1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
66 this GNU Manual. Buying copies from GNU Press supports the FSF in
67 developing GNU and promoting software freedom.''
71 @title Debugging with @value{GDBN}
72 @subtitle The @sc{gnu} Source-Level Debugger
74 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
75 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
79 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
80 \hfill {\it Debugging with @value{GDBN}}\par
81 \hfill \TeX{}info \texinfoversion\par
85 @vskip 0pt plus 1filll
86 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
87 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
88 Free Software Foundation, Inc.
90 Published by the Free Software Foundation @*
91 51 Franklin Street, Fifth Floor,
92 Boston, MA 02110-1301, USA@*
95 Permission is granted to copy, distribute and/or modify this document
96 under the terms of the GNU Free Documentation License, Version 1.1 or
97 any later version published by the Free Software Foundation; with the
98 Invariant Sections being ``Free Software'' and ``Free Software Needs
99 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
100 and with the Back-Cover Texts as in (a) below.
102 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
103 this GNU Manual. Buying copies from GNU Press supports the FSF in
104 developing GNU and promoting software freedom.''
106 This edition of the GDB manual is dedicated to the memory of Fred
107 Fish. Fred was a long-standing contributor to GDB and to Free
108 software in general. We will miss him.
113 @node Top, Summary, (dir), (dir)
115 @top Debugging with @value{GDBN}
117 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
119 This is the @value{EDITION} Edition, for @value{GDBN} Version
122 Copyright (C) 1988-2006 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Stack:: Examining the stack
137 * Source:: Examining source files
138 * Data:: Examining data
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Sequences:: Canned sequences of commands
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
159 * GDB Bugs:: Reporting bugs in @value{GDBN}
161 * Command Line Editing:: Command Line Editing
162 * Using History Interactively:: Using History Interactively
163 * Formatting Documentation:: How to format and print @value{GDBN} documentation
164 * Installing GDB:: Installing GDB
165 * Maintenance Commands:: Maintenance Commands
166 * Remote Protocol:: GDB Remote Serial Protocol
167 * Agent Expressions:: The GDB Agent Expression Mechanism
168 * Target Descriptions:: How targets can describe themselves to
170 * Copying:: GNU General Public License says
171 how you can copy and share GDB
172 * GNU Free Documentation License:: The license for this documentation
181 @unnumbered Summary of @value{GDBN}
183 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
184 going on ``inside'' another program while it executes---or what another
185 program was doing at the moment it crashed.
187 @value{GDBN} can do four main kinds of things (plus other things in support of
188 these) to help you catch bugs in the act:
192 Start your program, specifying anything that might affect its behavior.
195 Make your program stop on specified conditions.
198 Examine what has happened, when your program has stopped.
201 Change things in your program, so you can experiment with correcting the
202 effects of one bug and go on to learn about another.
205 You can use @value{GDBN} to debug programs written in C and C@t{++}.
206 For more information, see @ref{Supported Languages,,Supported Languages}.
207 For more information, see @ref{C,,C and C++}.
210 Support for Modula-2 is partial. For information on Modula-2, see
211 @ref{Modula-2,,Modula-2}.
214 Debugging Pascal programs which use sets, subranges, file variables, or
215 nested functions does not currently work. @value{GDBN} does not support
216 entering expressions, printing values, or similar features using Pascal
220 @value{GDBN} can be used to debug programs written in Fortran, although
221 it may be necessary to refer to some variables with a trailing
224 @value{GDBN} can be used to debug programs written in Objective-C,
225 using either the Apple/NeXT or the GNU Objective-C runtime.
228 * Free Software:: Freely redistributable software
229 * Contributors:: Contributors to GDB
233 @unnumberedsec Free Software
235 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
236 General Public License
237 (GPL). The GPL gives you the freedom to copy or adapt a licensed
238 program---but every person getting a copy also gets with it the
239 freedom to modify that copy (which means that they must get access to
240 the source code), and the freedom to distribute further copies.
241 Typical software companies use copyrights to limit your freedoms; the
242 Free Software Foundation uses the GPL to preserve these freedoms.
244 Fundamentally, the General Public License is a license which says that
245 you have these freedoms and that you cannot take these freedoms away
248 @unnumberedsec Free Software Needs Free Documentation
250 The biggest deficiency in the free software community today is not in
251 the software---it is the lack of good free documentation that we can
252 include with the free software. Many of our most important
253 programs do not come with free reference manuals and free introductory
254 texts. Documentation is an essential part of any software package;
255 when an important free software package does not come with a free
256 manual and a free tutorial, that is a major gap. We have many such
259 Consider Perl, for instance. The tutorial manuals that people
260 normally use are non-free. How did this come about? Because the
261 authors of those manuals published them with restrictive terms---no
262 copying, no modification, source files not available---which exclude
263 them from the free software world.
265 That wasn't the first time this sort of thing happened, and it was far
266 from the last. Many times we have heard a GNU user eagerly describe a
267 manual that he is writing, his intended contribution to the community,
268 only to learn that he had ruined everything by signing a publication
269 contract to make it non-free.
271 Free documentation, like free software, is a matter of freedom, not
272 price. The problem with the non-free manual is not that publishers
273 charge a price for printed copies---that in itself is fine. (The Free
274 Software Foundation sells printed copies of manuals, too.) The
275 problem is the restrictions on the use of the manual. Free manuals
276 are available in source code form, and give you permission to copy and
277 modify. Non-free manuals do not allow this.
279 The criteria of freedom for a free manual are roughly the same as for
280 free software. Redistribution (including the normal kinds of
281 commercial redistribution) must be permitted, so that the manual can
282 accompany every copy of the program, both on-line and on paper.
284 Permission for modification of the technical content is crucial too.
285 When people modify the software, adding or changing features, if they
286 are conscientious they will change the manual too---so they can
287 provide accurate and clear documentation for the modified program. A
288 manual that leaves you no choice but to write a new manual to document
289 a changed version of the program is not really available to our
292 Some kinds of limits on the way modification is handled are
293 acceptable. For example, requirements to preserve the original
294 author's copyright notice, the distribution terms, or the list of
295 authors, are ok. It is also no problem to require modified versions
296 to include notice that they were modified. Even entire sections that
297 may not be deleted or changed are acceptable, as long as they deal
298 with nontechnical topics (like this one). These kinds of restrictions
299 are acceptable because they don't obstruct the community's normal use
302 However, it must be possible to modify all the @emph{technical}
303 content of the manual, and then distribute the result in all the usual
304 media, through all the usual channels. Otherwise, the restrictions
305 obstruct the use of the manual, it is not free, and we need another
306 manual to replace it.
308 Please spread the word about this issue. Our community continues to
309 lose manuals to proprietary publishing. If we spread the word that
310 free software needs free reference manuals and free tutorials, perhaps
311 the next person who wants to contribute by writing documentation will
312 realize, before it is too late, that only free manuals contribute to
313 the free software community.
315 If you are writing documentation, please insist on publishing it under
316 the GNU Free Documentation License or another free documentation
317 license. Remember that this decision requires your approval---you
318 don't have to let the publisher decide. Some commercial publishers
319 will use a free license if you insist, but they will not propose the
320 option; it is up to you to raise the issue and say firmly that this is
321 what you want. If the publisher you are dealing with refuses, please
322 try other publishers. If you're not sure whether a proposed license
323 is free, write to @email{licensing@@gnu.org}.
325 You can encourage commercial publishers to sell more free, copylefted
326 manuals and tutorials by buying them, and particularly by buying
327 copies from the publishers that paid for their writing or for major
328 improvements. Meanwhile, try to avoid buying non-free documentation
329 at all. Check the distribution terms of a manual before you buy it,
330 and insist that whoever seeks your business must respect your freedom.
331 Check the history of the book, and try to reward the publishers that
332 have paid or pay the authors to work on it.
334 The Free Software Foundation maintains a list of free documentation
335 published by other publishers, at
336 @url{http://www.fsf.org/doc/other-free-books.html}.
339 @unnumberedsec Contributors to @value{GDBN}
341 Richard Stallman was the original author of @value{GDBN}, and of many
342 other @sc{gnu} programs. Many others have contributed to its
343 development. This section attempts to credit major contributors. One
344 of the virtues of free software is that everyone is free to contribute
345 to it; with regret, we cannot actually acknowledge everyone here. The
346 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
347 blow-by-blow account.
349 Changes much prior to version 2.0 are lost in the mists of time.
352 @emph{Plea:} Additions to this section are particularly welcome. If you
353 or your friends (or enemies, to be evenhanded) have been unfairly
354 omitted from this list, we would like to add your names!
357 So that they may not regard their many labors as thankless, we
358 particularly thank those who shepherded @value{GDBN} through major
360 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
361 Jim Blandy (release 4.18);
362 Jason Molenda (release 4.17);
363 Stan Shebs (release 4.14);
364 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
365 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
366 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
367 Jim Kingdon (releases 3.5, 3.4, and 3.3);
368 and Randy Smith (releases 3.2, 3.1, and 3.0).
370 Richard Stallman, assisted at various times by Peter TerMaat, Chris
371 Hanson, and Richard Mlynarik, handled releases through 2.8.
373 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
374 in @value{GDBN}, with significant additional contributions from Per
375 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
376 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
377 much general update work leading to release 3.0).
379 @value{GDBN} uses the BFD subroutine library to examine multiple
380 object-file formats; BFD was a joint project of David V.
381 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
383 David Johnson wrote the original COFF support; Pace Willison did
384 the original support for encapsulated COFF.
386 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
388 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
389 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
391 Jean-Daniel Fekete contributed Sun 386i support.
392 Chris Hanson improved the HP9000 support.
393 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
394 David Johnson contributed Encore Umax support.
395 Jyrki Kuoppala contributed Altos 3068 support.
396 Jeff Law contributed HP PA and SOM support.
397 Keith Packard contributed NS32K support.
398 Doug Rabson contributed Acorn Risc Machine support.
399 Bob Rusk contributed Harris Nighthawk CX-UX support.
400 Chris Smith contributed Convex support (and Fortran debugging).
401 Jonathan Stone contributed Pyramid support.
402 Michael Tiemann contributed SPARC support.
403 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
404 Pace Willison contributed Intel 386 support.
405 Jay Vosburgh contributed Symmetry support.
406 Marko Mlinar contributed OpenRISC 1000 support.
408 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
410 Rich Schaefer and Peter Schauer helped with support of SunOS shared
413 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
414 about several machine instruction sets.
416 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
417 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
418 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
419 and RDI targets, respectively.
421 Brian Fox is the author of the readline libraries providing
422 command-line editing and command history.
424 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
425 Modula-2 support, and contributed the Languages chapter of this manual.
427 Fred Fish wrote most of the support for Unix System Vr4.
428 He also enhanced the command-completion support to cover C@t{++} overloaded
431 Hitachi America (now Renesas America), Ltd. sponsored the support for
432 H8/300, H8/500, and Super-H processors.
434 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
436 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
439 Toshiba sponsored the support for the TX39 Mips processor.
441 Matsushita sponsored the support for the MN10200 and MN10300 processors.
443 Fujitsu sponsored the support for SPARClite and FR30 processors.
445 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
448 Michael Snyder added support for tracepoints.
450 Stu Grossman wrote gdbserver.
452 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
453 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
455 The following people at the Hewlett-Packard Company contributed
456 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
457 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
458 compiler, and the Text User Interface (nee Terminal User Interface):
459 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
460 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
461 provided HP-specific information in this manual.
463 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
464 Robert Hoehne made significant contributions to the DJGPP port.
466 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
467 development since 1991. Cygnus engineers who have worked on @value{GDBN}
468 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
469 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
470 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
471 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
472 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
473 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
474 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
475 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
476 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
477 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
478 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
479 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
480 Zuhn have made contributions both large and small.
482 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
483 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
485 Jim Blandy added support for preprocessor macros, while working for Red
488 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
489 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
490 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
491 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
492 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
493 with the migration of old architectures to this new framework.
495 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
496 unwinder framework, this consisting of a fresh new design featuring
497 frame IDs, independent frame sniffers, and the sentinel frame. Mark
498 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
499 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
500 trad unwinders. The architecture-specific changes, each involving a
501 complete rewrite of the architecture's frame code, were carried out by
502 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
503 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
504 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
505 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
508 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
509 Tensilica, Inc.@: contributed support for Xtensa processors. Others
510 who have worked on the Xtensa port of @value{GDBN} in the past include
511 Steve Tjiang, John Newlin, and Scott Foehner.
514 @chapter A Sample @value{GDBN} Session
516 You can use this manual at your leisure to read all about @value{GDBN}.
517 However, a handful of commands are enough to get started using the
518 debugger. This chapter illustrates those commands.
521 In this sample session, we emphasize user input like this: @b{input},
522 to make it easier to pick out from the surrounding output.
525 @c FIXME: this example may not be appropriate for some configs, where
526 @c FIXME...primary interest is in remote use.
528 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
529 processor) exhibits the following bug: sometimes, when we change its
530 quote strings from the default, the commands used to capture one macro
531 definition within another stop working. In the following short @code{m4}
532 session, we define a macro @code{foo} which expands to @code{0000}; we
533 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
534 same thing. However, when we change the open quote string to
535 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
536 procedure fails to define a new synonym @code{baz}:
545 @b{define(bar,defn(`foo'))}
549 @b{changequote(<QUOTE>,<UNQUOTE>)}
551 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
554 m4: End of input: 0: fatal error: EOF in string
558 Let us use @value{GDBN} to try to see what is going on.
561 $ @b{@value{GDBP} m4}
562 @c FIXME: this falsifies the exact text played out, to permit smallbook
563 @c FIXME... format to come out better.
564 @value{GDBN} is free software and you are welcome to distribute copies
565 of it under certain conditions; type "show copying" to see
567 There is absolutely no warranty for @value{GDBN}; type "show warranty"
570 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
575 @value{GDBN} reads only enough symbol data to know where to find the
576 rest when needed; as a result, the first prompt comes up very quickly.
577 We now tell @value{GDBN} to use a narrower display width than usual, so
578 that examples fit in this manual.
581 (@value{GDBP}) @b{set width 70}
585 We need to see how the @code{m4} built-in @code{changequote} works.
586 Having looked at the source, we know the relevant subroutine is
587 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
588 @code{break} command.
591 (@value{GDBP}) @b{break m4_changequote}
592 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
596 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
597 control; as long as control does not reach the @code{m4_changequote}
598 subroutine, the program runs as usual:
601 (@value{GDBP}) @b{run}
602 Starting program: /work/Editorial/gdb/gnu/m4/m4
610 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
611 suspends execution of @code{m4}, displaying information about the
612 context where it stops.
615 @b{changequote(<QUOTE>,<UNQUOTE>)}
617 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
619 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
623 Now we use the command @code{n} (@code{next}) to advance execution to
624 the next line of the current function.
628 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
633 @code{set_quotes} looks like a promising subroutine. We can go into it
634 by using the command @code{s} (@code{step}) instead of @code{next}.
635 @code{step} goes to the next line to be executed in @emph{any}
636 subroutine, so it steps into @code{set_quotes}.
640 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
642 530 if (lquote != def_lquote)
646 The display that shows the subroutine where @code{m4} is now
647 suspended (and its arguments) is called a stack frame display. It
648 shows a summary of the stack. We can use the @code{backtrace}
649 command (which can also be spelled @code{bt}), to see where we are
650 in the stack as a whole: the @code{backtrace} command displays a
651 stack frame for each active subroutine.
654 (@value{GDBP}) @b{bt}
655 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
657 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
659 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
660 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
662 #4 0x79dc in expand_input () at macro.c:40
663 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
667 We step through a few more lines to see what happens. The first two
668 times, we can use @samp{s}; the next two times we use @code{n} to avoid
669 falling into the @code{xstrdup} subroutine.
673 0x3b5c 532 if (rquote != def_rquote)
675 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
676 def_lquote : xstrdup(lq);
678 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
681 538 len_lquote = strlen(rquote);
685 The last line displayed looks a little odd; we can examine the variables
686 @code{lquote} and @code{rquote} to see if they are in fact the new left
687 and right quotes we specified. We use the command @code{p}
688 (@code{print}) to see their values.
691 (@value{GDBP}) @b{p lquote}
692 $1 = 0x35d40 "<QUOTE>"
693 (@value{GDBP}) @b{p rquote}
694 $2 = 0x35d50 "<UNQUOTE>"
698 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
699 To look at some context, we can display ten lines of source
700 surrounding the current line with the @code{l} (@code{list}) command.
706 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
708 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
711 538 len_lquote = strlen(rquote);
712 539 len_rquote = strlen(lquote);
719 Let us step past the two lines that set @code{len_lquote} and
720 @code{len_rquote}, and then examine the values of those variables.
724 539 len_rquote = strlen(lquote);
727 (@value{GDBP}) @b{p len_lquote}
729 (@value{GDBP}) @b{p len_rquote}
734 That certainly looks wrong, assuming @code{len_lquote} and
735 @code{len_rquote} are meant to be the lengths of @code{lquote} and
736 @code{rquote} respectively. We can set them to better values using
737 the @code{p} command, since it can print the value of
738 any expression---and that expression can include subroutine calls and
742 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
744 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
749 Is that enough to fix the problem of using the new quotes with the
750 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
751 executing with the @code{c} (@code{continue}) command, and then try the
752 example that caused trouble initially:
758 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
765 Success! The new quotes now work just as well as the default ones. The
766 problem seems to have been just the two typos defining the wrong
767 lengths. We allow @code{m4} exit by giving it an EOF as input:
771 Program exited normally.
775 The message @samp{Program exited normally.} is from @value{GDBN}; it
776 indicates @code{m4} has finished executing. We can end our @value{GDBN}
777 session with the @value{GDBN} @code{quit} command.
780 (@value{GDBP}) @b{quit}
784 @chapter Getting In and Out of @value{GDBN}
786 This chapter discusses how to start @value{GDBN}, and how to get out of it.
790 type @samp{@value{GDBP}} to start @value{GDBN}.
792 type @kbd{quit} or @kbd{Ctrl-d} to exit.
796 * Invoking GDB:: How to start @value{GDBN}
797 * Quitting GDB:: How to quit @value{GDBN}
798 * Shell Commands:: How to use shell commands inside @value{GDBN}
799 * Logging Output:: How to log @value{GDBN}'s output to a file
803 @section Invoking @value{GDBN}
805 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
806 @value{GDBN} reads commands from the terminal until you tell it to exit.
808 You can also run @code{@value{GDBP}} with a variety of arguments and options,
809 to specify more of your debugging environment at the outset.
811 The command-line options described here are designed
812 to cover a variety of situations; in some environments, some of these
813 options may effectively be unavailable.
815 The most usual way to start @value{GDBN} is with one argument,
816 specifying an executable program:
819 @value{GDBP} @var{program}
823 You can also start with both an executable program and a core file
827 @value{GDBP} @var{program} @var{core}
830 You can, instead, specify a process ID as a second argument, if you want
831 to debug a running process:
834 @value{GDBP} @var{program} 1234
838 would attach @value{GDBN} to process @code{1234} (unless you also have a file
839 named @file{1234}; @value{GDBN} does check for a core file first).
841 Taking advantage of the second command-line argument requires a fairly
842 complete operating system; when you use @value{GDBN} as a remote
843 debugger attached to a bare board, there may not be any notion of
844 ``process'', and there is often no way to get a core dump. @value{GDBN}
845 will warn you if it is unable to attach or to read core dumps.
847 You can optionally have @code{@value{GDBP}} pass any arguments after the
848 executable file to the inferior using @code{--args}. This option stops
851 @value{GDBP} --args gcc -O2 -c foo.c
853 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
854 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
856 You can run @code{@value{GDBP}} without printing the front material, which describes
857 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
864 You can further control how @value{GDBN} starts up by using command-line
865 options. @value{GDBN} itself can remind you of the options available.
875 to display all available options and briefly describe their use
876 (@samp{@value{GDBP} -h} is a shorter equivalent).
878 All options and command line arguments you give are processed
879 in sequential order. The order makes a difference when the
880 @samp{-x} option is used.
884 * File Options:: Choosing files
885 * Mode Options:: Choosing modes
886 * Startup:: What @value{GDBN} does during startup
890 @subsection Choosing Files
892 When @value{GDBN} starts, it reads any arguments other than options as
893 specifying an executable file and core file (or process ID). This is
894 the same as if the arguments were specified by the @samp{-se} and
895 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
896 first argument that does not have an associated option flag as
897 equivalent to the @samp{-se} option followed by that argument; and the
898 second argument that does not have an associated option flag, if any, as
899 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
900 If the second argument begins with a decimal digit, @value{GDBN} will
901 first attempt to attach to it as a process, and if that fails, attempt
902 to open it as a corefile. If you have a corefile whose name begins with
903 a digit, you can prevent @value{GDBN} from treating it as a pid by
904 prefixing it with @file{./}, e.g.@: @file{./12345}.
906 If @value{GDBN} has not been configured to included core file support,
907 such as for most embedded targets, then it will complain about a second
908 argument and ignore it.
910 Many options have both long and short forms; both are shown in the
911 following list. @value{GDBN} also recognizes the long forms if you truncate
912 them, so long as enough of the option is present to be unambiguous.
913 (If you prefer, you can flag option arguments with @samp{--} rather
914 than @samp{-}, though we illustrate the more usual convention.)
916 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
917 @c way, both those who look for -foo and --foo in the index, will find
921 @item -symbols @var{file}
923 @cindex @code{--symbols}
925 Read symbol table from file @var{file}.
927 @item -exec @var{file}
929 @cindex @code{--exec}
931 Use file @var{file} as the executable file to execute when appropriate,
932 and for examining pure data in conjunction with a core dump.
936 Read symbol table from file @var{file} and use it as the executable
939 @item -core @var{file}
941 @cindex @code{--core}
943 Use file @var{file} as a core dump to examine.
945 @item -pid @var{number}
946 @itemx -p @var{number}
949 Connect to process ID @var{number}, as with the @code{attach} command.
951 @item -command @var{file}
953 @cindex @code{--command}
955 Execute @value{GDBN} commands from file @var{file}. @xref{Command
956 Files,, Command files}.
958 @item -eval-command @var{command}
959 @itemx -ex @var{command}
960 @cindex @code{--eval-command}
962 Execute a single @value{GDBN} command.
964 This option may be used multiple times to call multiple commands. It may
965 also be interleaved with @samp{-command} as required.
968 @value{GDBP} -ex 'target sim' -ex 'load' \
969 -x setbreakpoints -ex 'run' a.out
972 @item -directory @var{directory}
973 @itemx -d @var{directory}
974 @cindex @code{--directory}
976 Add @var{directory} to the path to search for source and script files.
980 @cindex @code{--readnow}
982 Read each symbol file's entire symbol table immediately, rather than
983 the default, which is to read it incrementally as it is needed.
984 This makes startup slower, but makes future operations faster.
989 @subsection Choosing Modes
991 You can run @value{GDBN} in various alternative modes---for example, in
992 batch mode or quiet mode.
999 Do not execute commands found in any initialization files. Normally,
1000 @value{GDBN} executes the commands in these files after all the command
1001 options and arguments have been processed. @xref{Command Files,,Command
1007 @cindex @code{--quiet}
1008 @cindex @code{--silent}
1010 ``Quiet''. Do not print the introductory and copyright messages. These
1011 messages are also suppressed in batch mode.
1014 @cindex @code{--batch}
1015 Run in batch mode. Exit with status @code{0} after processing all the
1016 command files specified with @samp{-x} (and all commands from
1017 initialization files, if not inhibited with @samp{-n}). Exit with
1018 nonzero status if an error occurs in executing the @value{GDBN} commands
1019 in the command files.
1021 Batch mode may be useful for running @value{GDBN} as a filter, for
1022 example to download and run a program on another computer; in order to
1023 make this more useful, the message
1026 Program exited normally.
1030 (which is ordinarily issued whenever a program running under
1031 @value{GDBN} control terminates) is not issued when running in batch
1035 @cindex @code{--batch-silent}
1036 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1037 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1038 unaffected). This is much quieter than @samp{-silent} and would be useless
1039 for an interactive session.
1041 This is particularly useful when using targets that give @samp{Loading section}
1042 messages, for example.
1044 Note that targets that give their output via @value{GDBN}, as opposed to
1045 writing directly to @code{stdout}, will also be made silent.
1047 @item -return-child-result
1048 @cindex @code{--return-child-result}
1049 The return code from @value{GDBN} will be the return code from the child
1050 process (the process being debugged), with the following exceptions:
1054 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1055 internal error. In this case the exit code is the same as it would have been
1056 without @samp{-return-child-result}.
1058 The user quits with an explicit value. E.g., @samp{quit 1}.
1060 The child process never runs, or is not allowed to terminate, in which case
1061 the exit code will be -1.
1064 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1065 when @value{GDBN} is being used as a remote program loader or simulator
1070 @cindex @code{--nowindows}
1072 ``No windows''. If @value{GDBN} comes with a graphical user interface
1073 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1074 interface. If no GUI is available, this option has no effect.
1078 @cindex @code{--windows}
1080 If @value{GDBN} includes a GUI, then this option requires it to be
1083 @item -cd @var{directory}
1085 Run @value{GDBN} using @var{directory} as its working directory,
1086 instead of the current directory.
1090 @cindex @code{--fullname}
1092 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1093 subprocess. It tells @value{GDBN} to output the full file name and line
1094 number in a standard, recognizable fashion each time a stack frame is
1095 displayed (which includes each time your program stops). This
1096 recognizable format looks like two @samp{\032} characters, followed by
1097 the file name, line number and character position separated by colons,
1098 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1099 @samp{\032} characters as a signal to display the source code for the
1103 @cindex @code{--epoch}
1104 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1105 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1106 routines so as to allow Epoch to display values of expressions in a
1109 @item -annotate @var{level}
1110 @cindex @code{--annotate}
1111 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1112 effect is identical to using @samp{set annotate @var{level}}
1113 (@pxref{Annotations}). The annotation @var{level} controls how much
1114 information @value{GDBN} prints together with its prompt, values of
1115 expressions, source lines, and other types of output. Level 0 is the
1116 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1117 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1118 that control @value{GDBN}, and level 2 has been deprecated.
1120 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1124 @cindex @code{--args}
1125 Change interpretation of command line so that arguments following the
1126 executable file are passed as command line arguments to the inferior.
1127 This option stops option processing.
1129 @item -baud @var{bps}
1131 @cindex @code{--baud}
1133 Set the line speed (baud rate or bits per second) of any serial
1134 interface used by @value{GDBN} for remote debugging.
1136 @item -l @var{timeout}
1138 Set the timeout (in seconds) of any communication used by @value{GDBN}
1139 for remote debugging.
1141 @item -tty @var{device}
1142 @itemx -t @var{device}
1143 @cindex @code{--tty}
1145 Run using @var{device} for your program's standard input and output.
1146 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1148 @c resolve the situation of these eventually
1150 @cindex @code{--tui}
1151 Activate the @dfn{Text User Interface} when starting. The Text User
1152 Interface manages several text windows on the terminal, showing
1153 source, assembly, registers and @value{GDBN} command outputs
1154 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1155 Text User Interface can be enabled by invoking the program
1156 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1157 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1160 @c @cindex @code{--xdb}
1161 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1162 @c For information, see the file @file{xdb_trans.html}, which is usually
1163 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1166 @item -interpreter @var{interp}
1167 @cindex @code{--interpreter}
1168 Use the interpreter @var{interp} for interface with the controlling
1169 program or device. This option is meant to be set by programs which
1170 communicate with @value{GDBN} using it as a back end.
1171 @xref{Interpreters, , Command Interpreters}.
1173 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1174 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1175 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1176 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1177 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1178 @sc{gdb/mi} interfaces are no longer supported.
1181 @cindex @code{--write}
1182 Open the executable and core files for both reading and writing. This
1183 is equivalent to the @samp{set write on} command inside @value{GDBN}
1187 @cindex @code{--statistics}
1188 This option causes @value{GDBN} to print statistics about time and
1189 memory usage after it completes each command and returns to the prompt.
1192 @cindex @code{--version}
1193 This option causes @value{GDBN} to print its version number and
1194 no-warranty blurb, and exit.
1199 @subsection What @value{GDBN} Does During Startup
1200 @cindex @value{GDBN} startup
1202 Here's the description of what @value{GDBN} does during session startup:
1206 Sets up the command interpreter as specified by the command line
1207 (@pxref{Mode Options, interpreter}).
1211 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1212 DOS/Windows systems, the home directory is the one pointed to by the
1213 @code{HOME} environment variable.} and executes all the commands in
1217 Processes command line options and operands.
1220 Reads and executes the commands from init file (if any) in the current
1221 working directory. This is only done if the current directory is
1222 different from your home directory. Thus, you can have more than one
1223 init file, one generic in your home directory, and another, specific
1224 to the program you are debugging, in the directory where you invoke
1228 Reads command files specified by the @samp{-x} option. @xref{Command
1229 Files}, for more details about @value{GDBN} command files.
1232 Reads the command history recorded in the @dfn{history file}.
1233 @xref{Command History}, for more details about the command history and the
1234 files where @value{GDBN} records it.
1237 Init files use the same syntax as @dfn{command files} (@pxref{Command
1238 Files}) and are processed by @value{GDBN} in the same way. The init
1239 file in your home directory can set options (such as @samp{set
1240 complaints}) that affect subsequent processing of command line options
1241 and operands. Init files are not executed if you use the @samp{-nx}
1242 option (@pxref{Mode Options, ,Choosing Modes}).
1244 @cindex init file name
1245 @cindex @file{.gdbinit}
1246 @cindex @file{gdb.ini}
1247 The @value{GDBN} init files are normally called @file{.gdbinit}.
1248 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1249 the limitations of file names imposed by DOS filesystems. The Windows
1250 ports of @value{GDBN} use the standard name, but if they find a
1251 @file{gdb.ini} file, they warn you about that and suggest to rename
1252 the file to the standard name.
1256 @section Quitting @value{GDBN}
1257 @cindex exiting @value{GDBN}
1258 @cindex leaving @value{GDBN}
1261 @kindex quit @r{[}@var{expression}@r{]}
1262 @kindex q @r{(@code{quit})}
1263 @item quit @r{[}@var{expression}@r{]}
1265 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1266 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1267 do not supply @var{expression}, @value{GDBN} will terminate normally;
1268 otherwise it will terminate using the result of @var{expression} as the
1273 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1274 terminates the action of any @value{GDBN} command that is in progress and
1275 returns to @value{GDBN} command level. It is safe to type the interrupt
1276 character at any time because @value{GDBN} does not allow it to take effect
1277 until a time when it is safe.
1279 If you have been using @value{GDBN} to control an attached process or
1280 device, you can release it with the @code{detach} command
1281 (@pxref{Attach, ,Debugging an Already-running Process}).
1283 @node Shell Commands
1284 @section Shell Commands
1286 If you need to execute occasional shell commands during your
1287 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1288 just use the @code{shell} command.
1292 @cindex shell escape
1293 @item shell @var{command string}
1294 Invoke a standard shell to execute @var{command string}.
1295 If it exists, the environment variable @code{SHELL} determines which
1296 shell to run. Otherwise @value{GDBN} uses the default shell
1297 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1300 The utility @code{make} is often needed in development environments.
1301 You do not have to use the @code{shell} command for this purpose in
1306 @cindex calling make
1307 @item make @var{make-args}
1308 Execute the @code{make} program with the specified
1309 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1312 @node Logging Output
1313 @section Logging Output
1314 @cindex logging @value{GDBN} output
1315 @cindex save @value{GDBN} output to a file
1317 You may want to save the output of @value{GDBN} commands to a file.
1318 There are several commands to control @value{GDBN}'s logging.
1322 @item set logging on
1324 @item set logging off
1326 @cindex logging file name
1327 @item set logging file @var{file}
1328 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1329 @item set logging overwrite [on|off]
1330 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1331 you want @code{set logging on} to overwrite the logfile instead.
1332 @item set logging redirect [on|off]
1333 By default, @value{GDBN} output will go to both the terminal and the logfile.
1334 Set @code{redirect} if you want output to go only to the log file.
1335 @kindex show logging
1337 Show the current values of the logging settings.
1341 @chapter @value{GDBN} Commands
1343 You can abbreviate a @value{GDBN} command to the first few letters of the command
1344 name, if that abbreviation is unambiguous; and you can repeat certain
1345 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1346 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1347 show you the alternatives available, if there is more than one possibility).
1350 * Command Syntax:: How to give commands to @value{GDBN}
1351 * Completion:: Command completion
1352 * Help:: How to ask @value{GDBN} for help
1355 @node Command Syntax
1356 @section Command Syntax
1358 A @value{GDBN} command is a single line of input. There is no limit on
1359 how long it can be. It starts with a command name, which is followed by
1360 arguments whose meaning depends on the command name. For example, the
1361 command @code{step} accepts an argument which is the number of times to
1362 step, as in @samp{step 5}. You can also use the @code{step} command
1363 with no arguments. Some commands do not allow any arguments.
1365 @cindex abbreviation
1366 @value{GDBN} command names may always be truncated if that abbreviation is
1367 unambiguous. Other possible command abbreviations are listed in the
1368 documentation for individual commands. In some cases, even ambiguous
1369 abbreviations are allowed; for example, @code{s} is specially defined as
1370 equivalent to @code{step} even though there are other commands whose
1371 names start with @code{s}. You can test abbreviations by using them as
1372 arguments to the @code{help} command.
1374 @cindex repeating commands
1375 @kindex RET @r{(repeat last command)}
1376 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1377 repeat the previous command. Certain commands (for example, @code{run})
1378 will not repeat this way; these are commands whose unintentional
1379 repetition might cause trouble and which you are unlikely to want to
1380 repeat. User-defined commands can disable this feature; see
1381 @ref{Define, dont-repeat}.
1383 The @code{list} and @code{x} commands, when you repeat them with
1384 @key{RET}, construct new arguments rather than repeating
1385 exactly as typed. This permits easy scanning of source or memory.
1387 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1388 output, in a way similar to the common utility @code{more}
1389 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1390 @key{RET} too many in this situation, @value{GDBN} disables command
1391 repetition after any command that generates this sort of display.
1393 @kindex # @r{(a comment)}
1395 Any text from a @kbd{#} to the end of the line is a comment; it does
1396 nothing. This is useful mainly in command files (@pxref{Command
1397 Files,,Command Files}).
1399 @cindex repeating command sequences
1400 @kindex Ctrl-o @r{(operate-and-get-next)}
1401 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1402 commands. This command accepts the current line, like @key{RET}, and
1403 then fetches the next line relative to the current line from the history
1407 @section Command Completion
1410 @cindex word completion
1411 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1412 only one possibility; it can also show you what the valid possibilities
1413 are for the next word in a command, at any time. This works for @value{GDBN}
1414 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1416 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1417 of a word. If there is only one possibility, @value{GDBN} fills in the
1418 word, and waits for you to finish the command (or press @key{RET} to
1419 enter it). For example, if you type
1421 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1422 @c complete accuracy in these examples; space introduced for clarity.
1423 @c If texinfo enhancements make it unnecessary, it would be nice to
1424 @c replace " @key" by "@key" in the following...
1426 (@value{GDBP}) info bre @key{TAB}
1430 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1431 the only @code{info} subcommand beginning with @samp{bre}:
1434 (@value{GDBP}) info breakpoints
1438 You can either press @key{RET} at this point, to run the @code{info
1439 breakpoints} command, or backspace and enter something else, if
1440 @samp{breakpoints} does not look like the command you expected. (If you
1441 were sure you wanted @code{info breakpoints} in the first place, you
1442 might as well just type @key{RET} immediately after @samp{info bre},
1443 to exploit command abbreviations rather than command completion).
1445 If there is more than one possibility for the next word when you press
1446 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1447 characters and try again, or just press @key{TAB} a second time;
1448 @value{GDBN} displays all the possible completions for that word. For
1449 example, you might want to set a breakpoint on a subroutine whose name
1450 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1451 just sounds the bell. Typing @key{TAB} again displays all the
1452 function names in your program that begin with those characters, for
1456 (@value{GDBP}) b make_ @key{TAB}
1457 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1458 make_a_section_from_file make_environ
1459 make_abs_section make_function_type
1460 make_blockvector make_pointer_type
1461 make_cleanup make_reference_type
1462 make_command make_symbol_completion_list
1463 (@value{GDBP}) b make_
1467 After displaying the available possibilities, @value{GDBN} copies your
1468 partial input (@samp{b make_} in the example) so you can finish the
1471 If you just want to see the list of alternatives in the first place, you
1472 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1473 means @kbd{@key{META} ?}. You can type this either by holding down a
1474 key designated as the @key{META} shift on your keyboard (if there is
1475 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1477 @cindex quotes in commands
1478 @cindex completion of quoted strings
1479 Sometimes the string you need, while logically a ``word'', may contain
1480 parentheses or other characters that @value{GDBN} normally excludes from
1481 its notion of a word. To permit word completion to work in this
1482 situation, you may enclose words in @code{'} (single quote marks) in
1483 @value{GDBN} commands.
1485 The most likely situation where you might need this is in typing the
1486 name of a C@t{++} function. This is because C@t{++} allows function
1487 overloading (multiple definitions of the same function, distinguished
1488 by argument type). For example, when you want to set a breakpoint you
1489 may need to distinguish whether you mean the version of @code{name}
1490 that takes an @code{int} parameter, @code{name(int)}, or the version
1491 that takes a @code{float} parameter, @code{name(float)}. To use the
1492 word-completion facilities in this situation, type a single quote
1493 @code{'} at the beginning of the function name. This alerts
1494 @value{GDBN} that it may need to consider more information than usual
1495 when you press @key{TAB} or @kbd{M-?} to request word completion:
1498 (@value{GDBP}) b 'bubble( @kbd{M-?}
1499 bubble(double,double) bubble(int,int)
1500 (@value{GDBP}) b 'bubble(
1503 In some cases, @value{GDBN} can tell that completing a name requires using
1504 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1505 completing as much as it can) if you do not type the quote in the first
1509 (@value{GDBP}) b bub @key{TAB}
1510 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1511 (@value{GDBP}) b 'bubble(
1515 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1516 you have not yet started typing the argument list when you ask for
1517 completion on an overloaded symbol.
1519 For more information about overloaded functions, see @ref{C Plus Plus
1520 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1521 overload-resolution off} to disable overload resolution;
1522 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1526 @section Getting Help
1527 @cindex online documentation
1530 You can always ask @value{GDBN} itself for information on its commands,
1531 using the command @code{help}.
1534 @kindex h @r{(@code{help})}
1537 You can use @code{help} (abbreviated @code{h}) with no arguments to
1538 display a short list of named classes of commands:
1542 List of classes of commands:
1544 aliases -- Aliases of other commands
1545 breakpoints -- Making program stop at certain points
1546 data -- Examining data
1547 files -- Specifying and examining files
1548 internals -- Maintenance commands
1549 obscure -- Obscure features
1550 running -- Running the program
1551 stack -- Examining the stack
1552 status -- Status inquiries
1553 support -- Support facilities
1554 tracepoints -- Tracing of program execution without
1555 stopping the program
1556 user-defined -- User-defined commands
1558 Type "help" followed by a class name for a list of
1559 commands in that class.
1560 Type "help" followed by command name for full
1562 Command name abbreviations are allowed if unambiguous.
1565 @c the above line break eliminates huge line overfull...
1567 @item help @var{class}
1568 Using one of the general help classes as an argument, you can get a
1569 list of the individual commands in that class. For example, here is the
1570 help display for the class @code{status}:
1573 (@value{GDBP}) help status
1578 @c Line break in "show" line falsifies real output, but needed
1579 @c to fit in smallbook page size.
1580 info -- Generic command for showing things
1581 about the program being debugged
1582 show -- Generic command for showing things
1585 Type "help" followed by command name for full
1587 Command name abbreviations are allowed if unambiguous.
1591 @item help @var{command}
1592 With a command name as @code{help} argument, @value{GDBN} displays a
1593 short paragraph on how to use that command.
1596 @item apropos @var{args}
1597 The @code{apropos} command searches through all of the @value{GDBN}
1598 commands, and their documentation, for the regular expression specified in
1599 @var{args}. It prints out all matches found. For example:
1610 set symbol-reloading -- Set dynamic symbol table reloading
1611 multiple times in one run
1612 show symbol-reloading -- Show dynamic symbol table reloading
1613 multiple times in one run
1618 @item complete @var{args}
1619 The @code{complete @var{args}} command lists all the possible completions
1620 for the beginning of a command. Use @var{args} to specify the beginning of the
1621 command you want completed. For example:
1627 @noindent results in:
1638 @noindent This is intended for use by @sc{gnu} Emacs.
1641 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1642 and @code{show} to inquire about the state of your program, or the state
1643 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1644 manual introduces each of them in the appropriate context. The listings
1645 under @code{info} and under @code{show} in the Index point to
1646 all the sub-commands. @xref{Index}.
1651 @kindex i @r{(@code{info})}
1653 This command (abbreviated @code{i}) is for describing the state of your
1654 program. For example, you can show the arguments passed to a function
1655 with @code{info args}, list the registers currently in use with @code{info
1656 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1657 You can get a complete list of the @code{info} sub-commands with
1658 @w{@code{help info}}.
1662 You can assign the result of an expression to an environment variable with
1663 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1664 @code{set prompt $}.
1668 In contrast to @code{info}, @code{show} is for describing the state of
1669 @value{GDBN} itself.
1670 You can change most of the things you can @code{show}, by using the
1671 related command @code{set}; for example, you can control what number
1672 system is used for displays with @code{set radix}, or simply inquire
1673 which is currently in use with @code{show radix}.
1676 To display all the settable parameters and their current
1677 values, you can use @code{show} with no arguments; you may also use
1678 @code{info set}. Both commands produce the same display.
1679 @c FIXME: "info set" violates the rule that "info" is for state of
1680 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1681 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1685 Here are three miscellaneous @code{show} subcommands, all of which are
1686 exceptional in lacking corresponding @code{set} commands:
1689 @kindex show version
1690 @cindex @value{GDBN} version number
1692 Show what version of @value{GDBN} is running. You should include this
1693 information in @value{GDBN} bug-reports. If multiple versions of
1694 @value{GDBN} are in use at your site, you may need to determine which
1695 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1696 commands are introduced, and old ones may wither away. Also, many
1697 system vendors ship variant versions of @value{GDBN}, and there are
1698 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1699 The version number is the same as the one announced when you start
1702 @kindex show copying
1703 @kindex info copying
1704 @cindex display @value{GDBN} copyright
1707 Display information about permission for copying @value{GDBN}.
1709 @kindex show warranty
1710 @kindex info warranty
1712 @itemx info warranty
1713 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1714 if your version of @value{GDBN} comes with one.
1719 @chapter Running Programs Under @value{GDBN}
1721 When you run a program under @value{GDBN}, you must first generate
1722 debugging information when you compile it.
1724 You may start @value{GDBN} with its arguments, if any, in an environment
1725 of your choice. If you are doing native debugging, you may redirect
1726 your program's input and output, debug an already running process, or
1727 kill a child process.
1730 * Compilation:: Compiling for debugging
1731 * Starting:: Starting your program
1732 * Arguments:: Your program's arguments
1733 * Environment:: Your program's environment
1735 * Working Directory:: Your program's working directory
1736 * Input/Output:: Your program's input and output
1737 * Attach:: Debugging an already-running process
1738 * Kill Process:: Killing the child process
1740 * Threads:: Debugging programs with multiple threads
1741 * Processes:: Debugging programs with multiple processes
1742 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1746 @section Compiling for Debugging
1748 In order to debug a program effectively, you need to generate
1749 debugging information when you compile it. This debugging information
1750 is stored in the object file; it describes the data type of each
1751 variable or function and the correspondence between source line numbers
1752 and addresses in the executable code.
1754 To request debugging information, specify the @samp{-g} option when you run
1757 Programs that are to be shipped to your customers are compiled with
1758 optimizations, using the @samp{-O} compiler option. However, many
1759 compilers are unable to handle the @samp{-g} and @samp{-O} options
1760 together. Using those compilers, you cannot generate optimized
1761 executables containing debugging information.
1763 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1764 without @samp{-O}, making it possible to debug optimized code. We
1765 recommend that you @emph{always} use @samp{-g} whenever you compile a
1766 program. You may think your program is correct, but there is no sense
1767 in pushing your luck.
1769 @cindex optimized code, debugging
1770 @cindex debugging optimized code
1771 When you debug a program compiled with @samp{-g -O}, remember that the
1772 optimizer is rearranging your code; the debugger shows you what is
1773 really there. Do not be too surprised when the execution path does not
1774 exactly match your source file! An extreme example: if you define a
1775 variable, but never use it, @value{GDBN} never sees that
1776 variable---because the compiler optimizes it out of existence.
1778 Some things do not work as well with @samp{-g -O} as with just
1779 @samp{-g}, particularly on machines with instruction scheduling. If in
1780 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1781 please report it to us as a bug (including a test case!).
1782 @xref{Variables}, for more information about debugging optimized code.
1784 Older versions of the @sc{gnu} C compiler permitted a variant option
1785 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1786 format; if your @sc{gnu} C compiler has this option, do not use it.
1788 @value{GDBN} knows about preprocessor macros and can show you their
1789 expansion (@pxref{Macros}). Most compilers do not include information
1790 about preprocessor macros in the debugging information if you specify
1791 the @option{-g} flag alone, because this information is rather large.
1792 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1793 provides macro information if you specify the options
1794 @option{-gdwarf-2} and @option{-g3}; the former option requests
1795 debugging information in the Dwarf 2 format, and the latter requests
1796 ``extra information''. In the future, we hope to find more compact
1797 ways to represent macro information, so that it can be included with
1802 @section Starting your Program
1808 @kindex r @r{(@code{run})}
1811 Use the @code{run} command to start your program under @value{GDBN}.
1812 You must first specify the program name (except on VxWorks) with an
1813 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1814 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1815 (@pxref{Files, ,Commands to Specify Files}).
1819 If you are running your program in an execution environment that
1820 supports processes, @code{run} creates an inferior process and makes
1821 that process run your program. In some environments without processes,
1822 @code{run} jumps to the start of your program. Other targets,
1823 like @samp{remote}, are always running. If you get an error
1824 message like this one:
1827 The "remote" target does not support "run".
1828 Try "help target" or "continue".
1832 then use @code{continue} to run your program. You may need @code{load}
1833 first (@pxref{load}).
1835 The execution of a program is affected by certain information it
1836 receives from its superior. @value{GDBN} provides ways to specify this
1837 information, which you must do @emph{before} starting your program. (You
1838 can change it after starting your program, but such changes only affect
1839 your program the next time you start it.) This information may be
1840 divided into four categories:
1843 @item The @emph{arguments.}
1844 Specify the arguments to give your program as the arguments of the
1845 @code{run} command. If a shell is available on your target, the shell
1846 is used to pass the arguments, so that you may use normal conventions
1847 (such as wildcard expansion or variable substitution) in describing
1849 In Unix systems, you can control which shell is used with the
1850 @code{SHELL} environment variable.
1851 @xref{Arguments, ,Your Program's Arguments}.
1853 @item The @emph{environment.}
1854 Your program normally inherits its environment from @value{GDBN}, but you can
1855 use the @value{GDBN} commands @code{set environment} and @code{unset
1856 environment} to change parts of the environment that affect
1857 your program. @xref{Environment, ,Your Program's Environment}.
1859 @item The @emph{working directory.}
1860 Your program inherits its working directory from @value{GDBN}. You can set
1861 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1862 @xref{Working Directory, ,Your Program's Working Directory}.
1864 @item The @emph{standard input and output.}
1865 Your program normally uses the same device for standard input and
1866 standard output as @value{GDBN} is using. You can redirect input and output
1867 in the @code{run} command line, or you can use the @code{tty} command to
1868 set a different device for your program.
1869 @xref{Input/Output, ,Your Program's Input and Output}.
1872 @emph{Warning:} While input and output redirection work, you cannot use
1873 pipes to pass the output of the program you are debugging to another
1874 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1878 When you issue the @code{run} command, your program begins to execute
1879 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1880 of how to arrange for your program to stop. Once your program has
1881 stopped, you may call functions in your program, using the @code{print}
1882 or @code{call} commands. @xref{Data, ,Examining Data}.
1884 If the modification time of your symbol file has changed since the last
1885 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1886 table, and reads it again. When it does this, @value{GDBN} tries to retain
1887 your current breakpoints.
1892 @cindex run to main procedure
1893 The name of the main procedure can vary from language to language.
1894 With C or C@t{++}, the main procedure name is always @code{main}, but
1895 other languages such as Ada do not require a specific name for their
1896 main procedure. The debugger provides a convenient way to start the
1897 execution of the program and to stop at the beginning of the main
1898 procedure, depending on the language used.
1900 The @samp{start} command does the equivalent of setting a temporary
1901 breakpoint at the beginning of the main procedure and then invoking
1902 the @samp{run} command.
1904 @cindex elaboration phase
1905 Some programs contain an @dfn{elaboration} phase where some startup code is
1906 executed before the main procedure is called. This depends on the
1907 languages used to write your program. In C@t{++}, for instance,
1908 constructors for static and global objects are executed before
1909 @code{main} is called. It is therefore possible that the debugger stops
1910 before reaching the main procedure. However, the temporary breakpoint
1911 will remain to halt execution.
1913 Specify the arguments to give to your program as arguments to the
1914 @samp{start} command. These arguments will be given verbatim to the
1915 underlying @samp{run} command. Note that the same arguments will be
1916 reused if no argument is provided during subsequent calls to
1917 @samp{start} or @samp{run}.
1919 It is sometimes necessary to debug the program during elaboration. In
1920 these cases, using the @code{start} command would stop the execution of
1921 your program too late, as the program would have already completed the
1922 elaboration phase. Under these circumstances, insert breakpoints in your
1923 elaboration code before running your program.
1925 @kindex set exec-wrapper
1926 @item set exec-wrapper @var{wrapper}
1927 @itemx show exec-wrapper
1928 @itemx unset exec-wrapper
1929 When @samp{exec-wrapper} is set, the specified wrapper is used to
1930 launch programs for debugging. @value{GDBN} starts your program
1931 with a shell command of the form @kbd{exec @var{wrapper}
1932 @var{program}}. Quoting is added to @var{program} and its
1933 arguments, but not to @var{wrapper}, so you should add quotes if
1934 appropriate for your shell. The wrapper runs until it executes
1935 your program, and then @value{GDBN} takes control.
1937 You can use any program that eventually calls @code{execve} with
1938 its arguments as a wrapper. Several standard Unix utilities do
1939 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1940 with @code{exec "$@@"} will also work.
1942 For example, you can use @code{env} to pass an environment variable to
1943 the debugged program, without setting the variable in your shell's
1947 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1951 This command is available when debugging locally on most targets, excluding
1952 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
1957 @section Your Program's Arguments
1959 @cindex arguments (to your program)
1960 The arguments to your program can be specified by the arguments of the
1962 They are passed to a shell, which expands wildcard characters and
1963 performs redirection of I/O, and thence to your program. Your
1964 @code{SHELL} environment variable (if it exists) specifies what shell
1965 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1966 the default shell (@file{/bin/sh} on Unix).
1968 On non-Unix systems, the program is usually invoked directly by
1969 @value{GDBN}, which emulates I/O redirection via the appropriate system
1970 calls, and the wildcard characters are expanded by the startup code of
1971 the program, not by the shell.
1973 @code{run} with no arguments uses the same arguments used by the previous
1974 @code{run}, or those set by the @code{set args} command.
1979 Specify the arguments to be used the next time your program is run. If
1980 @code{set args} has no arguments, @code{run} executes your program
1981 with no arguments. Once you have run your program with arguments,
1982 using @code{set args} before the next @code{run} is the only way to run
1983 it again without arguments.
1987 Show the arguments to give your program when it is started.
1991 @section Your Program's Environment
1993 @cindex environment (of your program)
1994 The @dfn{environment} consists of a set of environment variables and
1995 their values. Environment variables conventionally record such things as
1996 your user name, your home directory, your terminal type, and your search
1997 path for programs to run. Usually you set up environment variables with
1998 the shell and they are inherited by all the other programs you run. When
1999 debugging, it can be useful to try running your program with a modified
2000 environment without having to start @value{GDBN} over again.
2004 @item path @var{directory}
2005 Add @var{directory} to the front of the @code{PATH} environment variable
2006 (the search path for executables) that will be passed to your program.
2007 The value of @code{PATH} used by @value{GDBN} does not change.
2008 You may specify several directory names, separated by whitespace or by a
2009 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2010 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2011 is moved to the front, so it is searched sooner.
2013 You can use the string @samp{$cwd} to refer to whatever is the current
2014 working directory at the time @value{GDBN} searches the path. If you
2015 use @samp{.} instead, it refers to the directory where you executed the
2016 @code{path} command. @value{GDBN} replaces @samp{.} in the
2017 @var{directory} argument (with the current path) before adding
2018 @var{directory} to the search path.
2019 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2020 @c document that, since repeating it would be a no-op.
2024 Display the list of search paths for executables (the @code{PATH}
2025 environment variable).
2027 @kindex show environment
2028 @item show environment @r{[}@var{varname}@r{]}
2029 Print the value of environment variable @var{varname} to be given to
2030 your program when it starts. If you do not supply @var{varname},
2031 print the names and values of all environment variables to be given to
2032 your program. You can abbreviate @code{environment} as @code{env}.
2034 @kindex set environment
2035 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2036 Set environment variable @var{varname} to @var{value}. The value
2037 changes for your program only, not for @value{GDBN} itself. @var{value} may
2038 be any string; the values of environment variables are just strings, and
2039 any interpretation is supplied by your program itself. The @var{value}
2040 parameter is optional; if it is eliminated, the variable is set to a
2042 @c "any string" here does not include leading, trailing
2043 @c blanks. Gnu asks: does anyone care?
2045 For example, this command:
2052 tells the debugged program, when subsequently run, that its user is named
2053 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2054 are not actually required.)
2056 @kindex unset environment
2057 @item unset environment @var{varname}
2058 Remove variable @var{varname} from the environment to be passed to your
2059 program. This is different from @samp{set env @var{varname} =};
2060 @code{unset environment} removes the variable from the environment,
2061 rather than assigning it an empty value.
2064 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2066 by your @code{SHELL} environment variable if it exists (or
2067 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2068 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2069 @file{.bashrc} for BASH---any variables you set in that file affect
2070 your program. You may wish to move setting of environment variables to
2071 files that are only run when you sign on, such as @file{.login} or
2074 @node Working Directory
2075 @section Your Program's Working Directory
2077 @cindex working directory (of your program)
2078 Each time you start your program with @code{run}, it inherits its
2079 working directory from the current working directory of @value{GDBN}.
2080 The @value{GDBN} working directory is initially whatever it inherited
2081 from its parent process (typically the shell), but you can specify a new
2082 working directory in @value{GDBN} with the @code{cd} command.
2084 The @value{GDBN} working directory also serves as a default for the commands
2085 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2090 @cindex change working directory
2091 @item cd @var{directory}
2092 Set the @value{GDBN} working directory to @var{directory}.
2096 Print the @value{GDBN} working directory.
2099 It is generally impossible to find the current working directory of
2100 the process being debugged (since a program can change its directory
2101 during its run). If you work on a system where @value{GDBN} is
2102 configured with the @file{/proc} support, you can use the @code{info
2103 proc} command (@pxref{SVR4 Process Information}) to find out the
2104 current working directory of the debuggee.
2107 @section Your Program's Input and Output
2112 By default, the program you run under @value{GDBN} does input and output to
2113 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2114 to its own terminal modes to interact with you, but it records the terminal
2115 modes your program was using and switches back to them when you continue
2116 running your program.
2119 @kindex info terminal
2121 Displays information recorded by @value{GDBN} about the terminal modes your
2125 You can redirect your program's input and/or output using shell
2126 redirection with the @code{run} command. For example,
2133 starts your program, diverting its output to the file @file{outfile}.
2136 @cindex controlling terminal
2137 Another way to specify where your program should do input and output is
2138 with the @code{tty} command. This command accepts a file name as
2139 argument, and causes this file to be the default for future @code{run}
2140 commands. It also resets the controlling terminal for the child
2141 process, for future @code{run} commands. For example,
2148 directs that processes started with subsequent @code{run} commands
2149 default to do input and output on the terminal @file{/dev/ttyb} and have
2150 that as their controlling terminal.
2152 An explicit redirection in @code{run} overrides the @code{tty} command's
2153 effect on the input/output device, but not its effect on the controlling
2156 When you use the @code{tty} command or redirect input in the @code{run}
2157 command, only the input @emph{for your program} is affected. The input
2158 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2159 for @code{set inferior-tty}.
2161 @cindex inferior tty
2162 @cindex set inferior controlling terminal
2163 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2164 display the name of the terminal that will be used for future runs of your
2168 @item set inferior-tty /dev/ttyb
2169 @kindex set inferior-tty
2170 Set the tty for the program being debugged to /dev/ttyb.
2172 @item show inferior-tty
2173 @kindex show inferior-tty
2174 Show the current tty for the program being debugged.
2178 @section Debugging an Already-running Process
2183 @item attach @var{process-id}
2184 This command attaches to a running process---one that was started
2185 outside @value{GDBN}. (@code{info files} shows your active
2186 targets.) The command takes as argument a process ID. The usual way to
2187 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2188 or with the @samp{jobs -l} shell command.
2190 @code{attach} does not repeat if you press @key{RET} a second time after
2191 executing the command.
2194 To use @code{attach}, your program must be running in an environment
2195 which supports processes; for example, @code{attach} does not work for
2196 programs on bare-board targets that lack an operating system. You must
2197 also have permission to send the process a signal.
2199 When you use @code{attach}, the debugger finds the program running in
2200 the process first by looking in the current working directory, then (if
2201 the program is not found) by using the source file search path
2202 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2203 the @code{file} command to load the program. @xref{Files, ,Commands to
2206 The first thing @value{GDBN} does after arranging to debug the specified
2207 process is to stop it. You can examine and modify an attached process
2208 with all the @value{GDBN} commands that are ordinarily available when
2209 you start processes with @code{run}. You can insert breakpoints; you
2210 can step and continue; you can modify storage. If you would rather the
2211 process continue running, you may use the @code{continue} command after
2212 attaching @value{GDBN} to the process.
2217 When you have finished debugging the attached process, you can use the
2218 @code{detach} command to release it from @value{GDBN} control. Detaching
2219 the process continues its execution. After the @code{detach} command,
2220 that process and @value{GDBN} become completely independent once more, and you
2221 are ready to @code{attach} another process or start one with @code{run}.
2222 @code{detach} does not repeat if you press @key{RET} again after
2223 executing the command.
2226 If you exit @value{GDBN} while you have an attached process, you detach
2227 that process. If you use the @code{run} command, you kill that process.
2228 By default, @value{GDBN} asks for confirmation if you try to do either of these
2229 things; you can control whether or not you need to confirm by using the
2230 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2234 @section Killing the Child Process
2239 Kill the child process in which your program is running under @value{GDBN}.
2242 This command is useful if you wish to debug a core dump instead of a
2243 running process. @value{GDBN} ignores any core dump file while your program
2246 On some operating systems, a program cannot be executed outside @value{GDBN}
2247 while you have breakpoints set on it inside @value{GDBN}. You can use the
2248 @code{kill} command in this situation to permit running your program
2249 outside the debugger.
2251 The @code{kill} command is also useful if you wish to recompile and
2252 relink your program, since on many systems it is impossible to modify an
2253 executable file while it is running in a process. In this case, when you
2254 next type @code{run}, @value{GDBN} notices that the file has changed, and
2255 reads the symbol table again (while trying to preserve your current
2256 breakpoint settings).
2259 @section Debugging Programs with Multiple Threads
2261 @cindex threads of execution
2262 @cindex multiple threads
2263 @cindex switching threads
2264 In some operating systems, such as HP-UX and Solaris, a single program
2265 may have more than one @dfn{thread} of execution. The precise semantics
2266 of threads differ from one operating system to another, but in general
2267 the threads of a single program are akin to multiple processes---except
2268 that they share one address space (that is, they can all examine and
2269 modify the same variables). On the other hand, each thread has its own
2270 registers and execution stack, and perhaps private memory.
2272 @value{GDBN} provides these facilities for debugging multi-thread
2276 @item automatic notification of new threads
2277 @item @samp{thread @var{threadno}}, a command to switch among threads
2278 @item @samp{info threads}, a command to inquire about existing threads
2279 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2280 a command to apply a command to a list of threads
2281 @item thread-specific breakpoints
2282 @item @samp{set print thread-events}, which controls printing of
2283 messages on thread start and exit.
2287 @emph{Warning:} These facilities are not yet available on every
2288 @value{GDBN} configuration where the operating system supports threads.
2289 If your @value{GDBN} does not support threads, these commands have no
2290 effect. For example, a system without thread support shows no output
2291 from @samp{info threads}, and always rejects the @code{thread} command,
2295 (@value{GDBP}) info threads
2296 (@value{GDBP}) thread 1
2297 Thread ID 1 not known. Use the "info threads" command to
2298 see the IDs of currently known threads.
2300 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2301 @c doesn't support threads"?
2304 @cindex focus of debugging
2305 @cindex current thread
2306 The @value{GDBN} thread debugging facility allows you to observe all
2307 threads while your program runs---but whenever @value{GDBN} takes
2308 control, one thread in particular is always the focus of debugging.
2309 This thread is called the @dfn{current thread}. Debugging commands show
2310 program information from the perspective of the current thread.
2312 @cindex @code{New} @var{systag} message
2313 @cindex thread identifier (system)
2314 @c FIXME-implementors!! It would be more helpful if the [New...] message
2315 @c included GDB's numeric thread handle, so you could just go to that
2316 @c thread without first checking `info threads'.
2317 Whenever @value{GDBN} detects a new thread in your program, it displays
2318 the target system's identification for the thread with a message in the
2319 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2320 whose form varies depending on the particular system. For example, on
2321 @sc{gnu}/Linux, you might see
2324 [New Thread 46912507313328 (LWP 25582)]
2328 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2329 the @var{systag} is simply something like @samp{process 368}, with no
2332 @c FIXME!! (1) Does the [New...] message appear even for the very first
2333 @c thread of a program, or does it only appear for the
2334 @c second---i.e.@: when it becomes obvious we have a multithread
2336 @c (2) *Is* there necessarily a first thread always? Or do some
2337 @c multithread systems permit starting a program with multiple
2338 @c threads ab initio?
2340 @cindex thread number
2341 @cindex thread identifier (GDB)
2342 For debugging purposes, @value{GDBN} associates its own thread
2343 number---always a single integer---with each thread in your program.
2346 @kindex info threads
2348 Display a summary of all threads currently in your
2349 program. @value{GDBN} displays for each thread (in this order):
2353 the thread number assigned by @value{GDBN}
2356 the target system's thread identifier (@var{systag})
2359 the current stack frame summary for that thread
2363 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2364 indicates the current thread.
2368 @c end table here to get a little more width for example
2371 (@value{GDBP}) info threads
2372 3 process 35 thread 27 0x34e5 in sigpause ()
2373 2 process 35 thread 23 0x34e5 in sigpause ()
2374 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2380 @cindex debugging multithreaded programs (on HP-UX)
2381 @cindex thread identifier (GDB), on HP-UX
2382 For debugging purposes, @value{GDBN} associates its own thread
2383 number---a small integer assigned in thread-creation order---with each
2384 thread in your program.
2386 @cindex @code{New} @var{systag} message, on HP-UX
2387 @cindex thread identifier (system), on HP-UX
2388 @c FIXME-implementors!! It would be more helpful if the [New...] message
2389 @c included GDB's numeric thread handle, so you could just go to that
2390 @c thread without first checking `info threads'.
2391 Whenever @value{GDBN} detects a new thread in your program, it displays
2392 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2393 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2394 whose form varies depending on the particular system. For example, on
2398 [New thread 2 (system thread 26594)]
2402 when @value{GDBN} notices a new thread.
2405 @kindex info threads (HP-UX)
2407 Display a summary of all threads currently in your
2408 program. @value{GDBN} displays for each thread (in this order):
2411 @item the thread number assigned by @value{GDBN}
2413 @item the target system's thread identifier (@var{systag})
2415 @item the current stack frame summary for that thread
2419 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2420 indicates the current thread.
2424 @c end table here to get a little more width for example
2427 (@value{GDBP}) info threads
2428 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2430 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2431 from /usr/lib/libc.2
2432 1 system thread 27905 0x7b003498 in _brk () \@*
2433 from /usr/lib/libc.2
2436 On Solaris, you can display more information about user threads with a
2437 Solaris-specific command:
2440 @item maint info sol-threads
2441 @kindex maint info sol-threads
2442 @cindex thread info (Solaris)
2443 Display info on Solaris user threads.
2447 @kindex thread @var{threadno}
2448 @item thread @var{threadno}
2449 Make thread number @var{threadno} the current thread. The command
2450 argument @var{threadno} is the internal @value{GDBN} thread number, as
2451 shown in the first field of the @samp{info threads} display.
2452 @value{GDBN} responds by displaying the system identifier of the thread
2453 you selected, and its current stack frame summary:
2456 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2457 (@value{GDBP}) thread 2
2458 [Switching to process 35 thread 23]
2459 0x34e5 in sigpause ()
2463 As with the @samp{[New @dots{}]} message, the form of the text after
2464 @samp{Switching to} depends on your system's conventions for identifying
2467 @kindex thread apply
2468 @cindex apply command to several threads
2469 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2470 The @code{thread apply} command allows you to apply the named
2471 @var{command} to one or more threads. Specify the numbers of the
2472 threads that you want affected with the command argument
2473 @var{threadno}. It can be a single thread number, one of the numbers
2474 shown in the first field of the @samp{info threads} display; or it
2475 could be a range of thread numbers, as in @code{2-4}. To apply a
2476 command to all threads, type @kbd{thread apply all @var{command}}.
2478 @kindex set print thread-events
2479 @cindex print messages on thread start and exit
2480 @item set print thread-events
2481 @itemx set print thread-events on
2482 @itemx set print thread-events off
2483 The @code{set print thread-events} command allows you to enable or
2484 disable printing of messages when @value{GDBN} notices that new threads have
2485 started or that threads have exited. By default, these messages will
2486 be printed if detection of these events is supported by the target.
2487 Note that these messages cannot be disabled on all targets.
2489 @kindex show print thread-events
2490 @item show print thread-events
2491 Show whether messages will be printed when @value{GDBN} detects that threads
2492 have started and exited.
2495 @cindex automatic thread selection
2496 @cindex switching threads automatically
2497 @cindex threads, automatic switching
2498 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2499 signal, it automatically selects the thread where that breakpoint or
2500 signal happened. @value{GDBN} alerts you to the context switch with a
2501 message of the form @samp{[Switching to @var{systag}]} to identify the
2504 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2505 more information about how @value{GDBN} behaves when you stop and start
2506 programs with multiple threads.
2508 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2509 watchpoints in programs with multiple threads.
2512 @section Debugging Programs with Multiple Processes
2514 @cindex fork, debugging programs which call
2515 @cindex multiple processes
2516 @cindex processes, multiple
2517 On most systems, @value{GDBN} has no special support for debugging
2518 programs which create additional processes using the @code{fork}
2519 function. When a program forks, @value{GDBN} will continue to debug the
2520 parent process and the child process will run unimpeded. If you have
2521 set a breakpoint in any code which the child then executes, the child
2522 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2523 will cause it to terminate.
2525 However, if you want to debug the child process there is a workaround
2526 which isn't too painful. Put a call to @code{sleep} in the code which
2527 the child process executes after the fork. It may be useful to sleep
2528 only if a certain environment variable is set, or a certain file exists,
2529 so that the delay need not occur when you don't want to run @value{GDBN}
2530 on the child. While the child is sleeping, use the @code{ps} program to
2531 get its process ID. Then tell @value{GDBN} (a new invocation of
2532 @value{GDBN} if you are also debugging the parent process) to attach to
2533 the child process (@pxref{Attach}). From that point on you can debug
2534 the child process just like any other process which you attached to.
2536 On some systems, @value{GDBN} provides support for debugging programs that
2537 create additional processes using the @code{fork} or @code{vfork} functions.
2538 Currently, the only platforms with this feature are HP-UX (11.x and later
2539 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2541 By default, when a program forks, @value{GDBN} will continue to debug
2542 the parent process and the child process will run unimpeded.
2544 If you want to follow the child process instead of the parent process,
2545 use the command @w{@code{set follow-fork-mode}}.
2548 @kindex set follow-fork-mode
2549 @item set follow-fork-mode @var{mode}
2550 Set the debugger response to a program call of @code{fork} or
2551 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2552 process. The @var{mode} argument can be:
2556 The original process is debugged after a fork. The child process runs
2557 unimpeded. This is the default.
2560 The new process is debugged after a fork. The parent process runs
2565 @kindex show follow-fork-mode
2566 @item show follow-fork-mode
2567 Display the current debugger response to a @code{fork} or @code{vfork} call.
2570 @cindex debugging multiple processes
2571 On Linux, if you want to debug both the parent and child processes, use the
2572 command @w{@code{set detach-on-fork}}.
2575 @kindex set detach-on-fork
2576 @item set detach-on-fork @var{mode}
2577 Tells gdb whether to detach one of the processes after a fork, or
2578 retain debugger control over them both.
2582 The child process (or parent process, depending on the value of
2583 @code{follow-fork-mode}) will be detached and allowed to run
2584 independently. This is the default.
2587 Both processes will be held under the control of @value{GDBN}.
2588 One process (child or parent, depending on the value of
2589 @code{follow-fork-mode}) is debugged as usual, while the other
2594 @kindex show detach-on-fork
2595 @item show detach-on-fork
2596 Show whether detach-on-fork mode is on/off.
2599 If you choose to set @samp{detach-on-fork} mode off, then
2600 @value{GDBN} will retain control of all forked processes (including
2601 nested forks). You can list the forked processes under the control of
2602 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2603 from one fork to another by using the @w{@code{fork}} command.
2608 Print a list of all forked processes under the control of @value{GDBN}.
2609 The listing will include a fork id, a process id, and the current
2610 position (program counter) of the process.
2612 @kindex fork @var{fork-id}
2613 @item fork @var{fork-id}
2614 Make fork number @var{fork-id} the current process. The argument
2615 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2616 as shown in the first field of the @samp{info forks} display.
2618 @kindex process @var{process-id}
2619 @item process @var{process-id}
2620 Make process number @var{process-id} the current process. The
2621 argument @var{process-id} must be one that is listed in the output of
2626 To quit debugging one of the forked processes, you can either detach
2627 from it by using the @w{@code{detach fork}} command (allowing it to
2628 run independently), or delete (and kill) it using the
2629 @w{@code{delete fork}} command.
2632 @kindex detach fork @var{fork-id}
2633 @item detach fork @var{fork-id}
2634 Detach from the process identified by @value{GDBN} fork number
2635 @var{fork-id}, and remove it from the fork list. The process will be
2636 allowed to run independently.
2638 @kindex delete fork @var{fork-id}
2639 @item delete fork @var{fork-id}
2640 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2641 and remove it from the fork list.
2645 If you ask to debug a child process and a @code{vfork} is followed by an
2646 @code{exec}, @value{GDBN} executes the new target up to the first
2647 breakpoint in the new target. If you have a breakpoint set on
2648 @code{main} in your original program, the breakpoint will also be set on
2649 the child process's @code{main}.
2651 When a child process is spawned by @code{vfork}, you cannot debug the
2652 child or parent until an @code{exec} call completes.
2654 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2655 call executes, the new target restarts. To restart the parent process,
2656 use the @code{file} command with the parent executable name as its
2659 You can use the @code{catch} command to make @value{GDBN} stop whenever
2660 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2661 Catchpoints, ,Setting Catchpoints}.
2663 @node Checkpoint/Restart
2664 @section Setting a @emph{Bookmark} to Return to Later
2669 @cindex snapshot of a process
2670 @cindex rewind program state
2672 On certain operating systems@footnote{Currently, only
2673 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2674 program's state, called a @dfn{checkpoint}, and come back to it
2677 Returning to a checkpoint effectively undoes everything that has
2678 happened in the program since the @code{checkpoint} was saved. This
2679 includes changes in memory, registers, and even (within some limits)
2680 system state. Effectively, it is like going back in time to the
2681 moment when the checkpoint was saved.
2683 Thus, if you're stepping thru a program and you think you're
2684 getting close to the point where things go wrong, you can save
2685 a checkpoint. Then, if you accidentally go too far and miss
2686 the critical statement, instead of having to restart your program
2687 from the beginning, you can just go back to the checkpoint and
2688 start again from there.
2690 This can be especially useful if it takes a lot of time or
2691 steps to reach the point where you think the bug occurs.
2693 To use the @code{checkpoint}/@code{restart} method of debugging:
2698 Save a snapshot of the debugged program's current execution state.
2699 The @code{checkpoint} command takes no arguments, but each checkpoint
2700 is assigned a small integer id, similar to a breakpoint id.
2702 @kindex info checkpoints
2703 @item info checkpoints
2704 List the checkpoints that have been saved in the current debugging
2705 session. For each checkpoint, the following information will be
2712 @item Source line, or label
2715 @kindex restart @var{checkpoint-id}
2716 @item restart @var{checkpoint-id}
2717 Restore the program state that was saved as checkpoint number
2718 @var{checkpoint-id}. All program variables, registers, stack frames
2719 etc.@: will be returned to the values that they had when the checkpoint
2720 was saved. In essence, gdb will ``wind back the clock'' to the point
2721 in time when the checkpoint was saved.
2723 Note that breakpoints, @value{GDBN} variables, command history etc.
2724 are not affected by restoring a checkpoint. In general, a checkpoint
2725 only restores things that reside in the program being debugged, not in
2728 @kindex delete checkpoint @var{checkpoint-id}
2729 @item delete checkpoint @var{checkpoint-id}
2730 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2734 Returning to a previously saved checkpoint will restore the user state
2735 of the program being debugged, plus a significant subset of the system
2736 (OS) state, including file pointers. It won't ``un-write'' data from
2737 a file, but it will rewind the file pointer to the previous location,
2738 so that the previously written data can be overwritten. For files
2739 opened in read mode, the pointer will also be restored so that the
2740 previously read data can be read again.
2742 Of course, characters that have been sent to a printer (or other
2743 external device) cannot be ``snatched back'', and characters received
2744 from eg.@: a serial device can be removed from internal program buffers,
2745 but they cannot be ``pushed back'' into the serial pipeline, ready to
2746 be received again. Similarly, the actual contents of files that have
2747 been changed cannot be restored (at this time).
2749 However, within those constraints, you actually can ``rewind'' your
2750 program to a previously saved point in time, and begin debugging it
2751 again --- and you can change the course of events so as to debug a
2752 different execution path this time.
2754 @cindex checkpoints and process id
2755 Finally, there is one bit of internal program state that will be
2756 different when you return to a checkpoint --- the program's process
2757 id. Each checkpoint will have a unique process id (or @var{pid}),
2758 and each will be different from the program's original @var{pid}.
2759 If your program has saved a local copy of its process id, this could
2760 potentially pose a problem.
2762 @subsection A Non-obvious Benefit of Using Checkpoints
2764 On some systems such as @sc{gnu}/Linux, address space randomization
2765 is performed on new processes for security reasons. This makes it
2766 difficult or impossible to set a breakpoint, or watchpoint, on an
2767 absolute address if you have to restart the program, since the
2768 absolute location of a symbol will change from one execution to the
2771 A checkpoint, however, is an @emph{identical} copy of a process.
2772 Therefore if you create a checkpoint at (eg.@:) the start of main,
2773 and simply return to that checkpoint instead of restarting the
2774 process, you can avoid the effects of address randomization and
2775 your symbols will all stay in the same place.
2778 @chapter Stopping and Continuing
2780 The principal purposes of using a debugger are so that you can stop your
2781 program before it terminates; or so that, if your program runs into
2782 trouble, you can investigate and find out why.
2784 Inside @value{GDBN}, your program may stop for any of several reasons,
2785 such as a signal, a breakpoint, or reaching a new line after a
2786 @value{GDBN} command such as @code{step}. You may then examine and
2787 change variables, set new breakpoints or remove old ones, and then
2788 continue execution. Usually, the messages shown by @value{GDBN} provide
2789 ample explanation of the status of your program---but you can also
2790 explicitly request this information at any time.
2793 @kindex info program
2795 Display information about the status of your program: whether it is
2796 running or not, what process it is, and why it stopped.
2800 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2801 * Continuing and Stepping:: Resuming execution
2803 * Thread Stops:: Stopping and starting multi-thread programs
2807 @section Breakpoints, Watchpoints, and Catchpoints
2810 A @dfn{breakpoint} makes your program stop whenever a certain point in
2811 the program is reached. For each breakpoint, you can add conditions to
2812 control in finer detail whether your program stops. You can set
2813 breakpoints with the @code{break} command and its variants (@pxref{Set
2814 Breaks, ,Setting Breakpoints}), to specify the place where your program
2815 should stop by line number, function name or exact address in the
2818 On some systems, you can set breakpoints in shared libraries before
2819 the executable is run. There is a minor limitation on HP-UX systems:
2820 you must wait until the executable is run in order to set breakpoints
2821 in shared library routines that are not called directly by the program
2822 (for example, routines that are arguments in a @code{pthread_create}
2826 @cindex data breakpoints
2827 @cindex memory tracing
2828 @cindex breakpoint on memory address
2829 @cindex breakpoint on variable modification
2830 A @dfn{watchpoint} is a special breakpoint that stops your program
2831 when the value of an expression changes. The expression may be a value
2832 of a variable, or it could involve values of one or more variables
2833 combined by operators, such as @samp{a + b}. This is sometimes called
2834 @dfn{data breakpoints}. You must use a different command to set
2835 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2836 from that, you can manage a watchpoint like any other breakpoint: you
2837 enable, disable, and delete both breakpoints and watchpoints using the
2840 You can arrange to have values from your program displayed automatically
2841 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2845 @cindex breakpoint on events
2846 A @dfn{catchpoint} is another special breakpoint that stops your program
2847 when a certain kind of event occurs, such as the throwing of a C@t{++}
2848 exception or the loading of a library. As with watchpoints, you use a
2849 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2850 Catchpoints}), but aside from that, you can manage a catchpoint like any
2851 other breakpoint. (To stop when your program receives a signal, use the
2852 @code{handle} command; see @ref{Signals, ,Signals}.)
2854 @cindex breakpoint numbers
2855 @cindex numbers for breakpoints
2856 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2857 catchpoint when you create it; these numbers are successive integers
2858 starting with one. In many of the commands for controlling various
2859 features of breakpoints you use the breakpoint number to say which
2860 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2861 @dfn{disabled}; if disabled, it has no effect on your program until you
2864 @cindex breakpoint ranges
2865 @cindex ranges of breakpoints
2866 Some @value{GDBN} commands accept a range of breakpoints on which to
2867 operate. A breakpoint range is either a single breakpoint number, like
2868 @samp{5}, or two such numbers, in increasing order, separated by a
2869 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2870 all breakpoints in that range are operated on.
2873 * Set Breaks:: Setting breakpoints
2874 * Set Watchpoints:: Setting watchpoints
2875 * Set Catchpoints:: Setting catchpoints
2876 * Delete Breaks:: Deleting breakpoints
2877 * Disabling:: Disabling breakpoints
2878 * Conditions:: Break conditions
2879 * Break Commands:: Breakpoint command lists
2880 * Error in Breakpoints:: ``Cannot insert breakpoints''
2881 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2885 @subsection Setting Breakpoints
2887 @c FIXME LMB what does GDB do if no code on line of breakpt?
2888 @c consider in particular declaration with/without initialization.
2890 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2893 @kindex b @r{(@code{break})}
2894 @vindex $bpnum@r{, convenience variable}
2895 @cindex latest breakpoint
2896 Breakpoints are set with the @code{break} command (abbreviated
2897 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2898 number of the breakpoint you've set most recently; see @ref{Convenience
2899 Vars,, Convenience Variables}, for a discussion of what you can do with
2900 convenience variables.
2903 @item break @var{location}
2904 Set a breakpoint at the given @var{location}, which can specify a
2905 function name, a line number, or an address of an instruction.
2906 (@xref{Specify Location}, for a list of all the possible ways to
2907 specify a @var{location}.) The breakpoint will stop your program just
2908 before it executes any of the code in the specified @var{location}.
2910 When using source languages that permit overloading of symbols, such as
2911 C@t{++}, a function name may refer to more than one possible place to break.
2912 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
2916 When called without any arguments, @code{break} sets a breakpoint at
2917 the next instruction to be executed in the selected stack frame
2918 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2919 innermost, this makes your program stop as soon as control
2920 returns to that frame. This is similar to the effect of a
2921 @code{finish} command in the frame inside the selected frame---except
2922 that @code{finish} does not leave an active breakpoint. If you use
2923 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2924 the next time it reaches the current location; this may be useful
2927 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2928 least one instruction has been executed. If it did not do this, you
2929 would be unable to proceed past a breakpoint without first disabling the
2930 breakpoint. This rule applies whether or not the breakpoint already
2931 existed when your program stopped.
2933 @item break @dots{} if @var{cond}
2934 Set a breakpoint with condition @var{cond}; evaluate the expression
2935 @var{cond} each time the breakpoint is reached, and stop only if the
2936 value is nonzero---that is, if @var{cond} evaluates as true.
2937 @samp{@dots{}} stands for one of the possible arguments described
2938 above (or no argument) specifying where to break. @xref{Conditions,
2939 ,Break Conditions}, for more information on breakpoint conditions.
2942 @item tbreak @var{args}
2943 Set a breakpoint enabled only for one stop. @var{args} are the
2944 same as for the @code{break} command, and the breakpoint is set in the same
2945 way, but the breakpoint is automatically deleted after the first time your
2946 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2949 @cindex hardware breakpoints
2950 @item hbreak @var{args}
2951 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2952 @code{break} command and the breakpoint is set in the same way, but the
2953 breakpoint requires hardware support and some target hardware may not
2954 have this support. The main purpose of this is EPROM/ROM code
2955 debugging, so you can set a breakpoint at an instruction without
2956 changing the instruction. This can be used with the new trap-generation
2957 provided by SPARClite DSU and most x86-based targets. These targets
2958 will generate traps when a program accesses some data or instruction
2959 address that is assigned to the debug registers. However the hardware
2960 breakpoint registers can take a limited number of breakpoints. For
2961 example, on the DSU, only two data breakpoints can be set at a time, and
2962 @value{GDBN} will reject this command if more than two are used. Delete
2963 or disable unused hardware breakpoints before setting new ones
2964 (@pxref{Disabling, ,Disabling Breakpoints}).
2965 @xref{Conditions, ,Break Conditions}.
2966 For remote targets, you can restrict the number of hardware
2967 breakpoints @value{GDBN} will use, see @ref{set remote
2968 hardware-breakpoint-limit}.
2971 @item thbreak @var{args}
2972 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2973 are the same as for the @code{hbreak} command and the breakpoint is set in
2974 the same way. However, like the @code{tbreak} command,
2975 the breakpoint is automatically deleted after the
2976 first time your program stops there. Also, like the @code{hbreak}
2977 command, the breakpoint requires hardware support and some target hardware
2978 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2979 See also @ref{Conditions, ,Break Conditions}.
2982 @cindex regular expression
2983 @cindex breakpoints in functions matching a regexp
2984 @cindex set breakpoints in many functions
2985 @item rbreak @var{regex}
2986 Set breakpoints on all functions matching the regular expression
2987 @var{regex}. This command sets an unconditional breakpoint on all
2988 matches, printing a list of all breakpoints it set. Once these
2989 breakpoints are set, they are treated just like the breakpoints set with
2990 the @code{break} command. You can delete them, disable them, or make
2991 them conditional the same way as any other breakpoint.
2993 The syntax of the regular expression is the standard one used with tools
2994 like @file{grep}. Note that this is different from the syntax used by
2995 shells, so for instance @code{foo*} matches all functions that include
2996 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2997 @code{.*} leading and trailing the regular expression you supply, so to
2998 match only functions that begin with @code{foo}, use @code{^foo}.
3000 @cindex non-member C@t{++} functions, set breakpoint in
3001 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3002 breakpoints on overloaded functions that are not members of any special
3005 @cindex set breakpoints on all functions
3006 The @code{rbreak} command can be used to set breakpoints in
3007 @strong{all} the functions in a program, like this:
3010 (@value{GDBP}) rbreak .
3013 @kindex info breakpoints
3014 @cindex @code{$_} and @code{info breakpoints}
3015 @item info breakpoints @r{[}@var{n}@r{]}
3016 @itemx info break @r{[}@var{n}@r{]}
3017 @itemx info watchpoints @r{[}@var{n}@r{]}
3018 Print a table of all breakpoints, watchpoints, and catchpoints set and
3019 not deleted. Optional argument @var{n} means print information only
3020 about the specified breakpoint (or watchpoint or catchpoint). For
3021 each breakpoint, following columns are printed:
3024 @item Breakpoint Numbers
3026 Breakpoint, watchpoint, or catchpoint.
3028 Whether the breakpoint is marked to be disabled or deleted when hit.
3029 @item Enabled or Disabled
3030 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3031 that are not enabled.
3033 Where the breakpoint is in your program, as a memory address. For a
3034 pending breakpoint whose address is not yet known, this field will
3035 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3036 library that has the symbol or line referred by breakpoint is loaded.
3037 See below for details. A breakpoint with several locations will
3038 have @samp{<MULTIPLE>} in this field---see below for details.
3040 Where the breakpoint is in the source for your program, as a file and
3041 line number. For a pending breakpoint, the original string passed to
3042 the breakpoint command will be listed as it cannot be resolved until
3043 the appropriate shared library is loaded in the future.
3047 If a breakpoint is conditional, @code{info break} shows the condition on
3048 the line following the affected breakpoint; breakpoint commands, if any,
3049 are listed after that. A pending breakpoint is allowed to have a condition
3050 specified for it. The condition is not parsed for validity until a shared
3051 library is loaded that allows the pending breakpoint to resolve to a
3055 @code{info break} with a breakpoint
3056 number @var{n} as argument lists only that breakpoint. The
3057 convenience variable @code{$_} and the default examining-address for
3058 the @code{x} command are set to the address of the last breakpoint
3059 listed (@pxref{Memory, ,Examining Memory}).
3062 @code{info break} displays a count of the number of times the breakpoint
3063 has been hit. This is especially useful in conjunction with the
3064 @code{ignore} command. You can ignore a large number of breakpoint
3065 hits, look at the breakpoint info to see how many times the breakpoint
3066 was hit, and then run again, ignoring one less than that number. This
3067 will get you quickly to the last hit of that breakpoint.
3070 @value{GDBN} allows you to set any number of breakpoints at the same place in
3071 your program. There is nothing silly or meaningless about this. When
3072 the breakpoints are conditional, this is even useful
3073 (@pxref{Conditions, ,Break Conditions}).
3075 @cindex multiple locations, breakpoints
3076 @cindex breakpoints, multiple locations
3077 It is possible that a breakpoint corresponds to several locations
3078 in your program. Examples of this situation are:
3082 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3083 instances of the function body, used in different cases.
3086 For a C@t{++} template function, a given line in the function can
3087 correspond to any number of instantiations.
3090 For an inlined function, a given source line can correspond to
3091 several places where that function is inlined.
3094 In all those cases, @value{GDBN} will insert a breakpoint at all
3095 the relevant locations@footnote{
3096 As of this writing, multiple-location breakpoints work only if there's
3097 line number information for all the locations. This means that they
3098 will generally not work in system libraries, unless you have debug
3099 info with line numbers for them.}.
3101 A breakpoint with multiple locations is displayed in the breakpoint
3102 table using several rows---one header row, followed by one row for
3103 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3104 address column. The rows for individual locations contain the actual
3105 addresses for locations, and show the functions to which those
3106 locations belong. The number column for a location is of the form
3107 @var{breakpoint-number}.@var{location-number}.
3112 Num Type Disp Enb Address What
3113 1 breakpoint keep y <MULTIPLE>
3115 breakpoint already hit 1 time
3116 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3117 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3120 Each location can be individually enabled or disabled by passing
3121 @var{breakpoint-number}.@var{location-number} as argument to the
3122 @code{enable} and @code{disable} commands. Note that you cannot
3123 delete the individual locations from the list, you can only delete the
3124 entire list of locations that belong to their parent breakpoint (with
3125 the @kbd{delete @var{num}} command, where @var{num} is the number of
3126 the parent breakpoint, 1 in the above example). Disabling or enabling
3127 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3128 that belong to that breakpoint.
3130 @cindex pending breakpoints
3131 It's quite common to have a breakpoint inside a shared library.
3132 Shared libraries can be loaded and unloaded explicitly,
3133 and possibly repeatedly, as the program is executed. To support
3134 this use case, @value{GDBN} updates breakpoint locations whenever
3135 any shared library is loaded or unloaded. Typically, you would
3136 set a breakpoint in a shared library at the beginning of your
3137 debugging session, when the library is not loaded, and when the
3138 symbols from the library are not available. When you try to set
3139 breakpoint, @value{GDBN} will ask you if you want to set
3140 a so called @dfn{pending breakpoint}---breakpoint whose address
3141 is not yet resolved.
3143 After the program is run, whenever a new shared library is loaded,
3144 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3145 shared library contains the symbol or line referred to by some
3146 pending breakpoint, that breakpoint is resolved and becomes an
3147 ordinary breakpoint. When a library is unloaded, all breakpoints
3148 that refer to its symbols or source lines become pending again.
3150 This logic works for breakpoints with multiple locations, too. For
3151 example, if you have a breakpoint in a C@t{++} template function, and
3152 a newly loaded shared library has an instantiation of that template,
3153 a new location is added to the list of locations for the breakpoint.
3155 Except for having unresolved address, pending breakpoints do not
3156 differ from regular breakpoints. You can set conditions or commands,
3157 enable and disable them and perform other breakpoint operations.
3159 @value{GDBN} provides some additional commands for controlling what
3160 happens when the @samp{break} command cannot resolve breakpoint
3161 address specification to an address:
3163 @kindex set breakpoint pending
3164 @kindex show breakpoint pending
3166 @item set breakpoint pending auto
3167 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3168 location, it queries you whether a pending breakpoint should be created.
3170 @item set breakpoint pending on
3171 This indicates that an unrecognized breakpoint location should automatically
3172 result in a pending breakpoint being created.
3174 @item set breakpoint pending off
3175 This indicates that pending breakpoints are not to be created. Any
3176 unrecognized breakpoint location results in an error. This setting does
3177 not affect any pending breakpoints previously created.
3179 @item show breakpoint pending
3180 Show the current behavior setting for creating pending breakpoints.
3183 The settings above only affect the @code{break} command and its
3184 variants. Once breakpoint is set, it will be automatically updated
3185 as shared libraries are loaded and unloaded.
3187 @cindex automatic hardware breakpoints
3188 For some targets, @value{GDBN} can automatically decide if hardware or
3189 software breakpoints should be used, depending on whether the
3190 breakpoint address is read-only or read-write. This applies to
3191 breakpoints set with the @code{break} command as well as to internal
3192 breakpoints set by commands like @code{next} and @code{finish}. For
3193 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3196 You can control this automatic behaviour with the following commands::
3198 @kindex set breakpoint auto-hw
3199 @kindex show breakpoint auto-hw
3201 @item set breakpoint auto-hw on
3202 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3203 will try to use the target memory map to decide if software or hardware
3204 breakpoint must be used.
3206 @item set breakpoint auto-hw off
3207 This indicates @value{GDBN} should not automatically select breakpoint
3208 type. If the target provides a memory map, @value{GDBN} will warn when
3209 trying to set software breakpoint at a read-only address.
3212 @value{GDBN} normally implements breakpoints by replacing the program code
3213 at the breakpoint address with a special instruction, which, when
3214 executed, given control to the debugger. By default, the program
3215 code is so modified only when the program is resumed. As soon as
3216 the program stops, @value{GDBN} restores the original instructions. This
3217 behaviour guards against leaving breakpoints inserted in the
3218 target should gdb abrubptly disconnect. However, with slow remote
3219 targets, inserting and removing breakpoint can reduce the performance.
3220 This behavior can be controlled with the following commands::
3222 @kindex set breakpoint always-inserted
3223 @kindex show breakpoint always-inserted
3225 @item set breakpoint always-inserted off
3226 This is the default behaviour. All breakpoints, including newly added
3227 by the user, are inserted in the target only when the target is
3228 resumed. All breakpoints are removed from the target when it stops.
