach}.
21390 @subsubheading Example
21400 @subheading The @code{-target-disconnect} Command
21401 @findex -target-disconnect
21403 @subsubheading Synopsis
21409 Disconnect from the remote target. There's no output and the target is
21410 generally not resumed.
21412 @subsubheading @value{GDBN} Command
21414 The corresponding @value{GDBN} command is @samp{disconnect}.
21416 @subsubheading Example
21426 @subheading The @code{-target-download} Command
21427 @findex -target-download
21429 @subsubheading Synopsis
21435 Loads the executable onto the remote target.
21436 It prints out an update message every half second, which includes the fields:
21440 The name of the section.
21442 The size of what has been sent so far for that section.
21444 The size of the section.
21446 The total size of what was sent so far (the current and the previous sections).
21448 The size of the overall executable to download.
21452 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21453 @sc{gdb/mi} Output Syntax}).
21455 In addition, it prints the name and size of the sections, as they are
21456 downloaded. These messages include the following fields:
21460 The name of the section.
21462 The size of the section.
21464 The size of the overall executable to download.
21468 At the end, a summary is printed.
21470 @subsubheading @value{GDBN} Command
21472 The corresponding @value{GDBN} command is @samp{load}.
21474 @subsubheading Example
21476 Note: each status message appears on a single line. Here the messages
21477 have been broken down so that they can fit onto a page.
21482 +download,@{section=".text",section-size="6668",total-size="9880"@}
21483 +download,@{section=".text",section-sent="512",section-size="6668",
21484 total-sent="512",total-size="9880"@}
21485 +download,@{section=".text",section-sent="1024",section-size="6668",
21486 total-sent="1024",total-size="9880"@}
21487 +download,@{section=".text",section-sent="1536",section-size="6668",
21488 total-sent="1536",total-size="9880"@}
21489 +download,@{section=".text",section-sent="2048",section-size="6668",
21490 total-sent="2048",total-size="9880"@}
21491 +download,@{section=".text",section-sent="2560",section-size="6668",
21492 total-sent="2560",total-size="9880"@}
21493 +download,@{section=".text",section-sent="3072",section-size="6668",
21494 total-sent="3072",total-size="9880"@}
21495 +download,@{section=".text",section-sent="3584",section-size="6668",
21496 total-sent="3584",total-size="9880"@}
21497 +download,@{section=".text",section-sent="4096",section-size="6668",
21498 total-sent="4096",total-size="9880"@}
21499 +download,@{section=".text",section-sent="4608",section-size="6668",
21500 total-sent="4608",total-size="9880"@}
21501 +download,@{section=".text",section-sent="5120",section-size="6668",
21502 total-sent="5120",total-size="9880"@}
21503 +download,@{section=".text",section-sent="5632",section-size="6668",
21504 total-sent="5632",total-size="9880"@}
21505 +download,@{section=".text",section-sent="6144",section-size="6668",
21506 total-sent="6144",total-size="9880"@}
21507 +download,@{section=".text",section-sent="6656",section-size="6668",
21508 total-sent="6656",total-size="9880"@}
21509 +download,@{section=".init",section-size="28",total-size="9880"@}
21510 +download,@{section=".fini",section-size="28",total-size="9880"@}
21511 +download,@{section=".data",section-size="3156",total-size="9880"@}
21512 +download,@{section=".data",section-sent="512",section-size="3156",
21513 total-sent="7236",total-size="9880"@}
21514 +download,@{section=".data",section-sent="1024",section-size="3156",
21515 total-sent="7748",total-size="9880"@}
21516 +download,@{section=".data",section-sent="1536",section-size="3156",
21517 total-sent="8260",total-size="9880"@}
21518 +download,@{section=".data",section-sent="2048",section-size="3156",
21519 total-sent="8772",total-size="9880"@}
21520 +download,@{section=".data",section-sent="2560",section-size="3156",
21521 total-sent="9284",total-size="9880"@}
21522 +download,@{section=".data",section-sent="3072",section-size="3156",
21523 total-sent="9796",total-size="9880"@}
21524 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21530 @subheading The @code{-target-exec-status} Command
21531 @findex -target-exec-status
21533 @subsubheading Synopsis
21536 -target-exec-status
21539 Provide information on the state of the target (whether it is running or
21540 not, for instance).
21542 @subsubheading @value{GDBN} Command
21544 There's no equivalent @value{GDBN} command.
21546 @subsubheading Example
21550 @subheading The @code{-target-list-available-targets} Command
21551 @findex -target-list-available-targets
21553 @subsubheading Synopsis
21556 -target-list-available-targets
21559 List the possible targets to connect to.
21561 @subsubheading @value{GDBN} Command
21563 The corresponding @value{GDBN} command is @samp{help target}.
21565 @subsubheading Example
21569 @subheading The @code{-target-list-current-targets} Command
21570 @findex -target-list-current-targets
21572 @subsubheading Synopsis
21575 -target-list-current-targets
21578 Describe the current target.
21580 @subsubheading @value{GDBN} Command
21582 The corresponding information is printed by @samp{info file} (among
21585 @subsubheading Example
21589 @subheading The @code{-target-list-parameters} Command
21590 @findex -target-list-parameters
21592 @subsubheading Synopsis
21595 -target-list-parameters
21600 @subsubheading @value{GDBN} Command
21604 @subsubheading Example
21608 @subheading The @code{-target-select} Command
21609 @findex -target-select
21611 @subsubheading Synopsis
21614 -target-select @var{type} @var{parameters @dots{}}
21617 Connect @value{GDBN} to the remote target. This command takes two args:
21621 The type of target, for instance @samp{async}, @samp{remote}, etc.
21622 @item @var{parameters}
21623 Device names, host names and the like. @xref{Target Commands, ,
21624 Commands for Managing Targets}, for more details.
21627 The output is a connection notification, followed by the address at
21628 which the target program is, in the following form:
21631 ^connected,addr="@var{address}",func="@var{function name}",
21632 args=[@var{arg list}]
21635 @subsubheading @value{GDBN} Command
21637 The corresponding @value{GDBN} command is @samp{target}.
21639 @subsubheading Example
21643 -target-select async /dev/ttya
21644 ^connected,addr="0xfe00a300",func="??",args=[]
21648 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21649 @node GDB/MI File Transfer Commands
21650 @section @sc{gdb/mi} File Transfer Commands
21653 @subheading The @code{-target-file-put} Command
21654 @findex -target-file-put
21656 @subsubheading Synopsis
21659 -target-file-put @var{hostfile} @var{targetfile}
21662 Copy file @var{hostfile} from the host system (the machine running
21663 @value{GDBN}) to @var{targetfile} on the target system.
21665 @subsubheading @value{GDBN} Command
21667 The corresponding @value{GDBN} command is @samp{remote put}.
21669 @subsubheading Example
21673 -target-file-put localfile remotefile
21679 @subheading The @code{-target-file-put} Command
21680 @findex -target-file-get
21682 @subsubheading Synopsis
21685 -target-file-get @var{targetfile} @var{hostfile}
21688 Copy file @var{targetfile} from the target system to @var{hostfile}
21689 on the host system.
21691 @subsubheading @value{GDBN} Command
21693 The corresponding @value{GDBN} command is @samp{remote get}.
21695 @subsubheading Example
21699 -target-file-get remotefile localfile
21705 @subheading The @code{-target-file-delete} Command
21706 @findex -target-file-delete
21708 @subsubheading Synopsis
21711 -target-file-delete @var{targetfile}
21714 Delete @var{targetfile} from the target system.
21716 @subsubheading @value{GDBN} Command
21718 The corresponding @value{GDBN} command is @samp{remote delete}.
21720 @subsubheading Example
21724 -target-file-delete remotefile
21730 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21731 @node GDB/MI Miscellaneous Commands
21732 @section Miscellaneous @sc{gdb/mi} Commands
21734 @c @subheading -gdb-complete
21736 @subheading The @code{-gdb-exit} Command
21739 @subsubheading Synopsis
21745 Exit @value{GDBN} immediately.
21747 @subsubheading @value{GDBN} Command
21749 Approximately corresponds to @samp{quit}.
21751 @subsubheading Example
21760 @subheading The @code{-exec-abort} Command
21761 @findex -exec-abort
21763 @subsubheading Synopsis
21769 Kill the inferior running program.
21771 @subsubheading @value{GDBN} Command
21773 The corresponding @value{GDBN} command is @samp{kill}.
21775 @subsubheading Example
21779 @subheading The @code{-gdb-set} Command
21782 @subsubheading Synopsis
21788 Set an internal @value{GDBN} variable.
21789 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21791 @subsubheading @value{GDBN} Command
21793 The corresponding @value{GDBN} command is @samp{set}.
21795 @subsubheading Example
21805 @subheading The @code{-gdb-show} Command
21808 @subsubheading Synopsis
21814 Show the current value of a @value{GDBN} variable.
21816 @subsubheading @value{GDBN} Command
21818 The corresponding @value{GDBN} command is @samp{show}.
21820 @subsubheading Example
21829 @c @subheading -gdb-source
21832 @subheading The @code{-gdb-version} Command
21833 @findex -gdb-version
21835 @subsubheading Synopsis
21841 Show version information for @value{GDBN}. Used mostly in testing.
21843 @subsubheading @value{GDBN} Command
21845 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21846 default shows this information when you start an interactive session.
21848 @subsubheading Example
21850 @c This example modifies the actual output from GDB to avoid overfull
21856 ~Copyright 2000 Free Software Foundation, Inc.
21857 ~GDB is free software, covered by the GNU General Public License, and
21858 ~you are welcome to change it and/or distribute copies of it under
21859 ~ certain conditions.
21860 ~Type "show copying" to see the conditions.
21861 ~There is absolutely no warranty for GDB. Type "show warranty" for
21863 ~This GDB was configured as
21864 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21869 @subheading The @code{-list-features} Command
21870 @findex -list-features
21872 Returns a list of particular features of the MI protocol that
21873 this version of gdb implements. A feature can be a command,
21874 or a new field in an output of some command, or even an
21875 important bugfix. While a frontend can sometimes detect presence
21876 of a feature at runtime, it is easier to perform detection at debugger
21879 The command returns a list of strings, with each string naming an
21880 available feature. Each returned string is just a name, it does not
21881 have any internal structure. The list of possible feature names
21887 (gdb) -list-features
21888 ^done,result=["feature1","feature2"]
21891 The current list of features is:
21895 @samp{frozen-varobjs}---indicates presence of the
21896 @code{-var-set-frozen} command, as well as possible presense of the
21897 @code{frozen} field in the output of @code{-varobj-create}.
21899 @samp{pending-breakpoints}---indicates presence of the @code{-f}
21900 option to the @code{-break-insert} command.
21902 @samp{thread-info}---indicates presence of the @code{-thread-info} command.
21906 @subheading The @code{-interpreter-exec} Command
21907 @findex -interpreter-exec
21909 @subheading Synopsis
21912 -interpreter-exec @var{interpreter} @var{command}
21914 @anchor{-interpreter-exec}
21916 Execute the specified @var{command} in the given @var{interpreter}.
21918 @subheading @value{GDBN} Command
21920 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21922 @subheading Example
21926 -interpreter-exec console "break main"
21927 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21928 &"During symbol reading, bad structure-type format.\n"
21929 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21934 @subheading The @code{-inferior-tty-set} Command
21935 @findex -inferior-tty-set
21937 @subheading Synopsis
21940 -inferior-tty-set /dev/pts/1
21943 Set terminal for future runs of the program being debugged.
21945 @subheading @value{GDBN} Command
21947 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21949 @subheading Example
21953 -inferior-tty-set /dev/pts/1
21958 @subheading The @code{-inferior-tty-show} Command
21959 @findex -inferior-tty-show
21961 @subheading Synopsis
21967 Show terminal for future runs of program being debugged.
21969 @subheading @value{GDBN} Command
21971 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21973 @subheading Example
21977 -inferior-tty-set /dev/pts/1
21981 ^done,inferior_tty_terminal="/dev/pts/1"
21985 @subheading The @code{-enable-timings} Command
21986 @findex -enable-timings
21988 @subheading Synopsis
21991 -enable-timings [yes | no]
21994 Toggle the printing of the wallclock, user and system times for an MI
21995 command as a field in its output. This command is to help frontend
21996 developers optimize the performance of their code. No argument is
21997 equivalent to @samp{yes}.
21999 @subheading @value{GDBN} Command
22003 @subheading Example
22011 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22012 addr="0x080484ed",func="main",file="myprog.c",
22013 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
22014 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
22022 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22023 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
22024 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
22025 fullname="/home/nickrob/myprog.c",line="73"@}
22030 @chapter @value{GDBN} Annotations
22032 This chapter describes annotations in @value{GDBN}. Annotations were
22033 designed to interface @value{GDBN} to graphical user interfaces or other
22034 similar programs which want to interact with @value{GDBN} at a
22035 relatively high level.
22037 The annotation mechanism has largely been superseded by @sc{gdb/mi}
22041 This is Edition @value{EDITION}, @value{DATE}.
22045 * Annotations Overview:: What annotations are; the general syntax.
22046 * Server Prefix:: Issuing a command without affecting user state.
22047 * Prompting:: Annotations marking @value{GDBN}'s need for input.
22048 * Errors:: Annotations for error messages.
22049 * Invalidation:: Some annotations describe things now invalid.
22050 * Annotations for Running::
22051 Whether the program is running, how it stopped, etc.
22052 * Source Annotations:: Annotations describing source code.
22055 @node Annotations Overview
22056 @section What is an Annotation?
22057 @cindex annotations
22059 Annotations start with a newline character, two @samp{control-z}
22060 characters, and the name of the annotation. If there is no additional
22061 information associated with this annotation, the name of the annotation
22062 is followed immediately by a newline. If there is additional
22063 information, the name of the annotation is followed by a space, the
22064 additional information, and a newline. The additional information
22065 cannot contain newline characters.
22067 Any output not beginning with a newline and two @samp{control-z}
22068 characters denotes literal output from @value{GDBN}. Currently there is
22069 no need for @value{GDBN} to output a newline followed by two
22070 @samp{control-z} characters, but if there was such a need, the
22071 annotations could be extended with an @samp{escape} annotation which
22072 means those three characters as output.
22074 The annotation @var{level}, which is specified using the
22075 @option{--annotate} command line option (@pxref{Mode Options}), controls
22076 how much information @value{GDBN} prints together with its prompt,
22077 values of expressions, source lines, and other types of output. Level 0
22078 is for no annotations, level 1 is for use when @value{GDBN} is run as a
22079 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
22080 for programs that control @value{GDBN}, and level 2 annotations have
22081 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
22082 Interface, annotate, GDB's Obsolete Annotations}).
22085 @kindex set annotate
22086 @item set annotate @var{level}
22087 The @value{GDBN} command @code{set annotate} sets the level of
22088 annotations to the specified @var{level}.
22090 @item show annotate
22091 @kindex show annotate
22092 Show the current annotation level.
22095 This chapter describes level 3 annotations.
22097 A simple example of starting up @value{GDBN} with annotations is:
22100 $ @kbd{gdb --annotate=3}
22102 Copyright 2003 Free Software Foundation, Inc.
22103 GDB is free software, covered by the GNU General Public License,
22104 and you are welcome to change it and/or distribute copies of it
22105 under certain conditions.
22106 Type "show copying" to see the conditions.
22107 There is absolutely no warranty for GDB. Type "show warranty"
22109 This GDB was configured as "i386-pc-linux-gnu"
22120 Here @samp{quit} is input to @value{GDBN}; the rest is output from
22121 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
22122 denotes a @samp{control-z} character) are annotations; the rest is
22123 output from @value{GDBN}.
22125 @node Server Prefix
22126 @section The Server Prefix
22127 @cindex server prefix
22129 If you prefix a command with @samp{server } then it will not affect
22130 the command history, nor will it affect @value{GDBN}'s notion of which
22131 command to repeat if @key{RET} is pressed on a line by itself. This
22132 means that commands can be run behind a user's back by a front-end in
22133 a transparent manner.
22135 The server prefix does not affect the recording of values into the value
22136 history; to print a value without recording it into the value history,
22137 use the @code{output} command instead of the @code{print} command.
22140 @section Annotation for @value{GDBN} Input
22142 @cindex annotations for prompts
22143 When @value{GDBN} prompts for input, it annotates this fact so it is possible
22144 to know when to send output, when the output from a given command is
22147 Different kinds of input each have a different @dfn{input type}. Each
22148 input type has three annotations: a @code{pre-} annotation, which
22149 denotes the beginning of any prompt which is being output, a plain
22150 annotation, which denotes the end of the prompt, and then a @code{post-}
22151 annotation which denotes the end of any echo which may (or may not) be
22152 associated with the input. For example, the @code{prompt} input type
22153 features the following annotations:
22161 The input types are
22164 @findex pre-prompt annotation
22165 @findex prompt annotation
22166 @findex post-prompt annotation
22168 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
22170 @findex pre-commands annotation
22171 @findex commands annotation
22172 @findex post-commands annotation
22174 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
22175 command. The annotations are repeated for each command which is input.
22177 @findex pre-overload-choice annotation
22178 @findex overload-choice annotation
22179 @findex post-overload-choice annotation
22180 @item overload-choice
22181 When @value{GDBN} wants the user to select between various overloaded functions.
22183 @findex pre-query annotation
22184 @findex query annotation
22185 @findex post-query annotation
22187 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
22189 @findex pre-prompt-for-continue annotation
22190 @findex prompt-for-continue annotation
22191 @findex post-prompt-for-continue annotation
22192 @item prompt-for-continue
22193 When @value{GDBN} is asking the user to press return to continue. Note: Don't
22194 expect this to work well; instead use @code{set height 0} to disable
22195 prompting. This is because the counting of lines is buggy in the
22196 presence of annotations.
22201 @cindex annotations for errors, warnings and interrupts
22203 @findex quit annotation
22208 This annotation occurs right before @value{GDBN} responds to an interrupt.
22210 @findex error annotation
22215 This annotation occurs right before @value{GDBN} responds to an error.
22217 Quit and error annotations indicate that any annotations which @value{GDBN} was
22218 in the middle of may end abruptly. For example, if a
22219 @code{value-history-begin} annotation is followed by a @code{error}, one
22220 cannot expect to receive the matching @code{value-history-end}. One
22221 cannot expect not to receive it either, however; an error annotation
22222 does not necessarily mean that @value{GDBN} is immediately returning all the way
22225 @findex error-begin annotation
22226 A quit or error annotation may be preceded by
22232 Any output between that and the quit or error annotation is the error
22235 Warning messages are not yet annotated.
22236 @c If we want to change that, need to fix warning(), type_error(),
22237 @c range_error(), and possibly other places.