3230 @item set breakpoint always-inserted on
3231 Causes all breakpoints to be inserted in the target at all times. If
3232 the user adds a new breakpoint, or changes an existing breakpoint, the
3233 breakpoints in the target are updated immediately. A breakpoint is
3234 removed from the target only when breakpoint itself is removed.
3237 @cindex negative breakpoint numbers
3238 @cindex internal @value{GDBN} breakpoints
3239 @value{GDBN} itself sometimes sets breakpoints in your program for
3240 special purposes, such as proper handling of @code{longjmp} (in C
3241 programs). These internal breakpoints are assigned negative numbers,
3242 starting with @code{-1}; @samp{info breakpoints} does not display them.
3243 You can see these breakpoints with the @value{GDBN} maintenance command
3244 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3247 @node Set Watchpoints
3248 @subsection Setting Watchpoints
3250 @cindex setting watchpoints
3251 You can use a watchpoint to stop execution whenever the value of an
3252 expression changes, without having to predict a particular place where
3253 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3254 The expression may be as simple as the value of a single variable, or
3255 as complex as many variables combined by operators. Examples include:
3259 A reference to the value of a single variable.
3262 An address cast to an appropriate data type. For example,
3263 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3264 address (assuming an @code{int} occupies 4 bytes).
3267 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3268 expression can use any operators valid in the program's native
3269 language (@pxref{Languages}).
3272 You can set a watchpoint on an expression even if the expression can
3273 not be evaluated yet. For instance, you can set a watchpoint on
3274 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3275 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3276 the expression produces a valid value. If the expression becomes
3277 valid in some other way than changing a variable (e.g.@: if the memory
3278 pointed to by @samp{*global_ptr} becomes readable as the result of a
3279 @code{malloc} call), @value{GDBN} may not stop until the next time
3280 the expression changes.
3282 @cindex software watchpoints
3283 @cindex hardware watchpoints
3284 Depending on your system, watchpoints may be implemented in software or
3285 hardware. @value{GDBN} does software watchpointing by single-stepping your
3286 program and testing the variable's value each time, which is hundreds of
3287 times slower than normal execution. (But this may still be worth it, to
3288 catch errors where you have no clue what part of your program is the
3291 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3292 x86-based targets, @value{GDBN} includes support for hardware
3293 watchpoints, which do not slow down the running of your program.
3297 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3298 Set a watchpoint for an expression. @value{GDBN} will break when the
3299 expression @var{expr} is written into by the program and its value
3300 changes. The simplest (and the most popular) use of this command is
3301 to watch the value of a single variable:
3304 (@value{GDBP}) watch foo
3307 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3308 clause, @value{GDBN} breaks only when the thread identified by
3309 @var{threadnum} changes the value of @var{expr}. If any other threads
3310 change the value of @var{expr}, @value{GDBN} will not break. Note
3311 that watchpoints restricted to a single thread in this way only work
3312 with Hardware Watchpoints.
3315 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3316 Set a watchpoint that will break when the value of @var{expr} is read
3320 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3321 Set a watchpoint that will break when @var{expr} is either read from
3322 or written into by the program.
3324 @kindex info watchpoints @r{[}@var{n}@r{]}
3325 @item info watchpoints
3326 This command prints a list of watchpoints, breakpoints, and catchpoints;
3327 it is the same as @code{info break} (@pxref{Set Breaks}).
3330 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3331 watchpoints execute very quickly, and the debugger reports a change in
3332 value at the exact instruction where the change occurs. If @value{GDBN}
3333 cannot set a hardware watchpoint, it sets a software watchpoint, which
3334 executes more slowly and reports the change in value at the next
3335 @emph{statement}, not the instruction, after the change occurs.
3337 @cindex use only software watchpoints
3338 You can force @value{GDBN} to use only software watchpoints with the
3339 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3340 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3341 the underlying system supports them. (Note that hardware-assisted
3342 watchpoints that were set @emph{before} setting
3343 @code{can-use-hw-watchpoints} to zero will still use the hardware
3344 mechanism of watching expression values.)
3347 @item set can-use-hw-watchpoints
3348 @kindex set can-use-hw-watchpoints
3349 Set whether or not to use hardware watchpoints.
3351 @item show can-use-hw-watchpoints
3352 @kindex show can-use-hw-watchpoints
3353 Show the current mode of using hardware watchpoints.
3356 For remote targets, you can restrict the number of hardware
3357 watchpoints @value{GDBN} will use, see @ref{set remote
3358 hardware-breakpoint-limit}.
3360 When you issue the @code{watch} command, @value{GDBN} reports
3363 Hardware watchpoint @var{num}: @var{expr}
3367 if it was able to set a hardware watchpoint.
3369 Currently, the @code{awatch} and @code{rwatch} commands can only set
3370 hardware watchpoints, because accesses to data that don't change the
3371 value of the watched expression cannot be detected without examining
3372 every instruction as it is being executed, and @value{GDBN} does not do
3373 that currently. If @value{GDBN} finds that it is unable to set a
3374 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3375 will print a message like this:
3378 Expression cannot be implemented with read/access watchpoint.
3381 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3382 data type of the watched expression is wider than what a hardware
3383 watchpoint on the target machine can handle. For example, some systems
3384 can only watch regions that are up to 4 bytes wide; on such systems you
3385 cannot set hardware watchpoints for an expression that yields a
3386 double-precision floating-point number (which is typically 8 bytes
3387 wide). As a work-around, it might be possible to break the large region
3388 into a series of smaller ones and watch them with separate watchpoints.
3390 If you set too many hardware watchpoints, @value{GDBN} might be unable
3391 to insert all of them when you resume the execution of your program.
3392 Since the precise number of active watchpoints is unknown until such
3393 time as the program is about to be resumed, @value{GDBN} might not be
3394 able to warn you about this when you set the watchpoints, and the
3395 warning will be printed only when the program is resumed:
3398 Hardware watchpoint @var{num}: Could not insert watchpoint
3402 If this happens, delete or disable some of the watchpoints.
3404 Watching complex expressions that reference many variables can also
3405 exhaust the resources available for hardware-assisted watchpoints.
3406 That's because @value{GDBN} needs to watch every variable in the
3407 expression with separately allocated resources.
3409 If you call a function interactively using @code{print} or @code{call},
3410 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3411 kind of breakpoint or the call completes.
3413 @value{GDBN} automatically deletes watchpoints that watch local
3414 (automatic) variables, or expressions that involve such variables, when
3415 they go out of scope, that is, when the execution leaves the block in
3416 which these variables were defined. In particular, when the program
3417 being debugged terminates, @emph{all} local variables go out of scope,
3418 and so only watchpoints that watch global variables remain set. If you
3419 rerun the program, you will need to set all such watchpoints again. One
3420 way of doing that would be to set a code breakpoint at the entry to the
3421 @code{main} function and when it breaks, set all the watchpoints.
3423 @cindex watchpoints and threads
3424 @cindex threads and watchpoints
3425 In multi-threaded programs, watchpoints will detect changes to the
3426 watched expression from every thread.
3429 @emph{Warning:} In multi-threaded programs, software watchpoints
3430 have only limited usefulness. If @value{GDBN} creates a software
3431 watchpoint, it can only watch the value of an expression @emph{in a
3432 single thread}. If you are confident that the expression can only
3433 change due to the current thread's activity (and if you are also
3434 confident that no other thread can become current), then you can use
3435 software watchpoints as usual. However, @value{GDBN} may not notice
3436 when a non-current thread's activity changes the expression. (Hardware
3437 watchpoints, in contrast, watch an expression in all threads.)
3440 @xref{set remote hardware-watchpoint-limit}.
3442 @node Set Catchpoints
3443 @subsection Setting Catchpoints
3444 @cindex catchpoints, setting
3445 @cindex exception handlers
3446 @cindex event handling
3448 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3449 kinds of program events, such as C@t{++} exceptions or the loading of a
3450 shared library. Use the @code{catch} command to set a catchpoint.
3454 @item catch @var{event}
3455 Stop when @var{event} occurs. @var{event} can be any of the following:
3458 @cindex stop on C@t{++} exceptions
3459 The throwing of a C@t{++} exception.
3462 The catching of a C@t{++} exception.
3465 @cindex Ada exception catching
3466 @cindex catch Ada exceptions
3467 An Ada exception being raised. If an exception name is specified
3468 at the end of the command (eg @code{catch exception Program_Error}),
3469 the debugger will stop only when this specific exception is raised.
3470 Otherwise, the debugger stops execution when any Ada exception is raised.
3472 @item exception unhandled
3473 An exception that was raised but is not handled by the program.
3476 A failed Ada assertion.
3479 @cindex break on fork/exec
3480 A call to @code{exec}. This is currently only available for HP-UX
3484 A call to @code{fork}. This is currently only available for HP-UX
3488 A call to @code{vfork}. This is currently only available for HP-UX
3492 @itemx load @var{libname}
3493 @cindex break on load/unload of shared library
3494 The dynamic loading of any shared library, or the loading of the library
3495 @var{libname}. This is currently only available for HP-UX.
3498 @itemx unload @var{libname}
3499 The unloading of any dynamically loaded shared library, or the unloading
3500 of the library @var{libname}. This is currently only available for HP-UX.
3503 @item tcatch @var{event}
3504 Set a catchpoint that is enabled only for one stop. The catchpoint is
3505 automatically deleted after the first time the event is caught.
3509 Use the @code{info break} command to list the current catchpoints.
3511 There are currently some limitations to C@t{++} exception handling
3512 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3516 If you call a function interactively, @value{GDBN} normally returns
3517 control to you when the function has finished executing. If the call
3518 raises an exception, however, the call may bypass the mechanism that
3519 returns control to you and cause your program either to abort or to
3520 simply continue running until it hits a breakpoint, catches a signal
3521 that @value{GDBN} is listening for, or exits. This is the case even if
3522 you set a catchpoint for the exception; catchpoints on exceptions are
3523 disabled within interactive calls.
3526 You cannot raise an exception interactively.
3529 You cannot install an exception handler interactively.
3532 @cindex raise exceptions
3533 Sometimes @code{catch} is not the best way to debug exception handling:
3534 if you need to know exactly where an exception is raised, it is better to
3535 stop @emph{before} the exception handler is called, since that way you
3536 can see the stack before any unwinding takes place. If you set a
3537 breakpoint in an exception handler instead, it may not be easy to find
3538 out where the exception was raised.
3540 To stop just before an exception handler is called, you need some
3541 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3542 raised by calling a library function named @code{__raise_exception}
3543 which has the following ANSI C interface:
3546 /* @var{addr} is where the exception identifier is stored.
3547 @var{id} is the exception identifier. */
3548 void __raise_exception (void **addr, void *id);
3552 To make the debugger catch all exceptions before any stack
3553 unwinding takes place, set a breakpoint on @code{__raise_exception}
3554 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3556 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3557 that depends on the value of @var{id}, you can stop your program when
3558 a specific exception is raised. You can use multiple conditional
3559 breakpoints to stop your program when any of a number of exceptions are
3564 @subsection Deleting Breakpoints
3566 @cindex clearing breakpoints, watchpoints, catchpoints
3567 @cindex deleting breakpoints, watchpoints, catchpoints
3568 It is often necessary to eliminate a breakpoint, watchpoint, or
3569 catchpoint once it has done its job and you no longer want your program
3570 to stop there. This is called @dfn{deleting} the breakpoint. A
3571 breakpoint that has been deleted no longer exists; it is forgotten.
3573 With the @code{clear} command you can delete breakpoints according to
3574 where they are in your program. With the @code{delete} command you can
3575 delete individual breakpoints, watchpoints, or catchpoints by specifying
3576 their breakpoint numbers.
3578 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3579 automatically ignores breakpoints on the first instruction to be executed
3580 when you continue execution without changing the execution address.
3585 Delete any breakpoints at the next instruction to be executed in the
3586 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3587 the innermost frame is selected, this is a good way to delete a
3588 breakpoint where your program just stopped.
3590 @item clear @var{location}
3591 Delete any breakpoints set at the specified @var{location}.
3592 @xref{Specify Location}, for the various forms of @var{location}; the
3593 most useful ones are listed below:
3596 @item clear @var{function}
3597 @itemx clear @var{filename}:@var{function}
3598 Delete any breakpoints set at entry to the named @var{function}.
3600 @item clear @var{linenum}
3601 @itemx clear @var{filename}:@var{linenum}
3602 Delete any breakpoints set at or within the code of the specified
3603 @var{linenum} of the specified @var{filename}.
3606 @cindex delete breakpoints
3608 @kindex d @r{(@code{delete})}
3609 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3610 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3611 ranges specified as arguments. If no argument is specified, delete all
3612 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3613 confirm off}). You can abbreviate this command as @code{d}.
3617 @subsection Disabling Breakpoints
3619 @cindex enable/disable a breakpoint
3620 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3621 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3622 it had been deleted, but remembers the information on the breakpoint so
3623 that you can @dfn{enable} it again later.
3625 You disable and enable breakpoints, watchpoints, and catchpoints with
3626 the @code{enable} and @code{disable} commands, optionally specifying one
3627 or more breakpoint numbers as arguments. Use @code{info break} or
3628 @code{info watch} to print a list of breakpoints, watchpoints, and
3629 catchpoints if you do not know which numbers to use.
3631 Disabling and enabling a breakpoint that has multiple locations
3632 affects all of its locations.
3634 A breakpoint, watchpoint, or catchpoint can have any of four different
3635 states of enablement:
3639 Enabled. The breakpoint stops your program. A breakpoint set
3640 with the @code{break} command starts out in this state.
3642 Disabled. The breakpoint has no effect on your program.
3644 Enabled once. The breakpoint stops your program, but then becomes
3647 Enabled for deletion. The breakpoint stops your program, but
3648 immediately after it does so it is deleted permanently. A breakpoint
3649 set with the @code{tbreak} command starts out in this state.
3652 You can use the following commands to enable or disable breakpoints,
3653 watchpoints, and catchpoints:
3657 @kindex dis @r{(@code{disable})}
3658 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3659 Disable the specified breakpoints---or all breakpoints, if none are
3660 listed. A disabled breakpoint has no effect but is not forgotten. All
3661 options such as ignore-counts, conditions and commands are remembered in
3662 case the breakpoint is enabled again later. You may abbreviate
3663 @code{disable} as @code{dis}.
3666 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3667 Enable the specified breakpoints (or all defined breakpoints). They
3668 become effective once again in stopping your program.
3670 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3671 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3672 of these breakpoints immediately after stopping your program.
3674 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3675 Enable the specified breakpoints to work once, then die. @value{GDBN}
3676 deletes any of these breakpoints as soon as your program stops there.
3677 Breakpoints set by the @code{tbreak} command start out in this state.
3680 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3681 @c confusing: tbreak is also initially enabled.
3682 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3683 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3684 subsequently, they become disabled or enabled only when you use one of
3685 the commands above. (The command @code{until} can set and delete a
3686 breakpoint of its own, but it does not change the state of your other
3687 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3691 @subsection Break Conditions
3692 @cindex conditional breakpoints
3693 @cindex breakpoint conditions
3695 @c FIXME what is scope of break condition expr? Context where wanted?
3696 @c in particular for a watchpoint?
3697 The simplest sort of breakpoint breaks every time your program reaches a
3698 specified place. You can also specify a @dfn{condition} for a
3699 breakpoint. A condition is just a Boolean expression in your
3700 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3701 a condition evaluates the expression each time your program reaches it,
3702 and your program stops only if the condition is @emph{true}.
3704 This is the converse of using assertions for program validation; in that
3705 situation, you want to stop when the assertion is violated---that is,
3706 when the condition is false. In C, if you want to test an assertion expressed
3707 by the condition @var{assert}, you should set the condition
3708 @samp{! @var{assert}} on the appropriate breakpoint.
3710 Conditions are also accepted for watchpoints; you may not need them,
3711 since a watchpoint is inspecting the value of an expression anyhow---but
3712 it might be simpler, say, to just set a watchpoint on a variable name,
3713 and specify a condition that tests whether the new value is an interesting
3716 Break conditions can have side effects, and may even call functions in
3717 your program. This can be useful, for example, to activate functions
3718 that log program progress, or to use your own print functions to
3719 format special data structures. The effects are completely predictable
3720 unless there is another enabled breakpoint at the same address. (In
3721 that case, @value{GDBN} might see the other breakpoint first and stop your
3722 program without checking the condition of this one.) Note that
3723 breakpoint commands are usually more convenient and flexible than break
3725 purpose of performing side effects when a breakpoint is reached
3726 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3728 Break conditions can be specified when a breakpoint is set, by using
3729 @samp{if} in the arguments to the @code{break} command. @xref{Set
3730 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3731 with the @code{condition} command.
3733 You can also use the @code{if} keyword with the @code{watch} command.
3734 The @code{catch} command does not recognize the @code{if} keyword;
3735 @code{condition} is the only way to impose a further condition on a
3740 @item condition @var{bnum} @var{expression}
3741 Specify @var{expression} as the break condition for breakpoint,
3742 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3743 breakpoint @var{bnum} stops your program only if the value of
3744 @var{expression} is true (nonzero, in C). When you use
3745 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3746 syntactic correctness, and to determine whether symbols in it have
3747 referents in the context of your breakpoint. If @var{expression} uses
3748 symbols not referenced in the context of the breakpoint, @value{GDBN}
3749 prints an error message:
3752 No symbol "foo" in current context.
3757 not actually evaluate @var{expression} at the time the @code{condition}
3758 command (or a command that sets a breakpoint with a condition, like
3759 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3761 @item condition @var{bnum}
3762 Remove the condition from breakpoint number @var{bnum}. It becomes
3763 an ordinary unconditional breakpoint.
3766 @cindex ignore count (of breakpoint)
3767 A special case of a breakpoint condition is to stop only when the
3768 breakpoint has been reached a certain number of times. This is so
3769 useful that there is a special way to do it, using the @dfn{ignore
3770 count} of the breakpoint. Every breakpoint has an ignore count, which
3771 is an integer. Most of the time, the ignore count is zero, and
3772 therefore has no effect. But if your program reaches a breakpoint whose
3773 ignore count is positive, then instead of stopping, it just decrements
3774 the ignore count by one and continues. As a result, if the ignore count
3775 value is @var{n}, the breakpoint does not stop the next @var{n} times
3776 your program reaches it.
3780 @item ignore @var{bnum} @var{count}
3781 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3782 The next @var{count} times the breakpoint is reached, your program's
3783 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3786 To make the breakpoint stop the next time it is reached, specify
3789 When you use @code{continue} to resume execution of your program from a
3790 breakpoint, you can specify an ignore count directly as an argument to
3791 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3792 Stepping,,Continuing and Stepping}.
3794 If a breakpoint has a positive ignore count and a condition, the
3795 condition is not checked. Once the ignore count reaches zero,
3796 @value{GDBN} resumes checking the condition.
3798 You could achieve the effect of the ignore count with a condition such
3799 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3800 is decremented each time. @xref{Convenience Vars, ,Convenience
3804 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3807 @node Break Commands
3808 @subsection Breakpoint Command Lists
3810 @cindex breakpoint commands
3811 You can give any breakpoint (or watchpoint or catchpoint) a series of
3812 commands to execute when your program stops due to that breakpoint. For
3813 example, you might want to print the values of certain expressions, or
3814 enable other breakpoints.
3818 @kindex end@r{ (breakpoint commands)}
3819 @item commands @r{[}@var{bnum}@r{]}
3820 @itemx @dots{} @var{command-list} @dots{}
3822 Specify a list of commands for breakpoint number @var{bnum}. The commands
3823 themselves appear on the following lines. Type a line containing just
3824 @code{end} to terminate the commands.
3826 To remove all commands from a breakpoint, type @code{commands} and
3827 follow it immediately with @code{end}; that is, give no commands.
3829 With no @var{bnum} argument, @code{commands} refers to the last
3830 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3831 recently encountered).
3834 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3835 disabled within a @var{command-list}.
3837 You can use breakpoint commands to start your program up again. Simply
3838 use the @code{continue} command, or @code{step}, or any other command
3839 that resumes execution.
3841 Any other commands in the command list, after a command that resumes
3842 execution, are ignored. This is because any time you resume execution
3843 (even with a simple @code{next} or @code{step}), you may encounter
3844 another breakpoint---which could have its own command list, leading to
3845 ambiguities about which list to execute.
3848 If the first command you specify in a command list is @code{silent}, the
3849 usual message about stopping at a breakpoint is not printed. This may
3850 be desirable for breakpoints that are to print a specific message and
3851 then continue. If none of the remaining commands print anything, you
3852 see no sign that the breakpoint was reached. @code{silent} is
3853 meaningful only at the beginning of a breakpoint command list.
3855 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3856 print precisely controlled output, and are often useful in silent
3857 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3859 For example, here is how you could use breakpoint commands to print the
3860 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3866 printf "x is %d\n",x
3871 One application for breakpoint commands is to compensate for one bug so
3872 you can test for another. Put a breakpoint just after the erroneous line
3873 of code, give it a condition to detect the case in which something
3874 erroneous has been done, and give it commands to assign correct values
3875 to any variables that need them. End with the @code{continue} command
3876 so that your program does not stop, and start with the @code{silent}
3877 command so that no output is produced. Here is an example:
3888 @c @ifclear BARETARGET
3889 @node Error in Breakpoints
3890 @subsection ``Cannot insert breakpoints''
3892 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3894 Under some operating systems, breakpoints cannot be used in a program if
3895 any other process is running that program. In this situation,
3896 attempting to run or continue a program with a breakpoint causes
3897 @value{GDBN} to print an error message:
3900 Cannot insert breakpoints.
3901 The same program may be running in another process.
3904 When this happens, you have three ways to proceed:
3908 Remove or disable the breakpoints, then continue.
3911 Suspend @value{GDBN}, and copy the file containing your program to a new
3912 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3913 that @value{GDBN} should run your program under that name.
3914 Then start your program again.
3917 Relink your program so that the text segment is nonsharable, using the
3918 linker option @samp{-N}. The operating system limitation may not apply
3919 to nonsharable executables.
3923 A similar message can be printed if you request too many active
3924 hardware-assisted breakpoints and watchpoints:
3926 @c FIXME: the precise wording of this message may change; the relevant
3927 @c source change is not committed yet (Sep 3, 1999).
3929 Stopped; cannot insert breakpoints.
3930 You may have requested too many hardware breakpoints and watchpoints.
3934 This message is printed when you attempt to resume the program, since
3935 only then @value{GDBN} knows exactly how many hardware breakpoints and
3936 watchpoints it needs to insert.
3938 When this message is printed, you need to disable or remove some of the
3939 hardware-assisted breakpoints and watchpoints, and then continue.
3941 @node Breakpoint-related Warnings
3942 @subsection ``Breakpoint address adjusted...''
3943 @cindex breakpoint address adjusted
3945 Some processor architectures place constraints on the addresses at
3946 which breakpoints may be placed. For architectures thus constrained,
3947 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3948 with the constraints dictated by the architecture.
3950 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3951 a VLIW architecture in which a number of RISC-like instructions may be
3952 bundled together for parallel execution. The FR-V architecture
3953 constrains the location of a breakpoint instruction within such a
3954 bundle to the instruction with the lowest address. @value{GDBN}
3955 honors this constraint by adjusting a breakpoint's address to the
3956 first in the bundle.
3958 It is not uncommon for optimized code to have bundles which contain
3959 instructions from different source statements, thus it may happen that
3960 a breakpoint's address will be adjusted from one source statement to
3961 another. Since this adjustment may significantly alter @value{GDBN}'s
3962 breakpoint related behavior from what the user expects, a warning is
3963 printed when the breakpoint is first set and also when the breakpoint
3966 A warning like the one below is printed when setting a breakpoint
3967 that's been subject to address adjustment:
3970 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3973 Such warnings are printed both for user settable and @value{GDBN}'s
3974 internal breakpoints. If you see one of these warnings, you should
3975 verify that a breakpoint set at the adjusted address will have the
3976 desired affect. If not, the breakpoint in question may be removed and
3977 other breakpoints may be set which will have the desired behavior.
3978 E.g., it may be sufficient to place the breakpoint at a later
3979 instruction. A conditional breakpoint may also be useful in some
3980 cases to prevent the breakpoint from triggering too often.
3982 @value{GDBN} will also issue a warning when stopping at one of these
3983 adjusted breakpoints:
3986 warning: Breakpoint 1 address previously adjusted from 0x00010414
3990 When this warning is encountered, it may be too late to take remedial
3991 action except in cases where the breakpoint is hit earlier or more
3992 frequently than expected.
3994 @node Continuing and Stepping
3995 @section Continuing and Stepping
3999 @cindex resuming execution
4000 @dfn{Continuing} means resuming program execution until your program
4001 completes normally. In contrast, @dfn{stepping} means executing just
4002 one more ``step'' of your program, where ``step'' may mean either one
4003 line of source code, or one machine instruction (depending on what
4004 particular command you use). Either when continuing or when stepping,
4005 your program may stop even sooner, due to a breakpoint or a signal. (If
4006 it stops due to a signal, you may want to use @code{handle}, or use
4007 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4011 @kindex c @r{(@code{continue})}
4012 @kindex fg @r{(resume foreground execution)}
4013 @item continue @r{[}@var{ignore-count}@r{]}
4014 @itemx c @r{[}@var{ignore-count}@r{]}
4015 @itemx fg @r{[}@var{ignore-count}@r{]}
4016 Resume program execution, at the address where your program last stopped;
4017 any breakpoints set at that address are bypassed. The optional argument
4018 @var{ignore-count} allows you to specify a further number of times to
4019 ignore a breakpoint at this location; its effect is like that of
4020 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4022 The argument @var{ignore-count} is meaningful only when your program
4023 stopped due to a breakpoint. At other times, the argument to
4024 @code{continue} is ignored.
4026 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4027 debugged program is deemed to be the foreground program) are provided
4028 purely for convenience, and have exactly the same behavior as
4032 To resume execution at a different place, you can use @code{return}
4033 (@pxref{Returning, ,Returning from a Function}) to go back to the
4034 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4035 Different Address}) to go to an arbitrary location in your program.
4037 A typical technique for using stepping is to set a breakpoint
4038 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4039 beginning of the function or the section of your program where a problem
4040 is believed to lie, run your program until it stops at that breakpoint,
4041 and then step through the suspect area, examining the variables that are
4042 interesting, until you see the problem happen.
4046 @kindex s @r{(@code{step})}
4048 Continue running your program until control reaches a different source
4049 line, then stop it and return control to @value{GDBN}. This command is
4050 abbreviated @code{s}.
4053 @c "without debugging information" is imprecise; actually "without line
4054 @c numbers in the debugging information". (gcc -g1 has debugging info but
4055 @c not line numbers). But it seems complex to try to make that
4056 @c distinction here.
4057 @emph{Warning:} If you use the @code{step} command while control is
4058 within a function that was compiled without debugging information,
4059 execution proceeds until control reaches a function that does have
4060 debugging information. Likewise, it will not step into a function which
4061 is compiled without debugging information. To step through functions
4062 without debugging information, use the @code{stepi} command, described
4066 The @code{step} command only stops at the first instruction of a source
4067 line. This prevents the multiple stops that could otherwise occur in
4068 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4069 to stop if a function that has debugging information is called within
4070 the line. In other words, @code{step} @emph{steps inside} any functions
4071 called within the line.
4073 Also, the @code{step} command only enters a function if there is line
4074 number information for the function. Otherwise it acts like the
4075 @code{next} command. This avoids problems when using @code{cc -gl}
4076 on MIPS machines. Previously, @code{step} entered subroutines if there
4077 was any debugging information about the routine.
4079 @item step @var{count}
4080 Continue running as in @code{step}, but do so @var{count} times. If a
4081 breakpoint is reached, or a signal not related to stepping occurs before
4082 @var{count} steps, stepping stops right away.
4085 @kindex n @r{(@code{next})}
4086 @item next @r{[}@var{count}@r{]}
4087 Continue to the next source line in the current (innermost) stack frame.
4088 This is similar to @code{step}, but function calls that appear within
4089 the line of code are executed without stopping. Execution stops when
4090 control reaches a different line of code at the original stack level
4091 that was executing when you gave the @code{next} command. This command
4092 is abbreviated @code{n}.
4094 An argument @var{count} is a repeat count, as for @code{step}.
4097 @c FIX ME!! Do we delete this, or is there a way it fits in with
4098 @c the following paragraph? --- Vctoria
4100 @c @code{next} within a function that lacks debugging information acts like
4101 @c @code{step}, but any function calls appearing within the code of the
4102 @c function are executed without stopping.
4104 The @code{next} command only stops at the first instruction of a
4105 source line. This prevents multiple stops that could otherwise occur in
4106 @code{switch} statements, @code{for} loops, etc.
4108 @kindex set step-mode
4110 @cindex functions without line info, and stepping
4111 @cindex stepping into functions with no line info
4112 @itemx set step-mode on
4113 The @code{set step-mode on} command causes the @code{step} command to
4114 stop at the first instruction of a function which contains no debug line
4115 information rather than stepping over it.
4117 This is useful in cases where you may be interested in inspecting the
4118 machine instructions of a function which has no symbolic info and do not
4119 want @value{GDBN} to automatically skip over this function.
4121 @item set step-mode off
4122 Causes the @code{step} command to step over any functions which contains no
4123 debug information. This is the default.
4125 @item show step-mode
4126 Show whether @value{GDBN} will stop in or step over functions without
4127 source line debug information.
4130 @kindex fin @r{(@code{finish})}
4132 Continue running until just after function in the selected stack frame
4133 returns. Print the returned value (if any). This command can be
4134 abbreviated as @code{fin}.
4136 Contrast this with the @code{return} command (@pxref{Returning,
4137 ,Returning from a Function}).
4140 @kindex u @r{(@code{until})}
4141 @cindex run until specified location
4144 Continue running until a source line past the current line, in the
4145 current stack frame, is reached. This command is used to avoid single
4146 stepping through a loop more than once. It is like the @code{next}
4147 command, except that when @code{until} encounters a jump, it
4148 automatically continues execution until the program counter is greater
4149 than the address of the jump.
4151 This means that when you reach the end of a loop after single stepping
4152 though it, @code{until} makes your program continue execution until it
4153 exits the loop. In contrast, a @code{next} command at the end of a loop
4154 simply steps back to the beginning of the loop, which forces you to step
4155 through the next iteration.
4157 @code{until} always stops your program if it attempts to exit the current
4160 @code{until} may produce somewhat counterintuitive results if the order
4161 of machine code does not match the order of the source lines. For
4162 example, in the following excerpt from a debugging session, the @code{f}
4163 (@code{frame}) command shows that execution is stopped at line
4164 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4168 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4170 (@value{GDBP}) until
4171 195 for ( ; argc > 0; NEXTARG) @{
4174 This happened because, for execution efficiency, the compiler had
4175 generated code for the loop closure test at the end, rather than the
4176 start, of the loop---even though the test in a C @code{for}-loop is
4177 written before the body of the loop. The @code{until} command appeared
4178 to step back to the beginning of the loop when it advanced to this
4179 expression; however, it has not really gone to an earlier
4180 statement---not in terms of the actual machine code.
4182 @code{until} with no argument works by means of single
4183 instruction stepping, and hence is slower than @code{until} with an
4186 @item until @var{location}
4187 @itemx u @var{location}
4188 Continue running your program until either the specified location is
4189 reached, or the current stack frame returns. @var{location} is any of
4190 the forms described in @ref{Specify Location}.
4191 This form of the command uses temporary breakpoints, and
4192 hence is quicker than @code{until} without an argument. The specified
4193 location is actually reached only if it is in the current frame. This
4194 implies that @code{until} can be used to skip over recursive function
4195 invocations. For instance in the code below, if the current location is
4196 line @code{96}, issuing @code{until 99} will execute the program up to
4197 line @code{99} in the same invocation of factorial, i.e., after the inner
4198 invocations have returned.
4201 94 int factorial (int value)
4203 96 if (value > 1) @{
4204 97 value *= factorial (value - 1);
4211 @kindex advance @var{location}
4212 @itemx advance @var{location}
4213 Continue running the program up to the given @var{location}. An argument is
4214 required, which should be of one of the forms described in
4215 @ref{Specify Location}.
4216 Execution will also stop upon exit from the current stack
4217 frame. This command is similar to @code{until}, but @code{advance} will
4218 not skip over recursive function calls, and the target location doesn't
4219 have to be in the same frame as the current one.
4223 @kindex si @r{(@code{stepi})}
4225 @itemx stepi @var{arg}
4227 Execute one machine instruction, then stop and return to the debugger.
4229 It is often useful to do @samp{display/i $pc} when stepping by machine
4230 instructions. This makes @value{GDBN} automatically display the next
4231 instruction to be executed, each time your program stops. @xref{Auto
4232 Display,, Automatic Display}.
4234 An argument is a repeat count, as in @code{step}.
4238 @kindex ni @r{(@code{nexti})}
4240 @itemx nexti @var{arg}
4242 Execute one machine instruction, but if it is a function call,
4243 proceed until the function returns.
4245 An argument is a repeat count, as in @code{next}.
4252 A signal is an asynchronous event that can happen in a program. The
4253 operating system defines the possible kinds of signals, and gives each
4254 kind a name and a number. For example, in Unix @code{SIGINT} is the
4255 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4256 @code{SIGSEGV} is the signal a program gets from referencing a place in
4257 memory far away from all the areas in use; @code{SIGALRM} occurs when
4258 the alarm clock timer goes off (which happens only if your program has
4259 requested an alarm).
4261 @cindex fatal signals
4262 Some signals, including @code{SIGALRM}, are a normal part of the
4263 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4264 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4265 program has not specified in advance some other way to handle the signal.
4266 @code{SIGINT} does not indicate an error in your program, but it is normally
4267 fatal so it can carry out the purpose of the interrupt: to kill the program.
4269 @value{GDBN} has the ability to detect any occurrence of a signal in your
4270 program. You can tell @value{GDBN} in advance what to do for each kind of
4273 @cindex handling signals
4274 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4275 @code{SIGALRM} be silently passed to your program
4276 (so as not to interfere with their role in the program's functioning)
4277 but to stop your program immediately whenever an error signal happens.
4278 You can change these settings with the @code{handle} command.
4281 @kindex info signals
4285 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4286 handle each one. You can use this to see the signal numbers of all
4287 the defined types of signals.
4289 @item info signals @var{sig}
4290 Similar, but print information only about the specified signal number.
4292 @code{info handle} is an alias for @code{info signals}.
4295 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4296 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4297 can be the number of a signal or its name (with or without the
4298 @samp{SIG} at the beginning); a list of signal numbers of the form
4299 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4300 known signals. Optional arguments @var{keywords}, described below,
4301 say what change to make.
4305 The keywords allowed by the @code{handle} command can be abbreviated.
4306 Their full names are:
4310 @value{GDBN} should not stop your program when this signal happens. It may
4311 still print a message telling you that the signal has come in.
4314 @value{GDBN} should stop your program when this signal happens. This implies
4315 the @code{print} keyword as well.
4318 @value{GDBN} should print a message when this signal happens.
4321 @value{GDBN} should not mention the occurrence of the signal at all. This
4322 implies the @code{nostop} keyword as well.
4326 @value{GDBN} should allow your program to see this signal; your program
4327 can handle the signal, or else it may terminate if the signal is fatal
4328 and not handled. @code{pass} and @code{noignore} are synonyms.
4332 @value{GDBN} should not allow your program to see this signal.
4333 @code{nopass} and @code{ignore} are synonyms.
4337 When a signal stops your program, the signal is not visible to the
4339 continue. Your program sees the signal then, if @code{pass} is in
4340 effect for the signal in question @emph{at that time}. In other words,
4341 after @value{GDBN} reports a signal, you can use the @code{handle}
4342 command with @code{pass} or @code{nopass} to control whether your
4343 program sees that signal when you continue.
4345 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4346 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4347 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4350 You can also use the @code{signal} command to prevent your program from
4351 seeing a signal, or cause it to see a signal it normally would not see,
4352 or to give it any signal at any time. For example, if your program stopped
4353 due to some sort of memory reference error, you might store correct
4354 values into the erroneous variables and continue, hoping to see more
4355 execution; but your program would probably terminate immediately as
4356 a result of the fatal signal once it saw the signal. To prevent this,
4357 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4361 @section Stopping and Starting Multi-thread Programs
4363 When your program has multiple threads (@pxref{Threads,, Debugging
4364 Programs with Multiple Threads}), you can choose whether to set
4365 breakpoints on all threads, or on a particular thread.
4368 @cindex breakpoints and threads
4369 @cindex thread breakpoints
4370 @kindex break @dots{} thread @var{threadno}
4371 @item break @var{linespec} thread @var{threadno}
4372 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4373 @var{linespec} specifies source lines; there are several ways of
4374 writing them (@pxref{Specify Location}), but the effect is always to
4375 specify some source line.
4377 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4378 to specify that you only want @value{GDBN} to stop the program when a
4379 particular thread reaches this breakpoint. @var{threadno} is one of the
4380 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4381 column of the @samp{info threads} display.
4383 If you do not specify @samp{thread @var{threadno}} when you set a
4384 breakpoint, the breakpoint applies to @emph{all} threads of your
4387 You can use the @code{thread} qualifier on conditional breakpoints as
4388 well; in this case, place @samp{thread @var{threadno}} before the
4389 breakpoint condition, like this:
4392 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4397 @cindex stopped threads
4398 @cindex threads, stopped
4399 Whenever your program stops under @value{GDBN} for any reason,
4400 @emph{all} threads of execution stop, not just the current thread. This
4401 allows you to examine the overall state of the program, including
4402 switching between threads, without worrying that things may change
4405 @cindex thread breakpoints and system calls
4406 @cindex system calls and thread breakpoints
4407 @cindex premature return from system calls
4408 There is an unfortunate side effect. If one thread stops for a
4409 breakpoint, or for some other reason, and another thread is blocked in a
4410 system call, then the system call may return prematurely. This is a
4411 consequence of the interaction between multiple threads and the signals
4412 that @value{GDBN} uses to implement breakpoints and other events that
4415 To handle this problem, your program should check the return value of
4416 each system call and react appropriately. This is good programming
4419 For example, do not write code like this:
4425 The call to @code{sleep} will return early if a different thread stops
4426 at a breakpoint or for some other reason.
4428 Instead, write this:
4433 unslept = sleep (unslept);
4436 A system call is allowed to return early, so the system is still
4437 conforming to its specification. But @value{GDBN} does cause your
4438 multi-threaded program to behave differently than it would without
4441 Also, @value{GDBN} uses internal breakpoints in the thread library to
4442 monitor certain events such as thread creation and thread destruction.
4443 When such an event happens, a system call in another thread may return
4444 prematurely, even though your program does not appear to stop.
4446 @cindex continuing threads
4447 @cindex threads, continuing
4448 Conversely, whenever you restart the program, @emph{all} threads start
4449 executing. @emph{This is true even when single-stepping} with commands
4450 like @code{step} or @code{next}.
4452 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4453 Since thread scheduling is up to your debugging target's operating
4454 system (not controlled by @value{GDBN}), other threads may
4455 execute more than one statement while the current thread completes a
4456 single step. Moreover, in general other threads stop in the middle of a
4457 statement, rather than at a clean statement boundary, when the program
4460 You might even find your program stopped in another thread after
4461 continuing or even single-stepping. This happens whenever some other
4462 thread runs into a breakpoint, a signal, or an exception before the
4463 first thread completes whatever you requested.
4465 On some OSes, you can lock the OS scheduler and thus allow only a single
4469 @item set scheduler-locking @var{mode}
4470 @cindex scheduler locking mode
4471 @cindex lock scheduler
4472 Set the scheduler locking mode. If it is @code{off}, then there is no
4473 locking and any thread may run at any time. If @code{on}, then only the
4474 current thread may run when the inferior is resumed. The @code{step}
4475 mode optimizes for single-stepping. It stops other threads from
4476 ``seizing the prompt'' by preempting the current thread while you are
4477 stepping. Other threads will only rarely (or never) get a chance to run
4478 when you step. They are more likely to run when you @samp{next} over a
4479 function call, and they are completely free to run when you use commands
4480 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4481 thread hits a breakpoint during its timeslice, they will never steal the
4482 @value{GDBN} prompt away from the thread that you are debugging.
4484 @item show scheduler-locking
4485 Display the current scheduler locking mode.
4490 @chapter Examining the Stack
4492 When your program has stopped, the first thing you need to know is where it
4493 stopped and how it got there.
4496 Each time your program performs a function call, information about the call
4498 That information includes the location of the call in your program,
4499 the arguments of the call,
4500 and the local variables of the function being called.
4501 The information is saved in a block of data called a @dfn{stack frame}.
4502 The stack frames are allocated in a region of memory called the @dfn{call
4505 When your program stops, the @value{GDBN} commands for examining the
4506 stack allow you to see all of this information.
4508 @cindex selected frame
4509 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4510 @value{GDBN} commands refer implicitly to the selected frame. In
4511 particular, whenever you ask @value{GDBN} for the value of a variable in
4512 your program, the value is found in the selected frame. There are
4513 special @value{GDBN} commands to select whichever frame you are
4514 interested in. @xref{Selection, ,Selecting a Frame}.
4516 When your program stops, @value{GDBN} automatically selects the
4517 currently executing frame and describes it briefly, similar to the
4518 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4521 * Frames:: Stack frames
4522 * Backtrace:: Backtraces
4523 * Selection:: Selecting a frame
4524 * Frame Info:: Information on a frame
4529 @section Stack Frames
4531 @cindex frame, definition
4533 The call stack is divided up into contiguous pieces called @dfn{stack
4534 frames}, or @dfn{frames} for short; each frame is the data associated
4535 with one call to one function. The frame contains the arguments given
4536 to the function, the function's local variables, and the address at
4537 which the function is executing.
4539 @cindex initial frame
4540 @cindex outermost frame
4541 @cindex innermost frame
4542 When your program is started, the stack has only one frame, that of the
4543 function @code{main}. This is called the @dfn{initial} frame or the
4544 @dfn{outermost} frame. Each time a function is called, a new frame is
4545 made. Each time a function returns, the frame for that function invocation
4546 is eliminated. If a function is recursive, there can be many frames for
4547 the same function. The frame for the function in which execution is
4548 actually occurring is called the @dfn{innermost} frame. This is the most
4549 recently created of all the stack frames that still exist.
4551 @cindex frame pointer
4552 Inside your program, stack frames are identified by their addresses. A
4553 stack frame consists of many bytes, each of which has its own address; each
4554 kind of computer has a convention for choosing one byte whose
4555 address serves as the address of the frame. Usually this address is kept
4556 in a register called the @dfn{frame pointer register}
4557 (@pxref{Registers, $fp}) while execution is going on in that frame.
4559 @cindex frame number
4560 @value{GDBN} assigns numbers to all existing stack frames, starting with
4561 zero for the innermost frame, one for the frame that called it,
4562 and so on upward. These numbers do not really exist in your program;
4563 they are assigned by @value{GDBN} to give you a way of designating stack
4564 frames in @value{GDBN} commands.
4566 @c The -fomit-frame-pointer below perennially causes hbox overflow
4567 @c underflow problems.
4568 @cindex frameless execution
4569 Some compilers provide a way to compile functions so that they operate
4570 without stack frames. (For example, the @value{NGCC} option
4572 @samp{-fomit-frame-pointer}
4574 generates functions without a frame.)
4575 This is occasionally done with heavily used library functions to save
4576 the frame setup time. @value{GDBN} has limited facilities for dealing
4577 with these function invocations. If the innermost function invocation
4578 has no stack frame, @value{GDBN} nevertheless regards it as though
4579 it had a separate frame, which is numbered zero as usual, allowing
4580 correct tracing of the function call chain. However, @value{GDBN} has
4581 no provision for frameless functions elsewhere in the stack.
4584 @kindex frame@r{, command}
4585 @cindex current stack frame
4586 @item frame @var{args}
4587 The @code{frame} command allows you to move from one stack frame to another,
4588 and to print the stack frame you select. @var{args} may be either the
4589 address of the frame or the stack frame number. Without an argument,
4590 @code{frame} prints the current stack frame.
4592 @kindex select-frame
4593 @cindex selecting frame silently
4595 The @code{select-frame} command allows you to move from one stack frame
4596 to another without printing the frame. This is the silent version of
4604 @cindex call stack traces
4605 A backtrace is a summary of how your program got where it is. It shows one
4606 line per frame, for many frames, starting with the currently executing
4607 frame (frame zero), followed by its caller (frame one), and on up the
4612 @kindex bt @r{(@code{backtrace})}
4615 Print a backtrace of the entire stack: one line per frame for all
4616 frames in the stack.
4618 You can stop the backtrace at any time by typing the system interrupt
4619 character, normally @kbd{Ctrl-c}.
4621 @item backtrace @var{n}
4623 Similar, but print only the innermost @var{n} frames.
4625 @item backtrace -@var{n}
4627 Similar, but print only the outermost @var{n} frames.
4629 @item backtrace full
4631 @itemx bt full @var{n}
4632 @itemx bt full -@var{n}
4633 Print the values of the local variables also. @var{n} specifies the
4634 number of frames to print, as described above.
4639 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4640 are additional aliases for @code{backtrace}.
4642 @cindex multiple threads, backtrace
4643 In a multi-threaded program, @value{GDBN} by default shows the
4644 backtrace only for the current thread. To display the backtrace for
4645 several or all of the threads, use the command @code{thread apply}
4646 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4647 apply all backtrace}, @value{GDBN} will display the backtrace for all
4648 the threads; this is handy when you debug a core dump of a
4649 multi-threaded program.
4651 Each line in the backtrace shows the frame number and the function name.
4652 The program counter value is also shown---unless you use @code{set
4653 print address off}. The backtrace also shows the source file name and
4654 line number, as well as the arguments to the function. The program
4655 counter value is omitted if it is at the beginning of the code for that
4658 Here is an example of a backtrace. It was made with the command
4659 @samp{bt 3}, so it shows the innermost three frames.
4663 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4665 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4666 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4668 (More stack frames follow...)
4673 The display for frame zero does not begin with a program counter
4674 value, indicating that your program has stopped at the beginning of the
4675 code for line @code{993} of @code{builtin.c}.
4677 @cindex value optimized out, in backtrace
4678 @cindex function call arguments, optimized out
4679 If your program was compiled with optimizations, some compilers will
4680 optimize away arguments passed to functions if those arguments are
4681 never used after the call. Such optimizations generate code that
4682 passes arguments through registers, but doesn't store those arguments
4683 in the stack frame. @value{GDBN} has no way of displaying such
4684 arguments in stack frames other than the innermost one. Here's what
4685 such a backtrace might look like:
4689 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4691 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4692 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4694 (More stack frames follow...)
4699 The values of arguments that were not saved in their stack frames are
4700 shown as @samp{<value optimized out>}.
4702 If you need to display the values of such optimized-out arguments,
4703 either deduce that from other variables whose values depend on the one
4704 you are interested in, or recompile without optimizations.
4706 @cindex backtrace beyond @code{main} function
4707 @cindex program entry point
4708 @cindex startup code, and backtrace
4709 Most programs have a standard user entry point---a place where system
4710 libraries and startup code transition into user code. For C this is
4711 @code{main}@footnote{
4712 Note that embedded programs (the so-called ``free-standing''
4713 environment) are not required to have a @code{main} function as the
4714 entry point. They could even have multiple entry points.}.
4715 When @value{GDBN} finds the entry function in a backtrace
4716 it will terminate the backtrace, to avoid tracing into highly
4717 system-specific (and generally uninteresting) code.
4719 If you need to examine the startup code, or limit the number of levels
4720 in a backtrace, you can change this behavior:
4723 @item set backtrace past-main
4724 @itemx set backtrace past-main on
4725 @kindex set backtrace
4726 Backtraces will continue past the user entry point.
4728 @item set backtrace past-main off
4729 Backtraces will stop when they encounter the user entry point. This is the
4732 @item show backtrace past-main
4733 @kindex show backtrace
4734 Display the current user entry point backtrace policy.
4736 @item set backtrace past-entry
4737 @itemx set backtrace past-entry on
4738 Backtraces will continue past the internal entry point of an application.
4739 This entry point is encoded by the linker when the application is built,
4740 and is likely before the user entry point @code{main} (or equivalent) is called.
4742 @item set backtrace past-entry off
4743 Backtraces will stop when they encounter the internal entry point of an
4744 application. This is the default.
4746 @item show backtrace past-entry
4747 Display the current internal entry point backtrace policy.
4749 @item set backtrace limit @var{n}
4750 @itemx set backtrace limit 0
4751 @cindex backtrace limit
4752 Limit the backtrace to @var{n} levels. A value of zero means
4755 @item show backtrace limit
4756 Display the current limit on backtrace levels.
4760 @section Selecting a Frame
4762 Most commands for examining the stack and other data in your program work on
4763 whichever stack frame is selected at the moment. Here are the commands for
4764 selecting a stack frame; all of them finish by printing a brief description
4765 of the stack frame just selected.
4768 @kindex frame@r{, selecting}
4769 @kindex f @r{(@code{frame})}
4772 Select frame number @var{n}. Recall that frame zero is the innermost
4773 (currently executing) frame, frame one is the frame that called the
4774 innermost one, and so on. The highest-numbered frame is the one for
4777 @item frame @var{addr}
4779 Select the frame at address @var{addr}. This is useful mainly if the
4780 chaining of stack frames has been damaged by a bug, making it
4781 impossible for @value{GDBN} to assign numbers properly to all frames. In
4782 addition, this can be useful when your program has multiple stacks and
4783 switches between them.
4785 On the SPARC architecture, @code{frame} needs two addresses to
4786 select an arbitrary frame: a frame pointer and a stack pointer.
4788 On the MIPS and Alpha architecture, it needs two addresses: a stack
4789 pointer and a program counter.
4791 On the 29k architecture, it needs three addresses: a register stack
4792 pointer, a program counter, and a memory stack pointer.
4796 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4797 advances toward the outermost frame, to higher frame numbers, to frames
4798 that have existed longer. @var{n} defaults to one.
4801 @kindex do @r{(@code{down})}
4803 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4804 advances toward the innermost frame, to lower frame numbers, to frames
4805 that were created more recently. @var{n} defaults to one. You may
4806 abbreviate @code{down} as @code{do}.
4809 All of these commands end by printing two lines of output describing the
4810 frame. The first line shows the frame number, the function name, the
4811 arguments, and the source file and line number of execution in that
4812 frame. The second line shows the text of that source line.
4820 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4822 10 read_input_file (argv[i]);
4826 After such a printout, the @code{list} command with no arguments
4827 prints ten lines centered on the point of execution in the frame.
4828 You can also edit the program at the point of execution with your favorite
4829 editing program by typing @code{edit}.
4830 @xref{List, ,Printing Source Lines},
4834 @kindex down-silently
4836 @item up-silently @var{n}
4837 @itemx down-silently @var{n}
4838 These two commands are variants of @code{up} and @code{down},
4839 respectively; they differ in that they do their work silently, without
4840 causing display of the new frame. They are intended primarily for use
4841 in @value{GDBN} command scripts, where the output might be unnecessary and
4846 @section Information About a Frame
4848 There are several other commands to print information about the selected
4854 When used without any argument, this command does not change which
4855 frame is selected, but prints a brief description of the currently
4856 selected stack frame. It can be abbreviated @code{f}. With an
4857 argument, this command is used to select a stack frame.
4858 @xref{Selection, ,Selecting a Frame}.
4861 @kindex info f @r{(@code{info frame})}
4864 This command prints a verbose description of the selected stack frame,
4869 the address of the frame
4871 the address of the next frame down (called by this frame)
4873 the address of the next frame up (caller of this frame)
4875 the language in which the source code corresponding to this frame is written
4877 the address of the frame's arguments
4879 the address of the frame's local variables
4881 the program counter saved in it (the address of execution in the caller frame)
4883 which registers were saved in the frame
4886 @noindent The verbose description is useful when
4887 something has gone wrong that has made the stack format fail to fit
4888 the usual conventions.
4890 @item info frame @var{addr}
4891 @itemx info f @var{addr}
4892 Print a verbose description of the frame at address @var{addr}, without
4893 selecting that frame. The selected frame remains unchanged by this
4894 command. This requires the same kind of address (more than one for some
4895 architectures) that you specify in the @code{frame} command.
4896 @xref{Selection, ,Selecting a Frame}.
4900 Print the arguments of the selected frame, each on a separate line.
4904 Print the local variables of the selected frame, each on a separate
4905 line. These are all variables (declared either static or automatic)
4906 accessible at the point of execution of the selected frame.
4909 @cindex catch exceptions, list active handlers
4910 @cindex exception handlers, how to list
4912 Print a list of all the exception handlers that are active in the
4913 current stack frame at the current point of execution. To see other
4914 exception handlers, visit the associated frame (using the @code{up},
4915 @code{down}, or @code{frame} commands); then type @code{info catch}.
4916 @xref{Set Catchpoints, , Setting Catchpoints}.
4922 @chapter Examining Source Files
4924 @value{GDBN} can print parts of your program's source, since the debugging
4925 information recorded in the program tells @value{GDBN} what source files were
4926 used to build it. When your program stops, @value{GDBN} spontaneously prints
4927 the line where it stopped. Likewise, when you select a stack frame
4928 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4929 execution in that frame has stopped. You can print other portions of
4930 source files by explicit command.
4932 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4933 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4934 @value{GDBN} under @sc{gnu} Emacs}.
4937 * List:: Printing source lines
4938 * Specify Location:: How to specify code locations
4939 * Edit:: Editing source files
4940 * Search:: Searching source files
4941 * Source Path:: Specifying source directories
4942 * Machine Code:: Source and machine code
4946 @section Printing Source Lines
4949 @kindex l @r{(@code{list})}
4950 To print lines from a source file, use the @code{list} command
4951 (abbreviated @code{l}). By default, ten lines are printed.
4952 There are several ways to specify what part of the file you want to
4953 print; see @ref{Specify Location}, for the full list.
4955 Here are the forms of the @code{list} command most commonly used:
4958 @item list @var{linenum}
4959 Print lines centered around line number @var{linenum} in the
4960 current source file.
4962 @item list @var{function}
4963 Print lines centered around the beginning of function
4967 Print more lines. If the last lines printed were printed with a
4968 @code{list} command, this prints lines following the last lines
4969 printed; however, if the last line printed was a solitary line printed
4970 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4971 Stack}), this prints lines centered around that line.
4974 Print lines just before the lines last printed.
4977 @cindex @code{list}, how many lines to display
4978 By default, @value{GDBN} prints ten source lines with any of these forms of
4979 the @code{list} command. You can change this using @code{set listsize}:
4982 @kindex set listsize
4983 @item set listsize @var{count}
4984 Make the @code{list} command display @var{count} source lines (unless
4985 the @code{list} argument explicitly specifies some other number).
4987 @kindex show listsize
4989 Display the number of lines that @code{list} prints.
4992 Repeating a @code{list} command with @key{RET} discards the argument,
4993 so it is equivalent to typing just @code{list}. This is more useful
4994 than listing the same lines again. An exception is made for an
4995 argument of @samp{-}; that argument is preserved in repetition so that
4996 each repetition moves up in the source file.
4998 In general, the @code{list} command expects you to supply zero, one or two
4999 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5000 of writing them (@pxref{Specify Location}), but the effect is always
5001 to specify some source line.
5003 Here is a complete description of the possible arguments for @code{list}:
5006 @item list @var{linespec}
5007 Print lines centered around the line specified by @var{linespec}.
5009 @item list @var{first},@var{last}
5010 Print lines from @var{first} to @var{last}. Both arguments are
5011 linespecs. When a @code{list} command has two linespecs, and the
5012 source file of the second linespec is omitted, this refers to
5013 the same source file as the first linespec.
5015 @item list ,@var{last}
5016 Print lines ending with @var{last}.
5018 @item list @var{first},
5019 Print lines starting with @var{first}.
5022 Print lines just after the lines last printed.
5025 Print lines just before the lines last printed.
5028 As described in the preceding table.
5031 @node Specify Location
5032 @section Specifying a Location
5033 @cindex specifying location
5036 Several @value{GDBN} commands accept arguments that specify a location
5037 of your program's code. Since @value{GDBN} is a source-level
5038 debugger, a location usually specifies some line in the source code;
5039 for that reason, locations are also known as @dfn{linespecs}.
5041 Here are all the different ways of specifying a code location that
5042 @value{GDBN} understands:
5046 Specifies the line number @var{linenum} of the current source file.
5049 @itemx +@var{offset}
5050 Specifies the line @var{offset} lines before or after the @dfn{current
5051 line}. For the @code{list} command, the current line is the last one
5052 printed; for the breakpoint commands, this is the line at which
5053 execution stopped in the currently selected @dfn{stack frame}
5054 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5055 used as the second of the two linespecs in a @code{list} command,
5056 this specifies the line @var{offset} lines up or down from the first
5059 @item @var{filename}:@var{linenum}
5060 Specifies the line @var{linenum} in the source file @var{filename}.
5062 @item @var{function}
5063 Specifies the line that begins the body of the function @var{function}.
5064 For example, in C, this is the line with the open brace.
5066 @item @var{filename}:@var{function}
5067 Specifies the line that begins the body of the function @var{function}
5068 in the file @var{filename}. You only need the file name with a
5069 function name to avoid ambiguity when there are identically named
5070 functions in different source files.
5072 @item *@var{address}
5073 Specifies the program address @var{address}. For line-oriented
5074 commands, such as @code{list} and @code{edit}, this specifies a source
5075 line that contains @var{address}. For @code{break} and other
5076 breakpoint oriented commands, this can be used to set breakpoints in
5077 parts of your program which do not have debugging information or
5080 Here @var{address} may be any expression valid in the current working
5081 language (@pxref{Languages, working language}) that specifies a code
5082 address. In addition, as a convenience, @value{GDBN} extends the
5083 semantics of expressions used in locations to cover the situations
5084 that frequently happen during debugging. Here are the various forms
5088 @item @var{expression}
5089 Any expression valid in the current working language.
5091 @item @var{funcaddr}
5092 An address of a function or procedure derived from its name. In C,
5093 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5094 simply the function's name @var{function} (and actually a special case
5095 of a valid expression). In Pascal and Modula-2, this is
5096 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5097 (although the Pascal form also works).
5099 This form specifies the address of the function's first instruction,
5100 before the stack frame and arguments have been set up.
5102 @item '@var{filename}'::@var{funcaddr}
5103 Like @var{funcaddr} above, but also specifies the name of the source
5104 file explicitly. This is useful if the name of the function does not
5105 specify the function unambiguously, e.g., if there are several
5106 functions with identical names in different source files.
5113 @section Editing Source Files
5114 @cindex editing source files
5117 @kindex e @r{(@code{edit})}
5118 To edit the lines in a source file, use the @code{edit} command.
5119 The editing program of your choice
5120 is invoked with the current line set to
5121 the active line in the program.
5122 Alternatively, there are several ways to specify what part of the file you
5123 want to print if you want to see other parts of the program:
5126 @item edit @var{location}
5127 Edit the source file specified by @code{location}. Editing starts at
5128 that @var{location}, e.g., at the specified source line of the
5129 specified file. @xref{Specify Location}, for all the possible forms
5130 of the @var{location} argument; here are the forms of the @code{edit}
5131 command most commonly used:
5134 @item edit @var{number}
5135 Edit the current source file with @var{number} as the active line number.
5137 @item edit @var{function}
5138 Edit the file containing @var{function} at the beginning of its definition.
5143 @subsection Choosing your Editor
5144 You can customize @value{GDBN} to use any editor you want
5146 The only restriction is that your editor (say @code{ex}), recognizes the
5147 following command-line syntax:
5149 ex +@var{number} file
5151 The optional numeric value +@var{number} specifies the number of the line in
5152 the file where to start editing.}.
5153 By default, it is @file{@value{EDITOR}}, but you can change this
5154 by setting the environment variable @code{EDITOR} before using
5155 @value{GDBN}. For example, to configure @value{GDBN} to use the
5156 @code{vi} editor, you could use these commands with the @code{sh} shell:
5162 or in the @code{csh} shell,
5164 setenv EDITOR /usr/bin/vi
5169 @section Searching Source Files
5170 @cindex searching source files
5172 There are two commands for searching through the current source file for a
5177 @kindex forward-search
5178 @item forward-search @var{regexp}
5179 @itemx search @var{regexp}
5180 The command @samp{forward-search @var{regexp}} checks each line,
5181 starting with the one following the last line listed, for a match for
5182 @var{regexp}. It lists the line that is found. You can use the
5183 synonym @samp{search @var{regexp}} or abbreviate the command name as
5186 @kindex reverse-search
5187 @item reverse-search @var{regexp}
5188 The command @samp{reverse-search @var{regexp}} checks each line, starting
5189 with the one before the last line listed and going backward, for a match
5190 for @var{regexp}. It lists the line that is found. You can abbreviate
5191 this command as @code{rev}.
5195 @section Specifying Source Directories
5198 @cindex directories for source files
5199 Executable programs sometimes do not record the directories of the source
5200 files from which they were compiled, just the names. Even when they do,
5201 the directories could be moved between the compilation and your debugging
5202 session. @value{GDBN} has a list of directories to search for source files;
5203 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5204 it tries all the directories in the list, in the order they are present
5205 in the list, until it finds a file with the desired name.
5207 For example, suppose an executable references the file
5208 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5209 @file{/mnt/cross}. The file is first looked up literally; if this
5210 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5211 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5212 message is printed. @value{GDBN} does not look up the parts of the
5213 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5214 Likewise, the subdirectories of the source path are not searched: if
5215 the source path is @file{/mnt/cross}, and the binary refers to
5216 @file{foo.c}, @value{GDBN} would not find it under
5217 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5219 Plain file names, relative file names with leading directories, file
5220 names containing dots, etc.@: are all treated as described above; for
5221 instance, if the source path is @file{/mnt/cross}, and the source file
5222 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5223 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5224 that---@file{/mnt/cross/foo.c}.
5226 Note that the executable search path is @emph{not} used to locate the
5229 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5230 any information it has cached about where source files are found and where
5231 each line is in the file.
5235 When you start @value{GDBN}, its source path includes only @samp{cdir}
5236 and @samp{cwd}, in that order.
5237 To add other directories, use the @code{directory} command.
5239 The search path is used to find both program source files and @value{GDBN}
5240 script files (read using the @samp{-command} option and @samp{source} command).
5242 In addition to the source path, @value{GDBN} provides a set of commands
5243 that manage a list of source path substitution rules. A @dfn{substitution
5244 rule} specifies how to rewrite source directories stored in the program's
5245 debug information in case the sources were moved to a different
5246 directory between compilation and debugging. A rule is made of
5247 two strings, the first specifying what needs to be rewritten in
5248 the path, and the second specifying how it should be rewritten.
5249 In @ref{set substitute-path}, we name these two parts @var{from} and
5250 @var{to} respectively. @value{GDBN} does a simple string replacement
5251 of @var{from} with @var{to} at the start of the directory part of the
5252 source file name, and uses that result instead of the original file
5253 name to look up the sources.
5255 Using the previous example, suppose the @file{foo-1.0} tree has been
5256 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5257 @value{GDBN} to replace @file{/usr/src} in all source path names with
5258 @file{/mnt/cross}. The first lookup will then be
5259 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5260 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5261 substitution rule, use the @code{set substitute-path} command
5262 (@pxref{set substitute-path}).
5264 To avoid unexpected substitution results, a rule is applied only if the
5265 @var{from} part of the directory name ends at a directory separator.
5266 For instance, a rule substituting @file{/usr/source} into
5267 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5268 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5269 is applied only at the beginning of the directory name, this rule will
5270 not be applied to @file{/root/usr/source/baz.c} either.
5272 In many cases, you can achieve the same result using the @code{directory}
5273 command. However, @code{set substitute-path} can be more efficient in
5274 the case where the sources are organized in a complex tree with multiple
5275 subdirectories. With the @code{directory} command, you need to add each
5276 subdirectory of your project. If you moved the entire tree while
5277 preserving its internal organization, then @code{set substitute-path}
5278 allows you to direct the debugger to all the sources with one single
5281 @code{set substitute-path} is also more than just a shortcut command.
5282 The source path is only used if the file at the original location no
5283 longer exists. On the other hand, @code{set substitute-path} modifies
5284 the debugger behavior to look at the rewritten location instead. So, if
5285 for any reason a source file that is not relevant to your executable is
5286 located at the original location, a substitution rule is the only
5287 method available to point @value{GDBN} at the new location.
5290 @item directory @var{dirname} @dots{}
5291 @item dir @var{dirname} @dots{}
5292 Add directory @var{dirname} to the front of the source path. Several
5293 directory names may be given to this command, separated by @samp{:}
5294 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5295 part of absolute file names) or
5296 whitespace. You may specify a directory that is already in the source
5297 path; this moves it forward, so @value{GDBN} searches it sooner.
5301 @vindex $cdir@r{, convenience variable}
5302 @vindex $cwd@r{, convenience variable}
5303 @cindex compilation directory
5304 @cindex current directory
5305 @cindex working directory
5306 @cindex directory, current
5307 @cindex directory, compilation
5308 You can use the string @samp{$cdir} to refer to the compilation
5309 directory (if one is recorded), and @samp{$cwd} to refer to the current
5310 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5311 tracks the current working directory as it changes during your @value{GDBN}
5312 session, while the latter is immediately expanded to the current
5313 directory at the time you add an entry to the source path.
5316 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5318 @c RET-repeat for @code{directory} is explicitly disabled, but since
5319 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5321 @item show directories
5322 @kindex show directories
5323 Print the source path: show which directories it contains.
5325 @anchor{set substitute-path}
5326 @item set substitute-path @var{from} @var{to}
5327 @kindex set substitute-path
5328 Define a source path substitution rule, and add it at the end of the
5329 current list of existing substitution rules. If a rule with the same
5330 @var{from} was already defined, then the old rule is also deleted.
5332 For example, if the file @file{/foo/bar/baz.c} was moved to
5333 @file{/mnt/cross/baz.c}, then the command
5336 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5340 will tell @value{GDBN} to replace @samp{/usr/src} with
5341 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5342 @file{baz.c} even though it was moved.
5344 In the case when more than one substitution rule have been defined,
5345 the rules are evaluated one by one in the order where they have been
5346 defined. The first one matching, if any, is selected to perform
5349 For instance, if we had entered the following commands:
5352 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5353 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5357 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5358 @file{/mnt/include/defs.h} by using the first rule. However, it would
5359 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5360 @file{/mnt/src/lib/foo.c}.
5363 @item unset substitute-path [path]
5364 @kindex unset substitute-path
5365 If a path is specified, search the current list of substitution rules
5366 for a rule that would rewrite that path. Delete that rule if found.
5367 A warning is emitted by the debugger if no rule could be found.
5369 If no path is specified, then all substitution rules are deleted.
5371 @item show substitute-path [path]
5372 @kindex show substitute-path
5373 If a path is specified, then print the source path substitution rule
5374 which would rewrite that path, if any.
5376 If no path is specified, then print all existing source path substitution
5381 If your source path is cluttered with directories that are no longer of
5382 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5383 versions of source. You can correct the situation as follows:
5387 Use @code{directory} with no argument to reset the source path to its default value.
5390 Use @code{directory} with suitable arguments to reinstall the
5391 directories you want in the source path. You can add all the
5392 directories in one command.
5396 @section Source and Machine Code
5397 @cindex source line and its code address
5399 You can use the command @code{info line} to map source lines to program
5400 addresses (and vice versa), and the command @code{disassemble} to display
5401 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5402 mode, the @code{info line} command causes the arrow to point to the
5403 line specified. Also, @code{info line} prints addresses in symbolic form as
5408 @item info line @var{linespec}
5409 Print the starting and ending addresses of the compiled code for
5410 source line @var{linespec}. You can specify source lines in any of
5411 the ways documented in @ref{Specify Location}.
5414 For example, we can use @code{info line} to discover the location of
5415 the object code for the first line of function
5416 @code{m4_changequote}:
5418 @c FIXME: I think this example should also show the addresses in
5419 @c symbolic form, as they usually would be displayed.
5421 (@value{GDBP}) info line m4_changequote
5422 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5426 @cindex code address and its source line
5427 We can also inquire (using @code{*@var{addr}} as the form for
5428 @var{linespec}) what source line covers a particular address:
5430 (@value{GDBP}) info line *0x63ff
5431 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5434 @cindex @code{$_} and @code{info line}
5435 @cindex @code{x} command, default address
5436 @kindex x@r{(examine), and} info line
5437 After @code{info line}, the default address for the @code{x} command
5438 is changed to the starting address of the line, so that @samp{x/i} is
5439 sufficient to begin examining the machine code (@pxref{Memory,
5440 ,Examining Memory}). Also, this address is saved as the value of the
5441 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5446 @cindex assembly instructions
5447 @cindex instructions, assembly
5448 @cindex machine instructions
5449 @cindex listing machine instructions
5451 @itemx disassemble /m
5452 This specialized command dumps a range of memory as machine
5453 instructions. It can also print mixed source+disassembly by specifying
5454 the @code{/m} modifier.
5455 The default memory range is the function surrounding the
5456 program counter of the selected frame. A single argument to this
5457 command is a program counter value; @value{GDBN} dumps the function
5458 surrounding this value. Two arguments specify a range of addresses
5459 (first inclusive, second exclusive) to dump.
5462 The following example shows the disassembly of a range of addresses of
5463 HP PA-RISC 2.0 code:
5466 (@value{GDBP}) disas 0x32c4 0x32e4
5467 Dump of assembler code from 0x32c4 to 0x32e4:
5468 0x32c4 <main+204>: addil 0,dp
5469 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5470 0x32cc <main+212>: ldil 0x3000,r31
5471 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5472 0x32d4 <main+220>: ldo 0(r31),rp
5473 0x32d8 <main+224>: addil -0x800,dp
5474 0x32dc <main+228>: ldo 0x588(r1),r26
5475 0x32e0 <main+232>: ldil 0x3000,r31
5476 End of assembler dump.
5479 Here is an example showing mixed source+assembly for Intel x86:
5482 (@value{GDBP}) disas /m main
5483 Dump of assembler code for function main:
5485 0x08048330 <main+0>: push %ebp
5486 0x08048331 <main+1>: mov %esp,%ebp
5487 0x08048333 <main+3>: sub $0x8,%esp
5488 0x08048336 <main+6>: and $0xfffffff0,%esp
5489 0x08048339 <main+9>: sub $0x10,%esp
5491 6 printf ("Hello.\n");
5492 0x0804833c <main+12>: movl $0x8048440,(%esp)
5493 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
5497 0x08048348 <main+24>: mov $0x0,%eax
5498 0x0804834d <main+29>: leave
5499 0x0804834e <main+30>: ret
5501 End of assembler dump.
5504 Some architectures have more than one commonly-used set of instruction
5505 mnemonics or other syntax.
5507 For programs that were dynamically linked and use shared libraries,
5508 instructions that call functions or branch to locations in the shared
5509 libraries might show a seemingly bogus location---it's actually a
5510 location of the relocation table. On some architectures, @value{GDBN}
5511 might be able to resolve these to actual function names.
5514 @kindex set disassembly-flavor
5515 @cindex Intel disassembly flavor
5516 @cindex AT&T disassembly flavor
5517 @item set disassembly-flavor @var{instruction-set}
5518 Select the instruction set to use when disassembling the
5519 program via the @code{disassemble} or @code{x/i} commands.
5521 Currently this command is only defined for the Intel x86 family. You
5522 can set @var{instruction-set} to either @code{intel} or @code{att}.
5523 The default is @code{att}, the AT&T flavor used by default by Unix
5524 assemblers for x86-based targets.
5526 @kindex show disassembly-flavor
5527 @item show disassembly-flavor
5528 Show the current setting of the disassembly flavor.
5533 @chapter Examining Data
5535 @cindex printing data
5536 @cindex examining data
5539 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5540 @c document because it is nonstandard... Under Epoch it displays in a
5541 @c different window or something like that.
5542 The usual way to examine data in your program is with the @code{print}
5543 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5544 evaluates and prints the value of an expression of the language your
5545 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5546 Different Languages}).
5549 @item print @var{expr}
5550 @itemx print /@var{f} @var{expr}
5551 @var{expr} is an expression (in the source language). By default the
5552 value of @var{expr} is printed in a format appropriate to its data type;
5553 you can choose a different format by specifying @samp{/@var{f}}, where
5554 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5558 @itemx print /@var{f}
5559 @cindex reprint the last value
5560 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5561 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5562 conveniently inspect the same value in an alternative format.
5565 A more low-level way of examining data is with the @code{x} command.
5566 It examines data in memory at a specified address and prints it in a
5567 specified format. @xref{Memory, ,Examining Memory}.
5569 If you are interested in information about types, or about how the
5570 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5571 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5575 * Expressions:: Expressions
5576 * Ambiguous Expressions:: Ambiguous Expressions
5577 * Variables:: Program variables
5578 * Arrays:: Artificial arrays
5579 * Output Formats:: Output formats
5580 * Memory:: Examining memory
5581 * Auto Display:: Automatic display
5582 * Print Settings:: Print settings
5583 * Value History:: Value history
5584 * Convenience Vars:: Convenience variables
5585 * Registers:: Registers
5586 * Floating Point Hardware:: Floating point hardware
5587 * Vector Unit:: Vector Unit
5588 * OS Information:: Auxiliary data provided by operating system
5589 * Memory Region Attributes:: Memory region attributes
5590 * Dump/Restore Files:: Copy between memory and a file
5591 * Core File Generation:: Cause a program dump its core
5592 * Character Sets:: Debugging programs that use a different
5593 character set than GDB does
5594 * Caching Remote Data:: Data caching for remote targets
5595 * Searching Memory:: Searching memory for a sequence of bytes
5599 @section Expressions
5602 @code{print} and many other @value{GDBN} commands accept an expression and
5603 compute its value. Any kind of constant, variable or operator defined
5604 by the programming language you are using is valid in an expression in
5605 @value{GDBN}. This includes conditional expressions, function calls,
5606 casts, and string constants. It also includes preprocessor macros, if
5607 you compiled your program to include this information; see
5610 @cindex arrays in expressions
5611 @value{GDBN} supports array constants in expressions input by
5612 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5613 you can use the command @code{print @{1, 2, 3@}} to create an array
5614 of three integers. If you pass an array to a function or assign it
5615 to a program variable, @value{GDBN} copies the array to memory that
5616 is @code{malloc}ed in the target program.
5618 Because C is so widespread, most of the expressions shown in examples in
5619 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5620 Languages}, for information on how to use expressions in other
5623 In this section, we discuss operators that you can use in @value{GDBN}
5624 expressions regardless of your programming language.
5626 @cindex casts, in expressions
5627 Casts are supported in all languages, not just in C, because it is so
5628 useful to cast a number into a pointer in order to examine a structure
5629 at that address in memory.
5630 @c FIXME: casts supported---Mod2 true?
5632 @value{GDBN} supports these operators, in addition to those common
5633 to programming languages:
5637 @samp{@@} is a binary operator for treating parts of memory as arrays.
5638 @xref{Arrays, ,Artificial Arrays}, for more information.
5641 @samp{::} allows you to specify a variable in terms of the file or
5642 function where it is defined. @xref{Variables, ,Program Variables}.
5644 @cindex @{@var{type}@}
5645 @cindex type casting memory
5646 @cindex memory, viewing as typed object
5647 @cindex casts, to view memory
5648 @item @{@var{type}@} @var{addr}
5649 Refers to an object of type @var{type} stored at address @var{addr} in
5650 memory. @var{addr} may be any expression whose value is an integer or
5651 pointer (but parentheses are required around binary operators, just as in
5652 a cast). This construct is allowed regardless of what kind of data is
5653 normally supposed to reside at @var{addr}.
5656 @node Ambiguous Expressions
5657 @section Ambiguous Expressions
5658 @cindex ambiguous expressions
5660 Expressions can sometimes contain some ambiguous elements. For instance,
5661 some programming languages (notably Ada, C@t{++} and Objective-C) permit
5662 a single function name to be defined several times, for application in
5663 different contexts. This is called @dfn{overloading}. Another example
5664 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
5665 templates and is typically instantiated several times, resulting in
5666 the same function name being defined in different contexts.
5668 In some cases and depending on the language, it is possible to adjust
5669 the expression to remove the ambiguity. For instance in C@t{++}, you
5670 can specify the signature of the function you want to break on, as in
5671 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
5672 qualified name of your function often makes the expression unambiguous
5675 When an ambiguity that needs to be resolved is detected, the debugger
5676 has the capability to display a menu of numbered choices for each
5677 possibility, and then waits for the selection with the prompt @samp{>}.
5678 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
5679 aborts the current command. If the command in which the expression was
5680 used allows more than one choice to be selected, the next option in the
5681 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
5684 For example, the following session excerpt shows an attempt to set a
5685 breakpoint at the overloaded symbol @code{String::after}.
5686 We choose three particular definitions of that function name:
5688 @c FIXME! This is likely to change to show arg type lists, at least
5691 (@value{GDBP}) b String::after
5694 [2] file:String.cc; line number:867
5695 [3] file:String.cc; line number:860
5696 [4] file:String.cc; line number:875
5697 [5] file:String.cc; line number:853
5698 [6] file:String.cc; line number:846
5699 [7] file:String.cc; line number:735
5701 Breakpoint 1 at 0xb26c: file String.cc, line 867.
5702 Breakpoint 2 at 0xb344: file String.cc, line 875.
5703 Breakpoint 3 at 0xafcc: file String.cc, line 846.
5704 Multiple breakpoints were set.
5705 Use the "delete" command to delete unwanted
5712 @kindex set multiple-symbols
5713 @item set multiple-symbols @var{mode}
5714 @cindex multiple-symbols menu
5716 This option allows you to adjust the debugger behavior when an expression
5719 By default, @var{mode} is set to @code{all}. If the command with which
5720 the expression is used allows more than one choice, then @value{GDBN}
5721 automatically selects all possible choices. For instance, inserting
5722 a breakpoint on a function using an ambiguous name results in a breakpoint
5723 inserted on each possible match. However, if a unique choice must be made,
5724 then @value{GDBN} uses the menu to help you disambiguate the expression.
5725 For instance, printing the address of an overloaded function will result
5726 in the use of the menu.
5728 When @var{mode} is set to @code{ask}, the debugger always uses the menu
5729 when an ambiguity is detected.
5731 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
5732 an error due to the ambiguity and the command is aborted.
5734 @kindex show multiple-symbols
5735 @item show multiple-symbols
5736 Show the current value of the @code{multiple-symbols} setting.
5740 @section Program Variables
5742 The most common kind of expression to use is the name of a variable
5745 Variables in expressions are understood in the selected stack frame
5746 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5750 global (or file-static)
5757 visible according to the scope rules of the
5758 programming language from the point of execution in that frame
5761 @noindent This means that in the function
5776 you can examine and use the variable @code{a} whenever your program is
5777 executing within the function @code{foo}, but you can only use or
5778 examine the variable @code{b} while your program is executing inside
5779 the block where @code{b} is declared.
5781 @cindex variable name conflict
5782 There is an exception: you can refer to a variable or function whose
5783 scope is a single source file even if the current execution point is not
5784 in this file. But it is possible to have more than one such variable or
5785 function with the same name (in different source files). If that
5786 happens, referring to that name has unpredictable effects. If you wish,
5787 you can specify a static variable in a particular function or file,
5788 using the colon-colon (@code{::}) notation:
5790 @cindex colon-colon, context for variables/functions
5792 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5793 @cindex @code{::}, context for variables/functions
5796 @var{file}::@var{variable}
5797 @var{function}::@var{variable}
5801 Here @var{file} or @var{function} is the name of the context for the
5802 static @var{variable}. In the case of file names, you can use quotes to
5803 make sure @value{GDBN} parses the file name as a single word---for example,
5804 to print a global value of @code{x} defined in @file{f2.c}:
5807 (@value{GDBP}) p 'f2.c'::x
5810 @cindex C@t{++} scope resolution
5811 This use of @samp{::} is very rarely in conflict with the very similar
5812 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5813 scope resolution operator in @value{GDBN} expressions.
5814 @c FIXME: Um, so what happens in one of those rare cases where it's in
5817 @cindex wrong values
5818 @cindex variable values, wrong
5819 @cindex function entry/exit, wrong values of variables
5820 @cindex optimized code, wrong values of variables
5822 @emph{Warning:} Occasionally, a local variable may appear to have the
5823 wrong value at certain points in a function---just after entry to a new
5824 scope, and just before exit.
5826 You may see this problem when you are stepping by machine instructions.
5827 This is because, on most machines, it takes more than one instruction to
5828 set up a stack frame (including local variable definitions); if you are
5829 stepping by machine instructions, variables may appear to have the wrong
5830 values until the stack frame is completely built. On exit, it usually
5831 also takes more than one machine instruction to destroy a stack frame;
5832 after you begin stepping through that group of instructions, local
5833 variable definitions may be gone.
5835 This may also happen when the compiler does significant optimizations.
5836 To be sure of always seeing accurate values, turn off all optimization
5839 @cindex ``No symbol "foo" in current context''
5840 Another possible effect of compiler optimizations is to optimize
5841 unused variables out of existence, or assign variables to registers (as
5842 opposed to memory addresses). Depending on the support for such cases
5843 offered by the debug info format used by the compiler, @value{GDBN}
5844 might not be able to display values for such local variables. If that
5845 happens, @value{GDBN} will print a message like this:
5848 No symbol "foo" in current context.
5851 To solve such problems, either recompile without optimizations, or use a
5852 different debug info format, if the compiler supports several such
5853 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5854 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5855 produces debug info in a format that is superior to formats such as
5856 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5857 an effective form for debug info. @xref{Debugging Options,,Options
5858 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5859 Compiler Collection (GCC)}.
5860 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5861 that are best suited to C@t{++} programs.
5863 If you ask to print an object whose contents are unknown to
5864 @value{GDBN}, e.g., because its data type is not completely specified
5865 by the debug information, @value{GDBN} will say @samp{<incomplete
5866 type>}. @xref{Symbols, incomplete type}, for more about this.
5868 Strings are identified as arrays of @code{char} values without specified
5869 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5870 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5871 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5872 defines literal string type @code{"char"} as @code{char} without a sign.
5877 signed char var1[] = "A";
5880 You get during debugging
5885 $2 = @{65 'A', 0 '\0'@}
5889 @section Artificial Arrays
5891 @cindex artificial array
5893 @kindex @@@r{, referencing memory as an array}
5894 It is often useful to print out several successive objects of the
5895 same type in memory; a section of an array, or an array of
5896 dynamically determined size for which only a pointer exists in the
5899 You can do this by referring to a contiguous span of memory as an
5900 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5901 operand of @samp{@@} should be the first element of the desired array
5902 and be an individual object. The right operand should be the desired length
5903 of the array. The result is an array value whose elements are all of
5904 the type of the left argument. The first element is actually the left
5905 argument; the second element comes from bytes of memory immediately
5906 following those that hold the first element, and so on. Here is an
5907 example. If a program says
5910 int *array = (int *) malloc (len * sizeof (int));
5914 you can print the contents of @code{array} with
5920 The left operand of @samp{@@} must reside in memory. Array values made
5921 with @samp{@@} in this way behave just like other arrays in terms of
5922 subscripting, and are coerced to pointers when used in expressions.
5923 Artificial arrays most often appear in expressions via the value history
5924 (@pxref{Value History, ,Value History}), after printing one out.
5926 Another way to create an artificial array is to use a cast.
5927 This re-interprets a value as if it were an array.
5928 The value need not be in memory:
5930 (@value{GDBP}) p/x (short[2])0x12345678
5931 $1 = @{0x1234, 0x5678@}
5934 As a convenience, if you leave the array length out (as in
5935 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5936 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5938 (@value{GDBP}) p/x (short[])0x12345678
5939 $2 = @{0x1234, 0x5678@}
5942 Sometimes the artificial array mechanism is not quite enough; in
5943 moderately complex data structures, the elements of interest may not
5944 actually be adjacent---for example, if you are interested in the values
5945 of pointers in an array. One useful work-around in this situation is
5946 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5947 Variables}) as a counter in an expression that prints the first
5948 interesting value, and then repeat that expression via @key{RET}. For
5949 instance, suppose you have an array @code{dtab} of pointers to
5950 structures, and you are interested in the values of a field @code{fv}
5951 in each structure. Here is an example of what you might type:
5961 @node Output Formats
5962 @section Output Formats
5964 @cindex formatted output
5965 @cindex output formats
5966 By default, @value{GDBN} prints a value according to its data type. Sometimes
5967 this is not what you want. For example, you might want to print a number
5968 in hex, or a pointer in decimal. Or you might want to view data in memory
5969 at a certain address as a character string or as an instruction. To do
5970 these things, specify an @dfn{output format} when you print a value.
5972 The simplest use of output formats is to say how to print a value
5973 already computed. This is done by starting the arguments of the
5974 @code{print} command with a slash and a format letter. The format
5975 letters supported are:
5979 Regard the bits of the value as an integer, and print the integer in
5983 Print as integer in signed decimal.
5986 Print as integer in unsigned decimal.
5989 Print as integer in octal.
5992 Print as integer in binary. The letter @samp{t} stands for ``two''.
5993 @footnote{@samp{b} cannot be used because these format letters are also
5994 used with the @code{x} command, where @samp{b} stands for ``byte'';
5995 see @ref{Memory,,Examining Memory}.}
5998 @cindex unknown address, locating
5999 @cindex locate address
6000 Print as an address, both absolute in hexadecimal and as an offset from
6001 the nearest preceding symbol. You can use this format used to discover
6002 where (in what function) an unknown address is located:
6005 (@value{GDBP}) p/a 0x54320
6006 $3 = 0x54320 <_initialize_vx+396>
6010 The command @code{info symbol 0x54320} yields similar results.
6011 @xref{Symbols, info symbol}.
6014 Regard as an integer and print it as a character constant. This
6015 prints both the numerical value and its character representation. The
6016 character representation is replaced with the octal escape @samp{\nnn}
6017 for characters outside the 7-bit @sc{ascii} range.
6019 Without this format, @value{GDBN} displays @code{char},
6020 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6021 constants. Single-byte members of vectors are displayed as integer
6025 Regard the bits of the value as a floating point number and print
6026 using typical floating point syntax.
6029 @cindex printing strings
6030 @cindex printing byte arrays
6031 Regard as a string, if possible. With this format, pointers to single-byte
6032 data are displayed as null-terminated strings and arrays of single-byte data
6033 are displayed as fixed-length strings. Other values are displayed in their
6036 Without this format, @value{GDBN} displays pointers to and arrays of
6037 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6038 strings. Single-byte members of a vector are displayed as an integer
6042 For example, to print the program counter in hex (@pxref{Registers}), type
6049 Note that no space is required before the slash; this is because command
6050 names in @value{GDBN} cannot contain a slash.
6052 To reprint the last value in the value history with a different format,
6053 you can use the @code{print} command with just a format and no
6054 expression. For example, @samp{p/x} reprints the last value in hex.
6057 @section Examining Memory
6059 You can use the command @code{x} (for ``examine'') to examine memory in
6060 any of several formats, independently of your program's data types.
6062 @cindex examining memory
6064 @kindex x @r{(examine memory)}
6065 @item x/@var{nfu} @var{addr}
6068 Use the @code{x} command to examine memory.
6071 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6072 much memory to display and how to format it; @var{addr} is an
6073 expression giving the address where you want to start displaying memory.
6074 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6075 Several commands set convenient defaults for @var{addr}.
6078 @item @var{n}, the repeat count
6079 The repeat count is a decimal integer; the default is 1. It specifies
6080 how much memory (counting by units @var{u}) to display.
6081 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6084 @item @var{f}, the display format
6085 The display format is one of the formats used by @code{print}
6086 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6087 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6088 The default is @samp{x} (hexadecimal) initially. The default changes
6089 each time you use either @code{x} or @code{print}.
6091 @item @var{u}, the unit size
6092 The unit size is any of
6098 Halfwords (two bytes).
6100 Words (four bytes). This is the initial default.
6102 Giant words (eight bytes).
6105 Each time you specify a unit size with @code{x}, that size becomes the
6106 default unit the next time you use @code{x}. (For the @samp{s} and
6107 @samp{i} formats, the unit size is ignored and is normally not written.)
6109 @item @var{addr}, starting display address
6110 @var{addr} is the address where you want @value{GDBN} to begin displaying
6111 memory. The expression need not have a pointer value (though it may);
6112 it is always interpreted as an integer address of a byte of memory.
6113 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6114 @var{addr} is usually just after the last address examined---but several
6115 other commands also set the default address: @code{info breakpoints} (to
6116 the address of the last breakpoint listed), @code{info line} (to the
6117 starting address of a line), and @code{print} (if you use it to display
6118 a value from memory).
6121 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6122 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6123 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6124 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6125 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6127 Since the letters indicating unit sizes are all distinct from the
6128 letters specifying output formats, you do not have to remember whether
6129 unit size or format comes first; either order works. The output
6130 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6131 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6133 Even though the unit size @var{u} is ignored for the formats @samp{s}
6134 and @samp{i}, you might still want to use a count @var{n}; for example,
6135 @samp{3i} specifies that you want to see three machine instructions,
6136 including any operands. For convenience, especially when used with
6137 the @code{display} command, the @samp{i} format also prints branch delay
6138 slot instructions, if any, beyond the count specified, which immediately
6139 follow the last instruction that is within the count. The command
6140 @code{disassemble} gives an alternative way of inspecting machine
6141 instructions; see @ref{Machine Code,,Source and Machine Code}.
6143 All the defaults for the arguments to @code{x} are designed to make it
6144 easy to continue scanning memory with minimal specifications each time
6145 you use @code{x}. For example, after you have inspected three machine
6146 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6147 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6148 the repeat count @var{n} is used again; the other arguments default as
6149 for successive uses of @code{x}.
6151 @cindex @code{$_}, @code{$__}, and value history
6152 The addresses and contents printed by the @code{x} command are not saved
6153 in the value history because there is often too much of them and they
6154 would get in the way. Instead, @value{GDBN} makes these values available for
6155 subsequent use in expressions as values of the convenience variables
6156 @code{$_} and @code{$__}. After an @code{x} command, the last address
6157 examined is available for use in expressions in the convenience variable
6158 @code{$_}. The contents of that address, as examined, are available in
6159 the convenience variable @code{$__}.
6161 If the @code{x} command has a repeat count, the address and contents saved
6162 are from the last memory unit printed; this is not the same as the last
6163 address printed if several units were printed on the last line of output.
6165 @cindex remote memory comparison
6166 @cindex verify remote memory image
6167 When you are debugging a program running on a remote target machine
6168 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6169 remote machine's memory against the executable file you downloaded to
6170 the target. The @code{compare-sections} command is provided for such
6174 @kindex compare-sections
6175 @item compare-sections @r{[}@var{section-name}@r{]}
6176 Compare the data of a loadable section @var{section-name} in the
6177 executable file of the program being debugged with the same section in
6178 the remote machine's memory, and report any mismatches. With no
6179 arguments, compares all loadable sections. This command's
6180 availability depends on the target's support for the @code{"qCRC"}
6185 @section Automatic Display
6186 @cindex automatic display
6187 @cindex display of expressions
6189 If you find that you want to print the value of an expression frequently
6190 (to see how it changes), you might want to add it to the @dfn{automatic
6191 display list} so that @value{GDBN} prints its value each time your program stops.
6192 Each expression added to the list is given a number to identify it;
6193 to remove an expression from the list, you specify that number.
6194 The automatic display looks like this:
6198 3: bar[5] = (struct hack *) 0x3804
6202 This display shows item numbers, expressions and their current values. As with
6203 displays you request manually using @code{x} or @code{print}, you can
6204 specify the output format you prefer; in fact, @code{display} decides
6205 whether to use @code{print} or @code{x} depending your format
6206 specification---it uses @code{x} if you specify either the @samp{i}
6207 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6211 @item display @var{expr}
6212 Add the expression @var{expr} to the list of expressions to display
6213 each time your program stops. @xref{Expressions, ,Expressions}.
6215 @code{display} does not repeat if you press @key{RET} again after using it.
6217 @item display/@var{fmt} @var{expr}
6218 For @var{fmt} specifying only a display format and not a size or
6219 count, add the expression @var{expr} to the auto-display list but
6220 arrange to display it each time in the specified format @var{fmt}.
6221 @xref{Output Formats,,Output Formats}.
6223 @item display/@var{fmt} @var{addr}
6224 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6225 number of units, add the expression @var{addr} as a memory address to
6226 be examined each time your program stops. Examining means in effect
6227 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6230 For example, @samp{display/i $pc} can be helpful, to see the machine
6231 instruction about to be executed each time execution stops (@samp{$pc}
6232 is a common name for the program counter; @pxref{Registers, ,Registers}).
6235 @kindex delete display
6237 @item undisplay @var{dnums}@dots{}
6238 @itemx delete display @var{dnums}@dots{}
6239 Remove item numbers @var{dnums} from the list of expressions to display.
6241 @code{undisplay} does not repeat if you press @key{RET} after using it.
6242 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6244 @kindex disable display
6245 @item disable display @var{dnums}@dots{}
6246 Disable the display of item numbers @var{dnums}. A disabled display
6247 item is not printed automatically, but is not forgotten. It may be
6248 enabled again later.
6250 @kindex enable display
6251 @item enable display @var{dnums}@dots{}
6252 Enable display of item numbers @var{dnums}. It becomes effective once
6253 again in auto display of its expression, until you specify otherwise.
6256 Display the current values of the expressions on the list, just as is
6257 done when your program stops.
6259 @kindex info display
6261 Print the list of expressions previously set up to display
6262 automatically, each one with its item number, but without showing the
6263 values. This includes disabled expressions, which are marked as such.
6264 It also includes expressions which would not be displayed right now
6265 because they refer to automatic variables not currently available.
6268 @cindex display disabled out of scope
6269 If a display expression refers to local variables, then it does not make
6270 sense outside the lexical context for which it was set up. Such an
6271 expression is disabled when execution enters a context where one of its
6272 variables is not defined. For example, if you give the command
6273 @code{display last_char} while inside a function with an argument
6274 @code{last_char}, @value{GDBN} displays this argument while your program
6275 continues to stop inside that function. When it stops elsewhere---where
6276 there is no variable @code{last_char}---the display is disabled
6277 automatically. The next time your program stops where @code{last_char}
6278 is meaningful, you can enable the display expression once again.
6280 @node Print Settings
6281 @section Print Settings
6283 @cindex format options
6284 @cindex print settings
6285 @value{GDBN} provides the following ways to control how arrays, structures,
6286 and symbols are printed.
6289 These settings are useful for debugging programs in any language:
6293 @item set print address
6294 @itemx set print address on
6295 @cindex print/don't print memory addresses
6296 @value{GDBN} prints memory addresses showing the location of stack
6297 traces, structure values, pointer values, breakpoints, and so forth,
6298 even when it also displays the contents of those addresses. The default
6299 is @code{on}. For example, this is what a stack frame display looks like with
6300 @code{set print address on}:
6305 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6307 530 if (lquote != def_lquote)
6311 @item set print address off
6312 Do not print addresses when displaying their contents. For example,
6313 this is the same stack frame displayed with @code{set print address off}:
6317 (@value{GDBP}) set print addr off
6319 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6320 530 if (lquote != def_lquote)
6324 You can use @samp{set print address off} to eliminate all machine
6325 dependent displays from the @value{GDBN} interface. For example, with
6326 @code{print address off}, you should get the same text for backtraces on
6327 all machines---whether or not they involve pointer arguments.
6330 @item show print address
6331 Show whether or not addresses are to be printed.
6334 When @value{GDBN} prints a symbolic address, it normally prints the
6335 closest earlier symbol plus an offset. If that symbol does not uniquely
6336 identify the address (for example, it is a name whose scope is a single
6337 source file), you may need to clarify. One way to do this is with
6338 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6339 you can set @value{GDBN} to print the source file and line number when
6340 it prints a symbolic address:
6343 @item set print symbol-filename on
6344 @cindex source file and line of a symbol
6345 @cindex symbol, source file and line
6346 Tell @value{GDBN} to print the source file name and line number of a
6347 symbol in the symbolic form of an address.
6349 @item set print symbol-filename off
6350 Do not print source file name and line number of a symbol. This is the
6353 @item show print symbol-filename
6354 Show whether or not @value{GDBN} will print the source file name and
6355 line number of a symbol in the symbolic form of an address.
6358 Another situation where it is helpful to show symbol filenames and line
6359 numbers is when disassembling code; @value{GDBN} shows you the line
6360 number and source file that corresponds to each instruction.
6362 Also, you may wish to see the symbolic form only if the address being
6363 printed is reasonably close to the closest earlier symbol:
6366 @item set print max-symbolic-offset @var{max-offset}
6367 @cindex maximum value for offset of closest symbol
6368 Tell @value{GDBN} to only display the symbolic form of an address if the
6369 offset between the closest earlier symbol and the address is less than
6370 @var{max-offset}. The default is 0, which tells @value{GDBN}
6371 to always print the symbolic form of an address if any symbol precedes it.
6373 @item show print max-symbolic-offset
6374 Ask how large the maximum offset is that @value{GDBN} prints in a
6378 @cindex wild pointer, interpreting
6379 @cindex pointer, finding referent
6380 If you have a pointer and you are not sure where it points, try
6381 @samp{set print symbol-filename on}. Then you can determine the name
6382 and source file location of the variable where it points, using
6383 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6384 For example, here @value{GDBN} shows that a variable @code{ptt} points
6385 at another variable @code{t}, defined in @file{hi2.c}:
6388 (@value{GDBP}) set print symbol-filename on
6389 (@value{GDBP}) p/a ptt
6390 $4 = 0xe008 <t in hi2.c>
6394 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6395 does not show the symbol name and filename of the referent, even with
6396 the appropriate @code{set print} options turned on.
6399 Other settings control how different kinds of objects are printed:
6402 @item set print array
6403 @itemx set print array on
6404 @cindex pretty print arrays
6405 Pretty print arrays. This format is more convenient to read,
6406 but uses more space. The default is off.
6408 @item set print array off
6409 Return to compressed format for arrays.
6411 @item show print array
6412 Show whether compressed or pretty format is selected for displaying
6415 @cindex print array indexes
6416 @item set print array-indexes
6417 @itemx set print array-indexes on
6418 Print the index of each element when displaying arrays. May be more
6419 convenient to locate a given element in the array or quickly find the
6420 index of a given element in that printed array. The default is off.
6422 @item set print array-indexes off
6423 Stop printing element indexes when displaying arrays.
6425 @item show print array-indexes
6426 Show whether the index of each element is printed when displaying
6429 @item set print elements @var{number-of-elements}
6430 @cindex number of array elements to print
6431 @cindex limit on number of printed array elements
6432 Set a limit on how many elements of an array @value{GDBN} will print.
6433 If @value{GDBN} is printing a large array, it stops printing after it has
6434 printed the number of elements set by the @code{set print elements} command.
6435 This limit also applies to the display of strings.
6436 When @value{GDBN} starts, this limit is set to 200.
6437 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6439 @item show print elements
6440 Display the number of elements of a large array that @value{GDBN} will print.
6441 If the number is 0, then the printing is unlimited.
6443 @item set print frame-arguments @var{value}
6444 @cindex printing frame argument values
6445 @cindex print all frame argument values
6446 @cindex print frame argument values for scalars only
6447 @cindex do not print frame argument values
6448 This command allows to control how the values of arguments are printed
6449 when the debugger prints a frame (@pxref{Frames}). The possible
6454 The values of all arguments are printed. This is the default.
6457 Print the value of an argument only if it is a scalar. The value of more
6458 complex arguments such as arrays, structures, unions, etc, is replaced
6459 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6462 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6467 None of the argument values are printed. Instead, the value of each argument
6468 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6471 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6476 By default, all argument values are always printed. But this command
6477 can be useful in several cases. For instance, it can be used to reduce
6478 the amount of information printed in each frame, making the backtrace
6479 more readable. Also, this command can be used to improve performance
6480 when displaying Ada frames, because the computation of large arguments
6481 can sometimes be CPU-intensive, especiallly in large applications.
6482 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6483 avoids this computation, thus speeding up the display of each Ada frame.
6485 @item show print frame-arguments
6486 Show how the value of arguments should be displayed when printing a frame.
6488 @item set print repeats
6489 @cindex repeated array elements
6490 Set the threshold for suppressing display of repeated array
6491 elements. When the number of consecutive identical elements of an
6492 array exceeds the threshold, @value{GDBN} prints the string
6493 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6494 identical repetitions, instead of displaying the identical elements
6495 themselves. Setting the threshold to zero will cause all elements to
6496 be individually printed. The default threshold is 10.
6498 @item show print repeats
6499 Display the current threshold for printing repeated identical
6502 @item set print null-stop
6503 @cindex @sc{null} elements in arrays
6504 Cause @value{GDBN} to stop printing the characters of an array when the first
6505 @sc{null} is encountered. This is useful when large arrays actually
6506 contain only short strings.
6509 @item show print null-stop
6510 Show whether @value{GDBN} stops printing an array on the first
6511 @sc{null} character.
6513 @item set print pretty on
6514 @cindex print structures in indented form
6515 @cindex indentation in structure display
6516 Cause @value{GDBN} to print structures in an indented format with one member
6517 per line, like this:
6532 @item set print pretty off
6533 Cause @value{GDBN} to print structures in a compact format, like this:
6537 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6538 meat = 0x54 "Pork"@}
6543 This is the default format.
6545 @item show print pretty
6546 Show which format @value{GDBN} is using to print structures.
6548 @item set print sevenbit-strings on
6549 @cindex eight-bit characters in strings
6550 @cindex octal escapes in strings
6551 Print using only seven-bit characters; if this option is set,
6552 @value{GDBN} displays any eight-bit characters (in strings or
6553 character values) using the notation @code{\}@var{nnn}. This setting is
6554 best if you are working in English (@sc{ascii}) and you use the
6555 high-order bit of characters as a marker or ``meta'' bit.
6557 @item set print sevenbit-strings off
6558 Print full eight-bit characters. This allows the use of more
6559 international character sets, and is the default.
6561 @item show print sevenbit-strings
6562 Show whether or not @value{GDBN} is printing only seven-bit characters.
6564 @item set print union on
6565 @cindex unions in structures, printing
6566 Tell @value{GDBN} to print unions which are contained in structures
6567 and other unions. This is the default setting.
6569 @item set print union off
6570 Tell @value{GDBN} not to print unions which are contained in
6571 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6574 @item show print union
6575 Ask @value{GDBN} whether or not it will print unions which are contained in
6576 structures and other unions.
6578 For example, given the declarations
6581 typedef enum @{Tree, Bug@} Species;
6582 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6583 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6594 struct thing foo = @{Tree, @{Acorn@}@};
6598 with @code{set print union on} in effect @samp{p foo} would print
6601 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6605 and with @code{set print union off} in effect it would print
6608 $1 = @{it = Tree, form = @{...@}@}
6612 @code{set print union} affects programs written in C-like languages
6618 These settings are of interest when debugging C@t{++} programs:
6621 @cindex demangling C@t{++} names
6622 @item set print demangle
6623 @itemx set print demangle on
6624 Print C@t{++} names in their source form rather than in the encoded
6625 (``mangled'') form passed to the assembler and linker for type-safe
6626 linkage. The default is on.
6628 @item show print demangle
6629 Show whether C@t{++} names are printed in mangled or demangled form.
6631 @item set print asm-demangle
6632 @itemx set print asm-demangle on
6633 Print C@t{++} names in their source form rather than their mangled form, even
6634 in assembler code printouts such as instruction disassemblies.
6637 @item show print asm-demangle
6638 Show whether C@t{++} names in assembly listings are printed in mangled
6641 @cindex C@t{++} symbol decoding style
6642 @cindex symbol decoding style, C@t{++}
6643 @kindex set demangle-style
6644 @item set demangle-style @var{style}
6645 Choose among several encoding schemes used by different compilers to
6646 represent C@t{++} names. The choices for @var{style} are currently:
6650 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6653 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6654 This is the default.
6657 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6660 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6663 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6664 @strong{Warning:} this setting alone is not sufficient to allow
6665 debugging @code{cfront}-generated executables. @value{GDBN} would
6666 require further enhancement to permit that.
6669 If you omit @var{style}, you will see a list of possible formats.
6671 @item show demangle-style
6672 Display the encoding style currently in use for decoding C@t{++} symbols.
6674 @item set print object
6675 @itemx set print object on
6676 @cindex derived type of an object, printing
6677 @cindex display derived types
6678 When displaying a pointer to an object, identify the @emph{actual}
6679 (derived) type of the object rather than the @emph{declared} type, using
6680 the virtual function table.
6682 @item set print object off
6683 Display only the declared type of objects, without reference to the
6684 virtual function table. This is the default setting.
6686 @item show print object
6687 Show whether actual, or declared, object types are displayed.
6689 @item set print static-members
6690 @itemx set print static-members on
6691 @cindex static members of C@t{++} objects
6692 Print static members when displaying a C@t{++} object. The default is on.
6694 @item set print static-members off
6695 Do not print static members when displaying a C@t{++} object.
6697 @item show print static-members
6698 Show whether C@t{++} static members are printed or not.
6700 @item set print pascal_static-members
6701 @itemx set print pascal_static-members on
6702 @cindex static members of Pascal objects
6703 @cindex Pascal objects, static members display
6704 Print static members when displaying a Pascal object. The default is on.
6706 @item set print pascal_static-members off
6707 Do not print static members when displaying a Pascal object.
6709 @item show print pascal_static-members
6710 Show whether Pascal static members are printed or not.
6712 @c These don't work with HP ANSI C++ yet.
6713 @item set print vtbl
6714 @itemx set print vtbl on
6715 @cindex pretty print C@t{++} virtual function tables
6716 @cindex virtual functions (C@t{++}) display
6717 @cindex VTBL display
6718 Pretty print C@t{++} virtual function tables. The default is off.
6719 (The @code{vtbl} commands do not work on programs compiled with the HP
6720 ANSI C@t{++} compiler (@code{aCC}).)
6722 @item set print vtbl off
6723 Do not pretty print C@t{++} virtual function tables.
6725 @item show print vtbl
6726 Show whether C@t{++} virtual function tables are pretty printed, or not.
6730 @section Value History
6732 @cindex value history
6733 @cindex history of values printed by @value{GDBN}
6734 Values printed by the @code{print} command are saved in the @value{GDBN}
6735 @dfn{value history}. This allows you to refer to them in other expressions.
6736 Values are kept until the symbol table is re-read or discarded
6737 (for example with the @code{file} or @code{symbol-file} commands).
6738 When the symbol table changes, the value history is discarded,
6739 since the values may contain pointers back to the types defined in the
6744 @cindex history number
6745 The values printed are given @dfn{history numbers} by which you can
6746 refer to them. These are successive integers starting with one.
6747 @code{print} shows you the history number assigned to a value by
6748 printing @samp{$@var{num} = } before the value; here @var{num} is the
6751 To refer to any previous value, use @samp{$} followed by the value's
6752 history number. The way @code{print} labels its output is designed to
6753 remind you of this. Just @code{$} refers to the most recent value in
6754 the history, and @code{$$} refers to the value before that.
6755 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6756 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6757 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6759 For example, suppose you have just printed a pointer to a structure and
6760 want to see the contents of the structure. It suffices to type
6766 If you have a chain of structures where the component @code{next} points
6767 to the next one, you can print the contents of the next one with this:
6774 You can print successive links in the chain by repeating this
6775 command---which you can do by just typing @key{RET}.
6777 Note that the history records values, not expressions. If the value of
6778 @code{x} is 4 and you type these commands:
6786 then the value recorded in the value history by the @code{print} command
6787 remains 4 even though the value of @code{x} has changed.
6792 Print the last ten values in the value history, with their item numbers.
6793 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6794 values} does not change the history.
6796 @item show values @var{n}
6797 Print ten history values centered on history item number @var{n}.
6800 Print ten history values just after the values last printed. If no more
6801 values are available, @code{show values +} produces no display.
6804 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6805 same effect as @samp{show values +}.
6807 @node Convenience Vars
6808 @section Convenience Variables
6810 @cindex convenience variables
6811 @cindex user-defined variables
6812 @value{GDBN} provides @dfn{convenience variables} that you can use within
6813 @value{GDBN} to hold on to a value and refer to it later. These variables
6814 exist entirely within @value{GDBN}; they are not part of your program, and
6815 setting a convenience variable has no direct effect on further execution
6816 of your program. That is why you can use them freely.
6818 Convenience variables are prefixed with @samp{$}. Any name preceded by
6819 @samp{$} can be used for a convenience variable, unless it is one of
6820 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6821 (Value history references, in contrast, are @emph{numbers} preceded
6822 by @samp{$}. @xref{Value History, ,Value History}.)
6824 You can save a value in a convenience variable with an assignment
6825 expression, just as you would set a variable in your program.
6829 set $foo = *object_ptr
6833 would save in @code{$foo} the value contained in the object pointed to by
6836 Using a convenience variable for the first time creates it, but its
6837 value is @code{void} until you assign a new value. You can alter the
6838 value with another assignment at any time.
6840 Convenience variables have no fixed types. You can assign a convenience
6841 variable any type of value, including structures and arrays, even if
6842 that variable already has a value of a different type. The convenience
6843 variable, when used as an expression, has the type of its current value.
6846 @kindex show convenience
6847 @cindex show all user variables
6848 @item show convenience
6849 Print a list of convenience variables used so far, and their values.
6850 Abbreviated @code{show conv}.
6852 @kindex init-if-undefined
6853 @cindex convenience variables, initializing
6854 @item init-if-undefined $@var{variable} = @var{expression}
6855 Set a convenience variable if it has not already been set. This is useful
6856 for user-defined commands that keep some state. It is similar, in concept,
6857 to using local static variables with initializers in C (except that
6858 convenience variables are global). It can also be used to allow users to
6859 override default values used in a command script.
6861 If the variable is already defined then the expression is not evaluated so
6862 any side-effects do not occur.
6865 One of the ways to use a convenience variable is as a counter to be
6866 incremented or a pointer to be advanced. For example, to print
6867 a field from successive elements of an array of structures:
6871 print bar[$i++]->contents
6875 Repeat that command by typing @key{RET}.
6877 Some convenience variables are created automatically by @value{GDBN} and given
6878 values likely to be useful.
6881 @vindex $_@r{, convenience variable}
6883 The variable @code{$_} is automatically set by the @code{x} command to
6884 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6885 commands which provide a default address for @code{x} to examine also
6886 set @code{$_} to that address; these commands include @code{info line}
6887 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6888 except when set by the @code{x} command, in which case it is a pointer
6889 to the type of @code{$__}.
6891 @vindex $__@r{, convenience variable}
6893 The variable @code{$__} is automatically set by the @code{x} command
6894 to the value found in the last address examined. Its type is chosen
6895 to match the format in which the data was printed.
6898 @vindex $_exitcode@r{, convenience variable}
6899 The variable @code{$_exitcode} is automatically set to the exit code when
6900 the program being debugged terminates.
6903 On HP-UX systems, if you refer to a function or variable name that
6904 begins with a dollar sign, @value{GDBN} searches for a user or system
6905 name first, before it searches for a convenience variable.
6911 You can refer to machine register contents, in expressions, as variables
6912 with names starting with @samp{$}. The names of registers are different
6913 for each machine; use @code{info registers} to see the names used on
6917 @kindex info registers
6918 @item info registers
6919 Print the names and values of all registers except floating-point
6920 and vector registers (in the selected stack frame).
6922 @kindex info all-registers
6923 @cindex floating point registers
6924 @item info all-registers
6925 Print the names and values of all registers, including floating-point
6926 and vector registers (in the selected stack frame).
6928 @item info registers @var{regname} @dots{}
6929 Print the @dfn{relativized} value of each specified register @var{regname}.
6930 As discussed in detail below, register values are normally relative to
6931 the selected stack frame. @var{regname} may be any register name valid on
6932 the machine you are using, with or without the initial @samp{$}.
6935 @cindex stack pointer register
6936 @cindex program counter register
6937 @cindex process status register
6938 @cindex frame pointer register
6939 @cindex standard registers
6940 @value{GDBN} has four ``standard'' register names that are available (in
6941 expressions) on most machines---whenever they do not conflict with an
6942 architecture's canonical mnemonics for registers. The register names
6943 @code{$pc} and @code{$sp} are used for the program counter register and
6944 the stack pointer. @code{$fp} is used for a register that contains a
6945 pointer to the current stack frame, and @code{$ps} is used for a
6946 register that contains the processor status. For example,
6947 you could print the program counter in hex with
6954 or print the instruction to be executed next with
6961 or add four to the stack pointer@footnote{This is a way of removing
6962 one word from the stack, on machines where stacks grow downward in
6963 memory (most machines, nowadays). This assumes that the innermost
6964 stack frame is selected; setting @code{$sp} is not allowed when other
6965 stack frames are selected. To pop entire frames off the stack,
6966 regardless of machine architecture, use @code{return};
6967 see @ref{Returning, ,Returning from a Function}.} with
6973 Whenever possible, these four standard register names are available on
6974 your machine even though the machine has different canonical mnemonics,
6975 so long as there is no conflict. The @code{info registers} command
6976 shows the canonical names. For example, on the SPARC, @code{info
6977 registers} displays the processor status register as @code{$psr} but you
6978 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6979 is an alias for the @sc{eflags} register.
6981 @value{GDBN} always considers the contents of an ordinary register as an
6982 integer when the register is examined in this way. Some machines have
6983 special registers which can hold nothing but floating point; these
6984 registers are considered to have floating point values. There is no way
6985 to refer to the contents of an ordinary register as floating point value
6986 (although you can @emph{print} it as a floating point value with
6987 @samp{print/f $@var{regname}}).
6989 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6990 means that the data format in which the register contents are saved by
6991 the operating system is not the same one that your program normally
6992 sees. For example, the registers of the 68881 floating point
6993 coprocessor are always saved in ``extended'' (raw) format, but all C
6994 programs expect to work with ``double'' (virtual) format. In such
6995 cases, @value{GDBN} normally works with the virtual format only (the format
6996 that makes sense for your program), but the @code{info registers} command
6997 prints the data in both formats.
6999 @cindex SSE registers (x86)
7000 @cindex MMX registers (x86)
7001 Some machines have special registers whose contents can be interpreted
7002 in several different ways. For example, modern x86-based machines
7003 have SSE and MMX registers that can hold several values packed
7004 together in several different formats. @value{GDBN} refers to such
7005 registers in @code{struct} notation:
7008 (@value{GDBP}) print $xmm1
7010 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7011 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7012 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7013 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7014 v4_int32 = @{0, 20657912, 11, 13@},
7015 v2_int64 = @{88725056443645952, 55834574859@},
7016 uint128 = 0x0000000d0000000b013b36f800000000
7021 To set values of such registers, you need to tell @value{GDBN} which
7022 view of the register you wish to change, as if you were assigning
7023 value to a @code{struct} member:
7026 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7029 Normally, register values are relative to the selected stack frame
7030 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7031 value that the register would contain if all stack frames farther in
7032 were exited and their saved registers restored. In order to see the
7033 true contents of hardware registers, you must select the innermost
7034 frame (with @samp{frame 0}).
7036 However, @value{GDBN} must deduce where registers are saved, from the machine
7037 code generated by your compiler. If some registers are not saved, or if
7038 @value{GDBN} is unable to locate the saved registers, the selected stack
7039 frame makes no difference.
7041 @node Floating Point Hardware
7042 @section Floating Point Hardware
7043 @cindex floating point
7045 Depending on the configuration, @value{GDBN} may be able to give
7046 you more information about the status of the floating point hardware.
7051 Display hardware-dependent information about the floating
7052 point unit. The exact contents and layout vary depending on the
7053 floating point chip. Currently, @samp{info float} is supported on
7054 the ARM and x86 machines.
7058 @section Vector Unit
7061 Depending on the configuration, @value{GDBN} may be able to give you
7062 more information about the status of the vector unit.
7067 Display information about the vector unit. The exact contents and
7068 layout vary depending on the hardware.
7071 @node OS Information
7072 @section Operating System Auxiliary Information
7073 @cindex OS information
7075 @value{GDBN} provides interfaces to useful OS facilities that can help
7076 you debug your program.
7078 @cindex @code{ptrace} system call
7079 @cindex @code{struct user} contents
7080 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7081 machines), it interfaces with the inferior via the @code{ptrace}
7082 system call. The operating system creates a special sata structure,
7083 called @code{struct user}, for this interface. You can use the
7084 command @code{info udot} to display the contents of this data
7090 Display the contents of the @code{struct user} maintained by the OS
7091 kernel for the program being debugged. @value{GDBN} displays the
7092 contents of @code{struct user} as a list of hex numbers, similar to
7093 the @code{examine} command.
7096 @cindex auxiliary vector
7097 @cindex vector, auxiliary
7098 Some operating systems supply an @dfn{auxiliary vector} to programs at
7099 startup. This is akin to the arguments and environment that you
7100 specify for a program, but contains a system-dependent variety of
7101 binary values that tell system libraries important details about the
7102 hardware, operating system, and process. Each value's purpose is
7103 identified by an integer tag; the meanings are well-known but system-specific.
7104 Depending on the configuration and operating system facilities,
7105 @value{GDBN} may be able to show you this information. For remote
7106 targets, this functionality may further depend on the remote stub's
7107 support of the @samp{qXfer:auxv:read} packet, see
7108 @ref{qXfer auxiliary vector read}.
7113 Display the auxiliary vector of the inferior, which can be either a
7114 live process or a core dump file. @value{GDBN} prints each tag value
7115 numerically, and also shows names and text descriptions for recognized
7116 tags. Some values in the vector are numbers, some bit masks, and some
7117 pointers to strings or other data. @value{GDBN} displays each value in the
7118 most appropriate form for a recognized tag, and in hexadecimal for
7119 an unrecognized tag.
7123 @node Memory Region Attributes
7124 @section Memory Region Attributes
7125 @cindex memory region attributes
7127 @dfn{Memory region attributes} allow you to describe special handling
7128 required by regions of your target's memory. @value{GDBN} uses
7129 attributes to determine whether to allow certain types of memory
7130 accesses; whether to use specific width accesses; and whether to cache
7131 target memory. By default the description of memory regions is
7132 fetched from the target (if the current target supports this), but the
7133 user can override the fetched regions.
7135 Defined memory regions can be individually enabled and disabled. When a
7136 memory region is disabled, @value{GDBN} uses the default attributes when
7137 accessing memory in that region. Similarly, if no memory regions have
7138 been defined, @value{GDBN} uses the default attributes when accessing
7141 When a memory region is defined, it is given a number to identify it;
7142 to enable, disable, or remove a memory region, you specify that number.
7146 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7147 Define a memory region bounded by @var{lower} and @var{upper} with
7148 attributes @var{attributes}@dots{}, and add it to the list of regions
7149 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7150 case: it is treated as the target's maximum memory address.
7151 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7154 Discard any user changes to the memory regions and use target-supplied
7155 regions, if available, or no regions if the target does not support.
7158 @item delete mem @var{nums}@dots{}
7159 Remove memory regions @var{nums}@dots{} from the list of regions
7160 monitored by @value{GDBN}.
7163 @item disable mem @var{nums}@dots{}
7164 Disable monitoring of memory regions @var{nums}@dots{}.
7165 A disabled memory region is not forgotten.
7166 It may be enabled again later.
7169 @item enable mem @var{nums}@dots{}
7170 Enable monitoring of memory regions @var{nums}@dots{}.
7174 Print a table of all defined memory regions, with the following columns
7178 @item Memory Region Number
7179 @item Enabled or Disabled.
7180 Enabled memory regions are marked with @samp{y}.
7181 Disabled memory regions are marked with @samp{n}.
7184 The address defining the inclusive lower bound of the memory region.
7187 The address defining the exclusive upper bound of the memory region.
7190 The list of attributes set for this memory region.
7195 @subsection Attributes
7197 @subsubsection Memory Access Mode
7198 The access mode attributes set whether @value{GDBN} may make read or
7199 write accesses to a memory region.
7201 While these attributes prevent @value{GDBN} from performing invalid
7202 memory accesses, they do nothing to prevent the target system, I/O DMA,
7203 etc.@: from accessing memory.
7207 Memory is read only.
7209 Memory is write only.
7211 Memory is read/write. This is the default.
7214 @subsubsection Memory Access Size
7215 The access size attribute tells @value{GDBN} to use specific sized
7216 accesses in the memory region. Often memory mapped device registers
7217 require specific sized accesses. If no access size attribute is
7218 specified, @value{GDBN} may use accesses of any size.
7222 Use 8 bit memory accesses.
7224 Use 16 bit memory accesses.
7226 Use 32 bit memory accesses.
7228 Use 64 bit memory accesses.
7231 @c @subsubsection Hardware/Software Breakpoints
7232 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7233 @c will use hardware or software breakpoints for the internal breakpoints
7234 @c used by the step, next, finish, until, etc. commands.
7238 @c Always use hardware breakpoints
7239 @c @item swbreak (default)
7242 @subsubsection Data Cache
7243 The data cache attributes set whether @value{GDBN} will cache target
7244 memory. While this generally improves performance by reducing debug
7245 protocol overhead, it can lead to incorrect results because @value{GDBN}
7246 does not know about volatile variables or memory mapped device
7251 Enable @value{GDBN} to cache target memory.
7253 Disable @value{GDBN} from caching target memory. This is the default.
7256 @subsection Memory Access Checking
7257 @value{GDBN} can be instructed to refuse accesses to memory that is
7258 not explicitly described. This can be useful if accessing such
7259 regions has undesired effects for a specific target, or to provide
7260 better error checking. The following commands control this behaviour.
7263 @kindex set mem inaccessible-by-default
7264 @item set mem inaccessible-by-default [on|off]
7265 If @code{on} is specified, make @value{GDBN} treat memory not
7266 explicitly described by the memory ranges as non-existent and refuse accesses
7267 to such memory. The checks are only performed if there's at least one
7268 memory range defined. If @code{off} is specified, make @value{GDBN}
7269 treat the memory not explicitly described by the memory ranges as RAM.
7270 The default value is @code{on}.
7271 @kindex show mem inaccessible-by-default
7272 @item show mem inaccessible-by-default
7273 Show the current handling of accesses to unknown memory.
7277 @c @subsubsection Memory Write Verification
7278 @c The memory write verification attributes set whether @value{GDBN}
7279 @c will re-reads data after each write to verify the write was successful.
7283 @c @item noverify (default)
7286 @node Dump/Restore Files
7287 @section Copy Between Memory and a File
7288 @cindex dump/restore files
7289 @cindex append data to a file
7290 @cindex dump data to a file
7291 @cindex restore data from a file
7293 You can use the commands @code{dump}, @code{append}, and
7294 @code{restore} to copy data between target memory and a file. The
7295 @code{dump} and @code{append} commands write data to a file, and the
7296 @code{restore} command reads data from a file back into the inferior's
7297 memory. Files may be in binary, Motorola S-record, Intel hex, or
7298 Tektronix Hex format; however, @value{GDBN} can only append to binary
7304 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7305 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7306 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7307 or the value of @var{expr}, to @var{filename} in the given format.
7309 The @var{format} parameter may be any one of:
7316 Motorola S-record format.
7318 Tektronix Hex format.
7321 @value{GDBN} uses the same definitions of these formats as the
7322 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7323 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7327 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7328 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7329 Append the contents of memory from @var{start_addr} to @var{end_addr},
7330 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7331 (@value{GDBN} can only append data to files in raw binary form.)
7334 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7335 Restore the contents of file @var{filename} into memory. The
7336 @code{restore} command can automatically recognize any known @sc{bfd}
7337 file format, except for raw binary. To restore a raw binary file you
7338 must specify the optional keyword @code{binary} after the filename.
7340 If @var{bias} is non-zero, its value will be added to the addresses
7341 contained in the file. Binary files always start at address zero, so
7342 they will be restored at address @var{bias}. Other bfd files have
7343 a built-in location; they will be restored at offset @var{bias}
7346 If @var{start} and/or @var{end} are non-zero, then only data between
7347 file offset @var{start} and file offset @var{end} will be restored.
7348 These offsets are relative to the addresses in the file, before
7349 the @var{bias} argument is applied.
7353 @node Core File Generation
7354 @section How to Produce a Core File from Your Program
7355 @cindex dump core from inferior
7357 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7358 image of a running process and its process status (register values
7359 etc.). Its primary use is post-mortem debugging of a program that
7360 crashed while it ran outside a debugger. A program that crashes
7361 automatically produces a core file, unless this feature is disabled by
7362 the user. @xref{Files}, for information on invoking @value{GDBN} in
7363 the post-mortem debugging mode.
7365 Occasionally, you may wish to produce a core file of the program you
7366 are debugging in order to preserve a snapshot of its state.
7367 @value{GDBN} has a special command for that.
7371 @kindex generate-core-file
7372 @item generate-core-file [@var{file}]
7373 @itemx gcore [@var{file}]
7374 Produce a core dump of the inferior process. The optional argument
7375 @var{file} specifies the file name where to put the core dump. If not
7376 specified, the file name defaults to @file{core.@var{pid}}, where
7377 @var{pid} is the inferior process ID.
7379 Note that this command is implemented only for some systems (as of
7380 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7383 @node Character Sets
7384 @section Character Sets
7385 @cindex character sets
7387 @cindex translating between character sets
7388 @cindex host character set
7389 @cindex target character set
7391 If the program you are debugging uses a different character set to
7392 represent characters and strings than the one @value{GDBN} uses itself,
7393 @value{GDBN} can automatically translate between the character sets for
7394 you. The character set @value{GDBN} uses we call the @dfn{host
7395 character set}; the one the inferior program uses we call the
7396 @dfn{target character set}.
7398 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7399 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7400 remote protocol (@pxref{Remote Debugging}) to debug a program
7401 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7402 then the host character set is Latin-1, and the target character set is
7403 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7404 target-charset EBCDIC-US}, then @value{GDBN} translates between
7405 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7406 character and string literals in expressions.
7408 @value{GDBN} has no way to automatically recognize which character set
7409 the inferior program uses; you must tell it, using the @code{set
7410 target-charset} command, described below.
7412 Here are the commands for controlling @value{GDBN}'s character set
7416 @item set target-charset @var{charset}
7417 @kindex set target-charset
7418 Set the current target character set to @var{charset}. We list the
7419 character set names @value{GDBN} recognizes below, but if you type
7420 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7421 list the target character sets it supports.
7425 @item set host-charset @var{charset}
7426 @kindex set host-charset
7427 Set the current host character set to @var{charset}.
7429 By default, @value{GDBN} uses a host character set appropriate to the
7430 system it is running on; you can override that default using the
7431 @code{set host-charset} command.
7433 @value{GDBN} can only use certain character sets as its host character
7434 set. We list the character set names @value{GDBN} recognizes below, and
7435 indicate which can be host character sets, but if you type
7436 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7437 list the host character sets it supports.
7439 @item set charset @var{charset}
7441 Set the current host and target character sets to @var{charset}. As
7442 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7443 @value{GDBN} will list the name of the character sets that can be used
7444 for both host and target.
7448 @kindex show charset
7449 Show the names of the current host and target charsets.
7451 @itemx show host-charset
7452 @kindex show host-charset
7453 Show the name of the current host charset.
7455 @itemx show target-charset
7456 @kindex show target-charset
7457 Show the name of the current target charset.
7461 @value{GDBN} currently includes support for the following character
7467 @cindex ASCII character set
7468 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7472 @cindex ISO 8859-1 character set
7473 @cindex ISO Latin 1 character set
7474 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7475 characters needed for French, German, and Spanish. @value{GDBN} can use
7476 this as its host character set.
7480 @cindex EBCDIC character set
7481 @cindex IBM1047 character set
7482 Variants of the @sc{ebcdic} character set, used on some of IBM's
7483 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7484 @value{GDBN} cannot use these as its host character set.
7488 Note that these are all single-byte character sets. More work inside
7489 @value{GDBN} is needed to support multi-byte or variable-width character
7490 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7492 Here is an example of @value{GDBN}'s character set support in action.
7493 Assume that the following source code has been placed in the file
7494 @file{charset-test.c}:
7500 = @{72, 101, 108, 108, 111, 44, 32, 119,
7501 111, 114, 108, 100, 33, 10, 0@};
7502 char ibm1047_hello[]
7503 = @{200, 133, 147, 147, 150, 107, 64, 166,
7504 150, 153, 147, 132, 90, 37, 0@};
7508 printf ("Hello, world!\n");
7512 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7513 containing the string @samp{Hello, world!} followed by a newline,
7514 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7516 We compile the program, and invoke the debugger on it:
7519 $ gcc -g charset-test.c -o charset-test
7520 $ gdb -nw charset-test
7521 GNU gdb 2001-12-19-cvs
7522 Copyright 2001 Free Software Foundation, Inc.
7527 We can use the @code{show charset} command to see what character sets
7528 @value{GDBN} is currently using to interpret and display characters and
7532 (@value{GDBP}) show charset
7533 The current host and target character set is `ISO-8859-1'.
7537 For the sake of printing this manual, let's use @sc{ascii} as our
7538 initial character set:
7540 (@value{GDBP}) set charset ASCII
7541 (@value{GDBP}) show charset
7542 The current host and target character set is `ASCII'.
7546 Let's assume that @sc{ascii} is indeed the correct character set for our
7547 host system --- in other words, let's assume that if @value{GDBN} prints
7548 characters using the @sc{ascii} character set, our terminal will display
7549 them properly. Since our current target character set is also
7550 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7553 (@value{GDBP}) print ascii_hello
7554 $1 = 0x401698 "Hello, world!\n"
7555 (@value{GDBP}) print ascii_hello[0]
7560 @value{GDBN} uses the target character set for character and string
7561 literals you use in expressions:
7564 (@value{GDBP}) print '+'
7569 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7572 @value{GDBN} relies on the user to tell it which character set the
7573 target program uses. If we print @code{ibm1047_hello} while our target
7574 character set is still @sc{ascii}, we get jibberish:
7577 (@value{GDBP}) print ibm1047_hello
7578 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7579 (@value{GDBP}) print ibm1047_hello[0]
7584 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7585 @value{GDBN} tells us the character sets it supports:
7588 (@value{GDBP}) set target-charset
7589 ASCII EBCDIC-US IBM1047 ISO-8859-1
7590 (@value{GDBP}) set target-charset
7593 We can select @sc{ibm1047} as our target character set, and examine the
7594 program's strings again. Now the @sc{ascii} string is wrong, but
7595 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7596 target character set, @sc{ibm1047}, to the host character set,
7597 @sc{ascii}, and they display correctly:
7600 (@value{GDBP}) set target-charset IBM1047
7601 (@value{GDBP}) show charset
7602 The current host character set is `ASCII'.
7603 The current target character set is `IBM1047'.
7604 (@value{GDBP}) print ascii_hello
7605 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7606 (@value{GDBP}) print ascii_hello[0]
7608 (@value{GDBP}) print ibm1047_hello
7609 $8 = 0x4016a8 "Hello, world!\n"
7610 (@value{GDBP}) print ibm1047_hello[0]
7615 As above, @value{GDBN} uses the target character set for character and
7616 string literals you use in expressions:
7619 (@value{GDBP}) print '+'
7624 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7627 @node Caching Remote Data
7628 @section Caching Data of Remote Targets
7629 @cindex caching data of remote targets
7631 @value{GDBN} can cache data exchanged between the debugger and a
7632 remote target (@pxref{Remote Debugging}). Such caching generally improves
7633 performance, because it reduces the overhead of the remote protocol by
7634 bundling memory reads and writes into large chunks. Unfortunately,
7635 @value{GDBN} does not currently know anything about volatile
7636 registers, and thus data caching will produce incorrect results when
7637 volatile registers are in use.
7640 @kindex set remotecache
7641 @item set remotecache on
7642 @itemx set remotecache off
7643 Set caching state for remote targets. When @code{ON}, use data
7644 caching. By default, this option is @code{OFF}.
7646 @kindex show remotecache
7647 @item show remotecache
7648 Show the current state of data caching for remote targets.
7652 Print the information about the data cache performance. The
7653 information displayed includes: the dcache width and depth; and for
7654 each cache line, how many times it was referenced, and its data and
7655 state (dirty, bad, ok, etc.). This command is useful for debugging
7656 the data cache operation.
7659 @node Searching Memory
7660 @section Search Memory
7661 @cindex searching memory
7663 Memory can be searched for a particular sequence of bytes with the
7664 @code{find} command.
7668 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
7669 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
7670 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
7671 etc. The search begins at address @var{start_addr} and continues for either
7672 @var{len} bytes or through to @var{end_addr} inclusive.
7675 @var{s} and @var{n} are optional parameters.
7676 They may be specified in either order, apart or together.
7679 @item @var{s}, search query size
7680 The size of each search query value.
7686 halfwords (two bytes)
7690 giant words (eight bytes)
7693 All values are interpreted in the current language.
7694 This means, for example, that if the current source language is C/C@t{++}
7695 then searching for the string ``hello'' includes the trailing '\0'.
7697 If the value size is not specified, it is taken from the
7698 value's type in the current language.
7699 This is useful when one wants to specify the search
7700 pattern as a mixture of types.
7701 Note that this means, for example, that in the case of C-like languages
7702 a search for an untyped 0x42 will search for @samp{(int) 0x42}
7703 which is typically four bytes.
7705 @item @var{n}, maximum number of finds
7706 The maximum number of matches to print. The default is to print all finds.
7709 You can use strings as search values. Quote them with double-quotes
7711 The string value is copied into the search pattern byte by byte,
7712 regardless of the endianness of the target and the size specification.
7714 The address of each match found is printed as well as a count of the
7715 number of matches found.
7717 The address of the last value found is stored in convenience variable
7719 A count of the number of matches is stored in @samp{$numfound}.
7721 For example, if stopped at the @code{printf} in this function:
7727 static char hello[] = "hello-hello";
7728 static struct @{ char c; short s; int i; @}
7729 __attribute__ ((packed)) mixed
7730 = @{ 'c', 0x1234, 0x87654321 @};
7731 printf ("%s\n", hello);
7736 you get during debugging:
7739 (gdb) find &hello[0], +sizeof(hello), "hello"
7740 0x804956d <hello.1620+6>
7742 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
7743 0x8049567 <hello.1620>
7744 0x804956d <hello.1620+6>
7746 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
7747 0x8049567 <hello.1620>
7749 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
7750 0x8049560 <mixed.1625>
7752 (gdb) print $numfound
7755 $2 = (void *) 0x8049560
7759 @chapter C Preprocessor Macros
7761 Some languages, such as C and C@t{++}, provide a way to define and invoke
7762 ``preprocessor macros'' which expand into strings of tokens.
7763 @value{GDBN} can evaluate expressions containing macro invocations, show
7764 the result of macro expansion, and show a macro's definition, including
7765 where it was defined.
7767 You may need to compile your program specially to provide @value{GDBN}
7768 with information about preprocessor macros. Most compilers do not
7769 include macros in their debugging information, even when you compile
7770 with the @option{-g} flag. @xref{Compilation}.
7772 A program may define a macro at one point, remove that definition later,
7773 and then provide a different definition after that. Thus, at different
7774 points in the program, a macro may have different definitions, or have
7775 no definition at all. If there is a current stack frame, @value{GDBN}
7776 uses the macros in scope at that frame's source code line. Otherwise,
7777 @value{GDBN} uses the macros in scope at the current listing location;
7780 At the moment, @value{GDBN} does not support the @code{##}
7781 token-splicing operator, the @code{#} stringification operator, or
7782 variable-arity macros.
7784 Whenever @value{GDBN} evaluates an expression, it always expands any
7785 macro invocations present in the expression. @value{GDBN} also provides
7786 the following commands for working with macros explicitly.
7790 @kindex macro expand
7791 @cindex macro expansion, showing the results of preprocessor
7792 @cindex preprocessor macro expansion, showing the results of
7793 @cindex expanding preprocessor macros
7794 @item macro expand @var{expression}
7795 @itemx macro exp @var{expression}
7796 Show the results of expanding all preprocessor macro invocations in
7797 @var{expression}. Since @value{GDBN} simply expands macros, but does
7798 not parse the result, @var{expression} need not be a valid expression;
7799 it can be any string of tokens.
7802 @item macro expand-once @var{expression}
7803 @itemx macro exp1 @var{expression}
7804 @cindex expand macro once
7805 @i{(This command is not yet implemented.)} Show the results of
7806 expanding those preprocessor macro invocations that appear explicitly in
7807 @var{expression}. Macro invocations appearing in that expansion are
7808 left unchanged. This command allows you to see the effect of a
7809 particular macro more clearly, without being confused by further
7810 expansions. Since @value{GDBN} simply expands macros, but does not
7811 parse the result, @var{expression} need not be a valid expression; it
7812 can be any string of tokens.
7815 @cindex macro definition, showing
7816 @cindex definition, showing a macro's
7817 @item info macro @var{macro}
7818 Show the definition of the macro named @var{macro}, and describe the
7819 source location where that definition was established.
7821 @kindex macro define
7822 @cindex user-defined macros
7823 @cindex defining macros interactively
7824 @cindex macros, user-defined
7825 @item macro define @var{macro} @var{replacement-list}
7826 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7827 @i{(This command is not yet implemented.)} Introduce a definition for a
7828 preprocessor macro named @var{macro}, invocations of which are replaced
7829 by the tokens given in @var{replacement-list}. The first form of this
7830 command defines an ``object-like'' macro, which takes no arguments; the
7831 second form defines a ``function-like'' macro, which takes the arguments
7832 given in @var{arglist}.
7834 A definition introduced by this command is in scope in every expression
7835 evaluated in @value{GDBN}, until it is removed with the @command{macro
7836 undef} command, described below. The definition overrides all
7837 definitions for @var{macro} present in the program being debugged, as
7838 well as any previous user-supplied definition.
7841 @item macro undef @var{macro}
7842 @i{(This command is not yet implemented.)} Remove any user-supplied
7843 definition for the macro named @var{macro}. This command only affects
7844 definitions provided with the @command{macro define} command, described
7845 above; it cannot remove definitions present in the program being
7850 @i{(This command is not yet implemented.)} List all the macros
7851 defined using the @code{macro define} command.
7854 @cindex macros, example of debugging with
7855 Here is a transcript showing the above commands in action. First, we
7856 show our source files:
7864 #define ADD(x) (M + x)
7869 printf ("Hello, world!\n");
7871 printf ("We're so creative.\n");
7873 printf ("Goodbye, world!\n");
7880 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7881 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7882 compiler includes information about preprocessor macros in the debugging
7886 $ gcc -gdwarf-2 -g3 sample.c -o sample
7890 Now, we start @value{GDBN} on our sample program:
7894 GNU gdb 2002-05-06-cvs
7895 Copyright 2002 Free Software Foundation, Inc.
7896 GDB is free software, @dots{}
7900 We can expand macros and examine their definitions, even when the
7901 program is not running. @value{GDBN} uses the current listing position
7902 to decide which macro definitions are in scope:
7905 (@value{GDBP}) list main
7908 5 #define ADD(x) (M + x)
7913 10 printf ("Hello, world!\n");
7915 12 printf ("We're so creative.\n");
7916 (@value{GDBP}) info macro ADD
7917 Defined at /home/jimb/gdb/macros/play/sample.c:5
7918 #define ADD(x) (M + x)
7919 (@value{GDBP}) info macro Q
7920 Defined at /home/jimb/gdb/macros/play/sample.h:1
7921 included at /home/jimb/gdb/macros/play/sample.c:2
7923 (@value{GDBP}) macro expand ADD(1)
7924 expands to: (42 + 1)
7925 (@value{GDBP}) macro expand-once ADD(1)
7926 expands to: once (M + 1)
7930 In the example above, note that @command{macro expand-once} expands only
7931 the macro invocation explicit in the original text --- the invocation of
7932 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7933 which was introduced by @code{ADD}.
7935 Once the program is running, @value{GDBN} uses the macro definitions in
7936 force at the source line of the current stack frame:
7939 (@value{GDBP}) break main
7940 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7942 Starting program: /home/jimb/gdb/macros/play/sample
7944 Breakpoint 1, main () at sample.c:10
7945 10 printf ("Hello, world!\n");
7949 At line 10, the definition of the macro @code{N} at line 9 is in force:
7952 (@value{GDBP}) info macro N
7953 Defined at /home/jimb/gdb/macros/play/sample.c:9
7955 (@value{GDBP}) macro expand N Q M
7957 (@value{GDBP}) print N Q M
7962 As we step over directives that remove @code{N}'s definition, and then
7963 give it a new definition, @value{GDBN} finds the definition (or lack
7964 thereof) in force at each point:
7969 12 printf ("We're so creative.\n");
7970 (@value{GDBP}) info macro N
7971 The symbol `N' has no definition as a C/C++ preprocessor macro
7972 at /home/jimb/gdb/macros/play/sample.c:12
7975 14 printf ("Goodbye, world!\n");
7976 (@value{GDBP}) info macro N
7977 Defined at /home/jimb/gdb/macros/play/sample.c:13
7979 (@value{GDBP}) macro expand N Q M
7980 expands to: 1729 < 42
7981 (@value{GDBP}) print N Q M
7988 @chapter Tracepoints
7989 @c This chapter is based on the documentation written by Michael
7990 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7993 In some applications, it is not feasible for the debugger to interrupt
7994 the program's execution long enough for the developer to learn
7995 anything helpful about its behavior. If the program's correctness
7996 depends on its real-time behavior, delays introduced by a debugger
7997 might cause the program to change its behavior drastically, or perhaps
7998 fail, even when the code itself is correct. It is useful to be able
7999 to observe the program's behavior without interrupting it.
8001 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8002 specify locations in the program, called @dfn{tracepoints}, and
8003 arbitrary expressions to evaluate when those tracepoints are reached.
8004 Later, using the @code{tfind} command, you can examine the values
8005 those expressions had when the program hit the tracepoints. The
8006 expressions may also denote objects in memory---structures or arrays,
8007 for example---whose values @value{GDBN} should record; while visiting
8008 a particular tracepoint, you may inspect those objects as if they were
8009 in memory at that moment. However, because @value{GDBN} records these
8010 values without interacting with you, it can do so quickly and
8011 unobtrusively, hopefully not disturbing the program's behavior.
8013 The tracepoint facility is currently available only for remote
8014 targets. @xref{Targets}. In addition, your remote target must know
8015 how to collect trace data. This functionality is implemented in the
8016 remote stub; however, none of the stubs distributed with @value{GDBN}
8017 support tracepoints as of this writing. The format of the remote
8018 packets used to implement tracepoints are described in @ref{Tracepoint
8021 This chapter describes the tracepoint commands and features.
8025 * Analyze Collected Data::
8026 * Tracepoint Variables::
8029 @node Set Tracepoints
8030 @section Commands to Set Tracepoints
8032 Before running such a @dfn{trace experiment}, an arbitrary number of
8033 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8034 tracepoint has a number assigned to it by @value{GDBN}. Like with
8035 breakpoints, tracepoint numbers are successive integers starting from
8036 one. Many of the commands associated with tracepoints take the
8037 tracepoint number as their argument, to identify which tracepoint to
8040 For each tracepoint, you can specify, in advance, some arbitrary set
8041 of data that you want the target to collect in the trace buffer when
8042 it hits that tracepoint. The collected data can include registers,
8043 local variables, or global data. Later, you can use @value{GDBN}
8044 commands to examine the values these data had at the time the
8047 This section describes commands to set tracepoints and associated
8048 conditions and actions.
8051 * Create and Delete Tracepoints::
8052 * Enable and Disable Tracepoints::
8053 * Tracepoint Passcounts::
8054 * Tracepoint Actions::
8055 * Listing Tracepoints::
8056 * Starting and Stopping Trace Experiments::
8059 @node Create and Delete Tracepoints
8060 @subsection Create and Delete Tracepoints
8063 @cindex set tracepoint
8066 The @code{trace} command is very similar to the @code{break} command.
8067 Its argument can be a source line, a function name, or an address in
8068 the target program. @xref{Set Breaks}. The @code{trace} command
8069 defines a tracepoint, which is a point in the target program where the
8070 debugger will briefly stop, collect some data, and then allow the
8071 program to continue. Setting a tracepoint or changing its commands
8072 doesn't take effect until the next @code{tstart} command; thus, you
8073 cannot change the tracepoint attributes once a trace experiment is
8076 Here are some examples of using the @code{trace} command:
8079 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8081 (@value{GDBP}) @b{trace +2} // 2 lines forward
8083 (@value{GDBP}) @b{trace my_function} // first source line of function
8085 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8087 (@value{GDBP}) @b{trace *0x2117c4} // an address
8091 You can abbreviate @code{trace} as @code{tr}.
8094 @cindex last tracepoint number
8095 @cindex recent tracepoint number
8096 @cindex tracepoint number
8097 The convenience variable @code{$tpnum} records the tracepoint number
8098 of the most recently set tracepoint.
8100 @kindex delete tracepoint
8101 @cindex tracepoint deletion
8102 @item delete tracepoint @r{[}@var{num}@r{]}
8103 Permanently delete one or more tracepoints. With no argument, the
8104 default is to delete all tracepoints.
8109 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8111 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8115 You can abbreviate this command as @code{del tr}.
8118 @node Enable and Disable Tracepoints
8119 @subsection Enable and Disable Tracepoints
8122 @kindex disable tracepoint
8123 @item disable tracepoint @r{[}@var{num}@r{]}
8124 Disable tracepoint @var{num}, or all tracepoints if no argument
8125 @var{num} is given. A disabled tracepoint will have no effect during
8126 the next trace experiment, but it is not forgotten. You can re-enable
8127 a disabled tracepoint using the @code{enable tracepoint} command.
8129 @kindex enable tracepoint
8130 @item enable tracepoint @r{[}@var{num}@r{]}
8131 Enable tracepoint @var{num}, or all tracepoints. The enabled
8132 tracepoints will become effective the next time a trace experiment is
8136 @node Tracepoint Passcounts
8137 @subsection Tracepoint Passcounts
8141 @cindex tracepoint pass count
8142 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8143 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8144 automatically stop a trace experiment. If a tracepoint's passcount is
8145 @var{n}, then the trace experiment will be automatically stopped on
8146 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8147 @var{num} is not specified, the @code{passcount} command sets the
8148 passcount of the most recently defined tracepoint. If no passcount is
8149 given, the trace experiment will run until stopped explicitly by the
8155 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8156 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8158 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8159 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8160 (@value{GDBP}) @b{trace foo}
8161 (@value{GDBP}) @b{pass 3}
8162 (@value{GDBP}) @b{trace bar}
8163 (@value{GDBP}) @b{pass 2}
8164 (@value{GDBP}) @b{trace baz}
8165 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8166 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8167 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8168 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8172 @node Tracepoint Actions
8173 @subsection Tracepoint Action Lists
8177 @cindex tracepoint actions
8178 @item actions @r{[}@var{num}@r{]}
8179 This command will prompt for a list of actions to be taken when the
8180 tracepoint is hit. If the tracepoint number @var{num} is not
8181 specified, this command sets the actions for the one that was most
8182 recently defined (so that you can define a tracepoint and then say
8183 @code{actions} without bothering about its number). You specify the
8184 actions themselves on the following lines, one action at a time, and
8185 terminate the actions list with a line containing just @code{end}. So
8186 far, the only defined actions are @code{collect} and
8187 @code{while-stepping}.
8189 @cindex remove actions from a tracepoint
8190 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8191 and follow it immediately with @samp{end}.
8194 (@value{GDBP}) @b{collect @var{data}} // collect some data
8196 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8198 (@value{GDBP}) @b{end} // signals the end of actions.
8201 In the following example, the action list begins with @code{collect}
8202 commands indicating the things to be collected when the tracepoint is
8203 hit. Then, in order to single-step and collect additional data
8204 following the tracepoint, a @code{while-stepping} command is used,
8205 followed by the list of things to be collected while stepping. The
8206 @code{while-stepping} command is terminated by its own separate
8207 @code{end} command. Lastly, the action list is terminated by an
8211 (@value{GDBP}) @b{trace foo}
8212 (@value{GDBP}) @b{actions}
8213 Enter actions for tracepoint 1, one per line:
8222 @kindex collect @r{(tracepoints)}
8223 @item collect @var{expr1}, @var{expr2}, @dots{}
8224 Collect values of the given expressions when the tracepoint is hit.
8225 This command accepts a comma-separated list of any valid expressions.
8226 In addition to global, static, or local variables, the following
8227 special arguments are supported:
8231 collect all registers
8234 collect all function arguments
8237 collect all local variables.
8240 You can give several consecutive @code{collect} commands, each one
8241 with a single argument, or one @code{collect} command with several
8242 arguments separated by commas: the effect is the same.
8244 The command @code{info scope} (@pxref{Symbols, info scope}) is
8245 particularly useful for figuring out what data to collect.
8247 @kindex while-stepping @r{(tracepoints)}
8248 @item while-stepping @var{n}
8249 Perform @var{n} single-step traces after the tracepoint, collecting
8250 new data at each step. The @code{while-stepping} command is
8251 followed by the list of what to collect while stepping (followed by
8252 its own @code{end} command):
8256 > collect $regs, myglobal
8262 You may abbreviate @code{while-stepping} as @code{ws} or
8266 @node Listing Tracepoints
8267 @subsection Listing Tracepoints
8270 @kindex info tracepoints
8272 @cindex information about tracepoints
8273 @item info tracepoints @r{[}@var{num}@r{]}
8274 Display information about the tracepoint @var{num}. If you don't specify
8275 a tracepoint number, displays information about all the tracepoints
8276 defined so far. For each tracepoint, the following information is
8283 whether it is enabled or disabled
8287 its passcount as given by the @code{passcount @var{n}} command
8289 its step count as given by the @code{while-stepping @var{n}} command
8291 where in the source files is the tracepoint set
8293 its action list as given by the @code{actions} command
8297 (@value{GDBP}) @b{info trace}
8298 Num Enb Address PassC StepC What
8299 1 y 0x002117c4 0 0 <gdb_asm>
8300 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8301 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8306 This command can be abbreviated @code{info tp}.
8309 @node Starting and Stopping Trace Experiments
8310 @subsection Starting and Stopping Trace Experiments
8314 @cindex start a new trace experiment
8315 @cindex collected data discarded
8317 This command takes no arguments. It starts the trace experiment, and
8318 begins collecting data. This has the side effect of discarding all
8319 the data collected in the trace buffer during the previous trace
8323 @cindex stop a running trace experiment
8325 This command takes no arguments. It ends the trace experiment, and
8326 stops collecting data.
8328 @strong{Note}: a trace experiment and data collection may stop
8329 automatically if any tracepoint's passcount is reached
8330 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8333 @cindex status of trace data collection
8334 @cindex trace experiment, status of
8336 This command displays the status of the current trace data
8340 Here is an example of the commands we described so far:
8343 (@value{GDBP}) @b{trace gdb_c_test}
8344 (@value{GDBP}) @b{actions}
8345 Enter actions for tracepoint #1, one per line.
8346 > collect $regs,$locals,$args
8351 (@value{GDBP}) @b{tstart}
8352 [time passes @dots{}]
8353 (@value{GDBP}) @b{tstop}
8357 @node Analyze Collected Data
8358 @section Using the Collected Data
8360 After the tracepoint experiment ends, you use @value{GDBN} commands
8361 for examining the trace data. The basic idea is that each tracepoint
8362 collects a trace @dfn{snapshot} every time it is hit and another
8363 snapshot every time it single-steps. All these snapshots are
8364 consecutively numbered from zero and go into a buffer, and you can
8365 examine them later. The way you examine them is to @dfn{focus} on a
8366 specific trace snapshot. When the remote stub is focused on a trace
8367 snapshot, it will respond to all @value{GDBN} requests for memory and
8368 registers by reading from the buffer which belongs to that snapshot,
8369 rather than from @emph{real} memory or registers of the program being
8370 debugged. This means that @strong{all} @value{GDBN} commands
8371 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8372 behave as if we were currently debugging the program state as it was
8373 when the tracepoint occurred. Any requests for data that are not in
8374 the buffer will fail.
8377 * tfind:: How to select a trace snapshot
8378 * tdump:: How to display all data for a snapshot
8379 * save-tracepoints:: How to save tracepoints for a future run
8383 @subsection @code{tfind @var{n}}
8386 @cindex select trace snapshot
8387 @cindex find trace snapshot
8388 The basic command for selecting a trace snapshot from the buffer is
8389 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8390 counting from zero. If no argument @var{n} is given, the next
8391 snapshot is selected.
8393 Here are the various forms of using the @code{tfind} command.
8397 Find the first snapshot in the buffer. This is a synonym for
8398 @code{tfind 0} (since 0 is the number of the first snapshot).
8401 Stop debugging trace snapshots, resume @emph{live} debugging.
8404 Same as @samp{tfind none}.
8407 No argument means find the next trace snapshot.
8410 Find the previous trace snapshot before the current one. This permits
8411 retracing earlier steps.
8413 @item tfind tracepoint @var{num}
8414 Find the next snapshot associated with tracepoint @var{num}. Search
8415 proceeds forward from the last examined trace snapshot. If no
8416 argument @var{num} is given, it means find the next snapshot collected
8417 for the same tracepoint as the current snapshot.
8419 @item tfind pc @var{addr}
8420 Find the next snapshot associated with the value @var{addr} of the
8421 program counter. Search proceeds forward from the last examined trace
8422 snapshot. If no argument @var{addr} is given, it means find the next
8423 snapshot with the same value of PC as the current snapshot.
8425 @item tfind outside @var{addr1}, @var{addr2}
8426 Find the next snapshot whose PC is outside the given range of
8429 @item tfind range @var{addr1}, @var{addr2}
8430 Find the next snapshot whose PC is between @var{addr1} and
8431 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8433 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8434 Find the next snapshot associated with the source line @var{n}. If
8435 the optional argument @var{file} is given, refer to line @var{n} in
8436 that source file. Search proceeds forward from the last examined
8437 trace snapshot. If no argument @var{n} is given, it means find the
8438 next line other than the one currently being examined; thus saying
8439 @code{tfind line} repeatedly can appear to have the same effect as
8440 stepping from line to line in a @emph{live} debugging session.
8443 The default arguments for the @code{tfind} commands are specifically
8444 designed to make it easy to scan through the trace buffer. For
8445 instance, @code{tfind} with no argument selects the next trace
8446 snapshot, and @code{tfind -} with no argument selects the previous
8447 trace snapshot. So, by giving one @code{tfind} command, and then
8448 simply hitting @key{RET} repeatedly you can examine all the trace
8449 snapshots in order. Or, by saying @code{tfind -} and then hitting
8450 @key{RET} repeatedly you can examine the snapshots in reverse order.
8451 The @code{tfind line} command with no argument selects the snapshot
8452 for the next source line executed. The @code{tfind pc} command with
8453 no argument selects the next snapshot with the same program counter
8454 (PC) as the current frame. The @code{tfind tracepoint} command with
8455 no argument selects the next trace snapshot collected by the same
8456 tracepoint as the current one.
8458 In addition to letting you scan through the trace buffer manually,
8459 these commands make it easy to construct @value{GDBN} scripts that
8460 scan through the trace buffer and print out whatever collected data
8461 you are interested in. Thus, if we want to examine the PC, FP, and SP
8462 registers from each trace frame in the buffer, we can say this:
8465 (@value{GDBP}) @b{tfind start}
8466 (@value{GDBP}) @b{while ($trace_frame != -1)}
8467 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8468 $trace_frame, $pc, $sp, $fp
8472 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8473 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8474 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8475 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8476 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8477 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8478 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8479 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8480 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8481 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8482 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8485 Or, if we want to examine the variable @code{X} at each source line in
8489 (@value{GDBP}) @b{tfind start}
8490 (@value{GDBP}) @b{while ($trace_frame != -1)}
8491 > printf "Frame %d, X == %d\n", $trace_frame, X
8501 @subsection @code{tdump}
8503 @cindex dump all data collected at tracepoint
8504 @cindex tracepoint data, display
8506 This command takes no arguments. It prints all the data collected at
8507 the current trace snapshot.
8510 (@value{GDBP}) @b{trace 444}
8511 (@value{GDBP}) @b{actions}
8512 Enter actions for tracepoint #2, one per line:
8513 > collect $regs, $locals, $args, gdb_long_test
8516 (@value{GDBP}) @b{tstart}
8518 (@value{GDBP}) @b{tfind line 444}
8519 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8521 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8523 (@value{GDBP}) @b{tdump}
8524 Data collected at tracepoint 2, trace frame 1:
8525 d0 0xc4aa0085 -995491707
8529 d4 0x71aea3d 119204413
8534 a1 0x3000668 50333288
8537 a4 0x3000698 50333336
8539 fp 0x30bf3c 0x30bf3c
8540 sp 0x30bf34 0x30bf34
8542 pc 0x20b2c8 0x20b2c8
8546 p = 0x20e5b4 "gdb-test"
8553 gdb_long_test = 17 '\021'
8558 @node save-tracepoints
8559 @subsection @code{save-tracepoints @var{filename}}
8560 @kindex save-tracepoints
8561 @cindex save tracepoints for future sessions
8563 This command saves all current tracepoint definitions together with
8564 their actions and passcounts, into a file @file{@var{filename}}
8565 suitable for use in a later debugging session. To read the saved
8566 tracepoint definitions, use the @code{source} command (@pxref{Command
8569 @node Tracepoint Variables
8570 @section Convenience Variables for Tracepoints
8571 @cindex tracepoint variables
8572 @cindex convenience variables for tracepoints
8575 @vindex $trace_frame
8576 @item (int) $trace_frame
8577 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8578 snapshot is selected.
8581 @item (int) $tracepoint
8582 The tracepoint for the current trace snapshot.
8585 @item (int) $trace_line
8586 The line number for the current trace snapshot.
8589 @item (char []) $trace_file
8590 The source file for the current trace snapshot.
8593 @item (char []) $trace_func
8594 The name of the function containing @code{$tracepoint}.
8597 Note: @code{$trace_file} is not suitable for use in @code{printf},
8598 use @code{output} instead.
8600 Here's a simple example of using these convenience variables for
8601 stepping through all the trace snapshots and printing some of their
8605 (@value{GDBP}) @b{tfind start}
8607 (@value{GDBP}) @b{while $trace_frame != -1}
8608 > output $trace_file
8609 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8615 @chapter Debugging Programs That Use Overlays
8618 If your program is too large to fit completely in your target system's
8619 memory, you can sometimes use @dfn{overlays} to work around this
8620 problem. @value{GDBN} provides some support for debugging programs that
8624 * How Overlays Work:: A general explanation of overlays.
8625 * Overlay Commands:: Managing overlays in @value{GDBN}.
8626 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8627 mapped by asking the inferior.
8628 * Overlay Sample Program:: A sample program using overlays.
8631 @node How Overlays Work
8632 @section How Overlays Work
8633 @cindex mapped overlays
8634 @cindex unmapped overlays
8635 @cindex load address, overlay's
8636 @cindex mapped address
8637 @cindex overlay area
8639 Suppose you have a computer whose instruction address space is only 64
8640 kilobytes long, but which has much more memory which can be accessed by
8641 other means: special instructions, segment registers, or memory
8642 management hardware, for example. Suppose further that you want to
8643 adapt a program which is larger than 64 kilobytes to run on this system.
8645 One solution is to identify modules of your program which are relatively
8646 independent, and need not call each other directly; call these modules
8647 @dfn{overlays}. Separate the overlays from the main program, and place
8648 their machine code in the larger memory. Place your main program in
8649 instruction memory, but leave at least enough space there to hold the
8650 largest overlay as well.
8652 Now, to call a function located in an overlay, you must first copy that
8653 overlay's machine code from the large memory into the space set aside
8654 for it in the instruction memory, and then jump to its entry point
8657 @c NB: In the below the mapped area's size is greater or equal to the
8658 @c size of all overlays. This is intentional to remind the developer
8659 @c that overlays don't necessarily need to be the same size.
8663 Data Instruction Larger
8664 Address Space Address Space Address Space
8665 +-----------+ +-----------+ +-----------+
8667 +-----------+ +-----------+ +-----------+<-- overlay 1
8668 | program | | main | .----| overlay 1 | load address
8669 | variables | | program | | +-----------+
8670 | and heap | | | | | |
8671 +-----------+ | | | +-----------+<-- overlay 2
8672 | | +-----------+ | | | load address
8673 +-----------+ | | | .-| overlay 2 |
8675 mapped --->+-----------+ | | +-----------+
8677 | overlay | <-' | | |
8678 | area | <---' +-----------+<-- overlay 3
8679 | | <---. | | load address
8680 +-----------+ `--| overlay 3 |
8687 @anchor{A code overlay}A code overlay
8691 The diagram (@pxref{A code overlay}) shows a system with separate data
8692 and instruction address spaces. To map an overlay, the program copies
8693 its code from the larger address space to the instruction address space.
8694 Since the overlays shown here all use the same mapped address, only one
8695 may be mapped at a time. For a system with a single address space for
8696 data and instructions, the diagram would be similar, except that the
8697 program variables and heap would share an address space with the main
8698 program and the overlay area.
8700 An overlay loaded into instruction memory and ready for use is called a
8701 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8702 instruction memory. An overlay not present (or only partially present)
8703 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8704 is its address in the larger memory. The mapped address is also called
8705 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8706 called the @dfn{load memory address}, or @dfn{LMA}.
8708 Unfortunately, overlays are not a completely transparent way to adapt a
8709 program to limited instruction memory. They introduce a new set of
8710 global constraints you must keep in mind as you design your program:
8715 Before calling or returning to a function in an overlay, your program
8716 must make sure that overlay is actually mapped. Otherwise, the call or
8717 return will transfer control to the right address, but in the wrong
8718 overlay, and your program will probably crash.
8721 If the process of mapping an overlay is expensive on your system, you
8722 will need to choose your overlays carefully to minimize their effect on
8723 your program's performance.
8726 The executable file you load onto your system must contain each
8727 overlay's instructions, appearing at the overlay's load address, not its
8728 mapped address. However, each overlay's instructions must be relocated
8729 and its symbols defined as if the overlay were at its mapped address.
8730 You can use GNU linker scripts to specify different load and relocation
8731 addresses for pieces of your program; see @ref{Overlay Description,,,
8732 ld.info, Using ld: the GNU linker}.
8735 The procedure for loading executable files onto your system must be able
8736 to load their contents into the larger address space as well as the
8737 instruction and data spaces.
8741 The overlay system described above is rather simple, and could be
8742 improved in many ways:
8747 If your system has suitable bank switch registers or memory management
8748 hardware, you could use those facilities to make an overlay's load area
8749 contents simply appear at their mapped address in instruction space.
8750 This would probably be faster than copying the overlay to its mapped
8751 area in the usual way.
8754 If your overlays are small enough, you could set aside more than one
8755 overlay area, and have more than one overlay mapped at a time.
8758 You can use overlays to manage data, as well as instructions. In
8759 general, data overlays are even less transparent to your design than
8760 code overlays: whereas code overlays only require care when you call or
8761 return to functions, data overlays require care every time you access
8762 the data. Also, if you change the contents of a data overlay, you
8763 must copy its contents back out to its load address before you can copy a
8764 different data overlay into the same mapped area.
8769 @node Overlay Commands
8770 @section Overlay Commands
8772 To use @value{GDBN}'s overlay support, each overlay in your program must
8773 correspond to a separate section of the executable file. The section's
8774 virtual memory address and load memory address must be the overlay's
8775 mapped and load addresses. Identifying overlays with sections allows
8776 @value{GDBN} to determine the appropriate address of a function or
8777 variable, depending on whether the overlay is mapped or not.
8779 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8780 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8785 Disable @value{GDBN}'s overlay support. When overlay support is
8786 disabled, @value{GDBN} assumes that all functions and variables are
8787 always present at their mapped addresses. By default, @value{GDBN}'s
8788 overlay support is disabled.
8790 @item overlay manual
8791 @cindex manual overlay debugging
8792 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8793 relies on you to tell it which overlays are mapped, and which are not,
8794 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8795 commands described below.
8797 @item overlay map-overlay @var{overlay}
8798 @itemx overlay map @var{overlay}
8799 @cindex map an overlay
8800 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8801 be the name of the object file section containing the overlay. When an
8802 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8803 functions and variables at their mapped addresses. @value{GDBN} assumes
8804 that any other overlays whose mapped ranges overlap that of
8805 @var{overlay} are now unmapped.
8807 @item overlay unmap-overlay @var{overlay}
8808 @itemx overlay unmap @var{overlay}
8809 @cindex unmap an overlay
8810 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8811 must be the name of the object file section containing the overlay.
8812 When an overlay is unmapped, @value{GDBN} assumes it can find the
8813 overlay's functions and variables at their load addresses.
8816 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8817 consults a data structure the overlay manager maintains in the inferior
8818 to see which overlays are mapped. For details, see @ref{Automatic
8821 @item overlay load-target
8823 @cindex reloading the overlay table
8824 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8825 re-reads the table @value{GDBN} automatically each time the inferior
8826 stops, so this command should only be necessary if you have changed the
8827 overlay mapping yourself using @value{GDBN}. This command is only
8828 useful when using automatic overlay debugging.
8830 @item overlay list-overlays
8832 @cindex listing mapped overlays
8833 Display a list of the overlays currently mapped, along with their mapped
8834 addresses, load addresses, and sizes.
8838 Normally, when @value{GDBN} prints a code address, it includes the name
8839 of the function the address falls in:
8842 (@value{GDBP}) print main
8843 $3 = @{int ()@} 0x11a0 <main>
8846 When overlay debugging is enabled, @value{GDBN} recognizes code in
8847 unmapped overlays, and prints the names of unmapped functions with
8848 asterisks around them. For example, if @code{foo} is a function in an
8849 unmapped overlay, @value{GDBN} prints it this way:
8852 (@value{GDBP}) overlay list
8853 No sections are mapped.
8854 (@value{GDBP}) print foo
8855 $5 = @{int (int)@} 0x100000 <*foo*>
8858 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8862 (@value{GDBP}) overlay list
8863 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8864 mapped at 0x1016 - 0x104a
8865 (@value{GDBP}) print foo
8866 $6 = @{int (int)@} 0x1016 <foo>
8869 When overlay debugging is enabled, @value{GDBN} can find the correct
8870 address for functions and variables in an overlay, whether or not the
8871 overlay is mapped. This allows most @value{GDBN} commands, like
8872 @code{break} and @code{disassemble}, to work normally, even on unmapped
8873 code. However, @value{GDBN}'s breakpoint support has some limitations:
8877 @cindex breakpoints in overlays
8878 @cindex overlays, setting breakpoints in
8879 You can set breakpoints in functions in unmapped overlays, as long as
8880 @value{GDBN} can write to the overlay at its load address.
8882 @value{GDBN} can not set hardware or simulator-based breakpoints in
8883 unmapped overlays. However, if you set a breakpoint at the end of your
8884 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8885 you are using manual overlay management), @value{GDBN} will re-set its
8886 breakpoints properly.
8890 @node Automatic Overlay Debugging
8891 @section Automatic Overlay Debugging
8892 @cindex automatic overlay debugging
8894 @value{GDBN} can automatically track which overlays are mapped and which
8895 are not, given some simple co-operation from the overlay manager in the
8896 inferior. If you enable automatic overlay debugging with the
8897 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8898 looks in the inferior's memory for certain variables describing the
8899 current state of the overlays.
8901 Here are the variables your overlay manager must define to support
8902 @value{GDBN}'s automatic overlay debugging:
8906 @item @code{_ovly_table}:
8907 This variable must be an array of the following structures:
8912 /* The overlay's mapped address. */
8915 /* The size of the overlay, in bytes. */
8918 /* The overlay's load address. */
8921 /* Non-zero if the overlay is currently mapped;
8923 unsigned long mapped;
8927 @item @code{_novlys}:
8928 This variable must be a four-byte signed integer, holding the total
8929 number of elements in @code{_ovly_table}.
8933 To decide whether a particular overlay is mapped or not, @value{GDBN}
8934 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8935 @code{lma} members equal the VMA and LMA of the overlay's section in the
8936 executable file. When @value{GDBN} finds a matching entry, it consults
8937 the entry's @code{mapped} member to determine whether the overlay is
8940 In addition, your overlay manager may define a function called
8941 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8942 will silently set a breakpoint there. If the overlay manager then
8943 calls this function whenever it has changed the overlay table, this
8944 will enable @value{GDBN} to accurately keep track of which overlays
8945 are in program memory, and update any breakpoints that may be set
8946 in overlays. This will allow breakpoints to work even if the
8947 overlays are kept in ROM or other non-writable memory while they
8948 are not being executed.
8950 @node Overlay Sample Program
8951 @section Overlay Sample Program
8952 @cindex overlay example program
8954 When linking a program which uses overlays, you must place the overlays
8955 at their load addresses, while relocating them to run at their mapped
8956 addresses. To do this, you must write a linker script (@pxref{Overlay
8957 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8958 since linker scripts are specific to a particular host system, target
8959 architecture, and target memory layout, this manual cannot provide
8960 portable sample code demonstrating @value{GDBN}'s overlay support.
8962 However, the @value{GDBN} source distribution does contain an overlaid
8963 program, with linker scripts for a few systems, as part of its test
8964 suite. The program consists of the following files from
8965 @file{gdb/testsuite/gdb.base}:
8969 The main program file.
8971 A simple overlay manager, used by @file{overlays.c}.
8976 Overlay modules, loaded and used by @file{overlays.c}.
8979 Linker scripts for linking the test program on the @code{d10v-elf}
8980 and @code{m32r-elf} targets.
8983 You can build the test program using the @code{d10v-elf} GCC
8984 cross-compiler like this:
8987 $ d10v-elf-gcc -g -c overlays.c
8988 $ d10v-elf-gcc -g -c ovlymgr.c
8989 $ d10v-elf-gcc -g -c foo.c
8990 $ d10v-elf-gcc -g -c bar.c
8991 $ d10v-elf-gcc -g -c baz.c
8992 $ d10v-elf-gcc -g -c grbx.c
8993 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8994 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8997 The build process is identical for any other architecture, except that
8998 you must substitute the appropriate compiler and linker script for the
8999 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9003 @chapter Using @value{GDBN} with Different Languages
9006 Although programming languages generally have common aspects, they are
9007 rarely expressed in the same manner. For instance, in ANSI C,
9008 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9009 Modula-2, it is accomplished by @code{p^}. Values can also be
9010 represented (and displayed) differently. Hex numbers in C appear as
9011 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9013 @cindex working language
9014 Language-specific information is built into @value{GDBN} for some languages,
9015 allowing you to express operations like the above in your program's
9016 native language, and allowing @value{GDBN} to output values in a manner
9017 consistent with the syntax of your program's native language. The
9018 language you use to build expressions is called the @dfn{working
9022 * Setting:: Switching between source languages
9023 * Show:: Displaying the language
9024 * Checks:: Type and range checks
9025 * Supported Languages:: Supported languages
9026 * Unsupported Languages:: Unsupported languages
9030 @section Switching Between Source Languages
9032 There are two ways to control the working language---either have @value{GDBN}
9033 set it automatically, or select it manually yourself. You can use the
9034 @code{set language} command for either purpose. On startup, @value{GDBN}
9035 defaults to setting the language automatically. The working language is
9036 used to determine how expressions you type are interpreted, how values
9039 In addition to the working language, every source file that
9040 @value{GDBN} knows about has its own working language. For some object
9041 file formats, the compiler might indicate which language a particular
9042 source file is in. However, most of the time @value{GDBN} infers the
9043 language from the name of the file. The language of a source file
9044 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9045 show each frame appropriately for its own language. There is no way to
9046 set the language of a source file from within @value{GDBN}, but you can
9047 set the language associated with a filename extension. @xref{Show, ,
9048 Displaying the Language}.
9050 This is most commonly a problem when you use a program, such
9051 as @code{cfront} or @code{f2c}, that generates C but is written in
9052 another language. In that case, make the
9053 program use @code{#line} directives in its C output; that way
9054 @value{GDBN} will know the correct language of the source code of the original
9055 program, and will display that source code, not the generated C code.
9058 * Filenames:: Filename extensions and languages.
9059 * Manually:: Setting the working language manually
9060 * Automatically:: Having @value{GDBN} infer the source language
9064 @subsection List of Filename Extensions and Languages
9066 If a source file name ends in one of the following extensions, then
9067 @value{GDBN} infers that its language is the one indicated.
9088 Objective-C source file
9095 Modula-2 source file
9099 Assembler source file. This actually behaves almost like C, but
9100 @value{GDBN} does not skip over function prologues when stepping.
9103 In addition, you may set the language associated with a filename
9104 extension. @xref{Show, , Displaying the Language}.
9107 @subsection Setting the Working Language
9109 If you allow @value{GDBN} to set the language automatically,
9110 expressions are interpreted the same way in your debugging session and
9113 @kindex set language
9114 If you wish, you may set the language manually. To do this, issue the
9115 command @samp{set language @var{lang}}, where @var{lang} is the name of
9117 @code{c} or @code{modula-2}.
9118 For a list of the supported languages, type @samp{set language}.
9120 Setting the language manually prevents @value{GDBN} from updating the working
9121 language automatically. This can lead to confusion if you try
9122 to debug a program when the working language is not the same as the
9123 source language, when an expression is acceptable to both
9124 languages---but means different things. For instance, if the current
9125 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9133 might not have the effect you intended. In C, this means to add
9134 @code{b} and @code{c} and place the result in @code{a}. The result
9135 printed would be the value of @code{a}. In Modula-2, this means to compare
9136 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9139 @subsection Having @value{GDBN} Infer the Source Language
9141 To have @value{GDBN} set the working language automatically, use
9142 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9143 then infers the working language. That is, when your program stops in a
9144 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9145 working language to the language recorded for the function in that
9146 frame. If the language for a frame is unknown (that is, if the function
9147 or block corresponding to the frame was defined in a source file that
9148 does not have a recognized extension), the current working language is
9149 not changed, and @value{GDBN} issues a warning.
9151 This may not seem necessary for most programs, which are written
9152 entirely in one source language. However, program modules and libraries
9153 written in one source language can be used by a main program written in
9154 a different source language. Using @samp{set language auto} in this
9155 case frees you from having to set the working language manually.
9158 @section Displaying the Language
9160 The following commands help you find out which language is the
9161 working language, and also what language source files were written in.
9165 @kindex show language
9166 Display the current working language. This is the
9167 language you can use with commands such as @code{print} to
9168 build and compute expressions that may involve variables in your program.
9171 @kindex info frame@r{, show the source language}
9172 Display the source language for this frame. This language becomes the
9173 working language if you use an identifier from this frame.
9174 @xref{Frame Info, ,Information about a Frame}, to identify the other
9175 information listed here.
9178 @kindex info source@r{, show the source language}
9179 Display the source language of this source file.
9180 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9181 information listed here.
9184 In unusual circumstances, you may have source files with extensions
9185 not in the standard list. You can then set the extension associated
9186 with a language explicitly:
9189 @item set extension-language @var{ext} @var{language}
9190 @kindex set extension-language
9191 Tell @value{GDBN} that source files with extension @var{ext} are to be
9192 assumed as written in the source language @var{language}.
9194 @item info extensions
9195 @kindex info extensions
9196 List all the filename extensions and the associated languages.
9200 @section Type and Range Checking
9203 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9204 checking are included, but they do not yet have any effect. This
9205 section documents the intended facilities.
9207 @c FIXME remove warning when type/range code added
9209 Some languages are designed to guard you against making seemingly common
9210 errors through a series of compile- and run-time checks. These include
9211 checking the type of arguments to functions and operators, and making
9212 sure mathematical overflows are caught at run time. Checks such as
9213 these help to ensure a program's correctness once it has been compiled
9214 by eliminating type mismatches, and providing active checks for range
9215 errors when your program is running.
9217 @value{GDBN} can check for conditions like the above if you wish.
9218 Although @value{GDBN} does not check the statements in your program,
9219 it can check expressions entered directly into @value{GDBN} for
9220 evaluation via the @code{print} command, for example. As with the
9221 working language, @value{GDBN} can also decide whether or not to check
9222 automatically based on your program's source language.
9223 @xref{Supported Languages, ,Supported Languages}, for the default
9224 settings of supported languages.
9227 * Type Checking:: An overview of type checking
9228 * Range Checking:: An overview of range checking
9231 @cindex type checking
9232 @cindex checks, type
9234 @subsection An Overview of Type Checking
9236 Some languages, such as Modula-2, are strongly typed, meaning that the
9237 arguments to operators and functions have to be of the correct type,
9238 otherwise an error occurs. These checks prevent type mismatch
9239 errors from ever causing any run-time problems. For example,
9247 The second example fails because the @code{CARDINAL} 1 is not
9248 type-compatible with the @code{REAL} 2.3.
9250 For the expressions you use in @value{GDBN} commands, you can tell the
9251 @value{GDBN} type checker to skip checking;
9252 to treat any mismatches as errors and abandon the expression;
9253 or to only issue warnings when type mismatches occur,
9254 but evaluate the expression anyway. When you choose the last of
9255 these, @value{GDBN} evaluates expressions like the second example above, but
9256 also issues a warning.
9258 Even if you turn type checking off, there may be other reasons
9259 related to type that prevent @value{GDBN} from evaluating an expression.
9260 For instance, @value{GDBN} does not know how to add an @code{int} and
9261 a @code{struct foo}. These particular type errors have nothing to do
9262 with the language in use, and usually arise from expressions, such as
9263 the one described above, which make little sense to evaluate anyway.
9265 Each language defines to what degree it is strict about type. For
9266 instance, both Modula-2 and C require the arguments to arithmetical
9267 operators to be numbers. In C, enumerated types and pointers can be
9268 represented as numbers, so that they are valid arguments to mathematical
9269 operators. @xref{Supported Languages, ,Supported Languages}, for further
9270 details on specific languages.
9272 @value{GDBN} provides some additional commands for controlling the type checker:
9274 @kindex set check type
9275 @kindex show check type
9277 @item set check type auto
9278 Set type checking on or off based on the current working language.
9279 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9282 @item set check type on
9283 @itemx set check type off
9284 Set type checking on or off, overriding the default setting for the
9285 current working language. Issue a warning if the setting does not
9286 match the language default. If any type mismatches occur in
9287 evaluating an expression while type checking is on, @value{GDBN} prints a
9288 message and aborts evaluation of the expression.
9290 @item set check type warn
9291 Cause the type checker to issue warnings, but to always attempt to
9292 evaluate the expression. Evaluating the expression may still
9293 be impossible for other reasons. For example, @value{GDBN} cannot add
9294 numbers and structures.
9297 Show the current setting of the type checker, and whether or not @value{GDBN}
9298 is setting it automatically.
9301 @cindex range checking
9302 @cindex checks, range
9303 @node Range Checking
9304 @subsection An Overview of Range Checking
9306 In some languages (such as Modula-2), it is an error to exceed the
9307 bounds of a type; this is enforced with run-time checks. Such range
9308 checking is meant to ensure program correctness by making sure
9309 computations do not overflow, or indices on an array element access do
9310 not exceed the bounds of the array.
9312 For expressions you use in @value{GDBN} commands, you can tell
9313 @value{GDBN} to treat range errors in one of three ways: ignore them,
9314 always treat them as errors and abandon the expression, or issue
9315 warnings but evaluate the expression anyway.
9317 A range error can result from numerical overflow, from exceeding an
9318 array index bound, or when you type a constant that is not a member
9319 of any type. Some languages, however, do not treat overflows as an
9320 error. In many implementations of C, mathematical overflow causes the
9321 result to ``wrap around'' to lower values---for example, if @var{m} is
9322 the largest integer value, and @var{s} is the smallest, then
9325 @var{m} + 1 @result{} @var{s}
9328 This, too, is specific to individual languages, and in some cases
9329 specific to individual compilers or machines. @xref{Supported Languages, ,
9330 Supported Languages}, for further details on specific languages.
9332 @value{GDBN} provides some additional commands for controlling the range checker:
9334 @kindex set check range
9335 @kindex show check range
9337 @item set check range auto
9338 Set range checking on or off based on the current working language.
9339 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9342 @item set check range on
9343 @itemx set check range off
9344 Set range checking on or off, overriding the default setting for the
9345 current working language. A warning is issued if the setting does not
9346 match the language default. If a range error occurs and range checking is on,
9347 then a message is printed and evaluation of the expression is aborted.
9349 @item set check range warn
9350 Output messages when the @value{GDBN} range checker detects a range error,
9351 but attempt to evaluate the expression anyway. Evaluating the
9352 expression may still be impossible for other reasons, such as accessing
9353 memory that the process does not own (a typical example from many Unix
9357 Show the current setting of the range checker, and whether or not it is
9358 being set automatically by @value{GDBN}.
9361 @node Supported Languages
9362 @section Supported Languages
9364 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9365 assembly, Modula-2, and Ada.
9366 @c This is false ...
9367 Some @value{GDBN} features may be used in expressions regardless of the
9368 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9369 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9370 ,Expressions}) can be used with the constructs of any supported
9373 The following sections detail to what degree each source language is
9374 supported by @value{GDBN}. These sections are not meant to be language
9375 tutorials or references, but serve only as a reference guide to what the
9376 @value{GDBN} expression parser accepts, and what input and output
9377 formats should look like for different languages. There are many good
9378 books written on each of these languages; please look to these for a
9379 language reference or tutorial.
9383 * Objective-C:: Objective-C
9386 * Modula-2:: Modula-2
9391 @subsection C and C@t{++}
9393 @cindex C and C@t{++}
9394 @cindex expressions in C or C@t{++}
9396 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9397 to both languages. Whenever this is the case, we discuss those languages
9401 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9402 @cindex @sc{gnu} C@t{++}
9403 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9404 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9405 effectively, you must compile your C@t{++} programs with a supported
9406 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9407 compiler (@code{aCC}).
9409 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9410 format; if it doesn't work on your system, try the stabs+ debugging
9411 format. You can select those formats explicitly with the @code{g++}
9412 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9413 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9414 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9417 * C Operators:: C and C@t{++} operators
9418 * C Constants:: C and C@t{++} constants
9419 * C Plus Plus Expressions:: C@t{++} expressions
9420 * C Defaults:: Default settings for C and C@t{++}
9421 * C Checks:: C and C@t{++} type and range checks
9422 * Debugging C:: @value{GDBN} and C
9423 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9424 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9428 @subsubsection C and C@t{++} Operators
9430 @cindex C and C@t{++} operators
9432 Operators must be defined on values of specific types. For instance,
9433 @code{+} is defined on numbers, but not on structures. Operators are
9434 often defined on groups of types.
9436 For the purposes of C and C@t{++}, the following definitions hold:
9441 @emph{Integral types} include @code{int} with any of its storage-class
9442 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9445 @emph{Floating-point types} include @code{float}, @code{double}, and
9446 @code{long double} (if supported by the target platform).
9449 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9452 @emph{Scalar types} include all of the above.
9457 The following operators are supported. They are listed here
9458 in order of increasing precedence:
9462 The comma or sequencing operator. Expressions in a comma-separated list
9463 are evaluated from left to right, with the result of the entire
9464 expression being the last expression evaluated.
9467 Assignment. The value of an assignment expression is the value
9468 assigned. Defined on scalar types.
9471 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9472 and translated to @w{@code{@var{a} = @var{a op b}}}.
9473 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9474 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9475 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9478 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9479 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9483 Logical @sc{or}. Defined on integral types.
9486 Logical @sc{and}. Defined on integral types.
9489 Bitwise @sc{or}. Defined on integral types.
9492 Bitwise exclusive-@sc{or}. Defined on integral types.
9495 Bitwise @sc{and}. Defined on integral types.
9498 Equality and inequality. Defined on scalar types. The value of these
9499 expressions is 0 for false and non-zero for true.
9501 @item <@r{, }>@r{, }<=@r{, }>=
9502 Less than, greater than, less than or equal, greater than or equal.
9503 Defined on scalar types. The value of these expressions is 0 for false
9504 and non-zero for true.
9507 left shift, and right shift. Defined on integral types.
9510 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9513 Addition and subtraction. Defined on integral types, floating-point types and
9516 @item *@r{, }/@r{, }%
9517 Multiplication, division, and modulus. Multiplication and division are
9518 defined on integral and floating-point types. Modulus is defined on
9522 Increment and decrement. When appearing before a variable, the
9523 operation is performed before the variable is used in an expression;
9524 when appearing after it, the variable's value is used before the
9525 operation takes place.