22240 @section Invalidation Notices
22242 @cindex annotations for invalidation messages
22243 The following annotations say that certain pieces of state may have
22247 @findex frames-invalid annotation
22248 @item ^Z^Zframes-invalid
22250 The frames (for example, output from the @code{backtrace} command) may
22253 @findex breakpoints-invalid annotation
22254 @item ^Z^Zbreakpoints-invalid
22256 The breakpoints may have changed. For example, the user just added or
22257 deleted a breakpoint.
22260 @node Annotations for Running
22261 @section Running the Program
22262 @cindex annotations for running programs
22264 @findex starting annotation
22265 @findex stopping annotation
22266 When the program starts executing due to a @value{GDBN} command such as
22267 @code{step} or @code{continue},
22273 is output. When the program stops,
22279 is output. Before the @code{stopped} annotation, a variety of
22280 annotations describe how the program stopped.
22283 @findex exited annotation
22284 @item ^Z^Zexited @var{exit-status}
22285 The program exited, and @var{exit-status} is the exit status (zero for
22286 successful exit, otherwise nonzero).
22288 @findex signalled annotation
22289 @findex signal-name annotation
22290 @findex signal-name-end annotation
22291 @findex signal-string annotation
22292 @findex signal-string-end annotation
22293 @item ^Z^Zsignalled
22294 The program exited with a signal. After the @code{^Z^Zsignalled}, the
22295 annotation continues:
22301 ^Z^Zsignal-name-end
22305 ^Z^Zsignal-string-end
22310 where @var{name} is the name of the signal, such as @code{SIGILL} or
22311 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
22312 as @code{Illegal Instruction} or @code{Segmentation fault}.
22313 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
22314 user's benefit and have no particular format.
22316 @findex signal annotation
22318 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
22319 just saying that the program received the signal, not that it was
22320 terminated with it.
22322 @findex breakpoint annotation
22323 @item ^Z^Zbreakpoint @var{number}
22324 The program hit breakpoint number @var{number}.
22326 @findex watchpoint annotation
22327 @item ^Z^Zwatchpoint @var{number}
22328 The program hit watchpoint number @var{number}.
22331 @node Source Annotations
22332 @section Displaying Source
22333 @cindex annotations for source display
22335 @findex source annotation
22336 The following annotation is used instead of displaying source code:
22339 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
22342 where @var{filename} is an absolute file name indicating which source
22343 file, @var{line} is the line number within that file (where 1 is the
22344 first line in the file), @var{character} is the character position
22345 within the file (where 0 is the first character in the file) (for most
22346 debug formats this will necessarily point to the beginning of a line),
22347 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
22348 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
22349 @var{addr} is the address in the target program associated with the
22350 source which is being displayed. @var{addr} is in the form @samp{0x}
22351 followed by one or more lowercase hex digits (note that this does not
22352 depend on the language).
22355 @chapter Reporting Bugs in @value{GDBN}
22356 @cindex bugs in @value{GDBN}
22357 @cindex reporting bugs in @value{GDBN}
22359 Your bug reports play an essential role in making @value{GDBN} reliable.
22361 Reporting a bug may help you by bringing a solution to your problem, or it
22362 may not. But in any case the principal function of a bug report is to help
22363 the entire community by making the next version of @value{GDBN} work better. Bug
22364 reports are your contribution to the maintenance of @value{GDBN}.
22366 In order for a bug report to serve its purpose, you must include the
22367 information that enables us to fix the bug.
22370 * Bug Criteria:: Have you found a bug?
22371 * Bug Reporting:: How to report bugs
22375 @section Have You Found a Bug?
22376 @cindex bug criteria
22378 If you are not sure whether you have found a bug, here are some guidelines:
22381 @cindex fatal signal
22382 @cindex debugger crash
22383 @cindex crash of debugger
22385 If the debugger gets a fatal signal, for any input whatever, that is a
22386 @value{GDBN} bug. Reliable debuggers never crash.
22388 @cindex error on valid input
22390 If @value{GDBN} produces an error message for valid input, that is a
22391 bug. (Note that if you're cross debugging, the problem may also be
22392 somewhere in the connection to the target.)
22394 @cindex invalid input
22396 If @value{GDBN} does not produce an error message for invalid input,
22397 that is a bug. However, you should note that your idea of
22398 ``invalid input'' might be our idea of ``an extension'' or ``support
22399 for traditional practice''.
22402 If you are an experienced user of debugging tools, your suggestions
22403 for improvement of @value{GDBN} are welcome in any case.
22406 @node Bug Reporting
22407 @section How to Report Bugs
22408 @cindex bug reports
22409 @cindex @value{GDBN} bugs, reporting
22411 A number of companies and individuals offer support for @sc{gnu} products.
22412 If you obtained @value{GDBN} from a support organization, we recommend you
22413 contact that organization first.
22415 You can find contact information for many support companies and
22416 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
22418 @c should add a web page ref...
22420 In any event, we also recommend that you submit bug reports for
22421 @value{GDBN}. The preferred method is to submit them directly using
22422 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
22423 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
22426 @strong{Do not send bug reports to @samp{info-gdb}, or to
22427 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
22428 not want to receive bug reports. Those that do have arranged to receive
22431 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
22432 serves as a repeater. The mailing list and the newsgroup carry exactly
22433 the same messages. Often people think of posting bug reports to the
22434 newsgroup instead of mailing them. This appears to work, but it has one
22435 problem which can be crucial: a newsgroup posting often lacks a mail
22436 path back to the sender. Thus, if we need to ask for more information,
22437 we may be unable to reach you. For this reason, it is better to send
22438 bug reports to the mailing list.
22440 The fundamental principle of reporting bugs usefully is this:
22441 @strong{report all the facts}. If you are not sure whether to state a
22442 fact or leave it out, state it!
22444 Often people omit facts because they think they know what causes the
22445 problem and assume that some details do not matter. Thus, you might
22446 assume that the name of the variable you use in an example does not matter.
22447 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
22448 stray memory reference which happens to fetch from the location where that
22449 name is stored in memory; perhaps, if the name were different, the contents
22450 of that location would fool the debugger into doing the right thing despite
22451 the bug. Play it safe and give a specific, complete example. That is the
22452 easiest thing for you to do, and the most helpful.
22454 Keep in mind that the purpose of a bug report is to enable us to fix the
22455 bug. It may be that the bug has been reported previously, but neither
22456 you nor we can know that unless your bug report is complete and
22459 Sometimes people give a few sketchy facts and ask, ``Does this ring a
22460 bell?'' Those bug reports are useless, and we urge everyone to
22461 @emph{refuse to respond to them} except to chide the sender to report
22464 To enable us to fix the bug, you should include all these things:
22468 The version of @value{GDBN}. @value{GDBN} announces it if you start
22469 with no arguments; you can also print it at any time using @code{show
22472 Without this, we will not know whether there is any point in looking for
22473 the bug in the current version of @value{GDBN}.
22476 The type of machine you are using, and the operating system name and
22480 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
22481 ``@value{GCC}--2.8.1''.
22484 What compiler (and its version) was used to compile the program you are
22485 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
22486 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
22487 to get this information; for other compilers, see the documentation for
22491 The command arguments you gave the compiler to compile your example and
22492 observe the bug. For example, did you use @samp{-O}? To guarantee
22493 you will not omit something important, list them all. A copy of the
22494 Makefile (or the output from make) is sufficient.
22496 If we were to try to guess the arguments, we would probably guess wrong
22497 and then we might not encounter the bug.
22500 A complete input script, and all necessary source files, that will
22504 A description of what behavior you observe that you believe is
22505 incorrect. For example, ``It gets a fatal signal.''
22507 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
22508 will certainly notice it. But if the bug is incorrect output, we might
22509 not notice unless it is glaringly wrong. You might as well not give us
22510 a chance to make a mistake.
22512 Even if the problem you experience is a fatal signal, you should still
22513 say so explicitly. Suppose something strange is going on, such as, your
22514 copy of @value{GDBN} is out of synch, or you have encountered a bug in
22515 the C library on your system. (This has happened!) Your copy might
22516 crash and ours would not. If you told us to expect a crash, then when
22517 ours fails to crash, we would know that the bug was not happening for
22518 us. If you had not told us to expect a crash, then we would not be able
22519 to draw any conclusion from our observations.
22522 @cindex recording a session script
22523 To collect all this information, you can use a session recording program
22524 such as @command{script}, which is available on many Unix systems.
22525 Just run your @value{GDBN} session inside @command{script} and then
22526 include the @file{typescript} file with your bug report.
22528 Another way to record a @value{GDBN} session is to run @value{GDBN}
22529 inside Emacs and then save the entire buffer to a file.
22532 If you wish to suggest changes to the @value{GDBN} source, send us context
22533 diffs. If you even discuss something in the @value{GDBN} source, refer to
22534 it by context, not by line number.
22536 The line numbers in our development sources will not match those in your
22537 sources. Your line numbers would convey no useful information to us.
22541 Here are some things that are not necessary:
22545 A description of the envelope of the bug.
22547 Often people who encounter a bug spend a lot of time investigating
22548 which changes to the input file will make the bug go away and which
22549 changes will not affect it.
22551 This is often time consuming and not very useful, because the way we
22552 will find the bug is by running a single example under the debugger
22553 with breakpoints, not by pure deduction from a series of examples.
22554 We recommend that you save your time for something else.
22556 Of course, if you can find a simpler example to report @emph{instead}
22557 of the original one, that is a convenience for us. Errors in the
22558 output will be easier to spot, running under the debugger will take
22559 less time, and so on.
22561 However, simplification is not vital; if you do not want to do this,
22562 report the bug anyway and send us the entire test case you used.
22565 A patch for the bug.
22567 A patch for the bug does help us if it is a good one. But do not omit
22568 the necessary information, such as the test case, on the assumption that
22569 a patch is all we need. We might see problems with your patch and decide
22570 to fix the problem another way, or we might not understand it at all.
22572 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22573 construct an example that will make the program follow a certain path
22574 through the code. If you do not send us the example, we will not be able
22575 to construct one, so we will not be able to verify that the bug is fixed.
22577 And if we cannot understand what bug you are trying to fix, or why your
22578 patch should be an improvement, we will not install it. A test case will
22579 help us to understand.
22582 A guess about what the bug is or what it depends on.
22584 Such guesses are usually wrong. Even we cannot guess right about such
22585 things without first using the debugger to find the facts.
22588 @c The readline documentation is distributed with the readline code
22589 @c and consists of the two following files:
22591 @c inc-hist.texinfo
22592 @c Use -I with makeinfo to point to the appropriate directory,
22593 @c environment var TEXINPUTS with TeX.
22594 @include rluser.texi
22595 @include inc-hist.texinfo
22598 @node Formatting Documentation
22599 @appendix Formatting Documentation
22601 @cindex @value{GDBN} reference card
22602 @cindex reference card
22603 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22604 for printing with PostScript or Ghostscript, in the @file{gdb}
22605 subdirectory of the main source directory@footnote{In
22606 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22607 release.}. If you can use PostScript or Ghostscript with your printer,
22608 you can print the reference card immediately with @file{refcard.ps}.
22610 The release also includes the source for the reference card. You
22611 can format it, using @TeX{}, by typing:
22617 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22618 mode on US ``letter'' size paper;
22619 that is, on a sheet 11 inches wide by 8.5 inches
22620 high. You will need to specify this form of printing as an option to
22621 your @sc{dvi} output program.
22623 @cindex documentation
22625 All the documentation for @value{GDBN} comes as part of the machine-readable
22626 distribution. The documentation is written in Texinfo format, which is
22627 a documentation system that uses a single source file to produce both
22628 on-line information and a printed manual. You can use one of the Info
22629 formatting commands to create the on-line version of the documentation
22630 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22632 @value{GDBN} includes an already formatted copy of the on-line Info
22633 version of this manual in the @file{gdb} subdirectory. The main Info
22634 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22635 subordinate files matching @samp{gdb.info*} in the same directory. If
22636 necessary, you can print out these files, or read them with any editor;
22637 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22638 Emacs or the standalone @code{info} program, available as part of the
22639 @sc{gnu} Texinfo distribution.
22641 If you want to format these Info files yourself, you need one of the
22642 Info formatting programs, such as @code{texinfo-format-buffer} or
22645 If you have @code{makeinfo} installed, and are in the top level
22646 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22647 version @value{GDBVN}), you can make the Info file by typing:
22654 If you want to typeset and print copies of this manual, you need @TeX{},
22655 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22656 Texinfo definitions file.
22658 @TeX{} is a typesetting program; it does not print files directly, but
22659 produces output files called @sc{dvi} files. To print a typeset
22660 document, you need a program to print @sc{dvi} files. If your system
22661 has @TeX{} installed, chances are it has such a program. The precise
22662 command to use depends on your system; @kbd{lpr -d} is common; another
22663 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22664 require a file name without any extension or a @samp{.dvi} extension.
22666 @TeX{} also requires a macro definitions file called
22667 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22668 written in Texinfo format. On its own, @TeX{} cannot either read or
22669 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22670 and is located in the @file{gdb-@var{version-number}/texinfo}
22673 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22674 typeset and print this manual. First switch to the @file{gdb}
22675 subdirectory of the main source directory (for example, to
22676 @file{gdb-@value{GDBVN}/gdb}) and type:
22682 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22684 @node Installing GDB
22685 @appendix Installing @value{GDBN}
22686 @cindex installation
22689 * Requirements:: Requirements for building @value{GDBN}
22690 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22691 * Separate Objdir:: Compiling @value{GDBN} in another directory
22692 * Config Names:: Specifying names for hosts and targets
22693 * Configure Options:: Summary of options for configure
22697 @section Requirements for Building @value{GDBN}
22698 @cindex building @value{GDBN}, requirements for
22700 Building @value{GDBN} requires various tools and packages to be available.
22701 Other packages will be used only if they are found.
22703 @heading Tools/Packages Necessary for Building @value{GDBN}
22705 @item ISO C90 compiler
22706 @value{GDBN} is written in ISO C90. It should be buildable with any
22707 working C90 compiler, e.g.@: GCC.
22711 @heading Tools/Packages Optional for Building @value{GDBN}
22715 @value{GDBN} can use the Expat XML parsing library. This library may be
22716 included with your operating system distribution; if it is not, you
22717 can get the latest version from @url{http://expat.sourceforge.net}.
22718 The @file{configure} script will search for this library in several
22719 standard locations; if it is installed in an unusual path, you can
22720 use the @option{--with-libexpat-prefix} option to specify its location.
22726 Remote protocol memory maps (@pxref{Memory Map Format})
22728 Target descriptions (@pxref{Target Descriptions})
22730 Remote shared library lists (@pxref{Library List Format})
22732 MS-Windows shared libraries (@pxref{Shared Libraries})
22737 @node Running Configure
22738 @section Invoking the @value{GDBN} @file{configure} Script
22739 @cindex configuring @value{GDBN}
22740 @value{GDBN} comes with a @file{configure} script that automates the process
22741 of preparing @value{GDBN} for installation; you can then use @code{make} to
22742 build the @code{gdb} program.
22744 @c irrelevant in info file; it's as current as the code it lives with.
22745 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22746 look at the @file{README} file in the sources; we may have improved the
22747 installation procedures since publishing this manual.}
22750 The @value{GDBN} distribution includes all the source code you need for
22751 @value{GDBN} in a single directory, whose name is usually composed by
22752 appending the version number to @samp{gdb}.
22754 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22755 @file{gdb-@value{GDBVN}} directory. That directory contains:
22758 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22759 script for configuring @value{GDBN} and all its supporting libraries
22761 @item gdb-@value{GDBVN}/gdb
22762 the source specific to @value{GDBN} itself
22764 @item gdb-@value{GDBVN}/bfd
22765 source for the Binary File Descriptor library
22767 @item gdb-@value{GDBVN}/include
22768 @sc{gnu} include files
22770 @item gdb-@value{GDBVN}/libiberty
22771 source for the @samp{-liberty} free software library
22773 @item gdb-@value{GDBVN}/opcodes
22774 source for the library of opcode tables and disassemblers
22776 @item gdb-@value{GDBVN}/readline
22777 source for the @sc{gnu} command-line interface
22779 @item gdb-@value{GDBVN}/glob
22780 source for the @sc{gnu} filename pattern-matching subroutine
22782 @item gdb-@value{GDBVN}/mmalloc
22783 source for the @sc{gnu} memory-mapped malloc package
22786 The simplest way to configure and build @value{GDBN} is to run @file{configure}
22787 from the @file{gdb-@var{version-number}} source directory, which in
22788 this example is the @file{gdb-@value{GDBVN}} directory.
22790 First switch to the @file{gdb-@var{version-number}} source directory
22791 if you are not already in it; then run @file{configure}. Pass the
22792 identifier for the platform on which @value{GDBN} will run as an
22798 cd gdb-@value{GDBVN}
22799 ./configure @var{host}
22804 where @var{host} is an identifier such as @samp{sun4} or
22805 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22806 (You can often leave off @var{host}; @file{configure} tries to guess the
22807 correct value by examining your system.)
22809 Running @samp{configure @var{host}} and then running @code{make} builds the
22810 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22811 libraries, then @code{gdb} itself. The configured source files, and the
22812 binaries, are left in the corresponding source directories.
22815 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22816 system does not recognize this automatically when you run a different
22817 shell, you may need to run @code{sh} on it explicitly:
22820 sh configure @var{host}
22823 If you run @file{configure} from a directory that contains source
22824 directories for multiple libraries or programs, such as the
22825 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
22827 creates configuration files for every directory level underneath (unless
22828 you tell it not to, with the @samp{--norecursion} option).
22830 You should run the @file{configure} script from the top directory in the
22831 source tree, the @file{gdb-@var{version-number}} directory. If you run
22832 @file{configure} from one of the subdirectories, you will configure only
22833 that subdirectory. That is usually not what you want. In particular,
22834 if you run the first @file{configure} from the @file{gdb} subdirectory
22835 of the @file{gdb-@var{version-number}} directory, you will omit the
22836 configuration of @file{bfd}, @file{readline}, and other sibling
22837 directories of the @file{gdb} subdirectory. This leads to build errors
22838 about missing include files such as @file{bfd/bfd.h}.