9528 Pointer dereferencing. Defined on pointer types. Same precedence as
9532 Address operator. Defined on variables. Same precedence as @code{++}.
9534 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9535 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9536 to examine the address
9537 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9541 Negative. Defined on integral and floating-point types. Same
9542 precedence as @code{++}.
9545 Logical negation. Defined on integral types. Same precedence as
9549 Bitwise complement operator. Defined on integral types. Same precedence as
9554 Structure member, and pointer-to-structure member. For convenience,
9555 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9556 pointer based on the stored type information.
9557 Defined on @code{struct} and @code{union} data.
9560 Dereferences of pointers to members.
9563 Array indexing. @code{@var{a}[@var{i}]} is defined as
9564 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9567 Function parameter list. Same precedence as @code{->}.
9570 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9571 and @code{class} types.
9574 Doubled colons also represent the @value{GDBN} scope operator
9575 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9579 If an operator is redefined in the user code, @value{GDBN} usually
9580 attempts to invoke the redefined version instead of using the operator's
9584 @subsubsection C and C@t{++} Constants
9586 @cindex C and C@t{++} constants
9588 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9593 Integer constants are a sequence of digits. Octal constants are
9594 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9595 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9596 @samp{l}, specifying that the constant should be treated as a
9600 Floating point constants are a sequence of digits, followed by a decimal
9601 point, followed by a sequence of digits, and optionally followed by an
9602 exponent. An exponent is of the form:
9603 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9604 sequence of digits. The @samp{+} is optional for positive exponents.
9605 A floating-point constant may also end with a letter @samp{f} or
9606 @samp{F}, specifying that the constant should be treated as being of
9607 the @code{float} (as opposed to the default @code{double}) type; or with
9608 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9612 Enumerated constants consist of enumerated identifiers, or their
9613 integral equivalents.
9616 Character constants are a single character surrounded by single quotes
9617 (@code{'}), or a number---the ordinal value of the corresponding character
9618 (usually its @sc{ascii} value). Within quotes, the single character may
9619 be represented by a letter or by @dfn{escape sequences}, which are of
9620 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9621 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9622 @samp{@var{x}} is a predefined special character---for example,
9623 @samp{\n} for newline.
9626 String constants are a sequence of character constants surrounded by
9627 double quotes (@code{"}). Any valid character constant (as described
9628 above) may appear. Double quotes within the string must be preceded by
9629 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9633 Pointer constants are an integral value. You can also write pointers
9634 to constants using the C operator @samp{&}.
9637 Array constants are comma-separated lists surrounded by braces @samp{@{}
9638 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9639 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9640 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9643 @node C Plus Plus Expressions
9644 @subsubsection C@t{++} Expressions
9646 @cindex expressions in C@t{++}
9647 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9649 @cindex debugging C@t{++} programs
9650 @cindex C@t{++} compilers
9651 @cindex debug formats and C@t{++}
9652 @cindex @value{NGCC} and C@t{++}
9654 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9655 proper compiler and the proper debug format. Currently, @value{GDBN}
9656 works best when debugging C@t{++} code that is compiled with
9657 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9658 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9659 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9660 stabs+ as their default debug format, so you usually don't need to
9661 specify a debug format explicitly. Other compilers and/or debug formats
9662 are likely to work badly or not at all when using @value{GDBN} to debug
9668 @cindex member functions
9670 Member function calls are allowed; you can use expressions like
9673 count = aml->GetOriginal(x, y)
9676 @vindex this@r{, inside C@t{++} member functions}
9677 @cindex namespace in C@t{++}
9679 While a member function is active (in the selected stack frame), your
9680 expressions have the same namespace available as the member function;
9681 that is, @value{GDBN} allows implicit references to the class instance
9682 pointer @code{this} following the same rules as C@t{++}.
9684 @cindex call overloaded functions
9685 @cindex overloaded functions, calling
9686 @cindex type conversions in C@t{++}
9688 You can call overloaded functions; @value{GDBN} resolves the function
9689 call to the right definition, with some restrictions. @value{GDBN} does not
9690 perform overload resolution involving user-defined type conversions,
9691 calls to constructors, or instantiations of templates that do not exist
9692 in the program. It also cannot handle ellipsis argument lists or
9695 It does perform integral conversions and promotions, floating-point
9696 promotions, arithmetic conversions, pointer conversions, conversions of
9697 class objects to base classes, and standard conversions such as those of
9698 functions or arrays to pointers; it requires an exact match on the
9699 number of function arguments.
9701 Overload resolution is always performed, unless you have specified
9702 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9703 ,@value{GDBN} Features for C@t{++}}.
9705 You must specify @code{set overload-resolution off} in order to use an
9706 explicit function signature to call an overloaded function, as in
9708 p 'foo(char,int)'('x', 13)
9711 The @value{GDBN} command-completion facility can simplify this;
9712 see @ref{Completion, ,Command Completion}.
9714 @cindex reference declarations
9716 @value{GDBN} understands variables declared as C@t{++} references; you can use
9717 them in expressions just as you do in C@t{++} source---they are automatically
9720 In the parameter list shown when @value{GDBN} displays a frame, the values of
9721 reference variables are not displayed (unlike other variables); this
9722 avoids clutter, since references are often used for large structures.
9723 The @emph{address} of a reference variable is always shown, unless
9724 you have specified @samp{set print address off}.
9727 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9728 expressions can use it just as expressions in your program do. Since
9729 one scope may be defined in another, you can use @code{::} repeatedly if
9730 necessary, for example in an expression like
9731 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9732 resolving name scope by reference to source files, in both C and C@t{++}
9733 debugging (@pxref{Variables, ,Program Variables}).
9736 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9737 calling virtual functions correctly, printing out virtual bases of
9738 objects, calling functions in a base subobject, casting objects, and
9739 invoking user-defined operators.
9742 @subsubsection C and C@t{++} Defaults
9744 @cindex C and C@t{++} defaults
9746 If you allow @value{GDBN} to set type and range checking automatically, they
9747 both default to @code{off} whenever the working language changes to
9748 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9749 selects the working language.
9751 If you allow @value{GDBN} to set the language automatically, it
9752 recognizes source files whose names end with @file{.c}, @file{.C}, or
9753 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9754 these files, it sets the working language to C or C@t{++}.
9755 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9756 for further details.
9758 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9759 @c unimplemented. If (b) changes, it might make sense to let this node
9760 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9763 @subsubsection C and C@t{++} Type and Range Checks
9765 @cindex C and C@t{++} checks
9767 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9768 is not used. However, if you turn type checking on, @value{GDBN}
9769 considers two variables type equivalent if:
9773 The two variables are structured and have the same structure, union, or
9777 The two variables have the same type name, or types that have been
9778 declared equivalent through @code{typedef}.
9781 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9784 The two @code{struct}, @code{union}, or @code{enum} variables are
9785 declared in the same declaration. (Note: this may not be true for all C
9790 Range checking, if turned on, is done on mathematical operations. Array
9791 indices are not checked, since they are often used to index a pointer
9792 that is not itself an array.
9795 @subsubsection @value{GDBN} and C
9797 The @code{set print union} and @code{show print union} commands apply to
9798 the @code{union} type. When set to @samp{on}, any @code{union} that is
9799 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9800 appears as @samp{@{...@}}.
9802 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9803 with pointers and a memory allocation function. @xref{Expressions,
9806 @node Debugging C Plus Plus
9807 @subsubsection @value{GDBN} Features for C@t{++}
9809 @cindex commands for C@t{++}
9811 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9812 designed specifically for use with C@t{++}. Here is a summary:
9815 @cindex break in overloaded functions
9816 @item @r{breakpoint menus}
9817 When you want a breakpoint in a function whose name is overloaded,
9818 @value{GDBN} has the capability to display a menu of possible breakpoint
9819 locations to help you specify which function definition you want.
9820 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
9822 @cindex overloading in C@t{++}
9823 @item rbreak @var{regex}
9824 Setting breakpoints using regular expressions is helpful for setting
9825 breakpoints on overloaded functions that are not members of any special
9827 @xref{Set Breaks, ,Setting Breakpoints}.
9829 @cindex C@t{++} exception handling
9832 Debug C@t{++} exception handling using these commands. @xref{Set
9833 Catchpoints, , Setting Catchpoints}.
9836 @item ptype @var{typename}
9837 Print inheritance relationships as well as other information for type
9839 @xref{Symbols, ,Examining the Symbol Table}.
9841 @cindex C@t{++} symbol display
9842 @item set print demangle
9843 @itemx show print demangle
9844 @itemx set print asm-demangle
9845 @itemx show print asm-demangle
9846 Control whether C@t{++} symbols display in their source form, both when
9847 displaying code as C@t{++} source and when displaying disassemblies.
9848 @xref{Print Settings, ,Print Settings}.
9850 @item set print object
9851 @itemx show print object
9852 Choose whether to print derived (actual) or declared types of objects.
9853 @xref{Print Settings, ,Print Settings}.
9855 @item set print vtbl
9856 @itemx show print vtbl
9857 Control the format for printing virtual function tables.
9858 @xref{Print Settings, ,Print Settings}.
9859 (The @code{vtbl} commands do not work on programs compiled with the HP
9860 ANSI C@t{++} compiler (@code{aCC}).)
9862 @kindex set overload-resolution
9863 @cindex overloaded functions, overload resolution
9864 @item set overload-resolution on
9865 Enable overload resolution for C@t{++} expression evaluation. The default
9866 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9867 and searches for a function whose signature matches the argument types,
9868 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9869 Expressions, ,C@t{++} Expressions}, for details).
9870 If it cannot find a match, it emits a message.
9872 @item set overload-resolution off
9873 Disable overload resolution for C@t{++} expression evaluation. For
9874 overloaded functions that are not class member functions, @value{GDBN}
9875 chooses the first function of the specified name that it finds in the
9876 symbol table, whether or not its arguments are of the correct type. For
9877 overloaded functions that are class member functions, @value{GDBN}
9878 searches for a function whose signature @emph{exactly} matches the
9881 @kindex show overload-resolution
9882 @item show overload-resolution
9883 Show the current setting of overload resolution.
9885 @item @r{Overloaded symbol names}
9886 You can specify a particular definition of an overloaded symbol, using
9887 the same notation that is used to declare such symbols in C@t{++}: type
9888 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9889 also use the @value{GDBN} command-line word completion facilities to list the
9890 available choices, or to finish the type list for you.
9891 @xref{Completion,, Command Completion}, for details on how to do this.
9894 @node Decimal Floating Point
9895 @subsubsection Decimal Floating Point format
9896 @cindex decimal floating point format
9898 @value{GDBN} can examine, set and perform computations with numbers in
9899 decimal floating point format, which in the C language correspond to the
9900 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
9901 specified by the extension to support decimal floating-point arithmetic.
9903 There are two encodings in use, depending on the architecture: BID (Binary
9904 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
9905 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
9908 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
9909 to manipulate decimal floating point numbers, it is not possible to convert
9910 (using a cast, for example) integers wider than 32-bit to decimal float.
9912 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
9913 point computations, error checking in decimal float operations ignores
9914 underflow, overflow and divide by zero exceptions.
9916 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
9917 to inspect @code{_Decimal128} values stored in floating point registers. See
9918 @ref{PowerPC,,PowerPC} for more details.
9921 @subsection Objective-C
9924 This section provides information about some commands and command
9925 options that are useful for debugging Objective-C code. See also
9926 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9927 few more commands specific to Objective-C support.
9930 * Method Names in Commands::
9931 * The Print Command with Objective-C::
9934 @node Method Names in Commands
9935 @subsubsection Method Names in Commands
9937 The following commands have been extended to accept Objective-C method
9938 names as line specifications:
9940 @kindex clear@r{, and Objective-C}
9941 @kindex break@r{, and Objective-C}
9942 @kindex info line@r{, and Objective-C}
9943 @kindex jump@r{, and Objective-C}
9944 @kindex list@r{, and Objective-C}
9948 @item @code{info line}
9953 A fully qualified Objective-C method name is specified as
9956 -[@var{Class} @var{methodName}]
9959 where the minus sign is used to indicate an instance method and a
9960 plus sign (not shown) is used to indicate a class method. The class
9961 name @var{Class} and method name @var{methodName} are enclosed in
9962 brackets, similar to the way messages are specified in Objective-C
9963 source code. For example, to set a breakpoint at the @code{create}
9964 instance method of class @code{Fruit} in the program currently being
9968 break -[Fruit create]
9971 To list ten program lines around the @code{initialize} class method,
9975 list +[NSText initialize]
9978 In the current version of @value{GDBN}, the plus or minus sign is
9979 required. In future versions of @value{GDBN}, the plus or minus
9980 sign will be optional, but you can use it to narrow the search. It
9981 is also possible to specify just a method name:
9987 You must specify the complete method name, including any colons. If
9988 your program's source files contain more than one @code{create} method,
9989 you'll be presented with a numbered list of classes that implement that
9990 method. Indicate your choice by number, or type @samp{0} to exit if
9993 As another example, to clear a breakpoint established at the
9994 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9997 clear -[NSWindow makeKeyAndOrderFront:]
10000 @node The Print Command with Objective-C
10001 @subsubsection The Print Command With Objective-C
10002 @cindex Objective-C, print objects
10003 @kindex print-object
10004 @kindex po @r{(@code{print-object})}
10006 The print command has also been extended to accept methods. For example:
10009 print -[@var{object} hash]
10012 @cindex print an Objective-C object description
10013 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10015 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10016 and print the result. Also, an additional command has been added,
10017 @code{print-object} or @code{po} for short, which is meant to print
10018 the description of an object. However, this command may only work
10019 with certain Objective-C libraries that have a particular hook
10020 function, @code{_NSPrintForDebugger}, defined.
10023 @subsection Fortran
10024 @cindex Fortran-specific support in @value{GDBN}
10026 @value{GDBN} can be used to debug programs written in Fortran, but it
10027 currently supports only the features of Fortran 77 language.
10029 @cindex trailing underscore, in Fortran symbols
10030 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10031 among them) append an underscore to the names of variables and
10032 functions. When you debug programs compiled by those compilers, you
10033 will need to refer to variables and functions with a trailing
10037 * Fortran Operators:: Fortran operators and expressions
10038 * Fortran Defaults:: Default settings for Fortran
10039 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10042 @node Fortran Operators
10043 @subsubsection Fortran Operators and Expressions
10045 @cindex Fortran operators and expressions
10047 Operators must be defined on values of specific types. For instance,
10048 @code{+} is defined on numbers, but not on characters or other non-
10049 arithmetic types. Operators are often defined on groups of types.
10053 The exponentiation operator. It raises the first operand to the power
10057 The range operator. Normally used in the form of array(low:high) to
10058 represent a section of array.
10061 The access component operator. Normally used to access elements in derived
10062 types. Also suitable for unions. As unions aren't part of regular Fortran,
10063 this can only happen when accessing a register that uses a gdbarch-defined
10067 @node Fortran Defaults
10068 @subsubsection Fortran Defaults
10070 @cindex Fortran Defaults
10072 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10073 default uses case-insensitive matches for Fortran symbols. You can
10074 change that with the @samp{set case-insensitive} command, see
10075 @ref{Symbols}, for the details.
10077 @node Special Fortran Commands
10078 @subsubsection Special Fortran Commands
10080 @cindex Special Fortran commands
10082 @value{GDBN} has some commands to support Fortran-specific features,
10083 such as displaying common blocks.
10086 @cindex @code{COMMON} blocks, Fortran
10087 @kindex info common
10088 @item info common @r{[}@var{common-name}@r{]}
10089 This command prints the values contained in the Fortran @code{COMMON}
10090 block whose name is @var{common-name}. With no argument, the names of
10091 all @code{COMMON} blocks visible at the current program location are
10098 @cindex Pascal support in @value{GDBN}, limitations
10099 Debugging Pascal programs which use sets, subranges, file variables, or
10100 nested functions does not currently work. @value{GDBN} does not support
10101 entering expressions, printing values, or similar features using Pascal
10104 The Pascal-specific command @code{set print pascal_static-members}
10105 controls whether static members of Pascal objects are displayed.
10106 @xref{Print Settings, pascal_static-members}.
10109 @subsection Modula-2
10111 @cindex Modula-2, @value{GDBN} support
10113 The extensions made to @value{GDBN} to support Modula-2 only support
10114 output from the @sc{gnu} Modula-2 compiler (which is currently being
10115 developed). Other Modula-2 compilers are not currently supported, and
10116 attempting to debug executables produced by them is most likely
10117 to give an error as @value{GDBN} reads in the executable's symbol
10120 @cindex expressions in Modula-2
10122 * M2 Operators:: Built-in operators
10123 * Built-In Func/Proc:: Built-in functions and procedures
10124 * M2 Constants:: Modula-2 constants
10125 * M2 Types:: Modula-2 types
10126 * M2 Defaults:: Default settings for Modula-2
10127 * Deviations:: Deviations from standard Modula-2
10128 * M2 Checks:: Modula-2 type and range checks
10129 * M2 Scope:: The scope operators @code{::} and @code{.}
10130 * GDB/M2:: @value{GDBN} and Modula-2
10134 @subsubsection Operators
10135 @cindex Modula-2 operators
10137 Operators must be defined on values of specific types. For instance,
10138 @code{+} is defined on numbers, but not on structures. Operators are
10139 often defined on groups of types. For the purposes of Modula-2, the
10140 following definitions hold:
10145 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10149 @emph{Character types} consist of @code{CHAR} and its subranges.
10152 @emph{Floating-point types} consist of @code{REAL}.
10155 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10159 @emph{Scalar types} consist of all of the above.
10162 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10165 @emph{Boolean types} consist of @code{BOOLEAN}.
10169 The following operators are supported, and appear in order of
10170 increasing precedence:
10174 Function argument or array index separator.
10177 Assignment. The value of @var{var} @code{:=} @var{value} is
10181 Less than, greater than on integral, floating-point, or enumerated
10185 Less than or equal to, greater than or equal to
10186 on integral, floating-point and enumerated types, or set inclusion on
10187 set types. Same precedence as @code{<}.
10189 @item =@r{, }<>@r{, }#
10190 Equality and two ways of expressing inequality, valid on scalar types.
10191 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10192 available for inequality, since @code{#} conflicts with the script
10196 Set membership. Defined on set types and the types of their members.
10197 Same precedence as @code{<}.
10200 Boolean disjunction. Defined on boolean types.
10203 Boolean conjunction. Defined on boolean types.
10206 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10209 Addition and subtraction on integral and floating-point types, or union
10210 and difference on set types.
10213 Multiplication on integral and floating-point types, or set intersection
10217 Division on floating-point types, or symmetric set difference on set
10218 types. Same precedence as @code{*}.
10221 Integer division and remainder. Defined on integral types. Same
10222 precedence as @code{*}.
10225 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10228 Pointer dereferencing. Defined on pointer types.
10231 Boolean negation. Defined on boolean types. Same precedence as
10235 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10236 precedence as @code{^}.
10239 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10242 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10246 @value{GDBN} and Modula-2 scope operators.
10250 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10251 treats the use of the operator @code{IN}, or the use of operators
10252 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10253 @code{<=}, and @code{>=} on sets as an error.
10257 @node Built-In Func/Proc
10258 @subsubsection Built-in Functions and Procedures
10259 @cindex Modula-2 built-ins
10261 Modula-2 also makes available several built-in procedures and functions.
10262 In describing these, the following metavariables are used:
10267 represents an @code{ARRAY} variable.
10270 represents a @code{CHAR} constant or variable.
10273 represents a variable or constant of integral type.
10276 represents an identifier that belongs to a set. Generally used in the
10277 same function with the metavariable @var{s}. The type of @var{s} should
10278 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10281 represents a variable or constant of integral or floating-point type.
10284 represents a variable or constant of floating-point type.
10290 represents a variable.
10293 represents a variable or constant of one of many types. See the
10294 explanation of the function for details.
10297 All Modula-2 built-in procedures also return a result, described below.
10301 Returns the absolute value of @var{n}.
10304 If @var{c} is a lower case letter, it returns its upper case
10305 equivalent, otherwise it returns its argument.
10308 Returns the character whose ordinal value is @var{i}.
10311 Decrements the value in the variable @var{v} by one. Returns the new value.
10313 @item DEC(@var{v},@var{i})
10314 Decrements the value in the variable @var{v} by @var{i}. Returns the
10317 @item EXCL(@var{m},@var{s})
10318 Removes the element @var{m} from the set @var{s}. Returns the new
10321 @item FLOAT(@var{i})
10322 Returns the floating point equivalent of the integer @var{i}.
10324 @item HIGH(@var{a})
10325 Returns the index of the last member of @var{a}.
10328 Increments the value in the variable @var{v} by one. Returns the new value.
10330 @item INC(@var{v},@var{i})
10331 Increments the value in the variable @var{v} by @var{i}. Returns the
10334 @item INCL(@var{m},@var{s})
10335 Adds the element @var{m} to the set @var{s} if it is not already
10336 there. Returns the new set.
10339 Returns the maximum value of the type @var{t}.
10342 Returns the minimum value of the type @var{t}.
10345 Returns boolean TRUE if @var{i} is an odd number.
10348 Returns the ordinal value of its argument. For example, the ordinal
10349 value of a character is its @sc{ascii} value (on machines supporting the
10350 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10351 integral, character and enumerated types.
10353 @item SIZE(@var{x})
10354 Returns the size of its argument. @var{x} can be a variable or a type.
10356 @item TRUNC(@var{r})
10357 Returns the integral part of @var{r}.
10359 @item TSIZE(@var{x})
10360 Returns the size of its argument. @var{x} can be a variable or a type.
10362 @item VAL(@var{t},@var{i})
10363 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10367 @emph{Warning:} Sets and their operations are not yet supported, so
10368 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10372 @cindex Modula-2 constants
10374 @subsubsection Constants
10376 @value{GDBN} allows you to express the constants of Modula-2 in the following
10382 Integer constants are simply a sequence of digits. When used in an
10383 expression, a constant is interpreted to be type-compatible with the
10384 rest of the expression. Hexadecimal integers are specified by a
10385 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10388 Floating point constants appear as a sequence of digits, followed by a
10389 decimal point and another sequence of digits. An optional exponent can
10390 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10391 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10392 digits of the floating point constant must be valid decimal (base 10)
10396 Character constants consist of a single character enclosed by a pair of
10397 like quotes, either single (@code{'}) or double (@code{"}). They may
10398 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10399 followed by a @samp{C}.
10402 String constants consist of a sequence of characters enclosed by a
10403 pair of like quotes, either single (@code{'}) or double (@code{"}).
10404 Escape sequences in the style of C are also allowed. @xref{C
10405 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10409 Enumerated constants consist of an enumerated identifier.
10412 Boolean constants consist of the identifiers @code{TRUE} and
10416 Pointer constants consist of integral values only.
10419 Set constants are not yet supported.
10423 @subsubsection Modula-2 Types
10424 @cindex Modula-2 types
10426 Currently @value{GDBN} can print the following data types in Modula-2
10427 syntax: array types, record types, set types, pointer types, procedure
10428 types, enumerated types, subrange types and base types. You can also
10429 print the contents of variables declared using these type.
10430 This section gives a number of simple source code examples together with
10431 sample @value{GDBN} sessions.
10433 The first example contains the following section of code:
10442 and you can request @value{GDBN} to interrogate the type and value of
10443 @code{r} and @code{s}.
10446 (@value{GDBP}) print s
10448 (@value{GDBP}) ptype s
10450 (@value{GDBP}) print r
10452 (@value{GDBP}) ptype r
10457 Likewise if your source code declares @code{s} as:
10461 s: SET ['A'..'Z'] ;
10465 then you may query the type of @code{s} by:
10468 (@value{GDBP}) ptype s
10469 type = SET ['A'..'Z']
10473 Note that at present you cannot interactively manipulate set
10474 expressions using the debugger.
10476 The following example shows how you might declare an array in Modula-2
10477 and how you can interact with @value{GDBN} to print its type and contents:
10481 s: ARRAY [-10..10] OF CHAR ;
10485 (@value{GDBP}) ptype s
10486 ARRAY [-10..10] OF CHAR
10489 Note that the array handling is not yet complete and although the type
10490 is printed correctly, expression handling still assumes that all
10491 arrays have a lower bound of zero and not @code{-10} as in the example
10494 Here are some more type related Modula-2 examples:
10498 colour = (blue, red, yellow, green) ;
10499 t = [blue..yellow] ;
10507 The @value{GDBN} interaction shows how you can query the data type
10508 and value of a variable.
10511 (@value{GDBP}) print s
10513 (@value{GDBP}) ptype t
10514 type = [blue..yellow]
10518 In this example a Modula-2 array is declared and its contents
10519 displayed. Observe that the contents are written in the same way as
10520 their @code{C} counterparts.
10524 s: ARRAY [1..5] OF CARDINAL ;
10530 (@value{GDBP}) print s
10531 $1 = @{1, 0, 0, 0, 0@}
10532 (@value{GDBP}) ptype s
10533 type = ARRAY [1..5] OF CARDINAL
10536 The Modula-2 language interface to @value{GDBN} also understands
10537 pointer types as shown in this example:
10541 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10548 and you can request that @value{GDBN} describes the type of @code{s}.
10551 (@value{GDBP}) ptype s
10552 type = POINTER TO ARRAY [1..5] OF CARDINAL
10555 @value{GDBN} handles compound types as we can see in this example.
10556 Here we combine array types, record types, pointer types and subrange
10567 myarray = ARRAY myrange OF CARDINAL ;
10568 myrange = [-2..2] ;
10570 s: POINTER TO ARRAY myrange OF foo ;
10574 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10578 (@value{GDBP}) ptype s
10579 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10582 f3 : ARRAY [-2..2] OF CARDINAL;
10587 @subsubsection Modula-2 Defaults
10588 @cindex Modula-2 defaults
10590 If type and range checking are set automatically by @value{GDBN}, they
10591 both default to @code{on} whenever the working language changes to
10592 Modula-2. This happens regardless of whether you or @value{GDBN}
10593 selected the working language.
10595 If you allow @value{GDBN} to set the language automatically, then entering
10596 code compiled from a file whose name ends with @file{.mod} sets the
10597 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10598 Infer the Source Language}, for further details.
10601 @subsubsection Deviations from Standard Modula-2
10602 @cindex Modula-2, deviations from
10604 A few changes have been made to make Modula-2 programs easier to debug.
10605 This is done primarily via loosening its type strictness:
10609 Unlike in standard Modula-2, pointer constants can be formed by
10610 integers. This allows you to modify pointer variables during
10611 debugging. (In standard Modula-2, the actual address contained in a
10612 pointer variable is hidden from you; it can only be modified
10613 through direct assignment to another pointer variable or expression that
10614 returned a pointer.)
10617 C escape sequences can be used in strings and characters to represent
10618 non-printable characters. @value{GDBN} prints out strings with these
10619 escape sequences embedded. Single non-printable characters are
10620 printed using the @samp{CHR(@var{nnn})} format.
10623 The assignment operator (@code{:=}) returns the value of its right-hand
10627 All built-in procedures both modify @emph{and} return their argument.
10631 @subsubsection Modula-2 Type and Range Checks
10632 @cindex Modula-2 checks
10635 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10638 @c FIXME remove warning when type/range checks added
10640 @value{GDBN} considers two Modula-2 variables type equivalent if:
10644 They are of types that have been declared equivalent via a @code{TYPE
10645 @var{t1} = @var{t2}} statement
10648 They have been declared on the same line. (Note: This is true of the
10649 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10652 As long as type checking is enabled, any attempt to combine variables
10653 whose types are not equivalent is an error.
10655 Range checking is done on all mathematical operations, assignment, array
10656 index bounds, and all built-in functions and procedures.
10659 @subsubsection The Scope Operators @code{::} and @code{.}
10661 @cindex @code{.}, Modula-2 scope operator
10662 @cindex colon, doubled as scope operator
10664 @vindex colon-colon@r{, in Modula-2}
10665 @c Info cannot handle :: but TeX can.
10668 @vindex ::@r{, in Modula-2}
10671 There are a few subtle differences between the Modula-2 scope operator
10672 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10677 @var{module} . @var{id}
10678 @var{scope} :: @var{id}
10682 where @var{scope} is the name of a module or a procedure,
10683 @var{module} the name of a module, and @var{id} is any declared
10684 identifier within your program, except another module.
10686 Using the @code{::} operator makes @value{GDBN} search the scope
10687 specified by @var{scope} for the identifier @var{id}. If it is not
10688 found in the specified scope, then @value{GDBN} searches all scopes
10689 enclosing the one specified by @var{scope}.
10691 Using the @code{.} operator makes @value{GDBN} search the current scope for
10692 the identifier specified by @var{id} that was imported from the
10693 definition module specified by @var{module}. With this operator, it is
10694 an error if the identifier @var{id} was not imported from definition
10695 module @var{module}, or if @var{id} is not an identifier in
10699 @subsubsection @value{GDBN} and Modula-2
10701 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10702 Five subcommands of @code{set print} and @code{show print} apply
10703 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10704 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10705 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10706 analogue in Modula-2.
10708 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10709 with any language, is not useful with Modula-2. Its
10710 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10711 created in Modula-2 as they can in C or C@t{++}. However, because an
10712 address can be specified by an integral constant, the construct
10713 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10715 @cindex @code{#} in Modula-2
10716 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10717 interpreted as the beginning of a comment. Use @code{<>} instead.
10723 The extensions made to @value{GDBN} for Ada only support
10724 output from the @sc{gnu} Ada (GNAT) compiler.
10725 Other Ada compilers are not currently supported, and
10726 attempting to debug executables produced by them is most likely
10730 @cindex expressions in Ada
10732 * Ada Mode Intro:: General remarks on the Ada syntax
10733 and semantics supported by Ada mode
10735 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10736 * Additions to Ada:: Extensions of the Ada expression syntax.
10737 * Stopping Before Main Program:: Debugging the program during elaboration.
10738 * Ada Glitches:: Known peculiarities of Ada mode.
10741 @node Ada Mode Intro
10742 @subsubsection Introduction
10743 @cindex Ada mode, general
10745 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10746 syntax, with some extensions.
10747 The philosophy behind the design of this subset is
10751 That @value{GDBN} should provide basic literals and access to operations for
10752 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10753 leaving more sophisticated computations to subprograms written into the
10754 program (which therefore may be called from @value{GDBN}).
10757 That type safety and strict adherence to Ada language restrictions
10758 are not particularly important to the @value{GDBN} user.
10761 That brevity is important to the @value{GDBN} user.
10764 Thus, for brevity, the debugger acts as if there were
10765 implicit @code{with} and @code{use} clauses in effect for all user-written
10766 packages, making it unnecessary to fully qualify most names with
10767 their packages, regardless of context. Where this causes ambiguity,
10768 @value{GDBN} asks the user's intent.
10770 The debugger will start in Ada mode if it detects an Ada main program.
10771 As for other languages, it will enter Ada mode when stopped in a program that
10772 was translated from an Ada source file.
10774 While in Ada mode, you may use `@t{--}' for comments. This is useful
10775 mostly for documenting command files. The standard @value{GDBN} comment
10776 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10777 middle (to allow based literals).
10779 The debugger supports limited overloading. Given a subprogram call in which
10780 the function symbol has multiple definitions, it will use the number of
10781 actual parameters and some information about their types to attempt to narrow
10782 the set of definitions. It also makes very limited use of context, preferring
10783 procedures to functions in the context of the @code{call} command, and
10784 functions to procedures elsewhere.
10786 @node Omissions from Ada
10787 @subsubsection Omissions from Ada
10788 @cindex Ada, omissions from
10790 Here are the notable omissions from the subset:
10794 Only a subset of the attributes are supported:
10798 @t{'First}, @t{'Last}, and @t{'Length}
10799 on array objects (not on types and subtypes).
10802 @t{'Min} and @t{'Max}.
10805 @t{'Pos} and @t{'Val}.
10811 @t{'Range} on array objects (not subtypes), but only as the right
10812 operand of the membership (@code{in}) operator.
10815 @t{'Access}, @t{'Unchecked_Access}, and
10816 @t{'Unrestricted_Access} (a GNAT extension).
10824 @code{Characters.Latin_1} are not available and
10825 concatenation is not implemented. Thus, escape characters in strings are
10826 not currently available.
10829 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10830 equality of representations. They will generally work correctly
10831 for strings and arrays whose elements have integer or enumeration types.
10832 They may not work correctly for arrays whose element
10833 types have user-defined equality, for arrays of real values
10834 (in particular, IEEE-conformant floating point, because of negative
10835 zeroes and NaNs), and for arrays whose elements contain unused bits with
10836 indeterminate values.
10839 The other component-by-component array operations (@code{and}, @code{or},
10840 @code{xor}, @code{not}, and relational tests other than equality)
10841 are not implemented.
10844 @cindex array aggregates (Ada)
10845 @cindex record aggregates (Ada)
10846 @cindex aggregates (Ada)
10847 There is limited support for array and record aggregates. They are
10848 permitted only on the right sides of assignments, as in these examples:
10851 set An_Array := (1, 2, 3, 4, 5, 6)
10852 set An_Array := (1, others => 0)
10853 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10854 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10855 set A_Record := (1, "Peter", True);
10856 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10860 discriminant's value by assigning an aggregate has an
10861 undefined effect if that discriminant is used within the record.
10862 However, you can first modify discriminants by directly assigning to
10863 them (which normally would not be allowed in Ada), and then performing an
10864 aggregate assignment. For example, given a variable @code{A_Rec}
10865 declared to have a type such as:
10868 type Rec (Len : Small_Integer := 0) is record
10870 Vals : IntArray (1 .. Len);
10874 you can assign a value with a different size of @code{Vals} with two
10879 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10882 As this example also illustrates, @value{GDBN} is very loose about the usual
10883 rules concerning aggregates. You may leave out some of the
10884 components of an array or record aggregate (such as the @code{Len}
10885 component in the assignment to @code{A_Rec} above); they will retain their
10886 original values upon assignment. You may freely use dynamic values as
10887 indices in component associations. You may even use overlapping or
10888 redundant component associations, although which component values are
10889 assigned in such cases is not defined.
10892 Calls to dispatching subprograms are not implemented.
10895 The overloading algorithm is much more limited (i.e., less selective)
10896 than that of real Ada. It makes only limited use of the context in
10897 which a subexpression appears to resolve its meaning, and it is much
10898 looser in its rules for allowing type matches. As a result, some
10899 function calls will be ambiguous, and the user will be asked to choose
10900 the proper resolution.
10903 The @code{new} operator is not implemented.
10906 Entry calls are not implemented.
10909 Aside from printing, arithmetic operations on the native VAX floating-point
10910 formats are not supported.
10913 It is not possible to slice a packed array.
10916 @node Additions to Ada
10917 @subsubsection Additions to Ada
10918 @cindex Ada, deviations from
10920 As it does for other languages, @value{GDBN} makes certain generic
10921 extensions to Ada (@pxref{Expressions}):
10925 If the expression @var{E} is a variable residing in memory (typically
10926 a local variable or array element) and @var{N} is a positive integer,
10927 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10928 @var{N}-1 adjacent variables following it in memory as an array. In
10929 Ada, this operator is generally not necessary, since its prime use is
10930 in displaying parts of an array, and slicing will usually do this in
10931 Ada. However, there are occasional uses when debugging programs in
10932 which certain debugging information has been optimized away.
10935 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10936 appears in function or file @var{B}.'' When @var{B} is a file name,
10937 you must typically surround it in single quotes.
10940 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10941 @var{type} that appears at address @var{addr}.''
10944 A name starting with @samp{$} is a convenience variable
10945 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10948 In addition, @value{GDBN} provides a few other shortcuts and outright
10949 additions specific to Ada:
10953 The assignment statement is allowed as an expression, returning
10954 its right-hand operand as its value. Thus, you may enter
10958 print A(tmp := y + 1)
10962 The semicolon is allowed as an ``operator,'' returning as its value
10963 the value of its right-hand operand.
10964 This allows, for example,
10965 complex conditional breaks:
10969 condition 1 (report(i); k += 1; A(k) > 100)
10973 Rather than use catenation and symbolic character names to introduce special
10974 characters into strings, one may instead use a special bracket notation,
10975 which is also used to print strings. A sequence of characters of the form
10976 @samp{["@var{XX}"]} within a string or character literal denotes the
10977 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10978 sequence of characters @samp{["""]} also denotes a single quotation mark
10979 in strings. For example,
10981 "One line.["0a"]Next line.["0a"]"
10984 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10988 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10989 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10997 When printing arrays, @value{GDBN} uses positional notation when the
10998 array has a lower bound of 1, and uses a modified named notation otherwise.
10999 For example, a one-dimensional array of three integers with a lower bound
11000 of 3 might print as
11007 That is, in contrast to valid Ada, only the first component has a @code{=>}
11011 You may abbreviate attributes in expressions with any unique,
11012 multi-character subsequence of
11013 their names (an exact match gets preference).
11014 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11015 in place of @t{a'length}.
11018 @cindex quoting Ada internal identifiers
11019 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11020 to lower case. The GNAT compiler uses upper-case characters for
11021 some of its internal identifiers, which are normally of no interest to users.
11022 For the rare occasions when you actually have to look at them,
11023 enclose them in angle brackets to avoid the lower-case mapping.
11026 @value{GDBP} print <JMPBUF_SAVE>[0]
11030 Printing an object of class-wide type or dereferencing an
11031 access-to-class-wide value will display all the components of the object's
11032 specific type (as indicated by its run-time tag). Likewise, component
11033 selection on such a value will operate on the specific type of the
11038 @node Stopping Before Main Program
11039 @subsubsection Stopping at the Very Beginning
11041 @cindex breakpointing Ada elaboration code
11042 It is sometimes necessary to debug the program during elaboration, and
11043 before reaching the main procedure.
11044 As defined in the Ada Reference
11045 Manual, the elaboration code is invoked from a procedure called
11046 @code{adainit}. To run your program up to the beginning of
11047 elaboration, simply use the following two commands:
11048 @code{tbreak adainit} and @code{run}.
11051 @subsubsection Known Peculiarities of Ada Mode
11052 @cindex Ada, problems
11054 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11055 we know of several problems with and limitations of Ada mode in
11057 some of which will be fixed with planned future releases of the debugger
11058 and the GNU Ada compiler.
11062 Currently, the debugger
11063 has insufficient information to determine whether certain pointers represent
11064 pointers to objects or the objects themselves.
11065 Thus, the user may have to tack an extra @code{.all} after an expression
11066 to get it printed properly.
11069 Static constants that the compiler chooses not to materialize as objects in
11070 storage are invisible to the debugger.
11073 Named parameter associations in function argument lists are ignored (the
11074 argument lists are treated as positional).
11077 Many useful library packages are currently invisible to the debugger.
11080 Fixed-point arithmetic, conversions, input, and output is carried out using
11081 floating-point arithmetic, and may give results that only approximate those on
11085 The type of the @t{'Address} attribute may not be @code{System.Address}.
11088 The GNAT compiler never generates the prefix @code{Standard} for any of
11089 the standard symbols defined by the Ada language. @value{GDBN} knows about
11090 this: it will strip the prefix from names when you use it, and will never
11091 look for a name you have so qualified among local symbols, nor match against
11092 symbols in other packages or subprograms. If you have
11093 defined entities anywhere in your program other than parameters and
11094 local variables whose simple names match names in @code{Standard},
11095 GNAT's lack of qualification here can cause confusion. When this happens,
11096 you can usually resolve the confusion
11097 by qualifying the problematic names with package
11098 @code{Standard} explicitly.
11101 @node Unsupported Languages
11102 @section Unsupported Languages
11104 @cindex unsupported languages
11105 @cindex minimal language
11106 In addition to the other fully-supported programming languages,
11107 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11108 It does not represent a real programming language, but provides a set
11109 of capabilities close to what the C or assembly languages provide.
11110 This should allow most simple operations to be performed while debugging
11111 an application that uses a language currently not supported by @value{GDBN}.
11113 If the language is set to @code{auto}, @value{GDBN} will automatically
11114 select this language if the current frame corresponds to an unsupported
11118 @chapter Examining the Symbol Table
11120 The commands described in this chapter allow you to inquire about the
11121 symbols (names of variables, functions and types) defined in your
11122 program. This information is inherent in the text of your program and
11123 does not change as your program executes. @value{GDBN} finds it in your
11124 program's symbol table, in the file indicated when you started @value{GDBN}
11125 (@pxref{File Options, ,Choosing Files}), or by one of the
11126 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11128 @cindex symbol names
11129 @cindex names of symbols
11130 @cindex quoting names
11131 Occasionally, you may need to refer to symbols that contain unusual
11132 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11133 most frequent case is in referring to static variables in other
11134 source files (@pxref{Variables,,Program Variables}). File names
11135 are recorded in object files as debugging symbols, but @value{GDBN} would
11136 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11137 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11138 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11145 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11148 @cindex case-insensitive symbol names
11149 @cindex case sensitivity in symbol names
11150 @kindex set case-sensitive
11151 @item set case-sensitive on
11152 @itemx set case-sensitive off
11153 @itemx set case-sensitive auto
11154 Normally, when @value{GDBN} looks up symbols, it matches their names
11155 with case sensitivity determined by the current source language.
11156 Occasionally, you may wish to control that. The command @code{set
11157 case-sensitive} lets you do that by specifying @code{on} for
11158 case-sensitive matches or @code{off} for case-insensitive ones. If
11159 you specify @code{auto}, case sensitivity is reset to the default
11160 suitable for the source language. The default is case-sensitive
11161 matches for all languages except for Fortran, for which the default is
11162 case-insensitive matches.
11164 @kindex show case-sensitive
11165 @item show case-sensitive
11166 This command shows the current setting of case sensitivity for symbols
11169 @kindex info address
11170 @cindex address of a symbol
11171 @item info address @var{symbol}
11172 Describe where the data for @var{symbol} is stored. For a register
11173 variable, this says which register it is kept in. For a non-register
11174 local variable, this prints the stack-frame offset at which the variable
11177 Note the contrast with @samp{print &@var{symbol}}, which does not work
11178 at all for a register variable, and for a stack local variable prints
11179 the exact address of the current instantiation of the variable.
11181 @kindex info symbol
11182 @cindex symbol from address
11183 @cindex closest symbol and offset for an address
11184 @item info symbol @var{addr}
11185 Print the name of a symbol which is stored at the address @var{addr}.
11186 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11187 nearest symbol and an offset from it:
11190 (@value{GDBP}) info symbol 0x54320
11191 _initialize_vx + 396 in section .text
11195 This is the opposite of the @code{info address} command. You can use
11196 it to find out the name of a variable or a function given its address.
11199 @item whatis [@var{arg}]
11200 Print the data type of @var{arg}, which can be either an expression or
11201 a data type. With no argument, print the data type of @code{$}, the
11202 last value in the value history. If @var{arg} is an expression, it is
11203 not actually evaluated, and any side-effecting operations (such as
11204 assignments or function calls) inside it do not take place. If
11205 @var{arg} is a type name, it may be the name of a type or typedef, or
11206 for C code it may have the form @samp{class @var{class-name}},
11207 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11208 @samp{enum @var{enum-tag}}.
11209 @xref{Expressions, ,Expressions}.
11212 @item ptype [@var{arg}]
11213 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11214 detailed description of the type, instead of just the name of the type.
11215 @xref{Expressions, ,Expressions}.
11217 For example, for this variable declaration:
11220 struct complex @{double real; double imag;@} v;
11224 the two commands give this output:
11228 (@value{GDBP}) whatis v
11229 type = struct complex
11230 (@value{GDBP}) ptype v
11231 type = struct complex @{
11239 As with @code{whatis}, using @code{ptype} without an argument refers to
11240 the type of @code{$}, the last value in the value history.
11242 @cindex incomplete type
11243 Sometimes, programs use opaque data types or incomplete specifications
11244 of complex data structure. If the debug information included in the
11245 program does not allow @value{GDBN} to display a full declaration of
11246 the data type, it will say @samp{<incomplete type>}. For example,
11247 given these declarations:
11251 struct foo *fooptr;
11255 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11258 (@value{GDBP}) ptype foo
11259 $1 = <incomplete type>
11263 ``Incomplete type'' is C terminology for data types that are not
11264 completely specified.
11267 @item info types @var{regexp}
11269 Print a brief description of all types whose names match the regular
11270 expression @var{regexp} (or all types in your program, if you supply
11271 no argument). Each complete typename is matched as though it were a
11272 complete line; thus, @samp{i type value} gives information on all
11273 types in your program whose names include the string @code{value}, but
11274 @samp{i type ^value$} gives information only on types whose complete
11275 name is @code{value}.
11277 This command differs from @code{ptype} in two ways: first, like
11278 @code{whatis}, it does not print a detailed description; second, it
11279 lists all source files where a type is defined.
11282 @cindex local variables
11283 @item info scope @var{location}
11284 List all the variables local to a particular scope. This command
11285 accepts a @var{location} argument---a function name, a source line, or
11286 an address preceded by a @samp{*}, and prints all the variables local
11287 to the scope defined by that location. (@xref{Specify Location}, for
11288 details about supported forms of @var{location}.) For example:
11291 (@value{GDBP}) @b{info scope command_line_handler}
11292 Scope for command_line_handler:
11293 Symbol rl is an argument at stack/frame offset 8, length 4.
11294 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11295 Symbol linelength is in static storage at address 0x150a1c, length 4.
11296 Symbol p is a local variable in register $esi, length 4.
11297 Symbol p1 is a local variable in register $ebx, length 4.
11298 Symbol nline is a local variable in register $edx, length 4.
11299 Symbol repeat is a local variable at frame offset -8, length 4.
11303 This command is especially useful for determining what data to collect
11304 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11307 @kindex info source
11309 Show information about the current source file---that is, the source file for
11310 the function containing the current point of execution:
11313 the name of the source file, and the directory containing it,
11315 the directory it was compiled in,
11317 its length, in lines,
11319 which programming language it is written in,
11321 whether the executable includes debugging information for that file, and
11322 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
11324 whether the debugging information includes information about
11325 preprocessor macros.
11329 @kindex info sources
11331 Print the names of all source files in your program for which there is
11332 debugging information, organized into two lists: files whose symbols
11333 have already been read, and files whose symbols will be read when needed.
11335 @kindex info functions
11336 @item info functions
11337 Print the names and data types of all defined functions.
11339 @item info functions @var{regexp}
11340 Print the names and data types of all defined functions
11341 whose names contain a match for regular expression @var{regexp}.
11342 Thus, @samp{info fun step} finds all functions whose names
11343 include @code{step}; @samp{info fun ^step} finds those whose names
11344 start with @code{step}. If a function name contains characters
11345 that conflict with the regular expression language (e.g.@:
11346 @samp{operator*()}), they may be quoted with a backslash.
11348 @kindex info variables
11349 @item info variables
11350 Print the names and data types of all variables that are declared
11351 outside of functions (i.e.@: excluding local variables).
11353 @item info variables @var{regexp}
11354 Print the names and data types of all variables (except for local
11355 variables) whose names contain a match for regular expression
11358 @kindex info classes
11359 @cindex Objective-C, classes and selectors
11361 @itemx info classes @var{regexp}
11362 Display all Objective-C classes in your program, or
11363 (with the @var{regexp} argument) all those matching a particular regular
11366 @kindex info selectors
11367 @item info selectors
11368 @itemx info selectors @var{regexp}
11369 Display all Objective-C selectors in your program, or
11370 (with the @var{regexp} argument) all those matching a particular regular
11374 This was never implemented.
11375 @kindex info methods
11377 @itemx info methods @var{regexp}
11378 The @code{info methods} command permits the user to examine all defined
11379 methods within C@t{++} program, or (with the @var{regexp} argument) a
11380 specific set of methods found in the various C@t{++} classes. Many
11381 C@t{++} classes provide a large number of methods. Thus, the output
11382 from the @code{ptype} command can be overwhelming and hard to use. The
11383 @code{info-methods} command filters the methods, printing only those
11384 which match the regular-expression @var{regexp}.
11387 @cindex reloading symbols
11388 Some systems allow individual object files that make up your program to
11389 be replaced without stopping and restarting your program. For example,
11390 in VxWorks you can simply recompile a defective object file and keep on
11391 running. If you are running on one of these systems, you can allow
11392 @value{GDBN} to reload the symbols for automatically relinked modules:
11395 @kindex set symbol-reloading
11396 @item set symbol-reloading on
11397 Replace symbol definitions for the corresponding source file when an
11398 object file with a particular name is seen again.
11400 @item set symbol-reloading off
11401 Do not replace symbol definitions when encountering object files of the
11402 same name more than once. This is the default state; if you are not
11403 running on a system that permits automatic relinking of modules, you
11404 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11405 may discard symbols when linking large programs, that may contain
11406 several modules (from different directories or libraries) with the same
11409 @kindex show symbol-reloading
11410 @item show symbol-reloading
11411 Show the current @code{on} or @code{off} setting.
11414 @cindex opaque data types
11415 @kindex set opaque-type-resolution
11416 @item set opaque-type-resolution on
11417 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11418 declared as a pointer to a @code{struct}, @code{class}, or
11419 @code{union}---for example, @code{struct MyType *}---that is used in one
11420 source file although the full declaration of @code{struct MyType} is in
11421 another source file. The default is on.
11423 A change in the setting of this subcommand will not take effect until
11424 the next time symbols for a file are loaded.
11426 @item set opaque-type-resolution off
11427 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11428 is printed as follows:
11430 @{<no data fields>@}
11433 @kindex show opaque-type-resolution
11434 @item show opaque-type-resolution
11435 Show whether opaque types are resolved or not.
11437 @kindex maint print symbols
11438 @cindex symbol dump
11439 @kindex maint print psymbols
11440 @cindex partial symbol dump
11441 @item maint print symbols @var{filename}
11442 @itemx maint print psymbols @var{filename}
11443 @itemx maint print msymbols @var{filename}
11444 Write a dump of debugging symbol data into the file @var{filename}.
11445 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11446 symbols with debugging data are included. If you use @samp{maint print
11447 symbols}, @value{GDBN} includes all the symbols for which it has already
11448 collected full details: that is, @var{filename} reflects symbols for
11449 only those files whose symbols @value{GDBN} has read. You can use the
11450 command @code{info sources} to find out which files these are. If you
11451 use @samp{maint print psymbols} instead, the dump shows information about
11452 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11453 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11454 @samp{maint print msymbols} dumps just the minimal symbol information
11455 required for each object file from which @value{GDBN} has read some symbols.
11456 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11457 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11459 @kindex maint info symtabs
11460 @kindex maint info psymtabs
11461 @cindex listing @value{GDBN}'s internal symbol tables
11462 @cindex symbol tables, listing @value{GDBN}'s internal
11463 @cindex full symbol tables, listing @value{GDBN}'s internal
11464 @cindex partial symbol tables, listing @value{GDBN}'s internal
11465 @item maint info symtabs @r{[} @var{regexp} @r{]}
11466 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11468 List the @code{struct symtab} or @code{struct partial_symtab}
11469 structures whose names match @var{regexp}. If @var{regexp} is not
11470 given, list them all. The output includes expressions which you can
11471 copy into a @value{GDBN} debugging this one to examine a particular
11472 structure in more detail. For example:
11475 (@value{GDBP}) maint info psymtabs dwarf2read
11476 @{ objfile /home/gnu/build/gdb/gdb
11477 ((struct objfile *) 0x82e69d0)
11478 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11479 ((struct partial_symtab *) 0x8474b10)
11482 text addresses 0x814d3c8 -- 0x8158074
11483 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11484 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11485 dependencies (none)
11488 (@value{GDBP}) maint info symtabs
11492 We see that there is one partial symbol table whose filename contains
11493 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11494 and we see that @value{GDBN} has not read in any symtabs yet at all.
11495 If we set a breakpoint on a function, that will cause @value{GDBN} to
11496 read the symtab for the compilation unit containing that function:
11499 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11500 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11502 (@value{GDBP}) maint info symtabs
11503 @{ objfile /home/gnu/build/gdb/gdb
11504 ((struct objfile *) 0x82e69d0)
11505 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11506 ((struct symtab *) 0x86c1f38)
11509 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11510 linetable ((struct linetable *) 0x8370fa0)
11511 debugformat DWARF 2
11520 @chapter Altering Execution
11522 Once you think you have found an error in your program, you might want to
11523 find out for certain whether correcting the apparent error would lead to
11524 correct results in the rest of the run. You can find the answer by
11525 experiment, using the @value{GDBN} features for altering execution of the
11528 For example, you can store new values into variables or memory
11529 locations, give your program a signal, restart it at a different
11530 address, or even return prematurely from a function.
11533 * Assignment:: Assignment to variables
11534 * Jumping:: Continuing at a different address
11535 * Signaling:: Giving your program a signal
11536 * Returning:: Returning from a function
11537 * Calling:: Calling your program's functions
11538 * Patching:: Patching your program
11542 @section Assignment to Variables
11545 @cindex setting variables
11546 To alter the value of a variable, evaluate an assignment expression.
11547 @xref{Expressions, ,Expressions}. For example,
11554 stores the value 4 into the variable @code{x}, and then prints the
11555 value of the assignment expression (which is 4).
11556 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11557 information on operators in supported languages.
11559 @kindex set variable
11560 @cindex variables, setting
11561 If you are not interested in seeing the value of the assignment, use the
11562 @code{set} command instead of the @code{print} command. @code{set} is
11563 really the same as @code{print} except that the expression's value is
11564 not printed and is not put in the value history (@pxref{Value History,
11565 ,Value History}). The expression is evaluated only for its effects.
11567 If the beginning of the argument string of the @code{set} command
11568 appears identical to a @code{set} subcommand, use the @code{set
11569 variable} command instead of just @code{set}. This command is identical
11570 to @code{set} except for its lack of subcommands. For example, if your
11571 program has a variable @code{width}, you get an error if you try to set
11572 a new value with just @samp{set width=13}, because @value{GDBN} has the
11573 command @code{set width}:
11576 (@value{GDBP}) whatis width
11578 (@value{GDBP}) p width
11580 (@value{GDBP}) set width=47
11581 Invalid syntax in expression.
11585 The invalid expression, of course, is @samp{=47}. In
11586 order to actually set the program's variable @code{width}, use
11589 (@value{GDBP}) set var width=47
11592 Because the @code{set} command has many subcommands that can conflict
11593 with the names of program variables, it is a good idea to use the
11594 @code{set variable} command instead of just @code{set}. For example, if
11595 your program has a variable @code{g}, you run into problems if you try
11596 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11597 the command @code{set gnutarget}, abbreviated @code{set g}:
11601 (@value{GDBP}) whatis g
11605 (@value{GDBP}) set g=4
11609 The program being debugged has been started already.
11610 Start it from the beginning? (y or n) y
11611 Starting program: /home/smith/cc_progs/a.out
11612 "/home/smith/cc_progs/a.out": can't open to read symbols:
11613 Invalid bfd target.
11614 (@value{GDBP}) show g
11615 The current BFD target is "=4".
11620 The program variable @code{g} did not change, and you silently set the
11621 @code{gnutarget} to an invalid value. In order to set the variable
11625 (@value{GDBP}) set var g=4
11628 @value{GDBN} allows more implicit conversions in assignments than C; you can
11629 freely store an integer value into a pointer variable or vice versa,
11630 and you can convert any structure to any other structure that is the
11631 same length or shorter.
11632 @comment FIXME: how do structs align/pad in these conversions?
11633 @comment /doc@cygnus.com 18dec1990
11635 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11636 construct to generate a value of specified type at a specified address
11637 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11638 to memory location @code{0x83040} as an integer (which implies a certain size
11639 and representation in memory), and
11642 set @{int@}0x83040 = 4
11646 stores the value 4 into that memory location.
11649 @section Continuing at a Different Address
11651 Ordinarily, when you continue your program, you do so at the place where
11652 it stopped, with the @code{continue} command. You can instead continue at
11653 an address of your own choosing, with the following commands:
11657 @item jump @var{linespec}
11658 @itemx jump @var{location}
11659 Resume execution at line @var{linespec} or at address given by
11660 @var{location}. Execution stops again immediately if there is a
11661 breakpoint there. @xref{Specify Location}, for a description of the
11662 different forms of @var{linespec} and @var{location}. It is common
11663 practice to use the @code{tbreak} command in conjunction with
11664 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
11666 The @code{jump} command does not change the current stack frame, or
11667 the stack pointer, or the contents of any memory location or any
11668 register other than the program counter. If line @var{linespec} is in
11669 a different function from the one currently executing, the results may
11670 be bizarre if the two functions expect different patterns of arguments or
11671 of local variables. For this reason, the @code{jump} command requests
11672 confirmation if the specified line is not in the function currently
11673 executing. However, even bizarre results are predictable if you are
11674 well acquainted with the machine-language code of your program.
11677 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11678 On many systems, you can get much the same effect as the @code{jump}
11679 command by storing a new value into the register @code{$pc}. The
11680 difference is that this does not start your program running; it only
11681 changes the address of where it @emph{will} run when you continue. For
11689 makes the next @code{continue} command or stepping command execute at
11690 address @code{0x485}, rather than at the address where your program stopped.
11691 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11693 The most common occasion to use the @code{jump} command is to back
11694 up---perhaps with more breakpoints set---over a portion of a program
11695 that has already executed, in order to examine its execution in more
11700 @section Giving your Program a Signal
11701 @cindex deliver a signal to a program
11705 @item signal @var{signal}
11706 Resume execution where your program stopped, but immediately give it the
11707 signal @var{signal}. @var{signal} can be the name or the number of a
11708 signal. For example, on many systems @code{signal 2} and @code{signal
11709 SIGINT} are both ways of sending an interrupt signal.
11711 Alternatively, if @var{signal} is zero, continue execution without
11712 giving a signal. This is useful when your program stopped on account of
11713 a signal and would ordinary see the signal when resumed with the
11714 @code{continue} command; @samp{signal 0} causes it to resume without a
11717 @code{signal} does not repeat when you press @key{RET} a second time
11718 after executing the command.
11722 Invoking the @code{signal} command is not the same as invoking the
11723 @code{kill} utility from the shell. Sending a signal with @code{kill}
11724 causes @value{GDBN} to decide what to do with the signal depending on
11725 the signal handling tables (@pxref{Signals}). The @code{signal} command
11726 passes the signal directly to your program.
11730 @section Returning from a Function
11733 @cindex returning from a function
11736 @itemx return @var{expression}
11737 You can cancel execution of a function call with the @code{return}
11738 command. If you give an
11739 @var{expression} argument, its value is used as the function's return
11743 When you use @code{return}, @value{GDBN} discards the selected stack frame
11744 (and all frames within it). You can think of this as making the
11745 discarded frame return prematurely. If you wish to specify a value to
11746 be returned, give that value as the argument to @code{return}.
11748 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11749 Frame}), and any other frames inside of it, leaving its caller as the
11750 innermost remaining frame. That frame becomes selected. The
11751 specified value is stored in the registers used for returning values
11754 The @code{return} command does not resume execution; it leaves the
11755 program stopped in the state that would exist if the function had just
11756 returned. In contrast, the @code{finish} command (@pxref{Continuing
11757 and Stepping, ,Continuing and Stepping}) resumes execution until the
11758 selected stack frame returns naturally.
11761 @section Calling Program Functions
11764 @cindex calling functions
11765 @cindex inferior functions, calling
11766 @item print @var{expr}
11767 Evaluate the expression @var{expr} and display the resulting value.
11768 @var{expr} may include calls to functions in the program being
11772 @item call @var{expr}
11773 Evaluate the expression @var{expr} without displaying @code{void}
11776 You can use this variant of the @code{print} command if you want to
11777 execute a function from your program that does not return anything
11778 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11779 with @code{void} returned values that @value{GDBN} will otherwise
11780 print. If the result is not void, it is printed and saved in the
11784 It is possible for the function you call via the @code{print} or
11785 @code{call} command to generate a signal (e.g., if there's a bug in
11786 the function, or if you passed it incorrect arguments). What happens
11787 in that case is controlled by the @code{set unwindonsignal} command.
11790 @item set unwindonsignal
11791 @kindex set unwindonsignal
11792 @cindex unwind stack in called functions
11793 @cindex call dummy stack unwinding
11794 Set unwinding of the stack if a signal is received while in a function
11795 that @value{GDBN} called in the program being debugged. If set to on,
11796 @value{GDBN} unwinds the stack it created for the call and restores
11797 the context to what it was before the call. If set to off (the
11798 default), @value{GDBN} stops in the frame where the signal was
11801 @item show unwindonsignal
11802 @kindex show unwindonsignal
11803 Show the current setting of stack unwinding in the functions called by
11807 @cindex weak alias functions
11808 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11809 for another function. In such case, @value{GDBN} might not pick up
11810 the type information, including the types of the function arguments,
11811 which causes @value{GDBN} to call the inferior function incorrectly.
11812 As a result, the called function will function erroneously and may
11813 even crash. A solution to that is to use the name of the aliased
11817 @section Patching Programs
11819 @cindex patching binaries
11820 @cindex writing into executables
11821 @cindex writing into corefiles
11823 By default, @value{GDBN} opens the file containing your program's
11824 executable code (or the corefile) read-only. This prevents accidental
11825 alterations to machine code; but it also prevents you from intentionally
11826 patching your program's binary.
11828 If you'd like to be able to patch the binary, you can specify that
11829 explicitly with the @code{set write} command. For example, you might
11830 want to turn on internal debugging flags, or even to make emergency
11836 @itemx set write off
11837 If you specify @samp{set write on}, @value{GDBN} opens executable and
11838 core files for both reading and writing; if you specify @samp{set write
11839 off} (the default), @value{GDBN} opens them read-only.
11841 If you have already loaded a file, you must load it again (using the
11842 @code{exec-file} or @code{core-file} command) after changing @code{set
11843 write}, for your new setting to take effect.
11847 Display whether executable files and core files are opened for writing
11848 as well as reading.
11852 @chapter @value{GDBN} Files
11854 @value{GDBN} needs to know the file name of the program to be debugged,
11855 both in order to read its symbol table and in order to start your
11856 program. To debug a core dump of a previous run, you must also tell
11857 @value{GDBN} the name of the core dump file.
11860 * Files:: Commands to specify files
11861 * Separate Debug Files:: Debugging information in separate files
11862 * Symbol Errors:: Errors reading symbol files
11866 @section Commands to Specify Files
11868 @cindex symbol table
11869 @cindex core dump file
11871 You may want to specify executable and core dump file names. The usual
11872 way to do this is at start-up time, using the arguments to
11873 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11874 Out of @value{GDBN}}).
11876 Occasionally it is necessary to change to a different file during a
11877 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11878 specify a file you want to use. Or you are debugging a remote target
11879 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11880 Program}). In these situations the @value{GDBN} commands to specify
11881 new files are useful.
11884 @cindex executable file
11886 @item file @var{filename}
11887 Use @var{filename} as the program to be debugged. It is read for its
11888 symbols and for the contents of pure memory. It is also the program
11889 executed when you use the @code{run} command. If you do not specify a
11890 directory and the file is not found in the @value{GDBN} working directory,
11891 @value{GDBN} uses the environment variable @code{PATH} as a list of
11892 directories to search, just as the shell does when looking for a program
11893 to run. You can change the value of this variable, for both @value{GDBN}
11894 and your program, using the @code{path} command.
11896 @cindex unlinked object files
11897 @cindex patching object files
11898 You can load unlinked object @file{.o} files into @value{GDBN} using
11899 the @code{file} command. You will not be able to ``run'' an object
11900 file, but you can disassemble functions and inspect variables. Also,
11901 if the underlying BFD functionality supports it, you could use
11902 @kbd{gdb -write} to patch object files using this technique. Note
11903 that @value{GDBN} can neither interpret nor modify relocations in this
11904 case, so branches and some initialized variables will appear to go to
11905 the wrong place. But this feature is still handy from time to time.
11908 @code{file} with no argument makes @value{GDBN} discard any information it
11909 has on both executable file and the symbol table.
11912 @item exec-file @r{[} @var{filename} @r{]}
11913 Specify that the program to be run (but not the symbol table) is found
11914 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11915 if necessary to locate your program. Omitting @var{filename} means to
11916 discard information on the executable file.
11918 @kindex symbol-file
11919 @item symbol-file @r{[} @var{filename} @r{]}
11920 Read symbol table information from file @var{filename}. @code{PATH} is
11921 searched when necessary. Use the @code{file} command to get both symbol
11922 table and program to run from the same file.
11924 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11925 program's symbol table.
11927 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11928 some breakpoints and auto-display expressions. This is because they may
11929 contain pointers to the internal data recording symbols and data types,
11930 which are part of the old symbol table data being discarded inside
11933 @code{symbol-file} does not repeat if you press @key{RET} again after
11936 When @value{GDBN} is configured for a particular environment, it
11937 understands debugging information in whatever format is the standard
11938 generated for that environment; you may use either a @sc{gnu} compiler, or
11939 other compilers that adhere to the local conventions.
11940 Best results are usually obtained from @sc{gnu} compilers; for example,
11941 using @code{@value{NGCC}} you can generate debugging information for
11944 For most kinds of object files, with the exception of old SVR3 systems
11945 using COFF, the @code{symbol-file} command does not normally read the
11946 symbol table in full right away. Instead, it scans the symbol table
11947 quickly to find which source files and which symbols are present. The
11948 details are read later, one source file at a time, as they are needed.
11950 The purpose of this two-stage reading strategy is to make @value{GDBN}
11951 start up faster. For the most part, it is invisible except for
11952 occasional pauses while the symbol table details for a particular source
11953 file are being read. (The @code{set verbose} command can turn these
11954 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11955 Warnings and Messages}.)
11957 We have not implemented the two-stage strategy for COFF yet. When the
11958 symbol table is stored in COFF format, @code{symbol-file} reads the
11959 symbol table data in full right away. Note that ``stabs-in-COFF''
11960 still does the two-stage strategy, since the debug info is actually
11964 @cindex reading symbols immediately
11965 @cindex symbols, reading immediately
11966 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11967 @itemx file @var{filename} @r{[} -readnow @r{]}
11968 You can override the @value{GDBN} two-stage strategy for reading symbol
11969 tables by using the @samp{-readnow} option with any of the commands that
11970 load symbol table information, if you want to be sure @value{GDBN} has the
11971 entire symbol table available.
11973 @c FIXME: for now no mention of directories, since this seems to be in
11974 @c flux. 13mar1992 status is that in theory GDB would look either in
11975 @c current dir or in same dir as myprog; but issues like competing
11976 @c GDB's, or clutter in system dirs, mean that in practice right now
11977 @c only current dir is used. FFish says maybe a special GDB hierarchy
11978 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11982 @item core-file @r{[}@var{filename}@r{]}
11984 Specify the whereabouts of a core dump file to be used as the ``contents
11985 of memory''. Traditionally, core files contain only some parts of the
11986 address space of the process that generated them; @value{GDBN} can access the
11987 executable file itself for other parts.
11989 @code{core-file} with no argument specifies that no core file is
11992 Note that the core file is ignored when your program is actually running
11993 under @value{GDBN}. So, if you have been running your program and you
11994 wish to debug a core file instead, you must kill the subprocess in which
11995 the program is running. To do this, use the @code{kill} command
11996 (@pxref{Kill Process, ,Killing the Child Process}).
11998 @kindex add-symbol-file
11999 @cindex dynamic linking
12000 @item add-symbol-file @var{filename} @var{address}
12001 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12002 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12003 The @code{add-symbol-file} command reads additional symbol table
12004 information from the file @var{filename}. You would use this command
12005 when @var{filename} has been dynamically loaded (by some other means)
12006 into the program that is running. @var{address} should be the memory
12007 address at which the file has been loaded; @value{GDBN} cannot figure
12008 this out for itself. You can additionally specify an arbitrary number
12009 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12010 section name and base address for that section. You can specify any
12011 @var{address} as an expression.
12013 The symbol table of the file @var{filename} is added to the symbol table
12014 originally read with the @code{symbol-file} command. You can use the
12015 @code{add-symbol-file} command any number of times; the new symbol data
12016 thus read keeps adding to the old. To discard all old symbol data
12017 instead, use the @code{symbol-file} command without any arguments.
12019 @cindex relocatable object files, reading symbols from
12020 @cindex object files, relocatable, reading symbols from
12021 @cindex reading symbols from relocatable object files
12022 @cindex symbols, reading from relocatable object files
12023 @cindex @file{.o} files, reading symbols from
12024 Although @var{filename} is typically a shared library file, an
12025 executable file, or some other object file which has been fully
12026 relocated for loading into a process, you can also load symbolic
12027 information from relocatable @file{.o} files, as long as:
12031 the file's symbolic information refers only to linker symbols defined in
12032 that file, not to symbols defined by other object files,
12034 every section the file's symbolic information refers to has actually
12035 been loaded into the inferior, as it appears in the file, and
12037 you can determine the address at which every section was loaded, and
12038 provide these to the @code{add-symbol-file} command.
12042 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12043 relocatable files into an already running program; such systems
12044 typically make the requirements above easy to meet. However, it's
12045 important to recognize that many native systems use complex link
12046 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12047 assembly, for example) that make the requirements difficult to meet. In
12048 general, one cannot assume that using @code{add-symbol-file} to read a
12049 relocatable object file's symbolic information will have the same effect
12050 as linking the relocatable object file into the program in the normal
12053 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12055 @kindex add-symbol-file-from-memory
12056 @cindex @code{syscall DSO}
12057 @cindex load symbols from memory
12058 @item add-symbol-file-from-memory @var{address}
12059 Load symbols from the given @var{address} in a dynamically loaded
12060 object file whose image is mapped directly into the inferior's memory.
12061 For example, the Linux kernel maps a @code{syscall DSO} into each
12062 process's address space; this DSO provides kernel-specific code for
12063 some system calls. The argument can be any expression whose
12064 evaluation yields the address of the file's shared object file header.
12065 For this command to work, you must have used @code{symbol-file} or
12066 @code{exec-file} commands in advance.
12068 @kindex add-shared-symbol-files
12070 @item add-shared-symbol-files @var{library-file}
12071 @itemx assf @var{library-file}
12072 The @code{add-shared-symbol-files} command can currently be used only
12073 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12074 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12075 @value{GDBN} automatically looks for shared libraries, however if
12076 @value{GDBN} does not find yours, you can invoke
12077 @code{add-shared-symbol-files}. It takes one argument: the shared
12078 library's file name. @code{assf} is a shorthand alias for
12079 @code{add-shared-symbol-files}.
12082 @item section @var{section} @var{addr}
12083 The @code{section} command changes the base address of the named
12084 @var{section} of the exec file to @var{addr}. This can be used if the
12085 exec file does not contain section addresses, (such as in the
12086 @code{a.out} format), or when the addresses specified in the file
12087 itself are wrong. Each section must be changed separately. The
12088 @code{info files} command, described below, lists all the sections and
12092 @kindex info target
12095 @code{info files} and @code{info target} are synonymous; both print the
12096 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12097 including the names of the executable and core dump files currently in
12098 use by @value{GDBN}, and the files from which symbols were loaded. The
12099 command @code{help target} lists all possible targets rather than
12102 @kindex maint info sections
12103 @item maint info sections
12104 Another command that can give you extra information about program sections
12105 is @code{maint info sections}. In addition to the section information
12106 displayed by @code{info files}, this command displays the flags and file
12107 offset of each section in the executable and core dump files. In addition,
12108 @code{maint info sections} provides the following command options (which
12109 may be arbitrarily combined):
12113 Display sections for all loaded object files, including shared libraries.
12114 @item @var{sections}
12115 Display info only for named @var{sections}.
12116 @item @var{section-flags}
12117 Display info only for sections for which @var{section-flags} are true.
12118 The section flags that @value{GDBN} currently knows about are:
12121 Section will have space allocated in the process when loaded.
12122 Set for all sections except those containing debug information.
12124 Section will be loaded from the file into the child process memory.
12125 Set for pre-initialized code and data, clear for @code{.bss} sections.
12127 Section needs to be relocated before loading.
12129 Section cannot be modified by the child process.
12131 Section contains executable code only.
12133 Section contains data only (no executable code).
12135 Section will reside in ROM.
12137 Section contains data for constructor/destructor lists.
12139 Section is not empty.
12141 An instruction to the linker to not output the section.
12142 @item COFF_SHARED_LIBRARY
12143 A notification to the linker that the section contains
12144 COFF shared library information.
12146 Section contains common symbols.
12149 @kindex set trust-readonly-sections
12150 @cindex read-only sections
12151 @item set trust-readonly-sections on
12152 Tell @value{GDBN} that readonly sections in your object file
12153 really are read-only (i.e.@: that their contents will not change).
12154 In that case, @value{GDBN} can fetch values from these sections
12155 out of the object file, rather than from the target program.
12156 For some targets (notably embedded ones), this can be a significant
12157 enhancement to debugging performance.
12159 The default is off.
12161 @item set trust-readonly-sections off
12162 Tell @value{GDBN} not to trust readonly sections. This means that
12163 the contents of the section might change while the program is running,
12164 and must therefore be fetched from the target when needed.
12166 @item show trust-readonly-sections
12167 Show the current setting of trusting readonly sections.
12170 All file-specifying commands allow both absolute and relative file names
12171 as arguments. @value{GDBN} always converts the file name to an absolute file
12172 name and remembers it that way.
12174 @cindex shared libraries
12175 @anchor{Shared Libraries}
12176 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12177 and IBM RS/6000 AIX shared libraries.
12179 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12180 shared libraries. @xref{Expat}.
12182 @value{GDBN} automatically loads symbol definitions from shared libraries
12183 when you use the @code{run} command, or when you examine a core file.
12184 (Before you issue the @code{run} command, @value{GDBN} does not understand
12185 references to a function in a shared library, however---unless you are
12186 debugging a core file).
12188 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12189 automatically loads the symbols at the time of the @code{shl_load} call.
12191 @c FIXME: some @value{GDBN} release may permit some refs to undef
12192 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12193 @c FIXME...lib; check this from time to time when updating manual
12195 There are times, however, when you may wish to not automatically load
12196 symbol definitions from shared libraries, such as when they are
12197 particularly large or there are many of them.
12199 To control the automatic loading of shared library symbols, use the
12203 @kindex set auto-solib-add
12204 @item set auto-solib-add @var{mode}
12205 If @var{mode} is @code{on}, symbols from all shared object libraries
12206 will be loaded automatically when the inferior begins execution, you
12207 attach to an independently started inferior, or when the dynamic linker
12208 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12209 is @code{off}, symbols must be loaded manually, using the
12210 @code{sharedlibrary} command. The default value is @code{on}.
12212 @cindex memory used for symbol tables
12213 If your program uses lots of shared libraries with debug info that
12214 takes large amounts of memory, you can decrease the @value{GDBN}
12215 memory footprint by preventing it from automatically loading the
12216 symbols from shared libraries. To that end, type @kbd{set
12217 auto-solib-add off} before running the inferior, then load each
12218 library whose debug symbols you do need with @kbd{sharedlibrary
12219 @var{regexp}}, where @var{regexp} is a regular expression that matches
12220 the libraries whose symbols you want to be loaded.
12222 @kindex show auto-solib-add
12223 @item show auto-solib-add
12224 Display the current autoloading mode.
12227 @cindex load shared library
12228 To explicitly load shared library symbols, use the @code{sharedlibrary}
12232 @kindex info sharedlibrary
12235 @itemx info sharedlibrary
12236 Print the names of the shared libraries which are currently loaded.
12238 @kindex sharedlibrary
12240 @item sharedlibrary @var{regex}
12241 @itemx share @var{regex}
12242 Load shared object library symbols for files matching a
12243 Unix regular expression.
12244 As with files loaded automatically, it only loads shared libraries
12245 required by your program for a core file or after typing @code{run}. If
12246 @var{regex} is omitted all shared libraries required by your program are
12249 @item nosharedlibrary
12250 @kindex nosharedlibrary
12251 @cindex unload symbols from shared libraries
12252 Unload all shared object library symbols. This discards all symbols
12253 that have been loaded from all shared libraries. Symbols from shared
12254 libraries that were loaded by explicit user requests are not
12258 Sometimes you may wish that @value{GDBN} stops and gives you control
12259 when any of shared library events happen. Use the @code{set
12260 stop-on-solib-events} command for this:
12263 @item set stop-on-solib-events
12264 @kindex set stop-on-solib-events
12265 This command controls whether @value{GDBN} should give you control
12266 when the dynamic linker notifies it about some shared library event.
12267 The most common event of interest is loading or unloading of a new
12270 @item show stop-on-solib-events
12271 @kindex show stop-on-solib-events
12272 Show whether @value{GDBN} stops and gives you control when shared
12273 library events happen.
12276 Shared libraries are also supported in many cross or remote debugging
12277 configurations. A copy of the target's libraries need to be present on the
12278 host system; they need to be the same as the target libraries, although the
12279 copies on the target can be stripped as long as the copies on the host are
12282 @cindex where to look for shared libraries
12283 For remote debugging, you need to tell @value{GDBN} where the target
12284 libraries are, so that it can load the correct copies---otherwise, it
12285 may try to load the host's libraries. @value{GDBN} has two variables
12286 to specify the search directories for target libraries.
12289 @cindex prefix for shared library file names
12290 @cindex system root, alternate
12291 @kindex set solib-absolute-prefix
12292 @kindex set sysroot
12293 @item set sysroot @var{path}
12294 Use @var{path} as the system root for the program being debugged. Any
12295 absolute shared library paths will be prefixed with @var{path}; many
12296 runtime loaders store the absolute paths to the shared library in the
12297 target program's memory. If you use @code{set sysroot} to find shared
12298 libraries, they need to be laid out in the same way that they are on
12299 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
12302 The @code{set solib-absolute-prefix} command is an alias for @code{set
12305 @cindex default system root
12306 @cindex @samp{--with-sysroot}
12307 You can set the default system root by using the configure-time
12308 @samp{--with-sysroot} option. If the system root is inside
12309 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
12310 @samp{--exec-prefix}), then the default system root will be updated
12311 automatically if the installed @value{GDBN} is moved to a new
12314 @kindex show sysroot
12316 Display the current shared library prefix.
12318 @kindex set solib-search-path
12319 @item set solib-search-path @var{path}
12320 If this variable is set, @var{path} is a colon-separated list of
12321 directories to search for shared libraries. @samp{solib-search-path}
12322 is used after @samp{sysroot} fails to locate the library, or if the
12323 path to the library is relative instead of absolute. If you want to
12324 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
12325 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
12326 finding your host's libraries. @samp{sysroot} is preferred; setting
12327 it to a nonexistent directory may interfere with automatic loading
12328 of shared library symbols.
12330 @kindex show solib-search-path
12331 @item show solib-search-path
12332 Display the current shared library search path.
12336 @node Separate Debug Files
12337 @section Debugging Information in Separate Files
12338 @cindex separate debugging information files
12339 @cindex debugging information in separate files
12340 @cindex @file{.debug} subdirectories
12341 @cindex debugging information directory, global
12342 @cindex global debugging information directory
12343 @cindex build ID, and separate debugging files
12344 @cindex @file{.build-id} directory
12346 @value{GDBN} allows you to put a program's debugging information in a
12347 file separate from the executable itself, in a way that allows
12348 @value{GDBN} to find and load the debugging information automatically.
12349 Since debugging information can be very large---sometimes larger
12350 than the executable code itself---some systems distribute debugging
12351 information for their executables in separate files, which users can
12352 install only when they need to debug a problem.
12354 @value{GDBN} supports two ways of specifying the separate debug info
12359 The executable contains a @dfn{debug link} that specifies the name of
12360 the separate debug info file. The separate debug file's name is
12361 usually @file{@var{executable}.debug}, where @var{executable} is the
12362 name of the corresponding executable file without leading directories
12363 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
12364 debug link specifies a CRC32 checksum for the debug file, which
12365 @value{GDBN} uses to validate that the executable and the debug file
12366 came from the same build.
12369 The executable contains a @dfn{build ID}, a unique bit string that is
12370 also present in the corresponding debug info file. (This is supported
12371 only on some operating systems, notably those which use the ELF format
12372 for binary files and the @sc{gnu} Binutils.) For more details about
12373 this feature, see the description of the @option{--build-id}
12374 command-line option in @ref{Options, , Command Line Options, ld.info,
12375 The GNU Linker}. The debug info file's name is not specified
12376 explicitly by the build ID, but can be computed from the build ID, see
12380 Depending on the way the debug info file is specified, @value{GDBN}
12381 uses two different methods of looking for the debug file:
12385 For the ``debug link'' method, @value{GDBN} looks up the named file in
12386 the directory of the executable file, then in a subdirectory of that
12387 directory named @file{.debug}, and finally under the global debug
12388 directory, in a subdirectory whose name is identical to the leading
12389 directories of the executable's absolute file name.
12392 For the ``build ID'' method, @value{GDBN} looks in the
12393 @file{.build-id} subdirectory of the global debug directory for a file
12394 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12395 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12396 are the rest of the bit string. (Real build ID strings are 32 or more
12397 hex characters, not 10.)
12400 So, for example, suppose you ask @value{GDBN} to debug
12401 @file{/usr/bin/ls}, which has a debug link that specifies the
12402 file @file{ls.debug}, and a build ID whose value in hex is
12403 @code{abcdef1234}. If the global debug directory is
12404 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12405 debug information files, in the indicated order:
12409 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12411 @file{/usr/bin/ls.debug}
12413 @file{/usr/bin/.debug/ls.debug}
12415 @file{/usr/lib/debug/usr/bin/ls.debug}.
12418 You can set the global debugging info directory's name, and view the
12419 name @value{GDBN} is currently using.
12423 @kindex set debug-file-directory
12424 @item set debug-file-directory @var{directory}
12425 Set the directory which @value{GDBN} searches for separate debugging
12426 information files to @var{directory}.
12428 @kindex show debug-file-directory
12429 @item show debug-file-directory
12430 Show the directory @value{GDBN} searches for separate debugging
12435 @cindex @code{.gnu_debuglink} sections
12436 @cindex debug link sections
12437 A debug link is a special section of the executable file named
12438 @code{.gnu_debuglink}. The section must contain:
12442 A filename, with any leading directory components removed, followed by
12445 zero to three bytes of padding, as needed to reach the next four-byte
12446 boundary within the section, and
12448 a four-byte CRC checksum, stored in the same endianness used for the
12449 executable file itself. The checksum is computed on the debugging
12450 information file's full contents by the function given below, passing
12451 zero as the @var{crc} argument.
12454 Any executable file format can carry a debug link, as long as it can
12455 contain a section named @code{.gnu_debuglink} with the contents
12458 @cindex @code{.note.gnu.build-id} sections
12459 @cindex build ID sections
12460 The build ID is a special section in the executable file (and in other
12461 ELF binary files that @value{GDBN} may consider). This section is
12462 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12463 It contains unique identification for the built files---the ID remains
12464 the same across multiple builds of the same build tree. The default
12465 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12466 content for the build ID string. The same section with an identical
12467 value is present in the original built binary with symbols, in its
12468 stripped variant, and in the separate debugging information file.
12470 The debugging information file itself should be an ordinary
12471 executable, containing a full set of linker symbols, sections, and
12472 debugging information. The sections of the debugging information file
12473 should have the same names, addresses, and sizes as the original file,
12474 but they need not contain any data---much like a @code{.bss} section
12475 in an ordinary executable.
12477 The @sc{gnu} binary utilities (Binutils) package includes the
12478 @samp{objcopy} utility that can produce
12479 the separated executable / debugging information file pairs using the
12480 following commands:
12483 @kbd{objcopy --only-keep-debug foo foo.debug}
12488 These commands remove the debugging
12489 information from the executable file @file{foo} and place it in the file
12490 @file{foo.debug}. You can use the first, second or both methods to link the
12495 The debug link method needs the following additional command to also leave
12496 behind a debug link in @file{foo}:
12499 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12502 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12503 a version of the @code{strip} command such that the command @kbd{strip foo -f
12504 foo.debug} has the same functionality as the two @code{objcopy} commands and
12505 the @code{ln -s} command above, together.
12508 Build ID gets embedded into the main executable using @code{ld --build-id} or
12509 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12510 compatibility fixes for debug files separation are present in @sc{gnu} binary
12511 utilities (Binutils) package since version 2.18.
12516 Since there are many different ways to compute CRC's for the debug
12517 link (different polynomials, reversals, byte ordering, etc.), the
12518 simplest way to describe the CRC used in @code{.gnu_debuglink}
12519 sections is to give the complete code for a function that computes it:
12521 @kindex gnu_debuglink_crc32
12524 gnu_debuglink_crc32 (unsigned long crc,
12525 unsigned char *buf, size_t len)
12527 static const unsigned long crc32_table[256] =
12529 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12530 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12531 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12532 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12533 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12534 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12535 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12536 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12537 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12538 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12539 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12540 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12541 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12542 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12543 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12544 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12545 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12546 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12547 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12548 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12549 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12550 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12551 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12552 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12553 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12554 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12555 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12556 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12557 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12558 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12559 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12560 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12561 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12562 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12563 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12564 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12565 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12566 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12567 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12568 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12569 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12570 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12571 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12572 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12573 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12574 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12575 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12576 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12577 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12578 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12579 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12582 unsigned char *end;
12584 crc = ~crc & 0xffffffff;
12585 for (end = buf + len; buf < end; ++buf)
12586 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12587 return ~crc & 0xffffffff;
12592 This computation does not apply to the ``build ID'' method.
12595 @node Symbol Errors
12596 @section Errors Reading Symbol Files
12598 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12599 such as symbol types it does not recognize, or known bugs in compiler
12600 output. By default, @value{GDBN} does not notify you of such problems, since
12601 they are relatively common and primarily of interest to people
12602 debugging compilers. If you are interested in seeing information
12603 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12604 only one message about each such type of problem, no matter how many
12605 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12606 to see how many times the problems occur, with the @code{set
12607 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12610 The messages currently printed, and their meanings, include:
12613 @item inner block not inside outer block in @var{symbol}
12615 The symbol information shows where symbol scopes begin and end
12616 (such as at the start of a function or a block of statements). This
12617 error indicates that an inner scope block is not fully contained
12618 in its outer scope blocks.
12620 @value{GDBN} circumvents the problem by treating the inner block as if it had
12621 the same scope as the outer block. In the error message, @var{symbol}
12622 may be shown as ``@code{(don't know)}'' if the outer block is not a
12625 @item block at @var{address} out of order
12627 The symbol information for symbol scope blocks should occur in
12628 order of increasing addresses. This error indicates that it does not
12631 @value{GDBN} does not circumvent this problem, and has trouble
12632 locating symbols in the source file whose symbols it is reading. (You
12633 can often determine what source file is affected by specifying
12634 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12637 @item bad block start address patched
12639 The symbol information for a symbol scope block has a start address
12640 smaller than the address of the preceding source line. This is known
12641 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12643 @value{GDBN} circumvents the problem by treating the symbol scope block as
12644 starting on the previous source line.
12646 @item bad string table offset in symbol @var{n}
12649 Symbol number @var{n} contains a pointer into the string table which is
12650 larger than the size of the string table.
12652 @value{GDBN} circumvents the problem by considering the symbol to have the
12653 name @code{foo}, which may cause other problems if many symbols end up
12656 @item unknown symbol type @code{0x@var{nn}}
12658 The symbol information contains new data types that @value{GDBN} does
12659 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12660 uncomprehended information, in hexadecimal.
12662 @value{GDBN} circumvents the error by ignoring this symbol information.
12663 This usually allows you to debug your program, though certain symbols
12664 are not accessible. If you encounter such a problem and feel like
12665 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12666 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12667 and examine @code{*bufp} to see the symbol.
12669 @item stub type has NULL name
12671 @value{GDBN} could not find the full definition for a struct or class.
12673 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12674 The symbol information for a C@t{++} member function is missing some
12675 information that recent versions of the compiler should have output for
12678 @item info mismatch between compiler and debugger
12680 @value{GDBN} could not parse a type specification output by the compiler.
12685 @chapter Specifying a Debugging Target
12687 @cindex debugging target
12688 A @dfn{target} is the execution environment occupied by your program.
12690 Often, @value{GDBN} runs in the same host environment as your program;
12691 in that case, the debugging target is specified as a side effect when
12692 you use the @code{file} or @code{core} commands. When you need more
12693 flexibility---for example, running @value{GDBN} on a physically separate
12694 host, or controlling a standalone system over a serial port or a
12695 realtime system over a TCP/IP connection---you can use the @code{target}
12696 command to specify one of the target types configured for @value{GDBN}
12697 (@pxref{Target Commands, ,Commands for Managing Targets}).
12699 @cindex target architecture
12700 It is possible to build @value{GDBN} for several different @dfn{target
12701 architectures}. When @value{GDBN} is built like that, you can choose
12702 one of the available architectures with the @kbd{set architecture}
12706 @kindex set architecture
12707 @kindex show architecture
12708 @item set architecture @var{arch}
12709 This command sets the current target architecture to @var{arch}. The
12710 value of @var{arch} can be @code{"auto"}, in addition to one of the
12711 supported architectures.
12713 @item show architecture
12714 Show the current target architecture.
12716 @item set processor
12718 @kindex set processor
12719 @kindex show processor
12720 These are alias commands for, respectively, @code{set architecture}
12721 and @code{show architecture}.
12725 * Active Targets:: Active targets
12726 * Target Commands:: Commands for managing targets
12727 * Byte Order:: Choosing target byte order
12730 @node Active Targets
12731 @section Active Targets
12733 @cindex stacking targets
12734 @cindex active targets
12735 @cindex multiple targets
12737 There are three classes of targets: processes, core files, and
12738 executable files. @value{GDBN} can work concurrently on up to three
12739 active targets, one in each class. This allows you to (for example)
12740 start a process and inspect its activity without abandoning your work on
12743 For example, if you execute @samp{gdb a.out}, then the executable file
12744 @code{a.out} is the only active target. If you designate a core file as
12745 well---presumably from a prior run that crashed and coredumped---then
12746 @value{GDBN} has two active targets and uses them in tandem, looking
12747 first in the corefile target, then in the executable file, to satisfy
12748 requests for memory addresses. (Typically, these two classes of target
12749 are complementary, since core files contain only a program's
12750 read-write memory---variables and so on---plus machine status, while
12751 executable files contain only the program text and initialized data.)
12753 When you type @code{run}, your executable file becomes an active process
12754 target as well. When a process target is active, all @value{GDBN}
12755 commands requesting memory addresses refer to that target; addresses in
12756 an active core file or executable file target are obscured while the
12757 process target is active.
12759 Use the @code{core-file} and @code{exec-file} commands to select a new
12760 core file or executable target (@pxref{Files, ,Commands to Specify
12761 Files}). To specify as a target a process that is already running, use
12762 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12765 @node Target Commands
12766 @section Commands for Managing Targets
12769 @item target @var{type} @var{parameters}
12770 Connects the @value{GDBN} host environment to a target machine or
12771 process. A target is typically a protocol for talking to debugging
12772 facilities. You use the argument @var{type} to specify the type or
12773 protocol of the target machine.
12775 Further @var{parameters} are interpreted by the target protocol, but
12776 typically include things like device names or host names to connect
12777 with, process numbers, and baud rates.
12779 The @code{target} command does not repeat if you press @key{RET} again
12780 after executing the command.
12782 @kindex help target
12784 Displays the names of all targets available. To display targets
12785 currently selected, use either @code{info target} or @code{info files}
12786 (@pxref{Files, ,Commands to Specify Files}).
12788 @item help target @var{name}
12789 Describe a particular target, including any parameters necessary to
12792 @kindex set gnutarget
12793 @item set gnutarget @var{args}
12794 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12795 knows whether it is reading an @dfn{executable},
12796 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12797 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12798 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12801 @emph{Warning:} To specify a file format with @code{set gnutarget},
12802 you must know the actual BFD name.
12806 @xref{Files, , Commands to Specify Files}.
12808 @kindex show gnutarget
12809 @item show gnutarget
12810 Use the @code{show gnutarget} command to display what file format
12811 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12812 @value{GDBN} will determine the file format for each file automatically,
12813 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12816 @cindex common targets
12817 Here are some common targets (available, or not, depending on the GDB
12822 @item target exec @var{program}
12823 @cindex executable file target
12824 An executable file. @samp{target exec @var{program}} is the same as
12825 @samp{exec-file @var{program}}.
12827 @item target core @var{filename}
12828 @cindex core dump file target
12829 A core dump file. @samp{target core @var{filename}} is the same as
12830 @samp{core-file @var{filename}}.
12832 @item target remote @var{medium}
12833 @cindex remote target
12834 A remote system connected to @value{GDBN} via a serial line or network
12835 connection. This command tells @value{GDBN} to use its own remote
12836 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12838 For example, if you have a board connected to @file{/dev/ttya} on the
12839 machine running @value{GDBN}, you could say:
12842 target remote /dev/ttya
12845 @code{target remote} supports the @code{load} command. This is only
12846 useful if you have some other way of getting the stub to the target
12847 system, and you can put it somewhere in memory where it won't get
12848 clobbered by the download.
12851 @cindex built-in simulator target
12852 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12860 works; however, you cannot assume that a specific memory map, device
12861 drivers, or even basic I/O is available, although some simulators do
12862 provide these. For info about any processor-specific simulator details,
12863 see the appropriate section in @ref{Embedded Processors, ,Embedded
12868 Some configurations may include these targets as well:
12872 @item target nrom @var{dev}
12873 @cindex NetROM ROM emulator target
12874 NetROM ROM emulator. This target only supports downloading.
12878 Different targets are available on different configurations of @value{GDBN};
12879 your configuration may have more or fewer targets.
12881 Many remote targets require you to download the executable's code once
12882 you've successfully established a connection. You may wish to control
12883 various aspects of this process.
12888 @kindex set hash@r{, for remote monitors}
12889 @cindex hash mark while downloading
12890 This command controls whether a hash mark @samp{#} is displayed while
12891 downloading a file to the remote monitor. If on, a hash mark is
12892 displayed after each S-record is successfully downloaded to the
12896 @kindex show hash@r{, for remote monitors}
12897 Show the current status of displaying the hash mark.
12899 @item set debug monitor
12900 @kindex set debug monitor
12901 @cindex display remote monitor communications
12902 Enable or disable display of communications messages between
12903 @value{GDBN} and the remote monitor.
12905 @item show debug monitor
12906 @kindex show debug monitor
12907 Show the current status of displaying communications between
12908 @value{GDBN} and the remote monitor.
12913 @kindex load @var{filename}
12914 @item load @var{filename}
12916 Depending on what remote debugging facilities are configured into
12917 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12918 is meant to make @var{filename} (an executable) available for debugging
12919 on the remote system---by downloading, or dynamic linking, for example.
12920 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12921 the @code{add-symbol-file} command.
12923 If your @value{GDBN} does not have a @code{load} command, attempting to
12924 execute it gets the error message ``@code{You can't do that when your
12925 target is @dots{}}''
12927 The file is loaded at whatever address is specified in the executable.
12928 For some object file formats, you can specify the load address when you
12929 link the program; for other formats, like a.out, the object file format
12930 specifies a fixed address.
12931 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12933 Depending on the remote side capabilities, @value{GDBN} may be able to
12934 load programs into flash memory.
12936 @code{load} does not repeat if you press @key{RET} again after using it.
12940 @section Choosing Target Byte Order
12942 @cindex choosing target byte order
12943 @cindex target byte order
12945 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12946 offer the ability to run either big-endian or little-endian byte
12947 orders. Usually the executable or symbol will include a bit to
12948 designate the endian-ness, and you will not need to worry about
12949 which to use. However, you may still find it useful to adjust
12950 @value{GDBN}'s idea of processor endian-ness manually.
12954 @item set endian big
12955 Instruct @value{GDBN} to assume the target is big-endian.
12957 @item set endian little
12958 Instruct @value{GDBN} to assume the target is little-endian.
12960 @item set endian auto
12961 Instruct @value{GDBN} to use the byte order associated with the
12965 Display @value{GDBN}'s current idea of the target byte order.
12969 Note that these commands merely adjust interpretation of symbolic
12970 data on the host, and that they have absolutely no effect on the
12974 @node Remote Debugging
12975 @chapter Debugging Remote Programs
12976 @cindex remote debugging
12978 If you are trying to debug a program running on a machine that cannot run
12979 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12980 For example, you might use remote debugging on an operating system kernel,
12981 or on a small system which does not have a general purpose operating system
12982 powerful enough to run a full-featured debugger.
12984 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12985 to make this work with particular debugging targets. In addition,
12986 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12987 but not specific to any particular target system) which you can use if you
12988 write the remote stubs---the code that runs on the remote system to
12989 communicate with @value{GDBN}.
12991 Other remote targets may be available in your
12992 configuration of @value{GDBN}; use @code{help target} to list them.
12995 * Connecting:: Connecting to a remote target
12996 * File Transfer:: Sending files to a remote system
12997 * Server:: Using the gdbserver program
12998 * Remote Configuration:: Remote configuration
12999 * Remote Stub:: Implementing a remote stub
13003 @section Connecting to a Remote Target
13005 On the @value{GDBN} host machine, you will need an unstripped copy of
13006 your program, since @value{GDBN} needs symbol and debugging information.
13007 Start up @value{GDBN} as usual, using the name of the local copy of your
13008 program as the first argument.
13010 @cindex @code{target remote}
13011 @value{GDBN} can communicate with the target over a serial line, or
13012 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13013 each case, @value{GDBN} uses the same protocol for debugging your
13014 program; only the medium carrying the debugging packets varies. The
13015 @code{target remote} command establishes a connection to the target.
13016 Its arguments indicate which medium to use:
13020 @item target remote @var{serial-device}
13021 @cindex serial line, @code{target remote}
13022 Use @var{serial-device} to communicate with the target. For example,
13023 to use a serial line connected to the device named @file{/dev/ttyb}:
13026 target remote /dev/ttyb
13029 If you're using a serial line, you may want to give @value{GDBN} the
13030 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13031 (@pxref{Remote Configuration, set remotebaud}) before the
13032 @code{target} command.
13034 @item target remote @code{@var{host}:@var{port}}
13035 @itemx target remote @code{tcp:@var{host}:@var{port}}
13036 @cindex @acronym{TCP} port, @code{target remote}
13037 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13038 The @var{host} may be either a host name or a numeric @acronym{IP}
13039 address; @var{port} must be a decimal number. The @var{host} could be
13040 the target machine itself, if it is directly connected to the net, or
13041 it might be a terminal server which in turn has a serial line to the
13044 For example, to connect to port 2828 on a terminal server named
13048 target remote manyfarms:2828
13051 If your remote target is actually running on the same machine as your
13052 debugger session (e.g.@: a simulator for your target running on the
13053 same host), you can omit the hostname. For example, to connect to
13054 port 1234 on your local machine:
13057 target remote :1234
13061 Note that the colon is still required here.
13063 @item target remote @code{udp:@var{host}:@var{port}}
13064 @cindex @acronym{UDP} port, @code{target remote}
13065 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13066 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13069 target remote udp:manyfarms:2828
13072 When using a @acronym{UDP} connection for remote debugging, you should
13073 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13074 can silently drop packets on busy or unreliable networks, which will
13075 cause havoc with your debugging session.
13077 @item target remote | @var{command}
13078 @cindex pipe, @code{target remote} to
13079 Run @var{command} in the background and communicate with it using a
13080 pipe. The @var{command} is a shell command, to be parsed and expanded
13081 by the system's command shell, @code{/bin/sh}; it should expect remote
13082 protocol packets on its standard input, and send replies on its
13083 standard output. You could use this to run a stand-alone simulator
13084 that speaks the remote debugging protocol, to make net connections
13085 using programs like @code{ssh}, or for other similar tricks.
13087 If @var{command} closes its standard output (perhaps by exiting),
13088 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13089 program has already exited, this will have no effect.)
13093 Once the connection has been established, you can use all the usual
13094 commands to examine and change data. The remote program is already
13095 running; you can use @kbd{step} and @kbd{continue}, and you do not
13096 need to use @kbd{run}.
13098 @cindex interrupting remote programs
13099 @cindex remote programs, interrupting
13100 Whenever @value{GDBN} is waiting for the remote program, if you type the
13101 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13102 program. This may or may not succeed, depending in part on the hardware
13103 and the serial drivers the remote system uses. If you type the
13104 interrupt character once again, @value{GDBN} displays this prompt:
13107 Interrupted while waiting for the program.
13108 Give up (and stop debugging it)? (y or n)
13111 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13112 (If you decide you want to try again later, you can use @samp{target
13113 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13114 goes back to waiting.
13117 @kindex detach (remote)
13119 When you have finished debugging the remote program, you can use the
13120 @code{detach} command to release it from @value{GDBN} control.
13121 Detaching from the target normally resumes its execution, but the results
13122 will depend on your particular remote stub. After the @code{detach}
13123 command, @value{GDBN} is free to connect to another target.
13127 The @code{disconnect} command behaves like @code{detach}, except that
13128 the target is generally not resumed. It will wait for @value{GDBN}
13129 (this instance or another one) to connect and continue debugging. After
13130 the @code{disconnect} command, @value{GDBN} is again free to connect to
13133 @cindex send command to remote monitor
13134 @cindex extend @value{GDBN} for remote targets
13135 @cindex add new commands for external monitor
13137 @item monitor @var{cmd}
13138 This command allows you to send arbitrary commands directly to the
13139 remote monitor. Since @value{GDBN} doesn't care about the commands it
13140 sends like this, this command is the way to extend @value{GDBN}---you
13141 can add new commands that only the external monitor will understand
13145 @node File Transfer
13146 @section Sending files to a remote system
13147 @cindex remote target, file transfer
13148 @cindex file transfer
13149 @cindex sending files to remote systems
13151 Some remote targets offer the ability to transfer files over the same
13152 connection used to communicate with @value{GDBN}. This is convenient
13153 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13154 running @code{gdbserver} over a network interface. For other targets,
13155 e.g.@: embedded devices with only a single serial port, this may be
13156 the only way to upload or download files.
13158 Not all remote targets support these commands.
13162 @item remote put @var{hostfile} @var{targetfile}
13163 Copy file @var{hostfile} from the host system (the machine running
13164 @value{GDBN}) to @var{targetfile} on the target system.
13167 @item remote get @var{targetfile} @var{hostfile}
13168 Copy file @var{targetfile} from the target system to @var{hostfile}
13169 on the host system.
13171 @kindex remote delete
13172 @item remote delete @var{targetfile}
13173 Delete @var{targetfile} from the target system.
13178 @section Using the @code{gdbserver} Program
13181 @cindex remote connection without stubs
13182 @code{gdbserver} is a control program for Unix-like systems, which
13183 allows you to connect your program with a remote @value{GDBN} via
13184 @code{target remote}---but without linking in the usual debugging stub.
13186 @code{gdbserver} is not a complete replacement for the debugging stubs,
13187 because it requires essentially the same operating-system facilities
13188 that @value{GDBN} itself does. In fact, a system that can run
13189 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13190 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13191 because it is a much smaller program than @value{GDBN} itself. It is
13192 also easier to port than all of @value{GDBN}, so you may be able to get
13193 started more quickly on a new system by using @code{gdbserver}.
13194 Finally, if you develop code for real-time systems, you may find that
13195 the tradeoffs involved in real-time operation make it more convenient to
13196 do as much development work as possible on another system, for example
13197 by cross-compiling. You can use @code{gdbserver} to make a similar
13198 choice for debugging.
13200 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13201 or a TCP connection, using the standard @value{GDBN} remote serial
13205 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13206 Do not run @code{gdbserver} connected to any public network; a
13207 @value{GDBN} connection to @code{gdbserver} provides access to the
13208 target system with the same privileges as the user running
13212 @subsection Running @code{gdbserver}
13213 @cindex arguments, to @code{gdbserver}
13215 Run @code{gdbserver} on the target system. You need a copy of the
13216 program you want to debug, including any libraries it requires.
13217 @code{gdbserver} does not need your program's symbol table, so you can
13218 strip the program if necessary to save space. @value{GDBN} on the host
13219 system does all the symbol handling.
13221 To use the server, you must tell it how to communicate with @value{GDBN};
13222 the name of your program; and the arguments for your program. The usual
13226 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13229 @var{comm} is either a device name (to use a serial line) or a TCP
13230 hostname and portnumber. For example, to debug Emacs with the argument
13231 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13235 target> gdbserver /dev/com1 emacs foo.txt
13238 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13241 To use a TCP connection instead of a serial line:
13244 target> gdbserver host:2345 emacs foo.txt
13247 The only difference from the previous example is the first argument,
13248 specifying that you are communicating with the host @value{GDBN} via
13249 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13250 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13251 (Currently, the @samp{host} part is ignored.) You can choose any number
13252 you want for the port number as long as it does not conflict with any
13253 TCP ports already in use on the target system (for example, @code{23} is
13254 reserved for @code{telnet}).@footnote{If you choose a port number that
13255 conflicts with another service, @code{gdbserver} prints an error message
13256 and exits.} You must use the same port number with the host @value{GDBN}
13257 @code{target remote} command.
13259 @subsubsection Attaching to a Running Program
13261 On some targets, @code{gdbserver} can also attach to running programs.
13262 This is accomplished via the @code{--attach} argument. The syntax is:
13265 target> gdbserver --attach @var{comm} @var{pid}
13268 @var{pid} is the process ID of a currently running process. It isn't necessary
13269 to point @code{gdbserver} at a binary for the running process.
13272 @cindex attach to a program by name
13273 You can debug processes by name instead of process ID if your target has the
13274 @code{pidof} utility:
13277 target> gdbserver --attach @var{comm} `pidof @var{program}`
13280 In case more than one copy of @var{program} is running, or @var{program}
13281 has multiple threads, most versions of @code{pidof} support the
13282 @code{-s} option to only return the first process ID.
13284 @subsubsection Multi-Process Mode for @code{gdbserver}
13285 @cindex gdbserver, multiple processes
13286 @cindex multiple processes with gdbserver
13288 When you connect to @code{gdbserver} using @code{target remote},
13289 @code{gdbserver} debugs the specified program only once. When the
13290 program exits, or you detach from it, @value{GDBN} closes the connection
13291 and @code{gdbserver} exits.
13293 If you connect using @kbd{target extended-remote}, @code{gdbserver}
13294 enters multi-process mode. When the debugged program exits, or you
13295 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
13296 though no program is running. The @code{run} and @code{attach}
13297 commands instruct @code{gdbserver} to run or attach to a new program.
13298 The @code{run} command uses @code{set remote exec-file} (@pxref{set
13299 remote exec-file}) to select the program to run. Command line
13300 arguments are supported, except for wildcard expansion and I/O
13301 redirection (@pxref{Arguments}).
13303 To start @code{gdbserver} without supplying an initial command to run
13304 or process ID to attach, use the @option{--multi} command line option.
13305 Then you can connect using @kbd{target extended-remote} and start
13306 the program you want to debug.
13308 @code{gdbserver} does not automatically exit in multi-process mode.
13309 You can terminate it by using @code{monitor exit}
13310 (@pxref{Monitor Commands for gdbserver}).
13312 @subsubsection Other Command-Line Arguments for @code{gdbserver}
13314 You can include @option{--debug} on the @code{gdbserver} command line.
13315 @code{gdbserver} will display extra status information about the debugging
13316 process. This option is intended for @code{gdbserver} development and
13317 for bug reports to the developers.
13319 The @option{--wrapper} option specifies a wrapper to launch programs
13320 for debugging. The option should be followed by the name of the
13321 wrapper, then any command-line arguments to pass to the wrapper, then
13322 @kbd{--} indicating the end of the wrapper arguments.
13324 @code{gdbserver} runs the specified wrapper program with a combined
13325 command line including the wrapper arguments, then the name of the
13326 program to debug, then any arguments to the program. The wrapper
13327 runs until it executes your program, and then @value{GDBN} gains control.
13329 You can use any program that eventually calls @code{execve} with
13330 its arguments as a wrapper. Several standard Unix utilities do
13331 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
13332 with @code{exec "$@@"} will also work.
13334 For example, you can use @code{env} to pass an environment variable to
13335 the debugged program, without setting the variable in @code{gdbserver}'s
13339 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
13342 @subsection Connecting to @code{gdbserver}
13344 Run @value{GDBN} on the host system.
13346 First make sure you have the necessary symbol files. Load symbols for
13347 your application using the @code{file} command before you connect. Use
13348 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
13349 was compiled with the correct sysroot using @code{--with-sysroot}).
13351 The symbol file and target libraries must exactly match the executable
13352 and libraries on the target, with one exception: the files on the host
13353 system should not be stripped, even if the files on the target system
13354 are. Mismatched or missing files will lead to confusing results
13355 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
13356 files may also prevent @code{gdbserver} from debugging multi-threaded
13359 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
13360 For TCP connections, you must start up @code{gdbserver} prior to using
13361 the @code{target remote} command. Otherwise you may get an error whose
13362 text depends on the host system, but which usually looks something like
13363 @samp{Connection refused}. Don't use the @code{load}
13364 command in @value{GDBN} when using @code{gdbserver}, since the program is
13365 already on the target.
13367 @subsection Monitor Commands for @code{gdbserver}
13368 @cindex monitor commands, for @code{gdbserver}
13369 @anchor{Monitor Commands for gdbserver}
13371 During a @value{GDBN} session using @code{gdbserver}, you can use the
13372 @code{monitor} command to send special requests to @code{gdbserver}.
13373 Here are the available commands.
13377 List the available monitor commands.
13379 @item monitor set debug 0
13380 @itemx monitor set debug 1
13381 Disable or enable general debugging messages.
13383 @item monitor set remote-debug 0
13384 @itemx monitor set remote-debug 1
13385 Disable or enable specific debugging messages associated with the remote
13386 protocol (@pxref{Remote Protocol}).
13389 Tell gdbserver to exit immediately. This command should be followed by
13390 @code{disconnect} to close the debugging session. @code{gdbserver} will
13391 detach from any attached processes and kill any processes it created.
13392 Use @code{monitor exit} to terminate @code{gdbserver} at the end
13393 of a multi-process mode debug session.
13397 @node Remote Configuration
13398 @section Remote Configuration
13401 @kindex show remote
13402 This section documents the configuration options available when
13403 debugging remote programs. For the options related to the File I/O
13404 extensions of the remote protocol, see @ref{system,
13405 system-call-allowed}.
13408 @item set remoteaddresssize @var{bits}
13409 @cindex address size for remote targets
13410 @cindex bits in remote address
13411 Set the maximum size of address in a memory packet to the specified
13412 number of bits. @value{GDBN} will mask off the address bits above
13413 that number, when it passes addresses to the remote target. The
13414 default value is the number of bits in the target's address.
13416 @item show remoteaddresssize
13417 Show the current value of remote address size in bits.
13419 @item set remotebaud @var{n}
13420 @cindex baud rate for remote targets
13421 Set the baud rate for the remote serial I/O to @var{n} baud. The
13422 value is used to set the speed of the serial port used for debugging
13425 @item show remotebaud
13426 Show the current speed of the remote connection.
13428 @item set remotebreak
13429 @cindex interrupt remote programs
13430 @cindex BREAK signal instead of Ctrl-C
13431 @anchor{set remotebreak}
13432 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
13433 when you type @kbd{Ctrl-c} to interrupt the program running
13434 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
13435 character instead. The default is off, since most remote systems
13436 expect to see @samp{Ctrl-C} as the interrupt signal.
13438 @item show remotebreak
13439 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
13440 interrupt the remote program.
13442 @item set remoteflow on
13443 @itemx set remoteflow off
13444 @kindex set remoteflow
13445 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
13446 on the serial port used to communicate to the remote target.
13448 @item show remoteflow
13449 @kindex show remoteflow
13450 Show the current setting of hardware flow control.
13452 @item set remotelogbase @var{base}
13453 Set the base (a.k.a.@: radix) of logging serial protocol
13454 communications to @var{base}. Supported values of @var{base} are:
13455 @code{ascii}, @code{octal}, and @code{hex}. The default is
13458 @item show remotelogbase
13459 Show the current setting of the radix for logging remote serial
13462 @item set remotelogfile @var{file}
13463 @cindex record serial communications on file
13464 Record remote serial communications on the named @var{file}. The
13465 default is not to record at all.
13467 @item show remotelogfile.
13468 Show the current setting of the file name on which to record the
13469 serial communications.
13471 @item set remotetimeout @var{num}
13472 @cindex timeout for serial communications
13473 @cindex remote timeout
13474 Set the timeout limit to wait for the remote target to respond to
13475 @var{num} seconds. The default is 2 seconds.
13477 @item show remotetimeout
13478 Show the current number of seconds to wait for the remote target
13481 @cindex limit hardware breakpoints and watchpoints
13482 @cindex remote target, limit break- and watchpoints
13483 @anchor{set remote hardware-watchpoint-limit}
13484 @anchor{set remote hardware-breakpoint-limit}
13485 @item set remote hardware-watchpoint-limit @var{limit}
13486 @itemx set remote hardware-breakpoint-limit @var{limit}
13487 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
13488 watchpoints. A limit of -1, the default, is treated as unlimited.
13490 @item set remote exec-file @var{filename}
13491 @itemx show remote exec-file
13492 @anchor{set remote exec-file}
13493 @cindex executable file, for remote target
13494 Select the file used for @code{run} with @code{target
13495 extended-remote}. This should be set to a filename valid on the
13496 target system. If it is not set, the target will use a default
13497 filename (e.g.@: the last program run).
13500 @cindex remote packets, enabling and disabling
13501 The @value{GDBN} remote protocol autodetects the packets supported by
13502 your debugging stub. If you need to override the autodetection, you
13503 can use these commands to enable or disable individual packets. Each
13504 packet can be set to @samp{on} (the remote target supports this
13505 packet), @samp{off} (the remote target does not support this packet),
13506 or @samp{auto} (detect remote target support for this packet). They
13507 all default to @samp{auto}. For more information about each packet,
13508 see @ref{Remote Protocol}.
13510 During normal use, you should not have to use any of these commands.
13511 If you do, that may be a bug in your remote debugging stub, or a bug
13512 in @value{GDBN}. You may want to report the problem to the
13513 @value{GDBN} developers.
13515 For each packet @var{name}, the command to enable or disable the
13516 packet is @code{set remote @var{name}-packet}. The available settings
13519 @multitable @columnfractions 0.28 0.32 0.25
13522 @tab Related Features
13524 @item @code{fetch-register}
13526 @tab @code{info registers}
13528 @item @code{set-register}
13532 @item @code{binary-download}
13534 @tab @code{load}, @code{set}
13536 @item @code{read-aux-vector}
13537 @tab @code{qXfer:auxv:read}
13538 @tab @code{info auxv}
13540 @item @code{symbol-lookup}
13541 @tab @code{qSymbol}
13542 @tab Detecting multiple threads
13544 @item @code{attach}
13545 @tab @code{vAttach}
13548 @item @code{verbose-resume}
13550 @tab Stepping or resuming multiple threads
13556 @item @code{software-breakpoint}
13560 @item @code{hardware-breakpoint}
13564 @item @code{write-watchpoint}
13568 @item @code{read-watchpoint}
13572 @item @code{access-watchpoint}
13576 @item @code{target-features}
13577 @tab @code{qXfer:features:read}
13578 @tab @code{set architecture}
13580 @item @code{library-info}
13581 @tab @code{qXfer:libraries:read}
13582 @tab @code{info sharedlibrary}
13584 @item @code{memory-map}
13585 @tab @code{qXfer:memory-map:read}
13586 @tab @code{info mem}
13588 @item @code{read-spu-object}
13589 @tab @code{qXfer:spu:read}
13590 @tab @code{info spu}
13592 @item @code{write-spu-object}
13593 @tab @code{qXfer:spu:write}
13594 @tab @code{info spu}
13596 @item @code{get-thread-local-@*storage-address}
13597 @tab @code{qGetTLSAddr}
13598 @tab Displaying @code{__thread} variables
13600 @item @code{search-memory}
13601 @tab @code{qSearch:memory}
13604 @item @code{supported-packets}
13605 @tab @code{qSupported}
13606 @tab Remote communications parameters
13608 @item @code{pass-signals}
13609 @tab @code{QPassSignals}
13610 @tab @code{handle @var{signal}}
13612 @item @code{hostio-close-packet}
13613 @tab @code{vFile:close}
13614 @tab @code{remote get}, @code{remote put}
13616 @item @code{hostio-open-packet}
13617 @tab @code{vFile:open}
13618 @tab @code{remote get}, @code{remote put}
13620 @item @code{hostio-pread-packet}
13621 @tab @code{vFile:pread}
13622 @tab @code{remote get}, @code{remote put}
13624 @item @code{hostio-pwrite-packet}
13625 @tab @code{vFile:pwrite}
13626 @tab @code{remote get}, @code{remote put}
13628 @item @code{hostio-unlink-packet}
13629 @tab @code{vFile:unlink}
13630 @tab @code{remote delete}
13634 @section Implementing a Remote Stub
13636 @cindex debugging stub, example
13637 @cindex remote stub, example
13638 @cindex stub example, remote debugging
13639 The stub files provided with @value{GDBN} implement the target side of the
13640 communication protocol, and the @value{GDBN} side is implemented in the
13641 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13642 these subroutines to communicate, and ignore the details. (If you're
13643 implementing your own stub file, you can still ignore the details: start
13644 with one of the existing stub files. @file{sparc-stub.c} is the best
13645 organized, and therefore the easiest to read.)
13647 @cindex remote serial debugging, overview
13648 To debug a program running on another machine (the debugging
13649 @dfn{target} machine), you must first arrange for all the usual
13650 prerequisites for the program to run by itself. For example, for a C
13655 A startup routine to set up the C runtime environment; these usually
13656 have a name like @file{crt0}. The startup routine may be supplied by
13657 your hardware supplier, or you may have to write your own.
13660 A C subroutine library to support your program's
13661 subroutine calls, notably managing input and output.
13664 A way of getting your program to the other machine---for example, a
13665 download program. These are often supplied by the hardware
13666 manufacturer, but you may have to write your own from hardware
13670 The next step is to arrange for your program to use a serial port to
13671 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13672 machine). In general terms, the scheme looks like this:
13676 @value{GDBN} already understands how to use this protocol; when everything
13677 else is set up, you can simply use the @samp{target remote} command
13678 (@pxref{Targets,,Specifying a Debugging Target}).
13680 @item On the target,
13681 you must link with your program a few special-purpose subroutines that
13682 implement the @value{GDBN} remote serial protocol. The file containing these
13683 subroutines is called a @dfn{debugging stub}.
13685 On certain remote targets, you can use an auxiliary program
13686 @code{gdbserver} instead of linking a stub into your program.
13687 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13690 The debugging stub is specific to the architecture of the remote
13691 machine; for example, use @file{sparc-stub.c} to debug programs on
13694 @cindex remote serial stub list
13695 These working remote stubs are distributed with @value{GDBN}:
13700 @cindex @file{i386-stub.c}
13703 For Intel 386 and compatible architectures.
13706 @cindex @file{m68k-stub.c}
13707 @cindex Motorola 680x0
13709 For Motorola 680x0 architectures.
13712 @cindex @file{sh-stub.c}
13715 For Renesas SH architectures.
13718 @cindex @file{sparc-stub.c}
13720 For @sc{sparc} architectures.
13722 @item sparcl-stub.c
13723 @cindex @file{sparcl-stub.c}
13726 For Fujitsu @sc{sparclite} architectures.
13730 The @file{README} file in the @value{GDBN} distribution may list other
13731 recently added stubs.
13734 * Stub Contents:: What the stub can do for you
13735 * Bootstrapping:: What you must do for the stub
13736 * Debug Session:: Putting it all together
13739 @node Stub Contents
13740 @subsection What the Stub Can Do for You
13742 @cindex remote serial stub
13743 The debugging stub for your architecture supplies these three
13747 @item set_debug_traps
13748 @findex set_debug_traps
13749 @cindex remote serial stub, initialization
13750 This routine arranges for @code{handle_exception} to run when your
13751 program stops. You must call this subroutine explicitly near the
13752 beginning of your program.
13754 @item handle_exception
13755 @findex handle_exception
13756 @cindex remote serial stub, main routine
13757 This is the central workhorse, but your program never calls it
13758 explicitly---the setup code arranges for @code{handle_exception} to
13759 run when a trap is triggered.
13761 @code{handle_exception} takes control when your program stops during
13762 execution (for example, on a breakpoint), and mediates communications
13763 with @value{GDBN} on the host machine. This is where the communications
13764 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13765 representative on the target machine. It begins by sending summary
13766 information on the state of your program, then continues to execute,
13767 retrieving and transmitting any information @value{GDBN} needs, until you
13768 execute a @value{GDBN} command that makes your program resume; at that point,
13769 @code{handle_exception} returns control to your own code on the target
13773 @cindex @code{breakpoint} subroutine, remote
13774 Use this auxiliary subroutine to make your program contain a
13775 breakpoint. Depending on the particular situation, this may be the only
13776 way for @value{GDBN} to get control. For instance, if your target
13777 machine has some sort of interrupt button, you won't need to call this;
13778 pressing the interrupt button transfers control to
13779 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13780 simply receiving characters on the serial port may also trigger a trap;
13781 again, in that situation, you don't need to call @code{breakpoint} from
13782 your own program---simply running @samp{target remote} from the host
13783 @value{GDBN} session gets control.
13785 Call @code{breakpoint} if none of these is true, or if you simply want
13786 to make certain your program stops at a predetermined point for the
13787 start of your debugging session.
13790 @node Bootstrapping
13791 @subsection What You Must Do for the Stub
13793 @cindex remote stub, support routines
13794 The debugging stubs that come with @value{GDBN} are set up for a particular
13795 chip architecture, but they have no information about the rest of your
13796 debugging target machine.
13798 First of all you need to tell the stub how to communicate with the
13802 @item int getDebugChar()
13803 @findex getDebugChar
13804 Write this subroutine to read a single character from the serial port.
13805 It may be identical to @code{getchar} for your target system; a
13806 different name is used to allow you to distinguish the two if you wish.
13808 @item void putDebugChar(int)
13809 @findex putDebugChar
13810 Write this subroutine to write a single character to the serial port.
13811 It may be identical to @code{putchar} for your target system; a
13812 different name is used to allow you to distinguish the two if you wish.
13815 @cindex control C, and remote debugging
13816 @cindex interrupting remote targets
13817 If you want @value{GDBN} to be able to stop your program while it is
13818 running, you need to use an interrupt-driven serial driver, and arrange
13819 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13820 character). That is the character which @value{GDBN} uses to tell the
13821 remote system to stop.
13823 Getting the debugging target to return the proper status to @value{GDBN}
13824 probably requires changes to the standard stub; one quick and dirty way
13825 is to just execute a breakpoint instruction (the ``dirty'' part is that
13826 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13828 Other routines you need to supply are:
13831 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13832 @findex exceptionHandler
13833 Write this function to install @var{exception_address} in the exception
13834 handling tables. You need to do this because the stub does not have any
13835 way of knowing what the exception handling tables on your target system
13836 are like (for example, the processor's table might be in @sc{rom},
13837 containing entries which point to a table in @sc{ram}).
13838 @var{exception_number} is the exception number which should be changed;
13839 its meaning is architecture-dependent (for example, different numbers
13840 might represent divide by zero, misaligned access, etc). When this
13841 exception occurs, control should be transferred directly to
13842 @var{exception_address}, and the processor state (stack, registers,
13843 and so on) should be just as it is when a processor exception occurs. So if
13844 you want to use a jump instruction to reach @var{exception_address}, it
13845 should be a simple jump, not a jump to subroutine.
13847 For the 386, @var{exception_address} should be installed as an interrupt
13848 gate so that interrupts are masked while the handler runs. The gate
13849 should be at privilege level 0 (the most privileged level). The
13850 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13851 help from @code{exceptionHandler}.
13853 @item void flush_i_cache()
13854 @findex flush_i_cache
13855 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13856 instruction cache, if any, on your target machine. If there is no
13857 instruction cache, this subroutine may be a no-op.
13859 On target machines that have instruction caches, @value{GDBN} requires this
13860 function to make certain that the state of your program is stable.
13864 You must also make sure this library routine is available:
13867 @item void *memset(void *, int, int)
13869 This is the standard library function @code{memset} that sets an area of
13870 memory to a known value. If you have one of the free versions of
13871 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13872 either obtain it from your hardware manufacturer, or write your own.
13875 If you do not use the GNU C compiler, you may need other standard
13876 library subroutines as well; this varies from one stub to another,
13877 but in general the stubs are likely to use any of the common library
13878 subroutines which @code{@value{NGCC}} generates as inline code.
13881 @node Debug Session
13882 @subsection Putting it All Together
13884 @cindex remote serial debugging summary
13885 In summary, when your program is ready to debug, you must follow these
13890 Make sure you have defined the supporting low-level routines
13891 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13893 @code{getDebugChar}, @code{putDebugChar},
13894 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13898 Insert these lines near the top of your program:
13906 For the 680x0 stub only, you need to provide a variable called
13907 @code{exceptionHook}. Normally you just use:
13910 void (*exceptionHook)() = 0;
13914 but if before calling @code{set_debug_traps}, you set it to point to a
13915 function in your program, that function is called when
13916 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13917 error). The function indicated by @code{exceptionHook} is called with
13918 one parameter: an @code{int} which is the exception number.
13921 Compile and link together: your program, the @value{GDBN} debugging stub for
13922 your target architecture, and the supporting subroutines.
13925 Make sure you have a serial connection between your target machine and
13926 the @value{GDBN} host, and identify the serial port on the host.
13929 @c The "remote" target now provides a `load' command, so we should
13930 @c document that. FIXME.
13931 Download your program to your target machine (or get it there by
13932 whatever means the manufacturer provides), and start it.
13935 Start @value{GDBN} on the host, and connect to the target
13936 (@pxref{Connecting,,Connecting to a Remote Target}).
13940 @node Configurations
13941 @chapter Configuration-Specific Information
13943 While nearly all @value{GDBN} commands are available for all native and
13944 cross versions of the debugger, there are some exceptions. This chapter
13945 describes things that are only available in certain configurations.
13947 There are three major categories of configurations: native
13948 configurations, where the host and target are the same, embedded
13949 operating system configurations, which are usually the same for several
13950 different processor architectures, and bare embedded processors, which
13951 are quite different from each other.
13956 * Embedded Processors::
13963 This section describes details specific to particular native
13968 * BSD libkvm Interface:: Debugging BSD kernel memory images
13969 * SVR4 Process Information:: SVR4 process information
13970 * DJGPP Native:: Features specific to the DJGPP port
13971 * Cygwin Native:: Features specific to the Cygwin port
13972 * Hurd Native:: Features specific to @sc{gnu} Hurd
13973 * Neutrino:: Features specific to QNX Neutrino
13979 On HP-UX systems, if you refer to a function or variable name that
13980 begins with a dollar sign, @value{GDBN} searches for a user or system
13981 name first, before it searches for a convenience variable.
13984 @node BSD libkvm Interface
13985 @subsection BSD libkvm Interface
13988 @cindex kernel memory image
13989 @cindex kernel crash dump
13991 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13992 interface that provides a uniform interface for accessing kernel virtual
13993 memory images, including live systems and crash dumps. @value{GDBN}
13994 uses this interface to allow you to debug live kernels and kernel crash
13995 dumps on many native BSD configurations. This is implemented as a
13996 special @code{kvm} debugging target. For debugging a live system, load
13997 the currently running kernel into @value{GDBN} and connect to the
14001 (@value{GDBP}) @b{target kvm}
14004 For debugging crash dumps, provide the file name of the crash dump as an
14008 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14011 Once connected to the @code{kvm} target, the following commands are
14017 Set current context from the @dfn{Process Control Block} (PCB) address.
14020 Set current context from proc address. This command isn't available on
14021 modern FreeBSD systems.
14024 @node SVR4 Process Information
14025 @subsection SVR4 Process Information
14027 @cindex examine process image
14028 @cindex process info via @file{/proc}
14030 Many versions of SVR4 and compatible systems provide a facility called
14031 @samp{/proc} that can be used to examine the image of a running
14032 process using file-system subroutines. If @value{GDBN} is configured
14033 for an operating system with this facility, the command @code{info
14034 proc} is available to report information about the process running
14035 your program, or about any process running on your system. @code{info
14036 proc} works only on SVR4 systems that include the @code{procfs} code.
14037 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14038 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14044 @itemx info proc @var{process-id}
14045 Summarize available information about any running process. If a
14046 process ID is specified by @var{process-id}, display information about
14047 that process; otherwise display information about the program being
14048 debugged. The summary includes the debugged process ID, the command
14049 line used to invoke it, its current working directory, and its
14050 executable file's absolute file name.
14052 On some systems, @var{process-id} can be of the form
14053 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14054 within a process. If the optional @var{pid} part is missing, it means
14055 a thread from the process being debugged (the leading @samp{/} still
14056 needs to be present, or else @value{GDBN} will interpret the number as
14057 a process ID rather than a thread ID).
14059 @item info proc mappings
14060 @cindex memory address space mappings
14061 Report the memory address space ranges accessible in the program, with
14062 information on whether the process has read, write, or execute access
14063 rights to each range. On @sc{gnu}/Linux systems, each memory range
14064 includes the object file which is mapped to that range, instead of the
14065 memory access rights to that range.
14067 @item info proc stat
14068 @itemx info proc status
14069 @cindex process detailed status information
14070 These subcommands are specific to @sc{gnu}/Linux systems. They show
14071 the process-related information, including the user ID and group ID;
14072 how many threads are there in the process; its virtual memory usage;
14073 the signals that are pending, blocked, and ignored; its TTY; its
14074 consumption of system and user time; its stack size; its @samp{nice}
14075 value; etc. For more information, see the @samp{proc} man page
14076 (type @kbd{man 5 proc} from your shell prompt).
14078 @item info proc all
14079 Show all the information about the process described under all of the
14080 above @code{info proc} subcommands.
14083 @comment These sub-options of 'info proc' were not included when
14084 @comment procfs.c was re-written. Keep their descriptions around
14085 @comment against the day when someone finds the time to put them back in.
14086 @kindex info proc times
14087 @item info proc times
14088 Starting time, user CPU time, and system CPU time for your program and
14091 @kindex info proc id
14093 Report on the process IDs related to your program: its own process ID,
14094 the ID of its parent, the process group ID, and the session ID.
14097 @item set procfs-trace
14098 @kindex set procfs-trace
14099 @cindex @code{procfs} API calls
14100 This command enables and disables tracing of @code{procfs} API calls.
14102 @item show procfs-trace
14103 @kindex show procfs-trace
14104 Show the current state of @code{procfs} API call tracing.
14106 @item set procfs-file @var{file}
14107 @kindex set procfs-file
14108 Tell @value{GDBN} to write @code{procfs} API trace to the named
14109 @var{file}. @value{GDBN} appends the trace info to the previous
14110 contents of the file. The default is to display the trace on the
14113 @item show procfs-file
14114 @kindex show procfs-file
14115 Show the file to which @code{procfs} API trace is written.
14117 @item proc-trace-entry
14118 @itemx proc-trace-exit
14119 @itemx proc-untrace-entry
14120 @itemx proc-untrace-exit
14121 @kindex proc-trace-entry
14122 @kindex proc-trace-exit
14123 @kindex proc-untrace-entry
14124 @kindex proc-untrace-exit
14125 These commands enable and disable tracing of entries into and exits
14126 from the @code{syscall} interface.
14129 @kindex info pidlist
14130 @cindex process list, QNX Neutrino
14131 For QNX Neutrino only, this command displays the list of all the
14132 processes and all the threads within each process.
14135 @kindex info meminfo
14136 @cindex mapinfo list, QNX Neutrino
14137 For QNX Neutrino only, this command displays the list of all mapinfos.
14141 @subsection Features for Debugging @sc{djgpp} Programs
14142 @cindex @sc{djgpp} debugging
14143 @cindex native @sc{djgpp} debugging
14144 @cindex MS-DOS-specific commands
14147 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14148 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14149 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14150 top of real-mode DOS systems and their emulations.
14152 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14153 defines a few commands specific to the @sc{djgpp} port. This
14154 subsection describes those commands.
14159 This is a prefix of @sc{djgpp}-specific commands which print
14160 information about the target system and important OS structures.
14163 @cindex MS-DOS system info
14164 @cindex free memory information (MS-DOS)
14165 @item info dos sysinfo
14166 This command displays assorted information about the underlying
14167 platform: the CPU type and features, the OS version and flavor, the
14168 DPMI version, and the available conventional and DPMI memory.
14173 @cindex segment descriptor tables
14174 @cindex descriptor tables display
14176 @itemx info dos ldt
14177 @itemx info dos idt
14178 These 3 commands display entries from, respectively, Global, Local,
14179 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14180 tables are data structures which store a descriptor for each segment
14181 that is currently in use. The segment's selector is an index into a
14182 descriptor table; the table entry for that index holds the
14183 descriptor's base address and limit, and its attributes and access
14186 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14187 segment (used for both data and the stack), and a DOS segment (which
14188 allows access to DOS/BIOS data structures and absolute addresses in
14189 conventional memory). However, the DPMI host will usually define
14190 additional segments in order to support the DPMI environment.
14192 @cindex garbled pointers
14193 These commands allow to display entries from the descriptor tables.
14194 Without an argument, all entries from the specified table are
14195 displayed. An argument, which should be an integer expression, means
14196 display a single entry whose index is given by the argument. For
14197 example, here's a convenient way to display information about the
14198 debugged program's data segment:
14201 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14202 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14206 This comes in handy when you want to see whether a pointer is outside
14207 the data segment's limit (i.e.@: @dfn{garbled}).
14209 @cindex page tables display (MS-DOS)
14211 @itemx info dos pte
14212 These two commands display entries from, respectively, the Page
14213 Directory and the Page Tables. Page Directories and Page Tables are
14214 data structures which control how virtual memory addresses are mapped
14215 into physical addresses. A Page Table includes an entry for every
14216 page of memory that is mapped into the program's address space; there
14217 may be several Page Tables, each one holding up to 4096 entries. A
14218 Page Directory has up to 4096 entries, one each for every Page Table
14219 that is currently in use.
14221 Without an argument, @kbd{info dos pde} displays the entire Page
14222 Directory, and @kbd{info dos pte} displays all the entries in all of
14223 the Page Tables. An argument, an integer expression, given to the
14224 @kbd{info dos pde} command means display only that entry from the Page
14225 Directory table. An argument given to the @kbd{info dos pte} command
14226 means display entries from a single Page Table, the one pointed to by
14227 the specified entry in the Page Directory.
14229 @cindex direct memory access (DMA) on MS-DOS
14230 These commands are useful when your program uses @dfn{DMA} (Direct
14231 Memory Access), which needs physical addresses to program the DMA
14234 These commands are supported only with some DPMI servers.
14236 @cindex physical address from linear address
14237 @item info dos address-pte @var{addr}
14238 This command displays the Page Table entry for a specified linear
14239 address. The argument @var{addr} is a linear address which should
14240 already have the appropriate segment's base address added to it,
14241 because this command accepts addresses which may belong to @emph{any}
14242 segment. For example, here's how to display the Page Table entry for
14243 the page where a variable @code{i} is stored:
14246 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14247 @exdent @code{Page Table entry for address 0x11a00d30:}
14248 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14252 This says that @code{i} is stored at offset @code{0xd30} from the page
14253 whose physical base address is @code{0x02698000}, and shows all the
14254 attributes of that page.
14256 Note that you must cast the addresses of variables to a @code{char *},
14257 since otherwise the value of @code{__djgpp_base_address}, the base
14258 address of all variables and functions in a @sc{djgpp} program, will
14259 be added using the rules of C pointer arithmetics: if @code{i} is
14260 declared an @code{int}, @value{GDBN} will add 4 times the value of
14261 @code{__djgpp_base_address} to the address of @code{i}.
14263 Here's another example, it displays the Page Table entry for the
14267 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14268 @exdent @code{Page Table entry for address 0x29110:}
14269 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14273 (The @code{+ 3} offset is because the transfer buffer's address is the
14274 3rd member of the @code{_go32_info_block} structure.) The output
14275 clearly shows that this DPMI server maps the addresses in conventional
14276 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
14277 linear (@code{0x29110}) addresses are identical.
14279 This command is supported only with some DPMI servers.
14282 @cindex DOS serial data link, remote debugging
14283 In addition to native debugging, the DJGPP port supports remote
14284 debugging via a serial data link. The following commands are specific
14285 to remote serial debugging in the DJGPP port of @value{GDBN}.
14288 @kindex set com1base
14289 @kindex set com1irq
14290 @kindex set com2base
14291 @kindex set com2irq
14292 @kindex set com3base
14293 @kindex set com3irq
14294 @kindex set com4base
14295 @kindex set com4irq
14296 @item set com1base @var{addr}
14297 This command sets the base I/O port address of the @file{COM1} serial
14300 @item set com1irq @var{irq}
14301 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
14302 for the @file{COM1} serial port.
14304 There are similar commands @samp{set com2base}, @samp{set com3irq},
14305 etc.@: for setting the port address and the @code{IRQ} lines for the
14308 @kindex show com1base
14309 @kindex show com1irq
14310 @kindex show com2base
14311 @kindex show com2irq
14312 @kindex show com3base
14313 @kindex show com3irq
14314 @kindex show com4base
14315 @kindex show com4irq
14316 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
14317 display the current settings of the base address and the @code{IRQ}
14318 lines used by the COM ports.
14321 @kindex info serial
14322 @cindex DOS serial port status
14323 This command prints the status of the 4 DOS serial ports. For each
14324 port, it prints whether it's active or not, its I/O base address and
14325 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
14326 counts of various errors encountered so far.
14330 @node Cygwin Native
14331 @subsection Features for Debugging MS Windows PE Executables
14332 @cindex MS Windows debugging
14333 @cindex native Cygwin debugging
14334 @cindex Cygwin-specific commands
14336 @value{GDBN} supports native debugging of MS Windows programs, including
14337 DLLs with and without symbolic debugging information. There are various
14338 additional Cygwin-specific commands, described in this section.
14339 Working with DLLs that have no debugging symbols is described in
14340 @ref{Non-debug DLL Symbols}.
14345 This is a prefix of MS Windows-specific commands which print
14346 information about the target system and important OS structures.
14348 @item info w32 selector
14349 This command displays information returned by
14350 the Win32 API @code{GetThreadSelectorEntry} function.
14351 It takes an optional argument that is evaluated to
14352 a long value to give the information about this given selector.
14353 Without argument, this command displays information
14354 about the six segment registers.
14358 This is a Cygwin-specific alias of @code{info shared}.
14360 @kindex dll-symbols
14362 This command loads symbols from a dll similarly to
14363 add-sym command but without the need to specify a base address.
14365 @kindex set cygwin-exceptions
14366 @cindex debugging the Cygwin DLL
14367 @cindex Cygwin DLL, debugging
14368 @item set cygwin-exceptions @var{mode}
14369 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
14370 happen inside the Cygwin DLL. If @var{mode} is @code{off},
14371 @value{GDBN} will delay recognition of exceptions, and may ignore some
14372 exceptions which seem to be caused by internal Cygwin DLL
14373 ``bookkeeping''. This option is meant primarily for debugging the
14374 Cygwin DLL itself; the default value is @code{off} to avoid annoying
14375 @value{GDBN} users with false @code{SIGSEGV} signals.
14377 @kindex show cygwin-exceptions
14378 @item show cygwin-exceptions
14379 Displays whether @value{GDBN} will break on exceptions that happen
14380 inside the Cygwin DLL itself.
14382 @kindex set new-console
14383 @item set new-console @var{mode}
14384 If @var{mode} is @code{on} the debuggee will
14385 be started in a new console on next start.
14386 If @var{mode} is @code{off}i, the debuggee will
14387 be started in the same console as the debugger.
14389 @kindex show new-console
14390 @item show new-console
14391 Displays whether a new console is used
14392 when the debuggee is started.
14394 @kindex set new-group
14395 @item set new-group @var{mode}
14396 This boolean value controls whether the debuggee should
14397 start a new group or stay in the same group as the debugger.
14398 This affects the way the Windows OS handles
14401 @kindex show new-group
14402 @item show new-group
14403 Displays current value of new-group boolean.
14405 @kindex set debugevents
14406 @item set debugevents
14407 This boolean value adds debug output concerning kernel events related
14408 to the debuggee seen by the debugger. This includes events that
14409 signal thread and process creation and exit, DLL loading and
14410 unloading, console interrupts, and debugging messages produced by the
14411 Windows @code{OutputDebugString} API call.
14413 @kindex set debugexec
14414 @item set debugexec
14415 This boolean value adds debug output concerning execute events
14416 (such as resume thread) seen by the debugger.
14418 @kindex set debugexceptions
14419 @item set debugexceptions
14420 This boolean value adds debug output concerning exceptions in the
14421 debuggee seen by the debugger.
14423 @kindex set debugmemory
14424 @item set debugmemory
14425 This boolean value adds debug output concerning debuggee memory reads
14426 and writes by the debugger.
14430 This boolean values specifies whether the debuggee is called
14431 via a shell or directly (default value is on).
14435 Displays if the debuggee will be started with a shell.
14440 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
14443 @node Non-debug DLL Symbols
14444 @subsubsection Support for DLLs without Debugging Symbols
14445 @cindex DLLs with no debugging symbols
14446 @cindex Minimal symbols and DLLs
14448 Very often on windows, some of the DLLs that your program relies on do
14449 not include symbolic debugging information (for example,
14450 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
14451 symbols in a DLL, it relies on the minimal amount of symbolic
14452 information contained in the DLL's export table. This section
14453 describes working with such symbols, known internally to @value{GDBN} as
14454 ``minimal symbols''.
14456 Note that before the debugged program has started execution, no DLLs
14457 will have been loaded. The easiest way around this problem is simply to
14458 start the program --- either by setting a breakpoint or letting the
14459 program run once to completion. It is also possible to force
14460 @value{GDBN} to load a particular DLL before starting the executable ---
14461 see the shared library information in @ref{Files}, or the
14462 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
14463 explicitly loading symbols from a DLL with no debugging information will
14464 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
14465 which may adversely affect symbol lookup performance.
14467 @subsubsection DLL Name Prefixes
14469 In keeping with the naming conventions used by the Microsoft debugging
14470 tools, DLL export symbols are made available with a prefix based on the
14471 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
14472 also entered into the symbol table, so @code{CreateFileA} is often
14473 sufficient. In some cases there will be name clashes within a program
14474 (particularly if the executable itself includes full debugging symbols)
14475 necessitating the use of the fully qualified name when referring to the
14476 contents of the DLL. Use single-quotes around the name to avoid the
14477 exclamation mark (``!'') being interpreted as a language operator.
14479 Note that the internal name of the DLL may be all upper-case, even
14480 though the file name of the DLL is lower-case, or vice-versa. Since
14481 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
14482 some confusion. If in doubt, try the @code{info functions} and
14483 @code{info variables} commands or even @code{maint print msymbols}
14484 (@pxref{Symbols}). Here's an example:
14487 (@value{GDBP}) info function CreateFileA
14488 All functions matching regular expression "CreateFileA":
14490 Non-debugging symbols:
14491 0x77e885f4 CreateFileA
14492 0x77e885f4 KERNEL32!CreateFileA
14496 (@value{GDBP}) info function !
14497 All functions matching regular expression "!":
14499 Non-debugging symbols:
14500 0x6100114c cygwin1!__assert
14501 0x61004034 cygwin1!_dll_crt0@@0
14502 0x61004240 cygwin1!dll_crt0(per_process *)
14506 @subsubsection Working with Minimal Symbols
14508 Symbols extracted from a DLL's export table do not contain very much
14509 type information. All that @value{GDBN} can do is guess whether a symbol
14510 refers to a function or variable depending on the linker section that
14511 contains the symbol. Also note that the actual contents of the memory
14512 contained in a DLL are not available unless the program is running. This
14513 means that you cannot examine the contents of a variable or disassemble
14514 a function within a DLL without a running program.
14516 Variables are generally treated as pointers and dereferenced
14517 automatically. For this reason, it is often necessary to prefix a
14518 variable name with the address-of operator (``&'') and provide explicit
14519 type information in the command. Here's an example of the type of
14523 (@value{GDBP}) print 'cygwin1!__argv'
14528 (@value{GDBP}) x 'cygwin1!__argv'
14529 0x10021610: "\230y\""
14532 And two possible solutions:
14535 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14536 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14540 (@value{GDBP}) x/2x &'cygwin1!__argv'
14541 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14542 (@value{GDBP}) x/x 0x10021608
14543 0x10021608: 0x0022fd98
14544 (@value{GDBP}) x/s 0x0022fd98
14545 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14548 Setting a break point within a DLL is possible even before the program
14549 starts execution. However, under these circumstances, @value{GDBN} can't
14550 examine the initial instructions of the function in order to skip the
14551 function's frame set-up code. You can work around this by using ``*&''
14552 to set the breakpoint at a raw memory address:
14555 (@value{GDBP}) break *&'python22!PyOS_Readline'
14556 Breakpoint 1 at 0x1e04eff0
14559 The author of these extensions is not entirely convinced that setting a
14560 break point within a shared DLL like @file{kernel32.dll} is completely
14564 @subsection Commands Specific to @sc{gnu} Hurd Systems
14565 @cindex @sc{gnu} Hurd debugging
14567 This subsection describes @value{GDBN} commands specific to the
14568 @sc{gnu} Hurd native debugging.
14573 @kindex set signals@r{, Hurd command}
14574 @kindex set sigs@r{, Hurd command}
14575 This command toggles the state of inferior signal interception by
14576 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14577 affected by this command. @code{sigs} is a shorthand alias for
14582 @kindex show signals@r{, Hurd command}
14583 @kindex show sigs@r{, Hurd command}
14584 Show the current state of intercepting inferior's signals.
14586 @item set signal-thread
14587 @itemx set sigthread
14588 @kindex set signal-thread
14589 @kindex set sigthread
14590 This command tells @value{GDBN} which thread is the @code{libc} signal
14591 thread. That thread is run when a signal is delivered to a running
14592 process. @code{set sigthread} is the shorthand alias of @code{set
14595 @item show signal-thread
14596 @itemx show sigthread
14597 @kindex show signal-thread
14598 @kindex show sigthread
14599 These two commands show which thread will run when the inferior is
14600 delivered a signal.
14603 @kindex set stopped@r{, Hurd command}
14604 This commands tells @value{GDBN} that the inferior process is stopped,
14605 as with the @code{SIGSTOP} signal. The stopped process can be
14606 continued by delivering a signal to it.
14609 @kindex show stopped@r{, Hurd command}
14610 This command shows whether @value{GDBN} thinks the debuggee is
14613 @item set exceptions
14614 @kindex set exceptions@r{, Hurd command}
14615 Use this command to turn off trapping of exceptions in the inferior.
14616 When exception trapping is off, neither breakpoints nor
14617 single-stepping will work. To restore the default, set exception
14620 @item show exceptions
14621 @kindex show exceptions@r{, Hurd command}
14622 Show the current state of trapping exceptions in the inferior.
14624 @item set task pause
14625 @kindex set task@r{, Hurd commands}
14626 @cindex task attributes (@sc{gnu} Hurd)
14627 @cindex pause current task (@sc{gnu} Hurd)
14628 This command toggles task suspension when @value{GDBN} has control.
14629 Setting it to on takes effect immediately, and the task is suspended
14630 whenever @value{GDBN} gets control. Setting it to off will take
14631 effect the next time the inferior is continued. If this option is set
14632 to off, you can use @code{set thread default pause on} or @code{set
14633 thread pause on} (see below) to pause individual threads.
14635 @item show task pause
14636 @kindex show task@r{, Hurd commands}
14637 Show the current state of task suspension.
14639 @item set task detach-suspend-count
14640 @cindex task suspend count
14641 @cindex detach from task, @sc{gnu} Hurd
14642 This command sets the suspend count the task will be left with when
14643 @value{GDBN} detaches from it.
14645 @item show task detach-suspend-count
14646 Show the suspend count the task will be left with when detaching.
14648 @item set task exception-port
14649 @itemx set task excp
14650 @cindex task exception port, @sc{gnu} Hurd
14651 This command sets the task exception port to which @value{GDBN} will
14652 forward exceptions. The argument should be the value of the @dfn{send
14653 rights} of the task. @code{set task excp} is a shorthand alias.
14655 @item set noninvasive
14656 @cindex noninvasive task options
14657 This command switches @value{GDBN} to a mode that is the least
14658 invasive as far as interfering with the inferior is concerned. This
14659 is the same as using @code{set task pause}, @code{set exceptions}, and
14660 @code{set signals} to values opposite to the defaults.
14662 @item info send-rights
14663 @itemx info receive-rights
14664 @itemx info port-rights
14665 @itemx info port-sets
14666 @itemx info dead-names
14669 @cindex send rights, @sc{gnu} Hurd
14670 @cindex receive rights, @sc{gnu} Hurd
14671 @cindex port rights, @sc{gnu} Hurd
14672 @cindex port sets, @sc{gnu} Hurd
14673 @cindex dead names, @sc{gnu} Hurd
14674 These commands display information about, respectively, send rights,
14675 receive rights, port rights, port sets, and dead names of a task.
14676 There are also shorthand aliases: @code{info ports} for @code{info
14677 port-rights} and @code{info psets} for @code{info port-sets}.
14679 @item set thread pause
14680 @kindex set thread@r{, Hurd command}
14681 @cindex thread properties, @sc{gnu} Hurd
14682 @cindex pause current thread (@sc{gnu} Hurd)
14683 This command toggles current thread suspension when @value{GDBN} has
14684 control. Setting it to on takes effect immediately, and the current
14685 thread is suspended whenever @value{GDBN} gets control. Setting it to
14686 off will take effect the next time the inferior is continued.
14687 Normally, this command has no effect, since when @value{GDBN} has
14688 control, the whole task is suspended. However, if you used @code{set
14689 task pause off} (see above), this command comes in handy to suspend
14690 only the current thread.
14692 @item show thread pause
14693 @kindex show thread@r{, Hurd command}
14694 This command shows the state of current thread suspension.
14696 @item set thread run
14697 This command sets whether the current thread is allowed to run.
14699 @item show thread run
14700 Show whether the current thread is allowed to run.
14702 @item set thread detach-suspend-count
14703 @cindex thread suspend count, @sc{gnu} Hurd
14704 @cindex detach from thread, @sc{gnu} Hurd
14705 This command sets the suspend count @value{GDBN} will leave on a
14706 thread when detaching. This number is relative to the suspend count
14707 found by @value{GDBN} when it notices the thread; use @code{set thread
14708 takeover-suspend-count} to force it to an absolute value.
14710 @item show thread detach-suspend-count
14711 Show the suspend count @value{GDBN} will leave on the thread when
14714 @item set thread exception-port
14715 @itemx set thread excp
14716 Set the thread exception port to which to forward exceptions. This
14717 overrides the port set by @code{set task exception-port} (see above).
14718 @code{set thread excp} is the shorthand alias.
14720 @item set thread takeover-suspend-count
14721 Normally, @value{GDBN}'s thread suspend counts are relative to the
14722 value @value{GDBN} finds when it notices each thread. This command
14723 changes the suspend counts to be absolute instead.
14725 @item set thread default
14726 @itemx show thread default
14727 @cindex thread default settings, @sc{gnu} Hurd
14728 Each of the above @code{set thread} commands has a @code{set thread
14729 default} counterpart (e.g., @code{set thread default pause}, @code{set
14730 thread default exception-port}, etc.). The @code{thread default}
14731 variety of commands sets the default thread properties for all
14732 threads; you can then change the properties of individual threads with
14733 the non-default commands.
14738 @subsection QNX Neutrino
14739 @cindex QNX Neutrino
14741 @value{GDBN} provides the following commands specific to the QNX
14745 @item set debug nto-debug
14746 @kindex set debug nto-debug
14747 When set to on, enables debugging messages specific to the QNX
14750 @item show debug nto-debug
14751 @kindex show debug nto-debug
14752 Show the current state of QNX Neutrino messages.
14757 @section Embedded Operating Systems
14759 This section describes configurations involving the debugging of
14760 embedded operating systems that are available for several different
14764 * VxWorks:: Using @value{GDBN} with VxWorks
14767 @value{GDBN} includes the ability to debug programs running on
14768 various real-time operating systems.
14771 @subsection Using @value{GDBN} with VxWorks
14777 @kindex target vxworks
14778 @item target vxworks @var{machinename}
14779 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14780 is the target system's machine name or IP address.
14784 On VxWorks, @code{load} links @var{filename} dynamically on the
14785 current target system as well as adding its symbols in @value{GDBN}.
14787 @value{GDBN} enables developers to spawn and debug tasks running on networked
14788 VxWorks targets from a Unix host. Already-running tasks spawned from
14789 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14790 both the Unix host and on the VxWorks target. The program
14791 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14792 installed with the name @code{vxgdb}, to distinguish it from a
14793 @value{GDBN} for debugging programs on the host itself.)
14796 @item VxWorks-timeout @var{args}
14797 @kindex vxworks-timeout
14798 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14799 This option is set by the user, and @var{args} represents the number of
14800 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14801 your VxWorks target is a slow software simulator or is on the far side
14802 of a thin network line.
14805 The following information on connecting to VxWorks was current when
14806 this manual was produced; newer releases of VxWorks may use revised
14809 @findex INCLUDE_RDB
14810 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14811 to include the remote debugging interface routines in the VxWorks
14812 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14813 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14814 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14815 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14816 information on configuring and remaking VxWorks, see the manufacturer's
14818 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14820 Once you have included @file{rdb.a} in your VxWorks system image and set
14821 your Unix execution search path to find @value{GDBN}, you are ready to
14822 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14823 @code{vxgdb}, depending on your installation).
14825 @value{GDBN} comes up showing the prompt:
14832 * VxWorks Connection:: Connecting to VxWorks
14833 * VxWorks Download:: VxWorks download
14834 * VxWorks Attach:: Running tasks
14837 @node VxWorks Connection
14838 @subsubsection Connecting to VxWorks
14840 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14841 network. To connect to a target whose host name is ``@code{tt}'', type:
14844 (vxgdb) target vxworks tt
14848 @value{GDBN} displays messages like these:
14851 Attaching remote machine across net...
14856 @value{GDBN} then attempts to read the symbol tables of any object modules
14857 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14858 these files by searching the directories listed in the command search
14859 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14860 to find an object file, it displays a message such as:
14863 prog.o: No such file or directory.
14866 When this happens, add the appropriate directory to the search path with
14867 the @value{GDBN} command @code{path}, and execute the @code{target}
14870 @node VxWorks Download
14871 @subsubsection VxWorks Download
14873 @cindex download to VxWorks
14874 If you have connected to the VxWorks target and you want to debug an
14875 object that has not yet been loaded, you can use the @value{GDBN}
14876 @code{load} command to download a file from Unix to VxWorks
14877 incrementally. The object file given as an argument to the @code{load}
14878 command is actually opened twice: first by the VxWorks target in order
14879 to download the code, then by @value{GDBN} in order to read the symbol
14880 table. This can lead to problems if the current working directories on
14881 the two systems differ. If both systems have NFS mounted the same
14882 filesystems, you can avoid these problems by using absolute paths.
14883 Otherwise, it is simplest to set the working directory on both systems
14884 to the directory in which the object file resides, and then to reference
14885 the file by its name, without any path. For instance, a program
14886 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14887 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14888 program, type this on VxWorks:
14891 -> cd "@var{vxpath}/vw/demo/rdb"
14895 Then, in @value{GDBN}, type:
14898 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14899 (vxgdb) load prog.o
14902 @value{GDBN} displays a response similar to this:
14905 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14908 You can also use the @code{load} command to reload an object module
14909 after editing and recompiling the corresponding source file. Note that
14910 this makes @value{GDBN} delete all currently-defined breakpoints,
14911 auto-displays, and convenience variables, and to clear the value
14912 history. (This is necessary in order to preserve the integrity of
14913 debugger's data structures that reference the target system's symbol
14916 @node VxWorks Attach
14917 @subsubsection Running Tasks
14919 @cindex running VxWorks tasks
14920 You can also attach to an existing task using the @code{attach} command as
14924 (vxgdb) attach @var{task}
14928 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14929 or suspended when you attach to it. Running tasks are suspended at
14930 the time of attachment.
14932 @node Embedded Processors
14933 @section Embedded Processors
14935 This section goes into details specific to particular embedded
14938 @cindex send command to simulator
14939 Whenever a specific embedded processor has a simulator, @value{GDBN}
14940 allows to send an arbitrary command to the simulator.
14943 @item sim @var{command}
14944 @kindex sim@r{, a command}
14945 Send an arbitrary @var{command} string to the simulator. Consult the
14946 documentation for the specific simulator in use for information about
14947 acceptable commands.
14953 * M32R/D:: Renesas M32R/D
14954 * M68K:: Motorola M68K
14955 * MIPS Embedded:: MIPS Embedded
14956 * OpenRISC 1000:: OpenRisc 1000
14957 * PA:: HP PA Embedded
14958 * PowerPC Embedded:: PowerPC Embedded
14959 * Sparclet:: Tsqware Sparclet
14960 * Sparclite:: Fujitsu Sparclite
14961 * Z8000:: Zilog Z8000
14964 * Super-H:: Renesas Super-H
14973 @item target rdi @var{dev}
14974 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14975 use this target to communicate with both boards running the Angel
14976 monitor, or with the EmbeddedICE JTAG debug device.
14979 @item target rdp @var{dev}
14984 @value{GDBN} provides the following ARM-specific commands:
14987 @item set arm disassembler
14989 This commands selects from a list of disassembly styles. The
14990 @code{"std"} style is the standard style.
14992 @item show arm disassembler
14994 Show the current disassembly style.
14996 @item set arm apcs32
14997 @cindex ARM 32-bit mode
14998 This command toggles ARM operation mode between 32-bit and 26-bit.
15000 @item show arm apcs32
15001 Display the current usage of the ARM 32-bit mode.
15003 @item set arm fpu @var{fputype}
15004 This command sets the ARM floating-point unit (FPU) type. The
15005 argument @var{fputype} can be one of these:
15009 Determine the FPU type by querying the OS ABI.
15011 Software FPU, with mixed-endian doubles on little-endian ARM
15014 GCC-compiled FPA co-processor.
15016 Software FPU with pure-endian doubles.
15022 Show the current type of the FPU.
15025 This command forces @value{GDBN} to use the specified ABI.
15028 Show the currently used ABI.
15030 @item set arm fallback-mode (arm|thumb|auto)
15031 @value{GDBN} uses the symbol table, when available, to determine
15032 whether instructions are ARM or Thumb. This command controls
15033 @value{GDBN}'s default behavior when the symbol table is not
15034 available. The default is @samp{auto}, which causes @value{GDBN} to
15035 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15038 @item show arm fallback-mode
15039 Show the current fallback instruction mode.
15041 @item set arm force-mode (arm|thumb|auto)
15042 This command overrides use of the symbol table to determine whether
15043 instructions are ARM or Thumb. The default is @samp{auto}, which
15044 causes @value{GDBN} to use the symbol table and then the setting
15045 of @samp{set arm fallback-mode}.
15047 @item show arm force-mode
15048 Show the current forced instruction mode.
15050 @item set debug arm
15051 Toggle whether to display ARM-specific debugging messages from the ARM
15052 target support subsystem.
15054 @item show debug arm
15055 Show whether ARM-specific debugging messages are enabled.
15058 The following commands are available when an ARM target is debugged
15059 using the RDI interface:
15062 @item rdilogfile @r{[}@var{file}@r{]}
15064 @cindex ADP (Angel Debugger Protocol) logging
15065 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15066 With an argument, sets the log file to the specified @var{file}. With
15067 no argument, show the current log file name. The default log file is
15070 @item rdilogenable @r{[}@var{arg}@r{]}
15071 @kindex rdilogenable
15072 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15073 enables logging, with an argument 0 or @code{"no"} disables it. With
15074 no arguments displays the current setting. When logging is enabled,
15075 ADP packets exchanged between @value{GDBN} and the RDI target device
15076 are logged to a file.
15078 @item set rdiromatzero
15079 @kindex set rdiromatzero
15080 @cindex ROM at zero address, RDI
15081 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15082 vector catching is disabled, so that zero address can be used. If off
15083 (the default), vector catching is enabled. For this command to take
15084 effect, it needs to be invoked prior to the @code{target rdi} command.
15086 @item show rdiromatzero
15087 @kindex show rdiromatzero
15088 Show the current setting of ROM at zero address.
15090 @item set rdiheartbeat
15091 @kindex set rdiheartbeat
15092 @cindex RDI heartbeat
15093 Enable or disable RDI heartbeat packets. It is not recommended to
15094 turn on this option, since it confuses ARM and EPI JTAG interface, as
15095 well as the Angel monitor.
15097 @item show rdiheartbeat
15098 @kindex show rdiheartbeat
15099 Show the setting of RDI heartbeat packets.
15104 @subsection Renesas M32R/D and M32R/SDI
15107 @kindex target m32r
15108 @item target m32r @var{dev}
15109 Renesas M32R/D ROM monitor.
15111 @kindex target m32rsdi
15112 @item target m32rsdi @var{dev}
15113 Renesas M32R SDI server, connected via parallel port to the board.
15116 The following @value{GDBN} commands are specific to the M32R monitor:
15119 @item set download-path @var{path}
15120 @kindex set download-path
15121 @cindex find downloadable @sc{srec} files (M32R)
15122 Set the default path for finding downloadable @sc{srec} files.
15124 @item show download-path
15125 @kindex show download-path
15126 Show the default path for downloadable @sc{srec} files.
15128 @item set board-address @var{addr}
15129 @kindex set board-address
15130 @cindex M32-EVA target board address
15131 Set the IP address for the M32R-EVA target board.
15133 @item show board-address
15134 @kindex show board-address
15135 Show the current IP address of the target board.
15137 @item set server-address @var{addr}
15138 @kindex set server-address
15139 @cindex download server address (M32R)
15140 Set the IP address for the download server, which is the @value{GDBN}'s
15143 @item show server-address
15144 @kindex show server-address
15145 Display the IP address of the download server.
15147 @item upload @r{[}@var{file}@r{]}
15148 @kindex upload@r{, M32R}
15149 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
15150 upload capability. If no @var{file} argument is given, the current
15151 executable file is uploaded.
15153 @item tload @r{[}@var{file}@r{]}
15154 @kindex tload@r{, M32R}
15155 Test the @code{upload} command.
15158 The following commands are available for M32R/SDI:
15163 @cindex reset SDI connection, M32R
15164 This command resets the SDI connection.
15168 This command shows the SDI connection status.
15171 @kindex debug_chaos
15172 @cindex M32R/Chaos debugging
15173 Instructs the remote that M32R/Chaos debugging is to be used.
15175 @item use_debug_dma
15176 @kindex use_debug_dma
15177 Instructs the remote to use the DEBUG_DMA method of accessing memory.
15180 @kindex use_mon_code
15181 Instructs the remote to use the MON_CODE method of accessing memory.
15184 @kindex use_ib_break
15185 Instructs the remote to set breakpoints by IB break.
15187 @item use_dbt_break
15188 @kindex use_dbt_break
15189 Instructs the remote to set breakpoints by DBT.
15195 The Motorola m68k configuration includes ColdFire support, and a
15196 target command for the following ROM monitor.
15200 @kindex target dbug
15201 @item target dbug @var{dev}
15202 dBUG ROM monitor for Motorola ColdFire.
15206 @node MIPS Embedded
15207 @subsection MIPS Embedded
15209 @cindex MIPS boards
15210 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15211 MIPS board attached to a serial line. This is available when
15212 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15215 Use these @value{GDBN} commands to specify the connection to your target board:
15218 @item target mips @var{port}
15219 @kindex target mips @var{port}
15220 To run a program on the board, start up @code{@value{GDBP}} with the
15221 name of your program as the argument. To connect to the board, use the
15222 command @samp{target mips @var{port}}, where @var{port} is the name of
15223 the serial port connected to the board. If the program has not already
15224 been downloaded to the board, you may use the @code{load} command to
15225 download it. You can then use all the usual @value{GDBN} commands.
15227 For example, this sequence connects to the target board through a serial
15228 port, and loads and runs a program called @var{prog} through the
15232 host$ @value{GDBP} @var{prog}
15233 @value{GDBN} is free software and @dots{}
15234 (@value{GDBP}) target mips /dev/ttyb
15235 (@value{GDBP}) load @var{prog}
15239 @item target mips @var{hostname}:@var{portnumber}
15240 On some @value{GDBN} host configurations, you can specify a TCP
15241 connection (for instance, to a serial line managed by a terminal
15242 concentrator) instead of a serial port, using the syntax
15243 @samp{@var{hostname}:@var{portnumber}}.
15245 @item target pmon @var{port}
15246 @kindex target pmon @var{port}
15249 @item target ddb @var{port}
15250 @kindex target ddb @var{port}
15251 NEC's DDB variant of PMON for Vr4300.
15253 @item target lsi @var{port}
15254 @kindex target lsi @var{port}
15255 LSI variant of PMON.
15257 @kindex target r3900
15258 @item target r3900 @var{dev}
15259 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
15261 @kindex target array
15262 @item target array @var{dev}
15263 Array Tech LSI33K RAID controller board.
15269 @value{GDBN} also supports these special commands for MIPS targets:
15272 @item set mipsfpu double
15273 @itemx set mipsfpu single
15274 @itemx set mipsfpu none
15275 @itemx set mipsfpu auto
15276 @itemx show mipsfpu
15277 @kindex set mipsfpu
15278 @kindex show mipsfpu
15279 @cindex MIPS remote floating point
15280 @cindex floating point, MIPS remote
15281 If your target board does not support the MIPS floating point
15282 coprocessor, you should use the command @samp{set mipsfpu none} (if you
15283 need this, you may wish to put the command in your @value{GDBN} init
15284 file). This tells @value{GDBN} how to find the return value of
15285 functions which return floating point values. It also allows
15286 @value{GDBN} to avoid saving the floating point registers when calling
15287 functions on the board. If you are using a floating point coprocessor
15288 with only single precision floating point support, as on the @sc{r4650}
15289 processor, use the command @samp{set mipsfpu single}. The default
15290 double precision floating point coprocessor may be selected using
15291 @samp{set mipsfpu double}.
15293 In previous versions the only choices were double precision or no
15294 floating point, so @samp{set mipsfpu on} will select double precision
15295 and @samp{set mipsfpu off} will select no floating point.
15297 As usual, you can inquire about the @code{mipsfpu} variable with
15298 @samp{show mipsfpu}.
15300 @item set timeout @var{seconds}
15301 @itemx set retransmit-timeout @var{seconds}
15302 @itemx show timeout
15303 @itemx show retransmit-timeout
15304 @cindex @code{timeout}, MIPS protocol
15305 @cindex @code{retransmit-timeout}, MIPS protocol
15306 @kindex set timeout
15307 @kindex show timeout
15308 @kindex set retransmit-timeout
15309 @kindex show retransmit-timeout
15310 You can control the timeout used while waiting for a packet, in the MIPS
15311 remote protocol, with the @code{set timeout @var{seconds}} command. The
15312 default is 5 seconds. Similarly, you can control the timeout used while
15313 waiting for an acknowledgement of a packet with the @code{set
15314 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
15315 You can inspect both values with @code{show timeout} and @code{show
15316 retransmit-timeout}. (These commands are @emph{only} available when
15317 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
15319 The timeout set by @code{set timeout} does not apply when @value{GDBN}
15320 is waiting for your program to stop. In that case, @value{GDBN} waits
15321 forever because it has no way of knowing how long the program is going
15322 to run before stopping.
15324 @item set syn-garbage-limit @var{num}
15325 @kindex set syn-garbage-limit@r{, MIPS remote}
15326 @cindex synchronize with remote MIPS target
15327 Limit the maximum number of characters @value{GDBN} should ignore when
15328 it tries to synchronize with the remote target. The default is 10
15329 characters. Setting the limit to -1 means there's no limit.
15331 @item show syn-garbage-limit
15332 @kindex show syn-garbage-limit@r{, MIPS remote}
15333 Show the current limit on the number of characters to ignore when
15334 trying to synchronize with the remote system.
15336 @item set monitor-prompt @var{prompt}
15337 @kindex set monitor-prompt@r{, MIPS remote}
15338 @cindex remote monitor prompt
15339 Tell @value{GDBN} to expect the specified @var{prompt} string from the
15340 remote monitor. The default depends on the target:
15350 @item show monitor-prompt
15351 @kindex show monitor-prompt@r{, MIPS remote}
15352 Show the current strings @value{GDBN} expects as the prompt from the
15355 @item set monitor-warnings
15356 @kindex set monitor-warnings@r{, MIPS remote}
15357 Enable or disable monitor warnings about hardware breakpoints. This
15358 has effect only for the @code{lsi} target. When on, @value{GDBN} will
15359 display warning messages whose codes are returned by the @code{lsi}
15360 PMON monitor for breakpoint commands.
15362 @item show monitor-warnings
15363 @kindex show monitor-warnings@r{, MIPS remote}
15364 Show the current setting of printing monitor warnings.
15366 @item pmon @var{command}
15367 @kindex pmon@r{, MIPS remote}
15368 @cindex send PMON command
15369 This command allows sending an arbitrary @var{command} string to the
15370 monitor. The monitor must be in debug mode for this to work.
15373 @node OpenRISC 1000
15374 @subsection OpenRISC 1000
15375 @cindex OpenRISC 1000
15377 @cindex or1k boards
15378 See OR1k Architecture document (@uref{www.opencores.org}) for more information
15379 about platform and commands.
15383 @kindex target jtag
15384 @item target jtag jtag://@var{host}:@var{port}
15386 Connects to remote JTAG server.
15387 JTAG remote server can be either an or1ksim or JTAG server,
15388 connected via parallel port to the board.
15390 Example: @code{target jtag jtag://localhost:9999}
15393 @item or1ksim @var{command}
15394 If connected to @code{or1ksim} OpenRISC 1000 Architectural
15395 Simulator, proprietary commands can be executed.
15397 @kindex info or1k spr
15398 @item info or1k spr
15399 Displays spr groups.
15401 @item info or1k spr @var{group}
15402 @itemx info or1k spr @var{groupno}
15403 Displays register names in selected group.
15405 @item info or1k spr @var{group} @var{register}
15406 @itemx info or1k spr @var{register}
15407 @itemx info or1k spr @var{groupno} @var{registerno}
15408 @itemx info or1k spr @var{registerno}
15409 Shows information about specified spr register.
15412 @item spr @var{group} @var{register} @var{value}
15413 @itemx spr @var{register @var{value}}
15414 @itemx spr @var{groupno} @var{registerno @var{value}}
15415 @itemx spr @var{registerno @var{value}}
15416 Writes @var{value} to specified spr register.
15419 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
15420 It is very similar to @value{GDBN} trace, except it does not interfere with normal
15421 program execution and is thus much faster. Hardware breakpoints/watchpoint
15422 triggers can be set using:
15425 Load effective address/data
15427 Store effective address/data
15429 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
15434 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
15435 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
15437 @code{htrace} commands:
15438 @cindex OpenRISC 1000 htrace
15441 @item hwatch @var{conditional}
15442 Set hardware watchpoint on combination of Load/Store Effective Address(es)
15443 or Data. For example:
15445 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15447 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
15451 Display information about current HW trace configuration.
15453 @item htrace trigger @var{conditional}
15454 Set starting criteria for HW trace.
15456 @item htrace qualifier @var{conditional}
15457 Set acquisition qualifier for HW trace.
15459 @item htrace stop @var{conditional}
15460 Set HW trace stopping criteria.
15462 @item htrace record [@var{data}]*
15463 Selects the data to be recorded, when qualifier is met and HW trace was
15466 @item htrace enable
15467 @itemx htrace disable
15468 Enables/disables the HW trace.
15470 @item htrace rewind [@var{filename}]
15471 Clears currently recorded trace data.
15473 If filename is specified, new trace file is made and any newly collected data
15474 will be written there.
15476 @item htrace print [@var{start} [@var{len}]]
15477 Prints trace buffer, using current record configuration.
15479 @item htrace mode continuous
15480 Set continuous trace mode.
15482 @item htrace mode suspend
15483 Set suspend trace mode.
15487 @node PowerPC Embedded
15488 @subsection PowerPC Embedded
15490 @value{GDBN} provides the following PowerPC-specific commands:
15493 @kindex set powerpc
15494 @item set powerpc soft-float
15495 @itemx show powerpc soft-float
15496 Force @value{GDBN} to use (or not use) a software floating point calling
15497 convention. By default, @value{GDBN} selects the calling convention based
15498 on the selected architecture and the provided executable file.
15500 @item set powerpc vector-abi
15501 @itemx show powerpc vector-abi
15502 Force @value{GDBN} to use the specified calling convention for vector
15503 arguments and return values. The valid options are @samp{auto};
15504 @samp{generic}, to avoid vector registers even if they are present;
15505 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
15506 registers. By default, @value{GDBN} selects the calling convention
15507 based on the selected architecture and the provided executable file.
15509 @kindex target dink32
15510 @item target dink32 @var{dev}
15511 DINK32 ROM monitor.
15513 @kindex target ppcbug
15514 @item target ppcbug @var{dev}
15515 @kindex target ppcbug1
15516 @item target ppcbug1 @var{dev}
15517 PPCBUG ROM monitor for PowerPC.
15520 @item target sds @var{dev}
15521 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
15524 @cindex SDS protocol
15525 The following commands specific to the SDS protocol are supported
15529 @item set sdstimeout @var{nsec}
15530 @kindex set sdstimeout
15531 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
15532 default is 2 seconds.
15534 @item show sdstimeout
15535 @kindex show sdstimeout
15536 Show the current value of the SDS timeout.
15538 @item sds @var{command}
15539 @kindex sds@r{, a command}
15540 Send the specified @var{command} string to the SDS monitor.
15545 @subsection HP PA Embedded
15549 @kindex target op50n
15550 @item target op50n @var{dev}
15551 OP50N monitor, running on an OKI HPPA board.
15553 @kindex target w89k
15554 @item target w89k @var{dev}
15555 W89K monitor, running on a Winbond HPPA board.
15560 @subsection Tsqware Sparclet
15564 @value{GDBN} enables developers to debug tasks running on
15565 Sparclet targets from a Unix host.
15566 @value{GDBN} uses code that runs on
15567 both the Unix host and on the Sparclet target. The program
15568 @code{@value{GDBP}} is installed and executed on the Unix host.
15571 @item remotetimeout @var{args}
15572 @kindex remotetimeout
15573 @value{GDBN} supports the option @code{remotetimeout}.
15574 This option is set by the user, and @var{args} represents the number of
15575 seconds @value{GDBN} waits for responses.
15578 @cindex compiling, on Sparclet
15579 When compiling for debugging, include the options @samp{-g} to get debug
15580 information and @samp{-Ttext} to relocate the program to where you wish to
15581 load it on the target. You may also want to add the options @samp{-n} or
15582 @samp{-N} in order to reduce the size of the sections. Example:
15585 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15588 You can use @code{objdump} to verify that the addresses are what you intended:
15591 sparclet-aout-objdump --headers --syms prog
15594 @cindex running, on Sparclet
15596 your Unix execution search path to find @value{GDBN}, you are ready to
15597 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15598 (or @code{sparclet-aout-gdb}, depending on your installation).
15600 @value{GDBN} comes up showing the prompt:
15607 * Sparclet File:: Setting the file to debug
15608 * Sparclet Connection:: Connecting to Sparclet
15609 * Sparclet Download:: Sparclet download
15610 * Sparclet Execution:: Running and debugging
15613 @node Sparclet File
15614 @subsubsection Setting File to Debug
15616 The @value{GDBN} command @code{file} lets you choose with program to debug.
15619 (gdbslet) file prog
15623 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15624 @value{GDBN} locates
15625 the file by searching the directories listed in the command search
15627 If the file was compiled with debug information (option @samp{-g}), source
15628 files will be searched as well.
15629 @value{GDBN} locates
15630 the source files by searching the directories listed in the directory search
15631 path (@pxref{Environment, ,Your Program's Environment}).
15633 to find a file, it displays a message such as:
15636 prog: No such file or directory.
15639 When this happens, add the appropriate directories to the search paths with
15640 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15641 @code{target} command again.
15643 @node Sparclet Connection
15644 @subsubsection Connecting to Sparclet
15646 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15647 To connect to a target on serial port ``@code{ttya}'', type:
15650 (gdbslet) target sparclet /dev/ttya
15651 Remote target sparclet connected to /dev/ttya
15652 main () at ../prog.c:3
15656 @value{GDBN} displays messages like these:
15662 @node Sparclet Download
15663 @subsubsection Sparclet Download
15665 @cindex download to Sparclet
15666 Once connected to the Sparclet target,
15667 you can use the @value{GDBN}
15668 @code{load} command to download the file from the host to the target.
15669 The file name and load offset should be given as arguments to the @code{load}
15671 Since the file format is aout, the program must be loaded to the starting
15672 address. You can use @code{objdump} to find out what this value is. The load
15673 offset is an offset which is added to the VMA (virtual memory address)
15674 of each of the file's sections.
15675 For instance, if the program
15676 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15677 and bss at 0x12010170, in @value{GDBN}, type:
15680 (gdbslet) load prog 0x12010000
15681 Loading section .text, size 0xdb0 vma 0x12010000
15684 If the code is loaded at a different address then what the program was linked
15685 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15686 to tell @value{GDBN} where to map the symbol table.
15688 @node Sparclet Execution
15689 @subsubsection Running and Debugging
15691 @cindex running and debugging Sparclet programs
15692 You can now begin debugging the task using @value{GDBN}'s execution control
15693 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15694 manual for the list of commands.
15698 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15700 Starting program: prog
15701 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15702 3 char *symarg = 0;
15704 4 char *execarg = "hello!";
15709 @subsection Fujitsu Sparclite
15713 @kindex target sparclite
15714 @item target sparclite @var{dev}
15715 Fujitsu sparclite boards, used only for the purpose of loading.
15716 You must use an additional command to debug the program.
15717 For example: target remote @var{dev} using @value{GDBN} standard
15723 @subsection Zilog Z8000
15726 @cindex simulator, Z8000
15727 @cindex Zilog Z8000 simulator
15729 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15732 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15733 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15734 segmented variant). The simulator recognizes which architecture is
15735 appropriate by inspecting the object code.
15738 @item target sim @var{args}
15740 @kindex target sim@r{, with Z8000}
15741 Debug programs on a simulated CPU. If the simulator supports setup
15742 options, specify them via @var{args}.
15746 After specifying this target, you can debug programs for the simulated
15747 CPU in the same style as programs for your host computer; use the
15748 @code{file} command to load a new program image, the @code{run} command
15749 to run your program, and so on.
15751 As well as making available all the usual machine registers
15752 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15753 additional items of information as specially named registers:
15758 Counts clock-ticks in the simulator.
15761 Counts instructions run in the simulator.
15764 Execution time in 60ths of a second.
15768 You can refer to these values in @value{GDBN} expressions with the usual
15769 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15770 conditional breakpoint that suspends only after at least 5000
15771 simulated clock ticks.
15774 @subsection Atmel AVR
15777 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15778 following AVR-specific commands:
15781 @item info io_registers
15782 @kindex info io_registers@r{, AVR}
15783 @cindex I/O registers (Atmel AVR)
15784 This command displays information about the AVR I/O registers. For
15785 each register, @value{GDBN} prints its number and value.
15792 When configured for debugging CRIS, @value{GDBN} provides the
15793 following CRIS-specific commands:
15796 @item set cris-version @var{ver}
15797 @cindex CRIS version
15798 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15799 The CRIS version affects register names and sizes. This command is useful in
15800 case autodetection of the CRIS version fails.
15802 @item show cris-version
15803 Show the current CRIS version.
15805 @item set cris-dwarf2-cfi
15806 @cindex DWARF-2 CFI and CRIS
15807 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15808 Change to @samp{off} when using @code{gcc-cris} whose version is below
15811 @item show cris-dwarf2-cfi
15812 Show the current state of using DWARF-2 CFI.
15814 @item set cris-mode @var{mode}
15816 Set the current CRIS mode to @var{mode}. It should only be changed when
15817 debugging in guru mode, in which case it should be set to
15818 @samp{guru} (the default is @samp{normal}).
15820 @item show cris-mode
15821 Show the current CRIS mode.
15825 @subsection Renesas Super-H
15828 For the Renesas Super-H processor, @value{GDBN} provides these
15833 @kindex regs@r{, Super-H}
15834 Show the values of all Super-H registers.
15836 @item set sh calling-convention @var{convention}
15837 @kindex set sh calling-convention
15838 Set the calling-convention used when calling functions from @value{GDBN}.
15839 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
15840 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
15841 convention. If the DWARF-2 information of the called function specifies
15842 that the function follows the Renesas calling convention, the function
15843 is called using the Renesas calling convention. If the calling convention
15844 is set to @samp{renesas}, the Renesas calling convention is always used,
15845 regardless of the DWARF-2 information. This can be used to override the
15846 default of @samp{gcc} if debug information is missing, or the compiler
15847 does not emit the DWARF-2 calling convention entry for a function.
15849 @item show sh calling-convention
15850 @kindex show sh calling-convention
15851 Show the current calling convention setting.
15856 @node Architectures
15857 @section Architectures
15859 This section describes characteristics of architectures that affect
15860 all uses of @value{GDBN} with the architecture, both native and cross.
15867 * HPPA:: HP PA architecture
15868 * SPU:: Cell Broadband Engine SPU architecture
15873 @subsection x86 Architecture-specific Issues
15876 @item set struct-convention @var{mode}
15877 @kindex set struct-convention
15878 @cindex struct return convention
15879 @cindex struct/union returned in registers
15880 Set the convention used by the inferior to return @code{struct}s and
15881 @code{union}s from functions to @var{mode}. Possible values of
15882 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15883 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15884 are returned on the stack, while @code{"reg"} means that a
15885 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15886 be returned in a register.
15888 @item show struct-convention
15889 @kindex show struct-convention
15890 Show the current setting of the convention to return @code{struct}s
15899 @kindex set rstack_high_address
15900 @cindex AMD 29K register stack
15901 @cindex register stack, AMD29K
15902 @item set rstack_high_address @var{address}
15903 On AMD 29000 family processors, registers are saved in a separate
15904 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15905 extent of this stack. Normally, @value{GDBN} just assumes that the
15906 stack is ``large enough''. This may result in @value{GDBN} referencing
15907 memory locations that do not exist. If necessary, you can get around
15908 this problem by specifying the ending address of the register stack with
15909 the @code{set rstack_high_address} command. The argument should be an
15910 address, which you probably want to precede with @samp{0x} to specify in
15913 @kindex show rstack_high_address
15914 @item show rstack_high_address
15915 Display the current limit of the register stack, on AMD 29000 family
15923 See the following section.
15928 @cindex stack on Alpha
15929 @cindex stack on MIPS
15930 @cindex Alpha stack
15932 Alpha- and MIPS-based computers use an unusual stack frame, which
15933 sometimes requires @value{GDBN} to search backward in the object code to
15934 find the beginning of a function.
15936 @cindex response time, MIPS debugging
15937 To improve response time (especially for embedded applications, where
15938 @value{GDBN} may be restricted to a slow serial line for this search)
15939 you may want to limit the size of this search, using one of these
15943 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15944 @item set heuristic-fence-post @var{limit}
15945 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15946 search for the beginning of a function. A value of @var{0} (the
15947 default) means there is no limit. However, except for @var{0}, the
15948 larger the limit the more bytes @code{heuristic-fence-post} must search
15949 and therefore the longer it takes to run. You should only need to use
15950 this command when debugging a stripped executable.
15952 @item show heuristic-fence-post
15953 Display the current limit.
15957 These commands are available @emph{only} when @value{GDBN} is configured
15958 for debugging programs on Alpha or MIPS processors.
15960 Several MIPS-specific commands are available when debugging MIPS
15964 @item set mips abi @var{arg}
15965 @kindex set mips abi
15966 @cindex set ABI for MIPS
15967 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15968 values of @var{arg} are:
15972 The default ABI associated with the current binary (this is the
15983 @item show mips abi
15984 @kindex show mips abi
15985 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15988 @itemx show mipsfpu
15989 @xref{MIPS Embedded, set mipsfpu}.
15991 @item set mips mask-address @var{arg}
15992 @kindex set mips mask-address
15993 @cindex MIPS addresses, masking
15994 This command determines whether the most-significant 32 bits of 64-bit
15995 MIPS addresses are masked off. The argument @var{arg} can be
15996 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15997 setting, which lets @value{GDBN} determine the correct value.