22840 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22841 However, you should make sure that the shell on your path (named by
22842 the @samp{SHELL} environment variable) is publicly readable. Remember
22843 that @value{GDBN} uses the shell to start your program---some systems refuse to
22844 let @value{GDBN} debug child processes whose programs are not readable.
22846 @node Separate Objdir
22847 @section Compiling @value{GDBN} in Another Directory
22849 If you want to run @value{GDBN} versions for several host or target machines,
22850 you need a different @code{gdb} compiled for each combination of
22851 host and target. @file{configure} is designed to make this easy by
22852 allowing you to generate each configuration in a separate subdirectory,
22853 rather than in the source directory. If your @code{make} program
22854 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22855 @code{make} in each of these directories builds the @code{gdb}
22856 program specified there.
22858 To build @code{gdb} in a separate directory, run @file{configure}
22859 with the @samp{--srcdir} option to specify where to find the source.
22860 (You also need to specify a path to find @file{configure}
22861 itself from your working directory. If the path to @file{configure}
22862 would be the same as the argument to @samp{--srcdir}, you can leave out
22863 the @samp{--srcdir} option; it is assumed.)
22865 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22866 separate directory for a Sun 4 like this:
22870 cd gdb-@value{GDBVN}
22873 ../gdb-@value{GDBVN}/configure sun4
22878 When @file{configure} builds a configuration using a remote source
22879 directory, it creates a tree for the binaries with the same structure
22880 (and using the same names) as the tree under the source directory. In
22881 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22882 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22883 @file{gdb-sun4/gdb}.
22885 Make sure that your path to the @file{configure} script has just one
22886 instance of @file{gdb} in it. If your path to @file{configure} looks
22887 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22888 one subdirectory of @value{GDBN}, not the whole package. This leads to
22889 build errors about missing include files such as @file{bfd/bfd.h}.
22891 One popular reason to build several @value{GDBN} configurations in separate
22892 directories is to configure @value{GDBN} for cross-compiling (where
22893 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22894 programs that run on another machine---the @dfn{target}).
22895 You specify a cross-debugging target by
22896 giving the @samp{--target=@var{target}} option to @file{configure}.
22898 When you run @code{make} to build a program or library, you must run
22899 it in a configured directory---whatever directory you were in when you
22900 called @file{configure} (or one of its subdirectories).
22902 The @code{Makefile} that @file{configure} generates in each source
22903 directory also runs recursively. If you type @code{make} in a source
22904 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22905 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22906 will build all the required libraries, and then build GDB.
22908 When you have multiple hosts or targets configured in separate
22909 directories, you can run @code{make} on them in parallel (for example,
22910 if they are NFS-mounted on each of the hosts); they will not interfere
22914 @section Specifying Names for Hosts and Targets
22916 The specifications used for hosts and targets in the @file{configure}
22917 script are based on a three-part naming scheme, but some short predefined
22918 aliases are also supported. The full naming scheme encodes three pieces
22919 of information in the following pattern:
22922 @var{architecture}-@var{vendor}-@var{os}
22925 For example, you can use the alias @code{sun4} as a @var{host} argument,
22926 or as the value for @var{target} in a @code{--target=@var{target}}
22927 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22929 The @file{configure} script accompanying @value{GDBN} does not provide
22930 any query facility to list all supported host and target names or
22931 aliases. @file{configure} calls the Bourne shell script
22932 @code{config.sub} to map abbreviations to full names; you can read the
22933 script, if you wish, or you can use it to test your guesses on
22934 abbreviations---for example:
22937 % sh config.sub i386-linux
22939 % sh config.sub alpha-linux
22940 alpha-unknown-linux-gnu
22941 % sh config.sub hp9k700
22943 % sh config.sub sun4
22944 sparc-sun-sunos4.1.1
22945 % sh config.sub sun3
22946 m68k-sun-sunos4.1.1
22947 % sh config.sub i986v
22948 Invalid configuration `i986v': machine `i986v' not recognized
22952 @code{config.sub} is also distributed in the @value{GDBN} source
22953 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22955 @node Configure Options
22956 @section @file{configure} Options
22958 Here is a summary of the @file{configure} options and arguments that
22959 are most often useful for building @value{GDBN}. @file{configure} also has
22960 several other options not listed here. @inforef{What Configure
22961 Does,,configure.info}, for a full explanation of @file{configure}.
22964 configure @r{[}--help@r{]}
22965 @r{[}--prefix=@var{dir}@r{]}
22966 @r{[}--exec-prefix=@var{dir}@r{]}
22967 @r{[}--srcdir=@var{dirname}@r{]}
22968 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22969 @r{[}--target=@var{target}@r{]}
22974 You may introduce options with a single @samp{-} rather than
22975 @samp{--} if you prefer; but you may abbreviate option names if you use
22980 Display a quick summary of how to invoke @file{configure}.
22982 @item --prefix=@var{dir}
22983 Configure the source to install programs and files under directory
22986 @item --exec-prefix=@var{dir}
22987 Configure the source to install programs under directory
22990 @c avoid splitting the warning from the explanation:
22992 @item --srcdir=@var{dirname}
22993 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22994 @code{make} that implements the @code{VPATH} feature.}@*
22995 Use this option to make configurations in directories separate from the
22996 @value{GDBN} source directories. Among other things, you can use this to
22997 build (or maintain) several configurations simultaneously, in separate
22998 directories. @file{configure} writes configuration-specific files in
22999 the current directory, but arranges for them to use the source in the
23000 directory @var{dirname}. @file{configure} creates directories under
23001 the working directory in parallel to the source directories below
23004 @item --norecursion
23005 Configure only the directory level where @file{configure} is executed; do not
23006 propagate configuration to subdirectories.
23008 @item --target=@var{target}
23009 Configure @value{GDBN} for cross-debugging programs running on the specified
23010 @var{target}. Without this option, @value{GDBN} is configured to debug
23011 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
23013 There is no convenient way to generate a list of all available targets.
23015 @item @var{host} @dots{}
23016 Configure @value{GDBN} to run on the specified @var{host}.
23018 There is no convenient way to generate a list of all available hosts.
23021 There are many other options available as well, but they are generally
23022 needed for special purposes only.
23024 @node Maintenance Commands
23025 @appendix Maintenance Commands
23026 @cindex maintenance commands
23027 @cindex internal commands
23029 In addition to commands intended for @value{GDBN} users, @value{GDBN}
23030 includes a number of commands intended for @value{GDBN} developers,
23031 that are not documented elsewhere in this manual. These commands are
23032 provided here for reference. (For commands that turn on debugging
23033 messages, see @ref{Debugging Output}.)
23036 @kindex maint agent
23037 @item maint agent @var{expression}
23038 Translate the given @var{expression} into remote agent bytecodes.
23039 This command is useful for debugging the Agent Expression mechanism
23040 (@pxref{Agent Expressions}).
23042 @kindex maint info breakpoints
23043 @item @anchor{maint info breakpoints}maint info breakpoints
23044 Using the same format as @samp{info breakpoints}, display both the
23045 breakpoints you've set explicitly, and those @value{GDBN} is using for
23046 internal purposes. Internal breakpoints are shown with negative
23047 breakpoint numbers. The type column identifies what kind of breakpoint
23052 Normal, explicitly set breakpoint.
23055 Normal, explicitly set watchpoint.
23058 Internal breakpoint, used to handle correctly stepping through
23059 @code{longjmp} calls.
23061 @item longjmp resume
23062 Internal breakpoint at the target of a @code{longjmp}.
23065 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
23068 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
23071 Shared library events.
23075 @kindex maint check-symtabs
23076 @item maint check-symtabs
23077 Check the consistency of psymtabs and symtabs.
23079 @kindex maint cplus first_component
23080 @item maint cplus first_component @var{name}
23081 Print the first C@t{++} class/namespace component of @var{name}.
23083 @kindex maint cplus namespace
23084 @item maint cplus namespace
23085 Print the list of possible C@t{++} namespaces.
23087 @kindex maint demangle
23088 @item maint demangle @var{name}
23089 Demangle a C@t{++} or Objective-C mangled @var{name}.
23091 @kindex maint deprecate
23092 @kindex maint undeprecate
23093 @cindex deprecated commands
23094 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
23095 @itemx maint undeprecate @var{command}
23096 Deprecate or undeprecate the named @var{command}. Deprecated commands
23097 cause @value{GDBN} to issue a warning when you use them. The optional
23098 argument @var{replacement} says which newer command should be used in
23099 favor of the deprecated one; if it is given, @value{GDBN} will mention
23100 the replacement as part of the warning.
23102 @kindex maint dump-me
23103 @item maint dump-me
23104 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
23105 Cause a fatal signal in the debugger and force it to dump its core.
23106 This is supported only on systems which support aborting a program
23107 with the @code{SIGQUIT} signal.
23109 @kindex maint internal-error
23110 @kindex maint internal-warning
23111 @item maint internal-error @r{[}@var{message-text}@r{]}
23112 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
23113 Cause @value{GDBN} to call the internal function @code{internal_error}
23114 or @code{internal_warning} and hence behave as though an internal error
23115 or internal warning has been detected. In addition to reporting the
23116 internal problem, these functions give the user the opportunity to
23117 either quit @value{GDBN} or create a core file of the current
23118 @value{GDBN} session.
23120 These commands take an optional parameter @var{message-text} that is
23121 used as the text of the error or warning message.
23123 Here's an example of using @code{internal-error}:
23126 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
23127 @dots{}/maint.c:121: internal-error: testing, 1, 2
23128 A problem internal to GDB has been detected. Further
23129 debugging may prove unreliable.
23130 Quit this debugging session? (y or n) @kbd{n}
23131 Create a core file? (y or n) @kbd{n}
23135 @kindex maint packet
23136 @item maint packet @var{text}
23137 If @value{GDBN} is talking to an inferior via the serial protocol,
23138 then this command sends the string @var{text} to the inferior, and
23139 displays the response packet. @value{GDBN} supplies the initial
23140 @samp{$} character, the terminating @samp{#} character, and the
23143 @kindex maint print architecture
23144 @item maint print architecture @r{[}@var{file}@r{]}
23145 Print the entire architecture configuration. The optional argument
23146 @var{file} names the file where the output goes.
23148 @kindex maint print c-tdesc
23149 @item maint print c-tdesc
23150 Print the current target description (@pxref{Target Descriptions}) as
23151 a C source file. The created source file can be used in @value{GDBN}
23152 when an XML parser is not available to parse the description.
23154 @kindex maint print dummy-frames
23155 @item maint print dummy-frames
23156 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
23159 (@value{GDBP}) @kbd{b add}
23161 (@value{GDBP}) @kbd{print add(2,3)}
23162 Breakpoint 2, add (a=2, b=3) at @dots{}
23164 The program being debugged stopped while in a function called from GDB.
23166 (@value{GDBP}) @kbd{maint print dummy-frames}
23167 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
23168 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
23169 call_lo=0x01014000 call_hi=0x01014001
23173 Takes an optional file parameter.
23175 @kindex maint print registers
23176 @kindex maint print raw-registers
23177 @kindex maint print cooked-registers
23178 @kindex maint print register-groups
23179 @item maint print registers @r{[}@var{file}@r{]}
23180 @itemx maint print raw-registers @r{[}@var{file}@r{]}
23181 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
23182 @itemx maint print register-groups @r{[}@var{file}@r{]}
23183 Print @value{GDBN}'s internal register data structures.
23185 The command @code{maint print raw-registers} includes the contents of
23186 the raw register cache; the command @code{maint print cooked-registers}
23187 includes the (cooked) value of all registers; and the command
23188 @code{maint print register-groups} includes the groups that each
23189 register is a member of. @xref{Registers,, Registers, gdbint,
23190 @value{GDBN} Internals}.
23192 These commands take an optional parameter, a file name to which to
23193 write the information.
23195 @kindex maint print reggroups
23196 @item maint print reggroups @r{[}@var{file}@r{]}
23197 Print @value{GDBN}'s internal register group data structures. The
23198 optional argument @var{file} tells to what file to write the
23201 The register groups info looks like this:
23204 (@value{GDBP}) @kbd{maint print reggroups}
23217 This command forces @value{GDBN} to flush its internal register cache.
23219 @kindex maint print objfiles
23220 @cindex info for known object files
23221 @item maint print objfiles
23222 Print a dump of all known object files. For each object file, this
23223 command prints its name, address in memory, and all of its psymtabs
23226 @kindex maint print statistics
23227 @cindex bcache statistics
23228 @item maint print statistics
23229 This command prints, for each object file in the program, various data
23230 about that object file followed by the byte cache (@dfn{bcache})
23231 statistics for the object file. The objfile data includes the number
23232 of minimal, partial, full, and stabs symbols, the number of types
23233 defined by the objfile, the number of as yet unexpanded psym tables,
23234 the number of line tables and string tables, and the amount of memory
23235 used by the various tables. The bcache statistics include the counts,
23236 sizes, and counts of duplicates of all and unique objects, max,
23237 average, and median entry size, total memory used and its overhead and
23238 savings, and various measures of the hash table size and chain
23241 @kindex maint print target-stack
23242 @cindex target stack description
23243 @item maint print target-stack
23244 A @dfn{target} is an interface between the debugger and a particular
23245 kind of file or process. Targets can be stacked in @dfn{strata},
23246 so that more than one target can potentially respond to a request.
23247 In particular, memory accesses will walk down the stack of targets
23248 until they find a target that is interested in handling that particular
23251 This command prints a short description of each layer that was pushed on
23252 the @dfn{target stack}, starting from the top layer down to the bottom one.
23254 @kindex maint print type
23255 @cindex type chain of a data type
23256 @item maint print type @var{expr}
23257 Print the type chain for a type specified by @var{expr}. The argument
23258 can be either a type name or a symbol. If it is a symbol, the type of
23259 that symbol is described. The type chain produced by this command is
23260 a recursive definition of the data type as stored in @value{GDBN}'s
23261 data structures, including its flags and contained types.
23263 @kindex maint set dwarf2 max-cache-age
23264 @kindex maint show dwarf2 max-cache-age
23265 @item maint set dwarf2 max-cache-age
23266 @itemx maint show dwarf2 max-cache-age
23267 Control the DWARF 2 compilation unit cache.
23269 @cindex DWARF 2 compilation units cache
23270 In object files with inter-compilation-unit references, such as those
23271 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
23272 reader needs to frequently refer to previously read compilation units.
23273 This setting controls how long a compilation unit will remain in the
23274 cache if it is not referenced. A higher limit means that cached
23275 compilation units will be stored in memory longer, and more total
23276 memory will be used. Setting it to zero disables caching, which will
23277 slow down @value{GDBN} startup, but reduce memory consumption.
23279 @kindex maint set profile
23280 @kindex maint show profile
23281 @cindex profiling GDB
23282 @item maint set profile
23283 @itemx maint show profile
23284 Control profiling of @value{GDBN}.
23286 Profiling will be disabled until you use the @samp{maint set profile}
23287 command to enable it. When you enable profiling, the system will begin
23288 collecting timing and execution count data; when you disable profiling or
23289 exit @value{GDBN}, the results will be written to a log file. Remember that
23290 if you use profiling, @value{GDBN} will overwrite the profiling log file
23291 (often called @file{gmon.out}). If you have a record of important profiling
23292 data in a @file{gmon.out} file, be sure to move it to a safe location.
23294 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
23295 compiled with the @samp{-pg} compiler option.
23297 @kindex maint set linux-async
23298 @kindex maint show linux-async
23299 @cindex asynchronous support
23300 @item maint set linux-async
23301 @itemx maint show linux-async
23302 Control the GNU/Linux native asynchronous support of @value{GDBN}.
23304 GNU/Linux native asynchronous support will be disabled until you use
23305 the @samp{maint set linux-async} command to enable it.
23307 @kindex maint show-debug-regs
23308 @cindex x86 hardware debug registers
23309 @item maint show-debug-regs
23310 Control whether to show variables that mirror the x86 hardware debug
23311 registers. Use @code{ON} to enable, @code{OFF} to disable. If
23312 enabled, the debug registers values are shown when @value{GDBN} inserts or
23313 removes a hardware breakpoint or watchpoint, and when the inferior
23314 triggers a hardware-assisted breakpoint or watchpoint.
23316 @kindex maint space
23317 @cindex memory used by commands
23319 Control whether to display memory usage for each command. If set to a
23320 nonzero value, @value{GDBN} will display how much memory each command
23321 took, following the command's own output. This can also be requested
23322 by invoking @value{GDBN} with the @option{--statistics} command-line
23323 switch (@pxref{Mode Options}).
23326 @cindex time of command execution
23328 Control whether to display the execution time for each command. If
23329 set to a nonzero value, @value{GDBN} will display how much time it
23330 took to execute each command, following the command's own output.
23331 This can also be requested by invoking @value{GDBN} with the
23332 @option{--statistics} command-line switch (@pxref{Mode Options}).
23334 @kindex maint translate-address
23335 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
23336 Find the symbol stored at the location specified by the address
23337 @var{addr} and an optional section name @var{section}. If found,
23338 @value{GDBN} prints the name of the closest symbol and an offset from
23339 the symbol's location to the specified address. This is similar to
23340 the @code{info address} command (@pxref{Symbols}), except that this
23341 command also allows to find symbols in other sections.
23345 The following command is useful for non-interactive invocations of
23346 @value{GDBN}, such as in the test suite.
23349 @item set watchdog @var{nsec}
23350 @kindex set watchdog
23351 @cindex watchdog timer
23352 @cindex timeout for commands
23353 Set the maximum number of seconds @value{GDBN} will wait for the
23354 target operation to finish. If this time expires, @value{GDBN}
23355 reports and error and the command is aborted.
23357 @item show watchdog
23358 Show the current setting of the target wait timeout.
23361 @node Remote Protocol
23362 @appendix @value{GDBN} Remote Serial Protocol
23367 * Stop Reply Packets::
23368 * General Query Packets::
23369 * Register Packet Format::
23370 * Tracepoint Packets::
23371 * Host I/O Packets::
23374 * File-I/O Remote Protocol Extension::
23375 * Library List Format::
23376 * Memory Map Format::
23382 There may be occasions when you need to know something about the
23383 protocol---for example, if there is only one serial port to your target
23384 machine, you might want your program to do something special if it
23385 recognizes a packet meant for @value{GDBN}.
23387 In the examples below, @samp{->} and @samp{<-} are used to indicate
23388 transmitted and received data, respectively.
23390 @cindex protocol, @value{GDBN} remote serial
23391 @cindex serial protocol, @value{GDBN} remote
23392 @cindex remote serial protocol
23393 All @value{GDBN} commands and responses (other than acknowledgments) are
23394 sent as a @var{packet}. A @var{packet} is introduced with the character
23395 @samp{$}, the actual @var{packet-data}, and the terminating character
23396 @samp{#} followed by a two-digit @var{checksum}:
23399 @code{$}@var{packet-data}@code{#}@var{checksum}
23403 @cindex checksum, for @value{GDBN} remote
23405 The two-digit @var{checksum} is computed as the modulo 256 sum of all
23406 characters between the leading @samp{$} and the trailing @samp{#} (an
23407 eight bit unsigned checksum).
23409 Implementors should note that prior to @value{GDBN} 5.0 the protocol
23410 specification also included an optional two-digit @var{sequence-id}:
23413 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
23416 @cindex sequence-id, for @value{GDBN} remote
23418 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
23419 has never output @var{sequence-id}s. Stubs that handle packets added
23420 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
23422 @cindex acknowledgment, for @value{GDBN} remote
23423 When either the host or the target machine receives a packet, the first
23424 response expected is an acknowledgment: either @samp{+} (to indicate
23425 the package was received correctly) or @samp{-} (to request
23429 -> @code{$}@var{packet-data}@code{#}@var{checksum}
23434 The host (@value{GDBN}) sends @var{command}s, and the target (the
23435 debugging stub incorporated in your program) sends a @var{response}. In
23436 the case of step and continue @var{command}s, the response is only sent
23437 when the operation has completed (the target has again stopped).
23439 @var{packet-data} consists of a sequence of characters with the
23440 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
23443 @cindex remote protocol, field separator
23444 Fields within the packet should be separated using @samp{,} @samp{;} or
23445 @samp{:}. Except where otherwise noted all numbers are represented in
23446 @sc{hex} with leading zeros suppressed.
23448 Implementors should note that prior to @value{GDBN} 5.0, the character
23449 @samp{:} could not appear as the third character in a packet (as it
23450 would potentially conflict with the @var{sequence-id}).
23452 @cindex remote protocol, binary data
23453 @anchor{Binary Data}
23454 Binary data in most packets is encoded either as two hexadecimal
23455 digits per byte of binary data. This allowed the traditional remote
23456 protocol to work over connections which were only seven-bit clean.
23457 Some packets designed more recently assume an eight-bit clean
23458 connection, and use a more efficient encoding to send and receive
23461 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
23462 as an escape character. Any escaped byte is transmitted as the escape
23463 character followed by the original character XORed with @code{0x20}.
23464 For example, the byte @code{0x7d} would be transmitted as the two
23465 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
23466 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
23467 @samp{@}}) must always be escaped. Responses sent by the stub
23468 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
23469 is not interpreted as the start of a run-length encoded sequence
23472 Response @var{data} can be run-length encoded to save space.
23473 Run-length encoding replaces runs of identical characters with one
23474 instance of the repeated character, followed by a @samp{*} and a
23475 repeat count. The repeat count is itself sent encoded, to avoid
23476 binary characters in @var{data}: a value of @var{n} is sent as
23477 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
23478 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
23479 code 32) for a repeat count of 3. (This is because run-length
23480 encoding starts to win for counts 3 or more.) Thus, for example,
23481 @samp{0* } is a run-length encoding of ``0000'': the space character
23482 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
23485 The printable characters @samp{#} and @samp{$} or with a numeric value
23486 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
23487 seven repeats (@samp{$}) can be expanded using a repeat count of only
23488 five (@samp{"}). For example, @samp{00000000} can be encoded as
23491 The error response returned for some packets includes a two character
23492 error number. That number is not well defined.
23494 @cindex empty response, for unsupported packets
23495 For any @var{command} not supported by the stub, an empty response
23496 (@samp{$#00}) should be returned. That way it is possible to extend the
23497 protocol. A newer @value{GDBN} can tell if a packet is supported based
23500 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
23501 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
23507 The following table provides a complete list of all currently defined
23508 @var{command}s and their corresponding response @var{data}.
23509 @xref{File-I/O Remote Protocol Extension}, for details about the File
23510 I/O extension of the remote protocol.
23512 Each packet's description has a template showing the packet's overall
23513 syntax, followed by an explanation of the packet's meaning. We
23514 include spaces in some of the templates for clarity; these are not
23515 part of the packet's syntax. No @value{GDBN} packet uses spaces to
23516 separate its components. For example, a template like @samp{foo
23517 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
23518 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
23519 @var{baz}. @value{GDBN} does not transmit a space character between the
23520 @samp{foo} and the @var{bar}, or between the @var{bar} and the
23523 Note that all packet forms beginning with an upper- or lower-case
23524 letter, other than those described here, are reserved for future use.
23526 Here are the packet descriptions.
23531 @cindex @samp{!} packet
23532 @anchor{extended mode}
23533 Enable extended mode. In extended mode, the remote server is made
23534 persistent. The @samp{R} packet is used to restart the program being
23540 The remote target both supports and has enabled extended mode.
23544 @cindex @samp{?} packet
23545 Indicate the reason the target halted. The reply is the same as for
23549 @xref{Stop Reply Packets}, for the reply specifications.
23551 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
23552 @cindex @samp{A} packet
23553 Initialized @code{argv[]} array passed into program. @var{arglen}
23554 specifies the number of bytes in the hex encoded byte stream
23555 @var{arg}. See @code{gdbserver} for more details.
23560 The arguments were set.
23566 @cindex @samp{b} packet
23567 (Don't use this packet; its behavior is not well-defined.)
23568 Change the serial line speed to @var{baud}.
23570 JTC: @emph{When does the transport layer state change? When it's
23571 received, or after the ACK is transmitted. In either case, there are
23572 problems if the command or the acknowledgment packet is dropped.}
23574 Stan: @emph{If people really wanted to add something like this, and get
23575 it working for the first time, they ought to modify ser-unix.c to send
23576 some kind of out-of-band message to a specially-setup stub and have the
23577 switch happen "in between" packets, so that from remote protocol's point
23578 of view, nothing actually happened.}
23580 @item B @var{addr},@var{mode}
23581 @cindex @samp{B} packet
23582 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23583 breakpoint at @var{addr}.
23585 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23586 (@pxref{insert breakpoint or watchpoint packet}).
23588 @item c @r{[}@var{addr}@r{]}
23589 @cindex @samp{c} packet
23590 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23591 resume at current address.
23594 @xref{Stop Reply Packets}, for the reply specifications.
23596 @item C @var{sig}@r{[};@var{addr}@r{]}
23597 @cindex @samp{C} packet
23598 Continue with signal @var{sig} (hex signal number). If
23599 @samp{;@var{addr}} is omitted, resume at same address.
23602 @xref{Stop Reply Packets}, for the reply specifications.
23605 @cindex @samp{d} packet
23608 Don't use this packet; instead, define a general set packet
23609 (@pxref{General Query Packets}).
23612 @cindex @samp{D} packet
23613 Detach @value{GDBN} from the remote system. Sent to the remote target
23614 before @value{GDBN} disconnects via the @code{detach} command.
23624 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23625 @cindex @samp{F} packet
23626 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23627 This is part of the File-I/O protocol extension. @xref{File-I/O
23628 Remote Protocol Extension}, for the specification.
23631 @anchor{read registers packet}
23632 @cindex @samp{g} packet
23633 Read general registers.
23637 @item @var{XX@dots{}}
23638 Each byte of register data is described by two hex digits. The bytes
23639 with the register are transmitted in target byte order. The size of
23640 each register and their position within the @samp{g} packet are
23641 determined by the @value{GDBN} internal gdbarch functions
23642 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
23643 specification of several standard @samp{g} packets is specified below.
23648 @item G @var{XX@dots{}}
23649 @cindex @samp{G} packet
23650 Write general registers. @xref{read registers packet}, for a
23651 description of the @var{XX@dots{}} data.
23661 @item H @var{c} @var{t}
23662 @cindex @samp{H} packet
23663 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23664 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23665 should be @samp{c} for step and continue operations, @samp{g} for other
23666 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23667 the threads, a thread number, or @samp{0} which means pick any thread.
23678 @c 'H': How restrictive (or permissive) is the thread model. If a
23679 @c thread is selected and stopped, are other threads allowed
23680 @c to continue to execute? As I mentioned above, I think the
23681 @c semantics of each command when a thread is selected must be
23682 @c described. For example:
23684 @c 'g': If the stub supports threads and a specific thread is
23685 @c selected, returns the register block from that thread;
23686 @c otherwise returns current registers.
23688 @c 'G' If the stub supports threads and a specific thread is
23689 @c selected, sets the registers of the register block of
23690 @c that thread; otherwise sets current registers.
23692 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23693 @anchor{cycle step packet}
23694 @cindex @samp{i} packet
23695 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23696 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23697 step starting at that address.
23700 @cindex @samp{I} packet
23701 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23705 @cindex @samp{k} packet
23708 FIXME: @emph{There is no description of how to operate when a specific
23709 thread context has been selected (i.e.@: does 'k' kill only that
23712 @item m @var{addr},@var{length}
23713 @cindex @samp{m} packet
23714 Read @var{length} bytes of memory starting at address @var{addr}.
23715 Note that @var{addr} may not be aligned to any particular boundary.
23717 The stub need not use any particular size or alignment when gathering
23718 data from memory for the response; even if @var{addr} is word-aligned
23719 and @var{length} is a multiple of the word size, the stub is free to
23720 use byte accesses, or not. For this reason, this packet may not be
23721 suitable for accessing memory-mapped I/O devices.
23722 @cindex alignment of remote memory accesses
23723 @cindex size of remote memory accesses
23724 @cindex memory, alignment and size of remote accesses
23728 @item @var{XX@dots{}}
23729 Memory contents; each byte is transmitted as a two-digit hexadecimal
23730 number. The reply may contain fewer bytes than requested if the
23731 server was able to read only part of the region of memory.
23736 @item M @var{addr},@var{length}:@var{XX@dots{}}
23737 @cindex @samp{M} packet
23738 Write @var{length} bytes of memory starting at address @var{addr}.
23739 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23740 hexadecimal number.
23747 for an error (this includes the case where only part of the data was
23752 @cindex @samp{p} packet
23753 Read the value of register @var{n}; @var{n} is in hex.
23754 @xref{read registers packet}, for a description of how the returned
23755 register value is encoded.
23759 @item @var{XX@dots{}}
23760 the register's value
23764 Indicating an unrecognized @var{query}.
23767 @item P @var{n@dots{}}=@var{r@dots{}}
23768 @anchor{write register packet}
23769 @cindex @samp{P} packet
23770 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23771 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23772 digits for each byte in the register (target byte order).
23782 @item q @var{name} @var{params}@dots{}
23783 @itemx Q @var{name} @var{params}@dots{}
23784 @cindex @samp{q} packet
23785 @cindex @samp{Q} packet
23786 General query (@samp{q}) and set (@samp{Q}). These packets are
23787 described fully in @ref{General Query Packets}.
23790 @cindex @samp{r} packet
23791 Reset the entire system.
23793 Don't use this packet; use the @samp{R} packet instead.
23796 @cindex @samp{R} packet
23797 Restart the program being debugged. @var{XX}, while needed, is ignored.
23798 This packet is only available in extended mode (@pxref{extended mode}).
23800 The @samp{R} packet has no reply.
23802 @item s @r{[}@var{addr}@r{]}
23803 @cindex @samp{s} packet
23804 Single step. @var{addr} is the address at which to resume. If
23805 @var{addr} is omitted, resume at same address.
23808 @xref{Stop Reply Packets}, for the reply specifications.
23810 @item S @var{sig}@r{[};@var{addr}@r{]}
23811 @anchor{step with signal packet}
23812 @cindex @samp{S} packet
23813 Step with signal. This is analogous to the @samp{C} packet, but
23814 requests a single-step, rather than a normal resumption of execution.
23817 @xref{Stop Reply Packets}, for the reply specifications.
23819 @item t @var{addr}:@var{PP},@var{MM}
23820 @cindex @samp{t} packet
23821 Search backwards starting at address @var{addr} for a match with pattern
23822 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23823 @var{addr} must be at least 3 digits.
23826 @cindex @samp{T} packet
23827 Find out if the thread XX is alive.
23832 thread is still alive
23838 Packets starting with @samp{v} are identified by a multi-letter name,
23839 up to the first @samp{;} or @samp{?} (or the end of the packet).
23841 @item vAttach;@var{pid}
23842 @cindex @samp{vAttach} packet
23843 Attach to a new process with the specified process ID. @var{pid} is a
23844 hexadecimal integer identifying the process. If the stub is currently
23845 controlling a process, it is killed. The attached process is stopped.
23847 This packet is only available in extended mode (@pxref{extended mode}).
23853 @item @r{Any stop packet}
23854 for success (@pxref{Stop Reply Packets})
23857 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23858 @cindex @samp{vCont} packet
23859 Resume the inferior, specifying different actions for each thread.
23860 If an action is specified with no @var{tid}, then it is applied to any
23861 threads that don't have a specific action specified; if no default action is
23862 specified then other threads should remain stopped. Specifying multiple
23863 default actions is an error; specifying no actions is also an error.
23864 Thread IDs are specified in hexadecimal. Currently supported actions are:
23870 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23874 Step with signal @var{sig}. @var{sig} should be two hex digits.
23877 The optional @var{addr} argument normally associated with these packets is
23878 not supported in @samp{vCont}.
23881 @xref{Stop Reply Packets}, for the reply specifications.
23884 @cindex @samp{vCont?} packet
23885 Request a list of actions supported by the @samp{vCont} packet.
23889 @item vCont@r{[};@var{action}@dots{}@r{]}
23890 The @samp{vCont} packet is supported. Each @var{action} is a supported
23891 command in the @samp{vCont} packet.
23893 The @samp{vCont} packet is not supported.
23896 @item vFile:@var{operation}:@var{parameter}@dots{}
23897 @cindex @samp{vFile} packet
23898 Perform a file operation on the target system. For details,
23899 see @ref{Host I/O Packets}.
23901 @item vFlashErase:@var{addr},@var{length}
23902 @cindex @samp{vFlashErase} packet
23903 Direct the stub to erase @var{length} bytes of flash starting at
23904 @var{addr}. The region may enclose any number of flash blocks, but
23905 its start and end must fall on block boundaries, as indicated by the
23906 flash block size appearing in the memory map (@pxref{Memory Map
23907 Format}). @value{GDBN} groups flash memory programming operations
23908 together, and sends a @samp{vFlashDone} request after each group; the
23909 stub is allowed to delay erase operation until the @samp{vFlashDone}
23910 packet is received.
23920 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23921 @cindex @samp{vFlashWrite} packet
23922 Direct the stub to write data to flash address @var{addr}. The data
23923 is passed in binary form using the same encoding as for the @samp{X}
23924 packet (@pxref{Binary Data}). The memory ranges specified by
23925 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23926 not overlap, and must appear in order of increasing addresses
23927 (although @samp{vFlashErase} packets for higher addresses may already
23928 have been received; the ordering is guaranteed only between
23929 @samp{vFlashWrite} packets). If a packet writes to an address that was
23930 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23931 target-specific method, the results are unpredictable.
23939 for vFlashWrite addressing non-flash memory
23945 @cindex @samp{vFlashDone} packet
23946 Indicate to the stub that flash programming operation is finished.
23947 The stub is permitted to delay or batch the effects of a group of
23948 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23949 @samp{vFlashDone} packet is received. The contents of the affected
23950 regions of flash memory are unpredictable until the @samp{vFlashDone}
23951 request is completed.
23953 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
23954 @cindex @samp{vRun} packet
23955 Run the program @var{filename}, passing it each @var{argument} on its
23956 command line. The file and arguments are hex-encoded strings. If
23957 @var{filename} is an empty string, the stub may use a default program
23958 (e.g.@: the last program run). The program is created in the stopped
23959 state. If the stub is currently controlling a process, it is killed.
23961 This packet is only available in extended mode (@pxref{extended mode}).
23967 @item @r{Any stop packet}
23968 for success (@pxref{Stop Reply Packets})
23971 @item X @var{addr},@var{length}:@var{XX@dots{}}
23973 @cindex @samp{X} packet
23974 Write data to memory, where the data is transmitted in binary.
23975 @var{addr} is address, @var{length} is number of bytes,
23976 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23986 @item z @var{type},@var{addr},@var{length}
23987 @itemx Z @var{type},@var{addr},@var{length}
23988 @anchor{insert breakpoint or watchpoint packet}
23989 @cindex @samp{z} packet
23990 @cindex @samp{Z} packets
23991 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23992 watchpoint starting at address @var{address} and covering the next
23993 @var{length} bytes.
23995 Each breakpoint and watchpoint packet @var{type} is documented
23998 @emph{Implementation notes: A remote target shall return an empty string
23999 for an unrecognized breakpoint or watchpoint packet @var{type}. A
24000 remote target shall support either both or neither of a given
24001 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
24002 avoid potential problems with duplicate packets, the operations should
24003 be implemented in an idempotent way.}
24005 @item z0,@var{addr},@var{length}
24006 @itemx Z0,@var{addr},@var{length}
24007 @cindex @samp{z0} packet
24008 @cindex @samp{Z0} packet
24009 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
24010 @var{addr} of size @var{length}.
24012 A memory breakpoint is implemented by replacing the instruction at
24013 @var{addr} with a software breakpoint or trap instruction. The
24014 @var{length} is used by targets that indicates the size of the
24015 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
24016 @sc{mips} can insert either a 2 or 4 byte breakpoint).
24018 @emph{Implementation note: It is possible for a target to copy or move
24019 code that contains memory breakpoints (e.g., when implementing
24020 overlays). The behavior of this packet, in the presence of such a
24021 target, is not defined.}
24033 @item z1,@var{addr},@var{length}
24034 @itemx Z1,@var{addr},@var{length}
24035 @cindex @samp{z1} packet
24036 @cindex @samp{Z1} packet
24037 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
24038 address @var{addr} of size @var{length}.
24040 A hardware breakpoint is implemented using a mechanism that is not
24041 dependant on being able to modify the target's memory.