15999 @item show mips mask-address
16000 @kindex show mips mask-address
16001 Show whether the upper 32 bits of MIPS addresses are masked off or
16004 @item set remote-mips64-transfers-32bit-regs
16005 @kindex set remote-mips64-transfers-32bit-regs
16006 This command controls compatibility with 64-bit MIPS targets that
16007 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16008 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16009 and 64 bits for other registers, set this option to @samp{on}.
16011 @item show remote-mips64-transfers-32bit-regs
16012 @kindex show remote-mips64-transfers-32bit-regs
16013 Show the current setting of compatibility with older MIPS 64 targets.
16015 @item set debug mips
16016 @kindex set debug mips
16017 This command turns on and off debugging messages for the MIPS-specific
16018 target code in @value{GDBN}.
16020 @item show debug mips
16021 @kindex show debug mips
16022 Show the current setting of MIPS debugging messages.
16028 @cindex HPPA support
16030 When @value{GDBN} is debugging the HP PA architecture, it provides the
16031 following special commands:
16034 @item set debug hppa
16035 @kindex set debug hppa
16036 This command determines whether HPPA architecture-specific debugging
16037 messages are to be displayed.
16039 @item show debug hppa
16040 Show whether HPPA debugging messages are displayed.
16042 @item maint print unwind @var{address}
16043 @kindex maint print unwind@r{, HPPA}
16044 This command displays the contents of the unwind table entry at the
16045 given @var{address}.
16051 @subsection Cell Broadband Engine SPU architecture
16052 @cindex Cell Broadband Engine
16055 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16056 it provides the following special commands:
16059 @item info spu event
16061 Display SPU event facility status. Shows current event mask
16062 and pending event status.
16064 @item info spu signal
16065 Display SPU signal notification facility status. Shows pending
16066 signal-control word and signal notification mode of both signal
16067 notification channels.
16069 @item info spu mailbox
16070 Display SPU mailbox facility status. Shows all pending entries,
16071 in order of processing, in each of the SPU Write Outbound,
16072 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16075 Display MFC DMA status. Shows all pending commands in the MFC
16076 DMA queue. For each entry, opcode, tag, class IDs, effective
16077 and local store addresses and transfer size are shown.
16079 @item info spu proxydma
16080 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16081 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16082 and local store addresses and transfer size are shown.
16087 @subsection PowerPC
16088 @cindex PowerPC architecture
16090 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16091 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16092 numbers stored in the floating point registers. These values must be stored
16093 in two consecutive registers, always starting at an even register like
16094 @code{f0} or @code{f2}.
16096 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16097 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16098 @code{f2} and @code{f3} for @code{$dl1} and so on.
16101 @node Controlling GDB
16102 @chapter Controlling @value{GDBN}
16104 You can alter the way @value{GDBN} interacts with you by using the
16105 @code{set} command. For commands controlling how @value{GDBN} displays
16106 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16111 * Editing:: Command editing
16112 * Command History:: Command history
16113 * Screen Size:: Screen size
16114 * Numbers:: Numbers
16115 * ABI:: Configuring the current ABI
16116 * Messages/Warnings:: Optional warnings and messages
16117 * Debugging Output:: Optional messages about internal happenings
16125 @value{GDBN} indicates its readiness to read a command by printing a string
16126 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
16127 can change the prompt string with the @code{set prompt} command. For
16128 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
16129 the prompt in one of the @value{GDBN} sessions so that you can always tell
16130 which one you are talking to.
16132 @emph{Note:} @code{set prompt} does not add a space for you after the
16133 prompt you set. This allows you to set a prompt which ends in a space
16134 or a prompt that does not.
16138 @item set prompt @var{newprompt}
16139 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
16141 @kindex show prompt
16143 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
16147 @section Command Editing
16149 @cindex command line editing
16151 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
16152 @sc{gnu} library provides consistent behavior for programs which provide a
16153 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16154 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16155 substitution, and a storage and recall of command history across
16156 debugging sessions.
16158 You may control the behavior of command line editing in @value{GDBN} with the
16159 command @code{set}.
16162 @kindex set editing
16165 @itemx set editing on
16166 Enable command line editing (enabled by default).
16168 @item set editing off
16169 Disable command line editing.
16171 @kindex show editing
16173 Show whether command line editing is enabled.
16176 @xref{Command Line Editing}, for more details about the Readline
16177 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
16178 encouraged to read that chapter.
16180 @node Command History
16181 @section Command History
16182 @cindex command history
16184 @value{GDBN} can keep track of the commands you type during your
16185 debugging sessions, so that you can be certain of precisely what
16186 happened. Use these commands to manage the @value{GDBN} command
16189 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
16190 package, to provide the history facility. @xref{Using History
16191 Interactively}, for the detailed description of the History library.
16193 To issue a command to @value{GDBN} without affecting certain aspects of
16194 the state which is seen by users, prefix it with @samp{server }
16195 (@pxref{Server Prefix}). This
16196 means that this command will not affect the command history, nor will it
16197 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
16198 pressed on a line by itself.
16200 @cindex @code{server}, command prefix
16201 The server prefix does not affect the recording of values into the value
16202 history; to print a value without recording it into the value history,
16203 use the @code{output} command instead of the @code{print} command.
16205 Here is the description of @value{GDBN} commands related to command
16209 @cindex history substitution
16210 @cindex history file
16211 @kindex set history filename
16212 @cindex @env{GDBHISTFILE}, environment variable
16213 @item set history filename @var{fname}
16214 Set the name of the @value{GDBN} command history file to @var{fname}.
16215 This is the file where @value{GDBN} reads an initial command history
16216 list, and where it writes the command history from this session when it
16217 exits. You can access this list through history expansion or through
16218 the history command editing characters listed below. This file defaults
16219 to the value of the environment variable @code{GDBHISTFILE}, or to
16220 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16223 @cindex save command history
16224 @kindex set history save
16225 @item set history save
16226 @itemx set history save on
16227 Record command history in a file, whose name may be specified with the
16228 @code{set history filename} command. By default, this option is disabled.
16230 @item set history save off
16231 Stop recording command history in a file.
16233 @cindex history size
16234 @kindex set history size
16235 @cindex @env{HISTSIZE}, environment variable
16236 @item set history size @var{size}
16237 Set the number of commands which @value{GDBN} keeps in its history list.
16238 This defaults to the value of the environment variable
16239 @code{HISTSIZE}, or to 256 if this variable is not set.
16242 History expansion assigns special meaning to the character @kbd{!}.
16243 @xref{Event Designators}, for more details.
16245 @cindex history expansion, turn on/off
16246 Since @kbd{!} is also the logical not operator in C, history expansion
16247 is off by default. If you decide to enable history expansion with the
16248 @code{set history expansion on} command, you may sometimes need to
16249 follow @kbd{!} (when it is used as logical not, in an expression) with
16250 a space or a tab to prevent it from being expanded. The readline
16251 history facilities do not attempt substitution on the strings
16252 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
16254 The commands to control history expansion are:
16257 @item set history expansion on
16258 @itemx set history expansion
16259 @kindex set history expansion
16260 Enable history expansion. History expansion is off by default.
16262 @item set history expansion off
16263 Disable history expansion.
16266 @kindex show history
16268 @itemx show history filename
16269 @itemx show history save
16270 @itemx show history size
16271 @itemx show history expansion
16272 These commands display the state of the @value{GDBN} history parameters.
16273 @code{show history} by itself displays all four states.
16278 @kindex show commands
16279 @cindex show last commands
16280 @cindex display command history
16281 @item show commands
16282 Display the last ten commands in the command history.
16284 @item show commands @var{n}
16285 Print ten commands centered on command number @var{n}.
16287 @item show commands +
16288 Print ten commands just after the commands last printed.
16292 @section Screen Size
16293 @cindex size of screen
16294 @cindex pauses in output
16296 Certain commands to @value{GDBN} may produce large amounts of
16297 information output to the screen. To help you read all of it,
16298 @value{GDBN} pauses and asks you for input at the end of each page of
16299 output. Type @key{RET} when you want to continue the output, or @kbd{q}
16300 to discard the remaining output. Also, the screen width setting
16301 determines when to wrap lines of output. Depending on what is being
16302 printed, @value{GDBN} tries to break the line at a readable place,
16303 rather than simply letting it overflow onto the following line.
16305 Normally @value{GDBN} knows the size of the screen from the terminal
16306 driver software. For example, on Unix @value{GDBN} uses the termcap data base
16307 together with the value of the @code{TERM} environment variable and the
16308 @code{stty rows} and @code{stty cols} settings. If this is not correct,
16309 you can override it with the @code{set height} and @code{set
16316 @kindex show height
16317 @item set height @var{lpp}
16319 @itemx set width @var{cpl}
16321 These @code{set} commands specify a screen height of @var{lpp} lines and
16322 a screen width of @var{cpl} characters. The associated @code{show}
16323 commands display the current settings.
16325 If you specify a height of zero lines, @value{GDBN} does not pause during
16326 output no matter how long the output is. This is useful if output is to a
16327 file or to an editor buffer.
16329 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
16330 from wrapping its output.
16332 @item set pagination on
16333 @itemx set pagination off
16334 @kindex set pagination
16335 Turn the output pagination on or off; the default is on. Turning
16336 pagination off is the alternative to @code{set height 0}.
16338 @item show pagination
16339 @kindex show pagination
16340 Show the current pagination mode.
16345 @cindex number representation
16346 @cindex entering numbers
16348 You can always enter numbers in octal, decimal, or hexadecimal in
16349 @value{GDBN} by the usual conventions: octal numbers begin with
16350 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
16351 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
16352 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
16353 10; likewise, the default display for numbers---when no particular
16354 format is specified---is base 10. You can change the default base for
16355 both input and output with the commands described below.
16358 @kindex set input-radix
16359 @item set input-radix @var{base}
16360 Set the default base for numeric input. Supported choices
16361 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16362 specified either unambiguously or using the current input radix; for
16366 set input-radix 012
16367 set input-radix 10.
16368 set input-radix 0xa
16372 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
16373 leaves the input radix unchanged, no matter what it was, since
16374 @samp{10}, being without any leading or trailing signs of its base, is
16375 interpreted in the current radix. Thus, if the current radix is 16,
16376 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
16379 @kindex set output-radix
16380 @item set output-radix @var{base}
16381 Set the default base for numeric display. Supported choices
16382 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
16383 specified either unambiguously or using the current input radix.
16385 @kindex show input-radix
16386 @item show input-radix
16387 Display the current default base for numeric input.
16389 @kindex show output-radix
16390 @item show output-radix
16391 Display the current default base for numeric display.
16393 @item set radix @r{[}@var{base}@r{]}
16397 These commands set and show the default base for both input and output
16398 of numbers. @code{set radix} sets the radix of input and output to
16399 the same base; without an argument, it resets the radix back to its
16400 default value of 10.
16405 @section Configuring the Current ABI
16407 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
16408 application automatically. However, sometimes you need to override its
16409 conclusions. Use these commands to manage @value{GDBN}'s view of the
16416 One @value{GDBN} configuration can debug binaries for multiple operating
16417 system targets, either via remote debugging or native emulation.
16418 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
16419 but you can override its conclusion using the @code{set osabi} command.
16420 One example where this is useful is in debugging of binaries which use
16421 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
16422 not have the same identifying marks that the standard C library for your
16427 Show the OS ABI currently in use.
16430 With no argument, show the list of registered available OS ABI's.
16432 @item set osabi @var{abi}
16433 Set the current OS ABI to @var{abi}.
16436 @cindex float promotion
16438 Generally, the way that an argument of type @code{float} is passed to a
16439 function depends on whether the function is prototyped. For a prototyped
16440 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
16441 according to the architecture's convention for @code{float}. For unprototyped
16442 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
16443 @code{double} and then passed.
16445 Unfortunately, some forms of debug information do not reliably indicate whether
16446 a function is prototyped. If @value{GDBN} calls a function that is not marked
16447 as prototyped, it consults @kbd{set coerce-float-to-double}.
16450 @kindex set coerce-float-to-double
16451 @item set coerce-float-to-double
16452 @itemx set coerce-float-to-double on
16453 Arguments of type @code{float} will be promoted to @code{double} when passed
16454 to an unprototyped function. This is the default setting.
16456 @item set coerce-float-to-double off
16457 Arguments of type @code{float} will be passed directly to unprototyped
16460 @kindex show coerce-float-to-double
16461 @item show coerce-float-to-double
16462 Show the current setting of promoting @code{float} to @code{double}.
16466 @kindex show cp-abi
16467 @value{GDBN} needs to know the ABI used for your program's C@t{++}
16468 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
16469 used to build your application. @value{GDBN} only fully supports
16470 programs with a single C@t{++} ABI; if your program contains code using
16471 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
16472 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
16473 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
16474 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
16475 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
16476 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16481 Show the C@t{++} ABI currently in use.
16484 With no argument, show the list of supported C@t{++} ABI's.
16486 @item set cp-abi @var{abi}
16487 @itemx set cp-abi auto
16488 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16491 @node Messages/Warnings
16492 @section Optional Warnings and Messages
16494 @cindex verbose operation
16495 @cindex optional warnings
16496 By default, @value{GDBN} is silent about its inner workings. If you are
16497 running on a slow machine, you may want to use the @code{set verbose}
16498 command. This makes @value{GDBN} tell you when it does a lengthy
16499 internal operation, so you will not think it has crashed.
16501 Currently, the messages controlled by @code{set verbose} are those
16502 which announce that the symbol table for a source file is being read;
16503 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
16506 @kindex set verbose
16507 @item set verbose on
16508 Enables @value{GDBN} output of certain informational messages.
16510 @item set verbose off
16511 Disables @value{GDBN} output of certain informational messages.
16513 @kindex show verbose
16515 Displays whether @code{set verbose} is on or off.
16518 By default, if @value{GDBN} encounters bugs in the symbol table of an
16519 object file, it is silent; but if you are debugging a compiler, you may
16520 find this information useful (@pxref{Symbol Errors, ,Errors Reading
16525 @kindex set complaints
16526 @item set complaints @var{limit}
16527 Permits @value{GDBN} to output @var{limit} complaints about each type of
16528 unusual symbols before becoming silent about the problem. Set
16529 @var{limit} to zero to suppress all complaints; set it to a large number
16530 to prevent complaints from being suppressed.
16532 @kindex show complaints
16533 @item show complaints
16534 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16538 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16539 lot of stupid questions to confirm certain commands. For example, if
16540 you try to run a program which is already running:
16544 The program being debugged has been started already.
16545 Start it from the beginning? (y or n)
16548 If you are willing to unflinchingly face the consequences of your own
16549 commands, you can disable this ``feature'':
16553 @kindex set confirm
16555 @cindex confirmation
16556 @cindex stupid questions
16557 @item set confirm off
16558 Disables confirmation requests.
16560 @item set confirm on
16561 Enables confirmation requests (the default).
16563 @kindex show confirm
16565 Displays state of confirmation requests.
16569 @cindex command tracing
16570 If you need to debug user-defined commands or sourced files you may find it
16571 useful to enable @dfn{command tracing}. In this mode each command will be
16572 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16573 quantity denoting the call depth of each command.
16576 @kindex set trace-commands
16577 @cindex command scripts, debugging
16578 @item set trace-commands on
16579 Enable command tracing.
16580 @item set trace-commands off
16581 Disable command tracing.
16582 @item show trace-commands
16583 Display the current state of command tracing.
16586 @node Debugging Output
16587 @section Optional Messages about Internal Happenings
16588 @cindex optional debugging messages
16590 @value{GDBN} has commands that enable optional debugging messages from
16591 various @value{GDBN} subsystems; normally these commands are of
16592 interest to @value{GDBN} maintainers, or when reporting a bug. This
16593 section documents those commands.
16596 @kindex set exec-done-display
16597 @item set exec-done-display
16598 Turns on or off the notification of asynchronous commands'
16599 completion. When on, @value{GDBN} will print a message when an
16600 asynchronous command finishes its execution. The default is off.
16601 @kindex show exec-done-display
16602 @item show exec-done-display
16603 Displays the current setting of asynchronous command completion
16606 @cindex gdbarch debugging info
16607 @cindex architecture debugging info
16608 @item set debug arch
16609 Turns on or off display of gdbarch debugging info. The default is off
16611 @item show debug arch
16612 Displays the current state of displaying gdbarch debugging info.
16613 @item set debug aix-thread
16614 @cindex AIX threads
16615 Display debugging messages about inner workings of the AIX thread
16617 @item show debug aix-thread
16618 Show the current state of AIX thread debugging info display.
16619 @item set debug displaced
16620 @cindex displaced stepping debugging info
16621 Turns on or off display of @value{GDBN} debugging info for the
16622 displaced stepping support. The default is off.
16623 @item show debug displaced
16624 Displays the current state of displaying @value{GDBN} debugging info
16625 related to displaced stepping.
16626 @item set debug event
16627 @cindex event debugging info
16628 Turns on or off display of @value{GDBN} event debugging info. The
16630 @item show debug event
16631 Displays the current state of displaying @value{GDBN} event debugging
16633 @item set debug expression
16634 @cindex expression debugging info
16635 Turns on or off display of debugging info about @value{GDBN}
16636 expression parsing. The default is off.
16637 @item show debug expression
16638 Displays the current state of displaying debugging info about
16639 @value{GDBN} expression parsing.
16640 @item set debug frame
16641 @cindex frame debugging info
16642 Turns on or off display of @value{GDBN} frame debugging info. The
16644 @item show debug frame
16645 Displays the current state of displaying @value{GDBN} frame debugging
16647 @item set debug infrun
16648 @cindex inferior debugging info
16649 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16650 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16651 for implementing operations such as single-stepping the inferior.
16652 @item show debug infrun
16653 Displays the current state of @value{GDBN} inferior debugging.
16654 @item set debug lin-lwp
16655 @cindex @sc{gnu}/Linux LWP debug messages
16656 @cindex Linux lightweight processes
16657 Turns on or off debugging messages from the Linux LWP debug support.
16658 @item show debug lin-lwp
16659 Show the current state of Linux LWP debugging messages.
16660 @item set debug lin-lwp-async
16661 @cindex @sc{gnu}/Linux LWP async debug messages
16662 @cindex Linux lightweight processes
16663 Turns on or off debugging messages from the Linux LWP async debug support.
16664 @item show debug lin-lwp-async
16665 Show the current state of Linux LWP async debugging messages.
16666 @item set debug observer
16667 @cindex observer debugging info
16668 Turns on or off display of @value{GDBN} observer debugging. This
16669 includes info such as the notification of observable events.
16670 @item show debug observer
16671 Displays the current state of observer debugging.
16672 @item set debug overload
16673 @cindex C@t{++} overload debugging info
16674 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16675 info. This includes info such as ranking of functions, etc. The default
16677 @item show debug overload
16678 Displays the current state of displaying @value{GDBN} C@t{++} overload
16680 @cindex packets, reporting on stdout
16681 @cindex serial connections, debugging
16682 @cindex debug remote protocol
16683 @cindex remote protocol debugging
16684 @cindex display remote packets
16685 @item set debug remote
16686 Turns on or off display of reports on all packets sent back and forth across
16687 the serial line to the remote machine. The info is printed on the
16688 @value{GDBN} standard output stream. The default is off.
16689 @item show debug remote
16690 Displays the state of display of remote packets.
16691 @item set debug serial
16692 Turns on or off display of @value{GDBN} serial debugging info. The
16694 @item show debug serial
16695 Displays the current state of displaying @value{GDBN} serial debugging
16697 @item set debug solib-frv
16698 @cindex FR-V shared-library debugging
16699 Turns on or off debugging messages for FR-V shared-library code.
16700 @item show debug solib-frv
16701 Display the current state of FR-V shared-library code debugging
16703 @item set debug target
16704 @cindex target debugging info
16705 Turns on or off display of @value{GDBN} target debugging info. This info
16706 includes what is going on at the target level of GDB, as it happens. The
16707 default is 0. Set it to 1 to track events, and to 2 to also track the
16708 value of large memory transfers. Changes to this flag do not take effect
16709 until the next time you connect to a target or use the @code{run} command.
16710 @item show debug target
16711 Displays the current state of displaying @value{GDBN} target debugging
16713 @item set debug timestamp
16714 @cindex timestampping debugging info
16715 Turns on or off display of timestamps with @value{GDBN} debugging info.
16716 When enabled, seconds and microseconds are displayed before each debugging
16718 @item show debug timestamp
16719 Displays the current state of displaying timestamps with @value{GDBN}
16721 @item set debugvarobj
16722 @cindex variable object debugging info
16723 Turns on or off display of @value{GDBN} variable object debugging
16724 info. The default is off.
16725 @item show debugvarobj
16726 Displays the current state of displaying @value{GDBN} variable object
16728 @item set debug xml
16729 @cindex XML parser debugging
16730 Turns on or off debugging messages for built-in XML parsers.
16731 @item show debug xml
16732 Displays the current state of XML debugging messages.
16736 @chapter Canned Sequences of Commands
16738 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16739 Command Lists}), @value{GDBN} provides two ways to store sequences of
16740 commands for execution as a unit: user-defined commands and command
16744 * Define:: How to define your own commands
16745 * Hooks:: Hooks for user-defined commands
16746 * Command Files:: How to write scripts of commands to be stored in a file
16747 * Output:: Commands for controlled output
16751 @section User-defined Commands
16753 @cindex user-defined command
16754 @cindex arguments, to user-defined commands
16755 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16756 which you assign a new name as a command. This is done with the
16757 @code{define} command. User commands may accept up to 10 arguments
16758 separated by whitespace. Arguments are accessed within the user command
16759 via @code{$arg0@dots{}$arg9}. A trivial example:
16763 print $arg0 + $arg1 + $arg2
16768 To execute the command use:
16775 This defines the command @code{adder}, which prints the sum of
16776 its three arguments. Note the arguments are text substitutions, so they may
16777 reference variables, use complex expressions, or even perform inferior
16780 @cindex argument count in user-defined commands
16781 @cindex how many arguments (user-defined commands)
16782 In addition, @code{$argc} may be used to find out how many arguments have
16783 been passed. This expands to a number in the range 0@dots{}10.
16788 print $arg0 + $arg1
16791 print $arg0 + $arg1 + $arg2
16799 @item define @var{commandname}
16800 Define a command named @var{commandname}. If there is already a command
16801 by that name, you are asked to confirm that you want to redefine it.
16803 The definition of the command is made up of other @value{GDBN} command lines,
16804 which are given following the @code{define} command. The end of these
16805 commands is marked by a line containing @code{end}.
16808 @kindex end@r{ (user-defined commands)}
16809 @item document @var{commandname}
16810 Document the user-defined command @var{commandname}, so that it can be
16811 accessed by @code{help}. The command @var{commandname} must already be
16812 defined. This command reads lines of documentation just as @code{define}
16813 reads the lines of the command definition, ending with @code{end}.
16814 After the @code{document} command is finished, @code{help} on command
16815 @var{commandname} displays the documentation you have written.
16817 You may use the @code{document} command again to change the
16818 documentation of a command. Redefining the command with @code{define}
16819 does not change the documentation.
16821 @kindex dont-repeat
16822 @cindex don't repeat command
16824 Used inside a user-defined command, this tells @value{GDBN} that this
16825 command should not be repeated when the user hits @key{RET}
16826 (@pxref{Command Syntax, repeat last command}).
16828 @kindex help user-defined
16829 @item help user-defined
16830 List all user-defined commands, with the first line of the documentation
16835 @itemx show user @var{commandname}
16836 Display the @value{GDBN} commands used to define @var{commandname} (but
16837 not its documentation). If no @var{commandname} is given, display the
16838 definitions for all user-defined commands.
16840 @cindex infinite recursion in user-defined commands
16841 @kindex show max-user-call-depth
16842 @kindex set max-user-call-depth
16843 @item show max-user-call-depth
16844 @itemx set max-user-call-depth
16845 The value of @code{max-user-call-depth} controls how many recursion
16846 levels are allowed in user-defined commands before @value{GDBN} suspects an
16847 infinite recursion and aborts the command.
16850 In addition to the above commands, user-defined commands frequently
16851 use control flow commands, described in @ref{Command Files}.
16853 When user-defined commands are executed, the
16854 commands of the definition are not printed. An error in any command
16855 stops execution of the user-defined command.
16857 If used interactively, commands that would ask for confirmation proceed
16858 without asking when used inside a user-defined command. Many @value{GDBN}
16859 commands that normally print messages to say what they are doing omit the
16860 messages when used in a user-defined command.
16863 @section User-defined Command Hooks
16864 @cindex command hooks
16865 @cindex hooks, for commands
16866 @cindex hooks, pre-command
16869 You may define @dfn{hooks}, which are a special kind of user-defined
16870 command. Whenever you run the command @samp{foo}, if the user-defined
16871 command @samp{hook-foo} exists, it is executed (with no arguments)
16872 before that command.
16874 @cindex hooks, post-command
16876 A hook may also be defined which is run after the command you executed.
16877 Whenever you run the command @samp{foo}, if the user-defined command
16878 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16879 that command. Post-execution hooks may exist simultaneously with
16880 pre-execution hooks, for the same command.
16882 It is valid for a hook to call the command which it hooks. If this
16883 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16885 @c It would be nice if hookpost could be passed a parameter indicating
16886 @c if the command it hooks executed properly or not. FIXME!
16888 @kindex stop@r{, a pseudo-command}
16889 In addition, a pseudo-command, @samp{stop} exists. Defining
16890 (@samp{hook-stop}) makes the associated commands execute every time
16891 execution stops in your program: before breakpoint commands are run,
16892 displays are printed, or the stack frame is printed.
16894 For example, to ignore @code{SIGALRM} signals while
16895 single-stepping, but treat them normally during normal execution,
16900 handle SIGALRM nopass
16904 handle SIGALRM pass
16907 define hook-continue
16908 handle SIGALRM pass
16912 As a further example, to hook at the beginning and end of the @code{echo}
16913 command, and to add extra text to the beginning and end of the message,
16921 define hookpost-echo
16925 (@value{GDBP}) echo Hello World
16926 <<<---Hello World--->>>
16931 You can define a hook for any single-word command in @value{GDBN}, but
16932 not for command aliases; you should define a hook for the basic command
16933 name, e.g.@: @code{backtrace} rather than @code{bt}.
16934 @c FIXME! So how does Joe User discover whether a command is an alias
16936 If an error occurs during the execution of your hook, execution of
16937 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16938 (before the command that you actually typed had a chance to run).
16940 If you try to define a hook which does not match any known command, you
16941 get a warning from the @code{define} command.
16943 @node Command Files
16944 @section Command Files
16946 @cindex command files
16947 @cindex scripting commands
16948 A command file for @value{GDBN} is a text file made of lines that are
16949 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16950 also be included. An empty line in a command file does nothing; it
16951 does not mean to repeat the last command, as it would from the
16954 You can request the execution of a command file with the @code{source}
16959 @cindex execute commands from a file
16960 @item source [@code{-v}] @var{filename}
16961 Execute the command file @var{filename}.
16964 The lines in a command file are generally executed sequentially,
16965 unless the order of execution is changed by one of the
16966 @emph{flow-control commands} described below. The commands are not
16967 printed as they are executed. An error in any command terminates
16968 execution of the command file and control is returned to the console.
16970 @value{GDBN} searches for @var{filename} in the current directory and then
16971 on the search path (specified with the @samp{directory} command).
16973 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16974 each command as it is executed. The option must be given before
16975 @var{filename}, and is interpreted as part of the filename anywhere else.
16977 Commands that would ask for confirmation if used interactively proceed
16978 without asking when used in a command file. Many @value{GDBN} commands that
16979 normally print messages to say what they are doing omit the messages
16980 when called from command files.
16982 @value{GDBN} also accepts command input from standard input. In this
16983 mode, normal output goes to standard output and error output goes to
16984 standard error. Errors in a command file supplied on standard input do
16985 not terminate execution of the command file---execution continues with
16989 gdb < cmds > log 2>&1
16992 (The syntax above will vary depending on the shell used.) This example
16993 will execute commands from the file @file{cmds}. All output and errors
16994 would be directed to @file{log}.
16996 Since commands stored on command files tend to be more general than
16997 commands typed interactively, they frequently need to deal with
16998 complicated situations, such as different or unexpected values of
16999 variables and symbols, changes in how the program being debugged is
17000 built, etc. @value{GDBN} provides a set of flow-control commands to
17001 deal with these complexities. Using these commands, you can write
17002 complex scripts that loop over data structures, execute commands
17003 conditionally, etc.
17010 This command allows to include in your script conditionally executed
17011 commands. The @code{if} command takes a single argument, which is an
17012 expression to evaluate. It is followed by a series of commands that
17013 are executed only if the expression is true (its value is nonzero).
17014 There can then optionally be an @code{else} line, followed by a series
17015 of commands that are only executed if the expression was false. The
17016 end of the list is marked by a line containing @code{end}.
17020 This command allows to write loops. Its syntax is similar to
17021 @code{if}: the command takes a single argument, which is an expression
17022 to evaluate, and must be followed by the commands to execute, one per
17023 line, terminated by an @code{end}. These commands are called the
17024 @dfn{body} of the loop. The commands in the body of @code{while} are
17025 executed repeatedly as long as the expression evaluates to true.
17029 This command exits the @code{while} loop in whose body it is included.
17030 Execution of the script continues after that @code{while}s @code{end}
17033 @kindex loop_continue
17034 @item loop_continue
17035 This command skips the execution of the rest of the body of commands
17036 in the @code{while} loop in whose body it is included. Execution
17037 branches to the beginning of the @code{while} loop, where it evaluates
17038 the controlling expression.
17040 @kindex end@r{ (if/else/while commands)}
17042 Terminate the block of commands that are the body of @code{if},
17043 @code{else}, or @code{while} flow-control commands.
17048 @section Commands for Controlled Output
17050 During the execution of a command file or a user-defined command, normal
17051 @value{GDBN} output is suppressed; the only output that appears is what is
17052 explicitly printed by the commands in the definition. This section
17053 describes three commands useful for generating exactly the output you
17058 @item echo @var{text}
17059 @c I do not consider backslash-space a standard C escape sequence
17060 @c because it is not in ANSI.
17061 Print @var{text}. Nonprinting characters can be included in
17062 @var{text} using C escape sequences, such as @samp{\n} to print a
17063 newline. @strong{No newline is printed unless you specify one.}
17064 In addition to the standard C escape sequences, a backslash followed
17065 by a space stands for a space. This is useful for displaying a
17066 string with spaces at the beginning or the end, since leading and
17067 trailing spaces are otherwise trimmed from all arguments.
17068 To print @samp{@w{ }and foo =@w{ }}, use the command
17069 @samp{echo \@w{ }and foo = \@w{ }}.
17071 A backslash at the end of @var{text} can be used, as in C, to continue
17072 the command onto subsequent lines. For example,
17075 echo This is some text\n\
17076 which is continued\n\
17077 onto several lines.\n
17080 produces the same output as
17083 echo This is some text\n
17084 echo which is continued\n
17085 echo onto several lines.\n
17089 @item output @var{expression}
17090 Print the value of @var{expression} and nothing but that value: no
17091 newlines, no @samp{$@var{nn} = }. The value is not entered in the
17092 value history either. @xref{Expressions, ,Expressions}, for more information
17095 @item output/@var{fmt} @var{expression}
17096 Print the value of @var{expression} in format @var{fmt}. You can use
17097 the same formats as for @code{print}. @xref{Output Formats,,Output
17098 Formats}, for more information.
17101 @item printf @var{template}, @var{expressions}@dots{}
17102 Print the values of one or more @var{expressions} under the control of
17103 the string @var{template}. To print several values, make
17104 @var{expressions} be a comma-separated list of individual expressions,
17105 which may be either numbers or pointers. Their values are printed as
17106 specified by @var{template}, exactly as a C program would do by
17107 executing the code below:
17110 printf (@var{template}, @var{expressions}@dots{});
17113 As in @code{C} @code{printf}, ordinary characters in @var{template}
17114 are printed verbatim, while @dfn{conversion specification} introduced
17115 by the @samp{%} character cause subsequent @var{expressions} to be
17116 evaluated, their values converted and formatted according to type and
17117 style information encoded in the conversion specifications, and then
17120 For example, you can print two values in hex like this:
17123 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
17126 @code{printf} supports all the standard @code{C} conversion
17127 specifications, including the flags and modifiers between the @samp{%}
17128 character and the conversion letter, with the following exceptions:
17132 The argument-ordering modifiers, such as @samp{2$}, are not supported.
17135 The modifier @samp{*} is not supported for specifying precision or
17139 The @samp{'} flag (for separation of digits into groups according to
17140 @code{LC_NUMERIC'}) is not supported.
17143 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
17147 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
17150 The conversion letters @samp{a} and @samp{A} are not supported.
17154 Note that the @samp{ll} type modifier is supported only if the
17155 underlying @code{C} implementation used to build @value{GDBN} supports
17156 the @code{long long int} type, and the @samp{L} type modifier is
17157 supported only if @code{long double} type is available.
17159 As in @code{C}, @code{printf} supports simple backslash-escape
17160 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
17161 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
17162 single character. Octal and hexadecimal escape sequences are not
17165 Additionally, @code{printf} supports conversion specifications for DFP
17166 (@dfn{Decimal Floating Point}) types using the following length modifiers
17167 together with a floating point specifier.
17172 @samp{H} for printing @code{Decimal32} types.
17175 @samp{D} for printing @code{Decimal64} types.
17178 @samp{DD} for printing @code{Decimal128} types.
17181 If the underlying @code{C} implementation used to build @value{GDBN} has
17182 support for the three length modifiers for DFP types, other modifiers
17183 such as width and precision will also be available for @value{GDBN} to use.
17185 In case there is no such @code{C} support, no additional modifiers will be
17186 available and the value will be printed in the standard way.
17188 Here's an example of printing DFP types using the above conversion letters:
17190 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
17196 @chapter Command Interpreters
17197 @cindex command interpreters
17199 @value{GDBN} supports multiple command interpreters, and some command
17200 infrastructure to allow users or user interface writers to switch
17201 between interpreters or run commands in other interpreters.
17203 @value{GDBN} currently supports two command interpreters, the console
17204 interpreter (sometimes called the command-line interpreter or @sc{cli})
17205 and the machine interface interpreter (or @sc{gdb/mi}). This manual
17206 describes both of these interfaces in great detail.
17208 By default, @value{GDBN} will start with the console interpreter.
17209 However, the user may choose to start @value{GDBN} with another
17210 interpreter by specifying the @option{-i} or @option{--interpreter}
17211 startup options. Defined interpreters include:
17215 @cindex console interpreter
17216 The traditional console or command-line interpreter. This is the most often
17217 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
17218 @value{GDBN} will use this interpreter.
17221 @cindex mi interpreter
17222 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
17223 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
17224 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
17228 @cindex mi2 interpreter
17229 The current @sc{gdb/mi} interface.
17232 @cindex mi1 interpreter
17233 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
17237 @cindex invoke another interpreter
17238 The interpreter being used by @value{GDBN} may not be dynamically
17239 switched at runtime. Although possible, this could lead to a very
17240 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
17241 enters the command "interpreter-set console" in a console view,
17242 @value{GDBN} would switch to using the console interpreter, rendering
17243 the IDE inoperable!
17245 @kindex interpreter-exec
17246 Although you may only choose a single interpreter at startup, you may execute
17247 commands in any interpreter from the current interpreter using the appropriate
17248 command. If you are running the console interpreter, simply use the
17249 @code{interpreter-exec} command:
17252 interpreter-exec mi "-data-list-register-names"
17255 @sc{gdb/mi} has a similar command, although it is only available in versions of
17256 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
17259 @chapter @value{GDBN} Text User Interface
17261 @cindex Text User Interface
17264 * TUI Overview:: TUI overview
17265 * TUI Keys:: TUI key bindings
17266 * TUI Single Key Mode:: TUI single key mode
17267 * TUI Commands:: TUI-specific commands
17268 * TUI Configuration:: TUI configuration variables
17271 The @value{GDBN} Text User Interface (TUI) is a terminal
17272 interface which uses the @code{curses} library to show the source
17273 file, the assembly output, the program registers and @value{GDBN}
17274 commands in separate text windows. The TUI mode is supported only
17275 on platforms where a suitable version of the @code{curses} library
17278 @pindex @value{GDBTUI}
17279 The TUI mode is enabled by default when you invoke @value{GDBN} as
17280 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
17281 You can also switch in and out of TUI mode while @value{GDBN} runs by
17282 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
17283 @xref{TUI Keys, ,TUI Key Bindings}.
17286 @section TUI Overview
17288 In TUI mode, @value{GDBN} can display several text windows:
17292 This window is the @value{GDBN} command window with the @value{GDBN}
17293 prompt and the @value{GDBN} output. The @value{GDBN} input is still
17294 managed using readline.
17297 The source window shows the source file of the program. The current
17298 line and active breakpoints are displayed in this window.
17301 The assembly window shows the disassembly output of the program.
17304 This window shows the processor registers. Registers are highlighted
17305 when their values change.
17308 The source and assembly windows show the current program position
17309 by highlighting the current line and marking it with a @samp{>} marker.
17310 Breakpoints are indicated with two markers. The first marker
17311 indicates the breakpoint type:
17315 Breakpoint which was hit at least once.
17318 Breakpoint which was never hit.
17321 Hardware breakpoint which was hit at least once.
17324 Hardware breakpoint which was never hit.
17327 The second marker indicates whether the breakpoint is enabled or not:
17331 Breakpoint is enabled.
17334 Breakpoint is disabled.
17337 The source, assembly and register windows are updated when the current
17338 thread changes, when the frame changes, or when the program counter
17341 These windows are not all visible at the same time. The command
17342 window is always visible. The others can be arranged in several
17353 source and assembly,
17356 source and registers, or
17359 assembly and registers.
17362 A status line above the command window shows the following information:
17366 Indicates the current @value{GDBN} target.
17367 (@pxref{Targets, ,Specifying a Debugging Target}).
17370 Gives the current process or thread number.
17371 When no process is being debugged, this field is set to @code{No process}.
17374 Gives the current function name for the selected frame.
17375 The name is demangled if demangling is turned on (@pxref{Print Settings}).
17376 When there is no symbol corresponding to the current program counter,
17377 the string @code{??} is displayed.
17380 Indicates the current line number for the selected frame.
17381 When the current line number is not known, the string @code{??} is displayed.
17384 Indicates the current program counter address.
17388 @section TUI Key Bindings
17389 @cindex TUI key bindings
17391 The TUI installs several key bindings in the readline keymaps
17392 (@pxref{Command Line Editing}). The following key bindings
17393 are installed for both TUI mode and the @value{GDBN} standard mode.
17402 Enter or leave the TUI mode. When leaving the TUI mode,
17403 the curses window management stops and @value{GDBN} operates using
17404 its standard mode, writing on the terminal directly. When reentering
17405 the TUI mode, control is given back to the curses windows.
17406 The screen is then refreshed.
17410 Use a TUI layout with only one window. The layout will
17411 either be @samp{source} or @samp{assembly}. When the TUI mode
17412 is not active, it will switch to the TUI mode.
17414 Think of this key binding as the Emacs @kbd{C-x 1} binding.
17418 Use a TUI layout with at least two windows. When the current
17419 layout already has two windows, the next layout with two windows is used.
17420 When a new layout is chosen, one window will always be common to the
17421 previous layout and the new one.
17423 Think of it as the Emacs @kbd{C-x 2} binding.
17427 Change the active window. The TUI associates several key bindings
17428 (like scrolling and arrow keys) with the active window. This command
17429 gives the focus to the next TUI window.
17431 Think of it as the Emacs @kbd{C-x o} binding.
17435 Switch in and out of the TUI SingleKey mode that binds single
17436 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
17439 The following key bindings only work in the TUI mode:
17444 Scroll the active window one page up.
17448 Scroll the active window one page down.
17452 Scroll the active window one line up.
17456 Scroll the active window one line down.
17460 Scroll the active window one column left.
17464 Scroll the active window one column right.
17468 Refresh the screen.
17471 Because the arrow keys scroll the active window in the TUI mode, they
17472 are not available for their normal use by readline unless the command
17473 window has the focus. When another window is active, you must use
17474 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
17475 and @kbd{C-f} to control the command window.
17477 @node TUI Single Key Mode
17478 @section TUI Single Key Mode
17479 @cindex TUI single key mode
17481 The TUI also provides a @dfn{SingleKey} mode, which binds several
17482 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
17483 switch into this mode, where the following key bindings are used:
17486 @kindex c @r{(SingleKey TUI key)}
17490 @kindex d @r{(SingleKey TUI key)}
17494 @kindex f @r{(SingleKey TUI key)}
17498 @kindex n @r{(SingleKey TUI key)}
17502 @kindex q @r{(SingleKey TUI key)}
17504 exit the SingleKey mode.
17506 @kindex r @r{(SingleKey TUI key)}
17510 @kindex s @r{(SingleKey TUI key)}
17514 @kindex u @r{(SingleKey TUI key)}
17518 @kindex v @r{(SingleKey TUI key)}
17522 @kindex w @r{(SingleKey TUI key)}
17527 Other keys temporarily switch to the @value{GDBN} command prompt.
17528 The key that was pressed is inserted in the editing buffer so that
17529 it is possible to type most @value{GDBN} commands without interaction
17530 with the TUI SingleKey mode. Once the command is entered the TUI
17531 SingleKey mode is restored. The only way to permanently leave
17532 this mode is by typing @kbd{q} or @kbd{C-x s}.
17536 @section TUI-specific Commands
17537 @cindex TUI commands
17539 The TUI has specific commands to control the text windows.
17540 These commands are always available, even when @value{GDBN} is not in
17541 the TUI mode. When @value{GDBN} is in the standard mode, most
17542 of these commands will automatically switch to the TUI mode.
17547 List and give the size of all displayed windows.
17551 Display the next layout.
17554 Display the previous layout.
17557 Display the source window only.
17560 Display the assembly window only.
17563 Display the source and assembly window.
17566 Display the register window together with the source or assembly window.
17570 Make the next window active for scrolling.
17573 Make the previous window active for scrolling.
17576 Make the source window active for scrolling.
17579 Make the assembly window active for scrolling.
17582 Make the register window active for scrolling.
17585 Make the command window active for scrolling.
17589 Refresh the screen. This is similar to typing @kbd{C-L}.
17591 @item tui reg float
17593 Show the floating point registers in the register window.
17595 @item tui reg general
17596 Show the general registers in the register window.
17599 Show the next register group. The list of register groups as well as
17600 their order is target specific. The predefined register groups are the
17601 following: @code{general}, @code{float}, @code{system}, @code{vector},
17602 @code{all}, @code{save}, @code{restore}.
17604 @item tui reg system
17605 Show the system registers in the register window.
17609 Update the source window and the current execution point.
17611 @item winheight @var{name} +@var{count}
17612 @itemx winheight @var{name} -@var{count}
17614 Change the height of the window @var{name} by @var{count}
17615 lines. Positive counts increase the height, while negative counts
17618 @item tabset @var{nchars}
17620 Set the width of tab stops to be @var{nchars} characters.
17623 @node TUI Configuration
17624 @section TUI Configuration Variables
17625 @cindex TUI configuration variables
17627 Several configuration variables control the appearance of TUI windows.
17630 @item set tui border-kind @var{kind}
17631 @kindex set tui border-kind
17632 Select the border appearance for the source, assembly and register windows.
17633 The possible values are the following:
17636 Use a space character to draw the border.
17639 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
17642 Use the Alternate Character Set to draw the border. The border is
17643 drawn using character line graphics if the terminal supports them.
17646 @item set tui border-mode @var{mode}
17647 @kindex set tui border-mode
17648 @itemx set tui active-border-mode @var{mode}
17649 @kindex set tui active-border-mode
17650 Select the display attributes for the borders of the inactive windows
17651 or the active window. The @var{mode} can be one of the following:
17654 Use normal attributes to display the border.
17660 Use reverse video mode.
17663 Use half bright mode.
17665 @item half-standout
17666 Use half bright and standout mode.
17669 Use extra bright or bold mode.
17671 @item bold-standout
17672 Use extra bright or bold and standout mode.
17677 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17680 @cindex @sc{gnu} Emacs
17681 A special interface allows you to use @sc{gnu} Emacs to view (and
17682 edit) the source files for the program you are debugging with
17685 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17686 executable file you want to debug as an argument. This command starts
17687 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17688 created Emacs buffer.
17689 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17691 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17696 All ``terminal'' input and output goes through an Emacs buffer, called
17699 This applies both to @value{GDBN} commands and their output, and to the input
17700 and output done by the program you are debugging.
17702 This is useful because it means that you can copy the text of previous
17703 commands and input them again; you can even use parts of the output
17706 All the facilities of Emacs' Shell mode are available for interacting
17707 with your program. In particular, you can send signals the usual
17708 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17712 @value{GDBN} displays source code through Emacs.
17714 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17715 source file for that frame and puts an arrow (@samp{=>}) at the
17716 left margin of the current line. Emacs uses a separate buffer for
17717 source display, and splits the screen to show both your @value{GDBN} session
17720 Explicit @value{GDBN} @code{list} or search commands still produce output as
17721 usual, but you probably have no reason to use them from Emacs.
17724 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17725 a graphical mode, enabled by default, which provides further buffers
17726 that can control the execution and describe the state of your program.
17727 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17729 If you specify an absolute file name when prompted for the @kbd{M-x
17730 gdb} argument, then Emacs sets your current working directory to where
17731 your program resides. If you only specify the file name, then Emacs
17732 sets your current working directory to to the directory associated
17733 with the previous buffer. In this case, @value{GDBN} may find your
17734 program by searching your environment's @code{PATH} variable, but on
17735 some operating systems it might not find the source. So, although the
17736 @value{GDBN} input and output session proceeds normally, the auxiliary
17737 buffer does not display the current source and line of execution.
17739 The initial working directory of @value{GDBN} is printed on the top
17740 line of the GUD buffer and this serves as a default for the commands
17741 that specify files for @value{GDBN} to operate on. @xref{Files,
17742 ,Commands to Specify Files}.
17744 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17745 need to call @value{GDBN} by a different name (for example, if you
17746 keep several configurations around, with different names) you can
17747 customize the Emacs variable @code{gud-gdb-command-name} to run the
17750 In the GUD buffer, you can use these special Emacs commands in
17751 addition to the standard Shell mode commands:
17755 Describe the features of Emacs' GUD Mode.
17758 Execute to another source line, like the @value{GDBN} @code{step} command; also
17759 update the display window to show the current file and location.
17762 Execute to next source line in this function, skipping all function
17763 calls, like the @value{GDBN} @code{next} command. Then update the display window
17764 to show the current file and location.
17767 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17768 display window accordingly.
17771 Execute until exit from the selected stack frame, like the @value{GDBN}
17772 @code{finish} command.
17775 Continue execution of your program, like the @value{GDBN} @code{continue}
17779 Go up the number of frames indicated by the numeric argument
17780 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17781 like the @value{GDBN} @code{up} command.
17784 Go down the number of frames indicated by the numeric argument, like the
17785 @value{GDBN} @code{down} command.
17788 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17789 tells @value{GDBN} to set a breakpoint on the source line point is on.
17791 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17792 separate frame which shows a backtrace when the GUD buffer is current.
17793 Move point to any frame in the stack and type @key{RET} to make it
17794 become the current frame and display the associated source in the
17795 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17796 selected frame become the current one. In graphical mode, the
17797 speedbar displays watch expressions.
17799 If you accidentally delete the source-display buffer, an easy way to get
17800 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17801 request a frame display; when you run under Emacs, this recreates
17802 the source buffer if necessary to show you the context of the current
17805 The source files displayed in Emacs are in ordinary Emacs buffers
17806 which are visiting the source files in the usual way. You can edit
17807 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17808 communicates with Emacs in terms of line numbers. If you add or
17809 delete lines from the text, the line numbers that @value{GDBN} knows cease
17810 to correspond properly with the code.
17812 A more detailed description of Emacs' interaction with @value{GDBN} is
17813 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17816 @c The following dropped because Epoch is nonstandard. Reactivate
17817 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17819 @kindex Emacs Epoch environment
17823 Version 18 of @sc{gnu} Emacs has a built-in window system
17824 called the @code{epoch}
17825 environment. Users of this environment can use a new command,
17826 @code{inspect} which performs identically to @code{print} except that
17827 each value is printed in its own window.
17832 @chapter The @sc{gdb/mi} Interface
17834 @unnumberedsec Function and Purpose
17836 @cindex @sc{gdb/mi}, its purpose
17837 @sc{gdb/mi} is a line based machine oriented text interface to
17838 @value{GDBN} and is activated by specifying using the
17839 @option{--interpreter} command line option (@pxref{Mode Options}). It
17840 is specifically intended to support the development of systems which
17841 use the debugger as just one small component of a larger system.
17843 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17844 in the form of a reference manual.
17846 Note that @sc{gdb/mi} is still under construction, so some of the
17847 features described below are incomplete and subject to change
17848 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17850 @unnumberedsec Notation and Terminology
17852 @cindex notational conventions, for @sc{gdb/mi}
17853 This chapter uses the following notation:
17857 @code{|} separates two alternatives.
17860 @code{[ @var{something} ]} indicates that @var{something} is optional:
17861 it may or may not be given.
17864 @code{( @var{group} )*} means that @var{group} inside the parentheses
17865 may repeat zero or more times.
17868 @code{( @var{group} )+} means that @var{group} inside the parentheses
17869 may repeat one or more times.
17872 @code{"@var{string}"} means a literal @var{string}.
17876 @heading Dependencies
17880 * GDB/MI Command Syntax::
17881 * GDB/MI Compatibility with CLI::
17882 * GDB/MI Development and Front Ends::
17883 * GDB/MI Output Records::
17884 * GDB/MI Simple Examples::
17885 * GDB/MI Command Description Format::
17886 * GDB/MI Breakpoint Commands::
17887 * GDB/MI Program Context::
17888 * GDB/MI Thread Commands::
17889 * GDB/MI Program Execution::
17890 * GDB/MI Stack Manipulation::
17891 * GDB/MI Variable Objects::
17892 * GDB/MI Data Manipulation::
17893 * GDB/MI Tracepoint Commands::
17894 * GDB/MI Symbol Query::
17895 * GDB/MI File Commands::
17897 * GDB/MI Kod Commands::
17898 * GDB/MI Memory Overlay Commands::
17899 * GDB/MI Signal Handling Commands::
17901 * GDB/MI Target Manipulation::
17902 * GDB/MI File Transfer Commands::
17903 * GDB/MI Miscellaneous Commands::
17906 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17907 @node GDB/MI Command Syntax
17908 @section @sc{gdb/mi} Command Syntax
17911 * GDB/MI Input Syntax::
17912 * GDB/MI Output Syntax::
17915 @node GDB/MI Input Syntax
17916 @subsection @sc{gdb/mi} Input Syntax
17918 @cindex input syntax for @sc{gdb/mi}
17919 @cindex @sc{gdb/mi}, input syntax
17921 @item @var{command} @expansion{}
17922 @code{@var{cli-command} | @var{mi-command}}
17924 @item @var{cli-command} @expansion{}
17925 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17926 @var{cli-command} is any existing @value{GDBN} CLI command.
17928 @item @var{mi-command} @expansion{}
17929 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17930 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17932 @item @var{token} @expansion{}
17933 "any sequence of digits"
17935 @item @var{option} @expansion{}
17936 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17938 @item @var{parameter} @expansion{}
17939 @code{@var{non-blank-sequence} | @var{c-string}}
17941 @item @var{operation} @expansion{}
17942 @emph{any of the operations described in this chapter}
17944 @item @var{non-blank-sequence} @expansion{}
17945 @emph{anything, provided it doesn't contain special characters such as
17946 "-", @var{nl}, """ and of course " "}
17948 @item @var{c-string} @expansion{}
17949 @code{""" @var{seven-bit-iso-c-string-content} """}
17951 @item @var{nl} @expansion{}
17960 The CLI commands are still handled by the @sc{mi} interpreter; their
17961 output is described below.
17964 The @code{@var{token}}, when present, is passed back when the command
17968 Some @sc{mi} commands accept optional arguments as part of the parameter
17969 list. Each option is identified by a leading @samp{-} (dash) and may be
17970 followed by an optional argument parameter. Options occur first in the
17971 parameter list and can be delimited from normal parameters using
17972 @samp{--} (this is useful when some parameters begin with a dash).
17979 We want easy access to the existing CLI syntax (for debugging).
17982 We want it to be easy to spot a @sc{mi} operation.
17985 @node GDB/MI Output Syntax
17986 @subsection @sc{gdb/mi} Output Syntax
17988 @cindex output syntax of @sc{gdb/mi}
17989 @cindex @sc{gdb/mi}, output syntax
17990 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17991 followed, optionally, by a single result record. This result record
17992 is for the most recent command. The sequence of output records is
17993 terminated by @samp{(gdb)}.
17995 If an input command was prefixed with a @code{@var{token}} then the
17996 corresponding output for that command will also be prefixed by that same
18000 @item @var{output} @expansion{}
18001 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
18003 @item @var{result-record} @expansion{}
18004 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
18006 @item @var{out-of-band-record} @expansion{}
18007 @code{@var{async-record} | @var{stream-record}}
18009 @item @var{async-record} @expansion{}
18010 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
18012 @item @var{exec-async-output} @expansion{}
18013 @code{[ @var{token} ] "*" @var{async-output}}
18015 @item @var{status-async-output} @expansion{}
18016 @code{[ @var{token} ] "+" @var{async-output}}
18018 @item @var{notify-async-output} @expansion{}
18019 @code{[ @var{token} ] "=" @var{async-output}}
18021 @item @var{async-output} @expansion{}
18022 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
18024 @item @var{result-class} @expansion{}
18025 @code{"done" | "running" | "connected" | "error" | "exit"}
18027 @item @var{async-class} @expansion{}
18028 @code{"stopped" | @var{others}} (where @var{others} will be added
18029 depending on the needs---this is still in development).
18031 @item @var{result} @expansion{}
18032 @code{ @var{variable} "=" @var{value}}
18034 @item @var{variable} @expansion{}
18035 @code{ @var{string} }
18037 @item @var{value} @expansion{}
18038 @code{ @var{const} | @var{tuple} | @var{list} }
18040 @item @var{const} @expansion{}
18041 @code{@var{c-string}}
18043 @item @var{tuple} @expansion{}
18044 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
18046 @item @var{list} @expansion{}
18047 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
18048 @var{result} ( "," @var{result} )* "]" }
18050 @item @var{stream-record} @expansion{}
18051 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
18053 @item @var{console-stream-output} @expansion{}
18054 @code{"~" @var{c-string}}
18056 @item @var{target-stream-output} @expansion{}
18057 @code{"@@" @var{c-string}}
18059 @item @var{log-stream-output} @expansion{}
18060 @code{"&" @var{c-string}}
18062 @item @var{nl} @expansion{}
18065 @item @var{token} @expansion{}
18066 @emph{any sequence of digits}.
18074 All output sequences end in a single line containing a period.
18077 The @code{@var{token}} is from the corresponding request. Note that
18078 for all async output, while the token is allowed by the grammar and
18079 may be output by future versions of @value{GDBN} for select async
18080 output messages, it is generally omitted. Frontends should treat
18081 all async output as reporting general changes in the state of the
18082 target and there should be no need to associate async output to any
18086 @cindex status output in @sc{gdb/mi}
18087 @var{status-async-output} contains on-going status information about the
18088 progress of a slow operation. It can be discarded. All status output is
18089 prefixed by @samp{+}.
18092 @cindex async output in @sc{gdb/mi}
18093 @var{exec-async-output} contains asynchronous state change on the target
18094 (stopped, started, disappeared). All async output is prefixed by
18098 @cindex notify output in @sc{gdb/mi}
18099 @var{notify-async-output} contains supplementary information that the
18100 client should handle (e.g., a new breakpoint information). All notify
18101 output is prefixed by @samp{=}.
18104 @cindex console output in @sc{gdb/mi}
18105 @var{console-stream-output} is output that should be displayed as is in the
18106 console. It is the textual response to a CLI command. All the console
18107 output is prefixed by @samp{~}.
18110 @cindex target output in @sc{gdb/mi}
18111 @var{target-stream-output} is the output produced by the target program.
18112 All the target output is prefixed by @samp{@@}.
18115 @cindex log output in @sc{gdb/mi}
18116 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
18117 instance messages that should be displayed as part of an error log. All
18118 the log output is prefixed by @samp{&}.
18121 @cindex list output in @sc{gdb/mi}
18122 New @sc{gdb/mi} commands should only output @var{lists} containing
18128 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
18129 details about the various output records.
18131 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18132 @node GDB/MI Compatibility with CLI
18133 @section @sc{gdb/mi} Compatibility with CLI
18135 @cindex compatibility, @sc{gdb/mi} and CLI
18136 @cindex @sc{gdb/mi}, compatibility with CLI
18138 For the developers convenience CLI commands can be entered directly,
18139 but there may be some unexpected behaviour. For example, commands
18140 that query the user will behave as if the user replied yes, breakpoint
18141 command lists are not executed and some CLI commands, such as
18142 @code{if}, @code{when} and @code{define}, prompt for further input with
18143 @samp{>}, which is not valid MI output.
18145 This feature may be removed at some stage in the future and it is
18146 recommended that front ends use the @code{-interpreter-exec} command
18147 (@pxref{-interpreter-exec}).
18149 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18150 @node GDB/MI Development and Front Ends
18151 @section @sc{gdb/mi} Development and Front Ends
18152 @cindex @sc{gdb/mi} development
18154 The application which takes the MI output and presents the state of the
18155 program being debugged to the user is called a @dfn{front end}.
18157 Although @sc{gdb/mi} is still incomplete, it is currently being used
18158 by a variety of front ends to @value{GDBN}. This makes it difficult
18159 to introduce new functionality without breaking existing usage. This
18160 section tries to minimize the problems by describing how the protocol
18163 Some changes in MI need not break a carefully designed front end, and
18164 for these the MI version will remain unchanged. The following is a
18165 list of changes that may occur within one level, so front ends should
18166 parse MI output in a way that can handle them:
18170 New MI commands may be added.
18173 New fields may be added to the output of any MI command.
18176 The range of values for fields with specified values, e.g.,
18177 @code{in_scope} (@pxref{-var-update}) may be extended.
18179 @c The format of field's content e.g type prefix, may change so parse it
18180 @c at your own risk. Yes, in general?
18182 @c The order of fields may change? Shouldn't really matter but it might
18183 @c resolve inconsistencies.
18186 If the changes are likely to break front ends, the MI version level
18187 will be increased by one. This will allow the front end to parse the
18188 output according to the MI version. Apart from mi0, new versions of
18189 @value{GDBN} will not support old versions of MI and it will be the
18190 responsibility of the front end to work with the new one.
18192 @c Starting with mi3, add a new command -mi-version that prints the MI
18195 The best way to avoid unexpected changes in MI that might break your front
18196 end is to make your project known to @value{GDBN} developers and
18197 follow development on @email{gdb@@sourceware.org} and
18198 @email{gdb-patches@@sourceware.org}.
18199 @cindex mailing lists
18201 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18202 @node GDB/MI Output Records
18203 @section @sc{gdb/mi} Output Records
18206 * GDB/MI Result Records::
18207 * GDB/MI Stream Records::
18208 * GDB/MI Async Records::
18211 @node GDB/MI Result Records
18212 @subsection @sc{gdb/mi} Result Records
18214 @cindex result records in @sc{gdb/mi}
18215 @cindex @sc{gdb/mi}, result records
18216 In addition to a number of out-of-band notifications, the response to a
18217 @sc{gdb/mi} command includes one of the following result indications:
18221 @item "^done" [ "," @var{results} ]
18222 The synchronous operation was successful, @code{@var{results}} are the return
18227 @c Is this one correct? Should it be an out-of-band notification?
18228 The asynchronous operation was successfully started. The target is
18233 @value{GDBN} has connected to a remote target.
18235 @item "^error" "," @var{c-string}
18237 The operation failed. The @code{@var{c-string}} contains the corresponding
18242 @value{GDBN} has terminated.
18246 @node GDB/MI Stream Records
18247 @subsection @sc{gdb/mi} Stream Records
18249 @cindex @sc{gdb/mi}, stream records
18250 @cindex stream records in @sc{gdb/mi}
18251 @value{GDBN} internally maintains a number of output streams: the console, the
18252 target, and the log. The output intended for each of these streams is
18253 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
18255 Each stream record begins with a unique @dfn{prefix character} which
18256 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
18257 Syntax}). In addition to the prefix, each stream record contains a
18258 @code{@var{string-output}}. This is either raw text (with an implicit new
18259 line) or a quoted C string (which does not contain an implicit newline).
18262 @item "~" @var{string-output}
18263 The console output stream contains text that should be displayed in the
18264 CLI console window. It contains the textual responses to CLI commands.
18266 @item "@@" @var{string-output}
18267 The target output stream contains any textual output from the running
18268 target. This is only present when GDB's event loop is truly
18269 asynchronous, which is currently only the case for remote targets.
18271 @item "&" @var{string-output}
18272 The log stream contains debugging messages being produced by @value{GDBN}'s
18276 @node GDB/MI Async Records
18277 @subsection @sc{gdb/mi} Async Records
18279 @cindex async records in @sc{gdb/mi}
18280 @cindex @sc{gdb/mi}, async records
18281 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
18282 additional changes that have occurred. Those changes can either be a
18283 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
18284 target activity (e.g., target stopped).
18286 The following is the list of possible async records:
18290 @item *stopped,reason="@var{reason}"
18291 The target has stopped. The @var{reason} field can have one of the
18295 @item breakpoint-hit
18296 A breakpoint was reached.
18297 @item watchpoint-trigger
18298 A watchpoint was triggered.
18299 @item read-watchpoint-trigger
18300 A read watchpoint was triggered.
18301 @item access-watchpoint-trigger
18302 An access watchpoint was triggered.
18303 @item function-finished
18304 An -exec-finish or similar CLI command was accomplished.
18305 @item location-reached
18306 An -exec-until or similar CLI command was accomplished.
18307 @item watchpoint-scope
18308 A watchpoint has gone out of scope.
18309 @item end-stepping-range
18310 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
18311 similar CLI command was accomplished.
18312 @item exited-signalled
18313 The inferior exited because of a signal.
18315 The inferior exited.
18316 @item exited-normally
18317 The inferior exited normally.
18318 @item signal-received
18319 A signal was received by the inferior.
18322 @item =thread-created,id="@var{id}"
18323 @itemx =thread-exited,id="@var{id}"
18324 A thread either was created, or has exited. The @var{id} field
18325 contains the @value{GDBN} identifier of the thread.
18330 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18331 @node GDB/MI Simple Examples
18332 @section Simple Examples of @sc{gdb/mi} Interaction
18333 @cindex @sc{gdb/mi}, simple examples
18335 This subsection presents several simple examples of interaction using
18336 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
18337 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
18338 the output received from @sc{gdb/mi}.
18340 Note the line breaks shown in the examples are here only for
18341 readability, they don't appear in the real output.
18343 @subheading Setting a Breakpoint
18345 Setting a breakpoint generates synchronous output which contains detailed
18346 information of the breakpoint.
18349 -> -break-insert main
18350 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18351 enabled="y",addr="0x08048564",func="main",file="myprog.c",
18352 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
18356 @subheading Program Execution
18358 Program execution generates asynchronous records and MI gives the
18359 reason that execution stopped.
18365 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
18366 frame=@{addr="0x08048564",func="main",
18367 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
18368 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
18373 <- *stopped,reason="exited-normally"
18377 @subheading Quitting @value{GDBN}
18379 Quitting @value{GDBN} just prints the result class @samp{^exit}.
18387 @subheading A Bad Command
18389 Here's what happens if you pass a non-existent command:
18393 <- ^error,msg="Undefined MI command: rubbish"
18398 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18399 @node GDB/MI Command Description Format
18400 @section @sc{gdb/mi} Command Description Format
18402 The remaining sections describe blocks of commands. Each block of
18403 commands is laid out in a fashion similar to this section.
18405 @subheading Motivation
18407 The motivation for this collection of commands.
18409 @subheading Introduction
18411 A brief introduction to this collection of commands as a whole.
18413 @subheading Commands
18415 For each command in the block, the following is described:
18417 @subsubheading Synopsis
18420 -command @var{args}@dots{}
18423 @subsubheading Result
18425 @subsubheading @value{GDBN} Command
18427 The corresponding @value{GDBN} CLI command(s), if any.
18429 @subsubheading Example
18431 Example(s) formatted for readability. Some of the described commands have
18432 not been implemented yet and these are labeled N.A.@: (not available).
18435 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18436 @node GDB/MI Breakpoint Commands
18437 @section @sc{gdb/mi} Breakpoint Commands
18439 @cindex breakpoint commands for @sc{gdb/mi}
18440 @cindex @sc{gdb/mi}, breakpoint commands
18441 This section documents @sc{gdb/mi} commands for manipulating
18444 @subheading The @code{-break-after} Command
18445 @findex -break-after
18447 @subsubheading Synopsis
18450 -break-after @var{number} @var{count}
18453 The breakpoint number @var{number} is not in effect until it has been
18454 hit @var{count} times. To see how this is reflected in the output of
18455 the @samp{-break-list} command, see the description of the
18456 @samp{-break-list} command below.
18458 @subsubheading @value{GDBN} Command
18460 The corresponding @value{GDBN} command is @samp{ignore}.
18462 @subsubheading Example
18467 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
18468 enabled="y",addr="0x000100d0",func="main",file="hello.c",
18469 fullname="/home/foo/hello.c",line="5",times="0"@}
18476 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18477 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18478 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18479 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18480 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18481 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18482 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18483 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18484 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18485 line="5",times="0",ignore="3"@}]@}
18490 @subheading The @code{-break-catch} Command
18491 @findex -break-catch
18493 @subheading The @code{-break-commands} Command
18494 @findex -break-commands
18498 @subheading The @code{-break-condition} Command
18499 @findex -break-condition
18501 @subsubheading Synopsis
18504 -break-condition @var{number} @var{expr}
18507 Breakpoint @var{number} will stop the program only if the condition in
18508 @var{expr} is true. The condition becomes part of the
18509 @samp{-break-list} output (see the description of the @samp{-break-list}
18512 @subsubheading @value{GDBN} Command
18514 The corresponding @value{GDBN} command is @samp{condition}.
18516 @subsubheading Example
18520 -break-condition 1 1
18524 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18525 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18526 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18527 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18528 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18529 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18530 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18531 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18532 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18533 line="5",cond="1",times="0",ignore="3"@}]@}
18537 @subheading The @code{-break-delete} Command
18538 @findex -break-delete
18540 @subsubheading Synopsis
18543 -break-delete ( @var{breakpoint} )+
18546 Delete the breakpoint(s) whose number(s) are specified in the argument
18547 list. This is obviously reflected in the breakpoint list.
18549 @subsubheading @value{GDBN} Command
18551 The corresponding @value{GDBN} command is @samp{delete}.
18553 @subsubheading Example
18561 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18562 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18563 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18564 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18565 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18566 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18567 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18572 @subheading The @code{-break-disable} Command
18573 @findex -break-disable
18575 @subsubheading Synopsis
18578 -break-disable ( @var{breakpoint} )+
18581 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18582 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18584 @subsubheading @value{GDBN} Command
18586 The corresponding @value{GDBN} command is @samp{disable}.
18588 @subsubheading Example
18596 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18597 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18598 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18599 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18600 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18601 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18602 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18603 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18604 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18605 line="5",times="0"@}]@}
18609 @subheading The @code{-break-enable} Command
18610 @findex -break-enable
18612 @subsubheading Synopsis
18615 -break-enable ( @var{breakpoint} )+
18618 Enable (previously disabled) @var{breakpoint}(s).
18620 @subsubheading @value{GDBN} Command
18622 The corresponding @value{GDBN} command is @samp{enable}.
18624 @subsubheading Example
18632 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18633 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18634 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18635 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18636 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18637 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18638 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18639 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18640 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18641 line="5",times="0"@}]@}
18645 @subheading The @code{-break-info} Command
18646 @findex -break-info
18648 @subsubheading Synopsis
18651 -break-info @var{breakpoint}
18655 Get information about a single breakpoint.
18657 @subsubheading @value{GDBN} Command
18659 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18661 @subsubheading Example
18664 @subheading The @code{-break-insert} Command
18665 @findex -break-insert
18667 @subsubheading Synopsis
18670 -break-insert [ -t ] [ -h ] [ -f ]
18671 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18672 [ -p @var{thread} ] [ @var{location} ]
18676 If specified, @var{location}, can be one of:
18683 @item filename:linenum
18684 @item filename:function
18688 The possible optional parameters of this command are:
18692 Insert a temporary breakpoint.
18694 Insert a hardware breakpoint.
18695 @item -c @var{condition}
18696 Make the breakpoint conditional on @var{condition}.
18697 @item -i @var{ignore-count}
18698 Initialize the @var{ignore-count}.
18700 If @var{location} cannot be parsed (for example if it
18701 refers to unknown files or functions), create a pending
18702 breakpoint. Without this flag, @value{GDBN} will report
18703 an error, and won't create a breakpoint, if @var{location}
18707 @subsubheading Result
18709 The result is in the form:
18712 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18713 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18714 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18715 times="@var{times}"@}
18719 where @var{number} is the @value{GDBN} number for this breakpoint,
18720 @var{funcname} is the name of the function where the breakpoint was
18721 inserted, @var{filename} is the name of the source file which contains
18722 this function, @var{lineno} is the source line number within that file
18723 and @var{times} the number of times that the breakpoint has been hit
18724 (always 0 for -break-insert but may be greater for -break-info or -break-list
18725 which use the same output).
18727 Note: this format is open to change.
18728 @c An out-of-band breakpoint instead of part of the result?
18730 @subsubheading @value{GDBN} Command
18732 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18733 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18735 @subsubheading Example
18740 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18741 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18743 -break-insert -t foo
18744 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18745 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18748 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18749 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18750 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18751 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18752 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18753 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18754 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18755 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18756 addr="0x0001072c", func="main",file="recursive2.c",
18757 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18758 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18759 addr="0x00010774",func="foo",file="recursive2.c",
18760 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18762 -break-insert -r foo.*
18763 ~int foo(int, int);
18764 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18765 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18769 @subheading The @code{-break-list} Command
18770 @findex -break-list
18772 @subsubheading Synopsis
18778 Displays the list of inserted breakpoints, showing the following fields:
18782 number of the breakpoint
18784 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18786 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18789 is the breakpoint enabled or no: @samp{y} or @samp{n}
18791 memory location at which the breakpoint is set
18793 logical location of the breakpoint, expressed by function name, file
18796 number of times the breakpoint has been hit
18799 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18800 @code{body} field is an empty list.
18802 @subsubheading @value{GDBN} Command
18804 The corresponding @value{GDBN} command is @samp{info break}.
18806 @subsubheading Example
18811 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18812 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18813 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18814 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18815 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18816 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18817 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18818 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18819 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18820 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18821 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18822 line="13",times="0"@}]@}
18826 Here's an example of the result when there are no breakpoints:
18831 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18832 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18833 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18834 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18835 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18836 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18837 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18842 @subheading The @code{-break-watch} Command
18843 @findex -break-watch
18845 @subsubheading Synopsis
18848 -break-watch [ -a | -r ]
18851 Create a watchpoint. With the @samp{-a} option it will create an
18852 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18853 read from or on a write to the memory location. With the @samp{-r}
18854 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18855 trigger only when the memory location is accessed for reading. Without
18856 either of the options, the watchpoint created is a regular watchpoint,
18857 i.e., it will trigger when the memory location is accessed for writing.
18858 @xref{Set Watchpoints, , Setting Watchpoints}.
18860 Note that @samp{-break-list} will report a single list of watchpoints and
18861 breakpoints inserted.
18863 @subsubheading @value{GDBN} Command
18865 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18868 @subsubheading Example
18870 Setting a watchpoint on a variable in the @code{main} function:
18875 ^done,wpt=@{number="2",exp="x"@}
18880 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18881 value=@{old="-268439212",new="55"@},
18882 frame=@{func="main",args=[],file="recursive2.c",
18883 fullname="/home/foo/bar/recursive2.c",line="5"@}
18887 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18888 the program execution twice: first for the variable changing value, then
18889 for the watchpoint going out of scope.
18894 ^done,wpt=@{number="5",exp="C"@}
18899 *stopped,reason="watchpoint-trigger",
18900 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18901 frame=@{func="callee4",args=[],
18902 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18903 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18908 *stopped,reason="watchpoint-scope",wpnum="5",
18909 frame=@{func="callee3",args=[@{name="strarg",
18910 value="0x11940 \"A string argument.\""@}],
18911 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18912 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18916 Listing breakpoints and watchpoints, at different points in the program
18917 execution. Note that once the watchpoint goes out of scope, it is
18923 ^done,wpt=@{number="2",exp="C"@}
18926 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18927 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18928 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18929 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18930 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18931 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18932 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18933 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18934 addr="0x00010734",func="callee4",
18935 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18936 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18937 bkpt=@{number="2",type="watchpoint",disp="keep",
18938 enabled="y",addr="",what="C",times="0"@}]@}
18943 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18944 value=@{old="-276895068",new="3"@},
18945 frame=@{func="callee4",args=[],
18946 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18947 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18950 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18951 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18952 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18953 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18954 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18955 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18956 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18957 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18958 addr="0x00010734",func="callee4",
18959 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18960 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18961 bkpt=@{number="2",type="watchpoint",disp="keep",
18962 enabled="y",addr="",what="C",times="-5"@}]@}
18966 ^done,reason="watchpoint-scope",wpnum="2",
18967 frame=@{func="callee3",args=[@{name="strarg",
18968 value="0x11940 \"A string argument.\""@}],
18969 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18970 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18973 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18974 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18975 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18976 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18977 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18978 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18979 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18980 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18981 addr="0x00010734",func="callee4",
18982 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18983 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18988 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18989 @node GDB/MI Program Context
18990 @section @sc{gdb/mi} Program Context
18992 @subheading The @code{-exec-arguments} Command
18993 @findex -exec-arguments
18996 @subsubheading Synopsis
18999 -exec-arguments @var{args}
19002 Set the inferior program arguments, to be used in the next
19005 @subsubheading @value{GDBN} Command
19007 The corresponding @value{GDBN} command is @samp{set args}.
19009 @subsubheading Example
19012 Don't have one around.
19015 @subheading The @code{-exec-show-arguments} Command
19016 @findex -exec-show-arguments
19018 @subsubheading Synopsis
19021 -exec-show-arguments
19024 Print the arguments of the program.
19026 @subsubheading @value{GDBN} Command
19028 The corresponding @value{GDBN} command is @samp{show args}.
19030 @subsubheading Example
19034 @subheading The @code{-environment-cd} Command
19035 @findex -environment-cd
19037 @subsubheading Synopsis
19040 -environment-cd @var{pathdir}
19043 Set @value{GDBN}'s working directory.
19045 @subsubheading @value{GDBN} Command
19047 The corresponding @value{GDBN} command is @samp{cd}.
19049 @subsubheading Example
19053 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19059 @subheading The @code{-environment-directory} Command
19060 @findex -environment-directory
19062 @subsubheading Synopsis
19065 -environment-directory [ -r ] [ @var{pathdir} ]+
19068 Add directories @var{pathdir} to beginning of search path for source files.
19069 If the @samp{-r} option is used, the search path is reset to the default
19070 search path. If directories @var{pathdir} are supplied in addition to the
19071 @samp{-r} option, the search path is first reset and then addition
19073 Multiple directories may be specified, separated by blanks. Specifying
19074 multiple directories in a single command
19075 results in the directories added to the beginning of the
19076 search path in the same order they were presented in the command.
19077 If blanks are needed as
19078 part of a directory name, double-quotes should be used around
19079 the name. In the command output, the path will show up separated
19080 by the system directory-separator character. The directory-separator
19081 character must not be used
19082 in any directory name.
19083 If no directories are specified, the current search path is displayed.
19085 @subsubheading @value{GDBN} Command
19087 The corresponding @value{GDBN} command is @samp{dir}.
19089 @subsubheading Example
19093 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
19094 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19096 -environment-directory ""
19097 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
19099 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
19100 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
19102 -environment-directory -r
19103 ^done,source-path="$cdir:$cwd"
19108 @subheading The @code{-environment-path} Command
19109 @findex -environment-path
19111 @subsubheading Synopsis
19114 -environment-path [ -r ] [ @var{pathdir} ]+
19117 Add directories @var{pathdir} to beginning of search path for object files.
19118 If the @samp{-r} option is used, the search path is reset to the original
19119 search path that existed at gdb start-up. If directories @var{pathdir} are
19120 supplied in addition to the
19121 @samp{-r} option, the search path is first reset and then addition
19123 Multiple directories may be specified, separated by blanks. Specifying
19124 multiple directories in a single command
19125 results in the directories added to the beginning of the
19126 search path in the same order they were presented in the command.
19127 If blanks are needed as
19128 part of a directory name, double-quotes should be used around
19129 the name. In the command output, the path will show up separated
19130 by the system directory-separator character. The directory-separator
19131 character must not be used
19132 in any directory name.
19133 If no directories are specified, the current path is displayed.
19136 @subsubheading @value{GDBN} Command
19138 The corresponding @value{GDBN} command is @samp{path}.
19140 @subsubheading Example
19145 ^done,path="/usr/bin"
19147 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
19148 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
19150 -environment-path -r /usr/local/bin
19151 ^done,path="/usr/local/bin:/usr/bin"
19156 @subheading The @code{-environment-pwd} Command
19157 @findex -environment-pwd
19159 @subsubheading Synopsis
19165 Show the current working directory.
19167 @subsubheading @value{GDBN} Command
19169 The corresponding @value{GDBN} command is @samp{pwd}.
19171 @subsubheading Example
19176 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
19180 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19181 @node GDB/MI Thread Commands
19182 @section @sc{gdb/mi} Thread Commands
19185 @subheading The @code{-thread-info} Command
19186 @findex -thread-info
19188 @subsubheading Synopsis
19191 -thread-info [ @var{thread-id} ]
19194 Reports information about either a specific thread, if
19195 the @var{thread-id} parameter is present, or about all
19196 threads. When printing information about all threads,
19197 also reports the current thread.
19199 @subsubheading @value{GDBN} Command
19201 The @samp{info thread} command prints the same information
19204 @subsubheading Example
19209 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
19210 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},
19211 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
19212 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
19213 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}@}],
19214 current-thread-id="1"
19218 @subheading The @code{-thread-list-ids} Command
19219 @findex -thread-list-ids
19221 @subsubheading Synopsis
19227 Produces a list of the currently known @value{GDBN} thread ids. At the
19228 end of the list it also prints the total number of such threads.
19230 @subsubheading @value{GDBN} Command
19232 Part of @samp{info threads} supplies the same information.
19234 @subsubheading Example
19236 No threads present, besides the main process:
19241 ^done,thread-ids=@{@},number-of-threads="0"
19251 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19252 number-of-threads="3"
19257 @subheading The @code{-thread-select} Command
19258 @findex -thread-select
19260 @subsubheading Synopsis
19263 -thread-select @var{threadnum}
19266 Make @var{threadnum} the current thread. It prints the number of the new
19267 current thread, and the topmost frame for that thread.
19269 @subsubheading @value{GDBN} Command
19271 The corresponding @value{GDBN} command is @samp{thread}.
19273 @subsubheading Example
19280 *stopped,reason="end-stepping-range",thread-id="2",line="187",
19281 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
19285 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
19286 number-of-threads="3"
19289 ^done,new-thread-id="3",
19290 frame=@{level="0",func="vprintf",
19291 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
19292 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
19296 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19297 @node GDB/MI Program Execution
19298 @section @sc{gdb/mi} Program Execution
19300 These are the asynchronous commands which generate the out-of-band
19301 record @samp{*stopped}. Currently @value{GDBN} only really executes
19302 asynchronously with remote targets and this interaction is mimicked in
19305 @subheading The @code{-exec-continue} Command
19306 @findex -exec-continue
19308 @subsubheading Synopsis
19314 Resumes the execution of the inferior program until a breakpoint is
19315 encountered, or until the inferior exits.
19317 @subsubheading @value{GDBN} Command
19319 The corresponding @value{GDBN} corresponding is @samp{continue}.
19321 @subsubheading Example
19328 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
19329 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
19335 @subheading The @code{-exec-finish} Command
19336 @findex -exec-finish
19338 @subsubheading Synopsis
19344 Resumes the execution of the inferior program until the current
19345 function is exited. Displays the results returned by the function.
19347 @subsubheading @value{GDBN} Command
19349 The corresponding @value{GDBN} command is @samp{finish}.
19351 @subsubheading Example
19353 Function returning @code{void}.
19360 *stopped,reason="function-finished",frame=@{func="main",args=[],
19361 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
19365 Function returning other than @code{void}. The name of the internal
19366 @value{GDBN} variable storing the result is printed, together with the
19373 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
19374 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
19375 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19376 gdb-result-var="$1",return-value="0"
19381 @subheading The @code{-exec-interrupt} Command
19382 @findex -exec-interrupt
19384 @subsubheading Synopsis
19390 Interrupts the background execution of the target. Note how the token
19391 associated with the stop message is the one for the execution command
19392 that has been interrupted. The token for the interrupt itself only
19393 appears in the @samp{^done} output. If the user is trying to
19394 interrupt a non-running program, an error message will be printed.
19396 @subsubheading @value{GDBN} Command
19398 The corresponding @value{GDBN} command is @samp{interrupt}.
19400 @subsubheading Example
19411 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
19412 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
19413 fullname="/home/foo/bar/try.c",line="13"@}
19418 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
19423 @subheading The @code{-exec-next} Command
19426 @subsubheading Synopsis
19432 Resumes execution of the inferior program, stopping when the beginning
19433 of the next source line is reached.
19435 @subsubheading @value{GDBN} Command
19437 The corresponding @value{GDBN} command is @samp{next}.
19439 @subsubheading Example
19445 *stopped,reason="end-stepping-range",line="8",file="hello.c"
19450 @subheading The @code{-exec-next-instruction} Command
19451 @findex -exec-next-instruction
19453 @subsubheading Synopsis
19456 -exec-next-instruction
19459 Executes one machine instruction. If the instruction is a function
19460 call, continues until the function returns. If the program stops at an
19461 instruction in the middle of a source line, the address will be
19464 @subsubheading @value{GDBN} Command
19466 The corresponding @value{GDBN} command is @samp{nexti}.
19468 @subsubheading Example
19472 -exec-next-instruction
19476 *stopped,reason="end-stepping-range",
19477 addr="0x000100d4",line="5",file="hello.c"
19482 @subheading The @code{-exec-return} Command
19483 @findex -exec-return
19485 @subsubheading Synopsis
19491 Makes current function return immediately. Doesn't execute the inferior.
19492 Displays the new current frame.
19494 @subsubheading @value{GDBN} Command
19496 The corresponding @value{GDBN} command is @samp{return}.
19498 @subsubheading Example
19502 200-break-insert callee4
19503 200^done,bkpt=@{number="1",addr="0x00010734",
19504 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19509 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
19510 frame=@{func="callee4",args=[],
19511 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19512 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19518 111^done,frame=@{level="0",func="callee3",
19519 args=[@{name="strarg",
19520 value="0x11940 \"A string argument.\""@}],
19521 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19522 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19527 @subheading The @code{-exec-run} Command
19530 @subsubheading Synopsis
19536 Starts execution of the inferior from the beginning. The inferior
19537 executes until either a breakpoint is encountered or the program
19538 exits. In the latter case the output will include an exit code, if
19539 the program has exited exceptionally.
19541 @subsubheading @value{GDBN} Command
19543 The corresponding @value{GDBN} command is @samp{run}.
19545 @subsubheading Examples
19550 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19555 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
19556 frame=@{func="main",args=[],file="recursive2.c",
19557 fullname="/home/foo/bar/recursive2.c",line="4"@}
19562 Program exited normally:
19570 *stopped,reason="exited-normally"
19575 Program exited exceptionally:
19583 *stopped,reason="exited",exit-code="01"
19587 Another way the program can terminate is if it receives a signal such as
19588 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19592 *stopped,reason="exited-signalled",signal-name="SIGINT",
19593 signal-meaning="Interrupt"
19597 @c @subheading -exec-signal
19600 @subheading The @code{-exec-step} Command
19603 @subsubheading Synopsis
19609 Resumes execution of the inferior program, stopping when the beginning
19610 of the next source line is reached, if the next source line is not a
19611 function call. If it is, stop at the first instruction of the called
19614 @subsubheading @value{GDBN} Command
19616 The corresponding @value{GDBN} command is @samp{step}.
19618 @subsubheading Example
19620 Stepping into a function:
19626 *stopped,reason="end-stepping-range",
19627 frame=@{func="foo",args=[@{name="a",value="10"@},
19628 @{name="b",value="0"@}],file="recursive2.c",
19629 fullname="/home/foo/bar/recursive2.c",line="11"@}
19639 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19644 @subheading The @code{-exec-step-instruction} Command
19645 @findex -exec-step-instruction
19647 @subsubheading Synopsis
19650 -exec-step-instruction
19653 Resumes the inferior which executes one machine instruction. The
19654 output, once @value{GDBN} has stopped, will vary depending on whether
19655 we have stopped in the middle of a source line or not. In the former
19656 case, the address at which the program stopped will be printed as
19659 @subsubheading @value{GDBN} Command
19661 The corresponding @value{GDBN} command is @samp{stepi}.
19663 @subsubheading Example
19667 -exec-step-instruction
19671 *stopped,reason="end-stepping-range",
19672 frame=@{func="foo",args=[],file="try.c",
19673 fullname="/home/foo/bar/try.c",line="10"@}
19675 -exec-step-instruction
19679 *stopped,reason="end-stepping-range",
19680 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19681 fullname="/home/foo/bar/try.c",line="10"@}
19686 @subheading The @code{-exec-until} Command
19687 @findex -exec-until
19689 @subsubheading Synopsis
19692 -exec-until [ @var{location} ]
19695 Executes the inferior until the @var{location} specified in the
19696 argument is reached. If there is no argument, the inferior executes
19697 until a source line greater than the current one is reached. The
19698 reason for stopping in this case will be @samp{location-reached}.
19700 @subsubheading @value{GDBN} Command
19702 The corresponding @value{GDBN} command is @samp{until}.
19704 @subsubheading Example
19708 -exec-until recursive2.c:6
19712 *stopped,reason="location-reached",frame=@{func="main",args=[],
19713 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19718 @subheading -file-clear
19719 Is this going away????
19722 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19723 @node GDB/MI Stack Manipulation
19724 @section @sc{gdb/mi} Stack Manipulation Commands
19727 @subheading The @code{-stack-info-frame} Command
19728 @findex -stack-info-frame
19730 @subsubheading Synopsis
19736 Get info on the selected frame.
19738 @subsubheading @value{GDBN} Command
19740 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19741 (without arguments).
19743 @subsubheading Example
19748 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19749 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19750 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19754 @subheading The @code{-stack-info-depth} Command
19755 @findex -stack-info-depth
19757 @subsubheading Synopsis
19760 -stack-info-depth [ @var{max-depth} ]
19763 Return the depth of the stack. If the integer argument @var{max-depth}
19764 is specified, do not count beyond @var{max-depth} frames.
19766 @subsubheading @value{GDBN} Command
19768 There's no equivalent @value{GDBN} command.
19770 @subsubheading Example
19772 For a stack with frame levels 0 through 11:
19779 -stack-info-depth 4
19782 -stack-info-depth 12
19785 -stack-info-depth 11
19788 -stack-info-depth 13
19793 @subheading The @code{-stack-list-arguments} Command
19794 @findex -stack-list-arguments
19796 @subsubheading Synopsis
19799 -stack-list-arguments @var{show-values}
19800 [ @var{low-frame} @var{high-frame} ]
19803 Display a list of the arguments for the frames between @var{low-frame}
19804 and @var{high-frame} (inclusive). If @var{low-frame} and
19805 @var{high-frame} are not provided, list the arguments for the whole
19806 call stack. If the two arguments are equal, show the single frame
19807 at the corresponding level. It is an error if @var{low-frame} is
19808 larger than the actual number of frames. On the other hand,
19809 @var{high-frame} may be larger than the actual number of frames, in
19810 which case only existing frames will be returned.
19812 The @var{show-values} argument must have a value of 0 or 1. A value of
19813 0 means that only the names of the arguments are listed, a value of 1
19814 means that both names and values of the arguments are printed.
19816 @subsubheading @value{GDBN} Command
19818 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19819 @samp{gdb_get_args} command which partially overlaps with the
19820 functionality of @samp{-stack-list-arguments}.
19822 @subsubheading Example
19829 frame=@{level="0",addr="0x00010734",func="callee4",
19830 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19831 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19832 frame=@{level="1",addr="0x0001076c",func="callee3",
19833 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19834 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19835 frame=@{level="2",addr="0x0001078c",func="callee2",
19836 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19837 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19838 frame=@{level="3",addr="0x000107b4",func="callee1",
19839 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19840 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19841 frame=@{level="4",addr="0x000107e0",func="main",
19842 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19843 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19845 -stack-list-arguments 0
19848 frame=@{level="0",args=[]@},
19849 frame=@{level="1",args=[name="strarg"]@},
19850 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19851 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19852 frame=@{level="4",args=[]@}]
19854 -stack-list-arguments 1
19857 frame=@{level="0",args=[]@},
19859 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19860 frame=@{level="2",args=[
19861 @{name="intarg",value="2"@},
19862 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19863 @{frame=@{level="3",args=[
19864 @{name="intarg",value="2"@},
19865 @{name="strarg",value="0x11940 \"A string argument.\""@},
19866 @{name="fltarg",value="3.5"@}]@},
19867 frame=@{level="4",args=[]@}]
19869 -stack-list-arguments 0 2 2
19870 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19872 -stack-list-arguments 1 2 2
19873 ^done,stack-args=[frame=@{level="2",
19874 args=[@{name="intarg",value="2"@},
19875 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19879 @c @subheading -stack-list-exception-handlers
19882 @subheading The @code{-stack-list-frames} Command
19883 @findex -stack-list-frames
19885 @subsubheading Synopsis
19888 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19891 List the frames currently on the stack. For each frame it displays the
19896 The frame number, 0 being the topmost frame, i.e., the innermost function.
19898 The @code{$pc} value for that frame.
19902 File name of the source file where the function lives.
19904 Line number corresponding to the @code{$pc}.
19907 If invoked without arguments, this command prints a backtrace for the
19908 whole stack. If given two integer arguments, it shows the frames whose
19909 levels are between the two arguments (inclusive). If the two arguments
19910 are equal, it shows the single frame at the corresponding level. It is
19911 an error if @var{low-frame} is larger than the actual number of
19912 frames. On the other hand, @var{high-frame} may be larger than the
19913 actual number of frames, in which case only existing frames will be returned.