24043 @emph{Implementation note: A hardware breakpoint is not affected by code
24056 @item z2,@var{addr},@var{length}
24057 @itemx Z2,@var{addr},@var{length}
24058 @cindex @samp{z2} packet
24059 @cindex @samp{Z2} packet
24060 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
24072 @item z3,@var{addr},@var{length}
24073 @itemx Z3,@var{addr},@var{length}
24074 @cindex @samp{z3} packet
24075 @cindex @samp{Z3} packet
24076 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
24088 @item z4,@var{addr},@var{length}
24089 @itemx Z4,@var{addr},@var{length}
24090 @cindex @samp{z4} packet
24091 @cindex @samp{Z4} packet
24092 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
24106 @node Stop Reply Packets
24107 @section Stop Reply Packets
24108 @cindex stop reply packets
24110 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
24111 receive any of the below as a reply. In the case of the @samp{C},
24112 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
24113 when the target halts. In the below the exact meaning of @dfn{signal
24114 number} is defined by the header @file{include/gdb/signals.h} in the
24115 @value{GDBN} source code.
24117 As in the description of request packets, we include spaces in the
24118 reply templates for clarity; these are not part of the reply packet's
24119 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
24125 The program received signal number @var{AA} (a two-digit hexadecimal
24126 number). This is equivalent to a @samp{T} response with no
24127 @var{n}:@var{r} pairs.
24129 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
24130 @cindex @samp{T} packet reply
24131 The program received signal number @var{AA} (a two-digit hexadecimal
24132 number). This is equivalent to an @samp{S} response, except that the
24133 @samp{@var{n}:@var{r}} pairs can carry values of important registers
24134 and other information directly in the stop reply packet, reducing
24135 round-trip latency. Single-step and breakpoint traps are reported
24136 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
24140 If @var{n} is a hexadecimal number, it is a register number, and the
24141 corresponding @var{r} gives that register's value. @var{r} is a
24142 series of bytes in target byte order, with each byte given by a
24143 two-digit hex number.
24146 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
24150 If @var{n} is a recognized @dfn{stop reason}, it describes a more
24151 specific event that stopped the target. The currently defined stop
24152 reasons are listed below. @var{aa} should be @samp{05}, the trap
24153 signal. At most one stop reason should be present.
24156 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
24157 and go on to the next; this allows us to extend the protocol in the
24161 The currently defined stop reasons are:
24167 The packet indicates a watchpoint hit, and @var{r} is the data address, in
24170 @cindex shared library events, remote reply
24172 The packet indicates that the loaded libraries have changed.
24173 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
24174 list of loaded libraries. @var{r} is ignored.
24178 The process exited, and @var{AA} is the exit status. This is only
24179 applicable to certain targets.
24182 The process terminated with signal @var{AA}.
24184 @item O @var{XX}@dots{}
24185 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
24186 written as the program's console output. This can happen at any time
24187 while the program is running and the debugger should continue to wait
24188 for @samp{W}, @samp{T}, etc.
24190 @item F @var{call-id},@var{parameter}@dots{}
24191 @var{call-id} is the identifier which says which host system call should
24192 be called. This is just the name of the function. Translation into the
24193 correct system call is only applicable as it's defined in @value{GDBN}.
24194 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
24197 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
24198 this very system call.
24200 The target replies with this packet when it expects @value{GDBN} to
24201 call a host system call on behalf of the target. @value{GDBN} replies
24202 with an appropriate @samp{F} packet and keeps up waiting for the next
24203 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
24204 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
24205 Protocol Extension}, for more details.
24209 @node General Query Packets
24210 @section General Query Packets
24211 @cindex remote query requests
24213 Packets starting with @samp{q} are @dfn{general query packets};
24214 packets starting with @samp{Q} are @dfn{general set packets}. General
24215 query and set packets are a semi-unified form for retrieving and
24216 sending information to and from the stub.
24218 The initial letter of a query or set packet is followed by a name
24219 indicating what sort of thing the packet applies to. For example,
24220 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
24221 definitions with the stub. These packet names follow some
24226 The name must not contain commas, colons or semicolons.
24228 Most @value{GDBN} query and set packets have a leading upper case
24231 The names of custom vendor packets should use a company prefix, in
24232 lower case, followed by a period. For example, packets designed at
24233 the Acme Corporation might begin with @samp{qacme.foo} (for querying
24234 foos) or @samp{Qacme.bar} (for setting bars).
24237 The name of a query or set packet should be separated from any
24238 parameters by a @samp{:}; the parameters themselves should be
24239 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
24240 full packet name, and check for a separator or the end of the packet,
24241 in case two packet names share a common prefix. New packets should not begin
24242 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
24243 packets predate these conventions, and have arguments without any terminator
24244 for the packet name; we suspect they are in widespread use in places that
24245 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
24246 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
24249 Like the descriptions of the other packets, each description here
24250 has a template showing the packet's overall syntax, followed by an
24251 explanation of the packet's meaning. We include spaces in some of the
24252 templates for clarity; these are not part of the packet's syntax. No
24253 @value{GDBN} packet uses spaces to separate its components.
24255 Here are the currently defined query and set packets:
24260 @cindex current thread, remote request
24261 @cindex @samp{qC} packet
24262 Return the current thread id.
24267 Where @var{pid} is an unsigned hexadecimal process id.
24268 @item @r{(anything else)}
24269 Any other reply implies the old pid.
24272 @item qCRC:@var{addr},@var{length}
24273 @cindex CRC of memory block, remote request
24274 @cindex @samp{qCRC} packet
24275 Compute the CRC checksum of a block of memory.
24279 An error (such as memory fault)
24280 @item C @var{crc32}
24281 The specified memory region's checksum is @var{crc32}.
24285 @itemx qsThreadInfo
24286 @cindex list active threads, remote request
24287 @cindex @samp{qfThreadInfo} packet
24288 @cindex @samp{qsThreadInfo} packet
24289 Obtain a list of all active thread ids from the target (OS). Since there
24290 may be too many active threads to fit into one reply packet, this query
24291 works iteratively: it may require more than one query/reply sequence to
24292 obtain the entire list of threads. The first query of the sequence will
24293 be the @samp{qfThreadInfo} query; subsequent queries in the
24294 sequence will be the @samp{qsThreadInfo} query.
24296 NOTE: This packet replaces the @samp{qL} query (see below).
24302 @item m @var{id},@var{id}@dots{}
24303 a comma-separated list of thread ids
24305 (lower case letter @samp{L}) denotes end of list.
24308 In response to each query, the target will reply with a list of one or
24309 more thread ids, in big-endian unsigned hex, separated by commas.
24310 @value{GDBN} will respond to each reply with a request for more thread
24311 ids (using the @samp{qs} form of the query), until the target responds
24312 with @samp{l} (lower-case el, for @dfn{last}).
24314 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
24315 @cindex get thread-local storage address, remote request
24316 @cindex @samp{qGetTLSAddr} packet
24317 Fetch the address associated with thread local storage specified
24318 by @var{thread-id}, @var{offset}, and @var{lm}.
24320 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
24321 thread for which to fetch the TLS address.
24323 @var{offset} is the (big endian, hex encoded) offset associated with the
24324 thread local variable. (This offset is obtained from the debug
24325 information associated with the variable.)
24327 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
24328 the load module associated with the thread local storage. For example,
24329 a @sc{gnu}/Linux system will pass the link map address of the shared
24330 object associated with the thread local storage under consideration.
24331 Other operating environments may choose to represent the load module
24332 differently, so the precise meaning of this parameter will vary.
24336 @item @var{XX}@dots{}
24337 Hex encoded (big endian) bytes representing the address of the thread
24338 local storage requested.
24341 An error occurred. @var{nn} are hex digits.
24344 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
24347 @item qL @var{startflag} @var{threadcount} @var{nextthread}
24348 Obtain thread information from RTOS. Where: @var{startflag} (one hex
24349 digit) is one to indicate the first query and zero to indicate a
24350 subsequent query; @var{threadcount} (two hex digits) is the maximum
24351 number of threads the response packet can contain; and @var{nextthread}
24352 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
24353 returned in the response as @var{argthread}.
24355 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
24359 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
24360 Where: @var{count} (two hex digits) is the number of threads being
24361 returned; @var{done} (one hex digit) is zero to indicate more threads
24362 and one indicates no further threads; @var{argthreadid} (eight hex
24363 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
24364 is a sequence of thread IDs from the target. @var{threadid} (eight hex
24365 digits). See @code{remote.c:parse_threadlist_response()}.
24369 @cindex section offsets, remote request
24370 @cindex @samp{qOffsets} packet
24371 Get section offsets that the target used when relocating the downloaded
24376 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
24377 Relocate the @code{Text} section by @var{xxx} from its original address.
24378 Relocate the @code{Data} section by @var{yyy} from its original address.
24379 If the object file format provides segment information (e.g.@: @sc{elf}
24380 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
24381 segments by the supplied offsets.
24383 @emph{Note: while a @code{Bss} offset may be included in the response,
24384 @value{GDBN} ignores this and instead applies the @code{Data} offset
24385 to the @code{Bss} section.}
24387 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
24388 Relocate the first segment of the object file, which conventionally
24389 contains program code, to a starting address of @var{xxx}. If
24390 @samp{DataSeg} is specified, relocate the second segment, which
24391 conventionally contains modifiable data, to a starting address of
24392 @var{yyy}. @value{GDBN} will report an error if the object file
24393 does not contain segment information, or does not contain at least
24394 as many segments as mentioned in the reply. Extra segments are
24395 kept at fixed offsets relative to the last relocated segment.
24398 @item qP @var{mode} @var{threadid}
24399 @cindex thread information, remote request
24400 @cindex @samp{qP} packet
24401 Returns information on @var{threadid}. Where: @var{mode} is a hex
24402 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
24404 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
24407 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
24409 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
24410 @cindex pass signals to inferior, remote request
24411 @cindex @samp{QPassSignals} packet
24412 @anchor{QPassSignals}
24413 Each listed @var{signal} should be passed directly to the inferior process.
24414 Signals are numbered identically to continue packets and stop replies
24415 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
24416 strictly greater than the previous item. These signals do not need to stop
24417 the inferior, or be reported to @value{GDBN}. All other signals should be
24418 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
24419 combine; any earlier @samp{QPassSignals} list is completely replaced by the
24420 new list. This packet improves performance when using @samp{handle
24421 @var{signal} nostop noprint pass}.
24426 The request succeeded.
24429 An error occurred. @var{nn} are hex digits.
24432 An empty reply indicates that @samp{QPassSignals} is not supported by
24436 Use of this packet is controlled by the @code{set remote pass-signals}
24437 command (@pxref{Remote Configuration, set remote pass-signals}).
24438 This packet is not probed by default; the remote stub must request it,
24439 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24441 @item qRcmd,@var{command}
24442 @cindex execute remote command, remote request
24443 @cindex @samp{qRcmd} packet
24444 @var{command} (hex encoded) is passed to the local interpreter for
24445 execution. Invalid commands should be reported using the output
24446 string. Before the final result packet, the target may also respond
24447 with a number of intermediate @samp{O@var{output}} console output
24448 packets. @emph{Implementors should note that providing access to a
24449 stubs's interpreter may have security implications}.
24454 A command response with no output.
24456 A command response with the hex encoded output string @var{OUTPUT}.
24458 Indicate a badly formed request.
24460 An empty reply indicates that @samp{qRcmd} is not recognized.
24463 (Note that the @code{qRcmd} packet's name is separated from the
24464 command by a @samp{,}, not a @samp{:}, contrary to the naming
24465 conventions above. Please don't use this packet as a model for new
24468 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
24469 @cindex supported packets, remote query
24470 @cindex features of the remote protocol
24471 @cindex @samp{qSupported} packet
24472 @anchor{qSupported}
24473 Tell the remote stub about features supported by @value{GDBN}, and
24474 query the stub for features it supports. This packet allows
24475 @value{GDBN} and the remote stub to take advantage of each others'
24476 features. @samp{qSupported} also consolidates multiple feature probes
24477 at startup, to improve @value{GDBN} performance---a single larger
24478 packet performs better than multiple smaller probe packets on
24479 high-latency links. Some features may enable behavior which must not
24480 be on by default, e.g.@: because it would confuse older clients or
24481 stubs. Other features may describe packets which could be
24482 automatically probed for, but are not. These features must be
24483 reported before @value{GDBN} will use them. This ``default
24484 unsupported'' behavior is not appropriate for all packets, but it
24485 helps to keep the initial connection time under control with new
24486 versions of @value{GDBN} which support increasing numbers of packets.
24490 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
24491 The stub supports or does not support each returned @var{stubfeature},
24492 depending on the form of each @var{stubfeature} (see below for the
24495 An empty reply indicates that @samp{qSupported} is not recognized,
24496 or that no features needed to be reported to @value{GDBN}.
24499 The allowed forms for each feature (either a @var{gdbfeature} in the
24500 @samp{qSupported} packet, or a @var{stubfeature} in the response)
24504 @item @var{name}=@var{value}
24505 The remote protocol feature @var{name} is supported, and associated
24506 with the specified @var{value}. The format of @var{value} depends
24507 on the feature, but it must not include a semicolon.
24509 The remote protocol feature @var{name} is supported, and does not
24510 need an associated value.
24512 The remote protocol feature @var{name} is not supported.
24514 The remote protocol feature @var{name} may be supported, and
24515 @value{GDBN} should auto-detect support in some other way when it is
24516 needed. This form will not be used for @var{gdbfeature} notifications,
24517 but may be used for @var{stubfeature} responses.
24520 Whenever the stub receives a @samp{qSupported} request, the
24521 supplied set of @value{GDBN} features should override any previous
24522 request. This allows @value{GDBN} to put the stub in a known
24523 state, even if the stub had previously been communicating with
24524 a different version of @value{GDBN}.
24526 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
24527 are defined yet. Stubs should ignore any unknown values for
24528 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
24529 packet supports receiving packets of unlimited length (earlier
24530 versions of @value{GDBN} may reject overly long responses). Values
24531 for @var{gdbfeature} may be defined in the future to let the stub take
24532 advantage of new features in @value{GDBN}, e.g.@: incompatible
24533 improvements in the remote protocol---support for unlimited length
24534 responses would be a @var{gdbfeature} example, if it were not implied by
24535 the @samp{qSupported} query. The stub's reply should be independent
24536 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
24537 describes all the features it supports, and then the stub replies with
24538 all the features it supports.
24540 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
24541 responses, as long as each response uses one of the standard forms.
24543 Some features are flags. A stub which supports a flag feature
24544 should respond with a @samp{+} form response. Other features
24545 require values, and the stub should respond with an @samp{=}
24548 Each feature has a default value, which @value{GDBN} will use if
24549 @samp{qSupported} is not available or if the feature is not mentioned
24550 in the @samp{qSupported} response. The default values are fixed; a
24551 stub is free to omit any feature responses that match the defaults.
24553 Not all features can be probed, but for those which can, the probing
24554 mechanism is useful: in some cases, a stub's internal
24555 architecture may not allow the protocol layer to know some information
24556 about the underlying target in advance. This is especially common in
24557 stubs which may be configured for multiple targets.
24559 These are the currently defined stub features and their properties:
24561 @multitable @columnfractions 0.35 0.2 0.12 0.2
24562 @c NOTE: The first row should be @headitem, but we do not yet require
24563 @c a new enough version of Texinfo (4.7) to use @headitem.
24565 @tab Value Required
24569 @item @samp{PacketSize}
24574 @item @samp{qXfer:auxv:read}
24579 @item @samp{qXfer:features:read}
24584 @item @samp{qXfer:libraries:read}
24589 @item @samp{qXfer:memory-map:read}
24594 @item @samp{qXfer:spu:read}
24599 @item @samp{qXfer:spu:write}
24604 @item @samp{QPassSignals}
24611 These are the currently defined stub features, in more detail:
24614 @cindex packet size, remote protocol
24615 @item PacketSize=@var{bytes}
24616 The remote stub can accept packets up to at least @var{bytes} in
24617 length. @value{GDBN} will send packets up to this size for bulk
24618 transfers, and will never send larger packets. This is a limit on the
24619 data characters in the packet, including the frame and checksum.
24620 There is no trailing NUL byte in a remote protocol packet; if the stub
24621 stores packets in a NUL-terminated format, it should allow an extra
24622 byte in its buffer for the NUL. If this stub feature is not supported,
24623 @value{GDBN} guesses based on the size of the @samp{g} packet response.
24625 @item qXfer:auxv:read
24626 The remote stub understands the @samp{qXfer:auxv:read} packet
24627 (@pxref{qXfer auxiliary vector read}).
24629 @item qXfer:features:read
24630 The remote stub understands the @samp{qXfer:features:read} packet
24631 (@pxref{qXfer target description read}).
24633 @item qXfer:libraries:read
24634 The remote stub understands the @samp{qXfer:libraries:read} packet
24635 (@pxref{qXfer library list read}).
24637 @item qXfer:memory-map:read
24638 The remote stub understands the @samp{qXfer:memory-map:read} packet
24639 (@pxref{qXfer memory map read}).
24641 @item qXfer:spu:read
24642 The remote stub understands the @samp{qXfer:spu:read} packet
24643 (@pxref{qXfer spu read}).
24645 @item qXfer:spu:write
24646 The remote stub understands the @samp{qXfer:spu:write} packet
24647 (@pxref{qXfer spu write}).
24650 The remote stub understands the @samp{QPassSignals} packet
24651 (@pxref{QPassSignals}).
24656 @cindex symbol lookup, remote request
24657 @cindex @samp{qSymbol} packet
24658 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24659 requests. Accept requests from the target for the values of symbols.
24664 The target does not need to look up any (more) symbols.
24665 @item qSymbol:@var{sym_name}
24666 The target requests the value of symbol @var{sym_name} (hex encoded).
24667 @value{GDBN} may provide the value by using the
24668 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24672 @item qSymbol:@var{sym_value}:@var{sym_name}
24673 Set the value of @var{sym_name} to @var{sym_value}.
24675 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24676 target has previously requested.
24678 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24679 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24685 The target does not need to look up any (more) symbols.
24686 @item qSymbol:@var{sym_name}
24687 The target requests the value of a new symbol @var{sym_name} (hex
24688 encoded). @value{GDBN} will continue to supply the values of symbols
24689 (if available), until the target ceases to request them.
24694 @xref{Tracepoint Packets}.
24696 @item qThreadExtraInfo,@var{id}
24697 @cindex thread attributes info, remote request
24698 @cindex @samp{qThreadExtraInfo} packet
24699 Obtain a printable string description of a thread's attributes from
24700 the target OS. @var{id} is a thread-id in big-endian hex. This
24701 string may contain anything that the target OS thinks is interesting
24702 for @value{GDBN} to tell the user about the thread. The string is
24703 displayed in @value{GDBN}'s @code{info threads} display. Some
24704 examples of possible thread extra info strings are @samp{Runnable}, or
24705 @samp{Blocked on Mutex}.
24709 @item @var{XX}@dots{}
24710 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
24711 comprising the printable string containing the extra information about
24712 the thread's attributes.
24715 (Note that the @code{qThreadExtraInfo} packet's name is separated from
24716 the command by a @samp{,}, not a @samp{:}, contrary to the naming
24717 conventions above. Please don't use this packet as a model for new
24725 @xref{Tracepoint Packets}.
24727 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
24728 @cindex read special object, remote request
24729 @cindex @samp{qXfer} packet
24730 @anchor{qXfer read}
24731 Read uninterpreted bytes from the target's special data area
24732 identified by the keyword @var{object}. Request @var{length} bytes
24733 starting at @var{offset} bytes into the data. The content and
24734 encoding of @var{annex} is specific to @var{object}; it can supply
24735 additional details about what data to access.
24737 Here are the specific requests of this form defined so far. All
24738 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
24739 formats, listed below.
24742 @item qXfer:auxv:read::@var{offset},@var{length}
24743 @anchor{qXfer auxiliary vector read}
24744 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
24745 auxiliary vector}. Note @var{annex} must be empty.
24747 This packet is not probed by default; the remote stub must request it,
24748 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24750 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
24751 @anchor{qXfer target description read}
24752 Access the @dfn{target description}. @xref{Target Descriptions}. The
24753 annex specifies which XML document to access. The main description is
24754 always loaded from the @samp{target.xml} annex.
24756 This packet is not probed by default; the remote stub must request it,
24757 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24759 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
24760 @anchor{qXfer library list read}
24761 Access the target's list of loaded libraries. @xref{Library List Format}.
24762 The annex part of the generic @samp{qXfer} packet must be empty
24763 (@pxref{qXfer read}).
24765 Targets which maintain a list of libraries in the program's memory do
24766 not need to implement this packet; it is designed for platforms where
24767 the operating system manages the list of loaded libraries.
24769 This packet is not probed by default; the remote stub must request it,
24770 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24772 @item qXfer:memory-map:read::@var{offset},@var{length}
24773 @anchor{qXfer memory map read}
24774 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
24775 annex part of the generic @samp{qXfer} packet must be empty
24776 (@pxref{qXfer read}).
24778 This packet is not probed by default; the remote stub must request it,
24779 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24781 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
24782 @anchor{qXfer spu read}
24783 Read contents of an @code{spufs} file on the target system. The
24784 annex specifies which file to read; it must be of the form
24785 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24786 in the target process, and @var{name} identifes the @code{spufs} file
24787 in that context to be accessed.
24789 This packet is not probed by default; the remote stub must request it,
24790 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24796 Data @var{data} (@pxref{Binary Data}) has been read from the
24797 target. There may be more data at a higher address (although
24798 it is permitted to return @samp{m} even for the last valid
24799 block of data, as long as at least one byte of data was read).
24800 @var{data} may have fewer bytes than the @var{length} in the
24804 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24805 There is no more data to be read. @var{data} may have fewer bytes
24806 than the @var{length} in the request.
24809 The @var{offset} in the request is at the end of the data.
24810 There is no more data to be read.
24813 The request was malformed, or @var{annex} was invalid.
24816 The offset was invalid, or there was an error encountered reading the data.
24817 @var{nn} is a hex-encoded @code{errno} value.
24820 An empty reply indicates the @var{object} string was not recognized by
24821 the stub, or that the object does not support reading.
24824 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24825 @cindex write data into object, remote request
24826 Write uninterpreted bytes into the target's special data area
24827 identified by the keyword @var{object}, starting at @var{offset} bytes
24828 into the data. @var{data}@dots{} is the binary-encoded data
24829 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24830 is specific to @var{object}; it can supply additional details about what data
24833 Here are the specific requests of this form defined so far. All
24834 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
24835 formats, listed below.
24838 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24839 @anchor{qXfer spu write}
24840 Write @var{data} to an @code{spufs} file on the target system. The
24841 annex specifies which file to write; it must be of the form
24842 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24843 in the target process, and @var{name} identifes the @code{spufs} file
24844 in that context to be accessed.
24846 This packet is not probed by default; the remote stub must request it,
24847 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24853 @var{nn} (hex encoded) is the number of bytes written.
24854 This may be fewer bytes than supplied in the request.
24857 The request was malformed, or @var{annex} was invalid.
24860 The offset was invalid, or there was an error encountered writing the data.
24861 @var{nn} is a hex-encoded @code{errno} value.
24864 An empty reply indicates the @var{object} string was not
24865 recognized by the stub, or that the object does not support writing.
24868 @item qXfer:@var{object}:@var{operation}:@dots{}
24869 Requests of this form may be added in the future. When a stub does
24870 not recognize the @var{object} keyword, or its support for
24871 @var{object} does not recognize the @var{operation} keyword, the stub
24872 must respond with an empty packet.
24876 @node Register Packet Format
24877 @section Register Packet Format
24879 The following @code{g}/@code{G} packets have previously been defined.
24880 In the below, some thirty-two bit registers are transferred as
24881 sixty-four bits. Those registers should be zero/sign extended (which?)
24882 to fill the space allocated. Register bytes are transferred in target
24883 byte order. The two nibbles within a register byte are transferred
24884 most-significant - least-significant.
24890 All registers are transferred as thirty-two bit quantities in the order:
24891 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24892 registers; fsr; fir; fp.
24896 All registers are transferred as sixty-four bit quantities (including
24897 thirty-two bit registers such as @code{sr}). The ordering is the same
24902 @node Tracepoint Packets
24903 @section Tracepoint Packets
24904 @cindex tracepoint packets
24905 @cindex packets, tracepoint
24907 Here we describe the packets @value{GDBN} uses to implement
24908 tracepoints (@pxref{Tracepoints}).
24912 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24913 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24914 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24915 the tracepoint is disabled. @var{step} is the tracepoint's step
24916 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24917 present, further @samp{QTDP} packets will follow to specify this
24918 tracepoint's actions.
24923 The packet was understood and carried out.
24925 The packet was not recognized.
24928 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24929 Define actions to be taken when a tracepoint is hit. @var{n} and
24930 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24931 this tracepoint. This packet may only be sent immediately after
24932 another @samp{QTDP} packet that ended with a @samp{-}. If the
24933 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24934 specifying more actions for this tracepoint.
24936 In the series of action packets for a given tracepoint, at most one
24937 can have an @samp{S} before its first @var{action}. If such a packet
24938 is sent, it and the following packets define ``while-stepping''
24939 actions. Any prior packets define ordinary actions --- that is, those
24940 taken when the tracepoint is first hit. If no action packet has an
24941 @samp{S}, then all the packets in the series specify ordinary
24942 tracepoint actions.
24944 The @samp{@var{action}@dots{}} portion of the packet is a series of
24945 actions, concatenated without separators. Each action has one of the
24951 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24952 a hexadecimal number whose @var{i}'th bit is set if register number
24953 @var{i} should be collected. (The least significant bit is numbered
24954 zero.) Note that @var{mask} may be any number of digits long; it may
24955 not fit in a 32-bit word.
24957 @item M @var{basereg},@var{offset},@var{len}
24958 Collect @var{len} bytes of memory starting at the address in register
24959 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24960 @samp{-1}, then the range has a fixed address: @var{offset} is the
24961 address of the lowest byte to collect. The @var{basereg},
24962 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24963 values (the @samp{-1} value for @var{basereg} is a special case).
24965 @item X @var{len},@var{expr}
24966 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24967 it directs. @var{expr} is an agent expression, as described in
24968 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24969 two-digit hex number in the packet; @var{len} is the number of bytes
24970 in the expression (and thus one-half the number of hex digits in the
24975 Any number of actions may be packed together in a single @samp{QTDP}
24976 packet, as long as the packet does not exceed the maximum packet
24977 length (400 bytes, for many stubs). There may be only one @samp{R}
24978 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24979 actions. Any registers referred to by @samp{M} and @samp{X} actions
24980 must be collected by a preceding @samp{R} action. (The
24981 ``while-stepping'' actions are treated as if they were attached to a
24982 separate tracepoint, as far as these restrictions are concerned.)
24987 The packet was understood and carried out.
24989 The packet was not recognized.
24992 @item QTFrame:@var{n}
24993 Select the @var{n}'th tracepoint frame from the buffer, and use the
24994 register and memory contents recorded there to answer subsequent
24995 request packets from @value{GDBN}.
24997 A successful reply from the stub indicates that the stub has found the
24998 requested frame. The response is a series of parts, concatenated
24999 without separators, describing the frame we selected. Each part has
25000 one of the following forms:
25004 The selected frame is number @var{n} in the trace frame buffer;
25005 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
25006 was no frame matching the criteria in the request packet.
25009 The selected trace frame records a hit of tracepoint number @var{t};
25010 @var{t} is a hexadecimal number.
25014 @item QTFrame:pc:@var{addr}
25015 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25016 currently selected frame whose PC is @var{addr};
25017 @var{addr} is a hexadecimal number.
25019 @item QTFrame:tdp:@var{t}
25020 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25021 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
25022 is a hexadecimal number.
25024 @item QTFrame:range:@var{start}:@var{end}
25025 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25026 currently selected frame whose PC is between @var{start} (inclusive)
25027 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
25030 @item QTFrame:outside:@var{start}:@var{end}
25031 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
25032 frame @emph{outside} the given range of addresses.
25035 Begin the tracepoint experiment. Begin collecting data from tracepoint
25036 hits in the trace frame buffer.
25039 End the tracepoint experiment. Stop collecting trace frames.
25042 Clear the table of tracepoints, and empty the trace frame buffer.
25044 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
25045 Establish the given ranges of memory as ``transparent''. The stub
25046 will answer requests for these ranges from memory's current contents,
25047 if they were not collected as part of the tracepoint hit.
25049 @value{GDBN} uses this to mark read-only regions of memory, like those
25050 containing program code. Since these areas never change, they should
25051 still have the same contents they did when the tracepoint was hit, so
25052 there's no reason for the stub to refuse to provide their contents.
25055 Ask the stub if there is a trace experiment running right now.
25060 There is no trace experiment running.
25062 There is a trace experiment running.
25068 @node Host I/O Packets
25069 @section Host I/O Packets
25070 @cindex Host I/O, remote protocol
25071 @cindex file transfer, remote protocol
25073 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
25074 operations on the far side of a remote link. For example, Host I/O is
25075 used to upload and download files to a remote target with its own
25076 filesystem. Host I/O uses the same constant values and data structure
25077 layout as the target-initiated File-I/O protocol. However, the
25078 Host I/O packets are structured differently. The target-initiated
25079 protocol relies on target memory to store parameters and buffers.
25080 Host I/O requests are initiated by @value{GDBN}, and the
25081 target's memory is not involved. @xref{File-I/O Remote Protocol
25082 Extension}, for more details on the target-initiated protocol.
25084 The Host I/O request packets all encode a single operation along with
25085 its arguments. They have this format:
25089 @item vFile:@var{operation}: @var{parameter}@dots{}
25090 @var{operation} is the name of the particular request; the target
25091 should compare the entire packet name up to the second colon when checking
25092 for a supported operation. The format of @var{parameter} depends on
25093 the operation. Numbers are always passed in hexadecimal. Negative
25094 numbers have an explicit minus sign (i.e.@: two's complement is not
25095 used). Strings (e.g.@: filenames) are encoded as a series of
25096 hexadecimal bytes. The last argument to a system call may be a
25097 buffer of escaped binary data (@pxref{Binary Data}).
25101 The valid responses to Host I/O packets are:
25105 @item F @var{result} [, @var{errno}] [; @var{attachment}]
25106 @var{result} is the integer value returned by this operation, usually
25107 non-negative for success and -1 for errors. If an error has occured,
25108 @var{errno} will be included in the result. @var{errno} will have a
25109 value defined by the File-I/O protocol (@pxref{Errno Values}). For
25110 operations which return data, @var{attachment} supplies the data as a
25111 binary buffer. Binary buffers in response packets are escaped in the
25112 normal way (@pxref{Binary Data}). See the individual packet
25113 documentation for the interpretation of @var{result} and
25117 An empty response indicates that this operation is not recognized.
25121 These are the supported Host I/O operations:
25124 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
25125 Open a file at @var{pathname} and return a file descriptor for it, or
25126 return -1 if an error occurs. @var{pathname} is a string,
25127 @var{flags} is an integer indicating a mask of open flags
25128 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
25129 of mode bits to use if the file is created (@pxref{mode_t Values}).
25130 @xref{open}, for details of the open flags and mode values.
25132 @item vFile:close: @var{fd}
25133 Close the open file corresponding to @var{fd} and return 0, or
25134 -1 if an error occurs.
25136 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
25137 Read data from the open file corresponding to @var{fd}. Up to
25138 @var{count} bytes will be read from the file, starting at @var{offset}
25139 relative to the start of the file. The target may read fewer bytes;
25140 common reasons include packet size limits and an end-of-file
25141 condition. The number of bytes read is returned. Zero should only be
25142 returned for a successful read at the end of the file, or if
25143 @var{count} was zero.
25145 The data read should be returned as a binary attachment on success.
25146 If zero bytes were read, the response should include an empty binary
25147 attachment (i.e.@: a trailing semicolon). The return value is the
25148 number of target bytes read; the binary attachment may be longer if
25149 some characters were escaped.
25151 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
25152 Write @var{data} (a binary buffer) to the open file corresponding
25153 to @var{fd}. Start the write at @var{offset} from the start of the
25154 file. Unlike many @code{write} system calls, there is no
25155 separate @var{count} argument; the length of @var{data} in the
25156 packet is used. @samp{vFile:write} returns the number of bytes written,
25157 which may be shorter than the length of @var{data}, or -1 if an
25160 @item vFile:unlink: @var{pathname}
25161 Delete the file at @var{pathname} on the target. Return 0,
25162 or -1 if an error occurs. @var{pathname} is a string.
25167 @section Interrupts
25168 @cindex interrupts (remote protocol)
25170 When a program on the remote target is running, @value{GDBN} may
25171 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
25172 control of which is specified via @value{GDBN}'s @samp{remotebreak}
25173 setting (@pxref{set remotebreak}).
25175 The precise meaning of @code{BREAK} is defined by the transport
25176 mechanism and may, in fact, be undefined. @value{GDBN} does
25177 not currently define a @code{BREAK} mechanism for any of the network
25180 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
25181 transport mechanisms. It is represented by sending the single byte
25182 @code{0x03} without any of the usual packet overhead described in
25183 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
25184 transmitted as part of a packet, it is considered to be packet data
25185 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
25186 (@pxref{X packet}), used for binary downloads, may include an unescaped
25187 @code{0x03} as part of its packet.
25189 Stubs are not required to recognize these interrupt mechanisms and the
25190 precise meaning associated with receipt of the interrupt is
25191 implementation defined. If the stub is successful at interrupting the
25192 running program, it is expected that it will send one of the Stop
25193 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
25194 of successfully stopping the program. Interrupts received while the
25195 program is stopped will be discarded.
25200 Example sequence of a target being re-started. Notice how the restart
25201 does not get any direct output:
25206 @emph{target restarts}
25209 <- @code{T001:1234123412341234}
25213 Example sequence of a target being stepped by a single instruction:
25216 -> @code{G1445@dots{}}
25221 <- @code{T001:1234123412341234}
25225 <- @code{1455@dots{}}
25229 @node File-I/O Remote Protocol Extension
25230 @section File-I/O Remote Protocol Extension
25231 @cindex File-I/O remote protocol extension
25234 * File-I/O Overview::
25235 * Protocol Basics::
25236 * The F Request Packet::
25237 * The F Reply Packet::
25238 * The Ctrl-C Message::
25240 * List of Supported Calls::
25241 * Protocol-specific Representation of Datatypes::
25243 * File-I/O Examples::
25246 @node File-I/O Overview
25247 @subsection File-I/O Overview
25248 @cindex file-i/o overview
25250 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
25251 target to use the host's file system and console I/O to perform various
25252 system calls. System calls on the target system are translated into a
25253 remote protocol packet to the host system, which then performs the needed
25254 actions and returns a response packet to the target system.
25255 This simulates file system operations even on targets that lack file systems.
25257 The protocol is defined to be independent of both the host and target systems.
25258 It uses its own internal representation of datatypes and values. Both
25259 @value{GDBN} and the target's @value{GDBN} stub are responsible for
25260 translating the system-dependent value representations into the internal
25261 protocol representations when data is transmitted.
25263 The communication is synchronous. A system call is possible only when
25264 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
25265 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
25266 the target is stopped to allow deterministic access to the target's
25267 memory. Therefore File-I/O is not interruptible by target signals. On
25268 the other hand, it is possible to interrupt File-I/O by a user interrupt
25269 (@samp{Ctrl-C}) within @value{GDBN}.
25271 The target's request to perform a host system call does not finish
25272 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
25273 after finishing the system call, the target returns to continuing the
25274 previous activity (continue, step). No additional continue or step
25275 request from @value{GDBN} is required.
25278 (@value{GDBP}) continue
25279 <- target requests 'system call X'
25280 target is stopped, @value{GDBN} executes system call
25281 -> @value{GDBN} returns result
25282 ... target continues, @value{GDBN} returns to wait for the target
25283 <- target hits breakpoint and sends a Txx packet
25286 The protocol only supports I/O on the console and to regular files on
25287 the host file system. Character or block special devices, pipes,
25288 named pipes, sockets or any other communication method on the host
25289 system are not supported by this protocol.
25291 @node Protocol Basics
25292 @subsection Protocol Basics
25293 @cindex protocol basics, file-i/o
25295 The File-I/O protocol uses the @code{F} packet as the request as well
25296 as reply packet. Since a File-I/O system call can only occur when
25297 @value{GDBN} is waiting for a response from the continuing or stepping target,
25298 the File-I/O request is a reply that @value{GDBN} has to expect as a result
25299 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
25300 This @code{F} packet contains all information needed to allow @value{GDBN}
25301 to call the appropriate host system call:
25305 A unique identifier for the requested system call.
25308 All parameters to the system call. Pointers are given as addresses
25309 in the target memory address space. Pointers to strings are given as
25310 pointer/length pair. Numerical values are given as they are.
25311 Numerical control flags are given in a protocol-specific representation.
25315 At this point, @value{GDBN} has to perform the following actions.
25319 If the parameters include pointer values to data needed as input to a
25320 system call, @value{GDBN} requests this data from the target with a
25321 standard @code{m} packet request. This additional communication has to be
25322 expected by the target implementation and is handled as any other @code{m}
25326 @value{GDBN} translates all value from protocol representation to host
25327 representation as needed. Datatypes are coerced into the host types.