19915 @subsubheading @value{GDBN} Command
19917 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19919 @subsubheading Example
19921 Full stack backtrace:
19927 [frame=@{level="0",addr="0x0001076c",func="foo",
19928 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19929 frame=@{level="1",addr="0x000107a4",func="foo",
19930 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19931 frame=@{level="2",addr="0x000107a4",func="foo",
19932 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19933 frame=@{level="3",addr="0x000107a4",func="foo",
19934 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19935 frame=@{level="4",addr="0x000107a4",func="foo",
19936 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19937 frame=@{level="5",addr="0x000107a4",func="foo",
19938 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19939 frame=@{level="6",addr="0x000107a4",func="foo",
19940 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19941 frame=@{level="7",addr="0x000107a4",func="foo",
19942 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19943 frame=@{level="8",addr="0x000107a4",func="foo",
19944 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19945 frame=@{level="9",addr="0x000107a4",func="foo",
19946 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19947 frame=@{level="10",addr="0x000107a4",func="foo",
19948 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19949 frame=@{level="11",addr="0x00010738",func="main",
19950 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19954 Show frames between @var{low_frame} and @var{high_frame}:
19958 -stack-list-frames 3 5
19960 [frame=@{level="3",addr="0x000107a4",func="foo",
19961 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19962 frame=@{level="4",addr="0x000107a4",func="foo",
19963 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19964 frame=@{level="5",addr="0x000107a4",func="foo",
19965 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19969 Show a single frame:
19973 -stack-list-frames 3 3
19975 [frame=@{level="3",addr="0x000107a4",func="foo",
19976 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19981 @subheading The @code{-stack-list-locals} Command
19982 @findex -stack-list-locals
19984 @subsubheading Synopsis
19987 -stack-list-locals @var{print-values}
19990 Display the local variable names for the selected frame. If
19991 @var{print-values} is 0 or @code{--no-values}, print only the names of
19992 the variables; if it is 1 or @code{--all-values}, print also their
19993 values; and if it is 2 or @code{--simple-values}, print the name,
19994 type and value for simple data types and the name and type for arrays,
19995 structures and unions. In this last case, a frontend can immediately
19996 display the value of simple data types and create variable objects for
19997 other data types when the user wishes to explore their values in
20000 @subsubheading @value{GDBN} Command
20002 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
20004 @subsubheading Example
20008 -stack-list-locals 0
20009 ^done,locals=[name="A",name="B",name="C"]
20011 -stack-list-locals --all-values
20012 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
20013 @{name="C",value="@{1, 2, 3@}"@}]
20014 -stack-list-locals --simple-values
20015 ^done,locals=[@{name="A",type="int",value="1"@},
20016 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
20021 @subheading The @code{-stack-select-frame} Command
20022 @findex -stack-select-frame
20024 @subsubheading Synopsis
20027 -stack-select-frame @var{framenum}
20030 Change the selected frame. Select a different frame @var{framenum} on
20033 @subsubheading @value{GDBN} Command
20035 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
20036 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
20038 @subsubheading Example
20042 -stack-select-frame 2
20047 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20048 @node GDB/MI Variable Objects
20049 @section @sc{gdb/mi} Variable Objects
20053 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20055 For the implementation of a variable debugger window (locals, watched
20056 expressions, etc.), we are proposing the adaptation of the existing code
20057 used by @code{Insight}.
20059 The two main reasons for that are:
20063 It has been proven in practice (it is already on its second generation).
20066 It will shorten development time (needless to say how important it is
20070 The original interface was designed to be used by Tcl code, so it was
20071 slightly changed so it could be used through @sc{gdb/mi}. This section
20072 describes the @sc{gdb/mi} operations that will be available and gives some
20073 hints about their use.
20075 @emph{Note}: In addition to the set of operations described here, we
20076 expect the @sc{gui} implementation of a variable window to require, at
20077 least, the following operations:
20080 @item @code{-gdb-show} @code{output-radix}
20081 @item @code{-stack-list-arguments}
20082 @item @code{-stack-list-locals}
20083 @item @code{-stack-select-frame}
20088 @subheading Introduction to Variable Objects
20090 @cindex variable objects in @sc{gdb/mi}
20092 Variable objects are "object-oriented" MI interface for examining and
20093 changing values of expressions. Unlike some other MI interfaces that
20094 work with expressions, variable objects are specifically designed for
20095 simple and efficient presentation in the frontend. A variable object
20096 is identified by string name. When a variable object is created, the
20097 frontend specifies the expression for that variable object. The
20098 expression can be a simple variable, or it can be an arbitrary complex
20099 expression, and can even involve CPU registers. After creating a
20100 variable object, the frontend can invoke other variable object
20101 operations---for example to obtain or change the value of a variable
20102 object, or to change display format.
20104 Variable objects have hierarchical tree structure. Any variable object
20105 that corresponds to a composite type, such as structure in C, has
20106 a number of child variable objects, for example corresponding to each
20107 element of a structure. A child variable object can itself have
20108 children, recursively. Recursion ends when we reach
20109 leaf variable objects, which always have built-in types. Child variable
20110 objects are created only by explicit request, so if a frontend
20111 is not interested in the children of a particular variable object, no
20112 child will be created.
20114 For a leaf variable object it is possible to obtain its value as a
20115 string, or set the value from a string. String value can be also
20116 obtained for a non-leaf variable object, but it's generally a string
20117 that only indicates the type of the object, and does not list its
20118 contents. Assignment to a non-leaf variable object is not allowed.
20120 A frontend does not need to read the values of all variable objects each time
20121 the program stops. Instead, MI provides an update command that lists all
20122 variable objects whose values has changed since the last update
20123 operation. This considerably reduces the amount of data that must
20124 be transferred to the frontend. As noted above, children variable
20125 objects are created on demand, and only leaf variable objects have a
20126 real value. As result, gdb will read target memory only for leaf
20127 variables that frontend has created.
20129 The automatic update is not always desirable. For example, a frontend
20130 might want to keep a value of some expression for future reference,
20131 and never update it. For another example, fetching memory is
20132 relatively slow for embedded targets, so a frontend might want
20133 to disable automatic update for the variables that are either not
20134 visible on the screen, or ``closed''. This is possible using so
20135 called ``frozen variable objects''. Such variable objects are never
20136 implicitly updated.
20138 The following is the complete set of @sc{gdb/mi} operations defined to
20139 access this functionality:
20141 @multitable @columnfractions .4 .6
20142 @item @strong{Operation}
20143 @tab @strong{Description}
20145 @item @code{-var-create}
20146 @tab create a variable object
20147 @item @code{-var-delete}
20148 @tab delete the variable object and/or its children
20149 @item @code{-var-set-format}
20150 @tab set the display format of this variable
20151 @item @code{-var-show-format}
20152 @tab show the display format of this variable
20153 @item @code{-var-info-num-children}
20154 @tab tells how many children this object has
20155 @item @code{-var-list-children}
20156 @tab return a list of the object's children
20157 @item @code{-var-info-type}
20158 @tab show the type of this variable object
20159 @item @code{-var-info-expression}
20160 @tab print parent-relative expression that this variable object represents
20161 @item @code{-var-info-path-expression}
20162 @tab print full expression that this variable object represents
20163 @item @code{-var-show-attributes}
20164 @tab is this variable editable? does it exist here?
20165 @item @code{-var-evaluate-expression}
20166 @tab get the value of this variable
20167 @item @code{-var-assign}
20168 @tab set the value of this variable
20169 @item @code{-var-update}
20170 @tab update the variable and its children
20171 @item @code{-var-set-frozen}
20172 @tab set frozeness attribute
20175 In the next subsection we describe each operation in detail and suggest
20176 how it can be used.
20178 @subheading Description And Use of Operations on Variable Objects
20180 @subheading The @code{-var-create} Command
20181 @findex -var-create
20183 @subsubheading Synopsis
20186 -var-create @{@var{name} | "-"@}
20187 @{@var{frame-addr} | "*"@} @var{expression}
20190 This operation creates a variable object, which allows the monitoring of
20191 a variable, the result of an expression, a memory cell or a CPU
20194 The @var{name} parameter is the string by which the object can be
20195 referenced. It must be unique. If @samp{-} is specified, the varobj
20196 system will generate a string ``varNNNNNN'' automatically. It will be
20197 unique provided that one does not specify @var{name} on that format.
20198 The command fails if a duplicate name is found.
20200 The frame under which the expression should be evaluated can be
20201 specified by @var{frame-addr}. A @samp{*} indicates that the current
20202 frame should be used.
20204 @var{expression} is any expression valid on the current language set (must not
20205 begin with a @samp{*}), or one of the following:
20209 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20212 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20215 @samp{$@var{regname}} --- a CPU register name
20218 @subsubheading Result
20220 This operation returns the name, number of children and the type of the
20221 object created. Type is returned as a string as the ones generated by
20222 the @value{GDBN} CLI:
20225 name="@var{name}",numchild="N",type="@var{type}"
20229 @subheading The @code{-var-delete} Command
20230 @findex -var-delete
20232 @subsubheading Synopsis
20235 -var-delete [ -c ] @var{name}
20238 Deletes a previously created variable object and all of its children.
20239 With the @samp{-c} option, just deletes the children.
20241 Returns an error if the object @var{name} is not found.
20244 @subheading The @code{-var-set-format} Command
20245 @findex -var-set-format
20247 @subsubheading Synopsis
20250 -var-set-format @var{name} @var{format-spec}
20253 Sets the output format for the value of the object @var{name} to be
20256 @anchor{-var-set-format}
20257 The syntax for the @var{format-spec} is as follows:
20260 @var{format-spec} @expansion{}
20261 @{binary | decimal | hexadecimal | octal | natural@}
20264 The natural format is the default format choosen automatically
20265 based on the variable type (like decimal for an @code{int}, hex
20266 for pointers, etc.).
20268 For a variable with children, the format is set only on the
20269 variable itself, and the children are not affected.
20271 @subheading The @code{-var-show-format} Command
20272 @findex -var-show-format
20274 @subsubheading Synopsis
20277 -var-show-format @var{name}
20280 Returns the format used to display the value of the object @var{name}.
20283 @var{format} @expansion{}
20288 @subheading The @code{-var-info-num-children} Command
20289 @findex -var-info-num-children
20291 @subsubheading Synopsis
20294 -var-info-num-children @var{name}
20297 Returns the number of children of a variable object @var{name}:
20304 @subheading The @code{-var-list-children} Command
20305 @findex -var-list-children
20307 @subsubheading Synopsis
20310 -var-list-children [@var{print-values}] @var{name}
20312 @anchor{-var-list-children}
20314 Return a list of the children of the specified variable object and
20315 create variable objects for them, if they do not already exist. With
20316 a single argument or if @var{print-values} has a value for of 0 or
20317 @code{--no-values}, print only the names of the variables; if
20318 @var{print-values} is 1 or @code{--all-values}, also print their
20319 values; and if it is 2 or @code{--simple-values} print the name and
20320 value for simple data types and just the name for arrays, structures
20323 @subsubheading Example
20327 -var-list-children n
20328 ^done,numchild=@var{n},children=[@{name=@var{name},
20329 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20331 -var-list-children --all-values n
20332 ^done,numchild=@var{n},children=[@{name=@var{name},
20333 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20337 @subheading The @code{-var-info-type} Command
20338 @findex -var-info-type
20340 @subsubheading Synopsis
20343 -var-info-type @var{name}
20346 Returns the type of the specified variable @var{name}. The type is
20347 returned as a string in the same format as it is output by the
20351 type=@var{typename}
20355 @subheading The @code{-var-info-expression} Command
20356 @findex -var-info-expression
20358 @subsubheading Synopsis
20361 -var-info-expression @var{name}
20364 Returns a string that is suitable for presenting this
20365 variable object in user interface. The string is generally
20366 not valid expression in the current language, and cannot be evaluated.
20368 For example, if @code{a} is an array, and variable object
20369 @code{A} was created for @code{a}, then we'll get this output:
20372 (gdb) -var-info-expression A.1
20373 ^done,lang="C",exp="1"
20377 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
20379 Note that the output of the @code{-var-list-children} command also
20380 includes those expressions, so the @code{-var-info-expression} command
20383 @subheading The @code{-var-info-path-expression} Command
20384 @findex -var-info-path-expression
20386 @subsubheading Synopsis
20389 -var-info-path-expression @var{name}
20392 Returns an expression that can be evaluated in the current
20393 context and will yield the same value that a variable object has.
20394 Compare this with the @code{-var-info-expression} command, which
20395 result can be used only for UI presentation. Typical use of
20396 the @code{-var-info-path-expression} command is creating a
20397 watchpoint from a variable object.
20399 For example, suppose @code{C} is a C@t{++} class, derived from class
20400 @code{Base}, and that the @code{Base} class has a member called
20401 @code{m_size}. Assume a variable @code{c} is has the type of
20402 @code{C} and a variable object @code{C} was created for variable
20403 @code{c}. Then, we'll get this output:
20405 (gdb) -var-info-path-expression C.Base.public.m_size
20406 ^done,path_expr=((Base)c).m_size)
20409 @subheading The @code{-var-show-attributes} Command
20410 @findex -var-show-attributes
20412 @subsubheading Synopsis
20415 -var-show-attributes @var{name}
20418 List attributes of the specified variable object @var{name}:
20421 status=@var{attr} [ ( ,@var{attr} )* ]
20425 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20427 @subheading The @code{-var-evaluate-expression} Command
20428 @findex -var-evaluate-expression
20430 @subsubheading Synopsis
20433 -var-evaluate-expression [-f @var{format-spec}] @var{name}
20436 Evaluates the expression that is represented by the specified variable
20437 object and returns its value as a string. The format of the string
20438 can be specified with the @samp{-f} option. The possible values of
20439 this option are the same as for @code{-var-set-format}
20440 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
20441 the current display format will be used. The current display format
20442 can be changed using the @code{-var-set-format} command.
20448 Note that one must invoke @code{-var-list-children} for a variable
20449 before the value of a child variable can be evaluated.
20451 @subheading The @code{-var-assign} Command
20452 @findex -var-assign
20454 @subsubheading Synopsis
20457 -var-assign @var{name} @var{expression}
20460 Assigns the value of @var{expression} to the variable object specified
20461 by @var{name}. The object must be @samp{editable}. If the variable's
20462 value is altered by the assign, the variable will show up in any
20463 subsequent @code{-var-update} list.
20465 @subsubheading Example
20473 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20477 @subheading The @code{-var-update} Command
20478 @findex -var-update
20480 @subsubheading Synopsis
20483 -var-update [@var{print-values}] @{@var{name} | "*"@}
20486 Reevaluate the expressions corresponding to the variable object
20487 @var{name} and all its direct and indirect children, and return the
20488 list of variable objects whose values have changed; @var{name} must
20489 be a root variable object. Here, ``changed'' means that the result of
20490 @code{-var-evaluate-expression} before and after the
20491 @code{-var-update} is different. If @samp{*} is used as the variable
20492 object names, all existing variable objects are updated, except
20493 for frozen ones (@pxref{-var-set-frozen}). The option
20494 @var{print-values} determines whether both names and values, or just
20495 names are printed. The possible values of this option are the same
20496 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
20497 recommended to use the @samp{--all-values} option, to reduce the
20498 number of MI commands needed on each program stop.
20501 @subsubheading Example
20508 -var-update --all-values var1
20509 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20510 type_changed="false"@}]
20514 @anchor{-var-update}
20515 The field in_scope may take three values:
20519 The variable object's current value is valid.
20522 The variable object does not currently hold a valid value but it may
20523 hold one in the future if its associated expression comes back into
20527 The variable object no longer holds a valid value.
20528 This can occur when the executable file being debugged has changed,
20529 either through recompilation or by using the @value{GDBN} @code{file}
20530 command. The front end should normally choose to delete these variable
20534 In the future new values may be added to this list so the front should
20535 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
20537 @subheading The @code{-var-set-frozen} Command
20538 @findex -var-set-frozen
20539 @anchor{-var-set-frozen}
20541 @subsubheading Synopsis
20544 -var-set-frozen @var{name} @var{flag}
20547 Set the frozenness flag on the variable object @var{name}. The
20548 @var{flag} parameter should be either @samp{1} to make the variable
20549 frozen or @samp{0} to make it unfrozen. If a variable object is
20550 frozen, then neither itself, nor any of its children, are
20551 implicitly updated by @code{-var-update} of
20552 a parent variable or by @code{-var-update *}. Only
20553 @code{-var-update} of the variable itself will update its value and
20554 values of its children. After a variable object is unfrozen, it is
20555 implicitly updated by all subsequent @code{-var-update} operations.
20556 Unfreezing a variable does not update it, only subsequent
20557 @code{-var-update} does.
20559 @subsubheading Example
20563 -var-set-frozen V 1
20569 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20570 @node GDB/MI Data Manipulation
20571 @section @sc{gdb/mi} Data Manipulation
20573 @cindex data manipulation, in @sc{gdb/mi}
20574 @cindex @sc{gdb/mi}, data manipulation
20575 This section describes the @sc{gdb/mi} commands that manipulate data:
20576 examine memory and registers, evaluate expressions, etc.
20578 @c REMOVED FROM THE INTERFACE.
20579 @c @subheading -data-assign
20580 @c Change the value of a program variable. Plenty of side effects.
20581 @c @subsubheading GDB Command
20583 @c @subsubheading Example
20586 @subheading The @code{-data-disassemble} Command
20587 @findex -data-disassemble
20589 @subsubheading Synopsis
20593 [ -s @var{start-addr} -e @var{end-addr} ]
20594 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
20602 @item @var{start-addr}
20603 is the beginning address (or @code{$pc})
20604 @item @var{end-addr}
20606 @item @var{filename}
20607 is the name of the file to disassemble
20608 @item @var{linenum}
20609 is the line number to disassemble around
20611 is the number of disassembly lines to be produced. If it is -1,
20612 the whole function will be disassembled, in case no @var{end-addr} is
20613 specified. If @var{end-addr} is specified as a non-zero value, and
20614 @var{lines} is lower than the number of disassembly lines between
20615 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
20616 displayed; if @var{lines} is higher than the number of lines between
20617 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
20620 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
20624 @subsubheading Result
20626 The output for each instruction is composed of four fields:
20635 Note that whatever included in the instruction field, is not manipulated
20636 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
20638 @subsubheading @value{GDBN} Command
20640 There's no direct mapping from this command to the CLI.
20642 @subsubheading Example
20644 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
20648 -data-disassemble -s $pc -e "$pc + 20" -- 0
20651 @{address="0x000107c0",func-name="main",offset="4",
20652 inst="mov 2, %o0"@},
20653 @{address="0x000107c4",func-name="main",offset="8",
20654 inst="sethi %hi(0x11800), %o2"@},
20655 @{address="0x000107c8",func-name="main",offset="12",
20656 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
20657 @{address="0x000107cc",func-name="main",offset="16",
20658 inst="sethi %hi(0x11800), %o2"@},
20659 @{address="0x000107d0",func-name="main",offset="20",
20660 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
20664 Disassemble the whole @code{main} function. Line 32 is part of
20668 -data-disassemble -f basics.c -l 32 -- 0
20670 @{address="0x000107bc",func-name="main",offset="0",
20671 inst="save %sp, -112, %sp"@},
20672 @{address="0x000107c0",func-name="main",offset="4",
20673 inst="mov 2, %o0"@},
20674 @{address="0x000107c4",func-name="main",offset="8",
20675 inst="sethi %hi(0x11800), %o2"@},
20677 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20678 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20682 Disassemble 3 instructions from the start of @code{main}:
20686 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20688 @{address="0x000107bc",func-name="main",offset="0",
20689 inst="save %sp, -112, %sp"@},
20690 @{address="0x000107c0",func-name="main",offset="4",
20691 inst="mov 2, %o0"@},
20692 @{address="0x000107c4",func-name="main",offset="8",
20693 inst="sethi %hi(0x11800), %o2"@}]
20697 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20701 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20703 src_and_asm_line=@{line="31",
20704 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20705 testsuite/gdb.mi/basics.c",line_asm_insn=[
20706 @{address="0x000107bc",func-name="main",offset="0",
20707 inst="save %sp, -112, %sp"@}]@},
20708 src_and_asm_line=@{line="32",
20709 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20710 testsuite/gdb.mi/basics.c",line_asm_insn=[
20711 @{address="0x000107c0",func-name="main",offset="4",
20712 inst="mov 2, %o0"@},
20713 @{address="0x000107c4",func-name="main",offset="8",
20714 inst="sethi %hi(0x11800), %o2"@}]@}]
20719 @subheading The @code{-data-evaluate-expression} Command
20720 @findex -data-evaluate-expression
20722 @subsubheading Synopsis
20725 -data-evaluate-expression @var{expr}
20728 Evaluate @var{expr} as an expression. The expression could contain an
20729 inferior function call. The function call will execute synchronously.
20730 If the expression contains spaces, it must be enclosed in double quotes.
20732 @subsubheading @value{GDBN} Command
20734 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20735 @samp{call}. In @code{gdbtk} only, there's a corresponding
20736 @samp{gdb_eval} command.
20738 @subsubheading Example
20740 In the following example, the numbers that precede the commands are the
20741 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20742 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20746 211-data-evaluate-expression A
20749 311-data-evaluate-expression &A
20750 311^done,value="0xefffeb7c"
20752 411-data-evaluate-expression A+3
20755 511-data-evaluate-expression "A + 3"
20761 @subheading The @code{-data-list-changed-registers} Command
20762 @findex -data-list-changed-registers
20764 @subsubheading Synopsis
20767 -data-list-changed-registers
20770 Display a list of the registers that have changed.
20772 @subsubheading @value{GDBN} Command
20774 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20775 has the corresponding command @samp{gdb_changed_register_list}.
20777 @subsubheading Example
20779 On a PPC MBX board:
20787 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
20788 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
20791 -data-list-changed-registers
20792 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20793 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20794 "24","25","26","27","28","30","31","64","65","66","67","69"]
20799 @subheading The @code{-data-list-register-names} Command
20800 @findex -data-list-register-names
20802 @subsubheading Synopsis
20805 -data-list-register-names [ ( @var{regno} )+ ]
20808 Show a list of register names for the current target. If no arguments
20809 are given, it shows a list of the names of all the registers. If
20810 integer numbers are given as arguments, it will print a list of the
20811 names of the registers corresponding to the arguments. To ensure
20812 consistency between a register name and its number, the output list may
20813 include empty register names.
20815 @subsubheading @value{GDBN} Command
20817 @value{GDBN} does not have a command which corresponds to
20818 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20819 corresponding command @samp{gdb_regnames}.
20821 @subsubheading Example
20823 For the PPC MBX board:
20826 -data-list-register-names
20827 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20828 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20829 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20830 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20831 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20832 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20833 "", "pc","ps","cr","lr","ctr","xer"]
20835 -data-list-register-names 1 2 3
20836 ^done,register-names=["r1","r2","r3"]
20840 @subheading The @code{-data-list-register-values} Command
20841 @findex -data-list-register-values
20843 @subsubheading Synopsis
20846 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20849 Display the registers' contents. @var{fmt} is the format according to
20850 which the registers' contents are to be returned, followed by an optional
20851 list of numbers specifying the registers to display. A missing list of
20852 numbers indicates that the contents of all the registers must be returned.
20854 Allowed formats for @var{fmt} are:
20871 @subsubheading @value{GDBN} Command
20873 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20874 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20876 @subsubheading Example
20878 For a PPC MBX board (note: line breaks are for readability only, they
20879 don't appear in the actual output):
20883 -data-list-register-values r 64 65
20884 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20885 @{number="65",value="0x00029002"@}]
20887 -data-list-register-values x
20888 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20889 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20890 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20891 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20892 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20893 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20894 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20895 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20896 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20897 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20898 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20899 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20900 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20901 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20902 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20903 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20904 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20905 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20906 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20907 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20908 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20909 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20910 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20911 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20912 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20913 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20914 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20915 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20916 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20917 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20918 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20919 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20920 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20921 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20922 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20923 @{number="69",value="0x20002b03"@}]
20928 @subheading The @code{-data-read-memory} Command
20929 @findex -data-read-memory
20931 @subsubheading Synopsis
20934 -data-read-memory [ -o @var{byte-offset} ]
20935 @var{address} @var{word-format} @var{word-size}
20936 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20943 @item @var{address}
20944 An expression specifying the address of the first memory word to be
20945 read. Complex expressions containing embedded white space should be
20946 quoted using the C convention.
20948 @item @var{word-format}
20949 The format to be used to print the memory words. The notation is the
20950 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20953 @item @var{word-size}
20954 The size of each memory word in bytes.
20956 @item @var{nr-rows}
20957 The number of rows in the output table.
20959 @item @var{nr-cols}
20960 The number of columns in the output table.
20963 If present, indicates that each row should include an @sc{ascii} dump. The
20964 value of @var{aschar} is used as a padding character when a byte is not a
20965 member of the printable @sc{ascii} character set (printable @sc{ascii}
20966 characters are those whose code is between 32 and 126, inclusively).
20968 @item @var{byte-offset}
20969 An offset to add to the @var{address} before fetching memory.
20972 This command displays memory contents as a table of @var{nr-rows} by
20973 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20974 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20975 (returned as @samp{total-bytes}). Should less than the requested number
20976 of bytes be returned by the target, the missing words are identified
20977 using @samp{N/A}. The number of bytes read from the target is returned
20978 in @samp{nr-bytes} and the starting address used to read memory in
20981 The address of the next/previous row or page is available in
20982 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20985 @subsubheading @value{GDBN} Command
20987 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20988 @samp{gdb_get_mem} memory read command.
20990 @subsubheading Example
20992 Read six bytes of memory starting at @code{bytes+6} but then offset by
20993 @code{-6} bytes. Format as three rows of two columns. One byte per
20994 word. Display each word in hex.
20998 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20999 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
21000 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
21001 prev-page="0x0000138a",memory=[
21002 @{addr="0x00001390",data=["0x00","0x01"]@},
21003 @{addr="0x00001392",data=["0x02","0x03"]@},
21004 @{addr="0x00001394",data=["0x04","0x05"]@}]
21008 Read two bytes of memory starting at address @code{shorts + 64} and
21009 display as a single word formatted in decimal.
21013 5-data-read-memory shorts+64 d 2 1 1
21014 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
21015 next-row="0x00001512",prev-row="0x0000150e",
21016 next-page="0x00001512",prev-page="0x0000150e",memory=[
21017 @{addr="0x00001510",data=["128"]@}]
21021 Read thirty two bytes of memory starting at @code{bytes+16} and format
21022 as eight rows of four columns. Include a string encoding with @samp{x}
21023 used as the non-printable character.
21027 4-data-read-memory bytes+16 x 1 8 4 x
21028 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
21029 next-row="0x000013c0",prev-row="0x0000139c",
21030 next-page="0x000013c0",prev-page="0x00001380",memory=[
21031 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
21032 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
21033 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
21034 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
21035 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
21036 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
21037 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
21038 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
21042 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21043 @node GDB/MI Tracepoint Commands
21044 @section @sc{gdb/mi} Tracepoint Commands
21046 The tracepoint commands are not yet implemented.
21048 @c @subheading -trace-actions
21050 @c @subheading -trace-delete
21052 @c @subheading -trace-disable
21054 @c @subheading -trace-dump
21056 @c @subheading -trace-enable
21058 @c @subheading -trace-exists
21060 @c @subheading -trace-find
21062 @c @subheading -trace-frame-number
21064 @c @subheading -trace-info
21066 @c @subheading -trace-insert
21068 @c @subheading -trace-list
21070 @c @subheading -trace-pass-count
21072 @c @subheading -trace-save
21074 @c @subheading -trace-start
21076 @c @subheading -trace-stop
21079 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21080 @node GDB/MI Symbol Query
21081 @section @sc{gdb/mi} Symbol Query Commands
21084 @subheading The @code{-symbol-info-address} Command
21085 @findex -symbol-info-address
21087 @subsubheading Synopsis
21090 -symbol-info-address @var{symbol}
21093 Describe where @var{symbol} is stored.
21095 @subsubheading @value{GDBN} Command
21097 The corresponding @value{GDBN} command is @samp{info address}.
21099 @subsubheading Example
21103 @subheading The @code{-symbol-info-file} Command
21104 @findex -symbol-info-file
21106 @subsubheading Synopsis
21112 Show the file for the symbol.
21114 @subsubheading @value{GDBN} Command
21116 There's no equivalent @value{GDBN} command. @code{gdbtk} has
21117 @samp{gdb_find_file}.
21119 @subsubheading Example
21123 @subheading The @code{-symbol-info-function} Command
21124 @findex -symbol-info-function
21126 @subsubheading Synopsis
21129 -symbol-info-function
21132 Show which function the symbol lives in.
21134 @subsubheading @value{GDBN} Command
21136 @samp{gdb_get_function} in @code{gdbtk}.
21138 @subsubheading Example
21142 @subheading The @code{-symbol-info-line} Command
21143 @findex -symbol-info-line
21145 @subsubheading Synopsis
21151 Show the core addresses of the code for a source line.
21153 @subsubheading @value{GDBN} Command
21155 The corresponding @value{GDBN} command is @samp{info line}.
21156 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
21158 @subsubheading Example
21162 @subheading The @code{-symbol-info-symbol} Command
21163 @findex -symbol-info-symbol
21165 @subsubheading Synopsis
21168 -symbol-info-symbol @var{addr}
21171 Describe what symbol is at location @var{addr}.
21173 @subsubheading @value{GDBN} Command
21175 The corresponding @value{GDBN} command is @samp{info symbol}.
21177 @subsubheading Example
21181 @subheading The @code{-symbol-list-functions} Command
21182 @findex -symbol-list-functions
21184 @subsubheading Synopsis
21187 -symbol-list-functions
21190 List the functions in the executable.
21192 @subsubheading @value{GDBN} Command
21194 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
21195 @samp{gdb_search} in @code{gdbtk}.
21197 @subsubheading Example
21201 @subheading The @code{-symbol-list-lines} Command
21202 @findex -symbol-list-lines
21204 @subsubheading Synopsis
21207 -symbol-list-lines @var{filename}
21210 Print the list of lines that contain code and their associated program
21211 addresses for the given source filename. The entries are sorted in
21212 ascending PC order.
21214 @subsubheading @value{GDBN} Command
21216 There is no corresponding @value{GDBN} command.
21218 @subsubheading Example
21221 -symbol-list-lines basics.c
21222 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
21227 @subheading The @code{-symbol-list-types} Command
21228 @findex -symbol-list-types
21230 @subsubheading Synopsis
21236 List all the type names.
21238 @subsubheading @value{GDBN} Command
21240 The corresponding commands are @samp{info types} in @value{GDBN},
21241 @samp{gdb_search} in @code{gdbtk}.
21243 @subsubheading Example
21247 @subheading The @code{-symbol-list-variables} Command
21248 @findex -symbol-list-variables
21250 @subsubheading Synopsis
21253 -symbol-list-variables
21256 List all the global and static variable names.
21258 @subsubheading @value{GDBN} Command
21260 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
21262 @subsubheading Example
21266 @subheading The @code{-symbol-locate} Command
21267 @findex -symbol-locate
21269 @subsubheading Synopsis
21275 @subsubheading @value{GDBN} Command
21277 @samp{gdb_loc} in @code{gdbtk}.
21279 @subsubheading Example
21283 @subheading The @code{-symbol-type} Command
21284 @findex -symbol-type
21286 @subsubheading Synopsis
21289 -symbol-type @var{variable}
21292 Show type of @var{variable}.
21294 @subsubheading @value{GDBN} Command
21296 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
21297 @samp{gdb_obj_variable}.
21299 @subsubheading Example
21303 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21304 @node GDB/MI File Commands
21305 @section @sc{gdb/mi} File Commands
21307 This section describes the GDB/MI commands to specify executable file names
21308 and to read in and obtain symbol table information.
21310 @subheading The @code{-file-exec-and-symbols} Command
21311 @findex -file-exec-and-symbols
21313 @subsubheading Synopsis
21316 -file-exec-and-symbols @var{file}
21319 Specify the executable file to be debugged. This file is the one from
21320 which the symbol table is also read. If no file is specified, the
21321 command clears the executable and symbol information. If breakpoints
21322 are set when using this command with no arguments, @value{GDBN} will produce
21323 error messages. Otherwise, no output is produced, except a completion
21326 @subsubheading @value{GDBN} Command
21328 The corresponding @value{GDBN} command is @samp{file}.
21330 @subsubheading Example
21334 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21340 @subheading The @code{-file-exec-file} Command
21341 @findex -file-exec-file
21343 @subsubheading Synopsis
21346 -file-exec-file @var{file}
21349 Specify the executable file to be debugged. Unlike
21350 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
21351 from this file. If used without argument, @value{GDBN} clears the information
21352 about the executable file. No output is produced, except a completion
21355 @subsubheading @value{GDBN} Command
21357 The corresponding @value{GDBN} command is @samp{exec-file}.
21359 @subsubheading Example
21363 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21369 @subheading The @code{-file-list-exec-sections} Command
21370 @findex -file-list-exec-sections
21372 @subsubheading Synopsis
21375 -file-list-exec-sections
21378 List the sections of the current executable file.
21380 @subsubheading @value{GDBN} Command
21382 The @value{GDBN} command @samp{info file} shows, among the rest, the same
21383 information as this command. @code{gdbtk} has a corresponding command
21384 @samp{gdb_load_info}.
21386 @subsubheading Example
21390 @subheading The @code{-file-list-exec-source-file} Command
21391 @findex -file-list-exec-source-file
21393 @subsubheading Synopsis
21396 -file-list-exec-source-file
21399 List the line number, the current source file, and the absolute path
21400 to the current source file for the current executable. The macro
21401 information field has a value of @samp{1} or @samp{0} depending on
21402 whether or not the file includes preprocessor macro information.
21404 @subsubheading @value{GDBN} Command
21406 The @value{GDBN} equivalent is @samp{info source}
21408 @subsubheading Example
21412 123-file-list-exec-source-file
21413 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
21418 @subheading The @code{-file-list-exec-source-files} Command
21419 @findex -file-list-exec-source-files
21421 @subsubheading Synopsis
21424 -file-list-exec-source-files
21427 List the source files for the current executable.
21429 It will always output the filename, but only when @value{GDBN} can find
21430 the absolute file name of a source file, will it output the fullname.
21432 @subsubheading @value{GDBN} Command
21434 The @value{GDBN} equivalent is @samp{info sources}.
21435 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
21437 @subsubheading Example
21440 -file-list-exec-source-files
21442 @{file=foo.c,fullname=/home/foo.c@},
21443 @{file=/home/bar.c,fullname=/home/bar.c@},
21444 @{file=gdb_could_not_find_fullpath.c@}]
21448 @subheading The @code{-file-list-shared-libraries} Command
21449 @findex -file-list-shared-libraries
21451 @subsubheading Synopsis
21454 -file-list-shared-libraries
21457 List the shared libraries in the program.
21459 @subsubheading @value{GDBN} Command
21461 The corresponding @value{GDBN} command is @samp{info shared}.
21463 @subsubheading Example
21467 @subheading The @code{-file-list-symbol-files} Command
21468 @findex -file-list-symbol-files
21470 @subsubheading Synopsis
21473 -file-list-symbol-files
21478 @subsubheading @value{GDBN} Command
21480 The corresponding @value{GDBN} command is @samp{info file} (part of it).
21482 @subsubheading Example
21486 @subheading The @code{-file-symbol-file} Command
21487 @findex -file-symbol-file
21489 @subsubheading Synopsis
21492 -file-symbol-file @var{file}
21495 Read symbol table info from the specified @var{file} argument. When
21496 used without arguments, clears @value{GDBN}'s symbol table info. No output is
21497 produced, except for a completion notification.
21499 @subsubheading @value{GDBN} Command
21501 The corresponding @value{GDBN} command is @samp{symbol-file}.
21503 @subsubheading Example
21507 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
21513 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21514 @node GDB/MI Memory Overlay Commands
21515 @section @sc{gdb/mi} Memory Overlay Commands
21517 The memory overlay commands are not implemented.
21519 @c @subheading -overlay-auto
21521 @c @subheading -overlay-list-mapping-state
21523 @c @subheading -overlay-list-overlays
21525 @c @subheading -overlay-map
21527 @c @subheading -overlay-off
21529 @c @subheading -overlay-on
21531 @c @subheading -overlay-unmap
21533 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21534 @node GDB/MI Signal Handling Commands
21535 @section @sc{gdb/mi} Signal Handling Commands
21537 Signal handling commands are not implemented.
21539 @c @subheading -signal-handle
21541 @c @subheading -signal-list-handle-actions
21543 @c @subheading -signal-list-signal-types
21547 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21548 @node GDB/MI Target Manipulation
21549 @section @sc{gdb/mi} Target Manipulation Commands
21552 @subheading The @code{-target-attach} Command
21553 @findex -target-attach
21555 @subsubheading Synopsis
21558 -target-attach @var{pid} | @var{file}
21561 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
21563 @subsubheading @value{GDBN} Command
21565 The corresponding @value{GDBN} command is @samp{attach}.
21567 @subsubheading Example
21571 @subheading The @code{-target-compare-sections} Command
21572 @findex -target-compare-sections
21574 @subsubheading Synopsis
21577 -target-compare-sections [ @var{section} ]
21580 Compare data of section @var{section} on target to the exec file.
21581 Without the argument, all sections are compared.
21583 @subsubheading @value{GDBN} Command
21585 The @value{GDBN} equivalent is @samp{compare-sections}.
21587 @subsubheading Example
21591 @subheading The @code{-target-detach} Command
21592 @findex -target-detach
21594 @subsubheading Synopsis
21600 Detach from the remote target which normally resumes its execution.
21603 @subsubheading @value{GDBN} Command
21605 The corresponding @value{GDBN} command is @samp{detach}.
21607 @subsubheading Example
21617 @subheading The @code{-target-disconnect} Command
21618 @findex -target-disconnect
21620 @subsubheading Synopsis
21626 Disconnect from the remote target. There's no output and the target is
21627 generally not resumed.
21629 @subsubheading @value{GDBN} Command
21631 The corresponding @value{GDBN} command is @samp{disconnect}.
21633 @subsubheading Example
21643 @subheading The @code{-target-download} Command
21644 @findex -target-download
21646 @subsubheading Synopsis
21652 Loads the executable onto the remote target.
21653 It prints out an update message every half second, which includes the fields:
21657 The name of the section.
21659 The size of what has been sent so far for that section.
21661 The size of the section.
21663 The total size of what was sent so far (the current and the previous sections).
21665 The size of the overall executable to download.
21669 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21670 @sc{gdb/mi} Output Syntax}).
21672 In addition, it prints the name and size of the sections, as they are
21673 downloaded. These messages include the following fields:
21677 The name of the section.
21679 The size of the section.
21681 The size of the overall executable to download.
21685 At the end, a summary is printed.
21687 @subsubheading @value{GDBN} Command
21689 The corresponding @value{GDBN} command is @samp{load}.
21691 @subsubheading Example
21693 Note: each status message appears on a single line. Here the messages
21694 have been broken down so that they can fit onto a page.
21699 +download,@{section=".text",section-size="6668",total-size="9880"@}
21700 +download,@{section=".text",section-sent="512",section-size="6668",
21701 total-sent="512",total-size="9880"@}
21702 +download,@{section=".text",section-sent="1024",section-size="6668",
21703 total-sent="1024",total-size="9880"@}
21704 +download,@{section=".text",section-sent="1536",section-size="6668",
21705 total-sent="1536",total-size="9880"@}
21706 +download,@{section=".text",section-sent="2048",section-size="6668",
21707 total-sent="2048",total-size="9880"@}
21708 +download,@{section=".text",section-sent="2560",section-size="6668",
21709 total-sent="2560",total-size="9880"@}
21710 +download,@{section=".text",section-sent="3072",section-size="6668",
21711 total-sent="3072",total-size="9880"@}
21712 +download,@{section=".text",section-sent="3584",section-size="6668",
21713 total-sent="3584",total-size="9880"@}
21714 +download,@{section=".text",section-sent="4096",section-size="6668",
21715 total-sent="4096",total-size="9880"@}
21716 +download,@{section=".text",section-sent="4608",section-size="6668",
21717 total-sent="4608",total-size="9880"@}
21718 +download,@{section=".text",section-sent="5120",section-size="6668",
21719 total-sent="5120",total-size="9880"@}
21720 +download,@{section=".text",section-sent="5632",section-size="6668",
21721 total-sent="5632",total-size="9880"@}
21722 +download,@{section=".text",section-sent="6144",section-size="6668",
21723 total-sent="6144",total-size="9880"@}
21724 +download,@{section=".text",section-sent="6656",section-size="6668",
21725 total-sent="6656",total-size="9880"@}
21726 +download,@{section=".init",section-size="28",total-size="9880"@}
21727 +download,@{section=".fini",section-size="28",total-size="9880"@}
21728 +download,@{section=".data",section-size="3156",total-size="9880"@}
21729 +download,@{section=".data",section-sent="512",section-size="3156",
21730 total-sent="7236",total-size="9880"@}
21731 +download,@{section=".data",section-sent="1024",section-size="3156",
21732 total-sent="7748",total-size="9880"@}
21733 +download,@{section=".data",section-sent="1536",section-size="3156",
21734 total-sent="8260",total-size="9880"@}
21735 +download,@{section=".data",section-sent="2048",section-size="3156",
21736 total-sent="8772",total-size="9880"@}
21737 +download,@{section=".data",section-sent="2560",section-size="3156",
21738 total-sent="9284",total-size="9880"@}
21739 +download,@{section=".data",section-sent="3072",section-size="3156",
21740 total-sent="9796",total-size="9880"@}
21741 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21747 @subheading The @code{-target-exec-status} Command
21748 @findex -target-exec-status
21750 @subsubheading Synopsis
21753 -target-exec-status
21756 Provide information on the state of the target (whether it is running or
21757 not, for instance).
21759 @subsubheading @value{GDBN} Command
21761 There's no equivalent @value{GDBN} command.
21763 @subsubheading Example
21767 @subheading The @code{-target-list-available-targets} Command
21768 @findex -target-list-available-targets
21770 @subsubheading Synopsis
21773 -target-list-available-targets
21776 List the possible targets to connect to.
21778 @subsubheading @value{GDBN} Command
21780 The corresponding @value{GDBN} command is @samp{help target}.
21782 @subsubheading Example
21786 @subheading The @code{-target-list-current-targets} Command
21787 @findex -target-list-current-targets
21789 @subsubheading Synopsis
21792 -target-list-current-targets
21795 Describe the current target.
21797 @subsubheading @value{GDBN} Command
21799 The corresponding information is printed by @samp{info file} (among
21802 @subsubheading Example
21806 @subheading The @code{-target-list-parameters} Command
21807 @findex -target-list-parameters
21809 @subsubheading Synopsis
21812 -target-list-parameters
21817 @subsubheading @value{GDBN} Command
21821 @subsubheading Example
21825 @subheading The @code{-target-select} Command
21826 @findex -target-select
21828 @subsubheading Synopsis
21831 -target-select @var{type} @var{parameters @dots{}}
21834 Connect @value{GDBN} to the remote target. This command takes two args:
21838 The type of target, for instance @samp{async}, @samp{remote}, etc.
21839 @item @var{parameters}
21840 Device names, host names and the like. @xref{Target Commands, ,
21841 Commands for Managing Targets}, for more details.
21844 The output is a connection notification, followed by the address at
21845 which the target program is, in the following form:
21848 ^connected,addr="@var{address}",func="@var{function name}",
21849 args=[@var{arg list}]
21852 @subsubheading @value{GDBN} Command
21854 The corresponding @value{GDBN} command is @samp{target}.
21856 @subsubheading Example
21860 -target-select async /dev/ttya
21861 ^connected,addr="0xfe00a300",func="??",args=[]
21865 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21866 @node GDB/MI File Transfer Commands
21867 @section @sc{gdb/mi} File Transfer Commands
21870 @subheading The @code{-target-file-put} Command
21871 @findex -target-file-put
21873 @subsubheading Synopsis
21876 -target-file-put @var{hostfile} @var{targetfile}
21879 Copy file @var{hostfile} from the host system (the machine running
21880 @value{GDBN}) to @var{targetfile} on the target system.
21882 @subsubheading @value{GDBN} Command
21884 The corresponding @value{GDBN} command is @samp{remote put}.
21886 @subsubheading Example
21890 -target-file-put localfile remotefile
21896 @subheading The @code{-target-file-get} Command
21897 @findex -target-file-get
21899 @subsubheading Synopsis
21902 -target-file-get @var{targetfile} @var{hostfile}
21905 Copy file @var{targetfile} from the target system to @var{hostfile}
21906 on the host system.
21908 @subsubheading @value{GDBN} Command
21910 The corresponding @value{GDBN} command is @samp{remote get}.
21912 @subsubheading Example
21916 -target-file-get remotefile localfile
21922 @subheading The @code{-target-file-delete} Command
21923 @findex -target-file-delete
21925 @subsubheading Synopsis
21928 -target-file-delete @var{targetfile}
21931 Delete @var{targetfile} from the target system.
21933 @subsubheading @value{GDBN} Command
21935 The corresponding @value{GDBN} command is @samp{remote delete}.
21937 @subsubheading Example
21941 -target-file-delete remotefile
21947 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21948 @node GDB/MI Miscellaneous Commands
21949 @section Miscellaneous @sc{gdb/mi} Commands
21951 @c @subheading -gdb-complete
21953 @subheading The @code{-gdb-exit} Command
21956 @subsubheading Synopsis
21962 Exit @value{GDBN} immediately.
21964 @subsubheading @value{GDBN} Command
21966 Approximately corresponds to @samp{quit}.
21968 @subsubheading Example
21977 @subheading The @code{-exec-abort} Command
21978 @findex -exec-abort
21980 @subsubheading Synopsis
21986 Kill the inferior running program.
21988 @subsubheading @value{GDBN} Command
21990 The corresponding @value{GDBN} command is @samp{kill}.
21992 @subsubheading Example
21996 @subheading The @code{-gdb-set} Command
21999 @subsubheading Synopsis
22005 Set an internal @value{GDBN} variable.
22006 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
22008 @subsubheading @value{GDBN} Command
22010 The corresponding @value{GDBN} command is @samp{set}.
22012 @subsubheading Example
22022 @subheading The @code{-gdb-show} Command
22025 @subsubheading Synopsis
22031 Show the current value of a @value{GDBN} variable.
22033 @subsubheading @value{GDBN} Command
22035 The corresponding @value{GDBN} command is @samp{show}.
22037 @subsubheading Example
22046 @c @subheading -gdb-source
22049 @subheading The @code{-gdb-version} Command
22050 @findex -gdb-version
22052 @subsubheading Synopsis
22058 Show version information for @value{GDBN}. Used mostly in testing.
22060 @subsubheading @value{GDBN} Command
22062 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
22063 default shows this information when you start an interactive session.
22065 @subsubheading Example
22067 @c This example modifies the actual output from GDB to avoid overfull
22073 ~Copyright 2000 Free Software Foundation, Inc.
22074 ~GDB is free software, covered by the GNU General Public License, and
22075 ~you are welcome to change it and/or distribute copies of it under
22076 ~ certain conditions.
22077 ~Type "show copying" to see the conditions.
22078 ~There is absolutely no warranty for GDB. Type "show warranty" for
22080 ~This GDB was configured as
22081 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
22086 @subheading The @code{-list-features} Command
22087 @findex -list-features
22089 Returns a list of particular features of the MI protocol that
22090 this version of gdb implements. A feature can be a command,
22091 or a new field in an output of some command, or even an
22092 important bugfix. While a frontend can sometimes detect presence
22093 of a feature at runtime, it is easier to perform detection at debugger
22096 The command returns a list of strings, with each string naming an
22097 available feature. Each returned string is just a name, it does not
22098 have any internal structure. The list of possible feature names
22104 (gdb) -list-features
22105 ^done,result=["feature1","feature2"]
22108 The current list of features is:
22112 @samp{frozen-varobjs}---indicates presence of the
22113 @code{-var-set-frozen} command, as well as possible presense of the
22114 @code{frozen} field in the output of @code{-varobj-create}.
22116 @samp{pending-breakpoints}---indicates presence of the @code{-f}
22117 option to the @code{-break-insert} command.
22119 @samp{thread-info}---indicates presence of the @code{-thread-info} command.
22123 @subheading The @code{-interpreter-exec} Command
22124 @findex -interpreter-exec
22126 @subheading Synopsis
22129 -interpreter-exec @var{interpreter} @var{command}
22131 @anchor{-interpreter-exec}
22133 Execute the specified @var{command} in the given @var{interpreter}.
22135 @subheading @value{GDBN} Command
22137 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
22139 @subheading Example
22143 -interpreter-exec console "break main"
22144 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
22145 &"During symbol reading, bad structure-type format.\n"
22146 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
22151 @subheading The @code{-inferior-tty-set} Command
22152 @findex -inferior-tty-set
22154 @subheading Synopsis
22157 -inferior-tty-set /dev/pts/1
22160 Set terminal for future runs of the program being debugged.
22162 @subheading @value{GDBN} Command
22164 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
22166 @subheading Example
22170 -inferior-tty-set /dev/pts/1
22175 @subheading The @code{-inferior-tty-show} Command
22176 @findex -inferior-tty-show
22178 @subheading Synopsis
22184 Show terminal for future runs of program being debugged.
22186 @subheading @value{GDBN} Command
22188 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
22190 @subheading Example
22194 -inferior-tty-set /dev/pts/1
22198 ^done,inferior_tty_terminal="/dev/pts/1"
22202 @subheading The @code{-enable-timings} Command
22203 @findex -enable-timings
22205 @subheading Synopsis
22208 -enable-timings [yes | no]
22211 Toggle the printing of the wallclock, user and system times for an MI
22212 command as a field in its output. This command is to help frontend
22213 developers optimize the performance of their code. No argument is
22214 equivalent to @samp{yes}.
22216 @subheading @value{GDBN} Command
22220 @subheading Example
22228 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22229 addr="0x080484ed",func="main",file="myprog.c",
22230 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
22231 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
22239 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22240 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
22241 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
22242 fullname="/home/nickrob/myprog.c",line="73"@}
22247 @chapter @value{GDBN} Annotations
22249 This chapter describes annotations in @value{GDBN}. Annotations were
22250 designed to interface @value{GDBN} to graphical user interfaces or other
22251 similar programs which want to interact with @value{GDBN} at a
22252 relatively high level.
22254 The annotation mechanism has largely been superseded by @sc{gdb/mi}
22258 This is Edition @value{EDITION}, @value{DATE}.
22262 * Annotations Overview:: What annotations are; the general syntax.
22263 * Server Prefix:: Issuing a command without affecting user state.
22264 * Prompting:: Annotations marking @value{GDBN}'s need for input.
22265 * Errors:: Annotations for error messages.
22266 * Invalidation:: Some annotations describe things now invalid.
22267 * Annotations for Running::
22268 Whether the program is running, how it stopped, etc.
22269 * Source Annotations:: Annotations describing source code.
22272 @node Annotations Overview
22273 @section What is an Annotation?
22274 @cindex annotations
22276 Annotations start with a newline character, two @samp{control-z}
22277 characters, and the name of the annotation. If there is no additional
22278 information associated with this annotation, the name of the annotation
22279 is followed immediately by a newline. If there is additional
22280 information, the name of the annotation is followed by a space, the
22281 additional information, and a newline. The additional information
22282 cannot contain newline characters.
22284 Any output not beginning with a newline and two @samp{control-z}
22285 characters denotes literal output from @value{GDBN}. Currently there is
22286 no need for @value{GDBN} to output a newline followed by two
22287 @samp{control-z} characters, but if there was such a need, the
22288 annotations could be extended with an @samp{escape} annotation which
22289 means those three characters as output.
22291 The annotation @var{level}, which is specified using the
22292 @option{--annotate} command line option (@pxref{Mode Options}), controls
22293 how much information @value{GDBN} prints together with its prompt,
22294 values of expressions, source lines, and other types of output. Level 0
22295 is for no annotations, level 1 is for use when @value{GDBN} is run as a
22296 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
22297 for programs that control @value{GDBN}, and level 2 annotations have
22298 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
22299 Interface, annotate, GDB's Obsolete Annotations}).
22302 @kindex set annotate
22303 @item set annotate @var{level}
22304 The @value{GDBN} command @code{set annotate} sets the level of
22305 annotations to the specified @var{level}.
22307 @item show annotate
22308 @kindex show annotate
22309 Show the current annotation level.
22312 This chapter describes level 3 annotations.
22314 A simple example of starting up @value{GDBN} with annotations is:
22317 $ @kbd{gdb --annotate=3}
22319 Copyright 2003 Free Software Foundation, Inc.
22320 GDB is free software, covered by the GNU General Public License,
22321 and you are welcome to change it and/or distribute copies of it
22322 under certain conditions.
22323 Type "show copying" to see the conditions.
22324 There is absolutely no warranty for GDB. Type "show warranty"
22326 This GDB was configured as "i386-pc-linux-gnu"
22337 Here @samp{quit} is input to @value{GDBN}; the rest is output from
22338 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
22339 denotes a @samp{control-z} character) are annotations; the rest is
22340 output from @value{GDBN}.
22342 @node Server Prefix
22343 @section The Server Prefix
22344 @cindex server prefix
22346 If you prefix a command with @samp{server } then it will not affect
22347 the command history, nor will it affect @value{GDBN}'s notion of which
22348 command to repeat if @key{RET} is pressed on a line by itself. This
22349 means that commands can be run behind a user's back by a front-end in
22350 a transparent manner.
22352 The server prefix does not affect the recording of values into the value
22353 history; to print a value without recording it into the value history,
22354 use the @code{output} command instead of the @code{print} command.
22357 @section Annotation for @value{GDBN} Input
22359 @cindex annotations for prompts
22360 When @value{GDBN} prompts for input, it annotates this fact so it is possible
22361 to know when to send output, when the output from a given command is
22364 Different kinds of input each have a different @dfn{input type}. Each
22365 input type has three annotations: a @code{pre-} annotation, which
22366 denotes the beginning of any prompt which is being output, a plain
22367 annotation, which denotes the end of the prompt, and then a @code{post-}
22368 annotation which denotes the end of any echo which may (or may not) be
22369 associated with the input. For example, the @code{prompt} input type
22370 features the following annotations:
22378 The input types are
22381 @findex pre-prompt annotation
22382 @findex prompt annotation
22383 @findex post-prompt annotation
22385 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
22387 @findex pre-commands annotation
22388 @findex commands annotation
22389 @findex post-commands annotation
22391 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
22392 command. The annotations are repeated for each command which is input.
22394 @findex pre-overload-choice annotation
22395 @findex overload-choice annotation
22396 @findex post-overload-choice annotation
22397 @item overload-choice
22398 When @value{GDBN} wants the user to select between various overloaded functions.
22400 @findex pre-query annotation
22401 @findex query annotation
22402 @findex post-query annotation
22404 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
22406 @findex pre-prompt-for-continue annotation
22407 @findex prompt-for-continue annotation
22408 @findex post-prompt-for-continue annotation
22409 @item prompt-for-continue
22410 When @value{GDBN} is asking the user to press return to continue. Note: Don't
22411 expect this to work well; instead use @code{set height 0} to disable
22412 prompting. This is because the counting of lines is buggy in the
22413 presence of annotations.
22418 @cindex annotations for errors, warnings and interrupts
22420 @findex quit annotation
22425 This annotation occurs right before @value{GDBN} responds to an interrupt.
22427 @findex error annotation
22432 This annotation occurs right before @value{GDBN} responds to an error.
22434 Quit and error annotations indicate that any annotations which @value{GDBN} was
22435 in the middle of may end abruptly. For example, if a
22436 @code{value-history-begin} annotation is followed by a @code{error}, one
22437 cannot expect to receive the matching @code{value-history-end}. One
22438 cannot expect not to receive it either, however; an error annotation
22439 does not necessarily mean that @value{GDBN} is immediately returning all the way
22442 @findex error-begin annotation
22443 A quit or error annotation may be preceded by
22449 Any output between that and the quit or error annotation is the error
22452 Warning messages are not yet annotated.
22453 @c If we want to change that, need to fix warning(), type_error(),
22454 @c range_error(), and possibly other places.
22457 @section Invalidation Notices
22459 @cindex annotations for invalidation messages
22460 The following annotations say that certain pieces of state may have
22464 @findex frames-invalid annotation
22465 @item ^Z^Zframes-invalid
22467 The frames (for example, output from the @code{backtrace} command) may
22470 @findex breakpoints-invalid annotation
22471 @item ^Z^Zbreakpoints-invalid
22473 The breakpoints may have changed. For example, the user just added or
22474 deleted a breakpoint.
22477 @node Annotations for Running
22478 @section Running the Program
22479 @cindex annotations for running programs
22481 @findex starting annotation
22482 @findex stopping annotation
22483 When the program starts executing due to a @value{GDBN} command such as
22484 @code{step} or @code{continue},
22490 is output. When the program stops,
22496 is output. Before the @code{stopped} annotation, a variety of
22497 annotations describe how the program stopped.
22500 @findex exited annotation
22501 @item ^Z^Zexited @var{exit-status}
22502 The program exited, and @var{exit-status} is the exit status (zero for
22503 successful exit, otherwise nonzero).
22505 @findex signalled annotation
22506 @findex signal-name annotation
22507 @findex signal-name-end annotation
22508 @findex signal-string annotation
22509 @findex signal-string-end annotation
22510 @item ^Z^Zsignalled
22511 The program exited with a signal. After the @code{^Z^Zsignalled}, the
22512 annotation continues:
22518 ^Z^Zsignal-name-end
22522 ^Z^Zsignal-string-end
22527 where @var{name} is the name of the signal, such as @code{SIGILL} or
22528 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
22529 as @code{Illegal Instruction} or @code{Segmentation fault}.
22530 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
22531 user's benefit and have no particular format.
22533 @findex signal annotation
22535 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
22536 just saying that the program received the signal, not that it was
22537 terminated with it.
22539 @findex breakpoint annotation
22540 @item ^Z^Zbreakpoint @var{number}
22541 The program hit breakpoint number @var{number}.
22543 @findex watchpoint annotation
22544 @item ^Z^Zwatchpoint @var{number}
22545 The program hit watchpoint number @var{number}.
22548 @node Source Annotations
22549 @section Displaying Source
22550 @cindex annotations for source display
22552 @findex source annotation
22553 The following annotation is used instead of displaying source code:
22556 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
22559 where @var{filename} is an absolute file name indicating which source
22560 file, @var{line} is the line number within that file (where 1 is the
22561 first line in the file), @var{character} is the character position
22562 within the file (where 0 is the first character in the file) (for most
22563 debug formats this will necessarily point to the beginning of a line),
22564 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
22565 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
22566 @var{addr} is the address in the target program associated with the
22567 source which is being displayed. @var{addr} is in the form @samp{0x}
22568 followed by one or more lowercase hex digits (note that this does not
22569 depend on the language).
22572 @chapter Reporting Bugs in @value{GDBN}
22573 @cindex bugs in @value{GDBN}
22574 @cindex reporting bugs in @value{GDBN}
22576 Your bug reports play an essential role in making @value{GDBN} reliable.
22578 Reporting a bug may help you by bringing a solution to your problem, or it
22579 may not. But in any case the principal function of a bug report is to help
22580 the entire community by making the next version of @value{GDBN} work better. Bug
22581 reports are your contribution to the maintenance of @value{GDBN}.
22583 In order for a bug report to serve its purpose, you must include the
22584 information that enables us to fix the bug.
22587 * Bug Criteria:: Have you found a bug?
22588 * Bug Reporting:: How to report bugs
22592 @section Have You Found a Bug?
22593 @cindex bug criteria
22595 If you are not sure whether you have found a bug, here are some guidelines:
22598 @cindex fatal signal
22599 @cindex debugger crash
22600 @cindex crash of debugger
22602 If the debugger gets a fatal signal, for any input whatever, that is a
22603 @value{GDBN} bug. Reliable debuggers never crash.
22605 @cindex error on valid input
22607 If @value{GDBN} produces an error message for valid input, that is a
22608 bug. (Note that if you're cross debugging, the problem may also be
22609 somewhere in the connection to the target.)
22611 @cindex invalid input
22613 If @value{GDBN} does not produce an error message for invalid input,
22614 that is a bug. However, you should note that your idea of
22615 ``invalid input'' might be our idea of ``an extension'' or ``support
22616 for traditional practice''.
22619 If you are an experienced user of debugging tools, your suggestions
22620 for improvement of @value{GDBN} are welcome in any case.
22623 @node Bug Reporting
22624 @section How to Report Bugs
22625 @cindex bug reports
22626 @cindex @value{GDBN} bugs, reporting
22628 A number of companies and individuals offer support for @sc{gnu} products.
22629 If you obtained @value{GDBN} from a support organization, we recommend you
22630 contact that organization first.
22632 You can find contact information for many support companies and
22633 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
22635 @c should add a web page ref...
22637 In any event, we also recommend that you submit bug reports for
22638 @value{GDBN}. The preferred method is to submit them directly using
22639 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
22640 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
22643 @strong{Do not send bug reports to @samp{info-gdb}, or to
22644 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
22645 not want to receive bug reports. Those that do have arranged to receive
22648 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
22649 serves as a repeater. The mailing list and the newsgroup carry exactly
22650 the same messages. Often people think of posting bug reports to the
22651 newsgroup instead of mailing them. This appears to work, but it has one
22652 problem which can be crucial: a newsgroup posting often lacks a mail
22653 path back to the sender. Thus, if we need to ask for more information,
22654 we may be unable to reach you. For this reason, it is better to send
22655 bug reports to the mailing list.
22657 The fundamental principle of reporting bugs usefully is this:
22658 @strong{report all the facts}. If you are not sure whether to state a
22659 fact or leave it out, state it!
22661 Often people omit facts because they think they know what causes the
22662 problem and assume that some details do not matter. Thus, you might
22663 assume that the name of the variable you use in an example does not matter.
22664 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
22665 stray memory reference which happens to fetch from the location where that
22666 name is stored in memory; perhaps, if the name were different, the contents
22667 of that location would fool the debugger into doing the right thing despite
22668 the bug. Play it safe and give a specific, complete example. That is the
22669 easiest thing for you to do, and the most helpful.
22671 Keep in mind that the purpose of a bug report is to enable us to fix the
22672 bug. It may be that the bug has been reported previously, but neither
22673 you nor we can know that unless your bug report is complete and
22676 Sometimes people give a few sketchy facts and ask, ``Does this ring a
22677 bell?'' Those bug reports are useless, and we urge everyone to
22678 @emph{refuse to respond to them} except to chide the sender to report
22681 To enable us to fix the bug, you should include all these things:
22685 The version of @value{GDBN}. @value{GDBN} announces it if you start
22686 with no arguments; you can also print it at any time using @code{show
22689 Without this, we will not know whether there is any point in looking for
22690 the bug in the current version of @value{GDBN}.
22693 The type of machine you are using, and the operating system name and
22697 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
22698 ``@value{GCC}--2.8.1''.
22701 What compiler (and its version) was used to compile the program you are
22702 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
22703 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
22704 to get this information; for other compilers, see the documentation for
22708 The command arguments you gave the compiler to compile your example and
22709 observe the bug. For example, did you use @samp{-O}? To guarantee
22710 you will not omit something important, list them all. A copy of the
22711 Makefile (or the output from make) is sufficient.
22713 If we were to try to guess the arguments, we would probably guess wrong
22714 and then we might not encounter the bug.
22717 A complete input script, and all necessary source files, that will
22721 A description of what behavior you observe that you believe is
22722 incorrect. For example, ``It gets a fatal signal.''
22724 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
22725 will certainly notice it. But if the bug is incorrect output, we might
22726 not notice unless it is glaringly wrong. You might as well not give us
22727 a chance to make a mistake.
22729 Even if the problem you experience is a fatal signal, you should still
22730 say so explicitly. Suppose something strange is going on, such as, your
22731 copy of @value{GDBN} is out of synch, or you have encountered a bug in
22732 the C library on your system. (This has happened!) Your copy might
22733 crash and ours would not. If you told us to expect a crash, then when
22734 ours fails to crash, we would know that the bug was not happening for
22735 us. If you had not told us to expect a crash, then we would not be able
22736 to draw any conclusion from our observations.
22739 @cindex recording a session script
22740 To collect all this information, you can use a session recording program
22741 such as @command{script}, which is available on many Unix systems.
22742 Just run your @value{GDBN} session inside @command{script} and then
22743 include the @file{typescript} file with your bug report.
22745 Another way to record a @value{GDBN} session is to run @value{GDBN}
22746 inside Emacs and then save the entire buffer to a file.
22749 If you wish to suggest changes to the @value{GDBN} source, send us context
22750 diffs. If you even discuss something in the @value{GDBN} source, refer to
22751 it by context, not by line number.
22753 The line numbers in our development sources will not match those in your
22754 sources. Your line numbers would convey no useful information to us.
22758 Here are some things that are not necessary:
22762 A description of the envelope of the bug.
22764 Often people who encounter a bug spend a lot of time investigating
22765 which changes to the input file will make the bug go away and which
22766 changes will not affect it.
22768 This is often time consuming and not very useful, because the way we
22769 will find the bug is by running a single example under the debugger
22770 with breakpoints, not by pure deduction from a series of examples.
22771 We recommend that you save your time for something else.
22773 Of course, if you can find a simpler example to report @emph{instead}
22774 of the original one, that is a convenience for us. Errors in the
22775 output will be easier to spot, running under the debugger will take
22776 less time, and so on.
22778 However, simplification is not vital; if you do not want to do this,
22779 report the bug anyway and send us the entire test case you used.
22782 A patch for the bug.
22784 A patch for the bug does help us if it is a good one. But do not omit
22785 the necessary information, such as the test case, on the assumption that
22786 a patch is all we need. We might see problems with your patch and decide
22787 to fix the problem another way, or we might not understand it at all.
22789 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22790 construct an example that will make the program follow a certain path
22791 through the code. If you do not send us the example, we will not be able
22792 to construct one, so we will not be able to verify that the bug is fixed.
22794 And if we cannot understand what bug you are trying to fix, or why your
22795 patch should be an improvement, we will not install it. A test case will
22796 help us to understand.
22799 A guess about what the bug is or what it depends on.
22801 Such guesses are usually wrong. Even we cannot guess right about such
22802 things without first using the debugger to find the facts.
22805 @c The readline documentation is distributed with the readline code
22806 @c and consists of the two following files:
22808 @c inc-hist.texinfo
22809 @c Use -I with makeinfo to point to the appropriate directory,
22810 @c environment var TEXINPUTS with TeX.
22811 @include rluser.texi
22812 @include inc-hist.texinfo
22815 @node Formatting Documentation
22816 @appendix Formatting Documentation
22818 @cindex @value{GDBN} reference card
22819 @cindex reference card
22820 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22821 for printing with PostScript or Ghostscript, in the @file{gdb}
22822 subdirectory of the main source directory@footnote{In
22823 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22824 release.}. If you can use PostScript or Ghostscript with your printer,
22825 you can print the reference card immediately with @file{refcard.ps}.
22827 The release also includes the source for the reference card. You
22828 can format it, using @TeX{}, by typing:
22834 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22835 mode on US ``letter'' size paper;
22836 that is, on a sheet 11 inches wide by 8.5 inches
22837 high. You will need to specify this form of printing as an option to
22838 your @sc{dvi} output program.
22840 @cindex documentation
22842 All the documentation for @value{GDBN} comes as part of the machine-readable
22843 distribution. The documentation is written in Texinfo format, which is
22844 a documentation system that uses a single source file to produce both
22845 on-line information and a printed manual. You can use one of the Info
22846 formatting commands to create the on-line version of the documentation
22847 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22849 @value{GDBN} includes an already formatted copy of the on-line Info
22850 version of this manual in the @file{gdb} subdirectory. The main Info
22851 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22852 subordinate files matching @samp{gdb.info*} in the same directory. If
22853 necessary, you can print out these files, or read them with any editor;
22854 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22855 Emacs or the standalone @code{info} program, available as part of the
22856 @sc{gnu} Texinfo distribution.
22858 If you want to format these Info files yourself, you need one of the
22859 Info formatting programs, such as @code{texinfo-format-buffer} or
22862 If you have @code{makeinfo} installed, and are in the top level
22863 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22864 version @value{GDBVN}), you can make the Info file by typing:
22871 If you want to typeset and print copies of this manual, you need @TeX{},
22872 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22873 Texinfo definitions file.
22875 @TeX{} is a typesetting program; it does not print files directly, but
22876 produces output files called @sc{dvi} files. To print a typeset
22877 document, you need a program to print @sc{dvi} files. If your system
22878 has @TeX{} installed, chances are it has such a program. The precise
22879 command to use depends on your system; @kbd{lpr -d} is common; another
22880 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22881 require a file name without any extension or a @samp{.dvi} extension.
22883 @TeX{} also requires a macro definitions file called
22884 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22885 written in Texinfo format. On its own, @TeX{} cannot either read or
22886 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22887 and is located in the @file{gdb-@var{version-number}/texinfo}
22890 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22891 typeset and print this manual. First switch to the @file{gdb}
22892 subdirectory of the main source directory (for example, to
22893 @file{gdb-@value{GDBVN}/gdb}) and type:
22899 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22901 @node Installing GDB
22902 @appendix Installing @value{GDBN}
22903 @cindex installation
22906 * Requirements:: Requirements for building @value{GDBN}
22907 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22908 * Separate Objdir:: Compiling @value{GDBN} in another directory
22909 * Config Names:: Specifying names for hosts and targets
22910 * Configure Options:: Summary of options for configure
22914 @section Requirements for Building @value{GDBN}
22915 @cindex building @value{GDBN}, requirements for
22917 Building @value{GDBN} requires various tools and packages to be available.
22918 Other packages will be used only if they are found.
22920 @heading Tools/Packages Necessary for Building @value{GDBN}
22922 @item ISO C90 compiler
22923 @value{GDBN} is written in ISO C90. It should be buildable with any
22924 working C90 compiler, e.g.@: GCC.
22928 @heading Tools/Packages Optional for Building @value{GDBN}
22932 @value{GDBN} can use the Expat XML parsing library. This library may be
22933 included with your operating system distribution; if it is not, you
22934 can get the latest version from @url{http://expat.sourceforge.net}.
22935 The @file{configure} script will search for this library in several
22936 standard locations; if it is installed in an unusual path, you can
22937 use the @option{--with-libexpat-prefix} option to specify its location.
22943 Remote protocol memory maps (@pxref{Memory Map Format})
22945 Target descriptions (@pxref{Target Descriptions})
22947 Remote shared library lists (@pxref{Library List Format})
22949 MS-Windows shared libraries (@pxref{Shared Libraries})
22953 @cindex compressed debug sections
22954 @value{GDBN} will use the @samp{zlib} library, if available, to read
22955 compressed debug sections. Some linkers, such as GNU gold, are capable
22956 of producing binaries with compressed debug sections. If @value{GDBN}
22957 is compiled with @samp{zlib}, it will be able to read the debug
22958 information in such binaries.
22960 The @samp{zlib} library is likely included with your operating system
22961 distribution; if it is not, you can get the latest version from
22962 @url{http://zlib.net}.
22966 @node Running Configure
22967 @section Invoking the @value{GDBN} @file{configure} Script
22968 @cindex configuring @value{GDBN}
22969 @value{GDBN} comes with a @file{configure} script that automates the process
22970 of preparing @value{GDBN} for installation; you can then use @code{make} to
22971 build the @code{gdb} program.
22973 @c irrelevant in info file; it's as current as the code it lives with.
22974 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22975 look at the @file{README} file in the sources; we may have improved the
22976 installation procedures since publishing this manual.}
22979 The @value{GDBN} distribution includes all the source code you need for
22980 @value{GDBN} in a single directory, whose name is usually composed by
22981 appending the version number to @samp{gdb}.
22983 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22984 @file{gdb-@value{GDBVN}} directory. That directory contains:
22987 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22988 script for configuring @value{GDBN} and all its supporting libraries
22990 @item gdb-@value{GDBVN}/gdb
22991 the source specific to @value{GDBN} itself
22993 @item gdb-@value{GDBVN}/bfd
22994 source for the Binary File Descriptor library
22996 @item gdb-@value{GDBVN}/include
22997 @sc{gnu} include files
22999 @item gdb-@value{GDBVN}/libiberty
23000 source for the @samp{-liberty} free software library
23002 @item gdb-@value{GDBVN}/opcodes
23003 source for the library of opcode tables and disassemblers
23005 @item gdb-@value{GDBVN}/readline
23006 source for the @sc{gnu} command-line interface
23008 @item gdb-@value{GDBVN}/glob
23009 source for the @sc{gnu} filename pattern-matching subroutine
23011 @item gdb-@value{GDBVN}/mmalloc
23012 source for the @sc{gnu} memory-mapped malloc package
23015 The simplest way to configure and build @value{GDBN} is to run @file{configure}
23016 from the @file{gdb-@var{version-number}} source directory, which in
23017 this example is the @file{gdb-@value{GDBVN}} directory.
23019 First switch to the @file{gdb-@var{version-number}} source directory
23020 if you are not already in it; then run @file{configure}. Pass the
23021 identifier for the platform on which @value{GDBN} will run as an
23027 cd gdb-@value{GDBVN}
23028 ./configure @var{host}
23033 where @var{host} is an identifier such as @samp{sun4} or
23034 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
23035 (You can often leave off @var{host}; @file{configure} tries to guess the
23036 correct value by examining your system.)
23038 Running @samp{configure @var{host}} and then running @code{make} builds the
23039 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
23040 libraries, then @code{gdb} itself. The configured source files, and the
23041 binaries, are left in the corresponding source directories.
23044 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
23045 system does not recognize this automatically when you run a different
23046 shell, you may need to run @code{sh} on it explicitly:
23049 sh configure @var{host}
23052 If you run @file{configure} from a directory that contains source
23053 directories for multiple libraries or programs, such as the
23054 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
23056 creates configuration files for every directory level underneath (unless
23057 you tell it not to, with the @samp{--norecursion} option).
23059 You should run the @file{configure} script from the top directory in the
23060 source tree, the @file{gdb-@var{version-number}} directory. If you run
23061 @file{configure} from one of the subdirectories, you will configure only
23062 that subdirectory. That is usually not what you want. In particular,
23063 if you run the first @file{configure} from the @file{gdb} subdirectory
23064 of the @file{gdb-@var{version-number}} directory, you will omit the
23065 configuration of @file{bfd}, @file{readline}, and other sibling
23066 directories of the @file{gdb} subdirectory. This leads to build errors
23067 about missing include files such as @file{bfd/bfd.h}.
23069 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
23070 However, you should make sure that the shell on your path (named by
23071 the @samp{SHELL} environment variable) is publicly readable. Remember
23072 that @value{GDBN} uses the shell to start your program---some systems refuse to
23073 let @value{GDBN} debug child processes whose programs are not readable.
23075 @node Separate Objdir
23076 @section Compiling @value{GDBN} in Another Directory
23078 If you want to run @value{GDBN} versions for several host or target machines,
23079 you need a different @code{gdb} compiled for each combination of
23080 host and target. @file{configure} is designed to make this easy by
23081 allowing you to generate each configuration in a separate subdirectory,
23082 rather than in the source directory. If your @code{make} program
23083 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
23084 @code{make} in each of these directories builds the @code{gdb}
23085 program specified there.
23087 To build @code{gdb} in a separate directory, run @file{configure}
23088 with the @samp{--srcdir} option to specify where to find the source.
23089 (You also need to specify a path to find @file{configure}
23090 itself from your working directory. If the path to @file{configure}
23091 would be the same as the argument to @samp{--srcdir}, you can leave out
23092 the @samp{--srcdir} option; it is assumed.)
23094 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
23095 separate directory for a Sun 4 like this:
23099 cd gdb-@value{GDBVN}
23102 ../gdb-@value{GDBVN}/configure sun4
23107 When @file{configure} builds a configuration using a remote source
23108 directory, it creates a tree for the binaries with the same structure
23109 (and using the same names) as the tree under the source directory. In
23110 the example, you'd find the Sun 4 library @file{libiberty.a} in the
23111 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
23112 @file{gdb-sun4/gdb}.
23114 Make sure that your path to the @file{configure} script has just one
23115 instance of @file{gdb} in it. If your path to @file{configure} looks
23116 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
23117 one subdirectory of @value{GDBN}, not the whole package. This leads to
23118 build errors about missing include files such as @file{bfd/bfd.h}.
23120 One popular reason to build several @value{GDBN} configurations in separate
23121 directories is to configure @value{GDBN} for cross-compiling (where
23122 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
23123 programs that run on another machine---the @dfn{target}).
23124 You specify a cross-debugging target by
23125 giving the @samp{--target=@var{target}} option to @file{configure}.
23127 When you run @code{make} to build a program or library, you must run
23128 it in a configured directory---whatever directory you were in when you
23129 called @file{configure} (or one of its subdirectories).
23131 The @code{Makefile} that @file{configure} generates in each source
23132 directory also runs recursively. If you type @code{make} in a source
23133 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
23134 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
23135 will build all the required libraries, and then build GDB.
23137 When you have multiple hosts or targets configured in separate
23138 directories, you can run @code{make} on them in parallel (for example,
23139 if they are NFS-mounted on each of the hosts); they will not interfere
23143 @section Specifying Names for Hosts and Targets
23145 The specifications used for hosts and targets in the @file{configure}
23146 script are based on a three-part naming scheme, but some short predefined
23147 aliases are also supported. The full naming scheme encodes three pieces
23148 of information in the following pattern:
23151 @var{architecture}-@var{vendor}-@var{os}
23154 For example, you can use the alias @code{sun4} as a @var{host} argument,
23155 or as the value for @var{target} in a @code{--target=@var{target}}
23156 option. The equivalent full name is @samp{sparc-sun-sunos4}.
23158 The @file{configure} script accompanying @value{GDBN} does not provide
23159 any query facility to list all supported host and target names or
23160 aliases. @file{configure} calls the Bourne shell script
23161 @code{config.sub} to map abbreviations to full names; you can read the
23162 script, if you wish, or you can use it to test your guesses on
23163 abbreviations---for example:
23166 % sh config.sub i386-linux
23168 % sh config.sub alpha-linux
23169 alpha-unknown-linux-gnu
23170 % sh config.sub hp9k700
23172 % sh config.sub sun4
23173 sparc-sun-sunos4.1.1
23174 % sh config.sub sun3
23175 m68k-sun-sunos4.1.1
23176 % sh config.sub i986v
23177 Invalid configuration `i986v': machine `i986v' not recognized
23181 @code{config.sub} is also distributed in the @value{GDBN} source
23182 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
23184 @node Configure Options
23185 @section @file{configure} Options
23187 Here is a summary of the @file{configure} options and arguments that
23188 are most often useful for building @value{GDBN}. @file{configure} also has
23189 several other options not listed here. @inforef{What Configure
23190 Does,,configure.info}, for a full explanation of @file{configure}.
23193 configure @r{[}--help@r{]}
23194 @r{[}--prefix=@var{dir}@r{]}
23195 @r{[}--exec-prefix=@var{dir}@r{]}
23196 @r{[}--srcdir=@var{dirname}@r{]}
23197 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
23198 @r{[}--target=@var{target}@r{]}
23203 You may introduce options with a single @samp{-} rather than
23204 @samp{--} if you prefer; but you may abbreviate option names if you use
23209 Display a quick summary of how to invoke @file{configure}.
23211 @item --prefix=@var{dir}
23212 Configure the source to install programs and files under directory
23215 @item --exec-prefix=@var{dir}
23216 Configure the source to install programs under directory
23219 @c avoid splitting the warning from the explanation:
23221 @item --srcdir=@var{dirname}
23222 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
23223 @code{make} that implements the @code{VPATH} feature.}@*
23224 Use this option to make configurations in directories separate from the
23225 @value{GDBN} source directories. Among other things, you can use this to
23226 build (or maintain) several configurations simultaneously, in separate
23227 directories. @file{configure} writes configuration-specific files in
23228 the current directory, but arranges for them to use the source in the
23229 directory @var{dirname}. @file{configure} creates directories under
23230 the working directory in parallel to the source directories below
23233 @item --norecursion
23234 Configure only the directory level where @file{configure} is executed; do not
23235 propagate configuration to subdirectories.
23237 @item --target=@var{target}
23238 Configure @value{GDBN} for cross-debugging programs running on the specified
23239 @var{target}. Without this option, @value{GDBN} is configured to debug
23240 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
23242 There is no convenient way to generate a list of all available targets.
23244 @item @var{host} @dots{}
23245 Configure @value{GDBN} to run on the specified @var{host}.
23247 There is no convenient way to generate a list of all available hosts.
23250 There are many other options available as well, but they are generally
23251 needed for special purposes only.
23253 @node Maintenance Commands
23254 @appendix Maintenance Commands
23255 @cindex maintenance commands
23256 @cindex internal commands
23258 In addition to commands intended for @value{GDBN} users, @value{GDBN}
23259 includes a number of commands intended for @value{GDBN} developers,
23260 that are not documented elsewhere in this manual. These commands are
23261 provided here for reference. (For commands that turn on debugging
23262 messages, see @ref{Debugging Output}.)
23265 @kindex maint agent
23266 @item maint agent @var{expression}
23267 Translate the given @var{expression} into remote agent bytecodes.
23268 This command is useful for debugging the Agent Expression mechanism
23269 (@pxref{Agent Expressions}).
23271 @kindex maint info breakpoints
23272 @item @anchor{maint info breakpoints}maint info breakpoints
23273 Using the same format as @samp{info breakpoints}, display both the
23274 breakpoints you've set explicitly, and those @value{GDBN} is using for
23275 internal purposes. Internal breakpoints are shown with negative
23276 breakpoint numbers. The type column identifies what kind of breakpoint
23281 Normal, explicitly set breakpoint.
23284 Normal, explicitly set watchpoint.
23287 Internal breakpoint, used to handle correctly stepping through
23288 @code{longjmp} calls.
23290 @item longjmp resume
23291 Internal breakpoint at the target of a @code{longjmp}.
23294 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
23297 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
23300 Shared library events.
23304 @kindex maint set can-use-displaced-stepping
23305 @kindex maint show can-use-displaced-stepping
23306 @cindex displaced stepping support
23307 @cindex out-of-line single-stepping
23308 @item maint set can-use-displaced-stepping
23309 @itemx maint show can-use-displaced-stepping
23310 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
23311 if the target supports it. The default is on. Displaced stepping is
23312 a way to single-step over breakpoints without removing them from the
23313 inferior, by executing an out-of-line copy of the instruction that was
23314 originally at the breakpoint location. It is also known as
23315 out-of-line single-stepping.
23317 @kindex maint check-symtabs
23318 @item maint check-symtabs
23319 Check the consistency of psymtabs and symtabs.
23321 @kindex maint cplus first_component
23322 @item maint cplus first_component @var{name}
23323 Print the first C@t{++} class/namespace component of @var{name}.
23325 @kindex maint cplus namespace
23326 @item maint cplus namespace
23327 Print the list of possible C@t{++} namespaces.
23329 @kindex maint demangle
23330 @item maint demangle @var{name}
23331 Demangle a C@t{++} or Objective-C mangled @var{name}.
23333 @kindex maint deprecate
23334 @kindex maint undeprecate
23335 @cindex deprecated commands
23336 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
23337 @itemx maint undeprecate @var{command}
23338 Deprecate or undeprecate the named @var{command}. Deprecated commands
23339 cause @value{GDBN} to issue a warning when you use them. The optional
23340 argument @var{replacement} says which newer command should be used in
23341 favor of the deprecated one; if it is given, @value{GDBN} will mention
23342 the replacement as part of the warning.
23344 @kindex maint dump-me
23345 @item maint dump-me
23346 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
23347 Cause a fatal signal in the debugger and force it to dump its core.
23348 This is supported only on systems which support aborting a program
23349 with the @code{SIGQUIT} signal.
23351 @kindex maint internal-error
23352 @kindex maint internal-warning
23353 @item maint internal-error @r{[}@var{message-text}@r{]}
23354 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
23355 Cause @value{GDBN} to call the internal function @code{internal_error}
23356 or @code{internal_warning} and hence behave as though an internal error
23357 or internal warning has been detected. In addition to reporting the
23358 internal problem, these functions give the user the opportunity to
23359 either quit @value{GDBN} or create a core file of the current
23360 @value{GDBN} session.
23362 These commands take an optional parameter @var{message-text} that is
23363 used as the text of the error or warning message.
23365 Here's an example of using @code{internal-error}:
23368 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
23369 @dots{}/maint.c:121: internal-error: testing, 1, 2
23370 A problem internal to GDB has been detected. Further
23371 debugging may prove unreliable.
23372 Quit this debugging session? (y or n) @kbd{n}
23373 Create a core file? (y or n) @kbd{n}
23377 @kindex maint packet
23378 @item maint packet @var{text}
23379 If @value{GDBN} is talking to an inferior via the serial protocol,
23380 then this command sends the string @var{text} to the inferior, and
23381 displays the response packet. @value{GDBN} supplies the initial
23382 @samp{$} character, the terminating @samp{#} character, and the
23385 @kindex maint print architecture
23386 @item maint print architecture @r{[}@var{file}@r{]}
23387 Print the entire architecture configuration. The optional argument
23388 @var{file} names the file where the output goes.
23390 @kindex maint print c-tdesc
23391 @item maint print c-tdesc
23392 Print the current target description (@pxref{Target Descriptions}) as
23393 a C source file. The created source file can be used in @value{GDBN}
23394 when an XML parser is not available to parse the description.
23396 @kindex maint print dummy-frames
23397 @item maint print dummy-frames
23398 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
23401 (@value{GDBP}) @kbd{b add}
23403 (@value{GDBP}) @kbd{print add(2,3)}
23404 Breakpoint 2, add (a=2, b=3) at @dots{}
23406 The program being debugged stopped while in a function called from GDB.
23408 (@value{GDBP}) @kbd{maint print dummy-frames}
23409 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
23410 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
23411 call_lo=0x01014000 call_hi=0x01014001
23415 Takes an optional file parameter.
23417 @kindex maint print registers
23418 @kindex maint print raw-registers
23419 @kindex maint print cooked-registers
23420 @kindex maint print register-groups
23421 @item maint print registers @r{[}@var{file}@r{]}
23422 @itemx maint print raw-registers @r{[}@var{file}@r{]}
23423 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
23424 @itemx maint print register-groups @r{[}@var{file}@r{]}
23425 Print @value{GDBN}'s internal register data structures.
23427 The command @code{maint print raw-registers} includes the contents of
23428 the raw register cache; the command @code{maint print cooked-registers}
23429 includes the (cooked) value of all registers; and the command
23430 @code{maint print register-groups} includes the groups that each
23431 register is a member of. @xref{Registers,, Registers, gdbint,
23432 @value{GDBN} Internals}.
23434 These commands take an optional parameter, a file name to which to
23435 write the information.
23437 @kindex maint print reggroups
23438 @item maint print reggroups @r{[}@var{file}@r{]}
23439 Print @value{GDBN}'s internal register group data structures. The
23440 optional argument @var{file} tells to what file to write the
23443 The register groups info looks like this:
23446 (@value{GDBP}) @kbd{maint print reggroups}
23459 This command forces @value{GDBN} to flush its internal register cache.
23461 @kindex maint print objfiles
23462 @cindex info for known object files
23463 @item maint print objfiles
23464 Print a dump of all known object files. For each object file, this
23465 command prints its name, address in memory, and all of its psymtabs
23468 @kindex maint print statistics
23469 @cindex bcache statistics
23470 @item maint print statistics
23471 This command prints, for each object file in the program, various data
23472 about that object file followed by the byte cache (@dfn{bcache})
23473 statistics for the object file. The objfile data includes the number
23474 of minimal, partial, full, and stabs symbols, the number of types
23475 defined by the objfile, the number of as yet unexpanded psym tables,
23476 the number of line tables and string tables, and the amount of memory
23477 used by the various tables. The bcache statistics include the counts,
23478 sizes, and counts of duplicates of all and unique objects, max,
23479 average, and median entry size, total memory used and its overhead and
23480 savings, and various measures of the hash table size and chain
23483 @kindex maint print target-stack
23484 @cindex target stack description
23485 @item maint print target-stack
23486 A @dfn{target} is an interface between the debugger and a particular
23487 kind of file or process. Targets can be stacked in @dfn{strata},
23488 so that more than one target can potentially respond to a request.
23489 In particular, memory accesses will walk down the stack of targets
23490 until they find a target that is interested in handling that particular
23493 This command prints a short description of each layer that was pushed on
23494 the @dfn{target stack}, starting from the top layer down to the bottom one.
23496 @kindex maint print type
23497 @cindex type chain of a data type
23498 @item maint print type @var{expr}
23499 Print the type chain for a type specified by @var{expr}. The argument
23500 can be either a type name or a symbol. If it is a symbol, the type of
23501 that symbol is described. The type chain produced by this command is
23502 a recursive definition of the data type as stored in @value{GDBN}'s
23503 data structures, including its flags and contained types.
23505 @kindex maint set dwarf2 max-cache-age
23506 @kindex maint show dwarf2 max-cache-age
23507 @item maint set dwarf2 max-cache-age
23508 @itemx maint show dwarf2 max-cache-age
23509 Control the DWARF 2 compilation unit cache.
23511 @cindex DWARF 2 compilation units cache
23512 In object files with inter-compilation-unit references, such as those
23513 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
23514 reader needs to frequently refer to previously read compilation units.
23515 This setting controls how long a compilation unit will remain in the
23516 cache if it is not referenced. A higher limit means that cached
23517 compilation units will be stored in memory longer, and more total
23518 memory will be used. Setting it to zero disables caching, which will
23519 slow down @value{GDBN} startup, but reduce memory consumption.
23521 @kindex maint set profile
23522 @kindex maint show profile
23523 @cindex profiling GDB
23524 @item maint set profile
23525 @itemx maint show profile
23526 Control profiling of @value{GDBN}.
23528 Profiling will be disabled until you use the @samp{maint set profile}
23529 command to enable it. When you enable profiling, the system will begin
23530 collecting timing and execution count data; when you disable profiling or
23531 exit @value{GDBN}, the results will be written to a log file. Remember that
23532 if you use profiling, @value{GDBN} will overwrite the profiling log file
23533 (often called @file{gmon.out}). If you have a record of important profiling
23534 data in a @file{gmon.out} file, be sure to move it to a safe location.
23536 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
23537 compiled with the @samp{-pg} compiler option.
23539 @kindex maint set linux-async
23540 @kindex maint show linux-async
23541 @cindex asynchronous support
23542 @item maint set linux-async
23543 @itemx maint show linux-async
23544 Control the GNU/Linux native asynchronous support of @value{GDBN}.
23546 GNU/Linux native asynchronous support will be disabled until you use
23547 the @samp{maint set linux-async} command to enable it.
23549 @kindex maint show-debug-regs
23550 @cindex x86 hardware debug registers
23551 @item maint show-debug-regs
23552 Control whether to show variables that mirror the x86 hardware debug
23553 registers. Use @code{ON} to enable, @code{OFF} to disable. If
23554 enabled, the debug registers values are shown when @value{GDBN} inserts or
23555 removes a hardware breakpoint or watchpoint, and when the inferior
23556 triggers a hardware-assisted breakpoint or watchpoint.
23558 @kindex maint space
23559 @cindex memory used by commands
23561 Control whether to display memory usage for each command. If set to a
23562 nonzero value, @value{GDBN} will display how much memory each command
23563 took, following the command's own output. This can also be requested
23564 by invoking @value{GDBN} with the @option{--statistics} command-line
23565 switch (@pxref{Mode Options}).
23568 @cindex time of command execution
23570 Control whether to display the execution time for each command. If
23571 set to a nonzero value, @value{GDBN} will display how much time it
23572 took to execute each command, following the command's own output.
23573 The time is not printed for the commands that run the target, since
23574 there's no mechanism currently to compute how much time was spend
23575 by @value{GDBN} and how much time was spend by the program been debugged.
23576 it's not possibly currently
23577 This can also be requested by invoking @value{GDBN} with the
23578 @option{--statistics} command-line switch (@pxref{Mode Options}).
23580 @kindex maint translate-address
23581 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
23582 Find the symbol stored at the location specified by the address
23583 @var{addr} and an optional section name @var{section}. If found,
23584 @value{GDBN} prints the name of the closest symbol and an offset from
23585 the symbol's location to the specified address. This is similar to
23586 the @code{info address} command (@pxref{Symbols}), except that this
23587 command also allows to find symbols in other sections.
23591 The following command is useful for non-interactive invocations of
23592 @value{GDBN}, such as in the test suite.
23595 @item set watchdog @var{nsec}
23596 @kindex set watchdog
23597 @cindex watchdog timer
23598 @cindex timeout for commands
23599 Set the maximum number of seconds @value{GDBN} will wait for the
23600 target operation to finish. If this time expires, @value{GDBN}
23601 reports and error and the command is aborted.
23603 @item show watchdog
23604 Show the current setting of the target wait timeout.
23607 @node Remote Protocol
23608 @appendix @value{GDBN} Remote Serial Protocol
23613 * Stop Reply Packets::
23614 * General Query Packets::
23615 * Register Packet Format::
23616 * Tracepoint Packets::
23617 * Host I/O Packets::
23620 * File-I/O Remote Protocol Extension::
23621 * Library List Format::
23622 * Memory Map Format::
23628 There may be occasions when you need to know something about the
23629 protocol---for example, if there is only one serial port to your target
23630 machine, you might want your program to do something special if it
23631 recognizes a packet meant for @value{GDBN}.
23633 In the examples below, @samp{->} and @samp{<-} are used to indicate
23634 transmitted and received data, respectively.