25330 @value{GDBN} calls the system call.
25333 It then coerces datatypes back to protocol representation.
25336 If the system call is expected to return data in buffer space specified
25337 by pointer parameters to the call, the data is transmitted to the
25338 target using a @code{M} or @code{X} packet. This packet has to be expected
25339 by the target implementation and is handled as any other @code{M} or @code{X}
25344 Eventually @value{GDBN} replies with another @code{F} packet which contains all
25345 necessary information for the target to continue. This at least contains
25352 @code{errno}, if has been changed by the system call.
25359 After having done the needed type and value coercion, the target continues
25360 the latest continue or step action.
25362 @node The F Request Packet
25363 @subsection The @code{F} Request Packet
25364 @cindex file-i/o request packet
25365 @cindex @code{F} request packet
25367 The @code{F} request packet has the following format:
25370 @item F@var{call-id},@var{parameter@dots{}}
25372 @var{call-id} is the identifier to indicate the host system call to be called.
25373 This is just the name of the function.
25375 @var{parameter@dots{}} are the parameters to the system call.
25376 Parameters are hexadecimal integer values, either the actual values in case
25377 of scalar datatypes, pointers to target buffer space in case of compound
25378 datatypes and unspecified memory areas, or pointer/length pairs in case
25379 of string parameters. These are appended to the @var{call-id} as a
25380 comma-delimited list. All values are transmitted in ASCII
25381 string representation, pointer/length pairs separated by a slash.
25387 @node The F Reply Packet
25388 @subsection The @code{F} Reply Packet
25389 @cindex file-i/o reply packet
25390 @cindex @code{F} reply packet
25392 The @code{F} reply packet has the following format:
25396 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
25398 @var{retcode} is the return code of the system call as hexadecimal value.
25400 @var{errno} is the @code{errno} set by the call, in protocol-specific
25402 This parameter can be omitted if the call was successful.
25404 @var{Ctrl-C flag} is only sent if the user requested a break. In this
25405 case, @var{errno} must be sent as well, even if the call was successful.
25406 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
25413 or, if the call was interrupted before the host call has been performed:
25420 assuming 4 is the protocol-specific representation of @code{EINTR}.
25425 @node The Ctrl-C Message
25426 @subsection The @samp{Ctrl-C} Message
25427 @cindex ctrl-c message, in file-i/o protocol
25429 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
25430 reply packet (@pxref{The F Reply Packet}),
25431 the target should behave as if it had
25432 gotten a break message. The meaning for the target is ``system call
25433 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
25434 (as with a break message) and return to @value{GDBN} with a @code{T02}
25437 It's important for the target to know in which
25438 state the system call was interrupted. There are two possible cases:
25442 The system call hasn't been performed on the host yet.
25445 The system call on the host has been finished.
25449 These two states can be distinguished by the target by the value of the
25450 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
25451 call hasn't been performed. This is equivalent to the @code{EINTR} handling
25452 on POSIX systems. In any other case, the target may presume that the
25453 system call has been finished --- successfully or not --- and should behave
25454 as if the break message arrived right after the system call.
25456 @value{GDBN} must behave reliably. If the system call has not been called
25457 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
25458 @code{errno} in the packet. If the system call on the host has been finished
25459 before the user requests a break, the full action must be finished by
25460 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
25461 The @code{F} packet may only be sent when either nothing has happened
25462 or the full action has been completed.
25465 @subsection Console I/O
25466 @cindex console i/o as part of file-i/o
25468 By default and if not explicitly closed by the target system, the file
25469 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
25470 on the @value{GDBN} console is handled as any other file output operation
25471 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
25472 by @value{GDBN} so that after the target read request from file descriptor
25473 0 all following typing is buffered until either one of the following
25478 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
25480 system call is treated as finished.
25483 The user presses @key{RET}. This is treated as end of input with a trailing
25487 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
25488 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
25492 If the user has typed more characters than fit in the buffer given to
25493 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
25494 either another @code{read(0, @dots{})} is requested by the target, or debugging
25495 is stopped at the user's request.
25498 @node List of Supported Calls
25499 @subsection List of Supported Calls
25500 @cindex list of supported file-i/o calls
25517 @unnumberedsubsubsec open
25518 @cindex open, file-i/o system call
25523 int open(const char *pathname, int flags);
25524 int open(const char *pathname, int flags, mode_t mode);
25528 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
25531 @var{flags} is the bitwise @code{OR} of the following values:
25535 If the file does not exist it will be created. The host
25536 rules apply as far as file ownership and time stamps
25540 When used with @code{O_CREAT}, if the file already exists it is
25541 an error and open() fails.
25544 If the file already exists and the open mode allows
25545 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
25546 truncated to zero length.
25549 The file is opened in append mode.
25552 The file is opened for reading only.
25555 The file is opened for writing only.
25558 The file is opened for reading and writing.
25562 Other bits are silently ignored.
25566 @var{mode} is the bitwise @code{OR} of the following values:
25570 User has read permission.
25573 User has write permission.
25576 Group has read permission.
25579 Group has write permission.
25582 Others have read permission.
25585 Others have write permission.
25589 Other bits are silently ignored.
25592 @item Return value:
25593 @code{open} returns the new file descriptor or -1 if an error
25600 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
25603 @var{pathname} refers to a directory.
25606 The requested access is not allowed.
25609 @var{pathname} was too long.
25612 A directory component in @var{pathname} does not exist.
25615 @var{pathname} refers to a device, pipe, named pipe or socket.
25618 @var{pathname} refers to a file on a read-only filesystem and
25619 write access was requested.
25622 @var{pathname} is an invalid pointer value.
25625 No space on device to create the file.
25628 The process already has the maximum number of files open.
25631 The limit on the total number of files open on the system
25635 The call was interrupted by the user.
25641 @unnumberedsubsubsec close
25642 @cindex close, file-i/o system call
25651 @samp{Fclose,@var{fd}}
25653 @item Return value:
25654 @code{close} returns zero on success, or -1 if an error occurred.
25660 @var{fd} isn't a valid open file descriptor.
25663 The call was interrupted by the user.
25669 @unnumberedsubsubsec read
25670 @cindex read, file-i/o system call
25675 int read(int fd, void *buf, unsigned int count);
25679 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
25681 @item Return value:
25682 On success, the number of bytes read is returned.
25683 Zero indicates end of file. If count is zero, read
25684 returns zero as well. On error, -1 is returned.
25690 @var{fd} is not a valid file descriptor or is not open for
25694 @var{bufptr} is an invalid pointer value.
25697 The call was interrupted by the user.
25703 @unnumberedsubsubsec write
25704 @cindex write, file-i/o system call
25709 int write(int fd, const void *buf, unsigned int count);
25713 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
25715 @item Return value:
25716 On success, the number of bytes written are returned.
25717 Zero indicates nothing was written. On error, -1
25724 @var{fd} is not a valid file descriptor or is not open for
25728 @var{bufptr} is an invalid pointer value.
25731 An attempt was made to write a file that exceeds the
25732 host-specific maximum file size allowed.
25735 No space on device to write the data.
25738 The call was interrupted by the user.
25744 @unnumberedsubsubsec lseek
25745 @cindex lseek, file-i/o system call
25750 long lseek (int fd, long offset, int flag);
25754 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
25756 @var{flag} is one of:
25760 The offset is set to @var{offset} bytes.
25763 The offset is set to its current location plus @var{offset}
25767 The offset is set to the size of the file plus @var{offset}
25771 @item Return value:
25772 On success, the resulting unsigned offset in bytes from
25773 the beginning of the file is returned. Otherwise, a
25774 value of -1 is returned.
25780 @var{fd} is not a valid open file descriptor.
25783 @var{fd} is associated with the @value{GDBN} console.
25786 @var{flag} is not a proper value.
25789 The call was interrupted by the user.
25795 @unnumberedsubsubsec rename
25796 @cindex rename, file-i/o system call
25801 int rename(const char *oldpath, const char *newpath);
25805 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
25807 @item Return value:
25808 On success, zero is returned. On error, -1 is returned.
25814 @var{newpath} is an existing directory, but @var{oldpath} is not a
25818 @var{newpath} is a non-empty directory.
25821 @var{oldpath} or @var{newpath} is a directory that is in use by some
25825 An attempt was made to make a directory a subdirectory
25829 A component used as a directory in @var{oldpath} or new
25830 path is not a directory. Or @var{oldpath} is a directory
25831 and @var{newpath} exists but is not a directory.
25834 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
25837 No access to the file or the path of the file.
25841 @var{oldpath} or @var{newpath} was too long.
25844 A directory component in @var{oldpath} or @var{newpath} does not exist.
25847 The file is on a read-only filesystem.
25850 The device containing the file has no room for the new
25854 The call was interrupted by the user.
25860 @unnumberedsubsubsec unlink
25861 @cindex unlink, file-i/o system call
25866 int unlink(const char *pathname);
25870 @samp{Funlink,@var{pathnameptr}/@var{len}}
25872 @item Return value:
25873 On success, zero is returned. On error, -1 is returned.
25879 No access to the file or the path of the file.
25882 The system does not allow unlinking of directories.
25885 The file @var{pathname} cannot be unlinked because it's
25886 being used by another process.
25889 @var{pathnameptr} is an invalid pointer value.
25892 @var{pathname} was too long.
25895 A directory component in @var{pathname} does not exist.
25898 A component of the path is not a directory.
25901 The file is on a read-only filesystem.
25904 The call was interrupted by the user.
25910 @unnumberedsubsubsec stat/fstat
25911 @cindex fstat, file-i/o system call
25912 @cindex stat, file-i/o system call
25917 int stat(const char *pathname, struct stat *buf);
25918 int fstat(int fd, struct stat *buf);
25922 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25923 @samp{Ffstat,@var{fd},@var{bufptr}}
25925 @item Return value:
25926 On success, zero is returned. On error, -1 is returned.
25932 @var{fd} is not a valid open file.
25935 A directory component in @var{pathname} does not exist or the
25936 path is an empty string.
25939 A component of the path is not a directory.
25942 @var{pathnameptr} is an invalid pointer value.
25945 No access to the file or the path of the file.
25948 @var{pathname} was too long.
25951 The call was interrupted by the user.
25957 @unnumberedsubsubsec gettimeofday
25958 @cindex gettimeofday, file-i/o system call
25963 int gettimeofday(struct timeval *tv, void *tz);
25967 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25969 @item Return value:
25970 On success, 0 is returned, -1 otherwise.
25976 @var{tz} is a non-NULL pointer.
25979 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25985 @unnumberedsubsubsec isatty
25986 @cindex isatty, file-i/o system call
25991 int isatty(int fd);
25995 @samp{Fisatty,@var{fd}}
25997 @item Return value:
25998 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
26004 The call was interrupted by the user.
26009 Note that the @code{isatty} call is treated as a special case: it returns
26010 1 to the target if the file descriptor is attached
26011 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
26012 would require implementing @code{ioctl} and would be more complex than
26017 @unnumberedsubsubsec system
26018 @cindex system, file-i/o system call
26023 int system(const char *command);
26027 @samp{Fsystem,@var{commandptr}/@var{len}}
26029 @item Return value:
26030 If @var{len} is zero, the return value indicates whether a shell is
26031 available. A zero return value indicates a shell is not available.
26032 For non-zero @var{len}, the value returned is -1 on error and the
26033 return status of the command otherwise. Only the exit status of the
26034 command is returned, which is extracted from the host's @code{system}
26035 return value by calling @code{WEXITSTATUS(retval)}. In case
26036 @file{/bin/sh} could not be executed, 127 is returned.
26042 The call was interrupted by the user.
26047 @value{GDBN} takes over the full task of calling the necessary host calls
26048 to perform the @code{system} call. The return value of @code{system} on
26049 the host is simplified before it's returned
26050 to the target. Any termination signal information from the child process
26051 is discarded, and the return value consists
26052 entirely of the exit status of the called command.
26054 Due to security concerns, the @code{system} call is by default refused
26055 by @value{GDBN}. The user has to allow this call explicitly with the
26056 @code{set remote system-call-allowed 1} command.
26059 @item set remote system-call-allowed
26060 @kindex set remote system-call-allowed
26061 Control whether to allow the @code{system} calls in the File I/O
26062 protocol for the remote target. The default is zero (disabled).
26064 @item show remote system-call-allowed
26065 @kindex show remote system-call-allowed
26066 Show whether the @code{system} calls are allowed in the File I/O
26070 @node Protocol-specific Representation of Datatypes
26071 @subsection Protocol-specific Representation of Datatypes
26072 @cindex protocol-specific representation of datatypes, in file-i/o protocol
26075 * Integral Datatypes::
26077 * Memory Transfer::
26082 @node Integral Datatypes
26083 @unnumberedsubsubsec Integral Datatypes
26084 @cindex integral datatypes, in file-i/o protocol
26086 The integral datatypes used in the system calls are @code{int},
26087 @code{unsigned int}, @code{long}, @code{unsigned long},
26088 @code{mode_t}, and @code{time_t}.
26090 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
26091 implemented as 32 bit values in this protocol.
26093 @code{long} and @code{unsigned long} are implemented as 64 bit types.
26095 @xref{Limits}, for corresponding MIN and MAX values (similar to those
26096 in @file{limits.h}) to allow range checking on host and target.
26098 @code{time_t} datatypes are defined as seconds since the Epoch.
26100 All integral datatypes transferred as part of a memory read or write of a
26101 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
26104 @node Pointer Values
26105 @unnumberedsubsubsec Pointer Values
26106 @cindex pointer values, in file-i/o protocol
26108 Pointers to target data are transmitted as they are. An exception
26109 is made for pointers to buffers for which the length isn't
26110 transmitted as part of the function call, namely strings. Strings
26111 are transmitted as a pointer/length pair, both as hex values, e.g.@:
26118 which is a pointer to data of length 18 bytes at position 0x1aaf.
26119 The length is defined as the full string length in bytes, including
26120 the trailing null byte. For example, the string @code{"hello world"}
26121 at address 0x123456 is transmitted as
26127 @node Memory Transfer
26128 @unnumberedsubsubsec Memory Transfer
26129 @cindex memory transfer, in file-i/o protocol
26131 Structured data which is transferred using a memory read or write (for
26132 example, a @code{struct stat}) is expected to be in a protocol-specific format
26133 with all scalar multibyte datatypes being big endian. Translation to
26134 this representation needs to be done both by the target before the @code{F}
26135 packet is sent, and by @value{GDBN} before
26136 it transfers memory to the target. Transferred pointers to structured
26137 data should point to the already-coerced data at any time.
26141 @unnumberedsubsubsec struct stat
26142 @cindex struct stat, in file-i/o protocol
26144 The buffer of type @code{struct stat} used by the target and @value{GDBN}
26145 is defined as follows:
26149 unsigned int st_dev; /* device */
26150 unsigned int st_ino; /* inode */
26151 mode_t st_mode; /* protection */
26152 unsigned int st_nlink; /* number of hard links */
26153 unsigned int st_uid; /* user ID of owner */
26154 unsigned int st_gid; /* group ID of owner */
26155 unsigned int st_rdev; /* device type (if inode device) */
26156 unsigned long st_size; /* total size, in bytes */
26157 unsigned long st_blksize; /* blocksize for filesystem I/O */
26158 unsigned long st_blocks; /* number of blocks allocated */
26159 time_t st_atime; /* time of last access */
26160 time_t st_mtime; /* time of last modification */
26161 time_t st_ctime; /* time of last change */
26165 The integral datatypes conform to the definitions given in the
26166 appropriate section (see @ref{Integral Datatypes}, for details) so this
26167 structure is of size 64 bytes.
26169 The values of several fields have a restricted meaning and/or
26175 A value of 0 represents a file, 1 the console.
26178 No valid meaning for the target. Transmitted unchanged.
26181 Valid mode bits are described in @ref{Constants}. Any other
26182 bits have currently no meaning for the target.
26187 No valid meaning for the target. Transmitted unchanged.
26192 These values have a host and file system dependent
26193 accuracy. Especially on Windows hosts, the file system may not
26194 support exact timing values.
26197 The target gets a @code{struct stat} of the above representation and is
26198 responsible for coercing it to the target representation before
26201 Note that due to size differences between the host, target, and protocol
26202 representations of @code{struct stat} members, these members could eventually
26203 get truncated on the target.
26205 @node struct timeval
26206 @unnumberedsubsubsec struct timeval
26207 @cindex struct timeval, in file-i/o protocol
26209 The buffer of type @code{struct timeval} used by the File-I/O protocol
26210 is defined as follows:
26214 time_t tv_sec; /* second */
26215 long tv_usec; /* microsecond */
26219 The integral datatypes conform to the definitions given in the
26220 appropriate section (see @ref{Integral Datatypes}, for details) so this
26221 structure is of size 8 bytes.
26224 @subsection Constants
26225 @cindex constants, in file-i/o protocol
26227 The following values are used for the constants inside of the
26228 protocol. @value{GDBN} and target are responsible for translating these
26229 values before and after the call as needed.
26240 @unnumberedsubsubsec Open Flags
26241 @cindex open flags, in file-i/o protocol
26243 All values are given in hexadecimal representation.
26255 @node mode_t Values
26256 @unnumberedsubsubsec mode_t Values
26257 @cindex mode_t values, in file-i/o protocol
26259 All values are given in octal representation.
26276 @unnumberedsubsubsec Errno Values
26277 @cindex errno values, in file-i/o protocol
26279 All values are given in decimal representation.
26304 @code{EUNKNOWN} is used as a fallback error value if a host system returns
26305 any error value not in the list of supported error numbers.
26308 @unnumberedsubsubsec Lseek Flags
26309 @cindex lseek flags, in file-i/o protocol
26318 @unnumberedsubsubsec Limits
26319 @cindex limits, in file-i/o protocol
26321 All values are given in decimal representation.
26324 INT_MIN -2147483648
26326 UINT_MAX 4294967295
26327 LONG_MIN -9223372036854775808
26328 LONG_MAX 9223372036854775807
26329 ULONG_MAX 18446744073709551615
26332 @node File-I/O Examples
26333 @subsection File-I/O Examples
26334 @cindex file-i/o examples
26336 Example sequence of a write call, file descriptor 3, buffer is at target
26337 address 0x1234, 6 bytes should be written:
26340 <- @code{Fwrite,3,1234,6}
26341 @emph{request memory read from target}
26344 @emph{return "6 bytes written"}
26348 Example sequence of a read call, file descriptor 3, buffer is at target
26349 address 0x1234, 6 bytes should be read:
26352 <- @code{Fread,3,1234,6}
26353 @emph{request memory write to target}
26354 -> @code{X1234,6:XXXXXX}
26355 @emph{return "6 bytes read"}
26359 Example sequence of a read call, call fails on the host due to invalid
26360 file descriptor (@code{EBADF}):
26363 <- @code{Fread,3,1234,6}
26367 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
26371 <- @code{Fread,3,1234,6}
26376 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
26380 <- @code{Fread,3,1234,6}
26381 -> @code{X1234,6:XXXXXX}
26385 @node Library List Format
26386 @section Library List Format
26387 @cindex library list format, remote protocol
26389 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
26390 same process as your application to manage libraries. In this case,
26391 @value{GDBN} can use the loader's symbol table and normal memory
26392 operations to maintain a list of shared libraries. On other
26393 platforms, the operating system manages loaded libraries.
26394 @value{GDBN} can not retrieve the list of currently loaded libraries
26395 through memory operations, so it uses the @samp{qXfer:libraries:read}
26396 packet (@pxref{qXfer library list read}) instead. The remote stub
26397 queries the target's operating system and reports which libraries
26400 The @samp{qXfer:libraries:read} packet returns an XML document which
26401 lists loaded libraries and their offsets. Each library has an
26402 associated name and one or more segment or section base addresses,
26403 which report where the library was loaded in memory.
26405 For the common case of libraries that are fully linked binaries, the
26406 library should have a list of segments. If the target supports
26407 dynamic linking of a relocatable object file, its library XML element
26408 should instead include a list of allocated sections. The segment or
26409 section bases are start addresses, not relocation offsets; they do not
26410 depend on the library's link-time base addresses.
26412 @value{GDBN} must be linked with the Expat library to support XML
26413 library lists. @xref{Expat}.
26415 A simple memory map, with one loaded library relocated by a single
26416 offset, looks like this:
26420 <library name="/lib/libc.so.6">
26421 <segment address="0x10000000"/>
26426 Another simple memory map, with one loaded library with three
26427 allocated sections (.text, .data, .bss), looks like this:
26431 <library name="sharedlib.o">
26432 <section address="0x10000000"/>
26433 <section address="0x20000000"/>
26434 <section address="0x30000000"/>
26439 The format of a library list is described by this DTD:
26442 <!-- library-list: Root element with versioning -->
26443 <!ELEMENT library-list (library)*>
26444 <!ATTLIST library-list version CDATA #FIXED "1.0">
26445 <!ELEMENT library (segment*, section*)>
26446 <!ATTLIST library name CDATA #REQUIRED>
26447 <!ELEMENT segment EMPTY>
26448 <!ATTLIST segment address CDATA #REQUIRED>
26449 <!ELEMENT section EMPTY>
26450 <!ATTLIST section address CDATA #REQUIRED>
26453 In addition, segments and section descriptors cannot be mixed within a
26454 single library element, and you must supply at least one segment or
26455 section for each library.
26457 @node Memory Map Format
26458 @section Memory Map Format
26459 @cindex memory map format
26461 To be able to write into flash memory, @value{GDBN} needs to obtain a
26462 memory map from the target. This section describes the format of the
26465 The memory map is obtained using the @samp{qXfer:memory-map:read}
26466 (@pxref{qXfer memory map read}) packet and is an XML document that
26467 lists memory regions.
26469 @value{GDBN} must be linked with the Expat library to support XML
26470 memory maps. @xref{Expat}.
26472 The top-level structure of the document is shown below:
26475 <?xml version="1.0"?>
26476 <!DOCTYPE memory-map
26477 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
26478 "http://sourceware.org/gdb/gdb-memory-map.dtd">
26484 Each region can be either:
26489 A region of RAM starting at @var{addr} and extending for @var{length}
26493 <memory type="ram" start="@var{addr}" length="@var{length}"/>
26498 A region of read-only memory:
26501 <memory type="rom" start="@var{addr}" length="@var{length}"/>
26506 A region of flash memory, with erasure blocks @var{blocksize}
26510 <memory type="flash" start="@var{addr}" length="@var{length}">
26511 <property name="blocksize">@var{blocksize}</property>
26517 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
26518 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
26519 packets to write to addresses in such ranges.
26521 The formal DTD for memory map format is given below:
26524 <!-- ................................................... -->
26525 <!-- Memory Map XML DTD ................................ -->
26526 <!-- File: memory-map.dtd .............................. -->
26527 <!-- .................................... .............. -->
26528 <!-- memory-map.dtd -->
26529 <!-- memory-map: Root element with versioning -->
26530 <!ELEMENT memory-map (memory | property)>
26531 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
26532 <!ELEMENT memory (property)>
26533 <!-- memory: Specifies a memory region,
26534 and its type, or device. -->
26535 <!ATTLIST memory type CDATA #REQUIRED
26536 start CDATA #REQUIRED
26537 length CDATA #REQUIRED
26538 device CDATA #IMPLIED>
26539 <!-- property: Generic attribute tag -->
26540 <!ELEMENT property (#PCDATA | property)*>
26541 <!ATTLIST property name CDATA #REQUIRED>
26544 @include agentexpr.texi
26546 @node Target Descriptions
26547 @appendix Target Descriptions
26548 @cindex target descriptions
26550 @strong{Warning:} target descriptions are still under active development,
26551 and the contents and format may change between @value{GDBN} releases.
26552 The format is expected to stabilize in the future.
26554 One of the challenges of using @value{GDBN} to debug embedded systems
26555 is that there are so many minor variants of each processor
26556 architecture in use. It is common practice for vendors to start with
26557 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
26558 and then make changes to adapt it to a particular market niche. Some
26559 architectures have hundreds of variants, available from dozens of
26560 vendors. This leads to a number of problems:
26564 With so many different customized processors, it is difficult for
26565 the @value{GDBN} maintainers to keep up with the changes.
26567 Since individual variants may have short lifetimes or limited
26568 audiences, it may not be worthwhile to carry information about every
26569 variant in the @value{GDBN} source tree.
26571 When @value{GDBN} does support the architecture of the embedded system
26572 at hand, the task of finding the correct architecture name to give the
26573 @command{set architecture} command can be error-prone.
26576 To address these problems, the @value{GDBN} remote protocol allows a
26577 target system to not only identify itself to @value{GDBN}, but to
26578 actually describe its own features. This lets @value{GDBN} support
26579 processor variants it has never seen before --- to the extent that the
26580 descriptions are accurate, and that @value{GDBN} understands them.
26582 @value{GDBN} must be linked with the Expat library to support XML
26583 target descriptions. @xref{Expat}.
26586 * Retrieving Descriptions:: How descriptions are fetched from a target.
26587 * Target Description Format:: The contents of a target description.
26588 * Predefined Target Types:: Standard types available for target
26590 * Standard Target Features:: Features @value{GDBN} knows about.
26593 @node Retrieving Descriptions
26594 @section Retrieving Descriptions
26596 Target descriptions can be read from the target automatically, or
26597 specified by the user manually. The default behavior is to read the
26598 description from the target. @value{GDBN} retrieves it via the remote
26599 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
26600 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
26601 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
26602 XML document, of the form described in @ref{Target Description
26605 Alternatively, you can specify a file to read for the target description.
26606 If a file is set, the target will not be queried. The commands to
26607 specify a file are:
26610 @cindex set tdesc filename
26611 @item set tdesc filename @var{path}
26612 Read the target description from @var{path}.
26614 @cindex unset tdesc filename
26615 @item unset tdesc filename
26616 Do not read the XML target description from a file. @value{GDBN}
26617 will use the description supplied by the current target.
26619 @cindex show tdesc filename
26620 @item show tdesc filename
26621 Show the filename to read for a target description, if any.
26625 @node Target Description Format
26626 @section Target Description Format
26627 @cindex target descriptions, XML format
26629 A target description annex is an @uref{http://www.w3.org/XML/, XML}
26630 document which complies with the Document Type Definition provided in
26631 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
26632 means you can use generally available tools like @command{xmllint} to
26633 check that your feature descriptions are well-formed and valid.
26634 However, to help people unfamiliar with XML write descriptions for
26635 their targets, we also describe the grammar here.
26637 Target descriptions can identify the architecture of the remote target
26638 and (for some architectures) provide information about custom register
26639 sets. @value{GDBN} can use this information to autoconfigure for your
26640 target, or to warn you if you connect to an unsupported target.
26642 Here is a simple target description:
26645 <target version="1.0">
26646 <architecture>i386:x86-64</architecture>
26651 This minimal description only says that the target uses
26652 the x86-64 architecture.
26654 A target description has the following overall form, with [ ] marking
26655 optional elements and @dots{} marking repeatable elements. The elements
26656 are explained further below.
26659 <?xml version="1.0"?>
26660 <!DOCTYPE target SYSTEM "gdb-target.dtd">
26661 <target version="1.0">
26662 @r{[}@var{architecture}@r{]}
26663 @r{[}@var{feature}@dots{}@r{]}
26668 The description is generally insensitive to whitespace and line
26669 breaks, under the usual common-sense rules. The XML version
26670 declaration and document type declaration can generally be omitted
26671 (@value{GDBN} does not require them), but specifying them may be
26672 useful for XML validation tools. The @samp{version} attribute for
26673 @samp{<target>} may also be omitted, but we recommend
26674 including it; if future versions of @value{GDBN} use an incompatible
26675 revision of @file{gdb-target.dtd}, they will detect and report
26676 the version mismatch.
26678 @subsection Inclusion
26679 @cindex target descriptions, inclusion
26682 @cindex <xi:include>
26685 It can sometimes be valuable to split a target description up into
26686 several different annexes, either for organizational purposes, or to
26687 share files between different possible target descriptions. You can
26688 divide a description into multiple files by replacing any element of
26689 the target description with an inclusion directive of the form:
26692 <xi:include href="@var{document}"/>
26696 When @value{GDBN} encounters an element of this form, it will retrieve
26697 the named XML @var{document}, and replace the inclusion directive with
26698 the contents of that document. If the current description was read
26699 using @samp{qXfer}, then so will be the included document;
26700 @var{document} will be interpreted as the name of an annex. If the
26701 current description was read from a file, @value{GDBN} will look for
26702 @var{document} as a file in the same directory where it found the
26703 original description.
26705 @subsection Architecture
26706 @cindex <architecture>
26708 An @samp{<architecture>} element has this form:
26711 <architecture>@var{arch}</architecture>
26714 @var{arch} is an architecture name from the same selection
26715 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
26716 Debugging Target}).
26718 @subsection Features
26721 Each @samp{<feature>} describes some logical portion of the target
26722 system. Features are currently used to describe available CPU
26723 registers and the types of their contents. A @samp{<feature>} element
26727 <feature name="@var{name}">
26728 @r{[}@var{type}@dots{}@r{]}
26734 Each feature's name should be unique within the description. The name
26735 of a feature does not matter unless @value{GDBN} has some special
26736 knowledge of the contents of that feature; if it does, the feature
26737 should have its standard name. @xref{Standard Target Features}.
26741 Any register's value is a collection of bits which @value{GDBN} must
26742 interpret. The default interpretation is a two's complement integer,
26743 but other types can be requested by name in the register description.
26744 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
26745 Target Types}), and the description can define additional composite types.
26747 Each type element must have an @samp{id} attribute, which gives
26748 a unique (within the containing @samp{<feature>}) name to the type.
26749 Types must be defined before they are used.
26752 Some targets offer vector registers, which can be treated as arrays
26753 of scalar elements. These types are written as @samp{<vector>} elements,
26754 specifying the array element type, @var{type}, and the number of elements,
26758 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
26762 If a register's value is usefully viewed in multiple ways, define it
26763 with a union type containing the useful representations. The
26764 @samp{<union>} element contains one or more @samp{<field>} elements,
26765 each of which has a @var{name} and a @var{type}:
26768 <union id="@var{id}">
26769 <field name="@var{name}" type="@var{type}"/>
26774 @subsection Registers
26777 Each register is represented as an element with this form:
26780 <reg name="@var{name}"
26781 bitsize="@var{size}"
26782 @r{[}regnum="@var{num}"@r{]}
26783 @r{[}save-restore="@var{save-restore}"@r{]}
26784 @r{[}type="@var{type}"@r{]}
26785 @r{[}group="@var{group}"@r{]}/>
26789 The components are as follows:
26794 The register's name; it must be unique within the target description.
26797 The register's size, in bits.
26800 The register's number. If omitted, a register's number is one greater
26801 than that of the previous register (either in the current feature or in
26802 a preceeding feature); the first register in the target description
26803 defaults to zero. This register number is used to read or write
26804 the register; e.g.@: it is used in the remote @code{p} and @code{P}
26805 packets, and registers appear in the @code{g} and @code{G} packets
26806 in order of increasing register number.
26809 Whether the register should be preserved across inferior function
26810 calls; this must be either @code{yes} or @code{no}. The default is
26811 @code{yes}, which is appropriate for most registers except for
26812 some system control registers; this is not related to the target's
26816 The type of the register. @var{type} may be a predefined type, a type
26817 defined in the current feature, or one of the special types @code{int}
26818 and @code{float}. @code{int} is an integer type of the correct size
26819 for @var{bitsize}, and @code{float} is a floating point type (in the
26820 architecture's normal floating point format) of the correct size for
26821 @var{bitsize}. The default is @code{int}.
26824 The register group to which this register belongs. @var{group} must
26825 be either @code{general}, @code{float}, or @code{vector}. If no
26826 @var{group} is specified, @value{GDBN} will not display the register
26827 in @code{info registers}.
26831 @node Predefined Target Types
26832 @section Predefined Target Types
26833 @cindex target descriptions, predefined types
26835 Type definitions in the self-description can build up composite types
26836 from basic building blocks, but can not define fundamental types. Instead,
26837 standard identifiers are provided by @value{GDBN} for the fundamental
26838 types. The currently supported types are:
26847 Signed integer types holding the specified number of bits.
26854 Unsigned integer types holding the specified number of bits.
26858 Pointers to unspecified code and data. The program counter and
26859 any dedicated return address register may be marked as code
26860 pointers; printing a code pointer converts it into a symbolic
26861 address. The stack pointer and any dedicated address registers
26862 may be marked as data pointers.
26865 Single precision IEEE floating point.
26868 Double precision IEEE floating point.
26871 The 12-byte extended precision format used by ARM FPA registers.
26875 @node Standard Target Features
26876 @section Standard Target Features
26877 @cindex target descriptions, standard features
26879 A target description must contain either no registers or all the
26880 target's registers. If the description contains no registers, then
26881 @value{GDBN} will assume a default register layout, selected based on
26882 the architecture. If the description contains any registers, the
26883 default layout will not be used; the standard registers must be
26884 described in the target description, in such a way that @value{GDBN}
26885 can recognize them.
26887 This is accomplished by giving specific names to feature elements
26888 which contain standard registers. @value{GDBN} will look for features
26889 with those names and verify that they contain the expected registers;
26890 if any known feature is missing required registers, or if any required
26891 feature is missing, @value{GDBN} will reject the target
26892 description. You can add additional registers to any of the
26893 standard features --- @value{GDBN} will display them just as if
26894 they were added to an unrecognized feature.
26896 This section lists the known features and their expected contents.
26897 Sample XML documents for these features are included in the
26898 @value{GDBN} source tree, in the directory @file{gdb/features}.
26900 Names recognized by @value{GDBN} should include the name of the
26901 company or organization which selected the name, and the overall
26902 architecture to which the feature applies; so e.g.@: the feature
26903 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
26905 The names of registers are not case sensitive for the purpose
26906 of recognizing standard features, but @value{GDBN} will only display
26907 registers using the capitalization used in the description.
26913 * PowerPC Features::
26918 @subsection ARM Features
26919 @cindex target descriptions, ARM features
26921 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
26922 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
26923 @samp{lr}, @samp{pc}, and @samp{cpsr}.
26925 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
26926 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
26928 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
26929 it should contain at least registers @samp{wR0} through @samp{wR15} and
26930 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
26931 @samp{wCSSF}, and @samp{wCASF} registers are optional.
26933 @node MIPS Features
26934 @subsection MIPS Features
26935 @cindex target descriptions, MIPS features
26937 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
26938 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
26939 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
26942 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
26943 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
26944 registers. They may be 32-bit or 64-bit depending on the target.
26946 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
26947 it may be optional in a future version of @value{GDBN}. It should
26948 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
26949 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
26951 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
26952 contain a single register, @samp{restart}, which is used by the
26953 Linux kernel to control restartable syscalls.
26955 @node M68K Features
26956 @subsection M68K Features
26957 @cindex target descriptions, M68K features
26960 @item @samp{org.gnu.gdb.m68k.core}
26961 @itemx @samp{org.gnu.gdb.coldfire.core}
26962 @itemx @samp{org.gnu.gdb.fido.core}
26963 One of those features must be always present.
26964 The feature that is present determines which flavor of m86k is
26965 used. The feature that is present should contain registers
26966 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
26967 @samp{sp}, @samp{ps} and @samp{pc}.
26969 @item @samp{org.gnu.gdb.coldfire.fp}
26970 This feature is optional. If present, it should contain registers
26971 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
26975 @node PowerPC Features
26976 @subsection PowerPC Features
26977 @cindex target descriptions, PowerPC features
26979 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
26980 targets. It should contain registers @samp{r0} through @samp{r31},
26981 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
26982 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
26984 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
26985 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
26987 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
26988 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
26991 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
26992 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
26993 @samp{spefscr}. SPE targets should provide 32-bit registers in
26994 @samp{org.gnu.gdb.power.core} and provide the upper halves in
26995 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
26996 these to present registers @samp{ev0} through @samp{ev31} to the
27011 % I think something like @colophon should be in texinfo. In the
27013 \long\def\colophon{\hbox to0pt{}\vfill
27014 \centerline{The body of this manual is set in}
27015 \centerline{\fontname\tenrm,}
27016 \centerline{with headings in {\bf\fontname\tenbf}}
27017 \centerline{and examples in {\tt\fontname\tentt}.}
27018 \centerline{{\it\fontname\tenit\/},}
27019 \centerline{{\bf\fontname\tenbf}, and}
27020 \centerline{{\sl\fontname\tensl\/}}
27021 \centerline{are used for emphasis.}\vfill}
27023 % Blame: doc@cygnus.com, 1991.