23636 @cindex protocol, @value{GDBN} remote serial
23637 @cindex serial protocol, @value{GDBN} remote
23638 @cindex remote serial protocol
23639 All @value{GDBN} commands and responses (other than acknowledgments) are
23640 sent as a @var{packet}. A @var{packet} is introduced with the character
23641 @samp{$}, the actual @var{packet-data}, and the terminating character
23642 @samp{#} followed by a two-digit @var{checksum}:
23645 @code{$}@var{packet-data}@code{#}@var{checksum}
23649 @cindex checksum, for @value{GDBN} remote
23651 The two-digit @var{checksum} is computed as the modulo 256 sum of all
23652 characters between the leading @samp{$} and the trailing @samp{#} (an
23653 eight bit unsigned checksum).
23655 Implementors should note that prior to @value{GDBN} 5.0 the protocol
23656 specification also included an optional two-digit @var{sequence-id}:
23659 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
23662 @cindex sequence-id, for @value{GDBN} remote
23664 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
23665 has never output @var{sequence-id}s. Stubs that handle packets added
23666 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
23668 @cindex acknowledgment, for @value{GDBN} remote
23669 When either the host or the target machine receives a packet, the first
23670 response expected is an acknowledgment: either @samp{+} (to indicate
23671 the package was received correctly) or @samp{-} (to request
23675 -> @code{$}@var{packet-data}@code{#}@var{checksum}
23680 The host (@value{GDBN}) sends @var{command}s, and the target (the
23681 debugging stub incorporated in your program) sends a @var{response}. In
23682 the case of step and continue @var{command}s, the response is only sent
23683 when the operation has completed (the target has again stopped).
23685 @var{packet-data} consists of a sequence of characters with the
23686 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
23689 @cindex remote protocol, field separator
23690 Fields within the packet should be separated using @samp{,} @samp{;} or
23691 @samp{:}. Except where otherwise noted all numbers are represented in
23692 @sc{hex} with leading zeros suppressed.
23694 Implementors should note that prior to @value{GDBN} 5.0, the character
23695 @samp{:} could not appear as the third character in a packet (as it
23696 would potentially conflict with the @var{sequence-id}).
23698 @cindex remote protocol, binary data
23699 @anchor{Binary Data}
23700 Binary data in most packets is encoded either as two hexadecimal
23701 digits per byte of binary data. This allowed the traditional remote
23702 protocol to work over connections which were only seven-bit clean.
23703 Some packets designed more recently assume an eight-bit clean
23704 connection, and use a more efficient encoding to send and receive
23707 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
23708 as an escape character. Any escaped byte is transmitted as the escape
23709 character followed by the original character XORed with @code{0x20}.
23710 For example, the byte @code{0x7d} would be transmitted as the two
23711 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
23712 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
23713 @samp{@}}) must always be escaped. Responses sent by the stub
23714 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
23715 is not interpreted as the start of a run-length encoded sequence
23718 Response @var{data} can be run-length encoded to save space.
23719 Run-length encoding replaces runs of identical characters with one
23720 instance of the repeated character, followed by a @samp{*} and a
23721 repeat count. The repeat count is itself sent encoded, to avoid
23722 binary characters in @var{data}: a value of @var{n} is sent as
23723 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
23724 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
23725 code 32) for a repeat count of 3. (This is because run-length
23726 encoding starts to win for counts 3 or more.) Thus, for example,
23727 @samp{0* } is a run-length encoding of ``0000'': the space character
23728 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
23731 The printable characters @samp{#} and @samp{$} or with a numeric value
23732 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
23733 seven repeats (@samp{$}) can be expanded using a repeat count of only
23734 five (@samp{"}). For example, @samp{00000000} can be encoded as
23737 The error response returned for some packets includes a two character
23738 error number. That number is not well defined.
23740 @cindex empty response, for unsupported packets
23741 For any @var{command} not supported by the stub, an empty response
23742 (@samp{$#00}) should be returned. That way it is possible to extend the
23743 protocol. A newer @value{GDBN} can tell if a packet is supported based
23746 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
23747 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
23753 The following table provides a complete list of all currently defined
23754 @var{command}s and their corresponding response @var{data}.
23755 @xref{File-I/O Remote Protocol Extension}, for details about the File
23756 I/O extension of the remote protocol.
23758 Each packet's description has a template showing the packet's overall
23759 syntax, followed by an explanation of the packet's meaning. We
23760 include spaces in some of the templates for clarity; these are not
23761 part of the packet's syntax. No @value{GDBN} packet uses spaces to
23762 separate its components. For example, a template like @samp{foo
23763 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
23764 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
23765 @var{baz}. @value{GDBN} does not transmit a space character between the
23766 @samp{foo} and the @var{bar}, or between the @var{bar} and the
23769 Note that all packet forms beginning with an upper- or lower-case
23770 letter, other than those described here, are reserved for future use.
23772 Here are the packet descriptions.
23777 @cindex @samp{!} packet
23778 @anchor{extended mode}
23779 Enable extended mode. In extended mode, the remote server is made
23780 persistent. The @samp{R} packet is used to restart the program being
23786 The remote target both supports and has enabled extended mode.
23790 @cindex @samp{?} packet
23791 Indicate the reason the target halted. The reply is the same as for
23795 @xref{Stop Reply Packets}, for the reply specifications.
23797 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
23798 @cindex @samp{A} packet
23799 Initialized @code{argv[]} array passed into program. @var{arglen}
23800 specifies the number of bytes in the hex encoded byte stream
23801 @var{arg}. See @code{gdbserver} for more details.
23806 The arguments were set.
23812 @cindex @samp{b} packet
23813 (Don't use this packet; its behavior is not well-defined.)
23814 Change the serial line speed to @var{baud}.
23816 JTC: @emph{When does the transport layer state change? When it's
23817 received, or after the ACK is transmitted. In either case, there are
23818 problems if the command or the acknowledgment packet is dropped.}
23820 Stan: @emph{If people really wanted to add something like this, and get
23821 it working for the first time, they ought to modify ser-unix.c to send
23822 some kind of out-of-band message to a specially-setup stub and have the
23823 switch happen "in between" packets, so that from remote protocol's point
23824 of view, nothing actually happened.}
23826 @item B @var{addr},@var{mode}
23827 @cindex @samp{B} packet
23828 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23829 breakpoint at @var{addr}.
23831 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23832 (@pxref{insert breakpoint or watchpoint packet}).
23834 @item c @r{[}@var{addr}@r{]}
23835 @cindex @samp{c} packet
23836 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23837 resume at current address.
23840 @xref{Stop Reply Packets}, for the reply specifications.
23842 @item C @var{sig}@r{[};@var{addr}@r{]}
23843 @cindex @samp{C} packet
23844 Continue with signal @var{sig} (hex signal number). If
23845 @samp{;@var{addr}} is omitted, resume at same address.
23848 @xref{Stop Reply Packets}, for the reply specifications.
23851 @cindex @samp{d} packet
23854 Don't use this packet; instead, define a general set packet
23855 (@pxref{General Query Packets}).
23858 @cindex @samp{D} packet
23859 Detach @value{GDBN} from the remote system. Sent to the remote target
23860 before @value{GDBN} disconnects via the @code{detach} command.
23870 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23871 @cindex @samp{F} packet
23872 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23873 This is part of the File-I/O protocol extension. @xref{File-I/O
23874 Remote Protocol Extension}, for the specification.
23877 @anchor{read registers packet}
23878 @cindex @samp{g} packet
23879 Read general registers.
23883 @item @var{XX@dots{}}
23884 Each byte of register data is described by two hex digits. The bytes
23885 with the register are transmitted in target byte order. The size of
23886 each register and their position within the @samp{g} packet are
23887 determined by the @value{GDBN} internal gdbarch functions
23888 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
23889 specification of several standard @samp{g} packets is specified below.
23894 @item G @var{XX@dots{}}
23895 @cindex @samp{G} packet
23896 Write general registers. @xref{read registers packet}, for a
23897 description of the @var{XX@dots{}} data.
23907 @item H @var{c} @var{t}
23908 @cindex @samp{H} packet
23909 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23910 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23911 should be @samp{c} for step and continue operations, @samp{g} for other
23912 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23913 the threads, a thread number, or @samp{0} which means pick any thread.
23924 @c 'H': How restrictive (or permissive) is the thread model. If a
23925 @c thread is selected and stopped, are other threads allowed
23926 @c to continue to execute? As I mentioned above, I think the
23927 @c semantics of each command when a thread is selected must be
23928 @c described. For example:
23930 @c 'g': If the stub supports threads and a specific thread is
23931 @c selected, returns the register block from that thread;
23932 @c otherwise returns current registers.
23934 @c 'G' If the stub supports threads and a specific thread is
23935 @c selected, sets the registers of the register block of
23936 @c that thread; otherwise sets current registers.
23938 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23939 @anchor{cycle step packet}
23940 @cindex @samp{i} packet
23941 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23942 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23943 step starting at that address.
23946 @cindex @samp{I} packet
23947 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23951 @cindex @samp{k} packet
23954 FIXME: @emph{There is no description of how to operate when a specific
23955 thread context has been selected (i.e.@: does 'k' kill only that
23958 @item m @var{addr},@var{length}
23959 @cindex @samp{m} packet
23960 Read @var{length} bytes of memory starting at address @var{addr}.
23961 Note that @var{addr} may not be aligned to any particular boundary.
23963 The stub need not use any particular size or alignment when gathering
23964 data from memory for the response; even if @var{addr} is word-aligned
23965 and @var{length} is a multiple of the word size, the stub is free to
23966 use byte accesses, or not. For this reason, this packet may not be
23967 suitable for accessing memory-mapped I/O devices.
23968 @cindex alignment of remote memory accesses
23969 @cindex size of remote memory accesses
23970 @cindex memory, alignment and size of remote accesses
23974 @item @var{XX@dots{}}
23975 Memory contents; each byte is transmitted as a two-digit hexadecimal
23976 number. The reply may contain fewer bytes than requested if the
23977 server was able to read only part of the region of memory.
23982 @item M @var{addr},@var{length}:@var{XX@dots{}}
23983 @cindex @samp{M} packet
23984 Write @var{length} bytes of memory starting at address @var{addr}.
23985 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23986 hexadecimal number.
23993 for an error (this includes the case where only part of the data was
23998 @cindex @samp{p} packet
23999 Read the value of register @var{n}; @var{n} is in hex.
24000 @xref{read registers packet}, for a description of how the returned
24001 register value is encoded.
24005 @item @var{XX@dots{}}
24006 the register's value
24010 Indicating an unrecognized @var{query}.
24013 @item P @var{n@dots{}}=@var{r@dots{}}
24014 @anchor{write register packet}
24015 @cindex @samp{P} packet
24016 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
24017 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
24018 digits for each byte in the register (target byte order).
24028 @item q @var{name} @var{params}@dots{}
24029 @itemx Q @var{name} @var{params}@dots{}
24030 @cindex @samp{q} packet
24031 @cindex @samp{Q} packet
24032 General query (@samp{q}) and set (@samp{Q}). These packets are
24033 described fully in @ref{General Query Packets}.
24036 @cindex @samp{r} packet
24037 Reset the entire system.
24039 Don't use this packet; use the @samp{R} packet instead.
24042 @cindex @samp{R} packet
24043 Restart the program being debugged. @var{XX}, while needed, is ignored.
24044 This packet is only available in extended mode (@pxref{extended mode}).
24046 The @samp{R} packet has no reply.
24048 @item s @r{[}@var{addr}@r{]}
24049 @cindex @samp{s} packet
24050 Single step. @var{addr} is the address at which to resume. If
24051 @var{addr} is omitted, resume at same address.
24054 @xref{Stop Reply Packets}, for the reply specifications.
24056 @item S @var{sig}@r{[};@var{addr}@r{]}
24057 @anchor{step with signal packet}
24058 @cindex @samp{S} packet
24059 Step with signal. This is analogous to the @samp{C} packet, but
24060 requests a single-step, rather than a normal resumption of execution.
24063 @xref{Stop Reply Packets}, for the reply specifications.
24065 @item t @var{addr}:@var{PP},@var{MM}
24066 @cindex @samp{t} packet
24067 Search backwards starting at address @var{addr} for a match with pattern
24068 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
24069 @var{addr} must be at least 3 digits.
24072 @cindex @samp{T} packet
24073 Find out if the thread XX is alive.
24078 thread is still alive
24084 Packets starting with @samp{v} are identified by a multi-letter name,
24085 up to the first @samp{;} or @samp{?} (or the end of the packet).
24087 @item vAttach;@var{pid}
24088 @cindex @samp{vAttach} packet
24089 Attach to a new process with the specified process ID. @var{pid} is a
24090 hexadecimal integer identifying the process. The attached process is
24093 This packet is only available in extended mode (@pxref{extended mode}).
24099 @item @r{Any stop packet}
24100 for success (@pxref{Stop Reply Packets})
24103 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
24104 @cindex @samp{vCont} packet
24105 Resume the inferior, specifying different actions for each thread.
24106 If an action is specified with no @var{tid}, then it is applied to any
24107 threads that don't have a specific action specified; if no default action is
24108 specified then other threads should remain stopped. Specifying multiple
24109 default actions is an error; specifying no actions is also an error.
24110 Thread IDs are specified in hexadecimal. Currently supported actions are:
24116 Continue with signal @var{sig}. @var{sig} should be two hex digits.
24120 Step with signal @var{sig}. @var{sig} should be two hex digits.
24123 The optional @var{addr} argument normally associated with these packets is
24124 not supported in @samp{vCont}.
24127 @xref{Stop Reply Packets}, for the reply specifications.
24130 @cindex @samp{vCont?} packet
24131 Request a list of actions supported by the @samp{vCont} packet.
24135 @item vCont@r{[};@var{action}@dots{}@r{]}
24136 The @samp{vCont} packet is supported. Each @var{action} is a supported
24137 command in the @samp{vCont} packet.
24139 The @samp{vCont} packet is not supported.
24142 @item vFile:@var{operation}:@var{parameter}@dots{}
24143 @cindex @samp{vFile} packet
24144 Perform a file operation on the target system. For details,
24145 see @ref{Host I/O Packets}.
24147 @item vFlashErase:@var{addr},@var{length}
24148 @cindex @samp{vFlashErase} packet
24149 Direct the stub to erase @var{length} bytes of flash starting at
24150 @var{addr}. The region may enclose any number of flash blocks, but
24151 its start and end must fall on block boundaries, as indicated by the
24152 flash block size appearing in the memory map (@pxref{Memory Map
24153 Format}). @value{GDBN} groups flash memory programming operations
24154 together, and sends a @samp{vFlashDone} request after each group; the
24155 stub is allowed to delay erase operation until the @samp{vFlashDone}
24156 packet is received.
24166 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
24167 @cindex @samp{vFlashWrite} packet
24168 Direct the stub to write data to flash address @var{addr}. The data
24169 is passed in binary form using the same encoding as for the @samp{X}
24170 packet (@pxref{Binary Data}). The memory ranges specified by
24171 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
24172 not overlap, and must appear in order of increasing addresses
24173 (although @samp{vFlashErase} packets for higher addresses may already
24174 have been received; the ordering is guaranteed only between
24175 @samp{vFlashWrite} packets). If a packet writes to an address that was
24176 neither erased by a preceding @samp{vFlashErase} packet nor by some other
24177 target-specific method, the results are unpredictable.
24185 for vFlashWrite addressing non-flash memory
24191 @cindex @samp{vFlashDone} packet
24192 Indicate to the stub that flash programming operation is finished.
24193 The stub is permitted to delay or batch the effects of a group of
24194 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
24195 @samp{vFlashDone} packet is received. The contents of the affected
24196 regions of flash memory are unpredictable until the @samp{vFlashDone}
24197 request is completed.
24199 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
24200 @cindex @samp{vRun} packet
24201 Run the program @var{filename}, passing it each @var{argument} on its
24202 command line. The file and arguments are hex-encoded strings. If
24203 @var{filename} is an empty string, the stub may use a default program
24204 (e.g.@: the last program run). The program is created in the stopped
24207 This packet is only available in extended mode (@pxref{extended mode}).
24213 @item @r{Any stop packet}
24214 for success (@pxref{Stop Reply Packets})
24217 @item X @var{addr},@var{length}:@var{XX@dots{}}
24219 @cindex @samp{X} packet
24220 Write data to memory, where the data is transmitted in binary.
24221 @var{addr} is address, @var{length} is number of bytes,
24222 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
24232 @item z @var{type},@var{addr},@var{length}
24233 @itemx Z @var{type},@var{addr},@var{length}
24234 @anchor{insert breakpoint or watchpoint packet}
24235 @cindex @samp{z} packet
24236 @cindex @samp{Z} packets
24237 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
24238 watchpoint starting at address @var{address} and covering the next
24239 @var{length} bytes.
24241 Each breakpoint and watchpoint packet @var{type} is documented
24244 @emph{Implementation notes: A remote target shall return an empty string
24245 for an unrecognized breakpoint or watchpoint packet @var{type}. A
24246 remote target shall support either both or neither of a given
24247 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
24248 avoid potential problems with duplicate packets, the operations should
24249 be implemented in an idempotent way.}
24251 @item z0,@var{addr},@var{length}
24252 @itemx Z0,@var{addr},@var{length}
24253 @cindex @samp{z0} packet
24254 @cindex @samp{Z0} packet
24255 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
24256 @var{addr} of size @var{length}.
24258 A memory breakpoint is implemented by replacing the instruction at
24259 @var{addr} with a software breakpoint or trap instruction. The
24260 @var{length} is used by targets that indicates the size of the
24261 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
24262 @sc{mips} can insert either a 2 or 4 byte breakpoint).
24264 @emph{Implementation note: It is possible for a target to copy or move
24265 code that contains memory breakpoints (e.g., when implementing
24266 overlays). The behavior of this packet, in the presence of such a
24267 target, is not defined.}
24279 @item z1,@var{addr},@var{length}
24280 @itemx Z1,@var{addr},@var{length}
24281 @cindex @samp{z1} packet
24282 @cindex @samp{Z1} packet
24283 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
24284 address @var{addr} of size @var{length}.
24286 A hardware breakpoint is implemented using a mechanism that is not
24287 dependant on being able to modify the target's memory.
24289 @emph{Implementation note: A hardware breakpoint is not affected by code
24302 @item z2,@var{addr},@var{length}
24303 @itemx Z2,@var{addr},@var{length}
24304 @cindex @samp{z2} packet
24305 @cindex @samp{Z2} packet
24306 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
24318 @item z3,@var{addr},@var{length}
24319 @itemx Z3,@var{addr},@var{length}
24320 @cindex @samp{z3} packet
24321 @cindex @samp{Z3} packet
24322 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
24334 @item z4,@var{addr},@var{length}
24335 @itemx Z4,@var{addr},@var{length}
24336 @cindex @samp{z4} packet
24337 @cindex @samp{Z4} packet
24338 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
24352 @node Stop Reply Packets
24353 @section Stop Reply Packets
24354 @cindex stop reply packets
24356 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
24357 receive any of the below as a reply. In the case of the @samp{C},
24358 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
24359 when the target halts. In the below the exact meaning of @dfn{signal
24360 number} is defined by the header @file{include/gdb/signals.h} in the
24361 @value{GDBN} source code.
24363 As in the description of request packets, we include spaces in the
24364 reply templates for clarity; these are not part of the reply packet's
24365 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
24371 The program received signal number @var{AA} (a two-digit hexadecimal
24372 number). This is equivalent to a @samp{T} response with no
24373 @var{n}:@var{r} pairs.
24375 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
24376 @cindex @samp{T} packet reply
24377 The program received signal number @var{AA} (a two-digit hexadecimal
24378 number). This is equivalent to an @samp{S} response, except that the
24379 @samp{@var{n}:@var{r}} pairs can carry values of important registers
24380 and other information directly in the stop reply packet, reducing
24381 round-trip latency. Single-step and breakpoint traps are reported
24382 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
24386 If @var{n} is a hexadecimal number, it is a register number, and the
24387 corresponding @var{r} gives that register's value. @var{r} is a
24388 series of bytes in target byte order, with each byte given by a
24389 two-digit hex number.
24392 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
24396 If @var{n} is a recognized @dfn{stop reason}, it describes a more
24397 specific event that stopped the target. The currently defined stop
24398 reasons are listed below. @var{aa} should be @samp{05}, the trap
24399 signal. At most one stop reason should be present.
24402 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
24403 and go on to the next; this allows us to extend the protocol in the
24407 The currently defined stop reasons are:
24413 The packet indicates a watchpoint hit, and @var{r} is the data address, in
24416 @cindex shared library events, remote reply
24418 The packet indicates that the loaded libraries have changed.
24419 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
24420 list of loaded libraries. @var{r} is ignored.
24424 The process exited, and @var{AA} is the exit status. This is only
24425 applicable to certain targets.
24428 The process terminated with signal @var{AA}.
24430 @item O @var{XX}@dots{}
24431 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
24432 written as the program's console output. This can happen at any time
24433 while the program is running and the debugger should continue to wait
24434 for @samp{W}, @samp{T}, etc.
24436 @item F @var{call-id},@var{parameter}@dots{}
24437 @var{call-id} is the identifier which says which host system call should
24438 be called. This is just the name of the function. Translation into the
24439 correct system call is only applicable as it's defined in @value{GDBN}.
24440 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
24443 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
24444 this very system call.
24446 The target replies with this packet when it expects @value{GDBN} to
24447 call a host system call on behalf of the target. @value{GDBN} replies
24448 with an appropriate @samp{F} packet and keeps up waiting for the next
24449 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
24450 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
24451 Protocol Extension}, for more details.
24455 @node General Query Packets
24456 @section General Query Packets
24457 @cindex remote query requests
24459 Packets starting with @samp{q} are @dfn{general query packets};
24460 packets starting with @samp{Q} are @dfn{general set packets}. General
24461 query and set packets are a semi-unified form for retrieving and
24462 sending information to and from the stub.
24464 The initial letter of a query or set packet is followed by a name
24465 indicating what sort of thing the packet applies to. For example,
24466 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
24467 definitions with the stub. These packet names follow some
24472 The name must not contain commas, colons or semicolons.
24474 Most @value{GDBN} query and set packets have a leading upper case
24477 The names of custom vendor packets should use a company prefix, in
24478 lower case, followed by a period. For example, packets designed at
24479 the Acme Corporation might begin with @samp{qacme.foo} (for querying
24480 foos) or @samp{Qacme.bar} (for setting bars).
24483 The name of a query or set packet should be separated from any
24484 parameters by a @samp{:}; the parameters themselves should be
24485 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
24486 full packet name, and check for a separator or the end of the packet,
24487 in case two packet names share a common prefix. New packets should not begin
24488 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
24489 packets predate these conventions, and have arguments without any terminator
24490 for the packet name; we suspect they are in widespread use in places that
24491 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
24492 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
24495 Like the descriptions of the other packets, each description here
24496 has a template showing the packet's overall syntax, followed by an
24497 explanation of the packet's meaning. We include spaces in some of the
24498 templates for clarity; these are not part of the packet's syntax. No
24499 @value{GDBN} packet uses spaces to separate its components.
24501 Here are the currently defined query and set packets:
24506 @cindex current thread, remote request
24507 @cindex @samp{qC} packet
24508 Return the current thread id.
24513 Where @var{pid} is an unsigned hexadecimal process id.
24514 @item @r{(anything else)}
24515 Any other reply implies the old pid.
24518 @item qCRC:@var{addr},@var{length}
24519 @cindex CRC of memory block, remote request
24520 @cindex @samp{qCRC} packet
24521 Compute the CRC checksum of a block of memory.
24525 An error (such as memory fault)
24526 @item C @var{crc32}
24527 The specified memory region's checksum is @var{crc32}.
24531 @itemx qsThreadInfo
24532 @cindex list active threads, remote request
24533 @cindex @samp{qfThreadInfo} packet
24534 @cindex @samp{qsThreadInfo} packet
24535 Obtain a list of all active thread ids from the target (OS). Since there
24536 may be too many active threads to fit into one reply packet, this query
24537 works iteratively: it may require more than one query/reply sequence to
24538 obtain the entire list of threads. The first query of the sequence will
24539 be the @samp{qfThreadInfo} query; subsequent queries in the
24540 sequence will be the @samp{qsThreadInfo} query.
24542 NOTE: This packet replaces the @samp{qL} query (see below).
24548 @item m @var{id},@var{id}@dots{}
24549 a comma-separated list of thread ids
24551 (lower case letter @samp{L}) denotes end of list.
24554 In response to each query, the target will reply with a list of one or
24555 more thread ids, in big-endian unsigned hex, separated by commas.
24556 @value{GDBN} will respond to each reply with a request for more thread
24557 ids (using the @samp{qs} form of the query), until the target responds
24558 with @samp{l} (lower-case el, for @dfn{last}).
24560 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
24561 @cindex get thread-local storage address, remote request
24562 @cindex @samp{qGetTLSAddr} packet
24563 Fetch the address associated with thread local storage specified
24564 by @var{thread-id}, @var{offset}, and @var{lm}.
24566 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
24567 thread for which to fetch the TLS address.
24569 @var{offset} is the (big endian, hex encoded) offset associated with the
24570 thread local variable. (This offset is obtained from the debug
24571 information associated with the variable.)
24573 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
24574 the load module associated with the thread local storage. For example,
24575 a @sc{gnu}/Linux system will pass the link map address of the shared
24576 object associated with the thread local storage under consideration.
24577 Other operating environments may choose to represent the load module
24578 differently, so the precise meaning of this parameter will vary.
24582 @item @var{XX}@dots{}
24583 Hex encoded (big endian) bytes representing the address of the thread
24584 local storage requested.
24587 An error occurred. @var{nn} are hex digits.
24590 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
24593 @item qL @var{startflag} @var{threadcount} @var{nextthread}
24594 Obtain thread information from RTOS. Where: @var{startflag} (one hex
24595 digit) is one to indicate the first query and zero to indicate a
24596 subsequent query; @var{threadcount} (two hex digits) is the maximum
24597 number of threads the response packet can contain; and @var{nextthread}
24598 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
24599 returned in the response as @var{argthread}.
24601 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
24605 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
24606 Where: @var{count} (two hex digits) is the number of threads being
24607 returned; @var{done} (one hex digit) is zero to indicate more threads
24608 and one indicates no further threads; @var{argthreadid} (eight hex
24609 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
24610 is a sequence of thread IDs from the target. @var{threadid} (eight hex
24611 digits). See @code{remote.c:parse_threadlist_response()}.
24615 @cindex section offsets, remote request
24616 @cindex @samp{qOffsets} packet
24617 Get section offsets that the target used when relocating the downloaded
24622 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
24623 Relocate the @code{Text} section by @var{xxx} from its original address.
24624 Relocate the @code{Data} section by @var{yyy} from its original address.
24625 If the object file format provides segment information (e.g.@: @sc{elf}
24626 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
24627 segments by the supplied offsets.
24629 @emph{Note: while a @code{Bss} offset may be included in the response,
24630 @value{GDBN} ignores this and instead applies the @code{Data} offset
24631 to the @code{Bss} section.}
24633 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
24634 Relocate the first segment of the object file, which conventionally
24635 contains program code, to a starting address of @var{xxx}. If
24636 @samp{DataSeg} is specified, relocate the second segment, which
24637 conventionally contains modifiable data, to a starting address of
24638 @var{yyy}. @value{GDBN} will report an error if the object file
24639 does not contain segment information, or does not contain at least
24640 as many segments as mentioned in the reply. Extra segments are
24641 kept at fixed offsets relative to the last relocated segment.
24644 @item qP @var{mode} @var{threadid}
24645 @cindex thread information, remote request
24646 @cindex @samp{qP} packet
24647 Returns information on @var{threadid}. Where: @var{mode} is a hex
24648 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
24650 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
24653 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
24655 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
24656 @cindex pass signals to inferior, remote request
24657 @cindex @samp{QPassSignals} packet
24658 @anchor{QPassSignals}
24659 Each listed @var{signal} should be passed directly to the inferior process.
24660 Signals are numbered identically to continue packets and stop replies
24661 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
24662 strictly greater than the previous item. These signals do not need to stop
24663 the inferior, or be reported to @value{GDBN}. All other signals should be
24664 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
24665 combine; any earlier @samp{QPassSignals} list is completely replaced by the
24666 new list. This packet improves performance when using @samp{handle
24667 @var{signal} nostop noprint pass}.
24672 The request succeeded.
24675 An error occurred. @var{nn} are hex digits.
24678 An empty reply indicates that @samp{QPassSignals} is not supported by
24682 Use of this packet is controlled by the @code{set remote pass-signals}
24683 command (@pxref{Remote Configuration, set remote pass-signals}).
24684 This packet is not probed by default; the remote stub must request it,
24685 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24687 @item qRcmd,@var{command}
24688 @cindex execute remote command, remote request
24689 @cindex @samp{qRcmd} packet
24690 @var{command} (hex encoded) is passed to the local interpreter for
24691 execution. Invalid commands should be reported using the output
24692 string. Before the final result packet, the target may also respond
24693 with a number of intermediate @samp{O@var{output}} console output
24694 packets. @emph{Implementors should note that providing access to a
24695 stubs's interpreter may have security implications}.
24700 A command response with no output.
24702 A command response with the hex encoded output string @var{OUTPUT}.
24704 Indicate a badly formed request.
24706 An empty reply indicates that @samp{qRcmd} is not recognized.
24709 (Note that the @code{qRcmd} packet's name is separated from the
24710 command by a @samp{,}, not a @samp{:}, contrary to the naming
24711 conventions above. Please don't use this packet as a model for new
24714 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
24715 @cindex searching memory, in remote debugging
24716 @cindex @samp{qSearch:memory} packet
24717 @anchor{qSearch memory}
24718 Search @var{length} bytes at @var{address} for @var{search-pattern}.
24719 @var{address} and @var{length} are encoded in hex.
24720 @var{search-pattern} is a sequence of bytes, hex encoded.
24725 The pattern was not found.
24727 The pattern was found at @var{address}.
24729 A badly formed request or an error was encountered while searching memory.
24731 An empty reply indicates that @samp{qSearch:memory} is not recognized.
24734 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
24735 @cindex supported packets, remote query
24736 @cindex features of the remote protocol
24737 @cindex @samp{qSupported} packet
24738 @anchor{qSupported}
24739 Tell the remote stub about features supported by @value{GDBN}, and
24740 query the stub for features it supports. This packet allows
24741 @value{GDBN} and the remote stub to take advantage of each others'
24742 features. @samp{qSupported} also consolidates multiple feature probes
24743 at startup, to improve @value{GDBN} performance---a single larger
24744 packet performs better than multiple smaller probe packets on
24745 high-latency links. Some features may enable behavior which must not
24746 be on by default, e.g.@: because it would confuse older clients or
24747 stubs. Other features may describe packets which could be
24748 automatically probed for, but are not. These features must be
24749 reported before @value{GDBN} will use them. This ``default
24750 unsupported'' behavior is not appropriate for all packets, but it
24751 helps to keep the initial connection time under control with new
24752 versions of @value{GDBN} which support increasing numbers of packets.
24756 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
24757 The stub supports or does not support each returned @var{stubfeature},
24758 depending on the form of each @var{stubfeature} (see below for the
24761 An empty reply indicates that @samp{qSupported} is not recognized,
24762 or that no features needed to be reported to @value{GDBN}.
24765 The allowed forms for each feature (either a @var{gdbfeature} in the
24766 @samp{qSupported} packet, or a @var{stubfeature} in the response)
24770 @item @var{name}=@var{value}
24771 The remote protocol feature @var{name} is supported, and associated
24772 with the specified @var{value}. The format of @var{value} depends
24773 on the feature, but it must not include a semicolon.
24775 The remote protocol feature @var{name} is supported, and does not
24776 need an associated value.
24778 The remote protocol feature @var{name} is not supported.
24780 The remote protocol feature @var{name} may be supported, and
24781 @value{GDBN} should auto-detect support in some other way when it is
24782 needed. This form will not be used for @var{gdbfeature} notifications,
24783 but may be used for @var{stubfeature} responses.
24786 Whenever the stub receives a @samp{qSupported} request, the
24787 supplied set of @value{GDBN} features should override any previous
24788 request. This allows @value{GDBN} to put the stub in a known
24789 state, even if the stub had previously been communicating with
24790 a different version of @value{GDBN}.
24792 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
24793 are defined yet. Stubs should ignore any unknown values for
24794 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
24795 packet supports receiving packets of unlimited length (earlier
24796 versions of @value{GDBN} may reject overly long responses). Values
24797 for @var{gdbfeature} may be defined in the future to let the stub take
24798 advantage of new features in @value{GDBN}, e.g.@: incompatible
24799 improvements in the remote protocol---support for unlimited length
24800 responses would be a @var{gdbfeature} example, if it were not implied by
24801 the @samp{qSupported} query. The stub's reply should be independent
24802 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
24803 describes all the features it supports, and then the stub replies with
24804 all the features it supports.
24806 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
24807 responses, as long as each response uses one of the standard forms.
24809 Some features are flags. A stub which supports a flag feature
24810 should respond with a @samp{+} form response. Other features
24811 require values, and the stub should respond with an @samp{=}
24814 Each feature has a default value, which @value{GDBN} will use if
24815 @samp{qSupported} is not available or if the feature is not mentioned
24816 in the @samp{qSupported} response. The default values are fixed; a
24817 stub is free to omit any feature responses that match the defaults.
24819 Not all features can be probed, but for those which can, the probing
24820 mechanism is useful: in some cases, a stub's internal
24821 architecture may not allow the protocol layer to know some information
24822 about the underlying target in advance. This is especially common in
24823 stubs which may be configured for multiple targets.
24825 These are the currently defined stub features and their properties:
24827 @multitable @columnfractions 0.35 0.2 0.12 0.2
24828 @c NOTE: The first row should be @headitem, but we do not yet require
24829 @c a new enough version of Texinfo (4.7) to use @headitem.
24831 @tab Value Required
24835 @item @samp{PacketSize}
24840 @item @samp{qXfer:auxv:read}
24845 @item @samp{qXfer:features:read}
24850 @item @samp{qXfer:libraries:read}
24855 @item @samp{qXfer:memory-map:read}
24860 @item @samp{qXfer:spu:read}
24865 @item @samp{qXfer:spu:write}
24870 @item @samp{QPassSignals}
24877 These are the currently defined stub features, in more detail:
24880 @cindex packet size, remote protocol
24881 @item PacketSize=@var{bytes}
24882 The remote stub can accept packets up to at least @var{bytes} in
24883 length. @value{GDBN} will send packets up to this size for bulk
24884 transfers, and will never send larger packets. This is a limit on the
24885 data characters in the packet, including the frame and checksum.
24886 There is no trailing NUL byte in a remote protocol packet; if the stub
24887 stores packets in a NUL-terminated format, it should allow an extra
24888 byte in its buffer for the NUL. If this stub feature is not supported,
24889 @value{GDBN} guesses based on the size of the @samp{g} packet response.
24891 @item qXfer:auxv:read
24892 The remote stub understands the @samp{qXfer:auxv:read} packet
24893 (@pxref{qXfer auxiliary vector read}).
24895 @item qXfer:features:read
24896 The remote stub understands the @samp{qXfer:features:read} packet
24897 (@pxref{qXfer target description read}).
24899 @item qXfer:libraries:read
24900 The remote stub understands the @samp{qXfer:libraries:read} packet
24901 (@pxref{qXfer library list read}).
24903 @item qXfer:memory-map:read
24904 The remote stub understands the @samp{qXfer:memory-map:read} packet
24905 (@pxref{qXfer memory map read}).
24907 @item qXfer:spu:read
24908 The remote stub understands the @samp{qXfer:spu:read} packet
24909 (@pxref{qXfer spu read}).
24911 @item qXfer:spu:write
24912 The remote stub understands the @samp{qXfer:spu:write} packet
24913 (@pxref{qXfer spu write}).
24916 The remote stub understands the @samp{QPassSignals} packet
24917 (@pxref{QPassSignals}).
24922 @cindex symbol lookup, remote request
24923 @cindex @samp{qSymbol} packet
24924 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24925 requests. Accept requests from the target for the values of symbols.
24930 The target does not need to look up any (more) symbols.
24931 @item qSymbol:@var{sym_name}
24932 The target requests the value of symbol @var{sym_name} (hex encoded).
24933 @value{GDBN} may provide the value by using the
24934 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24938 @item qSymbol:@var{sym_value}:@var{sym_name}
24939 Set the value of @var{sym_name} to @var{sym_value}.
24941 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24942 target has previously requested.
24944 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24945 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24951 The target does not need to look up any (more) symbols.
24952 @item qSymbol:@var{sym_name}
24953 The target requests the value of a new symbol @var{sym_name} (hex
24954 encoded). @value{GDBN} will continue to supply the values of symbols
24955 (if available), until the target ceases to request them.
24960 @xref{Tracepoint Packets}.
24962 @item qThreadExtraInfo,@var{id}
24963 @cindex thread attributes info, remote request
24964 @cindex @samp{qThreadExtraInfo} packet
24965 Obtain a printable string description of a thread's attributes from
24966 the target OS. @var{id} is a thread-id in big-endian hex. This
24967 string may contain anything that the target OS thinks is interesting
24968 for @value{GDBN} to tell the user about the thread. The string is
24969 displayed in @value{GDBN}'s @code{info threads} display. Some
24970 examples of possible thread extra info strings are @samp{Runnable}, or
24971 @samp{Blocked on Mutex}.
24975 @item @var{XX}@dots{}
24976 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
24977 comprising the printable string containing the extra information about
24978 the thread's attributes.
24981 (Note that the @code{qThreadExtraInfo} packet's name is separated from
24982 the command by a @samp{,}, not a @samp{:}, contrary to the naming
24983 conventions above. Please don't use this packet as a model for new
24991 @xref{Tracepoint Packets}.
24993 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
24994 @cindex read special object, remote request
24995 @cindex @samp{qXfer} packet
24996 @anchor{qXfer read}
24997 Read uninterpreted bytes from the target's special data area
24998 identified by the keyword @var{object}. Request @var{length} bytes
24999 starting at @var{offset} bytes into the data. The content and
25000 encoding of @var{annex} is specific to @var{object}; it can supply
25001 additional details about what data to access.
25003 Here are the specific requests of this form defined so far. All
25004 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
25005 formats, listed below.
25008 @item qXfer:auxv:read::@var{offset},@var{length}
25009 @anchor{qXfer auxiliary vector read}
25010 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
25011 auxiliary vector}. Note @var{annex} must be empty.
25013 This packet is not probed by default; the remote stub must request it,
25014 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25016 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
25017 @anchor{qXfer target description read}
25018 Access the @dfn{target description}. @xref{Target Descriptions}. The
25019 annex specifies which XML document to access. The main description is
25020 always loaded from the @samp{target.xml} annex.
25022 This packet is not probed by default; the remote stub must request it,
25023 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25025 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
25026 @anchor{qXfer library list read}
25027 Access the target's list of loaded libraries. @xref{Library List Format}.
25028 The annex part of the generic @samp{qXfer} packet must be empty
25029 (@pxref{qXfer read}).
25031 Targets which maintain a list of libraries in the program's memory do
25032 not need to implement this packet; it is designed for platforms where
25033 the operating system manages the list of loaded libraries.
25035 This packet is not probed by default; the remote stub must request it,
25036 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25038 @item qXfer:memory-map:read::@var{offset},@var{length}
25039 @anchor{qXfer memory map read}
25040 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
25041 annex part of the generic @samp{qXfer} packet must be empty
25042 (@pxref{qXfer read}).
25044 This packet is not probed by default; the remote stub must request it,
25045 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25047 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
25048 @anchor{qXfer spu read}
25049 Read contents of an @code{spufs} file on the target system. The
25050 annex specifies which file to read; it must be of the form
25051 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25052 in the target process, and @var{name} identifes the @code{spufs} file
25053 in that context to be accessed.
25055 This packet is not probed by default; the remote stub must request it,
25056 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25062 Data @var{data} (@pxref{Binary Data}) has been read from the
25063 target. There may be more data at a higher address (although
25064 it is permitted to return @samp{m} even for the last valid
25065 block of data, as long as at least one byte of data was read).
25066 @var{data} may have fewer bytes than the @var{length} in the
25070 Data @var{data} (@pxref{Binary Data}) has been read from the target.
25071 There is no more data to be read. @var{data} may have fewer bytes
25072 than the @var{length} in the request.
25075 The @var{offset} in the request is at the end of the data.
25076 There is no more data to be read.
25079 The request was malformed, or @var{annex} was invalid.
25082 The offset was invalid, or there was an error encountered reading the data.
25083 @var{nn} is a hex-encoded @code{errno} value.
25086 An empty reply indicates the @var{object} string was not recognized by
25087 the stub, or that the object does not support reading.
25090 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25091 @cindex write data into object, remote request
25092 Write uninterpreted bytes into the target's special data area
25093 identified by the keyword @var{object}, starting at @var{offset} bytes
25094 into the data. @var{data}@dots{} is the binary-encoded data
25095 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
25096 is specific to @var{object}; it can supply additional details about what data
25099 Here are the specific requests of this form defined so far. All
25100 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
25101 formats, listed below.
25104 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
25105 @anchor{qXfer spu write}
25106 Write @var{data} to an @code{spufs} file on the target system. The
25107 annex specifies which file to write; it must be of the form
25108 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
25109 in the target process, and @var{name} identifes the @code{spufs} file
25110 in that context to be accessed.
25112 This packet is not probed by default; the remote stub must request it,
25113 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25119 @var{nn} (hex encoded) is the number of bytes written.
25120 This may be fewer bytes than supplied in the request.
25123 The request was malformed, or @var{annex} was invalid.
25126 The offset was invalid, or there was an error encountered writing the data.
25127 @var{nn} is a hex-encoded @code{errno} value.
25130 An empty reply indicates the @var{object} string was not
25131 recognized by the stub, or that the object does not support writing.
25134 @item qXfer:@var{object}:@var{operation}:@dots{}
25135 Requests of this form may be added in the future. When a stub does
25136 not recognize the @var{object} keyword, or its support for
25137 @var{object} does not recognize the @var{operation} keyword, the stub
25138 must respond with an empty packet.
25142 @node Register Packet Format
25143 @section Register Packet Format
25145 The following @code{g}/@code{G} packets have previously been defined.
25146 In the below, some thirty-two bit registers are transferred as
25147 sixty-four bits. Those registers should be zero/sign extended (which?)
25148 to fill the space allocated. Register bytes are transferred in target
25149 byte order. The two nibbles within a register byte are transferred
25150 most-significant - least-significant.
25156 All registers are transferred as thirty-two bit quantities in the order:
25157 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
25158 registers; fsr; fir; fp.
25162 All registers are transferred as sixty-four bit quantities (including
25163 thirty-two bit registers such as @code{sr}). The ordering is the same
25168 @node Tracepoint Packets
25169 @section Tracepoint Packets
25170 @cindex tracepoint packets
25171 @cindex packets, tracepoint
25173 Here we describe the packets @value{GDBN} uses to implement
25174 tracepoints (@pxref{Tracepoints}).
25178 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
25179 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
25180 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
25181 the tracepoint is disabled. @var{step} is the tracepoint's step
25182 count, and @var{pass} is its pass count. If the trailing @samp{-} is
25183 present, further @samp{QTDP} packets will follow to specify this
25184 tracepoint's actions.
25189 The packet was understood and carried out.
25191 The packet was not recognized.
25194 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
25195 Define actions to be taken when a tracepoint is hit. @var{n} and
25196 @var{addr} must be the same as in the initial @samp{QTDP} packet for
25197 this tracepoint. This packet may only be sent immediately after
25198 another @samp{QTDP} packet that ended with a @samp{-}. If the
25199 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
25200 specifying more actions for this tracepoint.
25202 In the series of action packets for a given tracepoint, at most one
25203 can have an @samp{S} before its first @var{action}. If such a packet
25204 is sent, it and the following packets define ``while-stepping''
25205 actions. Any prior packets define ordinary actions --- that is, those
25206 taken when the tracepoint is first hit. If no action packet has an
25207 @samp{S}, then all the packets in the series specify ordinary
25208 tracepoint actions.
25210 The @samp{@var{action}@dots{}} portion of the packet is a series of
25211 actions, concatenated without separators. Each action has one of the
25217 Collect the registers whose bits are set in @var{mask}. @var{mask} is
25218 a hexadecimal number whose @var{i}'th bit is set if register number
25219 @var{i} should be collected. (The least significant bit is numbered
25220 zero.) Note that @var{mask} may be any number of digits long; it may
25221 not fit in a 32-bit word.
25223 @item M @var{basereg},@var{offset},@var{len}
25224 Collect @var{len} bytes of memory starting at the address in register
25225 number @var{basereg}, plus @var{offset}. If @var{basereg} is
25226 @samp{-1}, then the range has a fixed address: @var{offset} is the
25227 address of the lowest byte to collect. The @var{basereg},
25228 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
25229 values (the @samp{-1} value for @var{basereg} is a special case).
25231 @item X @var{len},@var{expr}
25232 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
25233 it directs. @var{expr} is an agent expression, as described in
25234 @ref{Agent Expressions}. Each byte of the expression is encoded as a
25235 two-digit hex number in the packet; @var{len} is the number of bytes
25236 in the expression (and thus one-half the number of hex digits in the
25241 Any number of actions may be packed together in a single @samp{QTDP}
25242 packet, as long as the packet does not exceed the maximum packet
25243 length (400 bytes, for many stubs). There may be only one @samp{R}
25244 action per tracepoint, and it must precede any @samp{M} or @samp{X}
25245 actions. Any registers referred to by @samp{M} and @samp{X} actions
25246 must be collected by a preceding @samp{R} action. (The
25247 ``while-stepping'' actions are treated as if they were attached to a
25248 separate tracepoint, as far as these restrictions are concerned.)
25253 The packet was understood and carried out.
25255 The packet was not recognized.
25258 @item QTFrame:@var{n}
25259 Select the @var{n}'th tracepoint frame from the buffer, and use the
25260 register and memory contents recorded there to answer subsequent
25261 request packets from @value{GDBN}.
25263 A successful reply from the stub indicates that the stub has found the
25264 requested frame. The response is a series of parts, concatenated
25265 without separators, describing the frame we selected. Each part has
25266 one of the following forms:
25270 The selected frame is number @var{n} in the trace frame buffer;
25271 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
25272 was no frame matching the criteria in the request packet.
25275 The selected trace frame records a hit of tracepoint number @var{t};
25276 @var{t} is a hexadecimal number.
25280 @item QTFrame:pc:@var{addr}
25281 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25282 currently selected frame whose PC is @var{addr};
25283 @var{addr} is a hexadecimal number.
25285 @item QTFrame:tdp:@var{t}
25286 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25287 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
25288 is a hexadecimal number.
25290 @item QTFrame:range:@var{start}:@var{end}
25291 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
25292 currently selected frame whose PC is between @var{start} (inclusive)
25293 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
25296 @item QTFrame:outside:@var{start}:@var{end}
25297 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
25298 frame @emph{outside} the given range of addresses.
25301 Begin the tracepoint experiment. Begin collecting data from tracepoint
25302 hits in the trace frame buffer.
25305 End the tracepoint experiment. Stop collecting trace frames.
25308 Clear the table of tracepoints, and empty the trace frame buffer.
25310 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
25311 Establish the given ranges of memory as ``transparent''. The stub
25312 will answer requests for these ranges from memory's current contents,
25313 if they were not collected as part of the tracepoint hit.
25315 @value{GDBN} uses this to mark read-only regions of memory, like those
25316 containing program code. Since these areas never change, they should
25317 still have the same contents they did when the tracepoint was hit, so
25318 there's no reason for the stub to refuse to provide their contents.
25321 Ask the stub if there is a trace experiment running right now.
25326 There is no trace experiment running.
25328 There is a trace experiment running.
25334 @node Host I/O Packets
25335 @section Host I/O Packets
25336 @cindex Host I/O, remote protocol
25337 @cindex file transfer, remote protocol
25339 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
25340 operations on the far side of a remote link. For example, Host I/O is
25341 used to upload and download files to a remote target with its own
25342 filesystem. Host I/O uses the same constant values and data structure
25343 layout as the target-initiated File-I/O protocol. However, the
25344 Host I/O packets are structured differently. The target-initiated
25345 protocol relies on target memory to store parameters and buffers.
25346 Host I/O requests are initiated by @value{GDBN}, and the
25347 target's memory is not involved. @xref{File-I/O Remote Protocol
25348 Extension}, for more details on the target-initiated protocol.
25350 The Host I/O request packets all encode a single operation along with
25351 its arguments. They have this format:
25355 @item vFile:@var{operation}: @var{parameter}@dots{}
25356 @var{operation} is the name of the particular request; the target
25357 should compare the entire packet name up to the second colon when checking
25358 for a supported operation. The format of @var{parameter} depends on
25359 the operation. Numbers are always passed in hexadecimal. Negative
25360 numbers have an explicit minus sign (i.e.@: two's complement is not
25361 used). Strings (e.g.@: filenames) are encoded as a series of
25362 hexadecimal bytes. The last argument to a system call may be a
25363 buffer of escaped binary data (@pxref{Binary Data}).
25367 The valid responses to Host I/O packets are:
25371 @item F @var{result} [, @var{errno}] [; @var{attachment}]
25372 @var{result} is the integer value returned by this operation, usually
25373 non-negative for success and -1 for errors. If an error has occured,
25374 @var{errno} will be included in the result. @var{errno} will have a
25375 value defined by the File-I/O protocol (@pxref{Errno Values}). For
25376 operations which return data, @var{attachment} supplies the data as a
25377 binary buffer. Binary buffers in response packets are escaped in the
25378 normal way (@pxref{Binary Data}). See the individual packet
25379 documentation for the interpretation of @var{result} and
25383 An empty response indicates that this operation is not recognized.
25387 These are the supported Host I/O operations:
25390 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
25391 Open a file at @var{pathname} and return a file descriptor for it, or
25392 return -1 if an error occurs. @var{pathname} is a string,
25393 @var{flags} is an integer indicating a mask of open flags
25394 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
25395 of mode bits to use if the file is created (@pxref{mode_t Values}).
25396 @xref{open}, for details of the open flags and mode values.
25398 @item vFile:close: @var{fd}
25399 Close the open file corresponding to @var{fd} and return 0, or
25400 -1 if an error occurs.
25402 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
25403 Read data from the open file corresponding to @var{fd}. Up to
25404 @var{count} bytes will be read from the file, starting at @var{offset}
25405 relative to the start of the file. The target may read fewer bytes;
25406 common reasons include packet size limits and an end-of-file
25407 condition. The number of bytes read is returned. Zero should only be
25408 returned for a successful read at the end of the file, or if
25409 @var{count} was zero.
25411 The data read should be returned as a binary attachment on success.
25412 If zero bytes were read, the response should include an empty binary
25413 attachment (i.e.@: a trailing semicolon). The return value is the
25414 number of target bytes read; the binary attachment may be longer if
25415 some characters were escaped.
25417 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
25418 Write @var{data} (a binary buffer) to the open file corresponding
25419 to @var{fd}. Start the write at @var{offset} from the start of the
25420 file. Unlike many @code{write} system calls, there is no
25421 separate @var{count} argument; the length of @var{data} in the
25422 packet is used. @samp{vFile:write} returns the number of bytes written,
25423 which may be shorter than the length of @var{data}, or -1 if an
25426 @item vFile:unlink: @var{pathname}
25427 Delete the file at @var{pathname} on the target. Return 0,
25428 or -1 if an error occurs. @var{pathname} is a string.
25433 @section Interrupts
25434 @cindex interrupts (remote protocol)
25436 When a program on the remote target is running, @value{GDBN} may
25437 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
25438 control of which is specified via @value{GDBN}'s @samp{remotebreak}
25439 setting (@pxref{set remotebreak}).
25441 The precise meaning of @code{BREAK} is defined by the transport
25442 mechanism and may, in fact, be undefined. @value{GDBN} does
25443 not currently define a @code{BREAK} mechanism for any of the network
25446 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
25447 transport mechanisms. It is represented by sending the single byte
25448 @code{0x03} without any of the usual packet overhead described in
25449 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
25450 transmitted as part of a packet, it is considered to be packet data
25451 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
25452 (@pxref{X packet}), used for binary downloads, may include an unescaped
25453 @code{0x03} as part of its packet.
25455 Stubs are not required to recognize these interrupt mechanisms and the
25456 precise meaning associated with receipt of the interrupt is
25457 implementation defined. If the stub is successful at interrupting the
25458 running program, it is expected that it will send one of the Stop
25459 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
25460 of successfully stopping the program. Interrupts received while the
25461 program is stopped will be discarded.
25466 Example sequence of a target being re-started. Notice how the restart
25467 does not get any direct output:
25472 @emph{target restarts}
25475 <- @code{T001:1234123412341234}
25479 Example sequence of a target being stepped by a single instruction:
25482 -> @code{G1445@dots{}}
25487 <- @code{T001:1234123412341234}
25491 <- @code{1455@dots{}}
25495 @node File-I/O Remote Protocol Extension
25496 @section File-I/O Remote Protocol Extension
25497 @cindex File-I/O remote protocol extension
25500 * File-I/O Overview::
25501 * Protocol Basics::
25502 * The F Request Packet::
25503 * The F Reply Packet::
25504 * The Ctrl-C Message::
25506 * List of Supported Calls::
25507 * Protocol-specific Representation of Datatypes::
25509 * File-I/O Examples::
25512 @node File-I/O Overview
25513 @subsection File-I/O Overview
25514 @cindex file-i/o overview
25516 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
25517 target to use the host's file system and console I/O to perform various
25518 system calls. System calls on the target system are translated into a
25519 remote protocol packet to the host system, which then performs the needed
25520 actions and returns a response packet to the target system.
25521 This simulates file system operations even on targets that lack file systems.
25523 The protocol is defined to be independent of both the host and target systems.
25524 It uses its own internal representation of datatypes and values. Both
25525 @value{GDBN} and the target's @value{GDBN} stub are responsible for
25526 translating the system-dependent value representations into the internal
25527 protocol representations when data is transmitted.
25529 The communication is synchronous. A system call is possible only when
25530 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
25531 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
25532 the target is stopped to allow deterministic access to the target's
25533 memory. Therefore File-I/O is not interruptible by target signals. On
25534 the other hand, it is possible to interrupt File-I/O by a user interrupt
25535 (@samp{Ctrl-C}) within @value{GDBN}.
25537 The target's request to perform a host system call does not finish
25538 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
25539 after finishing the system call, the target returns to continuing the
25540 previous activity (continue, step). No additional continue or step
25541 request from @value{GDBN} is required.
25544 (@value{GDBP}) continue
25545 <- target requests 'system call X'
25546 target is stopped, @value{GDBN} executes system call
25547 -> @value{GDBN} returns result
25548 ... target continues, @value{GDBN} returns to wait for the target
25549 <- target hits breakpoint and sends a Txx packet
25552 The protocol only supports I/O on the console and to regular files on
25553 the host file system. Character or block special devices, pipes,
25554 named pipes, sockets or any other communication method on the host
25555 system are not supported by this protocol.
25557 @node Protocol Basics
25558 @subsection Protocol Basics
25559 @cindex protocol basics, file-i/o
25561 The File-I/O protocol uses the @code{F} packet as the request as well
25562 as reply packet. Since a File-I/O system call can only occur when
25563 @value{GDBN} is waiting for a response from the continuing or stepping target,
25564 the File-I/O request is a reply that @value{GDBN} has to expect as a result
25565 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
25566 This @code{F} packet contains all information needed to allow @value{GDBN}
25567 to call the appropriate host system call:
25571 A unique identifier for the requested system call.
25574 All parameters to the system call. Pointers are given as addresses
25575 in the target memory address space. Pointers to strings are given as
25576 pointer/length pair. Numerical values are given as they are.
25577 Numerical control flags are given in a protocol-specific representation.
25581 At this point, @value{GDBN} has to perform the following actions.
25585 If the parameters include pointer values to data needed as input to a
25586 system call, @value{GDBN} requests this data from the target with a
25587 standard @code{m} packet request. This additional communication has to be
25588 expected by the target implementation and is handled as any other @code{m}
25592 @value{GDBN} translates all value from protocol representation to host
25593 representation as needed. Datatypes are coerced into the host types.
25596 @value{GDBN} calls the system call.
25599 It then coerces datatypes back to protocol representation.
25602 If the system call is expected to return data in buffer space specified
25603 by pointer parameters to the call, the data is transmitted to the
25604 target using a @code{M} or @code{X} packet. This packet has to be expected
25605 by the target implementation and is handled as any other @code{M} or @code{X}
25610 Eventually @value{GDBN} replies with another @code{F} packet which contains all
25611 necessary information for the target to continue. This at least contains
25618 @code{errno}, if has been changed by the system call.
25625 After having done the needed type and value coercion, the target continues
25626 the latest continue or step action.
25628 @node The F Request Packet
25629 @subsection The @code{F} Request Packet
25630 @cindex file-i/o request packet
25631 @cindex @code{F} request packet
25633 The @code{F} request packet has the following format:
25636 @item F@var{call-id},@var{parameter@dots{}}
25638 @var{call-id} is the identifier to indicate the host system call to be called.
25639 This is just the name of the function.
25641 @var{parameter@dots{}} are the parameters to the system call.
25642 Parameters are hexadecimal integer values, either the actual values in case
25643 of scalar datatypes, pointers to target buffer space in case of compound
25644 datatypes and unspecified memory areas, or pointer/length pairs in case
25645 of string parameters. These are appended to the @var{call-id} as a
25646 comma-delimited list. All values are transmitted in ASCII
25647 string representation, pointer/length pairs separated by a slash.
25653 @node The F Reply Packet
25654 @subsection The @code{F} Reply Packet
25655 @cindex file-i/o reply packet
25656 @cindex @code{F} reply packet
25658 The @code{F} reply packet has the following format:
25662 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
25664 @var{retcode} is the return code of the system call as hexadecimal value.
25666 @var{errno} is the @code{errno} set by the call, in protocol-specific
25668 This parameter can be omitted if the call was successful.
25670 @var{Ctrl-C flag} is only sent if the user requested a break. In this
25671 case, @var{errno} must be sent as well, even if the call was successful.
25672 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
25679 or, if the call was interrupted before the host call has been performed:
25686 assuming 4 is the protocol-specific representation of @code{EINTR}.
25691 @node The Ctrl-C Message
25692 @subsection The @samp{Ctrl-C} Message
25693 @cindex ctrl-c message, in file-i/o protocol
25695 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
25696 reply packet (@pxref{The F Reply Packet}),
25697 the target should behave as if it had
25698 gotten a break message. The meaning for the target is ``system call
25699 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
25700 (as with a break message) and return to @value{GDBN} with a @code{T02}
25703 It's important for the target to know in which
25704 state the system call was interrupted. There are two possible cases:
25708 The system call hasn't been performed on the host yet.
25711 The system call on the host has been finished.
25715 These two states can be distinguished by the target by the value of the
25716 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
25717 call hasn't been performed. This is equivalent to the @code{EINTR} handling
25718 on POSIX systems. In any other case, the target may presume that the
25719 system call has been finished --- successfully or not --- and should behave
25720 as if the break message arrived right after the system call.
25722 @value{GDBN} must behave reliably. If the system call has not been called
25723 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
25724 @code{errno} in the packet. If the system call on the host has been finished
25725 before the user requests a break, the full action must be finished by
25726 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
25727 The @code{F} packet may only be sent when either nothing has happened
25728 or the full action has been completed.
25731 @subsection Console I/O
25732 @cindex console i/o as part of file-i/o
25734 By default and if not explicitly closed by the target system, the file
25735 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
25736 on the @value{GDBN} console is handled as any other file output operation
25737 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
25738 by @value{GDBN} so that after the target read request from file descriptor
25739 0 all following typing is buffered until either one of the following
25744 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
25746 system call is treated as finished.
25749 The user presses @key{RET}. This is treated as end of input with a trailing
25753 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
25754 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
25758 If the user has typed more characters than fit in the buffer given to
25759 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
25760 either another @code{read(0, @dots{})} is requested by the target, or debugging
25761 is stopped at the user's request.
25764 @node List of Supported Calls
25765 @subsection List of Supported Calls
25766 @cindex list of supported file-i/o calls
25783 @unnumberedsubsubsec open
25784 @cindex open, file-i/o system call
25789 int open(const char *pathname, int flags);
25790 int open(const char *pathname, int flags, mode_t mode);
25794 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
25797 @var{flags} is the bitwise @code{OR} of the following values:
25801 If the file does not exist it will be created. The host
25802 rules apply as far as file ownership and time stamps
25806 When used with @code{O_CREAT}, if the file already exists it is
25807 an error and open() fails.
25810 If the file already exists and the open mode allows
25811 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
25812 truncated to zero length.
25815 The file is opened in append mode.
25818 The file is opened for reading only.
25821 The file is opened for writing only.
25824 The file is opened for reading and writing.
25828 Other bits are silently ignored.
25832 @var{mode} is the bitwise @code{OR} of the following values:
25836 User has read permission.
25839 User has write permission.
25842 Group has read permission.
25845 Group has write permission.
25848 Others have read permission.
25851 Others have write permission.
25855 Other bits are silently ignored.
25858 @item Return value:
25859 @code{open} returns the new file descriptor or -1 if an error
25866 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
25869 @var{pathname} refers to a directory.
25872 The requested access is not allowed.
25875 @var{pathname} was too long.
25878 A directory component in @var{pathname} does not exist.
25881 @var{pathname} refers to a device, pipe, named pipe or socket.
25884 @var{pathname} refers to a file on a read-only filesystem and
25885 write access was requested.
25888 @var{pathname} is an invalid pointer value.
25891 No space on device to create the file.
25894 The process already has the maximum number of files open.
25897 The limit on the total number of files open on the system
25901 The call was interrupted by the user.
25907 @unnumberedsubsubsec close
25908 @cindex close, file-i/o system call
25917 @samp{Fclose,@var{fd}}
25919 @item Return value:
25920 @code{close} returns zero on success, or -1 if an error occurred.
25926 @var{fd} isn't a valid open file descriptor.
25929 The call was interrupted by the user.
25935 @unnumberedsubsubsec read
25936 @cindex read, file-i/o system call
25941 int read(int fd, void *buf, unsigned int count);
25945 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
25947 @item Return value:
25948 On success, the number of bytes read is returned.
25949 Zero indicates end of file. If count is zero, read
25950 returns zero as well. On error, -1 is returned.
25956 @var{fd} is not a valid file descriptor or is not open for
25960 @var{bufptr} is an invalid pointer value.
25963 The call was interrupted by the user.
25969 @unnumberedsubsubsec write
25970 @cindex write, file-i/o system call
25975 int write(int fd, const void *buf, unsigned int count);
25979 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
25981 @item Return value:
25982 On success, the number of bytes written are returned.
25983 Zero indicates nothing was written. On error, -1
25990 @var{fd} is not a valid file descriptor or is not open for
25994 @var{bufptr} is an invalid pointer value.
25997 An attempt was made to write a file that exceeds the
25998 host-specific maximum file size allowed.
26001 No space on device to write the data.
26004 The call was interrupted by the user.
26010 @unnumberedsubsubsec lseek
26011 @cindex lseek, file-i/o system call
26016 long lseek (int fd, long offset, int flag);
26020 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
26022 @var{flag} is one of:
26026 The offset is set to @var{offset} bytes.
26029 The offset is set to its current location plus @var{offset}
26033 The offset is set to the size of the file plus @var{offset}
26037 @item Return value:
26038 On success, the resulting unsigned offset in bytes from
26039 the beginning of the file is returned. Otherwise, a
26040 value of -1 is returned.
26046 @var{fd} is not a valid open file descriptor.
26049 @var{fd} is associated with the @value{GDBN} console.
26052 @var{flag} is not a proper value.
26055 The call was interrupted by the user.
26061 @unnumberedsubsubsec rename
26062 @cindex rename, file-i/o system call
26067 int rename(const char *oldpath, const char *newpath);
26071 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
26073 @item Return value:
26074 On success, zero is returned. On error, -1 is returned.
26080 @var{newpath} is an existing directory, but @var{oldpath} is not a
26084 @var{newpath} is a non-empty directory.
26087 @var{oldpath} or @var{newpath} is a directory that is in use by some
26091 An attempt was made to make a directory a subdirectory
26095 A component used as a directory in @var{oldpath} or new
26096 path is not a directory. Or @var{oldpath} is a directory
26097 and @var{newpath} exists but is not a directory.
26100 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
26103 No access to the file or the path of the file.
26107 @var{oldpath} or @var{newpath} was too long.
26110 A directory component in @var{oldpath} or @var{newpath} does not exist.
26113 The file is on a read-only filesystem.
26116 The device containing the file has no room for the new
26120 The call was interrupted by the user.
26126 @unnumberedsubsubsec unlink
26127 @cindex unlink, file-i/o system call
26132 int unlink(const char *pathname);
26136 @samp{Funlink,@var{pathnameptr}/@var{len}}
26138 @item Return value:
26139 On success, zero is returned. On error, -1 is returned.
26145 No access to the file or the path of the file.
26148 The system does not allow unlinking of directories.
26151 The file @var{pathname} cannot be unlinked because it's
26152 being used by another process.
26155 @var{pathnameptr} is an invalid pointer value.
26158 @var{pathname} was too long.
26161 A directory component in @var{pathname} does not exist.
26164 A component of the path is not a directory.
26167 The file is on a read-only filesystem.
26170 The call was interrupted by the user.
26176 @unnumberedsubsubsec stat/fstat
26177 @cindex fstat, file-i/o system call
26178 @cindex stat, file-i/o system call
26183 int stat(const char *pathname, struct stat *buf);
26184 int fstat(int fd, struct stat *buf);
26188 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
26189 @samp{Ffstat,@var{fd},@var{bufptr}}
26191 @item Return value:
26192 On success, zero is returned. On error, -1 is returned.
26198 @var{fd} is not a valid open file.
26201 A directory component in @var{pathname} does not exist or the
26202 path is an empty string.
26205 A component of the path is not a directory.
26208 @var{pathnameptr} is an invalid pointer value.
26211 No access to the file or the path of the file.
26214 @var{pathname} was too long.
26217 The call was interrupted by the user.
26223 @unnumberedsubsubsec gettimeofday
26224 @cindex gettimeofday, file-i/o system call
26229 int gettimeofday(struct timeval *tv, void *tz);
26233 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
26235 @item Return value:
26236 On success, 0 is returned, -1 otherwise.
26242 @var{tz} is a non-NULL pointer.
26245 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
26251 @unnumberedsubsubsec isatty
26252 @cindex isatty, file-i/o system call
26257 int isatty(int fd);
26261 @samp{Fisatty,@var{fd}}
26263 @item Return value:
26264 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
26270 The call was interrupted by the user.
26275 Note that the @code{isatty} call is treated as a special case: it returns
26276 1 to the target if the file descriptor is attached
26277 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
26278 would require implementing @code{ioctl} and would be more complex than
26283 @unnumberedsubsubsec system
26284 @cindex system, file-i/o system call
26289 int system(const char *command);
26293 @samp{Fsystem,@var{commandptr}/@var{len}}
26295 @item Return value:
26296 If @var{len} is zero, the return value indicates whether a shell is
26297 available. A zero return value indicates a shell is not available.
26298 For non-zero @var{len}, the value returned is -1 on error and the
26299 return status of the command otherwise. Only the exit status of the
26300 command is returned, which is extracted from the host's @code{system}
26301 return value by calling @code{WEXITSTATUS(retval)}. In case
26302 @file{/bin/sh} could not be executed, 127 is returned.
26308 The call was interrupted by the user.
26313 @value{GDBN} takes over the full task of calling the necessary host calls
26314 to perform the @code{system} call. The return value of @code{system} on
26315 the host is simplified before it's returned
26316 to the target. Any termination signal information from the child process
26317 is discarded, and the return value consists
26318 entirely of the exit status of the called command.
26320 Due to security concerns, the @code{system} call is by default refused
26321 by @value{GDBN}. The user has to allow this call explicitly with the
26322 @code{set remote system-call-allowed 1} command.
26325 @item set remote system-call-allowed
26326 @kindex set remote system-call-allowed
26327 Control whether to allow the @code{system} calls in the File I/O
26328 protocol for the remote target. The default is zero (disabled).
26330 @item show remote system-call-allowed
26331 @kindex show remote system-call-allowed
26332 Show whether the @code{system} calls are allowed in the File I/O
26336 @node Protocol-specific Representation of Datatypes
26337 @subsection Protocol-specific Representation of Datatypes
26338 @cindex protocol-specific representation of datatypes, in file-i/o protocol
26341 * Integral Datatypes::
26343 * Memory Transfer::
26348 @node Integral Datatypes
26349 @unnumberedsubsubsec Integral Datatypes
26350 @cindex integral datatypes, in file-i/o protocol
26352 The integral datatypes used in the system calls are @code{int},
26353 @code{unsigned int}, @code{long}, @code{unsigned long},
26354 @code{mode_t}, and @code{time_t}.
26356 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
26357 implemented as 32 bit values in this protocol.
26359 @code{long} and @code{unsigned long} are implemented as 64 bit types.
26361 @xref{Limits}, for corresponding MIN and MAX values (similar to those
26362 in @file{limits.h}) to allow range checking on host and target.
26364 @code{time_t} datatypes are defined as seconds since the Epoch.
26366 All integral datatypes transferred as part of a memory read or write of a
26367 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
26370 @node Pointer Values
26371 @unnumberedsubsubsec Pointer Values
26372 @cindex pointer values, in file-i/o protocol
26374 Pointers to target data are transmitted as they are. An exception
26375 is made for pointers to buffers for which the length isn't
26376 transmitted as part of the function call, namely strings. Strings
26377 are transmitted as a pointer/length pair, both as hex values, e.g.@:
26384 which is a pointer to data of length 18 bytes at position 0x1aaf.
26385 The length is defined as the full string length in bytes, including
26386 the trailing null byte. For example, the string @code{"hello world"}
26387 at address 0x123456 is transmitted as
26393 @node Memory Transfer
26394 @unnumberedsubsubsec Memory Transfer
26395 @cindex memory transfer, in file-i/o protocol
26397 Structured data which is transferred using a memory read or write (for
26398 example, a @code{struct stat}) is expected to be in a protocol-specific format
26399 with all scalar multibyte datatypes being big endian. Translation to
26400 this representation needs to be done both by the target before the @code{F}
26401 packet is sent, and by @value{GDBN} before
26402 it transfers memory to the target. Transferred pointers to structured
26403 data should point to the already-coerced data at any time.
26407 @unnumberedsubsubsec struct stat
26408 @cindex struct stat, in file-i/o protocol
26410 The buffer of type @code{struct stat} used by the target and @value{GDBN}
26411 is defined as follows:
26415 unsigned int st_dev; /* device */
26416 unsigned int st_ino; /* inode */
26417 mode_t st_mode; /* protection */
26418 unsigned int st_nlink; /* number of hard links */
26419 unsigned int st_uid; /* user ID of owner */
26420 unsigned int st_gid; /* group ID of owner */
26421 unsigned int st_rdev; /* device type (if inode device) */
26422 unsigned long st_size; /* total size, in bytes */
26423 unsigned long st_blksize; /* blocksize for filesystem I/O */
26424 unsigned long st_blocks; /* number of blocks allocated */
26425 time_t st_atime; /* time of last access */
26426 time_t st_mtime; /* time of last modification */
26427 time_t st_ctime; /* time of last change */
26431 The integral datatypes conform to the definitions given in the
26432 appropriate section (see @ref{Integral Datatypes}, for details) so this
26433 structure is of size 64 bytes.
26435 The values of several fields have a restricted meaning and/or
26441 A value of 0 represents a file, 1 the console.
26444 No valid meaning for the target. Transmitted unchanged.
26447 Valid mode bits are described in @ref{Constants}. Any other
26448 bits have currently no meaning for the target.
26453 No valid meaning for the target. Transmitted unchanged.
26458 These values have a host and file system dependent
26459 accuracy. Especially on Windows hosts, the file system may not
26460 support exact timing values.
26463 The target gets a @code{struct stat} of the above representation and is
26464 responsible for coercing it to the target representation before
26467 Note that due to size differences between the host, target, and protocol
26468 representations of @code{struct stat} members, these members could eventually
26469 get truncated on the target.
26471 @node struct timeval
26472 @unnumberedsubsubsec struct timeval
26473 @cindex struct timeval, in file-i/o protocol
26475 The buffer of type @code{struct timeval} used by the File-I/O protocol
26476 is defined as follows:
26480 time_t tv_sec; /* second */
26481 long tv_usec; /* microsecond */
26485 The integral datatypes conform to the definitions given in the
26486 appropriate section (see @ref{Integral Datatypes}, for details) so this
26487 structure is of size 8 bytes.
26490 @subsection Constants
26491 @cindex constants, in file-i/o protocol
26493 The following values are used for the constants inside of the
26494 protocol. @value{GDBN} and target are responsible for translating these
26495 values before and after the call as needed.
26506 @unnumberedsubsubsec Open Flags
26507 @cindex open flags, in file-i/o protocol
26509 All values are given in hexadecimal representation.
26521 @node mode_t Values
26522 @unnumberedsubsubsec mode_t Values
26523 @cindex mode_t values, in file-i/o protocol
26525 All values are given in octal representation.
26542 @unnumberedsubsubsec Errno Values
26543 @cindex errno values, in file-i/o protocol
26545 All values are given in decimal representation.
26570 @code{EUNKNOWN} is used as a fallback error value if a host system returns
26571 any error value not in the list of supported error numbers.
26574 @unnumberedsubsubsec Lseek Flags
26575 @cindex lseek flags, in file-i/o protocol
26584 @unnumberedsubsubsec Limits
26585 @cindex limits, in file-i/o protocol
26587 All values are given in decimal representation.
26590 INT_MIN -2147483648
26592 UINT_MAX 4294967295
26593 LONG_MIN -9223372036854775808
26594 LONG_MAX 9223372036854775807
26595 ULONG_MAX 18446744073709551615
26598 @node File-I/O Examples
26599 @subsection File-I/O Examples
26600 @cindex file-i/o examples
26602 Example sequence of a write call, file descriptor 3, buffer is at target
26603 address 0x1234, 6 bytes should be written:
26606 <- @code{Fwrite,3,1234,6}
26607 @emph{request memory read from target}
26610 @emph{return "6 bytes written"}
26614 Example sequence of a read call, file descriptor 3, buffer is at target
26615 address 0x1234, 6 bytes should be read:
26618 <- @code{Fread,3,1234,6}
26619 @emph{request memory write to target}
26620 -> @code{X1234,6:XXXXXX}
26621 @emph{return "6 bytes read"}
26625 Example sequence of a read call, call fails on the host due to invalid
26626 file descriptor (@code{EBADF}):
26629 <- @code{Fread,3,1234,6}
26633 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
26637 <- @code{Fread,3,1234,6}
26642 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
26646 <- @code{Fread,3,1234,6}
26647 -> @code{X1234,6:XXXXXX}
26651 @node Library List Format
26652 @section Library List Format
26653 @cindex library list format, remote protocol
26655 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
26656 same process as your application to manage libraries. In this case,
26657 @value{GDBN} can use the loader's symbol table and normal memory
26658 operations to maintain a list of shared libraries. On other
26659 platforms, the operating system manages loaded libraries.
26660 @value{GDBN} can not retrieve the list of currently loaded libraries
26661 through memory operations, so it uses the @samp{qXfer:libraries:read}
26662 packet (@pxref{qXfer library list read}) instead. The remote stub
26663 queries the target's operating system and reports which libraries
26666 The @samp{qXfer:libraries:read} packet returns an XML document which
26667 lists loaded libraries and their offsets. Each library has an
26668 associated name and one or more segment or section base addresses,
26669 which report where the library was loaded in memory.
26671 For the common case of libraries that are fully linked binaries, the
26672 library should have a list of segments. If the target supports
26673 dynamic linking of a relocatable object file, its library XML element
26674 should instead include a list of allocated sections. The segment or
26675 section bases are start addresses, not relocation offsets; they do not
26676 depend on the library's link-time base addresses.
26678 @value{GDBN} must be linked with the Expat library to support XML
26679 library lists. @xref{Expat}.
26681 A simple memory map, with one loaded library relocated by a single
26682 offset, looks like this:
26686 <library name="/lib/libc.so.6">
26687 <segment address="0x10000000"/>
26692 Another simple memory map, with one loaded library with three
26693 allocated sections (.text, .data, .bss), looks like this:
26697 <library name="sharedlib.o">
26698 <section address="0x10000000"/>
26699 <section address="0x20000000"/>
26700 <section address="0x30000000"/>
26705 The format of a library list is described by this DTD:
26708 <!-- library-list: Root element with versioning -->
26709 <!ELEMENT library-list (library)*>
26710 <!ATTLIST library-list version CDATA #FIXED "1.0">
26711 <!ELEMENT library (segment*, section*)>
26712 <!ATTLIST library name CDATA #REQUIRED>
26713 <!ELEMENT segment EMPTY>
26714 <!ATTLIST segment address CDATA #REQUIRED>
26715 <!ELEMENT section EMPTY>
26716 <!ATTLIST section address CDATA #REQUIRED>
26719 In addition, segments and section descriptors cannot be mixed within a
26720 single library element, and you must supply at least one segment or
26721 section for each library.
26723 @node Memory Map Format
26724 @section Memory Map Format
26725 @cindex memory map format
26727 To be able to write into flash memory, @value{GDBN} needs to obtain a
26728 memory map from the target. This section describes the format of the
26731 The memory map is obtained using the @samp{qXfer:memory-map:read}
26732 (@pxref{qXfer memory map read}) packet and is an XML document that
26733 lists memory regions.
26735 @value{GDBN} must be linked with the Expat library to support XML
26736 memory maps. @xref{Expat}.
26738 The top-level structure of the document is shown below:
26741 <?xml version="1.0"?>
26742 <!DOCTYPE memory-map
26743 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
26744 "http://sourceware.org/gdb/gdb-memory-map.dtd">
26750 Each region can be either:
26755 A region of RAM starting at @var{addr} and extending for @var{length}
26759 <memory type="ram" start="@var{addr}" length="@var{length}"/>
26764 A region of read-only memory:
26767 <memory type="rom" start="@var{addr}" length="@var{length}"/>
26772 A region of flash memory, with erasure blocks @var{blocksize}
26776 <memory type="flash" start="@var{addr}" length="@var{length}">
26777 <property name="blocksize">@var{blocksize}</property>
26783 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
26784 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
26785 packets to write to addresses in such ranges.
26787 The formal DTD for memory map format is given below:
26790 <!-- ................................................... -->
26791 <!-- Memory Map XML DTD ................................ -->
26792 <!-- File: memory-map.dtd .............................. -->
26793 <!-- .................................... .............. -->
26794 <!-- memory-map.dtd -->
26795 <!-- memory-map: Root element with versioning -->
26796 <!ELEMENT memory-map (memory | property)>
26797 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
26798 <!ELEMENT memory (property)>
26799 <!-- memory: Specifies a memory region,
26800 and its type, or device. -->
26801 <!ATTLIST memory type CDATA #REQUIRED
26802 start CDATA #REQUIRED
26803 length CDATA #REQUIRED
26804 device CDATA #IMPLIED>
26805 <!-- property: Generic attribute tag -->
26806 <!ELEMENT property (#PCDATA | property)*>
26807 <!ATTLIST property name CDATA #REQUIRED>
26810 @include agentexpr.texi
26812 @node Target Descriptions
26813 @appendix Target Descriptions
26814 @cindex target descriptions
26816 @strong{Warning:} target descriptions are still under active development,
26817 and the contents and format may change between @value{GDBN} releases.
26818 The format is expected to stabilize in the future.
26820 One of the challenges of using @value{GDBN} to debug embedded systems
26821 is that there are so many minor variants of each processor
26822 architecture in use. It is common practice for vendors to start with
26823 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
26824 and then make changes to adapt it to a particular market niche. Some
26825 architectures have hundreds of variants, available from dozens of
26826 vendors. This leads to a number of problems:
26830 With so many different customized processors, it is difficult for
26831 the @value{GDBN} maintainers to keep up with the changes.
26833 Since individual variants may have short lifetimes or limited
26834 audiences, it may not be worthwhile to carry information about every
26835 variant in the @value{GDBN} source tree.
26837 When @value{GDBN} does support the architecture of the embedded system
26838 at hand, the task of finding the correct architecture name to give the
26839 @command{set architecture} command can be error-prone.
26842 To address these problems, the @value{GDBN} remote protocol allows a
26843 target system to not only identify itself to @value{GDBN}, but to
26844 actually describe its own features. This lets @value{GDBN} support
26845 processor variants it has never seen before --- to the extent that the
26846 descriptions are accurate, and that @value{GDBN} understands them.
26848 @value{GDBN} must be linked with the Expat library to support XML
26849 target descriptions. @xref{Expat}.
26852 * Retrieving Descriptions:: How descriptions are fetched from a target.
26853 * Target Description Format:: The contents of a target description.
26854 * Predefined Target Types:: Standard types available for target
26856 * Standard Target Features:: Features @value{GDBN} knows about.
26859 @node Retrieving Descriptions
26860 @section Retrieving Descriptions
26862 Target descriptions can be read from the target automatically, or
26863 specified by the user manually. The default behavior is to read the
26864 description from the target. @value{GDBN} retrieves it via the remote
26865 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
26866 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
26867 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
26868 XML document, of the form described in @ref{Target Description
26871 Alternatively, you can specify a file to read for the target description.
26872 If a file is set, the target will not be queried. The commands to
26873 specify a file are:
26876 @cindex set tdesc filename
26877 @item set tdesc filename @var{path}
26878 Read the target description from @var{path}.
26880 @cindex unset tdesc filename
26881 @item unset tdesc filename
26882 Do not read the XML target description from a file. @value{GDBN}
26883 will use the description supplied by the current target.
26885 @cindex show tdesc filename
26886 @item show tdesc filename
26887 Show the filename to read for a target description, if any.
26891 @node Target Description Format
26892 @section Target Description Format
26893 @cindex target descriptions, XML format
26895 A target description annex is an @uref{http://www.w3.org/XML/, XML}
26896 document which complies with the Document Type Definition provided in
26897 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
26898 means you can use generally available tools like @command{xmllint} to
26899 check that your feature descriptions are well-formed and valid.
26900 However, to help people unfamiliar with XML write descriptions for
26901 their targets, we also describe the grammar here.
26903 Target descriptions can identify the architecture of the remote target
26904 and (for some architectures) provide information about custom register
26905 sets. @value{GDBN} can use this information to autoconfigure for your
26906 target, or to warn you if you connect to an unsupported target.
26908 Here is a simple target description:
26911 <target version="1.0">
26912 <architecture>i386:x86-64</architecture>
26917 This minimal description only says that the target uses
26918 the x86-64 architecture.
26920 A target description has the following overall form, with [ ] marking
26921 optional elements and @dots{} marking repeatable elements. The elements
26922 are explained further below.
26925 <?xml version="1.0"?>
26926 <!DOCTYPE target SYSTEM "gdb-target.dtd">
26927 <target version="1.0">
26928 @r{[}@var{architecture}@r{]}
26929 @r{[}@var{feature}@dots{}@r{]}
26934 The description is generally insensitive to whitespace and line
26935 breaks, under the usual common-sense rules. The XML version
26936 declaration and document type declaration can generally be omitted
26937 (@value{GDBN} does not require them), but specifying them may be
26938 useful for XML validation tools. The @samp{version} attribute for
26939 @samp{<target>} may also be omitted, but we recommend
26940 including it; if future versions of @value{GDBN} use an incompatible
26941 revision of @file{gdb-target.dtd}, they will detect and report
26942 the version mismatch.
26944 @subsection Inclusion
26945 @cindex target descriptions, inclusion
26948 @cindex <xi:include>
26951 It can sometimes be valuable to split a target description up into
26952 several different annexes, either for organizational purposes, or to
26953 share files between different possible target descriptions. You can
26954 divide a description into multiple files by replacing any element of
26955 the target description with an inclusion directive of the form:
26958 <xi:include href="@var{document}"/>
26962 When @value{GDBN} encounters an element of this form, it will retrieve
26963 the named XML @var{document}, and replace the inclusion directive with
26964 the contents of that document. If the current description was read
26965 using @samp{qXfer}, then so will be the included document;
26966 @var{document} will be interpreted as the name of an annex. If the
26967 current description was read from a file, @value{GDBN} will look for
26968 @var{document} as a file in the same directory where it found the
26969 original description.
26971 @subsection Architecture
26972 @cindex <architecture>
26974 An @samp{<architecture>} element has this form:
26977 <architecture>@var{arch}</architecture>
26980 @var{arch} is an architecture name from the same selection
26981 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
26982 Debugging Target}).
26984 @subsection Features
26987 Each @samp{<feature>} describes some logical portion of the target
26988 system. Features are currently used to describe available CPU
26989 registers and the types of their contents. A @samp{<feature>} element
26993 <feature name="@var{name}">
26994 @r{[}@var{type}@dots{}@r{]}
27000 Each feature's name should be unique within the description. The name
27001 of a feature does not matter unless @value{GDBN} has some special
27002 knowledge of the contents of that feature; if it does, the feature
27003 should have its standard name. @xref{Standard Target Features}.
27007 Any register's value is a collection of bits which @value{GDBN} must
27008 interpret. The default interpretation is a two's complement integer,
27009 but other types can be requested by name in the register description.
27010 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
27011 Target Types}), and the description can define additional composite types.
27013 Each type element must have an @samp{id} attribute, which gives
27014 a unique (within the containing @samp{<feature>}) name to the type.
27015 Types must be defined before they are used.
27018 Some targets offer vector registers, which can be treated as arrays
27019 of scalar elements. These types are written as @samp{<vector>} elements,
27020 specifying the array element type, @var{type}, and the number of elements,
27024 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
27028 If a register's value is usefully viewed in multiple ways, define it
27029 with a union type containing the useful representations. The
27030 @samp{<union>} element contains one or more @samp{<field>} elements,
27031 each of which has a @var{name} and a @var{type}:
27034 <union id="@var{id}">
27035 <field name="@var{name}" type="@var{type}"/>
27040 @subsection Registers
27043 Each register is represented as an element with this form:
27046 <reg name="@var{name}"
27047 bitsize="@var{size}"
27048 @r{[}regnum="@var{num}"@r{]}
27049 @r{[}save-restore="@var{save-restore}"@r{]}
27050 @r{[}type="@var{type}"@r{]}
27051 @r{[}group="@var{group}"@r{]}/>
27055 The components are as follows:
27060 The register's name; it must be unique within the target description.
27063 The register's size, in bits.
27066 The register's number. If omitted, a register's number is one greater
27067 than that of the previous register (either in the current feature or in
27068 a preceeding feature); the first register in the target description
27069 defaults to zero. This register number is used to read or write
27070 the register; e.g.@: it is used in the remote @code{p} and @code{P}
27071 packets, and registers appear in the @code{g} and @code{G} packets
27072 in order of increasing register number.
27075 Whether the register should be preserved across inferior function
27076 calls; this must be either @code{yes} or @code{no}. The default is
27077 @code{yes}, which is appropriate for most registers except for
27078 some system control registers; this is not related to the target's
27082 The type of the register. @var{type} may be a predefined type, a type
27083 defined in the current feature, or one of the special types @code{int}
27084 and @code{float}. @code{int} is an integer type of the correct size
27085 for @var{bitsize}, and @code{float} is a floating point type (in the
27086 architecture's normal floating point format) of the correct size for
27087 @var{bitsize}. The default is @code{int}.
27090 The register group to which this register belongs. @var{group} must
27091 be either @code{general}, @code{float}, or @code{vector}. If no
27092 @var{group} is specified, @value{GDBN} will not display the register
27093 in @code{info registers}.
27097 @node Predefined Target Types
27098 @section Predefined Target Types
27099 @cindex target descriptions, predefined types
27101 Type definitions in the self-description can build up composite types
27102 from basic building blocks, but can not define fundamental types. Instead,
27103 standard identifiers are provided by @value{GDBN} for the fundamental
27104 types. The currently supported types are:
27113 Signed integer types holding the specified number of bits.
27120 Unsigned integer types holding the specified number of bits.
27124 Pointers to unspecified code and data. The program counter and
27125 any dedicated return address register may be marked as code
27126 pointers; printing a code pointer converts it into a symbolic
27127 address. The stack pointer and any dedicated address registers
27128 may be marked as data pointers.
27131 Single precision IEEE floating point.
27134 Double precision IEEE floating point.
27137 The 12-byte extended precision format used by ARM FPA registers.
27141 @node Standard Target Features
27142 @section Standard Target Features
27143 @cindex target descriptions, standard features
27145 A target description must contain either no registers or all the
27146 target's registers. If the description contains no registers, then
27147 @value{GDBN} will assume a default register layout, selected based on
27148 the architecture. If the description contains any registers, the
27149 default layout will not be used; the standard registers must be
27150 described in the target description, in such a way that @value{GDBN}
27151 can recognize them.
27153 This is accomplished by giving specific names to feature elements
27154 which contain standard registers. @value{GDBN} will look for features
27155 with those names and verify that they contain the expected registers;
27156 if any known feature is missing required registers, or if any required
27157 feature is missing, @value{GDBN} will reject the target
27158 description. You can add additional registers to any of the
27159 standard features --- @value{GDBN} will display them just as if
27160 they were added to an unrecognized feature.
27162 This section lists the known features and their expected contents.
27163 Sample XML documents for these features are included in the
27164 @value{GDBN} source tree, in the directory @file{gdb/features}.
27166 Names recognized by @value{GDBN} should include the name of the
27167 company or organization which selected the name, and the overall
27168 architecture to which the feature applies; so e.g.@: the feature
27169 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
27171 The names of registers are not case sensitive for the purpose
27172 of recognizing standard features, but @value{GDBN} will only display
27173 registers using the capitalization used in the description.
27179 * PowerPC Features::
27184 @subsection ARM Features
27185 @cindex target descriptions, ARM features
27187 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
27188 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
27189 @samp{lr}, @samp{pc}, and @samp{cpsr}.
27191 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
27192 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
27194 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
27195 it should contain at least registers @samp{wR0} through @samp{wR15} and
27196 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
27197 @samp{wCSSF}, and @samp{wCASF} registers are optional.
27199 @node MIPS Features
27200 @subsection MIPS Features
27201 @cindex target descriptions, MIPS features
27203 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
27204 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
27205 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
27208 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
27209 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
27210 registers. They may be 32-bit or 64-bit depending on the target.
27212 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
27213 it may be optional in a future version of @value{GDBN}. It should
27214 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
27215 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
27217 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
27218 contain a single register, @samp{restart}, which is used by the
27219 Linux kernel to control restartable syscalls.
27221 @node M68K Features
27222 @subsection M68K Features
27223 @cindex target descriptions, M68K features
27226 @item @samp{org.gnu.gdb.m68k.core}
27227 @itemx @samp{org.gnu.gdb.coldfire.core}
27228 @itemx @samp{org.gnu.gdb.fido.core}
27229 One of those features must be always present.
27230 The feature that is present determines which flavor of m86k is
27231 used. The feature that is present should contain registers
27232 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
27233 @samp{sp}, @samp{ps} and @samp{pc}.
27235 @item @samp{org.gnu.gdb.coldfire.fp}
27236 This feature is optional. If present, it should contain registers
27237 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
27241 @node PowerPC Features
27242 @subsection PowerPC Features
27243 @cindex target descriptions, PowerPC features
27245 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
27246 targets. It should contain registers @samp{r0} through @samp{r31},
27247 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
27248 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
27250 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
27251 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
27253 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
27254 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
27257 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
27258 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
27259 @samp{spefscr}. SPE targets should provide 32-bit registers in
27260 @samp{org.gnu.gdb.power.core} and provide the upper halves in
27261 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
27262 these to present registers @samp{ev0} through @samp{ev31} to the
27277 % I think something like @colophon should be in texinfo. In the
27279 \long\def\colophon{\hbox to0pt{}\vfill
27280 \centerline{The body of this manual is set in}
27281 \centerline{\fontname\tenrm,}
27282 \centerline{with headings in {\bf\fontname\tenbf}}
27283 \centerline{and examples in {\tt\fontname\tentt}.}
27284 \centerline{{\it\fontname\tenit\/},}
27285 \centerline{{\bf\fontname\tenbf}, and}
27286 \centerline{{\sl\fontname\tensl\/}}
27287 \centerline{are used for emphasis.}\vfill}
27289 % Blame: doc@cygnus.com, 1991.